SITE INFORMATION AND CORRESPONDENCE

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`► Page 3 of 5 �.r 7 Chronology Former Morita Brothers 814 E. Charter Way, Stockton, CA 95206 of methyl tert-butyl ether (MTBE), demonstrating a late migrating shallow plume from the source area. Monitoring well MW-104 has been a consistent "non-detect" well, demonstrating the vertical extent of impacted groundwater in the source area. Monitoring wells MW-106 and MW-107 have been fairly consistently impacted by low concentrations of MTBE and moderate concentrations of TPHg. BTEX was initially encountered in the two wells, but has not yielded quantifiable concentrations of those compounds for several years. 12/19/00 Date of Additional Site Characterization report that discusses the November 2000 work. 04/24/2002 The EHD directed by letter of this date additional lateral delineation of impacted groundwater in the intermediate depth level based on continued and increasing contaminant concentrations in existing groundwater monitoring wells reported in Work Plan, Risk Assessment & Appendix B Closure Checklist, dated 18 March 2002. 12/15/2003 Dates monitoring wells MW-11 (screened 27.5 to 42.5 feet bsg), MW-108 and through MW-109 (screened 47 to 52 feet bsg), MW-111 (screened 48-53 feet bsg), MW- 12/18/2003 202 (screened 70 to 80 feet bsg), MW-208 (screened 65 to 75 feet bsg) and MW- 209 (screened 68 to 73 feet bsg) were installed. Since installation, groundwater samples from MW-11 and MW-111 have been "non-detect" for all chemicals of concern, except for initial low toluene 'hits', demonstrating the northwestward extent of impacted groundwater in the shallow and intermediate depth zones, and showing that the depth zones in that locality had not been impacted by migrating dissolved contaminants from the 749 E. Charter Way site. Also, monitoring well MW-108 has yielded samples primarily impacted by moderate TPHg concentrations, but has mostly been "non-detect" for BTEX compounds since November 2005. MW-208 samples have yielded similar results, except the TPHg concentrations generally increased to a high of 1,650 pg/L in November 2005, and have slowly, generally declined since. Since installation, groundwater samples from monitoring well MW-109 increased from <0.5 or nearly ND to a recent high of 26.1 pg/L (3rd Qtr, 2009); the slow, steady increasing concentrations demonstrating a migrating low-intensity plume. Monitoring well MW-209 samples have consistently been impacted by MTBE, but concentrations have been fairly steadily declining from a high of 13 pg/L in 2005 to a recent 2.9 pg/L (3rd Qtr, 2009). The data suggests that this well screen is near the base of the MTBE-impacted groundwater. Both MW-110 and MW-210 groundwater samples have been consistently "non- detect", demonstrating the southeastern limit of impacted groundwater at their depth intervals. 12/23/2003 Dates monitoring wells MW-110 (screened 42 to 47 feet bsg) and MW-210 (screened 70 to 80 feet bsg) were installed. Groundwater samples from MW-110 have been consistently "non-detect" for all chemicals of concern, except for an