Tetra Tech Nitrate Mapping
To aid in the targeting of nonpoint source pollution reduction measures, this project supports the development of a groundwater contour mapping modeling tool in the Lower Yakima Valley, utilizing existing ambient groundwater data collected from July 2021 through June 2022 by the Washington State Department of Ecology (Ecology). Groundwater contour mapping increases the visible connection between land use practices on the surface and groundwater recharge, including nitrate contamination, and allows growers to observe the potential radius of their fields’ influence and for stakeholders to identify influences that are up-gradient of the wells. Developing a model for mapping groundwater elevations and nitrate concentrations provides partners with a valuable tool for tracking changes in nitrate concentrations in relation to management measures used. This methodology document summarizes the available data sources and the methodology for developing the groundwater contour mapping tool.
The Tetra Tech study is one of many tools used by the implementation team to focus efforts. The Tetra Tech Study should not be used by residents to determine if their well is contaminated. Residents within the GWMA area concerned about nitrate levels in their private drinking water wells should call 1-866-886-7117 to schedule testing.
Ecology originally intended to use existing monitoring wells from this area but were unable obtain access to them. Ecology worked to find private drinking water wells to use, but many homes had water treatment systems installed at the wellhead or were not interested in participating in this study. Numerous groundwater wells in this area are being monitored by EPA. This data is available from US EPA.