Superfund Record of Decision Chevron Chemical Company Ortho Division Orlando FL


                                    EPA/ROD/R04-96/263
                                    1996
EPA Superfund
     Record of Decision:
     CHEVRON CHEMICAL CO. (ORTHO DIVISION)
     EPA ID: FLD004064242
     OU01
     ORLANDO, FL
     05/22/1996

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RECORD OF DECISION DECLARATION
SITE NAME AND LOCATION

Chevron Chemical Company Orlando, Florida

STATEMENT OF BASIS AND PURPOSE

This decision document presents the selected remedial action for the Site noted above. The
remedy was chosen in accordance with the Comprehensive Environmental Response, Compensation and
Liability Act of 1980 (CERCLA) , as amended by the Superfund Amendments and Reauthorization Act
of 1986 (SARA) , and to the extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). This decision is based on the administrative record for this
Site.

The State of Florida, as represented by the Florida Department of Environmental Protection
(FDEP), has been the support agency during the Remedial Investigation (RI) and Feasibility Study
(FS) process for the Chevron Chemical Company Site. In accordance with 40 CFR 300.430, FDEP, as
the support agency, has provided input during the RI/FS process. FDEP agrees with the
groundwater remedy, but does not agree with no further action for soil. FDEP is unwilling to
concur with the ROD because the State would prefer a risk level no greater than 1 x 10-6. The
potential risk associated with future residential exposure at the adjacent trailer park is 9.0 x
10-6. The potential risk associated with future commercial exposure at the Site is 2.0 x 10-6.

ASSESSMENT OF THE SITE

Unacceptable risk associated with this Site is due to the potential future consumption of
groundwater containing contaminants above either federal or State of Florida groundwater
standards. Actual or threatened releases of hazardous substances from this Site, if not
addressed by implementing the response action selected in this Record of Decision (ROD), may
present an imminent and substantial endangerment to public health, welfare of the environment.

DESCRIPTION OF THE SELECTED REMEDY

This remedy addresses the principal threats posed by the environmental conditions at this Site.

The major components of the remedy include:

• Natural attenuation

• Groundwater monitoring to document achievement of the groundwater cleanup levels.

• A contingency plan that includes the installation of a subsurface filter wall if
natural attenuation does not continue as expected. Additional enhancements, such as
limited air sparing, hydraulic gradient control, or source removal will be
implemented if necessary.

• Institutional controls

STATUTORY DETERMINATIONS

The selected remedy is protective of human health and the environment, complies with Federal and

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State requirements that are legally applicable or relevant and appropriate to the remedial
action, and is cost- effective.  This remedy utilizes extent practicable for this Site.  This
remedy does not satisfy the statutory preference for treatment as a principal element. However,
the contaminants in groundwater are expected to naturally attenuate within 8-10 years.  In
addition, given that there is no current exposure to groundwater, there is no need for immediate
active treatment measures.

Because the remedy will result in hazardous substances remaining on- site, a review will be
conducted within five years after commencement of remedial action to ensure that the remedy
continues to provide adequate protection of human health and the environment.  The reviews will
be conducted every five years thereafter until health based levels are achieved. Groundwater
monitoring data will also be reviewed annually to gauge the effectiveness of natural attenuation
and to determine if the contingency remedy should be implemented.

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THE DECISION SUMMARY

1.0 SITE LOCATION AND DESCRIPTION

The Chevron Orlando site is located at 3100 North Orange Blossom Trail (Highway 441) in
Orlando, Orange County, Florida (see Figure 1). The site is in Township 22 S, Range 29 E,
Section 15. As shown on Figure 2, the site is bordered on the east by Orange Blossom Trail and
to the south by active railroad tracks. The land use in the areas to the south and west of the
site is light industrial. The Armstrong Trailer Park, which is a residential mobile home park,
borders the site to the north. The 441 Trailer Park is north of the Armstrong Trailer Park, and
across Orange Blossom Trail to the east of the site. The Lake Fairview Commerce Center is
directly across Orange Blossom Trail to the east of the site.

The site is 4.39 acres in size and is currently cleared, vegetated with grass, fenced, and
unoccupied. Lake Fairview is approximately 700 feet northeast of the site. Lake Fairview is a
remnant karst lake, which is approximately 400 acres in size.

2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES

The Chevron Chemical Company facility was in operation between 1950 and 1976 as a pesticide
formulation plant. The facility received unblended products in bulk liguid and powder form, and
blended the products to make pesticides and nutritional sprays for bulk wholesale distribution.
The unblended products were shipped in primarily by rail, formulated, packaged in drums, and
shipped out by truck. The historic site features included several above ground storage tanks,
a drum storage area, a drum rinse area, two pesticide rinsate ponds, three septic tank drain
fields, and an underground petroleum storage tank. The above ground tanks were used to store
the petroleum distillates which were used as blending agents (e.g., xylene, ethylbenzene, and
mineral spirits). As shown on Figure 3, the rinsate ponds were located in the northwestern
portion of the site. The ponds were used for the collection and disposal of storm water,
pesticide formulating rinse water, drum rinse water, and floor wash-down water. The underground
storage tank was used to store vehicle fuel. A floor drain was located in the formulating
warehouse in a liguid pesticide formulation area. The floor drain discharged onto the ground
surface near an abandoned rail spur located along the southern property boundary.

Parathion, chlordane, phaltan, captan, malathion, and paraguat were formulated at the site.
DDT, difolatan, BHC-lindane, dieldrin, aldrin, bromamine, and nutritional sprays (agueous
solution of copper, zinc, manganese, sulfur, and boron) were also formulated during this period
of operation. Chemicals used in pesticide formulation included xylene, kerosene, mineral oil,
mineral spirits, ethylbenzene, and aromatic naphtha.

Chevron discontinued the formulation of pesticides in 1976. According to Chevron sources,
Chevron removed the chemical inventory from the site, drained the eguipment lines and backfilled
the rinsate ponds with soil.

In 1978, the property was sold and Central Florida Mack Trucks, a truck sales and service
company, began operations at the Site. Central Florida Mack Trucks repaired and serviced diesel
engine trucks. Body work and painting were also conducted at the site. The facility generated
waste oil and waste degreasing solvent (from engine and parts cleaning operation). A waste oil
through was located along the railroad spur on the southwestern side of the site. Used oil
filters, waste oil, diesel fuel, paint, and partially filled drums of powdered pesticides were
later discovered in the rinsate pond area during the first Removal Action, along with discarded
truck parts and debris.

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In March 1984, during the operation of Central Florida Mack Trucks, a tanker truck (owned by
Waste Management, Inc.) filled with 3% hydrochloric acid and an unknown amount of nitric acid,
was stored on-site for repair. The tanker leaked an estimated 3,000 to 6,000 gallons of acid,
which resulted in an explosion in the spill area and disposed of the contaminated soils.

Central Florida Mack Trucks discontinued its operation at the Site in November 1986. On March
1, 1991, the pesticide formulating/warehouse building on site burned down. The building debris
was cleared from the rail spur area and the south side of the site was fenced. Chevron
purchased the property in foreclosure from First Union Bank and the Resolution Trust Company in
1993 and 1994, respectively.

During the period from 1982 to 1989, several investigations were conducted to assess the
conditions at the site. The results of these studies indicated the presence of some pesticides,
VOCs, and metals in soil and/or groundwater samples.

In May 1989, an EPA contractor conducted a field investigation under the authority of the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Samples from
the surface and subsurface soils and the groundwater were collected at the site. The results of
the sampling activities identified the presence of pesticides, benzene, toluene, xylene,
naphthalene compounds, and metals in soil samples collected along the rail spur adjacent to the
former outfall from the floor drain. Chlordane was detected in soil samples collected in the
southwest corner of the site. Pesticides, metal, benzene, toluene, xylene, and naphthalene
compounds were detected in soil samples collected in the vicinity of the former rinsate ponds.

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indicator chemical because chlordane was considered the most prevalent and most toxic compound
to humans and was found in the highest concentrations.

Prior to the removal action, additional sampling was conducted to evaluate the potential for
off-site migration of contaminants in the groundwater and to evaluate the magnitude and extent
of soil contamination. Soil samples were collected using a 50-foot by 50-foot grid established
across the site. Samples were collected from 2 to 4 feet below land surface (BLS), 4 to 6 feet
BLS, and 8 to 10 feet BLS. Groundwater samples were collected via a Hydropunch and the
installation of four additional clusters of wells. Petroleum hydrocarbons such as benzene,
ethylbenzene, and xylene were the predominant groundwater contaminants. Chlorinated pesticides
were detected sporadically; a-BHC and b-BHC were the most freguently detected pesticides.

The removal action was conducted during the period from December 1991 through September 1992.
All site structures were demolished and removed. Approximately 17,780 tons of pesticide
contaminated soil were excavated and disposed of; 4,900 tons of petroleum contaminated soil were
excavated and treated; and 126,000 gallons of recovered stormwater and groundwater were treated
and discharged into an on site infiltration trench. All of the excavated areas were backfilled
with clean soil and the site was graded and seeded. Figure 4 shows the areas that were
excavated, and the depths of each excavation.

In April 1993, Chevron and EPA entered into a separate AOC to conduct an RI/FS pursuant to the
EPA policy known as the Superfund Accelerated Cleanup Model (SACM). The purpose of the RI/FS
was to evaluate groundwater contamination at the Site and to evaluate potential soil
contamination in an adjacent trailer park and areas of off-site drainage.

Soil sampling was conducted in two phases at the adjacent Armstrong Trailer Park. Based on the
results of the sampling, a removal action was conducted at the trailer park during March and
April 1994. The soil cleanup level was 4.9 ppm of chlordane. Approximately 230 tons of
contaminated soil was excavated from the trailer park. Most of the contaminated soil was
removed from an area adjacent to the northwest corner of the Site, a probable location for
surface water runoff (see Figure 5).

Groundwater sampling was also conducted in phases during the RI. Nine existing monitoring wells
were sampled in April 1993. Seventeen additional wells were installed and subseguently sampled
during September and October 1993.

The site was finalized on the NPL during May 1994. The RI/FS documents were finalized during
March 1995.

3.0 HISTORY OF COMMUNITY RELATIONS

A public meeting was held on November 20, 1991, prior to the on-site removal action. In
addition, an administrative record and public comment period were also established for the
removal action.

A public meeting was held on July 29, 1993 to explain the upcoming RI/FS activities at the Site.
The meeting was held at the Fire Fighters Council Hall in Orlando. Another public meeting was
held on March 17, 1994 prior to the removal action at the Armstrong Trailer Park. The meeting
was conducted at the trailer park.

A fact sheet describing the status of Superfund activities was mailed to the community during
July 1994.

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The Florida Department of Health and Rehabilitative Services (HRS) held a meeting on March 9,
1995 at the Armstrong Trailer Park. HRS held the meeting to discuss their health assessment of
the Site. EPA staff were present to discuss Superfund activities.

The Proposed Plan fact sheet was mailed to the community on July 18, 1995. The administrative
record was updated and relocated to the Edgewater Branch Public Library, which is closer to the
Site. A public meeting was held on July 26, 1995 at the Edgewater Branch Public Library. The
public comment period was held from July 21, 1995 to August 18, 1995.

4.0 SCOPE AND ROIiE OF ACTION

The planned actions for this Site address groundwater contamination. The ROD further describes
this remedy and is the only ROD anticipated for this Site.

5.0 SUMMARY OF SITE CHARACTERISTICS

5.1 Geology

The Chevron Orlando site is located in north-central Orange County, on the Florida Peninsula.
The topography of Orange County includes a highland region which extends across the western part
of the county, and a lowland region in the eastern portion of the county along the St. Johns
River. The Orlando Ridge, Mount Dora Ridge, and part of the Lake Wales Ridge make up the
highland region, which is mostly sand hills of remnants of fossil beach ridges that parallel the
Atlantic coast.

The site lies within the Osceola Plain, in a small area between the Orlando and Mount Dora
Ridges. The ridges are differentiated from surrounding plains by the profusion of mature karst
lakes. The drainage in the vicinity of the site is controlled by the topography, with the
drainage basins for groups of lakes defined by relic beach ridges.

The main drainage features in Orange County include small seasonal streams, lakes and sinkholes.
Drainage in Orange County, specifically in the Orlando area, also occurs through drainage wells.
Between 1906 to 1961, approximately 300 drainage wells were drilled in Orange County to control
the county have no natural drainage outlets, except for infiltration into the surficial aguifer.
The maximum water level elevation in a lake is controlled by a fixed-elevation weir. As the
water level in the lake rises in response to rainfall and overtops the weir, the overflow is
channeled into the drainage wells. The drainage wells are constructed into the Floridan
aguifer. Lake Fairview is the closest lake to the Site. The southernmost edge of the lake is
located approximately 700 feet northwest of the Site.

The land surface elevation of the site ranges between 97 and 102 feet above mean sea level. The
elevation decreases to the north and east. Historically, stormwater runoff flowed across the
site to the north into a drainage ditch, which discharged into a small pond in the northwest
comer of the site. The site topography was modified during the first Removal Action to promote
on-site infiltration of stormwater. Prior to the Removal Action, the eastern portion of the
site (which was covered with asphalt) drained to the east into the storm drain system along
Orange Blossom Trail.

5.2 Area Hydrogeology

Orange County is underlain by a wedge of marine limestone, dolomite, shale, sand and anhydrite
that is approximately 6,500 feet thick. Overlying the crystalline basement in succession are
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the Eocene age Lake City limestone (over 700 feet thick), the Avon Park limestone (400 to 600
feet thick), and the Ocala limestone (0 to 125 feet thick) which may be highly eroded or missing
in some parts of the county. These formations, and permeable portions of the Hawthorn
formation, comprise the Floridan aguifer.

The Floridan aguifer is divided into two major producing zones, the upper zone (between 150 and
600 feet BLS) and the lower zone (between 1,100 feet and 1,500 feet BLS). The producing zones
are composed of dolomitic limestone and are separated by less permeable layers of soft
limestones. The lower producing zone is a main source of municipal water supply for much of
Orlando and Winter Park.

The Miocene age Hawthorn formation (50 to 300 feet thick) overlies the Ocala limestone. The
upper Hawthorn is made up of gray-green, clayey, guartz sand and silt, and acts as a confining
unit between the surficial aguifer and the Floridan aguifer. The lower part of the Hawthorn
formation is comprised of limestone with phosphorite and guartz sand. In areas where the lower
part of the formation produce water, it is considered to be part of the Floridan aguifer.
However, this water producing unit of the Hawthorn formation may not be present in all parts of
the county.

Discharge from the surficial aguifer occurs through domestic water supplies throughout Orange
County. Most of the wells constructed in the unconfined aguifer are small in diameter and
produce approximately 5 to 10 gallons per minute. Additional discharge from the surficial
aguifer occurs through seepage into lakes and streams during periods of low flow and drought, as
well as downward leakage to the Floridan aguifer. The majority of recharge to the surficial
aguifer comes from rainfall, and infiltration from surface water bodies. However, upward
leakage from the Floridan aguifer may recharge the surificial aguifer in areas where the
potentiometric surface of the Floridan aguifer is above the water table. The direction of
groundwater flow in the surficial aguifer is controlled by topography.

Some recharge to the Floridan aguifer occurs through infiltration of rainfall through
semi-permeable confining layers, but most occurs through the drainage wells in the county. The
groundwater flow direction in the Floridan aguifer is generally easterly and northeasterly. The
regional flow in influenced locally by the effects of pumping wells, seasonal fluctuations, and
drainage wells.

The climate in the area is semi-tropical with an average annual temperature of 71.8 degrees
Fahrenheit (°F) with minor seasonal fluctuations. The average temperature in the winter is 61.1
°F and 81.1 °F in the summer.

Rainfall is approximately 48 inches per year, with the most precipitation occurring between June
and September. November is the driest month with an average rainfall of 1.78 inches. July is
the wettest month with an average rainfall of 7.78 inches. The wind flow in the area is
predominantly from the north and east. However, the wind does not blow in a single direction
more than 10 percent of the time.

5.3 Site Hydrogeology

The shallow lithology underlying the site was defined during construction of monitor wells and
soil borings. Quartz sand, with varying amounts of silt and organic material was encountered
from 0 to 27 feet below land surface (BLS). The sand is fine to medium grained, and ranges in
color from brown to light tan. Organic material was observed in the upper 10 to 15 feet of the
sand unit, along with stringers of clay. The lower portion of the unit grades from sand in an
organic matrix to sand in a light tan calcareous mud matrix.
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The contract with the Hawthorne formation appears to be an erosional surface, represented by a
decreasing percentage of sand an increasing percentage of calcareous clay. In MW-14, a
distinctive clay horizon was encountered at 40-feet below land surface. The gray silty clay
layer is approximately 20 feet thick. Olive green clay with phosphorite nodules, which is
characteristic of the upper Hawthorn formation, was encountered in MW-14 at approximately
65-feet BLS. The first limestone unit of the Hawthorn formation was encountered at 78-feet BLS.
The limestone is light grey, with distinctive phosphorite nodules.

The saturated thickness of the surficial aguifer at the site is 17 to 20 feet. The depth to
groundwater at the site is usually within 10 feet of the land surface. The groundwater flow
across the site is to the northeast toward Lake Fairview with a gradient of approximately .006
feet/feet. The potentiometric surface elevation in the upper Floridan aguifer, as measured in
MW-14, is approximately 20 feet lower than the water table elevation measured on the site.

An aguifer performance test was conducted at the site to determine the characteristics of the
surficial aguifer. The data produced by the pumping test were evaluated using various methods
to best address the anticipated delayed yield and partial penetration. The static water level
was measured in two monitor wells to identify potential areal influences on the water table
elevation for a period of 24-hours before the pumping test began. The pumping test data
interpretation provided a range of transmissivity values from 700 to 1000 feet2/day. A
hydraulic conductivity value of 52 feet/day was selected for use in the groundwater flow model,
as most representative of the areawide surficial aguifer.

The water level in MW-14 (the Hawthorn formation monitor well) was also measured during the
pumping test, to determine whether a connection between the surficial aguifer and the first
water level was measured in MW-14 that could be related to the test.

A well survey was conducted within a radius of one mile around the site. The files at the
Florida Department of Environmental Regulation (now the Department of Environmental Protection),
the St. Johns Water Management District, and the U.S. Geological Survey were reviewed to
complete the survey. Eight wells were identified within a one mile radius of the site, but none
of these wells are down gradient of the site. The closest well is located approximately 3800
feet northwest of the Site.

5.4 Soil Contamination

The previous on-site removal addressed much of the soil contaminated with chlorinated pesticides
(including chlordane) and petroleum at the Site. The soil cleanup level was a chlordane
concentration of 50 ppm in the upper one foot of soil 100 ppm for the deeper soils. Excavation
depths varied from 0-10 feet and, as a result, 50 percent of the surface area and 17 percent
of the deeper soil was excavated and replaced by clean fill.

The contaminants of concern in on-site soil are summarized in Tables 1 and 2. Other organic
compounds and pesticides were detected but are not evaluated further due to low detection
freguencies of low concentrations relative to screening values. The contaminants of concern in
off-site soil are summarized in Table 3. The exposure point concentration listed in the
following tables is the statistical 95% UCL for the average value unless it exceeds the maximum
value detected or is below the minimum value detected. In those cases, the maximum detected
value is used.

The removal at the adjacent trailer park addressed soil contaminated by surface water runoff
from the Site. The soil cleanup level for the trailer park was a chlordane concentration of 4.9
ppm and was based on protecting human health in a residential setting.
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TABIiE 1: CONTAMINANTS OF CONCERN IN ON-SITE SURFACE SOIL
Contaminant
Frequency of
Point Detection
(mg/kg)
Range of Detected
Concentrations
(mg/kg)
Exposure
4,4' -ODD
4,4' -DDE
4,4' -DDT
Aldrin
b-BHC
Chlordane
Dieldrin
Heptachlor
Epoxide
25/81
12/79
27/81
5/82
7/82
54/82
12/79
4/80
.04-21
.147-3.1
.053-58
.019-13
.005-21
.088-79
.029-11
.0058-0.6
2,
1.
1.
1.
1.
8,
1.
0,
.5
.1
.4
.2
.1
.6
.2
.6
Concentration
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TABIiE 2: CONTAMINANTS OF CONCERN IN ON-SITE SURFACE SOIL
Contaminant
Frequency of
Point Detection
(mg/kg)
Range of Detected
Concentrations
(mg/kg)
Exposure
4,4' -ODD
4,4' -DDE
4,4' -DDT
Aldrin
a-BHC
b-BHC
Chlordane
Dieldrin
g-BHC (lindane)
Endrin
126/271
49/215
50/271
19/225
13/225
15/225
187/273
56/222
12/225
14/216
.01-210 17
.007-21 2.1
.053-58 2.7
.019-23 1.5
.5-130 1.4
.005-21 1.2
.048-350 46
.029-16 2
.3-19 1.4
.014-6.7 6.7
Concentration
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TABIiE 3: CONTAMINANTS OF CONCERN IN ON-SITE SURFACE SOIL
Contaminant
Frequency of
Point Detection
(mg/kg)
Range of Detected
Concentrations
(mg/kg)
Exposure
Concentration
Chlordane
Lead
Dieldrin
50/53
7/7
16/53
.004-5.3
15-130
.079-1.1
3.9
79
0.066
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5.5 Groundwater Contamination

Certain VOCs, pesticides, and metals have been detected in some monitoring wells at the Site.
The groundwater contaminants vary in concentration, location and depth underneath and adjacent
to the Site. Groundwater contamination has been found at depths ranging from approximately 5 to
30 feet BLS. Low level groundwater contamination extends in a northeast direction under the
Site and the eastern portion of the upgradient trailer park. Site contaminants have not been
detected in the monitoring well located upgradient of Lake Fairview. The contaminants of
concern in groundwater at the Site are summarized in Table 4. Other organic compounds and
pesticides were detected but are not evaluated further due to low detection freguencies or low
concentrations relative to screening values. The locations of the groundwater monitoring wells
are shown in Figure 6. One well, MW-14, was installed and screened at a depth of 82-94 feet.
Trace amounts of chromium and lead were detected along with bis(2-ethyl hexyl) phthlate and
di-n-octyl phthlate.

6.0 SUMMARY OF SITE RISKS

CERCIA directs EPA to conduct a baseline risk assessment 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 taking action and
indicates the exposure pathways that need to be addressed by the remedial action. This section
of the ROD reports the results of the baseline risk assessment conducted for this Site.
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GROUNDWATER
CONTAMINANT

Benzene
Ethylbenzene
Xylenes
Total
Napthalenes
4,4' -DDD
a-BHC
b-BHC
g-BHC
(Lindane)
Chlordane
Arsenic
Chromium
Lead

FREQUENC
DETECTIC
1995)
9/25
12/25
13/25
3/25

4/25
10/25
12/25
3/25

3/25
2/25
2/25
8/25

RANGE OF CLEANUP
DETECTED STANDARD
CONCENTRATIONS(ug/1) (ug/1)
1.1-23

.9-380

4-1,100

25-26
1

100
.12-2.2

.16-19

.15-47

.87-2.4
0.1

0.05

0.1

0.2
1.1-17

10-34

70-3,200

5-66
2

100

15
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6.1 Contaminants of Concern

The chemicals measured in the various environmental media during the RI were included in this
discussion of the site risks if the results of the risk assessment indicated that a contaminant
might pose a significant current or future risk of contribute to a cumulative risk which is
significant. The criteria for a significant risk was a carcinogenic risk level above the
acceptable risk range, i.e., 1x10-4 to 1x10-6, or a hazard guotient (HQ) greater than 1.0
(unity). See tables 1-4 for the contaminants of concern in each medium.

The exposure point concentrations for each of the chemicals of concern and the exposure
assumptions for each pathway were used to estimate the chronic daily intakes for the potentially
complete pathways. The baseline risk assessment is based on the reasonable maximum exposure
(RME) that may be encountered during the various Site use scenarios. The RME concentrations are
either the calculated 95% Upper Confidence Limit of the aritmetic mean or the maximum
concentration detected during sampling. The intent of the RME is to estimate a conservative
exposure case (i.e., well above the average case) that is still within the range of possible
exposures. If the calculated UCL exceeded the maximum level measured at the Site, then the
maximum concentration detected was used to represent the reasonable maximum concentration. The
chronic daily intakes were then used in conjunction with cancer slope factors and
noncarcinogenic reference doses to evaluate risk.

The exposure point concentrations for on-site soil are based on analytical data collected prior
to and as part of the on-site removal action conducted in 1992. The data can be found in the
July 1991 Removal Action Plan (see Figure 4-1 and Appendix C) and the December 1992 Removal
Action Report (see Appendices E and F). Table 3-5 of the Baselins Risk Assessment, dated March
1995 lists the particular sample points used in the exposure point concentrations. The Baseline
Risk Assessment used only those samples collected from areas after excavation was completed or
from the remaining areas where no removal excavation was necessary.

The exposure point concentrations for off-site (Armstrong Trailer Park) and the current
groundwater conditions are presented in the RI Report dated November 1994. There was a removal
of some surface soil conducted at the Armstrong Trailer Park during March 1994. Again, the
Baseline Risk Assessment used only those samples collected from areas after excavation was
completed or from the remaining areas where no removal excavation was necessary.

6.2 Exposure Assessment

Whether a chemical 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 seguence of events leading to contact
with a chemical) is defined by the following four elements:

• 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).

An evaluation was undertaken of all potential exposure pathways which could connect chemical
sources at the Site with potential receptors. All possible pathways were first hypothesized and
evaluated for completeness using the above criteria. The current pathways represent exposure
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pathways which could exist under current Site conditions while the future pathways represent
exposure pathways which could exist, in the future, if the current exposure conditions change.
Exposure by each of these pathways was mathematically modeled using generally conservative
assumptions.
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TABIiE 5: POTENTIAL EXPOSURE PATHWAYS

Media Scenario

Groundwater Future
On-site Surface
Dermal Contact
Current
Future
Receptor

Adult & Child
Inhalation

Trespasser
Trespasser &
Worker
Exposure Pathways

Ingestion & Resident

Ingestion & Soil
Ingestion & Adult
Dermal Contact
On-site
Subsurface Soil
Worker

Off-site Soil
Future
Current
Adult
Construction
Child & Adult
Dermal Contact
Ingestion &
Dermal Contact
Ingestion & Resident
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Vegetation and ground cover present at the Site will impede wind erosion of soil at the Site.
Therefore, exposure to constituents in air, either as vapor or adsorbed to dust, is not
considered significant at the Site under current land use conditions. The presence of
vegetation also reduces direct contact with surface soils by Site visitors.

The baseline risk assessment considered commercial and residential land use. There is a mobile
home park located just north of the Site and industrial/commercial operations on the all other
sides of the Site. Future residential use of the Site is not likely. The current zoning and
future land use planning both designate commercial use for the Site and the surrounding area.

6.3 Toxicity Assessment

Toxicity values are used in conjunction with the results of the exposure assessment to
characterize Site risk. EPA has developed critical toxicity values for carcinogens and
noncarcinogens. Cancer slope factors (CSFs) have been developed for estimating excess lifetime
cancer risk associated with exposure to potentially carcinogenic chemicals. CSFs, which are
expressed in units of (mg/kg/day)-1, are multiplied by the estimated intake of a potential
carcinogen, in mg/kg/day, to provide an upper-bound estimate of the excess lifetime cancer risk
associated with exposure at the intake level. The term "upper bound" reflects the conservative
estimated of the risks calculated from the CSF. Use of this conservative approach makes
underestimation of the actual cancer risk highly unlikely. GSRs are derived from the results of
human epidemiological studies or chronic animal bioassays to which animal-to-human extrapolation
and uncertainly factors have been applied.

Reference doses (RfDs) have been developed by EPA for indicating the potential for adverse
health effects from exposure to chemicals exhibiting noncarcinogenic effects. RfDs, which are
expressed in units of mg/kg/day, are estimates of lifetime daily exposure levels for humans,
including sensitive individuals. Estimated intakes of chemicals from environmental media can be
compared to the RfD. RfDs are derived from human epidemiological studies or animal studies to
which uncertainty factors have been applied (e.g., to account for the use of animal data to
predict efforts on humans). These uncertainty factors help ensure that the RfDs will not
underestimate the potential for adverse noncarcinogenic effects to occur.

6.4 Risk Characterization

Human health risks are characterized for potential carcinogenic and noncarcinogenic effects by
combing exposure and toxicity information. Excessive lifetime cancer risks are determined by
multiplying the estimated daily intake level with the CSF. These risk are probabilities that
are generally expressed in scientific notation (e.g., 1x10-6). An excess lifetime cancer risk
of 1x10-6 indicates that, as a plausible upper boundary, an individual has a one in one million
additional (above their normal risk) chance of developing cancer as a result of Site-related
exposure to a carcinogen over a 70-year lifetime under the assumed specific exposure conditions
at a Site.

EPA considers individual excess cancer risks in the range of 1x10-4 to 1x10-6 as protective;
however the 1x10-6 risk level is generally used as the point of departure for setting cleanup
levels at Superfund sites. The point of departure risk level of 1x10-6 express EPA's preference
for remedial actions that result in risk at the more protective end of the risk range. The
health-based risk levels for the Site are shown in Table 6. The health-based risk levels for
off-site soil are shown in Table 7.

Potential concern for noncarcinogenic effects of a single contaminant in a single medium is
expressed as the hazard guotient (HQ) (or the ratio of the estimated intake derived from the
contaminant concentration in a given medium to the contaminants's reference dose). A HQ which
-------
exceeds unity (1) indicates that the daily intake from a scenario exceeds the chemical's
reference dose. By adding the HQs for all contaminants within a medium or across all media to
which a given population may reasonably be exposed, the Hazard Index (HI) can be generated. The
HI provides a useful reference point for gauging the potential significance of multiple
contaminant exposures within a single medium or across media. An HI which exceeds unity
indicates that there may be a concern for potential health effects resulting form the cumulative
exposure to multiple contaminants within a single medium or across media. The HI for the Site
are shown in Table 6. The His for the off-site soil are shown in Table 7.

Exposure to on-site soil under existing conditions and land use does not present an unacceptable
carcinogenic risk. Exposure to on-site subsurface soil by a future construction worker yields a
hazard index slightly above unity. However, given the conservative assumptions used in the risk
assessment, the actual exposure and associated risk is expected to be acceptable. EPA's
definition of acceptable risk is found in 40 CFR 300.430 (e) (2).

Future residential use of the site poses an unacceptable risk, primarily due to ingestion of
contaminated groundwater. Currently, no drinking water wells are located within the area of the
groundwater plume. Exposure to on-site surface soil by a future residential child yields a
hazard index slightly above unity. However, given the conservative assumptions used in the risk
assessment the actual exposure and associated risk is expected to be acceptable.

Current and future exposure to soil at the adjacent Armstrong Trailer Park does not pose an
unacceptable risk. Ingestion of contaminated groundwater would pose an unacceptable risk, but
no private wells are used at the trailer park. Area residences and business are currently
supplied by municipal water supply systems; therefore, the groundwater in the surficial aguifer
is not consumed and poses no foreseeable risk.

Unacceptable risk associated with this Site is due to the potential future consumption of
groundwater containing contaminants above either federal or State of Florida groundwater
standards. Actual or threatened releases of hazardous substances from this Site, if not
addressed by implementing the response action selected in this ROD, may present an imminent and
substantial- endangerment to public health, welfare, of the environment.

6.5 Environment Risk

A gualitative and guantitative risk assessment was conducted to determine if contaminants
present in site soils and groundwater have impacted or can potentially impact flora and fauna in
the area.

The site is now a vacant lot and much of the surface soil has been removed and backfilled with
clean soil. Grasses and weeds have revegetated most of the Site and birds and insects have been
observed on site. No endangered or threatened species have been identified in the immediate
vicinity of the Site.

The risk assessment considered potential on-site ecological impacts by calculating His for
exposure of surrogate species to on-site soil. The calculations were produced in a manner
similar to the HIi calculated for human exposure. Calculated potential intakes were compared to
No-Observed-Adverse-Effects-Levels, Lowest-Observed-Adverse-Effects, or other toxicological
data. Given the conservative assumptions used to calculate potential exposure and associated
risk, the ecological risk for on-site species is not considered significant.
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TABIiE 6: RISK SUMMARY FOR CURRENT AND FUTURE USE: ON-SITE SOIL AND GROUNDTCATER

Land Use/Receptor Pathway Noncarcinogenic Carcinogenic Risk
(Hazard Index) Risk
Current Use/Adolescent
Ingestion of Soil 0.2
5x10-6 Trespasser

Dermal Contact 0.1 5x10-6 with Soil

TOTAL: 0.3 1x10-5

Future Use/Adolescent Ingestion of Soil 0.2 5x10-6 Trespasser

Dermal Contact 0.1 5x10-6 with Soil

TOTAL: 0.3 1x10-5

Future Use/Adult Construction Ingestion of Soil 2.0 4x10-6 Worker

Dermal Contact with Soil 0.3 8x10-7

TOTAL: 2.3 5x10-6

Future Use/Adult Worker Ingestion of Soil 0.1 9x10-6

Dermal Contact with Soil 0.08 8x10-6

TOTAL: 0.18 2x10-5

Future Use/Child Resident Ingestion of soil 3.0 6x10-5

Dermal contact with soil 0.8 2x10-5

Ingestion of groundwater 10 2x10-3

Inhalation of groundwater 0.9 4x10-6

TOTAL: 15 2x10-3

Future Use/Adult Resident Ingestion of soil 0.4 3x10-5

Dermal Contact 0.3 3x10-5 with Soil

Ingestion of groundwater 5.0 3x10-3

Inhalation of groundwater 0.4 7x10-6

TOTAL: 6.1 3x10-3
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TABIiE 7: RISK SUMMARY FOR CURRENT AND FUTURE USE: ON-SITE SOIL AND GROUNDTCATER

Land Use/Receptor Pathway Noncarcinogenic Carcinogenic Risk
(Hazard Index) Risk

Child Resident Ingestion of soil 0.8 7x10-6

Dermal contact with soil 0.3 2x10-6

TOTAL: 1.1 9x10-6

Adult Resident Ingestion of soil 0.09 3x10-6

Dermal contact with soil 0.1 3x10-6

TOTAL: 0.19 6x10-6
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6.6 Uncertainties

At all stages of the risk assessment, conservative estimates and assumption were made so as not
to underestimate potential risk. Nevertheless, uncertainties and limitations are inherent in
the risk assessment process.

The estimates of exposure point concentrations of the chemicals of concern probably overstate
actual concentrations to which individuals would hypothetically be exposed and therefore, the
health risk estimates are very conservative. In addition, no attenuation of the chemicals was
considered; however, this may reduce concentrations of chemicals over time.

The assumed exposure pathways evaluated in the risk assessment are conservative in nature and
may overstate the actual risk by this Site.

Summing risks or hazard indices for multiple contaminants ignores the possibility of synergistic
or antagonistic activities in the metabolism of the contaminants.

7.0 DESCRIPTION OF ALTERNATIVES FOR GROUNDWATER

The following Site specific alternatives represent a range of distinct actions addressing human
health and environmental concerns. The analysis presented below reflects the fundamental
components of the various alternatives considered feasible for this Site.

The various alternatives were based on achieving groundwater cleanup levels. Most of these
cleanup levels are based in the primary Maximum Contaminant Levels (MCLs) for drinking water.
However, the cleanup levels for ethylbenzene and xylene are based on their respective secondary
MCLs. It is apparent that these two contaminants may contribute to increased mobilization of
the BHC isomers. Thus, the secondary standards were considered appropriate for the protection
of groundwater.

MCLs were not available for alpha-BHC, and 4,4-DDD'. Therefore, groundwater cleanup levels for
these contaminants were based on the State's preferred risk levels for carcinogens.

Seven alternatives were selected for detailed analysis and are listed below:

Alternative No. 1 No future action
Alternative No. 2 Natural attenuation and monitoring
Alternative No. 3 Removal, treatment, and disposal of groundwater
Alternative No. 4 Bioactive filter
Alternative No. 5 Hydrologic flow barrier
Alternative No. 6 Combined alternative
Alternative No. 7 Source removal

Alternative No. 1 - No future action: This alternative serves as a baseline with which other
alternatives can be compared and includes maintenance of the existing fence and warning signs,
and mowing of the grass at the site for a 30-year period. Conservative estimates of
biodegradation rates indicate that ARARs for mobile contaminants will be met in approximately 10
years. However, this alternative does not include monitoring to verify the rate of degradation.

Under this alternative, no further cleanup would occur at the site. A removal action was
completed on-site during 1992 and a removal action was completed at the adjacent trailer park
during 1994. Groundwater at the Site is not presently consumed and poses no current risk.
However, no controls would be placed on future groundwater use. Area residences and businesses
are currently supplied by municipal water supply systems.
-------
Alternative No. 2 - Natural attenuation and monitoring: Alternative No. 2 includes the
implementation of regulatory or institutional controls to limit the future use of the site, and
the initiation of a long-term groundwater monitoring program. This alternative relies on the
natural attenuation processes and continued natural degradation to reduce contaminant
concentrations. Conservative estimates of biodegradation rates indicate that ARARS for mobile
contaminants will be met in approximately 10 years.

Institutional controls utilize regulatory agency procedures or deed restrictions to restrict
access to or usage of contaminated groundwater. Although the surficial aguifer is not used for
water supply in the vicinity of the site, deed restrictions would be placed on the site to
specify that groundwater withdrawals from the site (other than sampling to determine water
guality) are restricted until the ARARs are achieved. Institutional controls would be used,
as necessary, to control access to contaminated groundwater outside the Chevron property
boundary. Since all residences and businesses in the vicinity of the site are supplied by the
city and county municipal water supply systems, it is unlikely that the surficial aguifer will
be used for water supply in the near future.

This alternative also includes a long-term monitoring program to monitor contaminant
concentrations in the groundwater beneath and downgradient of the site.

Alternative No. 3 - Removal, treatment, and disposal of groundwater: This alternative consists
of the installation of extraction wells (or a combination of extraction wells and horizontal
wells) to remove contaminated groundwater. The contaminated groundwater would then be treated by
air stripping and carbon adsorption. The treated groundwater will be discharged into on-site
infiltration trenches. Numerical simulations indicate that this alternative will achieve the
ARARs for all of the mobile COCs at the property boundary within 3 years. Existing information
is insufficient to accurately predict the time reguired for groundwater to comply with ARARs at
all locations across the site, but may be similar to that reguired for the no-action alternative
(i.e., 8-10 years). Natural attenuation may be necessary to completely satisfy the cleanup
levels. Contaminant concentrations may reach asymptotic levels slightly above the cleanup the
cleanup levels in a typical pump and treat system.

The purpose of air stripping is to bring the groundwater into contact with air so that the
volatile compounds migrate from the water to air. Although the pesticides of concern generally
have low Henry's law constants (i.e., are not very volatile), stripping can be enhanced by using
a high air-to-water ratio to create an environment in which each compounds concentration in air
is always low. Under these conditions, the system will tend toward an eguilibrium condition
where the concentration in the water is lowered. Vapor emission controls are reguired to
capture the volatilized pesticides by passing the emissions through activated carbon cylinders.

Granular activated carbon (GAG) adsorption is a physical adsorption process that has been shown
to be successful in reducing the concentrations of pesticides in wastewater. The groundwater is
brought into direct contact with the GAG filter beds, usually two columns in series and/or
parallel, to facilitate continuous operation and to allow for replacement of exhausted beds.
Although disposal of spent carbon is a major expense, GAG beds designed for low pesticide
concentrations can often last about 3 months before replacement is needed.

Alternative No. 4 - Bioactive filter: The bioactive filter alternative is an innovative
technology that involves installation of a permeable, biologically active wall to intercept
groundwater contaminants migrating off-site. The filter extends vertically from land surface to
approximately 30 ft below the surface, and horizontally to encomposed of native sand mixed with
a carbon material that will selectively adsorb dissolved organic species migrating in the
groundwater. The filter is designed such that COG concentrations in groundwater exiting the
downgradient edge of the filter material will meet ARARs. In addition, if a natural material
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like peat is used for the filter, the organic compounds collected by the filter may biodegrade
more rapidly when adsorbed to this more biologically active material. COG concentrations
upgradient of the filter will be reduced by ongoing natural biodegradation. ARARs for organic
contaminants are expected to be met downgradient of the Site within 3 years. Cleanup levels are
expected to be met on-site within 10 year, similar to the timeframe associated with the natural
attenuation alternatives.

Alternative No. 5 - Hydrologic flow barrier: The hydrologic flow barrier considered for this
alternative is a slurry wall, which is a low-permeabilty barrier that will be constructed along
the downgradient edges of the site. The slurry wall will decrease the flow of contaminated
groundwater from the site to downgradient areas. The portion of the plume that is currently
downgradient of the site will continue to degrade. Contaminant migration will be eliminated.
Cleanup levels for mobile contaminants are expected to be met downgradient of the Site within 3
years. The downgradient concentrations will decrease because the flow of upgradient, on-site
contaminant will be greatly reduced and thus will no longer contribute to the downgradient
contamination. Cleanup levels are expected to be met on-site within 10 years, similar to the
timeframe associated with the natural attenuation alternatives.

Alternative No. 6 - Combined alternative: This alternative includes guarterly groundwater
sampling and additional groundwater assessment. After one year, the groundwater data would be
reviewed to determine if natural attenuation has reduced the levels of contaminants such as
xylene and alpha- BHC by 10 to 15 percent. If those levels are achieved, then the natural
attenuation and groundwater sampling would continue. If not, then the permeable filter wall
(alternative 4) would be implemented along with other measures such as limited air sparging of
hydraulic gradient control, or source removal, if necessary. The contingency may also be
reguired if contaminant concentrations do not decrease as predicted during subseguent years or
if contaminants are detected in monitoring well MW-11D. This alternative also includes deed
restrictions to prohibit the residential use of the Chevron Site and institutional controls to
prohibit the potential consumption of groundwater from the area of the contaminant plume until
groundwater standards have been achieved. Cleanup levels are expected to be achieved within
8-10 years and groundwater monitoring will continue until those levels are achieved.

Alternative No. 7 - Source Removal: Under this alternative, contaminated soil that may as a
source of COCs to groundwater would be located, excavated, and transported to an approved TSD
facility. Once the sources have been removed, groundwater concentrations of COCs would be
expected to decrease rapidly due to natural attenuation mechanisms (i.e., biodegradation).
Cleanup levels would be expected to be met within 3 years after the source has been removed.
However, the locations of potential limited sources to groundwater are not known with certainty,
despite extensive site investigations and soil removal actions. As a result, this remedy may
still rely on natural attenuation to ultimately achieve cleanup levels and may reguire
approximately 10 years to achieve cleanup levels.

This alternative would likely be combined with any of the alternatives 2-6, if necessary, to
achieve an effective cleanup.

8.0 COMPARATIVE ANALYSIS OF ALTERNATIVES

The alternatives are evaluated against on another by using the following nine criteria:

• Overall protection of human health and the environment.
• Compliance with Applicable or Relevant and Appropriate Reguirements (ARARs).
• Long term effectiveness and permanence.
• Reduction of toxicity, mobility, or volume through treatment.
• Short term effectiveness.
-------
• Implementability.
Costs.
• Community Acceptance.
• State Acceptance.

The NCP categorized the nine criteria into three groups:
(1) Threshold criteria: the first two criteria, overall protection of human health and the
environment and compliance with ARARs (or invoking a waiver), are the minimum criteria that
must be met in order for an alternative to be eligible for selection

(2) Primary balancing criteria: the next five criteria are considered primary balancing
criteria and are used to weigh major trade-offs among alternative cleanup methods

(3) Modifying criteria: state and community acceptance are modifying criteria that are formally
taken into account after public comment is received on the proposed plan. Community
acceptance is addressed in the responsiveness summary of the ROD.

The comparative analysis of the seven alternatives proposed for this Site are presented in the
following section.

8.1 Comparative Analysis of Remedial Alternatives

1. Overall Protection of Human Health and the Environment

Each alternative, except for the no-action alternative, would provide protection of human health
and the environment given the current conditions at the Site. Removal actions to address
contaminated soil have been completed at the Site and the adjacent trailer park. The
groundwater within the surficial aguifer beneath and downgradient of the site is not currently
used as a potable, irrigation, or industrial supply. Potable water is provided to surrounding
residents and businesses by the City of Orlando and Orange County municipal water supply
systems. The groundwater in the surficial aguifer is not currently being used, and the plume is
at steady state. Therefore, there is no risk to human health of the environment associated with
the groundwater in its current condition. There is potential future risk if a private drinking
water well was installed in the area of the plume before the contaminants had degraded.

2. Compliance with ARARs

Each alternative is expected to comply with federal and state ARARs for groundwater
contaminants. It is expected that the various alternatives will achieve compliance with
groundwater ARARs within 8-10 years. However, alternative 1, would not provide the necessary
monitoring to verify the expected degradation of contaminants. The ARARs include federal and
state MCLs for drinking water. State guidance concentrations or federal action levels are used
for contaminants that do not have MCLs.

3. Long-Term Effectiveness and Permanence

The long-term effectiveness of all of the alternatives, except the no-action alternative, is
similar. All alternatives will eventually result in reduction of contaminant concentrations to
achieve cleanup levels. Alternatives 3,4 and 6 reduce the toxicity, mobility, and volume of
contaminants through treatment. Continued groundwater monitoring will provide the additional
data to refine the predictions of the time reguired for the selected alternative to achieve the
cleanup levels.
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4. Reduction of Toxicity, Mobility, or Volume

Alternatives 3 and 4 (and possibly 6) reduce the toxicity, mobility, and volume of contaminants
through treatment. Alternative 5, which involves a physical barrier, will reduce the mobility
of contaminants and also indirectly reduce the toxicity and volume. Alternatives 1 and 2 will
reduce the toxicity, mobility, and volume of contaminants by natural attenuation.

5. Short-Term Effectiveness

Those alternatives that require disruption of on-site soils (Alternatives 3, 4, 5, 7, and
possibly 6) pose a greater short-term risk to site workers and adjacent residents than the no
action and natural attenuation alternatives. The trench construction alternatives also pose a
greater risk to site workers due to the use of heavy equipment and high-pressure hydraulic
systems.

Alternatives 1, 2, and 6 may result in satisfaction of cleanup levels within 8- 10 years.
Alternatives 3, 4, 5, and 7 may result in satisfaction of cleanup levels for the organic
contaminants within 2 to 3 years at the north boundary and downgradient of the site. However,
it may still take 8-10 years for cleanup levels to be met at the Site.

6. Implementability

All alternatives ate technically implementable. Alternative No. 3-groundwater extraction,
treatment, and disposal-requires pilot testing and long-term operation and maintenance and is
therefore more difficult to implement. The Soil Saw, which may be used for Alternatives 4, 5,
and possibly 6, is an innovative technology, and is currently available only through Brown and
Root. However, conventional trenching technology can be used to implement these alternatives.

7. Cost

The net present value (NPV) cost estimates for the alternatives range from $92,200 for the no
action alternative, to $3,553,800 for groundwater recovery and treatment. The cost estimates
are approximate.
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TABIiE 8: COST COMPARISON OF CLEANUP ALTERNATIVES
Groundwater Alternative
Capital Costs
1 - No Action

2 - Natural Attenuation

3 - Pump and Treat

4 - Bioactive Filter Wall
$ 0

$ 10,000

$ 583,800

$ 1,053,100
5 - Hydrologic Flow Barrier $1,610,000

6 - Alternative 2 with $ 10,000
Alternative 4 as contingency*
$ 1,053,000
7 - Excavation of source
$ 1,035,000
Annual
Operation & (based
Present Maintenance
Worth) (O&M)

$ 6,000

$ 17,160

$ 193,200

$ 17,510

$ 17,610

$ 17,160

$ 17,200
Total Cost
$ 92,000

$247,700 and Monitoring

$3,553,800

$ 1,316,900

$1,873,800

$247,000

$ 1,316,900

$ 1,558,200 material
*Cost are shown here both without the contingency and with the contingency.
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8. Community Acceptance

Based on the responses received during the public comment period, the community accepts the
selected remedy.

9. 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 (RI) and Feasibility Study
(FS) process for the Chevron Chemical Company Site. In accordance with 40 CFR 300.430, FDEP, as
the support agency, has provided input during the RI/FS process. FDEP agrees with the
groundwater remedy, but does not agree with no further action for soil. FDEP is unwilling to
concur with the ROD because the State would prefer a risk level no greater than 1x10-6. The
potential risk associated with future residential exposure at the adjacent trailer park is 9.0 x
10-6. The potential risk associated with future commercial exposure at the Site 2.0 x 10-5.

9. 0 SEIiECTED REMEDY

Based upon consideration of the reguirements of CERCLA, the NCP, the detailed analysis of
alternatives and public and state comments, EPA has selected a remedy for groundwater at this
Site. At the conclusion of the remedy, the potential rise associated with exposure to
groundwater at the Site will be in the range 10-5 to 10-6. EPA considers these risks levels to
be protective of human health and the environment as they fall within EPA' risk range and are
based on an EPA approved site specific risk assessment. The total present worth cost of the
selected remedy, Alternative No. 6,is estimated at $247,000. The cost will increase to
approximately $1.3 million if the contingency plan is implemented.

EPA has determined that no further action is necessary for soil at the Site. The potential risk
associated with current or future commercial exposure at the Site is 2.0 x 10-5. The potential
risk associated with future residential exposure at the adjacent trailer park is 9.0 x 10-6.
EPA considers these risk levels to be protective of human health and the environment as they
fall within EPA' risk range and are based on an EPA approved site specific risk assessment.
However, on September 29, 1995, FDEP issued guidance suggesting soil cleanup goals which are
based on a risk level of 1 x 10-6. Attainment of the more stringent risk level may be necessary
to obtain FDEP's concurrence with deletion of this Site from the National Priorities List in the
future.

The remedy for groundwater is summarized in the following items:

1. Deed restrictions/notices or institutional controls to prohibit consumption of
contaminated groundwater until the cleanup standards have been met.

2. routine maintenance of the Site including fence maintenance, grass mowing, etc.

3. natural attenuation of contaminants in groundwater and guarterly groundwater
monitoring.

4. a contingency plan which includes the installation of a subsurface filter wall. Events
that would trigger the contingency are detailed below.
A. Deed Restrictions of Institutional Controls and Site Maintenance

Deed restrictions or institutional controls are intended to prohibit consumption of contaminated
-------
groundwater until the cleanup standards have been achieved.

Site maintenance includes those routine tasks such as fence maintenance, grass mowing, etc.
Site maintenance shall be conducted for up to 30 years or until cleanup levels are achieved,
whichever comes first.

B. Groundwater Remediation

B.I. The major components of groundwater remediation to be implemented include:

- Natural degradation and/or attenuation of groundwater contaminants

- Groundwater monitoring to document the expected reduction in contaminant concentrations
and to evaluate potential contaminant migration.

- A contingency plan which includes the installation of a subsurface filter wall. Other
measures such as limited air sparging, hydraulic gradient control, or source removal,
would be implemented as necessary. The contingency would be invoked if one of the
following conditions is met:

• contaminant concentrations do not decrease by 10-15% within one year.

• contaminant concentrations in subseguent years do not decrease as expected.

• organic contaminants are detected in monitoring well MW-11 or MW- 15.

The groundwater monitoring program will initially consist of guarterly monitoring during the
first year. The monitoring program will also include additional groundwater assessment. This
assessment will include installation of additional monitoring wells as necessary to further
define the extent of the groundwater contamination.

If, after one year, there is a 10 to 15% reduction in contaminant concentrations, then a new
model for natural attenuation will be developed based upon the available groundwater sampling
data. Future contaminant reduction by natural attenuation will be evaluated relative to the
predicted reductions of the new natural attenuation model.

If contaminant concentrations are not reduced by 10-15% within one year, then the surface filter
wall will be installed. Additional enhancements, such as limited air sparging, hydraulic
gradient control, or source removal will be implemented as necessary. The contingency may also
be reguired if future monitoring data does not continue to demonstrate contaminant reduction as
predicted by the attenuation model.

The degree of contaminant attenuation will be measured relative to the concentrations in
groundwater samples collected in April 1995. The initial one year sampling period will begin
with the first sampling event conducted subseguent to the April 1995 sampling event.

The focus of this groundwater remedy is upon the BETX compounds (benzene, ethylbenzene, and
xylene) and the pesticides. Therefore, it may not be necessary to analyze for total
naphthalenes and metals as freguently as the other contaminants. Total naphthalenes and arsenic
were detected below their associated above its cleanup level in one well, located off-site.
Lead was detected sporadically on site around the Site.

In addition, it is possible there may be other, off-site sources of some groundwater
contaminants. The groundwater sampling data should be reviewed for evidence of contaminant
-------
migration to the Site from off-site sources.

The groundwater monitoring will continue until groundwater cleanup standards have been achieved
for two consecutive monitoring periods. EPA, in consultation with FDEP, will conduct an annual
review the groundwater monitoring data to evaluate the effectiveness of this remedy. Others
actions may be implemented, if necessary.

C. Compliance Testing

Groundwater samples will be collected and analyzed for the parameters listed in the table below.
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TABIiE 9: COMPLIANCE MONITORING

GROUNDWATER

Benzene

Ethylbenzene

Xylenes

Total naphthalenes

4,4-DDD

a-BHC

1 Primary MCL
2 Secondary MCL
3 State target level
4 State Guidance Concentration
5 Federal action level
CLEANUP
STANDARD (ug/1)
1-1
30-2
20-2
100-3
0.4
0.05-4
CLEANUP CONTAMINANT

b-BHC
g- bhc
Chlordane
Arsenic
Chromium
Lead
STANDARD
(ug/1)
0.1-4
.2-1 (Lii
2-1
50-1
100-1
15-5
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10.0 STATUTORY DETERMINATIONS

EPA has determined that the selected remedy will satisfy statutory determinations of Section 121
of CERCLA. The remedy will be protective of human health and the environment, will comply with
ARARs, will be cost effective, and will use permanent solutions and alternative treatment
technologies to the maximum extent practicable.

10.1 Protection of Human Health and The Environment

This remedy is protective of human health and the environment due to several factors. First,
removal actions have reduced soil contaminants to levels that will not contribute to an
unacceptable risk given future commercial use of the Site or continued residential use of the
trailer park. Secondly, groundwater contaminants will naturally degrade and/or attenuate to
levels that comply with groundwater cleanup levels. Finally, there are no private wells located
in the area of groundwater contamination and State law restricts installation of new wells in
areas of known contamination.

10.2 Compliance with ARARs

Implementation of this remedy will comply with all federal and State ARARs and will not reguire
a waiver. This remedy will comply with the ARARs that are listed Table 10.
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TABIiE 10: ARARS

LOCATION SPECIFIC

Citation Location/Description

• Florida Administrative Code 62-524 and Florida Statute Areas of known contamination.
Regulatory clearance A 373.309 required to use potable water wells in area of known
contamination.

• Florida Administrative Code 62-736 Hazardous waste sites. Requires use of warninq siqns to
A Inform public of potentially harmful conditions at sites.

CHEMICAL-SPECIFIC AND ACTION-SPECIFIC

SAFE DRINKING WATER ACT-40 USC Section 300

40 CFR Part 141 - National Primary Drinkinq Water Establishes maximum contaminant levels
(MCLs) which are A Standards health-based standards for public water systems.

STATE ARARS

R & A FAC 62-550 State of Florida Primary Drinkinq Water Standards

TO BE CONSIDERED (TBC)

FAC 62-550 State of Florida Secondary Drinkinq Water Standards

FAC 62-770.730 State of Florida Petroleum Contamination Site Cleanup Criteria.

June 21, 1990 Memorandum from U.S. EPA Action level for lead in drinkinq water.
Established by U.S. EPA OERR/OWPE

1994 Florida Groundwater Guidance Concentrations State of Florida minimum
criteria that consider potential carcinoqenic of toxic effects for contaminants
in qroundwater

A= APPLICABLE REQUIREMENTS WHICH WERE PROMULGATED UNDER FEDERAL LAW TO SPECIFICALLY ADDRESS A
HAZARDOUS SUBSTANCE, POLLUTANT, CONTAMINANT, REMEDIAL ACTION LOCATION OR OTHER CIRCUMSTANCE AT
THE SITE.

R & A= RELEVANT AND APPROPRIATE REQUIREMENTS WHICH WHILE THEY ARE NOT "APPLICABLE" TO A
HAZARDOUS SUBSTANCE, POLLUTANT, CONTAMINANT, REMEDIAL ACTION, LOCATION OR OTHER CIRCUMSTANCE AT
THE SITE, ADDRESS PROBLEMS OR SITUATIONS SUFFICIENTLY SIMILAR TO THOSE ENCOUNTERED AT THE SITE
THAT THEIR USE IS WELL SUITED TO THE SITE.

1 = CHEMICAL-SPECIFIC REQUIREMENT 2 = ACTION-SPECIFIC REQUIREMENT
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10.3 Cost-Effectiveness

The selected remedy, Alternative 6, is a cost effective remedy. The selected remedy includes
natural attenuation and monitoring and a contingency remedy which includes a subsurface filter
wall. The total estimated present worth cost of this alternative is approximately $247,00 which
includes capital costs and annual operation and maintenance costs. The cost increase to
approximately $1.3 million if the contingency is implemented. EPA has determined that the cost
of implementing the remedy is proportionate to the overall effectiveness of the remedy and is a
reasonable value.

10.4 Use of Permanent Solutions and Treatment Technologies

The selected remedy uses permanent solutions and treatment technologies to the maximum extent
practicable. Natural attenuation is expected to permanently achieve the groundwater cleanup
standards within a reasonable timeframe of 8-10 years.

10.5 Preference for Treatment as a Principal Element

This remedy does not satisfy the statutory preference for treatment as a principal element.
However, the groundwater contaminants are expected to naturally degrade and/or attenuate within
8-10 years.

11.0 DOCUMENTATION OF SIGNIFICANT CHANGES

The remedy described in this Record of Decision is the preferred alternative described in the
Proposed Plan for this Sit. There have been no significant changes in the selected remedy.
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APPENDIX A: RESPONSIVENESS SUMMARY CHEVRON NPL SITE

1. One person was concerned that contaminants may have been carried by surface water drainage
along paths that have not been investigated. The drainage paths includes a portion of the
Armstrong Trailer Park plus an area that starts near the railroad track to the west of the
Chevron property.

RESPONSE: The transport of contaminants via surface water drainage from the Chevron property
across the Armstrong Trailer Park has been addressed. The Removal Action Report, dated July
1994, summarizes the soil sampling conducted across the trailer park and the subseguent soil
removal. Figure 1-2 shows the location of soil samples collected throughout the trailer park.
Figure 2-2 shows the extent of contaminated soil which reguired removal from the trailer park.

The sampling results indicate that the extent of contamination was well defined and that no
further soil removal is necessary in the trailer park.

Concerns about other drainage paths are addressed by various drainage studies conducted at the
Site. A surface and groundwater hydrology evaluation was prepared in March 1995 and is part of
the administrative record for this Site. The evaluation confirmed that surface water drainage
across the Site is predominantly to the northwest corner of the Site. An earlier drainage
evaluation was conducted at the Site during 1991. Surface elevations measured at various
locations across the Site indicate that the surface water would have drained to northwest corner
of the Site.

Some localized surface water may have drained along the railroad tracks located south and west
of the Site. This surface water drainage would have been limited to the immediate area around
the railroad tracks. The drainage is not likely to have included surface water from most of the
Site, as explained above.

2. One person asked if dust generated during the 1992 removal could have affected him at his
workplace across North Orange Blossom Trail.

RESPONSE: No. Air sampling was conducted during the removal and no excessive levels were
detected. The cleanup workers wore protective eguipment, including respirators, because they
were so close to the disturbed soil. In addition, the cleanup workers wear protective eguipment
because they are subject to freguent exposures from working at many different sites.

3. One person recommended alternative one, no further action. The person noted that if no one
is drinking the water and the contaminants are expected to degrade naturally, then the
government should not spend more money at the Site.

RESPONSE: It is correct that no one is drinking the groundwater and that the contaminants are
expected to degrade naturally. However, it is necessary to spend some money to collect
groundwater samples to confirm that degradation occurs as expected. The government will not pay
for the sampling. Chevron will conduct the sampling and will be supervised by EPA.

4. One person was concerned that no baseline was established to measure the reguired 10-15%
reduction during the first year. The person also guestioned what would happen if some
contaminants decline as reguired, but others do not decline.

RESPONSE: The first year of additional monitoring data will be compared to result for samples
collected during April 1995.

The focus of this groundwater remedy is upon benzene, ethylbenzene, xylene and the pesticides.
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These contaminants were the most frequently detected (and apparently mobile) contaminants in the
groundwater. Statistical analyses of all available groundwater data may be useful to evaluate
the degradation of contaminants.

5. FDEP stated that the potential risk levels associated with current or future use of the Site
exceed FDEP's target risk of 10-6.

RESPONSE: EPA is aware of FDEP's long standing preference for attaining risk no greater than
10-6 for carcinogens. However, at this Site, the risk assessment does not support further
action for soil to achieve a target risk remediation goals which attain risk between 10-4 to
10-6. Use of a risk range is a necessary process to account foot factors such as toxicological
uncertainty and/or confidence. FDEP's preference was also factored into the risk management
process prior to the determination that no further action was necessary for soil. The potential
risk associated with exposure to soil at the Site is already within EPA's risk range.
Therefore, no further action for soil is necessary.

6. One person stated that ethylbenzene and xylene have minimal co- solvency effects,
particularly at the current concentrations, and do not contribute to the migration of
pesticides in groundwater. Therefore, the issue of co-solvency is not relevant in the
decision to use the lower secondary groundwater standards for ethlbenzene and xylene as
cleanup standards.

RESPONSE: There is site specific evidence that suggests the synchronous movement of solvents
and pesticides in groundwater. The sampling data show that generally, the concentrations of Bhc
pesticides are elevated in the same wells where the organic solvents are elevated.

7. One person stated that the secondary groundwater standards for ethylbenzene and xylene are
based on odor. These standards are much lower than the primary groundwater standards which
are based on protection of human health. Therefore, if EPA intends to use odor based
standards, then it must establish background odor standards and adjust the cleanup standards
accordingly.

The person also stated that the cleanup standards for 4,4'-ODD. a-BHC, and b-BHC are state
guidance concentrations, not groundwater or drinking water standards. Therefore, these
standards are to be considered by EPA, but are not ARARs.

Finally, the person noted that language in Florida code 62-520.520 exempts a facility from
compliance with secondary standards. The exemption may be applied if the installation
discharged to groundwater prior to July 1982 and if the installation operated consistently
with regulations related to the discharge at the time of the operation.

RESPONSE: Secondary standards are based on aesthetic qualities relating to the public
acceptance of drinking water. In addition, the State of Florida encourages the use of secondary
standards to prevent the impairment of potential drinking water supplies.

The Florida secondary standard for odor from groundwater is 3, the odor threshold number. This
specific secondary standard for odor is not used as a basis to evaluate the groundwater
alternatives at this Site.

The cleanup standards for 4,4'-ODD, a-BHC, and b-BHC are defined as "To Be Considered" (TBC) in
Section 10 of this ROD. These standards are based on carcinogenic health based data. The
secondary standards for ethylbenzene and xylene are also defined as TBC. Guidelines defined as
TBC may be used in the remedy selection process.
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Finally, given the available data, it is apparent that the use of secondary groundwater
standards will not increase the timeframe required to achieve groundwater cleanup. The
timeframe for overall groundwater cleanup was estimated at 8-10 years due to the time necessary
to achieve compliance with the primary standard for benzene. EPA has recalculated selected
individual contaminant degradation rates using the secondary standards for ethylbenzene and
xylene and the state guidance concentrations for the BHC compounds. These standards were
coupled with the April 1995 groundwater contaminant concentrations in the biodegradation model.
The results indicate that the timeframes required to comply with these secondary standards
should still be less than the expected overall cleanup timeframe.

8. One person noted that metals detected in groundwater at the site are not site related. In
addition , there are off-site sources of metals that are not addressed, then the
concentrations found at the Site may not decline with time. Therefore, metals should not be
included as cleanup levels that must be met at the Site. In addition, upgradient, off-site
sources of petroleum should be addressed because they are impacting groundwater at the Site.

RESPONSE: There was a documented case of an acid spill in the vicinity of the western rinstat
pond. Soil from the affected area was excavated and disposed offsite. However, it is possible
that the low pH of the acid did temporarily increase the mobility of metals from soil to
groundwater. Therefore, it is possible that the presence of metals in groundwater is related to
site activities.

EPA agrees that the groundwater sampling data should be reviewed for indications of off-site
contamination migrating to the Site. Also, see the response to comment #8 below.

9. One person noted that the estimated costs for groundwater monitoring presented in the FS
were based on purgeable aromatic compounds and chlorinated pesticides only. The addition of
naphthalenes, arsenic, chromium, and lead will triple the testing costs for each sample,
thus impacting the cost effectiveness of the remedy.

RESPONSE: The monitoring costs in the FS considered a worst case scenario of sampling for
thirty years. A more realistic monitoring period is ten years, given that cleanup levels should
be achieved within that timeframe. Thus, the additional costs associated with analyzing several
additional contaminants will be more than offset by the expected shorter duration of sampling.

Nevertheless, the focus of this groundwater remedy is upon the BETX compounds (benzene,
ethylbenzene, and xylene) and the pesticides. Therefore, it may not be necessary to analyze for
total naphthalenes and metals as frequently as the other contaminants. Total naphthalenes and
arsenic were detected below their associated cleanup levels during the last sampling event.
Chromium was detected above its cleanup level in one well, located off-site. Lead was detected
sporadically on site and around the Site.
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