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602 Park Point Drive, Suite 275. Golden, CO 80401 <br />Phone: (303) 526-2600.Fax:(303) 526-2624 <br />E-mail: mwi@marfinandwood.com <br />May 13, 2004 <br />Mr. Paul Banks <br />Banks & Gesso LLC <br />720 Kipling Street, Suite 117 <br />Lakewood, Colorado 80215 <br />Re: Trans Colorado Concrete <br />St. Bazbaza Sand And Gravel Mine <br />Dewatering Modeling Analysis <br />Project Number 608.1 <br />Dear Paul: <br />This letter report presents the results of our analyses to date into the predicted impacts on <br />local ground water conditions resulting from the planned dewatering of the proposed St. Barbara <br />Sand and Gravel Mine located near Avondale, Colorado. This assessment was carried out to <br />determine how the mining operations might affect nearby wells and the Excelsior Ditch (Figure <br />1, Site Vicinity map; Map used courtesy of Banks and Gesso, LLC). The analysis was <br />performed via the construction and operation of a numerical ground water flow simulation and <br />the USGS model code "MODFLOW". <br />The proposed gravel mine is situated adjacent to the Arkansas River approximately 11 <br />miles east of I-25 in the City of Pueblo. The property contains post-Piney Creek alluvial sands <br />and gravels deposited by the river and by Chico creek, the drainage of which intersects the <br />Arkansas River just to the northeast of the mine property (Figure 1). <br />The Arkansas alluvial aquifer is a typical sand-gravel deposit capable of producing <br />relatively high yields of water to wells. The alluvial valley is generally bounded on the north and <br />south by terrace deposits mapped as "calcareous disintegration residuum" on the north side of the <br />valley and by eolian sand and sheetwash alluvium on the south side. However, the alluvium <br />associated with Chico Creek does enter the Arkansas valley northeast of the mine. This has the <br />effect of extending the alluvial valley northward for some distance along the axis of the Chico <br />Creek drainage. <br />Available information of the alluvial deposits in the vicinity of the St. Bazbaza property <br />indicate that there is some 25-feet of saturated sands and gravels present, underlying varying <br />thicknesses (5 to 9 feet) of lean clay. The non-irrigation ambient water table appears to.be <br />approximately 8-feet below the ground surface at the property, although monitoring well data <br />indicate that there may be some local confinement under the clays. The current channel of the <br />