2012 Master of Landscape Architecture Thesis

NORTHFORK OR NORTHFAX? THE ROLE OF ECOLOGICAL INFRASTRUCTURE IN SHAPING TOMORROWS URBAN VILLAGE

Luke A. VanBelleghemVirginia Polytechnic Institute and State University

MLA Thesis

TABLE OF CONTENTS

ACKNOWLEDGEMENTS

ABSTRACT

CONTEXT

INVESTIGATION

ALTERNATIVE VISION

REFLECTIONS

WORKS CITED

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3

5

21

35

69

73

1ACKNOWLEGEMENTS

My Thesis Committee: Dean Bork, Paul Kelsch, and Kris Wernst-ed; for their time, patience, instruc-tion, and suggestions. This was a long educational journey and I would not have made it across the finish line without their support.

Special thanks go to Dean Bork who spent many, many hours help-ing me tease out ideas and keep focus.

My Peers at the Washington-Al-exandria Architecture Center for their willingness to teach me, to let me teach them, and to collaborate on problems large and small.

My friends at the National Park Service who gave me real-life experience with urban ecology and showed me the importance of maintenance in landscape design.

The Fairfax City government which was very helpful in provid-ing technical information and an-swering questions.

My Family who never complained about my absence even when it meant picking up my slack.

Special thanks to Stacey who made it all possible and to Laila who inspires me every day.

I would like to thank:

3ABSTRACTThe problem: Redevelopment of suburban spaces into denser, more urban arrangements is fa-vored by Smart Growth proponents and the EPA as a more efficient, environmentally sound land use practice. At the heart of their argu-ment is the idea that more compact development reduces both fossil fuel consumption and the demand pressures on undeveloped green space. Assuming for a moment that this idea is correct, this means that smaller areas of land will be forced to bear the environmental impact of increased population densities. Moreover, it means that the im-mediate environment that we live, work, and play in will also bear these burdens. However, the rede-velopment of sprawling suburban greyfields into compact, mixed-use urban villages will require recon-figuring the basic infrastructure that forms and sustains our inhabita-tion of the land. This represents a rare opportunity to reimagine local infrastructure in a way that meets our basic ecological and cultural needs.

The question: What role can ecological or green infrastructure play in suburban infill develop-ment?

The Site: The intersection of Chain Bridge Road (Route 123) and Fairfax Boulevard (Route 50) in Fairfax City, Virginia. Currently occupied by a low density configu-ration of office space, automobile dealerships, retail, and restaurants. The site is the central urban node, dubbed Northfax, in a draft Mas-ter Plan that proposes to redevelop the Route 50 corridor throughout Fairfax City according to New Ur-banist principles including higher density, mixed use buildings, walk-able streets, and facades lining the street edge. A central component of the plan is to install a multi-way boulevard format along this section of Route 50.

5CHAPTER 1

CONTEXT

6INTRODUCTIONA channel-ized stretch of the North Fork branch of Accotink Creek emerges from underground outside the Fair-fax Shopping Center

A bioretention planter outside the Washington, DC headquar-ters of Casey Trees can capture, detain, and filter up to five inches of rain water run-off from adja-cent impervious surfaces.

As the American population has grown and become concentrated in metro-politan areas, the need to actively manage natural resources has become more appar-ent. Prior to the industrial revolution, the proportion of wilderness to civilization was such that to drain a swamp here or clear a forest there was of no great consequence. The sheer scale of the wilderness provided a resilience and redundancy to the natural systems that made the physical environment habitable. With each successive generation, however, the amount of space consumed by civilization has increased steadily relegat-ing wilderness to the places in between or inconvenient to urbanity. With wilderness diminished and less robust natural systems, the impacts of human occupation and con-centration on our physical environment are more clearly manifest. The hydrological cycle, for example, carries ever greater concentrations of civili-zations effluent into waterways threatening, freshwater supplies and endangering flora and fauna on local and global scales. In part, this is because the urbanization of land has altered hydrological regimes creating increased volumes and velocities of pol-luted stormwater runoff that do not infiltrate into soil. The process of urbanization has replaced ephemeral streams with gutters and underground pipes which feed buried, chan-nelized or otherwise degraded urban water-ways.

Increasing demand for developable space will further stress waterways and other natural systems. A widespread acknowledge-ment of this situation has generated regula-tions, strategies, and new technologies to mitigate the consequences of urbanization. Federal, state, regional and local regulations require that local governments address the quantity and quality of their stormwater run-off. Additionally, there is a growing environ-mental awareness in our cultural conscious-ness of the impacts of development practices and patterns on the quality and long term sustainability of our physical environment. These and other factors are creating an open-ness to alternative means of engaging natural processes to confront environmental prob-lems.

In newly developing regions, the conservation of strategic areas of unde-veloped land can form the core of a green infrastructure network that creates a bulwark against flooding, protects water and air qual-ity, provides wild life habitat, and affords recreational opportunities. However, in built out communities, the possibilities for acquir-ing and setting aside land for an open space green infrastructure network are severely limited. In these places, green infrastructure takes on a different meaning. Here it refers to the design of small urban spaces to engage natural processes and achieve some ecologi-cal function that benefits the human environ-ment and local ecologies.

The high contribution of transport systems to total imperviousness in suburban areas offers a rich opportunity for design intervention in public space to address man-made imbalances in urbanized hydrological systems (Center for Watershed Protection, 1994, 100). Furthermore, transport systems are directly connected to municipal separate storm sewer systems (MS4s) and can account for a range of 20% to 50% of total impervi-ousness (Center for Watershed Protection, 1994, 100). Street trees in particular offer promising possibilities to increase stormwater infiltration and detention because of their required soil volumes and their location in transport systems. Invariably, aging infrastructure will need to be repaired, upgraded, or replaced, creating an opportunity to retrofit public space with these new green infrastructure technologies. Moreover, some portion of the demand for new buildings will be channeled into previously developed, low density areas. This investigation will explore alternative models for green infrastructure design in the context of watershed-sensitive urban redevel-opment. Specifically, the planning and de-sign of public spaces and green infrastructure will be examined to see what contributions they can make to hydrological improvement and what forms they can take. By designing stormwater, urban forest, and public space infrastructure together, perhaps an economy can be realized and effectiveness increased.

7Left: The exisiting condi-tions, Fairfax Boulevard draft master plan proposed conditions, and the Bork and Franklin altern-taive scenario for Kamp Wash-ington in Fairfax City, VA.

The T5 Urban Zone from the The Rural-Urban Transect. Duany Plater-Zyberk & Com-pany

NORTH FORK OR NORTHFAX? CHAPTER 1

In Revitalizing Urbanized Water-sheds though Smart Growth: The Fairfax Boulevard Case Study Bork and Franklin examine an alternative scenario for the rede-velopment of the Kamp Washington urban center in the draft Fairfax Boulevard Master Plan (FBMP). The authors attempt to ascer-tain the total possible reduction in stormwa-ter runoff possible if SmartCode principles for T5 areas (as defined by the SmartCode) were applied to their limits. Their findings suggest that significant reductions were possible, but that the resulting urban form resembled a high density suburban office park much more closely than the pedestrian friendly, livable city form that New Urbanism proponents are seeking. Where the Bork and Franklin study focused on private parcel development, this

investigation will examine possible reduc-tions in stormwater volumes and velocities generated in public space. It will examine the ability of SmartCode principles for street design to integrate green infrastructure and facilitate urban hydrologic improvement while simultaneously creating unique, pe-destrian friendly, and livable urban environ-ments. Finally, the field of landscape archi-tecture is concerned with the aesthetics of landscapes and their contribution to society as well as their performance. This investiga-tion will examine the aesthetic value of vari-ous design alternatives. Public streets must unite the useful, the natural, and the beautiful by utilizing the unique qualities of place and context. Thus, any designed green infra-structure must be in balance with the cultural

qualities of the street (Thayer, 1989, 107). Furthermore, in the context of urbanism, the term landscape invokes the functioning ma-trix of connective tissues that organizes not only objects and spaces but also the dynamic processes and events that move through them (Wall, 1999, 233). Thus, there is some responsibility for the Landscape Architect to acknowledge and reveal natural processes to connect the public with their environment, especially in sustainable landscapes (Thayer, 1989, 108). Reimagining the subjective experience of hydrological processes in the context of the T5 commercial landscapes requires some examination of the nexus between public infrastructure and public space. Currently, commercial corridors are dominated by the automobile with some segregated space for pedestrians and maybe

some vegetation. Water is typically relegated to the margins (gutters) and to underground conveyances. SmartCode principles imagine streets with wide sidewalks, steady street tree planting and buildings set close to the sidewalks (SmartCode Version 9.2, 2009, xi). Reconfiguring public streets to serve multiple purposes, including the facilitation of natural processes will be critical to height-ening perceptions of the physical environ-

8BACKGROUND

Right: Pour-ous concrete is a BMP that allows water to infiltrate into underlying soil. www.cement.org

Left: Infiltra-tion planters help water from the street and the sidewalk to slow velocity, drop sediment, be filtered by plant materieal and infiltrate into soil. Lee & Associates

Right: A deten-tion pond as part of a stream restoration proj-ect allows sedi-ment removal and velocity control. The Dell, Nelson, Byrd, Woltz.

A primary concern of early storm-water management efforts was not environ-mental or resource protection, but rather the rapid removal of stormwater from roads and property (Berke et al, 2003, 398). Stormwater was directed into engineered conveyances to prevent flooding and facilitate drainage. In the twentieth century, stormwater con-veyance technology continued to be based primarily on early infrastructure examples in older, northeastern cities (Webb Tunney, 2001, 1). At first the consequences of urbaniza-tion on water quality escaped the notice of most people except in the most egregious examples of pollution and flooding. Perhaps this is because cities represented a small fraction of overall land use with large areas of rural and undeveloped land surrounding settled urban areas. However, the advent of the automobile and the Federal-Aid High-way Act of 1956 (among other governmental policies) opened up vast areas of land for suburban and exurban development. Con-sequently, the overall amount of urbanized land has increased and the disruption of natural hydrologic regimes has become more pronounced. As these and other environmental impacts emerged in the twentieth century, an environmental awareness was growing that culminated in the development of national, state and local regulation that addressed the impact of civilization on the physical

environment. Passage of the Clean Water Act (CWA) and subsequent amendments has forced jurisdictions to address the quantity and quality of their stormwater runoff. The National Pollutant Discharge Elimination System (NPDES), in particular, regulates how jurisdictions handle their stormwater run-off. MS4s, or conveyance systems owned by a state, city, town, village, or other public entity that discharges stormwater to waters of the U.S., have been regulated by the Envi-ronmental Protection Agency (EPA) since the 1990 Phase I and 1999 Phase II rules of the NPDES. Thus, managing stormwater runoff has become an increasingly important duty of local governments and has spurred exami-nation of urbanized hydrological systems. Since the 1960s a correlation be-tween increased volume and decreased quality of stormwater runoff on one hand and high levels of landscape imperviousness on the other has become well established (Moglen, 2007, 161). Similarly, it has been generally observed that the more densely developed an urban area is the higher the proportion of impervious surfaces it has. The Center for Watershed Protections Impervi-ous Cover Model suggests that streams are impacted when their watershed reaches approximately 10 percent impervious cover, and when they reach 25 percent impervi-ous cover predevelopment channel stability and biodiversity cannot be fully maintained (Schueler, 1994, 8-9).

In order to meet the minimum re-quirements of the NPDES, the EPA has been encouraging and requiring local governments in urbanized areas to use Best Management Practices (BMPs) to address stormwater problems associated with high quantities of impervious surface area. BMPs are defined by the EPA as a technique, measure or structural control that is used for a given set of conditions to manage the quantity and improve the quality of storm water runoff in the most cost-effective manner. However, the effectiveness of BMPs are notoriously difficult to quantify in a generalized way as their effectiveness depends on a number of factors, many of which are determined at the site level (Strecker et all, 2001, 144).

9NORTH FORK OR NORTHFAX? CHAPTER 1Left: The density driven approach to watershed health

Middle: A chan-nelized head-waters stream

Right top: Stream bank undercutting as a result of high peak flows

Right bottom: A roadside stream with minimal riparian buffer

While growth pressures necessitate the ongoing development of dwellings, com-mercial space, roads, etc., the form and pat-tern this development takes is highly relevant to watershed health. Movements such as Smart Growth and New Urbanism are direct-ing new development and redevelopment of suburban areas toward denser, mixed-use forms. This density driven approach to wa-tershed health has gained widespread accep-tance and has been adopted in the planning process of many communities. It should be noted that besides the environmental prom-ise of density, market forces such as lifestyle preferences, higher energy costs, and an aging population are fueling demand for this type of compact development (Nelson, 2006, 394-397). The EPA has promoted Smart Growth principles as a means of limiting impervious area, reducing stormwater runoff, and meeting CWA requirements (EPA, 2004, 5). However, like BMPs, how and where those principles are applied are key determi-nants to their effectiveness in protecting or improving watershed health. In a density driven approach to achieving watershed health, championed by the EPA and Smart Growth proponents, there is a presumed tradeoff between preserving undeveloped space (greenfields) and chan-neling development into compact forms. In this tradeoff, the preservation of greenfields protects regional watershed health because it reduces the overall percentage of impervi-

ous surfaces in the watershed by achieving a lower per unit or per person amount of imperviousness.

However, in this scenario the urban-ized watersheds hosting the compact devel-opment with impervious surface coverage of 25-100% will experience concentrated runoff volumes, rates, and pollutant loading. Essentially, this approach sacrifices the health of urban watersheds for overall or regional watershed health (Schueler, 1994, 8-9). If we take this approach to watershed manage-ment at face value it could be a dispensation to disregard urban streams as a lost cause. To do so may be to miss a tremendous opportu-nity to re-imagine urban infrastructure as we redevelop low density commercial areas into dense mixed-use communities. Predevelopment stream quality may be an unobtainable goal at this level of ur-banization, but can smart growth-guided sub-urban redevelopment yield any hydrological improvement to local urbanized watersheds

(Borke and Franklin, 2010, 6)? Due to the high proportion of impervious area coverage manifest in roads, sidewalks, roofs, and park-ing, the answer to this question is no unless urban infrastructure can be re-imagined and designed in concert with social and environ-mental needs. Just because predevelopment stream quality cannot be achieved, does not mean we cannot design our communities to produce the best urban stream quality pos-sible. After all, we do not expect the urban forest to function like the primordial forest. To do so would be to expect human presence to have no impact at all. Perhaps instead we should strive to maximize the benefits of natural systems in highly altered environ-ments, in some cases attempting to restore natural function and in other cases using the best means available to mimic it.

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THE SMARTCODE

The Rural-Urban Transect. Duany Plater-Zyberk & Com-pany

Some communities have adopted the SmartCode as a way of reducing traditional zoning restrictions to New Urbanist develop-ment. The SmartCode is a form-based code that incorporates Smart Growth and New Urbanism principles. It is a unified develop-ment ordinance, addressing development at all scales of design, from regional planning on down to the building signage. It is based on the rural-to-urban transect rather than sep-arated-use zoning, thereby able to integrate a full range of environmental techniques (SmartCode Version 9.2, 2009, iv). It is a tool that guides the form of the built environ-ment in order to create and protect develop-

ment patterns that are compact, walkable, and mixed use. These traditional neighbor-hood patterns tend to be stimulating, safe, and ecologically sustainable. The SmartCode requires a mix of uses within walking dis-tance of dwellings, so residents arent forced to drive everywhere. It supports a connected network to relieve traffic congestion (Smart-Code Version 9.2, 2009, v). Aging commercial corridors in suburban areas are prime candidates for redevelopment according to the SmartCode. They often contain large parcels with single owners adjacent to existing road networks and buildings with relatively short lifespans

(Nelson, 2006, 398-402). They are low den-sity developments with large parking areas that can be more densely developed with mixed use, multistory buildings and decked parking. Generally, a redeveloped commer-cial corridor would fall into the T-5 Urban Center Zone of the SmartCodes rural to urban transect. The T-5 Urban Center Zone consists of higher density mixed use build-ings that accommodate retail, offices, row-houses and apartments. It has a tight network of streets, with wide sidewalks, steady street tree planting and buildings set close to the sidewalks (SmartCode Version 9.2, 2009, xi).

FAIRFAX CITY

DISTRICT OF COLUMBIA

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Fairfaix City, VA lies 13.5 miles west of Wahington, DC. The Fairfax Boulevard draft master planning area is shaded in yellow.

FAIRFAX BOULEVARD DRAFT MASTER PLANFairfax City is a small municipality in the Washington, DC metropolitan region. It is located approximately 13.5 miles west of Washington, DC in the center of Fairfax county. It has a population of approximately 25,000 and holds a Phase II NPDES permit.

In 2007 the City of Fairfax and the firm Do-ver, Kohl and Partners began the process of creating a master plan for the redevelopment of Fairfax Boulevard. It is a three-mile long commercial corridor bounded by Jerman-town Road to the west and Picket Road to

the east. For that length it carries both Route 50 and Route 29. The study area for the Master plan is bounded approximately 200 feet north and south of the boulevard roughly equivalent to the borders of the Fairfax Bou-levard Business Improvement District (BID).

The area has experienced very little commer-cial development in recent years and 80 per-cent of the retail space is over 25 years old. The strip development format here is seen to be dated and inefficient. Vast amounts of surface parking beckon to be reimagined.

FAIRFAX BOULEVARD DRAFT MASTER PLAN

Kamp Washington East Connector West Connector Fairfax CircleNorthfax

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FAIRFAX BOULEVARD DRAFT MASTER PLAN

enhance the human landscape.

The Fairfax Boulevard draft master planning area. The Northfax mixed-use cen-ter is shaded in yellow. Dover Kohl Partners.

Opposite: An aerial image of the Northfax area. USGS.

The goal of the plan is to be a model for corridor redevelopment. The draft master plan is a comprehensive strategy for growth and redevelopment of the corridor; it seeks to improve the safety and operational efficiency for all modes of travel, while creating a more economically productive address. The plan envisions that Fairfax Boulevard can be more than just improved; it can be one of the most

memorable streets in America (Dover, Kohl, and Partners, 2007, Executive Summary). The Vision of the Fairfax Boulevard draft master plan is to transform Fairfax Bou-levard into a combination of well-designed, walkable, lively, mixed-use centers joined together by commercial connectors in a way that enhances the existing character of the city and its neighborhoods (City of Fairfax,

2008, 1). The draft master plan identifies three of these mixed-use centers: Kamp Washing-ton; Northfax; and Fairfax Circle; and two connectors: West Connector and East Con-nector. This investigation will focus on the Northfax mixed-use center or urban node. The plans stated goals include:

using infrastructure for multiple purposes 6

implementing watershed management practices 6providing adequate storage & runoff control 6reducing the velocity of stormwater flows 6collecting & spreading rain into multiple areas 6getting water into the ground for storage & recharge 6maintaining/improving ecological processes 6incorporating rainwater oriented civic art to 6

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Soil volume required for trees of size indicated by the draft master plans rendered images & ac-companing drainage area.

OPPORTUNITIES This thesis investigation begins where Dean Bork and Josh Franklins research on watershed sensitive suburban redevelopment left off. Bork and Franklin examined five case studies of T5 redevelopment patterns and found that none of them appreciably reduced the amount of impervious area of the project sites. This is because reductions in impervious parking lots were traded for increases in roof area and street infrastruc-ture. When they further explored the case study of the Kamp Washington center in the Fairfax Boulevard redevelopment corridor they found that when SmartCode principles for T5 areas were pushed to the limit for hydrological purposes, the resulting urban form resembled a suburban office park more than a traditional, walkable downtown. In other words, in order to achieve significant reductions in impervious area and greater infiltration rates, the resulting urban form would subvert the goals of creating a well-designed, walkable, lively, mixed-use cen-ter. Their research primarily focused on alternative building dimensions and open space runoff coefficients. They did not consider the runoff generated by the street system which comprises a large proportion of the plans impervious area. The next step to this research addresses possible runoff reduc-tions in public spaces, specifically, the rights of way and civic spaces outlined by the Fairfax Boulevard draft master plan and the

SmartCode. Moreover, it addresses the cre-ation of runoff reductions in the context of a multipurpose infrastructure system in concert with the goals of creating a well-designed, walkable, lively, mixed-use center and one of the most memorable streets in America. Furthermore, this investigation is congruent with the Fairfax Boulevard draft master plans stated goals. The spine of the plan is Fairfax Bou-levard itself. The proposed boulevard as-sembly or form, a (BV) 50-126, is said to be inspired by the Avenue Montaigne in Paris. According to the SmartCode, which is con-sistent with the plans rendered images the street trees should be a single species, plant-ed in a row 30 on center. Assuming a crown diameter of 30 feet, the crown spread of each tree will be approximately 700 square feet. This additional tree canopy will make a significant contibution to rainfall interception (USDA, 2006, 4). Moreover, these trees will require approximately 1000 cubic feet of soil volume, at least 20% of which can be used to store, filter and infiltrate stormwater (Urban, 2007, 1). The resulting 200 cubic feet of stormwater storage could accommo-date more than the first 2 inches of rain for a 30 foot segment of the 15 foot sidewalk area, the 8 foot parking lane, and the 10 foot frontage road. The medians could accom-modate similar soil volumes and could easily drain their respective half of the travel lanes (a 30 foot length of 2.5 travel lanes or 25

feet). If the trees are allowed to share rooting space, as with a continuous planting trench, the required soil volume per tree may be reduced to as little as 6oo cubic feet. This would create 120 cubic feet of stormwater storage capacity which could still accommo-date the drainage for the first inch and a half of precipitation for the same drainage areas. Thus, at first glance it looks like the required soil volumes for the proposed trees could make a significant contribution to infiltrating the runoff from the streets and sidewalks.

There are other thoroughfare assem-blies included in the Fairfax Boulevard draft master plan that will require trees with simi-lar soil volumes which also should be able to handle significant amounts of the drainage of their respective pavements. Because of

their large numbers, regular distribution, and adjacency to surface conveyors, street tree infrastructure could be the work horse of a stormwater infiltration and detention system. Moreover, other less busy thoroughfares, rear alleys, and parking areas may be able to host other infiltration and detention applica-tions besides stormwater planters. Vegetated swales, rain gardens, stomwater curb exten-sions, green gutters, pervious paving, weirs, and check damns are all possible options from the sustainable stormwater design pal-ette. Another opportunity to facilitate storm water detention and infiltration is in the civic spaces planned for Northfax and mandated by the SmartCode. In the Smart-Code they are categorized as greens, plazas, and squares. These civic spaces present further opportunities to apply the aforemen-tioned sustainable stormwater design palette. Finally, the location of the under-ground length of the Northfork presents an opportunity to amplify the unique qualities of the site. Daylighting or otherwise acknowl-edging this stream length could go a long way to making Fairfax Boulevard one of the most memorable streets in America.

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COSTS To be sure, there will be substantial costs associated with providing soil volumes for the envisioned urban forest enhance-ments. But perhaps these costs are not as great as initially imagined, especially if con-sidered in the context of a planned redevel-opment of the area. If implemented, the Fair-fax Boulevard draft master plan represents a unique opportunity to re-imagine urban infrastructure. The re-creation of the street system is a rare event. Surely it would be less expensive to integrate these soil volumes into the construction of the new streets than it would be to retrofit them at a later date. The plan will require capital improvements one way or the other so it would be prefera-ble to create a well-considered, integrated in-frastructure that allows for the greatest return on investment. For example, the creation of additional roadways outlined in the plan will require significant enlargement of the storm sewer system to service the new roads. By themselves these enlargements would not address the stormwater volume and velocity that is plaguing Accotink Creek and degrad-ing the communitys natural resources or meet Clean Water Act requirements. Moreover, the proposed investment in trees is significant. In the Northfax sec-tion alone well over 1,000 trees are called for. Providing the necessary requirements for the trees survival is crucial to protecting the initial investment in tree stock, avoiding ex-orbitant replacement costs, and allowing the

trees to provide ecological function. Both Bethesda, MD and Charlotte, NC provide excellent case studies of municipalities that have used suspended pavements to provide soil volumes with a 25 year track record of success (MacDonagh, 2010, 55-57). Unlike other infrastructure, trees actually appreciate in value and perform some ecological func-tions better with age. Furthermore, the careful installation of these soil volumes will integrate stormwa-ter, urban forestry, and pavement infrastruc-tures and will allow them to outperform other systems that are considered individually. The soil volumes will simultaneously nourish the urban forestry infrastructure, prevent the stormwater infrastructure from overburden, and reduce stormwater volumes, velocities, and pollutant loading. Additionally, porous pavements will allow water infiltration into the soil vaults which will protect pavement from heaving and pipes from root intrusion. Likewise, the canopy of the urban forest will shade pavements thereby extending their lifespan while simultaneously intercept-ing rainfall and reducing the burden on the stormwater sewer system (McPherson and Muchnick, 2005, 303). Finally, the creation of this inte-grated system will have significant external benefits including: healthier urban streams; cleaner air; cooler ambient temperatures in the summer (due to evapotranspiration and a reduction in the heat loading of buildings

and pavements); carbon sequestration; and a a more robust urban ecosystem with greater connectivity. In short, these benefits help to create the livability sought after in the Fairfax Boulevard draft master plan. Thus, it may be argued that an inte-grated urban forestry, stormwater, and pave-ment infrastructure will carry larger upfront costs. However, the promise of long term benefits and a significant return on invest-ment are powerful arguments in their favor.

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St. Marks Place between Third & Second Avenues in the East Village. The pedestrian realm hosts many infrastruc-tural layers on this cowded and lively street.Photo: www.wikimedia.org

Right: Parking day. Photo: www.parking-day.org, Rebar

THE RIGHT-OF-WAy Streets move more than just cars and stormwater. They encompass and facilitate several layers of movement and use. There is no doubt that the proposed thoroughfare assembly for Fairfax Boulevard is designed primarily to facilitate through traffic. None-theless, ten foot local traffic lanes (or front-age roads) and eight foot parking lanes are provided on each side of the right-of-way. Wide sidewalks (15 feet) are provided to facilitate pedestrian circulation. Finally, the park-like medians (20 feet) are envisioned to mark the beginning of the pedestrian realm. Planted rows of trees provide enclosure, helping to manage center street speeds. The median provides shade and protection for pedestrians and the shared-use path allows bicycling, roller-blading, and strolling, with ample benches and pedes-trian features. The median is a centerpiece of the boulevard design (Dover, Kohl, and Partners, 2007, 5.8) However, the experi-ence of the public right-of-way is not always

about moving. Whether its resting, chatting, people-watching, eating, browsing, or even enjoying a street performance, the street can host several types of sedentary activities. There are multiple infrastructural components and amenities that are accom-modated by the public right-of-way. For example, signs, public lighting, bus stops, parking meters, mail boxes, benches, bicycle racks, fire hydrants, and awnings are located in the pedestrian realm of the right-of-way. Finally, there is the issue of utilities. Many utilities like gas, water, and sanitary sewers connect to buildings underground from the street. Other utilities like power and telephone lines that may be currently strung from poles are proposed to be un-dergrounded by the Fairfax Boulevard draft master plan At this point, precise locations of the newly undergrounded utilities are unknown. However, their future location is likely to be approximately underneath their current location because the work will be phased and connectivity will need to be maintained. Any type of green infrastructure will need to allow for sufficient access to utility lines for repair or replacement. Other utility conflict issues with green streets and parking lots include, but are not limited to: providing adequate soil cover around util-ity lines and gravel envelopes; minimizing the migration of infiltrated stormwater; and finding adequate space for vaults and valve boxes next to stormwater facilities. (Ne-

vue Ngan Associates and Sherwood Design Engineers, 2009, 120) Utilities are a vital part of the right-of-way infrastructure system and they will need to be accounted for in any scenario. Creating the most memorable street in America will require the harmonious integration of a variety of sometimes conflict-ing needs. The Fairfax Boulevard draft master plan adopts the language of Alan Jacobs, author of the Boulevard Book and Great Streets. The plan emphasizes its goal to make Fairfax Boulevard a Great Street that accommodates accessibility, commerce, rec-reation, an urban experience, parking, and through traffic. In this way, the plan echoes the concerns of the Complete Streets move-ment. The street is public space and most of it is typically dedicated to vehicles. There is growing pushback to this situation embodied by parking day, where activists in cities across the world transform metered park-ing spots into temporary parks for the public

good. This cultural phenomenon is signifi-cant because it represents a nascent aware-ness of the consumption of public space by the automobile and a desire for more non-automotive space in the public right-of-way.

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CONFLICTS AND CHALLENGES

(BV) 50-126 cross section. Dover Kohl Partners

Avenue Mon-taigne cross section. The Boulevard Book

It is simple enough to call for a series green infrastructure deployments in the pro-posed street system of the Fairfax Boulevard draft master plan with the proper dimensions to capture, detain, and infiltrate stormwater. However, once you attempt to site these de-ployments in a real world scenario, conflicts begin to arise rapidly. Moreover, designing these infra-garden elements with an appro-priate urban aesthetic that highlights natural processes and contributes to the Fairfax Bou-levard draft master plans vision of creating great streets creates even more challenges. For example, the Fairfax Boulevard draft master plan and the SmartCode seem to call for an unidentified species of tree to be planted along the access road edge at 30 foot intervals. However, a cursory examina-tion of this arrangement reveals that on street parking spaces with a standard length of 18 or 20 feet will quickly begin to conflict with this street tree arrangement. Furthermore, a 25-30 foot diameter crown spread, suggested by the Fairfax Boulevard draft master plan rendering, will conflict with building front-ages when placed 2 to 3 feet inside the curb of a 15 foot sidewalk with a zero setback for building frontages. If a denser arrangement of trees with a more columnar form is adopt-ed, the conflict of trees with parking spaces and building frontages may be eliminated while achieving the continuous overhead canopy called for by the Boulevard Book. Similarly, the Fairfax Boulevard draft

master plan renderings and the SmartCode call for continuous planters on Boulevard-type thoroughfares. An open planter may use 30% or more of the sidewalk width, which is needed to host several of the afore-mentioned infrastructural components. The use of suspended pavements may allow for continuous planters while preserving surface space. However, covering continuous plant-ers may detract from the goal of revealing natural processes. The benefits of various ap-proaches to providing continuous tree plant-ers must be weighed against one another and evaluated for appropriateness. Moreover, the Fairfax Boulevard draft master plan calls for wide sidewalks but the widest sidewalks in the plan are 15 feet. Fifteen feet is not particularly wide. The sidewalks on King Street in Alexandria (west of Washington Street), not known for their width, are about 12 feet wide. Karen Kumm Morris, a former Landscape Architect and Ur-ban Planner for the Maryland National Capi-tal Park and Planning Commission, identified a 15 foot width as the minimum necessary for good, walkable sidewalks in a lecture on Urban Design in Bethesda, MD. This mini-mum was not meant for the most important sidewalks next to the main thoroughfares but rather the minimum width for secondary sidewalks. There are several of components to shoehorn into a fifteen foot sidewalk in a manner that does not inhibit circulation.

On the other hand, widening a sidewalk too much may reduce its liveliness. The proposed boulevard width is already 156 feet and it does not necessarily stand to benefit from being any wider. However, the medians offer an alternative for place-ment of some components like benches and bus stops. Overly wide sidewalks may be counterproductive. Unless they are full of people they may look desolate and uninvit-ing. Wide medians, on the other hand, may provide more attractive strolling and places, especially if a second line of trees can be incorporated (Jacobs, 2002, 227). While there are similarities with the Avenue Montaigne and the proposed Fairfax Boulevard assembly, there are also several important differences. One of the most important differences is in the scale of the boulevard and the volume of space contained between buildings. The Avenue Montaigne is 126 feet wide with buildings six to seven stories high and 50 plus foot tall chestnut trees planted 15 to 18 foot on cen-ter. By contrast, the proposed Fairfax Boule-vard assembly is 156 feet wide with buildings three to four stories high and trees appearing in cross sections to be 20 feet high planted 30 feet on center. The smaller stature of the buildings and the wider street combined with smaller, less densely planted trees will create a vast volume of space that will undermine the sense of enclosure needed on the boule-vard.

Perhaps one of the greatest challeng-es will be reconciling green infrastructure or infragardens to their urban context while simultaneously amplifying natural processes. A recent Washington Post article discussing possible regulations designed to protect the Chesapeake Bay juxtaposes well-manicured lawns with rain gardens and shaggy fields of native plants. (Fahrenthold, 2010, 1) This highlights the perception that bioretention fa-cilities lack the formalized look of status quo suburban vegetation. While green infrastruc-ture can certainly be designed to accommo-date the cultural context of a given street, it will take careful consideration.

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Artful Rainwater Design: SW 12th Avenue Green Street Project, Kevin Perry, Sustain-able Stormwater Mangement Program, City of Portland.

Waterworks Garden, Lorna Jordan. Photo: Joe Mabel

Joan Nassauers Maplewood Rainwater Gar-dens. Maple-wood, MN.

REVIEW OF THE LITERATURE Beyond the technical issues of pre-cipitation amounts, soil volumes, and infiltra-tion rates, how design factors can affect the cultural success of the proposed landscape interventions must be examined. In his book Between Landscape Architecture and Land Art Udo Weilacher writes, One of the main issues of our age is the disturbed relationship of man to nature and the ensuing world-wide threat to the ecological balance The realization that the crisis facing the environ-ment is being caused by man, who is not just a factor to be predicted by rational means and researched by science, but is also a be-ing perceiving through his senses and often acting intuitively, is only very gradually gain-ing acceptance Ultimately, the question as to whether we can overcome ecological and social crisis is primarily a question of human behavior (Weilacher, 1999, 1). In other words, it is not enough to try to ad-dress stormwater technologically. Design of stormwater infrastructure must appeal to the subjective experience of natural processes to alter cultural perception of rainwater and ulti-mately human behavior. To some extent, this is acknowledged by the EPA which includes Public Education and Public Involvement as types of BMPs. The authors of From Stormwater Management to Artful Rainwater Design analyze the social goals of stormwater re-lated design. Echols and Pennypacker coin the term artful rainwater design (ARD) to

describe employing environmental BMPs in designs that call attention to stormwater management in ways that educate and de-light (Echols and Pennypacker, 2008, 268). They introduce the concept of stormwater as a site amenity which allows one to experi-ence stormwater in a way that increases the landscapes attractiveness or value (Echols and Pennypacker, 2008, 268). In Toward a New Garden: A Model for an Emerging Twenty-first Century Middle Landscape MacElroy and Winterbottom dis-cuss the conflict between designers who val-ue ordered geometry foremost and those who reject orderly geometry in favor of ecological values. This conflict is put in the context of an evolving aesthetic middle ground be-tween formal urban landscapes and dynamic natural processes. They critique Waterworks Garden in Renton, WA as a new typology of constructed landscape that blends technolog-ical, ecological, and community values with art. They coin the term infra-garden as a landscape utilizing infrastructure facilities to support ecological and social values (MacEl-roy and Winterbottom, 1997, 11). In his 1989 essay The Experience of Sustainable Landscapes Robert Thayer discusses cultural conceptions of aesthetics and the emerging field of sustainable design. He describes aesthetics as an inadequate way to describe the social benefits of sustain-able landscapes. To Thayer, the landscape architects role is to interpret the relationship

of cultures to their environment in visual and spatial terms. For Thayer, using natural analogs in an urbanized environment does not fulfill the designers responsibility. Ap-plying a wild riverbank plant association verbatim to an urban drainage swale ignores the fundamental addition of human use in the ecological equation (Thayer, 1989, 108). Joan Nassauer discusses the differ-ence between aesthetic qualities and eco-logical qualities in her 1995 article Messy Ecosystems, Orderly Frames. She echoes Thayers notion that Americans discern eco-logical quality through a cultural lens rooted in picturesque notions of nature. She adds the idea that neighborhood landscapes repre-sent residents images of themselves. Conse-quently, communicating care and intention is vital for designing aesthetically successful sustainable landscapes. However, appearance is not the only consideration in how natural processes are perceived. James Corner examines ways in which landscape projects may serve as means to critically intervene in cultural habit and convention. (Corner, 1999, 4) To Cor-ner, how landscapes work are connected to their appearance. What matters is how the form and geometry of a project make sense with regard to the specific issues it is trying to address and the effects it is trying to precipi-tate. (Corner, 1999, 4)

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CHAPTER 2

INVESTIGATION

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The Chesa-peake Bay watershed

WaTershed CharaCTerisTiCs The Chesapeake Bay is the largest estuarine system in the contiguous United states. it is a mixture of tidal and nontidal fresh waters, salt waters, and wetlands fed by a 64,000 square mile watershed with 100,000 streams and rivers. it is facing several water quality issues including nutrient enrichment, low dissolved oxygen, sedi-ment deposition, toxic pollutants, and acid precipitation. its land-to-water ratio is 14:1 making the terrestrial parts of the ecosystem extremely important to the overall health of the aquatic environment. Fairfax City lies within the Piedmont physiographic province. The city is located in the head waters of accotink Creek which is part of the Potomac river watershed and the Cheasapeake Bay watershed respectively. specifically, the draft Fairfax Boulevard Mas-ter Plan study area lies within the North Fork accotink Creek and Central Fork accotink Creek drainages. The Northfax center is contained in three subwatersheds of the North Fork. The area is highly developed with an impervious surface coverage of approximately 40% and limited potential for open space infrastructure creation. There is, however, a network of 100 foot stream buffers, called resource pro-tection areas (rPas), mandated by state law. The exception to this is a 1,500 foot length of the North Fork that runs underground adja-cent to Fairfax Boulevard. stormwater outlets empty directly into the North Fork untreated.

Thus, a high proportion of impervious surface coverage and limited undeveloped space have led to degraded urban stream condi-tions. according to the 2005 Fairfax City Watershed Management Plan, The primary cause of stream degradation in the City of Fairfax is directly related to elevated volumes of uncontrolled stormwater runoff (Fairfax City Watershed Management Plan 2005, 1-1). These elevated volumes of uncontrolled run-off have caused the city to undertake signifi-cant stream stabilization efforts. While these efforts have had some success in stabilizing stream banks and preventing further bank sloughing, they have not improved in-stream water quality or biological habitat because the elevated volumes of uncontrolled storm-water runoff continue (ePa, 2008, iii). More-over, a 2010 draft Benthic Total Maximum daily Load development report for accotink Creek by the ePa identified sedimentation caused by excessive stormwater runoff as the primary stressor impacting benthic inverte-brates in the biologically impaired segment of accotink Creek just downstream from the North Fork. in addition to impacting aquatic life, stormwater runoff has drastically modified the hydrological characteristics of accotink Creek as a result of increased urban-ization and development. The watershed is characterized by a very flashy hydrology, caused by large volumes of stormwater runoff and increased flow velocity (ePa, 2010, 4-8).

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Left: The Potomac river watershed within the Chesapeake Bay watershed

right: The accotink Creek Watershed within the Potomac river watershed within the Chesapeake Bay watershed

NOrTh FOrK Or NOrThFaX? ChaPTer 2

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Accotink Creek precipitation & stream discharge 2000-2009

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drainage area 22.4 square miles piedmont condition: forested and agricultural

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A comparison of Accotink Creeks urban-ized water-shed with an analagous rural watershed high-lights Accotink Creeks flashy hydrology.

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BOULeVards

Tree-LiNed raMParTs, aNTWerP COUrs de La reiNe, Paris

OCeaN ParKWaY, NeW YOrKaVeNida POrTUGaL, Madrid

deFeNse reCreaTiON

TraFFiC hierarChYaesTheTiC

One of the central components of the Fairfax Boulevard draft master plan is to in-stall a true multi-way boulevard format along the urban nodes of this central corridor. The inspiration of the form of this boulevard is said to be the avenue Montaigne in Paris.This prompted a brief investigation of the origins and evolution of boulevards to get a grounding in the subject and to help refine project goals. Boulevards were originally garden allee style tree plantings adapted to the tops of earthworks or bulwarks that fortified cities against siege. Their original function was pri-marily defensive but over time people began to use them recreationally as well. advances in warfare technology eventually made their defensive function obsolete, but the social and recreational functions remained. Gradu-ally a hierarchy of movement developed with carriages and horses moving in the center and strollers using the side lanes or contra allees. it was not until urban expansion moved well past city walls that boulevards were brought down to street level and became integrated into the transportation infrastructure of the city. The new wide thoroughfares were an integral part of urban renewal and were seen as environmental improvements that allowed greater sunlight penetration and air circulation into city streets. even with the addition of transporta-tion and environmental functions, boulevards

retained important civic, social, and recre-ational functions. a review of a number of modern boulevards revealed that the best examples were those that accommodated a mixture of functions and users. however, in several modern examples of boulevards, their func-tions seemed limited to segregating traffic flows and hosting trees and turf. in light of the thesis inquiry, it seemed possible to deploy a richer array of boulevard functions in this new 21st century manifestation. The proposed Fairfax Boulevard medians could be a much greater resource for the communi-ty than 20 foot tree lawns being considered. They could help to create landscape infra-structure that provides social, recreational, economic and ecological enhancement. however, although the analogs exam-ined were helpful, a Boulevard format from Paris, New York, or Madrid could not be transplanted to Fairfax City. in order to make Fairfax Boulevard successful, it would need a design that would tell the story of this place and enhance its unique qualities in a way that would engage people and invite them to participate in the life of the street. if people could be active in Fairfax Boulevard and engage in it socially then it would become invested in the story of their lives and it could become a truly memorable place.

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NOrTh FOrK Or NOrThFaX? ChaPTer 2

GraNd BOULeVarT, Paris GraNds BOULeVards, POrTe saiNT-deNis , Paris aVeNUe des ChaMPs-eLYsees, Paris GraNds BOULeVards, POrTe saiNT-deNis, Paris

rOThsChiLd BOULeVaerd, TeL aViVsT. CharLes aVeNUe, NeW OrLeaNsaVeNida LiBerdade, LisBON aVeNUe haBiB BOUrGUiBa, TUNis

reCreaTiON POLiTiCaL aesTheTiC TraNsPOrTaTiON

POLiTiCaLTraNsiT iNFrasTrUCTUreresTOraTiVe COMMerCe & CONGreGaTiON

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The siTe - deVeLOPMeNT

1912 POsTaL deLiVerY rOUTes 1915 UNiTed sTaTes GeOLOGiCaL sUrVeY

1971 UNiTed sTaTes GeOLOGiCaL sUrVeY 2010 UNiTed sTaTes GeOLOGiCaL sUrVeY

1862 Us arMY COrPs

1948 Us arMY 1952 Us arMY

For most of its recorded history, the area has been largely rural and agricultural in nature. The City of Fairfax was founded in 1805 and its heart was the crossroads of Chain Bridge road and Main street also known as Little river turnpike. The proposed Northfax urban node lies a little less than a mile north of the historic town center. The earliest maps of the area show Chain Bridge road connecting the downtown, then the county seat, with the district of Columbia. in 1904, an electric trolley line crossed the area increasing connectivity with the regions central hub. The line ceased service in 1939 but its influence in the form of the area can still be seen. in 1934 Fair-fax Boulevard was built as a bypass to the historic downtown. (FBMP 1.3) in this phase of development the automobile was to have the most influence on the form and character

of the area. Over time, the area took on a more commercial nature with strip retail, car dealerships, and offices. historic maps document the devel-opment of the area, showing its transition from agriculture, to bedroom community and

local government hub, to its current status as a crossroads in the Washington metropolitan suburban matrix. however, there was one constant throughout the maps and it surely predated historic records. This section of Fairfax Boulevard is a stream valley. Over the

course of its development, its riparian char-acter was obscured as, bit by bit, the stream was culverted, channelized and buried. Moreover, the draft master plan proposes to continue a trend of dense development along this sream valley where a rPa should be.

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The three sub-basins that feed the portion of the the North Fork on the site.

Left: North Fork subbasin 9

Middle: North Fork subbasin 8

Right: North Fork subbasin 7

The siTe - hYdrOLOGY When this project began, the original focus had been the plans supplement of the urban forest and the possibility of using soil volumes to store and treat stormwater. after the realization that the defining characteristic of this place was the stream itself, a closer look at the local hydrological system was required. This channel is a first order stream in the North Fork of accotink Creek. it is fed by three subbasins with an elevation range between 462 and 324 feet above sea level covering 385 acres, of which about five are forested. The other 380 acres are developed to varying densities. The soils in the North-fax area are class B hydrologic soils mean-ing that they are moderate to well-drained (Fairfax City Watershed Management Plan, 2005, 25). however, the floodplain areas im-mediately adjacent to the North Fork contain poorly drained soils (Fairfax City Watershed Management Plan, 2005, appendix a). Monitoring data taken from down-stream reveal that the fundamental problem with this local system was its flashy nature of high peak flows during storm events and re-duced base flows during dry weather. These conditions are causing stream instability, scouring, high sediment loads and reduced macro benthic habitat quality. Moreover, Northfaxs location in stream headwaters makes it an ideal candidate for the applica-tion of detention practices.

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The three sub-basins that feed the portion of the the North Fork on the site viewed from the east in an aerial perspective

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riPariaN CONdiTiONsLeft: Algae in a concrete chan-nel

Right: Mallards

Left: Water Strider

Right: Minnows

Left: Grass and damsel fly

Right: Red tailed hawk

1The last under-ground length under the Wil-lowWoodPlaza park-ing lot seems to have been constructedwell after the Chesapeake Bay Preservation Act and the mandat-ing of RPAs.

site visits revealed a stream of al-ternating character and significance. Back-yard brook, channelized drainage ravine, streetside creek, forest remnant, feral reach, underground pipe, and culverted rivulet are all terms that can be used to describe various sections of the North Fork. From its begin-ings in a low density neighborhood through its travels along Fairfax boulevard, the stream is at times very present but at others almost completely forgotten. although impaired, this first order stream is far from dead. early assumptions were that this section of the northfork would exhibit little life, given the developed nature of the watershed. however, the resilience of natural forces is aparent. even in the open areas of concrete channel algae, grasses, dragonflies, damselflies, water striders, and minnows were not difficult to find. The only truly sterile places were the sections of un-derground pipe. in the upper forested patch of the stream the occurence of mallards, song brids, small mammals, and raptors indicated the presence of lower faunal trophic groups. The most consequential revelation occured in a July 2011 visit and contained ecological and cultural components. Two of the car dealerships abuting the stream granted access to their property to scout the fence line for remnants of the Fairfax line of the electric trolley. however, hiding behind vine-covered, chain link fences a fully intact, poured in place concrete trolley bridge was

found straddling the stream. a century old cultural artifact in this landscape was excit-ing, but the true cultural revelation was the extent to which this trolley line had defined the edges and connections of these three watershed subbasins. Moreover, the bridge illustrated a two to three foot change in the historic elevation of the waters surface and its current level, which is most likely a result of the incising caused by high volumes and velocities of stormwater. Perhaps most suprising, however, was the discovery of four to six inch fish in the pools surrounding the bridge. This indi-cated that the stream was habitable for these fish and whatever prey they were subsiding on. Moreover, it indicated that although the underground section down stream was not productive, it was not an impermeable bar-rier to biological connectivity. This discovery considerably raised the value of this section of the stream and the adjacent remnant forest patch. Not far from the trolley bridge the stream disappears into a five and a half foot diameter pipe for the most developed length of its journey. here very little trace of the stream can be discerned. it occasion-ally re-emerges briefly in concrete or riprap channels only to dissapear under parking lots and roads before it finally joines the Mosby Woods tributary in the rPa stream valley system becoming a second order stream.1

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CHAPTER 3

ALTERNATIVE VISION

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DESIGN BEGININGS Armed with the knowledge that the stream was a defining characteristic of the site, the stresses it faced, the baseline urban ecology, and the general vision of dense, mixed-use redevelopment, a set of general design goals emerged. Making the stream more apparent, integrating it into the life of the area, and enhancing its ecologic value were becoming critical to creating a unique place with a high quality of life and robust natural systems. One of the operating assumptions of this investigation is that the obscured ripar-ian character of the area leads people to undervalue the stream. For people to value natural resources, they have to be relevant to daily life. To make the stream relevant, the streams cultural value would need to be enhanced along with its ecological value. Three alternative design scenarios emerged for consideration; the open space corridor, the fountain, and the canal. The open space corridor scenario involved rerout-ing the stream away from Fairfax Boulevard and creating a Resource Protection Area with 100 foot buffers on either side of the stream. The fountain scenario involved creating a reservoir to feed a pump that would bring the stream flow up to street level and leaving the pipe in place to handle large storm events. Finally, the canal scenario involved replacing the pipe with an open channel and creating a forebay for sediment removal. The scenarios were evaluated with

both objective and subjective criteria. The open space corridor was rejected first for several reasons including its reduction in density and developable land. It was eas-ily the most land consumptive option. Also, the relocation of the stream would require a tremendous amount of earth moving that was ultimately deemed to be too costly, not environmentally sound, and ultimately foolish since the center of the stream valley will al-ways be Fairfax Boulevard. Most importantly, it moved the stream into the backyard of the development and diminished its significance. Choosing between the canal and the fountain scenarios proved to be more dif-ficult. They both kept the stream in the heart of the urban node along the Fairfax Boule-vard. By bringing the stream to street level, the fountain scenario seemed to be the most successful in making the stream present in the life of the street. However, the cost of this success was diminished biological productiv-ity. Moreover, the reservoir needed to control the flow of water would be very land con-sumptive. Furthermore, the constant pump-ing of water seemed energy intensive and unsustainable. In the end, the canal scenario was adopted as the option most capable of ad-dressing cultural, ecological, development, and sustainability concerns. The forebay component was eventually dropped in favor of a weir system. This exercise was very pro-ductive in helping to refine project goals.

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DESIGN GOALSEarly sketches of forms and spacing

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Reflection on the alternative design scenario exercise, the decisions made so far, and the developing overall vision, yielded goals that fell along cultural and ecological lines. A principal challenge would be recon-ciling their sometimes conflicting demands.

Cultural goals:

1. Daylight the stream: open the channel to allow visual accessibility and the opportunity for physical proximity or contact.

2. Create a transition from the isolated for-est patch on the western end of the site into parkland, then the commercial or urban environment and eventually into the stream valley network on the eastern side.

3. Create a place for social interaction and recreation unique to this location.

4. Create a center or heart to this proposed urban village. A place to host special events or farmers markets.

5. Create living space for the new residents of the proposed multifamily housing.

6. Allow for connectivity between the adja-cent neighborhoods and the new develop-ment.

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NORTH FORK OR NORTHFAX? CHAPTER 3Later iterationsEcological goals:

7. Create a soft bottomed stream with pool and riffle habitats to accommodate differ-ent types of organisms and create different flow conditions along the length of the urban stream.

8. Enhance vegetative cover to intercept rain-fall, filter pollutants, and provide food and habitat for wild organisms.

9. Create opportunities for rainfall infiltration through open space and permeable pave-ments.

10. Create short and midterm storage for rainwater.

11. Increase ecological connectivity between the forest patch and the stream valley net-work and along the length of the stream.

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EXISTING CONDITIONS

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PROPOSED INTERVENTION

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EXISITING HYDROLOGIC CONDITIONS

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PROPOSED HYDROLOGIC SYSTEMSINTERCEPTION, FILTRATION, EVAPOTRANSPIRATION

INFILTRATION, STORAGE

OPEN SPACE, PERMEABLE PAVEMENT

UNCOMPACTED SOIL VOLUMES

FILTRATION, STORAGE

CATCH BASINS, WEIRS, CHECK DAMS

VELOCITY & SEDIMENT CONTROL, STORAGE

TREE CANOPY, STREAMSIDE VEGETATION

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AQUATIC PLANTING & HABITAT PALLETTEAquatic vegetation chosen for its ability to provide habitat for benthic fauna, withstand inundation and stream velocity, and live under dappled light.

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TERRESTRIAL PLANTING & HABITAT PALLETTETerrestrial vegetation chosen for its ability to withstand periodic inundation, resist road salts, provide canopy and understory, exhibit urban form, and provide habitat for wildlife.

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FOREST PATH & NEIGHBORHOOD CONNECTIVITYLeft: Elevated path staging plan

Right Top: North-South planting grid

Right Middle: Initial species selection

Right Bottom: Potential 10-20 year winners, losers and op-portunists

Starting in the northwestern corner of the site the remnant forest patch is preserved and enhanced while increasing accessibility. The total size of the forested patch is increased from five to seven acres. The added forested area will create a buffer on the east side of the stream and create more interior habitat. An elevated path will connect pedestrian and bicycle traffic from the boulevard to the Western neighborhoods. The path will have a light footprint and will be constructed in a manner as to only create as mi-nor a disturbance in the forest patch as possible.

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Helical pilings and support beams

Metal grating surface

Handrails and gabions (filled in place)

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WEIRS & FLOOD STORAGEThe installation of a weir system reduces the scouring ability of large storm events. The weirs opening sizes will back water up to depth of one foot during the two year storm and up to two feet of depth during the 25 year storm after which the weirs will be over-

topped. This will provide additional flood water storage. The weirs will provide repeti-tive visual elements that will tie the forest patch materially to the rest of the design.

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FOREST PATH & WEIRThe elevated path will provide a throughway for nonmotorized traffic and will allow local ecology to be more present in the experience of residents and visitors.

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FOREST EDGESome new commercial development will abut the forest patch allowing for scenic views, wildlife observation, and pleasant outdoor seating.

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HEADWATERS PARKThis park and open space, named Headwa-ters Park, will provide a recreational re-source to serve the anticipated denser popu-lation and views for the multifamily housing adjacent to it. It will feature the same weir and flood plain system. The parks position of prominence at this main intersection will express the value the community puts on the quality of its environment and will make eco-logical processes present in every day life.

The grade of the electric railroad tracks has defined the edge of these three drain-age subbasins for over a century. Now this line will mark the edge of the forest patch and the park. The 100 year old, poured-in-place concrete trolley bridge will serve as the weir entering the park from the forest patch. Railroad tie-like stepping stones will mark the rail line and will point towards the Trolleys next stream crossing and trailhead

in the stream corridor just to the north. The preserved bridge and path along the electric rail line will remember the areas history as a bedroom community.

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INFILTRATION BASINSThe Northfax section of Fair-fax Boulevard

Right: Uncom-pacted soil volumes

Infiltration basins will line fairfax boule-vard in place of median tree lawns.

Medians will host infiltration basins along most of the boulevard. The basins will drain into the same uncompacted soil volumes that support the urban forest system. The basins will be equiped with underdrains to prevent anaerobic conditions in the soil. Designed to accommodate two year storm events, they will enter an overflow system after larger rainfalls. Basins adjacent to the North Fork will drain directly into the stream.

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Left: Infiltration basin from the south side of Fairfax Boule-vard.

Right: Infiltra-tion basin from the north side of Fairfax Boule-vard along the North Fork.


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DRAGONFLY POOLThe north eastern corner of the Chain Bridge Road, Fairfax Boulevard intersection will feature an open catch basin with terraced gabion walls. It will receive water from the stream across Chain Bridge Road and a small residential area north of the intersection. Its edges will be planted with blue flag iris to provide some filtering, phytoremediation, and wildlife value. The inlet to this pool shares a similar form as the remnant trolley bridge.

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THE BOULEVARD

POOLRIFFLE

As the stream crosses Chain Bridge Road it begins its most urban or developed phase. Forest and park landscapes give way to an area dominated by commercial land uses. After water leaves the dragonfly pool it will enter the constructed pool and riffle habitat. The form of the stream along the boulevard is derived from the limnological phenomenon that pools typically occur at intervals of five to seven stream widths. The pools will occur at alternate sides of the stream channel creat-ing an urban meander.

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Gabion walls filled with river stone will armor the stream channel while remaining permeable, allowing for the migration of groundwater into the stream. A micha-schist quartzite capstone is similar to the properties of the underlying geology.

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THE BOULEVARDAs the stream alternates from pool to riffle, terrestrial benches and shallow water host shrubs, marginals, and emergents that will stabilize the stream banks, cleanse the water, and add ecological value.

Terraces offer social space and closer prox-imity to stream while small waterfalls amplify its presence.

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NORTH FORK OR NORTHFAX? CHAPTER 3Suspended permeable pavement and soil volumes will infiltrate and filter water from adjacent impervious surfaces.

A mulch layer will filter out large debris, salts, and pollutants. Likewise, the surface area of the streamside vegetation will filter stream water.

Roots and their microbial associations will continue the remediation of tainted water.

Under drains will allow the water to migrate to the stream and prevent anaerobic condi-tions.

interception & evapotranspiration

mulch filter

soil filter

microbial remediation

bank stabilization

foliage filter

rhizoremediation

permeable gabion wall

underdrain

infiltration

sheet flow utility duct bankdry laid cobbles

soil volume detention

aggregate reservoir

pavement suspension

permeable pavers

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THE BOULEVARDThe integration of public transportation is a critical element of a lively boulevard. A small footbridge allows access to a bus stop and a crosswalk.

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NORTH FORK OR NORTHFAX? CHAPTER 3Open areas provide space for congregation, cafe seating, and special event needs. The open plazas offer the closest proximity to the stream along the Boulevard. The stream and social spaces are connected to the interior parking areas.

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THE BOULEVARDAlong the Boulevard, spaces and plantings are more formal. Like the stream, the social spaces will alternate between motion and resting, pools and riffles. Visitors will be able to stroll, sit, gather, eat, and people watch. Some resting spaces are smaller, private, and shady while others are larger, open, and sunny. Small terraces will allow closer proximity to the stream.

Along these two blocks, the environ-ment will favor pedestrian and non-motor-ized traffic. The area takes on some of the attributes of a woonerf with concrete road paving, no curbs, and a cobblestone parking strip that doubles as a detectable warning.

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TRANSITION TO PARKAs the stream crosses University Way, it will meet another catch basin and receive wa-ter from University Way and across Fairfax Boulevard. The stream area now gets wider and the faade wall accommodates more meander.

The banks of the stream now become sloped instead of shear and the greatest change in elevation over the course of the site will take place now. For a brief time, the stream adopts a step pool configuration.

Large terraced planters will accept stormwa-ter from the north and the gentle flood plain provides flood water storage.

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RETURN TO THE FORESTFinally, the stream and trail crosses Eaton Place where it will connect with the stream valley park system. Some of the parking lot from WillowWood Plaza has been removed and tied back with more stormwater planters.

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CHAPTER 4

REFLECTIONS

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THE ROLE OF ECOLOGICAL INFRASTRUCTURE IN SUBURBAN INFILL DEVELOPMENTLeft, top to bottom: foam flower, bluets, and wakerobin are all spring ephemerals that can exist in the riparian forest patch. These fleeting spring beauties con-nect observers with the seasons and the com-plex ecology that sustains life around us.

Right top: the 100+ year old trolley bridge that has defined the edge of three subba-sins since its construction remembers the areas history.

Right bottom: The trolley bridge separates the forest patch from headwa-ters park cel-ebrating its role as a cultural icon.

Given the broad outlines of the de-sign, I needed to ask what did this process teach me about the role of ecological infra-structure in suburban infill development.? Upon reflection, I have made several obser-vations that speak to this question.

Resilience of Urban Ecology

I have been heavily influenced by my landscape architecture studies, my natural resources studies, and my work with the Na-tional Park Service. They have all allowed me to notice relationships in the environ-mental matrix that I did not previously see, and I believe that my life is much richer because of it. Extrapolating from my own experience, I see tremendous opportunities for making stronger connections between ourselves and the natural resources around us, thereby making a much more nourishing everyday experience. My observations have shown me that there is a resilience in the urban ecology that we can exploit for both human advantage but also to the benefit of other organisms. Several plants and animals are existing on the margins of the human-dominated landscape and with a little bit of intention we can both increase biological diversity and invite it into our midst.

The Qualities of Place

One of the more powerful results of this design is that it celebrates the stream in a way that is unique to this location. By allowing the presence of the stream to be felt in the center of the urban node and by intermingling the stream with the commercial environment, it changes the community from Northfax, a made up, generic name, to North Fork a unique, identifiable and memorable place. I had considered alternative treat-ments of the stream at different points in this process. One of them included relocating the stream along a continuous strip of open park space in the interior of the develop-ment. However the iteration I settled on has the effect of both creating a unique hybrid commercial and riparian environment and also, perhaps more importantly, of putting the stream front and center where it makes a more powerful statement on the value the community puts on a healthier habitat. Fur-thermore, this treatment of the stream as the central element around which to organize the redevelopment of the area allows the unique local qualities of place to be ex-pressed in a way that the likely generic, new urbanist redevelopment of this node could never achieve.

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Left top: The Scarlet Tanager, a neotropical migrant, known to nest in the forest interior and mature ur-ban forests, underscoring the value of post develop-ment natural systems.

Right top: The draft plan con-tinues the trend of burying the North Fork.

Left bottom: A stream with an urban form can be both ecologi-cally productive and delightful.

Right middle: The elevated path through the forest patch favors bicycle and pedestrian connectivity.

Right bottm: Besides the ban-ners, there is nothing in this rendering that would indicate it was a part of Fairfax Boule-vard, Fairfax City, or even the DC region.Dover, Kohl Partners.

NORTH FORK OR NORTHFAX? CHAPTER 4Perspectives on the Land

On the one hand you have the Fairfax Boulevard draft master plan which treats the stream almost entirely as a cultural artifact and storm water conveyance. On the other hand, you have the EPA judging the quality of the stream based on predistur-bance levels. This stream has to be mea-sured by both standards and it probably will not meet the optimal levels of either. Pre-disturbance levels are a bad measure of the usefulness or success of a natural resource in an urban environment because, in Robert Thayers words, they ignore the fundamen-tal addition of human use in the ecological equation (Thayer, 1989, 107). We do not judge the success or usefulness of an urban forest by how closely it resembles a predis-turbance forest. Moreover, to ignore the biological importance of the stream and treat it as purely cultural is to disconnect ourselves somewhat from the larger ecosystem and to create a more sterile human habitat. Thus, green infrastructure in an urban environment has both ecological and cultural demands that have to be addressed through a hybrid approach.

Fairfax Boulevard Draft Master Plan

These observations also made me reflect on the Fairfax Boulevard draft master plan and what might be lacking from this type of new urbanist master planning. One of the stated goals of the draft plan is to increase connectivity. But when you drill down a little deeper, it seems that automobile connectivity is the primary focus. If the au-thors of the draft plan are serious about mak-

ing livable places that are more environmen-tally sound, then that might indicate in some places we should forgo automobile connec-tivity in favor of other types of connectivity. Ecological connectivity, for instance, gets short shrift in the Northfax node of the plan as even more of the stream is proposed to be buried. Furthermore, in some places, like the elevated path through the forest patch, it may be desireable to priviledge pedestrian and bi-cycle connectivity as an incentive to leaving the car at home for short, neighborhood trips. Moreover, this section of the mas-ter plan is localized in a way that the other nodes and connectors do not seem to be. I do not mean to suggest that the same type of treatment should be applied to the whole plan, but rather that a greater effort is needed to find the unique qualities of each place and let them influence the development in a way that allows a better chance of creating unique places.

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REFLECTIONS NORTH FORK OR NORTHFAX? CHAPTER 4

Left: The proposed slow release, open drainage system is compat-ible with a full palette of storm water control technologies and strategies.

Right top: The Chesapeake Bay watershed with the Potomac and Accotink watersheds nested respec-tively.

Right bottom: The Accotinnk watershed with the three sub-basins of the design area.

Climate Change

While this scheme is designed for todays no-tion of two or twenty five year storm events, I recognize that these ideas may change over time whether it be increased storm frequen-cy, duration, or total rainfall. However, this design creates some resiliency, especially through its added armor and retention capac-ity that is likely to be helpful no matter which shape climate change takes. Moreover, this design can be seen as the first piece of a broader rainwater detention and infiltration strategy for these subbasins. There is nothing to stop other rainfall capture and harvest-ing methods from being deployed in the area and adapted to what is basically a slow release open drainage system.

Scale

Finally, this process has been an interesting look into the appropriateness and scale of in-terventions. This may seem like a lot of trou-ble to go through for a first order stream that is easy to bury and forget about. Some might argue that we should just treat the water much further downstream in large impound-ments. However, that strategy just gives us license to further degrade the few remaining suburban forested spaces and streams, makes for a degraded and less rich human habitat, and does not make us confront the conse-quences of our choices. It allows us to view natural resources as divorced from our day-to-day existence and nature as something that exists elsewhere. It lets us off the hook and allows us to repeat past mistakes. This particular community has the interesting characteristic of being a head-waters subbasin, meaning that they are fully responsible for the condition of their riparian environment. They cannot blame the com-munity upstream for its poor quality. Thus, the condition of the stream and its immedi-ate environment is a direct expression of the values and attitudes of the community.

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WORKS CITED

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WORKS CITEDBerke, P.R., J. MacDonald, N. White, M. Holmes, D. Line, K. Outry, and R. Ryznar. Greening Development to Protect Watersheds Journal of the American Planning Association 69(4) (2003):397-413.

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Corner, James. Recovering Landscape. New York: Princeton Architectural Press, 1999.

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Fahrenthold, David A. EPA Tries to Get Chesapeake Bay Back on Track. Washington Post, 7 Nov. 2010: http://www.washingtonpost.com/wp-dyn/content/article/2010/11/07/AR2010110705206_pf.html (Accessed 21 Nov. 2010). Jacob, J. and Lopez, R. Is Denser Greener? An Evaluation of Higher Density Development as an Urban Stormwater-Quality Best Management Practice. Journal of the American Water Resources As-sociation 45, no. 3 (2009): 687-701.

Jacobs, Allan B., MacDonald, Elizabeth, Rofe, Yodan. The Boulevard Book: History, Evolution, Design of Multiway Boulevards. Cambridge, Massachusetts: The MIT Press, 2002.

MacDonagh, L. Peter, Big Trees in the City: Suspended Pavement Urban Trees Urban Soils Stormwater Management. (2010) http://www.bonestroo.com/client_files/Tree_Symposium/Peter_Mac-Donagh.pdf (accessed November 2010).

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Meyer, Judy L., Geoffrey C. Poole, and Krista L. Jones. Buried Alive: Potential Consequences of Burying Headwater Streams In Drainage Pipes. Proceedings of the Georgia Water Resources Confer-ence, 25-27 April. 2005: University of Georgia.

Moglen, Glen E. and Sunghee Kim. Limiting Imperviousness: Are Threshold-Based Policies a Good Idea? Journal of the American Planning Association 73(2)(2007): 161-171.

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WORKS CITEDMcPherson, Gregory and Muchnick, Jules. Effects of Street Tree Shade on Asphalt Conconrete Pavement Performance. Journal of Arboriculture 31(6) (2005): 303-310.

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Nelson, A.C. Leadership in a New Era Journal of the American Planning Association 72(4) (2006): 393-407.

Nevue Ngan Associates and Sherwood Design Engineers. San Mateo County Sustainable Green Streets and Parking Lots Design Guidebook. First Edition, (2009) www.flowstobay.org/ms_sustain-able_guidebook.php (accessed September 2010).

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Documents

2012 Master of Landscape Architecture Thesis