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A r <br /> J <br /> PUBLIC HEALTH SERVICES 'oP C, <br /> SAN JOAQUIN COUNTY Z` <br /> a: :{ <br /> to: <br /> JOGI KHANNA M.D.,M.P.H. <br /> Healdl Officer P <br /> P.O. Box 2009 • (1601 East Hazelton Avenue) Stockton, California 95201 <br /> (209)468-3400 <br /> FEB 2 5 1991 <br /> CLINT ROGERS O <br /> CHEVRON USA Fly <br /> P O BOX 5004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Chevron SS#9-4275 IN REPLY REFER TO SITE CODE: 1952 <br /> 2905 W. Benjamin Holt <br /> Stockton, CA <br /> We have completed our review of the Work Plan for Cone Penetrometer Testing, BAT TM Probe Installation <br /> and Groundwater Sampling dated January, 1991. We do not want to impede new technologies,but wp have <br /> several reservations about the use of the BAT Probe. <br /> Reliable chemical test results are currently in the research and development phase with this system. Protocol <br /> for sample collection has not been established by EPA or Department of Health Services. In addition, <br /> protection of the underground water is of great concern to us. The idea of ramming a steel casing through <br /> contaminated soils and into groundwater, possibly causing contamination of equipment and groundwater, <br /> is not favorable. The length of the vertical seal around the steel casing is limited and the length of unsealed <br /> vertical steel casing may provide a physical connection between sources of pollution and the groundwater. <br /> The installation of the BAT Probe at this site is for test purposes only and does not constitute approval for <br /> its use at other sites in this county. Installation is being allowed at this site because the site has relatively <br /> shallow groundwater,there are existing monitoring wells with which data can be compared, and it has been <br /> shown that a clay layer was not encountered in the first 30 feet below the surface. This last fact should <br /> eliminate the possibility of penetrating a clay layer and causing intermingling of groundwater aquifers. The <br /> use of the BAT Probe at other sites will be decided on a site specific basis. <br /> BAT Probes are to be installed only adjacent to existing monitoring wells at this site. Comparison of results <br /> from the existing monitoring wells and the BAT Probe samples for a period of six (6) months or longer with <br /> a minimum of two (2) rounds of sampling per quarter must be accomplished before installation of additional <br /> BAT Probes will be considered. The installation will be stopped, if first water is not encountered within the <br /> first 32 feet of the subsurface. <br /> An annular seal shall be placed between the BAT Probe casing and the wall of a drilled hole and shall be <br /> two (2) inches or more in thickness according to San Joaquin County Well Ordinance No. 1862. The seal <br /> shall be at least three (3) feet in length. <br /> A permit application and $89.00 fee, a site specific health and safety plan and a disposal plan for the <br /> removed soil are to be submitted to this office prior to start date. <br /> A Division of San Joaquin County Dcalth Carc Scniccb 110 <br />