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J R ' Mr. David Nettles, PE <br />Re: Request for approval of Wellington Downs Reservoir Liner <br />May 24, 2005 <br />Page 2 of 3 <br />station allowed verification of the rain gage data. According to the rain gage, a total of 3.10 <br />inches of precipitation fell during the test period. <br />On April 30, 2005, the Arthur Lateral Ditch, adjacent to the Wellington Downs site, was turned <br />on and resulted in the ditch overtopping. Water from the ditch flowed into the Wellington <br />Downs Reservoir from the top of the embankment (see attached pictures). The ditch ran for <br />approximately two days before it was turned off. We notified you at this time via email. With <br />three days remaining in the leak test, it was decided to perform the leakage calculations prior to <br />trying to calculate the amount of water that spilled into the test area. The amount of water <br />entering the pit did not appear excessive and did not result in exceeding the performance <br />standard set by the state. <br />The data used to determine the size of the reservoir to determine allowable seepage was taken <br />from survey data received from Connell Resources on January 6, 2005. <br />Calculations <br />A simple mass balance equation was used to calculate the seepage in the Wellington Downs <br />Reservoir. The precipitation was considered inflow. The water was not pumped from the <br />reservoir; therefore evaporation was considered outflow in the calculation. The initial volume <br />was 0.300 ac-ft; hence, the total amount of seepage is equal to the final volume plus the <br />precipitation less the evaporation and initial volume. <br />Evaporation data for the site was somewhat problematic to obtain. The records for pan <br />evaporation data collected by the Colorado Climate Center at Colorado State University started <br />in March. They were only able to supply us with records from March through May. The reason <br />these records are not collected is that evaporation rates drop dramatically in the winter months. <br />A conservative assumption was made to assume negligible evaporation during the month of <br />February. If the calculated seepage is still well below the State Engineer standards, then it would <br />conclusively prove that the pit was performing properly, even with a lack of official records. <br />The allowable seepage according to state guidelines is 42.19 acre-feet. This number was <br />determined using the following~rocedure. The total wall azea (94,440 ftz) is multiplied by the <br />allowable wall seepage ((0.03 ft /day/ft2)/43560 ft3/acre) multiplied by the number of days of the <br />test (90). This number (5.85 acre-feet) is added to the result of the reservoir floor surface area <br />(60.80 acres) multiplied by the number of days of the test (90) multiplied by the allowable floor <br />seepage (0.0015 ft /day/ftz). This results in a design standard of allowable seepage of 14.06 <br />acre-feet. The performance standard is three times the design standard. Therefore the <br />Wellington Downs Reservoir must not exceed 42.19 acre-feet of seepage during the 90 day test. <br />Results <br />The calculated seepage is 13.24 acre-feet over a 90 day period. Wellington Downs Reservoir <br />met the design and performance standazds set by the State Engineer. Therefore, we respectfully <br />request that the Wellington Downs Reservoir be approved by the State Engineers Office as <br />having met the Guidelines for Lining Criteria for Gravel Pits. <br />