City of Tumwater
Project: Groundwater Resource Evaluation
Location: Tumwater, Washington
The City of Tumwater formerly obtained its water supplies from a very
limited number of high-capacity groundwater sources. To provide for future
growth and increased water supply security, Tumwater needed to develop
additional groundwater sources.
Although the gross layering of aquifers and aquitards is consistent across
most of the City, the productivity of the primary water supply aquifer
is not uniform. In addition, existing, and potential future pollution
sources as well as proximity to the salmon-bearing streams imposed restrictions
on feasible well sites.
To locate possible areas for exploration, we created maps of drainage
features during the last ice age, and showed that they correlated to well
productivity in the primary water supply aquifer. We then assessed the
vulnerability of each potential wellfield site to water quality impacts
and conflicts with surface water resources. We also analyzed water rights
information. Based on this work, we recommended drilling and testing wells
in several areas.
Subsequent explorations confirmed that yields of up to 2,350 gpm were
available (the single highest City well yield) at the sites we recommended.
During the next phase of this project, we assisted the City in installing
production wells and addressing water rights issues.