The Alaska Contractor, Publication of the Associated General Contractors of Alaska; Fall 2007
Erv Long is in the business of freezing ground and keeping it frozen. The founder and owner of Anchorage-based Arctic Foundations Inc. began delving into the subject of permafrost within a year of beginning work with the Army Corps of Engineers in 1948.
Long began work on his first experimental thermopile in 1956 and received his first patent in 1965, followed by other patents of thermosyphons and similar ground-freezing systems.
Long and his associates at AFI have been developing, designing and fabricating ground-freezing systems in Alaska since 1972.
Since then he’s seen an increase in business as the topic of climate change becomes more heated, he said.
“Temperature change acts as a little more kick in the behind in selecting a type of foundation,” Long said.
Data collected at the University of Alaska Fairbanks Geophysical Institute indicates that from 1949 to 2004, average annual temperatures increased 3.7 degrees Fahrenheit in Anchorage, 3.9 degrees in Fairbanks, 3.3 degrees in Barrow and 3.6 degrees in Juneau.
That warming trend could be tough on Alaska’s infrastructure.
A report released in June by researchers at the Institute of Social and Economic Research at the University of Alaska Anchorage estimates damage from climate change could add $3.6 billion to $6.1 billion maintenance and replacement costs to the state’s public infrastructure.
That’s on top of the estimated $32 billion the ISER study estimates the state would spend in the next 20 years anyway maintaining and replacing federal, state, and local infrastructure.
Tundra on the move
Michael Rabe, managing principal of Anchorage engineering firm CRW Engineering Group, said the ISER report mostly matches what he and his fellow engineers are observing in the Arctic.
“We’re getting more freeze/thaws in a year, more degradation, more depth of thaw in a year than 10 years ago,” Rabe said. “That impacts foundation design.” He said contractors working in Western Alaska’s frigid climate have seen significantly more movement in the tundra’s top layer that seasonally freezes and thaws.
Typically, the active layer in Western Alaska measures between 1 and 2 feet, but Rabe said that it is increasing significantly.
“Ten years ago, we might have laid pipeline right on the tundra with the understanding we might get some ground movement,” he said.
Today increased horizontal and vertical shifting of the active layer has prompted contractors to build such pipelines on pile foundations drilled well below the permafrost, Rabe said. More thermosyphons also are being installed along the piling to pull warm air out, maintaining the permafrost’s core temperature, he said.
And that can drive construction costs up by as much as 20 percent, Rabe said.
“Adjusting construction practices has been ongoing,” he said of engineers in the state. “It’s just probably a little more prevalent with public perception of global warming.”
Other Arctic challenges
Working in Alaska’s dark, harsh environment poses a host of other unique challenges not necessarily related to climate change.
Logistics is a big one, said Angela Barr, a principal with the architectural firm Kumin Associates Inc.
Across much of Alaska, waterways are the major means of ground transportation. But some sites require needed equipment and materials to be flown in. And other still more remote sites are accessible only by cat train.
That gets quite expensive, she said. Barr recalled one project in Chalkyitsik that required an ice extension to be added to the runway so building materials could be delivered.
Changing weather patterns are shrinking the window of time when ice roads can be built, Barr said.
Duane Miller, of the Arctic and geotechnical engineering firm Duane Miller Associates LLC, said the state’s warming temperatures also have impacted the time allowed for accessing remote sites and completing the work.
“We do a lot of work in the winter when the world is frozen,” Miller said. “We’re seeing a later freeze-up and earlier breakup.”
Alaska’s permafrost is warming
Whether snowmachining, mushing dogs or transporting construction materials, people across Alaska rely on its frozen rivers as major transportation arteries in winter, Miller said.
“If it’s a mild winter, we lose our main construction road for winter work,” he said.
Early spring thaws have forced drill rigs to remain in remote villages and be barged out later, he said.
Miller said there is no question Alaska’s permafrost is warming.
Compared to 25 years ago, ground temperatures in the lower part of the Kuskokwim River have increased 1.5 degrees, he said.
However, scientists haven’t determined whether climate warming is here to stay or part of cycle.
Kumin principal Barr said its engineers and architects already are designing buildings with warming temperatures in mind. As an example, she used the design of the Norton Sound Regional Hospital in Nome where permafrost temperatures at a depth of 12 feet range between 28 degrees to 30 degrees Fahrenheit.
She said 10 years ago the design of such a structure in Nome might have called for little or no insulation under the gravel pad.
Construction for conservation
In order to protect the gravel and permafrost beneath the hospital, Kumin Associates’ designs call for 5 feet of structural fill laid over 4 inches of rigid insulation and geotextile fabric to be put in place while the Nome tundra is still frozen, Barr said.
Construction for the Indian Health Services hospital in Nome has yet to receive construction funding, though the project has received some money for design and site work.
Barr said after the pad has settled, the hospital’s pilings will be drilled 30 feet, through permafrost and set in the bedrock. Designs call for a minimum of 4 feet of air space between the top of the gravel pad and the bottom of the first floor, she said.
Barr said leaving space beneath a structure is a standard Arctic building technique that allows wind to scour through, preventing heat transfer from building to pad.
Vertical thermosyphons will be installed adjacent to pile groupings. They will also be utilized outside the south face of the building to compensate for additional heat reflected off the glazing, Barr said.
A pipe string of thermometers also will be installed along some of the piling to detect any warming of soil temperature that might occur, she said.
“It’s cheap insurance,” Barr said of the thermometers. “You think something’s moving – get hard data.”
|Changing weather forces engineers, architects to alter Arctic building techniques
It makes sense that the new Barrow Arctic Research Complex is in Barrow, given the city’s long history as a permafrost observation and research site.
Barrow’s ties to permafrost observations and research stretch all the way back to the First International Polar Year in 1882-83.
In January, the 25th Alaska Legislature designated Barrow as the state’s Arctic Science City, and the focal point for this year’s celebration of the 125th anniversary of the International Polar Year 2007-09.
The new 20,000 square-foot climate change research facility sits adjacent to the Barrow Environmental Observatory, 7,466 acres of relatively undisturbed tundra set aside for research in 1992 by the
Ukpeagvik Inupiat Corporation (UIC). The observatory is one of only a few international sites with a long history of climate observations.
The first of five phases, Phase I provides for the initial laboratory, administrative and community outreach space needed, yet also houses the mechanical, electrical and IT infrastructure that will eventually support the entire 80,000 square foot facility, according to Richard Reich, program manager for the new facility. Reich also is general manager of BTS Professional Services, a subsidiary of UIC.
A grant of $19.9 million obtained through a cooperative agreement with the National Oceanic and Atmospheric Administration provided for overall project planning, conceptual design of the entire facility and completion of Phase I, Reich said.
Designing and building the new state-of-the-art facility also was an exercise in applying the latest in Arctic design and construction techniques, he said.
Arctic environment, design consultant LCMF LLC staff had to be forward thinking in terms of how they designed the building, Reich said.
“The difficulty in using customary engineering guidelines and design parameters, such as depth for pile installation, or 100-year flood elevation data, is based on the fact that global warming is creating more coastal erosion and flooding and impacting depth of thaw in permafrost in Arctic regions,” Reich said.
“Barrow’s 50-year flood elevation has been exceeded twice in recent storm events that were less than five years apart.”
The research complex sits within a half mile of the Beaufort Sea.
The roadway and gravel pad for the facility were designed at an elevation of 13 feet – just 1 foot above the 100-year flood elevation.
To account for possible flood inundation associated with storm surges, the main floor elevation was set at elevation 20 feet, much higher than other nearby structures.
Pilings supporting the research complex were also installed much deeper than previous structures due to warming trends and increased depth of seasonal thaw, according to LCMF engineers.
“The challenge will be to determine how to economically minimize the impacts of the changing climate,” said Reich, a registered professional engineer.
BY NANCY ERICKSON
Nancy Erickson is a freelance writer who lives in Seward