PERMFILE103738 - Laserfiche WebLink

Home Browse Search

Please clarify the period of time and maximum de-watering rate that will occur at a time of maximum pit disturbance, ie: the rate and length of time for the maximum drawdown of the groundwater surface within the affected land and surrounding area. 3. The applicant specifies that pit water from de-watering operations will be discharged according to an approved plan into existing sloughs in order to return the water to the Colorado River system. (Exhibit C -Mine Plan Map shows a total of 4 locations for conveyance of pit water to the Colorado River. It appears there will need to be a conduit or water transfer system of almost two hundred (200) feet for each point of water conveyance). In conformance with Rule 6.4.7(2) (c), please describe and provide representative cross sectional diagrams of how the pit water will be managed, routed, and dischazged into the Colorado River in a manner that protects against pollution of either surface or groundwater resources and minimizes the potential for erosion of the affected land. Please respond. 4. The applicant has proposed a 100-foot setback from the Colorado River to the neazest point of pit excavation in order to ensure that during high-water events, the river does not capture the pit. Prior to approval of the proposed application, the applicant will need to provide a map or maps that depict the boundaries of the 100-yeaz floodplain and verify whether the proposed excavations will be within or outside the boundaries of the 100-year floodplain. Also, the limits of the Colorado River "floodway" will also need to be defined, and shown on a revised map. The applicant may want to provide this information on a "water features" map which also shows the locations of the pit excavations. In addition, the Division requests that the applicant provide adequate survey data to characterize the elevation(s) of the affected lands to be excavated in relation to the Colorado River. At a minimum, there should be at least one (1) profile that runs from the east edge of Cell B to the west edge of Cell A; and two (2) representative cross sections for each cell that depict the following elevations and features: • Northern edge of each pit excavation • Southern edge of each pit excavation • Top of bank for the north bank of the Colorado River Top of bank for the south bank of the Colorado River • Ordinary high water mazk • Any intermediate terrace • Colorado River channel invert • Slough, overflow channel, or other significant channel feature • Irrigation channel(s) or return flow ditch(s), if present Please provide. 5. The applicant specifies that a primary crusher will be located adjacent to the active mining area, and then the sand and gravel materials will be transported across the Colorado River via conveyor to the Mamm Creek operation on the south side of the Colorado River. The applicant will need to provide plan view maps and representative cross-sectional engineering designs of the conveyor system and structural supports needed. Further, the applicant will need to clarify whether any portion of the conveyor/bridge system will remain during final reclamation. Finally,