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WSP05020
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Last modified
1/26/2010 2:16:36 PM
Creation date
10/12/2006 12:47:52 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.131.J
Description
Yellow Jacket Project
State
CO
Basin
Yampa/White
Water Division
6
Date
9/13/1982
Title
Yellow Jacket Project Study for the CWCB: Avery Dam-Seismic Refraction Study
Water Supply Pro - Doc Type
Report/Study
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<br />C> <br />J:> <br />M <br />OJ tours drawn from results of the seismic refraction study are superimposed <br />on the plan. Two geologic sections based on the seismic data are also <br /> <br />shown. <br /> <br />CONCLUSIONS <br /> <br />The seismic refraction survey not only confirmed the depth of terrace allu- <br /> <br />vium overlying bedrock to be + 100 ft on the left abutment at Avery Dam <br />site, but determined that in general the alluvium is much deeper, possibly <br />exceeding 185 ft at the north east end of the abutment plateau. The top of <br /> <br />rock does in fact occur at normally higher elevations to the south, but only <br />along a narrow rib trending north-east exposed in the road cut. This exposure <br />disappears to the east at the fork in the road to the Lake Avery recreation <br />area and is replaced with what appears to be a gravel filled paleo-channel <br /> <br />hundreds of feet wid~ The unusually deep, for the small drainage area, <br /> <br />southerly trending gully bisecting the left abutment plateau, is apparently <br /> <br />caused by erosion of another gravel-filled channel. The southwestern end of <br />the left abutment also appears to be an old channel. Therefore, the plateau <br /> <br />forming the left abutment would seem to be the remnants of an ancient oxbow <br />of the White River bordered on the south east by sliver-shaped outlier of <br />sandstone that once formed the left bank of the river. This elongated rock <br />outcrop was dissected in several places in the past by the meandering river. <br /> <br />The existence of 100 to 200 ft of gravel strewn with large boulders for a <br /> <br />distance of about 3000 ft along the left abutment at Avery Dam makes con- <br /> <br />struction of a positive cutoff uneconomical. However, the occurrence of the <br /> <br />upper layer of sandy silt overlying the gravel would indicate a design that <br /> <br />utilizes this material as an upstream impervious blanket. This natural cover <br /> <br />, <br />, <br />, <br />L <br />'" <br />f <br /> <br />would have to be extended in the form of an impervious layer, upstream to <br /> <br />," <br />f <br />, <br />
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