Remediation of contaminated sites with cement

Solidification/Stabilization (S/S) with Cement (also known as Remediation of Contaminated Sites with Cement) is a common method for the safe treatment, management and reuse of contaminated waste. Developed in the 1950s, the technology is widely used today to treat industrial hazardous waste and contaminated material at brownfield sites i.e. abandoned or underutilized properties that are not being redeveloped because of fears that they may be contaminated with hazardous substances. Modifications of this technology have also been developed and have been successfully used. (ImmoCem)

S/S, which involves mixing Portland cement into contaminated material, protects the environment and our health by immobilizing hazardous contaminants within the treated material. Solidification refers to changes in the physical properties of a waste including an increase of its compressive strength enabling it to support more weight, a decrease in its permeability reducing water infiltration and encapsulation of hazardous constituents preventing their escape into the environment. Stabilization refers to chemical changes of the hazardous constituents in a waste. The desired changes include converting the constituents into a less soluble, mobile, or toxic form. The popularity of S/S is because it can be used for a wide variety of contaminants in many types of contaminated material. Soil, sediment and sludge impacted with a variety of organic and inorganic contaminants have been treated successfully using this versatile technology.

There are two distinct methods for the treatment of material. It may be excavated and treated on-site using a mobile S/S treatment plant brought to the site or it may be left in place during treatment with cement being directly added to contaminated materials. The treated material may be stored safely in a designated land fill site or reused on-site.

The U.S. Environmental Protection Agency (EPA) has identified S/S with cement as a Best Demonstrated Available Technology for more than 50 Resource Conservation and Recovery Act (RCRA) listed wastes. This means that the technology is an accepted treatment to ensure safe land disposal of these wastes. For years, S/S has been used to treat such wastes, eliminating their hazardous characteristics, lowering the hazard class of the material and cutting the cost of disposal. Furthermore, S/S is a common remediation technique for American Superfund sites. Since that program’s inception in 1980, 24% of selected Superfund site source-control remedies have included S/S. It is receiving increasing interest and use in Canada, contributing to the sustainable redevelopment of both urban and industrial properties.

S/S provides an economically viable means of treating contaminated sites. This technology treats and contains contaminated soil on site thereby reducing the need for landfill. It protects surrounding communities and water resources by preventing leaching of contaminants into groundwater.

For more information see: Cement Association of Canada

The governments of Canada and the province of Nova Scotia agreed in January 2007 to clean up the infamous Sydney Tar Ponds contaminated site using S/S technology. Cement will be mixed into the contaminated waste to solidify and stabilize it. When the S/S process is complete, the solidified areas will be covered with an engineered cap consisting of a high-density polyethylene liner or clay, followed by layers of gravel and soil. Finally, the surface will be planted with grass and other vegetation. See: Sydney Tar Ponds Agency