Laserfiche WebLink
Memo to Greae Squire ~ March 13 2001 <br />3. Financial Wattanty Implications <br />With specifications and a construction quality assurance plan in place, the Division may bond for less <br />than a full installation or replacement of the pit liner. In accordance with the Division's policies and <br />guidance for lined pits ("Guide to Specification Preparation for Slurry Walls and Clay Liners as a <br />Component of a Colorado Mined Land Reclamation Permit," September 2000) the amount of required <br />bond will be based on lining the open area of the pit at the point of maximum disturbance during <br />phase 3 of the mine plan plus an amount adequate to reline 20 percent of the previously lined area. A <br />copy of the cited document is included with this memo. The direct cost for pit lining derived below <br />should be included in the amount of reclamation bond to be required for permit issuance. <br />Pit dewatering. This unit cost assumes that in a bond forfeiture situation, the Division would be <br />required to pump down a flooded pit in order to implement the approved reclamation plan, and <br />would have to continue dewatering until the liner is installed. Assuming that ground water would <br />flood the pit to a level 12 feet below the ground surface, as indicated in Exhibit G to the <br />application, with an average 17.5 foot pit depth (Exhibit D) over an area of 69.9 acres (sum of the <br />acreage of the three proposed mining cells) the total volume to be dewatered is: <br />5.5 ft. (vertical extent of water column) * 69.9 acres * 43,560 sq.ft.lacre = 1 b,746,642 cu.ft. <br />= 125.3 million gallons <br />Dewatering costs derived from 1994 CDOT data for awarded bids is $201.46 per million gallons. <br />($230.00 per million gallon awarded bid minus 12.41 percent indirect cost). Hence the direct cost <br />for dewatering at the Bonser Pit is 125.3 m.g. * $201.46/m.g. _ $25,242.94. Additional direct <br />dewatering cost incutted during liner installation is assumed to be negligible and is not included. <br />The direct cost estimated here may require modification depending on the Applicant's response to <br />questions about the water table elevation posed above. <br />Ripping the weathered shale on the floor of the pit. The amount of shale required for construction <br />of the pit liner in a bond forfeiture situation is derived as follows: <br />23.3 acres in Pit #3 plus 20 percent of the area in pits #I & 2 (23.3*2*0.20=9.32 acres) require <br />lining, for a total of 23.3 + 9.32 = 32.62 acres. 32.62 acres with a 2 foot thick liner requires <br />105,254 c.y. of compacted clay. <br />The estimating form for ripping work attached to this memo provides the direct cost for ripping the <br />weathered shale on the floor of the pit at $17,213.00. <br />Excavation of the ripped shale and placement in thin lifts on the area to be lined. The attached <br />estimating form for scraper work provides the direct cost for this reclamation task at $84,002.00. <br />The derivation of the average scraper haul distance used in the estimate is as follows: <br />