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<br />Reclamation Plan <br />sEP 2 ~ 2oos <br />Divi~:on of Reclamation, <br />Mining and Sarety <br />EXHIBIT E <br />Developed water storage will be the final reclaimed use for the Hokestra Pit site. In this area of <br />Weld County, agriculture, mining, and post mining open space aze predominant land uses along <br />the St. Vrain River. Therefore, the proposed post mining use is compatible with surrounding <br />land uses. <br />The reclamation will occur in phases consistent with mining activities. When reclamation is <br />complete, three lined storage reservoirs will be created with an approximate capacity of 1,320 <br />acre-feet. Phase II will consist of an approximately 815 acre-foot reservoir. Phase III will <br />contain a 135 acre-foot reservoir and it is anticipated that Phase IV will encompass a 370 acre- <br />foot reservoir (see Reclamation Plan Map, Exhibit F). <br />Water Storage Reservoirs <br />Weld County is not required to bond for reclamation, therefore the following discussion is <br />provided to assist the DRMS in its understanding of this project. In general, the mining areas <br />will be mined to the claystone bedrock. The relatively impermeable bedrock will make up the <br />bottom of the reservoirs in all phases. The reservoir created in Phase II will also be separated <br />from the surrounding alluvial aquifer by a clay liner. The clay liner will use on-site materials. <br />The geotechnical firm, Kumaz and Associates, tested the on-site materials for suitability for <br />reservoir construction. The liner will be part of the reservoir embankment, keyed into the <br />bedrock material, and extend upwazd through the entire height of the alluvium. The slopes will <br />be reclaimed at a minimum of 3H:1 V. Design specifications and quality control procedures used <br />during construction of the liner will ensure that the reservoirs meet State Engineer's Office <br />(SEO) performance standards for permeability. Quatiry control procedures include construction <br />observation and frequent goetechnical testing for neaz optimal moisture and a minimum of 95% <br />compaction. Final reclamation by capping with topsoil and re-vegetating above the expected <br />reservoir water level will follow liner construction operations closely to minimize the amount of <br />disturbance at any one time. Once construction of the liner is complete, the liner will be <br />monitored for compliance with design specifications as required by the State Engineer's <br />certification process for lined storage reservoirs. <br />The reservoirs completed as part of Phase III and Phase IV will be hydrologicly separated from <br />the surrounding alluvial aquifer by a slurry wall. The slurry wall will encompass both reservoir <br />azeas and will be installed prior to mining activities. The slurry wall will consist of a bentonite <br />slurry mixture that meets SEO specifications. The soil material will use on-site materials. The <br />slurry wall will be keyed into competent bedrock a minimum of three feet. Competent bedrock <br />is defined as non weathered clay shale. The site is relatively flat, so there should be no issue <br />with constructability of a slurry wall in terms of staging area and platform space. Material tests <br />will occur during construction and construction observation by an engineer will occur. Once <br />construction is complete and the majority of the mining has occurred, the reservoir will be <br />Weld County Hokesba Pit <br />DMG 112 Permit Amendment <br />Page 6 <br />