Before I continue, allow me to throw out some specifications and logistics.
The pondsite is at the end of a 2000 ft entry drive that was blazed last year. The last leg of this entry is about 200 ft, straight, and into the east end of the pond at a gradual slope. We knew right away that it would serve well as a boat launch. The launch will be 72' long, 12' wide, and about 6 - 7" thick. At the end of the launch, the normal pool water depth will be 5 feet. The launch is reinforced with #3 epoxy coated rebar (3/8" dia) set at 12" on-center, each way. They are set on bar chairs to elevate them. Rebar is too thick and heavy to reach into the concrete, during the pour, and just pull up from flat on the ground, like wire mesh. We are pouring the launch in sections, the first two will be 31' long. This was selected because we are using 16' long lumber for the forms AND the sides are really not accessible for a concrete truck so the pour must be done from the end. The chutes on the trucks only reach out about 20 feet or so. We used 2 x 6 for the forms. The form at the top of the pour (where the next pour will attach and continue) is drilled out with 2" dia holes at 12" o.c. and 3/4" x 18" epoxy coated dowels are laid in half way into the form zone. They will harden within the concrete, and the larger dia 2" holes should allow us to still remove the 2 x 6 form. These dowels will tie the next pour to the previous.
The round concrete piers are drilled with a 12" dia bit. They all average 48" long from the base of the hole to the top of the tube. The holes within the water are not as deep within the soil since frost heave should not be a problem there. They are, tho, drilled thru the topsoil and into the clay below for a firm bearing surface. Each hole is reinforced with a cage of epoxy coated rebar that is 4 verticals with 4 square ties of #3 rebar. The cages were pre-fab'd in the cool of the basement and the the vertical members were manufactured long. I trimmed these vertical members to length, on site, to be 8" longer the actual depth of each hole as we drilled them. This was done because the hole depths did vary somewhat. Then, each cage was set within the tube/hole and pounded with a 3# sledge until the entire cage was about 2" below the top of the tube. This centralized and stabilized the cage for the concrete pour.