Grey vs. Green: Daylighting the Saw Mill River

Spanning the corridor between the 42nd Street/Bryant Park BDFV station and the 5 Av 7 station, Samm Kunce’s mosaic “Under Bryant Park” is an evocative imagining of the root and water paths behind the tiled walls. Photo by Zach Youngerman.

Spanning the corridor between the 42nd Street/Bryant Park BDFV station and the 5 Av 7 station, Samm Kunce’s mosaic “Under Bryant Park” is an evocative imagining of the root and water paths behind the tiled walls. Photo by Zach Youngerman.

Unexpected stalactites drip down from the ceilings. Along the center of the tracks are rills. Somehow in the subways, there is always water. Pulled by gravity, it moves through the small spaces in concrete and soil – technically called pores – and seeps out through the tile grout. Like the puddle we step over at the corner, most of us don’t spend much time thinking about how the water got there or where it’s going.

The movement of water is universal. What takes it out of the ordinary is the infrastructure we have built around and in spite of it. Dr. Eric Sanderson’s decade-long project and eponymous book to reconstruct the ecology of 1607 Mannahatta notes that there were once 34.9 miles of “rocky headwater stream communities” and 14.2 miles of “marsh headwater stream communities” on our island, in addition to numerous springs, ponds, and intermittent streams.

There are some remote places of the outer boroughs where ancient but small waterways run above ground. Though fed by storm drains, Gerritsen Creek travels uncovered in Marine Park, Brooklyn, creating a estuarine ecology in an otherwise saltwater marsh. Similarly, Alderbrook in the Riverdale neighborhood of the Bronx emerges from storm drains before rushing down steep slopes to the Hudson. Tibbets Brook, whose headwaters are in sylvan Westchester, is the reverse. Its uncovered route collects in charming Van Cortlandt Lake before being sent through culverts alongside the Major Deegan Expressway and unnoticed into the Harlem River.

But all of Manhattan’s water paths were filled in or covered over. Now, the city’s 46 inches of annual rainfall are blocked by impervious tar roofs, concrete sidewalks and asphalt streets. To handle the water that once moved over and through the ground are storm drains and thousands of miles of pipes that lead the water into sewers. With even minor rainfall, the combined sewers overflow with rainwater and untreated wastewater into receiving waterbodies, violating the Clean Water Act.

The entity in charge of stormwater, the Department of Environmental Protection has undertaken a substantial effort to integrate natural systems with infrastructure, partly in response to groups like the Stormwater Infrastructure Matters (SWIM) Coalition and the New York State Department of Environmental Conservation, which imposes Clean Water Act fines. The DEP outlined its system-wide endeavor to improve water quality in its recently-released Green Infrastructure Plan. In place of traditional grey infrastructure like pipes and storage basins, the plan details their methods for capturing and absorbing water through green infrastructure – enlarged street tree pits, rain gardens, and greenspace.

The wonder of green infrastructure is that it involves plants and a host of other species which become more productive and therefore more valuable over time. Plant a sapling and fifteen years later it absorbs more water, provides more shade, produces more oxygen. The microorganisms in its soil filter more pollutants. As written about in an Omnibus feature last month, the DEP has created a model strategy for addressing runoff in spacious Staten Island through “Blue Belts” which take advantage of natural mechanisms.


Rendering of Saw Mill River after daylighting | Courtesy of Saratoga Associates

Rendering of Saw Mill River after daylighting | Courtesy of Saratoga Associates

Work is now underway to make visible the Saw Mill River in Yonkers, which is currently covered by a public parking lot called Larkin Plaza. The raison d’etre of that industrial city, the River had been put into a flume in the 1920s by the Army Corps of Engineers as a sanitation and flood control measure. The support of ever-broadening stakeholders, including Governor Pataki, Yonkers mayor Philip A. Amicone, former State Senator Nick Spano and opponent-turned-proponent developers, culminated in the groundbreaking of the project last month. The discovery of American Eel in the River by local environmental group Groundwork Hudson Valley critically shifted the project design from an open hard-edged channel to a recreated habitat.

Not that the Saw Mill’s “daylighting” means restoration to a former ecological functionality. In fact, the water flowing over replanted reeds and rocks arranged just-so will be ancillary to the flume. Such limits to ecological restoration force us to evolve past a dualistic stance that puts storm drains in one category and naturalized creeks in another. The water-oriented environmental comeback stories in New York have come because groups like the New York Restoration Project, the Bronx River Alliance, and the Parks Department’s Natural Resources Group have embraced such an understanding.

Every couple of years, the New York Times runs an article about a leaky basement which proved mysterious until a fortuitous discovery placed the site in the path of an ancient stream bed. Scott Cuppett, who works for the NYS DEC’s Hudson River Estuary Program, is skeptical about any permanent streams hidden beneath Manhattan, though. “Once you cover it over and put it into a pipe, you disconnect it longitudinally and laterally from groundwater, which is what feeds streams in dry weather.”

Doing so also disconnects us, simultaneously mediating our interactions with and altering the environment. We encounter water at our faucet and toilet, occasionally in the street, and abstractly on our bills. We are ignorant of, and thereby dangerously irresponsible for, our combined and individual actions. Making our water infrastructure more visible and highlighting where our water is already in sight will help educate us.

New York’s Green Infrastructure Plan calls for capturing 10% of the first inch of rainfall (consistently the most polluted) through green infrastructure. Hopefully these new infrastructures will consider how heuristic the user interfaces with that system are. Are there innovative ways to let residents know that they’re in the Gerritsen Creek watershed even if the Creek remains channelized at its source? Could the markers that read “Don’t Pollute. Drains to River” be put at the edge of subway platforms?


The views expressed here are those of the author only and do not reflect the position of Urban Omnibus editorial staff or the Architectural League of New York.

Zach Youngerman is a designer who works broadly on integrating cities and ecology. He grew up in Riverdale, in the Bronx. He spent four years in New Orleans after Hurricane Katrina and the breaching of the Federal levees doing recovery planning and green stormwater management. His goal is to help citizens understand, enjoy, evaluate and manage urban structures and their associated natural environments.

The views expressed here are those of the authors only and do not reflect the position of The Architectural League of New York.


Nathan Glazer January 13, 2011

Fascinating–the uncovering or recovering of paved over or concreted rivers (Seoul, Los Angeles) is an important and recurrent issue in the improvement of cities.