Well test discharge of approximately 1,000 gpm flows from 10" diameter irrigation pipe into a nearby canal.

16" bit and casing are shown during cable tool drilling of alluvial aquifer wells.
Alluvial Aquifer Wells
City of Hamilton, Montana

Planning, design and construction services were provided for two alluvial aquifer wells completed with 16" diameter casing and telescoping well screen to depths of about 70 feet.

Both wells yield 800 gpm during summer when water table elevation rises due to irrigation canal leakage in the valley. Winter-time production is reduced to 400 to 600 gpm using variable frequency drives.

Submersible pumps were set in flow sleeves below the screen interval in order to maximize available drawdown in the wells. This design also reduces turbulent head loss related to water entry.

Selection of large screen apertures, specified at 70% passing (and slightly greater) resulted in well efficiencies of 80% and 102% for the two wells.

Cable tool drilling of both wells handled the 20" surface casing hole and production casing hole drilled at 16" with casing. The spudding action of surge blocks run by the cable tool rig provides an excellent means of well development.

Pump testing and over-pumping to finalize well development was run at sustained rates of 850 and 1,000 gpm, and short-term rates up to 1,800 gpm.

About 3 to 4 cubic feet of sand was developed per foot of well screen. The large pile of sand shown in the photo came from development of one well (~40 hrs of development time).