Laserfiche WebLink
Appendix K-5 <br />• and provided for the total storal;e of all accumulated storm water runoff originating above and <br />conveyed to this pond site. (In fact, there has been no reported spillway flow from the <br />pond facility since its original construction, circa 1980.) The1995 precipitation period is <br />discussed in detail in the CEC 1996 Annual Hydrology Report. <br />CEC implemented a dewatering scheme for Sediment Pond 2 in 1997, to be used on an as- <br />needed basis. If necessary, CEC personnel will pump excess runoff water accumulated in this <br />pond back to the Dugout Pond, which is located about 700 feet slightly upgradient and to the <br />south-southeast on CEC property. The Dugout Pond is designated as an on-site permanent <br />impoundment and has an available storage capacity that exceeds the total contributing runoff <br />volume associated with a 100-year, 24-hour design storm (refer to "Technical Revision <br />Drainage Control Plan II," dated January, 1995). A bank of pumps (maximum combined <br />sustained pumping rate of 1200 gallons per minute (gpm)) can be used to evacuate the <br />accumulated runoff water in Sediment Pond 2 back to the Dugout Pond within a maximum <br />time frame of 72 hours, thus meeting a reasonable evacuation time period for the Sediment <br />Pond 2 dewatering. Also, in this manner, CEC can maintain a continued lowered pond level <br />in Sediment Pond 2 during prolonged periods of excess rainfall and runoff on site such as was <br />experienced during 1995. <br />Since the sediment level in Sediment Pond 2 has been virtually non-existent to very little after <br />twelve years of use, and since this pond facility has never had any measurable water stored in <br />it for more than a 24-hour period, except during the unusual prolonged period of excess <br />precipitation events in 1995, and during which time period there was never any observed <br />spillway discharge, all previously existing man-made temporary pond sites have been removed <br />for CEC Plan purposes. The Dugout Pond, however, will remain as a permanent <br />impoundment in the post-closure period. Under the currently approved Permit, the Sediment <br />Pond 2 facility will be backfilled at site closure and reclaimed.. <br />• <br />3 <br />BE&K/TerraNext <br />