An on-the-spot news account of this Chicago seiche: http://www.kacm.com/Tidalwave.htm

Information picked up from various sites:
Large seiches are particularly dangerous because they hit suddenly and without warning. This seiche was about 10 feet [3 meters] high (about the maximum on Chicago's lake), and was quick: at one location "the water surged more than 10 feet within a few minutes."