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Heating with geothermal systems 193

Table 5.3 Production well information for CB system [17].

BGL-2 BGL-3 BGL-4 Inj. well
Year Drilled 1981 1981 1981 1999
Depth, m 268 579 335 1097

Temperature, C 80.6 72.2 80.6 46.1 a
Pump power, kW 93 149 37 N.A.
Max. flow rate, kg/s 73.6 122.6 49 219
Max. flow rate, GPM 1200 2000 800 3500
a
Injectate average temperature.

There are some cross-over connections between the supply and collection lines that
can be used to maintain the water velocity. A few users actually use the lower-
temperature water for specific purposes. Disposal is via an injection well about
370 m from the Boise River. It is about 1.8 km southwest of the production wells,
but is significantly deeper than the production wells, namely, about 1100 m deep. Be-
ing w2 km from the Foothills Fault, the injection well may have found a permeable
layer within a rhyolite formation or perhaps at the interface of the rhyolite and the
granitic formations; see Fig. 5.12.
The water level in the producing wells has recovered to essentially its preproduction
levels after reinjection began. Prior to using the injection well, the water level had been
drawn down by about 10 m below the original level, but as soon as injection began in
1999, the level began to rise and now (2018) has stabilized at about 0.6e0.9 m below
the undisturbed level. This is crucial because the pumps must be set below the water
level to function. Based on the pressure recovery observed in the monitoring wells that
are close to the Foothills Fault, there is hydraulic connection between the production
wells and the injection well, but it is not too strong since the production temperature
has so far been unaffected.

5.3.2.4 Veteran’s Administration (VA)
The United States Veterans Administration (VA) owns two wells, one producer
(VA#1) and one injector (VA#2), that allow the VA to heat their complex of buildings
with geothermal water. The wells were drilled in 1983 and have the following dimen-
sions: VA#1: 508 m (1666 ft) deep, 16-in casing to 43 m (140 ft), 12-in to 244 m
(802 ft), 8-in perforated to 457 m (1500 ft), open hole to depth; VA#2: 561 m
(1840 ft) deep, 10-in casing to 40 m (130 ft), 7-in perforated to 451 m (1480 ft),
open hole to depth. The wells are separated by about 538 m [18].
The production well appears to penetrate the fracture zone associated with the Foot-
hills Fault, the same area feeding the nearby City of Boise wells, and possibly a portion
of the upper rhyolite formation used by the SICM injection well [18]; see Figs. 5.10
and 5.15.