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44 D15 (filter) (2) 5 ~ 015 (base) ~ 40 D15 (filter) (3) D65 (base) ~ 5. If a plastic filter cloth is used, care must be taken not to puncture the cloth when the ciprap is placed. It would be a good practice to place a layer of gravel over the cloth before placing the ciprap. All ciprap must be made of durable rock that will not be destroyed by the flows. Since the culverts were sized assuming no tailwater effects from the down- stream channel, they must be constructed so this is true. The channel im- L mediately below the culvert outlets must be prctected from the high velocities created in the culverts. Additional protection or energy dissipators must be ~' added if the culverts plunge into the channel. The inclusion of trash racks • was not considered. AL1 culverts have straight sections and can be cleaned. • The addition of trash racks would just increase the likelihood of clogging and also reduce the culvert capacities. 6.3 Sediment Pond Evaluation and Desi Sediment ponds are required to store runoff from disturbed areas and reclaimed/revegetated areas until the sediment runoff is equivalent to natural conditions. The regulations require design of sediment ponds for the runoff volume from a 10-year, 24-hour precipitation event and the emergency spillray must be designed to handle the peak discharge from a 25-year, 24-hour precipi- tation event. The proposed G.E.C. mine plan incorporates four existing sediment ponds and four proposed sediment ponds (see Hydrology Map 2, Appendix A). The present progress of mining has eliminated the storage area above Sediment Pond "D" and only the pond embankment exists. Proposed Sediment Pond "E" is located such that it will intercept the runoff from the entire Magpie Creek drainage and relocation of this sediment pond is recommended. The adequacy of the existing and proposed sediment pond designs are determined considering both snowmelt and rainfall precipitation events.