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HomeMy WebLinkAboutStormwater Management for BuildersDevelopment Best Practices for Stormwater Control Stormwater Management for Builders Measures to control stormwater on your construction site Good stormwater management not only decreases the amount of polluted stormwater entering nearby lakes and streams, it protects your project and nearby properties from flooding. Measures you can take on your construction site include the following: • Reduce soil compaction by designating specific construction paths for equipment and limiting the access of equipment to other areas. • Create better drainage by loosening compacted soils through raking, tilling, or other methods to a minimum depth of 6 inches. • Place new, organic-rich topsoil to a minimum depth of 4 inches on areas of disturbance. • Place sod or seed and mulch on exposed soils as soon as practical. • Control stormwater flow using swales, depressions, soil amendments, and engineered pervious pavements. • Where necessary, use structural practices that infiltrate, divert, or filter stormwater (e.g., underground infiltration, infiltration trenches). • Develop a grading plan that allows water to flow away from a home’s foundation toward storm sewers (not neighboring property). • Inspect your site on a regular basis. • Clean and replace inlet protection regularly to retain the drainage service of the storm sewer system. Increase your inspection frequency in fall and spring when leaves and snow melt can cause issues with performance. For more information on stormwater management for builders, contact the Engineering Department at 952-826-0371, or refer to the Edina Building Safety Policy/Information document found here: https://www.edinamn.gov/DocumentCenter/View/399/Storm-Water-for-SingleDouble-Dwelling-Units-PDF A vegetated swale is a broad, shallow channel with dense vegetation covering the side slopes and bottom. Along with directing water away from buildings, vegetated swales can also provide filtration as water permeates the planted areas—controlling stormwater runoff and pollution. Using swales to control drainage on your property 1. Stormwater runo 2. Maximum 5% channel slope 3. Check dams recommended for slopes over 5% 4. 6-inch grass height recommended 5. Maximum treatment depth 2/3 of grass height 6. Trapezoidal form 7. 10-foot maximum channel bottom width 8. 3:1 maximum channel bank slope 9. Inltration where feasible 1 1 2 3 6 4 5 Stormwater flows away from structures into swale A maximum cross slope of 5% is maintained 3:1 side slopes should be maintained Ideal width of swale base 2’ Maximum depth of swale is 6” Allow infiltration where feasible 1 2 3 4 5 6 Development Best Practices for Stormwater Control Stormwater Management for Builders What does the City of Edina require? Depending on the nature of your project, you may be required to provide either a grading or stormwater plan. Plan requirements depend on a few key factors: • The scope of the project (the extent of the disturbance and the extent of new impervious surface) • Property drainage (property draining to an area with structural or regional flooding issues or private property) • Site-specific conditions (existing stormwater facilities or recent projects) You can contact the City for a list of engineering/surveying firms that can help you prepare a stormwater management plan or for more information about requirements (952-826-0371). The City’s water resources map may also be helpful: https://edinagis.maps.arcgis.com/apps/webappviewer/index.html?id=aeb57968722e476f9b6ef2b86d9326b8 The City takes proper stormwater management seriously. Failure to properly manage stormwater, including during construction, may result in a Stop Work Order until corrections are made consistent with the submitted stormwater management plan. For more information on stormwater management for builders, contact the Engineering Department at 952-826-0371, or refer to the Edina Building Safety Policy/Information document found here: https://www.edinamn.gov/DocumentCenter/View/399/Storm-Water-for-SingleDouble-Dwelling-Units-PDF Considerations during construction and before scheduling a site inspection with City staff • Determine how stormwater runoff has changed from existing to proposed conditions and how it aligns with your stormwater management plan. • Identify low points of entry for the subject property and neighboring properties, such as window wells. Take care to limit and manage risk. • Direct stormwater flows to an infiltration feature, the street, or public storm sewer system. • Ensure no new runoff or concentrated runoff is directed to neighboring property. • Verify your drainage facilities are built and working as designed. This also means ensuring they have not filled with sediment. • Ensure features such as berms, landscaping, retaining walls, and temporary stockpiles do not block existing or designed flow paths. • Ensure erosion and sediment control measures are appropriate, clean, and working as designed. • Don’t grade a flat side yard where a swale is proposed. Inlet control devices need to be regularly maintained by the builder and approved by the City. To prevent runoff from overtopping the curb and causing flooding and erosion, devices should be no more than one-third full. Images above show an incorrect and unmaintained inlet control device on the left and a preferred version on the right. Development Best Practices for Stormwater Control Stormwater Management for Builders Drainage do’s and don’ts There are many ways to combat construction drainage issues, with varying levels of effort and cost. When working to correct any drainage issues on your project, make sure you don’t create water problems in adjacent areas. See below for photos of common mistakes and the ways you can properly address them. Common Mistake: Concentrating new flows towards the structure being built, as well as downstream and adjacent structures. This includes the foundations, window wells, and other low openings. By grading away from low entries or providing a protective window well with height above the adjacent grade, homeowners can ensure water will move away from entryways and avoid flooding and damage to foundations. Common Mistake: Making window wells flush with adjacent grade Allow a few inches above the surrounding grade, so runoff does not pour into the bottom of the window wells. For more information on controlling stormwater runoff, contact the Engineering Department at 952-826-0371. Common Mistake: Driving over curb and gutter during construction Curb and gutter is considered part of the stormwater infrastructure. In some cases, curb and gutter prevents street runoff from entering adjacent private property. Use rock entrances to construction areas to avoid damaging the curb and tracking sediment into the street.