Thermal pollution

When we think of how stormwater impacts lakes, rivers and streams, we tend to think of sediment and other contaminants that degrade water quality. We rarely think of how elevated runoff temperatures, known as thermal pollution, can greatly alter the temperature regime of natural water bodies. On hot days, impervious surfaces, such as parking lots and roofs, absorb and emit heat.  When it rains, heated runoff that flows over these surfaces can potentially increase the temperature of receiving waters. Increased temperatures can negatively impact coldwater fish populations by interfering with spawning and migration patterns, decreasing dissolved oxygen levels and even resulting in fish kills.

Stormwater Best Management Practices have an effect on runoff temperature, and the University of New Hampshire's Stormwater Centre has been researching the effectiveness of various BMPs in regulating thermal pollution from stormwater runoff.

They found that surface systems, such as retention ponds, that are exposed to direct sunlight provide little no reduction of high runoff temperatures and can potentially increase already elevated summer runoff temperatures. Various infiltration and filtration systems were best able to moderate runoff temperatures by thermal exchange with cooler subsurface materials. Systems with a large subsurface area had the greatest ability to buffer runoff temperatures. The full report titled 'Examination of Thermal Impacts from Stormwater Best Management Practices' can be found here. 

Brook Trout. (Photo: Source)

Pioneer Park Stormwater Management Project

The Town of Richmond Hill, Ontario, created a stormwater management park to collect and treat runoff as well as provide flood and erosion protection to neighbouring communities. Originally built in the 1980's, Pioneer Park treated runoff from 26 ha of residential development. Redesigned in 2009/2010, the improved stormwater management park now provides water quality and quantity services to a 740 ha catchment area.

The park consists of a wet pond to treat runoff from everyday rain events, a dry pond to collect and treat runoff from major, intense rainfall events, an oil grit separator for pre-treatment and a channel for fish passage. This project was a 2010 winner of Insurance Bureau of Canada's Watershed Awards.

The completed stormwater management park. Photo: www.rmconstruction.ca

Under construction in 2010. Photo: www.rmconstruction.ca

Check out this great video to learn more about how Pioneer Park was created and the many environmental and economic benefits it provides to the Town of Richmond Hill. This video was provided by Insurance Bureau of Canada.

Backwater valves

Basement flooding can be caused by a number of reasons including cracks or leaks in basement walls, blocked pipes, failure of foundation drains (weeping tiles) and poor lot drainage. Heavy rain events can also overload city sewer systems and lead to sewage backing up through house sewer lines and flowing into unprotected basements. Damage from sewer backups is costly for homeowners and municipalities. The Canadian insurance industry pays an estimated $1.7 billion each year in claims due to water damage. 

A backwater valve is a flood-proofing device that prevents sewage in an overloaded public sewer system from backing up into your basement. This fixture, placed on a sewer line in your basement, works as a one way system - sewage can go out, but not back in. The backwater valve automatically closes if sewage backs up from the main sewer line. You should contact a licensed plumber to install a mainline backwater valve and to obtain the proper plumbing permits.

Backwater valve (source: plumber-master.com)

 

Since decades ago, the National Plumbing Code has required the installation of a backwater valve. In HRM, construction or renovation projects have been required to follow the National Plumbing Code including the installation of backwater valves. This became more closely monitored after HRM amalgamation in 1996, when all of HRM required inspections with the issuance of a permit for construction or renovation projects.

Today you are required to get a construction permit (and inspection) for any renovation or construction exceeding $5,000 or when performing structural work. This would include adding or altering a connection to the storm or ssystem such as installing a backwater valve (the only exemption is when replaceing a plumbing fixture).

For more tips on reducing the risk of basement flooding, check out this brochure and video provided by the Insurance Bureau of Canada.