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<br />~ <br /> <br />';,> <br /> <br />H. How will the project affect the environmental factors in F? <br />1. Physical Environment: <br />Although the Big Thompson Canyon is very scenic, none of the geologic condi. <br />tions noted within the project are of rare, unique or especially fragile, and none <br />have special cultural or academic value. The mica schists, gneisses, and granitic <br />rocks underlie (and are exposed across) many square miles, and are non.fossili- <br />ferous. <br /> <br />'d~ <br /> <br />The principal geology-related hazards include earthquakes (both ground motion <br /> <br />and ground displacement) and debris slides. The earthquake risk is judged to be <br /> <br />low even though a major fault, the Big Thompson, trends beneath the generat- <br /> <br />ing station site and neighbors the dam and reservoir site. This fault is a geologi- <br /> <br />cally ancient structure for which no evidence of recent movement has been <br /> <br />documented. If an earthquake were to occur sufficiently to destroy the dam, <br /> <br />the release of 85 acre feet of water would not cause damage or endanger lives <br /> <br />downstream. <br /> <br />There is no evidence of any archaeological sites within the Canyon. Therefore, <br />any excavation required should not present a hazard from an archaeological <br />point of view. Extreme caution will be exercised during excavating operations <br />to be alert for human and other remains which might be left as a result of the <br />flood. <br /> <br />Investigations have been unable to produce any historical resources within the <br />Canyon which are worthy of designation in the National Register of Historical <br />Places (Ref. 8 & 9). Most certainly Big Thompson Canyon has an interesting <br />history, but designation from a national standpoint does not seem warranted. <br /> <br />The reconstruction of the diversion dam will occur in precisely the same <br />location as before. The elevation of the spillway at 6024 will also coincide with <br />the elevation of the splash boards on the old dam. The resultant reservoir will <br />be at the same elevation and will be approximately the same size and configura- <br />tion as before. (Scouring action from the flood has slightly altered the river <br />bottom and the north bank at the site, but not significantly.) <br /> <br /> <br />,", <br /> <br />r <br /> <br />Prior to the flood the pipeline from the dam to Idlewild (approximately 3000 <br />feet) was layed on the surface of the river bank and rip-rapped with hand cut <br />stone resulting in an aesthetically pleasing and natural appearance. Approxi- <br /> <br />~;-:. <br /> <br />~ <br />i- . <br /> <br />19 <br />