This paper presents the results of a field study to assess post-construction changes in the volumetric water content (θ) of a soil-bentonite (SB) slurry trench cutoff wall. Time domain reflectometry (TDR) sensors were installed in a newly-constructed SB cutoff wall in the summer of 2008 and were used to monitor θ as a function of depth within the SB backfill for approximately one year. The methods used to install the probes are described and the measured θ distributions are presented and discussed. A general trend of decreasing θ with time was observed at all sensor locations. Decreases in θ within the portion of the wall below the water table are attributed to backfill consolidation, whereas the larger decreases in θ near the top of the wall (above the water table) are likely due to a combination of backfill consolidation and backfill drying. A field sampling program is recommended to confirm the moisture profiles obtained from the TDR sensors.