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EPA Releases Draft Settlement Agreement & Proposed Revisions to MS4 Permit

January 13th, 2020

On December 27, 2019, EPA released a proposed settlement agreement and corresponding revised sections of the New Hampshire Phase II MS4 Permit as a result of litigation between EPA and a number of parties. While changes and clarification were provided throughout the permit, the most significant changes are:

  • New development and Redevelopment have been redefined as sites with less than 40% existing impervious surface and sites with 40% or more of existing impervious surface, respectively. These definitions must be incorporated into regulatory mechanisms for new development and redevelopment projects and determine which performance criteria these sites must meet.
  • Select communities in the Great Bay Watershed must include a 50% nitrogen removal requirement in their regulatory mechanisms for new development and redevelopment projects.
  • Communities will be given an extra year to enact regulatory mechanisms covering new and redevelopment projects.
  • Roadway maintenance and improvement projects that disturb >1 acre without increasing the amount of impervious area will no longer be exempt from the redevelopment performance specifications.
  • Communities can propose and alternative schedule to meet some phosphorus TMDL requirements.

Other changes include:

  • In addition to the SWMP and annual reports, all documents submitted to EPA in accordance with Appendix F of the permit (TMDL requirements), must be made available to the public.
  • The required pollutant removals for new development sites have been reduced. Specifically, removal of total suspended solids has been reduced from 90% to 80%, and removal of total phosphorus has been reduced from 60% to 50%.
  • Redevelopment projects will be required to disconnect or treat at least 30% of the existing impervious cover as well as 50% of the additional proposed impervious surfaces through the application of filtration media; OR implement other LID techniques onsite to the maximum extent practicable to provide treatment for at least 50% of the entire site area. Off-site mitigation can be used within the same drainage area of the receiving water body where on-site treatment is not feasible to meet the proposed standards.
  • When notified by EPA or MassDEP that the permittee is discharging to a new waterbody impaired for nitrogen, phosphorus, bacteria, or solids/metals/grease, communities will have 90 days to update their Stormwater Management Program (SWMP), after which the deadlines in Appendix H will be extended based on the updated SWMP date. 


It is anticipated that the above will become final pending completion of a public comment period.  For now, written comments on the proposed settlements agreement only are being accepted through January 27, 2020.  Comments may be submitted online through www.regulations.gov referencing Docket ID number EPA-HQ-OGC-2019-0685.  After this comment period closes, it is anticipated that a second public comment period will commence on a future date to allow permittees to comment on the proposed permit changes themselves. 

If you have any questions on the above, please feel free to contact Rebecca Balke or Nick Cristofori at 800.725.2550 x308 and x303, respectively, or at [email protected] or [email protected].

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Posted in the categories Compliance, News, Stormwater, Watershed Management.