Stormwater Pollution Prevention Plan - Phoenix Sky Harbor ...

Non-mining MSGP 2010 General Permit
Natural background pollutant levels: Following the first 4 rounds of benchmark monitoring
(or sooner if the exceedance is triggered by less than 4 samples, see above), if the average
concentration of a pollutant exceeds a benchmark value, and the exceedance of the
benchmark is attributable solely to the presence of that pollutant in the natural background,
corrective actions and additional benchmark monitoring are not required, provided that:
The average concentration of the benchmark monitoring results is less than or equal to
the concentration of that pollutant in the natural background;
Documentation of the permittee’s supporting rationale for concluding that benchmark
exceedances are in fact attributable solely to natural background pollutant levels. This
documentation must be maintained with the SWPPP, as required in Part 5.4. The
permittee’s supporting rationale shall include any data previously collected by anyone
(including data reported in the literature) that describe the levels of natural background
pollutants in the facility’s stormwater discharge; and
Notify ADEQ on the final benchmark monitoring report that the benchmark exceedances
are attributable solely to natural background pollutant levels.
Natural background pollutants include those substances that are naturally occurring in soils
or groundwater. Natural background pollutants do not include legacy pollutants from earlier
activity on the site, or pollutants in run-on from neighboring sources that are not naturally
occurring.
6.2.1.4 Exception for Inactive and Unstaffed Sites.
The requirement for benchmark monitoring does not apply at a facility that is inactive and
unstaffed, provided that no industrial materials or activities are exposed to stormwater. To
invoke this exception, the permittee shall do the following:
Maintain a statement onsite with the SWPPP stating that the facility is inactive and
unstaffed, and that there are no industrial materials or activities exposed to stormwater in
accordance with the substantive requirements in 40 CFR 122.26(g) and sign and certify
the statement in accordance with Appendix B, Subsection 9; and
If circumstances change and industrial materials or activities become exposed to
stormwater or the facility becomes active and/or staffed, this exception no longer applies
and the permittee shall immediately begin complying with the applicable benchmark
monitoring requirements under Part 6.2.1 as if it were the permittee’s first year of permit
coverage. The permittee shall indicate in the first benchmark monitoring report that the
facility has materials or activities exposed to stormwater or has become active and/or
staffed.
If, during the period of coverage under this permit, the facility becomes qualified for the
inactive and unstaffed exception and there are no industrial materials or activities
exposed to stormwater, the permittee shall notify ADEQ of this change in the facility’s
next benchmark monitoring report. Benchmark monitoring may be discontinued once
ADEQ is notified, and the permittee signs the certification statement in Appendix B,
Subsection 9 concerning the facility’s qualification for this special exception is prepared
and signed.
6.2.1.5 Exception to Monitoring Requirements for Ephemeral Waters.
Facilities authorized for coverage under this permit that discharge to ephemeral waters are
not required to monitor for Total Suspended Solids (TSS) and turbidity as part of the
benchmark monitoring requirements when the parameters specify TSS and turbidity in the
sector-specific section of Part 8. Monitoring for any remaining parameters in Part 8 may be
performed once each wet season, for a total of twice per year. The permittee is required to
collect at least two samples in a permit term, even if it extends beyond this one year period.
Once the two samples have been collected, the permittee shall evaluate the data in
accordance with Part 6.2.1.3.
Stormwater Discharges Associated with Industrial Activity 28