|
Fair Meadows Pit Groundwater Evaluation
<br /> November 19, 2022 Page 10 of 28
<br /> aquifer is permeable enough to quickly respond to changes in groundwater levels caused by the
<br /> slurry wall.
<br /> Model Uncertainty
<br /> There is uncertainty in our predictions related to measurement and modeling error. USGS 1 Om DEM Data
<br /> was used to assign ground elevations to off-site wells. The overall accuracy of expressed as the root mean
<br /> square error(RMSE)for 1 Om DEM data for one study in(Haneberg, 2006) is 1.87 m or approximately+/-
<br /> 6 ft. The accuracy of surveyed site well elevations data is much higher,probably within a tenth of a foot,
<br /> and the accuracy of hand-measured water levels can vary several inches.
<br /> Our modeled predictions(Figure A9)include three types of error: 1)conceptual error(how the model is set
<br /> up and what boundary conditions are used); 2)parametric error (how aquifer properties are measured and
<br /> calculated); and 3) predictive error (which includes other influences such as seasonal recharge or climate
<br /> change variations). It was beyond the scope of this project to quantitatively evaluate the sum of these
<br /> errors. However, based on our professional opinion, we believe our results are reasonably accurate.
<br /> Sources
<br /> CDM-Smith, April, 2013a. South Platte Decision Sport System Alluvial Groundwater Model Report.
<br /> CDM-Smith, December 6, 2006. SPDSS Phase 3 Task 34.3 South Platte Alluvium Region Aquifer
<br /> Property Technical Memoradum.
<br /> CDM-Smith, June 9, 2006. SPDSS Phase 3, Task 34.3 Streambed Conductance Technical Memoradum.
<br /> Colorado Division of Water Resources(CDWR), June, 2019. Well permit websit search:
<br /> httl2://www.dwr.state.co.us/WeIlPermitSearch/
<br /> Cesare, Inc., May 2, 2019. Preliminary Materials Study—Fair Meadows Mine Permitting Monitoring
<br /> Well Installation Weld County, Co. Project No. 19.3016. Letter report to J.C. York, J&T Consulting, Inc.
<br /> Colorado State University (CSU), December, 31, 2013. HB12-1278 Study of the South Platte River
<br /> Alluvial Aquifer. Report to the Colorado Legislature.
<br /> Haneberg, August, 2006. Effects of Digital Elevation Model Erros on Spatially Distributed Seismic Slope
<br /> Stability Calculations: An Example from Seattle, Wa. Environmental & Engineering Geoscience, Vol.
<br /> XII, no. 3,August, 2006,pp. 247-260.
<br /> Hurr,R.Theodore, Schneider,Paul A.,and Others, 1972. Hydro eg ologic Characteristics of the Valley-Fill
<br /> Aquifer in the Greeley Reach of the South Platte River Valley, Colorado. USGS Open File Report 93-124.
<br /> Prepared in cooperation with the Colorado Water Conservation Board.
<br /> Lindsay,D.A.,Langer,W.H.,and Knepper,D.H.,2005.Stratig_raphy,Lithology,and Sedimentary Features
<br /> of Quaterna!y Alluvial Deposits of the South Platte River and Some of its Tributaries East of the Front
<br /> Range, Colorado. U.S. Geological Survey Professional Paper 1705.
<br /> Lindsey,D.A.,Langer,W.H.,and Shary,J.F., 1998,Gravel deposits of the South Platte River valley north
<br /> of Denver Colorado Part B-Quality of gravel deposits for aggregate:U. S.Geological Survey Open-File
<br /> Report 98-148-B, 24 p.
<br /> McGrane Water Engineering, LLC
<br /> 1669 Apple Valley Rd. *Lyons,CO 80540 •Phone:(303)917-1247
<br /> E-Mail:dennis@mcgranewater.com Web:ttp://www.mcgranewaterengineering.com
<br />
|