§ 90.311. Baseline determination and compliance monitoring for pre-existing discharges at remining operations.
(a) The procedures in this section 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. A monthly (single-observation) procedure and an annual procedure shall be applied.
(b) At least one sample result per month shall be obtained for 12 months to characterize pollutant loadings for:
(1) Baseline determination.
(2) Each annual monitoring period. It is required that at least one sample be obtained per month for 12 months.
(c) Calculations described in this subchapter shall be applied to pollutant loadings.
(d) Each loading value shall be 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.
(e) If the baseline concentration in a baseline sample is below the daily maximum effluent limits established in § 90.102 (relating to hydrologic balance: water quality standards, effluent limitations and best management practices), the baseline sample concentration may be replaced with daily maximum effluent limit for the purposes of some of the statistical calculations in this subchapter.
(f) The substituted values should be used for all methods in this subchapter except for:
(1) The calculation of the interquartile range (R) in Method 1 for the annual trigger (Step 3).
(2) Method 2 for the single observation trigger (Step 3).
(g) The interquartile range (R) is calculated as the difference between the quartiles M-1 and M1; the values for quartiles M-1 and M1 should be calculated using actual loadings (based on measured concentrations) when they are used to calculate the interquartile range (R).
Authority The provisions of this § 90.311 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 § 90.311 adopted October 21, 2016, effective October 22, 2016, 46 Pa.B. 6780.
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