Tollway Runoff Monitoring Project Begins

ISGS scientist Charlie Knight collects discharge data from a roadsideA ditch at the future site of a bioswale along I-294 in Des Plaines, Illinois.Wetland scientists at the Illinois State Geological Survey began a 3-year water-quality monitoring project for the Illinois State Toll Highway Authority to determine the effectiveness of bioswales that are now under construction along a section of I-294, which is being widened. Bioswales, or vegetated wetland drainageways, are intended to improve tollway runoff by increasing contact time with wetland vegetation and soils, which transform nutrients and remove suspended sediment and certain other pollutants. The first phase of this project involves the emplacement of automated samplers, flow meters, and water-quality data loggers at three stations along the tollway to monitor runoff prior to construction of the bioswales and to establish the baseline loads of target contaminants leaving the roadway onto adjacent lands owned by the Forest Preserve District of Cook County or directly into the Des Plaines River. Later phases will measure the effectiveness of the bioswales after construction and compare the quality of runoff discharged by the bioswales to the present load.