Ribbons of tundra ice
Evolving ice-road construction techniques extend North Slope exploration seasons
With virtually all exploration drilling on Alaska’s North Slope done in the winter when snow and ice protect the tundra from vehicles and other equipment, the construction of ice roads has become a vital factor in maximizing the length of the annual exploration season. Consisting of multiple layers of solid ice formed by spraying water along a required transportation route, ice roads melt and disappear in the summer, typically leaving no trace of their existence within a relatively short time.
Government agencies only allow vehicles to operate off the regular North Slope road system in appropriate winter conditions, when the ground is sufficiently frozen and the snow cover sufficiently deep to protect the delicate Arctic tundra: The construction of ice roads enables operators to build the necessary tundra protection along required transportation routes.
And at the ice and snow road conference in Anchorage on March 30 experts in ice-road construction provided insights into the evolving world of ice-road design.
Extended seasonsGary Schultz from the Alaska Department of Natural Resources, the agency that oversees off-road travel on state land, described to the conference the particular value of using low-impact, tundra-certified vehicles to pre-pack snow and spray water along a road route, before the natural snow and ice conditions reach the threshold for the general opening of winter tundra off-road travel. In years with low snow coverage, the road construction crew may even use ice chips from frozen lakes instead of snow for this type of pre-packing operation.
The pre-packing enables an early start to road construction, prevents winds from blowing the snow cover from the road route, speeds up the freezing of the ground and provides maximum protection to the tundra, Schultz said.
“Pre-packing works really, really well,” he said.
Early planningBut successful ice-road construction depends on the planning, permitting and stakeholder communication that starts as much as a year before the ice road is needed, said Jeff Osborne from ConocoPhillips, a company that makes much use of North Slope ice roads.
And a key component of this planning is the clarification of the scope and purpose of the road, as a prelude to applying for the necessary permits for road construction, Osborne said.
“Take the time … to understand the work and who’s going to utilize the ice road,” Osborne said. Then, having established the scope, allow for the unexpected by permitting the road for a bigger operation than is planned, he said.
It’s best to check out the potential ice-road routing during the winter prior to the one in which the ice road is needed, Osborne said. It may prove beneficial, for example, to pre-stage equipment at a distant point on the route, to enable an early start to road construction — pre-staging equipment is best done during the winter off-road travel season, perhaps using an ice road built in that earlier winter. It is also essential to book the helicopter time needed to survey the route during the summer, given the high demand for summer helicopters use.
“The earlier you can get in front of what you need to do, the better off you are,” Osborne said.
Summer route planningSummer is then the time for discussions with landowners and government agencies about ice-road plans, while figuring out the precise route to be followed and determining any archaeological clearances that might be required.
One issue in route planning is the avoidance of ponds with water more than two feet deep, because these ponds will not be fully frozen by January and so could wreck havoc when a heavy load traverses an overlying road.
“You’d better go out and fly (the route) and walk it,” Osborne said, commenting that some ponds may be too small for depiction on a map.
September and October are the months to meet with contractors to pin down a realistic road construction schedule and to set parameters for safety and other considerations.
It is also necessary to obtain approval from government agencies to start pre-packing the road route. And once construction of the road is complete, the opening of the road brings issues that include road maintenance, the establishment of security checkpoints and perhaps the publication of a milepost guide for drivers.
The ice road is closed out at the end of the winter season, but the ice-road project doesn’t end until August of the following year, when, following aerial surveys of the road route by helicopter, it is necessary to apply to the government agencies for final close out.
Jeff Miller, general manager of Cruz Construction, a company with extensive experience of building ice roads, confirmed the importance of early planning and good communications in ice-road projects.
Local knowledgeMiller emphasized the importance of using local knowledge of an area where an ice road is planned. He also commented on the importance of identifying suitable water supplies for road construction.
“We need this information early, so we can figure out deals and make sure that we’re going to be able to hit the (water) production that we anticipate,” Miller said.
And during the summer the Cruz Construction would typically install ground temperature measuring equipment and weather stations along the road route, in preparation for the construction season, he said.
Miller confirmed the value of pre-packing the ice-road route prior to the winter tundra travel season, using summer approved vehicles.
“To me this is the most important part of the construction process. … If it’s done right, it’ll just set the framework for making a pretty successful project,” Miller said.
Schultz also emphasized the importance of surveying road routes during the summer, when it is possible to see what type of tundra vegetation covers the ground and plan routes that cross the more resilient vegetation types. It is also possible to use data from geographic information systems to assess the vegetation cover, he said. There is also a project in progress to develop a new North Slope map depicting the vegetation cover.
“That’s something that would be really useful for planning the ice-road routes,” Schultz said.
Melissa Head from DNR said that she has been assembling vegetation cover data, to help companies with ice-road planning.
Sedge most resilientExperience over multiple ice-road construction seasons has shown that sedge vegetation is especially resilient to any ice road impacts, Schultz said.
“In all the ice roads we’ve monitored after construction we’ve never seen a measurable impact on wet sedge vegetation,” Schultz said. There was an instance where there was some thickness reduction in the active growth layer in moist sedge along an ice-road route, but that disturbance recovered within about four years, he said.
Tussock vegetation is, however, much more delicate than sedge and takes a long time to recover from any disturbance, Schultz said.
“The bulk of the plant is above ground,” he said. “… Tussock tundra is just really a challenge for ice-road construction.”
The pre-packing of snow and the side-casting of water onto a road route have proved especially beneficial in protecting tussock tundra, Schultz said. He cited the example of a road pre-packed particularly early, ahead of the winter 2008-09 off-road travel season in the White Hills area of the North Slope. This road had to cross ground with tussocks but caused virtually no damage to the tussock vegetation, with the road location barely visible on the ground when checked out after the snow and ice had melted, Schultz said.
On the other hand, Head cited an example of a winter trail in the Brooks Range foothills, where tundra travel had opened but where it turned out that thin snow conditions in the area of the trail had resulted in significant tussock damage from vehicles. A similar trail in a higher-snow year had little tundra impact, she said.
Gordon Brower, deputy director for the planning department in the North Slope Borough, said that local knowledge from subsistence hunters on the North Slope confirms that wet areas of sedge vegetation are among the best places to travel.
Brower said that the borough works with North Slope operators to try to improve ice-road construction from one year to the next. A major issue for the borough is how ice roads under construction in the fall might impact the migration of caribou, he said. Involving local people with their experience of the land in the road permitting process has proved valuable, he said.
Stream crossingsMatthew Whitman, a fisheries biologist with the U.S. Bureau of Land Management, spoke about the design of ice-road stream crossings. With a need to minimize impacts on winter fish habitats, stream locations that freeze over completely in the winter are best for these crossings, he said.
And with several species of Arctic fish using North Slope rivers and streams as migration routes for spring spawning, effective slotting and breaching of stream crossings at the end of the winter are especially important, Whitman said. For example, stream channels after breaching need to be broad enough to allow free fish movement and to avoid excessively fast water currents.
“By far the most prevailing problems are due to not breaching the crossing,” Whitman said. “… On the other hand when crossings are slotted or breached properly they appear to be largely meeting their objectives.”
Decision support systemGiven all of the ice-road-impacting variables such as temperatures, snow depths and stream crossings, the U.S. Department of Energy is sponsoring the development of an Internet-based ice-road decision support system for ice-road planning. The system development, conducted by PBSJ Corp., Texas A&M University and the University of Alaska Fairbanks, is in the second year of a three-year program slated to end in September 2011, said Stephen Bourne, a project manager in PBSJ.
The system will integrate a wide variety of data, including North Slope topography, hydrology and vegetation, to help assess the optimum route for a proposed road. The idea is that if a system user specifies the end points of the road, the system will assemble all relevant data, analyze options and present the relevant information and potential routes to the user, said Kelly Brumbelow, associate professor of engineering at Texas A&M.
Michael Lilly, president of GW Scientific, told the conference about a computer-based decision support system that his company is developing in partnership with ConocoPhillips, DNR and BLM, with DOE funding, to improve the efficiency of the winter ice-road transportation network on the North Slope, including ice roads that support existing oilfield operations.
The objective is to improve various aspects of Arctic transportation by gaining a better understanding of factors such as snow distribution, soil strengths, soil temperature forecasting and water use, Lilly said. The system will enable access to a large amount of data relating to ice-road construction, he said.
Loss of experienceThere was also discussion at the conference about the loss of experienced people, in both designing and building ice roads, as the workforce ages. Walker said that quite a bit of important knowledge about construction on the North Slope tundra has already been lost.
Miller said that Cruz Construction makes sure that it trains people who can work with and ultimately replace retirees who leave the company.
“We have a training program that does just that,” he said.
And Osborne commented on the importance of ensuring that people coming out of high school and college realize that it takes several seasons on the Slope to really learn the ropes. Building ice roads is not something that people can simply learn to do in a classroom, Osborne said.