Inspector
Nyuck, Nyuck, Nyuck!
Duh! Just occurred to me that you could get some pressure treated wood, 4x2 and 2x6 or treated plywood and build a box around it with screws and construction adhesive. Radius both ends so there are no sharp edges. Make the U shape, put it in the trench and put the "lid" on it. Appropriate for woodworkers me thinks.
Pete
Pete