Erosion and Sediment Control
30 Minute Presentation
Natural and Biological Resource Considerations: SWPPP Development and Site Monitoring
The U.S. Environmental Protection Agency (EPA) requires a National Pollutant Discharge Elimination System (NPDES) Permit (NPDES Permit) for stormwater discharges from construction activities that disturb 1 or more acres of land or from smaller sites that are part of a larger, common plan of development or sale which will disturb a cumulative total of 1 or more acres. For the purposes of the NPDES program, construction activities are defined as clearing, grubbing, grading, and excavation.
Generally, coverage under the NPDES Permit is obtained by developing a site-specific Stormwater Pollution Prevention Plan (SWPPP) and submitting a Notice of Intent (NOI) to the appropriate regulatory agency. The site-specific SWPPP establishes a plan to manage the quality of stormwater runoff from construction activities associated with the project. The SWPPP identifies a set of best management practices (BMPs) to be implemented on the project site; however, BMPs must be moved, added, or redesigned as needed to control erosion and sedimentation to the extent practicable. Primarily, the SWPPP is to be used by onsite construction personnel to reduce soil erosion and to minimize the potential for sediment and other onsite pollutants to leave the project area and enter waters of the state. Additionally, the SWPPP should discuss the natural and biological resources in and adjacent to the project area and the considerations to avoid, minimize, or mitigate impacts to these resources.
Generally, desktop and field surveys are conducted during the project development phase to facilitate design alternatives that can avoid or minimize impacts to existing natural or biological resources. In situations where avoidance is not possible, the project must mitigate and implement best management practices, which are often permit driven. At a minimum, the SWPPP narrative should outline the biological and natural resources present on the project site, such as; aquatic resources and receiving waters, soils, threatened and endangered species and their habitats, cultural resources, etc. The Erosion and Sediment Control Plan (ESC Plan) drawings should depict the locations of each identified resource and prescribe BMPs to avoid or otherwise minimize impacts. Examples could include depicting exclusion fencing and signage, secondary BMPs protecting high value water bodies, or referencing seasonal limitations for working near protected species habitats or for tree clearing. In some cases, designing a separate ESC Plan for tree clearing activities and construction is a good practice, when considering access, BMPs, and that the contractor will likely differ between the two activities.
The final step is implementing the prescribed BMPs on the project site and monitoring them for compliance with the conditions of all applicable permits. It is important for the inspector to have a comprehensive knowledge of not only the NPDES Permit conditions, but also the special resource permits. By understanding the locations of resources on the project site, any special conditions of the permits, and the purpose of the specifically prescribed BMPs, the inspector and the project are better positioned for success.