SINK HOLE ! Why and How to fix ??

[SCAPEASAURUSREX]

A friend of mine called me this afternoon and asked me to come and look at this hole in his back yard.. I go there and there is a serious hole...... I mean the part that collapsed is 3' deep and about 2' wide and then goes under about three quarters of the way around that 2' hole and I put a tape measure in there and got it in 7 feet in all directions, down and across... ughhhh..
In talking with his dad , he said it was all forest area 30 years ago when they built this house.. So I would suspect that lots of trees and stumps were buried and rotted and now there is a cavern down there.. Or could I be looking for another cause as well ???? And now What do I do to repair this situation safly and thouroghly ??? Should I just jam stuff down there or excavate the area and then fill once I get the hole open ?? I read another post that said to start filling with sand and then fill ???? I have no experience with this type of situation and want to get it corrected the right way , so no future problems arise.... WHAT DO I DO ??????????? Help.......

[CT18fireman]

I would start excavating far back where the digging is safe. Then fill and work in towards the original hole. You will probably end up using a lot of fill to do the job right. Once you have the area totally cleared then it is just a matter of filling the hole and topping with topsoil.

[KenH]

Make sure it is from rotten debris and not running water (spring.) We did a sinkhole from a spring which involved perf pipe and stone to move water through the hole as opposed to having the water wash the hole out.
If its from debris, do as the others said and excavate and fill. No sand/stone needed.

[little green guy]

We just did a sink hole simular to your about two weeks ago exept it was in a driveway. We dug it out with a backhoe, it was all rutted stumps from about 20 years ago. We ended up having to dig a hole 35' long x 12' wide x 10' deep. Then we filled it with 125 tons of qp, compacting it every 1-1.5' with a 6 ton bomag vibe roller. Where gonna let it settle for a little while before we repave it. If it's just an area thats part of a yard i'm sure it's not nesseary to use 125 tons of qp, we did because it was under a driveway.