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Page 30 6.0 CONCLUSIONS AND RECOMMENDATIONS The new mine plan utilizing submersible pumps and balancing of the in-cavern fluid pressures with the surrounding groundwater pressures relieves the requirement of maintaining structural integrity of the roof materials above the Boies Bed. If collapse of the overlying strata were to occur, flow would also be in balance. Solution mining of the nahcolite above the Boies Bed would be possible if the permit constraints of the Environmental Impact Statement were not violated. This report addresses the potential impact of high-extraction solution mining of the Boies Bed and overlying strata on the two controlling permit requirements: (1) to maintain the minability of the high-grade oil shale in the "Mahogany Zone" and (2) to protect the B-Groove aquifer from adverse impacts associated with solution mining operations. To assess the potential impacts of high extraction on the minability of the oil shale and aquifer protection, the available resource was reviewed, the shape and extent of potential cavities evaluated, and the cavity shape that would have the most impact on aquifer protection and min- ability of the "Mahogany Zone" evaluated. To assess the impact of solution mining on aquifer protection, the deformation, strains and changes in hydraulic conductivity in the aquitazd below I ' the B-Groove aquifer were evaluated. To assess the impact of solution mining on the minability of the oil shale in the "Mahogany Zone," examples of multi-seam mining involving caving with lower seam mining were evaluated and criteria established in the literature applied to the White River Nahcolite, Inc. case. High-extraction mining within panels sepazated by barrier pillars is recommended to control the potential caving above the mine panels and to minimize surface sub- sidence. Forty-percent extraction of the available nahcolite resource in and above the Boies Bed and below the dissolution surface within such panels is possible without adverse impact on the - ~ minability of the "Mahogany" oil shale or the B-Groove aquifer. Recovery of more than 40% nahcolite is possible without damage to the aquifer or oil shale minability, but the upper limit of the allowable or acceptable nahcolite extraction was not established in this study. Collapse of the overlying strata, bulking of the caved material, and deformation of the overlying strata including the R-6 aquitazd, the B-Groove aquifer and the "Mahogany Zone" were shown to be acceptable while preserving the integrity of the aquitazd and the aquifer, and the minability of the "Mahogany Zone." Agapito Associates, Inc.