News

Jul 13, 2023

Tunnel

HOT SPRINGS -- Miss Elaine is in Lake Ouachita almost a year after the micro tunnel boring machine was launched into the southern slope of Blakely Mountain. Hot Springs Utilities Director Monty

HOT SPRINGS -- Miss Elaine is in Lake Ouachita almost a year after the micro tunnel boring machine was launched into the southern slope of Blakely Mountain.

Hot Springs Utilities Director Monty Ledbetter said Monday that Miss Elaine, named in honor of former City Director Elaine Jones, reached the lake earlier this month. It cleared the way for the 60-inch diameter pipe Michels Corp. pushed 2,600 feet through the mountain.

The pipe will gravity feed water from the intake structure Michels' marine crew will begin building next month on the north slope of the mountain to the large diameter raw waterline that will feed the new treatment plant the city is building 17 miles to the south off Amity Road.

The ability to gravity feed water to the new plant is a feature of the more than $150 million water supply project.

The Hot Springs Board of Directors awarded Michels the $19.27 million tunnel and intake project in the winter of 2021. The city told the Waterworks Advisory Committee last week the intake should be completed by the end of September.

Ledbetter said Monday Belt Construction will soon begin installing the 900-foot section of 48-inch pipe connecting the raw waterline to the south portal of the mountain tunnel. The city expects the connector to be completed by the end of the year, allowing the treatment plant on upper Lake Hamilton to begin processing Lake Ouachita water by December.

The plant was built in 1967 to treat water collected by the city's Lake Hamilton intake.

"This will be the first time in our history we'll be able to pull water from two basins," City Manager Bill Burrough told the committee. "That's one of the reasons we put that pipe in from Ouachita to the existing plant to immediately give us the ability to do that once the intake is complete."

Ledbetter said divers moored Miss Elaine about 40 feet below the surface of Lake Ouachita. Michels will retrieve its machine next month with cranes carried by a barge launched from Brady Mountain Boat Ramp.

The Wisconsin company expected its drilling machine to reach the lake by last winter, but it hadn't crossed the halfway point when Michels' special activity permit from the U.S. Army Corps of Engineers expired in February.

"The way that geology is the back half of the drill should be the same as the front half, but when they got into the center they ran into a lot of quartz, a lot of granite, some really hard rock," Burrough told the committee.

The pipe was welded to the power unit at the rear of the drilling machine. As the rotating drill head on the front churned through the mountain, a thruster's hydraulic cylinders pulled 240-foot pipe sections into the tunnel Miss Elaine had left.

"They had to change the heads several times," Burrough said. "The drill is taking the pipe with it as it drills. Every time they had to bring the machine out they had to bring all of the pipe with it and make cuts during that time. Each one of the welds take eight hours."

The city told the committee the plant under construction in south Garland County is expected to begin treating Lake Ouachita water by the end of 2025. The raw waterline south of the upper Lake Hamilton plant has to be completed before then.

Ledbetter was at Mazarn Creek Monday, overseeing where pits are being dug for the tunnel Michels will bore under the creek bed. The $14 million contract the city awarded Michels last year included the 300-foot micro tunnel for the raw waterline and floating and sinking the line across upper Lake Hamilton.

The city told the committee the float and sink is scheduled to begin after the lake is lowered in the fall. A January completion date is expected.

The city said materials are being ordered for the last 9 miles of the 24-inch ductile iron line that will distribute treated water from the new plant off Amity Road. The board awarded three bids totaling more than $16 million for the waterline in June. Diamond Construction Co. was the low bidder for all three.

The three segments include a 1.75-mile section from north of the Carpenter Dam Road bridge to the Shady Grove Road and Broderick Street intersection. From there the line will connect to the 20-inch diameter transmission main that runs along the King Expressway and feeds the elevated storage tank behind Cornerstone Market Place.

A 3.7-mile segment will end south of the Carpenter Dam Road bridge, and a 3.6-mile section will start near the intersection of highways 7 south and 290.

The board awarded Kajacs Contractors the $1.42 million contract for the 1,000-foot segment that will cross upper Lake Catherine. The city said the Arkansas Department of Transportation has permitted it to hang the line under the deck of the Carpenter Dam Road bridge.

Print Headline: Tunnel-boring machine reaches Lake Ouachita

Copyright © 2023, Arkansas Democrat-Gazette, Inc.

All rights reserved.

This document may not be reprinted without the express written permission of Arkansas Democrat-Gazette, Inc.

Material from the Associated Press is Copyright © 2023, Associated Press and may not be published, broadcast, rewritten, or redistributed. Associated Press text, photo, graphic, audio and/or video material shall not be published, broadcast, rewritten for broadcast or publication or redistributed directly or indirectly in any medium. Neither these AP materials nor any portion thereof may be stored in a computer except for personal and noncommercial use. The AP will not be held liable for any delays, inaccuracies, errors or omissions therefrom or in the transmission or delivery of all or any part thereof or for any damages arising from any of the foregoing. All rights reserved.