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South west Kyd~o-Logic <br />265 Ridge Road <br />Durango, Colorado 81303 <br />Office: (970) 259-2851 <br />Mobile: (970) 749-3950 <br />Email: infoGdswhvdroloftio.com <br />Website: wwu'swhvdroloeiacom <br />Frank Ancsi <br />P.O. Box 2185 <br />Durango, Colorado 81302 <br />From: Winfield G. Wright, Professional HydrologisdCivil Engineer/Owner <br />Re: Ground-water levels near the proposed Sandco gravel-pit lake <br />August 4, 2004 <br />The Sandco gravel-pit lake will be enlarged at a rate oC about 2 acres per year for 20 <br />years. For many of the early years of excavation, there will probably be little effect of the <br />excavation on ground-water levels in the surrounding area (like digging a hole in a cup of <br />saturated sand). After the Sandco gravel-pit lake is completed, the water level in the lake will <br />be dependent on the permeability of the material in the 300-fr buffer behveen the lake and the <br />Animas River. Ground-water levels in the properties upgradient from the lake (to the east) <br />will be dependent on the water level in the fake. Lower penncabi(ity of the buffer material <br />will contribute to a higher lake level, hence higher ground-water levels upgradient from the <br />lake. However, there are no data on the permeability of the material in the 300-fr buffer. <br />The lake level also will be dependent on the ground-water recharge to the valley <br />upgradient from the lake, or the amount ofground-water flowing towards the river from the <br />valley margins. Ground-water recharge to the area comes from flood irrigation, leaking <br />ditches, and ground water and surface water from Freed Canyon. Ground-water recharge has <br />been severely reduced during the ongoing drought. A return to normal climatic conditions <br />will mean increased ground-water recharge to the valley, hence higher ground-water levels in <br />the area. <br />A question has been presented whether formation of the gravel-pit lake will lower the <br />water table beneath properties adjacent to the lake. Specifically, the question is whether a <br />lower water table will prevent the conveyance of flood irrigation water across the land to <br />reach the far extent of irrigable property. The ability to convey water across the land is <br />dependent on the permeability of the surface soils and the rate offlood-irrigation application <br />(contributing to saturation of the soils). The water table is currently about l2 feet below land <br />surface. If, for example, the water table was I foot below land surface, and the water table <br />was lowered to 12 feet below land surface--that could affect the saturation of the soils and the <br />ability to convey water across the land. If the water table was 12 feet below land surface (the <br />current situation), and the water table was, for example, lowered to 14 feet below land <br />surface, the ability to convey water across the land would not be affected. <br />/ ' y {L~ <br />1~~~~~~- 1~~~ <br />