By Dominique Otiepka
Pompton Lakes has been exposed to a
variety of toxic chemicals that were released by DuPont Chemical Company. Over the
course of the semester, I have been conducting extensive research on soil
contamination in Pompton Lakes.
I explored the soil types,
the ways the soil responds to chemicals, considering weather impacts, and
reviewed the remediation and toxicity of contaminated sites. This
research considers each of these topics because soil contributes to the health
of the community.
Analyzing the soil will help further understand how the released chemicals
influence different components throughout Pompton Lakes and how they remain
within the environment, unless proper remediation efforts are completed.
The DuPont Chemical Company site
itself was never fully remediated; it is a source for constant chemical
migration from the property. Some chemicals released included lead, mercury,
chromium, and copper, which had absorbed into the soil throughout DuPont
Village. The soil type within Pompton Lakes is permeable and can easily absorb
water and chemicals more readily than other soil types. Such toxins are
capable of remaining in the soil for extended periods of time, which is
referred to as soil persistence. Soil persistence occurs in various ways.
Soil persistence occurs in every type of soil, though lasts for a prolonged
time in clay-based soils.
Regarding soil persistence, the
released contaminants that have been found in the soil can either volatize,
evaporate, bind tightly to the soil, end up in the water held within the soil
particles or in the underlying groundwater. Sandy loam tends to have
much larger pore spaces because the sand grains are more irregular in shape and
do not compact as readily as other soil types. The arrangement and size of soil
particles within the soil can change the flow path for water, gases, and pollutants.
Pore spaces are further identified
by macropores and micropores. Macropores tend to allow movement of air
and percolating water very readily, whereas micropores are the first to be
filled with water in a moist field soil and do not permit much air movement
into or out of the pores. The size of the sandy loam particles varies, since
the soil consists of sandy loam, fine sandy loam, and coarse sandy loam in the
alternating soil layers. Measurements of particles range from 0.1 to 1mm.
Due to this porous soil type, chemicals do not have the ability to bind tightly
to the particles because sandy loam is not aggregated. Instead, the soil
structure allows for both the absorption and evaporation of chemicals.
Impacts
from Rainfall and Wind on Soil in Pompton Lakes
The DuPont plant site was built on a
higher elevation that drains to a small stream called Acid Brook. Hurricane Irene and Hurricane Sandy and other storms caused
Acid Brook to overflow. The soil, which was originally sandy loam, was
excavated approximately eight feet down, then filled with clay on contaminated
properties in DuPont Village between the years of 1992 and 1996. This in turn,
led to the soil being clay on resident’s properties in DuPont Village, since it
was used to fill the excavated areas. The clay that was utilized was from a
location outside of Pompton Lakes that was brought in by truckloads and was
chosen to prevent further absorption of chemicals.
Clay absorbency properties are
limited, and clay does not percolate, although, it furthers the spread of
chemicals from flooding throughout the town and have forced water into the
lower levels of homes that were remediated with the clay. Clay soil drains
poorly, and only absorbs approximately ¼ of an inch of water every hour.
Meanwhile, sandy loam absorbs water at a rate of more than 2 inches per hour.
Pompton Lakes has excessive flooding
in the southern end of the town, which has flooded up to four feet in the past
due to hurricanes. When there is intense rainfall, the topsoil may be easily
removed and carried by the water runoff, which can pick up other contaminated
soil particles and transfer them as well. The average annual precipitation
ranges from about 47-54 inches throughout the county, with about 33
thunderstorms each year. Partly thawed soils tend to be very erodible
during periods of heavy rainfall, especially during the winter months. With
flooding, contamination within the water bodies can spread outward to
neighboring towns.
Wind may also carry and relocate
chemicals, which are then deposited on the surface of soils; this soil
structure allows particles to be moved readily. The direction of wind in this
region is from the Northwest. The soil pile placed near Lakeside School
after dredging Pompton Lake could have been deposited in the Southeast
direction off site, either in the Pompton Lake or across it, towards Wayne.
Dust monitoring was utilized to
assess potential impacts of the remedial action on the surrounding environment
and community. Dust monitoring was conducted at one upwind and two downwind
locations. The forecast wind direction for each day was considered.
Locations that were upwind of the activity measured dust levels coming into the
processing area as well. Monitoring activities were performed during
excavation, dredging, material handling and processing, and will be performed
when the eco-layer placement occurs during the final steps of remediation. The
final phase of soil removal from Pompton Lake is on schedule to occur in May
2018.
The average hourly wind speed in
Passaic County has significant seasonal variation over the course of the year.
The windier part of the year lasts for 5 months, from November to
April, with average wind speeds of 5.6 miles per hour (m/hr). The wind
velocity must be greater than 15 m/hr for wind erosion to occur on bare soil,
but if the surface is disturbed by buildings or cultivation, then a wind speed
of only 3 m/hr is required to start soil moving and once moving, it will
continue to move. The annual wind speed in Passaic County of 5.6 m/hr is
greater than the wind speed that can move soil particles in this occupied area,
which is only 3m/hr. The climate conditions in Pompton Lakes can evidently
spread the chemicals throughout the town through wind and flooding.
Vapor
Intrusion Pathway
DuPont’s toxic waste has
contaminated the soils and sediments by absorbing the contaminated water from
overflow events. Much of the contamination came from previously detonated
blasting caps which contained mercury, lead salts, and chlorinated solvents.
Chlorinated VOCs volatilizing from shallow groundwater are a potential source
of VOCs in soil gas and sub-slab soil gas overlying the groundwater plume.
Vapor intrusion refers to the migration of VOC vapors from a subsurface source,
through the soil, and into overlying homes and buildings where people can be
exposed. Since the soil located in the plume absorbed chemicals, toxic vapors
have migrated into households located over the groundwater plume. The
vapors move from the groundwater and through the cracks in the structure of the
lower part of the house.
The carcinogenic chemicals released
are PCE and TCE. The impacted soil is a result from toxic vapors rising
from the groundwater, located beneath the soil layers. The chemicals are
released through gas and migrate upward. Residents have not been removed from
their houses, even though chemicals migrated to places underneath their houses,
so Vapor Intrusion Mitigation Systems have been installed.
Acid Brook Delta and Pompton Lake: Soil and Sediment Removal
Hydraulic dredging of a 36-acre
portion of the Pompton Lake has been completed, according to the New Jersey
Department of Environmental Protection. A final remediation step includes
restoring the previously dredged materials with the placement of an
ecological-layer consisting of naturally washed sand. Shoreline areas
will be stabilized and planted, and wetland areas disturbed by dredge
operations will be restored through backfilling and installation of materials
such as coir logs. The input of sand will be approximately 6 inches in depth,
though the US Fish and Wildlife Service argued for a thicker cap; any
contaminants remaining in the sediment and soils that had not been dredged
could move up through the sand layer by way of the water that fills the spaces
between each grain of sand.
Where the Acid Brook flows into
Pompton Lake, known as the Acid Brook Delta (ABD), approximately 128,000 cubic
yards of sediment and soil were removed. Results from investigations at the ABD
show that the greatest total mercury (THg) and methylmercury concentrations in
sediments and soil were near the mouth of Acid Brook.
An expansion of the ABD removal area
was initiated in 2016 and will be developed over a five-year monitoring period.
Expansion of the ABD removal area consists of additional locations between the
Lakeside Avenue Bridge and the Pompton Lake Dam. The other two are Area A and
Island Area. Island Area is defined as the soils between Lakeside Avenue and
the edge of the water in Pompton Lake.
In expanding the removal area, the
locations for potential exposure with elevated mercury concentrations in
sediments will be removed. Methylmercury concentrations measured in the
water were in the upper range in areas of Pompton Lake outside of the ABD.
Additional sediment removal reduces the overall exposure to methylmercury
within the expanded ABD removal area. Area A is a shallow, near-shore area
adjacent to the southern extent, which has the potential to being exposed to
materials containing THg. With the elevated subsurface, the removal of THg
concentrations in sediment in Area A is being conducted to reduce the potential
for future exposure of subsurface materials that may contain elevated THg
concentrations.
Acid Brook Remediation
Removal of contaminated soils and
sediments has been completed in Acid Brook as well as on the properties that
surround residential houses alongside Acid Brook. In 1991, DuPont
began the remediation of contaminated sediments in Acid Brook and on
residential properties; this was completed in 1997. The recorded removal depths
generally ranged from 0.5 to 9 feet below the ground surface. The current
total of estimated removal volume was approximately 3,160 cubic yards.
Lead and mercury were the
constituents driving the remediation in both extent and depth in Acid Brook.
The highest mercury concentrations, greater than 100 milligrams per
kilogram, (mg/kg) were generally found in the sediment near the Acid Brook
discharge.
In Conclusion
Since the 1990s, efforts have been
made to try and clean the soils affected by the chemical release from DuPont
Chemical Company. But residents believe that it is not enough or thorough,
since their health has been impacted directly and indirectly. Most of the soil
remediation in Pompton Lake will come to an end in the summer of 2018, although
it will continue in the Acid Brook Delta expanded removal areas.
Dominique
Otiepka is a graduating senior at Ramapo College with a BA in Environmental
Studies. She has dedicated time to
various environmental research projects and has completed an Environmental
Impact Statement with the Environmental Studies senior class in her final
semester. She is thrilled to use her knowledge after graduation and make a
positive impact wherever she is.
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