Stormwater Best Management Practices (BMPs) and Site Plan Development
Every construction site starts with moving, compacting, and excavating dirt. During these phases of construction there is usually some amount of rainfall, which results in stormwater. Its runoff picks up dangerous pollutants such as sediment, debris, chemicals, and heavy metals. This polluted runoff creates a domino effect, damaging every body of water it encounters, wreaking havoc with erosion, pollution, and killing wildlife, their habitats, and aquatic life.
Unmanaged stormwater and its polluted runoff also have a significant economic impact on a construction site. Many contractors know how expensive and labor intensive it is to repair gullies, banks, and washed-out construction roads, replace vegetation, clean sediment-clogged storm drains, redo badly installed BMPs and make damage restitution to surrounding properties.
The EPA, though the Clean Water Act, is helping the construction industry lead in preventing these scenarios and more, with a series of Best Management Plans (BMPs).
What is a BMPBest Management Practice (BMP) is a method used to prevent or control stormwater runoff and the discharge of pollutants, including sediment, into local bodies of water. Silt fences, inlet protection, washout pans, and site-stabilization techniques are typical BMPs on a construction site.
Two BMP TypesThere are two main types of BMPs: structural and non-structural.
1. Structural BMPs are designed to remove stormwater pollutants from runoff or reduce the volume of stormwater runoff.
2. Non-structural BMPs are focused on pollutant reduction, pollutant management, and preservation of natural features. Management techniques are usually highly specific to the activity taking place and involve structural and non-structural practices.
Site Plan DesignBefore you can incorporate BMPs into your site, you need to first develop a comprehensive site plan design. Luckily, most of the practices that should be included in your plan are already SOP at most construction sites.
See the list of websites at the bottom of this article for resources in helping you create a plan design and more information about BMPS.
Here are 10 elements for developing a well-thought-out plan; most will be very familiar to you:
- Reduce Clearing and Grading to stream buffers, wetland, forest conservation sites, springs, erosive soils, steep slopes, environmental features, and stormwater infiltration areas. Fingerprint the site and map, flag, and discuss Limits of Disturbance (LOD) with your construction team.
- Protect and Preserve Waterways on and adjacent to the site. Minimize all clearing and grading. Install silt fencing, earthen dikes, or other appropriate tools.
3. Break Construction into Phases and limit grading only to the current phase to minimize exposure. Schedule erosion and sediment control installs before construction starts. Allow time for soil stabilization and BMP maintenance.
4. Stabilize Exposed Soil within two weeks of exposure. Establish permanent long-term vegetation after each construction phase. Mulching, hydroseeding, or other erosion control BMPs offer erosion protection while permanent vegetation grows. Include vegetation specs, time to be established, and weather and climate details in your plan.
5. Protect Steep Slopes and Cliffs by avoiding cutting whenever possible. Redirect all water flowing down steep slopes and cliffs. Install and securely anchor silt fencing at the top and bottom. Jute netting and geotextile erosion control blankets may also be needed alongside seeding and mulching.
6. Install Perimeter Controls such as silt roll with silt fencing behind it. Build earthen dikes with stabilized outlets for heavy runoff flows, or if you’re concerned about a breach. Use a catch basin inlet with erosion controls for stormwater.
7. Build Sediment Basins for Added Sediment Control if space allows. Basin discharge should be non-turbid. Use skimmers and multi-cell basin construction to help with sediment drop-out.
8. Train and Certify All Contractors, Subcontractors and Staff on erosion and sediment control devices, and how to properly use them.
9. Include Site Waste Control on Your Plan. Be sure to detail the types of waste at your site such as; concrete truck washout, construction debris, discarded building materials, litter, and sanitary waste. Ensure site waste is located away from all water sources and catch basin inlets. Describe how site waste will be controlled and disposed.
10. Inspect and Maintain BMPs. Your plan should specifically detail the site operator’s BMP inspection and maintenance, who will conduct these tasks, how often the site will be inspected, and maintenance details. The site should be inspected immediately before and after rain.
ResourcesIf you need more information or help in designing a site plan, here are some invaluable resources:
- Green Infrastructure Modeling Toolkit | US EPA
- Stormwater and Construction Industry (epa.gov)
- White Cap Construction & Industrial Full Line Catalog, p. 761
- Stormwater Management Best Practices - White Cap News
Don’t forget to contact your permitting authority for additional guidance materials. And you can always contact your White Cap professional if you need assistance with stormwater products, procedures, or any other related questions.