Evaluation of Erosion and Sediment Control Best Management Practices: Use of Silt Fence Tieback Systems and Anionic Polyacrylamide on Highway Construction Sites

Abstract

Every year the construction process exposes millions of acres of earth to the elements of wind, rain, and snow. This greatly increases the potential for erosion; therefore, the need for efficient erosion and sediment control practices is a high priority. In this research, silt fence tieback (a.k.a. “j-hook”) systems and anionic polyacrylamide (PAM) were investigated to determine their effectiveness as erosion and sediment control technologies. In the first phase of this research effort, a computational design procedure used to determine the storage capacity of silt fence tieback systems was outlined and a Visual Basic (VBA) coded spreadsheet design tool was developed to assist practitioners in the proper design of silt fence tieback systems. This tool was then used to design a silt fence tieback system on an Alabama Department of Transportation (ALDOT) job site and the performance was monitored over multiple rainfall events. The results from this phase of the study show that the silt fence tiebacks were very effective at containing transported sediment from their contributing drainage areas and preventing erosion from occurring along the toe of the fence.

In the second phase of the research effort, intermediate-scale experiments were performed to determine the effectiveness of dry granular anionic polyacrylamide (PAM) as an erosion control BMP. Three experimental scenarios were evaluated which included a bare untreated soil (control experiment) and PAM treated soil at application rates of 20 and 40 lb/ac. We also investigated whether PAM, when used as an erosion control BMP, provided sediment control benefits by decreasing the settling time of suspended solids in the surface runoff. The results from this phase of the research show that PAM applied at 40 lb/ac effectively reduced erosion and the settling time of suspended solids in the surface runoff. PAM applied at 20 lb/ac, on the other hand, provided little erosion control benefits but did reduce the settling time of suspended solids in most instances.