Footings issue

Okay, just broke ground on a 8x16' coop today since we have several days of warm weather expected here. I have ground-contact 4x4s that I was going to cut in 4' lengths. I'm digging the holes for them now: 2'4" deep, 12" diameter. Frost line is supposed to be 18-20" in this area. Will fill with 4" of gravel, place post, and fill with concrete, leaving me 2" of post above ground to build the coop on.

Here's the problem: two of the six holes that I've dug so far have hit water at 20-24" down. I hit basically large natural gravel if I dig further. One of these water holes is on a corner.

So, how would you approach? Would you set the post and just use gravel packed around it? Would you throw some gravel into the hole until the waterline disappears, then set post a bit less buried than you were planning (making the post shorter to compensate) and fill with concrete? Would you throw a bag of concrete into the water and set the post on top of that? Would you go ahead and set the post as you originally planned?

If this was a fence, I wouldn't worry so much. Instead it's a significantly large coop that I designed so I can add onto it later, so I wanted to build it pretty stable this go-round!

I have a large coop as well. I did not want it raised so I used the blocks that Home Depot and others sell and built the base on that.
I just could not see myself going under such a large structure to fetch a hidden clutch of eggs or a chicken in need of aid.

This is my coop.



http://www.homedepot.com/p/8-in-x-8-in-x-8-in-Concrete-Deck-Block-55N1AN/206125490

This link takes you to the kind of blocks we used. They are under the corners and everywhere else I could put them.

It sounds like this may be a better option since you have a high water table.