NYC to curb water runoff with blue and green roofs

NYC is trying to be more efficient with their water. Storms are sending rainwater into sewers which is causing waterways to overflow with sewage. Planting blue roofs would help save water as well as prevent too much water from flowing into sewers. These blue roofs would be roofs on buildings covered in a type of grass or ivy. Using this way to become more "green", would end up saving NYC over $2.4 billion in just over 20 years! I think its a great idea and a very creative way to store and save our resources.