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`��-./ GROUP 5✓ERy'CES 10-foot sample from GP-1 indicated 2,900 mg/kg and the 10-foot sample from GP-9 ' indicated 140 mg/kg diesel range hydrocarbons Each of these samples was collected from the pea gravel present in the bottom of the former excavation No benzene, toluene, ethylbenzene, or xylene (BTEX) compounds were detected in any of the soil samples and ' gasoline range hydrocarbons were only detected in the 10-foot sample from GP-9, at a concentration of 3 3 mg/kg ' Detectable concentrations of diesel and gasoline range hydrocarbons persist within the bounds of the former tank excavation and appeared to have migrated laterally up to 20 feet Diesel range hydrocarbons in the groundwater beneath this area ranged from 5 3 ' milligrams per liter(mg/1) to 330 mg/1 and gasoline range hydrocarbons ranged from 0 15 to 0 87 mg/l Concentrations of diesel range hydrocarbons fell off rapidly to levels below 10 mg/1 in the surrounding area Gasoline range hydrocarbons were not detected outside ' the area described above The limited migration of this material is likely due to the fine- grained nature, and related low permeability, of the soil at the site ' BTEX was not detected in groundwater samples collected outside the bounds of the former tank excavation The benzene concentrations in the groundwater beneath the former UST location showed a marked decrease from those reported at the time of the tank removal Benzene concentrations ranged to 8 6 micrograms per liter (lig/l), whereas, at the time of the tank removal, benzene was reported at 80 µg/1 Methyl tertiary butyl ether (MTBE) concentrations also showed a significant decrease from the 3,200 µg/l reported at the time of the tank removal to a maximum of 36 pg/l during the Kleinfelder sampling The bulk of the MTBE concentrations was present ' within the tank excavation and immediate vicinity and also did not appear to be migrating significantly ' The Learner Company forwarded the January 12, 2001 Kleinfelder, Inc report to the EHD on April 9, 2001 In addition to the work performed under the Assessment, The Learner Company evaluated public well information in the vicinity of 2711 Navy Drive ' and determined that no public wells existed within 2000 feet of the subject facility In addition, no vulnerability areas (potential threats to drinking water sources) were identified in the vicinity of the facility' The Department of Homeland Security has classified locations of water supply wells, however, it was recently confirmed that no water supply wells exist within 2,000 feet of the site ' On June 4, 2001, The Learner Company forwarded a letter and data package to the EHD that utilized the information contained in the Kleinfelder report to develop an estimate of the residual contaminant mass in the soil (see Appendix for a copy of this document) I Data source January 2001 search using lid /lgeotracker2 arsenaultlegg_com iz Telephone conversation between Mr Jeff Bennett of Clayton Group Services, Inc and Mr Dennis ' DeCoite of the Stockton Municipal Water District, May 27, 2004 2 S\PwjM2263Trojec1 Summary and Request(or Closurc doc