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Ms. Ioana Comaniciu, P.E. <br /> June 22, 2015 <br /> Page 3 <br /> ■ Precipitation <br /> Direct precipitation falling on the site will be measured. Daily rainfall will be manually <br /> measured and recorded with an on-site rain gauge. Any snow fall depth will be measured <br /> and converted to an equivalent rainfall value based on local weather station data. i <br /> Precipitation will be incorporated into the water balance equation at a rate less than 100 <br /> percent based on an evaluation of the duration and frequency of precipitation events <br /> during the leak test period. <br /> ■ Pump Discharges <br /> i <br /> Figure 2 shows the approximate location of the dewatering sumps in the bottom of the <br /> Stagecoach Pit. The northeastern sump (Sump #1)will pump water via a pipeline with a <br /> totalizing flow meter to the recharge pond on an as need basis. A pump with a totalizing <br /> flow meter will be used to discharge seep water out of the pit from sump#2 to the South <br /> Platte River. Any water pumped from either sumps will be measured. The data will be <br /> used in the water balance equation for the leak test. <br /> ALLOWABLE LEAKAGE <br /> The allowable leakage rate conforming to the design standard criteria defined by the guidelines is <br /> 0.03 feet'/day/feet2 for the perimeter liner surrounding the reservoir and 0.0015 feet'/day/feet2 <br /> for the floor of the reservoir. The allowable leakage for design and performance standards has <br /> been calculated below. The allowable leakage for the Stagecoach Slurry Wall is based on the <br /> following dimensions: <br /> ■ Length of the as-constructed slurry wall is approximately 6,770 linear feet <br /> ■ The weighted average of the liner height is approximately 36.0 feet <br /> ■ The floor area of the pit is approximately 44.2 acres, or 1,924,868 feet2 <br /> Design Standard for Stagecoach Sluriw Wall <br /> Qdesign= Qdesign wall'+Qdesign floor <br /> Qdesign= (6,770 feet x 36.0 feet x 0.03 feet'/day/feetz) + <br /> (1,924,868 feeC x 0.0015 feet'/day/feet) <br /> Qdesign= 7,314 feet'/day+ 2,887 feet'/day= 10,201 feet'/day=53.0 gpm <br /> Performance Standard for Stagecoach Slurry Wall <br /> The performance standard is three times the design standard: <br /> Qperformance= 3 x 10,201 feet'/day=30,603 feet'/day <br /> Qperformance= 159.0 gpm <br /> I <br />