UWEC CERCA 2025

Dunn County Potter’s Field contains over 100 unmarked graves of persons from the County Poor House and the County Asylum (both now demolished) in Menomonie, Wisconsin. Community interest in locating the graves prompted non-invasive scans of Potter’s Field using ground penetrating radar (GPR). GPR transmits electromagnetic (EM) pulses into the ground, which reflect off subsurface changes before being received and recorded digitally. A 16x50m grid was collected along the site’s western boundary with a Sensors and Software pulseEKKO Pro GPR unit with 500MHz antennae. GPR traces were triggered every 0.02m via odometer wheel, and lines were collected with a spacing of 0.25m. Alternating strong and weak reflections are repeated in a sub-parallel, semicontinuous pattern throughout the grid. The strong reflections are often underlain by steep-angled hyperbolics. The reflections were identified 0.6–1.5m below the surface, each measuring 1.0m by 2.25m, and spaced 1.0m apart. Reflections were interpreted as two probable rows of individual graves. In Fall 2024, 42 crosses were placed at each probable grave, however further scanning is recommended to locate remaining lost graves. The GPR work at Dunn County Potter’s Field is a model for other cemeteries; providing means of locating and restoring honor upon unmarked graves worldwide.

During the Holocaust from the 15-17 of December 1941, ~2,749 Jewish women and children were massacred behind a foredune along the coastline of Šķēde, Latvia. The execution trench has not been located, despite numerous photos of the killings. The research aims to identify the location of the trench using shallow, non-invasive subsurface imaging tools to respect Jewish Halacha burial laws, avoiding disruption of the deceased. Based on earlier research including current and past aerial imagery, witness testimonies, and historical photos of the killings, a 15x30m (NW-SE) GPR grid was laid down within the foredune. Using a Sensors & Software pulseEKKO Pro GPR system, lines were collected every 0.25m with 500MHz antennae and a step size of 0.02m, which allowed subsurface depths of ~4m (0.10m/ns velocity). The subsurface reflections dip at a 30-34° angle, with erosional truncation occurring at ~17-21m and extending ~3.1m below the surface; these dipping layers are interpreted as a probable trench ~5m wide throughout the grid. Based on witness testimonies, the trench is hypothesized to be ~100m long (S-N). The findings have been shared with the local Jewish community for memorialization, and the research provides a framework for identifying unmarked graves worldwide.