Posted on December 16, 2021
Veit & Company, Inc. is a company that specializes in earthwork, utilities, foundations, demolition, dredging and industrial cleaning and is located in Rogers, Minnesota.
The Minnesota Department of Natural Resources (DNR) was facilitating a multi-year, $18-million Kingsbury Bay – Grassy Point Habitat remediation and restoration, a site located in St. Louis County, Minnesota.The goal of the project was to restore 240 acres of fish and wildlife habitat within a part of the St. Louis River Area of Concern (AOC). Critical to the project was to excavate and reuse excess sediment, remediate and reuse legacy wood waste and remove non-native vegetation. The DNR contacted Barr Engineering to manage the engineering and design, construction administration and quality control oversight, andVeit& Company, Inc. for the construction effort.
For the Kingsbury Bay–Grassy Point Habitat project, GPS-guided machine control on excavators was particularly valuable, especially when combined with an underwater dredge guidance solution.
Whether for dredging, building, or demolition, accurately monitoring progress underwater is challenging, particularly in turbid water with suspended sediments and materials.
Working with SITECH Northland, a Trimble dealer, Veit selected the Trimble Marine Construction system on the excavator to better track material movement.
The Trimble Marine Construction system can be integrated with a single beam echo sounder (SBES) to acquire pre-/post-dredge survey data from below the water and then quickly identify high and low spots, calculate progress volumes and send grid model updates to both the office and the dredge vessel.
“We use the Trimble Marine Construction system to track the bucket location in real-time in 3D—a huge advantage in water,” said Britton Lawson, Director of Construction Technology at Veit. “Essentially, the 3D map created by Trimble is the only eyes for the excavator operators to know where they’ve been and where they need to go. Project managers are also able to track progress and material quantities moved.”
Dredged with Accuracy
For the Grassy Point job, Veit used two Liebherr excavators with clamshell buckets on barge spreads. Each was equipped with Trimble Earthworks Grade Control Platform using the Minnesota Department of Transportations’ MnCORS VRSVirtual reference station network for instant access to RTK positioning services.
“One machine would excavate to design and load the material. Two tugboats moving four hopper barges were used to transport the material to the placement site. The other unit would unload the material, placing it on the seabed to a design grade. This was all achieved with Trimble guidance,” Lawson said. “We also had a Trimble Siteworks Positioning System with a TSC7 Controller that was performing quality control/quality assurance checks behind both spreads.” The Veit team relied on a remote connectivity cloud platform to remotely manage the units.
Bi-weekly as-built progress surveys were completed by survey crews using a single beam sonar. The subsequent surveys were then uploaded to the machines for reference.
“The data from the single beam echo sounder was compiled in Trimble Business Center and sent out with plan sheets,” said Lawson. “We used aerial drones to gather topographic data of the island surface above the water and then combined those surveys with the machine mapping data. That process helped significantly to reduce rework. We never had to go back because it was field-verified right away.”
The Trimble Marine Construction System makes the process much faster and more accurate. Lawson estimates that the initial excavation is about 50% quicker than traditional methods because operators know where the bucket has been and where it needs to go. Lawson added, “With the 3D visualization we have greater assurance that cut depths are accurate as compared to a mark on the stick. Reducing the time spent returning to a site for rework is invaluable.”
Enabled by technology, Veit crews worked 24-hours a day, Monday-Saturday, for three months to complete the required tasks.Veit concluded the restoration project by finishing the cap on the Grassy Point islands using clean sediment removed from Kingsbury Bay, dredging remaining excess sediment from open water portions of Kingsbury Bay, restoring Grassy Point wood removal areas using sediment from Kingsbury Bay and restoring and reseeding disturbed areas.
“I cannot imagine performing this project without 3D positioning technology,” said Lawson.“Using the Trimble workflow greatly contributed to our success and reduced our rework to almost none.We would not want to tackle this type of project without the 3D tools we had available to us from Trimble.”
Trimble has a range of solutions for dredging, placement, hydrographic surveying, visit us at trimble.com/marine to learn more.