(a) To
establish the alternative effluent limitations of Group B or C in §
90.102(a)
(relating to hydrologic balance: 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 §
90.102, 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 §
90.102 (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 § 90.102, 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 §
90.102(a).
(b) The 1-year
and 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 coal refuse disposal permittee to
demonstrate that the event has for the mine area been exceeded, or that dry
weather flow conditions did not exist, the permittee shall comply with
paragraph (1), (2) or (3).
(1) The permittee
shall:
(i) Collect 24-hour rainfall
information from official United States Weather Bureau Stations within a
25-mile distance-radius-of the site.
(ii) Calculate the estimated rainfall event
for the site by appropriate interpolation of the data collected under this
paragraph. 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)
Complying 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 event for which the exemption is sought and shall be secure 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 1-year or 10-year, 24-hour precipitation event specified for the mine
area.
(3) 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 precipitation 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 precipitation event.
(e) The permittee is not
entitled to claim a greater than 1-year or 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).