Washington

Kennewick and Kalama, Washington

Source Number: 2.5.3

Source Description
Mikels, Susan M. "Characterizing the Influence of Surface Water on Water Produced by Collector Wells." Journal of the American Water Works Association. Volume 84, No. 9. September 1992.

Key Words
bank filtration; collector wells; alluvial aquifers; Kennewick; Kalama; Washington; Columbia River; Kalama River; algae; diatoms; Giardia; Coccidia; nematodes; pollen; amoebae; ciliates; flagellates; crustaceans; rotifers; insects; turbidity; temperature

Executive Summary
Eleven samples were collected over a period of 15 months (December 1987 to March 1990) from two collector well, bank filtration systems in Washington: one adjacent to the Columbia River and the other adjacent to the Kalama River. Simultaneous samples were collected in the adjacent river. These wells were constructed in 1959 and 1975, respectively, with capacities of 2.6 and 3.0 million gallons per day (MGD) and horizontal well depths of 39 and 30 feet. The aquifers comprise gravel and sand. The Kennewick site is in a confined aquifer with a permeability of 6,510 gallons per day per square foot (gpd/sf), while the Kalama site is in an unconfined aquifer with a permeability of 2,780 gpd/sf. Filtration rates were estimated at 23,900 and 227,000 gpd/acre, respectively. This is within a reported range of 9,800 to 418,000 gpd/acre for bank filtration systems, as computed by W.C. Walton (Groundwater Resource Evaluation, McGraw Hill, New York, 1970).

Temperatures at the two sites varied seasonally. For Kennewick, the collector well temperature ranged from 13 to 16°C, whereas the river temperature ranged from 3 to 21°C. For Kalama, the collector well temperature varied from 5 to 16°C, whereas the river temperature varied from 0 to 17°C. No information was provided regarding total suspended solids concentration of the water; however, a reasonable estimate is under 100 milligrams per liter (mg/l).

Water quality data were collected for a broad range of microbiological constituents, including algae, diatoms, Giardia lamblia and also Coccidia, Nematodes, Pollen, Amoebae, Ciliates, Flagellates, Crustaceans, Rotifers and insects. At the Kennewick site, Giardia were absent in all collector well samples. River samples also showed no Giardia except for one sample, which showed 35 cysts in the concentrate gathered during the analytical procedure. For the Kalama River site, Giardia was absent in all the collector well samples but was present in half of the river samples at concentrations up to 274 cysts.

No large diameter pathogens such as Giardia were found in the water from the collector wells. Results paralleled data from two other sites in California and Oregon, both of which showed no occurrence of Giardia in the collector wells despite its occurrence in the adjacent river water.

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