WSP05020

• 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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The data indicate that in general four distinct types of material were pene-

trated by the seismic waves in the study area and can be described as follows:

An upper mantle of low density material corresponding to the sandy silt from
ground level to a depth of 10-20 ft, with a velocity of less than 100 fps. A
velocity of 610 fps as defined by the two 25-ft offset shot points was used for
this material in all calculations.

The data indicate gravel from 10-20 to + 185 ft. This gravel can be subdivided

generally into a less dense type with a velocity of about 3000-5000 fps and a
denser type probably containing large boulders with a velocity of from 5000-7500

fps. The dividing line between these gravels is by no means constant and is

sometimes nonexistent, as in some cases either high or low velocity gravel is

absent. There also exists the possibility that the higher velocity material is

not a boulder strewn gravel but highly weathered bedrock, although this is un-
likely, or a mud flow deposit such as can be seen in road cuts upstream along the

White River.

Bedrock, which from outcrops appears to be red sandstone of the Maroon Forma-
tion striking NE and dipping 30NW, is characterized by velocities above 8,500

fps generally in the 12,000-17,000 fps range. The upper contact with bedrock

ranged from a depth of 84 ft at the east end of line No.3 to +185 ft at the

west end of line No. 11.

A composite drawing is attached showing site topography, geologic contacts,
drill holes, and locations of geophone lines and shot points. Top of rock con-

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