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Groundwater Monitoring Well,CPT,and Ozone Microsparge System Installation Report Tosco(76)Service Station No 11192,Stockton,California May 9 2003 collected during monitoring indicates that no free product or sheen has been observed in any of the monitoring wells Since 1998, depth to groundwater has been measured between approximately 11 to 19 feet bgs During the past year(2002) groundwater flow has been toward the northeast with an average gradient of 0 001 feet/feet 4.0 FIELD WORK Field work was conducted in accordance with GR's Field Methods and Procedures (Appendix A) and the Site Safety Plan dated December 3, 2002 Drilling permits were obtained from the PHS-EHD (permit No SR-0032060 and SR-0032061) Underground Service Alert was notified as required prior to drilling at the site (reference No 489572) In addition, Cruz Brothers, Inc, a private utility locating service, visited the site prior to drilling to check and clear the proposed boring locations 4.1 Drilling Achvities adoneforing Wells and Sparge PmnJ4 On December 4 through 6, 2002, a GR geologist observed Cascade Drilling (C-57 #717510) advance twelve onsite soil bonngs (monitoring wells MW-12 and MW-13, and sparge points SP-A through SP-H, SP-J, and SP-K) at the locations shown on Figure 2 The two monitoring wells were drilled to depths of approximately 30 5 and 31 5 feet bgs, and the ten sparge points were dnlled to a depth of 30 feet bgs, using 8-inch hollow-stem augers driven by a truck-mounted drill ng Soil samples were collected every 5 feet from the well bonngs The sparge point bonngs were drilled with a wooden plug installed in the auger bit The GR geologist prepared a log of the monitoring well bonngs and field screened the soil samples for the presence of volatile organic compounds utilizing a photoionization detector (PID) Field screening data are presented on the boring Iogs (Appendix B) Upon completion of soil sampling, the well bonngs were converted to groundwater momtonng wells by the installation of 2-inch diameter poly-vinyl chloride (PVC) well casing through the hollow-stern augers The well casing consisted of blank scheduled 40 PVC casing from the ground surface to 10 feet bgs, and 0 020-inch machine slotted PVC well screen from 10 feet to 30 feet bgs Lonestar # 3 sand was installed in the annular space from the bottom of the boring to two feet above the top of the screened interval (8 feet bgs) The well was then sealed with hydrated bentonite followed by neat cement containing approximately 5% bentonite to a depth of 15 feet bgs The remainder of the annular space was filled with concrete and a steel, water-resistant, traffic-rated well box An expandable locking well cap was placed on the top of the PVC casing and secured with a lock Well construction details are presented on the boring logs in Appendix B Borings SP-A through SP-H, SP-J, and SP-K were completed as sparge points with the installation of casing through the hollow-stem augers The casing consisted of 2-mch diameter KVA microsparge points attached to 3/-inch blank schedule 80 PVC casing The sparge point tips are 1402458 5