Developed by Citizens Energy Group, the Citizens Reservoir project will ensure adequate water supply to accommodate population and regional economic growth over the next 20 years at a fraction of the cost of building a conventional reservoir. When construction is complete in 2021, the 88-acre, 250-foot-deep former limestone quarry will become the largest reservoir built in Central Indiana since 1968.

Citizens Reservoir will be vital to helping the region surmount serious drought conditions that caused mandatory water restrictions in the past. The reservoir will store 3.5 billion gallons of water, or about 50% of the capacity of adjacent Geist Reservoir but with a much smaller footprint. As the geotechnical engineer of record, Schnabel was instrumental in evaluating design alternatives to help the owner select a cost-effective approach.

The selected plan incorporated key design elements including a raw water intake, pump station, raw water transmission main, access road, rock and soil slope stabilization of the quarry high-walls and rim, and site perimeter fencing. Our project scope comprised subsurface investigation, hydrogeologic model review of groundwater influence on neighboring properties during reservoir filling and operations, development of geotechnical data and engineering reports, and design of the facility’s tunnels, shafts, and tunnel protection canopies to prevent rockfall blockage.

The raw water intake features a 220-foot-deep shaft and a 235-foot-long tunnel, and the pump station has four 220-foot-deep, 60-inch excavated diameter well shafts and a 250-foot-long tunnel. Construction of the tunnels and intake shaft will use the drill and blast method, while the raise boring method will be used for the pump station shafts.