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PUBLIC YiEALTH SERVICES <br /> SAN JOAQUIN COUNTY ` <br /> ENVIRONMENTAL HEALTH DIVISION w <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer F <br /> 304 E. Weber Ave., Third Floor • P. O. Box 388 • Stockton, CA 95#i-'0388 1 <br /> 2091468-3420 <br /> JIM ADAMS SEP 12 ISN6 <br /> DIRECTOR OF ENVIRONMENTAL SERVICES <br /> CATELLUS DEVELOPMENT CORPORATION <br /> 201 MISSION ST 30TH FL <br /> SAN FRANCISCO CA 94105 <br /> RE: Catellus Development Property SITE CODE: 1284 <br /> 1325 West Weber <br /> Stockton CA 95203 <br /> San Joaquin County, Public Health Services, Environmental Health Division (PHSIEHD) has completed review <br /> of the "1st Quarter 1996 Groundwater Monitoring Event" report dated August 12, 1996 and prepared by ERM- <br /> West. PHS/EHD has the following comments for your consideration. <br /> The report included a proposal to install magnesium peroxide socks (oxygen releasing compound: ORC) in <br /> monitoring wells: MW1, MW4, MW5, MW1A, MW2A, MW3A, and MW4A and in the vapor extraction well <br /> installed in the formerly excavated area. ORC socks release oxygen that enhances aerobic bioremediation as <br /> oxygen is typically a limiting factor. Extremly high concentrations of petroleum hydrocarbon contamination <br /> continues to be evidenced up to 5,I00 ppb TPH-gas and 1,200 ppb benzene in MWIA. PHSIEHD agrees that <br /> groundwater contamination concentrations have decreased since the October 1993 excavation; however, you <br /> should be aware that the migration of groundwater contamination at the site is controlled by additional factors <br /> besides intrinsic bioremediation. Prior to the placement of the ORC socks, background oxygen concentrations <br /> will be monitored and will be used for future reference when evaluating the effectiveness of the ORC socks. <br /> You may proceed with the installation of the ORC socks. Groundwater samples should be collected quarterly <br /> and reported in a timely manner. MTBE analysis was performed on the last groundwater samples which were <br /> collected on March 7, 1996 and should have been reported with the other groundwater monitoring results in <br /> summary tables. <br /> Once concentrations have been sufficiently reduced to warrant closure evaluation, PHS/EHD will direct you to <br /> submit a closure summary report containing the information which is outlined in the Appendix B: Requests for <br /> Closure dated March 1, 1994 and prepared by the Staff of the Central Valley Regional Water Quality Control <br /> Board. <br /> Please notify PHS/EHD at least two working days prior to initiating the proposed field activities. If you have <br /> any questions or comments, please do not hesitate to contact me at (209) 468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> YYA C-(� <br /> Mary Meays, Senior REHS Margare agorio, REHS <br /> Site Mitigation Unit Supervisor <br /> MM11325WW <br /> cc: Elizabeth Thayer, CVRWQCB cc: Jill Quillin, ERM-West <br /> A Division of San Joaquin County Health Care Semites <br />