The cleanup of tar-like residue from a former gas plant will require cofferdams on the edge of the Congaree River near the Gervais Street bridge for three summers, according to plans by the U.S. Army Corps of Engineers.
The detailed plans for the project are included in a public notice filed by the Corps on Friday. River users have noticed bits of black goo on the river bottom in that area for several years. Testing revealed it was residue from SCE&G’s former manufactured gas plant on nearby Huger Street.
State health officials determined it was only a danger if people had direct skin contact with the goo. Signs have been posted at the river’s edge, warning of that danger, until the polluted sediment is removed.
Cofferdams will block the river from flowing in that area, allowing the excavation of river bottom sediment. SCE&G is paying for the removal of the 27,000 cubic yards of tar-laden sediment.
The work will be done only from May 1 through Oct. 1 each year to minimize impact on spawning fish, according to the Corps document. No starting date is listed in the plan.
Workers will build temporary cofferdams each year, moving downstream each year. Based on the illustrations in the plan, the work will block access to the Senate Street landing in the first year. The second and third phases appear to be downstream of Senate Street, but the staging of equipment could prevent river access there.
The footprint for the project is 23 acres – 10.5 acres under the river and 12.5 acres on land.