Sankoty Aquifer

The Sankoty aquifer provides groundwater to a number of communities in northwestern and central Illinois. The sand which comprises the Sankoty aquifer was named after a railroad siding near Peoria, Illinois in 1946 by Leland Horberg. The legal description given by Horberg in identifying the type locality for the Sankoty sand is T9N, R8E, Section 15 (Peoria County, Illinois). The Sankoty sand is classified as a member of the Banner Formation and occupies the same stratigraphic position as the Mahomet sand.

Lithologic description

The Sankoty sand differs from most other deposits because of its distinctive characteristics which are readily recognized in sample cuttings. In its most typical aspect, the Sankoty is composed of 70 to 90 percent quartz grains of which 25 percent or more are pink, rounded, and polished. The texture is usually medium-grained but varies from silty fine sand to coarse gravelly sand. It is an unconsolidated deposit lying in a bedrock valley formerly occupied by the ancestral Mississippi River.

The Sankoty sand serves as one of the most extensive aquifers in the State. The Sankoty sand frequently is 100 feet thick and tends to lie below elevations of 520 to 530 feet (above sea level). It has been used as a water source, in the Peoria area, since at least 1892. By 1909, it was observed that groundwater levels, at the North Field in Peoria, varied with the Illinois River stage. The Sankoty aquifer extends beyond the width of the Illinois River valley and occurs beneath the uplands. In these locations, it is frequently confined by clayey deposits of glacial till (which may include other sands). Consequently, the groundwater may occur under confined (artesian) condtions.