MARQUETTE - Marquette City officials discovered two significant sources of tar contamination during excavation at the former Cliffs Dow site Wednesday.
The city's investigation revealed a buried trench, lined with wooden timbers, which contained significant amounts of debris and tar material. Through excavation, city officials were able to follow the trench all the way to the former Cliffs Dow property's western border. They also found two vats or holding tanks of tar along the trench.
Director of Planning and Community Development Dennis Stachewicz Jr. said the holding tanks are about 15 feet long, 8 feet wide and 2 feet deep. One is covered with wood on top and the other is underneath a concrete foundation.
Stachewicz said the city bypassed the vats Wednesday in order to continue its investigation along the trench to the property line. He said they will go back today and dig up the contents of the vats. Through Wednesday the city has had 315 cubic yards of tar-impacted soil and debris hauled to the Marquette County Landfill.
Stachewicz said the underground trench probably continues west to an area outside the property boundary where tar ponds used to be located.
"I don't quite know what that means yet in terms of how the overall scope of responsibility plays out, but what we do know is we are now 99.9 percent confident of where we are at on the site in terms of the old layout," he said.
The city has an old schematic of the site provided by the Marquette County History Museum.
"With everything being underground before we were kind of unsure - we had an educated idea of where things were at but now we're confident we know exactly where things are at," Stachewicz said.
Stachewicz said the trench may have been used to hold or transport tar or other byproducts of past industrial operations. Since the trench is right above the water table, Stachewicz said the city currently has no plans to dig it up.
He said excavation will likely conclude on Friday.
The city has been diligent about monitoring any odors emanating from the excavation, Stachewicz said. He said once every hour someone will travel by vehicle around the perimeter of the property to monitor any odor leaving the site. In addition any holes dug into the ground were filled with clean fill every afternoon after digging stopped.
The site, located on Lakeshore Boulevard, was used for industrial purposes throughout the 20th century. Most notably, the Cliffs Dow Chemical Company - comprised of Cleveland Cliffs and Dow Chemical Company - used the site from 1935 to 1968 to produce charcoal, methanol, acetic acid, wood creosote and other chemicals.
Wood tar, a byproduct of the site's operations, is the main contaminant still on the site.
In 1968 the Cliffs Dow Chemical Company was sold to Georgia-Pacific and E.L. Bruce companies who changed the company name to Royal Oak Charcoal. The wood chemical refining process continued at the site until the plant closed in 1969. The city bought the property for $1 in 1997.
Christopher Diem can be reached at 906-228-2500, ext. 242.