A fluid containment apparatus including a fluid tank, a well wall and a closure system. The tank has a tank shell, which defines at least in part a fluid containment compartment and has a tank shell opening therethrough. The well wall is secured to the tank shell, positioned at the shell opening, recessed into the fluid containment compartment and defines at least in part a recessed well. The well wall has a well wall end and a well wall end opening. The closure system selectively opens and closes the well wall end opening. The closure system includes a well head connected to the well wall generally at the well wall end, a sealing gasket, an elliptical manway cover having a plurality of drilled and tapped blind holes, a separate fastening ring having a plurality of circumferential drilled through-holes and a clamp for clamping the manway cover and the fastening ring together and sandwiching the sealing gasket on the well head. The clamp includes a plurality of bolts boltable through the through-holes and into the blind holes.