The South Carolina Department of Transportation has selected Balfour Beatty Construction Inc. (BBCI) as the managing partner and lead contractor on the SC 170 Widening Project, located west of the city of Beaufort. The $105 million design/build project involves the widening of 12.5 mi. (20 km) of roadway east of SC 462 to just west of S-761. It also includes the replacement of bridges over both the Broad and Chechessee Rivers.
When completed, this project will present the residents and visitors of Beaufort County with a new divided highway that will help alleviate traffic congestion and increase safety on this heavily traveled route to and from Hilton Head Island.
The widening project is divided into three phases. Phase I, which ends at the Broad River Bridge, will involve widening the road to five lanes. The embankment on both sides of the highway has been placed in preparation for the widening. Earthwork, drainage, curb, sidewalk and gutter, and subbase operations are nearly complete. Approximately 90 percent of Phase I is on asphalt binder course grade and a section of the roadway is already being used for travel.
Phase II, occurring on Lemon Island between the Broad and Chechessee Rivers, involves the central part of the roadway, which will be widened to four lanes plus a divided median. Embankment and drainage are in place, and paving will begin in the next few months.
Work on Phase III will be from the Chechessee River and tie into the recently completed four-lane roadway project on SC 170 near Cherry Point. It will include a combination of five lanes and a divided median. This portion of the project has been cleared and utilities are relocating their lines. Earthwork, drainage, and embankment procedures are under way, and the placement of subbase operations will begin soon.
In the meantime, the two bridges are in separate stages of construction. The Chechessee River Bridge and the Broad River Bridge both span waters used by boat traffic. The bridges are unique and will be aesthetically agreeable with components that will form graceful curves with gentle and gradual grades. The bridges will be supported by 102-in. (259 cm) diameter drilled shafts, architectural columns and caps.
The girders used in the construction of the bridges are cast in Florida, and 97 percent of the beams are cast at the Balfour Beatty yard in Green Cove Springs, FL. The beams are transported by barge to the construction site in Beaufort. A typical beam is approximately 146 ft. (44.5 m) long, 6-ft. (1.8 m) high, 5 ft. (1.5 m) wide and weighs 92 tons (83 t).
When finished, the 1.6-mi. (2.6 km) Broad River Bridge will be four lanes divided by a concrete, or “Jersey” barrier, for added safety. Presently, all substructure, which includes drilled shafts, the twin columns and the caps, is complete.
Crews have completed the west abutment and backwall. All of the beams for the Broad River Bridge have been fabricated, and approximately 350 – 92 percent – have been installed. Bridge deck construction is under way with 80 percent of the deck poured.
Construction of the much smaller 1,920-ft. (58.5 m), four lane Chechessee River Bridge is under way with all substructure finished. Beam erection is about 60 percent complete on this bridge, and the bridge deck construction has begun.
According to David Glenn, district maintenance construction engineer for SCDOT, both bridges should be complete by October or November. However, the roadway will take a little longer than the original 42-month estimate.
“The roadway portion has been delayed because of rain mostly,” said Glenn. “It hit them [crews] at the time when they needed to do the road work.”
The project will require substantial quantities of material before its adjusted completion date of February 2004. Approximately 100,000 cu. yds. (76,000 cu m) of concrete and 9,000 tons (8,200 t) of reinforcing steel will be used during construction. The project also requires 43,240 tons (39,200 t) in precast concrete girders and 198,000 tons (180,000 t) of asphalt. Earthwork borrow has consisted of nearly 626,600 cu. yds. (480,000 cu m).
A challenge for BBCI on this project has been minimizing the impact of construction on the surrounding environment. The SC 170 corridor is amongst estuarine marsh systems and freshwater wetland habitats. SCDOT and the BBCI construction team plan to use top-to-bottom bridge construction to lessen any possible impact to the wetland and waterway. A drainage system, removing oils and debris from the bridge structure, will be used prior to dispersing runoff drainage into the area. Similarly, the roadway design will incorporate a drainage system protecting discharge. The team is also incorporating existing natural vegetation into the design.
The construction team had to take into consideration the preservation of trees and continuation of a usable boat ramp for the SC 170 Widening project.
SCDOT, the BBCI team and Beaufort County decided to move the alignment of the widening to spare eight majestic oak trees from destruction.
“It was everybody’s decision,” explained Glenn. “During our partnership meetings we had a concern about the trees, so we moved the road to keep the larger oak trees.”
In another section, the Edgar Glenn Boat Landing will remain open while a new boat ramp is being built to tie into the new highway. As requested by the community, there will always be a functioning boat ramp during construction.
When working on a fast-track project, the design/build approach is often implemented to finish in the desired timeframe. The BBCI team is working along with the Lawrie & Associates, lead engineer; Site Consultants, roadway design engineers; Moreland Altobelli Associates Inc., right-of-way services; Haley & Aldrich Inc., geotechnical engineering services; Ayres Associates, hydraulic analysis; Huff & Good Architects LLC, assisting with the aesthetics of the bridge design, roadway widening and improvements.
In addition to the design/build team, Carolina Asphalt Paving, Hilton Head, SC, is the prime subcontractor performing the road work. Cleland Construction, Hilton Head, SC, is a subcontractor working on drainage and grading among other things.
In a cooperative effort, Beaufort County, the State Highway Infrastructure Bank and SCDOT secured funding for the SC 170 widening project. To facilitate the design/build project, BBCI joined this partnership to make the project a success.
Balfour Beatty Construction, Inc. is based in Atlanta and is part of the Balfour Group based in London.