Looking closer I do think you are correct.

I have personally had 2 different 4 post lifts, and have been involved with install of quite a few more on various GC projects we have done over a 20 yr period, and all have had some piling movement. It is the nature of the beast, especially with your water depth, as installer told. If they were jetted, movement might dissipate a bit, as backfill around pilings sets/packs up over time. If they were straight up driven, then probably not so much.

Sure looks like more wobble than I'd be comfortable with. With your water depth there is quite a bit of unsupported piling above where the piling is driven in so 20 something feet of freestanding unsupported piling is going to move around. I'd think that front to back X bracing between the pilings on either side of the lift would help stabilize things in the bow to stern direction. Some batter pilings driven at an angle on the outside of the right side section and fastened towards the top would stabilize that portion in the side to side direction. Connecting the left side into the existing dock would stabilize that side. Batter pilings are used regularly in marine construction to reinforce free standing pilings so if your guys can drive pilings they should be able to do that I'd think?

It looks like the bridge dock, stairs and upper deck are fixed and the lower horseshoe shaped dock is a floater, so it can't be attached.

crossbracing will stiffen the pilings but with the weight of the boat it wouldn't be surprising if they settled deeper and the the thing goes all leaning tower.

aggravating for sure, even the best contractors make mistakes. There has to be a formula for piling depth depending on the river bed material/piling material & dimension requirements/water depth and load. Maybe 30 foot 10x10 or whatever size they are is at the max end of that formula for the material used. Either way, hope it gets resolved.

Utility poles are in the ground 10% of their height plus 2ft. So a 30ft pole would be installed 5ft. That is on dry, stable ground. In a swamp area, deeper.

I work with a guy that had a dock building business with his father for many years. I'll reach out to him on Monday and ask him.

My dock contractor in west Florida/Panhandle said 8' (subterranean) is the code for pilings...I had mine done 10'.

We have a 450 Nor-tech sitting on a 8-post 32k lb lift here in Cape Coral, it does exactly the same thing. It Does it with the boat on it or off of it. Remember its like a flag pole, that's a lot stick sticking out of the ground and water is not solid. In a previous chapter of my life I set a lot of telephone poles and they have movement at the top if you move them by hand(standing in a bucket truck). I had the exact same questions for the lift contractor down here in the Cape. Nice Dock!!!!

I just measured and the lift posts are 8X8 inch which is the same as our dock posts. Lot of mixed reactions on this thread, I think I'm going to have a different dock builder/lift installer come out next week and offer a second opinion and to see if there's a fix for this situation.

This new lift can't be mounted to the dock because our walkways are floating, but the main dock structure is on fixed poles.

Was the original piling & lift installer a licensed/bonded company with a good local reputation?
Can you visit another (more mature) site/lift the installer has done to compare?

This is a good suggestion that I was thinking about. Might have to hop on the PWC and see if I can find similar lifts in the area. Then hope I don’t freak out the homeowners by pushing on their lift pilings, lol.