4 The record articles

Vermont Stormwater Permitting: The 3-Acre Rule

Posted: March 29th, 2022

Authors: Clayton Q. 

To address the growing concerns of pollutant loading to the state’s waterways, especially Lake Champlain, the state of Vermont passed the Vermont Clean Water Act of 2015. In meeting the goals of the Clean Water Act, the Vermont Department of Environmental Conservation (DEC) has implemented several changes to the operational stormwater permitting program, including requiring stormwater management for large areas of impervious surfaces. Recently Vermont made changes to operational permits under general permit 3-9050 (general permit), with initial permitting action required, based on geography, beginning in January of 2022. The most significant change is the requirement that sites with three or more acres of impervious surface obtain coverage under the general permit, often referred to as the 3-Acre Permit. An impervious surface is defined as a manmade surface from which precipitation runs off rather than infiltrates into the ground. Prior to this change, some parcels were grandfathered out of the system by not having an expansion or redevelopment of greater than one acre or by being permitted prior to the publication of the 2002 Stormwater Management Manual.


Existing sites that have three or more acres of impervious surface and that do not currently have coverage under previous iterations of the operational general permit will receive (or will already have received) a letter from the Vermont DEC indicating the need to seek coverage within a specified period of time. DEC developed this list based on digital mapping of Vermont communities conducted in 2011 and 2016. Sites that receive a letter will be required to submit a Notice of Intent (NOI).


  • The initial NOI will need to include general site information, including a delineation of the impervious area, a project description, and copies of any permits obtained under Act 250 (Vermont’s land use and development law). The submission of the initial NOI will result in the site receiving 18 months of coverage under the operational permit.
  • The full NOI must be submitted during the 18-month initial coverage and will include a site plan, an engineering feasibility analysis to identify if the site can support stormwater retrofits, a stormwater system design, and any technical supporting documents. Stormwater system design must be based on the Vermont Stormwater Manual and will include systems that range from traditional infiltration systems to the implementation of green infrastructure.
  • Implementation of the approved design must occur within five years of approval of the full NOI. The implementation will include a post-installation certification once the work is completed. Owners/operators of the sites will be required to properly maintain the systems and take necessary corrective actions upon discovery of problems.
  • Each year, an annual inspection report must be submitted to the DEC along with an annual operating fee.

If you have determined your site meets the requirements for coverage under the 3-Acre Rule, but have not received a letter of notification, it may be due to the geographic-based phase in schedule, with initial NOIs due based on the following schedule:

  • January 1, 2022 for stormwater discharged into the Lake Champlain basin with the resulting water flowing into Missisquoi Bay, Main Lake, Burlington Bay, or Shelburne Bay or discharge into stormwater impaired waters.
  • June 1, 2022 for discharges to all other portions of Lake Champlain.
  • January 1, 2023 for discharges into Lake Memphremagog.
  • October 1, 2023 for discharges into all other watersheds. The DEC has indicated that this final date is subject to change.

Vermont operational stormwater permits are just one piece of the Vermont stormwater protection program. Other components, such as construction stormwater, industrial stormwater and some redevelopment nuances of the 3-Acre Permit, will be addressed in subsequent ALL4 articles.

Please reach out to Clayton Queen (cqueen@all4inc.com), John Hinckley (jhinckley@all4inc.com), or Paul Hagerty (phagerty@all4inc.com) for questions on Vermont stormwater permitting.


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