Laserfiche WebLink
<br />within the sediment control structure. Principle spillways of <br />these control structures consist of a 24" CMP with a perforated <br />riser. A perforated riser is a 24" CMP with approximately 1" <br />diameter holes on 6" centers throughout its length. The top of <br />which is located .1 feet below the elevation of the emergency <br />spillway. The emergency spillways are designed utilizing the <br />Manning Equation for the peak flow value determined for a 25-year <br />24-hour precipitation event. In addition, 1 foot of free board is <br />added to the elevation of the emergency spillway when discharging <br />the peak flow of a 25-year 24-hour event to determine the elevation <br />of the top of the settled structure. Five precept has been added <br />to the total embankment height to allow for settling after construc- <br />tion, Table 2.05.7, Sediment Pond Data - Constructed Size. Design <br />•calculations are located within Exhibit 1. Atypical cross section <br />of a sediment control structure is located on Figure 2.05-5. Table <br />2.05-8 also shows the critical design values to be utilized by the <br />• mine personnel for the construction of these embankments. <br />Diversion Ditches A and B have been designed utilizing a 2-year <br />24-hour precipitation event to determine the peak flows anticipated <br />for drainage areas. These structures will be constructed prior to <br />any surface disturbance by mining operations. <br />GEC Minerals, Inc. plans to utilize crawler tractors, scrapers, <br />motor graders and water trucks supervised by experienced personnel <br />to ensure that these surface water control structures are constructed <br />in accordance with the applicable permanent Performance Standards of <br />the Rules and Regulations. Each of these structures has been designed <br />with regard to meeting the Performance Standards with each constructed <br />structure at its critical pre-planned location, to ensure that mining <br />can continue in an environmentally sound and safe manner. <br />All existing water control structures have been designed and <br />• constructed with respect to meeting or exceeding the Performance <br />2.05-13 <br />