Source: Michael Wright, Bozeman Chronicle Staff Writer

Yellowstone National Park will replace a stretch of sewer line sometime over the next two years in an attempt to solve arsenic problems that led to a lawsuit against the park last year.

A U.S. Department of Interior attorney sent a letter to an attorney for the Gardiner-Park County Water and Sewer District that says Yellowstone plans to remove 2,700 feet of clay sewer line near Mammoth Hot Springs and replace it with PVC pipe.

The district sued the National Park Service in December 2016 because of heightened arsenic levels in its sludge ponds that it attributes to Yellowstone National Park.

The Interior attorney, Colleen Burnidge, wrote that the pipe project may take two years to complete, but they think it will help solve the problem.

“We believe that this project will address arsenic inflow and infiltration into the District’s sewage line,” she wrote.

Yellowstone National Park spokeswoman Morgan Warthin said in an email that the project has been funded and would begin either this year or next year. She couldn’t say how much the project would cost or whether it was a result of the lawsuit or a previously planned improvement.

She said they couldn’t give out further details because it’s part of a lawsuit.

Todd Shea, an attorney for the Gardiner-Park County Water and Sewer District, declined to comment.

The Gardiner-Park County Water and Sewer District sued Yellowstone in December 2016 over high levels of arsenic found in the district’s sewage treatment facilities. The district asked the court to force Yellowstone to give the district money, fix the leak and monitor its sewer lines in the future.

Sewage from Mammoth Hot Springs has gone to the district’s treatment facilities north of Gardiner for years. The district uses sludge ponds to treat wastewater, and the ponds need to be emptied periodically. Sludge removal is expensive, and high arsenic levels make it even more expensive.

According to the complaint, an engineer told the district in February 2015 that high levels of the odorless chemical were entering the treatment facility. The engineer also said that 95 percent of the arsenic was coming from Yellowstone, and testing showed the park’s sewage had arsenic levels nearly 40 times that of the Gardiner sewage.

The Montana Department of Environmental Quality had directed the district to empty the ponds, but the engineer recommended they wait to do so until the park fixed its arsenic problems, according to the complaint.

The district told the park in a 2015 letter that it couldn’t drain its sludge ponds until the arsenic problem from the park was solved. In 2016, the park finally responded, saying there likely wouldn’t be funding to fix the problem until 2020.

The district sued in December 2016, asking both for the park to fix the arsenic leak and to help pay for sludge removal — the cost of which was estimated at $2 million.

Funding has apparently come through for the project, according to the Interior Department letter, which was attached to a court filing that essentially puts the lawsuit on hold. The letter says the project will replace “deteriorated sewer lines” between the youth camp and Mammoth. The youth camp is south of the park headquarters and the Mammoth Terraces.

There is no mention of what the Park Service might contribute to the sludge removal — the other claim in the lawsuit — but Burnidge did write that they hope “the parties can work together to resolve any issues.”