In Situ Solidification/Stabilization at Koppers Co. (Charleston Plant) Ashley River Superfund Site, South Carolina

Site Name:

Koppers Co. (Charleston Plant) Ashley River Superfund Site


South Carolina

Period of

September - December, 2001




Mark A. Fleri, P.E.Vice President
Williams Environmental Services, Inc.
2075 West Park Place
Stone Mountain, GA 30087
Telephone: (800) 247-4030/(770) 879-4075
Fax: (770) 879-4831

In situ solidification/stabilization (S/S)
- In situ S/S using a slurry of cement-based grout augmented with proprietary chemicals
- “Tubular injector” used for injecting and mixing reagents; special amphibious “marsh excavator” used to inject and mix cement-based grout into the upper two feet of sediment
- S/S began at the riverbank and progressed towards the central channel, about 25 feet deep
- Mixing plant was mobilized on site for mixing grout; 181,303 gallons of grout were mixed with the sediment; grout consisted of 632 tons of cement, 3,971 gallons of proprietary chemicals, and 160,000 gallons of water

Cleanup Authority:
- ROD signed April 1998
- ESD signed August 2001

EPA Contact
Craig Zeller
Remedial Project Manager
Environmental Protection Agency Region 4
61 Forsyth Street SW
Atlanta, GA 30303
Telephone: (404) 562-8827
Fax: (404) 562-8788

Polycyclic aromatic hydrocarbons and DNAPL

Waste Source:
Wastewater discharges from wood treating and storage of waste oil

Type/Quantity of Media Treated:
- 2,450 cubic yards of sediment were solidified to a depth of 2 feet

Purpose/Significance of Application:
Use of solidification/stabilization in river sediments

Regulatory Requirements/Cleanup Goals:
- The goal for the S/S treatment was to eliminate contaminant exposure to the benthic community and preclude further potential risks to upper trophic level receptors

No information was provided about the performance of the solidified sediment and whether/how it met the performance goals

Cost Factors:
- The total cost for this application was $561,154, including the use of a tubular injector and marsh excavator, as well as the grout chemicals, and $242,300 for equipment mobilization and demobilization
- The calculated unit cost was $229 per cubic yard., based on 2,450 cubic yards of sediment

The Koppers Co., Inc. Charleston Plant is located on 102 acres north of downtown Charleston, South Carolina. The site includes part of the Ashley River that is used as a barge canal. Koppers operated the site as a wood-treating facility from 1940 to 1977, primarily treating raw lumber and utility poles with creosote, as well as pentachlorophenol and copper-chromated-arsenate (CCA). The majority of wood-treating operations were conducted in the eastern portion of the site, identified as the Former Treatment Area. Wastewater from these processes was discharged into a ditch. From 1978 to the early 1980s, the site was used for storing wastes, including waste oil. The results of site investigations showed that sediments at the site were contaminated with PAHs and DNAPL, including sediments in the Ashley River.

In situ solidification/stabilization was identified as the remedy for one acre in the active marine area of the river. Bench- and pilot-scale testing were performed to develop a suitable grout and to assess the effectiveness of the remedy at full-scale. Specially-designed equipment was used to solidify an estimated 2,450 cubic yards of sediment in the Ashley River, extending from the riverbank into a channel about 25-ft deep. This included a “tubular injector” used for injecting and mixing reagents, and a special amphibious “marsh excavator” used to inject and mix cement-based grout into the upper two feet of sediment. According to the vendor, this type of equipment allowed grout to be injected at the required depths, and made it possible to use solidified sediment as a platform to reach untreated sediment.