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CHAPTER 8. DAM FAILURE <br />8-5 <br />Name National <br />ID # Water Course Owner Year <br />Built <br />Dam <br />Typea <br />Crest <br />Length <br />(feet) <br />Height <br />(feet) <br />Surface <br />Area <br />(acres) <br />Drainage <br />area <br />(sq. mi.) <br />Hazard <br />Classb <br />Roza <br />Diversion <br />WA00275 Yakima River BOR 1939 CN, <br />PG <br />486 67 100 1,650 3 <br />Snoqualmie <br />Pass PUD- <br />Sewer Lagoon <br />#1 <br />WA00472 Tr-Lake <br />Keechelus- <br />Off-Stream <br />Wenatchee National <br />Forrest <br />1982 RE 1110 23 8.4 0.01 3 <br />Tjossem Pond WA01228 Wilson Creek- <br />Off-Stream <br />Morris P. Sorenson 1890 RE 154 12 7.8 0.01 3 <br />Twardoski <br />Dam <br />WA01991 Unnamed Tr – <br />Yakima River <br />Brian Twardoski 1980 RE 280 13 3 1.35 3 <br />Upper <br />Sunlight Lake <br />WA00666 Yakima River Sunlight Waters <br />Country Club <br />1967 RE 325 25 5 7.8 1C <br />a. RE = Earth Fill Dam; CN, PG = Concrete Gravity Dam <br />b. See Section 8.2.4 for definition of hazard classes <br />The DSO has prepared dam failure inundation mapping for the Hazard Class 1A and 1B dams. Individual <br />mapping was created for the Class 1A Cle Elum Dam (Figure 8-2) and Class 1B Easton Diversion Dam <br />(Figure 8-3). The DSO prepared a single inundation-area map for failure of the Class 1A Kachess and <br />Keechelus Dams (Figure 8-4). These inundation maps are used in the assessment of exposure and <br />vulnerability for the dam failure hazard. <br />The inundation areas for the Cle Elum Dam and the Kachees and Keechelus Dams would impact the <br />jurisdictions of Cle Elum, Ellensburg, and South Cle Elum. The Easton Diversion Dam inundation area <br />would also impact Cle Elum and South Cle Elum. All inundation areas impact areas of Unincorporated <br />Kittitas County. The Kachees and Keechelus Dam is estimated to have the largest impact on the planning <br />area. For more information on loss estimates, see Section 8.6.2.