Abstract: An impoundment leak detection, location, and containment system includes a leak detection and location structure positioned below the impoundment with a system of conduit spanning substantially all of the extent under the impoundment. A mobile sensor system can be maneuvered through the conduit and into the leak detection and location structure to identify and locate leaks in the impoundment above. The system also includes a hydrocarbon sealing compound which has a sealing effect when exposed to fluids containing water and/or hydrocarbon liquids.