On a September morning nearly a generation ago, America’s soul was tested. Fire and smoke rose over Manhattan, heartbreak and loss reverberated across the nation, and nearly 3,000 lives—office workers, teachers, service members, mothers and fathers—were extinguished in a moment that still echoes. Out of that darkness, however, came a defiance that revealed itself in firefighters climbing stairwells burdened by danger, in police officers racing toward collapse, and in passengers aboard Flight 93 who chose courage in their final breaths so that others might live.
That defiance, and the unity it sparked, endures today at Ground Zero. It is heard in the rush of water and seen in the seemingly endless cascade of the 9/11 Memorial Pools—two square voids occupying the footprints of the Twin Towers. These pools are not merely architectural monuments. They are living systems, blending art, engineering, and remembrance in a way that demands both awe and care.
Listen to the episode on the September 11th Memorial here 👇
A Monument of Water and Memory
Spanning almost an acre each, the Memorial Pools at Ground Zero are a sight to behold—these are the largest human-made waterfalls you’ll find anywhere in North America. The water drops down thirty feet, then slips quietly into a lower basin; the sound is steady, almost meditative, yet carries a certain weight. Every morning, a fine mist settles onto the granite edges, touching the engraved names as if the city itself were reaching out in remembrance.
But there’s much more happening beneath the surface. These pools are alive with movement—kept spotless thanks to a mix of clever engineering, chemistry, and dedicated daily care.
What You Don’t See
Eight heavy-duty pumps work nonstop, pushing water through each basin at a clip—about 30,000 gallons every single minute. The whole thing cycles through in just twenty minutes, so you’re never looking at anything less than fresh, clear water. The waterfalls are carefully crafted, their stainless steel edges designed so the water sheets out evenly, no matter if the wind’s blowing or the temperature’s dropping. The city never really pauses, and neither do these waterfalls.
The entire volume circulates every twenty minutes so that the water always looks clear and alive. The waterfalls themselves rely on stainless steel ledges, crafted with extreme precision, to create that even sheet of water—even as the wind shifts, temperatures drop, and the city’s rhythm never slows.
The water is not simply chlorinated, as in an ordinary fountain. Instead, engineers turned to bromine, a disinfectant less volatile and more stable across the wide pH ranges of an outdoor, high-flow system. Bromine carries risks—its byproduct, bromate, is dangerous if ingested—but unlike chloramines formed by chlorine, it does not create an inhalation hazard. No one drinks from these pools, but millions stand nearby. In this setting, bromine is the safer choice.
Layered on top of this chemical shield is ultraviolet disinfection. UV reactors bombard circulating water with germicidal light, scrambling the DNA and RNA of microorganisms. Together, bromine and UV form a dual-barrier system, an approach now considered best practice in advanced aquatic engineering.
At night, after the crowds disperse, crews descend into the pools. For eight hours they vacuum debris, brush granite walls, polish bronze parapets, and reset the surface for the following day. Machines may sustain sanitation, but only human hands can preserve the material dignity of the space.
Year-Round Vigilance
Unlike ornamental fountains that shut down with winter, the Memorial Pools run continuously. Submerged heat exchangers keep water above freezing, preventing ice from forming on weirs while minimizing evaporative loss. This ensures that on the coldest mornings, when breath fogs in the air and the plaza lies hushed, the water still flows—unbroken, unyielding.
The Intersection of Memory and Mechanics
The Memorial Pools resist easy classification. They are neither recreational pools nor simple fountains. They are hybrids—part municipal waterworks, part national shrine. Beneath the surface: pumps, filters, ultraviolet reactors, and heating loops. Above: cascades of water that seem to fall forever into absence.
What emerges is not just a feat of civil and chemical engineering but an act of ongoing remembrance. The water does not rest because memory cannot rest. The nightly maintenance, the chemical balance, the relentless pumps—all of it is labor dedicated to ensuring that grief and honor remain palpable, present, and undiminished.
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An Invitation to Witness
Here’s the truth: you don’t have to be American to feel the weight of this place. You don’t even have to remember where you were on that day. These pools belong to humanity, because what happened on 9/11 wasn’t just an attack on New York or Washington—it was an attack on all of us who believe in living free, in raising kids without fear, in the idea that tomorrow should still be there when the sun comes up.
So when you stand there, don’t just look at the water disappearing into that endless void. Hear what it’s saying. It’s telling you that memory isn’t still. It moves. It flows. It gets carried forward, not locked away. And just like those crews that go down into the pools at night, it’s our job to keep tending it—to keep memory alive, to keep resilience moving, to keep courage from fading.
You leave that place changed. Because the 9/11 Memorial Pools aren’t just water features. They’re proof. Proof that grief doesn’t drown us. Proof that memory doesn’t die. Proof that, no matter what, we will always rise again.
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Transcript to Talking Pools Podcast episode 839, Honoring Heroes: the 9-11 Memorial Pools, September 11, 2025:
Rudy Stankowitz (00:00.203)
Hey everybody, welcome to the Talking Pools podcast. Today’s episode, it’s not like the others, not your normal broadcast, definitely not your normal Thursday. Today is Patriots Day, September 11th, a day of remembrance, a day of reflection, and a day of honor. This isn’t about pools or business. It’s about people. It’s about sacrifice, resilience, and the spirit of America. So as we begin,
I want to share some words to honor those we lost and the heroes that stood tall on that fateful day.
Rudy Stankowitz (00:44.6)
September 11th, was a day that tested the very soul of our nation. It was a day of fire and smoke, of heartbreak and loss. But it was also a day when the spirit of America revealed itself in ways that still inspire us nearly a generation later.
Rudy Stankowitz (01:07.298)
That morning, nearly 3,000 innocent men, women, and children had their lives stolen. They were office workers, teachers, service members, mothers and fathers, sons and daughters. They were ordinary Americans living ordinary lives. And that is exactly why their loss cuts so deep. They were us. They were the heartbeat of this nation. And yet, amid the darkness, we saw light.
Amid the chaos, we saw courage. Amid the destruction, we saw defiance. We saw firefighters climbing stairwells, carrying hope on their backs as the weight of danger bore down on them. We saw police officers racing toward danger, determined to save lives no matter what the cost. We saw first responders, paramedics, doctors, nurses, who would not rest.
until the injured were cared for. We saw passengers on Flight 93 who in their final moments chose bravery and sacrifice so countless others could live.
These men and women became the very definition of heroism. They embodied the words we hold dear. Greater love has no one than this, that someone laid down his life for his friends. And so many of them did. All gave, and some gave all. And when the dust began to settle, something extraordinary happened. Out of the ashes, America rose.
Neighbors became brothers and sisters. Flags flew proudly from porches, schools, firehouses and highways. Strangers embraced one another in grief and then in resolve. The world saw not a nation broken, but a nation united. That is the America we remember today. That is the America we must always strive to be.
Rudy Stankowitz (03:19.223)
We do not honor the fallen with silence alone. We honor them with action, by living lives worthy of their sacrifice, by standing tall when tested, by refusing to be divided by fear or hatred, by teaching our children what resilience looks like, what unity feels like, what courage means. The legacy of 9-11 is not just in the lives we lost, but in the spirit we found.
A spirit that says, we may be attacked, but we will not fall. We may mourn, but we will not surrender. We may bend, but we will never, ever break. So today as we bow our heads in remembrance, let us also raise our voices in pride. Pride in the heroes who ran toward the flames. Pride in the men and women in uniform who continue to protect us. Pride.
in the enduring promise of freedom that no enemy can take away. We are Americans. And because of that, we will always rise from the ashes. We will always stand together. And we will always honor those who gave their last breath so that others might see another sunrise.
May God bless the fallen. May God bless the heroes. And may God forever bless the United States of America.
President George W. Bush (05:28.00) Good evening. Today, our fellow citizens, our way of life, our very freedom came under attack in a series of deliberate and deadly terrorist acts. The victims were in airplanes or in their offices, secretaries, businessmen and women, military and federal workers, moms and dads, friends and neighbors.
Rudy Stankowitz (05:29.312)
The 9-11 Memorial Pools in New York City represent not only a commemorative landscape, but also a complex engineering and water treatment system. Each pool, occupying nearly one acre of surface area, integrates advanced hydraulics, chemical disinfection, ultraviolet oxidation, and rigorous maintenance protocols. Today I want to examine the construction, hydraulic systems, disinfection methodologies, seasonal adaptations, and operational care of the pools.
situating them within the broader field of applied aquatic engineering and large-scale water feature management.
Rudy Stankowitz (06:06.719)
Urban memorials are typically considered static works of architecture and art. The 9-11 Memorial Pools, however, are dynamic water features that function simultaneously as cultural monuments and complex aquatic systems. Located at the footprints of the former Twin Towers, each pool is designed as a square void with water continuously cascading down its vertical walls. From an engineering perspective, the pools represent a unique integration of civil engineering
fluid mechanics, and water chemistry under extreme operating conditions.
Rudy Stankowitz (06:43.807)
The pools measure approximately 176 feet on each visible side, with an additional eight feet water table extending the total edge length to nearly 196 feet. The vertical drop is approximately 30 feet, followed by a secondary drop into a central void. These parameters make the feature the largest man-made waterfall in North America. The structural engineering required significant adaptation to withstand environmental stressors,
including freeze-thaw cycles, wind shear within the urban canyon, and long-term exposure to chemically treated water. Stainless steel waterfall weirs were fabricated with sub-millimeter tolerances to ensure uniform laminar flow across the perimeter. The supporting plumbing system, consisting of hundreds of feet of pipe, is joined using grooved mechanical couplings, allowing for sectional disassembly, inspection, and biofilm control.
Each pool is powered by eight industrial-scale pumps, achieving a combined flow rate of 30,000 gallons per minute per pool. System reports suggest higher combined flows across both pools ranging from 26,000 to over 50,000 gallons per minute, depending on operational demand. The design achieves complete water turnover approximately every 20 minutes. Automation and control are achieved through Siemens TYA programmable logic controllers
which monitor flow rates, adjust valves, and maintain stable water levels. This level of automation is critical for preventing disruptions to the waterfall uniformity and for integrating chemical dosing and ultraviolet disinfection systems in real time. Unlike most outdoor fountains that rely primarily on chlorine, the 9-11 Memorial Pools employ bromine as the principal chemical disinfectant. Bromine was selected for its stability across a broad pH range
and for its reduced production of volatile byproducts compared to chlorine. In an open-air high-volume water feature subject to variable pH and organic loading, bromine provides greater persistence and efficacy. The pools also employ UV disinfection systems as secondary oxidizers. UV reactors operate continuously, exposing circulating water to germicidal wavelengths. This process induces DNA,
Rudy Stankowitz (09:05.297)
and RNA disruption in microorganisms, rendering them non-viable. The integration of bromine and UV represents a dual-barrier approach, consistent with best practices in advanced aquatic engineering. Filtration banks remove suspended solids and organic debris, preventing turbidity and reducing the chemical oxidant demand. The turnover rate, 20 minutes per pool, ensures rapid dilution of contaminants and uniform disinfectant distribution.
I know what you’re asking yourself. What about the EPA’s ban on bromine in swimming pools because of harmful disinfectant byproducts? You’re absolutely right. Bromate is the concern. But here’s the distinction you need to keep in mind. Chlorine systems can generate chloramines, and those pose a real inhalation risk to swimmers and bystanders. Bromate, on the other hand, is only a threat when ingested. Since no one is drinking from the 9-11 Memorial Fountains,
Bromine actually presents a far lower risk in this unique application than chlorine ever would.
The pools operate year-round, including during winter conditions where ambient temperatures fall below freezing. To prevent ice accumulation along the weirs, the water is heated through integrated exchangers, maintaining a temperature sufficient to inhibit freezing without inducing thermal stress or unnecessary evaporative losses. This adaptation ensures uninterrupted operation, a critical requirement given the pool’s symbolic role.
Unlike ornamental fountains that are typically decommissioned during cold seasons, the memorial’s design necessitates continuous hydraulic and chemical operation. Maintenance represents a significant operational component. Each weeknight, waterfalls are shut down and crews enter the pools for direct cleaning. Activities include vacuuming of the basins, brushing of vertical surfaces, polishing of granite, and cleaning of bronze parapets containing nearly 3,000 engraved names.
Rudy Stankowitz (11:06.173)
The cycle requires approximately eight hours to complete. From an operational perspective, this routine exemplifies the importance of human intervention in supplementing automated disinfection and filtration systems. Mechanical and chemical systems ensure microbial safety, while manual cleaning preserves aesthetic clarity and material integrity. The 9-11 Memorial Pools occupy a unique position in the taxonomy of aquatic systems.
They are neither recreational pools nor ornamental fountains in the traditional sense, but hybrid systems combining aspects of both. The design emphasizes symbolic reflection, yet requires continuous operation at scales typical of municipal water infrastructure.
The choice of bromine over chlorine indicates a preference for chemical stability and reduced volatilization, especially relevant in high-flow outdoor settings. The integration of UV disinfection provides redundancy and reduces reliance on halogenated compounds, aligning with contemporary approaches in sustainable water treatment. From a hydraulic standpoint, the pools represent one of the largest continuous waterfall systems in existence.
with flow demands exceeding many public aquatics facilities. The 20-minute turnover rate reflects not recreational necessity, but an engineering commitment to clarity and consistency of flow. The 9-11 Memorial Pools illustrate how Memorial architecture can intersect with advanced aquatic engineering. Beneath their surface lies an infrastructure of pumps, filtration banks, bromine dosing systems, ultraviolet reactors, and heating loops. Above,
The visible result is water falling, circulating, reflecting. These pools demonstrate that memorialization is not static. It requires continuous movement, chemical balance, hydraulic precision, and human care. Their operation represents an ongoing act of remembrance, maintained through engineering rigor and nightly labor. In this way,
Rudy Stankowitz (13:14.301)
The 9-11 Memorial Pools stand as both a technological achievement and a cultural symbol. They embody the intersection of memory and mechanics, where the language of hydraulics and disinfection sustains a monument dedicated to endurance, reflection, and the continuity of remembrance. If you have not yet visited the Memorial Fountains, make the trip to Manhattan. Go not only as a pool professional who can appreciate the engineering,
But as an American who understands the weight of history, the sound of the water, the sight of the names, the immensity of the voids, it is profoundly moving. Be prepared. It is not just a visit. It is an experience of remembrance, reflection, and reverence that will stay with you long after you leave.
O say can you see, by the dawn’s early light, What so proudly we
Rudy Stankowitz (14:38.529)
And the rockets’ red glare, the bombs bursting in air, gave
