Tom Heap visits New York to find out how the city is cleaning up its dirty waterways and bringing back oysters to the harbour.
New York is highly populated. The 8 and a half million inhabitants of the five boroughs of Manhattan, Queens, Brooklyn, The Bronx and Staten Island use a lot of water and create a lot of waste. As a result the myriad of waterways, streams and creeks that all flow around the city, the network of 'sewersheds' that meander below the sidewalks, not to mention the vast rivers: the Hudson and the East River have all, over several centuries become increasingly dirty, polluted with litter, oil and worst of all raw sewage. Each time rainfall exceeds around half an inch, the aged Combined Sewage Overflow systems discharge into the rivers.
But in light of 'Super Storm' events such as Sandy and Irene, New York has begun to tackle the problem.
The city's Department of Environmental Protection has embarked on on a 'Green Infrastructure Plan'. Over the next 15 or so years