Publication Summary

This is the study plan for the high-resolution, pore-water sampling near the groundwater/surface water interface.

A variety of complex biogeochemical processes can be active immediately below the sediment surface in aquatic environments. These processes can cause significant changes in the water quality of groundwater discharging to a surface water system. These changes can often occur within the last several feet, or even inches, of the groundwater flow path.

The groundwater monitoring tools and methods currently used by the Washington State Department of Ecology (Ecology) Environmental Assessment Program (EAP) for groundwater/ surface water interaction studies are not well-suited to accurately characterize changes in groundwater chemistry at this scale. Without accurate measurements of these changes, EAP estimates of groundwater discharge chemistry and pollutant loading to surface water can have a high degree of uncertainty. This uncertainty reduces our confidence in how accurately our models of groundwater/surface water exchange reflect the natural environment.

This project will focus on developing and testing a higher-resolution, pore-water sampling approach to improve description of groundwater discharge chemistry. These methods will in turn improve groundwater pollutant loading estimates developed for Total Maximum Daily Load (TMDL) numerical models. Test results and field procedures will be documented and evaluated, and if successful, applied in an ongoing TMDL groundwater study.

This test program is initially focused on improving methods for characterizing changes in nutrient concentration near the groundwater/surface water interface. The methods could also benefit evaluations of loading and attenuation for other groundwater-borne chemicals of interest entering surface water systems.

Each study conducted by Ecology must have an approved Quality Assurance Project Plan. The plan describes the objectives of the study and the procedures to be followed to achieve those objectives. After completion of the study, a final report describing the study results will be posted to the Internet, and a Standard Operating Procedure (SOP) for the method will be prepared.

Link to EIM data for User Study ID CHPI003