Figure 32. Frequency of flooding tides, 1989-1994

34

a. 1989.

b. 1990.

Figure 32. Frequency of flooding tides, 19891994,

assuming that the flats flooded each time Anchorage

tide tables predicted a high tide of 31 ft or greater.

32

31

10 20

May

Jun

Jul

Aug

Sept

Oct

the concentrations found in 1992 and 1994 were

Sources of uncertainty about this field-contami-

due solely to random error, the observation of an

nated site include the date it was contaminated, the

increase in concentration would be just as likely

type of round that produced the contamination

as an observation of a decrease. Of the 41 pairs

(mortar or howitzer), where the round exploded,

compared, 22 showed a decrease, 7 showed an in-

the type of fuse (point detonating or other) and the

crease, and 12 were below the detection limit (Fig.

initial white phosphorus concentration. However,

36). The number of samples showing a decrease

we do have this information for another site in the

between 1992 and 1994 is significant at the 0.05

intermittent pond of Area C, a site where unex-

significance level.

ploded ordnance (UXO), an 81-mm mortar round

31