Page 101 - Beaumont Basin Watermaster

Section 4

Water Quality Conditions

The purpose of this section is to document the water quality conditions in the Beaumont Basin
during the 2013-2017 reporting period. TDS and nitrate concentrations in the basin are
compared against groundwater quality objectives for anti-degradation and maximum benefit as
established by the Regional Board for TDS and nitrate-nitrogen in the Beaumont Management
Zone (BMZ). In addition, water quality concentrations for a number of compounds are
compared against Federal and State Drinking Water Standards. Figure 4-1 depicts all the
wells that have groundwater quality data for the reporting period.

Sources and Availability of Water Quality Information
There are two main sources of data used in the assessment of water quality conditions in the
Beaumont Basin and near surroundings; namely, the California Department of Public Health
database and the Beaumont Management Zone Maximum Benefit Monitoring Program. The
database obtained from the CDPH, which focuses primarily on drinking water sources,
contains water quality information for the 2013-2017 reporting period; conversely, water quality
from the BMZ Maximum Benefit Monitoring Program is only available through the end of 2016.
Usually this later database is available in February or early March; its results will be
incorporated in the final version of this annual report.

4.1 Comparison with Management Zone Objectives

Groundwater quality objectives for anti-degradation and maximum benefit have been
established by the Regional Board for TDS and nitrate-nitrogen in the BMZ, which
encompasses portions of the Beaumont Basin, the Singleton and South Beaumont basins, and
limited portions of Edgar Canyon above the Banning Fault as illustrated in Figure 4-1. The
anti-degradation objectives are based on the historic ambient TDS and nitrate-nitrogen
concentration of 230 mg/L and 1.5 mg/L respectively.

The maximum benefit objectives were adopted by the Regional Board in 2004 at the request
of STWMA and Beaumont to allow for recharge of imported water and the reuse of recycled
water. The maximum benefit objectives, set to 330 mg/L for TDS and 5.0 mg/L for Nitrate-N,
are relatively low compared to other basins and are protective of the beneficial uses of the
Basin groundwater. According to the Basin Plan, salt mitigation will be required once the
ambient TDS and nitrate-nitrogen concentration exceeds the BMZ maximum benefit
objectives.

4.1.1 Total Dissolved Solids

Figure 4-2 shows the maximum TDS concentrations for 60 wells measured within and in the
vicinity of the Beaumont Basin wells during the 2013-2017 reporting period. A total of 33 wells
are located inside the basin with the remaining 27 in the Singleton Basin / Edgar Canyon and
the South Beaumont Basin areas.

Beaumont Basin Watermaster 2017 Annual Report – DRAFT – February 2018 4-1