Artificial island to be built to support Alaska oil field project

The US Bureau of Land Management has published an environmental impact assessment for an oil field to be developed in the Arctic Alaska.

Energy provider ConocoPhillips wants to develop an oil field in the North Slope of the National Petroleum Reserve in Alaska under its Willow Master Development Plan. The area is estimated to hold 750 million barrels of oil.

The Native Village of Nuiqsut criticised the plans in 2018, saying, “We’re already experiencing negative impacts from existing development in the region and are feeling the effects from infrastructure and development activities circling our community. This project will involve an entirely new central processing facility, an airstrip, a gravel mine, and offshore barging activity. The additional aircraft traffic and offshore barging alone are potentially significant to our community’s subsistence hunting and whaling practices, in addition to the pipelines, pads, and roads while will further encircle us.”

Part of the project will include building a modular transport island (MTI) in the Harrison Bay to support module delivery for the Willow development. Modules for the Willow Central Facility (WCF) and drill sites would be delivered by sea lift barge to the MTI in 2023.

The environmental impact assessment describes the works as following:

“The MTI will build through placement of gravel fill from the Tinmiaqsiugvik area gravel mine in up to 3 m of water to a height of approximately 4 m above mean lower low water [MLLW]. The MTI will include a 55 m2 gravel work surface surrounded by side slopes with gravel bag armour slope protection, and a 61-m sheet pile dock face at 5 m above MLLW to facilitate barge offload.

Gravel haul and placement to construct the MTI will occur via ice road during the 2021/2022 winter season as soon as the ice roads have been completed. Winter island construction would occur from an ice pad located adjacent to the MTI site. Sea ice within the MTI footprint will be cut and removed at the island site and gravel will be pushed into the opening until the design volume and approximate shape of the island have been attained.

Installation of the sheet pile offload dock would occur once the initial gravel placement is sufficient to support pile driving activities and staging of materials and equipment. Sheet pile will be installed over a period of approximately 25–30 days, with about three hours of actual pile driving occurring per day using only vibratory driving equipment.

During the following summer open water season, construction equipment will be transported to the island by local barge, likely from Oliktok Point. Workers to support summer construction will be housed at a 100-person camp located on a barge moored on or near the island. Work on the island will recommence around early to mid-July once the risk of ice encroachment has passed.

The gravel work surface will be reworked and compacted to eliminate interstitial ice, and the gravel surface will be graded to the final design. Large, prefabricated filter fabric panels will be installed on the side slopes by crane, and slope protection, in the form of 3 m3 gravel-filled bags, will be installed from the seafloor to the work surface.

Finally, concrete footings for module storage will be installed on the compacted work surface. All construction equipment not needed for subsequent activities on the island will be demobilised as soon as summer construction activities are completed.

Modules would be offloaded by sea lift barges onto the MTI in 2023, after sea ice breakup but before the beginning of the whaling season. Modules would be stored on the concrete footings installed during the previous summer construction season and skirted to prevent snow and wildlife from moving underneath the stored modules.

At the end of the island design life, all gravel slope armouring and other anthropogenic materials will be removed from the island, and the island will be reshaped naturally by waves and ice. Based on observations from 16 exploratory islands in the Beaufort Sea, the MTI will be reshaped into a crescent reminiscent of a natural barrier island. The top of the island will likely drop to or below the water surface about 5 years following abandonment.

ConocoPhillips is continuing to evaluate alternative module transportation options; however, the MTI has carried out the proposed project description at this stage.”