The City of Brandon Utilizes Cement-Based Solidification/Stabilization
The City of Brandon chose the former site of the Brandon Scrap Metal and Iron company as the site for its new public safety building. At 10,000 square metres, the site occupies almost a full city block. The building, itself, will house both the fire and police services in a central location.
As part of Brandon Scrap Metal and Iron’s recycling program, lead cell batteries were broken up and the lead was extracted, leaving the uncleaned cases on site simply covered with earth. The lead from the battery casings resulted in localized contamination that required remediation. The environmental assessment showed that the site harboured contaminants at levels that exceed regulations – mostly heavy metals, lead and hydrocarbon pollution.
Before construction could begin, the site had to be cleaned up.
The City of Brandon researched various clean up solutions for the former battery breaking site. It was decided that a cement based solidification/stabilization (S/S) process would be the most effective and economical treatment for the lead contaminated soil.
The City of Brandon successfully remediated 600 tonnes of contaminated soil using the cement-based solidification and stabilization process. The result is a stable, non-hazardous material that will no longer be harmful to the public.
This site is an outstanding example of how cities can turn a non-productive, virtually unusable property back into a thriving part of the community.
What is Cement-Based S/S?
Solidification/stabilization (S/S) is a widely used treatment for the management and disposal of a broad range of contaminated materials and wastes – particularly those contaminated with substances classified as hazardous in the United States. The treatment involves mixing a binding reagent into the contaminated substance. This process protects human health and the environment by immobilizing contaminants within the treated material, preventing them from migrating to plants, animals and humans.
S/S treatment has been used to treat radioactive wastes since the 1950s and hazardous wastes since the 1970s. S/S continues as a cornerstone treatment technology for the management of radioactive and hazardous wastes, as well as site remediation and Brownfield redevelopment. The U.S. Environmental Protection Agency (EPA) considers S/S an established treatment technology. EPA has selected S/S treatment for 24% of its Superfund source-control remedial actions.
How S/S Works
S/S treatment involves mixing a binding reagent into the contaminated substance. Although the terms solidification and stabilization sound similar, they describe different effects that the binding reagents create to immobilize hazardous constituents. Solidification describes changes in the physical properties of a contaminated substance. The desired changes usually include an increase in compressive strength, a decrease in permeability, and encapsulation of hazardous constituents. Stabilization refers to chemical changes of the hazardous constituents in the treated substance. The desired changes include converting the constituents into a form that is less soluble, mobile, or toxic.
Effects of Binding Reagents on Waste – Inorganic & Organic
Commonly used binding reagents include Portland cement, cement kiln dust (CKD), and a number of proprietary reagents. Portland cement is a generic material principally used in concrete for construction. This material is also a versatile S/S binding reagent with the ability to both solidify and stabilize a wide variety of wastes. Portland cement-based mix designs have been the most popular S/S treatments and have been applied to a greater variety of wastes than any other S/S binding reagent.
Cement is frequently selected for the reagent’s ability to:
- chemically bind free liquids
- reduce the permeability of the waste form
- encapsulate waste particles, surrounding them with an impermeable coating
- chemically fix hazardous constituents by reducing their solubility
- help reduce the toxicity of some contaminants
This is accomplished by bringing about physical changes to the waste form and, often, chemical changes to the hazardous constituents themselves. Cement-based S/S has been used to treat wastes that have either or both inorganic and organic hazardous constituents.
Due to the great variation of waste constituents and media, a mix of reagents should be designed specifically for each waste that is to be treated. Mix designs often include by-products or additives in addition to Portland cement. Fly ash is often used to capitalize on the pozzolanic effect of this material when mixed with hydrating Portland cement. CKD and slag have minor cementitious properties and are sometimes used for economy. Lime can be used to adjust pH or to drive off water utilizing the high heat of hydration produced by these S/S binders.
|Owner||The City of Brandon|
|Engineer||Earth Tech Canada Inc.|