Removing Submerged Navigation Hazards

T.H.E. Binz · 07-19-2006, 11:03 AM

I've got two large rocks about 30' off the end of my dock that have a history of collisions with boat propellers. The size of the rocks (at least what is above the lake bottom) is about 4' x 4' x4'. At full lake elevation, they are about 24" below the surface. One of the largest barge-mounted excavators operating on the lake was unable to move these rocks. I am told that one cannot get a permit from the NHDES to dynamite the rocks.

Does anyone know of a marine contractor, or a drilling and blasting outfit, that could drill holes in these rocks and split them up using expansion agents, rock-splitters, etc.?

I was going to try to expose the rocks during the winter and drill holes for an expansion agent, but the lake was too high and the ice too thin this year!

Onshore · 07-19-2006, 11:07 AM

You can get a permit to "pop" rocks from the DES Wetlands Bureau. It would be recommended that you get the permit to either relocate them or "pop" them before hiring a contractor to do the work.

Dave R · 07-20-2006, 12:39 PM

I have no clue about the legality of the following advice.

I have sucessfully moved big boulders on land using chains, big nylon straps, come-alongs and trees. You need to make a lasoo around the rock with the chain and a slipper hook such that the end of the chain comes from the side of the rock opposite the direction of pull, and over the top of the rock. The nylon strap is used to connect to and protect the tree. When you apply tension this way, the rock will roll instead of slide and it is much easier to roll a rock than it is to slide it. If you can make a hole in the ground for the rock to roll into, your problem will be solved without a whole lot of effort or explosives.

You could also make some home made markers for the rocks and leave well enough alone.

They weigh about 6758.4 lbs under water if they are indeed 4x4x4 (and granite). Above water, they would weigh 10752 lbs.

T.H.E. Binz · 10-11-2006, 09:49 AM

For anyone interested, my application to remove the aforementioned rock was denied by the local Conservation Commission. Their suggestion was to move the dock; their main concern was environmental harm and setting prededent. When I look at some of the construction/demolition underway on the lake (i.e., 4,000 SF houses on 10,000 SF islands, tree removal along the shoreline, etc.) I find it pretty ironic that my rock has to stay!

feb · 10-11-2006, 10:21 AM

Does the local conservation commission have the last say though? I thought DES would take into consideration when the CC says but that the DES makes the final decision. I've seen many times in the DES Decision Reports where the local CC says one thing and the DES still approves the permit.

Onshore · 10-11-2006, 10:47 AM

In the State of NH the local Conservation Committees serve an advisory role. They do not have the authority to approve or deny applications as they do in MA. They can make recommendations If they do and the State chooses to take an action contrary to those recommendations the state must explain why through decision findings. The State is not required to follow the Conservation Commission's recommendation.

jrc · 10-11-2006, 11:07 AM

How can moving a dock have less environmental damage than moving a rock. Typical bureaucratic nonsense. Maybe the ice will move them for you this winter.

Yankee, the mass stays the same, but the force needed to lift the rock is less in water. Think about a tree, it weighs a ton on land but nothing in water, it floats.

Zeke · 10-11-2006, 11:39 AM

Quote:

Originally Posted by Yankee

Dave,

Why would the rock weigh less under water than above it?

The weight of an object in water, as compared to in a gas environment would be less due to it's specific gravity in comparison in the two envirornments. It still sounds like a damned heavy rock in either state. physics 101

Seaplane Pilot · 10-11-2006, 12:06 PM

These Conservation and Wetlands people need to get their heads out of the same sand that they are chartered to protect. Any given weekend dozens of cruisers leaving Mountainview, Silver Sands and the other yacht clubs in Gilford throw up enormous wakes and destroy the shoreline in front of my house on Dockham Shore. Where's the outrage over this shoreline destruction by the environmentalists? Yet moving a boulder is a major problem?

TomC · 10-11-2006, 12:19 PM

Quote:

Originally Posted by Yankee

Dave,

Why would the rock weigh less under water than above it?

terms which people tend to use interchangeably, but they do not mean the same thing...

SIKSUKR · 10-11-2006, 01:49 PM

I know what you mean Seaplane,I've seen the damage done at your Dockham Shore property.

Dave R · 10-11-2006, 02:12 PM

Any chance you can just mark the rocks well and leave them alone? I see plenty of privately maintained navigational aids on the lake. I can't imagine why marking would be a problem. Of course, being denied the option of moving them seems utterly silly to me. Love to hear a good reason why the rocks should stay.

ApS · 10-11-2006, 04:37 PM

Quote:

Originally Posted by T.H.E. Binz

"...One of the largest barge-mounted excavators operating on the lake was unable to move these rocks. I am told that one cannot get a permit from the NHDES to dynamite the rocks.

Does anyone know of a marine contractor, or a drilling and blasting outfit, that could drill holes in these rocks and split them up using expansion agents, rock-splitters, etc.?

I was going to try to expose the rocks during the winter and drill holes for an expansion agent, but the lake was too high and the ice too thin this year!

I watched one marine contractor "winterize" his steel barge by tying up to his next shoreline jobsite and filling the hull with water. In the spring, he just pumped it out and went on with his work there.

If your marine contractor removes the excavator and empties his hull, he can put a "necklace" of chain under the boulder and raise it off the bottom by pumping out the hull. He could then move it to deeper water.

(Or to my place—I could use a boulder to break up wakes.)

jrc · 10-11-2006, 10:41 PM

Quote:

Originally Posted by Yankee

I asked the question because I was curious about the answers that I’d get. Let me give you a brief high school level primer:

....

Don't be so pedantic, we answered the question how it was asked. We explained "Weigh" as an English word on a freindly website, not the formal scientific meaning.

fpartri497 · 10-12-2006, 06:28 AM

Quote:

Originally Posted by Yankee

I asked the question because I was curious about the answers that I’d get. Let me give you a brief high school level primer:

Specific gravity also known as relative density is the ratio of of an objects density (mass/volume) to a reference density, which is usually water but also can be a gas or any other form of matter. It has absolutely nothing to do with the weight of an object, in this case the aforementioned rock.

Weight is the force enacted upon a body (of a certain mass) when exposed to a gravitational field. This is why a person would weigh less on the moon than the Earth, but he would also maintain his same mass. It’s suffice to say, whether the rock is under or above the water, it will have the same mass and since the Earth’s gravitational field is constant, it will have the same weight. So it will be just as heavy no matter where on the Earth that it resides.

You got way to much time on your hands!!!!!!!!

Onshore · 10-12-2006, 07:01 AM

Quote:

Originally Posted by Seaplane Pilot

These Conservation and Wetlands people need to get their heads out of the same sand that they are chartered to protect. Any given weekend dozens of cruisers leaving Mountainview, Silver Sands and the other yacht clubs in Gilford throw up enormous wakes and destroy the shoreline in front of my house on Dockham Shore. Where's the outrage over this shoreline destruction by the environmentalists? Yet moving a boulder is a major problem?

How exactly do you propose we control that? A speed limit? Maybe a restriction on boat length, displacement, or hull type? Perhaps we should just accept the reality that in this state none of those things will come out of the legislature in our life time and just allow the construction of a wall around the entire lake? If you come up with any good solutions that might have even a remote chance of making it into rule or law please share it with the Wetlands people because we're all fresh out of ideas. (Oh yes, and while your at it, think about how you're going to sell it to those Safety people since they are the only authority that is allowed to regulate boating acting around here and if they won't support your idea it will be DOA.)

In the meantime, someone tell T.H.E. Binz to file a Standard Dredge and Fill Application to move that rock because the Town Clerk must forward that application type directly to the state. It cannot be held by the town.

Dave R · 10-12-2006, 07:23 AM

Quote:

Originally Posted by Yankee

I asked the question because I was curious about the answers that I’d get. Let me give you a brief high school level primer:

Specific gravity also known as relative density is the ratio of of an objects density (mass/volume) to a reference density, which is usually water but also can be a gas or any other form of matter. It has absolutely nothing to do with the weight of an object, in this case the aforementioned rock.

Weight is the force enacted upon a body (of a certain mass) when exposed to a gravitational field. This is why a person would weigh less on the moon than the Earth, but he would also maintain his same mass. It’s suffice to say, whether the rock is under or above the water, it will have the same mass and since the Earth’s gravitational field is constant, it will have the same weight. So it will be just as heavy no matter where on the Earth that it resides.

OK, what would happen if we were to hang the rock on a scale while it's in the water and while it's out? Would the scale read the same weight or not? That was my point. I realize the rock's mass never changed.

Seaplane Pilot · 10-12-2006, 10:02 AM

Quote:

Originally Posted by shore things

How exactly do you propose we control that? A speed limit? Maybe a restriction on boat length, displacement, or hull type? Perhaps we should just accept the reality that in this state none of those things will come out of the legislature in our life time and just allow the construction of a wall around the entire lake? If you come up with any good solutions that might have even a remote chance of making it into rule or law please share it with the Wetlands people because we're all fresh out of ideas. (Oh yes, and while your at it, think about how you're going to sell it to those Safety people since they are the only authority that is allowed to regulate boating acting around here and if they won't support your idea it will be DOA.)

In the meantime, someone tell T.H.E. Binz to file a Standard Dredge and Fill Application to move that rock because the Town Clerk must forward that application type directly to the state. It cannot be held by the town.

Shore Things: you are correct, it's unenforceable. However, the damage and erosion is real. With that said, why then do the wetlands and environmentalists continually put the screws to people that want to do a minor impact thing such as to move a boulder? Furthermore, if I wanted to put up some kind of solution to mitigate and prevent the erosion to my property, such as to put boulders on the shoreline, (the same property on which I am being taxed), then I would get soundly rejected by the wetlands. I know this is the case because my neighbor tried and got rejected. Wetlands is zealous in its efforts to regulate the small issues, but instead should be focusing on the bigger problems.

skprbob · 10-12-2006, 11:35 AM

The two-word answer to Dave R and Yankee: Archimedes' Principle.

The more detailed answer:

A 4 ft x4 ft x4 ft block of anything, fully submerged, displaces 64 cubic feet of water. Fresh water has a density of 62 lbs/cubic ft. By Archimedes' Principle, the block would thus have a buoyant force on it of 64 x 62, or 3970 lbs. If the block itself weighed less than that, the buoyant force would be greater, pushing the bnlock up, and the block would float. In fact it would rise out of the water until its weight and the weight of the water it displaces were equal, then sit there floating peacefully; so-called positive buoyancy. If the block's weight and the buoyant force were equal, the block would submerge completely and remain at whatever depth one wished to place it at; so-called neutral buoyancy and very hard to maintain for a number of reasons - just ask a SCUBA diver! If the block's weight was greater than the buoyant force, the block would submerge completely and continue to sink, since the downward force is greater; so-called negative buoyancy.

Example - Concrete has a density of roughly 100 lbs/cubic foot, so a 4x4x4 block would weigh 6400 lbs. That's greater than the buoyant force on it if it were completely submerged, so it sinks. It would also weighs only 6440 - 3970, or 2430 lbs underwater. You have to pour a block weighing over 3 tons in order to get just over one ton of holding weight!

SIKSUKR · 10-12-2006, 12:30 PM

Well,I just posted a disagreement with Skprbob and then did a little research.He/she is right on with the displacement calculation.By the way,granite weighs 165 pounds per cubic foot.You can do the math.

John A. Birdsall · 10-12-2006, 10:12 PM

Quote:

Originally Posted by Dave R

Any chance you can just mark the rocks well and leave them alone? I see plenty of privately maintained navigational aids on the lake. I can't imagine why marking would be a problem. Of course, being denied the option of moving them seems utterly silly to me. Love to hear a good reason why the rocks should stay.

I think I can see a reason why rocks should stay, specifically only along the shore line which is what I think they are talking about. and that is too stop the errosion of the beaches or land. I say that cause they said to "move the dock" why not find a way to anchor your dock on the rock. My dad often says that an old timer stated sonny if you find anything that can stay in that lake you will make your first million. Well boulders do stay put. Even when hit by boats or propellars.

Rayhunt · 10-13-2006, 08:38 AM

Quote:

Originally Posted by Seaplane Pilot

These Conservation and Wetlands people need to get their heads out of the same sand that they are chartered to protect. Any given weekend dozens of cruisers leaving Mountainview, Silver Sands and the other yacht clubs in Gilford throw up enormous wakes and destroy the shoreline in front of my house on Dockham Shore. Where's the outrage over this shoreline destruction by the environmentalists? Yet moving a boulder is a major problem?

Agreed 100% .. these monster boats are the worst problem on the lake. For some reason the pilots have less reguard than anyone else for the rules. I guess it takes too much gas to slow down and then speed up again so they just break a bunch of laws?? Forget the speed limit , the lake needs a 10,000 LB weight limit !
Another favorite of mine is when they run em half speed right up to the no wake sign as the 3 foot waves keep rolling for a half mile past the boat. The area between lockes and pig island needs to be a no wake zone !

Pineedles · 10-13-2006, 06:42 PM

Just blow the damn thing up and take the consequences if any.

skprbob · 10-16-2006, 09:38 PM

Hi Yankee,

At risk of being ostentatious, pedantic, elitist, and/or haughty, I will say the I probably should have used the term "apparent weight" for the block in the water. However, since you're an engineer, and I'm a former prep school Physics and Chemistry teacher, I suspect we know what the other means!

jrc · 10-16-2006, 09:46 PM

Quote:

Originally Posted by Yankee

....

jrc, excuse me! We? Do you have a mouse in your pocket or what? Jeesh! For what it's worth, I'd rather be pedantic in a post than haughty, like you....

Not too much time, just an engineer by trade, and a geek at heart!!

I guess, my point was that there are several engineer/geek people on the board that are well qualified to give you a scientific explanation. But since I didn't know a geek was asking, I gave a real world example. I am brusque and rude, but am I really haughty?

ITD · 10-17-2006, 06:30 AM

Mass, you people are talking about the mass of an object, which doesn't change. Weight is generally a measure of force exerted by an object due to gravity. Weight generally falls under the auspices of f=ma where f equals the force measured (weight in this case), m equals the mass of an object and a equals the acceleration due to gravity. Weight (the measure of force) is also influenced by the medium in which an object is weighed, even air has an effect. Also, although we generally consider the acceleration of gravity to be a constant, it does vary dependant upon your location on the earth. This variation is very small fortunately. The mass of an object is constant no matter where an object is weighed.

A rock, however, will weigh less in the water than on land.

SteveA · 10-17-2006, 07:00 AM

Maybe David Copperfield could make it disappear... worked for a 747 in 1981.

Another thought, maybe someone could go down to the dock and read this entire thread to the rock.... it may just leave on its' own. Considering that it has been suggested to tow it, drill it and even blow it up..

PS... I'd feel better if someone would admit to having had to look up the word pedantic like I did.

GWC... · 10-17-2006, 10:39 AM

Quote:

Originally Posted by SteveA

PS... I'd feel better if someone would admit to having had to look up the word pedantic like I did.

Okay, just to make your day, since you did such a great job with FFIII - I did, too.

Actually, reading the second definition made it seem an apposite choice.

For those less likely to exert the effort, here's the definition:
pedantic
One entry found for pedantic.

Main Entry: pe·dan·tic
Pronunciation: pi-'dan-tik
Function: adjective
1 : of, relating to, or being a pedant
2 : narrowly, stodgily, and often ostentatiously learned
http://www.m-w.com/dictionary/pedantic

Weirs guy · 10-17-2006, 12:01 PM

As a half-an-engineer, I think the real question all of us geeks at heart should be asking is this:

When do we get to blow up the rock, and how much explosives do we get to play with?

Airwaves · 10-17-2006, 12:14 PM

Quote:

J.A.B wrote
"move the dock" why not find a way to anchor your dock on the rock.

Actually that is a very good idea. If the rock is close enough to do damage to the boat when you come into the dock or leave it, why not look at using the rock as an anchor to the dock, or extending/moving the dock so that it covers the rock? I remember when we had a place on Dockham Shore there was a huge rock just off our dock. It didn't cause us any problem to our boats (I actually named it Big Bertha!) but if it had we certainly could have covered it with the dock itself.

Mee-n-Mac · 10-17-2006, 12:39 PM

Quote:

Originally Posted by Weirs guy

As a half-an-engineer, I think the real question all of us geeks at heart should be asking is this:

When do we get to blow up the rock, and how much explosives do we get to play with?

Sadly the answer is probably not as much as you'd like. A few bore holes and just a tiny bit would no doubt do the job. Wasn't there a MythBuster's episode where they re-created the water-in-a-safe + explosives to "crack" it ? I'm thinking T.H.E. Binz might be better off enlisted a squad of UDE rock bass. I mean they must be called rock bass for a reason !? Perhaps they could be enlisted to peck away at the rocks

Then it's all due to "nature" and he couldn't be blamed. Until then I' thinking the old Chlorox bottle(s) on a string is a legal alternative.

ITD · 10-17-2006, 06:16 PM

A series of holes with wedges tapped in could also be done, has worked for hundreds (thousands???) of years. Probably a little tougher to do underwater though.

Pineedles · 10-17-2006, 08:14 PM

Exactly, a few wedges and in a couple million years the rock will split. Problem solved.

T.H.E. Binz · 02-23-2007, 11:47 AM

I thought I actually received default approval for the "popping" of the rocks off my dock, i.e., I had an administratively complete application and hadn't heard back from the DES in several months. Unfortunately, DES had mailed a request for additional information to my P.O. Box in Meredith which I never received. As a result, my application was automatically denied and, if I wish to pursue, have to begin the application process (and $100 application fee) all over again.

However, I gather from the request for additional information (which the DES was kind enough to fax me) that NH Fish & Game is not too keen on popping rocks. They don't want rocks completely demolished, but popped to provide a useful size for fish habitat. I'm not sure this is practical for 4' rocks in 5' of water so I probably won't pursue this matter any further. They also wanted a construction sequence showing materials utilized with methods to control turbidity.

GWC... · 02-23-2007, 12:40 PM

The result of your legal effort to resolve a problematic situation is a sad commentary on life in NH when dealing with state government agencies.

Would seem that the DES and Fish & Game have yet to hear the expression "K.I.S.S." in their daily conversations.

Whatever happened to simple, common sense solutions?

Cow Man · 02-24-2007, 09:11 AM

For better or worse, I have found that these situations are best handled by a professional contractor. I have used Winnipesaukee Marine Construction. They deal with all the permits and have experience in dealing with the various officials and all the correspondence goes to them.
Sure it's more expensive then DIY but less stressful and it usually gets done!

Orion · 02-24-2007, 10:01 AM

I agree with Cow Man. I am an avid do-it-yourselfer, but when dealing with government agencies, the pros know what you can get away with and how to frame it in the application process. I've used Diversified Marine for several projects and he's always been able to "get 'er done".

07-19-2006, 11:03 AM	#1
T.H.E. Binz Senior Member Join Date: Apr 2004 Location: Meredith & Chadds Ford, PA Posts: 112 Thanks: 0 Thanked 11 Times in 8 Posts	Removing Submerged Navigation Hazards I've got two large rocks about 30' off the end of my dock that have a history of collisions with boat propellers. The size of the rocks (at least what is above the lake bottom) is about 4' x 4' x4'. At full lake elevation, they are about 24" below the surface. One of the largest barge-mounted excavators operating on the lake was unable to move these rocks. I am told that one cannot get a permit from the NHDES to dynamite the rocks. Does anyone know of a marine contractor, or a drilling and blasting outfit, that could drill holes in these rocks and split them up using expansion agents, rock-splitters, etc.? I was going to try to expose the rocks during the winter and drill holes for an expansion agent, but the lake was too high and the ice too thin this year!

10-11-2006, 09:49 AM	#4
T.H.E. Binz Senior Member Join Date: Apr 2004 Location: Meredith & Chadds Ford, PA Posts: 112 Thanks: 0 Thanked 11 Times in 8 Posts	Rock Removal Denied For anyone interested, my application to remove the aforementioned rock was denied by the local Conservation Commission. Their suggestion was to move the dock; their main concern was environmental harm and setting prededent. When I look at some of the construction/demolition underway on the lake (i.e., 4,000 SF houses on 10,000 SF islands, tree removal along the shoreline, etc.) I find it pretty ironic that my rock has to stay!

10-11-2006, 10:21 AM	#5
feb Senior Member Join Date: Apr 2004 Location: Meredith (Winnisquam) & Nashua, NH Posts: 213 Thanks: 25 Thanked 20 Times in 17 Posts	DES has last say, right? Does the local conservation commission have the last say though? I thought DES would take into consideration when the CC says but that the DES makes the final decision. I've seen many times in the DES Decision Reports where the local CC says one thing and the DES still approves the permit.

10-11-2006, 12:06 PM	#9
Seaplane Pilot Senior Member Join Date: Apr 2004 Posts: 1,177 Thanks: 664 Thanked 943 Times in 368 Posts	Barking up the wrong tree These Conservation and Wetlands people need to get their heads out of the same sand that they are chartered to protect. Any given weekend dozens of cruisers leaving Mountainview, Silver Sands and the other yacht clubs in Gilford throw up enormous wakes and destroy the shoreline in front of my house on Dockham Shore. Where's the outrage over this shoreline destruction by the environmentalists? Yet moving a boulder is a major problem?

10-11-2006, 01:49 PM	#11
SIKSUKR Senior Member Join Date: Apr 2004 Posts: 5,075 Thanks: 215 Thanked 903 Times in 509 Posts	I know what you mean Seaplane,I've seen the damage done at your Dockham Shore property. __________________ SIKSUKR

07-19-2006, 11:07 AM	#2
Onshore Senior Member Join Date: Apr 2004 Posts: 502 Thanks: 12 Thanked 423 Times in 145 Posts	You can get a permit to "pop" rocks from the DES Wetlands Bureau. It would be recommended that you get the permit to either relocate them or "pop" them before hiring a contractor to do the work.

07-20-2006, 12:39 PM	#3
Dave R Senior Member Join Date: Jul 2004 Posts: 2,984 Thanks: 246 Thanked 743 Times in 443 Posts	I have no clue about the legality of the following advice. I have sucessfully moved big boulders on land using chains, big nylon straps, come-alongs and trees. You need to make a lasoo around the rock with the chain and a slipper hook such that the end of the chain comes from the side of the rock opposite the direction of pull, and over the top of the rock. The nylon strap is used to connect to and protect the tree. When you apply tension this way, the rock will roll instead of slide and it is much easier to roll a rock than it is to slide it. If you can make a hole in the ground for the rock to roll into, your problem will be solved without a whole lot of effort or explosives. You could also make some home made markers for the rocks and leave well enough alone. They weigh about 6758.4 lbs under water if they are indeed 4x4x4 (and granite). Above water, they would weigh 10752 lbs.

10-11-2006, 10:47 AM	#6
Onshore Senior Member Join Date: Apr 2004 Posts: 502 Thanks: 12 Thanked 423 Times in 145 Posts	In the State of NH the local Conservation Committees serve an advisory role. They do not have the authority to approve or deny applications as they do in MA. They can make recommendations If they do and the State chooses to take an action contrary to those recommendations the state must explain why through decision findings. The State is not required to follow the Conservation Commission's recommendation.

10-11-2006, 11:07 AM	#7
jrc Senior Member Join Date: Apr 2004 Location: NH Posts: 2,689 Thanks: 33 Thanked 439 Times in 249 Posts	How can moving a dock have less environmental damage than moving a rock. Typical bureaucratic nonsense. Maybe the ice will move them for you this winter. Yankee, the mass stays the same, but the force needed to lift the rock is less in water. Think about a tree, it weighs a ton on land but nothing in water, it floats.

10-11-2006, 02:12 PM	#12
Dave R Senior Member Join Date: Jul 2004 Posts: 2,984 Thanks: 246 Thanked 743 Times in 443 Posts	Any chance you can just mark the rocks well and leave them alone? I see plenty of privately maintained navigational aids on the lake. I can't imagine why marking would be a problem. Of course, being denied the option of moving them seems utterly silly to me. Love to hear a good reason why the rocks should stay.

10-12-2006, 11:35 AM	#19
skprbob Senior Member Join Date: Sep 2006 Location: 19 Mile Bay Posts: 147 Thanks: 0 Thanked 90 Times in 29 Posts	granite The two-word answer to Dave R and Yankee: Archimedes' Principle. The more detailed answer: A 4 ft x4 ft x4 ft block of anything, fully submerged, displaces 64 cubic feet of water. Fresh water has a density of 62 lbs/cubic ft. By Archimedes' Principle, the block would thus have a buoyant force on it of 64 x 62, or 3970 lbs. If the block itself weighed less than that, the buoyant force would be greater, pushing the bnlock up, and the block would float. In fact it would rise out of the water until its weight and the weight of the water it displaces were equal, then sit there floating peacefully; so-called positive buoyancy. If the block's weight and the buoyant force were equal, the block would submerge completely and remain at whatever depth one wished to place it at; so-called neutral buoyancy and very hard to maintain for a number of reasons - just ask a SCUBA diver! If the block's weight was greater than the buoyant force, the block would submerge completely and continue to sink, since the downward force is greater; so-called negative buoyancy. Example - Concrete has a density of roughly 100 lbs/cubic foot, so a 4x4x4 block would weigh 6400 lbs. That's greater than the buoyant force on it if it were completely submerged, so it sinks. It would also weighs only 6440 - 3970, or 2430 lbs underwater. You have to pour a block weighing over 3 tons in order to get just over one ton of holding weight!

10-12-2006, 12:30 PM	#20
SIKSUKR Senior Member Join Date: Apr 2004 Posts: 5,075 Thanks: 215 Thanked 903 Times in 509 Posts	Well,I just posted a disagreement with Skprbob and then did a little research.He/she is right on with the displacement calculation.By the way,granite weighs 165 pounds per cubic foot.You can do the math. __________________ SIKSUKR

10-13-2006, 06:42 PM	#23
Pineedles Senior Member Join Date: Aug 2004 Location: Moultonborough & CT Posts: 2,542 Thanks: 1,071 Thanked 667 Times in 366 Posts	The heck with it Just blow the damn thing up and take the consequences if any.

10-16-2006, 09:38 PM	#24
skprbob Senior Member Join Date: Sep 2006 Location: 19 Mile Bay Posts: 147 Thanks: 0 Thanked 90 Times in 29 Posts	ostentatious precision Hi Yankee, At risk of being ostentatious, pedantic, elitist, and/or haughty, I will say the I probably should have used the term "apparent weight" for the block in the water. However, since you're an engineer, and I'm a former prep school Physics and Chemistry teacher, I suspect we know what the other means!

10-17-2006, 06:30 AM	#26
ITD Senior Member Join Date: Apr 2004 Location: Moultonboro, NH Posts: 2,925 Thanks: 476 Thanked 691 Times in 387 Posts	Mass, you people are talking about the mass of an object, which doesn't change. Weight is generally a measure of force exerted by an object due to gravity. Weight generally falls under the auspices of f=ma where f equals the force measured (weight in this case), m equals the mass of an object and a equals the acceleration due to gravity. Weight (the measure of force) is also influenced by the medium in which an object is weighed, even air has an effect. Also, although we generally consider the acceleration of gravity to be a constant, it does vary dependant upon your location on the earth. This variation is very small fortunately. The mass of an object is constant no matter where an object is weighed. A rock, however, will weigh less in the water than on land.

10-17-2006, 07:00 AM	#27
SteveA Deceased Member Join Date: Jul 2006 Location: Gilford, NH Posts: 2,311 Thanks: 1,070 Thanked 2,054 Times in 497 Posts	David Copperfield? Maybe David Copperfield could make it disappear... worked for a 747 in 1981. Another thought, maybe someone could go down to the dock and read this entire thread to the rock.... it may just leave on its' own. Considering that it has been suggested to tow it, drill it and even blow it up.. PS... I'd feel better if someone would admit to having had to look up the word pedantic like I did. __________________ "Before you criticize someone, walk a mile in his shoes. That way, if he gets angry he'll be a mile away and barefoot!" unknown

10-17-2006, 12:01 PM	#29
Weirs guy Senior Member Join Date: Feb 2006 Location: Weirs Beach, NH Posts: 1,067 Thanks: 0 Thanked 1 Time in 1 Post	As a half-an-engineer, I think the real question all of us geeks at heart should be asking is this: When do we get to blow up the rock, and how much explosives do we get to play with? __________________ Is it bikeweek yet? Now?

10-17-2006, 06:16 PM	#32
ITD Senior Member Join Date: Apr 2004 Location: Moultonboro, NH Posts: 2,925 Thanks: 476 Thanked 691 Times in 387 Posts	A series of holes with wedges tapped in could also be done, has worked for hundreds (thousands???) of years. Probably a little tougher to do underwater though.

10-17-2006, 08:14 PM	#33
Pineedles Senior Member Join Date: Aug 2004 Location: Moultonborough & CT Posts: 2,542 Thanks: 1,071 Thanked 667 Times in 366 Posts	ITD Got the Answer Exactly, a few wedges and in a couple million years the rock will split. Problem solved.

02-23-2007, 11:47 AM	#34
T.H.E. Binz Senior Member Join Date: Apr 2004 Location: Meredith & Chadds Ford, PA Posts: 112 Thanks: 0 Thanked 11 Times in 8 Posts	The End of the Story . . . I thought I actually received default approval for the "popping" of the rocks off my dock, i.e., I had an administratively complete application and hadn't heard back from the DES in several months. Unfortunately, DES had mailed a request for additional information to my P.O. Box in Meredith which I never received. As a result, my application was automatically denied and, if I wish to pursue, have to begin the application process (and $100 application fee) all over again. However, I gather from the request for additional information (which the DES was kind enough to fax me) that NH Fish & Game is not too keen on popping rocks. They don't want rocks completely demolished, but popped to provide a useful size for fish habitat. I'm not sure this is practical for 4' rocks in 5' of water so I probably won't pursue this matter any further. They also wanted a construction sequence showing materials utilized with methods to control turbidity.

02-23-2007, 12:40 PM	#35
GWC... Senior Member Join Date: Apr 2004 Posts: 1,325 Thanks: 5 Thanked 0 Times in 0 Posts	The result of your legal effort to resolve a problematic situation is a sad commentary on life in NH when dealing with state government agencies. Would seem that the DES and Fish & Game have yet to hear the expression "K.I.S.S." in their daily conversations. Whatever happened to simple, common sense solutions? __________________ [Assume funny, clever sig is here. Laugh and reflect... ]

02-24-2007, 09:11 AM	#36
Cow Man Member Join Date: Feb 2006 Location: Cow Island / Holderness, NH Posts: 46 Thanks: 4 Thanked 19 Times in 8 Posts	Hire a pro For better or worse, I have found that these situations are best handled by a professional contractor. I have used Winnipesaukee Marine Construction. They deal with all the permits and have experience in dealing with the various officials and all the correspondence goes to them. Sure it's more expensive then DIY but less stressful and it usually gets done!

02-24-2007, 10:01 AM	#37
Orion Senior Member Join Date: Feb 2003 Location: Cow Island Posts: 914 Thanks: 602 Thanked 193 Times in 91 Posts	Agree- let the pro's worry about it. I agree with Cow Man. I am an avid do-it-yourselfer, but when dealing with government agencies, the pros know what you can get away with and how to frame it in the application process. I've used Diversified Marine for several projects and he's always been able to "get 'er done".