Abstract: A modular self-supporting fluid reservoir that can be provided in an excavation and covered with the excavated fill. A stack of plastic core sheets is bundled to form each module.

Abstract: A basement below a dwelling structure has the walls covered by a rigid polystyrene panel that has raised lands to define a space on both sides to collect radon gas. An impermeable polyethlene sheet is sealed top and bottom to isolate the joint between the basement floor and the walls so radon gas is trapped in these spaces. A fan in a basement window is used to provide positive displacement of any radon gas trapped by this system.

Abstract: The device for detecting leaks in an underground fluid tank includes a tank liner extending across the bottom of the tank and upwardly substantially surrounding the sides of the tank. The tank liner includes a stiff plastic core having a surface defining a plurality of fluid passageways which is oriented tangentially to a drain pipe arranged below the tank and along the length of the tank and which has slots to provide passageways for fluid entering into the pipe. A permeable plastic membrane is wrapped around the core and the pipe to prevent fill from filling the passageways so defined. A leak tank is connected to the drain pipe for receiving fluid therefrom, and a pump is mounted in the leak tank to pump the fluid to a surface tank for inspection.