Page 57 - California Stormwater Workshop Handouts

Industrial General Permit Order

Sampling Guidance Document.19 An annual NAL exceedance occurs when
the average of all the analytical results for a parameter from samples taken
within a reporting year exceeds the annual NAL value for that parameter
listed in Table 2; and,

2. Instantaneous maximum NAL exceedance: The Discharger shall compare
all sampling and analytical results from each distinct sample (individual or
combined as authorized by XI.C.5) to the corresponding instantaneous
maximum NAL values in Table 2. An instantaneous maximum NAL
exceedance occurs when two (2) or more analytical results from samples
taken for any single parameter within a reporting year exceed the
instantaneous maximum NAL value (for TSS and O&G) or are outside of the
instantaneous maximum NAL range for pH.

B. Baseline Status

At the beginning of a Discharger’s NOI Coverage, all Dischargers have
Baseline status for all parameters.

C. Level 1 Status

A Discharger’s Baseline status for any given parameter shall change to Level 1
status if sampling results indicate an NAL exceedance for that same parameter.
Level 1 status will commence on July 1 following the reporting year during
which the exceedance(s) occurred.20

1. Level 1 ERA Evaluation

a. By October 1 following commencement of Level 1 status for any
parameter with sampling results indicating an NAL exceedance, the
Discharger shall:

b. Complete an evaluation, with the assistance of a QISP, of the industrial
pollutant sources at the facility that are or may be related to the NAL
exceedance(s); and,

c. Identify in the evaluation the corresponding BMPs in the SWPPP and
any additional BMPs and SWPPP revisions necessary to prevent future
NAL exceedances and to comply with the requirements of this General
Permit. Although the evaluation may focus on the drainage areas where
the NAL exceedance(s) occurred, all drainage areas shall be evaluated.

2. Level 1 ERA Report

19 U.S. EPA. NPDES Storm Water Sampling Guidance Document. <http://www.epa.gov/npdes/pubs/owm0093.pdf >.
[as of February 4, 2014]
20 For all sampling results reported before June 30th of the preceding reporting year. If sample results

indicating an NAL exceedance are submitted after June 30th, the Discharger will change status once
those results have been reported.

Order 2014-0057-DWQ 49