1. (a) Existing WWTPs and pump stations shall be:

   1. (1) Designed to provide for uninterrupted operation of all process units during a 25-year flood; and
   2. (2) Be placed above or otherwise protected against damage from a 100-year flood.

2. (b) New and modified critical components of WWTPs and pump stations shall be:

   1. (1) Designed to provide for uninterrupted operation of all process units during a 100-year flood; and

   2. (2) Be placed above or otherwise protected against damage from either:

      1. a. A water surface that is 3 feet above the 100-year flood elevation;
      2. b. The 500-year flood elevation; or
      3. c. An elevation determined from a best available scientific approach defined in (e)(3), below.

3. (c) Critical WWTP components which shall be protected from flooding include:

   1. (1) Preliminary treatment;
   2. (2) Influent pumping;
   3. (3) Primary treatment and sludge pumping;
   4. (4) Secondary treatment and sludge pumping;
   5. (5) Intermediate pumping;
   6. (6) Advanced treatment;
   7. (7) Disinfection;
   8. (8) Effluent pumping;
   9. (9) Power and electrical systems;
   10. (10) Control, communication, and alarm systems; and
   11. (11) Emergency generators.

4. (d) Critical pump station components which shall be protected from flooding include:

   1. (1) Pumping equipment;
   2. (2) Power and electrical systems;
   3. (3) Control, communication, and alarm systems; and
   4. (4) Emergency generators.

5. (e) Subject to (f) below, flood elevations shall be determined using:

   1. (1) Flood maps;
   2. (2) Methods defined in Env-Wq 1503.09 (f)(1) and (f)(2); or
   3. (3) A best available scientific approach that uses readily available, actionable hydrologic and hydraulic data, and methods that integrate current and future changes in flooding based on latest climactic predictions.
6. (f) If the project is for infrastructure having a projected life that extends beyond 2050 and is within at least one of New Hampshire’s 17 coastal zone municipalities, including Dover, Durham, Exeter, Greenland, Hampton, Hampton Falls, Madbury, New Castle, Newfields, Newington, Newmarket, North Hampton, Portsmouth, Rollinsford, Rye, Seabrook, and Stratham, determination of the flood hazard elevation specified in (b) and (e) above shall address projected storm surge, sea level rise, and precipitation events identified in the “New Hampshire Coastal Flood Risk Summary – Part I: Science and Part II: Guidance for Using Scientific Projections" prepared for the New Hampshire Coastal Flood Risk Science and Technical Advisory Panel 2019, available as noted in Appendix B. A representative concentration pathway (RCP) of RCP 4.5 or higher and a “low” or “very low” tolerance for flood risk shall be applied.

Source. (See Revision Note at chapter heading for Env-Wq 700) #8590, eff 3-25-06; ss by #10693, eff 10-15-14; ss by #14258, eff 7-1-25, EXPIRES: 7-1-35