Decades-old fuel spill surfaces in Chilkat River at slough near 15 Mile
July 25, 2019
Contaminated groundwater from a 51-year-old fuel spill at 15.5 Mile Haines Highway appears to be leaching into the Chilkat River slough, raising concerns about environmental damage.
The source of the contaminants was the 626-mile-long Haines-Fairbanks pipeline, used in the middle of the century to transport fuel from the Lutak Tank Farm to military installations in Interior Alaska. A 1968 leak in the now-decommissioned pipe spilled nearly 34,000 gallons of jet fuel into the surrounding soil.
A 2018 report by the Army Corps of Engineers, the agency responsible for monitoring and cleanup of the pipeline corridor, estimates that approximately 75,000 square feet of soil and 89,000 square feet of groundwater remains contaminated with fuel hydrocarbons, including benzene and napthalene.
Now, the revelation that fuel hydrocarbons may be seeping into slough of the Chilkat River is causing concerns.
“This is the culmination of the fears that people have had for 30 years,” said Derek Poinsette, executive director of the Takshanuk Watershed Council.
The Army Corps of Engineers has been monitoring the site since 2006. Testing has “consistently indicated” that the 15.5 Mile Haines highway shoulders “on either side are impacted by fuel contamination,” according to a fact sheet from the agency.
But concerns about leakage into the slough did not arise until 2016, when the Army Corps of Engineers first noticed a sheen at the edge of the waterway. At the time, the discovery did not ring alarm bells, said Anne-Marie Palmieri, project manager of the 15.5 Mile site with the Alaska Department of Environmental Conservation’s contaminated sites program.
“It did not look like a fuel sheen,” Palmieri said. “We didn’t really know what it meant at the time, because it was so small and localized.”
Testing of slough water in 2016 and 2017 showed no elevated contaminant levels. But last month, Palmieri received an email from the Corps of Engineers with test updates from April, with the news that the contaminated groundwater was likely leaching into the Chilkat River Slough.
“The (test) results suggest that there was contaminated groundwater seeping out of the river bank in April,” wrote Beth Astley, project manager with the agency’s Formerly Used Defense Sites Program.
But in emailed responses to questions from the Chilkat Valley News, the Corps of Engineers said that the contamination was not cause for concern.
“We have not observed any impacts to ecological receptors like plants or animals, and multiple surface water samples from the slough have not detected any petroleum contamination,” a Corps spokesperson wrote.
Though a cleanup of the area has been in the works for years, the discovery of the sheen “reiterates the need to address the soil as soon as possible,” said Palmieri. It also means that the area slated for cleanup must be revised.
Representatives from the Army Corps of Engineers met on July 18 with Haines representatives, including Palmieri and directors from Lynn Canal Conservation and Takshanuk Watershed Council.
“You can see a sheen,” said Jessica Plachta, executive director of Lynn Canal Conservation, who visited the site. “It’s clearly still an active contaminated site.”
Contaminants from the slough could eventually travel to the Chilkat River, where they might pose a threat to juvenile salmon, said Poinsette. “Theoretically, if any of them passed through that plume of benzene,” he said, “it would kill them.”
The Corps is currently preparing an environmental assessment of the site, the agency said in an emailed response. “We are considering removing soil from both sides of the highway, targeting the areas with the highest levels of soil contamination,” the response reads. “Residual contamination may remain underneath the highway, so we are considering the addition of an oxygen-releasing compound to the system to further promote microbial degradation of the residual petroleum.”
The agency said that “it is possible” the cleanup could take place in spring or summer of next year.
Cleanup plans at the site are complicated by construction plans on Haines Highway, which straddles the contamination site. Construction on the highway from milepost 12 to 23 is slated to begin in 2020.
“All this work we’re doing in partnership with the Corps and DEC in figuring out how to deal with that contamination,” said Department of Transportation spokeswoman Aurah Landau.
While Poinsette expressed support for the Corps of Engineers’ cleanup, he voiced concerns that the proposed action might leave contaminated soil underneath the Haines Highway.
“We’d like to see a complete cleanup, a cleanup of the entire site, and not just part of it,” he said.