Current through Register Vol. 55, No. 13, March 29, 2025
(a) To establish the alternative effluent
limitations of Group B or C in §
88.187(a)
(relating to hydrologic balance: effluent standards), a permittee shall
demonstrate to the Department's satisfaction that a precipitation event has
occurred, under the procedures in this section.
(1) The occurrence of a precipitation event
greater than a 10-year, 24-hour precipitation event may be demonstrated by
meeting the requirements of subsections (b)-(d) for each discharge that exceeds
the effluent limits specified in §
88.187, unless the permit
specifies a more stringent water quality based effluent limitation, in which
case no exemption will be available under this section. If the permittee
demonstrates to the Department's satisfaction that a greater than 10-year,
24-hour precipitation event has occurred, the permittee shall meet the effluent
limitation enumerated as Group C in §
88.187(a).
(2) The occurrence of a precipitation event
equal to or less than a 10-year, 24-hour precipitation event may be
demonstrated by meeting the requirements of subsections (c) and (d) for each
discharge that exceeds the effluent limits specified in §
88.187, unless
the permit specifies a more stringent water quality based effluent limitation,
in which case no exemption will be available under this section. If the
permittee demonstrates to the Department's satisfaction that a precipitation
event equal to or less than a 10-year, 24-hour precipitation event has
occurred, the permittee shall meet the effluent limitations of Group B in
§
88.187(a).
(b) The
10-year, 24-hour precipitation event for specific areas in this Commonwealth
shall be determined by reference to data provided by the National Oceanic and
Atmospheric Administration or equivalent resources.
(c) For the permittee to demonstrate that the
10-year, 24-hour precipitation event has for the mine area been exceeded, or
that dry weather flow conditions did not exist, the permittee shall do one of
the following:
(1) Collect 24-hour rainfall
information from official United States Weather Bureau Stations within a
25-mile distance (radius) of the site.
(2) Calculate the estimated rainfall event
for the site, by appropriate interpolation of the data collected under
paragraph (1). Appropriate interpolation shall be accomplished by:
(i) Construction of an isohyetal map in
accordance with the guidelines established by the Department.
(ii) Linear interpolation between the
isohytes.
(3) Prepare a
verified copy of the chart or readout from a Department-approved flow measuring
device which continuously records the influent to the permitted treatment
facility. The device shall be approved by the Department in writing prior to
the event for which the exemption is sought and shall be secure to prevent
tampering and acts of third parties.
(4) Prepare an analysis identifying the
runoff area tributary to the treatment facility and compare the actual runoff
as measured and depicted by the flow measuring device with the runoff expected
from the 10-year, 24-hour precipitation event specified for the mine
area.
(5) Develop alternative
documentation or data concerning the precipitation event. The method or system
for developing the documentation or data shall be approved in writing prior to
the occurrence of the event for which the exemption is being sought, and shall
guarantee the integrity of the information collected.
(d) When the discharge from the site exceeds
any effluent limit in the permit, the permittee shall notify the Department
within 5 days of the occurrence of the event that he is applying for an
exemption from that limit and shall within 30 days thereafter provide the
following to the Department:
(1) The data
required by subsection (c).
(2) A
showing that the facility from which the discharge occurred was designed,
maintained and operated during and prior to the event to accommodate or treat a
10-year, 24-hour precipitation event.
(e) The permittee is not entitled to claim a
greater than 10-year, 24-hour precipitation event storm exemption unless the
permittee has complied with subsections (c) and (d).
(f) Nothing in this section authorizes the
Department to grant an exemption for a discharge which the Department finds may
have caused or contributed to a violation of general or specific water quality
criteria in Chapter 93 (relating to water quality standards).
The provisions of this § 88.188 amended 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); section
3.2 of the Coal Refuse Disposal
Control Act (52 P.S. §
30.53b);
section 7(b) of The Bituminous Mine Subsidence and Land Conservation Act
(52 P.S. §
1406.7(b)); and
section 1920-A of The Administrative Code of 1929 (71 P.S. §
510-20).
This section cited in 25 Pa. Code §
88.187 (relating to hydrologic
balance: effluent standards).
