CHAPTER SIX: SPECIAL TOPICS
6.1 INTRODUCTION
This chapter results from the situation that some topics, considered of enough importance or interest
to be included somewhere, do not fit the specifie subject matter or format of other chapters, and are
individually too short to merit separate chapters. Topics are introduced or expanded upon in this
chapter to provide background to aid understanding of the results presented in Chapter Seven.
Startup operations in July 1977 were located on Island Janet, so this topic appears early. (One might
dispense with Chapter Six altogether by moving text into other chapters, but then the discussion of
IMP startup and preliminary surveys, on Island Janet, would not be encountered until nearly 100
pages into Chapter Seven.) The remainder of the chapter introduces topics in the approximate order
the described actions occurred.
Efforts directed toward subsurface sampling and characterization were divided into two distinct
phases, with a decision conference on 3-4 May 1978 as the dividing line. Prior to this date,
subsurface sampling was undertaken on the ground zero islands, as a group, without clear priorities.
After this date, the priorities of island cleanup provided guidance for a better directed effort. Also,
since sampling requirements were dictated by island cleanup priorities, the remaining subsurface
profiling was spread over the next year following the May conference and there was less need to
keep track of and map data from several islands at the same time. The sample location maps shown
in Section 6.9 were, therefore, never updated.
6.2 SURVEYS AND COORDINATE SYSTEMS (by Bert Friesen, H&N)
Testing of nuclear devices at Enewetak Atoll was a joint effort by military weapons specialists and
civilian scientists. Preparations for a device test usually included experiments to evaluate military
effects and to gather data critical to the understanding of nuclear explosion physics. Test structures
and recording stations were placed with extreme precision by careful triangulation between fixed
points on the atoll. The exact location of each structure or station was recorded for future
reference. Surveyed benchmarks were placed on eachisland to facilitate remeasurement following a
test and to reduce the time required to prepare for the next construction phase.
The early series of operations, like SANDSTONE and GREENHOUSE, utilized only local-control
survey markers based on work performed in 1944, 1947-48, and 1949-50, which had established the
locations of 16 stations covering the eastern portion of the atoll The survey was expanded in 195]
to meet additional program requirements; -however, an independent plane coordinate grid was still
established at each of the zero areas for location of scientific stations. The need for an overall atoll
grid was recognized at this time, and this recognition led to further expansion in 1952 to include the
entire atoll. A plane coordinate system was established with the origin located at a point in the
ocean southwest of the atoll such that the coral head Oscar, located in the lagoon, would have
coordinates 100,000N - 100,000E (in feet). This system wasinitially called the IVY grid, but later
came to be known as the OSCAR grid. After 1952, all locations on the atoll were specified utilizing
the Osear system. The coordinates of all survey benchmarks placed on the various islands are
positive values, in feet, north and east of the origin.
Attempts to recover benchmarks during cleanup were only partially successful; no markers were
found on several islands, and several markers were found with names that did not match available
reference lists.
Island maps in Chapter 7 show the approximate relationships between recovered
benchmarks and island grids. It should be possible, with surveyor assistance, to return approximately
to any soil sample or gamma scan point identified on the maps in Chapter 7, except on the few
islands where no benchmark wasrecovered.
Janet was the first island to be surveyed and staked during the cleanup, but was not representative
of work to be done later. On Janet, brush was cleared prior to surveying so placementof grid stakes
was relatively unencumbered,
Also, a known benchmark wasselected to be the intersection of the
north-south and east-west baselines. On islands staked later, the surveyors worked with the
bulldozer operators to clear access lanes suitable for placing stakes on a 25- or 50-meter grid. In
general, a baseline was located as a matter of convenience without regard to any benchmarks; if a
153