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Well Drillers Near Hill City, South Dakota

Hill City’s typical shallow geology consists of thin drift/overburden, with most groundwater production from fractured metasedimentary rocks (primarily schist, quartz, and lesser gneiss). Shallow unconsolidated alluvium is locally found, but deeper wells consistently encounter hard rock aquifers.

Showing contractors within 60 miles of Hill City. 16 results found.

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A geological estimate for the Hill City area.

90 ft

Typical Well Depth

30 ft

Static Water Level

Rotary - Mud Circulation

Recommended Method

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

Depth (Feet)Formation TypeDescriptionCharacteristics
0 – 7 ftDrift/Overburden/TopsoilThin cover of silty sand, clay, or gravel (occasionally with cobbles), moist to wet. Locally up to 7 ft, especially near drainages; up to 15 ft in some unconsolidated settings closer to valley floors.Color: Brown to dark brown, some red tinge; moist.
Hardness: Soft to firm
7 – 15 ftAlluvium (local, shallow borings only)Well-graded gravel, sand, and lean clay, sometimes saturated. Not present in all locations; typically in valleys or creek-adjacent settings.Color: Red, brown, black; wet/dark with organics.
Hardness: Loose to firm
15 – 50 ftMetamorphic Bedrock (Schist, locally with quartz seams)Dense, hard, gray schist with occasional fractured quartz veins and minor mica. Major aquifer zone. Slightly weathered near the surface.Color: Medium to dark gray with streaks of black (mica)
Hardness: Hard
50 – 125 ftFractured Schist/Quartz AquiferMassive to fractured schist, gray to black, with significant water-bearing fractures and occasional quartzite; yields often peak within this zone.Color: Dark gray, black seams with quartz (white/gray)
Hardness: Very hard
125 – 185 ftSchist and Quartzite (deep aquifer zone)Hard, massive bedrock; schist interlayered with quartzite and rare gneiss or local limestone/sandstone seams (infrequent). Occasional water-bearing fractures.Color: Gray to dark gray, occasional pink/red or white variations.
Hardness: Very hard