Designing, Implementing, and Managing Improvements to the National Mall

Honor Award

General Design

Washington, District of Columbia, United States
HOK
Client: National Park Service

Making and Restoring History

Our team’s restoration of the National Mall turf and soil for the National Park Service allows our nation to once again be proud of America’s most important landscape through a focus on the details, the underlying landscape structure and sustainability.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Not a Good Look

Existing conditions of America’s “front yard” were bleak. Unsustainable maintenance practices and a lack of public use standards created a cycle of heavy damage and truncated recovery. Symptoms included soil compaction, poor drainage, inconsistent turf, and broken irrigation.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Fixing America's “Front Lawn”

The project scope included design and engineering services to refurbish the National Mall’s eight central turf panels, granite curb edges including ADA accessibility, granular walkways, and storm drainage improvements.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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If You Build It, They Will Come

Phase 1, we replaced lawn panels from 3rd to 7th Streets NW in time for President Obama’s second inauguration. Phases 2 & 3, we replaced lawn panels from 7th to 14th Streets NW in time for President Trump’s inauguration.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Sustainable System

Before, the Mall consumed the most electricity and potable water of any national park. The restoration shifted the Mall’s main irrigation source from drinking water to rainwater captured in one of the largest rainwater collection /reuse systems in the world.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Draining the Swamp

Walkways and turf panels were graded to drain into the new subsurface drainage structures, while ADA-compliant granite curbs were designed to guide water to cisterns and redefine the edge of the Mall’s turf panels.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Catching Raindrops

Four 250,000-gallon cisterns collect stormwater runoff for irrigation. Efficient, robust advanced controls and smart scheduling were implemented for irrigation using the collected runoff.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Call in the Turf Expert

The design team assisted NPS in writing a Sustainable Operations and Maintenance Manual which was finalized in 2012. Our team collaborated with turf experts and folded in findings from a University study on optimal species mix and soil composition.

Photo Credit: Tim Brown
Media: Please submit high-resolution image requests to images@asla.org

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Finding the Right Mix

Once barely surviving, the new turf on the Mall features engineered soil to resist soil compaction. Incorporating coarse sand into the soil mix, which contains more oxygen than traditional loam soil, promotes a robust root system and resists physical compaction.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Turning a Corner

The existing perimeter of the Mall turf was undefined and deteriorating due to stormwater runoff and pedestrian damage. The corners were reshaped from square to round to accommodate natural circulation patterns and the grass panels were regraded to improve drainage.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Better Boundaries

The grass panels were framed in a light granite curb, designed to be handicap accessible, define the edge and protect the turf. The paths crisscrossing the Mall were broadened to keep feet, equipment and event structures off the grass.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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That’s a Big Tarp

Protecting the Mall turf involved the biggest installation of white lawn covers in history. Recommendation for plastic covering resulted from a Virginia Tech graduate student-led study researching the optimal material for protecting and maintaining turf.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Setting the Standard

Before this project, there were no national standards for maintaining public parks. We led a focus group with event coordinators/ vendors to set standards for the Mall, resulting in publication of the NPS Mall Turf Operation and Maintenance Manual.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Crowd Pleaser

The design and operations plan proved successful in preventing lawn degradation during the January 2013 presidential inauguration and subsequent events, gatherings and protests.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Serving the People

Throughout the project duration, the National Mall has hosted countless public events, proving the resilience of the updated system and long-term success of the NPS’s new standards and rules that our team helped establish.

Photo Credit: Blue Timeline: The National Park Service; National Book Festival: Library of Congress; The Monument Quilt: Nate Gregorio; Apollo on the Mall: Bill Ingels; Bottom Three Images: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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A Lasting Makeover

After the seven-year, $40 million reconstruction, our nation’s “front lawn” is looking the best it has in generations. The new, sustainable turf and irrigation system will maintain our nation’s stage for assembly, remembrance, and celebration for years to come.

Photo Credit: The National Park Service
Media: Please submit high-resolution image requests to images@asla.org

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Lawns these days can be polarizing, and perhaps none more so than the National Mall, which is often considered the country’s front lawn and plays host to celebrations and protests to the number of some 25 million annual visitors. Restoration of that turf surface has thus warranted a considered solution for long- term viability and sustainability that integrates strategic seeding and soil, a subtle crowning to improve drainage, and an irrigation approach that reduces potable water usage by 75 percent. While the technical solutions may seem straightforward, when expanded across nearly 31 acres of surface, their impact can expand beyond the scale of this grand, green monument to well-used parks across the nation.

- 2020 Awards Jury

Project Credits

Xingye Pan, ASLA, Landscape Architect

Clark Construction, General Contractor

Wiles Mensch Corporation , Civil Engineer, Land Surveyor

JVP Engineers, PC , Mechanical Engineer, Electrical Engineer, Commissioner

Schnabel Engineering, LLC , Geotechnical Engineer, Construction Engineer, Materials Engineer

Construction Consultants, Inc. , Cost Estimator

Cagley & Associates, Inc. , Structural Engineer, Facility Condition Assessment Specialist

Heritage Landscapes, Historic Landscape Architect

Brian Vinchesi - Irrigation Consulting, Inc., Irrigation Specialist

Steve LeGros - Le Grows, Inc. , Sports Field Consultant

James Urban - Urban Trees + Soils, Soil Consultant

Norm Hummel - Hummel & Co Inc., Soil Scientist

VeTalle Fusilier - JBV Production Inc., Event Planning Consultant

Andreas M. Chrysostomou - Alpha Corporation, Construction Manager

Brian Jencek, ASLA, Senior Principal

Jacalyn Pruitt, Landscape Architect

Suzette Goldstein, Lead Designer #1

Jose Chieng, Lead Designer #2

Brandon Hartz, Lead Designer #3

Michael Stachowicz and Andrea Lind, NPS, Phase 2/3

Patrick Macdonald and Alice McLarty, NPS, Phase 1

Andreas Chryosostomou and Eric Rowland, NPS, Construction Management Representatives

Sean Kennealy, NPS, Deputy Superintendent

Project Statement

The National Mall is arguably the most culturally important landscape in the United States. Known as America’s “Front Yard,” The Mall hosts nearly 30 million visitors and 3,000 special events annually. Millions of people visit The National Mall to demonstrate freedom of speech, commemorate presidential legacies, honor our nation’s veterans, make their voices heard, and celebrate our nation’s commitment to freedom and equality.

By the turn of the century our Nation’s most significant landscape had fallen into a disgraceful state. The project that ensued was not merely about planting grass; it was about creating a comprehensive landscape solution to protect and preserve our Nation’s cultural asset to achieve sustainability and resiliency. This story is not solely about the beauty of the landscape, but how what you see on the surface reflects what has been constructed below the surface and the establishment of best practices for maintenance and use. It is the artful compilation of beauty, preservation, detail and function that makes this an award-worthy landscape in addition to our national treasure.

Project Narrative

Every design exercise has a primary purpose; an issue the design is trying to solve. At first glance it appeared that our design challenge, while incredibly important, would be straightforward: restore the dignity to The National Mall, in Washington, DC, by replanting the turf. But as with most things, it was not as easy as it appeared on the surface. The issues that needed to be tackled fell into four broad categories: aesthetics, structural, sustainability, and function. It was only through the comprehensive solution of all four of these issues that we would end up with a National Mall that had the resiliency to survive and justify the extensive investment of public funds. The land area included in the scope encompassed 1,350,000 square feet (approximately 31 acres) of walkways and eight turf panels between 3rd Street NW and 14th Street NW in the nation’s capital. The reconstruction of the Mall has now survived seven years, thousands of events, and millions of visitors. It remains as intended – America’s most important landscape.

Our foremost goal was to restore the Mall’s grand aesthetics. The Mall had suffered from years of over-use and inadequate funding for proper maintenance. The turf was a patchy mix of thin grass, weeds, and mud. What should have been crisp edges of lush green lawn were instead a worn and uneven melding of gravel and the planting area. Our overall goal was to observe the length of the Mall and see a continuous green swath as the foreground to the Capitol Building. We employed a simple but effective technique of crowning the lawn panels. The crowning elevates the turf in your view plane so that the long view de-emphasizes walkways, streets and vehicles that bisect the Mall, giving the desired illusion of an unbroken band of green while ensuring affective drainage. To ensure these swaths of lawn were well defined, we designed a graceful ADA accessible granite curb to define the edge of the lawn. We paid special attention to the scale of the element to ensure the width worked with the monumental scale of the space. Finally, at a nearby sod farm, we cultivate a special blend of seed customized to the region and expectation of heavy usage. The seed blend had to be exactly right for this location.

The three simple moves visible on the surface are the basis for the project’s success, but it is the below-grade structure that sustains the long-term health of the turf. Our team included a soil scientist from commercial, sports and academia to develop the best specification for our situation. We needed a soil blend that would first and foremost withstand compaction while being sensitive to air filtration, water usage, and minimize the need for fertilizers and herbicides. These were in many ways contradictory goals. Our solution was a ‘dirty sand mix’ of 60 percent sand to resist compaction and 40 percent organics to sustain the turf’s healthy growth. Alternative soil mixtures containing varying levels of granular and organic content were researched to identify optimal capillary structure and pH duration, organic density, compaction resistance as well as each mixture’s ability to provide proper air, water and nutrient entrainment and infiltration. The design called for existing soils to be replaced to a depth of three feet with engineered soil that is permeable yet containing sufficient organic material to support turf grass growth and retains water within its subsurface structure.

Sustainability was, of course, also an important goal of the project. The question is: how do you sustainably grow grass? Turf is by its very nature not a typical sustainable solution, yet in this instance the only culturally appropriate material. So, we took on the core issue with maintaining turf: water. Our solution improves water quality, reduces storm water runoff, protects against flooding, reduces impacts on DC’s combined sewer treatment plant, reduces reliance on potable water, and at the same time successfully grows turf in a climate that necessitates irrigation. Walkways and turf panels were graded to the new granite curbs surrounding each lawn panel as well as to a subsurface drainage field. This water is directed to four cisterns with the collective storage capacity of 1.0 million gallons of storm water runoff which is filtered and reused for irrigation. The resulting sustainability benefits from the revitalization of this extraordinary civic space included a 75 percent reduction in potable water use consumption for irrigation. While carbon sequestration potential in turf grass is still under investigation, current studies have indicated that turf grass could sequester 2.3 grams of carbon per square foot of turf grass per year, at a minimum, for approximately 180 years before reaching full carbon saturation in the soil. With roughly 784,000 sq. ft. of turf within the scope of the Mall project, this has the potential for sequestering just under 2 tons of carbon per year.

Design often debates the virtues of form versus function. In this case there is no doubt that the two must go hand in hand. The primary function of the Mall is as an assembly space. There are more than twice as many events permitted on the Mall as there are days in the year. There is no more heavily used public landscape in the nation and the use of this space is protected by the First Amendment of the Constitution. At the same time, it is an historic cultural asset and must be protected as such. This place is a symbol of our believes, therefore, form is fundamental. The Mall represents the foundations of our republic: freedom of speech, assembly, religion, and expression, and the right of citizens to petition the government. How can one landscape fulfill such lofty aspirations for generations to come? The solution to this part of the design problem came in the form an events operation and maintenance manual created by the design team and the National Park Service and supported by a secretarial order by then-Secretary of the Interior Ken Salazar, Honorary ASLA. The Secretary formally directed the NPS to implement the policies set out in the manual to ensure the longevity of the new turf grass installation. Strategies to protect the lawns were established which allow for the preparation, protection and recovery of the turf. Rules were mandated for rest periods, relocation of events, weight restrictions, and protective translucent decking. In addition, guidance was provided for locations for temporary structures on the turf by ensuring that paved areas are sized support tents, jumbotrons, stages and the like. The manual also provides seasonally-based guidance on fertilizer use, parameters for applying low impact herbicides, thatching, mowing, over-seeding and repair requirements. The manual brings together management, policy, permitting and maintenance all in one document. In 2013, Landscape Architectural Magazine quoted Patrick MacDonald of NPS (now retired), as saying “In 35 years in the park service, I’ve never been involved in this kind of support document.”

The reconstruction project of the National Mall dates to 2009 with the first of three design and construction phases. It has survived two inaugurations, seven Fourth of July celebrations, countless demonstrations and marches, millions of tourists and the everyday joys of being a Washingtonian. Each member of our design team understood that it was a privilege and monumental responsibility to be a part of preserving our national landmark. This project is a prime example of how best to honor our public open spaces that have extraordinary national significance. Time has proven that this project has successfully preserved America’s “Front Yard.”

Products

Iron Age custom fabrication Trench Drain Grate
Rain Bird IC system
TORO dual trajectory sprinkler series
The North Carolina Granite

Plant List:

Wolfpack II tall fescue grass
Firenza tall fescue
Turbo tall fescue
Kentucky bluegrass