DRAFT CII GP

Who is Subject to CII GP?

 

You may be subject to this stormwater permit if:

• Your property is located in the Charles, Mystic, or Neponset River Watersheds.

• Your property has at least one acre of impervious surface. Impervious Surface is defined as “any surface that prevents or significantly impedes the infiltration of water into the underlying soil. This can include but is not limited to: roads, driveways, parking areas, and other areas created using nonporous material, buildings, rooftops, structures, artificial turf and compacted gravel or soil.”

• Your property is privately owned and classified under specific commercial, industrial, or institutional tax codes.

• Your property discharges stormwater into a municipal storm sewer system (MS4) or directly into local waterways.

 

This permit does not apply to municipal, state, or federally owned properties.

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Key Requirements for Property Owners

 

If your property is covered under this permit, you will need to take action to reduce phosphorus pollution in stormwater runoff. The main requirements include:

 

1. Submitting a Notice of Intent (NOI)

• You must submit an NOI to the EPA to obtain permit coverage.

• The deadline for NOI submission depends on the size of your impervious cover:

  • 5+ acres: Within 6 months of the permit’s effective date.

  • 2–5 acres: Within 12 months.

  • 1–2 acres: Within 24 months.

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2. Developing a Stormwater Pollution Control Plan (SPCP)

• Within 2 years of authorization, you must create a written SPCP detailing how you will manage and reduce stormwater pollution.

• The SPCP must include:

  • A map of your stormwater system, showing drainage areas, stormwater outfalls, and any treatment structures.

  • An inventory of impervious surfaces on your site.

  • A pollutant load calculation, determining how much phosphorus your property contributes.

  • A plan to reduce phosphorus using structural (e.g., retention ponds, infiltration systems) and non-structural (e.g., street sweeping, leaf collection) controls.

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3. Meeting Phosphorus Reduction Targets

• You must reduce phosphorus pollution from your property by:

  • 65% in the Charles River Watershed.

  • 62% in the Mystic River Watershed.

  • 60% in the Neponset River Watershed.

• The reduction can be achieved on-site or off-site (e.g., funding watershed improvement projects).

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4. Compliance Timeline

• Within 6 years, you must achieve at least 50% of the required phosphorus reduction.

• Within 11 years, you must achieve 100% compliance.

 

5. Implementing Stormwater Controls

• You may use:

  • Structural controls (e.g., detention basins, infiltration trenches, green infrastructure).

  • Non-structural controls (e.g., parking lot sweeping, catch basin cleaning).

  • Offsite mitigation by contributing to stormwater projects in the watershed.

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6. Recordkeeping & Annual Reports

• You must keep records of:

  • Stormwater control maintenance.

  • Pollution reduction progress.

  • Annual reports submitted to the EPA.

• Reports must be submitted 14 months after authorization and annually thereafter.

 

Why This Matters

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• CPII GP would regulate stormwater discharges from thousands of previously unregulated properties across the Greater Boston region in Massachusetts.

• Failure to comply may result in penalties under the CWA.

• Compliance can reduce flooding risks, improve local water quality, and support sustainable property management.

• Financial incentives may be available for properties that implement green infrastructure or participate in watershed-based solutions.