Bulletin 017

Bulletin 017

BUL 017

Groundwater Geology, Movement, Chemistry, and Resources near Olds, Alberta

Author(s) Toth, J. Date 1966-01-01

During 1964 the Research Council of Alberta carried out a groundwater exploration program to alleviate a water shortage problem in the town of Olds, a central Alberta farming community with a population of 3,000. A groundwater reserve estimated capable of yielding 375 igpm (1,700 l/min) for 20 years has been located, tested, and developed by means of three production wells approximately 5 miles (8 km) southeast of Olds. Another area, approximately 4 miles (6 km) northeast of the town is believed capable of producing groundwater at a rate of 200 igpm (900 l/min) for 20 years, although no pumping tests have been conducted here.

Detailed investigations were carried out in an area of approximately 17.5 square miles (45 square km). Nineteen test holes were drilled, the deepest 690 ft (210 m), in order to evaluate the geology, movement, chemistry, and resources of groundwater.

The geological investigations resulted in:

the discovery of a volcanic ash bed which may be a useful marker bed in the Tertiary succession of Alberta; the locating of a system of buried bedrock channels;

the finding of some evidence for faulting in Tertiary strata;

and evidence indicating a strong lithologic similarity between rock units believed to be of late Cretaceous and early Tertiary ages. Partly from theoretical considerations and partly from water-level measurements, the natural fluid-potential distribution and groundwater flow pattern have been established in the Olds area. One regional and five local flow systems have been outlined. Two anomalies in the configuration of the fluid-potential distribution are caused by an impermeable barrier and by a relatively high-permeability rock unit.

Chemically, the types of groundwater at Olds are either sodium bicarbonate or sodium sulfate, or, locally, calcium-magnesium bicarbonate, the total solids content varying between 288 ppm and 2,314 ppm. Areas of the different types of water are well separated, with total solids contents generally increasing in the direction of groundwater flow. Using Pipers method for representing the chemical composition of water, it is possible to separate groundwater flow systems on the basis of water quality.

Bail tests were conducted at a standard rate of 20 igpm (90 l/min) for two hours on each of the test holes. Three major pumping tests were carried out with durations of 69.5 hrs, 131 hrs, and 96 hrs, at pumping rates of 226 igpm (1,026 l/min), 155.6 igpm (706 l/ min), and 152 igpm (690 l/min), respectively. The recommended safe yield of the production wells at the same locations are: 35 igpm (159 l/min), 140 igpm (636 l/min), and 200 igpm (900 l/min), respectively. The respective average values for the coefficients of apparent transmissibility for the three test sites are 1,960 igpd/ft, 3,850 igpd/ft, and 6,175 igpd/ft, based on data taken after 24 hours of pumping. The maximum values for the transmissibility coefficients have been found in bedrock adjacent to buried preglacial (glacial?) river valleys. Extended pumping at the two major production wells may have adverse affects on water levels in private farm wells in an area of approximately 10 square miles.

The town of Olds spent in capital layout approximately $1.29 per thousand gallons of water for exploration and subsequent installations of equipment between 1946 and 1964. If groundwaters described here are to be used at the maximum possible rate for the next 20 years, expenditures are reduced to $0.058 per thousand gallons of water. If, however, the present population of 3,000 remains constant for the next 20 years the capital expenditures for groundwater at Olds will be $0.209 per thousand gallons of water.

Toth, J. (1966): Groundwater geology, movement, chemistry, and resources near Olds, Alberta; Research Council of Alberta, RCA/AGS Bulletin 17, 148 p.