No, there is no such thing as a “ground rule triple.” Ground rules shall not conflict with official playing rules (OBR 4.05), and ground rules may not supersede book rules (NFHS 4-1-2). A manager/coach may not propose any 3-base award as a ground rule, because balls that go out of play or become lodged are already covered by book rules (almost always 2 bases, though the time of enforcement varies by scenario). The only 3-base award in the rule book is touching a batted ball with detached equipment, which again isn’t a “ground rule” – it’s already in the rule book.
