PERFORMANCE EVALUATION OF SEDIMENT BASIN DESIGNS FOR HIGHWAY CONSTRUCTION SITES IN TENNESSEE

Performance of three sediment basin designs were tested; they were: 1) the TDEC standard design with a forebay, 2) the TDOT design with an inlet check dam, and 3) the TDOT standard design that does not include an inlet check dam. An 1/17 of an acre scaled physical model sediment basin, was constructed next to an elevated outdoor open flume used to mix known water volumes and sediment mass routed by gravity-flow into the basin. The measurement for performance was simply the percent sediment mass retained in the basin from the total input per experimental run (percent sediment removal). Three experimental replicates per design were completed. Sediment was analyzed by concentrations, loads, and particle size distributions (PSDs). All designs were above the 80% removal regulatory requirement for Tennessee: with TDOT, TDEC, and TDOT with check dam design achieving a total percent sediment removal of 95.4 %, 98.2 %, and 97.9 %, respectively. PSD data from the experiments provided key information for developing a sediment-basin design model to account for differential particle size settling. In addition, these experimental results were compared with sediment basin performance data collected at active highway construction sites, as well as from other published experimental studies.