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Franklin, the oldest
incorporated community in Idaho, lies along the west side of
Cache Valley, in the Bear River drainage (Figure 1). This
community of approximately 500 residents acquires its domestic
water from springs and wells located along the western front of
the Bear River mountain range. Several of the springs contain
particulate contaminants, forcing the community to either treat
the water, or develop a new ground water source. The IWRRI Rural
Community Water Project team completed a study of the Franklin
area hydrogeology, which culminated in the following
recommendations:
- The city of Franklin should abandon
the contaminated springs or install an adequate treatment
system.
- Drill a new well to replace water lost
by decommissioning the contaminated springs. A site was
defined east of town for a preliminary test well (Figure 2).
- Consider replacing existing,
inefficient wells by drilling a new well with a properly
engineered well screen.
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Paleozoic- and Tertiary-age sedimentary strata form
the bedrock under Cache Valley near Franklin. A diverse assemblage of
unconsolidated sediments rests above these older rocks. These
unconsolidated sediments include gravel, deposited from ancient streams,
and mud deposited from Glacial lake Bonneville. Lake Bonneville formed
in western Utah, eastern Nevada and southern Idaho approximately 12 to
15 thousand years before present, when the volume of glacial melt-water
exceeded the rate of evaporation from the internally drained Great
Basin.
Extensive deposits of mud and silt that
accumulated on the lake floor impede the flow of ground water in the
Franklin area. Well-test data show low yields in the lacustrine (lake)
mud and the older bedrock. Higher yields occur in the gravel deposits
that reside above the bedrock and below the Bonneville lakebeds.
Geological fieldwork and aerial photo interpretation in the project area
defined the distribution of these gravels (Figure 2). An analysis of
precipitation that falls in nearby drainage basins shows that the
Oxkiller drainage, located immediately east of town, may provide
adequate recharge into these gravels. The proposed test well is designed
to test this sequence of gravel.
Particulate
contamination continually occurs in Crooked Springs, one of Franklins
primary water sources. The contamination results from overland water
flow up gradient of the spring. Enhanced spring development will not
resolve this situation, so this source should be abandoned, or the water
treated. Dowdell and Kingsford Springs, the communities other
spring-water sources, continually provide clean water, so should be
maintained.
The community utilizes two wells that penetrate
Tertiary bedrock. The wells operate very inefficiently due to the type
of perforations where water enters the well casing. A new well in the
same location developed with an engineered well screen would provide a
similar volume of water much more cost effectively.
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