1. (a) Subject to (b), below, a tier 3 stream crossing shall be a crossing located:

   1. (1) On a watercourse where the contributing watershed is 640 acres or greater;

   2. (2) Within a designated river corridor, unless:

      1. a. The crossing would be a tier 1 stream based on contributing watershed size; or
      2. b. The structure does not create a direct surface water connection to the designated river as depicted on the national hydrography dataset as found on GRANIT;
   3. (3) Within a 100-year flood plain;
   4. (4) In a jurisdictional area having any protected species or habitat; or
   5. (5) In a prime wetlands or within a duly-established 100-foot buffer, unless a waiver has been granted pursuant to RSA 482-A:11, IV(b) and Env-Wt 706.
2. (b) The applicant for a project in which a stream crossing is categorized as tier 3 based solely on being in a 100-year floodplain may request that the crossing be categorized as a tier 1 or tier 2 stream crossing, as applicable based on watershed size, if the impacts to the floodplain are specifically mitigated in accordance with Env-Wt 800.

3. (c) The applicant for a project in which a stream crossing is categorized as tier 3 based solely on being in a jurisdictional area having any protected species or habitat may request that the crossing be categorized as tier 1 or tier 2 based on watershed size, provided:

   1. (1) The applicant consults with the ecological review section of the department to determine whether any protected species or habitat would be impacted; and
   2. (2) The ecological review section of the department recommends such a downgrade to the department in writing.
4. (d) A tier 3 stream crossing shall be a span structure or an open-bottomed culvert with stream simulation, not a closed-bottom culvert or pipe arch.
5. (e) The applicant may propose an alternative design by submitting a request as specified in Env-Wt 904.10.

6. (f) Compensatory mitigation shall not be required for:

   1. (1) Any new tier 3 stream crossing that:

      1. a. Meets the general design criteria in Env-Wt 904.01 and the tier-specific criteria of Env-Wt 904.07;
      2. b. Is self-mitigating; and
      3. c. Improves aquatic organism passage, connectivity, and hydraulics; or
   2. (2) Any replacement of a crossing that met all applicable requirements when originally installed but is in a location that results in the crossing being classified as tier 3 under these rules, provided the proposed stream crossing meets the requirements of Env-Wt 904.09.
7. (g) Plans for a tier 3 stream crossing shall be dated and bear the signature and seal of the professional engineer who prepared or had responsibility for and approved them, as required by RSA 310-A:18.

Source. #12809, eff 12-15-19; ss by #14349, INTERIM, eff 8-26-25; ss by #14471, eff 1-2-26, EXPIRES: 1-2-36