Well Drillers Near Hill City, South Dakota

A geological estimate for the Hill City area.

Detailed Summary

The typical Hill City geologic profile begins with a thin veneer of drift, overburden, or silty gravelly topsoil, sometimes extending up to 7 feet. Shallow areas and test borings (up to ~13-15 feet) reveal common sequences of well-graded gravel, sand, and lean clay, especially near creeks or lowlands. However, most domestic and public wells require drilling into the hard, fractured bedrock, characterized as schist (from 5-7 ft, often gray or with mica/black seams) and fractured quartz veins. The bedrock becomes the main aquifer, sometimes interlayered with minor quartzite or gneiss, yielding moderate to high flows at depths generally between 50 and 185 feet. In rare locations, limestone or red sandstone is present, but these are less laterally consistent than the schist-dominant section. Static water levels most commonly range from 8 to 59 feet, typical yield for residential supply exceeds 5 GPM at depths of 60-125 feet, and high-capacity wells are more likely completed at 170-185 feet. Well construction usually uses steel or PVC casing, grouted with Type II cement or bentonite.

Expected Geological Layers