1.12 Other Continental United States Sites Monthly fallout collectors are maintained at other sites within the continental United States. Exposed surfaces of the collectors are 0.82 et? except at Lemont, Ille (0075 rt") and Richmond, Calif. (4.91 rt"). At Pittsburgh, Pa., Westwood, N. Je, Houston, Texas, and Richmond, Calif., two collectors are exposede Table 2 summarizes the most recently analyzed monthly collections. The 3r99/gr90 ratios have been extrapolated to the midpoint of the collection period. The cumulative levels of strontium 90 for each site are plotted in Figure 2, pages 19 and 20, Explanation of Brror Terms in Table 2 The counting error is shown in the column “mc gr99/miee and 4e used to compute the cumulative error term when only one collector is exposed. For two collections, the standard error of the mean is incorporated into the cumulative error terme