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Ms.Ioana Comaniciu <br /> RE:SerFer Pit Lining <br /> May 20, 2015 <br /> Page 2 of 3 <br /> 40.45°, Lon: W 104.96°, and Elevation: 4,975 ft. The Highpointe Estates weather station is <br /> located at Lat: N 40.46°, Lon: W 104.95°, and Elevation: 4,955 ft. The source for this data is <br /> http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KCOWINDS9 and <br /> http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KCOWINDS3, <br /> respectively. The on-site rain gage data was used in calculating precipitation during this time; the <br /> weather stations allowed verification of the rain gage data. During the 91-day period a total of <br /> 4.64-in of precipitation was measured onsite. Rain was measured directly in the rain gage. Snow <br /> was melted with a known volume of hot water, which was subtracted from the total volume of <br /> melted snow plus added water in the rain gage, and the water content of the snow was recorded <br /> as precipitation in inches. A contributing area of 32.8 acres was used to calculate the volume of <br /> runoff into the test area, assuming a runoff ratio of 30%, the volume of water entering the test <br /> area was calculated to be 4.85 acre-ft. <br /> • <br /> Evaporation was calculated based on the guidance provided in the Colorado Department of <br /> Natural Resources, Division of Water Resources "General Guidelines for Substitute Water <br /> Supply Plans for Sand and Gravel Pits" (Guidelines). Map 3 in NOAA TR33 was used to <br /> estimate a total of 40 inches of annual evaporation for the project site. That annual evaporation <br /> was reduced for each month by the relative distribution recommended in section 11 of the <br /> Guidelines, and then reduced to a daily value. <br /> The seepage for the first phase of the testing was calculated to be 9.23 acre-feet. The seepage for <br /> the second phase of the testing was calculated to be -1.19 acre-feet. The negative number is <br /> indication that less water ran off into the test area than was allowed for in our calculations, and <br /> should be considered as zero rather than negative for the purposes of this study. The total <br /> infiltration for the 91-day period was 9.37 acre-feet. <br /> The allowable seepage for the reservoir was determined using the following procedure: The total <br /> wall area was multiplied by the allowable wall seepage ((0.03 ft3/day/ft2) /43560 ft3/acre) <br /> multiplied by the number of days of the test (91). This number is added to the result of the <br /> reservoir floor surface area, within the repair area multiplied by the number of days of the test <br /> (91) multiplied by the allowable floor seepage ((0.0015 ft3/day/ft2)/43560 ft3/acre). The <br /> performance standard is three times the design standard. The allowable seepage for the design <br /> and performance standard was calculated and compared to the seepage calculated through the <br /> mass balance equation. The surface area of the floor was 576,657 ft-. The allowable seepage <br /> volume through the floor is calculated to be 1.81 acre-ft. The 3-D surface area of the reservoir <br /> walls was 206,205 ft2. The allowable seepage volume through the wall is calculated to be 12.92 <br /> acre-ft. The calculated total allowable seepage for the design standard is 14.73 acre-ft, and the <br /> calculated total allowable seepage for the performance standard is 44.19 acre-ft. The allowable <br /> seepage for the 66-day first phase of the study was calculated to be 10.68 acre-ft for the design <br /> standard and 32.05 acre-ft for the performance standard. The reservoir performed within the <br /> design standard for seepage into a reservoir for each individual phase of the study as well as the <br /> entire study. A copy of the calculations is included as an attachment to this letter. <br />