Laserfiche WebLink
A ridge located approximately 3 miles east of the Site is formed by an upturn of the underlying claystone bedrock and <br />provides a definable eastern limit to the aquifer. The ridge represents a no flow boundary in the model. Refer to the <br />geological mapping of the Site on Figure 3. The eastern limit of the alluvial aquifer was confirmed by discussions with <br />farmers in the area who stated that there are no shallow alluvial wells east of the site, where the land transitions from flat <br />to steep near this ddge. <br />The South Platte River forms a natural hydrologic boundary. The South Platte River has an average slope of <br />approximately 0.1 percent along this western boundary of the model. The river stage was modeled to decrease as the <br />river flows north reflecting observed conditions. A summary of the boundary conditions is presented in Table 6 below. <br />Table 6 <br />Boundary Conditions <br />Area Boundary Notes <br />North Model extends 2.5 miles to the north Constant head nodes, see <br /> Fi ure 2 <br /> No flow approximately 2 miles east Modeled as no flow <br />see <br />East at location of Denver & Arapahoe , <br /> <br />formations Figure 2 <br />South Model extends 2.5 miles to the Constant head nodes, see <br /> south Fi ure 2 <br /> South Platte River located River bounds the western <br />West approximately 600 - 2000 feet west side of the model, see <br /> of site figure 2 <br />3.10 Site Groundwater <br />Civil Resources installed nine piezometers at the Site as part of our geotechnical investigations between June and <br />September, 2004 at the locations shown on Figure 2. Monthly groundwater levels were measured and are presented on <br />Figure 6. The data indicates a slight hydraulic gradient of approximately 0.17 percent toward the South Platte River to <br />the northwest. <br />The Site piezometers are monitored monthly in order to further evaluate the seasonal Fluctuations in the groundwater <br />surface. In addition, two control points have been installed along the South Platfe River so water levels can be <br />measured in order to evaluate the influence of the river on the groundwater gradient. <br />3.11 Surrounding Site Groundwater <br />Groundwater levels were taken on the Site on October 18, 2004, and at the two control points on the South Platte River. <br />These groundwater elevations were extrapolated to the river control points in order to evaluate the influence of the river <br />on local groundwater gradients. A three-point extrapolation of the groundwater surface projected an elevation of <br />4907.47 at the control paint. The measured level at the control point on that day was 4907.56, a difference of +0.09 feet. <br />The slightly higher elevation at the river indicated that the South Platte potentially is the controlling influence on local <br />groundwater conditions on the western side of the Site during early fall. The three-point data are included in Appendix B. <br />East of the Site, groundwater levels were obtained from reported depths on the Colorado Division of Water Resources <br />list of permitted wells. Reported levels ranged between 4 feet and 30 feet below the ground surface. A welt list is <br />attached in Appendix C. <br />Groundwater Model Report - SW TKO Water Storage Project - 6 - February 2005 <br />