We are designing the City of Atlanta's top priority infrastructure project – the Raw Water Delivery System. Current infrastructure dates back to the 1890s, with critical portions well beyond their design life. The new system will move raw water from the Chattahoochee River to two water treatment plants and storage facilities.
The project consists of 5 miles of 10-foot diameter tunnels in hard and abrasive Gneiss bedrock, use of the 2.4 billion gallon Bellwood Rock Quarry for raw water storage, two major construction shafts, a raw water intake, and three pump stations. The tunnel varies in depth from 250 feet to over 500 feet. The project will be delivered via a CM@Risk contract, making it one of the largest such tunnels ever built in North America.
Our design significantly reduces risk by making sure the tunnel is constructed in the best rock horizon/geology with shaft locations that minimize impacts. Our scope includes subsurface investigation, TBM boreability studies, selection of the tunnel horizon, hydraulic evaluation and modeling, pump type specifications, connection to the quarry, lining design, security measures, and surface works. Project challenges include mining near the river, the Brevard Fault system, and an inability to shutdown treatment facilities. We are also designing an energy recover system with power generating turbines in the drop shaft and specifying green construction methods in all above grade structures.