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Mr. Larry Thompson page 2 <br />Thompson Properties December ~, 1006 <br />elevation to areas of low land surface elevation, consistent with hydrologic <br />principles. The Colorado Division of Reclamation, Mining and Safety <br />correctly requested the collection of additional water level data so that seasonal <br />variations can be understood and documented prior to mining. Seasonally <br />collected data will be important to make sure the depth of the mine is <br />controlled and the water table is not encountered. ERO agrees that this data <br />should be collected for its intended purpose, but this data will not change the <br />basic conclusions regarding the hydrologic system. <br />2. Fairfield and Woods are confusing depth to water and water surface elevation. <br />The reported depth to water values are depth to water from the land surface. <br />Because the land surface is not flat, one can not directly use this information to <br />determine the direction of ground water flow. The depth to water data has to <br />be converted to elevation by knowing the elevation of the measuring point. <br />It is highly unlikely that the ground water flow direction is from the southwest <br />to the northeast, as reported by Fairfield and Woods. Nearly ! 00% of the time <br />in Colorado and other western states, shallow ground water moves from higher <br />topographic areas towards lower topographic areas, and therefore, towards the <br />Fraser River. However, regardless of whether the proposed pit is up or down <br />gradient of the water supply wells, if the excavation does not encounter ground <br />water, it cannot negatively impact the availability of ground water. <br />3. Fairfield and Woods state that ERO's recommendation that Thompson <br />Properties mitigate any future impacts to nearby ground water users <br />demonstrates a lack of confidence in our conclusions. In reality, the statement <br />was made because we are confident that there will be no impacts. Because we <br />are confident that there will be no impacts, we believe it should be the <br />responsibility ofthe well owners to demonstrate impact. <br />4. Fairfield and Woods makes the statement that "Once the aquifer is disturbed, it <br />may not be possible to restore conditions upon which the neighboring <br />properties rely:' This statement makes the assumption that the aquifer will be <br />disturbed. Thompson Properties has stated that the excavation will not extend <br />into the water table, so the aquifer can not be disturbed and their assumption is <br />incorrect. Secondly, this statement is based on speculation, rather than fact. <br />There is no technical justification for their conclusion. <br />ERO cannot comment on any other issue regarding the proposed expansion of the <br />Thompson gravel pit, but we are fully prepared to comment and provide opinions <br />regarding the hydrogeology. In our professional opinion, if the proposed pit does not <br />extend into the water table, there will be no negative impacts to the availability of <br />ground water to nearby ground water users. We believe that ground water availability <br />is not a critical issue for evaluating the proposed expansion. <br />ERo <br />Resa.~n <br />[°ryararion <br />