The purpose of a Stormwater Pollution Prevention Plan (SWPPP) is to identify potential stormwater pollution sources and guide facilities to reduce the potential for pollutants reaching nearby waterways. Establishing procedures and controls is necessary to accomplish the following SWPPP objectives:
- Identify pollutants that may come in contact with stormwater.
- Establish measures to prevent pollutants from interacting with stormwater
- Establish controls to reduce or eliminate the potential for contaminated storm water being released to the environment.
The Environmental Protection Agency (EPA) defines control measures as “any Best Management Practice (BMP) or other method used to prevent or reduce the discharge of pollutants.” The SWPPP requires that companies identify and document which BMPs will be installed at the facilities. BMPs may include:
- Schedules of implementation activities
- Prohibited practices
- Other management practices
- Treatment requirements
- Operating procedures
- Practices to control industrial stormwater runoff, spillage or leaks, sludge, waste disposal or drainage from raw material storage.
Facilities are not required to have structural best management practices implemented prior to a permit application for permit coverage. According to the requirements, a facility has one year from the time of submitting a permit application to implement structural best practices. However, the EPA recommends installing structural best management practices as soon as possible.
There are 3 main categories of BMPs. These include:
- Non-structural BMPs: examples include, but are not limited to:
- Optimize maintenance practices
- Control spills and leaks
- Manage wastes
- Employee training programs
- Optimize procedures and operations
- Simple structural BMPs: examples include, but are not limited to:
- Move significant materials and activities under cover
- Store materials in weatherproof containers, shelters, or dumpsters
- Use temporary shelters, like tarps, on a short-term basis only until permanent structures can be installed
- Complex structural BMPs: examples include, but are not limited to:
- Cover materials or operations with canopy or awning type structures
- Provide curb or slopes designed to prevent stormwater run-on or runoff
- Create stormwater ponds, sedimentary or wetland treatment systems
The following questions can assist in the evaluation of potential BMPs and implementation:
- Are the BMPs appropriate for my facility size/industrial activity/significant material?
- Are the BMPs the most cost effective to install?
- Is there another BMP that is simpler/more cost-effective that achieves SWPPP goals?
- Does the BMP require maintenance and is there adequate staffing for required activities?
- Can BMPs prevent precipitation from coming in contact with operations and/or significant material?
- Does the facility meet the criteria for ”No Exposure Exclusion”?
The content of the SWPPP will vary depending on site-specific conditions. According to The State of Washington’s Department of Ecology, the following BMPs common in SWPPPs:
Covered Storage: Chemicals stored outside should be covered so that rainfall does not become contaminated by contact with the chemical containers. The SWPPP should include this as a standard practice at the facility and a map should identify the covered storage areas.
Equipment Maintenance: The SWPPP should identify equipment that can spill or leak contaminants, such as petroleum products. Provide an inspection and maintenance schedule for each piece of equipment that is identified.
Employee Training: The first line of defense will often be an onsite employee. With proper training, facility personnel can properly manage stormwater and protect it from contamination.
Site Maintenance: Grading the site to provide even infiltration of rain and eliminating site debris will minimize contamination of stormwater.
Infiltration: Infiltration of all or part of the stormwater is preferred. A grassy swale, infiltration trench, or a constructed wetland may provide adequate infiltration for all or most stormwater events. However, when stormwater has become contaminated with pollutants such as oil and grease, treatment may be required before infiltration.
Detention Pond: At sites that discharge stormwater to surface water, a detention pond will typically be required to control turbidity. Careful attention to pond dimensions and design is necessary to accommodate major storms and provide adequate settling.