do you have any pictures of this in use? do I understand this correct, when trenching across a lawn you fill the trays then use them to backfill?
edit: never mind I just read down farther and saw where you explain it.
I looked, but I'm a failure at taking pictures. The whole assembly involves a 275 gallon oval tank cut in half. Each corner of the cut edge gets a short chain welded to it, as does the bottom center at each end.
To empty, set it beside the ditch, unhitch two of four chain hooks. lift slowly to dump. It won't all dump out, so I set it down & move the two hooks to the bottom chains. A 46" deep ditch is perhaps three feet wide at sod level. If I can limit my lawn repair & raking to a 3' wide strip, it saves a lot of raking, seeding, and mulching.