TMG was awarded the design/build contract to restore 365 linear feet of stream bank on the north side of Accotink Creek, and 135 linear feet of stream bank on the south side of the creek channel.
The stabilization efforts were designed to protect the shoreline from erosion and prevent the possible undermining of the campus’s re-chlorination plant. Based on a written narrative, construction efforts involved natural restoration techniques starting with locating the stream’s thalweg (the line defining the lowest points along the length of the riverbed). Then, using natural stream design, rocks, logs, soil and vegetation were place at designated locations along the stream banks to reshape the stream. Structures included installing Longitudinal Peaked Stone Toe Protection (LPSTP), Bendway Weirs, Keys, Living Dikes, Locked Logs and culvert repairs. TMG created temporary stream-flow diversions using inflatable cofferdams to control sediment, allowing work to be completed in a relatively dry environment. The final phase involved planting several thousand willow tree stakes to further stabilize and establish sediment control.
The project schedule was driven by the need to complete the work before the arrival of spring, and by the need to obtain the approval of various agencies, including the Virginia Department of Environmental Quality, prior to the commencement of work. TMG mitigated potential permitting delays by dedicating additional personnel to ensure that the permitting process was completed as expeditiously as possible. As a result, crews were able to complete the restoration months ahead of schedule and well before spring run-offs could once again threaten the stream banks.
Final reconciliation at project close-out yielded a credit in the categories of stone and aqua barriers, allowing the project to deliver under-budget in addition to ahead of contracted schedule.