Laserfiche WebLink
<br />UU33.::6 <br /> <br />Methodo logy <br /> <br />At the outset of this project considerable urgency was attached to making (~-" <br />a quick determination of the immediate potential of closure, because of <br />massive catastrophic landsliding, of 1-70, U,S. Highway 24, DRGWRR, and of <br />possible damming the Eagle River which could result in flooding to West Vail <br />and Minturn. Consequently we made a rapid field inspection of the apparently <br />active parts of all the landslides. What we found out, both initially and in <br />subsequent more detailed study is summarized below for each landslide area, <br /> <br />Meadow Mountain <br /> <br />( <br /> <br />The Meadow Mountain landslide, as generally outlined on the attached map, <br />is a compound slope-failure feature consisting of shallow to deep (up to 40 <br />ft) earthflows that occur on the surface of least three much deeper (90 to 160 <br />ft) translational landslides involving bedrock, These range in size from the <br />relatively small one affecting Highway 24, to the "intermediate" one extending <br />several hundred feet upslope and the remainder of the major feature, which is <br />probably made up of better stabilized older compound landslides covering more <br />than one half square mile, The most serious immediate threat to Highway 24 <br />and the Eagl e Ri ver Vall ey is from the "i ntermedi ate feature". It exhi bits <br />some surficial movement as shown by the EDM measurements (see attachment and <br />the data for EDM points la, 2a, 3a). It also lies immediately below a natural <br />bog or swamp area which becomes a small ephemeral pond during each snowmelt <br />season, Our initial assessment of the cause of landsliding in this area is <br />that seasonal groundwater surcharge from this ephemeral lake is very likely to <br />be a significant contributing cause, for movement of this landslide, It is <br />inconclusive whether movement of water from this landslide mass is directly <br />affecti.ng the more rapid movement of the smaller landslide adjacent to the <br />hi ghwayor not. However, it shoul d be noted that fi e 1 d observati on of <br />surface-water movement into earth cracks in both landslides in early May <br />correlates with the most rapid movement of the EDM points, This suggests, of <br />course, that removal or diversion of'water would slow or stop movement of <br />either landslide. Because of this we recommend that this pond be kept <br />drained, Local diversion of surface water was the approach used by CDOH to <br />attempt to slow movement of the small "highway" 1 andslide even before our <br />investigation began, <br /> <br />Because of the immediate concern for~valuating the possible loss of the <br />hi ghway and dammi ng of the Eagl e River, the fi rst work of instrumentati on of <br />the Meadow Mountain landslide ,consisted of installation of three EDM points at <br />the neadscarp oJ the "intermedJate". landslide, ,These were in a<!C!jtion to the <br />twelve EDM points <br /> <br />.. <br /> <br />- 4 - <br />