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3.0 DESIGN PARAMETERS <br />3.1 REGIONAL PARAMETERS <br />Geologic Setting--The proposed solution mine lies within the Piceance Basin in the <br />Parachute Creek member of the Green River formation. Figure 1 shows the site location and <br />Figure 2, the general strttigraphic column from core hole 26-88-1. The Green River formation <br />is overlain by the Uinta sandstones. <br />The horizon of interest to the proposed project is the Boies Bed, which averages 30 ft in <br />thickness and 80 to 85% crystalline nahcolite. The Boies Bed lies 320 ft below the rich oil shale <br />of the Mahogany Zone (R7), which is approximately 175 ft thick in this region. The Mahogany <br />Zone is generally an agtritard which separates the lower aquifer from the upper aquifer. The <br />Boies Bed is about 32 ft below the dissolution surface of the lower aquifer. The Boies Bed is <br />separated into the upper and lower sections by the OSMB. The OSMB consists of oil shale <br />honeycombed with nahcolite. The nahcolite content in the OSMB is approximately 50%. The <br />immediate roof of the Boies Bed is oil shale honeycombed with nahcolite with varying nah- <br />• colite/oil shale proportions. The "rubber beds" consist of up to three beds of highly deformable <br />oil shale layers each up to 1 ft thick. The zone containing the rubber beds can be up to 8 ft thick <br />~ in some holes. In 26-88-1, only a few inches of the rubber bed was identified, but could have <br />been the cause of one or more lost core zones. <br />Figure 3 shows an expanded view of Section 26 indicating the plant site, contours of the <br />thickness of the Boies Bed, and location of surface holes of interest The proposed cavity mining <br />will take place in the southeast half of the section below the transition zone. <br />Hydrologic Setting-Hydrologically, all materials below the dissolution surface are <br />essentially dry. Above the dissolution surface, the water is near fully saturated with sodium <br />bicarbonate with total dissolved solids above 20,000 ppm. The overlying strata are generally <br />divided into two aquifers known as the upperand lower aquifers, although many have identified <br />aquitards within these two aquifers. The Mahogany Zone separates the upperand lower aquifers. <br />The upper aquifer has reduced total dissolved solids but does not meet proposed Colorado <br />standards for drinking water nor irrigation water. The lower aquifer also does not meet either <br />standard. The water quality of the B-Groove is the lowest stratigraphic water protected by the <br />EPA. The R6 zone acu as an aquiclude separating the water from the B-Groove from the poorer <br />. quality water closer to t}te dissolution surface and in the RS zone. Figtue 4 shows the water <br />J. F. T. Agapito & Associates, Inc. 5 <br />