EFFECTS OF CONSTRUCTION SITE SEDIMENTATION BASINS ON RECEIVING STREAM ECOSYSTEMS

Abstract

The effects of sedimentation basin discharges on receiving stream ecosystems were investigated for threeconstruction sites in Lancaster County, Pennsylvania. Samples were collected in the receiving stream at two locationsupstream and downstream from the basin outlet pipe and directly from the outlet pipe while the basin was dischargingfollowing rainfall events. Suspended sediment concentration, particle size distribution, benthic macroinvertebrates, andtemperature were evaluated at each location. Stream temperature increased slightly (+0.3C) on the discharge side of thestreams immediately below the sedimentation basins, but the elevated temperatures did not extend farther downstream.Stream sediment concentrations increased significantly (p < 0.05), and the high concentrations persisted to the downstreamsampling site located 100 m below the basin discharge. During storm events, the basin effluent contributed a larger proportionof finer suspended sediments, as measured by particle size distribution, than the stream, and the smaller particle sizespersisted downstream. There was no significant change in number of macroinvertebrate individuals as a result of thesedimentation basin discharge, but there was a significant decrease in the number of taxa observed in the receiving streamdirectly below the basin outlet. However, this observed reduction in species richness was not significant 100 metersdownstream from the basin discharge pipe.