The US Environmental Protection Agency (EPA) has proposed a new stormwater permitting rule specific to the Charles River, Mystic River, and Neponset River Watersheds, which would regulate stormwater discharges from many commercial, industrial, and institutional (CII) properties that are presently unregulated.
Currently, the EPA regulates discharges of wastewater and certain categories of stormwater under the authority of the Clean Water Act (CWA) as part of the National Pollutant Discharge Elimination System (NPDES) regulatory program. The proposed new rule, known as the NPDES General Permit for Private Commercial Industrial, and Institutional Stormwater Discharges in the Charles, Mystic, and Neponset River Watersheds in Massachusetts, is proposed to be implemented under the CWA “residual designation authority” to extend NPDES jurisdiction to currently unregulated properties for the purpose of curtailing stormwater discharges potentially containing pollutants such as phosphorous, nitrogen, and harmful bacteria.
Commonly referred to as the “Draft CII GP,” the new rule would affect 70 communities in the Commonwealth within the Mystic, Charles, and Neponset River watersheds. Any CII properties that have at least one acre of total impervious cover (i.e., hard surfaces such as roofs, walkways, driveways, parking areas) and discharge stormwater runoff into waters of the U.S., would be subject to the new rule, and be required to apply for coverage under the new NPDES General Permit (GP).
If your property is subject to the new rule, new requirements include:
- Filing a Notice of Intent with EPA,
- Development of a Stormwater Pollution Control Plan, and
- Implementation of structural control measures and operation / maintenance practices, as described in the CII GP rule (phased in over a 2-11 year period), e.g., construction of rain gardens and other means of reducing nutrients and pollutants from stormwater generated on a property.
Notable Exemptions
- Residential and government-owned properties are exempt from the CII GP Rule.
- Commercial, Industrial, and Institutional properties would be covered if they have one of the MA Use Tax codes listed in Appendix H of the CII GP Rule (an extensive list covering diverse operations such as golf courses, colleges, museums, etc…)
- Impervious areas already covered under the Multi-Sector General Permit (MSGP) are exempt.
- Properties that discharge stormwater to a treatment plant (POTW) or to groundwater (e.g., via an on-site pond) are exempt.
Note that the CII GP Rule is in draft form and EPA is still accepting public comments until March 17, 2025. Details and requirements of the new rule are subject to change, and Epsilon will provide additional information upon finalization of the new rule.
Additional information is available from U.S. EPA at: https://www.epa.gov/npdes-permits/residual-designation-charles-river-watershed-mystic-river-watershed-and-neponset
Questions?
For additional information or support with your NPDES permitting needs, contact Daniel Fefer.
