Collection System Components Pipelines

The City’s collection and transmission system is comprised of approximately 2,126 miles of combined and separate sewer pipe. The system consists of lateral, collection and trunk sewers that convey wastewater from homes, businesses and institutional and industrial facilities to a treatment facility. This includes an estimated 86 miles of combined sewers, 1,610 miles of separate sanitary sewers (exclusive of sewer lines serving the Hartsfield-Jackson Airport), and 430 miles of lines of service laterals in public rights-of-way. The collection system contains a variety of pipe materials ranging in size from 8-inch diameter up to large 11-foot-diameter brick and concrete arch sewers constructed as part of the combined sewer system. The collection system also includes the wastewater pumping stations, force mains, tunnels which convey flow to the WRCs and CSO facilities. Effluent transmission mains include force mains, tunnels and gravity flow pipelines that are used to convey treated wastewater from a WRC to a receiving stream or river.

The City’s wastewater collection and transmission system, with a few exceptions, is geographically located within the City’s corporate limits. This system collects wastewater from the City of Atlanta. This system is also used to convey wastewater from portions of Clayton County (Forest Park), College Park, DeKalb County, East Point, Fulton County and Hapeville to the City’s WRCs for treatment.

As shown in Figure 3-2, the City’s collection system services 10 sewer basins, including the Camp Creek, Intrenchment Creek, Long Island Creek, Nancy Creek, Peachtree Creek, Proctor Creek, Sandy Creek, South River, Sugar Creek and Utoy Creek Basins.

Pump Stations

The City’s collection system includes 16 remote pump stations which are used throughout the system to pump wastewater to high points, after which the wastewater flows by gravity to the next pump station or a WRC. In addition, the Utoy Creek Influent Pump Station and the Jonesboro Road Pump Station, located at the Utoy Creek WRC and the South River WRC respectively, are used to pump wastewater from a low point in the collection system to the elevation of the WRC treatment process. The Utoy Creek Influent Pump Station and the Jonesboro Road Pump Station, along with the pump stations that are part of the WRC treatment processes, are considered part of the WRCs.

Figure 3-3 shows the locations of the remote pump stations. Table 3-5, which follows Figure 3-3, identifies the capacity of each pump station along with the general attributes of the pump stations.

Of the 16 remote pump stations, one is a pneumatic ejector station and 15 are centrifugal pump stations. The pump stations range in capacity from 20,000 gpd to 59 mgd. Four of the pump stations – Flint River, Bolton Road, Phillip Lee and Rebel Forest – are capable of pumping peak flows greater than one million gallons per day.

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3-11 FIGURE 3-2

Sewer Basins

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ENGINEER’S FINANCIAL FEASIBILITY STUDY SERIES 2009 WATER AND WASTEWATER REVENUE BONDS

3-12 FIGURE 3-3

Wastewater System Facilities

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3-13

Supervisors and operators from the Bureau of Wastewater Treatment and Collection operate the pump stations. Mechanics, process control technicians and electricians are routinely available during the day shift and are available “on call” during all other shifts to maintain the stations. Fourteen of the 16 pump stations are monitored by telemetry.

TABLE 3-5

1 Data reflects testing performed in 2008.

2 Annual Average Daily Flow = total volume of wastewater entering a wastewater facility during any consecutive 365 days, divided by 365.

3 Low Flow Rate = lowest flow rate the pumping station equipment can accommodate.

4 Peak Hour Flow Rate = highest observed flow rate.

5 Firm capacity with largest pump out of service and based on pump down tests and review of telemetry data with pumps operating 24 hours/day, 7 days/week.

Force Mains

Each of the pump stations listed above, as well as the South River and Intrenchment Creek WRC Effluent Pump Stations, have an associated force main. Of these force mains, five are of significant size and length. These are the:

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3-14

x 14,800 linear-foot, 54-inch diameter South River WRC Effluent Force Main

x 11,400 linear-foot, 36- and 42-inch diameter Intrenchment Creek WRC Effluent Force Main

x 3,000 linear foot, 36-inch-diameter Bolton Road Pump Station Force Main x 2,700-linear-foot, 42-inch diameter Philip Lee Drive Pump Station Force Main x 30,300-linear-foot, 24-inch-diameter Flint River Pump Station Force Main

Of the remaining force mains, three are 1,500 to 2,500 feet long and are 8-inches or less in diameter. The remaining ten are less than 1,000 feet long, and 8-inches or less in diameter.

Tunnels

The City’s collection and transmission system includes four operating tunnels: two wastewater tunnels and two CSO tunnels. The two wastewater tunnels are the Nancy Creek and the Three Rivers Tunnels which are discussed herein. The two CSO tunnels are discussed in Section 3.6, CSO Facilities. The 16-foot diameter Nancy Creek Tunnel extends approximately 8 miles and conveys wastewater from the City (specifically the Nancy Creek Basin), DeKalb County and unincorporated Fulton County to the R.M. Clayton WRC. This tunnel and the associated Nancy Creek Pump Station were completed in December of 2005 and are in service. The Three Rivers Tunnel is approximately 7 miles long and transmits treated effluent from the South River WRC to the Chattahoochee River. (The term “Three Rivers Tunnel” is used to refer to the entire effluent line between the South River WRC and the Chattahoochee River; however, this “tunnel” is actually comprised of three sections: a force main, a tunnel and a gravity outfall sewer. The tunnel is of varying diameter through its different component sections, but the tunnel itself is 10-feet in diameter.) The Nancy Creek and the Three Rivers Tunnels were shown on Figure 3-3.

Proctor Creek Diversion Structure

The Proctor Creek Diversion Structure is also part of the collection system. This structure is located on the Proctor Creek Trunk off of Perry Boulevard in northwest Atlanta as previously shown on Figure 3-3. Construction of a new diversion structure, including demolition of the existing structure, was completed in 2007. The new diversion facility includes two electrically actuated sluice gates for directing flow to the R.M. Clayton WRC and the Utoy Creek WRC.

3.5.2 Physical Condition Evaluation