South Van Dorn Emergency Sewer Sag and Stream Rehabilitation

Alexandria, VA
Overview

In the winter of 2015, Fairfax County Department of Public Works recognized a high-risk sewer sag in a section of 21-inch sewer pipe spanning Backlick Run in Alexandria, Virginia. Immediately, the county contacted Dewberry and HITT to assist with design, constructability, and pricing. Because the sewer sag was immediately adjacent to the railroad line and the sewer break was anticipated to occur within the flowing stream, the design and construction could not disturb the railroad embankment or tracks, nor affect the overall floodplain, wetlands, or natural stream habitat in this urban watershed.

Stream restoration was executed utilizing 5,000 tons of Class III rip rap and 1,200 tons of 3-foot-diameter boulders, placed to create a riffle core around the replacement sewer pipe. The new sewer pipe and encasement is protected from stream scour, hydraulic pressures, and debris washed downstream during storm events. In order to work directly in the stream, the entire flow of Backlick Run was diverted around the jobsite, utilizing 72-inch culvert pipe and earthen dams.

Project Highlights

2016 WBC Craftsmanship Award
APWA Mid-Atlantic Chapter, Project of the Year Award for Environmental Projects Under $5 Million
ABC Excellence in Construction Honorable Mention, Commercial / Residential Renovation, 2016