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years of Phase I may be entirely on the Central Quarry area to ensure delivery of Reservoir No. • 1 to Morrison in accordance with the Annexation Agreement. It is anticipated that the bench at EI 6455 ft in the North Quazry or the pad at EI 6490 ft north of Reservoir No. I will be utilized as an expansion of the present process and stockpile areas, including installation of concrete and/or asphalt batch plants. Phase II Phase II develops the North Quarry to its final buildout configuration down to approximately EI 5770 ft in preparation for Reservoir No. 2 and, late in the phase, opens the South Quarry to future development. Development will proceed in three cotuecutive subphases to open up limited land at any given time, to reduce potential visual impacts, and for operational considerations. Phase IIA will expand the platform at EI 6455 ft established during Phase I and develop access to the west end of the North Quarry along the north. Phis will facilitate mining the upper approximately seven new benches (40 ft highwalls with 60 ft benches and 40 ft highwalls with 40 ft benches) at the far west end of the North Quarry in preparation for re-reclamation of existing rock highwalls visible to viewers of the Front Range vista from the east. Note that visual impacts will be minimized by maintaining a natural ground ridge at EI 6525 ft along the east edge of the North Quarry. Phase IIB develops the quarry down to approximately EI 6450 ft and reclaims upper east facing slopes. Phase IIC develops the North Quarry to its final configuration down to approximately El 5770 ft and opens the South Quarry for future development. Phase III • Phase III develops the South Quarry to its final buildout configuration down to approximately EI 6000 ft in three subphases. Phase IIIA excavates the upper three benches (80 ft highwalls and 80 ft benches) and creates a platform at approximately EI 6720 ft. Phase IIIB continues development down to approximate El 6400 ft and reclaims the upper three benches to reduce visual impacts. Phase IIIC develops the South Quarry to its final configuration down to approximately EI 6000 ft. The quarry will be developed to the maximum volume recoverable within the footprint of the limits of mining and disturbance. Mining will occur within the limits of mining. Access an will occur in the areas between the limits of mining and the limits of tsturbance. The maximum recoverable volume ~s ependent on the n cut s ope ang es ~ mme w tch in turn are dependent on the strength and other properties of the rock mass. The mining plans shown in Figures D-2 through D-8 show the maximum possible buildout configurations which aze likely to be achieved if the rock mass properties are sufficient to support the steep walls shown. These anticipated maximum buildout conditions are based on the current database of geotechnical properties and slope stability modeling evaluations performed to date for the Central Quarry. Ongoing observations and evaluations will be used to refine slope configurations as various portions of the quarry are developed. Based on presently available information, it is not practical to model the rock mass in sufficient detail to predetermine absolute final slope configurations. Therefore, the "observational method" approach to determining stability of final cut slopes has been adopted. The observational method is a rigorous series of interactive steps of excavating rock, observing the condition of the rock mass and behavior of rock slopes, and refining the design based on updated information. Based on the observations and evaluations . •~+~.~ IV-2 tlt, ~ ~~:.