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My group of hunting buddies is planning to build a new blind two weeks from today. We have most of it planned, but we are stumped on the best way to set 4"x4"x12' pilings that it will be built on. We are dealing with a slough that cannot be drained and has about a foot of water in it. There is also about a foot of loose silt that you sink into when you walk and most likely another foot of semi-loose silt before hitting a solid clay pan (guessing 3' from water surface to hard clay).

I have used all sorts of post hole diggers for building blinds on dry ground but thats not an option here. We are looking into using a 2" trash pump necked down to "jet" the posts into the ground. None of us have done this before, so my question is, how solid are jetted pilings when setting them into a silty clay slough bottom and how far will we have to send them down to be sturdy? Blind planned is 6x24 on 10 4x4 posts to give an idea of the weight we are going to have on them.

Sorry for the long (and first ever) post. Any suggestions greatly appreciated.

jetting is usually used as a method to set piling/post in sands. It provides support for the point or tip of the piling.
In that slop you are wanting to support the piles...........friction is the key.
Chainsaw a point on each of the 4x4's and drive them. Get you a huge post holes driver ( i use to use one 6" diameter that weighed 85#), drive till you cant drive anymore or you start busting the top of the piling.

How high above ground does the platform need to be? Instead of trying to use the full length of the 12 ft post, figure out you maximum deck height and just frame up the floor like you would a house instead of using the 12ft lengths as vertical walls, then you dont have to worry about getting piles perfectly aligned. Depending on how much piling you have above the waterline, cross bracing will go a long way toward stability incase a few pilings aren't quiet as deep as you would want.
Nothing about it will be fun so have plenty of help.

If you don't have a good post driver, you can use a sledgehammer standing on the back of a 4wheeler or the roof of a ranger to start. I've don't it both ways, driver is much easier but neither are very fun. I don't think the jet method is gonna be stable enough to start.

No experience in using jetting on a blind, but my neighbor on Guntersville Lake rebuilt his dock using 4X6 posts and set them with a jet. It held up in a very high water situation last December when the water went over our docks. The trick is making the nozzle long enough to get down to the bottom below the silt, I would think.

How high will the water be? Would a floating blind be an option?

A floating blind is definitely an option. Could actually be better so that it could be moved if needed and this is a lease, so we could take it with us if that were necessary. The problem I have found with a floating blind is that it is much more expensive. What do y'all use as floats? I've seen plastic drums used but rarely used well. I'm also looking at a 12"x2'x3' dock float for $80. But that only has a 327# buoyancy so I would need several and would be cost-prohibitive.

We have 8 guys in this lease. The goal is to build a blind that can hold all 8 of us with comfort which to us means 24 feet long x 6 feet wide. I'm concerned about the stability for that size and keeping it from falling apart (flexing would be the major concern in a floating setup). The water level in this slough will not get over 1.5 feet and is held in by beaver dams so it is definitely not necessary to have a floater.

The weather is not looking good for this weekend and if its wet you can't get a truck back there through the gumbo. So I may have more time to do this planning.

My most recent idea was getting 3" galvanized metal alloy poles like are used as corner posts for big chain link fences. I have a 3" pile driver and I know those will sink in the mud easily. I could then either drill into them or use bolt-on collars to attach base boards to them. Cross-bracing may be necessary but tension bracing with 1/8 inch cable would be very easy with this setup.

From your first post you say total of 3 feet before you stop sinking. And you are hunting a slough which I would imagine has trees throughout it. Why not just everybody grab a tree or stand in the buck brush, hang your stuff on limbs and kill ducks. Much less work, produce same results, and you "might" even feel a little more manly about it at the end of the day.

Large blocks of EPS foam is what I have seen used or black marine block which would be more expensive.

I think we ruined a duck hole once by building a big booty blind in there. Prior to that, we stood beside trees & killed piles of them. Built the blind that summer & had very few good hunts the following year. Coincidence? maybe. We lost the lease the next year so never had a chance to figure it out. Granted, the blind was more convenient than hugging a tree, but I’ll take success over comfort any day of the week.

Bolt you a 6-8' piece of 3" angle iron on the bottom of each post hanging 3-4' below them and beat each post down as far as you can. My Uncle did this on a blind with a sandy bottom and it stood for almost 30 years. You should only need one piece of angle iron per post.
Barq's

I would drive them in as far as possible but really just enough to keep them in place then take plastic 55 gallon drums with 4 x 4 hole in the bottom and slide over the post and fill with quikrete. Should be more than sturdy enough. If you did that with the angle iron method you'd be more than good to go.

the doc

Thanks for help and ideas. And for some of the less useful information as well. We have a 2.5 mile drive in on buckshot roads and got rained out Saturday and Sunday. I had to carry a large trailer back there so couldn't make it in the truck. Weather is looking better and we will try again on Labor Day if it stays dry. For those of you wondering how we decided to do this, we have built two 6x12 bases that we can carry into this slough and can bolt together once in place. I have 10 2.5" diameter steel poles that we can drive into the ground with a pile driver. The frames will be bolted onto these steel posts with u-bolts made for attaching leaf springs to axles. We plan to do something much like Barq's idea by driving treated 2x4s into the mud with a cross brace to help keep the posts from sinking over time and keep everything level.

To the guys who think this blind is a terrible idea, I can agree with the sentiment and think hunting without them whenever possible is much more fun and effective. That is not the case with this location. The largest trees we have are 6" diameter willow trees and are pretty sparse. We have hunted standing in them for the past two years and just can't get hidden enough for big ducks to finish. This slough gets a lot of drift from aerial application from rice herbicides so it is pretty wide open.

Hopefully after next weekend we will be done with it and just have lots of brushing to do. I'll take some pictures for those of you who are interested in seeing how it pans out.