=======================Electronic Edition========================
RACHEL’S HAZARDOUS WASTE NEWS #163
—January 10, 1990—
News and resources for environmental justice.
——
Environmental Research Foundation
P.O. Box 5036, Annapolis, MD 21403
Fax (410) 263-8944; Internet: erf@igc.apc.org
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SUPERFUND–PART 3: GROUNDWATER CLEANUP IS HARDER THAN PREVIOUSLY
THOUGHT
[Continuing our series on Superfund cleanups. Page numbers in our
text refer to pages in the latest report from Congress’s Office
of Technology Assessment (OTA), cited in our last paragraph,
below.]
Groundwater is water that resides underground. Contrary to some
popular beliefs, most groundwater is not rushing along in
underground rivers. (In some limestone caves, there may be
occasional small underground rivers, but such rivers do not occur
elsewhere.) The vast majority of groundwater occurs not as rivers
but as a huge underground lake. Groundwater does move, but only
very slowly. Fast-moving groundwater may move one foot per day;
slow-moving groundwater may move one foot per year. Groundwater
moves because it is pulled by gravity, and its ultimate
destination is the nearest ocean. Once in the ocean, it
evaporates (because of sunlight), forms clouds, moves over the
land, rains down, sinks into the ground, becomes groundwater, and
starts moving slowly toward the ocean again. That is the
“hydrologic cycle.” As we saw in RHWN #155, there is 40 times as
much groundwater below the earth’s surface as there is in all the
world’s lakes and rivers.
Any place where groundwater can be pumped to the surface in
quantities that are useful to humans is called an “aquifer.”
The surface of the groundwater (the surface of the underground
lake) is called the “water table” and it resides about 30 feet
below the surface of the ground. Thirty feet is the average
depth, but the depth varies considerably from place to place.
When the water table sits on the surface of the land, we call
that a swamp. In some places–particularly in the far western
states–the water table may be several hundred feet below the
surface. The earth below the water table is called the “saturated
zone” because there the spaces (“pores”) between soil (or rock)
particles are filled with water; the earth above the water table
is called the “vadose zone” or the “unsaturated zone.”
In many places, groundwater and surface water intermingle.
Groundwater can feed streams by welling up from below, or pushing
into a stream from its sides; likewise, streams can lose water
from their bottom and sides, feeding the groundwater. These
relationships can change with the seasons and can vary from year
to year, depending on local and regional rainfall. The nature of
the connections between surface water and groundwater in a
particular place can be determined by hydrologists who study the
local situation carefully and thoroughly and for a sufficiently
long time to notice seasonal and annual variations. Usually such
study will require the drilling of wells and the taking of water
samples to determine the direction and speed of water flows.
When groundwater becomes contaminated, it does not cleanse itself
as surface water tends to do. The turbulent action of a flowing
river, which mixes oxygen into river water and tends to dilute
contaminated water with clean water, is absent in groundwater
flows. Likewise, there are fewer bacteria in contact with
groundwater, compared to surface water, so bacterial action does
not cleanse groundwater as it might surface water. Furthermore,
groundwater does not have the benefit of sunlight, and it is also
relatively cool. For all these reasons, contaminated groundwater
tends to remain contaminated for long periods of time measured in
decades or centuries or aeons. On a normal human time scale,
groundwater contamination can be considered permanent.
Half of all the people in the U.S. derive their drinking water
supplies from groundwater. Because of connections between
groundwater and surface water, contaminated groundwater can
affect the quality of surface waters and can thus impact wildlife
(including fish, and mammals that rely on surface water for
drinking). Therefore, groundwater is an essential ingredient for
life, a national resource that should be protected.
When Congress passed the Superfund law in 1980, part of the goal
of the program was to clean up contaminated groundwater. The U.S.
Environmental Protection Agency (EPA) took an optimistic view of
the problem and began using “pump and treat” technology at many
contaminated sites. Pump and treat means that groundwater is
pumped to the surface and treated in some fashion to remove
contaminants. The assumption is that the contamination will be
pumped to the surface with the water and can then be treated by
some process to remove it or detoxify it. The resulting clean
water can then be returned to the groundwater via an injection
well.
The EPA still takes an optimistic view of “pump and treat” but a
large body of scientific evidence has now accumulated showing
that pump and treat does not work and–given today’s
knowledge–cannot work. The latest Superfund study by the
Congress’s Office of Technology Assessment (OTA) discusses the
disappointing record of achievement by “pump and treat”
technology (see pgs. 151-157).
The OTA study, citing many scientific papers, makes the following
points about “pump and treat”:
1) Much contamination attaches itself to soil particles.
Therefore, using water samples to estimate the amount of
contamination will result in major underestimates of the size of
the problem because most of the contamination isn’t in the water
but is attached to the soil. The contamination detaches itself
from the soil and joins the water only very slowly, thus
requiring an exceedingly long pumping program–perhaps hundreds
of years–before all the contamination is pumped to the surface.
2) The soil and rock formations below ground are not uniform.
Mathematical models of groundwater flow are built on the
assumption of some “average” flow rate through the entire
aquifer. However, because groundwater flows rapidly through some
places and slowly through other places, pump and treat programs
will take a long time to flush contamination out of areas where
water-flow is slow. Calculations of “average” flow rates greatly
underestimate the time it will take to flush contaminants out of
the parts of an aquifer through which water moves slowly.
3) “Using current site investigation and remediation
technologies, it is not possible to locate all significant
contamination, nor can anyone accurately predict contaminant
movement, fate, exposure, or remedial technology performance.”
(pg. 151)
4) Particularly difficult to clean up are contaminants that do
not mix readily with water (such as oils), especially those that
are heavier than water and thus tend to sink rather than float on
the water table. Contaminants in this category include
chlorinated solvents (such as trichloroethylene, or TCE),
creosote, and PCB-rich oils. Very little success has been
achieved in even locating such contaminants, much less in
removing them. In general, it is appropriate to view pump and
treat programs for these contaminants as “remediation in
perpetuity” (pg. 153). That is to say, we should expect to have
to pump and treat into the foreseeable future with no end in
sight.
The implications of all this are profound. Pump and treat may
prevent contamination from spreading, because pumping disrupts
the normal flow of groundwater (which is toward the ocean) and
thus can prevent the spread of contaminants to new areas, which
is good. On the other hand, if most of the contamination is not
being removed by pump and treat, some day the money will run out
for maintaining the pumps; on that day the contamination will
resume its natural movement and citizens may be threatened. It is
therefore important to recognize that pump and treat is not a
permanent remedy; after the pump is turned off, the problem will
then have to be addressed by some different (hopefully permanent)
cleanup technology. (On permanent cleanup technologies see RHWN #150).
We must ask, instead of pump and treat, does digging up
the wastes make sense, removing the soil and chemically (or
thermally) processing it to detoxify the contaminants? Citizens
must now explore these alternatives wherever pump and treat
programs are under way or are contemplated.
Two excellent sources of information on groundwater:
David W. Miller, editor, WASTE DISPOSAL EFFECTS ON GROUNDWATER
(512 pages; this 1977 book is now officially out of print, but is
still available for $18 from Geraghty & Miller, 125 East Bethpage
Rd., Plainview, NY 11803; phone (516) 249-7600.
U.S. Environmental Protection Agency, HANDBOOK: GROUND WATER
(Washington, DC: U.S. Government Printing Office, 1987).
Available free from U.S. Environmental Protection Agency (U.S.
EPA) Office of Research and Development, Publications Office, 26
West MLK Drive, Cincinnati, Ohio 45268; phone (513) 569-7562; ask
for EPA Technology Transfer Publication 625/6-87/016.
Get: U.S. Congress, Office of Technology Assessment, CLEANING UP:
SUPERFUND’S PROBLEMS CAN BE SOLVED (Washington, DC: U.S.
Government Printing Office, 1989). Available for $10 from U.S.
Government Printing Office, Washington, DC 20402-9325; request
GPO stock No. 052-00301166-2. Phone (202) 783-3238. Charge it to
Visa, Mastercard or Choice.
–Peter Montague, Ph.D.
Descriptor terms: groundwater; landfilling; superfund; remedial
action; alternative treatment technologies; pump and treat; ota;
epa;