Better Roads Staff
“We’re doing more with less, like everyone else,” says Coffey, of Alaska DOT. “In the old days we might have had three trucks and a grader on a job, now it’s one truck and a grader. All the trucks have attachments like front plows, belly blades, and sanders so they can do multiple tasks.”
Coffey says the agency has reduced its inventory of specialized equipment, in some cases by renting, and in other by replacing specialized machines with multi-use units.
As in other places, safety problems trump all other priorities, even in this tight budget era. In the Fairbanks area, the state has recently invested in a salt-brining system to deal with a changing climate that makes the fall to winter transition longer, with more freeze-thaw cycles. Coffey says the transition begins in October and often includes heavy and freezing rains, in addition to traditional winter weather.
“We were exhausting our supply of brine that was based on a more traditional, shorter transition to winter,” says Coffey, “and that is dangerous.” The new system has five stations that produce an enhanced brine that includes sodium chloride and an organic ingredient.
In trying to stretch pavement life, Alaska’s road professionals face some unique problems. In the southeastern part of the state, cities like Anchorage and Juneau face the twin curse of soft local aggregate and a long season of studded tires that includes periods of clear streets. The result is premature rutting. To achieve a longer-lasting, more cost-effective solution, the DOT is importing harder aggregate from British Columbia for its surface asphalt mixes.
In Fairbanks and the northern part of the state, the most severe and unique road problems stem from the fact that roads are built on permafrost, which becomes a weak, unstable base when it thaws in the spring. “We can build a 20- to 25-year pavement,” says Coffey, “but the ground fails before the pavement does.”
Northern Alaska’s extreme weather and soil combination can produce awe-inspiring effects in the spring, including roller-coaster-like undulations and long horizontal cracks in the pavement. “The horizontal cracks stem from the fact that the roadway fill is thicker at the centerline and gets thinner as you move out,” explains Coffey. “If the road has a 2:1 slope, there may be 6 feet of fill under the center line tapering to 4 feet of fill just beyond the edge of the pavement. This means the center is more insulated than the shoulders from the cold and heat, and that causes the differential warming of the permafrost under the road and the damage that follows.”
As a result, Alaska reclaims a lot of surface pavement each summer in the north and invests less in traditional pavement maintenance interventions used in the lower 48 states.
The DOT has also worked to reduce the destructive effects of the pavement/permafrost temperature differentiation by developing its own snow plowing tactics. “We’re in the refrigeration business,” laughs Coffey. “To reduce the effects of differential heating, we’ve been experimenting with plowing the road shoulders when we clear the streets. If the snow is piled on the shoulder, it insulates that ground and increases the temperature differential between the pavement and the ground next to it, which causes cracking.” The shoulder-plowing technique has been an effective tactic in reducing that problem.
For Fairbanks’ maintenance supervisor Potter, the plowing solution is an important one. “We can’t use chemicals in much of the winter because our temperatures are too low,” he says. And winters are much longer in Fairbanks than elsewhere in the U.S. — “our temperatures go below zero F by the end of October and ground temperatures remain below zero F well into April.”
Potter’s road management interventions include prolific use of foamed asphalt and cold recycling, as well as warm-mix asphalt and some testing of open-graded asphalt.
Cities Taking Action
Paul Klope and the city of Eugene, Ore., serve to remind us that local governments find the means to do what must be done. Eugene, a city of 138,000 in west-central Oregon, passed a five-year, $36-million bond measure in 2008 to repair the city’s long-neglected roads. This, combined with a city gas tax, federal STP-U (Surface Transportation Program–Urban) funds, some recent state and county funding and a chunk of Stimulus money ramped up the funds to provide what Klope calls “an amazingly robust” pavement program. These funding levels will continue for at least another couple of years.
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