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Custer Avenue CSO Project FAQs

What is the purpose of the Custer Avenue CSO Storage & Dechlorination Facility Project?

The Custer Avenue CSO Storage Facility project & Treatment Facility upgrades is one part of a comprehensive plan for long-term control measures to bring the City’s combined sewer system into compliance with water quality standards. This facility is part of storage and treatment alternative that involves capturing and storing overflows from combined sewers that result from rainfall. The overflows are stored in a linear storage facility. When the rainfall is over, the captured CSO volume is conveyed via an existing tunnel to a separate treatment system for removal of pollutants and disinfection before discharge to receiving waters. As parts of the combined sewer system are separated, this same system can be used to treat stormwater runoff from the urban core portion of the CSO area.

Why is additional storage needed?

Additional storage is needed to increase the volume of CSO that is captured and treated so that the volume of
partially treated overflow discharged to Intrenchment Creek can be reduced to the level required to meet water
quality standards. During rain events, combined sewer overflows travel to the Custer CSO facility and are
directed into an existing tunnel and conveyed to the Intrenchment Creek CSO Treatment Facility. However,
during extended periods of rain, the existing tunnel reaches its capacity and some overflows discharge to
Intrenchment Creek with only disinfection treatment. The new storage facility will supplement the existing
tunnel storage capacity so that more CSO can be captured and treated at the Intrenchment Creek CSO
Treatment Facility.

How will the underground storage facility be constructed?

To construct the new storage facility, a 30-foot diameter vertical construction access shaft, approximately 120 feet deep, will be excavated into rock. Its walls will be reinforced with concrete where required for stability. This shaft will provide access to start constructing the below-ground storage facility. Contractors will excavate into solid rock using drill and blasting construction methods to create the storage cavern.

How was the alignment for the Custer Avenue linear storage structure selected?


The alignment for the Custer Avenue linear storage structure was selected based on the best possible rock
or geological conditions for constructing the underground storage facility, proximity to the existing tunnel, and minimum impact on private property.

How does this linear storage facility compare to tunnels in Atlanta?

Although the linear storage structure is excavated through mostly solid rock, existing tunnels are considerably deeper than the depth proposed for the Custer Avenue linear storage.


Will Easements be acquired for this Project?


The City will be acquiring one subsurface easement for this project. The remaining construction areas are along city streets or city owned property.

How will safety concerns be addressed with this project?


The City and its design engineer for the Custer Avenue Tunnel are committed to maintaining the City’s excellent safety record on all construction projects. The City will continue to require the contractor to develop and implement a safety program.


Will there be any odors associated with the operation of the Custer Avenue CSO project?


The entrance at the top of the construction access shaft to the linear storage facility will be sealed to eliminate odors.

Will any streets along the alignment be closed to traffic during construction? What about construction truck traffic?

No streets will be closed. Trucks hauling excavated rock from the shaft and underground storage facility will only be allowed to turn left onto Custer Avenue to Moreland Avenue to avoid residential areas as much as practicable. The contractor will be required to keep all streets free of refuge, rubbish, scrap materials and debris.

Why won't the stormwater and wastewater be separated in the entire Custer Basin?

Studies of the combined sewer system have shown that the proposed additional storage and upgraded treatment for CSO’s in the Boulevard CSO Basin is the most economical and effective approach to meeting water quality standards. Stormwater runoff from urban areas is polluted with solids, bacteria and heavy metals and will require additional controls in the future if water quality standards are to be met in all streams and rivers.

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