ARCHIVED REPORTS XR0011284 - Laserfiche WebLink

Home Browse Search

• 6.0 POTENTIAL EXPOSURE PATHWAYS AND SENSITIVE RECEPTORS The primary source of the hydrocarbon impact ,the UST, and therefore the primary potential source of exposure to COCs has been removed. Operation of the SVE system appears to have successfully reduced residual hydrocarbons from the soil beneath the former UST to a depth of at least 66 feet bgs. Non-aqueous phase hydrocarbons (free product), impacted surface or shallow soils, or impacted surface water are not potential sources of exposure to COCl at this site. Only secondary sources of exposure to COCs exist. These secondary sources include residual concentrations of petroleum hydrocarbons in the soil deeper than 66 feet bgs, and dissolved hydrocarbons in the groundwater. Potential exposure pathways associated with these secondary sources of exposure includes volatilization to indoor air. However, given the depth to groundwater beneath the site, this exposure pathway appears unlikely. An exposure pathway model for the site is presented in Figure 15. 6.1 Onsite Receptors SVE system operation appears to have successfully removed residual hydrocarbons from the soil in the vicinity of the former UST to a depth of at least 66 feet bgs. However, groundwater beneath the site is now encountered at approximately 44 feet bgs, and this groundwater is impacted with COCs. Therefore, residual hydrocarbons in soil beneath the former UST do not appear to be a likely source of exposure to CDCs. If residual concentrations of COCs remain in this area, exposure to CDCs from this source would be limited to potential volatilization to air inside the warehouse building. This exposure route is unlikely unless the slab foundation beneath the building has been compromised. Dissolved petroleum hydrocarbons are present in groundwater beneath the site. Based on the analytical data collected from borings CPT-1, CPT-8, and CPT-10, the dissolved hydrocarbon plume extends beneath the warehouse building. There is no direct route to groundwater exposure (i.e. a well) at the site. Therefore, exposure to the CDCs in the dissolved hydrocarbon plume appears limited to potential volatilization to air inside the warehouse building. This exposure route is unlikely unless the slab foundation beneath the building has been compromised. Given the depth to groundwater (approximately 44 feet bgs), it appears unlikely that vapors from the COCs in the dissolved hydrocarbon plume will be an exposure threat. There appears to be little risk of exposure to the dissolved petroleum hydrocarbons beneath the site. p;\Apache Plastics\Reports\Apache SCM.doc Page 12 ✓`tratu5