Monitoring the Effects of Highway Construction in the Sedgefield Lakes Watershed

This report summarizes the results of a water quality monitoring project to document the effects of the construction of the I40 bypass around Greensboro on the water quality of residential lakes in the Sedgefield and King’s Mill communities. Automated monitoring equipment were installed at 4 locations downstream of the highway corridor in the drainage area to the Sedgefield lake, while in the King’s Mill community, automated equipment was installed upstream and downstream of the corridor. At each monitoring site, discharge was monitored continuously and samples of stream discharge collected on a flow-proportional basis throughout the project. All samples were analyzed for total suspended solids (TSS), total solids, and turbidity, while selected samples were also analyzed for nitrogen and phosphorus forms. A recording raingage was also maintained for all of the monitoring period in the Sedgefield lakes watershed and in-situ measurements of temperature, dissolved oxygen, conductivity, and pH were made periodically at each site. Monitoring data at all sites documented increases in sediment loading and turbidity following the start of highway construction, although to different extents. The greatest increase in sediment loading and turbidity occurred at the upstream site on the Tilly tributary. For this site, which was located just downstream of the highway corridor, about 60% of the sediment load during construction was associated with two tropical storm systems that occurred in September 2004. At this time the highway was particularly susceptible to erosion because more than 20 ft of fill had recently been added to bring the road surface to near grade and the sideslopes were not vegetated yet. Increases in sediment loading and turbidity at the other sites during highway construction were less severe and more like what would be expected. Mean turbidity levels during construction at all sites downstream of highway construction were greater than 50 ntu. Limited monitoring of temperature, specific conductance, DO, and pH for all six sites showed that highway construction had little, if any, effect on these parameters, except possibly temperature, which appeared to increase at Tilly-up and King’s Mill-down, but this was not confirmed at the other sites. There was not enough samples analyzed for nitrogen and phosphorus to compare pre- to during-construction, but the data indicated that their levels in samples of stream discharge were sufficient to support nuisance aquatic growth in downstream lakes.

Language

  • English

Media Info

  • Media Type: Web
  • Edition: Final Report
  • Features: Figures; References; Tables;
  • Pagination: 33p

Subject/Index Terms

Filing Info

  • Accession Number: 01152604
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/NC/2006-07
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Feb 26 2010 11:46AM