Estimation of Leak Rates from Underground Storage Tanks

Abstract

AbstractA methodology for estimating the rate and volume of leakage from an underground storage tank (UST) is presented; by estimating leak rate and volume, the leak duration may be calculated. This is accomplished by measuring liquid hydrocarbon thickness upon the water table at two or more monitoring wells located at differing distances from the leaking UST. The methodology is based on Hantush (1967, 1968) and uses type‐curve fitting. Two solutions are developed: one for the case of a flat, rigid water table, and another for the case of a deflected water table. These solutions provide upper and lower estimates for leak rate and duration. The use of the technique is demonstrated by its application to a field case. The technique is best applied to sites with medium‐ to coarse‐grained sands and gravels with minimal capillary effects; application of the technique to sites of fine‐grained porous media may produce unreasonable results.