Abstract: The present invention provides for above-ground fluid storage tanks having an internal spill containment system. In particular, the present invention is directed to an oil storage tank with a valve and spill containment system, where the valves are kept in a warm and dry environment, protected from the elements, but which still readily accessible, and, further, where spillage from the valves is contained. Further, the containment system disclosed allows for convenient retrofit into existing tanks as well as new tank manufacture. The invention discloses a containment chamber that will fit into existing manways and which is bolted to the tank using the existing bolt pattern that held the manway door on.