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Nine Minimum Controls (NMC)
NMC No. 2 -
Maximum Use of Collection System for Storage
NMC
No. 2 requires maximizing storage in the collection system and making
modifications to the system components to enable the system itself to store
wet-weather flows until downstream facilities can accept the flows. Any
modifications are evaluated to ensure that they will not cause problems
such as basement or street flooding. All modifications anticipated or
completed are documented for the PaDEP. Examples of these control measures
may include:
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Collection
system inspection to identify deficiencies that restrict the use of the
system's storage capacity.
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Overflow
outfall gate maintenance and repair.
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Adjustment
of CSO regulator settings.
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Modification
of catch basin inlets to restrict the rate at which stormwater runoff enters
the system.
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Localized
upstream detention such as using parking lots to store runoff flow.
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Removal
of obstructions to the flow which could include pipe size restrictions.
All
demonstrated efforts to comply with this NMC are documented and may include the
following:
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Analyse
and/or study alternatives to maximize collection system storage.
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Describe
procedures in place for maximizing collection system storage.
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Prepare
a schedule for implementation of modifications to the CSS and CSO facilities
to maximize storage during wet weather events.
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Document
actions taken to minimize storage in the system.
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Identify
additional potential long-term measures to increase storage and/or reduce
inflow in the collection system. In general, these measures require
additional analysis and study.
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