Preliminary research by scientists at the Water and Environmental Research Institute found two sites with relatively high concentrations of perfluoroalkyl substances in the central region of Guam. WERI had been researching potential contamination sources affecting water wells A-23 and A-25 in Sinajana.
A-25, in particular, has the highest contamination level among water wells tested positive for perfluorooctane sulfonate, a type of PFAS. Both wells remain offline.
There were 22 potential PFAS contamination sites sampled in October 2018. Among sites tested, a point near a wastewater pump station, and a ponding basin above wells A-23 and A-25 had the highest PFAS concentrations. For PFOS specifically, the same ponding basin and a point along the Chaot River tested highest.
Early research data showed a relationship between rainfall and PFOS levels in A-25, according to Barry Kim, assistant professor of water engineering at WERI, and Gary Denton, former WERI director.
"We have monitored on a monthly basis and analyzed the relationship between PFOS level and rainfall event," Kim said. "For example, after a high rainfall event, at least 30 to 90 days, we got very high PFOS concentrations. So based on this preliminary result, our assumption was PFOS should be impacted in soil somewhere."
Working from that information, WERI set out to find contamination sites.
Primary PFOS sources identified in other places include landfill leachate and wastewater from sewage treatment plants, according to early WERI research. There are no landfills or sewage treatment facilities nearby, but the area has a history with heavy dumping and sewage pollution. The nearby Chaot River was chronically polluted with raw sewage for 25 years until the Guam Waterworks Authority upgraded a defective wastewater pump station in 2006, according to the research papers.
There were several potential sites identified. Some sites, such as the ponding basins, sat within largely urban areas. About 30% of the homes in this area utilize septic systems. The area is also prone to flooding and injection wells were built into the ponding basins to accommodate excess runoff.
The PFOS contamination level found at one of the ponding basins, called Site 12, is higher compared to other sites but is still on the low range for normal urban areas, according to Denton. A-25 may be connected to the site through groundwater.
The main source of PFOS is firefighting foams, said Denton.
"Part of our study, we have a graduate student who will be following this up, is to look at firefighting foam applications in that general watershed," he added. "You have Sinajana right up there on top of the plateau. There's probably been fires up there over the years. Whether foams were used, we don't know at the moment."
However, data that is available at the moment is supported by onetime sampling "so we cannot say that (sites are) fully contaminated at this time," Kim said.
WERI is in need of more funding, Kim said.
The current research was funded by a National Institute of Environmental Health grant, in collaboration with the University of Rhode Island. The sample analysis was conducted at URI, according to Kim. Funding is already running out and will expire by August. It doesn't appear WERI could take again from the same funding source, Kim said.
"We have to find another funding source; otherwise, we don't have money to take other samplings," he added.
WERI submitted an informal proposal last year to GWA for a three-year study on contaminated well sites to the tune of $300,000, Kim said. The focus at this time is A-25 due to limited funding, he added.
"WERI's proposal was provided to several entities at a presentation to the aquifer technical working group. GWA intends to provide funding in support of the effort, and has been discussing the study with other stakeholders, including Guam Environmental Protection Agency, who has the mandate to determine the source of contamination," said GWA General Manger Miguel Bordallo.
Bordallo also said he'd like to see an appropriation for GEPA to engage WERI in a study to determine the source of PFOS in the central water wells.
A filtration system has been placed on another contaminated well site, NAS-1. To install filtration systems on A-23 and A-25 could cost an additional $700,000 to $1 million, according to GWA. Part of WERI's early research was to determine whether remediation was needed.
Based on data so far, it appears the PFOS contamination will be around "for quite a while," Denton said.
"Our recommendation would be go ahead, and whatever remediation plans will be for GWA, go ahead and do it," Denton said.
GWA sampled all of its water wells in 2015 in accordance with U.S. Environmental Protection Agency regulations, according to Kim and Denton. While there is a lot of focus on PFAS at the moment, it appears the issue is contained within the few wells known to be contaminated, the men said.
"The way it's being presented is that there's widespread contamination on the island. There's no evidence to support that at all," Denton added.