Buy Woodland Scenics Medium Buff Ballast & Coal Ground Cover at Michaels. com. This lightweight and easy to use ground cover can be mixed to create realistic effects for a variety of creative projects. This lightweight and easy to use ground cover can be mixed to create realistic effects for a variety of creative projects. Ideal for holding railroad ties in place and modeling gravel roads, groundcover is a necessary foundation for any model landscape. Details: Buff 21.6 cu. in. Colorfast Realistic Easy to use Ages 14 and up | Woodland Scenics Medium Buff Ballast & Coal Ground Cover | Michaels.