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Derr Pit - Groundwater Modeling Report <br />January 31, 2020 Page 7 of 24 <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 />Table 3 shows that if the Loloff, Derr and amendment area slurry walls are installed, then <br />thirteen (13) wells could expect water levels to increase or decrease at least +/- 0.5 feet compared <br />to predevelopment conditions. The maximum increase is approximately 3.2 ft at the Davis well <br />and maximum decrease is -2.1 ft at the Murata well. Table 3 also compares the modeled <br />drawdown from predevelopment conditions to actual based on January, 2020 data (discussed <br />below). <br />Table 3 - Change in Water Levels Caused by Loloff, Derr and Derr Amendment Slurry <br />Walls <br />Well Location Well Owner (type)Well <br />Permit <br />Depth <br />(ft) <br />Modeled <br />Predevelop- <br />ment Depth <br />to Water (ft) <br />Modeled <br />Change in <br />Water Levels <br />(ft) <br />Modeled <br />Predicted <br />Depth* (ft) <br />Depth to <br />Water (ft) <br />1/9/2020 <br />Current <br />Drawdown* <br />from <br />Predevelopment <br />Conditions (ft) <br />Koehler (Domestic)314643 52 40.5 2.7 37.8 48.7 -8.2 <br />Koehler (Stock)314644 52 39.2 2.6 36.6 47.7 -8.5 <br />Koehler (Irrigation)11564-R 110 41.1 0.5 40.6 50.2 -9.1 <br />Davis (Irrigation)14960-R 101 38.8 3.2 35.6 47.2 -8.4 <br />Parker (Domestic)44673 72 35.9 1.4 34.5 42.1 -6.2 <br />Harrell (Domestic)226878-A 50 10.1 0.7 9.4 10.7 -0.6 <br />Harrell (Irrigation)287278 30 11.3 0.9 10.4 10.1 1.2 <br />Hofner (Domestic)13200-F 95 36.1 1.2 34.9 45.1 -9.0 <br />Ruland (domestic)421-WCB 87 23.5* 1.5 22.0*ND ND <br />Taylor (Domestic)223885-A 44 9.9 -0.9 10.8 18.0 -8.1 <br />Murata (Domestic)246784 80 39.5 -2.1 41.6 49.2 -9.7 <br />Baab, A C (domestic)620-WCB 45 9.3*-1.0 10.3*ND ND <br />Orona (Domestic)28174 ND 11.3*-0.8 12.1*ND ND <br />Notes:ND = No Data <br />*Calculated based on DEM data ground elevations <br />Upgradient <br />Wells <br />Downgradient <br />Wells <br />Benefits of Slurry Walls Compared to Existing Conditions <br />The installation of slurry walls benefits existing well owners by allowing pumping to cease so <br />ground water levels can recover. Tables 2 and 3 also show current dewatering at impacted wells <br />on the right side of each table which was determined by subtracting the measured January, 2020 <br />water level depths from the modeled depths at predevelopment <br />conditions. The resulting current drawdown ranges from a positive 1.2 feet (mounding) at the <br />Harrell irrigation well to -9.7 feet at the Murata domestic well. <br />The current rise of 1.2 ft in the Harrell well is caused by the Loloff pit slurry wall as predicted by <br />earlier modeling of impacts caused by the Loloff pit slurry wall (MWE, 2015). The Loloff slurry <br />wall was expected to increase water levels approximately +1.5 ft at the Harrell well and cause a - <br />1.5 ft drop downgradient. Therefore, the existing maximum -9.7 ft “impact” caused by Derr pit <br />dewatering at the Murata well location is 7.6 ft more (9.7 - 2.1 ft) than what was predicted by <br />the model. Therefore, it would benefit Murata and all other vicinity well owners if BAI installs <br />the Derr pit slurry wall as soon as possible to allow water levels to recover to the Modeled <br />Predicted Depths shown in ables 2 and 3.