With a traditional surface water intake structure, the mountainous topography surrounding Lake Ouachita would require large raw water pumps to deliver water to the water treatment plant. This is the case, even though the water surface elevation of Lake Ouachita is higher than the treatment plant elevation. An alternative approach to the planning of the water intake evaluated the feasibility of a “lake tap”, which would include a microtunnel through Blakely Mountain into Lake Ouachita.

The lake tap method of design was preferred for many reasons. The lake tap allows the water pressure from the lake to transmit raw water to the city by gravity flow, saving millions of dollars over the life of the intake. In addition, the intake design allows the intake to be installed “out of sight”, under water, eliminating any visual impact to beautiful Lake Ouachita.

Against all odds, the City and Crist Engineers were able to maneuver through the planning, design, and construction process to successfully install the lake tap. The project faced difficult challenges from the very beginning, including difficult geotechnical conditions, significant regulatory demands, construction method limitations, construction contract procurement complexities, budgetary constraints, and construction setbacks.

The lake tap includes a 2500-foot-long, 60-inch welded steel pipeline through Blakely Mountain to Lake Ouachita that will provide gravity flow of raw water to the water plant located in Hot Springs, approximately 17 miles away. It was the largest pipeline ever installed in North America by the Direct Pipe method.