Illustration by Todd Detwiler
In the prehistoric time before smartphones, the Cherokee Geyser was nothing more than an urban legend. Whenever people spoke of a three-story column of water erupting through a manhole cover at the intersection of Cherokee Street and Texas Avenue, listeners rolled their eyes. Then this summer, several residents and business owners captured the hydraulic explosion in eye-bugging videos, proving that the geyser was no myth. What produced this peculiar phenomenon? To find out, we called Jonathan Sprague, the Metropolitan Sewer District’s director of operations. He says the geyser is a “rare occurrence” that requires a “perfect storm.”
Combined sewer system: St. Louis’ underground pipes handle both wastewater from homes and stormwater from the streets.
Dry day: Waste in the Cherokee neighborhood flows into a sewer pipe that runs downhill under Texas Avenue before dropping into a large 10-foot-by-10-foot tunnel that carries water to the Bissell Point Wastewater Treatment Plant.
Heavy rain: The rush of storm-water into the sewer sometimes overloads that tunnel. Excess water then flows through a gate into the Mississippi River.
Flooded river: When the Mississippi floods its banks, the gate must be closed to prevent river water from entering the sewer system.
Heavy rain and flooded river: If a downpour fills the sewer while the gate is closed, excess water has nowhere to go. Pressure builds.
Geyser: Because Cherokee is one of the lowest points along the Texas sewer, the vertical shaft leading to its manhole cover becomes the release point for all of that pressure, producing the geyser.
Sewage: During a heavy rain, the first blast of water through the sewer flushes waste, no pun intended. That means 99 percent of what spouts out of the street is just dirty rain water. The geyser isn’t “Old Fecal.” But if people are showering or flushing their toilets during the storm, a bit of that could be in there, too. “Once it enters our sewer and then comes back out of our sewer, it’s called sewage,” Sprague says. “That’s the characteristic of a combined system.”
Future plans: MSD is not planning any action to fix the geyser. “Any solutions for this rare occurrence are very expensive, in the millions and millions of dollars,” Sprague says. “The cost benefit just wouldn’t be there.”
