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Mr. Bill Roberts Adequacy Review No. 2, Permit Application No. M-2006-046 October 4, 2006 a. A revised Mine Plan Map or a Water Features Exhibit that shows the location and ownership of any registered wells within 600 linear feet of the proposed excavation areas. If any such wells exist, the applicant should also supply available well completion and well type information, i.e.: irrigation vs. domestic well, well permit number, total well depth, depth to water table, well production, etc. b. The applicant has stated on page 17 of the application that the average groundwater elevation is 5 feet below ground surface across the site. Please provide a discussion of the depth to groundwater below existing wetland resources as well as woody riparian vegetation (cottonwoods, willows) and the seasonal variation in groundwater levels beneath these resources. Further, please provide a discussion of the hydraulic gradient and direction of groundwater flow for the alluvial aquifer to be mined through. c. The applicant has shown on Exhibits C-I & C-2 the locations of three (3) monitoring wells or piezometers for collection of static water level measurements. Please describe the nature and extent of measurements already collected. (As previously stated, it is the Division's practice to require constmction material operators to collect at least 5 quarters of baseline groundwater measurements prior to de-watering operations to accurately determine an undisturbed, baseline groundwater profile for the area(s) to be affected). Further, the Division requests that the applicant add at least two (2) more piezometers to provide an up-gradient and adown-gradient monitoring location. Specifically, the applicant should consider locating an up-gradient monitoring location in the southwest comer of the permit area and adown-gradient monitoring location near the cottonwood dominated riparian area in the northeast portion of the permit area. Please respond. d. The groundwater model and assessment prepared by Martin & Wood Consultants is based on assumption that mining and reclamation will be completed in Cell 1 before moving on to Cell 2, and completion of mining and reclamation in Ce112 prior to de-watering and mining in Cell 3, and so on. Typically, operators of similar sites begin de-watering of Cell 2 prior to completing reclamation of Cell 1, i.e.: begin de-watering in the next cell to be mined prior to completing al] backfill & re-grading, topsoil replacement, and pond filling requirements in the previous cell being reclaimed. As a result, the Division requests that the applicant commit to completing all reclamation measures in the preceding cell prior to initiation of de-watering activities in the following cell. As an option, the applicant may revise the existing groundwater model and assessment based on the maximum pit de-watering disturbance expected at any one time throughout the life of the operation, or the applicant may provide a comprehensive groundwater monitoring plan which verifies that all potential adverse groundwater impacts are being monitored and mitigated where necessary. The Comprehensive Groundwater Monitoring Plan will need to include the following components: 1. Map showing the location of all monitoring locations; 2. Frequency of monitoring water level measurements (Division recommends monthly measurements during mining); 3. Specific "trigger points" to determine when mitigation measures will be implemented*; 4. Reporting requirements of water level measurements collected throughout the year & data summary; 5. Reporting requirements to the Division in the event a "trigger point" elevation is experienced during monitoring; 6. Specific mitigation measures that the operator will implement if trigger points are reached and; 7. Duration of monitoring (should be at least throughout the mining phase of the operation). * The Division recommends that the "trigger point" be determined based on the maximum groundwater fluctuation (and elevation) expected throughout a normal year. However, the applicant should give special consideration to the groundwater fluctuations (and elevations) expected in the most sensitive areas that are likely to be impacted such as wetlands, willows, cottonwoods, etc to determine a "trigger" that will adequately protect these resources.