Dredging Up the Past

Nov. 10, 2021
Amphibious excavators, guided by a GNSS solution, are key in this northern Minnesota bay cleanup.

Contractors involved in underwater excavation projects have become some of the most ardent supporters of Global Navigation Satellite System (GNSS)-based solutions. The ability to “see” beneath the surface with their machines has proven invaluable in improving overall efficiency and minimizing the risk of over- or undercutting.

For Midwest Amphibious Equipment (MAE), making the move to GPS on two of its specialty excavators is doing precisely that, as the company tackles a huge restoration project on the waterfront in Duluth, Minn. Along with its newfound productivity, the company has discovered that incorporating the new solution will open the door to additional work, much of which had previously evaded them. Success begets success. Bogs Are Bogs

Although they bring decades of expertise to the job site, MAE has only been working the shallows for about five years. According to CEO Steve Gilbertson, the company’s origin stems from an unlikely source.

“Up until about five years ago, I was doing similar work for an equity firm that specializes in wetland mitigation banks around the U.S.,” he said. “That company had landed a project to handle restoration of 23,000 acres in an area known as the Sax-Zim Bog in northern Minnesota. After years of work to get the project permitted, it was finally approved, at which point the head of operations and I looked at each other and began considering the best way to remediate 36 square miles of bog that we couldn’t walk across. He suggested we look into a company from Louisiana that manufactures amphibious excavators — machines with pontoons that thrive in the swamps so common down there. I did, and quickly learned that they are very expensive, both to purchase and to move.”

According to Gilbertson’s calculations, in the course of that three-year project, they would have racked up about $2.5 million in mobility charges alone. Seeing that as bordering on overkill and knowing that potential swamp and bog work can also be plentiful in north central Minnesota, he opted instead to purchase the machines himself — and MAE was born.

“At the bog, we showed the benefits we can bring to the project,” he said. “Our big selling point is that we can get into places others can’t. We can literally unload off a truck, go to the middle of nowhere, do what needs to be done and move on to the next job. It’s a nice capability to have and provide. And, as a result of that job, we are now breaking into other markets, including regional utilities, the U.S. Fish and Wildlife Service, and the Minnesota Department of Natural Resources (DNR).”

Good as New

With the Sax-Zim job under their belts, MAE was primed for additional work and quickly landed it in a DNR-led effort to remediate a section of the St. Louis River on the waterfront in Duluth, Minn. As part of a larger project to restore more than 1,700 acres of the area’s Grassy Point and Kingsbury Bay, MAE, working as a subcontractor to Veit USA, was tasked with removing vast amounts of wood waste that sat at the bottom of the river for more than a century.

“In the late 1800s, this part of the waterfront was the home to a couple of sawmills and, as was common in those days, cuttings from the mills’ operations ended up in the river — that’s just the way things were done back then,” said Gilbertson. “Unfortunately, that debris, coupled with ongoing sediment deposits, has affected fish and wildlife habitat. By removing the wood waste and building a small island in the Grassy Point area, the DNR hopes to restore the damaged habitat and help fish and other wildlife thrive.”

To put the scope of the wood removal effort into perspective, MAE’s foreman Matt Brink said that, less than halfway into the project, they had already pulled out more than 100,000 cubic yards of material from the river bottom. And if such work conjures up images of soggy, decayed muck, nothing could be further from the truth.

“We are pulling up logs that are in amazingly great shape for being submerged for more than a century,” he said. “In fact, we’ve hit several pockets of material in which sawdust has come out relatively dry and fluffy — not what we’d expected to find at all.”

As mentioned, MAE’s past projects have included wetland mitigation and swamp work in which the machine operator could see where they were digging. They were also projects in which maintaining accurate river or lake bottom elevations was not that critical. This was not the case at Grassy Point, said Gilbertson.

“Here, inches really matter, both from a compliance and a materials standpoint,” he said. “Simply put, we won’t get paid for any material we over-dig, but it could cost us dearly if we were to under-dig. Given that we can see less than a foot into the murky water, it quickly became obvious we needed a more precise method of measuring our cuts as we removed debris.”

Baptism by Fire

Based on his past construction experience, Gilbertson suspected that the answer to his “digging blind” dilemma could be found in a GPS solution. Armed only with that general feeling, he contacted the Grand Rapids branch of McCoy Construction and Forestry, the local John Deere dealer, to explore his options. According to Lucas Weir, McCoy’s International GNSS Service (IGS) specialist, it was a call that would change the way in which Gilbertson and his team would work moving forward.

After hearing Gilbertson’s requirements, Weir suggested a Topcon HiPer VR with an FC-5000 field controller, as well as an X-53i system on MAE’s excavator.

“Working with our partner dealer, the Bloomington, Minn., branch of RDO Integrated Controls, we got it all for him in short order,” said Weir.

“Luke and the team at McCoy have been patient in getting us up to speed and the change for us has been dramatic,” said Gilbertson. “I can’t imagine where GPS could be more helpful than under water.”

On a traditional land-based operation, Gilbertson explained, it’s easy to look at an area and immediately see what needs to be done. “But once the water removes that visual element from the equation, it’s a whole new ballgame,” he said. The Topcon system is also set up to measure as-builts as the operator digs. “It is the ideal solution for us.”

Gilbertson’s focus on getting it right the first time is driven by the fact that MAE’s fee for the Grassy Point project is based on a unit price for the material recovered. If they were to undercut by six inches, for example, over the course of the six-acre job it would translate to 4,500 yards — or roughly $100,000 — for which they would not be compensated.

“Conversely, if we dig six inches too deep, we will not be paid for removing that additional material,” he said. “So, there’s the potential for a couple hundred thousand dollars that we could lose by not accurately knowing the surface we are dealing with.” The Topcon solution lets the team know exactly where the bucket is in relation to the plan provided by the engineers. “There is no guesswork; it is dead-on every time, with tolerances to one-tenth of a foot — far closer than we need it to be.”

Quick Studies

Although the Topcon excavator solution is designed to be inherently user-friendly, Weir said he has been impressed by MAE’s quick grasp of the overall GNSS environment. At the nine-month mark in the project, he said, their knowledge and utilization were on par with where most others are at 18 months.

“Both Steve and Matt have really taken to the technology,” he said. In fact, not long after the first system was installed, their goals evolved from just being able to see what they were doing under water to doing as-builts and finding an efficient way to monitor progress and generate reports right from their office.

“In short order,” Weir noted, “they went from [having] nothing to a nice package of solutions that included an indicate GPS system on two excavators, a pair of base/rover setups and Topcon SiteLink 3D.”

The challenges of seeing underwater and generating as-builts were immediately solved with the addition of GPS to the excavators. The last component was addressed through SiteLink 3D, a point-to-point communications solution. According to Gilbertson, the nature of their work — primarily in remote, swampy locations — means access to his machines can be challenging at best to sometimes near impossible.

“If I am at a mitigation site, there might be several miles between machines. Just getting to two machines in a day to see what they are doing is a real chore. Instead, with the click of a button I can do everything from verifying a machine’s position to sending the as-built back to the office to looking at their screen to answer a question the operator might have about the project itself. We’ve only scratched the surface of what can be done with SiteLink, but it’s still proving a really nice addition to our operation.”

Catching a Break

Gilbertson added that the new technology has given them the confidence not only to bid additional work like the Grassy Point project but also to better manage the work they currently have. To illustrate, he cites a discrepancy they recently uncovered that could have proven costly.

“There was an area in which we started digging and saw that we had already reached the halfway point in our quantities, yet it was obvious we were not halfway through the project. So, we did a surface calculation from the topo to the as-built and saw that it was off by 7,500 yards. Without the verification, I might have just dug and moved on, assuming that we removed 21,000 yards when, in reality, we did 28,500 yards. That’s the value these solutions bring to the job; that one catch will pay for everything we’ve invested in GPS to this date. In a very short time, we’ve figured out how critical this technology is to our future success. We’re going to embrace it and let the results speak for themselves.” SW

About the Author: Larry Trojak is owner and president of Trojak Communications, a Ham Lake, Minn.-based marketing communications company. Trojak has written extensively for a range of markets including: construction, recycling, geopositioning, aggregates processing, wastewater treatment and asphalt production.

Published in Stormwater magazine, November 2021.

About the Author

Larry Trojak

Larry Trojak is owner and president of Trojak Communications, a Ham Lake, Minn.-based marketing communications company. In his 30+ years in business, Trojak has written extensively for a range of markets including: construction, recycling, geopositioning, aggregates processing, wastewater treatment and asphalt production.


Photo 39297166 © Mike2focus | Dreamstime.com
Photo 140820417 © Susanne Fritzsche | Dreamstime.com
Microplastics that were fragmented from larger plastics are called secondary microplastics; they are known as primary microplastics if they originate from small size produced industrial beads, care products or textile fibers.
Photo 43114609 © Joshua Gagnon | Dreamstime.com
Dreamstime Xxl 43114609