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Hunley diver in full diving gear
DEPARTMENT OF THE NAVY -- NAVAL HISTORY & HERITAGE COMMAND
UNDERWATER ARCHAEOLOGY BRANCH


Martin PBM Mariner Patrol Bomber-BuNo 59172

History

The U.S. Navy Martin PBM-5 Mariner patrol bomber Bureau of Aeronautics serial number 59172 or "BuNo 59172," (meaning "bureau number 59172"), was constructed in 1944 under contract for the Navy by the Glenn L. Martin Company at their Baltimore, Maryland facility. Delivered to the Navy in January 1945, it was one of the 1,367 PBM Mariners constructed by Martin). During the World War II and Cold War eras, BuNo 59172 saw service with various Navy units in a number of capacities. Its last operational assignment was Naval Air Station, Seattle, Washington, in late 1948.

BuNo 59172 was wrecked on 6 May 1949 while being ferried across Lake Washington from Naval Air Station, Seattle to the Boeing seaplane ramp at Renton, Washington, where it was intended to be placed in storage. During a power taxi to the Boeing ramp, rapidly changing wind conditions contributed to a collision between the boat and an underwater obstruction, causing it to capsize and sink. The crew of the boat escaped unharmed.

Wreck

Today, the wreck of BuNo 59172 remains where the aircraft came to rest in 1949, in the southernmost end of Lake Washington, in the vicinity of Renton, just off the old seaplane ramp at the Boeing plant. The aircraft rests on its back in 71.5 feet of water, near the mouth of the Cedar River outflow, embedded in a dense silt bottom, with between five and nine feet of overburden deposited over the wreck, depending on wing depth and wreck orientation at the point measured. The hull projects approximately 12 feet above the bottom at its highest elevation.

BuNo 59172 has been the object of a number of previous unsuccessful salvage attempts. During one in 1980-81 over a hundred artifacts were removed and accessioned into the custody of the National Museum of Naval Aviation at Naval Air Station, Pensacola, Florida. Another took place in 1990 with assistance provided by Navy Supervisor of Salvage resources. A number of additional artifacts are thought to have been taken by sport divers over the last 20 years, as this wreck has traditionally constituted one of Lake Washington's most captivating and well known sport diving spots.

Today, custody of BuNo 59172 is assigned to the National Museum of Naval Aviation, and the flying boat continues to serve the Navy in several ways. In addition to constituting a valuable cultural resource which serves as a historical reminder to sport divers, it also provides a useful environment for the continuing training of Navy diving salvage personnel. In particular, this Navy aircraft wreck has long been associated with Naval Reserve Mobile Diving Salvage Unit One's Detachment 522 (NRMDSU-1 Det 522) of Naval Station Everett, Washington. This detachment has used the wreck as a staging site in their operations for a number of years and was involved in the 1990 attempt to recover the aircraft in cooperation with their parent command, Mobile Diving Salvage Unit One (MDSU-1) of Naval Station Pearl Harbor, Hawaii. The project was discontinued following the unfortunate work-related death of a Detachment 522 diver due to a preexisting heart condition.

Personnel from Mobile Diving Salvage Unit One returned to the wreck site in March of 1994 to assess the feasibility of another salvage attempt. They concluded that a recovery of the aircraft with minimal further damage was feasible, and that such a project would not only help to place this aircraft in the collections of the National Museum of Naval Aviation for the purpose of active preservation and public education, but would also provide a valuable and challenging training exercise for a number of Naval Reserve Mobile Diving and Salvage Unit Detachments.

In 1992, the non-profit Mariner/Marlin Association began formulating a plan for a potential future recovery effort. Their activities included identifing an appropriate museum to house the aircraft, helping to formulate a recovery plan, and determining the best means of transporting the aircraft to the museum. In 1995, the Association requested permission and assistance from the Chief of Naval Operations and the Naval Historical Center in recovering BuNo 59172. In 1996, Mobile Diving Salvage Unit One was tasked to undertake this activity. Some logistical support was provided by Naval Reserve Mobile Diving and Salvage Unit One Detachment 522, the Naval Historical Center, and the Mariner/Marlin Association. Other agencies which became involved in supporting this cooperative effort included the Washington State Office of Archaeology and Historic Preservation; the U.S. Army Corps of Engineers, Seattle District; and the Advisory Council on Historic Preservation, Western Review Office. The Boeing Corporation provided a substantial amount of additional cooperation and logistical support during the course of the project.

The project to recover BuNo 59172 took place from 19 August to 23 October 1996. The two basic objectives of the exercise were (1) to recover the aircraft, and (2) to provide a marine salvage training evolution for Naval Reserve Mobile Diving and Salvage Unit Detachments, while ensuring maximum safety protection for participating personnel, and protecting dedicated equipment resources to as great an extent as possible. Over 500 dives were conducted during the course of this project, providing an exceptional level of realistic training in difficult but controlled conditions using a variety of different tools and techniques. The training value of the activity became apparent when Mobile Diving Salvage Unit Two, Mobile Diving Salvage Unit One's east coast counterpart, was tasked to participate with the Navy Supervisor of Salvage in the recovery of the wreck of the TWA Flight 800 Boeing aircraft off East Moriches, New York. Mobile Diving Salvage Unit Two undertook this assignment during the same period that Mobile Diving Salvage Unit One and Mobile Diving Salvage Unit Two active duty and reserve personnel were training on the Martin Mariner site.

While the training objective of this mission was achieved with exceptional results, the concurrent goal of recovering the aircraft intact for museum preservation was not. After over a month and a half of laborious overburden removal efforts, and several unsuccessful attempts to free the upside-down aircraft from bottom suction and inertia in order to elevate it in preparation for righting, the final introduction of strain concluded with the rear of the aircraft separating from the rest of the fuselage. At this time it was decided to (1) recover the tail section, document it, and turn it over to the National Museum of Naval Aviation for a restoration project that may allow it to be displayed as a stand-alone exhibit for memorialization and educational purposes, (2) suspend salvage operations, (3) remove all potentially hazardous features on the site, and (4) seal off all accessible penetration points with mesh screens or blanking plates in order to make the site safe for sport divers. All four of these activities were successfully executed.

In terms of future site management strategies, three options presently exist for the wreck site: (1) complete recovery at a future time, (2) preservation in place, or (3) preservation in place coupled with its development as a dive preserve. The first option, complete recovery, does not presently constitute a realistic option for the short term. However, it should be considered as a potential long term possibility. The second option, preservation of the wreck in place as an archaeological reserve, is a feasible alternative that involves lower cost and lower maintenance, and would be intended not as much for diving and education purposes as it would be for simple physical preservation. This would also preserve it so that the rest of the aircraft might be recovered if funds and resources become available. It should be noted that any future salvage attempt would require revised and more extensive planning. The third alternative, development of the wreck site into a State of Washington underwater historic wreck preserve, is dependant upon the availability of resources and the permission of appropriate agencies. Such an objective could be achieved through a cooperative effort between the Washington State Office of Archaeology and Historic Preservation, the Naval Historical Center's Underwater Archaeology Branch, and perhaps Naval Reserve Mobile Diving Salvage Unit One's Detachment 522. The best answer for the short term seems to be preservation in place while exploring options for potentially developing it as a diver-accessible historic wreck preserve.


29 March 2009