I am in the process of building a 1 1/2 acre pond and for about $6000 I can line it with hauled in clay or I could use a plastic liner which would cost much less. I would appreciate input from others pro and con -- please.

The first consideration is whether you really need to line it. Is local soil leaky? Next, liners can be punctured by wildlife, cattle, just about everything. They are tough but certainly not bulletproof. One big consideration to me is that alkilinity comes from the soil. Liners prevent that. If you can go with clay, I'd do it.

a synthetic liner of good durability is going to cost a considerable amount more for a 1.5 acre pond
Robert B