Section Env-Or 305.08 - Secondary Containment for ASTs(a) Secondary containment for an AST shall be constructed so that spills will not permeate into the soil more than one foot in 72 hours, or infiltrate or otherwise escape to the groundwater or surface waters before cleanup can occur.(b) Secondary containment for an AST shall consist of dikes, liners, pads, ponds, impoundments, curbs, ditches, sumps, receiving tanks, or other equipment capable of containing the product stored, or any combination thereof.(c) Secondary containment for an AST shall have sufficient storage capacity to contain the full capacity volume of the largest single tank within its enclosure, if it is covered so as to prevent the collection of precipitation.(d) If the secondary containment is not covered so as to prevent the collection of precipitation, it shall have additional storage capacity to also contain the greater of: (1) Ten percent of the full capacity volume of the largest tank within its enclosure; or(2) The volume of precipitation that would fall within the containment area in a 24-hour period during a 10-year storm event, as determined by the rational method for determining stormwater runoff as described in the Stormwater Management and Erosion and Sediment Control Handbook for Urban and Developing Areas in New Hampshire, dated August 1992.(e) If the secondary containment for an AST consists of dikes surrounding the tank, construction of the dikes shall be in accordance with NFPA 30.(f) Secondary containment and lining materials shall be designed and constructed to meet permeability requirements for the operational life of the AST system.(g) The provisions of (a) through (f), above, shall not apply to any tank that is located inside a building, provided: (1) The installation of the tank complies with NFPA 30 or NFPA 31, as applicable;(2) The entire floor of the room in which the tank and its associated piping is located is constructed of concrete or an impervious material;(3) The floor does not have any floor drains, cracks, or openings that would permit the migration of oil through the floor; and(4) A release of the total contents of the tank would be contained in the room in which the system is situated.(h) A double-walled tank may be used in lieu of the requirements of (b) through (e), above, if the double-walled tank is installed with all of the following: (1) Overfill protection as specified in Env-Or 305.11;(2) Interstitial monitoring, as specified in Env-Or 305.12(a) and (b);(3) A mechanism that will automatically prevent the flow of oil to the tank when the tank is: a. Filled to 95 percent of the total capacity of the tank, for tanks with a storage capacity of 12,000 gallons or less; orb. Filled to one percent less than the calculated maximum safe fill height, for tanks with a storage capacity of greater than 12,000 gallons.(i) If the secondary containment area is not covered so as to prevent the collection of precipitation, it shall be equipped with a manually-operated device, such as a manually-controlled pump or siphon or a gravity drain pipe that has a manually-controlled valve, that will allow collected precipitation to be removed when no oil is present.(j) Gravity drain pipes shall be designed and constructed to prevent a release in the event of fire.(k) Any opening where piping passes through a secondary containment structure shall be sealed around the outside of the piping with an impervious, compatible material to prevent the discharge of oil from the containment.(l) With the exception of hand-filled ASTs and ASTs using vent whistles for overfill protection, any AST that has any vent located such that an overfill would not be contained within the secondary containment shall have additional overfill protection as specified in (h)(3), above.(m) With the exception of ASTs that are hand-filled and ASTs using vent whistles for overfill protection, any AST fill connection point that is not otherwise within secondary containment shall be within a covered spill container with a minimum capacity of 5-gallons in order to prevent the release of oil to the environment when a transfer hose is detached from a fill or transfer pipe.N.H. Admin. Code § Env-Or 305.08
(See Revision Note at chapter heading for Env-Or 300) #10487, eff 2-7-14