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RR F summed progressivOly vich vertical distance. This sum is referred to as a cumulative contamination level and is no longer expressed as a concencraeion. Tn deter- minae what the cumulat;-.e contamination level is at a particular depth (E) , add the concentration at that depth to the sum of the concencrations for, each inter- val above ic. Far example: the first sample (at a 15 £t. depth) - 4 omm, the second sample (ac a 20 ft. depth) - 5 mom, and the third samples (at a 25 f,. depth) - 1 Dom; cumulative contamination levels are 4 for the first sample. 9 (4+5) for the second sample. and 10 (9+1) for the third sample. -he last saw be included in the calculations £a cumu v scion must be at or above the detection limit. Do not whinh \ Oported as less than the detection limit 0.3 am . The calculation of cumulative contamination levels is only done for the zone of contaminated soil; the analysis stops at the lowest extent of contamination. (7) Use Tables 2-5 through 2-8 (pages 34 to 37) co - determine the acceptable cumulative soil contamination levels for each layer of contaminated soil. (F). The tables show distance from contamination cc ground water on the vertical axis and annual rainfall on the horizontal axis. Note than the tr.blcs xhnv distance r -- from ground water (D), not from the 5ur£ace of the soil (C). For example, the acceptable levels in the top row axe acceptable for the layer 5 to 10 feet above ground water, while the values in the bottom row are for the y layers which are more than 150 feet above ground water. The models were used to derive acceptable cumulative -a soil contamination levels, which the tables show as whole numbers ranging from 0 to 1004. The acceptable levels can be found on the table using the average annual precipitation (A) and the distance from the sample to ground water M. The models actually generated precise numbers, but it was decided to round the numbers down cc the left-most digit for two reasons. First, the more precise a numbar is, the more accurate it appears to be. The general- risk appra?.sal estimates, but does not pinpoint, the threat of ground vatar pollution. Second, the results were rounded down to lower numbers to provide an additional margin of ground water procection in the analysis. -33.