Page 103 - California Stormwater Workshop Handouts

Industrial General Permit Fact Sheet

kept onsite by Dischargers. Due to the limited availability of quality sampling data
and "level of effort" information contained in SWPPPs, the State Water Board is
unable to exercise best professional judgment to make the connection between
effluent quality (sampling results) and the level of effort, costs, and performance of
the various technologies that is needed in order to express the TBELs in this
General Permit numerically, as NELs.

Some stakeholders have suggested that separating the data sets by industry type
would lead to more reliable data with which to develop NELs. Advocates of this
approach suggest that the variability of the data may be caused in part by the mixing
of data from different industrial categories. The State Water Board believes that the
variation is primarily due to storm intensity, duration, time of year, soil saturation or
some other factors. It is necessary to collect information related to those factors and
BMPs implemented in order to evaluate the variability attributable to those factors.
There is currently too large of an information gap to begin the process of developing
NELs for all industrial sectors not currently subject to ELGs.

The State Water Board has proposed NELs in past drafts of this General Permit. In
comments, many stakeholders have highlighted the difficulty of developing statewide
NELs that are applicable to all industry sectors, or even NELs that cover any specific
industry sectors. For example, stakeholders have commented that:

a. Background/ambient conditions in some hydrogeologic zones may contribute
pollutant loadings that would significantly contribute to, if not exceed, the NEL
values;

b. Some advanced treatment technologies have flow/volume limitations as well as
economy of scale issues for smaller facilities;

c. Treatment technologies that require that sheet flows be captured and conveyed
via discrete channels or basins may not only result in significant retrofit costs, but
may conflict with local ordinances that prohibit such practices, as they can cause
damage or erosion to down gradient property owners, or cause other
environmental problems;

d. There is insufficient regulatory guidance and procedures to allow permit writers to
properly specify monitoring frequency and sampling protocols (e.g.,
instantaneous maximum, 1-day average, 3-day average, etc.), and for
Dischargers to obtain representative samples to compare to NELs for the
purpose of strict compliance; and,

e. NELs must be developed with consideration of what is economically achievable
for each industrial sector. These stakeholders point out that the U.S. EPA goes
to great lengths evaluating the various BMP technologies available for a
particular pollutant, the costs and efficiency of each BMP, and the applicability of
the BMPs to the industry as a whole or to a limited number of industrial sites
based upon the size of the facility, the quantity of material, and other
considerations.

Order 2014-0057-DWQ 19