Laserfiche WebLink
elevation of approximately 7,000 feet) the trench was extended down the <br /> face of the embankment, and an B-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 ou tlet 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 r eplacement. It should be noted that the <br /> replaceme nt of the principal sp illway 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, SEDCAD4 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 />performance requirements. The survey indicates a permanent pool elevation <br />is 7,015.3 ft, with a storage capacity of 7.5 acre-feet (ac-ft). The <br />SEDCAD9 modeling indicates that runoff volume and peak inflow for the 10- <br />year, 29-hour storm event (see Addendum 7-6f.3A) are 2.38 acre-feet and <br />13.39 cubic feet per second (cfs), respectively, with a calculated peak <br />stage of 7,016.0 feet. The corresponding peak discharge from the 10-year, <br />29-hour storm event was calculated as 0.71 cfs. The SEDCAD4 results also <br />• indicate the average settleable solids concentration in the pond discharge <br />during the peak 29-hour period will be 0.0 milliliters per liter (ml/1) . <br />The Water Quality Control Commission (WQCC) settleable solids effluent <br />concentration limit is 0.5 ml/1. The SEDCAD4 modeling demonstrates there <br />is sufficient storage capacity available, and that the settleable solids <br />effluent concentration is less than the applicable water quality standard. <br />Therefore, Pond 008 as constructed and operated meets the intentions of <br />Rule 9.05.6(3)(a). <br />The calculated peak stage from the 10-year, 29-hour storm event is 7,016.0 <br />£eet. This elevation is 0.9 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 />4.05.9(2)(b). <br />The modeled 25-year, 29-hour storm event peak inflow is 38.96 cfs, while <br />the calculated peak discharge is 10.9 cfs, with a corresponding peak stage <br />of 7,017.2 feet (see Addendum 7-6f.3B). The emergency spillway <br />configuration was checked using the SEDCAD4 Channel Utility (see Addendum <br />TR-42 3 Revised 09/07 <br />