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<br />HYDRAULIC ANALYSIS FOR RESTORED NEWLIN CREEK CHANNEL <br />I. INTRODUCTION <br />The design of restored Newlin Creek channel (Prospecting Pit) was pre- <br />sented in a report entitled "Backfilling/Reclamation Plan for the Prospecting <br />Pit Adequacy Review" dated January 15, 1981, by Simons, Li 6 Associates, Inc. <br />' The design recommended a channel with a 50-foot bottom width, 4-foot channel <br />depth, 4 to 1 side slope, and 4.3 percent channel slope to contain a 10-year, <br />24-hour peak runoff of 2278 cfs. A report entitled "Determination of <br />Hydrologic Consequences, G.E.C. Minerals, Inc." dated September 1981 was also <br />' prepared by Simons, Li & Associates, Inc. A detailed hydrologic analysis was <br />performed for the Prospecting Pit restored channel in the second report. The <br />10-year, 24-hour peak runoff was estimated to be 2325 cfs (Table 5, p. 21) and <br />the 100-year, 24-hour peak runoff was estimated to be 9789 cfs (Table 7, <br />p. 25). The restored Newlin Creek channel was designed with a 50-foot bottom <br />width, 4-foot channel depth, 4 to 1 side slope, and 4.9 percent channel slope <br />to contain the 10-year, 24-hour peak runoff. The overbank area was designed <br />for 10 to 1 side slope to contain the 100-year, 24-hour peak runoff. The <br />entire Newlin Creek channel and the 100-year floodplain overbank should be <br />protected with riprap. The detailed analysis and design were given in the <br />September 1981 report. <br />' The purpose of this analysis is to compare the as-built restored Newlin <br />Creek channel with the designed channel, address the differences between these <br />two channels, and perform hydraulic analysis to ensure the as-built channel <br />has the capacity to handle both the 10-year, 24-hour and 100-year, 24-hour <br />peak runoffs. <br />t <br />II. THE AS-BUILT CHANNEL <br />' An on-site investigation was conducted by staff of Simons, Li & <br />Associates, inc. on April 20, 1982. The restored Newlin Creek channel was <br />' approximately 40 percent completed at the time of the site visit. The channel <br />cross section was measured at a reach where riprap had not been installed. <br />' The measurements were taken along the gravel filter surface. The measured <br />cross section is given in Figure 1. The channel slope was estimated to be <br />between 3 to 4 percent. Riprap has been placed on top of sand and gravel <br />1 <br /> <br />