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STATE OF COLOlZADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1373 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 832-9106 <br />September 17, 2003 `~/ <br />Tug Martin <br />Banks and Gesso <br />720 Kipling St. Suite 117 <br />Lakewood, Colorado 80215 <br />DIVISION OF <br />MINERALS <br />GEOLOGY <br />RECLAMATION <br />Ml NING•SAFETY <br />Bill Owens <br />Governor <br />Greg E Wakher <br />Executive Director <br />Ronald W. Cattany <br />Acting Division Director <br />Re: Ha/dorson Sand and Grave/ Mine, App/ication No. M-2003-037, Hydro/ogica/ Review. '~/ <br />Dear Mr. Martin: <br />Please find enclosed a memo from the Division of Minerals and Geology, Specialist Kate <br />Pickford, concerning the hydrological review for the above referenced application. In <br />discussions with Ms. Pickford, the Division will ask the applicant to install a minimum of <br />three (3) groundwater monitoring wells up gradient of the proposed first phase and three <br />wells down-gradient for the purpose of monitoring depth to water prior to the beginning of <br />any mining activities. <br />A memo from Banks and Gesso's hydrology consultant, Mr. Don Day, recommends weekly <br />monitoring to collect data concerning the maximum height of the water table. DMG staff <br />concurs with that recommendation with a clarification that a year's worth of data must be <br />collected prior to any excavation below the committed 20-foot depth. Further, the <br />applicant will have to submit the same type of data at least 1 year prior to moving into the <br />next phase of mining. <br />The wells and duration of monitoring will give the operator and the Division a tull season <br />of groundwater data for analytical purposes. Staff feels that this data and the <br />commitment to a maximum mining depth of 20 feet will ensure that the hydrological <br />balance is understood prior to any impact from the mining operation. If the applicant <br />wishes in the future to excavate below the 20 foot maximum depth he will be required to <br />submit a modification to the permit prior to doing so. <br />As we discussed, staff feels it is important to get a written commitment from the applicant <br />to maintain a buffer zone between the active mining phase and any on going agricultural <br />endeavors on the permitted site. A minimum of half of the next consecutive phase (10 to <br />15 acres) should be fallow to ensure that the recharge field created by the irrigation water <br />is not prematurely intersected during mining. <br />