OK so I'm finally undertaking my permanent dock project, after procrastinating for 3 years now. My old floating dock is in dire need of repair and after 10 years I've decided to just retire it and start over.

I'm building this in the water so I have some of the standard issues with support installation...I have an idea.

I have a plethora of 8" heavy duty PVC conduit sections, 20' long. I was thinking that I'd drive these into the pond bottom at appropriate distances, pump the water out of the pipe, use a pressure washer with an extension to blast the mud out of the bottom, then set some rebar in and pour concrete in the pipe. Voila, solid, permanent pillars for my dock. The pipe stays obviously.

Yes I know getting the concrete in the pipe is gonna be a challenge....but where I'm building the dock off of my levee I have power, and I was going to use a cement mixer and split one of the conduits in half for a funnel of sorts to the pillars.

Sounds like a ton of work right? I was going to test out the process on shore - I need 4 pillars on the bank before I get to the water's edge. If it just sucks too bad to accomplish when I'm on terra-firma then I'll scratch the idea and just go with 4" galvanized pipe driven into the pond bottom.

What do y'all think?

I like it. Couple of thoughts:

after getting the water and soil out, there will be a significant buoyancy force trying to pop the tube upward. Best be ready to fill it with concrete. Maybe not take all the soil out - especially if you get into something solid.

To attach your joists/beams, drill holes for 5/8" or bigger galvanized all-thread and put them in as you pour.

My pond filled before I got to the dock so I drained it. Amazingly while using an auger the clay was still bone dry about 8 inches down. Note the bolts I have attaching my beams to my power pole pillars. edit - guess they are hard to see. Buddy had access to used power poles and hardware

I built my dock last summer using 16 inch concrete forms and 4x6's with rebar as well. I used ready mix a bag at a time adding water and more mix all the way to the top. The paper cylinders will eventually decompose and disappear. I'm hoping the concrete doesn't crumble and disappear as well. It's pretty solid

Good luck

Probably a dumb idea but, why not cap the ends of the PVC pipes before you drive them into the pond bottom and keep the mud and water from entering the pipes? Then just fill them with concrete.

Haven't tried it but I assume that'd make them essentially impossible to drive. You're displacing too much clay with that method, or at least I'd guess so.

You are probably right. FWIW Years ago my dad built a dock using a backhoe to drive telephone poles but, IIRC, he sharpened the ends of the poles first.