Gravity flowing water from Lake Ouachita to the treatment plant the city plans to build off Amity Road is critical to the $100 million project that will increase the regional water system's daily capacity by more than 60%.
Standing in the way is Blakely Mountain. Pumping raw water over it represents a significant recurring cost, one that can be avoided by boring a tunnel through the mountain. The Hot Springs Board of Directors tasked Michels Corp. to undertake the considerable feat of engineering, awarding the Brownsville, Wis., company a $19.27 million design-build contract last Tuesday.
Michels will push a 60-inch diameter micro-tunnel 300 feet under the mountain. The half-mile-long conduit will connect the intake Michels will build above Blakely Mountain Dam to the 17-mile-long raw waterline gravity flowing water to the treatment plant in south Garland County.
The intake the Arkansas Department of Health approved is in a cove that's part of a larger inlet east of the main channel. Its main port will be at 555 feet above sea level, or about 20 feet below the lake's normal pool elevation.
"We're really excited to start on this project," Todd Piller, the city's major capital projects manager, told the board. "It's very unique. There's going to be a lot of firsts. We have a competent staff of engineers to make this a successful project."
Piller said Michels' tunneling machine won't be on site until next year. In the interim, the company will secure the necessary permits from the U.S. Army Corps of Engineers. Craig Vandaelle, Michel's general manager of alternate delivery and business development, told the board retired Lt. Gen. Robert Flowers, the Corps' former chief engineer and commanding general, has been retained to shepherd the project through the Corps' dense bureaucracy.
It took the city and Mid Arkansas Water Alliance 13 years to get the Corps to reallocate 50,000-acre feet, or the amount of water that evaporates from the lake on a hot day, from power generation to municipal supply. The contract stipulates Michels will make a good-faith effort to submit all permit applications within six months.
"The permitting aspect of this job is critical," Vandaelle told the board. "(Flowers) will be the liaison between our team and the Corps."
The city began investigating the feasibility of the tunnel in 2019. Crist Engineers, the Little Rock firm awarded more than $7 million in contracts to design and prepare bid documents for the raw and finished waterlines and treatment plant and to manage and inspect construction, subcontracted REI Drilling of Utah to extract 2-inch core samples from the tunnel's half-mile path.
REI drilled about 1,400 feet into the mountain's southern slope, pulling core samples contractors used to determine equipment and manpower required to build a tunnel from the southern slope to the intake site east of the dam. Drillers encountered mostly shale, sandstone and groundwater.
Michels was one of the companies that responded to the request for qualifications the city issued last summer. Piller, Utilities Director Monty Ledbetter and Crist gave Michels the highest score, ranking it ahead of Bradshaw Construction, CCI & Associates and Garney/Garvey.
The $109 million bond issue the city floated last year will pay for the contract. The debt has already been drawn against for the $4.43 million contract the board awarded Kajacs Contractors Inc. of Little Rock in September for the first 2.5 miles of the finished waterline from the new plant and the $4.77 million contract awarded in August to Belt Construction of Texarkana for the first leg of the raw waterline.
The 2.5-mile segment will run from the mountain to the Ouachita Treatment Plant on Cozy Acres Road, giving the plant a second raw-water source. Per the city's withdrawal agreement with Entergy Arkansas, the Ouachita Plant's intake on upper Lake Hamilton can take up to 30 million gallons a day from the lake, with usage not to exceed a 20 million-gallon a day average calculated over a rolling three-month period.