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EPA’s Superfund program protects citizens from the dangers posed by abandoned
or uncontrolled hazardous waste sites. In the past, getting these
sites cleaned up often required a significant outlay of energy and non-sustainable resources.
The traditional approach for contaminated soil has been to excavate
the material and haul it away. Unfortunately, this operation has a domino effect,
by disturbing uncontaminated areas, including the clean fill needed to backfill the excavation.
Now EPA has introduced a Green Remediation initiative for these sites
that considers the environmental effects of the remedial strategy early in the process,
and incorporates options to maximize the net environmental benefit of the cleanup.
From the selection and design of the remediation technology, to the management of
on site activities, to the use of energy conservation and alternative sources of clean energy,
Green Remediation helps save natural resources and taxpayers dollars.
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Outside the small Virginia town of Crozet, EPA is doing just that,
by using phytoremediation to remove arsenic contamination from a residential property.
Phytoremediation uses specially selected plants to remove or reduce the risk of
contaminants in the soil, water, sediments, and air.
The 2 acre site, a former orchard, is contaminated with arsenic
which is a by-product of pesticide application on fruit trees.
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Myles Bartos: Prior to 1972 there was legal application of pesticides, lead arsenates,
DDT, DDE and DDD. EPA banned them in 1972. However, there’s a lot of
orchards that still had their product on the soils. And since then, a lot of these orchards
have been sold off and developed into residential properties.
Arsenic doesn’t break down like DDT, DDE and DDD does, so that is a little more
pervasive in sticking around. It’s not very mobile so it actually stays
in place where it is. And that’s actually helping us because we don’t have to go chasing
it to deep depths. Essentially the top roughly zero to six inches are contaminated.
The contaminated areas of the hillside are used by adults, children
and pets on a daily basis. Because Arsenic is a known carcinogen, mutagen,
and is detrimental to the immune system, the soil needed to be cleaned up.
Phytoremediation was chosen because if conditions are favorable,
the technology can be effective, while having minimal impact on existing topography and the ecosystem.
Phytoremediation is also considered an In-Situ, or in place remediation approach, which
means the contaminated media isn’t transported off site. And since plant cultivation
and harvesting are relatively inexpensive processes, phytoremediation has significant
cost saving advantages compared to traditional clean up methods.
Scott Fredericks: Superfund has been around 25 years. We’ve learned a lot about,
if you dig and haul, it’s a very energy-intensive operation. You have huge
equipment that takes a lot of money to operate.
Instead of bringing in a lot of heavy equipment, being very disruptive knocking down
all these trees, hauling off all this dirt and putting it someplace else,
and then trying to find some clean soil to bring back in here, they’re trying to do an
In-Situ extraction using these ferns.
The ferns being planted were developed at the University of Florida and licensed to
Edenspace, a leader in the use of plants for environmental protection and renewable fuels
Michael Blaylock: We’ve done a lot of work looking at different plants and their ability to
accumulate arsenic. And we found that really only ferns in this particular
genus - Pteris ferns - accumulate arsenic. And they take up arsenic to a very high concentration.
They tolerate high arsenic concentrations in their leaves and they do a remarkable
job of extracting it from the soil.
In fact, the hyper-accumulating 'Victory' variety of Pteris vittata (terrace vit-tah-ta)
sold by Edenspace, under the label Edenfern, holds concentrations greater than
200 times more than other plants tested for Arsenic phytoremediation,
and is adaptable to conditions in a variety of climates.
USEPAs relationship with the property owner also helped in choosing phytoremediation.
Jim Dugan: I feel a real close connection to the property. And I wanted to be at the
property sort of like if you have a patient in the hospital. You want to be there with that person.
And I consider this land my responsibility, and I have been able to work with the EPA members.
They’re really friendly and they don’t mind my so-called interference.
Getting the job done is relatively simple. Areas of the hillside with elevated levels of
arsenic were mapped into 30 by 30 foot plots, then tilled to a depth of approximately four inches.
Michael Blaylock: The goal here is to be able to optimize plant growth.
Because if we get the plant roots to develop well, and get the plants to grow well,
they will take out more arsenic from the soil. So we want to do everything we can to
prepare the site and to try to optimize the plant growth.
Myles Bartos: We did soil composition testing to see what sort of nutrients we need to apply.
In this case we did a very mild nitrogen-based fertilizer, slow-release formula,
put a little lime in to neutralize some of the soil. Once we do that, we lay down landscape fabric,
and cut holes in it in a one square foot area. And in this particular case you’re doing 30 X 30 grids.
Michael Blaylock: Then we transplant the ferns in. And from then on out it’s a matter of
keeping them wet until the roots get established in the soil. And providing the shade
that they need in an environment like this, that’s easy because of the trees.
In the few areas where direct sunlight could reach the ferns,
60% shade cloth was placed over the plot to improve plant growth.
For irrigation, the plots were divided into two systems. The first system utilizes a
spring at the top of the hill close to the residence which gravity feeds into a storage tank,
which in turn gravity feeds the fern plots.
The other half we’re going to use a solar panel pump. A low pressure drip tape irrigation
was installed to deliver fresh water to the ferns during dry spells. During periods
of adequate rainfall, water from the spring will be diverted and recovered into
the storage tanks for later use.
The ferns will be grown for approximately five months or until night temperatures drop
below freezing and plant growth and biomass production ceases.
The fern biomass will be harvested, and then sampled for arsenic content.
Because arsenic levels in the harvested plants are expected to be below prescribed levels,
they can then be disposed of in a municipal landfill.
Soil sampling will be conducted at the end of the growing season and compared
to pre-planting samples to determine the ferns effectiveness.
Michael Blaylock: In some areas the arsenic concentrations are higher and it will take more
than one season we anticipate. But for a large part of this site,
we think we can do in it one year.
Phytoremediation is idea for targeting small areas like the 30 by 30 plots at the Crozet
sites. The technology does have limitations though. At some sites contamination may
just be too deep for plant roots to reach. But under the right conditions,
phytoremediation is a win-win for clean up teams and the public.
Michael Blaylock: People generally like the idea of being able to use a plant to take contamination
out of the soil, that’s something that has a lot of public appeal and I get a lot
of positive feedback for it.
Scott Fredericks: And nothing succeeds like success. So this site is important,
I think, because it represents what’s it is we’re seeing more of across the country in other states,
especially on the west coast – old orchards that are being built upon,
people retiring on them or they’re just building homes as part of urban sprawl.
With this technology, It’s very low impact and you’re not using a lot of energy.
What we’re using here are sustainable, or clean energy forms. We’re using solar panels
to drive our pumps for the drip irrigation system and we’re
using a minimal amount of energy.
Myles Bartos: The goal here is not to be green, but it’s a really good secondary thing.
Our goal is to protect public health and the environment.
This happens to be an alternative technology that will do that with less waste and a
greener atmosphere. So it actually goes along with the EPA initiative
of going green and it also achieves our tasks within the removal progra.
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