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Ms. Erica Crosby <br />RE: Timnath Pit Technical Revision <br />May 10, 1007 <br />Page 2 of 3 <br />Wellington Downs Pit approximately one-half mile southwest of the Timnath Connell Pit. <br />Aggregate material was previously transported by truck from the Timnath Connell Pit to the <br />Wellington Downs Pit for use in the asphalt plant operations. Moving the asphalt plant to the <br />Timnath Connell Pit eliminates the need to transport aggregate material off the site for use in <br />asphalt plant operations. The asphalt batch plant will operate within the Timnath Connell Pit <br />permit boundary through the remaining life of the mining operation and use of the aggregate <br />materials produced. The asphalt plant is located outside of the 100-yeaz floodplain on <br />compacted backfill in the northwest corner of the site. The compacted backfill underlying the <br />plant will mitigate impacts if a spill was to occur minimizing the vertical mobility of the spill. <br />The site is also graded so that all spills will drain to an on-site holding pond. There aze also <br />drains within the building pad to carry any spills to the holding pond. Therefore, spilled waters <br />will be intercepted and not allowed to enter any state waters. <br />Petroleum related products will be'double contained in weather-proof containers and will be <br />stored off the ground surface on pallets or appropriate storage racks. The diesel tank is stored in <br />a concrete double lined container. Any petroleum product that is visually detected will be <br />responded to immediately. Any azeas discovered will be excavated and the material taken to the <br />fueling azea for holding prior to disposal off-site. There is sufficient earth-moving equipment <br />(front-end loaders) on-site to quickly contain a surface spill. Appropriate absorbent materials <br />will be kept on-site for initial containment and extracting of a spill. The Connells have several <br />properties in the same area and one SPCC plan covers the majority of these properties. <br />The addition of the asphalt plant has akeady been approved by the Larimer County URS <br />amendment process (99-Z1291). <br />Reclamation <br />The site is to be reclaimed for lined water storage. The original reclamation plan included trees <br />neaz the reservoir crest on the reclamation plan drawing. It is not recommended to locate trees <br />near the bank of a lined water storage reservoir due to the potential of undermining the integrity <br />of the liner. This Technical Revision proposes to remove the trees from the bank of the <br />reclaimed reservoir and from the reclamation plan. The revised reclamation plan is attached. <br />Seeding and revegetation will still occur as stated in the existing pernut. <br />The original reclamation plan shows that the reclaimed slopes will be covered with two feet of <br />gravel. The reclamation plan was originally derived without a stability analysis of the slopes, <br />therefore a conservative approach was taken and gravel was added to the slopes for additional <br />stability. A stability analysis, using XSTABL, has since been completed illustrating that the <br />slopes are stable without the additional weight of the gravel. This Technical Revision proposes <br />to remove the gravel shell. The slope stability calculations illustrate that the removal of this <br />gravel cover will not impact the stability of the slope. Calculations showed that the minimum <br />factor of safety was 1.22 for a rapid drawdown scenario and 1.86 for the reservoir full scenario. <br />Sensitivity analysis was performed on the model. The results of this analysis are included with <br />this Technical Revision. <br />