A secondary lid for restricting inflow of fluids into an interior of a containment sump of an underground storage tank having a secondary access opening, the secondary lid comprising: a cover having a top and bottom surface; a ring that is concentric with the cover, wherein the ring extends downwardly from the bottom surface of the cover to a free end of the ring; a flange extending outwardly from at least one of the cover and the ring an annular expandable pneumatic seal engaged to an outer surface of the ring, wherein when the seal is expanded the seal expands outwardly, and expands upwardly towards the flange, and expands downwardly towards the free end of the ring; a first tank containing a compressed gas and the first tank coupled in fluid communication with the pneumatic seal; a first valve coupled inline between the first tank of compressed gas and the pneumatic seal, wherein the first valve is configured to actuate between an open and closed position to control inflation of the pneumatic seal and delivery of gas from the first tank to the pneumatic seal; a second valve coupled in series to the pneumatic seal wherein the second valve is configured to actuate between an open and closed position to control deflation of the pneumatic seal and a release of gas from the seal into space below the cover; a third valve coupled to the cover to form a conduit between the bottom surface of the cover and the top surface of the cover, wherein the third valve is configured to actuate to allow gases to flow through the third valve from the space below the cover to space above the cover; characterised by a fourth valve coupled inline between the first tank and pneumatic seal wherein the fourth valve is solenoid actionable between open and closed positions, and further including a microprocessor coupled to the fourth valve wherein the microprocessor is configured to control actuation of the fourth valve. a cover having a top and bottom surface; a ring that is concentric with the cover, wherein the ring extends downwardly from the bottom surface of the cover to a free end of the ring; a flange extending outwardly from at least one of the cover and the ring an annular expandable pneumatic seal engaged to an outer surface of the ring, wherein when the seal is expanded the seal expands outwardly, and expands upwardly towards the flange, and expands downwardly towards the free end of the ring; a first tank containing a compressed gas and the first tank coupled in fluid communication with the pneumatic seal; a first valve coupled inline between the first tank of compressed gas and the pneumatic seal, wherein the first valve is configured to actuate between an open and closed position to control inflation of the pneumatic seal and delivery of gas from the first tank to the pneumatic seal; a second valve coupled in series to the pneumatic seal wherein the second valve is configured to actuate between an open and closed position to control deflation of the pneumatic seal and a release of gas from the seal into space below the cover; a third valve coupled to the cover to form a conduit between the bottom surface of the cover and the top surface of the cover, wherein the third valve is configured to actuate to allow gases to flow through the third valve from the space below the cover to space above the cover; characterised by a fourth valve coupled inline between the first tank and pneumatic seal wherein the fourth valve is solenoid actionable between open and closed positions, and further including a microprocessor coupled to the fourth valve wherein the microprocessor is configured to control actuation of the fourth valve.