Recent CCTV inspection showed the presence of large cracks in some of the outfall sewers downstream of pump stations. DCWASA was concerned that the damage may be extensive and required additional information before proceeding with rehabilitation.

Savin Engineers, working as a subconsultant to Greeley and Hansen, conducted an investigation of the large diameter outfall sewers to gather additional data for the design engineers. At seven different sites, Savin conducted hammer tests to determine the compressive strength of the pipe wall, core drilled through the wall to determine its thickness (up to 16 inches in some locations), and determined the spatial arrangement of the rebar with a magnetic locator.

The 9’ 6” horsehoe shaped sewers posed a special challenge since much of the work was done near the crown of the pipes. Also, special coordination with Bolling Air Force Base and the operation if the pump stations was required for the work, which was done at night under low-flow conditions.