We have installed hundreds and hundreds of geothermal systems in the east Tennessee region and have never run into a cave/void during horizontal trenching. On a current project we have hit a rough 8 feet deep 8 foot wide void with two small shafts running off to the side. Has anyone every run into a void like this? If so how did you fill the area? Our operator backfilled with clay, but the homeowner is concerning he should have bridged the two side shafts to prevent leakage down those shafts. Any and all thoughts and comments are greatly appreciated. Thanks.