The water supply for the Pueblo Army Depot, 15 miles wast of Pueblo, Colo., is obtained from wells that tap an aquifer in terrace alluvium. Withdrawals have resulted in a water-level decline of 27 feet, which adversely affects the discharge rate of individual wells. Furthermore, excessive pumpage has resulted in progressive deterioration of water quality. Over a 20-year period, hardness has increased from 70 milligrams per liter to 135 milligrams per liter and dissolved-solids content has increased from 250 milligrams per liter to 370 milligrams per liter.
Two new supply wells were drilled in the southern part of the Depot and were tested to determine aquifer properties and probable production rate. The hydraulic conductivity determined from these tests ranged from about 350 to nearly 600 gallons per day per square foot. The transmissivity for the full thickness of the aquifer is in the range of 7,500 to 12,000 gallons per day per foot.<.p>
The two new supply wells can be pumped at a combined rate of about 140 gallons per minute. If pumpage in the existing well field is reduced by the same amount, some recovery of water levels in the field will occur and the trend in water quality deterioration may slow or even reverse.
