WSP04525

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 2/7/1984
• Title: Analysis of Proposed salt Production from Thermal Waters at Glenwood Springs CO
• Water Supply Pro - Doc Type: Report/Study

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Limestone were at least 30 ft higher than the water table in the alluvium at the confluence of the
Colorado and Roaring Fork Rivers. This potentiometric head difference indicates the potential for
upward leakage of water from the Leadville Limestone into the alluvium that manifests itself as hot
water in alluvial wells and, ultimately, as hot springs. The alignment of hot springs, seepage areas, and
geothermal wells along the Redstone, Wright, and West Glenwood faults indicates that discharge
from the Leadville Limestone and Dyer Dolomite at Glenwood Springs is aided by these faults.
Site Geology and General HydlVlogy -- Rocks ranging in age from Precambrian to Permian
crop out in the vicinity of Glenwood Springs. The oldest rocks are Precambrian granite and Cam-
brian, Ordovician, and Devonian sedimentary rocks con-sisting of the Sawatch Quartzite, Dotsero
Formation, Manitou Dolomite, and Parting Formation. The Precambrian, Cambrian, Ordovician, and
Devonian rociq; crop out in Glenwood Canyon, east of Glenwood Springs, where the total thick-ness
of the lower Paleozoic rocks and Parting Formation is about 580 ft. This entire Precambrian to
Devonian sequence is either crystalline or fine-grained, with quartzite and fine-grained dolomite as
the predominant sedimentary rock types.
It is estimated that porosity in the Dyer Dolomite and Leadville Limestone at Glenwood
Springs averages only about 2 to 3 percent. However, fractures, vugginess, and cavern development
are characteristic features of these formations in the area, enabling them to transmit large quantities of
water.
The Paleozoic rocks are arched into an anticline that is breached at the crest by two steeply
dipping normal faults. From east to west, these faults informally are called the "Wright fault" and the
"Redstone fault", after geothermal wells located in each fault zone. At the crest of the breached
anticline, the Paleozoic rocks are refolded into a small syncline and anticline. The eastern limb of the
breached anticline is thrust over its western limb by a gently dipping thrust fault, which informally is
called the "West Glenwood thrust fault". According to Bass and Northrop (1963, p. 64), the plane of
this thrust fault probably dips northeastward at an angle of less than 10 degrees.
The largest spring in the area, the Yampa (Big) Spring was first developed for recreational use
in 1888. Successive modifications have made measurement of its discharge difficult. Currently, the
spring flows upward into a 60-ft diameter, rock-lined caisson with four outlets, one each to the
Glenwood Springs Lodge and Pool, and two to the Colorado River. The spring discharge varies as
the water level in the caisson is changed by manipulation of gates to the swimming pool and river.
Barrett and Pearl (1977, p. 92) report a discharge of 2,263 gal/min from this spring. Average dis-
charge from the caisson when all flow is diverted through the river gate is about 2,500 to 2,700 gal/
min (fom Zancanella, Wright Water Engineers, oral commun., 1985). Estimated discharge from the
spring during the second Red-stone well test (1984) varied between 2,800 and 2,950 gal/min as a
result of pool operations (derivation of these figures is discussed later in this report).
The conceptual model of ground-water flow in the Glenwood Springs area involves the
following processes. Water from a gradually melting snowpack and storms infiltrates Tertiary basalt
and upper Paleo-zoic sedimentary rocks at Lookout Mountain and in the Grand Hogback south of
Glenwood Springs. This water percolates down to the Leadville Limestone and Dyer Dolomite
through fractures and faults in overlying aquifers and confining layers. AI; the water descends through
the Eagle Valley Evaporite, it dissolves bedded halite and gypsum and becomes saline. After reaching
the Leadville Limestone and Dyer Dolomite, the hot, saline water flows through pores, bedding
planes, joints, faults, and solution channels toward discharge areas at Glenwood Springs. At
Glenwood Springs, the water from Lookout Mountain and the Grand Hogback mixes with cool,
relatively fresh water flowing south from the White River Plateau, seeps into overlying alluvium, and
discharges as hot springs along fault zones on the northeastern and northwestern edges of the city.

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