I�m in Douglass, so pretty close to you. You won�t have to worry much about shrink/swell clay in Rusk County. We have enough East TX sand mixed in to keep it from drying out and leaving a gapping crack.

Main thing to worry about is adequate emergency spillway width, and do something to carry the spring water so it isn�t going over your emergency spillway constantly. I�m convinced that continuous low-flows over a spillway can be just as dangerous as sporadic high flows. I would advise you to install a pipe to carry the continuous low flows, and keep them off your spillway.