Thirty-six test holes were augered by the U.S. Geological Survey in the vicinity of Sol,,r Creek, Rosebud Indian Reservation, Todd County, South Dakota. Wells prcducing more than S gallons per minute (0.32 litre per second) from the Tertiary deposits are rare. However, as much as 20 feet (6.1 metres) of permeable alluvial deposits were penetrated in several test holes. One test ell was pumped for hours at a rate of 10 gallons per minute (0.63 litre per second).