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Successful Hydraulic Dredging Relies on Critical Velocity

Posted by Sam Crawford, Project Manager on August 13, 2020

As a leader in inland waterway dredging, J.F. Brennan Company (Brennan) serves as a success story for hydraulically dredging and pumping sediments over long distances and changing elevations. The goal of most dredging projects is to maximize efficiency, which means maximizing the average percent solids in the pipeline. However, there is a fine balance between maximizing percent solids and surpassing critical velocity to transport dredge slurry. Therefore, a dredge operator must understand the importance of critical velocity and how it varies as the material in the dredge cut changes.

Critical velocity, in this case, is the minimum speed at which sediment and water (slurry) must be pumped to prevent the sediment from settling and subsequently plugging the dredge pipeline. Plugging the pipeline is the bane of any dredging operation and one of the few things that will set a dredge operator trembling in their boots. After all, if a pipeline gets plugged, the dredge must shut down, which means the entire project stops.

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River Restoration: Small Dredges Prove Useful in Waterways

Posted by Paul Olander, Senior Project Manager on March 25, 2020

As the sun on the dredging season in the Midwest inland areas began to set, operations were starting to heat up on the east coast for J.F. Brennan Company (Brennan). For a third straight year, Brennan has had the opportunity to procure work in the milder maritime climate throughout New England during the winter months. These months are key for in-water work on the east coast as they provide opportunities to revitalize salt marshes, re-nourish beaches and restore navigation outside of the fish migration and spawning windows. Generally, this work has been undertaken in and near the coastal salt marshes adjacent to the smaller resort communities.

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Most-Searched Blog Topics of 2019

Posted by Kimberly Walters on January 07, 2020

Brennan blog posts were viewed 13,622 times in 2019. Reviewing our most-searched blog topics helps us construct a list of the marine industry's most critical topics and those most pertinent to our company. So, what were the most-searched topics?

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5 Reasons We Customize Our Fleet: Increase ROI with Dredge Sense

Posted by Kimberly Walters on May 13, 2019

Equipment-heavy industries continually push for optimal uptimes. At J.F. Brennan Company, Inc. (Brennan), we’re committed to investing in our equipment not only during the purchasing process, but also during scheduled off-season maintenance. Internally, we coined the term “Brennanize” to refer to the custom alterations our team executes upon acquiring assets as well as our carefully regimented maintenance.

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7 Cost-Drivers of a Dredging Project

Posted by Dillon Hogan on November 13, 2018

Dredging projects are complex affairs that involve many components and significant planning before execution. The intricacy of these projects means that pricing is often multifaceted. Here are seven common areas that drive overall costs on a dredging project.

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The Basics of Using Polymers on Dredging Projects

Posted by Dillon Hogan on October 16, 2018

Why Add Polymers?

 

One of the biggest challenges on a dredging project is managing the water that is excavated and transported with the sediment. On hydraulic dredging jobs where sediment and water are pumped through a pipeline as a slurry, water can account for 90+ percent of the volumetric flow. After the slurry reaches the disposal area, the water must be separated from the sediment, collected, and often clarified or treated. This process must happen as fast as the water is being pumped, which for a 12-inch cutterhead dredge could be 5,000 gallons per minute.

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The Leverman's Challenge

Posted by Dillon Hogan on May 29, 2018

The Bureau of Labor Statistics classifies a dredge operator as a person who removes sand, gravel, or other material in order to excavate and maintain navigable channels in waterways. In the industry, we call the dredge operator a leverman. This is a historical remnant of the days when the pilothouse, or lever room, was full of mechanical levers that controlled various parts of the dredge. The levers eventually gave way to computerized control systems...

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QC-ing the QC Equipment

Posted by Dillon Hogan on April 03, 2018

All Systems Go

At Brennan, we utilize hydrographic survey systems to measure progress on all of our dredging projects. These systems typically include a positioning system, such as RTK-GPS, and a multi-beam echo-sounder. The Real Time Kinematic, Global Positioning System, or RTK-GPS, is a precise satellite navigation tool, whereas an echo-sounder is a sonar device for measuring depth. Combining the two allows us to achieve very accurate measurements on the location of the river bottom. We take the data points created during these measurements and create a 3-dimensional model using Hypack® software. By running a survey before we dredge, and then one afterward, we can create two models and compare them to one another. The difference between the two models is the total volume of in-situ yardage that we have removed. Typically, we are paid by the in-situ volume of sediment (in cubic yards) that we remove so it is very important that these measurements are extremely accurate. Therefore, establishing quality control checks on the equipment before we survey is an extremely important step in achieving accurate measurements.

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Waterway Infrastructure from the Eyes of Those Who Build It

Posted by Mark Binsfeld on March 22, 2018

There is a lot of buzz around the president’s infrastructure plan lately. It is clear that everyone wants better infrastructure, regardless to which party an individual may belong. The biggest challenge to getting what everyone wants is funding, and making matters more difficult, the allocation of this funding is another source of disagreement. As a contractor that provides construction services to owners of infrastructure, it is clear that the waterways are suffering the most from lack of investment.

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3 Crucial Steps for Dredging Near Utilities

Posted by Dillon Hogan on January 23, 2018

Dredging around utilities is challenging, and mistakes can be expensive and dangerous. When utilities, such as power lines, natural gas lines or fiber optics, are above ground they can be easily marked, and a plan can be developed to avoid them. However, when these same utilities are underwater, locating them and working around them adds an additional layer of risk for the contractor.

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