WALLA WALLA, Wash. – The Walla Walla District of the U.S. Army Corps of Engineers will hold a pre-planned security exercise at its headquarters building in downtown Walla Walla on Wednesday, May 4. Individuals or groups of district personnel may be seen participating in this exercise in the vicinity of the headquarters building at 201 North Third Avenue at any time that day. Exercise scenarios may occur indoors or outdoors.