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SEP-05-2003 FRI 09 26 AM BAI~ AND GE5S0 LLC FAX N0. 3274 8329 <br />.~ <br />September 4, 2003 <br />re: Haldorson and Sons, Inc. Sand and Gravel Mine, hydrology issues <br />rx: Paul Gesso, Tom Smith <br />Dear (vir. Hatdorson, <br />This letter repoR addresses the hydrologic issues pertinent to the Colorado State Division of Minerals <br />and Geobgy (DMG) review of the proposed Haldorson and Sons Inc., Sand and Gravel Mine located <br />on Spring Creek Mesa near Montrose, Colorado. These findings are based on a review of Exhibit D, <br />Mining Pian prepared by 9anks and Gesso, Exhibit G information from B nearby DMG permitted gravel <br />mining operations, results of six test holes drilled on the site, the WestWater Associates report. as well <br />as my on-site invesfigatton. <br />The following issues are addressed in this letter, <br />1. background <br />2. Hydrologic balance <br />3. Dry versus wet ptt <br />4. Storm water runoff <br />5. Water quality <br />6. Hydrologic impacts <br />7. Remedial action <br />B. Need for a comprehensive hydrologic study <br />1. Background <br />The WestWater report presents an accurate picture of the hydrologic conditions in this area. I concur <br />with-theirbasiaflndings, aRhough I have not confirmed specific numeric values presented in the report. <br />important conclusions are that groundwater is derived from preapitation, non-consumed Irrigation and <br />leakage from ditches and canals. Groundwater flow generally moves from the southwest to the <br />northeast along the gradient set by the top surface of the Mancos Shale fonnatlon. This is similar to the <br />slope and din:ctlon of the surface topography. Regional groundwater levels In the gravel deposits are <br />signfipMly affected by irrigation practices and vary, in Gme, with the irrigatlon cycle. Springs and ponds <br />occur in nearby grave! pits and along the natural and manmade slcpes that penetrate the gravel <br />deposits along the edge of the mesa. <br />Hydrologic effect of a gravalpit - Digging a gravel pit is analogous to drilling a well. In either case <br />the actual hole has little effect on the shape or location of the groundwater surface. If the bottom of <br />the well (pit) is deeper than the prevailing groundwater surface, then water will flow into the well {pit). <br />The well (pit) will fill to the same level as the sunounding groundwater surface. Once the well (pit) <br />has filled, water will flow through the well much the same as it did before the well was drilled with no <br />measurable effect on the gradient or elevation of the groundwater surface. Because a gravel pit is <br />much larger than a well then; may be a small variation between the with" and without" <br />groundwater surfaces. One might expect the water surface in the pit to be slightly higher than <br />without the pit due to reduced head loss in the flow over this distance. <br />With a well, the groundwater surface is not impacted unless you pump it. Pumping draws down the <br />water surface elevation in the wail, tteating an altered gradient on the surrounding groundwater <br />surface that now slopes toward the well (cone of depression). Groundwater within the influence of <br />this cone will flow towards the well instead of along the natural gradient (without pumping). The <br />radius of influence and the rate of flow associated with the cone of depression are dependent on the <br />amount of drewdown created by the pumping, the properties of the aquifer material and the <br />geometry of the area. <br />P. 02 <br />