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~nnuary 7000 C}prur Twrnq~mile'PonrlG Ecalualion ~ <br />Pond G has a principal and emergency spillway. As-built information for the nvo spillways was <br />• obtained from the Epp survey conducted in 1996 and 1999 survey information provided by TCC <br />personnel. <br />The principal spillway consists of a 8.8 foot tall cmp riser and an accompanying cmp outlet. The riser <br />is 2 feet in diameter and the outlet is l.i feet in diameter The riser is perforated at nvo elevations <br />(6832.2 and 6830.2) with four 4-inch holes. Modeling shows [hat the principal spIDway w1ll safely pass <br />the peak Flow from the 10-year, 24-hour storm event, without discharging from the emergency <br />spillwa}'~ <br />The emergency spillway consist of a 20-foot wide trapezoidal channel with 3H:IV side slopes. <br />Modeling of Pond G for the 100-year, 24-hour storm event shows that the entire peak Flow will pass <br />through the nP nci~al s illwa without discharging through the emergency spillway. This is typical of <br />some older ponds that were designed for larger disturbance areas during raining. As a result, the <br />freeboard is 3.G feet. A summary of Pond G is presented on Table 1.5, Pond G Summary. <br />As shown on the SEDCr1D4 printouts, Pond G has a total volume (up to the invert of the emergency <br />spillway) of 41.2 acre-feet. <br />Pond G has been in eststence for many years and historical discharge monitoring data that has been <br />submitted to the Department shows that the pond is in compliance with water quaGry regulations. <br />The stntcmral nature of the Pond was not evaluated as put of this report <br />• <br />• <br />Montgomery \\~a tson Mwng Group' IG$ S. Union Boulevard, Suite X10' Lakewood, Colorado ft0228 " (303) 763 5140 <br />