Coordination with RIDEM for PFAS Response Action for Small-Scale Public Water System
Rhode Island Department of Health and Brown University sampled 38 small-scale public water systems for the presence of poly and perfluorinated alkylated substances (PFAS) located near potential PFAS release sources. The Oakland Association water supply reported PFAS perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) above the health advisory of 70 parts per trillion. RIDEM contracted with Weston & Sampson to provide a coordinated response action. We helped RIDEM coordinate and deliver potable spring water to all impacted Oakland Association water users. We also provided spring water to users, gathered access agreements, and coordinated sampling of all private water supply wells in a ¼ mile radius of the Oakland Association supply well for PFAS analyses. We created a database of property owner and tenant contacts, well information, and PFAS results to allow for the plotting of information in a GIS environment. We also assisted in the presentation of the data to the public at a community meeting.
Following the initial response action, we developed and implemented a comprehensive site investigation plan. Using innovative sampling techniques, we collected discrete interval groundwater and soil samples from key locations both horizontally and vertically throughout the impacted area and used this data, along with the GIS mapping, to pinpoint the PFAS source. The data collected provided information necessary to develop a unique Conceptual Site Model detailing the release source area and multiple transport and dispersion mechanisms responsible for the distribution of PFAS observed. Laboratory results indicated a source of aqueous film forming foam (AFFF) was responsible for the water supply well contamination. Releases to near surface and subsurface stormwater control structures at the local fire department were pinpointed as the likely sources for AFFF introduction into the shallow soils. An intermittent shallow groundwater aquifer above bedrock provided for the transport of contaminants towards and into a nearby surface water supply. When shallow groundwater is not present, the releases migrated directly into fractured bedrock and were drawn to the highest volume wells. The site investigation report we generated provided the scientific conclusions needed for RIDEM to name the fire department as the responsible party for the contamination.