The Athabasca oil sands deposit, located in northeastern Alberta, represents in excess of 15% of Canada's oil production. The dominant byproducts of the oil extraction process are coarse sand tailings and fine tailings. The fine tailings (composed of approximately 85% process water by volume) are deposited into a tailings basin and pose long term stability and reclamation issues. In order to implement new dewatering techniques, it is desirable to determine the solids content of the fine tailings in the basin. The current methodology for determining solids content involves removing samples from the basin for thermogravimetric analysis. The objective of this research project was to assess the feasibility of time domain reflectometry (TDR) as an alternative means for determining the in situ solids content of mine tailings. The theory of time domain reflectometry is reviewed. A Windows based TDR waveform analysis algorithm was developed for calculating the apparent dielectric constant of soil media. Issues related to pore fluid chemistry, probe geometry and coaxial cable length are investigated. A calibration protocol for fine tailings and recommendations for the development of calibration curves are discussed. Finally, a preliminary probe geometry for a push technology TDR probe is proposed.