Page 138 - California Stormwater Workshop Handouts

Industrial General Permit Fact Sheet

Discharger to reduce the number of discharge locations sampled if two or more
discharge locations were substantially similar.

Dischargers are required to identify, when practicable, alternate discharge
locations if: (1) the facility’s industrial drainage areas are affected by storm water
run-on from surrounding areas that cannot be controlled, or (2) discharge
locations are difficult to observe or sample (e.g. submerged discharge outlets,
dangerous discharge location accessibility).

b. Representative Sampling Reduction

Some stakeholders have indicated that there are unique circumstances where
sampling a subset of representative discharge locations fully characterizes the
full set of storm water discharges. Stakeholders provided examples related to
drainage areas with multiple discharge locations where sampling only a subset of
these discharge locations produces results that are representative of the
drainage areas’ storm water discharges. In such situations, this General Permit
allows Dischargers to reduce the number of discharge locations. For each
drainage area with multiple discharge locations (e.g. roofs with multiple
downspouts, loading/unloading areas with multiple storm drain inlets), the
Discharger may reduce the number of discharge locations to be sampled if the
conditions in Section XI.C.4 of this General Permit are met.

c. Qualified Combined Samples

Dischargers may combine samples from up to four (4) discharge locations if the
industrial activities within each drainage area and each drainage area’s physical
characteristics (i.e. grade, surface materials) are substantially similar.

Dischargers are required to provide documentation in the Monitoring
Implementation Plan supporting that the above conditions have been evaluated
and fulfilled. A Discharger may combine samples from more than four (4)
discharge locations only with approval from the appropriate Regional Water
Board.

d. Sample Collection and Visual Observation Exceptions

Dischargers are not required to collect samples or conduct visual observations
during dangerous weather conditions such as flooding or electrical storms, or
outside of scheduled facility operating hours. A Discharger is not precluded from
conducting sample collection activities or visual observations outside of
scheduled facility operating hours.

In the event that a Discharger is unable to collect the required samples or
conduct visual observations due to the above exceptions, the Discharger must
include an explanation of the conditions obstructing safe monitoring in its Annual
Report. If access to a discharge location is dangerous on a routine basis, a
Discharger must choose an alternative discharge location in accordance with
General Permit Section XI.C.3.

Order 2014-0057-DWQ 54