Laserfiche WebLink
Stantec <br /> April 30, 2010 <br /> Page 8 of 14 <br /> Reference: First Quarter 2010 Site Status, Groundwater Monitoring and Remedial Summary Report-Stockton <br /> Terminals Technical Committee Facilities <br /> Several noteworthy decreases are mentioned below. <br /> • Well OW-8D - Analyte concentrations decreased from fourth quarter 2009, including <br /> benzene (41 pg/L), which decreased by more than an order of magnitude from 460 pg/L; <br /> MTBE and ethylbenzene were non-detect. <br /> • MTBE concentrations in 78 percent of the wells were below the WQO and/or MRL <br /> (Appendix Table D-4). <br /> 4.0 REMEDIATION ACTIVITIES AND RESULTS <br /> 4.1 HYDROGEN PEROXIDE INJECTION (HPI) PILOT STUDY - TESORO TERMINAL <br /> The final quarter of baseline metals data prior to the start of the two-phase pilot study (Table 8) was <br /> collected from wells TO/T-3, TS-4R, TS/M-2, and TS-5 during first quarter 2010. The first HPI <br /> event occurred on March 23, 2010. With initiation of HPI injection at the site ongoing metals <br /> monitoring and monthly evaluation monitoring will take place in accordance with the April 1, 2009 <br /> work plan. <br /> 4.2 OXYGEN INJECTION PILOT STUDY -TESORO TERMINAL <br /> Preliminary activities associated with the oxygen injection pilot study have been completed. During <br /> March 2010, wells TS/MW-3DR and TS/MW-4D were installed and developed. During second <br /> quarter 2010, the wells will be surveyed and a helium tracer test will be conducted to confirm <br /> hydraulic communication between wells TS/MW-3DR and TS/MW-2D. Documentation of well <br /> installation activities and the tracer test will be presented under separate cover, as requested by the <br /> RWQCB. <br /> 4.3 OVERPURGING OF SELECT BP/ARCO WELLS <br /> During fourth quarter 2008, a fire-suppression-foam release occurred on the BP/ARCO terminal. In <br /> accordance with the September 28, 2009 Workplan for Interim Response, sixteen wells (wells <br /> AR/MW-3A, -5A, -5C, -6AR, -613, -8A, -813, -10B, -11A, -11B, -13A, -13B, -13C, -18C, -22A, and - <br /> 23A) were overpurged during first quarter 2010. Overpurging was attempted on well AR/MW-5C, <br /> however, the well purged dry after one casing volume. Well AR/MW-14B was inaccessible during <br /> first quarter due to terminal activities and could not be overpurged. In general, analyte <br /> concentration decreases have been observed in wells across the Site since fourth quarter 2008 <br /> (including wells not being overpurged) (Tables 6 and 7). Overpurging during first quarter removed <br /> approximately 3,220 gallons of groundwater. Purged water was stored in onsite holding tanks until <br /> it was removed by Instrat for treatment and disposal. <br /> 4.4 OZONE INJECTION SYSTEMS <br /> Two ozone-injection systems (East and West Systems) currently operate at the Site (Tables 9 <br /> through 12). Descriptions of the East and West Systems are included in Appendix B. Remedial <br /> field data sheets for the ozone-injection systems are included in Appendix J. O&M visits were <br />