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�� � SNrrN <br /> { <br /> / ENVIRONMENTALTECHNOLOGIES CORPORATION `� <br /> 5 <br /> January 15, 1998 PAYMENT <br /> 94373 ' .\ Rr+e�lpr€? <br /> JAN 16 1998 <br /> SAN dOAOUIN COIN�Y <br /> Ms. Mary Meays w ENVI PUSO UCJOHE LT'E,S SH,6 S,pp: <br /> San Joaquin County <br /> Environmental Health Division <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> Subject: Addendum to Workplan for Subsurface Investigation at Former Thiemann's <br /> Service, 106 West Second Street, Ripon, California <br /> Dear Ms. Meays: <br /> Smith Technology Corporation (acquired by ATC Associates) has prepared this second workplan <br /> addendum to Smith Technology's Workplan for Suhsurface Investigation, dated May 3, 1996, <br /> and Smith Technology's first Addendum to Workplan for Suhsurface Investigation, dated May <br /> 15, 1996. This addendum addresses the changes in scope of work suggested in PHS/EHD <br /> correspondence dated October 16, 1997. <br /> The revised scope of work will include advancing one soil boring to approximately 60 feet below <br /> ground surface (bgs) and analyzing soil and groundwater samples collected during the installation <br /> of the vapor extraction wells and air sparge wells for oxygenate fuel additives. In addition, <br /> existing groundwater monitoring wells MW-1; MW-2, MW-4, and MW-5 will be sampled for- <br /> oxygenate fuel additives by EPA method 8260 during the next quarterly monitoring event. Wells <br /> MW-3 and MW-6 were sampled for oxygenate fuel additives during fourth quarter and oxygenate <br /> fuel additives were not detected. <br /> In the Addendum to Workplan for Subsurface Investigation, dated May 3, 1996, Smith <br /> Technology proposed to advance two onsite air sparge wells, one of them located inside the <br /> former tank excavation to approximately 35 feet bgs. To fully delineate the vertical extent of soil <br /> contamination, this soil boring will be advanced until field observations indicate that the soil is no <br /> longer impacted by petroleum hydrocarbons, approximately 60 feet bgs. Once the soil <br /> contamination has been defined, the soil boring will be backfilled with grout until the bottom of <br /> the boring is at approximately 37 feet bgs. The grout will be allowed to set overnight and two <br /> feet of bentonite will be placed on top of the grout. The air sparge well will then be completed as <br /> originally specified. <br /> v:04373\repotts\wpvesa.doc 1 <br /> 1260 Graphics Drive Modesto,CA 95351-1502 (209)579-2221 Fax(209)579-2225 <br /> Engineering Consulting Remediation Construction , <br />