An example of a successful public-private partnership involving sustainable stormwater management is RiverEast Center in Portland, Oregon. The site includes numerous vegetated infiltration swales that filter and cleanse runoff from the parking lot, walkways, building roof, and adjacent public street. The swales were constructed at a gentle gradient to allow the water to readily soak into the soil, rather than be rapidly carried off to storm drains. Plantings, mulch, and stones cover all the unpaved surfaces; no high-maintenance turfgrass can be found on the property. The site also includes several recycled concrete slabs, set on edge, that serve as sculptural and functional elements. The office building is a renovated warehouse (with a new façade) that has achieved LEED gold certification from the U.S. Green Building Council.
A vegetated infiltration swale is situated between a pedestrian walkway and the parking area. This walkway connects to a bicycle/pedestrian path along the Willamette River.
This infiltration swale is located between parking bays. A raised storm drain at the end of each swale takes in excess stormwater during heavy rain events.
Roof water from a building scupper is slowed by a gravel bed (edged with recycled concrete slabs) and is then directed through a slot in the taller slab to a vegetated infiltration bed on the left side of this photo.
During heavy rain storms, roof runoff that can’t entirely soak through the plant bed next to the building is conveyed through this walkway channel into an infiltration swale.
Stormwater from the adjoining public street is directed through several walkway channels into the adjacent infiltration swale on the RiverEast Center property.
Photos by Alice Webb
Portland, Oregon, is known as one of the greenest cities in the U.S., receiving high marks for public transportation, bicycle/carpool commuting, renewable energy usage, recycling, and number of LEED-certified buildings. It also has quite a few innovative environmentally-sustainable sites, including several “green streets”. These streetscapes incorporate special planters that decelerate runoff and filter pollutants from the water before it reaches the storm pipe system.
During a recent visit to Portland, I had the opportunity to see a couple of these green street projects in the downtown area: one on Southwest 12th Avenue within Portland State University, and another on Southwest Park Avenue across from Director Park. There are several other green streets scattered around the city, and many of these have their own unique design.
The 12th Avenue site was the first of its kind, built in 2005. In addition to its stormwater management function, it has enhanced the visual quality of the existing streetscape. In this case, stormwater flows into the first of four planters, and settles into the soil. During heavy storms, if the water level in this planter reaches more than 6 inches, the excess amount will flow back out into the gutter and then flow into the next planter for infiltration, repeating the process. Water exceeding 6 inches height in the last (lowest) planter will flow out to the street and enter the storm drain system. The number of planters functioning in this manner depends on the intensity and duration of each rain event. The planters are filled with a native species called Grooved Rush (Juncus patens), and each also includes a Black Gum tree (Nyssa sylvatica). Both of these species tolerate saturated soil conditions. In addition, a 3’-wide strip of pavers is located along the street side, providing space for access to parked cars. Pedestrian walkways are also situated between the planters, bounded by small shrubs.
The planters on Park Avenue are designed in a different manner. The largest planter (pictured below) is divided into three sections. Water enters the planters from drain inlets along the street side, and from gaps in the curbing along the sidewalk. When water in the highest planter section exceeds the height of the divider during large rain events, that runoff will flow over the divider into the next section. Most of the water will filter into the soil in the planters, but during the heaviest storms it may reach the third (lowest) planter section. If the water level in this section reaches the height of the elevated drain inlet located within it, this excess water will enter the inlet and flow into the storm pipe system.
Photos by Alice Webb