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San Joaquin County <br /> .� Environmental Health Department DIRECTOR <br /> ?• =��` � Donna Heran,RENS <br /> 1868 East Hazelton Avenue <br /> fig <br /> :{ Stockton, California 95205-6232 PROGRAM COORDINATORS <br /> fig - Robert McClellon, REHS <br /> Jeff Carruesco,REHS,RDI <br /> Linda <br /> Website: www.sjgov.org/ehd LFoley,RENS <br /> Linda Turkatte,REHS <br /> Phone: (209) 468-3420 Rodney Estrada,REHS <br /> Fax: (209)464-0138 Adrienne Ellsaesser,REHS <br /> February 13, 2014 <br /> Tracy Office Plaza LLC <br /> Mr. Michael R. Black <br /> 2423 W. March Lane Suite 202 <br /> Stockton, California 95207 <br /> Subject: Site Assessment Work Plan Approval <br /> Tracy Office Plaza Site Code: 0002083 <br /> 324 East 11th Street <br /> Tracy, California 95376 <br /> Dear Mr. Black: <br /> The San Joaquin County Environmental Health Department (EHD) has received and reviewed <br /> Workplan for Additional Assessment and Subslab Gas Sampling (WP), dated 22 November <br /> 2013, prepared by Pangea Environmental Services, Inc. The work plan was submitted in <br /> response to EHD directives issued by letter dated 21 August 2013. <br /> The proposed scope of work contained in the WP includes advancing up to four soil borings <br /> utilizing direct push technology to collect soil and groundwater samples to complete the lateral <br /> and vertical assessment of impacted media, and to install two temporary soil gas probes to <br /> collect soil gas samples from beneath the concrete slab foundation of the office building to <br /> assess the potential for vapor intrusion. <br /> To evaluate the potential impact of the unauthorized release (UAR) from the underground <br /> storage tank system formerly located on your site, the EHD considers proposed borings B-9 and <br /> B-10 to be the most important as the dominant groundwater flow direction is inferred to be <br /> toward the NNE to NNW; the data from these proposed borings and data previously collected <br /> from the Tracy High School monitoring wells MW-1, MW-2 and MW-3 will hopefully characterize <br /> the magnitude of the impact of the UAR in the downgradient directions. Only a groundwater <br /> sample from B-10 needs to be analyzed if soil samples yield no field indications of <br /> contamination. Proposed boring B-7 is also justified for vertical characterization, either in the <br /> proposed location or the proposed location for boring B-8, but the EHD does not consider <br /> borings in both locations necessary; however, if it is the professional opinion of the consultant <br /> that the fourth boring is necessary, based on field indications, it, too, can be advanced. The <br /> consultant should justify such a decision in the report of findings. <br /> The EHD does not approve the two proposed sub-slab soil gas vapor probes and sampling at <br /> this time as the data obtained from the three approved boring locations may be sufficient to <br /> characterize the release and form a professional opinion on the potential for vapor intrusion <br /> from the UAR. The State Water Resources Control Board's recently adopted Low-threat <br />