GREEN INFRASTRUCTURE PERMITTING AND ENFORCEMENT SERIES: FACTSMEET 1
Green roofs retain stormwater on site while providing
many other benefits such as heat island mitigation.
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United States
Environmental Protection
Agency
EPA832F12012
General Accountability
Considerations for Green
Infrastructure
This factsheet is the first in a series of six on integrating green
infrastructure concepts into permitting, enforcement, and
water quality standards actions.
Introduction
Terminology and Articulating Standards Page 3
Metrics and Performance Evaluation Page 3
Appropriate Schedules
Reporting Requirements
Enforceable Mechanisms for
Operations and Maintenance
Modification Provisions
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Integrating Green Infrastructure Concepts into
Permitting, Enforcement, and Water Quality
Standards Actions
This factsheet is the first in a series of
six factsheets in the U.S. EPA Green
Infrastructure Permitting and Enforcement
Series (http://water.epa.gov/infrastructure/
greeninfrastructure/gi_regulatory.
cfm#permittingseriesA This series
describes how EPA and state permitting and
enforcement professionals can incorporate
green infrastructure practices and approaches
into National Pollutant Discharge Elimination
System (NPDES) wet weather programs,
including stormwater permits, Total
Maximum Daily Loads (TMDLs), combined
sewer overflow (CSO) long-term control
plans (LTCPs), and enforcement actions.
This series builds upon EPA's continued
investment in green infrastructure and low
impact development. Existing EPA authority,
guidance, and agreements enable EPA
Regions and state agencies to work with
permittees to include green infrastructure
measures as part of control programs.
For additional resources on green infrastructure,
go to the EPA Green Infrastructure Web
page: http://water.epa.gov/infrastructure/
greeninfrastructure/index.cfm.
Key green infrastructure guidance issued
to date can be found at: http://water.epa.
gov/infrastructu re/green infrastructure/
gLpolicy.cfm.
Introduction
Accountability considerations are important in all actions
involving permits or enforcement orders, regardless of the
approaches used to achieve and maintain compliance with
established standards. Different accountability mechanisms
may be appropriate for permits and enforcement actions
with green infrastructure components, however, because
green infrastructure approaches function differently from
more traditional grey infrastructure approaches.
This fact sheet discusses six accountability mechanisms
that may be applied to permits or enforcement actions that
include green infrastructure. Permitting and enforcement
authorities can work with regulated entities to determine
the mix of accountability mechanisms most appropriate for
specific situations.
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GREEN INFRASTRUCTURE PERMITTING AND ENFORCEMENT SERIES: FACTSMEET 1
1) Terminology and Articulating Standards
Terms such as "green infrastructure," "low impact
development (LID)," and "conservation design" can apply
to a wide array of designs that achieve a wide range
of outcomes. For example, design manuals may apply
the label "LID" or "green infrastructure" to retention,
extended detention, and/or extended filtration devices,
even though the outcomes associated with these devices
are quite different. Because conceptual terms such as
"LID" and "green infrastructure" may be applied to a
range of practices resulting in a range of environmental
outcomes, these terms in and of themselves are inadequate
in articulating standards. For example, a standard
requiring permittees to "implement LID practices at new
development sites in your jurisdiction" would be a difficult
standard to implement and enforce. A more effective
approach would be to define the standard as the desired
result and allow for various green infrastructure or green-
grey combinations to achieve this result. For example, a
requirement that would be less ambiguous and easier to
implement and enforce might read as follows:
"The permittee must implement and enforce via
ordinance and/or other enforceable mechanism(s)
the following requirement for new and
redevelopment: Site design standards for all new
and redevelopment that require, in combination
or alone, management measures that keep and
manage on site the first one inch of rainfall from
a 24-hour storm preceded by 48 hours of no
measurable precipitation. This first one inch of
rainfall must be 100% managed with no discharge to
surface waters."
In certain contexts, standards based on environmental
outcomes may be supplemented with standards based on
implementation goals. This is especially important where
a long-term schedule of compliance is included. In such
cases, enforceable medium- and long-term targets can
be expressed in terms of environmental outcomes (e.g.,
number of CSO overflows), while enforceable interim
targets can be defined in terms of implementation goals
related to the desired environmental outcome (e.g.,
number of acres retrofitted to retain a certain volume
of stormwater). Water quality improvements on the
sewershed scale may not be measurable until a certain
amount of green infrastructure has been installed;
therefore, the inclusion of interim targets is essential
to evaluate progress over time and allow for adaptive
management as needed.
Stormwater wetlands can effectively absorb stormwater while also
providing natural habitatforwildlife. Photo courtesy of Philadelphia
Water Department
2) Metrics and Performance Evaluation
Quantifiable metrics are an essential part of a permit or
compliance order regardless of the types of practices that
will be implemented to meet performance requirements
and protect water quality. The need for such metrics
is no different for green infrastructure than for grey
infrastructure control measures, but the actual metrics that
may work best for green infrastructure measures may vary.
Quantifiable metrics are an essential part of a
permit or compliance order regardless of the types
of practices that will be implemented to meet per-
formance requirements and protect water quality.
Metrics are standard measures to assess performance
relative to a specific goal. Metrics and indicators are used
for all types of technologies to gauge implementation and
effectiveness. Tracking and reporting based on metrics is
appropriate for most permits and enforcement actions. It
may be advisable in many situations to have metrics that
gauge both implementation and effectiveness. See Box 1 for
examples of both implementation and effectiveness metrics.
In addition to metrics based on stormwater volumes, it
may be necessary to establish metrics based on pollutant
loadings. For example, meeting a waste load allocation
(WLA) established in a total maximum daily load (TMDL)
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Many cities have implementation targets for urban tree canopy. Trees in the urban environment provide many
environmental benefits, including stormwater management, air quality management, and urban heat island mitigation.
Boxl
Implementation metrics might include:
• Number, square footage, and capacity of green roofs in place
• Number and capacity of rain gardens and other infiltration practices
• Acreage of impervious surfaces in the service area where rainwater drains to a green infrastructure control measure
• Gallons kept out of the sewer system during 2- or 10-year storm events through the use of green infrastructure
• Reductions to Effective Impervious Area (EIA)
• Quantification of flow volume reductions, e.g., flows into or from the sewer system in various size storm events, on an
annual basis, or in a typical year
Effectiveness (receiving water response) metrics might include:
• Pre- and post-implementation water resources monitoring and assessment
• Assessment of erosion rates in receiving waters
• Attainment of water quality standards for specific pollutants
• Percent stormwater volume capture in combined sewer area
• Percent reduction in CSO volume as a result of green infrastructure
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GREEN INFRASTRUCTURE PERMITTING AND ENFORCEMENT SERIES: FACTSMEET 1
requires specific reductions in pollutant loads. Note
that continuous flow monitoring is generally advisable
for monitoring wet weather discharges. Grab samples
will, in many cases, vary depending on at what point in
the storm cycle the sample was collected, and may not
be representative of the pollutant concentrations in the
stormwater throughout the duration of the storm event.
It may also be appropriate in some cases to have metrics
for individual controls, or a sample set of controls. These
metrics could be used in combination with system-wide
measurements. Metrics for specific controls could include
volume reductions or reductions in pollutant loadings.
Percent pollutant removal is not a good measure of
performance of stormwater controls because it is very
dependent on the characteristics of the stormwater
entering the practice, and also may not account for the
volume reductions achieved through the management
practice. Event Mean Concentrations (EMCs) may be
appropriate for assessing the performance of a sample set
of green infrastructure practices.
It is important to carefully select a set of metrics and
incorporate them into evaluation requirements to ensure
that desired outcomes are being approached and/
or achieved. The ultimate desired outcomes are those
centered on environmental protection and improvement,
and metrics should be focused on those outcomes. In the
shorter term, it may be appropriate to establish interim
performance criteria. For example, interim criteria may
specify that discharges be reduced by a certain volume
orthat pollutant loadings be demonstrably reduced.
Evaluations may appropriately include field monitoring,
modeling, or a combination of methods.
It is important to carefully select a set of
metrics and incorporate them into evaluation
requirements to ensure that desired outcomes
are being approached and/or achieved.
For many types of metrics, tracking or monitoring data will
need to be compared to standards or thresholds (e.g., the
number and capacity of green infrastructure measures
installed might be compared to the number and capacity
planned). Standards or thresholds should be precise
enough to allow for such comparisons. There should also
be clear expectations for corrective action when observed
values and progress do not meet established standards or
thresholds. In some contexts, it is perfectly reasonable to
include a period for refinement of methods and thresholds.
However, there should also be a clear understanding of
the point at which data are considered representative and
actionable. It is important that information be relatively
unambiguous and interpretable. This will allow for effective
compliance monitoring and enforcement, if necessary, of
the permit or order provisions. In addition, for long-term
compliance schedules, performance data should be fed
back into an adaptive management framework so that
performance can be continuously improved overtime.
An example of language from a CSO enforcement action
dealing with metrics and performance evaluation:
"The Sewer District shall develop and submit to EPA
a Green Infrastructure Plan. The Plan shall propose
a process for locating, designing, constructing,
operating, and evaluating a set or sets of green
infrastructure control measures to capture a
minimum of [XX] million gallons of wet weather
flows in a typical year that would otherwise be
discharged bythe District as CSOs. This [XX] MG
volume of capture shall be in addition to the capture
pertypical yearthatwould be achieved by all of the
other grey infrastructure control measures required
underthe Consent Decree in the absence of the
Green Infrastructure control measures. ...
The Plan shall describe how the Sewer District
will adjust the hydrologic model parameters
directly related to the Green Infrastructure control
measures (prior to and during model recalibration)
as necessary to accommodate changes in model
parameterization caused by shifts in runoff
hydrology from the Green Infrastructure control
measures. The District shall then use the model in
two forms (the first encompassing all CSO control
measures including the Green Infrastructure
control measures proposed, and a second model
identical to the first, but without the Green
Infrastructure control measures), to simulate the
system's typical year performance. The District
shall use the difference in performance between
the two simulations to gauge compliance with the
requirement that Green Infrastructure measures
control a minimum additional CSO volume of [XX]
MG pertypical year."
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3) Appropriate Schedules
As in other contexts and with other control technologies,
it is important to establish schedules that are measurable
and realistic. Compliance schedules must conform to Clean
Water Act (CWA) requirements and EPA regulations (see 40
CFR § 122.47), as summarized in EPA guidance.
Compliance schedules may include:
• Dates/deadlines for updating ordinances;
• Dates for implementing pilot projects;
• Milestones for broad, systematic installation of
green infrastructure measures;
• Benchmarks and/or standards to quantify
green infrastructure performance and dates
for achieving benchmarks/standards (e.g.,
implement measures with a cumulative storage
capacity of [XX] gallons by [XX] date).
Additional information on the inclusion of compliance
schedules in NPDES permits can be found in the Office of
Wastewater Management Memo of May 10, 2007:
Compliance Schedules for Water Quality-Based Effluent
Limitations in NPDES Permits (available at: http://water.
epa.gov/lawsregs/guidance/wetlands/upload/
signed-hanlon-memo.pdf). The memo outlines the
situations in which it may be appropriate to develop
compliance schedules extending beyond a typical 5-year
permit term. For more information on compliance schedules
with large construction projects and significant
expenditures that may require more than one permit cycle,
see 40 C.F.R. §§ 122.44 and 122.47, and EPA's CSO policy
(found at: http://cfpub.epa.gov/npdes/cso/cpolicy.
cfm?program_id=5).
It is important to establish schedules that are
measurable and realistic.
4) Reporting Requirements
When implementing grey infrastructure approaches,
permittees will typically report on progress in meeting
schedules and milestones, and in many cases will monitor
and report on discharge characteristics. The same applies
to green infrastructure elements. See examples of reporting
activities in Box 2 below.
Along with standard reporting provisions in the permit,
administrative order, or judicial order, post-construction
monitoring and reporting should be implemented to ensure
the permittee has come into compliance with the CWA
and is required for CSO discharges. However, receiving
water monitoring and reporting should not wait until after
all green infrastructure projects have been constructed.
Rather, monitoring and reporting requirements must be
sufficient to measure the in-stream benefits of green
infrastructure as they begin to accrue and during the life of
a long-term implementation plan.
Box 2
Examples of Reporting and Tracking Activities
• Report on policy and administrative accomplishments, e.g., adoption of new ordinances, standards, site plan review
procedures, and operation and maintenance protocols. These are short-term elements that would typically be
expected to be completed in the first 2-5 years of the program.
• Report on implementation activities and accomplishments (e.g., number of green roofs or number of rain gardens).
• Report on the cumulative storage capacity of and/or cumulative runoff volume managed by installed green
infrastructure practices, and/or the extent of the service area where rainwater drains to a green infrastructure
control measure.
• Measure and report on flows to, through, or from the sewer system in different-sized rain events to quantify the flows
that are kept out of the system by green infrastructure practices.
• Monitor and report on a sampling of green infrastructure practices, where they adhere to standard community
designs, to gauge performance.
• Using performance data from a sampling of green infrastructure installations, periodically model and report on
annual discharges from the sewer system (e.g., CSO volume or pollutant loadings).
• Track and report on operation and maintenance (O&M) activities for all green infrastructure installations.
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GREEN INFRASTRUCTURE PERMITTING AND ENFORCEMENT SERIES: FACTSMEET 1
5) Enforceable Mechanisms for Operations and Maintenance
Operation and maintenance (O&M) are critical to ensure
the continuing effectiveness of any suite of controls,
including green infrastructure. For green and grey
infrastructure components, O&M plans and schedules
should be established, and accountability measures should
be included to assure that necessary O&M is carried out.
In some cases, the green infrastructure may be located on
private property. It is necessary to establish a provision(s)
to assure responsibility and accountability for the O&M.
This typically includes:
• Requirements in codes and ordinances for private prop-
erty owners to inspect and maintain practices, with pro-
visions for fines or cost recovery should this not occur;
• Maintenance agreements with similar elements;
• An inspection program, which could include private
property owner responsibility for 3rd party inspection
with subsequent reporting to the municipality; and/or
a municipal inspection program that prioritizes certain
practices for periodic inspections;
• Development of a municipally-operated tracking system
to document locations and types of practices, the party
responsible fortheir maintenance, maintenance reports,
and maintenance needs, as appropriate.
Most green infrastructure programs will also make
significant investment in publicly owned and operated
systems. In these cases, O&M planning must include:
• The development of protocols and schedules for
different types of green infrastructure practices (e.g.,
the frequency with which curb extension bioretention
cells need to be inspected, and their maintenance
needs, such as weeding or plant replacement);
• Identification of which municipal department(s) will
conduct or oversee O&M;
• Development of a tracking system to ensure all elements
of the O&M program are fulfilled and documented;
• Establishment of a reliable source of funding for
ongoing O&M.
O&M requirements often vary among sites or projects.
Therefore, it is importantthatthe permit or enforcement
document make clear what will constitute non-compliance.
Maintenance needs may vary notably depending on
soils, seasonal or annual climate conditions, land use,
and other factors. After initial vegetation establishment,
many practices need little or no maintenance to function
properly. Alternatively, due to a site-specific event, a given
practice may need additional attention to establish or
restore proper function.
Example language that could be used in a permit or
enforcement action:
"Maintenance. The Sewer District will establish
a database to manage information on all green
infrastructure practices (e.g., green roofs, rain
gardens, constructed wetlands) put in place
pursuant to this Order/Consent Decree. The
Sewer District will enter into the database
GPS coordinates for the practices and as-built
information. For each practice, the Sewer District
will also identify maintenance activities for
the practice and schedules for maintenance.
The Sewer District will use the database to
schedule/track maintenance activities and assure
maintenance is performed. Documentation such
as inspection reports or records relating to
maintenance conducted shall be maintained in the
database or linked to from the database."
6) Modification Provisions
Permits and enforcement orders typically include
modification provisions to deal with performance
issues or unexpected occurrences. Such modification
provisions should be included in permits or enforcement
orders focused on grey infrastructure solutions, green
infrastructure solutions, or a combination. In permits, this
may be accomplished through use of the standard NPDES
modification provision in 40 CFR 122.62. Enforcement orders
also should include an evaluation and revision process.
That is, if the compliance requirements are not met,
after sufficient compliance testing has been performed
and despite performance of the required projects, the
government should retain authority underthe decree or
orderto require additional compliance measures.
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Green Infrastructure Permitting and Enforcement Series
This series on integrating green infrastructure concepts into
permitting, enforcement, and water quality standards actions
contains six factsheets plus four supplemental materials
that can be found at http://water.epa.gov/infrastructure/
greeninfrastructure/gi_regulatory.cfm#permittingseries.
Factsheets
1. Potential Challenges and Accountability Considerations
2. Combined Sewer Overflows
3. Sanitary Sewer Overflows
4. Stormwater
5. Total Maximum Daily Loads
6. Water Quality Standards
Supplemental Materials
1. Consent Decrees that Include Green Infrastructure Provisions
2. Consent Decree Language Addressing Green for Grey
Substitutions
3. Green Infrastructure Models and Calculators
4. Green Infrastructure in Total Maximum Daily Loads (TMDLs)
United States
Environmental Protection
Agency
For additional resources on green infrastructure,
goto the EPA Green Infrastructure Web page:
http://www.epa.gov/greeninfrastructure/.
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