FOREWORD The following report, by Holmes & Narver, Inc., under contract to the United States Atomic Energy Commission, summarizes the planning, engineering, design, construction, maintenance and operation of Pacific Proving Groundfacilities over the eighteen month span of OPERATION CASTLE. Purely a documentary report, it has been consciously abbreviated to features relevant from the Contractor’s point of view as administratively significant to ultimate cause and effect. In this manner, much of the vital drama and import of this venture is not apparent in the report, although it was an important ingredient in the tireless enthusiasm of the men, and the generally high morale which characterized both the prolonged periods of tension and the brief emergencies. As was to be expected, OPERATION CASTLE went more smoothly for us than did previous operations. Problems originally encountered, once unique to the engineer and the constructor, were now ordinary. Procedures originally exploratory were now adjusted, revised, and proven. Past fore- casts, facing unknowns, contained uncertainties; present experience factors enabled most crises to be reliably provided for. Increased organizational efficiency resulted to our management. However, the success of an operation of the magnitude and complexity of CASTLE demands moreof any unit management than intrinsic efficiency; deeply involved are the broader aspects of effective liaison with other participating and supporting agencies. This requirement, arising, in part, from the large number and diversity of such other agencies, the experimental nature of the total mission, and the geographical isolation of the operational sites, was recognized at the outset as an important management consideration. Sensitivity was encouraged in our supervisory people to the manner in which all components of the test operation must be integrated during the planning and construction period, so as to all focus at the proper times on an inflexible end date—shot time. The mechanics of doing this were not always simple and did not always yield readily to predictable procedures, since some of the elements of OPERATION CASTLE were, as an engineering, construction and management job, without precedent. The perspective possible from serving two previous operations enables us to observe that the fact that OPERATION CASTLE, in spite of its complexities, proceeded through all of the pre-operational phases without serious delays and generally on schedule; and that the operational phase was successfully concluded in spite of unprecedented adversity, is a clear tribute to the outstanding cooperation between all of the diverse components of the JOINT TASK FORCE SEVEN, in a unit of which we proudly served. Page i