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Publication Number: FHWA-HRT-08-008
Date: November 2007
Alaska's unique terrain provided a valuable learning experience for participants in an August 2007 maintenance technology scanning tour organized by the Western Maintenance Partnership pooled fund program. Sponsored by the Utah Department of Transportation, the 3-year pooled fund is designed to promote effective maintenance strategies and to share experiences, innovations, expertise, and solutions in managing highway assets. Pooled fund participants include Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, Oklahoma, Texas, Utah, Washington State, and Wyoming, as well as the Federal Highway Administration (FHWA).
Hosted by the Alaska Department of Transportation and Public Facilities (DOT&PF), the tour featured stops along the Glenn Highway, the Trans Alaska pipeline, and the Prince William Sound. Topics of discussion included the DOT&PF's maintenance management system (MMS) and pavement management system (PMS), winter maintenance activities, and avalanche control work.
"It was particularly helpful to be able to talk one-on-one in small groups and learn from what Alaska is doing," says tour participant Ken Shultz, State Maintenance Engineer for the Wyoming Department of Transportation. "The maintenance challenges that we face out West, including high winds and mountainous terrain, are very different than those in urban areas."
|Alaska's varied terrain and maintenance challenges were the focus of the Western Maintenance Partnership's 2007 technology scanning tour. The tour included a visit to the Tazlina Maintenance Station in the State's Northern Region (below).|
The DOT&PF manages 9,012 centerline km (5,600 mi) of highway, 258 airports, marine highways, a State equipment fleet, and public facilities that include 643 buildings and 29 ports and harbors. The department frequently faces severe weather-related challenges, including landslides, flooding, avalanches, and tsunamis.
To effectively manage these responsibilities, the DOT&PF uses an automated MMS to track assets such as roads, bridges, airports, and water ports. The system reports the condition rating of an asset by latitude and longitude and allows the sharing of geographic information system (GIS) mapping of an asset with the public via the Internet. Now in use at all State maintenance stations, the MMS accurately tracks levels of services, including materials used, personnel hours, and equipment costs. "The system has been helpful statewide," says Jack Fullerton, Chief of Maintenance and Operations for the DOT&PF's Central Region. "We are in our second year of using it and we are starting to see the benefits, including assistance in better tracking costs and budget planning."
The department's innovative PMS, meanwhile, displays road pavement conditions using the Google EarthTM program. Prior to 2005, PMS data was displayed on maps in a PDF format created with GIS. These maps were accessible on the Web, but they were not interactive. Since 2005, map layers have been created for use in Google Earth that allow the user to more readily display and analyze pavement conditions relative to other reference data, including pavement photos that are taken every 15 m (50 ft). The maps also have a zoom/pan feature and easy-to-use interface and can easily be converted from GIS.
With visits to the Nelchina and Tazlina district offices, the scanning group was introduced to the challenges that permafrost presents to the construction and maintenance of highways in the State's North Region. Mike Coffey, M&O Manager in the North Region, noted that permafrost is defined as any rock or soil that has remained below 0 °C (32 °F) continuously for 2 or more years. Permafrost underlies approximately 85 percent of the Alaskan landscape and can vary from a couple of inches to over several thousand feet in depth. Approximately $10 million is spent annually in the North Region to address the effects of thawing permafrost, which often results in uneven settlement and pavement cracking and rutting. The DOT&PF normally constructs roadways on a 1.2-m (4-ft) subbase. This subbase serves as an insulation layer that protects the underlying permafrost and minimizes the build up of reoccurring frost. In some locations where changes in the permafrost are particularly active, the DOT&PF may have to add several additional feet to the subbase.
|Alaska uses an automated maintenance management system to track assets such as roads, bridges, airports, and water ports.|
Hairpin Thermosyphons and Air Convection Embankment (ACE) are two passive cooling systems used to minimize permafrost thawing. Thermosyphons works by moving heat from the permafrost layer to the air using compounds, such as freon or carbon dioxide, that change from liquid to gas and back at the proper temperature. ACE, meanwhile, uses the cooling characteristics of a clean, coarse rock layer to prevent an embankment from thawing. The use of large rock allows air to circulate through the embankment more vigorously during the winter when air temperatures are lower. The net effect is an enhanced cooling of the embankment and the permafrost layer below. By supplying enhanced cooling during the winter months, the permafrost is able to survive the warmer summer season.
Another challenge the department faces is keeping the Alaskan bridge network free of ice. To combat this continual problem on the 457-m long (1,500-ft) Knik River bridge, the DOT&PF installed an automated anti-icing system. The system relies on electronic sensors embedded in the roadway to record temperature and humidity conditions and assess whether the pavement is wet or dry. The system can then determine when ice will begin to form and spray anti-icing chemicals accordingly. One sensor performs its own quality control check by constantly heating up and cooling down to track the temperature at which ice will begin to form. "The system is working very well," says Fullerton. "This was a high accident area prior to installing the system, but last year no accidents were reported."
The DOT&PF's avalanche control program relies on the experience and knowledge of its team members. Hundreds of avalanches occur each winter on paths that threaten Alaska's highways, with about two dozen avalanches blocking roads annually. Department staff use a 105-mm howitzer field gun at established shooting platforms along the roadways to neutralize a potential avalanche.
The tour concluded with a visit to the 4-km (2.5-mi) Anton Anderson Memorial Tunnel in Whittier, which is the longest highway tunnel in North America. It was also the first U.S. tunnel with jet turbine and portal fan ventilation, the first to use computerized regulation of both rail and highway traffic, and the first tunnel designed to withstand temperatures below 4.4 °C (40 °F) and 241 km/h (150 mi/h) winds. Cars and trucks approaching the tunnel are separated from buses, and vehicles are then queued in a staging area. Cars and trucks are metered into the tunnel at 15-second intervals, while buses are metered in at 45-second intervals. At the speed limit of 40 km/h (25 mi/h), it takes approximately 7 minutes to drive through the tunnel from one end to the other.
For more information about the 2007 Western Maintenance Partnership Scan Tour, contact Christopher Schneider at FHWA's Office of Asset Management, 202-493-0551 (email: email@example.com). To learn more about the Western Maintenance Partnership, contact Richard Clarke at the Utah Department of Transportation, 801-965-4120 (email: firstname.lastname@example.org). The Partnership will hold its next scan tour in September 2008 in Wyoming.
|Alaska's Anton Anderson Memorial Tunnel in Whittier is the longest highway tunnel in North America.|
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