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1 <br />1 • r <br />i <br />August 19, 1999 <br />\ \GAI_DENI \PROJECTS \WP \99\205T2057TM1.DOC Golder Associates <br />MEMORANDUM <br />-11- 993 -2057 <br />of exposure for the vessel failure is negligible due to the ability to contain all process plant <br />vessel volumes in plant curbing and the 3 acre pond. The duration of exposure for the <br />extreme storm overtopping is expected to range up to medium risk due to the volume of <br />solution. While the duration of exposure is negligible for the vessel failure due to complete <br />containment. Pathways of exposure include medium risk for soils, surface water, and <br />groundwater due to overland flow of solutions. The environment at risk includes all <br />downstream drainages, which is considered a high risk. The consequence assessment is <br />very low to high due to the potential hazard and environment at risk. However, the overall <br />risk characterization is negligible due to negligible likelihood as well as magnitude and <br />duration of exposure for vessel failure and negligible likelihood for the extreme storm <br />overtopping. <br />The third potential failure mechanism is the direct access of the ponds by wildlife including <br />both bird and animals contact with solutions in the 3 acre and 7 acre ponds. The hazard <br />assessment indicates that both represent medium hazards. These hazards have not been <br />included on Table 2 but would involve the following: <br />• Birds: potential mortality due to sodium ingestion, or loss of buoyancy <br />due to saline solution contact with feathers <br />• Animals: drowning due to inability to climb out of the lined ponds <br />The exposure assessment for bird contact with the solution indicates a high likelihood of <br />occurrence due to the presence of open water, particularly in the winter months. However, <br />the magnitude of exposure is expected to negligible due to low operating concentrations of <br />sodium which is non -toxic to water fowl. The maximum sodium concentration will be <br />determined in consultation with the US Fish and Wildlife Service. The duration of <br />exposure is also negligible due the undesirable nature of the saline solutions. The pathway <br />of exposure is a high risk due to the potential direct access by birds. The environment at <br />risk is limited to birds. The consequence assessment and overall risk characterization is <br />negligible due to negligible magnitude and duration of exposure. <br />The exposure assessment for animals drowning in the ponds indicates the risk is negligible <br />due to wildlife fencing and operational controls. The magnitude and duration of exposure <br />are high risks if access is gained. The pathway of exposure has negligible risk due to <br />control of access. The consequence assessment indicates high potential consequences if <br />access is gained. The overall risk characterization is negligible due to negligible magnitude <br />and duration of exposure. <br />