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pipe crosses a terrace is bermed to provide at least two feet of protective cover over the <br />pipe. The berm over the letdown pipe is sloped so that stormwater runoff flows to the <br />riser inlets. <br />Initial closure phase letdown pipes will be installed to the 55 -foot terrace. The end of <br />the 24 -inch diameter HDPE letdown pipe will have an end cap to cover the upslope <br />pipe end. Future extension is accomplished by fuse -welding an additional section of <br />pipe to the next terrace. <br />Maintenance Procedures for Segment 1, Infill and Segment 2 Letdown Structures <br />To ensure proper performance, the stormwater letdown systems for the Segment <br />1/Segment 2 mound must be inspected at least on a quarterly basis and after each major <br />stormwater event (greater than three inches). <br />The letdowns on the northwest and southwest corner of Segment 1 are open flumes. <br />These flumes and the uniform section mat channels which convey stormwater should <br />be inspected for debris, possible blockage, and cracking. If debris which impedes flow <br />is located, it should be removed promptly. If the uniform section mat is damaged, it <br />should be grouted and repaired, or a new section should be "pieced" in. It is very <br />important to check the uniform section mat conveyance system for undermining and <br />erosion. Special attention should be given to the junction of terrace lateral ditches and <br />the letdown channel, and to the terminal end of the letdown at the perimeter ditch. <br />The Segment 2 letdown system and the infill segment letdowns use the same closed <br />pipe design. The entrance aprons to the riser inlets should be checked regularly for <br />744:4 'n kt7. isi�v}a1 IT Y t <br />F-31 <br />