On February 3, 2023, a freight train derailed near East Palestine, Ohio, releasing hazardous materials upon impact and during subsequent emergency vent-and-burn procedures. Among the contaminants of concern were polycyclic aromatic hydrocarbons (PAHs), combustion byproducts potentially generated during the ensuing fires. Extensive environmental monitoring was promptly initiated by local, state, and federal agencies, academic researchers, and Norfolk Southern contractors to characterize exposures across affected media. In response to ongoing public concern regarding continued environmental contamination, this study evaluated temporal trends in PAH concentrations in sediment samples collected along a nearby waterway, Sulphur Run, over a 36-month post-derailment monitoring period. Sediment samples collected by the United States Environmental Protection Agency (EPA) from locations along Sulphur Run between July 2023 and April 2025 were analyzed across five discrete sampling periods. PAH concentrations were log-transformed prior to analysis to address the right-skewed distribution. A linear mixed-effects model was fitted with sampling date as a continuous fixed effect and sampling period as a random intercept to account for within-period correlation. As samples were not collected from fixed locations between periods, the random effect captures between-period variability in baseline PAH concentrations rather than repeated measures. A case bootstrap procedure (999 iterations) was used to generate 95% confidence intervals robust to non-normal residuals and the clustered sampling structure. The model identified a statistically significant negative trend in log-transformed sediment PAH concentrations over time. The marginal R² indicated that time alone explained a modest proportion of total variance, while the substantially higher conditional R² demonstrated that the inclusion of sampling period as a random effect markedly improved model fit, reflecting considerable between-period variability in baseline concentrations. This highlights the importance of accounting for clustered sampling structure to limit residual error and potential inflation of the temporal trend significance. Collectively, these results demonstrate that PAH concentrations in EPA sediment samples from Sulphur Run have significantly decreased between 2023 and 2025.