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August 19, 1999 <br />• Access roads <br />The proposed experimental mine will involve drilling and casing wells into the Green River <br />Formation below the dissolution surface approximately 2,000 ft. below the ground surface. <br />Solution mining wells using a double hanging string would be installed in the cased <br />boreholes to allow the solution mining and development of cavities in the nahcolitic oil <br />shale. Hot water would be used to dissolve the nahcolite for conveyance to the surface. <br />Hot pregnant soda liquor would be piped to the pilot scale processing plant for extraction <br />of the sodium bicarbonate. Waste process solution will be evaporated. <br />3.0 RISK ASSESSMENT APPROACH <br />The risk assessment approach used for this analysis was described by Van Zyl and <br />Bamberg (1992) in a paper entitled Qualitative Environmental Risk Assessment for Mine <br />Development. This paper has been included as Attachment 1. The objective of this <br />analysis is to describe the risks associated with the development of this proposed <br />experimental mine and to make an evaluation of the adequacy of its design for <br />environmental protection. Following the identification of potential failure mechanisms of <br />concern, the four steps of a risk assessment are used in the development of this qualitative <br />risk assessment including: <br />• Hazard Assessment <br />• Exposure Assessment <br />• Consequence Assessment <br />• Risk Characterization <br />\ \GAI_DEN1 \PROJECTS \wP\99\205T2057TM1.DOC Golder Associates <br />MEMORANDUM <br />-2- 993 -2057 <br />Identification of potential failure mechanisms and each of these steps are discussed below <br />for the proposed experimental mine The overall qualitative risk assessment process is <br />summarized on Figure 1. <br />4.0 IDENTIFICATION OF POTENTIAL FAILURE MECHANISMS <br />This selection presents the range of potential failure mechanisms no matter how improbable <br />the occurrence may be due to design and operational controls. Potential failure <br />mechanisms and environmental concerns have been raised both in the Reclamation Permit <br />Application (Raytheon Engineers and Clark, 1999) as well as correspondence between the <br />Colorado Division of Minerals and Geology (DMG) and AmerAlia, Inc. Key project <br />components for which potential failure mechanisms are addressed in this memorandum <br />include: <br />