Contaminated soil at the Mendenhall Wastewater Treatment Plant appears to have come from a leaky diesel heating-fuel line, according to city wastewater utility Superintendent Scott Jeffers.
Workers began removing the soil this week. They found the contamination when installing a new ultraviolet disinfection system to treat effluent, Jeffers said.
"When (the line) was installed there wasn't a requirement to line the trench where the piping system would go," he said. "We found the broken line by pressure testing and finding a breach."
Bill Janes, an environmental specialist with the state Department of Environmental Conservation's contaminated sites program, said the agency will test to see if the contamination has reached the Mendenhall River.
"We are installed a monitoring well to see if groundwater is contaminated and then will see how far the excavation needs to go," he said. "The most critical factor is whether contamination is reaching the Mendenhall River. That's our main concern."
Jeffers said workers haven't observed a sheen on the river. Petroleum-contaminated soil is a common occurrence in Southeast Alaska because the region has many underground storage tanks, Janes said.
Between 20 and 50 cubic yards of material may be removed as part of the cleanup, Jeffers said. Fifty cubic yards is about five dump-truck loads, he said.