Laserfiche WebLink
Mr. Travis Marshall <br />Mr. David Bird <br />Division of Reclamation, Mining, & Safety <br />May 11, 2011 <br />Page 7 <br />compliance point. <br />Well Cluster 138-4-298 is located in the northeast corner of the East <br />RDD Lease. A revised map included with this response shows the well <br />locations at this well pad (Figure 36, attached). <br />6. Alternate Numeric Protection Levels are proposed without a rationale, other than the "2 <br />standard deviations " presented in the lower half of Table 5.2. Please provide the <br />rationale behind the Alternate Numeric Protection Levels, and also please add a column <br />to Table 5.2 showing the number of samples (n) upon which the statistical analyses are <br />based. <br />A revised Table 5.2 showing the number of samples (n) is provided with <br />this response. <br />The rationale for alternate numeric protection levels is as follows: <br />• The reported analyses are valid. All reported values have been <br />subjected to persistent field and lab QA/QC. <br />• Errant values are not included in statistics. QA tests include <br />an initial visual screening that looks for values that appear to <br />be more than 20% over or under prior values; when such <br />suspiciously high or low values are detected, the lab is notified <br />and, when appropriate, samples are re-run to verify precision. <br />• Value ranges are consistent, and show no seasonal variation. <br />Values that tend to exceed water quality criteria are consistent <br />between sampling events and show no seasonal variation in the <br />area of the East RDD. <br />• Analytes with elevated concentrations appear in many wells <br />regionally. Analytes that are proposed for alternate numeric <br />protection levels in this NOI tend to report above basic ground <br />water quality standards in wells over the larger area over which <br />Shell has drilled and sampled for approximately 10 years and in <br />nearly all wells in that WBI. <br />• Natural variability is confirmed; statistical normal <br />distributions are expected. Owing to the native variability and <br />lack of seasonal fluctuations, it is concluded that high values <br />are as valid a measure of ground water conditions at the time of <br />measurement as low values at their time of measurement. <br />Therefore, the reported variation in water chemistry is evidently <br />• the result of natural conditions and natural variation, not <br />analytical variation. Thus, any measured value found in future