Laserfiche WebLink
REGENED <br />APR 2 p 1999'/ <br />piviswn of Mmet~s & <br />to L1~Qa <br />F~° TTACHMENT 1 _ <br />A <br />• 'o: l~r't(r <br />FRom : Q,.,,ci~ ~ caw 56~~ <br />POND INFORMATION <br />The new 1-acre stormwater retention pond (Piceance stormwater retention pond) will <br />be located adjacent to the Piceance evaporation pond, as shown in Figure 1. Amore <br />detailed plan view of the Piceance stormwater retention pond is given in Figure 2. <br />Construction of the Piceance stormwater retention pond will involve approximately 1.6 <br />acres of disturbed surface area. Figures 3 provides a cross section of the pond. <br />Additional information on this pond is summarized in the following table. <br />Piceance stormwater Retention Pond Information <br />Surface Area 1 acre <br />Disturbed Area 1.6 acres <br />Berm Height 9 to 12 feet <br />Berm Side Slope 2 horizontal to 1 vertical *" <br />Volume Approximately 250,000 ft' <br />Freeboard I foot minimum <br />Overflow Provisions Sump area equipped with pump for water sampling and <br />discharge to spillway. Spillway is constructed with rip rap <br />materials and is located 1 foot below top of berm. <br />Liner 60 mil HDPE **" <br />' Berm will be constructed according to Kvaerner Metals General Specification GC-Ol Site Work <br />(copy cndosed). <br />'• Side slope requirements were determined by geotechnical engineering study (copy enclosed). <br />•••Liner will be installed according to Kvaerner Metals General Specification GC-18 Geosynthetic <br />Liner (copy enclosed). <br />The Piceance stormwater retention pond was sized by Kvaerner Metals using the <br />volume requirements summarized below: <br />100-year, 24-hour storm precipitation = 2.6 inches <br />Area of Piceance Site initial processing facility = 7 acres <br />Runoff factor = 0.75 <br />Safety Factor = 50'% <br />Precipitation Retention volume <br />(2.6/12 feet) x (7acres) x (43,560 ft=/acre) x (0.75) x (150°/~) = 74,325 ft' <br />Emergency retention volume =volume of largest on-site storage tank <br />(in case of rupture) <br />= 1,265,000 ~al <br />= 169,118 ft' <br />Total required retention volume = 74,325 ft' + 169,118 ft' = 243,443 ft' <br />Calculations of the pond design volume, performed by Kvaerner Metals, are enclosed. <br />