Ground water in Tooele Valley, Tooele County, Utah

Tooele Valley is a typical basin of the Basin and Range Province located about 30 miles southwest of Salt Lake City. It is roughly 15 miles long and 10 miles wide and has a population of about 7,000. Bordered on the west by the Stansbury Range, on the east by the Oquirrh Range, and on the south by South Mountain, it opens northward to Great Salt Lake. The bordering mountain ranges are formed by Paleozoic rocks ranging in age from Lower Cambrian to Pennsylvanian but with the Ordovician and Silurian periods unrepresented. There is no sedimentary record of the interval between Pennsylvanian and Tertiary times, and the Tertiary, Quaternary, and Recent sediments are of continental origin. These continental deposits play the dominant role in the ground-water hydrology of the basin, and were mapped and studied in detail. Pleistocene sediments are of major importance because they form the surface rock over most of the area, and give rise to conditions which yield water by artesian flow in the lower part of the valley.

The development of the present land forms in this area began with the folding of Paleozoic and probably Mesozoic sediments during the Laramide revolution. The cycle of highland erosion and lowland deposition thus initiated has continued through recurrent uplift along Basin-Range faults to the present day. The principal physiographic subdivisions of the valley were developed as a result of the Basin-Range faulting, which began early in the Tertiary and has continued to Recent times.

There are about 1,100 wells in Tooele Valley, about 90 per cent of which yield or have yielded water by artesian flow. Most of them are located in the lower part of the valley below an altitude of 4,400 feet. These wells and many of the springs derive their water from the unconsolidated Quaternary sediments, which include discontinuous, lenticular and commonly elongated bodies of sand, clay, gravel, and boulders of alluvial origin alternating and inter-fingered with lacustrine beds of the same materials which are more regularly stratified and better assorted. The larger springs are intimately related to the bedding planes and faults in the bedrock and alluvial formations. The well assorted sands and gravels deposited along the shore lines of Lake Bonneville are important as recharge areas for the artesian reservoir.