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Chronology 1401 W. Fremont, Stockton Page 2 7/30/02 On this date monitoring well MW101 was installed (screen from 3 7.5 to-40 . feet) to define the vertical extent of the groundwater contamination.: Also, MW7, MWS, IVIW9 were installed to the north to define the lateral extent of the shallow groundwater contamination. Analytical results of the groundwater samples from MW101 have been non detect. 10/15/02 A 2000 foot receptor survey was prepared this date. No municipal or private wells were identified within that area. 12/17/03 Date of the "Site Conceptual Model' that included the calculation of mass }' remaining in the soil to be approximately 74.9 gallons of TPH-g and :978 gallons of MTBE, and in the water .1 gallons of dissolved TI?H-g and .011 gallons of MTBE. The model concluded the plume is stable and reducing as 1 a result of natural attenuation. 8/23/04 Eight direct push borings 04GP-1 through 04GP-8 were advanced off site north (downgradient) of the property and east of the property to assess the lateral extent of the groundwater contamination on this date. Results of the soil samples were non detect and results of the grab groundwater samples were non detect except for MTBE in four of the samples. The highest MTBE concentration was 2.9 micrograms per liter. i 11/8/04 Date of"Site Characterization and Risk Evaluation report that includes F concentration contour maps and cross-sectional diagrams of the' contamination. The masses remaining were recalculated at 56.1 gallons of TPH-g and 0.041 of MTBE in the soil and .1 gallons of TPH-g and 0:034: gallons of MTBE in the groundwater. It was estimated it would take 200 years for the contamination remaining in the soil to leach into the groundwater and migrate off the property boundary. 11/17/04 Date of discussion with the Central Valley Regional Water Quality Control Board about site closure. I I 4