Heidi Underwood 540-387-5493


June 2, 2011

VDOT using side-scan sonar for the first time in southwestern Virginia

SALEM – As part of the initial plan development to replace the Interstate 81 bridge over the New River located at mile marker 105 at the Montgomery County and Pulaski County line, a Virginia Department of Transportation hydrographic survey team will use sonar to map the river bottom beneath the bridge.  The survey is scheduled for Wednesday, June 8.

The sub aqueous data collected from the hydrographic survey will be used to produce 3-D color contour maps, sonar images and elevations of the river bottom.  These maps will help designers to see the river bed under the bridge as they begin drawing up plans for a replacement.  

During the survey, a boat will crisscross the New River beneath the bridge and allow a Hampton-Roads-based, VDOT team to use side-scan sonar with a global positioning system (GPS) to collect the data.  VDOT has used this technology along the eastern shore, but this is the first time in southwestern Virginia.

The side-scan sonar and GPS combination allows for a wider scan area than traditional sonar that scans only straight down.  In addition, this technology will generate much more accurate images, reduce the scan time and make the images available sooner than scanning with traditional sonar.

Work to design a new bridge to replace the I-81 bridge over the New River is in the very early stages.  The project, estimated at $55.4 million, tentatively is scheduled to be advertised for construction bids in winter of 2017.


Editor’s Note: Members of the media who wish to have an opportunity to take photos of the hydrographic survey team while they are working on June 8 can contact Heidi Underwood at 540-387-5493.

Information in VDOT news releases was accurate at the time the release was published. For the most current information about projects or programs, please visit the project or program Web pages. You may find those by searching by keyword in the search Virginia DOT box above.

Page last modified: Oct. 17, 2012