Did a nuclear blast devastate Port Chicago on July 17, 1944?

Question

On July 17, 1944 at the Port Chicago naval base, near the San Francisco Bay area, an explosion of epic proportions occurred on a dock handling munitions.

The Evening Independent, Jul 18, 1944, via Google News makes mention of the following:

• ~350 dead
• almost every house in Port Chicago wrecked
• two ships destroyed
• felt for 50 miles to San Jose; broken windows 20-30 miles
• 300 lb chunk of steel blown one miles
• recorded on seismograph

Wikipedia cites additional details, treating this tragedy as a conventional blast caused by recklessness in loading munitions. The nuclear theory is mentioned but not advocated. see: Wikipedia Port Chicago Disaster.

At 10:18 p.m., witnesses reported hearing a noise described as "a metallic sound and rending timbers, such as made by a falling boom."[26] Immediately afterward, an explosion occurred on the pier and a fire started. Five to seven seconds later,[16][30][31] a more powerful explosion took place as the majority of the ordnance within and near the SS E. A. Bryan detonated in a huge fireball some 3 mi (4.8 km) in diameter.[31] Chunks of glowing hot metal and burning ordnance were flung over 12,000 ft (3,700 m) into the air.[16] The E. A. Bryan was completely destroyed and the Quinault was blown out of the water, torn into sections and thrown in several directions; the stern landed upside down in the water 500 ft (150 m) away. The Coast Guard fire boat CG-60014-F was thrown 600 ft (180 m) upriver, where it sank. The pier—along with its boxcars, locomotive, rails, cargo and men—was blasted into pieces. Nearby boxcars—waiting within their revetments to be unloaded at midnight—were bent inward and crumpled by the force of the shock. The port's barracks and other buildings and much of the surrounding town were severely damaged. Shattering glass and a rain of jagged metal and undetonated munitions caused many additional injuries among both military and civilian populations, although no one outside the immediate pier area was killed.[32] Nearly $9.9 million worth of damage ($131 million in current value) was caused to U.S. Government property.[33] Seismographs at the University of California, Berkeley sensed the two shock waves traveling through the ground, determining the second, larger event to be equivalent to an earthquake measuring 3.4 on the Richter scale.[34]

An online article in Lighthouse Digest on The Great Port Chicago Disaster and Mutiny mentions a large wave created by the blast:

Tidal Wave At The Lighthouse

At the Roe Island Lighthouse, keeper Erven Scott, his wife, Bernice, and the assistant keeper were just finishing a late cup of coffee. The explosion shook the house violently and broke all the windows. Mrs. Scott grabbed the two children and sent her husband upstairs for the baby. As he ran up the stairs, Scott saw a plume of smoke and flame rising above Port Chicago and a 20-30 foot high wave rolling toward the lighthouse from the direction of the explosion. He dashed back downstairs with the baby. By the time the tidal wave reached Roe Island, it had expended most of its energy. Still, it hit with such force to push the lighthouse about 40 feet up on the beach.

Peter Vogel's website and book is devoted to a nuclear theory of the explosion. As a book is involved there are numerous claims and it is difficult to list all of the key claims in the question... But the following excerpt, purportedly suggesting a cover-up, appears on the page for Chapter 2 of his book:

Of even more significance, Paul made an unauthorized copy of the document "History of 10,000 ton gadget" [referring to the atomic bomb] and removed that copy from Los Alamos in his shirt pocket.... ... the bottom line said the ball of fire of the 10,000 ton gadget would mushroom out at 18,000 feet in typical Port Chicago fashion. "

A Mushroom Cloud What really happened at Port Chicago in 1944, a nuclear explosion? by Harvey Martin, tries to argue that the flash and cloud observed at Port Chicago bear considerable similarity to the description of the mushroom clouds from atomic bomb detonations over Japan.

The story seems too incredible to believe - that the U.S. would test a weapon on itself. In order to ascertain the truth of this matter, one must study old reports. In the beginning of this series, the simplest reports to study are the uncensored news reports of local newspapers, such as the St. Helena Star and the Napa Journal - The Napa Journal was bought out in the 1950's and became the Napa Register. These eye witness reports were made in the pre-atomic age, when no one knew about atomic weapons - what they were, how they worked, what devastation they created, what they looked like, or for that matter, that they even existed. It was one of the most closely guarded top secrets of World War Two.

"One of the few to see the flash from here was Tom Street, who happened to be standing in the patio if his Spring Mountain home when the blast came," reported the July 21, 1944 edition of the St. Helena Star. "First there was a sudden mushroom of white light, followed an instant later by another, then a few moments later the intense roar and the concussion of the blast. At the rate of about a mile for every 5 seconds, it required a little over 4 minutes for the blast to reach St. Helena." In another account in the same newspaper, it states. "The force of the explosion was felt at the Mt. St. Helena observation tower, but apparently the range of the mountains at the end of the valley stopped the concussion, for Lake County residents didn't feel it."

"The hills of the Napa Valley were momentarily illuminated by sunlight." reported the Napa Journal.

He also mentions the famous Einstein letter to President Roosevelt describing detonating an atomic bomb in a port:

More than two years before the United States entered World War II, Albert Einstein sent a letter to President Franklin D. Roosevelt, informing him that a nuclear bomb was possible. That letter was written on August 2, 1939. "A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory," Einstein wrote. "However, such bombs might very well prove to be too heavy for transportation by air."

Of course, if the blast were nuclear, one might reasonably wonder: Where was the fallout? Where were the radiation casualties? This appears to be a weak point of these claims. The Martin article claims that Contra Costa county, where the blast occurred, has "one of the highest rates of cancer in the United States".

A hobbyist and self-proclaimed skeptic went looking for residual radiation, and found a little, in 2004-2005. Background Radiation Measurements near Port Chicago

Were the detonation of 4100 metric tons of explosives, possibly with 800,000 liters+ of fuel oil sufficient to cause the explosion described, or should the nuclear option be given serious consideration? If nuclear, this raises other questions such as "accidental event" or "intentional test" -- but the only claim being questioned here is whether the blast was nuclear.

Answer 1

The primary issue with the Port Chicago incident being due to a nuclear device is that it would require us completely rewrite the currently known history of the Manhattan Project [1][2]1 to include "The Gadget" not being the first nuclear device and that if one was created for Port Chicago that it predated The Gadget by almost a full year as the Trinity Test was on July 16, 1945 [3]. Given the degree of time and effort invested into the Manhattan Project I would be hard pressed to believe that a second, smaller project was running in parallel to it so if anything was going on, it would have been under the oversight of the Manhattan project. That said though, work was being conducted on a plutonium gun-type nuclear device known as Thin Man and work was abandoned on July 17, 1944 after determining that "the background fission rate of the plutonium was so high that it would be highly likely the plutonium would predetonate and blow itself apart in the initial forming of a critical mass" [4] 2

With regards to the explosion itself, one of the biggest strikes against a nuclear explosion is that the lack of fallout which is a major concern when it comes to surface burst explosions [5]. Given the nature of Port Chicago we can speculate that a surface burst explosion would have been the most likely to occur which would have lead to a significant amount of fallout being generated. Had nuclear material of some sort been involved then we can speculate that someone would have arrived to do extensive testing of the area around Port Chicago, for which no evidence appears to exist.

The next strike against things is there don't appear to be any thermal effects [6] visible in the photographs provided in the Wikipedia article and one of the pier itself (above) looks more like the aftermath of a conventional explosion that personally calls to mind photographs I've of the Halifax Explosion, such as the one below. You will not that in the picture of the Port Chicago pier you can still discern where the pier was and there is a considerable amount of rubble around the site, this is not what one would expect given that the equivalent ground zero at Hiroshima was effective laid bare following the detonation. [7]

In summary, based apparent lack of fallout and thermal effects visible in photographs following the incident, we can conclude that a nuclear explosion was not the cause of the incident. Additionally, based upon the currently accepted historical record and the declassified documents currently available, is is quite likely that a nuclear device was not involved with the event.

Notes:
1. Yes, a number of these sources are Wikipedia; however, it is convenient for timelines and the history of the Manhattan project is considered to be well established.
2. From a conspiracy theory standpoint, this is a very interesting coincidence and thinking creatively for a moment, an accidental predetonation while a device was in route to test site that was covered up for the war effort is not outside the realm of possibility. The strike against it is that it likely would have been declassified in the intervening years given that the majority of the non-restricted documents from the Manhattan project have been declassified [8].

Photo Credits:
1. Port Chicago Pier: http://en.wikipedia.org/wiki/File:Portchicago2.jpg
2. Halifax Disaster: http://museum.gov.ns.ca/imagesns/html/20099.html