Sidwell Friends Middle School

Challenge

Designers were challenged to meet the school’s ethic of environmental stewardship by treating all wastewater and stormwater on-site. Both systems would need to fit within the 9,000 sf courtyard, and the wastewater treatment system would need to be completely self-contained in order to prevent contamination of the stormwater system. Additional site constraints included a mature willow oak, which would require only minimal site disturbance inside of its dripline and critical root zone in order to ensure its survival.

Solution

Through careful sizing and placement of each component, the wastewater treatment system efficiently utilizes the courtyard space and responds to the site’s constraints and characteristics. The natural slope of the courtyard carries wastewater through the terraced wetlands and trickling filter. Proper sizing of the constructed wetlands and cistern ensures that the system is capable of treating all wastewater that enters it, minimizing the risk of contaminating the adjacent stormwater harvesting system. To preserve the mature willow oak, utilities were placed as close as possible to the building footprint, and monolithic stone tread pathways were installed under the tree canopy instead of traditional concrete pathways, which require compacting the soil.

• The terraced constructed wetlands are the centerpiece of the courtyard, and are filled with native plantings including iris, bullrush, cattail, horsetail, soft rush and sensitive fern. Downslope from the wetlands are the rain garden and biology pond, which includes native water plants such as water lillies, pickerel rushes and water shields. Access steps and terrace walls around the wetlands and pond transform the space into an outdoor classroom and laboratory for the 8th grade science class.
• The building captures and treats all rainwater through a closed-loop system. Rainwater from the green roof is filtered by soil media and stored in underground cisterns before being pumped to the biology pond during summer months. The adjacent rain garden also captures overflow from the pond during heavy storms. Water from paved surfaces is also directed to the pond and rain garden via vegetated swales, which filter run-off through plant materials and sand.
• Wastewater collected from the building’s toilets and faucets is treated on-site, flowing into settling tanks where solids are collected before water is released underground into the constructed wetland. The tiered wetlands treat roughly 3,000 gallons of wastewater per day using biological processes, with water circulating through the system for 3-5 days before reuse. Once water has passed through the wetland, treatment components include a trickling filter, a recirculating sand filter and a UV disinfection unit. The cleansed wastewater is then collected in greywater storage tanks, colored blue to denote that it is non-potable and reused in the school’s toilets.
• The on-site trickling filter behind the wetlands includes a diagram of the wastewater and rainwater management systems. Educational signage is also incorporated elsewhere on the site, including a mural illustrating the sedimentation process.
• Native plantings, including more than 80 species native to the Chesapeake Bay region, are used in place of lawn, eliminating the need for irrigation and use of pesticides. Plants and flowers in the courtyard and elsewhere on the middle school grounds include red maple, sassafras, oxeye sunflower, turtlehead and milkweed. Endangered species that may be attracted to the new habitat include the Snowy Owl and the Monarch Butterfly.
• The 1,000 sf rooftop classroom offers students a range of applied learning opportunities including vegetable gardening, green roof technology, storm water management strategies, and ecological stewardship awareness. The green roof has an average soil media depth of 4 inches, and plantings include sedums, grasses, aliums, aster and liatris. Photovoltaic panels on the roof generate 5% of the electrical load for the building.
• The building and landscape include a range of reclaimed materials from the region. All of the stone used in the wetland walls and stairs is reclaimed, with sources including an abandoned quarry and a dismantled railway bridge. The building’s cladding is made from 100-year-old wine barrels, and flooring and decking are made from pilings salvaged from Baltimore Harbor.

• Sustainable landscapes can have a positive impact on school identity and lead to a higher understanding of ecological awareness in students, teachers, and visitors. The design of the schoolyard fosters an ecological awareness through the landscape features, which middle school students interact with on a daily basis either through the school lavatories, giving tours to visitors or studying the health of the systems in Environmental Studies class. As a result, the school has been nationally recognized as a leader in green school design and continues to receive visitors who are interested in learning about the sustainable systems incorporated into this project.
• Complex projects of this scale are difficult to implement using a standard delivery method. A design, bid, build process does not foster collaboration and when feasible, a negotiated bid with a general contractor or a construction manager at risk may be a desirable option.

Project Team

Executive Architect: Kieran Timberlake Associates, LLP
Landscape Architect: Andropogon Associates
Environmental Engineer: Biohabitats, Inc
Structural Engineer: CVM Engineers
Owners Representative: JFW Project Management
MEP Engineer: Bruce Brooks Associates
Civil Engineer: Vika, Inc
Lighting Consultant: Sean O’Connor Associates, Benya Lighting Design
Wastewater Consultant: Natural Systems International
Green Roof Engineer: Furbish

Role of the Landscape Architect

The landscape architect worked with a team of architects, engineers, and wastewater consultants to draft a master plan for the schools grounds. The landscape architect completed the concept design, siting and design strategy for the wastewater system, as well as the planting design for the grounds and green roof.