2023-09-20_BONDING - M1980047 - Laserfiche WebLink

Home Browse Search

Colony Reclamation Cost Estimate, Update to Exhibit L Rev. Sept. 2023 a slope of 3H:1 VT or flatter. The newly exposed surface of the stockpiles, will then be revegetated using the permanent seed mixes in Tables E-3 and E-5. It has been previously assumed that the existing Davis Gulch Cofferdam/Sediment Pond and the three small lower valley sediment ponds (Pond's 3, 4 and 5, refer to Figure L-1 for locations) would be removed following complete reclamation. However, as was determined for Middle Fork Dam in the 2007 Area Reduction, at least the existing Davis Gulch dam and reservoir should be left in place post-reclamation to serve as an upland watering pond for the approved post—mining land use (range land) as well as a water storage facility of site maintenance. Colony holds sufficient storage rights for this pond. The original permit application does provide for leaving the dam in place subject to identifying a post-mining beneficial use and providing for the post-mining maintenance of the Davis Gulch dam and pond. This is also the case assumed for this estimate. Accordingly, no reclamation funds for the Davis Dam are included in this reclamation cost estimate. Basis for Earthwork Quantities in this Review Earthwork volumes are taken from previously submitted documents to the CDRMS (formerly MLRD) in various permit amendment and technical revision documents or internal Exxon cost estimates related to the 1984 amendment. In this review references to specific areas are as per in the 1984 amendment, and Fig L-1 in this cost estimate. Haul distances and elevation changes t obtain unit costs to haul and place the materials, were taken from the center-of-mass of the source to the center-of-mass of the destination as measured on the current AutoCad version of Figure L-1. These parameters are included in the basis for unit costs for earthwork described below. A "per acre" volume of 3,430 cy has been derived to address the requirement in Exhibit E to "remove the generally flat lying expanse" of the Plant Site (Area 18). This item is also included in the reclamation costs for the LaSal Laydown Area (Area 16A), the Coarse Ore Gulch disturbance (Area 17A), and the small area described as Summit Ridge (Area 8B). A one-half acre wedge 8.4 feet in height and 210 feet long by 105 feet wide was assumed to exist in each acre to be reclaimed, representing the work to regrade a flat square one acre square plot(210 ft by 205 ft) into a one acre plot sloping at about 8%. This approximates half of a flat one acre area being pushed uphill or downhill into the other half of that acre, resulting in the calculated 3,430 cy/acre for this component of the reclamation work. The yardage is shown on Table L-2. It not intended to actually produce a uniform 8% grade in these areas, and much of the affected area receiving this treatment is currently not level. Rather, this volume is used to approximate the earthwork cost to blend the affected areas into the surrounding terrain as is the intent of the language in Exhibit E. Earthwork movements used in developing the earthwork portions of the cost estimate have not been optimized. Instead, a simple approach based on moving volumes to the closest reasonable receiving point was used. In an actual reclamation program, all earthwork moves would be evaluated and optimized to minimize cost. It is therefore possible that more economic earthwork movements would be developed based on a more rigorous earthwork balance study. That suggests the costs developed herein may overestimate the actual cost to some extent. Nevertheless, the earthwork movements assumed herein, and the corresponding costs, are certainly feasible. Basis of Unit Costs Unit costs for earthwork are derived from the current hourly operating costs provided in published values obtained from Wyoming DEQ Guideline 12, Standardized Performance Bond Page 4