Cobb County Government



Stephen D. McCullers, P.E.
660 South Cobb Dr
Marietta, GA 30060
(770) 423-1000
(770) 419-6224 fax

Water System Website

Water / Sewer

Chattahoochee Tunnel
"Outstanding Civil Engineering Project of the Year"

SEPTEMBER 12, 2005 – The 9.5-mile-long Chattahoochee Tunnel in Cobb County, Georgia, was named the Outstanding Civil Engineering Project of the Year at the 2005 Georgia Section of the American Society of Civil Engineers (GA-ASCE) Annual Awards Banquet, held September 9 at Atlanta Marriott Century Center.

The Chattahoochee Tunnel project was a joint endeavor of Jordan, Jones & Goulding (JJG), an Atlanta-based consulting engineering firm responsible for the design and construction of the tunnel; project contractor Gilbert/Healy JV; construction management services of Parsons/Jacobs; and the Cobb County Water System (CCWS) as the owner.

As a good environmental steward, CCWS began proactively addressing the explosive growth occurring in East Cobb County long before the launch of this tunneling project in mid-2000. The goal was to provide sufficient build-out capacity to the existing network of some 500 miles of sewers in East Cobb by 2040. Options evaluated included conventional open-cutting, a deep tunnel and a combination of both methods. The deep rock tunnel, with the least amount of environmental and community impacts, was ultimately selected.

As the future sewer system of Cobb County, the Chattahoochee Tunnel stretches from near Lower Roswell Road in East Cobb to the Chattahoochee River. Taking approximately four years to construct, the tunnel measures 18 feet in diameter and over 200 feet deep. Its cost is $113.6 million.

This remarkable tunnel serves not only as a conveyance system, but one with flow equalization capability, shaving peak flows during wet weather events and minimizing the need for constructing costly treatment facilities with higher capacities. It also features sophisticated vortex type intake structures to divert flows into the deep tunnel. The construction documents embrace unique risk management tools, and CCWS controlled cutting-edge secondary grouting methods to minimize groundwater inflows into the tunnel.

The project was selected by GA-ASCE based on the following criteria: contributions to the well-being of people and communities; resourcefulness in planning and solving design challenges; pioneering in use of materials and methods; innovations in construction; impact on the physical environment; beneficial and adverse effects of the project, including aesthetic value; unique approaches and partnerships; risk management; fiscal responsibility; and consideration of sustainability or maintenance. This award recognizes the efforts of all involved to perceive future needs and marks a job well done.