STATEMENT OF BASIS
for Groundwater
Chevron Cincinnati Facility
Hooven, Ohio
EPA ID No. OHD 004 254 132
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April 2006
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TABLE OF CONTENTS
TABLE OF CONTENTS
I. INTRODUCTION
II. PROPOSED REMEDY 2
III. FACILITY BACKGROUND 3
IV. SUMMARY OF CONTMAINTION RISKS 9
V. SUMMARY OF ALTERNATIVES 19
VI. EVALUATION OF ALTERNATIVES 14
VII. SCOPE OF PROPOSED REMEDY 16
VIII. PUBLIC PARTICIPATION 26
IX. INDEX OF ADMINISTRATIVE RECORD 28
FIGURES
APPENDIX 1 - REGION 5 FRAMEWORK FOR MONITORED NATURAL
ATTENUATION DECISIONS FOR GROUNDWATER
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Statement of Basis for Groundwater
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Statement of Basis for Groundwater
Chevron Cincinnati Facility
Hooven, Ohio
I. INTRODUCTION
This Statement of Basis (SB) explains the proposed remedy for contaminated groundwater at the
former Chevron Refinery Facility (Chevron facility) in Hooven, Ohio. This is the final proposed
remedy for the site under the current Administrative Order on Consent (AOC) from 1993. This
proposed remedy addresses groundwater contamination's impact on soil vapor, surface water,
river bank soil, and current and future groundwater use. In addition, the SB includes summaries
of corrective measure alternatives, pertaining to contaminated groundwater, prepared by Chevron
and evaluated by the United States Environmental Protection Agency (U.S. EPA). U.S. EPA will
select a final remedy for contaminated groundwater at the Chevron facility only after the public
comment period has ended and the information provided by the public has been reviewed and
public comments considered. This SB to address groundwater contamination is being issued
separately from the soils remedy to expedite implementation of the soils remedy. The Final
Decision for Sludges and Contaminated Soils was issued by U.S. EPA in January 2004. A
Performance Agreement to implement the Sludges and Contaminated Soils between U.S. EPA
and Chevron was signed in March 2004 and is currently being implemented by Chevron with
U.S. EPA oversight.
This SB is being issued by U.S. EPA as part of its public participation responsibilities under the
Resource Conservation and Recovery Act (RCRA). The document summarizes information that
can be found in greater detail in the final RCRA Facility Investigation (RFI), Corrective Measure
Study (CMS) for Groundwater, Conceptual Groundwater Remedy Report, and other pertinent
documents contained in the Administrative Record. U.S. EPA encourages the public to review
these documents in order to gain a more comprehensive understanding of the Chevron facility
and the RCRA activities that have been conducted.
U.S. EPA may modify the proposed remedy or select another remedy based on new information
or public comments. Therefore, the public is encouraged to review and comment on the SB. The
public is involved in the remedy selection process by reviewing the SB, submitting written
comments, and attending the public hearing scheduled for May 9, 2006, at the Whitewater Senior
Center and Township Hall, 6125 Dry Fork Road, Whitewater Township, Ohio. The meeting is
also an opportunity to hear a summary of the proposed groundwater remedy and to provide
verbal comment on the SB.
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II. PROPOSED REMEDY
U.S. EPA is proposing the following remedy to address groundwater contamination from
Chevron facility:
The Proposed Remedy will consist of the following remedial components:
Periodic source removal of Light Non-Aqueous Phase Liquids (LNAPL) from the
subsurface through a high grade pumping scheme;
Monitor containment of Light Non-Aqueous Phase Liquids (LNAPL) and
dissolved contaminant plume. Gradually shut down hydraulic control wells and
restore natural gradients;
Contingencies: if performance measures are not met, the pumps will be turned
back on, and other alternative technologies will be analyzed and chosen to
remediate the plume (for example SVE, IAS, SEAR);
Engineered controls to stabilize the bank of the Great Miami River at both the
Refinery and Gulf Park, and continued monitoring of the Great Miami River bank
for releases;
Monitored Natural Attenuation (MNA) of dissolved contaminant plume and
LNAPL plume with associated sampling and 5 year review of the progress of the
natural attenuation with the performance measure of complete aquifer restoration
to below Safe Drinking Water Act Maximum Contaminant Levels (MCLs) in 30
years;
Institutional controls to include prohibitions on potable groundwater use and
basement construction on the refinery site;
Point of compliance (POC) and other performance monitoring;
Continued source removal of volatile petroleum constituent from the LNAPL
smear zone beneath the town of Hooven through soil vapor extraction (SVE)
during periods of high grade pumping;
Continued monitoring of soil vapor wells in Hooven.
Financial Assurance for implementation of the remedy
A more detail discussion of the proposed remedy is in Section YE - Scope of Proposed Remedy.
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III. FACILITY BACKGROUND
The Chevron facility is located in Whitewater Township, Hamilton County, Ohio, just east of the
town of Hooven, and west of the Great Miami River. Land use surrounding the Chevron facility
is residential, commercial, and wooded to the west. The site occupies approximately 600 acres
bordered on the north, east, and south by the Great Miami River. Commercial retail property is
developed along State Route 128, southwest of the Chevron facility (Figure 1). The Chevron
facility also includes a Land Treatment Unit (or Landfarm) located on a ridge northwest of the
main portion of the refinery area. Two islands (Number 1 and Number 2) in the Great Miami
River are also considered part of the Chevron facility because underground pipelines pass
beneath the islands. The pipeline also runs below portions of Gulf Park (where contamination
has been detected), and leads to a former loading dock for Chevron's refinery products on the
Ohio River.
The manufacturing and refinery portion of the Chevron facility was operated from 1931 until
1986. Gulf Oil Corporation operated the facility from 1931 until 1985. Chevron acquired Gulf
Oil Corporation in 1985 and assumed operation until May 1986, when refinery operations were
terminated. The refinery produced gasoline, jet fuels, diesel, home-heating fuels, asphalt, and
sulfur. Refinery sludges and solids, many of which are classified as hazardous wastes, were also
generated during manufacturing operations. A majority of the refinery structures have been
demolished. The remaining facility structures include an office building, a security building, a
maintenance shed, and various structures associated with ongoing interim measures and
remediation activities.
On January 21, 1985, a hydrocarbon sheen was observed seeping into the Great Miami River
near the southern boundary of the Chevron facility. The seep indicated a hydrocarbon plume in
groundwater beneath the facility. Petroleum hydrocarbon recovery systems were installed by
Chevron, and a larger network of recovery and extraction wells have been installed and operated
since 1985. Currently, the Chevron facility pumps and treats four to five million gallons of
groundwater on a seasonal basis. Analysis of the hydrocarbon waste in groundwater indicated it
was primarily refined leaded gasoline and a smaller part diesel fuel.
Chevron has been pumping large amounts of groundwater for over 20 years, and has recovered
significant amounts of petroleum hydrocarbons. The term Light Non Aqueous Phase Liquid
(LNAPL) is used to describe the pure petroleum hydrocarbons in liquid form that are not
dissolved in water. At the facility, the LNAPL includes primarily refined gasoline and a lesser
amount of diesel fuel. The quantity that originally leaked form the facility is estimated to have
been 5 million gallons in total. About 2.5 million gallons were recovered within the first three
years after pumping was initiated, and about one million gallons were recovered over the next 18
years. The Chevron facility has recovered between 10,000 to 200,000 gallons of LNAPL per year
since 1988. Over the years, pumping and treating has gradually become less and less efficient in
recovering LNAPL. The amount of LNAPL that is still remaining underground today is adhering
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to the soil particles at a depth of 10 feet below ground surface (bgs) to approximately 30 feet bgs.
This is known as the smear zone.
On May 13, 1993, Chevron entered into an Administrative Order on Consent (Consent Order)
with U.S. EPA that required Chevron to conduct the necessary investigations (i.e., RFI) to fully
identify the nature and extent of contamination at the facility, to evaluate the long-term corrective
measures (i.e., CMS) necessary to protect human health and the environment, to conduct interim
measures which involved closure of many of the higher priority Solid Waste Management Units
(SWMUs) and Areas of Concerns (AOCs) at the facility, and to continue groundwater pump and
treat with recovery of petroleum hydrocarbons from the groundwater. Separate CMSs were
subsequently performed for soils and sludges and for groundwater, resulting in two reports
entitled Chevron Cincinnati Facility Soils and Sludges Corrective Measures Study (URS 2001 a)
and Chevron Cincinnati Facility Groundwater Corrective Measures Study (URS 200 Ib). A
remedy was proposed for the soils and sludges by U.S. EPA in a Statement of Basis for Sludges
and Contaminated Soils that was issued in June 2003. The final remedy for sludges and
contaminated soils was subsequently selected by U.S. EPA in January 2004. The remedy
selected for soils and sludges was excavation and removal with domestic off-site disposal. This
remedy was put into a Performance Agreement on March 4, 2004 between Chevron and U.S.
EPA and is currently being implemented by Chevron using the approved June 2004 Work Plan to
perform the soils cleanup. The remedy for groundwater contamination is now being proposed in
this SB.
Since completion of the RFI and CMS, there have been continued efforts to further define the
nature and extent of the LNAPL and dissolved plume. Additional investigations have been
conducted for this purpose. Chevron submitted a Conceptual Groundwater Remedy Report
(Chevron, 2003) to U.S. EPA that provided further analysis and optimization of the remedial
option recommended in the groundwater CMS. This document was reviewed extensively by
U.S. EPA, which resulted in several remaining questions on the groundwater remedy. These
remaining questions have been the main focus of several studies at the facility, beginning in late
2004 up to the present.
Most recently, there have been a series of long-term, high grade LNAPL recovery tests and a
shutdown test at the facility to assess the feasibility of the proposed corrective measures
contained in the groundwater CMS. The implementation of these tests was outlined in two work
plans submitted to U.S. EPA by Chevron: the Work Plan for Long-Term High-Grade LNAPL
Recovery Test, Additional Assessment Activities to Support Groundwater Remedy (Chevron
2005a), and the Work Plan for Extended Non-Pumping Aquifer Evaluation, Additional
Assessment Activities to Support Groundwater Remedy (Chevron 2005b). The goal of the long-
term high grade pumping test was to determine if LNAPL recovery, under concentrated pumping
during occasional periods of naturally occurring low water table (referred to as high grade
pumping), was a viable option for LNAPL removal. The long-term high grade LNAPL recovery
test was performed during the seasonal low groundwater table. The shutdown test was
performed to verify the effects of shutting down the production wells at the outer edges of the
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plume and to evaluate the stability of the plume under natural hydraulic gradients.
A. Site Hydrogeology
The Chevron facility lies in a glacial valley cut into Ordovician-age shale and partially filled with
glacial outwash gravel and fluvial deposits of the Great Miami River. The steep-walled valley is
approximately one-half mile wide and 100 feet deep. The bedrock shale is consolidated and has
a low hydraulic conductivity, but is locally fractured and jointed and interbedded with thin layers
of limestone. Overbank silt and sand deposits derived from floods of the Great Miami River
generally overlie coarser-grained sand and gravel derived from glacial outwash.
The hydrogeology of the Great Miami River buried valley aquifer is characterized by high
hydraulic conductivity, textural heterogeneity, and rapid water level changes driven by river
stage. Investigations at the site confirm that discontinuous surficial flood plain deposits and fill
cover most of the refinery site and are up to 15 feet thick. Below this are highly conductive
sands and gravels up to 100 feet thick, which form the productive part of the aquifer. High
transmissivity and significant textural heterogeneity characterize these aquifer materials. This
aquifer has been designated a sole-source aquifer by the U.S. EPA, and is the principal source of
drinking water for the area and commonly yields more than 1,000 gallons per minute.
Groundwater and the river are both controlled by the bedrock structure of the system.
Groundwater and the Great Miami River are in direct hydraulic communication, and groundwater
flows in the same direction as the river (i.e., south/southwest) in the site vicinity. The water table
is affected mainly by the river stage, which is typically high during the spring and declines over
the summer into the fall. However, the river stage can change abruptly in response to storms.
Groundwater flow is from north to south, generally parallel to the river when pumping is not
taking place. Groundwater velocities are typically in the range of two to four feet/day.
The depth to the water table beneath the former refinery portion of the facility ranges from
approximately 15 to 40 feet below ground surface (bgs). The elevation of the water table varies
seasonally, generally reaching its seasonally lowest elevation in autumn and its seasonally highest
elevation in spring. The aquifer beneath the facility has a maximum saturated thickness of
approximately 65 to 80 feet.
B. Groundwater Contamination
Both LNAPL and dissolved-phase contamination occur at the Chevron facility. The two types of
contamination are closely related, with LNAPL being the primary source of the dissolved-phase
groundwater contamination. Both the LNAPL and dissolved phase plumes have been
extensively studied.
While the refinery was in operation, refined petroleum products were released to the surface and
subsurface. The petroleum products moved downward through the soil, leaving residual
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hydrocarbons in the subsurface. Where enough product was released, a layer of petroleum
product or LNAPL accumulated in the water table zone. These petroleum products did not
readily migrate deeper into the aquifer because they tend to float on the water table. However, as
the product layer thickens, LNAPL also tends to spread laterally on the water table. Thus, as the
result of the releases at the facility, the LNAPL plume spread, ultimately resulting in an
approximately 250-acre footprint of LNAPL and dissolved-phase contamination on the
groundwater. The LNAPL plume covers much of the facility and has spread under the southern
portion of Hooven and into the commercial area to the southwest of the facility referred to as the
Southwest Quadrant.
As LNAPL accumulates, thicker layers of LNAPL form and depress the water table. This layer
of LNAPL at the water table tends to move up and down with the water table. As the water table
moves up and down, LNAPL is retained as residual LNAPL in subsurface materials by capillary
forces, creating a smear zone around the water table. Water table fluctuations over the years and
the history of LNAPL release and movement resulted in a relatively thick hydrocarbon smear
zone in the central areas of the plume, but there is only a thin smear zone in the lateral and distal
portions of the plume in areas along the Great Miami River and in areas such as Hooven and the
Southwest Quadrant. The LNAPL smear zone extends from a depth of 10 feet bgs to a
maximum depth of approximately 30 feet bgs in the central area of the plume.
Although estimates are available for the amount of LNAPL released, the time and amount of the
LNAPL releases on site are uncertain. The petroleum product releases that caused the LNAPL
plume may have occurred at any time during the facility's 55-year operational history (1931 -
1986). Although details of the releases are unknown, LNAPL chemistry data, product history,
and production runs suggest that much of the LNAPL was released in the 1950s and 1960s.
Sampling of the LNAPL plume indicates that the LNAPL is a mixture of approximately 80
percent leaded gasoline and 20 percent diesel fuel. The LNAPL can be divided into two types
based on physical properties: a low viscosity, low density LNAPL and a higher viscosity, higher
density LNAPL. The latter LNAPL type is limited to a small area in the eastern portion of the
site.
The dissolved groundwater contamination observed at the Chevron facility consists primarily of
constituents derived from the petroleum products released at the site, although some
contamination may have been derived from the sludges formerly disposed on site. These sludges
are now being removed as part of the contaminated soil and sludges remedy. The sludges are
wastes from the refinery process and generally contain metals, semi-volatile organic compounds
(SVOCs), and volatile organic compounds (VOCs). The dissolved petroleum constituents
observed on site include benzene, ethylbenzene, and naphthalene. Benzene is the most
widespread contaminant, with concentrations as high as 5,000 micrograms per liter (ug/1) in
groundwater beneath the facility. The Maximum Contaminant Level (MCL) for benzene under
the Safe Drinking Water Act is 5 micrograms per liter (ug/1). Groundwater monitoring indicates
that the distribution of dissolved benzene is primarily limited to the shallow portions of the
saturated zone of the aquifer, within and beneath the LNAPL smear zone. However, benzene is
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observed in deep groundwater in the vicinity of the groundwater production wells used to control
plume migration. In these areas, the pumping has increased vertical gradients, drawing some
dissolved-phase hydrocarbons deeper into the aquifer. Dissolved benzene generally is not
detected outside the area containing residual LNAPL because of the inward gradient maintained
by the groundwater production wells. The source of the dissolved benzene currently observed in
groundwater is primarily the LNAPL in the subsurface, which contains benzene and related
petroleum constituents. These constituents dissolve out of the LNAPL and into the groundwater
as it flows through the LNAPL smear zone.
C. Interim Remedial Measures
In early 1985, in a response to a LNAPL sheen emanating from the river bank adjacent to the
then Gulf Oil refinery, focused groundwater and initial LNAPL recovery was initiated by
Chevron to contain and recover the LNAPL, as well as the dissolved-phased plumes. This
extraction well system has expanded over the years at the site to include 16 high-volume
groundwater production wells. These wells are installed at various locations throughout the
property. The number of wells in use has varied depending on containment and LNAPL recovery
needs. These production wells have been operated to create an inward hydraulic gradient that
captures LNAPL and prevents further lateral expansion of the LNAPL plume. The inward
hydraulic gradient also inhibits the migration of dissolved hydrocarbons from the site.
Approximately 3.5 million gallons of LNAPL have been recovered to date. The exact amount of
hydrocarbon remaining in the aquifer is uncertain and difficult to determine. However, based on
the historical recovery curves, more than half of the hydrocarbon has already been removed.
Seventy-three percent of the cumulative LNAPL recovery occurred during the first three years of
pumping at just two to three recovery wells, with the remaining 27 percent coming in the last 17
years from these, and several additional wells.
The LNAPL recovery rate has diminished over time, indicating that the recoverable fraction
remaining is relatively small and that the inherent mobility of the LNAPL plume has been greatly
reduced. Recovery rates over the last few years are only a fraction of the initial recovery rates
and are strongly linked to seasonal low water tables or periodic drought conditions that expose
the lower portion of the smear zone. These conditions allow LNAPL to drain to recovery
locations under increased gradient created by pumping large volumes of groundwater. As a
result, in recent years LNAPL recovery operations have been carried out mainly during the fall
low water-table season. During these times, partially penetrating wells (partially penetrating into
the zone of LNAPL contamination) are brought on line; these wells create cones of groundwater
depression that capture floating LNAPL. In these cones of depression, LNAPL is recovered by
skimming it from recovery wells located within or adjacent to the production wells. The
recovered LNAPL is pumped through metered lines for storage in above-ground tanks prior to
off-site shipment.
At other times, the water levels raise enough to trap and immobilize most of the LNAPL in soil
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pores. The LNAPL becomes less mobile and the plume becomes more stable during these
periods. Regardless, the productions wells are pumped year round at sufficient rates to ensure
hydraulic containment of both the dissolved and LNAPL plumes. Typical high water table
groundwater pumping rates are approximately 2.5 million gallons per day (mgd), while low water
table groundwater pumping rates are up to 5 mgd. The effectiveness of the hydraulic containment
system to control hydraulic gradients is evaluated by gauging an extensive network of monitoring
wells (more than 115 wells) and two river measuring points six times per year for water level and
LNAPL thickness.
Natural processes within LNAPL plumes tend to limit their spread. These natural processes
include the retention of residual LNAPL in soils and the dissipation of the pressure within the
LNAPL plume as the plume thins due to spreading. If LNAPL releases are stopped, the spread of
the resulting LNAPL normally stabilizes over time. The recovery of LNAPL further enhances
the stabilization of LNAPL. Due to the large amounts of LNAPL that have already been
recovered to date, the LNAPL plume may be approaching stability under natural hydraulic
gradients. A Shutdown test conducted from November 2005 to February 2006 demonstrated
plume stability in that period of time, and no measurable expansion of the LNAPL or dissolved
plume occurred.
In addition to the groundwater extraction program designed to recover and contain LNAPL and
dissolved plumes, horizontal soil vapor extraction (HSVE) was implemented beneath the
community of Hooven in 1999 to ensure that unacceptable vapor exposure was not occurring.
The HSVE system also serves as an additional measure for petroleum hydrocarbon removal.
Like the LNAPL recovery program, the HSVE system has experienced strongly diminishing
returns as the available vapor has been removed. Currently, only seasonal vapor recovery is
possible when the water table is low and the smear zone beneath Hooven is exposed.
D. Land Use
A conceptual future land use plan for the former Chevron facility (Figure 2) has been developed
with input from citizens and through Chevron's Community Advisory Panel. Future land reuse
option for the site is a mixed use scenario that includes potential industrial/commercial, open
space, and recreational uses. Due to the fact that the facility is located in the Great Miami River
floodplain, residential and institutional reuses are not viable; however portions are being
considered for recreational development. The area being considered for industrial/commercial
reuse is located inside the 100-year flood protection berm.
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IV. SUMMARY OF CONTAMINATION RISKS
A. Risk Assessment History and Review
A conceptual land use plan was prepared to guide risk assessment, remediation, and potential
redevelopment of the facility. The current land use plan is a mixed-use scenario, including
potential industrial/commercial, open space, and recreational uses (Figure 2). Assessment of risk
at the site was addressed in the Chevron Cincinnati Facility Phase IIFacility-Wide Human
Health and Ecological Risk Assessment (E&E 2000a). Additional assessment of risk to human
health in the town of Hooven and in the Southwest Quadrant was addressed in the Human Health
Risk Assessment of Potential Exposure to Volatile Compounds, Hooven, Ohio, Revision 2 (E&E
2000b), Human Health Assessment for Potential Ojfsite Volatiles Exposure at the Southwest
Quadrant (E&E 2002), and most recently Subsurface Investigation and Field Activities Report
and Human Health Risk Assessment, Chevron Cincinnati Facility, Hooven , Ohio (Trihydro,
2005). The sample results from the RFI and off-site vapor investigations were used as input
parameters in the risk assessments. The results were screened using risk values that relate to the
proposed reuse of the area (i.e., industrial, recreational). The human health screening values used
were the U.S. EPA Region 9 Preliminary Remediation Goals (PRGs). The results relating to
ecological areas were screened using the U.S. EPA Region 5 Ecological Data Quality Levels
(EDQLs). Using these screening methods, contaminants of potential concern (COPCs) were
identified. These COPCs were used in the conceptual site model (CSM) that summarized the
relationship between the sources and the receptors.
Using the CSM, contaminated media were identified as surface soils, subsurface soils, sediment,
groundwater, and surface water. The pathways of exposure for human health are dermal (skin)
contact, inhalation of vapors, inhalation of soil particles, and ingestion. The receptors for human
health pathways are future industrial workers, future recreational users, construction workers,
remediation workers, and residents of Hooven. The ecological receptors are terrestrial, wetland,
and aquatic plants and animals.
The risks associated with the sources of contamination in surface soils, subsurface soils, and
sediment were addressed and summarized in the Statement of Basis for Sludges and
Contaminated Soils (U.S. EPA 2003); therefore, these risks are not addressed in this SB. On
March 4, 2004 U.S. EPA signed a remedy for the sludges and contaminated soils, and Chevron is
performing the cleanup of the selected soils remedy.
B. Contaminants of Potential Concern (COPCs)
1. Groundwater COPCs
a. Facility property: The COPCs for human health in groundwater from refinery
operations at the Chevron facility are benzene, ethylbenzene, 1,4-dichlorobenzene,
acetophenone, bis(2-ethylhexyl)phthalate, naphthalene, pyrene, dissolved lead, and
total arsenic.
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b. Hooven: The COPCs for human health in groundwater at Hooven are benzene,
ethylbenzene, naphthalene, 1,2,4 trimethyl benzene, 1,3,5 trimethyl benzene,n-propyl
benzene, isopropyl benzene, n-Hexane, acetone, toluene and xylene.
c. Southwest Quadrant: The COPCs for human health in groundwater in the
Southwest Quadrant are benzene, ethylbenzene, naphthalene, 1,2,4 trimethyl
benzene, 1,3,5 trimethyl benzene,n-propyl benzene, isopropyl benzene, n-Hexane,
acetone, toluene and xylene.
2. Vapor COPCs
a. Facility property: COPCs for human health in groundwater vapor at the Chevron
facility are acetone, benzene, chlorobenzene, 1,3-dichlorobenzene, 1,4-
dichlorobenzene, naphthalene, and trichloroethene.
b. Hooven: The COPCs for human health in groundwater at Hooven are benzene,
ethylbenzene, naphthalene, 1,2,4 trimethyl benzene, 1,3,5 trimethyl benzene,n-propyl
benzene, isopropyl benzene, n-Hexane, acetone, toluene and xylene.
c. Southwest Quadrant: COPCs for human health in the groundwater vapor in the town
of Hooven are acetone, benzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-
dichlorobenzene, 1,4-dichlorobenzene, 1,1-dichloroethylene, ethlybenzene, methylene
chloride, naphthalene, toluene, 1,1,2-trichloroethane, m- and p-xylene, and o-xylene.
C. Human Health Risk Characterization
The human health risk characterization makes a quantitative estimate of risks at the Chevron
facility. The characterization uses the COPCs, the CSM, an assessment of the toxicity, and an
assessment of the exposure to calculate the risks. Calculations for risk characterization used two
different methods, the reasonable maximum exposure (RME), and the central tendency (CT)
method.
The noncarcinogenic risk characterization looks at all noncarcinogenic COPCs and arrives at a
hazard index (HI) for these contaminants. U.S. EPA specifies that an HI equal to, or less than
one, is considered acceptable, and an HI greater than one indicates an unacceptable risk to human
health. The noncarcinogenic risk exceeded the HI of one for the commercial/industrial receptor
in basement indoor air. This risk is addressed in this proposed remedy with institutional controls
through prohibition of basement construction on the facility.
1. Noncarncinogenic Risks in Recreational Reuse Area
a. Future Adolescent Recreator Calculations indicate negligible noncarcinogenic
inhalation hazards for outdoor inhalation of vapors based upon the RME and CT
assumptions. The HI for RME (0.029) and CT (0.014) methods were well below one.
1,3-dichlorobenzene was the primary contributor to the hazard values.
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b. Future Construction/Remediation Worker Calculations indicate negligible
noncarcinogenic inhalation hazards for outdoor inhalation of vapors based upon the
RME assumption. The HI for the RME (0.032) method was well below one.
2. Noncarcinogenic Risks in Industrial Reuse Area
a. Future Industrial/Commercial Worker Calculations indicate negligible
noncarcinogenic inhalation hazards for inhalation of vapors in a basement based upon
the RME and CT assumptions. The HI for RME (0.035) and CT (0.19) methods were
well below one. 1,3-Dichlorobenzene was the primary contributor to the hazard
value.
i. Basement Scenario (Working in basements) Calculations indicate unacceptable
noncarcinogenic inhalation hazards for inhalation of indoor vapors based upon the
RME assumption. The HI for the RME (1.4) method was slightly above one.
Toluene and ethylbenzene were the primary contributors to the hazard values.
b. Future Construction.Remediation Worker Calculations indicate negligible
noncarcinogenic inhalation hazards for inhalation of outdoor vapors based upon the
RME assumption. The HI for the RME (0.32) method was well below one.
3. Noncarcinogenic Risks in the Southwest Quadrant
a. Commercial Worker
i. Basement Scenario Calculations indicate unacceptable or significant
noncarcinogenic inhalation hazards for indoor chemicals in a basement, based upon
the RME assumptions. The HI for basement vapor inhalation (2.0) exposure using
the RME methods was greater than one. Benzene was the primary contributor to the
hazard value.
The risk characterization then looks at all carcinogenic COPCs and arrives at an estimated
carcinogenic risk. USEPA's range of acceptable risk is 1 x 10"4 to 1 x 10"6. This risk is
equivalent to one additional person in 10,000 to one additional person in 1,000,000 contracting
cancer from a lifetime exposure to these contaminants.
4. Carcinogenic Risks in Recreational Reuse Area
a. Future Adolescent Recreator Calculations indicate negligible carcinogenic risk for a
future adolescent due to inhalation of outdoor vapors. The total carcinogenic risk for
the vapor inhalation exposure pathway was calculated to be 1.8 x 10"7 using the RME
method and 6.9 x 10"8 using the CT method. This risk falls below the U.S. EPA
acceptable risk range. A subgroup of SVOCs, the polynuclear aromatic hydrocarbons
(PAHs), was the major source of carcinogenic risk in the Recreational Reuse Area.
b. Future Construction/Remediation Worker Calculations indicate negligible
carcinogenic risk for a future construction/remediation worker due to inhalation of
outdoor vapors. The total carcinogenic risk for the vapor inhalation exposure
pathway was calculated to be 1.7 x 10"7 using the RME method. This risk falls below
the U.S. EPA acceptable risk range.
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Carcinogenic Risks in Industrial Reuse Area
a. Future Industrial/Commercial Worker Calculations indicate negligible carcinogenic
risk for a future industrial/commercial worker due to inhalation of outdoor vapors.
The total carcinogenic risk was calculated to be 1.5 x 10"5 using the RME method and
2.0 x 10 "6 using the CT method. The calculated risks fall within the U.S. EPA
acceptable risk range.
i. Basement Scenario Calculations indicate significant carcinogenic risk for a future
industrial/commercial worker due to inhalation of vapors in a basement. The total
carcinogenic risk was calculated to be 1.7 x 10"2 using the RME method. This
risk is greater than the U.S. EPA acceptable risk range. The only contributor to
this risk was benzene. This value was derived following the assumption that a
commercial/industrial worker inhales the vapor in the basement for 8 hours day, 5
days a week for 25 years.
b. Future Construction/Remediation Worker Calculations indicate negligible
carcinogenic risk for a inhalation of outdoor vapors. The total carcinogenic risk was
calculated to be 4.1 x 10"6 using the RME method. This risk is within the U.S. EPA
acceptable risk range.
6. Carcinogenic Risks for the Southwest Quadrant
a. Commercial Worker
i. Basement Scenario Calculations indicate negligible carcinogenic risk for
basement vapor inhalation exposures. The total carcinogenic risk across all
exposure pathways was calculated to be 5.1 x 10"5 for the RME method. This risk
is within the U.S. EPA acceptable risk range. Benzene is the only contributor to
this risk.
Risk to Subpopulations in Hooven
The assessment of risk to human health in May 2000, indicated a noncarcinogenic inhalation
hazard of 3.0 as well as a carcinogenic inhalation risk of 8.0 x 10"5 for indoor chemicals for the
basement scenario in the town of Hooven. These values were derived following the assumption
that a resident lives in the basement for 24 hours a day, 350 days a year for 30 years. A follow-
up study was completed in June 2005 to update the human health risk assessment and to
reevaluate the crack ratio assumptions used in the subsurface vapor intrusion model in the risk
assessment report with the revised toxicity data currently available for some of the COPCs under
study. The analytical data from the recent study on the vertically nested wells showed that
petroleum hydrocarbon COPCs detected in vapor samples immediately above the LNAPL and
dissolved plume attenuate within a short distance above the groundwater table. The attenuation is
attributed to active biodegradation confirmed through oxygen and carbon dioxide profiles in the
plume area. Further, the soil gas concentrations of constituents identified in the
LNAPL/dissolved plume are below the generic screening levels at depths shallower than 30 ft.
below ground surface in all the nested wells inside the plume. As a result of these observations
Chevron Cincinnati Facility 12
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and in accordance with U.S. EPA's Office of Solid Waste and Emergency Response (OSWER)
draft vapor intrusion guidance, the vapor migration pathway from LNAPL or dissolved plume to
indoor air in the residents of Hooven is considered incomplete. Thus under current conditions,
carcinogenic risk and/or non-carcinogenic hazard from groundwater contamination is assumed to
be insignificant to Hooven residents as well as the school children and faculty as a result of this
incomplete pathway.
D. Ecological Risks
The ecological risk characterization looks at receptors classified into terrestrial, wetlands, and
Great Miami River components. The ecological risk characterization associated with the
terrestrial and wetland receptors was addressed in the Statement of Basis for Sludges and
Contaminated Soils (U.S. EPA 2003).
1. Aquatic Life Risk Analysis
The Great Miami River, which is adjacent to the facility on the north, east, and south, was
investigated. Surface water samples were taken to determine whether petroleum
contamination has been released to the river. No site-related petroleum contamination
was detected in surface water. Riverbank soil samples were also collected to evaluate
potential ecological receptors of riverbank contamination. Residual PAH contamination
from a release of hydrocarbon seepage to the river that was discovered on January 21,
1985, affects a small area of the riverbank along the southern extent of the refinery
property. Riverbank and surface water samples indicate that the impacts of this
contamination on aquatic life are expected to be minimal.
On May 16, 2005, oil releases the size of quarters were noticed in the Great Miami River
near Monitoring Well 85 along the western shore. A boom was placed in the river in the
area of the release, and initial erosion control measures were put in place. Investigations
revealed the impacted soil along the bank was eroding into the river and releasing
petroleum hydrocarbons. A similar situation arose on July 13, 2005 in Gulf Park on the
eastern bank of the Great Miami River where localized small releases of hydrocarbons
were observed. Surface water, river sediment and groundwater were sampled near these
releases and initial results show no exceedances of Ohio EPA regulatory standards.
Anticipated shoreline erosion controls in areas along the Great Miami River are expected
to prevent contaminated soil from eroding into the river, these controls are detailed in the
Scope of the Proposed Remedy (Section VII).
Groundwater pumping has occurred since 1985 to prevent discharges to the river.
Currently, preliminary modeling regarding potential flow to the river under natural
gradients is being developed. Groundwater monitoring wells are being installed and
sampled adjacent to the river to further develop the preliminary models and determine the
extent of contamination and the surface water groundwater interaction near the Great
Miami River.
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V. SUMMARY OF ALTERNATIVES
The corrective measure alternatives analyzed to clean up contaminated groundwater at and from
the Chevron facility are presented below.
Alternative 1: No-Action
Alternative 2: High Grade Pumping, Containment of plume, MNA, Institutional
Controls, Stabilization of Riverbank, Hooven SVE, and Vapor Well Monitoring.
Alternative 3: Sitewide Soil Vapor Extraction (SVE), Containment of plume,
MNA, Institutional Controls, Stabilization of Riverbank, Hooven SVE, and Vapor
Well Monitoring.
Alternative 4: Sitewide SVE and In-Situ Air Sparging (IAS), Containment of
plume, MNA, Institutional Controls, Stabilization of Riverbank, Hooven SVE, and
Vapor Well Monitoring.
Alternative 5: Sitewide Surfactant Enhanced Aquifer Remediation (SEAR),
Containment of plume, MNA, Institutional Controls, Stabilization of Riverbank,
Hooven SVE, and Vapor Well Monitoring.
Alternative 1: No-Action
The no-action alternative provides a baseline for comparing the benefits and costs of other
alternatives. This alternative assumes that no additional actions will occur at the facility to
remediate groundwater beyond what has already been completed.
Alternative 2: High Grade Pumping, Containment, MNA, and Institutional Controls
This alternative includes source removal (recovery of LNAPL); containment of the dissolved
phase and LNAPL plumes to prevent further migration of contamination; and natural attenuation
of both LNAPL and dissolved contaminants to ultimately achieve concentration levels of
dissolved contaminants in the ground water at or below Federal drinking water standards (Safe
Drinking Water Act Maximum Contaminant Levels (MCLs) in 30 years. Alternative 2, as well
as Alternatives 3, 4 and 5 also require implementation of institutional (non-engineering) controls
(e.g., deed restrictions, equitable servitude) to restrict certain land and ground water uses on the
facility. These institutional controls will prevent exposure to the LNAPL and groundwater
plumes throughout the on-site and off-site areas. See the more detailed discussion of the land
and water uses to be restricted in Section VII: Scope of the Proposed RemedyAlternative 2.
Recovery of LNAPL will be achieved through a high grade pumping scheme in the area of high
concentration (Figure 3) designed to remove LNAPL during periods of low water table
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elevations. Containment will be achieved through LNAPL plume stabilization supplemented
with hydraulic control if necessary. MNA will reduce the concentrations of dissolved
contaminants in down gradient areas of the plume. In addition to controlling down gradient
dissolved contaminants, MNA will be relied on, in part, to further deplete benzene and other
petroleum constituents from the LNAPL. The Hooven Soil Vapor Extraction (HSVE) system
will continue to be used to control vapors volatilizing from the LNAPL and further deplete
volatile constituents in the LNAPL plume beneath the town of Hooven. In addition, sampling of
vapor monitoring wells will be conducted in Hooven. This alternative also includes stabilization
of the bank at the refinery and Gulf Park along the Great Miami River, where releases were
previously observed. The company would have to provide an assurance that adequate financial
resources are available for implementation of the remedy. Analyses of mass loss on specific
contaminants at the site conducted by Chevron suggest that MCLs can be reached within 30
years.
Alternative 2 serves as the basis for the remaining three alternatives. These additional
alternatives differ from the Alternative 2 only in the additional technologies employed to enhance
the removal of LNAPL.
Alternative 3: Sitewide SVE, Containment, MNA, and Institutional Controls
This alternative would feature a sitewide SVE system in addition to the corrective measures
described in Alternative 2. The SVE system would be implemented via a network of mostly
parallel, horizontal wells underlying the entire site. These wells would be drilled from existing
north-south site roads and would be spaced approximately 300 feet apart. The system would be
composed of approximately 17 horizontal wells on site and three or four additional wells off site,
south of Hooven. The SVE system would be used to remove volatile contaminants, including
benzene, from the unsaturated zone. The system should increase the natural depletion of volatile
constituents from the upper portions of the LNAPL smear zone and thus reduce the time to
achieve the cleanup of the entire plume to MCLs. The system would be operated as long as it
continued to be effective in removing volatile constituents in the subsurface, which is estimated
to be a period of five to ten years. This is not the overall time frame, i.e., the time estimated to
reach MCLs.
Alternative 4: Sitewide SVE & IAS, Containment, MNA, and Institutional Controls
This alternative would feature an IAS system in addition to the corrective measures described in
Alternative 3. The IAS system would involve the injection of air below the LNAPL smear zone
via a network of vertical wells laid out in an orthogonal grid. Like SVE, the IAS system would
strip volatile components from the subsurface and facilitate biodegradation through aeration of
the subsurface. The IAS wells would be installed on 50-foot centers which would result in
approximately 3,500 wells for the two-acre plume area. The SVE system would operate
concurrently with the IAS system and capture the volatile constituents stripped from the
subsurface by the IAS system. Like the SVE system, the IAS system would be operated as long
Chevron Cincinnati Facility 15
Statement of Basis for Groundwater
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as it continued to be effective in removing volatile constituents in the subsurface, which is
estimated to be a period of five to ten years. This is not the overall time frame, i.e., the time
estimated to reach MCLs.
Alternative 5: Sitewide SEAR & SVE, Containment, MNA and Institutional Controls
Alternative 5 would feature SEAR in addition to the corrective measures described in Alternative
3. This alternative differs from Alternative 4 only by replacing SEAR for IAS as a means for
removing LNAPL from beneath the water table. Under this alternative, SEAR would be used to
flush most of the LNAPL from the saturated zone and remove the free phase, while SVE would
attack the vadose zone. SEAR would be implemented during periods of low water table to take
advantage of the natural vertical drainage of LNAPL under such conditions. The implementation
of SEAR during periods of low water table elevation would help to minimize the volume of
aquifer to be treated, and thus, the volume and cost of surfactant to be used. SEAR is different
from the other technologies considered because it would be implemented in small blocks referred
to as panels. A panel would be treated in a few weeks, after which time the operation would
move to the next down gradient panel. This process would extend over several low water
seasons, progressing down gradient until the entire site is treated. The surfactant mix would be
injected through a row of injection wells spaced 10 to 15 feet apart and extracted through a
parallel row of wells 50 feet from the injection row. Under these assumptions, approximately
17,000 wells would be drilled.
VI. EVALUATION OF ALTERNATIVES
A. Evaluation Criteria
This section presents the process used to evaluate the five cleanup alternatives and the results of
the evaluation for contaminated groundwater. The evaluation criteria used are described in the
May 1, 1996, Advance Notice of Proposed Rulemaking (ANPR) for Corrective Action at
Hazardous Waste Management Facilities 61 Federal Register 19432. Although the rule was
never published as a final rule, it is used by U.S. EPA as guidance for selecting corrective
measures at RCRA corrective action facilities. The ANPR criteria are applied in a two-phased
evaluation: Proposed remedies are screened to see if they meet the four threshold criteria. The
remedies that meet the threshold criteria are then evaluated using five balancing criteria to
identify the remedy that provides the best relative combination of attributes.
The threshold criteria require that all remedies: (1) be protective of human health and the
environment; (2) attain media cleanup standards (concentration levels of hazardous constituents
identified by U.S. EPA as protective of human health and the environment); (3) control the
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source(s) of releases of hazardous waste (including hazardous constituents) that pose threats to
human health and the environment; and (4) comply with applicable standards for waste
management. The cleanup standards for the contaminated groundwater at the Facility are Safe
Drinking Water Act Maximum Contaminant Levels (MCLs). The balancing criteria are: (1)
long-term reliability and effectiveness; (2) reduction of toxicity, mobility, or volume of wastes;
(3) short-term effectiveness; (4) implementability; and (5) cost.
B. Selection of the Proposed Remedy
U.S. EPA conducted a review of the corrective measure alternative in Chevron's October 2001
groundwater CMS. The threshold criteria have been evaluated by U.S. EPA for all the proposed
remedies. Alternative 1, the no action alternative, does not meet all of the threshold criteria and
is not considered for evaluation by the balancing criteria. Alternative 1 does not protect human
health and the environment, control the source, attain any cleanup standards, or propose any
waste management. U.S. EPA determined alternatives 2, 3, 4, and 5 meet the threshold criteria
and are evaluated relative to the balancing criteria.
1. Long-Term Reliability
While the pumping and wastewater treatment systems involved in Alternative 2 will
require some maintenance, this alternative has been shown to be reliable in short term
tests and has been proven reliable in the long term. Alternatives 3 and 4 are not routinely
operated at the scale envisioned at the Chevron site and can be considered less reliable in
the long term than Alternative 2. Alternative 5 is developmental and has been conducted
at the bench scale (laboratory test) only and is considered the least reliable in the long
term of all the alternatives considered.
2. Reduction of Toxicity, Mobility or Volume of Wastes
All of the proposed alternatives would reduce the toxicity of the residual LNAPL by
depletion of benzene and related compounds or through direct removal of LNAPL from
the subsurface. Recent tests have shown the mobility of LNAPL is not significant at the
Chevron site, and appears to be stable. Consequently, none of the alternatives offers any
significant advantages relative to reductions in mobility. With their more aggressive
approach to removal of LNAPL from the subsurface, AlternativesS, 4 and 5 appear to
offer advantages, as compared with alternative 2, with regard to the reduction in the
volume of residual LNAPL and the time frame for achieving MCLs. Alternative 2,
relying in large part on natural degradation, would generate less waste than the other
alternatives. Alternative 5 with its SEAR technology would result in the greatest
reductions in residual LNAPL volumes although it may increase mobility in the process.
3. Short-Term Effectiveness
The high grade pumping scheme in Alternative 2 is only operational and effective during
extended periods of low rainfall when groundwater levels expose the smear zone.
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Consequently, the short-term effectiveness of this alternative is dependent on weather
patterns. Alternative 2 also relies heavily on the volatilization of benzene into soil vapor
and the dissolution of benzene into groundwater to deplete the benzene and related
contaminants contained within the LNAPL. This reliance on natural attenuation
mechanisms adversely impacts the short-term effectiveness of Alternative 2. Although
somewhat more effective than Alternative 2, the short-term effectiveness of Alternative 3
is limited by the fact that SVE only addresses the contaminants in the unsaturated zone
and does not address the large amounts of LNAPL held below the water table in the
LNAPL smear zone. While the effectiveness of SVE in Alternative 3 would be enhanced
during low water table conditions, this alternative would then be subject to the same
limitations imposed on the high grade pumping by weather conditions. The addition of
IAS to Alternative 4 would help to more rapidly address the LNAPL below the water
table and would likely improve the short-term effectiveness of the remedy. The SEAR
technology in Alternative 5 is most effective at low water tables which are present only at
certain times of the year. SEAR would overall remove the most LNAPL, and
consequently would likely provide the greatest short-term effectiveness.
4. Implementability
Alternative 2 is readily implementable. The equipment necessary to implement the high
grade pumping scheme in Alternative 2 is already largely in place and the treatment
system has been in operation at the site. Although high grade pumping would require low
water table conditions, such conditions may be sufficiently frequent so as not to adversely
impact the implementability and therefore effectiveness of Alternative 2. Alternatives 3
and 4 require the installation of large networks of SVE and IAS (Alternative 4) wells.
While these technologies have been used on a lesser scale at many other sites, the scale
that would be involved in implementing these technologies at the Chevron site is very
large and reliability of the performance is unclear. Thus, Alternative 3 and 4 may be
considered less implementable than Alternative 2. The added complexity of the IAS
system in Alternative 4 and the major drilling effort required makes Alternative 4 less
implementable than Alternative 3. The implementation of the SEAR technology on this
scale in Alternative 5 would be unprecedented and would have to be considered
developmental. The extensive injection and recovery well system required for the SEAR
technology combined with the complexities of this technology clearly make Alternative 5,
as described, the least implementable of all the alternatives. In addition, both the IAS and
SEAR technologies may increase dissolved concentrations of contaminants thereby
spreading the plumes in groundwater and require additional containment measures, also
making Alternatives 4 and 5 less implementable. The high grade pumping scheme in
Alternative 2 has the advantage of having significant reach in the subsurface including
beneath portions of Hooven. Alternative 2 is the most readily implementable remedy.
5. Costs
The estimated costs for each Alternative in 2006 dollars are presented in Table 1 below.
The total cost figures here differ from the cost figures in the 2000 Groundwater CMS
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because the 2000 cost estimate included the cost of continued site wide pumping through
the life of the remedy. The 2006 estimates presumes that the hydraulic control wells will
gradually be shut down within a few years after the remedy is implemented.
Table 1. Present Worth of All Costs Associated with Alternatives 2 through 5
Alternative
2
3
4
5
Initial Source
Removal
Technology
High Grade
Pumping
SVE
IAS + SVE
SEAR + SVE
Present Worth ($ millions)
Initial Source Removal
Capital
$11,292,499
$20,690,474
$27,359,122
$99,102,293
O&M
$14,514,433
$26,250,945
$35,417,392
$18,163,889
Duration
(years)
30
12
10
8
Total
$25,806,932
$46,941,419
$62,776,514
$117,266,181
C. Summary
Alternative 2 appears to be the most easily implemented and most reliable in the long tern of all
the remedial alternatives considered. Alternative 2 is not the most effective in the short term nor
in reducing mobility, toxicity or volume of wastes. While considered less implementable and
reliable, Alternative 3 provides only modest improvement in the remedial time frame over
Alternative 2. Alternative 4 and particularly Alternative 5 have shown the potential for
significant reduction of residual LNAPL and significant improvements in the timeframe of the
remedy. The advantages of short-term effectiveness and reduction in volume of LNAPL in
Alternatives 3, 4 and 5 are balanced with the disadvantages regarding their implementability and
long-term reliability. The last balancing criteria U.S. EPA has to consider is costs, Alternatives
3, 4, and 5 are progressively more costly than Alternative 2. When all the balancing criteria are
weighed against the four alternatives, Alternative 2 outweighs Alternative 3, 4 and 5.
Consequently, Alternative 2 (Advantage-implementable, long-term reliability, and
costs/Disadvantage-short-term effectiveness; reduction in mobility, toxicity or volume of wastes)
is recommended as the proposed groundwater remedy at the Chevron facility.
VII. SCOPE OF PROPOSED REMEDY - ALTERNATIVE 2
The proposed remedy, Alternative 2, has been designed to be protective of human health and the
environment. The details of this proposed remedy are laid out in this section. The long-term
corrective action objective is to restore groundwater to its maximum beneficial uses by achieving
drinking water MCLs throughout the area of contaminated groundwater. Based on mass loss
estimates for contaminants at the facility, U.S. EPA expects that MCLs will be achieved
throughout the plume within 30 years. Thus the proposed remedy includes the long-term
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Statement of Basis for Groundwater
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performance standard of restoring the ground water to MCLs by 2036. However, because
achieving this long-term objective will take many years, a series of interim corrective action
objectives have been developed for the Chevron groundwater plume. These interim objectives
have been designed to ensure that human health and the environment are protected until the long-
term corrective action objective is achieved.
As indicated in the Summary of Facility Risks (Section IV) the principal contaminant of concern
in groundwater is benzene, although benzene, toluene, ethylbenzene, and xylene (BTEX)
compounds are found in groundwater above MCLs. Benzene poses a risk to human health
through ingestion via drinking water and inhalation. The discharge of BTEX compounds and
other contaminants to the Great Miami River also pose potential risks to ecological receptors.
The following interim remedial objectives have been identified:
- Protect human health and the environment
- Monitor soil vapor concentrations and prevent unacceptable indoor air exposures
- Maintain plume control to prevent migration of either LNAPL or dissolved phase
constituents
- Remove recoverable LNAPL to the extent practicable
- Stabilize riverbank to prevent erosion
These interim remedial objectives are interrelated and are to be achieved through the various
components of the proposed remedy.
A key component of the proposed remedy is the containment and stabilization of the LNAPL and
dissolved contaminant plumes. The LNAPL and dissolved contaminant plumes are currently
contained by the ongoing interim measure consisting of the operation of a recovery well system
that hydraulically controls the plumes. However, studies have indicated that the LNAPL plume
may be stable under natural gradients. Consequently, operation of the site-wide recovery system
may not be necessary to contain the LNAPL plume. In addition, the benzene and related
petroleum compounds that emanate from the LNAPL source are generally biodegradable in
groundwater. On-site monitoring has suggested that natural attenuation stabilizes the dissolved
plume emanating from the LNAPL plume. Consequently, hydraulic control may not be
necessary to contain the dissolved plume.
During the early phases of the remedy, hydraulic control of the plume will be gradually eased and
the migration of the plumes monitored carefully to verify that the LNAPL and dissolved plumes
are stable under natural groundwater gradients. The remedy includes an extensive ongoing
program of monitoring both the LNAPL and dissolved plumes to verify that both plumes are
stable.
For the dissolved plume, a network of monitoring wells establishes a "Containment Point of
Compliance" ("POC"), beyond which the LNAPL plume or dissolved contaminants above MCLs
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Statement of Basis for Groundwater
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will not be allowed to migrate. These monitoring wells are located at the approximate down-
gradient boundary of the current plume, and additional wells may be added to completely
monitor the down-gradient boundary (Figure 4). Sampling of these wells will be conducted
semiannually for the first five years, annually for the next five years (staggered to account for
seasonality), biennially for the next ten years, and every five years thereafter. Should the
performance monitoring indicate that MCLs have been exceeded at or beyond the Containment
POC, operation of the extraction well system will be resumed. If necessary, Chevron will
analyze and implement additional remedial measures in order to ensure containment of the
dissolved plume. Alternatives evaluated and Chevron's recommended alternative will be
submitted to U.S. EPA for review. Whenever new wells are installed, Chevron will develop an
initial data set for the new wells by sampling quarterly for the first two years.
To ensure containment of the LNAPL plume, the ROST wells and groundwater monitoring wells
outside the smear zone will be tested for the appearance of LNAPLs (Figure 4 & 5). These
monitoring wells will be sampled semiannually for the first five years, annually for the next five
years (staggered to account for seasonality), biennially for the next ten years and every five years
thereafter. The contingency, if LNAPL is seen migrating, is to resume year round pumping. In
addition, Chevron will analyze alternate LNAPL recovery mechanisms (including focused
aggressive source removal technologies such as air sparging and solvent flushing (SEAR)) and
propose a recommended alternative for U.S. EPA review. Chevron shall implement additional
remedial measures to ensure containment of the LNAPL plume.
The ongoing performance monitoring program will include close monitoring of the LNAPL and
dissolved plumes along the Great Miami River to ensure that discharges to the river do not occur.
Should this monitoring indicate that the LNAPL plume is not stable in the area adjacent to the
river, special engineered barriers to LNAPL migration will be implemented along the river.
Residual (immobile) LNAPL has been observed along the river bank. This residual has been
observed to be released to the river during periods of high river flow due to bank scour and
sloughing of contaminated soils along the river bank at the refinery and in Gulf Park. To
eliminate such releases, the proposed remedy may require the installation of engineered
structures along contaminated portions of the bank to stabilize the bank and prevent sloughing of
contaminated soil into the Great Miami River.
Since the LNAPL plume, more specifically the benzene and related volatile compounds
contained in the LNAPL, are the source of contaminants in the dissolved plume, the proposed
remedy includes measures to remove as much LNAPL from the subsurface as is practical. The
LNAPL recovery operations conducted to date as an interim measure have demonstrated
diminishing returns. The remaining LNAPL is held in the LNAPL smear zone located above and
below the water table. Most of this LNAPL is contained below the normal water table elevation
and is only available for recovery during periods of low water table elevations, typically early fall
to mid-winter. The proposed remedy includes a scheme of pumping during periods of naturally
occurring low water table to further lower the water table in order to exploit this LNAPL
behavior. This scheme has been termed high grade pumping. High grade pumping involves
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concentrated pumping during periods of naturally occurring low water table elevation to further
lower the water table in a localized area and enhance the recovery of LNAPL in that area. High
grade pumping will be operated in areas where significant quantities of potentially recoverable
LNAPL are known to exist starting in the northwest corner of the facility near Hooven and the
Southwest Quadrant and progressing eventually to other areas more centrally located in the
facility. LNAPL recovery operations during periods of normal and high water table elevations
will be suspended since recovery of reasonable amounts of LNAPL is no longer possible during
these periods. At the time of the 5 year review, we will evaluate the high grade LNAPL recovery
systems' performance to make sure we have controlled the sources of releases so as to reduce or
eliminate, to the extent practicable, further releases of hazardous waste (including hazardous
constituents) that might pose threats to human health and the environment. The high grade
pumping program will continue to recover LNAPL from the subsurface until this approach is no
longer capable of efficiently recovering further LNAPL.
Depletion of benzene and related volatile compounds in the LNAPL is necessary to meet the
long-term corrective action goal of returning groundwater to its most beneficial use and meeting
MCLs. This depletion is expected to occur through a number of processes in addition to
biodegradation. Benzene is removed from the LNAPL by dissolving into groundwater passing
through the smear zone. Benzene also continues to volatilize from the shallow portion of the
smear zone into the air contained in the vadose zone overlying the water table. Operation of the
SVE system beneath Hooven during periods of high grade pumping is included in the remedy to
further accelerate volatilization during these periods. The recovery of LNAPL through the high
grade pumping program is also intended to directly remove source material. Modeling and other
analysis have resulted in predictions that these mechanisms should remove sufficient benzene
and related compounds from the LNAPL to achieve the long-term performance measure of
attaining MCLs in groundwater within 30 years. In order to verify that these predictions are
correct, the performance monitoring component of the remedy includes periodic investigation of
the LNAPL extent and composition, combined with appropriate analysis of these data, to confirm
the timely achievement of the long-term performance measure. MNA parameters should be
collected and analyzed on a 5 year interval to properly gauge progress of predicted attenuation of
the hydrocarbons in the subsurface, Appendix 1 contains the U.S. EPA Region 5 Framework for
Natural Attenuation Decisions for Groundwater which lays out a flowchart for decision making
and indicator parameters to test for in the field. Should this performance monitoring indicate
that MCLs will not be achieved in a timely manner, i.e., within thirty years, additional removal of
LNAPL must be implemented by Chevron. Chevron will evaluate alternatives and submit its
recommended alternative to U.S. EPA for its review.
The remedy includes a number of institutional and engineering controls to address any potential
exposures that may occur during the interim remedial period. The institutional controls shall be
established in a manner to be legally enforceable against existing and future property owners, and
shall include the following use restrictions:
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Statement of Basis for Groundwater
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1) Land use restrictions on the facility property which are consistent with the soil
cleanup standards and anticipated future land uses;
2) Prohibitions on construction of basements or other sub-grade areas for human
occupancy on the facility;
3) Prohibitions on potable use of ground water on the facility; and
4) Notice to existing and future owners of off-site properties situated above the plume
emanating from the Chevron facility of prohibitions on well installation contained in
Ohio Revised Code Sections 3745-09-04.
The restrictions in 1) through 3) above will be in the form of restrictive covenants that run
with the land in conformance with the Ohio Universal Environmental Covenants Act,
Ohio Revised Code Section 5301.80 to 5301.92.
The remedial activities described in this section, including the land use controls, are designed to
allow for redevelopment of the refinery property during site remediation before final remedial
goals have been met.
The company will have to provide an assurance that adequate financial resources are available
for implementation of the remedy. The performance measures of the proposed remedy can be
viewed in terms of the receptors potentially impacted by the LNAPL and groundwater plumes.
These receptors can be grouped into the following categories based on location: 1) human
receptors in Hooven, 2) human receptors in the Southwest Quadrant, 3) the Great Miami River,
4) groundwater at and beyond the POC, and 5) on-site receptors. The strategy of the proposed
remedy for protecting each of these potential receptor groups is discussed below.
Human Receptors in Hooven: The LNAPL and dissolved groundwater plumes lie beneath a
portion of Hooven. The principal potential exposure pathway to human receptors in Hooven is
inhalation of constituents volatilized from the LNAPL and migrating through soil vapor to the
surface. The performance measures for Hooven are (1) to ensure that no constituents from the
Chevron plume exceed risk based residential standards in soil vapor at the ground surface (these
standards are identified in U.S. EPA Office of Solid Waste and Emergency Response (OSWER)
Draft Vapor Intrusion (VI) Guidance, 2002); (2) to remove as much LNAPL and associated
volatile constituents from the LNAPL plume beneath Hooven, as is practical; and (3) to stabilize
the LNAPL plume beneath Hooven under natural gradient conditions.
Recent investigations have demonstrated that the vapor inhalation pathway is incomplete.
Investigation of contaminant concentrations in subsurface vapor have demonstrated that benzene
quickly attenuates through biodegradation. To ensure that this pathway does not pose any
unexpected risks in the future, the proposed remedy includes ongoing soil vapor monitoring
beneath Hooven. The vapor monitoring wells that will be tested are nested vapor wells 93, 96,
99 and 129. These wells will be sampled at 5, and 10 feet below ground surface and at 10 foot
intervals to the groundwater table. These nested vapor wells will be tested once per year for the
first five years, then every three years thereafter. If conditions permit, the samples will be
Chevron Cincinnati Facility 23
Statement of Basis for Groundwater
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collected when the water table altitude is at or below 463.5 ft-elevation for one week or longer,
and before the HSVE system is operated. In addition, the SVE system installed beneath Hooven
will continue to operate during periods of low water table when the high grade pumping is
performed. The operation of the SVE system at this time will serve both to capture any volatile
constituents vaporizing from the smear zone and to further deplete these constituents from the
upper portion of the LNAPL smear zone beneath Hooven, thus reducing the future source of
benzene vapor beneath Hooven. If vapor samples show that there is a complete pathway from
groundwater to the surface in concentrations exceeding the risk-based levels, Chevron shall
implement measures to prevent the vapors from intruding into homes in Hooven. Such measures
may include year-round groundwater pumping, operation of SVE, and/or other engineered
control(s), and installing vapor vents or other engineered controls in foundations.
The high grade pumping program during periods of low water table will similarly remove
LNAPL from beneath Hooven, further reducing the source of benzene and stabilizing the LNAPL
plume beneath Hooven. The monitoring wells outside the smear zone will be tested to insure no
new LNAPL appearance. The monitoring wells to insure LNAPL stability will be sampled
semiannually for the first five years, annually for the next five years, staggered (to account for
seasonality) biennially for the next ten years, and every five years thereafter. The contingency, if
LNAPL is seen migrating, is to resume year-round pumping and re-evaluate alternate NAPL
recovery techniques, which may include focused aggressive source removal (e.g. air sparging,
solvent flushing etc.).
Human Receptors in the Southwest Quadrant: The LNAPL and dissolved groundwater plumes
also lie beneath the western portion of the Southwest Quadrant. The principal potential exposure
pathways to the human receptors in the Southwest Quadrant include the extraction and use of
contaminated groundwater and inhalation of benzene through vapor migration of benzene to the
ground surface. The performance standards in the southwest quadrant are to protect human
receptors from exposure to contaminants in groundwater and to stabilize the LNAPL and
groundwater plumes in this area. The proposed remedy includes engineering and land use
controls addressing the potential human exposures in the Southwest Quadrant. These controls
include the installation of vapor barriers in buildings in these areas, and a statutory prohibition on
groundwater use on the installation of wells where known contaminants will be conducted to a
well. The high grade pumping scheme is designed to remove LNAPL from beneath the
Southwest Quadrant and further stabilize the LNAPL plume in this area. Monitoring of the
LNAPL in the Southwest Quadrant will be accomplished using Rapid Optical Scanning
Technology (ROST) wells in three or four transects. These will be located outside the smear zone
and monitored semiannually for first five years, annually for next five years, staggered (to
account for seasonality) biennially for next ten years, every five years thereafter. If LNAPL is
detected at these ROST wells then Chevron must resume year-round pumping until compliance is
restored, and re-evaluate alternate LNAPL recovery techniques. The contingencies could include
focused aggressive source removal (e.g. air sparging, solvent flushing etc.)
Chevron Cincinnati Facility 24
Statement of Basis for Groundwater
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Great Miami River: The performance standards for the Great Miami River are to (1) prevent any
NAPL migration to the river and (2) to prevent the development of a NAPL sheen in the river.
The performance standards for the Great Miami River also include (3) the prevention of any
discharge of dissolved constituents to the river above appropriate Ohio EPA surface water
standards. While preliminary studies appear to indicate that the LNAPL plume will be stable
under natural gradients in the vicinity of the river, the proposed remedy requires engineered or
hydraulic barriers to contain the LNAPL plume should performance monitoring fail to
demonstrate that the LNAPL plume is stable in the area near the river. The monitoring program
includes surface and groundwater monitor locations along the Great Miami River, with "early"
warning components and monitoring locations at the river bank/smear zone interface.
Monitoring includes piezometers and monitoring wells near the river and wells to sample pore
space in river sediment. The frequency and locations of sampling are to be determined
depending on river study findings. Locations known today where sampling and stabilization are
needed are at the refinery and Gulf Park. If OEPA surface water standards are exceeded or
sheens appear on the Great Miami River, then the contingency is to resume year-round
groundwater pumping until compliance with the standard is restored. In addition, Chevron will
evaluate contingency alternatives, including perimeter treatment system (e.g. sparge curtain,
funnel/gate etc.), aggressive source removal (e.g. air sparging, SVE, solvent flushing (SEAR)
etc.), and implement additional corrective measures if necessary to meet the performance
standard of allowing no migration of LNAPL or dissolved constituents into the river above
OEPA surface water standards. Chevron shall analyze alternatives and submit its recommended
alternative to U.S. EPA for its review.
Groundwater at and Beyond the Point of Compliance (POC): The performance standard for the
proposed remedy in the downgradient area of the plume is to prevent the migration of LNAPL or
dissolved constituents above appropriate regulatory levels (i.e., MCLs) beyond the POC. This
POC will be established at the approximate boundaries of the current plume. Thus, the proposed
remedy is designed to prevent any further expansion of either the LNAPL or dissolved phase
plumes. It is expected that expansion of the LNAPL plume will be prevented by the natural
stabilization of the plume. The benzene and related petroleum compounds that emanate from the
LNAPL source are generally biodegradable in groundwater. On-site monitoring has confirmed
that natural attenuation stabilizes the dissolved plume emanating from the LNAPL plume.
Consequently, it is expected that the migration of the dissolved plume will be controlled by
MNA. Monitoring of the plume is key; therefore sampling will be conducted semiannually for
the first five years, annually for the next five years, (staggered to account for seasonality)
biennially for the next ten years, and every five years thereafter. This performance monitoring
will confirm if MCLs for groundwater will be exceeded at six monitoring wells near the POC
and no LNAPL detections in the three or four transects of ROST wells mentioned above.
However, should either plume prove not to be stable, Chevron will resume year-round pumping
until compliance is restored. In addition, Chevron will evaluate contingency alternatives,
including perimeter treatment system (e.g. sparge curtain, funnel/gate etc.), aggressive source
removal (e.g. air sparging, SVE, solvent flushing etc.), and implement additional corrective
measures if necessary to meet the performance standards of allowing no migration of LNAPL or
Chevron Cincinnati Facility 25
Statement of Basis for Groundwater
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dissolved constituents above MCLs beyond the POC. Chevron will evaluate alternatives and
submit its recommended alternative to U.S. EPA for its review.
On-Site Receptors: The performance standards for protecting people who will be working on-
site in the future are (1) to prevent exposures to vapor constituents, (2) prevent exposure to soil
containing residual contamination, and to (3) prevent groundwater use. These standards are to be
met, in part, by implementing engineering controls (e.g., vapor barriers) in buildings during the
redevelopment of the property. In addition, institutional controls that prevent exposure to
groundwater and residual contamination in soils will be implemented in an expeditious fashion.
See the discussion of appropriate land and groundwater use restrictions to be implemented in
Section VII. Scope of Proposed Remedy - Alternative 2.
VIII. PUBLIC PARTICIPATION
U.S. EPA solicits input from the community on the corrective measures proposed for clean up of
contaminated groundwater. The public is also invited to provide comment on corrective measure
alternatives not addressed in this SB. U.S. EPA has set a public comment period from April 12,
2006 through May 30, 2006, to encourage public participation in the selection process. The
comment period will include a public hearing where U.S. EPA will present the investigation
results and the proposed remedy, answer pertinent questions, and accept oral and written
comments. In addition, written comments will be accepted by U.S. EPA up to the close of the
comment period.
The public hearing is scheduled for May 9th, 2006, at the Whitewater Senior Center and
Township Hall, 6125 Dry Fork Road, Whitewater Township, Ohio.
The Administrative Record for the Chevron Facility is available at the following locations:
Public Library of Cincinnati
Miami Township Branch
8 N. Miami Rd.
Cleves, OH 45002
U.S. EPA, Region 5
Waste, Pesticides and Toxics Division Records Center
77 West Jackson Boulevard, 7th Floor
Chicago, Illinois 60604-3590
(312)886-0902
Hours: Mon-Fri, 8:00 a.m. - 4:00 p.m.
Chevron Cincinnati Facility 26
Statement of Basis for Groundwater
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General information about the site is available on U.S. EPA's Web page:
epa.gov/region5/sites/chevron
After consideration of the comments received, U.S. EPA will select the remedy and document
the selection in the Final Decision and Response to Comments. In addition, public comments
will be summarized and U.S. EPA's response provided. The Final Decision and Response to
Comments will be drafted at the conclusion of the public comment period and incorporated into
the Administrative Record.
To send written comments or request technical information on the Chevron facility, please
contact:
Mr. Christopher Black
EPA Project Coordinator
U.S. EPA, Region 5
77 West Jackson Boulevard
Corrective Action Section, DE-9J
Chicago, Illinois 60604-3590
(312)886-1451
E-mail: black.christopher@epa.gov
To request information on the public comment period process, please contact:
Ms. Briana Bill
Community Involvement Coordinator
U.S. EPA, Region 5
77 West Jackson Boulevard
Public Affairs, P-19J
Chicago, Illinois 60604-3590
(312)353-6646
E-mail: bill.briana@epa.gov
Chevron Cincinnati Facility 27
Statement of Basis for Groundwater
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IX. Index of the Administrative Record for the
Statement of Basis for the Chevron Cincinnati Facility Groundwater Remedy
Chevron Environmental Management Company. 2006. Plug and Abandonment Notification,
Groundwater Production Wells PROD 8, PROD 9, PROD 16, PROD 17, and
PROD 18. January 25, 2006.
USEP A. 2005. Comments Regarding Subsurface Investigation Field Activities Report and
Human Health Risk Assessment. October 21, 2005.
Aqui-Ver, Inc. 2005. PowerPoint Presented at September 14, 2005 Technical Meeting.
Chevron Cincinnati Facility, Remedy Performance Measures, (from CMS/Remedy Report
Update), Conceptual Thoughts. September 14, 2005.
Chevron Environmental Management Company. 2005. Work Plan for Extended Non-Pumping
Aquifer Evaluation, Additional Assessment Activities to Support Groundwater Remedy.
September 1, 2005.
Chevron Environmental Management Company. 2005. Work Plan for Long-Term High-Grade
LNAPL Recovery Test, Additional Assessment Activities to Support Groundwater
Remedy. August 23, 2005.
Chevron Environmental Management Company. 2005. Work Plan for Additional Assessment
Activities Along the East Bank of the Great Miami River. August 10, 2005.
Chevron Environmental Management Company. 2005. Second Progress Update, Additional
Assessment Activities to Support Groundwater Remedy. July 29, 2005.
Chevron Environmental Management Company. 2005. Subsurface Investigation Field Activities
and the Human Health Risk Assessment. June 30, 2005. (NEED HARD COPY)
Chevron Cincinnati Groundwater Task Force. 2005. Update to Site Conceptual Model and
Summary of Remedial Decision Basis Chevron Cincinnati Facility. June 30, 2005.
Chevron Environmental Management Company. 2005. Third Letter Workplan for Additional
Assessment Activities to Support the Groundwater Remedy. June 15, 2005.
Chevron Environmental Management Company. 2005. Response to USEP A Comments
Regarding the March 15, 2005 Letter Workplan for Additional Assessment Activities to
Support the Groundwater Remedy. April 19, 2005.
USEP A. 2005. Comments Regarding the March 15, 2005 Letter Workplan for Additional
Assessment Activities to Support the Groundwater Remedy. April 1, 2005.
Chevron Cincinnati Facility 28
Statement of Basis for Groundwater
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Chevron Environmental Management Company. 2005. Response to USEPA Comments dated
March 18, 2005, Hooven Vapor Investigation Sampling and Analysis Workplan. March
31,2005.
Chevron Environmental Management Company. 2005. Revisions to the Conceptual Framework
for a Groundwater Remedy Performance Based Order. March 25, 2005.
USEPA. 2005. Comments Regarding the Hooven Vapor Investigation Sampling and Analysis
Workplan. March 18, 2005.
Chevron Environmental Management Company. 2005. Second Letter Workplan for Additional
Assessment Activities to Support the Groundwater Remedy. March 15, 2005.
Aqui-Ver, Inc. 2005. PowerPoint Presented at the March 5, 2005 Technical Meeting.
Groundwater Conceptual Model Updates. March 1, 2005.
Try-Hydro Corporation and GeoSyntec Consultants. 2005. Hooven Vapor Investigation
Sampling and Analysis Workplan. March 3, 2005.
Chevron Environmental Management Company. 2005. Progress Update, Additional
Assessment Activities to Support Groundwater Remedy. February 18, 2005.
Chevron Environmental Management Company. 2005. Conceptual Framework for
Groundwater Remedy Performance Based Order. February 10, 2005.
Environmental Resources Management. 2005. Cincinnati Facility Deer Ingestion Pathway:
Risk Analysis. January 10, 2005.
Chevron Environmental Management Company. 2005. December 14, 2004 Meeting Summary
Regarding the Groundwater Remedy for the Chevron Cincinnati Facility. January 5,
2005.
Chevron Environmental Management Company. 2004. Response to USEPA Comment dated
July 13, 2004, Conceptual Groundwater Remedy Report Draft Version 0. December 9,
2004.
Chevron Environmental Management Company. 2004. First Workplan for Additional
Assessment to Support Groundwater Remedy Report. December 8, 2004.
Aqui-Ver, Inc. 2004. PowerPoint Presented at the November 18, 2004 Technical Meeting.
Cincinnati Groundwater Remedy Field Investigation Workplan (Data Gap Workscope).
November 23, 2004.
Chevron Cincinnati Facility 29
Statement of Basis for Groundwater
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Chevron Environmental Management Company. 2004. Summary and Follow-up from October
19, 2004 Meeting Regarding the Groundwater Remedy. October 25, 2004.
Aqui-Ver, Inc. 2004. PowerPoint Presented at the October 19, 2004 Technical Meeting. The
Conceptual Final Remedy. October 19, 2004.
Aqui-Ver, Inc. 2004. PowerPoint Presented at the October 19, 2004 Technical Meeting.
Groundwater Conceptual Remedy Discussion, Cincinnati EPA Meeting. October 19,
2004. (Two Sets)
Chevron Environmental Management Company. 2004. Letter Transmitting GAC
Influent/Effluent Data. August 17, 2004.
USEPA. 2004. Comments on the "Chevron Cincinnati Facility Conceptual Groundwater
Remedy Report Draft - Revision 0. " July 13, 2004.
USEPA. 2004. Comments Regarding the Risk Assessment on Hooven and Southwest Quadrant.
January 7, 2004.
Chevron Cincinnati Groundwater Task Force. 2003. Conceptual Groundwater Remedy Report
for the Chevron Cincinnati Facility. July 2003.
USEPA. 2003. Statement of Basis for Sludges and Contaminated Soils for Chevron/Texaco
Cincinnati Facility. June 2003.
Ecology & Environment, Inc. (E&E). 2002. Chevron Cincinnati Facility, Human Health Risk
Assessment for Potential Of/site Volatiles Exposure at the Southwest Quadrant. Revision
1. May 2002.
URS. 2001. Chevron Cincinnati Facility Groundwater Corrective Measures Study. October
2001.
URS. 2001. Chevron Cincinnati Facility Soils and Sludges Corrective Measures Study.
September 2001.
Environmental Science & Engineering, Inc. 2000. RCRA Facility Investigation Report for the
Chevron Cincinnati Facility. Revision 2. December 2000.
E&E. 2000. Chevron Cincinnati Facility, Phase II Facility-Wide Human Health and Ecological
Risk Assessment. Revision 2. November 2000.
E&E. 2000. Human Health Risk Assessment of Potential Exposure to Volatile Compounds
Hooven, Ohio. Revision 2. May 2000.
Chevron Cincinnati Facility 30
Statement of Basis for Groundwater
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Civil & Environmental Consultants, Inc. 1999. Hooven Water Use Survey: Report of Findings.
Octobers, 1999.
Chevron Cincinnati Groundwater Task Force. 2003. Conceptual Groundwater Remedy Report
for the Chevron Cincinnati Facility. July 2003.
Chevron Cincinnati Groundwater Task Force. 2005. Update to Site Conceptual Model and
Summary of Remedial Decision Basis Chevron Cincinnati Facility. June 2005.
Ecology & Environment, Inc. (E&E). 2000a. Chevron Cincinnati Facility, Phase IIFacility-
Wide Human Health and Ecological Risk Assessment. Revision 2. November 2000.
E&E. 2000b. Human Health Risk Assessment of Potential Exposure to Volatile Compounds
Hooven, Ohio. Revision 2. May 2000b.
E&E. 2002. Chevron Cincinnati Facility, Human Health Risk Assessment for Potential Ojfsite
Volatiles Exposure at the Southwest Quadrant. Revision 1. May 2002.
Environmental Science & Engineering, Inc. 2000. RCRA Faciltiy Investigation Report for the
Chevron Cincinnati Facility. Revision 2. December 2000.
Chevron Environmental Management Company. 2005a. Work Plan for Long-Term High-Grade
LNAPL Recovery Test, Additional Assessment Activities to Support Groundwater
Remedy. August 2005.
Chevron Environmental Management Company. 2005b. Work Plan for Extended Non-Pumping
Aquifer Evaluation, Additional Assessment Activities to Support Groundwater Remedy.
September 2005b.
Trihydro, 2005. Subsurface Investigation and Field Activities Report and Human Health Risk
Assessment, Chevron Cincinnati Facility, Hooven, Ohio. October, 18, 2005.
URS. 2001 a. Chevron Cincinnati Facility Soils and Sludges Corrective Measures Study.
September 2001.
URS. 2001b. Chevron Cincinnati Facility Groundwater Corrective Measures Study. October
2001.
USEP A. 2003. Statement of Basis for Sludges and Contaminated Soils for Chevron/Texaco
Cincinnati Facility. June 2003.
Chevron Cincinnati Facility 31
Statement of Basis for Groundwater
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Email Reference List for the
Statement of Basis for the Chevron Cincinnati Facility Groundwater Remedy
April 4, 2006
Keith, Kittle. Tri-Hydro. 2006. RE: Chevron GWMtg. Date. Emailed to Chris Black, USEPA.
March 16, 2006. (With Attachments-no hard copy) (Email submitting cost estimates of
the alternative remedies.)
Michalski, Paul. Tri-Hydro. 2006. Progress Update, Extended Non-Pumping Aquifer
Evaluation. Emailed to Chris Black, USEPA. February 16, 2006. (With Attachments)
Michalski, Paul. Tri-Hydro. 2006. Review of Preliminary Non-Pumping Aquifer Evaluation
Results. Emailed to Chris Black, USEPA. January 25, 2006. (With Attachments)
Kittle, Keith. Tri-Hydro. 2006. Shut-Down Test Data. Emailed to Chris Black, USEPA.
January 20, 2006. (With Attachments - NEED HARD COPY)
Rittle, Keith. Tri-Hydro. 2006. Extended Non-Pumping Aquifer Evaluation. Emailed to Chris
Black, USEPA. January 16, 2006. (With Attachments)
Michalski, Paul. Tri-Hydro. 2005. Progress Update, Extended Non-Pumping Aquifer
Evaluation. Emailed to Chris Black, USEPA. December 9, 2005. (With Attachments)*
Rittle, Keith. Tri-Hydro. 2005. Cincinnati High-Grade Pump-Test Status. Emailed to Chris
Black, USEPA. November 17, 2005.
Rittle, Keith. Tri-Hydro. 2005. Hooven Chromatograms Analysis. Emailed to Chris Black and
Bhooma Sundar, USEPA. September 19, 2005.
Michalski, Paul. Tri-Hydro. 2005. High Grade Pump Test/48-Hour Shut Down Event Wrap Up.
Emailed to Chris Black, USEPA. June 3, 2005. (With Attachments)*
Michalski, Paul. Tri-Hydro. 2005. 5/31/05 High Grade Pump Test/48-Hour Shut Down Event.
Emailed to Chris Black, USEPA. May 31, 2005. (With Attachments)*
Michalski, Paul. Tri-Hydro. 2005. 5/26/05 High Grade Pump Test Update. Emailed to Chris
Black, USEPA. May 26, 2005. (With Attachments)*
Black, Chris. USEPA. 2005. RE: Cincinnati Pump Test Update. Emailed to Paul Michalski,
Tri-Hydro and Gary Beckett, Aqui-Ver, Inc. May 26, 2005.*
Chevron Cincinnati Facility 32
Statement of Basis for Groundwater
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Beckett, Gary. Aqui-Ver, Inc. 2005. RE: Cincinnati Pump Test Update. Emailed to Paul
Michalski, Tri-Hydro and Chris Black, USEPA. May 26, 2005.*
Michalski, Paul. Tri-Hydro. 2005. RE: Cincinnati Pump Test Update. Emailed to Chris Black.
May 24, 2005. (With Attachments)*
Rittle, Keith. Tri- Hydro. 2005. Cincinnati Groundwater Update. Emailed to Chris Black.
May 20, 2005. (With Attachments)*
Rittle, Keith. Tri-Hydro. 2005. Update Regarding Great Miami River Observations. Emailed
to Chris Black, USEPA. May 18, 2005. (With Attachments)*
Rittle, Keith. Tri-Hydro. 2005. Chevron Cincinnati Facility Status Report. Emailed to Chris
Black, USEPA. May 16, 2005.*
Michalski, Paul. Tri-Hydro. 2005. Non-Pumping Aquifer Evaluation Update, Chevron
Cincinnati Facility. Emailed to Chris Black, USEPA. May 13, 2005. (With
Attachments)*
Michalski, Paul. Tri-Hydro. 2005. 5/11 Cincinnati Groundwater Remedy Meeting. Emailed to
Chris Black, USEPA. May 11, 2005.*
Chevron Cincinnati Facility 33
Statement of Basis for Groundwater
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FIGURES
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Figinel, Sit*Lsection aiicl
Put inn F*u ilily L H> u ti I JLi|«
<.'liyi ion i'."iii'.iiui -Hi F:n.itilx 'MI f.
HUVVHI, Ohio
-------
I . I.
LJ
Cmciitttati
Facility Site.
-!i .
-------
Figure 3. High Grade
Pumping Area (Red)
-------
aw
IMC
u MB)
Figure 4. Dissolved Phase Plume
and Smear Zone Extent in
Southwest Quadrant
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Estimated Extent of
LNAFL Smear Zone
1 POST Location
in Smear Zoic
2 ROST Locations
outside Smear Zone
LEGEIJ3
DTINT
,-c»«t
Figure 5. ROST Well locations to
monitor the edge of the Smear Zone
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APPENDIX 1
Region 5 Framework for Monitored Natural Attenuation Decisions for Groundwater
September, 2000
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