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<br />U". 1)~' 5 ". ! <br />'ul J't <br /> <br />Chapter 3 - Affected Environment and Environmental Consequences <br /> <br />In February and March 1988, movement of the landslide occurred again. No damage was done to <br />Reclamation facilities, but railroad traffic was disrupted as the tracks had to continually be <br />realigned. To halt the movement of the landslide, the Denver and Rio Grande Western Railroad, <br />owners of the railroad then, removed material from the top one-third of the slide and stockpiled it <br />just downstream of the slide. No evidence of further movement has been observed or reported <br />since this material was removed. <br /> <br /> <br />Figure 7 - Landslide location map <br /> <br />It is not known what triggered movement ofthis slide in 1950 and 1988. No clear correlation is <br />evident with high precipitation events. However, the entire area is over-steepened and in a state <br />of delicate balance. Long-term changes in moisture content within the slide mass, or removal of <br />supportive material at the toe may have contributed to the historic movement. <br /> <br />The stability of this landslide becomes an issue if the proposed fish passage significantly alters <br />river dynamics. The two basic concerns are: 1) potential erosion of the toe of the landslide <br />caused by increased flow velocities in the river, and 2) potential rise of the water table within the <br /> <br />32 <br />