Telegraph photo by ADAM URQUHART According to the U.S. Environmental Protection Agency, through the 1970s, solid and liquid hazardous wastes were disposed of in a sand and gravel pit behind this building, located at 57 Gilson Road in Nashua.

NASHUA — Federal regulators state that in 1979 alone, “over 800,000 gallons of hazardous wastes” were dumped directly onto the ground in the south end of Nashua, just west of Main Dunstable School along Gilson Road.

Nearly 40 years after The Telegraph originally reported on what would become the U.S. Environmental Protection Agency’s Sylvester Superfund site, more contaminants are being discovered. This time, levels of PFAS more than four times the limit regulators establish for the materials have been detected.

Formally known as per-and polyfluoroalkyl substances, PFAS are the same materials causing problems in Merrimack after being identified near the Saint Gobain Performance Plastics facility. The EPA states that health effects associated with exposure to PFAS can include low infant birth weights, immune system problems and even cancer.

“EPA does not believe significant public health risks exist at or near the site, but residents should not drink the groundwater,” EPA spokeswoman Kelsey Dumville said.

Michael Summerlin is an engineer with the Hazardous Waste Remediation Bureau of the New Hampshire Department of Environmental Services.

“Up until PFAS came along, it was doing pretty good,” Summerlin said of cleanup at the Sylvester site. “Now, we have to investigate the extent of this emerging contaminant.”

The Site

Officials with the EPA state the Sylvester site consists of 28 acres, generally located between West Hollis Street and Gilson Road in the southwest quadrant of Nashua.

Dumville said federal and state regulators began cleaning up the site in the early 1980s, first putting in a 100-foot deep clay slurry wall around a 20-acre area of the most highly contaminated groundwater, covering that area with a synthetic liner to isolate the waste. Two of the original contaminants included benzene and chlorobenzene, which are still present at slightly elevated levels in a small number of monitoring wells.

Moreover, after the slurry wall, federal and state regulators built a treatment plant that pumped and treated contaminated groundwater from the 20-acre containment area at 300-gallons per minute for 10 years between 1986 and 1996. According to a site overview on the NHDES website, it states that more than 1 billion gallons of groundwater was pumped through the treatment facility during its operation life, allowing for more than 430,000 pounds of contaminants to be removed. Dumville said in 1996, the EPA determined that original cleanup goals had been achieved.

“At this point, EPA and NHDES determined that natural attenuation – a process where contaminants naturally decrease over time – would continue to clean groundwater adequately,” Dumville said.

The groundwater is still contaminated in the containment area of the site, as well as in an extended plume of groundwater that is to the north of the site, and beneath a portion of the trailer park, River Pines by Jensen Communities. The plume stops at Trout Brook Drive, but Dumville said some of this groundwater discharges to Lyle Reed Brook, producing a smaller amount of orange sediment in the vicinity of Tumblebrook Lane.

“EPA continues to monitor groundwater contamination, and a decline in contaminant levels has been seen over the years,” Dumville stated. “It is anticipated that monitoring will continue to show a decline in concentration of contaminants in the groundwater plume.”

However, she also said the most ubiquitous contaminant is arsenic, which is likely not a waste disposed at the site, rather the result of the organic contaminants may have caused naturally occurring arsenic to become mobilized in the groundwater.

PFAS Found

When regulators collected the PFAS samples late last year, they were collected at an upgradient and downgradient area. In other words, the direction water flows toward is the downgradient, and the direction the water comes from is the upgradient. Sunmmerlin said the PFAS sample for the upgradient was just outside the slurry wall, and then the sample for the downgradient was taken where Lyle Reed Brook crosses Trout Brook Drive.

Summerlin said the levels of PFAS contamination that were found in what they call, the central area of the plume at concentrations of about 300 parts per trillion (ppt). However, he said that is in an area in the site that is well managed, and that it is central and well within the interior of the groundwater management zone. Moreover, he said the downgradient location showed PFAS levels of 74 ppt.

“So, that tells us we need to expand our search to make sure we get a good handle on the extent of the PFAS plume,” Summerlin said.

New Hampshire’s standard for PFAS is 70 ppt, meaning in the central area where samples were collected, these contaminants are more than four times the state limit. Summerlin said PFAS is sort of the catch-all for the group of around 3,000 compounds that fall into this category. However, he said they can only sample for roughly 30 of them if the right kind of lab is available.

“It’s all so new that the technology to evaluate the compounds is still coming to its full potential,” Summerlin said of understanding the many compounds in PFAS.

He said the groundwater management zone is established through an ordinance with the city that restricts the use of groundwater within that zone. In other words, he said people are not supposed to be drilling wells in that zone.

While officials from both NHDES and EPA are carefully keeping a watchful eye on the water situation in this area, that 70 ppt state standard could possibly be lowered in the future.

As far as the EPA five-year review goes, Dumville said it has begun and the final report should be completed this fall.