Permeable surfaces not so good near surface waters?

One of the ‘good ideas’ that has been widely adopted in developments by environmentally interested companies and municipalities is the ‘permeable surface’, often consisting of a brick or concrete pavement with perforations allowing surface water to permeate through to the underlying soil. In Toronto the municipality required a permeable parking area in one retail development in which Gallon Letter’s parent company, CIAL Group, had an environmental planning role.

Environmental planners in British Columbia are now rethinking this idea for developments close to the ocean. In Sooke, on Vancouver Island, a liquid waste management plan that is being touted as cutting-edge actually limits the extent to which permeable surfaces can be used and also seeks to control the rate at which rainwater flows into rivers and streams. The goal is to improve water quality in the harbour in order to be able to lift a long-standing ban on the harvesting of shellfish.

Permeable surfaces make sense where the underlying soil can act as a focus for biodegradation of contaminants, for example from parked vehicles, that may be in the runoff water. Where the surface is close to surface waters the permeable surface may just be a fast-track through which contaminants can flow into the river, lake or ocean. Proper planning for storm and surface water management requires more than a cookie-cutter approach. Gallon Letter urges municipalities and developers to look at each development site as an individual ecosystem with regulations and technologies appropriate to the situation.

For more information about the Sooke plan visit http://www2.news.gov.bc.ca/news_releases_2009-2013/2011ENV0021-000556.htm

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