1999-08-23_HYDROLOGY - M1999051 - Laserfiche WebLink

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August 1999 t: \99\2057\?057f n.xls • • TABLE 1 N Footnotes to Table 1: 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. 2 of 5 Golder Associates RISK ASSESSMENT SUMMARY ^\ Wells: Poor Cement Bond Corrosion/Leakage of Cemented Casing Pipelines: Rupture of Pipeline 1) Poor cementing work leads to upward solutioning of brine along casing Subsidence - Negligible Hazard Groundwater - Negligible to High Hazard Soil - Negligible Surface Water - Negligible 2) Heat damages a good cement seal leading to loss of gas control and upward solutioning of brine along casing bond Subsidence - Negligible Hazard Groundwater - Negligible to High Hazard Soil - Negligible Surface Water - Negligible 1) Hot fluids lead to corrosion casing failure Subsidence - Negligible Hazard Groundwater - Negligible to High Hazard Soil - Negligible Surface Water - Negligible 1) Rupture of pipeline due to equipment traffic, extreme storm events or vandalism Subsidence - Negligible Hazard Groundwater - Negligible (alluvial well) Soil - Medium to high Hazard Surface Water - Negligible Initiating events and likelihood: Negligible likelihood - while poor construction practices are possible the initial well testing and fluid pad volume monitoring would identify potential problems prior to failure Magnitude of exposure: Negligible because of real time fluid pad volume monitoring Duration of exposure: Negligible because of real time fluid pad volume monitoring Pathways: High risk due to direct pathway to aquifers Environment at risk: B Groove aquifer Initiating events and likelihood: Negligible likelihood - Any damage to the cement bond leading to potential leakage would first be detected in the volume monitoring of the fluid pad. Separation of high temperatures from cemented casing by use of dual hanging string. Magnitude of exposure: Negligible because of real time fluid pad volume monitoring Duration of exposure: Negligible because of real time fluid pad volume monitoring Pathways: High risk due to direct pathway to aquifers { Environment at risk: B Groove aquifer Initiating events and likelihood: Very low likelihood - Double casing and cemented wellbore provide additional barrier to fluid loss. Any corrosion and loss of containment would first be detected in the pressure monitoring of the pad fluid. Magnitude of exposure: Negligible because of real time gas pressure monitoring Duration of exposure: Negligible because of real time gas pressure monitoring Pathways: High risk due to direct pathway to aquifers Environment at risk: B Groove aquifer Initiating events and likelihood: Very low likelihood, the pipeline will be Sch. 80 steel pipe which required substantial force for rupture. Magnitude of exposure: Medium due to rapid recognition of the pipe rupture allowing system shut down. The pipeline will be placed in a bermed corridor that drains to a lined collection pond. Conservative assumptions for leakage volume 20 mins. 400 gpm results in a maximum of 8,000 gallon spill. Duration of exposure: Medium due to rapid recognition of the pipe rupture allowing system shut down. Most of the length of the pipeline will be monitored by camera, and the system will have automated warning sirens when there is a flow difference between the wells and plant. Pathways: very low risk due to drainage control and collection, rapid precipitation of approximately 70 percent of the sodium bicarbonate as the solution cools, and local soil uptake of the moisture minimizing runoff. Environment at risk: Topsoil will be removed and stockpiled in a safe location for reclamation outside the bermed pipeline corridor. The only environment at risk is the foundation material along the pipeline. Negligible consequence due to negligible likelihood magnitude ant exposure duration of Negligible consequence due to negligible magnitude and duration of exposure Negligible consequence due to negligible magnitude. Duration of mining fluids are double - walled contained. exposure and Very low consequences due to very low risk pathways for exposur . Also the environment at risk is within the industrial disturbance area. Negligible risk due to negligible probability of occurrence and negligible magnitude and duration of potential releases to the environment Negligible risk due to negligible probability of occurrence and negligible magnitude and duration of potential releases to the environment Negligible risk due to negligible magnitude and duration of potential releases to the environment Very low risk due to the industrial nature (topsoil removal and storage in safe location) of the environment at risk, and very low magnitude and duration of potential releases to the environment thereby minimizing potential for exposure. Likewise the pathway for exposure is within a bermed area Recommended Mitigation: Emergency Spill Response Plan; Employee Training Program; Warning Signs and Barriers; Well Defined Action Levels for Agency Reporting and Remediation; Employee Environmental Protection Incentive Program 993 -2057