LAND APPLICATION OF WASTEWATER AND ITS EFFECT ON GROUND-WATER QUALITY IN THE LIVERMORE-AMADOR VALLEY, ALAMEDA COUNTY, CALIFORNIA By Marc A. Sylvester U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 82-4100 Prepared in cooperation with the ALAMEDA COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT, ZONE 7 IT) O I \O O Oon March 1983 UNITED STATES DEPARTMENT OF THE INTERIOR JAMES G. WATT, SECRETARY GEOLOGICAL SURVEY Dallas L. Peck, Director For additional information, Copies of this report can be write to: purchased from: District Chief Open-File Services Section Water Resources Division Western Distribution Branch U.S. Geological Survey U.S. Geological Survey 2800 Cottage Way, Room W-2235 Box 25425, Federal Center Sacramento, Calif. 95825 Lakewood, Colo. 80225 Telephone: (303) 234-5888 CONTENTS Page Abstract---------------------------------------------------------------- 1 Introduction------------------------------------------------------------ 3 Background--------------------------------------------------------- 3 Purpose and scope-------------------------------------------------- 3 Well-numbering system---------------------------------------------- 7 Acknowledgments---------------------------------------------------- 7 Location and description of study area---------------------------------- 10 Hydrologic and geologic features----------------------------------- 10 Wastewater application areas--------------------------------------- 11 Live rmo re----------------------------------------------------- 11 Pleasanton---------------------------------------------------- 16 Castlewood---------------------------------------------------- 16 Dublin-San Ramon and Camp Parks Military Reservation---------- 18 Veterans Administration Hospital------------------------------ 18 Coast Manufacturing Company----------------------------------- 18 Data collection and methods--------------------------------------------- 21 Results and discussion-------------------------------------------------- 24 Areawide assessment------------------------------------------------ 24 Rainfall- ----- - -- ______ ___ __ _ 24 Ground-water movement----------------------------------------- 25 Ground-water quality------------------------------------------ 30 Site-specific assessment------------------------------------------- 37 Areal variations in ground-water quality in wastewater application areas------------------------------------------- 38 Castlewood and Pleasanton wastewater application areas-------------------------------------------------- 38 Dublin-San Ramon and Camp Parks Military Reservation wastewater application area---------------------------- 39 Veterans Administration Hospital wastewater application area--------------------------------------- 39 Livermore wastewater application areas------------------- 40 Temporal variations in ground-water quality in wastewater application areas------------------------------------------- 41 Castlewood wastewater application area------------------- 41 Pleasanton wastewater application area------------------- 41 Dublin-San Ramon and Camp Parks Military Reservation wastewater application area---------------------------- 42 Veterans Administration Hospital wastewater application area--------------------------------------- 43 Livermore wastewater application areas------------------- 44 Areas and times of water-quality impairment------------------------ 45 Future sampling programs------------------------------------------------ 47 Summary and conclusions------------------------------------------------- 50 References cited-------------------------------------------------------- 53 III ILLUSTRATIONS [Plates are in pocket] Plate 1. Graphs showing comparison of water quality at selected wells in wastewater application areas: A. Castlewood and Pleasanton B. Dublin-San Ramon and Camp Parks Military Reservation C. Veterans Administration Hospital D. Livermore Plate 2. Graphs showing changes in water level, specific conductance, pH, dissolved chloride, and dissolved nitrate, water years 1975 through 1980, for selected wells in wastewater application areas: A. Castlewood and Pleasanton B. Dublin-San Ramon and Camp Parks Military Reservation C. Veterans Administration Hospital D. Livermore Page Figures 1-2. Maps showing: 1. Location of study area------------------------------ 4 2. Generalized geology--------------------------------- 12 3-6. Maps showing wastewater application areas: 3. Livermore------------------------------------------- 14 4. Castlewood and Pleasanton--------------------------- 17 5. Dublin-San Ramon and Camp Parks Military Reservation--------------------------------------- 19 6. Veterans Administration Hospital-------------------- 20 7. Map showing location of wells where water-quality samples were collected---------------------------------- 22 8. Graph showing annual precipitation at the Livermore County Fire Department for water years 1975-80---------- 24 9-12. Maps showing: 9. Median water levels and general directions of ground-water movement, September and October 1977- 26 10. Median water levels and general directions of ground-water movement, March and April 1979------- 28 11. Median concentrations of dissolved nitrate as N for 1976 water year-------------------------- 32 12. Median concentrations of dissolved nitrate as N for 1980 water year-------------------------- 34 IV TABLES Page Table 1. Information about wells located in or near wastewater application areas-- - ---- - --- -- - - ----- g 2. Comparison of water quality among wastewater application areas - - - 36 3. Quality of effluent from wastewater treatment plants in the Livermore-Amador Valley- - ---- _____ _ _ __ __ 37 4. Maximum contamination levels used for determining areas and times of water-quality impairment 46 5. Wells having water that exceeded maximum contamination levels- 48 6. Summary of major findings from site-specific assessment of ground-water quality in wastewater application areas 52 V CONVERSION FACTORS For readers who may prefer to use International System of Units (SI) rather than inch-pound units, the conversion factors for the terms used in this report are listed below: Multiply To obtain acres 4047 m2 (square meters) ft (feet) 0.3048 m (meters) gal/d (gallons per day) 0.003785 m3 /d (cubic meters per day) inches 25.4 mm (millimeters) Mgal/d (million gallons 3785 m3/d (cubic meters per day) per day) mi (miles) .609 km (kilometers) mi 2 (square miles) .59 km2 (square kilometers) pmho/cm (micromhos per pS (microsiemens per centimeter) centimeter) Other abbreviations used: MCL (maximum contaminant levels) mg/L (milligrams per liter) Degrees Celsius (°C) are converted to degrees Fahrenheit (°F) by using the formula: Temp °F = (temp °C x 1.8) + 32 ALTITUDE DATUM National Geodetic Vertical Datum of 1929 (NGVD of 1929): A geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called mean sea level. DEFINITION OF WATER YEAR Water year is a 12-month period ending September 30 and is designated by the year in which it ends. TRADE NAME DISCLAIMER The use of brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. VI LAND APPLICATION OF WASTEWATER AND ITS EFFECT ON GROUND-WATER QUALITY IN THE LIVERMORE-AMADOR VALLEY, ALAMEDA COUNTY, CALIFORNIA By Marc A. Sylvester ABSTRACT Ground-water quality, ground-water level, and rainfall data collected from 1975 through the 1980 water year were analyzed to determine the effects of land application of effluent from wastewater treatment plants on ground-water quality in the LivermorerAmador Valley. Annual rainfall varied markedly during the study: 1976 and 1977 water years had less than one-half the normal rainfall; 1978 and 1980 water years had greater than normal rainfall; and 1975 and 1979 water years had nearly normal rainfall. The directions of ground-water movement in the valley are generally the same as the directions of surface-water flow. Median concentrations of dissolved nitrate as N were greater than 10 milligrams per liter in most wells sampled in the Livermore wastewater application area near the Livermore Municipal Airport and in that part of the Pleasanton wastewater application area downgradient from and north of the percolation ponds. Median concentrations of dissolved nitrate as N were less than 8.0 milligrams per liter in most wells in areas not receiving wastewater applications. In the Castlewood, Pleasanton, and Veterans Administration Hospital waste- water application areas and in the upper aquifer in the Livermore wastewater application areas, values of specific conductance, pH, dissolved solids, and dissolved chloride were very similar to those characteristic of effluent from wastewater treatment plants in the Livermore-Amador Valley. In the Dublin-San Ramon and Camp Parks Military Reservation wastewater application area, values of specific conductance, dissolved solids, and dissolved chloride were about 3 to 4 times those characteristic of effluent from wastewater treatment plants in the Livermore-Amador Valley. An area-by-area assessment of areal and temporal variations in ground-water quality and ground-water levels in wastewater application areas showed that rainfall, soil, and geology appeared to be the main determinants of ground-water quality in the Castlewood wastewater application area and in the Dublin-San Ramon and Camp Parks Military Reservation wastewater application area. Wastewater application appeared