A nearby pond and channel connected to the Columbia River provide surface water recharge to the aquifer.

Aquifer media provides aluminum and iron absorption sites. The positive charges on mineral surfaces electrostatically attract the negatively charged cell wall of Giardia and Crypto cysts.
Riverbank Filtration
City of Kennewick, Washington

Planning, management and technical services were provided to the City of Kennewick for a Riverbank Filtration (RBF) Study. A horizontal collector well that produces 12 mgd of water for the City was found to be directly influenced by surface water. A 1-year study of natural filtration by the aquifer was used to show that RBF could serve as a primary filtration treatment process. The RBF processes were designated an Alternative Filtration Technology, the first of its kind in Washington, and the second in the U.S.

The total well treatment package will combine RBF and UV-disinfection to provide in excess of 99.999% removal and inactivation of Giardia and Crypto. Chlorination will be used to inactivate 99.99% of viruses.

A comprehensive suite of physical, inorganic and microbiological parameters was used in the demonstration. Samples were collected from surface water, monitoring wells, and the production well.

Technical analyses focused on microbiological surrogates for Crypto. Groundwater-surface water mixing analysis, and computer modeling of the groundwater flow system provided a framework for data interpretation.

As a substitute for membrane filtration, rule compliance using RBF probably saved about $15,000,000 in public facilities construction costs.

Coarse-grained alluvium provides a highly productive aquifer setting. Finer grains occurring between larger gravels and cobbles act as filtration media.