Background
Atlanta and its surrounding counties have been growing at an incredible rate
for many years. The impact of the constant influx of people, construction of
new homes and commercial development has increased the stress on the infrastructures
that support everyday life. The increase in traffic is one of the most visible
aspects of this growth and development. One of the least visible aspects is the
aging underground infrastructure that carries sewage to our treatment facilities.
That is, it’s least visible until sewage backs up into backyards and basements or
flows into our creeks.
The City of Atlanta, DeKalb County and Fulton County have agreed to work together to
construct the Nancy Creek Tunnel to help an area that experiences recurring
problems with sewage overflows. The Nancy Creek drainage basin includes the
northern part of the City of Atlanta, parts of northeast Fulton County and a
portion of DeKalb County. Sewage from these areas is treated at Atlanta’s R.M.
Clayton Water Reclamation Center (WRC) on Bolton Road in northwest Atlanta.
When there is a heavy rain event, the existing sewer system does not have enough
capacity to carry both the raw sewage and the additional storm water that enters
the lines through manholes and cracks in the pipes. This problem has been ongoing
since the 1980s. Various options for increasing the sewer capacity were investigated
and the tunnel option was found to be the most environmentally sound and least
disruptive solution. The tunnel option is supported by most of the residents
who live within the Nancy Creek basin and have experienced sewage backups over
the years.
The existing Nancy Creek trunk sewers will remain in continuous operation through
the construction period. When completed, the tie-in of the Nancy Creek Tunnel at
the R.M. Clayton WRC will be accomplished without interrupting plant operation.
Description
Three construction shafts will be built as part of the tunnel project. The R.M.
Clayton and Johnson Ferry Road construction shaft will anchor the tunnel line,
with an intermediary shaft located at Roswell Road. Eight intakes will be used to
divert flow from shallow sewers down to the tunnel. One intake will be located at
each of the construction shaft sites. The other five intakes will be located at
remote sites, and will tie into the main Nancy Creek Tunnel through smaller
connecting tunnels. The Nancy Creek Tunnel Lift Station will be located at the end
of the tunnel, located inside the R.M. Clayton Plant. The lift station will be used to pump the wastewater from the Nancy
Creek Tunnel to the treatment center above. The lift station, which will have a capacity
of 100 million gallons per day (MGD), will remove wastewater from
the tunnel at a rate that will maximize the available capacity for the WRC.
The lift station design will allow the City flexibility to determine when and how
much flow is pumped to R.M. Clayton WRC or stored for later pumping to the plant.
The lift station will primarily be underground. The structure that is above ground
will be architecturally consistent with the existing facilities near it. Although
the design of the lift station will significantly reduce the potential for odors,
an odor control system will be installed as an added measure. Additionally, the
lift station is being designed for reliability, ease of operation, and the
capability to operate through power outages or flood conditions.
Benefits
A primary benefit, the Nancy Creek Tunnel and Lift Station project will provide
relief from sanitary sewer overflows for the Nancy Creek community
while protecting the ability of the R.M. Clayton WRC to continue serving northwest
Atlanta and northern DeKalb County.
Additional benefits of the construction include:
- Sewer rehabilitation without environmental destruction
- Minimal environmental impacts during construction
- Minimal disturbance of neighborhoods
- No restriction on property owners’ surface use of land
Milestones
Notice-to-Proceed was issued by the City of Atlanta to the construction contractor, Nancy Creek Constructors, on July 15, 2002. The contract calls for all work to be completed in 1,290 days, or by January 24, 2006. Substantial completion, defined as the point at which the tunnel must be ready to accept flow from the sewers, is required in 1,200 days, or by October 26, 2005. The Consent Decree requires relief from sewer overflows to be in place by December 31, 2005.