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What the Liberty environmental impact statement will consider Minerals Management Service will look at six alternatives, including different island location, deeper pipeline burial Kristen Nelson PNA News Editor
The Minerals Management Service held scoping meetings in 1998 in Anchorage, Barrow, Fairbanks, Kaktovik and Nuiqsut and published a scoping report which identifies significant environmental issues and alternatives which will be evaluated in the environmental impact statement — and also identifies alternatives which will not be evaluated further in the EIS.
Among the alternatives which will not be evaluated in the EIS are alternative island construction, alternative pipeline routes and construction and alternative gravel sources.
The agency said that while alternative island proposals were received during the scoping process, it evaluated them and determined that BP Exploration (Alaska) Inc.’s proposals for developing Liberty on a new island is adequate.
The old Tern Island exploration site is too far from the center of the reservoir. Some of the reservoir could be developed with extended reach wells in the 18,000-22,000 foot range, but, MMS said, the largest volume of reserves are in the far west and would not be produced from Tern Island.
Building the island closer to shore in 6-foot water depths would require extended reach wells in the 25,000-27,000 foot range, and “would make the project nonviable and cost prohibitive.” Similarly, developing Liberty from onshore would require 25,000-40,000 foot extended reach wells. The agency said it does not believe this would be technically viable; in addition, it would be cost prohibitive.
Using the caisson-retained island which has drilled exploration wells in the Beaufort Sea would require extensive redesign and modification — and could only be used for drilling. It is inadequate for other facilities.
Some pipeline routes, gravel sites eliminated Alternative pipeline routes which will not be pursued in the EIS include routing through the Boulder Patch to Endicott — dropped because of environmental consequences to the Boulder Patch, a sensitive underwater area lying between the Liberty project and Endicott; taking unprocessed oil to Badami for processing — dropped because of internal corrosion potential and the possibility that hydrates could plug the pipeline if low flows occurred at low temperatures; casing the pipeline and directionally drilling through the transitional zone — dropped because of problems of corrosion with buried casings.
The Oxbow lake system on the Kadleroshilik River will not be considered as a mine site because it is vegetated; the Sagavanirktok River already has a fish over wintering site while the lower Kadleroshilik does not; gravel at Tern Island is both insufficient and unsuitable; other abandoned gravel sources reasonably close to Liberty are not large enough.
Six alternatives to be evaluated Alternatives which MMS will evaluate in the EIS include BP’s proposal, a no action alternative as required by the National Environmental Policy Act, steel island construction, a different island location and pipeline route, a Duck Island gravel source and burying the offshore pipeline deeper in a 15-foot trench.
BP’s proposal is for a self-contained offshore drilling and production facility on a conventional gravel island and associated subsea pipelines to shore connecting to existing onshore pipelines.
The slope protection for the Liberty island includes a bench protected with concrete map slope armor with a system of overlapping gravel-filled bags at the top of the bench. The entire slope protection system lies on top of a durable and permeable filter fabric to prevent leaching of sediment into the water column.
The concrete mat provides structural protection. The bench and gravel bags dissipate wave energy and limit ice ride-up potential. BP said in its development and production plan for Liberty that the gravel-filled bags — which are at the top of the bench — do “not allow frequent exposure to damaging waves and ice, and loss of gravel bag fabric debris is expected to be negligible.”
The bag fabric will be polyester which is, BP said, heavier and about four times stronger than the polyethylene bags used in construction of 1980’s exploratory islands. Bags will be inspected annually, before breakup, and any damaged bags either repaired or removed and replaced.
Steel island alternative The steel island construction alternative will, MMS said, address a major issue identified in scoping — concern over whether the gravel bag island design is adequate and whether the gravel bags present a threat to navigation and to the environment. The steel island alternative would use steel fabrication (as at Northstar) rather than the gravel bags.
The fourth alternative is a southern island and eastern pipeline route. BP’s proposed island site is in 22 feet of water in Foggy Island Bay. At the Barrow scoping meeting, it was proposed that MMS look for alternatives that would put the island in 15-20 feet of water to reduce the impacts to bowhead whales.
MMS said it evaluated the suggestion and found that most locations that meet the criteria were too far away or place the island too close to the Boulder Patch. Moving the site into 15 feet of water would increase both risks and costs, and decrease the amount of resources that could be developed, and would in effect, MMS said, be the same as the no action alternative because the project would no longer be economically feasible.
One site near the southern boundary of the federal lease was identified that is in 20 feet of water and is along the alternative eastern pipeline considered by BP in its evaluation process, although it is closer to the Boulder Patch. It reduces the offshore pipeline from 5.5 miles to 4 miles, although it increases the onshore portion of the pipeline by more than a mile and will require additional drag-reducing agents to be added to the sales oil product.
MMS will evaluate this southern island and eastern pipeline route as an alternative in the EIS.
Different gravel sourcedeeper BP proposes to mine gravel for the Liberty project from an island in the Kadleroshilik River and rehabilitate the site so that it would flood and be available for use by fish as an over wintering habitat. MMS will evaluate an alternative gravel source on Duck Island.
BP proposes to bury the offshore portion of the pipeline in a trench 7 feet deep. The MMS trenching alternative would bury the pipeline 15 feet deep, doubling the amount of dredged material. Digging a pipeline trench deeper than 15 feet, MMS said, would make the project uneconomical, so deeper trenching will not be evaluated.
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