Laserfiche WebLink
elevation of approximately 7,000 feet) the trench was extended down the <br />face of the embankment, and an 6-inch diameter plastic corrugated pipe <br />extension was fitted to the end of the straight barrel pipe. Trench <br />material also was compacted around this extension pipe. The extension pipe <br />has an outlet elevation of 7,001.0 feet. Exhibit 7-17E, Pond 008 Principal <br />Spillway Replacement As-Built, presents the as-built configuration <br />following the principal spillway replacement. It should be noted that the <br />replacement of the principal spillway did not affect or include the <br />existing emergency spillway. <br />An as-built survey was completed in September 2005. Using the as-built <br />survey data, SE DCAD4 was used to check the as-built configuration with the <br />new principal spillway and show that the pond will meet or exceed the <br />CDMG's performance requirements. The survey indicates a permanent pool <br />elevation is 7,015.3 ft, with a storage capacity of 6.7 acre-feet (ac-ft). <br />The SE DCAD4 modeling indicates that runoff volume and peak inflow for the <br />10-year, 24-hour storm event (see Addendum 7-6f.3A are 1.29 acre-feet (ac- <br />ft) and 3.03 cubic feet per second (cfs), respectively, with a calculated <br />peak stage of 7,015.7 feet. The corresponding peak discharge from the 10- <br />year, 29-hour storm event was calculated as 0.99 cfs. The SEDDCAD9 results <br />also indicate he average settleable solids concentration in the pond <br />discharge during the peak 29-hour period will be 0.0 milliliters per liter <br />{ml/1). The Water Quality Control Commission (WQCC) settleable solids <br />effluent concentration limit is 0.5 ml/1. The SEDCAD9 modeling <br />demonstrates there is sufficient storage capacity available, and that the <br />settleable solids effluent concentration is less than the applicable water <br />quality standard. Therefore, Pond 008 as constructed and operated meets <br />the intentions of Rule 9.05.6(3)(a). <br />The calculated peak stage from the 10-year, 29-hour storm event is 7,OI5.7 <br />feet. This elevation is 1.2 feet below the emergency spillway invert <br />elevation (7,016.9 feet). This demonstrates that no flow will pass through <br />the emergency spillway during the 10-year, 24-hour storm event. Therefore, <br />the pond as constructed and operated meets the intentions of Rule <br />9.05.9(2)(b). <br />The modeled 25-year, 24-hour storm event peak inflow is 19.57 cfs, while <br />the calculated peak discharge is 5.98 cfs, with a corresponding peak stage <br />of 7,017.1 feet (see Addendum 7-6f.3B). The emergency spillway <br />configuration was checked using the SEDCAD9 Channel Utility (see Addendum <br />TR-37 3 Revised 10/05 <br />