Sources of heavy metals in the Snohomish River estuary system are influenced by both point and nonpoint sources; therefore, areas near the Snohomish River estuary are expected to have higher concentrations of heavy metals in the sediment during periods of high river discharge. At the Ocean Research College Academy, students develop research based studies through hands-on data collection in Possession Sound (P.S.). Our study focused on the effects of non-point sources on heavy metal deposits in P.S., both spatially and temporally. In consideration of the recent removal of the oil dock at Mukilteo, we hypothesized that higher levels of mercury and copper would be present at Mount Baker Terminal (MBT). Collection of arsenic and copper data involved in our group’s research were taken by previous cohorts at three sites in P.S.: Buoy, located closest to the mouth of the Snohomish River; Dolphin 1 (DOL), farther from shore near Hat Island and MBT, adjacent to Mukilteo. A Ponar type sediment grab was used to retrieve sediment from the various locations to be analyzed for heavy metal concentration at the Everett Environmental Laboratory. From 2012-2015, Buoy had higher heavy metal content than the other two stations; an average of 5.5 mg/L arsenic and 15.5 mg/L copper. Furthermore, Buoy showed the strongest seasonal correlations in 2014; DOL and MBT did not. The highest concentrations of heavy metals occurred during winter; an average of 6.5 mg/L arsenic and 16.1 mg/L copper. Buoy is nearest to the mouth of the Snohomish River; therefore, it is possible that river runoff heavily influenced arsenic and copper deposits at this station. Increased levels of heavy metals can be toxic for marine life and humans, which poses health concerns in environments with high concentrations. For future studies, the effects of heavy metal contamination on marine plants will be investigated.