On Saturday, record-setting swells tore apart the wreck of the historic concrete merchant vessel SS Palo Alto near Aptos, California.
The SS Palo Alto, known locally as the “Concrete Boat,” was an anomaly in merchant shipping. Towards the end of the First World War, German submarines were taking a severe toll on American shipping, and the government called for the creation of an "emergency fleet" to offset the losses. To conserve steel, the fleet would be built out of reinforced concrete. The Palo Alto was one of two concrete tankers laid down at the San Francisco Shipbuilding Company as part of this emergency experiment.
However, the vessel was delivered too late to help win the war, and she never entered commercial service. After ten years docked in San Francisco, she was towed to Aptos, California and intentionally grounded for use as an amusement hall. Two years later, a winter storm cracked her in half, and her owners abandoned their business plans. The state purchased the wreck and turned her into a fishing pier.
She has gradually deteriorated over the years, and has been open to visitors only sporadically. In 2006, her fuel tanks cracked open, and a salvage team had to board her to pump off about 500 gallons of bunker fuel.
The latest blow may prove to be the end of her service as a local attraction. On Saturday, a NOAA weather buoy inside the mouth of Monterey Bay recorded record-setting waves of up to 34 feet. The heavy swell tore the Palo Alto's stern free and flipped it on its side, exposing the tangled network of rebar reinforcement that gave the vessel her limited structural integrity.
As a concept, the concrete-hulled merchant vessel may have been best suited to stationary applications, like floating storage and pierside facilites. The fate of the SS Cape Fear, one of the other eleven concrete ships completed as part of the war effort, revealed a dangerous liability: the Fear collided with another merchant vessel in October of 1920 and shattered, taking 19 of her crew with her to the bottom.