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WELLS FARGO BANK PROPERTY REVISED 49 SOUTH WILSON WAY PRIVILEGED&CONFIDENTIAL STOCKTON, CALIFORNIA MAY 3, 1999 Page 3 September and October 1997, Additional Phase II Subsurface Investigation and Quarterly Monitoring Building Analytics completed an additional Phase 11 Subsurface Investigation and Quarterly Groundwater Monitoring in September and October 1997, which included the installation of one additional 80-foot deep soil boring and groundwater monitoring well (in the area of well MW-2), and the monitoring and sampling of the one new and three existing groundwater monitoring wells. The following is a summary of the findings from the investigation and monitoring event: • The groundwater flow direction was measured to be to the northeast with a hydraulic gradient of 0.0055; .� • TPH-g at concentrations of up to 75 ppm was reported in the soil samples collected from Boring B4, at depths between 35 and 45 feet bgs; • Benzene at concentrations of up to 0.057 ppm was reported in the soil samples collected from Boring B4, at a depth of approximately 45 feet bgs; • TPH-g and BTEX were not reported in groundwater samples collected from monitoring wells MW-1 or MW-3; • TPH-g was reported in the groundwater samples collected from MW-2 and MW-4 at concentrations of up to 3.4 ppm; • TPH (Carbon Range C8-C44+) was also reported in the groundwater sample collected from MW-2, at a concentration of 2.3 ppm; • Benzene was reported in the groundwater samples collected from MW-2 and MW-4 at concentrations of 1.2 parts per billion (ppb) and 11 ppb, respectively; and • MTBE was not reported in the soil or groundwater samples collected. w May 1997, Work Plan - Additional Phase II Subsurface Investigation Subsequent to the September 1997 Additional Phase II Subsurface Investigation, the SJCEHD requested that an additional soil boring be installed down-gradient from groundwater monitoring wells MW-2 and MW-4. Building Analytics submitted a Work Plan for the Additional Soil Boring and Quarterly Groundwater Monitoring to the SJCEHD on May 4, 1997, which was approved with comments on January 20, 1998. Final approval was issued after the SJCEHD received reports from adjacent LUST sites on July 20, 1998. October 1998, Additional Phase II Subsurface Investigation and Quarterly Monitoring ' In August 1998, Building Analytics completed an additional Phase II Subsurface Investigation and Quarterly Groundwater Monitoring, which included the installation of one additional 80-foot deep soil boring, and the monitoring and sampling of the four