- Four exceedances of any single metal in any 60-day period is not allowed.
• This determination should be made daily, beginning on the first day of daily monitoring. For example, if 4 exceedances of any single metal occur in the first 4 days of daily monitoring, do not wait until the end of the 60-day period; refer immediately to Step 11.
(11) A revised certification of precompliance shall be submitted to the department (or certification of compliance shall be submitted) if: (1) More than 3 exceedances of the “conservative" kiln dust metal concentration limit occur within any 60 consecutive daily samples; or (2) an exceedance of the “conservative" kiln dust metal concentration limit occurs in any weekly sample.
• The facility shall notify the department if a revised certification of precompliance shall be submitted.
• The facility has up to 720 waste-burning hours to submit a certification of compliance or a revised certification of precompliance. During this period, the feed rate of the metal in violation shall be reduced by 50%. In the case of a revised certification of precompliance, engineering judgement shall be used to ensure that the “conservative" kiln dust metal concentration will not be exceeded. Examples of how this goal might be accomplished include:
- Changing equipment or operating procedures to reduce the kiln dust metal concentration;
- Changing equipment or operating procedures, or using more detailed engineering judgement, to decrease the estimated SEF and thus increase the “conservative" kiln dust metal concentration limit;
- Increasing the “conservative" kiln dust metal concentration limit by imposing a stricter PM emissions standard; or
- Increasing the “conservative" kiln dust metal concentration limit by performing a more detailed risk assessment to increase the metal emission limits.
• Meanwhile, the facility shall continue with daily kiln dust metals monitoring (Step 5).
Appendix A to Appendix IX—Statistics
A.1 Determination of Enrichment Factor
After at least 10 initial emissions tests are performed, an enrichment factor for each metal shall be determined. At the 95% confidence level, the enrichment factor, EF95% s, is based on the test results and is statistically determined so there is only a 5% chance that the enrichment factor at any given time will be larger than EF95% . Similarly, at the 99% confidence level, the enrichment factor, EF99% , is statistically determined so there is only a 1% chance that the enrichment factor at any given time will be larger than EF99% .
For a large number of samples (n > 30), EF95% is based on a normal distribution, and is equal to:
EF95% = EF + zc ó
(1)
where:
For a 95% confidence level, zc is equal to 1.645.
For a small number of samples (n<30), EF95% is based on the t-distribution and is equal to:
EF95% = EF + tc S
(4)
where the standard deviation, S, is defined as:
tc is a function of the number of samples and the confidence level that is desired. It increases in value as the sample size decreases and the confidence level increases. The 95% confidence level is used in this method to calculate the “violation" kiln dust metal concentration limit; and the 99% confidence level is sometimes used to calculate the “conservative" kiln dust metal concentration limit. Values of tc are shown in table A-1 for various degrees of freedom (degrees of freedom = sample size-1) at the 95% and 99% confidence levels. As the sample size approaches infinity, the normal distribution is approached.
A.2 Comparison of Enrichment Factor Groups
To determine if the enrichment factors measured in the quarterly tests are significantly different from the enrichment factors determined in the initial Step 2 tests, the t-test is used. In this test, the value tmeas:
is compared to tcrit at the desired confidence level. The 95% confidence level is used in this method. Values of tcrit are shown in table A-1 for various degrees of freedom (degrees of freedom n
1+n2-2) at the 95% and 99% confidence levels. If tmeas is greater then tcrit, it can be concluded with 95% confidence that the 2 groups are not from the same population.
A.3 Rejection of Data
If the concentration of any hazardous metal in the “required" kiln dust sample exceeds the kiln dust metal concentration limit, the “spare" samples are analyzed. If the average of the combined “required" and “spare" values is still above the limit, a statistical test is used to decide if the upper value can be rejected.
The “Q-test" is used to determine if a data point can be rejected. The difference between the questionable result and its neighbor is divided by the spread of the entire data set. The resulting ratio, Qmeas, is then compared with rejection values that are critical for a particular degree of confidence, where Qmeas is:
The 90% confidence level for data rejection is used in this method. Table A-2 provides the values of Q
crit at the 90% confidence level. If Q
meas is larger than Q
crit, the data point can be discarded. Only one data point from a sample group can be rejected using this method.
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See PDF for table 
