Laserfiche WebLink
The embankment portion of the emergency spillway consists of a trapezoidal <br /> channel as shown on Exhibit 13-9A. The emergency spillway outflow channel <br /> consists of a riprapped trapezoidal channel which was underlain wi th Mirafi <br /> 600X geo textile. Assuming the principal spillway was plugged, the emergency <br /> spillway is constructed to safely pass the runoff volume from the 100-year, <br /> 29-hour storm (see Addendum 13-3A-C). The 100-year, 26-hour event was used <br /> because Pond 10 meets the criteria of Rule 4.05.9(4). The channel design in <br /> Addendum 13-3A-D shows that the emergency spillway can safely pass the peak <br /> runoff from a design storm of this magnitude. <br />Summary <br />The capacity of Pond 010 is attributed partially to the embankment and <br />partially to the pond excavation. During passage of the 10-year, 29-hour <br />storm the discharge through the principal spillway meets effluent <br />limitations. In addition, there is no flow through the emergency spillway. <br />The emergency spillway is designed and constructed to safely discharge the <br />100-year, 24-hour storm event. <br />The embankment was constructed to be stable and provide adequate freeboard. <br />Therefore, based on the design, this structure complies with the appropriate <br />rules and regulations for a sedimentation structure. A toe drain and <br />. horizontal discharge system were constructed to collect any seepage and <br />discharge below the embankment. Seneca Coal Company will periodically <br />inspect the structure for sediment storage, structural integrity, and <br />hazardous conditions. Maintenance or remedial work will be performed in <br />accordance with the approved mine permit. <br />Construction Summary <br />The earthen impoundment and spillway configurations are pre-existing. The <br />construction of Pond 010 was supervised on site by Mr. Chuck McCulloch, <br />Senior Engineer - Operations, at the Yoast Mine. Mr. McCulloch assured all <br />work was performed in accordance with the design and specifications. Mr. <br />Altavilla generally inspected the structure daily during its construction to <br />verify the pond's conditions during construction and upon completion for the <br />as-built. The geotechnical consultant, Northwest Colorado Consultants, Inc. <br />(NWCC) was also on site daily to do compaction testing, soil analysis, etc. <br />Mr. Brian Len, P.E. (of NWCC), was on site on three separate occasions during <br />the construction of the pond. NWCC's summary report for this project is <br />located in Addendum 13-3A-E. Pond 010 was constructed as shown on Exhibit <br />13-4A, As-Built Pond 010 and originally certified by Michael G. Altavilla, a <br />registered professional engineer in the State of Colorado experienced in the <br />design and construction of earthen impoundments <br />TR-30 13-3A.5 Revised 05/07 <br />