Nitrate Implementation Measures Study (NIMS) Final Report

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

This report summarizes the Nitrate Implementation Measures Study (NIMS) which addresses nitrate contamination in the groundwater basins underlying the floor of the Centra

This report summarizes the Nitrate Implementation Measures Study (NIMS) which addresses nitrate contamination in the groundwater basins underlying the floor of the Central Valley and appropriate implementation measures to mitigate nitrate contamination for these areas using a phased approach that includes providing safe drinking water, reducing or eliminating impacts to drinking water sources and implementing managed restoration activities where needed to restore beneficial uses in groundwater. These implementation measures will be incorporated into the SNMP. The findings from both the SSALTS and the NIMS will be used to guide discussions regarding the need for changes to the existing Basin Plan to facilitate salt disposal and mitigation measures for nitrate in a manner that is most beneficial to the region covered by the SNMP. 

Nitrogen Tracking and Reporting Task Force: Final Report

California Department of Food and Agriculture (CDFA) | December 6th, 2013

Agriculture in California is highly diverse in terms of food production, crop management, ecosystems, and climate. Nitrogen fertilizer is essential for crop food producti

Agriculture in California is highly diverse in terms of food production, crop management, ecosystems, and climate. Nitrogen fertilizer is essential for crop food production. Nitrogen fertilizer use over several decades in California has led to nitrates in groundwater. Recognizing that nitrates from agricultural nitrogen fertilizing materials have entered some California groundwater systems used for drinking water, CDFA convened the Nitrogen Tracking and Reporting Task Force in 2013 as part of a multi-pronged administration effort to address nutrient management and water quality. This Task Force was charged with implementing Recommendation 11 of several recommendations made to the Legislature by the State Water Board: “CDFA, in coordination with the Water Boards, should convene a Task Force to identify intended outcomes and expected benefits of a nitrogen mass balance tracking system in nitrate high-risk areas. The Task Force should identify appropriate nitrogen tracking and reporting systems, and potential alternatives, that would provide meaningful and high quality data to help better protect groundwater quality.” This charge was achieved through several measures including, among others, understanding and discussing the pros and cons of existing nitrogen tracking and reporting systems, identifying desirable components or elements of existing systems and evaluating the variability and complexity of California agriculture in relation to where existing systems have been implemented. Through several meetings, presentations by subject matter experts and discussion, the Task Force members came to general agreement on several components of an effective nitrogen tracking and reporting system. The recommended system addresses eight key topics including: (1) System Structure; (2) Data Elements; (3) Roles, Responsibilities and Data Accessibility; (4) Benefits of Participation; (5) Verifiability; (6) Societal Benefits of the Recommended System; (7) Limitations and (8) System Phase-in. This report presents the Task Force’s discussions and recommendations including intended outcome and anticipated benefits of such a tracking and reporting system for nitrogen use.

North San Francisco Bay Shallow Aquifer Study Unit, 2012: California GAMA Priority Basin Project (Version 1.1, February 2018)

U.S. Geological Survey (USGS) | February 23rd, 2018

Groundwater quality in the North San Francisco Bay Shallow Aquifer study unit (NSF-SA) was investigated as part of the Priority Basin Project of the California Grou

Groundwater quality in the North San Francisco Bay Shallow Aquifer study unit (NSF-SA) was investigated as part of the Priority Basin Project of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is in Marin, Mendocino, Napa, Solano, and Sonoma Counties and included two physiographic study areas: the Valleys and Plains area and the surrounding Highlands area. The NSF-SA focused on groundwater resources used for domestic drinking water supply, which generally correspond to shallower parts of aquifer systems than that of groundwater resources used for public drinking water supply in the same area. The assessments characterized the quality of untreated groundwater, not the quality of drinking water. This study included three components: (1) a status assessment, which characterized the status of the quality of the groundwater resources used for domestic supply for 2012; (2) an understanding assessment, which evaluated the natural and human factors potentially affecting water quality in those resources; and (3) a comparison between the groundwater resources used for domestic supply and those used for public supply. The status assessment was based on data collected from 71 sites sampled by the U.S. Geological Survey for the GAMA Priority Basin Project in 2012. To provide context, concentrations of constituents measured in groundwater were compared to U.S. Environmental Protection Agency (EPA) and California State Water Resources Control Board Division of Drinking Water regulatory and non-regulatory benchmarks for drinking-water quality. The status assessment used a grid-based method to estimate the proportion of the groundwater resources that has concentrations of water-quality constituents approaching or above benchmark concentrations. This method provides statistically unbiased results at the study-area scale and permits comparisons to other GAMA Priority Basin Project study areas. In the NSF-SA study unit as a whole, inorganic constituents with human-health benchmarks were detected at high relative concentrations (RCs) in 27 percent of the shallow aquifer system, and inorganic constituents with secondary maximum contaminant levels (SMCL) were detected at high RCs in 24 percent of the system. The inorganic constituents detected at high RCs were arsenic, boron, fluoride, manganese, nitrate, iron, sulfate, and total dissolved solids (TDS). Organic constituents with human-health benchmarks were detected at high RCs in 1 percent of the shallow aquifer system. Of the 148 organic constituents analyzed, 30 constituents were detected, although only 1, chloroform, had a detection frequency greater than 10 percent. Natural and anthropogenic factors that could affect the groundwater quality were evaluated by using results from statistical testing of associations between constituent concentrations and values of potential explanatory factors. Groundwater age class (modern, mixed, or pre-modern), redox class (oxic or anoxic), aquifer lithology class (metamorphic, sedimentary, or volcanic), and dissolved oxygen concentrations were the explanatory factors that explained distribution patterns of most of the inorganic constituents best. Groundwater classified primarily as pre-modern or mixed in age was associated with higher concentrations of arsenic and fluoride than waters classified as modern. Anoxic or mixed redox conditions were associated with higher concentrations of boron, fluoride, and manganese. Similar patterns of association with explanatory variables were seen for inorganic constituents with aesthetic-based benchmarks detected at high concentrations. Nitrate and perchlorate had higher concentrations in oxic than in the anoxic redox class and were positively correlated with urban land use. The NSF-SA water-quality results were compared to those of the GAMA North San Francisco Bay Public-Supply Aquifer study unit (NSF-PA). The NSF-PA was sampled in 2004 and covers much of the same area as the NSF-SA, but focused on the deeper public-supply aquifer system. The comparison of the NSF-PA to the NSF-SA showed that there were more differences between the Valleys and Plains study areas of the two study units than between the Highlands study areas of the two study units. As expected from the shallower depth of wells, the NSF-SA Valleys and Plains study area had a lesser proportion of pre-modern age groundwater and greater proportion of modern age groundwater than the NSF-PA Valleys and Plains study area. In contrast, well depths and groundwater ages were not significantly different between the two Highlands study areas. Arsenic, manganese, and nitrate were present at high RCs, and perchlorate was detected in greater proportions of the NSF-SA Valleys and Plains study area than the NSF-PA Valleys and Plains study area.

Opportunities to protect drinking water sources and advance watershed goals through the Clean Water Act

U.S. Environmental Protection Agency (EPA) | November 10th, 2014

We live in times of both declining public agency resources and increasing complexity of environmental and public health problems, like the increasing occurrence, intensit

We live in times of both declining public agency resources and increasing complexity of environmental and public health problems, like the increasing occurrence, intensity, and duration of harmful algal blooms and precursors to disinfection by-products in drinking water. These and other problems are compounded by population growth, climate extremes, and excess water in some places as well as insufficient water in others. Complex times demand creative and thoughtful approaches to challenges. It is critical that we find innovative solutions that leverage expertise, resources, efficiencies, and authorities to achieve our Nation’s water quality and source water protection goals. As part of a State-U.S. Environmental Protection Agency (EPA) collaboration initiative, a workgroup was formed to identify opportunities to coordinate among clean water and drinking water programs. This workgroup recognizes that many difficult issues cross program boundaries, and thus a coordinated approach has the potential to make greater headway nationally. In developing the product that follows, the workgroup also drew on the experiences of states and EPA practitioners managing these programs. This Toolkit is a result of state and EPA collaboration. It could not have been developed without the time, effort and dedication of those who contributed to it and particularly the expertise of the state and EPA regional participants who are implementing the practices in this report. This initiative and Toolkit invite a more holistic and coordinated planning and funding approach between the clean water and drinking water programs, and with other public and private partners at the federal, state, and local levels, including water and wastewater utilities. The opportunities outlined in this Toolkit do not reflect all possible environmental authorities that may work together to protect drinking water; it is beyond the scope of this document to acknowledge all threats to, and challenges involved in, protecting drinking water. Instead, the suggestions below describe the fundamental steps toward protective actions that may catalyze broader collaboration among a diversity of programs and entities. It is important to note that this Toolkit does not impose legally binding requirements on EPA, states, tribes, or the regulated community, nor does it confer legal rights or impose legal obligations on any member of the public. This Toolkit does not constitute a regulation, nor does it change or substitute for any Clean Water Act or Safe Drinking Water Act1 provision or EPA regulations. Rather, this Toolkit is designed to support discussion, institutional change, and advance water quality goals and the protection of drinking water sources of public water systems (PWSs)2, also known as source water protection.

Policy Considerations for Managing Agricultural Nitrogen to Reduce Groundwater Contamination in California

California Roundtable on Agriculture and the Environment (CRAE) | May 28th, 2013

Recent research, including “The California Nitrogen Assessment”1 and the UC Davis Report for the SWRCB SBX2 1 Report to the Legislature2, has produced an important co

Recent research, including “The California Nitrogen Assessment”1 and the UC Davis Report for the SWRCB SBX2 1 Report to the Legislature2, has produced an important collection of data about how nitrogen compounds move in the environment. Members of the California Roundtable on Agriculture and the Environment (CRAE) share an interest in meaningfully addressing water quality challenges while maintaining a healthy and prosperous agriculture sector. Because of the serious health concerns associated with nitrate in groundwater, CRAE members agree that the immediate goal should be to find cost-effective solutions to cleaning up drinking water supplies or providing safe alternate sources of drinking water to affected communities. We support ongoing efforts, such as the governor’s Drinking Water Task Force, to address this important issue. While CRAE’s ultimate interest is in addressing the full range of water quality challenges related to agriculture—from drinking water to legacy issues, groundwater to surface water, and nitrate to Total Maximum Daily Loads (TMDLs)—and supporting improved nutrient management broadly speaking, the group has chosen to focus specifically on the longer-term challenge of reducing nitrate loading in groundwater from agricultural sources. Recognizing that a range of research and policy processes to address the harmful impacts of excess reactive nitrogen-based compounds in the environment are ongoing, CRAE stakeholders agreed that a focus on preventing further contamination of groundwater from nitrate is an area where CRAE has a unique opportunity to contribute. Furthermore, we anticipate that approaches to reduce nitrate loading that adhere to the considerations below will simultaneously improve other challenges, including air quality, energy use, and climate change. Nitrate contamination is projected to increase in the coming years as legacy contributions work their way through the soil profile. The short-term remediation of groundwater basins is so costly as to be practically impossible. Therefore, CRAE has concentrated on intermediate and longer-term groundwater quality issues by helping to find practical solutions to groundwater quality challenges. Reflecting our membership composition, our focus is on the contribution of agricultural sources of nitrate in particular. CRAE has compiled the following set of key facts on our state of knowledge about nitrogen management and a set of considerations to inform related policy and programs focused on improving water quality.

Populations using public-supply groundwater in the conterminous U.S. 2010; Identifying the wells, hydrogeologic regions, and hydrogeologic mapping units

Science of the Total Environment (Elsevier) | September 28th, 2021

Most Americans receive their drinking water from publicly supplied sources, a large portion of it from groundwater. Mapping these populations consistently and at a high r

Most Americans receive their drinking water from publicly supplied sources, a large portion of it from groundwater. Mapping these populations consistently and at a high resolution is important for understanding where the resource is used and needs to be protected. The results show that 269 million people are supplied by public supply, 107 million are supplied by groundwater and 162 million are supplied by surface water. The population using public supply drinking water was mapped in two ways: the census-enhanced method (CEM) evenly distributes the population across populated census blocks, and the urban land-use enhanced method (ULUEM) distributes the population only to certain urban land use designations. In addition, a two-dimensional polygon data set was created for the conterminous U.S. that identifies 177 unique Hydrogeologic Mapping Units (HMUs) with similar hydrogeologic characteristics. The HMUs do not overlap, but they can delineate areas where stacked hydrogeologic regions (HRs) contribute drinking water from below the surface. HRs are water-bearing geologic regions identified as either a principal aquifers (PA) or secondary hydrogeologic regions (SHR). Within each HMU, the wells were used to determine the proportion of each HR that is providing groundwater to the HMU. In 63% of the HMUs, a single HR is providing water to the public supply wells located within it, while the rest of the HMUs show that the wells are tapping up to a maximum of four stacked HRs. In total, groundwater from 108 HRs provides drinking water for public supply, six of which provide more than 50% of the groundwater used for public supply drinking water. The aquifer serving the largest number of equivalent people (>17 million) is the glacial aquifer. The HR providing the greatest number of people per km2 is the Biscayne aquifer in Florida at nearly 453 people per km2.

Proposed Drinking Water Cost Assessment Model Assumptions on Physical Consolidation

California State Water Resources Control Board (SWRCB) | July 14th, 2023

The State Water Resources Control Board (State Water Board) is proposing an updated methodology for estimating potential modeled physical consolidation costs for Failing

The State Water Resources Control Board (State Water Board) is proposing an updated methodology for estimating potential modeled physical consolidation costs for Failing public water systems, At-Risk public water systems, state small water systems, and domestic wells. Non-consolidation options will be covered in detail in subsequent white papers.

Proposed Health-Protective Concentration for the Noncancer Effects of Hexavalent Chromium in Drinking Water

California Environmental Protection Agency (CalEPA) | November 21st, 2023

Public and private tapwater: Comparative analysis of contaminant exposure and potential risk, Cape Cod, Massachusetts, USA

Environment International (Elsevier) | March 19th, 2021

Humans are primary drivers of environmental contamination worldwide, including in drinking-water resources. In the United States (US), federal and state agencies regulate

Humans are primary drivers of environmental contamination worldwide, including in drinking-water resources. In the United States (US), federal and state agencies regulate and monitor public-supply drinking water while private-supply monitoring is rare; the current lack of directly comparable information on contaminant-mixture exposures and risks between private- and public-supplies undermines tapwater (TW) consumer decision-making. Methods: We compared private- and public-supply residential point-of-use TW at Cape Cod, Massachusetts, where both supplies share the same groundwater source. TW from 10 private- and 10 public-supply homes was analyzed for 487 organic, 38 inorganic, 8 microbial indicators, and 3 in vitro bioactivities. Concentrations were compared to existing protective health-based benchmarks, and aggregated Hazard Indices (HI) of regulated and unregulated TW contaminants were calculated along with ratios of in vitro exposure-activity cutoffs. Results: Seventy organic and 28 inorganic constituents were detected in TW. Median detections were comparable, but median cumulative concentrations were substantially higher in public supply due to 6 chlorine–disinfected samples characterized by disinfection byproducts and corresponding lower heterotrophic plate counts. Public-supply applicable maximum contaminant (nitrate) and treatment action (lead and copper) levels were exceeded in private-supply TW samples only. Exceedances of health-based HI screening levels of concern were common to both TW supplies. Discussion: These Cape Cod results indicate comparable cumulative human-health concerns from contaminant exposures in private- and public-supply TW in a shared source-water setting. Importantly, although this study’s analytical coverage exceeds that currently feasible for water purveyors or homeowners, it nevertheless is a substantial underestimation of the full breadth of contaminant mixtures documented in the environment and potentially present in drinking water. Conclusion: Regardless of the supply, increased public engagement in source-water protection and drinking-water treatment, including consumer point-of-use treatment, is warranted to reduce risks associated with long-term TW contaminant exposures, especially in vulnerable populations. 

Public drinking water contaminant estimates for birth cohorts in the Environmental Influences on Child Health Outcomes (ECHO) Cohort

Nature Portfolio (Springer Nature) | August 4th, 2024

We observed significant regional variability in contaminant concentrations across the US. ZCTAs were most likely to exceed the maximum contaminant level for arsenic (n 

We observed significant regional variability in contaminant concentrations across the US. ZCTAs were most likely to exceed the maximum contaminant level for arsenic (n = 100, 1.4%) and the health-protective threshold for total trihalomethanes (n = 3584, 64.0%). A 10% higher proportion of residents who were American Indian/Alaskan Native and Hispanic/Latino was associated with higher arsenic (11%, 95% CI: 7%, 15%; and 2%, 95% CI: 0%, 3%, respectively) and uranium (15%, 95% CI: 10%, 21%; and 9%, 95% CI: 6%, 12%, respectively) concentrations.