When building a property, a fully functional drainage system is crucial to ensure better drainage around the property. Such a system comes under the banner of lot grading. When executed, lot grading requires a Lot Grading Certificate prepared by certified authorities, which illustrates all the required grade elevations concerning the approved Lot Grading Plan. This certificate needs to be approved by the regulatory authority. However, some setbacks, minor or major, can affect the lot grading and result in an issue of non-compliance. Mentioned below are the many examples of non-compliance and their solutions.
Issue: The drainage swale is not defined.
Solution: Construction Abutting – Drainage swale is damaged by abutting property construction or unknown third-party activities. Adjust the drainage swale (as needed) to allow the flow of surface drainage.
Issue: Existing elevations on the Lot Grading Certificate do not meet the rough grade tolerance of 7 – 20 cm below the design grade elevation on the approved Lot Grading Plan.
Solution: Raise & Certify – Raise the existing elevation at the design point indicated such that it is 7 – 20 cm below the approved design elevation and adjust the drainage swale, as needed, to integrate the elevation change with the slope of the swale. Submit a new Lot Grading Certificate to verify that the corrected elevation is within the acceptable tolerance and that the adjusted swale has a minimum 1.5% slope.
Issue: The owner fails to control the release of stormwater and subsurface water when directed to do so.
Solution: Downspouts are connected to the Foundation Service. Remove the downspout connections and spill the roof water to the ground. Permanently cap the unused standpipes.
Issue: Backfill is required to provide a slope away from the foundation wall or to fill a void under a structure.
Solution: Deck – Add clay or topsoil beneath the deck to create a minimum 10% slope away from the foundation wall for a distance of at least 2 metres. If the distance from the foundation wall to a property line is less than 2 metres, create a slope with a minimum drop of 15 cm from the building to the property line.
Issue: Inconsistently sloped drainage swale does not allow the efficient flow of surface drainage.
Solution: Construction Abutting – Swale is damaged by abutting property activity or unknown third-party activities. Adjust the drainage swale as needed to promote the efficient flow of surface drainage.
Issue: There is a low area along the drainage swale. A consistent slope conveys surface drainage away from the foundation wall and off the lot.
Solution: Settlement – Raise the settled area and adjust the drainage swale, as needed, to promote the efficient flow of surface drainage. The grading next to the building foundation may also need to be raised.
Issue: Roof and Foundation Drainage systems must be configured to discharge water past the foundation excavation zone (approximately 1 m from the foundation wall) within the property and no closer than 15 cm to an abutting private lot or a city right-of-way.
Solution: Install a downspout extension or a splash pad.