2004-01-29_REVISION - M1987113 (2)

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Final OU 11 Combined Phases RFI/RI Report are intermittent and dry most of the year. Amore well-developed ripazian azea exists along Woman Creek approximately one-quarter mile to the south of iHSS 168. Flows in this section of Woman Creek are more persistent but vary widely through the yeaz Field surveys in 1992 through 1994 have not revealed the presence of any federal- or u•rp state-protected species in OU 11. Ripazian areas along North Walnut Creek and $"-- Woman Creek have been identified as potential habitat for Preble's meadow jumping mouse (Zapus hudsonius preblei), a federal category 2 species that is a candidate for listing as threatened under the Endangered Species Act. This species has been identified from the Woman Creek ripazian area but not from the North Walnut Creek area adjacent to OU 11. OU 11 also does not contain habitat suitable for the federally endangered Diluvium ladies' tresses (Spiranthes diluvialis) (EG&G, 1995e). Other protected wildlife species may occasionally use OU 11, but habitats critical to their survival are not present. General wildlife use of OU 11 may include browse-and resting areas for mule deer and hunting of small mammals and birds by mammalian and avian predators such as coyote, red fox, red-tailed hawks, and American kestrels. The site lacks trees and shivbs for tree-nesting birds but may be used by ground-nesting birds. 6.2.1.2 Nature and Extent of Contamination and Exposure Pathways Phase I RFUI2I activities conducted at OU 11 aze described in Section 2.2. Analytical data from site sampling were used to identify the PCOCs listed in Table 4.1-4 (see Section 4.1). PCOCs were identified only for soils (0 to 12 feet deep) and include the radionuclides americium-241, plutonium-239,240, and tritium, and nitrate/nitrite. Based on the PCOCs, the following potential exposure pathways were identified: • soil-~plants~herbivorous mammals, granivorous birds • soil invertebrates-+small mammals, insectivorous birds • soil-small mammals (incidental ingestion)~mammalian and avian predators • soil-mammalian and avian receptors (incidental ingestion) Based on the potential receptors, exposure, pathways, and PCOCs, small mammals were identified as the bounding exposure scenario because of their small home ranges and intimate association with surficial soil. RFETS site-specific radionuclide toxicity benchmazks were developed by Los Alamos National Laboratory (LANE) based on this assumption (Higley and Kuperman, 1995). tp~2509072\sec6.doc 6-4 6!8/95