United States
Environmental Protection
           City of Portland, Bureau of Environmental Services
                               Portland, Oregon
    District-Scale Green Infrastructure Scenarios for the Zidell

    Development Site, City of Portland

    An Exploration of Holistic, Adaptive, and Flexible Green Infrastructure Strategies
    within a 33-acre Remediated Brownfield Development

    Photo: River East, Portland
                                                                       AUGUST 2013
                                                                    EPA 830-R-13-002

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, the water is absorbed and
filtered by soil and plants. 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 and  discharged into nearby waterbodies. 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. These neighborhood  or site-
scale green infrastructure approaches are often  referred to  as  low
impact development.
EPA  encourages the use  of  green infrastructure to  help  manage
stormwater  runoff.  In April 2011, EPA  renewed its commitment to
green infrastructure with  the release  of  the Strategic Agenda to
Protect Waters and Build More Livable Communities through Green
Infrastructure. The  agenda identifies technical assistance as a  key
activity that  EPA will pursue to accelerate the implementation of
green infrastructure.

In February 2012,  EPA  announced the availability of $950,000 in
technical assistance to  communities working to overcome common
barriers to green infrastructure. EPA received letters of interest from
over 150 communities across the country, and selected 17 of these
communities to  receive technical assistance.  Selected communities
received  assistance with a range of projects aimed at addressing
common  barriers to green  infrastructure, including  code  review,
green infrastructure design, and cost-benefit assessments. The City of
Portland  was  selected to   receive assistance  identifying green
infrastructure opportunities for a 33-acre brownfield redevelopment
For more information, visit http://water.epa.gov/infrastructure/greeninfrastructure/gi  support.cfm.

Introduction	5
The Site	8
Master Plan	11
The Challenge	13
      Project Goals	13
      Key Design Assumptions	13
      Green  Infrastructure Toolbox	20
      Green  Infrastructure Integration	21
The Scenarios	23
      Diffuse and Embedded	25
      Clustered and Distinct	29
      Central and Focused	33
Scenario Comparison	36
Conclusion	39
Principal EPA Staff
Krista Mendelman, USEPA, Region 10
Tamara Mittman, USEPA
Christopher Kloss, USEPA

Community Team
Kaitlin Lovell, Portland Bureau of Environmental Services
Linda Dobson, Portland Bureau of Environmental Service
Tim Kurtz, Portland Bureau of Environmental Services
Geraldene Moyle, Portland Development Commission
Dennis Allen, ZRZ Realty

Consultant Team
Dave Elkin, GreenWorks, PC
Martina Frey, Tetra Tech, Inc.
This report was developed under EPA Contract No. EP-C-11-009 as part of the 2012 EPA Green Infrastructure
Technical Assistance Program.



This Zidell Yards project offers  the  first holistic,  comprehensive opportunity in Portland, Oregon to identify
solutions for applying green infrastructure to manage stormwater on one of the largest brownfield remediation and
redevelopment sites in  Portland—the Zidell site, a 33-acre industrial property adjacent to the Willamette River
and downtown Portland. The Zidell site is in the 120-acre South Waterfront District, which encompasses existing
and former industrial areas in Portland's Central City. Recently, the South Waterfront District has been a hub of
sustainable building and planning and, as a result, was identified as one of five pilot eco-districts in the city. With its
commitment to explore new applications of green infrastructure in our urban environments, the City of Portland,
supported by ZRZ Realty, applied for U.S. Environmental Protection Agency technical assistance to develop green
infrastructure scenarios  for the Zidell Yards site.
The goal of this effort is  to develop a range of green infrastructure scenarios consistent with the constraints of a
recently remediated brownfield that can be implemented within the framework of a 15-  to 20-year development
master plan. Conversations with local and national experts and stakeholders resulted in much consensus regarding
the application  of green infrastructure at this site and similar sites, but this effort is just the beginning of a broader
conversation that will continue as green infrastructure and brownfield redevelopment are studied and applied. This
report was written to collect and describe key findings during our exploration of this topic that can be applied to the
Zidell site and other redevelopment projects of similar character.
This is a critical time and opportunity to explore the use of green infrastructure on remediated sites specifically
because of the extensive remediation, redevelopment, and retrofit opportunities expected in the next decade in
former industrial areas locally and throughout the nation. As our urban areas continue to develop, the discussion of
redeveloping brownfields and its associated benefits and constraints has become more pertinent; an estimated 450,000
properties in the United States are brownfields.  The study of mobilization of pollutants and the advancement of
remediation solutions have allowed many of these brownfield properties to transcend their former uses and become
housing, new business incubators, productive greenspaces such as community gardens or urban farms, and hotbeds
of new jobs. Redeveloping these  properties can bring revenue to local municipalities through increase in property
values and taxes.
Property improvements  can also benefit natural systems. Many of the brownfields  in Portland are next to  the
Willamette River, which is  a significant and highly visible natural resource. The Willamette River is impaired for


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                                               section of the river are listed as threatened under the Endangered Species Act.

                                               The proximity of brownfields to significant natural resources is common as industry historically relied on our nation's
                                               waterways for transportation of goods. While remediation solutions for brownfields can remove and encapsulate
                                               pollutants from historic uses of the site, these natural resources  also need to be protected from the effects of future
                                               development. Specifically, green infrastructure is being applied throughout cities worldwide as a sustainable form of
                                               stormwater management.

                                               Green infrastructure solutions—such as green streets, ecoroofs, rain gardens, stormwater planters, open space or
                                               parks, permeable pavement, street trees, and cisterns—mimic the natural water cycle and integrate the management
                                               of stormwater into our urban fabric to help reduce the damaging effects of urbanization. By integrating these natural
                                               processes into the built environment, green infrastructure manages stormwater and provides additional benefits such
                                               as climate resiliency, air cooling and filtering, community beautincation, and multi-modal transportation benefits.
                                               Portland has received national and international recognition as a leader in the application of green infrastructure
                                               solutions through early adoption, research, and monitoring of these practices at new development and retrofit sites.

                                               The project team collaborated in a workshop-driven process to develop three alternative scenarios for the Zidell Yards.
                                               The conceptual design scenarios apply green infrastructure solutions that capitalize on infiltration and innovation for
                                               the remediated brownfield site with the goal of exceeding existing regulatory requirements for stormwater management
                                               and providing creative solutions with multiple community benefits. This report explores three alternative scenarios to
                                               maximize onsite  stormwater infiltration across the entire property. Though the stormwater techniques are familiar—
                                               green streets, ecoroofs, rain gardens,  stormwater planters, open space/parks, permeable pavement, street trees, and
                                               cisterns, among others—their application at a brownfield site is truly innovative.

The 33-acre project area is in the northern portion of
the South  Waterfront  District.  The site is  generally
flat, sloping gently from the northeast to southwest.
Elevations range from 35 feet along the north side of the
site to 28 feet along the south side. The site's riverbank
along the Willamette  River is approximately 2,700
feet long. An approximately 100-foot-wide greenway
setback is along the east edge of the  property, and this
segment  accounts for  approximately 40  percent of
the total length of the South Waterfront Greenway.
The Ross Island Bridge crosses the property from east
to west approximately 100  feet overhead, including
multiple  bridge footings. The bridge carries  Highway
26, a major east/west transportation corridor owned by
the Oregon Department of Transportation (ODOT).
The bridge  covers approximately 20,000 square  feet
of the site. The Zidell Corporation  maintains marine
operations fabricating barges in the two large buildings
in a small portion of the site  along its southern edge.

The site has been filled over the years; it is underlain
by construction fill material and  sediment deposits
from periodic flooding by the Willamette River.  The
sediments consist  of fine-grained, sandy silt and are
approximately 75  feet  thick. Groundwater is present
and  generally shallow,  ranging from 5 to 30  feet
deep. The groundwater depth varies seasonally, but it
generally flows from southwest to northeast toward the
Willamette River. The site is not connected to Portland's
stormwater infrastructure system. Stormwater from the
site was served by two private outfalls owned by ZRZ
Realty Company and one public outfall,  a brick pipe
built in 1892. The public outfall was decommissioned
as part of the recent site remediation. The two private
outfalls remain in service; one conveys overflows from
an infiltration basin that  was constructed  when the
public outfall was  decommissioned.  Along the  site's
north edge, a bridge landing is being constructed for the
city's newest light-rail extension to connect Portland to
Milwaukie to the south. To accommodate the height of
the new light-rail bridge, approximately 14  feet of fill
has been placed along the north side of the site. Future
roadways and development in that part of the site must
be raised to meet the new bridge landing.

Historical maps  identify the entire South Waterfront
District along   the  west bank  of the  Willamette
River as primarily floodplain marshes.  Small streams
conveyed water from the West Hills down  to a small
pond in the floodplain  and eventually flowed to the
Willamette River. Typical native tree species that grew
in these fertile  alluvial soils were Oregon ash,  black
cottonwood,  red alder,  and bigleaf maple. Much of
the fertile floodplain had been cleared of vegetation
for farm cultivation  by the 1850s. As  with many
floodplains next to growing urban areas, the farmland
was  eventually   filled over several  decades  to  meet
the ever-growing demand for industrial  land beside
the river. Many industrial businesses have  occupied
this site since the 1920s, most of which  were related
to ship building  and  dismantling. As  a result  of
historical industrial land uses, the Zidell Yards site and
adjacent river sediments were contaminated and were
entered into Oregon's Department of Environmental
Quality (DEQ) Voluntary Cleanup Program. For the
purposes of comparison of this site to other remediated
brownfields, the pollutants found during the remedial
investigation were asbestos materials, volatile organic
compounds (VOCs), total  petroleum hydrocarbons
(TPH),  metals,  polycyclic  aromatic  hydrocarbons
(PAHs),  polychlorinated biphenyls (PCBs),  dioxins,
and furans.
Site remediation work began in 2010 with excavation
and disposal  of upland hotspot soils. Riverbank and
river  sediment remediation  was conducted in  the
summer of 2011 including constructing a sediment
cap and landscaping the riverbank with thousands of
native plants. A 2-foot-thick soil cap was placed over
the greenway setback in 2012 to isolate residual low-
level soil contamination, and a gravel cap was placed
on the remaining upland areas under and north of the
Ross  Island Bridge. The remaining contaminants on
the remediation site are considered non-mobile and do
not pose a risk to groundwater. Because of this, Oregon
DEQ does  not prohibit stormwater infiltration on the
site. The remediation project enhances water quality in
the river and greatly improves fish and wildlife habitat
in and beside the water.


Master Plan Surfaces  Acres   Total % of plan
                                      38% (3817 sq1 overhang in greenway)
                                      100% (0.2 acre degree of accuracy)
       Building Footprints
Plaza and Curbless Streets
    Total Calculated Area

                                            MASTER  PLAN
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The site is in a dynamic development location catalyzed by recent development of the South Waterfront District,
expansion of Oregon Health Sciences University, and the new light-rail bridge terminus on the west side of the
Willamette River. This site is one of the largest remaining parcels of developable land that is immediately south of
downtown Portland. ZRZ Realty is developing a vision and master plan for their development, named Zidell Yards.
Development is planned to occur in several major phases over a 15- to 20-year time frame. The site is envisioned to
integrate buildings and open space into a sustainable, mixed-use development that embraces the history and ecology of
the Willamette River. ZRZ Realty provided a preliminary master plan to the project team to develop an understanding
of total impervious surface and approximate locations of buildings and other site elements. The preliminary master
plan is, of course, subject to change. The development is planned to have a mix of office, residential, retail, and hotels
with large areas of open space. Portland Parks and Recreation has identified the area under and next to the Ross Island
Bridge for park area up to 4 acres that would take advantage of its unique location under the bridge and its proximity
to the Willamette River.
The master plan diagram identifies the approximate location of buildings, streets, plazas, and open space in the future
development; the absolute and relative acreage of each feature type is indicated in the legend. The land area of the
master plan is 30 acres; an additional 3 acres are next to the site north of the light-rail bridge and are outside the
project's study area. A future greenway trail will be designed and constructed within the 100-foot greenway setback
area. For the purposes of this project, we used a snapshot of the master plan as ZRZ Realty continued to refine its
development concept. This project is not intended to finalize the master plan for the development but to use the
master plan as a framework in which to work.

                                                                       Conventional stormwater management would require redundant piped
                                                                        infrastructure systems that transect contaminated media, increasing
                                                                                               construction and permitting costs.
            V-.   \     \\ffAINFALL
   '. '2' THICK CAP >

                This system relies on a mixed public and private green infrastructure
             system that uses surface conveyyance to protect contaminated soils and
                     integrate stormwater maanagement within the development.
                           /MIXED        ^ / SURFACE
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                                      PROTECTED NON-MOBILE
                                                                           TO SOIL

The challenge of the Zidell Yards site project was to collaboratively develop an innovative green infrastructure system
to maximize stormwater capture and treatment through an integrated system of public and private facilities across
the entire site. The site's unique characteristics as a brownfield adjacent to the Willamette River combined with its
location at the nexus of sustainable planning and development in Portland provided the opportunity for an ambitious
and innovative conversation related to the future of green infrastructure and sustainable development. Early in the
process, the project team developed a list of goals (below) for a successful project.


•   Provide flexible and adaptive solutions for the specific conditions of a remediated brownfield
•   Support EPA's Strategic Agenda for Green Infrastructure
•   Evolve current sustainable stormwater management techniques
•   Provide a range of concepts
•   Minimize or eliminate the need for new piped outfalls to the river
Once the project goals were developed, a list of ground rules or design assumptions for the scenarios was established.
Although many design assumptions were developed early in the project, several arose as key assumptions as discussions
progressed. Each of the three scenarios meets the following assumptions.


Mixing of Private and Public Stormwater
This site provides a unique opportunity for a public-private partnership because the entire site has one property
owner, and the site will be developed over a 15- to 20-year time frame. To ensure the development of a flexible and
innovative stormwater management system, we assumed that stormwater from public areas (streets and rights of way)
and private land can be managed holistically in combined facilities and an integrated conveyance system. This concept
has been applied  at individual sites throughout Portland but never on a district scale.  This fundamental design
assumption allows us to explore a district-scale stormwater network that provides greater flexibility for placement of
buildings, infrastructure, and open space. The scenarios provide three examples as to how this integrated,  district-scale
concept could be applied.


Managing Stormwater on the Surface
Because this site is a brownfield, it requires special consideration during site design and development. Specifically,
a cap was  required for remediation to prevent disturbance or erosion of the remaining contaminated soils. As
development occurs on the site, contaminated soil disturbance should be minimized to prevent exposure, erosion,
or its costly hauling away. This constraint poses challenges for the traditional application of underground, piped
gray infrastructure, so the design team sought to focus on managing Stormwater on the surface. All three scenarios
developed for the site rely on a network of surface conveyance channels and infiltration facilities to manage Stormwater
and convey larger flows to the Willamette  River via an overland discharge system. Infiltration of Stormwater on this
site is possible because of the nature of the remaining soil contaminants and the extensive remediation that has already
The primary goal for applying a surface conveyance system is to reduce the potential for disturbing contaminated
media. A surface conveyance system would not penetrate the cap, therefore, avoiding the potentially significant costs of
excavating and disposing of contaminated soils. Furthermore, a surface conveyance network and green infrastructure
facilities will provide other benefits beyond a traditional piped system, including visible water flow, connecting people
to water, sustainable site identity, and treatment of Stormwater before it flows into the Willamette River.

Integrating Green Infrastructure
The concept of green infrastructure is inherently connected with integration. Whether it is a green roof, green street,
or flow-through planter, successful facilities are integrated in the  site  design to manage Stormwater and provide
multiple benefits. A district-scale system of green infrastructure can become a fundamental organizing element of the
site by influencing development patterns, views, and circulation corridors. If applied and organized as an amenity, the
green infrastructure system can begin to influence the marketability and potential value of a development.

The scenarios reveal a variety of ways  that green infrastructure can be implemented in  a phased, 15- to 20-year
development timeline. The owner can look to invest in and develop a full Stormwater network, as in the Central and
Focused scenario, and require building developers to connect to its system. Or the owner could require a performance-
based approach such as  the Diffuse and Embedded scenario and require building developers to manage their own
Stormwater at the source on the basis of a common model. Each  of these scenarios can be mixed and matched across
the site to accommodate multiple buildings, timing, or site-specific constraints.

                                 ZIDELL PROPERTY
                             ROOFTOPS^,  ....^ CONVEYANCE
                                  '        *l CHANNEL J
                                                                                                HYPORHEIC ZONE
                 RIPARIAN EDGE
                                              EMERGENT MARSH PLANTING
                                            INFILTRATION TO HYPORHEIC ZONE
                                                                                      CONSTRUCTED WETLANDS
                                                                                      — RESTORED RIPARIAN
                                      CONVEYANCE CHANNEL
                                        EMERGENT MARSH
           • ••••••••••••••••^
                                                                                           CONSTRUCTED WEIRS
                                  •I HIM*
                 RESTORED RIPARIAN
                                      CONVEYANCE CHANNEL
                                        EMERGENT MARSH

Overland Discharges to the River
Because the site is by the Willamette River, the surface conveyance network will convey treated stormwater directly
to the river. Typical stormwater infrastructure systems rely on a pipe outfall to discharge treated stormwater to a
water body. A piped outfall would require that a large-diameter pipe be installed through the cap, disturbing the
contaminated media. The permitting process for outfalls can be costly and a take a long time that could affect future
development. Furthermore, regardless of outfall size, there is a need to convey larger storm events such as the 50-year
and 100-year events safely across the surface of the site and to the Willamette River. With the overall project goals of
integration/flexibility and site constraints of the brownfield, in lieu of piped outfalls we have considered the use of an
indirect, overland discharge system to convey treated stormwater under the Willamette River Greenway Trail to the
Willamette River. Many potential benefits exist to indirect, overland discharge to the river, including the following:
    •   Reduced temperature of water because of underground,  hyporheic flow
    •   Additional treatment of water before discharge
    •   Visible flow connecting people  to natural processes
    •   No penetration of the cap, which reduces disturbance  of contaminated soils
    •   Increased natural area and integration in the development
    •   Potential ease of permitting compared to a piped outfall
To explore the overland discharge conversation more thoroughly, the team applied a different indirect discharge system
to each of the three scenarios. The systems are hyporheic  discharge ponds,  constructed wetlands, and a constructed
weir channel. We included these three concepts to demonstrate the range  of alternatives and weigh the advantages
and disadvantages of each. Any of the overland discharge concepts could be used for each scenario. A diagram of each
overland discharge concept has been provided to the left.

In addition to the Key Design Assumptions, the  following design assumptions  provided the foundation for each of
the three scenarios:
    •   Stormwater is allowed to infiltrate through the existing engineered cap and through the contaminated media.
    •   Solutions must be adaptable to a phased 15- to 20-year time frame of development.
    •   Reduce or eliminate disturbance of the cap and contaminated soil  beneath.
    •   Public street network can be crossed with surface conveyance systems.
    •   Vegetated facilities will manage up to the Type 1A, 10-year, 24-hour design storm.
    •   Pervious pavement can be applied only on private or semiprivate roadways and plazas and not in the public
        right of way.
    •   Green roofs can be applied on any and all buildings as necessary



    2YR             2.4
          NRCSTYPE 1A
Stormwater Modeling
The Santa Barbara Urban Hydrograph method was used to calculate flows and sizing for Stormwater facilities for the
three scenarios. This is an accepted approach for Stormwater calculations based on Portland's Stormwater Management
Manual.   Portland's Bureau of Environmental Services uses an NRCS Type 1A 24-hour  storm distribution. The
depth of rainfall for different storm sizes, from the water quality event to the 100-year storm event, is shown in the
table below. A 1-inch infiltration rate was assumed for all vegetated facilities managing Stormwater. The greenspace
is assumed to be approximately 50 percent pervious, providing for the likely design  of pathways and plaza spaces
in the greenspace areas. The impervious area of the Ross Island Bridge above the site (approximately  20,000  square
feet) drains through an ODOT drainage pipe away from the development and was removed from any Stormwater
calculations as impervious area.   Because of the  location of this property in the Stormwater system, Portland's
Stormwater Management Manual requires the developer to manage the water quality event onsite. Portland does not
require flow control when discharging directly to large water bodies such as the Willamette River or Columbia River.
Because this project was developed to advance Stormwater management techniques and exhibit innovation in public-
private partnerships, it was agreed that all three scenarios should meet the following requirements for storm events:

•   Manage the water quality storm event
•   Detain and infiltrate the 10-year, 24-hour design storm
•   Safely convey the 100-year, 24-hour design storm

These Stormwater modeling goals established the baseline Stormwater  management that must be met in all three
scenarios.  Each of the scenarios meets these goals  through applying green infrastructure in different combinations
and configurations.

Green Infrastructure Toolbox & Integration
In an effort to focus on solutions that manage Stormwater at the source, the design team early in the process developed
a toolbox of green infrastructure technologies (e.g., swales,  planters, and green roofs) that can be integrated into this
site and other, similar sites. The tools represent solutions for sustainable Stormwater management by either reducing
impervious area (green roofs and pervious pavement) or managing Stormwater via collection and infiltration. The
toolbox is meant to provide examples of the technologies applied in this project and not to be a comprehensive
list  of all  the variations  on green infrastructure solutions.  To broaden the conversation  about integrating green
infrastructure in development, various precedent projects  were reviewed from around the  world that demonstrate
successful  green infrastructure integration in the sites. The projects selected were ones most applicable to the Zidell
Yards site, relating to its context, master plan, and marine heritage. The following pages highlight the  tools and how
they are integrated into the precedent projects.

      Can capture, store, and filter runoff from rooftops.
      In Portland they can remove up to 50% of the total
      annual rainfall volume. Many additional benefits
      such as increasing roof membrane lifespans, insulat-
      ing  buildings, and providing wildlife habitat.
                                                        WARNER MILNE ROAD - OREGON CITY, OREGON
                                                        Can be located in almost any planting bed within a
                                                        site, such as adjacent to parking lots, roadways, and
                                                        sidewalks.  They are effective in providing infiltra-
                                                        tion and conveyance of runoff while also allowing
                                                        for the integration of plant material and artwork.
                                                        BEAUMONT VILLAGE LOFTS - PORTLAND, OREGON
                                                        Often located adjacent to roadways or buildings
                                                        and provide an efficient, focused treatment solution
                                                        for runoff. Are appropriate where space is tight and
                                                        where a more urban aesthetic is desired.
Can be integrated within site planting beds and can
provide treatment and infiltration of stormwater.
Often are shallow depressions which can blend in
with the surrounding plant material and become
integrated into the site.
Can provide a unique celebration of stormwater
and provide a more "visual" experience for visitors.
This project by Buster Simpson provided visitors
with a unique experience of stormwater while also
conveying and treating water from a rooftop.
Provide the opportunity to reduce impervious sur-
faces within a site. This project eliminated the need
for a piped outfall to the river through the applica-
tion of approximately 35 acres of pervious asphalt
at an auto storage facility.

Constructed as one of the amenities for the 2010
Winter Olympics athletes village. The project suc-
cessfully integrated the treatement of flow from a
zero-energy treatment plant within an urban park
The park was designed as the "peeling back" of the
urban fabric to reveal the wetland that once existed
in that location prior to western settlement. The
project successfully embeded the context of the site
within the park space
Built on a brownfield of a former industrial site, it
treats polluted river water and recover the degraded
waterfront in  an aesthetically pleasing way. It suc-
cessfully reclaimed industrial structures and materi-
als to acknowledge the heritage of the site.
Stormwater is collected from rooftops and impervi-
ous surfaces and directed in open channels to the
central spine, which is both a park and Stormwater
detention feature. This site successfully integrates
the conveyance of Stormwater at the surface.
Integrated LEED Silver rated senior housing, town
homes and market-rate apartments with the first
daylighted creek in the City, running the length of
the 2.8 acre property and numerous green street,
ecoroof and planter storm water facilities.
The wetlands 'daylight' the historic Waitangi Stream
and channel it through a series of treatment systems
designed into the park landscape. Th water passes
through both artificial and natural filtration systems
before discharge to the harbor.


                                         THE SCENARIOS
To develop the most credible and thorough scenarios, the design team recognized that the scenarios could not be
developed on a best-to-worst or high-to-low range. Each scenario had to be developed as a stand-alone solution to
meet the goals of the project and design assumptions. Early discussions of the project focused on the comparison
of a dispersed network versus a more focused or concentrated network of green infrastructure solutions. From that
comparison, three scenarios were developed to investigate the range of methods to embed green infrastructure in
a future development on a brownfield. The conceptual master plan provided by ZRZ Realty was used as the basis
for sizes and locations of general site elements such as buildings, plaza spaces, and roadway networks. The green
infrastructure network of green roofs, pervious pavement, and vegetated stormwater facilities was then applied in the
framework of the master plan according to each scenarios theme.
                                         A conceptual plan view and section/perspective were developed for each of the three scenarios to illustrate how the
                                         scenarios could be applied in the development.  Impervious area reduction techniques (green roofs and pervious
                                         pavement) were applied to each of the scenarios in varying amounts to investigate how their application might affect
                                         storm facility sizing, visibility of water in the site,  and site character. The total square footage of green roofs, pervious
                                         pavement, and facility sizing or depth is shown in the three-dimensional graph for each scenario. An example project
                                         photo is provided for each scenario that best shows what the green infrastructure facilities might resemble in the
                                         development. A description of each scenario follows.


The Diffuse and Embedded scenario collects, conveys, and treats stormwater adjacent to where it falls on Zidell
Yards. As an evenly distributed network, the site's green infrastructure maximizes stormwater infiltration through
an integrated network of techniques including ecoroofs, porous paving,  and small-scale vegetated facilities. The
stormwater collection and infiltration system relies on a network of small-scale vegetated facilities that mimic a
native wetland. The basins are linked through an interconnected network of v-channels, swales and trench grates that
collect and convey stormwater throughout public and private land. The distributed management approach means
that visitors might not see water during small storm events because it will be quickly absorbed by multiple small-
scale basins. This concept could be applied as a performance-based approach with a specific, defined plant palette to
ensure that each future building can be knitted into the existing pattern of the system. The dispersed network allows
for maximum flexibility to work around specific brownfield conditions. The collection capacity of the Diffuse and
Embedded system fosters many secondary distributed benefits, such as rich pockets of vegetation and opportunities for
storage and water reuse for building functions and irrigation. The distributed application of these green infrastructure
techniques provides a unifying identity and sense of place.

Green roofs cover 90 percent of the rooftops (10 acres) and pervious pavements cover 90 percent of the plazas (3.4
acres). Two acres of 6-inch-deep, small-scale vegetated facilities manage runoff from the site and convey the treated
stormwater through the surface conveyance network to a series of hyporheic ponds, which will indirectly discharge
flows to the Willamette River via subsurface flow. The site was  divided into  six basins for stormwater modeling
purposes, assuming that each basin might be developed at different times throughout the 15- to 20-year development
time frame. The western three subwatersheds (1,3, and 5) would connect to  the surface conveyance network in the
eastern subwatersheds to convey water safely to the river.

                                                                           Hyporheic Discharge
                                                                           Flow Direction, Roof
                                                                     Flow Direction, Street/Sidewalk
                                                                     Drainage Catchment Boundary
                                                                                 Green Roof
                                                                     •        Vegetated Facility
                                                                              Pervious Paving
                                                                       Impervious Roof/ Pavement

                                            6" DEPTH VEGETATED
        90% Green Roofs
        W* Potions Pavement
                                                                                                            VEGETATED FACILITY

                                                                                                            PERVIOUS PAVING

                                                                                                            SURFACE FLOW

                                                                                                            OPEN CHANNEL

                                                                                                            COVERED CHANNEL
                                                                                                            SUBSURFACE FLOW


The Clustered and Distinct scenario incorporates components of both centralized and distributed systems by managing
stormwater at a subdistrict or neighborhood scale. This management technique is uniquely tailored to groups of
buildings to create distinct management areas or neighborhoods. How and where water is stored, treated, collected and
infiltrated can vary depending on localized limitations and opportunities encountered in the development footprint.
These facilities would manage stormwater from a small subdistrict of buildings. This concept would provide flexibility
for developing smaller, subdistrict stormwater networks as  development occurs over the next 15 to 20 years. This
smaller network would allow for a reduced initial capital investment while maximizing the efficiency of construction
of only a handful of larger facilities. The system would rely  on 12 inch-deep, urban stormwater planters that, while
likely are more expensive to construct than the shallow facilities, provide a more efficient footprint for management
of stormwater. The visibility of stormwater in the conveyance network might be higher as smaller storm events would
be conveyed from rooftops, across plazas, and to the vegetated planter.
In this scenario,  50 percent of the rooftops (5.7 acres) are covered with green roofs and 25 percent (0.95  acre)
of the plazas are covered with pervious pavement.  These features reduce the effective impervious area of the site
to approximately 20 acres. Cumulatively, 1.9 acres  of 12-inch-deep, urban stormwater planters collect, treat, and
infiltrate runoff from the remaining impervious areas. A 12-inch-deep planter provides more capacity for each facility
than the Diffuse and Embedded scenario basins to accommodate the reduction in green roof and pervious pavement
applications. Overflow of the larger storm events is conveyed via a network of surface conveyance channels to a
constructed wetland complex that will indirectly discharge treated stormwater to the Willamette River. Flow from the
wetlands will pass under the greenway trail at three, overland discharge locations. These locations were identified to
provide the maximum flexibility for future phased development and to reduce conveyance distances.

          Flow Direction, Roof
Flow Direction, Street/Sidewalk
Drainage Catchment Boundary  •
                  Green Roof
            Vegetated Facility
              Pervious Paving
  Impervious Roof/ Pavement

            FACILITY I1 DEPTH
                                      STORMWATER CONVEYANCE IN
                                          SURFACE CHANNELS
10 AC
50% Green Roofs
29% tavious Pavement
 »**pVegetated Facilities
                                                                                                 VEGETATED FACILITY
                                                                                                 PERVIOUS PAVING
                                                                                          —^  SURFACE FLOW
                                                                                          —   OPEN CHANNEL
                                                                                          	   COVERED CHANNEL
                                                                                                 SUBSURFACE FLOW


In the Central and Focused scenario, stormwater is conveyed through a network of open channels to large, centralized,
district-scale facilities. Three subwatersheds collect stormwater from buildings and pavement areas before treatment
and infiltration in the large and integrated facilities. The stormwater facilities take the form of 24-inch-deep geometric
stormwater planters that are integrated with the surrounding plaza spaces. The reduction of green roofs and pervious
pavements provides more frequent filling of conveyance channels during smaller storm events, increasing the visibility
of water. Overflow from larger storm events is conveyed to a series of weirs to discharge runoff via overland flow to
the Willamette River. The larger size of this green infrastructure enhances the visual, recreational, and habitat value
of the water being conveyed.

In this scenario, 25 percent of the rooftops (2.9 acres) are covered with green roofs, and 10 percent of the plazas (0.38
acre) have pervious pavements. This reduces  the effective impervious area of the site to approximately 21.9 acres.
The facilities have been deepened to approximately 24 inches and cover approximately 1.5  acres to accommodate
the  additional stormwater volume. This district-sized scenario could be implemented through a more substantial,
up-front capital investment to fully define the site identity and major green infrastructure design elements. The size
of the green infrastructure facilities allows them to become the organizing element of the site, and their multiple
benefits can be realized early in the development timeline. The location of these facilities might be determined early in
the development process to avoid areas with contamination that could be mobilized by stormwater, or their location
could be flexible where contaminated media does not pose a risk, as was the case at our project site.

Flow Direction, Street/Sidewalk
Drainage Catchment Boundary  •
                 Green Roof  |
           Stormwater Facility  |
            Permeable Paving
  Impervious Roof/ Pavement

                                LARGE, CENTRALIZED
                                 TRFEATURES WITH
                                 2'DEPTHCAPACITY    pLflzflspflCE
25% Green Roofs
 1«Ptewious Pavement
 """"      Stated Facilities
                                                                                                   VEGETATED FACILITY

                                                                                                   PERVIOUS PAVING

                                                                                                   SURFACE FLOW

                                                                                            —   OPEN CHANNEL
                                                                                            .......   COVERED CHANNEL
                                                                                                   SUBSURFACE FLOW

    The three design scenarios developed for this report meet the project goals by providing flexible, sustainable stormwater management within the constraints

    of a remediated brownfield site using innovative green infrastructure techniques that offer multiple environmental, economic, and community benefits. The

    green infrastructure design principles presented here are not limited to brownfield sites but can be transferred to new development, redevelopment, and infill

    settings. Each of the scenarios offers viable alternatives for green infrastructure implementation in public and private spaces, and elements of the scenarios

    can be mixed and matched throughout the site as development begins, if desired.
      90% Green Roofs
      *% Pwvtous Pavement
                               SDK Green Roofs
                               29* Penious Pavement
29* Green Roofs
10% Fenious pavement
                                     CLUSTERED + DISTINCT
                      DIFFUSE + EMBEDDED
                       CONTINGENCY 140%)





TOTAL  S11.393.450
                                GREEN ROOF
                            PERVIOUS PAVEMENT]
                             12" DEEP PLANTERS"
                             24" DEEP PLANTERS"
                          CONVEYANCE CHANNELS"
                           OVERLAND DISCHARGE"








SUBTOTAL $8,750,946
CONTINGENCY 140%) $3,500,379



                 CONTINGENCY 140%)



Location of facilities can be easily modified to
accommodate brownfield constraints.
Facilities   can  be  implemented   through  a
performance-based approach  and required  as
each new building is constructed.
Embedded facilities throughout the development
would  create  a consistent  palette  of  plant
material and integrated design aesthetic.
Water might not be visible during smaller storm
events because  multiple smaller facilities would
serve as  a sponge for the stormwater before
entering major surface conveyance channels.
Green  roofs   and  pervious   pavement   are
essential  tools and must be either  required or
heavily suggested for each building rooftop or
plaza space.
Relies  on the  ability to  infiltrate  stormwater
throughout the development.
Can be implemented as each new subwatershed
or cluster of buildings is developed.
Facility  design  can  be integrated  with  new
buildings to create  unique neighborhoods as
phased development continues.
Facilities  can  be  shared   among  clusters
of buildings  to  provide  for more  efficient
Smaller storm events might  be more visible
because   stormwater   flows  from   buildings
through  surface  conveyance  channels  to  the
infiltration facility.
Green roofs and  pervious pavement are less
emphasized as  a  tool for  reducing  overall
impervious surfaces,  therefore  reducing  the
requirement for green roofs on buildings.
Facilities become  an organizing  element for
urban open space in the development.
Water would be most visible with this scenario
during all  types  of  storm   events  because
stormwater is conveyed from multiple buildings
and paved surfaces to larger central stormwater
Design and construction  of these facilities can
be done early in  the development process, and
building owners would pay into  a stormwater fee.
Centralized  facilities  can  be  in  areas  of
brownfields  that  do  not  pose  a  stormwater
contamination  risk.

Ji HUf

The scenarios can serve as a template for remediation and redevelopment of contaminated sites. Throughout the design
process, several key principles were identified that mitigate the concerns associated with stormwater management
on a remediated brownfield site. These principles can be applied at other brownfield sites to minimize exposure of
stormwater to legacy pollutants:
•   Proactively conduct brownfield remediation activities to remove or isolate pollutants  that stormwater could
    mobilize, ensuring that onsite stormwater management is feasible
•   Recognize that many contaminants (e.g., those that are insoluble or bound to soil particles) are not mobilized by
    infiltrating stormwater and therefore do not pose a threat to surface or groundwater
•   Place stormwater facilities away from contamination hot spots that stormwater could mobilize
•   Use surface conveyance rather than underground pipe conveyance to minimize soil disturbance below the cap
•   Reduce or eliminate the amount of trenching to minimize soil disturbance
As more former industrial properties are redeveloped, we will understand the opportunities and limitations of various
green infrastructure approaches on  them and be able to  test innovative stormwater solutions in areas previously
considered off limits because of contamination.
Portland has identified numerous benefits from green infrastructure, including clean water, clean and cooler air,
improved livability and health by encouraging people to walk and spend more active time outside, and most recently,
increasing pollinator and wildlife use and green jobs. These benefits could be realized through green infrastructure
implementation at this site and would improve conditions in the Willamette River and increase the attractiveness and
marketability of the site for economic development.
Because of its high visibility, strong public interest, and the significance of this project to pave the way for stormwater
management throughout the city, this project is receiving strong support across all city bureaus and with our elected
officials. Not only is Zidell Yards property on the waterfront, but it will also be  a hub for  mass transit activity,
including  a new light-rail line and stop, an expansion of the Portland Streetcar, and a new pedestrian bridge across
Interstate  5 to residential neighborhoods. The Zidell Yards project is an ideal showcase for highly visible, innovative,
multi-benefit stormwater management that residents and visitors can experience and enjoy daily.