Olympic Peninsula,
Washington

The series of measurements made in the northern part
of the Olympic Peninsula, Washington (Clallam Co.), were
of special interest since, over a distance of approxi-

mately 50 miles, the mean annual rainfall varies by a

factor of nearly 10 from east (Sequim) to west (Forks).
Under such conditions one might expect a substantial variation in the fallout level since fallout depostion is
strongly influenced by quantity of rainfall.
Alexander and
his co-workers have found a clear correlation between sr?°
deposition and mean rainfall levels at five sampling locations in Clallam Co.1°
Measurements of terrestrial gamma
levels at these and several other sites in early October
1962 are summarized in Table II. The increase of the fallout gamma dose rates with mean annual rainfall is noteworthy, and the degree of correlation seems quite as good
as that for the accumulated Sr?9 soil content.
But care
must be exercised here in coming to appropriate conclusions,
since the quantity of relatively short-lived gamma emitters
present depends on recent rainfall to a much greater ex-

tent than is the case with sr?99,

The Forks locations are of particular interest since
these measurements were made during or between periods of

heavy rainfall.

The spectra show a distorted K40 peak at

1.46 MeV, which is clearly the result of a considerable

Lal40 contribution at 1.6 MeV.

This implies substantial

recent fallout deposition; this fact is also evidenced by
the lack of agreement between the two methods of estimating

fallout dose rates.
As mentioned previously, recent
deposition generally implies a more nearly plane source

than in our model, and thus more peak counts per unit dose
rate for the various fallout isotopes.
Therefore, our peak
method would tend to overestimate the fallout dose rates.

In addition, the Lal40 contribution might also cause us
to overestimate the K49 and u238 dose rates, Fortunately,

the Forks locations were among the few where a significant
Lal40 contribution was observed.
The Olympic Peninsula area was also of interest in that
the natural levels (3-5 ur/hr) were among the lowest measured
by us during our various surveys.
These levels were about

Select target paragraph3