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%%Ole %ftwo <br /> VALLEY WHOLESALE DRUG CO., INC. <br /> 1401 FREMONT, STOCKTON <br /> PAGE 2 <br /> ppb of TPH-g. Thus far, GP-3, which was located at the southeast corner of the <br /> building, has been the northernmost boring drilled at the site. The deepest soil samples <br /> analyzed at this site since the tank removal in 1994 were collected at 23 feet bsg. <br /> PHS/EHD does not concur with the recommendation in the Second quarter 1999 <br /> groundwater monitoring report that additional investigative work is not required and <br /> that ORCO (oxygen releasing compound) be installed in MW-1. The lateral extent of <br /> the contamination in both soil and groundwater has not been defined. Based on the <br /> report, the lateral extent of the contamination in the soil is at least as far as the <br /> southeast corner of the building where GP-3 was advanced, and the extent of the <br /> contamination in groundwater is at least as far as GP-2 near the entrance of the <br /> building and GP3. Since groundwater flow has been consistently calculated by Wm.J. <br /> Hunter to be travelling to the north, the propensity for the plume to continue to <br /> migrate toward the north cannot be ignored. Before ORC can be considered as a <br /> potential corrective measure, the plume in both soil and groundwater must first be <br /> defined and the mass balance calculated. <br /> Submit a workplan to PHS/EHD that will define the lateral extent of the <br /> contamination in both soil and groundwater plume by May 1, 2000. The work plan <br /> should also include a proposal to conduct a 2000 feet well receptor survey in <br /> accordance with Appendix B of the Tri-Regional Board Staff Recommendations as a part <br /> of the requirements for closure of underground tank sites. All wells identified in the <br /> survey and the location/addresses on a map along with any known construction details <br /> of the wells should be provided in the same report of this proposed work. <br /> PHS/EHD recommends that oxygenate no longer be analyzed for in future quarterly <br /> reports or investigation of this site. PHS/EHD also recommends keeping all analytical <br /> results of groundwater samples in the table of all future quarterly reports and <br /> investigation reports in the same mathematical unit of ppb, rather than a confusing <br /> mixture of ppb and ppm. <br /> If you have any questions, please feel free to contact Jeffrey Wong at (209) 468-0335. <br /> Donna Heran, REHS, Directors <br /> Enr}ronxnntal �lt�ision <br /> ((JJ c <br /> Jffreey Wong , REHS �J Margareeagorio�, R&E�HS <br /> LOP/Site Mitigation Unit IV Supervisor <br /> c: RWQCB, Central Valley Region — Marty Hartzell <br /> c: Wm.J. Hunter & Associates <br />