The walls in the 425-foot chamber section were monitored during dewatering. Engineering Division monitored chamber wall movement throughout the dewatering/repair period. Targets had been installed along the lock wall at four locations on each side of the channel to monitor lateral movement at the locations. Lasers were mounted on the second floor of Coast Guard Facilities in order to sight the targets. A sketch showing the approximate set-up is shown . The equipment remained in place throughout the dewatering period. The survey data was continuously read in real time and fed to a computer. Readings were checked hourly while the water level was being lowered and for three days thereafter. Henceforth, data was read every eight hours. Vertical movement had been measured by a survey party. If lateral movement exceeded the permissible amount the dewatering was to be immediately halted and the lock chamber refilled. Under those emergency conditions, there was no limitation on the rate of rewatering the chamber. In order to continue repairs, ten feet of backfill had to be removed and stockpiled.