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~i <br />Ms. Sandy Emrich <br />September 29, 1983 <br />• Page 3 <br />The drainage system will meet the 2-year, 24-hour precipitation <br />event. As discussed later, a diversion will be constructed to <br />reroute the overall drainage away from the channel bottom. This <br />diversion will be on the north side of the road. A small ditch <br />will be constructed on the south side to handle approximately <br />17 acres of runoff. <br />A 24" CMP wi1T be installed on the west end of the road to allow <br />the haul road drainage to pass under the scraper road. Due to <br />the temporary nature of this road this culvert will be designed <br />for the 2-year, 24-hour precipitation event. <br />(5) Surfacing <br />This road will not be surfaced. <br />(6) Maintenance <br />Normal maintenance procedures will be used for this type of <br />road. <br />(7) Reclamation <br />When no longer needed for its intended use this road will be re- <br />• claimed unless retention is requested by PCC and approved by CMLR. <br />4.05.3 Diversions and Conveyance of Overland Flow and Shallow Ground Water <br />Flow, and Ephermeral Streams Draining a Watershed Less Than One <br />Square Mile. <br />A temporary diversion will be constructed on the north side of <br />the access road. The diversion, as shown by the attached cal- <br />culations, has been designed at minimum standards (ie. maximum <br />acceptable velocity). This is due to the temporary nature of <br />the diversion and that a wider diversion ditch would cause <br />more disturbance which is unwarranted. If erosion becomes a <br />problem, riprap or straw dikes will be placed in the diversion. <br />Runoff will be handled by this diversion and conveyed through a <br />culvert under the haul road to a natural channel and end up in <br />the downstream pond as shown on Exhibit "12-1". <br />Should you have any further questions, please do not hesitate to call. <br />Sincerely, <br />Tom Wainwright <br />TW/dks <br />Attachments <br />cc: Curt Belden, w/o att. <br />Floyd Johnson, OSM, w/att. <br />Kelly Vote, w/o att. <br />Don Zulian, w/ att. <br />