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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 4-3-WellMonitoring, Development, and Samnlino Monitoring, development, and sampling of the two newly installed wells was performed by GR personnel during the regularly scheduled quarterly monitoring and sampling event at the site Copies of the well development and field monitoring data sheets are included in Appendix D Monitoring data are summarized in Table 1 Wells MW-12 and MW-13 were developed and sampled on January 3, 2003 Depth to groundwater in the wells were measured and each well checked for the presence of separate phase hydrocarbons (SPH)prior to development SPSs were not observed in the two wells Neither of the wells dewatered during development and each yielded a minimum of 10 well volumes Immediately after the wells were properly developed, groundwater samples were collected in appropriate containers supplied by the laboratory Groundwater samples were submitted for chemical analysis under chain-of-custody documentation to Severn Trent Laboratories, Inc (STL) in Pleasanton, California 4.4 Wellhead Survey Following installation of the wells, the well casing elevations were surveyed by Virgil Chavez Land Surveying of Vallejo, California (California Land Surveyor No 6323) Top of casing and vault box elevations were measured relative to mean sea level (MSL), and the horizontal locations of the wells were measured by Global Positioning System (GPS) Well casing elevation data are presented in Table 1 A copy of the surveyor's report is included in Appendix E 4.5 Interim Remedial Action As an interim remedial action measure GR installed a K-V Associates, Inc (KVA) "C-Sparge" ozone microsparging system Ozone microsparging is a process where ozone in air is introduced into the groundwater at low flow rates (2-6 cubic feet per minute) through specially designed spargers to create small "microbubbles " As these microbubbles rise within the column of water, the volatile organic compounds (VOCs) are oxidized Ten KVA sparge points (SP-A through SP-H, SP-J, and SP-K)were installed at locations shown on Figure 2 The ten sparge points were installed to a depth of 30 feet bgs Sparge point construction details are presented on the boring logs in Appendix B The C-Sparger" panel was mounted on a unistrut frame in the northeast corner of the site The panel includes an ozone generator, air compressor, and a programmable timer/controller Sparge points are connected to the panel by 3/8" LDPE tubing Each sparge point has a dedicated line The tubing was run through schedule 80 PVC conveyance piping for added protection The process . flow diagram is presented as Figure 3 140245 8 7