What Philadelphia is Not Doing
Portland, Oregon is a great proponent of sustainable development and stormwater management through their
advancements with green streets and eco-districts. But, they have also decided to invest a LOT of time and money in the grey infrastructure side of stormwater management – something Philadelphia is trying to avoid having to do through a 25-year plan and $1.5 billion investment to integrate 9, 564 “Greened Acres” in to Philadelphia’s landscape to manage stormwater through the natural processes of infiltration, evapo-transpiration.
Philadelphia has established the “Greened Acre” metric as one acre within the City’s combined sewer system area that manages [at least] the first inch of runoff through green infrastructure with a focus on infiltration. The area measured includes both the stormwater facility itself and all lands that drain to the facility.
Portland and Philadelphia are just two of over 700 cities in the United States that have combined sewer systems. In combined sewer systems, rain water and waste water are funneled into the same pipe. In dry weather, the combined waters flow directly to the local water pollution control plant. However, in wet weather this toxic mixture cannot be contained by the combined sewer system and the excess is piped directly into the local water body. Combined sewer overflows (CSOs) from any of Philadelphia’s 164 CSO outfalls can cause massive environmental problems such as erosion and water pollution.
Philadelphia’s plan should be able to eliminate combined sewer overflows with green stormwater infrastructure (check out “My Ten Favorite SMPs” for a list of green stormwater management practices). On the other hand, Portland has built a “Big Pipe” to eliminate 95% of CSO events. How does this compare financially? Well, the Big Pipe which is 22 feet in diameter and six miles long, took 6 years to build and cost $430 million, PLUS $12 million for the tunnel boring machine itself (all of which went to a company in Germany…). The construction of this size pipe in Philadelphia would cause years and years of crippling disruption to the City’s transportation and utility infrastructures while thousands of smaller-scale projects over 25 years will produce less disruption and provide more benefits.
What are the other benefits of Portland’s Big Pipe? None.
What are the other benefits of Philadelphia’s green approach? Beautification of the City, removal of CO2, decrease the heat island impact, decrease vandalism and crime, provide green spaces for communities to be proud of, recharge the groundwater table, employ residents in green jobs opportunities, encourage residents to become involved with other green practices such as energy conservation and recycling.
Portland’s Tunnel Boring Machine: http://www.portlandonline.com/bes/index.cfm?a=277348&c=31030
More info on Portland and Philadelphia’s strategies: http://www.governing.com/topics/energy-env/New-Strategies-Controlling-Stormwater-Overflows.html
More info on Philadelphia’s Green City, Clean Waters plan: http://phillywatersheds.org/what_were_doing/documents_and_data/cso_long_term_control_plan