LID opportunities in park lands

LID opportunities in parks

The bioretention area installed at O’Connor Park in Mississauga is part of a stormwater management system that treats parking lot runoff prior to discharging to a local wetland. (Source: CVC)

Parks range from simple parcels of municipal property to complex outdoor recreational facilities that include parking, sidewalks, trails, sports fields, field houses, operations facilities, and washrooms. Each distinct area of your site can be a source for runoff (referred to as a ‘source area’). These areas should be targeted when introducing LID in your park.

Targeting hard surfaces

Hard surfaces like parking lots and internal driveways are the most obvious areas to target for both stormwater quality and water balance improvements. These features produce more runoff than any other area on your site. Water quality of runoff from parking lots and driveways is typically more polluted than other source areas. Common water quality concerns include sand and salt from winter de-icing operations, and hydrocarbons (gasoline) and metals from vehicle breakdowns Runoff from vegetated areas of parks will be relatively clean and more closely match the natural water balance. On municipal park properties, hard surfaces are usually located adjacent to pervious areas such as lawns, gardens or naturalized areas. This makes an ideal location for a LID retrofit. Where grading allows, you can construct bioswales and bioretention areas in these green areas to pre-treat water prior to infiltration. You can also design parking surfaces and internal roadways as infiltration systems using permeable pavement. This retrofit strategy can be combined with other LID practices. A pedestrian pathway paved with permeable pavement is another LID option for your park. They will reduce runoff volumes and encourage on-site infiltration. Pervious pipes are a viable option on many parks sites as well. They can be an alternative to conventional conveyance systems such as storm sewers. They encourage infiltration from hard surfaces and can be used to convey water to other LID features.

Accepting drainage from off-site areas

Urban parkettes may look small, but they have the potential to treat a large surface area of road. Typical ratios of impervious drainage area to bioretention range from 5:1 to 15:1. (Source: CVC)

Does municipally owned land drain into your retrofit site? If so, this is an opportunity to provide stormwater controls for these areas. Roads are the most common source of runoff from external properties into parks. Treating municipal road runoff in a park requires planning input from municipal roads department staff. For these projects, the team must understand how all roads activities, including winter maintenance and potential roadwork, will affect the operation of LID practices in the park.

Inter-municipal transfer of funds

Integrating LID practices into the municipal stormwater

management framework may change how municipal funds are managed. Traditional stormwater management maintenance resources and funds may have to be transferred to a more landscape-based stormwater management maintenance program. Instead of infrequent but expensive stormwater management pond sediment removal operations, time and resources will be spent on more frequent but inexpensive maintenance projects including pruning and weeding bioretention practices or sweeping permeable pavement. Municipalities generally have the required staff and infrastructure within departments (e.g. arborist and horticulturalists in parks departments) to manage the maintenance of LID measures; however, funding this maintenance may require a transfer of funding and additional training. The federal Gas Tax Fund (GTF) is another funding option for funding LID retrofits. This is a federal transfer that provides long term funding for municipalities to build and revitalize public infrastructure. Up to 30% of municipalities yearly GTF allotment can be used towards stormwater management.

Source Areas

The road surface (left) contributes significantly more stormwater pollutants than the parkland area (right). To achieve maximum watershed benefit a designer could consider accepting runoff from this external area. (Source: CVC)

The LID option that best fits your site will depend what types of source areas are present. Types of source areas include: • Active use area • Passive use area • Pedestrian walkway • Internal driveway • Parking lot On park sites, pollution prevention is often associated with changes to operations and maintenance practices and has not been included in Table 3.3.1. An aerial photo of a park with each of these source areas accompanies Table 3.3.1. Options and implementation strategies for a few of these source areas will give you some ideas for your park site.

LID Options for Parks
Source area	Permeable pavement	Bioretention	Enhanced grassed swales	Bioswales	Soakaways and infiltration chambers	Perforated pipe system	Landscape alternatives	Prefabricated modules
Active use area	**	o	*	*	**	*	o	o
Passive use area	o	**	**	**	**	**	**	**
Pedestrian walkway	**	**	**	**	**	*	*	o
Internal driveway	**	**	**	**	**	**	o	*
Parking lot	**	**	**	**	**	**	o	**
** Common option			* Possible option			o Unlikely

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

A vegetated area such as a bog, fen, marsh, or swamp, where the soil or root zone is saturated for part of the year.

Credit Valley Conservation

The land draining to a single reference point (usually a structural BMP); similar to a subwatershed, but on a smaller scale.

The accounting of inflow and outflow of water in a system according to the components of the hydrologic cycle.

Mineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.

The slow movement of water into or through a soil or drainage system.

Penetration of water through the ground surface.

An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.

A hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil.

The total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds.

Surface runoff from at-grade surfaces, resulting from rain or snowmelt events.

A body of water smaller than a lake, often artificially formed.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

The land draining to a single reference point (usually a structural BMP); similar to a subwatershed, but on a smaller scale.

An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.