Comments on and Protest of Temporary Urgency Change Petition Regarding Delta Water Quality

California State Water Resources Control Board (SWRCB) | February 17th, 2023

Comments on the Draft Pyrethroid Control Program and Research Plan

Delta Stewardship Council (Delta Council) | September 18th, 2023

Comments on the Scientific Basis for Implementation of Voluntary Agreements for the Sacramento River, Delta, and Tributaries

Delta Stewardship Council (Delta Council) | March 8th, 2023

Committee for Delta Resources Improvement Working Paper Regarding the Sacramento-San Joaquin Delta/San Francisco Bay Estuary

Committee for Delta Resources Improvement | December 1st, 1986

Communities that rely on a contaminated groundwater source for drinking water

California State Water Resources Control Board (SWRCB) | January 1st, 2013

AB 2222 (Caballero, Chapter 670, Statutes of 2008) requires the State Water Resources Control Board to submit a report to the Legislature that identifies: 1) communities

AB 2222 (Caballero, Chapter 670, Statutes of 2008) requires the State Water Resources Control Board to submit a report to the Legislature that identifies: 1) communities in California that rely on contaminated groundwater as a primary source of drinking water; 2) the principal contaminants and other constituents of concern; and 3) potential solutions and funding sources to clean up or treat groundwater or provide alternative water supplies. A “community,” for the purposes of this report, is defined as a Community Public Water System (Health and Safety Code Section 116395). When this report refers to communities that rely on a contaminated groundwater source, it is referring to community public water systems that draw water from a contaminated groundwater source prior to any treatment. Over 95 percent of the 38 million Californians get their drinking water from a public water system. The findings in this report do not reflect private domestic wells or other unregulated water systems since the state does not require these groundwater users to sample their wells, and consequently a comprehensive database for these groundwater sources does not exist. This report identifies 680 community water systems that, prior to any treatment, relied on a contaminated groundwater source during the most recent California Department of Public Health (CDPH) compliance cycle (2002-2010). It is important to note that, according to CDPH, over 98% of Californians on public water supply are served safe drinking water. Although many water suppliers draw from contaminated groundwater sources, most suppliers are able to treat the water or blend it with cleaner supplies before serving it to the public. Consequently, when this report refers to communities that rely on contaminated groundwater, it is referring to community public water systems that draw water from one or more contaminated groundwater wells prior to any treatment or blending. Some community water systems, however, cannot afford treatment or lack alternative water sources, and have served water that exceeds a public drinking water standard. Of the 680 community water systems that rely on a contaminated groundwater source, 265 have served water that exceeded a public drinking water standard during the most recent CDPH compliance cycle (2002-2010).

Community Perspectives and Environmental Justice in California's San Joaquin Valley

University of California, Merced | December 1st, 2022

Comparing domestic and public-supply groundwater quality in the northern San Joaquin Valley, 2019—California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | June 5th, 2023

Groundwater quality in the Northern San Joaquin Valley region of California was studied as part of California State Water Resources Control Board (SWRCB) Groundwater Ambi

Groundwater quality in the Northern San Joaquin Valley region of California was studied as part of California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment Program-Priority Basin Project (GAMA-PBP). The GAMA-PBP made a spatially unbiased assessment of the aquifer system used for domestic drinking-water supply in the study region and compared the results to the aquifer system used for public drinking-water supply. These assessments characterized the quality of raw groundwater to evaluate ambient conditions in regional aquifers and not the quality of treated drinking water. The study included two components: (1) a status assessment presenting study results summarizing the status of groundwater quality used for domestic supply in the Northern San Joaquin Valley and (2) a comparative assessment of groundwater resources used for domestic and public drinking-water supply in the study region.

Comparing Domestic and Public-Supply Groundwater Quality in the Northern San Joaquin Valley, 2019: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | June 5th, 2023

Analysis of construction data for wells included in the comparative assessment indicated that, although depth to top of perforations are comparable for domestic and publi

Analysis of construction data for wells included in the comparative assessment indicated that, although depth to top of perforations are comparable for domestic and public-supply wells in the Northern San Joaquin Valley (median depth about 60 meters [m]), public-supply wells have longer perforation intervals and extend to deeper parts of the aquifer system (exceeding 120 m) than domestic wells that typically draw exclusively from the shallower aquifer system in the upper 80 m of unconsolidated sediments. Analysis of the vertical and lateral distribution of constituents of interest (nitrate, fumigants, and arsenic) across domestic- and public-supply aquifers indicated that nitrate is prevalent in shallow aquifers throughout the Northern San Joaquin Valley but is potentially diluted by mixing with deeper, older groundwater at long-screened public-supply wells. Fumigants were prevalent in areas of urban and agricultural land use in the western part of the Northern San Joaquin Valley, particularly in areas near Lodi, California, but 1,2,3-TCP was more widespread than DBCP and was detected in shallow and deeper parts of the aquifer system, potentially because of its recalcitrance in groundwater and ability to be detected at low concentrations. Arsenic was most prevalent in the western part of the Northern San Joaquin Valley with proximity to deltaic sediments and was detected at high RCs in wells tapping shallow and deep parts of the aquifer system.

Comparing Groundwater Quality in Public-Supply and Shallow Aquifers in the Monterey Bay and Salinas Valley Basins, California

U.S. Geological Survey (USGS) | December 17th, 2018

Groundwater quality in the Monterey–Salinas Valley Public-Supply and Shallow Aquifer Systems was investigated by the GAMA-PBP. The Monterey–Salinas Valley Pub

Groundwater quality in the Monterey–Salinas Valley Public-Supply and Shallow Aquifer Systems was investigated by the GAMA-PBP. The Monterey–Salinas Valley Public-Supply Aquifer System study unit (MS-PA) initially was assessed in 2005 (Kulongoski and Belitz, 2011). The Mon-terey–Salinas Valley Shallow Aquifer System study unit (MS-SA) was sampled in 2012–13 (Burton and Wright, 2018). The MS-PA and the MS-SA largely coincide areally; however, they represent different parts of the aquifer system vertically. The MS-PA examined deeper groundwater primarily used for public supply, whereas the MS-SA examined relatively shallow groundwater primarily used for domestic supply. The MS-SA was divided into four study areas. Three of these study areas combined (MS-SA3) were equivalent to the MS-PA study unit excluding a small sliver along the Carmel River. The fourth MS-SA study area, Highlands, is composed of the hills and mountains bordering the Salinas Valley. The MS-PA and the MS-SA study units have warm, dry summers and cool, moist winters. The average annual rainfall is 331 millimeters (mm; 13 inches, in.) with average annual temperatures of14 degrees Celsius (57 degrees Fahrenheit) in Salinas. The study units are drained by three main rivers and their tributaries: the Salinas, Pajaro, and San Lorenzo Rivers. Groundwater quality status and understanding assessments of the study units were based on data collected by the U.S. Geological Survey (USGS). In the MS-PA, additional inorganic data was obtained from the California State Water Resources Control BoardDivision of Drinking Water Public- Supply Well Water-Quality Database (Kulongoski and Belitz, 2011). A grid-based method to select wells was applied in both study units, which allows for an estimation of the proportions of the aquifer system with constituents at low, moderate, or high concentrations relative to regulatory and non- regulatory benchmarks for drinking-water quality established by the U.S. Environmental Protection Agency (EPA) or California State Water Resources Control Board Division of Drinking Water. The grid-based method provides statistically unbiased results and permits comparison of those results to other GAMA Priority Basin Project study areas (Belitz and others, 2010).

Comparing imidacloprid, clothianidin, and azoxystrobin runoff from lettuce fields using a soil drench or treated seeds in the Salinas Valley, California

Environmental Pollution (Elsevier) | October 10th, 2022

Neonicotinoid insecticide use has increased over the last decade, including as agricultural seed treatments (application of chemical in a coating to the seed prior to pla

Neonicotinoid insecticide use has increased over the last decade, including as agricultural seed treatments (application of chemical in a coating to the seed prior to planting). In California, multiple crops, including lettuce, can be grown using neonicotinoid treated seeds or receive a direct neonicotinoid soil application (drenching) at planting. Using research plots, this study compared pesticide runoff in four treatments: (1) imidacloprid seed treatment; (2) clothianidin seed treatment; (3) imidacloprid drench and an azoxystrobin seed treatment; and (4) a control with no pesticidal treatment. Neonicotinoid and azoxystrobin concentrations were measured in surface water runoff during six irrigations events in the 2020 growing seasons. Results showed runoff concentrations up to 1308 (±1200) ng L−1 for imidacloprid drench treatment, 431 (±100) ng L−1 for clothianidin seed treatment, 135 (±60) ng L−1 for imidacloprid seed treatment, 13 (±10) ng L−1 for azoxystrobin seed treatment (treatments averaged). The percent of applied mass in runoff over the entire sampling period varied by compound; the imidacloprid seed treatment and drench were similar (0.015 and 0.019%, respectively) to the clothianidin seed treatment (0.036%) while the azoxystrobin seed treatment was much higher (15%). Although the proportion of imidacloprid in runoff was similar for imidacloprid treatments, the mass applied during soil drench was > 4x the amount applied from the imidacloprid seed treatment. Surface soils were collected before planting and at the end of the trial. The neonicotinoids were detected in soil throughout the study and average maximum concentrations were 9–13 ng g−1; azoxystrobin was detected in only two soils at concentrations up to 0.57 ng g−1. These results elucidate the comparative mass runoff resulting from planting treated seed and soil drench applications and highlight the value of additional work to characterize off-site transport from the many commodities that may be utilizing treated seeds.