The report documents the effects of the construction of the I-40 bypass around Greensboro, North Carolina on the water quality of tributaries to residentail lakes in the Sedgefield Lakes (SELCO) and King's Mill communities. In addition, data from two past projects is included to provide a comprehensive characterization of the water quality. Two unnamed tributaries draining to SELCO were monitored at two locations downstream of the highway corridor and one tributary draining to a lake in the King's Mill community was monitored upstream and downstream of the highway corridor. At each monitoring site, discharge was continuously monitored and flow-proportional samples were collected. Samples were analyzed for total suspended solids, total solids and turbitity. A recording raingage was also maintained in the watershed and in-situ measurements of temperature, dissolved oxygen (DO), conductivity and pH were made periodically at each site.
Monitoring data at all sites documented elevated sediment export and turbitity levels during the construction period as compared to the pre- and post-construction periods. The greatest increase in sediment export and turbitiy occurred at the upstream site on the Tilly tributary. Mean turbitity levels during construction at all sites downstream of highway construction were greater than 50 NTU. Post-construction mean turbitity levels were much less than during construction. Limited montitoring of temperature, specific conductance, DO and pH for all six sites showed that highway construction had little, if any, detectable effect on these parameters.
