EPA/ROD/R04-95/236
September 1995
EPA Superfund
Record of Decision:
Zellwood Groundwater Contamination,
OU2, FL
8/24/95
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RECORD OF DECISION
SUMMARY OF REMEDIAL AL TERNATIVE SELECTION
ZELLWOOD GROUND WATER CONTAMINA TION SITE
OPERABLE UNIT 2
ZELL WOOD, ORANGE COUNTY, FLORIDA
PREPARED BY
U. S. ENVIRONMENTAL PROTECTION AGENCY
REGION IV
A TLANT A, GEORGIA
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RECORD OF DECISION
DECLARATION
SITE NAME AND LOCATION
Zellwood Ground Water Contamination Superfund Site
Zellwood, Orange County, Florida
STATEMENT OF BASIS AND PURPOSE
This decision document (Record of Decision), presents the selected interim action for
Operable Unit 2 of the Zellwood Ground Water Contamination Superfund Site, Zellwood,
Orange County, Florida, developed 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), 42 U.S.c. S 9601 et seq.,
and to the extent practicable,. the National Contingency Plan (NCP), 40 CPR Part 300.
This decision is based on the administrative record for the Zellwood Ground Water
Contamination Superfund Site. The State of Florida, as represented by the Florida
Department of Environmental Protection (FOEP), has reviewed the reports which are
included in the administrative record for the Zellwood Ground Water Contamination Site.
In accordance with 40 CPR 300.430, as the support agency, FDEP has provided EP A with
input on those reports. Based on comments received from FDEP, it is expected that written
concurrence will be forthcoming; however, a letter formally recommending concurrence
with the interim action has not yet been received.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from the Zellwood Ground Water
Contamination Superfund Site, if not addressed by implementing the interim action selected
in this Record of Decision (ROD), may present an imminent and substantial endangerment
to public health, welfare, or the environment.
DESCRIPTION OF THE SELECTED REMEDY
This interim action is the second actiori planned for the Site. This interim action addresses
ground water contamination at the Site and calls for the implementation.of response
measures which will protect human health and the environment. In addition this action
addresses sediment in an onsite percolation pond which is a potential threat to ground
water contamination but was not :remediated in OUI.
Evaluation of the technical practicability of the selected remedy will be evaluated during
remedial design of the re~dy. The selected remedy includes extraction of contaminated
ground water, treatment as determined during the design to be necessary, and discharge of
ground water in a manner compatible with the treatment process. In addition,
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contaminated sediments in an onsite percolation pond will be excavated and disposed of in
accordance with applicable standards. The remedy also includes institutional controls in the
form of deed notices to limit access and exposure to contaminated ground water.
A ground water monitoring program would be necessary to ensure that the ground water
treatment system is efk:tive and that contaminants do not migrate. While this remedy
would likely achieve ground water remediation for the mobile inorganic contaminants of
concern at the Site (Le., ammonia, chloride, cyanide, nitrate, nitrite, and sulfate) within 10
years, it is likely that a much longer time would be required to remediate heavy metals
which may be present in the ground water. Therefore, this remedy is an interim action for
the purpose of eliminating a source of ground water contamination and evaluating the
technical practicability of achieving ground water cleanup at the Site. Pumping may
expedite the remediation time frame compared to natural attenuation but may still prove to
be impractica1. The ability of this action to remediate ground water in a reasonable
timefrarne would be further evaluated during remedial design and annually during this
interim action.
STATUTORY DETERMINATIONS
This interim action is protective of human health and the environment in the short term and
is intended to provide adequate protection until a final ROD is signed; complies \Vith
federal and state requirements that are legally applicable or relevant and appropriate to this
limited-scope action; and is cost-effective. Although this interim action is not intended to
address fully the statutory mandate for permanence and treatment to the maximum extent
practicable, this action does utilize treatment and thus is a furtherance of that statutory
mandate. Because this action does not constitute a final remedy for this operable unit, the
statutory preference for remedies that employ treatment that reduces toxicity, mobility, or
volume as a principal element, although partially addressed in this remedy, will be
addressed by the final response action.
Because this remedy will result in hazardous substances remaining onsite above health-
based levels, a review will be conducted to ensure that the remedy continues to provide
adequate protection to human health and the environment within five years after
commencement of the first remedial action. Because this is an interim action ROD, review
of this site and of this remedy will be ongoing as EPA continues to develop final remedial
alternatives for the Site.
~ ~~t~
RICHARD D. GREEN
ASSOCIA TE DIRECTOR OF SUPERFUND
AND EMERGENCY RESPONSE
~\ ~\}G- ~S
DATE
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1.0
2.0
3.0
4.0
5.0
5.1
5.2
5.3
5.4
5.5
6.0
TABLE OF CONTENTS
SITE LOCATION AND DESCRIPTION.......... ........ "" '.... 1
SITE HISTORY AND ENFORCEMENT ACTIVITIES. . . . . . . . . . . . . . .. 1
HIGHLIGHTS OF COMMUNITY P ARTICIP A TION . . . . . . . . . . . . . . . .. 5
SCOPE AND ROLE OF ACTION. . . . . ~ . . . . . . . . . . . . . . . . . . . . . . . .. 6
SUMMARY OF SITE CHARACTERISTICS. . . . . . . . . . . . . . . . . . . . . . .. 6
Physiography and Topography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6
Geology /Hydrogeology ...................................... 7
Surface Water Hydrology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ; . . . . . .. 8
Wildlife/Natural Resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8
Summary of Site Contaminants. . . . . . . . . . . . . . . . . ~ . . . . . . . . . . ~ . . .. 9
5.5.1 Substances Detected in Ground Water. . . . . . . . . . . . . . . . . . . . .. 9
5.5.1.1
5.5.1.2
5.5.1.3
5.5.1.4
Overview of Sampling. . . . . . . . . . . . .. 9
Contamination in the Surficial Aquifer. 9
Contamination in the Floridan Aquifer 15
Private Wells. . . . . . . . . . . . . . . . . . .. 15
5.5.2 Substances Detected In Surface Water. . . . . . . . . . . . . . . . . . . . .. 15
, 5.5.3 Substances Found In Sediments. . . . . . . . . . . . . . . . . . . . . . . . .. 21
SUMMARY OF SITE RISK. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23
6.1
6.2
Risk Assessment Overview. . . . . . . . . . . . . . . . . . . . . . . . . .'. . . . . . . .. 23
Contaminants of Potential Concern (COPCs) to Human ~ ....... 23
6.2.1 Screening Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23
6.2.2 Contaminants of Potential Concern in Surficial Ground Water. .. 24
6.2.3 Contaminants of Potential Concern in the Floridan Aquifer. . '," 24
6.2.4 Contaminants of Potential Concern in Private Wells. . . . . . . . . " 24
6.3
Exposure Assessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24
6.3.1 Introduction......................................... 24
6.3.2 Source, Mechanism of Release, and Transport. . . . . . . . . . . . . .. 25
i
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6.4
6.5
6.6
6.7
TABLE OF CONTENTS
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7.0
7.1
7.2
7.3
7.4
7.5
8.0
8.1
8.2
8.3
8.4
9.0
TABLE OF CONTENTS (continued)
DESCRIPTION OF AL TERNA TIVES . . . . . . . . . . . . . . . . . . . . . . . . . . ., 35
Remedial Action Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 35
Alternative No.1: No Action. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36
Alternative No.2: Limited Action. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37
Alternative No.3: Ground Water Extraction, Treatment Using Chemical
Precipitation, Air Stripping, and Biological Reaction, and Surface Water
Discharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 38
Alternative No.4: Ground Water Extraction, Treatment Using Chemical
Precipitation and Reverse Osmosis, and Surface Water Discharge. . . .. 41
SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES
44
Statutory Balancing Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 44
Threshold Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45
8.2.1 Overall Protection of Human Health and the Environment. . . .. 45
8.2.2 Compliance With.ARARs .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45
Primary Balancing Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 46
8.3.1 Long-Term Effectiveness and Permanence. . . . . . . . . . . . . . . . .. 46
8.3.2 Reduction of Toxicity, Mobility, or Volume Through Treatment.. 53
8.3.3 Short-Term Effectiveness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 53
8.3.4 Implementability...................................... 53
8.3.5 Cost............................................... 53
Modifying Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54
8.4.1 State Acceptance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 54
8.4.2 Community Acceptance.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54
SUMMARY OF SELECTED REMEDY. . . . . . . . . . . . . . . . . . . . . .. . . ., 55
9.1
Source Control. . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55'
9.1.1 Major Components of Source Control. . . . . . . . . . . . . . . . . . . . .. 55
9.1.2 Performance Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55
III
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9.2
10.0
10.1
10.2
10.3
10.4
10.5
11.0
TABLE OF CONTENTS (continued)
Ground Water Remediation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 56
9.2.1 Major Components of Ground Water Remediation. . . . . . . . . . " 56
9.2.2 Performance Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 56
9.2.2.1
9.2.2.2
9.2.2.3
9.2.2.4
9.2.3 Compliance Testing
Extraction Standards. . . . . . . . . . . . .. 56
Treatment Standards. . . . . . . . . . . . " 56
Discharge Standards. . . . . . . . . . . . .. 56
Design Standards. . . . . . . . . . . . . . . .. 56
""..........................,.... 57
STATUTORY DETERMINATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57
Protection of Human Health and the Environment. . . . . . . . . . . . . . . .. 59
Attainment of the Applicable or Relevant and Appropriate Requireme~ts
(ARARs) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 59
Cost Effectiveness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60
Utilization of Permanent Solutions to the Maximum Extent Practicable. 60
Preference for Treatment as a Principal Element. . . . . . . . . . . . . . . . . .. 61
DOCUMENTATION OF SIGNIFICANT CHANGES...... .......... 61
APPENDIX A - RESPONSIVENESS SUMMARY
r,
r
IV
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LIST OF TABLES
TABLE 5-1: MONITORING WELL SAMPLING SUMMARY. . . . . . . . .. . . . . . . . . . . . .. . . . . .. 12
TABLE 5-2: CONTAMINANTS DETECTED IN SURFICIAL AQUIFER SAMPLING........... 14
TABLE 5-3: CONTAMINANTS DETECTED IN FLORIDAN AQUIFER SAMPLING. . . . . . . . . .. 17
TABLE 5-4: CONTAMINANTS DETECTED IN PRIVATE WELLS SAMPLING. . . . . . . . . . . . . .. 18
TABLE 5-5: CONTAMINANTS DETECTED IN SURFACE WATER. ., . . . . . . .. .. ... .. . . . '" 21
TABLE 5-6: CONTAMINANTS DETECTED IN SEDIMENT. . . . .. . .. . . . . . . . . . . . .. . . . . .. .. 22
TABLE 6-;1: CONTAMINANTS OF POTENTIAL CONCERN. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25
TABLE 6-2: CONTAMINANTS OF POTENTIAL CONCERN IN GROUND
WATER AND TOXIOTY ASSESSMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29
TABLE 6-3: SUMMARY OF CANCER AND NONCANCER RISKS ........................ 31
TABLE 7-1: SUMMARY OF REMEDIAL ACTION PERFORMANCE STANDARDS. . . . . . . . . .. 37
TABLE 7-2: DISCHARGE STANDARDS............................................ 40
TABLE 8-1: POTENTIAL LOCATION SPECIFIC ARARS AND TBCs........ ....,..... ..... 47
TABLE 8-2: POTENTIAL ACTION SPECIFIC ARARS AND TBCs . . . . . . . . . . . . . . . . . . . . . . . .. 49
TABLE 8-3: POTENTIAL CHEMICAL SPEaFIC ARARS AND TBCs ...................... 51
TABLE 8-4: COMPARISON OF COSTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . :. 54
v
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FIGURE 1-1:
LIST OF FIGURES
GENERAL LOCATION MAP ...........................
2
FIGURE 1-2(a): ORIGINAL SITE BOUNDARY. . . . . . . . . . . . . . . . . . . . . . . . . . .
3
FIGURE 1-2(b): REVISED SITE BOUNDARY. . . . . . . . . . . . . . . . . . . . . . . . . . . .
FIGURE 5-1:
FIGURE 5-2:
FIGURE 5-3:
FIGURE 5-4:
FIGURE 5-5:
FIGURE 7-1:
FIGURE 7-2:
FIGURE 9-1:
3
OUI SAMPLING LOCATIONS. . . .. . .. .. .. . . . ... .... . ... 10
SRI GROUND WATER SAMPLING LOCATIONS. . . . . . . . . . .. 11
PRIVATE WELL SAMPLING LOCATIONS.. . . .. .... . . " ... 13
SITE RELATED GROUND WATER CONT AMINA TION
IN SURFICIAL AQUIFER. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16
SURFACE WATER AND SEDIMENT SAMPLING
LOCA TrONS ........................................ 20
ALTERNATIVE 3 PROCESS FLOW DIAGRAM. . . . . . . . . . . . .. 39
ALTERNATIVE 4 PROCESS FLOW DIAGRAM. . . . . . . . . . . . .. 43
RD IRA FLOW CHART. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 58
VI
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 1
1.0
SITE LOCATION AND DESCRIPTION
The Zellwood Ground Water Contamination Superfund Site (hereinafter referred to
as the "Zellwood Site" or the "Site") is located in the northwest corner of Orange
County, Florida (see Figure 1-1). It is situated approximately one-half mile west of
the rural, unincorporated town of Zellwood, approximately 15 miles northwest of
Orlando. The Site is situated in a rural area with small residential communities
located to the north and to the east. Agricultural lands are located to the south and
west.
The Site was originally defined as a 57-acre area occupied by several businesses and
a number of undeveloped properties (Figure 1-2 (a». After review of property
boundaries and investigation results, the Site boundaries are being defined by this
Record of Decision to include only those properties affected by. contamination. The
revised Site boundaries enclose approximately 40-acres (Figure 1-2 (b» and include
property occupied by Drum Services Company of Florida, Coatings Application &
Waterproofing Company, and Chemical Services Incorporated.
2.0
SITE HISTORY AND ENFORCEMENT ACTIVITIES
The industrialized section of the Site has been occupied since the 1960's by Zellwin
Farms Company and Drum Services Company of Florida. In the early 1970's,
Southern Liquid Fertilizer Company began its operation on the Site, as well. The
business was operated until 1981 when the plant was purchased and operations were
assumed by the Douglas Fertilizer and Chemical Company. Douglas Fertilizer sold
the property and moved its operation to a new location in 1984. The fonner fertilizer
production area is now occupied by Coatings Applications and Waterproofing
Company. Chemical Systems, Incorporated, commenced operations in 1982 on the
western part of the Site.
A variety of both solid and liquid wastes have been generated by previous activities
at the Site. Drum Services Company of Florida, a drum recycling facility, disposed of
wastewater generated through cleaning and draining procedures in two onsite
evaporation/percolation ponds and stored drums on several acres north of the
facility. Douglas Fertilizer and Chemical Company and the previous business,
Southern Liquid Fertilizer, had three unlined surface impoundments which received
wastewater from their production process. Chemical Systems, inc., reportedly, does
not generate solid or liquid wastes. The Zellwin Farms Company facility discharged
vegetable washing water to the southern drainage ditch, parallel to Jones Avenue. In
addition, the open field in the northern portion of the Site once contained both
abandoned drums and other wastes.
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Reco:.-d of Decision
Zellwood Ground Water Contamination Superfund Site
Ope::-able Unit No.2
Page 2
FIGURE 1-1
GENERAL LOCATION MAP
LAKE
COUNTY
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COUNTY
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ORANGE
COUNTY
NO SCJJ.I
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 3
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AVE
FIGURE 1-2(a):
ORIGINAL SITE BOUNDARY
Il
1nc...
.. ..' "........ ......" .. .. .. . ..:..",,:""...."
'.'"0.'. ...0.00.:: ":; :.0:..::0..::.- .,.....C!:!J.;o.:,"..
.. IZ .. .. .. ..,.. .." .18.... .'-'." .." .... ......'..".."" - .... ..
.,:,'",:,:':'...':.'.~.:.:.: .... .. ,.. .... . ...." ..' ..
.;...:.:: ':.:.:: ',::::' ::'.:::";':-.::':'.
.. .. °0 .. ~,.; ...: 0'; .. .. 0 .. .... 0" 00.." °0"" .. .. ,.,".. ....
IE]
HI
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FIGURE 1-2(b):
REVISED SITE BOUNDARY
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 4
There have been numerous investigations at this Site since 1980. FDER collected
wastewater and ground water samples in 1980 and 1981. Geophysical studies were
conducted in 1981 and 1982 by FDER and the EPA Field Investigation Team. During
July and August 1982, surface water, sediment, soil, and ground water samples were
collected from the Site and permanent monitor wells were installed in three locations.
The EPA's Environmental Services Division conducted an additional sampling
investigation in December 1982. In each of the studies, metals and organic
compounds were detected in the samples.
The Site was placed on the first National Priorities List (NPL) which was published
in the Federal Register in 1983. An emergency removal and cleanup of the
abandoned drum area was completed in 1983 under the direction of EPA. In 1984, a
Remedial Action Master Plan was developed and a Work PlaJ1 for the Remedial
Investigation/Feasibility Study (RI/FS) was formulated. Negotiations with the
Potentially Responsible Parties (PRPs) were initiated, but the PRPs indicated that they
did not wish to implement the EP A Work Plan.
The RIfFS was conducted by NUS corporation for EPA in 1985-1986. In December
1987, EP A approved a Record of Decision (ROD) recommending the following
actions:
Excavation and incineration of soils/sediments in the onsite ditches, temporary
sludge and two fonner percolation ponds, and waste piles.
Appropriate leachability testing and disposal of the incinerated soil.
Ground water removal and treatment for the surficial aquifer.
After review of the ROD, the Florida Department of Environmental Protection (FDEP)
concluded that the remedy selected by EP A was not substantiated by the RIfFS. In
1988, EP A initiated an additional study to re-assess ground water conditions at the
Site, to re-evaluate the risk assessment, and to reconsider the remedial alternatives for
the Site. In March 1990, EPA amendment the first ROD. The amended ROD
inc:uded the following changes:
Due to the complexity of the problems at the Zellwood Site, the first ROD was
amended to address only the sources of contamination at the Site and was
designated Operable Unit 1 (OUl). Ground water contamination at the Site
was to be addressed as a second operable unit (OU2).
I
Soils and sediments were to be excavated and stabilized, rather than
incinerated.
Stabilized soils and sediments were to be disposed of onsite and tested for
leachability.
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 5
Again, negotiations with the PRPs were initiated, but the PRPs indicated that they
did not wish to implement the remedy for aUl or conduct the Supplemental
Remedial Investigation/Focused Feasibility Study (SRI/FFS) for aU2. The Remedial
Design (RD) for aUl started September 1988 and the Remedial Action (RA) began
September 1991. Construction was complete by August 1993; however, leachability
test results were not available to demonstrate the protectiveness of the system until
December 1994.
The SRI/FFS for aU2 was conducted from February 1993 to January 1995. The
SRI/FFS addressed groundwater contamination and any remaining sources of
contamination at the Site. The results of the SRI/FFS verify that metals and other
inorganic contamination persists in ground water at the Site at levels that may be
harmful to human health and the environment.
3.0
HIGHLIGHTS OF COMMUNITY PARTIOPATION
All basic requirements for public participation under CERCLA sections
113(k)(2)(B)(i-v) and 117 were met in the remedy selection process. A Fact Sheet on
the Site was first distributed in November 1986. Since that time, a community
relations plan was developed and implemented at the Site. An information
repository was established in January 1987, at the Zellwood Elementary School, 3551
Washington Street, Zellwood, Florida. Documents related to aUl were placed in the
information repository in 1989. Public notices, public meetings, and a formal
comment period were held for aUl in September 1986 and August 1989.
The Supplemental Remedial Investigation/Focused Feasibility Study Report, the
Baseline Risk Assessment Report, and Proposed Plan for au 2 of the Zellwood
Ground water Contamination Site were released to the public in April 1995. These
documents are incorporated in the Administrative Record for the Site. A copy of the
Administrative Record, upon which the remedy is based, is located at the ZeUwood
Elementary School, East Washington Street, Zellwood, Florida. In addition, the
Administrative Record and the Site (project) files are available for review at the EP A
Region IV offices in Atlanta, GA. Notices of availability of these documents were
published in the Orlando Sentinel on April 23, 1995 and May 11, 1995.
On April 25, May 16, and May 17, 1995, EPA presented its preferred remedy for
Operable Unit 2 of the Zellwood Ground Water Contamination Site during public
meetings at the Willow Street Community Center, 6565 Willow Street, Zellwood,
Florida and the Zellwood Elementary School, 3551 Washington Avenue, Zellwood,
Florida. At these meetings, representatives of EP A answered questions about
sampling at the Site and the remedial alternatives under consideration. Transcripts of
the meetings were prepared and are available at the information repository.
A 60-day public comment period was held from April 19, 1995 through June 18, 1995.
EPA's responses to comments which were received during the comment period are
contained in Appendix A of this Record of Decision.
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 6
4.0
SCOPE AND ROLE OF ACTION
The work at the Zellwood Site was organized into two operable units (OUs):
.
OUI for source control of contamination from the soil and sediment;
and
.
OU2 for identification of any additional hot spots at the Site and
remediation of ground water, as necessary.
EP A selected a remedy for OUI in a ROD signed in December 1987 and a ROD
Amendment signed in March 1990. That action was completed in 1994.
This ROD addresses the second remedial action for the Site. Ground water at the Site
is contaminated with metals and other inorganics similar to those present in waste
streams at the Site. In addition, the Easternmost Douglas Fertilizer Pond, located on
the Former Douglas Fertilizer property, was identified as a potential source for
contamination at the Site during the SRI/FFS for OU2.
Based on the results of ground water studies in the SRI/FFS report, the ability of
current technology to restore the surficial aquifer to its current beneficial use could
not be confirmed. Since metals tend to bind to soil particles and become relatively
immobile, EP A is proposing an interim action to eliminate a source of ground water
contamination and evaluate the technical practicability of achieving ground water
cleanup at the Site.
The function of this remedy is to reduce the risks associated with exposure to
contaminated ground water and sediments by performing interim actions until final
remedial action goals can be set in a final record of decision for OU2. Although
ground water is affected, the contamination is moving very slowly and the surficial
aquifer is currently not used as a drinking water aquifer. The purpose of this
proposed interim action is to prevent exposure to contaminated ground water and to
determine how well the aquifer can be remediated.
5.0
SUMMARY OF SITE CHARACTERISTICS
5.1
Physiography and Topography
The Site is located in the Central Highlands Physiographic Province of Central
Florida, which is characterized by discontinuous, subparallel ridges separated by
broad valleys. The ridges are oriented roughly parallel to the Atlantic coastline. The
Zellwood Site is located in the Central Valley. This physiographic subdivision is
characterized by flat terrain, karst topography, and numerous lakes. From its
southern terminus south of Lake Apopka, the Central Valley opens to the northwest
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 7
into Lake County. Features of karst topography, such as sinkholes, are common in
Central Valley subdivisions of the Central Highlands. The development of karst is
typical of humid areas underlain by carbonate bedrock. Lake Apopka, a large
sinkhole related lake, is located approximately three and one-half miles south of the
Site.
The topographic relief over the Site is approximately 16 feet. The highest elevation of
86 feet above mean sea level (amsl) occurs at the northeast comer of the Site and the
lowest elevation of 70 feet amsl occurs on the southern site boundary. The surface
soils are sloped generally to the south-southwest at less than one percent grade.
5.2
GeologylHydrogeology
Orange County is underlain mostly by limestone, dolomite, shale, sand, and
anhydrite to about 6,500 feet, at which depth granite and other crystalline rock occur.
The upper three formations were investigated to characterize the geology /
hydrogeology at this Site: the unconfined surficial aquifer, a relatively low
permeability confining layer (Hawthorn formation), and an artesian aquifer (Floridan
Aquifer). .
The unconfined surficial aquifer is composed mainly of undifferentiated sediments
represented by distinct sand, clayey-sand, sandy-clay, and clay layers of varying
thickness across the Site. This formation varies in depth froin 24 to 46 feet below sea
level (bsl) around the Site, with the average depth of 31 feet bsl. Regionally, the
water level ranges from immediately below ground surface to greater than twenty
feet below ground surface. The shallow aquifer fluctuates in response to climatic
recharge (rainfall) and discharge mechanisms. Discharge from the surficial aquifer
occurs by evapotranspiration, seepage into surface water bodies, downward leakage
to the Floridan aquifer and pumpage. Seasonal fluctuation of up to ten feet are
common in the area. At the Site, the hydraulic gradient ranges from 0.35 to 0.63 feet
per 100 feet, which is somewhat steeper than is regionally normaL
The surficial aquifer is underlain by. the Hawthorn Formation. The Hawthorn
Formation is composed of clayey sands, phosphatic sands, dolomite, and phosphatic
limestone, with localized shell beds. Almost any combination of sand, silt, clay,
limestone, dolomite, and phosphate can be found within the Formation; however, the
predominant lithology in the area consists of a green to yellowish-green sandy clay
which is underlain by a brown to white dolomite or dolomite limestone. The clay-
like sand in the upper Hawthorne retards the vertical movement of water between
the surficial aquifer and the limestone of the Floridan. The thickness of the
Hawthorn Formation at the Site is estimated to be approximately 220 feet.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 8
The Floridan aquifer is composed of limestone, dolomite and marl, or any
combination of these. In the Floridan aquifer, water moves primarily through
underground cavities formed from solutioning in the limestone bedrock. These
solution channels generally form along fractures, joints, and bedding planes within
the limestone formation. The solution channels formed in the Floridan aquifer
provide water to most users in the area. Local ground water movement is difficult to
predict; however, regional potentiometric surface maps indicate a northeasterly
direction of flow in the Floridan aquifer in Orange County. References indicate that
the thickness of the Floridan ranges from SO feet to 100 feet in the region.
5.3
Surface Water Hvdrologv
Orange county has about 1,100 permanent bodies of open water ranging from large
water-filled sinkholes to stream channel widenings. Lakes occur in all parts of the
County with the vast majority located in the western half. There are several small
lakes within close proximity to the Site, including Lakes Maggiore and Minore to the
northeast and Lake Fanny to the northwest. Lake Apopka, a large lake, is located
three and one-half miles south of the Site.
Most of the surface waters in the county are recharged by rainfall. Approximately
72% of the rainfall returns to the atmosphere via evaporation and transpiration, 16%
flows out of the County in streams, and the remaining 12% seeps down through the
soils into the ground water system. Some surface waters are also recharged by
ground water discharge.
The Zellwood Site is located well outside of the SOO-year flood boundary associated
with Lake Apopka. The laO-year flood plain boundary associated with the marshy
areas located northwest of the Site, however, does include some of the abandoned
drum area north of the Site. Current Site drainage is through a system of
interconnected surface ditches and ponds.
WildlifelNaturai Resources
5.4
The vegetative habitats near the Zellwood Site include a mesic hammock community,
marsh/wetlands, agricultural land, and citrus groves. A biota investigation was
conducted during the 1986 RI. No ecological surveys were conducted but
information was obtained from the Fresh Water Fish Commission, the East Central
Florida Regional Planning Council, and personal communications with experts in the
field of ecology. The investigation concluded that there is a wide diversity of
habitats which support an abundance of plant and animal life, particularly migrating
birds.
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Record of Decision
ZeIlwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 9
5.5
Summary of Site Contaminants
5.5.1 Substances Detected in Ground Water
5.5.1.1
Overview of Sampling
Data gathered from ten surficial aquifer monitor wells, installed around the treated
soils disposal area (located in the former abandoned drum area) for OUI (Figure 5-1),
formed part of the data set used to determine ground water quality in the surficial
aquifer. Samples were collected in January 1994. The samples were sent to a
Contract Laboratory Program (CLP) laboratory for complete Target Compound List
(TCL) and, with the exception of cyanide, Target Analyte List (TAL) analyses.
In addition to the OUI data, ground water samples were taken in surficial monitor
wells around the Site in two phases to fully assess the types and concentrations of
contaminants present in the surficial aquifer system, and to determine the extent and
magnitude of site-related ground water contamination in the surficial aquifer.
Ground water sampling was also conducted in deep monitor wells to determine the
presence and nature of ground water contamination in the Floridan aquifer.
In Phase I, 16 existing monitor wells shown in Figure 5-2 were sampled and analyzed
for TCL/TAL analytes, as well as several other potential contaminants of concern
identified in previous investigations. In Phase II, 12 temporary monitor wells and 3
new permanent monitoring wells, as shown in Figure 5-2, were installed. Note that
monitor wells were designed to monitor the upper surficial aquifer (SA and T A
monitor wells), the lower surficial aquifer (SB and TB monitor wells), and the
Floridan aquifer (0 monitor wells) both upgradient and downgradient of the Site.
Based on the results of Phase I of the investigation, ground water samples were taken
during Phase II from the 12 temporary monitor wells, the three new monitor wells,
the 16 existing monitor wells, and 10 private water supply wells. As shown in Table
5-1, the 12 temporary wells were sampled and analyzed for the potential
contaminants of concern, whereas, the permanent well and private well samples were
analyzed for TAL metals, as well as for the other potential contaminants of concern.
Figure 5-3 shows the location of the 10 private wells sampled.
5.5.1.2
Contamination in the Surficial Aquifer
In Phase I of the investigation, Monitor Wells MW-OISA and MW-01SB were
designated as background wells for the surficial aquifer. Based on the results of
Phase I and II, twenty-two wells were designated as background wells and the
results from analyses of the remaining 16 wells were analyzed for Site-related
contamination. Fourteen surficial aquifer wells were analyzed twice and the
contaminant concentrations were averaged. The contaminant concentrations detected
in the surficial aquifer are summarized in Table 5-2.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 10
FIGURE 5-1 OUI SAMPLING LOCATIONS
CWS5/15
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!
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-------
Record of Decision
ZelIwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 11
FIGURE 5-2: SRI GROUND WATER SAMPLING LOCATIONS
010
(ASAHDONED 1994)
4SA/S8
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FORMER POND (NO lONGER PRESENT)
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 12
TABLE 5-1: MONITORING WELL SAMPLING SUMMARY
(1)
(2)
(3)
(4)
*
**
***
51/11 *
52/12 *
53 1I3 *
S4/14 *
55/15 *
1 SA/SB *
2 SA/SB *
3 SA/SB *
4 SA/5B *
S SA/SB *
6 SA/SB **
7 SA/SB *
30 ***
7D ***
1 TA/TB **
2 TA/TB **
3 TA/TB **
4 TA/TB ""*
S TA/TB **
6 TA/TB ""*
8 SA/SB
80
1 SA/SB *
2 SA/5B *
3 SA/SB *
4 SA/SB *
5 5A/SB *
6 5A/5B x-*
7 5A/SB *
8 SA/5B **
30 ***
70 ***
80 ***
OQO Level IV data. These results were used individually.
OQO Level IV data. These results were combined with the CLP sampling
round of Phase ii to calculate average concentrations for these locations.
OQO Level III data (quick turnaround analyses). Except for 8 SA/SB and 80,
these results were used individually. 8 SA/SB and 80 were not used because
DQO Level IV data were available from the CLP sampling round of Phase II.
DQO Level IV data. These results were combined with Phase I results to
calculate average concentrations for these locations.
Data used to calculate the average background for surficial aquifer (22
locations).
Data used to calculate exposure concentrations for surficial aquifer (16
locations).
Data used to calculate exposure concentrations for Floridan aquifer (3
locations).
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No, 2
Page 13
FIGURE 5-3 PRIVATE WELL SAMPLING LOCATIONS
I SAlVAC£ n
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EXISTINC POND
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EXISITINC INTERloIlTTENf POND
rORIoIER POND (NO lONCER PRESENT)
-------
Record of Decision
ZelJwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 14
TABLE 5-2: CONTAMINANTS DETECTED IN SURFICIAL AQUIFER SAMPLING
Site-Related Samvles Backe:round SamDles
Frequency Range of Average Frequency Range of
Ground Water Analyte Detected Detected Detected Average
of Concentrations Conc~~jtion of Concentrations conc~VLjti.on
Detection (pgfL) {p J Detection {pgfLJ (p )
INORGANICS:
Aluminum 4/4 3700-100 000 29,300 22/22 220-64000 5,021
Ammonia 16/16 40-340 000 83149 4/12 110-12500 1,348
Antimony ND/4 NO NO 2/22 35.5-43.5 20
Arsenic 6/16 6-73 31 1/22 12 1.8
Barium 3/4 36-460 185 22/22 12-410 108
Cadmium 8/16 0.1-22.1 6 ND /22 ND NO
Calcium 4/4 3,250-46,000 20.338 22/22 975-23 000 9,659
Chloride 16/16 1 ° 000-1 450 000 376 563 12/12 4.300-135 000 27,079
Chromium. total 7/16 14-270 76 19/22 7.2-475 72.5
Chromium. IV NO/4 NO NO NO/3 NO NO
Copper 4/4 123-1,000 483 19/22 5-46 13.1
Cvanide 5/16 9-930 240 NO /22 NO NO
Iron 3/4 665-3,800 1,905 19/22 152-7600 1,163
Lead 11/16 5-94 16 17/22 2.8-38 6.8
Ma~esium 4/4 2,100-13,000 8063 22/22 472-20000 9,078
Manganese 4/4 42.5-1 400 391 16/22 10-165 34.3
Mercury 4/16 02-24 6 4122 0.22-0.76 0.2
Nickel 8/16 56-150 99 8/22 12.8-309 34
Nitrate-Nitrite 4/4 11,000-145 000 59 000 10/12 130-21 000 4,880
Nitrate 10/12 30-144 000 21.721 NA NA NA
Nitrite 6/12 8-7350 1,262 NA NA NA
Nitrogen, Total 12/12 450-414000 56.385 NA NA NA
Nitrogen, Total Kieldahl 16/16 420-385,000 99.B44 9/12 400-15,000 1,977
Phosphorus Total 13/16 ~0-210,5oo 32.745 6/12 75-575 146
Potassium 16/16 1.810-1,050,000 316987 19/22 1 050-96,000 9,053
Selenium 4/4 21-86.5 41 5/22 5.2-28 5
Sodium 4/4 40,000-64,000 50,375 22/22 2,000-33,000 12,658
Sulfate 14/16 8 000-590 000 133143 11 /12 6000-95000 21,658
Vanadium 4/4 74.5-2000 720 16/22 9.4-160 18
Zinc 2/4 77.5-167.5 123 16/22 8-138 26.3
ORGANICS:
Bis(2-et h vlhexv \) Ph t halate NO/2 NO NO 3/22 33.67 12.2
Carbon Disulfide 1/2 5 5 N0122 NO NO
24-0ichlorophenol 1/2 3 3 NO /22 NO ND
Endosulfan Sulfate NO/2 NO NO 1122 0.12 O.OS
T etrach loroethene NO/2 NO NO 2/22 5.6 50
Ilg/L = micrograms per liter
ND = Not Detected above quantitation limit
NA = Not Analyzed
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 15
The concentrations of several inorganic chemicals detected in the surficial aquifer
ground water samples during the SRI are significantly (more than two times) higher
than the background concentrations. The majority of the ground water contamination
was found in monitor wells MW-06SA, MW-06SB, MW-08SA, MW-08SB, MW-02TB,
MW-05TB, and MW-06TB. Based on the analytical results of both Phase I and Phase
II and the analytical results of ground water monitoring results for OU#l, the area of
site-related ground water contamination in the surficial aquifer is estimated to be as
shown in Figure 5-4.
5.5.1.3
Contamination in the Floridan Aquifer
Three monitor wells screened in the Floridan aquifer were sampled; only two
inorganic chemicals (calcium and phosphorus) were detected at concentrations
significantly (more than two times) higher than the background concentrations
measured in the surficial aquifer. These two chemicals are naturally occurring in the
Floridan aquifer due to the presence of limestone in the Floridan aquifer and the
phosphate-containing Hawthorn Formation above it. In addition, calcium is
considered an essential nutrient and therefore is not regarded as a contaminant,
especially at the concentrations measured in the three deep monitor wells.
Consequently, the results of the Phase II sampling event did not show any real
indication that the Floridan aquifer has been adversely impacted by the Site. The
contaminant concentrations detected in the Floridan aquifer are summarized in Table
5:-3.
5.5.1.4
Private Wells
Of the ten private wells sampled during Phase II, only one well (PW-07) had a
chemical concentration significantly (more than two times) higher than the
background concentrations measured in the surficial aquifer, and the only chemical
measured at a significant concentration was calcium. As discussed above, calcium is
considered an essential nutrient and therefore is not regarded as a contaminant,
especially at the concentrations measured in the PW-07. Thus, none of the private
wells sampled are believed to have been adversely impacted by the Site.
Furthermore, because these private wells are more likely screened in the Floridan
aquifer or the Hawthorn Formation (actual well construction details are unknown),
these results further support the supposition that the Floridan aquifer has not been
impacted by site-related contamination. The contaminant concentrations detected in
the Private Wells are summarized in Table 5-4.
5.5.2 Substances Detected In Surface Water
One surface water sample (SW-Ol) was collected from the abandoned drum area
drainage pond and one surface water sample (SW-02) was collected from the
easternmost Douglas Fertilizer Pond. These surface water samples were taken to
-------
Record of Decision
Zellwood Ground Water Contamini\tlon Superfund S:te
Operable Unit No.2
Page 1(,
FIGURE 5-4: SITE-RELATED GROUND WATER CONTAMINATION
IN SURFICIAL AQUIFER
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-------
Record or Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 17
TABLE 5-3: CONTAMINANTS DEfECTED IN FLORIDAN AQUIFER SAMPLING
Samples Taken In Floridan Aquifer Back2J'ound Samples: Surficial Aquifer
Frequency Range of Average Range of
Ground Water Analyte Detected Frequency Detected Average
of Conce~;trons Conc~~tion of Concelr;;n.jtions Conc~~)tion
Detection (p ) (p ) Detection (p ) (p )
INORGANICS:
Aluminum 3/3 104.5-16000 5435 22/22 220-64 000 5021
Ammonia 213 140-555 348 4/12 11 0-12.500 1.348
Antimonv ND/3 ND ND 2/22 35.5-43.5 20
Arsenic ND/3 ND NO 1/22 12 1.8
Barium 213 62-300 181 22/22 12-410 108
Cadmium ND/3 NO NO ND/22. NO ND
Calcium 3/3 4,800-125000 50.600 22/22 975-23,000 9659
Chloride 3/3 7025-11 000 8.392 12/12 4.300-135 000 27 079
Chromium - total 3/3 5.8-10.5 8.4 19/22 7.2-475 72.5
Chromium - IV NA NA NA ND/3 ND ND
Copper 1/3 4.5 4.5 19/22 5-46 13.1
Cyanide ND/3 ND NO ND/22 ND ND
Iron 213 2~.500 . 3.371 19/22 152-7,600 1163
Lead 3/3 2.3-7 4.6 17/22 2.8-38 6.8
Marnesium . 3/3 1 055-13 000 5082 22/22 472-20000 9078
Manl!anese 1/3 90 90 16/22 10-165 34.3
Mercury ND/3 NO ND 4122 0.22-0.76 0.2
Nickel ND/3 ND ND 8/22 12.8-309 34
Nitrate-Nitrite 2/3 90-110 100 10/12 130-21,000 4,880
Nitrate NA NA NA NA NA NA
Nitrite NA NA NA NA NA NA
NitroSten Total NA NA NA NA NA NA
Nitrol!en, Total Kieldahl 213 200-765 483 9/12 400-15,000 1977
Phosuhorus Total 1/3 6600 6600 6/12 75-575 146
Potassium 213 8 900-84.500 46.700 19/22 1 050-96 000 9053
Selenium ND/3 ND ND 5/22 5.2-28 5
Sodium 3/3 8 700-54,500 27.7.33 22/22 2,000-33,000 12,658
Sulfate 3/3 3 800-9 950 6,017 11/12 6000-95,000 21 658
Vanadium ND/3 ND ND 16/22 9.4-160 18
Zinc 2/3 16-18.5 17.3 16/22 8-138 26.3
ORGANICS:
Bis(2-eth vlhexvl)Phthalate ND/2 ND ND 3/22 33-67 12.2
Carbon Disulfide ND/2 ND NO NO 122 NO ND
2 4-Dichlorophenol ND/2 ND ND ND122 ND ND
Endosulfan Sulfate ND/2 ND ND 1122 0.12 0.05
Tetrachloroethene ND/2 ND ND 2/22 5-6 5.0
\I~/L = micrograms p'er liter
ND = Not Defected above quantitation limit
NA = Not Analyzed
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 18
Samples Taken In Floridan Aquifer Back~round Samples: Surficial Aquifer
Range of Range of
Ground Water Analyte Frequency Detected Average Frequency Detected Average
of Concentrations Concentration of Conce~JL;tions Concentration
Detection (IIg!LJ (lIgfLJ Detection (II J (IIg!LJ
INORGANICS:
Alwnin um N0/10 NO NO 22/22 220-64,000 5,021
Ammonia 4/10 170-1800 708 4/12 110-12500 1,348
Antimony ND/10 ND ND 2/22 35.5-43.5 20
Arsenic N0/10 NO NO 1/22 12 1.8
Ban. um 8/10 11-120 30 22/22 12-410 108
Cadmium NO/I0 NO NO NO /22 NO NO
Calcium 10/10 2,800-55,000 29,880 22/22 975-23,000 9,659
Chloride 10/10 6200-34000 14520 12/12 4300-135000 27,079
Chromium - total N0/10 NO ND 19/22 72475 72.5
Chromium - IV NA NA NA NO/3 NO NO
Copper 1/10 12 NO 19/22 5-46 13.1
Cyanide N0/10 NO NO ND /22 NO NO
Iron NO/I0 NO NO 19/22 152-7,600 1.163
Lead NO/I0 NO NO 17/22 2.8-38 6.8
Magnesium 9/10 9200-18,000 11,678 22/22 472-20,000 9,078
Man
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
. Page 19
evaluate the potential ecological impacts from ground water contamination through
ground water discharge to surface water. Human exposure to surface water was not
evaluated for these ponds, since they are located in an industrial area and access is
restricted by fencing.
The surface water sample locations are shown on Figure 5-5. All surface water
samples were sent to a CLP laboratory for full TAL analyses, as well as for analysis
of the other inorganic chemicals of concern. The analytical results are summarized in
Table 5-5.
As indicated in Table 5-5, the concentrations of inorganic chemicals detected in
surface water sample collected from the abandoned drum area pond during the SRI
are near or below the ground water concentrations measured in the shallow
background monitoring wells (Le., MW-OISA, MW-02SA, MW-03SA, MW-04SA, MW-
OSSA, MW-07SA, GWS1, GWS2, GWS3, GWS4, and GWSS). Thus, ground water
contamination does not appear to be affecting this pond.
The concentrations of some of the inorganic chemicals detected in the surface water
sample collected from the easternmost Douglas Fertilizer Pond during the SRI,
however, are significantly (more than two times) higher than background ground
water concentrations. These chemicals incluq.e ammonia, manganese, total
phosphorus, and zinc. This pond previously received wastewater from' Douglas
Fertilizer operations and is thus a suspected source of contamination.
5.5.3 Substances Found In Sediments
Two sediment samples were collected from the easternmost Douglas Fertilizer Pond
to help evaluate whether this pond may still be acting as a primary source of ground
water contamination. Human exposure to sediment was not evaluated for these
ponds, since they are located in an industrial area and access is restricted by fencing.
The sediment sample locations are shown on Figure 5-5. The sediment samples were
sent to a CLP laboratory for full TAL analyses, as well as for analysis of the other
inorganic chemicals of concern. The analytical results are summarized in Table 5-6.
As indicated in Table 5-6, the concentrations of all of the inorganic chemicals detected
in the sediment samples collected from the easternmost Douglas fertilizer pond
during the SRI are significantly (more than two times) higher than background
sediment concentrations as identified in the 1986 RI. Like the surface water
contamination identified above, this sediment contamination likely represents the
residual contamination remaining due to Douglas Fertilizer operations, since this
pond previously received wastewater from Douglas Fertilizer operations.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 20
FIGURE 5-5: SURFACE WATER AND SEDIMENT SAMPLING LOCATIONS
\ \ SVi-OI -it ~RA;NACE SALVAG[ n
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JOO 0 300 0
r--- -
SCAlE IN fEET
LEGEND
6.
o
RAiLROAD
OITCH
SURfACE WATER SAMPLE
SEDIMENT SAMPLE
-
D
~
EXISiJlNG INTERMITTENT POND
EXISTING POND
-+-+-+-
roRMER POND (NO LONCER PRESENT)
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TABLE 5-5: CONTAMINANTS DEfECfED IN SURFACE WATER
.. :1;1::.I'I.~I'I.I'I!I:I:I'I:I'I'lililllll;lill'illl;I'1li!IIII.IIII.II~.~;i.;.:lllllilliill.II.II:II:~i..li:.i111'llli~llil~~!...III "
;!i[:[:1;1:1::1:~i::$111I~:[:[~::~~:;:[:[[[:~ illlllllliillllli.~I!i~lillllili ~lllliliiliilllllilllilll
:;::::;:;i:.:~:;::t.I{lIi~::!:i1::II::::
Aluminum 250 950 800 7800
Ammonia 20U 550 350 140
Barium 1 10J 20U] 6U] 96
Calcium 23000 19000 18000 25000
Chloride 37000 36000 37000 30000
Chromium 8U 12J 10 270
Iron 1300 -530 430 5400
Lead 3U 4 3U 17J
Magnesium 12000 13000 13000 20000
Manganese 91 1100 740 220
Potassium 9000 25000 23000 14000
Sodium 21000 40000 40000 33000
Sulfate 60000 34000 35000 1 10000
Total Kjeldahl 560 2100 2600 2400
Nitrogen
Total Phosphorus 20UR 12000J 13000J 1 100
Vanadium 9U 9U 1 IJ 91
Zinc SOU 180 150 57
Highest concentration measured in MW-OlSA, MW-02SA, MW-03SA, MW-04SA, MW-OSSA, MW-07SA, GWSl, GWS2,
GWS3, GWS4, and/or GWS5.
Data Qualifiers:
U = The chemical was analyzed for but not detected. The value preceding the "U" is the minimum quantitation limit.
J = The qualitative analysis of the chemical is acceptable, but the value cannot be considered as accurate. The value
preceding the "]" is the estimated value.
VJ = The chemical was analyzed for but not detected. The value is estimated for the minimum quantitation limit.
UR = The chemical was analyzed for but not detected. QC data indicate that the data are unusable, however, as the
compound mayor may not be present.
Concentrations are in ug/L. Concentrations printed in bold text are two or more times greater than background shallow ground
water concentrations.
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TABLE 5-6: CONTAMINANTS DETECTED IN SEDIMENT
Aluminum 24000 22000 21000 1600
Ammonia 2600 1400 1100 3
Arsenic 16 13 13 NO
Barium 270 410 300 NO
Beryllium 8.4 4U 7.6 NO
Cadmium 16 30 30 NO
Calcium 45000 36000 36000 1800
Chloride 310 160 140 NO
Chromium 390 210 250 NO
Cobalt 28 15 17 NO
Copper 5100 4900 4700 ND
Iron 52000 40000 45000 1200
Lead 600 460 450 9J
Magnesium 36000 19000 14000 NO
Manganese 19000 17000 17000 NO
Mercury 3 3.1 32 NO
Potassium 6200 4900 6700 NO
Sodium 1400 1400 1100 NO
Sulfate 170J 230J 1601 NA
Total Kjddahl Nitrogen 18000 5300 7800 700J
Total Phosphorus 140000 70000 18000 44
Vanadium 60 34 41 NO
Zinc 13000 13000 12000 NO
Background concentrations reported for the control pond in the Final Remedial Investigation Report, Zellwood
Groundwater Contamination Site (NUS, 1986).
Oa ta Qualifiers:
U = The chemical was analyzed for but not detected. The value preceding the "U" is the minimum quantitation limit.
J = The qualitative analysis of the chemical is acceptable, but the value cannot be considered as accurate. The value
preceding the "J" is the est,.h.ated value.
NO = The chemical was analyzed for but not detected. The minimum quantitation limit is unknown.
NA = The chemical was not analyzed for.
Concentrations are in mg/kg.
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6.0
SUMMARY OF SITE RISK
6.1
Risk Assessment Overview
CERCLA directs EP A to conduct a Baseline Risk Assessment (BRA) to determine
whether a Superfund site poses a current or potential threat to human health and the
environment in the absence of any remedial action. The baseline risk assessment
provides the basis for determining whether or not remedial action is necessary and
the justification for performing remedial action.
The risk assessment is based on the data gathered in the Supplemental Remedial
Investigation/Focused Feasibility Study (SRI/FFS) and includes analyses of samples
of ground water, surface water, and sediment. Estimates of current risks are based
on this investigation and in the absence of any site-specific remediation, future risk
estimates are based on the assumption that current soil and ground water chemical
concentrations will persist. Sections 6.2 through 6.6 address the risk assessment
evaluation for human health due to exposure to ground water. Section 6.7 describes
the potential impacts on aquatic and terrestrial life associated with contamination in
sediment and surface water at the ZeUwood Site.
6.2
Contam~ants of Potential Concern (COPCs) to Human ~
6.2.1 Screening Criteria
The chemicals measured in the various environmental media during the SRI/FFS
were evaluated for inclusion as chemicals of potential concern in the risk assessment
by application of screening criteria. The screening criteria which resulted in
elimination and selection of chemicals included the following:
.
Inorganic contaminant concentrations less than two times greater than
the average detected value of the respective background sample may be
deleted;
.
Essential nutrients present at low concentrations (Le., only slightly
elevated above naturally occurring levels) and only toxic at very high
doses may be deleted.
.
Inorganic and organic chemicals detected in ground water that exceed
state or federal maximum contaminant levels (MCLs) should be selected
as COpc.
.
Inorganic and organic chemicals detected in ground water that exceed
concentrations that represent a cancer risk level greater than 1 x 10-6 or a
Hazard Quotient (HQ) of 1 using residential tap water assumptions
should be selected as COPC.
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As a result of applying the above listed criteria, Table 6-1 lists the contaminants of
potential concern (COPC) associated with the Zellwood Site. The chemicals listed in
Table 6-1 are of greatest concern because of their toxicity, their relation to
background concentrations, their prevalence onsite, and the likelihood of human
exposure.
6.2.2 Contaminants of Potential Concern in Surficial Ground Water
Two inorganic chemicals were eliminated from the ground water pathway based on
the two times rule. Five naturally occurring essential nutrients were eliminated
because they are toxic only at very high doses. No organics were selected because
detected concentrations were below MCLs and risk based levels. Nineteen chemicals
reported in the site-related monitoring wells meet the COPC criteria (Table 6-1).
These were evaluated in the quantitative risk assessment.
6.2.3
Contaminants of Potential Concern in the Floridan Aquifer
All inorganics and organics were eliminated from the ground water pathway with
the exception of five contaminants. Aluminum, Iron, and Manganese were selected
because they were detected at concentrations that exceed secondary drinking water
standards in Florida. Barium and ammonia could not be eliminated based on the
criteria described above. Therefore, five COPC were reported for the Floridan
Aquifer (Table 6-1).
6.2.4 Contaminants of Potential Concern in Private Wells
Only ammonia and thallium were retained as COPC in the private wells sampled at
the Zellwood Site. Thallium was detected in one of the ten private wells at a level
that may be of concern, but there is no evidence linking it to the Site (i.e., it is not
detected in Site wells). Ammonia was detected in four of ten private wells at
concentrations above a 100 ug/L, the EP A guidance concentration used to select
COPCs, however, ammonia concentrations do not exceed two times the average
background concentration for ammonia in the surficial aquifer, indicating that it is
probably a regional problem unrelated to the Site.
6.3
Exposure Assessment
6.3.1 Introduction
The purpose of the exposure assessment is to estimate the magnitude of potential
human exposure to the contaminants of potential concern at the Zellwood Site.
Whether a contaminant is actually a concern to human health and the environment
depends upon the likelihood of exposure, i.e. whether the exposure pathway is
currently complete or could be complete in the future. A complete exposure
pathway (a sequence of events leading to contact with a contaminant) is defined by
the following four elements:
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TABLE 6-1: CONTAMINANTS OF POTENTIAL CONCERN
Contaminants Ground Water
Surficial Floridan Aquifer Private Wells
INORGANICS
Alumiz1um X X
Ammonia X X X
Arsenic X
Barium X X
Cadmium X
Chloride X
Chromium (Ill) X
Copper X
Cyanide X
Iron X X
Lead X
Manganese X X
Mercury X
Nickel X
Nitrate X
Nitrite X
Selenium X
Sulfate X
Thallium X
Vanadium X
.
a source and mechanism of release from the source;
.
a transport medium (e.g., surface water, air) and mechanisms 'of
migration through the medium;
.
the presence or potential presence of a receptor at the exposure point;
and
.
a route of exposure (ingestion, inhalation, dermal absorption).
If all four elements are present, the pathway is considered complete.
6.3.2 Source, Mechanism of Release, and Transport
The suspected primary sources of contamination at the Site are the percolation ponds
previously used by Douglas Fertilizer and Chemical Company and Drum Services
Company for the disposal of facility wastewaters. Most of the sources were
remediated during Operable Unit 1 (OU1) activities; however, the easternmost
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Page 26
Douglas Fertilizer Pond was not remediated in OUI and may still be serving as a
continuing source of contamination. The major constituent release and transport
mechanisms potentially associated with the Site is the infiltration of precipitation
through the percolation pond resulting in contaminants leaching into the ground
water.
6.3.3
Potential Receptors and Routes of Exposure
6.3.3.1
Current
Residents in the vicinity of the Site use private wells as their drinking water source.
There is no evidence of contamination in any of the ten private wells sampled during
the SRI that may be attributed to the Site. Thallium was detected in one of the ten
private wells at a level that may be of concern, but there is no evidence linking it to
the Site (i.e., it is not detected in Site wells). Ammonia was detected in four of ten
private wells at concentrations above a 100 ug/L, the EPA guidance concentration
used to select COPCs; however, 2.mmonia concentrations do not exceed two times the
average background concentration for ammonia in the surficial aquifer, indicating
that it is probably a regional problem unrelated to the Site. No other chemicals were
detected in private wells above the criteria established for COPC. Further, no other
water supply wells are known to be contaminated with chemicals attributable to the
Zellwood Site. Since no drinking water wells are known to be contaminated with
site-related chemicals, exposure to contaminants detected in ground water is not a
currently complete exposure route. Lacking a complete exposure route, there is no
current risk associated with consumption of ground water in the Site vicinity.
6.3.3.2
Future
In the future use scenario, new wells might be installed within the contaminant
plume in either the surficial or Floridan aquifer and utilized by potential residents.
Exposure assumptions for these receptors are:
.
the body weights for the adult and the child receptors are 70 kg and
15 kg, respectively;
.
the factor for ingestion of ground water for an adult resident is 2
liters/ day and for a child resident is 1 liter/day;
.
the averaging time is calculated over a period of 24 years for the adult
and 6 years for the child to yield an averaging time of 8,760 days and
2,190 days, respectively; and
.
for carcinogens, intakes are calculated by averaging the total cumulative
dose over a 70-year lifetime, a carcinogenic averaging time of 25,550
days, to yield a lifetime average daily intake.
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6.3.4 Pathways
In the future use scenario, new drinking water wells might be installed in either the
surficial or the Floridan aquifer and utilized by residents. Based on this
understanding of the Site, ground water is the only medium potentially available for
human contact. Ingestion of ground water is the most important potential pathway
for human exposure, and the only one evaluated in this assessment. Dermal
exposure to inorganics in ground water was considered to be negligible, and none of
the COPCs is volatile; for these reasons, neither of these potential pathways was
evaluated.
6.3.5 Exposure Point Concentrations and Dose Assumptions
The 95 percent upper confidence limit (DCL) on the arithmetic mean was calculated
and used as the reasonable maximum exposure (RME) point concentration of
contaminants of potential concern in each-media evaluated, unless it exceeded the
maximum concentration. Where this occurred, the maximum concentration was used
as the RME concentration for that contaminant. Exposures point concentrations are
summarized in Section 6.4, Tables 6-2. The exposure point concentrations for each of
the contaminants of potential concern and the exposure assumptions for each
pathway were used to estimate the chronic daily intakes for the potentially complete
pathways.
6.4
Toxicity Assessment
The purpose of the toxicity assessment is to assign toxicity values (criteria) to each
contaminant evaluated in the risk assessment. The toxicity values are used in
conjunction with the estimated doses to which a human could be exposed to evaluate
the potential human health risk associated with each contaminant. In evaluating
potential health risks, both carcinogenic and non-carcinogenic health effects were
considered.
Cancer slope factors (CSFs) are developed by EP A under the assumption that the risk
of cancer from a given chemical is linearly related to dose. CSFs are developed from
laboratory animal studies or human epidemiology studies and classified according to
route of administration. The CSF is expressed as (mg/kg/ day)"! and when multiplied
by the lifetime average daily dose expressed as mg/kg/ day will provide an estimate
of the probability that the dose will cause cancer during the lifetime of the exposed
individual. This increased cancer risk is expressed by terms such as 1x10-6. This is "a
hypothetical estimate of the upper limit of risk based on very conservative or health
protective assumptions and statistical evaluations of data from animal experiments or
from epidemiological studies. To state that a chemical exposure causes a lxlO-6
added upper limit risk of cancer means thaUf 1,000,000 people are exposed one
additional incident of cancer is expected to occur. The calculations and assumptions
yield an upper limit estimate which assures that no more than one case is expected
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and, in fact, there may be no additional cases of cancer. USEP A policy has
established that an upper limit cancer risk falling below or within the range of lxlO-6
to lxlO-4 is acceptable.
The toxicity criteria used to evaluate potential non-carcinogenic health effects are
reference doses (RIDs). The RID is expressed as mg/kg/ day and represents that
dose that has been determined by experimental animal tests or by human observation
to not cause adverse health effects, even if the dose is continued for a lifetime. The
procedure used to estimate this dose incorporates safety or uncertainty factors that
assume it will not over-estimate this safe dose. If the estimated exposure to a
chemical expressed as mg/kg/ day is less than the RID, the exposure is not expected
to cause any non-carcinogenic effects, even if the exposure is continued for a lifetime.
In other words, if the estimated dose divided by the RID is less than 1.0, there is no
concern for adverse non-carcinogenic effects.
Exposure Point Concentrations and Toxicity Potency Factors used to calculate Human
Health Risks are summarized in Table 6-2.
Risk Characterization
6.5
6.5.1 Overview
To evaluate the estimated cancer risks, a risk level lower than lxlO-6 is considered a
minimal or de minimis risk. The risk range of lxlO-6 to lxlO-4 is an acceptable risk
range and would not be expected to require a response action. A risk level greater
than lxlO-4 would be evaluated further and a remedial action to decrease the
estimated risk considered.
A hazard quotient (HQ) of less than unity (1.0) indicates that the exposures are not
expected to cause adverse health effects. An HQ greater than one (1.0) requires
further evaluation. For example, although the hazard quotients of the contaminants
present are added and exceed 1.0, further evaluation may show that their toxicities
are not additive because each contaminant affects different target organs. When the
total effect is evaluated on an effect and target organ basis the hazard index of the
separate chemicals may be at acceptable levels.
Carcinogenic risks and non-carcinogenic hazards were evaluated for potential
exposures to contaminants of potential concern in ground water. The receptor
population was current and future area residents that could, theoretically, use the
ground water for a household water source.
6.5.2 Current Use
I
,
There are no currently complete exposure routes to Site contaminants; therefore, there
is no risk associated with exposure to ground water in the current use scenario.
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TAB LE 6-2: CONTAMINANTS OF POTENTIAL CONCERN IN GROUND WATER AND
TOXICITY ASSESSMENT
Media and Chemical Exposure Point Concentrations Toxicity
Frequency of Exposure Pl RED Target Site/Effect CSF
Detection Cone. mg/kg/ day 1/(mg/kg/ day)
Aluminum 4/4 100,000 1.0E+OO (Ill) NA NA
Ammonia 16/16 340,000 lE+OO (c) Taste threshold NA
Arsenic 6/16 29 3E-04 (i) Skin, blood vessels 1.75E+OO (i)
Barium 3/4 460 7E-02 (0 Iner. blood pressure NA
Cadmium 8/16 22.1 5E-04 (i) Proteinuria NA
Chloride 16/16 1,450,000 NA NA NA
Chromium (III) 7/16 91 lE+OO (i) NOAEL NA
Copper 4/4 1,000 3.7-02 (h) CI irritation NA
Cyanide 5/16 138 2E-02 (i) NOAEL NA
Iron 3/4 3,800 NA NA NA
Lead 11/16 26 NA CNS effects, blood NA
Manganese 4/4 1,400 5E-03 (i) CNS effects NA
Mercury 4/16 2 3E-04 (h) Kidney NA
Nickel 8/16 121 2E-02 (0 Deereased weight NA
Nitrate 10/12 144,000 1.6E+OO (i) Methemoglobinemia NA
Nitrite 6/12 7,350 lE-Ol (i) Methemoglobinemia NA
Selenium 4/4 86.5 SE-03 (i) Selenosis NA
Sulfate 14/16 590,000 NA NA NA
Thallium NA NA 8E-OS (i) lner. SCOT and LDH NA
Vanadium 4/4 2000 7E-03 (h) None Observed NA
Aluminum 3/3 16000 lE+OO NA NA
Ammonia 2/3 555 lE+OO (c) Taste threshold NA
Barium 2/3 300 7E-02 (i) Iner. blood pressure NA
Iron 2/3 6500 NA NA NA
Manganese 1 /3 90 5E-03 (i) CNS Effects NA
NA = Not Applicable (no data)
(i) = IRIS
(h) = HEAST
(Ill) =
(c) = calculated from drinking water standard in HEAST
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6.5.3
Future Use
6.5.3.1
Ingestion of Ground Water: Surficial Aquifer
Estimated potential added cancer risks and non-carcinogenic hazards from the use of
contaminated ground water from the surficial aquifer for household use are outside
EPA's acce}-Jtable range. The estimated cancer risk exceedance is related to arsenic
concentrations. The estimated non-carcinogen risk exceedances are related to a
number of heavy metal and other inorganic concentrations. A summary of the risks
is provided in Table 6-3.
6.5.3.2
Ingestion of Ground Water: Floridan Aquifer
No carcinogens were detected in the Floridan aquifer; therefore calculation of an
excess cancer risk is not appropriate. Non-cancer effects are possible for child, adult,
and lifetime residents based on primary exposure to aluminum and manganese. A
summary of the risks is provided in Table 6-3.
6.5.3.3
Exposure to Lead
Neither a cancer slope factor nor reference dose value is available for lead. Instead,
blood lead concentrations have been accepted as the best measure of exposure. EP A
has developed an integrated exposure uptake biokinetic model to assess chronic,
noncancer exposures of children to lead. Version 0.99d of the model was used to
evaluate exposure of future child residents to lead.
The arithmetic mead of lead concentrations (using one-half the quantitation limit
where no lead was detected) in surficial aquifer ground water were used as the input
for the model. Default values for lead in air, soil and dust, and dietary ingestion
were used. No contribution from paint ingestion was included. The results of the
model indicate that projected blood lead levels are below 10 ug/dL for all age
groups. EPA uses a blood lead level of 10 ug/dL as the benchmark to evaluate lead
exposure.
6.6
Identification of Uncertainties
U!1certainty is inherent in the risk assessment process. Each of the three components
of risk assessment (data evaluation, exposure assumptions, and toxicity criteria)
contribute uncertainties. For example, the assumption that ground water
concentrations will remain constant over time may overestimate the lifetime
exposure. Contaminants are subject to a variety of attenuation processes. In
addition, for a risk to exist, both significant exposure to the pollutants of concern and
toxicity at these predicted exposure levels must exist. The toxicological uncertainties
primarily relate to the methodology by which carcinogenic and noncarcinogenic
criteria (i.e., cancer slope factors and reference doses) are developed. In general, the
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TAB LE 6-3: SUMMARY OF CANCER AND NON CANCER RISKS
Chemical of Potential Concern Child Resident Adult Resident Lifetime Resident
(6-yr + 24-yr)
Cancer HQ Cancer HQ Cancer HQ
:::il..~::~~mfl:;:i;::;:::i:::::~::i:::::;\!1i::::i::~~:;\\:~:::::::~:i::::;ili::i::i~ii:;::::::!!:i!i!~::i:i::::!:ii:::::::::!!i~::::i:::::::::::::::::;:::~::::~:::!:i!~:~:::::i:::,::::::i::i::::::i:::!:::::~:!::::::!!!::i::::!!::::!:!;::,!::::::i:::;~!:::::i!~::::~:!:!i!!!:::!:!:!:!,!:::::!:!!!!:i!:!;!!!!:!:::!!'::!::!:,:::!!::!!!!::!:!:::!!!::!:;!!!!
Aluminum NA 6.4 NA 2.7 NA 9.1
Ammonia NA 21.7 NA 9.3 NA 31.0
Arsenic 3M4 62 5E-04 2.7 8E-04 8.9
Barium NA 0.4 NA 02 NA 0.6
Cadmium NA 2.8 NA 12 NA 4.0
Chloride NA NA NA NA NA NA
Chromium (IIl)4 NA 0.01 NA 0.00 NA 0.Q1
Copper NA 1.7 NA 0.7 NA 2.4
Cyanide NA 0.4 NA 0.2 NA 0.6
Iron NA NA NA NA NA NA
Lead NA NA NA NA NA NA
Manganese NA 17.9 NA 7.7 NA 25.6
Mercury NA 0.5 NA 0.2 NA 0.7
Nickel NA 0.4 NA 02 NA 0.6
Nitrate NA 5.8 NA 2.5 NA 8.3
Nitrite NA 4.7 NA 2.0 NA 6.7
Selenium NA 1.1 NA 0.5 NA 1.6
Sulfate NA NA NA NA NA NA
Vanadium NA 18.3 NA 7.8 NA 26.1
TOTAL RISK (SURFICIAL AQUIFER) 3E-04 88 5E-04 38 8E-04 126
:!,::_miiw.:;:!!!:::::::::::!:!:!~!i:j:::;::::;;!!:::j\\:;;ii1!\:!:i1!:!!:~:::::1!::!!i:;:!!!;::::!!::!;::~:!:::1!il::::i::\i!:!::!!!:::::!!!:I!!:!ili:!:1!!i!il:::::'I::!i:!i::!:~i:::!1::':::i::~!;i::::::::::i~!:,::~:::::~::!!::'::i':::~!!!!:!::::::::;:::::::::,:::::~:::::::::::\::':::i::::::i:\:\:i:~:::~:::::::::::'::::;!::::::!!::!:!.!:::!::!\\::!::~!I:::::::
Aluminum NA 1.0 NA 0.4 NA 1 .5
Ammonia NA 0.04 NA 0.02 NA 0.06
Barium NA 0.3 NA 0.1 NA 0.4
Iron NA NA NA NA NA NA
Manganese NA 12 NA 0.5 NA 1 .7
I TOTAL RI-.3K (FLORIDAN AQUIFER) I NA I 2.5 I NA I 1 .1 I NA I 3.6 I
HQ Hazard Quotient (non cancer risk)
NA Not Applicable
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methodology currently used to develop cancer slope factors and reference doses is
very conservative, and likely results in an overestimation of human toxicity and
resultant risk.
The use of conservative assumptions throughout the risk assessment process are
believed to result in an over-estimate of human health risk. Therefore, actual risk
may be lower than the estimates presented here but are unlikely to be greater.
6.7
Ecological Evaluation
6.7.1
Overview
The risk to the environment is determined through the assessment of potentially
adverse effects to ecosystems and populations resulting from Site-related
contamination using qualitative methods. Surface water and sediments from the
easternmost Douglas Fertilizer Pond were sampled to determine the extent of
contamination, as described in Section 5. The ground water flow analysis showed
that contamination of surface water bodies as a result of groand water discharge is
not a concern. Lake Apopka, 3.5 miles south of the Site, is the nearest major surface
water body in the direction of surficial aquifer ground water flow. Because of the
location of the plume, the travel time of contaminants in ground water, and the
distance from the source of contamination, impacts on Lake Apopka are not
anticipated. Contaminants detected in each media are listed in Table 5-2 through 5-5.
6.7.2 Contaminants of Potential Ecological Concern
Contaminants of potential ecological concern (COPECs) were selected by eliminating
from the analysis essential nutrients considered toxic only at very high
concentrations, and by eliminating inorganic analytes whose concentrations were
within background concentrations.
6.7.2.1
Surface Water
During the 1986 Remedial Investigation (RI), the Northwest pond was selected as the
reference pond and represented local surface water and sediment quality. In Table
5-4, the concentrations of aluminum, ammonia, iron, lead, manganese, total Kjeldahl
nitrogen, phosphorus, vanadium, and zinc detected b the surface water sample
collected from the easternmost Douglas Fertilizer Pond are shown as significantly
higher (two or more times greater) than background surface concentrations in the
reference pond or were not detected. Calcium, chloride, magnesium, potassium,
sodium, and sulfate were eliminated as COPECs for surface water. COPECs for
surface water are provided in Table 6-4.
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6.7.2.2
Sediment
As shown in Table 5-5, the concentrations of all inorganics in the sediment samples
collected from the easternmost Douglas Fertilizer Pond are significantly (more than
two times) higher than background sediment concentrations as identified in the 1986
RI. Calcium, chloride, magnesium, potassium, sodium, and sulfate were eliminated
as COPECs. Aluminum, ammonia, arsenic, barium, beryllium, cadmium, cobalt,
copper, lead, iron, manganese, mercury, phosphorus, vanadium, and zinc were
retained as COPECs.
6.7.3 Exposure Assessment
Although the former percolation ponds at the Site are relatively small with no inlets
or outlets, there is a variety of flora, fauna, and wildlife at the Site. Investigations
were conducted in 1986 and July 1994 to gather information on ecological conditions
at the Site. Dominant vegetation at the Site includes mesic hammock. Marshy areas
are located north and west of the Site; whereas, very productive muck farms are
located to the south.
The various avifauna species observed or heard at the Site in 1994 are listed in Table
6-5. Two active eagle nests are in the vicinity of the Zellwood Site. Nest No. OR17 is
3 miles north of the Site and Nest No. LA27 is 5 miles northwest of the Site.
Aquatic vegetation, consisting of pennywort (Hydrocotyle umbellata), duckweed (Lemna
minor), and maidencane (Panicum hemitomon), cover approximately 90 percent of the
water surface in the easternmost Douglas Fertilizer Pond. Dragonflies were observed
on the pond. A Florida soft-shelled turtle (Trionyx ferox) was observed. on the banks.
The pond may support small forage fish like mosquito fish, though none were
observed. The substratum of the approximately 150 feet long and 30 feet wide pond
consists of 1 foot of muck.
The target receptors were divided into two main categories: terrestrial and aquatic.
Terrestrial and aquatic receptors may be exposed to the COPECs in the easternmost
Douglas Fertilizer Pond via the following pathways:
.
ingestion of surface water or sediment,
.
direct contact with surface water or sediment, and
.
ingestion of aquatic biota that may have bioaccuInulated COPECs
detected in sediment and surface water.
Since only on surface water and two sediment samples were collected, only
maximum concentrations of COPECs detected in the easternmost Douglas Fertilizer
pond were used as exposure point concentrations (EPCs). These estimated EPCs are
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 34
appropriate for evaluating potential adverse effects related to the direct exposure to
COPECs.
6.7.4 Toxicity Assessment
6.7.4.1
Ground Water/Surface Water
As a means of characterizing aquatic toxicity, the EP A Region IV Waste Management
Division has established screening levels for surface water at hazardous waste sites,
primarily based upon the Ambient Water Quality Criteria. Exceedance of these
screening levels might indicate a potential for adverse ecological effects (depending
upon factors such as frequency of detection, degree of exceedance, etc.), thus
indicating a need for more site-specific ecological investigations, such as toxicity
testing. Maximum surface water EPCs for each COPEC were compared to acute and
chronic screening values for a particular COPEe.
6.7.4.2
Sediments
The easternmost Douglas Fertilizer Pond sediment was evaluated by comparing
maximum sediment concentrations with EP A Draft Region IV Waste Management
Division Sediment Screening Values for pond benthic organisms (e.g., insect larvae,
oligochaetes). The EP A Region IV values provide a preliminary screening tool for the
review of chemical data associated with hazardous waste sites. Concentrations in
excess of the screening values may indicate a need for more investigation (e.g., site-
specific toxicity tests and literature reviews).
6.7.5 Risk Characterization
6.7.5.1
Ground Water ISurface Water
Comparison of the concentrations of COPECs in surface water with regional
screening values was used to assess the likelihood of adverse effects of surface water
to aquatic life. A number of contaminants in surface water exceeded regional
screening values. Water quality criteria were not available for all detected
contaminants; therefore, the contribution of all the contaminants of potential concern
could not be evaluated. Despite the absence of some criteria, the results show that
both chronic and acute adverse effects may have already occurred to aquatic life
inhabiting the easternmost Douglas Fertilizer Pond.
6.7.5.2
Sediment!
I
Comparison of the concentrations of COPECs in sediment with regional screening
values was used to assess the likelihood of adverse effects of sediment to aquatic life.
A significant number of contaminants in sediment exceeded regional screening
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Zel1wood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 35
values. Sediment screening levels were not available for all the detected
contaminants; therefore, the contribution of all the contaminants of potential concern
could not be evaluated. Despite the absence of some criteria, the results show that
benthic organisms may be severely affected by the presence of arsenic, cadmium,
chromium, copper, lead, mercury, and zinc. However, adult dragonflies were
observed on the pond, indicating that dragonfly larvae are in the sediment, and that
the larvae were able to develop and emerge to adults.
'6.7.6 Uncertainty Analysis
The main sources of uncertainty associated with this ecological evaluation can be
attributed to the items below.
.
Information necessary to evaluate the potential effects of aquatic
exposures to sediment chemicals is limited.
.
The possibility that organisms may be acclimated or adapted to chromc
exposure to some chemicals, such as metals was not considered, and as
a result, risks associated with toxic metal exposure may be
overes tima ted.
.
Risk estimates based solely on maximum concentrations in samples
collected during one sampling event may overestimate or underestimate
the actual population- or community-level effects.
.
Sediments and surface water constitute complex chemical mixtures and
it is possible that antagonistic or synergistic toxilogical effects may occur
between any of the chemical constituents. These factors were not.
accounted for.
7.0
DESCRIPTION OF ALTERNATIVES
7.1
Remedial Action Objectives
Since the contaminants of concern in ground water are metals and other inorganics,
the ability of current technology to remove the contaminants could not be confirmed.
Therefore, EP A is proposing that an interim ground water action be taken at this Site,
to eliminate a source of ground water contamination and evaluate the technical
practicability of achieving ground water cleanup at the Site. If preliminary design
studies indicate it is practicable to implement final remedial design, remediation
goals will be established for ground water.
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Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 36
Based on the limited surface water and sediment sampling conducted during this
SRI, sediments in the easternmost Douglas Fertilizer Pond could be a continuing
source to ground water contamination and adverse effects on aquatic and benthic
organisms in the pond have probably occurred and future effects are likely.
Contaminants in sediment at levels above those required for the protection of ground
water are listed in Table 7-1.
Actual or threatened releases of hazardous substances from this Site, if not addressed
by implementation of the response action selected in this ROD, may present an
imminent and substantial endangerment to public health, welfare, or the
environment.
The Focused Feasibility Study Report evaluated possible alternatives for remediation
of contamination at the Zellwood Site. Since the feasibility study is focused and since
the estimated extent of sediment contamination is relatively small, the development
of sediment process options and remedial alternatives for sediment contamination
was not performed. Instead, sediment contamination is addressed in this FFS by
including excavation and offsite disposal (either at a RCRA or a solid waste landfill)
of sediments in all of the OU2 alternatives ( with the exception of the No Action
Alternative).
A total of four (4) alternatives have been established for detailed analysis
consideration. These alternatives were selected to provide a range of remedial
actions for the Site.
7.2
Alternative No.1: No Action
The no action alternative was developed as required by the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP), the regulation
implementing the Superfund law. It is used as a baseline for comparing other
alternatives. Under this alternative, EP A would take no action to remedy any
contaminated media at the Site.
The only cost associated with this alternative relates to ground water monitoring.
Ground water monitoring wo-c.1ld be accomplished utilizing existing monitoring wells
plus additional new wells that would have to be installed. Expenditures include
capital costs for monitoring wells and equipment ($ 15,000), and annual and periodic
operations and maintenance costs ($ 598,000). The present worth cost estimate for
this alternative would be approximately $ 613,000.
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ZeUwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 37
TABLE 7-1: SUMMARY OF REMEDIAL ACTION PERFORMANCE STANDARDS
Chemical of Concern Sediment
Remediation Basis
Level (mg/L)
Arsenic 10 Protection Ground Water
Chromium III 100 OUI Remediation Goal
Lead 220 OUI Remediation Goal
Vanadium 1 Practical Quan. Limit
NOTE: It is generally the philosophy of EPA not to require remediation to less than average background levels.
7.3
Alternative No.2 - Limited Action
Alternative 2 consists of implementing the following remedial actionS:
.
Institutional Controls As Deed Notices;
Ground water monitoring of the surficial and Floridan aquifer; and
Excavation and off site disposal of contaminated sediments at a solid waste
landfill.
.
.
This remedial alternative includes implementation of institutional measures to
control, limit, and monitor activities onsite. The objectives of institutional actions are
to prevent prolonged exposure to contaminant concentrations, control future
development or excavation at the Site, and prevent the installation of water supply
wells within the boundaries of the Site. These objectives are accomplished by
monitoring ground water at the Site and limiting use and access by placing
institutional controls in the form of deed notices on all properties within potentially
contaminated areas. .
This alternative also includes excavation and offsite disposal of sediments from the
. easternmost Douglas Fertilizer Pond. Because it is not known whether sediments will
pass TCLP testing, this alternative is divided into two options. In Option A, it is
assumed that the sediments would pass TCLP testing, and could thus be disposed of
at a local industrial solid waste landfill. In Option B, it is assumed that the
sediments would not pass TCLP testing, and thus must be disposed of at a RCRA-
permi tted landfill.
This alternative may not remediate ground water in a reasonable timeframe (less than
100 years). However, an accurate timeframe for natural-attenuation of contaminants
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 38
has not been determined. Expenditures include capital costs for deed restrictions and
institutional controls, sediment excavation and disposat and monitoring wells and
equipment, and annual and periodic maintenance costs. The present worth cost
estimate for this alternative would be approximately $ 732,000 for Option A (i.e., $
134,000 in capital costs and $ 598,000 for O&M), and $ 841,000 for Option B (Le., $
243,000 in capital costs and $ 598,000 for O&M).
7.4
Alternative No.3 - Ground Water Extraction, Treatment Using Chemical
Precipitation, Air Stripping, and Biological Reaction, and Surface Water
Discharge
Alternative 3 consists of implementing the following remedial actions:
.
Institutional Controls As Deed Notices;
Ground water monitoring of the surficial aquifer;
Ground water recovery via extraction wells;
Ground water treatment, as determined by design studies to be necessary
using some or all of the following processes: spray irrigation, equalization,
precipitation/ flocculation/ sedimentation, filtration, air stripping, biological
reaction, and/or carbon adsorption;
Discharge compatible with treatment process, such as to onsite infiltration
gallery or surface water via onsite canal; and
Excavation and offsite disposal of contaminated sediments at a solid waste
landfill (non-hazardous disposal).
.
.
.
.
.
Figure 7-1 illustrates the treatment system proposed for this alternative based on
available information. Should design studies reveal suspected metal contaminants
are not dissolved, the treatment train may be modified accordingly. The processes
proposed in this alternative would be required to reduce alwninum, ammonia,
arsenic, cadmium, chloride, iron, lead, manganese, mercury, nitrate/nitrite, and
vanadium prior to surface water discharge. Waste by-products generated as a result
of treatment would have to be disposed of in either a solid waste landfill or a RCRA-
permitted landfill depending on the TCLP analysis.
Discharge to an onsite infiltration gallery is preferred at this Site should a system
similar to Figure 7-1 be required. If discharge to the infiltration gallery is detennined
to be infeasible during design, due to the volume of discharge or the elevation of the
water table, surface water discharge to an onsite canal would be considered. A
National Pollutant Discharge Elimination System (NPDES) pennit would be required
to discharge treated ground water to a surface water body. Requirements for
discharge to the infiltration gallery or surface water are provided in Table 7-2. Land
discharge woulO. be necessary should spray irrigation be determined appropriate
treatment during design studies.
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 39
o
q WELLS
FIGURE 7-1: ALTERNATIVE 3 PROCESS FLOW DIAGRAM
EOUALIZA TlON
TANK
~~~~\~lL FADJUSTMENT
r-,
~ 'CO,'''',,"", """I
~~g~~~fB?6'~ I I
LlJLI L_-!
OFF-GAS TO
ATMOSPHERE
AIR
pH
ADJUSTMENT
METHANOL
ADDITION
OVERFLOW
:::. DENITRIFiCATION
:::. FILTER
OFF-GAS
-.- NUTRIENT
ADDITION
."
BACKWASH TO
EOUILIZATION TANK
OR
SLUDGE TO
DISPOSAL
,1,
I f'~ER I DENITRIFIED
~LARII'IE WA TER
L_.J
w
....
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 40
TABLE 7-2: DISCHARGE STANDARDS
.
Jr
..
'."...'.' ."......,
~
5,021(0)
28,072(b)
50
2,000
5
250,000
100
1,000
200
1,163(0)
15
50
2
100
10,000
1,000
50
250,000
49
\.-r
lINt
'.
Aluminum
Ammonia (un-ionized)
Arsenic
Barium
Cadmium
Chloride
Chromium III
Copper
Cyanide
Iron
Lead
Manganese
Mercury
Nickel
Nitrate
Nitrite
Selenium
Sulfate
Vanadium
Note:
(a)
Background ground water concentration.
(b)
Based on risk.
(e)
.
..
II",,'H
.CE}
TO.. ...
'T".. ....
. .0'''''' :,.
~
130(C)
20
50
2,OOOCd)
e(OJ8S2IWiI-3.49) (e)
5,000
eIO.819[lnHj+1561) (e)
eIO.845[lnHJ-1.465) Ce)
5.2
1,000
15
50(d)
0.012
e
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Record cf Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 41
A ground water monitoring program would be necessary to ensure that the ground
water treatment system is effective and that contaminants do not migrate. It is likely
that a much longer time would be required to remediate the'heavy metals in the
ground water compared to the mobile inorganic contaminants of concern at the Site
(i.e., ammonia, chloride, cyanide, nitrate, nitrite, and sulfate). Therefore, this remedy
is an interim action for the purpose of eliminating a source of ground water
contamination and evaluating the technical practicability of achieving ground water
cleanup at the Site. Pumping may expedite the remediation time frame compared to
natural attenuation but may still prove to be impracticable to achieve drinking water
standards. The ability of this alternative to remediate ground water in a reasonable
timeframe would be further evaluated during remedial design and annually. during
remedial action.
This alternative includes institutional controls in the form of deed notices to prevent
access/ exposure to ground water by limiting what can be done at the Site. This
would prevent the use of drinking water wells and ban the installation of wells
within and downgradient of the contaminated area.
This alternative also includes excavation and offsite disposal of sediments from the
easternmost Douglas Fertilizer Pond. This alternative assumes that the sediments
would pass TCLP testing, and could thus be disposed of at a local industrial solid
waste landfill.
The present worth cost estimate for this alternative would be $ 5,141,000 (Le., $
1,305,000 in capital costs and $ 3,836,000 for O&M) and is based on surface water
discharge and a 30~year remediation timeframe, even though it is not known how
long this alternative would need to be implemented. The technical practicability of
continuing this remedy would need to be evaluated periodically.
7.5
Alternative No.4 - Ground Water Extraction, Treatment Using Chemical
Precipitation, Reverse Osmosis, and Surface Water Discharge
Alternative 4 consists of implementing the following remedial actions:
.
Institutional Controls As Deed Notices;
Ground water monitoring of the sUrficial aquifer;
Ground water recovery via extraction wells;
Ground water treatment, as determined by design studies to be necessary
using one or more of the following processes: equalization,
precipitation/flocculation/sedimentation, filtration, and reverse osmosis;
Discharge to onsite infiltration gallery or surface water via onsite canal; and
Excavation and offsite disposal of contaminated sediments at a solid waste
landfill (nonhazardous disposal). '\
.
.
.
.
.
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 42
Figure 7-2 illustrates the treatment system proposed for this alternative based on
available Site data. Should design studies reveal suspected metal contaminants are
not dissolved, the treatment train may be modified accordingly. The processes
proposed in this alternative would be required to reduce aluminum, ammonia,
arsenic, cadmium, chloride, iron, lead, manganese, mercury, nitrate/nitrite, and
vanadium prior to surface water discharge. Waste by-products generated as a result
of treatment would have to be disposed of in either a solid waste landfill or a RCRA-
permitted landfill depending on the TCLP analysis.
Discharge to an onsite infiltration gallery is preferred at this Site should a system
similar to Figure 7-2 be required. If discharge to the infiltration gallery is determined
to be infeasible during design, due to the volume of discharge or the elevation of the
water table, surface water discharge to an onsite canal would be considered. A
National Pollutant Discharge Elimination System (NPDES) permit would be required
to discharge treated ground water to a surface water body. Surface water discharge
requirements are provided in Table 7-2.
A ground water monitoring program would be necessary to ensure that the ground
water treatment system is effective and that contaminants do not migrate. It is likely
that a much longer time would be required to remediate the heavy metals in the
ground water compared to the mobile inorganic contaminants of concern at the Site
(i.e., ammonia, chloride, cyanide, nitrate, nitrite, and sulfate). Therefore, this remedy
is an interim action for the purpose of eliminating a source of ground water
contamination and evaluating the technical practicability of achieving ground water
cleanup at the Site. Pumping may expedite the remediation time frame compared to
natural attenuation but may still prove to be impracticable to achieve drinking water
standards. The ability of this alternative to remediate ground water in a reasonable
timeframe would be further evaluated during remedial design and annually during
remedial action.
This alternative includes institutional controls in the form of deed notices to prevent
access/ exposure to ground water by limiting what could be done at the Site. This
would prevent the use of drinking water wells and ban the installation of wells
within and downgradient of the contaminated area.
This alternative also includes excavation and offsite disposal of sediments from the
easternmost Douglas Fertilizer Pond. This alternative assumes that the sediments
would pass TCLP testing, and could thus be disposed of at a local industrial solid
waste landfill.
The present worth cost estimate for this alternative would be $ 7,945,000 (i.e., $
1,910,000 in capital costs and $ 6,035,000 for O&M) and is based on surface water
discharge and a 30-year remediation timeframe, even though it is not known how
long this alternative would need to be implemented. The technical practicability of
continuing this remedy would need to be evaluated periodically.
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Record of Decision
ZeIlwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 43
.
4 WELLS
FIGURE 7-2: ALTERNATIVE 4 PROCESS FLOW DIAGRAM
EOUALlZATlON
. TANK
BACKWASH
RETURNED TO
CHEMICAL EOUALIZA TlON TANK
ADDITlOl pH ADJUSTMENTt-
SAND
FIL TER
~ COAGULATIONI
FLOCCULATIONI -
SEDIMENTATION =
LLJLJ SO"" ..,,,
FOR BACKWASH
WATER
(CONDENSOR)
REVERSE
OSMOSIS
SYSTEM
OFFSITE
TREA TMENT
BRINE
OVERFLOW
EVAPORATOR
OFFStTE
DISPOSAL
EFFLUENT
DISCHARGE
TANK
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Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 44
8.0
SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES
8.1
Statutory Balancing Criteria
This section of the ROD provides the basis for determining which alternative
provides the best balance with respect to the statutory balancing criteria in Section
121 of CERCLA, 42 U.s.e. ~ 9621, and in the NCP, 40 CFR S 300.430. The major
objective of the feasibility study (FS) was to develop, screen, and evaluate alternatives
for the remediation of the Zellwood Site. A wide variety of alternatives and
technologies were identified as candidates to remediate the contamination at the
Zellwood Site. These were screened based on their feasibility with respect to the
contaminants present and the Site characteristics. After the initial screening, the
remaining alternatives/technologies were combined into potential remedial
alternatives and evaluated in detaiL One remedial alternative was selected from the
screening process using the following nine evaluation criteria:
.
overall protection of human health and the environment;
.
compliance with applicable relevant and appropriate requirements (ARARS);
.
long-term effectiveness and permanence;
.
reduction of toxicity, mobility, or volume of hazardous substances or
contaminants;
.
short-term effectiveness or the impacts a remedy might have on the
community, workers, or the environment during the course of implementation;
.
implementability, that is, the administrative or technical capacity to carry out
the alternative;
.
cost-effectivenes.s considering costs for construction, operation, and
maintenance of the alternative over the life of the project;
.
acceptance by the State, and
.
acceptance by the Community.
The NCP categorizes the nine criteria into three groups:
(1)
Threshold Criteria - overall protection of human health and the environment
and compliance with ARARs (or invoking a waiver) are threshold criteria that
must be satisfied in order for an alternative to be eligible for selection;
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 45
(2)
Primary Balancing Criteria - long-term effectiveness and permanence;
reduction of toxicity, mobility or volume; short-term effectiveness;
implementability and cost are primary balancing factors used to weigh major
trade-offs among alternative hazardous waste management strategies; and
(3)
Modifying Criteria - state and community acceptance are modifying criteria
that are formally taken into account after public comments are received on the
proposed plan and incorporated into the ROD.
The following analysis is a summary of the evaluation of alternatives for remediating
the Zellwood Site under each of the criteria. A comparison is made between each of
the alternatives for achievement of a specific criterion.
8.2
Threshold Criteria
8.2.1 Overall Protection of Human Health and the Environment
With the exception of the No Action alternative (Alternative I), all of the alternatives
would provide protection for human health and the environment to some degree.
Alternative 2 would limit access and exposure to contaminants but would not control
migration of contaminants. Alternatives 3 and 4 would limit access and exposure,
eliminate further migration, and reduce risk by removing contamination. Since
Alternative 1 did not pass this threshold criteria for providing protection of human
health and the environment, it will be eliminated from further consideration.
8.2.2 Compliance With ARARs
The remedial action for the Zellwood Site, under Section 121(d) of CERCLA, must
comply with federal and state environmental laws that either are applicable or
relevant and appropriate (ARARs). Applicable requirements are those standards,
criteria or limitations promulgated under federal or state law that specifically address
a hazardous substance, pollutant, contaminant, remedial action, location, or other
circumstance at a CERCLA site. Relevant and appropriate requirements are those
that, while not applicable, still address problems or situations sufficiently similar to
those encountered at the Site and that their use is well suited to the particular site.
To-Be-Considered Criteria (TBCs) are non-promulgated advisories and guidance that
are not legally binding, but should be considered in determining the necessary level
of cleanup for protection of human health or the environment. While TBCs do not
have the status of ARARS, EPA's approach to determining if a remedial action is
protective of human health and the environment involves consideration of TBCs
along with ARARs.
Location-specific ARARs are restrictions placed on the concentration of hazardous
substances or the conduct of activities solely on the basis of location. Examples of
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Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 46
location-specific ARARs include state and federal requirements to protect floodplains,
critical habitats, and wetlands, and solid and hazardous waste facility siting criteria.
Table 8-1 summarizes the potential location-specific ARARs for the Zellwood Site.
Action-specific ARARs are technology- or activity-based requirements or limitations
on actions taken with respect to hazardous wastes. These requirements are triggered
by the particular remedial activities that are selected to accomplish a remedy. Since
there are usually several alternative actions for any remedial site, various
requirements can be ARARs. Table 8-2 lists potential action-specific ARARs and
TBCs for the Zellwood Site.
Chemical-specific ARARs are specific numerical quantity restrictions on individually-
listed contaminants in specific media. Examples of chemical-specific ARARs include
the MCLs specified under the Safe Drinking Water Act as well as the ambient water
quality criteria that are enumerated under the Clean Water Act. Because there are
usually numerous contaminants of potential concern for any remedial site, various
numerical quantity requirements can be ARARs. Table 8-3 lists potential chemical-
specific ARARs for the ZeUwood Site.
Because of the uncertainty relative to ground water remediation at this Site, an
interim action is being taken to eliminate a source of contamination and to determine
if federal and state chemical specific ARARS (i.e., federal and state Maximum
Contaminant Levels (MCLs» can be met in ground water at the Zellwood Site within
a reasonable timeframe.
The treated effluent in Alternatives 3 and 4 will be capable of meeting chemical-
specific ARARs for discharge to ground water through a infiltration gallery or
discharge to surface water via an onsite canal.
Location- and action-specific ARAR5 need to be considered during the remedial
design of extraction wells, treatment system and excavation and disposal of pond
sediments. These ARARs should be easily met.
8.3
Primary Balancing Criteria
8.3.1 Long-Term Effectiveness and Permanence
Alternatives 2, 3, and 4 provide for the permanent removal of the only remaining
source of contamination (i.e., sediments in the Easternmost Douglas Fertilizer Pond).
Alternative 2 relies on n~~ural attenuation. If selected, detailed studies and modelling
would be necessary in another RI/FS to determine if natural attenuation would be
effective. Alternatives 3 and 4 may be effective and permanent if proven practicable
to implement, but might not remove all contamination due to Site geology and
contaminant behavior.
-------
TABLE 8-1: POTENTIAL LOCATION SPECIFIC ARARS AND TBCs
FEDERAL
Resource Conservation and Recovery
Act, as amended
Location Standards
Fish and Wildlife Coordination Act
Endangered Species Act
Aoodplain Management Executive Order
42 USC 6901
40 CFR 264.18(b)
16 USC 661-666
16 USC 1531 et. seq.
Executive Order 11988;
40 CFR 6.302,
Appendix A
Outlines the requirements (or constructing a
RCRA facility on a IOO-year floodplain.
Requires that Department of Fish and Wildlife be
consulted before federal agency alters a stream or
other water body.
.- .
.~.-:. "'.:. .
Action to conserve endangered or threatened
species. including consultation with the
Department of the Interior.
Federal agencies are required to reduce the risk
of flood loss. to minimize impact of floods, and
to restore and preserve the natural and beneficial
values of a floodplain.
Relevant and Appropriate
Relevant and Appropriate
Relevant and Appropriate
Relevant and Appropriare
.. n' ..
. n..
.. ...
"....
. .
. .
. ..
.FS.CliriSlderBtlon:
. . .. ..... .
. ".'..".."'."."...
. ... '..'. "....
". "', ........ ..
. . ::.:'::::::; ':: ..';:::::~':.::::::;:~:: ;';:: .
....
A facility located on a loo-year
floodplain must be designed,
constructed, operated, and maintained
to prevent washout or any hazardous
waste by a IOO-year flood, unless
waste may be removed safely before
floodwater can reach the facility or .
no adverse effectS on human health
and the environment would result if
washout occurred.
During the Identification. screening,
and evaluation of allematives, the
effects on streams and wetlands are
evaluated. If an allemative modifies
a body of water or potentially affects
fish or wildlife, EP A musty consult
the U.S. Fish and Wildlife Services.
During the idenlificalion. screening,
and evaluation of altematives, the
effects on endangered species. if any,
are evaluated.
The potential effects of any aClion
must be evaluated 10 ensure that the
planning and decision-making reflect
consideration of nood hazards and
floodplain management, including
restoration and preservation of
natural, undeveloped floodplain.
~
~
8-
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a
5
Po
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~
in
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-------
Protection of Wetlands
Rivers and Harbors Act of 1889
(Swion 10 Permit)
Coastal Zone Management Act
Clean Water Act
WiJderness Act
TABLE 8-1: POTENTIAL LOCATION SPECIFIC ARARS AND TBCs (continued)
Citalion
E~ecutive Order 11990;
40 CFR 6, AppendiJt A
33 USC 403
16 USC 1451 et. seq.
33 use 1251
16 USC 1311 et. seq.
Description
Action to minimize the destruction, los5, or
degradation of wetlands.
Restricts actions unden.aken in navigable waters.
Conduct activities in manner consistent with State-
approved management programs.
Restricts actions undernken in wilderness areas,
StMlls
Relevant and Appropriate
Relevanr and Appropriate
Relevanr and Appropriate
Relevant and Appropriate
FS Consideration
During the identification, screening.
and evaluation of alternatives. the
effects on wetlands must be
evaluated.
Requires permit for strucrures or
work in or affecting nayigable
waters.
The potential effects of any aClion
must be evaluated to ensure that the
alternatives renect consideration of
coastal zones.
Area must be managed in such a
manner as will leave it unimpaired as
wilderness and to preserve ils
wilderness character.
~
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-------
TABLE 8-2: POTENTIAL ACTION SPECIFIC ARARS AND TBCs
FEDERAL
Groundwater Extraction and Treatment
Resource Conservation and Recovery Act, as
amended
Identification of Hazardous Waste
Treatment of Hazardous Wastes in a Unit
Requirements for Generation, Storage,
Transportation, and Disposal of Hazardous Waste
Land Disposal Restrictions
DIsposal. Dlscharl!:e to Surface Water/POTW
Clean. Water Act
Requires Use of Best Available Treatment
Technology (BA TI)
Requires Use of Best Management Practices
National Pollutant Discharge Elimination System
Permit Regulations
42 USC 6901
40 CFR 261
40 CFR 264.601
40 CFR 265.400
40 CFR 263
40 CFR 264
40 CFR 268
33 USC dSI.
1376
40 CFR 122
40 CFR 125
40 CFR 122
(Subpart C)
Federal requiremenlS (or classification
and identification of hazardous wastes
Rules and requirements for the treatment
of hazardous wastes
Regulates storage, transportation, and
operation of hazardous waste generators
Prohibits dilution of as a substitute for
treatment.
.""'~ '..~" . '. .
Use of best available technology
economically achievable is required to
control discharge of toxic pollutants to
POTW
Requires development and
implementation of a Best Management
Practices program to prevent the release
of toxic constituents to surface water.
Use of best available technology
economically achievable for toxic
pollutants discharged to surface waters
Relevant and Appropriate
Relevantand Appropriate
Relevant and Appropriate
Applicable
Relevant and Appropriate
Relevant and Appropriate
~eJevant and Appropriate
This regulation ..,vill be applicable upon
withdrawal of groundwater for Iteatment if
hazardous sludges or resins are produced.
Performance standards will be specified for
compliance.
Performance standards will be specified for
compliance.
Treatment will be designed to treat waste
within regulatory guidelines.
BAIT will be considered when designing
the treatment system.
Proper management program will be
implemented to.ensure compliance with this
regulation.
The treatment system will be designed,
constructed, and operated to ensure that all
discharge effluents are in compliance with
the NPDES requirements.
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-------
TABLE 8-2: POTENTIAL ACTION SPECIFIC ARARS AND TBCs (continued)
Standard, Rcqt\trement, Criteria, or
Limitation
Discharge must be consistent with the
requirements of a Water Quality Management
Plan approved by EPA
Discharge must not increase contaminant
concentrations in offsite surface water
Underground Injection Control Program
OTHER
Occupational Safety and Health Administration
Sf ATE
Florida Air Pollution Control Requirements
Florida Surface Water Improvement and
Management Act
Florida Wastewater Facilities
Florida Underground Injection Control
40 CPR 122
40 CFR
121 (d)(2)(O)(iii)
40 CFR 144
29 CPR 1910
62 -4 F.A.C.
62-3 FAC.
62-6 FAC.
62 -28 FAC.
Discharge must comply with EPA.
approved Water Quality Management
Plan
Selected remedial action must establish
a standard of control to maintain surface
water quality
Provides criteria for injection of treated
groundwater
Provides safety rules for handling
specific chemical! for site workers
during remedial activities
Air pollution control, air quality, and
emissions standards
Regulates surface water' discharge and
discharges to P.QTW
Establishes that no wastes are to be
discharged to any waters of the state
without first being given the degree of
treatment necessary to protect the
beneficial uses of such water.
Regulates injection of
groundwater into aquifer.
treated
Re1cvant and Appropriate
Relevant and Appropriate
Relevant and Appropriate
Applicable
Relevanr and Appropriate
Relevant and Appropriate
Relevant and Appropriate
Relevant and Appropriate
Action To De Tnken
Treatment system will be designed to meet
regulatory guidelines.
Alternatives will be implemented 10 ensure
compliance with this regulation.
Treated water will be analyzed to meet
these criteria.
All appropriate safety equipment will be
onsire and appropriate procedures will be
followed during treatment activities.
Treatment system will be designed to
comply with these requirements.
Treated water will be analyzed to meet
criteria for discharge.
Treated water will be analyzed to meet
discharge criteria.
Compliance with this regulation will apply
when implementing discharge options.
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...
FEDERAL
Safe Drinking Water Act (SOW A)
National Primary Drinking Water Standards
(NPDWS)
National Secondary Drinking Water
Standards
Maximum Contaminant Level Goals
(MCLGs)
RCRA MCLs
TABLE 8-3: POTENTIAL CHEMICAL SPECIFIC ARARS AND TBCs
40 USC 300 et. seq.
40 CFR 141
Provides standards for 30 toxic compounds,
including the 14 compounds adopted as
RCRA MCLs, for public drinking system.
40 CFR 143
Establishes welfare-based standards for
public water systems (secondary maximum
contaminant levels)
Publication L. ND 99-399, 100
Stat. 642 (1986)
The MCLGs are non-enforceable health
goals set,~.t leY~ls that would result in no
known or aniicipated adverse health dfecu
with an adequate margin of safely.
40 CFR 264.94
Provides standards for 14 toxic compounds
and pesticides for protection of
groundwater. These standards are equal to
the MCLs established by the NPDWS.
This regulation also provides the basis for
application of alternate concentration limit
(ACL) on a site-specific basis,
Relevant and Appropriate
To Be Considered
Relevant and Appropriate
Relevant and Appropriate
Inorganic contamination WiI'
identified in groundwater II
Zellwood. The SDW A MCLs.
In conjunction with stale
standards. will be used to
sclect indicaror chemicals and
as treatment requirements.
The secondary MCLs fOI
inorganic contaminanu in
groundwater are .[0 bc
considered. guidelines.
Since the MCLGs arc non-
enforceable goals, they are
used as reference values to
indicate treatment sysl:m
performance only.
The promulgated values at"
included in the SDW A MCL~
The combined standards ar.
used to compare with the
maximum contaminant levels at
Zellwood to determine the
level of contamination.
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-------
TABLE 8-3: POTENTIAL CHEMICAL SPECIFIC ARARS AND TBCs (continued)
\.CJean Water Act
Water Quality Criteria (wQC)
'--
Clean Air Act
National Primary and Secondary Ambient
Air Quality Standards
National Emissions Standards for
HaZJIrdous Air Pollutants
Sf ATE
FIorida Water Quality Standards
(Groundwater Guidance Concentrations)
FIorida Surface Water Quality Standards
33 use 1351-1376
40 CFR 131
Sets criteria for water quality based on
toxicity to aquatic organisms and human
health.
40 USC 1857
40 CFR 50
Sets primary and secondary air standards at
levels 10 protect public health and welfare
40 erR 61
Provides emission standards for hazardous
air pollutants for which no ambient air
quality standard exists
.. -
62 -3 F.A.e.
Provides water
groundwater
qualiry
standards for
62 -3 F.A.C.
Provides surface water qualiry standards for
the protection and propagation of fish,
shellfish, and wildlife, as well as for
recreation in and on the water.
Status
Relevant and Appropriate
Relevant and Appropriate
Relevant and Appropriate
Applicable
Applicable
FS Consideration
Criteria available for water and
fish ingestion, and !ish
consumption for human health.
The promulgated values are
compared to the muimum
contaminants at Zellwaad to
determine levels of
contamination.
May be relevant and
appropriate if ansite treatment
units are part of remedial
action
May be relevant and
appropriate if onsite trearment
units are part of remedial
action
The guidelines for allowable
levels of toxic organic and
inorganjc contaminants are
applicable for groundwater at
the Zellwood Site.
Promulgated values restrict the
allowable discharge
concentrations of contaminants
present in groundwater.
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-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 53
8.3.2. Reduction of Toxicity, Mobility, or Volume Through Treatment
Alternative 2 would aid in the complete reduction of toxicity, mobility, and volume
of contaminated sediments but would be least effective at reducing toxicity, mobility,
and volume of contaminated ground water. Alternatives 3 and 4 both provide for
active ground water remediation through extraction, treatment, and discharge to
surface water, but both alternatives could require a long treatment period to reach
ARARs. Alternatives 3 and 4 satisfy CERCLA's statutory preference for treatment
and use of treatment to reduce toxicity, mobility, and volume of contaminants.
8.3.3 Short-Term Effectiveness
During the implementation of all the alternatives, both onsite workers and people
surrounding the site will be protected from possible impacts caused by construction
activities. In Alternatives 2, 3, and 4, deed restrictions and institutional controls
would be effective at limiting access and exposure to contaminants, and sediment
removal would eliminate the only remaining source of ground water contamination.
Alternatives 3 and 4, prevent migration of contaminants and several remedial action
objections can be achieved in a short timeframe. Alternatives 3 and 4 may increase
additional noise nuisance from the Site and handling of chemical additives for the
treatment system needs to be monitored. Alternative 3 removes or destroys the
contaminants from the liquid stream; whereas, Alternative 4 concentrates the
contaminants into a smaller liquid stream that requires subsequent treatment.
8.3.4 Implementability
The implementability of an alternative is based on technical feasibility, administrative
feasibility and the availability of services and materials. Alternative 2 is the easiest to
implement since it involves deed restrictions and institutional co.ntrols, limited
construction, and long term monitoring. Alternatives 3 and 4 utilize technology that
is well established but requires operator attention on a daily basis. Alternative 4
requires a great deal of energy to operate. Sediments and treatment system by.
products would require disposal off-site in a appropriate landfill.
Alternatives 3 and 4 require approximately 18 months for design and construction. A
number of engineering considerations are required. Long-term monitoring to verify
clean-up and system operation are required.
8.3.5 Cost
Alternative 2 (Option A and B) is the least costly alternative, other than the No
Action alternative. Of the treatment alternatives, Alternative 3 is cheaper than
Alternative 4. A summary of the present worth costs which includes the capital as
well as the operation and maintenance cost for each of the alternatives is presented in
Table 8-4.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 54
I TAB LE 8~4: COMP ARISON OF COSTS I
Alternative Present-worth Cost Capital Cost Operation and
Maintenance Cost
1. No-Action $ 613,000 $ 15,000 S 598,000
2. Limited Action
A. Nonhazardous
Sediment Disposal $732,000 $ 134,000 $ 598,000
B. Hazardous Sectiment
Disposal $841,000 $ 243,000 S 598,000
3. Ground Water Extraction, $ 5,141,000 $ 1,305,000 $ 3,836,000
Treatment (Using Olemical
Precipitation, Air Stripping,
and Biological Reaction or
Spray 1rrigation), and ~
~Discharge.
Nonhazardous Sediment
Disposal.
I 4. Ground Water Extraction, $ 7,945,000 $ 1,910,000 $ 6,035,000
Treatment (Using Gtemical
i Precipitation and Reverse
Osmosis), and Surface Water
Discharge.
Nonhazardous Sediment
Disposal.
8.4
Modifying Criteria
8.4.1
State Acceptance
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 (RI/FS) process for the Zellwood Site. In accordance with 40
c.F.R. ~ 300.430, FDEP as the support agency, has provided input during this process
by reviewing and providing comments to EP A on all major documents in the
Administrative Record. Based upon comments received from FDEP, it is expected
that written concurrence will be forthcoming; however, a letter formally
recommending concurrence with EP A's selected remedy has not yet been received.
8.4.2
Community Acceptance
Based on comments expressed at the April 25, 1995 public meeting and receipt of 6
written comments during the comment period, it appears that the Zellwood
community generally agrees with the selected remedy. Specific responses to issues
raised by the community can be found in Appendix A, The Responsiveness
Summary.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
, Operable Unit No.2
Page 55
9.0
SUMMARY OF SELECfED REMEDY
Based upon the comparison of alternatives in the feasibility study (FS) and upon
consideration of the requirements of CERCLA, the NCP, the detailed analysis of
alternatives and public and state comments, EP A has selected Alternative 3 as an
interim action for this Site. The selected alternative for the Zellwood Site is consistent
with the requirements of Section 121 of CERCLA and the NCP. Based on the
information available at this time, the selected alternative represents the best balance
among the criteria used to evaluate remedies. If during preliminary design it is
determined that it is feasible to implement this alternative, this selected alternative
will reduce the mobility, toxicity, and volume of contaminated ground water at the
Site. In addition, the selected alternative is protective of human health and the
environment, will attain all federal and state ARARs, is cost-effective and utilizes
permanent solutions to the maximum extent practicable. The estimated cost of
Alternative 3 is $ 5,141,000.
9.1
Source Control
9.1.1 Major Components of Source Control
The major components of source control in the selected remedy (Alternative 3) to be
implemented include:
.
Excavation of sediments in the easternmost Douglas Fertilizer Pond ,to a
depth required to meet performance standards;
.
Sediment disposal in accordance with applicable standards (Le., RCRA);
.
Backfilling the easternmost Douglas Fertilizer Pond with at least one
foot of clean fill; and
.
Placement of institutional controls in the form of deed notices which
restrict well construction on properties within area of contaminated
ground water plume.
9.1.2 Performance Standards
The performance standards for sediment remediation are based on protection of
ground water and are listed in Table 7-1.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 56
9.2
Ground Water Remediation
9.2.1
Major Components of Ground Water Remediation
The major components of the ground water remediation portion the selected remedy
(Alternative 3) are as follows:
.
Ground water monitoring of the surficial and Floridan aquifers;
.
Ground water recovery via extraction wells;
.
Ground water treatment, as determined by design studies to be necessary,
using one or more of the following processes: spray irrigation, equalization,
precipitation/ flocculation/ sedimentation, filtration, air stripping, biological
reaction, and/ or carbon adsorption; and
.
Discharge to ground water compatible with treatment process, such as, an
onsite infiltration gallery, surface water via an onsite canal, or land application.
9.2.2 Performance Standards
9.2.2.1
Extraction Standards
Ground water will be extracted from the surficial aquifer at a rate to be determined
during remedial design.
9.2.2.2
Treatment Standards
Ground water will be monitored until the to verify that the treatment system is
effective at removing contaminants from the aquifer.
9.2.2.3
Discharge Standards
Discharges from the ground water treatment system shall comply with all ARARs,
including, but not limited to, all effluent limits established by EP A in Table 7-2, and
substantive requirements of the NPDES permitting program under the Clean Water
Act, 33 U.s.C.9 1251 et sgq.
9.2.2.4
Design Standards
The design, construction and operation of the ground water treatment system shall be
conducted in accordance with all ARARs, including the RCRA requirements set forth
in 40 c.F.R. Part 264 (Subpart F).
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 57
A phased approach to remedial design is considered appropriate based on the
contaminants under consideration at this Site (Figure 9-1). Phase I of the Remedial
Design (RD) should include design of the ground water monitoring plan, design of
sediment removal and disposal for the sediments in the percolation pond, and design
of deed restrictions and institutional controls. In addition; the Phase I RD should
include design studies to determine the technical practicability of achieving ground
water cleanup at the Site, including but not limited to the following: aquifer pump
tests, treatability studies, additional sampling, private well investigation, discharge
option evaluation, and detailed ground water modelling.
Phase IT RD would be implemented only if the design studies conducted in Phase I
indicate it is practicable to implement Phase IT of the RD. If Phase IT is implemented,
a ground water extraction, treatment and disposal system will be constructed, as
appropriate, and operated. Results of the operation will be evaluated annually to
determine if it is practicable to continue operation of the system. If it is determined
by operation of the system that contaminant cleanup is impracticable at this Site, a
Record of Decision (ROD) will be written invoking a Technical Impracticability
Waiver. If it is determined that contaminant cleanup is practical to levels required to
meet ARARs or to Alternate Oeanup Levels, a Final ROD will be written to set
performance goals for .the system.
9.3
Compliance Testing
Ground water and surface water monitoring shall be conducted at this Site. Ground
water. shall be sampled from existing and new monitoring wells, as determined
during remedial design. Requirements for compliance testing will be set in the Final
Record of Decision.
10.0
STATUTORY DETERMINATION
Under Section 121 of CERCLA, 42 U.S.c. 9 9621, EP A must select remedies that are
protective of human health and the environment, comply with applicable or relevant
and appropriate requirements (unless a statutory waiver is justified), are cost
effective, and utilize permanent solutions and alternative treatment technologies or
resource recovery technologies to the maximum extent practicable. In addition,
CERCLA includes a preference for remedies that employ treatment that permanently
and significantly reduce the volume, toxicity, or mobility of hazardous wastes as their
principal element. The following sections discuss how the selected remedy meets
these statutory requirements.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 58
FIGURE 9-1: RD/RA FLOW CHART
I I~~~M I
PHASE I
REMEDIAL DESIGN
DESIGN STUDIES
REMEDIAL ACTION 1
Pun\P T cst
Tru,abelity Studies
Additional ~{'ILnC
Privati: Well InvC$tig~tion
D1Jd\utc. Option Ev~u~t\on
[)c.c.d RcstnC1'oru
Scdin'lCl1\ Rc.moY.lllDisp(n.,1
G\V Monitonnt
PHASE II
REMEDIAL DESIGN
ye,
EXTRACTION AND
DISCHARGE
TREAMENT
(Duign Spc.c.)
(perlo",..".,. Spc.c.)
REMEDIAL AC110N 2
Ground W &tet T rc:.atmen(
ye,
(~valuat~ TI 'annually
until final decision)
FINAL ROD
ye,
no
(f1 \V.ivc.r)
(S~l Pcdorm1l1cc Goals)
I
r
-------
Record of Decision
Zel1wood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 59
10.1
Protection of Human Health and the Environment
This selected remedy provides protection of human health and the environment in
the short term and is intended to provide adequate protection until a final ROD is
signed. The selected remedy provides protection by eliminating, reducing, and
controlling risk through engineering controls and/ or institutional controls and
ground water treatment as delineated through the performance standards described
in Section 9.0 - SUMMARY OF SELECTED REMEDY.
Ground water treatment will be implemented in accordance with Section 9.0 -
SUMMARY OF SELECTED REMEDY to ensure that no exposure through ingestion
or inhalation of contaminated ground water occurs. Implementation of this remedy
will not pose unacceptable short-term risks or cross media impact.
Attainment of the Applicable or Relevant and Appropriate Requirements
(ARARs)
10.2
Remedial actions performed under Section 121 of CERCLA, 42 D.S.C. S 9621, must
comply with all applicable or relevant and appropriate requirements (ARARs). All
alternatives considered for the Site were evaluated on the basis of the degree to
which they complied with these requirements. The selected remedy was found to
meet ARARs identified in Tables 8-1, 8-2, and 8-3. The following is a short narrative
explaining the attainment of pertinent ARARs.
Chemical-Specific ARARs
Discharge to ground water and surface water will meet standards identified as in this
ROD. Sediment excavation will be performed until remediation levels identified in
this ROD are achieved. The ability of Alternative 3 to remediate ground water "will
be evaluated during remedial design and remedial action. If it becomes apparent that
ground water remediation will not be met for metals and inorganics, EP A, in
consultation with FDEP, will recommend a technical impracticability waiver or
another technology in the Final ROD. If operation of alternative 3 effectively
remediates ground water, performance standards for ground water remediation
based on Federal and State drinking water standards will be designated in the Final
ROD. Performance standards are consistent with ARARs identified in Table 8-3.
Action-Specific ARARs
Performance standards are consistent with ARARs identified in Table 8-2.
Loca Hon-Specific ARARs
Performance standards are consistent with ARARs identified in Table 8-1.
-------
Record of Decision
Ze!lwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 60
Waivers
Results from remedial design and remedial action activities may be used to prove
that implementation of Alternative 3, as it pertains to ground water is technically
impracticable. A technical impracticability waiver may be warranted in the future,
but is not justified at this time.
Other Guidance To Be Considered
Other Guidance To Be Considered (TBCs) include health-based advisories and
guidance. TBCs have been utilized in estimating incremental cancer risk numbers for
remedial activities at the Site and in determining RCRA applications to contaminated
media.
10.3
Cost Effectiveness
After evaluating all of the alternatives which satisfy the two threshold criteria,
protection of human health and the environment and attainment of ARARs, EP A has
concluded that the selected remedy, Alternative 3, affords the highest level of overall
effectiveness proportional to its cost. Section 300.430(f)(1)(ii)(D) of the NCP also
requires EP A to evaluate three out of five balancing criteria to determine overall
effectiveness: long-term effectiveness and permanence; reduction of toxicity, mobility,
or volume through treatment; and short-term effectiveness. Overall effectiveness is
then compared to cost to ensure that the remedy is cost-effective. The selected
remedy provides for overall effectiveness in proportion to its cost.
The selected remedy has a relatively high present worth, capital, and operation and
maintenance cost compared to other remedies, but best satisfies the criteria for long-
term effectiveness and permanence and short-term effectiveness. This alternative will
reduce toxicity, mobility, or volume through treatment. The estimated present worth
cost for the selected remedy is $ 5,141,000.
10.4
Utilization of Permanent Solutions to the Maximum Extent Practicable
Although this interim action is not intended to address fully the statutory mandate
for pennanence and treatment to the maximum extent practicable, this interim action
does utilize treatment. Of those alternatives that are protective of human health and
the environment and comply with ARARs, EP A and the State have determined that
Alternative 3 provides the best balance of trade-offs in terms of long-term
effectiveness and permanence, reduction in toxicity, mobility, or volume achieved
through treatment, short-term effectiveness, implementability, and cost, while also
considering the statutory preference for treatment as a principal element and
consideration of state and community acceptance.
-------
Record of Decision
Zel1wood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 61
10.5
Preference for Treatment as a Principal Element
Because this action does not constitute a final remedy for this operable unit, the
statutory preference for remedies that employ treatment that reduces toxicity,
mobility, or volume as a principal element, although partially addressed in this
remedy, will be addressed by the fmal response action. Subsequent actions are
planned to address fully the threats posed by the conditions at this Site. Because this
remedy will result in hazardous substances remaining onsite above health-based
levels, a review will be conducted to ensure that the remedy continues to provide
adequate protection to human health and the environment within five years after
commencement of the remedial action. Because this is an interim action ROD, review
of this site and of this remedy will be ongoing as EPA continues to develop final
remedial alternatives for the Site.
11.0
DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan was released for public comment in April 1995. It identified'
Alternative 3, ground water extraction, treatment using chemical precipitation, air
stripping, and/or biological reaction; and surface water discharge, as the preferred
alternative for ground water remediation. EP A added spray irrigation to the possible
treatment technologies in Alternative 3, due to comments concerning the quality of
sampling data with regard to metals concentrations. In addition, Alternatlve 3
included proposed discharge of treated ground water to an onsite infiltration gallery
or Lake Maggiore. Based on public comments, discharge of treated ground water to
Lake Maggiore will not be considered an option if surface water discharge is
required. Finally, based on comments regarding sediment remediation goals, EP A re-
evaluated sediment remediation goals proposed in the Proposed Plan. EP A revised
the sediment remediation goals to be consistent with Operable Unit 1 (OUl) goals, to
eliminate contaminants that are not affecting ground water, and to eliminate
contaminants that may contribute to violations of less significant ground water
standards. Specific reasons for each change are provided in Table 11-1, below.
-------
Record of Decision
Zellwood Ground Water Contamination Superfund Site
Operable Unit No.2
Page 62
TABLE 11-1. REVISED SEDIMENT REMEDIATION GOALS
Contaminant Proposed Revised Comments
Remediation Goal (mg/kg) Remediation
Goal (mll/kll)
Alut:l\inum 1600 - GW goal based secondary
MCr;
Ammonia 3 - GW goal based on
or~oleptic effects.
Arsenic 10 10
Barium 1 - GW detects below primary
MCL
Cadmium 1.6 - Background Cone.
1&10 m~kg; sediment
detectS low backl/Tound.
Chloride 12 - GW goal based secondary
MCr;
ChromIum 7 100 Soils in aUl remediated to
100 rnll/kll chrome
Copper 200 - Max. detect GW ;
Secondary MCL
Iron 230 - Background Cone.
1200 mg/kg; GW ~oaJ based
on secondary stan ards
Lead 140 220 Soils in aUI remediated to
220 mll/killead
Manganese 25 - GW goal based secondary
MCr;
Mercury 14 - Detects in sedirnent are
below szeal.
Vanadium 1 1
- No goal established.
-------
APPENDIX A - RESPONSIVENESS SUMMARY
/1
(
-------
RESPONSIVENESS SUMMARY
OPERABLE UNIT 2
ZELLWOOD GROUND WATER CONTAMINATION SUPERFUND SITE
ZELLWOOD, ORANGE COUNTY, FLORIDA
Introduction
This responsiveness summary for the Zellwood Ground Water Contamination
Superfund Site documents for the public record concerns and issues raised during the
comment period on the proposed plan for operable unit 2 (OU2). EP A's responses to
these concerns and issues are included.
Overview of Comment Period
The proposed plan for operable unit 2 (OD2) at the Zellwood Ground Water
Contamination Superfund Site was issued on April 14, 1994. The sixty-day public
comment period for the proposed plan began April 19, 1994, and ended June 18,
1994. Eight written comments, some with multiple concerns, were received during
that comment period. Public meetings were held on April2S, 1995, and May 16,
1995, at the Willow Street Community Center at 6565 Willow Street, Zellwood,
Florida. A public meeting was held on May 17, 1995, at the Zellwood Elementary
School at 3551 Washington Avenue, Zellwood, Florida. Many comments were
received and addressed during those me.etings. Transcripts of the meetings were
prepared and are available at the information repository near the Site.
Concerns Raised During the Comment Period
Private Well User Concerns:
1.
Several private well users north of the Site expressed concern about ground
water quality near the Site and their general desire to be placed on public
water. Residents in the Willow Street community believe that their water
quality has been affected by the Site. Residents questioned why health officials
allowed builders to construct their wells in the surficial. aquifer, since most
communities have wells screened in the lower Floridan aquifer. They want to
know how they can get public water lines into their community. Several
residents indicated that they thought the money set aside to cleanup
contamination at the Site would be better spent providing public water to the
Willow Street community.
Response: The direction of ground water flow in the surficial aquifer at the
Site is south-southwest, away from the Willow Street community.
Contaminated ground water has historically moved in the direction of ground
water flow. Basei[ on sampling results, EP A has no reason to believe that
contamination fr6m the Site has effected private wells in the Willow Street
community.
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Orange County's Public Health Unit has agreed to perform a limited number
of tests on wells in the Willow Street community to assure residents that
ground water does not exceed the health standards for contaminants found at
the Site. Residents who want their water tested should contact Joyce Bittle,
with the Orange County Public Health Unit.
High levels of sulfur and iron are naturally occurring in the surficial aquifer
and may be causing the ground water to taste and smell bad. In addition,
residences constructed over old agricultural areas, as the Willow Street
community was, may experience water quality problems due to residual
pesticide and insecticide levels in soil. Residents should work with local
health officials to determine if previous agricultural activities have contributed
to poor water quality in their wells.
The Superfund program is not authorized to address naturally occurring
drinking water problems in local communities. The Superfund Program can
only provide alternative drinking water if private wells are being effected by
contamination from a Superfund Site. Therefore, the Superfund program
cannot spend money on a community water supply rather than on remediating
ground water at the Site.
Residents should direct questions concerning why builders were allowed to
construct drinking water wells in the surficial aquifer in their community to
local officials. The Saint John's Water Management District and the Orange
County Environmental Protection Department may be able to assist in
determining if builders are restricted in construction of potable water wells in
the surficial aquifer near the Site. Also, community members should be aware
that several state trust funds have been established to assist communities that
need public water supplies. The county health unit should be contacted to
determine if any of the trust funds can be accessed to assist their community.
2.
Several commentors requested that their water be tested.
Response: EP A recommended that concerned citizens contact the Orange
County Public Health Unit to request that their wells be tested.
3.
Several commentors expressed concern about the quality of water being used
by businesses adjacent to and on the Site. Specifically, they questioned
whether consumers of products from these businesses or workers at the
businesses being exposed to contamination.
Response: EP A tested 10 private wells on or adjacent to the Site. No
contamination was found in those wells; therefore, there is no reason to believe
that workers or consumers at these businesses are being exposed to Site
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contaminants. EP A does not known the exact depth that the wells are
screened; based on the quality of water in the wells it is suspected that the
wells are screened in the Floridan aquifer, rather than the surficial aquifer.
4.
One commentor requested that EPA retest the private wells tested in 1994, to
ensure that they have not been contaminated since EP A tested them in the
Remedial Investigation.
Response: EP A will establish a monitoring well network at the Site to track
the contaminated ground water. Private wells may be included in the network
if contamination is moving toward a well or wells. The details of ground
water monitoring at the Site will be determined during remedial design. If
private well users, including businesses, have concerns about their water
quality that have not been addressed in the ground water "monitoring
conducted by EP A, they should contact the Orange County Public Health Unit
to request that their wells be tested.
Concerns Related to Discharge Options
5.
A large number of commentors expressed concern about EPA's proposed
discharge of treated ground water to Lake Maggiore. Most of the commentors
lived on or near the lake, or used the lake for recreational activities or fishing.
These commentors do not want discharge from the Site to be directed to Lake
Maggiore. The commentors expressed a general distrust of the federal
government; they were concerned that the government would allow discharge
of contaminated water to the lake.
Response: Based on the great concern expressed by this community, EPA will
not discharge treated ground water from the Site into Lake Maggiore. EP A
will instead investigate use of an onsite infiltration gallery or percolation pit,
or surface water discharge to canals that end in the muck farm areas south of
the Site. Based on the distance from the Site to the muck farms and Lake
Opopka, it is likely that discharge water will infiltrate to ground water before
it can reach the muck farms or lake.
6.
One commentor asked what levels {)f chemicals of concern currently exist in
Lake Maggiore and how these levels will be effected by discharge from the
Site?
Response: EP A did not test surface water in Lake Maggiore. Discharge from
the Site has to meet surface water standards under a National Pollution
Discharge Elimination System (NPDES) Permit issued by the State of Florida.
Discharge from the Site should not effect the quality of water in Lake
Maggiore or any other surface water body.
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7.
One commentor asked if EPA can line onsite ponds and use them to evaporate
contaminated ground water or somehow containerize contaminated ground
water and dispose of it offsite rather than discharging the water to Lake
Maggiore.
Response: Only treated water which meets drinking water or surface water
standards will be discharged from the Site. For that reason, there is no reason
to line the percolation pit or containerize the discharge. Discharge to Lake
Maggiore has been eliminated from consideration based on community
concerns.
RIfFS Concerns:
8.
One commentor asked what Hazard Ranking Score (HRS) the Site received.
Response: The HRS for the Zellwood Ground Water Contamination Site was
calculated as 51.91. It should be noted that the HRS is not indicative of the
risk posed by the Site, rather is a tool to determine if the Site should be on the
NPL. Sites scoring greater than 28.5 may be recommended for inclusion on the
NPL.
9.
One commentor maintained that the analytical data which the Baseline Risk
Assessment is based on is flawed. Reasons cited for this conclusion are:
.
the wide range of ground water sample temperatures (shallow well
samples at 62.5 to 800P and deep well samples at 67.9 to 82.5°P) noted in
sampling logs;
Response: FDEP reports ground water temperatures in wells located
just south of the Site, in the Lake Opopka "Very Intensively Sampled
Area (VISA)" (see Figure 1) between 70 and 800P. The ground water
temperatures reported during well sampling did not vary significantly
from this range. Site-related samples were taken in March, which may
account for the lower temperature recordings. Temperatures were
determined to be stable in each well prior to sampling, in accordance
with the standard operating procedures specified in the Environmental
Compliance Branch Operating Procedures and Quality Assurance Manual,
US Environmental Protection Agency, Region IV, Environmental
Services Division, Athens, Georgia, February 1, 1991.
.
high ground water temperatures in two wells (MW-4TB and MW-3TA)
during well development may have facilitated metal ion dissolution and
increased metal concentrations in ground water;
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Response: High ground water temperatures have not been found to
increase metal concentrations in ground water. Temperatures recorded
during purging and sampling were at stable levels and were within the
range detected in FDEP's "Very Intensively Sampled Area (VISA)" wells,
south of the Site.
.
the wide range of pH values during sampling;
Response: FDEP reports ground water pH in wells located just south of
the Site, in the Lake Opopka "Very Intensively Sampled Area (VISA)"
(see Figure 1) between 4.90 and 6.94. pH measurements in wells which
define the contaminant plume vary between 5.15 and 8.10; pH
measurements in background wells at the Site vary from 4.14 to 7.50.
Based on this information, a wide range of pH levels are commonly
detected in surficial aquifer ground water near the Site.
Metals solubility is very sensitive to pH levels. EP A is concerned that
heavy metals discharged from the Site will be a persistent problem in
surficial ground water due to the pH conditions inherent in ground
water at the Site and down gradient of the Site.
.
the infrequent calibration of pH meters;
Response: The Environmental Compliance Branch Operating Procedures. and
Quality Assurance Manual (U.S. Environmental Protection Agency,
Region IV, Environmental Services Division, Athens, Georgia, February
1, 1991) requires daily calibration of pH meters during field activities.
EPA's contractor followed these standard operating procedures and
calibrated equipment daily.
.
elevated turbidity of some ground water samples;
Response: The Environmental Compliance Branch Operating Procedures and
Quality Assurance Manual (U.S. Environmental Protection Agency,
Region IV, Environmental Services Division, Athens, Georgia, February
1, 1991) requires that wells be purged before taking samples in order to
clear the well of stagnant water which is not representative of aquifer
conditions. The method of purging is to pump the ~.'ell until three to
five times the volume of standing water in the well has been removed
and until the specific conductance, temperature, and pH of the ground
water stabilizes. The standard operating procedures (SOPs) state that
when metals are being sampled, the turbidity should also be minimized.
Field logs indicate that monitoring wells were not sampled until pH,
conductivity, temperature, and turbidity were stabilized. Turbidity
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levels in some wells were higher than measured in other wells.
However, in each case, turbidity levels appeared to have stabilized and
there was no indication that further purging would have reduced
turbidity levels. The VISA well database indicates that the mean
turbidity of the wells proximal to the Site was 350 NTUs, with the range
being 8.2-1,000 NTUs.
.
poor instrument calibration in one of the fixed laboratory sample
batches (ba~ch B4-03-070, analyzed 3/4/94 by Bionomics, Ine.) may have
lead to erroneous arsenic readings;
Response: Arsenic levels detected in wells MW-1TA, MW-1TB, MW-
2TA, and MW-2TB were reported as below detection limits (BOU, 0.008
mg/L, BOL, and 0.011 mg/L, respectively. The two values detected
were flagged 'T' because calibration verification recovery was greater
than 110%. This means that arsenic was detected above the detection
limit (0.005 mg/L), but the actual value present may be higher or lower
than the reported value. Inclusion of these results is acceptable but
should not control the risk generated at the Site. Higher arsenic
concentrations were detected at the Site; therefore, the results from this
batch of laboratory analyses does not control the arsenic risk and these
results were considered appropriately in the risk assessment.
.
poor sample preservation of two ground water samples (MW-08-SA and
MW-08-SB);
Response: During sampling, the pH in MW-08-SA and MW-08-SB was
recorded at 6.46 and 7.5, respectively. Ground water samples for metals
analysis are typically placed in collection bottles with an acid
preservative to keep metals in solution and prevent the metals from
plating out of solution on the sides of the container (i.e., pH is kept <
2.0). In the sampling analysis report, the laboratory commented that the
pH of samples taken from MW-08-SA and MW-08-SB was 4.0 and 7.0,
respectively, when received at the laboratory, indicating that the
preservative may not have been added to the samples. This error
indicates to EP A that metals levels in these two wells are likely higher
than the levels determined in the analysis. These two wells have higher
detected metal concentrations than any other wells at the Site, and it
appears reasonable to use this data in estimating risk at the Site.
.
metals in well construction materials may have contaminated
monitoring wells due to the natural acidic environment in the surficial
aquifer (e.g., pH values of 4.12 and 4.34 were reported in MW-02-SA
during well development);
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Response: Well construction materials such as grout and cement tend
to increase pH due to their alkaline nature. As noted by the
commentor, pH values in MW-02-SA were relatively low during well
development; if any well was going to be affected by well materials
EP A would expect it to be MW-02-SA. However, low inorganic levels,
within the range considered as background concentrations, were
detected in MW-02-SA. MW-02-SA was used as a background well in
the baseline risk assessment. Therefore, EP A does not consider well
contamination from well construction materials to be a problem at this
Site.
.
rainfall may have occurred during sampling' of temporary ground water
well and compromised sampling results;
Response: Temporary wells were installed one day, developed over
two days, sampled after being developed, and decommissioned within
two days of being sampled. This sequence was followed for all
temporary wells to reduce any possible problems that might occur due
to the temporary nature of the wells. Since the wells were sampled
after being developed, EP A does not consider contamination from
surface water over the three to four day period that the well was in
place to be an issue.
.
well construction method, i.e. use of temporary wells for ground water
sampling;
Response: Temporary wells were used for determining the extent of
ground water contamination in order to reduce the costs of the
investigation.
.
elevated arsenic concentrations are observed locally in FDEP
background wells; ,
Response: The Site is located in Orange County. Arsenic
concentrations in FDEP background wells located in Orange County
have been reported from BDL to 4.3 ug/L. For well No.
284230081345302, a background well located less than three miles from
the Site, Arsenic levels were reported from BDL to 2.0 ug/L. In most of
the FDEP 'TISA wells, located south of the Site, the arsenic levels range
from BDL 10 21 ug/L. In two VISA wells located adjacent to Lake
Opopka, the detected arsenic levels were 52 ug/L and 54 ug/L in 1993.
Arsenic levels at the Site were recorded from BDL to 73 ug/L. The
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levels at the Site appear to be higher than occur in FDEP background
wells and VISA wells.
.
wide variability in metal concentrations between some of the Phase I
and Phase II ground water sampling; and
Response: Wells sampled during Phase I were all considered
background wells except for wells MW-06-SA and MW-06-SB. Phase I
and Phase II sampling results do not appear to vary widely for these
two wells with the exception of potassium concentrations in MW-06-SB.
.
arsenic concentrations may be due to local agricultural activities.
Response: If arsenic were the only contaminant of concern at the Site,
local agricultural activity might be considered more heavily as a
potential contributor to contamination. But the fact remains that metals
and inorganics, including arsenic, have been traced to discharges from
industries located at the Site since the Site was placed on the NPL in
1983. In the 12 years EP A has been involved at the Site, those
contaminants have remained in ground water at the Site at levels of
concern to human health and the environment and at levels above
background concentrations. Cleanup of this Site is not being motivated
by of the presence of arsenic, but by the presence and apparent
persistence of all contaminants detected at the Site.
Concerns about the Baseline Risk Assessment:
10.
One commentor questioned the use of estimated arsenic concentrations in the
risk assessment.
Response: EP A considers inclusion of estimated values acceptable as long as
remediation of the Site is not being driven by estimated values. Estimated
values are used to indicate that arsenic was detected but the amount of arsenic
present may be higher or lower than the estimated value. Arsenic
concentrations also were detected at measurable levels at the Site. As noted in
EPA's response to Comment No.9, metals and inorganics, including arsenic,
have been traced to discharges from industries located at the Site since the Site
was placed on the NPL in 1983. In the 12 years EPA has been involved at the
Site, those contaminants have remained in ground water at the Site at levels of
concern to human health and the environment and at levels above background
concentrations. Cleanup of this Site is not being motivated by of the presence
of arsenic alone, but by the presence and apparent persistence of all
contaminants detected at the Site.
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11.
One commentor questioned why the BRA focused on future ingestion of
ground water, disregarding the reasonable future land-use for the area. The
commentor suggested that the surficial aquifer is not used as a drinking water
source. The commentor further stated that current institutional controls will
prohibit the Site from being zoned residential in the future and prevent
potable water well construction, thereby eliminating the possibility of the
ground water being used as a drinking water source.
Response: The BRA considered future ingestion of ground water because
ground water is not restricted to the Site boundaries and migration of
contaminated ground water has already occurred. Although EP A is not aware
of any current users of contaminated ground water at the Site, there are
residents within 1/2 mile of the Site that drink ground water from wells
screened in the surficial aquifer. One of the institutional controls cited as
being protective is Rule 62-524, administered by the St. Johns Water
Management District. This rule does not allow the installation of potable
water wells in the surficial aquifer in the delineated area. Figure 11, attached
to the commentors written document, illustrates that the residential area where
drinking water wells are screened in the surficial aquifer is within the area
delineated by the St. Johns Water Management District as not allowing
installation of potable water wells. It is clear from this example that drinking
water wells have been installed within this area.
In addition to concerns about the surficial aquifer, EP A is also concerned about
contaminants migrating to the F10ridan aquifer. Contamination of the F10ridan
aquifer could occur if wells are improperly drilled through the confining layer
beneath the contamination or if localized discontinuities exist in the confining
~~ .
Concerns About The Remedy Selected:
12.
One commentor suggested that issuance of the Interim Action Record Of
Decision (ROD) is not appropriate at this time. The principle reason cited in
support of this conclusion is absence of exposure to contaminated ground
water or sediments. Rather than issue an Interim Action ROD at this time, it
was suggested that EP A reconsider the remedy and, if necessary, continue to
monitor the Site.
Response: The commentor suggested that the surficial aquifer, which is
contaminated, is not used for drinking water and will not be used for drinking
water in any future land use scenario. However, as discussed in Comment
No. 11, the surficial aquifer is being used as a drinking water source even in
the area delineated by current institutional controls. Sediment at the Site was
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identified as a possible source of contamination and a possible risk to
ecological life (plants and animals) at the Site. Therefore, EP A considers
issuance of an Interim Action ROD an appropriate action to take at this time.
The Site has been studied for over 12 years; further studies are not warranted.
13.
Two commentors recommended that Alternative 4 be selected to remediate the
Site but provided no specific reasons.
Response: Alternative 4 is considered a reasonable alternative. However,
Alternative 4 costs more and is more labor intensive than Alternative 3. EP A
determined that Alternative 3 will likely provide the same result in the same
time frame, but for less money than Alternative 3. Therefore, Alternative 3
was proposed as the most cost effective remedial alternative.
14.
One commentor suggested that if EP A is not sure that the remedy will work,
EP A should wait 20 years until a more appropriate technology can be found to
address contamination.
Response: EP A is confident that the ground water can be treated to meet
ground water or surface water standards using existing technology. The major
question is whether contaminants can be effectively removed from subsurface
soils; because of that uncertainty, EP A has proposed an Interim Action ROD at
this Site. EPA is proposing that the remedial design be approached in phases
to determine if contaminants can be effectively removed prior to construction
of the treatment system. If it is determined that it is technically impracticable
to remediate ground water at this Site at this time, EPA will recommend that
no action be taken (in a Final ROD) until technology is available to address
this Site. A No Action ROD would require monitoring of ground water until
remedial technologies improve or until the Site is no longer considered a risk.
15.
One comrnentor suggested that EP A publications and policies do not support
use of pump and treat technology for i) either heterogeneous aquifers where
low-permeability zones restrict contaminant flow toward the extraction wells;
or ii) for adsorptive soils where chemicals that are sorbed or precipitated on
the soil and slowly desorb back into the ground water as chemical equilibrium
changes in response to the extraction process.
Response: Although heterogeneous conditions exist in the aquifer beneath the
Site, several hundred productive potable water wells are in service and
extracting ground water from the surficial aquifer less than a half-mile north of
the Site. EP A has proposed that aquifer pump tests be conducted in the
contaminated plume during the initial design phase, to verify that reasonable
pumping rates are achievable at the Site. EPA has proposed using a number
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of extraction wells pumping at very low rates to remediate contamination at
the Site. EP A has used similar pump and treat technology in the surficial
aquifer in Orange County successfully, and EP A expects to demonstrate the
viability of pump and treat technology during the remedial design.
Sorption of chemicals to soils in the surficial aquifer is a concern to EP A. For
that reason, an interim ROD was proposed to determine if the ground water
should be remediated to drinking water standards, maximum contaminant
levels (MCLs), or alternative concentration limits (ACLs) based on equilibrium
concentrations. EPA has determined that detailed design studies and possibly
results from active remediation will be necessary to demonstrate whether or
not the contaminants can be removed, and to what level they can be removed.
16.
One commentor suggests that insufficient data exists to support the proposed
remedy for sediments and the proposed sediment remediation goals are
unjustified. Reasons cited for this conclusion are:
.
Use of 1986 RI for background data on sediment was improper because
the contractor did not reference where the samples were located and did
not describe the sampling method; and
Response: A footnote on Table 4-3 states that background sediment
concentrations are being reported for the control pond in the Final
Remedial Investigation Report prepared by NUS in 1986. The 1986 RI is
part of the administrative record for the Site and is available for public
review. The sediment sampling methodology is described on page 2-11
of the 1985 RI Site Operations Plan for Task 14: Surface Water and
Sediment Sampling and Analysis prepared by NUS. The 1985 plan is
part of the administrative record for the Site and is available for public
review.
.
Selection of sediment remediation goals, based on protection of ground
water, was improper because ground water sampling results,
particularly with respect to metals, may not be accurate.
Response: EPA plans to monitor ground water at the Site prior to
removing sediments from the onsite pond. Based on past sampling,
EP A anticipates that metals will be detected in future ground water
samples. If ground water monitoring demonstrates that any metals,
currently considered as contaminants of concern, are not dissolved in
ground water, then the need to remediate sediments in the pond for
those contaminants will be re-evaluated.
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.
Sediment Remediation Goals for protection of ground water are below
acceptable risk-based sediment concentrations published by EP A.
Response: Risk-based concentrations for soil and sediment are based on
incidental ingestion and dermal contact. Protection of ground water
concentrations address the possibility of contaminants leaching to
ground water at concentrations greater than acceptable ground water
levels. Depending on the contaminant, it is possible that remedial goals
required to protect ground water are lower than health-based remedial
goals.
.
Sediment Remediation Goals for chromium, lead, nitrate, nitrite,
cyanide, and iron are questionable.
Response: Sediment remediation goals were not proposed for nitrate,
nitrite, and cyanide. Based on this comment, EPA re-evaluated
sediment remediation goals proposed in the proposed plan. EP A is
revising the sediment remediation goals to be consistent with Operable
Unit 1 (OUI) goals, to eliminate contaminants that are not affecting
ground water, and to eliminate contaminants that may contribute to
violations of less significant ground water standards. The reasons for
each change are provided in Table 1, below.
.
The estimated volume of sediment contamination is unreliable; dispo::al
at a landfill may not be the most cost effective if the volume increases.
Response: Relative to the cost of ground water remediation at the Site
over a thirty-year period (present worth cost $5,141,000), EP A
considered the portion of costs related to disposal of contaminated
sediment (present worth cost $27,647, if non-hazardous) to be a minor
cost. EP A will evaluate the most cost effective disposal option during
detailed design.
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TABLE 1. REVISED SEDIMENT REMEDIA nON GOALS
Contaminant Proposed Revised Comments
Remediation Goal (mg/kg) Remediation
Goal (ma/ka)
Aluminum 1600 - GW goal based secondary
MCr:
Ammonia 3 - GW goal based on
orszanolePtic effects.
Arsenic 10 10
Barium 1 - GW detects below primary
MCL
Cadmium 1.6 - Background Cone.
1800 mt'kg; sediment
detects elow backlUOund.
Chloride 12 - GW goal based secondary
MCI:
Chromium 7 100 Soils in OUI remediated to
100 ml/:/kl/: chrome
Copper 200 - Max. detect GW c
Secondary MCL
Iron 230 - Background Cone.
1200 mg/kg; GW raal based
on secondaJ'v stan ards
Lead 140 220 Soils in OUI remediated to
220 mlZ/klZ lead
Manganese 2.5 - GW goal based secondary
MCI:
Mercury 14 - Detects in sediment are
below lZOal.
Vanadium 1 1
- No goal established.
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