United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R06-92/074
September 1992
PB93-964209
v°/EPA Superfund
Record of Decision:
Prewitt Abandoned Refinery,
NM
V
K
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NOTICE
The appendices listed in the index that are not found in this document nave been removed at the request of
the issuing agency. They contain material which supplement, but adds no further applicable information to
the content of the document Att supplemental material is, however, contained in the administrative record
for this site.
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50272-101
I REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R06-92/074
2.
I 4. Title and Subtitle
L SUPERFUND RECORD OF DECISION
• Prewitt Abandoned Refinery, NM
| First Remedial Action - Final
7. Author(«)
8. Performing Organization Name and Addreas
12. Sponaoring Organization Name and Addreaa
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
3. Recipient'* Accession No.
5. Report Date
09/30/92
6.
S. Performing Organization Rept No.
10. Project/Taskwork Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
13. Type of Report & Period Covered
800/000
14.
15. Supplementary Note*
PB93-964209
16. Abstract (UmH: 200 words)
The 70-acre Prewitt Abandoned Refinery site is an abandoned crude oil refinery near
the City of Prewitt in McKinley County, New Mexico. Land use in the area is
predominantly rural. Some of the estimated 75 people who reside within 1 mile of the
site use the Sonsela Sandstone Bed Aquifer as their drinking water supply source.
From 1938 to 1957, various companies, including the Atlantic Richfield Company (ARCO)
and El Paso Natural Gas (EPNG) Company, used the site for basic refining operations.
The main onsite processing units included a distillation plant, thermal cracker, and
reformer. Crude oil in storage tanks was separated into different fractions via a
distillation tower. Separated fractions were stored in tanks throughout the facility.
Because of a lack of waste management units, wastes were disposed of onsite near the
point of generation. Wastewaters and accidental spills were usually released in
unlined earthen ditches throughout the refinery area. These ditches led to a concrete
tank, which was used as an oil/water separator. Oil portions recovered from the
separator were returned to the refinery process, whereas water and heavier materials
were released to a nearby arroyo (gully). In the early operation of the plant, the
(See Attached Page)
NM
17. Document Analysis a. Descriptor*
Record of Decision - Prewitt Abandoned Refinery,
First Remedial Action - Final
Contaminated Media: soil, sludge, gw
Key Contaminants: VOCs (benzene, TCE, toluene, xylenes), other organics (PAHs),
metals (lead), inorganics (asbestos)
b. Identifiers/Open-Ended Terms
c. COSAT1 Field/Group
kl8. Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
129
22. Price
(See ANSI-Z39.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly N71S-35)
Department of Commerce
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EPA/ROD/R06-92/074
Prewitt Abandoned Refinery, MM
First Remedial Action - Final
^Abstract (Continued)
emergency release system consisted of releasing partially processed oil products to
bermed containment areas on the western edge of the facility. After the refinery closed
in 1957, the accompanying structures were dismantled, but the site still contains
processing remnants, including piping, pits, an oil/water separator, and other waste and
structural material. As a result of a citizen's complaint in 1980, PRPs conducted a
remedial investigation under EPA oversight that revealed metals, PAHs, and asbestos
contamination in soils; separator wastes; and Non-Aqueous Phase Liquids (NAPLs) in
addition to lead, 1,2 dichloroethane, benzene, toluene, ethylbenzene, and xylene in
ground water located beneath the site. In 1989, EPA directed the PRPs to fence the site
and install activated carbon filtration units on five affected residential wells. In
1991, PRPs removed approximately 800 cubic yards of asbestos-containing material offsite.
This ROD addresses remediation of all contaminated media at the site as a final action.
The primary contaminants of concern affecting the soil, sludge, and ground water are
VOCs, including benzene, TCE, toluene, and xylenes; other organics, including PAHs;
metals, including lead; and inorganics, including asbestos.
The selected remedial action for this site includes extracting contaminated ground water
and using an oil and water separator to remove NAPLs; treating approximately
43,000 gallons of extracted NAPLs onsite using soil vapor extraction to remove VOCs from
soil, along with a thermal catalytic oxidizer to destroy VOC vapor emissions; excavating,
consolidating, and onsite landfarming of approximately 1,175 cubic yards of waste from
the West Pits area and approximately 1,500 cubic yards of soil contaminated with high
levels of hydrocarbons, and placing a vegetative cover over the area after completion of
ktreatment; excavating, containerizing, and removing offsite 15 cubic yards of asbestos
contaminated material and soil; excavating and treating as necessary, 1,900 cubic yards
of lead-contaminated surface soil with levels in excess of 500 mg/kg or subsurface soil
with lead levels greater than 1,000 mg/kg, followed by offsite disposal; excavating any
sludge retrieved from the oil/water separator, with offsite pretreatment and/or disposal;
treating any contaminated soil identified beneath the separator onsite by landfarming or
offsite by incineration, pending testing results, and backfilling the separator area;
pumping and onsite treatment of the contaminated ground water using air sparging to
remove organics, and reinjecting the treated water onsite; installing and maintaining
activated carbon treatment units at domestic wells that exceed MCLs; monitoring soil,
ground water, private wells, and air; and implementing institutional controls, including
deed, land, and ground water use restrictions, and site access restrictions. The
estimated present worth cost for this remedial action is $16,301,576, which includes a
total O&M cost of $1,097,844 for 30 years.
PERFORMANCE STANDARDS OR GOALS:
Clean-up standards for soil and waste are based on health-based levels and EPA policy and
provide for the complete removal of asbestos, and the cleanup of lead to 500 mg/kg within
the top 2 feet of soil and 1,000 mg/kg of lead for soil depths greater than 2 feet.
Chemical-specific ground water clean-up goals are based on state standards and SDWA MCLs
and include benzene 5 ug/1; toluene 750 ug/1; xylenes 620 ug/1; and lead 15 ug/1.
Chemical-specific goals for soil and sludge include benzo(a)pyrene 0.9 mg/kg;
benzo(a)anthracene 9 mg/kg; and lead.
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RECORD OF DECISION
PREWITT ABANDONED REFINERY SITE
PREWITT, NEW MEXICO
SEPTEMBER 30, 1992
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PREWITT ABANDONED REFINERY
RECORD OF DECISION
STATUTORY PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT IS MET
AND FIVE - YEAR REVIEW IS REQUIRED
SITE NAME AND LOCATION
Prewitt Abandoned Refinery Site
Prewitt, New Mexico
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for the Prewitt Abandoned Refinery Site (hereinafter the
Site), in Prewitt, New Mexico developed in accordance with the
Comprehensive Environmental Response, Compensation, and
Liability Act, as amended by the Superfund Amendments and
Reauthorization Act (SARA), ("CERCLA"), 42 U.S.C. §9601 et
sea.. and to the extent practicable, the National Contingency
Plan 40, CFR Part 300. This decision is based on the
Administrative Record for this Site.
The State of New Mexico concurs on the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from
this Site, if not addressed by implementing the response
action selected in this Record of Decision ("ROD"), may
present an imminent and substantial endangerment to public
health, welfare, or the environment.
DESCRIPTION OF THE REMEDY
The Site is being handled as one operable unit, in which both
the surficial contamination (the waste pits, separator and its
contents, lead and asbestos contaminated soils, and the tarry
areas throughout) and the contaminated ground water are being
addressed.
The major components of the selected remedy include:
Institutional Controls: land use restrictions, access
restrictions, posting of signs, fencing, and restrictions
on the extraction and use of ground water from Site water
wells;
- Restoration of ground water as a potential source of
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drinking water through the process of extracting the Non-
Aqueous Phase Liquids and extracting, treating, and
reinjecting the ground water;
Continued ground water monitoring to determine whether
over time, conditions improve, remain constant, or
worsen;
- Extraction of the Non-Aqueous Phase Liquids using the
soil vapor extraction method;
Excavation and landfarming of West Pits contents and
Hydrocarbon contaminated soils;
- Excavation and off-site disposal of' lead and asbestos
contaminated soils and materials;
- Excavation and off-site disposal of Separator contents.
STATUTORY DETERMINATION "' ;
The selected remedy is protective of human health and the
environment, complies with Federal and state requirements that
are legally applicable or relevant and appropriate to the
remedial action, and is cost-effective. Non-Aqueous Phase
Liquids (NAPLs) in the ground water beneath the Site, sludges
in an oil-water separator, waste pit contents and "hot spots"
of heavily contaminated soils are considered to be principal
threats at the Site. This remedy does satisfy the statutory
preference for treatment that reduces toxicity, mobility or
volume as a principal element of the remedy. The selected
remedy utilizes permanent solutions and alternative treatment
technologies to the maximum extent practicable for this Site.
Since the ground water and Non-Aqueous Phase Liquids portions
of the remedy may result in hazardous substances remaining on
site above health-based levels, a review will be conducted
for these portions within five years after commencement of the
remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment.
It is anticipated that the selected remedy for to the surface
contamination will not result in hazardous substances
remaining on-site above health based levels. However, due to
some uncertainty that landfarming will achieve contaminant
concentrations below levels allowing for unrestricted
residential access, in the immediate landfarm area, a review
will be conducted for the surface remediation within five
years of commencement of the remedial action to ensure that
the remedy continues to provide adequate protection of human
health and the environment.
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lh
In that the selected remedy for the ground water and Non-
Aqueous phase Liquids portions of the remedy may result in
hazardous substances remaining on-site, above acceptable
health-based concentration levels, a review of the portions
will be conducted within five years of commencement of the
remedial action, to ensure that the remedy continues to
provide adequate protection of human health and the
environment.
B. J. Wynne
Regional Administrator
Date
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DECISION SUMMARY FOR THE
PREWITT ABANDONED REFINERY SITE
PREWITT, NEW MEXICO
I. SITE NAME AND LOCATION 1
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES 1
III. HIGHLIGHTS OF COMMUNITY PARTICIPATION 3
IV. SCOPE AND ROLE OF RESPONSE ACTION 4
V. SITE CHARACTERISTICS 5
Regional Geology ' 5
Regional Hydrogeology 6
Historic Site Operations and Potential Sources of
Contamination 6
Extent of Contamination 8
Ground water 8
NAPL 9
West Pits Area 10
Soil and Sediments 10
Separator 11
Exposure Routes 11
Surface Water and Sediment 12
Surface Soil 12
Ambient Air 12
Ground Water 12
VI. SUMMARY OF SITE RISKS 12
Contaminants of Concern 14
Toxicity Assessment 17
21
RISK CHARACTERIZATION FOR HUMAN HEALTH 21
Current Use Scenario 22
Future Use Scenario ..... 22
RISK CHARACTERIZATION OF THE ENVIRONMENT 25
Uncertainties Associated with the Human Health Risk
Calculations 26
Remediation Goals 28
VII. DESCRIPTION OF ALTERNATIVES 30
Common Elements 34
GROUND WATER ALTERNATIVES 34
NAPL ALTERNATIVES 39
WEST PITS ALTERNATIVES 41
SURFACE SOIL ALTERNATIVES 45
SEPARATOR ALTERNATIVES 50
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52
IX. SELECTED REMEDY 77
Ground Water Remediation Program 79
NAPL Soil Vapor Extraction 80
West Pits and Hydrocarbon Contaminated Soils 80
Lead Contaminated Soils 81
Asbestos Contaminated Substances 82
Separator 82
X. STATUTORY DETERMINATIONS 84
Protection of Human Health and the Environment 85
Compliance with Applicable or Relevant and Appropriate
Requirements 86
Cost-Effectiveness 86
Utilization of Permanent Solutions and Alternative
Treatment Technologies (or Resource Recovery
Technologies) to the Maximum Extent Practical ... 87
Preference for Tre? ~snt as a Principal Element .... 87
XI. DOCUMENTATION OF SIGNIFICANT CHANGES 87
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LIST OF FIGURES
FIGURE 1 SITE LOCATION MAP
FIGURE 2 SITE DIVISIONS FOR REMEDIAL INVESTIGATION
FIGURE 3 AREAS CONTAINING NON-AQUEOUS PHASE LIQUIDS
FIGURE 4 LEAD CONTAMINATED SOIL LOCATIONS
IX
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TABLE 1
TABLE 2
TABLE 3
TABLE 4
TABLE 5
TABLE 6
TABLE 7
LIST OF TABLES
CURRENT USE PATHWAYS
FUTURE USE PATHWAYS
MEDIA SPECIFIC CONTAMINANTS OF CONCERN, MAXIMUM
CONCENTRATIONS, AND REMEDIATION GOALS
EXPOSURE POINT CONCENTRATIONS USED IN RISK
CALCULATIONS FOR THE PREWITT ABANDONED REFINERY
UPTAKE RATES
ORAL DOSE/RESPONSE DATA FOR NONCARCINOGENS
ORAL DOSE/RESPONSE DATA FOR CARCINOGENS
TABLE 8
RANKING OF REMEDIAL ALTERNATIVES
TABLE 9
TABLE 10
APPLICABLE, RELEVANT OR APPROPRIATE REQUIREMENTS
RISK POSED BY CONTAMINATED SOILS: FUTURE
RESIDENTIAL SCENARIO
111
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ATTACHMENT 1
ATTACHMENT 2
ATTACHMENT 3
LIST OF ATTACHMENTS
PREWITT ABANDONED REFINERY RECORD OF DECISION
RESPONSIVENESS SUMMARY
PREWITT ABANDONED REFINERY ADMINISTRATIVE
RECORD INDEX
IV
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DECISION SUMMARY FOR THE
PREWITT ABANDONED REFINERY SITE
PREWITT, NEW MEXICO
I. SITE NAME AND LOCATION
The Prewitt Abandoned Refinery ("Site") is an abandoned crude oil
refinery on approximately 70 acres located near the town of Prewitt
in McKinley County, New Mexico. (Figure 1) The Site is located
approximately 20 miles northwest of Grants, New Mexico. The Site is
bounded on the south by Interstate Highway 40, and with the
exception of the North Pit area, on the north by the Atcheson,
Topeka and Santa Fe Railroad. Old U.S. Highway 66 divides the Site
into two tracts. The North Pit area is located in the northern
tract of the Site, north of the railroad track. This area received
waste during the operation of the refinery. Virtually all of the
Site is owned by the Navajo Nation. Currently the property remains
an abandoned refinery. The area in which the Site is located is
rural, with a cluster o?"^ix homes about one thousand feet east of
the Site. Approximately 75 people live within a 1 mile radius of
the Site.
A recent socioeconomic study included in the comments to the
Propose Plan indicates a strong loyalty to the area, and the
possibility that the area may continue to attract people seeking a
rural lifestyle. Recent census data for the area indicates a
slight growth in population.
The Site is located near the southwest edge of the Rio San Jose
Basin. The topography of the area at the Site is typified by a
linear valley floor to the north and rocky uplands to the south.
There are three major stratigraphic units at the site. These are
in ascending order, the San Andres/Glorieta Formations, the Lower
Chinle member, and the Sonsela Sandstone Bed.
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
The refinery was operated by various companies from 1938 to 1957.
In July 1957, the refinery was shut down. The main processing units
at the refinery were a distillation plant, a thermal cracker, and
a reformer. The auxiliary facilities included crude storage tanks,
intermediate storage tanks, final product storage tanks, product
caustic washing facilities, boilers, power generation station,
heaters, cooling towers, receiving and loadout facilities; lead
additive stations; maintenance facilities, laboratory facilities,
and an office.
Over an indefinite period since the refinery shut down, the
refinery and accompanying structures were dismantled. Remnants
include piping, pits, a separator, other waste and structural
material, including foundations. The site is covered with
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scattered demolished structures and foundations and sparse desert
vegetation and exposed fill.
The Site was called to the U.S. Environmental Protection Agency's
("EPA") attention by a citizen's complaint in 1980. The Site was
scored by the EPA on April 16, 1984, using the Hazard Ranking
System ("HRS") MITRE model. In June 1989, EPA issued an
Administrative Order to both El Paso Natural Gas Co. ("EPNG") and
Atlantic Richfield Company ("ARCO"). The order required EPNG and
ARCO to fence the Site, and to install and maintain an activated
carbon filtration treatment system on five residential wells
adjacent to the site. These treatment systems are currently
maintained by EPNG and ARCO. On August 30, 1990 (55 Fed. Reg.
33502, 33508), the EPA added the Prewitt Abandoned Refinery Site to
the National Priorities List ("NPL"), pursuant to Sections 105 of
the Comprehensive Environmental Response, Compensation, and
Liability Act as amended ("CERCLA"), 42 U.S.C. Section 9605,
qualifying the Site for investigation and remediation under CERCLA,
more commonly known as Superfund. On January 25, 1989, EPA issued
a Special Notice letter to both ARCO and EPNG regarding the
Remedial Investigation/Feasibility Study ("RI/FS") activities at
the Site. On June 22, 1989, ARCO and The El Paso Company ("TEPCO",
the parent company of EPNG) signed an Administrative Order on
Consent with EPA, which authorized the two companies to initiate
RI/FS activities at the Site.
The Remedial Investigation ("RI") was conducted in two defined
Phases during 1990 and 1991 to determine the nature and extent of
the problem presented by the release of contamination at the Site.
Phase I was the initial sampling and analysis phase. The purpose of
the Phase II activities was to resolve outstanding issues and fill
data gaps remaining at the conclusion of Phase I. During the RI,
contamination was detected in the surface soils and shallow ground
water. Figure 2 illustrates the way the Site was divided into the
various areas for the purpose of conducting the RI.
One of the activities that took place as part of the RI was the
abandonment of existing wells. The wells were abandoned or
modified to prevent them from being conduits of contamination to
lower ground water units. The abandonment/modification procedures
were specific for each well, depending upon the original
construction of the well, and its current condition. The following
wells were abandoned/modified: the Barnes, the Bluewater,
Monitoring Well ("MW") 1-S, MW 5-S, the Old Barnes, East, Gas, New
Railroad, Old Railroad, West, and the Wilcox well. A detailed
description of the abandonment activities is included in the
Prewitt Refinery Site Well Abandonment Report (March 30, 1992)
which is included in the Administrative Record.
Utilizing the findings of the RI, the Feasibility Study ("FS") was
initiated to develop and assess various remediation measures for
the areas of contamination at the Site. The process involved in
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conducting the FS and the detailed evaluations of the alternatives
are presented in the FS Report for the Prewitt Refinery Site which
is part of the Administrative Record. The remedial alternatives are
based on health risk, and were determined by the future residential
use of the Site.
A Preliminary Natural Resource Survey was conducted by the
Department of Interior ("DOI") in 1991, to determine if there were
any damages to natural resources. DOI indicated to EPA that there
is no evidence of direct injuries to natural resources under its
trusteeship. During the Ecological Assessment activities, it was
determined that no Federally-, State-, or Navajo Nation-listed
endangered species are found specifically at the Site.
III. HIGHLIGHTS OP COMMUNITY PARTICIPATION
The requirements of CERCLA Sections 113(k)(2)(B)(i-v) and 117, 42
U.S.C. §§9613(k)(2)(B)(i-v) and 9617, were met during the remedy
selection process, as illustrated in the following discussion.
A series of community interviews near the Site was conducted prior
to, and upon, listing of the Site on the NPL. Fact sheets
summarizing the progress of the RI/FS at the Site were mailed out
in September 1990 and July 1991. These fact sheets were mailed out
to all individuals on the Site mailing list, which has been
continually updated as Site activities progress.
The RI and FS Reports and the Proposed Plan for the Prewitt
Abandoned Refinery site were released to the public on July 18,
1992. These documents were made available to the public in the
Administrative Record and the information repositories which are
maintained at the Prewitt Fire House, Prewitt, New Mexico; at the
New Mexico Environment Department, Santa Fe, New Mexico, the Navajo
Superfund Office in Window Rock, Arizona and EPA's Region 6 Library
in Dallas, Texas. A summary of the Proposed Plan and the notice of
availability of these documents and the Administrative Record was
published in the Gallup Independent and Navajo Times Newspapers on
July 16, 1992. EPA held a public comment period regarding the
Proposed Plan, the RI and FS Reports and the Administrative Record
from July 18, 1992 through August 17, 1992. Due to a delay in
delivering the Administrative Record Files to the Repositories, and
a request for an extension to the public comment period, the public
comment period was extended to September 18, 1992. A notice of the
extension to the public comment period was published in the Gallup
Independent Newspaper on July 30, 1992 and was announced at the
July 29, 1992, public meeting.
An informal Open House was held on April 14, 1992 at the Prewitt
Fire House in Prewitt, New Mexico. At the Open House, EPA informed
the public that the investigations regarding the Site were
completed and that a Proposed Plan would be issued in the future.
Additionally, a public meeting was held by EPA on July 29, 1992 at
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the Prewitt Fire House. At the request of the Navajo Nation's Baca
Chapter, a second Public Meeting in English and Navajo was held by
EPA on September 3, 1992 at the Baca Chapter House. Representatives
from EPA participated in this meeting and answered questions about
problems at the Site and the remedial alternatives under
consideration. A response to the comments received during this
public comment period, including those expressed verbally at the
public meetings, is included in the Responsiveness Summary, which
is included as part of this Record of Decision ("ROD")(Attachment
1).
This ROD presents the selected remedial action for the Prewitt
Abandoned Refinery Site, in Prewitt, New Mexico, chosen in
accordance with CERLCA, as amended by Superfund Amendments and
Reauthorization Act ("SARA"), and, to the extent practicable, the
National Oil and Hazardous Substances Pollution Contingency Plan
("NCP"), 40 CFR Part 300. The decision for this Site is based on
the Administrative Record. An index for the Administrative Record
is included as Attachment 3 to this ROD.
XV. SCOPE AND ROLE OF RESPONSE ACTION
The studies undertaken at the Prewitt Abandoned Refinery Site have
identified the contaminated soils and ground water as a threat to
human health and the environment. Non-Aqueous Phase Liquids
("NAPLs") in the ground water beneath the Site, sludges in an oil-
water separator, waste pit contents and "hot spots" of heavily
contaminated soils are considered to be principal threats at the
Site. Waste pit contents and some of the contaminated soils are a
principal threat because high concentrations of lead or Polynuclear
Aromatic Hydrocarbons greatly exceed levels that are safe for
unrestricted use of the Site.
The contaminated ground water is a threat to human health due to
the potential for exposure of the public to the Site contaminants
via ingestion of contaminated ground water and because of the
threat of migration of contaminants to deeper zones of ground
water. Lead is detected above the Maximum Contaminant Levels
("MCL") established under the Safe Drinking Water Act, 42 U.S.C.
300f et. seq.. in one area of the site. The ground water is
contaminated primarily with benzene, toluene, ethyIbenzene, and
xylene ("BTEX"). Chlorinated hydrocarbons have also been detected
at concentrations which exceed drinking water standards. The most
recent sampling data do not show high concentrations of chlorinated
hydrocarbons.
The remedy to eliminate or minimize the threat from the
contaminated soils, the separator contents, the Non-Aqueous Phased
Liquids ("NAPL") and the ground water which is a potential source
of drinking water is included in this ROD and is addressed as one
operable unit. This is the final ROD planned for the Prewitt
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Abandoned Refinery Site. It addresses source control and
contaminated media, including ground water.
The remedial objectives for the Site are the following:
1. Removal of, or containment of, NAPL to prevent further
contamination of ground water in the A-G units of the Sonsela
aquifer. Since NAPL impacts ground water, remediation goals
for subsurface areas contaminated with NAPL are as described
below in the discussion of ground water remediation goals.
2. Prevent future exposure to the contaminated ground water
through the G, F, and E units, and restore the G, F, and E
units of the Sonsela Aquifer to their beneficial use, which is
at this site a drinking water aquifer.
3. Excavation and treatment of wastes in the West Pits Area to
prevent or reduce carcinogenic and noncarcinogenic risk to
human health and the environment and to eliminate the physical
hazard posed by the waste pits as they exist.
4. Control or eliminate the exposure to contaminated soils
including the North Pit contents, contaminated with lead,
asbestos or hydrocarbons.
5. Eliminate risk and hazards associated with exposure to the
separator unit and its contents. The separator and its
contents shall be removed such that there is no future risk to
human health and the environment.
V. SITE CHARACTERISTICS
Regional Geology
The Site is located near the southwest edge of the Rio San Jose
Basin. The topography of the area at the Site is typified by a
linear valley floor to the north and rocky uplands to the south.
There are three major stratigraphic units at the site. These are
in ascending order, the San Andres/Glorieta Formations, the Lower
Chinle member, and the Sonsela Sandstone Bed. The Sonsela
Sandstone Bed includes seven sandstone beds and eight partings.
Two of the upper sandstone beds have splits that have been
identified. A thick continuous parting labeled the upper confining
bed separates the two upper sandstones from the lower five.
Claystone, shale, and siltstone partings also occur between
sandstone beds and vary in thickness and lithology across the site.
Two prominent north-trending faults are identified in the western
half of the site. The fault offsets are less than 40 feet, with
offset decreasing higher in the stratigraphic section. Small- to
medium-scale fractures are common in all stratigraphic units.
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Regional Hydrogeology
The Site is situated above two significant aquifers. The Sonsela
Sandstone Bed compromises seven sandstone beds, designated A
through G, each separated by claystone/mudstone partings. The
uppermost sandstones are the F and G, which are separated from the
E through A sandstones by the upper confining bed. Ground water in
the F sandstone is perched upon the upper confining bed and flows
north according to the dip of the upper confining bed top
structure, although fractures in the upper confining bed may allow
fluid migration between the F and E sandstones. The A through E
sandstones are separated by partings consisting of claystone,
mudstone, shale and siltstone. Where present, these partings are
aquitards, as they restrict but do not prevent the flow of ground
water. The preferential flow path for ground vater is horizontal
through the sandstone beds. A lesser amount of water flows
vertically through low permeability partings.
Ground water in the A through E units of the Sonsela aquifer
generally flows to the"" 3t and southeast in the Prewitt area.
Ground water in the San Andres/Glorietta aquifer flows east-
northeast under confined conditions.
There are no surface water bodies in the area of the Site.
Historic Site Operations and Potential Sources of Contamination
The crude oil was delivered to storage tanks. From the crude
storage tanks the raw material was pumped to the distillation tower
where various fractions were recovered from various levels of the
tower based upon boiling point. Gasoline was recovered from the
top of the tower, kerosene from a lower level, diesel fuel from a
still lower level, gas oil from near the tower bottom and a bottoms
product from the very bottom. The top three materials were
transferred to interim storage and final blending while the bottom
two materials were taken to the thermal cracker for further
conversion to gasoline and coke. Some of the gasoline was
processed through the reformer which raised the octane rating of
the fuel.
The Prewitt Refinery did not have a large number of waste
management units; therefore, wastes were generally disposed at or
near the point of generation, and not in designated waste
management units. Thus, waste materials known to have been
spilled, dumped and spread in the refinery area have become
intermixed with the spills of petroleum products also known to have
occurred. Based on knowledge of plant processes and descriptions
of waste disposal by former plant employees, those wastes include
leaded tank bottoms which have been listed as a hazardous waste
under the Resource and Recovery Act ("RCRA"), 42 U.S.C. 6901 et
seq., as hazardous waste number KO52. Other such RCRA listed
hazardous waste found at the site include slop tank contents
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(KO49), primary separator sludges (FO37), and secondary separator
floats (F038).
Additionally, the operating history of the refinery was such that
wastewaters were routinely discharged into unlined, earthen ditches
throughput the refinery area. In addition to accidental spills,
these ditches are known to have carried off-specification petroleum
products, hydrocarbon laden wastewaters such as those generated
from the cleaning of the distillation unit, cooling tower overflow,
tank bottoms, and spent caustic materials from cleaning gasoline.
Releases in these ditches during the operating history included
RCRA listed hazardous waste F037.
The separator, that many of these ditches flowed into, was a
compartmentalized concrete tank, providing reduced flow conditions
which allowed the organics to float to the surface of the material
in the tank. These organics were pumped off the water surface and
returned to the process system. The water and heavier materials
(RCRA listed hazardous waste FO37) were drawn from the bottom of
the separator, and disc1 " jged into an arroyo leading to the north
edge of the Site and into^the North Pit. Steam was available to
heat the contents of the separator to enhance the oil-water
separation. Separator floats that passed through or over the
separator are listed as RCRA hazardous waste number FO38.
An area located on the west side of the site was originally used as
an emergency relief system. During the early years of operation
when a situation in the processing plant arose that required a
process unit to be quickly shut down, the contents of the unit were
directed through underground pipes to bermed containment areas, in
the west side of the Site, for containment. Later, this emergency
relief system was modified to provide tanks in this area to receive
this partially processed material, in order to facilitate the
return of the material to the crude oil refining process. Late in
the life of the plant, a flare, a device designed to burn vented
gases, was added to this area to burn processing vapors. Aerial
photographic analysis of the plant in 1958 indicates drainage from
spills or disposal in the storage and process areas leading to the
West Pits.
Since the waste materials disposed on the Site contain the same
contaminants, in varying amounts, as the spilled petroleum
products, specific origins of contaminants found in ground water
cannot be distinguished. The attempt to reliably differentiate
between specific sources of discrete areas of ground water
contamination is made much more difficult by the time that has
elapsed. Because of the complexities involved in multi-phase
leaching and transport processes, predictive modeling of oil waste
migration is extremely difficult, and results are subject to great
uncertainty. Furthermore, aerial photographs taken over time show
dramatic changes that weathering, degradation and penetration into
soil have had on surface contamination.
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Extent of Contamination
The media and associated contaminants of potential concern ("CPCs")
at the Site were identified in the RI. Not all CPCs are
contaminants that drive the risk or the need to remediate the Site.
The contaminants most critical to risk are discussed in detail in
Section VI. Summary Of Site Risks. Based on the results of the
report the following media/categories were identified:
Ground Water
NAPL
West Pits Area
Surface Soils including the North Pit
Separator
Ground water:
Shallow water underlying the Prewitt Abandoned Refinery Site has
been contaminated from past refinery related activities. BTEX has
been transported into the ground water. NAPL has accumulated on
the ground water surface. Contaminants have migrated under the
influence of gravity through bedrock fracture systems. It appears
that the dissolved phase BTEX contamination at the Site is highest
in the areas where NAPL is present.
Ground water contamination by organic compounds is generally
confined to the uppermost portion of the Sonsela aquifer, from 0 to
60 feet. Trace concentrations of BTEX compounds have also been
detected in the A-D Sonsela units and San Andres/Glorieta aquifer.
The contamination in the San Andres/Glorieta aquifer is related to
transport of contaminants downward from the shallow Sonsela aquifer
through the annular space or well casing of existing refinery site
wells.
Lead was detected in A-D units of the Sonsela aquifer at a
concentration range of 2.3 - 27.5 micrograms per liter ("ug/l").
It was detected in the E and F units at a range of 11.5 to 167
ug/1.
Ground water flow in the Sonsela aquifer is generally to the east
and southeast. The velocity of ground water flow in the E unit of
the Sonsela Aquifer has been calculated to be between 1 and 60
feet/year. Ground water velocity may be higher in some areas due
to the presence of fractures. BTEX concentrations in the E unit
range from 5 to 27,000 ug/1. Low levels of BTEX (less than 80
ug/1) occur in isolated areas in the C and D units of the Sonsela
Aquifer, with most detections less than 10 ug/1.
BTEX concentrations detected in the San Andres/Glorieta aquifer
range from 1 to 180 ug/1. This contamination is localized and
appears to be due to vertical leakage through annular space of the
monitoring wells, or through the inside of the well casing.
8
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1,2 Dichloroethane, a CERCLA hazardous substance, was detected at
concentrations in excess of the established MCL of 5 ug/1, during
four consecutive sampling events in one ground water monitoring
well (MW-22S) in the refinery. Recent sampling events have
indicated that concentrations have dropped below analytical
detection limits in that well and recently 1,2 dichloroehtane is
not detected in the other monitoring wells.
The CPC for the ground water media include antimony (which was
found at concentrations of 39-42 ug/1), benzene (0.6-3900 ug/1),
beryllium (1-1.7 ug/1), cadmium(4.9-6.5 ug/1), 1,2 dichloroethane
(3 - 510 ug/1), ethlybenzene (1-1800 ug/1), lead (1.4-167 ug/1),
naphthalene (6-920 ug/1), tetrachloroethylene (2-100 ug/1), toluene
(0.66-6200 ug/1), trichloroethlylene (4-30 ug/1), and total xylene
(0.6-9600 ug/1).
NAPL:
Seven NAPL areas were identified at the Site during the sampling
activities conducted as part of the RI. These areas include MW-
20S, MW-4S, the East well, N-8P, the gas well, MW-8S, and the N-22P
NAPL areas (See Figure 3). It is estimated that 43,500 gallons of
NAPL has accumulated in the E, F and G units of the Sonsela aquifer
and the upper confining bed. Staining noted during core logging
indicates that bedrock fractures have been a significant transport
mechanism for contaminants in the unsaturated zone.
One of the important findings of the FS was that removal or
containment of BTEX constituents of the NAPL was a necessary
initial step for ground water remediation, so that the NAPL poses
no risk of continued ground water contamination at the Site.
West Pits Area:
The West Pits were found to have varying amounts of tarry/
Polynuclear Aromatic Hydrocarbons ("PAHs") materials mixed with
soil. The lead concentrations in samples obtained from this area
ranged from below 1 milligram/kilogram ("mg/kg") to 177 mg/kg and
trivalent chromium ranged from 4.0 mg/kg to 12.8 mg/kg.
Benzo(a)pyrene was detected in samples in this area in the
concentration range of 800-17,000 ug/1. Anthracene was detected at
7,300 ug/kg. Chrysene was detected at concentrations ranging from
1,000 to 32,000 ug/kg. Other PAHs were also present in the west
pits area.
Soil and Sediments:
For soils, the CPCs were lead, mercury, chromium, nickel, BTEXs and
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PAHs. Hydrocarbons were found in scattered localized concentrations
at the Site. The highest concentrations occur in areas such as the
West Pits, North Pit, separator, compressor, vertical tanks, along
the railroad tracks, and process areas. The concentrations of PAHs
generally diminish below 2 feet of the ground surface. A notable
exception to this is in the vicinity of the separator, where PAH
contamination extends to 18 feet. Volatiles and semivolatiles are
found only in limited areas in soils across the Site. The highest
PAH concentrations are associated with surficial tarry materials
found in the railroad tar areas, the North Pit, the separator area,
and the West Pits area. For example, benzo(a)pyrene was detected at
concentrations as high as 185 mg/kg in the North Pit area and
Benzo(a)anthracene was detected at concentrations as high as 265
mg/kg in area outside the fence ( "area outside the fence" or
"unfenced" or "north tract") but within the Site boundaries.
Lead was the most prevalent metal contaminant; yet, its
distribution is limited. Lead concentrations range from 3 to
129,000 parts per million ("ppm") . The highest lead concentrations
were detected in the office, separator, vertical tanks, and product
#1 areas. The concentrations of lead in the vertical tank area
ranged from 20 -129,000 ppm. The lead concentrations in the former
office area ranged from 10.4 to 15,200 ppm. (Figure 4)
Some contamination still exists in the sediments in the Site
surface water drainage areas. Slightly elevated total petroleum
hydrocarbons ("TPH"), target analyte list ("TAL") metals, and
semivolatiles were detected in a drainage north of the Site. Two
near surface soil samples in a drainage north of the Site had TPH
concentrations of 170 ppm and 210 ppm. Semivolatile organic
contaminants found in sediments north of the Refinery were
phenanthrene and anthracene at 3.7 and 15.0 ppm, respectively.
Separator:
This separator contains petroleum sludges from refinery operations
which are listed as hazardous waste number FO37 under RCRA. Also,
RCRA Toxicity Characteristic Leaching Procedure ("TCLP") analyses
were performed on the waste samples collected from the separator
and detected concentrations of 230 ug/L TCLP-benzene. 230 ug/1
benzene is approximately 50 percent of the concentration required
to establish the separator waste as hazardous based on leachable
benzene. The concentration of remaining benzene is significant in
light of the fact that benzene is very volatile and it has been
over 30 years since the waste was generated.
Exposure Routes
The Prewitt Abandoned Refinery is located in a, predominantly
rural, desert setting in Prewitt, New Mexico. Approximately 15
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buildings, including various residences, a campground, operating
rodeo arena and a firehouse are located within one-mile of the
Site. The population in the vicinity of the Site is limited.
Approximately 10 residences within a one mile radius of the Site
are potentially downgradient of the Site. The camp ground is not
downgradient of the Site.
Humans may be exposed to contamination from the Site through
various pathways. These pathways are identified in Tables 1 and 2.
Table 1 addresses exposure pathways that exist at the Site as the
Site is currently being used. Table 2 addresses exposure pathways
that would exist under various possible future uses. The potential
receptor medium for contaminated ground water includes the Sonsela
aquifer. That is, humans may be exposed to contaminated ground
water through ingest ion of ground water from the Sonsela Aquifer.
There are no surface water bodies in the vicinity of the Site.
Under current use, which consists of use by trespassers, several
exposure routes were identified, dermal contact with, and
incidental ingestion of contaminated surface soil could result if
trespassing into the fenced area ("fenced area" or "south tract")
occurs. In addition, trespassing outside the fence area may result
in dermal contact with and ingestion of contaminated soil. In
addition to exposure to contaminated soils, residents of homes
located east of the fenced area could also ingest contaminated
ground water from private wells. They could contact contaminants
in ground water during showering, as well as inhaling any
volatilized contaminants. Current residents of the nearby homes
could potentially inhale fugitive dusts as a result of wind erosion
of Site soils.
For future use, scenarios which included unrestricted sheepherding
and residential use were considered. The exposure routes projected
under various future use scenarios include ingestion and direct
contact with the surface soils, ingestion of contaminated land or
mutton by a sheepherder or a resident, ingestion and dermal contact
with surface and subsurface soils by construction workers; and
ingestion of drinking water plus dermal contact and inhalation of
contaminants present in ground water while showering.
Surface Water and Sediment
Surface water bodies do not exist in the vicinity of the Site;
therefore a potential exposure route through surface water or
ingestion does not exist.
Surface Soil
Based on the analysis of site conditions and potential for
exposure, two routes for exposure to soils are considered:
ingestion of contaminated soil and dermal contact with contaminated
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soil.
Ambient Air
Volatile organic compounds ("VOCs") present in the ground water may
volatilize during showering, thus posing inhalation risk to the
person showering. Inhalation of particulates from contaminated
soil is an exposure route.
Ground Water
Contaminant transport along the shallow ground water pathway is
considered a primary exposure route of particular importance to
receptors located hydrologically downgradient of the Site.
VI. SUMMARY OF SITE RISKS
Using the data gathered during the RI, TEPCO and ARCO conducted a
risk assessment to characterize the current and potential threats
to human health and the environment that may be posed by
contamination at the Site under various possible exposure scenarios
including future residential use of the property. That is, this
part of the risk assessment was based on an assumption that people
would live on the site in residential housing. The risk assessment
indicated that contamination existing in the surface soils and
ground water at the Site would pose unacceptable health risks to
persons at the Site, if the Site is used for residential
development. The overall risk at the Site is driven by
"hotspots11. These "hotspots" contain contaminant concentrations
above health based action levels. These areas are the areas which
are targeted for remediation. They include the waste pits which
poses a risk of approximately 1.4 x 10'3 and the area outside the
fence, but inside the Site, with a risk of approximately 3.6 x 10"3.
The vertical tank and former office areas contain lead hotspots,
which at 129,000 ppm exceed the residential or industrial clean up
standards that range from 500-1000 ppm.
The baseline risk assessment was performed consistent with the
revised National Contingency Plan ("NCP") and current EPA risk
assessment guidelines including the EPA's Risk Assessment Guidance
for Superfund ("RAGS"). The risk assessment included a
quantitative assessment of human health risks and a qualitative
assessment of ecological impacts. The goal of the Risk Assessment
was to characterize the current and potential threats to human
health and the environment that may be posed by contaminants
migrating to ground water or surface water, releasing to air,
leaching through soil, remaining in the soil and bioaccumulating in
the food chain.
The baseline risk assessment is evaluated in the decision to take
action and indicates the exposure pathways that need to be
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addressed by the remedial action. It serves as the baseline
indicating what risks could exist if no action were taken at the
Site. The risk assessment should not be construed as presenting an
absolute estimate of risk to human populations. Rather, it is a
conservative analysis intended to indicate the potential for
adverse impacts to occur. This section of the ROD reports the
results of the baseline risk assessment conducted for this Site.
A locked fence surrounds the abandoned refinery site. A cluster of
homes are located in the vicinity of the Site. Because the fence
limits certain types of exposures, the Risk Assessment took this
into account. Consequently a separate analysis was conducted for
the area within the fence. Employing this "within" versus
"outside" the fence approach, the risk assessment evaluated
potential exposures to contaminated ground water, contaminated
surface soils and wind-eroded soil particles.
To further focus the risk assessment, the risks to human health
from exposures to surface soils were divided into five subparts (1)
the surface soils within the fence excluding the hotspots, (2) the
surface soils outside the fence and (3-5) three hot spot areas
within the fence. Although the risk assessment did not
specifically quantify risks from hotspots outside the fence, the RI
data does indicate that certain hotspots do present significant
risk. For example, the concentration of PAHs in the North Pit area
indicate that the risk in that hotspot would be several times
greater than the risk presented by the area outside the fence as a
whole. These hotspots are included in the areas targeted for
remediation. The identification of the hotspots was based upon
contaminant distribution patterns identified during the site
investigation.
Similarly, the assessment of human health risks from exposures to
ground water were separated into the threat of exposure to the
contaminated ground water from the E and F units of the Sonsela
Aquifer which are located closest to the ground surface, and the
threat of exposure to the contaminated ground water located in the
deeper Sonsela ABCD units and the San Andres-Glorieta Aquifer
("ABCD/SA-G") units. This separation of this assessment into the
examination of the two threats described above was based solely
upon contaminant distribution considerations.
EPA has established criteria for interpreting both noncarcinogenic
and carcinogenic risk estimates for Superfund sites. For
noncarcinogenic risks, a hazard index ("HI") that exceeds 1
indicates that contaminants at the Site may pose adverse health
effects. For carcinogenic risks, the NCP has established 1 X 10"*
as a point of departure for determining whether remediation is
necessary. The incremental lifetime cancer risk represents the
excess probability that an individual will develop cancer over a
lifetime due to exposure to a CPC. The background cancer risk in
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the United States is one in four or 0.25. An incremental lifetime
cancer risk of IxlO"6 indicates that an individual's chance of
developing cancer in his or her lifetime is increased from 0.25 to
0.250001. Put another way, if 1 million people were exposed to
site contamination, in a situation in which the risk was 1 X 10"*,
1 person would be expected to develop cancer due to site
contaminants. However, the actual excess cancer risk posed by the
Site is probably lower than estimates in the risk assessment and
can even be zero.
Contaminants of Concern
The contaminants of concern, those contaminants which are driving
the risk and the need for remediation at the site are as follows:
Ground water: Benzene, toluene, ethylbenzene, xylene, 1,2
dichloroethane and lead;
NAPL areas: Benzene, toluene, ethylbenzene, and xylene;
West Pits and Hydrocarbon contaminated soils: Benzo(a)pyrene
Soils: Lead and asbestos; and
Separator: Lead, benzene, toluene, xylene, and ethylbenzene.
Table 3 presents the maximum concentration for each contaminant of
concern, the remediation goals for each contaminant of concern
and/or each media.
Current Land and Ground Water Uses:
The 70 acre site includes the dismantled abandoned refinery and
associated contaminated areas which is currently owned by the PRPs.
The unfenced portions of the Site are occasionally traversed by
pedestrians and sheepherders. With regard to the current use of
the Sonsela aquifer, it is used as a drinking water source by the
current residents in the surrounding area.
Expected Future Land and Ground Water Uses;
The expected future land use for the site and the surrounding area
is residential. This is based on the dismantled condition of the
of the refinery, land use patterns in the area and factors
described in response to comment #1 included in the attached
Responsiveness Summary. The potential exists for the Site to
continue to be traversed by pedestrians. The Sonsela Aquifer is
expected to continue to be the drinking water source in the area.
start
Exposure Assessment
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The potentially exposed population considered under the current use
scenario at this site were the trespasser and the residents that
live near the Site. The area north of Old Highway 66 contains
soils which are contaminated with hydrocarbons. Direct contact
with the contaminated soils is the potential pathway of exposure to
contaminated soils considered in this scenario. Ingestion, dermal
contact and inhalation of contaminants during showering are the
potential pathways of exposure to contaminated ground water. The
ground water concentrations used for calculating current use risk
are those ground water concentrations currently measured off-site.
These exposure pathways are considered reasonable exposure pathways
for both adults and children residing in the area.
Under a future use scenario, the residents in the area are the
exposed population and the reasonable exposure pathways are
the same as for the current use. However, for future residential
use, the ground water concentrations used are those concentrations
detected on-site.
Risks to human health are calculated by first determining the
exposure point concentration for each pathway. The exposure point
concentration is the concentration of a contaminant that an
individual might be exposed to through any given pathway. Actual
site data is used to calculate an exposure point concentration.
The exposure point concentration is then multiplied by the human
intake variables (e.g. average daily water consumption, number of
days exposed, and body weight) to arrive at a chronic daily intake
value.
Exposure point concentrations for ingestion of ground water were
based on well monitoring data. Inhalation exposure point
concentrations for ground water were based on modeling.
Chronic daily intake values calculated for the soil ingestion
pathway consisted of two components: exposure point concentrations
and chemical-specific intake variables. Both the geometric mean
and the 95 percent Upper Confidence Limit for exposure point
concentrations were used in risk calculations for the current
exposure, future residential exposure and unrestricted access
exposure scenarios to represent exposure point concentrations for
soil ingestion. If the mean or the 95 percent Upper Confidence
Limit was found to exceed the maximum concentration, the maximum
value was used instead.
For ground water pathways, the maximum value used for exposure
point concentration was the mean of the contaminant concentration
values at a particular well location averaged over the sampling
rounds. Concentrations of contamination currently measured in
ground water in areas both within and outside of the fence were
used to project future exposure of future residential populations
to ground water contamination.
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In estimating exposure point concentrations for current and future
exposure to contaminated soils, it was conservatively assumed that
the concentrations would remain constant over time. Exposure to
soil contaminants was assessed separately for surface (0 to-2 feet)
soil, and also for surface soil and subsurface soil combined ( 0 to
4 feet). Surface and subsurface soils, sediments and waste piles
were combined for the purpose of estimating exposure and risk from
contaminated soils. Exposure to soil contaminants was considered
at five exposure points: within the fenced area (excluding the hot
spots), outside the fenced area, and at the three hot spots.
This exposure point concentration for current an future use
exposure to contaminated soils, as defined by the upper 95%
confidence interval for the average, together with the intake
variables was used to estimate the reasonable maximum exposure
("RME") baseline risk. Chemical-specific intakes for ingestion of
chemicals in drinking water were determined based on EPA's Exposure
Factors Handbook and Risk Assessment Guidance for Superfund: Volume
I Human Health Evaluation Manual Part A, Interim Final. The intake
variables used in the exposure assessment were as follows: ground
water ingestion rate of 2 liters/ day; soil ingestion rates of 100
mg/day for adults and 200 mg/day for children; inhalation rate of
0.6 cubic meters per hour; body weights of 70 kg for adults and 15
kg for children; exposure frequency of 350 day/year; and an
exposure duration of 30 years (6 years as a child and 24 years as
an adult). Tables 4 and 5 summarize the calculated exposure point
concentrations and the pathway-specific human intakes for the
pathways resulting in the calculated risks of most concern.
Exposure to lead in soil was not quantified in the same manner as
other chemicals due to the absence of a reference dose or slope
factor ("SF"). Instead, EPA's Lead Uptake Biokinetic ("UBK") Model
was utilized in assessing potential risks from environmental lead
contamination for residential land use. The established default
values were used in implementing the UBK model. These default
values include: ventilation rates of 2 m3/ day (0-1 year old child)
to 7 m3 (6-7 year old child); water consumption rates of 0.20 to
0.59 I/day; soil and dust ingestion rate of 100 mg; and diet intake
values ranging from 5.88 to 7.48 ug of lead per day depending on
the age of the child.
Tcxieity Assessment
The objective of the toxicity assessment is to weigh available
evidence regarding the potential for particular contaminants to
cause adverse effects in exposed individuals. Also, the toxicity
assessment provides, where possible, an estimate of the
relationship between the extent of exposure to a contaminant and
the increased likelihood and or severity of adverse effects. The
types of toxicity information considered in this assessment
include the reference dose ("RfD") used to evaluate noncarcinogenic
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effects and the SF to evaluate carcinogenic potential.
Noncarcinogenic toxicity
RfDs have been developed by EPA for indicating the potential for
adverse health effects from exposure to contaminants of concern
exhibiting noncarcinogenic effects. RfDs, which are expressed in
units of milligrams of contaminant per kilogram of body weight per
day ("mg/kg-day"), are estimates of acceptable lifetime daily
exposure levels for humans, including sensitive individuals.
Estimated intakes of contaminants of concern from environmental
media (e.g., the amount of a contaminated drinking water) can be
compared to the RfD. RfDs are derived from human epidemiological
studies or animal studies to which uncertainty factors have been
applied (e.g., to account for the use of animal data to predict
effects on humans and to protect sensitive subpopulations) to
ensure that it is unlikely to underestimate the potential for
adverse noncarcinogenic effects to occur. The purpose of the RfD
is to provide a benchmark against which the sum of the other doses
(i.e. those projected from human exposure to various environmental
conditions) might be compared. Doses that are significantly higher
than the RfD may indicate that an inadequate margin of safety could
exist for exposure to that substance and that an adverse health
effect could occur.
No RfDs or SFs are available for the dermal route of exposure. In
some cases, however, noncarcinogenic or carcinogenic risks
associated with dermal exposure can be evaluated using an oral RfD
or an oral SF. Exposures via the dermal route generally are
calculated and expressed as absorbed doses. These absorbed doses
are compared to an oral toxicity value that is also expressed as
an absorbed dose.
Toxicity information used in the toxicity assessment for the Site
was obtained from the Integrated Risk Information System ("IRIS") .
If values were not available from IRIS, the Health Effects
Assessment Summary Tables ("BEAST") were consulted. The toxicity
factors used in this evaluation for noncarcinogenic effects and
carcinogenic effects are summarized in Tables 6 and 7 respectively.
Carcinogenic toxicity
For chemicals that exhibit noncarcinogenic health effects,
authorities consider organisms to have repair and detoxification
capabilities that must be exceeded by some critical concentration
("threshold") before the health is adversely affected. For
example, an organ can have a large number of cells performing the
same or similar functions. To lose organ function, a significant
number of those cells must be depleted or impacted. This threshold
view holds that exposure to some amount of a contaminant is
tolerated without an appreciable risk of adverse effects.
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Health criteria for chemicals exhibiting noncarcinogenic effects
for use in risk assessment are generally developed using EPA's RfDs
developed by the Reference Dose/Reference Concentration ("RfD/RfC")
Work Group and included in the IRIS.
For chemicals that exhibit carcinogenic effects, most authorities
recognize that one or more molecular events can evoke changes in a
single cell or a small number of cells that can lead to tumor
formation. This is the non-threshold theory of carcinogenesis
which purports that any level of exposure to a carcinogen can
result in some finite possibility of generating the disease.
EPA's Carcinogenic Risk Assessment Verification Endeavor ("CRAVE")
has developed SFs (i.e., dose-response values) for estimating
excess lifetime cancer risks associated with various levels of
lifetime exposure to potential human carcinogens. The carcinogenic
SFs can be used to estimate the lifetime excess cancer risk
associated with exposure to potential human carcinogens. Risks
estimated using SFs are considered unlikely to underestimate actual
risks, but they may overestimate actual risks. Excess lifetime
cancer risks are generally expressed in scientific notation and
are probabilities. An excess lifetime cancer risk of l x 10"* (one
in one million), for example, represents the probability that one
additional individual in a population of one million will develop
cancer as a result of exposure to a carcinogenic chemical over a
70-year lifetime under specific exposure conditions.
SFs have been developed for estimating excess lifetime cancer risks
associated with exposure to potentially carcinogenic contaminants
of concern. SFs, which are expressed in units of milligram of
contaminant per kilogram of body weight per day (mg/kg-day)"1, are
multiplied by the estimated intake of a potential carcinogen, in
mg/kg-day, to provide an upper-bound estimate of the excess
lifetime cancer risk associated with exposure at that intake level.
The term "upper bound" reflects the conservative estimate of the
risks calculated from the SF. Use of this approach makes
underestimation of the actual cancer risk highly unlikely. SFs are
derived from the results of human epidemiological studies or
chronic animal bioassays to which animal-to-human extrapolation and
uncertainty factors have been applied ( e.g., to account for the
use of animal data to predict effects on humans).
There are varying degrees of confidence in the weight of evidence
for carcinogenicity of a given chemical. The EPA system involves
characterizing the overall weight of evidence for a chemical's
carcinogenicity based on the availability of animal, human, and
other supportive data. The weight-of-evidence classification is an
attempt to determine the likelihood that the agent is a human
carcinogen, and thus, qualitatively affects the estimation of
potential health risks. Three major factors are considered in
characterizing the overall weight of evidence for carcinogenicity:
(1) the quality of evidence from human studies; (2) the quality of
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evidence from animal studies, which are combined into a
characterization of the overall weight of evidence for human
carcinogenicity; and (3) other supportive information which is
assessed to determine whether the overall weight-of-evidence
should be modified. EPA uses the weight-of-evidence classification
system to categorize carcinogenicity of contamination as one of the
following five groups:
Group A - Human Carcinogen: This category indicates that there
is sufficient evidence from epidemiological studies to support
a causal association between an agent and cancer.
Group B - Probable Human Carcinogen: This category generally
indicates that there is at least limited evidence from
epidemiological studies of carcinogenicity to humans (Group
Bl) or that, in the absence of adequate data on humans, there
is sufficient evidence of carcinogenicity in animals (Group
B2)
Group C - Possible Human Carcinogen: This category indicates
that there is limited evidence of carcinogenicity in animals
in the absence of data on humans.
Group D - Not Classified: This category indicates that the
evidence for carcinogenicity in animals is inadequate.
Group E - No Evidence of Carcinogenicity to Humans: This
category indicates that there is no evidence for
carcinogenicity in at least two adequate animal tests in
different species, or in both epidemiological and animal
studies.
Several of the chemicals of concern have been classified as
potential carcinogens by EPA. Each of these also has been assigned
a carcinogenicity weight-of-evidence category. These chemicals
are:
Group A - Human Carcinogens
* benzene
Group B - Probable Human Carcinogens
* benzo(a)anthracene
* benz o(b) fluoranthene
* benzo(k)fluoranthene
* benzo(a)pyrene
* beryllium
* chrysene
* i,2-dichloroethane
* lead
* tetrachloroethylene
* trichlorethylene
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Lead, 1,2-dichloroethane, benzene and trichloroethylene do not have
toxicity values. For lead, neither an RfD or a SF is available.
Therefore, the potential blood lead concentration target range was
estimated and correlated with soil concentrations. The target
level in blood was identified as 10 ug/dl based on studies of young
children as a sensitive population. Using the EPA's Lead UBK
Model, this blood concentration range was correlated with a soil
lead range. The soil lead concentration of 800 ppm associates with
a target blood lead level of 10 ug/dl.
No RfD for 1,2-dichloroethane is available on IRIS or in HEAST. An
RfD was developed based on a long term HA for a 70 kg adult. The
current long term HA is 2.6 mg/L. The calculated RfD used for 1,2-
dichloroethane was 0.07 rag/kg/day.
No RfD exist for trichloroethylene in IRIS or HEAST. An RfD was
developed based on Drinking Water Equivalent Levels ("DWELs11). The
current DWEL is 0.3 rog/1. Using the same assumptions described
above, the RfD for tri ~*Jloroethylene was calculated to be 0.009
mg/kg/day.
Neither IRIS nor HEAST contains an RfD for benzene. No long-term
Health Advisories ("Has") or DWELs from which to calculate an RfD
are available. The noncarcinogenic effects of benzene were not
evaluated in the risk assessment. Carcinogenic effects were
evaluated however using a SF available in IRIS.
The SF for benzo(a) pyrene is 7.3 (mg/kg/day)'1. Sfs are not
available for other carcinogenic PAHs. Comparative potency factors
were used to estimate the carcinogenic potency of the other
carcinogenic PAHs relative to benzo(a)pyrene. The relative potency
factors for carcinogenic PAHs detected at the Site are listed
below:
Contaminant Relative Potency Factor
Benzo(a) pyrene 1.0
Ben z o(a)anthracene 0.l
Ben z o(b)fluoranthene 0.1
Benzo(k)fluoranthene 0.1
Chrysene 0.01
It was assumed that the benzo (a)pyrene relative potency estimate of
1.0 was equal to the SF of 7.3 (mg/kg/day)'1. SFs were then derived
for the other carcinogenic PAHs by using comparative ratios. These
SFs are listed below.
Contaminant Slope Factors
Benzo(a) pyrene 7.3
20
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Benzo(a)anthracene 0.73
Benzo(b)fluoranthene 0.73
Benzo(k)fluoranthene 0.73
Chrysene 0.073
These Sfs were used to calculate risks for carcinogenic PAHs at the
Site.
RISK CHARACTERIZATION FOR HUMAN HEALTH:
Risk calculations included in the following discussion are based on
the RME pursuant to EPA guidance. The risk tables presented in
the Risk Assessment prepared by the PRPs and dated June 12, 1991
are not based on RME. Although the risk assessment includes the
information necessary to calculate risk based on RME, the tables
presented rely on average concentrations rather than the upper 95%
confidence interval of the average. The risk assessment tables
used less intense exposure duration and frequency assumptions than
the exposure assumption?y used to calculate RME. Thus, risks
presented in the following discussion are greater than those
presented in the risk assessment report. The risk calculations
based on RME have been included in the Administrative Record for
this ROD.
Current Use Scenario: The total carcinogenic risk under the
current use scenario for the site, trespassing, was calculated to
be 3 X 10"6. This is within the EPA's range of acceptable exposure
levels. The remedial action at the Site is intended to address
likely exposure pathways ("pathways") by which humans could be
exposed to contaminants. The pathway that contributes most
significantly to the total risk is ingestion of untreated private
well water which has a risk of 2 X 10"6. The estimated risk of
3x10"* is based on a more conservative exposure assumption. Under
this more conservative exposure assumption, it is assumed that
exposure to untreated ground water will be for lifetime, with 70
years used as an average lifetime.
The total noncarcinogenic HI for the current use exposure pathway
is 0.0003, three orders of magnitude below the EPA's acceptable HI
value of l. That is, if current use of the Site continued, then
noncarcinogenic HI would be 0.0003, well below EPA's acceptable HI
value of 1. Dermal contact with soils from within and outside the
refinery area is also a primary contributor to the noncarcinogenic
HI. Toluene contributes most to the HI for untreated well water,
while the PAHs, including 2-methylnaphthalene and benzo(a)pyrene
are the contaminants which contribute the most to the
noncarcinogenic risk posed by contaminants which may reach humans
through soil pathways.
Future Use Scenario: Under this scenario the Site is used for
21
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residential housing in the future, the carcinogenic risks which an
individual could be exposed to would be 6 X 10'J on the north tract
of the site and 3 X 10"* on the south tract of the site, based on
the reasonable maximum exposure.
Soils
Projected future exposure to soils in the refinery area, which
includes the soil within the fenced area as well as the hotspots,
and projected future exposure to soils outside the fenced area
result in a HI of less than 1 under the residential scenario. PAHs
are the contaminants that contribute most to this HI. It should be
noted that the risk calculation performed did not include lead
which is discussed below.
Lead occurs naturally in soils in many areas of the U.S. in what is
termed "background11 levels. Lead was detected above background
levels in many areas of the Site. However, only seven sampling
locations were found with lead concentrations above the EPA
guidelines for residential cleanup. EPA recommends cleanup
concentration of 500 - 1000 ppm for lead in soil (Office of Solid
Waste and Emergency Response ("OSWER") Directive #9355.4-02.).
These seven samples which are located in the office, separator,
vertical tanks, and product #1 areas (see Figures 4), have been
used to define four areas that require remediation. Lead
concentrations ranged from 3 to 129,000 mg/kg in soil samples
throughout the Site. Most lead concentrations diminish to
background concentrations below 2 feet.
Asbestos in soil has been observed at, and near the ground surface
in the central portion of the Site. An extensive asbestos
abatement program was performed by ARCO and TEPCO in 1990. The
abatement was conducted for purposes of protecting workers during
RI field activities. Approximately 800 cubic yards of asbestos-
containing soils were removed from the Site. Only limited amounts
of asbestos-contaminated materials ("acm") remain in the Process
and Compressor areas of the Site (See Figure 2).
The Prewitt Abandoned Refinery Risk Assessment reveals that the
cancer risks associated with exposure to surface soils at the Site
are caused primarily by PAHs at or near the ground surface,
particularly
• Benzo(a)pyrene
• Benzo(a)anthracene
• Benzo(b)fluoranthene
• Benz o (k) fluoranthene
The projected cancer risk, under the future residential scenario,
posed by the PAHs in the soil in the area outside the fence,
inclusive of the North Pit area and tarry areas along the railroad
22
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track, is estimated to be 6 X 10'3 this is based on the reasonable
maximum exposure.
Under the future residential scenario, an evaluation was performed
of the risks associated with inhalation exposure to contaminated
wind-borne particulates at the Site. The resulting carcinogenic
risk was calculated at below 10'7, thus, it is less than the point
of departure established in the NCP of KT6 .
Overall, CPCs found at the Site and identified by the Risk
Assessment represent constituents common to materials handled at
petroleum refineries. The CPCs were utilized in the risk evaluation
based upon toxicity, frequency of detection, and concentration.
The CPCs that represent the contaminants that contribute most
significantly to human health risks at the Site are: 1) for ground
water: BTEX, lead and 1,2 dichloroethane; and 2) for soils: lead,
PAHs, and asbestos. Other contaminants detected at the Site above
background concentrations included chromium, beryllium, antimony,
mercury, nickel, and cadmium. Each of these constituents were
included in risk calculations, but it was determined that these
other constituents do not contribute significantly to carcinogenic
or noncarcinogenic risks at the concentrations detected at the
Site.
Ground Water
Ground water is currently used for drinking water and agricultural
purposes. This is not expected to change. The Sonsela's B unit is
by far the most productive unit of the Sonsela, and would
contribute a predominant portion of the ground water drawn from
existing and future wells. However, a well may draw water from any
of the Sonsela units A through F or combinations thereof.
Therefore, each of the A through F units contribute to the
reasonable maximum exposure to an individual human using ground
water.
Risk due to potential exposure to contaminants in the ground water
in the E and F units of the Sonsela Aquifer exceed the acceptable
exposure levels. Exposures to ground water in the ABCD-SA/G layers
are within the acceptable exposure levels.
In the ABCD-SA/G layer, underlying the fenced area, an HI of less
than one is calculated (0.003) for noncarcinogenic effects, based
on projected future use of the ground water if the area is used for
residential purposes. For ground water underlying the area outside
of the fenced area, the HI under the same circumstances is 0.03.
Projected future ingestion of ground water from the EF layer
23
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underlying the fenced area results in a HI greater than 1 under the
future residential scenario. Naphthalene contributes most
significantly to this estimate of risk. Projected future injection
of ground water from the EF layer underlying the area outside of
the fence, results in an HI of 1.5 which exceeds the acceptable HI
value of 1.
Presently, the San Andres-Glorieta ground water unit is not used as
a water source in the vicinity of the Site. Given the availability
of the shallower, palatable, non-staining Sonsela Aquifer, the San
Andres-Glorieta aquifer is not currently used as a domestic or
agricultural water supply, although, water from this unit is
suitable for domestic and agricultural purposes and future use is
possible.
For current uses, with access restricted by the fence, the total
cancer risk calculated for the Site is 3x1 (T6 which is within EPA's
acceptable exposure level. Of this cancer risk, 2 X 10"6 is based
on consumption of untreated ground water in the concentrations
currently existing offsite.
For future residential uses, projected exposure to onsite ground
water found in the EF units and hotspot soils resulted in a 9xl(T3
cancer risk and an HI of 3.0.
In summary, with the exception of the future residential scenario,
the present and future scenarios examined showed carcinogenic and
noncarcinogenic risk below or at the low end of the EPA target risk
range. Risks posed by a future residential exposure scenario
exceed the EPA target risk range for both carcinogenic and
noncarcinogenic risk.
RISK CHARACTERIZATION OF THE ENVIRONMENT:
The objective of the ecological assessment was to qualitatively
assess potential impacts of contaminants on the surrounding natural
environment. Wildlife in the Site area, including migrating
species, were the receptors considered in this study. The most
likely pathways by which wildlife could be exposed to contamination
from the Site were incidental ingestion of contaminated soil and
consumption of contaminated prey or plants. The Risk Assessment
found that exposure levels associated with site-related
contaminants were not significantly impacting ecological receptors.
The region surrounding the Prewitt Abandoned Refinery site contains
several major ecological community types, including cold desert and
semidesert, northern temperate grassland, southern temperate
grassland, and ecotone woodland and brushland communities. The
Site itself lies in a transitional zone between a valley floor to
the north and rocky uplands to the south. This transition in
topography and substrate has resulted in vegetational transition
24
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from semidesert shrub grassland in the valley floor to pinyon-
juniper woodland in the rocky uplands. The 40-acre fenced site and
adjacent off-site areas can be classified into three broad plant
community types: loamy uplands, loamy overflows, and rocky uplands.
No endangered plant species have been reported as occurring on or
near the Site.
Three federally-listed endangered species, peregrine falcon, bald
eagle, and the black footed ferret may occur in the region.
Additionally, two bird species listed on the State of New Mexico's
list of endangered species occur in McKinley County. They are the
gray vireo and willow flycatcher. In addition to the federally-
and state-listed species described above, the Navajo Fish &
Wildlife Department has compiled a list of species of concern for
the Navajo Nation. Of the species listed by .,the Navajo Fish &
Wildlife Department, it is expected that only the following six
bird species could potentially occur at the Site: Swainson's Hawk,
Northern Harrier, Ferruginous Hawk, Short-eared Owl, Willow
Flycatcher, and the Mountain Plover. These species are classified
in "Group 4" by the Navajo Fish & Wildlife Department indicating
that insufficient information is available to determine their
particular ecological status.
Peregrine falcon would probably only occur at the Site as migrants
or vagrants; bald eagle is not expected at the site because of the
absence of large trees for perches or roosts. It is also unlikely
that ferrets would occur at the Site due to the absence of its
primary prey, the prairie dog, as well as their general intolerance
of human activity. The gray vireo may occur in the pinyon-juniper
woodland south of the site, but probably would not occur onsite due
to the low density of junipers present. The willow flycatcher
prefers riparian habitats, which are not present on or near the
Site.
Uncertainties Associated with the Human Health Risk Calculations
Risk assessment is a scientific activity subject to uncertainty.
In addition to the uncertainty, and the use of conservative
assumptions, to calculate SFs and RfDs, the analysis of
environmental conditions is difficult and inexact. The Prewitt
Abandoned Refinery risk assessment is subject to uncertainty from
a variety of sources including:
- sampling and analysis;
- toxicological data;
- exposure estimation;
- fate and transport estimation; and
- risk characterization.
Uncertainties associated with sample collection include the
representativeness of the samples; sample cross contamination;
25
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statistically significant sample size; sampling strategy; temporal
changes; and seasonal variability.
Uncertainties associated with sample analysis include the inherent
variability in the laboratory equipment; laboratory contamination;
contamination introduced during dilution; and estimated values.
Although the quality assurance/quality control program used during
the RI serves to reduce the variability, it cannot eliminate all
variability associated with sampling and analysis.
Some of the exposure scenarios at the Site required modelling to
predict contaminant concentrations, thereby increasing
uncertainties. To estimate contaminant concentrations in air
associated with showering, it was assumed that contaminant
concentrations in ground water would volatilize according to a
shower model. This model however, was validated using actual
measurements obtained by another researcher. Thus, the degree of
uncertainty is lower.
There are uncertainties ^associated with exposure estimation in
current actual and future potential exposure scenarios. The
variables and assumptions in these scenarios include activity
patterns of potential receptors, physiological variability of
individuals, and the presence and exposure of sensitive
populations. There are a number of uncertainties regarding the
assumptions made for likelihood of exposure, frequency of contact
with contaminated media, the concentration of contaminants at
exposure points, and the time period of exposure. However,
standard exposure assumptions usually err on the side of
cons ervat i sm.
The use of toxicity parameters (e.g., RfDs, HAs, and SFs)
introduces additional uncertainties. These parameters are
generally based on animal studies, many of which include exposure
to doses much higher than those actually experienced at Superfund
sites. Estimation of risk at low-dose exposures therefore requires
extrapolation of the dose-response curve developed from high-dose
studies. For non-carcinogens, uncertainty factors are often
incorporated into RfDs to account for species-to-species and/or
route-to-route extrapolations. Incorporation of these factors
serve to lower the dose-response value, resulting in more health-
protective risk estimates.
Uncertainties associated with fate and transport can be attributed
to the estimation of chemical movement through different media and
the assumption that all conditions remain constant over time. The
baseline risk assessment assumed that individuals would be exposed
to the most contaminated conditions found at the Site.
At the Site, a mixture of chemicals is present in each media. To
assess the overall effects of multiple chemicals, EPA developed
"Guidelines for Health Risk Assessment of Chemical Mixtures". This
26
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guidance states that if sufficient data are not available on the
effects of the chemical mixture of concern, or a reasonably similar
mixture, the proposed approach is to assume "additivity".
Additivity means that the risk posed by each chemical in the
mixture is determined as if that chemical existed in isolation.
Then all of the risks for each of the chemicals are added to come
up with a total risk. This assumption, according to EPA, is
expected to yield generally neutral risk estimates. More recent
guidance from EPA also references "Guidelines for the Health Risk
Assessment of Chemical Mixtures", but further states that the
assumption of additivity assumes independence of action and that if
this assumption is incorrect, over- or under-estimation of the
actual multiple substance risk could result.
Uncertainties associated with risk characterization include
potential chemical interactions (e.g. synergy). There is no
guidance for determining synergistic effects (where the whole is
greater than the sum of the parts) in risk characterization.
Therefore, it is assumed that all risks are additive.
•-s,
Uncertainties in the baseline risk assessment are a function of
risk assessments in general and a function of the uncertainties
specific to the Site in particular. Although all risk assessments
contain a certain amount of uncertainty, an attempt to reduce the
uncertainty in the Site baseline risk assessment was made whenever
possible.
Actual or threatened releases of hazardous substances from this
Site, if not addressed by the preferred alternative, or one of the
other active measures considered, may present an imminent and
substantial threat to public health, welfare, or the environment.
Remediation Goals
Sludges in an oil-water separator, waste pit contents and "hot
spots" of heavily contaminated soils are considered to be principal
threats at the site. They are considered principal threats because
of the risks they pose through direct contact, ingestion, and
inhalation risks and because of the soils' impact on ground water.
The remedial objectives for the soil and west pit contents are: 1)
to eliminate potential exposure via ingestion, inhalation, or
direct contact with contaminants and 2) to reduce the potential for
the soil to act as a continued source for ground water
contamination.
All soil in the 0' to 2' interval containing lead shall be
remediated until the lead concentration in the soil does not exceed
the action level of 500 ppm. All soil beyond the 0' to 2' interval
which contains lead in excess of 1000 ppm shall be remediated until
27
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the lead concentration in the soil does not exceed the action level
of 1000 ppm.
Hydrocarbon contaminated soils and west pit contents ("hotspots")
will be excavated and treated to a level such that a risk of 10''
is not exceeded. The remedial action level will be 0.9
benzo(a)pyrene equivalents, which translates to 0.9 mg/kg for
benzo(a)pyrene; 9.0 mg/kg for benzo(a)anthracene,
benzo(k)fluoranthene, benzo(b)fluoranthene; 90 mg/kg for chrysene;
The cleanup level of 0.9 mg/kg benzo(a)pyrene equivalents will
ensure that a risk of 10~5 is not exceeded. When carcinogenic PAHs
are found in combination with each other, their carcinogenic risks
are considered additive. Thus, when two or more carcinogenic PAHs
are found together in a location, the individual PAH concentrations
to be met following excavation, will be adjusted to meet the
cleanup standard of total sum of 0.9 mg/kg benzo(a)pyrene
equivalents. Excavated areas will be backfilled with clean soil to
further reduce exposure and risk from the excavated hot spots. The
treatment goal for soils and wastes to be left in the closed
landfarm upon complet / of treatment, should be below a
concentration of 4.5 ppm for benzo(a)pyrene (approximately a 5 X
10"5 excess cancer risk). These levels are achievable using the
landfarm treatment technology and are protective of human health
and the environment including ground water.
Upon completion of soil and west pits remedy implementation,
overall site risk is expected to be below the acceptable risk level
for non-carcinogens and approximately l X 10"6 excess cancer risk.
The hot-spots will be excavated to a level that assures no greater
than 1 X 10's excess cancer risk at the excavation depth of each hot
spot. However, when the excavated areas are back-filled with clean
soil, the actual risk at the surface where exposure is most likely
to occur will be 1 X 10* or less. The concentrations of
carcinogenic PAHs in other soils throughout the site, not
designated as hydrocarbon contaminated soils, are generally less
than detection limits (0.330 ppm). Treatment levels for
carcinogenic PAHs within the landfarm will be 4.5 benzo(a)pyrene
equivalents, which translates to; 4.5 mg/Kg benzo(a)pyrene,45 mg/kg
for benzo (a) anthracene, benzo (k) f luoranthene, benzo (b) f luoranthene;
and 45 mg/kg for chrysene. When the PAH constituents are found in
combination with each other, their carcinogenic risks will be
considered additive. Thus, the individual carcinogenic PAH
concentrations, when different PAH's are found in combination, will
be adjusted to benzo(a)pyrene equivalents, such that the total
benzo(a)pyrene equivalent concentration in the landfarm does not
exceed 4.5 mg/kg. This will ensure that the cumulative excess
cancer risk from all carcinogenic PAHs present in the landfarm,
upon closure of the landfarm, does not exceed 5 X 10'5. The treated
soils in the landfarm, which will present an excess cancer risk
less than or equal to 5 X 10"5, will be covered with a vegetative
cover upon completion of active biotreatment. Thus, the actual
28
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risk at the soil surface in the area of the landfarm will be l X
1CT6. The treatment goal prescribed for PAHs in the landfarm is
protective of human health and the environment and achievable using
landfarming technology.
The NAPL in the ground water also were determined to be a principal
threat at the Site both because of the potential exposure of the
public to the Site contaminants and because of the threat of
migration of contaminants to deeper zones of ground water. The
deeper ground water zones are used for industrial, irrigation, and
drinking water purposes. The remedial objective for NAPLs is to
prevent the exposure of potential receptors to contamination in
amounts above human health-based standards and to restore ground
water quality to MCLs.
BTEX and lead in the ground water, and lead and PAHs in the soil
were determined to be the contaminants contributing most to the
risk and the need for remediation at the Site. The remediation
goal for contaminants detected during the ground water remediation
program, including but "x3t limited to lead, benzene, toluene,
ethylbenzene and xylene "will be to treat until MCLs or State
standards, whichever is more stringent, are met in the aquifer.
MCLs are considered to be applicable or relevant and appropriate
requirements ("ARARs") because the aquifers in the area are
potential sources of drinking water. During implementation of the
remedy, all of the contaminants identified during the RI will
continue to be monitored and evaluated to determine if MCLs or
acceptable risk ranges have been exceeded. If additional
contaminated areas are found during the remediation of the Site,
these areas will be remediated using the alternative appropriate
for the contamination.
The selection of appropriate remediation levels is based primarily
on an evaluation of the potential health effects caused by human
exposure to the contaminants, assuming that the future land use
will be residential. Currently, several homes are located within
less than a quarter mile of the Site. These homes are downgradient
of the Site. Therefore, EPA has assumed that the area in which the
Site is located will continue to be residential. This is supported
by a socioeconomic study conducted on the Bluewater Uranium Mill
Vicinity which is near the town of Prewitt. The study indicates
that the area will continue to be a sparsely populated area
characterized by open rangeland and rural single family dwellings.
The report indicates the area may attract new residents to the area
who are seeking a rural lifestyle. It states that the people are
expected to be long term residents and to rely on local ground
water wells for household water use. The 1990 census data
indicates that the population in the area continues to grow.
VII. DESCRIPTION OF ALTERNATIVES
The alternatives considered for remediation of the ground water,
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NAPL areas, separator and soils at the Site are as follows:
GROUND WATER ALTERNATIVES:
Alternative
1A - No Action
IB - Restricted Use
1C - Ground Water
Extraction &
Reinj ection
ID - Vapor Extraction
NAPL ALTERNATIVES:
Alternative
2A - No Action
Remedial Activities
• Use Restrictions
• Long-Term Monitoring
• Use Restrictions
• Long-Term Monitoring
• Home Treatment Units
• Use Restrictions
• Long-Term Monitoring
• Extraction Wells'
• Reinjection Wells
• Air Stripping
• Home Treatment Units
• Use Restrictions
• Long-Term Monitoring
• Vapor Extraction Wells
• Vapor Treatment
• Home Treatment Units
Remedial Activities
• Use Restrictions
• Monitoring
2B -
2C -
Extraction Wells in
the E, F, and G
Units
Vapor Extraction E,
F and G Units;
Extracted Water
Treatment;
Produced Vapor
and NAPL
Use Restrictions
Monitoring
Extraction Wells
Air Stripping
Surface Discharge
Contract Recycling
Use Restrictions
Long-Term Monitoring
Home Treatment Units
Combination Extraction Wells
Air Injection/Air Sparging Wells
Air Stripping
Surface Discharge
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WEST PITS AREA ALTERNATIVES:
Onsite Catalytic Oxidation
Alternative
Remedial Activities
3A - No Action
3B - Native Soil Capping
3D - Thin Spreading
3E - Stabilization
SURFACE SOIL ALTERNATIVES:
None
Capping with clean soil and
vegetation
3C - Excavation/Landfarming • Excavation
• Landfarming
• Monitoring
Excavation
Enhance Natural Bi©degradation
Short-term monitoring
In-situ stabilization,
cover, vegetation
soil
Alternative
Remedial Activities
4A - No Action
None
Soils Containing Lead
4B - Excavation - Off-Site
Disposal
Soils Containing Asbestos
Excavation and Off-Site
Transportation
Stabilization as Required
Disposal in a RCRA Facility
4C - Excavation - Off-site
Disposal
Excavation and Off-Site
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Soils Containing Hydrocarbons
Transportation
Disposal in Industrial Landfill
4D - Excavation - Off-Site
Disposal
4E - Excavation - Landfarming •
4F - Thin Spreading
Excavation and Off-Site
Transportation
Disposal in Industrial Landfill
Excavation
Landfarming
Monitoring
Excavating
Enhanced Natural Biodegradation
Short-term monitoring
SEPARATOR ALTERNATIVES:
Alternative
Remedial Activities
5A - No Action
Use Restrictions
Fencing
Monitoring
5B - Excavation - Off-Site
Disposal
Excavation and Off-site
Transportation
Treatment and Disposal in Off-
site RCRA Facility
The ground water beneath the abandoned refinery has petroleum
hydrocarbon layers floating on it. This hydrocarbon layer consist
of light NAPL. The layer is the result of contaminant migration
32
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from the surface. It contains high concentrations of BTEX
constituents which are a component of petroleum products and
refinery wastes including primary separator sludges which are RCRA
listed wastes FO37.
Under current CERCLA authority, ground water contaminated with
petroleum hydrocarbon product that is commingled with a CERCLA
hazardous substance, pollutant or contaminant can be addressed.
Common Elements
This section discusses common elements of remedial alternatives
considered for the Site.
• Off-site disposal Vof discrete portions of the soil
contamination is a component of all the remedial alternatives
to reduce overall site risk.
• Each of the alternatives which require excavations,
backfilling and off-site disposal, require that the off-site
disposal occur at a appropriate permitted facility.
• Many of the alternatives require land use restrictions such
that the land could not be used in the future as a residential
area.
• All of the alternatives can be initiated within a one-year
period.
• Tne «No Action" alternative for each of the media does not
meet the remedial objectives that have been identified for the
Site. Since it has been determined that the No Action
alternative will not provide protection of human health and
the environment; it has been modified somewhat to provide for
institutional controls.
• The costs values for each alternative are estimates which are
calculated pursuant to RI/FS guidance. The cost may be up to
50% higher or up to 30% lower. One exception is the cost
estimate for thin spreading, which would be substantially
higher if a liner is required.
• The time indicated for implementation of the alternatives are
estimates.
• The Operations and Maintenance ("O & M") cost for each
alternative is an annual cost.
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GROUND WATER ALTERNATIVES:
Contaminants of Concern: Benzene, toluene, xylene, ethylbenzene,
1,2 dichloroethane, and lead
Waste Volumes: Approximately 50,000 gallons
Remediation Goals for Ground Water: Benzene (0.005 mg/1); toluene
(0.75 mg/1); ethylbenzene (0.7 mg/1); xylene (0.62 mg/1); 1,2
dichloroehtane (0.005 mg/1) and lead (0.015 mg/1)
Contingency provisions:
The goal of the remedial action is to remove the NAPL as a
continuing source of contamination to ground water and to the
maximum extent practicable, return all the units of the Sonsela
Aquifer to their beneficial use. Additionally, ground water that
is not currently a drinking water source, but is potentially a
drinking water source in the future, will be protected to levels
appropriate to its use as a drinking water source. Based on
information obtained during the remedial investigation,
supplemental sampling, and analysis of all remedial alternatives,
EPA believes that the selected remedy will achieve this goal.
Ground water contamination may be especially persistent in the
immediate vicinity of the NAPL where concentrations are relatively
high. The ability to achieve cleanup levels at all points
throughout the area of attainment, or plume, cannot be determined
until the extraction system has been implemented, modified as
necessary, and plume response monitored over time. If the selected
remedy cannot meet the specified remediation levels, which are MCLs
for all contaminants (such as but not limited to, lead, benzene,
toluene, and xylene) at any or all of the monitoring points during
implementation, the contingency measures described in this section
may replace the selected ground water remedy and remediation levels
for these portions of the plume. Such contingency measures will,
at a minimum, prevent further migration of the plume and include a
combination of containment technologies and institutional controls.
These contingency measures are considered to protect human health
and the environment and are technically practicable under the
corresponding circumstances.
The selected alternative includes ground water extraction for an
estimated period in excess of 30 years, during which time the
system's performance will be carefully monitored on a regular basis
and adjusted as warranted by the performance data collected during
operation. Modifications may include, but are not limited to, any
or all of the following :
Discontinuing pumping at individual wells where cleanup
goals have been attained.
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Alternating pumping among the various wells to eliminate
stagnation points.
Pulse pumping to allow aquifer equilibration, and to
encourage adsorbed contaminants to partition into ground
water .'
Installing additional extraction wells to facilitate or
accelerate cleanup of the contaminant plume.
Air sparging to enhance creation of the vapor phase of
the contaminants.
Ground Water Alternative 1A; Mo Action
Time to Implement: Not Applicable (NA)
Capital Cost: $ 37,600.00
O & M Cost: $ 17,800.00 per year
Present Worth Cost: $ 319,000.00
Ground Water Alternative 1A involves the following:
• Installation of 2 additional monitoring wells
• Quarterly monitoring of the 2 monitoring wells and private
wells
» Use of institutional controls to eliminate additional drinking
water wells in contaminated ground water
EPA is required by the NCP (40 CFR 300) to consider the No Action
alternative as a basis of comparison when evaluating other
alternatives. This alternative also assumes that no offsite or
onsite ground water remediation would be performed. No action
would be taken to prevent migration of contaminated ground water at
the Site. The cost associated with this alternative reflects the
cost of 1)Installation of two monitoring wells completed in the B
unit of the Sonsela Aquifer unless wells presently onsite are
determined to be acceptable for this purpose; 2) Quarterly
monitoring of two monitoring wells and two private wells for BTEX;
and 3)Use of institutional controls to eliminate the installation
of water supply wells in contaminated ground water, (i.e. New
Mexico Regulations Governing Water Supply Wells).
If the contamination within the E,F, and G Sonsela beds were to
reach the underlying deeper Sonsela beds and migrate further
offsite, future use of contaminated ground water offsite could
result in unacceptable public health risks. Since this alternative
does not provide for the Sonsela aquifer to be restored to its
beneficial use; will not ensure overall protection of human health
and the environment; compliance with ARARs; long-term or short-term
effectiveness; or, reduce toxicity, mobility or volume of hazardous
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substances it is not favored by EPA.
Ground Water Alternative IB; Restricted Use
Time to Implement: 1 year
Capital Cost: $ 44,500.00
O & M Cost: $ 40,800.00 per year
Present Worth Cost: $668,500.00
Ground Water Alternative IB involves the following:
• Installation of 2 additional monitoring wells
• Quarterly monitoring of the 2 monitoring wells and private
wells
• Use of institutional controls to eliminate additional drinking
water wells in contaminated ground water
• Installation of water treatment units on domestic wells
• Quarterly sampling of private wells at the point of
consumption
This alternative meets the NCP (40 CFR 300) requirements for the
development of an alternative that involves little or no treatment
but may provide protection of human health and the environment if
properly implemented primarily by preventing or controlling
exposure to hazardous substances.
This alternative provides for the following: 1) All the components
of Alternative 1A; 2) The installation of water treatment units on
existing domestic wells that exceed MCLs. These units are
activated carbon treatment canisters have an expected life of 10
years. They are periodically serviced and will be replaced as
needed. 3) Quarterly sampling of domestic wells at the point of
consumption to insure effectiveness of the carbon treatment units.
The carbon treatment units are considered an institutional control
and do not provide for EPA's objective to restore the ground water
to beneficial use. The alternative also does not provide for the
treatment of NAPL which is considered a principal threat at the
Site.
Ground Water Alternative 1C; Extraction/Reinfection
Time to Implement: 1 year
Capital Cost: $ 2,156,000.00
O & M Cost: $ 367,200.00 per year
Present Worth Cost: $7,957,000.00
Ground Water Alternative 1C involves the following:
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• Installation of 2 additional monitoring wells
• Quarterly monitoring of the 2 monitoring wells and private
wells
• Use of institutional controls to eliminate additional drinking
water wells in contaminated ground water
• Installation of water treatment units on domestic wells
• Quarterly sampling of private wells at the point of
consumption
• Installation of ground water extraction wells.
• Ground water treatment plant (Air stripper).
• Installation of injection wells.
The use of an extraction and reinjection well system is commonly
used to attempt to restore an aquifer to aid-in flushing. The
system removes ground water via extraction wells and then reinjects
the treated ground water into the aquifer. The reinjection wells
may be located upgradient of the contaminant plume, around the
perimeter of the contaminant plume, or interspersed with the
extraction wells. This alternative will provide for restoration of
the aquifer at a faster pace than the No Action or Restricted use
alternatives. This alternative is implementable concurrently with
the removal of the NAPL which is a source of ground water
contamination. The efficiency of the remediation system, to achieve
the remediation goals for ground water will be assessed throughout
the implementation process. The extraction system may require
modification through the remediation period due to potential
variations in ground water flow and extraction efficiency.
Ground Water Alternative ID; Vapor Extraction
Time to Implement: 5-7 years
Capital Cost: $ 2,214,500.00
O & M Cost: $ 411,700.00 per year
Present Worth Cost: $8,718,900.00
This alternative involves the following:
• Installation of 2 additional monitoring wells
• Quarterly monitoring of the 2 monitoring wells and private
wells
• Use of institutional controls to eliminate additional drinking
water wells in contaminated ground water
• Installation of water treatment units on domestic wells
• Quarterly sampling of private wells at the point of
consumption
• Installation of vapor extraction wells for the ground water
remediation of the E unit.
• Installation of rotary blowers.
This alternative employs soil vapor extraction to restore the
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aquifer. Wells are drilled across the contaminated area to just
above the saturated zone. The wells are sealed at the surface to
prevent short circuiting of air into the system. A vacuum system
induces air flow through the soil stripping the volatile
pollutants from the soil matrix into the air stream. Treatment may
be required to remove the VOCs from the air stream. Liquid water
is removed in a knock-out drum ahead of the blower and may also
require treatment. Injection of air into the ground water may be
required to enhance removal of the VOC. This alternative
remediates only contaminants that can be transported to the vapor
phase and not the actual ground water.
NAPL ALTERNATIVES:
Contaminants of Concern: Benzene,toluene, ethylbenzene, and xylene
Waste Volumes: Approximately 43,500 gallons
Remediation Goals for I""~^: Benzene (0.005 mg/1); toluene (0.75
mg/1); ethylbenzene (0.7 mg/1); and xylene (0.62 mg/1)
NAPL Alternative 2A; No Action
Time to Implement: NA
Cost: No cost associated
NAPL Alternative 2A is the No Action Alternative. EPA is required
by the NCP (40 CFR 300) to consider the No Action alternative as a
basis of comparison when evaluating other alternatives. This
alternative assumes that nothing would be done to restrict site
access or monitor offsite NAPL contamination. No monitoring,
engineering, construction or treatment is included for the removal
of a source of ground water contamination. Natural degradation and
attenuation are relied upon, under this alternative, over an
unknown period of time, to eliminate a source of contamination.
Exposure to NAPL would be controlled through the use of
institutional controls, i.e., existing New Mexico regulations that
prohibit the installation of a drinking water well in a
contaminated aquifer. No costs are associated with the
alternative. This alternative does not meet the EPA's objective of
restoration of the ground water to beneficial use.
MAPI, Alternative 2Bi Extraction
Time to Implement: 1 year
Capital Cost: $ 743,900.00
O & M Cost: $ 238,900.00 per year
Present Worth Cost: $1,785,000.00
This alternative involves the following:
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Institutional controls
Installation of NAPL extraction wells in the E, F and G units.
Ground water extraction, as necessary.
Ground water treatment, as necessary.
Disposal of NAPL to a commercial recycler.
NAPL Alternative 2B involves the pumping of NAPL from the saturated
surface of the E, F and G units of the Sonsela Aquifer. Ground
water that is concurrently removed will be treated by air stripping
and released to surface drainage in compliance with National
Pollution Discharge Elimination System (NPDES) requirements. The
NAPL that is extracted will be separated from any aqueous phase,
and sent to a commercial recycler for disposal. The goal of this
alternative is to remove the free liquid phase NAPL from the water
surface, thus, removing the primary remaining^ source of ground
water contamination.
Although this alternative addresses a significant source of ground
water contamination, it does not provide for restoration of the
aquifer to beneficial ur^^as a result of the remediation.
NAPL Alternative 2C; Vapor Extraction
Time to Implement: 7 years
Capital Cost: $ 1,429,672.00
O & M Cost: $ 430,444.00 per year
Present Worth Cost: $4,185,576.00
This alternative involves the following:
• Continued use of home treatment units throughout the period of
remediation.
• The installation of vapor extraction wells.
• The installation of combination air injection/air sparging
wells.
• The installation of a vapor treatment system.
• The installation of combination Soil Vapor Extraction (SVE)
and ground water pumping wells.
• Long term air and ground water monitoring
• Surface Discharge
• Onsite Catalytic oxidation
NAPL Alternative 2C involves the use of soil vapor recovery for
removal of the NAPL as a source of ground water contamination. A
negative pressure is imposed on the soil through a series of well
points, to sweep the contaminated zone with air, allowing the VOC
contaminants to be carried up to the surface where they are removed
from the gas stream. The VOC laden gas stream is contacted with
carbon to adsorb the VOCs from the gas. The extracted soil vapor
will be piped to an onsite treatment area. Air emissions in the
treatment area will be controlled and in compliance with all
applicable regulations. The NAPL pilot study conducted during the
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RI indicated that would be an effective method for remediating both
the NAPL and the ground water.
This alternative includes ground water remediation measures that
will be applied upon completion of the NAPL extraction phase of the
remedy.
This alternative provides for the remedial objectives pertaining to
both NAPL and ground water to be met.
WEST PITS ALTERNATIVES:
Contaminants of Concern: benzo (a) pyrene, benzo (a) anthracene,
chrysene, pyrene.
Waste Volumes: Approximately 1175.4 cubic yards
Remediation Goals for West Pit Contaminants: benzo (a) pyrene, (0.9
rog/kg) / 9-0 mg/kg for benzo (a) anthracene, benzo (k)fluoranthene,
benzo(b)fluoranthene; 90 mg/kg for chrysene; 82,330 mg/kg pyrene;
and 220 mg/kg for benzene.
West Pits Area 3A; No Action
Time to Implement: NA
Cost: No Cost Associated
As previously stated, EPA is required by the NCP (40 CFR 300) to
consider the No Action alternative as a basis of comparison when
evaluating other alternatives. The No Action alternative would not
involve any remedial actions. The Site would remain as it exists
at the present time. This alternative does not meet the remedial
objectives set for this area.
West Pits Area Alternative 3B: Native Soil Cap
Time To Implement: 1 Year
capital cost: $ 27,300.00
O & M Cost: $ 0.00
Present Worth Cost: $ 27,300.00
This alternative involves the following:
• Use restriction for residential scenario
• Placement of a soil cap
• Revegetation
This alternative meets the NCP (40 CFR 300) requirements for the
development of an alternative that involves little or no treatment
but may provide protection of human health and the environment if
properly implemented primarily by preventing or controlling
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exposure to hazardous substances.
West Pits Area Alternative 3B involves the capping of the pits with
two feet of native soil to recontour the area and to remove local
depressions. Approximately 1300 cubic yards of native soil would
be placed in compacted lifts over the surface of the pits. The
area would be seeded for revegetation with native plant species.
Due to the arid conditions at the Site, it is not known if the
grass for the vegetative cover will grow thus erosion of the cover
may occur.
West Pits Area Alternative 3C; Excavation/Landfarming
Time to Implement: 1 year
Capital cost: $862,300.00
O & M cost: $150,100.00 per year
Present Value Cost: $1,142,400.00
This alternative includes the following:
• Excavation of the west pits contents and contaminated soils
• Landfarming of excavated materials
• Monitoring of degradation of contaminants and of migration of
contaminants into deeper zones.
Landfarming, or land treatment, involves tillage, fertilization and
irrigation of the contaminated soil in a controlled treatment area
to maximize biological degradation of the contaminants.
Landfarming has been used effectively throughout the country on
contaminated soils similar to those found at the Site. The process
relies on aerobic digestion, generally by naturally occurring
microorganisms, under conditions designed to maximize aerobic
biological activity. Removal by volatilization and
photodegradation may also occur. The soil containing hydrocarbons
would be consolidated in a central location within an area of
contamination ("AOC") and would be landfarmed.
A landfarming treatability study was conducted to determine the
effectiveness of landf arming on the waste in the west pits area.
The results of the treatability study were that without the
addition of nutrients and moisture only 44 % reduction in
contaminants were achieved. The addition of nutrients and moisture
will improve the reduction of contaminants to approximately 90%
following 12 weeks of treatment.
The landf arm would be constructed in the western end of the site
and would consist of runon-runoff protection, near flat treatment
area, irrigation system, and a nutrient addition system. Treatment
would consist of mechanically working the material to allow air to
penetrate, and providing moisture and nutrients at near optimal
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conditions during allowable weather. Monitoring of the soil PAH
content would be performed to measure degradation until the
remedial action objectives/goals are met.
It is expected that within 2 years from implementation, the risk
posed by the waste pits will be reduced such that residential use
of the property can occur. This alternative is expected to meet
all ARARs regarding landfarming. Since treatment will occur within
the AOC, the movement of waste will not constitute placement; thus,
RCRA's Land Disposal Restrictions ("LDRs") , 40 CFR 268, are not
ARARs.
Since this alternative provides for monitoring of the vadose zone
to ensure that contaminants are not migrating into the deeper
zones, a liner is not necessary. The decision not to include a
liner is also based on the finding that the materials to be treated
in the landfarm contain relatively low concentrations of mobile
constitutents such as BTEX. If monitoring indicates that migration
is occurring, a liner will be incorporated into the treatment area.
This alternative meets the remedial objectives and reduces the
toxicity, mobility, and volume of the waste through treatment.
The main disadvantage of this alternative is that it relies on
microorganism to degrade the contamination. These microorganism
depend on water and sunlight and favorable temperature; thus, the
effectiveness of this alternative is weather dependent.
West Pits Area Alternative 3D; Thin Spreading
Time to Implement: 1 year
Capital Cost: $ 113,700.00
O & M Cost: $ 22,200.00 per year
Present Worth Cost: $ 134,800 *
* This cost does not include the cost associated with a liner which
would be required to prevent migration of contaminants. A liner
would be required due to uncertainty of achieving adequate
treatment of wastes in the treatment zone. Requiring a liner would
substantially increase the cost of thin spreading.
This alternative involves the following:
Excavation of the pit material
Backfilling the excavated areas
Spreading of the pit materials on uncontaminated soils
Tilling the surface soil in the treatment area
Implementing a Soil monitoring program
West Pits Area Alternative 3D involves excavating the pits to the
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bottom of the tarry material and stockpiling that material. The
excavated pit material would then be spread over an area of
approximately five acres. The material would be mechanically
worked to generate a maximum of surface area to allow for an
increase in biodegradation. The excavations would then be
backfilled and the Site leveled after treatment is completed.
Treatment will be determined through the soil monitoring.
Thin spreading is a form of landfarming, but based on a
treatability study conducted by the PRPs it will not be able to
meet RCRA 40 CFR 264.270 subpart M requirement to maximize
biodegradation, and may not be able to ensure degradation of
contaminants in the treatment zone prior to transport into ground
water. In analyzing the composite waste samples for the
treatability study, it was determined that due to a deficiency in
nitrogen and phosphorous, fertilizer will be required for
biological treatment to occur. The study also indicates that
moisture control will be an important factor for effective
biodegradation.
The results of the treatability study were that without the
addition of nutrients and moisture only 44 % reduction in
contaminants can be achieved. The addition of nutrients and
moisture will improve the reduction of contaminants to
approximately 90%. Thus, without the addition of nutrients or
moisture, the degradation of the waste was not maximize and the
remedial objectives for the area may not be reached.
Due to the lack of vadose zone monitoring, a liner to prevent
migration of contaminants to the ground water would be required
under this alternative. Due to the large area required for thin
spreading, installation of a liner would raise the cost
substantially over that presented in the proposed plan.
West Pits Area Alternative 3E; Stabilization
Time to Implement: 1 year
Capital Cost: $ 83,400.00
O & M Cost: $ 0.00
Present Worth Cost: $ 83,400.00
This alternative includes:
• Stabilization of Pit Materials
• Placement of Soil Cover on the treatment area
• Establishing a Vegetative Cover on the Soil Cover
• Use restriction for residential scenario
Stabilization is a means of minimizing the risks associated with
the hazardous waste by limiting the solubility and mobility of
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contaminants thus, minimizing their potential for leaching into the
ground water and thus preventing ingestion or direct contact.
West Pits Area Alternative 3E involves mixing the top two feet of
the pit contents with lime and compacting the material back into
the excavation. This compacting will form a stable base over which
soil can be placed and contoured to eliminate ponding. The area
would then be seeded with native species. Although this
alternative meets the remedial objectives set for the West Pits
area, land use restrictions would prevent the property from being
used for residential purposes.
Some test work would need to be done to develop an appropriate mix
design for the use at the Site. Due to high organic levels
detected at the Site, stabilization may not be effective, and thus,
may not produce a permanent remedy. This alternative reduces
mobility of the contaminants but it does not reduce volume or
toxicity through treatment.
SURFACE SOIL ALTERNATIVES:
Contaminants of Concern: Lead, benzo(a)pyrene, benzo(a)
anthracene, anthracene, chrysene, pyrene, phenanthrene, asbestos
Waste Volumes: Lead contamination approximately 664.4 cubic yards;
asbestos contaminated soils and materials at least 15 cubic yards;
hydrocarbon contaminated soils approximately 1500 cubic yards
Remediation Goals: Hydrocarbon contaminated soils: 0.9 mg/kg
for benzo(a)pyrene; 9.0 mg/kg for benzo(a)anthracene,
benzo(k)fluoranthene, benzo(b)fluoranthene; 90 mg/kg for chrysene;
82,330 mg/kg pyrene; and 220 mg/kg for benzene.
All asbestos containing material; Lead contaminated soils: 0' to
2' interval 500 ppm. Beyond the 0' to 2' interval 1000 ppm
Surface Soils Alternative 4A: No Action
Time to Implement: NA
Cost: No Cost Associated
EPA is reguired by the HCP (40 CFR 300) to consider the No Action
alternative as a basis of comparison when evaluating other
alternatives. The no action alternative would not involve any
remedial actions. The Site would remain as it exists at the
present time. The No action alternative does not provide for means
to eliminate or control exposure to contaminated soils, nor does it
provide for treatment.
Surface Soils Alternative 4B; Lead contamination; Excavation - Qff-
Site
Time to Implement: 1 year
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Capital Cost: $ 1,605,000.00
O & M Cost: $ 0.00
Present Worth Cost: $ 1,605,000.00
This alternative involves the following:
• Excavation of lead-contaminated soil
• Transport of the soil
• Chemical stabilization (if required)
• Disposal of the soil in a RCRA landfill
Lead alternative 4B involves the excavation of soil containing lead
at concentrations above the 500 ppm action level at the 0' to 2'
interval and above 1000 ppm at beyond the 2'depth. The soil will
be chemically stabilized onsite if the material exhibits the
characteristic of lead toxicity under RCRA (See EPA hazardous waste
number D008 under 40 CFR 261.24) prior to transporting it the
material to a RCRA landfill for disposal. The RCRA landfill will
be required to be permitted for the disposal of lead contaminated
soils. Stabilization has been shown to be a proven technology for
treating lead. This alternative meets the remedial action
objectives for lead contaminated soil, it provides for treatment as
necessary and eliminates the potential for human health and the
environment to be exposed to lead.
Surface Soil Alternative 4C; Asbestos Contamination; Excavation -
Off-Site Disposal
Time to Implement: 1 Year
Capital Cost: $ 9,300.00*
0 & M Cost: $ 0.00
Present Worth Cost: $ 9,300.00*
*At the completion of the removal which occurred during the RI, it
was determined that approximately 15 cubic yards of asbestos
contaminated soils remained. The cost shown is based on the removal
of only excavating approximately 15 cubic yard. The cost may be
higher due to the requirement to removal all asbestos-contaminated
soil and material.
This alternative involves the following:
• Excavation of the asbestos material
• Containerizing the asbestos material
• Transport asbestos material
• Disposal of the asbestos material in an asbestos-approved
landfill
Asbestos Alternative 4C involves the excavation of soil containing
asbestos and any additional asbestos containing materials (ACM)
present at the Site. The ACM is a result of the dismantling of the
refinery building and machinery. Approximately 800 cubic yards of
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ACM was removed from the Site in 1991 by the PRPs. The removal
occurred as a health and safety precaution for workers on Site.
Post removal investigations revealed 5 locations that still contain
ACM. These pockets of remaining ACM will be excavated, placed in
sealed containers, transported to and disposed in an approved
landfill. During the removal activities, air monitoring will be
performed in accordance with Occupational Safety and Health
Administration ("OSHA") (29 CFR 1910) and National Emissions
Standards For Hazardous Air Pollutants ("NESHAP") requirements.
This method of asbestos abatement is an acceptable practice. This
alternative will eliminate the possibility of exposure to asbestos
containing material at the Site. This alternative meets the
remedial action objectives pertaining to the asbestos contaminated
soils.
Surface soil Alternative 4P; Hydrocarbon Contamination;
Excavation - Off-Site Disposal
Time to Implement: 1 Year
Capital Cost: ^y 681,300.00
O & M Cost: $ 0.00
Present Worth Cost: $ 681,300.00
This alternative involves the following:
• Excavation of the hydrocarbon material.
• Transportation of the material off-site.
• Disposal of the material in a landfill.
• Backfill of the excavations.
Hydrocarbon Alternative 4D involves the selective excavation of
major surface deposits of hydrocarbon material. The quantity of
this material is estimated to be 1,500 cubic yards, approximately
58 truckloads. This material would be loaded into trucks and
transported to the nearest landfill that is permitted to accept the
hydrocarbon contaminated soils. The excavations would then be
backfilled. RI data indicates that some of the PAH concentrations
in hydrocarbon contaminated soils exceed levels permissible for
land disposal of refinery related hazardous wastes. Thus, offsite
land disposal which constitutes placement without treatment would
not meet ARARs.
Surface Soil Alternative 4E; Hydrocarbon Contamination; Excavation
—LandFarminq
Time to Implement: 1 year
Capital Cost: $ 875,600.00*
O & M Cost: $ 150,100.00 per year
Present Value Cost: $ 1,286,300.00
* The cost incurred for this alternative will be lower than
presented in this Proposed Plan and in FS report. This is due to
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the fact that many of these cost have already been taken into
account in Alternative 3C. ^^
This alternative involves the following:
• Excavation of the hydrocarbon contaminated soils throughout
the Site
• Consolidation of excavated materials with the West Pits
materials
• Landfarming of excavated materials
• Monitoring of degradation of contaminants and of migration of
contaminants into deeper zones.
Alternative 4E involves the excavation and consolidation of the
major hydrocarbon occurrences in a prepared landfarm site. The
landfarm would be the same as the one constructed for Alternative
3C. This is acceptable since the waste are compatible and
conducive of being landfarmed together and since the contamination
is in one AOC; thus, p"Cement would not be occurring and LDRs
would not be applicable, relevant or appropriate. This alterative
meets the remedial action objective for residential use by
providing risk levels that are within the EPA's acceptable risk
range. Risk is expected to be reduced to levels acceptable for
residential use within two years after the start of landfarming.
A landfarming treatability study was conducted to determine the
effectiveness of landfarming on the hydrocarbon contaminated soils
and similar waste in the west pits area. The results of the
treatability study were that without the addition of nutrients and
moisture only 44 % reduction in contaminants can be achieved. The
addition of nutrients and moisture will improve the reduction of
contaminants to approximately 90%.
The landfarm would be constructed in the western end of the site
and would consist of runon-runoff protection, near flat treatment
area, irrigation system, and a nutrient addition system. Treatment
would consist of mechanically working the material to allow air to
penetrate, and providing moisture and nutrients at near optimal
conditions during allowable weather. Monitoring of the soil PAH
content would be performed to measure degradation until the
remedial action objectives/goals are met.
It is expected that within 2 years from implementation, the risk
posed by the hydrocarbon contaminated soils will be reduced such
that residential use of the property can occur. This alternative
is expected to meet all ARARs regarding landfarming. Since
treatment will occur within the AOC, the movement of waste will not
constitute placement; thus, RCRA's Land Disposal Restrictions
("LDRs"), 40 CFR 268, are not ARARs.
As indicated by the treatability study, sufficient biodegradation
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of pollutants to be landfarmed should occur within the treatment
zone of the landf arm. Since the materials to be landf armed, contain
relatively small concentrations of mobile contaminants such as
BTEXs and since this alternative provides for monitoring of the
vadose zone to ensure that contaminants are not migrating into the
deeper zones, a liner is not necessary. If monitoring indicates
that migration is occurring, a liner will be incorporated into the
treatment area.
This alternative meets the remedial objectives and reduces the
toxicity, mobility, and volume of the waste through treatment.
The main disadvantage of this alternative is that it relies on
microorganism to degrade the contamination. These microorganism
depend on water and sunlight and temperature dependent; thus, the
effectiveness of this alternative is weather dependent.
Surface Soil Alternative 4F: Hydrocarbon Contamination; Thin
Spreading
r - -* s
Time to Implement: 1 year
Capital Cost: $ 134,900.00
O & M Cost: $ 22,200.00 per year
Present Worth Cost: $ 156,000.00
This alternative involves the following:
Excavation of the hydrocarbon material
Transportation to the west end of the Site
Backfill of the excavations
Thin spreading of the material
Tilling into the surface
Hydrocarbon Alternative 4F involves the excavation of major surface
deposits of hydrocarbon material, and transporting the material to
the west end of the Site, inside the fenced area. The areas
excavated would then be backfilled. The excavated material
(approximately 1,500 cubic yards) would then be spread over an area
of approximately five acres. The material would be mechanically
worked to generate a maximum of surface area to allow for an
increase in biodegradation. The excavations would then be
backfilled and the Site leveled after treatment is completed.
Treatment will be determined through the soil monitoring.
Thin spreading is a form of landf arming, but may not be able to
meet RCRA 40 CFR 264.270 subpart M requirement to maximize
biodegradation or to ensure degradation of contaminants in the
treatment zone prior to transport into ground water. In analyzing
the composite waste samples for the treatability study, it was
determined that due to a deficiency in nitrogen and phosphorous,
fertilizer will be required for biological treatment to occur.
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The results of the treatability study were that without the
addition of nutrients and moisture only 44 % reduction in
contaminants can be achieved. The addition of nutrients and
moisture will improve the reduction of contaminants to
approximately 90%. Thus, without the addition of nutrients or
moisture, the degradation of the waste was not maximize and the
remedial objectives for the area may not be reached.
SEPARATOR ALTERNATIVES:
Contaminants of Concern: Lead, Benzene, Toluene, Ethylbenzene, and
Xylene
Waste Volumes: Approximately 80 cubic yards
Remediation Goals: complete removal of all separator contents.
Separator Alternative SA; No Action
Time to Implement: less than 1 year
Capital Cost: $ 3,700.00
O & M Cost: $ 200.00 per year
Present Worth Cost: $ 7,200.00
The No Action Alternative would consist of installing a fence
around the separator. Warning signs would be affixed to the fence
to prevent unauthorized access. The posting of warning signs
provide for implementation institutional controls; yet does not
provide for remediation of the separator contents which posed a
risk to human health and the environment. This alternative is not
favored by EPA because it does not meet the remedial objectives
established for the separator and its contents.
Separator Alternative SB; Excavation - Off-site Treatment
Time to Implement: 1 year
Capital Cost: $ 116,000.00
O & M Cost: $ 0.00
Present Worth Cost: $116,000.00
This alternative involves the following:
• Excavation of separator contents
• Transport of the contents
• Treatment to meet LDR limits
• Disposal of the contents at a RCRA facility
Separator Alternative 5B involves the excavation of the separator
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contents by pumping or mechanical excavation, loading into trucks,
and hauling the contents off-site to a permitted RCRA landfill.
The waste shipped off-site will be treated at the disposal site as
required in order to comply with RCRA disposal requirements. The
separator contains approximately 83 cubic yards of material that
will require approximately 4 trucks.
After the separator contents are removed, holes will be broken into
the bottom to permit drainage and the sampling of soil below the
separator. If contaminated soil is found beneath the separator,
additional remediation will be performed. Provided the soils are
amenable to landfarming, they will be included with the landfarmed
wastes. If not, they will be treated by other methods such as, but
not limited to, soil washing or off-site incineration. After all
separator contents and associated contaminated soils have been
removed, the separator will be backfilled with local material.
If any of these treatment alternatives are necessary, either an
explanation of significant difference or an amendment to the ROD
pursuant to the NCP will be issued.
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The nine criteria used to evaluate each alternative identified in
the FS are as follows:
- Overall protection of human health and the environment;
- Compliance with applicable or relevant and appropriate
requirements;
- Long-term effectiveness and permanence;
- Reduction of toxicity, mobility, or volume through
treatment;
- Short-term effectiveness;
- Implementability;
- Cost;
— State/Support Agency Acceptance; and
- Community acceptance.
These nine criteria are categorized into three groups. The first
group contains what are referred to as the Threshold Criteria.
These criteria are: 1) Overall Protection of Human Health and the
Environment and 2) Compliance with Applicable or Relevant and
Appropriate Requirements. In order for a remedial alternative to
be selected, it must satisfy both Threshold Criteria. The second
group of criteria contains what are referred to as the Primary
Balancing Criteria. These criteria include: 1) Cost Effectiveness,
2) Short Term Effectiveness, 3) Long-Term Effectiveness, 4)
Reduction of Toxicity, Mobility, and Volume of Contaminants Through
Treatment, and 5) Implementability. These criteria are used to
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weigh major tradeoffs among alternatives in making the final remedy
selection decision. The third group of criteria are referred to as
the Modifying Criteria. The criteria consist of 1) State
Acceptance and 2) Community Acceptance. These criteria are
considered by EPA in making its final remedy selection decision.
THRESHOLD CRITERIA
Overall Protection of Human Health and Environment addresses
whether or not a remedy provides adequate protection and
describes how risks posed through each pathway are eliminated,
reduced, or controlled through treatment, engineering controls
or institutional controls.
Compliance with ARARs addresses whether or, not a remedy will
meet all of the applicable or relevant and appropriate
requirements of other Federal and State environmental statutes
and/or provide grounds for invoking a waiver.
PRIMARY-BALANCING CRITERIA
Long-term effectiveness and permanence refers to the magnitude
of residual risk and the ability of a remedy to maintain
reliable protection of human health and the environment over
time once cleanup goals have been met.
Reduction of toxicity, mobility, or volume through treatment
is the anticipated performance of the treatment technologies
that may be employed in a remedy.
Short-term effectiveness refers to the speed with which the
remedy achieves protection, as well as the remedy's potential
to create adverse impact on human health and the environment
that may result during the construction and implementation
period.
Implementability is the technical and administrative
feasibility of a remedy, including the availability of
materials and services needed to implement the chosen
solution.
Cost includes capital and operation and maintenance costs.
MODIFYING CRITERIA
State Acceptance indicates whether, based on its review of the
RI/FS and Proposed Plan, the State concurs with, opposes, or
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has no comment on the preferred alternative.
The Community Acceptance includes determining which components
of the alternatives interested persons in the community
support, have reservations about, or oppose.
A symbolic ranking of the comparative analysis for the each of the
remedial alternatives is included as part of this ROD (see Table
8) . The symbolic ranking is based on the narrative analysis that
follows.
REMEDY SELECTION CRITERIA ANALYSIS
Based on current information, the preferred alternatives 1C, 2C,
3C, 4B, 4C,4E, and 5B appear to provide the best balance between
the alternatives with respect to the nine criteria that EPA uses to
evaluate alternatives. This section describes the performance of
the preferred alternatives against the nine criteria and discusses
how each portion compares to other alternatives in the same
category within this Proposed Plan.
WEST PITS AREA, SURFACE SOILS, AND SEPARATOR ALTERNATIVES
THRESHOLD CRITERIA
Criterion 1, Overall Protection of Human Health and the Environment
The No Action alternative for all the west pits area, the surface
soils and the separator does not provide protection of human health
and the environment. Therefore, it will not be discussed further in
the criteria analysis.
West Pits Area Alternatives
Alternative 3C provides for the reduction of risks posed by the
waste pits and its contents to meet remediation goals, through the
use of landf arming. This alternative is protective of human health
and the environment. It is expected that the West Pits and
landfarmed areas will be able to be used for residential purposes
upon completion of the landf arming and landf arm closure. Monitoring
programs will be established to ensure that contaminants are not
leaching into the ground water during implementation; thus,
providing protection of the ground water. Of the alternatives
discussed, this alternative provides the highest degree of
protectiveness to human health and the environment by reducing
exposures to remediation goal levels. This alternative provides
for treatment and for a reduction in mobility, toxicity and volume.
The treatability study conducted during the Rl demonstrated that
90% of the waste could be reduced with the addition of controlled
amounts of water and nutrients. Also, this alternative provides
long-term effectiveness and permanence since the waste will be
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treated until the remedial objectives are met; thus, a risk to
human health and the environment will be eliminated. Monitoring of
potential contaminant release and the optional addition of a
liner, if necessary based on monitoring results, will provide
protection of human health and the environment through prevention
of contaminant migration until remediation is complete.
Human health and the environment may be protected by alternative 3B
through the elimination of the physical hazard and isolation of the
wastes in the pits as they now exist. The cap would eliminate the
potential for storm water collection in the depressions. For the
residential scenario, restrictions would be required to prevent
construction of housing in the West Pits Area to ensure the
integrity of the cap. It will reduce exposure to remediation
goals; however it does not provide for overall,protection because
treatment is not taking place. Since the alternative does not
provide for continual maintenance, the potential for erosion of the
protective cap exists, making it less effective in the long term.
It is doubtful that Alternative 3D will be protective of the human
health and the environment by utilizing the natural degradation of
the pit contents. Natural degradation may eventually result in a
reduction of risk to levels that would be acceptable for
residential use. Yet, the thin spreading alternative does not
ensure substantial treatment of contaminants in the treatment zone
and does not provide for monitoring of the vadose zone or of the
treated soils; thus, a liner would be required to prevent migration
of the contaminants into the ground water in order for this
alternative to provide adequate protection of human health and the
environment. Thin spreading may not be able to meet the RCRA
requirement to ensure degradation of contaminants in the treatment
zone prior to transport into ground water; therefore, it may not be
protective of human health and the environment. The treatability
study conducted on the west pit waste material indicated that
initially the waste degraded rapidly, then remained unchanged until
nutrients and moisture were added. In analyzing the composite
waste sample used in the treatability study, it was determined that
due to a deficiency in nitrogen and phosphorous, fertilizers would
be needed to promote degradation of the waste. Since in the thin-
spreading alternative nutrients and water are not included, the
possibility of achieving the remedial objectives for the west pits
is low.
Alternative 3E may be protective of human health and the
environment by removing the physical hazards now associated with
the West Pits area. It may be protective of the environment
through the chemical stabilization of hydrocarbons near the soil
surface. Yet, due to the high organic content of the waste found
at the Site, it is not known whether the waste would be effectively
stabilized. Under the residential scenario, restrictions would be
required to prevent the construction of housing in the West Pits
area to prevent disturbance of the stabilized material.
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Alternative 3E may not reduce exposure to within remediation goals.
Surface soils Alternatives
The risk associated with lead will be reduced with alternative 4B
by removing soil from 0' to 2' depth which contains lead above the
action level of 500 ppra. Soils beyond the 2' depth will be
remediated to an action level of 1000 ppm. Risks due to potential
exposure to inhalation of asbestos would be eliminated by
alternative 4C. Both of these alternatives provide the highest
degree of protection to human health and the environment for soil
contaminated with lead and asbestos by addressing areas of elevated
levels of contamination. Also, by properly disposing of the
contaminated soils and materials off-site the' highest degree of
overall protection is provided.
As with Alternative 3C, Alternative 4E (both are landfarming
alternatives) provides the highest degree of protection to human
health and the environment of any of the west pits alternatives
discussed. Monitoring programs will be established to ensure that
contaminants are not leaching into the ground water during
implementation, thus providing protection of the ground water.
This alternative provides for treatment and for a reduction in
mobility, toxicity and volume. The treatability study conducted
during the RI demonstrated that 90% of the waste could be reduced
with minimal amounts of water and nutrients. Also, this
alternative provides long-term effectiveness and permanence since
the waste will be treated until the remedial objectives are met;
thus, risk to human health and the environment will be reduced.
Alternative 4D is protective of human health and the environment in
that it removes most of the hydrocarbon material from the Site,
thereby reducing levels of exposure to meet remediation goals.
Treatment of the waste may be necessary prior to disposal in an
off-site RCRA permitted landfill.
It is doubtful that Alternative 4F will be protective of human
health and the environment by utilizing the natural degradation of
the hydrocarbon contaminated soils. Thin spreading may not be able
to meet the RCRA requirement to maximize biodegradation. Moreover,
thin spreading may not be able to meet the RCRA requirement to
ensure degradation of contaminants in the treatment zone prior to
transport into ground water; therefore, it may not be protective of
human health and the environment. Degradation which takes place
under thin spreading may not be sufficient to meet cleanup levels
for the Site. The treatability study conducted on the west pit
waste material indicated that initially the waste degraded rapidly,
up to 44% of the organic compounds, then remained unchanged until
nutrients and moisture were added. In analyzing the composite
waste sample used in the treatability study, it was determined
that, due to a deficiency in nitrogen and phosphorous, fertilizers
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would need to be added to enhance degradation. Since in the thin-
spreading alternative nutrients and water are not included, the
possibility of ever achieving the remedial objectives for the west
pits is very low.
Separator Alternatives
Through Alternative SB, the potential risks due to contact and
ingestion of the separator sludge would be eliminated due to the
removal of the sludge. The potential exists for soils under the
separator to be contaminated and thus a risk to human health and
the environment as well as a source of ground water contamination.
This alternative provides protection to human health by specifying
that this contamination source, if present, .will be addressed.
Thus, the public will not be affected by any contamination stemming
from any leaking from the separator or the soils located underneath
the separator. This alternative is protective of human health and
the environment.
Criterion 2, Compliance with ARARs
The Navajo Superfund Office has indicated that Tribal ARARs do not
exist. Consequently, Tribal ARARs are not discussed.
a
New Mexico is authorized under RCRA to operate its hazardous waste
management program in lieu of the Federal RCRA programs. When
Federal RCRA requirements are cited in the description of ARARs
which follows, the intention is also to reference the corresponding
New Mexico regulation if the New Mexico regulations are applicable.
Table 9 lists the ARARs that apply to the West Pits and Surface
Soils and Separator Alternatives.
West Pits Area
There are no chemical- or location-specific ARARs that apply to the
West Pits Area. The treatment taking place is in-situ within one
area of contamination (AOC); thus, placement will not be occurring
and LDRs will not be applicable, relevant or appropriate. RCRA 40
CFR Part 264, Subpart M is considered an action-specific
requirement for the thin spreading and landfarming alternatives
(Part 264 Subpart M subsumes Part 265 Subpart M). Compliance with
the requirements set forth in RCRA 40 CFR Part 264, Subpart M will
help ensure that contaminants do not migrate beyond the treatment
zone in concentrations above risk based levels. This is an
equivalent requirement to assuring "No-Migration" under the LDRs.
State of New Mexico Underground Storage Tank (UST) Regulations
address cleanup criteria for hydrocarbon contaminated soils.
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However, since the West Pits contain relatively little of the BTEX
constituents such as are contained in the contaminated soils
regulated by the New Mexico Underground Storage Tank regulation,
EPA believes these standards are most appropriately standards "To
Be Considered". EPA considered the UST standards and determined
that since the waste contains little of the mobile BTEX material,
such as is contained in the soils contaminated with petroleum
products which are contemplated in the UST regulations, these UST
regulations would not be applied.
Landfarming, when implemented properly, will meet the action
specific ARARs of RCRA 40 CFR Part 264, Subpart M, and is
demonstrated to result in significant (i.e. 95 to 99%) reduction of
toxic organic compounds such as PAHs.
The effectiveness of thin spreading to ensure treatment of
contaminants within the treatment zone, as required by RCRA 40 CFR
Part 264, Subpart M, is less certain. Thin spreading does not
include unsaturated zone monitoring to detect contaminant leachate.
Thus, thin spreading, as presented in the FS, will not comply with
RCRA 40 CFR.Part 264, subpart M requirements.
RCRA closure requirements (RCRA 40 CFR Part 264, Subparts G and M)
for landfarming are action ARARs for the landfarming and thin
spreading alternatives. The thin spreading alternative will not
comply with RCRA closure requirements. The landfarming alternative
will include a soil cover and monitoring upon completion of
biodegradation to comply with closure requirements.
Surface Soils
The remedial action goal for the lead contaminated soil is 500 ppm,
or 1000 ppm beyond two foot excavation depth. The presence of the
lead in the soil may result in designation of the excavated soil as
exhibiting the characteristic of lead toxicity under RCRA, EPA
hazardous waste number D008 under 40 CFR Part 261.23.
Consequently, the soil will be treated onsite to satisfy the LDRs
(40 CFR Part 268) which set treatment standards for D008
characteristic wastes prior to land disposal in a compliant RCRA
permitted landfill.
There are no location-specific ARARs for the lead excavation
alternative.
The 500 - 1000 ppm action level is a range set by EPA in Office of
Solid Waste and Emergency Response ("OSWER") Directive #9355.4-02.
The exact action level is selected based on site-specific factors.
Some of the soils containing high lead may also contain either
F037- or F052- RCRA hazardous wastes. Review of data in the RI,
indicates that contaminants, other than lead, in the high lead
soils are below levels that can be land disposed pursuant to the
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LDRs. In the event that EPA finds soils that must be removed, due
to high lead content, which also contain high concentrations of
organic constituents in excess of the LDR limits, a ROD amendment
will be necessary to address those soils.
Under 40 CFR Part 61, Subpart M, if asbestos containing material
(ACM) is found improperly disposed of, it must all be removed down
to background levels. There is no ACM located in background
samples at the Site; thus, all ACM would have to be removed. Part
61 subpart M is a chemical-specific ARAR for asbestos at the Site
and shall be met. All asbestos-contaminated material which is
removed will be sent to an approved landfill. There are no
location-specific ARARs for the asbestos removal alternative.
There are no chemical-specific ARARs which address hydrocarbons in
soil. RCRA treatment, storage, disposal and transportation
regulations and LDRs are considered ARARs for Alternative 4D.
There are no chemical specific ARARs for the remedial alternatives
discussed for surface soils containing hydrocarbons. There are no
location-specific ARARs for Alternative 4E and 4F. Landfarming
RCRA requirements inclusive of closure requirements are considered
action-specific ARARs for Alternatives 4E and 4F. Since treatment
will be occurring within the AOC, placement will not be occurring;
therefore, land disposal restrictions are not considered ARARs for
4E and 4F. EPA considered the UST standards and determined that
since the waste contains little of the mobile BTEX material, such
as is contained in the soils contaminated with petroleum products
which are contemplated in the UST regulations, these UST
regulations would not be applied.
Separator
With Alternative 5B, there are no chemical-specific ARARs which
address the separator residues remaining in the unit. LDRs (40 CFR
Part 268) which require that waste be properly disposed in a
permitted facility are action-specific ARARs that apply to this
alternative. When the residues are removed for disposal, they will
be manifested as RCRA hazardous waste number F037 (40 CFR §261.31)
primary separator sludges, or as D008 or D018 (if they exhibit the
toxicity characteristic for lead or benzene respectively)(40 CFR §
261.24), and will be treated to comply with LDRs prior to disposal
at an approved RCRA disposal facility. There are no location-
specific ARARs for the separator residue removal alternative. Of
the action alternatives considered for the separator, this
alternative most meets ARARs.
PRIMARY -BALANCING CRITERIA
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Criterion 3, Long—Term Effectiveness and Permanence
West Pits Area
Alternative 3B is only as permanent as the cap itself. Provided
the cap is effective, this alternative would meet the remedial
action objective for the residential scenario by controlling or
eliminating exposure from PAHs. Some constituents may continue to
leach to ground water under Alternative 3B; and therefore, would
not meet the remedial objective and would not be providing an
effective or permanent remedy.
Alternative 3C provides the highest degree of long-term
effectiveness because it will treat the hydrocarbon contained in
the pits through enhanced biodegradation and'will eliminate the
need for operation and maintenance. Bench-scale testing has shown
that landfarming can be effective in treating hydrocarbons. The
waste reduction achieved in the treatability study was 90%. This
alternative provides for risk levels to be reduced such that
residential use of the c.'." x-a can occur. This alternative provides
a long-term and permanent solution.
There is little certainty that Alternative 3D, thin spreading, will
reduce the health risk and contaminant migration to ground water
may occur. The long-term effectiveness of this alternative is
uncertain. The treatability study conducted on the west pit waste
material indicated that initially the waste degraded rapidly up to
about 44 % degradation, then remained unchanged until nutrients and
moisture were added, and since the thin-spreading alternative does
not require the addition of nutrients and moisture, the long-term
effectiveness criteria may not be met. Thin spreading waste may
also increase long-term risks if contaminants are very slowly
degraded.
Alternative 3E may reduce the magnitude of residual risk to meet
the remedial action objective for the residential scenario, by
controlling or eliminating exposure from PAHs. High organic
content waste is difficult to stabilize, and the waste at the Site
has high organic content. Therefore, long term effectiveness of
Alternative 3E is doubtful. The physical hazards posed by the West
Pits will be permanently eliminated from the Site under Alternative
3E.
Surface soils
Alternative 4B will provide for the highest degree of long-term
effectiveness for the lead contaminated soils because all
contaminated soil will be excavated, treated, and disposed of
off site thereby eliminating operation and maintenance requirements.
Alternative 4B will reduce the magnitude of residual risk to meet
the remedial objective to control or eliminate exposure to lead
contaminated soils. Since soil containing lead in concentrations
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above the action level will be removed from the Site, the action
will maintain adequate and reliable protection for human health and
the environment over time. Backfilling of excavated areas will
eliminate potential physical risk and will eliminate any residual
risk by reducing exposure to deeper soils. This alternative will
be effective in the long term and permanent.
Alternative 4C for the asbestos containing soils will provide for
the highest degree of long-term effectiveness because all
contaminated soil will be excavated, treated, and disposed of
off site thereby eliminating operation and maintenance requirements.
Alternative 4C will control or eliminate the exposure to asbestos-
contaminated soil. No risk to human health and the environment is
expected to remain once the remedial action is complete and the ACM
is disposed of in an approved landfill. Such removal has been
proven to be a reliable and effective remediation of asbestos-
contaminated soil. The problem will be permanently solved so that
controls will not be required. This alternative provides a long-
term permanent solution to the asbestos contamination.
Alternative 4D will provide for the highest degree of long-term
effectiveness for hydrocarbon contaminated soils because all
contaminated soil will be excavated, treated, and disposed of
off site thereby eliminating operation and maintenance requirements.
Alternative 4D reduces the magnitude of residual risk to meet the
remedial action objective for the residential scenario. This
alternative provides long term effectiveness and permanence by
excavating the contaminated soils and disposing of them off-site
and backfilling the area with clean soils from the local area.
Alternative 4E will treat hydrocarbon-contaminated soils through
enhanced biodegradation. Bench scale testing has shown that
landfarming can be effective and reliable in treating hydrocarbon
contamination. This alternative provides for risk levels to be
permanently reduced for the long term such that residential use of
the area can occur. The waste reduction achieved in the
treatability study was 90%. This alternative provides a long-term
and permanent solution.
It is doubtful that Alternative 4F will reduce the magnitude of
residual risk from exposure to hydrocarbon contaminated soils
sufficient to meet the remedial action objectives. 4F may not be
adequate or reliable because there is less certainty that thin
spreading will reduce the magnitude of residual risk due to
contaminant migration to ground water which may occur. The long-
term effectiveness of this alternative is uncertain. Thin
spreading waste which exceeds EPA's acceptable risk range may
increase long term risks due to possible migration of contaminants
to ground water, and due to the fact that it increases the aerial
extent of contamination, thereby increasing the possibility of
exposure. The treatability study conducted on the west pit waste
material indicated that, initially, the waste degraded rapidly, up
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to 44% degradation of contaminants, then remained unchanged until
nutrients and moisture were added, and since the thin-spreading
alternative does not require the addition of nutrients and
moisture, the long-term effectiveness criteria may not be met.
Thin spreading waste may also increase long-term risks if
contaminants are very slowly degraded.
Separator
Alternative 5B will provide for the highest degree of long-term
effectiveness for the separator contents because all waste will be
excavated, treated, and disposed of off-site thereby eliminating
operation and maintenance requirements. Alternative 5B is
reliable, effective and permanent. After completion of remediation
all separator contents will have been removed.- This alternative
will eliminate substantially all residual risk of exposure to
separator contents; therefore/this alternative is permanent and
effective in the long term. This alternative provides additional
long-term effectiveness by specifying that any contaminated soil
beneath the separator b "Remediated. Thus, the public will not be
affected by any contamination stemming from any leaking from the
separator or the soils located underneath the separator.
Criterion 4, Reduction of Toxicity, Mobility, and Volume Through
Treatment
West Pits Area
Alternative 3C provides for the reduction in toxicity, mobility,
and volume of contaminants through irreversible biodegradation.
The quantity of residual contamination will be up to 99% less than
before treatment,-though it will be spread over a larger area. It
is expected that the risk posed by the waste will be reduced to
residential levels within two years. Monitoring data collected
during treatment will be used to determine if contaminant migration
is occurring. If contaminant migration occurs beyond the treatment
zone in levels above the cleanup standards this alternative
provides for a liner to be incorporated into the treatment zone.
The native soil cap in alternative 3B does not meet this criterion
because it does not provide for the reduction in toxicity, mobility
or volume of contaminants through treatment.
Alternative 3D will enhance the natural degradation of the wastes
now contained in the pits. Since thin spreading will result in
only partial treatment, this criteria is not met fully. Toxicity
and volume may be reduced over time. However, the reduction in
toxicity is uncertain. Moreover, mobility may not be reduced due
to the possibility that contaminants may migrate into the ground
water undetected. Spreading the contaminants over a large area of
soil without effective biodegradation may result in an increased
volume of hazardous material.
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Alternative 3E will reduce toxicity and mobility through treatment.
The volume occupied by the contaminants will increase due to the
fact that it is mixed with lime. However, the total amount of
contaminants will remain the same. Due to the high organic content
of the waste, the waste may not be effectively stabilized,
therefore, the mobility of the contaminants may not be reduced.
Surface Soils
Alternative 4B does not reduce toxicity, mobility or volume of the
lead contaminated soils through treatment. The only treatment to
take place may occur off-site in order to comply with LDRs prior to
disposal.
Alternatives 4C and 4D do not meet this criterion since there is no
treatment.
Alternative 4E provides for the reduction in toxicity, mobility and
volume of contaminants though landfarming. Landfarming is a form
of land treatment which enhances the biodegradation of
contaminants. It is expected that the risk posed by the waste will
be reduced to residential levels within two years. Monitoring data
collected during treatment will be used to determine if contaminant
migration is occurring. If migration is occurring this alternative
provides for a liner to be incorporated into the treatment zone.
Alternative 4F will increase the surface area in which the wastes
occupy, thereby enhancing the natural degradation of the surface
soil waste at the Site, since thin spreading relies on incidental
and partial treatment, this criteria is not fully met. Toxicity
and volume may be reduced over time. However, the reduction in
toxicity is uncertain. Moreover, mobility may not be reduced due
to the possibility that contaminants may migrate into the ground
water undetected.
Separator
Alternative 5B provides for treatment to take place to comply with
LDRs, if necessary.
Criterion 5, Short-Term Effectiveness
Due to the lack of environmental targets as shown in the
environmental risk assessment and confirmed by the DOI's natural
resource damage assessment, no alternative when implemented would
negatively affect the environment.
West Pits
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Alternative 3B can be completed relatively quickly (less than one
year) once workers have been mobilized. There are risks associated
with the construction of the cap, but these are normal for the type
of work and can be mitigated through the implementation of a safety
program. Risk to the community and the environment during
construction are low. Alternative 3B is effective in the short
term.
For both Alternatives 3C and 3D there will be short-term hazards to
construction personnel. These are the hazards common to any
excavation operation and may be mitigated through safety
precautions. The excavations associated with these remediations do
not involve trenching operations which have higher accident rates.
Alternative 3C is expected to reach remedial action goals within
two years of implementation. It is unknown how long it will take
for Alternative 3D to reach the remedial action goals; thus, there
is a potential for added short term risk. The treatability study
conducted on the west pit waste material indicated that initially
the waste degraded rapidly, up to 44% reduction in organics, then
remained unchanged until nutrients and moisture were added, and
since the thin-spreading alternative does not require the addition
of nutrients and moisture, it will take longer than landfarming to
achieve protection. Thin spreading waste which exceeds EPA's
acceptable risk range will increase short term risks due to
increasing the areal extent and probability for exposure to the
contaminated wastes and may also increase long-term risks. These
risks can be controlled by limiting access until sufficient
degradation of contaminants is complete. Thin spreading may result
in airborne emissions. Air monitoring will be required to protect
construction workers and nearby residents. Thin spreading the
waste which exceeds EPA's acceptable risk range will increase short
term risks due to increasing the areal extent, and probability for
exposure.
With alternative 3E, there will be short-term hazards to
remediation personnel and the local inhabitants from airborne
particulates during the mixing of lime and the recontouring. This
hazard can be mitigated by the use of personal protective equipment
by remediation workers, and the use of dust suppression water.
Work would not be allowed during times of high winds that would
carry particulates past the Site boundaries. This alternative is
implementable within a year; therefore, short-term risks will not
exceed one year.
Surface Soils
Short term risks to the public from alternative 4B are associated
with the ingestion of airborne particles generated during
excavation, loading and transporting of the contaminated materials.
Safety measures such as dust suppression sprays and tarping of the
trucks would be implemented to prevent exposing the public to
contaminants. Operating during periods of high wind would not be
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allowed. Traffic control in the vicinity of the Site and the use
of qualified, experienced haulage contractors would minimize the
risk from the trucks. For workers, the risks are greater because
of directly handling the soil. An appropriate health and safety
program will be developed and enforced to mitigate these risks.
The excavations associated with these remediations do not involve
trenching operations which have higher accident rates. Access to
the area is good and no new roads or other disturbances are
required. Alternative 4B is effective in the short term.
Protection is expected to be achieved within a year.
In implementing Alternative 4C, the excavation, removal and
handling of the asbestos containing material will be conducted in
accordance with OSHA and NESHAP regulations, which ensure the
protection of workers, environment and the public. The excavations
associated with these remediations do not involve trenching
operations which have higher accident rates. The time until
protection will be achieved is estimated to be less than one year
upon mobilization of workers and equipment. This alternative is
effective in the short term.
Risks to workers and the community through Alternative 4D will be
ingestion of airborne particles generated during excavation,
loading and transporting. Safety measures such as dust suppression
sprays and tarping of trucks will be implemented to prevent
exposing the remediation personnel and the public to the
hydrocarbons. The excavations associated with these remediations
do not involve trenching operations which have higher accident
rates. Protection is expected to be achieved within a year.
Through Alternatives 4E and 4P, there will be short-term hazards to
construction personnel. These are hazards common to any excavation
operation and may be mitigated through safety precautions. The
excavations associated with these remediations do not involve
trenching operations which have higher accident rates. Both
alternatives are effective in the short term.
Alternative 4E is expected to reach remedial action goals within
two years of implementation. It is unknown how long it will take
for Alternative 4F to reach the remedial action goals; therefore,
it may not be effective in the short term. The treatability study
conducted on the west pit waste material indicated that with
natural biodegradation, such as that which occurs with thin
spreading, degradation occurred rapidly, up to 44% reduction of
organics, then remained unchanged until nutrients and moisture were
added, since thin spreading does not include the addition of these
materials, further degradation is doubtful. The short term risks
to the community and the environment may increase with Alternatives
4E and 4F by increasing the areal extent of the West Pit contents,
and therefore the exposure possibilities.
Short-term risks for both 4E and 4F will be lessened with certain
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techniques. Exposure possibilities can be controlled by
restricting access until sufficient degradation is completed.
Short-term risk to the community will be reduced by conducting air
monitoring during implementation to ensure risks due to inhalation
are within EPA's acceptable risk range.
Separator
There should be minimal risk to the public during removal of the
separator sludge. There are risks for workers exposed to the
sludge during removal, but these can be mitigated through the
implementation of an effective health and safety program. A risk
to the community and workers is present during transportation of
the material from the Site to a RCRA permitted landfill.
Protection is expected to be achieved within one year. Thus,
Alternative 5B is effective in the short-term.
Criterion 6, Implementability
West Pits
Alternatives 3B, 3C, 3D, and 3E are all implementable within a one-
year period. Adequate work force and equipment as well as
chemicals are available in the area and native soil for the cap is
available on site or near by.
Alternative 3C requires that a water source be present. In order
to have an uncontaminated water supply, water may need to be
transported from an off-site source. Consequently, water rights
may need to be negotiated.
Surface Soils
All of the alternatives which involve transportation of waste will
be required to meet U.S. Department of Transportation regulations
for the shipment of contaminated waste to the disposal facility.
All surface soils alternatives are implementable in a one-year
period. EPA has extensive experience with the excavation,
transport and disposal of contaminated soils. The excavations are
shallow and of relatively small areal extent so that common
construction equipment can be utilized. Clean, native soil for
backfill, if needed, should be available either on site or locally.
Alternatives 4B and 4C are easily implemented within a one-year
period, as the technologies involved are relatively common practice
and proven reliable. Alternative 4C will require coordination
with the State of New Mexico.
Alternatives 4D, 4E, and 4F are implementable within a one-year
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period. The work force and equipment required are readily
available in the area. Alternative 4E requires that a water source ^^
be present. In order to have an uncontaminated water supply, water ^H
may need to be transported from an off-site source. Consequently, ^^
water rights may need to be negotiated.
The administrative feasibility of implementing Alternative 4D would
involve locating a landfill which is permitted to accept the
hydrocarbon contaminated waste. It would also require that the
same landfill agree to treat the waste at the facility.
Separator
The technologies proposed for Alternative 5B are proven reliable
and have become relatively common practice,. Equipment and
personnel should be readily available. This alternative is
implementable within a one-year period. The administrative
feasibility problems associated with this alternative include the
problem of locating a RCRA permitted facility that would accept the
waste.
Criterion 7. Cost
West Pits
The alternatives considered for the West Pits area ranged in cost
from $27,300 to $1,142,400. The Selected Remedial Alternative 3C
is the most expensive for remediation of the west pits at an
estimated $1,142,400.00.
Surface soils
The alternatives considered for the Surface Soils individually
ranged in cost from $9,300 to $1,605,000. The cost of the selected
soil remedial alternative, which is the combination of alternatives
4B, 4C, and 4E, will be approximately $2,900,600.00.
Separator
The least expensive alternative for remediation of the separator is
the no action alternative at a present value of $7,200.00. The
selected alternative, 5B, is also the most expensive alternative at
$116,000.00.
MODIFYING CRITERIA
Criterion 8, State Acceptance
The State of New Mexico through the New Mexico Environment
Department has reviewed and commented on the Proposed Plan.
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Concurrence was given contingent on EPA addressing the comments to
NMED's satisfaction. The submitted comments were incorporated and
answered as appropriate (See Responsiveness Summary, and
communications with the State included in the Administrative
Record). The State ARARs of concern, including UST and solid waste
regulations, are discussed in the Responsiveness Summary and in the
Section VIII of the ROD.
The Navajo Nation through the Navajo Environmental Protection
Administration and the Navajo Superfund Office has reviewed and
commented on the Proposed Plan. The submitted comments were
incorporated and answered as appropriate (See Responsiveness
Summary, and communications with the Navajo Nation and its agencies
included in the Administrative Record). The ffavajo Nation stated
that it did not have any ARARs applicable to the Site.
State and Navajo Nation representatives participated in the
preparation of the final ROD at Region 6 offices, in a work session
with EPA staff.
GROUND WATER AND NAPL ALTERNATIVES:
THRESHOLD CRITERIA
Criterion 1, Overall Protection of Human Health and the Environment
The no action alternatives 1A and 2A do not provide overall
protection of human health and the environment; therefore, they
will not be discussed further in the criteria analysis.
Home treatment units provide effective removal of the ground water
contaminants though they do not address the source of
contamination. The treatment units must be maintained to be
effective and are not a permanent solution to the problem. They
eliminate the health risk to the public from ingestion and
inhalation of the contaminants provided they are properly monitored
and filters are replaced and/or regenerated. Institutional controls
are used to insure that no new domestic wells will be installed in
the contaminated portions of the Sonsela aquifer. Thus,
alternatives 1C and ID are protective of human health and the
environment. Alternative IB is not protective of the environment,
it is protective of human health provide the home treatment units
are maintained and new aquifer users are identified.
Alternative 1C requires active remediation of the aquifer through
extraction, treatment and reinjection of ground water. This
alternative also includes the institutional controls previously
discussed. Upon completion of the remedial action, this
alternative will reduce the risk associated with ingestion of
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contaminated ground water. It is protective of human health and
the environment.
Alternative ID requires active remediation of the aquifer through
the use of vapor extraction and treatment, and institutional
controls. Upon completion of the remedial action, this
alternative will reduce the risk associated with ingestion of
contaminated ground water, with the exception of lead which is not
amenable to vapor extraction. It is, therefore, somewhat less
protective of human health and the environment than Alternative 1C.
Alternative 1C provides the highest protection of human health and
the environment by eliminating, reducing, or controlling risk
through treatment of the contaminated ground water.
Alternative 2B achieves the remedial action objective of reducing
or eliminating a source of ground water contamination. Extraction
of the NAPL, and institutional controls, make this alternative
protective of human health and the environment.
Alternative 2C involves the removal and destruction of volatile
organics in NAPL and ground water and is expected to achieve ground
water MCLs for volatile organics in a reasonable time frame.
During implementation of the remedy, home treatment units eliminate
the health risk to the public from ingestion and inhalation of
contaminants. Use restrictions insure that no new domestic wells
will be installed in the contaminated portion of the Sonsela
aquifer. This alternative, in combination with alternative 1C,
provides the highest degree of protection of human health and the
environment. Alternative 1C will be necessary to remove the lead,
which does not volatilize. Lead, above action levels, occurs only
in one area of ground water.
Criterion 2f Compliance with ARARs
The Navajo Superfund office has indicated that Tribal ARARs do not
exist. Consequently, Tribal ARARs are not discussed.
Table 9 lists the ARARs that apply to the Ground Water and NAPL
Alternatives.
New Mexico is authorized under RCRA to operate its hazardous waste
management program in lieu of the Federal RCRA programs. When
Federal RCRA requirements are cited in the description of ARARs
which follows, the intention is also to reference the corresponding
New Mexico regulation if the New Mexico regulations are applicable.
Under the restricted use alternative IB, chemical-specific ARARs,
including MCLs, will almost certainly not be attained within any
reasonable time period in the Sonsela sandstones; consequently, the
aquifer will not be returned to beneficial use as expected in the
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NCP. Home treatment units will attain ARARs at the point of
exposure to domestic ground water provide the treatment units are
maintained and all aquifer users are identified. There are no
action- or location-specific ARARs for the Restricted Use
alternative IB.
Due to the heterogeneous nature of the Sonsela sandstone it is
uncertain whether chemical-specific ARARs, including MCLs, will be
attained throughout the aquifer in a reasonable period of time
utilizing Alternatives 1C and ID. Based on common practice of
assuming operating plant life to be 30 years, this time frame has
been selected as a reasonable period in which to obtain the goals.
For Alternatives 1C and ID, the New Mexico State Engineer's Office
Rules and Regulations, Article 1-17 are considered action-specific
ARARs with regards to well construction.
Under Alternatives 1C and ID, the aqueous discharge from the air
stripper will be required to attain the New Mexico Water Quality
Control Commission Regul^ons, Part 3, Section 3-100, "Regulations
for Discharges Onto or Below the Surface of the Ground." Thus,
metal contaminant concentrations must meet these standards, or
additional treatment may be required.
The action specific requirements applicable to discharges onto the
ground surface that apply to the ground water and NAPL alternatives
are found at New Mexico Water Quality Control Commission
Regulations ("NMWQCCR") Section 3-103 and include, but are not
limited to:
Benzene - 10
Ethyl Benzene - 750
Toluene - 750 /Kf/1
Xylenes - 620 M9/1
Naphthalene - 30 jug/1
Lead - 50
Water Quality Standards for Interstate and Intrastate streams in
New Mexico Section 1-102 is an action-specific ARAR for discharges
to surface water. For the site, ground water which has been
treated to drinking water MCLs and discharged into watercourses
should meet these surface water standards.
There are no location specific ARARs for the ground water
Alternatives 1C and ID.
For Alternatives 2B and 2C the New Mexico State Engineer's Office
Rules and Regulations, Article 1-17 are considered action-specific
ARARs.
There are no chemical-specific ARARs for NAPL, except to the extent
that NAPL impacts ground water, in which case MCLs apply.
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Under Alternative 2B, the aqueous discharge from the air stripper
will be required to attain the New Mexico Water Quality Control
Commission Regulations, Part 3, Section 3-100', "Regulations for
Discharges Onto or Below the Surface of the Ground." Thus, metal
contaminant concentrations must meet these standards, or additional
treatment may be required.
The action-specific requirements applicable to discharges onto the
ground surface that apply to the ground water and NAPL alternatives
are found at New Mexico Water Quality Control Commission
Regulations ("NMWQCCR") Section 3-103 and include, but are not
limited to:
Benzene - 10
Ethyl Benzene - 750
Toluene - 750 jig/1
Xylenes - 620
Naphthalene - 30
Lead - 50
With alternative 2C, compliance with chemical-specific ARARs,
including MCLs for ground water may be attainable in 30 years.
Action-specific ARARs will be met. The NAPL extraction part of
this alternative will result in a substantial reduction, if not
elimination, of NAPL as a source of ground water contamination and
will also substantially reduce the high BTEX concentrations in
ground water in the vicinity of the E Sandstone NAPL plume.
Emissions from the vapor extraction and air stripper units will
meet action specific requirements of New Mexico Environmental
Improvement Board Air Control Regulation 702.
PRIMARY-BALANCING CRITERIA
Criterion 3. Long— Term Effectiveness and Permanence
Home treatment units in Alternative IB will provide long-term
effectiveness only if maintained and serviced properly, and if all
aquifer users are identified. This alternative does not provide a
permanent solution to the problem. The use of these units would be
required until natural biodegradation and attenuation reduce
contaminant levels to below action levels. The time required for
this to occur is unknown. The remediation rate for natural
degradation and attenuation at the Site is difficult to predict as
long as NAPL is present. It is almost certain that natural
degradation and attenuation will not reduce the magnitude or
residual risk within any reasonable period of time. Four home
treatment units have been installed on the existing local wells at
the present time. Institutional controls will insure that no new
domestic wells are installed in the contaminated portions of the
aquifer.
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The long-term effectiveness and permanence of Alternative 1C is
uncertain. In similar pump and treat remediations at other sites,
after target levels were initially achieved, the contaminant
concentrations in the water increased to above target levels.
However, when appropriately designed, this system will control the
migration of contaminants which will certainly reduce the magnitude
of residual risk to those who utilize the aquifers in question.
The long-term effectiveness of Alternative ID is uncertain.
Insufficient data is available to determine whether vapor
extraction systems exhibit a increase in concentrations after the
target levels have been reached similar to pump and treat systems.
Experience at other sites, such as the Tysons Superfund site in
King of Prussia, Pennsylvania, has shown that vapor extraction
removal of volatile contaminants from fractured rock is difficult,
if not impossible, to complete. Additionally, the low permeability
of the fractured formation at the Prewitt Abandoned Refinery Site
suggests that vapor extraction will not reach sufficient water
surface area to obtain MCLs. Consequently, it appears that residual
risk would remain high under ID.
Remedial action objectives are achieved at the completion of
Alternative 2B. It is uncertain how long it will take for the
remediation to be completed using this alternative and how
successful this alternative will be. Provided that the alternative
is successful in reducing or eliminating the NAPL as a source of
ground water contamination, this alternative will be both permanent
and effective in the long term.
The NAPL remediation alternative consists of a combination of
Alternative 2C and Alternative 1C. This combination is expected to
be the most effective alternative in the long-term. This
combination offers the most permanent solution to the problem posed
by the NAPL and contaminated ground water. This combination will
be reliable and effective method for removing lead, and reducing
the volume of BTEX in vapor, adsorbed on soil and rock and in a
liquid phase from the E, F, and 6 sandstone units. From the pilot
test results, it is believed that the remedial action goals for the
NAPL will be met within 5 years. Alternative 2C results in a
substantial reduction if not elimination of NAPL as a source of
ground water contamination and also substantially reduces the
level of contamination in ground water where concentrations are
highest. Further air sparging and extraction of ground water
through Alternative 1C, where these remediation approaches can be
effective, combined with natural restoration where they cannot,
will result in attainment of ground water MCLs, eliminating
residual risk (subject to the qualification expressed in the
discussion of the implementability of Alternative 1C which
follows). Thus this alternative will provide both long-term
effectiveness and permanence.
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Criterion 4. Reduction of Toxicity* Mobility,, and Volume Through
Treatment
Alternative IB will not reduce the toxicity, mobility or volume of
the contaminants in the ground water through treatment, therefore
this alternative does not meet this criterion. This alternative
does treat the ground water at point of exposure by removing the
contaminants into the carbon treaters, but does not address the
source of the ground water contamination. The aquifer may
ultimately be remediated by natural attenuation and contaminant
degradation at some unknown time in the future.
Alternative 1C will reduce the volume, toxicity, and mobility of
the contaminants through treatment. Toxicity of ground water is
irreversibly reduced by the removal of BTEX from the ground water
and through treatment of the ground water prior to reinjection.
Ultimately volume and toxicity of the BTEX will be irreversibly
reduced by recycling of the BTEX as a fuel when it is burned.
Alternative ID removes the contaminants thus reducing the toxicity
and mobility of the contaminants through treatment of the vapor
phase.
Alternative 2B provides for the removal of NAPL thus reducing the
toxicity of the NAPL and eliminates a source for further
contamination of ground water. Mobility and volume of a source
for contamination in the affected ground water is reduced by
Alternative 2B. Since extracted NAPL will be sent to a recycling
firm and ultimately burned as a fuel, treatment will be taking
place and an irreversible reduction in toxicity and volume will
occur. Also, the ground water which is extracted along with the
NAPL will be treated prior to being discharged, which will reduce
the toxicity, mobility and volume of contaminated ground water.
Based on the pilot test results, Alternative 2C effectively removes
the NAPL which acts as a source of contamination to the ground
water. Toxicity, mobility, and volume of the contaminated ground
water is reduced through vapor extraction and treatment of the BTEX
fraction within the NAPL. Volume reduction will occur not only as
a result of the reduction of the BTEX within the NAPL via soil
vapor extraction but also from vapor extraction of a considerable
portion of other volatile and semivolatile constituents in NAPL.
The NAPL volume will also be reduced by combination liquid/vacuum
NAPL extraction. The toxicity, mobility and volume of BTEX
compounds in ground water are also reduced by extraction, treatment
and air sparging, through the implementation of Alternative 1C.
Criterion 5. Short-Term Effectiveness
Due to the lack of environmental targets as shown in the
environmental risk assessment and confirmed by the DOI's natural
resource damage assessment, no alternative when implemented would
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negatively affect the environment.
Home treatment units and institutional controls in alternative IB
are effective in the short-term protection of human health, provide
the units are properly maintained and all aquifer users are
identified.
Under Alternative 1C, the use of institutional controls and Home
Treatment Units will protect human health during the remediation
period. Risks associated with installation of the system are
minimal. Workers will not be directly exposed to the contaminants
except for the short period of well completion. Alternative 1C is
effective in the short term. Risk to the environment will be
minimal since ground water will be treated and reinjected.
Alternative ID provides for the use of institutional controls and
Home Treatment Units will protect human health during the
remediation period. Risks associated with installation of the
system are minimal. Workers will not be directly exposed to
contamination except fo_\Jhe short period of well completion. Risk
to the environment are expected to be minimal.
Risk to workers with Alternative 2B is minimal. This alternative is
effective in the short term. Risks to workers associated with
installation ad operation of the system will be minimized by
compliance with OSHA Health and Safety regulations. Risk to the
community and the environment during implementation of this
alternative is minimal. Air emissions would comply with regulatory
standards.
The use of institutional controls, Home Treatment Units and
compliance with action specific ARARs will protect human health and
the environment during the remediation period involved with
alternative 2C. Risks to workers associated with installation and
operation of the system will be minimized by compliance with OSHA
Health and Safety regulations.
Criterion 6. JmpIementaJbility
Alternative IB is iroplementable. The units are available and
service of the units is available in the area. Institutional
controls exist in the form of New Mexico regulations which prohibit
installation of water supply wells in known areas of contamination.
Under Alternative 1C, mechanical installation of the system is
standard practice and can be easily accomplished within one year.
Alternative 1C is implementable simultaneously with Alternative 2C.
The design and installation of vapor extraction systems, such as
that required for Alternative ID, has become common practice.
Experienced contractors are available to conduct the necessary pre-
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design testing, design and installation of the system. The
equipment required for the installation is readily available.
Alternative ID is an innovative use of existing technology for
remediating ground water in a fractured aquifer. Existing
technologies are available to implement this remedy. This
alternative is implementable concurrently with Alternative 2C.
The technologies proposed for alternative 2B are implementable.
Equipment and workers to implement the alternative are available.
Recyclers are available in the area to provide a disposal source
for the recovered NAPL. Some uncertainty exists as to the length
of time required to remove the NAPL.
As far as the implementability of Alternative 2C-is concerned, home
treatment units have already been implemented. Pilot test results
have demonstrated that NAPL extraction, ground water pump and
treat, air injection, and air sparging features of the combination
alternative are implementable. Mobilization, installation and
start-up should be able T> be accomplished within a year.
Criterion 7. Cost
The least expensive alternative considered for ground water
remediation is the 1A, No Action alternative, at $ 319,500.00. The
selected remedial alternative, 1C, costs $ 7,957,000.00. The most
expensive alternative is alternative ID at $ 8,718,900.
The cost associated with the alternatives considered for the NAPL
remediation ranged from $1,785,000.00 to $4,185,576.00. The most
expensive NAPL alternative considered is Alternative 2C. This is
the selected remedial alternative for NAPL remediation.
MODIFYING CRITERIA
Criterion 8, State Acceptance
The State of New Mexico through the New Mexico Environment
Department has reviewed and commented on the Proposed Plan.
Concurrence was given contingent on EPA addressing the comments to
NMED's satisfaction. The submitted comments were incorporated and
answered as appropriate (See Responsiveness Summary, and
communications with the State included in the Administrative
Record). The State ARARs of concern, including UST and solid waste
regulations, are discussed in the Responsiveness Summary and in the
Section VIII of the ROD.
The Navajo Nation through the Navajo Environmental Protection
Administration and the Navajo Superfund Office has reviewed and
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commented on the Proposed Plan. The submitted comments were
incorporated and answered as appropriate (See Responsiveness
Summary, and communications with the Navajo Nation and its agencies
included in the Administrative Record). The Navajo Nation stated
that it did not have any ARARs applicable to the Site.
State and Navajo Nation representatives participated in the
preparation of the final ROD at Region 6 offices, in a work session
with EPA staff.
Criterion 9, Conaaanity Acceptance
Various comments were voiced during the two public meetings and
were submitted during the public comment period. These comments
have been incorporated and answered as appropriate in the
Responsiveness Summary. In general, the public indicated that it
wanted the remedy completed expeditiously.
IX. SELECTED REMEDY
As previously stated in Section IV of this ROD, the goal of the
remedial action is to: 1) remove or contain the NAPL to prevent
further contamination to ground water; 2) prevent future exposure
to the contaminated ground water through the G, F, and E units and
restore the G, F, and E units of the Sonsela Aquifer to their
beneficial use, which is at this site a drinking water aquifer; 3}
prevent or reduce carcinogenic and noncarcinogenic risk to human
health and the environment from wastes in the West Pits Area and to
eliminate the physical hazard posed by the waste pits as they
exist; 4) control or eliminate the exposure to contaminated soils;
and 5) eliminate risk and hazards associated with exposure to the
separator unit, its contents and any contaminated soils associated
with the separator.
Based on consideration of the requirements of CERCLA, the detailed
analysis of the alternatives, and public comments, EPA has
determined that the combination of Alternative 1C (Ground Water
Extraction & Reinjection), Alternative 2C (Soil Vapor Extraction),
Alternative 3C (Excavation/Landfarming of West Pits Area),
Alternative 4B (Excavation and Off-Site Disposal of Lead
Contaminated Soils), Alternative 4C (Excavation and Off-Site
Disposal of Asbestos Contaminated Materials and Soils) Alternative
4E (Excavation/Landfarming of Soil Containing Hydrocarbons) and
Alternative 5B ( Excavation and Off-Site Disposal of the Separator
and its Contents) constitutes the most appropriate remedy for the
Prewitt Abandoned Refinery Site, in Prewitt, New Mexico, and
therefore, EPA hereby selects these alternatives, as described
below and in the previous descriptions of these alternatives in
this ROD, as the remedy for the Prewitt Abandoned Refinery Site.
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During the design and implementation phases of the remedial action,
air monitoring of the Site shall be conducted to ensure that
airborne particulates or other air emissions from the Site do not
pose a risk to the workers or inhabitants in the area.
EPA's selected remedial alternative for remediating the ground
water at the Site is a combination of Alternatives 1C Ground Water
Extraction/Reinjection and 2C NAPL Vapor Extraction.
The goal of the remedial action is to remove the NAPL as a
continuing source of contamination to ground water and return all
units of the Sonsela Aquifer to their beneficial use.
Additionally, ground water that is not currently used but is a
future drinking water source shall be protected to levels
appropriate for a drinking water source. Based on information
obtained during the remedial investigation, supplemental sampling,
and analysis of all remedial alternatives, EPA believes that the
selected remedy will achieve this goal. Ground water contamination
may be especially persistent in the immediate vicinity of the NAPL
where concentrations are relatively high. The ability to achieve
cleanup levels at all points throughout the area of attainment, or
plume, cannot be determined until the extraction system has been
implemented, modified as necessary, and plume response monitored
over time. If the selected remedy cannot meet the specified
remediation levels, which are MCLs for all contaminants (such as
but not limited to, lead, benzene, toluene, and xylene) at any or
all of the monitoring points during implementation, the contingency
measures described in this section may replace the selected ground
water remedy and remediation levels for these portions of the
plume. Such contingency measures will, at a minimum, prevent
further migration of the plume and may include a combination of
containment technologies and institutional controls. These
contingency measures are considered to protect human health and the
environment and are technically practicable under the corresponding
circumstances.
The selected alternative includes ground water extraction,
treatment and reinjection for an estimated period in excess of 30
years, during which time the system's performance shall be
carefully monitored on a regular basis and adjusted as warranted by
the performance data collected during operation. Modifications
required by EPA may include, but are not limited to, any or all of
the following :
Discontinuing pumping at individual wells where cleanup
goals have been attained.
Alternating pumping among the various wells to eliminate
stagnation points.
Pulse pumping to allow aquifer equilibration, and to
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encourage adsorbed contaminants to partition into ground
water.
Installing additional extraction wells to facilitate or
accelerate cleanup of the contaminant plume.
Air sparging to enhance creation of the vapor phase of
the contaminants.
EPA's selected remedy to address the soil and separator
contamination consists of a combination of alternatives. The
selected remedy does not leave waste in place at levels which pose
an unacceptable risk to human health and the environment.
The selected remedy for the entire Site is protective of human
health and the environment, complies with Federal and State
requirements that are legally applicable or relevant and
appropriate to the remedial action, and is cost-effective. This
remedy utilizes permanent solutions for the Site in that its goal
is to remove contaminants from ground water, surface structures and
soil and to treat these contaminants to ARARs or acceptable risk
levels.
The specific remediation program shall be developed as a part of
remedy design.
Ground Water Remediation Program
The volume of contaminated ground water is estimated to be
approximately 49 million gallons. The water shall be extracted from
the ground, treated, and reinjected. Institutional controls, and
water treatment units will also be employed. Ground water
contaminated with contaminants in excess of 0.005 mg/1 for benzene,
0.75 mg/1 toluene, 0.7 mg/1 ethylbenzene, 0.62 mg/1 xylene, or
0.005 mg/L 1,2 Dichloroethane shall be extracted, treated to meet
the levels cited in this sentence, and reinjected.
The ground water remediation program shall be implemented
simultaneously with the NAPL remediation. The ground water
remediation program shall contain at a minimum:
Installation of two monitoring wells completed in the B unit
if wells presently onsite are unacceptable for this purpose;
Quarterly monitoring of two monitoring wells and two private
wells for BTEX;
Use of institutional controls to eliminate the installation of
water supply wells in contaminated ground water, (New Mexico
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State Engineer Office Rules and Regulations, Article 1-17)
The installation of water treatment units on existing domestic
wells that exceed MCLs. These units are activated carbon
treatment canisters that are periodically serviced and
replaced.
Quarterly sampling of domestic wells at the point of
consumption to insure effectiveness of the carbon treatment
units.
Maintenance of the carbon treatment units.
The installation of approximately 20 ground water extraction
wells.
A ground water treatment plant, which will treat the water
extracted from the 20 new wells, and from existing wells which
are to be used for ground water extraction.
The installation of, and implementation of, approximately 35
injection wells. During remedial design other treated water
disposal alternatives shall be evaluated and the optimum
alternative will be selected.
It is expected that water will be pumped out of the ground at
approximately 0.2 gallons per minute ("gpm") per well, or a total
of approximately 5,000 gallons per day, unless this rate is
determined by EPA to interfere with the NAPL remediation program.
The ground water shall be treated, at the ground water treatment
plant, prior to reinjection. The estimated costs for this component
of the remedy are Capital costs: $2,156,000, Annual O & M costs:
$367,200, and Present Worth: $7,957,000.
KAPL Soil Vapor Extraction:
Approximately 43,000 gallons of Non-Aqueous Phase liquids and the
volatile BTEX constituents in the NAPL will be extracted to prevent
further contamination of ground water in the A-E units of the
Sonsela Aquifer. The soil vapor extraction system for the site
shall be combined with air injection, air sparging, and ground
water pumping where appropriate. A minimum of 38 remediation wells
shall be installed for the purpose of vapor extraction.
A single vacuum pump located in the South Area is expected to
extract soil vapor from all NAPL areas, including the North Area.
Piping shall convey extracted soil vapor from the North Area and
the South Area to the pump. A thermal/catalytic oxidizer shall be
utilized to destroy volatile organic compounds in the extracted
soil vapor. All ground water produced shall be piped to the air
stripper for treatment prior to being reinjected. The estimated
costs for this component of the remedy are:
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-------
Capital costs: $1,429,672.00
Annual p * M costs: $389,644.00 plus $40,800 for long-term
monitoring, and
Present Worth: $4,185,576.00.
West Pits and Hydrocarbon Contaminated Soils:
Approximately 1175 cubic yards of pit material and approximately
1,500 cubic yards of hydrocarbon contaminated soils shall be
excavated and treated. Major surface deposits of hydrocarbon
material will be excavated and transported to the landfarm
treatment area which is located within the western portion of the
Site and within the hydrocarbon Area of Contamination (AOC) .
Landfarming shall involve tillage, fertilization and irrigation of
the contaminated soil in a controlled treatment area to maximize
biological degradation of the contaminants. The soil containing
hydrocarbons shall be consolidated in a central location within an
AOC and shall be landfarmed.
The landfarm shall be c"" x;tructed in the western end of the site
and shall consist of runon-runoff protection, near flat treatment
area, irrigation system, a nutrient addition system, and a vadose
zone monitoring system. Monitoring of the soil carcinogenic PAH
content shall be performed to measure degradation, and shall
continue, until the remedial action objectives/goals are met.
Treatment shall consist of mechanically working the material to
allow air to penetrate, and providing moisture and nutrients at
near optimal conditions during weather which permits this activity.
If monitoring indicates that contaminant migration, is occurring or
will occur immanently, in concentrations which exceed the PAH
treatment standards for the landfarm as specified later in this
chapter of the ROD, a liner shall be incorporated into the
treatment area. The estimated costs for this component of the
remedy are:
Capital costs: $ 1,737,900.00,
O & M costs: $300,200.00, and
Present Worth: $2,428,700.
These cost do not reflect the additional cost of a liner, should a
liner be necessary due to the threat of contaminant migration, as
determined from the monitoring data.
Upon completion of the landf arming remedy, as determined by the
successful treatment of carcinogenic PAHs to the prescribed
treatment levels specified later in this chapter of the ROD, a
clean soil cover shall be placed over the landfarm to complete
closure.
Lead Contaminated Soils:
Soil in the 0' to 2' depth which contains lead in concentrations in
78
-------
excess of 500 ppm shall be excavated and transported to a RCRA
landfill for disposal. Soil beyond 2' depth which contains lead in
concentrations in excess of 1000 ppm shall be excavated and
transported to a RCRA landfill for disposal. The soil shall be
treated prior to disposal if the material exhibits a toxic
characteristic. The soil shall be excavated to an appropriate
depth, as verified by the sampling data, over an area of
approximately 50,000 square feet. The soil to be excavated
occupies approximately 1,900 cubic yards. This soil removal is
expected to require approximately 73 truck loads to be hauled off-
site. The estimated costs for this component of the remedy are:
Capital costs: $1,605,000.00,
Annual O & M costs: $0.00, and
Present Worth: $1,605,000.
Asbestos Contaminated Substances:
All asbestos-contaminated materials including soils shall be
excavated, placed in ""^iled containers, transported to, and
disposed in, a landfill approved by EPA. A total of approximately
15 cubic yards of asbestos-contaminated material shall be removed
from at least 5 locations throughout the site. During removal
activities, air monitoring shall be performed in accordance with
OSHA and NESHAP requirements. The estimated costs for this
component of the remedy are:
Capital costs: $9,300.00,
Annual O & M costs: $0.00,
and Present Worth: $9,300.
Separator :
The Separator contains approximately 83 cubic yards of material
that shall be entirely removed. The material amounts to
approximately four truckloads. The separator contents to be
shipped off-site shall by analyzed prior to shipment to confirm the
levels of Toxicity Characteristic Leaching Procedure (TCLP)
hazardous constituents. The separator contents shall be excavated
by pumping or mechanical excavation. The Separator contents shall
be loaded into trucks, and hauled to a RCRA landfill approved by
EPA. The waste shipped off-site shall be disposed in accordance
with RCRA disposal requirements for F037 RCRA hazardous wastes, and
also any hazardous waste designation appropriate base on the TCLP
test. If necessary to meet the RCRA requirements for land
disposal, the separator contents shall be pretreated at the RCRA
disposal site prior to disposal.
After the separator contents are removed, holes shall be made
through the bottom of the Separator, to permit drainage, and to
permit the sampling of soil below the separator. If contaminated
soil is found beneath the separator, in excess of cleanup standards
79
-------
defined in this ROD, remediation of those soils shall be performed.
If those contaminated soils are amenable to landfarming, they shall
be treated by landfarming along with the other wastes treated at
the Site. Contaminated soils beneath the separator shall not be
deemed amenable to landfarming if they contain lead above 500 ppa
or any constituents which exceed the TCLP limits designating
hazardous wastes. If such contaminated soils are not amenable to
landfarming, they shall be treated by other methods such as, but
not limited to, soil washing or off-site incineration. After all
separator contents and associated contaminated soils have been
removed, the separator shall be backfilled with local material.
The estimated costs for this component of the remedy are:
Capital costs: $116,000.00,
Annual 0 & M costs: $0.00, and
Present Worth: $116,000.
Cleanup Levels For Ground Water, NAPL, West Pit Contents and
Hydrocarbon Contaminated Soils
The purpose of this response action is to control risk posed by
direct contact with soils, and ground water and to minimize
migration of contaminants to ground water.
The ground water remedy will address the ground water contaminated
with BTEX, 1,2 Dichloroethane, and lead. The cleanup levels shall
be 0.015 mg/1 for lead, 0.005 mg/1 for benzene, 0.750 mg/1 toluene,
0.7 mg/1 ethylbenzene, 0.62 mg/1 xylene, and 0.005 mg/1 1,2
dichloroethane. These cleanup levels, are based on Federal Safe
Drinking Water Act Standards and New Mexico Water Quality Control
Commission Regulations (ARARs) for all chemicals with the exception
of lead. The lead standard is an action level prescribed by EPA
policy (June 21, 1990 Memorandum from Henry L. Longest, Office of
Emergency and Remedial Response of EPA) Treatment shall be
monitored to ensure that cleanup levels are achieved.
Hydrocarbon contaminated soils and west pit contents ("hotspots")
shall be excavated and treated to a level such that a risk of 10"s
is not exceeded. The remedial action level will be 0.9
benzo(a)pyrene equivalents, which translates to 0.9 mg/kg for
benzo(a)pyrene; 9.0 mg/kg for benzo(a)anthracene,
benzo(k)fluoranthene, benzo(b)fluoranthene; 90 mg/kg for chrysene;
The cleanup level of 0.9 mg/kg benzo(a)pyrene equivalents will
ensure that a risk of 10*5 is not exceeded. When carcinogenic PAHs
are found in combination with each other, their carcinogenic risks
shall be considered additive. Thus, when two or more carcinogenic
PAHs are found together in a location, the individual PAH
concentrations to be met following excavation, shall be adjusted to
meet the total sum cleanup level of 0.9 mg/kg benzo(a)pyrene
equivalents. Excavated areas shall be backfilled with clean soil
80
-------
to further reduce exposure and risk from the excavated hot spots.
The treatment goal for soils and wastes to be left in the closed
landfarm upon completion of treatment, shall be below a
concentration of 4.5 ppm for benzo(a)pyrene (approximately a 5 X
10'5 excess cancer risk). These levels are achievable using the
landfarm treatment technology and are protective of human health
and the environment including ground water.
Upon completion of soil and west pits remedy implementation,
overall site risk is expected to be below the acceptable risk level
for non-carcinogens and approximately 1 X 10"* excess cancer risk.
The hot-spots shall be excavated to a level that assures no greater
than 1 X 10~5 excess cancer risk at the excavation depth of each hot
spot. However, when the excavated areas are back-filled with clean
soil, the actual risk at the surface where exposure is most likely
to occur will be 1 X KT6 or less. The concentrations of
carcinogenic PAHs in other soils throughout the site, not
designated as hydrocarbon contaminated soils, are generally less
than detection limits (0.330 ppm). Treatment levels for
carcinogenic PAHs within the landfarm shall be 4.5 benzo(a)pyrene
equivalents, which translates to; 4.5 mg/kg benzo(a)pyrene, 45
mg/kg for benzo(a)anthracene, benzo(k)fluoranthene,
benzo(b)fluoranthene; and 45 mg/kg for chrysene. When the PAH
constituents are found in combination with each other, their
carcinogenic risks will be considered additive. Thus, the
individual carcinogenic PAH concentrations, when different PAH's
are found in combination, shall be adjusted to benzo(a)pyrene
equivalents, such that the total benzo(a)pyrene equivalent
concentration in the landfarm does not exceed 4.5 mg/kg. This will
ensure that the cumulative excess cancer risk from all carcinogenic
PAHs present in the landfarm, upon closure of the landfarm, does
not exceed 5 X 10'5. The treated soils in the landfarm, which will
present an excess cancer risk less than or equal to 5 X 10'5, shall
be covered with a vegetative cover upon completion of active
biotreatment. Thus, the actual risk at the soil surface in the
area of the landfarm will be 1 X 1CT*. The treatment goal
prescribed for PAHs in the landfarm is protective of human health
and the environment and achievable using landfarming technology.
X. STATUTORY DETERMINATIONS
Under its legal authorities, EPA's primary responsibility at
Superfund sites is to undertake remedial actions that achieve
adequate protection of human health and the environment. In
addition, Section 121 of CERCLA, 42 U.S.C. $ 9621, establishes
several other statutory requirements and preferences that the
selected remedy must meet. Section 121 specifies that when
complete, the selected remedial action for this Site must comply
with ARARs established under Federal and State environmental laws
unless a statutory waiver is justified. The Navajo Nation has
indicated that it has no ARARs for the Site. The selected remedy
81
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also must be cost-effective and utilize permanent solutions and
alternative treatment technologies or resource recovery
technologies to the maximum extent practicable. Finally, the
statute includes a preference for remedies that employ treatment
that permanently and significantly reduces the volume, toxicity, or
mobility of hazardous wastes as their principal element.
If following implementation of the selected ground water remedy, it
fails to achieve the contaminant concentrations in accordance with
the performance standards set forth in the ROD, the contingency
measures will be implemented at the Site. The following sections
describe how the selected remedy meets the statutory requirements.
Protection of Hunan Health and the Environment;
The selected remedy protects human health and the environment by
eliminating the direct contact and ingestion risks associated with
the contaminated soils, sludges and ground water. Landfarming will
eliminate the risk associated with direct contact of hydrocarbon
contaminated soils. Off-site disposal will eliminate the risk
associated with direct contact of separator contents and asbestos
contaminated materials, Excavating soil in the 0' to 2' interval
which contains lead in excess of 500 ppm, and soil beyond the 2'
depth containing lead in excess of 1000 ppm, followed by treatment
and offsite disposal will eliminate the risk associated the direct
contact of lead contaminated soils. With regards to ground water
remediation, the use of extraction, treatment and reinjection of
ground water will eliminate the risk associated with ingestion,
dermal contact and inhalation of contaminated ground water. In
addition, through the implementation of the soil vapor extraction
alternative, the NAPL, which is a continuing source of ground water
contamination will be eliminated or controlled.
The selected remedy reduces the potential for contaminants to
migrate from the NAPL source, the soils and West Pits to the ground
water. This will help achieve protection of human health and the
environment by ensuring that ground water, once treated, will not
become recontaminated by contamination from the Site.
Through the combined use of institutional controls and the home
treatment units, the ground water well monitoring program, and the
extraction, treatment and reinjection of the ground water, the
potential for exposure from ingestion of contaminated ground water
is greatly reduced. During remedy implementation, access to the
Site will be restricted to authorized individuals. This restricted
access will prevent the public from coming into direct contact with
residual contamination during cleanup.
The cancer risk posed by surface contamination at the Site, under
the future residential scenario at reasonable maximum exposure
levels is 3 X 10"4 in the southern tract of the Site and 6 X 10'3 in
the northern tract of the Site. By excavating the soils, pits, and
82
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separator contents, the cancer risk from exposure will be reduced
to less than IXKr6. This level falls within the EPA's acceptable
risk range of l(T* to 10*. There are no short-term threats
associated with the implementation of the selected remedy
components that cannot readily be controlled.
By utilizing the soil vapor extraction alternative for the NAPL and
pumping and treating the contaminated ground water through air
stripping the threat of exposure through ingestion will be
eliminated. By treating the ground water and then reinjecting it
into the aquifer, the excess cancer risk associated with this
pathway, under the future residential use scenario will be reduced
from 2 X ID'3 to less than 1 X icr6, which is within the EPA-
acceptable risk range. There are no short-term-threats associated
with the implementation of the selected remedy components that
cannot readily be controlled.
Compliance with Applicable or Relevant and Appropriate
Requirements;
Each component of the selected remedy for the Site complies with
all applicable or relevant and appropriate action-, chemical-, and
location-specific requirements ARARs. The Site-specific ARARs are
presented in Table 9.
Cost-Effectiveness;
The NCP requires that remedial alternatives are determined to be
adequately protective of human health and the environment, and are
ARAR-compliant before cost-effectiveness is considered in remedy
selection, however, the NCP recognizes that in some instances, a
range of remedial alternatives can be protective and ARAR-
compliant, and that cost is a legitimate factor for choosing among
such alternatives. In the remedy selection process concerning the
Site, several alternatives were considered, including the thin-
spreading alternative for treatment of hydrocarbon-contaminated
soils, where determined to be unacceptable because they did not
meet ARARs and were not adequately protective. Other alternative
remedies were rejected because they either did not meet ARARs or
were not adequately protective. Comments which suggested that
vapor extraction of the NAPL be implemented, without concurrent
extraction, treatment, and reinjection of contaminated ground
water, were rejected because such an approach would not be
adequately protective. When choosing among the alternatives that
were both adequately protective and ARAR-compliant, EPA considered
cost, and selected a remedy which has been determined to provide
overall effectiveness proportional to its costs, the net present
worth being $16,301,576.00. Any other combination of ARAR-
compliant alternatives would not meet the remediation objectives
for the site, and would provide less protection of human health and
the environment.
83
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Utilization of Permanent Solutions and Alternative Treatment
Technologies (or Resource Recovery Technologies) to the Maximum
Extent Practical:
The selected remedy utilizes permanent solutions and alternative
treatment technologies to the maximum extent practicable at the
Prewitt Abandoned Refinery Site.
Of those alternatives that are protective of human health and the
environment, and comply with ARARs, EPA has determined that the
selected remedy provides the best balance of trade of f s in terms of
long-term effectiveness and permanence, reduction in toxicity,
mobility, or volume achieved through treatment, short-term
effectiveness, implementability, costs, also considering the
statutory preference for treatment as a principal element, and
taking into consideration State, Navajo Nation, and community
acceptance.
The selected ground water remedy satisfies the long-term
effectiveness and perma: ^ :e criterion by preventing future spread
of contamination to receptors by promoting restoration of ground
water quality. It satisfies the implementability and short term
effectiveness criteria better than all of the other alternatives
investigated for possible solutions to the ground water
contamination problems at the Prewitt Abandoned Refinery Site. It
satisfies the reduction in toxicity, mobility and volume criterion
by utilizing the pump and treat system for groundwater and the
vapor extraction system for NAPLs.
The selected contaminated soil remedy satisfies the long-term
effectiveness and permanence criterion by destroying hydrocarbon
contaminants through biological degradation in a landfarm. Lead,
which is not amenable to destruction, will be stabilized and
removed permanently from the Site.
Preference for Treatment as a Principal Element;
The statutory preference for remedies that employ treatment as a
principal element will be satisfied through implementation of the
selected remedy. This remedy utilizes permanent solutions for the
Site in that its goal is to remove contaminants from ground water,
surface structures and soil and to treat these contaminants to
ARARs or acceptable risk levels.
XI. DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan for the Prewitt Abandoned Refinery Site was
released for public comment in July 1992. The Proposed Plan
identified Alternatives: 1C (Ground Water Extraction &
Reinjection) , 2C (Soil Vapor Extraction), 3C
84
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(Excavation/Landfarming of West Pits Area) , 4B (Excavation and Off-
Site Disposal of Lead Contaminated Soils), 4C (Excavation and Off-
site Disposal of Asbestos Contaminated Materials and Soils) 4E
(Excavation/Landfarming of Soil Containing Hydrocarbons) and 5B (
Excavation and Off-Site Disposal of the Separator and its Contents)
as the selected alternatives for the Site. EPA reviewed all
written and verbal comments submitted during the public comment
period. Upon review of these comments, it was determined that the
cleanup goal for lead contaminated soil at depth greater than 2
feet could be changed to 1000 ppm (from 500 ppm) without impacting
the protectiveness level established. This change is a logical
outcome of the discussion of EPA's action levels for lead as
discussed in the Proposed Plan.
85
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FIGURES
-------
Navajo
Indian
Reservation
Prewitt
Refinery
Super-fund Site
Zuni Indian
Reservation
Raman Navajo
Indian Reservation
Site Location Map
PREWITT SUPERFUND SITE
PREWITT, NEW MEXICO
Figure 1
-------
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-------
TABLES
-------
EXPOSURE MEDIUM/
EXPOSURE ROUTE
Dermal Contact
TABLE 1
CURRENT EXPOSURE PATHWAYS
PREWITT REFINERY SITE
PREWITT, NEW MEXICO
EXPOSURE
POINT
CURRENT EXPOSURE
GROUNDWATER
Ingestion
Private Wells
Private Wells
RESIDENTIAL
POPULATION
INCIDENTAL EXPOSED
POPULATION
SURFACE SOIL
Ingestion
Dermal Contact
Ingestion
Dermal Contact
Within Fenced Area
Within Fenced Area
Outside Fenced Area
Outside Fenced Area
Lead Hot Spots - Vertical Tanks and Former Office Area
Ingestion Within Fenced Area
Dermal Contact Within Fenced Area
Organic Hot Soot - Waste Pit Area
Ingestion Within Fenced Area
Dermal Contact Within Fenced Area
AIR
Inhalation During
Showering
Private Wells
Y
Y
Y
Y
Y
Y
Y
Y
-------
TABLE 2
FUTURE EXPOSURE PATHWAYS
PREWITT REFINERY SITE
PREWITT, NEW MEXICO
EXPOSURE MEDIUM/ EXPOSURE RESIDENTIAL INCIDENTAL EXPOSED
EXPOSURE ROUTE POINT POPULATION POPULATION
FUTURE - RESIDENTIAL USE
GROUNDWATER
Ingestion MW Within Fenced Area
Outside Fenced Area
and Private Wells A
Dermal Contact MW Within Fenced Area
Outside Fenced Area
and Private Wells A
SURFACE SOIL
Ingestion Within Fenced Area
Outside Fenced Area A,C
Dermal Contact Within Fenced Area
Outside Fenced Area A.C
Lead Hot Spots - Vertical Tanks and Former Office Area
Ingestion Within Fenced Area A,C
Dermal Contact Within Fenced Area A,C
Organic Hot Soot • Waste Pit Area
Ingestion Within Fenced Area A,C
Dermal Contact Within Fenced Area A,C
-------
TABLE Z(Continued)
FUTURE EXPOSURE PATHWAYS
PREWITT REFINERY SITE
PREWITT, NEW MEXICO
EXPOSURE MEDIUM/ EXPOSURE RESIDENTIAL INCIDENTAL EXPOSED
EXPOSURE ROUTE POINT POPULATION POPULATION
AIR
Inhalation During MW Within Fenced Area,
Showering Outside Fenced Area
and Private Wells A
FUTURE NON-RESTRICTED USE - YOUTH AND YOUNG ADULTS
SURFACE SOIL
Ingestion Within Fenced Area Y
Dermal Contact Within Fenced Area Y
Ingestion Outside Fenced Area Y
Dermal Contact Outside Fenced Area Y
Lead Hot Soots - Vertical Tanks and Former Office Area
Ingestion Within Fenced Area Y
Dermal Contact Within Fenced Area Y
Organic Hot Spot - Waste Pit Area
Ingestion Within Fenced Area Y
Dermal Contact Within Fenced Area Y
-------
TABLE 2(Continued)
FUTURE EXPOSURE PATHWAYS
PREWITT REFINERY SITE
PREWITT, NEW MEXICO
EXPOSURE MEDIUM/
EXPOSURE ROUTE
EXPOSURE
POINT
RESIDENTIAL
POPULATION
INCIDENTAL EXPOSED
POPULATION
FUTURE NON-RESTRICTED USE - SHEEPHERDERS
SURFACE SOIL
Ingestion Within Fenced Area
Dermal Contact Within Fenced Area
Ingestion Outside Fenced Area
Dermal Contact Outside Fenced Area
Lead Hot Spot - Former Office Area
Ingestion Within Fenced Area
Dermal Contact Within Fenced Area
Organic Hot Spot - Waste Pit Area
Ingestion Within Fenced Area
Dermal Contact Within Fenced Area
FUTURE FOOD EXPOSURES - LAMB AND MUTTON
Ingestion
Ingestion
Within Fenced Area
Outside Fenced Area
Lead Hot Spot - Former Office Area
Ingestion Within Fenced Area
A
A
S
S
S
S
S
S
S
S
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TABLE 2 (Continued)
FUTURE EXPOSURE PATHWAYS
PREWITT REFINERY SITE
PREWITT, NEW MEXICO
EXPOSURE MEDIUM/ EXPOSURE RESIDENTIAL INCIDENTAL EXPOSED
EXPOSURE ROUTE POINT POPULATION POPULATION
Organic Hot Soot - Waste Pit Area
Ingestion Within Fenced Area A
FUTURE CONSTRUCTION
SURFACE AND SUBSURFACE SOIL -
s
Ingestion Within Fenced Area CO
Dermal Contact Within Fenced Area CO
Ingestion Outside Fenced Area CO
Dermal Contact Outside Fenced Area CO
Lead Hot Spots - Vertical Tanks and Former Office Area
Ingestion Within Fenced Area CO
Dermal Contact Within Fenced Area CO
Organic Hot Spot - Waste Pit Area
Ingestion Within Fenced Area CO
Dermal Contact Within Fenced Area CO
Notes:
A = Adult (18-70 years)
Y = Youth and Young Adults (12-25 years)
C = Child (1-6 years)
CO = Construction worker (18-70 years)
S = Shepherd (16 -70 years)
-------
TABLE 3
GROUND WATER AND NON-AQUEOUS PHASE LIQUIDS
CONTAMINANTS OF CONCERN
WASTE VOLUMES & REMEDIATION GOALS
CONTAMINANT
Benzene
1,2
D ichlor oethane
Ethylbenzene
Lead
Toluene
Xylene
WASTE VOLUME
Approximately
50,000 gallons
contaminated
water
-
Approximately
43,500 gallons
of NAPL
MAXIMUM
CONTAMINANT
CONCENTRATION
3900 ug/1
510 ug/1
1800 ug/1
167 ug/1
6200 ug/1
9600 ug/1
REMEDIATION
GOAL & BASIS
0.005 mg/1 MCL
0.005 mg/1 MCL
0.700 mg/1 MCL
0.015 mg/1 AL
0.750 mg/1 NMW
0.620 mg/1 NMW
MCL = Maximum Contaminant Level As per Safe Drinking Water Act
AL = Action level June 21, 1990 Memorandum from Henry L. Longest,
Office of Emergency and Remedial Response of EPA, Washington, DC
NMW = New Mexico Water Control Commission RegulationsPart 3,
Section 3-100
Risk posed by contaminated ground water is approximately 2 X 10
,-3
-------
TABLE 3 (Continued)
SURFACE SOILS
CONTAMINANTS OF CONCERN
WASTE VOLUMES & REMEDIATION GOALS
CONTAMINANT
Asbestos
Benzo (a) anthra
-cene
Benzo (a) pyrene
Benzo (b)fluor
anthene
Benzo (k)fluor
anthene
Chrysene
Lead
WASTE VOLUME
15+ cy -
asbestos
containing
matierial
Appr ox imat e ly
1500 cy of PAH
contaminated
soils
Approximately
665 cy of lead
contaminated
soils
MAXIMUM
CONTAMINANT
CONCENTRATION
above
background
—
265 ppm
215 ppm
146 ppm
146 ppm
220 ppm
129,000 ppm
REMEDIATION
GBAESS&
Remove all
9.0 ppm* HBR
0.9 ppm HBR
0.9 ppm* HBR
0.9 ppm* HBR
90.0 ppm*
HBR
500 ppm EPA
(0'-2')
1000 ppm EPA
(beyond 2')
* Since these contaminants do not have slope factors, the
remediation goal is base on the contaminants relative potency to
benz o(a}pyrene.
Upon completion of remediation risk to human health via the soils
will not exceed 1 X KT6.
HRB = Health Based Risk developed by EPA, Region 6
EPA = National EPA Policy Office of Solid Waste and Emergency
Response (OSWER) Directive #9355.4-02
-------
TABLE 3 (Continued)
SEPARATOR WASTE AND SOILS
CONTAMINANTS OF CONCERN
WASTE VOLUMES & REMEDIATION GOALS
CONTAMINANT
WASTE VOLUME
MAXIMUM
CONTAMINANT
CONCENTRATION
REMEDIATION
GOALS FOR
RESIDENTIAL
USE
Benzene
Ethylbenzene
Lead
Toluene
Xylene
80 cy of
sludges
Unknown if
soils
underneath
separator are
contaminated
or what level
of
contamination
230 ug/1 -TCLP
4200 ppb
Complete
removal of
sludges with
treatment
prior to
disposal.
If soils are
contaminated
and do not
interfere with
RCRA
landfarming
requirements
they will be
landfarmed. If
not, they will
be treated
through other
means.
Upon completion of remediation, risk posed by separator contents
and any contaminated soil underneath separator will be less than
1 X 10*.
-------
CHEMICAL
TABLE 4
EXPOSURE POINT CONCENTP raethane
Ethyl benzene
Toluene
Trichloroethylene
Xylene
* In cases where the
Heir r*almilatiAn0 TV
.
1
"" ,
4
3
2
3
2
3
95% upper confidence limit exceeded the maximum
ktt mavtnnimn *^^n«*An+ra*i/tn rA^Ar* +« 4ttA vMawiMnnwt ****
.
8*
-
7*
3*
3*
6*
3*
4*
concentration
if***^t*tr mUfm a*
0.7
41
252
894
185
403
2127
.
2851
detected, the
«k v*
-------
TABLE 4 (Continued)
CHEMICAL
EXPOSURE POINT CONCENTRATIONS
FOR INHALATION OF CHEMICALS OF CONCERN IN GROUNDWATER
WITHIN FENCED AREA (mg/rrf
PREWTTT REFINERY SITE
PREWITT, NEW MEXICO
.30
WITHIN FENCED AREA
ABCD-SA/G LAYER
GEOMETRIC 95% UPPER
MEAN CONFIDENCE
LIMIT
EF LAYER
GEOMETRIC 95% UPPER
MEAN CONFIDENCE
LIMIT
Volatiles
Benzene
1,2-Dichloroe thane
Ethyl benzene
Toluene
Trichloroethylene
Xylene
0.004
0.003
0.002
0.003
0.002
0.003
0.038*
0.012*
0.014*
0.03*
0.013*
0.019*
" 9.56
1.80
3.81
2.14
-
1.55
9.6*
1.8*
3.8*
21.4*
-
27.1*
* In cases where the 95% upper confidence limit exceeded the maximum concentration detected, the maximum was used in the
risk calculations.
Notes:
1 These concentrations were calculated from a volatilization model presented in Appendix C.
** These tables were taken out of the Risk Assessment Report which was conducted by the PRPs. (June 12, 1991)
EPA's risk calculations were based on the 95% Upper Confidence Limit shown in these tables.
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TABLE 4 (Continued)
EXPOSURE POINT CONCENTRATIONS
FOR CHEMICALS OF CONCERN IN SURFACE AND SUBSURFACE SOIL
OUTSIDE AND WITHIN FENCED AREAS (mg/kg)
PREWITT REFINERY SITE
PREWITT, NEW MEXICO
WITHIN FENCED AREA OUTSIDE FENCED AREA
CHEMICAL
Inorganics
Chromium
Lead
Mercury
Nickel
Semivolatiles
Anthracene
Benzo(a)anthracene
8enzo(a)pyrene
Benzo(b)fluoranthene
Benzo(g,h.i)perylene
Bemo(k)fluoranlhene
Chrysene
Fluoranthero
Fluorene
2-Methytoaphthalene
Naphthalene
Phenanthrene
Pyrene
Volatilea
Benzene
Ethyibenzene
Tetrachloroethylene
Toluene
Trichloroethylene
Xylene
GEOMETRIC
MEAN
12
17
0.1
6
1.0
0.6
0.5
0.5
-
.
0.6
0.5
0.5
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0.8
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0.007
0.009
0.006
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95% UPPER
CONRDENCE
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115
270
1
31
150
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GEOMETRIC
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0.3
0.6
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0.4
0.6
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0.8
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95% UPPER
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141
109
1
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113
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451
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* In cases where the 95% upper confidence limit exceeded the maximum concentration detected, the maximum was used in the
risk calculations.
•* These tables were taken out of the Risk Assessment Report which was conducted by the PRPs. (June 12, 1991)
EPA's risk calculations were based on the 95% Upper Confidence Limit shown in these tables.
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TABLE 4 (Continued)
EXPOSURE POINT CONCENTRATIONS
FOR CHEMICALS OF CONCERN IN SURFACE SOIL
OUTSIDE AND WITHIN FENCED AREAS (mg/kg)
pREwrrr REFINERY SITE
PREWITT, NEW MEXICO
WITHIN FENCED AREA
OUTSIDE FENCED AREA
CHEMICAL
GEOMETRIC
MEAN
95% UPPER
CONFIDENCE
LIMIT
GEOMETRIC
MEAN
95% UPPER
CONFIDENCE
LIMIT
Inorganics
Chromium
Lead
Mercury
Nickel
Semivolaliles
Anthracene
Benzo (a)anthracene
Benzo (a)pyrene
Benzo(b)fluoranthene
Benzo (g,h,i)perylene
Benzo (k)fluoranthene
Chrysene
Fluoranthene
Fluorene
2-Methylnaphthal«ne
Naphthalene
Pnenanthrene
Pyrene
Volatiles
Benzene
Ethylbenzene
Tetrachloroethylene
Toluene
Trichloroethylene
Xylene
13
17
0.09
6
1.1
0.5
0.2
0.5
0.6
0.4
0.4
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0.004
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129
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11*
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0.5
0.3
0.3
0.4
0.6
0.2
0.2
0.5
0.6
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0.03
0.03
99
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6.6
3.9
113
273
0.08"
0.1*
0.1*
• In cases where the 95% upper confidence limit exceeded the maximum concentration detected, the maximum was used in the
risk calculations.
•n,ese tables were taken out of the Risk Assessment Report which was conducted by the PRPs. (June 12, 1991)
EPA's risk calculations were based on the 95% Upper Confidence Limit shown in these tables.
-------
TABLE 5
UPTAKE RATES
PREWtTT REFINERY SITE
PREWITT. NEW MEXICO
r
i;
LJ
UPTAKE RATES FOR ORGANIC COMPOUNDS
COMPOUND logKow PLANT UPTAKE SHEEP UPTAKE
(mg/kg DW plant (day/kg)
per mg/kgDW soil)
2-METHYLNAPHTHALENE
ANTHRACENE
BENZENE
BEN20(A)ANTHRACENE
BENZO(A)PYRENE
BENZO(B)FLUORANTHENE
BENZO(GHI)PERYLENE
BENZO(K)FLUORANTHENE
CHRYSENE
ETHYLBENZENE
FLUORANTHENE
FLUORENE
NAPHTHALENE
PHENANTHRENE
PYRENE
TETRACHLOROETHYLENE
TOLUENE
TRICHLOROETHYLENE
XYLENE
4.10 (2)
4.45 (1)
2.12 (1)
5.60 (1)
6.06 (1)
6.06 (1)
6.51 (1)
6.06 (1)
' 5.61 (1)
3.15 (1)
4.90 (1)
4.18 (1)
3.40 (1)
4.46 (1)
4.88 (1)
2.60 (1)
2.73 (1)
2.38 (1)
3.26 (1)
1.7E-01
1.0E-01
2.3E+00 '
2.2E-02
1.2E-02
1.2E-02
6.7E-03
1.2E-02
2.2E-02
5.9E-01
5.7E-02
1.5E-01
4.2E-01
1.0E-01
5.9E-02
1.2E+00
1.0E+00
1.6E+00
5.1E-01
7.0E-05
7.0E-05
1.6E-05
7.0E-05
7.0E-05
7.0E-05
7.0E-05
7.0E-05
7.0E-05
1.7E-04
7.0E-05
7.0E-05
3.0E-04
7.0E-05
7.0E-05
4.8E-05
6.5E-05
2.9E-05
2.2E-04
UPTAKE RATES FOR INORGANIC COMPOUNDS
COMPOUND PLANT UPTAKE (3,4) SHEEP UPTAKE (3,5)
(mg/kgDW plant (day/kg)
per mg/kg soil)
CHROMIUM
MERCURY
NICKEL
7.5E-03
9.0E-01
6.0E-02
9.2E-03
2.7E-02
2.0E-03
Notes:
(1) USEPA, 1986c
(2) Karickhoff et al. 1979
(3)SCAQMD. 1988
(4) Uptake factor adjusted for dry weight
(5) Uptake factor for beef cattle
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NOTES:
IRIS - Integrated Risk In
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Effects Assessmei
HEAST - USEPA Health
HA - Health Advisory
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Q
e
a
7.30E-02
Chrysene(2)
1
Hemangio&
3
1
CQ
CQ
1
9.10B-02
o
I
1
3
1
S
S
0
t/\
i
S.10E-02
|| Tetrachloroethylene
|
3
i
-
s
a
s
o
H
OQ
i
o
|| Trichloroethylene
-------
TABLE 8
COMPARATIVE ANALYSES FOR GROUND WATER REMEDIAL ALTERNATIVES
PREWITT ABANONDED REFINERY
CRITERION
ALTERNATIVE
Overall Protection of Human
Health and
the Environment
Most
1C, ID
IB
1A
Least
Compliance with ARARs
Most
1C, ID
1A, IB
Least
Long-Term Effectiveness and
Permanence
Most
1C, ID
IB
1A
Least
Reduction of Toxicity,
Mobility, or Volume
through Treatment
Most
1C
ID
1A, IB
Least
Short Term Effectiveness
Most
IB
1C, ID
1A
Least
Implementabilty
Most
1A,1B
1C, ID
Least
Cost
Least Expensive
1A
IB
1C
ID
Most Expensive
-------
TABLE 8
COMPARATIVE ANALYSES FOR NON-AQUEOUS PBASR LIQUIDS REMEDIAL
ALTERNATIVES
PREWITT ABANONDED REFINERY
CRITERION
ALTERNATIVE
Overall Protection of Human
Health and
the Environment
Most
2C
2B
2A
Least
Compliance with ARARs
.Most
2B, 2C
2A
Least
Long-Term Effectiveness and
Permanence
Most
2C
2B
2A
Least
Reduction of Toxicity,
Mobility, or Volume
through Treatment
Most
2Bf 2C
2A
Least
Short Term Effectiveness
Most
2A
2B, 2C
Least
Implementabilty
Most
2C
2B
2A
Least
Cost
Least Expensive
2A
2B
2C
Most Expensive^
-------
TABLE 8
COMPARATIVE ANALYSES FOR SURFACE SOILS REMEDIAL ALTERNATIVES
PREWITT ABANONDEO REFINERY
CRITERION
ALTERNATIVE
Overall Protection of Human
Health and
the Environment
Most
4B,4E,4C
4D,4F
4A
Least
Compliance with ARARs
-Most
4B,4C,4E
4Df4F
4A
Least
Long-Term Effectiveness and
Permanence
Most
4B,4C,4D
4E
4F
4A
Least
Reduction of Toxicity,
Mobility, or Volume
through Treatment
Most
4E
4A, 4B, 4Cf 4D, 4F
Least
Short Term Effectiveness
Most
4B,4C,4D,4E
4F
4A
Least
ImplementabiIty
Most
4B, 4C, 4F
4D, 4E
4A
Least
Cost
Least Expensive
4A
4C
4F
4D
4B, 4E
Most Expensive
-------
TABLE 8
COMPARATIVE ANALYSES FOR WEST PITS REMEDIAL ALTERNATIVES
PREWITT ABANONDED REFINERY
CRITERION
ALTERNATIVE
Overall Protection of Human
Health and
the Environment
Most
3C
3B
3D, 3E
3A
Least
Compliance with ARARs
Kost
3C
3B, 3D, 3E
3A
Least
Long-Term Effectiveness and
Permanence
Most
3C
3B, 3D, 3E
3A
Least
Reduction of Toxicity,
Mobility, or Volume
through Treatment
Most
3C
3E
3D
3A, 3B
Least
Short Term Effectiveness
Most
3B
3C, 3D, 3C
3A
Least
Implementabilty
Most
3B, 3D, 3E
3C
Least
Cost
Least Expensive
3A
3B
3E
3D
3C
Most Expensive
-------
TABLE 8
COMPARATIVE ANALYSES FOR SEPARATOR CONTENTS AND SOILS
REMEDIAL ALTERNATIVES
PREWITT ABANONDED REFINERY
CRITERION
Overall Protection of Human
Health and
the Environment
Compliance with ARARs
Long-Term Effectiveness
Permanence
Reduction of Toxicity,
Mobility, or Volume
through Treatment
Short Term Effectiveness
ImplementabiIty
Cost
ALTERNATIVE
Most
5B
5A
Least
'Most
5B
5A
Least
Most
5B
5A
Least
Most
5B
5A
Least
Most
5B
5A
Least
Most
5B,5A
Least
Least Expensive
5A
SB
Most Expensive
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TABLE 9
APPLICANT OR RELEVANT AND APPROPRIATE REQUIREMENTS
GROUND WATER and NON-AQUEOUS PHASE LIQUIDS:
ACTION SPECIFIC;
* New Mexico State Engineers's Office Rules and Regulations
(Article 1-17) (Well Construction)
* New Mexico Water Quality Control Commission Regulation Part 3,
Section 3-100, "Regulations for Discharges Onto or Below the
Surface of the Ground."
* New Mexico Water Qu.-'ity Control Commission Regulation Part 3,
Section 3-103 ^
* Water Quality Standards for Interstate and Intrastate Streams
in New Mexico, Section 1-102
* New Mexico Environmental Improvement Board Air Control
Regulation 702
CHEMICAL SPECIFIC;
* National Primary Drinking Water Regulations (40 CFR Part 141)
Maximum Contaminant Levels
* National Emission standards for Hazardous Air Pollutant (40
CFR Part 61)
LOCATION SPECIFIC;
THERE ARE NO LOCATION SPECIFIC ARARs THAT APPLY TO THE GROUND WATER
AND NON-AQUEOUS PHASE ALTERNATIVES
-------
TABLE 9
WEST PITS AREA:
ACTION SPECIFIC;
* Resource Conservation and Recovery Act (40 CFR § 264.270
Subpart M)
* Resource Conservation and Recovery Act (40 CFR § 264 Subpart
G)
* New Mexico Environmental Improvement Board Air Control
Regulation 702
CHEMICAL SPECIFIC:
THERE ARE NO CHEMICAL SPECIFIC ARARs THAT APPLY TO THE WEST PITS
AREA
LOCATION SPECIFIC;
THERE ARE NO LOCATION SPECIFIC ARARs THAT APPLY TO THE WEST PITS
AREA
TO BE CONSIDERED;
* New Mexico Underground Storage Tank Regulation
-------
TABLE 9
SEPARATOR:
ACTION SPECIFIC:
* Resource Conservation and Recovery Act (40 CFR 268) (land
disposal restrictions)
* Resource Conservation and Recovery Act (40 CFR § 261.31 (F037
waste listing)
* Resource Conservation and Recovery Act (40 CFR § 261.24
(toxicity characteristic for lead)
CHEMICAL SPECIFIC:
THERE ARE NO CHEMICAL F~"":iFIC ARARs THAT APPLY TO THE SEPARATOR
ALTERNATIVES.
LOCATION SPECIFIC:
THERE ARE NO LOCATION SPECIFIC ARARs THAT APPLY TO ANY OF THE
SEPARATOR ALTERNATIVE
TO BE CONSIDERED;
* New Mexico Underground Storage Tank Regulation
-------
TABLE 9
SURFACE SOILS:
ACTION SPECIFIC;
* Resource Conservation and Recovery Act (40 CFR 268) (land
disposal restrictions)
* Resource Conservation and Recovery Act (40 CFR § 264.270
Subpart M) (landfarming requirements)
* Resource Conservation and Recovery Act (40 CFR § 264 Subpart
G) (landfarming requirements)
CHEMICAL SPECIFIC:
* National Emission Standards for Hazardous Air Pollutant (40
CFR Part 61 subpart M) (asbestos)
LOCATION SPECIFIC;
THERE ARE NO LOCATION SPECIFIC ARARs THAT APPLY TO ANY OF THE
SURFACE SOIL ALTERNATIVES
TO BE CONSIDERED:
* New Mexico Underground Storage Tank Regulation
-------
TABLE 10
RISK POSED BY CONTAMINATED SOILS
FUTURE RESIDENTIAL SCENARIO
CARCINOGENIC RISK POSED BY INGESTION OF CONTAMINATED SOIL FROM
THE SITE
WASTE PITS
VERTICAL TANKS
FORMER OFFICE
OUTSIDE FENCED AREA
2 x 10'3
5 X ID'9 *
1 X ID"4
6 X 10"3
ENTIRE INSIDE FENCE AREA 3 X lO"4
* This site contains lead in excess of the 500-1000 ppm remediation
goal.
-------
RESPONSIVENESS SUMMARY
FOR THE PREWITT REFINERY
RECORD OF DECISION
This Responsiveness Summary has been prepared to provide written
responses to comments submitted regarding the Proposed Plan of
Action for the Prewitt Refinery Superfund Site. Two Public
Meetings were conducted during the Public Comment Period.
Transcripts of these meetings are included in the Administrative
Record. Written comments on the proposed plan were submitted by
the New Mexico Environment Department and the Navajo Indian Nation.
Also, the Atlantic Richfield Company (ARCO) and The El Paso Company
(TEPCO) jointly submitted comments including comments that were
prepared on behalf of ARCO and TEPCO by -Applied Hydrology
Associates, Inc., and ERM-Rocky Mountain, Inc.
Many of the comments, particularly those prepared by the
consultants to ARCO and TEPCO were similar. The comments have been
grouped according to their subject matter, and responded to
accordingly. Many detailed comments were submitted to support
larger general comments. The responsiveness summary addresses
these many detailed comments as part of the response to the general
comments, thus making several of the responses lengthy and very
technical.
COMMENT #1: FUTURE RESIDENTIAL USE IS UNREASONABLE.
The proposed alternatives for surface materials including
Alternative 3C, 4B, 4C, 4E, and 5B are unreasonably based on future
residential use of the site. The commenter cites EPA risk
assessment guidance to support that a risk assessor need not assume
residential use at every site. An aerial photograph was submitted
that indicates no industrial activities in the area. A
socioeconomic report for a nearby area, prepared by Dames and
Moore, was also submitted to support future land use patterns.
Several commenters offered verbal or written comments either in
support of or opposition to future residential land use.
RESPONSE #1:
The commenter, who stated that all of the above alternatives, which
are preferred by EPA for the remediation of the Site, are based
solely on a future residential use scenario, is not correct.
Although future residential use was used in the baseline risk
assessment to evaluate site risks, other factors also indicate a
need for the preferred remedy alternatives. The West Pit and North
Pit contents (addressed by Alternatives 3C and 4E) are principal
threats at the Site due to the high concentration of carcinogenic
polynuclear aromatic hydrocarbons (PAHs). The preamble to the
National Contingency Plan (NCP), 55 Fed. Reg. 8666, 8703,
describes principal threats as wastes that contain
-------
high concentrations of toxic compounds (e.g., several
orders of magnitude above levels that allow for
unrestricted use and unlimited exposure).
As an example, the concentration of benzo(a)pyrene that allows for
unlimited, unrestricted use (i.e. residential) is 0.09 mg/Kg in
surface soils. The average concentration of benzo(a)pyrene found
in the North Pit area exceeds 150 mg/Kg; more than three orders of
magnitude greater than a concentration which allows unrestricted
use of that area. The separator contents (addressed by Alternative
5B) are also principal threats due to the high concentrations of
contaminants and the high mobility of some of the chemicals in the
separator (e.g., the BTEX constituents). The same section of the
preamble to the NCP also describes "highly mobile materials" as
principal threats.
As stated in the NCP (40 CFR Part 300.430 (a) (iii) (A)) "EPA expects
to use treatment to address principal threats posed by a site,
wherever practicable." The NCP preamble 55 Fed Reg. at 8701 also
states that this expectation
reflects CERCLA's preference for achieving protection
through the use of treatment technologies that destroy or
reduce the inherent hazards posed by wastes, and ... to
significantly reduce the toxicity and/or mobility of the
contaminants posing a significant threat.
Alternative 4C, for asbestos abatement, would be required for
future commercial or industrial use as well as residential use.
Lead removal would also be required for any future land use that
includes commercial or residential (although the cleanup standard
may be raised). The lead contaminated soils are also identified as
a principal threat due to the very high concentrations of lead and
the apparent mobility of that lead. Groundwater beneath the high
lead soil areas exceeds drinking water standards for lead.
As to future use of the property, the EPA guidance (OSWER Directive
9355.0-30) cited in Atlantic Richfield Company (ARCO) and El Paso
Natural Gas Co. (EPNG) comments and the preamble to the NCP state
that EPA will consider future land use to be residential in many
cases. The referenced guidance ,OSWER Directive 9355.0-30 at page
5 further states (emphasis added),
residential areas should be assumed to remain
residential; and undeveloped areas can be assumed to be
residential in the future unless sites are in areas where
residential land use is unreasonable.
The guidance mentions sites surrounded by operating industrial
facilities as an example of sites where future residential use may
-------
be unreasonable.
As the commenter notes, surrounding land use at the Site is not
industrial. Immediately to the Northeast of the Site, is a cluster
of residential homes. Another group of homes is located to the
West of the Site. A fire station and other light commercial
operations that support a rural residential community are also
located near the Site. The report submitted by the commenter,
entitled "Final Socioeconomic Report For Bluewater Uranium Mill
Vicinity", an area near the Prewitt Site, states (emphasis added) ,
Much of the land in the study area is open rangeland.
Ranchers will continue to live in the study area as will
others seeking a rural lifestyle. Results from the
survey conducted for this study suggest that quality of
life is an important motivation for residents to remain
in the area. The fact that only 3 of the 24 households
interviewed indicated that they intended to move
indicates a significant loyalty to the area. In short,
the population in the area is likely to remain small but
they are also expected to remain in the area for a long
time.
This loyalty to the area and expectation for the future was
expressed during public meetings held by EPA to accept comments on
the proposed plan. One member of the public expressed that the
land was particularly valuable due to its location and easy access,
and hopes for future growth in the area.
The commenter also claims declining population trends in this non-
densely populated area. The commenter states that a reference
attached to the comment shows declining population trends. EPA has
reviewed that citation and can find no such data for declining
populations. To the contrary, data obtained by EPA (United States
Census Bureau: General Population Characteristics - New Mexico),
indicates a growing population for the area. The most recent
census data, taken in 1990, indicates that population in the area
has actually increased from 56,449 to 60,680 since the last census
in 1980. While this is only about an 8% increase, it is certainly
not evidence of declining population trends.
Also, the Dames and Moore report cited by the commenter (page 23)
indicates impediments to physical barriers to development such a
steep topography and poor soil conditions, including malpais lava.
The physical conditions in the vicinity of the Prewitt Site do not
preclude development, as evidenced by the existing community
adjacent to the Site. This is part of its value even within an
expansive area of sparsely populated land.
The State of New Mexico, through the New Mexico Environment
Division (NMED), has submitted comments (letter dated 16 September
1992) that projected future use of the site should be classified
-------
as residential in order to gain State acceptance of the remedy.
The Navajo Nation has submitted statements regarding future land
use. In a letter dated September 18, 1992, the Navajo
Environmental Protection Administration indicates that the Navajo
Nation has entered into an agreement to exchange the land which the
Site occupies for some other land provided by ARCO and EPNG, the
potentially responsible parties (PRPs); consequently, according to
the letter, a future residential scenario is no longer the most
appropriate. This same letter also states that the future
residential scenario should be abandoned due to the fact that the
PRPs are going to relocate the Navajo families in the area. The
letter does not address the non-Navajo families who live adjacent
to the Site. A separate memorandum from the Navajo Superfund
Program, submitted as part of the comments on'the Proposed Plan,
dated September 16, 1992, states
... the Navajo Superfund Program supports U.S. EPA's
preferred alternatives selected in the Proposed Plan for
the future residen ' 1 scenario.
In response to all of these comments, and the uncertainty regarding
future land use, EPA reevaluated the risk assessment.
Based on statements made, in the land exchange agreement between
the Navajos and the PRPs, regarding potential future commercial
use of the Site property, EPA evaluated the risk posed by future
commercial/industrial use of the property. Furthermore, based on
comments made by various individuals who indicated that they had
frequently traversed the Site and, consequently, had frequent
contact with the surficial areas of the Site, and based on the
propensity for individuals to reside in the area for many years, as
indicated in the Socioeconomic Report cited above, EPA also
reevaluated residential and trespasser exposure assumptions. EPA's
conclusions are presented in the discussions of risk presented in
the Record of Decision (ROD). In short, EPA has concluded that the
future residential use scenario is appropriate. Additionally, EPA
has determined, based on the contaminant concentrations, that for
certain areas throughout the site, treatment of surface
contamination would be warranted regardless of which future use
scenario is considered.
COMMENT #2: INSTITUTIONAL CONTROLS OR THIN SPREADING ARE SUPERIOR
THAN LANDFARMING AS REMEDY FOR WASTE PIT SLUDGES AND HYDROCARBON
CONTAMINATED SOILS.
Even assuming future residential use of the site, the selection of
landfarming for the West Pits area and for the hydrocarbon
contaminated soils is an inappropriate choice of alternatives when
compared against NCP criteria. Institutional controls are
protective of human health (any construction activity performed for
surface materials unreasonably raises the risk to human health and
-------
the environment beyond the No Action alternative). Thin spreading
is more protective than landfarming. Thin spreading satisfies
ARARs, and thin spreading is cost effective.
RESPONSE #2:
The commenter expresses a preference for institutional controls
based primarily on risk assumptions, namely existing risk posed by
the site versus the potential risk to workers during implementation
of a remedy. The commenter cites data that suggests that,
the risks of death from excavation and construction
activities required for thin spreading or landfarming
soil currently pose a risk of between 33 and 42
accidental deaths per 100,000 worker years. Using site
specific factors this translates to a minimum mortality
risk of 1.7 X 10*.
EPA disagrees with the conclusions of the commenter for the
following reasons. The ^.chnical data on work accidents is based
on the broad category of "construction". However, the supporting
documentation on the nature of excavation accidents, submitted by
the commenter, 54 Fed. Reg. at 45897, indicates that the danger of
excavation occurs during "cave-ins" to workers in trenches that
collapse. The type of excavations expected during the Site
remediation are not expected to require workers to be working in
trenches. The excavations will typically be shallow, and not
expected to require steep sides such as those involved in
"trenching" operations. Also, the mortality statistics presented
by the commenter are based on all construction accidents, not just
those construction accidents associated with construction
activities conducted in compliance with Occupational Safety and
Health Administration Standards (OSHA). Any construction
activities performed at the Site will be required to comply with
OSHA standards, including new safety standards for excavation
activities; therefore, the commenters statistics are not persuasive
evidence that thin spreading or land farming will result in the
risk levels associated with excavation in general.
The wastes to be treated by remediation are principal threats at
the Site. The NCP (40 CFR Part 300.430(a) (iii) (A)) clearly
includes an expectation to treat principal threats at a Superfund
site. The preamble to the NCP , 55 Fed. Reg. at 8706, states
EPA agrees that institutional controls should not
substitute for more active response measures that
actually reduce, minimize, or eliminate contamination
unless such measures are not practicable, as determined
by the remedy selection criteria.
For reasons stated in the ROD and reasons to be further discussed
-------
in the response to this comment, EPA disagrees that evaluation
based on the nine remedy selection criteria dictate selection of
institutional controls as the preferred remedy.
The commenter asserts that the risk of construction activities to
implement a Super fund remedy, at the commenter's projected 1.7 X 10"4
mortality risk, exceeds EPA's acceptable risk range for final
remedies (1.0 X W4 to 1.0 X 10"*). EPA disagrees that the
commenter has correctly evaluated potential risks to workers.
However, even if the commenter's evaluation were correct, EPA
adoption of such a standard would unduly restrict EPA's ability to
select remedies which would protect the public at large. The
preamble to the NCP , 55 Fed. Reg. at 8717, states,
EPA will use an individual lifetime excess cancer risk of
10"6 as a point of departure for establishing remediation
goals for the risks from contaminants at specific sites.
Clearly, the commenter's interpretation unduly prohibits
implementing most remedies where construction is required to meet
requirements of the NCP and CERCLA.
EPA disagrees that thin spreading is more protective than
landfarming. The commenter has not presented any specific data
which shows why thin spreading is more protective than landf arming.
The commenter asserts that thin spreading will result in protective
levels, but the commenter does not compare the level of
protectiveness against landf arming. For reasons that are described
in the ROD and below in this response, EPA believes that
landfarming is more protective than thin spreading. Based on
treatability studies conducted by the ARCO and The El Paso Company
(TEPCO), thin spreading is expected to result in far less
degradation than aggressive biological treatment such as that which
occurs in landfarming. Thus, thin spreading relies more on
dilution than on treatment to reach protective concentrations.
Therefore, thin spreading does less to reduce toxicity, mobility,
and volume. Landfarming requires closure by placement of a soil
cap over the landf arm. Such a cap further increases the
protectiveness of the remedy by isolating the treatment residuals
to prevent exposure by contact. The thin spreading alternative
proposed by the commenter does not include a soil cover upon
completion.
EPA disagrees with the commenters assertion that thin spreading
will meet the Resource Conservation and Recovery Act (RCRA) Subpart
M requirements of treating waste by land application (landf arming) .
The thin spreading alternative does not address closure
requirements of RCRA Subpart M and does not include any specific
procedures to ensure treatment within the treatment zone. The
commenter states that it is unreasonable to control the rate of
degradation. This comment is apparently directed to the
expectation that biodegradation be maximized. However,
-------
maximization of degradation, transformation, and immobilization of
hazardous constituents in the treatment zone is a specific
requirement of 40 CFR Part 264.273 (a), and, therefore, ARAR. This
is discussed in the ROD. EPA also disagrees with the commenters
contention that the thin spreading does not need to conform to RCRA
ARARs for landfarming because, according to the coamenter, the
wastes due to be thin spread are not RCRA wastes. As stated in the
ROD and response to Comment #3, EPA believes the wastes are RCRA
wastes, and thus, RCRA requirements are applicable. Even if the
wastes were hazardous substances but not RCRA listed hazardous
wastes, the RCRA land treatment requirements would be relevant and
appropriate due to the nature of the practice to be employed, which
utilizes land application as a method to treat materials with high
concentrations of contaminants similar to those regulated by RCRA.
In the comments related to cost effectiveness (for both West Pits
and hydrocarbon contaminated soils), the commenter does not
specifically discuss cost. Rather, the comment is supported only
with the commenters general statements that,
thin spreading has seen widespread use with state
approval for petroleum contaminated soils in the Western
United States... It is effective in locations where
current use does not demand rapid treatment, and arid
conditions do not provide a mechanism for potentially
leaching waste constituents downward into the soil.
The commenter offers no data or studies to support these claims.
In fact, there is substantial evidence to the contrary, which was
submitted by ARCO and TEPCO, as part of a treatability study which
they performed. This treatability study report suggests that thin
spreading will not be effective. The report, entitled "Final
Report - New Mexico Treatability Study Update for ARCO's Prewitt
Refinery Site" (Administrative Record pages 30736 to 30863)
indicates that little or no biological activity, which is required
for effective treatment, was detected at the lower water contents
which exist under the natural arid conditions at the site. Thin
spreading is dependent upon natural conditions; therefore, the
study results indicate that thin spreading would not be effective
treatment. The report further concluded that the composite waste
would be deficient in nitrogen and phosphorous for biological
treatment, and that addition of fertilizer will be required for
biological treatment. A Bench-Scale degradation study included in
this report indicated that Total Petroleum Hydrocarbons decreased
by only 44 percent before leveling off under the passive conditions
upon which thin spreading would depend.. However, the preamble to
the NCP, 55 Fed. Reg. at 8701, states,
the Superfund program also uses as a guideline for
effective treatment the range of 90 to 99 percent
reduction in the concentration or mobility of
contaminants of concern...in general, treatment
-------
technologies or treatment trains that cannot achieve this
level of performance on a consistent basis are not
sufficiently effective and generally will not be
appropriate.
The treatability study report indicated that vigorous methods were
required (e.g., nutrient addition and inoculation with known
hydrocarbon degrading organisms) to achieve 90% degradation of
total petroleum hydrocarbons in twelve weeks. Finally, the
treatability study report concludes that biological treatment will
be effective, but only if the system is managed to ensure control
of moisture and nutrient content. Thus, EPA concludes that the
treatability study report submitted by the PRPs indicates that the
passive biological treatment that results from thin spreading will
not reach acceptable levels or rates of degradation of organic
contaminants.
A comment concerning protectiveness of ground water was made to
support the commenter's statement "that thin spreading satisfies
ARARs11 for treatment of the hydrocarbon contaminated soils. The
commenter asserts tha'.^thin spreading will actually be more
protective than landfarming, because the only moisture to transport
contaminants will come from precipitation. EPA strongly disagrees
with this conclusion. As the New Mexico Environment Department
(NMED) observed during the first Public Meeting on July 29, 1992,
thin spreading may result in increased contaminant migration to
groundwater due to changing the physical nature of the waste.
Moisture addition during landfarming, as discussed above, is
necessary to increase biologic activity and reduce the total
concentration of contaminants before they can be transported to
groundwater. Under landf arming, the carefully controlled addition of
moisture enhances biologic activity; moreover, well monitors, under
landfarming, watch for contaminant migration, so that it can be
stopped before it gets too far. Thin spreading does not include
equally protective provisions.
Both the NMED and the Navajo Super fund Program have commented that
a liner should be installed to prevent infiltration to groundwater.
The Navajo Superfund Program's comments state that a liner should
be used even if thin spreading were the selected alternative. The
response to those comments will be addressed in response to comment
15. However, it is expected that thin-spreading with a liner would
cost more that landf arming due to the increased cost of excavating
the larger land area required by thin spreading and installing a
larger liner.
COMMENT #3: SURFACE CONTAMINATION AT THE SITE IS EXEMPT FROM
CERCLA.
Selection or implementation of a remedy, under CERCLA authority, is
not warranted for the West Pits, the North Pit and hydrocarbon
contaminated soils, the separator contents, and the lead
contaminated soils due to the Petroleum Exclusion. A number of
8
-------
specific comments were made to support this general comment. The
specific comments included results of "fingerprinting" analyses,
analysis of processes that generated wastes, and testimony of
former employees. Specific comments will also be addressed in the
following response.
RESPONSE #3:
As part of the ongoing dialogue with the PRPs concerning whether
the Petroleum Exclusion prohibits a response action at the Prewitt
Site under CERCLA authority, EPA informed the PRPs, by letter dated
June 16, 1992, of specific reasons why EPA does not believe the
Petroleum Exclusion applies to certain wastes found at the Site.
That letter is in the Administrative Record for the Prewitt
Refinery Site and is also attached to this responsiveness summary.
It should be considered as part of this response, particularly
since it contains an evaluation of data which the PRPs did not
address in their comments on the proposed plan,concerning EPA's
CERCLA authority and its applicability to the Site. EPA has
considered all the comir.._.^s submitted in response to the Proposed
Plan of Action for the Prewitt Site and EPA has decided that they
do not appreciably alter EPA's conclusions as expressed in the June
16, 1992 letter.
In one specific comment, which attempts to support the contention
that RCRA wastes are not present at the site, the commenter alleges
that, because the waste streams at the Prewitt Site were
fundamentally different from the waste streams associated with the
petroleum refinery industry studied by EPA when listing the wastes,
the wastes at the Site cannot be RCRA wastes. This commenter
bases the allegation, that the wastes at the Site were not the
listed RCRA wastes in question, on the commenter's statement that
the Prewitt Refinery had no air or water pollution treatment
devices,
so that hazardous constituents that would have been
concentrated in solid wastes in a contemporary refinery
were dispersed in wastewater and storm water discharges
and emitted to the atmosphere at the Prewitt Refinery.
In short, the commenter contends that, because wastes at the Site
were discharged in an uncontrolled fashion, certain types of RCRA
hazardous waste could not have been generated, and, therefore,
according to the commenter, CERCLA authority cannot apply. EPA
disagrees with the commenter's contention. As long as a waste,
meets the description of the listed hazardous waste promulgated in
the RCRA regulations, as codified at 40 CFR Part 261, the waste in
question is that listed waste. RCRA regulations contain no
provisions to exempt a listed hazardous waste from regulation based
on a difference in a specific process which difference is not
reflected in the listing (e.g. pretreatment in a refinery
wastewater processing). Rather, the RCRA regulations allow a
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petitioner to seek "delisting" of a RCRA hazardous waste. The EPA
RCRA regulations describe the procedures for delisting a waste
produced at a particular facility. That regulatory provision
reguires that the petitioner show
that the waste produced by a particular generating
facility does not meet any of the criteria under which
the waste was listed, and... the Administrator must
determine, where he has a reasonable basis to believe
that factors (including additional constituents) other
than those for which the waste was listed could cause the
waste to be a hazardous waste, that such factors do not
warrant retaining the waste as a hazardous waste.
40 CFR § 260.22 (emphasis added). As EPA said'in its June 16, 1992
letter, the wastes at the Site do meet the criteria under which the
wastes were listed as set forth at 40 CFR Part 261 and in the
relevant Federal Register notices. Moreover, the high
concentrations of hazardous constituents in the subject waste would
certainly prevent the waste at the Site from ever meeting delisting
criteria.
Furthermore, it is clear in the Final Rule listing F037 and F038
floats and sludges, that the listing is not predicated on the waste
material succeeding the referenced air and water pretreatment
devices. For example, the regulation (40 CFR 261.37) lists any
sludge generated from the gravitational separation of any storage
or treatment of process wastewaters. The listing of sludges
resulting from storage indicates that the wastewaters need not have
already passed through any specific treatment devices. Also, the
listing of F037 and F038 wastes applies to sludges generated in
ditches and sumps. Many ditches (conveyances) and sumps at
refineries precede pretreatment devices. The Final Rule for these
wastes, 55 Fed. Reg. 46354 (November 2, 1990), discusses the
processes involved, but does not indicate that concentration of
contaminants in pretreatment devices is a prerequisite for the
identification of those contaminants as F037 or F038. To the
contrary, EPA's F037 and F038 is not exclusionary, but expansive.
In fact, the EPA begins its discussion of the F037 and f038 rules
by stating,
[t]odays rulemaking will extend RCRA and CERCLA coverage
to all oil/water/solids separation sludges and floats
generated from wastewaters from petroleum refineries
regardless of the type of device used to separate the
wastes from the process wastewaters and oil cooling
wastewaters and regardless of where treatment takes
place.
55 Fed. Reg. 46354, 46354 (November 2, 1990)(emphasis added).
A comment has been submitted that "inconsistencies exist in
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retroactively applying current regulatory standards to a refinery
operation whose processes and technology predates the refinery
technology and all of the environmental regulations and associated
treatment systems for which the current hazardous waste listing was
developed. As stated above, EPA disagrees that there is a
difference, based on technological factors, between the wastes
found at the Prewitt Site, and the RCRA listed hazardous wastes for
the petroleum refinery industry. On the general issue of
identifying a waste generated before that waste is listed as a
RCRA hazardous waste, EPA policy is that
hazardous waste listings are retroactive, so that once a
particular waste is listed, all wastes meeting that
description are hazardous wastes no matter when
disposed. For example, if on August 9, 1988, EPA were to
list distillation bottoms from production of X as a
hazardous waste, all such distillation bottoms would be
hazardous wastes, regardless of when they are or were
generated. They are the thing that is listed....Spent
solvent still bottoms disposed of in 1979 (before Agency
action listing these wastes as hazardous) are as much
spent solvent still bottoms as those disposed in 1981
(after listing took effect). In addition, there are a
whole series of statutory provisions that give
retroactive application to hazardous waste listings
[including Section 103(c) of CERCLA].
40 CFR 31138, 31147 (August 17, 1988). The Feasibility Study,
previously submitted by the commenter, identified, without
qualification, that the contents of the concrete oil water
separator, were F037 listed hazardous wastes. In response to the
Proposed Plan, it is asserted that this identification was a
precautionary measure. However, it is clear from the plant
processes, as explained in EPA's June 16, 1992 letter, that the
separator contents at the Prewitt Site are either K051 or F037
listed hazardous wastes. It is well documented that the contents
of the separator routinely flowed out to the North, along earthen
ditches, and eventually to the area known as the North Pit. Thus
deposits along this flow path are also listed hazardous wastes, and
soils are contaminated with listed hazardous wastes.
Several comments were submitted to support the notion that the
wastes generated at the Prewitt site are significantly different
than the wastes that have been listed as RCRA hazardous wastes.
Statistical tests were performed to determine if populations of
wastes at the site (based on chemical profiles) are identical to
populations of wastes studied when listing the various RCRA
hazardous wastes.
While EPA does not dispute that the statistical analyses
demonstrate differences, EPA does not agree that the statistics can
be used to support a claim that the wastes are not RCRA hazardous
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wastes. All of the statistical analyses and their underlying
assumptions have been considered by EPA. There are several
significant flaws in the analyses. For numerous reasons described
below, EPA concludes that the analyses are not valid.
As described above, slight differences in process flows, or even
composition of constituents do not justify delisting (excluding) a
listed hazardous wastes. The statistical analyses presented by
the commenter demonstrates that the population of samples taken
from the Prewitt Site are not identical to the wastes studied by
EPA during the listing of these wastes as listed RCRA hazardous
wastes. However, they would not be expected to be identical. It
is most important to understand that the analyses performed by the
commenter compared data from fresh pure wastes and sludges with
data that was not from pure wastes, but' rather of soils
contaminated by wastes. It is expected that as wastes flow along
soil pathways, metals and other pollutants from the wastes are
deposited along the pathway and eventually migrate vertically down
into the soil. The effect of this process is that specific
contaminants are "smeared" in the environment and their
concentrations will be much different than in the fresh pure
wastes used in the listing.
The hazardous wastes at the Prewitt Refinery have, for the most
part been altered by mixing with environmental media and the
effects of weathering and smearing. There is a continuing
presumption of hazardousness attached to hazardous waste which
changes form or is combined with other substances. That is,
although RCRA hazardous waste may change form or combine with soil
and other substance, it is still RCRA hazardous waste.
As the commenter notes, volatile organics were not studied, because
the Prewitt Site wastes have been exposed for many years, and most
of those organics would have evaporated or migrated to the ground
water. The data tables for Prewitt samples presented by the
commenter are dominated by samples with "SSM and "DS" designations.
As described in the RI Report, "SS" samples are shallow soil
samples and "DS" are deep soil samples. The commenter based his
findings on only a few samples that were purely waste samples and
not soil samples. It should be noted that the samples that are
purely waste samples can only be looked at qualitatively and not
quantitatively because the size of the sample population for waste
samples cited by the commenter is too small to meet the sample
population requirements for the statistical test used by the
commenter; therefore, the statistical conclusions reached by the
commenter are invalid. Moreover, when just those vaste samples
are looked at qualitatively , they are still remarkably similar to
the waste samples upon which the RCRA hazardous waste listings were
based, considering the number of years that weathering, smearing
and other environmental influences have had the opportunity to
exert changes on the waste at the Site.For example, the highest
arsenic, chromium, lead, and zinc concentrations were all found in
either or both of the waste samples used in the analysis for the
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Railroad /3 Area (samples designated as W-12 and W-8). Although
zinc statistical analyses were not performed, the Railroad #3 Area
pure waste samples for chromium, lead, and arsenic fit neatly
within the distribution pattern for listed RCRA hazardous wastes as
displayed by the histograms prepared by the commenter. Although
the commenter (in Applied Hydrology Associates Inc., Specific
Comment 2.3, as submitted) states that semivolatile organics
observed in the Railroad #3 Area are also significantly lower than
expected, it should be noted that the only two pure waste samples
included in the analyses did not include data for semi-volatile
organics; the only semi-volatile organic data included in the
commenter's analyses pertained to soils, not wastes.
A similar examination of the thirty-three (33) Prewitt Site samples
used to compare the wastes found at the "separator area" portion of
the Site to the samples used in the studies supporting the RCRA
listing of the hazardous wastes in question finds that only one
(1) of those samples were actually from waste taken from the
separator. The other thirty-two samples used in the analyses were
samples taken of contaminated environmental media (i.e. soils).
The one waste sample (sample W-131) is invalid for use in this
test, because the laboratory procedure used to analyze it was a
specialized test to evaluate extract from the waste and not the
total waste itself. The commenter's conclusion that lead in the
separator area is significantly lower than the wastes studied by
EPA ,to support the F037 and F038 hazardous waste listing, is
meaningless because soils contaminated by hazardous wastes over
thirty years ago cannot be validly compared to the fresh, pure
wastes studied by EPA during the hazardous waste listing process.
EPA does not believe that the commenter's analysis is valid.
Although only the Railroad #3 Area and the separator Area metals
have been discussed in detail, EPA's assessment of the commenter's
analyses extend to all of the areas for the general reasons cited
above. To summarize, throughout the commenters analysis, the
commenter compares 30-year-old, weathered waste that is mixed with
other media (generally soil) with the fresh, pure waste used in the
studies which support EPA's listing of the RCRA hazardous wastes in
question; therefore, the commenters conclusions are invalid. That
is to say, the commenter's conclusions are not valid because the
commenter compares apples with oranges.
There is another extremely significant reason why the statistical
test used by the commenter, the Kolmogorov-Smirnov "two-sample"
test, is not a valid tool to use to make the conclusion that the
wastes at the Prewitt Site are different from the wastes studied
in the rulemaking, and, therefore, not hazardous wastes. The
Kolmogorov-Smirnov test analyzes frequency distributions within a
population and compares them with frequency distributions in
another population, to determine if the two populations are
identical. The flaw in the commenter's particular application of
the Kolomogorov-Smirnov test is that the data used in the studies
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which support EPA's listing of F037 and F038 as RCRA hazardous
wastes is very heterogenous. That is, in the studies, EPA analyzed
data from many types of sludges taken from many different
refineries; whereas, the data used in the commenter's analysis of
Site wastes would likely be very homogenous by comparison (i.e.
thirty two samples taken from one specific area at the site such as
the separator area). When comparing frequency distributions of a
metal in two populations of samples (for example, a comparison
which seeks to determine how many times lead is found between 10-20
parts per million (ppm)in each population, how many times lead is
found between 20-50 ppm in each population, and so on), one of
which is a heterogenous population and one of which is a homogenous
population, it is expected that the populations will not be
identical. That does not mean that the homogenous population does
not represent a subset of the heterogenous population. To
analogize, if one were to compare demographics of a particular
community in America inhabited by a large population of a
particular ethnic group, with the population of Americans as a
whole, and conclude that the ethnic community is not American
because it is not identical to the population as a whole, one would
be committing an error similar to the commenter's misapplication of
the Kolmogorov-Smirnov test.
In the Final Rule and response to comments on the FO37 and F038
wastes, EPA acknowledged that there is sometimes great variability
in particular constituents among the various sludges studied,
sometimes several orders of magnitude of difference may exist
between the measured concentrations of particular constituents in
two sludges both of which meet the listing. Yet, the sludges were
very similar in that each of the wastes studied generally contained
some concentration of each hazardous constituent, and one or
several of those hazardous substances exceeded health based levels.
The commenter states that the semi-volatile organic constituents
found in samples taken in the separator area at the Site are also
below the levels detected in the wastes studied to support the F037
and F038 hazardous waste listing. However, the commenter
acknowledges that no valid conclusion could be drawn, based on
statistical analysis, due to the small sample size. Again, the
data analysis performed by the commenter utilizes contaminated soil
rather than waste from the separator, another attempt to compare
waste mixed with soil to pure waste (apples and oranges).
Since the contents of the separator are known to have been
discharged to the North Pit over the years, it is somewhat useful
to evaluate that data when evaluating the semivolatile organic
content of the separator discharge. The commenter states in the
commenter's comparison of Site samples to semivolatile organic
compounds found in the in Oil/Water/Separator (0/W/S) separation
wastes used in the studies which support EPA's listing of the
hazardous wastes in question, that
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only the North Pit Area samples contain semivolatiles in
concentrations similar to the O/W/S separator sludge used
by EPA for the F037 listing.
The commenter concludes that the metals and semivolatile organics
observed in the North Pit are consistent with contamination from
petroleum product and not from process wastes. However, no
analyses are offered to compare the North Pit contents with
petroleum product. EPA disagrees with the commenter's conclusion,
that the waste in the North Pit is petroleum product, in light of
the substantial testimony from former employees concerning the
origin of materials in the North Pit, and the data gathered during
the Remedial Investigation. EPA reaffirms the conclusions set
forth in its June 16, 1992 letter (attached) which states that
based on information which EPA has placed in-the administrative
record, EPA believes that the material in the North Pit is RCRA
hazardous waste.
A specific comment states that RCRA K052 Hazardous Waste, leaded
tank bottom waste, is not present at the Site. The statement is
allegedly supported by a claim that former employees have stated
that leaded tanks were never cleaned and therefore leaded tank
bottoms were never deposited on site. In its review of the
deposition of former employees, EPA can find no such assertions by
former employees. Former employees were asked whether spills or
dumping had occurred from the lead house and the operations at the
lead house. The responses to those questions did not include an
assessment of whether any leaded products stored in tanks
throughout the site had experienced releases of bottom contents.
The assertion that leaded tank bottoms are not present at the
Prewitt Refinery Site is also based, in the commenter's statement,
on a statistical comparison of contaminated soils in the horizontal
and vertical tank areas with the wastes EPA studied to make the
K052 listing. This comparison suffers the same limitations as
those discussed above. The bi-variable graphical comparisons are
misleading and the pairing of metals used in the graphs is
arbitrary. The Horizontal Tank Area nickel concentrations actually
fall within the range in EPA's study data, but by pairing nickel
concentrations with arsenic concentrations, the commenter's
analysis shows it falling out of the range. The concentrations of
lead in the Vertical Tank Area match concentrations of lead which
appear in the study supporting EPA's listing of the RCRA hazardous
wastes in question. It should be recognized that metals are
relatively soluble in water and relatively mobile through sandy
soils. It should be expected that as the metals are "smeared"
through the soil horizon over a thirty year period, that the
concentrations in each sample will decrease; therefore, the
comparative analyses presented by the commenter are meaningless
under the conditions examined.
The commenter states (in Applied Hydrogeology specific comment 2.7
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on the leaded tank bottom wastes (emphasis added)) that
no explanation for the source of the high lead at this
location can be offered at this time other than it
apparently is not from either petroleum products or
petroleum refinery listed waste.
Lead, by itself, is a CERCLA hazardous substance not subject to the
Petroleum Exclusion, except when it is associated with a petroleum
product as a normal part of the refining process and in
concentrations expected from its normal use as an additive. In
this case, even if the lead were not from K052 listed wastes, it is
a CERCLA hazardous substance since it is not associated with
petroleum product; therefore, EPA has CERCLA authority to order the
cleanup of this waste.
Comments are offered that the contents of the West Pits are not
subject to CERCLA authority. The commenter bases these comments,
in part, on the statements of former employees that the West Pit
Area was used for storage of crude oil and petroleum products at
various stages in the refinery process. Also, statistical
comparisons of the West Pit Area and RCRA hazardous wastes are
submitted by the commenter. The testimony of the former Prewitt
employees is replete with statements concerning the routine
drainage of tank bottoms. The depositions of Watkins and Wallace
also describe the discharge of hydrocarbon laden wastewaters such
as those generated from the cleaning of the distillation unit,
cooling tower overflow, and spent caustic from cleaning gasoline.
See EPA's June 16, 1992 letter (attached). These discharges were
transported by earthen ditches. Historic aerial photographs
illustrate that some of these ditches eventually emptied into the
West Pits. According to the Final Rule, listing F0#7 and F038 as
RCRA hazardous wastes, 55 Fed. Reg. 46354, 46364 (November 2,
1990), F037 and F038 sludges are generated from process wastewaters
which include, but are not limited to, tank emulsion and water
draw-offs, product treating wastewater (such as the spent caustic
known to have been discharged at the site, cooling waters, and
uncontrolled oily storm water from refinery processing and tankage
areas. Therefore, given that all of the above listed wastewaters
are known to have emptied into ditches at the site, and that some
of the ditches eventually drained to the West Pits area, EPA has
authority under CERCLA to remediate wastes in the West Pits.
The depositions of former employees, concerning the West Pits, are
not conclusive, and certainly do not preclude consideration of the
operational and photographic evidence cited in the preceding
paragraph. For example, the deposition of Watkins (pages 59
through 62) indicates that the area of the West Pits may have been
alternately a "flare pit" or a pit to contain hot product. That
testimony also indicates the presence of a buried tank, in the West
Pits area, to contain hot product or other hydrocarbons. That
tank is no longer present, or if the tank is present, it does not
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appear to be associated with the sludges remaining in the West
Pits. The testimony of Yates (at pages 59 through 64) contains a
similar description, including mention of the use of buried tanks
to contain hot product or other hydrocarbons; however, the buried
tanks are not present in the sludge laden West Pits. Since the
underground tanks which were, according to Yates and Wallace, in
the area of the Site used to contain hot product, are not in the
West Pits area, it follows that either the West Pits areas were not
the area of the Site used to contain hot product, or that the
underground tanks were removed from the West Pits area.
COMMENT #4: GROUND WATER CONTAMINATION AT THE SITE DERIVES
ENTIRELY FROM CERCLA EXEMPT SOURCES.
One commenter said that
selection of a remedy for groundwater at the Prewitt
Refinery Site is not authorized under CERCLA because
groundwater contamination observed in the Sonsela Aquifer
at the Site is due entirely to NAPL[non-aqueous phase
liquids] from petroleum product spills and leaks which
are exempt from CERCLA. Site information confirms that
surface deposits which are not exempt from the petroleum
exclusion have not contributed to groundwater
contamination at the Prewitt Site.
The commenter goes on to make a number of specific comments to
support this conclusion.
RESPONSE #4.
The following discussion addresses comment #4, including the
specific comments offered, by the commenter, to support comment #4.
EPA outlined many of the factors leading to the conclusion that
groundwater has been impacted by RCRA hazardous waste at the
Prewitt Refinery Site in a letter, dated June 16, 1992, to the
PRPs, NMED, and the Navajo Superfund Office. Hydrologists for both
the NMED and the Navajo Superfund Office have continuously
reaffirmed the conclusions reached in that letter. A copy of the
June 16, 1992, letter is included in the Administrative Record, and
a copy is attached as part of this responsiveness summary.
The following enumerated paragraphs show that there are obvious
errors in the commenters statement. These errors show that the
commenters statements are not valid.
(1) the RI report, previously submitted by the commenter,
states that soils in the separator area are likely to still be
impacting ground water. It is clear that these soils have
been impacted by releases from the separator. The RI report
describes the contents of the separator as F037 RCRA hazardous
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waste.
(2) A different comment (see comment #3 in this Responsiveness
Summary), submitted by the commenter, acknowledges that
groundwater has been contaminated by 1,2 dichloroethane (1,2
DCA) . 1,2 DCA is not a petroleum product or a constituent of
petroleum products; it is a CERCLA hazardous substance.
(3) The highest concentration of lead in groundwater is found
beneath the area of high lead contamination in the soils at
the Site. The commenter admits, in a previous statement,that
this area is contaminated by lead which did not come from
petroleum product, and therefore, is not subject to the
Petroleum Exclusion. As described in EPA's June 16, 1992
letter, in the ROD, in the Administrative Record for this
site, and in this Responsiveness Summary, surface
contamination at the Prewitt Site (including, but not limited
to, the areas in the three examples above) is largely
comprised of CERCLA hazardous substances.
To support the commenters' general claim that groundwater
contamination at the Site is entirely subject to the Petroleum
Exclusion, the commenters submitted a number of specific comments
to demonstrate their contentions: (1) that waste pits have not
impacted groundwater, (2) that groundwater contamination derives
exclusively from Non-Aqueous Phase Liquids (NAPLs) on the water
table, (3) that NAPLs result entirely from petroleum product, and
that (4) "wastewaters" have not impacted groundwater in a way that
would be expected.
EPA disagrees with each of the specific comments, for reasons
explained in the following discussion.
Separator contents are known to have contained high levels of
benzene, toluene, ethylene, and total xylenes (BTEX) constituents.
This is clear from the presence of volatile BTEX constituents still
in the separator after thirty years, from the presence of BTEX in
the soils near the separator in the discharge pathway, and from
EPA's knowledge of the type of waste streams entering the
separator. Throughout the RI process, the EPA, the NMED, and the
Navajos asserted that the conceptual diagram of the groundwater
plume portrayed in the RI reports was the sort of plume that would
be expected from infiltration of contamination along the separator
drainage pathway. It is to be expected that more mobile
constituents, such as BTEX, would have infiltrated fairly rapidly
under the normally arid conditions that prevented rapid and
complete flow of the separator discharge to the North Pit. It is
to be expected that less mobile constituents which do not
infiltrate the soil as rapidly as BTEX, such as those PAHs
currently found in the North Pit, would have remained on the
surface long enough so that they would eventually be washed down
the arroyo to the North Pit during high flow conditions such as
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those which follow rains. These expectations were fulfilled in the
RI reports and the data supporting those reports. That is, those
BTEX materials and those PAHs were found where expected.
During development of the RI, the Potentially Responsible Parties
asserted that if EPA's and the other agencies' theory regarding the
fate and transport of the separator discharge, as described in the
preceding paragraph, were true, monitoring well 21-S (MW-21S),
would show contamination, which, they asserted, it did not.
Subsequently, by samples taken February 1, 1991 and again on April
15, 1992 it was demonstrated that MW-21S does indeed exhibit very
significant BTEX contamination, thereby supporting the EPA's and
the agencies' theory.
One commenter made the statement that BTEX contamination at the
Site is directly attributable to NAPL sources. The PRPs, who made
the comment, have constructed a conceptual model, and adapted a
computer model that, they maintain, supports this theory . The
groundwater contaminant concentration contours, as drawn in the RI
Report, depict decreasing concentrations moving away from the NAPL
sources. Figure 6-16 in the Remedial Investigation report,
illustrates the conceptual model developed by the commenter (an
adapted version of this same figure was submitted in the comments
to the Proposed Plan). The model shows that the inferred
concentration of total BTEX drops to approximately 100 parts per
billion (ppb) as it approaches MW-31E, and that the BTEX plume is
totally absent farther to the Northwest at MW-21S in the E-split
sandstone. However, data from MW-21S exposes the fallacy of the
conceptual model, developed by the commenter, concerning the shape
and boundaries of the contaminant plume in groundwater, and it
also exposes the fallacy of the contention that all contamination
within the plume comes from NAPLs.
When data from MW-21S (sample taken 2/1/91 reveals 715 ppb BTEX,
4/15/92 sample shows 617 ppb BTEX) and MW-31E (sample taken 4/15/92
shows 284 ppb BTEX) is considered, the only conclusion can be that
the commenter's conceptual model is wrong. MW-21S is outside the
boundary of the plume drawn in the commenter's model. The model
predicts very low concentrations of BTEX at the boundary of the
plume, since the boundary is farthest away from the NAPL which the
model states to be the source of the plume. Therefore, if the
model were correct, BTEX concentrations in MW-21S would not be
detected. Clearly, the high levels of BTEX found in MW-21S far
exceed the projected BTEX concentrations at the boundary of the
commenter's model; therefore, the BTEX cannot be emanating from the
NAPL source. Furthermore, if the model plume is redrawn to address
the data from these two wells, a portion of the plume extends back
towards the separator discharge path and the North Pit which means
that the ground water contamination which is confirmed within the
conceptual plume migrated, at least in part, by way of the
separator's drainage pathway. EPA's' June 16, 1992 letter
(attached) describes other problems with the conceptual plume
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model.
In a report titled, "Prewitt Refinery Site, Ground-Water Quality
Sampling Results, Ongoing Ground-Water Monitoring," prepared for
the PRPs by Morrison Knudson Corporation, dated June 1992, it is
postulated that the contamination in MW-21S may be due to
contaminant migration from the East Well/N-8P area located within
the conceptualized plume. This is unlikely since the general flow
direction of groundwater in the E sandstone is to the East, and MW-
2IS lies far to the Northwest. It also contradicts several other
of the commenter's assertions about the Site hydrogeology.
For example, the RI, and the comments submitted in response to the
proposed plan (page 29 of the comments prepared for the PRPs by
Applied Hydrology) indicate that groundwater flow at the Site is
generally from the West to the East. Yet, the Morrison-Knudson
report, cited above, suggests that MW-21S is contaminated by
groundwater in the E-Sandstone flowing across the site from East to
West. A second contradiction between the Morrison Knudson report,
previously submitted bi ^ne PRPs, and the specific comments that
the PRPs submitted to the Proposed Plan, concerns the impact of
permeability on contaminant migration. In specific comments to the
Proposed Plan, concerning the likely source of NAPLs in the East
Well/N-8P area, the statement is made that
...the migration of NAPLs and BTEX dissolved in groundwater
beneath most of the Prewitt Refinery Site is severely
restricted by the low permeability of the F Sandstone and
Upper Confining Zone beneath the site. Only in the areas
immediately east of the Loading Rack Area have the bedrock
fractures permitted the lateral and vertical migration of
NAPLs and BTEX dissolved in ground water.
Clearly, if the above comment were correct, BTEX found in MW-21S
could not have migrated from the NAPL areas indicated.
A specific comment was made that
the only occurrences of saturated fractures noted in
borings were at locations of former processing, piping,
and transfer areas.
EPA does not consider the commenter's use of the term "saturated"
fractures to be meaningful, since "stained" fractures are ample
evidence that a fracture has served as a pathway for contaminant
migration. EPA strongly disagrees that fracture pathways of
contaminant migration exist only at locations of former processing,
piping, and transfer areas. EPA particularly questions what the
commenter means by "former processing areas." For example, the
area monitored by MW-4S and MW-20S, near the separator, and which
show ample evidence of fracture staining, is not an exclusive
process area. It is also a waste management area.
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Every area studied, as presented in Chapter 5 of the RI, showed
evidence of fracture staining. Also, a number of borings showed
evidence of fracture staining, yet no NAPL. This suggests that
contaminants migrated to groundwater through fractures in those
areas, even though NAPL is not present in those areas. Thus,
conclusions that contamination in the groundwater results
exclusively from NAPL migration through fractures in process,
piping, and transfer areas, is not supported by the data in the RI.
EPA agrees that BTEX concentrations in the vicinity of NAPL sources
will, in most cases, be higher than throughout a plume in general
(as predicted by the comntenter's equilibrium modeling) . This is
obvious since NAPL exists because the constituents of NAPL are
present at concentrations above their equilibrium concentrations in
water. However, EPA does not agree that .the BTEX plume in
groundwater, can be attributed solely as a result of BTEX emanating
from the NAPL areas. For the reasons cited above, and in the June
16, 1992, EPA letter which described evidence of BTEX contamination
upgradient from the NAPL plumes in the E Sandstone, EPA believes
the commenter's concept .'.r^ model overlooks some important parts of
the actual data collected in the field.
A comment was made that laboratory analyses of NAPL samples from
the six NAPL locations identified at the Site confirm the
conclusion that NAPLs found in the subsurface is entirely derived
from petroleum product.
As stated above, EPA does not agree that BTEX, or other groundwater
contamination such as 1,2 Dichloroethane, derives exclusively from
NAPL sources. Moreover, for reasons described below, EPA does
not agree that the NAPL sources are exclusively petroleum product.
NAPL accumulates "on top" of the water table. Thus, a single NAPL
source does not necessarily represent a single release event,
releases in a single location, or even one or several large
releases. In other words, multiple releases of substances from
product and waste will combine to form a single or several NAPL
areas, as long as the releases contain concentrations of
contaminants greater than that which can dissolve in the ground
water.
EPA addressed the issue of whether laboratory analyses confirm that
NAPL is pure in the June 16, 1992 letter from EPA concerning the
applicability of the Petroleum Exclusion. In that letter, EPA
pointed out that, in the six NAPL areas identified at the Site,
some of the NAPL was "undefined" (Table 5-8 in the RI) . In the
comments to the proposed plan, reference is made to laboratory
analyses of the NAPL samples from these same six areas. However,
the commenter subsequently states that the "undefined"
hydrocarbons from these six areas were not submitted for analysis.
This subsequent statement by the commenter leads EPA to the
conclusion that the commenter's statement that
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the laboratory analyses of NAPL samples from the six NAPL
locations identified at the site confirms this conclusion
[that the NAPL derives solely from product]
is really not based on laboratory data for several of the areas in
question.
In any event, EPA disagrees that laboratory analyses confirm that
the NAPL results exclusively from petroleum product. There is both
bias and uncertainty in the test method used. The bias exists in
the nature of the test procedure itself. The test is an industry
standard used to identify petroleum fractions, on the premise that
they are product, and not on the basis that they contain the same
constituents as petroleum product. The laboratory results are
compared against "standards" that are petroleum product. In other
words, the test is not designed to find waste, only to identify
types of product.
To further explain, gasoline is not a pure chemical; it is a
combination of many chemicals including BTEX. F037 and F038 wastes
are derived, in part, because wastewaters come in contact with
petroleum product and thus pick up constituents common to petroleum
product, including nontoxic "gasoline" constituents other than
BTEX. Once in the waste, those petroleum constituents are
transported through soil and groundwater, and exhibit the same
solubility (or insolubility that results in floating NAPL
formation), regardless of whether they result from product or
waste.
The laboratory test procedure utilizes a principle similar to the
one used to refine crude oil into various products; that is,
"gasoline" will separate from other fractions at different
temperatures when distilled or passed through a specialized column.
The separation is not discrete, and specific distillates are not
identified individually. That is, gasoline is characterized by what
is "distilled" through a range of temperatures. That same range
includes the range through which BTEX will separate from the
matrix, whether the BTEX comes from waste or product. Thus, when
the laboratory procedure indicates that a test yields 100%
gasoline, it means that the material undergoing the testing all
came out in the "gasoline" fraction. However, the material could
be BTEX and other constituents of F037 or F038 waste. In fact, if
a test yields 100% "gasoline", it necessarily means that BTEX was
also present since BTEX comprises approximately twenty percent of
what is known as "gasoline." Thus, the test procedures only
identify, generically, fractions and not whether the material
derives from pure product, or from waste that contains constituents
in common with pure product.
The inherent bias in the test procedure can be seen in the
memorandum from A.V. Nowack to John Zannos, dated December 11,
1990, and included as part of Appendix E to the comments on the
22
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Proposed Plan prepared for the PRPs by Applied Hydrology. The
description of MW-20 states (emphasis added):
Physical appearance - a very dark brown liquid with an oily
aroma unlike that of gasoline. It is basically all diesel
type material which contains some heavier boiling range
material. 87% of the material boils below 87 degF and it has
a 900 degF endpoint. There is virtually no C5 material in the
sample to indicate the presence of gasoline. It could be
mostly crude with some diesel contamination.
This description illustrates the non-specificity of the test and
the interpretations applied to the test. It also illustrates that
despite the obvious uncertainty of what the material's exact nature
is, the only terms used to attempt to describe the sample are terms
related to petroleum product. The description of MW-45 (MW-4S?,
the report identifies the sample as MW-45, but this must be MW-4S
since there is no MW-45) provided in the Nowack memorandum cited
above is similar. MW-20 and MW-4S are each in the area of the
separator, an area with deep penetration of contamination from the
separator, and an area where PAHs common to F037 and F038 wastes
were detected in ground water. Yet, the laboratory procedure does
not provide for interpretation of test results with that framework
in mind.
Although Table 5-8 of the RI does not cite the specific date of
the analyses that were included in Table 5.8, it is clear that
there is a large discrepancy between the above description
pertaining to the MW-20 sample analyzed by the laboratory and the
presentation of MW-20 in Table 5-8. The description provided to
EPA in Table 5-8 is simply that the sample was 70% diesel. Thus,
the validity of the information presented in Table 5-8 is highly
questionable.
True chemical "fingerprinting11, to identify the source of a sample,
can be attempted, with some degree of success, by looking at fuel
additives since additives would usually be unique to product. Such
an effort would not yield conclusive results since product combined
with waste would still show the presence of additives. However, as
indicated by the commenter, and in the Nowack memorandum cited
above, fingerprinting based on laboratory analyses, was attempted
with the NAPL from the Prewitt Site, to look for fuel additives,
but no fuel additives were found. This failure to find additives
would also tend to lead to the conclusion that laboratory analyses
have not confirmed that the source of the NAPL is entirely from
petroleum product, as the commenter claims.
The NAPLs were also subjected to metals analyses, as described by
the referenced memorandum. The results showed lead still present
in some of the NAPL samples (some lead will dissolve in
groundwater) at a concentration that was at least an order of
magnitude greater than expected based on current standards for
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leaded gasoline. The magnitude of difference is actually larger
considering that the NAPL was considered to be only partly "leaded
gasoline." Again, despite the apparent disparity between expected
and actual lead concentrations, the laboratory analyses were only
interpreted in the context of petroleum products, and not with the
understanding that they may not be purely product.
In summary, EPA agrees that some of the NAPL plumes, particularly
the small plumes in the loading rack area, may have significant
contribution from product spills. However, EPA strongly disagrees
that the laboratory analyses confirm, or are capable of confirming,
that the NAPL derives exclusively from product.
A number of specific comments concern the general lack of
polynuclear aromatic hydrocarbons (PAHs) in groundwater as evidence
that waste sources have not impacted groundwater. EPA strongly
disagrees. It is clear, that in its original form, the wastes
would contain BTEX constituents which are very mobile through soil,
and PAHs, which are relatively immobile. The general lack of PAHs
in groundwater is not unusual due to the relative immobility of
PAHs. The evidence, that pits and sludges contain high PAH
concentrations and only nominal BTEX concentrations, simply point
out the effect of soil as a "sieve" which separates specific
chemical constituents contained in a waste.
Furthermore, it is not true, as commented, that groundwater is void
of PAHs associated with F037 and F038 waste. To the contrary,
groundwater in the area of MW-4S and MW-20S, nearest the separator,
includes F037 PAH constituents such as Phenanthrene and Pyrene.
That these constituents are found in these wells and not in others,
is explained by the degree to which surface contamination has
penetrated the soil in the vicinity nearest the separator. Page 7-
61 of the RI acknowledges that the deep penetration into soil in
this area is impacting the G Sandstone shallow groundwater.
The commenters assert that a lack of groundwater contamination from
specific wells near the West Pit and the North Pit, proves that
groundwater contamination at the Site does not result from waste
management. First, EPA reiterates that the North Pit did not
receive flow quickly upon discharge from the separator. The
sludges in the North Pit accumulated through the years as heavy,
but intermittent, flows carried the surface waste deposits, which
came from the separator, along the ditch to the North Pit. It is
expected that BTEX, which is highly mobile through soils, would
have leached through soil prior to reaching the North Pit. Upon
entry to groundwater, the BTEX would have migrated in the general
direction of groundwater flow, generally to the East and crossway
to the North Pit. The same mechanism operated for flows to the
West Pits.
Secondly, as discussed in the following paragraphs, it must be
pointed out that the wells referenced are not very useful for the
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purpose employed as part of this discussion.
The commenters discussion on the North Pit cites MW-28E as the well
relied on, and it is said that it is "immediately downgradient of
the North Pit." MW-28E appears to be at least 200 feet from the
North Pit according to maps in the RI. Also, according to
potentiometric maps in the RI used to determine groundwater flow
direction, MW-28E is to the side of a downgradient flow. Perhaps
this can best be seen by superimposing the BTEX conceptualized
plume, and its direction, for the E Sandstone (the same sandstone
where MW-28E is completed) onto the Site map as if the plume
originated from the North Pit. This simulation shows that such a
plume would not even cross MW-28E.
A comment is made that data in the RI report indicates that
contaminants are not migrating from the West Pits. It is not
stated, which monitoring well data was used to make this
determination. The closest monitor wells to the West Pit, MW-32F
and MW-32E are not downgradient. There are several downgradient
wells in the E-Sandstone which are contaminated, but they are too
far away to monitor waste from the West Pits. Despite the
installation of over forty groundwater monitoring wells, and
numerous other borings, none of the wells or borings are
particularly well suited to detect contamination resulting
specifically from the West Pits.
Comments have been made that the operational history of the site,
as described by former employees, combines with other factors to
show that groundwater contamination derives exclusively from
petroleum product.
EPA believes that the testimony of former employees concerning the
routine drainage of tank bottoms onto the soil and the routine
discharge of separator contents via ditches to the North Pit speaks
for itself. EPA acknowledges that the testimony also mentions a
number of product spills, some of them quite large. However, it
should be noted, that almost without exception, the former
employees testified that the product spills were contained and
recovered, or in some cases, routed away from the spill area to the
separator where they would have become intermixed with waste in the
separator. Product intermingled with hazardous wastes must be
treated as hazardous waste.
As examples, the Wallace deposition (page 79) addresses spills that
occurred in the loading rack area. Mr. Wallace states that such
spills were diverted from the loading rack area to the "pit" (the
separator) . On the following page of that deposition, he describes
other spills that were also diverted to the separator. The
deposition of Mr. Watkins (pages 21-23) describes small spills that
were allowed to soak into the ground, and a very large spill that
went to the sewer and eventually to the separator. The testimony
of Wallace (at page 71) describes a very large spill that was
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contained and pumped back into the tank within hours. Mr.
Wallace's deposition reflects a history of quickly pumping spills
back into tanks.
A comment was made that, if waste waters had impacted groundwater,
chromium and sodium would have been elevated in certain areas of
the site. The commenter has not established whether the
concentration of chromium combined with its mobility through soil,
would have been sufficient to result in significant ground water
contamination. Chromium was not particularly high in the separator
contents (Chromium ranged from a very low 3 parts per million (ppm)
to a very high 2290 ppm in the F037 wastes studied by EPA in the
rulemaking). Chromium in waste diluted in soil from the separator
area ranged from 3.5 to 79.8 ppm in samples taken during the RI.
Since the waste was diluted in soil, it would'not be expected to
have as high a concentration of chromium as the pure waste tested
to support EPA's listing of F037; yet, the concentration of
chromium in the waste diluted in soil which came from the separator
area was still within the range found in wastes tested to support
the F037 listing. "~;
The commenter has also not established that the sodium
concentration in waste water was at such a high level that a
significant impact on ground water would be seen after thirty
years. Furthermore, a study was not designed or performed to
specifically define the ground water contamination along the
drainage pathway. One ground water monitoring well (MW-21S), that
the PRPs have identified as useful to evaluate drainage through the
ditch to the North Pit, was heavily contaminated with BTEX as would
be expected if, as EPA believes, the BTEX were migrating into the
soil before it reached the North Pit.
The commenter states that sodium in groundwater ranged from 49.2 to
98.5 milligrams per liter (mg/L). It is not clear which data the
commenter used in the evaluation since it was not included with the
comments. However, Table 6.4 in the RI indicates that sodium was
detected at 134 mg/L in MW-4S. Since MW 4S lies to the North of the
separator, along the drainage pathway; and since MW-4S contains
much higher sodium ("Na" in Table 6.4) than the highest sodium
concentration reported in the commenter's statement; the
commenter's assertion that separator discharges have not impacted
ground water must be wrong, based on the commenter's assumptions
about sodium in ground water.
As stated in the Proposed Plan, EPA acknowledges that both products
and wastes have been discharged, dumped or spilled throughout the
Site. It is virtually impossible to try to quantify the impacts of
large product spills that were either pumped back into tanks or
routed to the separator through ditches, relative to the impacts
of routine and systematic discharge of wastewaters, tank bottoms,
and separator contents which took place without attempts to capture
or contain. Furthermore, EPA concludes that it will not be
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possible to remediate just the waste contribution of contaminants
in the groundwater since they are intermixed with product to a
large degree. Even if specific areas of contamination are mostly
petroleum product, the petroleum product will interfere with
remediation of the CERCLA hazardous substances, and, therefore,
must be cleaned up as well.
COMMENT #5: PHASING OF NAPL AND GROUND WATER REMEDY:
A comment is made that it is unreasonable to select a remedy for
groundwater at this time beyond the removal of NAPL and associated
ground water treatment proposed in Alternative 2C. Groundwater
pumping would be counterproductive to the NAPL removal. EPA
guidance indicates the remediation should be phased. Simultaneous
ground water treatment and NAPL removal is inconsistent with NCP
remedy selection criteria.
RESPONSE #5:
EPA believes that c~ ^and water remediation can proceed,
particularly in areas at the downgradient boundary of the ground
water contamination plume and in areas not in close proximity to
the NAPL, such that it will no interfere with NAPL extraction.
The commenter referenced the EPA Directive which discusses the
phased approach for remediation of the NAPL plume. At this time
EPA Region 6 is willing to allow a phased approach to be taken in
remediating the NAPL and ground water; but, the phasing that EPA
has in mind would only pertain to the number and extent of pumping
wells, not to the initiation of the remediation technology. That
is, EPA intends to begin NAPL vapor extraction, and extraction,
treatment, and reinjection of the ground water simultaneously, but
EPA will consider a phased approach to the wells used in these
projects. Under the phased approach, wells would be operated
depending on results attained by wells in use at any given time.
The extent of the contaminated plume is such that ground water
remediation via pump, treat and reinjection could take place
without affecting the NAPL remediation. By controlling the pumping
rate and placement of extraction wells, any possible negative
effects on the NAPL extraction program would be avoided.
Instituting ground water remediation concurrently with the NAPL
vapor extraction would allow for the ground water that is extracted
during the NAPL remediation to be treated and reinjected, instead
of being lost to surface discharge. The need to remediate ground
water simultaneously with the NAPL remediation is also due to the
fact that MCLs are exceeded in the ground water throughout the
Site, and due to the fact that contamination in ground water is
migrating off-site, impacting drinking water wells in the area, and
creating a potential health risk.
The EPA guidance cited by the commenter (OSWER Directive 9283.1-06)
supports EPA's decision to begin extraction, treatment and
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reinjection of the groundwater as soon as possible. It states on
page 6,
1. Contain the plume early. Aqueous phase contaminant plumes
should generally be contained early, while determining that
further remedial action is needed. A containment system, such
as pumping to control hydraulic gradients or other methods,
should be implemented expeditiously in order to
prevent/minimize migration of contaminants.
The feasibility of pump and treat technology will be tested in the
first phase of ground water remediation. The five-year review will
assess the feasibility of the technology. It is inappropriate to
assume, at this time, that pump and treat will be ineffective for
the Site.
As to the usefulness of the pump and treat method, as long as
contamination is successfully removed in substantial amounts from
the ground water, then the method is effective in controlling the
migration of contamination, even if all the contamination cannot be
removed from the entire aquifer.
There is a difference between implementing a remedy in phases, and
selecting a remedy in phases, as requested by the commenter. EPA
guidance (OSWER Directive 9283.1-06) calls for implementing a
remedy in phases, not selecting a remedy in phases.
It is clear in the EPA guidance cited by the commenter (OSWER
Directive 9283.1-06) that the ground water remedy decision should
not be delayed. Moreover, on page 10 of that guidance, in
reference to modifications that need to be made due to findings of
impracticability or other factors, it states
Also for Superfund sites, an Explanation of Significant
Differences (BSD) or Record of Decision (ROD) Amendment will
be required to document the changed remedial action
objectives.
Since ROD amendment would only be required if the remedy decision
initially made required ground water remediation objectives which
it was later determined could not be met, it is clear that the
guidance contemplates that a more protective cleanup objective be
made a part of the ground water remedy and then modified if it was
found to be impracticable. The commenter would have EPA first
prove the practicability of the more protective cleanup standard,
and then add the more protective standard to the ROD. The
commenter's position is not supported by EPA guidance. Moreover,
pilot tests conducted during the FS indicate to EPA that
groundwater pump and treat will be an effective method for ground
water treatment at the Site.
Thus, for reasons stated above, EPA disagrees with the separate
specific comment that implementing ground water pump and treat
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simultaneously with NAPL extraction does not satisfy criteria of
the NCP. (i) to be protective (2) to reduce toxicity, mobility, and
volume, (3) and to be cost effective. EPA believes that
implementing ground water remediation simultaneously with NAPL
extraction will be more protective and will reduce toxicity,
mobility and volume. Prevention of ground water plume migration
will result in a smaller plume to remediate, and thus, should also
prove to be cost effective.
COMMENT #6: THE F AND 6 UNITS OF THE SONSELA AQUIFER ARE NOT
USEABLE AQUIFERS, AND SHOULD NOT BE REMEDIATED.
Commenters stated that due to the small amount of water in the F
and G units and the low recovery rates, it was unreasonable to
assume that these units can be considered -aquifers and have
beneficial uses under any future scenario. A second, similar
comment states that even though 1,2 dichloroethene, a CERCLA
hazardous substance was detected; it was insignificant since the
detection was in the F sandstone.
RESPONSE #6:
New Mexico Water Quality Control Commission (WQCC) regulations are
designed
to protect all ground water in the state of New Mexico
which has an existing concentration of 10,000 mg/1 or
less TDS for present and potential future use as domestic
and agricultural water supply.
WQCC regulation 3-101A. The water in the F and G units of the
Sonsela Aquifer meet the standard set by the WQCC. EPA considers
WQCC standards reasonable in light of the arid and desert climates
that dominate much of New Mexico and the resulting scarcity of
water. Therefore, under the NCP, EPA considers it reasonable to
consider the F and G units aquifers which should be returned to
beneficial use as drinking water aquifers. In addition, since the
upper confining bed contains fractures can allow fluid movement
between the F and E sandstones, and since there is a direct fluid
connection between the F and G sands, contamination within the F
and G sands may serve as a source for contamination within the E
sand. Therefore, remediation of the F sand includes the additional
benefit of protecting the lower sands of the Sonsela aquifer.
The State of New Mexico considers a water source to be of usable
quantity if it can supply one person or one cow. Thirty gallons
per day (gpd) is enough water to suit this criterion. The Navajo
Nation considers any well which encounters water to be usable, and
considers that sandstone which contains the water to be an
aquifer. By these criteria, the F and G sands are aquifers.
Comments concerning the areal extent of the F and G sands are
spurious, since the extent of these sandstones is unknown, as was
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stated in the RI and in the Comments.
In short, these units are considered an aquifer and require
remediation.
COMMENT #7: LEAD CLEAN UP LEVELS FOR SOILS:
The soil clean up level of 500 parts per million (PPM) for lead is
unreasonable.
RESPONSE #7:
In the Risk Assessment for the Site, the EPA's Uptake/Biokinetic
Model was used to determine a lead concentration in soils such that
95% of the exposed population would have resulting blood lead
levels less than 10 ug/dl. The soil lead concentration which
results in the 10 ug/dl is 800 ppm. Background concentrations of
lead in soils at the Site are substantially less than 500 ppm. In
an industrial scenario, the lead contaminated soils would require
remediation to a level within the 500-1000 ppm range. The cost to
remediate the lead contaminated soils to 500 ppm compared to the
cost it would take to remediate the soils to 800 ppm is small
(approximately $50,000). The RI data indicates that only one small
area at the Site which requires remediation at the 1000 ppm
standard, Product Area #1, would not require remediation based on
a remediation level of 800 ppm . The RI data also indicates that
the lead contamination is expected to be below 500 ppm beyond the
2 foot depth. Based on this information, EPA has revised its
stated remediation goal such that soils contaminated with lead at
the 0-2 foot interval will be remediated to 500 ppm. Any
additional soils beyond the 2 foot depth that contain lead in
excess of 1000 ppm will be remediated to 1000 ppm.
COMMENT #8: THE CHOICE OF A PAH ACTION LEVEL IS ARBITRARY:
The commenter questions the means by which the risk of 1 X 10"5 was
calculated from a level of 3.0 ppm carcinogenic PAHs. The
commenter stated that the 3 ppm action was arbitrary and
inappropriate.
RESPONSE #8:
The 3 ppm action level was established after a review of national
EPA Records Of Decisions (RODs) to determine the remediation levels
that were used throughout the U.S. for carcinogenic PAHs. The 3
ppm carcinogenic action level, in particular is consistent (not
identical) with other RODs, and is meant to simplify the process of
determining whether clean up levels have been achieved. It assumes
a mixture of carcinogenic PAHs. It provides a clean up level with
flexibility concerning the concentration of each of the several
carcinogenic PAHs, yet is still protective.
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However, in response to the comment, EPA has revised the action
levels at the Site to reflect a remediation level based on each of
the carcinogenic PAHs of concern at the Site such as,
benzo(a)pyrene, rather than using 3 ppm total carcinogenic PAHs.
Utilizing the relative potency factors discussed in the Summary of
Site Risks and Human Health Risks portions of the ROD, the
remedial action levels for the carcinogenic PAHs were calculated.
The actual excavation concentration for carcinogenic PAHs is
established in the ROD to be protective at the 1 X 10"5 excess
cancer risk level. This level of protectiveness, at the excavation
boundaries, is the same level that the 3 ppm total carcinogenic
PAHs was expected to achieve, as presented in the Proposed Plan.
There were no comments on the Proposed Plan pertaining to using the
1 X 10'5 protectiveness level. The specific basis for this level
is described in the Remedy Selection portion of the ROD. Please
refer to the remedy selection discussion in the ROD.
In short, EPA has changed the PAH cleanup standard from a combined
level of 3 ppm total carcinogenic PAHs to the specific level for
each separate PAH that will afford protectiveness at 1 X 10's,
assuming additivity of the cancer causing effect of each PAH at the
Site.
COMMENT #9: SEPARATOR SUBSOILS SHOULD MOT BE TREATED DIFFERENTLY
TEAM OTHER SOILS AT THE SITE.
The commenter states it is arbitrary to treat separator subsoils in
a manner different from other petroleum contaminated soils at the
site.
RESPONSE #9:
The Proposed Plan of Action for the Site states
After the separator contents are removed, holes will be
broken into the bottom to permit drainage and the
sampling of soil below the separator. If leakage of the
separator contents is found, additional remediation of
contaminated soils will be performed through landfarming
provided the leachability of contaminants does not
interfere with landfarming ARARs. If leachability of
contaminants from soils taken from under the separator
does interfere with landfarming ARARs, then the soils
taken from under the separator will be treated through
other methods such as, but not limited, to stabilization,
off-site incineration, or soil washing.
It was not the intent of the Proposed Plan to treat the soil which
is located under the separator differently from the hydrocarbon
contaminated soils found throughout the Site, unless sampling
indicates that they should be treated differently. The ROD
indicates that the hydrocarbon contaminated soils beneath the
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Separator may be landfarmed, unless leachable constituents of soils
beneath the Separator are present above TCLP levels, or if lead
concentrations exceed 500 ppm. If contaminated soils are found
beneath the separator they may fail the TCLP for leachable benzene
(based on other data from separator wastes exposed to
volatilization which had high levels of benzene).
The presence of high concentrations of leachable benzene would not
be appropriate for land treatment without pretreatment. This is
particularly important given the determination not to install a
liner beneath the landfarmed area.
In addition, the lead content may not allow for the soils to be
landfarmed without treatment. The Proposed Plan was taking this
information into account, in requiring that the soils may not be
able to be treated through landfarming. Adding hazardous waste,
with a high potential to generate leachate, to the landfarmed area
would necessitate the addition of a liner to the landfarm which
would significantly increase the cost of the landfarming
remediation.
**
COMMENT #10: BASED ON THE LAND EXCHANGE, RESIDENTIAL USE IS
INAPPROPRIATE.
Comments were made that, based on the proposed land exchange
between the Navajo Nation, which is the current owner, and ARCO and
EPNG, EPA's remedy decision should not be based on projected future
residential use of the area.
RESPONSE #10:
The land exchange between the Navajo Nation, which is the current
owner, and ARCO and EPNG has not taken place. EPA cannot alter its
remedy decision based on a land exchange that may never take place.
Furthermore, if the land exchange did take place under the
September 11, 1992 Land Exchange Agreement Between the Navajo
Nation, El Paso Natural Gas Company, and the Atlantic Richfield
Company (the "agreement"), as part of the agreement, the Navajo
Nation will have first right to purchase should the companies
decide to sell the property. The land use restrictions, which are
supposed to be put in effect through the agreement, may be
eliminated should the land be sold back to the Navajo Nation or to
any other party. Consequently, it would be inappropriate for EPA
to change its remedy decision even if the terms of the agreement
were put into effect.
Finally, in any case, it would be inappropriate for EPA to select
a remedy based upon future ownership of the Site by a certain
party. EPA's remedies must be protective of human health and the
environment. In making its remedy decision, EPA must consider what
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cleanup levels would be appropriate for the anticipated future use
of the area. The area near the site, though sparsely populated, is
currently in residential use. Thus, the future use of the site is
considered residential, for reasons described in response to
comment #1, and the remedy selection reflects residential use of
the area. The preamble to the NCP indicates that the same level of
protectiveness will be afforded in remedy selection for sites in
sparsely populated areas, as for more heavily populated areas. 55
Fed. Reg. at 8718.
COMMENT #11: Future Use scenario
Future residential use of the Site should be the scenario which
guides risk calculation and cleanup decisions.
RESPONSE #11:
EPA agrees. Based on the response to comment #1, concerning the
reasonableness of futur Residential use, site cleanup standards
are set at levels that will be protective of human health and the
environment.
COMMENT #12: Need for Additional Sampling Throughout Remedial
Design/Remedial Action
Sampling should continue in order to ensure that no additional
contaminated areas exist outside those presently designated. If
additional contaminated areas are discovered, they will be
remediated in the same fashion as similar areas previously
designated.
RESPONSE #12:
Additional sampling may be necessary during the remedial design and
remedial action phases. Any additional areas that posed a risk to
human health and the environment will be remediated as appropriate.
COMMENT #13: NMED Involvement in RD/RA
NMED should be afforded the opportunity to be substantively
involved in the Remedial Design/Remedial Action activities.
RESPONSE #13:
EPA encourages State participation at all Superfund Sites. This
comment will not alter the remedy.
COMMENT #14: Concurrent Remediation of NAPL and Ground Water
The ground water remedy should begin concurrently with the NAPL
remedy. Ground water removed as part of the NAPL extraction
33
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program should be remediated in accordance with the selected remedy
for ground water.
RESPONSE #14:
EPA agrees that the ground water remediation should begin
concurrently with the NAPL remediation. See Response to Comment
#5. The ROD requires that the ground water remediation begin
concurrently with the NAPL extraction; yet, in a phased approach
such that interference with the NAPL remediation program does not
take place. By conducting the concurrent remediation, the ground
water that is extracted as part of the NAPL extraction program will
be remediated in accordance with the selected ground water remedy
and reinjected into the aquifer in lieu of discharging it to the
surface.
COMMENT #15: Need for Liner in Landfarming and Thin Spreading
Alternatives
The Navajo Superfund Office indicated that a liner should be
required for either the thin spreading alternative or the
landfarming alternative. NMED, in commenting on EPA's preferred
alternative, landfarming, indicated that a liner should be a
necessary component of the landfarming alternative under State
underground storage tank (UST) and State solid waste disposal
regulations, in order to prevent seepage of contaminants to ground
water.
Response #15:
EPA has evaluated the need of a liner for the landfarming and thin
spreading alternatives. In order to comply with RCRA 40 CFR
264.270 subpart M requirements, the ROD requires that the
landfarming alternative will require a monitoring program of both
the soils to determine degradation and of the vadose zone to
determine if migration of contaminants is taking place.
The State's comment that New Mexico Solid Waste Regulations are an
ARAR which require a liner at the landfarm are incorrect in that
the definition of solid waste under the State regulations do not
include the waste to be landfarmed (a RCRA waste). Moreover, the
solid waste regulations do not apply to facilities design and
operated to dispose of sludge on land such as land application.
Therefore, the regulations are not applicable. Furthermore, the
regulations pertain to placement of waste in a landfill. Placement
is not occurring at the landfarm; rather, the waste is being moved
to an area of contamination where it will be treated along with the
waste already located in the landfarm area. Therefore, the State
Solid Waste regulations are not relevant or appropriate.
Additionally, the ROD includes a provision for requiring a liner
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should vadose zone monitoring indicate that migration of hazardous
constituents in hazardous concentrations is taking place or will
take place.
With regard to the thin spreading alternative, EPA agrees that a
liner may be appropriate. It is unlikely, based on results of the
treatability study submitted by the PRPs, that the thin spreading
alternative would be able to comply with RCRA 40 CFR 264.270
subpart M requirement, to ensure degradation of contaminants in the
treatment zone prior to transport into ground water. A lack of
such assurance supports the need for a liner.
The New Mexico UST regulations are not considered Applicable or
Relevant and Appropriate Requirements ("ARARs") for the soils at
the Site that will be remediated through landfarming since the
regulations are meant to address contamination resulting from
liquids likely to contain very high concentrations of mobile BTEX
constituents present in a situation of a leaking underground
storage tank. The soils at the Site contain less mobile
contaminants, which did not come from underground storage tanks,
While, the actual implementation of a landfarming or thin spreading
alternative may increase the potential for contaminants in the
wastes to migrate, the landfarming alternative will be able to
address this concern.
The New Mexico Solid Waste regulations will be met through the
implementation of a monitoring program by which the need for the
liner will be determined. Since, the waste has already been
"placed" at the site, and the treatment at the Site is "in situ",
technical requirements for new landfarm construction are not
applicable.
As described above, and in the ROD, the "appropriateness" of a
liner requirement can be evaluated through the monitoring program.
COMMENT #16: Remediation of Lead in Ground Water
There was a significant concentration range (11.5 ug/1 to 167 ug/1)
of lead detected in the E and F hydrogeologic units of the Sonsela
Sandstone beds. The Federal Safe Drinking Water Standard for lead
is 50 ug/1. The of primary concern in the ground water
contamination at the Site is the presence of BTEX compounds. One
can only assume that the aerial extent of lead contamination is
below that of the BTEX and that the existing lead contamination
will be addressed during remediation of the ground water BTEX
contamination.
RESPONSE #16:
The ROD requires that the ground water be remediated and that all
35
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contaminants present in the ground water, which are above the Safe
Drinking Water Act standards, be remediated. Thus, lead in excess
of Safe Drinking Water Act standards will be remediated.
COMMENT #17: Monitoring of Aquifers
Monitoring of the D Sonsela ground water unit and the San Andreas
Limestone/Glorietta Sandstone layers should be in place to detect
any vertical migration of contaminants.
RESPONSE #17:
A ground water monitoring program will be established as part of
the ground water remediation to determine whether vertical or
horizontal migration of the contaminants is'taking place. If
monitoring so indicates, appropriate remedial action, as determined
by EPA, will be required.
COMMENT #18: Inclusion of Lead in Risk Calculations
Inclusion of lead in the risk calculation for soil exposure may
result in a concentration which exceeds U.S. EPA's acceptable HI.
Response #18:
Hazard Indices are based on Reference Doses for specific chemicals.
To date, there is not an accepted Reference Dose for lead.
Therefore, risks posed by exposure to lead are calculated using
the methods discussed in the ROD. Current EPA policy suggests lead
cleanup levels between 500-1000 ppm.
COMMENT #19: Concurrent Implementation of NAFL and Ground Water
Remediation
The proposed plan of action implies, in one section, that the
extraction/reinjection ground water alternative (1C) is to be
implemented simultaneously with the NAPL vapor extraction
alternative (2C). Elsewhere in the Proposed Plan of Action, the
implementation of the extraction/reinjection work will be
undertaken during the vapor extraction of NAPL, which is considered
the source of the ground water contamination. Does this imply that
some extraction/reinjection work will be undertaken during the
vapor extraction of NAPL?
RESPONSE #19:
As stated in response to comment #5, the ROD requires that the
ground water remediation begin concurrently with the NAPL
extraction; yet, in a phased approach such that interference with
the NAPL remediation program does not take place. By conducting
the concurrent remediation, the ground water that is extracted as
part of the NAPL extraction program will be remediated in
36
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accordance with the selected ground water remedy and reinjected
into the aquifer in lieu of discharging it to the surface.
COMMENT #20: Air sparging as Part of Ground Water Remediation
Why is air sparging being considered within the NAPL vapor
extraction alternative and not the ground water vapor extraction
alternative?
RESPONSE #20:
The ROD does identify air sparging as a technique which can be used
as a contingency measure to enhance creation of the vapor phase of
the contaminants during the ground water remediation.
COMMENT #21: Effectiveness of Thin Spreading in a Residential
Scenario
Under the residential scenario contemplated in the proposed plan of
action, the thin spread?^ remedial alternative for hydrocarbons
contaminated soils may not be as effective as the landfarming
alternative, considering that some of the PAH concentrations in the
hydrocarbon contaminated soils exceed the levels permissible for
land disposal of refinery related hazardous waste. As can be
expected, there will be concern that the contaminants will remain
in high enough concentration in pockets of the "thin spread" that
they will continue to pose a risk to any future residential use.
RESPONSE #21:
The landfarming treatability study conducted as part of the RI
indicated that, without the addition of nutrients or moisture, the
degradation of contaminants would not exceed 44%. Thus, a risk to
human health and the environment would still be posed by the
hydrocarbon contaminated soils if the thin spreading alternative as
presented in the Feasibility Study Report and the Proposed Plan
would not be protective of human health and the environment. Since
the future use for the site is expected to be residential, the thin
spreading alternative was determined to be unacceptable and the ROD
requires that the hydrocarbon contaminated soils be remediated
through landfarming.
RCRA land disposal restrictions (LDRs) are not applicable, or
relevant and appropriate to the landfarming operation set forth in
the ROD because, since the contaminated soil is being treated in an
area of contamination, placement of the contaminated soil will not
occur. EPA considered the LDRs in making its remedy decision;
however, since the area that is being used for the landfarm is
already contaminated, and will be remediated as part of the
landfarming operation, LDRs should not be applied.
COMMENT #22: Sampling south of Interstate 40
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A former employee of the refinery questioned whether the area south
of 1-40 was ever investigated because he recalled that some dumping
of petroleum from the refinery had taken place in that location.
RESPONSE #22:
The Navajo Superfund Office informed EPA of the possibility that
some dumping took place in the area south of Interstate 40. As a
result, EPA requested that the area be investigated. Data from the
July 1991 and December 1991 sampling indicated that the chemicals
were not above an action level.
A stated in response to comment #12, additional sampling may be
necessary during the remedial design and remedial action phases.
Any additional areas that posed a risk to human health and the
environment will be remediated as appropriate.
COMMEKT #23: Use of Dam/Slurry Wall for Containment
Why was an underground method of containment such as a dam not used
to prevent contaminants from spreading?
RESPONSE #23:
Various containment alternative such as a slurry wall and a grout
curtain were considered in the initial screening of alternatives in
the Feasibility Study. These alternatives were rejected in the
evaluation of process options due to the inability to be used in
all areas. It was determined that the vertical barriers such as
the slurry wall could not be implemented in the unit due to the
lack of a confining structure under the E unit. In other words, a
wall would not be useful since the contamination would be free to
go under any such wall.
COMMENT #24: Blood Lead Sampling Results
What are the results of the blood samples that were collected?
RESPONSE #24:
ATSDR has informed EPA that they were not the group that conducted
the blood samples. The State of New Mexico conducted the sampling
activities and have not furnished EPA or ATSDR with the results.
COMMENT #25: Effectiveness of Vapor Extraction
Is there a vapor extraction system in operation somewhere in the
United States? And if so, how effective is it?
RESPONSE #25:
38
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Vapor extraction has been proven to be an effective method of
remediation. It is currently being used at various sites including
the South Valley Superfund Site in Albuquerque, New Mexico and
Tinker Air Force Base in Oklahoma City, Oklahoma.
COMMENT #26: Fault Location
There appears to have been a fault or a hole in the area near the
Baca Water Well. Was there any indication of such?
RESPONSE #26:
As part of the Rl, a seismic survey was conducted. The information
regarding the fault indicated that two prominent north-trending
faults are identified in the western half of the site. The fault
offsets are less than 40 feet, with offset decreasing higher in the
stratigraphic section.
COMMENT #27: Air Monitoring During Remedy Implementation
Will air monitoring units be in place during the remediation
activities?
RESPONSE #27:
Air monitoring will be utilized during the remedial activities. As
a precautionary measure excavation activities will not be allowed
during times of high winds that would carry particulates past the
Site boundaries. In addition, safety measures such as dust
suppression sprays and tarping of the trucks would be implemented
to prevent exposing the public to contaminants.
COMMENT #28: Home Treatment Units Provide Adequate Protection
Home treatment units are a cost effective means of providing
protection of human health and the environment.
RESPONSES #28:
Home treatment units may be cost effective; yet, they do not
provide the highest degree of protection to human health and the
environment. Home treatment units provide effective removal of the
ground water contaminants , but they do not address the source of
contamination. The treatment units must be maintained to be
effective and are not a permanent solution to the problem. They
eliminate the health risk to the public from ingestion and
inhalation of the contaminants provided they are properly monitored
and filters are replaced and/or regenerated. Home treatment units
do not provide for the restoration of the aquifer to its beneficial
use as established in the NCP. Home treatment units may not prove
effective, if a ground water user is not identified so that a home
treatment unit can be installed.
39
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COMMENT #29: Simultaneous Implementation of NAPL and Ground Water
Remedy
The proposed plan of action implies in one section that the
extraction/reinjection ground water alternative (1C) is to be
implemented simultaneously with the NAPL vapor extraction
alternative (2C) . Elsewhere in the "Proposed Plan of Action", the
implementation of the extraction reinjection groundwater
alternative is said to be contingent upon the removal of NAPL,
which is considered the source of the ground water contamination.
Does this imply that some extraction/rein jection work will be
undertaken during the vapor extraction of NAPL?
RESPONSE #29:
This issue has been clarified in the ROD. The remedies will be
implemented simultaneously. (See also comment #5)
40
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 6
1445 ROSS AVENUE, SUITE 1200
DALLAS, TX 75202-2733
CERTIFIED MAIL RETURN RECEIPT REQUESTED
Neal S. Brody
Atlantic Richfield Company
515 South Flower Street
BOX 2697-T.A.
Los Angeles, California 90051
Joanne Manygoats
Program Manager
Navajo Superfund Office
P.O. Box 2946
Window Rock, Arizona 86515
Paul Hilios
El Paso Natural Gas Company
P.O. BOX 1492
El Paso, Texas 79978
Ron Ziegler
ARCO-Bluewater Mill
P.O. Box 638
Grants, New Mexico 87020
Clovis W. McArthur, Jr., Esq.
El Paso Natural Gas Company
304 Texas Street
P.O. Box 1492
El Paso, Texas 79901
Stephen Wust
New Mexico Environment Department
Superfund Section
P.O. Box 26110
Santa Fe, New Mexico 87502
Re: Prewitt Refinery superfund site - Revaluation of Remedial
Investigation Data; Preparation of the Proposed Plan; Review
of the Administrative Record.
Dear Sir or Madam:
This letter has two purposes. The first purpose of this letter is
to inform you that the U.S. Environmental Protection Agency (EPA)
has reevaluated the data presented in the Remedial Investigation
Report for the Prewitt Refinery Superfund Site (hereinafter
"Prewitt" or the "site") submitted by The El Paso Company and the
Atlantic Richfield Company (August 1991), and decided that EPA does
not agree with some of the conclusions reached in the Remedial
Investigation Report (the "RI"). The second purpose of this letter
is to inform you that EPA is developing a Proposed Plan for remedy
selection at the Prewitt Refinery Site. The Proposed Plan will be
made available soon for public comment along with the Remedial
Investigation and Feasibility Study reports and the rest of the
Administrative Record.
EPA disagrees with certain conclusions set forth in the RI.
In that the RI fulfilled the requirements of the Scope of Work and
provided information necessary to develop and evaluate effective
"& Printed on Recycled Paper
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remedial alternatives as required by 40 CFR § 300.430(d), it was
a'pproved by EPA on February 4, 1992. Therefore, no further
Remedial Investigation activity will be required, from the Atlantic
Richfield Company or the El Paso Company, regarding Prewitt, at
this time. However, as indicated above, this letter identifies
disagreements that EPA has with certain conclusions presented in
the RI. Specifically, EPA disagrees with the conclusion that the
totality of contamination found in the groundwater derives from
"petroleum products, primarily gasoline and diesel." EPA has
reached a different conclusion based on EPA's reevaluation of the
technical data, responses to previous comments, and information in
the Administrative Record, including new information that has been
made available to EPA subsequent to the RI.
EPA disaorees with the characterisation of all oroundvater
In the Executive Summary portion of the RI, and throughout the RI,
reference is made to groundwater that has been contaminated "by
petroleum products, primarily gasoline and diesel." Although it is
true that groundwater has been contaminated "by petroleum
products", this description of the contamination is not complete.
Groundwater contamination results from both spilled petroleum
products and from Resource Conservation and Recovery Act (RCRA)
hazardous wastes and other Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA) hazardous substances
released at Prewitt. EPA relies on specific technical information
in the RI report as well as testimony of past Prewitt Refinery
employees to conclude hazardous substances including hazardous
wastes contributed to the groundwater contamination. The enclosed
document entitled EPA Reevaluation of Remedial Investigation at
Prewitt Refinery Superfund site describes some specific factors
considered in reaching this conclusion.
This letter does not attempt to quantify the relative contributions
of hazardous substances and petroleum products to the groundwater
contamination, if that is even possible. The contamination to be
addressed under Superfund authorities, if any, will be described in
the Record of Decision.
If you have any questions please call me at (214) 655-6730
Sincere
Remedial Project Manager
OK/MM Superfund Enforcement Section (6H-EO)
enclosures
cc: Randy Merkur - NMED
Bill Bowen - COE Albuquerque
Diane Malone - Navajo Superfund Office
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Enclosure 1
EPA REEVALDATION OF REMEDIAL INVESTIGATION AT
FREWITT REFINERY SUPERFDKD SITE
A. Groundvater Cox
Hazardous Wastes.
EPA has reviewed certain factors, enumerated below, and concluded
that soil, and groundwater in the vicinity of the concrete
structure and associated pit used to separate oil and water (the
"separator") at the Prewitt Refinery Superfund Site (the "site",
the "facility", or "Prewitt") has been contaminated with listed
Resource Conservation and Recovery Act (RCRA) hazardous waste K051,
or listed RCRA hazardous waste F037, or with both K051 and F037.
40 CFR SS 261.32 and 261.31.
1. The testimony of various former Prewitt refinery employees
describes the operation of the separator as an API separator
which generated, via gravitational separation, sludges which
were eventually released onto the soil around the separator.
See e.g. Deposition of Pete Watkins generally, but especially
at pp. 29, 32, 33-34, 50-53, and 76; see also e.g. Deposition
of Steve Wallace generally, but especially at pp. 78, 81-85,
95-98, 109-110, 120-126 and 169. These sludges, released from
the API separator qualify as K051 wastes. Indeed, soil
samples from the separator area indicate elevated levels of
lead, one of the hazardous constituents for which API
separator sludge was listed. 40 CFR Part 261, Appendix VII.
K051 was listed in 1980. Since 1980, data collected by EPA
has demonstrated that K051 also contains significant levels of
hazardous organic constituents including benzene,
benzo(a)pyrene, and chrysene. 55 Fed. Reg. 46354, 46376 (Nov.
2, 1990). Soil samples from the separator area contain
elevated levels of benzene, and chrysene.
Past comments of the El Paso Company and Atlantic Richfield
Company (hereinafter the PRPs) have been critical of EPA's
characterization of the separator as an API separator, and the
characterization of any sludge as API separator sludge. See
e.g. the Woodward-Clyde report dated August 1988; see also.
Perkins Coie letter dated August 22, 1988. However, such
comments predate the listing of F037 waste as a RCRA hazardous
waste. 55 Fed. Reg. 46354 (Nov. 2, 1990). The intention of
the F037 listing and the simultaneous listing of F038 waste as
hazardous waste was to include, as listed RCRA hazardous
wastes, all oily separation sludges and floats of similar
composition in the same manner regardless of the primary
wastewater treatment unit generating the waste. 55 Fed. Reg.
at 46359. The listing of F037 renders moot the PRPs argument
that the separator is not an API separator, for if the sludge
in question is not K051 waste, it is most certainly F037
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waste. The Feasibility Study Report (the "FS") submitted by
the PRPs (February 1992) stipulates, at page 2-11, the
presence of F037 listed hazardous waste sludge in the
separator at Prewitt. The above-referenced testimony of the
former Prewitt employees documents the release of the
separator sludge onto the soils in the separator area, and
soil and sludge samples from the separator and the surrounding
area show elevated levels of F037 constituents including
benzene, chrysene and lead.
Additionally, the F037 hazardous waste listing includes
sludges formed by deposition in ditches or other conveyances
receiving dry weather flow. This means that the F037 listing
includes sludges in drainage and collection systems leading to
and away from the separator. See 55 Fed.'Reg. at 46358 and
46363; see also Deposition of Pete Watkins generally, but
especially at pp. 29, 32, 33-34, 50-53, and 76, and Deposition
of Steve Wallace generally, but especially at pp. 78, 81-85,
95-98, 109-110, 120-126 and 169 (this is testimony of former
Prewitt Refinery em- '^yees describing the release of sludges
and floats from the separator).
Consequently, it is clear that the sludge deposited in the
separator, which was subsequently released from the separator
onto the soil near the separator, is either K051 or F037,
while the sludges formed by deposition in the ditches or other
conveyances leading to and away from the separator are F037.
2. F037 sludges generally contain, among other constituents,
lead, benzene, chrysene, pyrene, and phenanthrene. 55 Fed.
Reg. 46354, 46365 (Nov. 2, 1990). In the same final rule, EPA
says that benzene, chrysene and lead are among the
constituents that form the basis for the listing of F037
sludges as RCRA hazardous wastes. Id.
3. The RI shows, as seen in sample W-140, Table 7.13 (RI at 7-
58), that samples taken near the separator establish the
presence of benzene. Other benzene, toluene, ethylbenzene and
total xylenes (BTEX) constituents (xylenes and ethylbenzene)
occur in high amounts in the separator area as shown on Table
7.11. See RI at 7-53. Surface waste samples also reveal the
presence of semi-volatile organic compounds such as pyrene,
phenanthrene, and chrysene in the separator area. See Table
7.12, RI at 7-54.
4. Soil samples taken in the immediate vicinity of the separator
contain these semi-volatile organic compounds in
concentrations that are among the highest found in any soil
samples on the site; the primary exception being soils in the
North Pits area. See samples DS-llla,b,and c, Table 7.7, RI
at 7-42. Soil samples taken near the separator also show
among the highest concentrations of BTEX constituents found in
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soils. See Table 7.6, RI at 7-36 and 7-37. The DS-llla
sample is also described by the term "black tar" in Table 7.4
(RI at 7-23) , indicating a waste-like component to the soil
sample.
5. Soil samples taken next to the separator contained among the
highest concentrations of lead. See SS-lll, Table 7.5, RI at
7-33.
6. Page 7-61 of the RI report states (emphasis added) "based on
distribution patterns of soil and ground-water contamination,
unsaturated soils are not presently impacting groundwater at
the majority of the site. The exception is in the separator
area, where the 6 sandstone may be impacted by surface
contamination." Obviously, given the age of the site, soil
contamination, from areas not presently impacting groundwater,
has also migrated into the non-aqueous phase liquids (NAPL)
plumes which are presently impacting groundwater.
7. Groundwater contamir Mon in the area of Monitoring Wells 4S
and 20S, nearest the separator, includes F037 waste
constituents such as phenanthrene and pyrene. The
concentrations of these less mobile chemicals are higher than
measured in other wells throughout the facility. See Table
6.6, RI at 6-48. Groundwater contamination also includes BTEX
constituents, which are components of both petroleum products
and the F037 waste.
8. The testimony of former Prewitt Refinery employees portrays an
operating history in which separator sludges routinely exited
the separator in an uncontrolled fashion. Mr. Wallace
testified that waste contents of the separator were discharged
down an arroyo. See Deposition of Steve Wallace at pp. 84,
96, and 110. Another former employee, Mr. Watkins, also
indicated that the separator emptied into an open ditch. See
Deposition of Peter Watkins at p. 32. Mr. Watkins testified
that the contents of the Separator overflowed into a ditch.
See Watkins at p. 50. When questioned, neither recalled
sludges from the separator ever being removed on purpose.
This leads to the conclusion that sludges generated en route
to the separator, within the separator, or deposited in the
discharge path from the separator contaminated nearby soils
either by discharge or overflow to surface drainage pathways.
The failure to remove sludges from the separator created a
certain situation that sludges exited the separator either
through discharge, overflow or leaks. The integrity of the
separator has not been verified. The separator was installed
about 1939. Thus sludges, or wastewaters containing non-
settled sludges, were emptied from the separator, onto soils
around the separator, for approximately 20 years. This
undoubtedly has impacted the underlying groundwater.
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The above factors contribute to EPA's conclusion that groundwater
in the vicinity of the separator has not been contaminated solely
by "petroleum products, primarily gasoline and diesel," but also by
hazardous wastes F037 or K051, or both.
B. Greundwater Contamination in the Refinery Area _ (N-2?p)
includes aon— etroled* hazardous
EPA has reviewed certain factors, enumerated below, and concluded
that groundwater in the Refinery Area (N-22P) at Prewitt is
contaminated with non-petroleum hazardous substances including 1,2
Dichlorethane and tank bottoms including leaded tank bottoms, which
are listed as RCRA hazardous waste K052 (40 CFR S 261.32) ; slop oil
emulsions, which are listed as RCRA hazardous waste K049 (40 CFR S
261.32); and petroleum refinery primary oil/water/solids separator
sludge F037 (40 CFR S 261.31).
l. 1,2 Dichlorethane, a non-petroleum hazardous substance, was
found in significant Concentrations (above EPA's acceptable
carcinogenic risk range for groundwater consumption) during
four consecutive sampling events of monitoring well MW-22S.
See Table 6.5A, RI at 6-21. However, the RI concludes, based
on a fifth sample taken October 13, 1990, that the four
sampling events indicated false positives. A close
examination of the data reveals that the detection limit on
the first four sampling events was 5 ug/1; whereas, the
detection limit was raised to 500 ug/1 on the fifth sample,
even though 500 ug/1 was higher than previously detected
concentrations of 1,2 Dichlorethane in monitoring veil MW-22S.
EPA commented on the draft RI report (EPA letter May 16, 1991
from Chapa) , that due to changes occurring through time, there
is no basis for a conclusion that the four detections of 1,2
Dichlorethane were false. In response, the August: 1991 RI
report changed page 2-14 to state that the earlier detections
were "not representative of the aquifer water quality," while
pages 6-2, 6-62 and 6-66 continue to state the results are
false positive. There is simply no basis to conclude that the
four samples were invalid. A more recent sample showing non-
detect in MW-22S does not change the validity of earlier
samples; it may indicate that conditions have changed. In
short, EPA concludes that groundwater in the area of MW-22S
has exhibited evidence of contamination by 1,2 Dichlorethane.
2. Page 7-46 of the RI stipulates that tank bottoms may have been
dumped in the horizontal tank area. Testimony of former
Prewitt Refinery employees describe this dumping. As noted in
the Wallace deposition (pages 143-145) and Watkins deposition
(pages 55-57) , tank bottoms throughout the plant were
routinely drained onto the soil, and ultimately soaked into
the ground, during the operating history of the plant. The
deposition of Yates (page 43) indicates that heavy oily
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sludges were pushed out the door of a crude tank and spread
around within the diked area. Leaded products were stored in
tanks on the site. In a letter dated March 6, 1989, the New
Mexico Environmental Improvement Division (NMEID) concluded
that leaded tank bottoms (K052 RCRA hazardous waste) disposal
onto soils at the site was likely. Depositions and technical
data appear to support NMEID's conclusion.
3. Soil lead concentrations are very high in the vertical and
horizontal tank areas. Groundwater in the area around the
vertical and horizontal tanks (where the highest lead
concentrations were detected in soils) exceeds drinking water
standards for lead, and contains the highest lead
concentrations found in groundwater on the site. The RI
report states that metals are "associated with the presence of
NAPLs" and Table 6.4 is provided to illustrate. See RI at 6-
19. It is very important to note that in the few examples of
lead in groundwater, given in Table 6.4, none are in an area
where lead in groundwater exceed drinking water standards or
lead in soil is fount?-at extremely high levels. The only area
where lead dissolved ^n groundwater exceeded drinking water
standards was in the areas where soil lead concentrations are
highest, but these areas were not included in Table 6.4. EPA
believes that while lead may be associated with NAPLs, other
sources, such as lead leaching from contaminated soils, also
contribute to lead in groundwater.
4. Despite the facts described above in paragraphs B(2) and (3),
the RI attributes lead at the site to lead from paint.
Specifically, the RI states fsee RI at 7-1, 7-61 and
throughout), "lead occurs [at the site] as basic lead
carbonate, which is generally associated with paint." At this
time, EPA rejects the RI's statement, which overgeneralizes
regarding the nature of lead at the site. The RI's statement
characterizing lead at the site is based upon only three
shallow soil samples, taken from one type of area at the
facility (crude storage), where soil lead concentrations were
relatively low. A 1958 aerial photograph of that area shows
very little soil staining, and the presence of large, probably
painted, tanks that have since been dismantled. Some of the
lead in the areas where the samples were taken is probably
from the practice of painting tanks, but, in other places
where lead was found in very much higher concentrations, the
excess lead found in these other places on the site was
probably not from paint. According to the testimony of former
Prewitt Employees, lead was stored in a tank on the site, and
was added to various products stored in tanks on the site.
The lead was, evidently, part of various waste materials,
including tank bottoms, released onto the soil at the site
when these tanks were cleaned out and the tank bottoms were
dumped onto the soil at the site. In short, the RI's sweeping
generalization that lead at the site is lead associated with
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paint is based on samples which are not representative of the
entire site, and it ignores the history of the site. A more
reasonable conclusion is that at least a portion of the lead
in the soil and in the groundwater at the site is lead
released when tank bottoms were dumped onto the soil at the
site.
The lead speciation conducted as part of the Remedial
Investigation was not part of the Remedial Investigation
workplan. EPA will soon receive additional analysis of lead
speciation in other areas, and will then re-evaluate.
The depositions of Watkins (page 55-57) and Wallace also
indicate that slop tank contents were drained to the ground or
into the earthen ditch sewer system within the refinery which
led to the separator. Slop oil emulsion solids are listed
hazardous waste K049. 40 CFR S 261.32. The slop tank also
contained sludges from the separator (F037 and F038 waste) as
indicated by Wallace's deposition (page 95). Therefore, when
the slop tank was drained, hazardous wastes K049, F037 and
F038 were released onto the soil at the site.
The RI attributes groundwater contamination to "petroleum
products, primarily gasoline and diesel." Table 5.8 (see RI
at 5-61) presents an analysis of the type of hydrocarbon from
various KAPL areas. Only one area, MW-8S is attributed 100%
to petroleum product. At the N-22P NAPL area, none of the
NAPL was identified as gasoline or diesel. Rather this area,
which also shows the impact of lead and chlorinated
hydrocarbons is "undefined." The fact that the RI was unable
to identify the NAPL in these areas as solely petroleum
product, lends further credence to EPA's affirmation that the
hazardous substances described in section B of this document
contributed to groundwater contamination in these areas.
The operating history of the refinery was such that
wastewaters were routinely discharged through unlined, earthen
ditches throughout the refinery area. In addition to
accidental spills, these ditches are known to have carried
off-spec petroleum products (see Deposition of Steve Wallace
at pp. 169-171), hydrocarbon laden wastewaters such as those
generated from the cleaning of the distillation unit (see
Wallace at pp. 119-121), cooling tower overflow and tank
bottoms (see Wallace at p. 109), and spent caustic from
cleaning gasoline (see Deposition of Pete Watkins at pp. 28-
30). Deposits in these ditches include F037 wastes. The
deposition of F037 wastes in the drainage ditches leading from
the refinery operations to the separator, undoubtedly, has
contributed to the contamination that has "migrated downward
through the colluvium and G sandstone and into the F
sandstone," (RI at 5-57) in this area.
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Due to the routine disposal of tank bottoms in the Refinery Area
(N-22P) of the site, the presence of chlorinated hydrocarbons in
the groundwater in this area, the extremely high concentrations of
lead in soils in this area, the draining of slop tank contents
(K049) onto the ground or into the earthen ditch sewer system in
this area, and the impact of contaminant infiltration from tank
bottoms and F037 waste in ditches, EPA does not agree with the
impression created by the RI that the groundwater in the Refinery
Area has been contaminated solely by "petroleum products, primarily
gasoline and diesel. " Instead, EPA has concluded that groundwater
in the Refinery Area is also contaminated with non-petroleum
hazardous substances including 1,2 Dichlorethane, RCRA F037 and
K049 wastes, and constituents inherent in tank bottoms including
leaded tank bottoms which are listed as RCRA hazardous waste K052.
40 CFR S 261.32.
The Prewitt Refinery is unique from other refineries in that it
does not have a large number of waste management units such as
surface impoundments receiving outflow from the separator and
sludge disposal pits. It is clear from the operating history of
the Prewitt Refinery that wastes were generally disposed at or near
the point of generation and not in designated waste management
units. Thus, waste materials known to have been spilled, dumped
and spread in the refinery area have become intermixed with the
spills of petroleum products known to have occurred. Since the
waste materials contain the same contaminants of concern, in
varying amounts, as the spilled petroleum products, specific
origins of contaminants found in groundwater cannot be
distinguished. To reliably differentiate between specific sources
of discrete areas of groundwater contamination is made much more
difficult by the time that has elapsed. Groundwater has moved.
Aereal photographs taken over time show dramatic changes that
weathering, degradation and penetration into soil have had on
surface contamination. The hazardous wastes cited above have been
listed as hazardous wastes and hazardous substances because of
their known potential to adversely impact the environment,
including groundwater, when improperly managed. Due to the
systematically poor waste management practices at the Prewitt
Refinery, and the local geology conducive to penetration of surface
contamination to groundwater, it is unreasonable to conclude that
groundwater has been impacted solely by "petroleum products,
primarily gasoline and diesel."
C. C?tt^rMJM^i?P in th> "B-Baadstopa11 Mortb and East of
Due to the factors enumerated below, EPA concludes that groundwater
contamination plume defined for the E sandstone derives largely
from contamination from the separator and tank areas of the
refinery, and their contaminant sources as described above,
including hazardous substances.
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1. By letter to the PRPs dated July 2, 1991, EPA commented that
the plume in the E Sandstone appeared to mirror the discharge
path from the Separator. EPA also said that a portion of the
BTEX compounds present underground must have come to the E
Sandstone from the separator, having been dissolved into water
that percolated from the surface.
By letter of October 29, 1991, the PRPs responded that the
absence of BTEX contamination in MW21S, among other monitoring
wells in the separator discharge path, was strong evidence
that groundwater contamination in the E sandstone at Prewitt
does not originate from the oil water separator.
Section A of this enclosure addressed releases of hazardous
substances from the separator and their impact on the soil and
groundwater in the immediate vicinity of the separator.
Bedrock fractures in the vicinity of the separator could allow
releases of hazardous substances from the separator to migrate
further underground.
During a telephone conversation which took place on May 27,
1992, Paul Milios and Nat Patel of the El Paso Company (TEPCO)
and the Atlantic Richfield Company (ARCO), respectively,
informed Monica Chapa, EPA's site project manager, of high
concentrations of BTEX detected in MW21S. MW21S is screened
in, and monitors, the E Sandstone. Based on the high
concentrations of BTEX, which MW21S detected in the E
Sandstone, EPA vigorously reaffirms its statement that the
BTEX contamination in the E Sandstone must have come, at least
in part, to the E Sandstone from releases of hazardous
substances from the separator which were dissolved in water
that percolated from the surface in the separator area and
along its discharge pathways. In short, F037 waste
constituents have also impacted the groundwater in the E
Sandstone.
2. Figure l-i in the draft Feasibility Study (FS) report, depicts
two large plumes of groundwater contamination separated by a
narrow uncontaminated band. By letter dated July 2, 1991, EPA
stated that this narrow band, may have been drawn as shown to
artificially buttress the proposition that the contamination
in the two groundwater plumes came from separate sources which
did not intermingle. According to this proposition, the
contamination in each of the two groundwater plumes cane from
separate overlying NAPL plumes.
By letter of October 29, 1991, ARCO and TEPCO responded that
the plumes were drawn separately because they are in distinct
separate sandstone units, separated by an upper confining
layer.
However, the RI documents that the confining beds are
8
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extensively fractured. During the drilling of several NAPL
boreholes, continuous contamination was noted in several
boreholes due to interception of a fracture system. Page 5-1
of the RI report states that "NAPL has moved downward from the
surface under the influence of gravity through fracture
systems."
Furthermore, reevaluation of the data, by EPA, indicates that
there is intermingling of these two plumes of contaminated
groundwater. In other words, it is likely that the source of
the contamination for the contaminated groundwater plume in
the F Sandstone has also been the source of contamination for
the contaminated groundwater plume in the E Sandstone. This
conclusion is supported by the existence of BTEX in both the
F and E Sandstones, as found in borings N-7 (RI at 5-40), N-9
(RI at 5-41), N-19 (RI at 5-51), N-20 (RI at 5-52) and N-29
(RI at 5-57). When the contaminated groundwater plumes are
redrawn to include the information from these borings, the
plume within both sandstones now appears as shown in enclosure
2.
The fact that the NAPL within the F Sandstone is a source for
groundwater contamination within the E Sandstone is also
supported by groundwater flow data. The groundwater flow in
the E sandstone is to the east, and groundwater flow in the F
sandstone is to the northeast. These groundwater flows
closely match the direction of migration of the contaminated
groundwater plumes in both sandstones, if a single
contamination source in the separator and tanks area is
considered. Moreover, it seems unlikely that the small NAPL
bodies present in N-8P and N-6P could be sufficient sources
for the dissolved contamination plume in the E sandstone. It
is much more reasonable for the source of contamination in the
groundwater plume in the E sandstone to be the contamination
in the F sandstone, with the contamination spreading in the
direction of groundwater flow in each sandstone.
Due to the factors enumerated above in section C of this document,
EPA concludes, contrary to the RI, that the NAPL within the F
Sandstone has contaminated both the F and the E Sandstones. As
explained elsewhere in this document, this contamination includes
hazardous substances including BTEX which is normally associated
with F037, K049 and K051 hazardous wastes and tank bottoms.
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