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This chapter provides detailed guidance on the design, construction, and maintenance of the structural stormwater Best Management Practices (BMPs) contained in this Manual. The table on the right lists each of the stormwater BMPs for which detailed guidance is provided. It is important to note this is not intended to be an exhaustive list, but rather a method to provide the soundest science available and develop guiding principles to BMP design. Hyperlinks are provided corresponding to sections of this chapter where information on specific BMPs can be found. Guidance for multiple types of BMPs is provided in a single combined section for several categories of BMPs (Pretreatment BMPs, Stormwater Pond and Wetland BMPs).
The following BMP-specific design guidance is provided in each section:
- Description: A brief description of the stormwater BMP and common design variations. The stormwater management benefits of the BMP (runoff volume and pollutant reduction, stormwater runoff quantity control, etc.) and effectiveness for removal of specific categories of pollutants are summarized at the beginning of each section for quick reference and screening.
- Advantages: The major beneficial factors or considerations (e.g., environmental, economic, safety) for selecting a specific stormwater BMP.
- Limitations: The major limitations or drawbacks of a stormwater BMP that may preclude its use for a given site.
- Siting Considerations: The site conditions required for implementation of a stormwater BMP such as subsurface conditions and minimum setbacks.
- Soil Evaluation: Where necessary, evaluation of the soil characteristics and subsurface conditions at the location of the proposed system including soil type, depth to the seasonal high groundwater table, depth to bedrock, and soil infiltration rate (for infiltration systems).
- Design Requirements: Specific technical requirements for designing the major elements of a stormwater BMP such as pretreatment, system sizing and dimensions for retention and treatment, drain time, conveyance, materials, vegetation, etc.
- Construction Requirements: Recommended construction procedures and methods, as well as recommended stages of construction to be inspected by a qualified inspector as defined in the General Permit for the Discharge of Stormwater and Dewatering Wastewaters from Construction Activities, to ensure that stormwater BMPs are constructed as designed.
- Maintenance Requirements: Routine and non-routine operation and maintenance, including inspection frequencies, required for the stormwater treatment practice to function properly over time.