Permeable paving offers environmental benefits
By Chad Ingram
The Coalition of Haliburton County Property Owners’ Association is encouraging any property owners who are undertaking paving projects on their properties to consider the use of permeable paving.
“In the Lake Simcoe area, permeable paving is becoming almost mandatory,” CHA board chairman Paul MacInnes told county councillors during a recent meeting.
Permeable paving is a method of paving that allows for the infiltration of liquids. In this way, the pavement reduces runoff and actually acts as a filter of contaminants such as phosphorous.
Phosphorous is public enemy No. 1 when it comes to lake health in Haliburton County and is the culprit behind algae blooms. When large enough, algae blooms not only make lakes unsafe for swimming, but also, in severe cases, render them effectively dead. There was one confirmed algae bloom in Haliburton County last summer, and eight reported.
Credit Valley Conservation conducted a case study on the benefits of permeable paving, with a report published in 2018. One of the test sites used was the parking lot of an IMAX office in the Sheridan Business Park in Mississauga.
“The parking lot was expanded and retrofitted with a combination of traditional asphalt and permeable pavement,” the report reads. “The asphalt runoff drains to one of three bioretention units. The permeable pavement section is divided into three catchments with differing subsurface materials. The parking lot runoff is collected, absorbed and filtered by these LID [low impact development] practices before entering a wetland adjacent to the parking lot.”
The data shows a substantial load reduction in contaminant levels from the portion of the parking lot done with permeable paving. The test sites showed up to a 99 per cent reduction in suspended solids (small particles suspended in water); 98 per cent reduction in phosphorous; 98 per cent reduction in Kjeldahl nitrogen (total concentration of organic nitrogen and ammonia); 94 per cent reduction in nitrates; 98 per cent reduction in copper; and up to a 99 per cent reduction in zinc.
“As part of adaptive management, stormwater management has evolved over time from flood control requirements, to water quality and erosion requirements, to water balance requirements,” the report reads. “The cost and complexity of these engineered system has increased. In light of the current spotlight on climate change and aging infrastructure there is growing awareness that stormwater management has become more than just treating a storm event, it’s also about maintaining stream flows during dry weather periods for wastewater assimilation, fisheries, and water takings.
“Results from IMAX and other similar performance studies will provide private land owners and municipalities with the knowledge they need to make informed decisions on the role of green infrastructure for stormwater management. They are essential to gain insights into preferred designs and advancements which may be needed to meet stormwater management and other objectives cost-effectively. This data can help inform the planning and implementation processes required for green infrastructure, such as informing the credit application process for the City of Mississauga’s stormwater charge. Studies such as IMAX are also providing the local, long-term performance data needed to conduct the integrated life-cycle analysis required for asset management, including tracking operations and maintenance activity need, frequency and cost.”
While permeable paving is currently more expensive than regular paving, MacInnes also noted that along with its environmental benefits, it is not subject to the heaving and cracking that comes along with regular paving, and is therefore more durable as well. The only contaminant that permeable paving does not seem to filter out is road salt.