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Of the 20 potable wells, only two wells had a maximum concentration below the anti-
degradation objective of 1.5 mg/L, 12 wells were between the anti-degradation and maximum
benefit objective of 5.0 mg/L, and six exceeded the maximum benefit objective for the BMZ.
None of the production wells samples exceeded the primary federal or state drinking water
standard for Nitrate-N (10 mg/L). BCVWD wells along Edgar Canyon were not included in the
analysis of domestic wells.
In the Singleton Basin / Edgar Canyon area, eight wells had a maximum concentration below
the anti-degradation objective, five wells had concentrations between the anti-degradation and
maximum objective while four wells exceeded the maximum benefit objective of 5.0 mg/L.
In the South Beaumont Basin, two wells had concentrations below the maximum objective
while the remaining eight exceed it with four of these wells also exceeding drinking water
standards. There were no wells with nitrate concentrations below the anti-degradation limit.
Table 4-1 presents the average and maximum TDS and Nitrate (as N) concentration for all the
wells in the Beaumont Basin and surrounding areas.
4.1.3 Nitrate Studies in the Beaumont Management Zone
Rising nitrate concentrations observed in 2005 along the northern portion of the Basin
prompted STWMA to launch an investigation in 2006 to determine the potential impact on
groundwater quality from on-site waste disposal systems (OSWDS) commonly used in the
Cherry Valley Community of Interest (CVCOI). STWMA retained the services of Wildermuth
Environmental Inc. (WEI) to conduct this study.
The results of this study were disputed by the Beaumont Board of Supervisors’ Groundwater
Quality Evaluation Committee (Committee) as they identified potential shortcomings in
sampling design and project execution. The Committee recommended that an independent
assessment be conducted. They recommended that the second study should expand the
study area, consider reasonable build-out projections and other sources of groundwater
contamination. This independent study was conducted by scientist at the University of
California, Riverside and funded as a Supplemental Environmental Project by the State Water
Resources Control Board. The results of this study were published in early 2012. A brief
summary and their findings is presented below for information purposes only.
Summary of Wildermuth Environmental Inc. Study
This study is titled: “Water Quality Impacts from On-Site Waste Disposal Systems in the
Cherry Valley Community of Interest” (WEI, 2007). The bases for this study include the
following:
A review of scientific literature,
A field study to estimate nitrogen concentrations in soil water below selected OSWDS,
A tracer study of nitrogen isotope and pharmaceutical and personal care products
(PPCP) to confirm the presence of effluent from OSWDS,
An estimation of current and future discharge from OSWDS to groundwater,
Beaumont Basin Watermaster 2017 Annual Report – DRAFT – February 2018 4-4
