PROJECT LEADER:
John C. Hayes
COOPERATOR:
Mark Corley, South Carolina Department of Natural Resources, Columbia, South Carolina
FUNDING AGENCIES:
South Carolina Department of Health and Environmental Control (DHEC)
South Carolina Agricultural Experiment Station
DESCRIPTION
This project will install and demonstrate sediment control methods that show how to improve water quality (turbidity) from small construction sites by incorporating site specific information into design of sediment controls. Sites demonstrating the importance of properly estimating eroded sediment sizes during construction activities such as land development and road building will be located in Cupboard Creek/Lake Broadway (3060103-070) watersheds. These basins are typical of many Piedmont watersheds across the Southeast in topography, soils, and previous land use. The area, consisting of 128,810 acres, is listed as a priority watershed in the South Carolina Management Program because recreational and aquatic life uses are only partially supported due to sediment-caused turbidity and fecal coliform bacteria.
Each site will be less than 5 acres in order to avoid conflict with NPDES regulated activities and will be divided into areas where specific erosion/sediment control practices will be installed on exposed subsoils. Relatively little is known about erosion control from subsoils, but they do not react to rainfall as do top soils and have quite different sediment characteristics because of structural, textural, and chemical differences. A computer controlled portable rainfall simulator will apply rainfall to the areas so that runoff rates and sediment samples can be collected from each treatment for comparison. For BMP effectiveness, erosion and sedimentation rates will be compared pre- and post-project. This information will provide an evaluation of BMP methods. These results and relationships between subsoil characteristics and erosion will be shared at field days and through agency newsletters.
SIGNIFICANCE
The recently enacted South Carolina Stormwater and Sediment Reduction Regulations require use of eroded size distributions, but no field data has been collected to show that the recommended methods actually works. Eroded size distribution probably has more impact on the trapping efficiency of a sediment control structure than does any other input. Errors in size can easily change the size of a pond by an order of magnitude or more. However, very little quantitative information is available to assist the engineer in determining whether the size distribution is being used properly. This project will evaluate the size distribution in a variety of situations and determine if the sizes selected for design purposes are reasonable.