*>EPA Environmental Protection
United States 2014 GREEN INFRASTRUCTURE TECHNICAL ASSISTANCE PROGRAM
Environmental Protection . _ , , _
AgenCy City and County of Denver
Denver, CO
Green Infrastructure Checklists and Renderings
Tools to Assist Local Governments in Promoting and Implementing Green
Infrastructure Practices
SEPTEMBER 2016
EPA 832-R-16-006
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About the Green Infrastructure Technical Assistance Program
Stormwater runoff is a major cause of water pollution in urban areas. When rain falls in undeveloped
areas, soil and plants absorb and filter the water. When rain falls on our roofs, streets, and parking lots,
however, the water cannot soak into the ground. In most urban areas, stormwater is drained through
engineered collection systems (storm sewers) and discharged into nearby water bodies. The stormwater
carries trash, bacteria, heavy metals, and other pollutants from the urban landscape, polluting the
receiving waters. Higher flows also can cause erosion and flooding in urban streams, damaging habitat,
property, and infrastructure.
Green infrastructure uses vegetation, soils, and natural processes to manage water and create healthier
urban environments. At the scale of a city or county, green infrastructure refers to the patchwork of
natural areas that provides habitat, flood protection, cleaner air, and cleaner water. At the scale of a
neighborhood or site, green infrastructure refers to stormwater management systems that mimic nature
by soaking up and storing water. Green infrastructure can be a cost-effective approach for improving
water quality and helping communities stretch their infrastructure investments further by providing
multiple environmental, economic, and community benefits. This multibenefit approach creates
sustainable and resilient water infrastructure that supports and revitalizes urban communities.
The U.S. Environmental Protection Agency (EPA) encourages communities to use green infrastructure to
help manage stormwater runoff, reduce sewer overflows, and improve water quality. EPA recognizes
the value of working collaboratively with communities to support broader adoption of green
infrastructure approaches. Technical assistance is a key component to accelerating the implementation
of green infrastructure across the nation and aligns with EPA's commitment to provide community
focused outreach and support in the President's Priority Agenda Enhancing the Climate Resilience of
America's Natural Resources. Creating more resilient systems will become increasingly important in the
face of climate change. As more intense weather events and dwindling water supplies stress the
performance of the nation's water infrastructure, green infrastructure offers an approach to increase
resiliency and adaptability.
For more information, visit http://vifww.eDa.aov/areeninfrastructure.
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Acknowledgements
Principal CPA Staff
Stacey Eriksen, EPA Region 8
William Bunch, EPA Region 8
Jamie Piziali, EPA Office of Wastewater Management
Christopher Kloss, EPA Office of Wastewater Management
Key Denver Area Stakeholders
Sarah Anderson, City and County of Denver
Holly Piza, Denver Urban Drainage and Flood Control District
Ken MacKenzie, Denver Urban Drainage and Flood Control District
Consultant Team
Erica Keyser, Tetra Tech
Martina Frey, Tetra Tech
Robert Naeser, Tetra Tech
Jason Wright, Tetra Tech
Heather Conn, Tetra Tech
Nicole Chapman, Tetra Tech
This report was developed under EPA Contract No. EP-C-11-009 as part of the 2014 EPA Green
Infrastructure Technical Assistance Program.
Cover Photo and Rendering: Tetra Tech
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Contents
1 Overview 1
2 Guidance for Reviewing Green Infrastructure Components in Development Project Plans 2
2.1 Green Infrastructure Practice Selection, Design, and Maintenance 3
2.2 Green Infrastructure Components for Plan Review 7
2.2.1 Basic Components 7
2.2.2 Plan Sheet Components 7
2.3 Specific Green Infrastructure Design Components 9
3 Guidance for Inspecting and Maintaining Green Infrastructure Practices 10
3.1 Maintenance Guidelines for Green Infrastructure 10
3.1.1 Bioretention 10
3.1.2 Tree Trenches and Pits 11
3.1.3 Permeable Pavement 12
4 References 13
Appendix A: Development Plan Review Checklist for Bioretention A-l
Appendix B: Development Plan Review Checklist for Tree Trench/Pit B-l
Appendix C: Development Plan Review Checklist for Permeable Pavement C-l
Appendix D: Post-Construction Inspection Checklist for Green Infrastructure D-l
Appendix E: Maintenance Checklist for Green Infrastructure E-l
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Figures
Figure 1. Rendering of a combination of a streetside stormwater planter and a mid-block streetside
bump-out stormwater planter along the 60-foot ROW of a typical local street. This combination is
estimated to provide 525 cubic feet of stormwater storage, assuming a WQCV depth of
12 inches 4
Figure 2. Rendering of a combination of two tree trenches (three trees with three water quality
control structures at 2% slope) along the 60-foot ROW of a typical local street. This combination
is estimated to provide 492 cubic feet of stormwater storage, assuming a WQCV depth of
12 inches 5
Figure 3. Rendering of a combination of two streetside stormwater planters and one corner
streetside bump-out stormwater planter along the 110-foot ROW of a typical 4-lane arterial
street with no parking. This combination is estimated to provide 822 cubic feet of stormwater
storage, assuming a WQCV depth of 12 inches 6
Figure 4. Rendering of a combination of a streetside stormwater planter and a mid-block streetside
bump-out stormwater planter along the 60-foot ROW of a typical local street. This combination is
estimated to provide 525 cubic feet of stormwater storage, assuming a WQCV depth of
12 inches 8
Figure 5. Rendering of a combination of four streetside stormwater planters along the 110-foot ROW
of a typical 4-lane arterial street with no parking. This combination is estimated to provide
936 cubic feet of stormwater storage, assuming a WQCV depth of 12 inches 9
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Acronyms
DWR Colorado Division of Water Resources
EPA U.S. Environmental Protection Agency
FEMA Federal Emergency Management Agency
ROW right-of-way
UDFCD Urban Drainage and Flood Control District
USDCM Urban Storm Drainage Criteria Manual
WQCV water quality control volume
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! Overview
The City and County of Denver (Denver) is making green infrastructure a fundamental part of the city's
long-term stormwater management strategy by looking at ways to integrate small, site-scale, and
subregional green infrastructure practices into the existing large-scale network of parks and open space.
To further this goal, Denver developed the City and County of Denver Ultra-Urban Green Infrastructure
Guide (Green Infrastructure Guide) (City and County of Denver 2016) to provide a technical resource and
design information for green infrastructure practitioners.
The U.S. Environmental Protection Agency (EPA), through its Green Infrastructure Technical Assistance
Program, helped Denver to develop a set of tools to streamline review, approval, and implementation of
green infrastructure practices. Specifically, EPA developed the following:
• Green infrastructure plan review checklists (section 2 and Appendices A-C) to assist planning
review boards in evaluating both public and private development projects that seek to
implement green infrastructure designs. These checklists will ensure that all required
information is included in design plans and submittals and that plan submittals meet Denver's
Storm Drainage Design and Technical Criteria (City and County of Denver 1992) and Urban
Drainage and Flood Control District (UDFCD) criteria for green infrastructure projects on
Colorado's Front Range. UDFCD criteria are published in Urban Storm Drainage Criteria Manual
(USDCM) Volume 3 (UDFCD 1992).
• Green infrastructure inspection checklists (section 3) for two types of inspections: post-
construction inspections (Appendix D) to assist local planning authorities in ensuring that green
infrastructure facilities are installed as specified in approved plans using the appropriate
materials, and maintenance inspections (Appendix E) to assist owners and operators of green
infrastructure facilities in determining when maintenance is needed (i.e., maintenance triggers)
and what needs to be done to ensure the facilities continue to function as designed over the
long term.
• Renderings of green infrastructure practices (Figures 1-5) to enhance Denver's Green
Infrastructure Guide. The renderings show green infrastructure practices integrated into Denver
streetscapes; the specific combinations of practices shown can provide stormwater storage for
different types of road rights-of-way (ROWs). The renderings are included throughout this
report with descriptions of roadway types and expected water quality control volumes
(WQCVs).
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2 Guidance for Reviewing Green infrastructure Components in Development
Project Plans
Design, construction, and implementation of green infrastructure in Denver, and throughout the Front
Range, are influenced by the state's semiarid climate and the system of administering surface water
rights:
• Semiarid climate. Denver's semiarid climate requires modifying green infrastructure practices
adopted from other U.S. locations. Stormwater controls typically must be xeriscaped with a
focus on native plants, because they use less water and perform better in a semiarid
environment. Though native species will likely need supplemental irrigation during
establishment, nonnative plants generally will not survive without irrigation (Taupe
infrastructure 2014). Rain events in Denver tend to be high intensity and infrequent, resulting in
a water quality event that is heavy with sediments and other pollutants that have accumulated
since the previous storm. As a result, forebays, presedimentation basins, or other forms of
pretreatment are recommended to remove some of the particulate matter before it reaches a
green infrastructure facility.
• Surface water rights. Surface water in Colorado is administered through a priority system, the
Doctrine of Prior Appropriation, in which "first in time" equals "first in right." Water users with
earlier water rights decrees (i.e., senior rights) have first right in times of short supply and can
fill their needs before the junior rights users can begin to use water. The Colorado Division of
Water Resources (DWR) administers this program and in 2011 circulated a memorandum on the
subject of DWR's administrative approach to storm water management. That document details
administrative allowances the state is currently willing to make to accommodate detention,
infiltration, and green roofs as stormwater management activities. Under the program, only
three green infrastructure practices are allowed: detention areas, infiltration areas, and green
roofs. Specific limitations on these practices include the following:
• Stormwater detention areas must release all of the water detained from the site within
72 hours of the end of a precipitation event, should be designed to release the water
from the site as quickly as downstream conditions allow, and must be designed to
minimize consumption from vegetation.
• Infiltration areas must be designed to infiltrate the water into the underlying aquifer as
quickly as possible, not result in an exposed water surface beyond 72 hours after the
end of a precipitation event, and must be designed to minimize consumption from
vegetation.
• Green roofs may intercept only precipitation that falls directly onto the landscaped
portion of the roof. The landscaping may not intercept and consume concentrated flow
and may not store water below the root zone.
• Stormwater may not be diverted from detention, infiltration, or green roof areas for any
beneficial uses.
In 2014, the DWR clarified that these administrative allowances are made expressly for an
individual site, being defined as a discrete area that has been developed through one
development effort, and do not extend beyond that narrow definition. Most Colorado
stormwater and floodplain managers disagree with this interpretation, and a concerted effort is
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underway to seek a legislative solution that will broaden the scope of allowable stormwater
management activities and protect those activities from lawsuits by water rights holders.1
Meanwhile, property owners can employ practices that detain or infiltrate stormwater if that
water will either be completely released or infiltrated within 72 hours of the end of the
precipitation event that generated the runoff.
, , .ri Infrastrucfc actice Selection, Design, and Maintenance
Green infrastructure practice selection and design are driven by a site's physical characteristics,
including soils, contributing drainage area, ground water, and development conditions in the tributary
watershed (e.g., construction activity). UDFCD describes physical site characteristics that support or
constrain the selection of green infrastructure practices:
• Soils. Soils with good permeability, typically associated with hydrologic soil groups A and B,
provide opportunities for infiltration of runoff and are well suited for infiltration-based
practices—such as streetside stormwater planters, bump-out stormwater planters, green
gutters, tree trenches and pits, and green alleys—often without the need for an underdrain
system. Even when soil permeability is low, these types of practices might be feasible if soils are
amended to increase permeability or an underdrain system is used. In some cases, however,
soils limit the use of infiltration-based practices. When soils with moderate-to-high swell
potential are present, infiltration should be avoided to minimize damage to adjacent structures
from water-induced swelling. In some cases, infiltration-based designs can still be used if an
impermeable liner and underdrain system are included in the design; however, if the risk of
damage to adjacent infrastructure is high, infiltration-based practices might not be appropriate.
In all cases, a geotechnical engineer should be consulted when designing infiltration practices
near structures to evaluate the suitability of soils for different practice types and establish
minimum distances between infiltration practices and structures (UDFCD 1992).
• Contributing drainage area. The contributing drainage area is an important consideration both
on the site level and at the regional level. On the site level, there is a practical minimum size for
certain practices, largely related to the ability to drain the WQCV over the required drain time.
For example, it is technically possible to size the WQCV for an extended detention basin for a
half-acre site; however, designing a functional outlet to release the WQCV over a 40-hour drain
time is practically impossible due to the very small orifices that would be required. For a half-
acre site, a filtering practice such as bioretention would be more appropriate. At the other end
of the spectrum, there should be a limit on the maximum drainage area for a regional facility to
ensure adequate treatment of rainfall events that could produce runoff from only a portion of
the area draining to the practice. If the overall drainage area is too large, runoff from only a
portion of the contributing area will pass through the practice outlet sized for the full drainage
area without adequate residence time in the practice. As a practical limit, the maximum
drainage area contributing to a water quality facility should be no larger than 1 square mile
(UDFCD 1992).
1 For example, in 2016 state law was amended to allow the use of rain barrels and other collection devices on certain residential
properties.
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Figure I. Rendering of a combination of a streetside stormwater planter and a mid-block streetside
bump-out stormwater planter along the 60-foot ROW of a typical local street. This combination is
estimated to provide 525 cubic feet of stormwater storage, assuming a WQCV depth of 12 inches.
• Ground water. Shallow ground water on a site presents challenges both for green infrastructure
practices that rely on infiltration and for facilities that are intended to be dry between storm
events. Shallow ground water could limit the ability to infiltrate runoff or result in unwanted
subsurface storage of ground water in areas intended for storage of the WQCV (e.g., the porous
subbase of a permeable pavement system or in the bottom of an otherwise dry facility such as
an extended detention basin). Conversely, for some types of practices such as wetland channels
or constructed wetland basins, shallow ground water can be beneficial by providing saturation
of the root zone and/or a source of base flow. Protection of ground water quality is an issue that
should be considered for infiltration-based practices.
Infiltration practices might not be appropriate for land uses that involve storage or use of
materials that have the potential to contaminate ground water underlying a site (e.g., hot spot
runoff from fueling stations, materials storage areas). If ground water or soil contamination
exists on a site (i.e., a brownfield) and the contamination will not be remediated or removed as
part of construction, it might be necessary to avoid infiltration-based practices or to use a
durable liner to prevent infiltration into areas contaminated with pollutants that could be
mobilized by stormwater (UDFCD 1992).
• Watershed development activities. When development in the watershed is phased or when erosive
conditions—such as steep slopes, sparse vegetation, and sandy soils—exist in the watershed, a
treatment train approach might be appropriate. Practices that use filtration should follow other
measures to collect sediment loads (e.g., a forebay). For phased developments, these measures
must be in place until the watershed is completely stabilized. When naturally erosive conditions exist
in the watershed, the measures should be permanent. The designer should consider existing,
interim, and future conditions in selecting the most appropriate practices (UDFCD 1992).
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In addition to recognizing that practices must be appropriate to a site's physical characteristics,
designers, planners, and reviewers must recognize that for practices to function effectively, meet
performance expectations, and provide for public safety, they must be:
1. Designed according to Denver and UDFCD criteria, taking into account site-specific conditions.
2. Constructed as designed. This is important for all practices but is particularly critical for the
practices included in this document as many of the critical components are subsurface. This
requires more frequent construction observation compared to other practices, which can
typically be inspected postconstruction (e.g., extended detention basins).
3. Properly maintained to function as designed. Although all stormwater management practices
require maintenance, infiltration-oriented facilities are particularly susceptible to clogging
without proper maintenance. Underground facilities can be vulnerable to maintenance neglect
because maintenance needs are not evident from the surface without special diagnostic tools
and procedures for access. Maintenance is not only essential for proper functioning, but also for
aesthetic and safety reasons. Inspection of facilities is an important step in identifying and
planning for needed maintenance.
Source: Tetra Tech, Inc.
Figure 2. Rendering of a combination of two tree trenches (three trees with three water quality control
structures at 2% slope) along the 60-foot ROW of a typical local street. This combination is estimated
to provide 492 cubic feet of stormwater storage, assuming a WQCV depth of 12 inches.
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Public access to green infrastructure practices also should be considered from a safety perspective. The
highest priority of engineers and public officials is to protect public health, safety, and welfare. Green
infrastructure practices must be designed and maintained in a manner that does not pose health or
safety hazards to the public. Safety features such as rails and curbs should be incorporated as
appropriate. Facilities should be designed to reduce the likelihood and extent of shallow standing water
that can allow mosquitoes to breed, which can be a nuisance and a public health concern. The potential
for nuisances, odors, and prolonged soggy conditions should be evaluated for green infrastructure
practices, especially in areas with high pedestrian traffic or visibility.
Maintenance should be considered early in the planning and design phase. Clear, legally binding written
agreements assigning maintenance responsibilities and committing adequate funds for maintenance
also are critical.
'wmM
Source: Tetra Tech, Inc.
Figure 3. Rendering of a combination of two streetside stormwater planters and one corner streetside
bump-out stormwater planter along the I 10-foot ROW of a typical 4-lane arterial street with no
parking. This combination is estimated to provide 822 cubic feet of stormwater storage, assuming a
WQCV depth of 12 inches.
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2.2 Green Infrastructi impoiierits for Plan ieview
This section presents an overview of components that every project development plan containing green
infrastructure should incorporate. It does not discuss all of the components included on the full plan
submittal checklists that Denver uses (i.e., Concept Submittal Checklist or Formal Site Development Plan
Submittal Checklist), but identifies items that would help city staff in performing plan reviews for green
infrastructure designs.
~ Vicinity map showing project boundary, adjacent streets and nearby hydrologic features (e.g.,
streams, reservoirs), and Federal Emergency Management Agency (FEMA) floodplain
delineations (if applicable).
~ Total project area within the site boundary in acres or square feet.
~ Description of existing site drainage, including conveyance network; discharge locations, size,
and capacity for each discharge point; contributing drainage area and design flow; and off-site
drainage areas, design flows, and locations.
~ Description of proposed project site drainage, including conveyance network; discharge
locations, size, and capacity for each discharge point; contributing drainage area and design
flow; and off-site drainage areas, design flows, and locations.
~ Increase or decrease in impervious area in the proposed condition as compared to the
preproject condition.
~ Total planned impervious area within the site boundary, expressed in acres or square feet and
as a percentage of the total project area.
~ Receiving waters to which the project site discharges, whether the waters are listed as impaired
on the EPA-approved 303(d) list or an EPA-approved TMDL applies to the water bodies.
~ Identification and description of all source control measures implemented on the project site.
~ Sizing calculation for each proposed practice, including water quality design flow, design
volume, outlet design, overflow design, drawdown, and ponding depth.
~ Map or source identifying justification for rainfall data selection.
2.2.2 F ;¦< ' =; -
~ Vicinity map showing project boundary, adjacent streets, and nearby hydrologic features (e.g.,
streams, reservoirs).
~ Mapped FEMA floodplain limits in relation to the project site, if applicable.
~ Locations where off-site drainage enters the project site, if applicable.
~ The total planned impervious area within the site boundary.
~ Details regarding the proposed project site drainage network, including storm drains, concrete
channels, swales, detention facilities, stormwater treatment facilities, natural and constructed
channels, and the method for conveying off-site flows through or around the proposed project.
~ All discharge locations from the proposed project site with appropriately sized energy
dissipation, if applicable.
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~ Areas within the site designated for preservation, such as stream corridors, open space, coarse
sediment areas, and other natural resources.
~ Areas of high infiltration potential.
~ Details of planned slope protection measures to improve geotechnical stability and mitigate
potential erosion.
~ Downspout disconnections with standard detail.
~ Areas of active landscaping that will require irrigation.
~ Invert elevation and opening width for curb cuts.
~ Invert elevation and overflow elevation for each identified treatment control, flow control
practice, and low-flow diversion practice.
~ All orifice invert elevations when multistage outlets are proposed.
~ Invert elevation and outlet elevation for each pretreatment facility, if applicable.
~ Sufficient grading details so runoff is properly directed to the design inflow location.
Source: Tetra Tech, Inc.
Figure 4. Rendering of a combination of a streetside stormwater planter and a mid-block streetside
bump-out stormwater planter along the 60-foot ROW of a typical local street. This combination is
estimated to provide 525 cubic feet of stormwater storage, assuming a WQCV depth of 12 inches.
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2.3 Specific Green Infrastructure Design Components
Successful construction, effectiveness, and long-term operation of green infrastructure are a result of
sound design and engineering. Design components are specific to green infrastructure type, volume of
runoff treated, and intended removal efficiency (if applicable). The design must satisfy applicable
regulatory requirements that could vary locally. In Denver, green infrastructure design specifications are
outlined in the USDCM Volume 3 (UDFCD 1992). The checklists presented in Appendices A, B, and Cfor
three green infrastructure types—bioretention, tree trenches/pits, and permeable pavement—are
intended to provide guidance to development plan reviewers in determining whether design
requirements are met. The checklists should be used in combination with the USDCM Volume 3, which
provides more detailed design specifications and calculations (UDFCD 1992).
Source: Tetra Tech, Inc.
Figure 5, Rendering of a combination of four streetside stormwater planters along the I 10-foot ROW of
a typical 4-lane arterial street with no parking. This combination is estimated to provide 936 cubic feet
of stormwater storage, assuming a WQCV depth of 12 inches.
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3 Guidance for Inspecting and Maintaining Green Snfrastructi ictices
Proper inspection and ongoing maintenance are essential for green infrastructure to be effective. A
postconstruction inspection should occur as soon as construction is complete, and maintenance
inspections should occur regularly at least once or twice per year for the life of the practice. This
inspection and maintenance guidance focuses on both types of inspection for bioretention and
permeable pavement green infrastructure practices.
An inspector undertaking a postconstruction inspection evaluates the ability of a newly installed green
infrastructure practice to perform effectively and as planned. The inspector evaluates the constructed
green infrastructure practice against approved design drawings and plans. The postconstruction
inspection checklist provided in Appendix D can be used to ensure that green infrastructure is properly
constructed as designed and that stormwater management will be effective.
Ongoing maintenance of green infrastructure includes both routinely scheduled activities (e.g.,
landscape maintenance) and nonroutine activities that might be required after large storms (e.g.,
sediment removal and redistribution of mulch). UDFCD presents maintenance considerations, in
addition to specifications and standards, in USDCM Volume 3 (UDFCD 1992). A summary of
maintenance considerations and maintenance activities and their frequency is presented in section 3.1,
and a maintenance checklist is provided in Appendix E.
aintenance Guidelines for Green Infrastructure
Maintenance considerations for bioretention, tree trench and tree pits, and permeable pavement are
presented in the following sections. Bioretention maintenance considerations are applicable to
streetside stormwater planters, bump-out stormwater planters, and green gutters. The permeable
pavement maintenance considerations can be applied to green alley applications and permeable
pavement areas integrated into tree trench/pit and bioretention configurations.
3. U. 1! £-. .
The primary maintenance requirement for bioretention is regular plant, soil, and mulch layer (if
applicable) maintenance to ensure a healthy vegetation system that promotes infiltration, storage, and
pollutant removal. A healthy and densely vegetated system should be free of excess sediment and trash,
and the system typically should drain within 12 hours of a storm. Replacement of vegetation might be
necessary to maintain optimal performance. Bioretention maintenance requirements are applicable to
all forms of bioretention. Maintenance is typical of general landscape care and consists of the following:
~ Sediment removal. Sweep or shovel sediment from the sediment collection pad/forebay
approximately two times per year, and dispose of sediment outside the planter.
~ Watering. Vegetation must be drought-tolerant and not require watering after a 2-3-year
establishment period. Watering could be required during prolonged dry periods after vegetation
has been established.
~ Debris and litter removal. Remove debris and litter from the infiltration surface to minimize
clogging of the media. If applicable, remove debris and litter from the overflow structure. The
degree of debris and litter accumulation is variable and is influenced by surrounding land uses,
pedestrian traffic or activities, and the presence of trees.
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~ Landscaping. Mow grasses as desired or needed for weed control. Native or drought-tolerant
grasses should be maintained at a height of at least 6 inches; mowing might not be necessary.
Occasional pruning or removal of dead plant or tree material (e.g., leaf litter) and periodic
weeding might be necessary depending on the selected plants. Periodic weeding might be
necessary during the establishment period until the soil media is covered with mulch or dense
vegetation.
~ Mulch, In areas where heavy metal deposition is likely (e.g., contributing areas that include
industrial and auto-related businesses, parking lots, and roads), replace mulch annually. In areas
where metal deposition is not a concern, add mulch as needed to maintain a mulch depth of up
to 3 inches. Mulch should be replaced every 2-5 years where metal deposition is not a concern.
~ Nutrients and pesticides. Bioretention soil mix and plants are selected for optimum fertility,
plant establishment, and growth. Nutrients and pesticides should not be applied, as they can
degrade the pollutant removal capability of the bioretention system and contribute pollutant
loads to receiving waters.
~ Inlet. Inspect inlets for sediment accumulation and signs of erosion. Excess sediment can
accumulate at inlets where curb cuts or bypass structures are used and should be inspected
regularly. Any accumulated sediment that impedes flow into the bioretention area should be
removed and disposed of properly (not placed elsewhere in the planter). When the system is
first installed, inlets should be inspected after each storm event to identify any potential inflow
and sediment issues that require design modifications. After an initial period, inlets should be
inspected quarterly and after a significant storm event.
~ Overflow and underdraws. Sediment accumulation in the overflow device or underdrain system
can cause prolonged ponding and potential flooding. Excess ponding can damage vegetation
and create mosquito-breeding habitat. Inspect overflow and underdrain systems to ensure that
cleanouts are watertight and there is no visible debris inside the overflow structure.
Inspection of bioretention practices should occur at least twice annually following runoff-generating
storms to determine if each practice is providing acceptable infiltration. If standing water persists for
more than 24 hours after runoff has ceased, the possibility of clogging should be investigated and
remedied. Areas where erosion has occurred should be inspected, as they are potential sources of
sediment if not repaired.
Maintenance for tree trenches and pits is necessary for tree health and to ensure a functioning system
in which water is conveyed through the inlet and throughout the system effectively. Typical
maintenance of tree trenches and pits consists of the following:
~ Debris and litter removal. Remove debris and litter from the infiltration surface to minimize
clogging of the media. The degree of debris and litter accumulation is variable and is influenced
by surrounding land uses, pedestrian traffic or activities, and season (e.g., tree litter is expected
each fall).
~ Landscaping. Occasional pruning, removal of dead tree material (e.g., leaf litter), and periodic
weeding might be necessary.
~ Inlet. Inspect inlets for sediment accumulation and signs of erosion. Excess sediment can
accumulate at inlets where curb cuts or bypass structures are used and should be inspected
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regularly. Any accumulated sediment that impedes flow into the tree trench or pit should be
removed and disposed of properly (not placed elsewhere in the planter). When the system is
first installed, inlets should be inspected after each storm event to identify any potential inflow
and sediment issues that require design modifications. After an initial period, inlets should be
inspected quarterly and after a significant storm event.
~ Forebay. The aggregate in the forebay should be vacuumed regularly (monthly during the wet
season is recommended) and replaced routinely (when significant clogging is observed).
Maintenance frequency is dependent on the rate at which the media clogs. Media clogging is a
function of drainage area size, presence or amount of construction activity, and pollutant loads
in the runoff. Inspections are recommended once or twice per year to detect early visual signs of
clogging.
~ Overflow and underdrains. Sediment accumulation in the overflow device or underdrain system
can cause prolonged ponding and potential flooding. Excess ponding can damage the soil media
and create mosquito-breeding habitat. Inspect overflow and underdrain systems to ensure that
cleanouts are watertight and there is no visible debris inside the overflow structure.
Inspection of tree trenches and pits should occur at least twice annually following runoff-generating
storms to determine if runoff is flowing through the system properly. If standing water persists for more
than 24 hours after runoff has ceased, the possibility of clogging should be investigated and remedied.
Areas where erosion has occurred should be inspected, as they are potential sources of sediment if not
repaired.
3.1.3 Permeable Paweraent
The key maintenance objective for permeable pavement systems is to prevent void spaces from
becoming clogged or requiring sediment removal. Infiltration issues can be identified when runoff ponds
on the surface or is no longer infiltrating into the surface rapidly. Key maintenance considerations and
procedures consist of the following (refer to USDCM Volume 3 for further details regarding specific
permeable pavement types):
~ Debris removal, sweeping, and vacuuming. Remove debris routinely as a source control
measure. Sweeping with a regenerative air sweeper (not a broom sweeper) should be
performed approximately two times per year. Frequency can be adjusted according to the run-
on ratio and deposition rate on the permeable pavement surface. Frequent sweeping is an
excellent measure to prevent clogging, and sweeping with a vacuum sweeper has proven to be
effective for removing solids and debris from the void space of permeable pavement.
~ Weed control. Use weed control applications on any weeds that grow in the permeable
pavement. Where underdrains provide a hard connection to a storm drain, either burn weeds or
spot treat them with an herbicide that does not contain polyethoxylated amine. Weeds should
not be pulled, as doing so can damage the fill media.
~ Snow removal. Plowing is a recommended snow removal process. Conventional liquid
treatments (deicers) will not stay at the surface of a permeable pavement long enough to be
effective. Sand should never be applied to a permeable pavement, as it will reduce infiltration.
Inspection of pavement condition and verification of infiltration should be performed at least annually,
either during a rain event or with a garden hose to ensure that water infiltrates into the surface.
12
-------
4 References
City and County of Denver. 1992. Storm Drainage Design & Technical Criteria. Department of Public
Works, Denver CO. Amended 2013.
httos:/7www.clenveraov.org/content/clatn/clenveraov/Portals/711/clocuments/
StormMasterPlan/StormDrainaaeDesianTechnicalCriteria.Ddf
City and County of Denver. 2016. Ultra-Urban Green Infrastructure Guidelines. Department of Public
Works, Denver CO.
h tips:f/www, den veraov. or a/con ten t/dam/den verao v/Portals/705/documen ts/auidelin es/ul tra-
urban~areen-infrastructure~Quidelines~manual.pdf
UDFCD (Urban Drainage and Flood Control District). 1992. Urban Storm Drainage Criteria Manual
Volume 3. Urban Drainage and Flood Control District, Denver, CO. Updated November 2010;
accessed July 7, 2014. http://udfcd.org/volume-three
Colorado's "taupe infrastructure." 2014, February 5. The Stormwater Report. Water Environment
Federation website. Accessed July 7, 2014.
http://stormwater.wef.org/2014/02/colorados-taupe-infrastructure/
13
-------
Appendix A: Development Plan Review Checklist for Bioretention
BIORETENTION
Streetside Stormwater Planters, Bump-Out Stormwater Planters, and Green
Gutters
Green Infrastructure Design
Plan Review Checklist
Bioretention is an engineered, depressed landscape area designed to capture and filter or infiltrate the water quality capture
volume (WQCV). Bioretention areas typically consist of a flow regulating structure, a pretreatment element, an engineered soil
mix planting bed, vegetation, and an outflow regulating structure. Bioretention areas are designed to hold and remove
stormwater pollutants through a variety of chemical, physical and biological processes in a manner similar to natural ecosystems.
Bioretention systems are flexible, adaptable and versatile stormwater management facilities that can fit readily into parking lot
islands; street medians; residential, commercial and industrial campus landscaping; and urban and suburban green spaces and
corridors. Bioretention is a type of green infrastructure that can be configured as streetside stormwater planters, bump-out
stormwater planters, and green gutters to fit in ultra-urban settings.
Technical guidance is provided in italics below, including references to the Urban Drainage and Flood Control District (UDFCD)
Urban Storm Drainaae Criteria Manual Volume 3. which is available online at htto://udfcd.ora/volume-three.
Plan Review Checklist for Bioretention
Questions Yes No N/A Notes
Site Applicability and Considerations
Siting
Is the site location and size reasonable for the drainage area to
be treated? For example, a green gutter is appropriate for
treating runoff from public ROW only; inclusion of runoff from
adjacent development would require a stormwater planter.
~
~
~
Is the practice installed at the downstream end of the block, if
possible?
~
~
~
Is there a nearby inlet or manhole that would provide a
convenient location to discharge the underdrain to?
~
~
~
Pedestrian Considerations
Are pedestrian edge barriers appropriately sized to provide
pedestrian safety (i.e., 6 inches minimum along long sides
parallel to street and 15 inches minimum along short sides)? This
requirement is not applicable to green gutters.
~
~
~
Maximum depth to the surface of the bioretention media does
not exceed 20 inches.
~
~
~
Are access paths a minimum of 4 feet wide and in compliance
with ADA design guidelines?
~
~
~
Are step-out zones appropriately sized between the curb and
bioretention per City and County of Denver requirements? This
requirement is not applicable to green gutters.
~
~
~
Geometry
Is the bioretention no longer than 40 feet?
~
~
~
Is the top of the bioretention horizontal in longitudinal profile,
regardless of street slope?
~
~
~
Other
Was a soil investigation performed by a registered geologist, soil
scientist, or professional engineer?
~
~
~
Were recommendations in a geotechnical report followed?
~
~
~
Is there positive drainage away from adjacent buildings at all
locations?
~
~
~
A-1
-------
Questions
Yes
No
N/A
Notes
Design Considerations
Water Quality Capture Volume Zone
Does the design allow for the recommended storage volume
(above the surface) per USDCM Volume 31
~
~
~
Does the design filter area (bottom surface of facility) meet or
exceed the minimum calculated filter area per USDCM Volume 31
~
~
~
Inlet and Outlet Controls
Is the inlet sized to convey the water quality event assuming an
appropriate amount of debris blockage (i.e., debris factor)?
~
~
~
Is energy dissipation provided at concentrated points of inflow?
~
~
~
Is the outlet control orifice sized to drain the design volume in 12
hours or more and is a minimum orifice size of 3/8-inch used (to
avoid clogging)?
~
~
~
Pretreatment
Is pretreatment provided (forebay in conjunction with the inlet)?
~
~
~
Does pretreatment allow for sediment deposition without bypass
of the practice and is this clearly detailed in section on the plans?
~
~
~
Underdrain System
Does the facility design include an underdrain system?
An underdrain system may be necessary if infiltration tests show
percolation drawdown rates slower than two times the rate
needed to drain the WQCV over 12 hours, or where required to
divert water away from structures as determined by a
professional engineer.
~
~
~
Do all references to the underdrain clearly call for slotted pipe
(not perforated) and are the slot widths included in the plan?
~
~
~
Are cleanouts provided to enable underdrain inspection and
maintenance?
~
~
~
Is the underdrain system placed within a section of CDOT Class C
filter material (not bioretention media) and is this material
specified on the plans?
~
~
~
Do the plans specifically state that no geotextile fabric shall be
placed between the underdrain and the filter material or
between the filter material and the bioretention media?
~
~
~
Walls and Spillway
Are subgrade conditions necessary to ensure suitable foundation
for the walls and reduce potential settling specified?
~
~
~
Does the design provide an outlet or other means of overflow
(spillway) at the elevation of maximum ponding depth?
~
~
~
A-2
-------
Design Considerations (continued)
Impermeable Liners
If a liner is not required, is the facility at least 10 feet away from
any structure?
~
~
~
If a liner is required, are the following conditions met:
• Is a 30 mil (minimum) PVC liner installed on the bottom and
sides of the basin, extending up at least to the top of the
underdrain layer?
~
~
~
• Does the liner have a minimum of 9 inches of cover over the
membrane to protect the membrane from UV
deterioration?
~
~
~
• Is the attachment of the liner to a solid reinforced concrete
wall detailed on the plans?
~
~
~
• Do the plans call for heat welding and testing of all seams
and specify to contact the engineer to be present during
testing of all seams?
~
~
~
• Does the liner meet the physical requirements presented in
Table B-5 of the USDCM Volume 3?
~
~
~
Bioretention Media and Vegetation
For bioretention media, is a minimum of 18 inches of growing
medium provided to support the establishment of vegetation
roots?
~
~
~
If trees are to be installed, is the filter media depth at least 2
feet? (3 to 4 feet recommended)
~
~
~
Is the identified growing medium (per Volume 3 requirements)
for bioretention structures and is this clearly referred to as
bioretention media (not "growing media") in all locations
referenced?
~
~
~
Is the bioretention media specified on the plans?
~
~
~
Does the design incorporate drought tolerant vegetation that
thrives in sandy soil and is non-invasive?
~
~
~
Additional Comments
A-3
-------
Additional Comments
A-4
-------
Appendix B: Development Plan Review Checklist for Tree Trench/Pit
TREE TRENCH/PIT
Green Infrastructure Design
Plan Review Checklist
A tree trench provides stormwater quality treatment for streets and adjacent pedestrian zones. Stormwater enters the tree
trench through a curb opening, passes through a pea gravel filter for pretreatment and is conveyed through an underdrain to one
or more tree plantings. Treatment processes include filtration, soil adsorption, and uptake by the roots of the trees. A tree trench
that features a single tree is called a tree pit.
Technical guidance is provided in italics below. Note that the Urban Drainage and Flood Control District (UDFCD) Urban Storm
Drainage Criteria Manual Volume 3 does not contain a practice description for infiltration trenches. Specifications on this Plan
Review Checklist were obtained from the Colorado Department of Transportation's Drainage Design Manual (see
{http://www.coloradodot.info/proarams/environmental/water-aualitv/documents/drainaae-desian-manual).
Plan Review Checklist for Tree Trench/Pit
Questions Yes No N/A Notes
Site Applicability and Considerations
Siting
Are the trees sited in the amenity zone between the step-out
zone and sidewalk?
~
~
~
Are the trees sited in a manner that preserves sidewalk width
and will not hinder high pedestrian traffic?
Are City and County of Denver requirements for step-out zones
followed and appropriately considered when adjacent parking
exists and does not exist?
~
~
~
Is the bottom of the tree trench at least five feet above the
seasonal high water table or bedrock?
~
~
~
Is there a nearby inlet or manhole that would provide a
convenient location to discharge the underdrain to?
~
~
~
Pedestrian Considerations
Are tree grates or paver grates designed to meet ADA
requirements?
~
~
~
Will the pretreatment filter and inlet be covered by removable
or accessible grate panels meeting ADA requirements?
~
~
~
Geometry
Tree trench sections do not have more than three trees.
~
~
~
Other
Was a soil investigation performed by a registered geologist, soil
scientist, or professional engineer?
~
~
~
Were recommendations in a geotechnical report followed?
~
~
~
Is there positive drainage away from adjacent buildings at all
locations?
~
~
~
B-l
-------
Design Considerations
Water Quality Capture Volume Zone
Does the design allow for the recommended storage volume
(above the surface) per USDCM Volume 31
~
~
~
Is the tree trench designed as a flow-through system to provide
equal to or greater capacity than peak discharge during the
water quality storm event?
~
~
~
Inlet and Outlet Controls
Is an inlet and water control structure provided for every trench
section (or every three trees)?
~
~
~
Will the street inlet be located at the upstream end of the tree
trench?
~
~
~
Will the inlet convey runoff from the curb and gutter and across
the step-out zone?
Is the inlet sized to convey the water quality event assuming an
appropriate amount of debris blockage (i.e., debris factor)?
~
~
~
Is the outlet control orifice sized to drain the design volume in 12
hours or more and is a minimum orifice size of 3/8-inch used (to
avoid clogging)? See USDCM Volume 3 for appropriate release
rate.
~
~
~
Does the outlet control structure provide an adjustable control
weir to assist with the wetting of the structural media and tree
roots?
~
~
~
Is an observation well/clean out provided?
CDOTrecommends an observation well of 100-150 mm
perforated PVC pipe.
~
~
~
Pretreatment
Is pretreatment provided to function in conjunction with the
inlet?
~
~
~
Is the pretreatment filter designed with media (e.g., pea gravel)
that allows for relatively high-flow through capacity?
~
~
~
Is the sizing of the pre-treatment filter based on an infiltration
rate of 4 inches per minute?
~
~
~
Underdrain System
Does the facility design include an underdrain system
(recommended)?
An underdrain system may be necessary if infiltration tests show
percolation drawdown rates slower than two times the rate
needed to drain the WQCV over 12 hours, or where required to
divert water away from structures as determined by a
professional engineer.
~
~
~
Is the underdrain system designed to meet the capacity required
to convey the peak discharge of the water quality event?
~
~
~
Do all references to the underdrain clearly call for slotted pipe
(not perforated) and are the slot widths included in the plan?
~
~
~
Are cleanouts provided to enable underdrain inspection and
maintenance?
~
~
~
B-2
-------
Design Considerations (continued)
Is the underdrain system placed within a section of CDOT Class C
filter material (not bioretention media) and is this material
specified on the plans?
~
~
~
Do the plans specifically state that no geotextile fabric shall be
placed between the underdrain and the filter material or
between the filter material and the bioretention media?
~
~
~
Impermeable Liners
Is a liner required? (if yes, select the type below)
~ One trench sidewall
~ Both trench sidewalls
~ Fully lined installation (constraints on tree root system are
expected and considered in tree selection)
~
~
~
If a liner is required, are the following requirements met:
• Is a 30 mil (minimum) PVC liner installed on the bottom and
sides of the basin, extending up at least to the top of the
underdrain layer?
~
~
~
• Does the liner have a minimum of 9 inches of cover over the
membrane to protect the membrane from UV
deterioration?
~
~
~
• Is the attachment of the liner to a solid reinforced concrete
wall detailed on the plans?
~
~
~
• Do the plans call for heat welding and testing of all seams
and specify to contact the engineer to be present during
testing of all seams?
~
~
~
• Does the liner meet the physical requirements presented in
Table B-5 of the USDCM Volume 3?
~
~
~
Bioretention Media and Vegetation
Is the bioretention media (placed above the root ball and in
structural media) consistent with the criteria outlined in the
Bioretention Section in USDCM Volume 3 and specified on all
plans?
~
~
~
Is the structural media composition supportive of tree growth
and tree grate and pavers? (one part bioretention media with
two parts 1-1/2 inch crushed gravel is recommended)
~
~
~
Is the total bioretention media and structural media depth at
least 2 feet? (3 to 4 feet recommended)
~
~
~
Are appropriate trees and tree spacing used per City of Denver
Forestry Department's list of approved street trees?
~
~
~
If magnesium chloride de-icer is used on the streets adjacent to
a proposed tree trench, will trees with a tolerance to saline soils
be planted?
~
~
~
If shade trees will be used, are trees with strong central leaders
that branch out 6 feet high or higher planned to avoid creating
barriers and hazards to pedestrians?
~
~
~
In areas with overhead powerlines, has the height of the tree
been considered?
~
~
~
B-3
-------
Additional Comments
B-4
-------
Appendix C: Development Plan Review Checklist for Permeable Pavement
PERMEABLE PAVEMENT
Green Infrastructure Design
Plan Review Checklist
Permeable pavement allows streets, parking lots, sidewalks, and other impervious covers to maintain their structural and
functional features while restoring natural infiltration capacity. Permeable pavement contains small voids that allow rainfall and
runoff to drain through the pavement and eventually into the underlying soils. It can be used at various sites with low traffic
frequency such as parking lots, sidewalks, and driveways. Many permeable pavement surfaces are available, including pervious
concrete, porous asphalt and permeable interlocking concrete pavers. As an example, the following plan review checklist is
intended for reviewing green alleys where permeable pavement is the primary green infrastructure reviewed. A green alley is
designed to provide water quality treatment and infiltration of runoff though the use of permeable pavement. Green alleys may
include other green infrastructure applications.
Technical guidance is provided in green text below, including references to the Urban Drainage and Flood Control District (UDFCD)
Urban Storm Drainaae Criteria Manual (USDCM) Volume 3. which is available online at http://udfcd.ora/volume-three.
Plan Review Checklist for Permeable Pavement
Questions Yes No N/A Notes
Site Applicability and Considerations
Siting
Has the appropriate application of pervious pavement (e.g., use,
traffic loading, slopes) been considered?
Permeable pavement is not appropriate for runoff from erosive
areas such as steep slopes and/or areas of sparse vegetation
where sediment-laden runoff could clog the system.
~
~
~
Is there a nearby inlet or manhole that would provide a
convenient location to discharge the underdrain to?
~
~
~
Pedestrian Considerations
Does the design meet ADA guidelines?
~
~
~
Is the permeable surface constructed with the heaviest duty
materials and interlocking patterns to withstand the heavy truck
traffic common to most alleys?
~
~
~
Geometry
Is the minimum width of permeable pavement equal to one third
of the alley width?
~
~
~
Is the permeable pavement the central flow line of the alley?
The longitudinal slope should match the alley's gradient.
~
~
~
Other
Was a soil investigation performed by a registered geologist, soil
scientist, or professional engineer?
~
~
~
Were recommendations in a geotechnical report followed?
~
~
~
Is there positive drainage away from adjacent buildings at all
locations?
~
~
~
Design Considerations
Is the ratio of upstream impervious area to permeable pavement
area 2:1 (as recommended in USDCM Volume 3)?
~
~
~
Is a perimeter barrier installed where appropriate and detailed in
section based on permeable pavement type?
~
~
~
Does the design include an observation well to monitor drain
time of the pavement system over time?
~
~
~
c-i
-------
Underdrain System and Filter Material
Does the facility design include an underdrain system
(recommended)?
An underdrain system may be necessary if infiltration tests show
percolation drawdown rates slower than two times the rate
needed to drain the WQCV over 12 hours, or where required to
divert water away from structures as determined by a
professional engineer.
~
~
~
Do all references to the underdrain clearly call for slotted pipe
(not perforated) and are the slot widths included in the plan?
~
~
~
Are cleanouts provided to enable underdrain inspection and
maintenance?
~
~
~
Is the underdrain system placed within a section of CDOT Class C
filter material (not bioretention media) and is this material
specified on the plans?
~
~
~
Do the plans specifically state that no geotextile fabric shall be
placed between the underdrain and the filter material or
between the filter material and the bioretention media?
~
~
~
Does the design section provide specific and appropriate filter
layer details?
~
~
~
Impermeable Liners
If a liner is required, are the following conditions met:
• Is a 30 mil (minimum) PVC liner installed on the bottom and
sides of the basin, extending up at least to the top of the
underdrain layer?
~
~
~
• Does the liner have a minimum of 9 inches of cover over the
membrane to protect the membrane from UV
deterioration?
~
~
~
• Is the attachment of the liner to a solid reinforced concrete
wall detailed on the plans?
~
~
~
• Do the plans call for heat welding and testing of all seams
and specify to contact the engineer to be present during
testing of all seams?
~
~
~
• Does the liner meet the physical requirements presented in
Table B-5 of the USDCM Volume 3?
~
~
~
If a liner is not required, do subgrade soils have a minimum
infiltration rate of 2 times the rate needed to drain the WQCV
over 12 hours?
~
~
~
C-2
-------
Additional Comments
C-3
-------
Appendix D: Post-Construction Inspection Checklist for Green Infrastructure
PROJECT INFORMATION
Green Infrastructure
Post-Construction
Inspection Checklist
Project name:
Inspection date:
Site address:
Weather at time of inspection (rainy,
cloudy, sunny, etc.):
Inspector(s):
Date of last rainfall:
Bioretention
Type(s) present: ~ Streetside Stormwater Planter ~ Bump-Out Stormwater Planter ~ Green Gutter
Inspection summary:
Tree Trench/Tree Pit
Type(s) present: ~ Tree Trench ~ Tree Pit
Inspection summary:
Permeable Pavement (Green Alley)
~ Permeable Interlocking Concrete Pavers (PICP) ~ Porous Gravel
Type(s) present:
~ Concrete Grid Pavement ~ Reinforced Grass
Inspection summary:
D-l
-------
BIORETENTION
Streetside Stormwater Planters, Bump-Out Stormwater Planters, and Green Gutters
Green Infrastructure
Post-Construction
Inspection Checklist
Inspection Item
Yes No N/A
Corrective action (if "no")
1. Will site runoff enter the practice as intended?
~
~
~
2. Will flow be evenly dispersed following the inlet? Are there
signs of or potential for concentrated flow?
~
~
~
3. Is pretreatment in place according to construction drawings?
~
~
~
4. Do the bioretention dimensions match those specified in the
construction drawings?
~
~
~
5. Are step-out zone dimensions (if applicable) according to
plans?
~
~
~
6. Are pedestrian barriers in place and sized according to plans?
~
~
~
7. Are underdrains installed? If so, are the slots oriented and
sized according to the plans?
~
~
~
8. If applicable, are underdrain cleanouts visible and sealed? If
in a valve box, ensure filter material has also been placed
between the valve box and cleanout.
~
~
~
9. If applicable, are cleanouts configured according to plans and
located a maximum of every 300 feet? Are riser pipes solid
(not slotted)?
~
~
~
10. Are walls and spillway constructed as planned?
~
~
~
11. Is the distance from the surface of the filter area to the
outflow (spillway and top of the weir inside the water control
structure) appropriate to provide the ponding depth per the
construction drawing?
~
~
~
12. Is the outlet control weir set to the elevation shown on the
construction drawings?
~
~
~
13. Does the bioretention media match the description of the
media provided in the submittal?
~
~
~
14. Has the bioretention media infiltration rate been tested
according to the plans and specifications? Verify infiltration
rate test records.
~
~
~
15. If applicable, is mulch finely shredded hardwood and 3 inches
in depth?
~
~
~
16. If plans include a liner, is it sufficiently covered by media and
not visible?
~
~
~
17. If applicable, ensure weed barrier is not used under mulch or
rock.
~
~
~
18. Is the vegetation the type, size, and maturity as specified in
the plans? (e.g., grasses versus plantings, seed versus sod)
~
~
~
19. If sod is used, it is sand-grown sod?
~
~
~
20. Is the vegetation planted and staked properly according to
the plans? (e.g., orientation, proximity, overall placement)
~
~
~
21. Does vegetation appear healthy?
~
~
~
D-2
-------
TREE TRENCH/PIT
Green Infrastructure
Post-Construction
Inspection Checklist
Inspection Item
Yes No N/A
Corrective action (if "no")
1. Will site runoff enter the practice as intended?
~
~
~
2. Is pretreatment filter in place according to construction
drawings? Is there at least 6 inches of fall from the invert of
the chase to the top of the aggregate?
~
~
~
3. Do dimensions of the tree trench/tree pit match those
specified in the construction drawings?
~
~
~
4. Are step-out zone dimensions according to plans?
~
~
~
5. Are underdrains installed? If so, are the slots oriented and
sized according to the plans?
~
~
~
6. If applicable, are underdrain cleanouts visible and sealed? If
in a valve box, ensure filter material has also been placed
between the valve box and cleanout.
~
~
~
7. If applicable, are cleanouts configured according to plans and
located a maximum of every 300 feet, with cleanouts at every
junction and bend in the pipe? Are riser pipes solid (not
slotted)?
~
~
~
8. Is the distance from the surface of the tree area (filter area)
to the tree gate as specified in the plans?
~
~
~
9. Is the outlet control weir set to the elevation shown on the
construction drawings?
~
~
~
10. Does the bioretention media match the description of the
media provided in the submittal?
~
~
~
11. Has the bioretention media infiltration rate been tested
according to the plans and specifications? Verify infiltration
rate test records.
~
~
~
12. If applicable, is mulch finely shredded hardwood and 3 inches
in depth?
~
~
~
13. If plans include a liner, is it sufficiently covered by media and
not visible?
~
~
~
14. If applicable, ensure weed barrier is not used under mulch or
rock.
~
~
~
15. Is the tree type, size, and maturity as specified in the plans?
~
~
~
16. If multiple trees, are the trees spaced according to the plans?
~
~
~
17. Does the tree(s) appear healthy?
~
~
~
D-3
-------
PERMEABLE PAVEMENT
Green Alley
Green Infrastructure
Post-Construction
Inspection Checklist
Inspection Item
Yes No N/A
Corrective action (if "no")
Common Elements
1. Does the alley drainage area appear to drain centrally
towards the permeable pavement (away from buildings)?
~
~
~
2. Is the width of the permeable pavement as specified in
the plans?
~
~
~
3. Is the surface even with no evidence of cracks or
depressions?
~
~
~
4. Is the storage or structural layer firm and unyielding?
~
~
~
5. Is a transition strip of standard concrete provided at all
transitions from asphalt to permeable pavement unless
otherwise specified in the plans?
~
~
~
6. Are underdrains installed? If so, are the slots oriented and
sized according to the plans?
~
~
~
7. If applicable, are underdrain cleanouts visible and sealed?
If in a valve box, ensure filter material has also been
placed between the valve box and cleanout.
~
~
~
8. If applicable, are cleanouts configured according to plans
and located a maximum of every 300 feet, with cleanouts
at every junction and bend in the pipe? Are riser pipes
solid (not slotted)?
~
~
~
9. Is the outlet constructed per construction drawings?
Permeable Interlocking Concrete Pavers
(PICP)
1. Is a leveling layer of washed No. 8 stone included
between the structural layer and the permeable
interlocking concrete paver?
~
~
~
2. Are all voids filled with washed No. 8 stone to the surface
of the interlocking concrete paver?
~
~
~
3. Is the pavement surface firm and unyielding?
~
~
~
4. If for vehicular use, is the outer edge of PICP area
bordered by concrete, and are uncut blocks used adjacent
to the concrete border?
~
~
~
5. Are cut pavers at least 40% of their uncut size?
~
~
~
6. Is a herringbone pattern used for PICP areas intended for
vehicular traffic?
~
~
~
Concrete Grid Pavers
1. Is the outer edge of the paver area bordered by concrete?
~
~
~
2. If uncut blocks are used, are they adjacent to the concrete
border?
~
~
~
3. If visible, does the bedding layer consist of No. 8 stone
unless otherwise specified in the plans?
~
~
~
4. If vegetation is specified, is the grid paver filled with a soil
media or seeded according to the plan?
~
~
~
D-4
-------
Appendix E: Maintenance Checklist for Green Infrastructure
GREEN INFRASTRUCTURE
Ongoing Maintenance
Inspection Checklist
Facility Information
Property owner:
Inspection date:
Property address:
Inspection type:
~ After first rainfall event of season
~ Monthly (during wet season)
~ Other:
Inspector(s):
Bioretention
Type(s) present: ~ Streetside Stormwater Planter ~ Bump-Out Stormwater Planter ~ Green Gutter
Post-inspection summary:
Tree Trench/Tree Pit
Type(s) present: ~ Tree Trench ~ Tree Pit
Post-inspection summary:
Permeable Pavement (Green Alley)
~ Permeable Interlocking Concrete Pavers (PICP) ~ Porous Gravel
Type(s) present:
~ Concrete Grid Pavement ~ Reinforced Grass
Post-inspection summary:
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GREEN INFRASTRUCTURE
Ongoing Maintenance
Inspection Checklist
Additional Notes
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BIORETENTION
Streetside Stormwater Planter, Bump-Out Stormwater Planter, Green Gutter
Defect and Conditions Indicating
Maintenance Needed?
Results Expected When
Maintenance is Needed
Y/N
Comments
Maintenance is Performed
1. Standing water
Water ponds in the bioretention area
between storms and does not drain
within 24 hours after rainfall.
There should be no areas of standing water
once inflow has ceased. This is typically an
issue of sediment or debris accumulation on
top of the media or when flow to the
underdrain is inhibited.
2. Sediment
Evidence of accumulated sediment in
the bioretention area or forebay.
Forebay should be cleaned out regularly so
that material does not accumulate in the
forebay or bioretention area.
3. Erosion
Channels have formed around inlets,
there are areas of bare soil, or there is
other evidence of erosion.
Obstructions and sediment should be removed
and disposed of properly so that water flows
freely and disperses evenly.
4. Debris and litter
Debris and litter accumulated in the
bioretention area and around the inlet
and outlet.
Debris and litter removed from the
bioretention area and disposed of properly.
5. Vegetation
Vegetation is dead, diseased or
overgrown.
Vegetation is healthy and attractive. If
applicable, grass is maintained at least 3 inches
in height.
Vegetation is maintained and clear of
leafy debris.
Bioretention area should be clear of leafy
debris (dead leaves and plant matter) and
trimmed, as needed.
Leafy debris (litter) will require removal each
fall (October). Perennials and grasses require
cutting in late winter/early spring (March).
Soils have sufficient moisture to support
growth during the growing season
(March - October).
Based on plant type, soil moisture should be
sufficient for healthy plant growth. Soil
moisture should be inspected as needed
throughout the growing season (March -
October).
Prevalent weeds.
Weeds need to be extracted and physically
removed (not sprayed or pulled and left to
wither) to prevent deep rooted infestations
(monthly).
6. Mulch (if applicable)
Mulch is displaced, missing or patchy.
Areas of bare earth are exposed or
mulch layer is less than 3 inches deep.
Mulch is clogging the overflow or in the
gutter.
All bare earth is covered, except mulch is kept
6 inches away from trunks of trees and shrubs.
Mulch is even at a depth of 3 inches. Upon
inspection, if vegetation is healthy without
mulch, mulch may be removed as it may not
be necessary.
7. Inlet/outlet
Sediment accumulations.
Inlet/outlet is clear of sediment and debris and
allows water to flow freely.
8. Other
Any condition not covered above that
needs attention for the bioretention
area to function as designed. Any
impairment of surrounding structures
(e.g., buildings, pavement) as a result of
poor drainage or uprooting.
The design specifications are met and no
effects on surrounding structures.
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BIORETENTION Streetside Stormwater Planter, Bump-Out Stormwater Planter, Green Gutter
Describe maintenance that was completed; if the needed maintenance was not conducted, note when it will be done.
Notes:
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TREE TRENCH/TREE PIT
Defect and Conditions Indicating
Maintenance is Needed
Maintenance Needed?
Results Expected When
Maintenance is Performed
Y/N
Comments
1. Standing water
Water in the observation well under the
tree grate does not drain within
24 hours after rainfall.
Water should not remain stagnant in the
observation well under the tree grate beyond
24 hours after a rainfall. There should also be
no areas of standing water in the forebay.
Standing water is typically an issue of clogging
in the forebay or poor flow through the system
underdrain.
2. Debris and litter
Debris and litter accumulated in tree
area and around the inlet and outlet.
Debris and litter should be removed from the
tree area and disposed of properly.
3. Sediment
Slow drainage in the forebay indicating
that the stone is clogged with sediment.
Forebay should be cleaned out regularly so
that material does not accumulate in the
stone. Forebay should be vacuumed about
monthly during the wet season, and
replacement of material can be expected
every 2-3 years.
4. Tree
Tree is dead, diseased or unkempt. Are
there dead tree limbs, odd colors on
leaves or bark, or trunk damage?
Tree maintenance (e.g., pruning) may be
required on a regular basis in early years based
on tree type.
Prevalent weeds.
Weeds need to be extracted and physically
removed (not sprayed or pulled and left to
wither) to prevent deep rooted infestations
(monthly).
5. Inlet/outlet
Slow drainage due to sediment
accumulation.
Inlet/outlet is clear of sediment and debris and
allows water to flow freely.
6. Other
Any condition not covered above that
needs attention for the tree trench/pit
to function as designed. Any impairment
of surrounding structures (e.g.,
buildings, pavement) as a result of poor
drainage or tree uprooting.
The design specifications are met and no
effects on surrounding structures.
Describe maintenance that was completed; if the needed maintenance was not conducted, note when it will be done.
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TREE TRENCH/TREE PIT
Notes:
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PERMEABLE PAVEMENT
PICP, Concrete Grid Pavement, Porous Gravel, Reinforced Grass
Defect and Conditions Indicating
Maintenance Needed?
Results Expected When
Maintenance is Needed
Y/N
Comments
Maintenance is Performed
1. Standing water
Water ponds or runs off of the surface.
Areas of ponding can be observed
during snow melt.
There should be no areas of ponded/standing
water during snow melt. This is typically a
result of poor maintenance; restoration may
be required.
2. Debris and litter
Leaves, grass clippings, trash, etc., are
preventing water from draining into the
permeable pavement and are unsightly.
Area is free of all debris and the permeable
pavement is draining properly.
3. Vegetation
Weeds are growing on the surface of
the permeable pavement.
Area adjacent to pavement is well-maintained
and no bare soil/exposed areas exist.
No weeds present in the pavement area.
4. Deteriorating surface
The pavement is cracked; paver blocks
are misaligned or have settled.
The surface area is stabilized, exhibiting no
signs of cracks or uneven areas in the
pavement area.
5. Other
Any condition not covered above that
needs attention for the permeable
pavement area to function as designed.
The design specifications are met.
Describe maintenance that was completed; if the needed maintenance was not conducted, note when it will be done.
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PERMEABLE PAVEMENT
PICP, Concrete Grid Pavement, Porous Gravel, Reinforced Grass
Notes:
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