A water table pond will fluctuate with the level of the water in the ground. (I have one and all it's disadvantages - mine is about 4 1/2' low right now)

If you cannot find clay to line the whole pond basin with, you will be at the mercy of the groundwater level. A liner would work, but there's more to just digging it out and laying a liner over it....

As you found out, there are guys that can move dirt, but finding a good experienced pond builder is difficult. Maybe Bill Cody knows someone that you could call for another estimate.

If it was mine, I would taper the banks at a minimum of 3:1, 4:1-5:1 would be even better because you will have to walk down the banks to get to the water when the water is low.

If you don't change the current outflow device (if there's a huge rain event, where does the water go once it is full?) you shouldn't have to worry about flooding anybody downstream.

If you don't dig it any deeper, it might go dry again this year if it's a dry year. In any case, I'd stock Fathead Minnows (FHM)in it, just a pound or so. They will eat the mosquitoe larvae and help with the West Nile problem.

To keep fish in it all yar round, you should plan on having 12' of water in it to allow the fish to overwinter. That is 12' from low pool, not the top of the bank. A client had ponds dug 12' deep, but the contractor only dug down about 8' and piled up dirt 3'-4' around the ponds. So, during the wnter, there is only 4'-5' of water in the ponds. If he didn't have an electric aeration system in the ponds, he would have lost all the fish due to winterkill. I think he dodged a bullet this winter due to the aeration and the mild winter.

Dave is right on the money about the water quality issues.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).