If you could tour the pipeline route

Foothills, Brooks Range portion of gas line route runs between Arctic National Wildlife Refuge, Gates of the Arctic National Park

Bill White

Researcher/writer for the Office of the Federal Coordinator

Alaska LNG project sponsors often remind people it’s really three projects - a gas treatment plant on the North Slope, a long pipeline bisecting the state and a liquefaction plant at coastal Nikiski. Each would cost billions of dollars, and need tons of steel, thousands of workers and years to construct.

But the middle segment of this trinity - the 800-mile natural gas pipeline from Prudhoe Bay to Nikiski - is the symbol of Alaska’s 40-year quest for North Slope natural gas development.

The project sponsors are still working out the exact route for the 42-inch-diameter pipeline, testing soils, searching for earthquake faults, scoping the most buildable corridor with the least environmental impact and the fewest construction problems. It’s all part of their preliminary front-end engineering and design efforts, expected to last through 2015. The “study corridor” is 2,000 feet wide. The pipeline’s ultimate right of way and footprint would be much narrower.

Preliminary maps filed in February 2015 with the Federal Energy Regulatory Commission provide a general path the sponsors and their teams are reviewing.

If you could walk, drive or fly over the route, this is what you would see and could learn about the people and places along the way. (We consulted a variety of public filings from current and past projects along the corridor, as well as other publications, in preparing this narrative.)

Miles 65 to 240: Foothills and Brooks Range

The pipeline here would cross the northernmost advance of the Anaktuvuk Glaciation, which occurred perhaps 100,000 years ago. It was one of the older of several glaciations in recent Brooks Range ice ages that helped sculpt the mountains into their present topographic profiles.

Near Milepost 90. The Happy Valley camp is a former pipeline construction camp and current base for road crews and a leisure and recreation operator offering meals, lodging and flightseeing trips over the Brooks Range and Arctic flats.

The oil pipeline crosses to the west side of the Sag River a few miles back and angles back to the east side a few miles to the north. The gas pipeline would hug the river’s east bank, as does the Dalton Highway.

The gas pipeline’s route is generally plotted but not finalized. Alaska LNG says the gas pipeline would cross the oil line multiple times. But the specific locations and exactly how the crossings would be constructed are details to be worked out. Pipeline safety regulators would have to sanction the crossings. Alaska LNG’s engineers are working on the plans. Typically, the gas line would go under the oil line, but it could rise over its older cousin. Note, however, that Alaska LNG plans to bury the gas line along most of its route, while the oil line is above ground for a good portion of the 400 miles that the lines run parallel.

Plans are similarly unspecific for road crossings. The gas pipeline would parallel the Dalton Highway for about 400 miles and the Parks Highway farther south for about 200 miles, according to Alaska LNG filings with the Federal Energy Regulatory Commission. Besides the Dalton and Parks, the pipeline would parallel or intersect 44 other roads. Typically, a pipe is buried well below the roadbed, and stronger steel gets used for the pipeline because of the extra weight it will bear.

Near Milepost 110. The oil pipeline’s Pump Station 3 is still operating. Only four of the 11 started up by 1980 still pump the oil today.

Because of glaciation, the Brooks Range hills often feature glacial moraines covered with loess. Whatever the soil type, ice commonly is found in it and permafrost under it. Because the surface layer - called the active layer - can thaw seasonally, and the ground can be sloped, movement called solifluction (saturated surface layer slowly slides downhill) can occur and must be avoided or engineered around when a pipeline is buried. Gelifluction is even possible, in which relatively flat saturated soils atop frozen ground start to creep.

Near Milepost 115. The pipeline would have been on state-managed land to this point. Now it would be crossing onto federally managed land. Soon it would be running a gauntlet between the Gates of the Arctic National Park and Preserve to the west and the Arctic National Wildlife Refuge to the east. The preliminary route would have the pipeline avoid both areas, although it would pass within 0.2 miles of ANWR at its nearest point, roughly 35 miles south of here.

To the west lies Slope Mountain, elevation 4,010 feet, composed of sedimentary rocks deposited about 100 million years ago. Across the Sag River to the southeast is one of the older archaeological sites in northern Alaska, with human evidence - charcoal within loess - from as long as 10,000 years ago.

Near Milepost 130. Another 20 miles down the Dalton is the Toolik Field Station. The University of Alaska Fairbanks’ Institute of Arctic Biology runs the station, and scientists there study arctic ecosystems and global climate change. The station provides meals, lodging, laboratories, mapping services, equipment and environmental data to visiting researchers from around the world. But it’s closed to the public.

The preliminary gas pipeline route would have it zig to the east a few miles before Toolik then zag back in sync with the Dalton Highway and oil pipeline several miles south of the science station.

Near Milepost 145. Here lies Galbraith Lake, which once occupied the entire Atigun Valley. The lake is named for Bush pilot Bart Galbraith, who died in a 1950 plane crash while flying from Barter Island off Alaska’s northeast coast to Barrow. The Native name is Natravak, which means “big lake,” a name shared by many water bodies in a state with perhaps 3 million lakes.

The lake is a notable landmark along the route because of the nearby campground with picnic tables and bear-proof containers for tent campers. The Dalton is a corridor for hunters - bow hunters. No firearm hunting along the oil pipeline, please. Moose, caribou and Dall sheep are among their targets.

Today’s hunters follow a long tradition of pitching camp here. Archaeological evidence found near the lake during oil pipeline construction in the 1970s indicates humans had used the area for thousands of years.

The Alyeska Pipeline Service Co., which runs the oil pipeline on behalf of the oil company owners, also has buildings nearby Galbraith Lake and there is an airstrip.

Near Milepost 150. Alyeska’s Pump Station 4 is here. It is the last pump station tasked with pulsing North Slope oil over the Brooks Range. It also sits at the highest elevation among the oil pipeline’s pump stations, at 2,760 feet. This wouldn’t be the gas pipeline’s highest elevation, however. That spot lies roughly 25 miles ahead at Atigun Pass.

The pipeline would have said farewell to the Sag River by now. The Atigun River would lie just west and escort the line for a while, up a broad valley pocked with wet sedge meadows.

The Brooks Range would be all around. The mountains span northern Alaska and part of Canada’s Yukon Territory. The tallest peaks along the pipeline route top 8,000 feet. The pipeline would be in the range or its southern foothills for another 100 miles or so.

The terrain is generally rugged, with land shaped by alpine glaciers and eroded over time into cirques and U-shaped valleys, talus slopes and alluvial fans. Past glaciation shoveled coarse-grained sands and gravels, now typically frozen, beneath sometimes-peaty soils. Permafrost still is the norm, although on the Brooks Range southern slopes some discontinuous permafrost can be found.

Near Milepost 175. Atigun Pass at 4,739 feet would be the pipeline’s apex.

This is a tricky channel. The gas pipeline would need thread through without disrupting the road or oil pipeline, which is buried in places because of avalanches and falling rocks.

The pass approach is steep - the highway gains/loses about 1,000 feet both north and south in just a few miles. The pass proved problematic for the oil pipeline in its early years, with damage from buckling and settlement on either side before Alyeska figured out Atigun. In places Alyeska has buried the oil line in insulated concrete cribbing, or added steel supports, or slid a concrete slurry beneath the line for support.

Atigun Pass is the Brooks Range’s continental divide. Rivers north of it, such as the Sag and Atigun, drain to the Arctic Ocean. Rivers south drain to the Bering Sea.

The southern flanks offer the classic collection of Alaska critters: caribou, Dall sheep, brown bear, beaver, marten, mink - each in its own preferred habitat, of course. Moose density increases the farther south one goes as the foraging grounds improve. Arctic ground squirrels live in colonies on well-drained mountainous tundra, and they are meals for bear, wolves, wolverines and weasels.

Near Milepost 181. The pipeline would cross the Chandalar Shelf, a mile-long plain that offers impressive views looking east toward the Chandalar River headwaters. The vista is unobstructed by trees. On descending the shelf, the route would cross the tree line’s northern extreme. Some very old white spruce might be found around here.

The name “Chandalar” is a slur from the name Hudson’s Bay Co. French employees, based in Fort Yukon, gave Gwich’in Indians along the river. They called them “Gens de Large,” or “nomadic people.” When later transcribed into English, voila: Chandalar.

Near Milepost 183. The pipeline would exit the North Slope Borough for the first time. At 95,000 square miles, the borough is an Alaska-sized local government. If a state, its area would rank it 12th largest, just behind Michigan and ahead of Minnesota. The gas pipeline would not again penetrate a local-government boundary until around Milepost 420.

The Dietrich and Koyukuk rivers systems start here. These have steeper gradients and are extensively braided.

The Alaska LNG project sponsors have told regulators that on this portion of the route they prefer to follow river valleys, where thin soils cover bedrock, or thin surface peat might cover rock fragments at the foot of cliffs or sand, silt and rocks deposited by the moving water. “For example, thin peats and wet mineral soils with shallow permafrost are present where the Mainline corridor traverses valley bottoms along the Dietrich and Koyukuk rivers,” they told the Federal Energy Regulatory Commission in February 2015. Up higher in the Brooks Range, soils are thin to nonexistent.

Near Milepost 205. This is around the northern limit of the paper birch. Black spruce trees - some leaning - are common enough by now. Tree cover still is thin, though.

The Dietrich River will join the Koyukuk’s middle fork just ahead. The preliminary route would place the pipeline on the Koyukuk’s west bank for the first two or three miles before it crossed over to the east bank for the next 20 miles or so to the town of Wiseman, the first community it would encounter.

Near Milepost 225. Wiseman lies just west of the oil pipeline and Dalton Highway. It also would be just west of the gas line.

Wiseman would signal the gas pipeline’s passage onto ground linked to Alaska’s gold-mining history. The region from here south on the line’s route was where some of Alaska’s first economic boom played out roughly 100 years ago.

Editor’s note: This is a reprint from the Office of the Federal Coordinator, Alaska Natural Gas Transportation Projects, online at www.arcticgas.gov/if-you-could-tour-pipeline-route. The Office of the Federal Coordinator closed March 7. Until further notice, this website is preserved for research and informational purposes by the U.S. Arctic Research Commission and is administered by the Alaska Resources Library and Information Services at the University of Alaska Anchorage. Part 1 of this story ran in the July 19 issue.