25 Pa. Code § 89.53 - Precipitation event exemption
(a) To
establish the alternative effluent limitations of Group B or C in §
89.52(c)
(relating to water quality standards, effluent limitations and best management
practices), 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 §
89.52, unless the permit specifies
a more stringent water quality based effluent limitation, in which case no
exemption is 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 of Group C
in §
89.52
(c).
(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 §
89.52, unless the permit specifies
a more stringent water quality based effluent limitation, in which case no
exemption is 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 §
89.52(c).
(b) The 10-year, 24-hour rainfall events 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 event has for the mine area been
exceeded, or that dry weather flow conditions did not exist, the permittee
shall comply with one of the following:
(1)
The permittee shall comply with subparagraphs (i) and (ii).
(i) Collect 24-hour rainfall information from
official United States Weather Bureau Stations within a 25-mile
distance-radius-of the site.
(ii)
By appropriate interpolation of the data collected under subparagraph (i),
calculate the estimated rainfall event for the site. Appropriate interpolation
shall be accomplished by:
(A) Construction of
an isohyetal map in accordance with the guidelines established by the
Department.
(B) Linear
interpolation between the isohytes.
(2) The permittee shall comply with the
following:
(i) 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 rainfall
event for which the exemption is sought and shall be secured to prevent
tampering and acts of third parties.
(ii) 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 rainfall event specified for the mine area.
(3) Develop alternative
documentation or data concerning the rainfall event. The method or system for
developing the documentation or data shall be approved in writing prior to the
occurrence of the rainfall 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 an 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 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 rainfall.
(e) The
permittee is not entitled to claim a greater than 10-year, 24-hour
precipitation event storm exemption unless the permittee has fully 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).
Notes
The provisions of this § 89.53 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).
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