Abstract: A highwall mining borehole backfill composition utilizing waste glass and fly ash can be used as a backfill utilizing waste products that would normally have to be landfilled. The composition is a cost effective mixture of cement, fly ash, glass and water and may incorporate additional fine and coarse aggregates as well as chemical admixtures. Fly ash takes the place of some or all of the fine aggregate, and cullet takes the place of coarse aggregate in a mixture of concrete. Use of the backfill supports the overlying strata so as to eliminate or reduce the need for barrier pillars.