The air is damp and metallic, echoing with the low hum of machinery. Beneath northeast D.C., a tunnel-boring machine the length of a football field grinds through clay and rock, carving a path wide enough for a Metro car.

Workers in orange vests and hard hats move in and out of its shadow, radios crackling over the rumble, as concrete liner segments swing into place like pieces of a colossal jigsaw.

This is the Northeast Boundary Tunnel (NEBT)—a linchpin in the chain of hidden systems that keep the capital from flooding, stalling or going dark. Placed into service on September 15, 2023—more than 18 months ahead of its March 23, 2025, federal deadline—it joins a network of deep-bore stormwater tunnels that most residents will never see but rely on every day.

Stormwater: The Clean Rivers Project

Some of D.C.’s sewer lines are still stuck in the 1800s—stormwater and sewage crammed into the same pipes. When heavy rain hits, the system chokes. Overflow dumps into the Potomac and Anacostia rivers, and in neighborhoods like Bloomingdale and Le Droit Park, it backs straight into basements.

The fix is as massive as the problem: DC Water’s Clean Rivers Project—more than 18 miles of tunnels, deeper than building foundations and big enough for a Metro train. When finished in 2030, it’s designed to cut combined-sewer overflows by 96% citywide and 98% in the Anacostia watershed, nearly eliminating flooding in the worst-hit spots.

The NEBT runs 5.1 miles, 23 feet across and can hold about 90 million gallons, part of the network’s total roughly 157-million-gallon storage capacity. Along with the Anacostia River Tunnel, the system stores around 190 million gallons and has already slashed Anacostia overflows in line with its 98% target. From March 20, 2018, through January 31, 2024, it captured more than 16 billion gallons of combined sewage and removed more than 10,000 tons of trash and debris from local waterways.

Getting there meant more than digging. Before the cutterhead touched soil, crews had to relocate water, sewer, gas, electric and communications lines—dozens of agencies, competing standards and work where one wrong cut could blow up the schedule. Shared digital platforms kept everyone on the same drawings in real time.

Other segments, like the First Street Tunnel, pushed technique to the edge—ground-freezing excavation to cut noise and vibration in tight neighborhoods, plus real-time monitoring to protect people living just feet above.

Transit: Metro’s Arteries

Moving millions of gallons of stormwater is one thing. Moving hundreds of thousands of people every day is another.

Under the city, more than 50 miles of Metro tunnels carry weekday riders through cut-and-cover trenches and deep-bored tubes under bedrock.

Right now, the Washington Metropolitan Area Transit Authority (WMATA) is in the thick of its biggest underground upgrade in years. In June 2025, Automatic Train Operation (ATO) came back online for parts of the Blue, Orange and Silver Lines—trains hitting 65–75 mph on outer runs, cutting travel times and holding tighter schedules. By year’s end, the plan is to replace aging signals, boost tunnel lighting, run new fiber and radio networks and make the system faster without compromising safety.

Above ground, the Bladensburg Bus Garage is getting a sustainability-first rebuild: compressed natural gas fueling, solar panels, rainwater harvesting and 31 maintenance bays. LEED Platinum is the target, but the real win is a tougher, cleaner transit backbone without touching a single route.

Capitol Power Plant and Secure Corridors

If water and people flow beneath D.C., so does power—and in this city, that means politics.

Built in 1908, the Capitol Power Plant was originally there to feed electricity and steam to the U.S. Capitol. Today, five walkable utility tunnels run steam, chilled water, fiber and phone lines to 23 federal buildings, including the Supreme Court and Library of Congress. Secure pedestrian corridors let lawmakers and staff move between offices without braving traffic or weather—part convenience, part security, all about keeping government on its feet.

Green Roofs and Wastewater Heat

Not every hidden system is buried deep. At DC Water’s headquarters, a wastewater thermal recovery system pulls heat from sewage to warm or cool the building. Up top, a green roof cuts stormwater runoff before it hits the sewer system. The LEED Platinum-certified facility proves some of the smartest infrastructure hides in plain sight.

The Coordination Thread

Whether it’s a stormwater tunnel, train control or secure corridor, none of it works if the teams aren’t locked in from day one.

The Clean Rivers Project—a 20-year, multibillion-dollar infrastructure program featuring more than 18 miles of deep sewer tunnels and green infrastructure—is helping DC Water reduce combined sewer overflows and improve regional water quality. Utilities like WMATA are also tapping advanced signaling technology: its renewed ATC system—including ATP, ATS and ATO—enables far more precise coordination and scheduling of train movements.

Meanwhile, water-sector professionals increasingly rely on digital-twin modeling—fed by real-time sensor data—to run simulations and “what-if” scenarios before executing changes in the field.

When that coordination fails, the fallout isn’t a line item; it’s flooded basements, stalled trains and offices gone dark.

Why It Matters

You don’t get a ribbon-cutting for a sewer tunnel. No applause for a signal upgrade. But every dry street after a storm, on-time train and steady degree of heat in a Senate office comes from the same place: careful planning, steady investment and crews who do the job right.

With harder rains, hotter summers and heavier demand pressing on transit and utilities, these hidden systems aren’t extras.

They’re the difference between a capital that runs—and one that fails.