§ 88.512. Procedure for calculating and applying a single-observation (monthly) trigger.
(a) This section contains two alternative methods for calculating a single-observation trigger. One method must be proposed by the applicant to be approved and applied by the Department for a remining permit.
(b) Method 1 for calculating a single observation trigger (L) is accomplished by completing the following steps:
(1) Count the number of baseline observations taken for the pollutant of interest. Label this number n. To sufficiently characterize pollutant loadings during baseline determination and during each annual monitoring period, it is required that at least one sample result be obtained per month for 12 months.
(2) Order all baseline loading observations from lowest to highest. Let the lowest number (minimum) be x(1), the next lowest be x(2), and so forth until the highest number (maximum) is x(n).
(3) If fewer than 17 baseline observations were obtained, the single observation trigger (L) will equal the maximum of the baseline observations (x(n)).
(4) If at least 17 baseline observations were obtained, calculate the median (M) of all baseline observations. If n is odd, then M equals x(n/2+1/2). If n is even, then M equals 0.5* (x(n/2) + x(n/2+1)).
(5) Next, calculate M1 as the median of the subset of observations that range from the calculated M to the maximum x(n); that is, calculate the median of all x larger than or equal to M.
(6) Next, calculate M2 as the median of the subset of observations that range from the calculated M1 to x(n); that is, calculate the median of all x larger than or equal to M1.
(7) Next, calculate M3 as the median of the subset of observations that range from the calculated M2 to x(n); that is, calculate the median of all x larger than or equal to M2.
(8) Finally, calculate the single observation trigger (L) as the median of the subset of observations that range from the calculated M3 to x(n).
(9) When subsetting the data for each of the steps in paragraphs (5)—(8), the subset should include all observations greater than or equal to the median calculated in the previous step. If the median calculated in the previous step is not an actual observation, it is not included in the new subset of observations. The new median value will then be calculated using the median procedure, based on whether the number of points in the subset is odd or even.
(c) The method for applying the single observation trigger (L) to determine when the baseline level has been exceeded is as follows:
(1) If two successive monthly monitoring observations both exceed L, immediately begin weekly monitoring for 4 weeks (four weekly samples).
(2) If three or fewer of the weekly observations exceed L, resume monthly monitoring.
(3) If all four weekly observations exceed L, the baseline pollution loading has been exceeded.
(d) Method 2 for calculating a single observation trigger (L) is accomplished by completing the following steps:
(1) Follow Method 1 in subsection (b) to obtain M1 (the third quartile, that is, the 75th percentile).
(2) Calculate M-1 as the median of the baseline data which are less than or equal to the sample median M.
(3) Calculate the interquartile range, R = (M1 - M-1).
(4) Calculate the single observation trigger L as L = M1 + 3 * R.
(5) If two successive monthly monitoring observations both exceed L, immediately begin weekly monitoring for 4 weeks (four weekly samples).
(6) If three or fewer of the weekly observations exceed L, resume monthly monitoring.
(7) If all four weekly observations exceed L, the baseline pollution loading has been exceeded.
Authority The provisions of this § 88.512 issued under section 5 of The Clean Streams Law (35 P.S. § 691.5); sections 4(a) and 4.2 of the Surface Mining Conservation and Reclamation Act (52 P.S. § § 1396.4(a) and 1396.4b); and section 1920-A of The Administrative Code of 1929 (71 P.S. § 510-20).
Source The provisions of this § 88.512 adopted October 21, 2016, effective October 22, 2016, 46 Pa.B. 6780.
Cross References This section cited in 25 Pa. Code § 88.513 (relating to procedure for calculating and applying an annual trigger).
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