MARINETTE - After more than two decades of negotiations and research, Tyco has reached an agreement to begin removing arsenic-contaminated sediment from the Menominee River.

A two-phase work plan is scheduled to begin in July, according to John Perkins, Tyco's director of environmental health and safety.

Tyco Fire Products LP (formerly known as Ansul Inc.) reached agreement with the U.S. Environmental Protection Agency and the Wisconsin Department of Natural Resources to remove approximately 250,000 cubic yards of soft sediment and deeper semi-consolidated material (SCM) from a portion of the main channel, the turning basin, areas directly east of the turning basin, the Sixth Street Slip and the south channel.

The dredging operation will be protected with a turbidity curtain, marked by buoys, and will utilize both environmental and standard clamshell buckets.

The soft sediments and SCM is being removed from specific areas where testing has shown arsenic contamination greater than or equal to 50 parts per million.

Arsenic contamination was caused by Ansul's storage of manufacturing byproducts on the property in the 1950s through the 1970s.

Tyco addressed contamination of the groundwater by installing a vertical barrier wall and a groundwater extraction and treatment system around the property in 2009 and 2010.

Earlier reports from Tyco indicated the plan is to reduce the contamination in the sediments from 50 PPM to 20 PPM within 10 years.

The company received permission from the city of Marinette Wednesday to use a substantial portion of the Sixth Street Slip as a temporary water treatment facility. The launch will be closed to boaters this season.

Perkins said that the company has hired Sevenson Environmental Services of New York as the general contractor; Sevenson and subcontractors will work with Tyco this month to stage the area and bring in equipment.

Work is expected to begin in July and end for the season in late October or November.

Perkins said he anticipates the dredging of the turning basin to be completed this year with the exception of some work on the near shore.

The turning basin will be the first phase of the dredging for several reasons, he said. "Logically, it's because we are working from upstream to downstream," he said. "Also, we are working collaboratively with Marinette Marine, who is the major user of the turning basin."

Sediments will be brought to the Sixth Street Slip to have the water removed and treated, and the dried material will be trucked from Sixth Street, along Water Street to Ogden Street and across the bridge to be disposed of the Waste Management landfill in Menominee Township.

Perkins said the company has an agreement with the city that limits the hours for the trucks on Mondays through Fridays, and provides an option for Saturdays.

"Once we get into the activity, it could be as much as 100 trucks per day," Perkins said. "It's something we're very much paying attention to."

Perkins said every precaution is being taken to ensure the safety of the contractors, Tyco employees and the public.

"It's all about safety," he said. "We want to assure the contractors, our employees and the community that (we've taken) every precaution possible."

The dredging operation will be closely monitored by the company, the EPA (which is the lead governmental agency) and WDNR.

The second phase of the project is expected to begin in mid-April 2013 with completion targeted for November of that year.

Dredging and treatment activities could run 24/7, according to Tyco.

Perkins said more information will be shared at an upcoming meeting of the Lower Menominee River Area of Concern Citizens Advisory Committee, which is set for June 14 in the geography/geology classroom at UW-Marinette's Max E. Peterson Field House.

The meeting is open to the public, and Perkins said he plans to attend to answer questions from the committee and citizens.

Perkins told the EagleHerald that he would be able, at that meeting, to say what the dredging operation is expected to cost. In November 2011, it was estimated at around $24 million. But that plan included capping some of the SCM with uncontaminated sand, which would have been covered with small stone and then large stone.

Perkins said that plan, which was shot down by the EPA, led to the agreement for full dredging.