Page 108 - California Stormwater Workshop Handouts

Industrial General Permit Fact Sheet

In order for the above waste load allocations to effectively be implemented as effluent
limits under the General Permit, the Water Boards must (1) identify which discharges
the waste load allocations apply to, (2) identify the acreages of the individual facilities,
(3) convert the waste load allocations from grams/year/acre (or milligrams/year/acre) to
grams/year (or milligrams/year) based on the acreage at each identified facility, (4)
assign the effluent limits to the identified Dischargers, (5) determine appropriate
monitoring to assess compliance with the effluent limits, and (6) develop a tracking
mechanism for each identified facility and their individual effluent limits. A similar
stepwise process is necessary for each TMDL with waste load allocations assigned to
industrial storm water discharges. For TMDLs where effluent limits will be expressed as
BMPs, analysis must to be performed to determine the appropriate BMPs and the
corresponding effectiveness to comply with the assigned waste load allocations.

Some waste load allocations are already expressed as concentration based numbers.
It may appear simple to incorporate these values into this General Permit as effluent
limits, but the questions still remain regarding how to determine compliance. The
monitoring requirements in this General Permit are not designed to measure
compliance with a numeric effluent limit or to measure the effect of a discharge on a
receiving water body. (See the discussion on monitoring requirements in Fact Sheet
Section II.J.) This General Permit requires sampling of four (4) storm events a year,
with certain limitations as to when a discharge may be sampled. This method of
monitoring may not appropriately serve as TMDL compliance sampling since grab
samples are only representative of the particular moment in time when the sample was
taken. Since storm water is highly variable, four grab samples per year may not provide
sufficient confidence that the effluent limit is being met. An alternative monitoring
scheme may be necessary to determine the facility’s impact on the receiving water and
to determine compliance with any assigned effluent limits. Questions concerning
whether sampling results should be grab samples, composite samples, flow-weighted
averaged over all drainage areas, etc. cannot be determined for each concentration-
based TMDL without a more thorough analysis.

Additionally, monitoring and assessment requirements must be developed for all of the
TMDLs to determine compliance with or progress towards meeting TMDL requirements.
The proposed monitoring requirements in this General Permit are not designed to
assess pollutant loading or determine compliance with TMDL-specific effluent limits.

Due to the large number and variety of discharges subject to a wide range of TMDLs
statewide, to prevent a severe delay in the adoption of this General Permit, TMDL-
specific permit requirements for the TMDLs listed in Attachment E will be proposed by
the Regional Water Boards. Since the waste load allocations and/or implementation
requirements apply to multiple discharges in the region(s) the TMDL were developed,
the development of TMDL-specific permit requirements is best coordinated at the
Regional Water Board level. The development of TMDL-specific permit requirements is
subject to notice and a public comment period prior to incorporation into this General
Permit.

Order 2014-0057-DWQ 24