WSP11936

• File Number: 8276.500
• Description: Glenwood-Dotsero Springs Unit - Salinity Control Projects
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1983
• Author: Golder Associates
• Title: Geology Working Paper for the Contour Ponds Site Near Mack, Colorado
• Water Supply Pro - Doc Type: Report/Study

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'C.) 'packer tests were performed in the Mancos shale at depths ranging
from 11 to 56 feet below the ground surface. In general, the
rock quality (RQD) was poor across the site at these depths and
permeability within the Mancos was generally high, averaging 1.4
x 10-4 em/see (0.2 in/hr). This average is from permeabilities
that ranged from 1 x 10-3 to 1.4 x 10-7 cm/sec (1.4 in/hr to
2 x 10-4 in/hr). Consistently lower permeabilities were reported
at boreholes C-13, C-15, C-18, and C-19. In each of these areas
. bedrock was relatively shallow and the RQD of the rock was more
consistent with depth and generally higher.

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A detailed summary of all the permeability test results are
provided on the borehole logs and in Table A-2, both in
Appendix A.

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5.2 Recompacted Properties

Bulk samples of both the pediment and residual soils were
obtained during the field investigation so that the recompacted
properties of these materials could be evaluated. Of primary
concern is the permeability of the on-site soils when used as a
compacted clay liner, as well as the potential for these
materials to shrink when exposed or disperse when wetted.
Therefore, the following tests were performed on samples of
pediment soils obtained from borehole locations C-4, C-17, and
EP-1 and residual soils obtained from borehole locations C-13,
C-18, and EP-2:

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o Atterberg and Shrinkage Limits.
o X-Ray Diffraction
o Compaction
o Consolidation-Swell (EP-1, EP-2, C-18, and C-13 only)
o Constant Head Permeability
o Pinhole Dispersion

The results of the Atterberg Limit, Shrinkage Limit, X-ray
diffraction, and consolidation-swell tests are summarized in
Table 5-1. The results show that all the soils are relatively
inactive since they all have low liquid limits and plasticity
indices; their shrinkage limits are close or equal to their
plastic limits; they are comprised of only minor amounts of clay;
and they generally swelled less than 1% upon inundation.

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