BY TOM DONALDSON
In a remote area of the Gila National Forest near Glenwood, New Mexico, about 250 miles southwest of Albuquerque, you will find a diamond in the rough – a gem hidden among the canyons and mesas: the historic — and newly restored — Catwalk Trail.
Originally constructed in the 1930’s by the Civilian Conservation Corps, the trail follows the path of a pipeline built in the 1890’s to serve an old mining settlement. The pipeline was suspended on narrow canyon walls, in places as much as 20 feet above the canyon floor. Despite being considered an engineering marvel at the time, the pipeline needed constant maintenance. To access the sections needing repairs the workers had to walk on the pipeline itself. This led them to nickname it “the catwalk.” The pipeline is long gone, but the name stuck.
In recent years Mother Nature delivered a devastating one-two punch resulting in the destruction of the trail. First, in 2012 the Whitewater/Baldy fire burned more than 290,000 acres in the trail vicinity. This was quickly followed in 2013 by torrential rains which cascaded through the burn scar, flooding the canyon and taking the Catwalk with it.
In 2015, the Federal Highway Administration, Central Federal Lands Division/U.S. Forest Service awarded a $4.6 million design-build contract to AUI Inc. of Albuquerque, New Mexico, to reconstruct the trail. AUI, a New Mexico Building Branch and Associated Contractors of New Mexico member, formed a team including lead engineer firm Bohannan-Huston, Inc., also of Albuquerque, and began design work in August of that year. The project entailed three steel bridges, 700 feet of suspended catwalk in the narrow slot canyon, restoration of trails leading to the structure, removal of obstructions in the creek bed, and rehabilitation and expansion of the parking lot at the trailhead.
The Forest Service required the design and construction to be completed in just nine months. To adhere to such an aggressive schedule, an experienced design-build team leader was needed; one that would not only have expertise in the construction methods required for such a unique project, but also well-versed in areas such as erosion control, historic restorations, and maneuvering the complicated permitting processes. They found just such a leader in AUI, the deserving recipient of the 2017 Alliant Build America Award in the category of Design-Build – Civil.
First and foremost among some of the unique challenges was obtaining the necessary permits. For there to be any chance of completing the project within the nine-month window, the permitting process had to be started immediately and efficiently managed. Obtaining 401/404 EPA permits can often take years, so the process had to be fast-tracked. To do this, a permitting expert joined the team, NV5, to handle permitting and geotechnical engineering. They worked closely with Forest service personnel to resolve issues as they arose so that construction was not delayed.
Another challenge was the remoteness of the project site. The nearest town, Silver City, is 60 miles from the site, and the nearest major city is over 200 miles away. Team members could not just run to the neighborhood hardware store to pick up supplies on short notice – acquisition of materials had to be carefully planned, well in advance.
The only way to get materials and equipment to the construction site from the parking lot was through a half mile of narrow canyon, along a creek bed with one to two feet of flowing water in it. Transported equipment included excavators, loaders, forklifts and manlifts, some being very large and heavy. To protect the fragile creek bed, the team implemented cleaning and spill prevention measures. Access to the site was further complicated by the presence of large boulders blocking the narrow canyon, which had to be removed before the equipment could be transported to the site.
Once construction started, one of the most complicated hurdles to overcome was the installation of the anchor bolts into the canyon wall. These anchors formed the base point for the catwalk structure; therefore, exact location and proper installation were critical. The canyon walls had deviating faces including pockets and overhangs which presented a challenging surface to attach structures to. In addition, subsurface conditions varied significantly at each anchor point, and these variations only revealed themselves as the anchors were being drilled and epoxy-set, so the installers had to be flexible and creative. Following the setting of the anchors, each one was pull-tested to ensure the structural integrity of the catwalk.
To ensure exact placement of the catwalk anchors in the canyon walls, high tech surveying methods were employed. The AUI team accomplished this by using Light Detection and Ranging (LiDAR) along with supplemental ground surveying to map the exact position of each support. LiDAR is a remote sensing method that uses light pulses to measure variable distances to land features. These light pulses, combined with other data, generate precise three-dimensional data of the features and surface characteristics. Next, the team embedding rebar in the walls and bent them to match the required beam bearings.
Another creative approach that saved time and money was to have the steel walkway prefabricated in 12- to 20-ft long sections. As every piece was unique, the fabricator created a three-dimensional model to ensure each section would fit accurately. This innovation minimized field-fitting which helped maintain the aggressive project schedule.
EXCELLENCE IN PROJECT MANAGEMENT
Completing such a complex project in a short time frame requires expert project management. Putting the right personnel in key positions, coordinating the many moving parts, acquiring materials and equipment in a timely manner, and efficient planning of the sequence of tasks are all essential steps. AUI was up to the task.
Building the right team for the project was the critical piece. As previously noted, they recognized right from the start that one of the first and most important steps was to secure the EPA permits, and to do that required inclusion of an expert in this field on the team. The selection of lead engineer Bohannan-Huston (BHI) also proved critical for their expertise in key aspects of the design. BHI utilized no fewer than 11 different software tools to provide the modeling and accuracy required to produce a buildable set of construction plans. Further, a Quality Control expert was maintained on site full-time to ensure tasks were completed correctly, minimizing time lost to rework.
Partnering and communication were also critical to keeping the project on track. The constant, open communication of all team members resulted in trust-based relationships. As noted by Darrin Howells, president of AUI Inc., “the Design Build Procurement method set forth by Central Federal Lands allowed for true collaboration between all stakeholders, ultimately leading to the successful completion of the project.”
Absent a strong leader, chaos ensues and nothing gets done. A strong leader creates an environment of purpose, respect and trust that inspires all participants to do their part and work together. AUI was the kind of leader this project needed to be completed on time and under budget. They not only met the project schedule, they beat it by a full month, which meant that the trail was reopened in time for the busy 2016 Memorial Day weekend. For a region that depends on the money generated by tourism, this was huge.
Even more impressive, they accomplished this without cutting corners. They ensured a structurally sound catwalk while preserving historic features and protecting the fragile ecosystems of the canyon and creek.
And in addition to all that, they found time to be good citizens in the local community. A local citizen’s group was working to get funding and approval to expand the trail. AUI and their team assisted this group by allowing access to the construction site for tours, and provided construction cost estimates for the extension that helped the group prepare grant funding proposals.