Laserfiche WebLink
Applicant's Response to Second Adequacy Letter <br />Grantl River Park Project, DRMS File M-2006-046 <br />January 2, 2007 <br />Page 20 <br />Analysis of drawdown potential and seepage less shows that such losses are <br />occurring in the existing condition, and the presence or absence of groundwater <br />in the vicinity of the channel does not cause any significant degree of variation in <br />the inherent leakiness of the channel. <br />Even if localized depression of the water table did exhibit a significant effect on <br />ditch seepage, and even if that effect was adverse, the land owner's portfolio and <br />the general market for water rights available to the operator, including the land <br />owner's portfolio, provide a straightforward means to absorb or redress any injury <br />to ditch rights that may be incidental to the proposed operation. <br />The proposed mining and reclamation plans include specific measures to ensure <br />that significant, adverse impacts to ditches will not be an issue under the M- <br />2006-046 permit. <br />24. Review of the Pre-Mining and Mining Plan Maps indicates that most of the <br />proposed mining operation will take place within the 100-year floodplain of the <br />Colorado River. In order to minimize the potential for flood related impacts, i. e.: a <br />significant flood event capturing the pif and causing off site damage, the <br />applicant has proposed monitoring the forecast flood stage, turning off de- <br />watering pumps in anticipation of the flood stage, installing an armored (8-inch or <br />larger riprap) spillway in each mined cell, and installing a spillway between the <br />clarification basin and the production area of Cell 1. In order to approve these <br />measures, the Division requests that the applicant provide the following <br />information: <br />a. Plan view and cross sectional diagrams for each spillway to be installed`, <br />b. discussion of the flow capacity and maximum permissible velocity for each <br />design spillway; <br />c. revised Mine Plan & Reclamation Plan Maps to show the location of all <br />five (5) spillways; <br />d. discussion of when (during the mining sequence) that each spillway will be <br />installed; <br />e. characterization of the soil types on the site (sand, silt, loam, sandy loam, <br />etc) for all exposed surfaces; <br />f. characterization of the 25-year and 100-year peak flow velocities & flow <br />volumes expected in the main channel of the Colorado River and <br />surrounding excavation areas and; <br />g. cross-sectional schematic depicting the elevations of the invert and top of <br />righUleft banks for the Colorado, 200' setback zone, 4 excavation cells, <br />base flood elevation for the 25-year flood, base flood elevation for the 100- <br />year flood, significant wetland features, and significant riparian features <br />(cottonwoods, willows, etc.). <br />