New Hampshire Code of Administrative Rules
Env - Department of Environmental Services
Subtitle Env-Wq - Water Quality and Quantity Programs
Chapter Env-Wq 1500 - ALTERATION OF TERRAIN
Part Env-Wq 1508 - PERMANENT METHODS FOR PROTECTING WATER QUALITY
Section Env-Wq 1508.15 - Pretreatment Practices: Flow-Through Devices

(a) The devices shall be designed according to the manufacturer's recommendations based on the WQF to remove a minimum of 80% of U.S. Silica grade OK-110 sand at the WQF;

(b) Water quality inlets and oil/particle separators shall have a 4 foot minimum sump;

(c) Water quality inlets shall be a 3-chamber design, with the first and second chambers having a minimum of 400 cubic feet of storage per acre of contributing impervious area;

(d) Each water quality inlet and oil/particle separator chamber shall be accessible by means of a separate manhole;

(e) The contributing area to the oil/particle separator shall not exceed 1.0 acre of impervious area;

(f) Oil/particle separators shall only be used in an off-line configuration to treat the WQF; and

(g) Oil/particle separators shall have a minimum of 400 cubic feet of permanent pool storage per acre of contributing impervious area.