Section 1: Source Control
Best management practices that address stormwater often fall into two categories commonly known as source-control BMPs and stormwater treatment BMPs.
Source control, or non-structural, BMPs focus on preventing stormwater from coming into contact with pollutants. Stormwater-treatment BMPs usually involve building structures or installing devices to treat or manage runoff. Source-control BMPs are generally preferred because they usually cost less and can keep most, if not all, pollutants out of the water.
By the end of this section, you should be able to:
- Explain why incorporating low impact development options into site design are preferred to traditional stormwater management alternatives.
- Identify several approaches to reduce the total volume of runoff from your facility (e.g., vegetated areas, pervious surfaces, and water reuse).
- Understand why maintenance and work areas should be designated and closely managed.
- Prepare to locate and label all storm drains, indicating drainage to water body.
Best Management Practices for Source Control
- Practice low impact development
- Plant and maintain vegetated areas
- Minimize impervious areas
- Capture and reuse roof water
- Minimize pollution in runoff
- Control sediment from construction sites
- Stencil storm drains
Permits and Plans
As discussed in the Legal Setting for this unit:
- Obtain required stormwater permits.
- If required, do you have a Stormwater Pollution Prevention Plan (SWPPP). See Legal Setting for details.
- If a SWPPP is not required, develop a stormwater information map.
Practice Low Impact Development
Traditional stormwater management uses structures like curbs, gutters, and storm drains to move water offsite as efficiently as possible; this causes unnaturally high volumes of runoff to flow into receiving waters at high velocity. In comparison, low impact development maximizes a site’s natural features, such as vegetation, and minimizes the need for expensive stormwater control devices.
Low impact development (LID) is a cornerstone of stormwater management with the goal of mimicking a site’s predevelopment hydrology (e.g., water quality and quantity) by using design techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source. Because LID uses a variety of useful techniques for controlling runoff, designs can be customized according to local regulatory and resource protection requirements, as well as site constraints. LID practices offer additional benefits. They can be integrated into the existing infrastructure and are often more cost effective and aesthetically pleasing than traditional, structural stormwater conveyance systems.
- Design your facility to collect, infiltrate and/or treat stormwater runoff.
Low Impact Development in Design Phase
- Concentrate development. Cluster structures on the lot to avoid sensitive resources, steep slopes, riparian buffers, wetlands, and floodplains without sacrificing development.
- Minimize soil compaction. To maintain drainage and protect established vegetation, minimize damage to soil by reducing disturbance through design and construction practices, limiting areas where heavy equipment is operated, and avoiding unnecessary clearing or stockpiling of topsoil.
- Protect natural flow pathways. Identify, protect, and use natural drainage features, such as swales, depressions, and watercourses to help protect water quality. Designers can use natural drainage features to reduce or eliminate the need for structural drainage systems.
- Protect riparian buffer areas. Riparian buffer areas protect water quality by cooling water, stabilizing banks, mitigating flow rates, and providing for pollution and sediment removal by filtering overland sheet runoff before it enters the water.
- Protect sensitive areas. Protecting sensitive areas, such as floodplains, riparian areas, wetlands, woodlands, prairies, natural flow pathways, steep slopes will provide benefits for stormwater management, erosion control, fish and wildlife habitat and aesthetics.
- Reduce impervious surface. Reducing impervious surfaces includes minimizing areas such as streets, parking lots, and driveways. By reducing the amount of paved surfaces, stormwater runoff is decreased while infiltration and evapotranspiration opportunities are increased.
- Stormwater disconnection. Minimize stormwater volume by disconnecting roof leaders, impervious roads, and driveways and rerouting runoff to areas that allow infiltration at the site.
For more information, see the “Incorporating LID into the Site Design Process” chapter of the Low Impact Development Manual for Michigan.
- Low Impact Development Techniques (Low Impact Development Center)
- Low Impact Development Manual for Michigan (Southeast Michigan Council of Governments)
Healthy soil and vegetation capture, treat, and slowly release stormwater. The water is cleaned through a combination of microbial action in the soil, vegetative uptake, evaporation and transpiration. To make the most of these natural processes:
- Maintain vegetated drainage areas and retain vegetated buffers along the waterfront.
- Preserve areas of natural vegetation where possible.
- Retain or restore wetlands to remove pollutants, shelter the coast from storms, and provide habitat for fish and birds.
- Plant or restore vegetation between your upland property and the water’s edge.
- When landscaping, use native species, which offer numerous benefits including reduced maintenance needs.
- To provide a buffer between your facility and the water body, retain a vegetated filter strip (also called a vegetated buffer). Vegetation — either grass or a combination of trees and shrubs — planted as a buffer along the water’s edge filter stormwater runoff and remove contaminants and soil particles before they reach surface waters. The vegetation slows runoff carrying sediments, chemicals and nutrients. This causes the particles to settle out before reaching the surface water. In some cases, nutrients or chemicals in the runoff may be taken up by the vegetation, rather than going into the nearby body of water.
- Where impervious surfaces are necessary, direct runoff to vegetated areas.
- Roofs and sidewalks can drain to a “rain garden” instead of a storm drain. Rain gardens are low-lying areas designed to naturally absorb and filter stormwater. They are built with specific layers of soil, sand, and organic mulch that filter the rain as it enters; the soil absorbs and stores rainwater to nourish the surrounding grasses, trees, and flowers. Rain gardens have the added advantage of being attractive areas that can provide shade and wildlife habitat.
- Position roof downspouts so that they drain to vegetated areas — avoid draining to concrete or asphalt. When doing this, crushed stone or some other material to restrict or slow the water’s pace at discharge is needed. This will minimize erosion and allow water to drain into vegetated areas at a manageable pace. You can also use rain barrels or a cistern to capture downspout water and use it to irrigate landscaping during dry weather.
- Parking lots should only drain to biofiltration areas, due to the potential for pollutants in the runoff. A biofiltration area is specially engineered to provide treatment for vehicle fluids before infiltrating stormwater to ground water or drinking water supplies. Also, plant additional vegetation at the edge of parking lots and within islands in parking lots to absorb runoff. For more information, see the Section 2: Stormwater Treatment.
The fewer impervious areas there are on site, the less runoff you will have to manage.
- Pave only the necessary areas or use pervious pavers.
- Check with local authorities to ensure compliance with local zoning ordinances. Facilities are advised to check with local authorities about local requirements for road and parking lot surfaces. Many communities still have “aesthetic” requirements that are consistent with traditional concrete and asphalt paving. A marina facility may have to request a variance to utilize porous surfaces.
To reduce the amount of impervious surface:
- Pave only those areas that are absolutely necessary.
- Minimize the length of new road required to serve new or expanding marinas.
- Plan roads so they do not cross sensitive areas, such as wetlands.
- Consider alternatives to asphalt for parking lots and boat storage areas, such as gravel, pervious pavers, or engineered porous pavement.
Install a rain water capture system to intercept and store runoff from rooftops at your facility. This reduces your overall volume of runoff and allows for an alternate water source. Gutters direct rain water into a cistern for temporary storage. This water is typically reused for irrigation or other water needs. Cisterns are either high-density polyethylene chambers or metal containers resembling small silos. They often are accompanied by a pump and a water distribution system (valves, pipes, and hoses).
Runoff is a concern for all developed areas, but is a special concern for marinas providing boat maintenance services and designated work areas. The materials and compounds used to repair boats, control fouling and corrosion, and the wastes generated by sanding, scraping, painting, varnishing, and fiberglassing can contain metals, solvents, hydrocarbons and other contaminants.
- Cover work and storage areas to avoid contact between rainfall and equipment, fueling and work areas. Sources of polluted runoff at marinas and boatyards include:
- Material, equipment or boat storage
- Sanding or scraping
- Engine maintenance
- Pressure washing
- Waste handling
- Vehicle parking
- Train for best material management practices.
- Control stormwater runoff from dry-stack areas as well as from any expanded parking areas.
- Maintain structures using Clean Marina practices:
- Scrape, sand, and paint land-side structures according to the same management principles as for vessels. For more information, see: Boat Maintenance Unit.
- If feasible, move floating structures to prescribed areas on shore for scraping, painting, and major repairs.
For details on how to minimize contamination in runoff, see Boat Maintenance Unit.
- Use devices such as straw bales, silt fences, storm drain filters, sediment traps, and earth dikes to prevent sediments from leaving construction areas.
- Refer to Legal Setting for Stormwater Management for more information on construction site requirements. Also, consult your state for erosion control standards.
- Stencil or label storm drains with the words “Don’t Dump—Drains to Lake (River)”. Stencils and instructions are available from local watershed groups and councils. Be sure to get permission from the county or city department that maintains storm drains in your community prior to applying any stencils or labels. Generally, the appropriate municipal authority would be the Department of Public Works. Note: Many new drains have the message stamped into the design.
For more information on stormwater best management practices, see: National Menu of Stormwater Best Management Practices (EPA). Topics include: public education, public involvement, illicit discharge, construction, post-construction, and good housekeeping.