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View from top of the wetland terrace towards the new extension of the Middle School building.

Sidwell Friends School (Middle School renovation and addition)

Size & Type of Project:
less than 5 acres on a 15-acre campus; Greyfield redevelopment; K-12 education

Location:
Washington, DC

Budget:
Approximately $4 million (for site-related work)

Project Phase:

Completed 2007

Project Overview

The renovation and addition project at Sidwell Friends School (SFS) campus transforms the Middle School's fifty-year-old facility into an exterior and interior teaching landscape.  Designed to foster an ethic of social and environmental responsibility in each student, the facility demonstrates a responsible relationship between the natural and the built environment.  Smart water management was the focus of the project design. A central courtyard with a rain garden, pond, and constructed wetland has been designed to utilize storm and wastewater for both ecological and educational purposes.  More than 50 plant species, all native to the Chesapeake Bay region, were introduced in the landscape and there was extensive use of reclaimed stone for steps and walls and concrete containing recycled slag for walkways. In 2007, the Middle School project was the first K-12 school to achieve a Leadership in Energy and Environmental Design (LEED) Platinum rating from the U.S. Green Building Council.

Site Context

Washington D.C. is in the Southeastern Plains ecoregion. It has a humid subtropical climate with four distinct seasons, typical of Mid-Atlantic U.S. areas removed from bodies of water.  Spring and fall are mild, with low humidity, while winter brings sustained cool temperatures and annual snowfall averaging approximately 16 inches. 
The Sidwell Friends School facilities sit on the fifteen-acre Wisconsin Avenue campus in the historic Tenleytown section of northwest Washington D.C. The entire campus is in a fairly dense urban location in the watershed of Rock Creek Park.
To create the new Middle School, the design team renovated the existing 33,000 square-foot building and expanded it with a 39,000-square-foot addition. The old and new wings meet to form a U-shaped courtyard.


Two students on the border between the rain garden and the pond.

Sustainable Practices

Sustainable awareness and education
Deeply committed to practicing and promoting environmental stewardship, SFS requested environmentally responsible stormwater and wastewater management systems to be designed as educational and awareness-building tools and to design these systems to be highly visible in the landscape.   With that in mind, the centerpiece of the new Middle School is a natural wastewater treatment and reuse system that produces high-quality water suitable for non-potable uses.  A constructed wetland forms the heart of this system, using biological processes to clean water and serving as a living laboratory where students can learn about biology, ecology, and chemistry. For their Environmental Science class, 8th Grade students participate in labs in which they measure and compare nitrogen and phosphorus levels in various levels of the wetland and in the basement reuse holding tank, and learn the valuable role that wetlands play in purifying water. The AP Environmental Science students conduct labs including comparing water quality in the on-campus biology pond to water in a nearby tributary, studying the invertebrate biodiversity in the soil on the green roof, and comparing stormwater runoff from the green roof with runoff from the conventional roof.  Students and others at SFS are also encouraged to record wildlife sightings such as a Snowy Owl or Monarch Butterflies through the school's website. The biodiversity in the woods, wetlands and native vegetation provide real-life lessons for the science classes.  On the green roof, students also learn how to grow vegetables and herbs which are used in the school's cafeteria.

Integrated wastewater management system
Entering the sunken courtyard in the front of the Middle School building provides a dramatic and immersive experience of water. The constructed wetland natural treatment system, the first of its kind for D.C., is the most prominent element of the integrated wastewater management system.  All of the wastewater from the Middle School building is processed in a multi-step system that incorporates a variety of ecologies to provide robust, diverse treatment.  System components include a passive primary treatment tank, followed by a series of terraced subsurface-flow constructed wetland cells, a recirculating sand filter and trickling filter, which are all tightly integrated into the courtyard's landscape. The wetland is a subsurface-flow type, as opposed to the surface-flow type, which reduces or eliminates odor and prevents contact with the water.  All water flows beneath layers of planted gravel so that no surface water is exposed. A variety of native and local wetlands plants provide not only aesthetic beauty, but play host among their roots to a wide diversity of microorganisms that help break down contaminants from the water. The trickling filter and sand filter provide further polishing and reduction of nutrients such as nitrogen.  

Wastewater is processed through the courtyard systems for approximately three to five days before entering a storage tank in the basement.  When non-potable water is needed for toilet-flushing or cooling tower make-up within the building, clean water from the reuse tank is filtered through a fine screen, disinfected using ultraviolet light and pumped back into the building in a parallel set of pipes designated for only recycled water. The wetland system will receive up to 3000 gallons per day and the high-quality reclaimed water is recycled into the building for reuse.  Any unused water passively overflows as clean water back to the municipal system.

Integrated stormwater management system
The Middle School's stormwater system is equally dynamic to the wastewater treatment system with a combination of rain gardens, swales and biofiltration and habitat pools that double as outdoor classroom space.  All site runoff is directed to the rain garden, planted with native meadow species, for infiltration. A green roof also reduces runoff volumes and improves the quality of infiltrated runoff.  To address improving runoff water quality, the overland flow of runoff from paved areas is routed through a storm filter to remove suspended solids and excess nutrients.  Excess water from the roof and lawn also flows to the courtyard's pond. Some of the roof runoff is stored in an underground cistern which provides additional water for the pond during dry weather. During heavy rains, excess water flows from the pond into the rain garden. No permanent irrigation system was installed. 

Recycling and material reuse
Most of the hardscape elements in the landscape are reclaimed or recycled. Material for the boardwalks and decks is lumber pilings reclaimed from Baltimore Harbor.  Flagstone was reused from sidewalks, and stone for steps and walls came from a dismantled railroad bridge about 200 miles from the project site.

On-site recycling
Recycling allows Sidwell Friends to reduce their burdens on the environment as a result of both solid waste disposal and the extraction of the natural raw materials. They recycle mixed paper, cardboard, cans, glass, and type 1 (PETE) and 2 (HDPE) plastics. Additionally, they use a solar-powered trash compactor that operates on 100 percent solar energy. While its footprint is the same as an ordinary trash receptacle, its capacity is five times greater. This increased capacity reduces collection trips and can cut fuel use and greenhouse gas emissions.

Construction Cost

N/A

Monitoring Information

SFS students monitor the building functions and constantly measure the "health" of the facility. Teachers of every grade level have access to the building's exposed systems for the study of flora and fauna, rainforests, human cellular structure and environmental science, as well as many aspects of the mechanical, electrical, structural and plumbing systems.

Sidwell Friends School has engaged Lucid Design Group to monitor water quality within the constructed wetland system, and to display the data on a website for classroom use. The District of Columbia further requires both regular water quality monitoring of the waste water system and periodic groundwater monitoring, to confirm that the system is functioning as planned.

The Center for Sustainable Environmental Design, a collaborative effort between the Yale School of Forestry and Environmental Studies and the Yale School of Architecture, is conducting research to connect environmental science and management with architectural design and engineering.  At SFS, a research team is studying the school to determine if the project's green strategies have a measurable effect on student and faculty performance and health. While the school was still using the older building, extensive questionnaires were administered to students, teachers, and staff. Numerous questions probed their awareness of the building, satisfaction, and environmental sensitivity. The response to these questionnaires will act as the baseline for the study.  Additional surveys will continue to be conducted. This data will provide the first analytical examination of the effect of biophilic design on occupant satisfaction and performance.

Maintenance

Sidwell Friends School will be maintaining the site systems in-house, including the wastewater system and constructed wetlands, the biology pond, and plantings, and will contract with outside consultants or services as needed.  For example, the Primary Treatment Tank will require periodic pumping (tank will be checked quarterly and pumped approximately once every year). 


A constructed wetland forms the heart of the natural wastewater treatment and reuse system, using biological processes to clean water and serving as a living laboratory where students can learn about biology, ecology, and chemistry.

Issues/Constraints of the Site

Lessons Learned

When site systems become highly integrated, they achieve both efficiency and interdependence. For example, the green roof provides efficiency for both the storm water system and the building HVAC systems; this efficiency also means that the stormwater system and the HVAC system also became dependent on the green roof for their efficient sizing. Consequently in integrated designs of this type, changes to project scope - whether for budgetary of philosophical reasons - need to be considered holistically.  Projects of this complex nature are difficult to implement with a standard project delivery system. A very close partnership between the design team, the client, and the construction team, is needed in order to help the contractors effectively organize and build these new, sustainable, site systems.

More project details

http://www.sidwell.edu/about_sfs/envstewardship.aspx

http://www.natsys-inc.com/portfolio/schools/sidwell-friends-middle-school/

http://kierantimberlake.com/pdf_news/sidwell-friends-school.pdf

Project Consultants

Client
Sidwell Friends School

Prime Consultant & Architect
Stephen Kieran, Principal
KieranTimberlake

Landscape Architect
Jose Alminana, Principal
Andropogon Associates

Wastewater Engineer
Michael Ogden, Principal
Natural Systems International