Small amounts of gravel can go in your garbage can - be sure not to exceed weight limits. Use in your landscape or give to neighbors - stacks of rocks provide homes for beneficial insects.
Otherwise, dispose of as garbage at your local landfill.
You may also contact a local bulk or containerized waste removal company found it the Yellow Pages under the heading rubbish removal. Mars Environmental is one of those companies that may service your area.
Reusing an item is always one of the best options when considering disposal of an item.
This item may be disposed at curbside in your regular waste collection program.
This item may be disposed at a garbage drop off location such as a landfill or transfer station.