Laserfiche WebLink
<br />",,"' i;!N not, <br /> <br />001033 <br /> <br />POTENTIAL GEOLOGIC HAZARDS <br /> <br />""-""\ <br />, <br />, <br /> <br />The size. shape, and distribution of the four major earthflows and <br /> <br /> <br />their relationship to the highways. railroad, and river are indicated on <br /> <br /> <br />Map 1, Since 1975 when the maps were drawn, some enlargement of the <br /> <br />slide masses could be expected. Whiskey Creek, the largest earthflow. is <br /> <br /> <br />approximately 2,5 miles long with a vertical height of 2.100 feet and an <br /> <br />areal extent of approximately 600 acres with an average slope of 17 <br /> <br />percent. If it averages 50 feet in depth (a, conservative estimate). it <br /> <br />contains over 48 million cubic yards of material, If it averages a more <br /> <br />probable 100 feet of depth, it contains some 97 million cubic yards, For <br /> <br />comparison the Thistle slide was 1.5 miles long, 1.600 feet (lastest maps <br /> <br />indicate 1.000 feet) in vertical height. and covered 90 acres with an <br /> <br />average slope of 17 percent. More complete estimates and calculations of <br /> <br />the four earthflows and comparison with Thistle are included in Table 2, <br /> <br />..; <br /> <br />Site evaluations indicate that a prehistoric slide may have dammed <br /> <br />the Eagle River. Since the Eagle River Valley at Dowds Junction is <br /> <br />narrow. a relatively small amount of material could dam the river, Test <br /> <br />-, holes will be drilled in the next few weeks to determine earthflow <br /> <br />depths; however. enough material could be released to form a 100 to 200 <br /> <br />feet high dam, The factors affecting the impacts would be the rate of <br /> <br />slide movement and the rate of stream inflow if a dam is formed. <br /> <br />The possible scenarios could be characterized by level of effort <br /> <br />required by Highway. local and state agencies as follows: <br /> <br />Scenario 1 - <br /> <br />.continuous but slow moving soil which would require <br /> <br />highway equipment on-site at all times to clear <br /> <br />Highway 24. <br /> <br />Scenario 2 - <br /> <br />A large volume of material making removal impossible <br /> <br />resulting in the closure of Highway 24 and rerouting <br /> <br />of traffic across the river to the county dirt road, <br /> <br />The bridge over the Eagle River can handle the legal <br /> <br />load but needs surface repair, Vehicle length may be <br /> <br />a problem on some curves, <br />