Improving the Design and Performance of Double-Row Sediment Barriers Used During Highway Construction

Abstract

Sediment barriers (SBs) are stormwater management devices often installed along the perimeter of a construction site to intercept and treat overland sediment-laden flow before discharge into the surrounding environment. Effective SB practices remove stormwater pollutants by creating a temporary impoundment upstream of the practice which facilitates sediment capture via sedimentation. Controlling agencies and design practitioners often specify the installation of two SB practices (i.e., primary and secondary SB) in areas where enhanced stormwater treatment is critical because of downstream environmental concerns (e.g., impaired waters). This study sought to identify the overall performance of a commonly specified double-row SB (i.e., double-row silt fence), as well as six alternative designs that utilized various secondary SB practices that could be easily paired with a primary silt fence SB. Small-scale experiments were conducted on each of these double-row design configurations to develop a comprehensive understanding of their performance capabilities. A statistical analysis conducted on 700 water quality data points suggests that all six alternative double-row designs significantly outperformed the double-row silt fence installation. Water quality improvements achieved using alternative secondary SBs ranged from 11% to 71% during the 30 min test period and 14% to 60% during the 90 min dewatering period. In comparison, the double-row silt fence installation only achieved 5% and 1%, respectively. Additionally, post-test observations of secondary SB cross sections indicate that, at best, only half of the matrix filter media within the secondary SB contacts sediment-laden flow. This observation suggests that alternative cross-sectional designs could improve media utilization.