South Carolina Department of Transportation

Free to grow┬áThe South Carolina Department of Transportation has accelerated an ambitious highway development program to relieve congestion, and John OÔÇÖHanlon learns about progress on its concluding phase, the Palmetto Parkway/Interstate 520, from project manager Claude Ipock. South Carolina is the 11th fastest-growing state in the country, outpacing the national average in terms of major economic indicators.  Growth driven by tourism, business services and international trade has created pressures on the stateÔÇÖs transportation infrastructure. With its location at the heart of the Southeast, South CarolinaÔÇÖs transportation network has to serve not only its residents but also tourists and cross-state traffic heading for the expanding Port of Charleston. Augusta, Georgia, is to the west, just over the state border, but North Augusta, the fastest-growing part of the city, is in Aiken County, South CarolinaÔÇöand it has plenty of room for more development north and east of the Savannah River waterfront. The citizens of Augusta must be resigned to traffic delays by now. For years the local infrastructure has been struggling to cope with volumes of interstate and commuter traffic in South Carolina and Georgia that have more than doubled in the last six years. Since work started in 2007 on the Interstate 520 Phase II of the Palmetto Parkway, a new stretch of highway approximately six and a half miles long linking US Route 1 and I-20, lane shifts and congestion caused by the road work have tested driversÔÇÖ patience. But they wonÔÇÖt have to wait much longer, says Claude IpockÔÇöthe entire job is scheduled to be completed by December 31 this year. ÔÇ£A little more patience and the whole area round North Augusta will move a lot more freely once the Palmetto Parkway is open,ÔÇØ he says.The Palmetto Parkway will complete the I-520 beltway around metropolitan Augusta, reduce the current ÔÇ£infrastructure deficitÔÇØ in the area, and encourage economic development in the region, it is hoped. The North Augusta riverfront and the whole northern area of the city within Aiken County are expanding rapidly, and there was a need to provide a further crossing over the Savannah River. ÔÇ£This road will not only make the whole economy around Aiken County work better; it will make a big contribution to road safety and cut accidents at four of the eight worst black spots.ÔÇØThe $152 million funding for the project was provided by the South Carolina Transportation Infrastructure Bank (SCTIB), a body set up in 1997 to finance large-scale road and bridge projects. ItÔÇÖs not like the commercial banks that have featured so bleakly in recent news, existing solely to accelerate vital infrastructure projects and in particular the road network. The South Carolina Department of Transportation (SCDOT) maintains the fourth-largest highway system in the US, which includes 42,000 miles of state highways and 800 miles of interstates. Traditional highway funding sources on a pay-as-you-go basis were insufficient to finance the necessary highway improvements. Not only does the state rank low in terms of federal funds, but only five states have lower gasoline and diesel taxes than South Carolina.SCTIB differs in a number of ways from other state infrastructure banks (SIBs), says Ipock. It is focused on transportation projects exceeding $100 million, it is one of only two SIBs nationally that is currently leveraging its capital through the issuing of bonds, and it has authority to provide grants as well as loans for project financing. The result has been that SCDOT has been able to compress what would have been 27 years of road and bridge projects into just seven years. Phase II was launched in 2005 with an SCTIB grant of $95 million. Further federal funding and local sales tax revenue were added to a second SCTIB injection of $18 million for the project to include improvements to US 25, the Exit 5 interchange and Belvedere-Clearwater Road that had initially been excluded to reduce the overall cost.To fast-track the project once the funding had been secured, SCDOT handed over the outline plans on which Phase II was based to a design-build team under the leadership of United Contractors Inc., which put together a partnership of expertise under the title of Team United. Key members of this loose consortium, all local firms, were US Constructors, RE Goodson, Triplett-King & Associates, Coleman-Snow Consultants, Florence & Hutcheson, F&ME Consultants, S&F Engineering, Palmetto Safety Solutions, and Public Strategy, LLC. The amount of earth and the lay of the site was a huge challenge to the excavation process. Almost five million cubic yards of earth had to be moved to level the area for the highway. ÔÇ£In the space of a few hundred feet there would be a difference in elevation of 70 or 80 feet from one side of the right-of-way to the other,ÔÇØ recalls Ipock. That part of the job was accomplished by RE Goodson. He says the coming together of so many specialistsÔÇöas many as 275 people working on site on any one day with different working cultures and employment practicesÔÇömight have been a challenge, but it was successfully overcome by the creation of Team United, with communications a priority. ÔÇ£If you contact one of them, you contact them all.ÔÇØ Design of the bridges fell to Triplett-King & Associates. The design-build concept allowed them to introduce innovative pipe piles to carry the deck across the unstable soils that are a feature of the Savannah basin. ÔÇ£Pipe piles are hollow steel tubes that are used instead of the more common H-section girders that are normally driven into the ground,ÔÇØ Ipock explains. ÔÇ£Pipe piles give you maximum surface contact, being up to a yard in diameter, so you have the benefit of increased friction.ÔÇØ With sand going down as much as 120 feet before bedrock was reached, the performance of these piles was crucial; each ÔÇ£bent,ÔÇØ or transverse support, on the bridges is sustained by eight 24-inch and three 36-inch piles, filled with sand topped with concrete.Another challenge that came up was the last-minute addition of a pedestrian bridge at the request of Aiken County. This marks the first time a bicycle/pedestrian facility was constructed parallel to a freeway in South Carolina within the same right-of-way. The plan had to be discussed with the Federal Highway Administration, which only demanded there be a distinct separation between the highway and the path, 50 to 200 feet away. The path will only be accessible from side roads, and there will be no access points from the interstate.┬á