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NPCA Stormwater Manual – Appendices - Niagara Peninsula ...

NPCA Stormwater Manual – Appendices - Niagara Peninsula ...

Stormwater Management, Erosion and Sediment Policies and Criteria Niagara Region and Niagara Peninsula Conservation Authority – DRAFT Q4 1.7 Trends and Advances Third pipe systems designed to drain foundations and convey the water to a separate outlet have been implemented across Ontario. Developments constructed adjacent to a sensitive watercourse include a third pipe that conveys foundation drainage separate of the storm sewer, by-passing the stormwater facility directly to the stream. 1.8 Roof Leaders Typical policies regarding roof leaders include: • Connection to storm and sewer prohibited; • Drain to pervious surfaces wherever possible; • To be discharged to grassed or garden areas; • Commercial areas can discharge to storm sewer using controlled release devices; • Disconnect where able; and • Direct to splash pads and protect against erosion. 1.8.1 Trends and Advances Municipalities recognize that roof water should be infiltrated to the ground and diverted away from impervious surfaces such as driveways wherever possible. The use of rain gardens is a practice where roof leaders are discharged into landscaped areas that can be designed in such a way as to create a depression that collects rainwater and allow it to gradually infiltrate into the ground. Consideration must be given to ensure they are situated far enough away from the home to prevent damage to the foundation. They also need to drain within a specific period of time to prevent standing water concerns. Methods such as this are an excellent way to infiltrate clean rainwater. Some municipalities offer free downspout disconnections to help alleviate pressure on combined sewer systems. Disconnecting roof leaders helps reduce the risk of basement flooding and provides the opportunity to detain and infiltrate a portion of the roof water depending on the soil type. 1.9 Combined Sewers Niagara Region’s Water and Wastewater Master Servicing Plan Update (2003) notes that combined sewer systems are still active in Niagara-On-The-Lake, St. Catharines, Welland, and Niagara Falls. The combined sewer overflows from these municipalities release large amounts of sanitary sewage mixed with stormwater that includes bacteria, oxygen demanding substances, heavy metals, and industrial chemicals. The pollutants cause problems for bathing beaches, aquatic life, and potentially water supplies. The report recommends that the MOE control policy outlined in Procedure F-5-5: Determination of Treatment Requirements for Municipal and Private Combined and Partially Combined Sewer Systems be adopted. This would lead to control of 90% of the wet weather flow in a combined system. Control options that can be used include many of the measures typically used for SWM such as: roof leader/foundation drain disconnection; sewer separation; in-line and off line storage; high-rate treatment of overflows with disinfection; sewer rehabilitation; and replacement to reduce inflow and infiltration. It is a concern that combined sewer separation might lead to untreated storm sewer discharges to the waterways. It is recommended that measures that control the total discharge be favoured, or that stormwater be controlled

Stormwater Management, Erosion and Sediment Policies and Criteria Niagara Region and Niagara Peninsula Conservation Authority – DRAFT Q5 separately to a minimum level of treatment to provide a normal level of protection for fisheries (70% TSS removal). 1.10 Natural Watercourses The following summarizes some of the policies currently in use relating to watercourse alterations: • Reference the MNR adaptive management of stream corridors in Ontario 2001 • Permits from NPCA and DFO for watercourse alterations; • Consider maintenance requirements (e.g., utilities); • Multi-disciplinary design approach; • Utilize guidelines such as MNR, Rosgen, Annable, and Newbury; • Erosion control measures must preserve natural valley aesthetics; • Protection could be required to the 1:100 flood level; • Where control of flow is not feasible or ineffective, design of channel alterations may be considered; and • Design according to Natural Channel Design Principles (1994). 1.10.1 Trends and Advances Municipalities are conducting geomorphic inventories or stream erosion studies of all streams within their jurisdiction. The studies help to prioritize restoration projects based on both risk to public safety and environmental enhancement. Municipalities that have policies stemming from watershed studies require that softer erosion and stabilization methods such as soil bioengineering practices be considered first when altering or stabilizing a watercourse. Channel hardening techniques such as amour stone are sometimes required depending on space requirements and locations of utilities. The City of Vancouver, through their sewer separation program, is taking the opportunity to daylight streams or create artificial streams when replacing aging sewer infrastructure. The City examines the possibility of constructing open watercourses rather than expensive storm sewers when the opportunities exist. 1.11 Storm Outfalls Several municipalities have developed policies relating to stormwater outfalls into watercourses. The following summarizes some of the policies currently in use: • Outfalls to be designed to prevent erosion; • Prevent access by public (grates); • Require permits from the NPCA; • Outlets to be designed to dissipate energy to not cause erosion and supported with design calculations; • Designed to be aesthetically pleasing; • Appropriate bank scouring protection; • Drop structures for steep valleys; • Must not interfere with natural channel forming processes; • Installed above the normal water level; • Place on a skew with flow; • Dynamic beaches and potential obstruction considerations (i.e., damage from sheet ice); and

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