Polychlorinated biphenyl (PCB) concentrations were measured in the lower Ottawa River in 2009 before dredging and after dredging in 2011, 2012, 2013, and 2015. Media collected for analysis included sediment, water, macroinvertebrates, and tetragnathid spiders at 18 stations. At each station 16 surface sediment core samples (top 15 cm) were collected and composited together with a mechanical mixer to achieve a homogeneous composite sample. Mid-depth water column samples were collected using a Van Dorn, Niskin or similar type sampler. Artificial substrate samplers (Hester Dendys) were used to collect aquatic macroinvertebrates. Riparian spiders (family Tetragnathidae) were collected from their webs by gloved hand at night within 1 meter of the shoreline at each sampling station. All extracts were analyzed for 121 PCB congeners via gas chromotography mass spectroscopy in the selected ion monitoring mode based on U.S. EPA Method 1668A and quantified using the method of internal standards.