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EPA/ROD/RO6-907062
Crystal Chemical, TX
First Remedial Action - Final
Abstract (Continued)
dismantling and decontaminating structures, constructing drains and fencing, and placing
fill material onsite. The primary contaminant of concern affecting the soil, sediment,
and ground water is arsenic.
The selected remedial action for this site includes excavating approximately 55,000 cubic
yards of offsite soil and sediment with arsenic levels greater than 30 mg/kg and
redepositing the materials onsite; treating approximately 16,500 cubic yards of onsite
soil and sediment with levels of arsenic greater than 300 mg/kg using in-situ
vitrification; covering the onsite area with a multi-layer cap; pumping and treating
approximately 3 million gallons of contaminated ground water using ferric hydroxide
precipitation, flocculation, clarification, filtration, and ion exchange; discharging the
treated water offsite to a publicly owned treatment works (POTW), to surface water, or
reinjecting the treated water onsite; disposing of residual sludges at an offsite
facility; conducting long-term ground water monitoring; and implementing institutional
controls including land use restrictions. The estimated present worth cost for this
remedial action is $18,590,740, which includes an annual O&M cost of $140,079 for 30
years.
PERFORMANCE STANDARDS OR GOALS: The excavation level of arsenic is 30 mg/kg for offsite
soil and sediment and is based on calculated health standards. Treatment of onsite soil
with greater than 300 mg/kg arsenic will effectively treat 95% of the onsite
contamination and will reduce the amount of leachable arsenic to 5 mg/kg. The cleanup
standard for ground water is arsenic 0.05 mg/kg, which is based on the Federal MCL.
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Record of Decision
Crystal Chemical Company Site
U.S. Environmental Protection Agency
Region 6
September 1990
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Statutory Preference for Treatment as a
Principal Element is Met
and Five-Year site Review is Required
SITE NAME AND LOCATION
Crystal Chemical- Company
3502 Rogerdale Road
Houston, Texas
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for
the Crystal Chemical Company site, Houston, Texas, was chosen in
accordance with Comprehensive Environmental Response, Compensation,
and Liability Act, as amended by Superfund Amendments and
Reauthorization Act, 42 U.S.C. Section 9601, et seq., and to the
extent practicable the National Oil and Hazardous Substances
Pollution Contingency Plan, 40 CFR Part 300. This decision is
based on the administrative record for this site.
The State of Texas concurs with 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, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
DESCRIPTION OF THE REMEDY
This Record of Decision addresses the contaminated soils on and
off-site as well as the contaminated groundwater as one unit. The
remedy for the soil contamination addresses the principal threats
at the site by eliminating potential exposure via ingestion,
inhalation or direct contact with contaminants and by reducing the
potential for the soil to act as a continued source for surface
water and ground water contamination. The remedy for the ground
water contamination, too, addresses the principal threats by
eliminating potential exposure via ingestion and direct contact
with contaminants and by eliminating the potential for migration
of contaminants to deeper zones of ground water.
The major components of the selected remedy include:
Excavate arsenic-contaminated soil above 30 parts per
million (ppm) from off-site and place it on the site.
Treat soil with arsenic contamination greater than 300
ppm with the in-situ vitrification process.
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- * Install a multi-layer cap over the entire site.
- Pump ground water from contaminated aquifer (s) , and treat
the groundwater onsite by chemical precipitation,
filtration, and ion exchange.
Discharge treated water to Publicly Owned Treatment
Works, an area surface water, or reinject into the
ground.
DECLARATION
The selected remedy is protective of public health and welfare 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 arid alternative treatment technologies to the maximum
extent practicable and satisfies the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or
volume as a principal element.
Because this remedy will result in hazardous substances remaining
on site (i.e., soils contaminated with arsenical compound
concentrations less than 60 parts per million), a review will be
conducted within five years after commencement of remedial action
to ensure that the remedy continues to provide adequate protection
of public health and welfare and the environment.
Robert E. Layton JV., P.E.
Regional Administrator
Region VT
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RECORD OF DECISION
CRYSTAL CHEMICAL COMPANY SITE
HOUSTON, TEXAS
CONCURRENCE
SEPTEMBER 1990
Stan Hitt, Section Chief
Texas Enforcement Section 6H-ET
(2A
R"enee Holmes/Alexander Schmandt
Assistant Regional Counsel 6C-WT
Pam Phillips j
Assistant Regional Counsel 6C-WT
irjbara Greenfield
Regional rounsel 6C-W
eorge Alexander
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TABLE OF CONTENTS
I. SITE NAME AND LOCATION 1
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES 1
III. HIGHLIGHTS OP COMMUNITY PARTICIPATION 7
IV. SITE CHARACTERISTICS 8
Regional Geology 8
Regional Hydrogeology 8
Historic Site Operations and Potential Sources of
Contamination 9
Chemistry, Mobility, and Toxicity of Contaminants ... 10
Chemistry of Arsenic 10
Mobility of Arsenic 11
Toxicological Properties of Arsenic 13
Extent of Contamination 14
Air and Surface Soils 14
Surface Water/Sediments 22
Subsurface Soil and Ground Water 23
Exposure Routes 39
V. SUMMARY OF SITE RISKS 47
Evaluation of Noncarcinogenic Risks 55
Evaluation of Carcinogenic Risks 57
Remediation Goals 57
VI. SCOPE AND ROLE OF RESPONSE ACTION 60
VII. DESCRIPTION OF ALTERNATIVES 61
Soil Contamination Remedial Alternatives 61
Ground Water Remedial Alternatives 73
VIII. SUMMARY OF COMPARATIVE ANALYSIS OP ALTERNATIVES ... 79
Analysis of Soil Remedial Alternatives 80
Analysis of Ground Water Remedial Alternatives 89
IX. SELECTED REMEDY 91
X. STATTJTORY DETERMINATIONS 97
XI. DOCUMENTATION OF SIGNIFICANT CHANGES 104
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LIST OF FIGURES
FIGURE 1 SITE AREA MAP 2
FIGURE 2 HISTORIC SITE MAP . . . .- 3
FIGURE 3 CURRENT SITE MAP . . • 4
FIGURE 4 BACKGROUND SOIL SAMPLE LOCATIONS 15
FIGURE 5 SURFACE SOIL SAMPLING LOCATIONS 17
FIGURE 6 ESTIMATED CONTOUR MAP OF ARSENIC CONTAMINATED
SOILS 21
FIGURE 7 SURFACE WATER/SEDIMENT SAMPLE LOCATIONS ... 26
FIGURE 8 SUBSURFACE SOIL SAMPLING LOCATIONS 27
FIGURE 9 ISOPACH OF THE 15' WATER-BEARING ZONE .... 35
FIGURE 10 ISOPACH OF THE 35' WATER-BEARING ZONE .... 36
FIGURE 11 MONITORING WELL AND PIEZOMETER LOCATIONS ... 37
FIGURE 12 DEEP WELL LOCATIONS 43
FIGURE 13 ESTIMATED EXTENT OF ARSENIC CONTAMINATED GROUND
WATER 45
FIGURE 14 IN-SITU VITRIFICATION SCHEMATIC 93
FIGURE 15 ONSITE GROUND WATER TREATMENT SYSTEM
SCHEMATIC 96
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LIST OF TABLES
TABLE 1 BACKGROUND SOIL SAMPLE ANALYTICAL RESULTS 16
TABLE 2 SUMMARY OF SURFACE SOIL SAMPLING 18
TABLE 3 SUMMARY OF SURFACE WATER SAMPLING 24
TABLE 4 SUMMARY OF SEDIMENT SAMPLING 25
TABLE 5 SUMMARY OF POND SAMPLING 29
TABLE 6 SUMMARY OF SUBSURFACE SOIL SAMPLING 30
TABLE 7 SUMMARY OF MONITORING WELL ZONES 38
TABLE 8 SUMMARY OF GROUND WATER SAMPLING 40
TABLE 9 SUMMARY OF DEEPER AREA WELL SAMPLING 44
TABLE 10 SUMMARY OF EXPOSURE POINT CONCENTRATIONS OF ~
ARSENIC 49
TABLE 11A SUMMARY OF ESTIMATED SUBCHRONIC HUMAN INTAKE
LEVELS OF ASENIC 51
TABLE 11B SUMMARY OF ESTIMATED CHRONIC HUMAN INTAKE
LEVELS OF ARSENIC 52
TABLE 11C SUMMARY OF SUBCHRONIC NONCARCINOGENIC RISKS
FROM ARSENIC 53
TABLE 11D SUMMARY OF CHRONIC NONCARCINOGENIC RISKS
FROM ARSENIC 54
TABLE 12 SUMMARY OF NONCARCINOGENIC RISKS FROM ARSENIC ... 56
TABLE 13 SUMMARY OF CARCINOGENIC RISKS FROM ARSENIC .... 58
TABLE 14 SOIL REMEDIAL ALTERNATIVES COST ESTIMATES
AND IMPLEMENTATION TIMES 63
TABLE 15 SUMMARY OF BENCH SCALE TREATABILITY TESTING .... 68
TABLE 16 GROUND WATER REMEDIAL ALTERNATIVES COSTS ESTIMATES
AND IMPLEMENTATION TIMES 74
TABLE 17 COMPARATIVE ANALYSIS SOIL REMEDIAL ALTERNATIVES . . 81
TABLE 18 COMPARATIVE ANALYSIS GROUND WATER REMEDIAL
ALTERNATIVES 83
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LIST OF ATTACHMENTS
ATTACHMENT 1 - RESPONSIVENESS SUMMARY
ATTACHMENT 2 - STATE OF TEXAS CONCURRENCE LETTER
ATTACHMENT 3 - ADMINISTRATIVE RECORD INDEX
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DECISION SUMMARY
FOR THE
CRYSTAL CHEMICAL SITE
HOUSTON, TEXAS
I. SITE NAME AHD LOCATION
The Crystal Chemical Company site ("Crystal Chemical site" or "the
site") is located at 3502 Rogerdale Road, in southwestern Houston,
Harris County, Texas. The company operated on approximately 6.8
acres. The acreage is bounded on the west by the Harris County
Flood Control Channel and lies immediately south of Westpark Drive.
The areal extent of contamination, however, covers approximately
24.4 acres. (All further discussions referring to the "onsite
contamination" refer to the 6.8 acres on which the Crystal Chemical
Company operated, and discussions of "offsite contamination" refer
to the estimated areal extent of contamination off of the site that
covers approximately 17.6 acres.) The site is located east of the
area of Harris County known as Alief (see Figure 1) . While the
Crystal Chemical Company was operating, four evaporation ponds,
several structures, and many storage tanks existed on the site (see
Figure 2). The site is now fenced, and all above ground structures
have been removed. The site has also been capped and graded in
order to promote drainage (see Figure 3). The land immediately
surrounding the site is vacant, commercial, and industrial. An
estimated 20,000 people, however, live within a one-mile radius of
the site. Approximately 20 water wells are located within a one-
mile radius of the Crystal Chemical site. These include public
drinking water wells, and industrial, irrigation, and observation
wells.
The Harris County Flood Control Channel bounds the Crystal Chemical
site on the west. Surface waters that enter the flood control
channel flow south and are discharged into the Brays Bayou,
approximately one mile south of the site. Brays Bayou eventually
drains into the Houston Ship Channel, which enters Scott Bay and
eventually Galveston Bay. There is no designated Texas significant
habitat, agricultural land, or historic/landmark site directly or
potentially effected. A Preliminary Natural Resource Survey was
conducted by the National Oceanic and Atmospheric Administration
("NOAA") in February 1989. To date, NOAA has not indicated whether
that there is direct impact to NOAA resources. Additionally, there
are no endangered species or critical habitats within close
proximity of the site.
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
Crystal Chemical Company produced arsenical, phenolic and amine-
based herbicides from 1968 to 1981. Operation and maintenance
problems at the Crystal Chemical facility during the late 1970s
resulted in several violations of the environmental standards of
the Texas Department of Water Resources ("TDWR"), now the Texas
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PROPERTY LINE
40
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FIGURE 2
HISTORIC SITE MAP
SOURCE: D'APPOLONIA/ERT/BFI
SITE INVESTIGATION
JANUARY, 1984
METCALF & EDD>
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Water commission ("TWC"). The primary problem was repeated flooding
of the site which carried arsenic-contaminated wastewater offsite.
In 1978 the Crystal Chemical Company applied to the State of Texas
for an onsite deep well injection permit to dispose of the
facility's wastewaters which were being stored in the four onsite
wastewater evaporation ponds. The permit was denied.
In September 1981, Crystal Chemical filed for bankruptcy and
abandoned the site, leaving approximately 99,000 gallons of arsenic
trioxide in a storage tank and approximately 600,000 gallons of
wastewater in the evaporation ponds. Arsenic trioxide is a
substance used in the manufacturing of weed killers, enamels, and
pesticides. It may be highly toxic and a potential cause of
cancer.
The United States Environmental Protection Agency ("EPA") initiated
a number of Emergency Removal Actions between September 1981 and
February 1983 to stabilize the site. During the first EPA emergency
cleanup, the wastewater was removed from the ponds and disposed of
at an offsite commercial waste disposal facility. The top foot of
soil was removed, mixed with lime, then deposited back into the
wastewater ponds. A temporary cap, which included a plastic cover
topped by a layer of clay, was placed over the area to limit the
infiltration of water into contaminated soil. The arsenic trioxide
was sold, and the buildings and process equipment were
disassembled, decontaminated and sold, essentially leaving the site
vacant. The only remaining structures onsite are two concrete
slabs. Subsequently, EPA has taken further measures to control
surface runoff and site access, and to enhance the integrity of the
temporary cap. Steps taken by EPA in 1983 and 1988 included
construction of drains, fencing, and placement of additional fill
onsite. The total cost of these removal actions was approximately
$1.3 million.
In 1983, the Crystal Chemical property was added to the National
Priorities List ("NPL"), pursuant to Section 105 of the
Comprehensive Environmental Response, Compensation, and Liability
Act ("CERCLA"), 42. U.S.C. Section 9605, as amended, qualifying the
site for investigation and remediation under CERCLA, more commonly
known as Superfund.
In 1982 and 1983, EPA identified 13 potentially responsible parties
("PRPs") for the site. All PRPs declined the opportunity to
participate in the Remedial Investigation/Feasibility Study
("RI/FS") for the site. Therefore in 1983, TDWR through a
cooperative agreement with EPA.initiated a study of the site to
define the types and extent of contamination at the Crystal
Chemical site. The investigation involved field sampling and
testing of surface sail, subsurface soil, sediment, storm water,
site runoff, and air at and near the site. Ground water wells were
also installed to collect samples and to define subsurface
conditions. Arsenic and, to a lesser degree, phenol were among the
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contaminants detected in surface and subsurface soil and ground
water. Phenol is a chemical used in the production of plastics,
disinfectants, Pharmaceuticals, and other industrial compounds, and
it may be toxic. The report was completed in January 1984 and is
entitled "Final Report Site Investigation "Crystal Chemical Company
Houston, Texas."
The initial Feasibility Study ("FS") was completed in June 1984.
This study described a range of alternatives to treat and contain
contaminated soil and ground water. EPA selected Alternative F as
its preferred alternative for remediation of the site. This
alternative called for extensive excavation of the contaminated
soils on site, construction of slurry walls around the site to
isolate the contaminated ground water, removal of the contaminated
soils offsite to a level of 100 parts per million ("ppm"), offsite
disposal of all excavated soils, and capping of the site.
Public comments, however, questioned the cost associated with
Alternative F's proposal. The public questioned if after
excavation of the offsite soils and the construction of a cap
onsite, was the offsite disposal of the soils more protective of
public health and the environment. In response to these comments,
EPA and TDWR conducted an Addendum Feasibility Study ("AFS") to
evaluate Alternative G, which proposed to cap the onsite
contaminated area after excavating all offsite soils contaminated
with arsenic greater than 100 ppm. The AFS was completed in
December 1984, and it concluded that Alternatives F and G would
protect the public health and welfare and the environment equally
well. Accordingly, the EPA selected Alternative G as its preferred
remedy for the site since Alternative G was more cost-effective.
Between May 1985 and October 1986, EPA negotiated with Southern
Pacific Transportation Company ("Southern Pacific") to conduct the
Remedial Design/Remedial Action ("RD/RA") for the site. Southern
Pacific previously owned the property on which the site is located
and responded to EPA's request in August of 1984 to participate in
the RD/RA process.
The negotiations, however, were superseded by the passage of the
Superfund Amendments and Reauthorization Act of 1986 ("SARA"). EPA
determined that the Crystal Chemical Remedial Investigation and
Feasibility Study ("RI/FS") should be supplemented with an
additional study (the Supplemental Feasibility Study) which would
focus on the use of technologies to treat contaminants at Crystal
Chemical. SARA expresses a strong legislative preference for
remedial actions in which hazardous wastes are treated to
"permanently and significantly" reduce their volume, toxicity or
mobility over remedial actions not involving such treatment. The
FS and AFS for the ,site did not fully investigate treatment
options.
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On May 3, 1987, EPA entered into an Administrative Order on Consent
("AOC") with Southern Pacific Transportation Company to conduct the
Supplemental Feasibility Study ("SFS"). The SFS involved
additional field sampling and testing of surface soil, sediment and
surface water. Additional ground water wells were installed to
collect samples and to examine the movement of ground water in the
upper soil layers. Samples from the former pond areas were taken
in order to evaluate technologies which might be used to treat
contaminated soils at the site.
Southern Pacific suspended work on the SFS in January 1988, because
existing federal regulations prohibited Southern Pacific from
conducting the offsite bench-scale treatability studies required
to complete the SFS. Southern Pacific agreed to a revised schedule
to complete the SFS in February 1989 .after new regulations
authorizing offsite treatability studies were promulgated. In
September 1989, Southern Pacific requested an extension of time to
complete the SFS, a request EPA denied. EPA completed the SFS in
May 1990.
III. HIGHLIGHTS OF COMMUNITY PARTICIPATION
The SFS and the Proposed Plan for the Crystal Chemical site were
released to the public in June 1990. These documents were made
available to the public at both the administrative record and the
information repository locations. A summary of the Proposed Plan
and the notice of availability of these documents and the
administrative record was published in the Houston Post on May 27,
1990. A public comment period was held from June 11, 1990 through
July 11, 1990. Informal Open Houses were held in the Houston area
on two separate occasions, April 10 and June 5, 1990.
Additionally, a public meeting was held on June 21, 1990.
Representatives from EPA, TWC, the Agency for Toxic Substances and
Disease Registry ("ATSDR"), and from the Texas Health Department
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 period including
those expressed verbally at the public meeting is included in the
Responsiveness Summary, which is part of this Record of Decision
as Appendix A. This decision document presents the selected
remedial action for the Crystal Chemical site, Houston, Texas,
chosen in accordance with CERLCA, as amended by 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
document.
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IV. SITE CHARACTERISTICS
The principal threats identified at the Crystal Chemical site are
the contaminated soils and sediments and the shallow ground water.
The contaminated soils and sediments were determined to be a
principal threat at the site because of direct contact, ingestion,
and inhalation risks and because of the soil's impact on ground
water. The contaminated shallow ground water was also determined
to be a principal problem at the site 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.
Regional Geology
The Crystal Chemical site is located within an outcrop of the
Beaumont Formation which is of Pleistocene age (approximately 1.6
million years old). The Beaumont Formation is characterized by
backswamp, point bar, natural levee and stream channel deposits
consisting of silt, clay, and sand. Such depositional environments
are typified by predominantly fine-grained deposits representing
low energy deposition. These are the clays, silty clays and clayey
silts. Interspersed within this fine-grained matrix are the
channel deposits generally consisting of fine sand and silty fine
sand. The channel deposits typically are thin (less than 20 feet
in thickness) and of limited areal extent. Because of the
depositional environment of these sands, their geometry is commonly
narrow and sinuous. They are often completely isolated in three
dimensions because of channel cut-offs and reworking of channel
sediments. Iron concretions along with calcium carbonate deposits
are commonly present in the first 30 feet of weathered zones.
Underlying the Beaumont Formation are the Montgomery, Bently and
Willis Formations which are of Pleistocene age, and the Goliad
Sand and Fleming Formations which are of Pliocene age.
Regional Hydrogeology
There are four aquifers of regional significance in the area of the
Crystal Chemical site. These aquifers are the Upper Chicot
Aquifer, the Lower Chicot, the Evangeline Aquifer, and the Jasper
Aquifer.
The Upper unit of the Chicot Aquifer occurs within the Beaumont and
Montgomery Formations and is a minor source of water in the area.
The base of this unit,occurs at an elevation of approximately -
180 feet National Geodetic Vertical Datum ("NGVD") in the site
area.
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The Lower unit of the Chicot Aquifer occurs within the Montgomery,
Bently and Willis Formations and is a source of water in the area.
The base of the unit occurs at an elevation of about -650 to -700
feet NGVD.
The Evangeline Aquifer is the major source of ground water in the
area and occurs within the Goliad Sand and the upper portion of the
Fleming Formation. It represents the deepest aquifer in the area
containing water with less than 1,000 mg/1 (ppm) of total dissolved
solids. The base of the aquifer occurs at an elevation of about -
2200 to -2300 feet NGVD. The Burkeville Confining Layer occurs
within the Fleming Formation and separates the Evangeline Aquifer
from the more highly mineralized Jasper Aquifer. It occurs in the
approximate interval of -2200 to -2300 feet NGVD in the area.
The Jasper Aquifer occurs within the Fleming Formation and is
generally not used for water supply due to the high dissolved
solids concentration. Direction of ground water flow in both the
Chicot Aquifer and the Evangeline Aquifer is toward centers of
ground water withdrawal. Generally, the regional gradient from the
site is north.
Historic Sit* Operations and Potential Sources of Contamination
The Crystal Chemical site is an abandoned herbicide manufacturing
plant. During its operation, the production facilities were
located on the southwestern portion of the property. Dikes around
the site perimeter were constructed to contain production
wastewater and surface water run-off on the property. Surface
water run-off and process wastewater was diverted away from the
process operations to storage/treatment ponds. There were four
of these ponds on the site: three ponds at the north end of the
property and one smaller pond in the southeastern corner (see
Figure 2).
The ponds were constructed at different times during the plant's
operation and were used for various purposes. Pond No. 4 was the
first pond constructed and was used as a water recycling lagoon.
Pond No. 1 served as a spray evaporation pond and as a holding pond
for process wastes. Pond Nos. 2 and 3 which were constructed in
early 1978 provided storage for process and surface run-off water.
Pond No. 2 received surface run-off from the west side (i.e., the
process side) of the plant, while Pond No.3 collected run-off from
the east side (i.e., the non-process side) of the plant. During
EPA's first Emergency Removal Action, approximately 825,000 gallons
of contaminated liquid were removed from the ponds. Arsenic
concentrations in the liquid averaged 15,000 ppm.
One of the most significant factors that contributed to the spread
of arsenic-containing materials (arsenic has been identified as the
only contaminant of concern, see Section V. SUMMARY OF SITE RISK
for a complete discussion) outside of the process areas and offsite
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was the periodic flooding of the site due to poor site drainage and
the site's proximity to Harris County Flood Control Channel, D-
124-00-00. In June 1976, an extended period of wet weather flooded
the site. The capacity of the dikes was exceeded and surface run-
off from process and material storage areas flowed in a northerly
direction toward the property line. The discharges led to
litigation between the State of Texas and Crystal Chemical Company
in December 1977. Initially, the perimeter dikes contained the
water on the site, however, sampling conducted during the SI (1984)
and for the SFS indicated that water overflowed and seeped into
adjacent drainage ditches. These drainage ditches discharge into
Brays Bayou.
Airborne arsenic was released offsite during the plant's operation
through aerosol drift from the mechanical aeration in the
wastewater evaporation ponds. Arsenic contamination in air
conditioning filters in downwind residences was reported by
citizens of the Brays Village apartment complex (SI, 1984).
During the plant operations from 1968 to 1981, Crystal Chemical
Company produced arsenic-based herbicides such as monosodium
methylarsenate ("MSMA" or "mesamate (R)"), along with a wide
spectrum of phenolic-and amine-based herbicides (Dinitro General,
Dinitro 3, Naptalam, Naptro, Dimethoate 267 and Crysthyon 2-L) .
These arsenic- and phenol-based products, along with the raw
materials required for their production (e.g., arsenic trioxide,
sodium arsenite, dinitrophenol) were major sources of the
contamination at the site. Both raw and finished containerized
(e.g., drummed) materials were stored on the ground, in the open.
These materials occasionally spilled and, therefore, leaked onto
and into surface soils. Arsenic trioxide was received in bulk from
rail cars, and poor containment of the arsenic during loading and
unloading operations was a frequent source of contamination.
Chemistry, Mobility, and Toxicity of Contaminants
Chemistry of Arsenic
Arsenic is a metalloid with chemical properties intermediate
between metallic and nonmetallic elements. It ranks twentieth
(20th) in abundance among the elements of the earth's crust. The
chemistry of arsenic in the environment is fairly well understood,
and arsenic is often used for the control of fungus, weeds, and
parasites.
Arsenic is usually found in one of two valence states, trivalent
arsenite (As*3) and the pentavalent arsenate (As*5) . These two
valence states have markedly different toxicities, solubilities and
soil binding characteristics.
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Arsenic trioxide was historically and is currently used as a raw
material in the manufacturing of herbicides. in today's market,
however, the primary active ingredients in arsenic-based herbicides
are methylated arsenic acid salts (monosodium methanearsonic acid
and disodium methanearsonic acid). Vegetable crops are less
susceptible to these active ingredients. Methylated arsenical
compounds are also preferred since they are two orders of magnitude
less toxic to man and domestic animals.
In most aerobic soil and aquatic environments, arsenical compounds
are readily oxidized or dimethylated to form arsenates. While
arsenate will be the primary form, some methylated arsenates may
also be present. Given anaerobic conditions, arsenites (e.g.,
arsenosulfides), which are significantly more toxic, may be
present. Soil microbial action can also result in the evolution
of alkylarsine gases, but the concentrations are sufficiently low
to be of limited concern to public health. Arsine gas may also be
generated chemically by the action of strong acids on arsenic
compounds. This is considered to be unlikely under present site
conditions, since previous acid spills have been largely
neutralized by natural soil buffering, and no remaining sources of
concentrated acids are known.
Regardless of the compound applied, arsenic is primarily found as
arsenate in most biologically active and aerated soils. In
anaerobic soils (especially stream sediments), arsenite may be the
predominant form. The solubility of arsenite (e.g., as arsenic
trioxide) is four to ten times greater than for arsenates; however,
microbial activity in most soils readily converts arsenite to
arsenate. When applied as a methylarsenical compound (e.g., MSMA,
DSMA), the arsenical compound is converted in most aerobic soils
into inorganic arsenate within a half year. Arsenate can also be
methylated by bacterial activity, therefore, competing mechanisms
and the form and method of the arsenic application determine the
relative quantities of organic and inorganic arsenic in soils.
Most arsenites and arsenates are relatively insoluble, nevertheless
they generally nucleate and precipitate very slowly. Solubility
products for many inorganic compounds range from 10"15 to 10"22.
Arsenites and alkylarsenates are the most mobile. Because of the
significant differences in the toxicities and mobility of arsenical
compounds, the identification of the arsenic species present is
important in the determination of the potential for future
migration and the assessment of environmental risk. Tests to
assess the amount of available or soluble arsenic are also
important.
Mobility of Arsenic
In contact with soil, arsenates and methylarsenates are relatively
insoluble. The amount of soluble arsenic in soils depends on the
11
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relative amounts of sorptive components, principally iron,
aluminum, calcium, and magnesium. Trimethylarsine (probably as an
oxide, "TMO") also has a correspondingly low solubility. Mobility
of inorganic arsenic in ground water is often controlled by the
redox potential, with mildly reducing conditions generally
producing the greatest mobility.
The texture of the soil (i.e., soil surface area), oxidation-
reduction potential, soil pH, and time elapsed since application
or contamination also are factors which affect the relative amount
of fixed or soluble arsenic in the soil. Under the appropriate
conditions, significant leaching and removal of arsenic from soils
can occur. However, continual arsenic application and the
predominance of fine-textured soils (such as the clays covering the
upper 20 to 30 feet of the site) usually result in accumulation
since little arsenic is available for solubilization (i.e.
dissolving). In such soils, the vertical penetration is limited.
Wind and water erosion and, to a limited extent, reduction to
alkylarsines emitted to the atmosphere are the primary loss
mechanisms. Arsenic loss from clay soils through plant uptake is
relatively insignificant.
The arsenic not bound to soil particles and in solution is
available for uptake by plants or for migration through the soil
profile. Depending on the plant species and soil type, soluble (or
available) arsenic levels of 3 to 28 ppm are phytotoxic. Species
tolerant to 5 ppm available arsenic include most grasses,
specifically, sensitive species that include alfalfa and legumes.
Arsenic uptake by plants and the resulting impact on animals
consuming the plants are usually of limited concern. Plants seldom
accumulate dangerous levels since arsenic is toxic to many plant
species (i.e., the plants would die before they could accumulate
concentrations high enough to be toxic to anything that might eat
the vegetation). In addition, biomagnification (as occurs with
mercury) does not occur with arsenic. Animals readily excrete
ingested arsenic. Consequently, plant ingestion does not produce
intoxication in animals. Cases of arsenic intoxication by foraging
animals are attributable to ingestion of dusted vegetation or
contaminated soil rather than arsenic uptake by plants.
Several investigators have proposed models to explain observed
arsenic movement and transformations within aqueous ecosystems.
In water, arsenite is readily oxidized to arsenate. Methylated
arsenical compounds are usually adsorbed by sediments in streams
and demethylated. Consequently, most arsenic is found as arsenates
fixed to bottom sediments. Desorption into solution or methylation
and reduction to form volatile alkylarsines and perhaps arsine can
occur. The volatile alkylarsines persist in the atmosphere only
a short while before being oxidized, eventually carried by rain and
12
-------
then readsorbed to sediments. Arsenosulfides (arsenites) may form
in anaerobic sediments when sufficient sulfur compounds are
present.
Arsenic can be introduced into the atmosphere as dust or as a gas.
Arsine gas and alkylarsine gases are readily oxidized to form
oxides that fall as dust or are washed from the air by rain.
Toxicological Properties of Arsenic
The toxicological properties and health effects associated with
arsenic compounds have been thoroughly reviewed by the Agency of
Toxic Substances and Disease Registry ("ATSDR") in the
Toxicological Profile for Arsenic (March 1989). Arsenic is a
naturally occurring element which exists in a variety of chemical
forms with variable toxicities. In general inorganic forms of
arsenic, such as oxides and salts, are more toxic than methylated
or more complex organic arsenic compounds. Organic arsenicals,
which occur naturally in some foods such as fish, are more readily
metabolized and excreted than inorganic forms of arsenic.
Consequently, organic arsenic compounds are not generally
considered to be of major importance in most discussions of ambient
environmental exposures.
Among inorganic arsenic compounds, those containing trivalent
arsenic (As*3) are generally observed to be more toxic than
pentavalent arsenic (As ) species. The pentavalent arsenate is the
form most commonly encountered in nature. In this form, arsenate
tends to be fairly rapidly excreted by the kidneys and probably
does not accumulate to any great extent . Trivalent arsenites,
such as arsenic trioxide, are the most commonly encountered man-
made forms of arsenic. However, trivalent arsenic compounds also
occur naturally. Trivalent arsenites have greater ability to bind
with tissue proteins and interfere with enzymatic functions than
other forms of arsenic. Inorganic forms of arsenic are viewed
collectively when discussing ambient exposures.
Inorganic arsenic is almost ubiquitous in the ambient environment.
Consequently, humans and other animals experience ongoing exposures
to naturally occurring levels or arsenic. Ground water may contain
concentrations of inorganic arsenic ranging from 0.2 to 10 M9/1-
Epidemiologic evidence suggests that ingestion of drinking water
containing approximately 400 ng arsenic/1 or higher may be
associated with signs of systemic toxicity. Concentrations of
arsenic in ambient are usually in the range of 2 to 10 ng/m .
These concentrations have not been associated with systemic
toxicity. Dietary sources provide the largest portion of human
intake of inorganic arsenicals. U.S. EPA has estimated that diet
contributes approximately 25 to 50 nq arsenic per day.
Studies indicate that humans are more sensitive to the toxic
effects of arsenicals than laboratory animals. Lethal doses of
inorganic arsenic reported for animals (10 to 300 mg/kg) are higher
13
-------
than lethal doses reported in humans (0.6 to 2 mg/kg). Humans
exposed to chronic oral doses of 50 to 100 ^g inorganic arsenic/kg
per day may display toxic effects on the nervous system
(neurological) and/or blood (hematologicaj.) .
Extent of Contamination
Air and Surface Soils
In January 1989, surface soils samples were collected for the SFS
to determine background levels of arsenic in soils around the
Crystal Chemical site. Samples were collected from the upper three
to four inches of soil in empty fields adjacent to commercial or
residential areas (see Figure 4) , and the samples were analyzed for
the site's primary contaminant, arsenic. The samples contained
arsenic at levels below the analytical laboratory's detection limit
(see Table 1). The values were reported as less than 1.2 to 1.6
mg/kg or ppm total arsenic.
Soils samples were collected from 1983 to 1989 in the vicinity of
the site. Figure 5 illustrates the location from where these
samples were taken, and a summary of the analytical results are
presented in Table 2. The approximate extent of soils contaminated
with arsenic is presented in Figure 6. Based on this figure, the
areal extent of contamination covers approximately 24.4 acres.
All further discussions referring to the "onsite contamination"
refer to the 6.8 acres on which the Crystal Company operated, and
discussions of "offsite contamination" refer to the estimated areal
extent of contamination off of the site that covers approximately
17.6 acres. The volume of offsite soils contaminated with arsenic
greater than 30 ppm is estimated to be 55,000 cubic yards. The
volume of onsite soils contaminated with arsenic greater than 300
ppm is estimated to be 16,500 cubic yards, and there is estimated
to be 101,000 cubic yards of onsite soil contaminated with arsenic
greater than 30 ppm.
The current spread of contaminants through the air and onto surface
soils is assumed to be negligible since plant operations ceased in
1981 and since the entire site was capped during the EPA Emergency
Removal Action in 1983. However, the primary sources of airborne
contamination during plant operations were most likely wind-blown
raw materials, aerated pond mist, cooling tower drift and wind
blown dust.
The levels of airborne arsenic measured in the vicinity of the site
during the SI (1984) ranged from 0.0005 to 0.50 jig/m3. These
levels are higher than background levels measured by the Harris
County Health Department but of the same order of magnitude as
documented airborne arsenic concentrations in industrial urban
centers (EPA Endangerment Assessment, 1988). If remediation of the
site were not planned and the temporary cap constructed on the site
14
-------
f-
CRYSTAL
CHEMICAL
CHKT1BYTRH
BYTRH
Applied
Engineering
Science
BACKGROUND SOIL -
SAMPLE LOCATIONS
SPTC -CRYSTAL CHEMICAL
BATE
MARCH.99
HO.
4056 A
SHEET NO
I
-------
TABLE 1
SUMMARY OF BACKGROUND SOIL SAMPLING
Crystal Chemical Site
January 26, 1989
Sample I.D. Total Arsenic
(mg/kg)
1 <1.40
2 <1.40
3 <1.40
4 <1.40
5 <1.20
6 <1.30
7 <1.20
8 <1.30
9 <1.30
10 <1.40
10 (DUP) <1.40
11 <1.40
12 <1.60
13 <1.30
14 <1.50
15 <1.40
Note;
( ) - Duplicate Sample Analysis
-------
. i
si
IH
f!
-------
TABLE 2
SUMMARY OF
SURFACE SOIL SAMPLING
Crystal Chemical Company Site
Saaple
Number
0
P
R
S
J
P(l)
P(2)
P(3)
1
3
4
5
6
9
10
12
13
1
2
3
4
5
6
7
8
9
10
11
SS-1
SS-2
SS-3
SS-4
SS-5
SS-6
SS-7
SS-8
SS-9
SS-10
SS-11
SS-12
SS-13
SS-14
SS-15
SS-16
Date
1/27/81
2/10/81
2/16/81
2/16/81
7/07/81
8/05/81
8/05/81
8/05/81
1/7/83
1/7/83
1/7/83
1/7/83
1/7/83
1/7/83
1/7/83
1/7/83
1/7/83
4/26/83
4/26/83
4/26/83
4/26/83
4/26/83
4/26/83
4/26/83
4/26/83
4/26/83
4/26/83
4/26/83
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
Total
Arsenic
(ma/ka)
1629.5
38.1
163.3
100.3
0.39
15244
7357
9191
11
18
23
32
62
670
130
47
172
520
4385
2128
3599
1597
605
510
5749
7936
4222
802
636
242
345
23
39
26
66
49
52
72
37
33
28
45
49
34
Total
Phenols
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
*NA
NA
NA
NA
-------
TABLE 2 (continued)
SUMMARY OF
SURFACE SOIL SAMPLING
Crystal chemical Company Site
Sample
Number
SS-17
SS-18
SS-19
SS-20
SS-21
SS-22
SS-23
SS-24
SS-25
SS-26
SS-27
SS-28
SS-29
SS-30
SS-21
SS-22
SS-22
SS-34
SS-25
SS-26
SS-27
SS-28
SS-39
SS-40
SS-41
SS-42
SS-43
SS-44
SS-45
SS-46
SS-47
SS-48
SS-49
SS-1*
SS-2*
SS-3*
SS-4*
SS-5*
SS-6*
SS-7*
SS-8*
SS-9*
SS-10*
SS-11*
SS-12*
SS-13*
Date
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
1983 SI
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
1Q/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
Total
Arsenic
(ma/ka)
36
36
7.5
17
41
43
NA
5
NA
4
NA
<2
<2
12
3
3
9
30
38
41
5
4
4
20
2
7
NA
39
6
9
12
9
77
52
50
156
107
41
265
127
957
866
281
23
336
561
Total
Phenols
(ma/ka)
NA
NA
<1.8
NA
<1.9
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
3.0
1.8
1.9
1.9
4.0
2.4
4.5
1.2
<0.1
.1.9
2.2
2.6
3.4
-------
TABLE 2 (continued)
SUMMARY OF
SURFACE SOIL SAMPLING
Crystal Chemical Company Site
Sample
Number
SS-14*
SS-15*
SS-16*
SS-17*
SS-18*
SS-19*
SS-20*
SS-21*
Date
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
Total
Arsenic
rma/ka)
520
250
423
352
14.2(11.8)
886(750)
97.1
1220
Total
Phenols
2.5
3.5
2.2
2.1
2.5(2.3)
2.7(2.7)
4.6
4.2
Notes;
NA = Not analyzed
SI Site Investigation
* Sampling performed by Applied Engineering and Science,
Inc.
( ) Duplicate Sample
-------
It
•
g
1
s
o
S
hU
iif
|§ S
II 1'
1 1
. I
\\
!
-------
in 1983 was not maintained, the degradation of the cap could result
in higher ambient arsenic releases, therefore, potentially
increasing the risk to nearby populations.
Surface soil contamination, possibly related to past airborne
releases of arsenic, may be the source for the 72 ppm of arsenic
that was detected in 1984 (SI) on the west side (site is on the
east side) of the Harris County Flood Control Channel. This is the
highest level of contamination found in nearby offsite surface
soils that may not be attributable to surface water or ground water
transport. However, as the flood control channel was not
constructed until 1977, it is possible that surface water run-off
from the Crystal Chemical site may have crossed the farm road which
previously existed at the present right-of-way of the channel and
ponded in this area.
Surface Water/Sediments
There are three major surface water features in the site area:
Harris County Flood Control Channel (D-124-00-00), Brays Bayou (D-
100-00-00), and Buffalo Bayou (W-100-00-00). The flood control
channel has an average depth of 15 feet and flows southward to
Brays Bayou, which is located about one mile south of the site.
The bayou drains in an easterly direction to the Houston Ship
Channel and ultimately into Galveston Bay.
Buffalo Bayou is located about 2.5 miles north of the site. A
Texas Water Quality Board Memorandum (August 5, 1977) reported that
drainage from the Crystal Chemical site and from the area around
the site had been directed into Buffalo Bayou until March 3, 1977.
This was conceivably before the flood control channel directing
drainage into Brays Bayou had been completed. Buffalo Bayou also
drains to the Houston Ship Channel and Galveston Bay.
Drainage ditches to the north and south of the site receive
drainage directly from the site and discharge into the Harris
County Flood Control Channel. Along the western site boundary,
surface drainage, as well as subsurface seepage from the site
enters the flood control channel directly.
Although the Crystal Chemical site is not located within a flood
prone area as defined by the Federal Emergency Management Agency,
it has flooded repeatedly. In fact, local studies indicate that
the site lies within the limits of the 100-year floodplain of the
adjacent Harris County Flood Control Channel.
Contamination of surface water is likely attributable to a
combination of three factors: (l) continuing seepage from beneath
the clay cap and liner during and following rainfall events,
especially apparent along the western site boundary; (2) residual
contaminants from previous events leached or re-suspended from
22
-------
drainageways, contaminated off site soils and standing water pools
during and following rainfall events, (3) residual contaminants
being leached or re-suspended in run-off directly from the capped
site. The 1984 SI report estimated that the annual run-off from
the site is 633,798 ftr/yr.
Tables 3 and 4 present a summary of surface water and sediment
samples taken in the site vicinity. Sample locations are
illustrated in Figure 7. Two series of samples were taken, in
April 1983 and October 1987. Three of the samples collected in
1987 show that arsenic contamination exceeded the ambient water
standard of 0.0175 Mg/1 (ppb) for arsenic (Clean water Act, as
amended, 33 CFR 303). However, overall trends over time are
inconclusive, with some areas showing increases in contamination
and others showing decreases.
Most of the arsenic in surface run-off is deposited or adsorbed to
sediments. After adsorption, the arsenic undergoes desorption in
solution and further transport, or methylation/reduction to form
organoarsenical compounds.
During heavy rains, water in the drainage ditches may backup into
connecting ditches, creating the potential for contamination of
upstream sediments. Several deep erosion gullies (formed due to
lack of vegetation) are present in the bank of the flood control
channel along the west side of the site.
With time, it is possible that the extent of contamination will
spread to previously uncontaminated downstream sediments as
arsenic-bearing sediments migrate. The rate of migration depends
primarily on sediment transport rates and on arsenic dissolution
and precipitation mechanisms. Insufficient data are available to
predict the rate of migration but the rate was judged to be
relatively slow in the SI (1984).
Subsurface Soil and Ground Water
Results of 1983 and 1987 soil and ground water sampling in onsite
and offsite monitor wells and in subsurface borings indicate that
arsenic and phenol contamination has occurred in the subsurface
environment. Contamination of ground water and subsurface soils
at the Crystal Chemical site has probably been advanced by
percolation of surface water into the subsurface through the soil
matrix, through natural subsurface discontinuities and
imperfections, and/or by previous site and construction and
operating activities. Offsite subsurface soil contamination is
most likely associated with past storm water run-off episodes and
percolation with time into the subsurface.
Subsurface soil arsenic contamination has been identified across
the site to an average depth of five to six feet. Figure 8
*
23
-------
TABLE 3
SUMMARY OF
SURFACE WATER SAMPLING
Crystal Chemical Company Site
Sample
K«mh0p
SW-1
SW-2
SW-3
SW-4
SW-15
Total
Arsenic
(ma/1)
<0. 005(0. 016)
0.017
0.066
0.060
0.506
Total
Phenols
(ma/1)
0.059(0.62)
NA
0.045
0.068
0.092
Notes;
NA = Not analyzed, container broken in transit
( ) Duplicate Sample
Samples taken on 10/23/87 by Applied Engineering and
Science, Inc.
-------
TABLE 4
SUMMARY OF
SEDIMENT SAMPLING
Crystal Chemical Company Site
Sample
Number
AB-1
AB-2
AB-3
AB-4
AB-5
AB-6
SED-1
SED-2
SED-3
SED-4
SED-5
SED-6
SED-7
SED-8
SED-9
SED-10
SED-11
SED-12
SED-13
SED-14
SED-15
SED-16
Date
APRIL 1983
APRIL 1983
APRIL 1983
APRIL 1983
APRIL 1983
APRIL 1983
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
10/23/87
Total
Arsenic
(moVXa)
227.0
51.7
32.2
22.4
20.3
49.4
28(27)
278
54
5.2
66
44
37
904
306
924
850
437
482
53
98
35
Total
Phenols
NA
NA
NA
NA
NA
NA
3.0
1.2
2.3
2.0
1.3
2.6
3.2
2.5
6.1
5.2
5.3
2.9
3.1
2.1
1.9
2.6
Notes;
NA = Not analyzed
( ) Duplicate Sample
-------
f i
D
S
i
*»-
S •
a s
I * .0
- Q (/)
« tu _
- « •
W
•
JO
-------
i «
, §
1 g
!• X
u.
§
ji
il
%
i
-------
illustrates subsurface soil sampling locations (soil borings and
borings associated with monitoring well construction) and Tables
5 and 6 show the summary of the analytical results. Gross arsenic
contamination of 5,000 ppm arsenic has penetrated nearly three to
four feet (not including the cap thickness) in the rail car off
loading area, nearly five to six feet in the arsenic trioxide tank
area and below Pond No. 2 and to depths greater than ten feet below
the bottom of Pond No. 1 (assuming its working depth was about
seven to eight feet). Offsite borings revealed arsenic
concentrations greater than 50 ppm at depths ranging from two and
one-half to seven feet and to as deep as nine feet. These samples
were collected within 70 feet of the site boundaries.
Selected soil samples collected from the monitoring well
installations and during the pond borings were analyzed further for
the purposes of identifying the types or forms of the arsenic.
Both organic and inorganic forms of arsenic were found. The
principle forms of organic arsenic were cacodylic acid and methane
arsenic acid. Inorganic arsenic was found to occur as arsenite
(As*3) and arsenate (As ). The concentrations of the organic and
inorganic forms of arsenic were found to vary throughout the site.
The maximum concentration of phenolic compounds detected in soil
was 157 ppm in MW-4 at a depth of 40 feet. A phenolic
concentration of 0.75 ppm was detected in a water sample collected
from MW-4. Analysis of soil collected from boring B-7, about 120
feet northeast of the Crystal Chemical site, recorded a phenol
concentration of 110 ppm at a depth of 8.5 feet. This boring was
located.in the abandoned flood control channel right-of-way which
may have served, up through 1977, as the primary offsite drainage
path to Buffalo Bayou. In ten other subsurface soil samples,
phenolic concentrations ranged from 2 to 28 ppm. The samples were
collected at depths of 1.5 to 20 feet, in locations onsite or
within about 35 feet of the site. In the remaining soil samples,
concentrations of phenolics were below the detection limit (2 ppm) .
Subsurface information gathered from the 24 monitoring well borings
was used to create a generalized three dimensional geologic model
(SFS 1990). Three water-bearing zones were identified at 15 feet,
35 feet, and 100 feet below the ground surface. All three of these
water-bearing zones are classified as Class lib ground water units
Per "EPA Guidelines for Ground-Water Classification" - Final Draft,
December 1986.
Stratigraphically, the top 13 feet consists of dark-gray silty
clay, grading to a calcareous clay with calcareous nodules and
iron-rich concretions. Underlying this unit is a very fine reddish
sand which ranges from 0 to 13 feet thick. This unit is also
referred to as the 15-foot water-bearing zone, and occurs only in
the north central and northeastern portion of the area. Underlying
this unit is calcareous clay and calcarenite (a. deposit of sand-
sized grains composed of calcite) which range from 10 to 20 feet
28
-------
TABLE 5
SUMMARY OF
POND BORING SAMPLING
Crystal Chemical Company. Site
Sample
Mymba^
PB-l,ST-4
PB-l,ST-8
PB-1,ST-12
PB-1A,ST-14
PB-1A,ST-17
PB-1A,ST-19
PB-1A,ST-21
PB-3,ST-3
PB-3,ST-5
PB-3,ST-9
PB-4,ST-3
PB-4,ST-7
PB-6,ST-2
PB-6,ST-2W
PB-6,ST-4
PB-6,ST-5
PB-6,ST-7
PB-6,ST-10
Notes;
NA = Not analyzed
From 1984 Site Investigation Report
[
;
.2
•14
•17
•19
•21
I
I
I
r
i
!W
!
f
.0
Sample
Depth
(ft)
4
7.5
11
13.5
18
21
24
2
4
10
2.5
8
2
2.5
5
6.5
9.5
14
Total
Arsenic
(ma/Xa)
26800
12300
15300
10800
5850
928
923
2360
2490
531
3150
71
NA
NA
NA
8460
3620
932
Phenol
19.0
8.0
<2.2
4.0
1.8
<1.9
NA
NA
<2.2
3.5
7.4
2.7
-------
TABLE 6
SUMMARY OF SUBSURFACE SOIL SAMPLING
Crystal Chemical Company Site
Sample
Number
B-1,ST-1D
B-1,ST-2A
B-1,ST-3B
B-1,ST-3A
B-1,ST-3A
B-1,ST-4B
B-1,ST-5A
B-1,ST-6B
B-2,ST-2A
B-2,ST-4
B-2,ST-6
B-3,ST-2
B-3,ST-4
B-3,ST-6
B-4,ST-2A
B-4,ST-4
B-4,ST-6B
B-5,ST-1
B-5,ST-2
B-5,ST-3
B-5,ST-4
B-5,ST-5
B-6,ST-2
B-6,ST-4
B-6,ST-5
B-7,ST-2
B-7,ST-4
B-7,ST-6
B-8,ST-2
B-8,ST-4
B-8,ST-6
B-9,ST-1
B-9,ST-3
B-9,ST-4
B-9,ST-6
B-10,ST-1
B-10,ST-2
B-10,ST-3
Sample
Depth
-------
TABLE 6 (continued)
SUMMARY OF SUBSURFACE SOIL SAMPLING
Crystal Chemical Comapny Site
Sample
B-10,ST-4
B-11,ST-1
B-ll,ST-3
B-ll,ST-4
B-ll,ST-5
B-12,ST-2
B-12,ST-3
B-12,ST-5
B-12,ST-6
B-13,ST-2
B-13,ST-3
B-13,ST-5
B-13,ST-6
B-14,ST-2
B-14,ST-3
B-14,ST-5
B-15,ST-2
B-15,ST-3
B-15,ST-5
MW-1<2),ST-1
MW-l,ST-2
MW-l,ST-5
MW-1,ST-10
MW-1,ST-13
MW-1,S-1
MW-1,ST-14T
MW-1,ST-14B
MW-2<2>,ST-1
MW-2,ST-2
MW-2,ST-3
MW-2,ST-5
MW-2,ST-8A
MW-2,ST-11
MW-2,ST-12
MW-2,S-2
MW-3C2),ST-1
MW-3,ST-2
MW-3,ST-3A
MW-3,ST-3B
Sample
Depth
(ft)
5.5
1
4.5
6
8
2.5
4
7
8.5
2.5
4
7
8.5
2.5
4
7
2.5
4
8.5
I
3
9.5
19.5
34
39
39.5
41.5
1.5
3.5
5.5
9.5
15
30
35
39
1.5
2.5.
3.5
4
Total
Arsenic
(mo/leg)
34
27
42
41
NA
30
32
40
3
28
35
395
<1
55
32
NA
56
45
642
65
3690
73
68
42.6
18.7
7
10
191
48
49
30
221
224
12
36
62
7280
16140.
27310
Phenol
(ma/ ka)
<2.1
<1.6
<2.8
30
<2.2
<2.6
<2.1
<2.4
NA
<2.0
<2.0
<2.1
NA
<1.5
<1.6
<1.5
<2.0
<1.6
<1.8
<2.2
<2.2
<1.9
<2.0
NA
<1.9
<1.5
<2.2
7.6
4.8
2.0
45
<2.3
<1.4
<2.1
22
2.7
142
2.0
2.6
-------
TABLE 6 (continued)
SUMMARY OF SUBSURFACE SOIL SAMPLING
Crystal Chemical Company Site
Sample
Number
MW-3(2),ST-4
MW-3,ST-6
MW-3,ST-12
MW-3,ST-13A
MW-3,ST-15A
MW-3,S-1
MW-3,ST-16
MW-4<3),ST-1B
MW-4,ST-2
MW-4,ST-3
MW-4,ST-4
MW-4,ST-10
MW-4,ST-13
MW-4,ST-14
MW-4,ST-15
MW-4,ST-16
MW-4,ST-18
MW-4,ST-20
MW-4,S-1
MW-5(2),B-1
MW-5,ST-1
MW-5,ST-2
MW-5,ST-5
MW-5,ST-7
MW-5,ST-10
MW-5,ST-1T
MW-5,S-1
MW-5,S-1B
MW-5,ST-13
MW-6C2),ST-1
MW-6,ST-2
MW-6,ST-5
MW-6,S-1
MW-7(2),ST-1A
MW-7,ST-2B
MW-7,ST-3B
MW-7,S-1B
MW-8(2),ST-1
MW-8,ST-2
MW-8,ST-3
MW-8,S-1A
Sample
Depth
(ft)
5
9.5
19
23.5
34
42
45
1.5
3.5
5
7
24
39
44
49
54
69
89
99
0.5
2
4
10
14
20
34.5
35
35.5
39
1
3
9
39
1
3
5
33
1
3
5
33
Total
Arsenic
(mcr/kcn
5930
1750
NA
28
12
46
252
2470
2510
346
19
30
21
NA
54
59
22.1
43.3
12
<2
2
<2
4
<1
4
2
9
18
<2
5
1
8
<1
<2
<1
9
13
12
4.4
-------
TABLE 6 (continued)
SUMMARY OF SUBSURFACE SOIL SAMPLING
Crystal Chemical Comapny Site
Sample
Number
MW-9(2),ST-1
MW-9,ST-4
MW-9,S-1
MW-10(2),ST-1
MW-10,ST-4
MW-10,ST-7
MW-11(2),ST-1
MW-ll,ST-4
MW-11,S-1
MW-12(2),ST-1
MW-12,ST-4
MW-12,ST-5A
MW-13(2),ST-1
MW-13,ST-4
MW-13,ST-7
Sample
Depth
(ft)
1
5
34
1
5
36
1
5
33
1
5
25
1
5
36
Notes:
13
6
116
17
13
16
11
12
12
3(
8
9
6
Phenol
(mg/fca)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA = Not analyzed
(1) Monitoring Wells Screened in 15 Foot Water-Bearing Zone
(2) Monitoring Wells Screened in 35 Foot Water-Bearing Zone
(3) Monitoring Well Screened in 100 Foot Water-Bearing Zone
(4) Average of Two Readings
These data were collected for the 1984 Site Investigation
-------
t
thick.. At a depth of about 30 feet, a reddish-gray very fine sand
is encountered with a thickness ranging from 0 to 17 feet. This
sand unit is also referred to as the 35-foot water-bearing zone,
and appears to grade to silty clay and pinch out to the south and
west of the site.
The 35-foot water-bearing zone is underlain by a thick clay unit
which separates it from the 100-foot water-bearing zone. This
lower confining unit is approximately 60 feet thick at MW-4, the
only monitoring well on site which extends into the 100-foot zone.
Logs of other wells in the vicinity of the Crystal Chemical site
indicate that this confining unit is laterally extensive and is
relatively uniform in thickness.
Isopach maps, showing the thickness of the units, have been
prepared for the 15-foot and 35-foot water-bearing zones and are
presented as Figures 9 and 10.
Several sets of static water levels taken from the monitoring wells
and piezometers have not indicated a consistent ground water flow
gradient over time. Seasonal fluctuations may be responsible for
these variations.
Hydrologic aquifer testing (slug, step drawdown, and pump tests)
was conducted during the spring of 1989 for the SFS. The hydraulic
conductivity of the 15-foot water-bearing zone ranges from 1.0 x
10'4 to 3.3 x 10 cm/sec. For the 35-foot water-bearing zone,
transmissivity ranges from 80 to 360 ft /day while storativity
ranges from 3.6 x 10~4 to 2.4 x 10"3. The 15-foot water-bearing zone
is under water table conditions while the 35-foot zone is under
leaky artesian conditions. The vertical hydraulic conductivity of
the confining unit between the two water-bearing zones ranges from
1.8 x 10"6 to 7.4 x 10"5 cm/sec. Given these numbers, the response
of the 35-foot water-bearing zone to pumping and the contaminant
distribution, it is apparent that the 35-foot zone is recharged
from the shallower unit. During SFS field activities conducted in
the spring of 1989, the vertical gradient between the 15- and 35-
foot water-bearing zones was downward in some areas of the site and
upward in at least one location. It is possible that this head
relationship varies seasonally or with individual rainfall events
as well as aerially over the site.
For the 1984 SI, 13 monitoring wells were installed. For the SFS,
eight additional monitoring wells were installed. Two wells (CC-
1 and CC-2) existed on site prior to EPA's removal activities in
1982. Of these 21 wells, six are screened in the 15-foot water-
bearing zone, 14 in the 35-foot zone, and one in the 100-foot zone.
Well locations are presented in Figure 11, and a listing of the
monitoring wells and the zones that they monitor are presented in
Table 7.
34
-------
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i £
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-------
TABLE 7
SUMMARY OF MONITORING WELL ZONES
Crystal Chemical Company site
Monitoring Wells screened in 15-Foot Water-Bearing Zone
Well No. Elev. of Screened Interval
MW-14 63.4 - 53.4
MW-15 63.2 - 58.2
MW-16 62.0 - 57.0
MW-18 61.7 - 56.7
MW-19 65.1 - 55.1
MW-21 64.8 - 59.8
Monitoring Wells Screened in 35-Foot Water-Bearing Zone
Well No. Elev. of Screened Interval
MW-l 44.9 - 40.2
MW-2 48.3 - 38.3
MW-3 46.0 - 36.0
MW-5 45.9 - 40.9
MW-6 43.9 - 38.9
MW-7 44.8 - 24.8
MW-8 46.8 - 41.8
MW-9 45.0 - 40.0
MW-10 43.0 - 38.0
MW-11 47.9 - 42.9
MW-12 56.6 - 51.6
MW-13 39.1 - 34.1
MW-17a • 44.5 - 29.5
MW-20 42.3 - 32.3
Monitoring Well Screened in 100-Foot Water-Bearing Zone
Well No. Elev. of Screened Interval
MW-4 -20.8 30.8
-------
Ground water samples collected from these monitoring wells have
been analyzed during several rounds of sampling in 1983, 1987, and
1989. A summary of the analyses are presented in Table 8
(additional field parameters and additional analytical constituents
detected in lower concentrations are included in the SFS report).
In July 1989, nine water supply wells in the vicinity of the site
were sampled. Their locations are illustrated on Figure 12, and
analytical results are included in Table 9. Based on all the past
ground water sampling data, the estimated extent of ground water
contamination is presented in Figure 13. The volume of ground
water contaminated with arsenic is estimated to be approximately
3,000,000 gallons.
Exposure Routes
There is a potential for the contaminants at the Crystal Chemical
site to reach the public through a number of pathways.
Approximately 20,000 people live within a one-mile radius of the
site. The routes with the most potential appear to be ingestion
of or direct contact with either onsite or offsite contaminated
soils and sediments. The other pathways identified include
ingestion of or direct contact with surface water or ground water,
inhalation of ambient air and ingestion of contaminated crawfish.
Each identified pathway is described below:
Contaminated Soils
Possible ingestion of or direct contact with contaminated soils and
sediments on site and off site constitute major exposure routes.
Although the degree of arsenic contamination is less at the offsite
exposure locations, it is important because the public has direct
access to these soils. The area of concern for direct physical
contact is the site itself and a minimum area around the site of
approximately 100 to 150 feet.
Surface Water and Sediment
Exposure to arsenic can occur by ingestion of or direct contact
with contaminated surface water or sediments. The primary exposure
point for this pathway is in the flood control channel west of the
site. Contaminants are leached from the site soils by surface
water run-off and carried over land or by drainageways to the flood
control channel where the contaminated water collects. As the
contaminated surface run-off flows over land and in drainageways
and the flood control channel, contaminants are spread to offsite
soils and sediments, thereby contaminating these media. Dilution
39
-------
TABLE 8
SUMMARY OF GROUNDWATER SAMPLING
Crystal Chemical Company Site
Monitor
Well
NO.
MW-1
MW-1
MW-1
MW-1
MW-1
MW-1
MW-2
MW-2
MW-2
MW-2
MW-2
MW-2
MW-3
MW-3
MW-3
MW-3
MW-3
MW-3
MW-4
MW-4
MW-4
MW-4
MW-4
MW-4
MW-4
MW-5
MW-5
MW-5
MW-5
MW-5
MW-5
MW-5
MW-5
MW-5
MW-5
Sample
Mum>>»T-
GW-7
GW-12
GW-21
GW-35
GW-47
—
GW-4
GW-16
GW-26
GW-37
GW-50
—
GW-5
GW-15
GW-25
GW-36
GW-49
—
GW-6
GW-10
GW-20
GW-31
GW-4 6
-
-
GW-8
GW-18
GW-27
GW-28
GW-29
GW-30
GW-38
GW-51
GW-5 3
-
Date
Sampled
05-20-83
05-28-83
06-07-83
08-26-83
11-05-83
10-21-87
05-18-83
05-28-83
06-07-83
08-26-83
11-05-83
10-22-87
05-19-83
05-28-83
06-07-83
08-26-83
11-05-83
10-22-87
05-20-83
05-27-83
06-07-83
08-26-83
11-04-83
10-21-87
04-17-89
05-23-83
05-28-83
06-07-83
06-07-83
06-07-83
06-07-83
08-26-83
11-05-83
12-20-83
10-22-87
Concentrations (ppm)
As<1)(6> Phenol TOC & TOC <3>
0.19
1.1
0.56
0.07
0.06
0.02
73
70
384
388
623(5)
291
29
95
225
341(5)
363
359
0.04
0.08
NA
NA
0.01
0.007
0.004/
0.003
504
101
390
310
400
-
607
517(5>
-
366
<0.05
<0.05
0.04
NA
NA
0.025
<0.05
<0.05
0.11
NA
NA
0.061
0.10
<0.05
0.03
NA
NA
0.23
<0.05
0.75
NA
NA
NA
<0.01
<0.01
0.60
0.05
NA
NA
0.04
NA
NA
NA
NA
0.12
22
12
NA
NA
NA
NA
160
220
NA
NA
NA
NA
10
25
NA
NA
NA
NA
21
<1
NA
NA
NA
NA
NA
360
260
NA
NA
NA
NA
NA
NA
NA
NA
NA <4)
NA
3400
NA
NA
NA
NA
NA
10000
NA
NA
NA
NA
NA
6200
NA
NA
NA
NA
NA
NA
NA .
NA
NA
NA
NA
NA
NA
NA
6400
NA
NA
NA
NA
NA
-------
TABLE 8 (continued)
SUMMARY OF GROUNDWATER SAMPLING
Crystal Chemical Company Bite
Monitor
Well
No.
MW-6
MW-6
MW-6
MW-6
MW-6
MW-6
MW-7
MW-7
MW-7
MW-7
MW-7
MW-8
MW-8
MW-8
MW-8
MW-8
MW-9
MW-9
MW-10
MW-10
MW-11
MW-11
MW-12
MW-12
MW-13
MW-13
MW-14
Sample
Mu^hity
GW-9
GW-13
GW-23
GW-32
GW-44
—
GW-11
GW-14
GW-22
GW-33
GW-45
GW-19
GW-24
GW-34
GW-41
—
GW-43
—
GW-48
—
GW-42
—
GW-39
—
GW-40
—
—
Date
Sampled
05-26-83
05-28-83
06-07-83
08-26-83
11-04-83
10-21-87
05-27-83
05-28-83
06-07-83
08-26-83
08-04-83
05-28-83
06-07-83
08-26-83
11-04-83
10-21-87
11-04-83
10-22-87
11-05-83
10-20-87
11-04-83
10-20-87
11-04-83
10-22-87
11-04-83
10-21-87
04-18-89
Concentrations (ppm)
As<1}<6) Phenol TOG (*> TOG (3)
4
6.1
0.04
0.02
0.01
<0.005
0.13
2.4
0.08
0.02
0.01
12
0.04
0.02
0.03
<0.005
0.01
0.005
0.01
<0.005
0.01
<0.005
0.01
<0.01
0.01
<0.005
0.029/
0.005
0.12
<0.05
0.02
NA
NA
<0.01
<0.05
<0.05
0.03
NA
NA
0.05
0.03
NA
NA
<0.01
NA
0.053
NA
0.049
NA
0.059
NA
0.029
NA
0.01
0.01
7
<1
NA
NA
NA
NA
5
<1
NA
NA
NA
4
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
2300
NA
NA
NA
NA(4)
NA
905
NA
NA
NA
1400
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
MW-15
04-18-89 161/171 <0.01
NA
NA
-------
TABLE 8 (continued)
SUMMARY OF GROUNDWATER SAMPLING
Crystal Chemical Company Site
Monitor
Well Sample
No. Number
MW-16
MW-17A
MW-18
MW-19
MW-20
MW-21
P-la
CC-1 GW-1
CC-1
CC-2 GW-2
CC-2
Guyon
Well
Date
Sampled
04-18-89
04-18-89
04-18-89
04-17-89
04-17-89
04-18-89
04-18-89
05-17-83
10-22-87
05-17-83
10-22-87
05-11-83
08-26-83
11-04-83
10-23-87
04-18-89
Concentrations (ppm)
As<1)(6> Phenol TOG <*> TOC <3)
0.031/
0.033
0.036/
0.006
0.014/
0.017
0.021/
0.033
258/272
0.006/
0.007
<0.002/
<0.002
0.03
0.006
0.23
0.483
0.06
0.01
0.002
<0.005
<0.002/
<0.002
<0.01
<0.01
<0.01
<0.01
0.022
<0.01
<0.01
<0.05
0.057
<0.05
0.046
<0.05
NA
NA
0.034
<0.010
NA
NA
NA
NA
NA
NA
NA
29
NA
25
NA
2
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Notes;
(2)
(3)
(4)
(5)
(6)
Total Dissolved Arsenic
Total Organic Carbon
Total Dissolved Solids
NA = Not Analyzed-
Average of two readings
(Total/Dissolved) = Total
and Dissolved Arsenic Concentrations
-------
-------
TABLE 9
SUMMARY OF DEEPER AREA WELL SAMPLING
July 25, 26, and 27, 1989
Crystal Chemical Site
Sampling
Location
Total Arsenic
(ppb)
Total Arsenic
Split Sample Phenol
(ppb)
(ppb)
Onsite Well WSW-l 928
Onsite Well WSW-l
(duplicate) 751
Tap on City Supply Line 10.5
CW-1
Andrau Airport #1 <3.3
AA-1
Andrau Airport #2 7.6
AA-2
Western Atlas #2 32.4
WA-2
Western Atlas #3 <3.3
WA-3
City Well 51-1 4.4
City Well 51-2 4.9
HL&P Substation 4.0
HLP-l
HL&P Substation
(duplicate) 55.4
1700
3600
5
BDL
BDL
BDL
BDL
5
9
BDL
NA
10.0
15.0
<10.0
<10.0
<10.0
<10.0
<10.0
10.0
<10.0
<10.0
<10.0
Notes;
BDL =
NA =
Below Detection Limits (for split samples, detection
limit is 5 ppb)
Not analyzed
-------
S
o
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> §
< £
i II
i
nit
-------
of the flood control channel water as it is washed downstream
reduces contaminant concentrations in the surface water and
sediments downstream.
Ambient Air
Airborne migration is not a pathway posing an immediate risk.
Although offsite surface soils contain arsenic, air sampling during
the site investigation indicated that these soils are not causing
air releases. This pathway remains a concern, however, since the
potential for erosion and degradation of the temporary cap exists.
Ground Water
Potential exposure to arsenic may occur by ingestion of or direct
contact with contaminated ground water pumped to the surface by
water supply wells. Twenty water wells exist (or have existed)
within a one-mile radius of the Crystal Chemical site. These wells
include observation wells, public supply wells, industrial wells
and irrigation wells that pump primarily from the Upper Chicot
aquifer and aquifers below it, where the extent of the
contamination has been minimal. These major aquifers are unlike.-/
to become contaminated in the future unless an artificial
penetration or unknown natural conduits allow the contaminants to
bypass the overlying thick clay formation.
High levels of arsenic contamination have been found at relatively
shallow depths compared to the depths of major aquifer supplies.
The major ground water contamination occurs in the 35- to 50-foot
sand layer. Currently, this layer is not used for water supplies
and no known exposure points exist for the shallow, contaminated
ground water. A future installation could constitute an exposure
point if the 35-foot water-bearing zone is encountered (e.g.,
digging that may be required as a part of remedial action efforts,
the installation of a water supply or test well or eventual
development of neighboring properties that may employ excavation
work). Depending on the relative location of the exposure point
to the contaminant plume, contact with the 35-foot water-bearing
zone could be a significant exposure route because of the high
levels of arsenic present.
Food Chain
Arsenic is bioaccumulated from water in fish, shellfish and
crustaceans, but the arsenic in the tissues of these organisms
("Fish arsenic") is in an organic form that has very low toxicity.
Consequently, human exposure to arsenic due to ingestion of aquatic
species (e.g., crawfish from the flood control channel) is not
generally considered to be a significant health risk (ATSDR 1987).
46
-------
V. SUMMARY OF SITE RISKS
During the SFS, a Health Assessment was prepared for EPA by the
Agency for Toxic Substances and Disease Registry ("ATSDR"). This
report reviewed the potential risks to human health posed by the
Crystal Chemical site in regards to contaminant sources and
potential contacts to the population. The ATSDR determined that
arsenic was the only contaminant of concern with respect to public
health. Arsenic ranks twentieth (20th) in abundance among the
natural elements in the Earth's crust and, therefore, is found
naturally occurring in rocks and soils. It is widely used in
herbicides and is found in both organic as well as inorganic forms
on the Crystal Chemical site. The arsenic found on the Crystal
Chemical site exhibits characteristics of a substance that is
regulated under the Resource Conservation and Recovery Act
("RCRA"), as amended, 42 U.S.C. Section 6901, et seq., and a
specific type of arsenic (i.e., K031 - by-product salts generated
in the production of monosodium methylarsenate ("MSMA") and
cacodylic acid) that is listed and regulated under RCRA was
produced on the site. ATSDR determined that the areas of concern
where potential exposure to the arsenic contamination was most
likely to occur would be surface soil and surface water. The
susceptible populations were identified as children who may play
in the immediate vicinity of the site and workers who may be
involved in maintenance and remediation activities at the site.
The identified exposure pathways include direct skin contact,
ingestion of contaminated ground water, surface water and surface
soil, and inhalation of contaminated airborne dusts.
Also, during the SFS, an analysis was conducted to estimate the
health or environmental problems that could result if no action
were taken on the soil contamination at the Crystal Chemical site.
This analysis is commonly referred to as an endangerment
assessment. The primary purpose of the endangerment assessment is
to evaluate potential health effects that could result from direct
exposure to the contaminant as a result of contaminated soil,
surface water or airborne dust coming in contact with an individual
through direct contact with the skin, ingestion (eating or
drinking), or inhalation, and to determine appropriate remediation
levels of the contaminant of concern. In this case, arsenic in its
most toxic form (trivalent, inorganic arsenic) is the contaminant
of concern. Although phenol has been found onsite, the ATSDR
Health Assessment determined that phenolic compounds did not
present a potential health problem to area residents and workers
in the area due to the low levels that were detected at the site.
Although phenol has been found onsite at a maximum concentration
of 157 ppm, the endangerment assessment did not evaluate risk
because concentrations of this compound were well below any health-
based levels of concern.
With respect to potential health effects, the results of the
endangerment assessment supported the ATSDR Health Assessment and
47
-------
t
identified the following five specific potential ways in which
individuals could become exposed at the site:
Ingestion of or direct contact with soil and sediments,
ingestion of or direct contact with surface water,
ingestion of shallow ground water,
inhalation of wind dispersed dust, or
ingestion of contaminated fish.
Human exposure levels were developed by assuming daily intakes for
two exposure durations, and their respective exposure
concentrations, subchronic and chronic. Subchronic exposures were
developed for average concentrations expected during a 10- to 90-
day period, while chronic exposures assumed a 70-year lifespan.
The calculations for the Human Intake Factors ("HIF") for the
various exposure rates are provided in Appendix 1 of the Crystal
Chemical Endangerment/Risk Assessment (1988) . Some assumptions V"
utilized in these HIF calculations are as follows:
Area children residents were assumed to be six years old, with
a potential for swimming (water or sediment ingestion) in the
flood control ditch three days per week, nine months per year.
Chronic exposures of area children to future well water,
offsite surface soils, and solids suspended in air (dust) were
assumed to occur seven days per week, 12 months per year.
Area adult residents were assumed to have chronic exposures
to flood control waters and sediments two days per week, nine
months per year. Chronic exposures of area adults to future
well water, offsite surface soil, and dust were assumed to
occur seven days per week, 12 months per year.
Onsite workers were assumed to have subchronic exposures to
ingestion of standing water two days per week, ingestion of
and dermal contact with soils for five days per week, and
inhalation of dust eight hours per day, five days per week.
The concentrations of arsenic on which the endangerment assessment
was based are derived from the site investigation data and are
presented in Table 10. These data evaluate exposure based on a
best-estimate and worst-case (upper-bound) of the environmental
concentrations. The best estimate at each exposure point is taken
to be the mean of all monitoring data in each medium, and the
worst-case (upper-bound) is taken to be the highest value detected
in each medium.
In December 1989, EPA's Office of Emergency and Remedial Response
published the interim final Risk Assessment Guidance for Superfund
48
-------
TABLE 10
SUMMARY OF EXPOSURE POINT CONCENTRATIONS OF ARSENIC
Crystal Chemical Company Site
Exposure
Point
On-site
Off-site
Medium
Soil (1-10 feet)
Storm water
Surficial soil
Flood control
channel water
Flood control
channel sediment
Ambient air
Ground water
(35-foot sand)
Ground water
(100-foot sand)
Concentration, ppm
Best-Estimate Upper-Bound
3,700 27,310
200 3,740
51 636
0.11 0.51
200
1.9E-5
455
0.063
(a)
1,340
5.0E-5(a>
917
0.17
f
Notes:
Units are mg/m .
-------
("RAGS'") - Volume I. The purpose of this guidance was to supersede
the Superfund Public Health Evaluation Manual ("SPHEM") and
Endangerment Assessment Handbook which, to that date, had been used
for assessing the effects of chemical contamination on human
health. RAGS revised the SPHEM methodology in several ways,
including the introduction of the concept of Reasonable Maximum
Exposure ("RME"). RME is defined as the highest exposure that
could reasonably be expected to occur at a site. This approach
differs from the SPHEM approach of defining worst-case exposure to
site contaminants. While SPHEM utilized a "worst-case" scenario
based on continued exposure to the maximum detected concentration
of a chemical constituent as the site, RME bases the maximum
exposure on the 95% upper confidence limit of the mean, providing
a spatially averaged exposure concentration.
This Record of Decision summarizes the results of the risk
assessment conducted in 1988 under SPHEM guidance. While there are
advantages and disadvantages realized in both the SPHEM and RAGS
methods, the underlying assumptions utilized under SPHEM were at
least as conservative as those in RAGS. Therefore, the results of
the site risk assessment are at least as protective as those which
would have been derived under exposure parameters (i.e., body
weight, ingestion rates, exposure frequency and duration, etc.)
consistent with the RAGS. However, whenever the terminology used
for SPHEM and for RAGS is interchangeable, RAGS terminology is
used.
The endangerment assessment went further to conclude that the most
prominent risks posed to the public by the site involved those
listed below:
Noncarcinogenic risk to onsite workers, or area residents
(children or adults) resulting from incidental ingestion
or dermal (skin) contact with contaminated soil or
surface water (i.e., ingestion of arsenic can cause skin
abnormalities such as dark and light spots on the skin
and direct contact with the skin can result in mild to
severe irritation of the skin, eyes or throat).
Risk of skin cancer in area residents due to chronic
(lifetime) ingestion or dermal contact with contaminated
soil, surface water or sediment.
Risk of lung cancer in area resident due to chronic
(lifetime) inhalation of arsenic contaminated soil
particles suspended in air.
The risk characterization for each population by each pathway is
presented in Table II.
50
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A Preliminary Natural Resource Survey was conducted by the National
Oceanic and Atmospheric Administration ("NOAA") in February 1989.
To date, NOAA has not indicated whether that there is direct impact
to NOAA resources. Additionally, there are no endangered species
or critical habitats within close proximity of the site.
Evaluation of Noncarcinogenic Risks
Potential concern for noncarcinogenic effects of a single
contaminant in a single medium (e.g. soil or water) is expressed
as the hazard quotient ("HQ"). By adding the HQs for all
contaminants within a medium or across all media to which a given
population may reasonably be exposed, the hazard index ("HI") can
be generated. The HI provides a useful reference point for gauging
the potential significance of multiple contaminant exposures within
a single medium or across media.
The risk of adverse noncarcinogenic effects of exposure to arsenic
is expressed in terms of the HI. The HI is the ratio of the
estimated dose which a human receives to the estimated dose level
believed to be safe, and is calculated both for chronic and
subchronic exposures. A summary of the calculations of
noncarcinogenic risks is provided in Table 12.
Reference doses (RfDs) have been developed by EPA for indicating
the potential for adverse health effects fron exposure to chemicals
exhibiting noncarinogenic effects. RfDs, which are exposed in
units of mg/kg-day, are estimates of lifetime daily exposure levels
for humans, including sensitive individuals. Estimated intakes of
chemicals from environmental media (e.g., the amount of a chemical
ingested from 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).
These uncertainty factors help ensure that RfDs will not
underestimate the potential for adverse noncarcinogenic effects to
occur. The RfD for arsenic for the oral pathway is l x 10"3 mg/kg-
day.
Based on the calculated HI values, it is evident that unprotected
workers onsite may experience significant risk of noncarcinogenic
health effects due to ingestion or dermal contact with surface
water or soil. Similarly, area children playing in nearby yards
and fields or in the flood control channel may experience
noncarcinogenic risk due to ingestion or dermal contact with
surface soils or contaminated sediments. Area adults and flood
control channel maintenance workers are not likely to experience
noncarcinogenic effects except under worst-case (upper bound)
exposure conditions. The concentration of arsenic in the 100-foot
aquifer is slightly too high to be acceptable for use as human
drinking water, while the water in the 35-foot water-bearing zone
55
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TABLE 12
SUMIAJtY OF MCNCARC IMOGEN 1C IISXS FROM ARSENIC
Crystal Chearic*l Coapany Site
Subchronic HI
Chronic HI
Exposed
Population
On- site
workers
Child residents;
area school
chi Idren
Exposure
Route
Ingest ion
Derawl
Inhalation
Ingest ion
Dermal
Exoosure Medium
Soil
Surface water
Soil
Surface water
Soil in air
Total: All values less than 0.005 (5.0E-3) reported here as 0.00.
(d) Does not include risk from dermal absorption from water.
-------
in its present condition is grossly contaminated and is entirely
unfit for human use.
Evaluation of Carcinogenic Risks
The risk of cancer from exposure to a chemical is described in
terms of the probability that an individual exposed for his or her
entire lifetime will develop cancer. Cancer slope factors ("CSFs")
have been developed by EPA's Carcinogenic Assessment Group for
estimating excess lifetime cancer risks associated with exposure
to potentially carcinogenic chemicals. CSFs, which are expressed
in units of (mg/kg-day)"1 are multiplied by the estimated intake of
a potential carcinogen to provide an upper-bound estimated of the
excess lifetime cancer risk associated with exposure at the intake
level. The term "upper bound" reflects the conservative estimate
of the risks calculated from the CSF. Use of this approach makes
underestimation of the actual cancer risk highly unlikely. CSFs 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.
The CSFs for arsenic for the oral and inhalation exposure routes
are 1.5 and 50 (mg/kg-day)'1, respectively. A summary of
calculations of carcinogenic risks is included as Table 13.
The cancer risk calculations indicate that chronic exposure to
soils and sediments around the site is associated with significant
risk of cancer. The principal risk associated with exposure by
ingestion or dermal absorption is skin cancer. The principal risk
associated with inhalation exposure is lung cancer. All of these
exposure pathways are of concern, with substantial combined risks.
Remediation Goals
The contaminated soil was determined to be a principal threat at
the site because of direct contact, ingestion, and inhalation risks
and because of the soil's impact on ground water. The remedial
objectives for the soil are to eliminate potential exposure via
ingestion, inhalation or direct contact with contaminants and by
reducing the potential for the soil to act as a continued source
for surface water and ground water contamination.
The contaminated shallow ground water was also determined to be a
principal problem at the site 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
57
-------
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-------
drinking" water purposes. The remedial objective is to reduce the
amount of contamination to human health-based standards in order
to eliminate or minimize the risks associated with the contaminated
shallow ground water.
Arsenic was determined by ATSDR to be the contaminant of concern
at the Crystal Chemical site, therefore, all remediation goals are
set for arsenic. The only other contaminant found at the site
which may be of concern was phenol. Remediation levels assuming
chronic daily exposure in order to protect against noncarcinogenic
effects were calculated for the phenolic compounds. The
remediation levels were calculated to be 420,000 ppm for an adult
and 50,000 ppm for a child. The remediation levels for phenolics
have no significant effect on the volumes of soil or ground water
requiring remediation at the site, and because these levels are
relatively high compared to phenolic levels found at the site
(approximately 160 ppm), the remediation levels for the phenols are
not discussed in the review and evaluation of remedial
technologies.
The selection of an appropriate remediation level for arsenic was
based primarily on an evaluation of the potential health effects
caused by human exposure to the contaminant, assuming that the
future land use will be residential and commercial/industrial. The
reasoning behind designating the future land use as possibly
residential is that the City of Houston does not, at this time,
have zoning ordinances, therefore, EPA takes a conservative
approach and calculates risk so that all potential scenarios are
taken into consideration.
To a lesser extent remediation levels for arsenic were based on the
naturally occurring background conditions of arsenic in soils.
Arsenic is a naturally occurring metallic constituent of soils,
derived from the rock or parent materials, from which the soil was
formed. Background concentrations of metals in soil may vary from
region to region. For example, the United States Geological Survey
(1975) reports that the mean and range of background arsenic
concentrations in western soils is 6.1 ppm and 0.2-97 ppm,
respectively.
A limited number of soil samples collected from offsite areas
within two miles of the Crystal Chemical site found background
arsenic concentrations to be less than 1.6 ppm. Soil sampling at
the site found arsenic concentrations on the order of several
hundred to several thousand ppm. As determined in the endangerment
assessment, leaving this contamination on site without treatment
would result in a one in ten thousand (10~4) risk of cancer over the
lifetime of individuals who may come in contact with this
contamination. This estimate was developed by taking into account
various conservative assumptions about the likelihood of a person
being exposed to the contaminated soil, and in consideration of the
toxicological effects of arsenic exposure.
59
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The national risk of getting some form of cancer over a 70 year
life span is very high, estimated at one chance in five or 0.2.
The one in five probability is the baseline situation or "natural
incidence" of cancer. A one in ten thousand (10~4) risk is an
increment above the baseline risk (an increase from 0.200 to
0.201). EPA policy calls for an evaluation of remediation levels
that range from a cancer risk of one in ten thousand to one in one
million (10"4 to 10"6) , using one in one million as a point of
departure.
Utilizing conclusions made concerning the public to be protected
and the amount and duration of exposure, the endangerment
assessment calculated health standards for arsenic in surface soil
and sediment. These goals call for the removal of offsite soils
to a concentration of 30 ppm for arsenic, which represents a one
in one hundred thousand (10 ) cancer risk level. Since the average
background concentration of arsenic in western soils (6.1 ppm)
exists at a level in excess of EPA's standard point of departure
(one in one million cancer risk - at a 3 ppm concentration of
arsenic), 30 ppm was determined to represent a safe health-based
action level. These soils will be placed back on to the Crystal
Chemical site. Additionally, the selected remedy will require that
all heavily contaminated areas onsite with soil-arsenic
concentrations in excess of 300 ppm be treated using in-situ
vitrification. Such an approach will effectively treat 95% of the
arsenic found on the site. The treatment goal for the soils is to
eliminate potential exposure and to reduce the amount of arsenic
that is able to leach to 5,0 ppm of arsenic after treatment when
analyzed using the Toxicity Characteristic Leaching Procedure
("TCLP"), 40 CFR 261.25. The entire site will be covered with a
multi-layer cap after the treatment has been completed. The
average concentration of arsenic found in these remaining areas
(not subject to treatment) is 60 ppm. Once the entire remedy is
complete, the resulting cancer risk will be reduced to less than
one in one million (at or near the original background conditions) .
The endangerment assessment did not address cleanup levels in
ground water. The Maximum Contaminant Level ("MCL") standard for
arsenic is considered an applicable or relevant and appropriate
federal requirement ("ARAR") for the Crystal Chemical Company site.
Therefore, EPA has determined that the MCL standard for arsenic,
0.05 ppm, will be the target remediation level for ground water.
Actual or threatened releases of hazardous substances from this
site, if not addressed by implementing the response action selected
in this ROD, may present an imminent and substantial endangerment
to public health, welfare, or the environment.
VI. SCOPE AND ROLE OF RESPONSE ACTION
The studies undertaken at the Crystal Chemical site have identified
two principal threats (i.e., contaminated soil and shallow ground
60
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water),*and the remedies to eliminate or minimize these threats
that are included in this Record of Decision and are addressed as
one operable unit.
The contaminated soil was determined to be a principal threat at
the site because of direct contact, ingestion, and inhalation risks
and because of the soil's impact on ground water. The remedial
objectives for the soil are to eliminate potential exposure via
ingestion, inhalation or direct contact with contaminants and by
reducing the potential for the soil to act as a continued source
for surface water and ground water contamination.
The contaminated shallow ground water was also determined to be a
principal problem at the site 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 is to reduce the
amount of contamination to human health-based standards in order
to eliminate or minimize the risks associated with the contaminated
shallow ground water.
VII. DESCRIPTION OF ALTERNATIVES
The descriptions of remedial alternatives are separated into those
addressing soil contamination and those addressing ground water
contamination.
A. Soil Contamination Remedial Alternatives
The alternatives for the soil remediation are the following:
Alternative A-l:
Alternative A-2:
Alternative A-3:
Alternative A-4:
Alternative A-5:
Alternative A-6:
Alternative A-7:
Alternative A-8:
Alternative A-9:
Alternative A-10:
Excavation and Offsite Disposal
In-Situ Vitrification
Solidification/Stabilization
Soil Washing
Partial In-Situ Vitrification and Capping
Partial Solidification/Stabilization and
Capping
Partial Soil Washing and Capping
Capping
No Action
Limited Action
Common Elements. Except for the "No Action" and "Limited Action"
alternatives, all of the alternatives that were considered for the
site included a number of common elements. Each of the
alternatives includes long-term operation and maintenance (O&M)
activities for ground water treatment, which could take as long as
30 years to complete, and all the alternatives call for long-term
monitoring. These monitoring activities will be conducted to
61
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ensure 'that the remedy is effective. In addition, restrictions
will be placed on the site to prohibit certain activities, such as
soil removal or any type of commercial or residential activity on
the site, and site access will be restricted.
All of the alternatives involve the removal of offsite soil and
sediments with arsenic contamination greater than 30 ppm, EPA's
offsite remediation level, and these offsite areas will be
backfilled to previously existing grades. See Section V. summary
of Sit* Risks for a complete explanation of the remediation goals.
Alternative A-l proposes to dispose of the contaminated soils at
an offsite landfill; all other alternatives involve onsite
placement of the offsite soil and sediments. With all the
alternatives, the onsite water supply wells and all of the
monitoring wells not necessary for the remedial action or for the
long-term O&M will be closed in accordance with regulations of the
State of Texas. Two concrete slabs remain on the site. Soil
alternatives A-l through A-4 call for removing the slabs and
disposing of them off site. Alternatives A-5 through A-8 call for
removing the slabs, breaking them into smaller pieces, and placing
them under the multi-layer cap that is to be constructed over the
site. All costs and time required to implement all of the
alternatives are estimates. Table 14 summarizes estimated costs
and implementation times for all of the alternatives.
When remediating a site, there are applicable or relevant and
appropriate requirements ("ARARs) that the remedy(s) must meet in
order to be in compliance with Federal and State laws. Given that
the arsenic found on the site exhibits characteristics of a
substance that is regulated under RCRA, 40 CFR Subpart C, and that
a type of arsenic (i.e., K031 - by-product salts generated in the
production of MSMA and cacodylic acid) that is specifically listed
and regulated under RCRA, 40 CFR Subpart D, was produced on the
site, certain ARARs apply. If a waste leaches above 5.0 ppm of
arsenic when analyzed using TCLP, it is considered a hazardous
waste and is regulated under RCRA. Furthermore, if a RCRA
regulated waste is treated, additional ARARs apply.
On June 1, 1990 a regulation identifying vitrification as the best
demonstrated available treatment technology ("BOAT") for arsenic
as a RCRA characteristic waste as well as a RCRA listed waste was
published (55 Fed. Reg. 106 at 22556 to 22561). The effective date
of this regulation was August 8, 1990. Associated with the BOAT
is a concentration-based treatment standard of 5.6 ppm for K031
nonwastewaters, and the BOAT concentration-based treatment standard
for arsenic as a characteristic (D004) nonwastewater is 5.0 ppm.
When the soils treatment and replacement triggers placement (Soils
Alternatives A-3, A-4, A-6, and A-7) or when offsite disposal of
contaminated soil is involved which, too, triggers placement (Soil
Alternative A-l) under RCRA's Land Disposal Restrictions
("Landban"), 40 CFR 268, the 5.6 ppm treatment standard for
nonwastewaters is required per 40 CFR 268.9.
*
62
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The treatment goal for those alternatives that do not trigger
placement under RCRA is to reduce the amount of leachable arsenic
after treatment to 5.0 ppm.
Soil Alternative A-l:
EXCAVATION AND OFF8ITE DISPOSAL
This alternative calls for excavating all onsite and all offsite
soils and sediments with arsenic contamination greater than 30 ppm.
The estimated volume of soils contaminated with arsenic greater
than 30 ppm is 156,000 cubic yards. These excavated soils would
then be transported offsite for disposal in a landfill that is
allowed to accept arsenic-contaminated soils. All excavated areas
would be back-filled with soil to previously existing grades and
the area would be revegetated. The total cost of this alternative
is approximately $76,004,379, and the estimated time required to
implement this alternative would be 2.5 years.
Although this alternative reduces the risk at the site itself, it
would require the removal of and disposal of soil that is
contaminated at levels which may pose health or environmental
risks. Therefore, this alternative may not be implementable due
to Federal Landban regulations.
Soil Alternative A-2:
IN-SITU VITRIFICATION
This alternative calls for the excavation of offsite contaminated
soils and sediments, placing these soils and sediments on the site,
and the treatment of all arsenic-contaminated soils using the in-
situ vitrification technology. The volume of soils estimated to
require treatment with this alternative is 156,000 cubic yards.
In-situ vitrification is a process which uses electricity to
generate heat which will melt the contaminated soil. The equipment
necessary to conduct this technology consists of four electrodes
which are inserted into the contaminated soils and a mobile hood
which is placed over the area undergoing treatment. The electrodes
are placed into the soils 3.5 meters to 5.5 meters apart to form
a square which defines the area to undergo treatment. This hood
captures and collects any gases that may be formed or released
during the treatment process. The off-gas treatment system cools,
scrubs, and filters the gaseous effluents exhausted from the hood.
A major element of the off-gas support system is a glycol cooling
system. This system cools the scrub solution by extracting thermal
energy that builds up in the off-gas treatment system. The heat
is released to the atmosphere through an air-cooled heat exchanger.
Any arsenic that is captured in the off-gas system is collected and
placed in the next area of treatment. The process destroys many
contaminants when the soil is heated and permanently bonds other
contaminants into the glass-like material as it cools. The average
66
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in-situ vitrification processing rate is 4.58 tons per hour. The
glass-like, material is expected to remain stable for thousands of
years.
Soils from the Crystal Chemical site were actually treated using
this process, and tests conducted on the "glass-like material have
shown that only a very small amount of arsenic is able to leach
after treatment (see Table 15) . The levels that do leach are below
the treatment goal set for treatment technologies that do not
trigger placement at the Crystal Chemical site, i.e., 5.0 ppm of
arsenic. Therefore, this alternative satisfies the Federal
environmental regulations that request that contamination be
reduced in volume, toxicity, or ability to move in soil, air, and
water. The cost of this alternative is approximately $76,800,000
and would take approximately 7.75 years to implement.
EPA does not favor this alternative because it is not as cost-
effective and is no more protective of human health than
alternative A-5.
Soil Alternative A-3:
SOLIDIFICATION/STABILIZATIOM
Solidification/stabilization is a process which mixes cement, lime,
or other kinds of binding materials with contaminated soil in order
to reduce the ability of the contaminants to leach out of the soil
into the surrounding environment. The stabilization is
accomplished through either chemical or physical immobilization of
contaminants. A treatment rate of 1,000 cubic yards per day is
possible. For this alternative, all offsite and onsite arsenic-
contaminated soils and sediments would be excavated and then
treated using the solidification/stabilization process. The site
would be backfilled with the treated soil. The volume of offsite
soils requiring excavation is estimated to be 55,000 cubic yards,
and the total volume of soils requiring treatment with this
alternative is estimated to be 156,000 cubic yards. The total cost
of this alternative is approximately $29,600,000 and it would take
approximately 3 years to implement this remedy.
Solidification/stabilization has been used successfully many times
on hazardous waste sites and does comply with the Federal
environmental regulations that require that contaminants be
treated. However, treatability tests conducted for the SFS on
contaminated soil from the Crystal Chemical site treated using the
solidification/stabilization process have shown that a high
concentration of the arsenic continues to leach out of the soil
after treatment (see Table 15) . Given that this treatment
technology triggers placement under RCRA, the levels that leach are
above 5.6 ppm of arsenic ARAR for the Crystal Chemical site.
Furthermore, this technology may significantly increase the volume
of the contaminated soil that will need to be put back on to the
$7
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site. EPA does not favor this alternative for these reasons, and
because it may not comply with Superfund mandates (i.e., reduction
of toxicity, mobility, or volume) as well as EPA's selected remedy
(A-5).
Soil Alternative A-4:
SOIL WASHING
Soil Washing is a process which removes contaminants from soil by
mixing the excavated contaminated soils with a liquid. During the
mixing process, the contaminants are washed from the soil. The
liquid containing the contaminants is then drained from the soil
and is treated using conventional wastewater treatment systems or
disposed in a landfill which is allowed to accept arsenic
contaminated liquids. The soil processing rate for this technology
is approximately 200 cubic yards per day. This alternative calls
for the excavation of all offsite and onsite arsenic-contaminated
soils and sediments. The volume of soils estimated to require
treatment with this alternative is 156,000 cubic yards. After the
washing process, the site would be backfilled with the washed soil.
This alternative would take approximately 6 years to implement and
would cost an estimated $121,510,580.
This alternative does involve treatment and does reduce the
toxicity, which is the degree of danger posed by the contaminant
to humans or animals, of the contaminants. However, the disposal
of the liquid containing the contaminants may be difficult and may
require pretreatment because of state and Federal environmental
regulations prohibiting land disposal of certain contaminants.
Additionally, tests conducted on contaminated soils from the
Crystal Chemical site treated using the soil washing process have
shown that high concentrations of arsenic continue to leach out of
the soil after treatment (see Table 15) . Given that this treatment
technology triggers placement under RCRA, the levels that leach are
above the 5.6 ppm of arsenic ARAR for the Crystal Chemical site.
Therefore, EPA does not favor this alternative because it is not
as protective of public health and the environment as EPA's
selected alternative (A-5).
Soil Alternative A-5:
PARTIAL IN-SITO VITRIFICATION AND CAPPING
This alternative is similar to Soil Alternative A-2, however, only
those soils with arsenic contamination greater than 300 ppm would
be treated using the in-situ vitrification process. The volume of
soils estimated to require treatment is 16,500 cubic yards. A
multi-layer cap consisting of clay, plastic, sand, topsoil, and
vegetation would be constructed over the entire site after the
soils have been treated. This cap acts as a barrier that restricts
the flow of water through the soils which are not subjected to
water table conditions and prevents the release of the soil and
70
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residual- contaminants into the air. The alternative will take
approximately 3 years to implement and will cost an estimated
$13,766,352.
Although only those soils contaminated wrth arsenic greater than
300 ppm would be treated using this alternative, calculations have
shown that approximately 95% of all the arsenic contamination on
the site would be treated with this alternative. That is to say
that, 95% of the arsenic on the site is found in areas where the
arsenic levels are above 300 ppm. This alternative not only
complies with Federal environmental regulations calling for
treatment, but also reduces the toxicity and volume of the
contaminated soils and the ability of the contaminants to leach
into the environment. EPA, therefore, favors this technology.
Soil Alternative A-6:
PARTIAL SOLIDIFICATION/STABILIZATION AND CAPPING
This alternative is similar to Soil Alternative A-3, however, only
those soils with arsenic contamination greater than 300 ppm would
be treated using the solidification/stabilization process. The
volume of soils requiring treatment is estimated to be 16,500 cubic
yards. A multi-layer cap consisting of clay, plastic, sand,
topsoil, and vegetation would be constructed over the entire site
after the soils had been treated. The cap acts as a barrier that
restricts the flow of water through the soils which are not
subjected to water table conditions and prevents the release of
soil and residual contaminants into the air. This alternative
would cost approximately $8,331,201 and would take an estimated 2.5
years to implement.
As in the discussion of Soil Alternative A-3, this alternative has
certain drawbacks that outweigh its effectiveness. This alternative
would decrease site risk by reducing the mobility of contaminants
present in the soil, is implementable, and it would comply with
Federal and State environmental laws. However, there would be no
reduction in the toxicity or volume of contaminants, therefore,
this alternative is not as protective of public health and the
environment as EPA's selected remedy (A-5).
Alternative A-7:
PARTIAL SOIL WASHING AND CAPPING
This alternative is similar to Soil Alternative A-4, however, only
those soils with arsenic contamination greater than 300 ppm we .^.d
be treated using the soil washing process. The volume estimated
to require treatment is 16,500 yards. A multi-layer cap consisting
of clay, plastic, sand, topsoil, and vegetation would be
constructed over the entire site after the soils had been treated.
The cap acts as a barrier that restricts the flow water through
*
71
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soils which are not subjected to water table conditions and
prevents the release of soil and residual contaminants into the
air. This alternative would cost approximately $19,498,844 and
would take an estimated 3.75 years to implement.
As with Soil Alternative A-4, there are certain drawbacks to this
alternative, the most important being its ineffectiveness in
treating the soils and the disposal of the liquid containing the
contaminants. Therefore, with the possibility of capacity problems
in offsite disposal areas coupled with other short-comings of this
approach, EPA does not favor this alternative.
Alternative X-8:
CAPPING
The capping alternative calls for all soils and sediments from
offsite that have arsenic contamination greater than 30 ppm to be
brought back on to the site. Then a cap consisting of clay,
plastic, gravel, topsoil, and vegetation would be constructed over
the entire site. No treatment of the soils would be done before
the site was capped.
Although the mobility of the contaminants in the soil would be
reduced if a cap were constructed over the site, neither the volume
of the contaminated soils nor the toxicity of the contaminants
would be reduced. Additionally, the Federal environmental
regulations prefer that contaminants be treated instead of
untouched under a cap. This alternative is not as protective of
public health and the environment as EPA's selected alternative (A-
5).
Alternative A-9:
NO ACTION
The Superfund program requires that a no action alternative be
considered at every site as a basis of comparison when evaluating
other alternatives. No action assumes that nothing would be done
to restrict site access, monitor offsite contaminated soil, or to
maintain the existing temporary cap. Therefore, there would be no
costs associated with this alternative. This alternative is not
favored by EPA because it would not decrease the toxicity,
mobility, or volume of contaminants or reduce public health or
environmental risks.
Alternative A-10:
LIMITED ACTION
This alternative involves site access and land use restrictions
that include prohibiting activities such as soil removal or any
72
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type of commercial or residential activity on the site. The costs
associated with this alternative are approximately $96,585, and the
restrictions would be enforced in perpetuity.
This alternative would somewhat reduce risks to public health and
the environment by restricting site use and access. However, it
would not prevent continued ground water contamination. EPA does
not favor this alternative because it would not comply with Federal
and State environmental laws, provide long-term protection to
public health or the environment, or reduce the toxicity, mobility,
or volume of contaminants.
B. Ground Water Remedial Alternatives
The alternatives for the ground water cleanup are the following:
Alternative B-la: Extraction and Discharge to a Publicly
Owned
Treatment Works ("POTW")
Alternative B-lb: Extraction, Treatment, and Discharge to
POTW, to surface water, or reinject
Alternative B-2
Alternative B-3
Alternative B-4
Slurry Wall
No Action
Limited Action
Common Elements. Except for the "No Action" and "Limited Action"
alternatives, all of the alternatives that were considered for the
site included a number of common elements. Each of the
alternatives includes long-term operation and maintenance (O&M)
activities for ground water extraction, treatment or monitoring,
with the more conservative time-frame for the O&M being 30 years.
In addition, site access and land use restrictions prohibiting
soil removal or any commercial or residential activity will be
placed on the site. With all the alternatives, the onsite water
supply wells and all of the monitoring wells not necessary for the
remedial action or for the long-term O&M will be closed in
accordance with regulations of the State of Texas. With
alternatives B-la and B-lb, a series of ground water recovery wells
will be installed. For alternatives B-la and B-lb the O&M will
include maintenance of the ground water extraction system that may
operate 24 hours per day. In addition to the extraction system for
alternative B-lb, a treatment system that may operate eight hours
per day must be maintained. Storage of water after extraction for
alternative B-la and B-lb or after extraction and treatment for
alternative B-lb may be necessary prior to discharge. Ground water
monitoring activities in the area around the site will be
maintained to ensure the effectiveness of the remedy for the B-l
alternatives and for "alternative B-2 for 30 years. All costs and
time required to implement all of the alternatives are estimates.
Table 16 summarizes estimated costs and implementation times for
all of the alternatives.
*
73
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For alternatives B-la and B-lb the goal of the remedial action is
to restore the ground water to a useable state, i.e., removing the
arsenic to the MCL throughout the area of attainment. The extent
of ground water contamination is illustrated on Figure 13. Based
on information obtained during the SI, the original FS, the SFS,
and the analysis of all four remedial alternatives, EPA believes
that this goal is attainable. Contamination of ground water by
arsenic may be especially persistent in the immediate vicinity of
the contaminants' source, where concentrations are relatively high.
The ability to achieve cleanup goals throughout the area of
attainment cannot be determined until the extraction system has
been implemented, modified as necessary, and the plume response
monitored over time. If the selected remedy cannot meet the
remediation goal of 0.05 ppm, the MCL for arsenic and an ARAR for
the Crystal Chemical site throughout the area of attainment during
the implementation, contingency measures and goals may replace the
selected remedy and goals. These measures will be protective of
human health and the environment, and are technically practicable
under the corresponding circumstances.
To determine if contingency measures are necessary, the ground
water extraction system for alternatives B-la and B-lb will be
closely monitored for an estimated period of 10 years. After 10
years, the system's performance will be carefully evaluated. If
it appears that the system cannot attain the remedial goals set for
the site, contingency measures including one, some or all of the
activities below will be implemented:
a) discontinuing operation of extraction wells in areas
where cleanup goals have been attained;
b) alternating pumping at wells to eliminate stagnation
points;
c) establishing an Alternate Concentration Limit ("ACL")
for arsenic throughout the area of attainment provided
compliance with CERCLA Section 121(d)(2)(B)(ii) can be
demonstrated;
d) waiving the ground water ARAR for those portions of the
aquifer based on the technical impracticability of
achieving further contaminant reduction;
e) implementing low level pumping as a long-term gradient
control or construction of a containment measure such as
a slurry wall; and/or,
f) implementing additional source control treatment to
further reduce arsenic migration to ground water.
76
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Ground Watar Alternative B-la:
EXTRACTION AND DISCHARGE TO A PUBLICLY OWNED TREATMENT WORKS (POTW)
This alternative calls for pumping ground water from the two
contaminated water-bearing zones and discharging this water
directly to the POTW. A ground water monitoring system utilizing
existing monitoring wells and area supply wells would be maintained
and restrictions prohibiting construction on the site would be
enforced. The volume of contaminated water requiring extraction
is estimated to be 3,000,000 gallons. The estimated time to
implement this alternative and to remove the contaminated water
down to the MCL for arsenic (0.05 ppm) is 30 years, and the cost
associated with this alternative is $957,830.
This alternative would reduce site risk by substantially decreasing
ground water contamination present in the area surrounding the
site. However, if the POTW does not accept the contaminated ground
water, this alternative may not be feasible. In fact, the Houston
Department of Public Works ("HDPW") has indicated that the
allowable arsenic limits for discharge to a POTW in the City of
Houston and surrounding communities are 0.2 ppm (composite sample)
and 0.3 ppm (grab sample). Given that ground water contamination
at the Crystal Chemical site ranges from 0 to 400 ppm, discharge
to a POTW without pretreatment may not be feasible. Additionally,
this alternative does not meet the Superfund preference for
treatment of contaminants. For these reasons EPA does not favor
this alternative.
Alternative B-lb:
EXTRACTION, TREATMENT, AND DISCHARGE TO POTW, TO AN AREA SURFACE
WATER, OR REINJECT
Like alternative B-la, the estimated 3,000,000 gallons of
contaminated ground water would be pumped from the two water-
bearing zones on the Crystal Chemical site, however, with this
alternative the ground water would be treated to remove the arsenic
prior to discharge. The treatment of contaminated ground water
would consist of ferric hydroxide precipitation and flocculation,
followed by clarification, filtration, and final polishing of the
water with ion exchange. Ion exchange treatment is a process where
contaminants are removed from water through the .exchange of
nontoxic materials (ions) from an ion exchange material. The toxic
materials are retained in the exchange material. A treatability
study to investigate the precise requirements of the treatment
system necessary to remove the arsenic contamination will have to
be conducted. Once treated, the water would be discharged either
to a POTW or into an area surface water (i.e., the Harris County
Flood Control Channel), or reinjected into the ground. If the
water is to be reinjected, injection wells will need to be
installed. The advantage to reinjection is that the contaminants
are flushed out, therefore possibly accelerating the removal of
77
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arsenic from the water-bearing zone and shortening the extraction
time required to meet the remediation goal. Additionally, an
onsite pilot study should be conducted to identify number of wells,
well placement for the most effective extraction method and to
fully investigate the reinjection option. The extraction and
treatment would continue until MCLs (0.05 ppm) for arsenic are met
throughout the area of attainment. The contaminants that would be
concentrated through the treatment process will need disposal in
a landfill approved to handle arsenic and may require treatment
prior to disposal. The time required to implement this alternative
is estimated to take 30 years and cost approximately $4,824,388.
Although this alternative provides for no net reduction of toxicity
or mobility of the contaminants, it does reduce site risks by
substantially decreasing the volume of contaminated ground water
present on and in the vicinity of the site. It would comply with
Federal and State environmental laws and the Superfund preference
for treatment of contaminants even though the arsenic will be
concentrated in a sludge. Although the sludge may require offsite
treatment prior to disposal due to the fact that the untreated
sludge may exhibit characteristics that would disallow its disposal
given the RCRA Landban ARAR, EPA favors this technology.
Ground Water Alternative B-2:
SLURRY WALL
This alternative calls for construction of a slurry wall around the
ground water contamination. A slurry wall is a trench filled with
materials that limit the flow of ground water through the area
surrounded by the trench. The objective of installing a slurry
wall is to minimize the lateral migration of contamination in the
two water-bearing zones. The low permeability of the naturally
occurring clay layer separating the 35-foot and 100-foot water-
bearing zones minimizes any vertical movement of ground water. As
part of this alternative, a pressure relief system would have to
be installed within the containment areas to prevent the rise of
ground water levels. Ground water removed from the pressure relief
wells would be transported offsite for treatment. This alternative
would cost approximately $6,196,038 and take 1.25 years to
implement.
A slurry wall would reduce site risk by minimizing further
migration of contaminants. This alternative, however, would not
reduce the toxicity or volume of contaminants present in ground
water, and it would not meet the Superfund preference for treatment
of contaminants. Additionally, it may be difficult to locate a
facility willing to take the contaminated ground water recovered
from the pressure relief system. This alternative would be the
most expensive ground water alternative to implement, and the
additional costs do not increase the overall protectiveness of the
alternative. Therefore, EPA does not favor this alternative.
78
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Ground Water Alternative B-3
NO ACTION
This alternative assumes that no offsite or onsite monitoring would
be performed. No action would be taken to prevent further
migration of contaminated ground water at the site, and no costs
are associated with the alternative. With this alternative, future
use of contaminated ground water offsite could result in
unacceptable public health risks. This alternative would not
reduce mobility, toxicity, or volume of contaminants and,
therefore, is not favored by EPA.
Ground Water Alternative B-4
LIMITED ACTION
This alternative calls for monitoring the existing monitoring wells
and ground water wells in the vicinity of the site. Additionally,
restrictions would be placed on the site to prohibit activities
such as soil removal or any type of commercial or residential
activity. The costs associated with this alternative are estimated
to be $73,822, and the situation would be monitored for 30 years.
This alternative reduces risk by restricting site use and access.
However, contaminants would continue to adversely affect the
surrounding environment. This alternative would not comply with
Federal and state environmental laws, therefore, it is not favored
by EPA.
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The nine (9) criteria used in evaluating all of the alternatives
identified in the SFS 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.
Explanation of Evaluation 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,
79
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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.
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.
State Acceptance indicates whether, based on its review of the
RI/FS and Proposed Plan, the State concurs with, opposes, or
has no comment on the preferred alternative.
Community Acceptance will be assessed in the Record of
Decision following a review of the public comments received
on the RI/FS report and the Proposed Plan.
A symbolic ranking of the comparative analysis for the soil
remedial alternatives and for the ground water alternatives are
included (see Tables 17 and 18). The symbolic ranking is based on
the narrative analysis that follows.
A. Analysis of Soil Remedial Alternatives
Overall Protection. All of the alternatives, with the exception
of the "No Action" and "Limited Action" alternatives, would provide
adequate protection of human health and the environment by
eliminating, reducing, or controlling risk through treatment,
capping, or deed and land use restrictions. The preferred
treatment technology is in-situ vitrification because it was the
only technology that significantly reduced the toxicity and
*
80
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TABLE 17
COMPARATIVE ANALYSIS FOR SOIL REMEDIAL ALTERNATIVES
Crystal chemical Company Site
CRITERION
Overall Protection of Human Health
and the Environment
ALTERNATIVE
Most
A-8
A-l
A-2 A-5
A-3 A-6
A-4 A-7
Least
Compliance with ARARs
A-3 A-4 A-6 A-7
Long-term Effectiveness and
Permanence
Reduction of Toxicity, Mobility, or Volume
through Treatment
Most
A-2
A-4
A-3
A-l
A-5
A-7
A-6
A-8
Least
Most
A-2
A-4
A-3
A-5
A-7
A-6
A-l
A-8
Least
-------
TABLE 17 (continued)
COMPARATIVE ANALYSIS FOR SOIL REMEDIAL ALTERNATIVES
Crystal Chemical Company Site
Short-term Effectiveness
Most
A-8
A-6 A-7
A-l A-3
A-4 A-5
A-2
Least
Implementability
COSt
Most
A-3 A-4
A-5
A-6 A-7
A-2
A-l A-8
Least
Least Expensive
A-8
A-6
A-5
A-7
A-3
A-l
A-2
A-4
Most Expensive
-------
TABLE 18
COMPARATIVE ANALYSIS
GROUND WATER ALTERNATIVES
Crystal Chemical Company Site
CRITERION
ALTERNATIVE
Overall Protection of Human Health
and the Environment
Most
B-lb
B-la
B-2
Least
Compliance with ARARs
Most
B-lb
B-la
B-2
Least
Long-term Effectiveness and
Permanence
Most
B-lb
B-la
B-2
Least
Reduction of Toxicity, Mobility, or Volume
through Treatment
Most
B-lb
B-la
B-2
Least
-------
TABLE 18 (continued)
COMPARATIVE ANALYSIS
GROUND WATER ALTERNATIVES
Crystal Chemical Company Site
Short-term Effectiveness
B-la
B-lb
B-2
Least
Most
Implementability B-lb
B-la
B-2
Least
>>
•&
•:<
&
s
IS
%?5
Cost
Least Expensive
B-la
B-lb
B-2
Most Expensive
-------
mobility* of the arsenic contamination during the treatability
testing conducted on soils from the Crystal Chemical site, i.e.,
after the treatment the leachability of the arsenic was reduced to
below 5.0 ppm. Additionally, the treatment technology yielded a
20% to 30% volume reduction. The technology provides for a long-
term and permanent solution to the contamination problem at the
Crystal Chemical site. The reason for selecting the partial in-
situ vitrification and capping alternative over in-situ
vitrification of the entire site is that, although only those soils
contaminated with arsenic greater than 300 ppm would be treated
using this partial treatment remedy, calculations have shown that
approximately 95% of all the arsenic contamination on the site
would be treated with this alternative. That is to say that 95%
of the arsenic on the site is found in areas where the arsenic
levels are above 300 ppm.
Therefore, the highest level of contaminants (95% of the arsenic)
are captured or destroyed, the offsite soil and sediments that are
contaminated with arsenic greater than 30 ppm is excavated and
placed back on the site, and a cap is constructed over all of the
treated and excavated materials. The cap will eliminate the risks
associated with direct contact with the residual contamination,
will act as a barrier that restricts the flow of water through the
soils which are not subjected to water table conditions, and will
prevent the release of soil and contaminants into the air. The
partial in-situ vitrification alternative addresses the risks to
public health and welfare and the environment while being cost
effective.
Because the "No Action" and "Limited Action" alternatives are not
protective of human health and the environment, they will not be
discussed any further.
Compliance with Applicable or Relevant and Appropriate Requirements
("ARARs"). ARARs are the Federal and State requirements that a
selected remedy must meet. Given that the arsenic found on the
site exhibits characteristics of a substance that is regulated
under RCRA, 40 CFR Subpart C, and that a type of arsenic (i.e.,
K031 - by-product salts generated in the production of MSMA and
cacodylic acid) that is specifically listed and regulated under
RCRA, 40 CFR Subpart D, was produced on the site, certain ARARs
apply. If a waste leaches above 5.0 ppm of arsenic when analyzed
using TCLP, it is considered a hazardous waste and is regulated
under RCRA. Furthermore, if a RCRA regulated waste is treated,
additional ARARs apply.
On June 1, 1990 a regulation identifying vitrification as the best
demonstrated available treatment technology ("BOAT") for arsenic
as a RCRA characteristic waste as well as a RCRA listed waste was
published (55 Fed. Reg. 106 at 22556 to 22561). The effective date
of this regulation was August 8, 1990. Associated with the BOAT
*
85
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is a .concentration-based treatment standard of 5.6 ppm for K031
nonwastewaters, and the BOAT concentration-based treatment standard
for arsenic as a characteristic (D004) nonwastewater is 5.0 ppm.
When the soils treatment and replacement triggers placement (Soils
Alternatives A-3, A-4, A-6, and A-7) or when offsite disposal of
contaminated soil is involved which, too, triggers placement (Soil
Alternative A-l) under RCRA's Land Disposal Restrictions
("Landban"), 40 CFR 268, the 5.6 ppm treatment standard for
nonwastewaters is required per 40 CFR 268.9.
Alternatives A-l, A-3, A-4, A-6 and A-7 may fail to meet two
federal ARARs. The first ARAR regards closure requirements for
surface impoundments containing materials that migrate out of soil
above levels acceptable to EPA (i.e., TCLP level of 5.6 ppm for
arsenic). This ARAR is relevant and appropriate because the four
evaporation ponds that existed on the site during Crystal Chemical
Company's operation were not closed per the RCRA regulations during
the EPA Emergency Removal Actions conducted on site. The second
involves performance standards for redeposited, treated soil
regulated under the Landban restrictions. The in-situ
vitrification technology and the two alternatives that use this
technology, A-2 and A-5, will meet or exceed the ARARs and remedial
action goals for the Crystal Chemical site.
Long-tern Effectiveness and Permanence. The in-situ vitrification
technology (alternatives A-2 and A-5) provides a permanent
reduction in the volume, mobility, and the toxicity of the soil
contaminated with arsenic. In the case of partial in-situ
vitrification (A-5), the multi-layer cap would provide protection
from direct contact with the remaining contaminants on site and
prevent the release of soil and contaminants into the air.
Additionally, the vitrification with the cap will restrict the flow
of water through the soil containing the remaining 5% arsenic, thus
minimizing the ability of the arsenic to migrate into the ground
water.
Alternative A-l would eliminate the onsite and offsite risks of
direct contact and the continued release of contaminants into the
air and ground water, but offsite disposal of the contaminated soil
without treatment is not possible due to Landban restriction.
Alternative A-2 would provide long-term protection of human health
and the environment by vitrifying all soil above the health
standard. During bench scale treatability tests using actual
contaminated soils from the site, Alternatives A-3 and A-4 failed
to demonstrate that these treatment techniques will result in an
acceptable decrease (i.e., 5.6 ppm) in the amount of arsenic that
is able to leach out of the treated soil (see Table 15) .
Therefore, Alternatives A-3 and A-4 are not as effective therefore
not as permanent as the alternatives A-2 and A-5. However, the
addition of a multi-layer cap to these treatment methods
86
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(Alternatives A-6 and A-7) would reduce the ability of contaminants
to leach out of the treated soils by preventing water from flowing
through the soils therefore increasing its effectiveness. The cap
in these alternatives would also restrict.direct contact with the
treated soils as well as the untreated soils and reduce dust.
Alternative A-8 involves excavation of contaminated offsite soil
and capping all contaminated soils without performing any
treatment. This capping provides long-term reductions in the
amount of water that otherwise would pass through the contaminated
soil and would continue to carry the contaminants into surrounding
soils and ground water. Although the direct contact risk would be
eliminated with this alternative, because there is no treatment of
the contaminants involved, this alternative is only as permanent
as the cap.
Reduction of Toxicity, Mobility, or Volume of the Contaminants
Through Treatment. Three methods of treatment are proposed, alone
and in conjunction with capping. Alternatives A-2 and A-5 involve
treatment by in-situ vitrification, which destroys many
contaminants and permanently bonds other contaminants. This
technique was successful in the site's treatability study in
significantly reducing arsenic mobility to below acceptable (i.e.,
TCLP level of 5.0 ppm for arsenic as a RCRA regulated
characteristic waste) concentrations after treatment (see Table
15). The technique also yields a 20% to 30% volume reduction.
Alternatives A-3 and A-6 involve treatment by
solidification/stabilization which physically or chemically bonds
contaminants. The site's treatability study produced a stabilized
mixture with reduced arsenic mobility, but the mixture continued
to leach arsenic greater than 5.6 ppm of arsenic after treatment
(see Table 15). Also, this treatment process increases soil volume
after treatment by approximately 10% to 30%.
Alternatives A-4 and A-7 involve treatment by soil washing which
concentrates the contaminants into the wash liquid. The site's
treatability study produced a washed soil with reduced arsenic.
However, the mixture still allowed migration of arsenic greater
than 5.6 ppm (see Table 15).
Given that alternatives A-l and A-8 do not involve treatment, they
do not satisfy this criteria.
Short-term Effectiveness. Alternative A-8 would contain the
contaminated soil within an estimated 2.25 years, with a potential
risk to the community as a result of fugitive dust emissions during
excavation and construction. Two alternatives, A-l and A-6, could
be implemented in 2.5 years. Alternative A-l involves some risks
to the community related to dust production and transportation
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accidents. Alternative A-6 also includes the risk of dust
production during excavation and treatment of the soil.
Alternative A-5 would be implemented in Only a slightly longer
period, approximately 3 years. With this alternative, community
protection is easily accomplished. Air emissions produced by the
vitrification technology will be controlled by a gas collection
system over the area being treated. Dust control measures may be
required during the excavation and transfer of offsite soil that
are to be brought back on site.
Alternative A-2 would take an estimated 7.75 years to implement.
It involves the same potential risks to the community as
Alternative A-5. Alternative A-7 would take 3.75 years to
implement. It involves the risk of dust production during soil
excavation and treatment.
The short-term risks for all alternatives involve dust emission due
to excavation of offsite soils contaminated with arsenic in levels
greater than 30 ppm. Additionally, Alternatives A-3, A-4, A-6, and
A-7 would involve excavating onsite contaminated soils prior to
their treatment. Alternative A-l would also involve the onsite
excavation of soils prior to offsite disposal. Alternatives A-5
and A-2 do not require any excavation of onsite contaminated soils,
however, gases may be formed during the treatment process. The air
emissions formed during the vitrification will be controlled by a
gas collection system over the area being treated. With all these
alternatives, dust suppression measures and air monitoring would
take place to reduce the potential air emission problems.
Implementability. Alternative A-l calls for all contaminated soils
both offsite and onsite to be excavated and disposed offsite.
Federal regulations restricting offsite disposal of certain wastes
may preclude this alternative from being implementable.
Alternative A-2 and A-5 have some implementability limitations.
The number of commercial vendors that can perform the technology
are limited, and specialized workers are required. Also, once a
soil mass is vitrified to a certain depth, it is difficult to
perform additional vitrification.
Alternatives A-3 and A-4 (solidification/stabilization technology)
are technically easier to implement than alternatives A-6 and A-
7 (soil washing technology) and all are technically easier to
implement than the alternatives using the in-situ vitrification
technology. However, administratively, the in-situ vitrification
technology is easier to implement. The results of treatability
studies have indicated that the in-situ vitrification technology
is the most successful in reducing the amount of leachable arsenic
in the Crystal Chemical soils after treatment.
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Cost. The cost of alternative A-5 is $13,766,352. The lowest-
cost alternative is Alternative A-8 at $5,234,331. The highest-
cost alternative is Alternative A-4 at $121,510,580.
B. Analysis of Ground Water Remedial Alternatives
Overall Protection. Overall protection of human health and the
environment is provided by all of the alternatives, with the
exception of the No Action and Limited Action alternatives.
Alternative B-lb provides added protection because of pretreatment
of ground water prior to discharging.
The No Action and Limited Action alternatives are not protective
of human health and the environment, therefore, they will not be
discussed further in this analysis.
Compliance with Applicable or Relevant and Appropriate Requirements
("ARARs11). ARARs are the Federal and State requirements that a
selected remedy must meet. All of the ARARs for the extraction,
treatment, and discharge to a POTW or the Harris County Flood
Control Channel, or reinjection can be met. Alternatives B-la and
B-2 do not meet all of the ARARs because the alternatives either
do not call for treatment of the contaminated ground water to meet
the 0.05 ppm arsenic ARAR, or they do not include treatment prior
to discharge.
Alternative B-lb calls for the treatment of the contaminated ground
water, and the arsenic after treatment will be concentrated in a
sludge. The sludge may exhibit characteristics of a waste
regulated under RCRA, therefore, applicable RCRA requirements for
the handling of the sludge (40 CFR 262 and 264) and for possible
offsite treatment prior to disposal due to Landban (40 CFR 268)
will be applied. Additionally, if reinjection of the treated
ground water is chosen for B-lb, an ARAR detailing certain
reinjections requirements may be relevant and appropriate (40 CFR
144) to the Crystal Chemical site.
Short-term Effectiveness. Precautions will be taken to eliminate
any risk to the public during the construction of the extraction
wells that will be used to pump the ground water or during the
construction of the slurry wall. Other risks associated with
Alternative B-lb may come from the arsenic contaminated sludge that
will be generated during treatment. Furthermore, the sludge may
require offsite treatment prior to disposal due to the fact that
the untreated sludge may exhibit characteristics that would
disallow its disposal given land disposal restrictions. The actual
time to pump the ground water to a level that the arsenic
contamination is less than 0.05 parts ppm (the MCL for arsenic)
throughout the area of attainment may take up to 30 years.
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Long-tarn Effectiveness and Permanence. Alternatives B-la and B-
Ib call for the removal of arsenic down to 0.05 ppm in the ground
water. The risk from ingestion of or direct contact with the
contaminated ground water will be all but-eliminated, therefore,
these alternatives are very effective in the long-term and are
considered permanent. With Alternative B-2, unless deed and site
access restrictions are enforced, the risk to human health will be
the same as if nothing were done. Additionally, the slurry wall
cannot be considered a permanent remedy since no ground water
treatment will be effected. Although the actual time to pump the
ground water down to the 0.05 ppm of arsenic level may take up to
30 years, the adequacy and reliability of the pump and treat
technologies have been well proven.
Reduction of Toxicity, Nobility, or Volume of the Contaminants
through Treatment. Alternative B-la would result in the reduction
of volume of contaminants on the site but calls for discharging the
contaminated water to a POTW. Alternative B-lb provides more
control over the removal of arsenic through pretreatment and a
reduction in the volume of contaminated ground water, however, this
alternative provides for no net reduction of toxicity or mobility.
The arsenic with this alternative is concentrated in the sludge
generated from the ground water treatment, and this sludge may
require treatment prior to its ultimate offsite disposal.
Implementability. If the POTW does not accept the contaminated
ground water, alternative B-la may not be implementable. In fact,
the Houston Department of Public Works has indicated that the
allowable arsenic limits for discharge to a POTW in the City of
Houston and surrounding communities are 0.2 ppm (composite sample)
and 0.3 ppm (grab sample). Therefore, it appears that the
contaminated ground water from the Crystal Chemical site must
receive some form of pretreatment prior to discharge to a POTW,
like with alternative B-lb.
Cost. The cost of the preferred alternative is $4,824,388. The
most costly alternative is Alternative B-2 estimated to cost
$6,196,038, and the lowest cost alternative is B-la at a cost of
$957,830.
State Acceptance. The State of Texas, through the Texas Water
Commission, concurs with the remedy selected by EPA (Attachment 2) .
Community Acceptance. The community has voiced limited support for
the partial in-situ vitrification and capping remedy for the soils
and for the extraction, treatment, and discharge remedy for the
ground water.
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IX. SELECTED REMEDY
Based on consideration of the requirements of CERCLA, the detailed
analysis of the alternatives, and public comments, EPA has
determined that soil alternative A-5 (Partial in-situ Vitrification
and Capping), and that ground water alterative B-lb (Extraction,
Treatment, and Discharge to a POTW, the Harris County Flood Control
Channel, or reinjection) are the most appropriate remedies for the
Crystal Chemical Company site in Houston, Texas.
The remediation goals selected for both arsenic-contaminated soils
and ground water are protective of human health and welfare and the
environment. They were selected to eliminate or reduce risks
associated with potential exposure to the contaminants via
ingestion or direct contact with soil, sediments and surface water;
ingestion of contaminated shallow ground water and contaminated
fish; and inhalation of wind dispersed dust. The goals for the
soil contamination call for the removal of offsite soils and
sediments to a concentration of 30 ppm for arsenic, which
represents a one in one hundred thousand (10 ) excess cancer risk
level. Since the average background concentration of arsenic in
western soils (6.1 ppm) exists at a level in excess of EPA's
standard point of departure (one in one million cancer risk - at
a 3 ppm concentration of arsenic) , 30 ppm was determined to
represent a safe health-based action level. These soils will be
placed back on to the Crystal Chemical site. Additionally, the
selected remedy requires that all heavily contaminated areas onsite
with soil-arsenic concentrations in excess of 300 ppm, or a lower
concentration level if determined to be necessary and feasible
based on the evaluation defining the relationship between
contaminated soils and ground water to be conducted during the
remedial design, will be treated using in-situ vitrification. Such
an approach will effectively treat 95% of the arsenic found on the
site. The treatment goal for the soils is to the reduce the amount
of arsenic that is able to leach to 5.0 ppm of arsenic after
treatment when analyzed using the Toxicity Characteristic Leaching
Procedure ("TCLP"), 40 CFR 261.25. The entire site will be covered
with a multi-layer cap after the treatment has been completed. The
average concentration of arsenic found in these areas (not subject
to treatment) is 60 ppm. Once the entire remedy is complete, the
resulting cancer risk will be reduced to less than one in one
million (at or near the original background conditions). The MCL
standard for arsenic, 0.05 ppm, is an ARAR for the Crystal Chemical
site, and EPA has determined that the MCL will be the target
remediation level for ground water. The MCL will be met throughout
the area of attainment.
Approximately 55,000 cubic yards of offsite soils and sediments
contaminated with arsenic above 30 ppm will be excavated and
brought back on to the site. In order to ensure that all offsite
soils and sediments contaminated with arsenic greater than 30 ppm
from the Crystal Chemical site are identified, offsite areas
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previously identified as contaminated will be resampled to verify
the need for excavation. This will include, but will not be
limited to, adjacent properties, the Harris County Flood Control
Channel, and all properties potentially affected by drainage from
the site by way of the flood control channel. All soils
contaminated with arsenic greater than 300 ppm will be treated
using the in-situ vitrification technology. The volume, therefore,
requiring treatment is estimated to be 16,500 cubic yards.
During the design phase of this remedial action, an evaluation
defining the relationship between the contaminated soils and the
ground water will be conducted. This study will determine the
depth and arsenic concentration of the soils which require
treatment so as to allow the ground water remedial goal of 0.05 ppm
for arsenic to be achieved. The objective of this study will be
to determine the need for and feasibility of deeper and more
extensive soil treatment that will enable the ground water to be
remediated to the MCL within the shortest practical timeframe.
This study may include a further soils investigation to more fully
delineate subsurface arsenic distribution and speciation.
In-situ vitrification is a patented process for the indirect
treatment of contaminated soils. In-situ vitrification thermally
converts contaminated soil into a chemically inert, stable,
crystalline product. The treatment process consists of placing a
graphite-containing starter material on the surface of contaminated
soils between an array of electrodes which are placed in the
ground. The graphite starter material acts as a conductive path
between the electrodes. An electrical current is passed between
the electrodes which creates temperatures high enough to melt the
soil (1600 - 2000* Celsius). The molten zone grows downward and
outward destroying or encapsulating hazardous substances in the
soils. Upon cooling, the product of in-situ vitrification is a
glass-like material resembling natural obsidian.
Figure 14 illustrates the disposition of materials during the in-
situ vitrification process. Gases released during the melting
process are collected in an off-gas hood and treated. Inorganic
materials in the soil either melt, dissolve, or immobilize into the
molten mass.
The in-situ vitrification process can treat both large and small
areas of contamination, but the system is limited at the time of
this Record of Decision to treating soils no deeper than
approximately 25 feet below the ground surface.
This technology can be used on most known soils, including those
saturated with water. In doing so, the process heats the inorganic
matrix materials to, 100* Celsius, at which temperature water is
removed by vaporization. However, it requires approximately the
same amount of electrical energy to remove one pound of water as
it does to melt one pound of soil. Therefore, it is best maintain
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HOOD-
OFF GAS TO
TREATMENT
ELECTRODE
*—GRAPHITE AND
FRIT STARTER
MELT ZONE
BACKFILL
VITRIFIED SOIL
AND WASTE
FIGURE 14
IN-SITU VITRIFICATION SCHEMATIC
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the treatment volume in as dry a condition as possible prior to
implementation of this technology. Because of this, a temporary
dewatering system may be utilized during the implementation of the
remedial action if it is determined to be necessary during the
design phase of this project.
As subsidence of the soils occurs upon cooling of treated area,
backfill would be required to bring the treated area to grade.
Once the soils treatment has been completed, the site will then be
covered with a multi-layer cap consisting of clay, plastic, sand,
topsoil, and vegetation. Following the completion of the soils
treatment, verification of the success of the treatment technology
will be conducted. The verification process will include, but will
not be limited to, a subsurface investigation along the periphery
of the treatment areas to ensure that migration of arsenic outside
of the treatment areas has not occurred.
The ground water remedy calls for a ground water extraction system
that will pump arsenic-contaminated ground water from water-
bearing zones contaminated by the Crystal Chemical site. Because
arsenic contamination has been detected in the 100-foot water-
bearing zone (MW-4) and in the WSW-1 (one of the onsite water-
supply wells) on the Crystal Chemical site itself, additional
hydrogeologic and geochemical characterization of the 100-foot zone
and the zone in which WSW-1 is screened (at an approximate 300 foot
depth) needs to be done. Furthermore, valid monitoring points for
these two zones must be established to more fully identify the
possible extent of contamination. Attempts to verify the
construction of the two onsite water supply wells have been
unsuccessful, therefore, they are not considered valid monitoring
points. A naturally occurring arsenic background concentration in
the ground waters of the upper 2000 feet in the site vicinity will
also be established during this characterization. These data will
be used to evaluate detected levels of arsenic in area wells. If
after the completion of the characterization additional water-
bearing zones are determined to be contaminated, they will be
included in the ground water extraction and treatment remedy for
the site. The onsite water supply wells (WSW-1 and WSW-2) and all
of the monitoring wells not necessary for the remedial action or
for the long-term O&M will be closed in accordance with regulations
of the State of Texas.
The treatment of the contaminated ground water would consist of
ferric hydroxide precipitation and flocculation, followed by
clarification, filtration, and final polishing of the water with
ion exchange. Ion exchange treatment is a process where
contaminants are removed from water through the exchange of
nontoxic materials (ions) from an ion exchange material. The toxic
materials are retained in the exchange material. A treatability
study to investigate* the precise requirements of the treatment
system necessary to remove the arsenic contamination will need to
be conducted. Once treated, the water would be discharged either
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to a POTW or into an area surface water or it would be reinjected
into the ground (see Figure 15) . If the water is to be reinjected,
injection wells will have to be installed. The advantage to
reinjection is that the contaminants are flushed out and then
treated using this technology. Additionally, an onsite pilot study
should be conducted to identify well placement for the most
effective extraction method and to investigate the reinjection
option.
The goal of this remedial action is to restore the ground water to
a useable state, i.e., removing the arsenic to the MCL within the
area of attainment. The area of attainment constitutes the site
boundary and up to the boundary of the contaminant plume for the
shallow water-bearing zones (i.e., the 15' and 35' zones).
However, the area of attainment for any area in deeper water-
bearings zone found to be contaminated with arsenic from the
Crystal Chemical site will be the lateral extent of the contaminant
plume, due to the potential for migration into deeper zones. Based
on information obtained during the SI, the original FS, the SFS,
and the analysis of all four remedial alternatives, EPA believes
that the alternative selected will achieve this goal and therefore
meet the ARAR for remediating the ground water to 0.05 ppm arsenic.
Contamination of ground water by arsenic may be especially
persistent in the immediate vicinity of the contaminants' source,
where concentrations are relatively high. The ability to achieve
cleanup goals throughout the area of attainment cannot be
determined until the extraction system has been implemented,
modified as necessary, and the plume response monitored over time.
If the selected remedy cannot meet the remediation goal of 0.05
ppm, the MCL for arsenic throughout the area of attainment during
the implementation, contingency measures and goals may replace the
selected remedy and goals. These measures will be protective of
human health and the environment, and are technically practicable
under the corresponding circumstances.
To determine if contingency measures are necessary, the extraction
system which is part of the selected remedy will be closely
monitored for an estimated 10 years. During this time the system's
performance will be carefully evaluated using performance data
collected. If after the evaluation it appears that the system
cannot produce the remedial goals set for the site, contingency
measures including one, some or all of the activities below will
be implemented:
a) discontinuing operation of extraction wells in areas
where cleanup goals have been attained;
b) alternating pumping at wells to eliminate stagnation
points; and/or,
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c) establishing an Alternate Concentration Limit ("ACL")
for arsenic throughout the area of attainment provided
compliance with CERCLA Section 'I21(d) (2) (B) (ii) can be
demonstrated;
d) waiving the ground water ARAR for those portions of the
aquifer based on the technical impracticability of
achieving further contaminant reduction;
e) implementing low level pumping as a long-term gradient
control or construction of a containment measure such as
a slurry wall; and/or,
f) implementing additional source control treatment to
further reduce arsenic migration to ground water.
The decision to invoke any or all of these measures may be made
during a periodic review of the remedial action, which will occur
at five-year intervals. Depending on whether a significant or
fundamental change is proposed, an Explanation of Significant
Differences or an Amendment to the Record of Decision will be
issued to inform the public of the details of the modification.
A change from active restoration to passive restoration would be
considered a fundamental change.
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 establishes several other statutory
requirements and preferences that the selected remedy must meet.
Section 121 of CERCLA 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 selected remedy, 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
reduce the volume, toxicity, or mobility of hazardous wastes as
their principal element. The following sections discuss how the
selected soil and ground water remedies meet these statutory
requirements .
Protection of B Health and the Envir ?
The selected soil remedy protects human health and the environment
by excavating all offsite soils contaminated with arsenic above 30
ppm, treating by the in-situ vitrification process, all soils
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contaminated with arsenic greater than 300 ppm, and by capping the
entire site after the treatment has been completed. The site will
be covered with a multi-layer cap to - act as a barrier that
restricts the flow of water through the soil and to prevent the
release of the soil and residual contaminants into the air. Site
access and land use restrictions prohibiting soil removal and any
commercial or residential activity will be implemented.
Removing all offsite soils and sediments contaminated with arsenic
greater than 30 ppm will eliminate the threat of exposure from
direct contact with the contaminated soils outside of the current
boundaries of the site. The vitrification (i.e., melting) of the
arsenic-contaminated soil above 300 ppm will eliminate the threat
of exposure from direct contact, inhalation, or ingestion of the
heavily contaminated soil, and it will minimize leaching of arsenic
into the ground water. The melting process destroys many
contaminants and permanently bonds other contaminants when the soil
is melted and cools into a stable glass-like material.
The current risks associated with these exposure pathways from the
contaminated soils, as discussed in the SUMMARY OF BITE RISKS
Section of this ROD, are unacceptable. By treating the most highly
contaminated areas, i.e., those areas where the arsenic
contamination is greater than 300 ppm, calculations have shown that
approximately 95% of all the arsenic contamination on the site
would be treated. That is to say that 95% of the arsenic on the
site is found in areas where the arsenic levels are above 300 ppm.
The average concentration of arsenic found on the site, outside of
the heavily contaminated areas, is 60 ppm. Therefore, the residual
•contamination outside the current boundaries of the site will
constitute a two in one hundred thousand (10 ) cancer risk level.
As an added protective measure, the entire site, after treatment
has been completed, will be capped. The capping will eliminate all
threats relating to direct contact with and inhalation of the
residual contamination. This will reduce the risk posed by this
site to less than one in one ten million (10 ). EPA policy calls
for remediation levels that range from a cancer risk of one in ten
thousand to one in one million (10"4 to 10"6} . Additionally, the
soils treatment and site capping will all but eliminate the
continued migration of arsenic from the soils into the ground
water. There are no short-term threats associated with the
selected remedy that cannot be readily controlled. Further, no
adverse cross-media impacts are expected from the soil remedy.
The selected ground water remedy protects human health and the
environment by pumping ground water from the two contaminated
water-bearing zones (15' and 35') and then treating contaminated
ground water onsite by chemical precipitation, filtration, and ion
exchange treatment. Following treatment, the water will either be
discharged to a publicly owned treatment works ("POTW") or to the
Harris County Flood Control Channel, or it will be reinjected into
the ground. The current ground-water monitoring system will be
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maintained or a new system designed to ensure that the remedial
action goals are being met. Site access and land use restrictions
prohibiting soil removal and construction will be implemented.-
The capture and treatment of the arsenic-contaminated ground water
will eliminate threats of direct contact and ingestion posed by the
site. The current risks associated with these pathways are
unacceptable. The endangerment assessment for the Crystal Chemical
site did not address remediation levels in ground water, and no
risk ranges have been established for arsenic as it relates to this
site. EPA has determined, however, that the Maximum Contaminant
Level ("MCL") standard for arsenic, 0.05 ppm, will be the target
remediation goal for the ground water. However, if after
monitoring the contaminant levels in the ground water being pumped
for treatment it appears that the remediation goal cannot be met,
contingency measures may be implemented, as discussed in the
SELBCTIIP REMEDY Section of this ROD. By maintaining a ground water
monitoring program in conjunction with the pump and treatment
system, elimination of the threats posed by possible ingestion or
direct contact can be assured. There are no short-term threats
associated with the selected remedy that cannot be readily
controlled. Also, no adverse cross-media impacts are expected from
the selected ground water remedy.
Compliance with Applicable or Relevant and Appropriate
Requirements;
Soil Remediation:
The selected soil remedy of excavation of offsite arsenic-
contaminated soils greater than 30 ppm, in-situ vitrification of
soils contaminated greater than 300 ppm, and capping the entire
site will comply with all applicable relevant and appropriate
action-, chemical-, and location-specific requirements ("ARARs").
The ARARs are presented as follows:
Action-specific Soil Remediation AJtARa:
Applicable Resource Conservation and Recovery Act ("RCRA")
requirements for landfill closure, 40 CFR 264.111 Subpart G,
which specify a cap with a permeability less than or equal to
the permeability of any bottom liner or natural sub-soils
present at the site. In addition, applicable specific closure
requirements which are provided for surface impoundments, 40
CFR 264.228 Subpart K, and applicable requirements for
landfills, 40 CFR 264.310 Subpart N, nay also apply.
Post-closure and monitoring applicable requirements for 30
years or another period determined by the Regional
Administrator, 40 CFR 264.117 (a)(1).
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Applicable ambient air quality standards per 40 CFR 50 to
protect the quality of the air during the implementation of
the remedial action.
Chemical-specific Soil Remediation ARARs:
As required by the Clean Water Act ("CWA") (33 CFR 303),
onsite surface water must meet applicable ambient water
quality criteria for arsenic (0.0175 M9/1)•
Location-specific Soil Remediation ARARs:
Applicable RCRA requirements, 40 CFR 264.18, for location of
a Transportation, Storage or Disposal ("TSD") facility in a
100-year floodplain, and also general applicable requirements
for protection of floodplains, 40 CFR 6, Appendix A.
Ground vater Remediation:
The selected ground water remedy of extraction and treatment,
followed by discharge to a publicly owned treatment works ("POTW"),
surface water, or reinjection into the ground will comply with all
applicable or relevant and appropriate action-, chemical-, and
location-specific requirements ("ARARs"). The ARARs are presented
as follows:
Action-specific Ground Water Remediation ARARs:
Applicable Resource Conservation and Recovery Act ("RCRA")
requirements, 40 CFR 262, Subparts A-D. These requirements
detail standards applicable to generators of hazardous waste.
Applicable RCRA requirements, 40 CFR 264, Subparts A-G, J and
K. These requirements detail standards for owners and
operators of hazardous waste treatment, storage, and disposal
facilities and would apply with regard to hazardous sludges
generated by ground water treatment.
Applicable RCRA requirements, 40 CFR 268, Subparts A-E. These
requirements detail land disposal restrictions as they pertain
to any hazardous sludge resulting from ground water treatment.
Applicable RCRA requirements, 40 CFR 122-125, with regard to
the National Pollutant Discharge Elimination System ("NPDES")
program which requires permits for discharge to surface
waters.
Applicable RCRA requirements, 40 CFR 403.5 with regard to
allowed discharge to Publicly Owned Treatment Works ("POTW").
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Applicable requirements of the Clean Water Act ("CWA")(33 CFR
303) specifically regarding ambient water quality standards,
CWA 402.
Applicable Texas Ground Water Protection Act of 1989, as it
specifies the ground water protection goals for the state.
Chemical-specific around Water Remediation ARARs:
Applicable RCRA requirements, 40 CFR 264.94 with regard to
ground water protection standards (equivalent to Federal
Maximum Contaminant Levels ("MCLs"); 0.05 ppm arsenic
allowed).
Location-specific Ground Water Remediation ARARs:
Applicable RCRA requirements, 40 CFR 264.18 for location of
TSD facility in a 100-year floodplain and also general
applicable requirements for protection of floodplains, 40 CFR
6, Appendix A.
Cost—Effectivenesst
The selected soil remedy is cost-effective because it has been
determined to provide overall effectiveness proportional to its
costs, the net present worth value being $13,766,352. The
estimated costs of the selected soil remedy are within an order of
magnitude (less than three times) of the costs associated with
onsite capping of the contaminated soils, and yet the selected
remedy assures a much higher degree of certainty that the remedy
will be effective in the long-term due to the significant reduction
of the toxicity and mobility of the wastes achieved through in-
situ vitrification of heavily contaminated soils prior to capping.
While the selected soil remedy effectively reduces the hazards
posed by contaminants at the site by essentially treating an
estimated 95% of arsenic-contaminated soils onsite, its costs are
only 18 percent of the alternatives involving total excavation and
offsite disposal or in-situ vitrification of the entire site,
$76,004,379 and $76,709,543, respectively.
The selected ground water remedy is also cost-effective, its
present worth value being $4,824,388. The estimated costs of the
selected remedy are less than the cost associated with installation
of a slurry wall ($6,196,038) but are more than the costs
associated with directly discharging the extracted ground water to
a POTW ($957,830). However, it is unlikely that an untreated
discharge would have been allowed by the POTW due to contaminant
discharge requirements. Furthermore, the selected remedy is the
most protective due to the concentration of the contaminants
through treatment on site and the eventual disposal of these
contaminants in an approved manner.
*
101
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Utilisation of Permanent solutions and Alternative Treatment
Technologies (or Resource Recovery Technologies) to tftf HlTTJ"1""1
pxtent Practical;
EPA has determined that the selected soil and ground water remedies
represent the maximum extent to which permanent solution and
treatment technologies can be utilized in a cost-effective manner
for source control and remediation at the Crystal Chemical site.
Of those alternatives that are protective of human health and the
environment and comply with ARARs, EPA has determined that the
•elected soil and ground water remedies provide the best balance
of trade offs in terms of long-term effectiveness and permanence,
reduction in toxicity, mobility, or volume achieved through
treatment, short-term effectiveness, implementability, costs, also
considering the statutory preference for treatment as a principal
element and considering State and community acceptance.
The in-situ vitrification technology affords the most permanent and
long-term effective solution to the contamination problem posed by
the Crystal Chemical site. The rationale behind selecting the
partial implementation of the technology over treating the entire
site is that the partial approach will effectively treat 95% of the
arsenic found on the site. The increase in the cost associated
with treating the entire site to capture or destroy the remaining
5% does not afford any more protection given that the site must be
capped and the capped maintained in perpetuity.
The other two treatment technologies investigated as possible
remedies for the site were soil washing and
solidification/stabilization. Both of these treatment technologies
when implemented on a complete scale (i.e., is over the entire
site) and the excavation and offsite disposal alternative are more
permanent because all of the contamination is being addressed.
However, the long-term effectiveness of the two treatment
technologies has not been proven. The treated waste continues to
leach unacceptable concentrations of the contaminant into the
environment. The problems associated with offsite disposal
(alternative A-l) outweigh the benefits of onsite treatment.
The in-situ vitrification technology, again, affords the best
solution when addressing the reduction of toxicity, mobility, or
volume through treatment. When, again, considering the selection
of the partial over the complete treatment, the additional costs
associated with implementing the complete treatment, thus
addressing the other 5% of the contaminants onsite, provide for
very little added protection. The other treatment technologies do
address reduction of toxicity, mobility, or volume, however, the
disadvantages of the alternatives associated with the technologies
outweigh the benefits.
Admittedly, when discussing short-term effectiveness,
implementation, and the costs associated with the selected remedy,
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other alternatives better meet these criteria. Almost all of the
alternatives satisfy the short-tern effectiveness criteria better
than the alternatives utilizing the -in-situ vitrification
technology, however, the short-term- risk associated with
implementing the selected remedy are of a manageable magnitude,
therefore, do not tip the scale greatly when balancing all of the
criteria. The implementation of the selected remedy, too, will
not be accomplished as easily as would be implementing the
alternatives utilizing the solidification/stabilization technology.
There is, to date, only one commercial vendor that can perform the
technology. However, the implementation problems do not appear to
outweigh the benefits of this technology. Lastly, the selected
remedy is the not the least expensive alternative investigated nor
is it the most expensive. The least expensive alternative calls
for capping the site without any treatment of the contaminated
soils. The second least expensive alternative calls for
implementing solidification/stabilization technology on the most
heavily contaminated soils. The selected remedy falls third in the
hierarchy of expense. The cost savings of implementing one of the
less expensive alternatives do not outweigh the fact that these two
less costly alternatives are less protective of human health and
the environment. Cost is not a trade-off for protection.
The selected ground water remedy satisfies the long-term
effectiveness and permanence, reduction of toxicity, mobility, or
volume through treatment, and iaplementability criteria better than
all of the other alternatives investigated for possible solutions
to the contamination problems on the Crystal Chemical site. It
does, however, fall behind alternative B-la, which calls for the
extraction and discharge of contaminated ground water to a POTW,
when discussing the short-tern effectiveness and cost criteria.
The short-term risks associated with the selected ground water
remedy are composed of possible exposure of workers and the
community to the ground water treatment system, however, these
potential risks are easily controlled, therefore all but
eliminated. Again, the cost associated with implementing the
selected ground water remedy is more than the cost associated with
implementing the less protective extraction and discharge
alternative. However, discharge without treatment may not be
possible, and cost is not a trade-off for protection.
Preference for Trea^Bfp^ as a Principal Element?
By treating heavily contaminated soils with the in-situ
vitrification process, and by removal of contaminants in extracted
ground water through chemical precipitation, filtration, and ion
exchange, the selected soil and ground water remedies address the
principal threats posed by the site through the use of treatment
technologies. Therefore, the statutory preference for remedies
that employ treatment as a principal element is satisfied. Thus,
the selected remedies meet the statutory requirement to utilize
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permanent solutions and treatment technologies to the maximum
extent practicable.
XI. DOCUMENTATION OF SIGNIFICANT CHAKGBB
The Proposed Plan for the Crystal Chemical Company site was
released for public comment in June 1990. The Proposed Plan
identified soils alternative A-5 (Partial in-situ Vitrification and
Capping), and that ground water alterative B-lb (Extraction,
Treatment, and Discharge to a POTW, the Harris County Flood Control
Channel, or reinjection) as the preferred 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 no significant changes to the remedy, as it
was originally identified in the Proposed Plan, were necessary.
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ATTACHMENT 1
RESPONSIVENESS SUMMARY
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CRYSTAL CHEMICAL COMPANY SITE
RESPONSIVENESS SUMMARY
The Community Relations Responsiveness Summary has been prepared
to provide written responses to comments submitted regarding the
Proposed Plan at the Crystal Chemical Company site. The summary
is divided into two sections.
Section J. Background of Co^j1'jfiitv Involvement and Concerns. This
section provides a brief history of community interest and concerns
raised during the remedial planning activities at the Crystal
Chemical Company site.
Section II. ffmnnflrv of Mai or C.PBffl?nt? Received. The comments
(both oral and written) are presented and EPA's responses are
provided.
I. Background of Community Involvement and Concerns
The community has been involved on a limited basis with
activities at the Crystal Chemical Company site. They
attended the open houses and the public meeting in limited
numbers, however, approximately 300 people receive mailings
from EPA on Crystal Chemical Company site activities. The
comments that were received from the local community
concentrated on possible inconveniences that they might
experience during and following the completion of the remedial
action.
II. Summary of Major Comments
Public notice announcing the public comment period and the
public meeting was published in the Houston Post on May 27,
1990. The Proposed Plan was distributed through the mail in
early June 1990, and the public comment period began on June
11, 1990 and ended on July 11, 1990. Informal Open Houses
were held in the Houston area on two separate occasions, April
10 and June 5, 1990. The public meeting was held on June 21,
1990 at the Alief High School in Alief, Texas. The purpose
of this meeting was to discuss all the proposed alternatives
and EPA's preferred alternative for the Crystal Chemical
Company site.
Approximately 30 people attended the public meeting and 7
people asked questions or made comments. Four sets of written
comments were received during the public comment.
A. Comments and Questions received during the public meeting.
EPA received oral comments during a public meeting which was held
at the Alief Elsik High School in Houston, Texas, on June 21, 1990.
Comments pertinent to EPA's proposed plan of action are summarized
below followed by EPA's response. A full account of the public
meeting can be found in the public meeting transcripts* which are
documented in the Crystal Chemical Administrative Record.
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COMMENT - MR. ED WINTER (Citiien):
Mr. Winter made several comments and recommendations:
1) indicating that he had observed "plenty, of fish" in the flood
control ditch that runs adjacent to the site; 2) the flood control
ditch should be cleaned to more effectively handle the flow of
water; and, 3) Westpark should be open for traffic.
IPX RESPONSE:
EPA concurs that there are fish in the flood control ditch.
Relative to cleaning the flood control ditch, improvements will be
made to the ditch as part of the remedial action. Additionally,
the Harris County Flood Control District is responsible for
maintaining the flood control channels. With respect to Westpark
Drive, EPA will seek to have the contamination problems associated
with right-of-way remediated in an expeditious manner in order that
the entire east-west artery (Westpark Drive) can be placed into
service by the City of Houston.
COMMENT MR. WINTER (CITIZEN):
Wanted to know if the kids [found to have increased arsenic levels
in their urine samples] hadn't been playing on some yards that had
been sprayed with an arsenic-containing weed control, possibly in
addition to or instead of any contact with contaminated soils near
the site?
RESPONSE - DR. JEAN BRENDER (Texas Department of Health):
We [public health officials conducting the health study] asked the
parents of those children [included in the survey who lived and
played near the site] whether there had been any exposure to yards
and golf courses and other potential sources of contamination. And
we pretty much ruled out as many sources as we could.
COMMENT - MR. CLYDE BRAO6 (City of Houston Parks i Recreation):
Indicated that the City of Houston owned a piece of property south
of the Crystal Chemical Site. It is bounded by Harwin and the
common Harris County flood control drainage structure. His
question was what, if any, arsenic is in that ditch and at what
levels and should we be concerned in the development of that park?
Also, would EPA be willing to do further testing of the flood
control ditch?
EPA RESPONSE:
Based on the information provided in the Supplemental Feasibility
Study (p. 2-63) sediment in the drainage canal contains less than
60 ppm arsenic in samples collected north and northwest of the
site. Whereas, the sediment samples collected west of the site in
the drainage canal contained 278 ppm arsenic and south of the site
(downstream) arsenic, was detected at 28 ppm. Apparently, the
concentrations of arsenic decrease below levels of concern [from
a public health standpoint] as you move downstream to the park
referenced in Mr. Bragg's comment. However, EPA will require
further testing of the flood control ditch during remedial action
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to verify previous testing and further define the situation. Also,
upon completion of the remedy EPA will require stream sediment
sampling to evaluate the effectiveness of 'the remedy to eliminate
the migration of arsenic-contaminated soils.
COMMENT - MR. JIM MURPHY (WestChase Business Council):
Mr. Murphy indicated that his organization had the following
comments and recommendations: 1) they did not object to the
remediation plan established by EPA, they thought it was a good
plan; 2) their main concern was with the timing of cleanup (i.e.
they would like activities to proceed as quickly as possible); 3)
they felt that maybe there was an opportunity to clean-up the
Westpark right-of-way separate from cleaning up the whole site; 4)
the organization is concerned with the public awareness and the
possibility of exposure; 5) they were pleased to see that there is
off-site excavation of contaminated soil; and 6) urge EPA to
include continued testing of both water [surface water and ground
water] the soil, and maybe even the air, as part of the
remediation plan.
EPA RESPONSE:
EPA welcomes the support of the Westchase Business Council relative
to the agency's proposed plan for remedial action (i.e. partial in-
situ vitrification and ground water pump and treatment). Timing
is also of great concern to EPA. As an agency we are committed to
initiating remedial action as quickly as possible. After the
remedy is selected (evidenced by the signing of the Record of
Decision) EPA may provide the potentially responsible parties an
opportunity to negotiate the terms of a settlement to perform the
remedy. Such a settlement would be phrased in a Consent Decree and
entered in the local Federal District Court. If settlement can not
be reached, EPA will explore its enforcement options to ensure that
remediation is completed in a timely manner. This might include
EPA doing the work itself and seeking cost reimbursement from
potentially responsible parties. If settlement is achieved and the
Consent Decree signed by the Court, the remedial design can be
initiated and upon approval by EPA, the remedial action can begin.
With respect to Westpark Drive, EPA is committed to cleaning up the
right-of-way on an expedited schedule. Currently we are developing
the means by which contaminated soils would be removed from the
right-of-way in an effort to provide access to the City of Houston
for completion of the road.
Related to public awareness, EPA does its best to get the word out
to the public. Fact sheets, open houses, workshops, and community
meetings are used as tools by EPA to keep interested persons
informed of site activities. A toll free number (1-800-533-3508)
has been established: by EPA so that interested citizens can call
to obtain specific information to specific inquiries. At the
completion of the public health study conducted by the Agency of
Toxic Substances and Disease Registry, the Texas Department of
Health, and the City of Houston, a meeting was set up*with local
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residents to discuss the results. EPA also held two open houses
before the formal public meeting for the purpose of answering
questions concerning the site. We also intend on maintaining close
communications with the public as we proceed with the project.
Finally, EPA will require testing of ground water and air during
the remedial action and will further evaluate the need for surface
water testing.
COMHZNT - MR. ED WHITER (Citiien) :
Have they found any [arsenic] in the air? What is the worry about
Westpark — not letting people go through Westpark?
•PA RX8PON8I:
Initial air monitoring found inorganic arsenic levels at the site
ranged from 0.005 * 0.050 micro-grams per cubic meter (Table 5-
17, site Investigation Report, January 1984). Based on this study,
the air contaminant pathway does not appear to be presenting a
public health threat (Health Assessment, ATSDR, February 1988).
Regarding Westpark Drive as it passes by the Crystal Chemical site,
there are some highly contaminated soils on the Westpark right-
of-way that, if people came into contact with these soils, might
present a public health threat. These contaminated soils have to
be removed from the right-of-way to the level prescribed by EPA
(30 ppm) before the agency will consider the area safe for public
use.
COKMZNT - MR. JOHK ELDRIDGE (Andrews i Kurth representing McKinney
Properties which is owned by Texas Commerce Bank)
McKinney owns a nearby property at 11111 Wilcrest Green, it is a
recently acquired commercial office building. Mr. Eldridge
expressed the following concerns: 1) In general terms, his client
is interested that the site be cleaned up adequately to protect
human health, the environment and the long-term property values in
the neighborhood; 2) that the site be cleaned up expeditiously; 3)
that the clean-up process not affect nearby properties any more
than necessary; 4) that interested persons such as McKinney and the
bank be apprised of the process appropriately so that they can
participate when decisions that will affect them are being made and
that the appearance of the site be maintained as adequately as
possible during the remedial process; 5) with respect to the
remedial alternatives presented in the Supplemental Feasibility
Study (SFS), the bank considers options A-l, A-8, A-9 and A-10 to
be unacceptable; and, 6) based on their review of the SFS, they
would be inclined to support the vitrification remedy. With regard
to whether it's the partial or the complete option on
vitrification, soil .washing or solidification, cost would be a
concern.
They believe that the cutoff of 300 parts per million arsenic in
soil would be protective of human health and the environment, and
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that it would not be necessary to clean up to 30 parts per million
or below in order to accomplish those necessary goals.
With regard to ground water options they felt that the EPA's
recommendation was appropriate. They do believe that ground water
remedial efforts are necessary given the arsenic levels that are
indicated. They did have some concerns about how expeditiously the
ground water can be remediated. The sooner the better. If that
involves the reinjection process, they would prefer that.
Concerning air emissions, whether it be fugitive emissions from
dust or gases from the in-situ vitrification process, or even
potential emissions or odors from the waste water treatment
facility that would be constructed, those are going to be concerns
for neighboring property owners. And they ask that EPA take, very
seriously, those items into account in adopting your technology
requirements and implementing the remedy.
One final point, and this may be more important than some of the
others even for the nearby neighbors of this facility. That is
truck traffic patterns. There will be trucks and equipment moving
through the area as this process begins and gets implemented. And
the routes that those trucks take can have quite an impact on the
neighborhood and on the streets. So they urge the agency to
carefully consider traffic patterns and restrict some of those
times when the traffic will be moving through the area.
EPA RESPONSE:
Superfund law mandates that selected remedies must be protective
of human health and the environment. EPA's preferred methods of
treatment (i.e. partial in-situ vitrification and ground water pump
and treatment) satisfies this mandate. On the other hand, EPA has
very little control over the impact that a Superfund site might
have on surrounding property values. Property values depend almost
entirely on peoples' perception; therefore, they will plummet if
people perceive the area as unsafe, whether it is or is not safe.
If enough hysteria develops about the area being unsafe, property
values suffer greatly. EPA can only make assurances to the public
that the selected remedy will ensure protection of human health and
the environment.
As indicated in a previous response above, timing is also of great
concern to EPA and we are committed to initiating remedial action
as quickly as possible. Furthermore, the EPA has a great deal of
interest in ensuring minimal impact to any adjacent property owner.
We don't anticipate any problems during remedial action, however,
we are always willing to listen to concerned citizens or other
groups and will try to accommodate there concerns. Information
concerning the progress of the project will be released by EPA
through various mechanisms such as newsletters, facts sheets,
informal open houses, workshops, and community meetings. We
welcome input from any party throughout the remediation process.
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EPA's preferred alternative for soils is partial in-situ
vitrification. This remedy includes removing arsenic-contaminated
soils from offsite areas that exhibits concentrations greater than
30 ppm. This standard is based on EPA methodologies for
determining long-term exposure to arsenic-contaminated soils. EPA
feels that for areas outside the fence line of the site, 30 ppm is
a safe level. Treating onsite soils that exceed 300 ppm takes care
of an estimated 95 percent of the arsenic on the site. EPA
believes that this rationale provides a cost effective remedy that
effectively treats the contamination problem and provides a safe
and protective solution.
Relative to the comments on the preferred alternative for ground
water, EPA appreciates the support and concurs with the notion that
the quicker the remedy can be completed the better.
As far as air emissions are concerned, EPA is equally concerned
about air emissions during remedial action. The in-situ
vitrification process itself includes devices that would control
emissions. Additionally, we would include some type of
particulate sampling during remedial action to ensure that we don't
create a problem during soil disturbance activities. In most
remedial actions you will have dust suppression activities on-
going to minimize any such problems.
Regarding truck traffic, EPA will be willing to listen to any party
who may have a particular concern. If a problem arises, we will
work very hard to resolve the issue.
COKMZNT - MR. v. F. HILL (Halliburton Environmental Technologies):
1) How widely has in-situ vitrification been used? 2) How many
successful applications of that particular technique have been
made? 3) How many unsuccessful attempts have been made [using in-
situ vitrification], and what lead to the unsuccessful application?
4) Was the solidification test (carried out during the feasibility
study) done by a firm that specializes in solidification, that does
it for their living? 5) If evidence could be supplied to you that
this material can be successfully stabilized, would that affect
your selection of the remedy?
IPA RZSPOXff:
Battelle Memorial Institute is exclusively licensed by the U.S.
Department of Energy to perform in-situ vitrification. Geosafe
Corporation, primarily owned by Battelle, holds the exclusive
sublicense to perform in-situ vitrification commercially. Geosafe
and Battelle combined have performed more than 70 tests of various
scales for the Department of Energy and other clients. At the
Department of Energy Hanford site in Washington state, in-situ
vitrification has successfully treated soils contaminated with
radioactive wastes. In-situ vitrification has also been selected
for evaluation under EPA's Superfund Innovative Technology
Evaluation (SITE) Program. Currently, in-situ vitrification has
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been selected for use at three EPA Superfund sites. EPA has no
information related to any unsuccessful attempts at using this
technology.
The solidification tests performed during the Supplemental
Feasibility Study were conducted by vendors selected by the
potentially responsible parties. These parties had to invest a
great deal of money for soil samples to be collected and the tests
to be performed. It is in there best interest to use a reputable
vendor(s) to run the analyses.
The remedy selection process depends on an evaluation of nine
criteria, namely l) overall protection of human health and the
environment, 2) compliance with regulations (ARARs), 3) long-term
effectiveness and permanence, 4) reduction of toxicity, mobility,
or volume through treatment, 5) short-term effectiveness, 6}
implementability, 7) cost, 8) community acceptance, and 9) state
acceptance. Therefore, in response to the question, if there was
evidence of "successful" stabilization, would that affect EPA's
decision? EPA would have to evaluate the approach against the nine
criteria identified above. It is not as straight forward as
determining the success or failure of the treatment technology.
COMMENT - MR. STEPHEN WENTLAND (Citisen):
Mr. Wentland commented that he felt 30 parts per million was a good
cleanup level. He also inquired as to how much of a financial
burden it would be to get the arsenic down to even lover
concentrations and whether arsenic from the Crystal Chemical
Company has seeped into the drinking water supply.
EPA RESPONSE:
First, the financial demand of treating greater volumes of
contaminants is great. For example, EPA estimates that the cost
using in-situ vitrification over the entire site would increase the
cost (compared to partial vitrification) from $14 million to
approximately $76 million. Secondly, all of the drinking water
wells within a one-mile radius of the site were sampled in 1989 and
no contamination problems were evident.
COMMENT - MS. JULIE 8CHOENEBERG (Advocate Newspaper):
Asked where funding will come for these different [treatment]
alternatives?
EPA RESPONSE:
Our first approach will be to notify the various potentially
responsible parties of the opportunity to come forward and conduct
the remedy themselves, in which case we would negotiate a document,
referred to as a Consent Decree, that outlines what is to be done
in terms of the remedial 'action. The Consent Decree would be
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lodged in the Federal District Court. And during those
negotiations we would establish who would be paying for what
activities, both past and future.
If we do not receive any favorable response from responsible
parties, then we would evaluate our enforcement options. We could
perform the remedial action ourselves and try and recover our costs
from these parties through future legal actions. Or we could issue
a Unilateral Administrative Order to these parties essentially
ordering them to conduct the action. If they do not comply with
the Order then EPA can choose to conduct the remedial action itself
or can take legal action against the parties.
B. Comments and Questions received during the
period.
Comment:
Section I. General Comments.
"The NCP, however, supports selection of a remedy in the range of
10"* to 10'6."
Response:
Content noted. National Oil and laiardous Substances Pollution
Contingency Plan; Final Rule 55 Fed. Reg. 4« (March §, 19*0).
Note: All comments made by Southern Pacific Transportation Company
in Section II. pertain to their evaluation of the
solidification/stabilization technology. Subpart A. specifically
pertains to additional treatability studies on
solidification/stabilization studies that were performed under the
initiative of Southern Pacific Transportation Company and the data
was sent to EPA during the public comment period. This data is not
included in the Remedial Investigation/Feasibility Study ("RI/FS")
or Supplemental Feasibility Study ("SFS") reports for the Crystal
Chemical Company site.
Comment:
Section II. A. 1. pg. 7
"The laboratory analysis was performed according to Contract
Laboratory Program (CLP) procedures which included required
duplicate sample analysis, matrix spikes and matrix spike
duplicates. The matrix spike and matrix spike duplicate analysis
data are not included in the summarized data... however, they are
available upon request."
Response:
In order to certify compliance with CLP procedures and to document
the integrity of the data presented, QA/QC documentation as veil
8
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mm chain of custody reports, sample analysis request forms,
laboratory notes/logbook entries, and any other information that
is customarily required to ensure high quality data should have
been includad with tha submission of tha data.
Comment:
Saction II. A. 1. pg. 7
"Results from these treatability studies are included... Included
are the analytical data from untreated soil samples. As can be
seen from the results of treated samples, three vendors...were able
to reduce the leachable concentrations of arsenic to near 5.0 ppm."
Saction II. B. 1. pg. 13-14
"EPA's conclusion that solidification/stabilization does not meet
ARARs was based on Wastech data that has subsequently been refuted
by the more recent treatability data."
Section II. C. pg. 23
"The treatability data discussed above indicates that
stabilization/solidification will reduce the leachability of
arsenic to the same extent as [in-situ vitrification]."
Response:
This recent treatability study data was submitted during the
comment period, therefore, was not available during the initial
evaluation of the solidification/stabilisation technology.
Additionally/ in order to certify compliance vith CLP procedures
and to document the integrity of the data presented, QA/QC
documentation as veil as chain of custody reports, sample analysis
request forms, laboratory notes/logbook entries, mad any other
information that is customarily required to ensure high quality
data should have been included vith the submission of the data.
Hovever, according to the information that vas submitted to EPA,
in only one of seven samples, from these three vendors, had the
leachability of arsenic reduced to belov 5.0 ppm. The other
treated samples leached during TCLP testing. The samples leached
from 6.4 ppm to 24.0 ppm of arsenic after treatment. The other
seven vendors vere not able to reduce the leachability of arsenic
to acceptable levels after treatment, i.e., the samples leached
arsenic from C2.0 ppm to 410.8 ppm. Therefore, IPA disagrees that
the treatability studies vere as successful as the treatability
studies utilising the vitrification technology.
Comment:
Section II. A. 3. pg. 9
"As part of the treatability studies, the four vendors were
requested to provide information related to the process used to
treat the samples of soils and costs for full scale treatment."
Response:
Complete cost information associated vith the implementing the
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solidification/stabilisation technology from the new vendors were
not included, therefore, EPA cannot evaluate this technology for
its cost-offectiveness.
Comment:
Section II. B. 2. pg. 14
"Southern Pacific disagrees that [Land Disposal Restrictions]
should be ARAB*. In the Preamble to the NCP, EPA identifies the
issues that are being considered by EPA at the national level in
the debate over whether LDRs should be ARARs at CERCLA sites.
These issues include whether replacement of treated residuals in
the proximate area should constitute [sic] placement, whether LDRS
will support CERCLA's carefully articulated and balanced approach
to remedy selection, and whether an entire CERCLA site should be
considered one unit."
Response:
Many discussions continue on the national level. lovever, this not
the proper forum for commenting on IPX's position regarding the
applicability of RCRA Land Disposal Restrictions ("LDRs") at a
CERCLA site. The commentor should have addressed any such comments
to the proposed revisions to the NCP, rather than to IPA's Proposed
Plan for the remediation of the crystal Chemical site. IPA's
position on the applicability of LDRs at CIRCLA sites is discussed
at 55 red. Reg. 46 at s7sa-s7co, and this position was applied to
the Crystal Chemical Company site.
Comment:
Section II. B. 2. pg. 21
"To the extent that solidification/stabilization would need a
[treatability] variance, however, EPA should set forth the
information in the SFS to support a variance,..."
Response:
EPA has selected a technology and a remedy that meets or exceeds
the treatment standards that are required, therefore, no
treatability variance is required.
Comment:
Section II. B. 3. pg. 21
"Southern Pacific also disagrees that the EP Toxicity level for
arsenic should be an ARAR."
Response:
Arsenic is a designated toxic pollutant, 40 CPR 401.15, and is
a characteristic hazardous vaste if it exceeds 5 mg/1 when
subjected to the EP Toxicity Test, 40 C7R 2«1.24. Additionally,
by-product salts that are generated in the production of caeodylic
acid and of monosodium methylarsenate ("MJXA") are a listed
hatardous vaste (K031), 40 C7R 261.32. XflMA was one the major
10
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product* that crystal Chemical Company produced and is a
contaminant on the site. All corresponding regulatory requirements
are ARARs.
Comment:
Section II. B. 3. pg. 22
"EPA, in fact, expressly stated in its recent toxicity
characteristic rulemaking that the characteristic levels are not
cleanup standards."
Response:
IPA has never stated that arsenic IP Toxicity characteristic levels
are the "cleanup" standards for the Crystal Chemical.
Comment:
Section II. B. 4. pg. 22
"The SFS discussion of this ARAR [surface impoundment closure
requirement] is premised on the conclusion that soils redeposited
into an excavation would be characteristic for arsenic."
Response:
The ARAR for surface impoundment closure was included in the 8?s
because the four surface evaporation ponds on the site were not
closed as required by the RCRA regulations during the EPA Emergency
Removal Actions, therefore, the surface impoundment closure
requirement is an applicable requirement for the crystal Chemical
site during the remedial action.
Comment:
Section II. C. pg. 23
"[T]his alternative [solidification/stabilization] should be
considered irreversible since the soils will be separated from any
leaching fluids or subsurface conditions by a subsurface cap."
Response:
BPA is unclear as to what the commentor means by a "subsurface
cap." However if by a "subsurface cap" the commentor meant a
subsurface liner, a liner was not evaluated in the 878 nor is it
considered necessary with the in-situ vitrification remedy selected
in this Record of Decision.
Comment:
Section II. C. pg. 24
"In several other RODS...EPA has concluded that solidification is
permanent and is capable of locking contaminants both physically
and chemically into an unreactive product."
Section II. G. pg. '30
"A review of RODs involving cleanup of arsenic in soils also
indicate EPA's confidence in this [solidification/stabilization]
technology."
11
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Response:
•PA Region « is not disputing the effectiveness of the
solidification/stabilisation technology, but it believes that in-
•itu vitrification is more effective in this case. The selection
of the in-situ vitrification technology is being Bade following
completion of a study to identify all possible treatment
technologies and alternatives that could address the contamination
problem at the site. Solidification/stabilisation was oae of the
treatment technologies that was evaluated for the site. Although
•PA acknowledges that the solidification/stabilisation technology
has been proven effective oa other sites aad specifically those
sites ooatamiaated with arsenic, «PA, based oa specific data
generated for the Crystal Chemical Company site aad based OB the
Agency's general knowledge of the teehaology, has ia good faith
proposed a remedy for ths Crystal Chemical company site that
utilises the in-situ vitrification technology.
Comment:
Section II. D. pg. 25
"EPA's proposed Plan of Action at page 6 incorrectly describes this
criterion as requiring a reduction of toxicity, mobility and
volume. The NCP carefully follows the statutory language in
requiring a reduction of toxicity, mobility, or volume."
Response:
Comment noted.
Comment:
Section II. D. pg. 26
"While the SFS claims that volume of the material will increase
(see SFS at 5-46), actually the volume of hazardous substances will
remain the same. Section 121 (b) of CERCLA, 42 U.S.C. [Section]
9621, requires that the volume of only hazardous substances, not
the entire waste material, be taken into account."
Response:
•PA disagrees with this interpretation of the CXRCLA statutory
provision. The statutory provision states in part "...treatment
which permanently and significantly reduces the volume, tozicity
or mobility of the hasardous substances/ pollutants, and
contaminants [emphasis added] ...** The *CP, 40 C7R
300.430(e) (f)Uii) (DM3) (55 *•«• *«g. 4( at ••4*) specifically
states that certain factors shall be considered when evaluating the
reduction of tozicity, mobility, or volume through treatment, one
of the factors is "[t]he degree of expected reduction in tozicity,
mobility, or volume of the waste due to treatment or recycling aad
the specification of which reduction(•) are occurring;** Further,
the RCRA "Derived-from Rule" ia 40 CTR 2«1.3(c) (2) states that any
solid waste derived from the treatment, storage, or disposal of a
listed RCRA hasardous waste is itself a listed hatardous waste
regardless of the concentration of hazardous constituents.
Furthermore, the RCRA "Mixture Rule", 40 CFR 261.3(a)12), states
12
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that vhen any solid vaate and a listed hasardous vast* are mixed,
th« entire mixture is a listsd hazardous vast* and that mixtures
of solid vasts* and characteristic hasardous vast*s ar* hasardous
if th* mixture exhibits a characteristic of hatardous vast*.
Comment:
Section II. G. pg.29
"Lime is th* only contaminant that would b* «xp*ct*d to interfere
with the stabilization treatment process for soils at the Crystal
site. As discussed previously, the addition of lime [during an EPA
Emergency Removal Action] to the former pond areas increased the
leachability of arsenic.1*
Responses
•PA is unfamiliar vita th* basis for Southern Pacific
Transportation Company's conclusion that th* addition of lime to
arsenic contaminated soil incr*as*s th* arsanic's l*achability.
Zn r*vi*ving available literature on th* fat* and transport of
arsanic in soil syst*ms, EPA vas unabl* to locat* any r*f*r*nc* to
th* addition of hydroxyl ions causing incr*as*d solubility of
ars*nic. Th* solubility of sodium m*than*arsonat* is 57 g/ioo cm
in vater, vhich is mor* than 4,000 tim*s gr*at*r than that of
calcium arsenate vhich has a solubility of 0.013 g/100 cm3 in
vat*r. Additionally, comments provided to BPA by Idvin A. woolson
on behalf of the Voluntary Purchasing Group, inc. indicate that the
addition of lime during removal action vould not have increased the
leaehability of arsanic. Or. Woolson stataa that th* arsenic
b*com*s fixed in environments rich in iron and hydroxyl ions. Dr.
Woolson is th* author or co-author of 71 publications dealing vith
arsenical chemicals and their fat* and transport in the
environment.
Comment:
Section II. G. pg. 31
"With respect to the Midco [a Superfund site in Gary, IN - Region
4] ROD, EPA rejected [in-situ vitrification] in favor of
solidification partly because [in-situ vitrification] had not been
demonstrated in a full scale application and the commercial
availability of the equipment was limited."
R*spons*:
Th* CERCLA statute states in part that "[t]he President may select
an alternative r*m*dial action meeting th* objectives of this
subsection vh*th*r or not such action has b«*n achieved in practice
at any other facility or sit* that has similar characteristics"
Section 121 (b)(2) of CIRCLA, 42 U.I.C. lection »«21. Th* in-situ
vitrification technology vas s*l*ct*d b*caus* it is th* most-
•ff*ctiv* technology. *valuat*d for th* Crystal Chemical site.
Additionally, vitrification has been identified as the best
demonstrated available technology ("BDAT") for arsenic
characteristic vasts and for X031 (by-product salts generated in
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the production of MfiXA and eaeodylie acid) listed vast* (55 red.
Reg. 10< At 225SC to 225*1).
Comment:
Section II. H. pg. 31
"While the pretreatment step to reduce the pH of the wastes will
increase the costs over those taken into account in the SFS, the
costs of solidification/stabilization are still much less than
those for [in-situ vitrification]."
Section II. H. pg. 33
"Information on cost also dictates that
solidification/stabilization is cost-effective."
Responses
The eest difference between the alternative involving partial
implementation of solidification/stabilisation and the partial
implementation of in-situ vitrification is $5,435,151, the in-situ
vitrification being the more expensive alternative. IPX cannot
evaluate the cost-effectiveness of the solidification/stabilisation
technology using the pretreatment step because the eest figures for
such a scenario have not been provided to IPX. Vote that cost vas
not the deciding factor between choosing the selected remedy over
the partial implementation of the solidification/stabilisation
technology.
Comment:
Section II. H. pg. 32
"At the Midco II site, EPA specifically rejected [in-situ
vitrification] in favor of solidification/stabilization partly
because it vas more expensive and 'would do little to further
reduce risk.'... At the Palmetto Wood Preserving site in South
Carolina, the ROD ... eliminated [in-situ vitrification] during the
screening process because it was 'expensive, [had] high energy
requirements, [and was] unproven1."
Response:
Again, IPX is not disputing the effectiveness or the
appropriateness of this technology (i.e.
solidification/stabilisation) at other sites. The in-situ
vitrification technology has proven to be overall the best
technology for the Crystal Chemical site.
Comment:
Section III. A. pg.35
"[The] Section Chief of EPA Waste Treatment Section, advised A£S
on November 1, 1989 that EPA had only one pilot scale study of
arsenic, which was performed at Montana State University, to
support the BOAT for K031 wastes... The information currently
available to.us indicates that the Montana study show that arsenic
migrates in an uncontrolled manner."
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Response:
Data generated from a study conducted at the Montana Collage of
Mineral Science and Technology ("Montana Tech"), not Montana state
University, vas used in developing the BOAT concentration-based
treatment standard of S.« mg/1 for arsanic in a IP tozieity
leachate. Mr. L.O. Tvidvell of Montana Tech conducted some
immobilisation and leach tests of arsenic-bearing copper smelter
flue dust. X summary paper on MX. Tvidvell*• vork vas published
Bearing Copper Smelter Flue oust", Vol.5, pp 297-303, IMS).
The Montana Tech tests vere designed to assess the leachability of
arsenic from stabilised flue dust. Stabilisation processes
included melting and chemical stabilisation. The study did
demonstrate how arsenic can be effectively dissolved into a molten
iron silicate slag matrix vithout volatilisation of arsenic oxide.
Following their reviev of Mr. Tvidvell*s paper and based on
discussions vith Mr. Tvidvell, oeosafe Corporation has informed EPA
that it does not believe that the subject flue dust vork is at all
applicable to the potential use of in-situ vitrification at the
crystal Chemical site. The flue dust test vork identified that
arsenic leachability vas a functiuon of pH. Such vould not be the
case for in-situ vitrification because the matrix in vhich the
arsenic is immobilized is a silicate vith strong covalent and ionic
bonds, and this type of chemical structure is very resistant to
leaching by vater in a vide range of pH levels. The results of the
Montana Tech tests, hovever, do not indicate that arsenic during
the process vould migrate avay from the treatment center in an
uncontrolled manner, relieving the in-situ vitrification process,
the arsenic is immobilised in a silicate matrix vith strong
covalent and ionic bonds making uncontrolled migration unlikely.
Comment:
Section III. B. pg. 36
"EPA has not compared the radioactive properties of the soils
treated in the four large scale applications to the Crystal soils."
Response:
BPA is assuming that the commentor is questioning vhether the
physical properties of the soils contaminated vith radioactive
vaste vhere the four large-scale applications of the in-situ
vitrification technology has been applied, and the physical
properties of the soils at the Crystal Chemical company site ver«
compared. BPA is assuming that this is vhat the commentor meant
because there are no radioactive vastes at the crystal Chemical
Company site.
The textural variability of soils has very little to do vith the
ability to vitrify it using the in-situ vitrification technology.
The textural differences betveen the soils at the Hanford
Department of Energy site vhere the in-situ vitrification
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technology baa been implemented on a large scale and the aoila at
tha Crystal Chemical aita, aeeording to Oeoaafa Corporation are
great. However, the important faetora in determining the aueoess
of the technology are the eoneentrationa of the ozidea of ailicon,
aluminum, calcium and the monovalent alkali earth elemeata, with
the eoaeentrationa of ailieon and the alkali aarth elementa being
the most important factors. Tha data provided to BPA from Oeoaafe
Corporation illustrates that the eoneentrationa of these important
elements are similar for tha Cryatal Chemical site soils and for
tha Hanford site soils.
Comment:
Section III. B. pg. 36
"Southern Pacific retained Geoaafe to conduct a second treatability
teat on the Crystal soils... A review of that report highlights
the uncertainties associated with this technology. Geosafe could
not account for 50 percent of the arsenic in this treatability
test. Without any supporting data, it assumed that the unaccounted
50 percent arsenic fraction was locked in the vitrified glass.
Geosafe failed to explain why 17.5 grama of arsenic out of the
total 51.4 grams was determined to be in the resultant glass when
25.9 grams could not be identified through the analytical results."
Section III. B. pg. 37 gjL
"In the second treatability test, migration of arsenic to the f|P
uncontaminated area, which is beyond the so-called 'projected1 6.7
grams, could also have occurred."
Reaponae:
According to Geoaafa Corporation, the data provided to Southern
Pacific Transportation company in the second treatability atudy
supports the conclusion that tha 25.» grama of arsenic ia contained
in the glass product. As shown in the report, the arsenic
eoneantrationa in tha glass and sintered regions ranged from 96 to
1800 mg/kg. Therefore, there is an uneven distribution of the
arsenic throughout the glass matrix after the in-situ vitrification
process. Based on the statistical variation in the concentration
of arsenic in the glaaa, the araenie could eaaily be preaant and
not be found even with additional sampling. The only way to ahov
100% confidence ia the concentration of the arsenic ia the glass
is to analyse the eatire glass aad aintared matrix; i.e., to create
a homogeneous mass by even distribution of the arsenic (that is now
immobilised in the matrix) prior to analysis.
The amount of arsenic believed to be ia the adjacent soils is based
upon the aaaa concentration of arsenic found in tha adjacent soils
averaged over tha upper • inches of aoil and within 2 inches of the
vitrified Bass, according to Oeoaafe Corporation. Since arsenic
cannot exiat in the vapor atate below a teaperature of C15*c, it
is reaaonable to assuae that if the arsenic is there it will be
detected. Therefore, without analysing all of the aoil within tha
test container for the second treatability study which contained
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approximately 1000 pounds of Material, 100% confidence in the
statistics cannot be verified.
Comment:
Section III. B. pg. 37
"Although the chemical nature of the arsenic is not well known, it
can be reasoned that most is in the form of various metal arsenates
or arsenious (ic) acid chemisorbed on clay. Virtually all will
thermally decompose to volatile oxides of arsenic well below the
anticipated soil fusion temperature. Arsenic should, therefore,
migrate awav from the fusion zone and form a condensation halo in
the surrounding cooler soil or be recovered in the vapors emanating
from the perisphere of the treatment zone. In the former instance,
arsenic will neither be stabilized nor recovered."
"In the field, this [arsenic] migration could result in additional
groundvater or soil contamination. This fraction could also be
present in the 'Isothermal Band,1 which was not specifically
checked and which could perpetually migrate without recourse to
treatment."
Response:
Arsenic sublimes into its vapor state at <1S*C, and according to
Oeosafe Corporation/ can exist between the ilS'C isotherm and melt
during the entire period of vitrification. Since the vapor is
thermally buoyant/ it continuously moves toward the surface of the
melt due to its density-related buoyancy, as was the ease in the
treatability studies conducted on soils from the Crystal Chemical
site. Therefore/ any arsenic in the vapor state that escapes the
melt would be captured by the off-gassing system.
Based upon previous tests performed on arsenic-contaminated soil
and upon the anomalous soil conditions present in the second
Crystal Chemical test/ Oeosafe believes that no statistically or
environmentally significant amount of arsenic will diffuse outward
or downward from the treatment area. Since the soils at the
Crystal Chemical site are predominantly clay and clay-containing
sands and possess significant water saturation/ the pathways
through which arsenic vapors can diffuse are minimal.
However/ in the second treatability study/ Oeosafe Corporation
documented large voids in the soils while they were being prepared
for treatment. These large voids allowed arsenic vapors to diffuse
uninhibited into the soils adjacent to the melt. As a result,
arsenic was found next to the vitrified mass. Oeosafe Corporation
did state that the voids which caused the diffusion of the arsenic
are not likely to be> found at the site since the soil at the site
has not been disrupted in the manner that the soil was disrupted
for the treatability test. However/ if conditions exist that allow
for such a diffusion of arsenic out into adjacent soils/ the design
implementation of the technology can allow for overlapping of the
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treatment areas BO that any arsenic that may have diffused from the
treatment araa vill ba incorporated.
Comment:
Section III. B. pg. 38
"EPA, however, does not address why "placement" would not occur
when volatile arsenic recovered in the off-gas system is recycled
back to contaminated soil for further treatment."
Response:
As discussed in rat's Cuperfuad LDR Ouide IS, "Determining When
Land Disposal Restrictions (LDRs) Are Applicable to CIRCLA Response
Actions" (OIWBR 9347.3-05M) (July !»§»), placement is triggered
when wastes are "(e]xcavated from an [area of contamination]/
placed ia a separate unit, such as aa iaeiaerator or taaJc that is
within the [area of contamination], and redeposited late the same
[area of contamination]." The operative word ia this statement is
"excavated.11 With an in-situ treatment technology, placement under
LDRs does not occur when wastes are treated in-situ. fee LDR Quide
*5. Additionally, the LDR regulations state that "movement within
the unit does not constitute placement" and that "[p]lacement does
aot occur whea waste is coasolidated within aa [area of
contamination]..." MCP 55 Fed. Reg. 4< at §75t. Recycling of the
arseaic captured ia the off-gas system back for treatment,
therefore would aot trigger placement because it is consolidation,
Comment:
Section III. B. pg. 38
"The SFS has also failed to address how the reinjection would
comply with underground injection control requirements under the
Safe Drinking Water Act."
Response:
The only restraints or requirements that have been identified to
date as impacting the iajectioa of the treated ground water or of
any water from actions associated with the remedial actioa are the
requirements under the UIC Program, 40 CFR 144. The proposal for
the injection of treated ground water or scrubbed water will comply
with aay applicable requirements.
Comment:
Section III. £. pg. 40
"[T]he combination of extremely high temperatures and toxic gases
(arsenic sublimes at 613*C) may require greater levels of
protection to workers. The possibility of exposure to danger could
include explosion or rapid evolution of gas and molten product due
to unknown pressure build-up of entrapped steam, and is of major
concern due to lack of full scale testing."
Section III. E. pg. 41
"The application of large-scale electrothermic fusion is a physical
situation characterized by a moist foundation, or substrate is
18
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inherently dangerous."
Section III. E. pg. 41
"The hood control system could also fail as a result of a breakdown
of the vapor sump fan or scrubber pumps, or the plugging of the
scrubber... Emissions of toxic gases, vapors, and dust may not be
limited to the hooded area."
Response:
The pyrolysis products produced by the in-situ vitrification
treatment process, according to information supplied to EPA by the
Oeosafe Corporation, combust immediately upon reaching the surface
because they are so hot. These gases never have an opportunity to
accumulate, therefore, there is no danger of explosion.
The buildup of pressure in the in-situ vitrification treatment
process is not possible unless a pressurised container is present
in the treatment volume. During the treatment process, most of the
water is vaporised adjacent to the base of the molten ione since
the predominant melt growth is downward. When the water is
converted to steam, it is buoyant. Because there is nothing to
contain or pressurise the steam in this environment, the steam and
any other associated vapors immediately rise in the molten liquid
as bubbles. These bubbles, according to Geosafe Corporation, rise
slowly through the melt, and when they reach the surface, release
their contents under the off-gas hood.
The in-situ vitrification off-gas treatment system is equipped with
a completely independent, self powered back-up off-gas treatment
system in case of a failure of the main system. Zn the event of
a failure of some type, power to the electrodes is immediately and
automatically shut down. At the same time the diesel-powered
generator starts and supplies power to the back-up off-gas
treatment system which continues to process the off-gas. This
entire process occurs automatically thus minimising the chance for
hood pressurisation.
Gases generated during the in-situ vitrification process will find
their way to the surface via the path of least resistance. This
path is either through the melt as bubbles form along side the melt
in the dry sone where gas permeabilities are highest. Escape of
gas outside of the hood, according to Geosafe Corporation, has
never been detected. During the implementation of the remedial
action at the Crystal Chemical site, EPA will require air
monitoring to ensure safety to human health.
Comment: , -
Section III. E. pg. E. pg. 42
"Geosafe's .estimates of the melt progress of 1 to 2 inches per hour
may not apply to engineering scale equipment and is not proven in
any full scale application."
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Response:
The rate of melting (l to 2 inches per hour) is based upon full
seal* operations monitored by thermocouples, according to Oeosafe
Corporation. This rate can be controlled by variation of the power
level applied to the system. Oeosafe1s treatability test system
was designed to duplicate the measured full-scale pover density.
Therefore/ tests performed with the engineering-scale system are
representative of a full-scale application. There is no reason to
assume that conditions during engineering scale operations are
different than those for full-scale operations.
Comment:
Section III. 6. pg. 44
•According to Davy Environmental, the scale-up problems in actual
full-scale work could be formidable."
Response:
The only "problems" associated with applying the technology at
full-scale at the Crystal Chemical site, according to Oeosafe
Corporation/ are those which would be experienced with any mobile
technology such as damage to equipment in transit/ transport
permits/ assuring that utilities are in place upon arrival/ and
site security. The worst case scenario would involve severe damage
to the in-situ vitrification transformer in transit.
Comment:
Section III. G. pg. 44
"The Crystal site is located in the Houston area which experiences
high precipitation... Moreover, sudden or continuous heavy
precipitation would have a tendency to hinder [in-situ
vitrification], if not completely prevent [in-situ vitrification]
from being performed."
Response:
As a prudent operations policy/ the in-situ vitrification system
would be shut down for very heavy thunderstorms. However/ the
treatment process can continue during rainfall in most cases. The
concern is not related to lightning or other electrical phenomenon
but to general site safety.
Comment:
Section III. 6. pg. 44
H[S]oil moisture content of the tested Crystal sample was 22
percent by weight. Under field conditions, the moisture could be
much higher and thus lead to higher costs."
Section III. H. pg. 47
"The costs of treating the soils in the former pond areas were
provided at $225 to $240 per ton [for the in-situ vitrification
technology]. During the additional treatability tests completed
by Geosafe,...the costs for treatment increased to $280 to $305 per
ton."
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Section III. H. pg.48
"[I]ncreases in the soil moisture content results in increased
power requirements, thus increased cost."
Section III. H. pg. 48
"Portions of the site would require treatment of soils through the
15-foot water bearing zone. In order for the melt to go through
the 15-foot zone, the water would need to be evaporated. This
evaporation would require a significant increase in power
requirements. Geosafe did not take this factor into consideration
when developing its cost estimate. This factor will lead to an
increase in costs for [in-situ vitrification] treatment."
Response:
According to Oeosafe corporation, hydraulic conductivities of
aquifers or water-bearing tones >1 x 10"* em/sec, within tbe depth
range tbat in-situ vitrification is to be processed, will result
in water flow into tbe process area at rates wbicb will inbibit the
vitrification process. Tbis situation, bowever, does not preclude
tbe use of tbe technology. If tbis is tbe ease as it is at Crystal
Chemical, temporary dewatering measures in tbe treatment area must
be implemented. These temporary dewatering measures can include
installation of a slurry wall or sbeet pile, installation of
dewatering well points or tbe installation of well points where
slug material (i.e., slurried bentonite) would be injected to
inbibit tbe flow of water temporarily.
Qeosafe Corporation bas performed price sensitivity analysis for
moisture and bas determined tbat it bas tbe effect of approximately
fl.oo to $2.00/moisture weight percent/ton of waste.
Oeosafe Corporation acknowledges tbat tbere was an erroneous
statement made in tbe second treatability study. Tbe second
treatability study suggests that tbe increased cost per ton is
attributable to a bigber soil moisture content when in actuality
tbe soils moisture were approximately tbe same. According to
Oeosafe, tbe predominant factor which changed tbe unit price was
tbe assumed depth ef processing. The assumed depth of processing
used to estimate costs in the first treatability study was 24 feet,
whereas the second study assumed 12 feet. The cost of treatment,
according to Oeosafe, in inversely proportional (non-linear) to the
depth of processing because the treatment is a batch process.
Comment:
Section III. G. pg. 46
"Unlike solidification/stabilization involving an above-ground
process where the performance of the technology can be certified,
the in situ process roccurs in an uncontrolled environment where it
is impossible to certify the results."
Response:
verifying tbe effectiveness of the in-situ vitrification technology
21
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can be easily accomplished. During the process, the depth and
width of the vitrified mass is continuously monitored using on* or
more of several techniques including thermocouples, fiber optic
array/ seismic profiling and depth sensing with movable electrodes.
Dua to tba high resistivity of tha melt and tha behavior of
alaetrieal currant in this media, tha Bait alvaya forma a
symmetrical ahapa. onca tha proeaaa has baan completed,
Tarification of suecass can ba aoco«pliahad with a simple drilling
and boring tachniqua.
Conunant:
Saction IV. pg. 49
•Prior to tha full acala implementation of thia [ground vatar]
treatment system, additional tasting should ba parforaad to
demonstrate that this complete system will ba affactiva in treating
tha groundwater, especially with respect to tha polishing step of
ion exchange."
"With respect to the extraction of groundwater, further aquifer
teats are required to determine the potential affects of long term
pumping on groundwater levels and contaminant removal. These tests
should be completed prior to initiating the design of the
extraction and treatment system."
Response:
Tha Record of Decision for tba Crystal Chaaieal states that a
traatability study for contaminant removal from tha ground water
ahould ba conducted. Additionally, tha Record of Daeiaioa calls
for an onaita pilot atudy to be conducted during design in order
to fully investigate well placement and tha moat affective
extraction method, and to fully investigate the injection option.
Additionally, during the deaign phaae of thia remedial action, an
evaluation defining the relationship between the contaminated aoils
and the ground water will be conducted. From thia evaluation, the
effects of the contaminated soils on the ability for tha remedial
action for the ground water to meet the remedial goal of 0.05 ppm
of arsenic shall ba determined. The objective of the study will
ba to determine tha optimum depth to treatment, technically
feasible, that will enable the ground water to ba remediated to the
NCL within the shorteat practical timeframe.
Comment:
Section IV. pg. 50
"Throughout the STS, the O6M costs presented for groundwater
remediation alternatives B-la, b, c and d were stated as annual
costs when in fact these costs were present worth costs for over
a 30 year time frame....This point should be clarified throughout
the text of the SFS."
Response:
Comment noted.
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Note: All-comments made by Southern Pacific Transportation Company
in Section V. pertain to a memo dated March 20, 1990 written by Jon
Rauscher, EPA Region 6 Toxicologist, ,to the Remedial Project
Managers for the Crystal Chemical Company site regarding the risk
assessment basis for remediation goals.
Comment:
Section V. B. 1. a. Gastrointestinal Absorption from Soil. pg. 53
"The Rauscher memorandum applied the assumption of an arsenic oral
absorption fraction from soil of 0.05 (5 percent). The basis for
this assumption is unclear."
Response:
The arsenic oral absorption fraction from soil of e.os vas based
en a conservative default assumption given that aa assumption of
100% would be overally conservative and inappropriate. Metals,
like arsenic, tend to be poorly absorbed by the gastrointestinal
tract, therefore in the absence of chemical specific data, the
relatively conservative 5% absorption fraction vas used.
Comment:
Section V. B. 1. and 2. b. Oral Slope Factor, pgs. 54 and 56
"The current EPA oral slope for inorganic arsenic is 1.75
(mg/kg/day)' vs. 1.5 (mg/kg/day) (applied in the Rauscher
memorandum). This discrepancy should be corrected."
Response:
The slope factor used in the Rauseher memorandum vas not a
discrepancy, but vas based on risk assessment information available
at the time of the drafting of the risk assessment for the crystal
Chemical site. Admittedly, the EPA oral slope factor for inorganic
arsenic has undergone several modifications as aev toxicological
information has become available. However, the oral slope factor
for inorganic arsenic presented in the Crystal Chemical Company
Endangerment Assessment (1988) and TERRA, Znc.'s response to the
assessment vas 1.5 (mg/kg/day) . Therefore, for consistency the
Rauscher memorandum used this oral slope factor for inorganic
arsenic.
Comment:
Section V. B. 1., 2., and 3. c. Exposure Duration, pgs. 54, 56, 58
"The Rauscher memorandum assumes that exposure to soil at the site
occurs over an individual's entire (i.e., 70-year) lifetime. This
is in contrast with the average and reasonable maximum residential
exposure durations of 9 to 30 years, respectively, recommended by
EPA."
Response:
The average and reasonable maximum residential exposure duration
of 9 and 30 years, respectively, assumes daily exposure (365 days
per year). The Rauscher memorandum assumed a lifetime exposure (70
23
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years) with aa exposure frequency of 2 days per week tad 9 month*
per year.
The eoaaeator auggested an exposure duration of 30 years be applied
to the estiaatioa of mediation goals. lovever, the eoaaeator
used the aaae exposure frequency as tba Rauscher aeaoraadua. Tbis
azposura fraquaaey ia aot acceptable to IPX for a 30-year exposure
tiaefraae. Xf axposura duration of 30 yaara ia used, tba exposure
fraquaaey sbould ba scs days par yaar.
Comaant:
Saction V. B. 2. a. Surface Adharanea Factor, pg. 55
"The Rauscher aaaorandua appliad a aurfaca adharanca factor of 2.8
x 10 Kg/cm . Tha raaulta of a racant atudy conductad for EPA of
aoil adharanca factora in varioua aoil typaa indicataa that the
factor appliad in tha aaaaaaaant vaa a substantial overestimate...
We propose that tha mean adherence factor of 0.58 x 10"* Kg/cm2 is
a aore appropriate assumption to apply."
Respoase:
Tbe Rauachar aeaoraadua appliad aa adbareaee factor suggeated in
tba fuperfuad Sxpoaure Aaseaaaaat Maaual, April Itaa (OBITER
Directive i2§S.5-l), which was guidaaee ia affect at tha tiae of
the draftiag of the Badaagaraeat Asseasaeat for the Crystal
Cheaical site.
Comment:
Section V. B. 3. a. Air Arsenic Concentration from Contaminated
Soil. pg. 57
"The [Air Arsenic Concentration for Surficial Soil] applied in the
[Rauscher] memorandum was 3.7 x 10 Xg/m (» 370 nq/vr), with the
reference for this factor reported to be the Endangerment
Assessment. Upon reviewing the Endangerment Assessment, it appears
that this factor is actually a aoil concentration in air, rather
than an arsenic air concentration."
Respoase:
Coaaeat aoted.
Comment:
Section V. B. 3. b. Inhalation Slope Factor, pg. 57
"The current EPA inhalation alope factor for inorganic arsenic is
50 (mg/kg/day)M baaed upon a 30 percent absorbed dose. The
calculation of the inhalation human intake factor in the Rauscher
memorandum, however, vaa based upon a 100 percent absorbed dose...
On tha basis of this error the resultant inhalation risk estimated
is too high by a factor of 3.33 (i.e., I/.3)."
Respoaset
The SPA Endangerment Assessment for the Crystal Cheaical company
site was writtea ia July l»aa under the guidaaee of the Superfund
Public Baalth Evaluation Maaual ("8PEEK"). Tae propoaed
-*
24
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remediation goals of 15.0, 1.5, and 0.15 mg/kg for the excess
lifetime cancer risk levels of 10 , 10 , 10 , respectively. These
levels were subsequently adjusted to account for site specific
exposure patterns. The adjusted remediation goals vere 300, 30.0
and 3.0 »g/kg for the excess lifetime cancer risk levels of 10"*,
10 , 10"*, respectively (Reitman memo, September ltS8) .
The commentor is correct in identifying that the current inhalation
slope factor is adjusted for absorption, however, the inhalation
slope factor for the original end*ngerment assessment did not taJct
into account this adjustment because 8FK2JC did not differentiate
between administered dose and absorbed dose. Therefore, for
consistency the Rauscher memorandum used this inhalation slope
factor.
Although the Rauscher memorandum states that adjustments vere made
to account for not only site specific conditions but also tc
account for changes in risk assessment guidance from SPHZM to the
Risk Assessment Guidance for Super fund, Human Health Manual, Volume
1, Part A ("RAGS11}, the memorandum vas incorrect. The adjustments
to the excess lifetime cancer risk levels vere made prior to the
RAGS guidance, therefore, the citation of RAGS guidance is not
appropriate in this instance.
Comment:
Section v. c. l. a. Ingestion of Contaminated Soil. pg. 59
The commentor, based on differing assumptions, calculated a KIF frr
ingestion.
Response:
EPA does not agree with the exposure duration used in the
calculation. The commentor suggested an exposure duration of 30
years be applied in the calculation. However, the commentor used
the same exposure frequency as the Rauscher memorandum. This
exposure frequency is not acceptable to EPA for a 30-year exposure
timeframe. If the exposure duration of 30 years is used, the
exposure frequency should be 365 days per year.
Comment:
Section V. C. 1. c. Remediation Goal Based on Ingestion and Dermal
Exposure Combined, pg. 61
Section V. C. 1. d. Remediation Goal Based on Ingestion Exposure.
pg. 61
The conmentor, based on differing assumptions, calculated
remediation goals based on ingestion and denial exposure combir.ei
and on ingestion exposure.
Response:
The EPA target risk range is 10'6 or one in one million to 10"* or
one in ten thousand excess lifetime cancer risk. If this risk
range proposed by the commentor were used, the remediation goal
25
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based oa a combined iagestioa aad dermal exposure, and for an
ingestioa exposure vould ba from 1C mg/kg. to 1C20 mg/kg aad from
it mg/kg to 1790 mg/kg, respectively. EPA doaa aot agraa with the
paraaetera within which thaaa exposure aeaaarioa wara formulated
aor doaa IPA agraa with tha basic aasumptioas uaad whaa calculating
thaaa valuaa. However, tha 30 ppm araanic offaita remediation goal
aad tha 300 pp» araaaic oaaita treatment laval do fall withia the
oommeator's risk raaga.
Comment:
Section V. D. pg. 63
Commentor requests that EPA adopt a remediation goal for the site
at the upper end of the acceptable risk range, i.e., at the 1C*
level instead of the 10 level.
Reapoasa:
The NCP, 40 C7R 300.430(e) (2), states la part that for kaown or
suspected carciaogaaa *'[t]he 10"* risk level shall be used aa tha
point of departure for determining remediatioa goals..."
Therefore, the 10 risk level is the startiag point whan
determining remediation goals aad departure from this 10** is to be
based oa site-specific or remedy-specific coaditions. IB the case
of Crystal Chemical where the 10 to 10"' raage is from 3 to 300
ppa, the 10'5 risk level was determined to be acceptable. For a
complete explanation of tha remediation goals, refer to the SUMMARY
o? BITE RISKS Section of this Record of Decision.
Comment:
Section V. D. 1. pg. 65
"The current maximum contaminant level (MCL) for arsenic ir.
drinking water is 50 ng/l. This level corresponds to an excess
lifetime cancer risk of one in 400, assuming the EPA-derived CPF
is correct. Although ve understand that the MCL may be lowered,
a 10-fold lowering will not reduce risk below one in 4,000. This
suggests either a major shift in EPA policy regarding levels of
tolerable risk for arsenic or substantial doubt within the agency
about the reliability or the CPF."
Respoase:
"BPA's Superfuad program uses IPA's Orouad-Watar Protection
Strategy as guidaace whea determiaing tha appropriate remediation
for coataminatad grouad water at CERCLA sites... For Class I and
II grouad waters, preliminary remediatioa goala are geaerally set
at maximum contaminant levels...*1 55 Fed. Reg. 44 at §732. HCLs
are eaforceable limits sat as close to maximum coaceatration limit
goals (XCLOs) as feasible/ however other factors are takea into
coasideratioa (e.g., availability of treatment technologies an<2
cos- of compliaace) '. MCLGs are aoa-eaforceabla health-baaed limits
set at a level at which BO adverse effects oa humaa health exist.
The MCLG for arsenic is sere (0). Tryiag to equate a site-
specific excess lifetime caacer risk of a eoatamiaaat to ita ground
water MCL is inappropriate.
26
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Comment:
Section V. D. 2. pg. 66
"It is not at all clear why EPA's CPF might be in error."
Section V. D. 2. pg. 67
"Given the considerable uncertainty related to the cancer potency
factor for arsenic, and the strong evidence that it likely
overestimates substantially the cancer risk associated with lew
level exposures, a relatively high acceptable risk level 15
supported when this CPF is applied."
Response:
The cancer unit risk for arsenic provided in the Integrated Risk
Information system baa undergone extensive peer review by the IPX-
wide Carcinogenic Risk Assessment Verification Endeavor ("CRAVE";
workgroup and represents an Agency consensus.
Comment:
Section V. D. 3. pg. 68
"Arsenic at the Crystal Chemical site is primarily in organic
forms...which are generally considered less toxic than the
inorganic salts. The cancer potency factors that EPA has
developed, however, apply to inorganic arsenic, and would therefore
likely overestimate the cancer potential of the arsenic fonts a-
the Crystal Chemical site."
Response:
Arsenic speciation is important, however/ organisms can transfers
arsenic from a less toxic form to a more toxic form. EPA
approaches risk conservatively and, therefore calculated risk for
the Crystal Chemical Company site using the most toxic fora of
arsenic.
Corjnent:
Section V. D. 4. pg. 68
"The remediation goals for the Crystal Chemical site were estimated
based on the assumption that future land use will be strictly
residential... [T]he total potential arsenic exposure to ar
industrial receptor would likely be substantially less than that
to a lifetime resident."
Response:
Although a site may be used for commercial or industrial use or
located in an area that is predominantly commercial or industrial
at the time of remediation and institutional controls or site-
restrictions may be placed on the sits, there are no assurances
that the arsa land uss vill remain the same. The City of Houston
does not at this time have soning ordinances, therefore EPA takes
a conservative approach and calculates risk so that all potential
scenarios ars taken into consideration.
27
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Comment:
Section V. D. 5. pg. 69
"Ingested inorganic arsenic is associated with a nonfatal form of
skin cancer. On the basis of the nonfatality of this tumor type,
EPA has issued guidance that a 10-fold higher acceptable risk level
may be justified."
Response:
IPX if unclear as to what specific guidaaoa tha oommentor is
rafarriag to, however, avaa if IPX assumad a 10-fold highar risk
level, this would aot affact IPX's remediation goala for arsenic
at tha Crystal Chemical Company sita.
Commtats received from Waco yiaaaeial Corporation
Question:
"We would like to Know if the fact that your preferred plan of
action calls for all off-site soils to have up to 30 parts per
million (ppm) of arsenic would limit any future activities we might
have for our property; that is, if that would preclude us frer.
having apartments or single family residences, ate."
Raspoasa:
Tha 30 ppm arsaaie contamination laval was determined to represent
a 10 azcass lifetime eaacar risk laval. IPX requires that
remediation levels ba sat some where between a 10'4 aad a 10*' cancer
risk. Tor tha Crystal Chemical sita that traaslatas iato a range
from 300 ppm to 3 ppm. Tha 10 (i.e., 30 ppm arsenic) remediation
laval was determined to raprasaat a safa health-based action level.
Therefore, this would aot preclude aay future use of tha offsite
areas affected by tha remedial action, once the contaminated soil
has baan removed from the property. For a complete discussion of
the remediation goals for tha site see Section v. aCMMxav or BITE
RISKS ia this Record of Decisioa.
Question:
"It appears to us that through the remediation process, which
includes capping, there would be no arsenic present on the surface
of the Crystal Sita, but your plan calls for leaving 30 ppm on off-
site properties. We wonder why you would leave higher levels of
arsenic off-site than would be present after the remediation of the
site itself."
Raspoasa:
Tha remediation goals for tha Crystal Chemical sita wara addressed
ia aa earlier questioa from Waco financial, however, the
ramediatioa of tha sita itsalf has othar factors iavolvad. Tha cap
that will b« constructed on tha sita aftar tha in-situ
vitrification treatment process has baaa completed will serve two
purposes. Tha maia purpose of the cap is to prevent the continued
infiltration of water (i.e., rain) through tha soils containing
28
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residual amount• of arsenic contamination. This cap will eliminate
the potential migration pathway from the residual arsenic
contaminated into the ground water. The second purpose of the cap
ia to prevent direct contact with the treated material on site.
The in-«itu vitrification technology baaically Belts the
contaminated soil. When it cools/ it resembles glass. Although
the structural integrity of the mass is not in question, EPA would
prefer not to leave the treated mass exposed to the elements.
Question:
"The proposed cap appears to be 5 feet in thickness and we wish t =
know exactly what sort of grading or drainage provisions will be
nade so that our tract will not be adversely be affected."
Response:
During the design phase of the remedial process/ the engineering
design specifications required to ensure proper onsite and offsite
drainage will be determined. A public workshop at the end of
design will be conducted so that EPA can discuss and you can
evaluate the impacts of the drainage control systea.
Question:
"Addressing the treatment of the underground water, we wish tc fcr.ov.
if it would be necessary for any pumps to be placed or. our
property, and if our property's use will be restricted in any wa/
during the treatment of the underground water."
Response:
Again, during the design phase of the reaedial process for the
Crystal Cheaical site, a study will be conducted on the site to
investigate the most effective method for extracting the
contaminated ground water. The extraction method will include the
placeaent of wells/ however, the location of these wells won't be
determined until the site is Bore thoroughly investigated. It is
possible that wells Bay need to be located on your property,
however, their placeaent would not be finalised until we have
contacted you and obtained your permission. If EPA does place
extraction or reinjection wells on your property, the restrictions
on your use of your property would be limited to ensuring that any
activities that you planned for the property would not adversely
affect the wells or the ground water flow in the area.
Question:
"We wish to ascertain as to whether or not the treatment of the
Crystal Site will create any nuisances, such as noise, dust, odcr,
etc."
Response:
Given that offsite soils contaminated with arsenic will need to be
excavated and relocated back on to the site, heavy equipment such
as bulldozers and trucks will be used and there is a possibility
of dust emissions during the excavation. However, precautions such
29
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a* dust suppression and heavy equipment traffic control vill be
implemented during the remedial activities onsits to minimita any
problems.
Comments received fryg Xjdrew t Kurth
Comment:
"The arsenic and other contaminants at the site should be cleaned
up adequately to protect the environment and the health and safety
of those working and living nearby."
Response:
Protection of human health and the environment is a mandate of
•uperfund lav. IPX*a preferred method of treating the
contamination problems at the Crystal site satisfies this mandate
and should satisfy your concerns.
Comment:
"The site should cleaned up expeditiously.
Comment noted.
Comment:
"The clean-up project should be designed and implemented so as net
to affect nearby property owners or residents any more than
absolutely necessary."
Comment noted.
Comment:
"Interested persons should be kept informed of EPA's work and the
remedial process so that they may participate adequately to protect
their interests."
Response:
Fact sheets, open houses/ workshops/ and community meetings are
used as tools by EPA to keep interested persons informed of sita
activities. A toll free number (1-SOO-533-350S) has been
established by EPA so that interested citisens can call to obtain
specific information to specific inquiries.
Comment:
"Alternatives A-8 (capping only), A-9 (no action) and A-10 (limited
action) for soil contamination are unacceptable to McKinney because
they would not provide sufficient "source control" of the
contamination."
Comment noted.
Comment:
"Alternative A-l (excavation/o-ffsite disposal) is Unacceptable
30
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because massive soil excavation and transportation through the
neighborhood would have major negative impacts on the health a.-.d
safety of people living and working nearby (e.g.. due to true*
traffic and contaminated dust)."
Comment noted.
Comment:
"EPA's determination to clean or remove soil that is contaminate!
with arsenic at levels above 300 ppm appears to be reasonable.11
Response:
Actually, IF* vill be excavating all offaita aoila contaminated
with araanic above 30 ppm, and vill ba treating all aoila with the
in-aitu vitrification treatment procaaa that ara contaminated with
araanic greater than 300 ppm.
Comment:
"Alternatives A-2 (vitrification) and A-4 (soil washing) would take
roughly twice as long to implement as Alternatives A-:
(solidification), A-5 (partial solidification), A-6 (partial
solidification) and A-7 (partial soil washing), and are therefore
less desirable."
Comment noted.
Comment:
"EPA has determined that in situ vitrification substantially
reduces the likelihood of arsenic leaching to the groundwater >as
compared the post-solidification leaching). To the extent that
this critical determination is accurate, vitrification would appear
to be the preferred alternative."
Comment noted.
Comment:
"EPA should carefully evaluate and plan for the movement cf
construction vehicles in the neighborhood. The transportation
routes should avoid residential and commercial properties such as
McKinney's whenever possible."
Response:
EPA vill make every attempt during the implementation of the
remedial action to inconvenience everyone aa little aa poaaible.
Comment:
"Of the groundwater,remedial alternatives, B-3 (no action) and B-
4 (limited action)' are unacceptable because they do not provide
source control and do not prevent or reverse offsite migration cf
contamination. Alternative B-2 (slurry wall) would be intended tc
prevent further migration but would not reduce the contasinatic.-
levels."
31
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Comment noted.
Comment:
"Groundwater remediation alternatives B-la (extraction, discharge
to POTW) and B-lb (extraction, treatment, discharge to surface
water) appear to be reasonable and supported by the information
contained in the administrative record. The difficulty cf
discharging to a POTW appears to constitute a basis for selecting
option B-lb over B-la."
Comment noted.
Comment:
"Air emissions from onsite activities, especially fugitive dust and
gases from the groundvater treatment plant, must be stringently
controlled and carefully monitored."
Response:
EPA will implement actions to minimise air emissions and will
monitor for air emissions during all phases of the remedial action
pursuant to 40 CFR so.
Comments received from Mr. Steve Sheffield
Comment:
"I am of the understanding that there are not l, but :.
contaminated aquifers (one at 15', one at 35') - your report only
addresses one - the shallow one."
Response:
The Record of Decision addresses both the 15' and 35' water-
bearing tones at the Crystal Chemical Company site. Collectively,
they are referred to as the shallow water-bearing tone since they
are hydraulically interconnected. Additionally, the Record of
Decision calls for a more thorough investigation of the deeper
water-bearing sones and calls for their remediation if warranted.
Comment:
"Children do play in the immediate area. Adults also frequent this
area,... On more than one occasion, I've kicked several kids our
from inside the fence (on the site)."
Response:
SPA fenced the perimeter of the site and posted the fence with.
warning signs documenting that the site is a haiardous waste site.
The public in the area has been notified of the haiards of the site
through BPA's community relations outreach. Although IPA has
undertaken actions to prohibit unauthorised entry to the site, it
is acknowledged that there may be some unauthorised entry.
32
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Comment:
"[Regarding the 5 specific potential pathways of exposure at the
site listed [in the proposed plan], 15 "[ingestion of contaminated
fish from the flood control ditch] is virtually impossible...
Also, no one ingests the shallow ground water (from the 15'
aquifer), so this route of exposure is virtually impossible."
Response:
IPX and the Agency for Toxic Substances and Disease Registry
approach health assessments and exposure scenarios conservatively.
The five specific exposure scenarios are potentials and are
identified as such, it has been documented that people have been
seen fishing in the Harris County Flood Control Channel, therefore
BPA «ust assume that they may eat whatever they catch. The is1
water-bearing tone, because it is hydraulically interconnected with
the 35* water-bearing tone and meets the Class ZIb aquifer flov
potential/ constitutes a potential public water source. Therefore,
it must be considered a potential exposure pathway.
Comment:
"My biggest problem with your plan of action isn't the plan itself,
but what your numbers that you're using are based on. For example,
you are using western US arsenic [concentrations] as backgrounds -
it is a well-known fact that soils in the west are naturally cue-
more rich in arsenic than soils in the east... I think you shc-lz
have used arsenic [concentrations] from the eastern US as
backgrounds. This would provide us with more natural background
numbers, and would provide the people who live out near Crystal
with more protection."
"Removal of off-site soils to a [concentration] of 30 ppm is net
enough! 30 ppm of [arsenic] can cause a lot of problems in the
environment. Besides, the 30 ppm is based on the background
[concentration] of arsenic in western soils,..."
Response:
The soil remediation goals for the Crystal Chemical site are risk-
based generated numbers and are not based on naturally occurring
background levels of arsenic in either the western or eastern
soils. The 30 ppm arsenic offsite contamination level was
determined to represent a 10'* cancer risk level. BPA requires that
remediation levels be set some where between a 10 and a 10~* cancer
risk. Tor the Crystal Chemical site that translates into a range
from 300 ppm to 3 ppm. The 10 (i.e., 30 ppm arsenic) remediation
level was determined to represent a safe health-based action level
and was deemed appropriate mince background mean arsenic levels
found in natural soils is 6.1 and 4.8 ppm in western and in eastern
soils, respectively. Therefore, there is not a significant
difference in the mean concentration of arsenic detected in western
and eaatsrn soils. Per a complete discussion of the remediation
goals for the site see Section V. SUMMARY OP SITE RISKS in this
Record of Decision.
33
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Comment:
"I don't understand how you are going to deal with vitrifying the
soil between the aquifers. The soil is contaminated at the site
down to 40 feet; how will you deal with getting at the deeper soil?
How do you vitrify through an aquifer?
Response:
The in-situ vitrification technology at this time is limited in its
effective treatment depth. To date, in-situ vitrification has been
affectively used to treat contaminated soils to a depth of 1C feet.
However, at the time of the implementation of tha technology, the
affective treatment depth may be graatar. Regardless, the depth
limitation of tha technology is an acceptable limitation to BPA
because of tha seleetad ground" vatar remedy. additionally,
saturated soils do not inhibit the vitrification treatment process,
though it does make it more oostly. Zf it is determined that
treatment mist be done below the permanent water table to ensure
the effectiveness of the total remedy and it is technically
feasible to do so, then soae sort of dewatering may be required to
extend the depth of treatment.
Comment:
"I believe that the treatment alternatives that you've chosen are
probably the best that you've got and seem to make sense. I
question the figures and concentrations that you are using, though.
I think they are biased and unsound. I really don't think 30 ppr
should be left outside the site, but I could probably live with the
95% of all the arsenic on the site being vitrified as long as the
other 5% is guaranteed contained by the multi-layer cap."
Response:
The multi-layer cap will be constructed over the entire site once
the soils treatment has been completed. The site will require
long-term 04M and the cap will have to be maintained in perpetuity.
Comments received on behalf on voluntary Purchasing Group. Inc.
Comment:
INTRODUCTION pg. 4
"The ponds were emptied of water, and the site sealed with plastic
and capped with a clay layer by EPA under an Emergency Action in
1983/1984 era."
Response:
The evaporation ponds contained coo,000 gallons of wastewater with
an average concentration of arsenic of 15,000 ppm. This material
was pumped and disposed. The IPX Emergency Removal Action
commenced in September 1981 and was completed in February 1983.
Comment:
The author of the comments, Edwin A. Woolson, Ph.D., suggests that
34
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a remedial plan that "includes treating selected portions of
arsenic laden soils with ferrous sulfate, reworking some surface
soils on-site to facilitate surface runoff management, building a
cap, and constructing a parking lot/building to isolate
contaminated soils" be implemented at the Crystal Chemical Company
site.
Response:
Solidification/stabilisation technology was evaluated during the
course of completing the supplemental Feasibility Study for the
•ite. specifically/ the addition of ferroue eulfate a* the
solidification/stabilisation agent was not explored during the
treatability studies. Therefore/ its appropriateness cannot be
evaluated.
Comment:
Dr. Woolson proposes remedial action arsenic-contaminated scil
levels different from EPA. "Threshold concentrations for arser.ic
in a soil are suggested to be set at 0 to 200 ppm (acceptable tc
leach in place; not phytotoxic) , 200 to 1,5000 ppm (stable ir.
native soils; no need for isolation unless at surface), 1,500 tr
5,000 ppm (stable in native soils; recommended for isolation), ar.d
greater than 5,000 ppm (appear stable in native soils; recommer.de::
for chemical stabilization and isolation)."
Response:
EPA's remediation goals for the arsenic-contaminated soils at the
Crystal Chemical company site are risk-based numbers and are not
based on the stability of the arsenic in a soil matrix.
Comment:
"CZRCLA requires that the Site be placed under institutional
control if any contamination remains after completion of the
Remedial Action... However, permitting this land to remain fallc-
would also be disadvantageous to the continued economic growth cf
the surrounding property, and might tend to diminish the value cf
any adjoining land."
Response:
CZRCLA does require that the a review of the remedial action occur
"no less often than each 5 years after the initiation of such
remedial action to assure that human health and the environment are
being protected by the remedial action being implemented" if the
remedial action results in any hasardous substances, pollutants,
or contaminants remaining at the site/ CERCIA Section 121(c), 42
D.8.C. Section 9621. Such is the case with the selected remedial
action for the site and it would also be the case with the
implementation of the remedial action proposed by Dr. Woolson. In
addition to the 5 year review, because of the implementation of a
ground water remedy, site access and land use restrictions would
be enforced until the ground water remediation goal was. met, which
could take as long as 30 years, furthermore, the implementation
35
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of BPA's selected remedy as well as in the case of the remedial
action proposed by Dr. Woolson, requires that a multi-layer cap be
constructed over the site following completion of the soils
treatment. Zf the site were allowed to be used as a parking lot
or as the foundation for a building, special and maybe very costly
site preparation would be required. Additionally, the site would
have to be maintained in such a way as to not compromise the
integrity of the multi-layer cap and to ensure that the treated
soils remain intact and protected fro* exposure.
Any remediation of the Crystal Chemical company site should improve
existing conditions. IPA's job, however, is to protect human
health, welfare, and the environment, not to ensure that the value
of property surrounding a C1RCLA site either increases or decreases
in value.
Comment:- Mr. Halliburton, on behalf of his company, commented that
he concurred that in-situ vitrification "can be used effectively
to remediate soils contaminated with heavy metals", however, he
felt that solidification/stabilization had not been given a
"comprehensive evaluation." Mr. Halliburton offered, on behalf cf
his company, to perform treatability tests at not cost to EPA.
Response:
The selection of this remedy is being made following completion of
a study to identify all possible treatment technologies and
alternatives that could address the contamination problem at the
site. Solidification/stabilisation was one of the treatment
technologies that was evaluated for the site. Although EPA
acknowledges that the solidification/stabilisation technology has
been proven effective on other sites and specifically those sites
contaminated with arsenic, EPA, based on specific data generated
for the Crystal Chemical Company site and based on the Agency's
general knowledge of the technology, has in good faith proposed a
remedy for the Crystal Chemical Company site that utilises the in-
situ vitrification technology. Therefore, KPA will not be
conducting any additional treatability tasting for the site. KPA
did, however, appreciate the offer of conducting additional
treatability studies.
C. Comments Received from Texas Water
TWC Comment:
"Section 300.430(f)(1)(ii)(B) of the National Contingency Pla:
(NCP) requires that on-site remedial actions selected in a ROD zus'
36
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attain those applicable or relevant and appropriate requirements
(ARARs) that are identified at the tine of ROD signature ... The
maximum contaminant level (MCL) for arsenic of 0.05 mg/1 is an ARAR
for the ground water...feasibility study (FS) ... fail to
comprehensively evaluate the range of available source control and
ground water remedial actions necessary to ensure compliance with
this ground water ARAR."
SPA Response:
The MCP citation in question deals with the "attainment of ARARs."
The argument as to whether the SF8 "comprehensively evaluates the
range of alternatives necessary to ensure compliance" with the
ground water ARAR, is a matter of opinion which is net shared by
IPA.
According to IPA guidance (i.e. Guidance on Remedial Actions for
Contaminated Ground Water at Superfund Sites, December 1988), tbe
Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA), as amended by the Superfund Amendments and
Raauthorisatioa Act (SARA) principally requires that remedial
actions protect human health and the environment and meet ARARs.
This requirement is essentially reiterated in the MCP.
Examination of the 8F8 will reveal that there are ten (10) source
control alternatives and four ground water alternatives, that
survived initial screening, for consideration of use at the site.
BPA'a preferred alternative of partial in-situ vitrification (for
the source) and pump and treat (for the ground water) satisfy the
requirements of both the statute and the MCP. Relative to the
attainment of ARARs, the ground water alternatives described under
the "Extraction and Treatment" scenarios will have a goal of
meeting the 0.05 mg/1 MCL for arsenic (which is the ARAR), as
discussed in the Section 5.3.1.2 entitled "ARARs Compliance."
These discussions are also carried forward in the Record of
Decision.
TWC Comment:
The [S]FS does not satisfy the requirement of Section
300.430(e)(9)(iii)(C)...to assess the long-term effectiveness ..."
EPA Response:
Section 300.430 (e) (9) (iii) (C) of the HCP establishes the procedures
set forth by EPA to perform the detailed analysis of alternatives
in the feasibility study, specifically the evaluation of each
alternative against the nine criteria (i.e. (1) overall protection
of human health and the environment, (2) compliance with ARARs, (3)
long-term effectiveness and permanence, (4) reduction of toxicity,
mobility, or volume through treatment, (5) short-term
effectiveness, (C) implementability, (7) cost, (8) state
acceptance, and (9) community acceptance.
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The NCP requires that in evaluating alternatives for "long-term
effectiveness" the following factor* be "considered" as
appropriate: (1) magnitude of residual risk remaining after
treatment; and, (2) adequacy and reliability of controls necessary
to manage treatment raaiduala and untreated waatee. EPA's
evaluation of the alternative* in the IF8 eompliaa vith the NCP.
For example, BPA*s preferred alternative (A-3 - in Situ
Vitrification/Kulti-layer Cap) in lection 5.2.S.4 of the 878 (page
$•39) entitled "Long-Term Effectiveness nfl FtrBMfBfff" indicates
that "the magnitude of risk ... vill be be lev the 10"* increaaed
cancer [risk] level. The remaining aourcea of inhalation and
direct eontaet riak from untreated (deep) soils following the
remedial action vill be insignificant ... ftudiea have suggested
that the vitrified soils, however, vill retain their physical and
chemical integrity in excess of 1000 years." The §78 goes on to
say that the "adequacy and reliability" of the treatment technology
has been demonstrated thorough numerous bench* and pilot-seal*
testa. Relative to the controls necessary to manage treatment
residuala and untreated wastes/ EPA proposed the use of a cap to
reduce the potential for migration of contaminants from the site
and to minimise any direct contact threat. Maintenance activities
are also proposed in the 8F8 and the Record of Decision to ensure
proper operation of the remedy. Institutional controls
(restricting site use) are propoaed in the Record of Decision to
further ensure proper operation of the remedy and also to reduce
the probability of any direct contact threat vith contaminant
residuals. Finally, the 5-year reviev mandated by the Buperfuad
statute vill provide EPA an opportunity to monitor the long-term
effectiveness of the remedy.
TWC Comment:
"The available documents fail to adequately consider the
relationship between the extent of the source control remedial
action and the ability to restore ground water at the site to the
required level."
"These soil remediation levels were not based on an evaluation of
the soil arsenic levels that will allow the MCL for arsenic to be
achieved in ground water ... there is no analysis in ... the TS to
demonstrate that the selected soil remediation level will allow
the ground water to be adequately restored."
EPA Responae:
The eommentor is correct in pointing out that the soil remediation
plan does not consider the relationship betveen the extent of
source control and the ability to restore the ground vater. EPA's
preferred remedy ia comprised of tvo components, vhich together
are conceived to address both the arsenic contaminated toils (the
aource) and the contaminated ground vater. During the design phase
of the remedial action, an evaluation vill be conducted to assess
the relationship betveen the contaminated soils and- the ground
vater. From this evaluation, the effects of the contaminated soils
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on the ability for the ground water remedial action to achieve the
remediation goal of 0.05 mg/1 of arsenic .shall be determined. The
objective of the study will be to determine the optimum depth of
•oil treatment, technically feasible, that will enable the ground
water to be remediated to the NCL within the shortest practical
timeframe.
In response to the second comment, Section 300.430 of the NCP
mandates that remedies be selected that eliminate, reduce, or
control risks to human health and the environment. To help meet
this mandate, 1PA has developed a human health evaluation process
as part of its remedial response program. The process of gathering
and assessing human health risk information is described in IPX
guidance entitled "Risk Assessment Guidance for Superfund, Volume
1, Human Health evaluation Manual (Part A)", December itt». The
risk assessment for the Crystal Chemical site eaa be found in
Appendix D of the 878 (Volume II). Soil remediation levels
outlined in the 878 are based on the findings of the risk
assessment as discussed in Section 2.4 of the S78 (pages 2-94 -
2-102). The resulting remediation goals established by EPA art
consistent with the intent of the HCP in that they succeed in
providing EPA with a remedy that is protective of human health and
the environment.
TWC Comment:
B. Maximum Depth of Treatment
"An arbitrary assumption was made in the FS with regard to t.-.e
maximum depth of treatment."
EPA Response:
For the purposes of the flFS, the selection of "15 feet below the
ground surface, or to the ground water level, whichever is less"
was a logical demarcation. Assumptions have to be made in the 6FS
to allow for the development of cost estimates. Additionally, EPA
is obligated to considered the various limitations of the
technology including the maximum achievable depth of treatment,
variability associated with dewatering, and cost of primary
treatment v. secondary recovery and treatment of ground water
through pump and treatment. Many of these unknowns will be
determined during the remedial design. Additionally, as indicated
in EFA's response to TWC Comment 3, the optimal depth of treatment
will be specified as a result of this additional work.
TWC Comment:
"This approach is not consistent with Section 300.430(e)(3)(i) cf
the NCP which requires the lead agency to develop a range cf
alternatives in which treatment that reduces the toxicity,
mobility, or volumV ... as a principle element" [referring to the
depth of treatment].
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IPX
The NCP citation above includes clarifying statements to the extent
that the range of alternatives be "appropriate1* and include options
that "removes or destroys hasardous substances, pollutants, or
contaminants to the iinjinum. extent feasible. ..." "Appropriate and
feasible" are important elements of this requirement. The 878
establishes a vide range of alternatives that address both the
source and ground vater contamination problems at the crystal
Chemical site. Considering the limited feasibility of gaining
access to contaminants beneath a depth of 15 feet or beneath the
ground vater table, the source control alternatives outlined in the
878 are appropriate and comply with the requirements of the HCP.
The TWC comments maintain that there are significant levels of
contaminants below the vater table at the site vhich may slov the
rate of ground vater cleanup. The draft BOD aeknovledges this
possibility by costing the remediation using a 30-year extraction
and treatment period. This timeframe vould allov for numerous pore
volumes of contaminated vater (up to 10) to be removed so that the
contamination sorbed to the aquifer skeleton can desorb and also
be treated. However, regardless of the assumptions made in the 87s
and draft ROD, more data vill be evaluated in during the remedial
design vhich vill allov for the determination an optimum depth of
treatment.
TWC Comment:
"EPA's rationale for selection of the partial treatment remedy is
not consistent with Section 300.430(f)(1)(D) of the NCP. This
section requires each remedial action selected to be cost-effective
provided that it first satisfies the threshold criteria of being
protective of human health and the environment and attaining
ARARS."
EPA Response:
Section 300.430(f)(1) (i) of the NCP establishes that the criteria
noted in Section 300.430(e)(9)(iii) shall be used to select a
remedy. Section VIII. of the Record of Decision, entitled ffu.ar'n'
of Comparative Analysis of Alternatives, sets forth EPA's
evaluation of the various alternatives against the nine criteria
(cited in Section 300.430(0)(t) (iii)). Table 17 presents this
evaluation in tabular font for all of the soil remedial
alternatives. This information establishes EPA*s preferred
alternatives as the remedies of choice, thus is in compliance with
the NCP. However, the above comment appears to question whether
EPA's selected remedy is protective of human health and the
environment and attains ARARs. EPA's response to TWC Comment 3
above set forth th,» rationale for incorporating the human health
evaluation process into the remedial response program. EPA's risk
assessment (as outlined in Section 2.4 and Appendix D of the 878)
established a remediation plan that is both protective of human
health and the environment and meet the intent of the-NCP. Th«se
findings as veil as the recommended soil and ground vater
40
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remediation goals have been reviewed by .the proper public health
agencies and have been aeeaptad. IPX'a raaponaa to TWO comment 1
addraaaad tha iaaua of attaining ARARs. Again, IPX baa established
tba MCL (0.05 »g/l) for araanic aa tba remediation goal in ground
vatar. Tba MCL ia tba ARAB, tbua BPA baa oompliad vitb in MCP.
TWC Comment:
2. Ground Water Alternatives for the 15 and 35 Foot Aquifers
A. Range of Alternatives
"the FS does not comply with Section 300.430(e) (4) of the NCP which
requires the lead agency to develop a United number of remedial.
alternatives that will attain site-specific remediation levels
within different restoration time periods ..."
BPA Response:
Given tbe small areal extant and deptb of tbe plusa at tbe site,
tbe time needed to attain remedial goals vill be governed largely
by tbe partitioning behavior of arsenic ratber tbat tbe number of
extraction veils or pumping rate. Therefore, in theory, it would
be a somewhat meaningless exercise to vary pumping rates and
numbers of veils to develop different timeframea for vbat is
essentially tbe same alternative. During tbe design of tbe remedy,
pilot testing vill be conducted to optimise tbe efficiency of tbe
extraction system to achieve remedial goals as quickly as possible.
TWC Comment:
"It is clear . . . that the 30 year remediation period is based cr.
a standard assumption rather than a calculated or other realistic
estimate of the restoration timeframe ... the NCP describes EFA's
expectation of returning useable ground water to their beneficial
use whenever practicable, within a time frame that is reasonable
... a reasonable time frame cannot be made given the analysis ..."
EPA Response:
The commentor is correct in stating tbat it is not possible to
determine the exact restoration timeframe from tbe ROD since only
a worst-case timeframe of 30 years is discussed. However, given
tbe problems tbat have been encountered in predicting cleanup
timeframes at ground vater sites acroaa tbe country, BPA determined
it appropriate to use a vorst-case scenario rather than an estimate
calculated on insufficient data. Before a revised estimate ia
made, pilot testing vill be conducted in the design phase of tbe
project.
TWC Comment:
B. Off-Site Water Supply Wells Within About 1000 Feet
C. Off-Site Water Supply Wells Within About 1 Mile
"EPA should pursue whatever additional analysis of study is
necessary to provide satisfactory explanation of these higher tnar.
expected ground water arsenic values."
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EPA R««pon««:
Tb« dataction of arsanic at lavala balov tha MCL in off-*it« ¥•!!•
do«« not warrant a troubl«-«hooting «xp«dition to find a
"satisfactory azplanation" for th«»« valu«s.
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ATTACHMENT 2
STATE OF TEXAS CONCURRENCE LETTER
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TEXAS WATER COMMISSION
B J W?nne 11! :~i—:- f >L, , John J Vav.Ge=e-
John E Birduell J.-- :.-.-- , - Michael E Field C
Cli'f Jo-.rsoi I :----• Brenda \A Foster
Allen BemUe Eve; .• .€ It re:-::
September 25, 199C
Allyn M. Davis, Ph.D., Director
Hazardous Waste Management Division
U. S. Environmental Protection Agency
Region 6
1445 Ross Avenue
Dallas, Texas 75202-2733
Re: Crystal Cheir.ical Cor.pany Superfund Site
Draft Record of Decision
Dear Dr. Davis:
We have reviewed the proposed Record of Decision (ROD) for the
Crystal Chemical Company Superfund site. We note that EPA has
addressed many of the issues raised by TWC after review of the ir=:'
ROD. The most significant issues were the need for further
investigation of the 100 foot aquifer and our concern as to wr.et.-.sr
the source control was comprehensive enough to ensure the attair.rer
cf ground water ARARs. We are encouraged by your statement in tr.e
revised ROD that a study of the relationship between the contar.ir.a-
oils and the ground water will be conducted during the remedial
sign in order "to determine the need for and feasibility of deec
1 more extensive soil treatment that will enable the ground wate
ie remediated to the MCL within the shortest practical timefrsr
»lieve that this is a key component of the proposed remedy, w
r with the proposed reaedy as presented to us on the ccnditi;
EPA ensure that all necessary and feasible efforts be made tc
si sources of contamination affecting attainment of the grc-.-.
MCL.
ely,
einke
ve Director
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ATTACHMENT 3
ADMINISTRATIVE RECORD INDEX
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