Kristin Anderson and Sabine Datum attended the Washington Hydrogeology Symposium on April 23-24, 2024, where they presented methods and data analyses for slug testing at a Willamette River site in Portland, Oregon. There presentation described how groundwaterfor a shallow aquifer at this riverfront site. Due to certain site constraints, such as site size and the lack of grouped pumping and observation wells, slug testing was selected in favor of pump testing as a means to determine hydraulic conductivity.

Slug testing was performed at five monitoring well locations screened in four different aquifer zones: unconfined shallow dredge fill, unconfined shallow native alluvium, confined deep native alluvium, and a perched zone overlying a confining overbank deposit. At each well, tests consisted of three iterations of slug in/ out tests, switching between two slug sizes.

Data from the slug test was evaluated per the Butler 2020 “The Design, performance, and analysis of Slug Tests,” which provides a means to process and interpret non-ideal slug test data. Results and challenges of data evaluation were presented, and Butler recommended solutions paths were compared to solutions from AQUTESOLV, a software program for the evaluation of hydrogeologic tests.

The Willamette River site is located adjacent to the Portland Harbor Superfund Site. Slug test data will be used to evaluate contaminant loads from the groundwater pathway to river sediments and surface water to determine post-remedial construction re-contamination risk.

Click here to view Kristin and Sabine’s poster.