Did I take this wrongly?

Tell me if I took this wrong...

My marina is dredging our entrance channel. The population is comprised of roughly 20% power, 80% sail craft. I have a trawler. I advised the dock-master of several variable depth readings I found 3 days ago between 4 foot and 8 foot. I recommended he should check real well before releasing the dredge operator from the work, because the channel seemed inconsistent.

And I was told:
I found that a might bit high-falutin', but nevertheless replied that I was contacting the Garmin Corporation to advise them their transducers are ineffective, and I would be removing my 3. What I did not include is that my Garmin 740s includes a log of my depth history with GPS coordinates.

I don't doubt that they will check the depths, but found his reply a bit condescending. Am I making mushroom clouds from mouse farts?

guy that is doing the dredging is probably a brother-n-law or something of the harbor master. Always something going on.

Dredging

How did they dredge?
Randy

What's wrong with having a deeper marina? I would assume they would be dredging it with a backhoe not quite this big but similar.

Greetings,
Mr. B. Just write it off to a dumb-ass dock master. Short of a lead line, the depth sounders in use today are the most effective way of determining depth IMO.

From my experience with dredging small places...it's not uncommon for them to leave the bottom pretty ragged and eventually it settles out to a constant depth. I have been towing dredges in and out of small harbors for a decade now and it always seems the bottom is very ragged...usually not up to 4 feet...but lets say they want an 8 foot controlling depth...I would expect to see some 6's and a bunch of 10-12 depth readings so that everything settles out where they want it.

That's with a hydraulic dredge...not as familiar with bucket dredging.

Ben said:

Am I making mushroom clouds from mouse farts?

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Made me laugh...I'm stealing it. Regarding the reply you received..eh. You voiced your concern. Best you can do...

Reminds me of another sayin'
"Not my pig, not my farm"

Ben, the harbor master must have been from up North. That is not the way we do it down South. We have just got to get our green head flies and no see'ems to working better. Yankees don't like them.

Ben I think they know well how deep the water is and the HM probably thought your comment was "condescending". He probably thought you were trying to tell him how to do his job and that you didn't approve of his performance.

Yup .. it's mouse farts.

Let's leave it to the experts (?).

Ben said:

Tell me if I took this wrong...

My marina is dredging our entrance channel. The population is comprised of roughly 20% power, 80% sail craft. I have a trawler. I advised the dock-master of several variable depth readings I found 3 days ago between 4 foot and 8 foot. I recommended he should check real well before releasing the dredge operator from the work, because the channel seemed inconsistent.

And I was told:

Transducers are not an effective way to measure the depth of any channel. We have a surveyor that will certify the depth. I see you have a power boat, I doubt you will ever have an issue going anywhere.
​

I found that a might bit high-falutin', but nevertheless replied that I was contacting the Garmin Corporation to advise them their transducers are ineffective, and I would be removing my 3. What I did not include is that my Garmin 740s includes a log of my depth history with GPS coordinates.

I don't doubt that they will check the depths, but found his reply a bit condescending. Am I making mushroom clouds from mouse farts?

Click to expand...

There is a simple way of resolving the issue. Take a sink line or pole and go back through the same areas. Compare what you find to what you recorded and told him earlier. Then simply state that as you'd depended on your equipment you did decide to double check it, how you did, and that you confirmed your data was reasonably accurate. Tell him you have attached your latest findings and that you were simply concerned the marina was being misled and looking out for them.

Maybe HM did not mind you "reporting", but did not like you "recommending".
Regardless, you reported, best you could do ... don't lose sleep over it.

Twice I've hired dredgers to dig under my docks. Two of the most frustrating experiences in my life. Both bucket/barge types. One was a flat out thief, the other a crackhead. No wonder the OP's dockmaster was a bit testy.

And yes, bucket dredging leaves a mix of divits and hills. Depth sounder concentrates on the hills. So yes, a sounder is not a good way to assess. Also tend to be inaccurate in shallows. I used pvc pipe with a flange glued to end, dipped it to sound from a jon boat. Big high spots got just a regular pvc pipe as a flag. Dredger then supposed to go fix those spots. I ended up firing both before they got all the spots. As other's posted, humps tend to level out.

Just remembering those episodes has got me tweaked!!

In our pits we used a 100 dollar fish finder with the transducer mounted on a piece of angle iron. Then again this was for depths ranging from 50-60ft and hard limestone.

Nice adverb! ;-)

It seems to me that the marina is the loser in this equation. Usually dredge jobs are surveyed by third party providers. Hills are then "knocked down" by various means to a consistent control depth, as agreed by the contract. Typically, several surveys before final monies are released. This process protects both parties.
Marina owner is a "chump" if he doesn't varify underwater work that he is paying for.

Side scan from Humminbird or Lowrance shows the dredge cuts like there is no water. Well done dredge looks like large weld bead. I have the HB 798 HD SI unit and it shows prop scars in the mud. Plus it records to a SD chip so you can play it back on a laptop. Maybe someone in your area with SI could record a pass through. It takes about 2 minutes to record the whole channel. Any misses would be obvious.

Richard W said:

Maybe HM did not mind you "reporting", but did not like you "recommending".
Regardless, you reported, best you could do ... don't lose sleep over it.

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You're probably right. I intended to be helpful, but maybe it wasn't received in that spirit.

In retrospect, maybe I should call Garmin back and tell them not to remove all their transducers from the market...

Well, he said he was going to have it surveyed. I'd guess he is more concerned about sail boaters complaining about it, which likely drove the project in the first place. Last thing he wants to put up with is more of that noise.

Yeah…that was probably a bit of an over-reaction. Probably left them quite perplexed as to what particular bee got in your bonnet.

The Everett marina on a regular bases dredges the marina entrance, the boat ramp when they replace/move docks around. The way they take down the high spots is using the push boat prop wash. There are places at extreme low tide, -12 ft, that deep keel boat still touch. The Eagle goes a ground at our dock, but I figure it help keep the bottom clean.

I like deep keel sail boats as they make great bottom finders!

Peter B said:

Yeah…that was probably a bit of an over-reaction. Probably left them quite perplexed as to what particular bee got in your bonnet.

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I'm pretty much a data-driven person. So my interpretation of helpfulness (free information) might be perceived as intrusive (unsolicited advice/nagging) if the dock-master has been hearing it all month. Good call.

Plus, something is going on with my marina - they had a boat show scheduled there for April and it suddenly switched locations to the marina across town with little forward notice. Someone pissed in somebody's cornflakes presumably. Shortly after that switch, the dredging was announced.

So, one could infer...?

The link shows the approach channel that has been dredged. In the field of view to the left is the marina where the boat show is switched to. Maybe I picked at a scab wound with my dock master...

Pecan Cam, Pecan Grove Marina Channel Web Cam | TownDock.net, Oriental, NC

Heck... let the blow hole owners worry about it. It's them who will get grounded first in areas to shallow. They usually have more to worry about than power boaters do anyway. This can be another on their post it board.

Ski in NC said:

Twice I've hired dredgers to dig under my docks. Two of the most frustrating experiences in my life. Both bucket/barge types. One was a flat out thief, the other a crackhead. No wonder the OP's dockmaster was a bit testy.

And yes, bucket dredging leaves a mix of divits and hills. Depth sounder concentrates on the hills. So yes, a sounder is not a good way to assess. Also tend to be inaccurate in shallows. I used pvc pipe with a flange glued to end, dipped it to sound from a jon boat. Big high spots got just a regular pvc pipe as a flag. Dredger then supposed to go fix those spots. I ended up firing both before they got all the spots. As other's posted, humps tend to level out.

Just remembering those episodes has got me tweaked!!

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Really, I guess it's been blind luck that running in shallow water I've not run aground. Before I get shotgunned, I HAVE run aground before, just not in my current boat.

What you guys might be missing with sounders ....depending on the water depth and the cone the transducer puts out (first object encountered is the recorded depth even if most of the cone is deeper) there can be errors...granted not much...I wouldn't think enough in 8 feet of water...especially if the ducer tends to record the shallowest depth within the cone...

I have been on scene of dozens of dredging operations talking with the surveyors, dredge opertors and job supers.... and the most often used tool is a marked pole.

One of our yacht club members owns a floating suction dredge and uses it periodically to deepen the marina. As an aside, a slip hugger refused to move his boat out of the slip to allow the dredge access for two hours. Club response: move or get evicted. He moved the boat.

psneeld said:

What you guys might be missing with sounders ....depending on the water depth and the cone the transducer puts out (first object encountered is the recorded depth even if most of the cone is deeper) there can be errors...granted not much...I wouldn't think enough in 8 feet of water...especially if the ducer tends to record the shallowest depth within the cone...

I have been on scene of dozens of dredging operations talking with the surveyors, dredge opertors and job supers.... and the most often used tool is a marked pole.

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Yeah right. A pole is a great way to miss that shallow spot. Why that's just what you want, not to pick up the shallowest spot in what is a very narrow cone at depths< 20 ft (?!?!). A real survey for a channel like the OPs is done with equipment like this, someone paying to have a dredge job will demand it:

http://www.rosslaboratories.com/pdf/Model 960 Brochure 10.15.12.pdf

At the very very very least, someone will slowly run up and down there with a sounder a few times. The pole may be all right around someone's private dock, but doesn't pass muster for larger projects. A good sounder with a modern transducer can tell false bottoms (grass, plant life, stirred up sand) from hard bottoms.

Depth sounder should do just fine. Been there, done that.

Ask the Dockmaster for his survey certification results. Bet you don`t get em.
My guess: there is friction between him and the dredge contractor, you hit a tender spot, he went into denial mode saying "depth sounders are crap" to undermine valid concern. I like your, " Must tell Garmin their sounders are not worth a pinch of ****" response. Keep a good eye on your sounder.

caltexflanc said:

Yeah right. A pole is a great way to miss that shallow spot. Why that's just what you want, not to pick up the shallowest spot in what is a very narrow cone at depths< 20 ft (?!?!). A real survey for a channel like the OPs is done with equipment like this, someone paying to have a dredge job will demand it:

http://www.rosslaboratories.com/pdf/Model%20960%20Brochure%2010.15.12.pdf

At the very very very least, someone will slowly run up and down there with a sounder a few times. The pole may be all right around someone's private dock, but doesn't pass muster for larger projects. A good sounder with a modern transducer can tell false bottoms (grass, plant life, stirred up sand) from hard bottoms.

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Ill stand by what I see a lot every year...no matter what you dredge up on the internet..... around little projects like marinas...the marked pole is the tool of choice as Ski posted as well....

OK...I'll admit my area might be limited in terms of geography but I'll bet it isn't much different in places of the country where things are even a little more backward than from where I am....based on the piling and bulkhead jobs I've noticed.

Like the backhoe rigged dredger I just passed in Myrtle Beach that I saw doing a marina project when I went through in December...he would be lucky to have used a tape measure on his marked pole based on the equipment I saw.