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nbc <br />NHC Fir. No. OOIOOQlu <br />September 11, 2018 <br />Kittitas County Public Works Department <br />411 N Ruby ST, Suite 1 <br />Ellensburg, WA <br />98926 <br />Attention: Mark Cook, F.E. <br />Public Works Director <br />Via emall: mark.cookgffico.kittitas.wa.us <br />Re: Proposed fLIdk Creek Realignment <br />Assessment of Potential Changes to Morphodynwrdc Processes in the Noah Fork of the <br />Teansway River <br />Draft Assessment <br />INTRODUCTION <br />Northwest Hydraulic Consultants, Inc. (NHC) has been requested to assist Witas County with the design <br />of a new water crossing to convey Lick Creek under the North Fork (NF) Teanaway Road. One alternative <br />for the new Lick Creek water crossing is to relocate the current crossing to the east, along with realigning <br />the channel downstream of the NF Teanaway Road. This proposed new channel would joln the NF of the <br />Teanaway Rimer, approximately 2,500 feet upstream of the current confluence location; Increasing flows <br />In the reach between the current confluence location and the proposed confluence location. This change <br />could lead to potential impacts to channel morphodynamics, Including channel morphology and <br />migration rates. <br />The purpose of this memo is to provide the results of a geomorphic analysis of the potential changes to <br />channel migration rates or processes in the NF of the Teanaway Riverthat might result from changing <br />the confluence location of Lids Creek. This is not a comprehensive Investigation of geomorphic <br />conditions or processes occurring in the subject reach, but rather a focused evaluation of the potential <br />sensitivity of the river to a small change In hydrology, The assessment was completed with limited <br />available information on channel hydrology and hydraulics and was based on the substantial <br />assumptions that were outlined in the scope of work for Modification Number 1 to Delivery Order <br />Number 2 (dated May 23„ 203,8) for the Kittitas County Teanaway Road Hydraulic Improvements Project. <br />Observations of the river and computations used to evaluate the magnitude of potential Impact are <br />summarized in the following sections. This assessment will provide Klttltas County with additional <br />Information to determine the feasibility of the project given other project constraints. NHC Is also <br />yri�rr rrsouer sp#catlF <br />