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Memo to Celina Akin 2 October 26, 2004 <br />American Soda TR-04 Permit No. M-1999-002 <br />Since Q = 0.905 is greater than the 5 percent Dixon Critical Value oi~0.525, the 7 mg/L data point is an <br />outlier, and this data point is rejected for use in calculating the boron NPL for well 21-3U. The next data <br />point in the descending order can be checked as follows (note that the power of this test decreases as the <br />number of repetitions increases): <br />Q = (X~ - Xz)/ (Xi - XN) _ (3.2 - 3.12)/(3.2 - 2.8) = 0.2 <br />Since Q = 0.2 is less than the 5 percent Dixon Critical Value of 0.545, the 3.2 me,JL data point is not an <br />outlier, and this data point is used in calculating the boron NPL for we1121-3U. The low value in the data <br />set is also checked for outlier status as follows: <br />Q = (x, - xz)/ (x, - xN) _ (2s - z.89)/(z.a - 3.z) = o.2zs <br />Since Q = 0.225 is less than the 5 percent Dixon Critical Value of 0.546, the 2.8 mg/L data point is not an <br />outlier, and this data point is used in calculating the boron NPL for we1121-3U. <br />We now have a useable baseline data set with 14 data points for calculation of the NPL. <br />3.2 3.12 3 3 3 3 3 3 3 3 2.9 2.9 2.89 2.8 <br />Use the Dixon calculation to solve for the NPL as follows: <br />Q = 0.546 = (NPL - 3.12)/(NPL - 2.8) <br />0.546(NPL - 2.8) = NPL - 3.12 <br />(0.546)(NPL) -1.53 = NPL - 3.12 <br />(0.546)(NPL) - NPL = -1.59 <br />(0.454)(NPL) = 1.59 <br />NPL = 3.5 mg/L <br />Note the di fference between this calculated NPL of 3.5 opposed to American Soda's suggested NPL of <br />3.2 considering that a sample containing 3.4 mg/L boron was collected in November 2002. <br />The remaining tasks for American Soda to gain approval of TR-04 :ire to calculate the other necessary <br />NPLs and EWIs and provide a submittal for DMG review and approval, and to compile a report, also to <br />be reviewed and accepted by DMG, as to the sampling and analytical difficulties experienced, and their <br />impact on the scatter of the deep monitoring well water quality data. <br />attachment(s) <br />cc: Erica Crosby, DMG (via email) <br />Carl Mount, DMG (via email) <br />Harry Posey, DMG (via email) <br />C:~acs\[AANER MACNME\My Documents~am soda h4 npls.doc <br />