Atkinson Construction in July began assembling the 12-ft tunnel boring machine that will complete the City of Atlanta Water Supply project. The TBM arrived to the jobsite in sections on more than 70 trucks. The TBM is being assembled on the quarry floor and will be used to excavate a five-mile tunnel to connect the Chattahoochee River and the Hemphill Water Treatment Plant to the former Bellwood Quarry. The Water Supply Project, scheduled for completion in 2018, will increase the City of Atlanta’s water reserve from 3 to 30 days.
The City of Atlanta’s raw water system infrastructure forms the foundation and starting point for delivering clean and reliable drinking water as well as fire protection service for more than 1 million system users. In the 1890s, when Atlanta faced major public health issues with water quality and water availability, the investment in raw water conveyance and storage was the first step in securing a sound future for the City. Since then, that investment has been integral to the success of Atlanta’s economy and the health of its citizens. Now, over 120 years later, Mayor Kasim Reed recognizes the critical need for reliable delivery of clean and safe drinking water to the City and neighboring jurisdictions that rely on the City for this vital resource.
The original raw water pipelines are still in service. Cast iron mains of diameters 30, 36 and 48 in. and were installed in 1893, 1908 and 1924, respectively. Although these were renewed with a cement liner in the 1950s, they have far exceeded their design life. A fourth line, a 72-in. steel main, was built in 1975 and metallurgical weaknesses restrict its operation to warm weather months. The vision of the next 100 years of drinking water for the Atlanta area includes renewing the foundation of the city’s water supply system and ensuring secure and reliable delivery.
The Chattahoochee River is the source of raw water for the entire Metro Atlanta. The path of the new conveyance system will follow closely the path of the current cast iron lines. The new 5-mile conveyance tunnel (10-ft ID) will end at a quarry site that will be transformed into a new water storage facility. Blasting at the quarry site began in April 2016. It will be designed to meet the current withdrawal permit limits and store any excess water not used for daily drinking water. Once filled, this facility will hold 2.4 billion gallons of water to provide the City a 30-day backup water supply.
The program design will address the objectives of achieving 100 years of asset lifecycle and flexibility in system operations. The estimated cost of design and construction for conveyance and water storage is approximately $300 million.