TYPE OF SYSTEM: Biotope for stormwater management
CLIMATE: Temperate, Annual Rainfall: 39.14 in
AREA: 0.4 ha / 1 acre
STORMWATER CAPACITY: The system has the capacity to capture the runoff of a 5-year storm.
|SCALE: Block Scale
BMPs: Urban Wetland construction, UV filter, cistern, bioswales
COST: $2.8 million +
Case Study Background
Tanner Springs Park designed by Atelier Dreiseitl in Portland’s Pearl District is an urban wetland constructed to manage and filter stormwater onsite. It is part of a tryptic of parks in the district envisioned by the Tanner Creek and Water Feature Steering Committee and approved by City Council.
The biotope, comprised primarily of coarse sand and plant media, functions as a wetland and supports native vegetation that begins the cleansing process. After moving through the soil and vegetation, water is treated with ultraviolet light via an underground utility vault, then pumped to the man-made springs at the top of the slope. The water then forms streams that are accessible to park visitors and slowly meanders through the site back to the biotope. Five-year storm events are managed on-site; additional storm-flow is sent to the public storm drain.
According to the Green Values National Stormwater Calculator, this project is able to The Green Stormwater BMP(s) applied in this scenario decrease the site impermeable area by 169.7% and capture 100% of the runoff volume required. Compared to conventional approaches, the green practices in this scenario will increase the total life-cycle construction and maintenance costs by 154% (in net present value).
The Friends of Tanner Springs maintain the park with assistance from volunteers.
-Ashley and Andrea