Safe Drinking Water Plan for California: Report to the Legislature in Compliance with Health and Safety Code Section 116365

California State Water Resources Control Board (SWRCB) | June 8th, 2015

The State Water Board recognizes that to fulfill the Human Right to Water in California, every resident should have access to affordable, safe drinking water regardless

The State Water Board recognizes that to fulfill the Human Right to Water in California, every resident should have access to affordable, safe drinking water regardless of the water system size. Provided data become available on this topic, in a future update of the Safe Drinking Water Plan the Water Board could expand the scope to include systems below 15 service connections, but to do that would require new and expanded authority, significantly more resources, as well as commitment and involvement of other local and state agency partners. At this time, this report contains 32 practical recommendations in 9 areas that would expand the State Water Board’s efforts to bring a greater number of systems into compliance and contribute to realizing the Human Right to Water in California. Each chapter provides a background discussion covering the areas mandated by the Legislature including a description of problems and issues and a set of conclusions and recommendations with the basis and justification for them. A detailed five-year implementation plan addressing the major recommendations is provided in Appendix 10.

Salinity of deep groundwater in California: Water quantity, quality, and protection

National Academy of Sciences (NAS) | July 12th, 2016

Deep groundwater aquifers are poorly characterized but could yield important sources of water in California and elsewhere. Deep aquifers have been developed for oil and g

Deep groundwater aquifers are poorly characterized but could yield important sources of water in California and elsewhere. Deep aquifers have been developed for oil and gas extraction, and this activity has created both valuable data and risks to groundwater quality. Assessing groundwater quantity and quality requires baseline data and a monitoring framework for evaluating impacts. We analyze 938 chemical, geological, and depth data points from 360 oil/gas fields across eight counties in California and depth data from 34,392 oil and gas wells. By expanding previous groundwater volume estimates from depths of 305 m to 3,000 m in California’s Central Valley, an important agricultural region with growing groundwater demands, fresh [<3,000 ppm total dissolved solids (TDS)] groundwater volume is almost tripled to 2,700 km3, most of it found shallower than 1,000 m. The 3,000-m depth zone also provides 3,900 km3 of fresh and saline water, not previously estimated, that can be categorized as underground sources of drinking water (USDWs; <10,000 ppm TDS). Up to 19% and 35% of oil/gas activities have occurred directly in freshwater zones and USDWs, respectively, in the eight counties. Deeper activities, such as wastewater injection, may also pose a potential threat to groundwater, especially USDWs. Our findings indicate that California’s Central Valley alone has close to three times the volume of fresh groundwater and four times the volume of USDWs than previous estimates suggest. Therefore, efforts to monitor and protect deeper, saline groundwater resources are needed in California and beyond.

San Fernando Groundwater Basin Remediation Program

Los Angeles Department of Water & Power (LADWP) | January 1st, 2018

San Gabriel Valley Superfund Sites Progress Updates

U.S. Environmental Protection Agency (EPA) | May 31st, 2021

San Joaquin Valley Drainage Monitoring Program 2006 - 2010

California Department of Water Resources (DWR) | September 20th, 2013

This report shares valuable information about agricultural drainage water in order to increase the understanding of its potential impacts and improve its management in th

This report shares valuable information about agricultural drainage water in order to increase the understanding of its potential impacts and improve its management in the San Joaquin Valley. The Drainage Monitoring Program is a cooperative effort of State, federal, and local agencies.  Program staff collect, assemble, review, evaluate, and disseminate data on both the quality of drainage water as well as the depth of shallow groundwater in the San Joaquin Valley.  Fifty-two drainage sump systems are monitored for flow, sodium, sulfate, total dissolved solids, selenium, and other constituents.  Staff also combine the Department of Water Resources' data with data from over 10 other agencies for this report. DWR used depth information, gathered from approximately 1200 shallow groundwater wells, to draw Present and Potential Drainage Problem Areas Maps for the period from 2006 through 2010.  These maps show over one million acres of potentially impacted lands.  Data provided by several agencies, including the Buena Vista Water Storage District, Central California Irrigation District, Firebaugh Canal Water District, Kern County Water Agency, Panoche Water and Drainage District, San Luis Canal Company, Westlands Water District, and DWR was combined to create the maps. DWR also drew electrical conductivity (EC) maps from ECs measured in about 690 of those wells for the years 2009 and 2010.  All off the maps help inform managers of potential drainage problems in their areas due to encroachment of shallow groundwater.  The number of agencies participating is a reflection of the significance of drainage problems in the San Joaquin Valley and the potential impacts. This report focuses on five years of data collection and compilation for the calendar years 2006 thought 2010, with a special focus on historical arsenic, boron, and selenium.  In addition, pesticide and nutrient data have been added to this report for your use..

Selected trace-elements in alluvium and rocks, western Mojave Desert, southern California

Journal of Geochemical Exploration (Elsevier) | September 3rd, 2018

Concentrations of twenty-seven elements, including naturally-occurring water-quality contaminants arsenic, chromium, and uranium, were measured in 217 samples of alluviu

Concentrations of twenty-seven elements, including naturally-occurring water-quality contaminants arsenic, chromium, and uranium, were measured in 217 samples of alluvium and rock from the western Mojave Desert, southern California, using portable (pXRF) and laboratory (LXRF) X-ray fluorescence. Comparison of measurements with NIST-traceable standards was good, although pXRF overestimated iron compared to LXRF. Results suggest pXRF survey data are sufficiently accurate to assess regional geochemical differences in geologic-source terrains. Principal component analysis showed rubidium and potassium were associated with alluvium eroded from felsic terrain, while iron, copper, chromium, and to a lesser extent titanium, manganese, and nickel were associated with alluvium eroded from mafic terrain. Zinc, vanadium, and arsenic were associated with alluvium eroded from hydrothermal terrain. Elemental assemblages associated with different source terrains were traced spatially to identify the source and composition of alluvium composing aquifers pumped for water supply. Changes in geologic source terrain to the Mojave River, associated with movement along the San Andreas Fault over the past one to five million years, reduced the mafic fraction and increased the felsic fraction of alluvium deposited to the regionally important floodplain aquifer along the Mojave River—lowering chromium concentrations in alluvium through geologic time. Comparison of pXRF and sequential extraction data from 40samples showed arsenic and uranium were more abundant on the surfaces of mineral grains, while chromium and vanadium remained mostly within unweathered mineral grains—suggesting arsenic and uranium may be more readily mobilized into groundwater with changes in pH, redox, or ionic strength than chromium or vanadium.

Soil and Groundwater Contamination: Nonaqueous Phase Liquids–Principles and Observations

American Geophysical Union (AGU) | January 1st, 2005

Published by the American Geophysical Union as part of the Water Resources Monograph Series, Volume 17. Nonaqueous phase liquids (NAPLs) are frequently found as soil a

Published by the American Geophysical Union as part of the Water Resources Monograph Series, Volume 17. Nonaqueous phase liquids (NAPLs) are frequently found as soil and groundwater contaminants. Highly toxic even in small volumes, NAPLs can pose a threat to human health and damage surface and subsurface ecosystems. In this book, we clarify the complex phenomena of NAPL migration and offer insight into the behavior of NAPLs at sites undergoing monitoring and remediation. Contents include discussion on: * Principles of NAPL behavior in the subsurface, including flow, transfer of components to water and gas phases, and transport * Migration and distribution * Site characterization and monitoring * Remediation methods, including hydraulic removal, pump and treat, and soil vapor extraction * Further discussion on gaps in our understanding of NAPLs at the field scale along with a thorough tutorial approach and supplemental CD, make this book an important guide and resource for practicing engineers and scientists, risk assessment professionals, teachers, and students.

Spectral characterization of dissolved organic matter in groundwater to assess mixing with oil-field water near selected oil fields, southern California

Science of The Total Environment (Elsevier) | September 16th, 2023

SSALTS Final Phase 3 Report: Evaluate Potential Salt Disposal Alternatives to Identify Acceptable Alternatives for Implementation

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) | October 31st, 2016

The purpose of the Strategic Salt Accumulation Land and Transportation Study (SSALTS) is to identify the range of viable Central Valley alternatives for salt disposal to

The purpose of the Strategic Salt Accumulation Land and Transportation Study (SSALTS) is to identify the range of viable Central Valley alternatives for salt disposal to provide input for consideration during development of the Salt and Nitrate Management Plan (SNMP) for the region under the jurisdiction of the Central Valley Regional Water Quality Control Board (Central Valley Water Board). The findings have been used to guide discussions regarding establishment of regional salt management policies and the need for changes to the existing Central Valley Water Board Water Quality Control Plans (Basin Plans) to facilitate salt disposal in a manner that is most beneficial to the region and consistent with the State Water Resources Control Board’s (State Water Board) Recycled Water Policy. This work is being conducted under the direction of the Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) initiative, which is developing the SNMP for the Central Valley. The SSALTS project has been conducted in three phases (Figure 1-1): Phase 1: Identify and Characterize Existing Salt Accumulation Study Areas – The selection of representative study areas served as archetype situational examples to facilitate discussions regarding salt accumulation and disposal in the Central Valley. Each of these study areas was characterized to establish baseline information that was subsequently used to support development of salt disposal alternatives in Phases 2 and 3. Phase 2: Develop Potential Salt Management Strategies – Phase 2 of SSALTS developed potential long-term salt disposal alternatives in three parts: (1) in-valley alternatives; (2) out-of-valley alternatives; and (3) hybrid alternatives that combined in-valley and out-of valley salt disposal options. Phase 3: Evaluate Potential Salt Disposal Alternatives to Identify Acceptable Alternatives for Implementation – Alternatives developed under Phase 2 were evaluated in this report using selected feasibility criteria (e.g., regulatory, institutional, economic, technological, etc.). The outcome of this evaluation was the identification and prioritization of acceptable salt disposal alternatives for potential incorporation into Central Valley SNMP as salt management implementation measures. The Phase 1 and Phase 2 SSALTS final reports were submitted to the CV-SALTS Executive Committee in December 2013 and September 2014, respectively (CDM Smith 2013; CDM Smith 2014). The Phase 3 SSALTS draft report was submitted to the CV-SALTS Executive Committee in March 2015. Comments were received and incorporated into the Phase 3 SSALTS draft report. The Executive Committee recommended postponing the finalization of the Phase 3 SSALTS report until a draft of the Nitrate Implementation Measures Study (NIMS) report was completed, so that salt and nitrate implementation measures and mitigation strategies could be coordinated. While based on the March 2015 Phase 3 SSALTS draft report – and thus including the changes based on the March 2015 Phase 3 SSALTS draft report – and thus including the changes based on the original comments, the September 2016 Phase 3 SSALTS draft report had major changes in terms of content and structure. The September 2016 Phase 3 SSALTS draft report was sent to the Project Committee on September 20, 2016 and comments were received on October 5, 2016. The second set of comments were addressed and incorporated into this October 2016 Phase 3 SSALTS final report. Appendix E. provides the comments and responses on the September 2016 Phase 3 SSALTS draft report. The Phase 3 SSALTS report provides a path forward, based on the foundation of Phases 1 and 2 and CV-SALTS Executive Committee discussions.

Status and Understanding of Groundwater Quality in the Monterey Bay and Salinas Valley Basins, 2005: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | May 4th, 2011

Groundwater quality in the approximately 1,000 square mile (2,590 km2) Monterey Bay and Salinas Valley Basins (MS) study unit was investigated as part of the Priority Bas

Groundwater quality in the approximately 1,000 square mile (2,590 km2) Monterey Bay and Salinas Valley Basins (MS) study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in central California in Monterey, Santa Cruz, and San Luis Obispo Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA MS study was designed to provide a spatially unbiased assessment of the quality of untreated (raw) groundwater in the primary aquifer systems (hereinafter referred to as primary aquifers). The assessment is based on water-quality and ancillary data collected in 2005 by the USGS from 97 wells and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifers were defined by the depth intervals of the wells listed in the CDPH database for the MS study unit. The quality of groundwater in the primary aquifers may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOC), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources in the primary aquifers of the MS study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than (>) 1.0 indicates a concentration greater than a benchmark, and less than or equal to (?) 1.0 indicates a concentration less than or equal to a benchmark. Relative-concentrations of organic and special interest constituents [perchlorate, N-nitrosodimethylamine (NDMA), and 1,2,3-trichloropropane (1,2,3-TCP)], were classified as “high” (relative-concentration > 1.0), “moderate” (0.1 < relative-concentration ? 1.0), or “low” (relative-concentration ? 0.1). Relative-concentrations of inorganic constituents were classified as “high” (relative-concentration > 1.0), “moderate” (0.5 < relative-concentration ? 1.0), or “low” (relative-concentration ? 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion was defined as the percentage of the area of the primary aquifers with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifers with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially-weighted estimates were comparable in the MS study unit (within 90-percent confidence intervals). Inorganic constituents with human-health benchmarks were detected at high relative-concentrations in 14.5 percent of the primary aquifers, moderate in 35.5 percent, and low in 50.0 percent. High aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of nitrate (7.9 percent), molybdenum (2.9 percent), arsenic (2.8 percent), boron (1.9 percent), and gross alpha-beta radioactivity (1.5 percent). Relative-concentrations of organic constituents (one or more) were high in 0.2 percent, moderate in 6.6 percent, and low in 93.2 percent (not detected in 48.1 percent) of the primary aquifers. The high aquifer-scale proportion of organic constituents primarily reflected high aquifer-scale proportions of tetrachloroethene (0.1 percent) and methyl tert-butyl ether (0.1 percent). Relative-concentration for inorganic constituents with secondary maximum contaminant levels, manganese, total dissolved solids, iron, sulfate, and chloride were high in 18.6, 8.6, 7.1, 2.9, and 1.4 percent of the primary aquifers, respectively. Of the 205 organic and special-interest constituents analyzed, 32 constituents were detected. One organic constituent, the herbicide simazine, was frequently detected (in 10 percent or more of samples), but was detected at low relative-concentrations. The second component of this study, the understanding assessment, identified the natural and human factors that affect groundwater quality by evaluating land use, physical characteristics of the wells, and geochemical conditions of the aquifer. Results from these evaluations were used to explain the occurrence and distribution of constituents in the study unit. The understanding assessment indicated that most wells that contained nitrate were classified as being in agricultural land-use areas, and depths to the top of perforations in most of the wells were less than 350 ft (76 m). High and moderate relative-concentrations of arsenic may be attributed to reductive dissolution of manganese or iron oxides, or to desorption or inhibition of arsenic sorption under alkaline conditions. Arsenic concentrations increased with increasing groundwater depth and residence time (age). Simazine was detected more often in groundwater from wells with surrounding land use classified as agricultural or urban, and with top of perforation depths less than 200 ft (61 m), than in groundwater from wells with natural land use or with deeper depths. Tritium, helium-isotope, and carbon-14 data were used to classify the predominant age of groundwater samples into three categories: modern (water that has entered the aquifer since 1953), pre-modern (water that entered the aquifer prior to 1953 to tens of thousands of years ago), and mixed (mixtures of modern- and pre-modern-age waters). Arsenic concentrations were significantly greater in groundwater with pre-modern age classification than in groundwater with modern-age classification, suggesting that arsenic accumulates with groundwater residence time.