1999-08-23_HYDROLOGY - M1999051 - Laserfiche WebLink

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August 1999 \99 2057\2O571in.th • D • N RISK ASSESSMENT SUMMARY TABLE 1 Evaporation and Drainage Ponds: Leaks Overtopping Wildlife contact with pond solution 1) Loss of containment due to poor construction Subsidence - Negligible Hazard Groundwater - Very Low Hazard (alluvial well) Soil - Very Low Hazard Surface Water - Negligible Hazard 2) Leak due to puncture of pond liner during operations Subsidence - Negligible Hazard Groundwater - Very Low Hazard (alluvial well) Soil - Very Low Hazard Surface Water - Negligible Hazard 1) Extreme storm event Subsidence - Negligible Hazard Groundwater - Very Low Hazard (alluvial well) Soil - Very Low Hazard Surface Water - Very Low Hazard 2) Plant vessel failure Subsidence - Negligible Hazard Groundwater - Very Low Hazard (alluvial well) Soil - Very Low Hazard Surface Water - Very Low Hazard 1) Bird contact with pond solutions - Medium Hazard 2) Animal contact with ponds - Medium Hazard Initiating events and likelihood: Negligible likelihood, construction quality assurance and liner testing prior to use will minimize any potential hazard Magnitude of exposure: Negligible hazard because of leak detection system monitoring and double liner reduces head gradient on lower liner reducing leakage rates to negligible volumes. Duration of exposure: Negligible hazard because of the 5 year facility life limits the potential duration. Pathways: Very low risk due to uptake of the moisture in the unsaturated upper fractured sandstone bedrock limiting migration. Environment at risk: The shallow aquifer. Initiating events and likelihood: Negligible likelihood due to control of access through fencing. Magnitude of exposure: Negligible hazard because of leak detection system monitoring and double liner reduces head gradient on lower liner reducing leakage rates to negligible volumes. Duration of exposure: Negligible hazard because of the 5 year facility life limits the potential duration. Pathways: Very low risk due to uptake of the moisture in the unsaturated upper fractured sandstone bedrock limiting migration. Environment at risk: The shallow aquifer. Initiating events and likelihood: Negligible likelihood, while extreme storms are possible the design of the pond sizing will account for this possibility. The ponds will have a minimum of 2 feet of freeboard above the maximum operational level. Magnitude of exposure: Very low risk due to specific gravity contrast between rainwater and the soda solutions resulting in the rainwater residing as the top layer in the pond during an extreme storm. Any overtopping would involve significantly diluted solutions. Duration of exposure: Medium risk, this is entirely dependent upon the magnitude and duration of the storm event Pathways: Medium risk due to the potential for overland flow of the solutions Environment at risk: Soils, vegetation, and water downstream of the ponds. Initiating events and likelihood: Negligible likelihood due to construction quality assurance, testing prior to start up, and operational monitoring Magnitude of exposure: Negligible risk due to 6 inch high curbing within the plant with a gravity flow connect to the 3 acre pond. This would allow complete containment of all process solutions stored in the tanks and vessels in the plant. Duration of exposure: Negligible exposure due to complete containment. Pathways: Negligible exposure due to complete containment in the plant. Outside the plant storm water controls will prevent flow from discharging outside the disturbed area. Environment at risk: Soils, vegetation, and water downstream of the ponds. Initiating events and likelihood: High likelihood due to exposure of open water in the winter Magnitude of exposure: Negligible risk due to low concentrations of sodium. The operation will limit the sodium concentration to below a critical toxicity level (To Be Determined in consultation with USF &WS) or in the case of upset conditions will provide hazing. Duration of exposure: Negligible risk due to low concentrations of sodium or hazing in the case of upset conditions. Pathways: High risk due to direct pathway for bird exposure. Environment at risk: Negligible risk, environmental not an issue Initiating events and likelihood: Very low likelihood due to wildlife fencing around ponds Magnitude of exposure: High risk if animals enter fenced area Duration of exposure: High risk if animals enter fenced area Pathways: Negligible risk due to control of access and no direct pathway for animal' exposure Environment at risk: Negligible risk, environmental not an issue Very low consequences due to very low hazard for soils and groun water, very low risk pathways for exposure \\ Very low consequences due to very low hazard for soils and grounrwater, very low risk pathways for exposure Very low to high consequences due to very low hazard to soils and water, and very low risk magnitude exposure while the environment at risk is high. Negligible to very low consequences due to negligible probability occurrence, magnitude, duration, and pathways for exposure. Medium to high consequences for impact to bird bouyancy and mo tality. High consequences if access is gained due to the magnitude and du ration. Negligible risk due to negligible probability of occurrence as well as negligible magnitude and duration of exposure. Negligible risk due to negligible probability of occurrence as well as negligible magnitude and duration of exposure. Negligible risk due to negligible probability of occurrence. Negligible risk due to negligible probability of occurrence Negligible risk due to negligible magnitude and duration of exposure. Negligible risk due to negligible pathway for exposure. Footnotes to Table I: Risk Assessment Components: Potential Failure Mechanisms: All identified potential mechanisms are included, regardless of likelihood of occurrence Hazard Assessment: An assessment of "what can happen ?" ranked according to risk to the environment (see Table 2) Exposure Assessment: Assessment of the likelihood and extent of any exposure. Consequence Assessment: An evaluation of the consequence of any exposure, regardless of how likely it is. Risk Characterization: An evaluation of the overall risk to the environment of the identified failure mechanism, based on the evaluation of hazard, exposure and consequence. 5 of 5 Golder Associates 993 -2057