(ec) Aniterative excavation plan will be executed to: l. Reduce the quarter hectare area average concentration below 40 pCifg. 2. Reduce the average concentration of the "defined region" to some lower number which shall be determined by cost-benefit considerations, but will usually not be below local background. (4) Condition D: An assay area whose average Pu concentration is any 5 cm thickness of soil below the surface layer when measured /6 (at the 67 percent confidence level) to exceed 400 pCi/g will be excavated and measured iteratively until its average Pu concentration in the new 5 em layer is found by measurement (at the 50 percent confidence level) to be reduced in the defined region to some lower number which shall be determined by cost-benefit considerations, but will usually not be below local background. Footnotes: fl Assay Area. The field of view of the in situ detector in its normal operating position; typically a 28 meter diameter circle of 3 - 5 em in depth. Scattered measurement can be used to estimate average concentrations between such measurements by means of a linear estimator program known as "Kriging." /2Statistically, two-thirds of the time the actual concentration will be below the guide number. One-third of the time the actual concentration may exceed the number by some percentage which must be empirically determined (up to 20-30 percent, as an estimate). This is similar to using a 50 pereent confidence level with a numerical guide 20-30 percent (estimated) lower. If a 90 percent confidence level were used with the numerical guide, the equivalent guide at a 50 percent confidence level would require a 40-50 percent (estimated) reduction of the numerical number. For example,if the guide number were 400 pCi/g, cleanup would be required at 400- ot, where o is the standard deviation of the measurement and t is the "student t" value, about 0 for 50 percent, .5 for 67 percent, 1.5 for 90 percent and 2.0 for 95 percent. The current estimate without data for a typical is 30-50 percent of the measurement(data and experience at Enewetak will be necessary to measure the sigma). Therefore, a 50 percent confidence level would require cleanup above 400 pCi/g, 67 percent would require cleanup at 320 pCi/g (estimated), and 90 percent would require cleanup at 250 pCi/g (estimated). /3 Local Background. In this plan, local background is defined as the average surface soil concentration which is expected to remain in the undisturbed region surrounding a cleaned up area. Identification of the surrounding region (which may be a portion of an island or at most an entire island) will result from examination of coarse survey data, evaluation of potential land use and accessibility, and economic and logistic factors. Thus, the decision as to what surface concentration is to be assumed in each case as local background is judgemental and is a key element in setting detailed cleanup objectives. /4Resuspension Potential. The product of an area multiplied by the average surface concentration of Pu over that area, hence the inventory of Pu readily available to be resuspended. potential is an index which has no meaning in terms of hazard. being worthy of the expenditure of cleanup resources. /5surface Concentration. Resuspension It serves only to compare areas as The apparent concentration on the surface, as viewed by the in situ detector. In reality, this is a complex function of the distribution of Pu in the top few em of soil. Normally expressed in pCi/g. £6soi1 profiles will (approximately 2 or more) be needed to estimate the assay area below the surface. (Predeployment Radiological Training is presented in the following section from the OPLAN. This Report has no counterpart sections.) E-12