A 1,123-foot test hole was core drilled near Wendell, Idaho, during 1981-82 as part of the Snake River Plain regional aquifer study. An upper basalt unit, an intermediate unconsolidated sedimentary rock unit, and a lower basalt unit were penetrated by the test hole. Drilling verified that the upper several hundred feet of high-resistivity material, as determined by surface electrical soundings, is basalt. Core examination, laboratory analysis, and correlation with other drill holes indicated that the basalt is typical of Quaternary basalt of the Snake River Group. Quaternary basalt in the test hole is 200 feet thick. Correlation with other drill holes and comparison with rock outcrops near the Snake River and in the Snake River canyon suggest that the underlying sediments and lower basalt unit are parts of the Tertiary and Quaternary Glenns Ferry Formation and Tertiary Banbury Basalt. Piezometers in the hole verify upward movement of water in a major discharge area for the regional aquifer. Hydraulic head in the bottom of the hole is about 155 feet higher than the water table. Lithologic sequence in the test hole correlates well with sequences in deep drill holes at scattered locations on the plain. (USGS)
