Sec. 599.9. Secondary containment for aboveground tanks

(a) General requirements.

(1) All new aboveground tanks used to store a hazardous substance must have a secondary containment system which collects and contains a leak or spill. The secondary containment system must prevent spills from entering the land or waters of the State that might result from tank rupture, failure of pumps, valves and other ancillary equipment and overfilling. In addition, the system must isolate and protect the tank from vehicular traffic, fire, and spills of incompatible substances which might occur in adjacent storage or work areas. Except for on-ground piping under section 599.14 of this Part, secondary containment is not required for aboveground piping. If the stored substance is a liquid at storage conditions and a gas at ambient conditions, then secondary containment must be provided to contain the liquid component of any spill until the phase change from liquid to gas occurs or the spill is cleaned up, whichever comes first. Secondary containment systems must consist of one of the following:

(i) a surrounding dike and impoundment system;

(ii) a remote catch tank or impoundment area; or

(iii) another system or practice which meets the requirements of paragraph (1) of this subdivision and which is designed and installed in accordance with a consensus code, standard or practice developed by a nationally recognized association or independent testing laboratory.

(2) The secondary containment system must be:

(i) designed and constructed with a permeability rate to the hazardous substance stored of 1 × 10^-6 cm/sec or less;

(ii) designed, installed, and operated to prevent any migration of hazardous substances out of the system to the environment before cleanup occurs;

(iii) designed so that overfills from connections, vents and pressure relief devices occur within the secondary containment system or are directed to another appropriate collection device;

(iv) constructed, coated or lined with materials that are compatible with the substance stored and the environment. All joints must be tight and leak-free using one or a combination of stops, grouts, coatings, gaskets or welds. The secondary containment system must have sufficient structural strength and thickness to withstand equipment and pedestrian traffic, hydrostatic forces, frost heaving and weathering;

(v) placed on a foundation which prevents settlement, compression or uplift;

(vi) equipped with a sump and manually controlled pump or siphon, manually controlled dike valve, or any other manually controlled drainage system to permit the drainage of liquids resulting from leaks, spills or precipitation. Control of the pump, siphon or valve must be possible from outside of the diked area. All valves for gravity drainage systems must be locked in a closed position except when the operator is draining accumulated liquids from the containment area. Spilled or leaked substances must be removed from the secondary containment system within 24 hours; and

(vii) capable of containing at least 110 percent of the capacity of the largest tank or manifolded tanks that are connected in such a way as to permit the combined contents to spill, whichever is greater.

(3) Stormwater discharges from a secondary containment system must be uncontaminated. Stormwater which is contaminated must be discharged and treated in accordance with department requirements imposed under Parts 701, 702, 703, and 750 of this Title, as applicable.

(4) If clay soil is used for the secondary containment system it must be installed in accordance with generally accepted engineering practices and must be of such character that any spill will be readily recoverable and will result in a minimal amount of soil contamination.

(5) If a pre-engineered manufactured clay liner is used, it must be installed in accordance with the manufacturer's instructions.

(6) If a synthetic liner is used, it must be compatible with the substance in storage, be at least 60 mils in thickness, not deteriorate in an underground environment and have a life expectancy defined in the spill prevention report based on manufacturer's specifications or warranty and operator use. All punctures, tears or inadequate seams in the liner must be repaired prior to placing in use. Since some chemicals will readily diffuse through a synthetic liner, the synthetic liner used must have been tested and found resistant to diffusion of the substance stored.

(b) Standards for dike and impoundment systems.

(1) In addition to the requirements of subdivision (a) of this section, a dike system used for secondary containment must be constructed in accordance with NFPA No. 30, sections 2-3.4.3 (see section 598.1[j] of this Title), unless specified otherwise in these regulations.

(2) All dikes and impoundment floors subject to hydraulic pressure must be designed to prevent migration of moisture into the dike system.

(3) If constructed within a floodplain, the dike must be designed and installed to withstand structural damage and overtopping by a 100 year flood.

(4) A slope of not less than one percent away from the tank must be provided for at least 50 feet or to the dike base, whichever is less.

(5) To permit access, the outside base of the dike at ground level must be no closer than 10 feet to any property line that is or can be built upon.

(6) The walls of the diked area must not exceed an average height of six feet above interior grade, unless provisions are made for safe access and egress to tanks, valves and other equipment.

(7) Each diked area with two or more tanks containing a flammable, combustible or unstable hazardous liquid must be subdivided pursuant to NFPA No. 30, section 2-3.4.3(g) (see section 598.1[j] of this Title). The subdivision may be by intermediate dikes, drainage channels or curbs, and must prevent spills from endangering adjacent tanks within the diked area.

(c) Standards for remote impounding.

Remote catch tanks and surface impounding areas used for secondary containment must comply with the following:

(1) All of the general requirements of subdivision (a) of this section must be followed;

(2) A slope of not less than one percent away from the tank must be provided so that accumulated liquid drains away from the tank to the sump;

(3) The route of the drainage system must be located so that if liquids in the drainage system are ignited, the fire will not affect tank systems or adjoining property; and

(4) The confines of the surface impounding area must be located so that when filled to capacity, the liquid level will be no closer than 50 feet from any property line that is or can be built upon, or from any tank.