Sewer overflow tunnel celebrated

Tonight, the city of Atlanta celebrates a victory over out-of-control sewage.

After three years of digging and pouring concrete, construction crews have completed a deep sewer tunnel that can carry and store up to 177 million gallons of rain and sewage —- enough to fill the Georgia Aquarium 21 times. The tunnel gives the city’s combined sewage overflow facilities time to fully treat the mixture of household waste and street wash before sending it back to the Chattahoochee River.

Before the West Area Combined Sewer Overflow Tunnel, the system was often overwhelmed when it rained. Storm water swelled the pipes, which already carried sewage, forcing shortcuts that sent undertreated sewage into the rivers and streams.

The $190 million tunnel has been the most controversial piece of the city’s $4 billion overhaul of its water and sewer system. Opponents wanted Atlanta to modernize its combined sewers by separating sewer pipes from storm drains, as most of the city’s pipes are. Only about 10 percent of Atlanta remains hooked to combined sewers, in the central city.

Officials opted for the tunnel because it could be done quicker and with less disruption. The city estimates the tunnel should reduce the number of spills from the combined system from about 300 a year down to 16, when it rains the most. The tunnel, in two sections, runs about 200 feet below the surface, from northwest Atlanta, through Georgia Tech, to southwest Atlanta. The other section runs under the Downtown Connector and over to Piedmont Park in Midtown.

Atlanta is working to update its sewer-only system by 2014.

THE DEGREES OF SEPARATION

The CSO Consent Decree Completion Celebration with Mayor Shirley Franklin. 6 p.m. today at the West CSO Treatment Facility, 2498 Coronet Way in Atlanta.

The history

1995: The Upper Chattahoochee Riverkeeper files a federal lawsuit against Atlanta, charging that state environmental officials are incapable of making the city stop polluting the river.

1998: The city signs a consent decree with the federal and state environmental regulators and the Riverkeeper, agreeing to fix its sewers and stop polluting the Chattahoochee and South rivers.

2002: Mayor Shirley Franklin enters office, dubbing herself “the sewer mayor” and vowing to finally get the city on track to rehab leaky water and sewer pipes, some a century old.

2004: Three of four city voters approve a 1 percent sales tax to help pay for the infrastructure improvements.

2005: Construction begins on the West Area Combined Sewer Overflow Storage Tunnel.

Nov. 10, 2008: Atlanta celebrates compliance with the 1998 consent decree on the city’s combined sewer system, which included 55 deadlines and cost $757 million.

They said it: Sally Bethea, (left) executive director of the Upper Chattahoochee Riverkeeper:

“I’ve been waiting for this day for a long time. I’m really excited.”

The consent decree included these projects:

> $25 million Greenway Acquisition Program, under which nearly 24 miles of stream buffers in Atlanta and eight metro counties were bought to protect the waterways from development;

> Separation of 33 miles of combined sewers;

> Construction of the West Area CSO Tunnel;

> Construction of the Custer Avenue Storage and Dechlorination Facility, which can store 10 million gallons of combined stormwater and sewage.

What else has the city done as part of the water and sewer overhaul?

> Inspected 1,111 of the 1,530 miles of sewer pipe, or 73.6%;

> Rehabbed 280 miles of sewer pipe, or nearly half the amount that may need repair;

> Replaced more than 60 miles of water pipes and mains.

Source: City of Atlanta Department of Watershed Management

 CHARLES W. JONES / Staff
a. Sewer lines carry waste from homes to the sewage treatment plant, where it is processed and released into a waterway.
b. When it rains, the sewage treatment plant reaches capacity. Sewage mixed with rain flows into a combined sewage 
overflow tunnel. 
It is held in the tunnel until it can be treated at the overflow facility. 
Once processed, the water is released into a waterway.

About the overflow tunnel
Capacity: 
177 million gallons of combined stormwater and sanitary sewage.
Length: 8.6 miles
Diameter: 24 feet

Diagram shows path of: 
Sewage from house
Sewer line 
Storm drain
a. Sewage treatment plant 
b. Overflow tunnel
Combined sewer overflow facility
Waterway

Source: City of Atlanta Department of Watershed Management