On the surface, the District is a sleek new city, full of modern office developments with large windows that gleam under the sun. But underground the city is a museum, an antiquated sewer system that Abraham Lincoln and Robert E. Lee might recognize.

City, state and federal officials plan to gather Tuesday at the Blue Plains Advanced Wastewater Treatment Plant to break ground on a $1.4 billion, three-year effort to reduce pollution. And in the fall, they plan to start work on a $2.6 billion effort to reduce sewage overflows by updating sewers built before the Civil War.

Tuesday’s groundbreaking will begin construction of a $1 billion facility to reduce nitrogen in wastewater. Nitrogen is a pollutant that helps create dead zones in the Chesapeake Bay and its tributaries by sucking up oxygen.

The next step will be installation of a $400 million thermo-hydrolysis system in which tanks pressure-cook solid waste to kill pathogens, feed the waste to bacteria that excrete methane, and use the methane to generate enough electricity to power 40 percent of Blue Plains, the world’s largest wastewater treatment plant. The process would turn sludge into a super fertilizer called a Class A biosolid.

Blue Plains is considered a state-of-the-art facility, but the underground pipes leading to it date to another century. In an effort to to end massive sewage overflows when it rains, officials at DC Water, which runs Blue Plains, plan to build a pipe as wide as a Metro tunnel about 100 feet underground from Nationals Park to the wastewater plant. Additional pipes are planned for other parts of the city over the next 14 years.

Environmentalists greeted the news with praise and concern.

“From the standpoint of keeping sewage out of these in­cred­ibly important water bodies, I say, ‘Yahoo,’ ” said Andrew Fahlund, senior vice president for conservation at American Rivers. “I’m glad we’re finally going from talking about implementation to doing it.”

But the billions of dollars being spent on underground renovations and processes that taxpayers can’t see is unsettling, Fahlund said. The money could be spent above ground on green roofs and public parks that would soak up much of the rainwater that causes the overflows, he said.

Overflows happen at 53 different places in the city, “about a third of the District,” said Carlton Ray, director of the DC Water’s Clean Rivers Project. Most of them occur downtown, including at the Capitol and the White House. In 1996, 3 billion gallons of raw sewage poured into the Potomac and Anacostia rivers and Rock Creek.

The new tunnels, about 23 feet high, will greatly reduce the overflows by diverting the sewage to a drop shaft and storing it, Ray said. A pump will send about a half-billion gallons per day to be treated before it is released into the rivers and the creek.

“In 2005, DC Water entered into a consent decree with the Environmental Protection Agency and the Department of Justice with a plan that significantly reduces the overflows . . . going into the waters,” Ray said.

The EPA also required the District and other governments in the Chesapeake watershed to take strides to reduce the bay’s “pollution diet,” mostly nitrogen from urban runoff during storms and rural phosphorous runoff from animal feed operations.

Part of Blue Plains effort is the facility that will get rid of human waste that becomes sludge by cooking it and feeding it to microbes that excrete it as methane in a system called thermo-hydrolysis and digestion.

The electricity produced by the methane could power 8,500 homes. By providing nearly half of the plant’s electricity, Blue Plains expects to save $20 million a year, according to Bailey.

The new process will eliminate half the sludge the plant currently converts into a controversial super fertilizer called a Class B biosolid, cutting the number of trucks needed to send the fertilizer to farms and saving more money.

The new Class A biosolid that will be produced is safer because it doesn’t contain pathogens that can sicken humans and animals.