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Ashland superfund project's Wet Dredge method so far successful.

An official with the Environmental Protection Agency said Xcel Energy's first efforts to demonstrate the practicality of the wet dredge method for contaminated lake bottom sediment removal at the Ashland Superfund location have been largely successful.

The cleanup aims at restoring land and lake bottom soils and sediments contaminated by a manufactured gas plant (MGP) that operated in the location from the late 19th century until the mid 1940s.

EPA Project Manager Scott Hanson said the company will be making "extended" dredges aimed at further showing that wet dredging will meet guidelines set down by the Department of Natural Resources and the Environmental Protection Agency.

Hanson made the comments at an informational meeting on the Lakefront Superfund site at the Our Lady of the Lake Social Hall.

"As a lot of you know in the record of decision, when we chose a remedy, it was for a dry excavation in the near shore," he said. "The record of decision allowed for a wet dredge pilot, to see if they could meet the same standards in the record of decision for the dry dredge. We looked at the preliminary results and they met all the performance standards."

Hanson said the pilot dredge met both water quality and air quality standards.

"Based on the preliminary results that we got that we would move into the extended pilot, and that is what they are doing right now," he said.

If the results from the extended pilot dredge form an area that is roughly the same size and adjacent to the original pilot dredge, Northern States Power/Xcel will likely seek to use the wet dredge method for the balance of the 16-acre lake bottom site.

Hanson said if the EPA decides to allow the wet dredge remedy, he will have to revise documents governing the cleanup and would call for another local meeting to discuss the change. He said a consent decree would also have to be filed with the federal court, and a 30-day comment period would take place, probably during the upcoming winter.

During the meeting, several area residents spoke about odors coming from the wet dredge site. Those odors were described as smelling like mothballs, which was identified as naphthalene, a constituent of the coal tar waste that forms the pollutant material at the site.

DNR Project Manager Jamie Dunn said that the odor was an inevitable part of the cleanup process.

"That smell is not a health concern," he said, pointing out that the health threshold on naphthalene, the main component that people were smelling was "much, much higher" than what people were smelling.

According to a handout made available at the event, the "Lowest Observed Adverse Effect Level" was set at 10 parts per million, while the Occupational and Health Administration's Permissible Exposure limit was 9.5 parts per million. The odor threshold, the level at which the smell becomes noticeable was far lower, .084 parts per million.

Meanwhile, monitors ringing the pilot dredge site had only turned up a single over-the-threshold reading, for the chemical anthracene, which the National Institute of Health said was a polycyclic aromatic hydrocarbon that was a component of coal tar. The site said the chemical was ubiquitous in the environment, having been identified in the smoke of cigarettes and cigars, smoked foods and other products.

The NIH said research on the chemical was limited, but that carcinogenicity studies generally produced negative results.

Despite the assurances that the smells were harmless, residents said the smells were causing issues. One speaker said she has experienced health problems that occur only when the odor is present.

Dunn said most of the complaints have been related to the large tent-like structure where the sediments are de-watered and prepared for shipment for a specialized landfill near Duluth, Minn. He said the way the dredged materials were handled in the main dredging component of the cleanup would be designed to take the odor into account.

He said much larger amounts of material would be removed in the main dredging phase, and part of the extended pilot project would be to look at ways to ramp up the project while remedying issues like odors.

Wisconsin DNR Northern Region Team Supervisor John Robinson said when the record of decision for the project was written, there were many concerns about how wet dredging would work.

"We will make our recommendations to the EPA who will ultimately make that decision," he said, referring to whether or not to continue with wet dredging for the remainder of the lake sediments cleanup.

Source: Rick Olivo, Ashland Daily Press
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Publication:Hazardous Waste Superfund Alert
Date:Sep 8, 2016
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