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Report-Groundwater Inveb,igation First Student Bus Facility(Former A.W. Hayes Facility) 2005 Navy Drive—Stockton, CA A. FINDING THE LOCATION OF MONITORING WELL MW-2 On May 25, 2010, KR Environmental conducted a visit to the Site to determine the location of monitoring well MW-2, and to sample monitoring wells MW-1, MW-3 and MW-4. A metal detector was used to successfully determine the location of MW-2, which was located beneath the asphalt driveway west of MW-4. The location of all four (4) monitoring wells is illustrated on Figure 2 — Site Plan. The asphalt located above MW-2 was removed to expose the traffic vault box and lid located above MW-2. Monitoring well MW-2 was not sampled during this sampling event. B. GROUNDWATER SAMPLE COLLECTION On May 25, 2010, groundwater samples were collected from monitoring wells MW-1, MW-3, and MW-4. Prior to beginning monitoring well sampling activities, the depth to groundwater was measured from the water surface confined within the PVC well casing to the top of each respective monitoring well casing. An electronic depth-sounding instrument was used for this activity. A notch located on top of each monitoring well casing serves as a permanent reference measuring point. The top of casing (TOC) elevations, measured depths to groundwater, and groundwater elevation for each of the three(3)monitoring wells are summarized below in Table 2. Table 2—Depth to Groundwater(May 25,2010 Monitoring Well TOC Elevation Measured Depth to I Groundwater Groundwater I Elevation (MSL) MW-1 5.24 Feet 8.61 Feet -3.37 Feet MW-3 6.53 Feet 11.29 Feet -4.76 Feet MW-4 6.00 Feet 10.81 Feet -4.81 Feet Approximately three (3) casing volumes (9 gallons) of groundwater was purged from monitoring wells MW-1 and MW-3, and approximately 3 casing volumes (21 gallons) of groundwater was purged from monitoring well MW-4 prior to collection of groundwater samples. The wells were purged using a new, disposable bailer for each well. Groundwater removed from all three (3) monitoring wells was cloudy and odorless. Neither floating product nor oily sheens were observed in the groundwater removed from MW-1, MW-3 or MW-4. A summary of purge volumes, pH, electrical conductivity, NTUs and temperature measurements made during well purging activities are presented below in Table 3. Copies of the Well Monitoring Data Sheets for sampling are included in Appendix B. 3