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geo-membrane liner to reduce seepage losses. Interior pond slopes will be graded at 3:1 <br />(horizontal: vertical) and exterior embankment slopes will be graded at 2.5:1 <br />(horizontal: vertical) or flatter. <br />The location of stormwater diversion channels around the West Pond are shown on <br />Figure 4. Channel segments 20 and 21 are existing channel segments that intercept <br />upland runoff from the hill slope north of the pond and divert it to the existing stormwater <br />detention basin in the West Pit Area. These 2 channel segments will remain in place and <br />not be disturbed by construction of the West Pond, however the capacity will be <br />increased due to the additional freeboard provided by construction of the perimeter berm <br />around the north side of the West Pond. A southern diversion channel, Segment 23, will <br />be constructed as a contact channel between the berm fill and the hill slope to the south of <br />the West Pond. Channel dimensions, bed slopes, and estimated peak flow depths and <br />velocities during the design storm event are included in Table 7. With the exception of <br />Segment 21, flow velocities during the design storm event are low enough that erosion <br />protection is not required. Channel Segment 21 is an existing channel and is riprap lined. <br />C.3.2.3 East Pond <br />The East Pond will also be constructed by excavating into the existing pit backfill, and <br />constructing a perimeter berm as shown in Figure G.2-5. A 10-foot high perimeter berm <br />will also be contructed around the East Pond, resulting in a non jurisdictional <br />impoundment according to SEO criteria. The East Pond will also be lined with a <br />synthetic geo-membrane. Interior pond slopes will be graded at 3:1 (horizontal: vertical) <br />and exterior embankment slopes will be graded at 2.5:1 (horizontal: vertical) or flatter. <br />The stormwater diversion around the East Pond will require construction of two <br />additional segments of stormwater channel, Segments 19 and 22, located as shown on <br />Figure 4. These channel segments route water from the Waste Rock C diversion <br />channels around the East Pond, as well as minor additional upland runoff from the hill <br />slopes north and east of the pond. These segments will be constructed as contact <br />channels between the embankment fill and the adjacent hill slopes. Channel dimensions, <br />bed slopes, and estimated peak flow depths and velocities during the design storm event <br />are included in Table 7. Peak flow velocities during the design storm event are low