|FHWA > HfL > Projects > South Carolina Demonstration Project > Project Overview And Lessons Learned|
South Carolina Demonstration Project: Black River Bridge Replacements on SC 377 in Williamsburg County
Project Overview And Lessons Learned
The project site is located on South Carolina Highway 377 south of Kingstree, SC, in Williamsburg County. The project involved replacement of four structurally deficient bridges on SC 377, along with geometric modifications to the existing roadway and the intersection of SC 377 and U.S. 521.
The project begins at the intersection of U.S. 521 and SC 377 and stretches about 1.5 mi north toward Kingstree. The main Black River Bridge is 360 feet (ft) long, with six spans of 60 ft each. The other three bridges are 420 ft long each with 30-ft spans. In addition, all bridges were widened to 44 ft from an existing width of 26 ft. The new bridges were built with staged construction alongside the existing bridges without significant traffic stoppage. The intersection of U.S. 521 and SC 377 was also improved as part of this project. The geometric design included removal of Spur U.S. 521 and other geometric modifications. The 2006 average daily traffic passing over the bridges on SC 377 was 3,000 with 6 percent commercial truck traffic. Because the existing bridges, built in 1955, were structurally deficient, they were posted with weight limits and truck traffic was diverted 14 mi before the start of the project.
SCDOT determined that the main bridge had a sufficiency rating of only 10.8 (on a scale of 0 to 100) and the adjacent three bridges were in poor condition as well. SCDOT approached the highway corridor as a whole using route management concepts to support the decision to reconstruct the four bridges at the same time. This was done to limit construction impact to one event rather than three. Traditionally, multiple contracts would have been let at different times to reconstruct all the bridges. The main river bridge would have been replaced first. Two years later, the adjacent bridges would have been replaced and the safety enhancements at the intersection would have been included under one of the bridge reconstruction contracts.
This project presented an opportunity to integrate several innovations that decreased the project delivery time and increased the overall project value. The following is a summary of the project's innovative features.
Road Safety Audit
Transportation experts from the SCDOT conducted a road safety audit (RSA) prior to construction to ensure that all aspects of safe operation of this roadway were noted and recorded to enable appropriate decisions on resource allocation. The RSA team noted that U.S. 521 is a designated evacuation route. While the team believed that the project would not have any major impact on the functionality of U.S. 521, the team noted that if an evacuation was ordered, the project's possible impact on traffic flow should be considered. In addition to traffic flow concerns, the RSA team made several other safety recommendations related to pavement markings, traffic transitions, sight distance, side slopes, and speed limits during construction.
Innovative A+B+C Contracting
Since time was of the essence in restoring truck traffic, a project-specific A+B+C bidding provision was developed to encourage the contractor to strive for the most efficient method to achieve the shortest possible construction time. This type of bidding provision has the following components:
A special contract provision specified a no-excuse incentive completion date, defined by the contractor's time bid from the winning A+B+C bid. The provision was developed for this project because truck traffic was detoured 14 mi due to the structural inadequacy of the existing bridges and it was imperative to eliminate the detour as soon as possible. The no-excuse incentive date could not be adjusted for any reason except a catastrophic event. The project was substantially finished by the no-excuse incentive completion date as defined in the contract, which entitled the contractor to the full incentive pay.
SCDOT developed a new ride quality specification based on the IRI target value of 65 inches per mile for each 0.1 mi section of pavement. The IRI is measured according to SCDOT specification SC-T-125. Payment is based on the original contract unit price per ton of final asphalt surface tested plus a bonus according to a graduated scale for IRI values below 65 inches per mile and a penalty for values exceeding 65 inches per mile.
Self-consolidating concrete (SCC) has excellent deformability and resistance to segregation, so it can be used in heavily reinforced formwork without difficulty and can result in high-quality smooth surfaces. SCDOT developed SCC mixes and special provisions with the University of South Carolina (USC) and a fabricator in order to use SCC in several bridge beams on this project.
HfL Performance Goals
Safety, construction congestion, quality, and user satisfaction data were collected before, during, and after construction to demonstrate that innovations can be deployed while simultaneously meeting the HfL performance goals in these areas:
The benefits and costs of this innovative project approach were compared with those of a project of similar size and scope with a more traditional delivery approach. The economic analysis indicates that SCDOT's innovative approach generated a cost savings of about $6.9 million or 40 percent of the total project cost over conventional construction practices. Construction efficiencies from combining the projects and reduced construction time had a significant impact on the cost savings.
Throughout this project, SCDOT gained valuable insights on the innovative processes deployed, both those that were successful and those that need improvement on future projects.
Benefits of the contracting and construction innovations used on this project include the following:
Areas needing improvement include the following:
This project achieved a high level of quality and was brought to completion quickly and with relative safety as a direct result of innovative contracting and construction methods. Lessons learned about A+B+C contracting will be beneficial on future SCDOT bridge projects.