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F12-402- aD11 Y AUG 17 2004 A-11i E , FILE ENVIRONMENTAL HEALTH DEPARTMENT SAN JOAQUIN COUNTY -Unit Supervisors Donna K.Heran,R.E.H.S. Carl-Borgman,R.E.H.S. 304 East Weber Avenue, Third Floor Director Mike Hu—ins,R.E.H.S.,R.D.I. • Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,RI.E.S. • Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. 6Laurie A.Cotulla,R.E.H.S. Fax: (209) 464-0138 Robert McClellon,R,E.H.S, Program Manager Mark Barcellos,R.E.H.S. JERRY MOORE AUG 16 2004 MOORE PETROLEUM 976 W MARIPOSA AVE STOCKTON CA $5204 RE: Workplan for a Limited Subsurface Site Investigation 5491 F Street Banta CA 95304 San Joaquin County Environmental Health Department (EHD) has received and reviewed Workplan Addendum Letter for a Limited Subsurface Site Investigation (WPAL) dated 02 June 2004, prepared by Apex Envirotech, Inc. (AEI) on your behalf. The WPAL was prepared in response to an EHD directive issued by letter dated 12 May 2004 to include•a boring/monitoring well for vertical assessment of impacted ground water and an EHD recommendation for relocating monitoring well MW-17 to more tightly delineate the plume of impacted ground water. AEI' addresses the EHD directive in the WPAL by proposing to install a cone penetration testing (CPT) boring near MW-12 to identify permeable sand units in the saturated zone to a target depth of 80 feet below surface grade (bsg), and collect ground water samples from the sand intervals identified in the Driller's log for the domestic well of interest. EHD notes that hydropunch-like ground water samples should be collected for laboratory analysis from each significant' interval of relatively higher permeability identified in the CPT log that may act as a lateral migration pathway for the dissolved contaminants. Information from the CPT is intended to be utilized for designing a.s6ntinel well to protect the Domestic water supply well east of the site. The CPT- should be located in line between the dispensers on the subject site and the domestic well of interest. AEI also intended the proposed CPT and related sampling to be utilized to complete the vertical assessment of impacted ground water on the site. EHD had also recommended installation of a CPT boring in the suspected source area, or slightly down-gradient of it for this purpose, although this may not have been stated as clearly as it could have been in the 12 May 2004 letter. EHD believes the location of the AEI-proposed boring, approximately 60 to 80 feet from the suspected source area, may be too far for this purpose. Please include a second CPT boring with ground water sampling in the suspected source area near the dispensers.