The contractor installed the pipe system. The
price was around $1000 and included 240' IPS
200 psi pipe and fittings. The overflows are
a foot above the permanent water level and a
couple of feet below the dam crest. They are bermed out from the dam ends about 150' to direct water away from the back of the dam. The earthen
spillway system alone would probably be adequate
if the pond was not on a creek with 165 acres of
watershed (according to the NRCS estimate). The
pond will extend about 1600' from the dam to the upper end, but will be contained mostly within
the creek area due to a county road constraint.
I'm guessing less than 5 acres of total surface.