About one year ago, I found my lab digging furiously in my backyard. After inspecting the hole, I found that he was digging by the septic tank and that the ground underneath was gone. I bought about 5 bags of dirt and filled in the hole. I just assumed that because my sprinkler system had been broken, that the clayish dirt had shrunk and it was no big deal. I now have the sprinkler system repaired. However, last week I found my lab had dug another small hole on the side of my home. I got the shovel and was prepared to cover the hole up until I got closer and realized that the hole went down very deep. Probably about 3 feet. I went and got a flash light and could see that he had just uncover a sink hole. There was standing water in the ground and it smelled like sulphur. From what I have read, this must be the leach field? My boys have been home from college this month and have been showering, washing clothes and I have been running the dishwasher more than normal. I have been told to fill the hole with pea gravel and then dirt. Should I be looking for broken pipe, or is it normal for water to seep into the ground from the septic system? I don't have any backup in the house and there is no smell coming from the pipes inside. I don't use my disposal and I rarely use bleach. But there has been alot of water usage this month. Any ideas or suggestions would be greatly appreciated. Right now I have the fence closed off to the BIG HOLE. I would say it is 3 feet deep and about four foot across both ways. It's not a small hole. My guess is that my dog was digging because of the smell. I was shocked when I saw the hole! HELP!