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State issues commissioner’s analysis for Northstar pipeline right-of-way leases Public hearings scheduled for Barrow, Anchorage, on proposed decision, draft leases for oil, gas pipelines Petroleum News Alaska Staff
The State Pipeline Coordinator’s Office has issued the analysis for the Northstar oil and gas pipeline right-of-way, a proposed decision and draft right-of-way leases.
The analysis by the commissioner of the Alaska Department of Natural Resources, signed July 6, reviews BP Exploration (Alaska) Inc.’s proposal for the two pipelines.
Written comments on the analysis, proposed decision and draft right-of-way leases will be accepted through close of business Aug. 20. Public hearings on the right-of-way lease applications will be held in Barrow Aug. 17 and Anchorage Aug. 20.
A final decision is anticipated within approximately 90 days of the close of public comment. If public comment indicates the need for substantial changes or additional analysis, additional public notice will be given on or about Nov. 1. If the commissioner, after review of comments received during the public comment period, does not find cause to amend the analysis or proposed decision, the analysis and proposed decision will become the final decision without further notice.
Capacity of crude oil line could be increased Recovery from Northstar is estimated at 145-172 million barrels of high quality crude oil. The 17.1-mile crude oil pipeline from the Northstar production facility on Seal Island to pump station No. 1 of the trans-Alaska pipeline is designed for 65,000 barrels per day. The commissioner’s analysis noted that, with modifications, the capacity could be increased to 70,000-75,000 barrels per day; and with additional modifications the capacity could increase to 85,000-90,000 barrels per day if additional pumping capacity was installed.
Design transportation capacity of the 16.3-mile gas pipeline is 100 million cubic feet per day. The gas pipeline will carry gas from the central compressor plant at Prudhoe Bay to Northstar for reservoir management and to provide fuel gas to Seal Island. Both pipelines will be 10.75 inches in diameter. Pipe materials for offshore installation have been specifically designed to withstand arctic conditions including ice gouge, ice scour and permafrost thaw subsidence.
The oil and gas pipelines will occupy the same right-of-way for approximately 13 miles from Seal Island to the point where the gas pipeline turns east to the central compression plant at Prudhoe Bay. The offshore portion of the pipelines will be buried in a six-mile long trench from Seal Island to approximately 150 feet south of the landfall near Point Storkersen.
The analysis says the “Northstar pipeline designs include pipe specifically engineered and manufactured for the environmental conditions along the rights-of-way.” The pipes have five times the flexibility required for the ice conditions and are 2.5 times thicker than required by industry design standards. The pipelines have dual leak detection systems and shutoff valves will be placed on both ends of the offshore pipelines. The pipelines burial depth is 3.5 times deeper than the deepest ice gouge recorded in the area and a 6-9 foot depth of backfill over the trenched buried pipelines will provide additional protection.
The offshore pipelines will transition to above ground on a 70-foot by 135-foot gravel pad, which will be constructed with a protective gravel berm to support the pipelines. The buried pipelines will have, at the time of construction, a setback of approximately 150 feet from the existing shoreline before the pipelines are elevated on vertical support members.
The analysis states that remedial action will be required to address shoreline erosion should the shoreline encroach to within 50 feet of the riser, or earlier if remedial action is determined by the commissioner of DNR to be necessary to maintain a safety margin and access.
The gravel pad will house the valve at the transition and will also serve as a helicopter landing area. Other valves will be at Seal Island, at the central compressor plant, and on each side of the Putuligayuk River crossing.
The pipelines take separate routes from an area approximately 3 miles north of pump station No. 1. The oil pipeline will turn southeast, across the Putuligayuk River and along existing pipelines north of the Spine Road to the vicinity of Pump Station 1 and will parallel the Endicott and Lisburne pipelines into the Pump Station 1 facilities. The gas pipeline travels west from the central compressor plant and follows the alignment of existing pipelines running to the C pad until it intersects the route of the Northstar oil pipeline.
Majority of pipeline construction in winter The majority of the pipeline work will be done during the winter from ice pads and an ice road along the right-of-way. Offshore work will be on grounded and floating sea ice with a thickened ice bridge to support construction.
A major portion of the construction work is proposed for the winter seasons from December 1999 through the fourth quarter of 2001. Offshore construction includes ice road and ice pad construction, trenching, pipe testing, pipe welding, pipe laying and trench back fill. The offshore construction will begin in December 1999 and continue until closure of winter tundra travel in the early spring of 2000.
Onshore construction will begin in the fourth quarter of 2000 and continue until closure of winter tundra travel in the early spring of 2001, and will include: landfall set back and pad construction, drilling and setting vertical support members for the pipeline, and pipe welding, testing, placement and pressure testing.
Limited summer construction will include installation of pipe casings at existing road and caribou crossings; pipeline installation activities at the central compressor plant, including tie-in and possible gravel work; pipeline installation inside and outside the fence area at pump station No. 1; pipeline vibration monitoring and restoration at the shoreline transition.
Start up of the Northstar oil pipeline is scheduled for the fall of 2001. The Northstar gas pipeline may start up as early as the end of 2000.
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