if your moving your boiler like Rob suggested , dont worry about it . If your leaving alone then you need to dig the thing up , This time make sure there is a place for water to drain from the ditch. It kinda looks like there is a little bit of grade to the side of the trench, dig a few laterals off the ditch to daylight . Next figure out what you want for pipe and insulation . Finally , fill the trench to 6" over the pipe with #2 washed stone(round golfball size) not sand or dirt. the stone will have air pockets which will keep the ground from stealing your heat. Wet sand or earth around your pipe is'nt any better than water. no water, no worries
Im shure it hurts but, you'll just have to burn coal a little longer to offset the cost. And if your gonna use a conduit it needs to be watertight till your above grade and Id still use the stone for fill.