An Insitu Level Troll 500 was deployed in the Brandon Road Lock chamber (BRLD) near Rockdale, Illinois between 12:09 Central Daylight Time (CDT) on October 19, 2015 and 14:57 CDT October 21, 2015 to monitor water-surface elevation in the lock chamber during a U.S. Geological Survey dye study conducted on October 20, 2015. The duration of the deployment included a day prior to and a day following the dye study to capture the lock operations leading up to and following the dye study. The instrument was deployed within conduit placed inside the ladder well near the 500-foot station on the right wall of the lock chamber (when looking downstream). At the time of deployment, the Level Troll was calibrated to the water surface elevation readings (headwater elevation; upstream gates open) as measured by the U.S. Army Corps of Engineers at Brandon Road Lock and Dam. On October 20, 2015, the lock chamber at BRLD was dyed with 4 liters of Rhodamine WT dye during a routine filling procedure. After filling and dye concentration measurements in the lock were complete, the lock was emptied and followed by a 17-minute flushing operation of the lock. Water surface elevation measurements were taken at a frequency of 1 measurement every minute by the Level Troll. Data logging was stopped and the data were recovered on October 21, 2015.