Some serious lumber

June 16, 2008

Last fall, the Washington State Department of Transportation (WSDOT) broke ground on a project to replace a stretch of unique guardrail in a unique location.

The historic significance of the 1930s log rail, and its location along a scenic byway and within a state park, meant that WSDOT had to meet the needs and regulations of multiple agencies before beginning construction. WSDOT developed a new barrier that replicated the appearance of the original log rail and met current safety standards for guardrail.

Maintaining Deception

Last fall, the Washington State Department of Transportation (WSDOT) broke ground on a project to replace a stretch of unique guardrail in a unique location.

The historic significance of the 1930s log rail, and its location along a scenic byway and within a state park, meant that WSDOT had to meet the needs and regulations of multiple agencies before beginning construction. WSDOT developed a new barrier that replicated the appearance of the original log rail and met current safety standards for guardrail.

Maintaining Deception

State Rte. 20 in northwest Washington passes through Deception Pass State Park and is the only land connection between Whidbey Island and the mainland. The park is one of the most popular in Washington, with 4,134 acres for camping and hiking and access to thousands of feet of both marine and freshwater shoreline. Visitors nationwide come to enjoy the park’s sheer cliffs, water views, forests and abundant wildlife.

The Civilian Conservation Corps (CCC) originally constructed the portion of S.R. 20 within the park in the mid 1930s. Part of that construction included the installation of a stone masonry bollard and log rail system to mark the edge of the road and prevent vehicles from running off of it. The bollards and log rails, as well as two nearby bridges, are eligible for the National Register of Historic Places due to their age, association with the CCC effort, quality of workmanship and importance to the surroundings.

Their historical and aesthetic value meant that WSDOT’s original plans to replace the bollards and log rails with W-beam guardrail were not well received by the Washington State Parks and Recreation Commission or the State Historic Preservation Office. These groups failed to reach a consensus on a design, or whether log rail replacement was really necessary.

“Our data showed that traffic and collisions were both on the increase, and the log rail wasn’t adequate to withstand strikes by today’s larger vehicles,” WSDOT Engineer Omar Jepperson said. “On the other side, we had the park and other groups saying, ‘Hey, you need to consider the history and visual appeal of the current log rail as well as regulations regarding their protection.’ We realized we needed to be sensitive to their concerns while educating them about ours.”

Highway usage has changed significantly since the 1930s. The population of Island County was 5,369 back then, but has grown to more than 78,000. Average daily traffic (ADT) is 15,000, and the 85th percentile speeds vary between 36 and 45 mph. Within the two-mile section of S.R. 20 inside Deception Pass State Park there were 10 collisions in 1980 and 22 in 2000. Fifty percent of the collisions involved vehicles hitting fixed objects along the roadside, with 45% of those involving the log rail. Sixty percent of the collisions involving the rail resulted in an injury. The majority of collisions occurred during the summer, which is the peak tourist season.

Beauty and brawn

WSDOT brought together multiple organizations, including the Island County Public Works, the Federal Highway Administration, Washington State Parks and Recreation, the State Office of Archaeology and Historical Preservation, and the Washington State Patrol to brainstorm solutions and educate each other on key issues.

“One of the first things we did was to come up with a mission statement,” Jepperson said. “We agreed our mission was to reduce the number and severity of injury collisions while maintaining the integrity of the park and the historic significance of the rail.”

The group then listed the key components necessary to create a barrier that was safe and visually appealing and came to a mutual agreement.

WSDOT contracted with the Texas Transportation Institute (TTI) to develop a barrier that incorporated as many of the character-defining features of the original bollard and log system as possible. It was assumed that since a rock support was desired, the barrier would have to be a rigid system with little or no deflection. The barrier design would be tested in accordance with the “National Cooperative Highway Research Program (NCHRP) Report 350” criteria for Test Level 2 conditions. For Test Level 2 conditions, a design force of 27 kips, distributed over a distance of 4 ft, was used to design the log rail and supports in accordance with the AASHTO LRFD Bridge Design Specifications. In addition to a conventional ultimate strength analysis of the log rail, structural computer modeling of the log rail design was performed using the structural engineering program RISA-3D.

The barrier that was developed replicates the look of the original while meeting current safety standards. It consists of a steel-backed log supported by rock-and-mortar bollards. The contractor was required to use a minimum of 50% of the original stone to make the new bollards, which have a reinforced concrete core connected to a reinforced concrete moment slab foundation. The steel-backed timber log rail consists of 12-in.-diam. “turned” Douglas fir log, cut flat across the back to accommodate a 6-in.-wide by 3/8 -in.-thick steel plate.

The bollards were designed for an 18-ft maximum spacing, but can be installed at lesser spacing to give the barrier a non-uniform appearance. It was determined, based on analyses and computer modeling, that an intermediate support would be necessary to achieve the 18-ft spacing. The intermediate support is provided by a steel pipe bolted to the moment slab foundation.

Extensive design and testing was done at the TTI before the final design was approved. A 126-ft test section of guardrail was built at TTI and crash-tested in accordance with the NCHRP Report 350 TL-2 criteria. This test involved impacting the rail with a full-size pickup at 45 mph at a 25° angle.

The location of the impact was important. For the first test, the critical impact location was selected to determine if the left front tire would snag on the rigid bollards. During the first test, the pickup was successfully redirected. No snagging occurred. The fir log sustained 0.8 in. of gouging; the bollard only displaced 0.4 in. The guardrail system was still in serviceable condition. Only 2.3 in. of deformation was experienced in the center of the vehicle’s floor pan. The test met all of the evaluation criteria of NCHRP Report 350 TL-2 criteria.

After the first successful test, the design was refined before the second test. The first test established that snagging on the bollards wasn’t critical, so the second test measured the strength of the intermediate support. Also, with installation and future maintenance in mind, the connection details were modified. Therefore, the second test evaluated the strength of these new connection details as well. The team also reduced the midspan support size to 6 in. in diameter so it would be less obvious.

Crafty veterans

Construction began last fall, and crews worked through the winter as weather permitted. Crews were required to complete the project during the off-peak months to reduce impacts to drivers, which meant no construction during the summer. To keep crews safe along the narrow, winding road, traffic was shifted to allow installation of temporary concrete barriers. During the import and export of materials, nighttime lane closures were required due to the narrow shoulders in several locations.

The slope and curvature of the roadway made survey and layout both challenging and critical to getting proper alignment of the railing. Unlike the original log rail, the new system uses a moment slab foundation that runs the entire length of the barrier. Original plans called for an 18-in.-diam. drilled shaft foundation, but nearby utilities and bedrock required a much shallower foundation.

After the moment slabs were poured, the bollard forms were set around the reinforcing steel extending from the moment slab. This was a critical step, helped by the innovative approach taken by the contractor. Bollards were constructed on center with a tolerance of ± 1/8 of an inch. To meet this tolerance, the contractor designed a form plate that was adjustable within the steel bollard forms. When the barrier changed angles, the form plate was adjusted for the necessary angle, allowing an almost-perfect alignment of the log rail and hardware.

Once the concrete bollards were poured, the masons took over, handcrafting the stonework to recreate the look of the original bollards. Once they got a good rhythm, the four- to five-man crew was able to complete about 10 of the 233 bollards per day.

As soon as the stonework was complete, another crew installed the hardware to the log rails and installed the rails to the bollards. Bollards were on typical 18-ft centers with exception of a few. Because the supporting log backer plates and doubler plates had minimal slide room in their slots, assembly was slow and very precise. Each log was measured and fitted to the bollards to ensure a proper fit.

“This project is unique in that much of the detail takes a real hands-on craftsman approach. While the footings and bollard cores are designed and built to very precise tolerances, the rock and mortar really is freehand,” said Larry Biggs, chief inspector for WSDOT. “The log installations required on-site drilling and fitting, too.”

Crews replaced the log rail at the highest-priority locations first. They built 4,285 lineal ft of guardrail, which is about half of the log rail that needs replacing in the park. More will be replaced once funding is available.

The total project cost was about $1,050 per lineal ft, compared to what would have been about $50 per lineal ft for W-beam guardrail. But getting consensus among several different agencies to build the new barrier will pay off with better safety for drivers, while maintaining the historic character of the park.

The project was slated to be complete by fall 2008, but crews expect to be done before summer. The foundations and bollards are complete, and crews are installing the last of the log rails. The project inspector contributes partnering cooperation between the state, primary contractor and subcontractors for completing the project safely and ahead of schedule.

(More about this project and crash test footage can be seen at

About The Author: Chesson is spokesperson for WSDOT, Burlington, Wash.

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