ALWI was engaged by Baltimore County to evaluate the probable source(s) of salt contamination of a domestic supply well in the northern part of the County. The well owner sued the County over the salt, which they alleged to originate from roadway deicing. The County was concerned both about the suit and its precedent, because there are many miles of County roadways in rural areas served by wells.
In service to the County as defending expert, we developed and supported a different hypothesis for the origin of the salt. The presence of elevated concentrations of sodium and chloride was verified through sampling and analysis we performed. The local groundwater naturally is acidic, and many domestic supplies are equipped with pH neutralizers and softeners in response. Softeners discharge a briny (i.e., salt-laden) backwash rinsate. Thus, we came to theorize on a briny discharge to the on-premises septic system.
If a septic-to-well connection could be proven, our hypothesis of an alternate salt source would be validated. We tested for a chemical tracer diagnostic of salt-contaminated septic effluent: Methylene Blue Activated Substances (MBAS). Optical brighteners in laundry detergent contain detectable MBAS concentrations. This tracer is unknown in the natural environment and thus, would be diagnostic of the trace presence of laundry detergent (and thus, salt-contaminated septic effluent) in the well water.
The confirmed presence of MBAS in the well water demonstrated the septic-to-well connection and cast doubt on the plaintiff’s allegation of a roadway deicing explanation. Combined with our topographic observations and other hydrogeologic evidence, this exonerative finding compelled the plaintiff to drop the lawsuit against Baltimore County.