In Portland, a city noted for pioneering and mandating use of new environmental technology, enhancing sustainability and mitigating environmental impact are critical goals. For this reason, Portland has already seen a proliferation of green roofs and LEED certified buildings. This project creatively departs from typical details for stormwater collection, detention and quality enhancement through its Persian garden inspired sculpted forms, textures and colors. The design intent of the courtyard garden at 10th@Hoyt Apartments was to imaginatively display stormwater and provide extended detention of nearly all the roof top stormwater runoff.
The City of Portland requires developers to mitigate the impact of any increase in impermeable surfaces of developed property. Many engineered mechanical solutions have been developed to satisfy the guidelines, but without due consideration of the aesthetic appeal of water. This project explores the aesthetic possibilities and choreographs stormwater through a variety of playful and sculptural devices that continue to be a source of inspiration for landscape architects.
Our design excites native Portlanders and new building residents alike. The landscape and the integral stormwater features make users aware and appreciative of this natural resource by temporarily diverting stormwater from its typical path to the urban stormwater mitigation structures and displaying, modulating and accentuating its delightful qualities. The entire landscape is built on a concrete structural slab over a parking garage limiting opportunities for infiltration and aquifer recharge within the project limits, but allows significant onsite detention. Stormwater can be detained for approximately 30 hours after each storm event, allowing time for sediments to settle out and the water to be cleansed naturally.
Three copper downspouts channel nearly all the roof stormwater into precast concrete runnels and chadars — two of which empty water into shallow detention basins, and a third emptying into a 40 foot long 4000 gallon detention cistern. Granite river rock adds textural contrast and secures the pools from being safety hazards. The basins and cisterns temporarily hold water and allow for recirculation over two sculptural Cor-ten weir boxes. Each water weir is also designed as a sculptural light feature that maintains interest wet or dry. Water in the cistern and basins begins to slowly weep into the district’s stormwater system after the initial storm event. The total holding capacity of the basins and cistern allows the detention of roof water equivalent to a 1/8” rainstorm event. This allowed the downsizing of the conventional stormwater detention device.
The inner courtyard also provides semi-private respite for occupants and is open for public enjoyment. The central community seating area is cradled between the stormwater features and includes a section of covered seating so spectators can gather and watch. Evergreen, flowering and fragrant plants such as Camellia sasanqua ‘Yuletide’, Sarcococca rusifolia and Daphne odora take turns providing aromatic and color interest. Gunnera tinctora offers a surprise of elaborate texture and flower form for those who explore the courtyard.
Stormwater that gathers from the encompassing building roof engages the entire courtyard space and presents a public display of light and energy. Even at night, the metal weirs pierced with glass buttons and illuminated by interior lights create a friendly space and add a lively presence to the otherwise out of sight - out of mind stormwater cycle. Night or day, rain or shine this courtyard remains a pleasant environment for residents.