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~l/OB/97 HON 1J:26 FAZ J07~6071 R8 SUPI:RFOND R~ BR DRAT Site Assessment Manager (SAM) Notes: Battle Mountain Gold The SI describes elevated concentrations of aluminum, manganese and iron in the aqueous surface water samples at the permit boundry and beyond. No analytes meeting release criteria were identified in the sediment samples. A No Further Action (NFA) decision is justified at this site for the following reasons: • The substances of initial concern relating to the site, particularly cyanide and mercury, were not found in surface water pathway samples. • There are indications that the iron and manganese at the site are likely related to the geology. • Substances other than iron which were found elevated below the site ih the surface water pathway are not decision critical for this site. Details below. • Iron is elevated above the environmental benchmark only at the downstream end of the wetlands segment rather than in samples at both ends, supporting the idea that geology or evaporation contribute to the increasing concentrations observed, and indicating a Level II wetlands segment ther hang L vel I segment I . /~/~7 Aluminum is sutFdently elevated to define a release ony at a downstream location, and not at the probable point of entry (PPE). In addition, there are no environmental or health-based benchmarks for aquatic life or the human food chain for aluminum in the Superfund Chemical Data Matrix (SCDMs 1995), and the bioaccumulation factor (BCF7 in SCDMs is less than 500. Aluminum is not the dri~verefor a dedsion at this site. Manganese and iron are eluted in both the PPE and the next downstream sample. These samples represent a 0.3 mile wetlandsZsegment and ishe ~ Human food chain BCFs for these substances are below 500, so these detections do not represent a human food chain risk under the Hazard Ranking System. There are no environmental ~b~,[~ ma r manganese, however the benchmark for iron is exceeded in one samTife owns am of the PPE by nearly a 10% margin. This excaedance is the driving factor in making a dedsion at the site. 002 Consultation with Harry Posey, at the Colorado Division of Minerals (DMG) and Geology, indicates that local eg oloay can explain the elevated manganese and Iron In this sys~tem~ The permit for the curtent operator covers an area which spans moun sins and val ey rill. available ground water data at the site, from wells located ~nnra is t and downgredient of the;lte sourr~s, indicate manganese and iron are both elevated In wells from the surfidal valley fill. ' Based on his work with the DMG permit, there is no indication of a release to ground water of these substances, but ambient ground water concentrations are higher in the sur~icial aquifer than in other area formations. ~a p ~o