Section 30.687 - Containment(1) Each container storage area shall have a containment system that is designed and operated in compliance with 310 CMR 30.687(2), except as otherwise provided by 310 CMR 30.687(3).(2) Each containment system shall be designed, constructed, operated and maintained as follows: (a) Underlying the containers shall be a base which is free of cracks and gaps and is sufficiently impervious to contain leaks, spills, and accumulated precipitation until the collected material is detected and removed;(b) Unless the containers are elevated or are otherwise protected from contact with accumulated liquids, the base shall be sloped or the containment system shall be otherwise designed, constructed, operated and maintained to drain and remove liquids resulting from leaks, spills, or precipitation.(c) For containers which are stored indoors or under a roof, the containment system shall have the capacity to contain either 10% of the total possible contained volume of the containers or 100% of the volume of the largest container, whichever is greater. For containers which are stored outdoors, the containment system shall have the capacity to contain either 10% of the total possible contained volume of the containers or 110% of the volume of the largest container, whichever is greater. Containers that do not contain free liquids need not be considered in determining the containment system's required capacity.(d) The owner or operator shall prevent run-on into the containment system, unless the collection system has sufficient excess capacity, in addition to that required by 310 CMR 30.687(2)(c), to contain the run-on which would enter the system from a 24-hour, 25-year storm.(e) To prevent overflow of the collection system, the owner or operator shall remove spilled or leaked waste and accumulated precipitation from the sump or collection area in as timely a manner as possible. If the collected material is hazardous waste pursuant to 310 CMR 30.100, it shall be managed as hazardous waste in compliance with 310 CMR 30.000.(3) Storage areas that store containers holding only hazardous wastes that do not contain free liquids and that do not contain any polyhalogenated aromatic hydrocarbons, need not have a containment system required by 310 CMR 30.687(2), if:(a) The storage area is sloped or is otherwise designed and operated to drain and remove liquid resulting from precipitation; or(b) The containers are elevated or are otherwise protected from contact with accumulated liquid.