Recommendations to Clean Up and Protect
the Biscayne Aquifer in Southeast Florida
n
Manatee
X
Okeechobee . i St. Lucie
Lake Okeechobee
West
Palm
Beach
HOLLINGSWORTH
DAVIE LANDFILL
Gulf of Mexico
Lauderdale
iRT^j
DRUM
EPPER'S STEEL
VARSOL SPILL (MIAMI AIRPORT)
GOLD COAST OIL
DAVIDSON S LUMBER
Superfund Hazardous Waste Site
O Municipality
Atlantic Ocean
An overview of a four year study by the EPA
of selected hazardous waste sites and
their effect on the Biscayne Aquifer.
Key West
&EPA
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Contacts
Dade County:
Bill Brant
Dade County Department of Environmental
Resources Management (DERM)
13th Floor
111 Northwest First Street
Metro-Dade Center
Miami, FL 33128
(305) 375-3321
State of Florida:
Roy Duke
Florida Department of Environmental
Regulation (DER)
3301 Gun Club Rd.
West Palm Beach, FL 33402
(305) 689-5800
EPA:
Jim Orban
U.S. EPA - Region IV
345 Court/and St. N.E.
Atlanta, GA 30365
(404) 347-2643
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Southeastern Florida and the Biscayne Aquifer
IF YOU LIVE IN SOUTHEASTERN FLORIDA
and dig a hole in your back yard, a few feet down
you'll strike water.
That water is a part of what is known as the
Biscayne Aquifer, an underground pool that
provides virtually all the water used by people
and businesses in the area. By nature, it's clean,
fresh water and that's fortunate. Thousands of
public and private wells are drilled into the aquifer,
and those wells supply water to about three million
people in Dade, Broward, southern Palm Beach,
and eastern Monroe Counties.
But even though it's underground, the water is
close to the surface and can easily get polluted.
In fact, contamination from man-made chemicals
has affected water quality in many areas of south-
eastern Florida. Dozens of chemicals and poten-
tially hazardous substances are known to have
been spilled and leaked into the aquifer, including
industrial solvents, sewage and other wastes,
runoff from industrial areas and landfills, and oil
and fuel.
There's no immediate health risk from this
contamination because the municipal wells that
currently supply most of the area's drinking water
are relatively clean. Nonetheless, it's clear that a
major effort on the part of the community and the
government is needed to ensure an adequate
supply of clean water for southeastern Florida's
future. Most groups and individuals agree that
action is necessary in two areas: to clean up the
contaminated parts of the aquifer, and to make
sure that there's no further contamination in years
to come.
There is a growing understanding of the major
sources of pollution that can affect the aquifer. The
Environmental Protection Agency has identified a
number of hazardous waste sites and industrial
locations that are likely sources of contaminants,
nine of which are on the EPA's National Priorities
List. That makes these nine sites eligible for
cleanup funding under CERCLA*, commonly
known as the "Superfund" legislation. A detailed
study of the effect of several of these sites on the
aquifer is summarized later in this report, with
suggestions for how to clean up the aquifer and
prevent further contamination. But the major sites
are just part of the overall problem.
Thousands of small pollution sources also affect
water quality, and these small sources are usually
under the jurisdiction of state and local govern-
ment. Even in the ordinary course of their daily
activities, businesses and individuals can affect
the purity of the water. A dry cleaner might empty
old cleaning solvents onto the ground, or a gas
station might wash spilled gasoline down a storm
drain that doesn't enter a sewer system. At home,
you might change the oil in your car and dump
the old oil on the ground, or put too much "weed
and feed" on your lawn. These chemicals often
end up in the same place you get your drinking
water.
Area of southeastern Florida supplied with water from the
Biscayne Aquifer.
"We've got a water table that's only a couple of
feet below the surface, and that's where we get
our drinking water," says Louis J.Devillon, Drinking
Water Engineer for the southeast district office of
Florida's Department of Environmental Regulation
(DER). "Whatever you spill on top of the ground,
you're going to find down below after a period of
time."
* CERCLA stands for the Comprehensive Environmental
Response, Compensation, and Liability Act of 7980
HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGE!,
WASHINGTON, D.C. 20460
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Governmental Concern
and Regulation
INDIVIDUALS, COMMUNITY GROUPS, AND
MANY GOVERNMENT AGENCIES on all levels
have been working on methods to clean up and
preserve the Biscayne Aquifer. The situation,
however, is complicated by the fact that responsi-
bility for environmental regulation and enforcement
is divided among many different levels of govern-
ment.
On the federal level, the Environmental Protec-
tion Agency regulates the transportation and
disposal of larger quantities of toxic substances,
and is responsible for cleaning up major old
hazardous waste sites.
State agencies such as the Florida Department
of Environmental Regulation (DER) regulate the
quality of drinking water, and deal with waste
disposal sites and substances that federal regula-
tions don't cover.
Counties are also concerned with environmental
matters. Dade County, through its Department of
Environmental Resources Management (DERM),
is fortunate to have the resources to actively
participate in many environmental areas. These
include controlling waste disposal, zoning, and
land use around well fields.
Overall, there has been a great deal of cooper-
ation and coordination on all levels between the
various agencies and community groups attempt-
ing to improve southeastern Florida's water. There's
a need to continue this cooperation because the
availability of safe drinking water in southeastern
Florida will depend on the decisions that are made
in the next few years to preserve and protect the
Biscayne Aquifer.
One of the purposes of the report you are now
reading is to assist this cooperative process by
providing an overview and understanding of the
Biscayne Aquifer and what affects it. The research
we've done, and the recommendations we make
as a result of it, can help give direction to state,
county, and local efforts to deal with the problem.
Let's take a more detailed look at the Biscayne
Aquifer to see why there's a problem.
The Biscayne Aquifer
AS WE'VE SEEN, THE BISCAYNE AQUIFER
plays a key role in the life of southeastern Florida.
Each day, over 300 million gallons of water are
drawn from the Biscayne Aquifer more water
than from any similar underground body of water
in the world. This water is replenished through
rainfall, streams, canals, and lakes.
The aquifer itself is like a huge triple layer cake,
BISCAYNE AQUIFER FED BY RAINFALL, LAKES & CANALS
RAINFALL
Over 300 million gallons of water are pumped from the Biscayne Aquifer each day. The water is restored by rainfall, streams.
lakes, and canals.
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with three layers of extremely porous limestone
separated by two relatively thin layers of sand and
clay. This "layer cake" is approximately 80 to 150
feet deep along Biscayne Bay, and thins out to
less than 10 feet in depth along the western edge
of Dade County.
The water in the aquifer flows eastward, toward
the sea, at an average rate of about two feet per
day. The three zones of porous limestone allow
water and pollutants to move easily through
the aquifer. There are channels within the aquifer,
however, where the rate of flow is much higher.
These channels can carry pollutants rapidly from
one part of the aquifer to another without diluting
them significantly. Because the water is so close
to the surface of the ground and pollutants can
travel through it without being diluted, the aquifer
is extremely vulnerable to contamination.
In some cases, an underground water system
can rid itself of pollutants by trapping them in
sediments and breaking them down with soil
bacteria. In other cases, "dilution is the solution to
pollution" where a hazardous substance can be
diluted with clean water to a level where it's no
longer harmful. But because of the Biscayne
Aquifer's physical characteristics, neither of these
processes can be relied on to clean it up.
Research conducted by the EPA and other
agencies indicates the situation is cause for seri-
ous concern. Contaminants were found in 80
percent of the public wells that the EPA tested in
south Florida in 1981 and 1982. From 1976 to 1983,
the quality of drinking water in northern parts of
Dade County was ranked among the worst in the
United States because of chemical contamination
from land uses near public wells. Remedial actions
such as the drilling of new, uncontaminated wells
in the northwestern part of Dade County have
temporarily brought this situation under control,
and the quality of drinking water is currently much
better.
In fact, a 1984 study conducted by the EPA's
National Enforcement Investigations Center
(NE'IC) has concluded that the drinking water from
most sources in use in the Miami area is essentially
free of contamination, mainly because the most
contaminated wells are no longer being used. Only
four of the 135 community water supplies sampled
had contamination levels that exceeded Florida's
maximum limits even slightly.
Highly porous limestone in the Biscayne Aquifer accounts for the relatively rapid movement of contaminants in the water system.
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A SIDE VIEW OF THE BISCAYNE AQUI
The three layers of porous limestone in the Biscayne Aquifer form a "layer cake" 80 to 150 feet deep along Biscayne Bay, and
less than 10 feet in depth in western Dade County.
Even so, the actions that have been taken to
provide clean water to most of the area are not
sufficient to sustain the region indefinitely, or to
supply water for the area's growth. However good
the condition of the water sources currently being
used, we still must deal with ongoing and future
contamination. Two of the most important factors
that can affect the quality of South Florida's drink-
ing water are waste management and land use.
Careless wasfe disposal can cause serious
problems. For instance, industrial chemicals
dumped near old factories can seep through the
ground and into the water. In some cases, indus-
trial waste may be discharged directly into the
municipal sewage system, which can't treat it
adequately. In your own neighborhood, septic
tanks and leaky sewers can release raw sewage
and waste into the water system.
Increasing development in the Miami area has
made land use an extremely important water
quality issue. If you spill a contaminant close to a
well, it's possible for the well to become polluted.
Contamination is most likely to occur when a
substance is spilled within the boundary of the
area the well draws water from. This area is called
the well's area of influence, or in some cases, its
cone of influence.
Obviously, if you locate a factory that produces
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waste products in a well's area of influence, there's
a risk that the waste will leak or spill onto the land
and contaminate the water. Landfills may also
contribute to the problem. As landfills soak up
rainwater, the water may dissolve various chemi-
cals and carry them deep into the ground beneath
the landfill, eventually polluting the aquifer.
The continuing threat to the Biscayne Aquifer
comes from many sources. Because there are so
many complex issues involved such as the
preservation of public health, land use, and waste
disposal cooperation among all levels of govern-
ment is necessary to implement an effective
course of action. It's not a problem with a single
solution, nor a problem that can be solved by a
single legislative or administrative authority.
Target: Four Key Sites
TO DETERMINE THE RISKS to public health
from contaminants in the Biscayne Aquifer, the
EPA and local agencies needed the answers to
two questions. To the extent that it can be deter-
mined, what is the nature and magnitude of the
risks from contaminants in the aquifer? And what
are the most effective actions we can take to
reduce the risks and make sure the aquifer is safe
to use both now and in the future?*
To help answer these questions, the EPA
targeted three of the nine Superfund sites in
southeastern Florida (along with an additional
area suspected of contributing to the water
quality problem) for intense study to see what
'See "Assessing Environmental Risks" and "Risk Manage-
ment" at the back of this report for further discussion of this
topic.
SP WITHIN WE L'SAREAOFINFLUENCI
As a well pumps water from the aquifer, it draws in contaminants from the surrounding area. This area is known as the well's
"cone of influence" or "area of influence."
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EXTENT OF BISCAYNE AQUIFER AND LOCATIONS
OF HAZARDOUS WASTE SITES ON EPA NATIONAL PRIORITIES LIST
HOLLINGS WORTH*
DAVIE LANDFILL*
PEPPER'S STEEL
AND ALLOYS "-
MIAMI DRUM
N.W.58TH ST. LANDFILL
VARSOL SPILL (MIAMI AIRPORT)
GOLD COAST OIL*
DAVIDSON'S LUMBER*
Atlantic Ocean
Ft. Lauderdale
Miami
Gulf of Mexico
LEGEND
Superfund Hazardous Waste Site
D Study Area
Key West
10 20
SCALE IN MILES
40
Southeastern Florida has nine hazardous waste sites on the EPA's National Priorities List. Four of these sites are in the area
studied in this report.
Cleaning UpThe Miami Drum Site
As one of the highest priority hazardous
waste sites slated for Superfund assistance,
the Miami Drum Site was the subject of inten-
sive cleanup efforts by Dade County, even
before the EPA study of the aquifer was com-
pleted.
The facility had been built to clean metal
drums of various chemical wastes. The drums
were washed with a caustic cleaning solution
which was then allowed to flow to a low area
at the back of the site. As a result, the soil
and water below the site were heavily contami-
nated. Moreover, Dade County researchers
feared that there were no barriers adequate
to keep the contaminants from continuing to
migrate into the water from the soil.
Removing the soil and treating the ground-
water appeared to be the most appropriate
option. In December 1981, a cleanup contrac-
tor removed 9,000 cubic yards of contami-
nated soil from the site and carried it to an
approved disposal facility. The remaining
aboveground structures, drums, and debris
also were removed. In addition, approxi-
mately 600,000 gallons of groundwater from
beneath the site were treated to remove con-
taminants and then returned to the Biscayne
Aquifer.
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effect they had on the Biscayne Aquifer. The sites
were treated as a single unit in the study. This was
a unique approach for the EPA to take in a Super-
fund investigation, but it made sense because the
sites were located close to each other, and be-
cause the high rate of flow within the aquifer made
it difficult to distinguish contamination from any
particular source.
Northwest 58th Street Landfill This 30-year-
old landfill is located in northwestern Dade County.
Tests of groundwater at or near the landfill had
resulted in public concern about contamination of
water supply wells in nearby areas, including
Miami Springs, Preston, and Medley.
Miami Drum Site This inactive drum recycling
facility is located south of N.W. 74th St. and east
of N.W. 72nd Avenue. Field investigations deter-
mined that the soil and water below the site were
contaminated with high concentrations of chemical
wastes, and presented a serious threat to the
water produced by the Medley, Miami Springs, and
Preston well fields. A surface cleanup was com-
pleted in early 1982. (See Box: "Cleaning UpThe
Miami Drum Site")
Miami International Airport The airport has
been the site of many accidental spills of industrial
chemicals and oils, and is located only about
2,000 feet from the Miami Springs well field. Since
1966, approximately 15 spills of hydrocarbon
chemicals (such as jet fuel) and leaks in fuel oil
storage and pipeline systems have been recorded.
More than 1.5 million gallons of a solvent are
believed to have been leaked in the late 1960s.
Unsewered Industrial Areas -- These sites
are in the towns of Medley and Hialeah Gardens
in northern Dade County. While at the time of the
investigation the Unsewered Industrial Areas were
not on the EPA's National Priorities List, one
location, Pepper's Steel and Alloys, has since been
added to the list. Overall, the Unsewered Industrial
LOCATION OF POTENTIAL CONTAMINATION SITES
AND PUBLIC WELL FIELDS IN THE STUDY AREA
L
PENSUCO
NORTHWEST
WELL FIELD
STUDY AREA BOUNDARY
Scale m Miles
05 1 0
UNSEWERED
INDUSTRIAL
AREAS (Medley and Hialeah Gardens)
DADE COUNTY
58TH STREET
LANDFILL
l_
MEDLEY
WELL FIELD
HIALEAH
OPA-LOCKA
MIAMI SPRINGS
MIAMI WELL FIELDS
SPRINGS
' / ' } LOWER
VIRGINIA
GARDENS
MIAMI
INTERNATIONAL
AIRPORT
Well fields in the study area are one of the most important sources of water for the region. The most contaminated wells in this
area are no longer being used. There are also numerous private wells throughout this area.
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Areas contain more than 1,000 potentially polluting
industries. These businesses include manufactur-
ing plants, reclamation facilities, land disposal
Key Contamination Sources In
The Study Area
Site Problem
Northwest 58th
Street Landfill
Miami Drum
Services
Miami International
Airport
Unsewered Industrial
Areas
Contaminated runoff is
seeping into soil and
groundwater.
Chemical wastes have
contaminated soil and
groundwater.
Aircraft fuel and sol-
vents have been
spilled.
There have been spills,
improper waste dis-
posal practices by
some industries, and
dangerous landfills.
Another Superfund
site (Pepper's Steel)
has been identified in
this area.
concerns, and abandoned landfills. Many of these
industries dispose of their waste in septic tanks,
which do not provide adequate treatment before
the waste enters the groundwater.
Until this study, no one had ever determined
exactly how these waste sites might be contribut-
ing to groundwater contamination. In 1982, the
EPA retained the consulting engineering firm
CH2M Hill to evaluate the Biscayne Aquifer ground-
water in an 80-square-mile study area containing
these four locations. The company would deter-
mine the types, concentrations, and sources of
contaminants in the water. It would also help
government agencies decide how to clean up the
aquifer in the study area and develop a program
to protect the water supply in the future.
-
Water Resources Engineer Udai Singh taking water samples
from the aquifer.
Risk Assessment How Do We
Determine Environmental Risk?
The EPA asks four main questions in asses-
sing whether or not a substance is an existing
or potential risk to public health. (See "Asses-
sing Environmental Risks" at the back of this
report for further discussion.)
Is the substance hazardous? In Hazard
Identification, scientists attempt to determine
if a particular substance will cause a health
problem such as cancer.
How much is harmful? In making a Dose-
Response Assessment, they determine how
potent the substance is and the risks that
occur at different levels of exposure.
How are people exposed to it? In Exposure
Assessment, scientists determine how many
people are exposed to the substance, and
how much exposure they receive. Low levels
of a substance that people are exposed to
constantly may be more dangerous than
relatively high levels of a substance that
people are exposed to only once.
What are the risks in a particular situation?
Risk Characterization is a specific numerical
estimate of the risk in a particular situation
and a qualitative determination of the hazard
potential, given the potency of the substance,
the level of exposure, and how many people
are exposed to it.
Hi
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Information Gathering
and Results
THE STUDY BEGAN WITH an extensive evalua-
tion of all the existing documents and data con-
cerning the types and sources of contaminants in
the aquifer. This evaluation showed that more
information was needed if regulatory agencies
were to be able to act effectively.
In late 1982, EPA's contractor CH2M Hill began
taking samples of groundwater in the study area
and analyzing them. Water Resources Engineer
Udai Singh was CH2M Hill's manager of the
project. 'This was the largest water sampling effort
in EPASuperfund history," he said. "The purpose
of our investigation was to find out enough about
the aquifer to be able to confidently recommend
what is needed to clean up and preserve it."
The results of the sampling showed the pres-
ence of contaminants in the groundwater beneath
most of the study area. Most of the contaminants
found are volatile organic compounds (VOCs), the
most common of which is vinyl chloride. VOCs are
volatile man-made chemicals that dissolve in the
water and can easily evaporate into the air. (See
Box: "VOCs And Their Effects on Health.") Heavy
metals and other contaminants were found in
several places throughout the study area, but
generally at less than the maximum level allowed
by the EPA for drinking water.
The concentrations of VOCs and other contami-
nants in the study area varied depending on the
area and the wells being tested. Of the geograph-
ical areas investigated, the water in Hialeah
showed the most contamination, followed by the
Upper and Lower Miami Springs areas. Of the well
fields investigated, water from the Preston, Miami
Springs, and Medley well fields was found to be
more contaminated than that from other wells in
the study area. The new Northwest Well Field was
found to be essentially free of contamination.
Monitoring wells, which were drilled to take
small samples of water from the aquifer, were
generally less contaminated than municipal pro-
duction wells in constant use. This seems to be
the result of the production wells' continuous
pumping, which may concentrate contaminated
water from the area of influence close to the well
field. The wells act almost like vacuum cleaners,
drawing in the contaminants which became an
important factor in the primary remedy recom-
mended as a result of this study.
VOCs And Their
Effects On Health
Volatile Organic Compounds, or VOCs, are
man-made chemicals that have a low boiling
point and can easily evaporate into the air. In
fact, they evaporate faster than water, which
makes it possible to remove them fairly easily
from contaminated water.
VOCs are found frequently throughout the
Biscayne Aquifer and, in fact, all around the
country. They're used as industrial solvents
and cleaners, and are contained in household
substances such as paint thinners, cleaning
fluids, gasoline, and even felt tip pens. They
might enter the aquifer from leaky storage
tanks or pipelines, or by being dumped into
septic tanks. Once in the aquifer, they dis-
solve and spread out.
The most prevalent VOC in the Biscayne
Aquifer is vinyl chloride. Vinyl chloride, how-
ever, is not a chemical that's used in great
quantities, though it's often an unwanted
byproduct during the manufacture of indus-
trial solvents. Scientists also believe that vinyl
chloride is produced when other chemical
substances break down in the aquifer.
For the most common VOCs in the aquifer,
an exposure level of 2 parts per billion or less
over the course of a lifetime is currently
believed to cause one additional case of
cancer per million persons exposed.
For the same reason, wells that draw from the
deeper layers of the aquifer may tend to pull
contaminants down to these levels. This may be
one reason that pollutants were detected at all
three levels of the aquifer, instead of just near the
surface.
One of the conclusions reached by the Super-
fund Implementation Group of the Centers for
Disease Control (CDC) after a review of the results
of the sampling was:
"All study areas show serious concentrations of
the Biscayne Aquifer groundwater with priority
pollutants and carcinogens. For many pollutants,
the chemical concentration is far above the EPA
ambient water quality criteria, the concentration
11
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associated with the EPA estimate of a lifetime
excess cancer risk of 1:100,000, or the national
drinking water standard... With this in mind, we
consider the Biscayne Aquifer a serious potential
threat to the public health."
First Steps
IT WAS CLEAR THAT SOMETHING needed to
be done as soon as possible, and local authorities
responded quickly. To help support and focus local
efforts, the EPA recommended a set of "first steps"
for the immediate treatment of the Biscayne
Aquifer:
Maximize use of the new Northwest Well Field,
which draws water from a clean part of the aquifer.
Monitor the quality of the finished water from the
Hialeah and Preston Water treatment plants
routinely for VOCs. If VOC concentrations increase
significantly, the most contaminated wells should
be found and their use discontinued.
Provide an alternative water supply for any
seriously contaminated private wells that are
currently used for drinking water.
As a result of cooperation between the EPA,
state, and county agencies, these initial remedies
for protection of the Biscayne Aquifer were well
underway by early 1984. However, the EPA and
local authorities felt there was a need to identify
additional actions to clean up and protect the
aquifer.
Evaluating the Alternatives
THROUGHOUT THE INVESTIGATION of the
Biscayne Aquifer and the process of devising
remedial actions, numerous public meetings were
held in the Miami area to inform local people of
the progress being made and respond to their
concerns and suggestions. Experts from the EPA,
the Centers for Disease Control, and the project
team were brought together to discuss topics such
as risk assessment and the significance of the
research findings. In addition, workshops for
public officials and the media were conducted to
keep legislators and administrators up-to-date on
the project, and a newsletter on the investigation
was published frequently and mailed to interested
groups and individuals.
Many alternatives for dealing with the contami-
nation in the study area were examined, and the
objectives were clear:
Provide uncontaminated drinking water to the
public.
Clean up the contaminated portion of the aquifer.
Protect the aquifer from further contamination.
BISCAYNE AQUIFER
PROTECTION PLAN
The EPA's Biscayne Aquifer Project Manager Jim Orban at a
public meeting during the project.
Jim Orban is the Biscayne Aquifer project
manager with the EPA's Atlanta office. He
explained that the EPA looked at two main
categories of possible recommendations: "Our
first group of recommendations will be aimed at
controlling the major sites as a continuing source
of contamination, and removing what's out there
before the people end up drinking it. The second
will be for a series of local actions to control the
future release of contaminants to the aquifer."
The EPA's first recommendations are for reme-
dial actions to control contamination at both the
source of the contamination ("onsite"), and at the
well or elsewhere ("offsite"). The second category
of actions is called the Biscayne Aquifer Protection
Plan, and is designed to prevent future contamina-
tion of the aquifer.
Remedial Actions
MANY DIFFERENT WAYS TO CLEAN UP the
sites and the aquifer were looked at from the point
of view of effective risk management (See Boxes:
"Alternatives Examined To Control Contamina-
tion"). Some were eliminated because they cost
more than other options without providing greater
protection to public health or the environment.
Others were eliminated because they didn't work
reliably, or because they caused other environmen-
tal hazards in the process. Finally, some were
12
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Alternatives Examined to Control Contamination in the Study Area
Onsite (at contamination source) Off site (in well fields or elsewhere)
1. No action
2. Relocate industrial plants from the un-
sewered industrial area to a safer place
3. Abandon septic tanks and provide waste
treatment at industrial sources
4. Abandon septic tanks and provide cen-
tralized waste collection and treatment
5. Develop land use restrictions to protect the
aquifer from the impacts of urbanization
6. Install recovery wells and provide water
treatment using air stripping, granular
activated carbon, or both prior to dis-
charging or reusing the water
7. Install recovery wells and inject all con-
taminated groundwater into deep wells
8. Provide containment measures for the
contaminants
9. Excavate and remove contaminated
material
10. Recover spilled fuel and treat contami-
nated groundwater at the airport
11. Develop spill prevention, containment,
and cleanup procedures
12. Develop leachate control measures at the
Northwest 58th St. Landfill
1. No action
2. Use well fields for contaminant recovery
and provide water treatment systems using
air stripping, granular activated carbon, or
both
3. Abandon contaminated well fields, find
clean well fields, and pump to existing water
treatment plants (WTPs)
4. Abandon contaminated well fields and
WTPs and relocate
5. Provide bottled water for consumption and
continue operating WTPs for non-con-
sumption purposes
6. Provide home treatment systems
7. Establish county-wide spill prevention, con-
tainment, and cleanup plans
8. Develop land-use restrictions to protect the
aquifer from the impacts of urbanization
9. Use the Medley Well Field for groundwater
recovery; treat using air stripping, granular
activated carbon, or a combination of both;
and discharge treated groundwater back to
the aquifer
10. Abandon septic tanks and provide central-
ized collection and treatment
eliminated because they couldn't be reliably imple-
mented with acceptable engineering practices.
This sort of analysis is typical of how risk man-
agement decisions are made. The cost of pollution
controls, the relative cost of alternatives, and the
benefits and disadvantages of simply maintaining
the status quo all entered into the decision-making
process.
After going through the risk management evalua-
tion process, one alternative was recommended as
the primary remedial action.
1. Use Well Fields to Remove Contaminants
and Provide A Water Treatment System That
Uses Air Stripping
This main recommendation will help clean up the
aquifer, and provide clean drinking water at the same
time. The proposal is to use the existing Miami
Springs and Preston well fields to take contaminated
water from the aquifer, and then treat the water, with
an air stripping process at the Preston and Hialeah
water treatment plants. This will remove the VOCs
that conventional water treatment cannot remove.
Because VOCs evaporate faster than water, air
stripping is an effective and relatively inexpensive
treatment. Water is sprayed down through a tower
filled with loose packing material. As air is blown
upward through the tower, the VOCs evaporate,
leaving clean water behind. Although the VOCs are
released into the air, the impact on air quality is
minor and within air quality standards. By removing
VOC contaminants from the groundwater, this
recommendation would, over time, help clean up
the contaminated portion of the aquifer.
The air stripping process is extremely effective
with two of the most critical VOCs targeted for
13
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removal. It's 99.87% effective with vinyl chloride,
and only slightly less so with 1,1 -dichloroethene.*
In both these cases, and for other VOCs found at
hazardous levels in the study area, air stripping
pretreatment effectively reduces the concentration
to a level lower than the EPA's target criteria.
In addition to the primary remedial action, five
other alternatives were chosen that would contrib-
ute significantly to the control of contaminants.
Some of these alternatives are designed to be
implemented directly on sites in the study area.
Others can be implemented elsewhere in the
study area, or throughout the entire Biscayne
Aquifer.
2. Abandon Septic Tanks and Provide Cen-
tralized Waste Collection and Treatment
Many homes and businesses in the three county
area dispose of their waste through septic tanks,
and this often results in contaminants being re-
leased directly into the aquifer. The recommenda-
tion is to abandon all existing septic tanks and
install sewer connections to wastewater treatment
plants.
'See "Supplement: Effectiveness of Air Stripping Treatment
on VOCs" at the back of this report for further details.
AIR STRIPPER CROSS SECTION
AIR WITH EVAPORATED
CONTAMINANTS
Clean Water Outflow
Diagram of an air stripper, showing how it removes VOCs
from contaminated water.
3. Develop Land Use and Zoning Restrictions
to Protect the Aquifer
Future development throughout the area of the
Biscayne Aquifer needs to be evaluated carefully,
especially near well fields. Land use restrictions
and zoning regulations to forbid land uses that
could result in contamination of the aquifer even
by accident are needed. In the study area, land
use restrictions would apply to the Miami Airport
and the Unsewered Industrial Area, but they are
also needed in other locations within the three-
county area. Such restrictions could also include
more stringent standards for the construction of
new sewers.
4. Recover Spilled Fuel and Treat Contami-
nated Groundwater at the Airport
During 1983, thousands of gallons of jet fuel were
found on the surface of the groundwater near
Concourses D and E of the Miami International
Airport. The spilled fuel is being removed through
newly installed recovery wells. In addition, how-
ever, the contaminated groundwater should be
withdrawn from the area and treated to reduce the
high concentration of dissolved pollutants, notably
benzene and napthalene.
5. Develop Procedures to Prevent Spills, and
to Contain and Clean Them Up When They
Occur
Accidental spills can threaten any part of the
Biscayne Aquifer. A pipe carrying toxic liquids can
break, or a pump at a gas station may jam open.
Without proper containment procedures and rapid
cleanup, the spill can get into the water. Each
industry that uses hazardous chemicals should be
required to submit to the county detailed plans to
prevent a major spill from occurring, to contain
spills that do occur, and to clean up spills before
they contaminate the groundwater.
6. Develop Leachate Control Measures at the
58th St. Landfill
When rain falls on a landfill, the water filters down
through it and often becomes contaminated by the
materials in the landfill. Without proper control
measures, this contaminated water, called
"leachate," can seep into the aquifer and contami-
nate the drinking water. At the Northwest 58th
Street Landfill, the leachate currently being gener-
ated at the landfill must be controlled, primarily by
developing a plan to close the landfill. Otherwise,
it may lead to significant long-term pollution and
further contamination of the municipal production
wells in the study area.
i i
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The Biscayne Aquifer Protection Plan
BESIDES THE REMEDIAL ACTIONS which the
EPA and local community authorities want to
implement immediately, the EPA has tried to look
ahead to see what is needed for the long-term
protection of human health and the environment.
"This is perhaps the most important part of our
recommendations," said Project Manager Jim
Orban. "If we clean up the pollution problems that
exist now, and don't do anything to stop future
problems, our work and the work of all the local
groups and agencies will have been wasted."
This long-term approach is particularly important
in light of continuing growth in the Biscayne Aquifer
area. While significant changes need to be made
to reduce the actual and potential danger of con-
taminating the aquifer, its doubly important to
make sure that new development does not en-
danger the water supply.
The result is a preventive action plan for protect-
ing the Biscayne Aquifer. The Biscayne Aquifer
Protection Plan consists of suggested actions to
be adopted and enforced locally by the com-
munities and counties in southeastern Florida.
Specifically, it was developed for Dade, Broward,
and Palm Beach counties. It recommends a com-
bination of regulations, waste management prac-
tices, construction and treatment guidelines, and
public information activities.
Some of these recommendations have already
been adopted by some cities and counties, but no
area has completely adopted all elements of the
plan. The Protection Plan contains 20 recommen-
dations that span the range of immediate, short-
term, and future implementation options. In
recognition of the fact that it may be difficult to
implement all 20 of them immediately, the recom-
mendations were ranked in importance to provide
the greatest benefit and the most efficient use of
resources according to risk management princi-
ples. Since contaminants have had the greatest
impact on some of the municipal well fields serving
metropolitan Miami and Fort Lauderdale, protec-
tion of the well fields in the three counties has
received the highest priority in the Protection Plan.
It's important to realize that similarfederal, state,
or local programs and legislation may already exist
but the coverage of these regulations may not
be adequate to protect the Biscayne Aquifer from
immediate and future pollution. In some cases
where current regulations do address the problem,
the financial and personnel resources of the
governmental agencies may not be sufficient to
enforce the regulations, and additional resources
may be needed.
In developing the Protection Plan, the EPA,
CH2M HILL, and local governments realized that
groundwater contamination has been caused not
only by larger industries and landfills, but also by
small sources. "Normal, everyday business and
personal activities may be adding even more
contamination to the aquifer than toxic waste sites
are," notes Jim Orban.
Small businesses have often been at fault
through careless operating practices that have
resulted in contaminated stormwater runoff and
the disposal of chemicals, solvents, and cleaning
fluids in the aquifer. On a smaller scale, individuals
also need to do their part in protecting the aquifer.
This is particularly critical in light of the lack of
current regulations governing "small polluters"
who may be closer to home than imagined. Consider
this editorial in a recent issue of the St. Petersburg
Times encouraging residents to take advantage of
the State of Florida Amnesty Days project to
collect and dispose of household pollutants:
"Most people don'tthink of themselves as hazard-
ous waste generators. Yet, most people are. Think
about the things you have stored around your
15
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house or business. Garden pesticides, her-
bicides, old paint, solvents, paint thinners, preser-
vatives, used motor oil, brake fluid, antifreeze,
and swimming pool chemicals are some of the
most common hazardous wastes gathering dust
in garages and sheds.
"The time you take to scour your garage for
hazardous materials and turn them over to the
state for safe disposal will be well spent. You will
be doing your part to ensure that all Floridians
have safe, clean water to drink."
While federal regulations govern the release of
pollutants by large-scale producers, there currently
are few guidelines to deter small sources from
releasing potentially hazardous materials into the
underground environment. Also, the public is
generally not aware of the importance of such
contamination. Acombination of regulation, educa-
tion, and waste management practices for small
waste producers will play an important part in
preventing further pollution of the Biscayne Aquifer.
The Protection Plan in Detail
INTHE FOLLOWING DESCRIPTION, the20-part
Biscayne Aquifer Protection Plan has been or-
ganized by its broad areas of concern. Each item
has been given a priority number from 1 to 20 to
indicate the urgency of implementing that particu-
lar element.
Waste Management
Local governments should consider providing
a local hazardous waste storage and transfer
facility for individuals and small waste
generators.
Simplifying the disposal of small amounts of
hazardous wastes would result in less risk of
contaminating the soil or water. So, to assist
individuals and small businesses in treating and
disposing of their materials, local governments
should establish central locations where waste
could be brought for final disposal by others at an
appropriate facility. Such an operation could be
implemented by each county or as a joint effort of
Dade, Broward, and Palm Beach Counties.
(Priority 1.)
A program for the handling and disposal of
liquid and other hazardous waste materials by
commercial haulers should be developed.
Federal regulations do not cover transportation
and disposal of all types of potentially hazardous
waste, or waste from smaller generators. There
have been numerous documented cases of illegal
dumping of chemicals and sludge, with the clear
potential for contamination of the drinking water
in Dade, Broward, and Palm Beach Counties.
Unless adequate regulations are enacted to con-
trol potentially hazardous wastes and materials
not already covered by state and federal regu-
lations, the difficulty and expense of properly dis-
posing these wastes will encourage continued
dumping. Rigorous enforcement of a liquid waste
transportation regulation program would have a
major positive effect on local government's ability
to monitor and control the transportation and
disposal of these wastes. (Priority 7.)
Leak-proof sewers should be provided in all
areas within well field protection zones and
ultimately in all commercial and industrial
areas.
Septic tanks and drainfields are often found at
commercial and industrial sites where sanitary
sewers are not available. Pollutants from industrial
operations are minimally affected by septic tank
treatment, and eventually enter the groundwater.
Therefore, commercial or industrial areas that can
affect the drinking water supply should have a
leak-proof sewage collection system. Any new
development that generates non-domestic waste
should not be allowed unless those facilities are
connected to a leak-proof sewage system that will
transmit the pretreated waste to a suitable treat-
ment plant. Provisions should also be made for
"infilling" previously developed areas. (Priority 8.)
Pretreatment of wastes from commercial and
industrial users should be required before
discharging wastewater to a sewer system.
Most municipal waste treatment plants are not
designed to treat chemical and industrial waste.
All industrial and commercial users that generate
16
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The Biscayne Aquifer Protection Plan
Immediate
Implementation
Recommended
1. Provide local waste storage/transfer facilities for small waste
generators, individuals
2. Regulate land use within well field protection zones
3. Monitor small quantity waste generators
4. Improve regulation of small quantity waste generators
5. Develop public awareness/education program
6. Regulate storage tanks
7. Control handling/disposal by commercial waste haulers
Short-term
Implementation
Recommended
8. Construct leak-proof sewers in well field protection zones
9. Develop a spill prevention, control, and countermeasure program
10. Pretreat commercial/industrial waste
11. Control leakage from existing sewers
12. Hold responsible parties liable for cleanup costs
13. Adopt emergency spill cleanup program
14. Encourage public reporting of improper waste disposal
Future
Implementation
Recommended
15. Control groundwater pollution from agriculture
16. Collect/recycle automobile drain oils
17. Establish tri-county coordinating committee
18. Review stormwater/wastewater systems
19. Determine "safe" soil contamination levels
20. Monitor groundwater near wells
17
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wastes should be required to provide pretreatment
of such wastes to reduce the contaminants prior
to discharging the material into public sewer
systems. Dumping of sludges generated by waste-
water treatment on land in well field protection
areas should be prohibited. (Priority 10.)
A program should be implemented to control
leakage from existing sewers.
It is a common practice to test sewer mains for
leakage. However, interim leaks may occur due to
ground settling, breaks or cracks in the pipe, poor
installation, and other causes. These leaks result
in the seepage of domestic and commercial sew-
age into the groundwater. The problem is even
more critical in well field areas. A program for the
periodic inspection and testing of sewers, espe-
cially in well field protection areas, should be
developed. Current allowable leakage rates in well
field areas should be tightened. (Priority 11.)
A program to collect and recycle automobile
drain oils should be developed.
It's difficult to dispose of auto drain oil properly. In
many cases, the oil is poured on the ground and
seeps rapidly into groundwater. A comprehensive
educational program would encourage people to
dispose of oil in neighborhood collection and
recycling facilities. Dade County DERM, with
support from the Florida Federation of Women's
Clubs and the Florida Petroleum Council, has
made an excellent start at this by developing and
promoting a waste oil recycling program with
collection centers throughout Dade County.
(Priority 16.)
A tri-county coordinating committee on hazard-
ous waste and related issues should be estab-
lished.
Dade, Broward, and Palm Beach Counties all get
their water from the Biscayne Aquifer, and have
similar contamination problems. A coordinating
committee, composed mainly of technical officials
from county governmental agencies, should be
established to share and exchange information on
groundwater pollution and related issues and pro-
cedures. Such a committee would help not only in
the exchange of information and in setting uniform
and effective policy, but would also assist in com-
bining the resources of the three counties, where
appropriate, to solve problems more efficiently.
(Priority 17.)
Land Use
A well field protection program should be
developed to regulate land use within the
areas of influence of producing wells.
Locating heavy commercial and industrial ac-
tivities near well fields has resulted in contami-
nated water supplies through leaks, spills, acci-
dents, and careless waste disposal. Therefore, a
regulation restricting certain land uses within the
cones of influence of wells and well fields would
help maintain the integrity of drinking water, espe-
cially around uncontaminated well fields. Such a
regulation would include limits on sewage loading
that become stricter as individual properties get
closer to the well field. It would also restrict the
use, storage, and disposal of polluting materials
within the protection area.
A well field protection program would start by
defining the protection area and the pollutants that
could contaminate the well field. Depending on
the circumstances, it might also restrict rock
mining activities, regulate development served by
gravity sewers, control stormwater disposal meth-
ods, and set stricter standards for sanitary sewers
in the protection areas. (Priority 2.)
A program to control groundwater pollution
from agricultural chemicals should be
developed.
This program should address control of ground-
water decontamination resulting from the use of
pesticides, fertilizers, and soil conditioners used
in agricultural areas and golf courses. The use of
pesticides known to contain toxic materials would
be regulated, and quantities of agricultural chem-
icals used would be modified where necessary. A
groundwater monitoring program in agricultural
areas would help identify problems and proper
solutions to them. (Priority 15.)
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Materials Handling, Transport, and
Storage
A program regulating the installation, mainte-
nance, and replacement of storage tanks
should be implemented.
Thousands of facilities store materials in under-
ground tanks or containers that are partially sub-
merged in the Biscayne Aquifer. The need for
increased control of underground storage tanks
has become apparent as a result of numerous
contamination incidents resulting from corrosion
and leakage. Regulations should be drafted to
include leak detection devices and spill prevention
measures, along with standards for installation,
operation, and control of both underground and
above-ground containers. Special protective
measures should be implemented for storage
facilities within the cone of influence of supply
wells. (Priority 6.)
A spill prevention, control, and countermea-
sure program should be developed.
Each county overlying the Biscayne Aquifer should
develop plans to prevent major chemical waste
spills and contain those that do occur before there
is extensive groundwater contamination. A local
program to require formal spill prevention meas-
ures for all storage tanks similar to federal require-
ments for underground petroleum storage tanks
should also be developed. (Priority 9.)
Responsible parties should be held liable for
contamination at the site and responsible for
paying the cost of groundwater cleanup.
When violations of regulations occur, the parties
responsible should be held liable for the contami-
nation at the site and assessed a fine, penalty,
temporary suspension of license, or other measure
deemed necessary to ensure the violation will not
be repeated. The liable parties should also be
responsible for removing and eliminating the
contamination from the site. A proof of insurance
requirement for even small businesses that need
a license or permit to operate should be a part of
the liability policy of each county. Another possibil-
ity is a program requiring testing and certification
that contaminants at a site are completely removed
or reduced to acceptable levels before title can be
transferred on property in high-risk land use classi-
fications. (Priority 12.)
An emergency spill cleanup program should
be developed.
A local emergency spill response program will help
prevent extensive contamination of groundwater.
Such a plan could involve contractors who would
respond to spill incidents and quickly contain or
clean up the spills. Funds to pay for cleanup
activities will have to be generated or allocated.
(Priority 13.)
Regulation and Monitoring
Existing local inspection and enforcement
programs should be examined for ways to
strengthen their ability to provide surveillance
over the multitude of small quantity producers
of industrial and commercial wastes.
Local authorities should establish or expand
programs to inventory and monitor potential small
waste producers according to industry, location,
kind of wastes produced, and other classifications
seen as necessary. Regular industry reporting and
periodic inspections would verify compliance with
proper disposal procedures. A current program
involves compiling an inventory of these small
waste producers. (Priority 3.)
The effectiveness of existing local programs
to regulate the activities of small quantity
industrial and commercial waste generators,
including their waste disposal practices,
should be increased or new programs de-
veloped.
Regulations on a local level should be adopted for
handling hazardous waste materials produced by
small waste generators those businesses
usually exempted from federal and state
guidelines for large industries. In many cases, the
small polluter is not even aware of the danger of
contamination or does not know the proper meth-
19
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ods of disposing of hazardous wastes. An en-
hanced local program would help these sources
identify hazardous materials, and would establish
methods of safe handling and disposal. (Priority 4.)
The public should be encouraged to report
improper disposal of hazardous wastes.
Similar to the Crime Stoppers Tip Line in many
areas of the country, each county would have local
phone lines for reporting suspected or confirmed
improper disposal of hazardous wastes. The
"pollution hotline" would assist discovery of con-
tamination and its sources, and discourage the
improper disposal of wastes. (Priority 14.)
Regulatory review of tenants in industrial
parks should be obtained to ensure that storm-
water and wastewater systems are adequate
for each tenant.
Local government should continue to inspect
tenants of industrial parks regarding their waste-
water systems and sewage collection, but the
inspection should also include drainage and
storm-water disposal. Spills that are washed into
the nearest drain also have the potential to con-
taminate groundwater. (Priority 18.)
A "safe" contamination level of pollutants in
local soils should be determined.
It is important to determine how much contamina-
tion can be left in the soil without endangering the
public health and welfare. Any chemicals left in
the soil have the potential to migrate into the
aquifer, and local standards specific to the condi-
tions of the Biscayne Aquifer should be developed.
Protocols are needed to determine the extent of
cleanup required at various sites in the area, as
well as to determine the safe level of contaminants
that may be applied to or allowed to remain on the
land in the future. (Priority 19.)
New groundwater monitoring systems should
be established or existing systems expanded
to study areas close to producing wells to re-
veal early signs of groundwater contamination.
The possibility of contamination of drinking water
wells and well fields is a problem that every water
utility faces. An adequate early warning system
and a method to provide safe water despite con-
tamination should be developed. Frequently sam-
pled monitoring wells located between potential
sources of contamination and the drinking water
wells should detect contamination before it
reaches the well field. (Priority 20.)
Public Awareness and Education
Programs
Public awareness and education programs on
hazardous waste issues should be developed.
A new public awareness and education program
in Broward and Palm Beach Counties, and continu-
ation and refinement of the program already
established in Dade County, will help gain support
for the implementation of plans to clean up and
protect the Biscayne Aquifer. The media could
cover water quality issues on local radio and
television talk shows, and through public advertise-
ments, press reports, and public meetings.
Schools could also implement an education pro-
gram, and citizen committees to review the issues
and progress of the hazardous waste programs
should be encouraged.
(Priority 5.)
20
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Mandate for Action
IMPLEMENTING THE REMEDIAL ACTIONS
and the initial phase of the Protection Plan would
require each county to allocate additional re-
sources personnel as well as financial. How-
ever, early implementation is essential if the trend
toward continuing groundwater pollution is to be
reversed.
The Environmental Protection Agency and
officials at the local, county, and state levels concur
that there is a clear need to continue action against
the pollution of the Biscayne Aquifer. The welfare
and health of virtually all of the people of southeast-
ern Florida is at stake some 3 million residents
who rely on the aquifer as their sole source of
drinking water and for their commercial and busi-
ness needs as well.
Projections of what would happen if no action
were taken show that there would be an increased
risk of drinking water contaminants causing health
effects. In some cases, pollutants are already
present in concentrations well above the national
drinking water standards.
"If we're going to be able to reduce the contami-
nation that enters the drinking water, we're all
going to have to play a part," said Jim Orban.
"There are certain things the federal government
can do to clean up Siiperfund sites: set regulations
for major industries, and even do studies like this
one. But much of the protection of your water
system things like controlling small waste
generators, day to day operations of industry, and
land use is really in your hands."
Many of the options and remedies addressing
the pollution of the aquifer already have been put
into action and with excellent results. Paul
Traina, the former Director of the EPA's Region IV
Water Management Division, notes that there has
been "a major improvement since 1982, when
about 1.3 million persons were receiving drinking
water with excessive levels of VOCs."
While progress has been made as a result of
actions taken in the last few years, the risk of
inaction is clear. Demographic experts estimate
that, by the year 2000, the population of southeast-
ern Florida will be 23 percent greater. The quality
of water that these residents share will depend on
the actions taken today.
"The battle isn't over," cautions Traina. It will take
implementation of the proposed remedial actions
and the Biscayne Aquifer Protection Plan, along
with close cooperation between individuals on a
local, county, state, and federal level to ensure a
bright future for southeastern Florida's water. D
Suggested Readings
Written materials pertaining to the Biscayne
Aquifer study can be reviewed at:
Miami-Dade County Public Library
Florida Collection
101 West Flagler St.
Miami, FL 33130
(305) 375-5023
Dade County Department of Environmental
Resources Management (DERM)
13th Floor
111 Northwest First Street
Metro-Dade Center
Miami, FL 33128
(305) 375-3321
21
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Supplement
Assessing Environmental Risks
TO BE ABLE TO DECIDE on the appropriate
course of action, it's necessary to take a look at
the human health risks caused by contaminants
in the study area, and how those risks can be
reduced to acceptable levels. As you can imagine,
determining the risks from contaminants in the
Biscayne Aquifer is a complex matter.
An environmental health risk is defined as a
probability the probability that injury, disease,
or death will result from human exposure to a
substance or group of substances in the environ-
ment. The reason for such widespread concern
about the water in the Biscayne Aquifer is that
some substances in it have the potential to harm
human health. It's important to keep in mind that
foreign substances, contaminants, or pollutants
aren't always a problem they only become a
problem when they can damage health or the
environment.
The question that focused scientists' efforts
was: What is the probability that contaminants will
adversely affect the health of people who drink or
are exposed to water from the Biscayne Aquifer?
The process that scientists go through to deter-
mine the risks associated with a particular sub-
stance or group of substances in the environment
is called Risk Assessment. It's a fairly complex
process that requires both careful research and
good judgment. An overview of the risk assess-
ment process is given here to explain some of the
ideas and procedures that provide the foundation
for assessing the hazard from substances in the
aquifer.
The first two parts of the risk assessment pro-
cess involve laboratory research and mathemati-
cal projections. The first step in the research is
called Hazard Identification. Scientists do studies,
usually with animals, to determine to the best of
their ability what substances are toxic or hazard-
ous. They expose animals to a substance and look
for health effects such as cancer, genetic damage,
and damage to major organs. A cancer-causing
substance is labeled a "carcinogen."
Then the researchers conduct a Dose-
Response Assessment, which allows them to
determine the potency of a hazardous contami-
nant. Given the results from the animal experi-
ments, mathematical models are used to estimate
the number of individuals who would have adverse
health effects when they're exposed to low concen-
trations, or doses, of the pollutant. Scientists are
also interested in whether or not there's a dosage
that can be considered "safe." For carcinogens,
because of the way scientists believe they act
in the body, the EPA has determined that there
is no truly "safe" level of exposure. Some non-
carcinogenic toxic substances, however, may be
safe in small amounts but unhealthy in larger
doses.
Scientists then apply their lab studies and
projections to the situation as it actually exists in
the environment. They do an Exposure >Assess-
ment to estimate how many people are exposed
to the substance, and how much exposure they
receive. Exposure can result from drinking contam-
inants in the water, inhalation, skin contact, or by
other means. The level of exposure can be deter-
mined by using mathematical models or by using
instruments that actually monitor the level of
contaminants.
The final step is Risk Characterization, which
results in an estimate of the human health risk that
is both qualitative (what're the substances and
circumstances causing the risk?) and quantitative
(what's the magnitude of the risk?). When they
characterize or define the risk, researchers use
information on the toxic potency of the substance,
its concentration in the environment, the number
of people exposed to it, and the extent and nature
of the hazard.
In a quantitative assessment of an environmen-
tal risk, the estimated risk posed by a substance
at a certain concentration is usually expressed as
a number such as 1 x 10"6, or 1 in 1,000,000. This
is another way of saying that one additional person
out of a million who are exposed to that concentra-
tion may have a health problem such as cancer
in his or her lifetime.* At a higher concentration,
To put such numbers in perspective, the probability that
the average person in the United States will get some form
of cancer in his or her lifetime is 1 in 4.
22
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such as 1 x 10"4, one additional person out of
10,000 people exposed to the substance may
develop a health problem. Risk numbers tend to
be conservative, so that if there's an error in the
estimate, it will be more likely that the risk is
actually less than stated.
It's important to realize, however, that all such
numbers are estimates of risk no scientist would
conduct an experiment that exposes people to
different levels of hazardous substances to see
how they actually respond. Also, scientists have
relatively little information from human studies
concerning the effects of long-term low level
exposure to substances in drinking water. Quan-
titative risk estimates are based primarily on the
scientist's best assumption of how to apply the
results of animal experiments in the lab to humans,
so there's always some uncertainty about the
accuracy of those numbers.
Furthermore, in the case of the Biscayne Aquifer,
the situation is complicated by the presence of
more than one contaminant. Little research has
been conducted on human health effects that are
the result of exposure to multiple toxic chemicals,
but it is suspected that there may be an additive
or synergistic effect when several chemicals are
present. A synergistic effect results when the
combined health effects from several chemicals
are greater or different than the effects from single
chemicals.
In addition, it is always possible that more
sensitive equipment with lower detection limits
would find more chemical contaminants in the
water. So even if the health effects of certain
combinations of chemicals were known, the pres-
ence of undetected chemicals might produce a
different level or type of health effect.
This means, essentially, that there is no precise
quantitative assessment of the health hazard from
the combined contaminants present in the Bis-
cayne Aquifer. Nonetheless, from the scientific
information available concerning individual conta-
minants, it is possible to make a qualitative assess-
ment of the health risk from contaminants in the
aquifer. We can say, for instance, that certain
contaminants in the water make the water quality
poor enough to warrant our serious concern and
some form of remedial action. Such assessments
of the public health impact of toxic chemicals in
the environment are often used by the EPA and
other federal and state agencies as the basis for
actions to reduce the risk from those chemicals.
So despite the element of uncertainty to risk
assessment, it's still our best tool to help us set
priorities and make informed decisions concern-
ing what to do about foreign substances in the
environment.
Risk Management
AFTER WE HAVE ESTIMATED the risks caused
by the presence of hazardous substances in the
environment, we have to make a decision about
what to do to bring those risks to an acceptable
level.
That process is called Risk Management, and
it's a familiar one to most of us. We do an informal
version of risk management when we perform
many common activities, even something as
simple as driving a car. (Is there enough time to
pull out into the street before on-coming traffic
reaches us? What's the chance of running out of
gas?) Our environment is f u II of hazards, and most
of us are constantly making "risk management"
decisions about the things we want to do based
on how much risk we decide is acceptable.
In a situation as complex as that in southeastern
Florida, there are risks from many substances and
sources to consider, and more than one option for
dealing with each risk. In such a case, risk manage-
ment also involves weighing one risk against
another to determine which are the most urgent.
Comparing environmental risk numbers such as
one additional cancer case in the lifetimes of
1,000,000 people vs. one in 10,000 is analogous
to comparing cars according to their EPA miles
per gallon rating. If you purchase a car that's rated
to get 30 miles per gallon, you know you probably
won't get exactly that mileage. But you also know
that everything else being equal, you'll get better
mileage than if you'd bought a car rated at 20 miles
per gallon.
Similarly, if it's determined in the Biscayne
Aquifer that a particular contaminant may cause
one additional case of cancer per 10,000 people,
we don't know if that will actually be the case. But
we can be fairly certain that such a risk is greater
than one which is estimated at one in 1,000,000.
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However, risk management decisions are made
not only on the scientific quantitative and qualita-
tive estimates of the risks, but on the economic
and social implications of the action being con-
sidered to control the risks. Possible solutions are
compared and evaluated to determine the most
appropriate response. For instance, one remedy
to reduce a risk may cost twice as much as another
and do essentially the same job, or one may not
be as effective as another. On the other hand, a
remedy may have too high a social cost: while
lowering the speed limit to 55 miles per hour
apparently resulted in fewer accidents on the
highways, most people would consider lowering
the limit to 45 miles per hour unacceptable.
Once relative risks are determined and the
various means of dealing with them evaluated,
priorities must be set. Since resources to deal with
risks are finite, it's essential that the worst and
most controllable risks be addressed first in any
comprehensive plan to clean up and protect the
aquifer. The recommendations in the Biscayne
Aquifer Protection Plan have been given a priority
rating according to these risk management criteria.
Effectiveness of Air Stripping
Treatment on VOCs
All concentrations are in \j,g/L (parts per billion).
voc
Vinyl Chloride
1,1-Dichloroethene
Maximum
Concentra-
tion Found in
Preston or
Upper Miami
Springs Well
Fields
21.21
5.12
Cleanup Level
Goal Set Reach-
by EPA able After
Air Strip-
ping
1.0
0.2
.03
.02
For additional technical information, consult the EPA's
Final Report: Phase III Feasibility of Remedial
Actions for the Protection of the Biscayne Aquifer in
Dade County, Florida.
This report has been prepared for the Environmental Protection Agency by Meridian Communications, Rifkin and Associates,
and CH2M HILL. November, 1985.
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