Hydrogeologic controls and geochemical indicators of groundwater movement in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California

Teague, Nicholas F.- nteague@usgs.gov, Izbicki, John A.- jaizbick@usgs.gov, Borchers, Jim, Kulongoski, Justin T.- kulongos@usgs.gov · 2019 · Report

Beginning in the 1970s, Alameda County Water District began infiltrating imported water through ponds in repurposed gravel quarries at the Quarry Lakes

This 2019 document, Hydrogeologic controls and geochemical indicators of groundwater movement in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, is preserved in the Mountain Man Mining Library for research and reference. Original source: pubs.usgs.gov.

U.S. Department of the Interior U.S. Geological Survey Scientific Investigations Report 2018-5003 Version 1.1, February 2019 Prepared in cooperation with the East Bay Municipal Utility District, City of Hayward, and Alameda County Water District Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins, Alameda County, California

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins, Alameda County, California By Nick Teague, John Izbicki, Jim Borchers, Justin Kulongoski, and Bryant Jurgens Prepared in cooperation with the East Bay Municipal Utility District, City of Hayward, and Alameda County Water District Scientific Investigations Report 2018-5003 Version 1.1, February 2019 U.S. Department of the Interior U.S. Geological Survey

U.S. Department of the Interior DAVID BERNHARDT, Acting Secretary U.S. Geological Survey William H. Werkheiser, Deputy Director exercising the authority of the Director U.S. Geological Survey, Reston, Virginia: 2019 First release: February 2018 Revised: February 2019 (ver. 1.1) For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1-888-ASK-USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Teague, Nick, Izbicki, John, Borchers, Jim, Kulongoski, Justin, and Jurgens, Bryant, 2018, Hydrogeologic controls and geochemical indicators of groundwater movement in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California (ver 1.1, February 2019): U.S. Geological Survey Scientific Investigations Report 2018-5003, 62 p., https://doi.org/10.3133/sir20185003. ISSN 2328-0328 (online)

Contents Abstract 1 Introduction 2 Purpose and Scope 2 Description of the Study Area 2 Hydrogeology 4 The Upper Aquifer System 5 Deep Aquifer 5 Recharge and Discharge 6 Groundwater Management 6 Methods 7 Groundwater-Level Measurement 7 InSAR Data Processing 8 Streamflow Gains and Losses Estimation 8 Water Sample Collection and Analysis 10 Collection and Analysis of Core and Cuttings Material 10 Hydrogeology 11 Groundwater Movement 11 Local Short-Term Land-Surface Displacement 11 Streamflow Gains and Losses in Alameda Creek 15 Geochemistry 18 Chemistry of Groundwater 18 Physical Properties and Chemical Characteristics of Groundwater 18 Major-Ion Composition 21 Chloride-to-Iodide Ratios 21 Geochemical Indicators of Groundwater Movement 23 Noble-Gas and Tritium Analysis 23 Tritium and Helium 25 Tritium-Helium-3 Ages 25 Helium-4 Ages 26 Isotopic Composition of Groundwater 27 Oxygen-18 and Deuterium 27 Carbon-14 and Carbon-13 29 Interpretation of Carbon-14 Data 30 Limitations of Carbon-14 Interpretations 33 Summary 34 References Cited 35 Appendix 1.  Location and Construction Data and Water-Level Measurements Collected by the U.S. Geological Survey During 2002 for Wells Drilled in the Niles Cone and Southern East Bay Plain Groundwater Subbasins 41 Appendix 2.  U.S. Geological Survey National Water-Quality Laboratory Analytical Methods and Reporting Levels for Analysis of Groundwater and Surface-Water Samples 45 References Cited 45

Appendix 3.  Aquifer Mineralogy, Niles Cone Groundwater Subbasin, Alameda County, California 47 References Cited 47 Appendix 4.  Streamflow Data Collected by the U.S. Geological Survey during April 2002 51 Appendix 5.  Physical Property, Major-Ion, Trace-Element, and Isotopic Data for Groundwater, Stream-Water, and Precipitation Samples Collected and Analyzed by the U.S. Geological Survey 53 Appendix 6.  Noble Gas and Tritium Data for Groundwater Samples Collected and Analyzed by the U.S. Geological Survey 59 Appendix 7.  Measured and Interpreted Carbon-13 and Carbon-14 Data for Groundwater Samples Collected and Analyzed by the U.S. Geological Survey 61 Contents—Continued Figures

1.  Map showing location of the Niles Cone and southern East Bay Plain groundwater subbasins and municipal wells, including aquifer reclamation program wells, Alameda County, California 3

2.  Graph showing generalized A-A' cross section showing groundwater aquifers of Niles Cone and southern East Bay Plain groundwater subbasins and well location and well construction for wells sampled as part of this study, Alameda County, California 4

3.  Map showing water-level elevation contours and water-level elevations in wells screened in the upper aquifer system, gaining and losing reaches along Alameda Creek, Quarry Lakes Regional Park recharge area, Alameda Creek, and Alameda County Water District aquifer reclamation program wells, Alameda County, California, April 2002 9

4.  Map showing water-level elevation contours and water-level elevations in wells screened in the Deep aquifer; Quarry Lakes Regional Park recharge area; Alameda Creek; and Alameda County Water District Aquifer Reclamation Program wells, Niles Cone groundwater subbasin, Alameda County, California, 2002 12

5.  Graphs showing precipitation at San Francisco International Airport, water-level elevation at infiltration pond Lago Los Osos, total pumpage from Alameda County Water District's Aquifer Reclamation Program wells, and groundwater elevations in selected wells north from Alameda Creek in the Niles Cone groundwater subbasin, Alameda County, California 13

6.  InSAR interferogram displaying relative subsidence or uplift in the Niles Cone groundwater subbasin during refilling of infiltration ponds at Quarry Lakes Regional Park, Alameda County, California 14

7.  Graphs showing streamflow and water-temperature measurements along Alameda Creek, April 24-25, 2002, Alameda County, California 16

8.  Cross-sectional bathymetry of Alameda Creek 17

9.  Boxplots showing pH, dissolved oxygen, and selected major-ion, nutrient, and trace-element concentrations in water from wells sampled in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 19

10.  Piper diagram showing major-ion composition of samples from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 20

11.  Chloride-to-iodide ratios as a function of chloride concentration in water from wells, Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 22

12.  Graph showing selected noble-gas concentrations in water from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 24

13.  Graph showing spatial distribution of tritium concentrations in groundwater from selected Deep aquifer wells in the Niles cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 26

14.  Map showing spatial distribution of 4He ages from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 28

15.  Graphs showing relations of delta oxygen-18 with delta deuterium (δD) in water from wells, Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 29

16.  Graphs showing selected changes in chemical and isotopic composition of water from wells used to interpret carbon-14 data along section B-B', Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03 31

17.  Plot of rank order carbon-14 data, expressed as cumulative exceedance percentage, in water from sampled wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03. Tritium concentrations are shown using filled and open circle symbols 33

3-1.  Scanning electron microscopy images of typical mineral grains from core material from selected sites in the Niles Cone groundwater subbasin, Alameda County, California 47 Figures—Continued Tables

1-1.  Location and construction data and water-level measurements collected by the U.S. Geological Survey during fall 2002 for wells drilled in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California 41

2-1.  U.S. Geological Survey National Water-Quality Laboratory analytical methods and reporting levels for analysis of groundwater samples 46

3-1.  Elemental composition of samples from Lake Chad well (4S/2W-14D3) at 517 feet deep and outcrop on northwest shore of Quarry Lakes, Niles Cone groundwater subbasin, Alameda County, California 48

3-2.   Mineralogical composition and optical observations of samples from Lake Chad well (4S/2W-14D3) at 517 feet deep and outcrop on northwest shore of Quarry Lakes, Niles Cone groundwater subbasin, Alameda County, California 49

4-1.  Streamflow data collected by the U.S. Geological Survey during April 2002, Alameda Creek, California 51

5-1.  Physical property, major-ion, selected trace-element, and isotopic data for groundwater, stream-water, and precipitation samples collected and analyzed by the U.S. Geological Survey, southern East Bay Plain and Niles Cone groundwater subbasins, Alameda County, California, 2002-03 53

6-1.  Noble gas and tritium data for groundwater samples collected from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, March-October, 2002-03 59

7-1.  Measured and interpreted carbon-13 and carbon-14 data for groundwater samples collected from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, March-October, 2002 61

7-2.  Chemical reactions used to interpret carbon-14 data 62 Tables—Continued Conversion Factors U.S. customary units to International System of Units Multiply By To obtain Length inch (in.) millimeter (mm) inch (in.) 25,400 micrometer (µm) foot (ft) meter (m) mile (mi) Area acre 4,047 square meter (m2) acre square kilometer (km2) square foot (ft2) square meter (m2) square foot (ft2) square centimeter (cm2) square mile (mi2) square kilometer (km2) Volume gallon (gal) liter (L) acre-foot (acre-ft) 1,233 cubic meter (m3) acre-foot (acre-ft) 1.233×109 cubic centimeter (cm3) acre-foot (acre-ft) 1.233×1012 micro-cubic centimeter (µcm3) Flow rate acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr) foot per day (ft/d) meter per day (m/d) foot per minute (ft/min) meter per minute (m/min) foot per second (ft/s) meter per second (m/s) gallon per day (gal/d) cubic meter per day (m3/d) gallon per minute (gal/min) cubic meter per minute (m3/min) Density pound-mass per cubic foot (lbm/ft3) grams per cubic centimeter (g/cm3) Mass pound, avoirdupois (lb) kilogram (kg) Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F (1.8 × °C) + 32. Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C (°F − 32) / 1.8. Specific storage is reported in units of per foot (ft−1).

Specific conductance is reported in units of microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25 °C). Concentrations of chemical constituents in water are reported either in units of milligrams per liter (mg/L) or micrograms per liter (μg/L). Concentrations of chemical constituents in sediment (alluvium) are reported either in units of milligrams per kilogram (mg/kg) or micrograms per cubic centimeter (µg/cm3). Concentrations of the noble gases helium (He), neon (Ne), and krypton (Kr) are reported in units of micro-cubic centimeters (at standard temperature and pressure) per kilogram of water (µcm3(STP)/kg). Concentrations of the noble gas argon (Ar) are reported in units of cubic centimeters (at standard temperature and pressure) per kilogram of water (cm3(STP)/kg). Deep crustal flux of helium-4 is reported in units of cubic centimeters (at standard temperature and pressure) per square centimeter per year (cm3(STP)cm−2yr−1). Concentrations of excess air are reported in units of cubic centimeters (at standard temperature and pressure) per kilogram of water (cm3/kg). Concentrations of uranium (U) and thorium (Th) are reported in units of milligrams per kilogram of alluvium (mg/kg, ppm). Concentrations of tritium (3H) are reported in units of tritium units (TU). The conversion of tritium units (TU) to picocuries per liter, based upon a tritium half-life of 12.32 years (Lucas and Unterweger, 2000), is 1 TU 3.22 picocuries per liter. Helium-3 (3He) data are reported as δ values computed from the formula:



R R Std

where Rx is the ratio of 3He to 4He in the sample, RSTD is the 3He to 4He ratio of the reference standard air (1.384×10−6), and δ3He is expressed in parts per hundred. Stable isotopes of water are reported as δ values computed from the formula:



R R Std ,

where Rx is the ratio of 2H to 1H or 18O to 16O in the sample, RSTD is the 2H to 1H or 18O to 16O ratio of the reference standard Vienna Standard Mean Ocean Water (VSMOW), and δ2H or δ18O is expressed in parts per thousand. Stable isotopes of carbon are reported as δ values computed from the formula:



R R Std ,

where Rx is the ratio of 13C to 12C in the sample, RSTD is the 13C to 12C ratio of the reference standard Vienna Peedee Belemnite, and δ13C is expressed in parts per thousand.

Datum Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88), unless otherwise noted. Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). Mean sea level is 6.75 feet above the station datum for station 9414750, Alameda, California, of 3.56 feet (NAVD 88). Abbreviations Ao

initial carbon activity ACWD Alameda County Water District ANOVA analysis of variance Ar

argon ARP aquifer reclamation program ASR aquifer storage and recovery BGP Bayside Groundwater Project °C

degrees Celsius

carbon-14, in percent modern carbon CE

closed system equilibrium cfs

cubic feet per second CO2

carbon dioxide; molecular formula DIC

dissolved organic carbon DOD U.S. Department of Defense EBMUD East Bay Municipal Utility District EPA U.S. Environmental Protection Agency GMWL Global Meteoric Water Line H2O water; molecular formula 2H

deuterium 3H

tritium He

helium 3He

helium-3; isotope of helium 3Hetrit

tritiogenic helium-3 4He

helium-4; isotope of helium 4Heex excess helium-4 InSAR interferometric synthetic aperture radar

Kr krypton kyr thousand years MCL maximum contaminant level Myr million years NGT groundwater recharge temperature Ne neon ΔNe neon oversaturation NWQL National Water Quality Laboratory 18O oxygen-18 pmC percent modern carbon ppm parts per million PR partial reequilibration SFPUC San Francisco Public Utilities Commission SI saturation indexes SMCL secondary maximum contaminant level STP standard temperature and pressure SWP State Water Project TU tritium unit UA unfractionated air USGS U.S. Geological Survey VSMOW Vienna Standard Mean Ocean Water ybp years before present Abbreviations—Continued

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins, Alameda County, California By Nick Teague, John Izbicki, Jim Borchers, Justin Kulongoski, and Bryant Jurgens Abstract Beginning in the 1970s, Alameda County Water District began infiltrating imported water through ponds in repurposed gravel quarries at the Quarry Lakes Regional Park, in the Niles Cone groundwater subbasin, to recharge groundwater and to minimize intrusion of saline, San Francisco Bay water into freshwater aquifers. Hydraulic connection between distinct aquifers underlying Quarry Lakes allows water to recharge the upper aquifer system to depths of 400 feet below land surface, and the Deep aquifer to depths of more than 650 feet. Previous studies of the Niles Cone and southern East Bay Plain groundwater subbasins suggested that these two subbasins may be hydraulically connected. Characterization of storage capacities and hydraulic properties of the complex aquifers and the structural and stratigraphic controls on groundwater movement aids in optimal storage and recovery of recharged water and provides information on the ability of aquifers shared by different water management agencies to fulfill competing storage and extraction demands. The movement of recharge water through the Niles Cone groundwater subbasin from Quarry Lakes and the possible hydraulic connection between the Niles Cone and the southern East Bay Plain groundwater subbasins were investigated using interferometric synthetic aperture radar (InSAR), water-chemistry, and isotopic data, including tritium/helium-3, helium-4, and carbon-14 age-dating techniques. InSAR data collected during refilling of the Quarry Lakes recharge ponds show corresponding ground-surface displacement. Maximum uplift was about 0.8 inches, reasonable for elastic expansion of sedimentary materials experiencing an increase in hydraulic head that resulted from pond refilling. Sodium concentrations increase while calcium and magnesium concentrations in groundwater decrease along groundwater flowpaths from the Niles Cone groundwater subbasin through the Deep aquifer to the northwest toward the southern East Bay Plain groundwater subbasin. Residual effects of pre-1970s intrusion of saline water from San Francisco Bay, including high chloride concentrations in groundwater, are evident in parts of the Niles Cone subbasin. Noble gas recharge temperatures indicate two primary recharge sources (Quarry Lakes and Alameda Creek) in the Niles Cone groundwater subbasin. Although recharge at Quarry Lakes affects hydraulic heads as far as the transition zone between the Niles Cone and East Bay Plain groundwater subbasins (about 5 miles), the effect of recharged water on water quality is only apparent in wells near (less than 2 miles) recharge sources. Groundwater chemistry from upper aquifer system wells near Quarry Lakes showed an evaporated signal (less negative oxygen and hydrogen isotopic values) relative to surrounding groundwater and a tritium concentration (2 tritium units) consistent with recently recharged water from a surface-water impoundment. Uncorrected carbon-14 activities measured in water sampled from wells in the Niles Cone groundwater subbasin range from 16 to 100 percent modern carbon (pmC). The geochemical reaction modeling software NETPATH was used to interpret carbon-14 ages along a flowpath from Quarry Lakes toward the East Bay Plain groundwater subbasin. Model results indicate that changes in groundwater chemistry are controlled by cation exchange on clay minerals and weathering of primary silicate minerals. Old groundwater (lower carbon-14 activities) is characterized by high dissolved silica and pH. Interpreted carbon-14 ages ranged from 830 to more than 7,000 years before present and are less than helium-4 ages that range from 2,000 to greater than 11,000 years before present. The average horizontal groundwater velocity along the studied flowpath, as calculated using interpreted carbon-14 ages, through the Deep aquifer of the Niles Cone groundwater subbasin is between 3 and 12 feet per year. The groundwater velocity decreases near the boundary of the transition zone to the southern East Bay Plain groundwater subbasin to about 0.5 feet per year. These changes may result from water recharged from different sources converging in flowpaths north of the transition zone, or a boundary to flow between the Niles Cone and southern East Bay Plain groundwater subbasins, likely owing to changes in lithology caused by depositional patterns.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Introduction Water agencies in the east San Francisco Bay area are developing alternate water supplies to supplement current sources largely imported from reservoirs in the Sierra Nevada or the Sacramento-San Joaquin River Delta. Conjunctive-use practices utilizing artificial storage and recovery of surface water in aquifers are being implemented as means to address water-supply issues related to the growing demand for municipal and industrial water and the temporal variability of the surface-water supply. In addition, increased development of local groundwater through managed aquifer recharge has been proposed as an alternative to imported water as a means to address the potential interruption of aqueduct flows during seismic or other emergencies (Alameda County Water District, 2001b). The study area, the Niles Cone and southern East Bay Plain groundwater subbasins, is in the alluvial plain south of Oakland, California, on the eastern shore of the south San Francisco Bay (fig. 1). The area is underlain by a complex aquifer system at least 650 feet (ft) thick (fig. 2). Several water management projects are being developed as alternate and emergency water sources in the area. The Alameda County Water District (ACWD) recharges aquifers by infiltrating surface water from local reservoirs and from the South Bay Aqueduct (not shown on figures) through abandoned gravel quarries at Quarry Lakes Regional Park and at impoundments behind inflatable rubber dams in the channel of Alameda Creek (Alameda County Water District, 2001a). The City of Hayward has constructed five deep water-supply wells in the aquifers underlying Hayward, Calif., to provide emergency water supply. The East Bay Municipal Utility District (EBMUD) has tested the feasibility of artificial storage and recovery (ASR) of water through deep wells near the San Francisco Bay (Bayside), just south from San Lorenzo Creek (fig. 1; Luhdorff and Scalmanini Consulting Engineers, 2003). Conjunctive-use programs store a combination of surface water and groundwater, and therefore, they require aquifer systems capable of storing and subsequently yielding large quantities of water (Mariño, 2001). The ability of aquifers shared by different water management agencies to fulfill competing storage and extraction demands may be difficult to evaluate in the absence of regional hydrogeology data. Characterization of storage capacities and hydraulic properties of the complex aquifers and the structural and stratigraphic controls on groundwater movement aids in optimal storage and recovery of recharged water. Local water agency staff, their consultants and representatives, and the U.S. Geological Survey (USGS) are collaborating to develop an understanding of hydrogeologic factors that affect groundwater development and successful operation of conjunctive-use facilities in the study area. Previously, the USGS, in cooperation with EBMUD, investigated the hydrogeology and geochemistry of aquifers underlying the southern East Bay Plain groundwater subbasin (Izbicki and others, 2003; Sneed and others, 2015). They found that (1) most recent recharge to the aquifer system is restricted to shallow aquifers near the mountain front; (2) recharge occurs as infiltration of streamflow during the winter and as infiltration from more diffuse sources such as precipitation, irrigation, and septic discharge; and (3) large amounts of recharge from imported water leaking from water supply pipes is not apparent. This report extends that work further south, describing the results of an investigation of parts of the Deep aquifer underlying the southern East Bay Plain and the northern Niles Cone groundwater subbasins that was completed cooperatively with ACWD, City of Hayward, and EBMUD. Purpose and Scope Given increasing demands on groundwater resources and often competing groundwater management projects in aquifers underlying the Niles Cone and southern East Bay Plain groundwater subbasins, local management agencies require improved understanding of the movement of recharged water within and between aquifers and the potential effect of groundwater recharge projects in urban areas. The purpose of this report is to document the methods and results of an evaluation of the geologic and hydrologic controls on groundwater movement through aquifers between the Niles Cone and southern East Bay Plain groundwater subbasins on the east side of San Francisco Bay, California. The scope of this report includes the methods for collection of hydrologic, InSAR, and geochemical data for 2002 and 2003; the description of the analysis of the data to evaluate movement of water from the Quarry Lakes Regional Park recharge ponds and Alameda Creek into the aquifer system of the Niles Cone groundwater subbasin; and the interaction of groundwater in the Niles Cone and southern East Bay Plain groundwater subbasins. Description of the Study Area The study area is composed of the alluvial fans (locally referred to as cones) of the San Lorenzo and Alameda Creeks and smaller tributaries, and it is separated into two distinct groundwater subbasins: the East Bay Plain groundwater subbasin and the Niles Cone groundwater subbasin. The East Bay Plain groundwater subbasin is about 120 square miles of tidal marshes and alluvial lowlands near Oakland, Calif., on the east side of San Francisco Bay (fig. 1). The Niles Cone groundwater subbasin is formed by the alluvial plain of Alameda Creek and is 103 square miles. The area has a Mediterranean climate with mild, wet winters and warm, dry summers. The average annual temperature is 15 °C and ranges from 11 °C (December-February) to 18 °C (June-September; National Oceanic and Atmospheric Administration, 2012). Most precipitation falls as rain between November and March and averages 23 inches (in.) annually (Muir, 1997). The area is highly urbanized with diverse residential, commercial, and industrial land uses. Although agriculture was important in the past, there is little agricultural land use in the study area at the present time.

Introduction    3 MISSION FAULT MISSION FAULT HAYWARD FAULT HAYWARD FAULT SILVER CREEK FAULT SILVER CREEK FAULT 10 MILES 10 KILOMETERS 17M7, 17M8, 17M6 13P4, 13P6, 12K10, 12K8 10E4 4R1 4F3 4E1 2H1 14D3, 14D4 13P7, 13P5 Well A Well A Mowry well field Mowry well field ARP wells ARP wells 19Q3 19Q3 Bayside Bayside DIABLO RANGE 121°55' 122°00' 122°05' 122°10' 122°15' 122°20' 37° 45' 37° 40' 37° 35' 37° 30' A A' Leandro synform Old Alameda Creek Old Alameda Creek Dry Creek Dry Creek Quarry Lakes Regional Park Quarry Lakes Regional Park Alameda Alameda Creek Creek Coyote Hills B B' Study area Sacramento- San Joaquin River Delta Hetch Hetchy Reservoir S E RR A N E A D A RA N GE Yosemite National Park Fremont Fremont Oakland Oakland San Lorenzo San Lorenzo Hayward Hayward San Leandro San Leandro San Francisco Bay S a n

e an d r o Cr e ek S a n

e an d r o Cr e ek S an o r e nzo Cr e e k S an o r e nzo Cr e e k EXPLANATION 12K10 12K10 13P5 13P5 19Q3 19Q3 Well A Well A A A' Municipal wells Wells sampled by Izbicki and others, 2003 Wells sampled as part of this study Upper aquifer system wells Deep aquifer wells Surface water site Transition zone (Luhdorff and Scalmanini Consulting Engineers, 2003) East Bay Plain subbasin Niles Cone subbasin Line of hydrogeologic section San Francisco International Airport Dry Creek Dry Creek Background image is the intellectual property of Esri and is used herein under license. Copyright © 2014 Esri and its licensors. All rights reserved. Base modified from U.S. Geological Survey digital data, various scales; Lambert Conformal Conic projection; North American Datum of 1983 Figure 1.  Location of the Niles Cone and southern East Bay Plain groundwater subbasins and municipal wells, including aquifer reclamation program (ARP) wells, Alameda County, California.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Hydrogeology The study area is located where the right-lateral San Andreas Fault splays into a number of active subparallel right-lateral fault zones, including the Hayward Fault (fig. 1). The San Francisco Bay, surrounding marshes, and alluvial plains lie in a depression in the San Francisco Bay block, a structural province between the Diablo Range and the Hayward fault zone to the east and the Santa Cruz Mountains and San Andreas Fault to the west (not shown on figures). East from the Hayward Fault, Tertiary volcanic and sedimentary rocks; pre-Tertiary, unmetamorphosed rocks of the Great Valley sequence; and rocks of the Franciscan complex crop out in the Diablo Range (Wallace, 1990; Graymer and others, 1995; Graymer, 2000; Graymer, 2003). Within the structural depression, sedimentary deposits of variable thickness overlie the buried erosional surface of consolidated Franciscan Complex bedrock (Rogers and Figuers, 1991). The underlying Franciscan bedrock is of limited importance for water supply (Fugro West Inc., 2000, 2001; Dave Thomas, California Department of Transportation, written commun., 2002). Where water is present within these deposits, it is more mineralized and less desirable for human consumption than fresher groundwater in the overlying alluvium. The thickness, extent, structure, and texture of the alluvial aquifer systems have been influenced by tectonic movement in the Hayward fault zone, paleoclimate and sea level changes, and differences in sediment source areas. 2H1 Deep aquifer Deep aquifer southern East Bay Plain upper aquifers (undifferentiated) southern East Bay Plain upper aquifers (undifferentiated) Deep aquifer Deep aquifer EXPLANATION Groundwater aquifer boundary Groundwater aquifer boundary, inferred Well Abbreviated well number Perforated interval and abbreviated well number (colors indicate perforated interval and well number for a well in a well cluster) Total depth 17M6 17M6 13P6 13P6 13P7 13P7 13P4 13P4 13P5 13P5 17M7 17M8 12K8 12K9 12K9 12K10 12K10 12K11 12K11 14D3 14D4 14D5 14D6 14D7 Upper aquifer system NORTHWEST SOUTHEAST Generalized cross section SOUTHERN EAST BAY PLAIN Elevation, in feet OLD ALAMEDA CREEK ALAMEDA CREEK 10E4 14D 13P 12K 4F3 4F3 4R1 4R1 4E1 4E1 17M TRANSITION ZONE NILES CONE −200 −400 −600 −800 −1,000 −1,200 70,000 30,000 40,000 50,000 60,000 35,000 45,000 55,000 65,000 20,000 10,000 25,000 15,000 5,000 FEET Fremont aquifer Fremont aquifer Fremont aquifer Centerville aquifer Centerville aquifer Centerville aquifer A A' Modified from Luhdorff and Scalmanini Consulting Engineers (2003) Scale, in feet Newark aquifer Newark aquifer Newark aquifer Figure 2.  Generalized A-A' cross section showing groundwater aquifers of Niles Cone and southern East Bay Plain groundwater subbasins and well location and well construction for wells sampled as part of this study, Alameda County, California.

Introduction    5 The principal water-bearing units in the Niles Cone and southern East Bay Plain groundwater subbasins are located west of the Hayward Fault, which acts as an effective groundwater boundary (Clark, 1915). Four primary aquifers composed of Quaternary sedimentary deposits underlie the Niles Cone groundwater subbasin and southern East Bay Plain groundwater subbasins (California Department of Water Resources, 2003). The California Department of Water Resources (2003) delineated the subbasin boundaries by considering the geomorphic expression of present day alluvial fans, location of groundwater divides, political boundaries, and other factors. The aquifers (from shallowest to deepest) are the Newark, Centerville, Fremont, and Deep aquifers (fig. 2). The aquifers were first defined in the Niles Cone groundwater subbasin (California Department of Water Resources, 1967) and projected to the southern East Bay Plain groundwater subbasin by Brown and Caldwell (1986), Maslonkowski (1988), and Figuers (1998). Collectively, the aquifers consist of alluvial sand and gravel deposited by flood flows in Alameda Creek, presumably during glacial periods about 20,000, 120,000, and 240,000 years ago (Maslonkowski, 1988; Koltermann and Gorelick, 1992), and are separated by estuarine mud or fine-grained alluvial flood-plain deposits. The Newark, Centerville, and Fremont aquifers are thicker and more continuous in the Niles Cone groundwater subbasin than in the East Bay Plain groundwater subbasin to the north (Luhdorff and Scalmanini Consulting Engineers, 2003). The Upper Aquifer System In the Niles Cone groundwater subbasin, the Newark aquifer crops out at land surface, near the apex of the Alameda Creek alluvial fan, where it is 140 ft thick and lies 140 ft below land surface on the western edge of the area, where it thins to about 20 ft thick (California Department of Water Resources, 1967, 1968). Groundwater in the Newark aquifer is confined except near recharge areas along the mountain front (California Department of Water Resources, 2003). The Centerville aquifer lies at an average depth of 180 to 200 ft below land surface and, similar to the Newark aquifer, thins to the west (California Department of Water Resources, 2003). The Fremont aquifer lies between 300 and 390 ft below land surface, also thinning to the west. Groundwater in the Centerville and Fremont aquifers is confined (California Department of Water Resources, 2003). In parts of the Niles Cone groundwater subbasin where clay-rich aquitards are absent or thin, the Centerville and Fremont aquifers are hydraulically connected (Alameda County Water District, 2001a). Given the Centerville and Fremont aquifers are adjacent and hydraulically connected to each other, they are often referred to as a single aquifer unit, the CentervilleFremont aquifer. Near the apex of the Niles Cone groundwater subbasin, the Hayward Fault hydraulically partitions the alluvial deposits (Clark, 1915), and Alameda County Water District (2001) manages groundwater upgradient and downgradient from the Hayward Fault as separate aquifer systems. Lithologic data from wells and aquifer-test data indicate that the Newark and Centerville aquifers extend westward under and beyond San Francisco Bay (California Department of Water Resources, 1967). Lithologic data also indicate that the aquifers of the Niles Cone groundwater subbasin thin and become finer grained to the southwest, eventually disappearing in a clay-rich zone in northern Santa Clara Valley (California Department of Water Resources, 1967). For the purpose of this study, the Newark, Centerville, and Fremont aquifers are collectively referred to as the upper aquifer system. Unlike the Niles Cone groundwater subbasin to the south, alluvial fans in the southern East Bay Plain groundwater subbasin were deposited by lower energy streams. It is difficult to correlate sand and gravel layers over great distances between wells in the southern East Bay Plain groundwater subbasin (Muir, 1993). Fine-grained sediments deposited between alluvial fans interrupt lateral continuity of coarse-grained layers and inhibit interfan flow of groundwater. The Hayward Fault forms the eastern boundary of aquifers in the southern East Bay Plain groundwater subbasin. Alluvial deposits in the area east of the Hayward Fault are thin and contain insubstantial amounts of groundwater. The degree of hydraulic connection between the three shallow aquifers in the Niles Cone groundwater subbasin and their time-equivalent units in the southern East Bay Plain groundwater subbasin is not well defined, although aquifer sediments in the two areas may become more hydraulically connected with depth (Figuers, 1998). For example, the Fremont aquifer in the Niles Cone groundwater subbasin may be connected hydraulically to the Fremont aquifer in the southernmost East Bay Plain groundwater subbasin because both are thought to be composed of sediment deposited in the alluvial fan of Alameda Creek. Fremont-age sediment has been translated about 1.5 miles to the northwest from the Niles Cone groundwater subbasin into the southern East Bay Plain groundwater subbasin by right-lateral motion on the Hayward Fault (assuming an average geologic rate of movement of 30 ft per thousand years; Maslonkowski, 1988; Koltermann and Gorelick, 1992). Deep Aquifer Permeable sand and gravel layers that underlie the three shallowest aquifers (the upper aquifer system) in the study area are termed the Deep aquifer. Because relatively few wells have been drilled into the Deep aquifer, the thickness, areal extent, sedimentology and structure of the Deep aquifer is less well described than for the upper aquifer system. Permeable sand and gravel beds within the Deep aquifer are shallowest in the Niles Cone groundwater subbasin and deepen to the north, where they lie between 500 and 650 ft below land surface (fig. 2). In some areas, the aquifer can be as much as 150 ft thick.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Thickness of the Deep aquifer does not decrease near the edge of the Niles Cone groundwater subbasin. In fact, the Deep aquifer is thickest and most continuous south of San Leandro, Calif. (Maslonkowski, 1988), and eventually thins, nearly disappearing to the north of the study area (not shown on fig. 2; CH2M-Hill, Inc., 2000). It is likely that the source of sediments in the Deep aquifer beneath San Lorenzo Creek alluvial fan, and perhaps even further north, is the Alameda Creek watershed and that tectonic activity has shifted the sediments to the north (Koltermann and Gorelick, 1992). Recharge and Discharge Under predevelopment (before the late 1850s) conditions, recharge to the aquifer systems occurred primarily as infiltration of streamflow from San Leandro, San Lorenzo, and Alameda Creeks. Smaller amounts of recharge are believed to have occurred as infiltration of precipitation. Muir (1996a) estimated that annual recharge from infiltration of streamflow and direct infiltration of precipitation in the East Bay Plain groundwater subbasin was about 3,500 and 800 acre-feet (acre-ft), respectively. In the Niles Cone groundwater subbasin, recharge from infiltration of streamflow was about 14,000 acre-feet per year (acre-ft/yr; Bailey, 1919; California Department of Water Resources, 1968). Bailey (1919) regarded recharge from infiltrating precipitation in the Niles Cone groundwater subbasin as insignificant, but California Department of Water Resources (1968) estimated such recharge at about 7,400 acre-ft/yr. As noted earlier, some inflow to the Deep aquifer in the southern East Bay Plain groundwater subbasin may have occurred as groundwater that flowed northward from the Deep aquifer in the Niles Cone groundwater subbasin. The Hayward Fault is a barrier to groundwater flow between sedimentary deposits east and west of the fault. Under predevelopment conditions, groundwater discharging along the fault from sediments to the east maintained flow of springs (Figuers, 1998) that discharged groundwater at a rate of about 5,000 acre-ft/yr to extensive willow marshes north of San Lorenzo Creek and to other locations (Grossinger and Brewster, 2003). West of the Hayward Fault, groundwater flowed toward San Francisco Bay, where it discharged to tidal wetlands or continued to flow west under San Francisco Bay (Muir, 1996b). Where westward flow of groundwater was impeded by Franciscan Formation rocks in the subsurface near the Coyote Hills, groundwater discharged to wetlands or was diverted north and south from the Coyote Hills (Figuers, 1998). As a result of agricultural and urban development beginning in the late 1800s, groundwater pumping became an important discharge mechanism in the study area. More than 15,000 wells were drilled in the southern East Bay Plain groundwater subbasin between 1886 and 1950 (Figuers, 1998). Most of these wells were less than 100 ft deep, although some wells were more than 400 ft deep, and a few were drilled to depths greater than 1,000 ft. About 250 wells within the ACWD service area are more than 400 ft deep (James Ingle, ACWD, written commun., 2004). In 1917, 1,450 wells withdrew 19,000 acre-ft from the aquifers of the Niles Cone groundwater subbasin (Bailey, 1919). In 1960, 1,042 wells withdrew about 46,500 acre-ft from wells in the aquifers of the Niles Cone groundwater subbasin (California Department of Water Resources, 1960). In 1990, estimated withdrawal was 32,000 acre-ft from the aquifers of the Niles Cone groundwater subbasin (Fio and Leighton, 1995). Groundwater pumping in excess of recharge caused water levels to decline to more than 100 ft below sea level during the mid-1920s, mid-1930s, and late 1940s (Figuers, 1998). Salty water from San Francisco Bay, or salt water evaporation ponds at the margin of San Francisco Bay, migrated inland through shallow aquifers to areas where sediments generally are coarser grained and more permeable than shoreward sediments. The California Department of Water Resources (1960) attributed increasing chloride concentrations in the Niles Cone groundwater subbasin to vertical flow from overlying intruded aquifers through permeable sediments in recharge areas near the mountain front, through gaps in clayey aquicludes, and through leaking and abandoned wells. Muir (1996a) estimated that recharge from leaky underground water-supply and sewer pipes was about 3,100 acre-ft/yr in the southern East Bay Plain groundwater subbasin. However, Izbicki and others (2003), using stable isotope data from groundwater samples, suggested that recharge from leaking pipes may be less important than reported by Muir (1996a) or may not be uniformly distributed across the southern East Bay Plain groundwater subbasin. Natural recharge may have decreased as a result of urbanization because streams were channelized and lined with concrete, and permeable soil surfaces were paved. Groundwater Management In the mid-1900s, water imported to the study area reduced the dependence on local groundwater for public supply (California Department of Water Resources, 1963). The EBMUD imported surface water from the Sierra Nevada and also collected surface water in reservoirs in the hills east of the study area. The City of Hayward contracted with the San Francisco Public Utilities Commission (SFPUC) to purchase water for public supply from Hetch Hetchy Reservoir in northern Yosemite National Park. The ACWD also contracted with the SFPUC to purchase water from the Hetch Hetchy Reservoir and with the State Water Project to import water originating in the Sierra Nevada through the South Bay Aqueduct from the Sacramento-San Joaquin River Delta (Alameda County Water District, 2001a). The SFPUC and ACWD also collected runoff in local reservoirs. As the area became increasingly urbanized, agricultural pumping declined, and recharge from infiltration of imported water used for landscape irrigation increased. Groundwater levels recovered to near predevelopment conditions owing to the decreased dependence on local groundwater supplies (California Department of Water Resources, 1963).

Methods    7 Managed aquifer recharge in the Niles Cone groundwater subbasin includes water infiltrated at the Quarry Lakes Regional Park and behind two rubber dams that are inflated seasonally to impound water in Alameda Creek. The Quarry Lakes are a series of abandoned gravel quarries that were graded and plumbed to allow ACWD to operate them as artificial groundwater recharge facilities (fig. 1). The sources of water to Quarry Lakes are runoff in the Alameda Creek watershed, State Water Project (SWP) water imported since 1962 from central California (primarily snowmelt from the Sierra Nevada), and water discharged from reservoirs in the Alameda Creek watershed, which contain both local runoff and SWP water. Part of the flow of Alameda Creek is groundwater pumped from gravel quarries in upstream parts of the watershed (Moran and Halliwell, 2004). During drought years prior to importation of SWP water, or later when SWP water was not available for flow augmentation in Alameda Creek, effluent discharged from wastewater treatment plants was a substantial component of streamflow (Lopp, 1981). In conjunction with managed aquifer recharge, ACWD's Aquifer Reclamation Program (ARP) wells (fig. 1), which extract stratigraphically-trapped salty water, has substantially decreased the area of the Niles Cone groundwater subbasin affected by salt-water intrusion. The ACWD adds about 30,000 acre-ft/yr to groundwater storage at Quarry Lakes and the rubber dam impoundments, and ACWD usually extracts less than 10,000 acre-ft/yr from ARP wells. The ACWD estimated that pumping of local groundwater for public and private supplies in the Niles Cone groundwater subbasin averaged about 24,000 acre-ft/yr during 1997-99 (Moran and Halliwell, 2004). An interferometric synthetic aperture radar (InSAR) interferogram (change from July 3, 1999, to January 29, 2000) indicated that land surface near ACWD's managed aquifer recharge facilities and along Alameda Creek to the west is displaced upward as much as 0.8 in. (20 millimeters, mm) relative to areas northwest and southwest of the facilities. Land surface displacements related to rising groundwater levels in recharge areas has been demonstrated in other areas of California (Galloway and others, 1999; Lu and Danskin, 2001; Bawden and others, 2001). These displacements may be a cause for concern in urban areas or may indicate potential for permanent (inelastic) subsidence of aquifer deposits should groundwater pumping lower water levels beyond previous levels (Galloway and others, 1999). In addition to managed aquifer recharge projects operated by ACWD, the City of Hayward has constructed five deep water-supply wells in the aquifers underlying Hayward, Calif., to provide emergency water supply, and EBMUD has tested the feasibility of artificial storage and recovery (ASR) of water through deep wells near the shore of San Francisco Bay, just south from San Lorenzo Creek (fig. 1; Luhdorff and Scalmanini Consulting Engineers, 2003). The EBMUD's Bayside Groundwater Project (BGP) may ultimately include 7 to 10 production/injection wells completed 500-650 ft below land surface, with groundwater extraction rates between 1 to 3 million gallons per day per well. During wet periods, EBMUD planned to inject treated surface water from reservoirs in the Sierra Nevada at a rate of about 1 million gallons per day per well and store it for use during droughts or times of surface-water scarcity (California Regional Water Quality Control Board, 2007). Projects operated by agencies in the Niles Cone and East Bay Plain groundwater subbasins may compete for limited groundwater storage capacity during wet periods, and because the subbasins may be hydraulically connected, recharged water may be extracted by nonparticipating agencies during dry periods. Methods Data collection included measurement of groundwater levels in wells; InSAR data compilation; streamflow measurements; measurements of physical parameters from streamflow and natural discharge; water-quality sample collection from 21 wells, 1 surface water site, and 1 precipitation sampler; and collection of core material for mineralogical analysis. Groundwater-level data were collected in accordance with the protocols established by the "Groundwater Technical Procedures of the U.S. Geological Survey" (Cunningham and Schalk, 2011), which provides standardized technical procedures of many aspects of groundwater science, including site and measuring-point establishment and measurement of water levels (Wilde and others, 1999a, b). Water-quality data were collected in accordance with the protocols established by the USGS National Field Manual (Wilde and others, 1999a). The water-quality sampling protocols ensure that a representative sample is collected at each site and that the samples are collected and handled in a way that minimizes the potential for contamination of samples. Groundwater-Level Measurement Groundwater levels were measured by USGS and ACWD personnel in 21 wells perforated in the Deep aquifer and in 24 wells perforated in the upper aquifer system during the spring and fall of 2002. All sites and water-level data were entered into the USGS National Water Information System (NWIS) database and are available from http://waterdata. usgs.gov/nwis. Location, construction, and water-level data for wells measured as part of this study are provided in appendix 1.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins InSAR Data Processing InSAR imagery was processed and analyzed to measure the long-term surface displacement patterns and magnitudes within the Niles Cone and southern East Bay Plain groundwater subbasins. Shorter-term interferograms, maps of relative surface displacement constructed from InSAR data, were processed to assess if InSAR could be used to detect the effects of groundwater management strategies. The ACWD recharges groundwater through infiltration ponds and impoundments at Quarry Lakes Regional Park near Fremont, Calif. (fig. 1), near the apex of the Alameda Creek alluvial fan in the Niles Cone groundwater subbasin. The synthetic aperture radar (SAR) data (radar scenes) used to construct the interferograms are from the SAR instrument on the European Space Agency ERS-2 satellite. The ERS-2 satellite has a steep look-angle (about 23° from vertical), which provides data sensitive to vertical deformation of the land surface (uplift and subsidence). The interferograms were constructed by the two-pass method using a USGS 30-meter digital elevation model and both Diapason and GAMMA InSAR processing software packages (Centre National d'Etudes Spatiales, 1997; Werner and others, 2000). The images were processed using methods similar to those used by Stork and Sneed (2002). The resolution of a pixel in the interferograms is 323 square feet (ft2; 30 square meters). The interferogram measurements are range change (distance: positive, or uplift, and negative, or subsidence) in the radar line-of-sight, where one complete cycle of the color fringe (warm to cool) on the interferograms (the scale factor) is 1.1 in. (28.3 mm). Under ideal conditions, it is possible to resolve changes in elevation on the order of 0.2 to 0.4 in. (5 to 10 mm) at the scale of one pixel (Galloway and others, 2000). Because of the high frequency of seismic activity in the densely populated San Francisco Bay area, scientists and government agencies are interested in monitoring techniques that provide information that may elucidate processes responsible for seismic geohazards. Each satellite can scan the same area every 35 days. Data were collected from January 1992 to May 1996 for ERS1 and from September 1995 to 2003 for ERS2. Interpretation and construction of interferograms from ERS2 data after December 2002 were difficult owing to a gyroscope failure that caused the satellite to wobble at a level that limited interferogram generation. The two satellites are coordinated so that they can scan the same track and frame grid location at approximately the same local time, but with a temporal offset that varies by a number of days. Interferograms can be constructed from scenes from either or both satellites. Streamflow Gains and Losses Estimation To provide information needed to interpret results from groundwater-flow modeling by ACWD, the interaction between Alameda Creek and the adjacent aquifer was investigated by a reconnaissance-level survey of flow gains and losses along Alameda Creek in April 2002. Streamflow gains and losses were determined by a series of streamflow measurements between Rubber Dam No. 2 and the tidally affected stream reach downstream from USGS stream gage 11180700 (Alameda Creek at Union City, Calif.; fig. 3). To assess chemical differences between stream water loss and groundwater, water temperature, pH, and specific electrical conductance were measured using standard field instruments and techniques (Wilde, 1998) at streamflow measurement sites and at three groundwater seeps and springs where they emerged from the flood plain and levee base. A potentiometric surface map (fig. 3) was constructed from water levels measured in ACWD observation wells monitoring the upper aquifer system (appendix 1) to provide information on the direction of groundwater flow in shallow sediments adjacent to Alameda Creek. The precipitation record from a nearby National Oceanic and Atmospheric Administration climate station (Newark, CA US) shows no precipitation in the area for at least 7 days prior to the streamflow measurements recorded on April 24, 2002 (https://www.ncdc.noaa.gov/ cdo-web/datasets/GHCND/stations/GHCND:USC00046144/ detail), and gage height measured in USGS gage 11180700 (https://nwis.waterdata.usgs.gov/nwis/measurements/?site_ no=11180700&agency_cd=USGS&) remained consistent over the period of the survey (morning April 24, 2002, to midday April 25, 2002). The absence of precipitation and the consistency of the flow in Alameda Creek indicate that flows were stable in the studied reaches during the measurements and were therefore comparable between stations. Most streamflow measurements were made using velocity-area methods (Rantz and others, 1982) using a Price pygmy current meter with a top setting wading rod. One day prior to velocity-area measurements, uniform-flow measuring sections were constructed by removing large cobbles from the stream bed and focusing flow to a single channel (where feasible) between parallel banks built using sand bags and planks. Where velocities were less than 0.2 feet per second (ft/s) and stream depths were less than 0.3 ft, streamflow measurements were made with modified 3-in. Parshall flumes. Flumes were used to measure small inflows from two tributary streams and were installed several hours prior to use. Streamflow measurements were rated from excellent to poor, depending on measurement technique and flow conditions. Poor ratings imply greater uncertainty and corresponded to measurements made with Price pygmy meters where stream depth and velocity approached the limitations of the method, less than 2 in. and 0.1 ft/s, respectively. Generally, streamflow measuring conditions were unsuitable in areas where water ponded behind stream channel vegetation or where the stream channel braided. Where feasible, streamflow measurement sites were selected in areas where sediment and vegetation had been recently removed by the Alameda County Flood Control and Water Conservation District to improve conveyance of winter storm flows. In the absence of these maintenance activities in Alameda Creek, it is likely that streamflow measurement would have been infeasible in most of the measured reaches.

Methods    9

A a m e d a A a m e d a Old Old Alameda Alameda Creek Creek HAYWARD FAULT HAYWARD FAULT Quarry Lakes Regional Park re ek re ek D ry

r e e k D ry

r e e k Mowry well field Mowry well field RUBBER DAM NO. 2 RUBBER DAM NO. 1 Site 3 Site 2 Site 1 X' Y Y' Site 6 Site 5 Z Z' Site 8 373630122010501 14D7 14H3 12K11 13E3 13P4 14R3 24F11 23J2 26K6 ARP wells ARP wells 25D3 30E4 19N14 19E2 18R1 30A5 19J6 17M8 28D12 29A6 20R4 20H3 20J6 Site 9 Site 7 Site 4 Lago Los Osos 122°04' 122°02' 122°00' 37° 34' 37° 36' EXPLANATION Base modified from U.S. Geological Survey digital data, various scales Lambert Conformal Conic projection North American Datum of 1983 1 MILE 1 KILOMETER Site 1 Upper aquifer system monitoring well, identifier, and water level altitude in feet above vertical datum (NAVD 88) Lakes and impoundments used for artificial recharge of ground water Gaining reach of Alameda Creek Losing reach of Alameda Creek Non gaining or losing reach of Alameda Creek Tidally affected reach of Alameda Creek Water-level altitude contour, in feet, in the upper aquifer system. Datum is the North American Vertical Datum of 1988 (NAVD 88). Synoptic streamflow water-quality sampling site and USGS site identifier Streamflow measurement station and USGS site identifier Synoptic streamflow measurement station and station identifier 373630122010501 Municipal wells 18R1 Figure 3.  Water-level elevation contours and water-level elevations in wells screened in the upper aquifer system, gaining and losing reaches along Alameda Creek, Quarry Lakes Regional Park recharge area, Alameda Creek, and Alameda County Water District (ACWD) aquifer reclamation program (ARP) wells, Alameda County, California, April 2002.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Water Sample Collection and Analysis In this study, samples were evaluated for major ions, selected minor ions, selected trace elements, stable isotopes of water, and age-dating tracers to determine groundwater quality, the sources of high chloride water to wells, and the effects of managed aquifer recharge on groundwater of the Niles Cone and southern East Bay Plain groundwater subbasins. The spatial distribution of surface sources of industrial chemicals, such as volatile organic carbon compounds or trace elements, was not evaluated as part of this study. Most samples collected as part of this study were from monitoring or production wells. Samples from monitoring wells in the Deep aquifer provide information on groundwater chemistry within the part of the Deep aquifer in which the monitoring well is screened and not necessarily for all of the Deep aquifer. Samples from production wells are a mix of groundwater that entered the well throughout the entire screened interval. As a result, it may be difficult to interpret samples collected from production wells that are screened in more than one aquifer. Samples also were collected from shallow monitoring wells (not in the Deep aquifer) in Deep aquifer recharge areas near Alameda Creek, Dry Creek, and Quarry Lakes at the head of the Alameda Creek alluvial fan. Comparisons of samples from the Deep aquifer and samples from shallow monitoring wells in recharge areas provide information on changes in groundwater chemistry and recharge age with depth. Twenty-three water samples were collected from 21 wells, 1 surface water site, and 1 precipitation sampler in the study area during 2002 to 2003. Water-quality samples were collected following the USGS field procedures outlined in the "U.S. Geological Survey Field Manual for Collection of Water Quality Data" (Wilde, 1999a). Samples were collected from production and monitoring wells after three casing volumes were removed from the well and field parameters stabilized. Existing pumps were used to collect samples from production wells. Temporary, positive-displacement sample pumps were used to collect samples from monitoring wells. Temperature, specific conductance, and pH were monitored in water from domestic, production, and monitoring wells during purging prior to sample collection. Sample collection, preservation, and analytical methods are given in appendix 2 at the back of this report. The precipitation sample is a composite of samples collected near Quarry Lakes from November 8, 2002, to June 5, 2003, and the stable-isotopic data can be considered as average values for winter and spring rainfall. The field parameters temperature, specific conductance, pH, and alkalinity were measured at the time of sample collection using calibrated thermometers and portable meters. Meters were calibrated in the field prior to measurement. Dissolved oxygen also was measured in the field using the colorimetric indigo-carmine method just prior to sample collection. Water samples for analyses of major ions, nutrients, and selected trace elements were pressure-filtered in the field using capsule filters that had a pore size of 0.45 micrometer (µm). Samples for the laboratory analysis of pH and specific conductance were not filtered. Noble-gas samples were analyzed by the USGS Noble Gas Laboratory in Reston, Virginia, following the methods of Poreda and others (1988), Bayer and others (1989), Solomon and others (1992, 1996), and Beyerle and others (2000). Recharge temperatures and excess air concentrations were determined from dissolved Neon (Ne), Argon (Ar), Krypton (Kr), and Xenon (Xe) using methods described in AeschbachHertig and others (1999). Tritiogenic helium-3 (3Hetrit) was computed as described in Solomon and Cook (2000). Water samples for carbon isotopes and carbon-14 activities were analyzed by the University of Waterloo laboratory under contract with the USGS using mass spectroscopy and accelerator mass spectroscopy, respectively. Statistical analysis of constituents was done using Kruskal-Wallis rank sum tests [kruskal.test(x, g)] in the computer program R (R Development Core Team, 2008). The Kruskal-Wallis test is used when there is one nominal variable and one measurement variable, and it does not require assumptions about the specific shape of the probability distribution. Data are ranked based on their measurement value from smallest to largest before the test statistic is calculated. The loss of information due to substituting ranks for original data make the test less powerful; however, data do not need to be normally distributed as in an analysis of variance (ANOVA) test. Small P-values (less than 0.05) at a significance level of 95 percent show that differences in the distribution of data between two or more groups are not due to random sampling error only, but in fact that at least one group has a statistically significant difference in the distribution; conclusions about the differences in the distribution of data cannot be made with P-values of 0.05 or greater. Collection and Analysis of Core and Cuttings Material Mineralogic analyses were done on four samples collected by drilling and coring. Drill cuttings and core material were collected from well 14D3 and of a composite of coarse-grained outcrop material at Quarry Lakes recharge pond. The elemental composition of cores and cuttings was determined by inductively coupled plasma-mass spectrometry (ICP-MS; Briggs and Meier, 2002). The mineralogy of selected cores and cuttings was determined by X-ray diffraction (Amonette and Zelazny, 1994). Images of selected materials were obtained using a scanning electron microscope equipped with a spectral analyzer to determine the primary or secondary minerals that might participate in dissolutionprecipitation reactions as groundwater interacts with sediments in the aquifer system and to determine the uranium and thorium composition of aquifer materials (Amonette and Zelazny, 1994). Information about the collection and analysis, as well as results from the analysis, is provided in appendix 3.

Hydrogeology    11 Hydrogeology Data and various analyses were used to evaluate the effect of groundwater management practices on the aquifer systems and movement of water through the Deep aquifer, including between subbasins. This section of the report presents and discusses results for groundwater movement, vertical displacement of the land surface, and streamflow gains and losses in the recharge area near the apex of the Alameda Creek alluvial fan. Groundwater Movement Water-level contours indicate that groundwater generally flows from the eastern recharge areas at Quarry Lakes and Alameda Creek to the north and west (figs. 3 and 4). Closely spaced contours to the south in the Deep aquifer (fig. 4) are the result of pumping from the nearby Mowry well field and Aquifer Reclamation Program (ARP) wells. Water-level data from wells completed solely in the upper aquifer system to the north of Old Alameda Creek were unavailable because the deposits that compose the upper aquifer system in this area are finer-grained, yield less water to wells than deposits to the south, and therefore, are not ideal locations for wells. Measurements collected in 2002 show that the elevation of water levels in wells completed in the upper aquifer system (wells 4S/1W-17M7, -17M8; 4S/2W-12K9, -12K10, -12K11; 4S/2W-13P4, -13P6, -13P7; and 4S/2W-14D5, -14D6, -14D7) were as much as 20 ft higher than water levels in wells completed in the Deep aquifer (wells 4S/1W-17M6; 4S/2W12K8; 4S/2W-13P5, and 4S/2W-14D3, -14D4; appendix 1). Water levels in the Deep aquifer indicate groundwater flows to the west and north from Quarry Lakes (fig. 4). The groundwater flowpath B-B' follows this general northwest trend and was used for the purpose of geochemical modeling described later in this report (fig. 4). Water-level elevation in the Deep aquifer were below sea level in most of the area, as low as about -9 ft in well (3L1) in the southern East Bay Plain groundwater subbasin within the transition zone (table 1-1). Water-level contours indicate that flow of groundwater in the Deep aquifer in 2002 was from recharge areas near the head of the alluvial fan of Alameda Creek to the southern East Bay Plain groundwater subbasin. The effects of tides in San Francisco Bay on groundwater levels in the Deep aquifer were not considered in figure 4. The effects of tidal loading on groundwater levels in the southern East Bay Plain groundwater subbasin measured by Izbicki and others (2003) show water levels in the Deep aquifer can change by more than 1.5 ft in a 6-hour period. The velocity and volume of the flow within the Deep aquifer, being dependent on the hydraulic gradient, may have increased since ACWD's managed aquifer recharge activities raised groundwater levels near Quarry Lakes. Under predevelopment conditions, the quantity of groundwater flowing to the northwest may have been substantially less than under conditions in 2002. During the mid-1900s when pumping was greater and water-level elevation dropped in some places to more than 100 ft below sea level, the magnitude and the direction of groundwater flow in the Deep aquifer was likely substantially different than today, either moving with less velocity toward the northwest or, in parts of the study area, even moving west to east from San Francisco Bay (California Department of Water Resources, 1963). Local Short-Term Land-Surface Displacement Beginning in the winter-spring of 1995, in preparation for pond reconstruction, ACWD reduced water volume in the ponds at Quarry Lakes Regional Park and increased pumping at Aquifer Reclamation Program (ARP) wells, lowering water levels in wells in both the upper aquifer system and the Deep aquifer (fig. 5). From April 10, 1997, to July 29, 1997, ACWD dewatered the ponds by pumping about 7,700 acre-ft of pond water to Alameda Creek. After reconstruction, the ponds were filled to capacity with local runoff from the Alameda Creek watershed, and ARP well pumpage was reduced (fig. 5). Above-average rainfall during fall 1997 and winter 1998 contributed to the availability of water from Alameda Creek for groundwater recharge (fig. 5). Groundwater levels in wells in the shallow aquifer system and the Deep aquifer underlying the Niles Cone groundwater subbasin increased about 20 ft during summer 1997-winter 1998 (fig. 5). InSAR was used to monitor land-surface displacement caused by pumping and subsequent recharge to the aquifer system. Two independent interferograms span the period of the refilling of the ponds (fig. 6); both interferograms indicate that as much as 0.8 in. (21 mm) of uplift, relative to uplift occurring at the ponds, occurred during this period in the area west from the ponds. The July 17, 1997, to March 19, 1998, interferogram shows a broad uplift feature in distal (lower) parts of the Alameda Creek alluvial fan, west from the Quarry Lakes infiltration ponds. Maximum relative uplift is about 0.8 in. (21 mm). The localized area of maximum uplift to the west of Quarry Lakes may reflect the lithology of the alluvial fan of Alameda Creek. Relative uplift was greater in distal parts of the alluvial fan west of the ponds where finergrained (clayey) deposits, which are more compressible and expandable than sand-and-gravel layers, compose a greater proportion of the sediments. Relative uplift was less (about 0.4 in. [10 mm]) in the fan near the ponds, which is composed of coarser-grained sediments. Increased hydraulic head from rising groundwater levels caused by pond refilling would be expected to translate rapidly through permeable coarse-grained parts of the aquifer system and then diffuse vertically into finer-grained, expandable deposits and clayey layers.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins B Hayward Hayward Fremont Fremont Alameda Alameda Creek Creek Creek Creek Dry Dry A a m e d a A a m e d a Old Old Quarry Lakes Regional Park r e e k r e e k San Francisco Bay Mowry well field Mowry well field B' HAYWARD FAULT MISSION FAULT MILES 2 KILOMETERS Background image is the intellectual property of Esri and is used herein under license. Copyright © 2014 Esri and its licensors. All rights reserved. Base modified from U.S. Geological Survey digital data, various scales; Lambert Conformal Conic projection; North American Datum of 1983 37°38' 37°36' 37°34' EXPLANATION B B' Water-level altitude contours in feet above the North American Vertical Datum of 1988 (NAVD 88) Deep aquifer monitoring well, identifier, and water-level altitude in feet above NAVD 88 Municipal wells Transition zone (Luhdorff and Scalmanini Consulting Engineers, 2003) Tidally influenced wetlands Faults Flowpath for geochemical analyses 37°32' DIABLO RANGE ARP wells ARP wells 122°02' 122°04' 122°06' 122°08' 122°10 122°00' 32D2 −5.7 4R1 −2.4 10E4 −1.4 35J11 −4.5 −9.1 −1.4 14D4 −1.5 12K8 −0.9 7P4 −0.1 17M6 13P5 26K4 25D1 30E3 −0.2 30A2 −0.4 28D1 −1.3 30E3 −0.2 Figure 4.  Water-level elevation contours and water-level elevations in wells screened in the Deep aquifer; Quarry Lakes Regional Park recharge area; Alameda Creek; and Alameda County Water District (ACWD) Aquifer Reclamation Program (ARP) wells, Niles Cone groundwater subbasin, Alameda County, California, 2002.

Hydrogeology    13 Deep aquifer well upper aquifer system well San Francisco International Airport (SFO WSP AP) Quarry Lakes (Lago Los Osos) Aquifer Reclamation Program (ARP) wells 4S/2W-12C1 4S/2W-13R7 January January January January January 2,500 2,000 1,500 1,000 Volume pumped, in acre feet per month Depth below land surface, in feet Depth below land surface, in feet −5 −10 Water surface elevation, in feet above mean sea level Precipitation, in inches per month Figure 5.  Precipitation at San Francisco International Airport, water-level elevation at infiltration pond Lago Los Osos, total pumpage from Alameda County Water District's Aquifer Reclamation Program (ARP) wells, and groundwater elevations in selected wells north from Alameda Creek in the Niles Cone groundwater subbasin, Alameda County, California. The highlighted areas mark the (green) period for the interferogram shown in figure 6A (July 17, 1997, to March 19, 1998) and (blue) period for the interferogram shown in figure 6B (September 6, 1997, to May 9, 1998).

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Water bodies ! ! ! ! ! ! ! B September 6, 1997, to May 9, 1998 A July 17,1997, to March 19, 1998 2 MILES 2 KILOMETERS 4S/2W-12C001 4S/2W-12C001 4S/2W-13R007 4S/2W-13R007 4S/2W-12C001 4S/2W-12C001 4S/2W-13R007 4S/2W-13R007 ~0.7 in. relative uplift ~0.7 in. relative uplift ~1.1 in. relative uplift ~1.1 in. relative uplift ~0.4 in. relative uplift ~0.4 in. relative uplift ~0.8 in. relative uplift ~0.8 in. relative uplift −122°03' −122°01' −121°59' −121°57' −121°55' −122°03' −122°01' −121°59' −121°57' −121°55' 37°37' 37°36' 37°35' 37°34' 37°33' 37°32' 37°31' 37°30' 37°37' 37°36' 37°35' 37°34' 37°33' 37°32' 37°31' 37°30' 1.1 in. (28 mm) 0.8 in. (21 mm) −0.7 in. (−17 mm) −1.1 in. (−28 mm) Relative Subsidence Uplift EXPLANATION Quarry Lakes Regional Park Quarry Lakes Regional Park Figure 6.  InSAR interferogram displaying relative subsidence or uplift in the Niles Cone groundwater subbasin during refilling of infiltration ponds at Quarry Lakes Regional Park, Alameda County, California. A, July 17, 1997, to March 19, 1998; B, September 6, 1997, to May 9, 1998. [Abbreviations: in., inch; mm, millimeter; about].

Hydrogeology    15 Similar relative uplift south of Quarry Lakes is indicated on the September 6, 1997, to May 9, 1998, interferogram; however, a region of relative subsidence is indicated southwest (band of dark blue between Quarry Lakes and the region of uplift) from Quarry Lakes (fig. 6B). The uplift feature on this interferogram is likely a continuation of the uplift seen on the previous interferogram that has increased in magnitude from March (the end date of the first interferogram, fig. 6A) to May (the end date of the second interferogram, fig. 6B) as the hydrostatic pressure from recharging water continued to propagate from the ponds. The subsidence feature is likely due to pumping of groundwater wells in the area, as the interferogram extends into May, which is within the beginning of the pumping season. Incoherent areas (areas of indiscernible color on figures 6A and 6B) in the western parts of the interferogram limit interpretation of the data in this area. The magnitude of relative uplift west from the recharge ponds is reasonable for elastic expansion of sedimentary materials experiencing an increase in hydraulic head similar to that resulting from pond refilling. Calculated expansion for 600 ft of unconsolidated sediment after a 20-ft increase of hydraulic head ranges from 0.3 to 1.1 in. (7 to 29 mm) for aquifer-system specific storage values ranging from 2 × 10-6 ft-1 to 8 × 10-6 ft-1, respectively (Francis Riley, USGS emeritus, written commun., 2004). Uncertainties regarding the mechanical properties and thickness of sedimentary deposits of the aquifer system preclude estimating a narrower range of likely uplift and complicate the assessment of differences in range change indicated on the interferograms. Elastic compaction of the aquifer system that occurred when ACWD lowered groundwater levels by about 20 ft in the Niles Cone groundwater subbasin prior to construction at the infiltration ponds (winter 1995-fall 1997) could have produced land subsidence of a magnitude similar to expansion of the aquifer indicated on the interferogram (fig. 6); unfortunately, compatible data bracketing the period of water-level decline are unavailable. Streamflow Gains and Losses in Alameda Creek Gaining and losing sections of Alameda Creek (fig. 3) were determined using streamflow measurements (fig. 7), along with comparisons of stream channel bathymetry with water levels from adjacent wells (fig. 8). Streamflow data are presented in appendix 4. The reach between site 1 and site 5 is generally a losing reach, and streamflow along this reach decreases with increasing distance downstream. The water level measured in well 4S/2W-19J6, located southwest of the channel just downstream from site 3, is lower in elevation than the thalweg of the channel (fig. 8A). Water from this reach likely recharges the upper aquifer system and the Deep aquifer because of the hydraulic connection between the two near Quarry Lakes. The reach from site 6 to just downstream of site 9 is gaining where the mound caused by groundwater recharge at Quarry Lakes intersects the stream, and streamflow along this reach increases with increasing distance downstream. Comparisons of two channel cross sections along the reach, between site 6 and site 9, with adjacent wells, one north of the channel (4S/2W-14H3) and one south of the channel (4S/2W-13E3; fig. 8B), show that water levels in the wells are higher in elevation than the thalweg of the channel. Additional groundwater discharge, in the form of seeps and springs, were present along this reach. Streamflow was measured during a low-flow period, and stream stage data from nearby gage 11180700 suggest that during high winter flows the reach between site 6 and site 9 may be losing. The seepage run results suggest that during the summer low-flow period, Alameda Creek gains about 3.5 cubic feet per second (cfs) between sites 6 and 9. This equates to about 1,270 acre-ft/yr, or about 4 percent of the 30,000 acre-ft/yr estimated to be infiltrated ("Groundwater Management" section), about 5 percent of local groundwater pumping of 24,000 acre-ft/yr, and about 13 percent of pumping at the ARP wells of 10,000 acre-ft/yr. The water temperature in Alameda Creek was measured at each stream gaging site (fig. 7) and ranged from 19 °C at site 1 to 23 °C at site 5 and averaged 21.3 °C. Water temperature in Alameda Creek was greater than the historical average summer temperature of the area, 18 °C, and was generally warmest downstream from Quarry Lakes. Temperature decreased in the downstream (between sites 6 and 9) gaining reaches of Alameda Creek as a result of groundwater discharge.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Streamflow, in cubic feet per second Water temperature, in degrees centigrade A. April 24, 2002, morning B. April 24, 2002, afternoon C. April 25, 2002, midday D. April 25, 2002, midday Distance, in miles downstream from site 1 at Rubber Dam No. 2 Streamflow, in cubic feet per second Streamflow, in cubic feet per second Figure 7.  Streamflow and water-temperature measurements along Alameda Creek, April 24-25, 2002, Alameda County, California.

Hydrogeology    17

Water-level altitude, in feet above sea level Thalweg altitude 7.7 feet April May X' South North South North South North A B Altitude, in feet above mean sea level Altitude, in feet above mean sea level Altitude, in feet above mean sea level −100 −200 Distance, in feet from flood channel centerline Distance, in feet from flood channel centerline −100 −200 Distance, in feet from flood channel centerline −200 −100 Land surface altitude from topographic survey by Alameda County Flood Control and Water Conservation District, written commun., 2002 Water level May 1, 2002, 19.45 feet above mean sea level Depth 125 feet Perforated interval -27.6 to -94.6 feet above mean sea level Perforated interval −37.1 to −92.1 feet above mean sea level Depth 125 feet Perforated interval unknown 4S/2W-19J6 Approximate altitude determined from U.S. Geological Survey (USGS) 7.5-minute topographic map Thalweg altitude 21.7 feet Land surface altitude from topographic survey by Alameda County Flood Control and Water Conservation District, written commun., 2002 Land surface altitude from topographic survey by Alameda County Flood Control and Water Conservation District, written commun., 2002 Approximate altitude determind from USGS 7.5-minute topographic map Approximate altitude determind from USGS 7.5-minute topographic map Y Y' Z' Z Thalweg altitude 9.9 feet 4S/1W-13E3 4S/1W-13E3 Water level May 2, 2002, 14.6 feet above mean sea level 4S/2W-14H3 Figure 8.  Cross-sectional bathymetry of Alameda Creek. A, along section X-X' with water-level elevation in adjacent well 4S/2W-19J6; B, along section Y-Y' with water-level elevation in adjacent well 4S/1W-13E3; and C, along section Z-Z' with water-level elevation in adjacent well 4S/2W-14H3, Alameda County, California.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Geochemistry This section begins with results and discussion of the groundwater chemistry in general and then continues with additional geochemical insights provided by analyses of ionic composition, a mixing model for a diagnostic ionic ratio, and analyses of noble gases, tritium, and other isotopes of water and dissolved carbon. Chemistry of Groundwater Chemistry of water in aquifers underlying the Niles Cone and southern East Bay Plain groundwater subbasins is influenced by the chemistry of the natural and managed aquifer recharge water and the geochemical reactions that occur within the aquifer system. Also, intruding seawater, mixing with water from surrounding and underlying deposits, or mixing with water from estuarine deposits near San Francisco Bay, may alter groundwater chemistry, increase chloride concentrations, and degrade the quality of groundwater. Flow from shallow aquifers into deeper aquifers occurs naturally along the eastern boundary of the study area, along the Hayward Fault, and also through the failed and leaking casings of abandoned wells (San Francisco Bay Regional Water Quality Control Board, 1999). Waterlevel elevation data are consistent with recharge from the Quarry Lakes Regional Park infiltration ponds reaching the upper aquifer system and the Deep aquifer in the immediate vicinity. Seawater intrusion in aquifers underlying the Niles Cone and southern East Bay Plain groundwater subbasins has been a problem since the late 1800s and was extensively studied in the early 1960s by the California Department of Water Resources (1960, 1963). Results of chemical analysis of 23 samples from 15 deep wells, 6 shallow wells, 1 stream, and 1 precipitation station collected by the USGS are given in appendix 5 at the back of this report. In addition, water chemistry results from a depth-dependent sample taken at 910 ft from 2S/3W-19Q3 (Izbicki and others, 2003) in the East Bay Plain groundwater subbasin are displayed in figures along with results from this study representing water from deep, consolidated sediments (connate water) adjacent to San Francisco Bay. Physical Properties and Chemical Characteristics of Groundwater The physical properties and the chemical characteristics of water from wells perforated in the upper aquifer system are different from those of water from wells perforated in the Deep aquifer (fig. 9). Infiltration of recharge water at Quarry Lakes has influenced the chemistry of water in nearby wells. In addition, water-chemistry data suggest that groundwater from wells may have been affected by seawater intrusion or mixing with poor-quality, high-chloride water from finegrained estuarine deposits near San Francisco Bay. The field pH of water sampled from the upper aquifer system and the Deep aquifer ranged from 6.9 to 7.2 and 7.2 to 8.6, with median pH of 7.1 and 7.5, respectively. The highest pH was in water from monitoring well 4S/2W14D3 completed in the Deep aquifer 400 to 450 ft below land surface. The pH of groundwater from the Deep aquifer was significantly higher than the pH of groundwater from the upper aquifer system (P-value 0.0007). In siliciclastic aquifers, groundwater pH increase from slightly acidic to neutral pH near recharge sources to more alkaline values with depth and distance along the groundwater flowpath as a result of primary mineral dissolution (feldspars and micas; Izbicki and others, 1992, 2003). Dissolved solids (as measured by residue on evaporation) of water sampled from wells in the upper aquifer system and Deep aquifer ranged from 420 to 880 milligrams per liter (mg/L) and 350 to 1,080 mg/L, with median concentrations of 590 and 480 mg/L, respectively. Higher dissolved solids in groundwater from the Deep aquifer were generally associated with higher chloride concentrations. Two monitoring wells in the Deep aquifer, 4S2W-15L5 and 4S/2W-13P5, had dissolved solids concentrations of 880 and 1,080 mg/L, respectively, and chloride concentrations of 346 and 315 mg/L, respectively. These wells represent water that has mixed with high-salinity water intruded from San Francisco Bay and has dissolved solids and chloride values that are not representative of the aquifer systems; to avoid skewing the data, they were excluded from analyses of dissolved solids and chloride data. Excluding wells impacted by high-chloride water (>250 mg/L), the median dissolved-solids concentration was significantly higher in water from wells in the upper aquifer system (fig. 9) than in water from wells in the Deep aquifer (P-value 0.0085). Higher dissolved solids concentrations in some of the upper-aquifer-system wells may reflect changes in recharge water chemistry as the Alameda Creek watershed has become more urbanized in recent years, increasing anthropogenic effects on water chemistry. Alternatively, the lower dissolved-solids concentrations in the Deep aquifer could be the result of geochemical reactions that remove constituents from groundwater, such as sulfate through sulfate reduction under reduced conditions, or calcium and sodium through cation exchange (fig. 10), as will be discussed in the "Major-Ion Composition" section below.

Geochemistry    19 Standard units pH Upper aquifer system Deep aquifer Upper aquifer system Deep aquifer Dissolved oxygen Milligrams per liter Dissolved solids Upper aquifer system Deep aquifer Milligrams per liter Upper aquifer system Deep aquifer Milligrams per liter 500 Calcium Upper aquifer system Deep aquifer Milligrams per liter Sodium Upper aquifer system Deep aquifer Milligrams per liter, as nitrogen 10 Nitrate Upper aquifer system Deep aquifer Milligrams per liter Chloride Upper aquifer system Deep aquifer Milligrams per liter, as calcium carbonate (CaCO3) Alkalinity Upper aquifer system Deep aquifer Milligrams per liter Sulfate Upper aquifer system Deep aquifer Micrograms per liter Iron Upper aquifer system Deep aquifer Micrograms per liter Manganese 1,000 1,200 EXPLANATION 95th percentile Number of samples 75th percentile 50th percentile (median) 25th percentile 5th percentile Differences in values between the Upper aquifer system and the Deep aquifer are significantly different based on the Kruskal-Wallis rank sum tests. α=0.05 Figure 9.  pH, dissolved oxygen, and selected major-ion, nutrient, and trace-element concentrations in water from wells sampled in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins

Upper aquifer system wells Deep aquifer wells Well 19Q3 (Izbicki and others, 2003) 19Q3 EXPLANATION 13P6 13P6 1 Wells near recharge areas along mountain front 2 Increasing chloride concentrations and cation exchange— Wells affected by seawater intrusion and mixing with highchloride water from fine-grained deposits 3 Calcite precipitation and cation exchange—Deep wells and wells at the downgradient end of long flow paths Calcium Magnesium Sodium plus potassium

Sulfate Chloride, fluoride, nitrite plus nitrate Carbonate plus bicarbonate Sulfate plus chloride Calcium plus magnesium PERCENT PERCENT PERCENT 19Q3 19Q3 13P6 13P6 17M8 17M8 13P7 13P7 13P4 13P4 17M7 17M7 12K10 12K10 13P5 13P5 17M6 17M6 10E4 10E4 14D4 14D4 14D3 14D3 4E1 4E1 4E1 4E1 4R1 4R1 4F3 4F3 2H1 2H1 12K8 12K8 Figure 10.  Major-ion composition of samples from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Geochemistry    21 Water from wells sampled in the upper aquifer system was both oxic (>0.30 mg/L) and suboxic (<0.30 mg/L; Tiedje, 1988), with dissolved oxygen concentrations ranging from 2.9 to 0.2 mg/L, whereas water from wells in the Deep aquifer was generally reduced, with dissolved oxygen concentrations no greater than 1 mg/L. The dissolved oxygen concentrations of water from sampled wells in the Deep aquifer were significantly less than the concentrations in water from wells in the upper aquifer system (P-value 0.0025). Differences in oxidation-reduction (redox) conditions between the upper aquifer system and the Deep aquifer may explain significantly lower concentrations of nitrate (P-value 0.0124) and higher concentrations of manganese (P-value 0.0005) and iron (P-value 0.0325) in water from wells in the Deep aquifer compared to the upper aquifer system. Although no wells exceeded the EPA drinking water maximum contaminant level (MCL) for nitrate of 10 mg/L as nitrogen, two wells completed in the upper aquifer system near recharge areas at Quarry Lakes and along Alameda Creek, 4S/2W-12K10 and 4S/2W-13P7, had nitrate concentrations of 8.1 and 9.5 mg/L as nitrogen, respectively. Similar to dissolved solids, higher nitrate concentrations in water from these wells also could result from changing land use and increased urbanization in the Alameda Creek watershed; specific sources may include agricultural or residential fertilizer use and septic discharges. Major-Ion Composition The major-ion composition of water from sampled wells was evaluated using a Piper (trilinear) diagram. A Piper diagram (Piper, 1944) shows the relative contribution of major cations and anions, on a charge-equivalent basis, to the total ionic content of the water. Percentage scales along the sides of the diagram indicate the relative concentration, in milliequivalents per liter, of each major ion. Cations are shown in the left triangle and anions are shown in the right triangle; the central diamond integrates the data. Water from upper-aquifer-system wells located near Quarry Lakes, 4S/2W-13P4, 13P6, 13P7; 4S/1W-17M7-8; and 4S/2W-12K10, has a major-ion composition marked by higher calcium and magnesium percentages than water from most wells in the Deep aquifer (fig. 10). These wells are possibly influenced by water recharged at Quarry Lakes, as well as water from the ponded areas behind the inflatable dams in Alameda Creek. Most water from wells in the Deep aquifer plot below data from the upper aquifer system on figure 10, because of an increase in sodium relative to calcium plus magnesium and an increase in bicarbonate as water flows through the aquifer. In coastal aquifers in California, including the East Bay Plain groundwater subbasin, similar trends have been attributed to precipitation of calcite and (or) exchange of calcium and magnesium for sodium on clay within aquifer deposits and dissolution of carbonate minerals, respectively (Izbicki and others, 1992, 2003). Water from wells 13P5, 17M6, and 4S/2W-10E4 in the Deep aquifer has elevated chloride concentrations and plots along a line above and to the right of data from the upper aquifer system in figure 10. This pattern is characteristic of groundwater intruded by seawater (Piper and Garrett, 1953; Izbicki, 1996; Izbicki and others, 2003) and is the result of the exchange of sodium for calcium and magnesium on clay in aquifer deposits. Similar patterns have been observed in the East Bay Plain groundwater subbasin (Muir, 1997; Izbicki and others, 2003). Water from well 4S/2W-15L5 has major-ion proportions similar to well 2S/3W-19Q3, which yields water from partly consolidated sediments underlying freshwater aquifers of the East Bay Plain groundwater subbasin (Izbicki and others, 2003), suggesting the source of high-chloride water to well 15L5 is likely from partly-consolidated marine rock. Chloride-to-Iodide Ratios Use of certain minor ions and trace elements to determine the source of high-chloride water to wells in the Long Beach and Santa Ana areas of southern California was demonstrated by Piper and Garrett (1953). Other studies have applied these techniques to the study of the source and movement of seawater and other brines in aquifers (Jones and Garbarino, 1999; Izbicki, 1996; Izbicki and others, 2003), and increasingly refined approaches have been developed to distinguish mixtures of native (fresh) water and seawater from mixtures of native water and high-chloride water from underlying partly consolidated rock in coastal California aquifer systems (Izbicki, 1991; Izbicki, 1996). In this report, chloride-to-iodide ratios were used to determine the source of high-chloride water to wells and to evaluate the geochemical evolution of water as it flows through unconsolidated deposits underlying the Niles Cone and southern East Bay Plain groundwater subbasins (fig. 11). Chloride is highly soluble and not readily sorbed on mineral surfaces or organic material. In addition, with the exception of evaporite salts, chloride does not occur at high concentrations in most rock-forming minerals or aquifer materials (Feth, 1981; Davis and others, 1998). Iodide is affected by biological and redox processes and is reactive in groundwater systems. Iodide concentrations in seawater are low, about 0.06 mg/L; however, iodide concentrations in marine rocks and unconsolidated material deposited in marine environments are elevated relative to seawater and nonmarine materials owing to concentration of iodide from seawater by nearshore marine vegetation (Hem, 1985). Previously reported iodide concentrations in high-chloride water from marine rocks that surround and underlie coastal aquifers in California are as high as 2.4 mg/L (Izbicki and others, 2003). Iodide concentrations in highly concentrated brines from some deep wells can be as high as 46 mg/L (Hem, 1985). Ratios are especially sensitive to mixing, and the addition of a small volume of water having different chloride and trace-element compositions may produce a large change in the trace-element-to-chloride ratio of water from a well.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Iodide concentrations in water from wells underlying the Niles Cone and southern East Bay Plain groundwater subbasins ranged from 0.002 to 0.632 mg/L. Chloride-toiodide ratios in wells in the upper aquifer system ranged from 7,600 to 135,000 (fig. 11). For waters having chloride concentrations below 250 mg/L (about 8 millimoles per liter; fig. 11), higher chloride-to-iodide ratios are typical in water from alluvium eroded from granitic terrain and from Franciscan rocks (Izbicki, 1991; Izbicki, 1996). The chlorideto-iodide ratios for water from wells 4S/1W-17M8 and 4S/2W13P4, the uppermost wells near Quarry Lakes, are lower than those of the three other upper-aquifer-system wells in the area with data (fig. 11). These ratios are probably representative of the water recharged at Quarry Lakes, owing to the close proximity to Quarry Lakes and shallow screens of the wells. Other upper-aquifer-system wells near the recharge area plot along a line representative of mixing of recharge through local rivers and streams, represented by a Dry Creek sample, and seawater (Hem, 1985). Water from most wells screened in the Deep aquifer has a chloride-to-iodide ratio around 1,000, typical of alluvial deposits weathered from marine rocks and water from partly consolidated marine rock (Piper and Garrett, 1953; Izbicki, 1991; Land and others, 2002). The chloride-to-iodide ratio is greatest in Deep aquifer well 13P5, with a value of 560,000, and plots slightly above the seawater mixing line (fig. 11). Dry Creek Brine (Hem, 1985) Seawater (Hem, 1985) 250 mg/L 1,000 10,000 100,000 1,000 10,000 100,000 1,000,000 10,000,000 1,000 10,000 Chloride to iodide molar ratio Chloride concentration, millimoles per liter EXPLANATION Upper aquifer system Deep aquifer Well sampled by Izbicki and others, 2003 Surface water Seawater Average composition of brines from partly consolidated rocks defined by Hem, 1985 Seawater mixing lines Brine mixing line Chloride concentration, in milligrams per liter 13P7 13P7 13P4 13P4 17M8 17M8 17M8 17M8 13P5 13P5 19Q3 19Q3 12K8 12K8 19Q3 19Q3 Figure 11.  Chloride-to-iodide ratios as a function of chloride concentration in water from wells, Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Geochemistry    23 Water in this well is likely influenced by past seawater intrusion. The highest iodide concentration (0.632 mg/L) was in the water collected from well 4S/2W-15L5. The chlorideto-iodide ratio in this well plots to the right of water from most wells in the Deep aquifer and could be a three-component mixture of brine, seawater, and native Deep aquifer water. The water in well 15L5 has the most similarity in composition to high-chloride brines from partly consolidated deposits that surround and underlie coastal aquifers in California (Izbicki, 1996; Izbicki and others, 2003). Consistent with major-ion data and data from well 19Q3, water from partly consolidated marine rock may be the primary source for elevated iodide in well 4S/2W-15L5. Geochemical Indicators of Groundwater Movement The major-ion and chloride-to-iodide data suggest that recently recharged water is the primary source of groundwater to wells in the upper aquifer system. Water recharged at Quarry Lakes primarily affects the uppermost and adjacent wells. Sources of recharge to other upper aquifer system wells include recharge through local rivers and streams. Majorion composition changes caused by interactions with aquifer material as groundwater moves away from recharge sources, and laterally through the Deep aquifer, are evident in data for wells in the northern part of the Niles Cone groundwater subbasin. The major-ion and chloride-to-iodide data for water from Deep aquifer wells adjacent to Quarry Lakes is characteristic of groundwater intruded by seawater, indicating that water recharged at Quarry Lakes is not a major source of recharge to the Deep aquifer. The major-ion and chlorideto-iodide data for water from well 4S/2W-15L5 is similar to groundwater mixing with water from partly consolidated sediments underlying freshwater aquifers of the East Bay Plain groundwater subbasin, suggesting that water from partly consolidated marine rock may be an important source of chloride in the western part of the Niles Cone groundwater subbasin. Noble-Gas and Tritium Analysis Dissolved noble gases measured as part of this study include helium (He), neon (Ne), argon (Ar), and krypton (Kr). The inert nature of these gases, coupled with their differences in solubility at different temperatures, makes them useful for studying groundwater chronology, paleoclimatology, and mechanisms of groundwater recharge. The solubility of the noble gases in groundwater can be estimated by Henry's law, as a function of the temperature and salinity of the water, and the atmospheric partial pressure of the gas (Ozima and Podosek, 1983). The total concentration of a gas in a sample is the sum of the equilibrium concentration and the excess air, radiogenic, and terrigenic components. Three models are commonly used to interpret dissolved gas concentrations in groundwater: (1) unfractionated air (UA) model (Heaton and Vogel, 1981), (2) partial reequilibration (PR) model (Stute and others, 1995), and (3) closed system equilibrium (CE) model (Aeschbach-Hertig and others, 2000). The UA model assumes the excess air component is atmospheric air resulting from complete dissolution of entrapped air bubbles. The PR model assumes elemental fractionation in the excess air component (lighter gases depleted relative to heavier gases) resulting from complete bubble dissolution followed by diffusive degassing. The CE model assumes that fractionation of excess air results from incomplete dissolution of entrapped air bubbles, and the fractionation factor is related to the individual gas solubilities. Neon oversaturation (positive ΔNe) has been used as a proxy for excess air and contamination during sample collection (Kipfer and others, 2002). Since Ne is not produced in the subsurface, any Ne in excess of that expected from solubility equilibrium is attributed to excess-air entrainment during recharge (ΔNe% [(Nemeasured/Neeq.) -1] 100) (Mazor, 1972). Large quantities of excess air reflect rapid recharge from focused recharge during floods (or managed aquifer recharge), resulting in the dissolution of trapped air bubbles by increased water pressure. Dissolution and reequilibration processes were evaluated using the program NOBLEGAS (Aeschbach-Hertig and others, 1999) and determined not to effect excess-air concentrations in groundwater samples from the study area. An iterative subtraction approach was used to calculate the amount of excess air in a sample and estimate groundwater temperature at the time of recharge (Stute, 1989; Stute and others, 1995). This approach uses temperature as the fit target and varies the parameter values for excess air and reequilibration, while keeping the values for salinity and atmospheric pressure constant, such that the spread of the temperatures calculated for each noble gas is minimized. The measured noble gas concentrations are corrected for excess air, and a temperature is calculated using the corrected noble gas concentration. This process is repeated until agreement between the temperatures for each gas reach a desired agreement. In this study, groundwater recharge temperatures (NGT) were estimated from neon, argon, and krypton concentrations in groundwater. Helium was not used to calculate NGT because the measured He concentrations are significantly in excess of anticipated air-equilibration values. The magnitude of the excess air component and NGT can be used as a proxy for relative infiltration conditions, as periods of recharge may be seasonal, and periods of greater recharge may result in the entrainment of larger amounts of excess air in groundwater (Heaton and Vogel, 1981; Heaton and others, 1986; Kulongoski and others, 2003). For the purpose of this study, groundwater NGT cooler than about 11 oC and excess-air concentrations greater than 10 cubic centimeters per kilogram (cm3/kg) are interpreted to be consistent with focused recharge from winter stormflows that infiltrated rapidly through the unsaturated zone (entrapping air). In contrast, groundwater NGT warmer than 11 °C and excess-air concentrations lower than 10 cm3/kg are consistent with recharge from sustained streamflows along losing stream reaches downstream from the mountain front, with areal recharge from precipitation, or irrigation return flows that infiltrated slowly through the unsaturated zone prior to recharge (Stute and Schlosser, 2000).

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins The noble gas concentrations measured in groundwater from the Niles Cone and southern East Bay Plain groundwater subbasins are presented in appendix 6, along with salinity, ΔNe, the calculated NGTs, helium-4 ages, tritium, and tritium/3He ages. The observed excess-air component, ΔNe, ranges from 22.2 to 126.1 percent (appendix 6). The median ΔNe values for the upper aquifer system and the Deep aquifer were 94.9 and 56.6 percent, respectively. Although the medians suggest that the excess air component is greater in the upper aquifer system than in the Deep aquifer, this difference was not significant (P-value 0.06). Values of NGTs in both the upper aquifer system and Deep aquifer range from near the average winter temperature of 11 °C to slightly greater than the average summer temperature of 18 °C. The median NGT of 15.4 °C was close to the average annual temperature of the area of 15 °C. Calculated NGTs derived from samples from wells in the upper aquifer system ranged from 10.6 ± 0.7 to 19.2 ± 0.8 °C (fig. 12 and appendix 6). Calculated NGTs derived from samples from wells in the Deep aquifer ranged from 10.1 ± 0.7 to 18.1 ± 0.8 °C. Differences in excess air values and NGTs in upper aquifer system wells and Deep aquifer wells in the southeastern part of the study area suggest that recharge processes were different before the introduction of managed aquifer recharge. Presently, the Deep aquifer wells near Quarry Lakes are recharged from the shallow aquifer; therefore, similar excess air and NGT values for the upper aquifer system and the Deep aquifer would be expected following propagation of managed aquifer recharge through the entire aquifer system. However, the range in NGTs was greatest in the upper aquifer system and the Deep aquifer wells near recharge areas adjacent to Quarry Lakes and along Alameda Creek. Historically, recharge may have occurred during seasonal flow in Alameda and Dry Creeks. Well 17M6, and also wells 12C1 and 2H1, has a slightly cooler NGT, and lower excess air value, than upper aquifer system well 17M7 and likely represents water that was recharged during sustained winter streamflow in Dry Creek. Well 13P5 has a slightly warmer NGT, and lower excess air value, than upperaquifer-system well 13P7 and likely represents water that was recharged during summer streamflows in Alameda Creek. The data also suggest that water in wells 15L5 and 4R1 may have been recharged from a source similar to that of well 13P5. The relative increase in excess air from the Deep aquifer wells 13P5 and 17M6 to their respective upper aquifer system wells 13P6 and 13P7, and 17M7 (fig. 12), is likely a result of rapid fluctuation of the water table, and resulting bubble entrapment and dissolution, possibly associated with managed aquifer recharge or rapid groundwater recharge along the mountain front. The shallowest wells near the recharge areas (17M8 and 13P4) have excess-air values less than the deeper wells in the area, suggesting that these wells may receive water that is diffusely recharged from precipitation or as water lost to the unsaturated zone surrounding the areas of managed aquifer recharge. Average winter air temperature 11 °C Average summer air temperature 18 °C Argon, in cubic centimeters per kilogram water Neon, in micro-cubic centimeters per kilogram water 13P4 13P4 Upper aquifer system wells Deep aquifer wells EXPLANATION 14D3 12K8 17M8 4E1 4F3 17M6 2H1 10E4 13P5 4E1 13P4 13P7 13P6 4R1 17M7 Excess air, in cubic centimeters per kilogram Water-air equilibrium line Recharge temperature, in degrees Celsius Figure 12.  Selected noble-gas concentrations in water from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Geochemistry    25 The excess-air values and NGTs for wells in the transition zone and the southern East Bay Plain groundwater subbasin suggest areal recharge from precipitation. Most of the wells in the transition zone (10E4, 3L1, 4F3, and 4E1) have excessair values less than those of wells near Dry Creek and NGTs near the average annual temperature of 15 °C. Wells located north of the transition zone, in the southern East Bay Plain groundwater subbasin (29L6 and 20L20), have low excessair values and NGTs near the average annual temperature of 15 °C. The NGTs for wells 29L6 and 20L20 were warmer than those estimated for groundwater recharged from San Lorenzo and San Leandro Creeks in the southern East Bay Plain groundwater subbasin to the north of the study area (Izbicki and others, 2003), suggesting that recharge in the area south of San Lorenzo Creek is from areal recharge from precipitation. Tritium and Helium Tritium (3H) was used to indicate the presence of recent (post-1950s) water. Tritium is a naturally occurring radioactive isotope of hydrogen that has a half-life of 12.43 years. In this study, tritium concentrations are reported in tritium units (TU); 1 tritium unit is equivalent to 1 tritium atom in 1018 atoms of hydrogen (Taylor and Roether, 1982). Prior to 1952, the tritium concentration in precipitation in coastal California was about 2 TU. About 800 kilograms (kg) of tritium was released to the atmosphere as a result of the atmospheric testing of nuclear weapons during 1952-62 (Michel, 1976), and the tritium concentration of precipitation increased to a maximum of about 1,200 TU. After the cessation of atmospheric testing of nuclear weapons in 1962, the tritium concentration of precipitation decreased and present-day tritium levels in precipitation are near the pre-1952 levels. Because tritium is part of the water molecule, tritium is not affected by reactions other than radioactive decay, and—neglecting the effects of dispersion—tritium is an excellent tracer of the movement of groundwater recharged less than 50 years before present. Helium has two stable isotopes, helium-3 (3He) and helium-4 (4He). Most helium in the natural environment (atmospheric) is helium-4; 3He concentrations are orders of magnitude smaller than 4He concentrations. As with many isotopes, the ratio of 3He to the more abundant isotope 4He can be measured more precisely than can the absolute abundance of a single isotope, and 3He data are reported as delta helium-3 (δ3He). Helium concentrations in groundwater originate from several sources; these sources must be accounted for in order to estimate tritium/helium-3 apparent ages. Water in contact with the atmosphere contains gases, including helium, as a result of equilibrium (Henry's law) partitioning between atmosphere and water. In groundwater, final solubility equilibration between water and air occurs as water reaches the water table. Concentrations of gasses in the groundwater are a function of recharge temperature. For example, 3He is naturally present in the atmosphere, and water at 10 oC in equilibrium with the atmosphere will have a 3He concentration of 63.7 cm3/kg at 10 oC (Solomon and Cook, 2000). Another source of gases to ground water is known as excess air (Heaton and Vogel, 1981; Busenberg and Plummer, 2000; Stute and Schlosser, 2000). Excess air is thought to result from dissolution of air bubbles entrained by a fluctuating water table or trapped near the water table by recharging water. Gases, including helium and neon, in excess air are assumed to be added to groundwater in the proportions in which they exist in the atmosphere (unfractionated air; Heaton and Vogel, 1981; Schlosser and others, 1989). Unlike helium, neon does not have significant subsurface sources, so 3He and 4He from excess air are assumed to be proportional to the neon from excess air. Excess air trapped during groundwater recharge will increase the 3He contribution from atmospheric sources. Cook and Solomon (1997) estimated that the sensitivity of tritium/helium-3 ages to excess air ranges from -5.0 years per cubic centimeter per kilogram (cm3/kg) of excess air for very young groundwater to -0.25 year per cm3/kg of excess air for groundwater recharged 25 years before present. Helium is also added to groundwater from uraniumand thorium-series decay reactions in the Earth's crust (radiogenic). Radiogenic 3He produced in the subsurface through the decay of lithium-6 is small and does not affect the tritium/helium-3 age in most groundwater systems (Solomon and Cook, 2000). Production of 4He is the result of the decay of elements in the uranium-thorium radioactive decay series, other than 6Li. The 3He/4He ratio of radiogenic helium in deep crustal material is about 3 × 10-8 (Mamyrin and Tolstikhin, 1984). Because the 3He term is small for most groundwater and the 4He from radioactive decay is usually small for young ground water, the radiogenic 3He and 4He terms are combined with the helium terms from mantle degassing. The ratio of 3He to 4He in mantle gases is between 1 × 10-5 and 1.4 × 10-5 (Torgersen and Clarke, 1987). Finally, 3He is produced by the radioactive decay of tritium (tritiogenic helium). Solomon and Cook (2000) published a simultaneous solution to the 3He and 4He massbalance equations that uses measured 4He concentrations, δ3He values, and neon concentrations (to constrain recharge temperatures and excess-air values) to calculate the concentration of 3He from the radioactive decay of tritium. Ground-water ages are then calculated on the basis of the radioactive decay of tritium. Tritium-Helium-3 Ages Tritium in water from sampled wells in the upper aquifer system and Deep aquifer ranged from 7.2 to 46.6 TU and from less than the reporting limit of 0.2 to 16.6 TU, respectively (table 6-1). Tritium was present in water from wells in the Deep aquifer near Quarry Lakes and Alameda Creek and concentration decreased with distance from the recharge area to values below the reporting level of 0.2 TU (fig. 13).

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Detections of tritium in Deep aquifer wells near recharge areas suggest a primary contribution of water recharged at the surface. Groundwater samples from Deep aquifer wells to the northwest have tritium levels less than the reporting limit of 0.2 TU and are considered "tritium dead." These waters have been isolated from surface recharge for more than 50 years. Tritium/helium-3 ages for groundwater range from 6 to >50 years (appendix 6). The tritium/helium-3 ages reflect the age of young fractions of groundwater recharged in the last 60 years. Water from Deep aquifer wells has less tritium and higher concentrations of helium, providing evidence that these groundwater samples are older than water from the upper-aquifer-system wells (appendix 6). Combined with lower recharge temperatures, this suggests that the Deep aquifer was mostly recharged under cooler, natural conditions (managed aquifer recharge leads to high ΔNe), occurring more than 50 years before the sample analyses year (2002). In the study area, none of the noble gas and tritium samples showed substantial mixing of young and old waters. Rather, there was a clear areal delineation between wells containing modern and pre-modern waters. In monitoring well nests 17M6-8 and 13P5-7, groundwater ages were younger at shallower depths and older at greater depths (appendix 6). Helium-4 Ages A naturally occurring isotope of helium present within the Earth's crust, 4He, was used to estimate time since recharge for groundwater that does not contain measurable tritium and is older than the range of tritium/helium-3 dating techniques. The 4He ages are calculated from the accumulation of produced radiogenic 4He in groundwater. Contributions to the 4He inventory include two components: in situ production within the aquifer and a deep crustal flux (J0). Assuming that the deep crustal flux may be quantified (or neglected), the former component has chronological significance for the groundwater age. Stute and others (1992) proposed an approach by which the different helium sources may be separated, enabling either groundwater ages or crustal helium fluxes to be estimated. The relationship between apparent (corrected) groundwater age (τcorr, in years) and deep crustal flux entering the aquifer (J0, 4He in cm3STPcm-2yr-1) is given by equation 1 (Stute and others, 1992): r e e k r e e k San Francisco Bay EXPLANATION 122°10' 37° 38' 37° 36' 37° 34' 37° 32' 122°05' 122°00' DIABLO RANGE MISSION FAULT MISSION FAULT HAYWARD FAULT HAYWARD FAULT Quarry Lakes Regional Park Quarry Lakes Regional Park MILES 2 KILOMETERS 13P5 13P5 17M6 17M6 12K8 12K8 2H1 2H1 10E4 10E4 4R1 4R1 4F6 4F6 4E1 4E1 14D3 14D3 Fremont Fremont Hayward Hayward Alameda Alameda Creek Creek A a m e d a A a m e d a Old Old Creek Creek Dry Dry Background image is the intellectual property of Esri and is used herein under license. Copyright © 2014 Esri and its licensors. All rights reserved. Base modified from U.S. Geological Survey digital data, various scales; Lambert Conformal Conic projection; North American Datum of 1983 Tritium activity, in tritium units ≤0.2 0.2-0.6 0.6-10 ≥10 Transition zone (Luhdorff and Scalmanini Consulting Engineers, 2003) Faults Roads Figure 13.  Spatial distribution of tritium concentrations in groundwater from selected Deep aquifer wells in the Niles cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Geochemistry    27

τ φ ρ corr ex o w sol He J z He

4Heex is the excess 4He (above concentrations expected from air equilibration and air bubble contamination),

ϕ is the effective porosity of the aquifer,

z0 is the depth (m) at which the deep crustal flux enters the aquifer, and

ρw is the density of water (~1 g/cm3). The 4He solution or accumulation rate (4Hesol in cm3STPg-1 H2O yr-1) is given by equation 2, which combines the radioelement content of the aquifer {in brackets} with its physical properties (Andrews and Lee, 1979): He U Th sol

(2) where [U] and [Th] are the uranium and thorium concentrations in the aquifer rock in parts per million (ppm),

ρ is the bulk density of the aquifer rock (g/cm3),

Ʌ is the fraction of helium produced in the rock that is released into the water, assumed to be unity, and

ϕ is the fractional effective porosity of the aquifer rock. Assuming aquifer properties for the Deep aquifer of porosity (ϕ) of 35 percent, and bulk density (ρ) of 1.76 g/cm3, with average uranium and thorium concentrations of 1.4 and 5.2 milligrams per kilogram of alluvium (ppm; appendix 3), then the groundwater accumulation rate for 4He in the study area would be 1.04 x 10-12 cm3STPg-1 H2O yr-1, which yields 4He groundwater ages uncorrected for crustal He flux ranging from 0.0007 to >3.8 million years (Myr; eq. 2). These ages are many orders of magnitude greater than ages determined by 14C (see "Carbon-14 and Carbon-13" section). These results imply the presence of a significant deep crustal contribution of helium to the study area. Adopting a crustal flux (J0) of 3 × 10-6 cm3STPcm-2yr-1 provides the best agreement between 4He and 14C ages and yields 4He ages between to >11,000 years (appendix 6). The distribution of 4He ages for Deep aquifer wells plotted on a map of the study area is presented in figure 14. Apparent 4He-derived ages are significantly younger for wells located near Quarry Lakes, with ages between to 26 years, whereas the ages of groundwater in wells to the west/northwest are greater, as much as >11,000 years. The old apparent 4He-derived ages for wells 15L5 and 14D3 could be influenced by a pocket of old water in the areas surrounding those wells. Isotopic Composition of Groundwater Oxygen-18 and Deuterium The proportion of the heavy stable isotopes of oxygen (18O) and hydrogen (2H, deuterium) in water molecules can be used to infer the source and evaporative history of water. Atoms of oxygen-18 (18O) and deuterium (2H) have more neutrons and a greater atomic mass than do atoms of the more common isotopes, oxygen-16 and hydrogen. The difference in weight results in differences in the physical and chemical behavior of the heavier, less abundant isotopes. Oxygen-18 and deuterium abundances are expressed as ratios of the heavy isotope to the light isotope, in delta notation (δ), as per mil (parts per thousand) differences, relative to Vienna Standard Mean Ocean Water (VSMOW; Gonfiantini, 1978). By convention, the value of both oxygen-18 and deuterium abundance ratios in VSMOW is 0 per mil. Oxygen-18 (δ18O) and deuterium (δD) ratios relative to VSMOW can be measured more precisely than absolute abundances, and these ratios are useful in hydrologic studies (International Atomic Energy Agency, 1981). Based on duplicate analyses presented elsewhere (Coplen, 1994; Izbicki, 1996), we have assumed a similar analytical precision of ±0.05 per mil for δ18O and ±1.5 per mil for δD for the results presented here. The δ18O and δD composition of a water sample can provide a record of the source and evaporative history of the water, and differences in isotopic composition can be used to trace the water as it moves through the aquifer. Most precipitation originates from the evaporation of seawater, resulting in a linear correlation of δ18O and δD (fig. 15) that plots along a line known as the global meteoric water line (GMWL; Craig, 1961). Deviations from the GMWL are caused by differences in isotopic composition of precipitation if water vapor originated from evaporation of cooler or warmer water, and heavier isotopes are preferentially removed by precipitation as moist air masses move across continents. At a given location, the isotopic composition of precipitation trends to be an average value and is ultimately determined by local differences in the temperature of condensation and evaporative sources. Water that condensed at cooler temperatures (associated with higher altitudes, cooler climatic regimes, or higher latitudes) is lighter (more negative δ values) than water that condensed at warmer temperatures (associated with lower altitudes, warmer climatic regimes, and lower latitudes). Also, water that has been partially evaporated becomes enriched in heavier isotopes relative to its original composition and plots to the right of the GMWL, along an evaporative-trend line.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Because of the temporal and spatial variability of δ18O and δD, and because precipitation is often not representative of groundwater, owing to runoff and recharge processes, shallow groundwater samples often are collected to characterize the stable isotopic composition of recharge (Kendall and Coplen, 2001). Izbicki and others (2003) defined a local groundwater meteoric line by characterizing the stable isotopic composition of groundwater in the southern East Bay Plain groundwater subbasin. This local groundwater line is shown in figure 15 and is useful for discussing the evaporative history of groundwater sampled during this study. Sources of recharge in the study area include diffuse infiltration from precipitation, infiltration from stream channels, and water artificially infiltrated at Quarry Lakes and behind seasonally inflated rubber dams in parts of Alameda Creek. Precipitation collected at a station near Quarry Lakes had δ18O and δD values of -7.7 and -45.8, respectively; for reasons stated in the "Methods" section, this single sample is not representative of annually weighted values (fig. 15). Some runoff in the Alameda Creek watershed is stored at reservoirs upstream from the study area where it may fractionate during evaporation before release downstream. Water in ACWD recharge ponds has a variable stable isotopic composition because it is derived from both local runoff in the Alameda Creek basin and water imported from the Sacramento-San Joaquin River Delta. Water imported from the Sacramento- San Joaquin River Delta may be mixed with local runoff stored in reservoirs in the Alameda Creek watershed or may be discharged directly to a tributary of Alameda Creek upstream from the study area. Water imported from the South Bay Aqueduct has a δ18O value of -9 to -10 per mil (Moran and Halliwell, 2004). Imported water deliveries began in the early 1960s partly to dilute effluent from wastewater treatment plants that was discharged to streams in the Alameda Creek watershed (Lopp, 1981). Although most wastewater has been exported via pipeline to the San Francisco Bay since 1980, the stable isotopic composition of groundwater near Alameda Creek that was recharged before 1980 may be partly influenced by wastewater. The δ18O and δD composition of the wastewater has not been characterized. During late summer, much of the water in Alameda Creek is derived from groundwater originating from Quarry Lakes. The stable isotopic composition of water in the recharge ponds (δ18O -5.71; δD -48), sampled in December 1997 (Moran and Halliwell, 2004), indicates that recharge water infiltrating from the ponds was evaporated (fig. 15). The relative volume of imported water and local Alameda Creek sources used for managed aquifer recharge at the ACWD recharge ponds varies considerably from year to year. San Francisco Bay r e e k r e e k Quarry Lakes Regional Park Quarry Lakes Regional Park DIABLO RANGE MISSION FAULT MISSION FAULT HAYWARD FAULT HAYWARD FAULT 13P5 13P5 17M6 17M6 12K8 12K8 14D3 14D3 10E4 10E4 2H1 2H1 4R1 4R1 4F6 4F6 4E1 4E1 Fremont Fremont Hayward Hayward A a m e d a A a m e d a Old Old Alameda Alameda Creek Creek Creek Creek Dry Dry EXPLANATION Helium ages, in years before present Transition zone (Luhdorff and Scalmanini Consulting Engineers, 2003) Faults Roads 1,000-<5,000 5,000-<10,000 ≥10,000 MILES 2 KILOMETERS 122°10' 37° 38' 37° 36' 37° 34' 37° 32' 122°05' 122°00' Background image is the intellectual property of Esri and is used herein under license. Copyright © 2014 Esri and its licensors. All rights reserved. Base modified from U.S. Geological Survey digital data, various scales; Lambert Conformal Conic projection; North American Datum of 1983 Figure 14.  Spatial distribution of 4He ages from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Geochemistry    29 The δ18O and δD composition of water from sampled wells in the study area ranged from -5.4 to -7.3 per mil and -42.5 to -50.5 per mil, respectively (table 5-1). The range in δ18O and δD values is small given the many sources of water having different isotopic compositions. Water from wells in the upper aquifer system and the Deep aquifer near Alameda Creek and Quarry Lakes (4S/2W-13P4-7 and 4S/1W-17M6-8) shows signs of evaporation and plot along an evaporation trend line (fig. 15). The evaporative signal apparent from wells near (within 2 miles) the Quarry Lakes recharge ponds is likely a result of isotopically depleted water (less negative values) recharging from the ponds. Wells screened in the upper aquifer system show heavier isotopic ratios, and plot further right along the evaporative trend line, than the Deep aquifer wells because of mixing of the managed recharge source with other water farther from the source. Most samples plot slightly below the meteoric water line along the local groundwater line of Izbicki and others (2003). Isotopic data from wells 20L20 and 19Q3 suggest that groundwater in the southern East Bay Plain groundwater subbasin is derived from a different source, likely areal recharge. The isotopic composition of water in well 4S/2W-2H1 has a δD value greater than the other Deep aquifer wells in the Niles Cone subbasin and is similar to local precipitation measured at USGS site 373425121582101, indicating that the source of water in this well is predominantly infiltration of precipitation. −90 −9 Evaporative trend line 19Q3 Seawater mixing line Meteoric mixing line Meteoric mixing line Local groundwater line Evaporative trend line −80 −70 −60 −50 −40 −30 −20 −10 −8 −7 −6 −5 −4 −3 −1 Deuterium/protium ratio Oxygen-18/oxygen-16 ratio Oxygen-18/oxygen-16 ratio −58 −56 −54 −52 −50 −48 −46 −44 −8.0 −7.0 −6.0 Deuterium/protium ratio −2 −42 −40 −5.0 EXPLANATION Seawater Quarry Lakes Regional Park recharge ponds (Moran and Halliwell, 2004) 13P6 Local precipitation measured at Alameda County Water District rooftop (USGS 373425121582101) on November 8, 2002 Well sampled by Izbicki and others, 2003 Upper aquifer system wells Deep aquifer wells 2H1 2H1 13P5 13P5 17M6 17M6 13P6 13P6 13P7 13P7 17M7 17M7 13P4 13P4 17M8 17M8 12K10 12K10 Carbon-14 and Carbon-13 Carbon-14 (14C) is a naturally occurring radioactive isotope of carbon having a half-life of 5,730 years (Manov and Curtiss, 1951). Carbon-14 is formed in the atmosphere by the interaction of cosmogenic radiation with nitrogen (Clark and Fritz, 1997). Atmospheric carbon-14 is present as carbon dioxide (CO2), which can then be incorporated into various hydrospheric (oceans, lakes, and groundwater) and biospheric (plants and animals) reservoirs. Whether through infiltration of water or the decay and release of biomass into the soil zone, once these intermediate sources of carbon are isolated from the atmosphere, the carbon-14 content in the dissolved carbon steadily decreases. Carbon-14 that has been isolated from the atmosphere is seldom only affected by radioactive decay. Chemical reactions can dilute carbon-14 by either the addition of dissolved inorganic carbon (DIC) that lacks carbon-14 or by the removal of DIC that contains carbon-14 (Clark and Fritz, 1997). Carbon-14 concentrations can be decreased when carbon is added to groundwater by the dissolution of calcite or dolomite, which are devoid of carbon-14 and are often said to contain "dead" carbon (Freeze and Cherry, 1979). The addition of DIC from these sources dilutes the original carbon-14 content to give the appearance of older water, as does the production of DIC from oxidation of organic matter that is devoid of carbon-14. Above ground nuclear testing increased the amount of carbon-14 in the atmosphere, similar to tritium, within the last 50 years. Groundwater recharged within this period likely contains 14C above natural background concentrations of 100 pmC. Figure 15.  Relations of delta oxygen-18 (δ18O) with delta deuterium (δD) in water from wells, Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Because of its long half-life, carbon-14 can be used to estimate groundwater ages ranging from 1,000 to less than 30,000 years before present (Clark and Fritz, 1997). Radiocarbon dating is based on measuring the loss of the parent radionuclide carbon-14 in a given sample, assuming the initial carbon-14 concentration is known and that losses or gains of carbon-14 are minimal or can be quantified (Clark and Fritz, 1997). The activity of carbon-14 in a sample is reported in percent modern carbon, which indicates the carbon-14 activity of the sample relative to that of modern carbon, defined as 95 percent of the carbon-14 activity of the National Bureau of Standards oxalic acid in 1950 (Clark and Fritz, 1997). Ratios of the stable isotopes carbon-13 to the far more abundant carbon-12 (delta carbon-13, δ13C) were used in this study as indicators of biogeochemical and carbon-exchange processes that can affect estimates of carbon-14 ages. Because carbonate minerals and DIC exchange carbon isotopes (equilibration), groundwater can acquire a less negative delta δ13C value as it moves through the aquifer. Values of δ13C can also be affected by decomposition (oxidation or mineralization) of organic matter buried in the aquifer because organic material has a more negative δ13C composition than does inorganic carbon so that carbon isotopes would become lighter. Values of δ13C were used to make qualitative inferences about the extent to which these processes have caused the carbon-14 age to overestimate the actual time elapsed since recharge in this study. Carbon-14 activities in DIC in the Deep aquifer ranged from 16 to 86 pmC and had a median of 50 pmC (table 5-1). These carbon-14 activities correspond to uncorrected ages ranging from 1,300 to 15,000 years before present (ybp), with a median uncorrected age of 5,700 ybp. Dissolved inorganic carbon delta carbon-13 values ranged from -13.3 to -15.3 per mil. Carbon-13 values became lighter with increasing distance along the groundwater flowpath, north from Quarry Lakes. Additionally, δ13C measured in water from wells within the Niles Cone groundwater subbasin (table 5-1) are generally less negative than in water from wells within the southern East Bay Plain groundwater subbasin (represented by wells 20L20 and 29L6), including wells sampled by Izbicki and others (2003). Interpretation of Carbon-14 Data The computer program NETPATH (Plummer and others, 1991) was used to account for reactions that affect DIC and adjust the measured carbon-14 activities to estimate the age (time since recharge) of groundwater along a flowpath extending from recharge areas along Alameda Creek near Quarry Lakes, through the transition zone within the Deep aquifer, into the East Bay Plain groundwater subbasin (flowpath B-B′; fig. 4). Restriction of groundwater flow near the transition zone that was not discernible from water-level data can be detected using groundwater ages of water from wells across the area (Izbicki and Martin, 1997). Inputs to NETPATH model calculations include changes in groundwater chemistry and isotopic composition along the study flowpath (fig. 16; appendix 7) and aquifer mineralogy (table 3-1). Chemical data are used to calculate saturation indexes (SI; fig. 16) that indicate if a mineral will tend to dissolve if present in the aquifer (negative values) or, in the absence of thermodynamic constraints, precipitate (positive values) from groundwater onto aquifer materials. Large magnitude values (either positive or negative) may indicate the presence of constraints on these processes. For example, primary minerals such as albite or mica cannot precipitate in comparatively low-temperature/low-pressure groundwater environments; similarly, there may be kinetic constraints on clay-mineral formation that limit their precipitation from groundwater. Chemical data and the mass-balance of the various elements in groundwater and minerals also constrain NETPATH model calculations representing the dissolution and precipitation and the mass-transfer of dissolved constituents along the flowpath (Plummer and others, 1991). The carbon-13 composition of organic material in the aquifer was assumed to be -25 per mil, consistent with carbon from a mixture of plants having C3 and C4 photosynthetic pathways and similar to the value used in NETPATH calculations used to estimate groundwater age in the East Bay Plain groundwater subbasin (Izbicki and others, 2003). For the purpose of model calculations, carbon-14 activity (Ao) of groundwater at the beginning of the flowpath through the aquifer was estimated using an approach described by Verhagen and others (1991; fig. 17). This approach, based on field data, is applicable in systems where groundwater may contain modern groundwater recharged after the atmospheric testing of nuclear weapons beginning in the early 1950s. Carbon-14 data are shown in rank order, expressed as percent greater than or equal to, from largest to smallest. Carbon-14 activities generally exceeded 69.37 pmC in water samples from wells containing tritium. This value was selected as the initial carbon activity, Ao, for modeling purposes and was also used to calculate uncorrected carbon-14 ages from the measured percent modern carbon values. Water from three wells having lower carbon-14 activities contain measurable tritium, suggesting that the water from these wells (1) is a mixture of modern water containing tritium and older water that does not contain tritium or (2) chemical reactions have occurred in water from these wells that has resulted in the addition of carbon from aquifer materials that does not contain carbon-14, resulting in a lower than expected carbon-14 activity. Water from one of these wells, 12C1 near Dry Creek, has comparatively high tritium activity of 7.8 TU, and the water likely contains a high fraction of modern groundwater. Water from well 14D3 near Alameda Creek has a tritium activity of 0.4 TU, indicating a smaller but measurable fraction of modern groundwater. Tritium also was detected in water from well 20L20 at an activity of 0.6 TU near the downgradient end of the study flowpath, suggesting a small amount of modern water consistent with recent recharge in that area. Carbon-14 ages for these wells were not adjusted for the presence of modern water, and actual ages of the older groundwater in these wells are likely older than the ages calculated by NETPATH.

Geochemistry    31 35,000 35,000 Concentration, in millimoles −4 −8 −6 −4 −3 −2 −2 −1 35,000 Cumulative mass transfer, in millimoles Saturation index

5,000 10,000 15,000 20,000 25,000 30,000 Under-saturated 5,000 10,000 15,000 20,000 25,000 30,000 5,000 10,000 15,000 20,000 25,000 30,000 Over-saturated pH

−1.0 −0.5 Cation exchange, in millimoles

4F3 4E1 B' (Southeast) B (Northwest) Direction of groundwater flow A B 12K8 Distance along flow path, in feet Distance along flow path, in feet Distance along flow path, in feet EXPLANATION EXPLANATION EXPLANATION Ca2+ SO4 2Mg2+ pH HCO3Cl− Na+ Calcite (CaCO3) Gypsum Montmorillonite Kaolinite Anorthite Albite Mica Ca/Na Exchange Carbonate Carbon Gypsum Silicate H2S Clay Figure 16.  Selected changes in chemical and isotopic composition of water from wells used to interpret carbon-14 data along section B-B', Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Major-ion composition of groundwater along flowpath B-B′ gradually changes from a mixed composition to a more sodium-type water downgradient (fig. 10), consistent with cation exchange previously identified as important reactions in the East Bay Plain groundwater subbasin (Izbicki and others, 2003). The largest changes in major-ion composition, accompanied by increases in pH, occur between wells 4F3 and 4E1 near the downgradient end of the transition zone between the Niles Cone and East Bay Plain groundwater subbasins within the Deep aquifer. NETPATH calculations provide estimates of (1) saturation indices for selected minerals at each well along the flowpath, (2) mass transfer of major cations and anions, and (3) cation exchange between each well. Positive mass transfer values indicate that the constituent is increasing in concentration, and negative values indicate that the constituent is decreasing in concentration. Positive cation exchange values indicate that calcium is exchanging for sodium on clay minerals, and negative values indicate that sodium is exchanging for calcium on clay minerals. The NETPATH calculations indicate saturation of groundwater with respect to calcite and exchange of sodium for calcium on clay minerals along flowpath B-B′ (fig. 16). Because calcium is a divalent cation, it is preferentially absorbed by exchange sites on clay minerals; however, in environments where the equilibrium is shifted to an oversaturation of sodium, such as aquifers influenced by seawater intrusion, sodium ions may replace calcium ions on exchange sites (Izbicki, 1991). NETPATH calculations also indicate consumption of organic carbon within the aquifer, likely through biological processes. Consistent with consumption of organic carbon from aquifer materials by microbiological processes, alkalinity increases and δ13C values become increasingly negative with distance downgradient along flowpath B-B′ (fig. 16). Measured and model-calculated δ13C values generally agree within 0.5 per mil. 35,000 35,000 5,000 10,000 15,000 20,000 25,000 30,000 5,000 10,000 15,000 20,000 25,000 30,000 4F3 4E1 B' (Southeast) B (Northwest) Direction of groundwater flow D E −16 −15 −14 −13 −12 12K8 Carbon-13/carbon-12 ratio, in per mil 2,000 4,000 6,000 8,000 10,000 Age, in years before present Distance along flow path, in feet Distance along flow path, in feet EXPLANATION EXPLANATION Calculated carbon-13 Measured carbon-13 Corrected carbon-14 ages Uncorrected carbon-14 ages Figure 16.  —Continued

Geochemistry    33 Field data and NETPATH results show a decrease in carbon-14 activity with distance downgradient along flowpath B-B′ (fig. 16). Uncorrected carbon-14 ages range from near modern near the recharge areas to as much as 9,000 years before present (ybp) downgradient. Interpreted carbon-14 ages are slightly less, ranging from modern to about 7,340 ybp (table 7-1). The difference between uncorrected and interpreted ages results from addition of carbon that does not contain carbon-14 from microbiological respiration of organic carbon within aquifer materials along the flowpath. Both uncorrected and interpreted ages indicate large changes in groundwater age near the downgradient end of the transition zone, whereas stable water isotope data (δ18O and δD; fig. 15) suggest the source of groundwater recharge in this area is relatively unchanged. The slight decrease in groundwater age in water from well 4E1 to 29L6 suggests that well 29L6 is not at the end of the B-B′ flowpath. Uncorrected carbon-14 age data from well 20L20 suggest that groundwater age increases from north to south in the East Bay Plain groundwater subbasin and that flowpaths may be converging at the transition zone between the Niles Cone and the East Bay Plain groundwater subbasins. Groundwater velocities calculated from interpreted carbon-14 ages range from 3 to 12 ft/yr in the Deep aquifer of the Niles Cone groundwater subbasin and decrease to as little as 0.5 ft/yr near the transition to the southern East Bay Plain groundwater subbasin. Groundwater flow rates within the Deep aquifer, calculated on the basis of groundwater 14C ages and distance along the flowpath, decrease by an order of magnitude from 11.6 ft/yr between wells 4S/2W-3L1 and 4S/2W-4F3 to 0.5 ft/yr between wells 4S/2W-4F3 and 4S/2W-4E1 just south of the southern East Bay Plain groundwater subbasin transition zone boundary (table 7-1). These results are consistent with lithologic changes (Luhdorff and Scalmanini Consulting Engineers, 2003) within the transition zone that separates the two groundwater subbasins and acts to limit flow between the Niles Cone and southern East Bay Plain groundwater subbasins. Because the converging flowpaths and lithologic changes at the transition zone restrict movement of groundwater from the Niles Cone groundwater subbasin into the East Bay Plain groundwater subbasin, water recharged at the Quarry Lakes likely remains within the Niles Cone groundwater subbasin. Limitations of Carbon-14 Interpretations Carbon-14 ages calculated using NETPATH are interpretive and subject to uncertainty. For aquifers for which the chemistry is well understood, interpreted carbon-14 ages are within ±20 percent of the actual value (Davis and Bentley, 1982). In areas where present-day recharge may not reflect the composition of recharge for older groundwater, the greatest source of uncertainty in interpreting carbon-14 data is in determining the initial chemistry, carbon-14 activity, and δ13C composition of the recharge water. In this study, the carbon-14 age calculated for water from well 12C1, which is a mixture of modern and older groundwater (samples with tritium detections greater than or equal to 0.8 TU and carbon-14 activities less than or equal to 95 pmC), is an average age. The age of the older fraction of groundwater composing this mixture was not calculated. It is likely that the age of the older fraction of water is greater than the age shown in table 7-1 and on figure 16. Carbon-14 activity, in percent modern carbon Percent greater than or equal to EXPLANATION Tritium activity greater than 0.2 tritium units Tritium activity less than 0.2 tritium units Figure 17.  Plot of rank order carbon-14 data, expressed as cumulative exceedance percentage, in water from sampled wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, 2002-03. Tritium concentrations are shown using filled and open circle symbols.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Summary The principal water-bearing units in the Niles Cone and southern East Bay Plain groundwater subbasins are located west of the Hayward Fault. The aquifers (from shallowest to deepest) are the Newark, Centerville, Fremont, and Deep aquifers; these were originally defined in the Niles Cone groundwater subbasin and projected to the southern East Bay Plain groundwater subbasin. The Newark, Centerville, and Fremont aquifers are thickest and most continuous in the Niles Cone groundwater subbasin. Unlike the Niles Cone groundwater subbasin to the south, alluvial fans in the southern East Bay Plain groundwater subbasin were not deposited by large streams, and as a result, sediments in shallow aquifers are finer grained and more discontinuous than in the Niles Cone groundwater subbasin. Fine-grained sediments deposited between the alluvial fans of the Niles Cone and southern East Bay Plain groundwater subbasins interrupt lateral continuity of coarse-grained layers and may restrict interbasin flow of groundwater. Beginning in 1974, ACWD imported water to supplement natural recharge to the aquifer system in the Niles Cone groundwater subbasin by recharging water through ponds at Quarry Lakes Regional Park. This recharged water was intended to increase hydraulic heads in the area and halt intrusion of water from San Francisco Bay into the aquifer systems, and along with other projects in the area, to improve groundwater quality. Although water levels in wells in the region increased, the effect of managed aquifer recharge was not otherwise quantified. Hydrologic, InSAR, and geochemical data for 2002 and 2003 were collected and analyzed to evaluate the geologic and hydrologic controls on groundwater movement through aquifers between the Niles Cone and southern East Bay Plain groundwater subbasins on the east side of San Francisco Bay, California, in cooperation with the East Bay Municipal Utility District, City of Hayward, and Alameda County Water District. Groundwater in the upper aquifer system and Deep aquifer flows to the west and north from recharge areas near Quarry Lakes and along Alameda Creek. Water levels were about 20 ft lower in the Deep aquifer than in the upper aquifer system. Water levels in the Deep aquifer were as much as 9 ft below sea level during this study. Steep water-level gradients to the south of the recharge areas are likely the result of pumping at the Mowry well field and Aquifer Reclamation Program (ARP) wells. To the north, fewer wells completed solely in the upper aquifer system were available to measure water levels because of the finer-grained nature of the aquifer deposits in this area. Water-level data show groundwater in the Deep aquifer flows to the north toward the southern East Bay Plain groundwater subbasin. Changes in the slope of the water-level contours near the transition zone between the Niles Cone and southern East Bay Plain groundwater subbasins are consistent with changes in lithology, or could indicate structural features such as faults or folds, that restrict groundwater flow. Water recharged at Quarry Lakes affects the hydraulic heads in nearby wells in which both the upper aquifer system and Deep aquifer respond rapidly and with little lag between recharge and the measured responses to recharge (fig. 5). InSAR data show land surface deformation in response to aquifer recharge of about 0.8 in. (20 mm). Measured deformation is greater to the west and northwest (fig. 6), downgradient from groundwater recharge areas where aquifers are finer-grained and elastic, and less near recharge areas where aquifers are coarser-grained. The extent of the uplift shown on interferograms may not represent the extent of the movement of water from managed aquifer recharge, but instead results from a pressure response. InSAR data also show land surface deformation in response to pumping, suggesting land surface deformation is elastic and occurs rapidly. Streamflow data show that during the period of the study, the section of Alameda Creek nearest Quarry Lakes was a losing section, and the reach of Alameda Creek as much as 1.5 miles (fig. 3) upstream from the tidally affected section was a gaining reach. Water from the losing reach of Alameda Creek likely recharges the upper aquifer system and the Deep aquifer. Large streamflows during winter months could cause losing conditions along the entire nontidally affected reach of Alameda Creek. Under predevelopment conditions, sustained flow in Alameda Creek may have been great enough to provide a consistent source of recharge to the local aquifers. Groundwater in the study area was fresh, with dissolved solids concentrations in sampled wells less than 1,080 mg/L. Values of pH were near neutral to alkaline, with increasing pH with depth and distance from groundwater recharge areas. Water from sampled wells in the upper aquifer system had varied dissolved oxygen concentrations ranging from oxic (2.9 mg/L) to reduced (<0.2 mg/L). Water from sampled wells in the Deep aquifer was generally reducing. Water from upperaquifer-system wells located near Quarry Lakes is marked by higher calcium and magnesium percentages than water from most wells in the Deep aquifer, indicating influence by water recharged at Quarry Lakes and from the ponded areas behind the inflatable dams in Alameda Creek. The effect of past intrusion of water from San Francisco Bay and high-chloride water from partly consolidated marine rock underlying the study area can be seen in water from some wells in the Deep aquifer that have chloride concentrations as high as 350 mg/L. Water from some Deep aquifer wells has elevated chloride concentrations and major-ion concentrations indicative of exchange of sodium for calcium and magnesium on clay in aquifer deposits. Water from well 4S/2W-15L5 has major-ion proportions suggesting the source of high-chloride water to well 15L5 is likely from partly consolidated marine rock.

References Cited    35 Groundwater recharge temperatures estimated using noble-gas data ranged from 10.1 ± 0.7 to 19.2 ± 0.8 oC, warmer than those estimated for focused recharge along San Lorenzo and San Leandro Creeks in the southern East Bay Plain groundwater subbasin, north of the study area (Izbicki and others, 2003). The warmer recharge temperatures in the study area may reflect year-round recharge from Quarry Lakes and Alameda Creek rather than winter recharge from infiltration of winter stormflows in the smaller, unmanaged streams that recharge the East Bay Plain groundwater subbasin. The δ18O and δD data in shallow wells near the recharge area indicate evaporative modification of water stored in the recharge ponds, or behind the rubber dams, prior to infiltration. In contrast, isotopic data from a few wells suggest that groundwater in the southern East Bay Plain groundwater subbasin is derived from a different source, likely areal recharge or infiltration of precipitation. Tritium/helium-3 age data show that upper aquifer system and Deep aquifer wells near Quarry Lakes contain water that has been recently recharged. Tritium/helium-3 ages for groundwater range from 6 to 50 years for these wells and were greater than 50 years for the rest of the wells in the study area. Tritium/helium-3 ages and tritium activities decreased away from Quarry Lakes with distance from the recharge area to values below the reporting level. Although 4He ages and uncorrected 14C ages differed, generally they both increased downgradient. NETPATH analyses of water-chemistry data show that as water flows through the aquifer systems, concentrations of sodium (plus potassium relative to calcium plus magnesium) increase owing to primary silicate weathering and (or) exchange of calcium and magnesium for sodium on clay within aquifer deposits (Izbicki and others, 1992; Izbicki and others 2003). Carbon-14 groundwater ages in the Deep aquifer, corrected for reactions that occur between groundwater and aquifer materials, range from 830 to 7,340 years before present. Ages increase northward along the flowpath from the Niles Cone groundwater subbasin toward the southern East Bay Plain groundwater subbasin, with large changes in groundwater age within the transition zone separating the Niles Cone from the southern East Bay Plain groundwater subbasins. Groundwater flow rates within the Deep aquifer decrease by an order of magnitude from 11.6 ft/yr between wells 4S/2W-3L1 and 4S/2W-4F3 to 0.5 ft/yr between wells 4S/2W-4F3 and 4S/2W-4E1 just south of the southern East Bay Plain groundwater subbasin transition zone boundary. These results are consistent with restricted groundwater flow between the two groundwater subbasins and consistent with the result of lithologic changes within the transition zone and converging groundwater flowpaths north of the transition zone. Additionally, converging groundwater flowpaths north of the transition zone from different recharge areas within the two subbasins may restrict transfer of water between the two subbasins. As a consequence, water recharged at Quarry Lakes directly affects water levels and water quality in wells in the vicinity of the recharge facility, and that water likely remains within the subbasin. References Cited Aeschbach-Hertig, W., Peeters, F., Beyerle, U., and Kipfer, R., 1999, Interpretation of dissolved atmospheric noble gases in natural waters: Water Resources Research, v. 35, no. 9, p. 2779-2792, https://doi.org/10.1029/1999WR900130. Aeschbach-Hertig, W., Peeters, F., Beyerle, U., and Kipfer, R., 2000, Palaeotemperature reconstruction from noble gases in ground water taking into account equilibration with entrapped air: Nature, v. 405, no. 6790, p. 1040-1044, accessed May 16, 2012, at https://doi.org/10.1038/35016542. Alameda County Water District, 2001a, Groundwater monitoring report fall 2000: Alameda County Water District, variously paginated. Alameda County Water District, 2001b, Groundwater management policy: Alameda County Water District, 11 p., accessed May 16, 2012, at http://www.acwd.org/DocumentCenter/View/125. Amonette, J.E., and Zelazny, L.W., eds., 1994, Quantitative methods in soil mineralogy—Proceedings of a symposium sponsored by Division S-9 of the Soil Science Society of America, San Antonio, Texas, October 23-24, 1990: Soil Science Society of America, 452 p. Andrews, J.N., and Lee, D.J., 1979, Inert gases in groundwater from the Bunter Sandstone of England as indicators of age and palaeoclimatic trends: Journal of Hydrology, v. 41, no. 3-4, p. 233-252, accessed May 16, 2012, at https://doi.org/10.1016/0022-1694(79)90064-7. Bailey, P., 1919, Engineer's report on pumping draught and irrigation from the underground water of the Alameda County Water District: State Water Commission of 1916, 126 p. Bawden, G.W., Thatcher, Wayne, Stein, R.S., Hudnut, K.W., and Peltzer, Gilles, 2001, Tectonic contraction across Los Angeles after removal of groundwater pumping effects: Nature, v. 412, p. 812-815, accessed March 10, 2003, at https://doi.org/10.1038/35090558. Bayer, R., Schlosser, P., Bönisch, G., Rupp, H., Zaucker, F., and Zimmek, G., 1989, Performance and blank components of a mass spectrometric system for routine measurement of helium isotopes and tritium by the 3He ingrowth method: Heidelberg, Springer-Verlag, v. 5, p. 241-279. Beukens, R.P., 1992, Radiocarbon accelerator mass spectrometry—Background, precision and accuracy, in Taylor, R.E., Long, Austin, and Kra, R.S., eds., Radiocarbon after four decades: New York, Springer-Verlag, p. 230-239, https://doi.org/10.1007/978-1-4757-4249-7_16.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Beyerle, Urs, Aeschbach-Hertig, Werner, Imboden, D.M., Baur, Heinrich, Graf, Thomas, and Kipfer, Rolf, 2000, A mass spectrometric system for the analysis of noble gases and tritium from water samples: Environmental Science and Technology, v. 34, no. 10, p. 2042-2050, accessed May 16, 2012, at https://doi.org/10.1021/es990840h. Briggs, P.H., and Meier, A.L., 2002, The determination of forty-two elements in geological materials by inductively coupled plasma-mass spectrometry, in Taggart, J.E., Jr., ed., Analytical methods for chemical analysis of geologic and other materials: U.S. Geological Survey OpenFile Report 02-223, p. M-1 to M-9, accessed May 4, 2012, at https://pubs.usgs.gov/of/2002/ofr-02-0223/ I20NAWQAPlus_M.pdf. Brown and Caldwell Consulting Engineers, 1986, Evaluation of groundwater resources and proposed design for emergency water supply wells: Pleasant Hill, Calif., variously paged. Busenberg, Eurybiades, and Plummer, L.N., 2000, Dating young groundwater with sulfur hexafluoride—Natural and anthropogenic sources of sulfur hexafluoride: Water Resources Research, v. 36, no. 10, p. 3011-3030, https://doi.org/10.1029/2000WR900151. California Department of Water Resources, 1960, Intrusion of salt water into ground water basins of southern Alameda County: Division of Resources Planning Bulletin No. 81, 44 p., accessed May 6, 2012, at http://www.water.ca.gov/ waterdatalibrary/docs/historic/Bulletins/Bulletin_81/ Bulletin_81__1960.pdf. California Department of Water Resources, 1963, Alameda County Investigation: California Department of Water Resources Bulletin No. 13, 195 p., accessed May 6, 2012, at http://www.water.ca.gov/waterdatalibrary/docs/historic/ Bulletins/Bulletin_13/Bulletin_13__1963.pdf. California Department of Water Resources, 1967, Evaluation of ground water resources—South Bay; Appendix A— Geology: California Department of Water Resources Bulletin 118-1, 153 p., accessed May 6, 2012, at http://www.dwr.water.ca.gov/pubs/groundwater/ bulletin_118/evaluation_of_ground_water_resource__ appa_geology_report_only.pdf. California Department of Water Resources, 1968, Evaluation of ground water resources—South Bay; Volume 1— Fremont study area: California Department of Water Resources Bulletin 118-1, , 117 p., accessed May 6, 2012, at http://www.dwr.water.ca.gov/pubs/groundwater/ bulletin_118/evaluation_of_ground_water_resource__ pdf. California Department of Water Resources, 2003, Bulletin 118 update, California's ground water: California Department of Water Resources, 246 p. Centre National d'Etudes Spatiales, 1997, PRISME/ DIAPASON software, version 1.0: Toulouse, France, Centre National d'Etudes Spatiales. CH2M-Hill, Inc., 2000, Regional hydrogeologic investigation of the south East Bay Plain: Oakland, Calif., CH2M-Hill. Clark, W.O., 1915, Ground-water resources of the Niles cone and adjacent areas, California: U.S. Geological Survey Water Supply Paper 345-H, p. 127-168, available at https://pubs.er.usgs.gov/publication/wsp345H. Clark, I.D., and Fritz, Peter, 1997, Environmental isotopes in hydrology: Boca Raton, Fla,, Lewis Publishers, 352 p. Cook, P.G., and Solomon, D.K., 1997, Recent advances in dating young groundwater—Chlorofuorocarbons, 3H/3He and 85Kr: Journal of Hydrology, v. 191, no. 1-4, p. 245-265, http://dx.doi.org/10.1016/S0022-1694(96)03051-X. Coplen, T.B., 1994, Reporting of the stable hydrogen, carbon, and oxygen isotopic abundances: Pure and Applied Chemistry, v. 66, no. 2, p. 273-276, https://doi.org/10.1351/pac199466020273. Craig, Harmon, 1961, Isotopic variation in meteoric waters: Science, v. 133, no. 2465, p. 1702-1703, accessed April 3, 2012, at https://doi.org/10.1126/science.133.3465.1702. Cunningham, W.L., and Schalk, C.W., comps., 2011, Groundwater technical procedures of the U.S. Geological Survey: U.S. Geological Survey Techniques and Methods 1-A1, 151 p., available only online at https://pubs.usgs.gov/tm/1a1/. Davis, S.N., and Bentley, H.W., 1982, Dating groundwater—A short review, chap. 11 in Currie, L.A., ed., Nuclear and chemical dating techniques—Interpreting the environmental record: American Chemical Society Symposium Series, v. 176, p. 187-222, https://doi.org/10.1021/bk-1982-0176.ch011. Davis, S.N., Whittemore, D.O., and Fabryka-Martin, June, 1998, Uses of chloride/bromide ratios in studies of potable water: Groundwater, v. 36, no., 2, p. 338-350, accessed April 4, 2012, at https://doi.org/10.1111/j.1745-6584.1998.tb01099.x. Epstein, S., and Mayeda, T., 1953, Variation of O18 content of waters from natural sources: Geochimica et Cosmochimica Acta, v. 4, no. 5, p. 213-224, https://doi.org/10.1016/0016-7037(53)90051-9.

References Cited    37 Feth, J.H., 1981, Chloride in natural continental water—A review: U.S. Geological Survey WaterSupply Paper 2176, 30 p., available at https://pubs.er.usgs.gov/publication/wsp2176. Figuers, S., 1998, Groundwater study and water supply history of the East Bay Plain, Alameda and Contra Costa Counties, California: Norfleet Consultants, 90 p., accessed at http://www.waterboards.ca.gov/sanfranciscobay/water_ issues/programs/groundwater/GW_East_Bay_Plain_report_ and_color_figures.pdf. Fio, J.L., and Leighton, D.A., 1995, Geohydrologic framework, historical development of the groundwater system, and general hydrologic and water-quality conditions in 1990, South San Francisco Bay and Peninsula area, California: U.S. Geological Survey OpenFile Report 94-357, 46 p., available at https://pubs.er.usgs.gov/publication/ofr94357. Fishman, M.J., ed., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey Open-File Report 93-125, 217 p., available at https://pubs.er.usgs.gov/publication/ofr93125. Fishman, M.J., ed., and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, Chapter A1, 545 p., available at https://pubs.er.usgs.gov/publication/twri05A1. Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood Cliffs, N.J., Prentice-Hall, 604 p. Fugro West, Inc., 2000, Hydrogeologic investigation East Bay Plain ASR project farmhouse site, Alameda County, California: For East Bay Municipal Utility District, 12 p. Fugro West, Inc., 2001, Well completion report Bayside wells nos. Q-1, R-1, S-1: For East Bay Municipal Utility District, variously paginated. Galloway, D.L., Jones, D.R., and Ingebritsen, S.E., 1999, Land subsidence in the United States: U.S. Geological Survey Circular 1182, 177 p., available at https://pubs.er.usgs.gov/publication/cir1182. Galloway, D.L., Jones, D.R., and Ingebritsen, S.E., 2000, Measuring land subsidence from space: U.S. Geological Survey Fact Sheet 051-00, 4 p., available at https://pubs.usgs.gov/fs/fs-051-00/. Gleason, J.D., Friedman, Irving, and Hanshaw, B.B., 1969, Extraction of dissolved carbonate species from natural water for carbon-isotope analysis: U.S. Geological Survey Professional Paper 650-D, p. D248-D250, available at https://pubs.er.usgs.gov/publication/pp650D. Gonfiantini, R., 1978, Standards for stable isotope measurements in natural compounds: Nature, v. 271, p. 534-536, accessed April 4, 2012, at https://doi.org/10.1038/271534a0. Graymer, R.W., 2000, Geologic map and map database of the Oakland metropolitan area, Alameda, Contra Costa, and San Francisco Counties, California: U.S. Geological Survey Miscellaneous Field Studies MF-2342, 1 sheet, scale 1:50,0000, available at http://geopubs.wr.usgs.gov/map-mf/mf2342/. Graymer, R.W., 2003, Long-term history of the Hayward fault zone, in Ponce, D.A., Bürgmann, Roland, Graymer, R.W., Lienkaemper, J.J., Moore, D.E., and Schwartz, D.P., eds., Proceedings of the Hayward Fault workshop, eastern San Francisco Bay area, California, September 19-20, 2003: U.S. Geological Survey Open-File Report 03-485, p. 14, available at https://pubs.er.usgs.gov/publication/ofr03485. Graymer, R.W., Jones, D.L., and Brabb, E.E., 1995, Geologic map of the Hayward fault zone, Contra Costa, Alameda, and Santa Clara Counties, California—A digital database: U.S. Geological Survey Open-File Report 95-597, 8 p., https://pubs.usgs.gov/of/1995/of95-597/. Grossinger, Robin, and Brewster, Elise, 2003, A geographic history of the San Lorenzo Creek watershed—Landscape patterns underlying human activities in the lands of the Yrgin; Mission San Jose Rancho, 1794-1834; San Leandro, San Lorenzo, and San Ramon Ranchos, 1830s-1849; towns of Hayward's, Squattersville, and Mt. Eden, 1850s; Cities of Hayward, San Lorenzo, and Castro Valley: San Francisco Estuary Institute Contribution 85, 23 p., accessed at http://www.sfei.org/sites/default/files/biblio_files/SLor_ Heaton, T.H.E., and Vogel, J.C., 1981, "Excess air" in groundwater: Journal of Hydrology, v. 50, p. 201-216, https://doi.org/10.1016/0022-1694(81)90070-6. Heaton, T.H.E., Talma, A.S., and Vogel, J.C., 1986, Dissolved gas paleotemperatures and 18O variations derived from groundwater near Uitenhage, South Africa: Quaternary Research, v. 25, no. 1, p. 79-88, https://doi.org/10.1016/0033-5894(86)90045-1. Hem, J.D., 1985, Study and interpretation of chemical characteristics of natural water (3rd ed.): U.S. Geological Survey Water-Supply Paper 2254, 263 p., available at https://pubs.er.usgs.gov/publication/wsp2254. International Atomic Energy Agency, 1981, Statistical treatment of environmental isotope data in precipitation: Technical Report Series No. 206, 255 p.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Izbicki, J.A., 1991, Chloride sources in a California coastal aquifer, in Peters, H.J., ed., Ground water in the Pacific Rim countries: American Society of Civil Engineers, Irrigation and Drainage Division Proceedings, p. 71-77. Izbicki, J.A., 1996, Seawater intrusion in a coastal California aquifer: U.S. Geological Survey Fact Sheet 125-96, 4 p., available at https://pubs.er.usgs.gov/publication/fs12596. Izbicki, J.A, and Martin, Peter, 1997, Use of isotopic data to evaluate recharge and geologic controls on the movement of ground water in Las Posas Valley, Ventura County, California, U.S. Geological Survey Water-Resources Investigations Report 97-4035, 12 p., available at https://pubs.er.usgs.gov/publication/wri974035. Izbicki, J.A., Michel, R.L., and Martin, Peter, 1992, 3H and 14C as tracers of ground-water recharge, in Engman, Ted, Irrigation and drainage—Saving a threatened resource— In search of solutions, Proceedings of the Irrigation and Drainage Sessions at Water Forum '92: Baltimore, Md., Proceedings of the American Society of Civil Engineers (ASCE) National Conference on Irrigation and Drainage, p. 122-127, accessed April 4, 2012, at https://pubs.er.usgs.gov/publication/70016870. Izbicki, J.A, Borchers, J.W., Leighton, D.A., Kulongoski, J.T., Fields, Latoya, Galloway, D.L., and Michel, R.L., 2003, Hydrogeology and geochemistry of aquifers underlying the San Lorenzo and San Leandro areas of the East Bay Plain, Alameda County, California: U.S. Geological Survey Water-Resources Investigations Report 2002-4259, 71 p., available at https://pubs.er.usgs.gov/publication/wri024259. Jones, S.R., and Garbarino, J.R., 1999, Methods of analysis by U.S. Geological Survey National Water Quality Laboratory—Determination of arsenic and selenium in water and sediment by graphite furnace atomic adsorption spectrometry: U.S. Geological Survey Open-File Report 98-639, 39 p., available at https://pubs.er.usgs.gov/publication/ofr98639. Kendall, Carol, and Coplen, T.B., 2001, Distribution of oxygen-18 and deuterium in river waters across the United States: Hydrological Processes, v. 15, p. 1363-1393, accessed May 16, 2012, at https://doi.org/10.1002/hyp.217. Kipfer, Rolf, Aeschbach-Hertig, Werner, Peeters, Frank, and Stute, Marvin, 2002, Noble gases in lakes and ground waters, chap. 14 in Porcelli, D.P., Ballentine, C.J., and Wieler, Rainer, eds., Noble gases in geochemistry and cosmochemistry: Mineralogical Society of America, v. 47, p. 615-700. Koltermann, C.E., and Gorelick, S.M., 1992, Paleoclimatic signature in terrestrial flood deposits: Science, v. 256, p. 1775-1782, accessed April 4, 2012, at https://doi.org/10.1126/science.256.5065.1775. Kulongoski, J.T., Hilton, D.R., and Izbicki, J.A., 2003, Helium isotope studies in the Mojave Desert, California— Implications for groundwater chronology and regional seismicity: Chemical Geology, v. 202, nos. 1-2, p. 95-113, https://doi.org/10.1016/j.chemgeo.2003.07.002. Land, Michael, Everett, R.R., and Crawford, S.M., 2002, Geologic, hydrologic, and water-quality data from multiple-well monitoring sites in the Central and West Coast basins, Los Angeles County, California, 1995- 2000: U.S. Geological Survey Open-File Report 2001- 277, 178 p., available at https://pubs.er.usgs.gov/publication/ofr01277. Lopp, L.E., 1981, An appraisal of surface-water quality in the Alameda Creek Basin, California, October 1974- June 1979: U.S. Geological Survey Water-Resources Investigations Report 81-46, 33 p., available at https://pubs.er.usgs.gov/publication/wri8146. Lu, Zhong, and Danskin, W.R., 2001, InSAR analysis of natural recharge to define structure of a groundwater basin, San Bernardino, California: Geophysical Research Letters, v. 28, no. 13, p. 2661-2664, https://doi.org/10.1029/2000GL012753. Lucas, L.L., and Unterweger, M.P., 2000, Comprehensive review and critical evaluation of the half-life of tritium: Journal of Research of the National Institute of Standards and Technology, v. 105, no. 4, p. 541-549, accessed April 14, 2012, at http://dx.doi.org/10.6028/jres.105.043. Luhdorff and Scalmanini Consulting Engineers, 2003, East Bay Plain aquifer test project—South East Bay Plain and Niles Cone groundwater basins: Luhdorff and Scalmanini Consulting Engineers, LSCE No. 01-1-080, 39 p. Mamyrin, B.A., and Tolstikhin, I.N., 1984, Helium isotopes in nature: Developments in Geochemistry, v. 3, 273 p. Manov, G.G., and Curtiss, L.F., 1951, The half-life of carbon 14: Journal of Research of the National Bureau of Standards, v. 46, no. 4, p. 328-333, accessed April 14, 2012, at http://dx.doi.org/10.6028/jres.046.037. Mariño, M.A., 2001, Conjunctive management of surface water and groundwater, in Regional management of water resources (Proceedings of symposium held during IAHS Scientific Assembly, 6th, at Maastricht, The Netherlands, July 2001): International Association of Hydrological Sciences Publication no. 268, p. 165-173, accessed April 10, 2012, at http://hydrologie.org/redbooks/a268/ iahs_268_0165.pdf. Maslonkowski, D., 1988, Hydrogeology of the San Leandro and San Lorenzo alluvial cones of the Bay Plain groundwater basin, Alameda County, California: San Jose State University, M.S. thesis, 143 p.

References Cited    39 Mazor, E., 1972, Paleotemperatures and other hydrological parameters deduced from noble gases dissolved in groundwaters; Jordan Rift Valley, Israel: Geochimica et Cosmochimica Acta, v. 36, no. 12, p. 1321- 1336, accessed May 16, 2012, at https://doi.org/10.1016/0016-7037(72)90065-8. Michel, R.L., 1976, Tritium inventories of the world's oceans and their implications: Nature, v. 263, p. 103-106. Moran, J., and Halliwell, M.S., 2004, Characterizing groundwater recharge—A comprehensive isotopic approach: American Water Works Association Research Foundation, Report 90941F, 228 p. Muir, K.S., 1993, Classification of groundwater recharge potential in the East Bay Plain area, Alameda County, California: Alameda County Flood Control and Water Conservation District, C-92-320, 10 p. Muir, K.S., 1996a, Groundwater recharge in the East Bay Plain area, Alameda County, California: Alameda County Flood Control and Water Conservation District, 17 p. Muir, K.S., 1996b, Groundwater discharge in the East Bay Plain area, Alameda County, California: Alameda County Flood Control and Water Conservation District, 17 p. Muir, K.S., 1997, Ground water quality in the East Bay Plain: Alameda County Department of Public Works, 7 p. National Oceanic and Atmospheric Administration, 2012, National centers for environmental information—Daily summaries station details, Hayward air terminal, CA US: National Oceanic and Atmospheric Administration web page, accessed May 11, 2012, at https://www. ncdc.noaa.gov/cdo-web/datasets/GHCND/stations/ GHCND:USW00093228/detail. Ozima, Minoru, and Podosek, F.A., 1983, Noble gas geochemistry: Cambridge University Press, 304 p. Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of total phosphorus by a Kjedahl digestion method and an automated colorimetric finish that includes dialysis: U.S. Geological Survey OpenFile Report 92-146, 39 p., available at https://pubs.er.usgs.gov/publication/ofr92146. Piper, A.M., 1944, A graphic procedure in the geochemical interpretation of water-analyses: EOS, Transactions American Geophysical Union, v. 25, no. 6, p. 914-928, accessed at http://onlinelibrary.wiley.com/doi/10.1029/ TR025i006p00914/full. Piper, A.M., and Garrett, A.A., 1953, Native and contaminated ground waters in the Long Beach-Santa Ana area, California: U.S. Geological Survey Water-Supply Paper 1136, 320 p., available at https://pubs.er.usgs.gov/publication/wsp1136. Plummer, L.N., Prestemon, E.C., and Parkhurst, D.L., 1991, An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH: U.S. Geological Survey Water-Resources Investigations Report 91-4078, 227 p., available at https://pubs.er.usgs.gov/publication/wri914078. Poreda, R.J., Cerling, T.E., and Salomon, D.K., 1988, Tritium and helium isotopes as hydrologic tracers in a shallow unconfined aquifer: Journal of Hydrology, v. 103, no. 1-2, p. 1-9, accessed May 16, 2012, at https://doi.org/10.1016/0022-1694(88)90002-9. R Development Core Team, 2008, R—A language and environment for statistical computing: R Foundation for Statistical Computing, http://www.R-project.org. Rantz, S.E., and others, 1982, Measurement and computation of streamflow; Volume 1, Measurement of stage and discharge: U.S. Geological Survey Water-Supply Paper 2175, 284 p., available at https://pubs.er.usgs.gov/publication/wsp2175_vol1. Rogers, J.D., and Figuers, S.H., 1991, Engineering geologic site characterization of the greater Oakland-Alameda area, Alameda and San Francisco Counties, California: Pleasant Hill, Calif., Rogers/Pacific, Inc., 59 p., https://doi.org/10.13140/RG.2.1.4785.6809. San Francisco Bay Regional Water Quality Control Board, 1999, East Bay plain groundwater basin beneficial use evaluation report, Final report: San Francisco Bay Regional Water Quality Control Board, 108 p., accessed March 1, 2003, at http://www.waterboards.ca.gov/sanfranciscobay/ water_issues/available_documents/ebplain.pdf. Schlosser, Peter, Stute, Martin, Sonntag, Christian, and Münnich, K.O., 1989, Tritiogenic 3He in shallow groundwater: Earth and Planetary Science Letters, v. 94, no. 3-4, p. 245-256, accessed May 16, 2012, at https://doi.org/10.1016/0012-821X(89)90144-1. Sneed, Michelle, Orlando, P.v.P., Borchers, J.W., Everett, Rhett, Solt, Mike, McGann, Mary, Lowers, Heather, and Mahan, Shannon, 2015, Lithostratigraphic, boreholegeophysical, hydrogeologic, and hydrochemical data from the East Bay Plain, Alameda County, California: U.S. Geological Survey Data Series 890, 56 p., available at https://doi.org/10.3133/ds890.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Solomon, D.K., Poreda, R.J., Schiff, S.L., and Cherry, J.A., 1992, Tritium and helium-3 as groundwater age tracers in the Borden aquifer: Water Resources Research, v. 28, no. 3, p. 741-755, accessed May 16, 2012, at https://doi.org/10.1029/91WR02689. Solomon, D.K., Hunt, A., and Poreda, T.J., 1996, Source of radiogenic helium-4 in shallow aquifers—Implications for dating young groundwater: Water Resources Research, v. 32, no. 6, p. 1805-1813, accessed May 16, 2012, at https://doi.org/10.1029/96WR00600. Solomon, D.K., and Cook, P.G., 2000, 3H and 3He, in Cook, P.G., and Herczeg, A., eds., Environmental tracers in subsurface hydrology: Dordrecht, Netherlands, Kluwer Academic Publishers, p. 397-424. Struzeski, T.M., DeGiacomo, W.J., and Zayhowski, E.J., 1996, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of dissolved aluminum and boron in water by inductively coupled plasma-atomic emission spectrometry: U.S. Geological Survey Open-File Report 96-149, 17 p., available at https://pubs.er.usgs.gov/publication/ofr96149. Stork, S.V., and Sneed, Michelle, 2002, Houston-Galveston Bay area, Texas, from space—A new tool for mapping land subsidence: U.S. Geological Survey Fact Sheet 110-02, 6 p., available at https://pubs.er.usgs.gov/publication/fs11002. Stute, M., 1989, Noble gases in groundwater—Regulation of paleotemperature and investigation of the dynamics of groundwater flow systems: Universitat Heidelberg, Ph.D. dissertation, 138 p. Stute, M., Sonntag, C., Deák, J., Schlosser, P., 1992, Helium in deep circulating groundwater in the Great Hungarian plain—Flow dynamics and crustal and mantle helium fluxes: Geochimica et Cosmochimica Acta, v. 56, no. 5, p. 2051-2067, https://doi.org/10.1016/0016-7037(92)90329-H. Stute, Martin, Clark, J.F., Schlosser, Peter, and Broecker, W.S., 1995, A 30,000 yr continental paleotemperature record derived from noble gases dissolved in groundwater from the San Juan Basin, New Mexico: Quaternary Research, v. 43, no. 2, p. 209-220, https://doi.org/10.1006/qres.1995.1021. Stute, Martin, and Schlosser, Peter, 2000, Atmospheric noble gasses, chap. 11 in Cook, P.G., and Herczeg, A.L., eds., Environmental tracers in subsurface hydrology: Boston, Kluwer Academic Publishers, p. 349-377. Taylor, C.B., and Roether, Wolfgang, 1982, A uniform scale for reporting low-level tritium measurements in water: International Journal of Applied Radiation and Isotopes, v. 33, no. 5, p. 377-382, https://doi.org/10.1016/0020-708X(82)90152-1. Thatcher, L.L., Janzer, V.J., and Edwards, K.W., 1977, Methods for determination of radioactive substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations Book 5, Chapter A5, 95 p., available at https://pubs.er.usgs.gov/publication/twri05A5. Tiedje, J.M., 1988, Ecology of denitrification and dissimilatory nitrate reduction to ammonium, in Zehnder, A.J.B., ed., Environmental microbiology of anaerobes: New York, John Wiley and Sons, p. 179-244. Torgersen, T., and Clarke, W.B., 1987, Helium accumulation in groundwater—III, Limits on helium transfer across the mantle-crust boundary beneath Australia and the magnitude of mantle degassing: Earth and Planetary Science Letters, v. 84, no. 2-3, p. 345-355, https://doi.org/10.1016/0012-821X(87)90098-7. U.S. Environmental Protection Agency, variously dated, National primary drinking water regulations: U.S. Environmental Protection Agency web page, accessed March 1, 2003, at https://www.epa.gov/dwstandardsregulations#List. Verhagen, Balthazar, Geyh, M.A., Fröhlich, Klaus, and Wirth, Klaus, 1991, Isotope hydrological methods for the quantitative evaluation of ground water resources in arid areas—Development of a methodology: Bonn, Germany, Federal Ministry of Economic Cooperation, 164 p. Wallace, R.E., 1990, General features, in Wallace, R.E., ed., The San Andreas fault system, California: U.S. Geological Survey Professional Paper 1515, p. 3-12, available at https://pubs.er.usgs.gov/publication/pp1515. Werner, C., Wegmüller, U., Strozzi, T., and Wiesmann, A., 2000, GAMMA SAR and interferometric processing software, ERS-ENVISAT Symposium, 4th, Gothenburg, Sweden, October 16-20, 2000 [Proceedings]: European Space Agency, abs. 51, p. 56, accessed August 3, 2002, at http://www.gamma-rs.ch/. Wilde, F.D., ed., 1998, Field measurements: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A6, with sec. 6.0-6.8, accessed November 2002 at http://pubs.water.usgs.gov/twri9A6/. Wilde, F.D., ed., 1999a, Collection of water samples: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A4, 231 p., accessed November 2002 at https://water.usgs.gov/owq/FieldManual/ chapter4/pdf/Archive/chapter4.pdf. Wilde, F.D., ed., 1999b, Processing of water samples: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A5, with sections 5.6.1.F, 5.6.4.A, and 5.6.4.B, 233 p., accessed November 2002 at https://water.usgs.gov/owq/FieldManual/chapter5/html/ Ch5_contents.html.

Appendix 1    41 Appendix 1.  Location and Construction Data and Water-Level Measurements Collected by the U.S. Geological Survey During 2002 for Wells Drilled in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Table 1-1.  Location and construction data and water-level measurements collected by the U.S. Geological Survey during fall 2002 for wells drilled in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California. [Water-level data shown in bold are used in figures 3 and 4. Abbreviations: bls, below land surface; bmsl, below mean sea level; F, flowing; ft, foot; mm/dd/yyyy, month/day/year; NAVD 88, North American Vertical Datum of 1988; USGS, U.S. Geological Survey; mean sea level is 6.75 ft above the station datum for Station 9414750, Alameda, Calif., of 3.56 ft (NAVD 88); —, no data; greater than] State well number USGS identification number Well type Primary aquifer contributing water to well Land-surface altitude, NAVD 88 (ft) Depth to upper-most perforation interval (ft) Depth to bottom-most perforation interval (ft) Well depth (ft bls) Depth to water (ft bls) Waterlevel altitude NAVD 88 (ft) Date of water-level measurement (mm/dd/yyyy) Waterlevel (ft bmsl)* Upper aquifer system 4S/1W-17M7 373457122002102 Observation Centerville-Fremont 03/19/2002 4S/1W-17M7 373457122002102 Observation Centerville-Fremont 10/28/2002 -4.8 4S/1W-17M8 373457122002103 Observation Newark 03/22/2002 4S/1W-17M8 373457122002103 Observation Newark 10/28/2002 4S/1W-18R1 373313122002401 Observation Newark — — 04/16/2002 4S/1W-19E2 373418122011901 Observation Newark — — 05/01/2002 4S/1W-19J6 373409122003601 Observation Newark — — 05/01/2002 4S/1W-19N14 373349122011803 Observation Newark — — 05/06/2002 4S/1W-20H3 373422121592201 Observation Newark — — 04/16/2002 4S/1W-20J6 373404121591901 Observation Newark — — 05/06/2002 4S/1W-20R1 373356121593302 Observation Newark — — 06/06/2002 4S/1W-28D12 373348121590401 Observation Newark — — 05/03/2002 4S/1W-29A6 373345121591701 Observation Newark — — 05/03/2002 4S/1W-29C7 373543121595901 Observation Newark — — 05/06/2002 4S/1W-29C8 373345121595101 Observation Newark — — 05/06/2002 4S/1W-30A5 373341122003703 Observation Newark — — 05/02/2002 4S/1W-30E4 373329122011802 Observation Newark — — 05/02/2002 4S/2W-12K9 373545122015002 Observation Fremont 11/05/2002 -10.3 4S/2W-12K10 373545122015003 Observation Centerville 11/05/2002 -9.0 4S/2W-12K11 373545122015004 Observation Newark 11/05/2002 Appendix 1

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins State well number USGS identification number Well type Primary aquifer contributing water to well Land-surface altitude, NAVD 88 (ft) Depth to upper-most perforation interval (ft) Depth to bottom-most perforation interval (ft) Well depth (ft bls) Depth to water (ft bls) Waterlevel altitude NAVD 88 (ft) Date of water-level measurement (mm/dd/yyyy) Waterlevel (ft bmsl)* Upper aquifer system—Continued 4S/2W-13E3 373514122022101 Observation Newark — — 04/25/2002 4S/2W-13P4 373447122021904 Observation Newark 03/27/2002 4S/2W-13P4 373447122021904 Observation Newark 10/28/2002 4S/2W-13P6 373447122021902 Observation Fremont 03/26/2002 -1.0 4S/2W-13P6 373447122021902 Observation Fremont 10/28/2002 -7.4 4S/2W-13P7 373447122021903 Observation Centerville 03/26/2002 -0.6 4S/2W-13P7 373447122021903 Observation Centerville 10/28/2002 -7.0 4S/2W-14D5 373521122033103 Observation Fremont 11/06/2002 -10.1 4S/2W-14D6 373521122033104 Observation Centerville 11/06/2002 -9.9 4S/2W-14D7 373521122033105 Observation Newark 11/06/2002 4S/2W-14H3 373517122024301 Observation Newark — — 05/02/2002 4S/2W-14L6 373507122031901 Observation Newark — — 04/17/2002 4S/2W-14R3 373441122024101 Observation Newark — — 04/16/2002 4S/2W-23J2 373403122024501 Observation Newark — — 05/06/2002 4S/2W-24F11 373421122021301 Observation Newark — — 04/16/2002 4S/2W-25D3 373343122022602 Observation Newark — — 04/26/2002 4S/2W-26K6 373321122025002 Observation Newark — — 05/01/2002 Deep aquifer 3S/2W-20L20 373912122065001 Public production Deep 03/07/2002 3S/2W-29L6 373832122064801 Public production Deep 10/30/2002 -9.8 3S/2W-32D2 373759122064901 Observation Deep — — -5.7 11/08/2002 -16.0 3S/2W-35J11 373733122025901 Observation Deep — — -4.5 11/13/2002 -14.8 4S/1W-7P4 373543122010101 Observation Deep — — -0.1 11/13/2002 -10.4 4S/1W-17M6 373457122002101 Observation Deep 03/19/2002 -3.8 4S/1W-17M6 373457122002101 Observation Deep 10/28/2002 -8.2 4S/1W-28D1 373348121590503 Observation Deep — — -1.3 11/08/2002 -11.6 Table 1-1.  Location and construction data and water-level measurements collected by the U.S. Geological Survey during fall 2002 for wells drilled in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California. Water—Continued [Water-level data shown in bold are used in figures 3 and 4. Abbreviations: bls, below land surface; bmsl, below mean sea level; F, flowing; ft, foot; mm/dd/yyyy, month/day/year; NAVD 88, North American Vertical Datum of 1988; USGS, U.S. Geological Survey; mean sea level is 6.75 ft above the station datum for Station 9414750, Alameda, Calif., of 3.56 ft (NAVD 88); —, no data; greater than]

Appendix 1    43 State well number USGS identification number Well type Primary aquifer contributing water to well Land-surface altitude, NAVD 88 (ft) Depth to upper-most perforation interval (ft) Depth to bottom-most perforation interval (ft) Well depth (ft bls) Depth to water (ft bls) Waterlevel altitude NAVD 88 (ft) Date of water-level measurement (mm/dd/yyyy) Waterlevel (ft bmsl)* Deep aquifer—Continued 4S/1W-30A2 373341122003701 Observation Deep — — -0.4 11/08/2002 -10.7 4S/1W-30E3 373329122011801 Observation Deep — — -0.2 11/08/2002 -10.5 4S/2W-2H1 373648122023601 Private production Deep 03/20/2002 -5.7 4S/2W-3L1 373646122042701 Private production Deep -9.1 11/07/2002 -19.4 4S/2W-4E1 373708122055101 Public production Deep 03/07/2002 -8.4 4S/2W-4F3 373702122052201 Observation Deep 03/21/2002 -7.4 4S/2W-4F6 373700122052301 Public production Deep 03/07/2002 -6.1 4S/2W-4R1 373638122045901 Public production Deep -2.4 10/29/2002 -12.7 4S/2W-10E4 373601122042901 Observation Deep -1.4 11/04/2002 -11.7 4S/2W-12C1 373620122015901 Public production Deep 03/20/2002 -5.5 4S/2W-12K8 373545122015001 Observation Deep -0.9 11/05/2002 -11.2 4S/2W-13P5 373447122021901 Observation Deep 03/26/2002 -2.3 4S/2W-13P5 373447122021901 Observation Deep 10/28/2002 -8.9 4S/2W-14D3 373521122033101 Observation Deep -2.2 11/06/2002 -12.5 4S/2W-14D4 373521122033102 Observation Deep -1.5 11/06/2002 -11.8 4S/2W-15L5 373457122041001 Observation Deep -1.4 10/29/2002 -11.7 4S/2W-25D1 373343122022601 Observation Deep — — 11/13/2002 -10.3 4S/2W-26K4 373321122024901 Observation Deep — — 11/13/2002 -9.9 Table 1-1.  Location and construction data and water-level measurements collected by the U.S. Geological Survey during fall 2002 for wells drilled in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California. —Continued [Water-level data shown in bold are used in figures 3 and 4. Abbreviations: bls, below land surface; bmsl, below mean sea level; F, flowing; ft, foot; mm/dd/yyyy, month/day/year; NAVD 88, North American Vertical Datum of 1988; USGS, U.S. Geological Survey; mean sea level is 6.75 ft above the station datum for Station 9414750, Alameda, Calif., of 3.56 ft (NAVD 88); —, no data; greater than]

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins

Appendix 2    45 Appendix 2.  U.S. Geological Survey National Water-Quality Laboratory Analytical Methods and Reporting Levels for Analysis of Groundwater and Surface-Water Samples Fishman, M.J., ed., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey Open-File Report 93-125, 217 p., available at https://pubs.er.usgs.gov/publication/ofr93125. Fishman, M.J., ed., and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of WaterResources Investigations 05-A1, 545 p., available at https://pubs.er.usgs.gov/publication/twri05A1. Gleason, J.D., Friedman, Irving, and Hanshaw, B.B., 1969, Extraction of dissolved carbonate species from natural water for carbon-isotope analysis: U.S. Geological Survey Professional Paper 650-D, p. D248-D250, available at https://pubs.er.usgs.gov/publication/pp650D. Jones, S.R., Garbarino, J.R., 1999, Methods of analysis by U.S. Geological Survey National Water Quality Laboratory—Determination of arsenic and selenium in water and sediment by graphite furnace atomic adsorption spectrometry: U.S. Geological Survey Open-File Report 98-639, 39 p., available at https://pubs.er.usgs.gov/publication/ofr98639. Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of total phosphorus by a Kjedahl digestion method and an automated colorimetric finish that include dialysis: U.S. Geological Survey OpenFile Report 92-146, 39 p., available at https://pubs.er.usgs.gov/publication/ofr92146. Struzeski, T.M., DeGiacomo, W.J., and Zayhowski, E.J., 1996, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of dissolved aluminum and boron in water by inductively coupled plasma-atomic emission spectrometry: U.S. Geological Survey Open-File Report 96-149, 17 p., available at https://pubs.er.usgs.gov/publication/ofr96149. Thatcher, L.L., Janzer, V.J., and Edwards, K.W., 1977, Methods for determination of radioactive substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations 05-A5, 95 p., available at https://pubs.er.usgs.gov/publication/twri05A5. Samples were collected by the U.S. Geological Survey during 2002-03. Samples from domestic and public production wells were collected using existing pumping systems; samples from unused wells and monitoring wells were collected using a small diameter, stainless steel, submersible pump (Wilde, 1999a). The surface-water sample from Dry Creek was collected using the pump-sampling method described in Wilde (1999a). Field parameters (pH, specific conductance, temperature, and alkalinity) were measured for each sample collected by the U.S. Geological Survey as described in Wilde (1999a). Dissolved oxygen was measured in the field by the U.S. Geological Survey using colorimetric methods (CHEMets Kit K-7512 or K7501). Selected samples were processed in the field and sent to the U.S. Geological Survey's National Water-Quality Laboratory (NWQL) for inorganic analysis. Samples for inorganic analysis of dissolved constituents were filtered in the field using a capsule filter having a pore size of 0.45 mm (Wilde, 1999b). Nutrients were preserved by chilling at 4 oC and were analyzed within seven days. Trace elements were preserved by acidification to pH <2.0. Stable isotope samples were sent to the USGS Reston Stable Isotope Laboratory. Carbon isotope samples were sent to the University of Waterloo Environmental Isotope Laboratory. Dissolved gas samples and tritium samples were sent to the University of Rochester Rare Gas Facility. Analytical methods and associated reporting limits are listed in table 2-1. References Cited Beukens, R.P., 1992, Radiocarbon accelerator mass spectrometry—Background, precision and accuracy, in Taylor, R.E., Long, Austin, and Kra, R.S., eds., Radiocarbon after four decades: New York, Springer-Verlag, p. 230-239, accessed April 4, 2012, at https://doi.org/10.1007/978-1-4757-4249-7_16. Coplen, T.B., Wildman, J.D., and Chen, Julie, 1991, Improvements in the gaseous hydrogen-water equilibration technique for hydrogen isotope-ratio analysis: Analytical Chemistry, v. 63, no. 9, p. 910-912, accessed April 4, 2012, at https://doi.org/10.1021/ac00009a014. Epstein, S., and Mayeda, T., 1953, Variation of O18 content of waters from natural sources: Geochimica et Cosmochimica Acta, v. 4, no. 5, p. 213-224, accessed May 16, 2012, at https://doi.org/10.1016/0016-7037(53)90051-9. Appendix 2

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Table 2-1.  U.S. Geological Survey National Water-Quality Laboratory analytical methods and reporting levels for analysis of groundwater samples. [ASF, automated-segmented flow; mg/L, milligram per liter; pCi/L, picocurie per mil; std, standard; ºC, degrees Celsius; μS/cm, microsiemen per centimeter at 25 ºC; μg/L, microgram per liter] Constituent Methodology Reporting limit Reference Field parameters pH pH electrode 0.1 std units Fishman and Friedman, 1989 Specific conductance Wheatstone bridge 1.0 μS/cm Fishman and Friedman, 1989 Alkalinity Titrimetry with sulfuric acid 1.0 mg/L Fishman and Friedman, 1989 Dissolved oxygen Colorimetric indigo-carmine 0.006 mg/L White and others, 1990 Major ions Calcium, dissolved Inductively coupled plasma 0.011 mg/L Fishman, 1993 Chloride, dissolved Ion chromatography 0.08 mg/L Fishman and Friedman, 1989 Dissolved solids Gravimetric, residue on evaporation at 180 ºC 10.0 mg/L Fishman and Friedman, 1989 Magnesium, dissolved Inductively coupled plasma 0.008 mg/L Fishman, 1993 Potassium, dissolved Atomic adsorption, flame 0.09 mg/L Fishman and Friedman, 1989 Silica, dissolved Colorimetry, ASF 0.48 mg/L Fishman and Friedman, 1989 Sodium, dissolved Inductively coupled plasma 0.06 mg/L Fishman, 1993 Sulfate, dissolved Ion chromatography 0.11 mg/L Fishman and Friedman, 1989 Nutrients Nitrite, dissolved Colorimetry, ASF, 0.006 mg/L Fishman, 1993 Nitrite + nitrate, dissolved Colorimetry, ASF, cadmium reduction-diazotization 0.047 mg/L Fishman, 1993 Ammonia, dissolved Colorimetry, ASF, salicylate-hypochlorite 0.041 mg/L Fishman, 1993 Ammonia + organic nitrogen, dissolved Colorimetry, ASF, microkjeldahl digestion 0.10 mg/L Patton and Truitt, 1992 Phosphorus, dissolved Colorimetry, ASF, microkjeldahl digestion 0.05 mg/L Patton and Truitt, 1992 Orthophosphate, dissolved Colorimetry, ASF, phosphomolybdate 0.018 mg/L Fishman, 1993 Trace elements Arsenic, dissolved Graphite furnace atomic adsorption 2.0 μg/L Jones and Garbarino, 1999 Barium, dissolved Inductively coupled plasma 0.9 μg/L Fishman, 1993 Boron, dissolved Inductively coupled plasma 13.0 μg/L Struzeski and others, 1996 Bromide, dissolved Colorimetry, ASF 0.01 mg/L Fishman and Friedman, 1989 Fluoride, dissolved ASF, ion-selective electrode 0.16 mg/L Fishman and Friedman, 1989 Iodide, dissolved Colorimetry, ASF, ceric-arseneous 0.001 mg/L Fishman and Friedman, 1989 Iron, dissolved Inductively coupled plasma 10.0 μg/L Fishman, 1993 Manganese, dissolved Inductively coupled plasma 3.2 μg/L Fishman, 1993 Isotopes Carbon-14 Accelerator mass spectrometry 0.3 percent Beukens, R.P., 1992 Carbon-13/carbon-12 Mass spectrometry 0.15 per mil Gleason and others, 1969 Deuterium/protium Mass spectrometry 2.0 per mil Coplen and others, 1991 Oxygen-18/oxygen-16 Mass spectrometry 0.2 per mil Epstein and Mayeda, 1953 Tritium Electrolytic enrichment and liquid scintillation 1.0 pCi/L Thatcher and others, 1977 White, A.F., Peterson, M.L., and Soibau, R.D., 1990, Measurement and interpretation of low levels of dissolved oxygen in ground water: Ground Water, v. 28, p. 584-590. Wilde, F.D., ed., 1999a, Collection of water samples: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A4, 231 p., accessed November 2002 at https://water.usgs.gov/owq/FieldManual/ chapter4/pdf/Archive/chapter4.pdf. Wilde, F.D., ed., Radtke, D.B., Gibs, Jacob, and Iwatsubo, R.T., 1999b, Processing of water samples: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A5, with sections 5.6.1.F, 5.6.4.A, and 5.6.4.B, 233 p., accessed November 2002 at https://water.usgs.gov/owq/FieldManual/chapter5/html/ Ch5_contents.html.

Appendix 3    47 Appendix 3.  Aquifer Mineralogy, Niles Cone Groundwater Subbasin, Alameda County, California (fig. 3-1), suggesting that this may be an important reaction between groundwater and aquifer materials. On the basis of scanning electron microscopy with spectral analysis, small amounts of chlorite were present in aquifer deposits. Highly soluble chloride minerals are not likely to be present within freshwater aquifers underlying the Niles Cone groundwater subbasin. Dissolution of chlorapatite, or recrystallization into the more common form apatite, may explain small increases in chloride concentrations that alter chloride-to-bromide and chloride-to-iodide ratios (fig. 11) as groundwater flows through aquifer deposits. These increases are not nearly as large as chloride concentrations measured in water from underlying aquifers or increases resulting from seawater intrusion. References Cited Amonette, J.E., and Zelazny, L.W., eds., 1994, Quantitative methods in soil mineralogy—Proceedings of a symposium sponsored by Division S-9 of the Soil Science Society of America, San Antonio, Texas, October 23-24, 1990: Soil Science Society of America, 452 p. Izbicki, J.A, Borchers, J.W., Leighton, D.A., Kulongoski, J.T., Fields, Latoya, Galloway, D.L., and Michel, R.L., 2003, Hydrogeology and geochemistry of aquifers underlying the San Lorenzo and San Leandro areas of the East Bay Plain, Alameda County, California: U.S. Geological Survey Water-Resources Investigations Report 2002-4259, 71 p., available at https://pubs.er.usgs.gov/publication/wri024259. Appendix 3 The elemental composition of cores and cuttings was determined by inductively coupled plasma-mass spectrometry (table 3-1; Briggs and Meier, 2002). The mineralogy of selected cores and cuttings was determined by X-ray diffraction (table 3-2; Amonette and Zelazny, 1994). Images of selected materials were obtained using a scanning electron microscope equipped with a spectral analyzer (Amonette and Zelazny, 1994). Mineralogic analyses were done on cuttings and core material from the Deep aquifer at a depth of 517 ft below land surface at well 14D3 and on a composite of coarse-grained outcrop material at Horseshoe Lake recharge pond (old gravel quarry) sampled from 2 ft and 20 ft below land surface, on the northwest shore (table 3-1). Mineralogic data were used as inputs to the computer program NETPATH for interpretation of carbon-14 data discussed in this report. Analysis of the uranium (U) and thorium (Th) content of coarse-grained sediments in both the Deep aquifer and surface deposits were used as a basis for estimating the magnitude of in situ generation of He and He isotopic composition. Results are similar to previous analyses of core material from the East Bay Plain groundwater subbasin (Izbicki and others, 2003) in that quartz is the dominant mineral and a smaller amount of feldspar minerals are present. Primary and secondary minerals are listed in table 3-1. Scanning electron microscope images show little evidence of weathering or dissolution of mineral grains in cores and cuttings (fig. 3-1). Grain morphology and spectral analysis suggest that the bulk of the aquifer is composed of relatively nonreactive quartz. This is consistent with X-ray diffraction data in table 3-1. Scanning electron microscope images collected as part of this study show evidence of secondary precipitation of calcite Northwest shore of Horseshoe Lake (Quarry Lakes) lithic fragment—quartz, potassium feldspar, albite 14D3 deep sand, overview—Q, quartz; A, albite; L, lithic fragment; K, potassium feldspar; M, mica 14D3 deep fines—calcite precipitation Figure 3-1.  Scanning electron microscopy (SEM) images of typical mineral grains from core material from selected sites in the Niles Cone groundwater subbasin, Alameda County, California [µm, micrometers].

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Table 3-1.  Elemental composition of samples from Lake Chad well (4S/2W-14D3) at 517 feet deep and outcrop on northwest shore of Quarry Lakes, Niles Cone groundwater subbasin, Alameda County, California. [ft, foot; kg, kiliogram; mg, milligram; NW, northwest; w/o, without; x, present; less than; ?, uncertain; —, not present] Sample identifier 4S/2W-14D3 (bulk) NW Quarry Lakes composite 4S/2W-14D3 (deep sand w/o fines) 4S/2W-14D3 (deep fines) Sample description Detection limit Drilling mud impregnated core, 517 ft deep Outcrop— sandy gravel near recharge ponds Washed and sieved core, 517 ft Hydrometer fines— native formation plus drilling mud from core, 517 ft deep Elements (mg/kg) Gold Ag

Arsenic As Barium Ba Beryllium Be Bismuth Bi Calcium Ca 8,280 13,400 6,620 11,700 Cadmium Cd Cerium Ce Cobalt Co Chromium Cr Ceasium Cs Copper Cu Iron Fe 27,200 31,500 18,700 41,200 Gallium Ga Potassium K 8,810 11,100 7,540 14,400 Lanthanum La Lithium Magnessium Mg 13,000 15,600 9,840 19,400 Manganese Mn Molybdenum Mo Sodium Na 14,200 16,900 16,200 38,100 Niobium Nb Nickel Ni Phosphorus P 27,000 Lead Pb Rubidium Rb Antimony Sb Scandium Sc Strontium Sr Tantalum Ta Thorium Th Titanium Ti 2,450 3,210 1,990 3,120 Thallium Tl Uranium U Vanadium Tungsten W Yttrium Y Zinc Zn

Appendix 3.  Aquifer Mineralogy, Niles Cone Groundwater Subbasin, Alameda County, California    49 Table 3-2.   Mineralogical composition and optical observations of samples from Lake Chad well (4S/2W-14D3) at 517 feet deep and outcrop on northwest shore of Quarry Lakes, Niles Cone groundwater subbasin, Alameda County, California. [ft, foot; kg, kiliogram; mg, milligram; NW, northwest; w/o, without; x, present; less than; ?, uncertain; —, not present] Sample identifier 4S/2W-14D3 (bulk) NW Quarry Lakes composite 4S/2W-14D3 (deep sand w/o fines) 4S/2W-14D3 (deep fines) Sample description Detection limit Drilling mud impregnated core, 517 ft deep Outcrop— sandy gravel near recharge ponds Washed and sieved core, 517 ft Hydrometer fines— native formation plus drilling mud from core, 517 ft deep Minerals (percent abundance) Quartz — Potassium feldspar — — Chlorite — Muscovite — Kaolinite —

? — — Monmorillonite — ? <2? — — Kao-mont mixed — Plagioclase feldspar — Hematite — ? ? — — Calcite — — — — Optical observations — Gravel—rounded rock fragments with some clay and iron coatings; fine-grained material-quartz sand, sandstone fragments. Gravel—rounded rock fragments with some large quartz and feldspar blocky fragments; finegrained material—rock fragments, quartz, clay coatings. Angular to semi-rounded quartz. Fine-grained quartz, large sheets of material. Minerals from X-ray diffraction Quartz — Albite — Kaolinite/montmorillonite — Orthoclase, brian — — — Orthoclase — — — — Clinochlore — Muscovite — Calcite — — — — — Kaolinite — ? — — Montmorillonite — — — Hematite — ? ? — — Minerals from scanning electron microscope (major or minor component) Organics — None None None None Lithics — — Major — — Quartz — Major Major Major Major Albite — Major Minor Major — Mica — Major — Major Minor Sodium phosphate — — — — Major Potassium feldspar — — — — Minor Andalusite barite — Minor — — — Ilmenite — Minor Minor Minor — Iron oxide — Minor Minor Minor — Rutile — Minor — — Minor Apatite — Minor — — — Clays — Minor Minor Minor — Mica — Major Minor Major — Calcite — — — — Minor Anorthite — — Major — —

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins

Appendix 4    51 Appendix 4.  Streamflow Data Collected by the U.S. Geological Survey during April 2002 Appendix 4 Table 4-1.  Streamflow data collected by the U.S. Geological Survey during April 2002, Alameda Creek, California. [ft3/s, cubic foot per second; N, North; W, West; °, degrees; ′, minutes; ″, seconds; —, no data] Site number (as shown in figure 3) Distance downstream from site 1, in miles April 24, 2002, morning April 24, 2002, afternoon April 25, 2002, midday Discharge, in ft3/s Gage height, in feet Rating Discharge, in ft3/s Gage height, in feet Rating Discharge, in ft3/s Gage height, in feet Rating Temperature, in degrees Celsius

Good Poor Poor Good Fair — — — — — — — — — Estimated — Fair — — — Poor — Good Poor — — — Poor Fair Poor Fair Fair — — — Good — — — Fair — Good — Good — Good *Site 1 is located at 37°33′57.13052″ N., 121°59′50.33553″ W.

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins

Appendix 5    53 Appendix 5.  Physical Property, Major-Ion, Trace-Element, and Isotopic Data for Groundwater, StreamWater, and Precipitation Samples Collected and Analyzed by the U.S. Geological Survey Appendix 5 Table 5-1.  Physical property, major-ion, selected trace-element, and isotopic data for groundwater, stream-water, and precipitation samples collected and analyzed by the U.S. Geological Survey, southern East Bay Plain and Niles Cone groundwater subbasins, Alameda County, California, 2002-03. [Data analyzed by U.S. Geological Survey (USGS). Location of sites shown in figure 1. Abbreviations: A, at; ACWD, Alameda County Water District; BLDG, building; CaCO3, calcium carbonate; E, approximate value; hhmm, 24-hour time format in hours and minutes; mg/L, milligram per liter; mm/dd/yyyy, month/day/year; N, nitrogen; PO4, phosphate; SiO2, silicon dioxide; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25 °C; actual value less than value shown; —, no data] State well number Aquifer Local name USGS identification number Date (mm/dd/yyyy) Time (hhmm) Dissolved oxygen (mg/L) pH, field (standard units) pH, lab (standard units) Specific conduc­ tance field (μS/cm) Specific conduc­ tance lab (μS/cm) Tempera­ ture water 4S/1W-17M7 Upper aquifer system Kraftile 373457122002102 03/19/2002 4S/1W-17M8 Upper aquifer system Kraftile 373457122002103 03/22/2002 4S/2W-12K10 Upper aquifer system Pacific 373545122015003 11/05/2002 E862 4S/2W-13P4 Upper aquifer system Rowland Park 373447122021904 03/27/2002 1,030 1,050 4S/2W-13P6 Upper aquifer system Rowland Park 373447122021902 03/26/2002 1,280 1,290 4S/2W-13P7 Upper aquifer system Rowland Park 373447122021903 03/27/2002 1,210 1,220 3S/2W-20L20 Deep aquifer Hayward D2 373912122065001 10/29/2002 3S/2W-29L6 Deep aquifer MMWA 4 373832122064801 10/30/2002 4S/1W-17M6 Deep aquifer Kraftile 373457122002101 03/19/2002 4S/2W-2H1 Deep aquifer BART 373648122023601 03/20/2002 4S/2W-3L1 Deep aquifer Danone 373646122042701 03/27/2002 4S/2W-4E1 Deep aquifer Hayward E 373708122055101 10/30/2002 E847 4S/2W-4F3 Deep aquifer City Yard B deep MW 373702122052201 03/21/2002 4S/2W-4R1 Deep aquifer Hayward C 373638122045901 10/29/2002 4S/2W-10E4 Deep aquifer Tidewater 373601122042901 11/04/2002 E806 4S/2W-12C1 Deep aquifer Whipple 373620122015901 03/20/2002 4S/2W-12K8 Deep aquifer Pacific 373545122015001 11/05/2002 4S/2W-13P5 Deep aquifer Rowland Park 373447122021901 03/26/2002 1,430 1,470 4S/2W-14D3 Deep aquifer Lake Chad 373521122033101 04/16/2003 4S/2W-14D4 Deep aquifer Lake Chad 373521122033102 11/06/2002 4S/2W-15L5 Deep aquifer Contempo Park 373457122041001 10/29/2002 1,550 1,520 Dry Creek near Union City — — 373630122010501 04/17/2003 USGS 373425121582101 PRECIP SAMPLER ACWD ROOFTOP INFLATION BLDG A NILES — — 373425121582101 11/08/2002 — — — —

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins State well number Date (mm/dd/yyyy) Hardness, total (mg/L as CaCO3) Calcium, dissolved (mg/L as Ca) Magnesium, dissolved (mg/L as Mg) Potassium, dissolved (mg/L as K) Sodium, dissolved (mg/L as Na) Alkalinity, dissolved (Gran titration) (mg/L as CaCO3) Chloride, dissolved (mg/L as Cl) 4S/1W-17M7 03/19/2002 4S/1W-17M8 03/22/2002 4S/2W-12K10 11/05/2002 4S/2W-13P4 03/27/2002 4S/2W-13P6 03/26/2002 4S/2W-13P7 03/27/2002 3S/2W-20L20 10/29/2002 3S/2W-29L6 10/30/2002 4S/1W-17M6 03/19/2002 4S/2W-2H1 03/20/2002 4S/2W-3L1 03/27/2002 4S/2W-4E1 10/30/2002 4S/2W-4F3 03/21/2002 4S/2W-4R1 10/29/2002 4S/2W-10E4 11/04/2002 4S/2W-12C1 03/20/2002 4S/2W-12K8 11/05/2002 4S/2W-13P5 03/26/2002 4S/2W-14D3 04/16/2003 4S/2W-14D4 11/06/2002 4S/2W-15L5 10/29/2002 Dry Creek near Union City 04/17/2003 USGS 373425121582101 PRECIP SAMPLER ACWD ROOFTOP INFLATION BLDG A NILES 11/08/2002 — — — — — — — Table 5-1.  Physical property, major-ion, selected trace-element, and isotopic data for groundwater, stream-water, and precipitation samples collected and analyzed by the U.S. Geological Survey, southern East Bay Plain and Niles Cone groundwater subbasins, Alameda County, California, 2002-03.—Continued [Data analyzed by U.S. Geological Survey (USGS). Location of sites shown in figure 1. Abbreviations: A, at; ACWD, Alameda County Water District; BLDG, building; CaCO3, calcium carbonate; E, approximate value; hhmm, 24-hour time format in hours and minutes; mg/L, milligram per liter; mm/dd/yyyy, month/day/year; N, nitrogen; PO4, phosphate; SiO2, silicon dioxide; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25 °C; actual value less than value shown; —, no data]

Appendix 5    55 State well number Date (mm/dd/yyyy) Fluoride, dissolved (mg/L as F) Silica, dissolved (mg/L as SiO2) Sulfate, dissolved (mg/L as SO4) Nitrogen, ammonia, dissolved (mg/L as N) Nitrogen, ammonia + organic, dissolved (mg/L as N) Nitrogen, nitrate + nitrite, dissolved (mg/L as N) Nitrogen, nitrite, dissolved (mg/L as N) 4S/1W-17M7 03/19/2002 4S/1W-17M8 03/22/2002 4S/2W-12K10 11/05/2002 4S/2W-13P4 03/27/2002 4S/2W-13P6 03/26/2002 4S/2W-13P7 03/27/2002 3S/2W-20L20 10/29/2002 E0.08 3S/2W-29L6 10/30/2002 4S/1W-17M6 03/19/2002 E0.07 4S/2W-2H1 03/20/2002 E0.004 4S/2W-3L1 03/27/2002 4S/2W-4E1 10/30/2002 4S/2W-4F3 03/21/2002 4S/2W-4R1 10/29/2002 E0.006 4S/2W-10E4 11/04/2002 E0.08 4S/2W-12C1 03/20/2002 4S/2W-12K8 11/05/2002 E0.004 4S/2W-13P5 03/26/2002 E0.1 E0.005 4S/2W-14D3 04/16/2003 E0.08 4S/2W-14D4 11/06/2002 4S/2W-15L5 10/29/2002 Dry Creek near Union City 04/17/2003 USGS 373425121582101 PRECIP SAMPLER ACWD ROOFTOP INFLATION BLDG A NILES 11/08/2002 — — — — — — — Table 5-1.  Physical property, major-ion, selected trace-element, and isotopic data for groundwater, stream-water, and precipitation samples collected and analyzed by the U.S. Geological Survey, southern East Bay Plain and Niles Cone groundwater subbasins, Alameda County, California, 2002-03.—Continued [Data analyzed by U.S. Geological Survey (USGS). Location of sites shown in figure 1. Abbreviations: A, at; ACWD, Alameda County Water District; BLDG, building; CaCO3, calcium carbonate; E, approximate value; hhmm, 24-hour time format in hours and minutes; mg/L, milligram per liter; mm/dd/yyyy, month/day/year; N, nitrogen; PO4, phosphate; SiO2, silicon dioxide; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25 °C; actual value less than value shown; —, no data]

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins State well number Date (mm/dd/yyyy) Phosphorous, total, dissolved (mg/L as P) Phosphorous, ortho, dissolved (mg/L as PO4) Solids, residue at 180 °C, dissolved (mg/L) Solids, sum of constituents, dissolved (mg/L) Arsenic, dissolved (μg/L as As) Barium, dissolved (μg/L as Ba) Boron, dissolved (μg/L as B) Bromide, dissolved (mg/L as Br) 4S/1W-17M7 03/19/2002 4S/1W-17M8 03/22/2002 4S/2W-12K10 11/05/2002 E0.03 4S/2W-13P4 03/27/2002 E0.02 4S/2W-13P6 03/26/2002 E0.03 4S/2W-13P7 03/27/2002 E0.04 3S/2W-20L20 10/29/2002 3S/2W-29L6 10/30/2002 4S/1W-17M6 03/19/2002 4S/2W-2H1 03/20/2002 E0.05 4S/2W-3L1 03/27/2002 E0.05 4S/2W-4E1 10/30/2002 4S/2W-4F3 03/21/2002 E0.04 4S/2W-4R1 10/29/2002 E0.04 4S/2W-10E4 11/04/2002 E0.03 4S/2W-12C1 03/20/2002 E0.05 4S/2W-12K8 11/05/2002 4S/2W-13P5 03/26/2002 1,080 4S/2W-14D3 04/16/2003 4S/2W-14D4 11/06/2002 4S/2W-15L5 10/29/2002 Dry Creek near Union City 04/17/2003 E0.03 USGS 373425121582101 PRECIP SAMPLER ACWD ROOFTOP INFLATION BLDG A NILES 11/08/2002 — — — — — — — — Table 5-1.  Physical property, major-ion, selected trace-element, and isotopic data for groundwater, stream-water, and precipitation samples collected and analyzed by the U.S. Geological Survey, southern East Bay Plain and Niles Cone groundwater subbasins, Alameda County, California, 2002-03.—Continued [Data analyzed by U.S. Geological Survey (USGS). Location of sites shown in figure 1. Abbreviations: A, at; ACWD, Alameda County Water District; BLDG, building; CaCO3, calcium carbonate; E, approximate value; hhmm, 24-hour time format in hours and minutes; mg/L, milligram per liter; mm/dd/yyyy, month/day/year; N, nitrogen; PO4, phosphate; SiO2, silicon dioxide; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25 °C; actual value less than value shown; —, no data]

Appendix 5    57 State well number Date (mm/dd/yyyy) Iodide, dissolved (mg/L as I) Iron, dissolved (μg/L as Fe) Manganese, dissolved (μg/L as Mn) Strontium, dissolved (μg/L as Sr) Delta deuterium (per mil) Delta oxygen-18 (per mil) Carbon-14 (percent modern) Carbon-13/ Carbon-12 ratio (per mil) Radiocarbonage (years before present) 4S/1W-17M7 03/19/2002 <10 -46 -5.91 -15.31 4S/1W-17M8 03/22/2002 <10 -43.6 -5.38 -12.04 4S/2W-12K10 11/05/2002 <10 1,140 -42.5 -6.25 -16.21 1,500 4S/2W-13P4 03/27/2002 <10 -44.4 -5.78 -16.2 4S/2W-13P6 03/26/2002 <10 1,800 -49.6 -6.51 -14.85 1,200 4S/2W-13P7 03/27/2002 <10 1,690 -44.7 -6.14 -15.09 3S/2W-20L20 10/29/2002 -45.3 -6.89 -15.01 7,700 3S/2W-29L6 10/30/2002 -48.5 -7.2 -15.04 12,000 4S/1W-17M6 03/19/2002 <10 1,330 -49.2 -6.81 -14.47 2,100 4S/2W-2H1 03/20/2002 -46.2 -7.23 -14.52 8,300 4S/2W-3L1 03/27/2002 <10 -49.8 -7.07 -13.65 5,100 4S/2W-4E1 10/30/2002 -49.1 -7.27 -15.29 12,000 4S/2W-4F3 03/21/2002 <10 -50.4 -7.13 -13.52 5,600 4S/2W-4R1 10/29/2002 -46.6 -7.02 -13.64 3,900 4S/2W-10E4 11/04/2002 E6 1,100 -48.8 -7.2 -14.04 5,100 4S/2W-12C1 03/20/2002 -48.4 -7.11 -13.26 5,800 4S/2W-12K8 11/05/2002 <10 -48.8 -7.12 -13.67 6,400 4S/2W-13P5 03/26/2002 <10 2,100 -50.5 -7.01 -15.11 1,300 4S/2W-14D3 04/16/2003 <10 -49.2 -7.14 -13.85 5,700 4S/2W-14D4 11/06/2002 <10 -49.6 -7.33 -15.1 13,000 4S/2W-15L5 10/29/2002 E10 -50.2 -7.32 -15.08 15,000 Dry Creek near Union City 04/17/2003 <10 — — — — — USGS 373425121582101 PRECIP SAMPLER ACWD ROOFTOP INFLATION BLDG A NILES 11/08/2002 — — — — -45.8 -7.65 — — — 1Alkalinity calculated using incremental titration, as milligrams per liter. Table 5-1.  Physical property, major-ion, selected trace-element, and isotopic data for groundwater, stream-water, and precipitation samples collected and analyzed by the U.S. Geological Survey, southern East Bay Plain and Niles Cone groundwater subbasins, Alameda County, California, 2002-03.—Continued [Data analyzed by U.S. Geological Survey (USGS). Location of sites shown in figure 1. Abbreviations: A, at; ACWD, Alameda County Water District; BLDG, building; CaCO3, calcium carbonate; E, approximate value; hhmm, 24-hour time format in hours and minutes; mg/L, milligram per liter; mm/dd/yyyy, month/day/year; N, nitrogen; PO4, phosphate; SiO2, silicon dioxide; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25 °C; actual value less than value shown; —, no data]

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins

Appendix 6    59 Appendix 6.  Noble Gas and Tritium Data for Groundwater Samples Collected and Analyzed by the U.S. Geological Survey Appendix 6 Table 6-1.  Noble gas and tritium data for groundwater samples collected from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, March-October, 2002-03. [cm3/kg, cubic centimeter per kilogram; ID, identification; mm/dd/yyyy, month/day/year; nd, not determined; RA, 3He/4He ratio of air (1.84×10-6); Rs, 3He/4He ratio of sample; USGS, U.S. Geological Survey; µcm3/kg, micro-cubic centimeter per kilogram; +/-, plus or minus; less than; greater than; helium-4 age calculated with crustal flux (J0) 3.0×10-6; Δ Ne, excess air (neon oversaturation); —, no data] State well number USGS site ID Sample date (mm/dd/yyyy) Noble gas recharge temperature, in degrees Celsius Salinity, in grams per kilograms RS/RA Helium-3 (3He), in × 10-8 µcm3/kg Helium-4 (4He) in µcm3/kg Neon (Ne), in µcm3/kg Upper aquifer system 4S/1W-17M7 373457122002102 03/19/2002 15.4 +/- 0.8 4S/1W-17M8 373457122002103 03/22/2002 19.2 +/- 0.8 4S/2W-13P4 373447122021904 03/27/2002 11.4 +/- 0.7 4S/2W-13P6 373447122021902 03/26/2002 16.6 +/-0.9 4S/2W-13P7 373447122021903 03/27/2002 10.6 +/- 0.7 Deep aquifer 3S/2W-20L20 373912122065001 10/29/2002 15.5 +/- 0.7 3S/2W-29L6 373832122064801 10/30/2002 18.1 +/- 0.8 4S/1W-17M6 373457122002101 03/19/2002 12.0 +/- 0.7 4S/2W-10E4 373601122042901 11/04/2002 14.3 +/- 0.8 1,494.6 4S/2W-12C1 373620122015901 03/20/2002 10.1 +/- 0.7 4S/2W-12K8 373545122015001 11/05/2002 13.1 +/- 0.7 4S/2W-13P5 373447122021901 03/26/2002 15.9 +/- 0.8 4S/2W-15L5 373457122041001 10/29/2002 10.5 +/- 0.9 2,396.4 4S/2W-02H1 373648122023601 03/20/2002 14.1 +/- 0.7 4S/2W-03L1 373646122042701 03/27/2002 13.5 +/- 0.7 4S/2W-04E1 373708122055101 10/30/2002 16.7 +/- 0.8 1,130.1 4S/2W-04F6 — 10/31/2002 15.1 +/- 0.8 4S/2W-04R1 373638122045901 10/29/2002 15.4 +/- 0.8 4S/2W-14D3 373521122033101 04/16/2003 13.4 +/- 0.7 2,274.9

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins State well number USGS Site ID Sample date (mm/dd/yyyy) Krypton (Kr), in µcm3/kg Argon (Ar), in cm3/kg) ∆ Ne (percent) Helium-4 (4He) Age*, in years before present Tritium, in tritium units Tritium/Helium-3 residence times, in years before present Upper aquifer system—Continued 4S/1W-17M7 373457122002102 03/19/2002 4S/1W-17M8 373457122002103 03/22/2002

4S/2W-13P4 373447122021904 03/27/2002 4S/2W-13P6 373447122021902 03/26/2002 4S/2W-13P7 373447122021903 03/27/2002

Deep aquifer—Continued 3S/2W-20L20 373912122065001 10/29/2002 nd 3S/2W-29L6 373832122064801 10/30/2002 >50 4S/1W-17M6 373457122002101 03/19/2002

4S/2W-10E4 373601122042901 11/04/2002 >50 4S/2W-12C1 373620122015901 03/20/2002 >50 4S/2W-12K8 373545122015001 11/05/2002 >50 4S/2W-13P5 373447122021901 03/26/2002 4S/2W-15L5 373457122041001 10/29/2002 >50 4S/2W-02H1 373648122023601 03/20/2002 >50 4S/2W-03L1 373646122042701 03/27/2002 nd 4S/2W-04E1 373708122055101 10/30/2002 >50 4S/2W-04F6 — 10/31/2002 >50 4S/2W-04R1 373638122045901 10/29/2002 >50 4S/2W-14D3 373521122033101 04/16/2003 >50 Table 6-1.  Noble gas and tritium data for groundwater samples collected from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, March-October, 2002-03.—Continued [cm3/kg, cubic centimeter per kilogram; ID, identification; mm/dd/yyyy, month/day/year; nd, not determined; RA, 3He/4He ratio of air (1.84×10-6); Rs, 3He/4He ratio of sample; USGS, U.S. Geological Survey; µcm3/kg, micro-cubic centimeter per kilogram; +/-, plus or minus; less than; greater than; helium-4 age calculated with crustal flux (J0) 3.0×10-6; Δ Ne, excess air (neon oversaturation); —, no data]

Appendix 7    61 Appendix 7.  Measured and Interpreted Carbon-13 and Carbon-14 Data for Groundwater Samples Collected and Analyzed by the U.S. Geological Survey Appendix 7 Table 7-1.  Measured and interpreted carbon-13 and carbon-14 data for groundwater samples collected from selected wells in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California, March-October, 2002. [m, meter; pmC, percent modern carbon; data interpreted using the NETPATH computer program (Plummer and others, 1991); uncorrected ages calculated using the calculated Ao value of 69.37 pmC] State well number Local name Distance along flow path, in feet Well construction Carbon-13/carbon-12, in per mil Carbon-14 Top of screened interval, in feet below land surface Bottom of screened interval, in feet below land surface Measured Interpreted* Measured, in percent modern carbon Uncorrected in years before present Interpreted age*, in years before present Interpreted groundwater flow rate, in feet per year 4S/2W-12K8 Pacific -13.67 — — — 4S/2W-12C1 Whipple 2,800 -13.26 -12.99 2,979 4S/2W-3L1 Danone 14,100 -13.65 -14.08 2,259 1,963 4S/2W-4F3 Well B 18,700 -13.52 -14.00 2,773 2,358 4S/2W-4E1 Well E 21,000 -15.29 -15.34 9,315 7,340 3S/2W-29L6 Mt. Eden 29,500 -15.04 -15.12 8,802 7,121 State well number Mass transfer and cation exchange, in millimoles Silicates Carbonates Cation exchange Clay precipitation Carbon Hydrogen sulfide (H2S) Gypsum 4S/2W-12K8 — — — — — — — 4S/2W-12C1 -0.14517 -0.25078 4S/2W-3L1 -0.17239 -0.45914 -0.13475 -0.07064 4S/2W-4F3 -0.20884 -0.06165 -0.08435 4S/2W-4E1 -0.34908 -0.1557 -3.50761 -0.42209 3S/2W-29L6 -0.26514 -0.00092 -2.45955 -0.35702

Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins Table 7-2.  Chemical reactions used to interpret carbon-14 data. Process Representative chemical equation Comments Cation exchange (Ca, Mg)+2 + Na2clay ↔ 2Na+ + (Ca, Mg)clay Simulated as exchange of equal parts dissolved Ca+2 and Mg+2 for each part Na+ on the clay-exchange sites. Carbonate precipitation HCO3 - + Ca+2 ↔ CaCO3 + H+ and HCO3 - + Mg+2 ↔ MgCO3 + H+ Simulated as separate phases. Precipitation of only small amounts of MgCO3 were needed to balance the mass-balance model. In the environment, Mg+2 probably substitutes for Ca+2 in variable amounts within carbonate minerals. Silicate weathering CaAl2Si2O8 + 8H+ → Ca+2 + 2Al+3 + 2H4SiO40 and NaAlSi3O8 + 4H2O + 4H+ → Al3+ + 3H4SiO40 + Na+ and KAlSi3O8 + 4H2O + 4H+ → Al+3 + 3H4SiO40 + K+ Simulated as dissolution of anorthite with smaller amounts of albite and potassium feldspar included to satisfy mass-balance constraints. In some settings, dissolution of chlorite or sepiolite also may occur. Although other primary silicates also may dissolve, thermodynamic data show that the system is supersaturated with respect to biotite (mica) and that dissolution of this mineral will not occur. Sulfate reduction 2CH2O + SO4 -2 → HS- + 2HCO3 Simulated as oxidation of organic matter having a δ13C of -21 per mil. Clay precipitation 0.33Na+ + 2.33Al(OH) + 3.67H4SiO40 + 2H+ → Na0.33Al2.33Si3.67O10(OH)2 + 12H2O or 2Al+3 + H2O + 2H4SiO40 → Al2Si2O5(OH)4 + 6H+ Only small differences in mass transfer result from simulation of clay precipitation as montmorillonite or as kaolinite. Both minerals detected by X-ray diffraction.

Publishing support provided by the U.S. Geological Survey Science Publishing Network, Sacramento Publishing Service Center For more information concerning the research in this report, contact the Director, California Water Science Center U.S. Geological Survey 6000 J Street, Placer Hall Sacramento, California 95819 https://ca.water.usgs.gov ISSN 2328-0328 (online) https://doi.org/10.3133/sir20185003

Teague and others—Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins, Alameda County, California (ver. 1.1, February 2019)—Scientific Investigations Report 2018-5003 ISSN 2328-0328 (online) https://doi.org/10.3133/sir20185003

Plates & figures from the original