Last week, the Economist in an articled titled “Trees grow in Brooklyn” reported on U.S. cities implementing green infrastructure strategies to address the pollution of their waterways from storm water runoff. The article focused primarily on New York City and Philadelphia.
According to the article nearly 27 billion gallons of untreated water overflows into the New York harbor each year. NYC’s recently released green infrastructure plan seeks to address run-off from 10% of the impervious surfaces in the City with green infrastructure storm water strategies that range from rain barrels to pervious pavements to green roofs.
The plan estimates that on average the cost per gallon of Combined Sewer Overflow (CSO) avoided ranges between $1 to $2 per gallon. In addition, the City calculates that over a twenty-year period, it will receive between $139 million and $418 million in additional triple-bottom line benefits (i.e. energy savings, increase in property values, health) from the green infrastructure.
While NYC’s strategy is also employing grey infrastructure, they see the combination of the two costing less than a grey only approach. The cost of the green-grey strategy is approximately $5.3 billion of which $2.4 billion makes up the cost of the green infrastructure. This is $1.5 billion less than the grey only solution.
Chris Strickland, a deputy commissioner with the New York’s Department of Environmental Protection sums it up in the article saying that this (green infrastructure plan) is a way of achieving more than one thing with tax dollars.