Urban explorers rediscover the oldest sewer in St. Louis

By Chris Naffziger
Photos by Jason Gray

Editor’s Note: Wherever we go, we are surrounded by human history, animal history, geologic history, and many other storylines. Human history consists of settlements, wars, architecture, culture and other interactions throughout time.

Many people pay attention to the history of the human-built environment, but how often do we think of the structures we step on every day? How often do we wonder about the public utilities pulsing below the surface? How about the sewer system? Advancements in how we drain away water, sewage and other effluents have dramatically influenced human settlement, health and other important courses of history.

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Intrigued by what lies underfoot, two urban adventurers explored a pre-Civil War sewer in downtown St. Louis that they recently rediscovered. They think it is the oldest sewer in St. Louis. If it had been completed, it likely would have been the oldest municipally funded sewer section in the country. Their investigation of the 300-foot-long limestone, brick and wood conduit reveals details about the early decades of stone construction in the city.

The explorers were surprised by how well the structure has endured the passage of time and the onslaught of water, freezing and thawing, and other debilitating elements. Traversing the sewer also provides a window into the earliest years of public infrastructure development in The Gateway City.

“On any given day, this tunnel’s entrance remains completely inaccessible because of rapid fluctuations in the Mississippi River’s water levels, but circumstances recently aligned for me and a companion to enter safely,” said one of the explorers. Access was safer because of near-drought conditions in the associated drainage basin.

“We entered on a warm day, first seeing a narrow, brick-lined tunnel that stretched about 150 feet into the darkness before opening onto the main, stone sewer. It was cool and cave-like inside. The tunnel was crisscrossed with webs and when our flashlight beams hit spider eyes, they sparkled like crystals.”

There are urban explorers who visit structures whenever the urge strikes and conditions align. Some of their visits would be frowned upon by city officials; therefore, their need to keep a low profile and the reason why the two sewer explorers in this article will remain nameless. Also, because exploring sewers can be unsafe, its precise location will not be given.

Built in the 1850s, this sewer section was originally part of a system designed to drain Mill Creek Valley. Mill Creek Valley stretched from the Mississippi River south of Walnut Street and north of Chouteau Avenue westward as far as Eighteenth Street. In the mid-20^th century, it was incorporated into the modern storm water runoff system and still serves that role today. In the years after the Great Cholera Epidemic of 1849 and the blame placed on Chouteau’s Pond for the spread of the disease, citizens clamored to have the long-detested lake drained as soon as possible. Part of Union Station sits where the pond once was. (See related article in Supplement St. Louis on the St. Louis cholera epidemic and the pond’s connection to the outbreak, http://www.supplementstlouis.com/2019/07/13/at-great-cost/)

The damming of Mill Creek created Chouteau’s Pond. Until recently, few people knew about the path the creek took past the dam to its termination at the Mississippi River. One would expect the stream to follow a relatively direct path, but it meandered considerably in the several hundred feet between the pond and river.

The sewer entered by the two explorers, constructed beginning in 1851 and built north of the natural channel of Mill Creek, was completed between the Mississippi River and First Street in 1853. The oldest municipal sewers in the U.S, located in Chicago and New York City, weren’t constructed until the late 1850s; although there were older private sewers in existence in St. Louis and elsewhere in the country, had this sewer been fully completed, it would have been the oldest municipal sewer in the United States.

On the opposite end, near Chouteau’s Pond, between Ninth and Eighth streets, another stretch of sewer was simultaneously built. Unfortunately, a large pocket of quicksand was discovered, halting further excavation and construction. That alignment was terminated. Quicksand has been the bane of subterranean excavations throughout St. Louis. By 1859, an engineer had written off the whole sewer project in that area as unworkable.

A well-justified expense

A change in plans was based on the quicksand discovery, logistics and the huge financial cost of $65,100 (about $2.63 million today). Using a new configuration by shifting the main sewer trunk over to the Mill Creek channel below Chouteau’s Pond would cost substantially less – but still the staggering amount of $44,600 (about $1.80 million). These were enormous sums of money about 175 years ago, and represented just how much investment St. Louis was willing to make to remove this impediment to development south of downtown. Among other infrastructure projects built in the ensuing decades, the backbone of the St. Louis railroad yards would be laid in the flats drained by the sewer system.

Perhaps what is so fascinating about this old sewer section is its incredible state of preservation. Beginning at the mouth, which is capped with a relatively short section of modern poured concrete dating to when it was incorporated into the current flood control system (most likely around the time of the construction above it of the Poplar Street Bridge in 1959), it continues for approximately 150 feet in an arched tunnel constructed of brick with rough flagstone walls. The floor is constructed of wood timber laid above a shallow void. In some sections the cottonwood planks covering the floor have deteriorated or are missing. The cavity beneath the planks was likely caused by erosion. “The texture of the wood planks was spongy,” said one explorer, “and a small amount of flowing water was ever-present throughout the tunnel. Sediment lined the walls of this chamber, giving it a cave-like feel, and the flowing water was cold to the touch.”

After this section of sewer, which is no more than five feet high and wide, the passageway opens onto a large chamber of an additional 150 feet that is approximately 15 feet high and wide. That space was likely built to handle overflow in the case of heavy rains or floods. The construction of this chamber is considerably different, using stone instead of bricks. Also, the vaulting is shaped more like a bell, sweeping around on both sides before again terminating in a cottonwood floor.

The vault is constructed of long, slender flagstones laid in a rough, almost rubblestone form. Although it is very rustic, it is also very durable, as its age attests. The explorers could not make a full inspection because large, dark brown sediment berms covered the base of the walls. At the rear of the chamber is a modern, poured concrete construction that forms a square space with two steel floodgates that can be lowered from an unknown location.

The original sewer was designed to taper toward the river at such an angle to prevent river backflow into the sewer past the levee, even from the highest floods observed at the time of its construction. The original stone sewer would have continued well past this infrastructure to where the quicksand was encountered. This segment was built to aid in flood mitigation efforts in the 1960s-1970s following the Flood Control Act of 1955 and is directly connected to a nearby pump station (part of a 28-pump system along the riverfront). The concrete wall that directly abuts the stone sewe­­r has a single, cylindrical tunnel opening (roughly five feet in diameter) that follows an s-curve back to a small transition chamber, which extends all the way up to the city street.

On the other side of this transition chamber are two outlets with the two metal floodgates previously described. One of these outlets leads to another enclosed, concrete room with several smaller offshoots (some too small to enter). This room is likely designed to hold overflow before that water can be redirected. It is unknown where the other outlet leads, though the explorers theorize it connects with a separate pump system designed to keep the underground areas of a well-known landmark dry (yup, that giant arch thingie), which would otherwise be inundated due to a natural spring.  

“It does not appear that this section of the old sewer is, in its current state, a combined sewer; those convey both storm water and sewage. Having been in other sewers around the city designed for this purpose,” said one explorer, “and accustomed to the smells of those locations – especially on warm days – this sewer appears remarkably clean, with the piles of sediment seeming to originate in flooding events – dirt, tree debris, et cetera – rather than the fats, oils and other flushed things that build up in combined sewer environments.”

While the tunnel’s original purpose of draining Mill Creek proved to be too difficult for conditions in the ground, the engineering and craftsmanship of the 1850s is still worth noting in this almost completely forgotten corner of the St. Louis underground. Perhaps other explorers will find the western end of the sewer, which may still exist. This sewer section may be one of the oldest major public works projects still surviving – and functioning! – in the city.

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Special thanks to Eric Sutterlin, Elizabeth Schaefer, Jason Gray and Eric Bothe for research assistance provided for this article.

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Chris Naffziger has written about history and architecture on his website, St. Louis Patina (http://www.stlouispatina.com), since May 2007. For the past 10 years, he has contributed to St. Louis Magazine, writing about the historical and architectural heritage of the Gateway City. For many years, Chris has specialized in examining the history of the brewing industry in St. Louis, focusing on the founding of the Anheuser-Busch Brewery and the life of Adam Lemp, founder of the Western Brewery. Chris has written a book, Adam Lemp and the Western Brewery, which will be published in July 2025. Chris has published multiple articles about German-American brewers in the British journal Brewing History.

Jason Gray is a freelance photographer and artist specializing in post-documentary work. His clients include Island Press, the Dallas Museum of Art, St. Louis Magazine, and Terrain Magazine. Gray has received awards and recognition from the Regional Arts Commission of St. Louis, the Missouri Arts Council, and the Riverfront Times. Jason’s first monograph, Mound City Chronicle, was published in 2022 by Vedere Press, Indianapolis, and his second book will be published later this year.  An exhibition of Jason’s work (Does a parasite know it’s a parasite?) is on view at St. Louis Lambert International Airport through December 2025. Jason has many superb photos on his website, http://cargocollective.com/jasongray/HOME.