Engineering
The finished Kwethluk K-12 School was designed to protect the building from spring flooding that is common in the area.

Stantec

Engineering
The finished Kwethluk K-12 School was designed to protect the building from spring flooding that is common in the area.

Stantec

Arctic Infrastructure Ingenuity
Engineering keeps old and new buildings stable and safe
By Vanessa Orr
C

ompanies that specialize in Arctic construction spend years perfecting their craft under the harshest conditions. As in many cases in Alaska, logistics plays a huge part of any undertaking.

“Any sort of development starts with the question, ‘How do you get there?’” says Jim Campbell, PE, principal engineer and president of PND Engineers, Inc. “Almost any project that you want to build in the Arctic requires that you build roads. While a small number of projects are roadless, most are not.”

“Building roads to some of these sites is no trivial task, either,” adds PND Principal and Lead Geotechnical Engineer Torsten Mayrberger, PE. For example, on one oil and gas project a company found a considerable amount of oil, but it required a 100-mile access road over extremely rugged terrain and fourteen bridges to reach it. “In that case, it was so expensive to get to the resource that the company had to weigh the costs to determine if it could still be profitable.”

Logistics also affects where a project can be built, especially in cases where soil conditions are unknown, according to Jeremiah Holland, PE, senior geotechnical engineer at DOWL. “Much of the work in the Arctic is done in remote locations where companies may not know the subsurface conditions,” he says. “Before we can start any design, we need to go explore the area with a drill rig or other tools. This requires personnel and equipment, which drives project costs up quickly.”

He gives the example of prospective projects around Nome. “On the shoreline, the soil could be thawed, while on the tundra it may be frozen five feet down,” he says. “That’s why we drill; it’s a challenge to know what we’re dealing with.”

Building on Permafrost
According to Holland, designing for a building on permafrost is inherently complicated. “You’re putting a warm building on frozen ground, which gives you two options—you either protect the permafrost or you thaw it,” he says. “In most cases, we go with protecting it, especially in areas where permafrost is pervasive.”
The water storage tank for the fire-suppression system at the Kwethluk K-12 School is perched atop a steel piling to keep it above any seasonal flooding.
The water storage tank for the fire-suppression system at the Kwethluk K-12 School is perched atop a steel piling to keep it above any seasonal flooding.

Stantec

In order to keep the ground frozen, buildings may be constructed at-grade on refrigerated gravel pads using passive thermosiphons or elevated above ground on thermopiles. Passive thermosiphons and thermopiles are long, sealed, steel pipes installed into the ground beneath the structure, with radiator fins or the top few feet of the thermopile exposed to cold air at the surface. Natural convection forms as pressurized gas exposed to cold winter air chills to liquid and drops down to the warmer permafrost.

DOWL recently provided geotechnical engineering design and recommendations for several projects built on permafrost including health clinics in St. Michael’s and Shishmaref, which are supported on thermopiles. A warehouse in Nome and a water treatment plant in Kotzebue will both be supported on refrigerated pads.

If permafrost thaws, buildings can experience severe settlement. “It can be as subtle as a few inches all the way to catastrophic failure,” says Holland.

This image shows the hinge between the top of the ramp and the structure at Kwethluk K-12 School. The hinge allows for the ramp to be useful as ground elevation changes.

Stantec

This image shows the hinge between the top of the ramp and the structure at Kwethluk K-12 School. The hinge allows for the ramp to be useful as ground elevation changes.
This image shows the hinge between the top of the ramp and the structure at Kwethluk K-12 School. The hinge allows for the ramp to be useful as ground elevation changes.

Stantec

“The general rule of thumb is if it’s frozen, keep it frozen, and if it’s thawed, keep it thawed,” says Bruce Hopper, PE, SE, associate and senior structural engineer at Stantec. “You need to consider the soil properties underneath. If it’s dry gravel, it’s not a problem. But in the southwest region, the soil is about 40 percent water, so you use the ice to make the load transfer happen.”

One increasing concern is that the thaw rate has substantially increased over the years, meaning that buildings that were expected to last a certain amount of time are failing at an alarming rate.

“In Nightmute, the school foundation built in the 1980s has failed as a result of the permafrost changing much more rapidly than was originally anticipated,” says Hopper. “When we were hired to build an addition, we found that the bottom of the stairs, which were built at grade in 1984, were now three feet above the ground.”

“The general rule of thumb is if it’s frozen, keep it frozen, and if it’s thawed, keep it thawed.”
—Bruce Hopper
Senior Structural Engineer, Stantec
PND and its drilling partners designed and constructed a light, mobile enclosed drilling sleigh that protects personnel from the environment. It can be pulled by lighter, more efficient tractors across the tundra without disturbing underlying vegetation.

PND

PND and its drilling partners designed and constructed a light, mobile enclosed drilling sleigh that protects personnel from the environment. It can be pulled by lighter, more efficient tractors across the tundra without disturbing underlying vegetation.
PND and its drilling partners designed and constructed a light, mobile enclosed drilling sleigh that protects personnel from the environment. It can be pulled by lighter, more efficient tractors across the tundra without disturbing underlying vegetation.

PND

Stantec is putting the new foundation deeper into the ice to provide more freezing capacity in the thermopile. They are also putting a hinge at the top of the stairs that will allow it to transform from a bridge into a ramp as the site settles over the next thirty years.

“You want to provide a design that will last for the building life, and that’s difficult with climatic conditions changing,” says Holland. “It’s a challenge to try to use the latest data to build something that will perform well in the Arctic for the next twenty to thirty years.”

Maintenance and Multiple Uses
Since it’s so difficult to get materials to a building site, the last thing designers want to do is create something that requires constant upkeep.
“Much of the work in the Arctic is done in remote locations where companies may not know the subsurface conditions. Before we can start any design, we need to go explore the area with a drill rig or other tools.”
—Jeremiah Holland
Geotechnical Engineer, DOWL
“From the project onset, the design team needs to work with the building’s users and owners to select materials that are durable and easy to maintain,” says Giovanna Gambardella, principal and architectural services manager for Stantec. “For example, custom siding is much harder to replace than a finish that is easily restocked. It is important that materials and building systems are selected collaboratively.”

“Sometimes, repairs may require highly skilled individuals that are not available in a village; flying people in to fix things is an added cost,” says Stantec Associate, Senior Architect, and Building Technology Specialist Ross Timm. “That’s why you want to make a building as simple as possible to maintain. That way, the owner may only need to bring in someone once a year from Anchorage or Fairbanks.”

Using the right materials is also important.

The timing and magnitude of spring breakup flooding on the rivers and streams in the Arctic are important considerations in the design and operation of structures in the area.
The timing and magnitude of spring breakup flooding on the rivers and streams in the Arctic are important considerations in the design and operation of structures in the area.

PND

“Yearly temperature variations can be extreme, especially in the Interior, so you have to use materials that are proven to work in these conditions like insulated metal panel siding,” says Timm. “You want to avoid more cutting-edge materials used in the Lower 48 or in Anchorage because this is not the place to test projects for the first time. You’re taking a big risk.”

Not only do designers need to know what materials will work—for example, some metals and plastics turn brittle in the Arctic cold—but they also need to think of the added expense while the building is under construction. “Certain sealants can’t be installed when it’s cold and concrete can’t be poured in the extreme cold,” says Timm. “You have to seal up the building envelope and add tenting or heating to do interior finishes; these are all added costs.

“A lot of contractors aren’t familiar with these issues, so you really have to have one who is experienced in true Arctic construction,” he adds.

Another concern is that many buildings, especially in rural villages, have multiple uses. Schools, for example, may not only be used for educating students but also serve as community centers and emergency shelters.

“You need to enhance the building to accommodate for that, increasing the structural design and taking into account safety factors to deal with wind, ice loads, earthquakes, and more,” says Hopper.

“All villages in Alaska are required to have a school, and it’s usually the nicest building in town,” adds Campbell. “While a village may not have a wastewater treatment system or potable water system, when you build the school, you need to provide that infrastructure, which makes it more expensive.”

A lot of Arctic construction is pre-fabricated elsewhere so it can be assembled quickly. “In the Lower 48, material costs drive each project; in the Arctic, labor and transportation costs drive prices,” says Mayrberger. “You reduce the amount of labor, you reduce costs.”

The Kuparuk bridge and roadway system, designed by PND, allows passage of annual floods and ice flows.

PND

The Kuparuk bridge and roadway system, designed by PND, allows passage of annual floods and ice flows.
The Kuparuk bridge and roadway system, designed by PND, allows passage of annual floods and ice flows.

PND

When building in the Arctic, it’s also important to respect the people—and the places—where things are built.

“Up here, there’s a really high value placed on making sure that the environment is protected; we think about minimizing our footprint as well as minimizing when and how we do work so that we don’t disturb fish and animals,” says Campbell. “This affects every aspect of the project—in a good way.”

PND also considers indigenous cultures in its design process. “We want to cause the least disturbance to their daily lives and also show respect for historical sites,” says Mayrberger. “In the whaling season, for example, all barges and marine construction stops. It’s a very cooperative process, and most people take it seriously even without the regulations.”

Water Issues
While the first choice is to avoid areas where flooding or spring break-up takes place, it’s not always easy to know where that might occur. In many places in Alaska, flood mapping is nonexistent and there are no stream gauges in place to provide the needed data.
The water treatment plant in Kotzebue is built on a refrigerated pad to keep the permafrost beneath it frozen.

DOWL

The water treatment plant in Kotzebue is built on a refrigerated pad to keep the permafrost beneath it frozen.
The water treatment plant in Kotzebue is built on a refrigerated pad to keep the permafrost beneath it frozen.

DOWL

“In the Lower 48, material costs drive each project; in the Arctic, labor and transportation costs drive prices.”
—Torsten Mayrberger
Lead Geotechnical Engineer, PND
When PND built the Colville River Bridge two years ago, they had to take into account that for at least a couple of weeks each year, the normally serene landscape would change.

“During spring break-up, the river is a nasty place,” says Mayrberger. “There are ice floes 30 feet in diameter and 7 feet thick roaring down the river. We had to design the bridge with ice breakers as part of the pier foundation so that the ice could ride up on ramps. There, the weight of the floe causes it to break so it can be redirected from the bridge foundations.”

PND has also designed bridges that can go underwater for a few days during peak flooding, similar to road crossings that go underwater in places vulnerable to flash flooding, like Arizona.

According to Chase Nelson, PE, a DOWL project engineer, in Arctic regions keeping water and wastewater systems above freezing is a challenge, as is protecting the frozen ground around heated water and sewer systems. “Melting the frozen ground and permafrost by introduction of a heated system can have fallout for other infrastructure, like the roadway above the pipes and adjacent buildings,” he explains.

Arctic water systems are designed to maintain constant circulation for freeze protection, and many systems include add-heat systems where the potable water is heated before distribution. Many communities also find ways to keep the water and sewer pipes heated, such as an electric heat trace or a glycol heat trace that accompanies the water and sewer mains.

Nelson adds that all water and sewer mains in the Arctic are designed with insulation around the mainline and an external pipe jacket to keep the fluid inside above freezing while protecting the surrounding frozen ground.

Bethel and many communities with significant ground movement from freeze/thaw cycles engineer aboveground pipes, because ground movement can damage the pipes. Kotzebue, on the other hand, buries its water and sewer mains in the shallow active layer above the permafrost.

“The pump station reservoirs often need to extend well into the permafrost, so the reservoir must be insulated to keep the surrounding permafrost frozen and the wastewater in the wet well above freezing,” explains Nelson, noting that a cooling system is often added to both above and below ground structures.

Little Time to Work
While construction winds down in the Lower 48 as winter approaches, it ramps up in the Arctic.

“The construction season usually runs from January to mid-April, which is a very small window to do a lot of work,” says Campbell. “Unfortunately, the window has been getting smaller in the last few years—April 15 is usually the end of the season.”

There are a lot of challenges with working at this time of year, including below freezing temperatures and darkness. “These temperatures are not good for man or machine,” says Hopper. “We’ve been delayed a month on jobs because of machines breaking. At Eielson Air Force Base we lost a month on a steel frame building because it was too cold to weld. This makes a major impact on scheduling.”

In addition, extreme wind conditions can make it impossible to keep temporary plastic sheeting in place, and lighting sites is also very difficult. Barge schedules and the availability of charter and commercial flights also limit opportunities to get materials in.

Despite the challenges, those who design and construct Arctic buildings find ways to make it work.

“The key word is resiliency—that’s what it’s all about,” says Gambardella. “You design it into whatever the facility is.”