MCM 5 Post-Construction Stormwater Management

Infiltration basin protected by silt fence during construction

Introduction

Paved surfaces exacerbate the negative impacts to stormwater, including a increasing the stormwater discharge volume and pollutants in stormwater. Managing stormwater onsite post-construction is the more effective way to mitigate these impacts. Minimum Control Measure (MCM) 5 of the municipal seperate storm sewer system (MS4) General Permit requires permittees to have and enforce a post-construction stormwater management program that prevents or reduces stormwater pollution in new- and re- development projects.

Requirements

The post-construction stormwater management program should include:

• A regulatory mechanism that requires proposers of construction activity to submit site plans with post-construction stormwater management best management practices (BMPs).
• A regulatory mechanism that requires the use of green infrastructure.
• A regulatory mechanism that specifies that there will be no net increase in stormwater volume, total suspended solids (TSS), and total phosphorus (TP) from new development projects; and a net decrease in volume, TSS, and TP for redevelopment projects. See MPCA this fact sheet for the different methodologies to employ to meet this requirement.
• A regulatory mechanism that prohibits infiltration in certain situations, and restricts it in others, as described here.
• Mitigation provisions if TSS and TP cannot be managed onsite.
• A long term maintenance agreement for private structural stormwater BMPs.
• Site plan review procedures to ensure the post-construction stormwater management is in accordance with the regulatory mechanism. See the Site Plan Review page for more information on what to look for during the site plan review.
• All documentation described here.

Resources

Click on the blue links above in the "Requirements" section to get more information and resources specific to those permit requirements. In addition, all resources related to MCM 5 are below.

Fact sheets and guidance documents

• EPA MCM 5 guidance - EPA's guidance and suggested BMPs for an effective post-construction stormwater management program
• MPCA Minimal Impact Design Standards guidance - MPCA fact sheet on Minimal Impact Design Standards (MIDS) and how communities can adopt the MIDS requirements
• MPCA MCM 5 Technical Support guidance - MPCA guide to how to comply with MCM 5 post-construction stormwater management requirements

Model language

• https://stormwater.pca.state.mn.us/index.php?title=Example_Maintenance_Agreement_2 Long-term maintenance agreement model] - MPCA's model long-term maintenance agreement template for general projects
• Long-term maintenance agreement model - MPCA's model long-term maintenance agreement template for rain gardens
• Long-term maintenance agreement model - MPCA's model long-term maintenance agreement template for stormwater quality treatment facilities
• Long-term maintenance agreement model - Middle St. Croix Watershed Management Organization's long-term maintenance agreement template
• Long-term maintenance agreement model - Cottage Grove's long-term maintenance agreement template

Documentation and tracking templates

• Enforcement action documentation template - MPCA's template for documenting all enforcement actions used to compel compliance with your regulatory mechanisms
• Documentation that MS4 staff should retain - List of all the documentation requirements (what information to keep, how long to keep it, level of detail to keep, etc.) for compliance with the MS4 permit

Checklists

• Site plan review checklist - MPCA's site plan review checklist
• Site plan review checklist - City of Cloquet's site plan review checklist

Example Procedures

• Site plan review procedure - City of Elk River's site plan review procedure
• Site plan review procedure - City of Cloquet's site plan review procedure