Chapter 18: Post-Construction Water Quality Best Management Practices (BMPs) of the MSD Design Manual establishes a water quality treatment standard pursuant to the Municipal Separate Storm Sewer System (MS4) permit and Article 6 of the MSD Wastewater/Stormwater Discharge Regulations (WDRs). Planning strategies must meet the minimum requirements outlined in the chapter to comply with MSD’s post-construction water quality requirements. Chapter 18 provides guidance for managing the water quality requirements on a project site and details the various BMPs available to provide water quality improvements before runoff leaves a site.
Post-Construction BMP Plan Review Checklists
The Post-Construction BMP Plan Review checklists provide the minimum requirements needed for MSD’s Development Review if BMPs are incorporated on a project site. Linked below are the checklists for each BMP type, as indicated in the top right corner of each page.
Post-Construction BMP Calculations
Post-Construction BMP calculations are required for MSD Development Review when submitting plans with BMPs on a project site. Below are the BMP Calculation sheets for each water quality BMP.
- Bioretention (Rain Garden, Bioswale, Tree Box or Planter)
- Constructed Wetland
- Green Wet Basin
- Green Dry Basin
- Green Roofs
- Open Infiltration Trench
- Permeable Pavers
- Proprietary Water Quality Unit
- Tree Box
- Vegetated Buffer
- Underground Infiltration Basin
Stormwater Quality Maintenance Agreements
All sites with post-construction water quality BMPs are required to enter into a long-term Stormwater Quality Maintenance Agreement (SWQMA) with MSD. This agreement outlines the inspection and maintenance requirements for the BMP. Related documents and forms are provided below.
- Stormwater Quality Maintenance Agreement
- Stormwater Quality Maintenance Agreement Instructions and Exhibits
- Stormwater Quality Maintenance Agreement Release Form
Fee In Lieu Of Program
The post-construction fee-in-lieu-of (FILO) program is available to development projects that are required to meet water quality requirements but are unable to provide post-construction BMPs onsite. FILO gives the developer the option to pay a calculated fee for off-site mitigation instead of constructing BMPs onsite. FILO funds will be used to construct alternative BMPs offsite on a watershed basis.
Projects must be located within MSD’s Drainage Service Area to be eligible for the FILO program. Eligible projects include but are not limited to:
- Projects in the combined sewer area
- Linear projects, such as road or sidewalk projects
- Projects with less than 2 acres of disturbance
- Projects that are located on contaminated soils
- Projects with site conditions that make it difficult to capture the minimum runoff to meet water quality treatment requirement
- Areas with high groundwater tables
- Projects in karst areas
- Projects with significant hazardous materials storage
- Other projects as approved by the Development and Stormwater Services Director
The FILO Application should be submitted to MSD Development Review during the development review process. MSD will determine whether the payment of the fee or another mitigation measure is appropriate for each development during the development review process.
