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Well Data

All well log information from the Montana Bureau of Mines and Geology Groundwater Information Center

How Deep is the Gneiss?

Notice that the range in depth to granite is between 62 feet to 380 feet, it really shifts around throughout the valley.

(1)

Lithology

From

To

Description

83.0

108.0

RED & WHITE GRANITE

(2)

Lithology

From

To

Description

380.0

420.0

DECOMPOSED GRANITE

(3)

Lithology

From

To

Description

0.0

180.0

CLAY TOPSOIL & ROCKY FORMATIONS

(4)

Lithology

From

To

Description

374.0

377.0

SAND-WET; GRANITE

(5)

Lithology

From

To

Description

62.0

76.0

GRANITE

Well Data

  Young Alluvium

Well 1: 83 ft to gneiss

  Terrace Deposits
Well 2: 380 ft to gneiss
  Old Alluvial Fan
Well 3: "Rocky Formations" from surface
  Tertiary Alluvium

Well 4: 374 ft to gneiss

  Rock (Gneiss)
Well 5: 62 ft to gneiss

How Deep Do I Need To Drill on the Valley Floor?

Notice here that gravels are quite shallow and drillers find enough viable amounts of water at shallow depths.

(A)

Lithology

From

To

Description

0.0

2.0

TOPSOIL

2.0

40.0

GRAVEL

(B)

Lithology

From

To

Description

0.0

5.0

PIT

5.0

16.0

COARSE ROCKS SAND & GRAVELS

16.0

24.0

SAND

24.0

26.0

SAND & GRAVELS

(C)

Lithology

From

To

Description

0.0

12.0

SOIL

12.0

24.0

SAND & GRAVEL

24.0

37.0

SAND GRAVEL & CLAY

37.0

38.0

WATER COARSE SMALL GRAVEL

*** All these wells are on the valley floor in the West Gallatin Alluvium.