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�t <br /> summed progressively with vertical distance This sum <br /> Is referred to a: a cumulative contamination level and <br /> is no longer expressed as a concentration To deter- <br /> mine what the cumulative contamination level is at a <br /> particular depth (E) , add the concentration at that <br /> depth to the suss of the concentrations for each inter- <br /> val above it For example the first sample (at a <br /> ' 15 €t depth) - 4ynm, the second sample (at a 20 ft <br /> depth) - 5 13-o m. and the third sample (at a 25 ft <br /> depth) m 1 vom, cumulative contamination levels are 4 <br /> for the first sample, 9 (4+5) for the second sample. <br /> ' and 10 (9+1) for the tha.rd samv3.e The 1 <br /> be included in the calculations for cumu ;L4 v <br /> ation smzst be at or above the detection limit Do not <br /> .inri„rla 1-mrrnm samnles which have coneont- nriaas <br /> _revorted as less than the detection limit _(O 3 ppm) <br /> The calculation of cumulative contamination levels is <br /> ' only done for the zone of contaminated soil, the <br /> analysis stops at the lowest extent of contamination <br /> (7) Use Tables 2-5 through 2-8 (pages 34 to 37) to <br /> ' <br /> determine the acceptadle cumulative soil eontam,Lnation <br /> levels for each layer of contaminated soil (F) The <br /> tables show distance from contamination to ground crater <br /> on the vertical axis and annual rainfall on the <br /> horizontal axis. Note that the tables show distance <br /> from ground water M . not from the surface of the soil <br /> (C). For example, the acceptable levels in the top roar <br /> ' <br /> are acceptable for the layer 5 to 10 fent above: ground <br /> crater, whil© the values in the bottom row are for the <br /> layers which are more than 150 feat above ground crater <br /> ' The models were used to derive acceptable cumulative <br /> soil contamination levels, which the tables show as <br /> whole numbers ranging from 0 to 1000 The acceptable <br /> levels can be found on the cable using the average <br /> assaual precipitation (A) and the distance from the <br /> samplo to ground raster (D) . The models actually <br /> ' generated precise numbers, but it crag decided to round <br /> the numbers down to th© left-most digit for two <br /> reasons First, the more preeisea a number is, the more <br /> accurate it appears to ba. The general risk appraisal <br /> estimates, but does not pinpoint, thea threat of ground <br /> orator pollution. Second, the results were rounded down <br /> to lower numbers to provide an additional margin of <br /> ' ground water protection in the analysis. <br /> -33- <br />