It’s the rainy season here in Austin, which means stormwater runoff (any precipitation that is not infiltrated into the ground) is of high concern. Instead of infiltrating, stormwater will run over the ground and pick up debris, chemicals, and a variety of pollutants while heading toward our storm sewer systems or directly depositing into our surface water bodies. With the expansion in urban development, stormwater volume is only anticipated to grow since the net area of impervious surfaces is also increasing. Therefore, it’s important to have regulations in place to protect the quality of our water systems, particularly at project sites where uncontrolled stormwater discharge can lead to impairment of downstream water bodies. A well-planned Stormwater Pollution Prevention Plan (SWPPP) is an invaluable resource in ensuring construction activity does not contribute to stormwater pollution.
What is an SWPPP? An SWPPP is a collection of documents that detail how stormwater related discharges from a project site will be addressed. These plans are required at construction sites that disturb more than one acre of land and at certain industrial facilities. If the site has low potential for erosion, it is possible that a waiver may be obtained in place of a SWPPP. The plan may be prepared in-house by the civil team, but generally project managers will hire an outside agent trained in the design of SWPPPs to ensure all the requirements are met. SWPPP designers must identify all potential sources of pollutants from the project site and ensure the proper management practices are followed to reduce the pollutants in stormwater discharge from the site.
Erosion and Sediment Control BMPs The displacement of soil particles is considered erosion. Once soil particles are deposited, they are referred to as sediment. Sediment is one of the greatest sources of pollution present in stormwater and can cause a multitude of problems in downstream waterbodies. Construction activities leave areas vulnerable to erosion since ground cover is removed and bare soil is exposed. For this reason, the two general types of best management practices (BMPs) employed on construction sites are those designed to prevent erosion (the first line of defense) and those that will control sediment loss (the safety net). Decreasing the amount of erosion that occurs will lessen the amount of contaminants that leave the project, so these types of BMPs are of high importance in the preparation and planning of SWPPPs.
The Development of an SWPPP There are several components that go into an SWPPP binder, and some may vary based on where the SWPPP is designed, as states and local governments may have different requirements. Some of the general components that go into the development of an SWPPP include:
General information regarding the construction activity. The project name, location, type, size, impervious surface area before and after construction, etc. all need to be displayed within the SWPPP.
Chain of responsibility and contact information. Everyone involved in the development and execution of the SWPPP should be identified to ensure all aspects of the plan are properly implemented.
Site map indicating location of BMPs and their type. Existing and proposed grades should be displayed along with depiction of steep slopes. Any amendments made to this site map during implementation needs to be documented.
Identification of pollution sources. This is one of the most important aspects of the SWPPP! Neglecting a pollutant source will make it hard to adequately design enough measures to control the pollutant’s treatment and/or release. It is better to be conservative in the design than surprised down the road.
Identification of surface waters that will receive stormwater runoff. Stormwater running from the project site needs to meet requirements for deposit into downstream water bodies.
Explanation and depiction of pollution reduction measures. Some BMPs will only be employed during the life of the project (temporary sediment basins, sediment traps, silt fences, buffer strips, etc.), while other practices are developed post-construction and are considered permanent stormwater management practices. Permanent stormwater management practices are required when more than one acre of continuous impervious surface is created. These practices are designed to maximize the volume of stormwater reduction and to treat the remainder of stormwater leaving the site. One popular type of permanent treatment system is a tree box/tree trench.
State and local plans. States and local governments may have their own requirements to accompany SWPPPs, so it is important to check the requirements for the area you are developing in.
Maintenance procedures and inspections of controls. Make sure everyone on your site is trained and aware of the upkeep and maintenance involved in the components of your SWPPP. The SWPPP is useless if it isn’t maintained and implemented correctly!
Lastly, when the project is complete, the site must be permanently stabilized. After this point, all temporary sediment and erosion control BMPs can be removed, and any post-constructions BMPs should be installed. With proper planning, even the largest project site can effectively mitigate stormwater runoff issues and be a good neighbor to nearby water sources.
About Foresite Group
Foresite Group is a multidisciplinary engineering, planning, and consulting firm providing services to public and private sector clients nationwide. Our team’s collaborative process results in creative products and services that help our clients achieve their goals. Our team takes pride in enhancing and developing the cities and communities where we live, work, and raise our families.