International Dredging Review

International Dredging Review

The Komatsu PC400LF is installed on a 40- by 80-foot deck barge and deposits material into an adjacent 100-cubic-yard scow.  The dredging area is a moon pool created by PVC pipe and silt curtains to contain turbidity.  Brian Alexander is the operator.

Last December Sevenson Environmental Services provided a test platform for the new marine construction software Trimble Marine Construction powered by Teledyne which was formally launched at CONEXPO-ConAgg three months later. 

Sevenson had been in contact with Trimble to make the Trimble GCS900 GPS/GNSS system which was commonly used for land-based construction activities applicable for use on the water.  

“We liked the robustness of the (GCS900) as well as the service provided by SITECH” which provides installation training and technical support for Trimble products said Ryan Killian Sevenson’s GPS manager.  

Measutronics which has sold and supported Trimble equipment since 1997 coordinated an interface of the Trimble hardware with Teledyne’s PDS software for a water-based use. 

Sevenson’s project in a back bay and channel is for maintenance dredging 95000 cubic yards of clean silt and sand by mechanical dredge followed by stabilizing it with Portland cement for use as construction fill. Two barge-mounted dredges — a Sennebogen 860 material handler and a Komatsu PC400LF excavator – are dredging into 100-cubic-yard scows which are unloaded into a mixing bin by a Sennebogen 860 material handler. The material then is amended with supersacks of Portland cement using a Komatsu PC 300. The PC 300 then unloads the amended material onto a holding pad for a two-day drying period. It is then transferred by wheel loader into tri-axle dump trucks and taken to a recycle stockpile. 

In the fall of 2016 the dredging was proceeding with only the Sennebogen excavator equipped with a 5-cubic-yard Cable Arm Environmental clamshell bucket. In November Sevenson brought in the Komatsu equipped with a standard excavator bucket. At that time the new Trimble/Teledyne marine construction package was ready for beta (field) testing and Sevenson agreed to a week-long test on the Komatsu. Measutronics installed the new system consisting of the GCS900 computers monitors cables antennas and other peripherals the PDS software and a BlueView multibeam system for stationary equipment mounted on a forward corner of the barge. The BlueView was used to scan the dredging area to identify high spots that can be taken out before moving the dredge.

The test took place from December 4 to 9 2016. The screen shots Trimble used in its CONEXPO-ConAgg display of the marine construction system were from this project showing Sevenson’s Komatsu and real data from a portion of the project.

Michael J. Crystal project superintendent praised the system for several key reasons.  

“It was a lot more user-friendly” he said. “It refreshed faster and tracked closer to the final elevation. It has better screen and colors. The previous system was two-dimensional and just showed red and green. The new system is easier for the operator to use because the 3-D display is more representative of the ongoing dredging” he said.  

For instance the existing bottom is displayed overall in dark gray with the maximum overdepth represented by a red line and the design depth by a green line giving the operator a goal of digging between those two lines. The design depth in this project is -7 foot elevation with between 1 and 6 feet of material to remove depending on the location making that feature a valuable one for the ease of staying at the right digging depth with widely varying thicknesses of material to remove.  

Another key point was that the operator could dig under the barge where he couldn’t see the bucket because the display showed the bucket location and the dredging progress Crystal said.

The dredge works in a 40-foot-wide 50-foot-long moon pool created by HDPE pipe and silt curtains to contain turbidity. The ability to dredge the full capability of the 60-foot-long excavator including under the dredge is a time saver calling for less repositioning of the equipment.

“The system is less ‘buggy’ and there were no system crashes” Crystal said. “Even the hardware components are sleek and up to date. The monitors antennas and other hardware are new and state-of-the-art with no wires to trip over. It’s updated and reconfigured like the difference between the first Macintosh computer and the latest Windows system” he said. 

At the end of the test the BlueView system was taken off eliminating the bottom scan to test for high spots but the PDS still allowed very few high spots even without it Crystal said.  He has recommended to the Sevenson home office that the system be purchased for all the company’s dredges. 

Sevenson purchased the system installed on the Komatsu and continues to use it on the project. 


This photo of the operator’s monitor taken during the project shows a split screen. On the top is a top view of
the dredge. The thicker black square is the moon pool and the thinner black line is the outline of the barge
the Komatsu PC400 is sitting on. The different shades of blue correlate to the depth of material needed to be
removed; the darker the blue the deeper the cut. Green is inside the design tolerance and red is just below.
(See color scale on the right side of the screen.) The bottom screen is a side profile of the bucket elevation
showing it at elevation 17.14 as the excavator reaches out to empty the bucket into the scow.