Conservation Commission Buffer Mitigation Policy

Approved September 27, 2022


Purpose 

This policy guides the recommendations of the Londonderry Conservation Commission (LCC) to the Londonderry Planning Board with respect to mitigating unavoidable impacts to wetland and stream buffers established by the Londonderry Zoning Ordnance, Section 4.6.1, Conservation Overlay District (“CO buffers”). 

Objectives 

  • Ensure that the sum of the wetland and stream functions and values of the project area as a whole are not reduced by the proposed impacts. 
  • Allow for flexible and creative approaches to mitigation. 
  • Ensure that mitigation measures build upon the measures required by NH DES for the direct impacts to wetlands and/or streams. 
  • Follow the guidance in NH DES rule Env-Wt 800, to the extent practicable.

Guidance 

CO buffer mitigation can be accomplished by:

  • Creating additional wetlands and associated buffers; and/or 
  • Providing a buffer for a wetland less than one-half acre in size that otherwise would not require a buffer; and/or 
  • Enlarging the required CO buffer over a portion or all of the project area; and/or 
  • Enhancing or restoring previously lost wetland and/or stream functions and values, e.g. by blocking old wetland drainage ditches (not part of an approved storm water management plan), removing invasive species, removing impervious surface in the CO buffer, replacing CMP culverts with open-bottom box culverts, and similar such enhancements and/or restoration. 

Criteria 

Mitigation measures must: 

  • Benefit wetlands and streams that have functions and values that meet or exceed those of the areas to be impacted (see rule Env-Wt 804.01(a)); and
  • Benefit the resource to be protected by maintaining or improving water quality, wildlife habitat or other functions and values of wetlands and/or streams (see rule Env-Wt 804.01 (b)); and
  • Be consistent with the purposes of the Londonderry Zoning Ordnance Conservation Overlay District, Section 4.6.1.1 (see rule Env-Wt 804.01 (c)); and 
  • In the absence of any other mitigation measure, enlarge the CO buffer(s) by an area equal to or greater than the area of the CO buffer being impacted.

Administration

  • When the LCC agrees that a project will produce unavoidable impacts to a wetland and/or stream, the LCC will, during the Design Review Committee process, include recommended buffer mitigation measures to the Planning Board along with its recommendations for the project as a whole. 
  • If the Planning Board concurs in whole or in part with the LCC-recommended buffer mitigation, such recommendation will be memorialized on the approved plan and in the conditions the Planning Board imposes as part of its approval. 
  • In accordance Londonderry Zoning Ordnance Section 4.6.1.4 B 3, an approved NH DES Dredge & Fill Permit eliminates the protected buffer around a filled wetland and, consequently, eliminates the requirement to mitigate the buffer around such filled area of the wetland.
  1. Londonderry Conservation Commission Buffer Mitigation Policy (PDF)