Groundwater Issues Relating to an Alaskan Methanol Spill
- S.B. Robertson (Arco Alaska Inc.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- August 1992
- Document Type
- Journal Paper
- 936 - 940
- 1992. Society of Petroleum Engineers
- 6.5.5 Oil and Chemical Spills, 6.5.2 Water use, produced water discharge and disposal, 6.5.1 Air Emissions, 4.3.4 Scale, 4.2 Pipelines, Flowlines and Risers, 4.6 Natural Gas, 4.3.1 Hydrates, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 3 Production and Well Operations, 1.6 Drilling Operations, 5.2.1 Phase Behavior and PVT Measurements
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A Dec. 1989 methanol spill resulted from sabotage to three railroad tank cars. Samples taken from nearby drinking-water wells and groundwater-monitoring wells were below the analytical detection limit. Monitoring well data demonstrated that groundwater flow was not toward local residential wells. Dilution by snow and subsequent freezing in the soil limited the downward spread of the methanol, an advantage not found in milder, more temperate conditions. Contaminated material was removed and processed to reclaim the methanol. Volatilization and biodegradation should remove any remaining methanol. Cleanup options were limited by the possible hazardous waste classification of the contaminated soil. The regulatory status of spilled methanol waste should be re-evaluated, especially if use of methanol as a motor fuel increases.
Methanol is used in the oil fields of the North Slope of Alaska for freeze protection. Air temperature, ground temperature (wells are drilled through 2,000 ft [610 m] of permafrost), and gas expansion are sources of cooling that may result in its use. For example, methanol is used to protect pipelines and shut-in water injection wells, to reduce the freezing point of water vapor and hydrates in natural gas handling, and as a component in water-based hydraulic fracturing for well stimulation. Before 1990, Arco Alaska Inc.'s standard practice was to transport the material by railroad tank car to its North Star Pipeyard, a material storage and transfer facility in Fairbanks, AK. There it was transferred to tank trucks and driven up the Dalton Highway (the TransAlaska Pipeline Haul Road) to Prudhoe Bay.
On Dec. 4, 1989, at approximately 2:30 a.m., while moving tank cars on a siding in the pipeyard, the railroad switching crew noticed methanol leaking from three 30,000-gal [114-m³] -capacity cars. The crew closed the valves on the bottom of the tank cars, which had been opened by saboteurs. Special tools are required to open the valves and seals had to be broken. Graffiti written on all three cars, also indicated that sabotage was involved. The Fire Dept. and other emergency personnel were quickly called to the scene. Because of the potential fire and health risks, nearby residents inhabiting homes southwest of the pipeyard were evacuated. After organic vapor analysis demonstrated little or no atmospheric contamination and no danger of explosion, the residents were allowed to return home. Because vents on top of the cars had not been opened, a partial vacuum developed upon drainage. This prevented release of the entire contents of the cars. Subsequent measurement of the remaining contents revealed that only about 9,300 gal [35 m³] of methanol had spilled, rather than the 67,000 gal [254 m³] originally feared.
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