The well-respected San Francisco Planning & Urban Research Association has come out with a comprehensive and multi-faceted new study on stormwater. SPUR promotes the fiscal and ecological benefits of channeling runoff away from municipal wastewater treatment systems.
A dry, wonky topic? Sure, but the SPUR idea could lead to a greener, more livable city, at the same time saving millions of dollars in capital expenditures for looming upgrades of overburdened sewage systems.
The SPUR plan is specifically directed at San Francisco. However, the same overall policy is comparably relevant for every city fronting San Francisco Bay and coping with an increased population served by an aging water dispersal infrastructure.
Right now, these cities face an all-too-common urban problem: When high rates of storm runoff enter the wastewater treatment system and overload its purification capacity, filthy water overflows into the Bay or floods the structures on low-lying streets.
The Bay Area has been facing this significant environmental and public health problem ever more frequently. Population is growing, infrastructure is reaching the end of its useful life and extra-strong storms appear to be arriving more often. Dedicated street drainage pipelines are no longer sufficient to handle the flow; creeks on the Peninsula regularly overflow their banks.
Many cities in the area have been forced to waste hard-gained budget resources on state fines levied for sewage flowing into the Bay. The standard engineering solution offered for stopping these damaging floods is to build additional wastewater treatment capacity. Unfortunately, with all the pressing demands made on municipal budgets, constructing new wastewater treatment plants and runoff pipelines capable of containing the occasional large storm can be too expensive.
The SPUR study suggests a way out of this impasse: Develop ways to prevent stormwater from entering the drainage system in the first place, using a new approach that visualizes rainwater as a valuable resource for helping create a greener city.
Among the specific remedies presented, the report calls for directing funds toward planting more of an urban forest. A single tree can intercept and absorb as much as 2,400 gallons of stormwater per year. Even rain that eventually falls through the leaf canopy goes into the ground more slowly and is absorbed better by the soil. San Francisco alone has nearly 70,000 available street tree sites not yet planted.
Green roof gardens in high-density areas can be virtually self-sufficient, retaining water year-round that lowers hot summer temperatures inside the building and dramatically cuts cooling costs. The roof greenery also helps maintain cleaner air quality.
Measures such as these are long-term solutions that would not prevent street flooding overnight. But the approach seems practical and could be cheaper than building more wastewater treatment plants and drainage pipelines. Plus, there’s a delightful side-effect: a greener, less polluted Bay Area cityscape.