Green Roof – Blue Roof

The environmental community is rallying behind efforts to reduce combined sewer overflow (CSO). CSO occurs in New York City when rainfall overwhelms sewage treatment plants resulting in raw sewage being dumped into the adjacent estuary. The city’s solution has been to build huge retention tanks to store the rainfall until the sewage plants can process the load. Unfortunately, retention tanks are extremely costly and the city can not afford to complete construction of the proposed tanks anytime soon.

In response to NYC’s procrastination, the environmental movement has proposed a myriad of best management practices including point of use retention and detention systems. The most popular solution is green roofs. Green roofs are simply roof top gardens that retain rain water to irrigate planting on the roof, hence retaining rainwater on the site. They have the added benefit of eliminating heat island effect, reducing CO2 and literally making the city a greener place. Green roofs are a very elegant solution when intelligently designed and maintained. The drawback is that in cash strapped properties green roofs would be the first system to be neglected. Since environmental realists do not want their solution dependent on building management, they have proposed blue roofs. The concept is quite simple; store rainfall on the roof and slowly allow it to trickle out of the building. In this manner you mitigate the effects of excessive rainfall on the sewage treatment plant.

Recently, many groups have been proposing mandating green and blue roofs. Proponents recommend that all buildings with flat roofs be required to install either a green or blue roof. I wholeheartedly encourage the proliferation of green and blue roofs. However, I oppose any efforts to mandate green or blue roofs. They are just one tool in a plumbing engineer’s toolbox to combat CSO but the toolbox also includes retention tanks, water reuse, irrigation, gray water and a myriad of other design choices. Do we really want to prohibit the installation of rooftop playgrounds and swimming pools? Do we want to find architects specifying sloped roofs solely to exempt a building from green roof requirements? I propose that we require any building applying for sewer permits (SD1&2) to demonstrate that they will retain enough water on site so as to eliminate local CSO occurrences. The DEP should specify retention/detention parameters to accommodate the local infrastructures. Some neighborhoods may not require any retention while other locations with poor sewer infrastructure may have to retain a large percentage of their rainfall. This customized solution might appear to be cumbersome but in reality it is similar to the current procedure used by the DEP to minimize storm water flooding. All the DEP has to do is enhance their requirements for storm water retention. With these requirements in hand, the plumbing engineer can devise an ingenious solution to meet the DEP’s parameters. After careful consideration the engineer might decide on a green roof, blue roof or devise a new solution and term it a yellow roof. The field of study is too new for the city to mandate a specific solution that applies across the board. The DEP should mandate specific requirements and allow the plumbing engineers to do their job.

New Stormwater Control Techniques Planned

On November 8, City Council Member James Gennaro will be joined by representatives of the Storm Waters Infrastructure Matters (SWIM) environmental coalition to announce the introduction of three stormwater management bills aimed at reducing the amount of raw sewage that flows into New York Harbor.

“The development and implementation of a Sustainable Stormwater Management Plan is essential to reducing stormwater runoff into the City’s sewers, which directly results in massive amounts of pollutants and pathogens being dumped into our waterways due to combined sewer overflows,” Councilman Gennaro said. “Introducing ‘green’ stormwater control techniques, such as maximizing the use of parks and other green spaces to capture and store water, building green roofs, and protecting wetlands, will not only take the strain off our over-taxed sewer system, it can also reduce flooding, which is a big deal in Queens, where flooding has repeatedly destroyed people’s homes and businesses. This progressive legislation will improve the City’s water quality, allowing for expanded recreational uses of our water; add new green spaces; mitigate flooding; and add capacity to a sewer system that, frankly, is in dire need of help.”

Water Watch NYC thanks SWIM for their press release about the press conference and hearing. More info can be found at the SWIM website here.

Water Watch NYC also wishes to commend Council Member Gennaro for his efforts to build a better economic and environmental stormwater management system for NYC’s home and business owners.

All are encouraged to attend tomorrow’s hearing, which begins at 1:00 pm, and to the press conference on the steps of City Hall which will take place prior to the meeting.