New York City is once again leading the way in sustainably planning for the future with forward thinking infrastructure development plans. The New York City Green Infrastructure Plan aims to reduce combined sewer overflows (CSOs) by 40 percent, while reducing energy consumption and the city's carbon footprint through "green infrastructure."
At its heart, the plan is a strategy for dealing with the large amounts of water in the city's sewer systems following heavy rainstorms and the consequent CSO discharge of raw sewage, industrial waste, and polluted run-off into the city's waterways. CSOs are set up to prevent sewage from backing up in an overloaded system by bypassing the treatment plant and discharging directly into overflow areas, which are usually nearby rivers, streams, lakes and shores (here is a map of the main locations of the more than 400 outlet pipes around NYC from a city water quality report [PDF]). A traditional approach to reducing CSOs would be investment in 'gray' infrastructure, such as by building more pipes, storage tanks and treatment plants, which increase the capacity of the sewage system to collect and treat water. New York is investing in a small amount of this, but with the Green Infrastructure Plan the aim is to reduce the amount of water going into the sewers in the first place. This can be achieved by investing in green roofs, planting in public spaces, and the use of more porous surfaces for side walks and car parks, amongst other measures.
In general, green infrastructure can provide other public benefits beyond reducing CSOs and improving water quality. For example, tree planting and swales along side walks make public spaces more attractive, and green roofs provide habitat. Additionally, increased planting in the city helps to reduce the heat island effect and helps to improve air quality.
Another benefit of green infrastructure is that it can be built up incrementally over time while also taking effect immediately. Each piece of a larger green infrastructure plan can start to work as soon as they're installed and while other pieces are yet to be installed, with the overall impact of the system building over time. In contrast, gray infrastructure can only become operational once the whole system is complete, meaning that there is a significant time lag when compared with the green option.
Using green infrastructure to control run-off and thereby reduce the storm water going into sewers is just one part of NYC's Green Infrastructure Plan. The other way to reduce the amount of waste water entering the system is through reducing water use by businesses and households throughout the city. To this end, automated meter readers are being installed and rebates are being considered for the installation of low water flow fixtures, such as shower heads and taps.
You can download and read the full plan here.
Alison Killing is an architect and urbanist based in Rotterdam, the Netherlands.
I'm very glad this type of thing is taking hold in a city as large and on the main stage as New York City. It's good to see the city taking this on and hopefully individual home owners can pick up on this as well. Ideally, the more momentum this type of thing can gain, the better it will be for everyone...eventually everyone in the country assuming other cities take note.
Much of New York City's momentum around green infrastrucutre comes from the longstanding work of Majora Carter and credit shoudl be given where credit is due! In order for environmental sustainability to be truly sustainable it needs to be aimed at a diversity of city users and residents. Contracts that provide extensive support for green jobs training for underemployed populations is a key part of a long-term green investment plan.