Soil questions

[reverseboB]

Last November my wife and I tore down a shed which was behind our garage. Not a surprise was the groundhog holes. Filling them has been hindered by occupants digging them out as fast as we could fill them. The surprise has been the discovery that the area was the storage area for the old coal burning water heater. So we have this area with a lot of coal in the dirt. This spring we intent to fill in the holes and grade the area and possibly plant a garden. The question is can we plant vegetables and safely eat them with the coal? Also, any suggestions on groundhog evictions? They have several dens in the neighborhood so they will stay around. I just don't want them digging near/under the garage. Part of me wants to light the coal on fire and drop into the holes and backfill.