10th@Hoyt 925 NW Hoyt Street • Portland , OR
Ankrom Moisan Associated Architects
Reduce downstream damage from runoff
Safely move, control, contain rainwater
Restore or create habitat
The basic stormwater management concept at 10th@Hoyt is capture, convey, detain, reuse in water features, and discharge. The city of Portland requires all developed and redeveloped sites with 500 SF or more of impervious surface to mitigate stormwater onsite, using a 10-year storm as the ‘design storm event’. The 10th@ Hoyt site posed a challenge to this requirement, as the entire landscape of this project is located on a concrete slab over a below-grade parking garage; consequently, there was no opportunity for infiltration and aquifer recharge. In other words, 10th@Hoyt is essentially a green roof over a below-grade parking garage.
Three copper downspouts carry all roof runoff down into the courtyard: one, on axis with the entry gate, carries ½ of the runoff into a 33’ long, 2,500 gallon raised concrete detention vault. Two other downspouts in the courtyard corners convey the other ½ of the runoff, each into a shallow, above-grade concrete container. Water recirculates to the surface of the large central vault, flowing over sculptural Cor-ten “weir boxes” and recirculating in a closed system not only during a rain event, but for a slow, extended, drainage period up to 48 hours.
The rainwater celebration at 10th@Hoyt is both elegant and fun. It presents a serene symmetry from the main street entrance; but, upon entry, what seemed peaceful and understated reveals a playful dimension in different Rube Goldberg-esque conveyance systems on each side. Ephemeral qualities are also important here: a rain event activates the recirculating rainwater system, transforming the quiet, elegant space into a noisy, bubbly, water-focused place; and night reveals a colorful, dramatic side thanks to lighting strategically placed behind colored glass buttons in the Cor-ten water-spreading surfaces (a move inspired by Mughal gardens). The combined drama and ephemeral enrichment of place by rain poses a great way to make us treasure rain’s value.