North Mountain Tower Road
Owner: City of Phoenix
Lead Design Firm/Civil Engineer: T.Y. Lin International
General Contractor: Hunter Contracting Co.
Engineer (Tower Design): Gannett Fleming
Communication Construction (Installed Tower): High Desert Communications
Construction of a 120-ft-high tower atop North Mountain, the site of a busy hiking trail that rises some 600 ft above street level, required both a new and renovated roadway to handle the 200,000-lb crane needed to erect the structure. In addition to making 4,400 ft of the winding road safer to travel, primarily by providing enough surface area to keep the crane stable, crews constructed the last 200 ft of roadway to make room for the hoist.
The scope of work called for a 13.5-ft-wide asphalt pavement and a 3-ft-wide compacted decomposed granite shoulder with a concrete ditch, drainage pipes, head walls and a custom-designed retaining wall that separates the road from steep drop-offs.
The road extension included an area for the crane to park while an excavator built a pad for it. Once work concluded, crews moved the crane into position on the pad. A forklift delivered tower pieces to the crane, and tower components were erected from there. The resulting tower—one of many sited atop the mountain for government use—meets new loading requirements for such structures. The improved road also created a safer environment for repair personnel and others headed up the mountain, including the many hikers who visit the trail.
During construction, the project team faced a risk from falling boulders, some as large as automobiles. Crews monitored the terrain and, in one instance, discovered a 12-ft-tall boulder had delaminated 2 ft from the mountainside, meaning that it could fall at any time. They cleared the area and dislodged the boulder without incident.