Current through Register Vol. 54, No. 45, November 9, 2024
Section 250.309 - MSCs for surface water(a) Any regulated discharge to surface waters shall comply with the applicable provisions of Chapters 91-96, 97 (reserved), 102, 103 and 105, including antidegradation requirements, and may not cause an exceedance of the applicable water quality standards for the surface water in question.(b) For point source discharges to surface water, compliance shall be measured at the point of discharge in accordance with limits specified in the NPDES permit.(c) For purposes of determining compliance with surface water quality standards from a diffuse surface or groundwater discharge, the person shall determine the expected instream regulated substance concentrations, that are attributable to releases at the site, using mass balance techniques for groundwater/surface water mixing at design flow conditions.(1) If the results indicate that surface water quality standards are being achieved, no action is required.(2) If results indicate that surface water quality standards are not being achieved, additional sampling may be performed to help evaluate whether surface water quality standards are being achieved.(3) If the results of the sampling indicate surface water quality standards are being met, no further action is required.(4) If the results of the modeling, and sampling if any, indicate that surface water quality standards are not being met, the person shall perform further remedial action to attain the surface water quality standards.(d) Except if an NPDES permit is required, for purposes of complying with surface water quality standards in a spring, the point of compliance is the point of first designated or existing use, as defined in §§ 93.1, 93.4 and 93.9 (relating to definitions; Statewide water uses; and designated water uses and water quality criteria). If the point of first designated or existing use occurs in a surface water into which a spring flows, compliance with surface water quality standards shall be determined in the manner specified in subsection (c). This section cited in 25 Pa. Code § 245.310 (relating to site characterization report); 25 Pa. Code § 250.303 (relating to aquifer determination; current use and currently planned use of aquifer groundwater); and 25 Pa. Code § 250.707 (relating to statistical tests).