doesn't sound worth messin with - if it's 2 feet deep and you can only use half the depth ..... how will they "go deeper" when hot or cold?

Bill

I agree with Bill. In addition to what he said here are some more issues to consider.
- It will take almost a cubic yard of sand/gravel to fill the bin up to ground level. Can you get that for free? If not you are starting with a big expense for your "free" bin. Even if you can get material for free, how much work will it be to get that material to the bin and dumped into it?
- It would be better to use sand. With gravel, the first castings produced will drop down into the gravel and be unreachable. It will take awhile before the cracks fill up enough that the castings will remain on top. You could put some weed cloth over the gravel but you would have to figure on emptying out the bin about once a year to replace the weed cloth.
- How close can you park to the bin? If you have to move everything in or out with a wheelbarrow it will be a lot of work.
- How close do you live to the park where the bin is located? If it is not convenient to go there you might not be able to give the bin the attention it needs.
- What is the bin made of? If it is wood then the part below ground could be rotted away.

You might have good answers to these questions which makes this a good deal for you. Either way I wish you success with your worming.

Mike