"Tom G" wrote in message
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"mmc" wrote in message
g.com...

"Dan Listermann" wrote in message
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I want to build two docks, one permanent and a floating one. The
floating one will be supported by 15 gallon plastic drums. I can get 55
gallon, but for a 4 x 8 dock, I worry about center of gravity issues.

The permanent one will be built of 55 gallon drums filled with dirt.
Any issues to look out for?

The 55 gallon drums filled with dirt may float because of the air trapped
in the dirt. If soaked after positioning and filling, they still won't
weigh much. Concrete blocks are something like 30-40% thier (in air)
weight when submerged.
You can "jet" pilings in with a trash pump. Last time I rented one was a
couple years ago and it cost me $25/day. In a day you can jet around a
bazillion pilings. Four of us non-professional jetted in 40 pilings in a
couple of hours.
I use an old pontoon platform for my dock but I'm interested in the
details of how you "jet" a piling in and exactly what a "trash pump" is.
I have need to put in a permanent short pier at the edge of the bank to
support the land side of my ramps to the dock. I had piers supported by 2
inch pipes driven into the shore bottom but last years flood lifted the
pier and the pipes right out of the ground and bent everything to hell. I
figure 4 inch well pipe would hold up but the only contractor on the river
with the equipment capable of driving them is apparently not interested in
any new business. I tried for 3 years to get him to give me a quote on
some rip rap or vinyl wall (his advertised business) but he doesn't seem
interested. I had $26,000 in my budget but I didn't really want to tell
him that up front.

Tom G.

Tom,
Check this link:
http://www.wikihow.com/Install-Posts...a-Dock-or-Pier
Good description and saved me the time of writing it.
The dock work I've helped with has been in Florida's Indian River with sand
bottom. I don't know how well this will work in other environments.
We used a rule of thumb of 1/3 the piling length and a minimum of 4 feet
buried. One of the docks I helped with got destroyed by a big storm fetch,
but the pilings were still standing.
The rental places here have pumps set up just for this with the pipe already
set up and pinched. All we did was plunge the pipe length (6') (1-3" water
depth) all the way down a couple of times, then stand the piling up and let
it sink in the hole. One guy holds it plumb while the other jets around it a
little, guy one keeps holding it plumb for a few minutes until the sand
settles. Doesn't take long.