The bobbing object looked like a mooring buoy at first to natural resources specialist James Shannon.
Shannon, a diver who monitors geoduck harvests for the state Department of Natural Resources, was motoring from a shellfish bed off Bainbridge Island toward Brownsville Tuesday morning when he spotted the mysterious shape drifting in the water. As he maneuvered his boat closer, he saw rods protruding from a corroded metal casing and realized he'd found something potentially explosive.
"It looked like something I'd seen in history books," he said.
Shannon had discovered a military relic.
The Navy, Coast Guard and local law enforcement responded to Shannon's report Tuesday and enforced a safety zone around the drifting object. Navy personnel towed the mine north into more open water near Keyport and detonated it at 8:04 p.m., generating a plume of water and a blast that reverberated across the channel. Because there was no secondary explosion the device was likely inert, according to a Navy news release.
Nobody can say for sure where the mine came from.
The Navy referred to the object as an unidentified "moored contact mine," but beyond that "it's difficult to determine exactly what type of mine it was without further examination or more detailed photographs,” U.S. Naval Undersea Museum curator Mary Ryan said.
In its news release, the Navy noted heavy growth on the mine suggested it had been in the ocean for decades. Shannon, who works on the water every day, said the entire surface of the 4-foot-in-diameter, oblong object was encrusted with sea life, indicating it had been fully underwater.
"This was completely covered in marine growth that led me to believe it had been submerged for a very long time and recently came to the surface," Shannon said.
Mines were likely used as protective measures in local waterways during World War II, much in the same way that giant submarine nets were used to prevent enemy submarine penetration into Puget Sound, said Puget Sound Navy Museum curator Megan Churchwell.
However, Churchwell said, it’s difficult to know how many mines could have been placed in the water or exactly where they might have been placed since the museum’s collection doesn't include any wartime records that confirm the existence of the program since it was likely classified.
"My assumption is that most of these protective efforts were classified at the time, meaning that individuals working on them wouldn't have had possession of anything confirming the mines' presence," Churchwell said. "Since our collection grows from donations by individuals, nothing about this classified venture has made it into our collection."
Norm Stevens with the Jefferson County Historical Society agreed the object appeared to be a moored contact mine that would have been tethered to an anchor on the seafloor.
Developed well before World War I, contact mines were designed to lie hidden beneath the surface of the ocean and detonate when a ship or submarine bashed into them. The devices remained in wide use through World War II because they were effective and cheap to manufacture.
"It's an old but deadly technology," Stevens said.
Stevens said it's possible contact mines were deployed as part of anti-submarine defenses in the area. Dummy mines may also have been used in training exercises, he added.
The Navy will continue to investigate the origins of the device, according to a news release.
A history of manufacturing munitions
The Navy has a long history of producing munitions, particularly mines, in the Puget Sound area during wartime, starting shortly after the turn of the century.
In 1901, the Navy constructed a brick building in Manchester that housed the assembly and storage of mines, mine cases, cables, anchors and other materials needed for an Army-designated minefield in Rich Passage, which is thought to be the first minefield in the area, according to Bremerton historian and author Fredi Perry in her book "Manchester: 100 years of Stewardship 1898-1998."
The operations center for the minefield was located right next door to the plant, complete with a table set up with a map of Rich Passage's waterways that had a grid on it to fix the position of enemy ships that might try to approach the naval shipyard.
"The operating room housed electric switches that were keyed to the grid and were capable of setting off any of the more than 100 mines in the waters offshore," Perry wrote. "It is not believed that any mines were ever detonated, except for practice."
During World War II, the assembly plant provided the mines for an underwater minefield, according to the website for Manchester State Park.
Across the water, Naval Magazine Puget Sound, which is presently the site of Naval Hospital Bremerton and the military housing complex at Jackson Park, was established in 1908 near Ostrich Bay.
While the depot originally provided ammunition storage for ships undergoing repairs or overhaul at Puget Sound Navy Yard, its role exponentially expanded after America entered World War II, according to a history of the depot provided by Puget Sound Navy Museum.
After the war ended, the Navy closed the depot in 1959, and by 1975, the area had been converted into the military housing complex that stands there today.
But ever since, the Navy has spent the past few decades cleaning up errant munitions left behind following the depot’s closure, especially those inadvertently dropped into the water during World War II while munitions were transferred from one of the two loading piers in Ostrich Bay.
The Navy estimates 200,000 pounds of munitions were transferred across the water each month during the war, during which time bullets, shotgun shells, fuses, 20 mm projectiles, 40 mm projectiles, 5-inch projectiles and 14-inch projectiles fell into the water during transport.
To date, more than 10,000 of these types of munitions have been discovered and removed from the bay, ranging from bullets to a single anti-submarine "Hedgehog" rocket, according to an October 2017 Navy environmental assessment on a proposal to clean up a portion of the bay.
Further north, Naval Magazine Indian Island was home to the net manufacturing depot that produced the giant, anti-submarine nets that were stretched across Puget Sound to prevent enemy submarines from entering waterways such as Rich Passage, Agate Pass and Port Townsend Bay during World War II.
While constructing those harbor defenses started out as one of the installation’s primary missions, the Bureau of Ordnance ordered the establishment of a mine assembly plant in 1942, according to a history of the installation provided by the Navy.
To meet wartime demands, the building was constructed in a mere 10 days, and workers immediately got started on an order to manufacture 600 mines to be set in Alaskan waterways. The Navy used that building for mine-related operations until that function was transferred to what was then-Naval Ammunition Depot Bangor in the 1950s.
