Page 106 - Beaumont Basin Watermaster

Zone 2 – Wildland and Low Density Septic Disposal Region. This zone is defined as the area
uphill of Edgar Canyon to the north of Cherry Valley. Water quality in this area had low to
moderate concentrations of TDS and nitrate.

Zone 3 – Urban Region with On-site Septic Disposal Systems. This zone overlies the Cherry
Valley area including the area around the Noble Creek and Little San Gorgonio Spreading
Ponds. Human waste from homes and business in this zone is primarily disposed of in on-site
waste disposal systems.

Zone 4 – Urban Region with Consolidate Sewer System. Zone 4 comprises those portions of the
City of Beaumont utilizing a municipal wastewater system.

The UCR report attempted to answer a series of questions; the questions and a summary of
their response is provided below.

1.- Can different groundwater regions within the BMZ be defined using isotope, PPCP, and
general chemical parameters?
According to the study,

ƒ Zone 1 was characterized by relatively high levels of PPCPs and it has the highest
likelihood for nitrate contamination from human waste.

ƒ Zone 2 had detectable levels of some PPCPs. Septic contributions to groundwater are
relatively minor.
ƒ Zone 3 had several wells with clear signs of contamination by septic systems.
Groundwater in the central portion of Cherry Valley appeared to be more strongly
affected by septic systems than on the periphery of Cherry Valley.
ƒ Zone 4 shows the fewest signs of human waste as most homes are served by
consolidated sewer systems.
1A.- Do areas with septic systems have different chemistry than areas with sewers?

The report indicates that there are statistically significant differences between groundwater in
areas with septic systems and groundwater where sewer service is available. The
concentrations of PPCPs, TDS, Nitrate-N, the sum of base cations, Boron, and Isotopes of
Nitrate were all significantly higher in areas with septic systems than in areas with sewer
service.

1B.- Do areas where groundwater recharge with water from the State Water Project or
wastewater treatment plant effluent have different chemistry from other areas?
Strong evidence of nitrate deriving from human waste was detected in Zone 1 as well as
strong biological attenuation of nitrate transported in groundwater.

2.- What sources contribute nitrate to groundwater of the BMZ?

The report indicates that in Zone 1 the isotopes of nitrate values overlap those expected for
human or animal waste. Similarly, in Zone 3 the isotopic composition of water suggest a high
probability of inputs of nitrate from human or animal waste. The presence of PPCPs in most

Beaumont Basin Watermaster 2017 Annual Report – DRAFT – February 2018 4-6