In the fall of 1997, officials at the airfield at Ft. Campbell, KY., faced a problem concerning the disposal of water contaminated with jet fuel. The problem was the result of storm water infiltration into 33 below-grade concrete vaults that house the valves and pumps for the pipes that transfer fuel to the airfield. The primary path of infiltration occurred around pipe penetrations and through cracks in the walls. To solve the problem, the Hazardous Waste Remedial Actions Program, a division of Lockheed Martin Energy Systems, decided to seal the cracks and pipe penetration in the vaults with polyurethane grouts and sealants. The author describes how it was done and what was learned, and gives recommendations for successful polyurethane grouting.