MARINETTE - Tyco is working with the Environmental Protection Agency and Wisconsin Department of Natural Resources to hammer out the details of a plan to remove contaminated sediment from the Menominee River.
Representatives of the company met with members of the Local Menominee River Area of Concern Citizens Advisory Committee Thursday to present a dredging and capping plan their consultants and experts believe will best remove the arsenic contaminated sediments along the southern bank of the river and the turning basin.
It was the first time the sediment removal plan had been shared publicly.
On hand to explain the Sediment Remediation Phase II plan were Rob Abfall, director of operations in Marinette; John Perkins, Tyco's director of environmental health & safety; Jeff Danko, an expert in design, dredging and capping implementation with CH2M Hill; and Steven Nadeau, an attorney and a national expert specializing in contaminated sediment policy.
What they brought to the committee, and have submitted to EPA, is a plan that would span two years, cost about $24 million, and would eventually remove more than 100,000 cubic yards of contaminated sediment.
The arsenic contamination is the result of manufacturing byproducts that were stored on the former Ansul Chemical property in the 1950s through the 1970s. Runoff from the site contaminated the soil, groundwater and river sediments.
The plan Tyco, which purchased Ansul, is proposing matches what the EPA will sign off on - with the exception of complete removal of semi-consolidated sediment in a 3- to 3.5-acre area within the 19-acre project.
Perkins said that Tyco has met with Marinette Marine Corp. and K&K Logistics to determine their needs in the river and to develop a plan to dredge the turning basin to accommodate the vessels that use it.
Testing done since the Phase I groundwater remediation project in 2009-2010 has identified the levels of arsenic contamination in the different areas along the bank and the turning basin, Danko said.
He said the slurry wall and sheet rock wall installed in 2009-2010 to surround the property has completely contained the arsenic still present in the groundwater on the land. A groundwater treatment system to treat the contaminated groundwater and more than 700 special trees have been planted in that area to absorb groundwater have been successful, Danko said.
The sampling that was done since has identified the areas of arsenic contamination in the riverbed sediments, Perkins said.
"The EPA wants full dredging," he said Thursday. "Tyco has a protective alternative to cap a portion of the river."
Tyco's plan was to remove some of the soft sediment in an area company officials describe as "the area around the Eighth Street Slip," and bring in similar, but uncontaminated sand from another area in the river to place atop the semi-consolidated material, which would then be covered with small stone and again with larger stone.
An initial plan to use only the uncont
aminated sand was shot down by the EPA in June.
"They determined it was not an effective cap for the arsenic," Perkins said of the review done by outside experts.
While the EPA still seeks full dredging, Tyco pushed to cap about 4.6 acres. The size of the capped area was reduced by another two acres in the turning basin after Tyco met with Marinette Marine Corp. in September.
Perkins said the new plan, to cap about 3.5 acres with several layers of materials, would not only save about $12 million, but would reduce the truck traffic through both cities to bring the dewatered sediment to the Waste Management Landfill in Menominee Township.
The cap, called a chemical isolation barrier not because it uses chemicals, but isolates them from disruption, would be outside the turning basin.
"We'll take out as much (of the soft sediment) as needed, and leave it no shallower than it is," Danko said. "The cap is entirely out of the navigational area."
By capping that 3.5 acres rather than removing it, Tyco officials say it would mean another 100,000 cubic yards would stay in place, rather than be disturbed by the dredging process.
"Contaminants that are deeply buried have no significant migration pathway to the surface, and are unlikely to be exposed in the future may not need removal because they do not necessarily contribute to site risks," Tyco officials said in a written statement.
The goal of the remediation is to bring the arsenic contamination from 50 ppm (parts per million) to 20 ppm within a 10-year period. Tyco would be responsible for monitoring the river and sharing reports with the EPA and WDNR during that time.
Nadeau said that removal of all the sediments might not be safer than just removing the soft sediments and capping the rest.
"Within a site, conditions can be different," he said. "Dredging has its complications - you can't get it all - but it is an important part of the tool box."
He called the project "a substantial dredge.
Bringing in a clean material to cap the area is also seen as a way to further the re-establishment of the riverbed's ecosystem, Nadeau said.
The company has looked at the option and continues to discuss it with EPA and WDNR, but needs to resolve the project scope soon, since work would have to begin sometime in later June, just after the end of the spring fish spawning season.
Rafael Gonzalez, EPA public affairs specialist, was also at the meeting, but could not say when the EPA will make its decision.