A small catch basin at the lowest spot will take care of any surface water that can reach it. 5 gallon bucket with a 12 inch frame and grate. Allow about 10 inches from the bottom of the pipe to the bottom of the bucket and pipe it with solid pipe with grade to an area that can carry it away. Clay is clay does not perc. If you do put in a curtain or french drain make sure that the drainrock comes completly to the surface. Use perforated PVC pipe 4inch. You can put colored rocks at the surface and put small plants in pots for decoration