FINAL SITE INSPECTION REPORT

159615971598159916001601160216031604160516061607160816091610161116121613161416151616the groundwater would not be expected. As agreed to in the TPP Memorandum, no groundwatersamples were planned or collected during the SI (Shaw, 2006b).9.4.3.1 Comparison to BackgroundAs agreed in the TPP Memorandum, no groundwater samples were collected from within theImpact Range AOC during the SI and no groundwater samples were collected from the AOCduring the PA/SI (Shaw, 2006b). However, as discussed in Section 2.5.3, samples werecollected down and cross gradient of the AOC and FUDS. The sampling results indicated thatno explosives were detected in any groundwater sample and perchlorate was detected in 18 of 25wells sampled in the PA/SI. In the 18 samples with perchlorate detections concentrations rangedbetween 0.46 g/L and 20.7 g/L. No background value for perchlorate was established in thePA/SI. However, based on studies completed by the ODEQ and EPA (ODEQ, 2005),perchlorate is found throughout the lower Umatilla Basin in wells located up, cross anddowngradient of the Boardman AFR. This indicates that the perchlorate detected in groundwatersamples is not originating from sources within this AOC or the Boardman AFR FUDS.9.4.3.2 Comparison to Human Health Screening ValuesThe DoD action level for perchlorate is 24 g/L. All detected concentrations of perchlorate inthe vicinity of Boardman AFR FUDS are below the DoD action level.9.4.4 Air PathwayAir is considered to be a potential pathway due to inhalation of MC in from blowing dust. Thepotential inhalation of soil particles is included in the development of health-based screeningvalues for soil.Boardman AFR Final SI Report.doc 9-4 Contract No. W912DY-04-D-0010 Delivery Order No. 003September 2007