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San Joaquin County DIRECTOR <br /> Donna Heran, REHS <br /> Environmental Health Department ASSISTANT DIRECTOR <br /> 600 East Main Street Laurie Cotulla, RENS <br /> { Stockton , California 95202 -3029 <br /> PROGRAM COORDINATORS <br /> :_ . Mike Huggins, REHS, RDI <br /> Margaret Lagorio, REHS <br /> Website: www.sjgov. org/ehd Robert McClellon, REHS <br /> / FOR <br /> Phone: (209) 468-3420 Jeff Carruesco, REHS, RDI <br /> Fax: (209) 464=0138 Kasey Foley, REHS <br /> 14 August 2009 <br /> Velma Masterson <br /> Beneto Inc. <br /> 4080 Seaport Blvd . <br /> West Sacramento, CA 95691 -3417 <br /> Subject: Darpetro, Inc. <br /> 749 E Charter Way <br /> Stockton , CA 95202 <br /> The San Joaquin County Environmental Health Department (EHD), has received and reviewed <br /> Updated Site Conceptual Model and Remedial Action Plan (SCM/RAP) , dated 22 December <br /> 2008 , prepared by Apex Envirotech , Inc. (AEI ) . In the report, AEI presented a history of the site <br /> investigation, discussed site characteristics and , based on those site characteristics and the <br /> remediation technology recommended by Advanced GeoEnvironmental Inc. (ACEI ) for a nearby <br /> site, AEI recommended dual phase extraction (DPE) to remediate residual impacted soil and <br /> impacted groundwater on your site. <br /> For the EHD to approve DPE as the remedial technology of choice for your site, it must be <br /> shown that not only will DPE be effective as a remedial technology, but that it is also the most <br /> cost-effective technology suitable for your site . This demonstration is usually presented in a <br /> corrective action plan (CAP) , wherein two potentially applicable remedial technologies are <br /> compared and one is presented as being the most cost-effective technology available. Soil <br /> vapor extraction was discussed in SCM/RAP, and was evaluated as not likely to be effective for <br /> addressing the remaining contamination; cost-effectiveness was not discussed . Recently, <br /> meeting the City of Stockton's discharge requirements has become more challenging , both <br /> technically and cost-wise, and this should be considered as part of the method evaluation . <br /> — Please evaluate the cost effectiveness of DPE for your site and provide the results of your <br /> evaluation in a report to be submitted to the EHD by 18 October 2009 . If DPE is still the <br /> preferred technology, the report can be part of a pilot test work plan to evaluate DPE for your <br /> site. <br /> In SCM/RAP , AEI stated that monitoring wells MW-2 and MW-6 needed to be destroyed to <br /> accommodate construction of a larger building on the site . MW-2 and MW-6 provide the <br /> northern on-site monitoring points for the dissolved plume; MW-6 , screened in a deeper zone, <br /> appears to demonstrate some recent plume instability, therefore the wells should be replaced <br /> after construction of the building . As both wells are impacted , it is required that they be <br /> destroyed by removal of all materials from the borehole prior to grouting . Please submit a work <br /> plan for the destruction and eventual replacement of monitor wells MW-2 and MW-6 to the EHD <br /> at least 60 days prior to the planned destruction of the wells . <br /> SCM/RAP Comment Letter 0809 . doc <br />