Sewer systems that convey both sanitary sewage and storm water through a single pipe are referred to as combined sewer systems (CSS). In dry weather and during light to moderate rainfall, the CSS is able to convey all flows to the wastewater treatment facility. During periods of heavy rainfall, however, the capacity of the CSS may be exceeded, often causing untreated combined sewage and storm water to back up into basements and to overflow from manholes onto surface streets. Traditionally, CSS outfalls were designed to discharge directly into receiving waters during combined sewer overflows (CSOs), increasing pollution to those waters.
Many cities have separated their sewers, but other regions are currently working to separate their combined sewers to reduce pollution, and the costs are high. King County's plan to reduce CSOs would cost a billion dollars.
An incremental and low cost step to reduce stormwater flows is to prevent the water from reaching the sewer in the first place. Green Infrastructure is an approach to using natural systems to reduce effects of urban development. The general principle is water dispersion rather than collection, and infiltration rather than retention. One great example is in Indianapolis. Stormwater planters and bioswales with native grasses run almost the entire length of the city’s Cultural Trail, a state-of-the-art bicycle and pedestrian route built over the past six years that wends its way for eight miles through the downtown streets of Indiana’s largest city.
The footage below offers a great look at how they work in action, with water filling up the trenches and then slowly draining off without ever entering the sewer system. The plantings also serve to separate bicycles from both car traffic and from pedestrians along the path. The project as a whole has added 500 trees and eight acres of green space to Indianapolis, and at the same time it's saving the city money in water treatment costs.
Stephen Kellert recently gave the keynote lecture at a symposium hosted by the Chicago Botanic Garden. During his talk, titled Biophilia, Biophilic Design, and Healing, Kellert described six biophilic design elements:
- Environmental features
- Natural shapes and forms
- Natural patterns and processes
- Light and space
- Place-based relationships
- Evolved human-nature relationships
The idea of biophilic design is that our (built) environment is critical to people's health, productivity, emotional, intellectual, and spiritual well-being. Buildings and landscape can support human health or they can be detrimental. The so-called sustainability movement (embodied most prominently by LEED standards) is more concerned with how people (through our buildings and landscape) affect nature than how nature affects people. It'd be good to shift the emphasis of our development to how we can make our built environments better for human health.
At the Chicago Botanic Garden Healthcare Garden Design course, listening to Bill Sullivan from the University of Illinois present research on how nature reduces stress, brings people together, and restores attention. In a too brief summary, access to and interaction with nature seems to positively affect an individual's ability to focus, increases social interaction, and quickly improve a host of physiological responses to stress. The results show a profound and significant positive effect on the quality and longevity of human health, a reduction of crime and undesirable behavior in high-risk populations, and relief from the symptoms of mental fatigue.