Organic constituents of wastewaters from the existing Athabasca oil sands extraction plant were characterized and quantified. Twenty-one chemical parameters were determined on a total of ten samples taken during November and December, 1975 from the tailings pond dike filter drainage system, the upgrading plant final effluent to the Athabasca River and the intake pond waters. In addition, a number of specific aromatic hydrocarbons and organic sulphur compounds were identified and heavy metals and vanadium were determined. Tailings pond dike filter drainage samples contained 100-120 mg/l of total organic carbon, 69% of which was extractable with organic solvents. Ninety-two percent of the extractable carbon was in the form of oxygenated compounds, including organic acids (79%), phenols (4.5%), ketones (2.7%), aldehydes (1.9%), organic acid esters (1.5%), amides (1.0%), and quinones (0.2%). Organic sulphur compounds averaged 5.3%, organic nitrogen compounds 1.1% and hydrocarbons 0.04% of the extractable material. Upgrading plant effluents contained an average of 36 mg/l of total organic carbon, only 15 mg/l of which was extractable. Oxygenated compounds accounted for 30% of the extractable organic carbon, organic sulphur compounds 17%, nitrogen compounds 7% and hydrocarbons 7%. The remaining 6 mg/l of organic carbon was not accounted for. On the basis of these findings and previously measured water flow data, a calculated daily average of 198 kg (435 lbs) of organic carbon was released to the river from the tailings pond dike filter system and 1460 kg (3,245 lbs) was discharged from the upgrading plant effluent. These amounts corresponded to about 0.8% of the natural organic load of the river. It is recommended that further studies be conducted on these and other wastewaters on a year-round basis to determine (a) the seasonal variations in amounts of organic constituents, (b) the identity of individual compounds, (c) the toxicity of compound groups and, (d) the physical state of existence of the organic compounds. It is also recommended that studies be extended to include the characterization of organic constituents in the Athabasca River in order that any environmental effects may be better understood. BACKGROUND AND PERSPECTIVE The research conducted for the Hydrology Technical Research Committee of the Alberta Oil Sands Environmental Research Program was based upon a short preliminary study by the same contractor ("Characterization of Wastewaters from the Great Canadian Oil Sands Bitumen Extraction and Upgrading Plant" EPS SNW-WP-7S-6) done under the supervision of the Federal Environmental Protection Services. These studies are the first published on the analytical methods necessary to quantify the organic chemical nature of two types of discharge to the Athabasca River from an existing oil sands extraction plant. The work provides information on the types of organic chemical compounds that enter the aquatic environment from an existing oil sands extraction plant, and, as such, will be useful to the Hydrology Technical Research Committee in developing the capability to predict the direct physical and chemical impacts in the aquatic environment of oil sands development and useful to other Technical Research Committees in predicting the biological impacts of development. ASSESSMENT It is the impression of the Hydrology Technical Research Committee that this work is of a completely satisfactory technical quality. The report has been reviewed extensively by members of the Hydrology Technical Research Committee and the Oil Sands Environmental Study Group. The researchers have incorporated all suggestions in a satisfactory manner. Study results appear to have several practical applications. The Hydrology Technical Research Committee has subsequently supported the application of this type of research to samples of Athabasca River water and sediments from above and below the oil sands extraction plant, of process effluent water and of coke storage runoff drainage, in order to predict the environmental impacts of organic chemical compounds. In addition, lethal and sub-lethal aquatic faunal studies could utilize the result of this study.