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Stormwater Management for Single Family & Duplex Developments

The City of North Vancouver’s recommended approach to stormwater management on private properties is capture and infiltration.  This approach provides the best benefit for both our infrastructure and the environment.  Infiltrating rainwater is the best option to recreate the natural process that would occur when our watersheds were forested.  This decreases peak flows during rainy days, and increases low flows following a rain storm.

Infiltration is not always possible or practical on every given property, due to high groundwater conditions, poor soil infiltration, presence of bedrock, or proximity to steep ravine slopes.  In these cases, alternate approaches to managing stormwater are possible.  Three recommended and three optional stormwater management tools are provided below.

 

Stormwater Tools


Optional Stormwater Tools

These tools are intended to complement the recommended tools. Ordinarily they cannot be used by themselves for achieving the Stormwater Management Plan requirements, and can have some challenges associated with meeting the City Building Bylaw.  These systems can also require more regular maintenance to ensure good operation.

4. Absorbent Landscapes: Providing a deep layer of organic soil can be a simple way of reducing stormwater runoff, while increasing the health of your plants. More information.

5. Rain Gardens: Providing a deep layer of organic soil can be a simple way of reducing stormwater runoff, while increasing the health of your plants. More information.
6. Roof Based Detention: Green roofs and Blue roofs are two types of engineered roofs that are designed to slow rainwater runoff. More information.

 

Recommended

Recommended Stormwater Tools

The following are recommended tools in the order of preference for meeting the Stormwater Management Plan submission requirements

1. Infiltration Chambers: Infiltration chambers are below-ground containers with a permeable bottoms. They are designed to temporarily hold stormwater and allow it to slowly seep into the ground. They can be located below lawn, planting beds, or pathways / patios. Infiltration chambers are the preferred method for stormwater management for one and two dwelling properties. More information.
2. Rainwater Tanks with Infiltration Chambers: If space is not adequate for a full-sized infiltration chamber, applicants can use rainwater tanks with smaller infiltration chambers. Rainwater tanks are available in a variety of sizes and shapes and can even be hidden below decks or within walls. More information.
3. Rainwater tanks with slow-release valves: If there isn’t enough space for an infiltration chamber of any size, applicants can use rainwater tanks with slow-release valves. This allows the rainwater tank to temporarily hold stormwater and then slowly release it into a suitable area. More information.

In addition to these tools you should slope all hard surfaces, such as patios and pathways, to soft landscape areas (e.g. lawns and planting beds). The recommended slope for hard surfaces is 2%, which equals a 2cm change in height over a 1m horizontal distance.

Optional

Optional Stormwater Tools

These tools are intended to complement the recommended tools. Ordinarily they cannot be used by themselves for achieving the Stormwater Management Plan requirements, and can have some challenges associated with meeting the City Building Bylaw.  These systems can also require more regular maintenance to ensure good operation.

4. Absorbent Landscapes: Providing a deep layer of organic soil can be a simple way of reducing stormwater runoff, while increasing the health of your plants. More information.

5. Rain Gardens: Providing a deep layer of organic soil can be a simple way of reducing stormwater runoff, while increasing the health of your plants. More information.
6. Roof Based Detention: Green roofs and Blue roofs are two types of engineered roofs that are designed to slow rainwater runoff. More information.

 


Infiltration of rainwater is a practice with a long history, where this was traditionally done in a “soak-away” rock pit or “dry-well”.  Rock pits have been used extensively in the City for rainwater management in the past; however, the City’s current guideline is for the use of infiltration chambers which are pre-engineered plastic chambers that allow storage and infiltration of rainwater.  Infiltration chambers are more efficient, allowing about two times more water storage in a smaller space and a much greater ability to inspect and maintain the facilities without disturbing the area, and a much longer serviceable life span.

As an applicant you can also propose other innovative approaches for managing stormwater, or use a combination of these tools to meet the target volume for infiltration. As systems become more complex, applicants may choose to hire design professionals (e.g. engineers, or landscape architects) or specialty contractors (e.g. licensed plumbers) with specific expertise in this area.

In the event that no rainwater source controls can be achieved on private property, a fee in lieu of the stormwater management works would be applied and dedicated to stormwater management projects on public property. Application of a stormwater management fee will only be considered when no other viable options exist.
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