LOCATION: Village of Glencoe, Portland, OR YEAR: 2003
TYPE OF SYSTEM: Detention System SCALE: Neighborhood
AREA: 1975sq.ft / 0.045 acres INFILTRATION: 52%
CLIMATE: marine Rainfall: 42.4 in BUILT CONTEXT: Suburban
STORMWATER CAPACITY: 6,500 gallons max COST: $98,000
The Glencoe Rain Garden is a detention rain garden. It’s designed to store, infiltrate, and filter street runoff. Because of its ability to control peak flows, flow volume, and pollutants, infiltration basin is a good option to control basement sewer backups, combined sewer overflows, open channel erosion and effluent water quality. This type of low-impact approach proves to be a valuable development strategy in Portland’s urban environments. (source:https://www.portlandoregon.gov/bes/article/63096)
1 Basic Information
- Year of Implementation: 2003
- Location: Village of Glencoe, Portland, OR
- Scale: Neighborhood
- Built Context: Suburban
Source: City of Portland-Bureau of Environmental Service
- A mean temperature of coldest month between 27°F (-3°C) and 65°F (18°C)
- A warmest month mean of less than 72°F (22°C)
- At least 4 months with mean temperatures more than 50°F (10°C)
- A dry season in summer. The cold season is October through March.
-annual rainfall 42.4 in.
-154 days precipitation (all higher than the US average)
● Type of System:
2 Catchment Area
The catchment area includes Morrison Street and SE 51st Avenue as well as the school parking lot. Also, there is an additional catchment area of SE Belmont St and SE 53 rd ave.
- Rain Garden Area: 1975sf
- Total Catchment Area: 34800 sf
- Additional Catchment Area: 10250 sf
- Maximum: 45050 sf
3 Runoff Reduction
According to the EPA calculator, in the site, 52% of ther water is infiltrated and there is a 3% reduction based on a baseline where the rain garden doesn’t exist.
The estimated cost of the project is $50,000-$100,000 and it’s supposed to obtain some local public funding. At last, the fully loaded cost is $98,000 which including charges for construction and planting, engineering oversight, construction management and inspection, and survey.
-Basic cost of construction :$82,000
-Construction contract: $69,500
-Cost for installation of the plants including tilling and mulch :$12,500
5 System Description
As is described in the Design Report of Glencoe Elementary School Rain Garden, stormwater enters the fore bay where the incoming energy of the stormwater is dismissed and sediments are trapped. When the fore bay is filled with enough water, it will then crest the fore bay weir before entering the main facility. The main facility is divided into sections by three rock “berms” which stacked rocks that allow water to move freely through. If water levels continue to rise, they overtop the drain field weir. The drain field is supposed to limit flow out of the facility. The limitation of speed is 220 gpm. If water levels continue to rise, flow will eventually spill into the “beehive” overflow and will move uncontrolled into the combined sewer. The rain garden was designed to handle the 25-Year Design Storm without overtopping the beehive.The total runoff will up to a depth of 5.5 inches before it begins to overflow into the drain field and back to the sewer through a 4 inches orifice. At that depth, the facility holds approximately 6,500 gallons of water.(source:https://www.portlandoregon.gov/bes/article/147510)
Diagram source: Chun Zheng
- The facility meets a number of design goals. It integrates well with its surroundings, is an attractive addition to the school grounds.
- Meets safety requirements for the school and community.
- The first school rain garden project in Portland.
- Serves as an outdoor classroom. It’s also a 4-H Wildlife Steward school and has created a wildlife garden right next to the rain garden.
The Bureau of Environmental Service is both the client and supervisor of the project, and they hired the landscape architecture Kevin Robert to bring this project to life. As public schools are generally lacking in resources to implement such projects, rain garden projects often involve outside funders, organizations and volunteers. The community effort put towards these projects, and the fact that they are installed in schools, raises awareness around the issues of urban rainwater management among lots of people.
8 Policies and Resources
- The Oregon Rain Garden Guide-Building a Rain Garden: A Step-by-Step Approach/ Rain Garden Plant List
- Portland Parks & Recreation-Public Involvement Procedures
- ENB-4.01 – Stormwater Management Manual
- ENB-4.13 – Administrative Rules for Discharges to the City Storm Sewer and Drainage System
- ENB-4.34 – Source Control Manual
- UTL-2.07 – Bull Run Water Supply Habitat Conservation Plan
- UTL-2.04 – Columbia South Shore Well Field Wellhead Protection Area Reference Manual
9 Possible Implications
- Maintenance Issues: The fore bay may be colonized by opportunistic plant species brought into the facility with sediment delivered by runoff. Large quantities of bark mulch were pushed into the drain field. This has also been an issue during some of the larger storm events over the past year.
- Design Constraints: The maximum ponding depth: for public safety, the depth was limited to 6-8 inches under most conditions. Limitation of the height of the plantings to a couple of feet which limited the list of potential plants.
flow test https://www.portlandoregon.gov/bes/article/63096
Rain Gardens and Public School Grounds:
Team Member: Chun Zheng, Tamara Cartwright, Yidan Gong