An occasional stream forming the NE boundary of the Randall Manor site has been blocked by earth dams at three points. In front of the lowest dam a lake has forms in periods of modest rainfall. A brick facing in an English Bond, inclined at 12 deg away from the lake, rested against the last 5 meters of the earth dam. A vertical slot in the brickwork extends downwards into the lake and is believed to be a sluice for controlling the level of the lake.