Mercer Plaza: Make Way for NYU Green Initiatives

Image: Pre-construction, 251 Mercer Street, facing south (source)

About four years ago, residents of the 250 Mercer Street co-op protested against NYU's underground heat and power plant renovation because approximately 18 mature trees would have to be removed.  An incomplete slum clearance/ urban renewal project in the 1950s resulted in superwide sidewalks on LaGuardia Place and Mercer Street between West 3rd and Houston Streets.  If any of the afore-mentioned trees were planted then, then they were at least 50 years old.  Opponents of the project argued that the trees could be saved if the university built its power plant underneath Gould Plaza instead of under the public right-of-way at 251 Mercer Street.The City eventually approved the university's plan and the trees were removed. 

Interestingly, the power plant project was endorsed by the U.S. EPA.  The agency cited a 43,315 ton reduction in annual carbon emissions with a combined heat and power (co-generation) system.  I wonder if the university, the City, and other institutional actors compared that reduction to the "net CO₂ reduction" of 113,016 tons across an estimated population of 592,130 street trees (source: New York Municipal Forest Resource Analysis, Paula J. Peper et al., 2007).

Image: Post-construction, Mercer Plaza at 251 Mercer Street, facing north

A 13,000 square foot plaza -- and sidewalk -- replaced the original parallel sidewalks and fenced landscape areas this fall.  (Is the plaza considered a POPOS or privately owned public open space?)  The plaza was designed by Mathews Nielsen Landscape Architects and planted with trees, shrubs, and herbaceous perennials.  The original tree palette listed witch hazel (Hammemelis virginiana is technically a shrub), hophornbeam (Ostrya virginiana), cockspur hawthorn (Crataegus crus-galli L.), tulip tree (Liriodendron tulipifera), willow and shingle oaks (Quercus phellos and Q. imbricaria), and sweetgum (Liquidambar styraciflua).  A Curbed NY story provided the species growing on the site in 2006: Japanese lilac (Syringa reticulata), honey locust (Gleditsia triacanthos) and Callery pear (Pyrus calleryana), none of which are native to the region.

Image: Trees at Mercer Plaza

The street trees -- willow oaks -- planted as part of the project are larger than the Parks Department's minimum size requirement (2.5 inch diameter).

Finally, a design element I particularly like is the elevated walkway through parts of the plaza which separates foot traffic from the root zones of the trees.  As a result, there should be less soil compaction and thus greater air and water penetration into the soil.  I wish the entire plaza had been constructed in this way.

Editor's note: August 2, 2011: I hope this boardwalk design is different from the one used at Washington Square Park in which the Zelkovas are dying.