Human Health Risk Assessment - Raytheon

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14 Human Health Risk Assessment DRAFT Notably, no CVOCs were detected in off-Site soil vapor samples. This is consistent with the SARA characteristics of the groundwater impacted by chlorinated VOCs which is present at the water table near the on-Site source area but is only found at depth off-Site. In off-Site areas, a clean water layer generated by infiltration of rainwater has built up over the impacted groundwater area and limits volatilization of constituents from groundwater. However, in the on- Site source area where buildings and asphalt pavement prevent infiltration of rainwater, constituents are found near the surface of the water table. To further evaluate the possibility that soil vapor may be migrating off-Site, a second round of soil vapor samples were collected in April 2008 at 11 locations within the perimeter of the facility and 8 locations in Azalea Park. Soil vapor sampling locations are shown in SARA Figure 3-4; analytical results are provided in SARA Table 12. As indicated in SARA Table 12, one soil vapor sample contained 1,1-dichloroethane (1,1-DCA) and one sample contained 1,4-dioxane; all other COPCs detected in soil vapor were chloroform, common solvents (acetone and MEK) and gasoline constituents (toluene, ethylbenzene and xylenes) 3 . These additional soil vapor sampling data do not indicate the presence of a soil vapor plume migrating off-Site. Other than chloroform, which is present in the reclaimed water used to irrigate the park, no chlorinated VOCs were detected in soil vapor samples collected in Azalea Park. The only other chemicals detected in the park were the common solvents acetone, MEK and the common gasoline constituents, toluene and xylenes. 3.2.2 Indoor Air Sampling Indoor air samples were collected from 8 locations within Building M, 3 locations within Building A, and 5 locations within Building E in November 2007. Sampling locations are shown in SARA Figure 3-4. Indoor air samples were analyzed for VOCs using a modified Method TO-15 and analytical data are reported in SARA Table 13. Only low levels of VOCs were detected in indoor air. At several locations, collocated soil vapor samples were collected from beneath the building slab and analyzed for the same suite of VOCs. In general, indoor air concentrations were uncorrelated to soil vapor levels. These data are shown in Table 3 of this report. As indicated in Table 3, indoor air levels for a number of constituents (acetone, carbon disulfide, MEK, toluene and xylene) were comparable to collocated subslab soil vapor concentrations. Constituents detected in indoor air at levels comparable to subslab soil vapor concentrations are likely originating from indoor sources. Indoor air concentrations for other constituents detected at much higher levels in soil vapor such as TCE, TCA and their degradation products (cis- and trans-1,2-DCE, 1,1-DCA and 1,1-DCE), may be attributed in part to the underlying soil vapor; however, concentrations detected in indoor air are low, indicating that soil vapor intrusion is not a significant exposure pathway for the three commercial buildings on-Site. 3 Two non-COPC constituents commonly found in gasoline were also detected in one soil vapor sample (tetrahydrofuran and 2,2,4-trimethylpentane).
3.2.3 Ambient Air Sampling 15 Human Health Risk Assessment DRAFT Four separate rounds of ambient air monitoring were conducted at the Site, in Azalea Park, and in the neighborhoods surrounding the Raytheon Facility. Ambient air monitoring locations are shown in Figure 3-4 of the SARA; analytical data are provided in SARA Table 13. The first round of ambient air samples were collected on December 4, 2007. After anomalous results were received in the first round of sampling, follow-up conversations with the analytical laboratory revealed that the Summa canisters were not 100% certified clean. As a result, a second round of sampling was conducted with 100% certified clean canisters on January 14, 2008. This sampling event was followed by a focused, third round of sampling on February 22, 2008 to further evaluate results obtained for one of the samples (AA-1). During the first two rounds of sampling, winds were blowing primarily from north to south. During the third round of sampling, winds were blowing primarily from the south/southwest. To evaluate the possibility that soil vapor originating on-Site may be diffusing through soil and entering outdoor air, a fourth round of ambient air monitoring was conducted. Ambient air monitors were set up at five locations surrounding the buildings on-Site (see Figure 3-4 of the SARA) and ambient air samples were collected over a period of approximately 8 hours on three separate days. Ambient air monitoring results are provided in Table 13 of the SARA. In addition to the four rounds of sampling described above, Pinellas County operates two ambient air monitoring stations as part of the National Air Toxics Trends (NATTS) program. One of the stations is located northwest of the Facility, adjacent to the tennis courts in Azalea Park. Summa canister samples are collected over a 24-hour period every six days and analyzed for VOCs using EPA Method TO-15. These data are summarized in Table 4 of this report and discussed in further detail in Section 7. 3.2.4 Surface Water Sampling Four surface water samples were collected from the drainage canal along Farragut Drive North and analyzed for VOCs and 1,4-dioxane using EPA Methods 8260B and 8260C SIM/ID. One COPC (1,4-dioxane) was detected in all four samples at concentrations ranging from 5.4 to 8.9 µg/L. These levels are well below the FDEP surface water criterion of 120 µg/L (FDEP, 2005), which is established based on protection of human health. FDEP does not have an ecological screening value for 1,4-dioxane; however, the USEPA Region V ecological screening level for 1,4-dioxane is 22,000 µg/L. 4 Because all of the surface water sampling results for 1,4-dioxane were well below both human health and ecological screening criteria, this constituent does not represent a significant risk to human health or the environment via surface water discharges. The only other COPC detected was cis-1,2-DCE at concentration of 0.68 µg/L, which is well below the federal and state drinking water standard of 70 µg/L. 4 http://www.epa.gov/reg5rcra/ca/ESL.pdf
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DRAFT Table A-13. Dose and Risk Cal
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