In Great Lakes Area, Diver-Operated Vehicle Installs New Tunnel Liners Without Need for Dewatering

A mission nearing completion within the Detroit space utilized a custom-built, diver-operated car that may function underwater and that changed concrete liners for 2 uncooked water tunnels, eliminating the necessity for dewatering and diversion or extended outages. 

The diver‑operated liner plate set up car is a modular, 25‑ft‑lengthy electrical‑over‑hydraulic transporter dubbed BURT, for Ballard’s Underwater Ring Transporter. Ballard Marine Construction, a part of the Traylor Building Group, led a staff that developed and examined BURT on land and on the O.H. Hinsdale Wave Analysis Laboratory at Oregon State College earlier than deploying it in 2022 on a 12‑ft-dia unreinforced forged‑in‑place concrete tunnel constructed within the Thirties and one 10‑ft-dia tunnel from the Nineteen Fifties. The tunnels each have precast main segments and a secondary unreinforced lining, and are owned by the Nice Lakes Water Authority.

BURT accomplished the liner installations final fall, after three years of October-to-April home windows for building. The roughly $90-million progressive design-build mission is slated to finish this spring with ultimate grouting operations.

“We initially have been going to go design-bid-build,” says Todd King, chief resiliency officer with GLWA. “We’d have dewatered the tunnels, take the therapy plant out of service, and do it piecemeal.” However after studying of the potential to keep away from that, the company pivoted to PDB.

The tunnels sit about 95 ft under grade in delicate clays and silts. Inspections had discovered cracking that was extreme sufficient {that a} lack of strain contained in the tunnel posed a structural threat, notes Shawn Drobney, Ballard lead engineer.

Ballard labored with Kelley Engineered Equipment to develop BURT. “They mentioned, we’ve got this fascinating downside—we need to try to reline this tunnel with out draining the water out of it,” remembers Matt Brief, Kelley mission engineer. The staff introduced within the Norwegian agency Innova, which focuses on options for high-voltage underwater hydraulic machines.

“It’s mainly a forklift—however working underwater with people round it,” says Brief. “How do you make a toaster protected underwater? We did a backwards and forwards with them on the way to shield BURT with a line insulation monitor. On the hydraulic facet, how will we hold it at the next strain so water doesn’t get into the machine?”

                                                                                                                Picture courtesy Ballard Marine Building

On web site, BURT was lowered by way of an 8‑ft‑dia entry shaft and reassembled on the invert 95 ft deep. “The water in winter hovers round 33° F,” notes Drobny. “The divers have been 1,800 ft from the restore websites with restricted timeframes.” Crews constructed tents over the entry shafts and heated them, he says.

A Deep Dive

A Ballard-authored technical overview co-written by Drobny describes the method. BURT’s primary physique homes a deep‑sea hydraulic energy unit with a {custom} bladder accumulator, a programmable logic‑managed electrical system sealed in a nitrogen‑crammed canister, and an onboard reel with greater than 1,100 ft of three/4-in. umbilical wire to energy and talk from the floor, says Drobny. 

4 independently-driven hydraulic wheels present optimistic traction; the system can hydraulically “lock” the drives so the 20,000‑lb car is safely secured throughout peak flows. Two onboard cameras and eight LED lights feed twin underwater displays on the operator’s station. “The underwater cameras and displays for divers have been essential to our success,” says Drobny.

A vivid orange pre‑put in cable centerline on the tunnel invert permits navigation to inside a half‑inch to keep away from contact between the liners and current concrete tunnel partitions. 

On the entrance working station, divers have been in a position to elevate and decrease two rings, ratchet up assemblies horizontally, and make intricate rotational and axial changes to align to the circumferential bolt patterns of the custom-designed liners. The HPU delivers 3,000 psi at simply over 9 gpm and permits divers to run two hydraulic instruments concurrently. The car’s payload capability exceeds 9,000 lb, enabling transport and placement of two full rings (roughly 7,500 lb of liner plate) per journey. These two liners enable for a complete of 9 ft of put in tunnel liner per journey down the tunnel.

Ballard’s engineering staff developed a stainless‑metal liner designed for a 95-ft hydrostatic head and a 50‑yr service life, grouted in place. Every ring is made up of three 120° curved plates, that are 54 in. extensive and have flanged and bolted longitudinal and circumferential joints for repeatable, inspectable meeting underwater. Built-in jack bolts and devoted grout ports enabled balanced, sequenced grouting. Bulkhead rings at 50‑ft intervals subdivide grout phases and shield water high quality all through the operation.

BURT’s electrical circuits are protected by a line insulation monitor that journeys energy inside milliseconds if isolation is compromised. The lighting system contains three hours of battery backup; twin air bottles mounted on the car present every diver as much as three extra hours of breathable air in an emergency. 

                                                                                                                Picture courtesy Ballard Marine Building

After training on a mock-up tunnel on land, the staff examined BURT on a 324‑ft‑lengthy, 12‑ft‑extensive, 15‑ft‑deep wave channel on the college. “We went from a pencil drawing to OSU in 10 months,” says Drobny.

The total‑scale mockups and trials knowledgeable particulars comparable to a symmetrical plate geometry permitting for a number of positions, gasket refinement, and a patented bolt‑by‑bolt sequencing plan that standardizes diver duties.

Finally, “there have been days … the place we positioned 4 rings in an 8-hour shift,” says Drobny. Between the 2 tunnels, some 13,000 ft have been repaired.

“We need to do extra tasks like this,” says Brief. “There are many water mains within the U.S. the place it’s a possible resolution versus constructing a brand new tunnel.”