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AmerAlia, Inc. <br />Experimental Pilot Project <br />SUBSIDENCE MONITORING PLAN <br />August 23, 1999 DRAFT <br />RECEIVED <br />AUG 2 3 1999 <br />Division of Minerals & Geology <br />1.0 Introduction <br />All solution mining for the AmerAlia Rock School Lease Project will occur well below <br />the Dissolution Surface where no aquifers exist. <br />The following description of the local strata is based on measurements taken from core <br />hole RS 96 -20 -1 located near the proposed production well field. At this location, the <br />deepest expected EPA protected drinking water aquifer (USDW) is the B- Groove aquifer <br />at a depth below surface of about 1400 feet. The depth to the dissolution surface is about <br />1700 feet, (300 feet below the B- Groove). The depth to the bottom of the lower salt <br />(NaC1) bed is 2025 feet. The depth to the top of proposed cavity is 2075 feet below <br />surface (50 feet below the lower salt, 375 feet below the dissolution surface, 675 feet <br />below the B- Groove aquifer). Each production well will be cased to the proposed top of <br />the mining cavity. Solution mining and vertical cavity development is anticipated to <br />extend upward into the cased portion of the wellbore near or just into the lower salt zone. <br />This subsidence - monitoring plan includes roof stability; subsurface and surface vertical <br />ground movement; cavity size, shape, and filling; and pillar shape and stability. <br />Subsidence will be monitored as needed to verify the protection of drinking water <br />aquifers and oil shale minability and to develop improved abilities to predict subsidence <br />and subsidence ramifications. <br />Basically: vertical strata movement will be determined by wireline geophysical logging; <br />roof fall will be monitored by mining solution salt assay; cavity, pillar, and roof <br />conditions will be observed by cross - borehole tomography; surface subsidence will be <br />monitored by observing surface monument movement. <br />