my parents had an underground leak (not heating related). the household insurance policy covered the finding of the leak and remedial repairs, but not the cost of fixing the leak itself. I know that this is commercial, but there may be some insurance in place that may help. the insurance co brought in a leak detection specialist, which ironically didn't find it, the plumber did who said "I bet that the supply comes in through there and that's where the leak will be". he was correct!