Background Radiation Measurements near Port Chicago

[image: area map, 18K download] by Ian Kluft
July 13, 2004
last updated October 15, 2006

On this page...

Before we start...

Before we get started, let me first make a few points about how I think this information should be handled. I don't condone reaching any conclusion yet with the amount of data collected so far. More data is needed. More questions need to be asked.

I started out trying to debunk an old local urban legend about the Port Chicago explosion of July 1944. Two munitions ships exploded at the dock while loading. Conspiracy theorists have claimed for years that the explosion included an atomic bomb. Most people brush it off since there is mathematically an area of overlap, a comparable amount of explosive energy, between the potential of a ship full of conventional munitions and a low-yield atomic bomb. The conspiracy theorists spent a lot of effort explaining why there would be no radiation because the explosion was in the water. That's bogus - there would have to be some residual evidence. It seemed obvious to me that this could be disproven with instruments available to the general public today. My thought was, "If they wanted to claim there was an atomic bomb on board the ships that exploded, they should be looking for radiation to the north, which is the typical downwind direction with the Summer breeze from San Franisco Bay to the Central Valley." So I was going to go up there with a geiger counter and laptop computer, show there was nothing, and be done with it.

This situation turned around on me when the data I collected failed to disprove the urban legend. Note that failure to disprove something is not proof. But now all of us looking at this objectively need to collect more data.

I found slightly elevated background radiation levels in a 2-mile wide area, less than you'd get from normal solar radiation on a trip to a higher elevation such as Yosemite or Denver. But it's twice as much as normal for sea level, and compared to other areas around it. It spans between the differing geology of the Suisun Bay marshes and the Montezuma Hills. 60 years later, that's also comparable to a trip to Hiroshima, which is why the urban legend remains plausible. Even though it wasn't what I expected, I posted my data anyway. I also included instructions for others to duplicate my experiment.

To me, this changed my position from an ardent skeptic out to disprove it, to having a more open mind about the possibility. I want to collect more data and see if it continues to support it or not. There just isn't enough to be conclusive either way yet.

Some conspiracy theorists have, of course, jumped to conclusions about what the data means. There's some of them in every crowd. As I said, I don't condone reaching any conclusion with this data yet.

So what do I think? The elevated background radiation is downwind across Suisun Bay from the Concord Naval Weapons Center (formerly known as Port Chicago.) Residents of the Bay Area, particularly Contra Costa and Solano Counties, and the media have reason to ask what has happenned there that could explain elevated background radiation levels downwind from the base. That's a reasonable question to ask right now.

We can't rule out other sources over the 60+ years since then. The naval base, the shipping channel and the nearby oil refineries seem like the places to look for a cause if one wants to be objective. Have I missed any other potential sources?

I'm willing to assist anyone in the mainstream media who would like to investigate this.


At the time this page was first written in July 2004, it was the 60th anniversary of the accident at Port Chicago on July 17, 1944, where a munitions ship exploded The explosion was so large that some myths and urban legends claim it was a nuclear accident, a year earlier than the Trinity test. This web page is about my effort to collect real data on background radiation levels in the area with a mobile geiger counter data collection system. Then the point is to see if the urban legends still hold water.

Another purpose of this page is to describe how I'm collecting the data so that others can collect mobile data this way. The idea credit goes to Phil Stuart - see below in the Data collection equipment and software section. I've augmented the idea by making it work with an off-the-shelf Linux laptop computer instead of custom microcontroller hardware. And like Mr Stuart did, I provided my software.

Except for collecting additional samples at the same or nearby places, I think I've done most of the research that I can as an amateur. If verified, we'll need to start turning this over to pros in the press to use their FOIA expertise and see where that goes.

Making a long story short... I had set out to disprove this local urban legend. I expected to go north of the accident site and say something like, "see, there's nothing here." I got a little more than I bargained for - some anomalous radiation readings which can only be detected with sensitive instruments. When I wasn't able to disprove the myth, I didn't hide my findings and posted my data anyway. What I found neither proves nor disproves the urban legend. But now I think it can use a further look.

I've tested a number of hypotheses and there are still many more to check as Spring 2005 dries out the terrain. As I do more tests, I'll post my data and my software so that anyone can duplicate this experiment if they want to.

Page updates
Date Description
July 13, 2004 The page was created.
July 16, 2004 This page has been updated with data from July 15. I found an area on the north shore of Suisun Bay at Grizzly Island with higher than normal radiation levels, 13-17 microRoentgens/hour (uR/hr) for a 2-mile stretch. The area of unexplained radiation is across the Bay facing Port Chicago. Even for a skeptic like me, that means I couldn't disprove the urban legend, and may have found a possible radioactive plume from the accident site at Port Chicago if this data is verified. I'll keep considering alteratives. It needs independent verification. I still consider the whole hypothesis conditional upon verification at this point.
July 23, 2004 The Open Source download page has new versions 0.2 of all the software from this experiment. The images were cleaned up after the "geiger-map" software was fixed. The previous algorithm wasn't handling the large amounts of data well. It failed to average nearby points as well as intended. And it took far too long (about an hour) to generate the images. A new algorithm dumps all the data into a "bucket" for each pixel (since there's usually enough data for multiple samples per pixel) and chooses the maximum or average of them, as selected from the command line. In the case of the posted images, these show the maximums. The program was also adjusted to use more colors to make the display more intuitive of the contents of the data. Now it runs in a few seconds - it's amazing what a paradigm shift will do for your run times, isn't it? :-)
May 27, 2005 After most of a year has passed, it's possible to take a step back. I've updated the page.
Oct 15, 2006 Just some touch-ups.

Historical background

The Port Chicago explosion occurred at 10:19PM on July 17, 1944. It was during World War II, while munitions where being loaded on cargo ships bound for the war in the Pacific. The total tonnage of explosives on board the ships amounted to an explosion equivalent to thousands of tons of TNT. Mathematically, it was literally larger than the explosive yield of the earliest atomic bombs that would be used a year later. The effects of the explosion were apparently of interest to the Manhattan Project, and their people arrived within days to study the effects of such a large explosion.

The event is better known for the effects on race relations in the US military. Most of the 300+ people who were killed were Black. Other Black sailors who refused to return to work immediately (loading munitions on ships) were charged with mutiny, but then pardoned decades later. The disparity and mistreatment led to reforms. The Port Chicago Mutiny has been the subject of books, documentaries (Discovery Channel and History Channel) and a TV mini series (NBC).

Urban legends

Over the years, the accident has spurred a conspiracy theory which has grown to urban legend status, claiming that the explosion was actually a nuclear detonation. Various versions of the urban legend have it as an accident, or even the most ludicrous versions claim it was an intentional test of the first uranium-based atomic bomb to measure the effects on an active port.

Some of the story seems to be because not everyone realizes that the explosive yield of a significantly large amount of conventional munitions overlaps with the low end of atomic (fission) bombs. Others are suspicious about how quickly staff from the Manhattan Project were on the scene, and that so many reports about the Port Chicago accident later turned up with the Manhattan Project documents that became declassified. But logically it's more than just plausible that they'd want to research the effects of any large explosion once it had happenned.

Whatever the story, I'm not into conspiracy theories. The "leaps of logic" typically found in them are annoying at best, and serious misinformation at worst. Most are written to sound convincing and can take in a large audience. The best-known example in this case is an online book released in 2002, "The Last Wave from Port Chicago" by Peter Vogel as an accumulation of his earlier research.

Digging into more details

However, some have been more careful in researching the story. For example, the Napa Sentinel reviewed Vogel's earlier articles and found things to agree and disagree with him at the 50-year anniversary of the explosion, which was itself 10 years ago. And they recorded an earlier series of articles from 1990.

Even a story about the damage at the Roe Island Lighthouse (3000 feet away from the explosion) has a footnote referring to the nuclear accident theory.

It's a local interest for residents of the San Francisco Bay Area. I live in San Jose which is about an hour's drive south of the site. As long as any doubt remains about it, we'd rather know one way or the other.

The Contra Costa County Office of Education has a page about the debate. (Though I noticed that the webmaster of the CCCOE site is also the domain contact for, where Vogel's online book is posted.)

"Why doesn't someone go look there?"

When the story broke about Vogel's 2002 online book, it reignited the debate as it was covered in articles on sites like Slashdot and SciScoop. As I mentioned in a reply in January 2003 to the Slashdot article, there seemed to be enough to this that was worth another look, even if just to settle the issue one way or the other.

Fast forward a year and a half. When I had reason to experiment with an electronic geiger counter for another project, the idea came up again to check on Port Chicago. The public doesn't have access to the Port Chicago base because it's still in active military use, now known as the Concord Naval Weapons Station. The downwind areas in the Sacramento River Delta (yes, we have an inland delta here) are very rural and have some roads. My thought on this was that if there's anywhere to check which could make or break the theory, someone had to check the potential downwind areas for any traces of radiation. Without that, it would be pretty much disproven. With that, it wouldn't prove it but the mystery would have to be allowed to continue.

Let's first look at the results of the visits to the area. I'll describe the equipment and software below.

[image: data plot, 31K download]

July 11, 2004 Expedition

The first expedition to measure background radiation in the area was also a shakedown trip for the software, which I had just completed that day. On the evening of July 11, 2004, my friend Justin Rocha helped with the experiment by operating the laptop computer which was recording the data. He also made some observations which helped fix some bugs in the software. I also needed the assistance because it's illegal in California to put a laptop computer where it can distract the driver - I intended to comply so without a helper I'd have had to stop any time I wanted to read the data.

As we drove up Highway 4 past Port Chicago then through Pittsburg and Antioch, there was nothing really out of the ordinary. Some occasional spikes within the normal range of background radiation are to be expected. It's a very random thing so you have to take averages of a lot of data. For that reason, there will have to be more trips to collect data. This simply isn't enough to reach any conclusions yet.

As the drive proceeded north on Highway 160 over the San Joaquin River and up to Rio Vista, there were a couple more minor spikes but it was all within the range of "normal". The plan from there was to take Highway 12 west from Rio Vista and check out any open roads closer to the north side of Suisun Bay (pronounced suh-soon), presumably what would have been downwind of the Port Chicago explosion.

There was nothing out of the ordinary on Highway 12, except that we missed the turnoff in the dark and had to backtrack to it. There was still nothing out of the ordinary for a mile on the dirt road. Just as we had almost talked ourselves out of the possibility of finding anything, the readings jumped from 6 to 10 microRoentgens/hour (uR/hr). It's still normal background, but we hadn't seen a jump like that before. As we continued south toward Suisun Bay, the high-end-of-normal readings continued, around 8-10 uR/hr. It reached 11 in the town of Bird's Landing, which is basically a road intersection with a few 1800's buildings and a few residents.

Then we seemed to get out the "other side" of the high-background area as levels returned to 6-7 uR/hr the rest of the way to Collinsville at the shore of the Bay. We turned around and saw the numbers pick up back to 11 again as we approached Bird's Landing. We tried the dead-end road west from there to Mein's Landing. The numbers stayed consistently elevated, reaching 13 uR/hr at the end of the road in the hamlet of Mein's Landing. That was almost the highest reading we saw on the trip, except for a 14 uR/hr spot on Shiloh Road on the way north back to Hwy 12. There were some more scattered high-normal readings on the way out, but none like that.

Download raw data from the July 11 drive (216K compressed, 1.8MB uncompressed)

[image: data plot, 30K download]

July 15, 2004 Expedition

I had lunch at the Suisun City Marina before starting the measurements for the afternoon. I'm sure everyone in Suisun City will be happy to know they have low-to-average background levels there. If this story should become news, I guess I need to become careful to mention things like that - so far all the cities are fine.

I went first to Grizzly Island State Wildlife Area, since I knew that was the next place that needed to be checked if the urban legend was to be thoroughly tested.

While at the Grizzly Island visitor station, I got a call from Justin that he was coming up to help after all. He had jury duty, but ended up not being selected for the case. I proceeded to do measurements on Grizzly Island while he drove up to meet me at the Suisun City Marina. (It's near the beginning of Grizzly Island Road at Hwy 12. So it's a good rendezvous point.)

Once off the paved road and driving on the levee on Grizzly Island, I was able to turn the screen so I could glance at the data collection. The highest number I saw here was 15 uR/hr, which is definitely not normal. What I didn't notice until reviewing the data at home was that the highest number at Grizzly Island was actually 17 uR/hr. There's at least a 2 mile stretch along Grizzly Island Road with these abnormally-high levels.

(Though these numbers are not dangerous, I only took them from on the road, which is made from imported materials. Levels could be different off the road. So Grizzly Island could use an inspection by experts.)

After I was done at Grizzly Island, I returned to Suisun City to meet Justin. We drove a loop around on the public roads surrounding Travis AFB, just to check or rule it out as the source, since there had been a "broken arrow" accident at the base in 1950. (On Aug 5, 1950, a B-29 carrying an atomic bomb, without its fissile core installed, crashed and caught fire. After 15 minutes, the high explosives on the bomb exploded, killing the firefighters and USAF General Robert Travis, for whom the base was renamed. The fissile core was probably elsewhere on the plane and was destroyed in the explosion.) There was a very isolated area of elevated background levels up to 15 uR/hr off the end of the runway, measured from Highway 12. Something tells me that could be explained as where the broken arrow accident occurred. But other than that, Travis seems to be ruled out as the source of the radiation on Grizzly Island, the Potrero Hills and the Montezuma Hills because there is no evidence of a plume leading there.

We also checked Bird's Landing and Mein's Landing again, to get numbers during the daytime and to cross-check with the July 11 drive..

I drew a new chart of this drive. Initially the colors didn't work well. And that's the hazard when trying to invent a new way to display such data. I found the problem in the color selections and now the colors portray the data much more intuitively. I also entered the significant numbers manually onto the graph, which was originally the only way to display the data. You can also browse a table of the data points which are 13 uR/hr and above.

Download raw data from the July 15 drive (267K compressed, 2.4MB uncompressed)


The Grizzly Island data is cause for concern, whatever its explanation. With the new data collected on July 15, one plausible hypothesis is that I've discovered a possible 2-mile wide radioactive plume which faces Port Chicago. The nuclear accident theory at Port Chicago isn't looking so far-fetched any more, because the center of area appears to line up with the location where the explosion took place. But it certainly isn't proven by a long shot either.

The 2-mile stretch has large patches of 13-17 uR/hr readings. 10-12 is about normal background, the highest you'd expect in most cities. (That's at sea level. Average background is higher with more elevation simply due to radiation from the Sun.)

Back on the July 11 drive, one possibility was that the elevated readings could be something natural in the Montezuma Hills, possibly granite rocks or something else in the ground there. But now we see it's also on the flats and marshes at the shore of the Bay. So we can rule out a geological cause linked to the hills. It certainly isn't just in the hills.

I saw a comment saying I "ruled out geological causes too quickly". This was just testing whether it was just related to the Montezuma Hills where elevated levels were first seen. It wasn't limited to that area. But I should point out that other geological causes remain possible, though less likely since it spans different geographic features. While a granite formation isn't likely at the shore of Suisun Bay, it would take a geological study to rule out any of a zillion other possibilities. I also checked for quake faults (as a possible path for Radon release), but the area doesn't correspond with any known faults.

We've also ruled out Travis AFB as the cause. There was no plume leading south from the base. There was an isolated area of elevated background at the end of the runway, which could be explained by the 1950 "broken arrow" accident.

So just like on July 11, the highest background radiation readings on the July 15 drive were at the point closest to the Port Chicago accident location, now only 5 miles from it. And it's in a directions which would be normally downwind on a clear Summer night in this area. I found both sides of the higher-background area, and the shape continues to match that of a northeast-bound plume from Port Chicago, or shipping on Suisun Bay in front of the base.

Here are some references on the web in order to compare these background radiation levels.

Let's look at what this data tells us, and what it doesn't. If we take the most careful conclusion, this is it...
Does this prove that Port Chicago was a nuclear accident? No. It confirms only that there's higher than normal background radiation in the places where it was measured.

This data needs to be verified by another source. Objectively, we need to check for things like other sources for elevated background radiation and need more samples for the data.

This doesn't tell us when or how the radiation got there. Lots of possible explanations remain "on the table." If natural sources for the radiation can be completely ruled out, then the apparent (but unproven) shape of the elevated background radiation seems to point at the Navy base at Port Chicago, now called the Concord Naval Weapons Station for some kind of radioactive release. But with a busy shipping channel there, you can't rule out ships either.

If we ask "what happenned there?" the July 17, 1944 explosion has to be included on the list. Because it did happen there. I can't ignore the coincidence that the measured elevated radiation is in the place it would have to be if the nuclear accident scenario was true. That doesn't prove it's true, but if confirmed it would take away an objection many of us had about it. Namely that no one knew of any radiation in the area.

If you want to know which way the winds usually blow in that area, look on the map for the runways at Travis AFB. The area that we found elevated background appears to me like it's parallel to the direction of the runways (wind direction). The center of the elevated readings appear to be close enough lined up with the site of the Port Chicago 1944 explosion to maintain plausibility for that as a source.

This is enough info that it should be turned over to the media so they can pursue this via the Freedom of Information Act and ask direct questions to the Navy and members of Congress. It is for these things that the Constitution gives the press the freedoms that it does.

If further studies confirm this, the Grizzly Island State Wildlife Area may need some review of its usage. It opens to hunting every year. But this data indicates people probably shouldn't eat anything hunted from Grizzly Island itself, and shouldn't have been for decades.

Data collection equipment and software

So now the big question is... how can someone reading this page duplicate or participate in these measurements? I got the idea of a mobile geiger counter data collection system from Phil Stuart's "My Radioactive Vacation". But the hardware I used is all off-the-shelf. And I've Open Sourced my software for you. This combination is experimental. And the software is provided only as-is the way I used them. Please let me know if you perform this experiment. Here's the list...
a geiger counter
I got an RM-80 micro-Roentgen electronic radiation monitor from Aware Electronics
an enclosure for the geiger counter
I used a 2-foot section of 4" PVC pipe with end caps for the enclosure. I held the geiger counter in place with zip-ties to a small frame of fiberglass rods I got at Tap Plastics. Though anything non-metallic which will hold the sensor sturdily in place and protect it from the wind will do.
a GPS with external antenna
I used an old Garmin GPS12CX (which I got in 2000) set to output an industry-standard NMEA 0183 data stream. The main thing you'll want to look for is something with an external antenna, so that you have the best possible view of the satellites while collecting data.
an attachment point to the outside of your vehicle
I strapped the PVC enclosure to the rack on my truck so that the sensor stuck out away from the vehicle. It was about 6' off the ground.
a laptop computer running Linux
The data collection software currently is specific to the Linux serial driver
a USB serial port
My laptop has only one serial port. But this application requires two. So I got a Keyspan 19H USB to serial adapter. I put the GPS on the Keyspan since it wasn't able to handle the RM-80.
the Device::Geiger::Aware perl module
I wrote the Device::Geiger::Aware module specifically for this project and another experiment. The July 11 drive was its first test run. I used it with my RM-80. But by the product specs, it should also be able to handle the RM-60 and RM-70.
gps-geiger Perl script
This is the real-time data collection and logging program. It reads data from the GPS and the RM-80 geiger counter.
geiger-map Perl script
This is the script which draws the raw map image of the background radiation measured on the drive.
You can access the software from my Open Source code page.

Coverage of this story on the web

I submitted the story to SciScoop. As a starter, that's good enough - the discussion provides some review. If I notice it gets any other attention, I'll add links here.