The soil-stream interface (SSI) is traditionally depicted as a static area. However, at Shale Hills, there is evidence it expands and contracts seasonally. A key SSI characteristic is anaerobic soils (Kaye et al., 2023). To detect this, I used oxidized steel Indicator of Reduction in Soils (IRIS) bars, which change color when reduced (Sapkota et al., 2022). Bars were installed in October, December, and February to observe spatial and temporal variability of Shale Hill’s SSI.