Dredging Operations

Our Marina is located on a salt water tidal river.   Because it is connected to and fed by the ocean, it ebbs and flows with the tide.  I share this with you so that you might understand the huge volume of water that rushes in from the ocean for six hours then rushes back out again.  Our tidal changes average out to be about seven feet.  Sometimes it’s higher than that and sometimes a little bit less.  The speed of this current flow is four and a half miles per hour at peak and dead calm at slack.

 

This movement of unbelievable quantities of water is a huge force to be reckoned with.  It moves things, particularly the silt and soil that the banks and bottom are made of.  This causes shoaling in certain areas and washouts in others.  The banks of these tidal rivers shift continually.

 

Our marina is subject to this shoaling and we have to dredge out the bottom about every ten years to keep the depth in and around the marina deep enough.  To do this effectively is a huge engineering feat and takes careful measurements, planning, and execution.

 

The first problem is where does one put all the mud and silt that we are going to suck up off the bottom to make the river deeper?  There are very rigid regulations concerning an operation like this and the permitting process is a long and drawn out affair involving the Corps of Engineers and the department of Natural Resources.  The process usually takes about two years just to obtain the proper permits.  The permit is not granted without a detailed account of how you are going to dispose of the spoil material.

 

There are three means of disposing spoil material legally.  One, you have a piece of land designated as a spoil area where you pump the material onto.  Two, you haul the material away by trucks to an approved spoil area.  Three, you pile the material onto a barge and ship it out to sea to an approved spoil area and dump it in the ocean.  In our case, we own the island across the creek from the marina and have kept it for many, many years as a designated spoil area.

 

Two months before the dredging operation began, a huge barge was brought to the shore of the island and heavy equipment was unloaded to plow and shape the area to receive the spoil material.  The area is surrounded by a tall dyke and shaped so the spoil material settles on one side and the water drains to the other and is filtered, clean, back into the river or creek.

 

Here are two aerial views of our spoil area.  The dredging had already begun when these were taken and you can see the solid material accumulating on the one side as the water settles to the other and drains.

 

  

 

The challenge for me, as Dock Master, during the dredging project is to clear the boats out of sections of the marina to allow the dredge to operate in the marina safely without the risk of damaging the boats. Moving the boats also allows the dredge to dig out areas where the boats would normally dock. Here is a picture of the dredging equipment tied up in an area where I had just moved out all the boats.  Notice the boats still left in the marina.

 

 

Here is another shot from a different angle.

 

 

The way the manager of the dredging operations and I worked out the plan, each section we cleared out would take about one week to complete.  So, each week, I had to clear out a section of the marina and park the boats in other parts of the marina.  Then, a week later, I had to move those boats back to their spots and clear out the next section to be dredged.  Here is a shot of the next section to be dredged after the section shown above.  Notice the boats have been moved back to the right side of the right hand dock and the lack of boats in the area between these two docks.

 

 

The equipment for this kind of operation can be just as interesting as the operation itself.  The company we hired for the job had a small little tugboat custom made for them to use with their dredging barge.  Here is a shot of “The Mighty Mouse” tug.  The tug was aptly named!

 

 

This next photo is a shot of the dredging barge shot from the rear.  The little skiff and the Mighty Mouse are docked in front of the barge.  The dredging barge has no engine for propulsion.  It is moved around by the tug and the little skiff.  The tall things that look like legs are called spuds.  Each spud is dropped down and digs into the bottom to hold the dredging barge in place to allow it to dig up a particular area.

 

 

The barge has an arm that moves up and down and can be manipulated to the right and to the left.  On the end of that arm is a rotating drill head with a pipe in the center of the drill head.  The drill head digs up the bottom and the pipe sucks up the material much the same as a vacuum cleaner would suck up dirt.

 

 

Here is a close up shot of the drilling head.  I’ve seen steel pipe that was laying on the bottom that was cut clean in two when hit with this drill head.  It is driven with awesome power and really did a great job in our marina.

 

 

Marina operations had to continue all during the dredging operations and I was continually radioing instructions to boats who were trying to get past the dredge while dredging was taking place.  The dredging in the creek, where all the above pictures were taken, is completed and they are now dredging out front in the river portion of the marina.  The entire project should be wrapped up in another two weeks, just in time for our summer boating season.

 

The dredging operation progressed through our marina in a very calm and orderly fashion.  This was due to great planning and good execution on the part of the marina staff as well as the dredging staff.  I am very pleased with the outcome and am already receiving congratulations from my boss on a job well done.  I have to say, though, that I am very glad this has to be done only once every ten years.

 

I’m going to leave you with one more aerial shot of the spoil island only because I think it’s pretty and I wanted to squeeze it in.

 

 

Today is my lovely wife's birthday and she has taken the day off.  I have plied Paulette with cards and gifts and will escort her later to the restaurant of her choice.  I think we're going to have a nice meal and a great time.  I hope you all have a great week!