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Groundwater Monitoring Well,CPT,and Ozone Microsparge System Installation Report Tosco(76) Service Station No 11192,Stockton,California Ma 9 2003 4.6-Ozone MicrospargeSystem Startup The system was placed into operation on December 20, 2002 The system cycles ozone/air injection between the ten sparge points The schedule is currently set to cycle through each point 16 times per day, for between 5 and 15 minutes per point per cycle The schedule can be vaned as part of the system evaluation process 4.7 Ozone Microsparge System 01)eration and Maintenance and Reporting System operation and maintenance (O&M) will be performed twice for the first month, then monthly Monthly groundwater samples will be collected from wells MW-3, MW-4, and MW-13 in order to evaluate the system effectiveness A system status report will be prepared after the first six months of operation, presenting the results of the remedial effectiveness and associated sampling program This evaluation report will be issued by August 1, 2003 At that time, the effectiveness of the system will be evaluated 5.0 RESET IT'S . 5.1 ';nhcvrface Conditions Detailed descriptions of the subsurface materials encountered during drilling are presented on the boring logs in Appendix B In monitoring well MW-12, the first 8 feet bgs were composed of clay, underlain by a clayey silt to a depth of approximately 12 feet bgs The silt was underlain by clay to approximately 22 feet followed by clayey sand with gravel and clay to the maximum explored depth of 31 5 feet bgs In monitoring well MW-13, the first 10 feet were composed of clay with minor amounts of sandy clay (4'-5' bgs)underlain by a sandy silt to approximately 15 feet bgs The sandy silt was underlain by 0 5 feet of poorly graded fine gramed sand underlain by well graded fine to coarse gramed sand to approximately 22 feet bgs The well graded sand was underlain by clay to the maximum explored depth of 30 5 feet bgs Groundwater was first encountered at approximately 15 feet bgs in both borings The CPT event determined that the site consists predominantly of interbedded clay and silt with occasional lenses of sand to a depth of 140 feet bgs CPT-2 interpreted that sand was first present from approximately 41-44 feet bgs and again from approximately 52-57 feet bgs Thin layers of sand of approximately 1 foot in thickness were intermittent throughout the remainder of the boring to a maximum depth of 130 feet bgs In CPT-3, sand was first interpreted from approximately 12- 22 feet bgs, and again from approximately 125-136 feet bgs CPT-3 was terminated at 140 feet bgs In addition, during the CPT event, three Pore Pressure Dissipation Tests were performed to determine if groundwater was present to the formation at the specific depth of the CPT The Pore Pressure Dissipation Test determined that sufficient groundwater was present in each of the test zones to allow for groundwater sampling 1402458 8