The Challenge
The City of Atlanta Water Supply Program was developed to address limited emergency raw water storage capacity and increasing vulnerability to drought and system disruptions. At the time, the City had only a three-day reserve of raw water, creating significant risk to residents, businesses, and economic stability. The program’s purpose was to establish a reliable, long-term water supply system by conveying raw water from the Chattahoochee River to the Quarry Water Storage Facility (QWSF) and distributing it to both the Hemphill Water Treatment Plant (HWTP) and the Chattahoochee Water Treatment Plant (CWTP). The project included a 4-mile-long, 10-foot diameter tunnel, multiple shafts, and major pump stations, requiring a complex hydraulic system integrating gravity flow, open channel conditions, diversion structures, and pumping systems.
The Solution
R2T served as the prime firm and led the hydraulic design and pump station engineering for the program. The team developed design documents using hydraulic similitude testing in coordination with the Clemson University Hydraulic Testing Facility, enabling more efficient sizing and configuration of shafts and wetwells and supporting multiple pump selections. R2T performed hydraulic modeling to determine pump sizing, water surface elevations, and operating conditions based on historical and projected demand trends, system configurations, and piping layouts. The team evaluated alternative pump configurations, coordinated with City staff to finalize selections, and completed detailed design of key facilities, including major pump stations at Bellwood Quarry, the Hemphill Water Treatment Plant, and the Chattahoochee River intake. The overall hydraulic design incorporated features such as dual-stage pumping, gravity flow integration, weir structures for flow control, and large open channels to optimize system performance.
The Results
R2T’s design contributed to a system that provides the City with significant operational flexibility and improved water supply resilience. The hydraulic configuration allows bi-directional flow within the tunnel and quarry system and enables water to be conveyed from either the river or the quarry to either treatment plant. Gravity flow from the quarry can supply the entire City for up to three days without pumping, supporting emergency operations. As part of the overall program, the City’s raw water reserve capacity increased from approximately three days to more than 30 days, significantly strengthening its ability to respond to drought conditions and supply disruptions.
Recognition
This project was recognized for its significant environmental impact, earning an Award of Merit in the Water/Wastewater category from ENR in December 2021. As part of this achievement, R2T was identified and listed as the Civil Engineer of Record, highlighting its key role in the project’s successful delivery and contribution to sustainable infrastructure.
