S.T. Wooten Makes Quality King on Crystal Coast Airport
BY Robert Len Hunt Jr.
In April 2017, construction of a new taxiway was completed at a 400-acre, three-runway air field on the crystal coast in Beaufort, North Carolina. Originally named the Beaufort-Morehead City Airport, the facility was renamed Michael J. Smith Field to honor one of the Space Shuttle Challenger pilots who was born and raised in Beaufort.
We overcame several challenges during the eight months we worked on this project, from tackling temperature dynamics for the asphalt laydown to taming the effects of tides and hurricanes with a unique drainage system.
Prepare for Takeoff
Beaufort-Morehead City Airport Authority originally planned for this project to take place in three phases over eight months to maximize open times on the primary runway. The airport allowed us to combine the first two phases and we completed those during the fall of 2016. We planned phase three for a 21-day period during the spring, which involved reconstruction work on a major taxiway intersection.
Taxiways and runways were shortened at times during construction, but remained open. At times we provided a flagger to help airplanes cross the work zone as well. All these actions helped pilots find their way around the work zone because there is no ground traffic control at the airport.
Secure the Foundation
In Beaufort we were excavating below sea level for construction, so groundwater was something that needed to be accounted for in stabilizing the underlying pavement base. To ensure a sound sub-base, we used a soil-cement stabilization method.
The process involved mixing Portland cement with existing soil and water under the taxiway to create a low-strength concrete located three feet below the pavement subgrade. The taxiway then received 8 inches of P-209 crushed aggregate base course and 4 inches of P-401 bituminous surface course placed in 2-inch lifts.
Pave the Runway
Temperature restrictions were a factor for us when it came time for the asphalt paving portion of the project. It was a long distance between the hot-mix asphalt plant and our project site, and we were doing most of the paving during the late fall and early spring when the weather could still be quite cold.
To ensure a quality product, we leveraged a Roadtec material transfer vehicle. This helped us keep the asphalt at optimal temperatures while we transferred it from the dump truck to the paver.
We used a traditional Caterpillar paver with an Asphalt Reheat Systems (ARS) joint heater attached over the longitudinal joint to pave abutting paving lanes. This system gave us more insurance on the joint densities as test cores are required at joints in P-401 specifications. It also helped to produce the smooth paving surface that S. T. Wooten runway projects are known for.
While the paving equipment helped us drive quality, a GPS grade control system also served as a tool for precision fine grading during the stone-base portion of the project. The technology allowed us to pave with the accuracy and reliability required under the airfield’s specifications, while also ensuring we met our quality control requirements and time deadlines.
Repairs and Finishing Touches
For the Michael J. Smith Field project, we also conducted rehabilitation work on a section of the existing parallel taxiway between runway 14-32 and runway 8. We installed a geo-textile fabric waterproofing interlayer, a double bituminous chip seal and 4 inches of P-401 bituminous surface course placed in two, 2-inch lifts. Crack sealing was also part of the repairs.
Upon completion of the paving, we marked the new parallel taxiway and remarked the runway 14 and runway 21 thresholds back to their preconstruction location to get things ready for use. We installed new edge lights along the taxiway pavement between Taxiway A and Runway 8, in addition to a taxiway guidance sign. Vault modifications were used as part of the electrical work, which included installation of a new 7.5kV regulator.
Stem the Tide
Groundwater was constant in the surrounding area and two major storms gave us additional drainage challenges for us to get the job done. Tropical Storm Hermine dropped about 8 inches of rain on us in September 2016. Then, an additional 12 to 13 inches of rain fell from Hurricane Matthew during the first week of October.
We only had to excavate 4 feet deep; we opted to use a sock-drain system to drain water away from the construction limits. We installed more than 7,000 linear feet of sock drain for dewatering. Sock drain is HDPE pipe perforated with holes and fitted into a fabric sleeve to filter dirt out of the water. A vacuum pump attached to the system helped pull water out of the ground and isolate the work area.
We used a trencher to install the sock-drain system around the perimeter of the site. Because it was positioned outside the edge of the pavement, the sock drain could be left in the ground after construction was finished for better ease-of-use.
Onsite, we used Hydrema articulated dump trucks for low ground-pressure—making them an ideal fit for the wet conditions we faced.
With flotation tires, these trucks allowed us to move heavy loads without pushing water to the surface. A swivel-dumping feature also gave us the capability to dump over the side and rear to minimize turning and backing.
Make the Grade
Throughout this process, adhering to stringent paving regulations from the Federal Aviation Administration (FAA) was a top priority. These specifications are some of the most difficult to deal with when it comes to mix designs and paving tolerances that are tighter than typical department of transportation paving.
By taking steps to establish a game plan, putting the right processes and equipment in play, we overcame some of the unique challenges that come with construction work near the coast in Eastern North Carolina. The careful project planning and management helped us meet all specifications and finished on time with no penalties.
Our crew’s hard work and ability to execute with a commitment to quality allowed us to be successful on this project. It’s safe to say our team passed the test, and we’ll take this knowledge with us to the next project as we strive to deliver the best results for our customers.
Robert Len Hunt Jr., P.E., is a division manager for S.T. Wooten.