I had a vertical system installed 10 years ago. The drillers unfortunately were inexperienced and abandoned 4 wells in my yard. Two of the wells seemed to have been adequately plugged but unfortunately two areas every spring seem to develop sinkholes. So unfortunately I don't think they were adequately filled with the bentonite. Does anyone have suggestions on how I find and cap the unfilled holes as I don't want to have to do this every spring for eternity?