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New Hampshire Department of Environmental Services

How much mitigation is required?

NHDES has adopted ratios for how much mitigation is required based on the type of resource and form of mitigation. These ratios help to ensure that there is no net loss of wetland functions and values.

Mitigation Ratio Table 800-1 (from Env-Wt 803.05)

Resource Type Bog Tidal Wetlands Forested Undev
Creation Ratio
(resource created:
size of impact)
N/A 3 :1 1.5 :1 N/A 1.5 :1
Restoration Ratio
(resource restored:
size of impact)
2 :1 2 :1 1.5 :1 2 :1 1 :1
Preservation of
Upland Buffer Area
(buffer area:
size of impact)
15:1 15:1 10:1 3:1 10:1

For example, for a project with permanent impacts of 15,000 square feet of forested wetlands, to mitigate using:

  • Wetland creation at a ratio of 1.5:1, the required amount of wetland creation is 22,500 square feet.
  • Wetland restoration at a ratio of 1.5:1, the required amount of restoration is 22,500 square feet.
  • Upland buffer preservation at a ratio of 10:1, the required amount of upland buffer preservation is 150,000 square feet.

What is the required documentation to submit to NHDES with the Standard Dredge and Fill application?
Specific items that would be required with an application are outlined in the Mitigation ChecklistMicrosoft Word Symbol.

For permanent impacts that will remain after avoidance and minimization measures have been addressed, the applicant shall submit at a minimum, a preliminary compensatory mitigation proposal that addresses the following items.

  • An explanation of which mitigation option(s) is/are being proposed
  • Communication with local Conservation Commission in development of the mitigation proposal.
  • A plan showing the location of the proposed mitigation site.
  • A functional assessment of the impacted jurisdictional area(s).
  • A functional assessment of the proposed mitigation site.
  • The Natural Community Classification of impacted jurisdictional areas.
  • Threatened/endangered/exemplary natural communities identified.
  • A completed agreement formMicrosoft Word Symbolsigned by the applicant and noting the date when a complete mitigation proposal will be submitted to NHDES. Assigning a date should take into consideration what work needs to be completed, what local approvals need to be acquired, potential meetings with the easement holder, attorney review of the document, and development of plans or property surveys for the mitigation site.
  • If the applicant elects to submit a complete mitigation proposal, see Env-Wt 506, for the submittal requirements.

A completed agreement formMicrosoft Word Symbolsigned by the applicant requesting acceptance of a payment into the ARM Fund.

Microsoft Word SymbolMicrosoft Word format: free viewer instructions from Microsoft.

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
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