Page 110 - Beaumont Basin Watermaster

Section 4
Water Quality Conditions

Average Avg Max
Well Classification No. of Wells Samples
Concentration Concentration
Beaumont Groundwater Basin

Appropriators 15 186 2.13 2.76
Overlyiers 11 85 3.18 3.91
Other 4 14 1.08 1.15
Total 30 285

Singleton Basin / Edgar Canyon Area

All Wells 16 52 3.06 3.94

South Beaumont Basin

All Wells 7 63 10.45 11.36

Of the 26 potable wells, only two wells had a maximum concentration below the anti-
degradation objective of 1.5 mg/L, 18 wells were between this objective and maximum benefit
objective of 5.0 mg/L; six wells 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).

In the Singleton Basin / Edgar Canyon area, six wells had a maximum concentration below the
anti-degradation objective, another six 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, only one well had a maximum concentration below the
maximum objective while the remaining eight exceed it with six 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

Beaumont Basin Watermaster 2018 Annual Report – DRAFT - February 2019 4-4