The Bureau of Land managment has resumed cleanup at the unofficial shooting range at 7 Mile Haines Highway.
This week a work crew marked 20-foot grid squares of dirt poisoned by lead, arsenic and antimony for removal. Two large cottonwood tree that have grown up in the contaminated zone will be removed as well.
According to Anne Marie Palmieri, an environmental specialist for the state Department of Environmental Conservation, the ground became contaminated after decades of spent ammunition rounds leached minerals into the soil. The area, which is now fenced off, is being signed over by the Federal Bureau of Land Management to the State of Alaska. The Department of Transportation plans to turn the area into a parking lot for Mount Rapinsky hikers who currently park on the side of the road.
This is the third clean up effort from the Bureau of Land Management.
In 2015, the BLM spent $366,000 removing 360 cubic yards of dirt from the depths of 6 inches to up to a foot. They returned in 2016 to clean up a few hot spots, said Larry Beck, environmental protection specialist for BLM.
“This year we’ve got thinner layers of soil to remove,” Beck said, estimating about 260 cubic yards of soil will be collected over the next two to three weeks. The clean-up crew is prepared to remove up to 100 cubic yards more, if needed.
The .75 acre parcel includes an exposed gravel hillside, or “backstop,” which has higher concentrations of toxins.
Rounds of ammunition have penetrated the backstop at different depths and then gravel and soil will slough down every year from the snowmelt and rain covering it over, and then more shooting adds another layer of rounds, Beck said. “The depth of the contaminated (soil) just kept getting deeper and deeper,” he said.
Once collected, the soil is placed in 20-foot cans. Then it is transported by barge and train to a hazardous waste disposal facility in Arlington, Ore.
A special x-ray device is used to analyze the soil content and identify what elements and minerals are present. “We use that to field-screen for the lead and the antimony,” Beck said.
A screening plant, basically a big shaker with bars on it, is then used to sift through the raw material.
Most of the spent rounds are .30 caliber and smaller birdshot. Any items or rocks larger than 1 1/2 inches, falls off to the screening plant and goes into a pile. The smaller bits are scooped up and placed in cans. Beck estimates the crew will fill about one can a day, according to Beck.
“We use a big excavator, but when it comes to identifying contaminants, it’s like we are doing it with a teaspoon,” Beck said. This isn’t like a construction project where they dig a big hole, he said. “We are just trying to gently scrape the top of the soil.”
“Antimony is really the tougher one to chase,” Beck said.
Antimony is silvery-white and brittle. It is commonly used in alloys and flame-retardants.
The goal is to clean-up the lead to 400 parts per million and the antimony to 4.6.
In order to get the antimony down to 4.6, the lead will also come down to about 100 parts per million, Beck said.
Soil samples from each clean-up grid, are sent to a lab for testing. In 2016, the focus was on cleaning areas that had been cleaned up in 2015, but still had high levels of antimony according to the lab work.