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\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
8 REGION 6
f 1445 ROSS AVENUE, SUITE 1200
DALLAS, TX 75202-2733
EXPLANATION OF SIGNIFICANT DIFFERENCES
INTRODUCTION
Site name and location
PAB Oil and Chemical Services, Incorporated
Abbeville, Louisiana
Identification of lead agencies and support agencies
Lead: U.S. Environmental Protection Agency (EPA)
Support: Louisiana Department of Fnvironmental Quality (LDEQ)
Citation of CERCLA Section 117fcl and NCP Section 300.435rd m(i)
This Explanation of Significant Differences (ESD) is prepared in
fulfillment of EPA's public participation responsibilities under
Section 117(c) of the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA), 42 U.S.C. §
9617(c), which provides that after adoption of a final remedial
action plan, if any remedial action, enforcement action, settlement
or consent decree under section 106 or Section 122 of CERCLA is
entered into, and if such action, settlement, or decree differs in
any significant respects from the final plan, the lead agency shall
publish an explanation of significant differences and the reasons
such changes were made. Moreover, pursuant to the National
Contingency Plan (NCP), 40 C.F.R. Part 300, EPA is required to
publish an ESD when, after adoption of the Record of Decision
(ROD), the remedial action or enforcement action taken, or the
settlement or consent decree entered into, differs significantly
from the remedy selected in the ROD with rpspect to scope,
performance, or cost (40 C.F.R. S 300.435(c)(2)(i)).
Summary of the circumstances that gave rise to the need for an ESD
On September 23, 1993, EPA issued a ROD which presented the EPA
selected remedy for the PAB Oil site clean up. The selected remedy
includes excavation and biological treatment for contaminated site
soils and sludges followed by solidification/stabilization of
biologically treated residues and disposal of treated residuals in
an onsite disposal unit.
On September 27, 1994, pursuant to Section 106 of CERCLA, 42 U.S.C.
S 9606, EPA issued a Unilateral Administrative Order (UAO) to a
number of Potentially Responsible Parties (PRPs) directing them to
perform the remedial design and remedial action. A group of PRPs
known as PAB Site Remediation Group, L.L.C., has undertaken
Rccyctod/ftocyclable Printed with Vegetable Oil Based Inks on 100% Recycled Paper (4O% Postconsumer)
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additional site investigations and treatability studies, and is
preparing preliminary plans and specifications for implementation
of the selected remedy. In the course of conducting these predesign
studies, data has been collected using new EPA-approved laboratory
procedures not previously available during Remedial Investigation
and Feasibility Study (RI/FS) activities. This data shows that
implementation of the biological treatment step of the selected
remedy is not necessary since the concentrations of organic
pollutants in the site soils and sludges are below the remedial
action objectives (RAOs) for biological treatment established in
the ROD.
Statement that the ESP will become part of the Administrative
Record File
This document presents only a summary of the changes to the remedy
and a synopsis of available information on the site. Pursuant to
the requirements of Section 300.825(a) (2) of the NCP, 40 CFR
§300.825(a) (2), this BSD will become part of the Administrative
Record for the PAB Oil site.
Address of locations where the file is available and hours of
availability of the file
U.S. Environmental Protection Agency
1445 Ross Avenue
Dallas, Texas 75202
(214) 665-6427
Monday - Friday 8 a.m. to 4:30 p.m.
Louisiana Department of Environmental Quality
7290 Bluebonnet Road
Baton Rouge, Louisiana 70809
(504) 765-0487
Monday - Friday 8 a.m. to 4 p.m.
Vermilion Parish Library
200 North Street
Abbeville, Louisiana 75010
(318) 893-2674
Monday - Friday 8a.m. to 5 p.m.
Saturday 9 a.m. to 4 p.m.
SUMMARY OF SITE HISTORY, CONTAMINATION PROBLEMS, AND SELECTED
REMEDY
Site history and contamination problems
The PAB Oil site is located approximately three miles north of
Abbeville, Louisiana, adjacent to U.S. Route 167 in Vermilion
Parish (Figure 1). The site encompasses approximately 16.7 acres of
land located in a rural area. The site was used for the disposal of
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SITE LOCATION MAP
PAB OIL AND CHEMICAL SERVICES, INC
VERMILION PARISH, LOUISIANA
REFERENCE JSGS 7 5 MINUTE TOPOGRAPHIC QUADRANGLE MAPS OF
L-IROY AND MILTON. LOUISIANA. DATED 1983
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oil and gas exploration and production wastes, including drilling
muds, drilling fluids and produced waters, from 1979 to 1983. The
site consists of three impoundments or pits which were used to
receive drilling wastes. Another impoundment, referred to as the
saltwater pond, was used to receive produced waters. Because of its
inability to meet the requirements of statewide order 29-B and lack
of funds for a proper closure, Pab Oil went out of business in 1983
and the site was abandoned. The site was added to the National
Priorities List (NPL) by EPA in March 1989.
EPA conducted the RI/FS between January 1991 and March 1993. All of
the contaminants found at the site are related to drilling muds,
drilling fluids, produced water and other associated wastes such as
workover fluids and tank bottoms. Contaminants detected in the pit
soils/sludges, pond sediments, and surface water include petroleum
hydrocarbons such as ethylbenzene, fluorene, methylnaphthalene,
phenanthrene, toluene, and xylene and heavy metals such as arsenic,
barium, chromium, copper, lead, and zinc.
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Selected remedy, as described in the ROD
The major components of the selected remedy include the following:
Excavation and onsite biological treatment of organic
contaminated sludges, soils, and sediments;
Solidification/stabilization of biologically treated residuals
to address inorganic contamination (metals) and, if necessary,
any remaining organic contaminants;
Final disposal of treated residuals in an onsite disposal unit;
Placement of a compacted clay cover over the disposal unit;
Removal and onsite treatment of all surface water with final
discharge to site drainage ditches;
Long-term ground water monitoring; and
Long-term site operation and maintenance.
DESCRIPTION OF SIGNIFICANT DIFFERENCES AND THE BASIS FOR THOSE
DIFFERENCES
Information that gave rise to significant differences
The Baseline Risk Assessment, dated January 1993, was used to
establish the following RAOs in the ROD for site clean up:
Arsenic - less than 10 parts per million (ppm)
Barium - less than 5400 ppm
Carcinogenic Polynuclear Hydrocarbons (cPAHs) - less than 3 ppm
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as benzo(a)pyrene (BAP) equivalent
Polynuclear Hydrocarbons (PAHs) - less than or equal to 1 Hazard
Index (HI)
Because of limitations in laboratory procedures at that time (i.e.
prior to 1991), the RI activities could not determine whether or
not the actual cPAHs and PAHs concentrations of site soils,
sludges, and sediments were above or below the RAOs. Instead, the
laboratory data showed only nondetect values of less than 15 to
less than 58 ppm for cPAHs and PAHs in the site media. To be
conservative, the Risk Assessment and FS estimated that cPAHs
concentration was about 20 ppm as BAP equivalent (about half the
average detection limit and substantially above the RAO value of 3
ppm) and the PAHs hazard index was about 400. Therefore, biological
treatment was selected as the remedy in the ROD to reduce the
concentrations of cPAHs and PAHs to acceptable levels.
The predesign investigation activities conducted in 1993 and 1995
by the PRPs used revised EPA analytical techniques (EPA method
8270-A, revised in 1993) for the determination of PAHs and cPAHs.
Site sludges, soils, and sediments sampling results have shown that
the cPAHs concentration is well below (less than 1 ppm) the RAO of
3 ppm as BAP equivalent. Also, the PAHs concentrations are well
below the hazard index of 1. Therefore, biological treatment is
unwarranted since the site soils, sludges, and sediments PAHs and
cPAHs concentrations are well below the RAOs established for
biological treatment.
Description of the significant differences between the remedy as
presented in the ROD and the action now proposed
Original ROD Remedy
The 1993 ROD selected the following remedy:
Excavation and onsite biological treatment of organic
contaminated sludges, soils, and sediments;
Solidification/stabilization of biologically treated residuals
to address inorganic contamination (metals) and, if necessary,
any remaining organic contc>minants;
Final disposal of treated residuals in an onsite disposal unit;
Placement of a compacted clay cover over the disposal unit;
Removal and onsite treatment of all surface water with final
discharge to site drainage ditches;
Long-term ground water monitoring; and
Long-term site operation and maintenance.
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Modified Remedy
Extensive sampling of site soils, sludges, and sediments conducted
during 1993 and 1995 has indicated that concentrations of cPAHs and
PAHs are well below the RAOs and therefore biological treatment is
not necessary. The following is the modified remedy:
Excavation and onsite solidification/stabilization of site
soils, sludges, and sediments containing arsenic and
barium above RAO levels of 10 ppm and 5400 ppm, respectively.
Also an organiophilic clay must be used in the
solidification/stabilization mix to chemically stabilize organic
compounds contained in the wastes;
Disposal of treated residuals in an onsite disposal unit;
Placement of a compacted clay cover over the disposal unit;
Removal and onsite treatment, jf all surface water with final
discharge to site drainage ditches;
Long-term ground water monitoring; and
Long-term site operation and maintenance.
The modified remedy is similar to the 1993 ROD remedy except that
biological treatment is not a component of the modified remedy.
SUPPORT AGENCY COMMENTS
Louisiana Department of Environmental Quality has reviewed this
ESD. The State's acceptance of this ESD can be found in
Attachment l.
AFFIRMATION OF THE STATUTORY DETERMINATIONS
Considering the new information that has been developed and the
changes that have been made to the selected remedy, the EPA
believes that the remedy remains protective of human health and the
environment, complies with Federal and State requirements that were
identified as applicable or relevant and appropriate in the ROD and
at the time tğvs ESD was signed, and is cost-effective. In
addition, the revised remedy utilizes permanent solutions and
alternative treatment technologies to the maximum extent
practicable for this site.
PUBLIC PARTICIPATION ACTIVITIES
The requirements of CERCLA Sections 113(K)(2)(B)(i-v) and 177, 42
U.S.C. SS 9613(K)(2)(B)(i-v) and 9617, were met as illustrated in
the following discussion.
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In December 1996, the Remedial Project Manager met with the Mayor
of Abbeville, Police Jury representatives, the Parish Sheriff, the
City Fire Marshall, and the Vermilion Association to Protect the
Environment (VAPE) Technical Assistance Grant (TAG) advisor to
explain the proposed change to the remedy, obtain their input to
the proposed change, and to inform them that EPA would be holding
an open house in Abbeville in mid January 1997 to explain the
proposed change and to obtain citizen comments. The response was
very positive and there were no objections to the proposed change.
A Superfund Site Update.Fact Sheet on the proposed change to the
remedy was mailed to the citizens on January 6, 1997. An open house
was held in Abbeville on January 16, 1997 to explain the proposed
change to the remedy, answer questions, and to solicit comments
from community members. Also, a 2-week comment period (from January
16th through 3lst, 1997) was provided. The community commented
through its TAG advisor (Attachment 2) stating that it had no
objection to the proposed change provided that solidification and
stabilization is conducted ex-situ.
t\ Regional Administrator
Date
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Attachment 1
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COMPANY
3008 SOUTHWEST DRIVE SOUTHWEST INDUSTRIAL PARK P.O. BOX 9813 NEW IBERIA, LA 70562-9813 (318) 367-2216
" ; - '-J U/-C\
January 21, 1997
M. S. Ramesh (6SF-LL)
Remedial Project Manager
US EPA, Region 6
1445 Ross Avenue
Dallas, TX 75202-2733
Re: PAB Superfund Site - Remedy Change
Dear Mr. Ramesh:
Or behalf of Vermilion Association to Protect the
Environment (VAPE), I would like to offer the following comments
in response to the PAB change in remedy.
The second step of the remedial process was #2 Excavation
and on s*te biological treatment for soils and sludges to degrade
organics such as naphthalene and xylene. With the removal of
biological treatment the excavation phase should still be
required.
The sludges and soils should be required to be excavated,
stabilized with an appropriate solidifying agent to bind the
organic fraction of the waste, and solidified with appropriate
materials to address the heavy metals.
Excavation in ex-sites solidification should be required.
This would enable complete removal of contaminated sludges and
soils from the waste impoundments areas. This is an important
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COMPANY
3008 SOUTHWEST DRIVE SOUTHWEST INDUSTRIAL PARK P.O. BOX 9813 NEW IBERIA, LA 70562-9813 (318) 367-22^6
requirement to insure appropriate removal and treatment prior to
the treated and solidification waste being placed back in the
impounded areas for final disposal.
If additional information is required, please contact me.
Thank you for the opportunity to participate in this process.
Sincerely,
\O
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Attachment 2
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, .T-.V ;r> ;:. -.",-: ).
:<. ....- ...,,
Stabilization/ f';
Solidification of
CERCLA and RCRA Wastes
Physical Tests, Chemical
Testing Procedures,
Technology
Screening, and
Field Activities
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lized waste. II the unstabilized,product is soil-like and
the stabilized product is cement-like, there should be
a marked increase in the Unconfined Compressive
Strength (10 to 20 psi).
4.5.2 Unconfined Compresslve Strength of
Cylindrical Cement Specimens (ASTM 01633-84)
For stabilized cement-like wastes, the Unconfined
Compressive Strength test can provide several pieces
of useful information, including the following:
The ability of the stabilized waste to with-
stand overburden loads.
The optimum water/additive ratios and
curing times for cement setting reactions.
The improvement in strength characteristics
from the unstabilized to the stabilized waste.
This test also is often conducted on samples sub-
jected to durability tests (Subsection 4.6).
4.5.2.1 Test Description
The test is completed on a cylindrical sample of the
materials (ASTM D1632-87). It can be completed
with two different cylinder height-to-diameter ratios:
1.15 and 2.0 (Methods A and B). The cylindrical test
specimen must be cured for a specified time in a room
with 100 percent humidity. Typical curing times for
cement are 1, 7, 14, and 28 days. The age of the
tested sample should be noted.
The two height-to-diameter ratios cause several dif-
ferences in testing and in results. Method A uses
equipment more readily available in soil-testing labo-
ratories; however, this test method may lead to more
complex stress conditions during crushing. There-
fore, Method A gives a relative measure of strength
rather than a rigorous determination as found in Method
B. Method A normally yields a higher compressive
strength than an identical sample tested by Method B.
Although no cons.stent preferences in test methods
are noted in the literature, comparisons in Unconfined
Compressive Strength should only be completed for
samples tested by the same method.
The testing apparatus is commonly called a "Com-
pression Testing Machine." The machine may take
on several forms, but most important, it must be able
to control the rate at which load (stress) is applied.
The machine has an upper and lower plate, and the
sample is placed upright (long axis vertically) on the
lower plate.
The upper plate is lowered and brought into contact
with the sample. Load is added continuously without
shock by a screw. A sample fails when it loses its
physical integrity by falling apart. The total load at
failure of the test specimen is recorded to the nearest
10 pounds of force. The Unconfined Compressive
Strength is the ratio of force applied at failure to the
original cross-sectional area of the cylinder, usually
expressed in pounds per square inch (psi). Uncon-
fined Compressive Strength is often expressed in
other units. Table 4-3 presents conversion factors for
the more common units.
In its methods description, ASTM reports that the
average strength difference of two duplicate samples
is 8.1 percent. The samples should be tested by the
same person to give the maximum precision when
interpreting the failure of the sample.
4.5.2.2 Interpretation and Application of Results
The EPA considers a stabilized/solidified material with
a strength of 50 psi to have a satisfactory Unconfined
Compressive Strength (USEPA OWSER Directive,
No. 9437.00-2A). This minimum guideline of 50 psi
has been suggested to provide a stable foundation for
materials placed upon it, including construction equip-
ment and impermeable caps and cover material. A
study by Stegemann et at. (1988) reported Uncon-
fined Compressive Strength values for 69 stabilized/
solidified wastes ranging from 10 to 2900 psi.
The minimum required Unconfined Compressive
Strength for a stabilized/ solidified material should be
evaluated on the basis of the design loads to which
the material will be subjected. The anticipated over-
burden pressure and other loads, along with appropri-
ate safety factors, can be used to calculate this.
Typical construction and compaction equipment can
generate very high contact pressures of 1000 psi or
more (e.g.. sheepsfoot rollers), but surface contact
pressures on the order of 50 to 100 psi are more
common. This surface load is attenuated with depth
so that bearing pressures are reduced to values on
the order of 10 to 20 psi at a depth of 2 feet and 3 to 7
psi at a depth of 5 feet below grade. Overburden
pressures will usually be on the order of 0.75 to 1.0
psi per foot of depth. If guidelines such as these are
used, the stresses to which the stabilized/solidified
waste will be subjected can be predicted, and design
criteria can be selected accordingly.
Martin et al (1987) suspect that one-dimensional
compressibility may be a more useful indicator of
mechanical stabilization/solidification in some situ-
ations than is Unconfined Compressive Strength. The
one-dimensional compressibility test (e.g., ASTM
02435-80) allows a prediction of fluid expulsion dur-
ing consolidation and evaluation of cover support.
For stabilized/solidified waste forms that are relatively
soft or ductile, this test can provide useful perform-
ance information; however, for stiff, cement-like, sta-
bilized/solidified waste, the Unconfined Compressive
Strength with a rational design criterion is probably
: I
i
4-13
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