Lawn care and stormwater pollution

Photo: www.inharmony.com

Pesticides and fertilizers are among the many common pollutants found in stormwater runoff that can impact water quality. When pesticides wash into local waters they contaminate the water and poison aquatic life. Fertilizers contain nutrients such as phosphorus and nitrogen. These nutrients can overload natural water bodies and result in the growth of algal blooms which use up the water's oxygen and impact fish and other aquatic organisms. 

To protect water quality of lakes, rivers and streams it is strongly recommended that property owners reduce or eliminate the use of cosmetic pesticides and fertilizers. You can still have a healthy, happy lawn without the use of chemicals. Here are some tips to protect your lawn and the surrounding environment:

•  Vinegar is one of the most easily accessible and safest ways to kill weeds. The acetic acid in vinegar breaks down plant cells and kills the top growth.  But, because it does not kill the roots, you’ll have to reapply.   

• Corn gluten meal, found at lawn and garden centres, acts as both a fertilizer and an all-natural herbicide that is effective at preventing the growth of dandelions and other weeds.  It can be applied to an established lawn in early spring before the weeds germinate.

• Kitchen compost and lawn waste make excellent natural fertilizer for your lawn. Or better yet, brew your own compost tea!

• Mow high (6-7 cm) and leave grass clippings on the lawn, which adds nutrients to the soil. The shade of tall, dense grass will overcrowd weeds and reduce growth.

• Aeration is the best fertilizer. Use an aerator to pull plugs of grass out of your lawn to allow more air to reach the roots. This promotes a healthy lawn and results in vigorous new growth.

•  Landscape with native species that will have less need for fertilizers and pesticides.

• Also, remember to pick up after your pets. Pet waste carries numerous bacteria which finds its way into the storm sewer system and ultimately into streams, rivers and lakes.
  

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.

Constructed wetlands

"S" shaped constructed wetland

At the headwaters of Frenchman's Creek in Dartmouth, a wetland was constructed to treat stormwater runoff from the adjacent sports fields and parking lot. The wetland has a serpentine shape and varying depths in order to maximize residence time of the runoff in the wetland. This allows for increased removal of nutrients and metals through plant uptake and adsorption. This stormwater treatment feature essentially acts as a kidney purifying the water. The runoff leaving this site now enters the natural environment at a much higher quality than it would if directly released without treatment. 

This wetland would require occasional maintenance to maximize function. Construction was done by Jeff Pinhey and Rob Leblanc in 2007. 

The marsh is predominantly vegetated with cattails

Urban Forests

What is a simple action that homeowners can take to reduce stormwater runoff leaving their property? Plant a tree.
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 Trees and forests benefit air quality, biodiversity, neighbourhood aesthetics and also play an essential role in managing stormwater. Tree canopies reduce stormwater runoff by intercepting, capturing and storing rainfall and releasing water into the atmosphere through evapotranspiration. In urban and suburban settings, a single deciduous tree can intercept between 500-760 gallons (~1,800-2,800 L) per year, while a mature coniferous tree can intercept over 4,000 gallons (~15,000 L) per year (PA Trees). In addition, tree roots and leaf little help promote infiltration of runoff into the soil.

Source: http://bit.ly/IcxK5H

Trees also act as filters, taking up nutrients and contaminants from the ground that may otherwise directly enter natural water bodies, or end up in wastewater treatment plants. As we begin to remove forest canopy and replace it with lawns and impervious surfaces, we immediately have an impact on quality and quantity of stormwater runoff. 
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Urban Forests in Halifax Regional Municipality             
                                                               
In HRM, it is estimated that street trees provide about $2.1 million in stormwater reduction services annually (HRM). HRM is currently developing an Urban Forest Master Plan (UFMP) with the goal of ensuring a sustainable future for our urban forest. The plan contains an overview of the issues and opportunities regarding sustainable urban forest management in HRM. Neighbourhood Factsheets have also been developed that describe the species composition and age distribution of trees found in each neighbourhood, as well as targets for urban forest restoration. Take a look at the draft UFMP and Neighbourhood Factsheets here. 

Engineered Wetlands

Appleton-Middleton Engineered Wetland Photo: www.abydoz.com

When the aging sewage treatment plants needed upgrades in the towns of Appleton and Glenwood in Newfoundland and Labrador, they took an innovative approach to improving stormwater and sewage treatment by implementing an engineered wetland. The towns were concerned  the quality of discharge that was entering the Gander River which was not meeting Provincial or Federal standards and about the increasing maintenance costs required by the older systems.


The newly constructed engineered wetland provides secondary treatment of wastewater, is cost-effective and has greatly improved the water quality discharged into the Gander River. This project was the Atlantic winner of the Watershed Awards, which recognizes community climate change adaptation efforts and is awarded by Insurance Bureau of Canada and the Federation of Canadian Municipalities. Check out this great video to see how the engineered wetland works. Video provided by the Insurance Bureau of Canada.

Managing Stormwater Quality in Urban Lakes

Stormwater runoff can have serious impacts on the water quality of urban lakes and other receiving water bodies. An innovative technique called Contaminant/Sediment Control (CSC) Filter Systems has been shown to greatly improve water quality by removing stormwater pollutants before they drain into the natural system. These filters have been placed at stormwater outfalls around First Lake in Lower Sackville, Nova Scotia, which has led to significant improvements in the lake's water quality. Check out our latest video, featuring Larry Bell of W.A.T.E.R Research Associates, to see the filters in action!