-3- (5) Other factclrs that might account for low or variable IMP readings are attenuation conditions at time of IMP readings were, apparently, Both wet and dry weights conditions not recorded. of soil samples are taken, but moisture on the islands change from day to day, and soil samples are not taken in conjunction expressed Soil moisture due to soil moisture or soil density. with most IMP readings. John Tipton the opinion that IMP errors due to soil moisture and density would be on the order of 10 to 15%. (6) The IMP is calibrated Am source in the field three times a day using a known (100 mCi*3%) through a 180° arc. suspended under the IMP detector and moved The detector has a lead and cadmium shield at an angle of 50° from the verticle. The iMP calibration assumes a soil density of 1.5 g/cm3. (7) The IMP has never been calibrated in the soil. done. against a known no pads available with 241Am NBS standard sources for field calibration. (8) Am concentration Everyone present seemed to agree that this should be There are, apparently, extensive 241 Experiments involving soil sampling would be necessary. Depth control on surface soil samples appears to be rather “sloppy” (my term). A cookie cutter designed to control depth has not been used since sometime in the period October-December. is to scoc)p from soil surface. Present procedure Only the top “3 cm” surface soil samples are used for cleanup calculations. Samples at 10 and 20 cm depths have been taken at each surface sample location, but only to indicate whether profiles to greater depths are required. (On May 3, 1978, M. Barnes informed me these 10 and 20 cm samples are no longer being taken, on orders from Bruce Church. the collection at those depths. ) analyzed by wet chemistry, He also initiated The 10 and 20 cm samples are but utility of data is decreased by the fact that soil from upper layers has sometimes fallen to lower cut levels during sampling operation. Apparently, these 10 and 20 cm cuts are the only profile data that may in some sense be labeled as representative. The profile data supplied to the Advisory Group for the April 26 and 27, 1978, meeting in Denver, CO, were taken in areas