Pond Boss Forums POND CONSTRUCTION Creating habitat PVC Piers for Dock Question

I am wondering if anyone has tried to make a dock with 8” PVC pipe filled with concrete for the posts? I have an existing dock that has seen its better days, and I want to build a new dock in its place.

Here is what I am thinking. I will take a piece of 8” PVC pipe and place a couple blocks of wood on top, and hammer it in to the pond floor with a sledge hammer. I have already test this out and I was able to hammer a piece in about 2 feet without a problem.

Then when I can’t hammer it any deeper, I will take my manual ice auger, with an 8 foot extension and start drilling the mud out of the pvc pipe. The Auger fits perfect inside the 8" pipe. This may be slow going, but I am persistent.

I may be able to then hammer the PVC pipe in deeper after augering some of the mud out. If I cannot hammer the pipe in deeper, I will still keep drilling deeper and deeper until I get down at least 4 feet.

Then I could place a couple of pieces of rebar in pipe and fill with concrete. And then put a J bolt in the top where I will secure my dock frame.

What do you guys think? Will it work? This is on a 2 acre pond.

My neighbor who is a perfectionist and has a 2 acre pond of his own, suggested that I drain the pond 6 foot. Then get our there and pour some footers and then a pier on top. I really didn’t want to do that…but I will if that is the right way to do it. I was hoping my idea above would work.

I guess I could try my idea and let everyone know if it was good idea or not.

btw...This forum is awesome! You guys have some great ideas on here!

Thanks!

Sean

It sounds crazy enough to work....maybe.
What about ice movement? Concrete has tremendous compressive strength, but terrible shear strength. In essence, the only lateral strength will be that of the PVC pipe. A few rebar verts in the pipe will help, but a true concrete pier would have a combination of verts and horizontal ties. An 8" dia is nearly impossible to install a rebar cage of verts and ties. You can't make a tie small enough and the 8" dia is too small a mass. So, we return to the PVC pipe to provide lateral shear strength.
If there will be little lateral force, it should work. The next issue would be how many to support the proposed load.

ooops...
Almost forgot. Welcome, Sean, to the Pond Boss forum. It's a real buzz.

This will be a small dock. Maybe 12’x8’ platform. I was thinking 4 to 6 piers.

My only fear was how much will the concrete expand when it freezes? Will it crack the PVC pipe? Is there something I could do to avoid it form cracking the pipe? I am not sure what it will matter if PVC cracks or not. It is basically the form for the concrete.

As far as some vertical rebar, I think you are right. There will not be much room for that.

Thanks for the welcome and the reply Brettski!

Sean

In the building of bridge column piers we often have rebar cages that are spiral pieces with vertical members tied inside them. Imagine a slinky with straight pieces tied inside. You could do something like this to give you more lateral support. I would think #2 (1/4) rebard would be pretty easy to bend around a piece of 6" pipe and fit nicely inside 8" pipe with #3 or #4 bar inside that. That would help increase your lateral strength. You could also use steel pipe with no rebar. Have you thought about installing your piers in at an angle leaning slightly towards the bank and towards the center of the dock and adjust your mounting brackets to level up your dock after? I have considered building something very similar, let us know what you do in the end. I am probably another year from building a dock financially, I am finishing the restoration of my house first. Heck I am lucky to have a pond at this point.

If you can get a pump or a garden hose out there, try sticking a piece of 1/2" PVC on the hose that is as long as the piece of 8" PVC. Turn the hose on, and stick the 1/2" PVC inside the 8" one to wash away the dirt inside the pipe. It may loosen the dirt enough so you can just gently tap the 8" PVC down to the depth that you want. My dad and I did this trick with a steel seawall (the pieces of steel interlocked and looked like W's) and 20' pieces of 2" galvanized pipe that we used as uprights for a boat hoist. We don't have to remove anything in the winter, the ice goes the other way and isn't a problem. When we did it, we put a shut-off valve at the end of the hose so we didn't have water spraying all over when we took it out of the pipe. If it works, stop washing the dirt away before you get to the target depth and pound it in the rest of the way. On the first one, we didn't do that and ended up pulling the pipe back up that winter because it sunk too low.

Sean
Welcome to the forum.
I like the idea and like Brettski think it is just crazy enough to work.

Otto

Sean,

Welcome to Pond Boss!

8" concrete pilings are plenty strong for an 8x12 deck. Even 4 of them is more than strong enough. Sounds like your driving method would work too. If the auger fits real close, I don't see why you couldn't drive the pipe pretty deep. Maybe you should wait for hot weather, because even with a wood block, the PVC will probably shatter if cold. I don't think more than 2'depth would be necessary for a deck that size. As mentioned, your problem is going to be ice, so you may need to drive a few rebars down inside the pipe before pouring. You can cheaply strengthen your concrete by adding a little pure Portland cement to the mix. 1 sack would be plenty enough to strengthen 4 piers.

I just had a thought that a small aerator at each pier would keep them ice free for a few feet around.

Would the weight of the concrete make the posts settle further over time?

Bobad I had the same idea as to how I plan to keep my dock from suffering ice damage someday. I would be turning the air pumps on today matter of fact, the ice is creaking and groaning hard today with a steady warm up predicted over the weekend. I will probably be ice free next week some time. When it goes off it can wreak havoc on anything sticking up thru it.

RobA I would say the weight of the entire dock would be more of a burden than the concrete alone. It would all settle to some extent unless you drove pilings.

good point about the weight of the dock.

Sean,

Sean, Last year me and a buddy built a T-dock in my pond.. I took 5 gallon buckets and cemented 4x4 treated post in the buckets, then we walked the buckets and post into the water. both of us stood on the bucket and wollered it down in the muck.. the dock has not moved...

We built the sub frame and put it in the water first..

[url=http://s616.photobucket.com/albums/tt249/hbao931_photo/?action=view¤t=FISHIN1.jpg][/url]

Okay, I think I am going to try it here in the next month or so. I agree that I should wait until it warms up a little so I don’t split the PVC when I am hammering on it. Maybe until then, I will work on welding up some sort of rebars with some circle verts in it. Maybe if I can find a post to drive all the way down, I can do that as well.

Will ¼ inch rebar be big enough?

I will take pictures and post them with the progress.

I am hoping that I can keep my piers under $300. $100 for the pipe and $200 for the concrete and rebar.

This may be a waste of money and time…we'll see.

If you guys have any other suggestions, I am very open-minded.

Thanks for all your replies!

Sean

Pond Owner…That is kind of what I want mine to look like. I am not sure that I could get 5-gallon thing to work for me. First of all my pond is only 4 years old and I am not sure that I could get them to sink very deep. Second of all, I am like a cat in water. I don’t belong.

Have you had any problem with the ice heaving the dock up? My last dock, I set it too low and the ice and a couple heavy rains heaved my post out of the ground. Now it looks like a ramp.

Here was my first attempt at making a dock.

Don’t laugh too hard!

btw. That is pea gravel rock on the right and left of the dock on top of the ice. They say that helps attract fish during the spawning season. We will see.

Thanks,
Sean

A guy from Alabama did the pvc and rebar deal and it worked good. No ice over though. I personally think 8 inch is way overkill. 6 inch will take little more than 1/2 the concrete and still be plenty sturday enough. Drive down several rebars inside the pvc, and drill some horizontal holes and lay rebar thru them. Make the support a few inches higher than needed and give it time to settle.
I will try and find the pics of the concrete posts.

2 sizes of pvc sounds like a good idea. This will allow for more expansion-contraction.

Another idea would be to use a treated post inside of the pvc and make the pvc only high enough to pour the concrete into it.

Hey Sean didn't I see Johnny Knoxville ride a rocket bike off that dock in a movie??? Seriously though, I would put two more piers in along side that dock and just raise the center up and put a header across for it to set on. If it still is in the pond that is.

As for the question at hand, I would say 1/4" rebar would work, just space it closer than what you would space larger bar. A 5 inch circle would be about 15 inches in circumference, 8 bars would fit at roughly 2 inch spacing more or less, tie them to every horizontal bar or use the slinky idea and you will have a steel structure that will be quite tough when suspended in crete. Just make sure you get your PVC in deep enough, I am gonna say 24 inches minimum to hold up to the ice. I worry more about when the ice shifts, a warm up in the winter can thaw the edges of a pond and the wind during such a storm pushes/pulls the remaining ice pack producing severe lateral shear. Many of these Texas guys have no idea how much force ice develops, not their fault, just geography has never forced them to deal with it. I can assure you the first time you see what the ice can do, you will wonder if you have them deep enough, as I said, I would also considering angling them to the center of the dock to help counter all this. Just my country boy idea on the subject. I still have 6 inches of soild ice on my pond, walked across it yesterday and jumped up and down on it, thaw is coming tonight I hear.

Yeah, that is the dock that is still there. I was going to use it until I can drive 4 new piers on the corners and rebuild.

With the rebar being submerged, does he have to worry about rust? I know that they epoxy coat the rebar that's used in bridges. Or is that something that is highway dept. overkill?

Sounds like you have a plan, I think you will do alright Sean. I was just pulling your leg a little, I like that T-style dock. you could make lifting that sucker a breeze with a couple plastic drums if you have an air compressor handy. Sink them by filling them with water, slide 'em under your dock headers and tie them to it, then pump them full of air to drive out the water and they will raise your dock for you. Then you can adjust the height to what you want and anchor in place. I have lots of ideas, If you were just down the road I'd be there to help out too, keep us posted.

I missed your post while I was typing Esshup, I have always been told epoxy coated rebar was there to combat salt damage, which occurs even if you have them in concrete, and hastens a bridges demise. The rust causes the concrete to spall and crack away, and weakens the structure. Obviously a bridge replacement being quite costly they want to avoid this. I would think you would suffer some weakening on a pond dock pier the same way, but it would take 50 years? for them to get really bad and I doubt they would cause trouble even then, being contained in the PVC. Just my thoughts, however misguided or obscure. I wouldn't expect too much trouble from that.

I had a post a while back similar to what you are planning. We built some docks on large reserviors by pounding pvc into the bottom, setting a 4x4 inside, and then cementing them in. You don't need to drill out the dirt from the inside. Think hydraulics, there is nowhere for the dirt to go unless there is enough downward pressure to push the cement out the top. I am planning on building this type of dock when I get around to it.

Joe, my only fear is the Ice and heavy rains lifting the piers up. I get a lot of run-off in to this pond in the spring. We will get a 5" rain, and my 8" main drain pipe will be completely covered and water will be pouring out of my aux spillway. So, want the new dock to be high enough I don't have to worry about that. That was my big mistake on the first one. I wanted the dock close to the water so my kids didn't have to lean way down to get their fish out of the water. That really shouldn't of mattered. The kids just sling-shot them out of the water with their rods.

Jeff, by not auguring the mud out of the center of your pipes, have you had any problems with the ice heaving them up? How far did you get them in the ground? What did you use? A track-ho or a back-ho would be nice. I bet they could just push them in the ground.

Just some FYI...

I called the "pipe" store today. The pipe will run me $40 each. They come in 14' pieces. Each of them has a bell on one end. I may just cut that bell off.

The deep end of my new dock will only be 6' deep and the shallow end is maybe 5'. So, if by chance I can get these things in the ground 4', and I have the pipe out of the water a foot, the biggest piece I will need is 6+4+1= 11 foot.

I'm getting the itch...you guys are getting me pumped up out trying this. I am about a week or two away from help out the local economy, so if you have any last minute ideas, please let me know.

Thanks guys!