Silent and Surreal: Inside the Old Croton Aqueduct

Critical—and admittedly romantic—urban impressions of the Old Croton Aqueduct, present and past, outside and in.
One of the most important pieces of infrastructure in New York's history, the famous channel now exists as a strange, glorious ruin, nearly hidden in plain sight. Travel inside, and you submerge into a landscape that is at once alien and oddly human—urban history writ on a monumental scale.

More than thirty miles north of Midtown Manhattan, deep in New York State's Westchester County, the Sing Sing Kill cuts a jagged, rocky ravine into the steep, riverine countryside. A small creek, it winds its way through the equally small town of Ossining, its waters carving out a succession of scenic vistas as they make their way down to the Hudson River. Its name alone is arresting. A dramatic juxtaposition, it combines the anglicized name of a Native American tribe—before it was appropriated, this land belonged to the Sintsink, part of the larger Algonquin-speaking Wappinger—with kill, an old Dutch word for creek. What has truly made the name infamous, however, is the metonymic prison which still stands near the stream's mouth. Indeed, by the turn of the Twentieth Century, the idiom "to be sent up the river"—that is, to be sentenced to Sing Sing Prison—had become so ubiquitous that the village itself decided to change its name to Ossining, just to avoid the association.

Unusual nomenclature, however, is only a part of what makes the small waterway worthy of note. A larger piece comes in the form of the towering, wall-like monolith which just so happens to intersect its course right in the middle of town. Built of well-weathered stone, the structure bursts from the ravine's rocky walls and soars across the creek's valley with an unmistakable human straightness. But while the crossing is clearly a product of engineering skill, its rough-hewn stone walls and rugged, aged demeanor also grant it an air of natural permanence, as if it has stood here since time immemorial. The grand viaduct bridges the kill itself by way of an impressive masonry arch—a spot known to locals as the Double Arch, thanks to the later stone arch bridge built underneath the original, larger one. By any measure, it is an impressive sight.

Left: The Double Arch as seen in a 1907 postcard. (Courtesy of Wikipedia)
Right:The arches today, seen from above and behind.

What truly makes this spot unique, however, is what that monolith contains. As you may have already surmised from the title of this piece, the crossing carries within its walls the former channel of the Old Croton Aqueduct, one of the most important pieces of infrastructure in New York City's history. More than that, however, this viaduct also offers the only place that a visitor can actually set foot inside this remarkable (and remarkably intact) structure. For anyone with even the slightest inkling of romanticism for either urban infrastructure or urban history, the trip is a surreal and affecting experience, one well worthy of the journey upstate.

Built between 1837 and 1842, few projects outside of the Erie Canal have affected the growth of New York City as much as the Old Croton Aqueduct. Access to clean water has always presented an obstacle to healthy urban growth, and by the early Nineteenth Century, New York's polluted streams, ponds, and wells were already deeply overtaxed—not to mention a major public health disaster. The Old Croton Aqueduct and its associated Croton System aimed to solve both problems. Beginning at a new dam constructed along the Croton River in the upper reaches of then then-rural Westchester County, it would carry clean water some 41 miles, all the way down to a massive distributing reservoir at 42nd Street and Fifth Avenue in Manhattan—the site of today's New York Public Library. Even by modern standards, the scale of the project was immense. The technology behind it, however, was anything but. The channel was dug, blasted, and bricked over entirely by hand. No pumps were involved in its operation: gravity alone carried water down the channel's gentle gradient, which artfully dropped a mere 13 inches per mile. To accommodate that incline, most of the aqueduct was built immediately beneath the surface, snaking along with the topography in order to ease construction and lessen long-term disruption. This meant, however, that the massive structure was only clearly visible when geography mandated that it be—such as, for instance, when it crossed the valley of the Sing Sing Kill.

The Croton System may have been a piece of functional infrastructure, but instead of taking refuge in its underground nature, it instead sought to continually remind denizens of its presence, of its importance in their lives, and perhaps—at least in the cynical minds of some of its political architects—of those who built it in the first place.

By almost any measure the Old Croton Aqueduct was a massive success. It not only supplied generations of New Yorkers with fresh, clean, naturally filtered water, but it also freed the city to grow seemingly unbounded. The original Croton System was so successful, in fact, that it soon rendered itself inadequate. Less than fifty years after its opening, the city would find it necessary to begin construction on a much larger, supplementary aqueduct of the same name, which would travel a similar course at a much greater depth. As New York continued to grow, two further aqueducts would be built, each deeper and longer than the last. All of these followed the model established by the Old Croton Aqueduct: preserve a natural valley from development, impound clean water, and deliver it to the city by gravity alone. In a very real sense, the Old Croton Aqueduct was both the blueprint and proof of concept for urban water delivery, both in New York City and across the country. By the time it was finally taken off-line for good in 1955, having finally been fully supplanted by the New Croton, Catskill, and Delaware Aqueducts that it had inspired, the original hand-laid conduit had earned its place as a near legendary piece of American urban history.

Historical importance, however, only explains half of the channel's popular notoriety. The other half lies with the structure itself. The Old Croton Aqueduct was built during an era which often lionized major public works. The feeling was not universal, of course—Americans have had a tradition of distrust in government for far too long for that. The public works which were built, however, perhaps thanks to the bruising political fights surrounding their construction—not to mention the Nineteenth Century's predilection for narratives of conquest over nature—were often celebrated with a passion and enthusiasm that is exceedingly rare today. To that end, the Croton System as a whole was consciously designed to be appreciated, enjoyed, and even venerated. It was built with a deliberate grandeur that was most obvious in its monumental structures. Consider, for instance, Midtown's sumptuous, Egyptianate distributing reservoir or the Bronx's glorious High Bridge—a mammoth, 16-arch stone crossing which vaulted the conduit and a public promenade across the Harlem River at a height of nearly 150 feet. This magniloquent nature, however, was also present in far smaller details as well, from the decorative ventilation shafts that poked out of the ground every mile to the grand, cast-iron fountain which stood in City Hall Park, spraying clean Croton water in joyous celebration day and night. The Croton System may have been a piece of functional infrastructure, but instead of taking refuge in its underground nature, it instead sought to continually remind denizens of its presence, of its importance in their lives, and perhaps—at least in the cynical minds of some of its political architects—of those who built it in the first place. In this regard, too, the aqueduct achieved remarkable success. Even nearly one hundred and eighty years after its opening, the channel is still firmly rooted in New York City's popular historical imagination.

Left: 1898 view of the Croton Distributing Reservoir in Midtown before its demolition (Wikipedia)
Center: High Bridge as seen in a print from 1900 (Wikipedia)
Right: A rendering of the original City Hall Fountain (Source)

All of which begins to explain why the chance to step inside is such an exciting proposition—and also why doing so is such a surreal experience. Even at the height of its veneration, the actual channel itself was off-limits to all but the occasional maintenance worker, for obvious reasons. For all of its amenities and decorations, the Old Croton Aqueduct was, at its heart, a functional underground waterway, churning away twenty-four hours a day, every day of the year. What's more, as clean water became less of a marvel and more of a quotidian expectation, the channel began to slowly dissolve into the background urban landscape, becoming functionally invisible over the years long before the water stopped running. Of course, the tunnel itself didn't suddenly cease to exist after it was shut down, but for most people it might as well have: it remained mostly inaccessible, located largely out of sight and out of mind. It is only thanks to the ongoing hard work of the volunteers at the non-profit Friends of the Old Croton Aqueduct that nowadays, any person willing to brave the trip underground can visit this once-hidden landscape, and experience the strange wonder of urban infrastructure writ on a monumental scale. And for anyone with an interest in urban function or urban history, the channel's unique combination of socioeconomic importance, cultural weight, and utile invisibility makes it a hard opportunity to resist.

The viaduct, like many parts of the Croton System, is neither wholly utilitarian infrastructure nor mere artistic folly; it is both, unified into a single, integrated whole.

Our tour begins with a trip across the top of the massive stone viaduct. Much like the Bronx's High Bridge, this crossing also sports a public path on its roof. Decorated with stately cast iron lamps and attractive wrought iron railings, the walkway is a gorgeous example of an early Victorian promenade—one which very nearly predates the eponymous Queen herself. In every direction there lies a beautiful vista of town, ravine, or both, evoking an almost impossible sense of Romantic whimsy. Standing up here, the viaduct ceases being infrastructure, and instead elicits a strange, dual affect. On the one hand, the crossing almost feels as if it were a giant piece of decorative art, a graceful work of landscape architecture deliberately designed to anchor a romantic Hudson River town. At the same time, the viaduct’s obvious age and tight-knit proximity to the roads and houses around it can also make it feel like an inevitable part of the natural landscape, a geographic landmark that a town built itself around by necessity. (Of course, given its age in relation to the settlement, perhaps in some strange way it was). In any event, like many parts of the Croton System, the viaduct is neither wholly utilitarian infrastructure nor mere artistic folly; it is both, unified into a single, integrated whole.

Happily, the promenade today is just as multifunctional as when it was built, if not more so. It serves in part as a link in the Old Croton Aqueduct Trail, a state hiking route which follows the conduit's course. Perhaps more importantly, it also acts a useful piece of pedestrian infrastructure, offering a welcome, level walking path across the ravine, linking the homes on one side with Ossining's downtown on the other. Even on a cold early winter's day, the nearly one hundred and eighty year old structure is still well-used, carrying a constant stream of people to and from the town center.

The busy promenade is still well used today, and continues into downtown Ossining atop the conduit.

Reaching the far side of the viaduct, we come to the gate house, a surprisingly tall, windowless structure built from the same stone as the crossing itself. Rebuilt in 1882, its simple yet stately lines will seem oddly familiar to anyone who has spent a significant amount of time in New York City's northern suburbs: subsequent aqueducts have used similar design cues for their own access points. Across New York State's lower Hudson Valley, similar tiny buildings dot the landscape at seemingly random intervals, almost as if they were part of a series of long abandoned architectural follies. While they vary a bit in exact style and material, these structures all clearly share a lineage of purpose and design. They also carry with them a sense of mystery, even for those of us who have some idea what they are: few things are quite as intriguing as a secret hidden in plain sight. On this tour, thankfully, we are with someone who has the key to the weathered iron door, and who will swing open the hefty portal and let us venture inside. Even as part of an organized group, stepping across that threshold feels more than a bit like an exciting act of transgression.

The gate house.

Inside, the gate house contains a single large open space, perhaps fifteen feet tall, lined floor to ceiling with red brick. Although it's almost fully enclosed, a small, square vent in the ceiling is fully open to the sky, letting in just enough light and air to make the space comfortable. The chamber is surprisingly large, but it is nonetheless dominated by the massive cast-iron sluice gate that hangs from the ceiling, still ready to be lowered into the cavity below by the equally substantial hand crank mechanism that supports it. In here, visitors stand on modern steel grates mounted a few inches off the floor, free to look over the railing into the well-lit space that lies below. The arrangement almost feels like the movie set version an archaeological dig, replete with a rising warm glow beckoning you down into the depths below. Head down the equally modern metal staircase, make a turn in either direction, and almost before you know it, you find yourself fully submerged in the cool, quiet confines of history.

Inside the Old Croton Aqueduct.

One of the more immediately surreal aspects of standing inside the Old Croton Aqueduct is just how comfortable of a space it is. The conduit is neither claustrophobic nor tight; in fact, the 8 1/2 foot high channel is shockingly human-scaled, especially given that it was never intended to be inhabited by people. Roughly pentagonal in cross section, only with a rounded ceiling and floor, the aqueduct is reassuringly wider at eye level than it is at your feet. The angled walls have a remarkably organic character to them: much like the columns of a classical Greek temple, they almost seem designed to emphasize their burden, as if bowing out from the load they carry. A substantial length of steel gangway has been installed within the conduit, allowing visitors to freely explore a small section of tunnel. As with the platform above, it sits one or two inches above the curved floor, protecting both structure and visitor alike. Peering in either direction, the conduit's gradient is entirely imperceptible. In fact, a visitor suddenly transported to this place might think they were standing in nothing but a long, oddly-shaped basement hallway—albeit one which just so happens to disappear in either direction into infinite black vanishing points. Standing down here, any logical understanding of the massive scale of civil infrastructure simply evaporates, replaced by the reassuringly immediate comfort of the channel's human proportions. It can almost feel as if the quiet, lonely tunnel is calling out for you to walk all of its 41 miles—and if it weren't for a handful of portions which have been filled, a few segments repurposed as underground cable paths, and a small section put back into service to bring water to Ossining, you still could. Perhaps anticipating this, New York State has installed steel bars across the channel to prevent any would-be spelunkers. While only barely visible in the inky distance, their presence somehow only make the prospect of exploration all the more intriguing—and the reality of the tunnel's continued existence all the more surreal.

The portion of the aqueduct open to visitors has been well chosen: this one short segment demonstrates all three of the most common forms of construction used along its length. We first enter the most common form of the conduit, a section built by cut-and-cover. Here, workers dug a trench (or, less commonly, if the elevation sunk too low, built a small berm), laid the brick channel, and then covered the entire structure over again with earth. These segments are easily the most surreal thanks to their oddly warm and human ambience, perhaps a result of the fact that every surface is built from hand-laid brick. As we proceed down the tunnel and towards the city, however, we begin to enter the viaduct that we crossed earlier, and the environment changes tenor. The walls inside the crossing are lined with hydraulic cement, presumably to prevent any water from leaking into the comparably delicate stone structure below. This grey lining dissolves the clear-cut definition of the walls and ceiling, making the conduit feel far more like the tube that it actually is. As an interesting aside, this crossing differs substantially from the Bronx's High Bridge, which instead carried water through large, cast-iron pipes—one of the few places along the aqueduct where metal piping was used. Finally, turning back in the other direction and heading upstream, we enter a portion of tunnel that was drilled and blasted into the ravine's rocky hillside. Unlike the rest of the conduit, this section has no man-made ceiling. Instead, a massive rock formation seems to float impossibly in the air, as if it were somehow hung above the still-sloped brick walls. While the rock face is surprisingly flat on the whole, its jagged texture leaves no doubt where we actually are. If the cut-and-cover sections could feel like a mere basement, this tunneled portion makes it emphatically clear that we are underground, firmly nestled in a sturdy mass of geology.

Top Left: Inside the viaduct the aqueduct is lined with hydraulic cement. Top Right: Looking deep into the tunneled hillside. Bottom Left: Tunneled to cut and cover transition. Bottom Right: Drilled and blasted.

While the lack of a finished ceiling in these mined sections of tunnel may seem an inconsequential detail, it actually helps elucidate some of the Old Croton Aqueduct's workings. To begin with, the channel was never intended to be filled to its roof. Unlike some of its deep replacements, this conduit was never pressurized. Instead, water simply flowed as if in an underground river, with an air gap above the current to help ensure a smooth, non-turbulent flow. As a result, even today, some sixty-five years after the last drop of Croton water was drained away, a faint line is still visible on the walls, deeply stained into the brick, evidencing how high the water once reached. On a personal—and admittedly highly sentimental—level, this small detail, more than anything else, hammered home the strange reality of this place. Almost as if possessed by some primal urge, I felt compelled to reach out and touch the line, to somehow complete a physical connection to the structure and the water that nourished generations of New Yorkers. The bricks left my hand lightly stained with a red dust that was surprisingly difficult to rub off, almost as if the past were clamoring to be brought back up to the surface, back to life. Down inside the aqueduct, the air is still musty and damp, as in a cave. Below the grates under your feet, a tiny rivulet of water still flows down the well-trodden path, having presumably seeped in through the slightly porous walls. A handful of weeds and tiny roots grow out of, through, and along the walls, having forced their way in from the ground outside. They serve as a reminder that, like everything else, this structure too will someday return to the soil into and out of which it was built. Underground, symbolism runs deep.

Touching the wall.

Stepping back from the precipice of bad poetry, the height of the water in the aqueduct also works to explain the purpose of the structure we entered through: it was built to house and service the Ossining weir. At first blush, a weir—a small dam built to hold back some amount of water while still allowing the rest to flow over its top—seems a strange thing to install in an aqueduct. It served the same purpose here, however, as most other weirs: to regulate the water's level. The gate house’s subterranean chamber originally had a half-height brick wall running parallel to the conduit, right at the bottom of today's stairs. This was the weir: in addition to keeping the water on its course, it allowed any excess to spill over its top and into what was, effectively, a large sump. From there, a valve could be opened allowing it to flow down into the Sing Sing Kill, safely away from the aqueduct. This ingeniously simple design was repeated wherever the aqueduct crossed a waterway, providing the system with a series of safe, convenient overflow valves. Sadly, the weir wall itself was largely destroyed when the gate house was opened to the public. However, if you glance at the chamber's walls, you can still clearly see evidence of where it once emerged from the brickwork.

Down inside the aqueduct, the air is still musty and damp, as in a cave. Below the grates under your feet, a tiny rivulet of water still flows down the well-trodden path, having presumably seeped in through the slightly porous walls. A handful of weeds and tiny roots grow out of, through, and along the walls, having forced their way in from the ground outside. They serve as a reminder that, like everything else, this structure too will someday return to the soil into and out of which it was built. Underground, symbolism runs deep.

The weir and gate house, however, had another purpose far more important than overflow control: they also allowed for maintenance and inspection of the conduit itself. Long before the remotely operated robot submersibles used today, the only way to assess the physical condition of the aqueduct was through manual inspection. To drain the entire forty-plus mile structure, however, would have taken at least a full day—with refilling taking another day more—denying the city vital water for an untenable amount of time. Therefore, to make inspection possible, each of these access points was built with a giant sluice gate, allowing the tunnel to be sealed off section by section, with any excess flow channeled over the weirs. Once one of these massive valves was closed, intrepid workers were then free to embark into the dark depths atop tiny boats, lying on their back and banging the ceiling with wooden rods, listening for any structural faults. Were any ever found, only that section of tunnel would then need to be drained for repairs to be made. Apparently, this harrowing inspection procedure was undertaken approximately once a year, at least until—in an act of foreshadowing—shrinking city budgets led to deferred maintenance.

Top:The location of the weir wall is visible to the right. Bottom: The sump chamber and the modern metal stairs.

The end of these regular inspections brought longer-term repercussions than one might suppose. As the engineer behind any critical system will tell you, you never close an important valve unless you are sure you can open it again. Regular use ensures that movable control structures stay moveable, and most vital systems are designed with periodic valve checks in mind. After years of disuse, however, resuming traditional inspections became nearly impossible: the risk of a stuck sluice gate stopping the flow of drinking water to the nation's largest city was simply too great.

Once one of these massive valves was closed, intrepid workers were then free to embark into the dark depths atop tiny boats, lying on their back and banging the ceiling with wooden rods, listening for any structural faults. Were any ever found, only that section of tunnel would then need to be drained for repairs to be made.

Sadly, this specter of deferred maintenance still haunts the in-use segments of New York's water supply system to this day. The mighty Delaware Aqueduct—not only the largest of the Old Croton's replacements, but also, by some measures, the longest continuous underground tunnel in the world—is currently leaking tens of millions of gallons of drinking water into the ground every day. Thanks to a design flaw, cracks have formed at the edge of the conduit's Hudson River crossing, which just so happens to lie hundreds of feet beneath the river's surface. Even if New York City could sustain a temporary Delaware shutdown to make repairs—a big ask in and of itself given the volume of water it supplies—a lack of use has made closing its valves a much more fraught process than it might otherwise have been. As a result, an entirely new, 2.5 mile long section of conduit is being built to replace the old, at a cost of over a billion dollars. Once complete, it will be spliced into the aqueduct, not only replacing the leaking section, but transforming the old portion of tunnel into a new, even more inaccessible ruin all its own.

The massive sluice gate hangs like a guillotine blade.

Oddly enough, at least to some extent a similar maintenance problem still looms over the Ossining weir today—quite literally. The facility's original cast iron sluice gate has been permanently mounted in its open position for visitors to see, hovering over the aqueduct channel like a guillotine blade, still poised to cleave and stop a flow which hasn't run for decades. The massive casting is suitably intimidating, its size alone hammering home the scale of the forces it was designed to hold back. As a result, even though the chains that hold it in the air have been firmly welded in place, some of today's volunteers pay it an understandable respect, concerned about the last time those welds, too, were inspected. Of course, the actual chances of an accident are vanishingly slim. Walking beneath the mighty iron panel, however, can't help but produce at least a tiny spike of adrenaline. The feeling serves as a powerful reminder that, no matter how human this hand-laid channel may feel—especially standing on its safe, modern gangways—it is still fundamentally an alien landscape, never meant to be occupied by people for any significant amount of time. The experience only reinforces the peculiar awe that is standing within the workings of a mammoth piece of fossilized infrastructure.

Before returning to the surface, as most of the group I was with began to slowly find their way towards the exit, I found myself taking my time in the channel, simply letting myself take in the space. There is something intoxicating in the tunnel's combination of historical notoriety, hidden grandeur, and quiet, eerie darkness. As a place, it almost seems to demand silent reverie. Of course, I'm sure some will scoff at my romanticism: after all, compared to the truly ancient ruins of, say, Roman, Hampi, or Incan aqueducts, this channel is a veritable newborn. However, (and perhaps this is simply the parochial American and New Yorker in me speaking) there is something deeply affecting about a ruin which, while clearly from another era, nonetheless dramatically and directly shaped the New York of today—a city whose very mythos is defined, however truthfully, by youth, change, and growth. The simple fact that the channel sits so complete while surrounded by nearly two centuries worth of shifting urban landscape is remarkable enough on its own.

While the Old Croton Aqueduct may still hold a powerful place in the region's historical imagination, in a very real sense it may also now exist more concretely in that lore than it does in the physical world.

That said, today, some sixty-five years after the last drops of drinking water were finally drained from its channel, the Old Croton Aqueduct exists in strangely liminal state: at once manifestly conspicuous, and yet also oddly invisible. It would obviously be impossible to hide a sprawling, handmade, 41-mile long structure—assuming that, for some strange reason, you wanted to in the first place. The channel has left an indelible mark on the landscape. Where it runs through towns and cities, it has carved out linear parks; where it runs adjacent to or under streets, they bear its name; and where it comes to the surface, as in Ossining, it does so with a flourish. What's more, you needn't be well acquainted with obscure maps to find it: the aqueduct's snaking path is clearly visible on the surface. Its right of way was always left undeveloped to protect the structure, and today, it is still preserved as the aforementioned hiking trail. Should the urge grab you, you can walk all the way from the summit of the Croton Dam in upper Westchester down to High Bridge at the foot of the Bronx, with the conduit still sitting beneath your feet almost the entire way. That said, even though you don't need one, if maps are your thing, the Friends of the Old Croton Aqueduct do sell two annotated maps of the route—one for Westchester and one for the Bronx—both of which are full of historical detail, and both of which are very much recommended.

The Old Croton Aqueduct today can almost be lost between the buildings. While still used as an odd linear park, few know know what it really is—or that it is still inside, intact.

At the same time as all of that, however, the Old Croton Aqueduct also has a strange ability to hide in plain sight. This isn't just a result of it being a narrow tunnel that runs mostly underground—although that certainly is a large part of it. Instead, the channel has simply been around for so long that it has become just another part of the urban landscape. As the city and its suburbs grew up around it, the tunnel has slowly dissolved into the background, blending in almost as if it were deliberately camouflaged. Of course, most of us already find it easy enough to forget the existence of the vital but hidden infrastructures that support our daily lives—at least until they malfunction. Thus, it is perhaps no surprise that an unused, abandoned piece of infrastructure—even one designed to be appreciated, like this one—should vanish into the layers of urban accretion that surround it. After over 180 years of surrounding development, the aqueduct has simply become such an integral part of the landscape as to be largely invisible, especially for locals. It would not surprise me to learn that most residents—even those who regularly walk its hiking trail—have no idea that the old structure still sits mostly intact, right beneath their feet. While the Old Croton Aqueduct may still hold a powerful place in the region's historical imagination, in a very real sense it may also now exist more concretely in that lore than it does in the physical world.

Downtown Ossining and the Hudson River at sunset.

And yet, to a surprising degree, it still does exist, a strange, glorious ruin hidden just beneath the surface. Yes, some parts may have been destroyed or repurposed, but for a 180 year old piece of disused infrastructure, it is still shockingly intact, a silent piece of living history that continues to snake its way through village, town, and city, mile after mile.

It isn't every day that most of us get a chance to venture inside a usually off-limits piece of civil infrastructure—let alone one so important to New York's urban history. Should you find yourself with the opportunity to travel with the Friends of the Old Croton Aqueduct down into their namesake, take it. You too will be able to touch this ruin of modern history, and you too, I hope, will not be disappointed.

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