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INTRODUCTION <br />This exhibit contains the methodology and design calculations utilized <br />to redesign the drainage and sediment control structures associated with <br />the refuse disposal area. The design revisions address the necessary <br />modifications resulting from the refuse pile expansion. Specifically, <br />those structures which handle surface drainage from an area above the <br />refuse disposal area and from the crest and face of the disposal area <br />include: <br />- Permanent Diversion No. 1 <br />- Refuse Collection Ditches <br />- Sediment Pond No. 4 <br />Permanent Diversion No. 1 routes clean surface water from an area south <br />and west of the refuse pile to natural drainages. The refuse collection <br />ditches collect surface drainage from the refuse pile and route it to <br />Sediment Pond No. 4. The structure locations are shown on Figure 1, <br />Refuse Disposal Area Drainage Plan. <br />The refuse pile is designed with approximately 0.5 percent grade to the <br />northeast on the eastern half of the pile, a 3H:IV transition slope near <br />the center of the pile, and a four (4) percent grade to the northeast on <br />the western half of the pile, as shown on Figure 1, Refuse Disposal Area <br />Drainage Plan. Due to the pile's configuration, all surface runoff from <br />the expanded pile area continues to flow to the south refuse collection <br />ditch. All remaining collection ditches and diversions receive the same <br />flow as prior to the pile expansion. <br />The south refuse collection ditch is the only drainage structure which <br />requires design revisions. It will continue to collect surface runoff <br />from the southern slope of the pile. Flow rate and channel slope values <br />did not change substantially, thus, only minor channel configuration <br />revisions were necessary. <br />-1R- Revised - November, 1989 <br />