Pond Boss Forums GENERAL QUESTIONS Property Projects & Construction Options for 6x6 dock posts

I am build a small dock. I decided to fix it rather than float it. I also am using 6x6 support posts instead of 4x4. The deck itself will be 8x12.

Here's my question, the pond bottom is muddy, likely a little clay under the muck. I am thinking I can dig down 1-2'in the pond for the support post, probably not more since I am working in 2' of water with just a post hole digger!

I was going to dig down 1-2', set the post and concrete it. They have concrete that will dry in water, but I have since been told all concete will set in water, just takes a little longer.

While looking for options I saw these pre-formed concrete supports (see the picture). Has anybody used them? Do they work, will they sink in the muck (they do have a wide base)?
Concrete Support

I am also thinking about digging down 6-12' and setting the pre-formed concrete support in that.

Thanks, and I am open for idea how to set these 6x6 posts! I know a 4x4 can be sledged hammered in some, but a 6x6 would be a challege!

Thanks in advance again!

Depending on how much mud you have before you get to firm clay, you might be able to put the posts on the bottom without doing any digging. I have built several piers in water up to 5 ft deep without setting the posts. I usually nail a 5 gallon bucket onto the bottom of the post and fill with rocks to help the post to stand up. The weight of the post, bucket of rocks, and framing lumber will cause the post to settle in the mud and the bucket will give you something to get a grip on to move the post around to get it set properly. That method has always worked well for me.

I did use those supports. They will "float" on clay and travel, so you will need to pin them to the substrate somehow.

What I did is dug a 1' hole where I was going to place these holders, pounded in 3' long masonry spikes so only 6-8 inches was remaining, then ran masonry wire between the holes of the spikes. Then I filled the hole just to the top of the spikes with concrete, then set the pre-formed post holders with pre-attached metal brackets for holding the 4x4s to the block. I forget what the brackets are called, but they are basic U-shaped brackets for decks with stainless masonry anchors in the block to hold it in place. Maybe overkill, but I was putting these on the slope of the dam which was full of stone and clay and had not settled yet.

I was able to see them two days ago as my clarity was excellent and they have shifted a bit as things settled under water. I am anticipating building up the dock soon as we are supposed to get unusually warm weather and I am doing to jump in with a wet suit and have at it!

I wanted something a bit more secure since I am expecting to install a small diving board, and I don't want my dam scooting around the pond.

Best way to set 6x6 is with a trackhoe bucket., beat it into the ground..

I used these post to build my dock. I did build it before I filed my pond. We leveled each one and I used rebar so they would not move around. I hammered the rebar in front and behind and the dock is as stable as all get out. They work great.