COLUMBIA, S.C. — Crews from South Carolina's Department of Health and Environmental Control (DHEC) say they have removed 20,000 tons of coal tar from along the Congaree River as part of Phase 1 of the Congaree River Clean Up Project.
The section of the river on the Columbia side, just below the Gervais Street Bridge, had a cofferdam installed and its water drained in May so that workers could remove the coal tar. According to DHEC, the coal tar was likely deposited as a byproduct by a former Manufactured Gas Plant located northeast of the river at 1409 Huger St. that was in operation from around 1906 to the mid-1950s.
Coal tar is created as a waste product in the conversion of coal into a flammable gas. The Huger Street operations were run by a predecessor company of SCE&G, now Dominion Energy, before the existence of environmental regulations and permitting. Back then, after the gas was created, the coal tar waste was simply discharged into a former stream in what is now Finley Park and eventually wound up in the Congaree River.
Dominion entered into a voluntary cleanup contract with DHEC in 2002 and years of environmental assessment and planning lead up to the current cleanup operation.
After the coal tar was excavated, DHEC says workers used high pressure water cannons to remove remaining coal tar and sediment until they reached the granite river bottom. The water used during the pressure washing was maintained within the cofferdam and pumped to a water treatment system for processing before going into the City of Columbia sewer system.
Workers also placed rocks along the river to reduce erosion.
Over the next few weeks, the Phase 1 cofferdam will be dismantled and the river will begin to flow freely again. Portions of the Phase 1 installation will be reused in a similar draining and cleaning process at another section down stream.
Phase 2 of the project is much smaller -- about one-fifth the size of the first cofferdam. Depending on the weather, the Phase 2 process of coal tar removal should be completed in about 2-4 weeks.
The removed coal tar and sediments are being taken to a landfill in Richland County where Dominion Energy has set up a special area for the material to be examined by a team of archeologists. The archeologists will sift through the material in an attempt to locate any artifacts that might not have been detected during the Unexploded Ordinance team's clearing of the Congaree before cleanup began. To date, several small Civil War artifacts have been identified.