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<br />east. Please clarify the horizonal distance from the toe of the initial cut to the nearest utility or <br />gas line along Brighton Road and the depth of the initial cut. Also, please identify the owner of <br />the gas line along the west side of Brighton Road and clarify whether the gas line is a high <br />pressure line or a low pressure line. <br />3. The applicant states on page 6 that an engineered, impermeable bentonite slurry wall will be <br />constructed prior to mining operations below groundwater elevations. Pertinent information that <br />will need to be reviewed by the Division prior to approval of this amendment application is 1) <br />the nature or type of geologic material that the slurry wall will be keyed into, 2) the depth of the <br />keyway, 3) any variability in the bedrock encountered during exploratory drilling, and 4) the <br />depth of weathering in the bedrock. Please respond. <br />4. Under the terms of the Division's policy on slurry walls the applicant will need to choose the <br />option to bond for 100% installation or replacement cost of the slurry wall or a 20% installation <br />or replacement bond. In order for the applicant to be eligible for the 20%o bonding option, the <br />Division must have a high degree of assurance that the slurry wall will meet the State Engineer's <br />performance standards. This assurance can be achieved through submittal of design documents, <br />plans and specifications, and a quality assurance program as an enforceable component of the <br />mining and reclamation permit. Attached are copies of the Division's policy memo and guide to <br />specification preparation for slurry walls. Please review the documents carefully to identify the <br />specific information needed for either the 100% or 20% bonding options. Please indicate which <br />bonding option you prefer and submit the requested information as specified in the attached <br />documents. <br />S. The applicant has indicated on page 8 that mining will maintain a minimum 200-foot setback <br />from the (South Platte) river's top of bank. Exhibit C-2 verifies that the limits of excavation will <br />also occur outside the floodway of the South Platte River. In order to ensure that these <br />commitments aze followed throughout mining and reclamation, the Division recommends that <br />the operator mazk in the field the location of the 200-foot setback prior to excavation. Also, we <br />have attached a copy of review comments from Brian Kohlenberg of the Urban Drainage & <br />Flood Control District regarding your proposed mining operation. Please respond. <br />6. The applicant states on page 10 that overburden averages 2.3 feet over the 32.5-acre azea that <br />will be stripped and excavated. (This equates to 120,572 cubic yards of overburden). The <br />applicant further states that 110,000 cubic yazds of overburden will be salvaged. Assuming these <br />volumes aze correct, the appeazs to be a discrepancy of 10,572 cubic yazds. Please clarify the <br />reason for the appazent discrepancy. This information is being requested in conformance with <br />Rule 6.4.4(f)(i). <br />6.4.5 EXHIBIT E -Reclamation Plan <br />7. The applicant states on page 6 that the edges of the reservoirs will be reclaimed to shoreline <br />with wetland vegetation gradually establishing itself. The Division is not opposed to allowing <br />for "volunteer" vegetative growth. However, the applicant will still need to provide an alternate <br />