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Solidification/Stabilization Treatment of
Arsenic- and Creosote-Impacted Soil at a Former Wood-Treating Site
Waste Treatment
Home > Brownfields > Port Newark
Port Newark, New Jersey
By: Charles M. Wilk and Robert DeLisio
 Recent
brownfield legislation and initiatives provide significant incentives
for the clean-up and redevelopment of commercial properties in prime
locations that have been left vacant due to environmental impacts
of past industrial practices. One such site is located in Port Newark,
New Jersey, one of the largest shipping ports in the New York/New
Jersey area. Located within the port, this 3-hectare (8-acre) property
was used for wood preserving operations from 1940 to 1991. Preservatives
used at the facility included creosote and chromated copper arsenate
(CCA). The property remained vacant from 1991 until redevelopment
began in 2000.
Redevelopment plans called for remediation of the arsenic- and creosote-impacted
soil at the site. Portland cement-based solidification/stabilization
(S/S) treatment was selected to address the impacted soil. S/S treatment
involves mixing cement into impacted media such as soil, sediment,
or sludge, in order to physically and chemically immobilize hazardous
constituents within the treated material. The U.S. Environmental
Protection Agency considers S/S to be an established treatment technology.
S/S technology has been selected for use at 23% of the nation’s
Superfund sites where the sources of contamination have been addressed.
S/S is designated as Best Demonstrated Available Technology (BDAT)
for over 50 RCRA-listed hazardous wastes. The technology has found
increasing use at brownfield remediation projects due to the ability
to reuse S/S-treated soil as an engineered fill or pavement base.
Site Impacts & Mixing Methods
Investigations at the site found free-phase creosote in "deep"
soil (0.6 to 4 meters [2-12 feet]), and arsenic-impacted surface
soil (0 to 0.6 meters [0-2 feet]). Two methods of mixing cement
into the impacted soil were used—in-situ mixing of deep soil,
and ex-situ mixing of surface soil.
In-Situ S/S Treatment of Deep Soil
 Wood
preserving activities involving creosote impacted a 0.8-hectare
(2-acre) area at the site. Within this area, approximately 18,000
m3 (24,000 cu yd) of soil was impacted with creosote
from a depth of 0.6 to 4 meters (2 to 12 feet) below grade.
Treatment of these deeper soil began with stripping the top 0.6
meters (2 feet) of surface soil from the site and staging it for
subsequent treatment. In-situ S/S treatment of the deep soil was
carried out by mixing cement into the soil in two subsequent mixing
lifts. After stripping the surface soil, crews excavated these
areas to a depth of 1/2 of the total depth of impacted soil. Soil
removed was staged at the edge of the excavation. Cement was mixed
into the remaining lower 1/2 portion of the impacted soil using
an in-situ blender.
The insitu blender resembles a rototiller mounted on the end of
an excavator arm. The mixing head of the blender is hydraulically
rotated. Cement slurry is first mixed in a separate mixer and pumped
to the blender by a grout pump. Then the slurry is delivered to
the working area of the blender by a jet mounted on the arm of the
excavator near the mixing head. After mixing cement into this lowest
layer of contaminated soil, the final 1/2 portion of soil was added
back into the excavated area and mixed. Using this mixing procedure,
the contractor treated an average of 340 m3 (450 cu
yd) of impacted soil per day.
An 8% addition (by weight) of cement was added to the deep impacted
soil. The target compressive strength for the treated deep soil
was set at 170 kPa (25 psi) at 28 days. The actual average compressive
strength measured on the treated material was 650 kPa (95 psi) at
7 days. A total of 3,200 metric tons (3,500 short tons) of cement
were used to treat the deep soil.
Cost of treating the deep soil—including obstruction removal,
stabilization, cement, winterization, environmental and safety control,
and mobilization/demobilization— was $1.5 million.
Ex-Situ S/S Treatment of Surface soil and Reuse as Soil-Cement
 Wood
preserving activities involving arsenic compounds impacted surface
soil at the site. This surface soil was treated using ex-situ mixing,
which not only treated the soil for contamination but also created
a construction material called soil-cement. Soil-cement is a mixture
of soil, portland cement, and water compacted to a high density.
It has been used in a variety of applications including base course
for pavement, slope protection, ditch lining, and foundation stabilization.
At this project site, the S/S-treated surface soil was reused as
subbase and base course for pavement constructed at the site.
Approximately 23,000 m3 (27,000 cu yd) of arsenic-impacted
surface soil were stripped from the surface of the site up to a
depth of 0.6 meters (2 feet). This soil was mixed with cement and
mixing water in a mobile pugmill erected at the site. A conveyor
scale on the pugmill equipment ensured that 8% (by weight) cement
was mixed into the soil. A total of 3,900 metric tons (4,300 short
tons) of cement were used in this process.
Using conventional soil-cement techniques for placement, grading,
and compaction, the treated soil was reused at the site as subbase
and base for subsequently-constructed pavement. The target compressive
strength for the treated soil was set at 1,700 kPa (250 psi) at
7 days. The actual average compressive strength measured on the
treated material was 4,000 kPa (600 psi) at 7 days. Depending on
site conditions, the contractor was able to mix and place the treated
soil at a rate of 150 to 500 m3 (200 to 700 cu yd) per
day.
Cost of treating the surface soil—including stabilization,
cement, screening/ crushing, placement, compaction, environmental
and safety control, mobilization, and demobilization—was $1.7
million.
Completed Remedy
 As
a result of the treatment, creosote- and arsenic impacted soil
were successfully treated and contained at the site, and the property
was returned to use by the current operator.
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Authors:
Charles M. Wilk
Portland Cement Association
Skokie, IL
Robert DeLisio
Key Environmental
Pittsburgh, PA
Design Engineer/Quality Control Engineer:
Key Environmental, Inc.
Whitehouse Station, New Jersey and Pittsburgh, PA
Contractor:
Jay Cashman, Inc.
Boston, MA
Owner:
Ciy of Newark, NJ
Photographs:
Key Environmental
Portland Cement Association
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