2008-04-24_REVISION - M1997054 - Laserfiche WebLink

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Parkdale Quarry Amendment #1 (M-1997-054) Bond Phasing Calculations Description In order to calculate the maximum potential reclamation liability to the State, it was determined that the maximum site disturbance is anticipated at approximately year 8. This point in time corresponds to the Reclamation Phase II of the Sand and Gravel operation and Reclamation Phase I of the Granite operation which results in the greatest area of disturbance over the entire permitted area. In an attempt to accurately reflect liability, unit costs are based on an average of unit costs from certified bids that we have received for similar projects and types of work as well as CDOT engineering estimates. A copy of the bond calculations is included as an attachment to this letter. A brief description of the bond calculation for the Sand and Gravel and the Granite mining operations is described below. SAND AND GRAVEL The aspects associated with each reclamation phase were calculated using similar methods and assumptions. All phases of the Sand and Gravel Reclamation calculations originated from the year 8 (Phase II) bond calculation. Therefore, Phase II is described in greater detail than Phase I and Phase tll. Sand and Gravel Reclamation Phase II (Year 81 This phase of the Sand and Gravel operation is characterized by active mining in the approximately middle 1/3 of the Sand and Gravel mining limit. Aspect A reclamation activities in the bonding calculations will take place in the approximately western 2/3 of the Sand and Gravel mining limit. This aspect assumes a portion of the area mined during Phase I has undergone reclamation so the clay blanket and 3:1 shell has been placed and seeded. This aspect also anticipates approximately 4000 linear feet of the 40-foot mining face highwalls will need to be backfilled. Clay blankets will be installed along a portion of the north mining highwall and the 30-ft high mining bench to the east leading up to the processing facility. Aspect A also assumes that approximately 4240 linear feet of shell material will be placed. Finally, this aspect includes placement of topsoil, seeding and mulching, as well as reseeding the slopes. Aspect B includes the placement of topsoil, seeding, mulching, and reseeding of the approximately central 1/3 of the Sand and Gravel mining limit, within the reclaimed slopes along the bottom of the mined pit. Aspect C includes the area contained by topsoil and overburden stockpiles from Phase I mining operations. Since the stockpile materials are used throughout the mining area for reclamation, the material within the stockpile is assumed to have been used during reclamation activities. The area _. 1~Page