Laserfiche WebLink
STATE OF COLORADO <br />DIVISION OF WATER RESOURCES <br />1313 Sherman St., Rm. 81.8 <br />Denver, CO 80203. <br />(303) 866-3581 <br />INTEROFFICE MEMORANDUM <br />TO: )USTIN.\ 1' F.M1111S, KT?.1TI VAN1?1'.11110125"1' <br />FROM: 111C1I.,W1, SCI IALIBS <br />SUBJECT: ItOBINSON 131tiC:K C`.UAtPANI' RIiC:fill'1'NO. 1ti43S31ti <br />DATE: 4/27/2010 <br />CC: D:\VE \ICli1.11ANF"Y, <br />At the present time the. I-lydrogeological Services Branch does not use the new Colorado Geological <br />Survey interpretation of the Denver Basin aquifers. This interpretation is considerably different than <br />previous interpretations of the basin. Senate Bill 5 and the Denver Basin rules control the <br />administration of the Deriver Basin aquifers and until these are changed, the Hydrogeological <br />Services Branch will provide evaluations consistent with previous interpretations. <br />I have reviewed the geology.of the area around the Robinson Brick Company= properties. I do not <br />agree with the previous evaluation for well permit 162619 showing that this well is completed in the <br />Dawson aquifer to a depth of 100 feet below the ground surface. If the elevation of the bottom of <br />this well were to represent the base of the Dawson, it would greatly expand the extent of the Dawson <br />aquifer over what had previously been delineated. This line is.shown in red on the map. <br />In this area there are a series of clay mines between elevations of 6600 and 6650 feet, These mines <br />are developed in the paleosol horizon at the top of the Denver aquifer/base of the Dawson aquifer. <br />The estimated position of this line is shown on the map in yellow. The northern part of this line <br />corresponds relatively closely with the extent of the Dawson shown on the USGS Denver I X2 <br />degree map. The Nussbaum alluvium is present immediately to the east of the Robinson Brick <br />Company properties at relatively higher elevations. Two gravel pits in sections 11 and 14 are <br />probably in the Nussbaum alluvium. <br />Based on this interpretation there is about 150 feet of Dawson between the paleosol horizons and <br />the Nussbaum. I-lie maximum thickness of the Dawson will be present on the east side of Section <br />21, and thinning to the west. <br />Because the Dawson has been stripped back by erosion in the drainage of East Branch Brackett <br />Creek, sandy units within. the. Dawson will be for the most part drained. This is apparently why S135 <br />and the Denver Basin Rules fail to recognize Dawson aquifer material in this area.