PB95-964026
EPA/ROD/R04-95/239
January 1996
EPA Superfund
Record of Decision:
Taylor Road Landfill Site,
Hillsborough County, FL
9/29/1995
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RECORD OF DECISION
TAYLOR ROAD LANDFILL
SUPERFUND SITE
Hillsborough County, Florida
Prepared By:
Environmental Protection Agency
Region IV
Atlanta, Georgia
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RECORD OF DECISION
TAYLOR ROAD LANDFILL ST7PERFT7ND SITE
DECLARATION
SITE NAME AND LOCATION
Taylor Road Landfill Superfund Site •
Hillsborough County, Florida
STATEMENT OF BASIS AND PURPOSE OF RECORD OF DECISION
This decision document presents the selected remedial action for
the Taylor Road Landfill Superfund Site, Hillsborough County,
Florida, which was chosen in accordance with the Comprehensive
Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA), and, to the extent
practicable, with the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP) . This decision is based on the
Administrative Record file for this site.
The State of Florida, as represented by the Florida Department of
Environmental Protection (FDEP), has been the support agency
during the Remedial Investigation and Feasibility Study process
for the Taylor Road Landfill site. As the support agency, FDEP
has provided input during the process, in accordance with 40 CFR
300.430. 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.
ASSESSMENT OF THE SITE
If not addressed by implementing the response action selected in
this Record of Decision (ROD), actual or threatened releases of
hazardous substances from this site may present an imminent and
substantial endangerment to public health, welfare, or the
environment.
DESCRIPTION OF THE REMEDY
This remedy is the final action for the site. The function of
this remedy is to reduce the risks associated with potential
exposure to contaminated ground water in the Floridan aquifer.
The major components of the selected remedy to be implemented
include
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The use of existing and future institutional controls to
restrict construction of new potable-water wells that would
extract water affected by the Taylor Road Landfill
Modification of the existing County ground water-monitoring
program to include quarterly monitoring of a "ring" of existing
and future monitor wells placed with the objective of better
defining and enclosing the area of ground water exceeding the
Florida Primary and Secondary Drinking Water Standards and
Minimum Criteria
Provision of County water service to human receptors (about 20
residences) within a "ring" of monitor wells and within a
"buffer zone" that extends 270 ft outward from the "ring"
Contingent expansion of monitor well "ring" and provision of
County water to additional receptors
Natural Attenuation with contingent corrective action if
monitoring reveals that it is needed
STATUTORY DETERMINATION
The selected remedy is protective of human health and the
environment, is cost, effective, and complies with federal and
state requirements that are legally applicable or relevant and
appropriate to the remedial action. Because of site-specific.
conditions, EPA used the flexibility provided in the NCP to set
the point of compliance with ground water Maximum Contaminant
Levels at the perimeter of an area containing all three of the
adjacent Study Area landfills. Landfill waste will be left in
place; therefore, this remedy does not satisfy the statutory
preference for treatment as a principal element.
Because 'this remedy will result in hazardous substances remaining
on-site in levels above health-based limits, a review will be
conducted within 5 years after commencement of the remedial
action to ensure that the remedy continues to provide adequate
human health and the environment .
Richard D. Green Date
Associate Director of Superfund
and Emergency Response,
U.S. Environmental
Protection Agency,
Region IV
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TABLE OF CONTENTS
PAGE
1. 0 Site Location and Description 2
2.0 Site History and Enforcement Activities 5
2 .1 Landfill Operation 5
2.2 Regulatory Response 6
3 . 0 Highlights of Community Participation 9
4.0 Scope and Role of Response Action 11
5.0 Summary of Site Characteristics 1-2
5.1 Topography and Surface Drainage 12
5 .2 Site Hydrogeology/Hydrostratigraphy 12
5.3 Sampling Results 13
6 . 0 Baseline Risk Assessment Summary 22
6.1 Chemicals of Potential Concern 22
6.2 Human Health Risks ..23 .
6.2.1 Exposure Assessment Summary 23
6.2.2 Toxicity Assessment Summary ...23
6.2.3 Risk Characterization 24
6.3 Summary of Environmental Assessment 26
7 .0 Description of Remedial Alternatives 27
7 .1 Alternative No. 1 - No Action 27
7.2 Alternative No. 2 - Prevent Human Exposure
to Contaminated Groundwater 27
7.2.1 Measures to Prevent Human Exposures
Under Alternative 2 27
7.2.2 Contingent and Noncontingent
Approaches to Prvent Human Exposures
Under Alternative 2 30
7.2.3 Role of Natural Attenuation in
Preventing Human Exposure Under
Alternative 2 31
7.3 Alternative No. 3 - Collect and Treat Ground
Water at Point of Compliance on a
Contingent Basis 32
7.3.1 Trend Analysis of Data to Substantiate
Attenuation 32
7.3.2 Vinyl Chloride Upgradient of Landfill..32
7.3.3 Control of Vapor-Phase Transport 33
7.4 Alternative No. 4 - Collect and Treat Ground
Water at Landfill Perimeter 33
7.4.1 Viny Chloride from Vapor-Phase
Transport 33
iii
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TABLE OF CONTNBNTS (CONTINUED)
PAGE
8.0 Comparative Analysis of Remedial Alternatives 34
8.1 Overall Protection of Human Health and the
Environment 34
8.2 Compliance with Applicable or Relevant and
Appropriate Requirements 36
8.3 Long-Term Effectiveness .36
8.4 Reduction of Toxicity, Mobility, or Volume
Through Treatment ; .36
8.5 Short-Term Effectiveness 37
8.6 Implementability 37
8.7 Cost 37
8.8 State Acceptance...' 38
8.9 Community Acceptance 38
9 . 0 Selected Remedy 39
9 .1 Major Components of the Remedy 39
. 9.1.1 Institutional Controls 39
9.1.2 Extension of Water Lines
and Montioring 39
9.1.3 Natural Attenuation with Contingent
Corrective Action . . .42
9 .2 Remediation Levels 43
9.3 Location of Point of Compliance 43
9.3.1 Site-Specific Factors 44
10.0 Statutory Determinations 47
10.1 Protection of Human Health and the
Environment 47
10.2 Compliance with Applicable or Relevant and
Appropriate Requirements (ARARs) 47
10 .3 Cost Effectiveness 48
10.4 Utilization of Permanent Solutions to the
Maximum Extent Practicable 49
10.5 Preference for Treatment as a Principal
Element 49
11.0 Documentation of Significant Changes 50
IV
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LIST OF FIGURES AND TABLES
FIGURES • Page
Figure 1.1 Study Area•Location . . 3
Figure 1.2 Study Area Map 4
Figure 5.1 East-West Hydrostratigraphic Geologic
Cross Section 14
Figure.5.2 North-South Hydrostratigraphic Geologic
Cross Section 15
Figure 5.3 Potentiometric Surface in April 1990... 16
Figure 5.4 Ground Water Monitoring Wells and Piezometers.... 17.
Figure 5.5 Ground Water Sample Analytical Results 20
Figure 7.1 Monitoring Ring and 270' Setback 29
Figure 8.1 Glossary of Evaluation Criteria 35
Figure 9.1 Location of Point of Compliance Wells 46
TABLES
Table 5.1 Occurrence and Distribution of Chemicals in
Ground Water 18
Table 6.1 Summary of Cancer and Noncancer Risks by
Exposure Route 25
APPENDIX A - Responsiveness Summary
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RECORD OF DECISION
SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
FOR THE TAYLOR ROAD LANDFILL SUPERFUND SITE,
HILLSBOROUGH COUNTY, FLORIDA
This decision document presents the selected remedial action for
the Taylor Road Landfill Site (the Site)/ in Hillsborough County,
Florida, chosen 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, to the extent practicable, with the National
Contingency Plan (NCP). This decision is based on the
Administrative Record for the Site.
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1.0 SITE LOCATION AND DESCRIPTION
The Site is located in eastern Hillsborough County, Florida, on
County-owned property, approximately 7 miles east of Tampa in the
Seffner-Thonotosassa area (see Figure 1.1). Interstate 4 borders
the Site to the south, and Mango Road (State Route 579) borders
the site to the west (see Figure 1.2) . The County property is
252 acres in size and contains three closed landfills (Figure
1.2) .
The 42-acre Taylor Road Landfill is located east of the 10.6-acre
Florida Department of Transportation (FDOT) Borrow Pit Landfill
and southeast of the 64-acre Hillsborough Heights Landfill. Only
the Taylor Road Landfill is on the National Priorities List
(NPL). However, ground water contamination has moved well beyond
the boundaries of the Taylor Road Landfill. Accordingly, the two
adjacent landfills were evaluated during the Remedial
Investigation/Feasibility Study (RI/FS) to determine if they are
contributing to ground water contamination. Also within the 252
acres are five stormwater-retention basins, County maintenance
facilities, and a community recycling collection center/refuse
collection area. In the RI/FS, the entire 252 acres of County
property, containing all three landfills, is referred to as the
"Study Area."
The land surrounding the landfills serves a variety of uses,
including residential, commercial, and agricultural uses. The
majority of area residents use well water.
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OURCE: ERM-RI
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STUDY AREA LOCATION
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SOURCE: ERM-R1
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STUDY AREA MAP
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TAYLOR ROAD LANDFILL STUDY AREA
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1.2
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2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
2.1 LANDFILL OPERATION
The three landfills were developed sequentially. The first,
known as the Taylor Road Landfill, had been an FDOT borrow pit
until it was permitted as a solid waste landfill for Hillsborough
County in 1975. The Taylor Road Landfill was not constructed
with a liner or leachate collection system. From May 1976 until
February 1980, the County operated the Taylor Road Landfill,
which was intended for the disposal of residential, commercial,
and industrial refuse. A total of 620,000 tons was disposed of
in the landfill. An unknown quantity of hazardous waste is
suspected to have been buried at this landfill. In the late
1970s, two events precipitated the development of capacity
problems within the Taylor Road Landfill. One of these events
was the settling of a legal dispute with EPA by the City of
Tampa, during which the city agreed to close its incinerator by
January 1. 1980. This event diverted an estimated 790 tons of
refuse per day to the Taylor Road Landfill. At the same time,
another local landfill was closed, adding 490 tons of solid waste
per day to the Taylor Road Landfill disposal load. Because of
the discontinuation of the incinerator operation/'waste generated
from area hospitals, clinics, and other health providers also
began to be buried at the Taylor Road Landfill.
In February 1980, the.Taylor Road Landfill reached its capacity,
and landfill operations were moved to an adjacent 10.6-acre
parcel known as the FDOT Borrow Pit Landfill. The Borrow Pit
Landfill was developed to operate as a high-rise sanitary
landfill for residential, commercial, industrial, and
agricultural wastes; dead animals; and water treatment sludge.
The Borrow Pit Landfill was constructed with a liner and a
leachate collection system, and was operated by Waste Management,
Inc., of Florida. The Borrow Pit Landfill was to serve as a
temporary site, pending the design, permitting, and construction
of a proposed 200-acre landfill on the adjacent property to the
north. A total of 320,000 tons of waste was disposed of in the
'Borrow Pit Landfill.
The application to extend the Taylor Road Landfill was met by
strong public opposition from a neighborhood group, later
organized as the Taylor Road Civic. Association (TRCA) . The
organization's petition to FDER (subsequently renamed FDEP)
charged that the County failed to properly maintain the Site.
On January 21, 1980, FDER initially approved the permit with
certain caveats, including FDER's warning that landfilling
.operations could not proceed should any determination be made
that ground water was being contaminated by the existing Taylor
Road Landfill or the Borrow Pit Landfill. Ultimately, however.
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FDER rejected the 200-acre landfill expansion project, resolving
that no guarantee of an environmentally safe operation could be
given, and that additional wastes deposited on the site would add
to the existing potential hazards.
The County continued to use the Borrow Pit Landfill until October
1980, when waste disposal operations were transferred to a third,
64-acre, property located north and west of the two previous
landfills. This property, known as the Hillsborough Heights
Landfill, was constructed and operated by Waste Management, Inc.,
of Florida.
The Hillsborough Heights Landfill was opened under emergency
order by FDER, and occupied a portion of the 200 acres that FDER
previously had rejected. In the landfill's early months of
operation, infectious wastes from hospitals, clinics,
laboratories, and doctors' offices were among the refuse disposed
of there. The landfill remained open for 4 years, until October
1984, when land disposal of wastes in that area of Hillsborough
County was discontinued. The Hillsborough Heights Landfill was
constructed with a liner and a leachate collection system.
Approximately 3,500,000 tons of waste was disposed of in the
Hillsborough Heights Landfill.
2.2 REGULATORY RESPONSE
In October 1979, as part of a nationwide program of ground water
sampling and analysis, EPA tested monitor wells and private wells
in the Taylor Road Landfill Site area. Results of the sampling
revealed the presence of volatile organic compounds (VOCs) and
metals contamination in site monitoring wells and numerous
private wells. The. highest contaminant concentrations were found
within the site. Subsequently, EPA advised residents in the
immediate vicinity of the site to discontinue use of their wells.
The County established a program of bottled-water delivery to 95
residences within a specified radial distance of the Taylor Road
Landfill, and authorized the construction of County water lines
to the affected areas. Further ground water investigations
revealed that a plume of VOCs at concentrations exceeding the
acceptable drinking-water standards established under the Safe
Drinking Water Act (SDWA) was migrating off-site into residential
areas. At one time, methane gas from the Taylor Road Landfill
was detected near residences adjacent to the Site, in potentially
explosive concentrations. In April 1980, water delivery was
expanded to 180 homes and businesses. About 400 residences and
businesses were eventually connected to the County water supply.
In October 1980, EPA filed suit against the County under the
Resource Conservation and Recovery Act (RCRA) and the SDWA,
alleging the existence of ground water contamination from solid
and hazardous waste. EPA sought injunctive relief and demanded
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the implementation of certain operational and remedial measures
at the site. The complaint also sought the abatement of hazards
caused by methane gas released at or attributable to the Taylor
Road Landfill.
Because of the ground water contamination, in October 1981, EPA
added the Taylor Road Landfill to the NPL of uncontrolled waste
sites under the federal Superfund program; The Taylor Road
Landfill received a Hazard Ranking System score of 51.,37, which
qualified the Site for inclusion on the NPL.
As EPA was developing administrative procedures for the newly
created Superfund program, it pursued cleanup of the Site under
RCRA, a previously established EPA program that, in part,
controls hazardous waste management. Under a Consent Decree
signed in September 1983 by EPA, FDER, and the County, the County
agreed to a 30-year maintenance and environmental monitoring
program governing all three landfills on County property. The
decree specified requirements for the cap, cover, and drainage
ditch, and for methane gas control. In February 1984, the County
began installing methane monitoring wells around all three
landfills in compliance with the Consent Decree, and commenced
construction of a gas collection system, cap, cover, and drainage
system at the Taylor Road Landfill. In addition, the County
installed a water supply system to serve residents in a specified
area south of the landfills, and proceeded with a routine
sampling program, which is currently ongoing.
The County's routine sampling-program demonstrated that VOCs
continued to appear in wells around the Site. In 1986, EPA
initiated a Forward Planning Study under the Superfund program to
investigate all potential contaminant sources in the Taylor Road
vicinity. In 1987, EPA initiated an area-wide private well
sampling effort that used information gathered during the Forward
Planning Study and previous studies to investigate further
possible sources of contamination.
In September 1987, EPA notified Hillsborough County and Waste
Management, Inc., that they were potentially responsible parties
(PRPs) relative to the Taylor Road Landfill site, and informed
them of their opportunity to participate in the RI/FS to be
performed under Superfund. Both PRPs requested that EPA
investigate additional PRPs. In addition, they asked to review
EPA's ground water study before they were to conduct negotiations
for the performance of the RI/FS.
In 1988, EPA contracted CDM Federal Programs Corporation (CDM) to
conduct a responsible party search. Investigative activities
during the next several years included the review and compiling
of documents from State and County agencies and the issuing of
information request letters. In July 1992, Special Notice
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Letters were issued to approximately 45 PRPs presenting them with
the opportunity to conduct the RI/FS. In February 1993, an
Administrative Order on Consent was signed by EPA and 19 PRPs.
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3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
In accordance with Sections 113 and 117 of CERCLA, EPA has
conducted community relations activities concerning the Site to
ensure that the public remains informed of activities at the
Site.
Community concern in the Site area was noted first in 1979 by
officials who received complaints of health problems. In 1980,
area residents organized in vocal protest to the County's
proposal to expand landfill activities. Area residents, who
subsequently formed the TRCA, complained to State and County
officials that the Taylor Road Landfill had been poorly managed
and that their well water had become contaminated. The TRCA
filed a formal petition to FDER objecting to the landfill
expansion, a.ttended meetings of the County Board of
'Commissioners, reviewed reports prepared for and by the County,
consulted with hydrogeologic experts, conducted public protest
demonstrations, distributed leaflets to Seffner area residents,
and routinely monitored"the landfill activities.
A community relations plan (CRP) was developed in 1989 and
revised in.1993 to establish EPA's plan for community
participation during remedial activities. A primary concern of
residents in the Site area continues to be current or future
contamination of their drinking-water wells. They express
concern that the monitor well network currently in place may not
detect periodic contaminant migration, and that, given the
sinkhole activity seen in the Site area, it is possible that the
landfill bottoms will collapse into the aquifer and cause
widespread contamination.
In December 1993, EPA approved the TRCA's application for a
Technical Assistance Grant (TAG). Congress included provisions
in SARA to establish the grant program to promote public
involvement in the decisions made on site-specific cleanup
strategies under Superfund. The TRCA has used the grant funds to
hire a technical advisor to help it understand and have input
into the RI/FS process. The community group's technical advisor
has attended several RI/FS planning meetings and has helped the
group to generate comments on draft versions of various RI/FS
documents. Many of these comments have been incorporated into or
considered in the final documents.
Following completion of the RI/FS, a Proposed Plan fact sheet was
mailed to local residents and public officials on July 14, 1995.
The fact sheet detailed EPA's preferred alternative for
addressing the Site contamination. Additionally, the
Administrative Record for the Site, which contains site-related
documents including the RI and FS reports and the Proposed Plan,
was made available for public review at the information
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repository located in the Thonotosassa Public Library. A notice
of the availability of the Administrative Record for the Taylor
Road Landfill site was published in the Tampa Tribune on July 16,
1995.
EPA held a public meeting on July 27, 19.95, at. the Evans Park
Community Center to discuss the remedial alternatives under
consideration and to answer any questions concerning the proposed
plan for the Site. A 30-day public comment period was held from
July 17, 1995, to August 16, 1996, to solicit public input on
EPA's preferred alternative. EPA's response to each of the
comments received at the public meeting or during the public
comment period is presented in the Responsiveness Summary
provided in Appendix A of this ROD.
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4.0 SCOPE AND ROLE OF RESPONSE ACTION
Remediation at the Site will address the ground water. The
Floridan aquifer is the source of drinking water for a large
number of local residents. A variety of site-related chemicals
pose the Site's principal threat to human health and the
environment because of the risks .associated with possible
ingestion or dermal contact. The cleanup objectives of the
selected remedy are to prevent current or future exposure to
contaminated ground water through provision of County water to
residents and through natural attenuation or active treatment of
ground water should future conditions indicate that it is
necessary.
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5.0 SUMMARY OF SITE CHARACTERISTICS
The following summaries of site characteristics are excerpts or
summaries of information from the Final Remedial Investigation
Report by ERM-South Inc. (ERM) , which is available in the site
repositories.
5.1 TOPOGRAPHY AND SURFACE DRAINAGE
The Taylor Road Landfill Study Area is located within an
internally drained portion of the Polk Upland karst escarpment
that has been called the Brandon Karst Terrain. The Study Area
is on a small ridge that extends northward from the Brandon Karst
Terrain. In the vicinity of the Study Area are sinkholes,
headlands of small drainage systems, and distinctive hills that
represent the accumulation of marine and coastal sands.
According to U.S. Geological Survey (USGS) topographic maps, the
original land surface in the quarter section that includes the
Study Area extended from a low of approximately 45 ft above mean
sea level (MSL) in the extreme southwestern corner to a high of
slightly more than 125 ft above MSL in the small hill upon which
the landfill complex has been developed.
5.2 SITE HYDROGEOLOGY/HYDROSTRATIGRAPHY
Figures 5.1 and 5.2 show the relationship of lithostratigraphy
and hydrostratigraphy at the Study Area. The surficial aquifer
is represented by the surficial sands elsewhere in the Brandon
area. At the Study Area, however, the sands are rarely
saturated, and a continuous surficial aquifer does not exist.
The intermediate confining system is represented by the residual
clays and sandy clays of the Hawthorn Group. Because these clays
are blocky and contain pipes and limestone pinnacles, minor
portions are shown to be connected to the underlying Floridan
aquifer. Because the intermediate confining system is not
continuous at the Site, the intermediate aquifer is considered
not to be present. The Floridan aquifer consists of the Tampa
Member and underlying limestones.
An approximate position of the water table is shown in Figures
5.1 and 5.2. This position is based on Hillsb6rough County
Department of Solid Waste (HCDSW) data from September 1992.
September reflects the end of the rainy season and relatively
high water-table positions. The data suggest that water levels
are within the clay section near the Site, and that seasonal
wetting and drying of the clays occurs.
The data clearly reflect the absence of a surficial aquifer at
the Study Area. The Floridan aquifer is generally unconfined or
very poorly confined. The clays of the intermediate confining
unit are apparently sufficiently permeable to show some hydraulic
12
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connection with the Floridan aquifer.
The potentiometric surface of the Floridan aquifer for April 1990
is depicted in Figure 5.3.
5.3 SAMPLING RESULTS
Leachate: The analytical results for leachate indicate the
presence of VOCs, semivolatile organic compounds (SVOCs) , one
pesticide, and inorganics. These samples were collected from
leachate chambers that are not accessible for exposure;
therefore, the leachate results were not further evaluated in the
risk assessment. However, the leachate results were used to
evaluate Site sources.
Surface Water and Sediments: The analytical results for surface
water and sediments taken from the Site infiltration ponds
indicate that inorganics were detected in surface water, and that
VOCs, SVOCs, pesticides, and inorganics were detected i'n
sediments. The types and levels of chemicals present were
determined during the RI to be typical of other stormwater
retention basins in the area. Because these samples were
collected from stormwater-runoff retention basins.., it is unlikely
that human exposure to the basins would occur under current
conditions. However, these media may be accessible for exposure
under future conditions. Therefore, surface water and sediment
data were evaluated during the human health risk assessment. In
addition, surface water and sediment data were evaluated for
potential impacts to ecological receptors.
Ground water: The ground water data selected for evaluation
during the RI were generated from 12 quarterly ground water-
sampling events conducted by the HCDSW from 1990 through 1992,
and from sampling conducted by ERM during August and September
1993. Figure 5.4 shows the locations of monitor wells and some
private wells in the vicinity of the Site. Ground water samples
were analyzed for a list of parameters that included selected
metals, physical parameters, nutrients, and inorganic analytes.
Data, both validated and qualified, that were reviewed are
summarized in Table 5.1, which shows those organic analytes and
selected inorganics that were positively identified in at least
one sample. This table shows the range of detections (minimum,
maximum, and average) above the sample quantitation limit (SQL),
the date on which the sample producing the maximum detection was
collected, the frequency of detection during each year of
sampling (defined as the ratio of detections above the SQL to the
number of samples collected) , and the maximum background
concentration levels (found in Well 27-D). The average
concentration was calculated based on detections only. Figure
5.5 shows the ground water analytical results for April 1993.
13
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Taylor Road Landfill Study Area
Hillsborough County. Florida
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SOURCE: ERM-RI
COM FEDERAL ARCS IV
GROUND WATER MONITORING WELLS AND PIEZOMETERS
CDU FEDERAL PROGRAMS CORPORATION
e< Cup Hi nil * HelCM IDC.
TAYLOR ROAD LANDFILL STUDY AREA
FIGURE NO.
5.4
-------
Table 5.1
OCCURRENCE AND DISTRIBUTION OF CHEMICALS IN GROUNDWATER
TAYLOR ROAD LANDFILL STUDY AREA
HILLSBOROUGH COUNTY, FLORIDA
CONCENTRATION (ug/l)
DETECTED ANALYTE
PURGEABLE ORGANICS
1.1-DICHLOROETHANE
1.1-DICHLOROETHENE
1,2-DICHLOROBENZENE
1,2-OICHLOROETHANE
1,3-DICHLOROBENZENE
1,2-DICHLOROPROPANE
1.4-DICHLOROBENZENE
CARBON DISULFIDE
ACETONE
BENZENE
CHLOROBENZENE
CHLOROFORM
CHLOROMETHANE
DIBROMOCHLOROMETHANE
ETHYLBENZENE
METHYLENE CHLORIDE
TETRACHLOROETHENE
TOLUENE
lrans-1 ,2-DICHLOROETHENE
cis-1 ,2-DICHLOROETHENE
STYRENE
TRICHLOROETHENE
VINYL CHLORIDE
XYLENES (TOTAL)
SELECTED INORGANICS
ARSENIC
BARIUM
CADMIUM
CHROMIUM
COPPER
LEAD
MANGANESE
MERCURY
NICKEL
NITRATES
SELENIUM
VANADIUM
ZINC
Sampling Date
Minimum Maximum Average of Maximum
0.4 192 22 4/90
279 31 1/90
198 20 7/90
3 1.9 7/91
3 2.0 11/91
6 2.0 7/91
45 5.7 4/91
2 3 2.5 11/91
2 279 30 4/91
0.6 12 3.1 1/90
1.1 5.3 3.1 10/92
1 1 1 4/90
222 8/93
666 10/90
1.4 18 5.7 7/91
0.7 54 11 1/90
0.8 145 23 4/90
0.2 82 9 7/91
0.3 135 32 1/90
3 45 16 8/93
333 7/91
1 180 19 10/92
1 105 24 4/90
2 85 12 7/91
3.7 3.7 3.7 8/93
14.2 221 97 8/93
555 4/92
11 11 11 4/92
200 200 200 1/91
1.3 13 4.5 4/92
12.4 2380 320 8/93
0.2 42.3 4.5 7/90
40.7 95.4 68 8/93
30 38700 5200 1/90
222 6/93
53.7 53.7 53.7 8/93
10 403 64 1/91
Frequency of Detection (1)
1990 1991 1992 1993
65/104 33/78 47/88 5/6
28/104 21/78 31/88 4/6
25/104 12/78 14/88 3/6
7/104 2/78 0/88 0/6
1/104 1/78 1/88 0/6
13/104 7/78 11/88 1/8
26/104 20/78 13788;- 3/6
0/104 2/78 0/88 "' 0/6
4/104 18/78 4/42 0/6
29/104 7/78 10/88 2/6
4/104 4/78 7/88 1/6
1/104 0/78 0/88 0/6
0/104 0/78 0/88 1/6
1/.104 0/78 0/88 0/6
Irt04 3/78 1/88 0/6
10/104 5/78 14/88 1/6
44/104 13/78 18/88 2/6
4/104 2/78 4/88 2/6
51/104 29/78 7/88 2/6
NA NA NA 4/6
0/104 1/78 6/88 0/6
56/104 28/78 43/88 4/6
28/104 16/78 23/88 3/6
6/104 8/78 1/88 0/6
NA NA 0/13 1/6
NA NA 1/13 4/6
NA NA 1/13 0/6
NA NA 1/13 0/6
0/16 1/5 0/11 0/6
NA NA 3/13 6/6
5/12 2/5 6/20 3/6
60/104 12/29 27/59 0/6
NA NA NA 2/6
94/104 23/26 44/62 3/6
NA NA NA 1/6
NA NA NA 1/6
8/12 4/5 5/13 1/6
Maximum
In Background
(Well 27-D)
1
5
2
311
2
4460
159
Federal Florida DER
MCL(2) Graundwater
Guidance (3)
7 7"
600 600"
5 3"
600
5 5"
75 75"
5 1"
100" 100"
100 6""
2.7""
4«**t
700 700-/30'"
5 5"
5 3"
1000 1000"/40'"
100 100"
70 70"
100 100"
5 3"
2 1"
10000 10000"/20"'
50 50"
2000 2000"
5 5"
100 100"
1000'"
15' 15"
50"*
2 2"
100 100"
10000 10000"
50 50"
5000'"
USEPA Region III (4,5)
Risk Level. :::HO=0.1:-
=1E-06 •.'•'; I.::.;:-;::?;:;:?:
81
0.044
37
0.12
53
0.16
0.44
2.1
370
0.36
3.9
0.15
1.4
0.13
130
4.1
1.1
75
12
6.1
160
1.6
0.019
1200
0.038 1.1
260
1.8
3700
140
18
1.1
73
5800
18
26
1100
0>p:c||
Y
Y
Y
Y
N
Y
Y
N'
N
Y
N'
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
Y
Y
N
N'
N
N'
N
N'
N
N'
Y
Y
N"
N
N'
N
Source: CDM - BRA
-------
Table 5.1 (continued)
NOTES:
1. Frequency of detection = # of detections/ft of samples.
2. MCL = Maximum Contaminant Level. * - Value for lead is an action level. EPA. December 1993.
3. Florida Department of Environmental Regulations Groundwater Guidance Concentrations. June 1994.
" - Primary Standard. *" - Secondary Standard. *"* - Guidance Concentration.
4. USEPA Region III - Risk-based Concentrations for tap water. January 7,1994.
5. HQ = Hazard Quotient.
6. COPC = Chemical of Potential Concern. Y = Yes. N= No. N* = Not selected as a COPC, because the chemical was not detected or detected at a low
frequency in the wells selected for the risk assessment. N" = Concentrations detected in wells selected for the risk assessment did not exceed two times
the background concentration.
-------
sutmcwL * noROON too.
TAYLOR ROAD LANDRLL STUDY AREA
RGURENO.
5.5
-------
6.0 Baseline Risk Assessment Summary
A baseline risk assessment was conducted by CDM Federal Programs
Corporation for EPA. The baseline risk assessment provides the
basis for taking remedial action, and indicates the exposure
pathways that need to be addressed by the remedial action. It
indicates the risks that could exist if no action were taken at
the Site. This section of the ROD reports the results of the
baseline risk assessment conducted for the Site.
6.1 CHEMICALS OF POTENTIAL CONCERN
Specific chemicals of potential concern (COPCs) were selected if
the results of the risk assessment indicated that they might pose
a significant current or future risk or might contribute to a
significant cumulative risk. COPCs were determined for ground
water as well as for surface water and sediment from the on-site
surface-water-retention ponds.
COPCs for ground water were selected from the list of detected
chemicals by comparing detected concentrations to federal and
state drinking-water standards and guidance concentrations,
action levels, EPA Region III risk-based concentrations1, and
Site background concentrations. In addition, frequency of
detection also was considered. Inorganic and organic chemicals
detected in ground water were selected as COPCs if their maximum
concentrations exceeded federal MCLs, maximum contaminant level
goals (MCLGs), and action levels; Florida Primary Drinking Water
Standards; or EPA Region III risk-based concentrations for tap
water. The Region III risk-based concentrations are derived for
carcinogens based on a risk level of 1E-06 and for noncarcinogens
based on a hazard quotient (HQ) of 1.0. Because simultaneous
exposure to multiple chemicals is possible, the risk-based
concentrations for noncarcinogens were adjusted to an HQ of 0.1,
and these values were used in the selection of COPCs. .Inorganics
were not selected as COPCs if the maximum concentration did not
exceed two times the background concentration. In addition,
inorganics that are essential nutrients or that are normal
components of human diets, such as calcium, iron, magnesium, and
potassium, were excluded from consideration as COPCs. These
inorganics are essential nutrients, for which no toxic effects
are known at any relevant dosage level. Table 5.1 indicates the
chemicals that were selected as COPCs for ground water.
Because no background samples were collected for surface water or
sediment, and because no risk-based concentrations for human
Region III risk-based concentrations are derived for
carcinogens based on a risk level of 1E-06 and for noncarcinogens
based on a hazard quotient of 0.1.
22
-------
exposure are available, no detected compounds except essential
nutrients could be eliminated as COPCs.
6.2 HUMAN HEALTH RISKS
6.2.1 Exposure Assessment Summary
In the risk assessment, landfill waste is considered to be a
chemical source, drinking water wells screened in the Floridan
aquifer are considered to be exposure points, and ingestion of
ground water and inhalation of volatiles released from ground
water are considered to be the feasible routes for human
exposure. Exposure to ground water is considered possible under
both a current-use scenario and a future-use scenario. The
potential receptors for the current and future scenarios are
child and adult residents, and adult workers.
The pathways for leachate and surface water and sediment exposure
are not considered to be complete under current conditions.
Leachate collected from the collection chambers is not considered
an exposure medium, because leachate chambers are enclosed and
are not accessible for exposure. As part of the site
investigation, the side slopes of all three landfills were
inspected for leachate seeps. No leachate seeps or areas of
moist soil were observed that would indicate leachate seepage.
Sediments and surface water in the five stormwater retention
basins are not likely exposure points under current conditions.
The water depths in the retention basins are shallow, ranging
from 0 to 3 ft, except during periods of heavy rainfall. The
ponds occupy a'bout 12 acres, and are fed by a system of concrete-
lined, open drainage ditches that collect surface-water runoff.
The current-use exposure pathway was evaluated for residents and
workers potentially using private supply wells. Because no
current exposure to ground water occurs within the Study Area,
the monitor wells that were used to assess exposures under the
current-use scenario are located in the residential areas
downgradient from the Study Area.
In the future, existing supply wells might become affected by the
chemical plume, or new supply wells might be installed within the
chemical plume within or near the Study Area. Therefore, wells
near the contamination source were used to assess resident and
worker exposure to ground water under a future-use scenario.
Also under the future-use scenario was an assessment of potential
exposure of a child resident to surface water and sediment.
6.2.2 TOXICITY ASSESSMENT SUMMARY
Toxicity assessment is a two-step process whereby the potential
23
-------
hazards associated with route-specific exposure to a given
chemical are (1) identified by reviewing relevant human and
animal studies; and (2) are quantified through analysis of dose-
response relationships. EPA has conducted numerous toxicity
assessments that have undergone extensive review within the
scientific community. EPA toxicity assessments and the resultant
toxicity values are used in the baseline evaluation to determine
both carcinogenic and noncarcinogenic risks with each COPC and
route of exposure.
The risk assessment draws carcinogenic and noncarcinogenic
toxicity information from EPA's Integrated Risk Information
System (IRIS) for each COPC to characterize site-specific risk.
i6.2.3 RISK CHARACTERIZATION
In the final step of the baseline risk assessment, human intakes
for each pathway of exposure are integrated with EPA reference
toxicity values to characterize risk. Carcinogenic and
noncarcinogenic effects are characterized separately.
To be considered in EPA's target risk range for Superfund
cleanups, the increased risk of cancer to an exposed individual
from COPCs should be no greater than a range from 1 additional
.case in 10,000 (1 x 10'4) to 1 in 1,000,000 (1 x 10'6) . Lifetime
cancer risks and noncancer risks were calculated under the
current-use and future-use scenarios. The results of these
calculations are presented in Table 6.1. for current exposure,
carcinogenic risks all are below or within EPA's target range.
However, potential future use of ground water by on-site workers
or on-site residents poses unacceptable risks (i.e., risks
greater than EPA's target range for Superfund cleanups).
For chemicals causing harmful effects other than cancer, EPA
calculates an HQ for each COPC that is based on risks of
deleterious effects caused by the chemical during a lifetime.
EPA then adds the HQs for each COPC to calculate a hazard index
(HI) . If the HI is greater than 1, then some cleanup action may
be warranted. For the current-use scenario, the HI does not meet
or exceed 1. However, if contaminated on-site ground water were
to be used, the HI would be greater than 1 (see Table 6.1.) ;
For those pathways with risks exceeding 10"4, the carcinogens
with risks exceeding 1 x 10"6 and noncarcinogens with HQs
exceeding 0.1 are identified as "contaminants of concern", and
are listed in Table 12 of the Baseline Risk Assessment.
If not addressed by implementing the response action selected in
this ROD, actual or threatened releases of hazardous substances
from this site may present an imminent and substantial
endangerment to public health, welfare, or the environment.
24
-------
Table 6.1
SUMMARY OF CANCER AND NONCANCER RISKS BY EXPOSURE ROUTE
CURRENT AND FUTURE USE SCENARIOS
TAYLOR ROAD LANDFILL STUDY AREA
HILLSBOROUGH COUNTY. FLORIDA
EXPOSURE
ROUTE
CURRENT USE SCENARIO
Graundwater
Ingestlon
Inhalation of VOCs
TOTAL
FUTURE USE SCENARIO
Groundwater
ngestion
Inhalation of VOCs
TOTAL
Surface Water
ngestion
Dermal Absorption
TOTAL
Sediment
Ingestlon
Dermal Absorption
TOTAL
Child Resident
Cancer HI
3E-05
8E-06
3E-05
9E-04
2E-04
1E-03
NA
NA
NA
3E-07
1E-05
1E-05
0.4
0.01
0.4
7
0.8
8
0.005
0.09
0.1
0.01
0.6
0.6
Adult Resident
Cancer HI
4E-05
1E-05
5E-05
1E-03
3E-04
1E-03
NA
NA
NA
NA
NA
NA
0.2
0.006
0.2
3
0.3
3
NA
NA
NA
NA
NA
NA
Lifetime Resident
(Child + Adult)
Cancer HI
7E-05
2E-05
9E-05
2E-03
5E-04
2E-03
NA
NA
NA
NA
NA
NA
0.6
0.02
0.6
10.0
1.1
11
NA
NA
NA
NA
NA
NA
Adult Worker::i
Cancer HI
2E-05
5E-06
2E-05
6E-04
1E-04
7E-04
NA
NA
NA
NA
NA
NA
0.1
0.002
0.1
1
0.1
1
NA
NA
NA
NA
NA
NA
HI Hazard Index
VOCs Volatile Organic Compounds
NA Not Applicable
Source: CDM - BRA
-------
6.4 SUMMARY OF ENVIRONMENTAL ASSESSMENT
The baseline risk assessment presents a preliminary environmental
assessment for the Taylor Road Landfill site. The assessment
summarizes for the Study Area and vicinity, the types of habitats
present, the dominant species of flora and fauna present, and any
possible habitats for endangered and threatened species. In
addition, the environmental assessment has qualitatively
evaluated the potential effects of Site contaminants on
significant receptor populations.
The Study Area is characterized primarily as disturbed grasslands
containing manmade retention basins surrounded by an area of
commercial/residential development containing small ponds and
springs. The Study Area originally consisted of high pine,
sandhill communities. Pockets of the original high pine
communities remain in the vicinity of the Study Area,
characterized primarily as Turkey Oak Barrens or Turkey Oak
Sandhills.
Although a variety of flora and fauna may be found in the 1.5^
mile radius of the area, and possibly may include-federal- and
state-listed species and state species of special concern, the
immediate area surrounding the three landfills is not likely to
serve as a significant habitat for these species. However,
wading birds, small amphibians and reptiles, and mammals may use
the stormwater-runoff-retention basin as a water source and
intermittent foraging area.
Metals, inorganic compounds, and organic compounds were detected
in the surface water of one retention basin, and in the sediments
of the retention basins—primarily in the southeastern basin.
During the remedial investigation, a review of a recent USGS
study of regional urban retention basins was conducted, which
suggested that some of these compounds are likely to be related
to non-Site sources. The maximum concentrations of a limited
number of contaminants exceeded Region IV screening values for
surface water and sediments. These exceedances of screening
values do not necessarily equate to adverse impact, but indicate
that, under a conservative evaluation, a potential for impact to
pelagic aquatic biota and benthic organisms is suggested.
Overall, the environmental assessment indicated that site-related
compounds are unlikely to significantly affect receptors.
26
-------
7.0 DESCRIPTION OF REMEDIAL ALTERNATIVES
The following alternatives for remediation were evaluated in the
FS.
• Alternative 1: No Action
• Alternative 2: Prevent Human Exposure to Contaminated Ground
water
• Alternative 3: Collect and Treat Ground water at Point of
Compliance on a Contingent Basis
• Alternative 4: Collect and Treat Ground water at Landfill
Perimeter
7.1 ALTERNATIVE 1: NO ACTION
The "no action" alternative provides a baseline for comparison
with other alternatives. The "no action" assumes that no
additional work will be required at the site to address the
ground water. Previous work to close the landfills included
construction of a cap, a cover, and a drainage ditch, and of
methane-gas-control systems for all three landfills, and the
implementation of long-term maintenance and monitoring programs.
7.2 ALTERNATIVE 2: PREVENT HUMAN EXPOSURE TO CONTAMINATED
GROUND WATER
This alternative encompasses two broad measures to prevent human
exposure to ground water having constituents in concentrations
exceeding Florida drinking-water standards. In addition, this
alternative relies on the natural processes of attenuation to
reduce constituent concentrations. These components of-
Alternative 2 are described in the following sections.
7.2.1 Measures to Prevent Human Exposures Under Alternative 2
Measure 1: Use existing and future institutional controls to
restrict construction of new potable-water wells that would
extract water affected by the Taylor Road Landfill.
Hillsborough County owns the various properties that constitute
the Study Area. Under Alternative 2, the County would use its
authority to write covenants into the deeds of these properties
that would restrict the County and any future property owners
from constructing potable-water wells in the Study Area. For
properties not owned by the County but near the Study Area, the
following, very explicit, regulatory measures currently are in
effect to restrict the construction of new potable-water wells:
27
-------
1. the 1983 RCRA Consent Decree, which requires all new
residential buildings in an area to the south of the Study
Area to be connected to the County water supply; and
2. establishment in 1991 of a delineated area in accordance
with FAC Chapter 62-524, which restricts the issuance of
permits for new potable-water wells within an area extending
500 ft from the County property boundary.
Measure 2: Provide water from the County supply to residences
surrounding the Study Area.
Under Alternative 2, water would be supplied to residents by the
County. Residents would not be responsible for hookup costs or
impact fees. However, residents would be responsible for water-
usage fees. A detailed search would be required to locate
residences south of Interstate 4 not connected to the County
water supply. In addition, because hookup to County water would
occur on a voluntary basis, a mechanism would be required to
inform those buyers of residences whose previous owners refused
to accept County water. How best to inform such buyers is a
complex question, and could involve various options, including
the submittal of notices accompanying annual real—estate-tax
bills.
28
-------
PROPOSED•
MONITORING
WELL
STUDY AREA PROPERTY LINE
PERIMETER OF
MONITORING WELLS OUTSIDE
OF EXCEEOANCES OF
FLORIDA DRINKING
WATER STANDARDS
PROPOSED
MONITORING
WELL
WERE 1 OR MORE ANALYTES
FLORIDA DRINKING WATER
STANDARDS (DASHED WHERE INFERRED)
REGION
EXCEED0D
PROPOSED
MONITORING
WEL
LEGEND
SURFTCUL It FLORIOAN AOUIFCR
UONnORlNC WELL LOCATION
DEEP fLORIDAN AQUIFER
UONITORINC WELL LOCATION
PROPOSED UONITORINC WELL
1600
FEET
SOURCE: ERM-RI
COM FEDERAL ARCS IV
ALTERNATIVE 2
MONITORING RING AND 270' SETBACK
COM FEDERAL PROGRAMS CORPORATION
at Coup El »iu * UdU. loc.
TAYLOR ROAD LANDFILL STUDY AREA
HILLSBOROUGH COUNTY, FLORIDA
RGURE NO.
7.1
-------
7.2.2 Contingent and Noncontingent Approaches to Prevent Human
Exposures Under Alternative 2
Alternative 2 has been subdivided into the following contingent
and noncontingent approaches.
Alternative 2a: Noncontingent Approach
Under the noncontingent approach. County water service would be
extended in the near future to specific areas surrounding the
Study Area, regardless of whether the ground water contaminant
plume is enlarging. These areas would be bordered by Highway 92
to the south, Pruett Road to the north. Black Dairy Road to the
west (including its projection south of Interstate 4), and a line
trending from north to south, 2,000 ft east of Taylor Road.
Approximately 490 residences would be connected to the County
water supply under this approach. The total capital .installation
costs under alternative 2a are estimated to be $4,560,000.
Alternative 2b: Contingent Approach
Under the contingent approach, County water service would be
extended to replace private wells contingent upon determination
that (1) the plume of contaminants exceeding Florida drinking-
water " standards is enlarging and that (2) those private wells
would be affected by the enlarging plume. This approach would
employ quarterly monitoring of a ring of wells surrounding the
Study Area. Confirmation of an exceedance of Florida guidance
concentrations at one of these wells would require the provision
of County water service to owners of potentially threatened
downgradient wells. The total capital installation costs under
alternative 2b are estimated to be $2,240,000.
A critical component of this approach is the determination of
potentially threatened downgradient wells. The Feasibility Study
established a 270-ft "setback" from the ring of monitor wells
(Figure 7.1), which takes into account the rate of ground water
migration, the time necessary to sample the monitor wells, and
the time necessary to provide the owners of potentially
threatened wells with County water.
This approach assumes the installation of four new monitoring
wells:
• one additional monitoring well northeast of the Study Area;
• two additional monitoring wells to the south—one located
approximately midway between existing wells F-3 and F-4, and
30
-------
one approximately midway between existing wells TR-2 and F-3;
and
• one additional monitor well located between 30d and F-l.
When beginning implementation of this approach, County water
would be provided to all residences within 270 ft from the
monitoring ring. About 20 existing residences are estimated to
be located within the 270-ft setback—about five along Mango Road
to the west, about ten along Taylor Road to the east, and about
five south of Interstate 4. If an exceedance were reported and
confirmed, then the monitoring ring would require expansion, and
the 270-ft setback also would be expanded accordingly. Residents
outside the original 270-ft setback, but within the expanded
setback, would be provided with the County water service. To
provide County water service within the desired response time of
'approximately 1 month, the existing County water-supply network
would require expansion before this approach is implemented.
7.2.3 Role of Natural Attenuation in Preventing Human Exposures
Under Alternative 2
Florida regulations require that ground water meet drinking-water
standards at the property boundary. Contouring interpolation
indicates that some exceedances may be present within short
distances to the south and east of the property line (Figure
7.1). Also, a parcel of privately owned property protrudes
between the Taylor Road Landfill and the County-owned property
around the East Basin, west of Taylor Road. A well on this
private parcel (well 28d) has periodically reported
concentrations of vinyl chloride above Florida drinking-water
standards. This well is upgradient of the Taylor Road Landfill;
vinyl chloride is present in the well as a result of the natural
degradation of other organic compounds in combination with vapor-
phase transport.
Natural attenuation now accounts for a decline in constituent
concentrations in monitor wells along the boundary of the Study
Area. To meet the applicable or relevant and appropriate
requirements (ARARs), Alternative 2 relies on the degradation
process, together with other attenuation processes. These
processes should reduce the concentrations of organic
constituents to levels that meet Florida requirements.
7.3 ALTERNATIVE 3: COLLECT AND TREAT GROUND WATER AT PROPERTY
BOUNDARY ON A CONTINGENT BASIS
Alternative 3 consists of all components of Alternative 2b, plus
the collection and treatment of ground water on a contingent
basis from along the property boundary south of the Taylor Road
Landfill. Alternative 3 also relies on the natural attenuation
31
-------
that now accounts for a decline in concentrations in wells along
the boundary of the Study Area. However, ground water monitoring
shows that this attenuation trend has reversed (that is to
produce consistently increased off-site migration of contaminants
exceeding the remediation goals), then extraction wells would be
constructed and operated. If this were to occur, then
Alternative 3 would be directed toward.collecting and treating
contaminated ground water. It would control ground water flow at
the property boundary and would reduce concentrations of chemical
constituents there to acceptable levels. In addition to
implementation of the ground water collection and treatment,
remedy, the integrity of the landfill cover should be
investigated if the attenuation trend were to reverse. The total
cost-of Alternative 3 if the active remediation is not required
is estimated at 2,240,000 (-the same as for Alternative 2b). The
total cost of Alternative 3 if active remediation is required is
estimated at $7,000,000.
7.3.1 Trend Analysis of Data to Substantiate Attenuation
Of critical importance.to Alternative 3 is an ongoing analysis of
attenuation trends. A determination in the future that the
attenuation trend has reversed downgradient of the Taylor Road
Landfill would trigger the installation and operation of the two
extraction wells and the treatment system. This determination
would be based on a statistical analysis of.time-series data, in
which trends are compared with performance criteria. The
specific methods for conducting such trend analysis would be
defined in the design process. One possible set of methods, is
found in Appendix C of the Feasibility Study.
7.3.2 Vinyl Chloride Upgradient of the Landfill
The ground water.monitoring program in the Study Area frequently
reports elevated concentrations of vinyl chloride in wells
upgradient and crossgradient of the Taylor Road Landfill.
Ground water collection at the property boundary will not address
these elevated upgradient concentrations, which result from
natural attenuation and vapor-phase transport. Concentrations of
vinyl chloride should decline through future attenuation to
acceptable levels. Remediation aimed at controlling vapor-phase
transport may be necessary to reach remediation goals at the
property boundary, and would require further study.
7.3.3 Control of Vapor-Phase Transport
At this time, it is difficult to determine how greatly the vapor-
phase-transported constituents are affected by the existing
landfill-gas-collection (LFG) system. More data are needed to
determine the degree to which specific measures could control gas
migration.
32
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7.4 ALTERNATIVE 4: COLLECT AND TREAT GROUND WATER AT LANDFILL
PERIMETER
This alternative is intended to comply with the CERCLA policy of
compliance with Federal drinking-water standards for ground water
at the outer perimeter of waste in the landfill. Alternative .4
includes all components of Alternative 2b plus collection,
treatment, and disposal of ground water. Unlike Alternative 3,
collection and treatment of ground water is not on a contingent
basis. Continued monitoring also is included. The total
present-worth cost of Alternative 4 is $10,200,000.
7.4.1 vinyl Chloride from Vapor-Phase Transport
Ground water collection at the landfill perimeter will not
address, the elevated concentrations of vinyl chloride detected,
upgradient of the landfill. These concentrations result from
vapor-phase transport, and should decline in the future to
acceptable levels. Remediation of vinyl chloride resulting from
vapor-phase transport, if necessary, would require further study.
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8.0 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES
A comparative analysis was performed on the remedial alternatives
developed during the FS, using the nine evaluation criteria set
forth in the NCP. The advantages and disadvantages of each
alternative were compared to identify that alternative achieving
the best balance among the nine criteria. Evaluation criteria
are defined in Figure 8.1. In the NCP, the first two criteria
are labeled "Threshold Criteria," relating to statutory
requirements that each alternative must satisfy to be eligible
for selection. The next five criteria are labeled "Primary
Balancing Criteria," and are the technical criteria upon which
the detailed analysis is primarily based. The final two criteria
are known as "Modifying Criteria," assessing the public's and
state agency's acceptance of the alternative. Based on these
final two criteria, EPA may modify aspects of the specific
alternative.
A summary of the relative performance of each alternative with
respect to the nine evaluation criteria is provided in the
following subsections. A comparison is made between each of the
alternatives for achievement of each specific criterion.
8.1 OVERALL PROTECTION OF HUMAN HEALTH AND ENVIRONMENT
All alternatives are protective of human health and the
environment to varying degrees.. Alternative 1 is protective
under current-use scenarios, because no known points of human
exposure to ground wate.r 'exist having concentrations in excess of
Florida drinking-water standards for constituents attributable to
the Study Area. Future human exposure could occur if property in
close proximity to the landfills is developed without the
provision of County water.
Alternative 2 eliminates this possibility for future human
exposure by using an existing institutional mechanism to prohibit
new wells on this property. Alternative 2a eliminates future
exposure of current population by providing for replacement of
residential wells in the surrounding community with County water
service. Alternative 2b offers County water to those residents
whose wells would be affected in the future if the ground water
constituent plume were to enlarge (as determined by quarterly
monitoring).
Some limited exposure may occur to those residents immediately
south of Interstate 4 who had refused connection to the County
water supply, and who continue to rely on domestic wells for
their water supply. However, the constituent concentrations in
these areas are below Florida drinking-water standards.
Alternatives 3 and 4 address this potential low-level exposure.
Alternative 3 depends on natural attenuation to reduce
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Figure 8-1
GLOSSARY OF EVALUATION CRITERIA
THRESHOLD CRITERIA:
Overall Protection of Human Health and the Environment -
Addresses whether or not a remedy provides adequate protection
and describes how risks posed through each pathway are
eliminated, reduced, or controlled through treatment, engineering
controls or institutional controls.
Complia«g«* with ARARs - addresses whether or not a remedy will
meet all of the applicable or relevant and appropriate
requirements of other federal and state environmental statutes
and/or provides grounds for invoking a waiver.
PRIMARY BALANCING CRITERIA:
Long-Term Effectiveness and Permanence - refers to the magnitude
of residual risk and the ability of a remedy to maintain reliable
protection of human health and the environment over time once
cleanup goals have been met.
Reduction of Toxicity. Mobility, or Volume Through Treatment -
addresses the anticipated performance of the treatment
technologies that may be employed in a remedy.
Short-Term Effectiveness - refers to the speed with which the
remedy achieves protection, as well as the remedy's potential to
create adverse impacts on human health and the environment that
may result during the construction and implementation period.
Implement ability - the technical and administrative feasibility
of a remedy, including the availability of materials and services
needed to implement the chosen solution.
Cost - includes capital and operation and maintenance costs.
MODIFYING CRITERIA:
State Acceptance - indicates whether the State concurs with,
opposes, or has no comment on the Proposed Plan.
Community Acceptance - the Responsiveness Summary in the appendix
of the Record of Decision responds to public comments received
from the Proposed Plan public meeting and the public comment
period and shows how the Agency used these comments to make the
remedy selection.
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concentrations south of Interstate 4; however, if the attenuation
trend were to reverse, Alternative 3 provides for containment of
the downgradient migration of constituents through use of a pump-
and-treat system at the Study Area property line. Alternative 4
is the same as Alternative 3, except that it provides for
collection and treatment of ground water on a noncontingent
basis, and that ground water is collected along the perimeter of
the Taylor Road Landfill. Alternatives 3 and 4, however, could
increase the potential for sinkholes, which present unknown
consequences.
8.2 COMPLIANCE WITH ARARs
Alternatives 1 and 2 do not address the FDEP requirement that
ground water at the property line should satisfy Florida
Drinking-Wat.er standards. Continuance of natural attenuation
1 should result in the attainment of drinking-water standards at
the property line. Alternatives 3 and 4 meet the FDEP
requirement for containment through natural attenuation or
through treatment of ground water.
8.3 LONG-TERM EFFECTIVENESS
The amount of residuals is essentially the same for all
alternatives. Alternative 3 is considered more reliable than
Alternative 2 because the former provides a contingency in case
attenuation trends do not continue or other -increases in
contaminant migration occur. Even so, the contingency is a pump-
and-treat system (or equivalent innovative technology to be
decided), estimated to be needed for 30 years, and perhaps for
much longer. The reliability of Alternative 3 is virtually equal
to that of Alternative 4, even though the pump-and-treat
component of Alternative 4 is not provided on a contingent basis.
This is because monitoring conducted as part of Alternative 3
would result in installation of a pump-and-treat system if and
when needed. The pumping involved in Alternatives 3 and 4 could
induce sinkholes, which present unknown consequences.
8.4 REDUCTION OF TOXICITY, MOBILITY, AND VOLUME THROUGH
TREATMENT
Only Alternatives 3 and 4 include treatment (treatment for
alternative 3 is on a contingent basis). The primary benefit of
treatment is a reduction in the mobility of chemical constituents
in ground water by containing them at the property line
(Alternative 3) or at the landfill perimeter (Alternative 4).
The treatment addresses contaminated ground water, not the
landfilled waste; therefore, the relative reduction in volume of
waste is minimal.
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8.5 SHORT-TERM EFFECTIVENESS
Alternatives 1 and 2 do not involve any actions that would result
in short-term exposure of the community to landfill gas or
contaminated ground water. Alternatives 3 and 4 are confined to
the Study Area, and are not anticipated to affect the community,
because necessary air-pollution controls would be included with
the treatment operations. Some exposures of workers could occur
under Alternatives 3 and 4, which would necessitate health and
safety precautions. Alternatives 2 through 4 will each require
approximately 2 years to implement. For Alternatives 3 and 4,
this period excludes the operational period, which could continue
for about 30 years after construction.
8.6 IMPLEMENTABILITY
None of the alternatives present a serious implementability
issue-, except possibly any difficulty in ensuring that buyers o'f
properties would be informed if previous owners had refused
connection to the County water supply. How best to inform such
buyers .is a complex question, and could involve various options,
including the submittal of notices accompanying annual real-
estate-tax bills. . . -
8.7 COSTS
The 'present-worth costs of each alternative are shown in the
following list. The costs do not include the estimated future
expense to the County for maintaining and monitoring the Study
Area. This is budgeted at $700,000 for 1995, yielding a present-
worth cost of $10,800,000 if continued for 30 years. For
purposes of calculating a present-worth cost, an effective
discount rate of 5% was used.
The following are the comparative total present-worth costs for
the alternatives (using an discount rate of 5% for 30 years).
. Alternative Cost
Alternative 1: $0
Alternative 2a: $4,600,000
Alternative 2b: $2,200,000
Alternative 3 (if ground water $2,200,000
treatment is not implemented) :
Alternative 3 (if contingent $7,000,000
ground water treatment is
implemented):
Alternative 4: $10,200,000
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8.8 STATE ACCEPTANCE
This criterion assesses the technical and administrative issues
and concerns that the state may have regarding each of the
remedial alternatives.
The State of Florida, as represented by FDEP, has been the
support agency during the RI/FS process for the Taylor Road
Landfill site. As the support agency, FDEP has provided input
during this process in accordance with 40 CFR 300.430. 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.
8.9 COMMUNITY ACCEPTANCE
This criterion assesses the issues and conqerns that the public
may have regarding each of the remedial alternatives. This
criterion is addressed in the Responsiveness Summary (Appendix A
of this document).
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9.0 SELECTED REMEDY
Based upon considerations of the requirements of CERCLA, the NCP,
the detailed analysis of the RI/FS, the risk assessment, and
public and state comments, EPA has .selected Alternative 3 as the
appropriate remedy for the Taylor Road Landfill Site.
Alternative 3 consists of institutional controls, provisions to
prevent human exposure to contaminated ground water (as described
under Alternative 2b), natural attenuation, and provisions for
active treatment of ground water, or other appropriate
containment methods, should future monitoring reveal that it is
necessary. This section outlines the components and objectives
of the selected remedy and includes several modifications and
details not in the Feasibility Study or section 7.4 of this ROD.
9.1 MAJOR COMPONENTS OF THE REMEDY
9.1.1 Institutional Controls
The use of existing and future institutional controls to
restrict construction of new potable-water wells that would
extract water affected by the Taylor Road Landfill
Hillsborough County owns the various properties that
constitute the Study Area. The County shall use its
authority to write covenants into the deeds of these
properties that would restrict the County and any future
property owners from constructing drinking-water wells in the
Study Area. For properties not owned by the County but near
the Study Area, two regulatory measures currently in effect
restrict the construction of new potable-water wells. First,
the 1983 RCRA Consent Decree requires all new residential
buildings in the area to the south of the Study Area to be
connected to the County water supply. Second, the 1991
establishment of a delineated area in accordance with FAC
Chapter 62-524 restricts the issuance of permits for new
potable-water wells in an area 500 ft from the County
property boundary.
9.1.2 Extension of Water Lines and Monitoring
Modification of the existing HCDSW ground water-monitoring
program to include quarterly monitoring of a "ring" of
existing and future monitor wells placed with the objective
of defining and enclosing the area of ground water exceeding
the Florida Primary and Secondary Drinking Water Standards
and Minimum Criteria
Figure 7.1 contains the wells to be included in the "ring"
and is based on data at the time of the Remedial
Investigation. Pursuant to FDEP comments, an additional well
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shall be added to the "ring" depicted in figure 7.1. This
well shall be located along the western side of Taylor Road,
about 2000 ft north of Sligh Ave. Additionally, recent
ground water data indicates that monitor well 30d is
contaminated with mercury above the 2-ppb MCL. Therefore,
the "ring" outlined in'Figure 7.1 may have to be expanded by
adding additional wells to be monitored so that the extent of
contaminants exceeding the Florida Primary and Secondary
Drinking Water Standards and Minimum Criteria is further
defined. The initial makeup of the monitor well "ring" shall
be detailed during the project planning stages, and will
consider the most recent data under the current HCDSW
monitoring program. It is anticipated that at least 13
existing and future wells will constitute the "ring."
The ground water contaminants to be analyzed for shall be
identified during the project planning stages and shall
consist of those chemicals identified in the Risk Assessment
as chemicals of concern, and of the chemicals previously
detected at the site.
Trend analysis shall be planned and conducted annually on the
sampling results to evaluate the temporal behavior of
contaminants in ground water. Results of trend analysis
shall be delivered to EPA and DEP.
The HCDSW monitoring program also shall be modified to
include enhanced reporting of results to the public. Results
shall be reported, after validation, in a form easy for the
layman to understand, and shall be sent by Express Mail to
the information repository, (currently located at the
Thonotosassa Public Library) and to the TRCA. All
exceedances of remediation levels shall be identified in the
reported results.
The described ground water monitoring shall be conducted at
least as long as ground water contaminants exceed the
Remediation Levels (section 9.2). However, it is possible
that future improvements in ground water quality will justify
a decrease in frequency of sampling or a decrease in the
number of wells to be sampled. EPA and FDEP will consider
future requests for modifications of ground water monitoring
program. EPA, in conjunction with FDEP, will make the final
determination on whether or not the monitoring program will
be modified in the future.
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Provision of County water service to human receptors within
the described "ring" of monitor wells and within a "setback"
that extends 270 ft outward from the "ring"
Figure 7.1 outlines a setback 270 ft from the "ring" of
monitor wells. This-setback takes into account the rate of
ground water migration and the time necessary to sample the
monitor wells and to provide owners of potentially threatened
wells with County'water. All residences or business that
rely on well water for human consumption within the 270-ft
setback shall be supplied with County water. Owners to be
supplied with municipal water would not be responsible for-
hookup costs or impact fees. A detailed search would be
required to locate residences south of Interstate 4 not
connected to the County water supply. In addition, because
hookup to County water would occur on a voluntary basis, a
mechanism would be required to inform those buyers of
residences whose previous owners refused to accept County
water. How best to inform such buyers is a complex question,
and could involve various options, including the submittal of
notices accompanying annual real estate tax bills.
Expansion of the County water-supply network -
The purpose of this expansion of water mains is three-fold:
to connect receptors within the previously described 270-ft
setback, to support the institutional controls under the
selected remedy, and to meet a response time of approximately
1 month for the hookup of additional receptors should an
increase in size occur .in the area found to exceed Florida
drinking-water standards.
Under FAC 62-524.300(2), permitting the construction of new
potable water wells on a property within a delineated area is
prohibited where a distribution line of an available potable
water system is within 500 feet of the boundary of the
property. The Feasibility Study indicates that the water .
main surrounding the Study Area does not qualify as a
distribution main, and would have to be upgraded or
supplemented. Very little of the delineated area at the
study area is within 500 feet of a public water distribution
line, thus under current conditions the delineated area will
not result in effective prevention of new potable well
construction within delineated area.
Contingent expansion of monitor well "ring"
If quarterly sampling of monitor wells in the "ring" (figure
7.1) reveals an exceedance of Florida Primary and Secondary
Drinking Water Standards or Minimum Criteria, and if the
exceedance is confirmed by subsequent sampling, then the
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"ring" shall be expanded by additional wells. Any receptors
included within the expanded "ring" and 270-ft setback shall
be supplied with County water.
An exceedance under this remedy shall trigger the following
series of actions.
— Report sampling results to receptors in the vicinity of
the affected well(s).
— Resample the monitor well.
— If confirmation sampling shows that the exceedance is
still present, then:
a. extend the "ring" of monitoring wells beyond the area
of affected ground water; and
b. provide County water service.to owners of downgradient
wells situated within 270 ft of the extended
monitoring "ring."
9'. 1.3 Natural Attenuation with Contingent Corrective Action
EPA has defined a boundary surrounding all three site landfills
at which this remedy will result in achievement of the
remediation levels (section 9.2). This boundary is termed the
point of compliance. The location and rational of the point of
compliance is outlined in section 9.3. . Remediation levels shall
be achieved at the point of compliance through one of the
following means:
Natural attenuation
Contouring interpolation indicates that some exceedances of
the remediation levels (section 9.2) may be present for short
distances to the south and east of the property line (See
Figure 7.1). To meet remediation levels at the point of
compliance, the natural degradation process is relied on,
together with other attenuation processes. These processes
should reduce concentrations of contaminants to meet the
remediation levels.
Contingent Corrective Action
Collection and treatment of ground water such that
exceedances of the remediation levels are contained within
the Point of Compliance shall be implemented if ground water
data indicate that it is necessary. The monitor wells that
define the Point of Compliance are identified in Section 9.3.
These wells shall be monitored quarterly. If quarterly
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sampling of monitor wells making up the Point of Compliance
reveals exceedances of Florida Primary and Secondary' Drinking
Water Standard or Minimum Criteria, and if the exceedances
are confirmed by subsequent sampling, then a report
evaluating the need for active treatment shall be submitted
to EPA and FDEP. The report shall consider all available
ground water data at the site including the annual trend
analysis as described previously in this ROD. Such reports
shall be submitted annually as long as ground water standards
are exceeded at the Point of Compliance. EPA, in conjunction
with FDEP, will consider the report recommendations and will
make the final determination of the need for a corrective
action.
If active aquifer pumping is required, then measures shall be
taken during the design and operation of extraction wells to
reduce the risk of inducing sinkhole's.
Treatment remedies were evaluated in the RI/FS, but because
rapid strides continue to be made in innovative technologies,
the contingent pump-and-treat may be modified or replaced by
future proposals to contain the contamination that may prove
more effective. The objective of containing ground water
exceeding Florida Primary and Secondary Drinking Water
Standards and Minimum Criteria to within the point of
compliance would remain the same.
The RI identifies a vapor-phase pathway to be responsible for
elevated contaminant -concentrations in ground water
upgradient of the source. This pathway may need to be
addressed as an additional part of any ground water
containment remedy.
9.2 Remediation Levels
The purpose of this response action is to control risk posed by
ingestion of and dermal contact with ground water and to limit
the migration of contaminated ground water. Potential
unacceptable risk at this site .is posed by a variety of VOCs and
metals. The Florida Primary and Secondary Standards and Minimum
Criteria shall be used as the remediation Levels for ground
water. The specific concentrations to be used as remediation
levels are found in "Ground water Guidance Concentrations,"
Florida, Department of Environmental Protection, Division of
Water Facilities, June, 1994. The baseline risk assessment
indicates that these remediation levels fall within the range
that EPA considers protective of human health.
9.3 Location of Point of Compliance
The NCP states as a final rule that "performance shall be
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measured at appropriate locations in the ground water ..." [FR
300.430(f) (5) (iii) (A)]. Discussion in the preamble of the NCP
indicates that EPA policy is generally to meet remediation levels
at the edge of the waste left in place (No. 46; March 8, 1990) .
However, the preamble continues, stating that "an alternative
•point of compliance may also be protective of public health and
the environment under site-specific circumstances." In this
case, EPA has established a Point of Compliance that surrounds
all three adjacent Study Area landfills. Compliance with the
remediation levels will be required at the line indicated in
Figure 9.1, defined by monitor wells encircling the three •
landfills. As indicated in the figure, additional wells will
need to be installed and monitored to assess ground water quality
at the Point of Compliance.
9.3.1 Site-Specific Factors
This Point of Compliance reflects the following site-specific
factors.
It is unlikely that ground water within the Point of
Compliance would be used.
Most of the area within the Point of Compliance-is covered by
three adjacent County landfills, the presence of which would
effectively prevent the future use of ground water beneath
them. Under the selected remedy, deed restrictions and other
institutional controls will be in place to prevent exposure
to ground water within the Point of Compliance
The historical shrinkage of the plume and the proven
stability of the area of contamination make containment
pumping unnecessary at this time.
A significant amount of ground water data, spanning a period
of 10 years or more, is available for area monitor wells.
Trend analysis for monitor wells downgradient of the Site
indicates that the area in violation of Florida drinking-
water standards has shrunk significantly in recent years.
Based on historic data it is anticipated that contaminant
concentrations will continue to decline in the area of the
landfill.
A consideration of cost indicates that the contingent
corrective action scenario is the most cost effective.
Requiring compliance with remediation levels immediately
adjacent to the landfill under Alternative 4 would cost an
estimated $10,200,000, compared with the probable cost of
$2,500,000 for the selected remedy. The protectiveness of
the selected remedy is ensured through contingent ground
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water treatment if ground water resources outside the Point
of Compliance become affected. Because the current extent of
impacted aquifer is limited, and in view of the other reasons
outlined herein, the significantly increased expense involved
in active aquifer remediation is not justified at this time.
EPA considers the outlined Point-of-Compliance to be protective
of human health when combined with the other described components
of the selected remedy.
It is possible that several of the defined Point-of-Compliance
wells will contain contaminants at levels exceeding the Florida
Primary and Secondary Drinking Water Standards or Minimum
Criteria. Such exceedances over two quarters will trigger an
evaluation of the need for a corrective action. All sampling
data will be evaluated as well as subjected to trend analysis to
help determine the need for an active ground water remedy.
Significant natural attenuation of the ground water plume has
occurred at the site in recent years. This remedy relies on the
continuing degradation process to reduce the concentration of
contaminants to levels that meet the Remediation Levels at the
Point of Compliance.
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* 3
II
38
is
Q
i
O p
m <
3
CO g
• a
—* rn
REGION WHERE I OR MORE ANALYTES
ESCEEOED FLORIDA ORINKMO WATER
STANDARDS IOASHED WHERE INFERRED)
LEGEND:
FLORIOAN AQUIFER COMPLIANCE
MONITORING WELL LOCATION
FLORIDAN AQUIFER COMPLIANCE
WELL TO BE CONSTRUCTED
•FPHOXUATI >C11C
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10.0 STATUTORY DETERMINATIONS
Under its legal authority, EPA's primary responsibility at
Superfund sites is to undertake remedial actions that achieve
adequate protection of health and the environment. In addition,
Section 121 of CERCLA establishes several other statutory
requirements and preferences. These specify that, when complete,
the selected remedial action for this site must comply with
applicable or relevant and appropriate environmental standards
established under federal and state environmental laws, unless a
statutory waiver is justified. The selected remedy also must be
cost effective, and must use permanent solutions and alternative
treatment technologies or resource recovery technologies to the
maximum extent practicable. Finally, the statute includes
preference for remedies that employ treatment technologies that,
as their principal element, permanently and significantly reduce
the toxicity, mobility, or volume of hazardous wastes. The
following subsections discuss the ways in which the selected
remedy for this site meets those statutory requirements.
10.1 Protection of Human Health and the Environment
The selected remedy protects human health and the-environment
through provisions to prevent human exposure to contaminated
ground water by supplying County water to residents, and through
provisions for active treatment of ground water if monitor well
data reveals that it is needed.
10.2 Compliance with Applicable or Relevant and Appropriate
Requ i rement s
Remedial actions performed under CERCLA must comply with all .
ARARs. All alternatives considered for the Taylor Road Landfill
site were evaluated on the basis of the degree to which they
complied with ARARs. The selected remedy was found to meet or
exceed the following ARARs.
Chemical-Specific ARARs
• The Safe Drinking Water Act (40 CFR 141.11-141.16.
141.50-141.51) is relevant and appropriate in development of
ground water action levels. The selected remedy will achieve
this ARAR, and the following chemical-specific ARARs for ground
water, at the Point of Compliance (defined in Section 9.3)
through two possible scenarios:
— containment of contaminants by ground water pumping should
monitoring data reveal that it is needed, and
— natural attenuation if past attenuation trends continue.
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• The Florida Primary and Secondary Drinking Water Standards and
Minimum Criteria (FAC 62-550 & 520) provide maximum contaminant
levels that are relevant and appropriate for ground water.
• Florida Minimum.Criteria for organoleptics, updated by FDEP's
June 1994 publishing of "Ground Water Guidance Concentrations,"
is to be considered in the development of remediation levels
for Site ground water.
- The Clean Air Act (40 CFR 50) provides National Ambient Air
Quality Standards that are relevant and appropriate for
emissions resulting from potential remedial activities
conducted at the Site.
• Florida Ambient Air Quality Standards (FAC 17-2.3) are relevant
and appropriate to remedial activities conducted at the Site
that may generate air emissions.
Location-Specific ARARs
• The Endangered Species Act (50 CFR 402) is applicable to
remedial activities conducted at a site located in the area of
a critical habitat for endangered or threatened--species.
- The Florida Rules on Hazardous Waste Warning Signs (FAC 17-736)
identify requirements applicable to signs around the perimeter
and at the entrance of the Site.
Action-Specific ARARs
• Florida Air Pollution Rules (FAC 17-2.1) are applicable to
remedial activities conducted at the Site that may generate air
emissions.
10.3 Cost Effectiveness
EPA's selected remedy affords a higher degree of overall
effectiveness in protecting the public against direct exposure
and in removing the threat posed by any future release of
contaminants. The most likely total-present-worth cost estimate
for this alternative is $2,500,000. If attenuation trends
reverse and pumping is required to contain Site contamination,
then the total-present-worth estimate would be $7,300,000.
The selected remedy affords overall effectiveness proportional to
its. cost, such that the remedy represents a reasonable value for
the money. When the relationship between cost and overall
effectiveness of the selected remedy is viewed in light of the
other alternatives, then the selected remedy appears to be cost
effective.
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10.4 Use of Permanent Solutions to the Maximum Extent
Practicable
EPA has determined that the selected remedy is the most
appropriate cleanup solution for remediating ground water at the
Taylor Road Landfill site, and that it provides the best balance
among the evaluation criteria for remedial alternatives
considered. This remedy provides effective protection to
potential human and environmental receptors in both the short and
long term, and is cost effective.
SARA provides for EPA to select permanent remedies where
feasible. Excavation of the landfill material is not considered
feasible. The selected remedy provides for a permanent solution
through prevention of exposure to contaminated ground water and,
if determined necessary, through active containment of ground
water.
10.5 Preference for Treatment as a Principal Element
By monitoring Site contamination and by restricting access to
affected ground water, the selected remedy addresses the threat
of future direct contact with, or ingestion of, contaminated
ground water. However, this remedy does not satisfy the
statutory preference for treatment as a principal element.
Treatment of source material at a landfill (where no hot spots
can be identified) is not practicable and is not EPA policy.
Implementation of ground water treatment would occur if future
ground water data indicates the need, and would contain ground
water contamination to within the Point of Compliance.
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11.0 DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan for the Taylor Road Landfill site, which was
released for public comment in July 1995, identified Alternative
3 as the preferred alternative for the Site. EPA reviewed all
written and verbal comments submitted during the public comment
period from July 17, 1995, through August 16, 1995.
Based upon the requirements of CERCLA section 117(b), EPA has
determined that -one significant change has been-made to the
selected remedy from the time that it was proposed in the
Proposed Plan until final adoption of the remedy in this Record
of Decision. The change is to the criteria to be used to
determine whether or not active ground water treatment is needed.
The Proposed Plan indicated that active treatment would be
required if trend analysis revealed a "reversal" of trends now
occurring at the site. While the trend analysis will still be
important in this determination,, there may be additional
unforeseen factors that will also, be considered. The remedy as
adopted in this decision document requires an evaluation of the
need for active treatment if remediation levels are exceeded in
the Point of Compliance wells, and the exceedance is confirmed.
Such evaluations will occur annually as long as the exceedances
continue. The evaluation/s will consider the trend analysis as
well as other site data. EPA and FDEP will consider the
evaluation recommendations and will then make the determination
of whether or not active ground water treatment is needed.
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APPENDIX A
RESPONSIVENESS SUMMARY
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RESPONSIVENESS SUMMARY
TAYLOR ROAD LANDFILL SUPERFUND SITE
The Environmental Protection Agency (EPA) held a public comment
period from July 17, 1995 to August 16, 1995 for interested
parties to comment on EPA's Proposed Plan. During this comment
period on July 27, 1995, EPA held a public meeting at the Evans
Park Community Center. At this time, EPA representatives
presented the results of the studies undertaken at the site and
also EPA's preferred alternative for the site.
A summary of EPA's response to comments received during the
public comment period, known as the responsiveness summary, is
required under Section 117 of CERCLA. EPA has considered all of
the comments summarized in this responsiveness summary in
determining the final selected remedy presented in the Record of
Decision.
This responsiveness summary consists of the following sections:
A. Background of Community Involvement and Concerns: This
section provides a brief history of community interest
and concerns regarding the Taylor Road 'Landfill Site.
B. Summary of Manor Questions and Comments Received During
the Public Comment Period and EPA's Responses: This
section presents both oral and written comments
submitted during the public meeting and public comment
period, and provides the responses to these comments.
A. Background of Community Involvement and Concerns
In accordance with Sections 113 and 117 of CERCLA, EPA has
conducted community relations activities at the Taylor Road
Landfill site to ensure that the public remains informed
concerning progress at the site.
A community relations plan (CRP) was developed in 1989 and
revised in 1993 to establish EPA's plan for community
participation during remedial activities. In December 1993, EPA
approved the Taylor Road Civic Association's (TRCA) application
for a Technical Assistance Grant (TAG). Congress included
provisions in SARA to establish the grant program to promote
public involvement in the decisions made on site-specific cleanup
strategies under Superfund. The TRCA has used the grant funds to
hire a technical advisor to help it understand and have input
into the RI/FS process. The community group's technical advisor
attended several RI/FS planning meetings and has helped the group
to generate comments on draft versions of various RI/FS
documents. Many of these comments have been incorporated into or
considered in the final documents.
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Following completion of the Feasibility.Study (FS), a Proposed
Plan fact sheet was mailed to local residents and public
officials in July, 1995. The fact sheet detailed EPA's preferred
alternative for addressing the ground water contamination at the
Taylor Road Landfill Site. Additionally, the Administrative
Record for the site, which contains site related documents
including the RI and FS reports and the Proposed Plan, was made
available for public review at the information repository in the
Thonotosassa Public Library. A notice of the availability of the
Administrative Record for the Taylor Road Landfill Site was
published in the Tampa Tribune on July 16, 1995.
Attendance at the July 27 public meeting was high and many
concerns and opinions were voiced. In addition EPA received
written comments during the comment period. The majority of the
comments indicated that a larger area should be supplied with
municipal water than that outlined in the proposed remedy.
Several comments indicated the need to clarify various aspects of
the proposed remedy. EPA's responses to specific comments and
concerns are summarized in Section B. Section 9 of the ROD
incorporates several changes or clarifications to the proposed
remedy which were made based on comments received during the
public comment period.
A transcript of the public meeting was prepared by a certified
court reporter, and this document is a part of the Administrative
Record upon which the remedy selected in the Record of Decision
is based.
Following the issuance of the final Record of Decision, EPA will
continue to keep the community informed about progress at the
site through fact sheets and informal information meetings.
Additionally, documents pertaining to the implementation of the
remedy will be placed in the information repository at the
Thonotosassa Public Library.
B. Summary of Manor Questions and Comments Received During the
Public Comment Period and EPA's Responses
1. COMMENT
Of the persons that sent in written comments, approximately
21 indicated that area residents should be supplied with
municipal water. Several additional commenters specified
that the area to be supplied with water should be larger
than that described under the proposed remedy (i.e., the
area should be at least as large as what is described in
alternative 2a) . Four residents indicated that they were
buying bottled water because they were afraid to drink their
well water.
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RESPONSE
During the remedial investigation, the extent of ground
water contamination was determined. In addition, the area
under which ground water exceeds Maximum Contaminant Levels,
or contains contaminants which could pose a significant risk
to human health, was defined. Under the proposed remedy all
residences within this area, and within a buffer zone
outward from this area, will be supplied with municipal
water (an estimated 20 residences) . This buffer zone
provides an extra margin of safety and will help insure that
the population is not exposed to site contaminants at levels
posing an unacceptable risk.
The RI/FS indicated that based on historical data, the plume
of contaminants under the site appears to be stable and thus
is not likely to spread significantly. Monitoring will
detect any expansion in the area of contaminated ground
water, and the buffer zone would be expanded if necessary.
It is EPA's position that based on current site conditions,
the federal government would not have the authority to
require Hillsborough County and the other responsible
parties to supply municipal water to a larger area than that
described in the proposed remedy. To require the larger
area to be hooked up, as described under alternative 2a, the
data would have to indicate that the landfill poses a
current threat, or a reasonable potential for a future
threat, to a much larger area.
EPA's decision not to require alternative 2a is based on
conditions related to the site, and'is not based on factors
or sources that may affect local ground water quality that
are not related to the site. The site is located in the
Brandon Karst Terrain, which is characterized by internal
drainage, sink holes, karst conduits, and the lack of a
competent confining layer above the Floridan aquifer.
Because of the geologic makeup of the area, residential
wells are particularly vulnerable to both point-source and
non point-source contamination. Residents in this area
should receive priority under any plans that Hillsborough
County has to develop its water supply network. The water
line extensions required under the proposed remedy could be
also be used by the County for such future development of
the water supply network.
2. COMMENT
A number of verbal and written comments indicated that the
residents to be supplied with water should get free water.
They said that they could not afford the water, or indicated
that because they did not cause the contamination that they
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should not have to pay for water.
RESPONSE
Under the selected remedy approximately 20 residents would
be supplied with municipal water. These 20 residents would
not be required to pay a hookup fee or an impact fee, but
would be resposible for paying their monthly water utility
fee.
3. COMMENT
A citizen expressed concern that if a sinkhole were to
'develop under the landfills the remedy would not prevent
private wells from being contaminated.
RESPONSE
EPA's preferred alternative will be designed to detect any
significant increase in contaminant migration from the study
area. A buffer zone within which people will be supplied
with municipal water will be established to provide an extra
measure of safety. If such an unforeseen change in site
conditions results in increased contaminant migration, this
buffer zone would be expanded. The remedy will be designed
to supply residents with municipal water before landfill-
related contaminants could potentially migrate into their
wells.
4. COMMENT
One commenter indicated that according to a recent
Wallstreet Journal article that none of the Superfund sites
in the Southeast had been "cleaned up".
RESPONSE
The article did indicate that only 1 site had been
"cleaned", and indicated falsely that EPA was the source of
this information. There is no category for "cleaned" sites
that EPA uses to-track the progress of superfund sites. EPA
responded to the article by providing the relevant, correct
and current information to the Wallstreet Journal. Of the
176 NPL sites in the southeast, 29 sites have had early
actions (removals) completed, 60 sites have substantial
construction work under way, construction has been completed
on 44 sites, and 10 sites have been deleted from the NPL.
5. COMMENT
A citizen asked if institutional controls would prevent new
drinking water wells in areas EPA felt were going to be
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contaminated.
RESPONSE
In January 1991, a delineated area was established under a
state rule, that would prevent new potable water wells
within 500 feet of the site property boundary. For the
delineated area to be enforceable a water distribution line
must be available in the area for residents to hook up to.
6. COMMENT
A citizen requested clarification on which wells would be
sampled quarterly.
RESPONSE
All wells in the "ring" of monitor wells described under the
proposed remedy will be sampled quarterly. Many additional
wells are located both within and outside of the study area
and have been sampled at varying intervals. The sampling
frequency of these additional wells will be determined
during the planning stages of the project.
7. COMMENT '
1 One citizen inquired about how the water would be treated if
the contingency pump-and-treat portion of the proposed
remedy was triggered.
RESPONSE
The specific treatment process would be planned during a
design process, and would depend on the concentrations in
the water. The water would be passed through an air
stripper and the volatile organics would go into the
. atmosphere. If concentrations were too high, one option
would be to treat the water with activated carbon. The
activated carbon would then be landfilled, incinerated, or
regenerated.
8. COMMENT
A commenter indicated that choosing alternative 2a in
conjunction with the proposed remedy instead of 2b would
result in a significantly decreased "per-house" cost
associated with supplying 490 residences with municipal
water as apposed to 20 residences. The commenter calculated
that the proposed remedy cost of 2.2 million dollars divided
among 20 residents would cost much more per house than
alternative 2a, which would supply approximately 490
residents for 4.6 million dollars.
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Response
It is true that supplying the greater number of residences
with municipal water would result in less money spent per-
household. This is because a certain portion of the water
distribution network would have to be constructed regardless
of whether or 20 residences were supplied or 490 residences
were supplied. Nevertheless, supplying the larger number of
residents with water would cost an estimated additional 2
million dollars; a cost which EPA could not force
Hillsborough County (and the other responsible parties) to
pay unless it were necessitated by site conditions.
Should Hillsborough County decide to incorporate the water
lines required under the proposed remedy into future plans
to develop its water distribution network (i.e. to supply
additional areas not required by the proposed remedy), some
of the cost of the water lines would be recuperated since
part of the water distribution infrastructure would already
be in place.
9. COMMENT
One citizen enquired about the cost saving from the
estimated cost of the proposed alternative if the County
extended the water main across 1-4 in conjunction with the
proposals and offer to share costs made by representatives
of the Lazy Days RV center. Many citizens expressed their
opinion at the public meeting and in written comments that
this "public-private" cooperation was a good idea and would
save money.
RESPONSE
Hillsborough County is currently pursuing an agreement with
representatives of the Lazy Days RV center to extend the
water main across 1-4. The extent to which the cost of the
remedy would be reduced will depend on the negotiated
agreement to share costs between the County and the private
interests. EPA has outlined the objectives of the proposed
remedy, but did not outline specifically how to fulfill
these objectives. It is in the County's and the other
responsible party's best interest to make the required
extensions of the water supply network in the most efficient
manner possible.
10. COMMENT
Several citizens questioned the conclusion of the Remedial
Investigation that the Hillsborough Heights landfill is not
contributing significantly to the ground water
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contamination. They questioned how contamination from the
Taylor Road Landfill have seeming migrated up-gradient to
areas along the western portion of the site. One commenter
asked why a dye test was not run to determine which
landfill/s are acting as a source.
RESPONSE
Significant effort was expended during the remedial
investigation to address the question of whether or not the
Hillsborough Heights Landfill is contributing significantly
to the ground water contamination. When considering the
many lines of investigation pursued in the Remedial
Investigation, the weight of evidence indicates that the
Taylor Road Landfill is the main source of ground water
contamination, and that the Hillsborough Heights landfill is
not contributing significantly.
There are several possible mechanisms that could explain how
contaminants at the site may appear somewhat up-gradient of
a source area under the Taylor Road Landfill. First, a
significant network of interconnected void space exists both
in the unconsolidated material above the limestone and in
the limestone itself. Contaminants can migrate through
these void spaces in a vapor phase and condense in up-
gradient areas. Second, migration of water through conduits
in the unsaturated zone is independent of the flow direction
in the saturated zone and may result in contamination of the
aquifer in areas up gradient of or lateral to the source.
Third, when the potentiometric surface is viewed on a local
scale, ground water mounding can be seen, which could result
in localized contaminant migration in all directions from
the source. This phenomenon was probably more pronounced
before the installation of the landfill cap, when
significant amounts of water could flush through the
landfill and disperse in all directions.
Conducting A dye tracer study was considered during the
scoping phase of the Remedial Investigation as a tool to
determine if the Hillsborough Heights landfill, is leaking.
The possibility was rejected based, in part, on previous
failed efforts to conduct dye studies in a Karst areas
similar to what exists at the site.
Even considering the results of the extensive work conducted
in the RI to distinguish between sources, EPA feels that it
is difficult to show conclusively at this site, that the
Hillsborough Heights Landfill is not a source- of
contamination. New evidence could reveal that it is a
source. Alternatively, conditions could change at the site
causing the Hillsborough Heights landfill to begin acting as
a source. The overall objectives of the proposed remedy
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would remain the same regardless of whether or not the
Hillsborough Heights landfill is ever determined to be
contaminating the ground water.
11. COMMENT
Several residents expressed concern that the County might
not comply with the requirements to conduct quarterly
monitoring and to deliver the results to interested parties.
RESPONSE
It will be the responsibility of EPA and DEP to enforce the
requirements of the selected remedy to conduct quarterly
monitoring and to send the results in a timely fashion to
the information repository (now located at the Thonotosassa
Public Library). It is also anticipated that a copy of
sampling results will be sent to the TRCA. The parties
responsible for conducting the remedy will be legally
required to implement all components of the remedy.
12. COMMENT
A commenter asked why there are no monitor wells north of
Pruett Road. ' . .
RESPONSE
There are fewer monitor wells north of the site because
ground water does not flow in that direction. Several wells
were place in these up-gradient areas to assess background
water quality conditions and to confirm that significant
migration of contaminants is not occurring to the north.
13. COMMENT
A few commenters inquired as to why residents to the south
of the site were supplied with water many years ago while
other residents were not hooked up.
RESPONSE
Residents to the south of the site were supplied with County
water because groundwater data taken during that time
indicated that a plume of ground water contamination was
. extending downgradient to the south. More recent data has
indicated significant attenuation of the plume.
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14. COMMENT
One resident commented that EPA's risk assessment does not
address the hospital waste buried in the landfills.
RESPONSE
EPA is not directed under CERCLA to consider hospital wastes
in the Risk Assessment process. However, human pathogens
are not expected to survive for long periods of time in a
landfill environment since the pathogens would be outside
the human body, and in competition with a host of other
microorganisms. In addition, hospital wastes disposed of at
the Hillsborough Heights Landfill are isolated from -direct
human exposure by the landfill cap and cover.
15. COMMENT
A commenter indicated that it has been taking too long for
sampling results to become available to the public.
RESPONSE
The detailed reporting requirements for the sampling results
will be outlined during the planning phases of the remedy..
A period of approximately 60 days from the sampling date to
the delivery of the results would seem appropriate. In
addition, it is anticipated that public input will be sought
to determine the most understandable format for the data.
16. COMMENT
One resident asked how much time a well in the "ring" has to
be contaminated to trigger an expansion of the "ring".
RESPONSE
If the remediation level is exceeded for two consecutive
quarterly sampling rounds, then the "ring" would be expanded
and any additional residents included within the "ring" and
270' buffer zone would be supplied with municipal water.
17 . COMMENT
One resident asked why well 3Id was being used in the "ring"
of wells to be monitored instead of well 32d. Specifically,
the commenter was concerned that based on past sampling
results for Mercury, detections in well 32d would not be
considered.
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RESPONSE
The particular wells making up the "ring" were chosen, in
part, to provide consistent spacing of wells and to
eliminate gaps in the monitor well "ring" . The wells in the
"ring" were also chosen to enclose the area exceeding the
remediation levels. Mercury levels at well 32d have not
exceeded the 2 ppb MGL in recent years. Well F-2 is
included in the defined "ring", and is located in close
proximity 'to well 32d. Any future elevated mercury
concentration affecting 32d will most likely be detected in
well F-2, and will cause the "ring" to be expanded.
18. COMMENT
What will be the screened depth and screened interval of the
perimeter monitor wells to be installed?
RESPONSE
The specific design of the monitoring wells will be outlined
during the planning stages of. the project. Typically ground
water monitoring wells have screened intervals of 10 feet.
The Remedial Investigation determined that the most
contaminated zone under the site is near the top of the
aquifer.' The wells will be screened within this zone.
19. COMMENT
Alternative 3 states that the recovery wells are to be
located "at the southern boundary" . What happens if the
contamination migrates to the east, east or north?
RESPONSE
The feasibility study is not intended to substitute for a
detailed design of the remedy, but rather to provide
preliminary information on which to base remedy decisions.
The statement that recovery wells would be located at the
southern boundary is based on the observed ground water flow
directions at the site. It would be determined during the
design of a pump and treat remedy, if triggered, the
specific means by which contaminants at concentrations
exceeding the remediation levels would be contained within
the defined point of compliance. This point of compliance-
encircles the site and would address the contamination no
matter which direction it migrated.
2 0. COMMENT
Recent testing of private well Pl-A has revealed levels of
Mercury above the MCL. Will the users of this well be
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supplied with potable water, and will the monitor well
"ring" be expanded?
RESPONSE
The resident nearest well PI-A and possibly other residents
along Mango road appear to be within the buffer zone and
thus will receive municipal water regardless of. whether or
not the "ring" is expanded. Recent sampling of monitoring
well 30d has revealed levels of mercury slightly above the
remediation level. There will be at least two additional
rounds of sampling results available for monitor well 30d by
the time the details of the remedy are planned and
implemented. If the levels of mercury above the remediation
level of 2 ppm persists in well 30d or increases in the
other wells in the "ring" then the "ring" and buffer zone
will be expanded.
21. COMMENT
A citizen was concerned that past data from several private
wells, including P-l, P-2, and 'P-3 was not considered during
the RI/FS, and that these wells have not been sampled
recently.
RESPONSE
It was decided at during RI/FS scoping to use data no older
that 19SO. A monitoring well is proposed to be installed in
the area of private wells P-l, P-2, and P-3. Sampling of
this well will reveal if contaminant levels in that area are
currently elevated, and if response actions need to be
taken.
22. COMMENT
What if the private property owners will not grant "right of
entry" for the placement and sampling of any needed monitor
wells?
RESPONSE
This issue is common to most sites with remedies calling for
significant monitoring. The steps or efforts required to
gain access to private property will be outlined in future
planning documents.
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23. COMMENT
Who chooses which wells will be sampled quarterly?
RESPONSE
All of the wells comprising the "ring" will be sampled
quarterly. The location and sampling frequency of the
remaining wells will be determined during the remedial
action planning phase.
24. COMMENT
Can "reverse osmosis" units be considered for the
individuals that are on bottled water now and until water
lines can be provide?
RESPONSE
The remedy, once detailed during the planning phase, will
include steps to supply potable water while a household is
awaiting hookup to municipal water. There is no current.
requirement that these residents be supplied-with a reverse
osmosis system.
25. COMMENT
Mercury has been detected periodically in private well P-la
and in monitoring well 30d at concentrations in excess of
the 2 micrbgrams/liter MCL. Most recently, concentrations
in well P-la remained above the MCL from October 1994 until
May 1995; however, the June 1995 sample concentration was
below the MCL. The remedial investigation examined the
1990-1993 detections and concluded that the mercury did not
derive from the Study Area landfills for the following
reasons:
a. If the mercury in well .P-la derived from ground water
transport from the Hillsborough Heights Landfill, it
would be necessary for the mercury to be in that
landfill's leachate. The analysis of leachate samples
did not detect mercury.
b. If the mercury in well P-la derived from vapor
transport, it would have to correlate with the sporadic
detections of VOCs in wells on the west side of the
Hillsborough Heights Landfill. It did not. The
mercury detections reported after 1993 (since the RI
data) still do not correspond with the VOCs.
Thus, the origin of the mercury is in question. It is
important to note that because the concentrations of mercury
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were low and sporadic over 1990-1993, the origin of the
mercury was not thoroughly investigated as part of the RI.
We understand that the remedial design is to locate any
additionally needed monitoring wells. Their locations
should be based in part on an analysis of the origin and
transport mode of the mercury detected in P-la and 30d.
RESPONSE
EPA agrees with the part of the comment indicating that the
origin of the mercury is in question, but questions the
assertion that the mercury is not a result of site
landfilling activities. The mercury could have migrated to
the western portion of the site in periods of ground water
mounding. The mounding may have resulted from high rainfall
events before the Taylor Road Landfill cap was installed.
Monitor well data seems to indicate that the mercury may be
originating from within the study area. Wells 16d, 17d,
23d, and TR-5d have not been sampled since 1990, but showed
mercury levels above the MCL that year (20.2 ppb, 20.3 ppb,
42.3 ppb, and 20.6 ppb respectively). No off-site source
has been identified that would explain these-elevated levels
of mercury.
The selected-remedy makes the conservative assumption that
the mercury is site related, and will protect human health
and the environment from this contaminant. Although EPA
does not find it necessary for implementation of the
proposed remedy to require further study to better define ''
the origins of the detected mercury, EPA will consider any
new information provided.
26. COMMENT
The current ground water monitoring program should be
adjusted as part of the remedial design. The adjustment
should accomplish the following:
a. For governmental efficiency reasons, the adjusted
monitoring program prepared under Superfund should
supersede the current monitoring requirements that
evolved from the September 1983 RCRA consent decree.
b. For cost effectiveness reasons, the adjusted program
should provide that the frequency of sampling and the
number of analytes should be reduced commensurate with
future reduction in the concentrations of contaminants.
c. Because of the better understanding provided by the RI
of ground water conditions, the frequency and scope of
the current monitoring of some existing wells should be
»
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reduced such that the new wells could be sampled at no
increase in total monitoring cost.
RESPONSE
The proposed remedy has been detailed in section 9 of the
ROD to allow for modification of the previous monitoring
program. The remedy requires that all the wells making up
the "ring" will be sampled quarterly, while allowing the
determination of sampling frequency of the remaining wells
to occur during the project planning stage. In addition,
the language of section 9 has been modified as a result of
this comment to allow for a future reduction in sampling if
site conditions warrant.
Although minimizing the cost of the modified ground water
sampling program is important to EPA, the ability of the
monitoring to identify threats to human health and the
environment is of primary concern.
27. COMMENT
Ground water extraction will increase the probability of
sink hole formation which could be detrimental to the
integrity of the landfills and could impact adjacent
infrastructure, such as .1-4. Therefore, ground water
extraction should only be contemplated if there is a
significant increase in ground water concentrations near
receptors.
RESPONSE
The proposed remedy does not require ground water extraction
unless monitoring data reveals that it is needed. Measures
would have to be taken during the design and implementation
of any required ground water extraction to address the
possible threat of inducing sink holes.
Threat to current receptors should not be the only criteria
used to determine whether or not to pump-and-treat.
Supplying residents with municipal water is important to
protect human health, but does nothing to protect the ground
water as a resource. The people of the Tampa area face a
significant challenge in meeting their future ground water
needs. Area municipalities may eventually need to rely on
the ground water resources in the immediate vicinity of the
site.
28. COMMENT
The increase in probability of sink hole formation should be
the major factor in the selection of the point of
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compliance. The point of compliance should not prolong or
trigger unnecessary ground water extraction.
RESPONSE
EPA has used the flexibility provided in the NCP to set a
point of compliance surrounding all three site landfills.
The point of compliance defined in section 9, along with the
other provisions of the selected remedy, does not result in
an unnecessary triggering of ground water extraction.
29. COMMENT
Under the "Compliance with ARARs" section of the EPA fact
sheet, it is stated that alternatives 1,2 and 3 do not
address the CERCLA policy that ground water at the landfill
perimeter should satisfy federal drinking water standards.
EPA has identified alternative 3 as the preferred course of
action. Is the CERCLA policy being waived as the result of
the selection of the U.S. EPA's preferred remedial
alternative 3? Can this CERCLA policy be waived? If so,
why can it be waived? Would the selection of' remedial
alternative 4 instead of preferred alternative 3 exclude the
collection and treatment of contaminated groundwater along
the margin of the waste footprint•for both the 10.6 FDOT
Borrow Pit Landfill and the 64 acre Hillsborough Heights
Landfill?
RESPONSE
Discussion in the preamble of the National Contingency Plan
(NCP)(No. 46; March 8, 1990) indicates that EPA policy is
generally to meet remediation levels at the edge of the
waste left in place. However, the preamble continues,
stating that "an alternative point of compliance may also be
protective of public health and the environment under
site-specific circumstances." EPA believes that factors
specific to the Taylor Road site justify a point of
compliance other than at the edge of the waste left in
place. A detailed description of these factors and the
location of the point of compliance is found in section 9.3
of the ROD. Because flexibility is provided in the NCP, a
formal waiver of the general CERCLA policy is not needed.
Alternative 4, if it were selected, would require compliance
with remediation levels at the edge of the Taylor Road
'Landfill. The RI concludes that the Hillsborough Heights
Landfill and FDOT Borrow Pit are not significant sources of
ground water contamination. If this conclusion is not
correct, or the landfills were to begin acting as a source
in the future, then alternative 4 would likely have to be
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modified during implementation to address the additional
sources.
30. COMMENT
How long is the quarterly monitoring proposed to be
continued?
RESPONSE
Monitoring of the wells will continue at least as long as
contaminants associated with the site exceed the remediation
levels. However, future ground -water quality improvements
may justify a reduction in frequency or number of wells to
be monitored. Future requests to modify the initial
monitoring program will be considered and must be approved
by EPA (upon consultation with FDEP) before such
modifications can be implemented.
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