The City of Atlanta Department of Watershed Management

A Decade of Progress (2000-2010)
In 2000, the City of Atlanta was facing what seemed a Sisyphean task: two federal consent Decrees requiring extensive repairs to its network of old, leaking sewer pipes--some of which were installed in the early 1900s.
     Atlanta had been a national leader in controlling and treating combined sewer overflows (CSOs), constructing a storage tunnel and treatment facility in the eastern part of the city in 1984 and CSO treatment facilities on the west side in 1995. While these facilities complied with regulations in place at the time, Atlanta's explosive growth during the 1990s led to increased demands on its infrastructure.
    By 1998, a lawsuit filed against the city by the Upper Chattahoochee Riverkeeper (UCR), a downstream plaintiff, and the EPA/EPD for violations of the state and federal clean water acts resulted in an agreement that Atlanta would significantly reduce CSOs by 2007. In 1999, Atlanta entered into a second consent decree that required the city to address overflows from sanitary sewers (SSOs) with a compliance date of 2014.
    Under a $4 billion program called Clean Water Atlanta, the city set about complying with both consent decrees, employing a combination of projects, including those described below.

CSO Consent Decree Projects
Sewer Separation
A small number of the city's older neighborhoods were served by a combined sewer system. During periods of heavy rainfall, combined flows often exceeded the capacity of the sewer pipes, resulting in CSOs that sent untreated or minimally treated wastewater into local streams. As part of the work under the CSO consent decree, the city embarked on an ambitious plan in the summer of 2005 to separate approximately 174,000 feet of combined sewers in the densely populated Greensferry and McDaniel basins and the Stockade sub-basin. Sewer separation was completed in conjunction with the CSO Remediation Program, under which aging water lines, hydrants, and valves in the same geographical areas were replaced to ensure reliable water distribution and fire protection. The Sewer Separation Project was substantially completed in the fall of 2007.

Custer Avenue CSO Storage &
Dechlorination Facility
The Custer Avenue CSO is a ten-million-gallon, underground linear storage facility completed in January 2007. This storage facility, along with the existing 34-million-gallon Intrenchment Creek CSO Storage Tunnel, increased total overflow storage capacity to 44 million gallons. As part of the project, crews upgraded the existing Intrenchment Creek CSO treatment facility, adding fine screening, filters, and enhanced disinfection systems to allow the facility to better treat harmful bacteria and other residuals. The resulting treated CSO flows discharge into Intrenchment Creek, a tributary of the South River.

West Area CSO Tunnel & Pump Station
The CSO tunnel captures and treats sewage and storm water from parts of the city that still have combined sewers. The tunnel can store 177 million gallons of combined sewage and stormwater and treat 80 million gallons a day. Prior to the tunnel's construction, those flows underwent screening to remove large solids and debris, and chlorination/dechlorination to control harmful bacteria and chlorine before being discharged to local streams. The tunnel's tremendous storage capacity makes it possible to hold the majority of the overflow volume for subsequent treatment in a separate treatment center where it receives primary treatment, filtration, and disinfection before being released to the Chattahoochee River. The ability to store then treat combined sewage/stormwater means that the number of CSO events throughout the city has dropped from 16 per facility per year to an average of four total. "Between November 2008 and the 500-year rain event in September 2009, there were no CSO events at any of the West area CSO sites that feed the tunnel," says David St. Pierre, DWM Deputy Commissioner for Operations.
    The completed tunnel is approximately 8.5 miles long and 24 feet in diameter--sized to transport combined sewage and stormwater overflow from the Clear Creek, Tanyard, and North Avenue drainage basins to a dedicated CSO treatment facility at the R.M. Clayton Water Reclamation Center.  DWM Commissioner Robert Hunter describes the "tunnel projects--especially Nancy Creek and the West Area CSO--as the most spectacular projects with the greatest individual impacts."
    The CSO Tunnel project was delayed in July 2006, when the main bearing in the tunnel boring machine's (TBM's) cutter head malfunctioned and had to be replaced. Although the bearing failed due to a flaw in the steel, and the contractor bore the brunt of all the replacement costs, the replacement process set the project back. EPA and EPD agreed to extend the project timeline one year from November 2007 to November 2008. Once the bearing was replaced and the TBM began operating, crews quickly got back to work and the tunnel was completed in November 2008.
   Although the tunnel was completed while the city--and most of North Georgia--suffered from a terrible drought, it was during flooding approximately one year later that the tunnel's storage capacity was truly tested. "It's difficult to take credit when something, like sewage overflows, doesn't happen," says Janet Ward, DWM Public Relations Manager. "But it was striking how well the city's tunnels performed during the 500-year floods of September 2009. The city's ability to handle extreme amounts of stormwater during that time was a credit to the decision to build the tunnels as a means of dramatically reducing pollution in our rivers."

SSO Consent Decree Projects
As with the combined sewer system, Atlanta's booming population growth during the 1990s put significant strain on already-burdened and aging sanitary sewer lines. Old lines had developed cracks that allow groundwater to enter the pipe and sewage to leak out. Instances of untreated sewage, groundwater, and stormwater overflows from pipes and manholes became commonplace.
    Under the First Amended Consent Decree, the City committed to ongoing sewer improvements through intensive evaluation of sewer lines, rehabilitation or replacement of sewer lines where needed, and implementation of grease management and capacity certification programs for new development. A series of construction projects designed to improve reliability of the city's sewage pump stations is also under way. The current consent decree deadline for sanitary sewer-related improvements is July 1, 2014. However, the city has requested a 15-year extension due to declining revenues related to reduced water use during the recent severe drought and the effects of the recession on the one-cent sales tax that provides one-third of the funding for the capital program.

Nancy Creek Tunnel
The Nancy Creek Tunnel was constructed by the city in partnership with DeKalb and Fulton counties. The eight-mile-long, 16-foot-diameter tunnel has contributed to a reduction of more than 70 percent of the sanitary sewer overflows in the North Atlanta/Dunwoody area. It came online January 1, 2006.
    George Barnes, former DWM Deputy Commissioner for Engineering and the person who managed most of the major Consent Decree projects, cites the Nancy Creek Tunnel as one of the most significant. "[It] eliminated the overflows from separate sanitary sewers in the Nancy Creek Basin, which amounts to about 65 percent of the total volume of SSOs for the entire city," he says.

South River Tunnel & Pumping Station
The South River Tunnel and Pumping Station are being constructed as part of the SSO program. The tunnel will collect flows from existing sanitary sewers and transport them to a newly constructed pump station at the South River Water Reclamation Center (WRC)--alleviating surcharging and increasing sewer capacity. 
    The completed tunnel, which will span approximately 9,000 feet with a 14-foot finished diameter, is on schedule for a May 2011 completion.

Sewer System Evaluation Survey
and Rehabilitation
The Sewer System Evaluation Survey (SSES) involves the inspection and inventory of the city's 1,600-mile sewer system--a critical step in the city's massive sewer system rehabilitation program. Using techniques such as smoke and dye tests, closed circuit television mapping, and flow and rain monitoring, city engineers can determine sewer pipe defects, blockages, and capacity problems.
    To prioritize the work, engineers divided the city's sewers into six distinct groups, with Sewer Group 1 the most in need of repair/rehab to Sewer Group 6 containing the sewers in the best condition. "To date, crews have inspected via CCTV 1400 miles of the system," says Rebecca Shelton, PE, SSES/Rehab Design Manager. "In addition, SSES crews have inspected over 35,000 manholes--including finding and surveying over 6,000 previously unmapped manholes--and removed over 3,500 tons of debris from the sewers."
    Commissioner Hunter says that roughly "88 percent [of the city's sewer lines] have been inspected and 68 percent of the budget [for this] has been expended," adding that four of the six sewer groups have already been completed on schedule.
    Crews are using methods such as pipe bursting and cured-in-place pipe lining whenever possible to repair/rehab sewers, since these methods are less intrusive than traditional open-cut pipe methods, which require large sections of asphalt and concrete to be removed and then replaced when the work is completed. However, open-cut pipe laying and manhole rehabilitation methods are employed when needed. The procedures will both reduce the number of sanitary overflow events and extend the structural life of Atlanta's sewers by 50 years. SSES of the entire sewer system is expected to be completed by the end of 2011, on schedule and on budget.

An Investment in the Future
Atlanta's investment in its water and sewer infrastructure places the city ahead of the curve compared to other metropolitan areas that have yet to replace or repair aging systems. "Creating the Department of Watershed Management and staffing it with competent professionals was one of Mayor Shirley Franklin's most important achievements," says Sally Bethea, Executive Director of Upper Chattahoochee Riverkeeper. Bethea and UCR became the city's allies when Franklin proved she was serious about fixing Atlanta's water infrastructure. That leadership, Bethea says, "has helped move the city into the 21st century by fixing the pipes that sustain the built environment and cleaning up our river."