PB97-963159
EPA/541/R-97/187
January 1998
EPA Superfund
Record of Decision Amendment:
Munisport Landfill
North Miami, FL
9/5/1997
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5 9 GC01
RECORD OF DECISION
AMENDMENT
MUNISPORT LANDFILL
SUPERFUND SITE
North Miami, Florida
Prepared by:
United States Environmental Protection Agency
Region IV, Atlanta, GA
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0002
DECLARATION
RECORD OF DECISION AMENDMENT
SITE NAME AND LOCATION
Munisport Landfill Site
North Miami, Dadc County, Florida
STATEMENT OF BASIS AND PURPOSE
This decision document represents an amendment to the Record of Decision (ROD) formerly
issued by the United States Environmental Protection Agency on July 26,1990. This amendment
was made in accordance with the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA), as amended by the Superfund Amendments and Reauthorization Act of
1986 (SARA) and the National Contingency Plan (NCP). This decision is based on the
administrative record for this site.
The State of Florida, as represented by the Florida Department of Environmental Protection
(FDEP), has been the support agency throughout this project In accordance with 40 CFR
300.430, FDEP, as the support agency, has provided input during the project Based upon "*"
comments received from FDEP, it is expected that concurrence will be forthcoming; however, a
formal letter of concurrence has not yet been received. Upon receipt, the State's concurrence
letter will be placed in the Administrative Record for this site. The Metropolitan Dade County
Department of Environmental Resources Management (DERM), as the local regulatory agency,
has been consulted throughout this process as well. Based on DERM's comments, it does not
object to EPA's determination to amend the ROD. A copy of DERM's comments regarding the
amendment will be placed in the Administrative Record for this site.
The National Oceanic and Atmospheric Administration (NOAA) was also consulted in the
development of the amendment NOAA concurs with EPA's determination and a copy of their
comments regarding this amendment will be placed in the Administrative Record for this site.
DESCRIPTION OF THE AMENDMENT
This amendment provides for no further remedial action under CERCLA.
DECLARATION STATEMENT
This amendment is protective of human health and the environment according to the requirements
set forth in CERCLA, and requires no further response by EPA pursuant to said requirements.
Actions to date have mitigated the significant threat to the environment posed by elevated
ammonia levels and toxic conditions in the Mangrove Preserve as established in the ROD, such
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9
0003
that further response by EPA is not necessary. Since this amendment relies on no engineering or
institutional controls to prevent unacceptable risks, a five-year review of the protectiveness of the
remedy is not needed. Finally, amendment of this ROD to no further remedial action constitutes
completion of construction of all Superfund-related activities. Therefore, this site now qualifies
for inclusion on the Construction Completion List
This amendment is separate from, and does not preclude, any actions the State of Florida and/or
Metropolitan Dade County may deem appropriate for the site.
Date
Richard D. Green, Acting Director
Waste Management Division
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RECORD OF DECISION AMENDMENT
DECISION SUMMARY
MUNISPORT LANDFILL SITE
NORTH MIAMI, DADE COUNTY, FLORIDA
Prepared by:
United States Environmental Protection Agency
Region IV, Atlanta, GA
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Table of Contents
Section Page No.
1.0
2.0
3.0
4.0
5.0
5.1
5.2
5.3
6.0
6.1
6.1.1
6.1.2
6.1.3
6.1.4
6.2
6.2.1
6.2.2
6.2.3
6.3
7.0
8.0
Introduction
Site Background
Community Participation
Scope and Role of Response Action
Site Characteristics
Causeway Breach
Service Road
Hydraulic Barrier System
Summary of Site Risks
Study Approach
Sample Locations
Tidal Assessment
Water Quality Assessment
Toxicity Assessment
Study Approach
Tidal Assessment
Water Quality Assessment
Toxicity Assessment
Conclusions
Description of No Action Alternative
Explanation of Significant Changes
1
1
6
7
8
8
11
11
13
15
15
18
18
22
22
22
23
27
27
29
30
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5 9 0006
Figures :
Figure No. Description Page No.
2-1 Site Location Map 2
2-2 Evolution of Information and Key Decisions 5
5-1 Remedial Action - Phase I Causeway Breach 9
5-2 Surface Water Quality Sampling Locations 10
5-3 Toxicity and Ammonia Correlation 12
5-4 Hydraulic Barrier Layout and Location of Verification Test 14
6-1 Study Area Location Map 16
6-2 1996 Mangrove Sample Locations 17
6-3 Dania Canal Reference Site 19
6-4 Biscayne Creek Reference Site 20
6-5 Black Point Reference Site 21
ii
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5 9 000?
Tables
Table No. Description Page No.
6-1 Initial Field Screening 24
6-2 Comparison of Total Ammonia Concentrations to Ambient
Water Quality 25
6-3 Comparison of Organic and Inorganic Concentrations in August
1996 to Ambient Water Quality Criteria 26
6-4 Summary of the Results of Toxicity Tests Performed on
Munisport Water Quality Samples, August 1996 28
IU
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Appendices
Description Appendix No.
Responsiveness Summary 1
IV
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5 9 OGC9
1.0 INTRODUCTION
The United States Environmental Protection Agency (EPA) issued a Record of Decision (ROD)
for the Munisport Landfill Superfund Site on July 26,1990, to address the significant threat posed
to the environment. This threat was documented by EPA in 1989, after the investigation of the
water quality and toxic conditions of a wetland adjacent to the landfill. This wetland is comprised
of a mangrove swamp that is pan of the State of Florida Biscayne Bay Aquatic Preserve,
consequently known as the Mangrove Preserve ("Preserve"). The ROD provided for the
interception of the flow of leachate-contaminated groundwater from the landfill to the Mangrove
Preserve to reduce the risks posed to aquatic organisms in the Preserve due to elevated levels of
ammonia. Through this remedy EPA intended to achieve the necessary degree of environmental
protection set forth in CERCLA. Results from the Remedial Investigation and Baseline Risk
Assessment conducted by EPA in 1988 documented no significant risks to human health.
Therefore, protection of human health was not a component of the ROD. Qosure of the landfill
and management of storm water runoff was not part of this ROD and was to be addressed
independently via State Landfill Qosure established in Section 62-701 of the Florida
Administrative Code.
Although this amendment supersedes the remedy originally established for this site, it will not
provide a detailed discussion of historical and technical information formerly presented in the
ROD. The ROD and other documents included in the Administrative Record for this site will still
be the proper source regarding such information.
2.0 SITE BACKGROUND
The Munsiport Landfill is a former municipal landfill, 170 acres in size, located within the City of
North Miami. Da
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5 9 ' 0010
RECREATION
FLORIDA
INTERNATIONAL
WIVERSITY
MUNISPORT
SITE?
FLORIDA"-.
""- STATE •.*
IMANGROVE-I
..PRESERVE-
IISUTK BAT
MUATIC DESERVE
203B5/012/TIC03.0CN
SOURCE: BE1 1997
Figure 2-1
Site Location Map
Munisport Site
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59"0011
Environmental Protection) in 1976. The U.S. Army Corps of Engineers also issued earlier in
1976 a dredge and fill permit pursuant to Section 404 of the Clean Water Act (CWA) to allow
the filling of "waters of the U.S." with clean fill.
EPA became involved with the site in 1980 in opposition to a request by Munisport, Inc., to the
Corps of Engineers to modify the dredge and fill permit to allow the use of garbage in the filling
of the wetlands. EPA formally issued a veto pursuant to Section 404(c) of the CWA to prevent
the use of garbage to fill the wetlands. Landfill activities subsequently ceased in 1981. To date,
however, the landfill has not been properly closed in •accordance with FAC 17-101.
In 1982, EPA evaluated the landfill for inclusion on the National Priorities List (NPL). The site
was added to the NPL in 1983, primarily due to the potential threat to nearby municipal wells.
These wells were subsequently taken out of service due to saltwater intrusion. As a result, the
City of North Miami petitioned EPA to remove the site from the NPL. Consistent with EPA's
policy of not rescoring sites that had been finalized on the NPL, EPA did not delete the site and
decided to conduct an RI to evaluate potential risks to human health and the environment
EPA completed an Rl of the site in 1988 that documented no threat to human health; however,
the threat to the environment was inconclusive. Because of the threat to the environment
appeared marginal, EPA proposed an action in July 1988 that included closure of the landfill in
accordance with State law. After review of public comments on the proposed plan, EPA
reevaluated the threat to the environment, and issued a second plan in November 1988 that
provided for no action. The proposal for no action was opposed by local environmental and
citizen groups, the National Oceanic and Atmospheric Administration (NOAA), and U.S. Fishlind
Wildlife Service. In response, EPA conducted a second study in 1989, that further evaluated the
threat to the environment
Results from the second study, the Water Quality and Toxic Assessment Study, Mangrove
Preserve, (1989), documented elevated levels of ammonia in the Preserve and toxicity among
laboratory organisms exposed to Mangrove Preserve surface water. EPA interpreted these results
as posing a significant threat to the environment Although elevated levels of ammonia were
believed to represent the primary contaminant of concern, other potential causes of the toxicity
could not be estimated at this time. Among other findings, EPA also concluded that culverts
tidally connecting the Preserve with Biscayne Bay were undersized, restricting the maximum tidal
exchange by as much as 40 percent The report also concluded that improved tidal circulation
would help to mitigate the environmental threat, but may not be adequate to fully achieve the
desired degree of environmental protection.
In absence of data to demonstrate that the observed toxicity in the Mangrove Preserve could have
been mitigated through increased tidal circulation, EPA selected a remedy in 1990 that provided
for the construction of a hydrologic barrier to prevent the discharge of leachate-contaminated
groundwater from the landfill to the Mangrove Preserve. The remedy also provided for the
treatment of the collected contaminated groundwater through air stripping. Treatment of the
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contaminated groundwater was necessary for disposal purposes, but it was not the intent of the
ROD to clean up the groundwater at the landfill, because the Risk Assessment had demonstrated
that groundwater quality did not pose and unacceptable risk to public health. As discussed in the
RI and ROD, the groundwater underlying the site was no longer suitable for drinking water due
to saltwater intrusion. Had EPA not believed that a hydraulic barrier was needed to protect the
aquatic life in the Mangrove Preserve, pumping and treating of the groundwater would not have
been necessary pursuant to the requirements of CERCLA. EPA's selected remedy also included
the tidal restoration of die Mangrove Preserve and hydrologically-altered wetlands.
EPA entered into a Consent Decree in 1992, with the City of North Miami to implement the
remedy set forth in the ROD. As part of the initial phases of the remedial design, additional data
were collected regarding the site-specific hydrologic conditions. The results from this study are
documented in a report titled Remedial Design Studies Report, Blasland, Bouck & Lee, 1994.
EPA also conducted a treatability study to verify the effectiveness of the selected treatment
alternative. Based on results from the treatability studies, EPA determined that air stripping was
not as effective as originally believed and subsequently issued an Explanation of Significant
Differences in 1994 changing the treatment and disposal alternative to off-site treatment and
disposal at the North Dade Wastewater Treatment Plant The treatability studies also
documented that elevated levels of un-ionized ammonia, not other "unknown" toxicants, were the
cause of the toxicity. Results from the treatability studies are documented in the following
reports: Pilot Study: Munisport Leachate Treatability, USEPA, Environmental Services Division,
November 5,1992; Toxicity Testing of Three Wellwater Samples, Munisport CERCLA Site,
USEPA, Environmental Services Division, June 4,1995; Toxicity Characterization of
Groundwater Samples, TRAC Laboratories, June 9,1993; Bioremediation Treatability
Verification Status Report, SECOR, September 1996,and can be found in the Administrative
Record for the Site.
Due to the varying degrees of complexity in scope of the different components of the remedy,
EPA decided to segment the design and construction process into the four following phases:
Causeway Breach, Service Road, Hydraulic Barrier, and Treatment and Disposal.
Construction of the causeway breaches was straightforward and was completed in September
1995. Associated with the causeway breaches was monitoring of the surface water quality in
Biscayne Bay and the Preserve before and after the construction of the causeway breaches.
Construction of the service road and recovery wells for the hydraulic barrier were substantively
completed in 1996. A draft preliminary design for the groundwater treatment and disposal system
was submitted to EPA for review and comment in December 1996. Peer review comments were
solicited on the draft design; however, due to the results of the surface water monitoring, EPA
decided not to continue with additional design work on the groundwater treatment system
pending a final decision by the Agency regarding the affect of the tidal restoration of the
Mangrove Preserve.
A timeline of key information gathered regarding the Munisport Landfill dating back to the mid-
1970's, and associated key decisions, is provided in Figure 2-2.
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tvolution of
Information and
Decisions
Environmental
Assessment
N. Miami Rec,
Development
SwUryljndfil
Site
pro-
posed
toNPL
1912
Ste
add »d to
to IWl
1IM
Munisport
applies for
modification
of CWA 404
ermit for
illing with
solid wortti
1977
State grants
Temporary
Operating Permit
for folia waste
fill above
water table
1975
Munisport
begins tilling
low
areas wi
clean fill
Wtfter Qualify &
Toxic Assessment
fPA
Munisport
Superfund Site
North Miami, Florida
ftftmedial
. Investigation
Haza faOUl COM IEPAI, INI ".\i
Wdste
Siite
Investigations | :,<
Site
Investigation]
Report JV
HJ.RMUAmc..lM74
Remedial
Design
Studies
Report/
BBil.1994
ISO Mils 2aquiiplfitv
21 due l«U. U SW
Public
Health
Assessment
; 1993
field
Verification
Test Results
iMfrjufc Bjnist. SfCO« 1996
Bioremediation
Treatability
Report
SECOfl Opi IMft
iftw, u-iowrtyi Water
I Quality &
Dynamic Toxicity
Sampling Assessment
of Hydraulic «*»<*» P™™
Barrier
S((0«. Oct. 1999
(M. 1997
COE issues
CWA 404
permit for
filling wetlands
with clean fill
•v»
CWA 404
permit
modification
requested, vetoed
by EPA
Treatability
Studies
EM. 199-94
D issued Consent
protect Decree
quatk life entered
roposed
Treatment
amended
toPOTW
ESD Construction
1994 of caui'Sway
complete
199:
UCfNO
Surface water
Groundwater
City petitions —.
to dellst site from
NPl (based on
closed water'
supply wells)
•plan forOplan for no
landfill Jyiif; action
closure i^v'*"1 '•"
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5 9 ' 0014
3.0 COMMUNITY PARTICIPATION
The Munisport Landfill Supcrfund project has involved extensive community participation dating
back to the early 1980's. Over the years various community-based organizations such as
homeowner associations and activist groups, as well as, local chapters of national environmental
organizations have commented on various aspects of the project Section 5.0 of the ROD
describes in detail community participation through the issuance of the ROD in 1990.
After the release of the ROD, EPA continued to involve the community in the remedial process.
The community's main group is the Munisport Dump Coalition (MDC), the recipient of a
Technical Assistance Grant (TAG) from EPA. Through the MDC the community has had an
opportunity to comment on documents required by the National Contingency Plan (NCP), and
other documents relating to the design and construction of components of the remedy set forth in
the ROD. In an effort to encourage community participation throughout the process, EPA has
issued several deviations from the original $50,000 grant, bringing the total funding for the TAG
to $150,000.
In addition to the coordination with the MDC, EPA has also worked with representatives of local
groups such as the Friends of the Oleta River, Keystone Point Homeowners Association,
Highland Village Homeowners Association, Florida and Tropical Audubon Societies, and
Concerned Citizens for the Public Use of Munisport EPA has also held numerous public and
technical meetings and issued numerous fact sheets to keep the community apprised of the
progress and to solicit input during the design and construction process. ,
The community has also been involved in this project through the Consent Decree entered by the
United States District Court in 1992. Although the only parties to the Consent Decree are the
United States of America and the City of North Miami, the District Court has allowed interested
non-parties in the community to file information and express concerns with regard to the .
implementation of the remedy set forth in the ROD.
With regard to community participation for this amendment to the ROD, EPA issued a Proposed
Plan and public notice on May 13,1997, announcing a 30-day public comment period and a
public meeting. Concurrent with the release of the Proposed Plan, the Administrative Record
was amended to include documents used in the development of the proposed amendment to the
ROD. Shortly after the release of the Proposed Plan, EPA received two requests for an
extension to the public comment period. These requests were granted and the comment period
formally extended through July 13,1997.
As a part of EPA's community involvement efforts, a public meeting was held locally from 7:00
p.m. until 10:30 p.m. on June 5,1997. This meeting was attended by approximately 50 people
from the community. While EPA used a local community paper with a circulation of about
80,000 for notification purposes, the City of North Miami also published a separate notification in
tile Miami Herald to fulfil] its own public notification requirements. EPA also notified a reporter
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5 9
for the Miami Herald that published a story on the site with an announcement of the public
comment period and public meeting date. Finally, EPA mailed copies of the Proposed Plan to
approximately 150 members of the community that had previously expressed interest in the site.
Some members of the community expressed concern that EPA had not advertized the meeting and
pubb'c comment period in a local paper of major circulation. In response to concerns of some
community members and the Agency's desire to ensure that everyone in the community interested
in the site had an opportunity to comment on the plan, a second notification of the public
comment period was issued. The second notification was published in the Neighbor's section of
the Miami Herald on June 15, 1997. The notification also announced additional meetings. In
response to requests from members of the community for a longer pubb'c meeting, EPA arranged
an informal public availability session from 12:00 p.m. until 4:00 p.m. and a second public meeting
from 6:00 p.m. until 9:00 p.m. on June 23, 1997. In contrast to the first public meeting, the
availability session and second public meeting was attended by less than ten people from the
public.
As a result of the public comment period, EPA received comments from individual members of
the community, a homeowners association, two municipality, and a community activist group.
Although no comments were received from federal, state, or county officials on the proposed
plan, these agency's did provide comments on the draft ROD Amendment as part of the peer
review process. Although some of the comments supported EPA's proposed action, many of the
comments from the community expressed concern regarding EPA's proposed action. Some of
the comments were of a technical nature regarding the effects of the tidal restoration of the ,
Mangrove Preserve and the results from the study to reassess the water quality and toxic
conditions after the tidal restoration. Other comments were of a pob'cy nature and dealt with
concerns for the future of the project should EPA amend the ROD to no action and refer the
--- :--.. »_ *L_ o^-* ---- 1 /-« ---- *_. f — c. — i __»i — it ---- —r ~i -------- »- ------- 1-_ I ------- 1 »u-
tu uic •Jtait- aiiu \_uiuity iui IJJKU a^uun. iviaiijr ui uit- uununciiia wtiu aiou LT^JTUIIU uii/
scope of this amendment and raised questions regarding the adequacy of prior studies and the
ROD. Though many of the comments were highly critical of EPA's management of this project,
most of the commenters desired that EPA stay involved in the project to retain federal oversight
of the project by the United States District Court and to provide a direct mechanism for
community involvement in the cleanup process pursuant to the requirements of CERCLA and the
NCP. A detailed summary of the comments and EPA's response to the comments are provided in
the Responsiveness Summary, Appendix A of this Amendment The actual comments and
transcripts from pubb'c meetings are included in the Responsiveness Summary.
4.0 SCOPE AND ROLE OF RESPONSE ACTION
Based on results of the reassessment of the water quality and toxic conditions in the Mangrove
Preserve in 1996, EPA has determined that the increased tidal circulation of the Mangrove
Preserve has significantly improved the surface water quality through dilution, increased dissolved
oxygen, and increased nitrification of the ammonia. EPA has, therefore, determined that the
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surface water toxicity documented in 1989 has been mitigated. Thus, EPA believes that no
further response under Superfund is warranted. EPA recognizes that implementation of the tidal
restoration only affected surface water conditions in the Preserve and has likely had little effect on
the quality of ground water underlying the landfill. However, the remedy selected in the 1990
ROD was to address the environmental threat, not restoration of the groundwater nor landfill
closure.
Remaining groundwater contamination and landfill closure will be addressed independently of
Superfund, pursuant to State and County regulations. Tidal restoration of the altered wetlands
will be addressed pursuant to the Clean Water Act through an Administrative Order with EPA.
i
5.0 SITE CHARACTERISTICS
A detailed discussion of the site characteristics are provided in Section 6.0 of the ROD. In
general, the Munisport Landfill remains in the same condition as described in 1990. Some
modifications to the landfill have occurred, however, as a result of the Superfund-related
construction activities. Changes in site conditions from those formerly discussed in the ROD are
presented in the following.
5.1 Causeway Breach
As previously discussed, because of the varying degrees of complexity in the scope of the design
and construction of the remedy, EPA separated the design and construction of the causeway
breach and tidal restoration of the Mangrove Preserve from the design and construction of the'
other Superfund components. The tidal flow to the Mangrove Preserve was reestablished through
the removal of two 66-inch diameter culverts and the construction of two 40-foot wide breaches
in the 135th Street causeway extension. The construction also involved the rerouting of a 30-inch
diameter water main along the causeway. Pedestrian access was maintained along the causeway
through the installation of a six and one-half foot wide concrete bridge at each causeway breach.
The location of the causeway breaches are shown in Figure 5-1. A detailed summary of Ac work
performed is contained in the remedial action report tided Remedial Action Report, Phase I -
Causeway Breach, Munisport Landfill Superfund Site, North Miami, Florida, September 4,1995.
Due to concerns of members of the community and local regulatory agencies regarding the
potential discharge of contaminants from the Mangrove Preserve to Biscayne Bay as a result of
the increased tidal circulation, a surface water monitoring program was incorporated into the
project The monitoring included the collection of surface water samples from the Preserve and
Biscayne Bay prior to and after the construction of the causeway breaches. Analytical parameters .
included ammonia and priority pollutants. Locations for the surface water monitoring stations are
shown in Figure 5-2.
Prior to the causeway breach, results from surface water monitoring did not indicate significantly
elevated levels of ammonia nor priority pollutants at stations in Biscyane Bay. Ammonia
8
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MONO A
WlCHHAIlONAI
UMVCAhlf
MCN
MOttAMft
COUUUMIf
en
o
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Figure 5-2
Surface Water
Qualify Sampling
Locations
BAY
FLORIDA
OATt M/2I/I7
JUU MO. 4COH-OfX-01
nue
5385 Stirling Rood
Oavte, Florida 33314
cn
o
C->
—^
CO
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5 9 "0019
concentrations were elevated in the Mangrove Preserve as formerly documented during the 1989
baseline study. After the tidal restoration of the Mangrove Preserve, results from the surface
water monitoring indicated a dramatic decrease in the concentration of ammonia in comparison
with levels in 1989. Figure 5-3 provides a correlation of ammonia vs. toxicity results from the
1989 study with ammonia levels detected at the two monitoring stations in the Mangrove
Preserve sampled after the tidal restoration. A comparison of the ammonia levels detected after
the causeway breach with toxiciry results from the 1989 study suggested that there may have been
a reduction in toxiciry as well. This prompted EPA to conduct an in-depth reassessment of the
changes in water quality and toxicity that may have resulted from the tidal restoration. The post-
breach monitoring also showed no significant increase in ammonia in samples collected from
Biscayne Bay. A summary of the results may be reviewed in a document titled (add citation).
5.2 Service Road
Portions of the remedy in support of the hydraulic barrier have been completed. This includes
construction of approximately 4000 feet of service road along the southwestern, southern, and
eastern perimeters of the landfill. This road was intended to provide access for the construction,
operation, maintenance of the hydraulic barrier system. Construction of the Service Road began
in June 1995 and was substantively completed in May 1996. In connection with the construction
of the road, approximately 1.4 acres of wetlands were impacted along the eastern landfill
perimeter. Impacts to these wetlands were mitigated pursuant to the requirements of the CWA,
resulting in the construction of a 2.4 acre wetland formerly filled with construction debris. A
detailed summary of the work performed is contained in the remedial action report tided ^
Munsiport Landfill Superfund Service Road, Final Remedial Action Report No. 2, Munispori
Landfill Superfund Site. SECOR International, Inc., September 1996.
5.3 HyHranlir Barrier Syctgm
As set forth in the ROD, the remedy included the installation of a hydraulic barrier system to
intercept the flow of leachate contaminated groundwater from the landfill prior to its discharge to
the Mangrove Preserve. A southern component of the hydraulic barrier system was subsequently
added based on recommendations from technical advisors for the Munisport Dump Coalition due
to concerns for potential flow of leachate contaminated groundwater from the landfill southward
to the Arch Creek Canal. Due to variations in hydrogeology and proximity to surface water, a
horizontal recovery well system was selected for the eastern landfill perimeter, while a
conventional vertical recovery well system was selected for the southern perimeter. Installation of
the recovery wells began in January 1996.
The southern vertical well recovery system construction included the installation of 15 recovery
wells. The wells were 4-inches diameter, and installed to an approximate depth of (-) 20.00 feet
National Geodetic Vertical Datum (NGVD). The vertical wells were installed approximately 100
feet apart along the southern access road. Each well was designed for an optimal pumping rate of
12 to 15 gaDons per minute (GPM). -
11
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K>
TOXICITY AND AMMONIA CORRELATION
ACUTE TOXICITY - INLAND SILVERSIDE
MUNISPORT LANDFILL SUPERFUND SITE
NORTH MIAMI, FLORIDA
20 40 60 80
% SURVIVAL - INLAND SILVERSIDES
Ammonia vs. Toxlclly - 1989 Study
Ammonia -1996 Post-Breach Monitoring
Cn
O
°.
f J
O
FIGURE 5-3
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5 9 " 0021
Installation of the horizontal recovery well system included the installation of 14 300-foot
segments along the eastern landfill perimeter. The wells were constructed of 8-inch diameter
flexible perforated pipe. Each 300-foot segment was capped at each end and had three well risers
for installation of pumps and future access for maintenance of the well. Each well was designed
for an optimal pumping rate of 55 GPM. The depth of the horizontal recovery well averaged
(-)lO-feet NGVD and was designed to capture the freshwater lens in the aquifer prior to discharge
to the Mangrove Preserve, without adversely affecting the saltwater interface. This recovery
depth is also consistent with the greatest mass of ammonia being concentrated in the upper
freshwater portion of the aquifer.
Construction of the recovery wells was completed in July 1996. Figure 5-4 denotes the location
of the finished wells. A detailed summary of the work performed is contained in the remedial
action report titled Munisport Landfill Superfund Site, Hydraulic Barrier, Recovery Well &
Monitoring Well Systems, Remedial Action Report No. 3, SECOR International, Inc., August
1996.
6.0 SUMMARY OF SITE RISKS
Potential risks to human health and the environment associated with the Munisport Landfill were
evaluated as part of the Final Remedial Investigation Report. Munisport Landfill Site, Remedial
Investigation. North Miami, Florida (J988) and Water Quality and Toxic Assessment Study,
Mangrove Preserve (J989). As discussed in these documents and summarized in Section 7.0 of
the ROD, there was no potential for unacceptable risks to human health related to releases of ^
contaminants from the Munisport Landfill documented using conventional exposure scenarios.
However, results from the baseline assessment of the water quality and toxic conditions of the
State Mangrove Preserve did document significant toxicity and adverse effects to the aquatic
vugailiSiTiS iii ui£ SiliiaCC w'aiCr. in£ CnYirCili7i€iiuLi uiJCai tO aCJuatIC OrgaluSiTlS Hi uiC m
Preserve was the basis for the remedy selected in the ROD. As discussed in the 1989 report, the
threat to the environment was based on the documentation of unacceptable levels of toxicity (e.g.,
greater than 80% mortality) of aquatic organisms exposed to surface water from the Mangrove
Preserve.
As discussed in Section 5.1, changes in water quality in the Mangrove Preserve after the tidal
restoration with Biscayne Bay prompted EPA to reassess the water quality and toxic conditions of
the Mangrove Preserve. Based on the results from the post-breach surface water monitoring,
EPA believed that there may have been a corresponding reduction in toxicity in the Preserve.
EPA, therefore, designed a study that incorporated critical elements of the 1989 study, but was
refined and more focused than the 1 989 study using information collected during the remedial
design studies and treatability studies. For example, one component of the 1989 baseline study
that assessed potential toxicity to the common Atlantic Sea Urchin, Arbacia punctulata, was not
conducted because no toxicity was observed in 1989.
13
-------
APPDOX1UAU ARCA Of OCtAl
sec rwuRC 7
tlftlft
_^. — pwcrtiw IM (AHiftonuAif
C»SIWC KOAD (PAVfO/MlPAVtD)
t mmo UKC BOUNOARV
au OOUNOAMT
roncc MAW
OMOCUCROUMO rOUCt MAW
........ w*n» stuvcc
--_-. HMlIOMtAl DCU
umnv rat
I. VMlIt ••«( tMUKI IICCMCH NtOUIII Ht> Mil
.. MCMHOTOMC
• SUW-4S MHOItS 1OAI SIAIKXIS
*«C-I BCMOICS HAWAII CAUONC
SIAIKJHS
(APPROXIUAU)
C3
O
K>
ro
SECOR
INtCRNAllONAL INCORI'URATCO
MMVOII i
-------
5 9 0023
Moreover, EPA believes that results from remedial design and treatability studies resolved the
questions from the 1989 baseline study as to whether or not ammonia was the main cause of the
toxicity. Concerns had been expressed by EPA, other agencies, and members of the community
that not all of the toxicity documented in 1989 may have been the result of elevated levels of
ammonia and that some of the toxicity may be associated with elevated levels of metals, organic
compounds, or other toxicants. However, as discussed below, EPA believes that data collected
during the design and treatability study demonstrate that the toxicity documented in the 1989
study was the result of elevated levels of ammonia, potentially compounded by low levels of
dissolved oxygen in the water.
EPA developed a collaborative approach that involved personnel from EPA, the Florida
Department of Environmental Protection (FDEP), Metro-Dade Department of Environmental
Resource Protection (DERM), NOAA and EPA's contractor, Bechtel Environmental. Bechtel
was tasked to prepare the planning documents, provide logistical support, lead in the field
investigation, and prepare a report of the study findings. Bechtel subcontracted with ICF Kaiser
Engineers to obtain assistance for the evaluation of potential environmental risks. Due to the
large sampling area and number of samples to be collected at the same tidal interval, FDEP,
DERM, and NOAA provided additional field personnel. DERM also provided logistical
assistance in the form of boats to access sampling stations in the bay. Water quality analyses and
toxicity testing support was provided by EPA.
The scope of the study and results are summarized below. A detailed discussion of study
approach and results may be reviewed in the Field Operations Plan for a Wetland Water Quality
and Toxicity Assessment, Munisport Landfill, Bechtel Environmental, 7996, and Water Quality
and Toxicity Reassessment Study, Mangrove Preserve, Munisport Landfill, Bechtel
Environmental, Inc., in consultation with ICF Kaiser Engineers, Inc., 7997, respectively, which
n HP found in th? Administrative Record fcr this Sits.
6.1 Study Approach
As discussed previously, the study was patterned after the 1989 baseline study. It incorporated a
tidal assessment, water quality assessment, and toxicity assessment As shown in Figure 6-1, the
study incorporated an area that ranged from Dainia Canal, approximately 1 1 miles north of the
Mangrove Preserve, to Black Point approximately 24 miles south of the Preserve. The main
focus of the sampling, however, was in the Mangrove Preserve area,
6.1.1 ftample Locations
Sampling locations in the Mangrove Preserve area included the 1 1 stations originally sampled
during the 1989 study, along with two new stations at the east and west causeway breaches.
Sampling locations in the area of the Mangrove Preserve are shown in Figure 6-2. Samples were
initially collected from each of these stations and screened in the field for the presence of
ammonia and other water quality parameters. Based on results from the field screening and using
15
-------
5 9 '0024
I
DAN1A CANAL REFERENCE SITE (DC)
BISCAYNE CREEK REFERENCE SITE (BC)
MUNISPORTSfTE
BLACK POINT REFERENCE SITE (BP)
16
SCALE IN MILES
203B5/OI2/FIC05.0CN
SOU2CC: B£l 1397
Figure 6-1
Study Area Location Map
Munisport Site
16
-------
5 9 '0025
MUNISPORT
SITE
•E5T
j COTS*
j 1*1
MANUMUVC
PRESERVE
in »b tb M« il« J J
41 ttl M< tfl M< Itf/ ^^
-""-* -1* -prr* «"LXy
-------
5 9 '0026
results from the 1989 study, four stations (i.e., D4, D5F, D6 (Mangrove Preserve) and ECC (east
causeway breach)) were selected for collection of samples for further water quality and toxicity
testing. These stations reflected a range of locations with high and low ammonia levels
throughout the Preserve.
Samples were also collected from three reference sites located at Dainia Cutoff Canal, Biscayne
Creek, and Black Point Locations for the reference stations are shown in Figures 6-3,6-4, and
6-5. In addition to the Preserve and reference locations, samples were also collected from the
confluence of the east and west causeway breaches (Figure 6-2), and the wetland mitigation area
(Figure 6-2).
6.1.2 Tidal Assessment
The 1996 tidal assessment conducted in 1989 was repeated during the 1996 study. Periods of
high and low tide in the Preserve and tidal water volume exchange between the Mangrove
Preserve and Biscayne Bay were assessed. Tidal stages were determined by measuring surface
water elevations at the east and west causeway breaches and the inland most station, D6, in the
Mangrove Preserve. Three submersible trolls (i.e., combined pressure transducer/electronic data
logger) were installed at each location and continuously operated for up to five days, collecting
data at ten-minute intervals.
Tidal water volume between the Mangrove Preserve and Biscayne Bay was determined from
surface water measurements, surveyed channel cross-sections, and velocity profiles at the east^and
west channels. Channel geometry was obtained from manual measurements of discrete intervals
of the channel. Velocity profile measurements were collected at the east and west causeway
breaches at two hour intervals, for a 12-hour period.
6.1.3 Water Quality Assessment
The water quality assessment was comprised of both point and diel measurements of ammonia,
pH, dissolved oxygen, temperature, and salinity at all of the surface water sampling locations
described in Section 6.1.1 at both high and low tide. Measurements were made in the field using
a Hydrolab water quality monitor. Additional water quality samples collected in March 1997,
were measured using YSI Model 85 water quality analyzer and an Oakton pH tester.
Point measurements of water quality parameters were collected during initial screening of the
1989 study locations. This data was used to select four stations for the collection of samples for
the 1996 chronic toxicity testing. Samples were also collected from these stations for water
quality analyses to aid in the interpretation of the toxicity data. Water quality parameters were
measured and chemical analyses included ammonia, purgable and extractable organic compounds,
pesticides/polychlorinated byphenyls (PCBs), and inorganic constituents. Chemical analyses were
conducted by EPA contract laboratories.
18
-------
5 9 0027
FORT 14UKRDAI.E-NOUTWO)
INTCRNATIONAL AIRPORT
DANIA
CANAL
REFERENCE
SfTE
20385/0!2/riC07.DCN
SOURCE: BE I 1997
Figure 6-3
Dania Canal Reference Site
Munisport Site
-------
5 9 0028
OLETA RIVER
STATE
CREEK
REFERENCE
SITE
MUNISPORT
MANGROVE
PRESERVE
- MMOKIVES
A KrcKKt sm
BISCiTK BAT
MIUTIC KESBNl
JOfUX. WTO» SUPl IK
LOUT KM
203BS/OI2/nC06.0CN
SOURCE: BE) I99T
Figure 6-4
Biscayne Creek Reference Site
Munisport Site
20
-------
5 9 0029
- BLACK POINT•>„.-
•REFERENCE SITE "5
20385/012/F1G08.DCN
SOURCE: BE I 199?
Figure 6-5
Black Point Reference Site
Munisport Site
21
-------
5 9 0030
6.1.4 Toxicitv Assessment
Surface water samples were collected from the three stations in the Mangrove Preserve (i.e., D4,
D5F, D6), the east causeway breach (ECQ, wetland mitigation area (WMA), confluence with
Biscayne Bay (CBB), and the three reference sites (i.e., DC, BC, BP). Samples were collected
at high and low tide. Toxicity tests were conducted using a coastal minnow, Menidia beryllina,
and a single cell algal species, Minutocellus polymorphic. Supplemental samples were collected
at stations D4, D5F, and D6, during 48-hour and 96-hour intervals for continued chronic toxicity
testing. Toxicity testing was conducted by EPA.
6.2 Study Results
Results from the reassessment of the water quality and toxicity conditions of the Mangrove
Preserve show that the tidal restoration has significantly improved the tidal exchange between the
Preserve and Biscayne Bay. The data also show a significant reduction in the levels of ammonia
and toxicity formerly documented in the 1989 study. The results of the tidal, water quality, and
toxicity assessment are discussed below.
6.2.1 Tidal Assessment
Former flood volumes at the historical culvert locations were calculated using velocity and flow
area data obtained from the 1989 study. Discharges at different times were computed by
multiplying velocity and flow area data, and the discharge versus time curve was integrated for the
duration of the flood tide to yield the flood volumes into the Mangrove Preserve. The flood
volumes calculated for the east and west culverts were estimated at 29.7 and 27.5 acre-feet,
respectively.
Tidal flow volumes at the causeway breaches were calculated by measuring the cross-sectional
area of the channels, and measuring velocities of the water in the channels at various depths.
Average velocities were multiplied by the cross-sectional areas for which they were considered
representative, and the resulting quantities added together to yield the total discharge for the tidal
interval evaluated. The discharge versus time curves were integrated for the duration of the flood
and ebb tides to yield, respectively, the flood and ebb volumes. Flood and ebb volumes estimated
for the east causeway breach were 34.4 and 31 acre-feet, respectively. Flood and ebb volumes
estimated for the west causeway breach were 39.7 and 37.0 acre-feet, respectively.
Based on an comparison of flood volumes before and after the causeway breaches, it is estimated
that the tidal flow into the Mangrove Preserve through the east culvert increased by
approximately 16 percent, with a tidal range of about 2.5 feet In fact, tidal flow to the Preserve
through the west culvert increased by approximately 44 percent This is consistent with the 1989
estimated restriction of tidal flow to the Preserve of 42 percent Based on the predictions made
in 1989, substantiated by this study, the removal of the two 66-inch diameter culverts and
construction of open flow channels significantly increased the tidal exchange with Biscayne Bay.
22
-------
5 9 0031
6.2.2 Water Quality Assessment
During the August 1996 study, ammonia concentrations were measured in the field, in the
laboratory by EPA, and its contract laboratory. Surface water samples collected in March 1997,
were analyzed by an off-site laboratory. A summary of the field screening measurements are
provided in Table 6-1. Analytical results in the laboratory are summarized in Table 6-2. A
comparison of these results to the ambient water quality criteria is also provided in the table.
Overall, ammonia concentrations measured during the 1996 and 1997 sampling events were
significantly lower than concentrations reported in 1989. Ammonia concentrations detected
among the ten samples collected in the Preserve in 1996 ranged from 0.06 mg/1 to 3.9 mg/1. In
contrast, ammonia levels in 1989 ranged from 1 mg/1 to 15 mg/1 in samples collected for water
quality analyses. Analyses of samples collected for toxicity tests in 1989 indicate a broader range
for ammonia concentrations, ranging from 0.023 mg/1 to 25.24 mg/1. As illustrated in Table 6-2,
both sets of analytical data for the sampling stations in 1996 indicate that total ammonia
concentrations are below chronic AWQC in the Mangrove Preserve. Thus, the potential for
adverse effects to aquatic organisms is unlikely, which is father substantiated by the absence of
toxicity as discussed below.
Due to concerns that the increased rainfall during the 1996 event may have diluted the potential
discharged of ammonia, additional sampling was conducted during a dry period in 1997 of four
stations in the Mangrove Preserve. Since the goal of the sampling was only to assess whether or
not there may be more concentrated discharges of ammonia during dry periods, the samples were
analyzed for ammonia only. The results demonstrated no significant difference in the discharge of
ammonia during dry or wet periods. The ammonia levels were still well below levels reported in
1989, but slightly elevated above the 1996 results. Total ammonia concentrations reported in
1997 ranged from 0.44 mg/1 to 4.8 mg/i. Consistent with the previous sampling events, station
D6, the inland most station, still had the highest level of ammonia. The ammonia level for this
station also exceeded the AWQC, but due to the consistency with the 1996 results, and
significantly lower level than observed in 1989, is not expected to pose any significant health
effects to aquatic organisms.
Diel measurements indicated that within the Mangrove Preserve, ammonia concentrations have
been reduced most likely as a result of increased tidal flushing of the Preserve and/or decreased
ammonia discharges from the landfill, as suggested by a general decrease in ammonia levels in the
groundwater from those formerly in the 1988 RI. Deil measurements are contained in Appendix
C of the Water Quality and Toxicity Reassessment Study, Mangrove Preserve, Munisport
Landfill, Bechtel Environmental, Inc., in consultation with ICF Kaiser Engineers, Inc., 7997, and
can be found in the Administrative Record for this Site.
A summary of the results from the analyses of surface water samples for the presence of purgable
and extractable organic compounds, pesticides/polychlorinated byphenyls (PCBs), and inorganic
constituents is provided in Table 6-3. Review of these results do not indicate the presence of
23
-------
5 9
0032
TABLE 6-1
INITIAL FIELD SCREENING
MUNISPORT SITE
LOCATION*
Hiek Tide
D1.5
D2
D3G
D4
D4D
DSC
D5F
D6
D7B
D7.5
DID
WCC
ECC
Low Tide
D1.5
D2
D3G
D4
D4D
DSC
D5F
D6
D7B
D7.5
D10
DATE
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
TEMP
(0
28.94
29.47
28.63
28.90
28.78
28.63
28.74
27.89
29.19
28.68
29.20
29.69
30.33
27.81
28.90
27.51
27.39
27.42
27.18
27.20
27.81
27.14
27.04
27.31
pH
7.24
7.18
7.26
7.30
7.28
7.29
7.40
6.79
7.17
7.19
6.98
7.16
7.46
7.21
7.18
7.25
7.37
7.40
7.43
7.21
6.78
7.21
7.29
6.96
SALINITY
(ppt)
30.8
30.2
32.7
24.4
9.9
27.6
31.5
31.6
31.7
31.4
30.5
9.6
9.9
.
23.3
30.9
9.4
9.9
26.3
22.8
30.7
32.1
12.1
31.0
30.6
AMMONIA
SCREEN
(me/L)
0.74
0.66
0.82
0.79
0.58
0.79
1.13
0.25
0.69
0.72
0.48
0.45
0.87
0.61
6.67
0.52
0.62
0.96
0.93
0.65
0.16
0.53
0.87
0.43
" Point measurements (ammonia, pH, dissolved Gj, temperature, and salinity) at 12 previous sample locations and east causeway bread to
select four final locations for sampling
A51lh.doc
u/ii/96
24
-------
5
O •"> ~> f
Ou33
TABLE 6-2
COMPARISON OF TOTAL AMMONIA CONCENTRATIONS TO AMBIENT WATER QUALITY
CRITERIA
(Concentrations in mg/L)
August 199<
March 1997
Sampling Location
Black Point
Biscayne Creek
Biscayne Creek
Biscayne Creek
Biscayne Creek
Confluence Biscayne Bay
Mangrove Preserve
Mangrove Preserve
Mangrove Preserve
t t mm mm HI m ftl • I • n 1 •
Mangrove rreserve
Mangrove Preserve
OaniaCut
East Causeway
West Causeway
Wetland Mitigation Area
Tidal
Period
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
Low Tide
High Tide
High Tide
Sample
Designation
BP1-L
BP1-H
BC1-L
BC1-H
BC1-L48
BC1-H48
BCI-L96
BC1-H96
BC1-L120
BC1-H120
CBB1-L
CBB1-H
D4-L
D4-H
D5F-L
D5F-H
D5F-L96
D5F-H96
D6-L
D6-H
D6-L96
D6-H96
DC1-L
DC1-H
ECC1-L
ECC1-H
WCC-L
WCC-H
WMA1
CLP Lab
Data**
0.05
0.05
0.05
0.05
NA
NA
NA
NA
0.05
0.05
0.05
0.05
1.4
1.6
«36
__ J-6 . .
NA
NA
23 "
33
NA
NA
0.06
0.05
; C^O
0.05
NC
NC
1.1
ESAT~Lab
Data**
0.1
0.1
0.1
0.1
. 0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
13
135
038
1.7
031
1
Z15
2.7
3.9
. . .3.2 .
0.1
0-1
. C19 "
0.1
NC
NC
935
Chronic
AWQC
4.1
031
0.81
033
0.81
OJ3
0.81e
033'
0.81'
033'
0.81
033
11
3.1
5.0
4.4
5.0e
4.4'
4.4
4.7
4.4'
4.7*
2.0
13
13
033
—
—
0.84
CLP Lab
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
2.01
1.13
0.904
. 2A6 .
NC
NC
4.83
4.77
NC
NC
NC
NC
0.443
0.05
0.993 ;
0.05
NC
Cbnalc
AWQC
•
—
—
—
—
—
—
_
—
—
—
—
23
4.1
7^
3.1
—
^ ~"~
2J9
23
•—
—
_
_
7.2
U
2^
}J>
—
* Detected concentrations are shaded; unshaded values are detection limits.
* Concentrations greater than AWQC are indicated with boldface typei
c Temperature, pH, and salinity data were not collected at these specific sampling hours. AWQC estimated based on physical data
collected at 0 hours.
0 Ambient Water Quality Criteria. Temperature. pH. and salinity data used to calculate AWQC for the 1996 and ! 997 sampling are
presented in Appendix C. Tables C-l and C-2, respectively.
NA-Not analyzed
NC-Not collected
ADIbdoc
12/11/96 3.25 PM
25
-------
TABLE 6-3
5
0034
COMPARISON OF ORGANIC AND INORGANIC CONCENTRATIONS
IN AUGUST 1996 TO AMBIENT WATER QUALITY CRITERIA
MUNISPORTSITE
(MmcMKTBuara mt wg/1-!
Chemical
Volatile*:
Chloromethane
1.1-Dich)orDethene
Toluene
PaailcMea;
Heptachter
Metals:
Areente
Copper
Iron
Lead
Oterta am saltwater chra
Frequency
2/17
2/17
1/17
1/17
1/17
1/17
1/17
1/17
lie AWQC (EPA 19
ttrouafltv standard.
Maximum
Detected
Concentration
2
4
1
0.083
13
41
540
3
Chronic AWQC*
NA
3.2*
5.000°
0.0036
36°
2.8 E
300*
8.5
Number of
Oetecta>
AWQC
_
1
None
1
None
1
1
• None
•
Sampling
Location with
Exeeedanee
_
WMA-1 High Tide
BP-1 Low Tide
—
BC-1 Low Tide
WMA-1 High Tide
—
c tmuffcfertfcltte to ctevatop a criterion. Vklut prntnM by EPA (1995) to a LOEL (UwMit Otawvrt Enact Uwl).
0 VWutforafMntem.
c Acute AWQC uMdbMauw no dvonte AWQC ««•
NA • No AWQC wen •vmBabte for into compound.
26
-------
5 9 0035
other contaminants at significant levels in the Preserve other than ammonia. Although some of
the chemicals detected exceeded federal or state water quality criteria, the chemicals were only
detected in one or two of the samples collected from the 17 stations. In addition, two of the
chemicals, heptachlor and copper, were only detected at the reference sites. The infrequent
detection and comparatively low concentrations of the chemicals do not suggest that current
chemical concentrations in the Mangrove Preserve pose any concern to aquatic organisms.
6.2.3 Toxicity Assessment
As previously discussed, potential toxic affects were evaluated using a coastal minnow, the Inland
Silverside, Menidia beryllina, and a single cell species of algae, Minutocellus polymorphic.
Results from the toxicity tests are summarized in Table 6-4. No toxic effects were detected in
either the fish or algae tests. Results from the fish toxicity tests indicate a survival rate ranging
from 95 to 100 percent, evidence of no unacceptable toxic effects. There was no distinction in
the survival offish tested for low and high tide, as was observed during the 1989 toxicity study.
Percent survival during the 1989 study ranged from 0 to 73 percent at low tide, and from 3 to 70
percent at high tide in samples collected from the Preserve. With regard to the algal toxicity test,
some significantly lower fluorometric readings were detected; however, the lower readings were
attributed to clumping of the cells by native micro flora. None of the lower readings were
attributed to inhibition or lack of cell growth from toxic conditions in the Mangrove Preserve
surface water.
6.3 Conclusions
,r jr
Superfund actions to date have improved the tidal circulation in the Mangrove Preserve by as
much as 40 percent, and have resulted in significant improvements in water quality and a
significant reduction in surface water toxiciry in the Preserve. Although aii of the stations
monitored in the Preserve showed improved water quality, the historically most contaminated and
toxic station showed the greatest improvements. Low-tide ammonia levels at station D6
decreased from 25.24 mg/1 to 2.15 mg/1 and 4.83 in 1996 and 1997, respectively. During the
1996 study, with the exception of the anomalous wetland mitigation area, there were no
exceedances of AWQC, nor were other organic or inorganic chemicals detected in the Preserve at
levels that exceeded the AWQC. With the exception of the exceedance of the AWQC for one
station, the ammonia levels detected in the 1997, sampling of the Preserve were consistent with
the trend documented in 1996. With regard to toxicity tests, survival rates ranged from 95 to 100
percent for the fish, and no significant adverse cell growth was observed in algae.
These results demonstrate that the tidal restoration has significantly reduced the surface water
ammonia contamination in the Mangrove Preserve documented in 1989; and as a result, the toxic
conditions observed in the Mangrove Preserve in 1989 are no longer present
27
-------
5 9
0036
TABLE 6-4
Summary of the results of toxicity tests performed on Munisport water samples. August 1996.
Simple ID
CONTROL
BC1-L
BC1-H
BP1-L
BP1-H
CBB1-L
CBB1-H
DC1-L
DC1-H .
D4-L
D4-H
D5F-L
D5F-H
D6-L •
D6-H
ECC1-L
ECC1-H
WMA1-H
Menidia 7-day Chronic Test
*4 Survival
90
100
100
100
100
97.5
97.5
100
97.5
97.5
100
100
95
95
97.5
100
97.5
100
Av. Weight per Fish (mg)
1.91 "
2.22
2.11
1.83
1.96
2.15
2.00
1.93
1.92
1.89
1.79
1.74
1.90
1.81
1.96
1.90
1.94
1.95
Minutocellui
Mean Cell Density
(in fluoromeier units) ' .
1.95
1.25
0.73*
2.72
2.92
0.08-
0.42-
-2.08-
-1.33*
1.45
1.35
1.84
1.83
1-39
1.45
1.00
-on*
1.15
' indicates thai (his value is significantly different statistically from the value for the control.
28
-------
5 9 0037
7.0 DESCRIPTION OF NO ACTION ALTERNATIVE
Based on the reduction in toxicity and ammonia concentrations in surface water through
Superfund actions conducted to date, resulting in the accomplishment of the intent of the ROD,
this amendment to the ROD will not involve any further action by EPA pursuant to CERCLA, as
amended by SARA, at the Munisport Landfill Superfund Site. No institutional controls, land use
restrictions, monitoring, nor five-year review requirements are necessary.
As documented in the RI and Baseline Risk Assessment, the site did not present any unacceptable
risk to human health, and the 1996 study has shown that actions to date by EPA have mitigated
the threat to the environment such that further response pursuant to CERCLA is not needed.
Consistent with these findings, no institutional controls or land-use restrictions are necessary.
Although the former ROD provided for monitoring to ensure compliance with performance
criteria, no future monitoring is required pursuant to CERCLA. Former compliance monitoring
was based on the premise that performance of the hydraulic barrier and natural degradation of the
ammonia with time would result in a reduction of ammonia levels in the groundwater discharging
to the Mangrove Preserve. However, as the 1996 reassessment showed, risks to aquatic
organisms were mitigated through the tidal restoration of the Mangrove Preserve such that
implementation of the hydraulic barrier pursuant to CERCLA would not be necessary.
Accordingly, compliance monitoring of groundwater performance criteria as established in the
former ROD would not be appropriate. With regard to the further monitoring of surface water
conditions in the Mangrove Preserve, EPA believes that the database used to formulate this
amendment is consistent with, and in some cases exceeds, the database used to develop the ,
original ROD. This amendment takes into account data collected as part of the surface water
monitoring prior to and after the breach of the causeway breach, as well, the 1996 reassessment,
and 1997 sampling. Furthermore, this ROD amendment takes to account the wealth of data
collected during the design process. This monitoring confirms the findings of the RI that
ammonia is the primary concern, and in addition to the RI, shows a general decrease in the
ammonia levels with time. Given the fact that this decision is based on a database at least
equivalent to that the database used to support the original action, and that continued monitoring
after the RI has not revealed anything to suggest that conditions may worsen in the future, EPA
believes that continued surface water monitoring pursuant to CERCLA is not warranted. With
regard to the need for a five-year review, in view of EPA's findings from the RI and Baseline Risk
Assessment, and based on the results from the 1996 reassessment of the Preserve, there is nothing
that would prevent unlimited use and unrestricted exposure at the site pursuant to CERCLA.
Therefore, no five-year review of the site is needed.
While not a pan of this Superfund action, landfill closure and groundwater contamination will be
addressed independently of Superfund, pursuant to State and County regulations. Finally,
amendment of this ROD to no further remedial action constitutes completion of construction of
all Superfund-related activities.
Based on the absence of significant toxicity and the threat to the aquatic life originally
29
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documented in 1989, and a lack of any further response actions pursuant to CERCLA, EPA
intends to proceed with the deletion of this site from the NPL and request termination of the
Consent Decree by the United States District Court, Southern District of Florida. Tidal
restoration of the altered wetlands will be addressed pursuant to the Clean Water Act through an
Administrative Order with EPA, in consultation with the State and County regarding the timing of
the breaches.
8.0 EXPLANATION OF SIGNIFICANT CHANGES
No new information was obtained during the comment period on the Proposed Plan that resulted
in any significant changes to the ROD Amendment
30
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Appendix 1
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RECORD OF DECISION AMENDMENT
RESPONSIVENESS SUMMARY
MUNISPORT LANDFILL SITE
NORTH MIAMI, DADE COUNTY, FLORIDA
Prepared by:
United States Environmental Protection Agency
Region IV, Atlanta, GA
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As part of EPA's community participation process and requirements of the
Comprehensive Environmental Response, Compensation, and Liability Act, as amended,
(CERCLA), and the National Contingency Plan (NCP), EPA solicited comments from the public
on the May 1997, Proposed Plan for an amendment to the Record of Decision issued by EPA on
July 26,1990. Comments were solicited through a 30-day comment period, with an additional
30-day extension to the comment period. Comments were accepted up to 10 days after the end of
the comment period as requested on an individual basis. As pan of the public comment period,
two public meetings and an informal public availability session were held to inform the public of
EPA's proposed plan and to obtain comments. Transcripts were maintained at each meeting and
are part of the Administrative Record.
This Responsiveness Summary addresses and responds to comments received during the
public comment period as well as comments as received during the public meetings and
availability session. Where multiple comments were received on the same issue, these comments
have been combined into one comment and a single response provided. In some cases, comments
were provided that were beyond the scope of this proposed amendment, dealing with such issues
as the adequacy of the Remedial Investigation and the original remedy. Comments formerly
addressed by EPA that are beyond the scope of this amendment will not be addressed in detail in
this responsiveness summary. Copies of original comments and transcripts from the public
meetings are included in the Administrative Record.
1. Comment: One commenter expressed concern that too little testing, if any, of the blue
crabs and food fish had been conducted in the area of the Oleta River. Concern was also
expressed regarding the risks calculated during the EPA Remedial Investigation (1988)
(RI), that estimated an excess cancer risk of 2.0 x 10"4 to 2.0 x 10"5that could result from
the ingestion of fish from the Mangrove Preserve area.
EPA Response: Although this comment is beyond the scope of this Record of Decision
(ROD) Amendment, and the issues of potential human health affects were addressed
during the RI and original ROD, a brief response is provided. First, several issues must be
considered in the evaluation of the estimated risk to human health associated with the
consumption of fish, including their mobility and the nature and concentration of
contaminants detected at the landfill. As noted in the RI, given the mobility of the fish
and the low concentration of contaminants detected at the landfill that were also detected
in the fish, the potential risk could not be associated with the landfill. These risks could be
associated with the numerous other point and non-point discharges to the Oleta River and
Biscayne Bay. In addition, these potential risks, though on the high end, are within EPA's
acceptable risk range of 1x10"* to 1x10"*.
2) Comment: Concern was expressed that although elevated levels of metals and organic
compounds were detected in the Mangrove Preserve area and fish collected from the
Preserve, signs were never posted warning the public of potential public health threats.
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EPA Response: Although this issue was beyond the scope of the ROD amendment, a
brief response is provided. Some metals and organic compounds were detected in samples
collected from the Mangrove Preserve area, however, evaluation of the data did not
indicate that the concentrations were significant enough, or detected with the frequency to
suggest a potential for adverse health affects. As a result, warning sign were not
considered necessary.
3) Comment: A question was asked whether or not EPA had considered consultations
regarding potential public health threats to Canadian citizens that reside in the Highland
Village community on a part time basis.
EPA Response: Although this comment is beyond the scope of this amendment, and deals
with public health issues documented in the RI and ROD, a brief response is provided.
Potential threats to human health were evaluated as part of the RI, and the only potential
threat to human health was associated with long-term exposures of subsurface soils to
future residents. Since Highland Village residents, including part-time Canadian residents,
live off-site, they would not be considered to be at risk from long-term exposure to
contaminated subsurface soils. Because of the lack of potential exposure routes to
Highland Village residents, and the part-time residency of Canadian citizens, any potential
adverse health affects could not be linked to the Munisport Landfill.
4) Comment: Some commcnters believe that there are still too many unanswered questions
concerning the Munisport Landfill Superfund Site and the threat it poses to public heajth.
EPA should, therefore, not proceed with the amendment and eventual delisting of the site
from the National Priorities List (NPL).
EPA Response: The commenters offered no specifics; thus a detailed response cannot be
given. EPA does disagree, however, that the studies are insufficient Numerous studies
have been conducted by EPA, the State, County and City of North Miami since the mid-
1970's at a cost of millions of dollars. A time-line of the work conducted is shown in
Figure 2-2 of the ROD Amendment Compared to most Superfund sites, a tremendous
amount of information has been gathered documenting the nature and extent of
contamination and potential risk to human health. The studies demonstrate that this
landfill is consistent with other municipal landfills in the State of Florida operated during
the same time period, and needs to be addressed pursuant to State and county regulations.
There is no evidence that the Munisport Landfill was operated as a hazardous waste
facility as some commenters allege.
5) Comment: Some of the commenters recommended an alternative by which EPA could
end its involvement in this project, but the U.S. District Court retain jurisdiction over the
project, and the community stay involved through the community participation process
provided in the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA), as amended.
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EPA Response: EPA appreciates the desire of some members of the community to keep
the US District Court involved, since the Court has formerly allowed parties without
standing to the Consent Decree between the US Government and the City of North Miami
to file pleadings with the Court and persuade the Court to require periodic status reports
and conferences by EPA and the City of North Miami. EPA further understands that the
community participation process pursuant to CERCLA is quite different from the State's
and County's participation process. However, community participation does not provide a
basis for continued response pursuant to Section 104 of CERCLA. EPA is authorized to
respond to the release or threat of release of hazardous substances, pollutants or
contaminants in order to protect human health, welfare, or the environment Since EPA
has determined that remedial actions to date have been adequate to achieve the necessary
degree of environmental protection, continued response by EPA, or the State through
delegation of EPA's authority, is not appropriate. In absence of a response pursuant to
CERCLA, there would no longer be a need for a Consent Decree to govern
implementation of the work. Finally, the Court affirmed at the June 26,1997, status
conference that the community's desire to have the Court retain jurisdiction was not a
basis for the Court's continued involvement
6) Comment: One commenter expressed concern for the financial liability the citizens may
be exposed to should the Site be deleted from the NPL. The commenter suggested that
without federal oversight the City could possibly do the wrong thing and incur
considerable expense that would be passed on to the taxpayers.
EPA Response: As stated above, an environmental threat of the magnitude which would
warrant Superfund action is no longer present as a result of cleanup actions taken to date.
FDEP is very capable of closing out municipal landfills under State regulations.
Therefore, EPA disagrees with the commenter trial the site must remain under the
oversight of EPA to ensure that the City does not do the wrong thing.
Furthermore, the City has secured grants from the State and County totaling
approximately $16,000,000 to provide for the proper closure of the landfill and to address
the groundwater contamination. In view of the funding received from the State and
County, and given the fact that the State and County, both of which have aggressive
environmental programs, will be overseeing any future work, the concern mat the
taxpayers may incur considerable expense in the future from failures by the City in
performing the work do not appear to be well founded.
7) Comment: Some of the commenters suggested that due to poor performances by the
State and County at this and other Sites in the area, neither the State nor County are
qualified to manage the closure of the landfill and groundwater contamination.
EPA Response: EPA strongly disagrees with this comment The State and County both
have comprehensive, aggressive, environmental programs based on regulations that are
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5 9' 0044
often more stringent than the Agency's own regulations. EPA is very confident that the
State and County can manage any future cleanup that may .be required by State or County
regulations.
8) Comment: One commenter expressed concern that if EPA amends the ROD to no action,
and the site is not cleaned up, it will have a severe impact on property values.
EPA Response: EPA disagrees that a lack of response by EPA will have an additional
detrimental affect on area property values. As discussed in the 1990 ROD, this site does
not pose a threat to pubb'c health, and as discussed in this amendment, EPA has
determined that actions taken to date have been adequate to mitigate the threat to the
environment such that further response pursuant to CERCLA is not warranted.
Nevertheless, it is the Agency's understanding that the State and County will continue
with the closure of the landfill and management of contaminated ground water in
accordance with State and County regulations.
9) Comment: A commenter expressed a strenuous objection to EPA's failure to invite
representatives of the Keystone Point Homeowners Association (KPHA) to attend a May
28,1997, meeting and site visit
EPA Comment: EPA regrets that members of the KPHA were not invited to the meeting.
The meeting was among EPA, DERM, FDEP, and City official's to discuss the terms of
an Administrative Order pursuant to the Clean Water Act to address the tidal restoration
of the altered wetlands. This meeting was coordinated by the Department of Justice
(DOJ), and as the recipient of a Technical Assistance Grant, the Munisport Dump
Coalition (MDC) was invited to attend the meeting. DOJ did not realize until shortly
before the meeting that Maureen Harwitz, Executive Director, MDC, was out of the
country. Moreover, until recently, EPA and DOJ was unaware that KPHA desired to be
involved directly, independent of the MDC. EPA had assumed that as the TAG recipient,
the MDC, would have communicated any KPHA concerns.
10) Comment: Some of the commenters disagreed with EPA's assertion that the tidal
restoration to the .Mangrove Preserve has reduced the ammonia levels and toxicity in the
Mangrove Preserve such that the Site no longer poses a significant threat to the
environment They argue that the testing criteria used in the 1996 and 1997 testing,
differed from the 1989 study, and therefore do not provide a reliable comparison. The
commenters argue that differences in rainfall, testing conditions, and test species do not
provide a valid comparison.
EPA Response: EPA disagrees with the commenters position that the 1996 and 1997
testing do not support EPA's determination that the site no longer poses a significant v
threat to the environment Significant amounts of information has been gained since the
1989 study, providing key insight into the cause of toxicity documented in 1989.
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Extensive information has been collected during treatability and design studies that show
that the toxicity observed in 1989 was the result of elevated levels of ammonia. Because
EPA was trying in 1989 to conduct a broad characterization of the problem, EPA used a
suite of test organisms and procedures to investigate toxicity in the form of mortality and
inhibition in growth and reproduction. However, with information from the 1989 study
and information from the more recent design and treatability studies, EPA was able to
refine the 1996 study to focus on the main problem in the Preserve...elevated levels of
ammonia.
As a result, EPA refined the scope of the study to focus on the toxicity associated with the
discharge of leachate-contaminated groundwater to the Preserve. The scope of the 1996
study incorporated two test organisms, both of which were used in the 1989 study and
have been shown to provide a reliable indication of toxicity.
With regard to variations in climatic conditions during the study, it is true that the 1989
study was conducted during an extended dry period, while the 1996 study was conducted
during a wet period. It should be noted that prior to the original ROD, some of the same
commcnters argued that the 1989 study under-estimated the toxicity, since the lack of
rainfall resulted in a reduction in the amount of leachate normally generated. These
commenters now argue that the increased rainfall would have diluted the leachate
discharge, again under-estimating the problem. If you apply the same logic used by the
commenters in 1989, a reduction in rainfall would have reduced the amount of leachate
formed, thus, under-estimating the problem. While an increase in rainfall as observed in
1996, should have resulted in an increase in the amount of leachate formed, contrary to
the commenters current position.
Nevertheless, EPA collected an additional set of surface water samples during a dry period
in 1997 to evaluate whether or not the increased rainfall had diluted the problem as alleged
by the commenters. The data showed no significant change in the ammonia concentration
from the wet and dry sampling events in 1996 and 1997, respectively.
In summary, it was not the intent of EPA, nor for the reasons discussed above, was it
necessary to exactly dupb'cate the 1989 study. The fact remains that EPA conducted a
valid water quality and toxicity assessment of the conditions in the Mangrove Preserve in
1996, that demonstrates that the actions taken to date have been adequate to reduce the
risks posed to the environment such that a response pursuant to CERCLA is no longer
warranted.
11) Comment* One of the commenters stated that by amending the ROD to no action, EPA is
abandoning its responsibility to stop the seepage of contaminants to Biscayne Bay and
Arch Creek Canal.
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EPA Response: EPA disagrees with the commenter. EPA believes that it has fulfilled its
obligation pursuant to CERCLA and has met the intent of the ROD to address the
environmental threat documented in 1989. Although the ROD incorporated the collection
and treatment of contaminated groundwater as part of the remedy, it was a vehicle by
which EPA could stop the exposure of aquatic organisms in the Mangrove Preserve to
elevated levels of ammonia being discharged from the landfill. Alternatively, had the 1989
study not documented any toxicity to aquatic organisms in the Preserve, EPA would not
have implemented a remedy to collect and treat contaminated groundwater.
Since EPA's actions to date have mitigated the threat documented in 1989, there is no
basis for groundwater collection and treatment pursuant to CERCLA. EPA is aware,
however, that contaminants are present in the groundwater that exceed county
regulations, and that DERM is pursuing with the City the implementation of a
groundwater collection and treatment system to attain the county's standards. It is
important to note that these standards are based on the potential for harm to occur and
provide a more conservative approach than the direct measurement of toxicity employed
by EPA. This approach is within the prerogative of DERM to follow, but exceeds the
requirements established in CERCLA.
12) Comment: In view of the delays in the construction of the remedy, and now that EPA
does not plan to complete construction of the remedy, a commenter restated a prior
objection to EPA requiring the City of North Miami to avoid its competitive bidding
process to expedite the construction process. ^
EPA Response: Although the comment is beyond the scope of this ROD amendment, a
brief response is provided. First, the City of North Miami chose to use their emergency
procurement procedures, and not use the competitive bid process, to avoid potential
monetary penalties for non-compliance with EPA's approved project schedule. Second,
the lapse of time since the initial construction of the recovery well system was the result of
delays encountered as a result of objections to the work in the fall of 1995 by local
activists, not as a result of mismanagement of the project by EPA.
*'
13) Comment: The City of North Miami expressed support for EPA's proposed amendment
The City also noted that had the Hazard Ranking System scoring been revised and based
on up to date information, taking into account the removal of municipal wells from service
due to saltwater intrusion, the site would have never been placed on the National Priorities
List (NPL).
EPA Response: EPA appreciates the City's position; however, as conveyed in its prior
response to this issue, as a matter of EPA policy, it does not rescore sites once they have
been placed on the NPL, since resources needed to rescore sites may be detracted from
the main focus of site remediation, if sites were rescored every time new information was
obtained. However, EPA does believe that with regard to this site, the diminished human
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health threat that resulted from the closing of the municipal wells is reflected in the lack of
threat to human health documented in the Remedial Investigation and Baseline Risk
Assessment
14) Comment: One of the commenters argued that the 1989 ambient water quality criteria
(AWQC) needed to be modified to correct for the 1996 variations in temperature, pH, and
salinity to provide for a valid comparison between the two studies.
EPA Response: EPA disagrees with the commenters assertion that modification of the
AWQC in the 1996 study using site-specific water quality parameters results in an invalid
comparison of the two studies. The goal of the AWQC is to provide some standard for
evaluation of a given set of data. Whether or not the AWQC is adjusted to the site-
specific data, or vice versa, is not relevant The important thing is that the comparison is
drawn between the AWQC and water quality data for a given sampling event As
appropriate, the AWQC should be adjusted using the same water quality parameters
indicative of the ambient conditions for which a given set of data were collected. It would
not be appropriate to make adjustments in the AWQC using indicators of ambient
conditions of a different study conducted seven years ago.
15) Comment: Some of the commenters continue to characterize the Munisport Landfill as an
hazardous waste facility. To support their position they refer to depositions and
interviews of former landfill operators gained by the City of North Miami during it
contribution action and EPA during its civil investigation work, respectively. One of the
commenters also uses the periodic detection of chemicals during the RI to support the'
position that this site was operated as a hazardous waste facility. The commenter reasons
that due to the occasional detection of polychlorinated biphenyls and disposal of liquids at
the landfill- dioxLn and dense non-aqueous phase liquids (DNAPLs) are likely preseni ai
the landfill. The commenter also raises the former issue of a Notice of Violation of
Hazardous Waste Disposal issued by DERM in 1976 regarding twelve drums as further
evidence of the operation of the Munisport Landfill as a hazardous waste facility.
EPA Response: EPA disagrees with the commenters' assertions that the Munisport
Landfill was operated as an hazardous waste facility. EPA believes that the extensive
chemical database and lack of specific documentation of routine hazardous waste disposal
supports EPA*s assessment that the wastes disposed of at this facility are consistent with
other solid waste landfills operated in the State of Florida during the same time period.
Over the years EPA has conducted comprehensive civil investigative work and has not
gained any direct evidence of hazardous waste disposal, other than the isolated incident
reported by DERM in 1976. Assuming there had been some wholesale hazardous waste
disposal, as alleged by the commenters, the comprehensive groundwater monitoring
network of over 100 monitoring wells at the site would have given some indication of the
contamination. With regard to the presence of a DNAPL, no chemicals were ever
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5 9' 0048
detected at the site with any consistency or at concentrations approaching the water
solubility of the compound that might suggest the presence of a DNAPL.
With regard to the commenter's assertion that the detection of PCBs are indicative of a
dioxin problem at the landfill, once again EPA questions the scientific basis for this
reasoning. The RI only reported PCB's in three of the 25 soil samples collected from the
landfill. Concentrations for the PCBs reported were very low, generally an order of
magnitude lower than any cleanup criteria. Clearly the infrequent detection of PCBs at
very low concentrations is not a sound scientific basis for suggesting that there is even a
PCB problem, much less a concern for dioxins at the site.
There is no evidence that this landfill was operated as a hazardous waste facility, or that is
was operated any differently than other solid waste landfills in Florida during the same
time period. Clearly this landfill did receive a large volume of solid waste, some of which
had hazardous constituents, that need to be addressed through a proper closure of the
landfill pursuant to state law.
16) Comment: Some of the commenters suggested that the calibration of wells along the
eastern hydraulic barrier during the 1996 study may have skewed the study results. They
seem to suggest that the pumping of the wells created a temporary hydraulic barrier, thus
reducing the amount of leachate discharging from the landfill.
EPA Response: EPA disagrees with the commenters allegations that the calibration of the
wells skewed the 1996 study results. First the commenters fail to acknowledge the limited
affect of the calibration test. Only one horizontal well was operated at a time, with a
pumping duration of between 24 to 48 hours. Secondly, the commenters fail to note that
during the August 19-27,1996, collection of samples, the horizontal wells being calibrated
were not in the vicinity of the surface water monitoring (i.e., they were south of the study
area). Finally, a single well, or several wells would not have had an instantaneous,
widespread affect, which would be needed to alter the amount of leachate discharged.
The calibration of the wells could not have had any significant impact on the surface water
monitoring. Had EPA been concerned that it may have caused a problem, we would have
easily rescheduled the calibration monitoring. EPA finds it difficult to follow the logic of
the commenter's arguments, since on the one hand they have argued that the long-term
operation of the barrier will not be effective in capturing the leachate from the landfill,
while on the other hand, they argue that the pumping of a well operated for a couple of
days could affect the amount of leachate discharged.
EPA's assessment of the lack of impact of the calibration test is further substantiated by
the results from the 1997 sampling. Had the calibration test affected the leachate
discharge as alleged by the commenters, there should have been a significant increase in
8
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5 9 • 0049
the concentrations of ammonia reported in the 1997 sampling. The 1997;kvels, however,
were consistent with those observed in 1996.
17) Comment: A commenter questioned why metal analyses were not conducted in the 1996
study.
EPA Response: Analyses for metals were conducted in accordance with the EPA
Contract Laboratory Program Target Analyte List for all 17 surface water samples
collected during the 1996 study. The results are summarized in Table 5-5 of the Water
Quality and Toxicity Reassessment Study (1997). The commenter may have overlooked
the results due to the small number of metals detected.
18) Comment: A commenter questioned why EPA had not attempted to disavow any of its
findings in the 1994 Explanation of Significant Differences changing the treatment from air
stripping to the Publicly Owned Treatment Works (POTW). The commenter noted that
the basis for the change in treatment was based on the lack of effectiveness in the removal
of ammonia.
EPA Response: After the BSD, and as the pumping rates needed to implement the
hydraulic barrier were refined during the design process, it became apparent that the
pumping rate needed to implement the barrier would exceed the capacity formerly allotted
by the POTW. The estimated cost associated with treatment of the waste at the POTW
was significantly higher than originally projected. Therefore, the City, in consultation with
EPA, FDEP, and DERM, decided to pursue other, more cost-effective, on-site treatment
options.
Treaiabiiiiy studies using biological processes demonstrated that the ammonia and
associated toxicity could be effectively removed from the contaminated groundwater.
These results are summarized in the Draft Design Report, Munisport Landfill Superfund
Site, SECOR International, 1996, Appendix A. If the 1996 reassessment of the
Mangrove Preserve had not shown that no further action was warranted pursuant to
CERCLA, the next step after the completion of the bioremediation treatability studies
would have been to proceed with a second ESD changing the treatment from POTW to
biological.
19) Comment: A commenter states that EPA does not and cannot assert that groundwater
discharging from the landfill is not currently in violation of State regulations for
Outstanding Florida Water.
EPA Response: EPA has never suggested that the water quality underlying the landfill
does not comply with State and County standards. The original ROD was issued solely to
address the environmental threat posed by the toxicity to aquatic organisms documented in
the Mangrove Preserve in 1989. EPA's action was not taken in an effort to remediate the
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groundwater, but was taken solely to abate the threat to aquatic organisms caused by the
toxic conditions in the Mangrove Preserve.
Furthermore, its is important to remember that due to the closing of municipal supply
wells, the City petitioned EPA to delete the site from the NPL. EPA cited its policy of not
rescoring sites after they are finalized on the NPL, but agreed to conduct an RJ and risk
assessment of the site, and if the site did not pose any threat to human health or the
environment, it would be deleted from the NPL. Therefore, had a toxicity problem not
been documented in 1989, EPA would not have taken likely taken an action in absence of
an environmental or human health threat
*
20) Comment: A commenter stated that the 1996 and 1997 studies are wholly inadequate to
support the amendment to the ROD to no further action. The commenter further argues
that the amendment would have the effect of deleting the site from the NPL, eliminating
the oversight by the United States District Court. The commenter also questions the
appropriateness of EPA's amendment of the ROD in light of the significant work already
conducted with regard to the installation of the groundwater recovery system.
EPA Comment: EPA disagrees with the commenters general assertion that the studies
have been inadequate to support EPA's basis for no further action under Superfund. With
regard to the lack of future oversight by the United States District Court, the Court's
future involvement is not a criterion used by EPA in deciding whether or not to amend
RODs nor to make any technical decision. The Court even noted at the June 26,1997,
status conference that the community's desire alone, is not enough to keep the Court'""
involved, should EPA decide that no further response under Superfund is warranted.
Finally, the degree of construction of the hydraulic barrier was not a consideration in the
amendment of the ROD. The ROD was amended solely based on the compelling
information that shows that the remedial actions to date have been adequate to abate the
threat to the environment such that no further action under Superfund is warranted.
21) Comment: S ome of the commenters argued that EPA had not completed all of the
components of the ROD nor had it attained the cleanup goals specified therein.
EPA Response: As EPA explain in its Proposed Plan, and stated during the public
meetings, it was not the intent of EPA's action to determine that all of the components of
the remedy were completed nor that all of die cleanup criteria had been attained. Rather,
it was the Agency's determination that the threat to the environment documented in 1989
had been abated through the implementation of the tidal restoration to the Mangrove
Preserve, thus meeting the intent of the 1990 ROD. Since the intent of the action was
achieved through the tidal restoration, it was no longer necessary to implement the balance
of the cleanup criteria pursuant to CERCLA.
10
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It is important to note, however, that groundwater contamination remains at the site,
primarily from ammonia levels that exceed Dade County water quality criteria. These
criteria were promulgated by the County and are more stringent than the requirements of
CERCLA. Therefore, DERM has advised EPA, the State, City, and public that it intends
to enforce its standards and require the City to adopt the same groundwater containment
system to minimize off-site discharges of contaminated groundwater at levels in excess of
the County's water quality standards.
22) Comment: A commenter questioned why EPA had not structured the Proposed Plan to
included a proposal of no action and the selected remedy in the 1990 ROD, and evaluate
the two options in accordance with the nine criteria (i.e., overall protection, compliance
with ARARs, long-term effectiveness and permanence, reduction in toxicity, mobility or
volume, short-term effectiveness, implementability, cost, state acceptance, and community
acceptance) established pursuant to 40 CFR 300.430(e).
EPA Response: As noted in other responses, the fundamental basis for EPA's decision is
that actions to date have remedied the problem such that further responses pursuant to
CERCLA are no longer needed. Had the actions only partially abated the threat such that
additional response pursuant CERCLA was needed, and EPA had proposed to continue
with a CERCLA response different ^rom the original action, the commenter would have
been correct in noting that an evaluation of any new alternatives with the old alternative
would have been necessary. However, in absence of the need for any further action under
CERCLA, there is no alternative for comparison as established in EPA guidance for
developing No Action Proposed Plans and RODs (See Interim Final Guidance on
Preparing Superfund Decision Documents, June 1989, OSWER Directive 93553-02).
23) Comment: One of the commenters suggested that EPA had attempted io replace its
remedy with landfill closure, but had not demonstrated to the public how the closure will
satisfy the requirements of the ROD.
EPA Comment: It was never the intent of the intent of EPA to suggest in the Proposed
Plan that the landfill closure would satisfy the requirements of the ROD. EPA's
determination of no further action was made independent of, and was not contingent on,
any actions that the State or County may require in the future. Information about possible
future actions was included in the Proposed Plan and the ROD Amendment, and was
discussed at the public meetings and the recent status conference for informational
purposes only. EPA, in consultation with the State and County, thought this information
may help to alleviate concerns of interested parties that felt that additional actions, beyond
the requirements of CERCLA were still needed at the site.
24) Comment: One of the commenters questions why, after requiring the City to implement
so much of the remedy required in the 1990 ROD, EPA is trying so hard to justify calling
die partial remedial action a successful cleanup. The commenter offers technical
11
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difficulties and high cost in implementing the remedy as possible explanations for EPA not
following through with the original remedy.
EPA Response: The commenter raised an interesting issue. EPA does not believe that
partial construction of the remedy (e.g., causeway breach, hydraulic barrier, and service
road) is proper justification for implementing the balance of the remedy. The only reason
for EPA to continue with the implementation of the remedy would be if it was necessary
to protect the environment pursuant to the requirements of CERCLA, which is no longer
the case. The commenter seems to suggest that in spite of the fact that there are statutory
and regulator limitations that would prohibit EPA from continuing to take an action in this
case, EPA should proceed with the work since it has already been started. Most certainly,
any party responsible for paying for the cost would object to this logic, since the bulk of
the cost would be incurred not with construction, but long-term operation and
maintenance. Since local governments and the State of Florida are bearing the financial
responsibilty of the cleanup, it is likely that the taxpayers of the State of Florida would
object to the concept
Futhermore, the record shows that the basis for the inclusion of the site on the NPL (i.e.,
closure of municipal wells due to saltwater intrusion) changed after the site was placed on
the NPL. Had EPA agreed to reevaluate the site using the new information, it would not
have scored high enough to remain on the NPL. Assessment of the potential threat
posed by the site during the RI identifed no threat to human health, and only a marginal
threat to the environment. A further assessment of the potential threat during the ^
Mangrove Study did indicate a threat to the environment EPA questioned at the time
whether or not the tidal restoration of the Mangrove Preserve would have been adequate
to mitigate the threat. However, in view of the community's and some regulatory
agency's objection to the no action alternative proposed in 1988, EPA felt that it must
proceed with a more proactive and comprehensive remedial alternative provided in the
1990 ROD.
25) Comment: One of the commenters argued that the selected remedy in the original ROD
was flawed. Specifically, the commenter felt that the containment strategy was flawed,
and should have adopted an approach that included 1) removal of 20% of the buried
waste, 2) capping of the landfill with a low permeabiliy cover, and 3) collection and
treatment of contamianted ground water in the saltwater portion of the aquifer.
EPA Response: The selected remedy in the original ROD was not the subject of review
during the comment period for the proposed ROD amendment These and other issues
were addressed during the comment period for the original ROD. Nevertheless, a brief
response to the commenters approach is provided.
The commenter makes several flaws in his reasoning that excavation of solid waste in
areas of hot spots of contamination is even feasible. First, with respect to the excavation
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and disposal of 20% (i.e., hot spots) of the solid waste, there are no disposal records, nor
does the information from the numerous investigations show that waste were disposed of
in discrete areas that could be identifed and excavated. EPA does not subscribe to the
theory that borrow pits that were backfilled with soild waste, or that monitoring wells with
elevated levels of ammonia, provide sufficient information to even identify a "hot spot",
much less define a discrete area for excavation. Secondly, in the unlikely event that
discrete areas of contamination could be identfied, based on the opposition received from
the commity during the clearing of vegetation during the construction of the road, it is
doubtful that the community would support the excavation of 1.2 million cubic yards (i.e.,
20% of landfill volume) of garbage. Excavation of this volume of garbage would involve
the loading and hauling of garbage using approximately 60,000 trucks, and take
approximately 4 years to complete. The excavation would also raise other logistical
problems such as the control of odors, transportation through congested areas, and the
identification of an acceptable disposal location. In addition to logistical problems, the
issue of cost would have to be addressed. The cost for excavation and disposal of 1.2
million could easily exceed $100,000,000, and as noted earlier, the local and state
governments (i.e., the taxpayers) would ultimately bear the cost of the cleanup. Finally,
there is no evidence to suggest that this approach would achive a higher degree of
protection than a containment approach, certainly not in view of the financial hardship and
other burdens it would place on the community.
The issue of whether or not to use a permeable or impermeable cover-has been debated
over the past serval years. As the commenter noted, there are advantages and
disadvantages with either approach. However, the selected remedy in the ROD was
developed using the premise that the landfill would be closed using a permable cover, an
approach endorsed by the Technical Advisory Committee. Nevertheless, regardless of
EPA's or the commenters views on the appropriate landfill cover, this is a landfill closure
issue that will ultimately be decided through the State's landfill closure process
With regard to the issue of the collection and treatment of deep groundwater
contamination at the base of the aquifer, results from the RI and other design studies
clearly show a decline in the contaminants below the transition from the freshwater to
saltwater portion of the aquifer. The degradation of the base of the aquifer by saltwater
has rendered the water unsuitable for potable purposes. Hydraulic influences of the ocean
would limit the environmental impact that low levels of contaminants could potentially
have on the Bay, as well as the effectiveness of a groundwater recovery and treatment
system in the lower saltwater portion of the aquifer.
26) Comment: A commenter questioned whether or not EPA had considered the impact of
the landfill on the Biscayne Bay by not addressing the deeper groundwater contamination
and DNAPLs, and not requiring the operation of the hydraulic barrier system.
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EPA Response: EPA disagrees with the commenters premise that there is a deep
groundwater contamination or DNAPL problem, or that contaminants that migrate to the
deep portion of the aquifer would pose a threat to Biscayne Bay. As explained in other
responses, the RI report and other design studies show that the contamination is primarly
limited to the upper, freshwater portion of the aquifer. Results from the Rl and design
studies also show a distinct freshwater-saltwater mixing zone, beneath which is saltwater
as a result of the migration of water from the ocean. Due to the hydraulic influence of the
ocean and inland encroachment of saltwater, low levels of contaminants that migrate into
the deeper saltwater portion of the aquifer would not be expected to discharge in
significant quantities in the Bay.
In contrast to the saltwater zone, the RI and design studies have defined a freshwater
gradient toward the east, southeast, and south, discharging into the Mangrove Preserve
and Bay. Years ago when there were higher levels of water in the aquifer, direct
discharges of freshwater in the form of springs had been documented. However, with the
increased demands placed on the aquifer from increases in population and agriculture in
south Florida, freshwater reserves have been reduced, resulting in saltwater intrusion and
in a decrease in the direct discharge of freshwater to Biscayne Bay. This change in the
aquifer is evident by the closing of local municipal wellfields near the coast, and a long-
range plan by the South Florida Water Management District to relocate other municipal
wellfields further inland.
Therefore, EPA's original remedy was designed to address the migration of leachate from
the landfill into the freshwater portion of the aquifer, and discharging into the Mangrove
Preserve. The remedy was also designed to indirectly address the migration of
contaminants into the Bay, through controlling the discharge of groundwater to surface
water of the Preserve that is tidally connected with the Bay. As noted, however, in
previous responses, the threat posed by the discharge of leachate-contaminated
groundwater to the Preserve has been mitigated through the increased tidal flow in the
Preserve such that an additional response pursuant to CERCLA is no longer warranted.
With regard to the commenter's allegation of DNAPLs at the base of the aquifer, EPA
explained in previous responses that there is no indication of the presence of DNAPL's.
27) Comment: A commenter questioned whether or not ammonia was the sole cause of the
toxicity. In support of his position, the commenter citevd references from studies and
observations from reports by EPA and other agencies in the 1980's. The commenter also
referred to EPA's change in the treatment approach from air stripping to off-site treatment
as evidence of other toxicants.
EPA Response: It is true that early in this project EPA questioned whether or not all of
the toxicity observed in the 1989 Mangrove Preserve study was attributable to ammonia.
However, as part of the remedial design process, EPA conducted several treatability
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studies that evaluated the effectiveness of various treatment approachs that eventually
demonstrated that ammonia was the cause of the toxicity...not some "unknown toxicant"
The treatability studies involved both bench and pilot-scale studies and involved full
chemical analyses and toxicity tests. Intitial tests were based on the the premise that
ammonia levels would need to be reduced to approximately 4 mg/1 to remove the toxicity.
A bench-scale test was conducted to evalutate the effectiveness of air stripping in the
removal of ammonia. Air stripping was effective in removal of ammonia down to the 4
mg/1, however, not all of the toxicity was removed. Although EPA used this information
to change the remedy from air stripping to off-site treatment and disposal at a local
POTW, concerns about high treatment volumes and costs prompted EPA and the City to
conduct additional treatability studies to evaluate other potentially viable alternatives.
To further evaluate treatment alternatives that would remove the toxicity, EPA and the
Qty conducted a series of treatability studies in 1995 and 1996 to evaulate the
effectiveness of biological processes in the treatment of the ammonia contaminated
groundwater. Although there were varing degrees in the effectiveness of the ammonia
removal among the vendors used, the successful vendors were able to reduce the ammonia
level to below 1 mg/1. No toxicity was reported below 1 mg/1. This result, coupled with
the fact that chemcial analyses of the samples revealed no other contaminants in the
samples at levels which could cause any toxicity led EPA to the conclusion that elevated
levels of ammonia were the cause of the toxicity. Since the commenter did not reference
the 1995 and 1996 treatability studies in his comments, it is possible that he was unaware
of the recent tests. The test results are presented in the Bioremediation Treatability
Verification Status Report Update, Munisport Landfill Superfund Site, SECOR
International, Inc., September 1996, and included in the Administrative Record for this
site.
28) Comment: A commenter questioned the reliabilty of the RI and whether or not EPA had
followed its guidance for investigating CERCLA municipal landfills. The commenter
primarily refers to comments from the Florida Health and Rehabilitative Services (FHRS)
regarding the recommendation for additional characterization of the contents of the
landfill. The commenter also suggested that EPA had not followed its own guidance of
conducting investigations at landfills when "hot spots" are known or suspected.
EPA Response: EPA disagrees with the commenter, and has publically stated its
disagreement with the recommendations of FHRS that the contents of the landfill be
characterized. EPA explained that given the large volume (i.e., 6,000,000 cubic yards) of
solid waste, and since there was no evidence of discrete hazardous waste disposal, EPA
employed a containment approach. Consistent with EPA's guidance, there was no need to
characterize the contents of the landfill unless an area or areas of managable size (i.e., less
than 100,000 cubic yards) could be located and delineated for management apart from the
landfill
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Unfortunately, only antic dotal information and generic dispoal records exist regarding the
disposal of waste at the landfill. Although there was an opportunity for the disposal of
hazardous waste at the landfill, the extensive groundwater mentoring well network of over
100 wells has not suggested the presence of discrete disposal areas. EPA was, therefore,
correct in the RI and original ROD for not attempting to characterize the landfill and
adopting a containment approach, respectively.
29) Comment: A commenter suggested that EPA had incorrectly arrived at the conclusion
that the landfill did not pose a threat to threat to public heatlh. The commenter cited
statements from the Florida Department of Natural Resoures that the ammonia plume
reported in the RI showed that there was discharge to Biscayne Bay that would affect the
aquatic life in the Bay and heatlh of recreactional users of the Oleta River Recreaction
Area. The commenter also voiced concern that there are other contaminants at the
landfill, other than ammonia, such as PCBs, that could pose a threat to human health and
the environment
EPA Response: EPA disagrees with the commenter's assertion that there are other
contaminants present at the landfill that would pose a threat to human health or the
environment The commenter refers to the infrequent detection of PCBs in surface soil as
evidence of the presence of other contaminants that could cause a threat As noted earlier,
there is no evidence that there is a PCB problem. PCBs were only detected at low-levels
in three of the 25 soil samples collected from the landfill. PCBs were not detected in any
of the groundwater or sediment samples which would have been a reliable indicator of,
whether or not PCBs, or other contaminants, were present and migrating from the landfill.
Although PCBs were detected in fish tissue samples collected from the perifery of the
landfill and Mangrove Preserve, comparable levels of PCBs were also detected in the
background samples as well. Given the lack of significant PCB contamination at the
landfill, and the detection of PCBs in background samples, EPA concluded that PCB
contamination detected in the fish was not related to the landfill, but other point and non-
point discharges to the Bay.
Another example of a problem in Biscayne Bay that was incorrectly associated with
Munisport by critics of EPA's assessement of the site was a problem of elevated levels of
fecal coliform detected in the northern portion of Biscayne Bay, that resulted in the
temporary closing of the Oleta River State Park to swimming. The critics first assumed .
that the landfill was the source of the contamination, in spite of the fact that colifiorm
bacteria would not have survived for a significant length of time without an ongoing or
renewed source, which was not the case with Munisport since the dumping of solid waste
ceased years ago. Samples were even collected from the perifery of the landfill to help
show that the landfill was not the source of the fecal coliform contamination. It was not
until a break in a sewage main crossing the Oleta River was discovered that the critics
were convinced that the landfill was not the source of the fecal coliform contamination.
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.'i
This is just one example of the discharge of contaminants to Bisycane Bay from sources
other than the Munisport Landfill.
30) Comment: A commemer suggested EPA had somehow limited or controlled the National
Oceanic and Atmospheric Adminsitration's (NOAA) (the marine natural resourse trustee
for this site) review of the proposed amendment of the ROD to no further action. The
commenter noted that NOAA had formerly opposed EPA's plan of no action, and implies
that NOAA must have been influenced by EPA in not objecting to the amendment of the
ROD.
EPA Comment: EPA objects to the commeter's allegation that EPA somehow influenced
NOAA's position. Moreover, these comments are not related to any technical issues.
One must ask that if EPA had the ability to influence NOAA's assessment of the site, it
would have been exercised with the 1988 proposal of no action. NOAA's opposition to
the proposal shows that its decisions are formulated independently of EPA's influence, and
reflect what NOAA believed was best for its trust resources at the time.
The commenter fails to note that NOAA has properly taken into account the additional
information that has been collected since the completion of the RI and the affect of the
tidal restoration on the Mangrove Preserve in formulating its current assessment site.
With regard to the reassessment of the Mangrove Preserve, NOAA was involved in the
formulation of the sampling strategy as well as participating in the field work. Clearly,
NOAA was intimately involved in the reassessment of the water quality and toxicity
conditions in the Mangrove Preserve. NOAA was also part of the peer review of the ^
report, draft Proposed Plan, and draft ROD Amendment NOAA provided some minor
comments on the report, and verbal conveyance of concurrence with the plan. After
review of the Proposed Plan and draft ROD amendment. NOAA provided formal
concurrence with the ROD Amendment on August 11,1997. NOAA's comments will be
included in the Administrative Record for the Site.
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