Survey of the Hennepin Lake Michigan Wreck (1888—1927) With Sidescan Sonar
Klein’s multi-purpose System 3000 is a simultaneous, dual-frequency side scan sonar that can be used to conduct a variety of survey applications in shallow and deep water. With operating frequencies of 100 and 500 kHz, the 3000 is designed for long range seafloor reconnaissance and object identification.
In 2007, while working for famed author Clive Cussler, Ralph Wilbanks of Diversified Wilbanks Inc was using a Klein System 3000 to conduct a search for the lost flight of Northwest Orient Airlines Flight 2501, which disappeared in 1950 under mysterious circumstances. During this search, Ralph utilized the 3000’s 500 kHz frequency to image the wreck of the Hennepin.
The Hennepin is significant as it was the first selfunloading bulk carrier.
Inclined walls within the hold dispensed cargo onto conveyors below deck which ran the length of the ship. The conveyors moved the cargo into a hopper where it was transferred to an inclined conveyor, up to the conveyor boom on deck, which swung over to deposit the bulk material on land. What made this advancement completely unique was that the ship would no longer require massive shore infrastructure at major harbors to unload its’ cargo. The Hennepin could discharge its stone not only in a small harbor, but along a river, into a construction caisson, or into trucks, something not possible before this development.
Today, the Hennepin liesin 61 meters of water in Lake Michigan near South Haven, Michigan. On August 18, 1927, around 10:30 AM, the Hennepin ran into a squall in the middle of Lake Michigan.
The vessel sprung a leak, and although the crew worked to save the ship, the pumps could not keep up with the volume of water coming in. The crew worked until 2:30 PM that afternoon, but they were unsuccessful, and the crew abandoned ship for the safety of the tugboat Lotus. The Hennepin finally sank around 6:00 PM. Upon the return to port, Captain Ole.
In this image the Klein October 2017 System 3000 was set at 500 kHz frequency and the range scale was set at 50 meters. The Towfish was flying down the axis of the wreck imaging the wreck of the Hennepin to its right. The bow of the wreck is at the top of the image. The sound waves are captured by the starboard transducer.
(1) Ship’s smokestack broken off and laying across the deck
(2). Along the direction of sound (in this case the wreck is insonified bottom- left to top-right) a shadow followed bylight indicates a depression, in the bottom
(3) Ladder-like structure that is in fact part of the ship’s self-unloading conveyor belt that runs the length along a portion of the main deckand all of the hold.
(4) Part of aft A-frame crane structure.
Hennepin Color Rendering by Robert Doornbos created from the detailed side scan sonar images. The most significant damage is to the stern and starboard hull, portions of which have fallen outward. The broken hull, however, conveniently provides a perfect cutaway view of the inner workings of the conveyor system which runs the length of the hold.
