02A city is one machine

The short version: The rest of this guide takes a city apart one system at a time, but none of those systems runs alone. Electricity drives the pumps, signals, trains and phone networks; water from the mains is what fire crews fight with; one shared strip of street holds nearly every pipe and cable; and a single storm can hit all of it at once. When one system fails, the failure often travels into others, from the Great Boston Fire of 1872 to the 2018 Merrimack Valley gas explosions. This section maps those connections, so each chapter after it reads as one part of a single machine.

Why can't you understand one system at a time?

Each chapter in this guide follows one network, and usually one owner. In Boston, a commission created by state law runs the local water mains, sewers and storm drains,⁴⁴ a state authority supplies the water and treats the sewage,⁴⁵ Eversource runs the poles and wires,⁴⁶ and the city's Transportation Department runs most traffic signals from City Hall.⁴⁷

The networks ignore those boundaries. A city is a set of systems that lean on each other: water needs electricity, firefighting needs water, the subway needs electricity and pumps, and almost everything needs a phone or data line to be watched and dispatched. We call this interdependency, and it is the main reason this guide exists. A pothole, a power cut or a cloudburst rarely stays inside its own chapter.

Electricity runs almost everything else

More of the city depends on power than on anything else.

• Water and sewage. Eversource's restoration order puts water and sewage plants among the "critical facilities" restored right after life-threatening calls and blocked roads, alongside hospitals and fire stations.⁴⁸ Sewers have needed pumps from the start: Bazalgette's London system of the 1860s had pumping stations at Abbey Mills, Deptford and Chelsea.¹⁵
• Tall buildings. Newer New York buildings increasingly pump water up from the basement instead of using a rooftop tank.⁴⁹ A gravity tank keeps flowing through a blackout until it runs dry, while a pump without backup power stops when the power does (more in Why water reaches the 40th floor).
• Traffic signals. Load switches in each cabinet turn the controller's 12-volt logic into the 120-volt AC that lights the lamps.⁵⁰
• Transit. Boston's subway lines run on 600 volts DC from 48 traction power substations, and the same network powers tunnel lighting and ventilation fans.⁵¹ New York's subway has 300 pump rooms that remove about 13 million gallons of water on a normal day.⁵²
• Telecom. Phone, cable and fiber lines hang on the same poles as the power lines,⁵³ and 5G small cells are mounted on streetlights.⁵⁴
• Heat. As of late 2025, Boston's district steam came partly from a 42-megawatt electric boiler,⁵⁵ and ISO New England expects winter peak demand to grow about 2.9% a year through 2035 as buildings switch to electric heat.⁵⁶

Phones need power too. In the US, the Federal Communications Commission (FCC) adopted a rule requiring at least 24 hours of backup power for equipment inside telephone central offices and eight hours for cell sites and remote switches,⁵⁷ but the White House Office of Management and Budget rejected it as too burdensome in 2008, and the FCC did not contest the decision, so the rule did not take effect.⁵⁸ In the August 2003 Northeast blackout, backup generators at some cell sites ran out of fuel, and Verizon's emergency generators failed several times, taking 911 out of service for about 15 minutes at a time.⁵⁹

The flow also runs the other way: Boston burns most of its residential trash at waste-to-energy plants,⁶⁰ and Copenhagen's CopenHill plant supplies power and heat for 150,000 homes.⁶¹

Water is the fire department's supply

A serious fire is fought with water from the city's mains. The Great Boston Fire of 1872 is the early lesson: the causes on record include weak water pressure and too few hydrants, with hose couplings that did not match.²¹

Each hydrant hangs off the street main on its own pipe, called the hydrant branch or lateral, with a valve that lets the water utility shut off that hydrant alone.⁶² The US Fire Administration's 2008 guide puts the minimum water need of most homes at 500 gallons per minute (about 1,900 liters per minute), while commercial properties can need up to 12,000 gallons per minute for four hours.⁶³ In Boston, the Boston Water and Sewer Commission runs fire flow tests at hydrants for engineers, developers and sprinkler designers, charging $660 per test as of 2026.⁶⁴

Tall buildings carry the link indoors. A standpipe feeds hose valves on each floor, and fire engines pump water into it through a Siamese connection on the outside wall.⁶⁵ In New York's rooftop tanks, the bottom of the tank is reserved for emergencies.⁶⁶

So a water main failure is also a firefighting problem. In May 2010, a main break showed that the tunnels carrying about 60% of metro Boston's daily water had no backup, which is why the Massachusetts Water Resources Authority (MWRA) is building two new deep tunnels.⁶⁷ Redundancy in the water system is also fire protection.

The street is a shared corridor

Under a Boston block can sit a water main and a sewer belonging to the Boston Water and Sewer Commission, which runs about 1,015 miles (1,630 km) of water main and 1,435 miles (2,310 km) of sewer and storm drain.⁴⁴ Gas, electric, telecom and, downtown, steam lines share the ground, each owned by someone else.

Every owner digs, and every dig risks someone else's line. In Massachusetts, anyone excavating must premark the area in white, then notify Dig Safe, reachable at 811, at least 72 business hours ahead, so the utilities can come and mark their lines.⁶⁸ Cambridge bars digging in a street resurfaced within five years except in an emergency or with approval.⁶⁹ (See Roads, bridges, tunnels and the hole in your street.)

The worst Massachusetts case of one buried job disturbing another came during work meant to improve safety. On September 13, 2018, a Columbia Gas crew replacing a cast-iron main abandoned the old pipe while the sensing lines for the area's pressure regulators were still attached.⁷⁰ The regulators read falling pressure and opened fully, sending high-pressure gas into homes.⁷¹ Fires and explosions damaged 131 structures, one person was killed, and 10,894 customers lost gas.⁷⁰ In our reading, it was at root a records failure, a matter of knowing what is connected to what.

What's under one downtown street?

A walk from the sidewalk down. The order and depth of the buried layers is our explanation; real streets vary, and only the owners' maps show what is where.

• On the sidewalk. A streetlight, one of about 71,000 the city owns,⁷² perhaps carrying a small cell.⁵⁴ A red fire alarm box, one of about 1,250.⁷³ A signal cabinet holding the controller.⁷⁴ A Siamese connection on a building wall.⁶⁵ Perhaps white paint and colored marks from a Dig Safe ticket.⁶⁸
• The pavement. A surface layer on crushed rock on native soil, the subgrade.⁷⁵
• Below the pavement. Mostly wire. Boston's streetlights alone use about 4 million feet of conduit and 32,000 pull boxes.⁷⁶ Downtown power runs through underground networks,⁴⁶ with transformers in vaults and a network protector that opens if power flows backward into a dead feeder.⁷⁷ The fire alarm boxes run on their own circuits, independent of the telephone and electric lines.⁷⁸
• Pipes. Gas (Massachusetts still had 4,049 miles of leak-prone cast-iron and bare-steel gas pipe in 2025),⁷⁹ district steam (about 25 miles of it in Boston and Cambridge),⁵⁵ water and sewer.⁴⁴ Sewers tend to sit lowest because they run downhill by gravity.
• Tunnels. Under parts of downtown, the subway. The 1897 Tremont Street tunnel was built cut-and-cover: a trench down the street, a box in it, a roof over it.⁸⁰
• Deep rock. MWRA's planned Northern and Southern water tunnels will run 200 to 450 feet (60 to 140 m) down.⁶⁷

Storms hit every system at once

• Rain. In combined sewers, heavy rain makes the pipes overflow untreated into rivers and harbors.⁸¹ New York's subway pumps remove about double their normal volume on a heavy-rain day.⁵²
• Wind and ice. Downed lines set off the restoration order: safety calls, blocked roads, critical facilities, the big lines, then single homes.⁴⁸
• Snow. Boston tows cars off main roads in a snow emergency so plows can work,⁸² and one season's update counted more than 74,862 tons of salt.⁸³ Salt then reaches the power system: 68% of Con Edison's 2014 manhole events came in January and February, when most road salt goes down.⁸⁴ Meltwater in cracked pavement freezes and leaves the voids that become spring potholes.⁷⁵
• Heat and sea. On June 24, 2025, New England's grid hit its highest peak in over a decade, with reserves short for more than three hours.⁸⁵ Climate Ready Boston found today's 1% annual-chance waterfront flood becoming a 10% chance after mid-century.⁴²

Data and telecom tie it together

Boston's Traffic Management Center had 699 of the city's almost 900 signals on its central system in 2020.⁴⁷ Columbia Gas's 2018 high-pressure alarms arrived at a monitoring center in Columbus, Ohio.⁸⁶ Eversource is installing smart meters and a distribution management system that show it where power is flowing.⁴⁶

Water and sewer utilities do the same with SCADA (supervisory control and data acquisition): sensors at pump stations and along the pipe network send readings in real time over a wide-area network to a primary control station, and controllers at treatment plants run the process automatically.³⁸ Those screens can be a target. In 2024, pro-Russia hacktivists reached internet-exposed control screens at water systems, pushed pumps and blowers past their normal limits, and locked operators out, forcing some utilities back to manual operation, according to the EPA and CISA.⁸⁷

The public sees the data layer too. Transit apps read GTFS schedules and live feeds, a real-time format the MBTA helped develop with Google.⁸⁸ 311 apps send a photo and GPS location to the city.⁸⁹ Networks swap internet traffic at the Boston Internet Exchange at One Summer Street.⁹⁰ (See 311, the wires under the street, and city data and From fire alarm boxes to 911.)

When one failure becomes several

• 1872, Boston. Locked alarm boxes, weak water pressure and mismatched hydrant couplings turned one fire into 776 burned buildings.²¹
• 2003, Northeast US and Ontario. On August 14, a blackout hit about 55 million people. In Cleveland, water service stopped when electric pumps lost power, and 4 million customers of Detroit's water system were told to boil water until August 18. In New York, more than 600 subway and commuter rail cars were trapped between stations; cell networks overloaded and some cell sites went dark when their power failed.⁵⁹
• 2005, New York. On the first day of a transit strike, NYC311 took a record 240,000 calls.⁹¹
• June 2024, Boston. During a 911 outage, the police commissioner told residents to use the street fire alarm boxes.⁷³
• December 2024, Boston. The day the MBTA cleared its last slow zone, a cracked rail near Wollaston put riders on shuttle buses; the governor said slow zones had cost "nearly a million dollars every day in GDP."⁹²
• Any day. A signal that loses its link to the control room keeps running, "out of sync with the rest of the signals in that corridor."⁴⁷

In Boston

Follow a glass of tap water: it leaves a state authority's tunnels, crosses into the commission's mains at one of 27 metered points,⁴⁴ and drains to MWRA's Deer Island plant.⁴⁵ Downtown, the power arrives underground⁴⁶ and the heat often as steam,⁹⁷ while the alarm boxes keep a wired network apart from the phone system.⁷⁸ Because the boxes do not share the phone network, they can still work when it fails; during the June 2024 911 outage, the police commissioner told residents to use them.⁷³

How it changed

Nobody planned the connections as a whole. Cities added a network roughly every decade: gas light in London from 1807, Edison's central power station in 1882, electric streetcars in Richmond in 1888.²²²⁵²⁶ One layer created the next. Richmond helped persuade Boston to electrify,²⁶ electric cars clogged downtown, and Boston dug the first US subway in 1897.² Each network went into the same streets as the last.

What's changing now (2026)

• More runs on the grid. Heat pumps push winter peaks up,⁵⁶ Boston's steam system is adding electric boilers and a river heat pump,⁵⁵ and regulators are asking whether every old gas main should be replaced.⁷⁹
• Signals that talk to cars. USDOT aims for vehicle-to-everything radios at 25% of signalized intersections in the 75 largest metros by 2028.⁹⁸
• 911 on internet protocol. In the US, FCC rules move emergency calls onto IP networks that carry text, photos and location.⁹⁹
• Shared flood risk. Many of the systems in the table share the same low-lying ground. Boston's planning watches low spots such as the land around Moakley Park and I-93, where water would enter and spread inland (see How cities are adapting to a changing climate).¹⁰⁰

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