Going-to-the-Sun-Road: Construction and Restoration
Glacier National Park is nearing completion of a major rehabilitation of one of its most popular features.
Going-to-the-Sun Road in Montana's Glacier National Park attracts millions of visitors each year to enjoy a drive through its beautiful scenery of lakes, streams, mountains, and facilities. Established as the tenth park in the Nation on May 11, 1910, Glacier National Park covers more than 1 million acres (400,000 hectares), including 175 mountains and 26 glaciers, with the Continental Divide essentially cutting the park in half. The 50-mile (80-kilometer) Going-to-the-Sun Road runs along and over these steep mountains. The elevation at Logan Pass, located in the midsection of the road and the highest point accessible by car, reaches 6,646 feet (2,026 meters).
"The road is not just a way to travel, it's a destination in itself," says Michael Traffalis, a project manager in the Federal Highway Administration's Western Federal Lands Division.
Its construction was a marvel of design and engineering in the face of unique challenges. Rustic stone masonry features include bridges, drainage structures, and horse underpasses. These significant features have led to Going-to-the-Sun Road being recognized as a Civil Engineering Landmark in the National Historic Register and as a National Historic Landmark.
However, decades of rockslides and avalanches, severe weather, and heavy traffic left the road in urgent need of repair. Without aggressive action, the historic structures for which the road is so admired might have been lost. In 2007, the National Park Service (NPS) and FHWA embarked on a monumental rehabilitation project, which is now coming to a close.
Collaborative Planning and Construction
The construction of Going-to-the-Sun Road launched a national cooperative agreement between the NPS and the Bureau of Public Roads (a predecessor of FHWA). At the time, it was the largest construction project ever undertaken by the two agencies.
In 1918, George Goodwin, the first NPS engineer, planned a route that became the guideline for the initial transmountain road construction in the early 1920s. Goodwin's proposal was similar to the current road, except that it would have made a steep climb up Logan Creek using 15 switchbacks before reaching the Continental Divide at Logan Pass. A later adjustment, suggested by NPS landscape architect Tom Vint, adopted an alternate approach requiring only a single switchback.
During the early 1920s, Congress provided annual appropriations of $100,000 for construction of the road. With this money, the park signed contracts to begin construction at both ends of the road. In 1924, Glacier's appropriation increased to $1 million for a 3-year road construction program.
Frank A. Kittredge of the Bureau of Public Roads directed a 1924 survey for the road. The project, which mapped out 21 miles (34 kilometers) over the Continental Divide, started in September, and Kittredge raced to finish the survey before winter weather ended activity. He and his team of 32 men often climbed 3,000 feet (914 meters) each morning to get to survey sites. The crew walked along narrow ledges and used ropes to suspend themselves over cliffs to take many of the measurements. The work was too challenging for some, and Kittredge's team suffered from a 300 percent labor turnover in the 3-month work period.
The road was an early example of context sensitive design. While the Bureau of Public Roads provided road-building expertise, NPS landscape architects, together with the Bureau's engineers, created the specifications for the road, working to blend it into the surrounding environment. The landscape architects required that the bridges, retaining walls, and guardrails be made of native materials. The engineers ensured that the integrity of the road and construction practices met the required safety standards of the time. Most of the structures along the road consisted of rock excavated from the adjacent mountainsides during construction. Contractors had to use numerous small blasts of explosives because large blasts would cause more destruction of the landscape. However, despite the architects' recommendation to exclude the use of power shovels, workers employed them because the expense of a road built exclusively with hand labor was too great.
The engineers, landscape architects, and laborers faced sheer cliffs, short construction seasons, snow, and removal of tons of rock to open the road. After more than 12 years of engineering and construction, the first automobile traversed the full 50-mile (80-kilometer) roadway in late 1932. The NPS officially opened the road in a dedication ceremony on July 15, 1933, and named it Going-to-the-Sun Road. It has endured since as one of the park's most popular features.
Reconstruction and Rehabilitation
By the mid-1990s, the NPS and FHWA worried that the road's structural integrity was in such disrepair that the road might have to be closed to visitor traffic. This led to a rigorous planning effort, starting with a $1 million appropriation for studies and reports that led to the alternatives outlined in the Going-to-the-Sun Road environmental impact statement, completed in 2003. An advisory committee recommended a shared-use approach to reconstructing the road with short weekly delays, shoulder season closures, and a visitor bus shuttle service.
Project planners estimated that rehabilitation work would take 7 to 8 years, pending funding. FHWA estimated the cost of the decision, including economic and visitor access mitigation, to be between $140 and $170 million.
As a first step, the NPS and FHWA's Western Federal Lands Highway Division jointly developed and implemented the Glacier National Park shuttle system in the summer of 2007. This shuttle bus system provided alternative transportation access and maintained capacity to accommodate visitors during reconstruction. The system continues to provide a means to reach Logan Pass.
Construction Strategies
The project implemented a number of strategies to minimize the impact to park visitors and reduce costs. Strategies used to improve building efficiencies included more night work when the NPS could implement long public road closures. Engineers worked with contractors to modify or adjust details to increase effectiveness for weather conditions, adjusting seasonal construction limits to match production rates to maximize work days.
One of the major cost-reducing strategies concentrated existing funds on the alpine section, the area in most need of repair. In contrast, the lower sections were subject to less extreme weather and experienced less freeze-thaw damage, so their masonry features were in better shape and the pavement in better condition.
To minimize gaps in construction time, crews moved from high elevations to low elevations based on weather factors. Spring construction work was done at lower elevations. The overall construction season stretched from April 1 to December 15, but work at higher altitudes took place from mid-June to mid-September when weather was not such a limiting factor. One complication was that these months account for the heaviest concentration of visitors, so the roadway had to remain accessible for tourists.
Overcoming Challenges
Construction began in 2007 and was substantially completed in 2019, with a few final efforts remaining, including masonry repair, vista clearing, staging area management, and construction of guardrails in isolated spots. The NPS and FHWA anticipate completing these final projects this fall.
The extensive project faced myriad challenges. In addition to the difficulties presented by the weather and the geography, these included maintaining shared use—limiting traffic delays to 30 minutes, accelerating shoulder season work, providing transit service during rehabilitation, and improving visitor use—by providing visitor orientation, information, and interpretation. The planners also needed to minimize effects on natural, cultural, and scenic resources; minimize impacts on local and regional economies; and limit the management of vegetation, all while completing the work within the planned timeframe and managing funding levels.
"The most important objectives were minimizing economic impacts, getting the transit system up and running, and maintaining visitation," says Traffalis.
Adjusting to Weather Conditions
The high alpine section had a tight weather window. Logan Pass can receive an annual accumulation of up to 80 feet (24 meters) of snow in the winter, and snow often continues into the summer months.
Construction relied heavily on the shoulder seasons, between the visitor peak of summer and the inaccessibility of winter, when the park closes its gates for snow plowing in the spring or winter preparations before the snow. This enabled construction to take place without public traffic. Snow runoff in the spring made construction difficult. Culverts plugged up with ice during the winter, resulting in water sheeting down the shoulder of the road and flowing over historic masonry rock walls, causing damage and making erosion control critical. As part of the rehabilitation project, crews constructed a series of gutters to direct the runoff flow to designated areas to avoid erosion.
The water flow also made paving in the spring difficult due to high water levels and runoff on the road. The surface had to be dry in order to pave, so the engineers typically had to wait until fall to pave. The road also had to be drivable between mid-June and July, so the construction was phased to have at least a temporary hardened roadway surface in place by winter shutdown. The park needed this temporary surface to enable both spring snow plowing and anticipated summer traffic. These weather considerations combined with a significant drop in tourists after Labor Day created a short window in the fall before October snows arrived to pave the alpine section.
Geographical Challenges
The limited width of the road made it difficult to move visitor traffic around construction equipment. Some areas were only 8 feet wide. Tunnels with restricted height clearance, such as Half Tunnel, meant that dump trucks could not completely lift to unload materials. Paving required a lot of handwork throughout the alpine section. In this area, paving had to be done up against guard walls and the exposed rock wall face.
On numerous occasions, ice and rock falls damaged construction equipment, workers' personal vehicles, and government vehicles. Unstable slopes and rockfall above the roadway required limiting rollers to no vibratory compaction of the road surface for the safety of the workers and public.
Rockfall mitigation work required completing a rockfall hazard rating system inventory along the entire roadway. The work included inventorying and rating rockfall-prone slopes to prioritize mitigation efforts. Engineers selected high-rated slopes for risk reduction and mitigation methods with minimal visual impacts. These methods involved slope scaling within 50 feet (15 meters) of the roadway, rock bolts with anchorage assemblies (bearing plates) removed, and sections of colored and textured shotcrete. The coloring and texturing preserved the historic appearance of the road.
The project used rock bolt reinforcement, the insertion of steel rods to provide support to a rock face, when scaling was not an option, usually when encountering large stone formations. The bolts were driven deep into the rock—15 feet (4.5 meters) or more—tensioned, then grouted solid. Engineers recessed the surface cover plates and covered them with colored masonry to match adjacent rock.
Assessing and Repairing Damage
The rehabilitation and reconstruction project included permanent repairs for areas of the road that had temporary measures installed in the past, as well as wear-and-tear damage from heavy use. In 2006, Glacier National Park saw one of the heaviest November precipitation events on record. The storm dropped approximately 11 inches (28 centimeters) of rain on top of 8 inches (20 centimeters) of snow over a short period, causing severe erosion of the slopes and six major failure locations. The storm washed out 120 feet (37 meters) of road, and FHWA used mechanically stabilized earth walls along with a temporary bridge to span one large erosional ravine along Going-to-the-Sun Road.
To permanently repair the damage, the reconstruction project installed stone masonry consisting of 582 square yards (487 square meters) of veneer, 1,233 linear feet (376 meters) of ashlar, and 574 square feet (53 square meters) of random rubble. Engineers reinforced a stone masonry wall, showing signs of instability and located where access was prohibitive, using micropiles. The crew installed the micropiles down through the existing stone masonry wall and into the underlying bedrock. The cap stones were replaced following construction to conceal the repairs.
The outboard lanes—those nearest the outer edge of the road—showed signs of fill slope settlement failures. The reconstruction stabilized the fill slope shoulders by placing flexible geogrid and select rock material in lifts under the surface. Pressure grouting stabilized the outside lanes, combined with underdrains, improved ditching, and culvert replacements. The project used a total of 6,900 cubic yards (5300 cubic meters) of riprap in some areas for slope repair.
The bridges and tunnels of Going-to-the-Sun Road are subject to extreme weather conditions. Over their service life, they have all experienced extensive freeze-thaw damage to exposed edges of the bridges and portals of the tunnels. The assessment team found additional deterioration in the stone masonry railing and piers, widths not meeting current standards, poor conveyance of stream hydraulics, porous concrete, and rising stream bed loads. Stream beds rise due to glacial melt, which releases thousands of years of rock frozen within—a challenge throughout the entire Northwest. As streambeds rise, the hydraulic capacity of existing culverts and bridges is negatively affected.
All of the bridges and tunnels included historic features. Following the NPS mission of preserving and protecting structures, engineers were charged with restoring the bridges in lieu of complete replacements. To accomplish this task, the NPS and FHWA partnered with cultural and historic preservationists, landscape architects, materials-testing firms, contractors, and resource biologists to develop custom solutions for each structure.
These activities required fully assessing and documenting existing conditions, evaluating those elements of the bridge that were still contributing (historic) features, and then undertaking strategies of restoration to remove and replace freeze/thaw-damaged concrete, reseal porous concrete, repair masonry, and clean channels. Teams cleaned each masonry face using relatively low-pressure washing and scrubbing with nylon brushes to expose the masonry and its grouted joints.
Innovating for Sustainability and Preservation
The project implemented several innovations to preserve the original features wherever possible and to minimize costs and labor.
In particular, the project reused existing asphalt concrete pavement in the structural pavement layers of the repaved roadway. The recycled asphalt pavement (RAP) was used throughout Going-to-the-Sun Road in two different forms. The first served as a direct one-to-one replacement for the aggregate base layer. This material was easier to maintain under traffic because it reduced dust and it required less maintenance and rework.
For the second recycling method, the RAP was hauled from the project, mixed with an engineered emulsion, and brought back to the construction site as a cold recycled asphalt base. This process reduced emissions because no hot plant was used, only a pugmill with emulsion and water injected into the material. The cold recycled asphalt became a structural layer placed directly below the alpine concrete pavement. The RAP mixture is twice as strong as an aggregate base layer and provided an opportunity to use sustainable materials, reduce the need to produce virgin materials to use on the project, use existing materials that were already within the project limits, save time and money, and reduce the carbon footprint inherent in using traditional methods. The use of RAP enabled Glacier National Park to lead the recycling efforts applied by the NPS.
In addition to recycling material, significant efforts went into assessing existing guard walls and guardrails to preserve as much of the original work as possible. For the areas where repair was unavoidable, only minor structural work, underpinning, and repointing were needed. When replacement was the only option, project engineers used a combination of rebuilding the masonry rails or replacing them with log railings or avalanche-resistant masonry rail.
These techniques alone could not solve the problem of yearly avalanche damage that would continue to occur. To address the issue, the NPS and FHWA developed a removable, crash-tested, log-guardrail system. These removable log rail sections have been installed within defined avalanche zones. The sections are taken out at the end of the tourist season and reinstalled the following year.
"This innovative feature prevents costly avalanche damage to the guardrails and ends the cycle of yearly replacement costs to sections of the roadway damaged by avalanches," says Traffalis.
Project Successes
At a cost of more than $160 million, the completed road reconstruction, rehabilitation, and repair project that began in 2007 has been largely completed. The work included retaining walls, arches, bridges, and tunnels; guard walls and removable guardrails; other roadside improvements; drainage; slope stability; pavement; transit system (buses, transit stops, and transit center) enhancements; and two new visitor center entrance stations. Visitor improvements at pullouts included upgrading trails for accessibility and several construction upgrades to view points. Additional viewing areas were enhanced with "crow's nests" to give visitors a true immersive experience. Turnouts were equipped with new interpretive panels, and the Sun Point visitor area adopted new interpretive messaging.
Other than the addition of the transit stops for the park shuttle operation, project engineers and architects ensured that the roadway would retain its important and inherent historic character through attention to fine details, such as using materials to match the historic character of the original road. The materials were salvaged from repair and construction segments, gleaned from roadside salvaging and sealing, or quarried and shaped from outside sources.
The investment into Going-to-the-Sun Road is nearly complete, with one remaining cleanup contract scheduled for this summer to repair any features that sustained wear and tear since the rehabilitation began. The NPS and FHWA can now welcome the hundreds of thousands of visitors that Glacier National Park receives per month during the open season.
"Today, Going-to-the-Sun Road is in better repair than ever before," says Traffalis, "Ushering in the next 100 years of the NPS opening its doors to visitors from all over the world."
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Major accomplishments include:
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Doug Hecox is the senior career spokesman with FHWA's Office of Public Affairs. He has a journalism degree from the University of Wyoming, has published two books, and teaches journalism and public relations writing at American University.