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- 0 :Egan �Mq. <br /> WORK PLAN FOR <br /> GROUNDWATER INVESTIGATION <br /> JUNE 1996 <br /> This work plan describes an investigation that will be conducted at the All Pure Chemical <br /> Company facility located at 26700 South Banta Road in Tracy, California (All Pure Tracy <br /> Facility) to evaluate the lateral and vertical extent of chloroform and carbon tetrachloride in <br /> shallow groundwater. The investigation is intended to address Central Valley Regional Water <br /> Quality Control Board (Regional Board) concerns that operation of the Tracy Defense Depot <br /> groundwater remediation system will capture chloroform and carbon tetrachloride in shallow <br /> groundwater in the vicinity of the All Pure Tracy Facility. This investigation uses the <br /> HydroPunch sampling methodology to qualitatively investigate the vertical and lateral extent of <br /> chloroform and carbon tetrachloride in shallow groundwater at the northeastern and southern <br /> boundaries of the All Pure Tracy Facility. Following evaluation of the HydroPunch data, <br /> locations for new groundwater monitoring wells will be selected, new wells will be constructed, <br /> and the wells will be sampled on a quarterly basis to define the limits of chemicals in <br /> groundwater. <br /> The following sections present the rationale for developing the Scope of Work proposed for the <br /> investigation of groundwater beneath the All Pure Tracy Facility and the tasks that will be <br /> conducted in completing the investigation. <br /> BASIS FOR INVESTIGATION <br /> Results of groundwater sampling conducted at monitoring and water supply wells in the vicinity <br /> of the Tracy Defense Depot show that carbon tetrachloride and chloroform are present in two <br /> domestic water supply wells located north of the All Pure Tracy Facility. During a recent <br /> meeting with Central. Valley Regional Water Quality Control Board staff, it was agreed that <br /> investigation of the All Pure Tracy Facility would be limited to the northeast and southwestern <br /> facility boundaries. Monitoring of the north boundary is not required because monitoring results <br /> do not verify the absence of carbon tetrachloride and chloroform in samples collected from Well <br /> MW-2 within the Lyoth Loading Station which is immediately north of the All Pure Tracy <br /> Facility. As such, it was agreed that the Regional Board would analyze groundwater samples <br /> collected from the two Lyoth Loading Station monitoring wells. <br /> Quarterly monitoring results for the All Pure Tracy Facility downgradient well, MW-4, show that <br /> carbon tetrachloride and chloroform are not present in groundwater samples. Laboratory results <br /> for samples collected from MW-4 have been determined to be appropriate for delineating the <br /> lateral extent of chloroform and carbon tetrachloride in the southwest direction. Thus, the <br /> Regional Board has determined that additional monitoring wells are not required in the southwest <br /> direction. <br /> All Pure Chemical Company-Tracy Facility HELMICK& LERNER INC <br /> HLI 00907 Page 1 <br /> �0'd SSA-1 I 'au ,a�i101wlaH WOa� 22b289V60CET 01 SS:ST 96, 9Z inf <br />