It’s the second-to-last week in February, and Dave Schnabl of Alaska Interstate Construction (AIC) is hoping for below-freezing temperatures at the job site.
One might think that when you’re working about 95 mi. (152 km) northeast of Anchorage, like Schnabl and his crew, the last thing you’d hope for is colder weather. But sub-freezing temperatures are needed in order for crews to build a temporary ice bridge that will help them construct a 360-ft. (109 m) concrete bridge over Hicks Creek, along the Glenn Highway.
Once the weather cooperates, it will only take two or three days to create the ice bridge using a water truck filled from the creek. After crews have built up the frozen surface of Hicks Creek, vehicles will be able to drive across and deliver girders for the permanent bridge. The piers and abutments for the three-span bridge have already been completed.
Building ice bridges is run-of-the-mill for AIC, the Anchorage-based company which takes on projects in arctic and sub-arctic areas of Alaska and Russia.
“If we didn’t have freezing temperatures in Alaska, we’d have to span [the creek] with a temporary bridge,” said Schnabl, project superintendent. “This is an easier method, when you can use Mother Nature to help you out.”
Once the ice bridge has served its purpose, AIC will dig it up and remove it while it is still frozen, which should result in little to no impact on the creek’s ecosystem.
Replacement of the Hicks Creek Bridge is part of a $26.2-million project that will improve safety and capacity from Glenn Highway’s milepost 92 to milepost 97.
Those 5 mi. (8 km) are part of a 135-mi. (217 km) section of Glenn Highway, beginning in Anchorage, that was designated a National Scenic Byway in 2002. Just a short drive from the job site is Matanuska Glacier State Recreation Site, from which visitors can see the miles-long glacier and the Chugach Mountains.
The Hicks Creek/Glenn Highway project, which broke ground April 2007, includes pavement reconstruction, some roadway re-alignment, and the creation of passing lanes, as well as the replacement of the Hicks Creek Bridge and installation of 2,297 linear ft. (700 linear m) of culvert.
All told, the project consists of more than 2.3 million cu. yd. (1.8 million cu m) of excavation, 35,800 sq. yd. (30,000 sq m) of geotextiles, and more than 3,580 sq. yd. (3,000 sq m) of a structurally engineered steel mesh for soil stabilization.
During the first construction season, April through November, AIC accomplished about 75 percent of the drilling and blasting phase: 107,600 sq. yd. (900,000 cu m) out of 1.5 cu. yd. (1.2 million cu m) total shot rock. AIC used five Ingersoll Rand ECM 590 rock drills and a Morooka tracked vehicle for hauling powder to the holes.
After a short seasonal hiatus, construction began again in February. Although weather is still a factor at this time of the year, increased daylight allows for efficient daytime operations. AIC expects to finish drilling by early this summer.
To date, crews also have placed approximately 50 percent of type C material, and completed nearly 25 of 35 culverts. Future phases will bring the roadbed up to grade and pave the entire length, as well as complete and pave the new Hicks Creek Bridge.
For the heavy civil work, AIC utilized Caterpillar dozers, excavators and rollers (D10s, D8s, D7s, D6s, 365, 330, 315), Volvo articulated trucks (A35s and A30s), Euclid B70s, Ingersoll-Rand ECM 590 drills and Volvo loaders.
Structurally, AIC has used a Manitowoc 777 crane, a hydraulic Link-Belt rough terrain crane, and a Genie 80-ft. (24 m) manlift.
AIC owns approximately 80 percent of the equipment employed on this job; 20 percent was rented because some of AIC’s fleet was committed to other projects.
AIC has faced many challenges on this project so far, mostly related to unexpected geologic conditions. In one area, AIC discovered a significant amount of additional overburden, compared to the geotechnical data. Gaining access to high, steep areas of rock also complicated blasting and excavation.
Despite these challenges, the federally-funded project is currently on schedule for completion in June 2009.
“The success of the Hicks Creek project is overwhelmingly due to the positive attitude and technical competence of my crew,” Schnabl said. “They have maintained safe and efficient production in all types of weather, and brought down a million cubic meters of earth on some of the most difficult terrain to work in.” CEG