The idea of subterranean Philadelphia captures the imagination. Walking down Broad Street, the roar of a passing subway rumbles up from the grate underfoot and invites questions: What’s down there? Where does it go? Who built it all? Why? How?

If there is a demogorgon lurking in this sprawling upside down world beneath Philadelphia’s streets, it lives in the combined sewers. For the uninitiated, these are 19-century engineering works that entombed many of the city’s creeks and streams, turning them instead into sewers, carrying away both sewage and stormwater. They’re now a major, and majorly expensive, problem for the city. The Philadelphia Water Department (PWD) is spending billions to try and rectify the fact that these sewers end up dumping billions of gallons of sewage-laden water into the city’s two rivers each year. How best to solve the puzzle is a bit of a controversial topic. Yet, PWD historical consultant Adam Levine is keeping his eye on the bigger picture.

In “Lost Creeks of Philadelphia: Burying the Streams, Building the City,” a special exhibition at the Athenaeum of Philadelphia, Levine and collaborating photographer Joseph Elliott place the city’s combined sewer system within a greater context, exploring the why and the how of their creation, while also examining the role they played in shaping the above-ground landscape of the city.

Indeed, the scale of their impact is vast. Combined sewers comprise the majority of the city’s 3,000 miles of sewage pipes, with some reaching 20 feet in diameter and running for miles. In the two centuries between the 1760s and 1960s, Levine noted, 73 percent of the city’s streams and creeks were buried, leaving only 118 linear miles of exposed waterways today out of an original 283 miles. That contributed much to the flattening, and graying, of the city’s once surprisingly complex landscape.

Levine, who also manages the resource-rich WaterHistoryPHL.org, sat down with me to discuss his exhibit, now open to the public through May 16, and how his decades of research has shaped his perspective on combined sewers.

Kyle Bagenstose (KB): I recently read that combined sewers are actually what got you into the PWD historian role back in the 1990s. Tell me about that and why they caught your fascination.

Adam Levine (AL): I was taking care of a community garden in West Philadelphia in the 1980s, and I was told there was a creek (Mill Creek) that had undermined the two houses on either side of the vacant lot that the garden was on. I considered myself an environmentalist and couldn’t understand why anyone would want to bury a stream. Nine years later, I was freelance writing for City Paper and suggested a story on Mill Creek, and the editor said, why not a story on the whole combined sewer system?

So, I contacted the water department, and they took me down into a sewer. The article was not like most articles about infrastructure these days, which are all, you know, saying how bad it is and how everything is falling apart. I was impressed by the idea that the water department was able to manage 3,000 miles of sewers. The [PWD’s] Office of Watersheds had just formed, and they wanted to know more about the history, so they hired me to start doing research. I’ve now been consulting since 1998.

KB: Of all the City agencies and institutions that could probably use a historian, PWD is an interesting one to actually have one. What do you think the value is?

AL: You know the water department is 225 years old. We started delivering water in 1801. We need to keep records because we have infrastructure that is very old that we need to keep track of. A lot of those records have now been digitized, and engineers are primarily focused on keeping the drinking water flowing and safe and properly treating the waste of the city. They don’t necessarily need a historian.

But I think it’s good for morale. Everybody likes feeling like they’re part of something bigger than themselves, and there is a long history here. It’s also been a really good way to engage neighborhoods where we’re doing big projects. To give them some idea that there is a larger vision that not only goes into the future, but stretches back 200 years. It’s part of a continuum.

KB: Let’s talk about the Athenaeum exhibit. Tell our readers how it came about and what they’ll see if they go there.

AL: The exhibit was really supposed to coincide with the release of my upcoming book with Joe Elliott, with a working title of The Lost Landscapes of Philadelphia. But as it became clear it was not going to happen as soon as we thought, we figured an exhibition was a way to jumpstart the process. The show covers a piece of the book on combined sewers, which hasn’t really had a big exhibit before.

What we try to do is take people through a history of their creation. We start with pictures showing the landscape of the city as it was. Then, there are watercolors that show some of the changes in the landscape as the city was being leveled out for development. We have items from the Historical Society of Pennsylvania, the Penn Museum, and from the water department’s own collection. There is artwork, drawings, watercolors, lithographs, and plans showing really amazing draftsmanship from the 19th century. Joe’s original photography. We also have artifacts–drafting tools, some things I dug up in an excavation of a filled area.

KB: I understand you’re a sucker for the draftsmanship. Tell us about that.

AL: Personally, I can’t even draw a stick figure. So, to see these drawings, the detail is just amazing. Sure, they’re just drawing sewers to carry the waste of the city. But they delineated every brick, every stone. I’m curious how they fixed their mistakes, because they can’t have been perfect. But they’re not all blotchy, you can’t tell where they’ve erased. Maybe they were just that careful.

KB: Let’s talk about the landscape. There is a geologic thing happening in Philadelphia, where you have a flat coastal plain in the old city and then piedmont to the west and north. But looking at some of the old topography maps, it’s clear that large parts of the city look much different now than they used to. Tell us what roles combined sewers played in transforming the landscape.

AL: The building of the city, period, involved a lot of cutting and filling. Cutting down high ground, filling in low ground. Forget sewers, just to get it so the streets would drain properly. [Engineers] also wanted a sort of leveling out. But we do still have elevation changes in Philadelphia: zero at the river, to about 250 feet at the Pennypack and West Philly, up to 400 in Chestnut Hill. They also didn’t level out every valley.

What’s missing is about 150 miles of streams. When you look at the historic streams map and compare it to what’s on the surface now, it’s shocking. Shocking that they had the hubris to do that, but also sort of awe-inspiring, just to think of the amount of work that was involved, especially since a lot was done by manual labor.

KB: Explain how combined sewers were actually built. Did they just put an archway over the stream, so there’s still a natural stream bed? Or somehow divert flow into a full pipe?

AL: The engineering is usually to build a solid pipe so that all the water is carried away. You build up the bottom first and then go section by section, diverting the creek as each section is finished. They wanted everything to be carried to where they were dumping it, whether that was to the river, or ultimately now the city’s three sewage treatment plants. If there were any springs or little tributaries to these larger creeks, they wanted to capture them, too, in smaller pipes, and create a whole sewer system.

It was variable enough that it’s hard to generalize. There are some streams–Mill Creek is one–that definitely still has a flow outside the city. It flows on the surface and when it reaches the city at Overbrook Train Station, it enters a pipe–it sort of ceases to be a creek and becomes a sewer. And at Dock Creek (in Old City), they actually walled it first, then did just put a big arch over it, so there’s no bottom to that particular sewer.

KB: Dock Creek brings up another point as one of the oldest to be buried. I thought combined sewers were made primarily to protect public health, but your research suggests they were also convenient to further real estate development. How much was it one or the other?

AL: Pollution was a reason. Dock Creek, Peggs Run (Northern Liberties), Cohocksink Creek (Kensington) were creeks flowing into the Delaware River that got badly polluted early by industry, which at the time were basically slaughterhouses and tanneries making leather. Then, as the city grew, in rural areas, creeks became the only way they knew to get sewage out of neighborhoods. So, instead of having a big open sewer going along, they figured, we’ll put it into a pipe. Why? Some of the engineers in the 19th century are not the best writers, so you have to sort of surmise their logic. When they started doing this in the 1850s, they still believed that odors were causing disease, not bacteria. So they thought it was much better to flush this out to the river.

Development was also an important part. When you have a stream meandering through a neighborhood, when you have hill and dale, you can’t really develop it on a grid, and Philadelphia is really big on the grid. So, you have to sort of level it out.

A third reason streams were put into sewers was because there’s really no other way to dig a channel that would flow by gravity. They had steam engines that could do some digging, but to dig a trench that flowed by gravity in the same way as a stream would have just been way too expensive. The city didn’t have to develop this way, but in the 19th century, engineers felt it was their duty to create as much real estate as possible to get as much tax revenue as possible. It was like a sort of micro manifest destiny.

KB: How does all of this make you think about the contemporary challenge for the PWD? I’m thinking of a line from one of the Daniel Craig’s James Bond movies: “You’re a kite dancing in a hurricane, Mr. Bond.” It’s wild to think this one City agency that’s just trying to keep the water clean has to grapple with an engineering challenge of this vintage and magnitude.

AL: The historical context is important because we [PWD] didn’t just start dealing with pollution. Until 1952 the water department wasn’t in charge of the sewer system–the Public Works Bureau of Surveys was doing sewers before a city charter change. Even before, the water department was interested in keeping pollution out of the rivers, because the rivers were the source of our drinking water, and we were killing people with that water in the 19th century.

The city from 1914 to the 1950s had a plan to collect, intercept all that sewage flowing into the rivers, and then treat it. It took until the mid-1950s before the three sewage treatment plants that we still have today were built, and we really made a huge dent in the pollution of the rivers. That was a huge step, and then the federal government finally got involved with the Clean Water Act and EPA in the 1970s to try and stem industrial pollution.

The rivers are much cleaner now, but it’s hardest to get the last little bit of pollution no matter what you’re doing. From my point of view, it’s actually a very small problem now. It’s not unimportant, don’t get me wrong. I understand the importance. Most people alive today have never experienced the horrible pollution before the 1950s. Today, we expect that when we have a body of water that we feel safe being near it.

KB: I think I can understand that perspective. The water department has long been the agency kind of tasked with confronting the sins of our past. Scientists develop germ theory, and suddenly it’s incumbent on the water department to overhaul all the engineering. Combined sewers are just another example.

AL: It’s not only the sins of the past. It’s the sins of the present. Plastics in the river, chemical spills in the water. The water department is the one responsible to try and make the final product safe.

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“Lost Creeks of Philadelphia: Burying the Streams, Building the City” is on view and open to the public through May 16. The Athenaeum of Philadelphia is free to visit and is located at 219 S. 6th Street. Adam Levine and Joseph Elliott’s book detailing the historic development of Philadelphia’s landscape is scheduled for release in fall 2027 by Temple University Press.

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