The target for the project has been shifted from filling, highwall mine adits to filling auger holes with FGD material to provide a stable highwall for automated highwall mining. As reported previously, this shift in emphasis is economically desirable and practical, as the filling operation is safer and permits access to locked in high quality coal behind existing auger holes. As also reported previously, the fill material was shifted from dry FGD materials to a Fluidized Bed Combustion fly ash from the Archer Daniel Midland No. 6 facility in Illinois. Previous reports have summarized the characterization of this material for the project. However, due mostly to economic concerns with prehydration and transport of the Archer Daniel Midland (ADM6) material, several new desulfurization by-products stored at the Costain facility in Allen, Kentucky were considered during, this quarter. At this stage of the project, the change in fill material required rapid assessment in much the same way an applied working project would demand quick evaluation. This change thus provided an opportunity to demonstrate a rapid assessment of material suitability. The results described below were obtained in a short time frame, and with the exception of characterizing the long term swell and durability of the products, the rapid assessment was a success. No rapid assessment methodology for long term behavior has been developed at this time. The mineralogical characteristics of the two Costain materials will not be summarized in detail here. Unlike the ADM6 ash, the spray dryer and FBC materials currently under review do not include the large percentages of free lime (CaO) that was shown to cause high mixing temperatures in the nonprehydrated ADM6 product. This absence of free lime in the raw by-products is immediately evident when mixing with water, as no significant heating of the mixture is observed.