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Well Drillers Near Rapid City, South Dakota

Typical Rapid City well log: clay-rich overburden, sand/gravel and/or weathered limestone, underlain by shale and limestone bedrock. Most residential wells reach limestone aquifers at ~120-300 ft. Water table is generally 10-60 ft below grade.

Showing contractors within 60 miles of Rapid City. 14 results found.

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A geological estimate for the Rapid City area.

220 ft

Typical Well Depth

45 ft

Static Water Level

Rotary - Mud Circulation

Recommended Method

Detailed Summary

The representative geological profile for the Rapid City region includes a surficial unit of fill, topsoil, or brown clay (often mixed with gravel or cobbles) extending to 3-10 ft. Below this, a clay-rich or silty sandy gravel (sometimes with boulders or limestone fragments) forms the next layer, typically reaching 10-40 ft. Weathered shale or fat clay is consistently encountered beneath the sand/gravel, often extending to 60-120 ft. The principal aquifer is usually contained within well-cemented limestone and interbedded sandstones, often beginning near 120 ft (Minnelusa or analogous formations) and extending as deep as 300 ft or more, locally underlain by additional sandstones. The static water level is most commonly reported 20-85 ft below surface. Domestic wells for 5-15+ GPM are typically completed at 200-260 ft.

Expected Geological Layers

Depth (Feet)Formation TypeDescriptionCharacteristics
0 – 3 ftTopsoil/FillBrown clay, local fill, or topsoil with some pebbles or concrete/asphalt in disturbed areas.Color: Brown, dark brown
Hardness: Soft
3 – 12 ftClay with Gravel/CobblesBrown or olive clay, silty sand, commonly with subrounded pebbles/cobbles; base course or sandy fat clay, local gravel.Color: Brown, olive-brown
Hardness: Firm-plastic
12 – 40 ftSandy Gravel/Fat ClayRusty brown, dense sandy gravel with silty/clayey matrix; common cobbles, some black staining, moisture increases at base.Color: Rusty brown, dark brown
Hardness: Dense
40 – 120 ftWeathered Shale/Fat ClayDark gray to olive-brown weathered shale or stiff high-plasticity clay; some sand or gravel lenses, gradual transition to limestone.Color: Dark gray, olive brown
Hardness: Stiff-hard
120 – 200 ftLimestone (Minnelusa/analog)Light to off-white, hard, well-cemented limestone bedrock with minor interbedded sandstones or shale; principal aquifer unit.Color: Light to off-white
Hardness: Hard
200 – 308 ftInterbedded Sandstone and LimestoneRed/yellow sandstone, interbedded with limestone streaks, minor shale partings; transition to lower pink sandstone at base.Color: Red, yellow, pink
Hardness: Hard