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ERG <br />FRO Resources (orp. <br />1811 Clorkson Street <br />Denver, (0 80118 <br />(303) 830.1188 <br />Fax: 830.1199 <br />Denver Boise <br />www.emresou«es.com <br />of o@eroresou rres, rom <br />Mr. Larry Thompson <br />Thompson Properties <br />P.O. Box 3 <br />Granby, CO 80446 <br />December 4, 2006 <br />Re: Aydrogeology -Thompson Gravel Pit Expansion, Granby, Colorado <br />Dear Mr. Thompson: <br />The objectives of this letter are to confirm our previous professional opinion regarding <br />potential impact to ground water users from the expansion of the Thompson gravel pit <br />operation and to respond to statements made by attorneys with Fairfield and Woods, <br />P.C., regarding the ERO report, dated May 1Q, 2006. <br />Previous Conclusions <br />As reported in the May 10 ERO report, the proposed gravel pit expansion will be <br />limited to removal of sand, gravel, and cobbles above the water table. The pit will not <br />extend below the water table. In our professional opinion, it is highly unlikely that an <br />excavation of this nature could impact ground water users in the vicinity of the <br />proposed pit. There is no known physical process that would cause an excavation that <br />does not encounter or produce ground water to negatively impact the availability of <br />ground water in the vicinity of the pit. Ordinarily, recharge to the aquifer from <br />precipitation occurs uniformly over the upland areas, limited by evapotranspiration <br />from vegetation, and the characteristics of surface soils. Expansion of the gravel pit <br />will not reduce the rate of recharge, and in fact, could increase the rate of recharge <br />because of the removal of approximately 40 feet of material above the aquifer and <br />removal of all vegetation in the footprint of the excavation. It is not known whether <br />the possible increase in infiltration rate would be significant enough to be measurable. <br />Response 1o Fairfield and Woods, P. C. <br />I. ERO used available ground water data combined with our hydrogeologic <br />experience to understand the hydrogeology of the area and to arrive at our <br />conclusions. The reported water level data are 7 to 20 years old. We believe <br />this data was adequate to confirm that the ground water flow direction is <br />generally towards the Fraser River and from areas of high land surface <br />kxsuhanfs in <br />p:\3600 projects\34$2 thompson gravel pit hydrology assessment, granby\response Ietter.doc Nolurd Resowta <br />and flw fnvronnwrl <br />