Superfund dredging spreads Duwamish River pollution
Seattle Times staff reporter
For watchdogs of the years-long Superfund cleanup of the river-turned-industrial waterway, a King County report released this week confirms their long-standing contentions that the county needs to change its haphazard methods of scooping out the toxic sediment.
"They used the sloppiest technology available, with unskilled operators," said B.J. Cummings, who heads the Duwamish River Cleanup Coalition. "The sediment they were dredging went all over the place."
While county officials agreed their contractors worked sloppily at times, they promised to clean up the remaining mess. And while they said they won't make the same mistakes in future dredging, they said the equipment changes and techniques sought by environmentalists are not needed.
"This was a good project that could have been better," said Don Theiler, director of King County's Wastewater Treatment Division. "But still, this is a much cleaner area than before we started."
At issue is a $10 million cleanup of the sediment surrounding a King County sewer outflow referred to as the "Duwamish/Diagonal," massive pipes that spill storm water and, after heavy rains, untreated sewage into the river just south of the West Seattle Bridge.
The seven-acre area below the pipes was the first of several "hot spots" along the river that have been slated to be dredged as part of an "early action" plan for the Superfund cleanup. The cleanup largely targets PCBs, polychlorinated biphenyls, which were used widely in industry until the 1970s and are toxic to fish habitat and are believed to cause cancer in humans.
The Environmental Protection Agency designated a five-mile stretch of the artificial river channel, from about South Park to Harbor Island, as a Superfund site three years ago.
The overall plan calls for hastened dredging of the most contaminated sediment in the river in the next few years, followed by extended mop-ups and habitat restoration that will take many more years and many more millions of dollars.
Over the winter, a county subcontractor, J.E. McAmis Industries of Chico, Calif., used a diesel front-loader on a floating barge to scoop out 66,000 cubic yards of sediment surrounding the Diagonal outflow. If the volume of extracted material had been concrete, it would have been more than enough to build the Kingdome.
The county reported that about 400 pounds of carcinogenic PCBs were removed in the sludge, which was sent by rail car to the Rabanco landfill in Klickitat County.
From the week the dredging began, watchdogs began complaining about the county contractor's methods. Specifically, they complained the county insisted on using a "clamshell bucket" on the digger, a standard digging attachment that scoops the mud just as its name implies.
The watchdogs say the clamshell is notoriously messy, and they urged the county to use a special "environmental" bucket, designed to let less mud spill back into the river, or to use siphon dredging, literally sucking out the sediment through a giant vacuum tube.
The county has maintained that the sediment beneath the sewer pipe was too hard, and too full of old logs and rocks and debris, to use the more environmentally friendly devices because they are not as heavy duty.
Within the first weeks of dredging in November, watchdogs and the EPA raised concerns that muck was spilling into the river and churning the brackish water. County officials admonished the dredgers to slow down and dig only by daylight. And they posted inspectors on the job.
Environmentalists weren't impressed. They said the county failed to stop churning up the sediment through the entire dig because it refused to abandon the clamshell bucket.
"Where did all that contaminated sediment go?" wondered Cummings, of the cleanup coalition. "We'd like to have an answer to that. We do know that they messed the project up."
The county had predicted before dredging that some spillage would occur, guessing that PCB levels at testing sites around the dig would see about a 2 percent increase.
The county's tests of sediment around the dredging site, taken before and after the dredging, show that about 8 pounds of PCBs were allowed to wash back into the river in all.
At nine of the test sites, the PCB levels ended up below predictions. At four sites, all near where the county says it did its earliest digging, the PCB levels were many times above the predictions and above maximum allowed limits.
Theiler, the county wastewater director, said the data show that after the county ordered changes, the spillover was greatly reduced. Theiler also stressed that the new contamination is several times less severe than the levels at existing "early action" sites on the river.
"The next time we do this, we will be much more diligent," Theiler said.
The county is evaluating the subcontractor's performance but has not decided whether to seek fines or compensation for extra cleanup costs. Theiler said the county intends to mop up the spilled sediment in a separate project later.
"Officials at the EPA and the state Department of Ecology (DOE) have agreed the dredging was sloppy, and they had joined the watchdogs in urging the county to order changes. But they have recently sided with the county that the clamshell bucket is acceptable in certain applications.
"We don't think it's the technology that was chosen, it was the way it was used," said Rick Huey, a toxic-cleanups specialist for DOE.
But Cummings and others aren't budging. They said they won't be satisfied until the county agrees to stop using the clamshell bucket. "Eight pounds of PCBs is not a trifling amount," Cummings said.
Ian Ith: 206-464-2109 or firstname.lastname@example.org
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