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Closure Report 27 <br /> Golden Grain Manteca Bean Facility,299 Moffat Boulevard,Manteca,California .July 16,1996 <br /> ' monocyclic aromatic constituents Based on the boiling point range of gasoline, polycyclic aromatic <br /> ' hydrocarbons (PAHs) are not expected to be prevalent in gasoline, with naphthalene_reported at an <br /> average weight percent of Q 79 percent <br /> ' Since toxicity values are available for only a limited number of petroleum hydrocarbons,the <br /> approach taken is to evaluate selected indicator chemicals that represent the gasoline-range <br /> compounds USEPA recommends the selection of surrogate compounds from petroleum <br /> ' hydrocarbon mixtures and evaluating nsks or determining nsk-based action levels based on these <br /> chemicals The surrogate compounds are selected based on fhe following criteria <br /> 1 a the chemical's percent contribution in a given petroleum product <br /> ■ mobility and persistence in the environmental media <br /> ■ availability of human toxicity data <br /> A USEPA reference dose (RfD) is available for only one alkane, n-hexane, (Massachusetts <br /> ' Department of Environmental Protection 1994), which is present in gasoline at an average of 6 65 <br /> percent by weight In this nsk-based approach, the aliphatic hydrocarbon compounds are grouped <br /> with n-hexane and are assigned the toxicity value of n-hexane Naphthalene is selected as the <br /> indicator chemical for the aromatic compounds of gasoline BTEX compounds present in gasoline <br /> are evaluated as separate COPCs <br /> t6.3 Exposure Assessment <br /> The exposure assessment identifies the current and future land use of the site Based on the <br /> ' identified land use, the individuals who may potentially come in contact with the chemicals in the soil <br /> and groundwater are identified The exposure routes through which the individuals may contact the <br /> ' chemicals of potential concern are also identified in the exposure assessment <br /> 6.31 Land Use <br /> One of the factors that would influence the calculation of nsk-based cleanup goals is the exposure <br /> ' scenano for the site The site is inactive and the future land use of the area is still undetermined, <br /> however the property is zoned as commercial within the city of Manteca The nsk-based calculations <br /> assume that the site+null be a potential commercial business area <br /> i <br /> ' 4202a2l3.CR <br /> FLUOR DANIEL GTI <br /> 1 <br />