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i 1 <br /> Closure report 28 <br /> Golden Grain Manteca Bean Facility,299 Moffat Boulevard,Manteca,California July 16,1996 <br /> ' 6 3.2 Identification of Potential Receptors and Exposure Pathways <br /> Based on the assumed commercial scenano,the on-site commercial employee and the hypothetical <br /> on-site construction worker are potential receptors to chemicals In the soil and groundwater <br /> Groundwater is not being currently used as a source of water supply The groundwater at the site is <br /> ' being or would be supplied by the municipal water system Predictive conservative modeling Indicates <br /> that natural attenuation to acceptable levels will occur on-sde within less than 10 years,thus,there will <br /> be no off-site migration of the chemicals that had been detected In the groundwater underneath the <br /> t site <br /> ' In order to provide comprehensiveness to the nsk-based approach,the future on-site commercial <br /> worker will be assumed to be using the groundwater as a source of water supply The future on-site <br /> commercial worker may be exposed to surface soil(0 to 6 inches bsg)and groundwater through <br /> tIncidental ingestion,dermal contact,and inhalation of dust-borne particles and volatile emissions <br /> During excavation or redevelopment activities,the hypothetical future on-site construction worker may <br /> 1 be exposed to both surface and subsurface (6 inches to 15 feet bsg)soils, as well as to groundwater, <br /> through incidental ingestion,dermal contact, and inhalation of dust-borne particles, and volatile <br /> emissions <br /> The potential exposure of off-site receptors to soil COPCs is less than the assumed exposure of the <br /> ' on-site receptors, thus, chemical levels that are protective of on-site receptors will also be protective <br /> of off-site receptors Similarly, although the groundwater COPCs are predicted to remain on-site, <br /> chemical concentrations are likely to decrease with increasing distance from the source of release, <br /> thus,the calculated cleanup goals for the on-site commercial worker will also be protective of the <br /> off-site commercial worker <br /> Chemical concentrations detected in the surface soil (0 to 6 inches bsg), subsurface sod (6 Inches to <br /> 10 feet bsg), and groundwater will be compared to the nsk-based cleanup goals If the maximum <br /> ' detected concentration or the 95 percent upper confidence limit of the arithmetic mean of the <br /> detected concentrations is lower than the calculated nsk-based cleanup goals, then the site will be <br /> proposed for closure <br /> ' 6 3 3 Exposure Parameters <br /> The matnx of exposure parameters used to calculate the dose for the potential commercial worker <br /> ' and the hypothetical construction worker is presented in table H-1 of appendix H Some of the <br /> • <br /> ' 42020213 CR <br /> FLUOR DANIEL GTI <br />