1. 100 NR-2 Evaluation Status TM Poston and JL Downs River Corridor End State and Final Closure Project Update And SAP Refinement Workshop June 1, 2006

2. 2 Objectives of Evaluation Evaluation of ecological receptor impacts at 100-N in the riparian and near-shore aquatic habitats Effectiveness of pump and treat; remedial action decisions Results to feed into River Corridor Baseline Risk Assessment (RCBRA)

3. 3 100-NR-2 Study Areas Suspected diesel area = SDA Strontium plume area = SPA Elevated metals area = EMA SDA SPA EMA

4. 4 Diesel Plume Spill in the 1960s Trenched to collect diesel – burned Residual plume still present Diesel residues observed at shoreline well sites Diesel odors detected during hyporheic shoreline sampling Low dissolved oxygen in aquifer tube samples Iron oxide deposits along shore Elevated manganese and iron in interstitial water

5. 5 RadionuclidesRadionuclides Strontium-90 is the driver RESRAD biota runs Surface soil and water concentrations pass screens Clam shell dose rates below screens Hypothetical Riverbank Spring Scenario Mouse lives in riprap, drinks 100% spring water Undiluted spring flows year round; 2410 pCi/L strontium- 90

6. 6 Strontium-90 in Clam Shells

7. 7 Polychlorinated Biphenyls Screened on 21 congeners Several congeners were detected Comparisons to benchmarks indicated measured values below ecological screening criteria levels and upstream reference levels

8. 8 MetalsMetals Elevated lead in mouse liver at SPA Iron and manganese elevated in SDA sub-surface water Barium (?), cadmium, nickel and zinc > some ecological benchmarks Uranium, arsenic, chromium elevated in riparian soils, at or < benchmarks levels ECEM modeling of metals (median concentration). Indicated low (acceptable) risk

9. 9 Weight of Evidence “Normal” distribution of mollusks “Normal” age distribution of “Corbicula” “Normal” distribution in aquatic invertebrates Highly reproductive mouse habitat No external abnormalities noted in biota Asiatic clam histology – variable responses, no correlation in ova condition with Sr-90, inconclusive with digestive system

10. 10 Continuing Activities Address/incorporate review comments on 100 NR- 2 report Transfer of 100 NR-2 data to RCBRA – inclusion into 100/300 Area RA Apatite injection is moving forward Characterize diesel plume area Continued monitoring of Sr-90