Figure 1: Pile-driving rig near active runway.

Detroit Metropolitan Airport’s South Access Road-Midfield Segment is a four-lane roadway with ramps that will connect it to the proposed World Travel Center. Due to poor soil conditions, the retaining walls adjacent to the access road construction site were designed with pile footings. Consequently, the contractor would have to mobilize a pile-driving rig only 160 feet (50 meters) from the centerline of an active taxiway (Figure 1).

FAA Approves Construction Plan

At the onset of the project, Wayne County officials sought approval from the Federal Aviation Administration (FAA) to allow equipment heights to penetrate the restricted airspace during construction of the road. FAA regulations generally prohibit tall equipment from operating in areas near active runways and taxiways or require lowering such equipment at the time of take-offs or landings.

The FAA approved the County’s construction safety plan and allowed equipment heights 65 feet (20 meters) over the seven horizontal to one vertical (7:1) slope of the “imaginary surface” defined by Federal Aviation Regulation Part 77: Objects, with continued use of the runways and taxiways for airport operations. This approval was for an 18-month construction schedule. As an added level of safety, specifications were written to require the contractor to lower the booms at the end of each workday, during marginal weather conditions, and within a half hour after specific notification from the air traffic control tower. FAA also required that cranes and backhoes penetrating the 7:1 slope be equipped with red flags.

Cost of Lowering the Boom

What wasn’t known until construction time neared was that lowering the boom on a pile driving rig is not simple. One must dismantle the hammer and rigging, a task that requires several hours of down time to the contractor. The cost of such an operation would be tremendous. In this case, pile-driving was an item on the contractor’s critical path schedule. Forcing the contractor to adhere to the letter of the specification could have delayed the project as much as 85 calendar days.

Upright Boom Approved

Wayne County officials submitted a plan to the FAA requesting that the contractor be allowed to leave the boom in the upright position during pile driving operations. The FAA required the contractor to place a red flashing beacon on the top of the boom to alert incoming planes and the tower of its location and issued a NOTAM (notification to airmen) to alert the pilots of the construction situation at the Detroit Metropolitan Airport.

Thus far, the contractor, airport operators and Wayne County Field personnel are pleased with the operation. The contractor is in daily contact with the tower, the project is on schedule and the solution works for all involved.