There is a reputable pond excavator right down the road from me. He moved in about 2 years after my pond was dug. (The irony of my leaky pond hurts) His specialty is wetland restoration so he is familiar with working with some wet soils. However, he doesn't appear to advertise at all, but he owns his own equipment. I will knock on his door when I get a chance, though you may be far from him.