PUB00006

• Year: 2005
• Title: Colorado's Historic Water Projects
• CWCB Section: Administration
• Author: Applegate Group, Inc
• Description: A calender with pictures and descriptions of historic water projects.
• Publications - Doc Type: Historical

Peter E. Barkmann

properties of the stratigraphic layer made up of that litho-
logic material may result in different hydrologic properties
of that layer that actually affect the hydrodynamic charac-
teristics of the aquifer system. For example, there may be
crosscutting stratigraphic relationships with other facies in
the interval increasing hydraulic connection across layers
and therefore increase the overall vertical hydraulic con-
ductivity of the interval. Similarly, bioturbation or fractur-
ing from diagenesis could increase vertical hydraulic
conductivity of the interval on a scale larger than measured
by the small core sample size. There is also the possibility
of tectonic fracturing and faulting that should not be dis-
missed in a synorogenic basin. To date, faulting has not
been identified within the central portion of the Denver
Basin on a scale that could increase vertical hydraulic con-
ductivity across the confining layers, but the possibility
exists that tectonic fracturing is present.
Data from pumping tests conducted at multiple-aquifer
pump facilities in Parker during May and December 2000
indicate that, locally, there is little vertical connection
hetween the aquifers (Barkmann and Edington, 2001). Pro-
duction wells completed in one Denver Basin aquifer were
pumped while water levels in wells completed in the other
Denver Basin aquifers were monitored. Water levels in the
monitored wells did not decline during pumping of the
nearby wells where the dynamic water levels declined as
much as 200 ft in response to pumping for up to 48 hours.
Although these results apply to a short time period of
testing and are limited to a small geographic area, they do
indicate limited vertical hydraulic connection between the
aquifers consistent with very low hydraulic conductivity in
the separating shale intervals.
With the considerable variability observed in the results
of vertical hydraulic conductivity analyses on this limited
set of data points, what can be said about the amount of
vertical groundwater flow in the Denver Basin? These val-
ues provide a steppingstone in analyzing the system. They
give end values from which to begin asking questions and
with which to validate modeling efforts. Most importantly,
the data suggest that the vertical hydraulic connection
between the principal aquifers and within the aquifers may
be very limited, changing the concept of how the aquifer
system as a whole will behave as exploitation progresses.

RECOMMENDATIONS FOR ADDmONAL DATA
COllECTION

The limited set of data reviewed here certainly begs for
more research and, as always, additional raw data from a
wider distribution of sites. Additional topics for research that
should help resolve the uncertainty in the results published
to date include, but are not limited to, robust analysis of
grain-size distribution as well as degree of compaction of

The Rocky Mountain Association of Geologists

samples analyzed for hydraulic conductivity. Much of the
core remains preserved for future analyses, although, over
time, the natural hydrologic characteristics of that material
have likely changed as a result of mechanical agitation and
dehydration.
Additional core samples should be collected over a
broader distribution across the Denver Basin. As future
core sampling efforts advance, the following details need
to be considered in order to obtain representative data:

· For core handling and hydraulic conductivity analytical
procedures:

· Follow standardized sample handling procedures to pre-
vent dehydration and mechanical agitation of the samples;

· Follow standardized methods for sample analyses, using
water as the testing media;

· Use native formation water;

· Perform detailed lithologic description of the samples,
including grain size distribution and compaction analyses.

Topics for additional investigation:

· Clay mineralogy studies of the fine-grain sediments as
well as the interstitial clays in the coarse-grain sediments;

. Determination of formation water composition in the
fine-grained sediments;

· Investigation of clay-water interactions and possible
changes to clay structure in both the fine- and coarse-
grained sediments resulting from changes in water
chemistry. This will be particularly vital as artificial
recharge with non-native water is implemented on a
large scale across the Basin;

. Compaction studies of the fine-grained sediments rela-
tive to position in the Basin and potential maximum
depth of burial.

· In situ testing at a number of sites across the basin using
multiple piezometers completed in individual sandstone
layers while pumping from deeper permeable layers.

ACKNOWLEDGEMENTS

The author wishes to acknowledge all those who
assisted, either directly or indirectly, with the preparation of
this article. In particular, thanks go to Dr. Robert Raynolds
for suggesting its inclusion in this issue of the Mountain
Geologist. The Parker Water and Sanitation District, Camp,
Dresser, and Mcgee, Inc., Mark Palumbo of HRS Water Con-
sultants, Inc., and Mr. Glenn Graham of the Division of
Water Resources graciously provided date incorporated into
this report. The author is especially grateful to Dr. John
Halepaska, Dr. Bob Raynolds, Mr. Andy Horn, and Mark
Longman for reviewing the manuscript.

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