Minimum depth of a grave

Hi,

The minimum depth of a grave is such that there will be three tefach (10.8 inches, per Rav Moshe Feinstein's measure of a tefach) of dirt atop the casket.

(Rav Moshe Feinstein, Igrot Moshe Yoreh Deah 1:233)

המצפה לישועה,
Mordechai