It isn’t often that I get really excited about the things I read but I positively nerded out when I started reading about a pilot program for Sustainable Stormwater Management that Kevin Robert Perry designed for the city of Portland. One of the most exciting things occurring in Urban Hydrology right now is a return to basic low-tech solutions that not only cost little to maintain, but beautify the area’s they serve.
The NE Siskiyou Green Street is a project that is so simple in its basic premise that the benefits become self evident as soon as you look at it. It is one of those visionary ideas that took a landscape architect willing to think outside of the high-tech box to come up with.
The premise, allow Mother Nature to do the work she is already equipped to do by bringing her back into the equation. The NE Siskiyou Green Street project removed a portion of the street’s parking zone and converted it into a pair of landscaped curb extensions. Curb extensions are ideally suited for residential applications on their own as they act as traffic calming devises and thereby increase pedestrian safety. In this case they go one step further. The curb extensions on this street also capture, cleanse and infiltrate storm water runoff.
The project basically removes NE Siskiyou St. from the city’s storm/sewer system and manages the runoff locally. Water flows down the approximately 10,000 square feet of of NE Siskiyou Street and the driveways leading off of it until it reaches the seven foot wide curb extensions. The curb extensions have an eighteen inch cut that allows the water to enter the curb extension. The landscaped area within is designed to hold up to seven inches of water, allowing the landscaped area to infiltrate the water. The water is slowed and contained using a series of rock berms that facilitate the curb extensions three inches per hour infiltration rate. In the event of a very intense storm there is a curb cut at the lower end of the planting that allows excess water to flow through and enter the city’s established storm/sewer system.
The extensions are planted with a series of native plants including Oregon grape, sword fern, and grooved rush. The grooved rush does the majority of the storm water management. The upright growth structure of the grooved rush slows down water flow and captures pollutants while its deep penetrating roots work well for water absorption.
Another advantage to this type of local solution is that it keeps the rain where nature put it. Part of the issue with the way that cities currently deal with storm water runoff is that the water is removed from where it fell and away from the local plants that could use it. This system restores water that had been shunted away, back to the local environment.
The most impressive thing about this system is that it manages nearly all of NE Siskiyou’s annual street runoff, estimated at 225,000 gallons, and deals with it locally. Taking the equivalent load off of the old city system. It gets even better, this low impact solution was built for less then $20,000