1. (a) All landfills shall include a stormwater management system to:

   1. (1) Divert run-on around or away from the facility;
   2. (2) Control run-off discharge from the facility;
   3. (3) Control erosion, sedimentation, siltation, and flooding; and
   4. (4) Minimize the generation of leachate.
2. (b) Stormwater management systems shall be designed to accommodate the 50-year/24-hour storm event.
3. (c) Stormwater management systems shall be designed to accommodate all phases of the landfill’s active life, as well as the closure and post-closure care period.
4. (d) Stormwater management systems shall be hydraulically separate from the leachate collection and removal system(s).
5. (e) Stormwater management systems shall be designed to function effectively during frozen ground conditions.
6. (f) Permanent sedimentation ponds and detention ponds shall be sized to handle the 50-year/24-hour storm event with no less than one foot of freeboard below the emergency spillway invert.
7. (g) Peak surface run-off from the landfill site during the 50-year storm event shall be controlled and maintained at the pre-development discharge rate, in accordance with RSA 485-A.
8. (h) All stormwater that contacts waste shall be managed as leachate unless representative analytical characterization conducted in accordance with the facility’s approved operating plan demonstrates the liquid may be lawfully discharged to ground or surface waters without treatment.
9. (i) Perimeter drainage swales shall be provided to channel run-off during facility development based on the planned sequence of filling pursuant to Env-Sw 806.02 and during the facility’s post-closure period.
10. (j) Perimeter drainage swales shall be designed and located to accommodate facility capping.
11. (k) Surface water run-on shall be diverted around and away from the facility by using berms and ditches, or similar methods.
12. (l) Surface water run-off shall be controlled by using benches, terraces, diversion berms and diversion swales, or similar methods.
13. (m) Erosion shall be controlled by using vegetation, terrace berms, silt fences and check dams, or similar methods.
14. (n) Drainage systems shall include provisions for inspections, monitoring, and maintenance.
15. (o) Stormwater design reports prepared to demonstrate compliance with this section shall be prepared in accordance with the requirements of Env-Wq 1500.

Source. #5172, eff 7-1-91; ss by #6535, INTERIM, eff 7-1-97, EXPIRES: 10-29-97; ss by #6619-B, eff 10-29-97; amd by #6894-B, eff 12-1-98; (See Revision Note at chapter heading for Env-Sw 800); ss by #8459, eff 10-28-05 (formerly Env-Wm 2505.09); ss by #10597, eff 7-1-14; ss by #14156, eff 12-21-24