The objectives of this project were to re-examine sediment toxicity at sites sampled previously on the Athabasca River, including sites in the oil sands area, and to conduct toxicity testing on a number of additional sites on the Athabasca, Smoky, and Peace rivers. Investigators tested suspended and bottom sediment samples using four species of freshwater benthic invertebrates in chronic exposure studies. Endpoints measured included survival, growth (amphipod, chironomid, and mayfly) and reproduction (oligochaete worm). Test results were compared with those using standard reference sediment samples for biological quality assurance.