HOT SPRINGS -- The $109.7 million bond issue the Hot Springs Board of Directors authorized last year won't cover the cost of the Lake Ouachita water supply project if Entergy Arkansas requires the 17-mile raw waterline to be bored under Lake Hamilton and Mazarn Creek, city officials say.
The line will gravity flow water from the intake the city will build above Blakely Mountain Dam to the treatment plant it will build 17 miles to the south on Little Mazarn Road. The large-diameter line would cross upper Lake Hamilton near the right of way for Entergy's overhead transmission lines, a crossing also used by the Permian Express crude oil pipeline.
The city said boring the line under upper Lake Hamilton and other parts of the lake's watershed would increase the project cost to $115.9 million, almost $10 million more than the $106 million in the bond issue's construction fund. The city has asked Entergy for permission to float and sink the line, a cheaper method that would anchor the line to a trench the city would dig across the lake bed.
The city said the technique was used for the two large-diameter transmission mains that carry finished water from the city's treatment plant on Cozy Acres Road. The more than 50-year-old plant treats water from the city's intake on upper Lake Hamilton. The two pressurized transmission trunks cross the Bull Bayou arm of Lake Hamilton en route to the storage tank on Music Mountain.
"We want to use a float-and-sink method, which is a common method used throughout the United States," City Manager Bill Burrough told the board last month. "We have two lines in Lake Hamilton that are float and sink. The [Permian Express] pipeline is a float and sink.
"Currently [Entergy] has restricted us to boring under the lake. To bore under Lake Hamilton, we need about a half-mile on each side to be able to bend the pipe enough to get under and come back up."
Entergy said it's evaluating the compatibility of the two methods with the license the Federal Energy Regulatory Commission granted it to use lakes Hamilton and Catherine for power generation. The 50-year license that took effect in March 2003 gives the utility authority over the lake bed and construction and recreational activities on the two lakes.
"Entergy does not have a preferred method of construction," Brandi Hinkle, the utility's communications specialist, said in a statement. "There is no final determination yet as to which method must be used for each of the proposed crossings.
"Entergy Arkansas is currently evaluating whether the city's construction plans associated with its six proposed crossings of the lake are compatible with the provisions of the FERC license, specifically whether the proposed methods comply with the provisions governing environmental protection of sensitive fish spawn areas and public safety."
Entergy's FERC-approved shoreline management plan limits activity affecting sensitive fish spawning and nursery habitats. Maintenance dredging in established boat channels and vegetation removal are reviewed on a case-by-case basis, but the plan generally prohibits new dredge or fill activities in environmentally sensitive areas.
"As part of Entergy's evaluation of the proposed crossings, the company will evaluate whether the proposed crossings will traverse environmentally sensitive areas and whether the proposed construction methods are compatible with the provisions of the FERC license," Hinkle said in her statement.
Entergy said no dredging or excavation is required for directional boring, which would allow the line to bypass sensitive areas.
"In contrast to the open trench and float-and-sink construction methods, directional boring passes under these environmentally sensitive areas and leaves the lake bed and sensitive environmental areas completely undisturbed," Hinkle said. "Like a worm hole, the tunnel for the bore would begin some distance from the shoreline and would go under the lake and then extend to a point, again some distance from the shoreline, on the other side of the lake, away from the water."
Three of the five contracts for the more than $50 million raw waterline have been awarded.
Crist Engineers, the Little Rock firm contracted to design the raw waterline and other project components, told the city putting the treatment plant 17 miles south of its raw water source would lower water age for customers on the south and east ends of the 145 square-mile service area and improve the hydraulics of the distribution system.
The city's two treatment plants feed the system from the northwest and north ends of the service area.