On 4/3/91 ADEC was informed that two one-million gallon underground storage tanks (one diesel, one JP-4 jet fuel) had failed tank tightness testing. Tanks #37 and #38 were unregulated underground storage tanks classified as field tanks. Tracer gas was detected in a soil gas probe adjacent to tank at a depth of five feet. The tanks have since been emptied of product and abandoned in place. The tanks were used on site for thirty-four years. Additional contamination likely resulted from ground disposal of sludge cleaned from the tanks and water drained from the tank bottoms. Above ground storage tanks holding JP-8 jet fuel have replaced the abandoned USTs. Air Force Installation Restoration Program Sites: Million Gallon Hill (CG001) and Missile Storage Area (CG002). The two IRP sites are believed to have common contamination sources, and are therefore treating as one site commonly referred to as Million Gallon Hill. Free-phase product and dissolved petroleum constituents above cleanup levels have been documented in monitoring wells downgradient of the tanks. Periodic free product recovery was conducted over the 1990s. The current remedial strategy is bioventing. --Updated 2011-- In August 2010 a field sampling plan for Million Gallon Hill and Missile Storage Area was developed. Million Gallon Hill was identified as a candidate for the site characterization pathway. The goal of the site characterization pathway is to characterize the lateral and vertical extend of the contamination. This plan was approved in 2011, and sampling was expected to begin during the summer of 2011. Data from this sampling event will be available following the 2011 field season. Missile Storage area is also on the site characterization pathway. Sampling for this area is expected to beging during the 2011 field season.