New York City v. Con Ed (P.A.G.E.)
Notes re Use of Shot-Rock as Fill Material
These notes are intended to complement and explain the graphics and document files on this
subject.
DRAFT - 25 February 2015
John S. Horvath Consulting Engineer
1. Extensive rock excavations have always been part of engineered construction performed in
New York City, especially on Manhattan Island which has always been where most major
transportation facilities and tall buildings have been constructed and where rock is at or close
to the surface in most areas. Shown here are examples of early subway construction and the
building of Pennsylvania Station and Grand Central Terminal at the beginning of the 20 th
century.
2. In addition to on-land excavation for transportation facilities and buildings, there has also been
extensive removal of rock within and for waterways, much of it done under the auspices of the
U.S Army Corps of Engineers as they have legal jurisdiction over navigable waterways. Notable
projects include removal of numerous rock obstructions both above and below water within the
East River, especially around Hell Gate, as well as the realignment of the Harlem River and
Spuyten Duyvil Creek, which together separated Manhattan from the Bronx, by creation of the
Harlem River Ship Canal at the northern tip of Manhattan Island as shown in this graphic.
3. All of these excavations produced huge quantities of excavated material that is colloquially
referred to as 'spoil' or 'muck'. Much of it is 'shot-rock' which is simply the broken pieces of
hard, sound bedrock, some of them boulder-size (feet in dimensions), that result from rock
excavation using controlled blasting. Until recent decades, controlled blasting using explosives
was the only way to remove hard, sound bedrock. Nowadays there are other methodologies
such as hydraulic splitting, hoe-rams, and tunnel boring machines (TBMs) but blasting still
remains the method of choice on most projects. For economic reasons, it has always been
desirable, if not necessary, to dispose of this excavation spoil, including the shot-rock, locally to
minimize transportation costs. This graphic shows the use of the Inwood Marble that was
excavated in the 1890s during creation of the aforementioned Harlem River Ship Canal to
create West 204th Street in Upper Manhattan. Looking at the landscape and streetscape today
one would never know that this street is underlain by boulder-size pieces of rock.
4. Much of the excavation spoil generated by centuries of construction in New York City in general,
and Manhattan Island in particular, has been used to extend the shorelines throughout the City.
Neither LaGuardia or Kennedy Airports would exist today without landfilling. This graphic
shows how the shoreline of Manhattan Island has been enlarged over the centuries, beginning
with the original Dutch colonization of the 17th century. The orange-colored portions of the
lower map represent landfill placed to extend the land areas of Manhattan Island into the
adjacent waterways (Hudson and East Rivers).
5. The use of excavation spoil in general, and shot-rock in particular, has continued into morerecent times. This graphic shows the location of the original World Trade Center (WTC) site
which itself was the result of colonial-era landfilling along the edges of Manhattan Island along
the Hudson River.
6. The large volume of excavation spoil generated by creation of the WTC site in the 1960s was
used to create a new landfill with the Hudson River that eventually became today's Battery Park
City (BPC) and World Financial Center (WFC) complex. This graphic shows the early stages of
landfilling within the new enclosure (called a cellular cofferdam) that was constructed
specifically to contain the excavation spoil from the WTC.
-1DRAFT - 25 February 2015
John S. Horvath Consulting Engineer
7.
8.
9. This series of three photos taken looking NW...N...NE from the southern edge of the WTC-BPC
landfill site during the final stages of filling shows the prominent use of very large pieces of
shot-rock within this landfill. Because bedrock was the last to be excavated within the WTC
'bathtub' it was the last material to be placed within the WTC-BPC landfill.
10. This photo shows the WTC-BPC landfill site near its completion. Note that there is no surface
evidence of the large pieces of shot-rock buried within the underlying fill. Certainly anyone
visiting that area today would not have any idea of the nature of the underlying material.
11. This document discusses the historical usage of shot-rock as fill material throughout New York
City as well as present usage. The only thing that has changed in the present is that we are now
more aware of some of the problems that can result from using large boulder-size pieces of rock
as fill material so sometimes crush the rock into soil-size particles to better control the
placement.
12. This article also discusses some of the current usage of shot-rock in New York City and points
out some of the problems with using large boulder-size pieces of material.
Prepared by John S. Horvath, Ph.D., P.E. d/b/a John S. Horvath Consulting Engineer
25 February 2015
-2DRAFT - 25 February 2015