EPA TO REPLACE MANHOLE VAULTS
The Ten Mile Drain Superfund Site is an area in St. Clair Shores, Michigan where oil laden with toxic polychlorinated biphenyl (PCB) was found in significant concentrations in sediment in a storm sewer or drain and at the bottom of two canals leading to Lake St. Clair.
The U.S. Environmental Protection Agency (EPA) had the sewer scoured and the canals dredged, but PCB reappeared.
PCB is a toxic fire retardant that was added to oil (in electric utility transformers, for example) to prevent the oil from burning. It’s likely that years ago somebody dumped the oil down sewer manholes in the street. Many sewers, especially older ones, are not water tight, so contaminants in the sewer can leak into the bedding underneath and/or the surrounding soil, and vice versa. Thus, contaminants may migrate downstream both within and outside the sewer.
Seventeen weirs were placed in the sewer system and a sediment trap installed at the outfall to help pinpoint the source of the contamination and inhibit migration. Also, numerous test borings were made in the area.
The highest PCB concentrations were found at the intersection of Harper Avenue and Bon Brae Street. This summer, EPA plans to remove and replace two manhole vaults, along with contaminated stone bedding and backfill. Four monitoring wells will be installed, as well.
The site is within the Clinton River Area of Concern, which encompasses the 760 square mile Clinton River watershed (mostly in Oakland and Macomb counties) and a portion of Lake St. Clair, into which the river empties.
An Area of Concern (AOC) is defined in a U.S.-Canadian agreement as a geographic area that does not meet the water quality objectives of the agreement, having conditions that harm or are likely to harm living things.
EPA’s Superfund National Priorities List is a compilation of the worst toxic waste sites in the country, eligible for extensive, long-term clean-up. The Ten Mile Drain site was placed on the list in 2010.