clay trench for dry pond

[petda]

Is a clay trench (a.k.a clay key-in, clay cut off) necessary for a dry pond?

 

[LHA]

It usually is in PA, USA - because local ordinances usually require it. But I have never been able to figure out why. Most dry ponds are 6 feet deep or less and drain within 24 hours of being filled. I don't know when or why piping is supposed to occur, but apparently someone thinks it will.

Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve