Water Resources Research Act Program

Principal Investigators: Heidi Yelin

Abstract: Perfluoroalkyl substances (PFASs) have received attention as emerging contaminants in drinking water sources. The US EPA had undertaken drinking water analyses for six selected PFASs from the US public water systems (PWSs). According to the third unregulated contaminant monitoring rule (UCMR3), over 4,900 of PWSs were chosen for sampling sites and the analysis results were published in January 2017. The US EPA established health advisories for two main PFASs, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in 2016, and based on the UCMR3 results, the US EPA has requested proper remedial actions from public water agencies (PWAs). The UCMR3 result revealed that drinking water contamination by PFASs in Saipan is more prevalent than in the US states. The Commonwealth Utilities Corporation (CUC), a public water and utility agency in Saipan, had collected water samples from 24 drinking water entry points. As the result of PFAS analysis, PFOS was detected in 5 wells and reservoirs. In particular, the production well IF-208, located within the Saipan International Airport (SIA) has been contaminated with the PFOS in the range of 4900 ~ 7000 ng/L, a value that is one hundred times higher than the US EPA’s lifetime health advisory concentration (70 ng/L). The Airport Rescue Firefighting Facility (ARFF) at the SIA is suspected as a major PFOS contamination area and a main source for groundwater contamination. In June 2016, CUC stopped using well IF-208 due to its high concentration of PFOS. CUC has also monitored PFOS in wells adjacent to well IF-208. CUC has monitored these wells biannually and found that PFOS concentrations have varied: wells that had high PFOS concentration in 2016 now have lower concentrations while wells with less than 40 ng/L PFOS in 2016 concentrations above 70 ng/L. There are several reasonable reasons:1) PFOS has also affected other wells and reservoirs, but PFOS had not been detected from two sampling attempts under UCMR3 due to some effects, such as rainfall and tide that influence volume and flow of groundwater and/or 2) groundwater pumping from wells changes in groundwater flow and PFOS concentration. Therefore, to understand the PFOS migration pattern in this area, 1) the PFOS contaminated site, ARFF, must be investigated, 2) regular PFOS monitoring from wells and reservoirs adjacent to the well IF-208 should be conducted, and 3) seasonal variation of PFOS concentration and its relationship between rainfall events should be analyzed. This research will help to identify PFOS migration pattern in groundwater and establish a proper remediation plan.