Pipe bursting and custom equipment enable a Utah contractor to separate a combined lateral in a prestigious historic district.
Acontractor lowering the basement floor of a historic mansion in Ogden, Utah, inspected the 6-inch clay lateral as part of dropping the plumbing. The pipe was broken.
Most properties on the block are listed on the National Register of Historic Places. The state historical society mandated minimal disruption and no trenching to replace the line.
“The homeowner shared his lateral with two other properties, all equally responsible for what is called a combined lateral,” says Jay Garrett, owner of Utah Pipebursting in Ogden. Garrett, who developed a procedure to replace combined laterals with two separate lines, promised to split this run into three individual lines.
“The job offered many challenges, but the greatest was keeping my nerves in check while trying something I’d never done,” he says. “The first time I tested my new plate design was during the burst.” It pulled a combined 360 feet of 4-inch HDPE pipe flawlessly and saved the homeowners $23,000 over traditional repairs.
Garrett’s three workers used a Rausch camera system to trace the client’s single lateral south under the driveway to a double wye in front of the neighbor’s detached garage. The wye connected to the 6-inch clay combined lateral. It ran west under the garage, the retaining wall behind it and another neighbor’s patio before picking up his lateral at 140 feet.
The pipe then ran 120 feet under home C’s driveway to the sewer in the street, dropping 20 feet in elevation along its total length. The inspection also revealed many cracked or broken sections and root intrusion.
The client’s house and adjacent property – homes A and B – were on the east side of the block, but home C with the third lateral was on the west side of the block. Reaching home C via the backyards was impossible. “Even with the best planning, we still loaded and moved equipment around the block every few hours,” says Garrett. “It stretched prepping to three days.”
The clients also requested that no work be done in their absence. The traveling couple was home for seven to 10 days, then left on business for two to 10 days. “Working within their schedule resulted in three postponements, and bad weather caused another delay,” says Garrett. “It put us almost a month behind schedule.”
The other absent homeowners granted permission for Garrett’s crew to work at will. “Having just one house to keep in service overnight was a big plus,” he says.
Ready, set …
Using a KX161-3S Kubota compact excavator, Garrett broke through concrete driveways and excavated 3- by 5- by 8-foot-deep pits where laterals left homes A and B and at the wye. Another operator using a KX41 Kubota mini-excavator with variable-width undercarriage eased the machine through the security gate and around the side of home C to dig a pit in the back lawn. He also excavated a 5-foot-deep pit at the connection to the combined lateral. All pits required hydraulic shores in the cobble and clay soil.
Home C’s driveway was long enough to fuse seven 20-foot sticks of 4-inch HDPE SDR 17 pipe. With the excavator’s help, workers moved two lengths of 140 feet east over the retaining wall, around the garage and into the backyard of home A.
The next day the men set up the cribbing, 1-inch-thick resistance plate and M50 ram (TRIC Tools) with 48 tons of pulling force in the third connection pit. The hydraulic system on the KX161 excavator powered the ram at 6 gpm/3,000 psi.
“We’ve been doing double pulls for years,” says Garrett. “My inspiration for it came from watching horizontal directional drillers. They use a disc with holes for mounting multiple pipes, then the reamer pulls back the assembly.”
Garrett designed a 1-inch-thick triangular steel plate with three holes: one for the burst head with pipe, another for the second HDPE pipe and the third for attaching the 7/8-inch swaged cable rated at 48 tons.
“The raised excavator arm supports the pipes as they must be level with each other at the beginning of the pull,” says Garrett. “After that, the hole created by the burst head holds the pipes in position.”
Double the pleasure
Garages A and B blocked the workers’ line of sight to the pits, so instead of communicating with hand signals they relied on two-way radios.
“That elevated the risk of something going wrong during the delay between sending and receiving transmissions,” says Garrett. “The ram was yanking in a combined 320 feet of pipe at 7 to 8 feet per minute.” The burst required 30 to 35 tons of force.
Once the pipes were in the pit, the crew disconnected the triangular plate and sent the cable upstream to pull in the individual 20-foot-long laterals for homes A and B. They sleeved the 4-inch HDPE pipe inside the original 6-inch clay lines, then connected the runs with PVC wyes.
A bypass wasn’t necessary. “We completed the pulls in two hours and made the connections in four hours,” says Garrett. “Then I went home and tried to sleep.”
He worried about his untested 9-inch circular steel plate design for mounting the triple pipes and if he had calculated the critical elevation change correctly to prevent bellies from forming in the run as the bundle twisted. “Based on research, I determined a 4.5-foot drop in 120 feet would compensate for one full rotation every 50 feet,” he says. “For that distance, the combined lateral fell 5 feet.”
Splitting the arrow
The 1.5-inch-thick steel plate had three holes for mounting pipe and a center hole for bolting it to the burst cone. “Experience said a 1-inch-thick plate would be sufficient, but I over-engineered it in case the pipe had some drag on it,” Garrett says.
The city wanted the 7-foot-square by 8-foot-deep pit at the sewer excavated and backfilled on the same day. “Considering this burst was the pilot test of new equipment, the deadline was additional stress,” Garrett says.
After he exposed the sewer connection with the KX161 excavator, the crew set up the ram while Garrett transported the machine to the third connection pit. As others fused three 120-foot lengths of HDPE pipe, Garrett staged them in the backyard of home C. The pipes, pull plate and burst head assembly weighed 300 pounds. To handle the weight, the men wrapped a chain around the bundle to help lower it into the pit.
Garrett positioned the pipes over the top of a 6-foot ladder using the excavator. With the bundle supported, he lined up the burst head before moving the machine to power the ram. This time everyone had an unobstructed line of sight.
Despite the addition of a larger plate and third pipe behind the bursting head, the ram used the same amount of force to pull in a combined 360 feet of pipe at 7 feet per minute. The pipes remained together until the ends passed over the ladder, then they fanned out slightly. During the pull, the bundle rotated 1.5 times.
“Because there was very little flow in the 8-inch clay sewer, we removed a 6-foot length rather than drill and tap it for the two new connections,” says Garrett. “We installed three 8-inch PVC wyes, connected all the pipes, backfilled and met the city’s deadline.”
The following morning, the crew sleeved home C’s 60-foot lateral and connected it. “The bursts went well, but I didn’t like the bundle rotating,” says Garrett. “I’m modifying the original design to correct it.”