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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />1.4 Spillway <br /> <br />The spillway is located in a natural low saddle at the northwest corner of the <br />reservoir. There are no man-made structures to control elevation or resi st <br />erosion. The channel downstream of the control point is very flat and heavily <br />forested with aspens and evergreens. It is doubtful that a large amounts of <br />flow could be discharged through the channel, especially considering the <br />driftwood debris that would accumulate between the trees should spilling occur. <br /> <br />1.5 Summary of Deficiencies <br /> <br />This section summarizes the technical deficiencies at Twin Lakes Oam, as noted <br />during the on-site inspections and from the review of project records. The <br />deficiencies are 1 isted in order of potential impact on the safety of the <br />existing structure. This prioritized list of deficiencies was used to lend <br />focus to the geotechnical evaluation and hydrologic analysis, and served as a <br />gUide for the development of rehabilitation alternatives. <br /> <br />o Severely deteriorated outlet works conduit and gate seat <br />o Potential instability of the oversteepened downstream slope. <br />o Uncontrolled embankment and foundation seepage. <br />o Inadequate spillway capacity to route the PMF. <br />o Absence of outlet energy dissipator structure. <br />o Heavily forested spillway channel that would severely restrict flow <br />during operation. <br />o Inadequate riprap slope protection. <br /> <br />2.0 GEOTECHNICAL EVALUATION <br /> <br />2.1 Field Investigation <br /> <br />2.1.1 General <br /> <br />The geotechni cal fi el d i nvesti gati ons at Twi n Lakes consi sted of surfi ci al <br />geologic mapping and subsurface exploration by means of bore holes, test pits <br /> <br />-45- <br />