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Exhibi(D - Mirtrnp Plan <br />Mining <br />Under this amendment, a total of approximately 57 acres of total lake surface will remain at <br />closure of Worthing Pit and an additional 50.3 acres within Expansion Area North will be <br />dewatered and then dry mined. The long-term mine development plan for Worthing Pit will <br />include mining the remaining sand and gravel reserves from Pit Lakes 1 and 2, construction of a <br />water storage facility (WSF), and development of a mixed residential and recreation area <br />containing three lakes. Should the geology be suitable, two of the existing pit lakes (Pit Lakes 1 <br />and 2) at Worthing Pit will be combined and deepened to develop a lined WSF. Short-term <br />dewatering will be required for additional dry mining of gravel in Pit Lakes 1 and 2, as well as for <br />dry mining at Expansion Area North. <br />Under this amendment, the mine and reclamation plan at Worthing Pit will be revised so that Pit <br />Lakes 1 and 2 may be deepened to mine additional sand and gravel and to generate sufficient <br />material to "minimally" backfill Expansion Area North afrer it has been mined out. If it is <br />determined that a WSF is feasible, the applicant will request a Technical Revision to instal] an <br />engineered lining, deepen the WSF, and revise the contours of the reclaimed Expansion Area <br />North to accommodate the additional fill generated by deepening the WSF. <br />Historic mining activities on Expansion Area North have produced one small pit lake and steep <br />slopes west of Brighton Road. No reclamation activities were conducted and much of the site <br />remains disturbed. Vegetative cover is minimal and topsoil was previously stripped. No topsoil <br />stockpiles were observed at the site. <br />The extraction of sand and grave] will be conducted by an open pit operation. No incidental <br />products will be mined or extracted. The proposed mining operation will conform with the <br />requirements and guidelines provided in Urban Drainage and Flood Control District's <br />(UDFCD's) Technical Review Guidelines for Gravel Mining Activities Within or Adjacent to 100- <br />Year Floodplains prepared in cooperation with Adams County and Colorado Rock Products <br />Association (Wright 2004). <br />Worthing Pit <br />Over 25 years of mining activities at the Worthing Pit have produced two large pit lakes and one <br />smaller pit lake. Under this amendment, three miuing scenarios are contemplated, as follows: <br />1. Remaining sand and gravel reserves will be mined out in Expansion Area North over athree- <br />year period. After Expansion Area North is mined out, it will be backfilled to at ]east two feet <br />above the groundwater table and slopes will be graded to no steeper than 3H:1V before <br />application of topsoil and revegetation (Exhibit F-1). Backfill will be generated by <br />excavating shale from the floor of existing Pit Lakes 1 and 2 at Worthing Pit. <br />2. If the geology is suitable, PiT Lakes 1 and 2 in the Worthing Pit will be combined, the pii <br />lakes enclosed by a liner (slurry wall, compacted clay, or combination), and the enclosed pit <br />lake will be deepened to develop a WSF. To accommodate the additional excavation <br />necessary to achieve water storage capacity, Expansion Area North will be backfilled to an <br />elevation approximately level with Brighton Road (Exhibit F-2). Should this plan be <br />feasible, the applicant will submit a request for a Technical Revision to include operational, <br />hydrologic, and bonding changes to this permit. <br />1898-Frei 112 Exhibits_(4.20.05).doc D-2 <br />