Kind of similar to my situation of installing a water and power line. I take my trencher and trench 150ft of trench. I threw the underground wire in the ditch and started glueing up the conduit for the bigger wires. Got late and started raining. I give it up until the next day and wake up to 3 1/2 inches of snow, then temps down to 8f for a couple days. I go back to the trench and the sides had fluffed off and filled the ditch in. I couldnt retrench because of the wire in the bottom. I take a set of post hole diggers and clean the ditch out, except for about 5 feet right in the middle where a big rock had broken from the side walls and was to hard to break up with the post hole digger. Over nite it rained again and refilled with loose dirt. Another hand digging with the post hole diggers . Next day I go to Tractor supply and buy a 17lb wrecking bar to break up the rock. By just luck I had pulled the wire out of the ditch. I get back to break up the rock and the last half of the ditch had fell in again. This was getting old, but there was no longer wire in the ditch so I fired up the trencher and retrenched the ditch. Dirt was falling back in ditch as fast as I could trench, but I got thru the big rock. I hurried and cleaned out the rest of the ditch, again with post hole digger and hurried threw in the electric and water lines. Probably wait another month and wont be a speck of dirt fall in that ditch. I ended up trenching that ditch twice and re-digging three times with the post diggers.