SITE INFORMATION AND CORRESPONDENCE

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# Page 1 of 2 Vicki McCartney [EH] To: Kirk Larson Subject: RE: UST Fund Reviews Kirk: 139 South Center Street, Stockton ' The former Chevron gasoline station at 139 South Center Street, Stockton, has significant concentrations of diesel and/or motor oil in groundwater collected from every on- and off-site monitoring well. Deep monitoring well, MW-18D2, installed in November 2007 and screened between 100 and 105 feet below surface grade (bsg), also has significant concentrations of motor oil, diesel, gasoline and BTEX in groundwater samples collected quarterly. The most impacted well is MW-15D, screened between 46 and 51 feet bsg. Soil and groundwater are not vertically and laterally delineated a1=this site. I believe a site conceptual model is needed before recommending additional borings, monitoring wells, or interim remediation. There are no buildings currently at this site so vapor intrusion evaluation is not a priority. h 106 (not 160) West Second Street, Ripon The former Thiemann's service station at 106 West Second Street, Ripon, had fieldwork involving the advancement of three cone penetration test(CPT) borings completed in October 2008. CPT-01 was advanced I depth of 123 feet bsg and grab groundwater samples were collected from discreet borings at 65 feet to Iota 9 9 p i bsg and 112 feet bsg. CPT-02 was advanced to total depth of 120 feet bsg and grab groundwater samples were collected from discreet borings at 65 feet bsg and 112 feet bsg. CPT-03 was advanced to total depth of 120 feet bsg and grab groundwater samples were collected from discreet borings at 35, 68, and 112 feet bsg. I have not received the report for this investigation so I will not comment whether additional investigation or remediation is needed at this site. 308 EI Dorado Street, Stockton I am currently reviewing ozone Injection Feasibility Study and Bench Scale Work Plan date January 30, 2009, and will comment by letter to the responsible party within the week. I have also received a request to suspend Il quarterly groundwater monitoring and sampling at this site and will comment concerning this request by letter next week. 4100 Fremont Street In April 2008, CPT borings P-15A, P-15B, and P-16 were advanced at locations on- and off-site and gasoline was detected at 800 ug/L in groundwater collected at 65 to 75 feet bsg in P-15B. Also MTBE continues to be detected at the MCL of 13 ug/L in MW-2;and 1,2-DCA continues to be detected in MW-4. For these ; reasons, a monitoring well was conditionally approved by letter dated January 23, 2009. Once data are collected from this new well and the site is well characterized, a corrective action plan may be appropriate. i 3250 (not 250)West Hammer Lane ..Stockton ° By e-mail on February 6, 2009, Stratus Environmental, Inc. notified our department that the ozone-bench-scale test has been delayed due to delays in reimbursement from the Cleanup Fund.. An ozone injection system is operating at the ConocoPhillips 76 Service Station adjacent to this site. For this reason, by letter dated February 27, 2009, our department recommended collecting groundwater samples from monitoring wells screened in the same depth interval as the ozone injection wells and down gradient of the injection wells at the ConocoPhillips 76 site during the next sampling event coordinated with the ConocoPhillips 76 site. If analytical results for metals indicate that groundwater quality'will not be adversely affected and if it can be demonstrated that this site and the adjacent ConocoPhillips 76 site have similar hydrogeological characteristics, the ozone bench-scale study may not be necessary. Our department is currently awaiting a response to this recommendation. 244 West Harding Way, Stockton By letter dated May 13, 2008, our department approved the installation of one additional well (MW-5) west of monitoring well MW-1. To date this monitoring well has not been installed. Currently MTBE is detected in i 3/20/2009