Erosion Control and the Impact of Highway Construction on Wetland Water Quality: A Case Study

To assess the efficacy of control on sedimentation and erosion during highway construction, the impact on water quality in adjacent wetlands was monitored. Water quality measures used were turbidity, suspended solids, conductivity, alkalinity, hardness, pH, organic carbon, dissolved oxygen, nitrate and phosphate. Heavy metal concentrations in surface waters and stream sediments were measured. Upstream measurements, used as controls, showed periodic, seasonal variations. Downstream measurements were not significantly different from upstream measurements except during an incident when erosion controls were neglected and during covert construction. Culvert construction resulted in resulted in increased sediment and turbidity from diversion and dewatering and increase in hardness, attributed to concrete leaching. Attention to sedimentation and erosion controls and seasonal scheduling of highway construction are advocated as a means of ameliorating the effects on wetlands.