S/S Treats River Sediment at Superfund Site

Solidification/stabilization (S/S) is frequently used to manage sediment from harbors, rivers, and wetlands. Often sediment is treated after it is removed or dredged, but it can also be treated in-place. A perfect example of in-place treatment of river sediment is the successfully completed in-situ treatment at the Koppers Co., Inc. Superfund Site in Charlestown, S.C. The site, formerly used for wood treatment operations, included a barge canal off of the Ashley River that was contaminated with polycyclic aromatic hydrocarbons (PAHs) and creosote.

The site remedy required protection of human health and the environment while still maintaining sufficient depth in the canal for barge operations. In-situ S/S treatment was selected to cover the canal bottom over other technologies including enhanced sedimentation or an engineered sub aqueous cap. S/S treated sediment would be less permeable than a sand cap, contribute a minimal elevation increase to the canal bottom permitting continued barge operation, and form a more cohesive canal bottom layer resisting erosion by tides and barge traffic.

The S/S treatment involved mixing cement grout into the upper two feet of canal sediment. The grout, which included an additive to prevent washout, was mixed in an upland batch plant. Hoses from the plant delivered the grout to a tubular injector mounted on a wide-tracked floatation hull excavator. The injector had four mixing tines to inject and rake the cement grout into the sediment. Quick-setting time of the mixture allowed the excavator to use treated sediment as a working platform for adjacent treatment. Nearly one acre area of canal sediment was treated. More information and photographs.

How can S/S be protective of human health and the environment if the technology does not lower the concentration of hazardous constituents in the treated material?

Solidification/stabilization (S/S) treatment does not generally result in a reduction of the total concentration of hazardous constituents (contaminants) in a treated material. S/S protects human health and the environment by immobilizing hazardous constituents within the treated material. Protection is achieved by preventing migration of hazardous constituent to human and environmental receptors.

In contrast with "dig and dump" remedies that merely move the hazardous constituents to another place, S/S fits into a risk-based remedy decision. Further, an in-situ remedy lowers risks to surrounding communities since less excavation is involved. S/S can treat a very broad group of hazardous constituents, both inorganic and organic. Most other remediation treatment technologies can not. This lowers cost of the remediation of properties. Protective remedies at a lower cost conserve resources that can be applied to other sites leading to greater overall protection of human health and the environment.

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U.S. Brownfields 2006

The 2006 EPA-sponsored National Brownfields Conference held last November in Boston drew a record attendance of more than 6,000. The conference included educational sessions, exhibits, and award ceremonies for Phoenix™ awards. This year’s Phoenix awards were especially significant for cement-based S/S treatment. A former manufactured gas plant site (MGP) remediated using cement based S/S was selected. The Genzyme Building at Kendall Square in Cambridge was announced as the grand prize winner out of the field of 10 regional Phoenix winners. PCA and the RETEC Group co-hosted a mobile workshop on the project. The workshop included presentations by the property owner, developer, and remediation designers and a tour of the buildings built on the former MGP site. More.

Canadian Brownfields 2006

Canada’s National Brownfield conference was held last October in Toronto. Registered attendees included representatives from industry, government, education, as well as remediation experts and contractors. PCA presented a paper highlighting case studies of S/S remediation projects in North America, including several in Canada. The Three Sisters Mountain Village development project in Canmore, Alberta won a “Brownie” Award for Sustainable Design and Technical Innovation on a Brownfield Site. Locally available waste materials (aggregate washings, coal spoils and cement kiln dust) mixed with cement to create a pumpable and flowable backfill was used to stabilize abandoned mine workings. This was used to address surface subsidence beneath the planned development. Site remediation and brownfields redevelopment in Canada is expected to be a significant growth market for S/S.

Phoenix-Award Winning Kendall Square Rises from Cement-Treated Brownfield Site
A project information sheet describing an award-winning Brownfield redevelopment in Cambridge, Mass. The Genzyme Building in Kendall Square was constructed on a former manufactured gas plant (MGP) site. In-situ cement-based solidification/stabilization (S/S) was used to remediate the site. SR854

Solidification/Stabilization with Cement CD
An updated collection of PCA, Cement Association of Canada, (CAC) and U.S. Environmental Protection Agency technical and promotional material on solidification/stabilization (S/S) treatment of waste. CD021

4th International Conference on Remediation of Contaminated Sediments
January 22-25, 2007 in Savannah Ga. Visit PCA and CAC staff at booth #107.

Innovative Remediation Solutions for Atlantic Canada Workshop
February 27-28, 2007, Halifax, Nova Scotia, Marriott Habourfront. Hosted by Industry Canada, Environment Canada and Public Works and Government Services Canada. Contact Nova Scotia Environmental Industry Association at nseia@sympatico.ca

Global Accomplishments in Environmental and Radioactive Waste Management February 25-March 1, 2007 Tucson, Ariz., Tucson Convention Center. PCA presentation on S/S Wednesday February 28, 1:30 pm.

Americana 2007-International Environmental Technology Trade Show and Conference March 20-22, 2007, Montreal, Quebec. CAC presentation March 21st. CAC booth #1604.

Ports 2007
March 25-27, 2007 in San Diego, Calif. Visit with PCA staff at booth #301.

USEPA/USACE 2007 Conference on Design and Construction Issues at Hazardous Waste Sites, April 4-5, 2007, Philadelphia, Pa.