[Code of Federal Regulations]
[Title 40, Volume 27]
[Revised as ofJuly 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR434.85]
[Page 292-297]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 434--COAL MINING POINT SOURCE CATEGORY BPT, BAT, BCT LIMITATIONS AND NEW SOURCE PERFORMANCE STANDARDS--Table of Contents
Subpart H--Western Alkaline Coal Mining
Sec. 434.85 New source performance standards (NSPS).
Any new source western coal mining operation with drainage subject
to this subpart must meet the effluent limitations in Sec. 434.82.
Appendix A to Part 434--Alternate Storm Limitations for Acid or
Ferruginous Mine Drainage
[[Page 293]]
[GRAPHIC] [TIFF OMITTED] TC01MY92.113
[[Page 294]]
Appendix B to Part 434--Baseline Determination and Compliance Monitoring
for Pre-existing Discharges at Remining Operations
I. General Procedure Requirements
a. This appendix presents the procedures to be used for establishing
effluent limitations for pre-existing discharges at coal remining
operations, in accordance with the requirements set forth in Subpart G;
Coal Remining. The requirements specify that pollutant loadings of total
iron, total manganese, total suspended solids, and net acidity in pre-
existing discharges shall not exceed baseline pollutant loadings. The
procedures described in this appendix shall be used for determining
site-specific, baseline pollutant loadings, and for determining whether
discharge loadings during coal remining operations have exceeded the
baseline loading. Both a monthly (single-observation) procedure and an
annual procedure shall be applied, as described below.
b. In order 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 a
period of 12 months.
c. Calculations described in this appendix must be applied to
pollutant loadings. Each loading value is calculated as the product of a
flow measurement and pollutant concentration taken on the same date at
the same discharge sampling point, using standard units of flow and
concentration (to be determined by the permitting authority). For
example, flow may be measured in cubic feet per second, concentration in
milligrams per liter, and the pollutant loading could be calculated in
pounds per year.
d. Accommodating Data Below the Maximum Daily Limit at subpart C of
this part. In the event that a pollutant concentration in the data used
to determine baseline is lower than the daily maximum limitation
established in subpart C of this part for active mine wastewater, the
statistical procedures should not establish a baseline more stringent
than the BPT and BAT effluent standards established in subpart C of this
part. Therefore, if the total iron concentration in a baseline sample is
below 7.0 mg/L, or the total manganese concentration is below 4.0 mg/L,
the baseline sample concentration may be replaced with 7.0 mg/L and 4.0
mg/L, respectively, for the purposes of some of the statistical
calculations in this Appendix B. The substituted values should be used
for all methods in this Appendix B with the exception of the calculation
of the interquartile range (R) in Method 1 for the annual trigger (Step
3), and in Method 2 for the single observation trigger (Step 3). The
interquartile range (R) is the difference between the quartiles
M-1 and M1; these values should be calculated
using actual loadings (based on measured concentrations) when they are
used to calculate R. This should be done in order to account for the
full range of variability in the data.
II. Procedure for Calculating and Applying a Single-Observation
(Monthly) Trigger
Two alternative methods are provided for calculating a single-
observation trigger. One method must be selected and applied by the
permitting authority for any given remining permit.
A. Method 1 for Calculating a Single Observation Trigger (L)
(1) Count the number of baseline observations taken for the
pollutant of interest. Label this number n. In order 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 a period of 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, then 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:
Instructions for calculation of a median of n observations:
If n is odd, then M equals x(n/2+1/2).
For example, if there are 17 observations, then M =
X(17/2+1/2) = x(9), the 9th highest
observation.
If n is even, then M equals 0.5 * (x(n/2) +
x(n/2+1)).
For example, if there are 18 observations, then M equals 0.5
multiplied by the sum of the 9th and 10th highest observations.
(a) 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.
(b) 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.
(c) 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.
(d) Finally, calculate the single observation trigger (L) as the
median of the subset of observations that range from the calculated
M3 to x(n).
[[Page 295]]
Note: When subsetting the data for each of steps 3a-3d, 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.
(5) Method for applying the single observation trigger (L) to
determine when the baseline level has been exceeded
If two successive monthly monitoring observations both exceed L,
immediately begin weekly monitoring for four weeks (four weekly
samples).
(a) If three or fewer of the weekly observations exceed L, resume
monthly monitoring
(b) If all four weekly observations exceed L, the baseline pollution
loading has been exceeded.
B. Method 2 for Calculating a Single Observation Trigger (L)
(1) Follow Method 1 above 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 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 four weeks (four weekly
samples).
(a) If three or fewer of the weekly observations exceed L, resume
monthly monitoring
(b) If all four weekly observations exceed L, the baseline pollution
loading has been exceeded.
III. Procedure for Calculating and Applying an Annual Trigger
A. Method 1 for Calculating and Applying an Annual Trigger (T)
(1) Calculate M and M1 of the baseline loading data as
described above under Method 1 for the single observation trigger.
(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) The annual trigger for baseline (Tb) is calculated as:
[GRAPHIC] [TIFF OMITTED] TR23JA02.002
where n is the number of baseline loading observations.
(5) To compare baseline loading data to observations from the annual
monitoring period, repeat steps 1-3 for the set of monitoring
observations. Label the results of the calculations M' and R'. Let m be
the number of monitoring observations.
(6) The subtle trigger (Tm) of the monitoring data is calculated as:
[GRAPHIC] [TIFF OMITTED] TR23JA02.003
(7) If Tm Tb, the median loading of the monitoring
observations has exceeded the baseline loading.
B. Method 2 for Calculating and Applying an Annual Trigger (T)
Method 2 applies the Wilcoxon-Mann-Whitney test to determine whether
the median loading of the monitoring observations has exceeded the
baseline median. No baseline value T is calculated.
(1) Steps for Conducting the Wilcoxon-Mann-Whitney Test
(a) Let n be the number of baseline loading observations taken, and
let m be the number of monitoring loading observations taken. In order
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 a period of 12
months.
(b) Order the combined baseline and monitoring observations from
smallest to largest.
(c) Assign a rank to each observation based on the assigned order:
the smallest observation will have rank 1, the next smallest will have
rank 2, and so forth, up to the highest observation, which will have
rank n + m.
(1) If two or more observations are tied (have the same value), then
the average rank for those observations should be used. For example,
suppose the following four values are being ranked:
3, 4, 6, 4
Since 3 is the lowest of the four numbers, it would be assigned a rank
of 1. The highest of the four numbers is 6, and would be assigned a rank
of 4. The other two numbers are both 4. Rather than assign one a rank of
2 and the other a rank of 3, the average of 2 and 3 (i.e., 2.5) is given
to both numbers.
(d) Sum all the assigned ranks of the n baseline observations, and
let this sum be Sn.
(e) Obtain the critical value (C) from Table 1. When 12 monthly data
are available for both baseline and monitoring (i.e., n = 12 and m =
12), the critical value C is 99.
(f) Compare C to Sn. If Sn is less than C,
then the monitoring loadings have exceeded the baseline loadings.
[[Page 296]]
(2) Example Calculations for the Wilcoxon-Mann-Whitney Test
BASELINE DATA
---------
8.0 9.0 9.0 10.0 12.0 15.0 17.0 18.0 21.0 23.0 28.0 30.0
---------
MONITORING DATA
---------
9.0 10.0 11.0 12.0 13.0 14.0 16.0 18.0 20.0 24.0 29.0 31.0
---------
BASELINE RANKS
---------
1.0 3.0 3.0 5.5 8.5 12.0 14.0 15.5 18.0 19.0 21.0 23.0
---------
MONITORING RANKS
---------
3.0 5.5 7.0 8.5 10.0 11.0 13.0 15.5 17.0 20.0 22.0 24.0
----------------------------------------------------------------------------------------------------------------
Sum of Ranks for Baseline is Sn = 143.5, critical value is Cn,m = 99.
(3) Critical Values for the Wilcoxon-Mann-Whitney Test
(a) When n and m are less than 21, use Table 1.
In order to find the appropriate critical value, match column with
correct n (number of baseline observations) to row with correct m
(number of monitoring observations)\*\.
Table 1--Critical Values (C) of the Wilcoxon-Mann-Whitney Test
(for a one-sided test at the 0.001 significance level)
--------------------------------------------------------------------------------------------------------------------------------------------------------
n m 10 11 12 13 14 15 16 17 18 19 20
-------------------------------------------
10........................................ 66 79 93 109 125 142 160 179 199 220 243
-------------------------------------------
11........................................ 68 82 96 112 128 145 164 183 204 225 248
-------------------------------------------
12........................................ 70 84 99 115 131 149 168 188 209 231 253
-------------------------------------------
13........................................ 73 87 102 118 135 153 172 192 214 236 259
-------------------------------------------
14........................................ 75 89 104 121 138 157 176 197 218 241 265
-------------------------------------------
15........................................ 77 91 107 124 142 161 180 201 223 246 270
-------------------------------------------
16........................................ 79 94 110 127 145 164 185 206 228 251 276
-------------------------------------------
17........................................ 81 96 113 130 149 168 189 211 233 257 281
-------------------------------------------
18........................................ 83 99 116 134 152 172 193 215 238 262 287
-------------------------------------------
19........................................ 85 101 119 137 156 176 197 220 243 268 293
-------------------------------------------
20........................................ 88 104 121 140 160 180 202 224 248 273 299
--------------------------------------------------------------------------------------------------------------------------------------------------------
(b) When n or m is greater than 20 and there are few ties, calculate
an approximate critical value using the following formula and round the
result to the next larger integer. Let N = n + m.
[GRAPHIC] [TIFF OMITTED] TR23JA02.004
[[Page 297]]
For example, this calculation provides a result of 295.76 for n = m
= 20, and a result of 96.476 for n = m = 12. Rounding up produces
approximate critical values of 296 and 97.
(c) When n or m is greater than 20 and there are many ties,
calculate an approximate critical value using the following formula and
round the result to the next larger integer. Let S be the sum of the
squares of the ranks or average ranks of all N observations. Let N = n +
m.
[GRAPHIC] [TIFF OMITTED] TR23JA02.005
In the preceding formula, calculate V using
[GRAPHIC] [TIFF OMITTED] TR23JA02.006
[67 FR 3408, Jan. 23, 2002]