United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROO/R04-87/027
September 1987
Superfund
Record of Decision:
NW 58th St. L.F., FL
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TECHNICAL REPORT DATA
(Pleau read Instructions on tHt rtvene btfort completing/
1. REPORT NO.
eA/ROD/R04-87/027
2.
'ITLE AND SUBTITLE
[s"UPERFUND RECORD OF DECISION
Northwest 58th Street Landfill, FL
Third Remedial Action
«. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
September 21. 1987
7. AUTHORIS)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final ROD Report
14. SPONSORING AGENCY CODE
800/00
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The Northwest 58th Street Landfill, one of three NPL sites that comprise the Biscayne
Aquifer Superfund Study, is a one-square-mile site in northwest Dade County, Florida,
which is bordered by a rock pit operation and a resource recovery plant. The site is
" seated in an area where the "ground water table is two to three feet below the ground
^face. From 1952 to 1982, the site operated as a municipal landfill receiving
.proximately 60,000 tons of waste in 1952 and increasing annually over the thirty years
of operation to over 1,000,000 tons per year in the.1980s. Small quantities of
hazardous materials from households (e.g., pesticides, paints, solvents, etc.) was
considered to be municipal waste and also disposed of at the landfill. In 1975, the
landfill operation initiated a program of providing daily cover to the site; however,
prior to this, the operation did not compact wastes or add daily cover. As a result of
earlier practices, the landfill is believed to be saturated with water so that the
volume of rainfall entering the land equals the volume of leachate released. Since
October 1982, the landfill has only received debris, quarry wastes an water paint
sludges. The primary route for human exposure to the contamination is through the
drinking water, and, in particular, two sets of public drinking water wells 2.5 miles
down gradient of the landfill. These wells serve an estimated 750,000 people. A 1986
(See Attached Sheet)
17.
KEY WORDS ANO DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Croup
Record of Decision
Northwest 58th Street Landfill, FL
Third Remedial Action
Contaminated Media: gw, soil
Key contaminants: VOCs, PCE, TCE, inorganics
•ISTRIBUTION STATEMENT
19. SECURITY CLASS iTIiit Report/
None
21. NO. OF PAGES
38
20. SECURITY CLASS /This pagtl
None
22. PRICE
ePA Form 2220-1 (R«v. 4-77) Previous IOITION is OCSOLKTC
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EPA/ROD/R01-87/023
Northwest 58th Street Landfill, PL
Third Remedial Action
16. ABSTRACT (continued)
Endangerment Assessment analysis identified eight contaminants of concern: arsenic,
chromium, zinc, benzene, chlorobenzene, 1,1,2,2-tetrachloroethane, trichloroethene and
vinyl chloride.
The selected remedial action for this site includes: controlling leachate generation
by a combination of grading, drainage control and capping; providing a public water
supply to approximately 60 underground wells; and landfill closure. The estimated
capital cost for this remedial action is $5,500,000 with annual O&M of $1,500,000.
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RECORD OF DECISION
SITE NAME AND LOCATION
NW 58th Street Landfill
Dade County, Florida
STATEMENT OF PURPOSE
This decision document represents the selected remedial action for this
site developed in accordance with CERCLA, as amended by SARA, and, to
the extent practicable, the National Contingency Plan.
The State of Florida has been consulted on the selected remedy.
STATEMENT OF BASIS
This decision is based upon the administrative record. The attached
index identifies the items which comprise the administrative record upon
which the selection of remedial action is based.
DESCRIPTION OF THE SELECTED REMEDY
The selected remedy is the final operable unit of the Biscayne Aquifer
Study Area, the previous operable units, and their Records of Decision,
were: Miami Drum Services - soils and groundwater contamination cleanup;
Miami Airport (Varsol Spill) - no action; Study Area Ground Water -
additional treatment of groundwater before distribution for public use.
This ROD is concerned with onsite soil contamination, site related ground
water contamination, and downgradient private well users associated with
the NW 58th Street Landfill.
The remedy selected for the NW 58th Street Landfill site is to:
0 Close the landfill in accordance with the technical requirements of
the applicable state regulation (FAC Chapter 17-7 (1985)), and the
relevant and appropriate EPA guidance document (Covers for Uncontrolled
Hazardous Waste Sites, EPA/540/2-85/002). The EPA document will provide
the specific methods for evaluation of the cover design.
• Provide municipal water to an area of private wells users
east of the landfill.
The closure will include leachate control through a combination of grading,
drainage control, and capping. This will minimize the infiltration of
stormwater into the landfill, thus controlling the leachate produced from
the landfill. If necessary, gas migration and odor controls will also be
implemented. Long t«rjn^monitoring of groundwater quality and O&M of the
closure is also required.
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The Biscayne Aquiftr is the sole source of drinking water for the Miami/Bade
County area. As suchr contamination of this aquifer is of special concern.
The Site Area Ground Water POD addressed area-wide groundwater contamination
by requiring additional treatment at the municipal water treatment plants.
The NW 58th Street Landfill BOD will provide public drinking water to the
last of the private well users believed to be at risk.
DECLARATION
The selected remedy is protective of human health and the environment,
attains Federal and State requirements that are applicable of relevant
and appropriate, and is cost-effective. The statutory preference for
treatment is not satisfied because treatment was found to be impracticable
due to the magnitude of waste to be treated (estimated at 27 million
cubic yards). In addition, the groundwater contamination in the Biscayne
Aquifer is widespread, so collecting and treating the groundwater around
the landfill would not adequately protect human health. This widespread
groundwater contamination is to be collected and treated by air strippers
at the water treatment plants serving the affected wellfields, and was the
remedial action selected in the Study Area Ground Water Record of Decision
(September 1985).
Lee A. DeHihns, III . Date
Acting Regional Administrator
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I. SITE NAME, LOCATION, AND DESCRIPTION
The Northwest 58th Street Landfill is a one square mile site in Northwest
Dade County, Florida near the western perimeters of the Town of Medley
and the City of Miami Springs (Figure 1). Along the eastern edge of the
landfill is a loaf-shaped mound 80-90 feet high which covers an area of
approximately 90 acres. In the middle of the site is a mound which is
50-60 feet high, and covers approximately 62 acres. In between the two
mounds is a small area of virgin land.
The site is bordered by industrial areas to the south across NW 58th
Street, and to the east across NW 87th Avenue. There is a rock pit
operation to the north across NW 74th Street, and undeveloped land and a
Resource Recovery Plant to the west across NW 97th Avenue. The site is
located in an area where the groundwater table is two to three feet below
the ground surface. The land in the area of the landfill is flat and at
an altitude of five feet above sea level. As a result, the drainage in
this area is poor. Intermittently during the rainy season (July through
September), the land is inundated and swampy conditions persist for ,
several weeks.
The Biscayne Aquifer is the sole source of drinking water for Dade County,
Florida. The major concern is public exposure via drinking contaminated
water. Several wellfields are located close to this site. Two public
water source wellfields (Preston and Miami Springs) are located within
2-1/2 miles downgradient (east), as well as about 60 private wells used for
commercial purposes. One public water source wellfield is located approx-
imately four miles upgradient and several private wells are within the
City limits to the north of the landfill. However, selective pumping
of wellfields has caused changes in the localized gradients.
The estimated annual rainfall in this area is 60 inches, 80% of which
falls during the rainy season (July through September). It was further
estimated that 33% of the rainfall is lost by evaporation, 33% by evapo-
transpiration, and 27-30% by coastal seepage. The remaining 3-7% is used
by man.
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Figure 1
rigure 1
LOG TION OF POTENTIAL CONTAMINATION SITES
•UBLIC WELL FIELDS, AND PRIVATE WELLS IN STUDY AREA
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II. SITE HISTORY
A. Operations
The site began operation as an open dump in 1952. Shallow trenches were
dug for waste disposal, resulting in deposition of refuse in the saturated
zone of the Biscayne Aquifer. In addition, open burning of waste for
volume reduction was practiced until it was banned in 1960. The landfill
received an estimated 60,000 tons of waste in 1952. The annual volume of
waste increased until the landfill was receiving over 1 million tons of
waste each year of operation in the 1980's. The landfill ceased accepting
municipal waste October, in 1982, and since then has received only construction
debris, quarry wastes, and water plant sludges. In January, 1975, a
program of providing daily cover was instituted. The cover utilized has
consisted of muck and crushed rock from quarry overburden and, more
recently, calcium carbonate sludge from water treatment plants.
The landfill was operated for over 30 years as a municipal landfill. It has
never been operated as a hazardous waste landfill. It must be recognized,
however, that over the last 35 years, the definition of a "hazardous waste"
has changed. Therefore, a substance which may be considered hazardous now
may have been accepted in the landfill at sane time in the past. Furthermore,
the normal operation of landfills which accept only municipal-type wastes
will include the disposal of very small quantities of hazardous materials
from households (e.g. insect spray containers, old paint, solvents, etc).
The quantities are small in comparision to the overall wastes contained in
a municipal landfill.
The landfill operation in the past did not include a program of compacting
the waste, nor did it include daily cover. Therefore, the landfill is
believed to be saturated with water. This means the volume of rainfall
which seeps into the landfill will be the volume of leachate released.
The quality of the leachate is a very good indicator of the potential
environmental problems the landfill could cause.
B. Studies Conducted
There have bMn several site investigations conducted under both state
and federal authority. The investigations include:
1) 1975 United States -Geological Service
Groundwater Quality Study
2) 1976 HI fcn Associates
Report on NW 58th Street Sanitary Landfill
3) 1981 Ecology and Environment, Inc.
Mitre Model Scoring of 56th Street Landfill
4 -
-3-
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4) 1981 Technos
Geophysical Surveys
5) 1981 Reynolds, Smith & Hill
Closure Plan (Preliminary Report)
6) 1982 Florida Department Of Environmental Regulation - Tallahassee
Chemical Analyses of Groundwater in the Vicinity of the
NW 58th Street Landfill, Dade County, Florida
7) 1982 CH2M Hill
Biscayne Aquifer/Dade County Study, Phase I, Volumes I - III.
8) 1983 Reynolds, Smith, and Hill
Technical Specifications for NW 58th St Landfill Closing (Draft)
9) 1984 Law Engineering Testing Co
Report on Geotechnical Engineering Evaluation: Sanitary
Landfill Cover Materials - Metro Dade Landfill Closeouts
Phase II North Dade and NW 58th St. Landfills.
10) 1984 CH2M Hill
Biscayne Aquifer/Dade County Study, Phase II »
Volumes I and II (Remedial Investigation)
»
11) 1984 Environmental Science & Engineering
Methane Gas Study
12) 1985 Dade County Department of Environmental Management
Northwest Vfellfield Protection Study
13) 1985 CH2M Hill
Biscayne Aquifer/Dade County Study,Phase III
(Feasibility Study)
14) 1987 Metro Dade Public Works Department
Summary of Ongoing Chemical Analysis of Aquifer Water
Quality Downstream of NW 58th St. Landfill
15) 1987 Florida Department of Environmental Regulation - West Palm Beach
Sunmary of Ongoing Chemical Analyses of Aquifer Water
Quality Downstream of NW 58th St. Landfill
16) 1987 Camp, Dresser, and McKee .Inc.
Evaluation of Atlematives Memorandum for the NW 58th
Street Landfill Site Dade County Florida
17) 1987 Florida Department of Environmental Regulation-
West Palm Beach
Recant^Data from Monitoring Wells Around the NW 58th
Street Landfill
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C. Results of- Studies
In 1986, an Endangerment Assessment (EA) was conducted, analyzing available
data for the groundwater quality in monitoring wells both upgradient and
downgradient of the NW 58th Street Landfill. The ranges of the contaminants
found are sunnarized in Table 1.
The analytical data which resulted in Table 1 values were compared to the
current drinking water MCLs. In 1982, the 1987 MCLs were violated for
Iron, Manganese, Mercury, 1,1,2,2-Tetrachloroethane, PCB's, Silvex, and
Chlorobenzene. Of these, Iron, Manganese, Methylene Chloride, and Silvex
were above the 1987 MCLs in the upgradient (uncontaminated) well during
at'least one of the sampling rounds.
In 1983 results indicated that Iron, Manganese, Mercury, 1,1,2,2-Tetra-
chloroethane, Silvex, Chlorobenzene, Benzene, Methylene Chloride, and
2,4-D exceeded the 1987 MCLs for drinking water.
In 1987, the contaminants which exceeded the 1987 MCLs were Iron, Methylene
Chloride, Lead, and Tetrachloroethene.
The EA then selected contaminants of concern based on the following
criteria: 1) detection of the chemical in at least two samples from a
well, 2) identification of at least two samples greater than the applicable
standards or criteria, and 3) information about the contaminant's mobility *
and persistence in the environment and its toxicity. This analysis produced
the following list of eight contaminants of concern: 1) Arsenic, 2) Chromium,
3) Zinc, 4) Benzene, 5) Chlorobenzene, 6) 1,1,2,2-Tetrachloroethane,
7)Trichlorethene, and 8) Vinyl Chloride. The mobility and toxicity of the
contaminants of concern are summarized in the following paragraphs.
Arsenic is most toxic and most soluble in its trivalent state. This is one
of the most prevalent states of arsenic found in nature. When in a reducing
environment, arsenic can be volatized. Arsenic sorbs onto clays, phosphates
and organic material. Some bioaccuraulation of arsenic occurs, but it does
not appear to biomagnify in the higher-level food chain organisms. The
levels found in the groundwater downgradient from the NW 58th Street Landfill
can easily be transported in the groundwater. Arsenic is carcinogenic and
mutagenic.
Benzene nig be biodegraded in the presence of the proper microbial population,
and may b& volatilized. Benzene has low sorptive properties and high
solubility* There is a high potential for the transport of this chemical
in the groundwater. Benzene is carcinogenic and mutagenic.
1,1,2,2 - Tetrachloroethane is a volatile organic chemical. It may adsorb
onto clay particles. It is considered to be a possible carcinogen and it may
be mutagenic.
*%*
Trichloroethene may be biotransformed and biodegraded. It is a very volatile
chemical, with an affinity for adsorption. The transport of this chemical
through the aquifer is expected to be rapid. Trichloroethene is considered
to be a probable carcinogen and weakly mutagenic.
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TABLE 1
RANGE OF GROUND WATER MONITORING RESULTS
NW 38th STREET LANDFILL
DADE COUNTY, FLORIDA
REM II
iminant
Concentration
R*ng«»
(ug/1)
f , .
^, fc V
••nie
rylliua
ron
daiua
b«lt
>pp«r
•on
) Ad
ircury
alyodwiuM
lekel
•Ivniua
llv«r
in
inc
ORITY POLLUTANTS-
ATILE ORGANICB
)r o«odl chl or OMtthann
;h 1 or ob«nz mnm
)i br o«oehl oro««th«n«
l, l-Dichloro«th*n«
L , 2-Dlchl oro«than«
l,l-Dichloro«th«n« «L%^
:is-l , 2-Oichloro«th«n«
tr«n«-l,2-Dichloro«th«n«
Ethyl b«nz«n«
n«thyl«n« Chlorid*
1,1,2, 2-T«tr achl or o«th*n«
T«tr »chl oro«th«n«
ND -
ND -
ND -
ND -
NO -
NO -
ND -
ND -
ND -
90 -
ND -
ND -
NO -
NO -
NO-
NO -
NO -
ND -
ND -
•
NO -
ND -
NO -
ND -
NO -
NO -
NO -
NO -
ND -
ND -
—
4 ""
) •»
-.
10,OOO
96
100
14
BOO
14
99
19
10O
91,700
110
630
19
9
48
13
9
40
28,000
a
0.02
16
9
17
17
3
96
29
6
9
9.7
9
11
1.13
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RANGE OF GROUND WATER nONXTORXNG RESULTS
NW S8th STREET LANDFILL
DAOE COUNTY, FLORIDA
REH II
Contaminant
Concentration
Ranges
2,4,S-T
MISCELLANEOUS
Cyanide
Oil V Greaee
NON-PRIORITY POLLUTANT-
OR6ANICS
Acetone
C3 Alkylbenzoic Acid
cz Alkylphenol *%«
Benzole Acid
Carbon Dleul-fide
Chlorotoluene
1,4-Dioxane
Ethylether
Hexadecane
NO
ND
NO
ND
ND
ND
NO
ND
ND
ND
NO
ND
ND
ND
ND
ND
ND
ND
1,000
ND
ND
ND
ND
ND
ND
ND
ND
ND
200
40
134
20
20
6
0.001
0.001
0.02
0.01
0.09
480
6.18
O.OO1
830
78
39
30
31,000
200
21
120
299
10
30,000
10
10
20
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TABLE 1
RANGE OF GROUND WATER MONITORING RESULTS
NW 38th STREET LANDFILL
OADE COUNTY, FLORIDA
R01 II
Concentration
Ranges
Contaminant
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Vinyl Chloride is readily volatilized and exhibits a low affinity for
sorption. It will move with the bulk flow of the groundwater. Vinyl
Chloride is carcinogenic and rautagenic.
Many studies of the quality of the Biscayne Aquifer have been conducted,
and several of the monitoring wells used in these studies are located in
such a way as to be useful in defining the effect of the landfill leachate
on the aquifer water quality. This is a major concern because the Biscayne
Aquifer is the sole source of drinking water for Dade County.
In 1975, the U.S. Geological Survey completed a study of groundwater
contamination around the NW 58th Street Landfill. The results of the
sampling conducted during this study indicated the presence of a plume
of contamination migrating downgradient from the landfill. The report
estimated that the plume, at that time, was located about one mile east
(downgradient) of the landfill. In 1982, CHoM Hill conducted a ground-
water quality study as part of the remedial investigation of the Biscayne
Aquifer study area. This study included the NW 58th Street Landfill, and
the results did not indicate the presence of any identifiable plume from
any of the sources in the study area. Rather, the study showed wide-
spread low to moderate levels of contaminants present in groundwater in
most of the study area. In the 1987 data from FDER, where they sampled
several monitoring wells around the NW 58th Street Landfill site, the low
to moderate levels of contaminants are still present. This study was
performed to determine the contaminants released from the landfill, not
to identify a plume.
Since the data are from several wells, however, some information about
the attenuation of the contaminants is available. Table 2 summarizes
the analytical data for several contaminants found in the set of wells
which best measure the effects of the NW 58th Street Landfill on the
groundwater. The wells are identified in the Table by their distance
downgradient from the landfill (Figure 2 and Table 3). There are data
for three sets of sampling, defining the attenuation possibilities over
time and distance.
D. Areawide Exposure Risks
The primary route for human exposure to the contamination is through
drinking tte water. Of major concern are the two sets of public drinking
water supply wells, the Preston and Miami Springs wellfields, and a set
of private-use wells which are located within 2-1/2 miles downgradient
of the NW 58th Street Landfill. The population served by the public
wellfields is estimated to be 750,000. The potential problem with these
downgradient wellfields is the migration of contaminants into the cone of
influence of drinking water supply wells. Currently, the water from
downgradient weHa is blended with uncontarainated water from upgradient
wells, and the use 3f downgradient wells is minimized, thus providing
safe drinking water for the public. There has been some concern, however,
that the influence of the upgradient wells may cause contaminated groundwater
to migrate toward them. TO help insure this migration does not occur,
the County has adopted a wellfield protection plan for the area.
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-------
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Figure 3' Location of pampling wells in study area
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TABLE 3
MONITOR WELL LOCATIONS
NW 58TH STREET LANDFILL
DADE COUNTY, FLORIDA
REN II
Well Cluster
Location
LM-1
LM-2
LM-4A
LM-5A
LM-6A
LM-7A
LM-8
Approximately 1.0 mile (5280 Ft) west of the landfill
site
On the western edge outside of the landfill site
Approximately 375 ft. west of the eastern edge, inside
the landfill site
Approximately 250 ft. east of the landfill site
Approximately 2250 ft. east of the landfill site
Approximately 6850 ft. east of the landfill site
Approximately 2250 ft. east of the landfill site and
2500 ft. north of LM-6A
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E. Areawide Actions to Minimize Exposure Risks
The wellfield protection plan is designed to push the cone of influence
of the uncontaminated Northwest Wellfield further to the west to maintain
its uncontaminated state. This is be be accomplished by creating an
hydraulic barrier with improvements to the existing drainage/ recharge
system. In addition, the land area over the cone of influence for this
wellfield will be protected from incompatible uses by zoning ordinances.
Another important aspect of this plan is to decrease the punpage rate
from the uncontaminated Northwest Wellfield. Currently, this is not
feasible due to the necessity to provide the cleanest possible drinking
water to the public. It is anticipated, however, that the air strippers,
when functioning at the water treatment plants, as described later in
this document, will allow increased pumping of contaminated groundwater.
The increased pumping from the contaminated wellfields will allow an
equal decrease in pumping from the uncontaminated wellfield.
The Biscayne Aquifer Superfund Study is an incorporation of three National
Priority List sites: Miami Drum Services; Miami International Airport
(Varsol Spill); and Northwest 58th Street Landfill. All of these sites
have caused some contamination of the Biscayne Aquifer. Each site represents
an operable unit of the entire remedy for this study area. The Miami k
Drum Services operable unit involved soils and groundwater cleanup, and a
Record of Decision (ROD) with a source control requirement was signed in
September, 1982. In March, 1985, a POD was signed for the Miami International
Airport (Varsol Spill) operable unit, and required no action. The Study
Area Ground Water (Biscayne Aquifer) operable unit POD was signed in
September of 1985. This ROD requires that air stripping be added to the
existing water treatment process in the study area. It also calls for
the two downgradient municipal water supply wellfields (Preston and Miami
Springs) to be operated for the dual purpose of providing potable water
and recovering contaminated water from the Aquifer. This system is
currently in the Remedial Design phase and will treat the contamination
which occurs in the cone of influence of these wellfields. The alternative
selected in this (NW 58th Street Landfill) ROD will minimize future
contamination of the aquifer by controlling the leachate production from
this source.
While the Action taken under the Biscayne ROD will treat the public drinking
water supply, there are still concerns with the downgradient private
(commercial) use wells in the study area. The concerns are addressed, in
part, by the source control actions taken under the area RODs which have
been signed as well as this ROD on the Northwest 58th Street Landfill.
Dade County is addressing the concerns for the private well users by
implementing special taxing districts to finance their plans to put the
private-well users on public water supplies. The cost per assessable
foot varies by the district involved. In one district, the assessment
will be $39.73 per "foot, and in another, the cost is $264.73 per assessable
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foot. One* .the public
personnel will insped
private wells are sevc
at the discretion of t
landfill within the C:
action has been unden
All the private wells
water by December 1985
rater is available to the district, Dade County
to ensure that all potable connections to the
3d. The wells nay still be utilized for irrigation
3 owners. Private wells to the north of the
r limits have been replaced by City water. This
ten by the cities of Hileah Gardens and Medley.
\ the area of concern should be replaced by municipal
The special taxing dis :ict is also being utilized for an unsewered
industrial area. Thei is concern that the use of septic tanks in these
industrial areas contz >ute to the areawide groundwater contamination
problem. ' Therefore, E le County has plans to provide sewer service
to these areas by Decs »r, 1989.
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III. ENFORCEMENT SUMMARY
In June, 1979, Dade County and the Florida Department of Environmental
Regulation entered into a Consent Order which required the County to
cease accepting waste at the NW 58th Street landfill by August 1, 1981.
This date was not met. The landfill did stop accepting wastes for
disposal in October, 1982, although it has never been officially
closed in accordance with Chapter 17-7, Florida Administrative Code (FAC).
The Consent Order with the State is still in effect; however, a Consent
Agreement with EPA will be negotiated with the County, and the State will
be asked for input to the Consent Agreement. This Record of Decision
requires the landfill to be closed in accordance with the technical
requirements of Chapter 17-7 FAC (1985), utilizing the implementation
guidance document "Covers for Uncontrolled Hazardous Waste Sites"
(EPA/540/2-85/1985). Once that is accomplished, the State's Consent
Order requirements will also be met.
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IV. COMMUNITY RELATIONS HISTORY
In July 1984, a Community Relations Plan (CRP) was completed for the
Biscayne Aquifer Site, which includes the NW 58th Street Landfill. The
CRP cites the major issues and concerns with this site as: 1) Potential
contamination of area drinking water supplies, 2) Comprehensive solutions
for the Biscayne Aquifer sites, 3) Relationship among key parties, and
4) Coordinated flow of information. The CRP futher noted that the location
and nature of the problem tends to encourage community involvement on an
area-wide, rather than site-specific, basis.
The Community Relations Plan responded to the identified issues and concerns
by providing public meetings to discuss ongoing work with concerned citizens.
The CRP also included workshops for the key parties to get together and
discuss any issues of concern. In addition, 3 mailings of a newsletter
entitled "Remedies* were sent to concerned citizens and elected officials.
These newsletters included updates on the sites in South Florida, summaries
of results of studies conducted, and meeting announcements. Furthermore,
a fact sheet entitled "Phase III Feasibility of Remedial Actions for the •
Protection of the Biscayne Aquifer, Dade County, Florida" and an executive
summary entitled "Recommendations to Clean Up and Protect the Biscayne
Aquifer in Southeast Florida" were printed and distributed. The media in
South Florida were also invited to many of the meetings, and press releases
were issued periodically. In addition, information has been made available
to the public by deposition of copies of documents placed in the Florida
Reference section of the downtown Miami-Bade County Public Library.
On October 25, 1983, a meeting was held to discuss the results of sampling
the groundwater in South Florida. During this meeting the results of the
Remedial Investigation and a list of preliminary alternatives were presented.
On March 20, 1984, a public meeting was held during which the results of
the initial screening of alternatives were presented, as well as the
detailed analysis of the remaining alternatives.
On July 17, 1984, a public meeting was held for comments on the Feasibility
Study and tte leommiBnded alternative. Two workshops on study findings,
risk iiimiMMiit. and proposed cleanup and prevention activities were held
for the ptMSr local officials, and the general public.
On February 7, 1985, a public meeting was held to discuss the results of the
Feasibility Study. At the meeting, it was stated that EPA would accept
written comments on the results of the Feasibility Study until February
28, 1985. No written comments were received throughout the comment period.
The attached responsiveness summary deals with issues brought up in the
public meeting orf-iabruary 7, 1985 (Attached).
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V. ALTERNATIVES ANALYSIS
The Feasibility Study considered several alternatives applicable to the
Northwest 58th Street Landfill site. These include:
1) No Action.
2) Onsite Groundwater Recovery Wells with Treatment Prior to
Discharge.
3) Onsite Groundwater Recovery Wells with Deep Injection Well Disposal.
4) Containment of Contaminants.
5) Excavate the Landfill.
6) Leachate Control Measures.
Each alternative was evaluated using the Evaluation Factors in Section 121
(b)(l) (A-G), of the Superfund Amendments and Reauthorization Act as well
as whether or not it attains the applicable or relevant and appropriate
requirements, which are described in Table 4.
1). No Action.
The "No Action" alternative provides no source control, so the landfill
will continue to contaminate the groundwater unchecked. It does not provide
tpxicity reduction, nor does it act to protect the community from exposure
to the contamination. This alternative does not reduce the migration
potential or the volume of leachate.
Attenuation must be considered under the no action alternative. The data
on this site indicate the groundwater contamination in the Biscayne Aquifer
study area (including the NW 58th Street Landfill) is low to moderate in
level and widespread. Although a plume of contamination was identified
and attributed to the NW 58th Street Landfill by the USGS in 1975, no
such plume was identified in the 1983 study conducted as part of the
remedial investigation. This study identified low to moderate contamination
as a generalized condition of the groundwater in the study area. In
results of sampling conducted by the Florida Department of Environmental
Regulation in-1987, a similar condition, was evident.
Table 2 allows a ready comparison of the effects of attenuation on
several contaminants. It compares the contaminants in the time parameter
as well as in a distance downgradient parameter. No pattern of attentuation
is noted. Therefore, the no action alternative will not provide attentuation
of the contaminants:*
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TABLE 4
APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS
Requirement
1. Chapter 17-7 PAC (1985)
2. Chapter 17-4 FAC
3. Chapter 17-3 FAC
4. Chapter 17-25 FAC
5. Chapter 17-28 FAC
6. 40E-4, Rules of the South Florida
Water Management District
7. 40E-3, Rules of the South Florida
Water Management District
8. Section 24-11, Metropolitan Dade
County Code
9. 'Section 24-58, Metropolitan Dade
County Code
10. Solid Waste Disposal Act
11. Resource Conservation and
Recovery Act - Subtitle D
12. Clean Utter Act
13. Safe Drinking Water Act
14. Clean Air Act
15. National Oil and Hazardous
Substances Pollution
Contingency Blag •
Substance
Resource Recovery and Management
Permits
Water Quality Standards
Storrawater Discharge
Underground Injection Control
Stornwater Controls
Monitoring Well Design and
Construction
Groundwater Standards
Permitting
Landfill Closure
Nonhazardous Landfill
Closure
Water Quality
Drinking Water Quality
Air Emissions Control
Remedy Evaluations/Selection
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This alternative is technically feasible and applicable but it does not
meet the goals established for this site. There are no costs for iraplera-
entation of this alternative.
2). Onsite groundwater recovery wells with treatment prior to discharge.
The treatment process considered in the "Evaluation of Alternatives
Memorandum for the NW 58th Street Landfill Site", consisted of recovery
wells pumping the contaminated groundwater from the aquifer to a two-stage
treatment process. The treated groundwater is then reinjected into the
aquifer, creating an hydraulic barrier to contaminant migration.
The first stage of the treatment system is a chemical/physical process for
the removal of metals. The effluent from this process would then be
directed to an air-stripping system for the removal of volatile contaminants.
This alternative does allow for the collection and treatment of the leachate,
thereby reducing the toxicity and controlling the migration of the ground- fc
water. The reliability of this system is anticipated to be good, and it
is technically feasible and applicable to this site.
A major concern is with the useful life of the physical and mechanical
equipment as well as the wells themselves. It can reasonably be anticipated
that this system will require replacing at some time in the future since it
does not provide for the reduction of leachate production.
The present-worth cost estimate of the capital and 30 year operation and
maintenance of this system is $3.9 million. This cost breaks down into:
Construction Costs - $2.5 million (present worth)
30-year O&M Costs - $1.4 million (present worth)
The proposed system will not meet Chapter 17-7 Florida Administrative
Code requirements for landfill closure and therefore, in addition
to the money expended for this system, a landfill closure will be
required. Another consideration is that the downgradient drinking water
wells already act as recovery wells for the contamination in the Biscayne
Aquifer. Since the aquifer is contaminated by sites in addition to the
NW 58th StXMt Landfill, this alternative will not alleviate the requirements
for the treatment of the aquifer water withdrawn by the public wells.
Another concern is the downgradient private well users. This alternative
does not alleviate that problem.
3). Onsite groundwater recovery and deep injection well disposal.
This alternative«ipyolves pumping out the contaminated groundwater under-
neath the landfill and pumping (injecting) it into a deep aquifer of
sea water quality. The Feasibility Study estimated that a depth of 3,000
feet for the deep injection well is necessary. To assure reliability and
continuous operation, a second injection well would be installed as a
backup. , *
-------
This process^is technically feasible; however, the applicability of the
process to the NW 58th Street site is questionable. The groundwater contamin-
ation level has been found to be consistently low in all studies conducted
in the aquifer. In fact, with proper treatment, this water could be used
for drinking water. Therefore, deep injection disposal of this contaminated
groundwater does not appear to be an appropriate action.
This alternative does allow for the collection and disposal of the leachate
in the groundwater, thereby reducing the toxicity and controlling the
migration of the groundwater. However, since no action to stop the
production of leachate would be taken, the equipment would need to operate
indefinitely. Thus, it is necessary to consider the useful life of the
mechanical and physical equipment, as well as the wells themselves. It
is reasonable to assume that they will need to be replaced at some time
in the future.
The present-worth cost estimate of the capital and 30 year operation
and maintenance of this system is $5.0 million. This breaks down into:
Construction Costs: $4.5 million (present worth)
30-year O&M Costs: $0.5 million (present worth) »
This system would not meet Chapter 17-7 Florida Administrative
Code requirements for landfill closure. Therefore, in addition to the *
money expended for this system, a closure would be required. Another
consideration is that the downgradient drinking water wells already act
as recovery wells for the contamination of the Biscayne Aquifer and could
be used as a more cost effective recovery system. Since the aquifer is
contaminated by sites in addition to the NW 58th Street Landfill, this
alternative will not alleviate the requirement for the treatment of the
aquifer water withdrawn by the public wells. Furthermore, the private wells
downgradient from the landfill are not addressed in this remedy.
4). Onsite containment of contaminants.
The Feasibility Study (FS) cited examples of grout curtains, slurry walls,
and sheet pile walls for onsite containment. The FS then questioned the
technical feasibility and constructability of this alternative. Some
of the oononH in a system of this type would be the depth to which the
barriers would need to be placed ( to the base of the aquifer, 60-90 feet),
the fast-ooving nature of the aquifer (2-4 feet per day), and the cavernous
nature of the aquifer. These concerns'-also bring the applicability
and reliability of the alternative into serious doubt.
Due to the doubts concerning the technical feasibility and constructability
of the processes included in this alternative, no cost analysis was conducted,
and this alternative is rejected from further consideration based on technical
infeasibility and non-constructability.
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5). Excavate/Dispose of the Landfill.
This alternative involves the excavation of nearly 27 million cubic yards
of landfill material. There are many health and technical feasibility
questions regarding this option. The present worth estimate of the cost
of excavation alone is $439 million. Since this is two orders of magnitude
higher than the other alternatives that would provide comparable protection,
this alternative is rejected on the basis of cost.
6). Leachate Control Measures.
This alternative will include some combination of capping, grading, drainage
control, and leachate collection. The specific actions considered in the
"Evaluation of Alternatives Memorandum for the NW 58th Street Landfill
Site" are cover, grading, and drainage control. This alternative
would also provide a monitoring plan to assess long term reliability
and to serve as an early warning system. Long term O&M of the implemented
alternative will be required, as will controls for gas migration and odors.
This plan will minimize leachate production by redirecting the rainfall which
would otherwise percolate through the landfill. This is a technically
feasible and applicable solution. It does provide for long-term protection*
of the groundwater, although it does not address the groundwater contamination
at the present time. Since the landfill is unlined, some leachate generation
will always occur at this site; however, a significant portion will be
eliminated. In addition, the groundwater will flush the same parts of
the landfill with each high water cycle, and so should result in decreasing
contamination of the aquifer over time.
This alternative acts to decrease the volume and (in time) the toxicity
of the leachate. It will not affect the migration of the leachate which
does form. However, downgradient public drinking water wells will act to
recover contaminated water from the Aquifer. This is addressed in the
Biscayne Aquifer POD, which requires air strippers to treat the drinking
water before distribution. Another concern is the downgradient private-use
wells. These will be addressed by Oade County. The solution will include
providing public drinking water to the affected area.
This alternative meets the technical requirements for landfill closure in
Chapter 17-7 Florida Administrative Code, (1985).
The estimated present-worth cost of this alternative is $7.0 million.
This breaks down into:
Construction Cost: 5.5 million (present worth)
30-year O&M Cost: $1.5 million (present worth)
-21-
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VI. SELECTED REMEDY
The NW 58th Street Landfill Record of Decision includes controlling
leachate generation at the landfill and supplying alternate drinking
water to selected areas. The selected remedy calls for the landfill to
be closed in accordance with Chapter 17-7 Florida Administrative Code
(FACH1985). Table 4 is a summary of the applicable or relevant and
appropriate requirements on the County, State, and Federal levels.
Chapter 17-7 FAC (1985) has emerged as a primary regulation of concern in
this Record of Decision. The National Contingency Plan (sections 300.6
and 300.7) identifies potential remedies for sites on the National
Priorities List and so it is clearly applicable to this site. In addition,
since the Biscayne Aquifer is the sole source of drinking water for Dade
County, the Safe Drinking Water Act and Chapter 17-3 (FAC) are of great
importance. The groundwater quality underneath and downgradient from the
landfill violates some of the MCLs for drinking water. However, before
distribution to the public, the groundwater is treated by traditional
lime-softening and sedimentation/ filtration techniques at water treatment
plants, and the Study Area Ground Water remedial action as required in
the ROD (1985) will provide air stripping to bring the remaining chemicals of
concern into compliance with the MCLs.
Chapter 17-7 FAC (1985) requires that leachata from landfills be minimized
by controlling the infiltration of stormwater. This will be achieved
by a combination of grading, drainage control and capping. It also
requires all closure plans to provide a groundwater monitoring system and
stormwatar control. Methods for monitoring gas migration and odors will
be included, and implemented if necessary. Chapter 17-7 FAC (1985)
requires longterm monitoring of the sysban in use for leachate minimization
as well as for groundwater monitoring. EPA has incorporated the guidance
for the evaluation of remedies into documents specific to the remedy.
The remedy Cor this site consists of landfill closure. The EPA document
"Covers for Uncontrolled Hazardous Waste Sites" (EPA/540/285/002) is the
applicable and relevant and appropriate document to guide the implementation
of this remedy under CERCLA. This document provides guidance for the
designer and the evaluator when implementing Sections 300.6 and 300.7 of
the NCP. The CERCLA guidance can be an effective implanentation tool
when designing under the FAC Chapter 17-7 (1985) regulation. Together,
they provide the appropriate regulatory requirements (Chapter 17-7 FAC
(1935) with the appropriate design criteria and evaluation procedure
(EPA/540/2-85/002) for the remedy.
Another major area of concern is the downgradient private well users.
The Feasibility Study identified approximately 60 downgradient wells
which were affected by the groundwater contamination from the landfill.
The ROD addresses this problem by requiring that these private well users
be provided with a public water supply. Dade County is already addressing
the problem by implementing a special taxing district encompassing the
private well users. Triis taxing district is designed to generate the
revenue necessary for Dade county to supply t'aa area with a public water
supply. It is anticipated that this will be accomplished by the end oE
1988.
4
*
-22-
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Dade County has contracted with Brown and Caldwell Engineers to prepare
the closure plan for this site. The current schedule calls for this
plan to be completed by February 1988. The consultants are considering
several different combinations of grading, drainage control, and capping
to design an optimal solution.
The Endangerment Assessment identified several possible pathways for
exposure to the contaminants at the site. Possible air emission of
methane gas was cited as one route of exposure. Direct contact was also
listed as a possible pathway, but the pathway of greatest concern is the
ingestion of contaminated water. The selected remedy will address all of
the exposure pathways of concern. A Chapter 17-7 Florida Administrative
Code (1985) closure will require methane control (if needed) and the
required landfill cover will eliminate the possibility of direct contact.
Leachate control (cover, grading, capping, etc), will minimize the production
of leachate. The downgradient private well users will be provided with
municipal water. The water withdrawn from the aquifer for the municipal
supply will be treated by air stripping currently scheduled for installation
at the municipal water treatment plants (Biscayne Aquifer area-wide
groundwater BOD September, 1985). Thus, the selected remedy addresses *%
all of the exposure pathways and is protective of human health and the
environment. • ,
The landfill will continue to leach due to groundwater intrusion. However,
minimizing stormwater infiltration will significantly reduce the volume
of leachate produced. Over time, as the groundwater flushes out the same
area of the landfill and rainfall infiltration into the landfill is minimized,
it is likely that the quality of the leachate from the landfill will improve.
Although this alternative is slightly more costly than roost of the other
alternatives considered, it is the most cost-effective solution which
will achieve compliance with the landfill closure requirements of Chapter
17-7 FAC (1985) and utilize a technically feasible and implementable
remedy. Brief descriptions of the other alternatives considered are
contained in Table 5. Only one other alternative would meet the require-
ments of Chapter 17-7 FAC (1985), and that is to excavate and dispose of
the landfill* The cost of this alternative, along with the health concerns
and technical feasibility questions, prohibits selection of this alternative
as the final remedy. The remaining alternatives did not meet Chapter
17-7 FAC (1985) requirements for landfill closure.
The ccnnunity comments to the Feasibility Study expressed concern that the
landfill be closed and cleaned up. As that is the required action in this
Record of Decision, ccnnunity support is expected to be widespread.
As stated earlier, the.landfill closure plan is scheduled for completion
by February, 1988?* The remainder of the schedule is to be negotiated
into a Consent Order in the first quarter of FY '88. The negotiations
will involve EPA, FDER and Dade County.
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COMMUNITY RELATIONS
RESPONSIVENESS SUMMARY
BISCAYNE AQUIFER SITES
FEASIBILITY STUDY
INTRODUCTION .
EPA held a public meeting on February 7, 1985 at the Miami
Springs City Hall to discuss the Feasibility Study (FS)
report for the Biscayne Aquifer site and to accept public
comment. The meeting, held from 7:30. to 11:00 p.m., was
attended by 34 people.
James Orban, EPA's site manager for the project, chaired the
meeting. He was assisted by Udai Singh and Ken Cable from
CH2M HILL, EPA's technical consultant. They provided a
brief description of the site history, the nature of the
problem and the findings of the Remedial Investigation (HI).
This was followed by a more detailed presentation of the
cleanup alternatives considered and the recommended actions.
Mr. Orban then requested questions and comments from the
audience and stated that EPA would also accept written
comments until February 28, 1985.. He indicated that all »
comments would be considered in 'the decision making process
and that a.written response to the comments would be ,
included in the Record of Decision.
SUMMARY OF PUBLIC COMMENT AND AGENCY RESPONSE
Questions and comments offered at the meeting are summarized
below.. They are divided into three categories: general
comments relating to the project as. a whole, those
pertaining to specific sites, and those concerning
recommended cleanup activities for the area's groundwater.
No written comments were received during the public comment
period.
GENERAL COMMENTS/QUESTIONS
1. Public Involvement: Speakers thought that public
notice for the meeting was inadequate, that there had
not been sufficient involvement of citizens during the
study process, and that the plans had been prepared
"behind closed doors"..
Response; Public notice for the meeting was provided
by display advertisements in the Ft. Lauderdale News
and the Miami Herald. A press release announcing the
meeting was distributed to all local newspapers. The
RIcdnd FS reports were available for public review at
the Palm Beach, Dade and Broward County offices. EPA
gnCM13/d.!602
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had previously implemented an extensive community
relations program for the site.
A public meeting was held in September 1982 to present
the results of the initial study and -to outline the
plans for Remedial Investigations. Three issues of
Remedies, a newsletter summarizing project activities
and reports, were mailed to over 400 individuals and
organizations in October 1983, March 1984 and
July 1984.
A public meeting to present the Remedial Investigation
findings, outline the Feasibility Study activities, and
solicit comments on possible cleanup alternatives to be
evaluated was held in October 1983* Preliminary
results of the detailed evaluation of the remedial
action alternatives were explained in a public meeting
in March 1984. Also presented for comments and
suggestions at this meeting was the preliminary outline
of the program for the protection of the Biscayne
Aquifer.
EPA sponsored another public meeting in July 1984 to fc
present and receive public comment on the recommended
alternatives and the Biscayne Aquifer Protection Plan*
Two workshops on study findings, risk assessments, and
proposed cleanup and prevention activities were held
for the press, elected and appointed officials and the
general public during July 1984. EPA believes these
activities provided excellent opportunities in both
formal and informal settings for two-way communication
between interested citizens and the agencies: EPA,
Florida Department of Environmental Regulation, Dsde
County Department of Environmental Resources
Management, and the Centers for Disease Control.
2. Funding for Cleanup; Questions concerned the
availability of EPA funds for implementation of cleanup
activities, private sector responsibility for cleanup,
and incentives to encourage private sector site
cleanup. Cbmmentors indicated that water user charges
should not be used to fund cleanup actions.
Response; EPA has identified the responsible parties,
and will influence these parties to do what is
necessary to cleanup the site. EPA will also use
available Superfund monies to implement the cleanup.
3. Local Agencies;. Speakers expressed a lack of
confidence in the ability of county agencies to deal
with 4**aardous waste issues. They were critical of the
County's hydrocarbon removal operation at the airport,
the lack of technical training of Dade County
4
>
gnCM13/d.!602 2
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Department of Community Affairs staff, inaccuracies in
the County's report on Munisport landfill, operation of
the S8tH Street landfill, and the lack of information
about contamination on the west side of the airport.
Response; EPA pursued the Remedial Investigation and
Feasibility Study for the Biscayn.e Aquifer and made
recommendations for cleanup activities under the
authority of the Superfund program, expenditure of
program funds is limited to cleanup, of existing
uncontrolled hazardous waste sites -and cannot be
extended to cover costs of developing and implementing
plans designed to prevent the occurrence of future
hazardous waste disposal problems. These are
responsibilities of local agencies<
4. Federal Agencies; Commentors indicated that the
process for study and cleanup of sites takes too long,
and that EPA should have proposed an Environmental
Impact Statement (EIS) on the use of wetlands near the
Northwest well field for industrial development.
Response; EPA recognizes that the length of the
Remedial Investigation and Feasibility Study process
causes frustration among local residents who are
concerned about the effects of the sites on their '
health and property values. Yet, if the problems arc
to be effectively solved it is essential that they be
thoroughly understood before long term cleanup actions
are recommended. At Biscayne Aquifer, this required
extensive testing at a number of different sites and
evaluation of 12 source control and 10 offsite remedial
action alternatives. These activities were
accomplished as expediently as. possible.
Responsibility for implementation of an EIS rests
within a different division of EPA. Officials will
refer the request to the appropriate section within EPA
for further consideration.
SITE SPECIFIC COMMENTS/QUESTIONS
1. Varsol Spill Site: Commentors thought the presence of
hydrocarbons at the airport site should have been a
target for Superfund action.
Response: As the speaker/indicated, hydrocarbons are
not included in the list of hazardous substances
regulated by the Superfund program. The project
studies did assist the State and local officials in
identifying and addressing the problem. However,
formal Superfund action is not appropriate.
gnCM13/d.!602
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Over 1.5 million gallons of Varsol were believed to
have been spilled at the site in 1968. EPA conducted
an extensive sampling program at the site, but was
unable to confirm the presence of a plume of toxic
substances. It is possible that the solvent was
biodegraded or dispersed through the aquifer.
2. Miami Drum Site and 58th Street Landfill!
a. Speakers suggested that EPA in its RI did not
identify a contaminant plume at the 58th Street
landfill because it did not have much concern
about contaminant migration since the adjacent
Miami Springs well field is only used as a back-up
water supply source.
Response: The presence of a contaminant plume in
groundwater downgrade of the 58th Street landfill
was documented in the late 1970s by the U.S.
Geological Survey and various studies by
consultants; however, that was a non-toxic,
non-organic substance survey. Between November »
1982 and March 1983 EPA conducted a more
comprehensive survey; a series of six sampling fc
programs which tested for all 129 priority
pollutants, including organic as well as inorganic
toxic substances.
b. Speakers thought EPA's focus on municipal drinking
water and groundwater was too"narrow and did not
permit sufficient consideration of problems that
require attention at these sites. They were
concerned about cleanup and closure of the 58th
Street landfill and felt these activities should
be included as recommended remedial actions.
Response: EPA considered a wide range of
alternatives for remedial action at the sites,
related both to specific sources of contamination
as well as to the offsite, area-wide nature of the
problem. EPA did .include in the FS an analysis of
remedial alternatives for the 58th Street
landfill, including proper closure.
RECOMMENDED ACTION COMMENTS/QUESTIONS
1. Recommendation Development; One speaker questioned the
process of developing recommendations for cleanup
actioas^and indicated he did not feel the
recommendations covered all problems identified by
project studies. He suggested consideration of a
variation of Alternative 3 that would keep Preston and
Miami Springs well fields open for emergency back-up
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and would implement plans to minimize future
contamination in the Miami Springs area.
Response; EPA performed a detailed evaluation of
Alternative 3 and found that it was not cost-effective
(the total present worth cost for Alternative 3 was
over $23 million as compared to the cost of the
recommended alternative; $8.5 million). Alternative 3
also would not satisfy one of the important goals of
the study; to cleanup the aquifer, which will be
accomplished by pumping from the Miami Springs and
Preston well fields.
2. Biscayne Aquifer Protection Plan; Speakers identified
the need for federal protection of-wetlands in the
Northwest well field area. They suggested preparation
of an EIS or use of EPA's veto power over Corps of
Engineers' 404C permits to control land development
near the new Northwest well field.
Response; The suggested actions are not within the
domain of the Superfund branch at EPA. Officials will
refer this recommendation for consideration to the
proper division within EPA.
»
3. Air Stripping; Commentors were concerned about the
health effects of airborne pollution on people living *
near the proposed tower.sites. They asked about the
benefits of air stripping and the end result of the
remedial action on water quality.
Response; EPA completed a detailed estimate of air
pollution resulting from air stripping towers and found
that air stripping meets all state air emission
requirements and is far below allowable air emission
limits. It will not have adverse impacts upon the
environment or human health. The benefit of air
stripping is that it will be removing 97 percent to
over 99 percent of the volatile organic compounds from
the water withdrawn from the Miami Springs and Preston
municipal well fields, thus considerably improving the
quality of potable water in the study area.
4. Effect on Land Values; One speaker was concerned about
.the effect of the cleanup activities on land values in
her Miami Springs neighborhood. She wanted to know the
effect of the recommended alternative on her property
value.
Response: The Miami Springs and Preston well fields
had been pumping for 20 to 30 years, artificially
lowering the water table in the area. When pumping
began at the new Northwest well field and the Miami
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Springs and Preston well fields were shut down, the
water table in the area rose, causing flooding of
residential properties.
EPA's recommendation is to begin pumping the Miami
Springs and Preston well fields, and to treat the water
by air stripping so as to provide, clean water to the
public. Although this study was not meant to address
the flooding problem at the sites, the effect of the
recommended action is to return the water table to its
former position, thus resolving the flooding problem.
WDR91/001
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4
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RECORD OF DECISION
SUMMARY OP REMEDIAL ALTERNATIVE SELECTION
3ISCAYNE AQUIFER SITES, DADE COUNTY, FLORIDA
BACKGROUND
INTRODUCTION
Three sites proposed for the National Priorities List in
October 1981 are located in northwest Dade County, Florida.
After consulting with the State and County, EPA decided to
address these sites as a single management unit for the
performance of the RI/FS. A major reason for this decision
is that all three sites affect the same general area of the
Biscayne Aquifer. The agencies recognized that the effects
of these sites on the aquifer could be interrelated and that
some of the problems believed to exist would not be solely
attributable to an individual site. This management scheme
worked well for the RI/FS and is also appropriate for the
remedy.
A package of five Records of Decision (RODs) that address
the three sites is planned. One ROD was signed on
September 13, 1982, for the Miami Drum source control.
The second ROD (Varsol) is included herein. This ROD
package will be completed in phases with the final ROD
(Phase IV) planned for fall 1985. In general, the RODs are
as follows:
Phase I: Varsol Spill Site—immediate area soil and
groundwater
Phase II: Miami Drum—immediate area groundwater
Phase Ila: Miami Drum—source control (soils and
encountered groundwater), completed
September 1982
Phac« IIIi 58th Street Landfill—immediate area soil,
surface and groundwater
Phase IV: Groundwater ih three-site area
SITE LOCATION AND DESCRIPTION
The Biscayne Aquifer is the sole source of drinking water
for three million residents of southeast Florida. Three
Biscayne Aquifiapr hazardous waste sites on the EPA National
Priorities List were addressed as one management unit for
remedial investigation and feasibility study: (1) Varsol
Spill Site (Miami International Airport), (2) Miami Drum
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Site, and: (3) Northwest 58th Street Landfill. These sites
are located close to each other in north Dade County,
Florida. .The study area including these sites is defined in
Figure 1. Locations of these sites and public well fields
as well as private wells within the study area are shown in
Figure 2. The topography in the study area is flat,
approximately 5 feet above sea level.
The Varsol Spill Site is located in the northeast section of
Miami International Airport (MIA). The airport is located
less than one-half mile south of the lower Miami Springs
municipal well field. The Miami Canal runs adjacent to the
northeast corner of the airport, the Tamiami Canal runs
immediately south of the airport, and two other canals are
located near the western edge of the airport.
Miami Drum Services was an inactive drum recycling facility
located west of Miami Springs at 7049 N.W. 70th Street in
Miami. The dimensions of this site are 242 feet
(north-south axis) by 230 feet (east-west axis), and it is
located in a predominantly industrial area. The FEC Canal
is located about one quarter of a mile east of the Miami
Drum Site, and the Miami Canal is located less than one mile
northeast of the site. The Medley well field is located
approximately 750 feet west of this site, while the Miami
Springs and Preston well fields are located about 5,000 feet
southeast of the site.
The Northwest 58th Street Landfill consists of a
one-square-mile area near the western perimeters of the Town
of Medley and the City of Miami Springs. Present
development adjacent to this landfill site consists of
industrial uses to the south (Northwest 58th Street) and
east (Northwest 87th Avenue), a rock- pit operation to the
north (Northwest 74th Street), and undeveloped land to the
west (Northwest 97th Avenue). A new resource recovery plant
is located directly west of, and adjacent to, the landfill.
The Medley and Miami Springs municipal well fields are
approximately one and one-half miles and two and one-half
miles downgradient from the eastern edge of the landfill,
respectively.
The average annual rainfall over the study area is
approximately 60 inches, of which as much as 80 percent
falls during the rainy season (June to September). Parts of
the study area are inundated intermittently during the rainy
season, and swampy conditions persist for several weeks each
year, mainly due to rising water table. The ma3or drainage
systems of the^rea are the Miami and Tamiami Canals
draining into the Biscayne Bay. The secondary drainage
systems include the 58th Street, Dressel, and 25th Street
Canals. The water table beneath the study area is located
approximately 2 to 3 feet below the natural land surface.
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The Biscayne 'Aquifer, which is a highly permeable,
wedge-shaped, unconfined shallow aquifer composed of
limestone and'sandstone, underlies the study area. The top
of the aquifer is near the natural ground surface, and its
base is approximately 60 feet below ground surface in the
"crthwest well field area and approximately 105 feet below
qround surface in the Miami International Airport area.
rigure 3 shows the geologic section of the Biscayne Aquifer
:.r. the Miami Springs/Preston well field area. In general,
this aquifer is divisible, from top to bottom, into three
distinct water-producing zones, each zone being 15 to 20
feet thick. These zones are separated by generally dense,
uilty to sandy limestones and well-cemented quartz sands
Oat act as aquitards. The cone of depression resulting
from the withdrawal of approximately 150 million gallons per
dcy (mgd) of water from the Miami Springs and Preston well
fields encompasses the northern half of the Airport, all of
the Miami Drum Site, and extends as far west as one-half
mile east of the 58th Street Landfill. The cone of
depression corresponding to a drawdown of 0.25 foot that
results from the withdrawal of 150 mgd of water from the new
Northwest well field and 75 mgd of water from the Miami
Springs well field encompasses the western edge of the 58th
Street Landfill.
SITE HISTORY
Varsol Spill Site
Industrial operations associated with a typical commercial
airport have resulted in hydrocarbon contamination of
surface and groundwaters in the vicinity of MIA. Since
1966, approximately 15 hydrocarbon spills and leaks have
beer recorded. The total discharge of hydrocarbon materials
is estimated to be approximately 2 million gallons. This
includes the loss of an estimated 1.5 million gallons of
varsol discovered at the Eastern Airlines maintenance base
in the northeast section of the airport around 1970. During
197C a jet fuel spill of approximately 66,000 gallons was
discovered near the west central area of Eastern Airlines
properties. In 1970, National Airlines accidentally spilled
an unknown amount of jet fuels into the drainage canals that
ultimately discharge into the Tamiami Canal. They were
ordered to stop discharging cleaning solvents and degreasers
to an airport drainage*canal at this time. In 1981, Braniff
Airlines was ordered to stop this same practice after it was
discovered. Several other smaller spills and discharges of
jet oil/ aviation gas, cleaning solvents, and degreasers
have also occurred at the airport. Several areas within MIA
have heavy accumulations of oil lying on the ground. This
is often the*»esuit of employees from various aircraft
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maintenance operations discharging oily wastes onto the
ground and into storm sewers. Another major underground jet
fuel spill was discovered in 1983 in the vicinity of
Concourse E as a result of ongoing construction and
improvements in the area.
Removal of underground hydrocarbons at the airport was
attempted in the early 1970's primarily at the Eastern
Airlines maintenance base. Hydrocarbon decontamination
separator trenches were installed by Eastern Airlines in
1971 to remove the 1.5 million gallons of varsol that had
spilled underground. The recovery operations were
terminated in August 1973 due to slime build-up in the
trenches and the extremely slow natural migration of
hydrocarbons into the trenches. Actual recovered volumes
were approximately 133,000 gallons of hydrocarbons, or less
than 10 percent of the estimated spill volume. Other
recovery procedures at the airport have been implemented
only in conjunction with dewatering operations at
construction sites within the airport and have been
unsuccessful in removing substantial quantities of
hydrocarbons. During April 1981, construction activities in
the west-central area of the Eastern Airlines maintenance
base revealed a thick hydrocarbon layer floating on the
water table in an excavated trench, probably from previous
fuel spills. Eastern Airlines installed 54 shallow
observation wells during the early 1970*s at their
maintenance base (the general area of the varsol spill).
Measurements of fluid levels in these monitoring wells,
specifically the water-table depth and hydrocarbon thickness
in the upper layer of the water table, were taken twice per
year, during the dry season and the wet season, from 1975 to
1981. The hydrocarbon layer thickness, according to these
data, shows a declining trend with time, and, in some wells,
the presence of the layer could not be detected in the
second year. In the Concourse E area, Dade County installed
43 monitoring wells to-determine the extent and magnitude of
jet fuel spilled. Dade County also installed three recovery
x.-ells in the Concourse E area and started the recovery
operation in mid-1983. Through May 1984, over 102,000
gallons of jet fuel had been recovered from this area.
Recovery operations are continuing in this area.
Miani Drum Site
The privately-owned Miami Drum Services (MDS) facility
operated for approximately 15 years before Dade County,
through a local court order, forced MDS to cease operation
in June 1981. As many as 5,000 drums of various chemical
waste materials, including corrosives, solvents, phenols,
and toxic metals, were observed on the site while the
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company was operating. Drums were washed with a caustic
cleaning. solution, which, along with drum residues
containing industrial solvents, acids, and heavy metals, was
disposed of onsite in open, unlined pits. Eventually; the
surface soils on the site became saturated.-
The abandoned Miami Drum Site was acquired by Dade County
for construction of the Palmetto Yard maintenance facility
of the Dade County Rapid Rail Transit Project. Based on a
brief study, extensive soil borings were performed at the
site during December 1981 and cores up to 10 feet deep were
analyzed for contaminants. Dade County contracted O. H.
Materials Company and directed them to remove the 400 to 500
existing drums from the cite, excavate contaminated soils
based on these analyses, and relocate them to an existing,
approved disposal facility. In addition to this action, the
contaminated water encountered during excavation was
removed, treated, and disposed of onsite. At the present
time, the maintenance facility of the Dade County Rapid Rail
Transit system is operating at this site.
Northwest 58th Street Landfill Site '
This landfill is owned by Dade County. It began operation
in 1952 as an open dump. Some waste was placed into shallow
trenches dug below the water table, resulting in deposition
of some refuse in the saturated zone of the aquifer. Open
burning of waste was used as a volume reduction method until
1960, when a ban was placed on such burning. Since the ban,
waste has accumulated at a rate approximately three times
the 1960-61 rate. Since its startup in 1952, this facility
has received from 100,000 to 1,000,000 tons per year of
municipal solid waste. Garbage from domestic and industrial
sources comprises about 65 percent of the wastes disposed of
at the site. The remainder is from other sources and
includes street debris, discarded autos and appliances,
furniture, tree trimmings, liquid wastes, and other rubbish.
The estimated recent disposal rate (applicable through
July 1982) for garbage and trash was about 90,000 tons per
month; for liquid wastes, consisting mainly of grease trap
pump-outs, it was about 200,06.0 to 400,000 gallons per
month. Since January 1975, this landfill has been receiving
daily cover provided by muck and crushed rock from quarry
overburden and, more recently, calcium carbonate sludge from
the Miami Dade Water and Sewer Authority water treatment
plants. Since September 1982, the landfill has been closed
for all purposes, except for the disposal of construction
debris.
This site is not permitted, as a sanitary landfill by the
Florida Department of Environmental Regulation (FDER) .
According to preliminary close-out plans for the landfill
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it is classified as an open dump and has been operating in
violation* of a~ consent order between the FDER and Metro Dade
County dated July 30, 1979. Final close-out plans for this
landfill are being prepared at this tine.
CURRENT SITE STATUS
The initial study/ conducted in 1982, involved compiling and
evaluating existing data relevant to the contamination
problem. This evaluation generally indicated the presence
of dispersed, low-level concentrations of numerous toxic
contaminants in the groundwater beneath the study area.
This was based on limited pertinent data, mostly inorganics.
A general lack of pertinent groundwater monitoring data,
especially drganics, was found.
The Remedial Investigation (RI), begun in late 1982,
consisted of a unified, planned, and intensive sampling
effort to fill in the d.ata gaps found in the Phase I study
end to determine the magnitude and extent of groundwater
contamination. Criteria for data classification were
developed from existing literature, and were based on
effects to human health. Data evaluation based on the Rl
indicated that widespread low to moderate levels of several
toxic contaminants, mostly in the volatile organics
category, are present in groundwater throughout the study
area. Vinyl chloride was the most common contaminant
detected and its concentration exceeded the FDER standard of
one ug/L (set in 1984) . Mo concentrated priority pollutant
plume could be found.
Earlier investigations by Eastern Airlines, based on varsol
fluid.level measurements on top of the water table, showed
declining thickness of the varsol layer with respect to
time. By 1981, most of Eastern Airlines data showed no
hydrocarbon thickness at the Varsol Spill Site. The RI in
1982 and 1983 did not find any plume or pockets of the
varsol in groundwater at and around the spill site and in
the neighboring lower Miami Springs area.
In late 1981 (prior to cleanup of the contaminated soils),
the Florida Department of Environmental Regulation (FDER)
contracted with Technos, Inc., to determine the extent of
groundwater pollution associated with the Miami Drum Site.
Geophysical measurements using electromagnetics (EM) and
ground penetrating radar (GPR) provided the data for this
study. The EM results showed a significant conductivity
anomaly coincident with the site. The conductivity anomaly
provided evidence of a strong plume-like trend to the
southeast in «the direction of groundwater flow and towards
the Miami Springs/Preston well fields. Several less
significant conductivity lobes were also detected towards-
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the west and north of the site toward the Medley well field.
However*, the RI as well as a separate remedial investigation
conducted during 1983 by FDER at the Miami Drum Site found
no evidence of a contaminant plume from the site.
During the late 1970's, investigations by the U. S.
Geological Survey and Technos, Inc., had determined that,
bised on the dissolved inorganic content of the groundwater,
1 :achate from the 58th Street Landfill had infiltrated the
E;scayne Aquifer beneath and adjacent to the landfill site
in the form of a grouitdwater plume moving in an easterly
direction along with the natural downgradient water
r.ovement. However, based on extensive priority pollutant
dita (heavy metals as well as organics) that were
n Mi-existent during the earlier USGS and Technos studies, no
c roundwater contaminant plume was found in the vicinity of
t:ie landfill from the 1982-1983 RI.
T'-.c results of these investigations indicate that, at this
time, there is no concentrated contaminant plume emanating
f-om any of the three sites in the study area. However,
widespread, low, dispersed levels of volatile organic
c x-nicals have been found all over the study area; plumes
h we blended together, and have now, with time, become
i -.distinguishable with the general poor groundwater quality
i.i the study area. The main explanation for this is the
c .-chydrologic conditions within the study area: the high
t •ansmissivity of the Biscayne Aquifer; the widespread
i vteraction of groundwater with surface-water bodies
t '.roughout the study area; and the high, continuous pumping
c* groundwater at the several municipal well fields. The
c-erall groundwater quality in the study area will be
a 'dressed in Phase IV.
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