Saginaw clean-up about to begin

Vol. 1, issue #15, 16 November 1999

A major environmental dredging project, designed to remove contaminated sediments from the Saginaw River in the US, was due to start as this issue of Dredging News Online was written.

The clean-up and removal of sediments contaminated by polychlorinated biphenyls (PCBs) is being funded by $28 million provided by General Motors after it was adjudged that the Saginaw River and Bay had been contaminated by PCBs and related compounds released from General Motors facilities since the early 1970s and by contaminants released from wastewater treatment plants in Bay City and Saginaw.

During the dredging process, approximately 345,000 cubic yards of contaminated sediments - or approximately 90 per cent of the mass of PCBs in the lower river - will be removed.

Although not all risk to natural resources will be removed, experts believe that additional restoration dredging would significantly increase physical injury to habitat with little additional removal of PCBs.

Once restored, the land will be managed by the State of Michigan, the Shiawassee National Wildlife Refuge, and the Saginaw Chippewa Tribe. Additional restoration is planned for land that was drained long ago for agricultural use.

The overall value of the settlement against General Motors may eventually be significantly greater than $28.22 million because the restoration project is also designed to increase recreational use by improving fishing and boating access and by increasingthe quality and quantity of habitat for fish, game, and wildlife.

A portion of the $28.22 million settlement payment is being used for habitat restoration for fish and wildlife in the Saginaw Bay watershed, known as one of the premier walleye and waterfowl locations in the Great Lakes area.

The Trustees of the restoration project have placed the US Army Corps of in charge to manage and oversee the dredging (the Trustees being the US Fish and Wildlife Service, the Michigan Department of Environmental Quality, the Michigan AttorneyGeneral'sOffice, and the Saginaw Chippewa Tribe).

The Army Corps of Engineers awarded the contract for the dredging project to Luedtke Engineering. They will be using a specially designed gasketted clamshell, and silt curtains will enclose the dredging operation.

Turbidity in the water and PCB concentrations in the water and air will be closely monitored. The dredged material will be transported by barge to a nearshore Confined Disposal Facility (CDF) which was designed to contain sediments dredged from the navigation channel in the Saginaw River.

The contractor is currently constructing a sub-cell to contain the material from this project within one part of the CDF.

Once the subcell is completed, dredging in the river will begin. It is anticipated that one of the five areas will be completed this autumn before the weather halts work. The remaining areas are scheduled to be completed by mid-October of 2000.

Luedtke is using a Cable-Arm environmental bucket. Ray Bergeronof Cable Arm is building a 15 cubic yard bucket for the project so as to maximise the efficiency of broad, rather than deep, grabs of primarily unconsolidated material (silts and sands rather than clays).

Dredging News Online