Stormwater Runoff

Stormwater run-off is often the leading cause of water pollution in urban areas. When built, about two-thirds of the Naito property will be covered with the impermeable surfaces of the large parking lot and buildings. When rainwater falls on paved surfaces, it doesn’t soak into the soil but instead picks up oil, metals and chemicals that are carried wherever the water goes—in this case, into the boat basin. Contaminated stormwater is a real concern in an enclosed bay like the basin with little flow. There is ample scientific data that poor stormwater management degrades fish habitat. On a more human level, those of us who use the basin for swimming would probably not like to emerge from the water with a thin sheen of oil and grease introduced to the basin via runoff from the Naito’s parking lot.

Water managers are realizing that if we design our communities to act more like natural systems, we can capture rain where it falls. A 1-inch rainstorm falling on a 1-acre meadow, for instance, would typically produce enough runoff to fill 28 bathtubs. The same storm falling on a 1-acre paved parking lot would produce 448 bathtubs of runoff—approximately 16 times as much.

We don’t expect the Naito property to be a grassy meadow, but they can create a similar effect by using green infrastructure, things like bio-swales to collect rainwater and green medians in the parking lot planted with trees. This kind of stormwater treatment has become the norm in Portland.

There are several ways that stormwater can be treated to make it safer for fish and humans. The Naitos have expressed a willingness to install a “salmon safe” system. We think there is a good solution for handling stormwater that both parties can agree on and which would provide a model for stormwater management at the waterfront generally.

Stormwater issues 101: