The Effect of In-stream Construction Activities on Turbidity and Suspended Sediment

In-stream construction activities involve the use of temporary enclosures that exclude water from the construction site. Cofferdams are one of the most common methods used by the Virginia Department of Transportation (VDOT) to enclose an area for the purpose of pumping out water and allowing work to be conducted in the dry. Properly designed cofferdams are effective at keeping sediment out of the adjacent waterbody during construction. The construction and removal of cofferdams, however, create some degree of sediment release as a result of unavoidable streambed disruptions. Some of VDOT’s in-stream construction activities take place in areas that may contain suitable habitat for freshwater mussel species, many of which are listed as state or federally threatened or endangered. To reduce potential impacts to mussels, VDOT and regulatory agencies coordinate with regard to area of impact determinations and associated stream surveys requirements. However, agencies lack the empirical data on which these decisions are based. This study will include evaluating stream data collected at in-stream construction sites for the purpose of informing decisions associated with protecting sensitive species. Specifically, turbidity and suspended sediment data will be collected at defined distances upstream and downstream of project sites before, during, and following cofferdam construction and removal. The findings from this research will provide a better understanding of the intensity, duration, and transport distances of sediment associated with the construction and removal of cofferdams and may result in refined distance requirements for habitat assessments and surveys. Study outcomes may also lead to a reduced frequency of consultations with regulatory agencies, thereby saving VDOT staff time and costs associated with coordination and survey work.

Language

• English

Project

• Status: Active
• Funding: $296786
• Contract Numbers:

  122843

• Sponsor Organizations:

  Virginia Transportation Research Council

  530 Edgemont Road
  Charlottesville, VA  United States  22903
• Performing Organizations:

  Virginia Transportation Research Council

  530 Edgemont Road
  Charlottesville, VA  United States  22903
• Principal Investigators:

  Lloyd, Lewis

  Donaldson, Bridget

• Start Date: 20230125
• Expected Completion Date: 20251231
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Cofferdams; Construction; Environmental impacts; Streams; Suspended sediments; Turbidity
• Subject Areas: Construction; Environment; Highways;

Filing Info

• Accession Number: 01872508
• Record Type: Research project
• Source Agency: Virginia Department of Transportation
• Contract Numbers: 122843
• Files: RIP, STATEDOT
• Created Date: Feb 4 2023 8:56AM