DC Combined Sewers/Fabridams

Category
Utility

Client
DC Water and Sewer Authority

Location
Washington, D.C.

Key Challenges & Project Details

• Modifications to combined sewer chambers and installation of 12 inflatable dams within the combined sewer system in various locations throughout Washington, D.C.
• The dams, approx. 12’ x 30’, are equipped with complex instrumentation systems which sense flow levels within the combined sewer chambers, inflating and deflating as appropriate during rain and non-rain periods
• Installed concrete pads, air piping, mechanical/electrical equipment, piping, valves, conduit, junction boxes, instruments and other devices at eight locations
• Deep excavations were required—up to 30’ in depth and 20’ in length within city streets
• Existing pipe lines were supported within each excavation and cast-in-place concrete structures 80 CY+ in volume were constructed over pipes up to 84″
• Installed approx. 220 LF of 10″, 12″ and 15″ sewer pipe, a 60″ diameter sewer manhole, a 72″ sewer manhole flow diameter and bypass pumping of sewers up to 78″ diameter to allow connection
• Most sites were in heavily traveled roadway
• Required extensive planning for traffic control, utility relocations and other areas of construction
• Pavement, curb, sidewalk and other disturbed areas were restored after dam and sewer modifications were complete
• Many safety considerations such as confined space entry, preparation for storm events and personal protective equipment
• Several of the sites are heavily influenced by tidal flow of the Anacostia River
• Temporary bulkheads equipped with “flap gates” to protect the work zone from tidal flow while still allowing storm water to run through were field fabricated
• Inserting and maneuvering the Fabridams through the sewer chambers was accomplished with custom lifting/winching/jacking/rolling devices
• Corman completed the project successfully and on time