8.65.A contractor or owner-builder may not construct a diked area for an aboveground tank, unless
(1) the diked area has a drainage system such as a sump or a channel located at its lowest point and has a closed valve to drain the water;
(2) the control for the drainage system valve is accessible at all times;
(3) the bottom of the diked area has a uniform slope of at least 1% between any tank and the lowest point; and
(4) the diked area complies with paragraph f of section 126.96.36.199.2 of NFPA Standard 30 Flammable and Combustible Liquids Code, published by the National Fire Protection Association, if it contains more than 1 tank.