Parking Lot Design with Winter in Mind: LSRCA’s Parking Lot Design Guidelines to Promote Salt Reduction

A properly signed and placed snow pile.

As discussed in my June post, the use of salt in parking lots can cause major issues for the parking lot and the building infrastructure surrounding it,  and ultimately the freshwater resources receiving the melt water. As this issue becomes more predominant, there has been a push to reduce salt use from many sources. In 2017, LSRCA worked with GHD to develop Parking Lot Guidelines to Promote Salt Reduction to help tackle this issue.

We developed these guidelines to demonstrate to those involved in the planning, design, and maintenance of parking lots that they can be designed to require less salt to maintain an acceptable level of service and safety. Through stakeholder interviews and design charrettes, we identified four design features that can help to reduce the amount of salt needed to maintain safe conditions. We also developed two companion documents to accompany the guidelines:

• a Fact Sheet that provides high level information;
• and template municipal policies to help municipal planners incorporate the guidelines into various municipal planning documents, from Official Plans to Site Plan Agreements. These template policies were developed collaboratively with planning and water resources staff from municipalities around the Lake Simcoe watershed to ensure they could be easily adapted and incorporated.

The following sections describe the design features identified in the Guidelines:

Effective Grading and Stormwater Collection: proper grading of parking lots can minimize freezing of wet pavement surfaces and reduce refreezing of meltwaters. The guidelines recommend the following:

• Slopes of 2-4% to minimize the potential for depressions forming.
• Directing melt water towards strategically placed stormwater collection infrastructure (e.g. catch basins, vegetated swales, landscaped areas, etc.), and ensuring that meltwater from high traffic areas drains to a nearby collection point.

Snow Pile Storage Location: strategically placing snow piles can accelerate melting, ensure that melt water is directed appropriately, and avoids high traffic areas. The following should be considered for snow pile placement:

• Situate where the pile can receive abundant sunlight.
• Prevent visual obstructions to drivers and pedestrians.
• Clearly mark with signage to inform contractors where to place snow.
• Ensure that melt water drains away from high traffic areas, preferably over a short distance, to a drainage feature.
• Minimize long plow routes.

Sidewalk Design and Pedestrian Flow : carefully considering and placing sidewalks and pedestrian walkways will eliminate the over-salting of unused sidewalks. One LSRCA study of salt application in a large commercial parking lot found that 15-30% of the salt applied in the lot was applied on sidewalks, many of which are rarely used, so this is an important consideration. Options include:

• Minimizing the number of walkways and focusing on those that lead from adjacent subdivisions and transit stops.
• Appropriate widths (e.g. >1.5 m wide) to allow contractors to plow rather than using salt to melt snow on sidewalks.
• Using alternative paving materials with more grip.
• Seasonal closures of unused walkways.
• Heated walkways, where appropriate (e.g. near store entrances).

Landscaping Features: Landscaping features can be used to reduce the amount of paved surface requiring maintenance. Vegetated swales, bioretention or landscaped islands with curb cuts can be used to collect and retain melt water runoff, thus reducing melt water ponding and refreezing. Considerations for landscaping features include:

• Strategic use of trees, either to provide windbreaks in the case of evergreens, and shade or sun at appropriate times of year in the case of deciduous trees.
• Ensuring that the vegetation used in areas receiving runoff are salt tolerant.

By incorporating these features into the design or retrofit of a parking lot winter maintenance will be more efficient and reduce infrastructure damage from salt. The addition of the guidelines in municipal planning documents will help normalize these practices, and, in time, reduce the amount of salt being applied in parking lots, ultimately saving our rivers and lakes from contamination.