SITE INFORMATION AND CORRESPONDENCE

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Page 4 of 5 Chronology Former Morita Brothers 814 E. Charter Way, Stockton, CA 95206 initial detection of a low concentration of toluene; Ground water samples from MW- 210 have only had rare, low concentrations of TPHg; the two wells provide delineation of the groundwater plume toward the southeast. 04/19/2004 Date of Additional Site Characterization Report that discusses the December 2003 work. 01/10/2006 Cone penetrations test borings CPT 1 through CPT-4 were installed during this through time to characterize the stratigraphy, and to collect soil and grab groundwater 01/11/2006 samples. Each soil sample from each boring, collected at 35, 37 or 40 feet bsg, had less than detectable concentrations of chemicals of concern. Grab groundwater samples, collected at 46 feet and 70 feet bsg in CPT-1 and CPT-2 contained between 5.8 and 150 pg/L tertiary butyl alcohol (TBA), the 70-foot samples also contained 66 pg/L and 81 pg/L TPHg. The groundwater sample collected at 70 bsg in CPT-3 contained 8.2 pg/L MTBE, which may be the off-site, down-gradient extension of the MTBE plume encountered in MW-107 and MW- 109 discussed above. The groundwater sample collected at 70 feet bsg in CPT-4 was "non-detect"for all chemicals of concern. 05/02/2006 Date of Site Conceptual Model (SCM) that discusses the January 2006 work. The SCM presented a site history, maps and cross sections in a hydrogeological model, and a dissolved contaminant mass estimate (1 pound). It was concluded that the monitoring well demonstrating increasing TPHg concentrations was being impacted by the contamination documented at a site at 749 E. Charter Way. 09/06/2006 By letter of this date the EHD concurred with most interpretations in the SCM, the EHD then directed performance of a risk/hazard evaluation using the San Francisco Bay Regional Water Quality Control Board ESLs, an evaluation of the potential for vapor intrusion, and a demonstration that impacted soil west of the former UST pit excavation was delineated. The EHD also directed validation of the model for the increasing TPHg concentrations in monitoring well MW-208 by collecting grab groundwater samples between the well and the suspected off-site source area. 02/27/2008 Date that soil boring SB1 was completed. 03/14/2008 Date that soil vapor probe GP1 was completed. 04/29/2008 Date of Risk Evaluation Soil and Soil Gas Investigation that discusses the February and March 2008 work. 6/5-6/2008 Dates that soil borings S132 and S133 were completed. 07/18/2008 Date of Addendum to Risk Evaluation Soil and Soil Gas Investigation that discusses the June 2008 work. 02/05/2009 By letter of this date, the EHD commented on theRisk Evaluation Soil & Soil Gas Investigation and Addendum to Risk Evaluation Soil & Soil Gas Investigation. EHD's internal evaluation of the site data lead the EHD to concur with the conclusion that there was a minimal vapor intrusion risk from residual