2006-06-13_REVISION - M2004009 - Laserfiche WebLink

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Page 2 dewatering water") to Boulder Creek. Cells 3 and 4 will discharge directly to Boulder Creek. Mine dewatering water from the remaining Cells will be routed to rechazge trenches for infiltration back into the alluvial aquifer. Per the substitute water supply plan submitted to the State Engineer, the trenches are located at the same distances from the creek as the centroids of the cells, to match in timing and amount the replacement of groundwater pumped from the cells. Sizes and locations of these recharge trenches are shown in Substitute Water Supply Plan Drawings that have been added to Exhibit G and aze enclosed. The pit boundaries for Cell 2 have been altered slightly to accommodate the recharge trench for this Cell, as reflected on Exhibit C-2. The mining schedule has been adjusted to accommodate the recharge trench for Cells 5-6, so Cells 5-6 will be mined prior to Cell 4 (see revised Exhibit D, also enclosed). These changes have been made as the result of the SWSP review and approval process. 6.4.4 EXHIBIT D - Minine Plan 6. The average depth of topsoil is 0.5 ft, as described in Exhibit D, and is located sporadically at this depth in the area to be mined. The entire permit area property has been overgrazed, eroded and compacted and any type of irrigation ceased long ago. The topsoil has been degraded over time and will be mixed with the underlying overburden for reclamation purposes. All salvaged overburden and topsoil is referred to as "overburden". All overburden will be either stockpiled for later backfilling or will be used immediately as backfill as part of the excavation of the Cell being mined. No overburden stockpile will remain for more than one year. 7. The proposed concrete plant has been removed from this operation. No aggregate will be washed at this site for concrete aggregate and therefore, there will be no washwater (clarification) ponds for this operation. All material mined and processed will be "dry". There will be no "wastewater" generated at this site. The only water "impoundment" will be the area called a "sump" at each discharge pipe location where collected water from the dewatering trenches will reside until pumped to the creek or rechazge trench, as discussed in Response 5. The sumps aze actually just an enlarged portion of the dewatering trench to encourage settling prior to discharge from the pit. A sump area will typically be about 8 ft in diameter and will be made up of very clean alluvial groundwater. The sumps, as with the trenches, will either be backFilled or become par[ of the base of the reclaimed water-storage reservoir. Exhibit G has been updated to include. specific descriptions of water diversions and impoundments and is enclosed. The current Stormwater Management Plan for this site, as approved by CDPHE, specifies revegetation and berms as stormwater quality control best management practices. 8. Concurrent reclamation will minimize the azea requiring reclamation at any one time. The largest un-reclaimed pit azea to be worked at any one time would exist around year 4, when Cell 2 is nearly half-mined (-34 acres). At this point, approximately 7,500 linear feet of pit wall at 0.5:1 will occur. Exhibit D has been revised to include this information and is enclosed. 9. The proposed concrete plant has been removed from this amendment and that has been reflected on the Mine Plan Map, Exhibit C-2. All facilities, including the gravel processing plant, will be portable. At this time, only the gravel plant is located on the permit area. It is unknown at this time if any other plants (asphalt, recycle) will be located on this site, as those uses have to be approved by Weld County, and batch plants are currently not approved at this site. The recycle plant would only be operated sporadically at the site, probably less than 6 months out of the year, and would be moved