» BATTELLE Dr. Rudolf J. Engelmann . D NORTHWEST -6- March 12, 1971 We know that initially the half-life is about 30-40 days for deposited radioactivity to weather into a relatively non-erodible state. However, we do not know the long-term time dependency of the half-life as a function of any variable. One variable influenc- ing the half-life is migration into the soil. For Pu, this weathering includes migration down into the SOil as far as 13 cm (HASL-235). As you can see, little is really known about particle resuspension. Consequently, we have tried within the question review to identify additional general problem areas which must be evaluated, Hazard appraisals to date have used the best estimates so far but these are really inadequate and misleading. Very truly yours, A nn ‘ we \o. og. JJF:ck In triplicate ccs James E. Milier Fuquay