Deep under the streets of New York City, in a massive three-dimensional tangle, are the city's critical organs: a water system, subways, trains, tunnels, sewers, drains, and electricity and cable cables. It's a huge network of pipes and pumps that keeps New York City alive and thriving. Some people may know that there are also oil reservoirs under New York City, but they're not usually thought of as part of the city's vital infrastructure. However, oil does play a role in modern day New York because it is used in gasoline and other products. If these oil reserves were to leak or spill into the city's waterways, it would be very dangerous for humans and animals alike. New York City is built on top of many layers of old garbage dumps and other polluted landfills. Underneath all that waste is hard bedrock that serves as an excellent barrier against contamination from above. But even with this protection, certain areas of the city have been affected by toxic chemicals from above that have seeped down through the rock into the groundwater supply. New York City has always relied on fresh water supplies brought in by tunnels from upstate New York and Pennsylvania. Once below New York City, these waters flow through canals into man-made lakes where they are treated before being released back into the surrounding area or returned directly to the Hudson River.