I'm looking for the best options to set either 4x4 or 4x6 pressure treated posts in a very small pond in the north Ga mountains. Dock will be approx. 10'x10' with a short 4' wide x 4' long walk way. Water depth for deep posts is about 4'-5' and shallow post 1'-2'.
The ground here has a lot of rock and clay in it so I don't think jetting would be a good option but I might consider a test hole if any of you have been successful in similar type of ground.
Its possible to take the water level down maybe 2 feet but I'll still be working in ~3' of water. Can't get any heavy equipment in drive posts but I'm not opposed to working a sledge hammer on a makeshift temporary platform if this will get them deep enough to be stable and not sink over time. I have also seen these post collars that can be attached to set on the bottom to help minimize or eliminate settling over time. Would the driven end of the post need to be taken down to a point or at least partially necked down or does this increase the likelihood of sinking over time?
Are there any other practical options that I should consider? I did see in the archives here some discussion about using buckets or tubs filled with concrete to spread the post loads but I'd be concerned about settling and sliding over time and the posts nearest the shoreline will be on a sloped bank so I'm not real comfortable with that option.
Bruce, I kicked around exactly how to do this at my place. I gave up on the treated posts and decided to set galvanized. My dock is 4' x 24' so not the width you have. I put a ladder in the water and sledged the heck out of them. I bet they went 2' into clay/much if not more. I belled out the tops of the posts pretty bad, but easily clean cut them off with a pipe cutter when the project was done. I bet you can space posts inside of your 10x10 frame and have them not protrude the decking. I'm very happy with the stability of the dock.
I would have rather had treated posts so hopefully someone has some ideas. Another dock I build years ago was done when I completely drained the pond so we had some really nice footers, forming tubes, and the 6x6 posts. That baby was solid.
Have you considered a floating dock. I read on hear were they made a dock that had a ramp on both sides to the bank of a 10 by 20 foot platform.You then could dig post hole and fill with concrete on dry ground to anchor the ramps. The 2 ramps made it stable in the wind and also let it go up and down with the water. Make sure the ramps would be attached at the same level or they would bind up and not go up and down very well. In Between the ramps you could net off for small kids to swim or to raise small fry to a larger size to put in your pond. I would of did my dock that way if I would have known about it.
I appreciate the inputs on a floating dock and I did consider going that rout but still prefer the stability of having it fixed in place. This is a very small pond that does not have any fluctuation of water level so it lends itself to something stationary.
The design I’m planning to use will only require 4 posts to be set in the water then double 2x10 beams to support the joists. The walkway will be anchored to posts I can set on the back.
As of now I’m leaning toward just partially tapering the posts and driving them as far as they go with a sledge hammer. Once set, then sliding a custom made steel collar (my son is a welder) down and pound it into the bottom to sit tight before bolting it to the post maybe with a couple of 2x4s on the sides of the post or steel ears coming up off the collar. I can then finish with cross bracing to stiffen everything up. This plan just means I’ll need to get wet to run a few lag bolts into the posts near the bottom.
Another option to avoid getting wet is estimate how far I can drive each post, bolt the steel plate and the cross brace lower bolt in place then drive the post.
Has anyone done something like this successfully or am I setting up for failure?
We had the dam on my new pond 99% done when a 6" rain nearly filled it overnight - before I got my dock piers in. I drained about 8' out of the 1.6 acre lake over a month to get the dock built. I used treated utility powerline poles set in holes dug by PTO auger. Interestingly, the top ~6" of clay was wet, but dry below that! I drove spikes into the sides of the poles near the bottom, then poured a "plug" of concrete in the bottom to engage the spikes - mainly to help resist any liftup.
So I would look seriously at lowering your pond, and also build a bigger dock than you think you need! They shrink fast with tables/chairs/coolers/tackle boxes/kids, etc.
Floating dock pinned with mud poles. It's been there almost a year with just three of them on the floating section and it's only recently started to get wiggly. If I'd put them all in instead of being lazy there would be zero wiggle. Maybe next week...
Another vote for the floating dock staying with the water height. Not a fan of the poles.
Pictures attached are the pier in my pond, the water can vary more than 18", dock stays with it.
It's anchored by one rod into the cement pad at the shore, and a set of two anchors under the floating section. The floating anchor sets are, one very heavy anchor at the bottom, and a second lighter weight keeping the cable tight, though a set of pulleys under the pier.
We built a "quickie" fixed dock a number of years ago by using an excavator to reach out and push the poles down while someone in a boat held them. It lasted about 12 years until ice/floods eventually worked a couple of poles out and it was ruined.