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<br />• <br />III IIIIIIIIIIIII III <br />~_ <br />--~ <br />_... _~ <br />..~. _.~ <br />~~ <br />TUTTLE APPLEGATE RINDAHL, INC. <br />Consultants for Land and Resource Development <br />August 16, 1989 <br />Mr. Michael Boyd <br />Mined Land Reclamation Division <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203-2273 <br />u <br />RE: File #M-89-~ Timnath Pit <br />Dear Hike: <br />~~~~~~~~ <br />p11f31 x,1989 <br />MBA p N ~~ ~„r~- <br />RECLA <br />We are in receipt of your adequacy memo of August 9, 1989. With this <br />letter we: wish to address your adequacy items in the same numerical <br />order. <br />Mining Plan (Exhibit D) <br />1. The revised estimate of the commencement day of mining is 1990. <br />2. The dewatering trenches will be dug around the perimeter of the <br />mining operation. The purpose of the trenches is to intercept <br />groundwater before it reaches the mining pit area. The dewatering <br />trenches themselves will be dug as deep as is necessary to catch <br />the groundwater. In some instances the trenches may be up to 18 <br />feet: deep, which is the maximum depth of mining. Experience has <br />shown that the Poudre Sand and Gravel Aquifer is densely <br />compacted. The trenches will be pumped during excavation so side <br />fai:Lure is not expected, <br />The water from the dewatering trenches will be <br />Pouc9re River from the Phase I mining operations a <br />I 1<ike when the Phase II area is being mined. We <br />a primping rate between 1,200 gallons per minute <br />per minute. The pumping will be continuous but <br />dur:Lng the year. <br />pumped into the <br />nd into the Phase <br />would anticipate <br />to 1,800 gallons <br />may vary in rate <br />Our experience indicates that a cone of depression may extend <br />beyond the dewatered pit edge from 300 feet to 600 feet. At this <br />distance the water in existing wells may drop one or two feet. As <br />mentioned on Page G-1 of the report, there is one well <br />approximately 2,600 feet away. This well is 23 feet deep and <br />permitted to pump 10 gallons per minute. Since this well is a <br />gre.st distance from the pit and deeper than the maximum mining to <br />be done, we anticipate no negative impacts on the well. <br />11990 Grant Street Suite 410 Denver, Colorado 80233 452-6611 <br />