McMillan Sand Filtration Site

This was the idea: that the McMillan Sand Filtration Site in Northwest DC could be the perfect union of public utility and public space.  It would meet the city’s burgeoning water needs while simultaneously offering local residents an over-sized and carefully manicured backyard, a public park on the grandest of scales designed by renowned City Beautiful architect Frederick Law Olmsted, Jr.  It was an idea both bold and of its time, and now in our time, all that remains are the ruins.

sunlight frame

The first thing you notice about the McMillan Sand Filtration Site is the vast, open green space.  Twenty-five acres of green crab grass extend from North Capitol Street to First Street Northwest in a neighborhood otherwise typified by its small, tightly packed houses.  Weeds have crept in over the intervening century, and the concrete of the promenades and grand staircases have cracked, but this still feels like the kind of place you’d want to spend some time. City Beautiful has become city vacant, keeping up with fashion in post-industrial America.  If you try, you can almost imagine the neighborhood kids darting in the cool spray of the towering McMillan fountain, now dismembered and transplanted, sadly.  They are chattering mirthfully in sing-song voices, improvising some elaborate variation on stickball amongst the grid of manhole covers that speckle the field like rusted red polka dots.

On those summer evenings – the kind where the air still hangs sticky and sweet for hours after the sun has set – their mothers and fathers would come down to join them, perhaps with a picnic dinner tucked under arm.  In the days before air conditioning and the menace of neighbor-on-neighbor violence, the heat in their little brick row houses would have been stifling and unbearable.  Half the neighborhood would sleep out here, staking out choice spots up on the embankment.  The cool night breeze would have swept over their weary heads, while the Washington Monument glowed in the moonlight, towering like an ivory sentinel on the horizon, standing tall and firm, belaying any ill-fortune.

This is what City Beautiful was all about – livable, breathable space that ennobles and enriches the lives of citizens.  The countless happy hours spent here over the years by countless happy people would have justified the efforts of its planners, because after all, what else are parks for?  All of that halcyon joie de vivre should have been enough.

But at McMillan Park, then and today, the main event is beneath your feet.

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Multi-story concrete hoppers once held massive quantities of sand and now stand empty, covered in summer months with a prodigious web of vines.  Great wooden doors, now decaying on their hinges, stand high over the cracked promenade.  Some have rotted completely free, laying before gaping black cave-mouths – yawning the entrances to some sublevel of Earth.  They open up on a whole other world, where Olmsted’s form gives way to industrial-scale municipal function.  Each arched doorway leads down a great concrete ramp into one of twenty vaulted filter cell catacombs that lie below the surface.

The temperature down here is noticeably cooler, and moisture hangs heavy in the still air.  My boots splash through mud puddles, the sound echoing back to me a moment later off the far wall.  Though the ceiling is only about ten feet overhead, the overall scale of this chamber is truly staggering – easily comparable in volume to a Metro station, but with all the lights out.  The manhole covers that the boys above used as bases were once used to replenish the sand supply down here.  From below, it’s easy to see which covers have gone missing over the years – a shower of light pours into the pitch dark, beckoning me to its warmth.

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When they were in operation, these cathedral-like chambers would have been filled with a sluice of sand and water – tens of millions of gallons a day carried in from the Potomac by way of an aqueduct.  Each filter cell is designed to hold some 3200 cubic yards of fine, alabaster sand – that’s about two hundred dump truck loads – with room for some three million gallons of water.  The top layer of that sand – the Schmutzdecke – served as a growth medium for protozoa, fungi, and rotifera, which did the happy work of feasting on whatever living bacteria was slurped along.

And now it stands vacant behind a high fence, its cylindrical sand storage towers an enigma to all but longtime residents of the surrounding Bloomingdale neighborhood.  Between 1905, when this slow filtration site opened, and 1986, when it was decommissioned, the vast majority of Washington’s potable tap water originated here.  Slow sand filtration is economical and great for the environment – it requires little maintenance and the process employs no chemicals, but it does require a lot of space.  The McMillan Sand Filtration Site just could not keep up with the District’s ever-growing demand for water, so the city shuttered the site in favor of a less land-intensive rapid filtration site across the street.

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As for the park above?  That was closed to the public much earlier.  After World War II, city planners became cognizant of just how vulnerable the park-purification pairing made the city’s water supply – the potential for sabotage was just too great.  That’s an era of civic trust – or naivete – that has long past…

In the early twenty-first century, there is talk of redevelopment.  There are controversial plans to pave the green space and seal off the disused filter cells below in favor of extensive housing and shopping developments above.  The city used to allow biannual tours of the site, opening the heavy wooden doors to any members of the public who wished to visit.  Recently, access to McMillan Sand Filtration Site has been further restricted as plans for redevelopment proceed.  Two of the cells have been excavated for use in emergency storm water retention in an effort to curb hazardous runoff from the still operational rapid filtration site nearby.

But as we look upon the McMillan Sand Filtration Site in its hobbled, faded glory, in what are very likely its final days, let’s not forget that first, original germ of an idea: that a single space can serve the public good on multiple levels all at once, all without an anchor store or parking garage in sight.  The McMillan Sand Filtration Site stands as a triumph of municipal design whose time has passed.  And perhaps, whose time has yet to arrive.  If ideas have an afterlife, maybe the elegant integration of form and function embodied here still has a chance.

Those manholes punctuate the mottled grass like some great ellipsis on one of the District’s finest open-ended thoughts…



An extensive redevelopment plan has been approved by the zoning commission.  Catch your last glimpse of this distinctive part of DC history before it disappears forever.



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DCinruins Volume 3: Daylight Underground published by Insignificant Press.



7 thoughts on “McMillan Sand Filtration Site

  1. OK this is cool — real scholarship and poetry — thanks for letting me know the Olmsted connection.
    I still think “gentrification” is inappropriate word for Forest Glen but I get where you’re coming from… ruins aren’t bad either.
    Thanks for your work.

    Posted by Robin | September 21, 2013, 11:26 pm
  2. Is access easy? I’ve been meaning to check this spot out.

    Posted by Alexander | April 10, 2014, 11:07 pm
  3. Cool location, would look awesome with some star trails at night. Google street view shows a solid fence all around. How does one get in to get photos like the above?

    Posted by AMW | October 29, 2015, 9:05 pm
  4. I made friends with a construction crew… I know there is a grounds crew that regularly cuts the grass… they may or may not be friendly as well… seems risky to hop the fence and dash across considering the wide open lawn, which is why I never dared to try that!

    Posted by Thomas Kenning | October 30, 2015, 12:14 am
  5. These photos, how did you take them? And when? Is there a way to access the site (without getting stuck on barbed wire)? I want to visit before it’s gone!

    Posted by enigmaticattic | July 1, 2016, 12:52 am
    • I actually walked up one day when there was a construction crew present… I introduced myself to the foreman, and he was really great… walked me through and showed me a few points of interest. It’s a hard place to access on the sly since it’s so wide open… but definitely a must see before it’s gone. Good luck!

      Posted by Thomas Kenning | July 1, 2016, 1:26 am

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