SITE INFORMATION AND CORRESPONDENCE

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s Mr. Travis Bryant "we Former Dolly Madison 1426 South Lincoln Street Page 2 of 3 • During five years of monitoring, TPH-g concentrations have declined to a range between the analytical method detection limit (50 ppb) and generally less than 100 ppb. Benzene has not been detected in samples from either well since June 2000. • Benzene was detected in soil samples collected from CPT-1 to depths as great as 64 feet bsg (140 ppb) and as great as 101 feet bsg in CPT-2 (19 ppb). • Dissolved benzene was detected in grab ground water samples to depths as great as 116 feet bsg in CPT-1 (1 ppb) and at concentrations as high as 580 ppb (CPT-2, 85 feet bsg). • Methyl tert-butyl ether (MTBE) has not been detected in any ground water samples from either monitoring well on the site. • Tert-butyl alcohol (TBA) has been detected in MW-2 ground water samples and on one occasion in an MW-1 sample. • 1,2-Dichloroethane (1,2-DCA) has been detected at concentrations as high as 42 ppb in samples from MW-2 and as high as 20 ppb in grab samples collected from CPT-2 (B-5), exceeding the maximum contaminant level (MCL) of 0.5 ppb. 1,2-DCA was encountered in a water sample collected at a depth of 85 feet bsg in CPT-2 (20 ppb). • The depth to ground water has ranged from approximately 18.6 to 25.2 feet below the top of the well casing of MW-1. • Based on data from adjacent and nearby sites, the ground water flow direction is inferred to vary from north to northeastward. The decline of TPH-g and BTEX concentrations in samples from MWA and MW-2 suggests natural attenuation of hydrocarbons in shallow ground water to levels warranting closure consideration, however, several problems remain to be resolved before this office can grant a 'no further action' status to the site. The occurrence of 1,800 ppb TPH-g, 580 ppb benzene, 4.6 ppb toluene, 2.7 ppb total xylenes and 20 ppb 1,2-DCA suggests a deeper extent of impacted ground water of unassessed lateral extent. Decline of contaminant concentrations to low or non-detectable levels at 116 feet bsg (CPT-1) and at 103 feet bsg (CPT-2) are suggestive of a vertical limit of impacted ground water. Ground water impacted by 1,2-DCA may be assessed vertically by data from CPT-2 at 103 feet bsg, but has not been assessed laterally. In the recent past, the Regional Water Quality Control Board has been unwilling to grant closure to sites with unassessed 1,2-DCA-impacted ground water. Stratus interprets the occurrences of hydrocarbons and 1,2-DCA in CPT-2 samples as being derived from adjacent sites. EHD regards this interpretation as a hypothesis that should be demonstrated with data from the subject site and nearby sites in the context of a site conceptual model (SCM). The SCM, consisting of maps, cross sections