Skanska was awarded a $47 million contract from the city of Atlanta to construct the new West Area Combined Sewer Overflow (CSO) Facility. Overflow from combined sewers, which carry wastewater and storm water, is a primary source of water pollution in major metropolitan areas. To protect water reclamation centers from flooding during heavy rain, regulators direct the combined flow to a CSO facility, which then treats the flow. During heavy storms, the flow can exceed the capacity of a CSO facility. The West Area CSO Facility, part of Atlanta’s plan to bring its combined sewer system into compliance with Federal and state water quality laws, reduces CSO discharge into waterways, reduces bacteria, and provides control over pollutants.
The scope of work on this project included construction of a drum screen building, a vortex solids complex, detritus separators, an electrical building and sedimentation basins where water is collected and stored. Other construction work included a chemical building, a new water filter system, a blower building and a dechlorination chamber. The process equipment package was valued at more than $10 million. Work also included construction of an operations building and junction/diversion structures.
Skanska installed 13,000 linear feet of piping, 20,000 cubic yards of concrete, a $3.3 million electrical package, a $2.8 million instrumentation package and more than $2 million of architectural work. Atlantic Skanska provided site grading, paving, and landscaping. Project operations included coordination with the city to accommodate the work of three other contractors at the site.
The new CSO plant has a treatment capacity of 85 mgd. The combined sewage stored in the tunnel system goes through physical and chemical treatment processes before being discharged into receiving waters. Treatment processes include clarification and filtration to remove suspended solids and disinfection with chlorine followed by dechlorinated with sodium hypochlorite and sodium bisulfite