pouring concrete pier for deck in disturbed soil
I am pouring piers for an exterior deck soon, but upon digging the holes, I realize/remember that close to the house the earth was dug out and back-filled for the basement. That was 3 years ago, but the earth is still really easy to dig through in some places. It is clay.
My questions are:
(1) is there a way to pack the bottom of the hole to help stabilize it? Fill it repeatedly with water? Beat on it with a 4x4?
(2) I'm thinking of pouring a footer to give some of the piers more stability. I know of a product Bigfoot, but it does not seem to be available in my area. Is it acceptable to make 2 pours, first a wide (16-20") spot at the bottom, then the pier (12") on a second pour? This article (click for link) makes it sound acceptable, if the junction is reinforced with rebar. (That way I could do the footers myself, then do all the piers at once with a truck delivery.)
Any other suggestions?