A secondary containment tank and ground level manhole cover provide access to a fill pipe for a main underground storge tank and prevent overflow of excess volatile liquid such as gasoline into the ground. The containment tank includes an upper ring or rim secured on an in-ground vertical skirt supported in a concrete base. An inner container is secured to the vertical skirt and has an open end adjacent to the upper ring. The cover fits into and is supported on a horizontal flange or step of the upper ring over the opening of the inner container and includes a vertical ring extending downwardly from the underside of the cover into a space between the inner container and vertical skirt. The vertical ring on the cover extends below the level of the container opening and thus bypasses any surface water leakage through the upper ring around the cover into the space adjacent to the container and into the ground below. The upper containment tank also includes means such as a manually operable sump pump or drain valve to empty excess liquid into the fill pipe of the main storage tank.
