My stalls are a little over 7 yearsd old. They were originally just dirt and are cleaned well daily but over the years a few of the stalls have been dug away to the point where there are large dips in the middle of the stall where all the urine and moisture gather. Its getting worse the more it goes on. I need to fill in these dips and level my stalls but I have no access to a bobcat or large machinary. I was wondering what are some good ideas for materials just as gravel, sand or dirt, or procedures to get my stalls level again?