It’s not uncommon for construction contractors to run into a big problem: pipelines accidentally filled with concrete, slurry or other kinds of debris.

But at Pacific Sewer Maintenance, these aren’t problems. Rather, they’re revenue-generating opportunities, thanks to robotic cutting machines from Sewer Robotics.

Scott Gayman, who co-owns the Los Angeles-based company, invested in the robotic machines — R125 and R160 crawlers paired with WJ125 and WJ180 waterjetting heads, respectively — about five years ago to diversify his customer base.

“We lost a big portion of our root control business, which made me think we needed to do more than just one thing,” says Gayman, whose father founded the company in 1979. It employs nine people and provides chemical root control service for municipal customers throughout southern California and removes pipe obstructions for municipalities and contractors nationwide.

Gayman says at that time he considered many different robotic technologies that used attachments to grind or cut through pipeline obstructions. But while attending a trade show, he was intrigued by the two Sewer Robotics machines, which use a high-pressure jet of water (15,000 to 40,000 psi at up to 12 gpm) to cut through rock-hard materials.

“The appeal was the water jetting capability,” he says. “These machines basically are water blasters on robotic wheeled crawlers. When I first saw one, I thought it was pretty revolutionary.”

CHALLENGING JOB

The all-wheel-drive, stainless steel, electric motor-powered robotic machines have proven their worth time and time again over the years, cutting through everything from concrete, slurry and grout to roots, tuberculation, calcium deposits and scale buildup, Gayman says.

But when asked about an instance where the R125 really proved its mettle, one job in particular stands out in in his mind: a slurry-filled, 7-1/2-inch-diameter fiberglass drainline laid under the concrete railbed of a new subway line under construction in New York City, in a tunnel about 200 feet underground.

Nine different contractors had already worked on the line for about 1 1/2 years to try and clear the roughly 70-foot-long slurry plug when Gayman got a call from the project’s general contractor in 2019.

“The drainline had to be opened up in order to certify the new line for operation,” Gayman says.

The job was complicated because of its location. To get to the clogged line, contractors had to drive 1 1/2 miles into a tunnel backward because at the end point there wasn’t enough room to turn around a truck. At that point, the clogged pipe still was two flights of stairs further down, then another 60 feet down to the actual work site.

“We had to carry our equipment down the flights of stairs,” Gayman says. “When we got there, we found about 30 feet of the pipe already was cleared. But there was very little pipe left — it was mostly destroyed by the previous contractors.”

SOLID RESULTS

After 20 minutes of jetting the plug with the R125, the Pacific Sewer crew had cleared a foot of the clogged pipe, which was completely encased inside the concrete railbed. About 20 minutes later, another foot of pipe was cleared.

“What really impressed me was that we were a couple hundred feet under the East River in New York City and the robotic system was another 60 feet below me. Within 20 minutes, we were outperforming every other contractor that had worked on the pipe,” Gayman says.

The entire job took 11 days, largely because another contractor had difficulty removing chunks of concrete debris with a vacuum truck. Furthermore, the Pacific Sewer crew could only work from 9 p.m. to 3 a.m. or they’d be blocked from leaving the tunnel by concrete trucks, which were still pouring concrete.

“Cleaning up the debris took way longer than actually cutting out the slurry,” Gayman says. “When we were done, the pipe was completely smooth except for some small nicks in the fiberglass where the nozzle hit the pipe.

“It was really, really impressive how well the equipment worked and the contractor that hired us was super thrilled.”

VERSATILE AND USER-FRIENDLY

Pacific Sewer owns three R160s/WJ180s and one R125/WJ125, plus various tool attachments that increase their versatility. The units are controlled via software from inside a box truck, which contains a control unit, a monitor, a water pump, hose and cable reels, and a 500-gallon water tank.

The R125 crawler with a WJ125 unit attached is about 29 inches long by 4 inches in diameter, weighs about 44 pounds and is designed to work in pipes from 6 to 24 inches in diameter. The R160 crawler with a WJ180 attached is about 27 inches long by nearly 5 inches in diameter, weighs about 65 pounds and is suited for cleaning pipes 8 to 20 inches in diameter.

There isn’t any concern about the high-pressure water jet damaging pipes as it clears clogs if it’s operated correctly, Gayman says.

“If you jet debris at a 90-degree angle to the pipe, it will drill a hole right through the pipe,” he says. “But if the jet is aimed at a 10- to 15-degree angle from horizontal, the water jet bounces off the pipe without damaging it.”

GREAT ROI

The robots alone cost about $60,000 each, but they pay for themselves quickly, Gayman says, noting his company charged $290,000 for the first job on which one of the machines was used.

So how do the robots actually make the company more money? 

“For us, it’s a matter of being able to use the equipment for long periods of time without stopping,” Gayman says. “Water never gets dull the way a drill bit or grinder can. You can cut concrete 12 hours a day.

“We never have to pull a robot out to swap a bit, unless it’s a toolhead. So we make more money by being really efficient at a relatively low cost.”

There’s also minimal required maintenance and the robots are well-engineered and very durable, he notes.

“The bottom line is we can do more work per day, which really adds up over the course of a year,” Gayman says. “We can do in a day what it might take another contractor a week to do.”