Fairfield County, S.C., is typical of many rural counties. Budgets are tight and the maintenance of approximately 220 miles of unpaved, gravel-surfaced county roads is an ongoing problem. The roads require frequent blading of the gravel and replenishing of the surface aggregate, costing the county about $200,000 annually. In addition, the citizens are faced with dust and other associated problems of unpaved surfaces.
Dennis Corp., an engineering consulting firm based in Columbia, S.C., was looking for a solution to help Fairfield County’s Transportation Committee upgrade the road conditions in a cost-conscious manner. The South Carolina Department of Transportation has been using full-depth reclamation (FDR) with cement for more than 10 years with excellent results, and Dennis Corp. thought the same procedure could be used in Fairfield County.
Their plan was to upgrade the gravel roads to a bituminous surface treatment (chip seal), which would provide a smoother, safer road surface. The FDR process would make use of the existing gravel by blending it with cement and subgrade materials to a depth of 6 in. This cement-stabilized material would make an excellent base for a triple bituminous surface treatment or a thin asphalt surface.
The cost evaluation showed that the FDR process, with the surface treatments, would save the county more than $70,000 per mile compared with the alternative of a standard asphalt pavement with a 2-in. surface and a 6-in. aggregate base. The county could upgrade 3 miles of road using the FDR with cement process for every 2 miles of asphalt pavement that could be constructed at the same cost.
In September 2006, the county contracted with Site Prep Inc., Monroe, N.C., to perform the upgrading of 14 sections, totaling 13.5 miles of unpaved road. The design called for 33 lb of cement per sq yd of roadway, mixed and compacted to a depth of 6 in. The FDR process also would improve the road template by establishing road crown and shoulders that improve drainage and road safety.
Construction was completed at the rate of 1,500-2,000 ft per day with a single treatment of chip seal applied the same day. The initial surface treatment provided protection for the new base and an improved surface for residents to travel on during construction. A double chip seal was applied to complete the triple surface treatment.
The county was extremely pleased with the final product, especially considering that the cost savings allowed more miles of roadway to be improved.
“We were able to save the taxpayers approximately $1.5 million and improve their quality of life by paving existing dirt roads that many citizens had driven on their entire lives,” Dennis Corp. President Dan Dennis, P.E., said.
The cement-stabilized base will improve the road’s long-term performance because the higher-strength base can carry heavier loads and is much less susceptible to water damage. The county plans to upgrade 16 more miles in 2007. By making improvements each year, it won’t take long for the county to substantially increase the quality of their road system and make excellent use of their scarce construction dollars.