In Brownfield Development these days crushing of concrete derived from old on-site buildings is an extremely attractive cost-cutting measure because it provides developers considerable savings on aggregate needed for various aspects of the final development such as road-base, granular used around storm and sanitary sewers and building drainage pipes etc. Crushing of concrete typically can be conducted for $5-6/tonne while a similar purchased aggregate from a quarry can cost anywhere between $19-24/tonne. Therefore, when a Brownfield property has concrete buildings/foundations, it is extremely popular these days to crush the concrete on-site from the demolished buildings and use the aggregate for future development needs. However, there are certain environmental issues that need to be considered when crushing concrete.
concrete crushing environmental issues
Although extremely popular, concrete crushing has a few environmental issues which are fairly important to consider whenever a crushing operation is being arranged. Most crushing plants are diesel operated or if electric, they are powered by generators with diesel engines. However diesel engines are tested for emissions by their manufacturers to ensure they meet appropriate environmental standards. Therefore emissions from all the diesel engines (Carbon Monoxide, Nitrogen Oxide and Particulate Matter) operating at any given site are significant and must be considered in any environmental approval. However, these emissions are really not the main environmental issues surrounding concrete crushing.
Crystalline Silica Ranks Highest For Environmental Issues of Concrete Crushing
You might ask what crystalline silica has to do with concrete, because we all know concrete is made with cement creating a hardened material whose composition is mainly calcium carbonate. This is true, however many concrete mixtures contain crystalline silica in the aggregate used in making concrete. If you look at the composition of typical concrete in the Material Safety Data Sheet (MSDS)obtained from the National Ready Mixed Concrete Association, you will notice that Crystalline Silica can vary in concrete from 0.5-80%. This is due to the variable nature of the aggregate used. Typically the aggregate on any construction site will be obtained from the closest sources. These sources may have varying amounts of crystalline silica depending on the type of aggregate locally available.
What is the Main Environmental Issue Around Crystalline Silica?
Crystalline Silica is quartz and is naturally present in numerous rock types in varying composition. It becomes a particulate contaminant when materials containing quartz are broken, crushed, chipped or hammered with tools and then screened and loaded into trucks. As described in this OSHA Fact Sheet, workers with prolonged exposure to crystalline silica dust can develop lung cancer, as such it is considered a carcinogen. In addition, it can cause silicosis which can severely scar lung tissue, leaving the individual debilitated. Workers in direct contact with dust containing crystalline silica are required to wear approved respirators to reduce their exposure.
How Crystalline Silica is Considered in Approvals
All concrete crushing operations in Ontario are required to have a Certificate of Approval (C of A) from the Ontario Ministry of the Environment. Crystalline silica is considered a particulate matter emission that would be created during the crushing and subsequent screening and loading operations of a typical crushing site. Concentrations for all sources are calculated for a worst-case scenario and are then modeled using an MOE approved dispersion model. The model considers the emission sources from the operation plant and calculates the maximum emissions that are to be expected at various distances from the crushing plant. These emissions are then compared with MOE Acceptable limits. The model is run a number of times to determine the set-back distance required from sensitive receptors in which the MOE Acceptable Limits are achieved. Modelling of each source in this manner ensures that there are no environmental issues when the plant is in operation.
Crushing Plants Must Have MOE Approvals
It is important for all owners of crushing plants in Ontario, to be aware that they require MOE Certificates of Approval for their crushing operations so that they avoid environmental issues and costly delays. If a crushing operation is discovered to be operating without an MOE approval, the ministry can impose high fines and will shut down the operation indefinitely until an approval is obtained. This can cause severe financial problems to a contractor on a deadline, as it may take months to get an approval.
Developers would also be wise to hire only those contractors who have taken the time and expense to get an MOE approval (Environmental Compliance Approval-ECA) for all their crushing and screening operations or they risk significant time delays in getting approvals while their projects are already under way.
The ministry does not tolerate ignorance of environmental issues. As discussed above, crystalline silica emissions in dust from concrete crushing can be a significant health hazard, for both workers and residents adjacent to major crushing operations. The best way to avoid all the environmental issues surrounding any crushing or screening operation is to have your equipment approved by the Ministry of Environment.
Maddalena Environmental Inc.
Al Maddalena, M.Sc, P.Geo.
As an environmental consultant, Mr. Maddalena has been obtaining environmental approvals for clients for over 25 years. Approvals have included crushing and screening operations, water treatment systems, injections systems as well as bioremediation systems. For more information email firstname.lastname@example.org.