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were originally designed and constructed by Morrison-Knudsen Company in May 1980 for the <br />previous operator/permittee, H-G Coal Company. The ponds have been referred to as Truck <br />Loop Pondl (Pond "A", Outfall 006) and Rail Loop Pond2 (Pond "B", Outfall 007}. HGTI <br />identifies the ponds as Truck Loop Pond and Rail Loop Pond - the ponds are permitted by the <br />Colorado Water quality Control Division as industrial wastewater treatment facilities under <br />Permit No. COG-850008. Exhibit 12-2 shows locations and contributing drainage areas for <br />both ponds. <br />The Rail Loop Pond was modified in 1985. A permit revision was submitted (by the previous <br />operator/permittee) to replace the culvert spillway with a trapezoidal spillway constructed <br />of fabriform. Certification reports for this pond modification are presented in Appendix <br />12-1A, Pond Certifications. <br />The Truck Loop Pond was modified by the previous operator/permittee in June 1992. This <br />modification was performed to meet CDRMS regulations regarding separate pipe spillways. A <br />12-inch diameter culvert was installed above the existing 29-inch diameter culvert spillway. <br />Certification reports for this pond modification are presented in Appendix 12-LA, Pond <br />Certifications. <br />Capacity tables for the two ponds are shown on Exhibit 12-3 for the Truck Loop Pond and,. <br />Exhibit 12-9 for the Rail Loop Pond. Per Exhibit 12-3, the Truck Loop Pond has a current <br />storage capacity of 0.97 acre-feet at the principal spillway elevation (29-inch drop inlet <br />pipe), and 1.93 acre-feet at the invert of the emergency spillway (12-inch straight pipe). <br />As shown on Exhibit 12-9, the Rail Loop Pond has a current storage capacity of 1.89 acre- <br />feet at the invert of the combination principal and emergency (trapezoidal) spillway. <br />Area-stage information was compiled from an October 1992 aerial photography survey, a 1991 <br />sediment survey and, £or the Rail Loop Pond only, a 1997 as-built survey. Certification of <br />these as-built drawings is limited to storage capacities only and is not intended to verify <br />design and/or construction standards. Design and construction certifications were completed <br />by the previous operator/owner and are referenced above. <br />Truck Loop Pond <br />Appendix 12-1, Sediment Control and Pond Design, presents a SEDCAD 4 modeling demonstration <br />that shows the existing storage capacity (0.97 acre-feet) is adequate to detain runoff from <br />the truck dump watershed area generated by the 10-year, 29-hour storm event and, that the <br />as-built pond configuration meets the requirements of Rules 4.05.6 and 4.05.9. <br />MR-15 2 Revised 03/07 <br />