WATER-QUALITY CONDITIONS AND AN EVALUATION OF GROUND- AND
SURFACE-WATER SAMPLING PROGRAMS IN THE LIVERMORE-AMADOR VALLEY,
CALIFORNIA
By Stephen K. Sorenson, Patricia V. Cascos, and Roy L. Glass
U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 84-4352
Prepared in cooperation with
ALAMEDA COUNTY FLOOD CONTROL AND
WATER CONSERVATION DISTRICT, ZONE 7
O O
Sacramento, California 1985 UNITED STATES DEPARTMENT OF THE INTERIOR
DONALD PAUL MODEL, Secretary
GEOLOGICAL SURVEY
Dallas L. Peck, Director
For additional information Copies of this report write to: (tan be purchased from: Open-File Services Section District Chief Western Distribution Branch U.S. Geological Survey U.S. Geological Survey Federal Building, Room W-2234 Box 25424, Federal Center 2800 Cottage Way Denver, CO 80225 Sacramento, CA 95825 elephone: (303) 236-7476 CONTENTS
Page
Abstract ------1 Introduction ------2 Purpose ------2 Location and description of study area ------2 Previous studies ------2 Geologic features ------2 Hydrologic features ------4 Past and present land use------4 Water-resources development------5 Wastewater treatment ------5 Design and implementation of the monitoring network------6 Field and laboratory methods ------10 Water levels and ground-water movement------11 G round-water quality------14 Specific conductance ------15 Water types ------15 Chloride 16 Nitrate - ---- 16 Boron ------17 Total organic carbon ------17 Differences in water quality between shallow and deep wells------17 Streamflow -- 25 Surface-water quality ------25 Specific conductance ------25 Water types ------._-_------______---_____----. 25 Water-quality objectives ------28 Changes in the existing monitoring network------32 References cited ------34
Contents III LLUSTRATIONS
[Plates are in pocket]
Plates 1-9. Maps of Livermore-Amador Valley, California, showing: 1 Areas of hydrologic significance and subbasin boundaries. Water level and direction of ground-water movement, 1980. 3-7 Areal distribution of: 3. Specific conductanc^ in ground water. 4. Cationic water type* in ground water. 5. Percentage chloride of total anions in ground water. 6. Nitrate concentrations in ground water. 7. Mean boron concentrations in ground water. 8. Hydrographs of mean monthly discharge at surface-water stations, 1974-81. Pie diagrams of mean ionic composition of water at surface-water stations, 1980-81.
Page Figure 1. Map showing location of study area 3 2. Graph showing water levels at four wells over their period of record ------12 Schematic plots showing variations i i water level, specific conductance, calcium, magnesium, sodium, alkalinity, sulfate, chloride, and nitrate at paired shallow-deep wells ------20 Schematic plot showing variability in specific conductance at the surface-water stations -- 26
TABLES
Page Table 1. Wells used for water-quality analyses 7 2. Surface-water sampling stations - 10 3. Wells with anionic water types that are not bicarbonate 16 4. Percentage of each major anion and cation at the surface- water stations, 1980-82 water years 27 5. Surface- and ground-water samples that exceeded water- quality objectives 29 6. Wells that have mean concentrations in excess of water- quality objectives ------31 7. Proposed key wells ------33
IV Contents CONVERSION FACTORS
For readers who prefer to use the International System of units (SI) rather than inch-pound units, the conversion factors for the terms used in this report are listed below:
Multiply By To obtain acre 0.4047 square hectometer acre-ft (acre-foot) 1,233 cubic meter ft (foot) 0.3048 meter ft 2 (square foot) 0.09294 square meter gal/min (gallon per minute) 0.2642 liter per minute mi (mile) 1.609 kilometer mi 2 (square mile) 2.590 square kilometer limho/cm (micromho per 1.000 microsiemens per centimeter) centimeter
Degree Fahrenheit is converted to degree Celsius by using the formula:
Temp °C = (temp °F-32)/1.8
Explanation of abbreviations mg/L Milligrams per liter yg/L Micrograms per liter meq/L Milliequivalents per liter
Chemical concentrations in water are given in milligrams per liter (mg/L) or micrograms per liter (ug/L). Milligrams per liter is a unit expressing the solute per unit volume (liter) of water. One thousand micrograms per liter is equivalent to one milligram per liter.
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.
Conversion Factors V WATER-QUALITY CONDITIONS AND AN EVALUATION OF GROUND- AND
SURFACE-WATER SAMPLING PROGRAMS IN THE
LIVERMORE-AMADOR VALLEY, CALIFORNIA
By Stephen K. Sorenson, Patricia V. Cascos, and Roy L. Glass
ABSTRACT ground water is the major problem with ground-water quality. Established water- quality objectives for dissolved solids A program to monitor the ground- and were exceeded in 70 of 137 wells. Con surface-water quality in the Livermore- centrations of dissolved nitrate in Amador Valley has been operated since excess of basin objectives and health the 1976 water year. As of 1982, standards also were detected in several this monitoring network consisted of areas in the valley. approximately 130 wells, about 100 of which were constructed specifically Water quality in both surface and for this program, and 9 surface water ground water is highly variable areal- stations. Increased demand on the ly. Magnesium to calcium magnesium ground water for municipal and indus bicarbonate ground water was detected trial water supply has caused a decline in areas where most of the high in water levels in the past resulting volume municipal wells are located. in a closed ground-water basin with no Large areas of sodium bicarbonate outflow. The result has been a gradual water occurred in the northern part buildup of salts from natural surface- of the valley. Surface water was water recharge and from land disposal mostly mixed cation, bicarbonate water of treated wastewater from several with the exception of the two stations waste-treatment plants. Results of this on Arroyo Las Positas, which had study show that salt buildup in the sodium chloride water.
Abstract 1 INTRODUCTION is 30-40 miles southeast of San Francisco (fig. 1). The ground-water basin covers about 63 mi 2 . Pleasanton, Water in the Livermore-Amador Valley Livermore, and Dublin are the major is both a vital and scarce resource. population centers. The rapidly expanding urban population demands not only more water but means of treatment and disposal of wastewater. Previous Studies Water use in the Livermore-Amador Val ley also has an impact on the water resources in the major ground-water Several studies of water-quality basin near the end of Alameda Creek, and water-resources development in the the only stream draining the valley. Livermore Valley have been done since Concerns for the quality and quantity the ^1950's. A report by the California of the limited water resources of this Department of Water Resources (1964) area have been the stimulus for scien was the first large scale study of tific study, litigation, and formation surfcice- and ground-water quality and of several private and governmental hydrology in the area. The California agencies since the early 1900's. This Department of Water Resources (1974) study is an outgrowth of recommenda discussed ground-water hydrology and tions and proposals from several of water quality with an emphasis on these previous studies, which indicated hydrologic subbasins and also pre that a comprehensive monitoring network sented a ground-water-flow model for of both surface water and ground water part of the Livermore Valley. One of was needed to document present condi the recommendations from that report tions and to detect long-term trends in was to install small-diameter, shallow- the valley's water resources. and medium-depth wells specifically for the purpose of monitoring water quality from known aquifers. That recommen Purpose dation was the basis for the present monitoring program. The primary purpose of this report Two studies of ground and surface is to describe water-quality condi waterf in the Alameda Creek drainage tions in surface and ground water in the Livermore-Amador Valley. The basis basirl have been published by the U.S. Geological Survey. Lopp (1981) made for this description is the data col an appraisal of surface-water quality lected, as a result of the cooperative in the Alameda Creek basin for the monitoring program between the U.S. period October 1974-June 1979. Geological Survey and the Alameda Sylvester (1983) studied land applica County Flood Control and Water Conser tion of wastewater and its effect on vation District, Zone 7, from 1975 ground-water quality in the Livermore- through 1982. An additional objective Amacor Valley. Sylvester's report of the report is to evaluate the cur deals with ground-water quality in rent monitoring program and to deter the wastewater-application areas in mine the frequency of sampling and much greater detail than is covered in type of analyses that will provide the this report. That report also deals best monitoring for future water- with time-trend variations in ground- quality protection. water quality in the wastewater- application areas. Location and Description of Study Area Geologic Features The study area includes Livermore and Amador Valleys and the southern The valley ground-water basin is part of San Ramon Valley. This area composed of alluvial deposits. The
2 Water-Quality Conditions in Livermore-Amador1 Valley STUDY AREA
0 20 40 60 80 100 MILES I I I I I I
FIGURE 1. - Location of study area.
Introduction maximum depth of these deposits is less Positas, which continues westward to than 100 feet in the eastern part of Arroyo Mocho north of Pleasanton. Livermore Valley and increases to Arroyo Mocho drains the uplands to the about 400 feet in the area east of southeast of the valley. After enter Pleasanton. The water-bearing alluvium ing the valley it runs northwest and in the valley is composed of sand, " west |until it joins Arroyo de la Laguna gravel, and clay and is moderately to just north of Pleasanton. Arroyo highly permeable. Confining beds of Valle drains the uplands south of silty clays are found at various depths the valley. It is impounded about throughout the valley, and are exten 1 mile upstream from the valley floor sive enough in some areas to define by Del Valle Dam, which is outside of totally separate aquifers. The valley the £tudy area. Arroyo Valle flows areas are underlain and are bordered generally west along the southern edge on the south by the Pleistocene and of the gravel pits, through the central Pliocene Livermore Formation (Clark, part of Pleasanton, and joins Arroyo 1930), which consists of sand, gravel, de la Laguna. South San Ramon Creek, and clay of moderate permeability. The which becomes Alamo Creek and then Pliocene Tassajara Formation, bor Alamc| Canal, flows south out of San dering the valley to the north, is Ramon Valley and becomes Arroyo de composed primarily of sandstone and la L^aguna at the confluence with claystone and is of low permeability. Arroyo Mocho. Arroyo de la Laguna, Both of these formations are from 4,000 the Only stream flowing out of the to 5,000 feet thick, and although the valley, connects with Alameda Creek. formations are water bearing, wells com Other streams contribute flow to the pleted in them are generally of low valley only during the rainy season. yield and produce moderately poor qual These include Tassajara Creek, ity sodium bicarbonate water. Non- Cayetano Creek, Collier Canyon Creek, water-bearing formations composed Arroyo Seco, and Dublin Creek. The mostly of marine sandstone, shale, Sout^ Bay aqueduct is located along siltstone, and conglomerate border the the southeastern edge of the valley. Amador and San Ramon Valleys on the Water; is discharged from this aqueduct west and the San Ramon Valley on the , periodically at Altamont Creek (prior east. to 1982), Arroyo Mocho, and Arroyo Valle, 1 A more detailed discussion of the , geology of the study area is contained ' The Livermore, Amador, and San in publications by the California Ramon Valleys have been divided into Department of Water Resources (1964 12 subbasins by the California Depart and 1974), and more recently in a ment of Water Resources (1974) (pi. 1). series of geologic maps by Dibblee (1980a, 1980b, and 1980c). A general These, subbasins were based on fault traces and hydrologic discontinuities. ized geologic map is presented by Mocho II, Amador, and Bernal are the Sylvester (1983). most | significant subbasins in terms of water capacity and usage.
Hydrologic Features
Past and Present Land Use Four major streams drain the uplands surrounding the valley (pi. 1). i Altamont Creek drains the northeastern The Spanish, who arrived in the early part of the valley, originating where 1800's, were the first western settlers Altamont Creek joins Arroyo Seco, and in the Livermore-Amador Valley area. the combined stream becomes Arroyo Las They established a large cattle indus-
4 Water-Quality Conditions in Livermore-Amador, Valley try that reached its peak in the 1850's domestic and industrial uses. These when about 50,000 cattle were in the agencies include California Water area. The first settlement, called Service Co., City of Livermore Water Amador, was established in the early Service, City of Pleasanton Water 1850's, and the 1860 census reported District, Valley Community Services that 513 people lived in the valley. District (now called Dublin-San Ramon In the late 1850's and early 1860's, Services District), and Alameda County agriculture became the predominant in Flood Control and Water Conservation dustry in the valley. The most common District, Zone 7 (hereinafter referred crops in the early years were to as Zone 7). wheat, barley, and hay. In the 1880's, irrigated agriculture became estab Until 1962, most of the water used in lished making it possible to grow such the Livermore-Amador Valley was pro crops as hops, sugar beets, tomatoes, vided by ground water, with small and grapes. Agriculture continues to quantities coming from local streams. be the predominant industry in the val This almost total dependence on ground ley, but has declined in recent years water caused a serious overdraft in the because of the loss of farmland to ur valley, with water levels dropping 100 banization and gravel-mining operations feet or more in some areas. In order (Alameda County Flood Control and to correct this overdraft situation, Water Conservation District, written Zone 7 signed an agreement with the commun., 1981). California State Water Project to provide water from the South Bay aqueduct starting in 1962. Zone 7 now operates two water-treatment plants Water-Resources Development in the Livermore Valley to directly treat the South Bay aqueduct water for Surface-water development in the domestic and industrial uses. Zone 7 Livermore-Amador Valley began in the also releases South Bay aqueduct late 1880's when small dams were con water to Arroyo Mocho and Arroyo structed to divert water for irriga Valle for ground-water recharge. tion. In 1898, the Spring Valley Currently (1983), Zone 7 has an annual Water Co. constructed a group of entitlement of 46,000 acre-ft of South wells in the Bernal well field west Bay aqueduct water. of Pleasanton. These wells were orig inally artesian. Water from these In 1969, Del Valle Dam and Reser wells was discharged into Arroyo de la voir were completed, providing storage Laguna where it was carried to the of South Bay aqueduct water and run Sunol filter galleries and then piped off from Arroyo Valle. This 77,000 to San Francisco. The city of San acre-ft reservoir is operated by the Francisco purchased the Spring Valley California Department of Water Water Co. in 1930 and continued to Resources. Releases from the reser pump water from the Bernal well field voir are used for ground-water re until 1934 when the Hetch Hetchy aque charge and municipal supply. duct was completed. Pumping by San Francisco was resumed for 2 years in 1948 when the second barrel of Hetch Wastewater Treatment Hetchy aqueduct was under construction (Alameda County Flood Control and Water Conservation District, written Wastewater in the valley has histor commun., 1981). ically been treated at various treat ment plants and either applied to the Several private and governmental ground surface by spray irrigation or water purveyors and wholesalers have discharged to percolation ponds and been established to provide water for then released to streams for disposal.
Introduction In the Livermore area prior to 1959, called for drilling a number of wells wastewater was treated at a plant lo specifically for water-quality monitor cated near the intersection of Pine ing and included four types of wells: Street and Rincon Avenue and then disposed into percolation beds. In 1. Q wells shallow wells (20 to 1959, the present (1983) wastewater- 80 feet) located in or near treatment plant, east of the Livermore wastewater disposal areas. Municipal Airport, was put into 2. wells other shallow wells service. This plant used percolation in areas between wastewater- ponds, spray irrigation at the airport, disposal sites. nearby golf course and farmlands, and 3. M wells medium depth wells Arroyo Las Positas for effluent dis (80 to 200 feet) in various posal. The Pleasanton wastewater- locations through the valley. treatment plant has operated since 4. D wells deep wells (200 to 1910. Until 1949, this plant consisted 600 feet) in various locations of a large septic tank. After 1949, throughout the valley. effluent was discharged to leach fields, used for spray irrigation, or The Q and S wells were designed to released to percolation ponds until monitor the shallow aquifer and were 1980 when the facility was closed. The expected to be the first to show indi Dublin-San Ramon Services District cations of water-quality degradation has operated a sewage-treatment plant from wastewater or other surface northwest of Pleasanton since 1961. sources. M and D wells were designed Sludge from this plant was discharged for rtionitoring the deeper aquifers, to to drying beds on the property, and determine if there were substantial effluent was discharged to Alamo Canal. differences in piezometric head and From 1940 to 1961, wastewater from waterl quality at different depths. Camp Parks was treated on site and discharged to surface water in the In 1975, the first 30 wells (Q 1940's, and to oxidation ponds from wells} were constructed using a hollow 1950 to 1961. Other smaller, waste- stem auger. The casings were 2.5-inch water-treatment plants are located at PVC pipe having a 5-foot perforated Castlewood Country Club southwest of section, between 5 and 10 feet from Pleasanton, the Veterans Administra the bottom of the well. Water-quality tion Hospital along Arroyo Valle, and sampling began in 1975 when the new Q Coast Manufacturing Co. in Livermore. wells and about 30 existing wells were Since January 1980, most effluent sampled. from the three major plants in the valley has been exported to San Fran Because of the high construction cost cisco Bay via a pipeline. of the proposed M and D wells, and the likelihood of long delays before the wells could be drilled, the deci- sion was made to substitute existing DESIGN AND IMPLEMENTATION OF THE wells for the deeper wells needed for MONITORING NETWORK the monitoring network. Zone 7 made an extensive survey of existing wells and chose wells that came closest to The monitoring program operated fulfilling the objective of monitoring jointly by the U.S. Geological Survey deeper aquifers. Initially, about and Alameda County Flood Control and 30 existing wells (designated E wells) Water Conservation District, Zone 7 were sampled. This list of E wells began in 1975. The original design of was revised periodically when better the ground-water-monitoring network monitoring wells were located.
6 Water-Quality Conditions in Livermore-Amador Valley In 1976, 27 S wells were drilled wells are perforated at several depths using the same construction techniques or continuously perforated from near and casings as the Q wells. Twenty-two the water table to the bottom. This additional S wells were drilled in results in a monitoring well that draws 1978, and 14 more in 1980, to complete water from several depths and possibly the monitoring network. The last 14 from two or more aquifers. The S and wells were drilled using the cable Q wells, on the other hand, were con tool method and have 4-inch PVC structed such that the sample water is casings. During the course of the drawn from a confined depth range, re study, several wells were destroyed, sulting in a sample that is more repre replaced, or otherwise determined as sentative of the aquifer. The wells unsuitable for sampling. The use of currently (1982) included in the existing wells as deep monitoring wells ground-water-monitoring program are was a compromise because most existing given in table 1.
TABLE 1.--Wells used for water-qua Iity analyses [Abbreviation: USGS, U.S. Geological Survey. USGS well identification number: First six digits are latitude, next seven digits are longitude, and final two digits are sequence number to uniquely identify each site. --, no data available. Type of well: C, well constructed for this study; E, existing well]
Period of water- USGS we I I Depth of we I I , Type of Perforation interval, qua 1 i ty record Wel 1 No. identification No. in feet we I I in feet (water year)
2S/1E-32N1 374242121533101 45 C 35-40 1976-83 2S/1W-14N1 374512121565201 48 C 38.5-43.5 1976-83 15B1 374557121573701 821 E 21 perforations 1978-83 from 50-710 15F1 374544121572501 60 C 50.3-55.3 1976-83 26C2 374418121563201 50 C 40-45 1976-83 36E3 374307121554601 60 C 50-55 1978-83 2S/2E-21L4 374439121454501 214 E 85-157 1976-83 27C2 374406121444201 108 E 41-45, 52-56 1976-83 27 P2 374326121442801 68 C 35-45, 58-63 1979-83 28D2 374416121455801 55 C 45-50 1976-83 28Q1 374325121452501 28 C 17.6-22.6 1976-83 32K2 374253121463601 48 C 33-38 1977-83 34E1 374258121445801 49 C 40-45 1977-83 3S/1E-1H3 374207121482101 80 C 70-75 1977-83 1P2 374147121485401 50 C 40-45 1975-83 1R2 374143121481801 56 C 49-54 1981-83 2K2 374203121493801 46.5 C 36.5-41 .5 1975-83 2N2 374154121501801 80 C 70-75 1978-83 2N3 374143121501601 316 E 157-167, 301-311 1976-83 2R1 374148121492301 33 C 21-26 1975-83 3G2 374214121505801 50 C 40-45 1978-83 4J4 374208121515801 107 C 96-101 1979-83 4Q2 374143121515101 90 C 80-85 1978-83 5F2 374209121532501 150 C 143-147 1979-83 5J2 374204121523901 100 C 90-95 1978-83 5M1 374155121533101 93 E -- 1977-83 5R2 374146121523701 230 E 190-220 1976-83 6F3 374211121542701 37 C 27-32 1976-83 6R2 374134121535201 74 C 64-69 1978-83 7B2 374137121541301 150 C 143-149 1979-83 7F1 374126121543201 75 C 64-69 1978-83 7M2 374118121544401 85 C 70-71, 78-85 1979-83 8B1 374133121530901 148 C 55-60, 74-82 1979-83
Design and Implementation of the Monitoring Network 7 TABLE 1.--Wells used for water quality anaIyses--Continued
Period of water- USGS we I I Depth of wel 1 , Type of Perforation interval, qua 1 i ty record Wel 1 No. identification No. in feet wel I in feet (water year)
3S/1E-8H2 374118121523801 205 E 124-139, 148-165 1981-83 8K1 374108121530701 99 C 89-94 1978-83 8N1 374054121533201 72.1 C 62-67 1976-83 9G1 374116121520001 160 E 77-149 1975-83 9P5 374058121520101 105 C 95-100 1978-83 9Q1 374052121515501 232 E 140-153, 170-211 1977-83 10A2 374130121502701 88 C 70-80 1979-83 10E1 374117121512201 195 E 1980-83 10G2 374117121505101 207 E 1977-83 10Q5 374054121505601 300 E 243-295 1975-83 11B1 374130121494201 43 C 33-38 1975-83 12A2 374132121483201 68.7 C 63.7-68.7 1975-83 12D2 374131121490701 46 C 36-41 1975-83 12F1 374112121485001 240 E 5 perforations 1959-83 from 115-234 12G1 374113121484601 73 C 63-38 1975-83 12H1 374117121483301 342 E 94-120, 157-172 1979-83 12N1 374056121491301 304 E 7 perforations 1980-83 from 112-295 12P1 374056121485001 348 E 262-290, 315-236 1959-83 13E1 374033121490901 100 C 75-97 1976-83 13N1 374003121491301 498 E -- 1980-83 13P2 373956121485501 400 E __ 1977-83 14A2 374039121493401 210 E 135-160, 170-205 1980-83 14F1 374026121500101 269 E -- 1977-83 14G1 374027121495201 500 E 150-500 1979-83 14K2 374012121494301 508 E 8 perforations 1980-83 from 120-480 15F3 374027121510601 640 E 7 perforations 1978-83 from 195-615 16E4 374024121523201 105 C 95-100 1978-83 16H2 374028121514001 94 C 82-92 1979-83 16L7 374037121534801 647 E 165-365, 371-647 1965-83 16P5 373955121521801 75 C 64-69 1978-83 17B4 374037121525601 248 E __ 1977-83 17Q4 373957121530601 84 C 74-79 1978-83 18A5 374037121534801 454 E 120-440 1967-83 18E4 374037121543201 83 C 69-79 1979-83 18J1 374011121535401 325 E 1980-83 18J2 374012121540201 71 C 61-66 1980-83 19A5 373942121534501 220 E -- 1946-83 19C4 373943121541901 78 C 68-73 1979-83 19K1 373921121540701 57.6 C 47.6-52.6 1975-83 20B2 373946121525601 500 E 218-500 1970-83 20 F5 373931121531901 46 C 36-41 1975-83 20J1 373919121525101 42 C 32-37 1976-83 20J4 373928121524901 72 C 62-67 1975-83 20M11 373919121532701 71 C 61-66 1978-83 20Q1 373906121525601 52 E 41-51 1977-83 22D2 373953121511601 72 C 62-67 1976-83 24K1 373924121484901 80 C 70-75 1978-83 29D2 373856121532801 64 C 54-59 1975-83 29E3 373840121532901 155 E 37-107 1960-83 29M4 373834121534301 57 C 47-52 1975-83 29P2 373817121531301 42 C 32-37 1975-83 30A8 373859121534801 61 C 51-56 1975-83 30A9 373843121535201 73 C 63-68 1979-83 30G3 373841121535801 61.3 C 51.3-56.3 1976-83 32G2 373756121530601 40 C 30-35 1976-83
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O -1 rt << (D m o 00 OOOOO ooo mm mm m O m o m m m m m o o o o OOOOO mm o o m ooomo ooomo (D (D 1 3 .0 0 C -ij to 01 o' ft co ® to -» ro o -1} D co coco vo -g vji vo 0 O to o-h -4 vji ro ON vji VJI -4 ' « ON -b 0 i * o 1-41 -1} -i> -13 i ro i TO 1 co -4 -2 K VJl 1 ro -»ON r+ -p-ro ro i ro -7-0 TTJ -i TJ -» COCO O (D vo 3 rt OT OOO O co co * O (D o .0 (D "^S - 03 O O vovo vovo VO vO VO VO VO vo vo vo vo vo vo vo vo vO vo vO vo vo vo vo VO vo vO VO VO VO vo VO VO VO VO VO vo VO VO vovo vovo vo vo vo vo vo vo rt CL -4-4 -4-4 4 4 4 4 4 4 4 4 4 4 COCO -4-4 -4 4 Vji Jr 4 4 " ^j ~^J 4 4 4 4 4 4 4 4 VJl-4 -J--JOO " ^j 4 -^J CO 4 4 4 -^J -^ 4 0) rt ON ON -4 VJl -4 -4 VJl VO ON 4 ON ON 4 ON O O ON-4 -4 00 CO VJICO ON ON 00 vo ON ON ONCO CO -4 ON 00-4 VOCOO ON 4 4 O 4 ON vji ON ON vo T<< O 1 1 1 1 1 1 1 1 1 III II II II 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 II III 1 1 1 1 1 I I i I I H) COCO 0000 00 00 CO CO CO CO CO CO 00 CO CO 00 00 CO 00 CO CO 00 00 00 0000 0000 00 CO 00 CO CO CO 0000 CO CO CO 00 CO 00 00 CO oo oo oo oo oo << T co co CO CO co coco co co co co co co co co co co co co to co co co co co co co co co co co co co co co co co co co to co co co co co coco co co (D (D < 0) O ^ T O rt ~-- -5 (D The surface-water-monitoring network stations, eight of which were equipped was started in 1979, superseding an with continuous specific conductance earlier network operated from 1974 to moniltors (table 2 and pi. 8). 1979. The earlier network was operated by a cooperative program between the FIELD AND LABORATORY METHODS Alameda County Water District, Livermore-Amador Valley Water Manage Wai:er samples from all 2.5-inch wells ment Agency, Zone 7, and U.S. Geolog constructed for this program were taken ical Survey. The program was designed usinci a 2-inch diameter air squeeze to find the sources of the increasing pump developed by the U.S. Geological amounts of dissolved solids in the Surv ey in Menlo Park, Calif.^, in 1975. streams. Increasing dissolved-solids This pump is driven with compressed concentrations were having a deleteri nitrogen and is capable of pumping at ous effect on the quality of water in a rate of about 1 gal/min. The pump is Alameda Creek, which recharges the designed so that the water never comes Niles Cone ground-water basin. Lopp in contact with nitrogen gas or air (1981) reported the results of the before it is discharged from the samp 1974-79 network program. ler hose. Samples from the existing With the establishment of a treated wells and larger constructed wells were wastewater-export pipeline in January taken using a portable, electric sub- 1980, treated wastewater releases to mers ble pump or using the pump streams ended. As a result, the already installed at the well. Prior surface-water-quality-monitoring network to sampling, water was pumped from was modified to determine water quality all wells until stable temperature, since the pipeline began operation. specific conductance, and pH readings The network consisted of nine gaging were obtained. TABLE 2.--Surface-water sampling stations Specific conductance and water discharge moni tored continuously for dates given, --, no data available] Period of record Drainage Physical a nd Stat ion a rea chemica 1 Specific Water No. Station name (mi 2 ) const ituen ts conductance discharge 1117U600 Alamo Canal near 40. 8 10/7U-10/81 10/79-10/81 10/79-10/81 Pleasanton 11176000 Arroyo Mocho near 38.2 12/79-10/8 1 1/79-10/81 1912-30; L i ve rmo re 10/63-10/81 11176145 Arroyo Las Positas 3/81-10/81 8/80-10/81 8/80-10/80 at Live rmo re 11176180 Arroyo Las Positas 75.0 12/79-10/8 1 12/78-10/81 10/77-10/81 at El Charro Rd., near Pleasanton 11176200 Arroyo Mocho near 142 11/70-3/71; 10/78-10/81 9/62-10/81 Pleasanton 3/81-10/81 11176300 Tassajara Creek 26.8 11/80-10/81 3/79-10/81 1914-19; 1921-30; near Pleasanton 10/78-10/81 11176500 Arroyo Va 1 le near 1U7 11/60-5/67 ; none 1 1912-30; L i ve rmo re 3/81- 10/8 i; 10/57-10/81 3/81-10/81 11176600 Arroyo Va 1 le at 171 1/75-10/75 ; 12/7U-10/81 10/57-10/81 Pleasanton 1/77 to 10 /81 11177000 Arroyo de la Laguna U05 7/79-10/81 8/79-10/81 "h912-30; near Pleasanton 10/69-10/81 Monthly discharge only. 10 Water-Quality Conditions in Livermore-Amador Valley Samples for the following dissolved pling. Grab samples were taken at mid constituents were collected at all stream 4 to 12 times a year at the wells: Ca, Mg, Na, K, HCO 3 , Cl, surface-water stations. Samples were SO 4 , NO 3 , P, and Fe. Hardness was processed and analyzed using the same calculated from Ca and Mg values. methods as the ground-water samples. Samples for total organic carbon and Samples were analyzed for major ions, chemical oxygen demand were collected B, Fe, Mn, and dissolved solids. at most wells. Water temperature, About three to six times per year samp specific conductance, pH, and water les were collected and analyzed for levels were determined at each well nutrient species (NO 2 + NO 3 , organic when sampled. Most wells were sampled nitrogen, NH 4 , and PO 4 ). In either monthly or quarterly for NO 2 , addition, field determinations of pH, NO 3 , Cl, and dissolved-solids residue specific conductance, and water temper at 180°C. Samples for other consti ature were made. tuents were usually collected once or twice a year. Wells in wastewater- disposal areas were sampled monthly prior to the 1977 water year, and bi WATER LEVELS AND GROUND-WATER monthly after that. MOVEMENT The major ions and residue on eva poration at 180°C were sampled to Ground-water-level contours in the assess the general quality of the water valley in the spring of 1980 are shown and to determine areas of similar on plate 2. This map was based on a water types. Nitrate, chloride, total large number of wells, many of which organic carbon, and chemical oxygen were not in the monitoring network. demand were sampled as possible Ground-water movement is in the gen tracers of areas affected by waste- eral direction of the gravel pits water discharge. (pi. 2). The gravel operations pump large quantities of water from the pits Samples for dissolved constituents to facilitate gravel mining, thus were filtered immediately after col creating a large artificial depression lection through a 0.45-micrometer mem in the valley ground-water system. The brane filter to remove suspended mate gravel pit operators also back fill rial. Cation samples were preserved some of the pits with silt and clay to with nitric acid, chemical oxygen de minimize further recharge and ground- mand samples with sulfuric acid, and water movement in the area. nutrient and total organic carbon sam ples were chilled to 4°C. The samples The extensive gravel mining has were sent for analyses to either the greatly altered the historical ground- U.S. Geological Survey Central water-flow regime. Originally the Laboratory in Denver, Colo., or the ground-water gradients were from east California Department of Water to west with outflow from the valley Resources Laboratory in Bryte, Calif. along Arroyo de la Laguna. This Prior to 1979, laboratory analyses outflow of ground water has stopped were done by methods given in Brown due to pumping for municipal and agri and others (1970). Beginning in 1979, cultural purposes in the Pleasanton the methods given in Skougstad and area. The directions of flow were others (1979) were used. Total organic later altered by gravel excavation carbon samples were analyzed by the activities. method given in Goerlitz and Brown (1972). In most of the valley, vertical flow is minimal because of the many clay Surface-water samples were taken over layers that tend to separate parts of a wide range of hydrologic conditions the permeable aquifer material (Cali with an emphasis on winter storm sam fornia Department of Water Resources, Water Levels and Ground-Water Movement 11 55 WELL3S/7E-9G? 60 SJ 65 u. Z K 70 !»Ul 0. 80 Ul o 85 90 i 1111 M 11111111111 Mi11111 ft 1111111 11111111111 23 WELL3S/1E-11B1 24 25 UJ Ul 26 UJ 27 99 9 O 28 9 9 H 9 JE 29 Ul 9 0 30 - 9 31 32 CM 8 « DATE SAMPLE WAS COLLECTED FIGURE 2. - Water levels at four wells Over their period of record. 12 Water-Quality Conditions in Livermore-Amador Valley 25 WELL3S/1E-12D2 27.5 111 £ 30 CC III < 32.5 O £ Ul 0 37.5 40 15 WELL 3S/1E-30A9 20 Ul u! 25 oc Ul 30 O 35 Ul 0 40 45 DATE SAMPLE WAS COLLECTED FIGURE 2. - Continued. Water Levels and Ground-Water Movement 13 1964). The clay layers are not contin The five wells around the Veterans uous, however, and some vertical flow Administration Hospital are considered does occur. In much of the southern anomalous to the rest of the valley's parts of the Amador and Mocho II sub- ground-water system. They are shallow basins, the clay layers are less exten wells| (14 to 25 feet) and, except for sive and vertical flow is more apparent 3S/2E--33C1, are primarily affected by from water-quality measurements. the nearby percolation ponds. Well 3S/2E:-33C1 is near Arroyo Valle, but Water levels in the valley have it is so shallow that it is probably generally increased in most parts of not representative of ground-water the valley from 1975 to 1982. The conditions in that area. , For these hydrograph of well 3S/IE-9CI (fig. 2) reasons, the hospital wells were not is typical of many wells throughout used when making the contour maps, the valley. It shows a substantial but specific reference to these wells increase in water level over the per is made where appropriate. The range iod of study. Some wells (particu in water levels during the period of larly in the Mocho II and Amador sub- record was generally greatest around basin) had water levels that fluctuated the gravel pits, the northern part of somewhat but showed no upward or Pleasanton, and around the Pleasanton downward trend over the monitoring wastewater-disposal area. The range in period. An example of this is the hy depth to water in these areas was typi drograph from 3S/1E-11B1 (fig. 2). Of cally greater than 30 feet during the the wells in the network that have study period. The depth to water in been monitored for more than 3 years, these areas tended to vary more in the only six wells have had a steady deeper wells than in the shallow wells. decline in water level. These include Much of the variability in the deeper 3S/1E-1P2 and 3S/1E-2N2, located north wells is probably due to greater pump- west of the Livermore sewage-treatment ing of those wells, or nearby wells, plant, and 3S/1E-16H2, located in the than would occur in the shallow wells western gravel pit area. Three other constructed for this study. wells with declining water levels during the study period are 3S/2E-7N1, 3S/2E-8H2, and 3S/2E-24A1. GROUND-WATER QUALITY The hydrographs of some wells indicate a decline in water levels, The areal distribution of selected corresponding to the 1977 drought. The water-quality properties and constitu wells southwest of the Pleasanton ents of ground water are presented on sewage-treatment plant showed this plates 3-7. The maps were constructed effect particularly well (fig. 2, usincj mean values for each well for the hydrograph of 3S/1E-30A9). Water period of record. This approach ig levels in many of the wells in the nores the possible variability of the valley, while generally showing in data over the period of record, and creases, were highly variable during since the period of record is different the period of record. Much of this at different wells, there is some un variability could be attributed to sea certainty as to the location of the sonal wet-dry cycles; however, some of contour lines. The contours near the the wells, particularly around the margins of the valley also contain some Livermore airport, had water levels uncertainty because of the lack of data that varied but not on a seasonal basis for some areas and are thus represented (fig. 2 hydrograph of 3S/1E-12D2). by clashed lines. In some areas there This is most likely due to on-land was a considerable difference in water wastewater-application practices that quality between deep and shallow wells are somewhat independent of seasonal in the same general area. In these cycles. area$, the mean value for the shallower Water-Quality Conditions in Livermore-Amador Valley wells was generally used. The mean of high conductivity water, probably value for wells that were anomalous to associated with these clay layers, were the contour area are indicated on the detected in the shallow aquifer to the plates. south (3S/1E-18J2). Overall there was a general decrease in specific conduc Three program wells, located in San tance from the military reservation Ramon Valley, north of San Ramon south to Pleasanton primarily due to Village, are not on any of the maps recharge from Arroyo Mocho and Arroyo because of restrictions in map size. Valle. The high specific conductance Reference to these wells are made in in wells near and west of the Livermore appropriate sections. airport probably is the result of high conductivity recharge water from Arroyo Las Positas. The three wells Specific Conductance in the San Ramon Valley that are not shown on the contour maps had a mean specific conductance of between 950 The lowest values of specific con and 1,080 ymho. The wells near the ductance were detected in wells along Veterans Administration Hospital had and near Arroyo Valle and Arroyo mean specific conductance ranging from Mocho (pi. 3). These are the princi 726 ymho in 3S/2E-33G1 to 2,420 ymho pal recharge areas for the ground- in 3S/2E-33G3 and therefore, were water basin, and the low specific con higher in specific conductance than ductance is indicative of the quality other wells in their contour area. of the recharge water carried by these two streams. The highest specific conductance occurred in the northwest Water Types part of the Amador Valley and the northeast corner of Livermore Valley where it was more than 2,000 ymho in The water-type map shows areas based some wells. The source of this high on the predominant cation (pi. 4). specific conductance water is probably These cationic water types were based the marine sediments that border the on the percentage of each cation in valley. In the northeast corner of the sample. For example, a magnesium- Livermore Valley, high specific con type water is one in which 50 percent ductance occurred in both shallow wells or more of the cations (in milliequi- (3S/2E-1F2) and deep wells (3S/2E-1P2). valents) are magnesium. When a single The high specific conductance in the cation does not make up at least military reservation area north of 50 percent of the total, the water Pleasanton was confined to the type is designated as a combination of shallow aquifer. In this area, there the two cations that contribute the is an extensive water-bearing confining largest percentage of the total. bed consisting of the clay and sandy clay that extends to a depth of about A large area of sodium water was 120 to 140 feet below land surface. detected along the north edge of the Wells completed below the confining bed valley, except in the San Ramon in the area (3S/1E-7B2 and 3S/1E-5R2) Valley. The source of this water type had a specific conductance value of is probably recharge from the local less than 1,000 ymho. The clay layer streams draining the Tassajara Forma probably is not continuous or of con tion, and underground recharge from stant thickness over this entire area. these areas. The large area of mag It seems that the clay layer may be a nesium water was generally the area series of smaller clay lenses that that is recharged by Arroyo Mocho. together form an effective confining bed with little hydrologic connection Water in the area along Arroyo to the lower aquifer. Smaller areas Valle was a calcium magnesium or mag- Ground-Water Quality 15 nesium calcium cationic type. An ex not on the map had mean chloride con ception to this is the area around centrations ranging from 61 to 134 mg/L. the Veterans Administration Hospital. These wells yielded sodium chloride Chloride is generally considered to water that is probably the result of be a cjood tracer of the movement of a localized geology or percolation from particular water through an aquifer the sewage-treatment ponds, and does becauie it is not absorbed appreciably not represent water recharged from by soil or organic particles. Waste Arroyo Valle. The three wells in discharges which are high in chloride the San Ramon Valley that are not will increase chloride concentrations shown on the map yielded calcium or in ground-water areas downgradient calcium sodium water. from effluent discharge if the efflu- ent reiaches the aquifers. Most of the Water from most of the wells in the valley had a percentage chloride of study area contained bicarbonate as the less than 30 (pi. 5). The source of predominant anion. Those wells from the increased percentage chloride west which samples had anything other than of L.ivermore's wastewater-treatment bicarbonate as the predominant anion plant is very likely effluent from the are given in table 3. Most of these plant that was discharged to Arroyo wells contain water that was predominant Las Positas and used for spray irriga either in chloride or a combination tion near the Livermore airport. of chloride and bicarbonate, and are Another area with high percentage located in the areas where sodium is chloride water was in the northeast the predominant cation. part of the valley. This area is re TABLE 3.--Wells with anionic water types charged by high chloride water from that are not bicarbonate local surface water. The percentage chloride in the area around the Pleasanton wastewater-treatment plant Water type was not as high as that around the Livermore plant. It is very difficult, Bica rbonate chloride or from the chloride data available, to Chloride Bica rbonate Sulfate trace effluent contributions to the b ica rbonate Ch loride sulfate ch loride ground water from the Pleasanton plant. 3S/1E-4Q2 3S/1E-7F1 3S/1W-12J1 3S/1E-6R2 2N2 7M2 3S/2E-33G1 2R1 22D2 8B1 3S/1W-1B5 Nitrate 3S/2E-11C1 2S/1E-32N1 2UA1 2S/2E-27P2 33G3 3S/2E-1F2 33L1 33K1 Water with nitrate concentrations 2S/2E-28D2 34E1 greater than the drinking water stan dard (U.S. Environmental Protection Agency, 1977) of 10 mg/L as N was de- Chloride tected[ in three parts of the study area (pi. 6j. The largest area covers much of Livermore and south to the valley Water having high chloride concen margin. The highest concentrations of trations (pi. 5) generally corresponded nitrates were in the Buena Vista Road to water having high specific conduc area where samples from well 3S/2E-15J2 tance (pi. 3). The highest mean had ci mean nitrate concentration of chloride concentration (3,070 mg/L) oc 20 mg/L. Water from the wells around curred at 3S/1E-7F1, east of the the Livermore airport and the Dublin-San Ramon Services District Pleasanton wastewater-treatment plant Sewage Treatment Plant. The three genercilly had nitrate concentrations wells in the San Ramon Valley that are greater than 10 mg/L. 16 Water-Quality Conditions in Livermore-Amador Valley High nitrate concentrations in water from all the network wells to trace has long been recognized as a primary areas that were high in organic carbon. water-quality problem in Livermore Such samples might indicate possible Valley. Sylvester (1983) gives a areas of organic pollution. Analysis detailed discussion of nitrate in the of the data showed TOC values ranging sewage-disposal areas, and Camp, from less than detection (0.5 mg/L) to Dresser, and McKee Inc. (1982) dis 23 mg/L. General background concentra cussed the presence of high nitrate tions of TOC appeared to be between concentrations in unsewered areas such 2 and 5 mg/L. Water with TOC greater as Buena Vista. than the background level were detected in various areas throughout the valley, The wells around the Veterans but were not necessarily associated Administration Hospital had mean with the wastewater-disposal areas. nitrate concentrations ranging from Further analysis of these data showed 0.09 to 3.1 mg/L. that in wells where several TOC ana lyses were made, the fluctuation in TOC concentrations was much greater than could reasonably be expected con Boron sidering the reported values of other constituents. The large fluctuations were probably attributed to sampling Concentrations of boron in ground and analytical error and not to actual water in the Livermore-Amador Valley fluctuations in TOC concentrations. were generally low (less than Because of the variability of the 1,000 yg/L and usually less than analyses, it was impossible to draw an 500 yg/L) (pi. 7). Notable exceptions accurate map of TOC concentrations in were the northeast part of Livermore ground water; however, it seems clear Valley where mean boron concentra that high TOC concentrations are not tions were as much as 16,000 yg/L in associated with the wastewater-disposal water from well 2S/2E-27P2, and the areas, and cannot be used as a tracer area west of the Livermore wastewater- of organic contamination in the treatment plant. Wells that yielded valley's aquifers. boron concentrations greater than 2,000 yg/L are all shallow (the deepest well is 2S/2E-27C2 at 108 feet). Boron in these areas is probably from the Differences in Water Quality Between marine sediments adjacent to these Shallow and Deep Wells areas. The three San Ramon Valley wells not shown on the map had mean boron concentrations ranging from The sampling network was designed to 160 to 216 yg/L. Water from the Veterans Administration Hospital provide data from deep and shallow wells near each other in various loca wells all had mean boron concen tions in the valley. This should show trations greater than 1,000 yg/L ex if there are any chemical differences cept in well 3S/2E-33C1, which had 533 yg/L. Water from the other four in ground water of the shallow and deep wells had mean boron concentrations aquifers, and if those differences are ranging from 1,800 to 6,350 yg/L. stable over time. Some of the paired wells used for these comparisons are not close enough together to make ideal comparisons but an attempt was made to Total Organic Carbon provide a deep-shallow comparison in several areas. Comparisons between data distributions of water-quality Samples were analyzed for total properties and constituents were made organic carbon (TOC) at least once using the Kruskal-Wallis (Chi-square Ground-Water Quality 17 approximation) test. This nonparamet- which were significantly different at ric statistical procedure was necessary the OJ05 level (fig. 3). The shallow because many of the data distributions well had a mean nitrate concentration were not normal. Normal distribution of 1.0 mg/L, the deeper well had mean of data is a condition assumed for nitrate concentration of 9.5 mg/L. most parametric tests. The Kruskal- Temporal variability of all the major Wallis tests were made using the constituents is much greater in the NPAR1WAY procedure in SAS (Helwig shallov/ well and seems to be linked and Council, 1979). Schematic boxplots closely to changes in water quality (fig. 3) were constructed for several in necirby Arroyo Valle. The deeper water-quality properties and constitu well has a mean water level about ents using the SPLOT procedure from 36 feet lower than in the" shallow SAS. These plots are useful in visu well. This indicates a possible perched alizing the data distributions and ground-water area. central tendencies. All the statisti cal tests and schematic plots for each 3S/1 E-12G1 (73 feet) and 3S/1E-12F1 well pair were made using data covering (240 feet). These two wells are loca- the same time period and approximately ted within 150 feet of one another, the same number of samples from each about a quarter of a mile southwest of pair of wells. the Livermore wastewater-treatment plant. The specific conductance and 3S/2E-14A3 (110 feet) and 3S/2E-14B4 the concentrations of major dissolved (260 feet). These two wells aTeloca- constituents in samples from the shal ted near the corner of Grant Street low well were significantly greater and Las Positas Avenue east of than in the deeper well. Variability Livermore. The shallower well had of the* data also is generally greater significantly higher specific conduc in these wells than others used in the tance and concentrations of all the deep-s;hallow comparisons. The water major dissolved constituents except types of the two wells were similar, sulfate (fig. 3). Water types were but the mean percentage bicarbonate in similar for both v^ells. Mean water the deeper well is 68 conlpared to 55 levels were not significantly dif in the shallow well. The percentage ferent at the 0.05 level. Well sodium was 26 in the shallow well com 3S/2E-11J2, about a quarter of a mile pared to 19 in the deeper well. Water north of well 14A3, is also 110 feet levels averaged about 55 feet lower in deep. The differences in water chem the deep well, indicating a multiple istry between wells 14A3 and 11J2 aquifer system in this area. These were much greater than the differ wells are adjacent to the wastewater- ences between wells 14A3 and 14B4. appliciJtion area near the Livermore Water in well 11J2 was lower in speci wastev/ater-treatment plants. This fic conductance than either of the probably accounts for the high nitrate other two wells and was also lower in concentrations and higher percentage of all major dissolved constituents sam sodium detected in the shallow well. pled. This indicates that in this part of the valley, differences in 3S/1 E-5J2 (100 feet) and 3S/1E-5R2 water quality are more likely to be (230 feet). These wells are located caused by the location of the well about a quarter of a mile south of the than by the depth of the well. Santa Rita Rehabilitation Center and along Tassajara Creek. Water in 3S/2E-29R (36 feet) and 3S/2E-20N1 the shallow well had a specific con feetj. These two wells are lo^ ductance nearly twice that of the cated in the southeastern part of the deeper well. Concentrations of major Amador subbasin near Arroyo Valle. dissoh/ed constituents also were about They have very similar water quality twice as high in the shallower well. in terms of major dissolved constitu Variability in these data is much less ents except nitrate concentrations, than in most of the other deep-shallow 18 Water-Quality Conditions in Livermore-Amador Valley comparison wells. Variability in water well having a sodium (82 percent) bi depth was much greater in the deeper carbonate type similar to wells north well even though the depth to water is of this area, and the shallow well hav much greater. This is most likely ing a mixed sodium magnesium, sulfate due to its location near a major chloride water similar to other wells ground-water pumping area. Fluctua that were finished in and above the tions, seasonal or otherwise, in confining clay layer in this area. pumping in this area probably influen Water levels in the two wells were ces ground-water levels in the deeper nearly identical. aquifer. The water types of these two wells were very similar. These two In most of the Bernal, Amador (except wells show that there are apparently the southeastern part along Arroyo two distinct aquifers in this area with Valle), and Mocho subbasins, the shal similar water types but very different low wells generally were higher in dis concentrations of dissolved con solved constituents than the deeper stituents. wells. In some areas west of Livermore, this is most likely caused 3S/1E-6R2 (74 feet) and 3S/1E-7B2 by wastewater application to the land (150 feet). These wells are located surface and to the percolation ponds. east of Hopyard Road and south of In the area northwest of Pleasanton Interstate 580. The differences in the buildup of salts in the shallow water quality between these wells are aquifer is probably due to the histor typical of the differences in this area ical runoff pattern in the valley which between the upper aquifer with poor caused water to pond in this low spot water quality, and the deeper aquifer and evaporate, leaving behind the salt with better water quality. In this and fine clay that now makes up the clay layer area, concentrations of all thick confining bed. In the Mocho major dissolved constituents, except subbasin where clay layers are less nitrate, were much greater in the shal extensive and shallow and deep ground low well. Nitrate was less than water can mix more readily, the differ 0.2 mg/L in both wells (fig. 3). Water ences in water quality at different types were very different with the deep depths becomes much less defined. Ground-Water Quality 19 oou 1 1 1 1 1 1 i i i i H 111 111 500 - 17 16 Z _T 19 ui > 450 _ , _ 111 17 -I E+3 111 111 400 i< ui 350 ~ 0 111 1 40 19 c^D 99 DC .5 tt -r -*.- _ K 300 -;- 5 y 250 i i i i i T i T i i m *t *t r- r- T- CN CN CN CN < CD LL. Z C3 "- ^ ^ C3) O CN £J Jt!2 UJ^ LU EXPLANATION 16 SCHEMATIC PLOTS (Tulcey, 1977) 1 16 NUMBER OF SAMPLES SEMIQUARTILE _ MEDIAN RANGE + MEAN 0 OUTSIDE VALUE * FAROUT VALUE Vertical lines from rectangle 4re the range of the data Upper and lower limits of rectangle are 25th and 75th percentiles (50 percent of saftiples located between limits) Outside values are between 1 and 1.5 times the semiquartile range from the top or bottom of th^ rectangle Far out values are more than 1.5 times the semiquartile range from the top or bottom of the rectangle FIGURE 3. - Schematic plots showing variations in water leve , specific conductance, calcium, magnesium, sodium, alkalinity, sulfate, chloride, and nitrate atJ paired shallow-deep wells. 20 Water-Quality Conditions in Livermore-Amado r Valley oc j" 5000 II I I I I I i 1 jjj 4000 ~ 8 £ 3000 _ 111 O OC 2000 - 40 15 111 Q. 0 -+- 1 * g 1500 § 1000 O - * I* 1I $o £ rf-i! - i 17 : t±d z .-_ * o * + i llf 500 r+i * ~" O z H 0 D O Z O o 0 o 0 il 0 O 1H 100 II 1 1 1 1 1 1 1 (0 350 300 oc UJ 250 oc a.111 CO 200 150 D 100 O 5 -+-* 50 SAMPLING SITES FIGURE 3. - Continued. Ground-Water Quality 21 0) 1 o c OJ r* SODIUM, IN MILLIGRAMS PER LITER MAGNESIUM, IN MILLIGRAMS PER LITER *< -.tvOOO-J^tJ1 _. >MN) o 0888800 S o o o o o I I I I 1 1 1 1 a <-* ' 5' 3S/2E-14A3 r~*° °* ~ -TI o> w 5' 3S/2E-14B4 - a- __ * 01 r; 3S/2E-29F4 -ED- EE>» -5 i =5 M 3S/2E-20N 1 +o 01 _ lo, o cz !> i 1 33 » CD m * 1 co ,2 3S/1E-12G1 - HI- an s 3 'i z 0) a 0* «, 3S/1E-12F1 - G-- = o-KHs o =3 _ 1 " g_ M 3S/1E-5J2 a » + 01 1 1 ? 3S/1E-5R2 B- -go, re + 3S/1E-6R2 i rs.nnLLJ i n ^ 3S/1E-7B2 i ^ 1 1 1 I 1 1 1 1 700 OC Ul eoo a.Ul CO < 500 oc 400 1 -+ O* 300 U u CO < 200 2 6 I-+-I 100 0 1400 -+- 1200 ac 2 Ul 1000 Ul a. co < 800 - ac C9 600 - z uf 400 D CO 200 - 10 ;_ 3 coco co co 00 00 00 00 SAMPLING SITES FIGURE 3. - Continued. Ground-Water Quality 23 0) n> i O c SL NITRATE (AS N), IN MILLIGRAMS PER LITER CHLORIDE, IN MILLIGRAMS PER LITER * * ^ ^ OOOOOOOoC O cD CJ1 O CJ1 O ^OOOOOOOOOC o 1 1 1 1 1 1 1 1 1 1 1 1 Q. o'r* 3S/2E-14A 3 -CD =5 - ffls 3 (/> 1 _. 3S/2E-14B4 ®{], « - }» ro 3 r; 3S/2E-29F4 +] * S -[TTf-s n> 3 3 w 3S/2E-20N1 -cn-= -B-a o g ^> CO Z 1 ' O _§^_i Co 3S/1E-12F1 _.. --EH-- .. 3' m < CD *° 3S/1 E-5J2 HD- -a »* zi _ 0) O. ST 3S/1E-5R2 T = - B = 3S/1E-6R2 h . . _*[ZI] - 3S/1E-7B2+* » - - «-{]* 1 1 1 1 1 1 I 1 1 1 1 1 STREAMFLOW local hydrologic and climatic condi tions. The distributions of specific Streamflow in the Livermore Valley is conductance at surface-water stations highly seasonal with most of the runoff over the period of record are shown in occurring during the winter from De figure 4. Because specific conductance cember through April. Natural flow is an indirect measurement of dissolved ceases in most streams during summer solids, this figure relates to dis and autumn in all but the wettest years. solved solids as well as specific con Hydrographs of mean monthly discharge ductance. The highest specific conduc at the nine surface-water network sta tance occurred at Arroyo Las Positas tions are exhibited on plate 8. Most at Livermore. This water is mostly of the hydrographs include data from natural discharge from a watershed that the pre-1980 period before treated is composed primarily of marine sedi sewage water was exported and the ments, which contributes large amounts 1980-81 water years after this export of dissolved material. Downstream from started. Close comparisons between this station at Arroyo Las Positas at hydrographs were hindered by the El Charro Road near Pleasanton, the limited number of years of records specific conductance was generally available at most of the stations. lower and the variability greater in Because these are small basins, the dicating some dilutions from other discharge each year is highly depen sources. In Arroyo Mocho, the up dent on seasonal rainfall and there is stream station (11176000 near Liver- little base flow in most of the more) has generally lower specific con streams. In addition, many artificial ductance than the downstream station situations affect discharge such as the (11176200 near Pleasanton). The down release of approximately 8,000 acre-ft stream Arroyo Valle station (11176600 of water from the South Bay aqueduct at Pleasanton) has much lower specific to Arroyo Mocho and Arroyo Valle for conductance than the upstream station purposes of ground-water recharge, and (11176500 near Livermore). This in the discharge of 6,000 to 7,000 acre- dicates that much of the flow that ft/yr ground water in Arroyo Valle reaches the lower station at Pleasanton from the dewatering operations at the is not the same water that naturally gravel pits. The release of water from occurs in the upper part of the basin Del Valle Reservoir for downstream stored in the Del Valle Reservoir, recharge in Miles Cone, accounted for or the same water released from the the increases in flow for the June South Bay aqueduct. through August period at Arroyo Valle near Livermore and at Pleasanton and Arroyo de la Laguna. Although the Water Types 1981 water year was a near normal rain fall year, large storms in February caused discharge peaks at all the sta The water types at each station tions. However, at these same sta were calculated using data from water tions, the March, April, and May mean years 1980 through 1982 (pi. 9 and discharge was at or below the mean for table 4). the previous years of record. Water in most of the streams sampled was on average a mixed cation, and SURFACE-WATER QUALITY mixed anion type. Exceptions to this were the two Arroyo Las Positas stations (11176180 and 11176145) and Specific Conductance Arryo Mocho near Livermore (11176000). Water in Arroyo Las Positas at the two sampling stations was a sodium The quality of the surface water, chloride type. These two stations like the flow, is highly dependent on also had the highest concentrations of Surface-Water Quality 25 cc IU 1- 4000 IU I 1 1 II I I 1 3000 z 111 261 0 _ o - 2oc 2000 111 I s ° Q. * ^+ I ° CO 1 6 r~l ° 0 I I 1 X r 1 v , o 1000 _ 1 I ' oc r r*-i 105 i3 0 " o I + o o + i 14 0 + 0 z * U oo * 73 j __ IU 500 * o 19 z 21 < o Io o ' ° 3 T sL- -fc 0 Z * 0 * O O LL O 111 gr 100 1 I I I I I I I (0 o o m o o 0000 0 0 * 00 0 o o o o o CM T- T- CO SURFACE-WATER STATIONS EXPLANATION 40 SCHEMATIC PLOT (Tukey, 1977) I 40 NUMBER OF SAMPLES SEMIQUARTILE _ MEDIAN RANGE + MEAN 0 OUTSIDE VALUE * FAROUT VALUE Vertical lines from rectangle are the range of the data Upper and lower limits of rectangle are 25th and 75th percentiles (50 percent oif samples located between limits) Outside values are between 1 and 1.5 times the semiquartile range from the top or bottom of the rectangle Far out values are more t ian 1.5 times the semiquartile range from the top or bottom of the rectangle FIGURE 4. - Schematic plot showing variability in specific conductance at the surface-water stations. 26 Water-Quality Conditions in Livermore-Amador Valley TABLE 4.--Percentage of each major anion and cation at surface-water stations, 1980-82 water years An ions Tota 1 Station A 1 ka 1 i n i ty Chloride Sulfate N it rate an i ons No. (meq/L) (percent) (meq/L) (percent) (meq/L) (percent) (meq/L) ( percent) (meq/L) 11174600 5.42 46 .6 3.43 29.5 2.77 23.8 0.003 <0.1 11. 62 11176000 6.23 77 .9 .84 10.5 .92 11.5 .008 . 1 8. 00 11176145 3.23 19 . 1 11.05 65.5 2.50 14.8 .109 .6 16. 89 11176180 3.68 26 .8 7.95 57.9 2.07 15.1 .008 . 1 13. 70 11176200 3.21 42 .7 3.16 42.1 1.13 15.0 .008 . 1 7. 51 11 176300 5.41 58 .7 1.66 18.0 2.15 23.3 .003 <. 1 9. 22 11176500 2.44 39 . 1 1.51 24.2 2.29 36.7 <.001 <. 1 6. 24 11176600 2.38 54 .7 1 .10 25.3 .87 20.0 .001 <. 1 4. 35 11177000 4.28 53 .5 2.23 27.9 1.49 18.6 .004 . 1 8. 00 South Bay 1 .02 32 .5 1 .28 40.9 .83 26.3 .009 .30 3. 14 aqueduct at De 1 Va 1 1 e water-treat ment plant. TABLE 4.-- Percentage of each major anion and cation at surface-water stat ions, 1980-82 water yea rs--Cont i nued Cat ions Potass ium Tota 1 Tota 1 Stat ions Ca 1 c i urn Maqnes i urn Sod ium Potass ium + sod i urn cat ions ions (meq/L) ( percent) (meq/L) ( percent) (meq/L) (meq/L) ( percent) (meq/L) (meq/L) 11174600 3.93 35. 5 2.80 25.3 4.29 0.06 39.2 11 .08 22. 70 11176000 1.64 20. 9 4.78 61.0 1.35 .07 18.1 7.84 15. 84 11176145 3.01 16. 6 3.79 20.8 11.3 .08 62.6 18.18 35. 07 11176180 2.42 17. 2 2.99 21 .2 8.58 .10 61.6 14.09 27. 79 11176200 2.43 27. 4 3.40 38.3 2.98 .07 34.3 8.88 16. 39 11176300 2.58 28. 2 2.26 24.7 4.19 . 11 47.0 9.14 18. 36 11176500 2.46 34. 6 2.28 32.1 2.29 .07 33.2 7.10 13. 34 11176600 1.48 34. 8 1.30 30.6 1.41 <.06 34.6 4.25 8. 60 11177000 2.40 32. 1 2.40 32.1 2.57 .10 35.7 7.47 15. 47 South Bay 1.13 30. 5 0.88 23.8 1.62 .07 45.7 3.70 6. 84 aqueduct at De 1 Va 1 1 e water- treat ment plant Surface-Water Quality 27 dissolved ions of any of the program (including Livermore-Amador Valley). stations. Another exception was The ground-water objectives are slight Arroyo Mocho near Livermore which ly different for two sections of the had a strong magnesium bicarbonate ground-water basin. The "central" water type. This water type is simi ground-water basin consists of the lar to that in the ground water in most Bernal, Amador, Mocho I, and Mocho II of the Mocho II subbasin through subbasins. These areas have the larg which Arroyo Mocho flows. The water est ground-water storage and are mostly quality at Arroyo Mocho near used for municipal and domestic water Livermore (11176000) is not very repre supplies. The remaining subbasins, sentative of the water farther down designated as "fringe" ground-water stream during low flow periods. Water basins, have generally poorer, ambient releases from the South Bay aqueduct, water4 quality and are less important which enter the stream downstream from for most uses than the central basin. the sampling site, make up almost the All water-quality objectives applicable entire flow of Arroyo Mocho during the to the study area, and for which data dry months. were obtained, are given in table 5 along with the number of wells that The water-quality sampling program have mean concentrations that exceeded was oriented to times of natural flow the objectives, and the surface-water in the streams. Because most of the stations that have had some samples flow in Arroyo Valle and Arroyo that exceeded water-quality objectives, Mocho is from South Bay aqueduct re The individual wells that have mean leases (97 percent of the time in values of properties and constituents Arroyo Valle in 1982), the diagram greater than the objectives are given representing water quality in the in table 6. South Bay aqueduct is more represen tative of water quality in these Because the sampling network wells streams. Streams draining the Liver- are more numerous in areas of known or more Formation south of the valley potential water-quality problems, there had lower concentrations of dissolved were probably a higher proportion of ions than streams draining the marine wells that exceeded objectives than and Tassajara Formations to the east would be detected if all the wells in and north. the valley were sampled. In addition, most of the wells that exceeded objec tives were shallow wells not used for publi^: water supply. The existing WATER-QUALITY OBJECTIVES large ground-water supplies all met water-quality objectives. Water-quality objectives for ground Th dissolved-solids objective was and surface water in the San Francisco exceesded in all but two of the wells in Bay area were established by the Cali the Bernal subbasin and in all the fornia Regional Water Quality Control wells along the northern part of the Board, San Francisco Bay Region (1982) Amador subbasin. Only 3S/1E-1R2 ex in 1982. This basin plan set objec ceeded the dissolved-solids objective tives for several water-quality prop in the Mocho subbasins. The areas in erties and constituents and in many the central basin that have dissolved cases set different objectives for mu solid:; below the objectives are along nicipal and agricultural uses. In ad Arroyo Mocho and Arroyo Valle, the dition to these objectives applicable principle recharge areas in the valley. for all surface and ground water in the All the wells that exceeded the nitrate San Francisco Bay area, separate and objective in the central basin are more specific objectives have been set located around the Livermore and for surface and ground water in the Pleadanton wastewater-disposal areas Alameda Creek basin above Miles with the exception of 3S/2E-19D6 and 28 Water-Quality Conditions in Livermore-Amador Valley CO PO PO t T OOOZ.Z.UL liv^iii Illlcococo IIVQIII 1 1 1 1 "V. >s. >s. W r- CM r- Is- 0 a ON CM E 0099AUL 1 1 1 00 1 1 1 1 1 1 1 1 CM CO 1 1 1 v. 1 1 1 l l l l 1 v. w -3" T r- (4- 0 ^ £_ 00 O\ PO CO CM 0 co vo f~- f~- O O 00 W II'V.'V.'V.'V. 1 1 1 1 I I- i- ON 3 E 0059Z.LLL I 1 it ro co h- I l l l I "v. >s. T- CO 3 CM i- T- it w s- C W ., 3 W V, 0 T5 0 + > C 0 i- i- o > s. o- O > " CO 3 ._ ._ CM CM CM CM CM P O wo P -P . . 1 1 "V. | >s. | 1 -V. I 1 it 1 "V. O CQ 0 CO O 009*7^- L L L IIOOIr-1 Ih-l 1 "V. | O 0 0 f- 4-> 0 PO it CM T- CM 3 S_ o) W ; CM N .£2 O O)< O OS- 0 5- 0 P T5 0 it CO **> C 4^ "D r- f 1 1 1 1 1 1 1 r- I p o in c CO 0 1 1 \ -s. | | | | | | 1 "V. | O CM 0 00£9Z.LU 1 1 O r- T- &_ 1 0 r r co >> 4J 0 0 0 3 4-> CO CQ O O O " ' co X r- t r- O O O 1 5- W «t- 0 CM r- CM CM 1 CM 1 1 1 1 CM i- CO 0*0 II'V.'V.'V.-X. 1-V.I | | |>v. 03 4-> 5- 3 4-> 0039Z.LU 1 1 CM r- r- i- r- CM per 0 0 a (/> CO r- r co E -P e JC > s_ co 4J 0 -P W ON T5 4-> C W 1 1 T- 1 1 1 1 1 1 1 1 1 1 0 CO 0 S_ S_ 0 0009Z.LLL 1 1 'V. | | | 1 1 1 1 1 1 1 T3 3C O 0 0 . . 0 O.-P Q 0 5- CO E O co 0 w 3t CO X C O.E 1 w 0O CO 0 *O W £_ O C|_ r- \D *>O *>O *O P 0) O 0)CO O 1 1 "V. f*. r- i- Ir-l 1 1 1 i- CO 0 H Water-Quality Objectives 29 19Rl. These two wells are in an un- The dfssolved-solids objective of 500 sewered area where septic tank leakage mg/L as a daily maximum was exceeded could cause nitrate in the ground at every station except Arroyo Valle water. The occurrence of high dis at P easanton. These violations are solved solids in ground water is most so w despread in both time and loca- likely a natural phenomenon in the tion that it is apparent the dissolved- shallow aquifers in most of the valley solids objective cannot be met in most that is away from Arroyo Mocho and of the valley's surface water. Samples Arroyo Valle. In addition, the waste- were too infrequent to evaluate the disposal practices at Livermore and 90-day mean and 90-day, 90th-percentile Pleasanton probably have increased the objectives, but it seems that these dissolved solids and nitrate but the objectives are regularly exceeded dur extent of these increases is not known. ing much of the year. The specific- An example of an increase in dissolved condiiictance objective was exceeded solids is shown by comparing dissolved- much less often than the dissolved- solids concentrations at well solids; objective. This is because the 3S/2E-7C1, located just upgradient from 1 ,600 -ymho specific conductance ob the Livermore sewage-treatment plant, jective is approximately equivalent with wells downgradient. Water from to a 1,000-mg/L dissolved-solids well 3S/2E-7C1 was below the dissolved- objective instead of the 500 mg/L solids and nitrate objectives, whereas, that is currently (1983) set. The most of the water from wells down- pH objective was exceeded (all greater gradient from the sewage-treatment than 8.5) at five stations, but so plant exceeded the objectives. infrequently that a water-quality prob em probably does not exist. Boron In several areas in the valley, dis concentrations in excess of the objec solved iron and manganese were detect- tive was detected only at Arroyo Las edin concentrations exceeding the re Positas at Livermore and near commended concentrations for public Pleasanton, Arroyo Mocho near drinking water supplies (U.S. Envi Pleasanton, and Arroyo Valle near ronmental Protection Agency, 1977). Livermore. These boron concentra The recommended maximum of 300 yg/L tions are naturally occurring. Manga for iron and 50 yg/L for manganese is nese concentrations in excess of the based on taste preference. Forty-six objective were common at most of the wells had mean manganese concentra stations during low flow periods. tions greater than 50 yg/L and five Theste occurrences, like that of boron, wells had mean iron concentrations are the result of upstream geology in greater than 300 yg/L (table 6). All the Dasin. The chloride objective was the wells with high iron concentra exceeded frequently at the Arroyo Las tions, except one (2S/2E-27C2), are Positas stations because of the nat located in the western edge of the urally occurring sodium chloride water valley. The highest mean concentra in the stream. The 27 samples taken tion of iron (2,900 yg/L) was detected from Alamo Canal that exceeded the in well 3S/1E-30A9. Wells with high chloride objective were detected prior manganese concentrations (greater than to February 1978. Most of these 50 yg/L) were detected generally in samples were taken during the the Dublin, Bernal, and Camp sub- 1976*77 drought when streamflow was basins. The highest concentrations generally less than normal in most in these areas were generally as streeims. The chloride objective has sociated with the clay layer north of not been exceeded in an Alamo Canal Pleasanton. sample since the export of treated effluent began in 1980. Sampling was Some violations of at least one of too infrequent to evaluate the 90-day the water-quality objectives occurred mean and 90-day, 90th-percentile chlor at all of the surface-water stations. ide objective. 30 Water-Quality Conditions in Livermore-Amador Valley TABLE 6.--Wells that have mean concentrations in excess of water-quality objectives [--, mean observations that did not exceed water-quality objectives] Specific Chloride, Di sso 1 ved Nitrate, Boron, I ron, Manganese, We II No. conductance dissolved so 1 ids d i sso 1 ved d i sso 1 ved dissolved dissolved (umho) (mg/L) (mg/L) (mg/L as N) (ug/L) (ug/L) (ug/L) 2S/1W-14N1 ______520 15F1 ------_ 1,200 36E3 ------450 2S/2E-21L4 -- 220 27C2 ' 3,040 780 1,710 16,000 470 160 27P21 4,890 1,500 2,650 __ 38,000 300 34E1 -- __ -- -- 240 3S/1E-1H3 __ 850 ______1P2 -- 870 -- 2,600 __ 1R2 __ __ 539 11 ______2K2} 1,650 14 2,000 __ 2N2 1 1,360 17 -- 77 2N3 __ __ 688 __ __ _- -- 2R1 __ __ 13 -_ __ 3G2 __ -- __ __ 660 4J4 __ -- __ -- 550 4Q2 1,600 -- __ 2,900 50 5J2 1 1,780 1,140 __ __ 917 5M1 _- __ -- __ __ 590 6F3 1 2,250 1,480 -- 5,600 210 6R21 4,620 690 3,380 -- -- 1,800 7B2 -- __ __ -- 60 7F11 9,930 3,000 6,550 __ _ _ 5,800 7M2} 2,180 1,350 -- -- 2,100 1,200 8B1 1 1,950 1,160 -- 2,300 260 8H2 __ 855 -- -- __ 8K1 __ 764 __ -- 70 8N1 1,670 1,110 __ _- __ 9G1 __ __ 808 -- __ -_ -_ 9P5 _- 774 -- -- __ 9Q1 __ 721 -- __ __ 10A2 1,730 1,000 -- 3,000 -- 10E1 __ 522 ______10G2 __ 794 -- -- __ 11B1 -- 949 11 2,900 -- 12A2 __ 688 12 __ 57 12D2 1,620 962 16 __ __ 12F1 __ __ 529 __ __ 51 12G1 -- 810 14 __ _ _ 12H1 -- 577 ______16E4 -- 604 __ __ _ 17B4 -- 652 -- -- __ 18E4 ______« H 660 18J1 -- 564 __ __ 18J2 2,350 1,520 __ __ 1,800 19C4 -- 648 __ __ 160 19K1 -_ 788 __ -- 2,500 20F5 -- 665 __ __ 20 Jl -- 861 11 __ _ _ 20J4 -- 821 14 _ _ 55 20M11 -- 896 13 __ 20Q1 1,620 932 14 180 22D2 -- __ 776 15 . *m __ -- 29D2 720 __- 29E3 -- 847 __ 2,300 100 29M4 -- -- -_ 670 200 29P2 -- 848 -- 340 Water-Quality Objectives 31 TABLE 6.--Wells that have mean concentrations in excefes of water-quality objectives--Continued Spec i f ic Chloride, Dissolved Nit ~ate, Boron, 1 ron, Manganese, Well No. conductance d i ssolved sol ids d i ss >lved dissolved dissolved dissolved ( umho) (mg/L) (mg/L) (mg/L as N) (ug/L) (ug/L) (ug/L) 3S/1E-30A8 730 -f 30A9 -f 2,900 510 32G2 2,140 1,170 4- 470 3S/1W-1B5 435 1L1 1 ______:1 2,000 450 12J1 1 1,980 1,330 --\ 830 13J1 -- __ 63 3S/2E-1F2"! 2,590 570 1,590 -f 6,600 __ 1P2 1 2,040 1,310 -t 5,400 -- 3K3 -- 560 ~f __ 5J1 -- 762 - 2,100 __ 7C2 -- 680 Ti. -- -- 7N1 ______. -_ 67 8H2 -- 638 1! -- 8K2 -- 573 1 i -- 9Q4 -- 603 1,; __ 10F3 -- 749 1! __ 10Q1 1,640 995 Tf __ 11A1 -- __ __ 1J> _ _ -- -- 11C1 -- 628 1(> __ 14A3 -- 638 -. . __ 14B4 -- 516 - __ 15J2 __ 715 2( > __ __ 16A3 -- 502 1 -- __ 16J1 -- __ -. . 130 19D6 -- __ 1() __ 19F4 -- 1() -- 21L13 ______. __ 180 22B1 -- 715 1() __ 24A1 -- 865 1(j __ 26J2 -- 598 - . 310 29 F4 -- __ - 160 30D2 __ __ _. __ 160 33G2 -- 656 - . 360 33G3 2,420 1,450 - 3,300 640 33K1 2,110 1,220 - 6,400 __ 33L1 -- 778 1,000 3S/3E-7D2"! 2,390 1,490 r 7,000 __ __ 7M2 ~~ __ _ _ ~ ~~ 63 1 Well located in fringe subbasin. CHANGES IN THE EXISTING Other wells could be sampled twice MONITORING NETWORK a year to establish long-term trends. In addition to the twice-yearly samp Analysis of data for the present well ling at most wells, a network of key network shows that variability of most wells; at various locations and depths water-quality constituents is high, is proposed. These key wells would be and that many wells have seasonal or sampled every 2 months and would be other periodic patterns to the varia concentrated near areas of known tions found. Because of this variabil ground-water contamination and major ity, continued sampling is desirable recharge areas. Sampling at these wells for all wells that have less than 5 would monitor short-term variability in years of data on a quarterly basis until water quality. A list of suggested key 5 years of data have been collected. wells is presented in table 7. 32 Water-Quality Conditions in Livermore-Amador Valley TABLE 7. Proposed key wells [U.S. Geological Survey identification well numbers are given in table 1. Type of well: C, wells constructed for this study; E, exi st ing we I I] Depth of Type of Perforation Period of water We 1 1 No . we I I wel 1 interva 1 qua I i ty record (feet) (feet) (water yea r) 2S/1E-32N1 45 C 35-40 1976-83 2S/2E-27P2 68 C 35-45; 59-63 1979-83 3S/1E-1R2 56 C 49-54 1981-83 2R1 33 C 21-26 1975-83 5J2 100 C 90-95 1978-83 7B2 150 C 143-149 1979-83 8H2 205 E 124-139; 148-165 1981-83 10A2 88 C 70-80 1979-83 11B1 43 C 33-38 1975-83 12G1 73 C 63-68 1975-83 12N1 304 E 7 perforations 1980-83 from 112-295 14G1 500 E 150-500 1979-83 16H2 94 C 82-92 1979-83 17Q4 84 C 74-79 1978-83 19C4 78 C 68-73 1979-83 20F5 46 C 36-41 1975-83 20Q1 52 E 41-51 1977-83 29D2 64 C 54-59 1975-83 29M4 57 C 47-52 1975-83 3S/1W-1B5 108 C 98-103 1979-83 12J1 62 C 52-57 1975-83 13J1 49 C 39-44 1976-83 3S/2E-8K2 74 C 64-69 1977-83 11J2 110 C 90-92; 102-108 1979-83 16E4 45 C 35-40 1978-83 19F4 164 E 100-160 1976-83 22B1 55 C 45-50 1976-83 30D2 44 C 24-29; 34-39 1979-83 3S/3E-7D2 74 C 64-69 1976-83 A complete analysis of major cations the presence of dissolved oxygen in and anions, plus boron, silica, and significant concentrations in ground manganese, would be collected once a water may be much more common than year at all network wells. Key wells widely believed. would have complete analyses taken every other bimonthly sample. Field The shallow, mostly unconfined aqui measurements for pH, specific conduc fers in the Livermore Valley should tance, temperature, alkalinity, dis have significant concentrations of solved oxygen, and water level, and a oxygen, except in areas where soil and nitrate and chloride sample would be aquifer bacteria use organic material taken at each well during each samp to consume the dissolved oxygen carried ling. Dissolved oxygen would be mea in the ground water by recharge. sured on a reconnaissance basis the first year to determine if it can be a Based on analysis of existing data, useful indicator of the presence of there is a consistent and reliable organic substances in ground water. dissolved-solids to specific-conductance Recent studies (Winograd and ratio in the network wells. This makes Robertson, 1982) have indicated that it possible to delete the dissolved- Changes in the Existing Monitoring Network 33 solids determination from the sampling REFERENCES CITED schedules for all wells that have at least 5 years of data. Dissolved Brown, D. M., Skougstad, M. W., and Fishman, solids could be calculated routinely by M. J., 1970, Methods for collection and analy use of the specific conductance and sis of water samples for dissolved minerals and gasses: U.S. Geological Survey Techniques the dissolved-solids to specific- of Water-Resources Investigations, Book 5, conductance ratio already established Chapter Al, 160 p. [superseded by Skougstad for that well. If a change in water and others, 1979]. California Department of Water Resources, 1964, type was detected at any one well, the Aliimeda Creek watershed above Niles: chemical ratio of dissolved solids to specific quality of surface water, waste discharges, and conductance would have to be verified ground water: Federal-State Cooperative Water Quality Investigations, 122 p., and appendixes. by further sampling. 1974, Evaluation of ground-water resources: Livermore and Sunol Valleys: California Depart The determination of organic carbon ment of Water Resources Bulletin 118-2, 153 p. California Regional Water Quality Control Board, content of the ground water is poten San Francisco Bay Region, Region Plan, 1982: tially useful means of determining Final report. areas of water-quality degradation. Camp, Dresser, and McKee Inc., 1982, Wastewater management study for the unsewered, unincorpor This study has shown that the use of ated area of Alameda Creed watershed above TOC is unreliable because of sampling, Niles: Final report, 27 p. analytical problems, and the uncer Clark^ B. L., 1930, Tectonics of the Coast Ranges of middle California: Geologic Society of Amer tainty of what changes occur to the ica Bulletin, v. 41, no. 4, p. 747-828. sample from the time of collection to Dibblee, T. W. Jr., 1980a, Geologic map of the analysis. A better method of sampling AHamont quadrangle, Alameda County, California: U.S. Geological Survey Open-File Report 80-538. organic carbon is to analyze dissolved 1980b, Geologic map of the Livermore quad organic carbon (DOC). Since ground rangle, Alameda and Contra Costa Counties, water is low in suspended material, California: U.S. Geological Survey Open-File Report 80-533-B. the DOC determination would closely |980c. Geologic map of the Dublin quadrangle, approximate actual TOC concentrations. Alcimeda and Contra Costa Counties, California: In addition, the method used for fil U. S. Geological Survey Open-File Report 80-537. Goerlitz, D. F., and Brown, Eugene, 1972, Methods tering DOC samples (silver membrane forj analysis of organic substances in water: filters) provides better sample preser U. S. Geological Survey Techniques of Water- vation and assures minimal change in Re sources Investigations, Book 5, Chapter A3, 40 organic carbon content between the Helwi 31 Water-Quality Conditions in Livermore-Amador Valley