24 July 1944

For: Rear Admiral W. R. Purnell, USN
From: Captain W. S. Parsons, USN
Subject: Port Chicago Disaster, Preliminary Data

  1. On 20 July I arrived in San Francisco, accompanied by Ensign Reynolds and Dr. Shapiro. I called on the Commandant (Rear Admiral C. H. Wright) and discussed the disaster briefly with him, emphasizing that my mission was to obtain data on effect rather than the cause of the detonation. Admiral Wright had been in command of the Naval Mine Depot, Yorktown, Virginia, as recently as 1940, and his executive there had been Captain A. G. Cook, now Captain of the Yard at Mare Island. Admiral Wright had, therefore, considered Cook well qualified and had appointed him President of the Court of Inquiry, with Captains J. S. Crenshaw and W. B. Holden as members.

    The cooperative spirit and helpfulness shown by Admiral Wright and his office was later found to obtain throughout the organization, including the Navy Yard, N.A.D. Mare Island and at Port Chicago. There was not the slightest tendency to cover up or stand on dignity or to raise questions regarding cognizance or infringement on the duties of the Court.

  2. My party arrived at Mare Island about noon 20 July and, with Captain Crenshaw, proceeded to Port Chicago. Enroute we looked at large windows broken in stores in Vallejo at 20 to 22,000 yards from the detonation. As we drew nearer to Port Chicago, the number of broken windows increased slightly and the minimum size decreased. The hilly terrain shielded most structures effectively. The first blast damage beyond broken windows, was seen in the town of Port Chicago, where the movie theater suffered severe C or moderate B damage. The side of the frame building was crushed in 5 to 10 feet and the roof sagged. This was the heaviest damage seen beyond one mile.

  3. At this point I will cease to be chronological and will present data obtained.

  4. Discussion

    If I were pressed for a figure for B damage now, before Ens. Reynolds and Dr. Shipiro have analyzed their records, I would guess that B damage would be 100% from 600 to say 800 yards, and would then taper off to 50% at 1,000 yards. At 1,500 yards only occasional structures would suffer B damage.

    The relative position of the empty ship, S.S. QUINALT VICTORY, is such that she might have acted as a reflector to increase the blast in the direction of the barracks area, and to decrease air blast and wave effect toward the channel and lighthouse (about 1,000 yards). More evidence on these points will be available when the Court has the eyewitness testimony of the steersman of a tug which was said to be in the channel at about 500 yards from the detonation.

    Ens. Reynolds and Dr. Shapiro were scheduled to inspect the lighthouse on 22 July, and on 24 July to discuss the seismic records with Professor Perry Byerly of the University of California. These data, together with analysis of fragment distribution, and discussion with the Court, of eyewitness testimony of an airliner pilot said to have seen the explosion from 7,000 feet altitude, should permit a fairly complete analysis of the more violent effect of the detonation.

    Various eyewitnesses interviewed by ONI agreed that the column of fire rose vertically and then mushroomed. A second detonation is supposed to have followed the first one at an interval estimated from 1/5 second to many seconds.

    Comparing loss of life to the Halifax disaster, it appears that all but some five of the victims at Port Chicago were right on top of the explosion, in a position corresponding to some 25 crew members and fire fighters at Halifax. Thus, the comparison for remote victims is Halifax about 1,475, Port Chicago less than 5. If the two explosions are considered to be of the same order of magnitude, the difference in loss of life can be attributed to the fact that Port Chicago was designed for large explosions.

  5. It is emphasized that the data and discussion given in this memorandum are preliminary and necessarily rough. Several weeks will be required to assemble and analyze data for an adequate report.

    W. S. Parsons
    Captain, USN


    Source: Parsons, William S., Memorandum on Port Chicago Disaster, Preliminary Data, 24 Jul. 1944, Box 671, World War II Command File, Operational Archives Branch, Naval Historical Center, Washington, DC].

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