Borrego Springs Groundwater Basin
Last updated 11/9/2023 at 1:16pm
The Borrego Springs Groundwater Basin is blessed with a watershed that is primarily State Park land and does not contain the typical potential contaminants found in developed and populated areas. Agricultural and turf irrigation uses inside the Basin creates potential for the influence of return flow that may have elevated levels of nitrates and or contaminants from pesticide/herbicide/fertilizers.
Approximately, five years ago at the suggestion of then Director Harry Ehrlich, BWD implemented a Program to sample water quality more frequently than required by the State. BWD has been accumulating data over this time period and recently hired Trey Driscoll from Intera Engineering to evaluate the data and determine if any potentially adverse trends exist. The results were reported to the Board on September 26, and the conclusions are:
*Nitrate across the basin was below the Maximum Contaminant Level (MCL) except for Fortnier #1, Monitoring Well -6S and DiGiorgio. Trend analysis indicated an increasing trend for ID4 - 18, JC Well, and RH -4 for nitrate.
*Sulfate concentrations exceeding secondary upper MCL at Fortiner #1 and in SMA wells JC Well, RH -1, and MW -5B.
*TDS concentrations exceeding secondary upper MCL at Fortiner #1, MW -6S and in SMA wells JC Well, RH -1, and MW -5B
*Wells in the North portion of the Basin typically show sodium chloride-type water with sodium and potassium dominant cations and sulfate dominant anions
*Wells in the Central portion typically show sodium chloride-type water with sodium and potassium dominant cations and no dominant anions
*Wells in the Southern area exhibit changing water quality over time due to increased production and declining groundwater levels.
*All active BWD production wells continue to meet drinking water standards without the need for treatment.
*Rising arsenic levels in SMA groundwater, declining levels, and shifting water quality pose a risk to BWD production well ID1-8. BWD should prepare to switch to alternative wells if arsenic levels surpass drinking water standards. •
*BWD should collect semi-annual data from the Borrego Springs Watermaster for quality assurance and anomaly detection. Additionally, conduct annual statistical trend analysis to identify potential water quality risks.
*Create educational materials on Subbasin water quality issues for pumpers and regulators. Outreach to domestic well owners in the area to assess groundwater quality and levels.
*Nitrate concentrations in NMA are of concenrn with exceedances in Fortiner, MW6S, and 904 DiGiorgio Road wells. BWD well ID4-18 time series plot and trend analysis shows an increasing trend in nitrate.
*More well head data from NMA and CMA wells is needed to improve the spatial groundwater quality understanding. Also, depth-specific water quality data is necessary for better depth-wise characterization.
*In response to documented nitrate contamination in the upper aquifer and the upper portion of the middle aquifer of the NMA, it is advised to formally recommend to the County of San Diego Department of Environmental Health the requirement for proper annular seals for wells spanning multiple aquifers.
*Additionally, conducting an updated well survey to identify inactive wells needing appropriate abandonment per County and State standards is recommended, as it aligns with the goal of preserving potable water quality in the Subbasin