By: Roads & Bridges
In early 2006, Fairfield County, S.C., was seeking a low-cost, easy-to-maintain product to pave its dirt roadways in order to provide better routes for its citizens.
With over 250 miles of county-maintained roads, Fairfield County needed a method of paving the roadways that was cost-effective. The county’s rural dirt roadways were often impassable during rainstorms, were narrow and unsafe and were affecting the quality of life for citizens.
Dennis Corp. was selected by the Fairfield County Council and the County Transportation Committee as the on-call engineering firm to implement a road improvement program. Serving as project manager, Tim Antley of Dennis Corp. selected an innovative recycling process of full-depth reclamation (FDR) for paving the existing dirt roads. The process conserved resources while also saving the county money.
Depth perception
When researching options for the program, Dennis Corp. first faced the question, How can Fairfield County provide its citizens with safer and more efficient roadways at an economical price while using an environmentally friendly product?
Antley considered the environmental, social, economic and sustainable design considerations, and after researching a variety of methods, he presented his findings to the Fairfield County Council and the County Transportation Committee. Antley identified FDR as a good fit for the needs of Fairfield County’s budget constraints. In addition, the process promoted conservation and recycling, which was a priority for Dennis Corp. and the county.
The process switched from a conventional pavement design, consisting of an aggregate base course and hot-mix asphalt surface course, to a more innovative and economical pavement section. Due to the rapid cost escalation of liquid asphalt, which was approaching $450/ton in South Carolina, Dennis Corp. specified an FDR process in which the existing dirt/gravel road was mixed with a high-speed reclaimer that adds cement and water. The result was a superior base course, 6 in. in depth, which was surfaced with a bituminous triple treatment.
For the project, the specified road construction process allowed for 1,500-2,000 ft of complete roadway construction per day and a cost savings of $70,000 per mile. The lower cost of this paving process allowed the county to pave more roadways, benefiting additional citizens, all while saving county taxpayers $3 million and conserving resources. In fact, the project was so successful that Fairfield County has decided to implement the process of FDR for the 2008 Road Improvement Program.
Commenting on the FDR process, Fairfield County Council Chairman David Ferguson stated, “This innovative design process allowed the county to stretch its dollars further allowing more roadways to be paved. This was especially important to the county considering the rapid rise in construction costs in the construction industry and our budget constraints.”
Better mileage
Dennis Corp. helped the county choose FDR based on the fact that it can eliminate problems with the asphalt layer and create a structurally sound base. The process also carried environmental benefits and allowed Fairfield County to reduce the use of raw materials and the cost of their transportation while also benefiting the environment through reduced emissions and natural resource conservation. The increase in costs of asphalt versus cement also was a large factor when determining which process to use on the county roadways. The FDR process allowed approximately 10 miles of roadway to be improved instead of 3 miles, which the county originally anticipated, using the conventional asphalt surfacing and stone base.
With cost a large factor for the programs, the county was pleased with the FDR process and the maintenance-free product that it produces. The superior base course is impervious to water and also eliminates potholes. In the 1930s the first road with this innovative process was paved in Johnsonville, S.C. To date, the roadway still has no recorded potholes, because the base is a superior product. Future maintenance costs also will be reduced, since these roads will only require a chip seal application versus a 2-in. asphalt overlay. These factors combine to mean fewer future maintenance issues for the county and additional cost savings in the future.
In addition, FDR helped the county address the complex issues of completing the project on an accelerated schedule while minimizing public impact. During the 2006 Road Improvement Program, specifically, the county had a short duration in which the contract had to be completed. Due to the approaching winter months, the contractor had 58 days to complete the project. The FDR process used a high-speed Caterpillar reclaimer, allowing paving at a rate of 1,500 to 2,000 linear ft per day. The speed of construction benefited the county’s residents who drive on the road each day by minimizing the total days of construction. Additionally, the new riding surface was able to eliminate washboard problems and loose aggregate in curves, resulting in safer driving conditions for the traveling public.
In an effort to further reduce public impact during both the 2006 and 2007 Road Improvement Programs, Dennis Corp. and the county implemented a program to educate local citizens about the project process and the project’s timeline. The goal of the public relations efforts was to minimize disruptions to the lives of local citizens and to keep the project area safe for the traveling public while still allowing the project to remain on schedule. Dennis Corp. kept local citizens informed by placing flyers on homes that were in the path of the construction projects with facts of the project and notification of any pending delays. In addition, signs were placed at the beginning of work zones to notify citizens of how their tax dollars were being used to improve their roadways. Due to this public relations effort, no vehicular accidents, public complaints, project delays or cost overruns occurred during the 2006 and 2007 Road Improvement Programs.
Shop talk
The Fairfield County Road Improvement Programs have received national recognition for their innovative use of recycling through FDR. In May 2007, Fairfield County and Dennis Corp. received the American Council of Engineering Companies Engineering Excellence Award for the state of South Carolina and represented the state at the national convention in Washington, D.C. Antley, the project manager for both Road Improvement Programs, won the Asphalt Recycling and Reclaiming Association’s (ARRA) Special Recognition Award for the 2007 Road Improvement Program. This award is given annually to honor public officials and consulting engineers who have made outstanding contributions to the asphalt recycling and reclaiming industry.
In addition to award recognition, the projects also are gaining attention in the engineering community for this recycling method. In October 2006, Dennis Corp., in conjunction with the Southeast Cement Association and Clemson University, held a one-day workshop highlighting the FDR process used on Fairfield County roadways. This workshop was attended by approximately 90 engineers from various consulting firms, cities, towns, counties and states. The workshop demonstrated how unpaved roads in Fairfield County are being rehabilitated and upgraded through innovative and economical design and smart constructability approaches. Also, in October 2007, Dennis Corp. sponsored a conference titled “Count on Concrete,” which further highlighted the FDR process to engineering professionals.
The 2006 and 2007 Road Improvement Programs were able to meet or exceed the objectives of Fairfield County for paving their dirt roadways through FDR. The programs were able to use an environmentally friendly process; pave roadways with a low-cost product that is easy to maintain; complete the project in a short duration while having minimal impact on the environment and surrounding homes; and accomplish the program with no vehicular accidents, public complaints, project delays or cost overruns. These programs are further evidence of how including recycling practices in project design can not only have a lasting positive environmental impact, but also can allow projects to be completed expeditiously and economically.
