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National Pretreatment
Program
(40CFR403)
Pretreatment Streamlining Rule
Fact Sheet 8.0: Slug Control Plans
Summary
What is a Slug
Discharge?
What other
measures can be
considered as slug
control plans?
The Pretreatment Streamlining Rule provides flexibility
for publicly owned treatment works (POTWs) to
determine how frequently to evaluate industrial users
(Ills) for the need for slug control plans, on the basis
of local conditions after the initial assessment has
been made. The rule also clarifies that an actual slug
control plan (e.g., the physical document itself) is not
the POTWs only option for controlling facilities with a
higher potential for Slug Discharges; instead, the
POTW may choose to require that the significant
industrial user (SIU) take specific, preventative
actions instead of requiring the development of a slug
control plan. Those preventative actions and any slug
control plan development requirements must be
included in the SIU's control mechanism.
A Slug Discharge is any discharge of a non-routine,
episodic nature, including but not limited to an
accidental spill or a non-customary batch discharge,
which has a reasonable potential to cause interference
or pass through, or in any other way violate the
POTWs ordinances, local limits or permit conditions.
POTWs are required to ensure that Ills have policies
and procedures in place to prevent or mitigate the
effects of Slug Discharges.
EPA recognizes that a number of existing
requirements under other statutes and regulations
could serve as components of a plan to control Slug
Discharges. For example, Spill Prevention, Control,
and Countermeasures plans or existing Emergency
and Hazardous Chemical Inventory reports may
address some components of a slug control plan.
Please note that a slug control plan is a specific type
Office of Water
EPA-833-F-07-004
June 2007
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What is the
minimum frequency
for POTWs to
evaluate an SIU's
need for a slug
control plan?
What factors should
the POTW consider
in determining how
often to conduct
evaluations at
individual facilities
concerning whether
a slug control plan is
needed?
of best management practice (BMP); more information
on BMPs can be found in Fact Sheet 7.0: Best
Management Practices (EPA-833-F-06-013).
EPA has removed the required minimum frequency
(once every two years) for POTWs to conduct SIU
evaluations for the need for slug control plans.
However, the Streamlining Rule specifies that POTWs
must evaluate, at least once, the SIU's need for a slug
control plan or other action to control Slug Discharges.
For Ills identified as significant prior to November 14,
2005, this evaluation must be conducted at least once
by October 14, 2006; additional SIUs must be
evaluated within one year of being identified as
significant.
EPA expects POTWs to evaluate all of their SIUs at
least once for the need for a slug control plan, conduct
follow-up evaluations for facilities not required to
develop a slug control plan or take other actions as
necessary, and inspect each SIU annually to
determine the adequacy of and compliance with
existing procedures and control measures.
Each POTW will need to determine the evaluation
frequency appropriate for its program and for
individual facilities. The POTW will need to consider
whether changes have occurred that would
necessitate a reevaluation of the need for slug control.
EPA recommends that POTWs consult with the
Agency's guidance document, Control of Slug Loadings
to POTWs (1991)
(http://www.epa.aov/npdes/pubs/owm021.pdn,
which suggests different ways to prioritize industrial
facilities according to Slug Discharge potential and
strategies for assessing the adequacy of existing plans
and programs. The guidance document highlights the
following as the most significant factors to consider:
(1) quantity and types of materials used or stored at
an IU and their potential for causing violation of local
limits or the general or specific prohibitions; (2)
potential for such materials to enter the sewer system
and cause damage (i.e., whether control measures
are in place); and (3) adequacy of existing controls to
prevent any potential slug loading.
Office of Water
EPA-833-F-07-004
June 2007
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What elements are
required in a slug
control plan?
Slug control
requirements must
be included in SIU
control mechanisms,
if applicable.
The minimum elements required in a slug control plan
are (1) a description of Discharge practices, (2) a
description of all stored chemicals at the facility, (3)
procedures for immediately notifying the POTW of the
Slug Discharge and providing written follow-up
notification, and (4) a variety of procedures (e.g.,
inspection and maintenance of chemical storage
areas) for preventing adverse impacts from any
accidental spills (40 CFR 403.8(f)(2)(vi)(A) to (D)).
The final rule at 40 CFR 403.8(f)(l)(iii)(B)(6) requires
that applicable slug control requirements be included
in the SIU's control mechanism. The rule allows
POTWs to incorporate specific, preventative actions
into an SIU's control mechanism instead of requiring
the development of a slug control plan.
Ills are required to
notify the POTW
immediately of any
changes at its
facility affecting the
potential for a Slug
Discharge.
The final rule at 40 CFR 403.8(f)(2)(vi) and 40 CFR
403.12(f) requires that lUs must notify the POTW
immediately of changes that occur at the facility
affecting the potential for a Slug Discharge, thereby
allowing the POTW to reevaluate the need for a slug
control plan or other actions to prevent such
discharges.
POTWs must
document that
facilities have been
evaluated for the
need for a slug
control plan.
The POTW must be able to demonstrate that each of
its SIUs has been evaluated at least once. For
Industrial Users identified as significant prior to
November 14, 2005, this evaluation must have been
conducted at least once by October 14, 2006;
additional Significant Industrial Users must be
evaluated within 1 year of being designated a
Significant Industrial User. EPA suggests that, where
a slug control plan or other action was not deemed
necessary, the POTW develop a plan to re-evaluate
the SIU as needed. The POTW may choose a specified
frequency level to re-evaluate the SIU, or it may
choose to re-evaluate the facility following a
notification of changed Discharge pursuant to 40 CFR
403.12Q) or 40 CFR 403.8(f)(2)(vi).
Office of Water
EPA-833-F-07-004
June 2007
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What steps are
required to
implement this
Streamlining
provision?
Once the POTW has determined what program
revisions are necessary to incorporate this provision of
the Streamlining Rule, it will submit the modifications
to the Approval Authority (either the state, if it has
Pretreatment Program authority, or the EPA Regional
Administrator) for approval. The program
modifications must include a statement of basis for
the changes, a description of the modifications, and
other information the Approval Authority may request
as appropriate. States and POTWs should make these
changes as soon as possible, and EPA and state
National Pollutant Discharge Elimination System
(NPDES) permitting authorities should revise NPDES
permits to incorporate adopted changes.
Office of Water
EPA-833-F-07-004
June 2007
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