6 hours ago
- New York City's underground infrastructure includes water lines, electrical grids, steam pipes, natural gas lines, telecommunications, sewers, subways, and deep water tunnels.
- Water mains run at high pressure to prevent contamination and are laid in grids for redundancy; NYC's water is gravity-fed from upstate and unfiltered, with over 900 sampling stations for quality testing.
- About 85% of electrical lines are underground, with a 'secondary network' system of 70 networks using underground transformers and redundant feeders for high reliability, though this contributes to higher electricity costs.
- NYC's district heating network is the world's largest, delivering steam for heating and other uses, facing challenges like thermal expansion and condensation managed with expansion loops and steam traps.
- Telecommunications lines run through standardized underground ducts managed by Empire City Subway, and the city is developing a 3D database to map the often unrecorded 'spaghetti' of old utilities.
- Combined sewer overflows occur during rain due to historic system design; NYC is addressing this with rain gardens, retention tanks, and separate storm sewers, while working under a consent decree.
- The subway system primarily uses cut-and-cover tunnels, with deeper sections bored by tunnel boring machines; deep water tunnels like Tunnel 3 (650 ft deep) bring fresh water from upstate and are still under construction.