Infiltration basin protected by silt fence during construction
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.
MS4 General Permit requirements for MCM 5
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.
- 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.
- All documentation described here.
Click on the blue links above in the "MS4 General Permit 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
Documentation and tracking templates