Opinion ID: 1176318
Heading Depth: 2
Heading Rank: 1

Heading: Gamma Radiation Threshold

Text: In its previous order, EFSC found that gamma radiation exposures from LRP and SL would not exceed 500 millirem per year, the threshold set by OAR 345-50-035. EFSC adhered to that finding in its present order. A reasonable person, viewing the evidence as a whole, could make the same finding. The record shows that gamma radiation from LRP and SL was measured at 0 to 280 millirem per year (exclusive of background radiation of approximately 90 millirem per year). Petitioners contend that the radiation measuring devices were placed at the perimeter of the sludge ponds and that this placement might have caused the measured gamma radiation to understate the true radiation emanating from the surface of the ponds. An expert witness for TWCA testified that the measuring devices were placed above the surfaces of the ponds but only 4 to 5 feet from their shores because their surfaces at the time of placement would not support the weight of the workers who placed the devices. The witness stated that the intensity of gamma radiation decreased rapidly with distance and that essentially all of the gamma radiation received by the measuring devices would be received from sources within a few feet of the devices. Consequently, placing the devices within a few feet of the shores would not underestimate the radiation emanating from the surface of the ponds. There is no evidence to contradict this testimony, and there is nothing in the record from which one could infer that the gamma radiation levels of LRP and SL would be higher at their centers than at their perimeters. More convincing measurements might have been made, but the evidence in the record is sufficient to make EFSC's findings reasonable.