Despite two major hurricanes, the first six-mile segment of the $386-million Conway Bypass in Horry County, SC, opened June 29, 2000 — ahead of schedule.
And, South Carolina Department of Transportation District Engineering Administrator Dave Lewis expects the entire 28.5-mile bypass to be done “significantly sooner” than its December 2001 contractual deadline.
A major reason for the project’s swift completion, Lewis said, is the “design-build” method used in carrying out the work.
“Generally, in highway construction, [the DOT] do the engineering work, decide the details and produce set plans and technical specifications, and tell the contractor exactly what we want him to do.”
“It’s a very structured kind of thing,” Lewis said, requiring a lot of detailed back-and-forth between the DOT and the contractor.
“That takes time,” Lewis said.
“For the Conway Bypass, we used the design-build contract in which the engineering work and the final design are done at the same time as the construction. We tell them we need a highway between here and there and give them the requirements and tell them ’now go do it.’ ”
“One of the concerns,” about the traditional approach to projects, Lewis said, “is that the DOT is constantly looking at you, and when questions arise, there’s no one to give a direct answer so you can keep it on schedule.
“We decided in the beginning on this project that there would be a single point of contact between the contractor and the DOT,” Lewis said.
Lewis is the DOT contact person and Jim Wiley of Fluor Daniel, which is managing the project, is the contact for the company. Fluor Daniel is the construction and engineering division of Fluor Corporation of Aliso Viejo, CA.
“We tried to streamline the process,” Lewis said, “so we get a quality roadway and don’t micromanager the project.”
The Conway Bypass will ease traffic congestion and provide a second major evacuation route during hurricanes from the Myrtle Beach area.
The first segment runs six miles, from Highway 17 to Highway 90, linking Myrtle Beach to Conway.
Despite facing two major hurricanes during construction of the first segment, the project team implemented a recovery schedule that allowed for early completion.
Hurricane Floyd passed up the South Carolina coast Sept. 16, 1999 with high winds and near-record rainfall. Hurricane Irene followed in October.
The bypass suffered many washouts, and bridge construction on Segment II was halted until the waters receded.
Thirty-one bridges are included in the total project — 15 flat slab and 16 girder bridges.
The flat slab design was selected for its rapid constructibility, economical cost and “top down construction” which Fluor said minimizes impact to sensitive wetlands.
The main structural components of the flat slab bridges are 18-in. (45.7 cm) square pre-stressed concrete piles, pre-cast concrete pile caps and pre-cast, pre-stressed concrete deck panels. A 4-in. (10.1 cm) overlay acts as a wearing surface. The advantage of the pre-casting operation is that the structural elements can be cast in a controlled casting yard weeks of months in advance.
Traylor Bros. Inc., of Evansville, IN, used a staging scheme from a crane trestle located in the highway median to construct the bridges.
First, temporary pipe plies are vibrated into place to support the trestle. After crawling out on the first spans of the trestle, the crane swings back to drive permanent piles for the bridges on both sides of the streets.
After a number of piles are driven, a second crane follows to set caps on the piles, which are grouted into place. The panels are then placed on the caps and tied together by post tensioning cables that are run through ducts cast into the panels. This “tag-team” effort is repeated until the basic structure is completed. Pouring the overlay concrete and the barrier parapet walls finalizes the structure.
The Billy Alford Bridge, where dedication ceremonies took place, was named after the former Commissioner of the South Carolina Highway Department who is credited with starting the original project.
The project was given notice to proceed on March 31, 1998. It includes 31 bridges, 318 acres of wetlands, 5,160 piles and a peak work force of 570.
The widest part of the roadway, from the U.S. 17 Interchange to the future Carolina Bays Parkway, will have six lanes with three 12-ft. travel lanes in each direction, separated by a 46-ft. earth median.
Approximately 9 million cu. yd. of earthwork borrow was used, along with 1.8 million cu. yd. (1.3 million cu m) of concrete, 618,000 tons (556,200 t) of paving, and another 618,000 tons (556,200 t) of asphalt.
If all the concrete trucks used on the Conway Bypass were lined up, bumper-to-bumper, they would span 125 miles. If all asphalt trucks dump trucks used on the project were lined up, they would span 150 miles. If all the dump trucks used were lined up, they would span 2,650 miles. The 9 million cu. yd. of earthwork moved could fill the Empire State Building 2.2 times or a baseball stadium more than 20 times.