I was wondering if anyone would know how to get rid of the smell and the garbage disposal matter that has built up to about one inch above the gravel and is about 4 inch's under the rock I was wondering if there is something to put on this that could help eat away the this stuff as it is making my house smell. Thanks

Are you saying this sink drain goes outside into or on gravel?/ I think I may be missing something here. Please describe further.

The first thing you must do is repair the broken drain line. The get some guick lime and spread it over the saturated ground. Good luck, Tom