PB95-963121
EPA/ESD/R09-93/127
March 1995
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Lawrence Livermore National
Laboratory, Livermore, CA
8/23/1993
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Explanation
of Significant Difference
for the
Change to Granular Activated Carbon
for Treatment of Vapor at Treatment Facility F,
Lawrence Livermore National Laboratory,
. Livermore Site
June 15,1993
Technical Editors
M. D. Dresen.
A. J. Boegel
J. P. Ziagos
Contributing Authors
J. K. Macdonald.
A. J. Boegel
*Weiss Associates, Inc., Emeryville, California
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UCRL-AR-112804
Explanation of Significant Difference
June 15,1993
Contents
1. Introduction .., ....... ..........................., ................. ......... ............ ...... ...... .:.................. """'" ............, .......... 1
2. Site Background................................ .................................. ............... ....,. ....... ....... ............... .... ....... ...... 2
2.1. Site Description and History ...,............................. [[[ 2
2.2. Site Characteristics ...... ......... .... .... .,. ........ ........, .... ..... ...... ....... ......................................... ... ...... .... 2
2.3. Remedies" Selected in the ROD [[[ 4
2.3.1. Ground Water ..... ....... ...................... ............. ........ ..... ............. .... ..... ..... .............. ..... ........ 4
2. 3.2. Unsaturated Zone....... ..,............ .... ......... ....... .... ........... ................. ...................... ..... ........ 7
3. Description of Significant Change to the Selected Remedy[[[ 7
4. Regulatory Agency Comments............ ...................... ....... ........ ......... ........... ...................... ...... ........, ...1 0
4.1
4.2
Responses to Department of Toxic Substances Control Comments ...........................................10
Responses to Regional Water Quality Control Board Comments ..............................................12
4.3
Responses to U.S. Environmental Protection Agency Comments ..............................................12
5. Statutory Determinations .. .....,........... ........... ....... ..................... ......... ........... ....... ............................ ..... 12
6. Public Participation Activities .......,. ...... ....... .................... ........ ............. ....... .............., ....... ............. ..... 13
7. References......................... ................. ..................................... ........... ........... ...... ......... ....... "" ......... .... .14
List of Figures
Figure 1.
Figure 2.
Location of the LLNL Livermore Site[[[ 3
Planned ground water extraction, recharge, and treatment facility locations .......................... 6
List of Tables
Table 2.
Remediation standards and State discharge limits for compounds of concern in ground
water at the LLNL Livermore Site (from the Record of Decision) '"'''''''''''''''''''''''''''''''''''''' 5
Chronology of events regarding change to granular activated carbon (GAC) from
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. UCRL-AR-112804
Explanation of Significant Difference
June 15. 1993
1.
Introduction
On August 5, 1992, the Record of Decision (ROD) was signed. documenting the final cleanup
plan for the Lawrence Livermore National Laboratory (LLNL) Livermore Site in Livermore,
California. As required under Section l17(c) of the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA), as amended by the Superfund Amendment
and Reauthorization Act of 1986 (SARA), and pursuant to 40 C.F.R. Section.300.435(c)(2)(i)
[Fed. Reg. VoL 55, No. 46 (March 8, 1990)], this Explanation of Significant Difference (ESD)
describes a change from the catalytic oxidation technology described in the ROD (DOE, 1992), to
granular activated carbon (GAC) for treatment of fuel hydrocarbon (FHC) and volatile organic
compound (VOC) vapors at Treannent Facility F (TFF). An ESD is required when significant, but
not fundamental, changes are made to the final remedial action plan described in the ROD. This
ESD describes information developed during the remedial design process that supports the subject
change.
The lead agency for this ESD is the U.S. Environmental Protection Agency (EP A). This ESD
includes a brief background of the LLNL Livermore Site, a summary of the remedy selected in the
ROD, a description of how the noted change affects the remedy described in the ROD, and an
explanation of why EP A and the U.S. Deparnnent of Energy (DOE)/LLNL are making this change
to the selected remedy presented in the ROD. This document is designed to (1) provide the public
with an explanation of the change made to the remedy as described in the ROD, (2) summarize the
information that led to the change, and (3) affirm that the revised remedy complies with the
statutory requirements of CERCLA Section 121. This ESD was prepared according to the
following EP A Guidance DocumentS: Guide to Addressing Pre-ROD and Post-ROD Changes
(EPA, 1991) and Interim Final Guidance on Preparing Superfund Decision Documents (EPA,
1989).
This ESD and supporting documentation will be placed in the LLNL repositories for interested
members of the public to review. One repository is located at the Livermore Public Library, 1000
South Livermore Avenue. Library hours are Monday through Thursday, 10:00 a.m. to 9:00 p.m.;
Friday and Saturday, 10:00 a.m. to 5:00 p.m.; and Sunday 1:00 p.m. to 5:00 p.m. The second
repository is at the LLNL Visitors Center on Greenville Road. Visitors Center hours are Monday
through Friday, 9:00 a.m. to 4:30 p.m.; and Saturday and Sunday 12:00 p.m. to 5:00 p.m. The
Visitors Center also contains the Administrative Record, which is comprised of all the documentS
that form the basis for LLNL's cleanup plan.
DOEJLLNL provided a comment period for the EPA, the California Regional Water Quality
Control Board (RWQCB), and the Department of Toxic Substances Control (DTSC) of the
California Environmental Protection Agency to comment on this ESD. All commentS and
responses are presented in this ESD and will be included in the LLNL Administrative Record file.
Pursuant to 40 c.F.R. Section 300.435(c)(2)(i), a public comment period is not required for an
ESD, and all regulatory agencies overseeing the LLNL Livermore Site agreed that a public
comment period was not necessary for this ESD.
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UCRL-AR-112804
Explanation 0/ Significant Difference
June 15,1993
2.
Site Background
This section provides a brief description and history of the LLNL Livennore Site, chemicals of
concern in the subsurface, and a summary of the remedy selected in the ROD. Further details ~an
be found in the ROD and in the Administrative Record.
2.1. Site Description and History
LLNL is an 800-acre, multidisciplinary research facility owned by the DOE and operated and
managed by the Regents of the University of California under contraCt with DOE. LLNL is located
at 7000 East Avenue in southeastern Alameda County, approximately 3 miles east of the
downtown area of Livermore, California (Fig. 1). The site is underlain by several hundred feet of
complexly interbedded alluvial and lacustrine (lake) sediments. Depth to ground water at the site
varies from about 120 ft in the southeast comer to about 25 ft in the northwest comer.
The LLNL site was converted from agricultural and cattle ranch land by the U.S. Navy in
1942. The Navy used the site until 1946 as a flight training base and for aircraft assembly, repair,
and overhaul. Solvents, paints, and degreasers were routinely used during this period. Between
1946 and 1950, the Navy housed the Reserve Training Command at the site. In 1950, the Navy
allowed occupation of the site by the Atomic Energy Commission (AEC), which formally received
transfer of the property in 1951. Under the ABC, the site became a weapons design and basic
physics research laboratory. In 1952, the site was established as a separate part of the University
of California Radiation Laboratory. Responsibility for the site was transferred from ABC to the
Energy, Research, and Development Administration in 1975. In 1977, responsibility for LLNL
was transferred to the DOE, which is currently responsible for the site. In addition to weapons
research, LLNL programs have been established in biomedicine, energy, lasers, magnetic fusion
energy, and environmental sciences. Details of the site history and the use, storage and disposal of
hazardous materials are presented in the Remedial Investigation (RI) (Thorpe et aL, 1990).
Initial releases of hazardous materials occurred at the LLNL site in the mid- to late 1940s when
the site was the Livermore Naval Air Station (Thorpe et aI., 1990). There is also evidence that
localized spills, leaking tanks and impoundments, and landfills contributed volatile organic
compounds (VOCs), FHCs, possibly lead, chromium, and tritium to ground water and
unsaturated sediment in the post-Navy era.
In 1987, the LLNL Livermore Site was added to the National Priorities List. In November
1988, DOE, EPA, DTSC, and RWQCB signed a Federal Facility Agreement, which named DOE
as the overall lead agency and the U.S. EPA as the lead regulatory agency for cleanup.
2.2.
Site Characteristics
A screening of all environmental media conducted for the RI (Thorpe et aL, 1990) showed that
ground water and unsaturated sediment are the only media that require remediation. The identified
compounds that exist in ground water at various locations beneath the site in concentrations above
drinking water standards are:
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. UCRL-AR-1l2804
Explanation of Significant Difference
June 15,1993
'Pacific' Ocean'
Miles
o 5 10 15 20
C:::t::::I::::C
ERlH.SR-92-0066
Figure 1. Location of the LLNL Livermore Site.
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UCRL-AR-112804
Explanation of Significant Difference
June 15,1993
. The VOCs trichloroethylene (TCE), perchloroethylene (PCE), 1.1-dichloroethylene (1,1-
DCE), 1,2-dichloroethylene (l,2-DCE), 1,I-dichloroethane (l,l-DCA), 1,2-dichloroethane (1,2-
. DCA), carbon tetrachloride, and chlorofonn.
. FHCs (leaded gasoline), including benzene, ethylbenzene, toluene, and ethylene
dibromide.
.
Chromium and possibly lead.
Tritium.
.
The VOCs in ground water beneath LLNL, predominantly TCE and PCE, occur in relatively
low concentrations that underlie about 85% of the LLNL site and a smaller area offsite, under a
total area of about 1.4 square miles. Higher VOC concentrations are localized. Total VOC
concentrations exceed 1 part per million (ppm) in ground water from only 10 out of a total of more
than 300 wells. The calculated total volume of undiluted VOCs in ground water is less than 200
gal. VOCs are seldom found below a depth of about 200 fL
FHCs occur almost exclusively where a leak of roughly 17,000 gal of leaded gasoline occurred
from a U.S. Navy-era underground fuel tank in the southern part of the site. Total FHC
concentrations in ground water range from 0.001 to 16 ppm, and are limited to an area within
about 500 ft from the leak poinL
Metals above Maximum Contaminant Levels (MCLs) are present in ground water in only a few
locations. Chromium in ground water exceeds the MCL (Table 1) in 16 wells scattered in the
northwest, central, and southwest parts of the study area and near Arroyo Seco, with a maximum
concentration of 160 pans per billion (ppb) in the northwest comer. Lead has exceeded the 15-
ppb remediation standard (Table 1) in only two wells in the Gasoline Spill Area in southern LLNL,
at a maximum concentration of 38 ppb.
Tritium in ground water exceeds its MCL of 20,000 picocuries per liter (pCiIL) in only one
well (MW -206). This occurrence of tritium is localized and well defined. Recent investigations
have identified five additional areas where tritium concentrations in unsaturated sediments at LLNL
are significantly elevated. However, the tritium activity in ground water in these areas is well
below the MCL.
2.3. Remedies Selected in the ROD
The selected remedies for ground water and the unsaturated zone as described in the ROD are
summarized below.
2.3.1.
Ground Water
The selected ground water remedy involves initial pumping of water from a minimum of 24
locations within the ground water plume (Fig. 2). The total rate of ground water removed under
this extraction plan is estimated to be about 350 gpm. Water will be pumped from one or more
wells at each of the locations using existing monitor and extraction wells, along with new
extrac~ion wells. The initial well locations will be located near plume margins to prevent any
VOCs from escaping from the area in concentrations above their MCLs (Table 1). To enable more
4
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UCRL-AR-1l2804
Explanation of Significant Difference
June 15, 1993
Table 1. Remediation standards and State discharge limits for compounds of concern in ground
water at the LLNL site (from the Record of Decision). .
Concentration limit Cor drinking water-
Pre-remediation
concentration
range at LLNL, Discharge limitb
Federal CaliCornia March 1990- for
MCL MCL March 1991 treated water
Constituent (ppb) (ppb) (ppb) (ppb)
PCE 5 5 <0.1-1,050 4
TCE 5 5 <0.1-4,800 5
1,1-DCE 7 6 <0.5-370 5
cis-l,2-DCE 70 6 <0.5-24 5 (total 1,2-DCE)
trans-l,2-DCE 100 10 <0.5-1 5
1,I-DCA 5 <0.5-60 5
1,2-DCA 5 0.5 <0.1-190 5
Carbon tetrachloride 5 0.5 <0.1-91 5
Total THMc 100e 100e <0.5-270 5
Benzene 5 1.0 <0.1-4,600 0.7
Ethyl benzene 700 680 <0.2-610 5
Toluene 1,000 <0.5-4,200 5
Xylenes (total) 10,000 1,750d <0.5-3,700 5
Ethylene dibromide 0.05 0.02 <0.1-51 0.02
Total VOCs up to 5,808 5
Chromium+3 50 (total Cr)e 50 (total Cr) <5-150 (total Cr) 50 (total Cr)
Chromium+6 50 (total Cr)e 50 (total Cr) <10-140 11
Lead 1St 50 <2-10 5.6
Tritiumg 20,000 pCi/L 20,000 pC ilL <200-33,100 (h)
- Human receptor. The more stringent concentration limits on this part of the tabie are shown In
a larger typeface to illustrate that LLNL will comply with the most stringent requirements.
b From National Pollutant Discharge Elimination System (NPDES) Permit No. CA0029289
(revised 8/1190) and RWQCB Order No. 91-091. Of the LLNL compounds of concern, VOC-
specific State discharge limits exist In RWQCB Order No. 91-091 only for PCE (4 ppb),
benzene (0.7 ppb), and ethylene dibromlde (0.02 ppb). Other VOCs listed In this table are
Included in the 5 ppb total VOC limit. Discharge llnilts for metals differ slightly according to
discharge location. .
C Total trlhalomethanes (THMs); Includes chloroform, bromoform, chlorodibromomethane, and
bromodlchloromethane (California Drinking Water Requirement).
d MCL is for either a single Isomer or the sum of the ortho, meta, and para isomers.
e National Interim Primary Drinking Water Regulation for total chromium is presently 50 ppb,
bllt will increase to 100 ppb In July 1992. No MCLs exist for Cr+3 or Cr+6.
r National Primary Drinking Water Regulation Enforceable Action Level (Federal Register,
volume 56, number 110, June 7, 1991, p. 26460).
g The RI shows that ground water in the one well that currently exceeds the tritium MCL will be
naturally remedlated long before It migrates offslte.
h There is currently no NPDES discharge limit for tritium. LLNL will use the MCL tor tritium as
the discharge limit.
5
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Figure 2. Planned ground water extraction, recharge, and treatment facility locations.
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UCRL-AR-112804
Explanation of Significant Difference
June 15,1993
[.
rapid remediation, wells will also be placed in all areas where VOC or FHC concentrations in
ground water exceed 100 ppb. Additional extraction locations may be added to ensure complete
hydraulic capture of the plume, and/or to expedite cleanup, if field data and/or modeling indicate
additional wells are necessary.
Seven onsite facilities (A to G) are planned to treat the extracted ground water (Fig. 2). Each
treatment facility will be designed to treat a somewhat different combination of compounds.
Treatment Facilities A, B, E, and F will use UV/oxidation as the primary treatment technology~
Treatment Facilities C, 0, and G will use air-stripping as the primary treatment technology. All
facilities will use GAC to remove VOCs and FHCs from air streams, and, if necessary, TFF will
use GAC to remove lead from ground water. Treatment Facility 0 and possibly Treatment Facility
C will use ion exchange to remove chromium from ground water.
The selected alternative addresses all ground water containing VOCS in excess of MCLs and
will assure that Applicable or Relevant and Appropriate Requirements for individual VOCs, FHCs,
lead, chromium, and tritium will be achieved.
2.3.2.
Unsaturated Zone
The selected remedy described in the ROD for the unsaturated zone is vacuum-induced venting
to extract contaminant vapors from the unsaturated sediments and treating the vapors by catalytic
oxidation. In this process, vapors from vent wells are heated and passed through a catalyst, where
organic compounds are converted to harmless oxidation products, including carbon dioxide and
water. As described in the ROD, if use of catalytic oxidation would result in emission of vapors
with compounds above regulatory standards, secondary treatment or alternative technologies, such
as GAC, would be evaluated and implemented to comply with regulatory standards.
3.
Description of Significant Change to the Selected Remedy
This ESD changes one portion of the ROD. To the extent that this ESD differs from the ROD,
it supersedes the ROD.
The treatment technology for treating VOC and FHC vapor at TFF was changed from catalytic
oxidation to GAC, as described below. Table 2 presents the chronology of events regarding the
change from catalytic oxidation to GAC from the time the ROD was signed to the present.
Included in Table 2 are teleconferences, report submittals, and agreements reached with the
regulatory agencies. .
Characterization of the Gasoline Spill Area in the southern part of the LLNL site has been
underway since 1983, and vadose zone pilot remediation by vacuum extraction has been underway
since 1988. For the pilot remediation, extracted FHC vapors from the subsurface were oxidized
with a permitted propane-fired burner or thermal oxidizer. VOCs (low concentrations of TCE and
1,2-DCA) are also present in the ground water containing FHCs.
At the time the RI (Thorpe et al., 1990) and Feasibility Study (Isherwood et al., 1990) were
being prepared, long-term plans called for the construction of TFF in the Gasoline Spill Area to
treat free-phase gasoline; FHCs and VOCs in ground water; and FHCs in the vadose zone.
However, LLNL Environmental Restoration staff had concerns that thermal treatment of
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UCRL-AR-112804
Explanation of Significant Difference
June 15,1993
Table 2. Chronology of events regarding change to granular activated carbon (GAC) from
catalytic oxidation for Treatment Facility F.
Date
August 5, 1992
Event
Record of Decision (ROD) is signed
incorporating catalytic oxidation as the
method to treat VOC and FHC vapors from
unsaturated sediments.
LLNL Engineering Group determines that
there are insufficient resources to perform
the EPA-required catalytic oxidation
treatability studies prior to beginning the
Dynamic Stripping Demonstration Project
(AiDes et al., 1992). In addition, with the
availability of onsite steam GAC
regeneration, use of GAC is determined to be
more cost-effective than catalytic oxidation.
Teleconference between Bella Dizon of DOE
and Michael Gill of EPA. The potential for
a ROD amendment to implement the change
is discussed.
October 22, 1992
October 23, 1992
October 27, 1992
Preliminary Draft Final Remedial Action
Implementation Plan (RAIP) sent to DOE for
review with change to GAC included.
Change to GAC is discussed with EPA and
DTSC during regulatory teleconference.
Draft Final RAIP is sent to regulators
including the change to GAC.
It is agreed at a meeting with DOE, LLNL,
EPA, DTSC, and the RWQCB that a ROD
amendment is not necessary and that an
Explanation of Significant Difference (ESD)
is the most appropriate way to implement
the change to GAC.
Comments on Draft Final RAIP received
from regulators. Mention of ESD in the
RAIP is recommended.
RAIP and ESD discussed during
teleconference with regulatory agencies.
RAIP is issued, including mention of an
ESD to explain change from catalytic
oxidation to GAC.
It was agreed that the Draft ESD would be
due on February 23 to the regulatory
agencies during a regulatory teleconference.
November 3, 1992
November 6, 1992
December 2, 1992
December 10, 1992
December 14, 1992
January 6, 1993
January 21, 1993
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, ' UCRL-AR-1l2804
Explanation 01 Significant Difference
June 15,1993
halogenated VOCs with FHCs could produce dioxins in the effluent of the thermal oxidizer. This
concern was voiced during the conceptual design phase ofTFF, circa 1991.
Thermal oxidation of aromatic compounds, such as benzene. in the presence of chlorinated
VOCs, such as TCE. can produce tetrachlorodibenzo-para-dioxin (TCDD). However. it has been
demonstrated that a recently developed catalyst efficiently destroys FHCs and halogenated VOCs
including dichlorobenzene (a surrogate for dioxin) (Lester, 1989). The oxidation of the
halogenated compounds also produces minor amounts of hydrogen chloride (HCl) and hydrogen
bromide (HBr). which can be removed by a c~ustic scrubber. The lower temperature of a catalytic
oxidizer (700°F versus 1 ,800°F for the thermal oxidizer) makes caUStic scrubbing much easier. In
addition, one-third of the supplemental fuel is required for a catalytic oxidizer compared to the
thermal oxidizer. As described in the Proposed Remedial Action Plan (Dresen et al., 1991) use of
a catalytic oxidizer would provide the flexibility to treat both FHCs and VOCs together. and would
substantially reduce the potential for producing dioxin compared to thermal, oxidation.
The GAC vapor treatment option. however. has no risk of producing TCDD. GAC is an
effective treatment alternative for FHC vapor and is considered Best Available Control Technology
(BACT) by the Bay Area Air Quality Managment District (BAAQMD). At TFF. vapors are
induced into the treatment system from the subsurface by a liquid ring vacuUm pump capable of
400 cubic feet per minute. The liquid ring pump exhausts to a demister. which collects water. The
vapor stream is passed through one of two 750-lb GAC canisters where FHCs. such as benzene.
are sorbed. The treated vapors pass a continuous-reading FHC sensor prior to discharge to the
atmosphere. Valves direct the vapor flow to the second GAC canister while the first is being
regenerated after a prescribed time that is based on GAC loading rate, or when breakthrough is
detected by a sensor linked to a control system. The first canister is flushed with steam to heat the
carbon. and to desorb and remove the FHCs. The steam and FHCs are removed from the canister
and condensed with a plate-type heat exchanger. which is cooled by clean process water. The
condensed steam (water) and FHCs are collected in a separa~on tank. Level switches within the
separation tank activate pumps for discharge to separate collection tanks for light (lighter than
water, such as benzene) and heavy (heavier than water, such as TCE) compounds. Details of the
remedial design will be addressed in a later design document that will be subject to regulatory
reVIew.
The cost of using GAC for vapor treatment at TFF is estimated to be about half of the original
catalytic oxidation cost estimate. Table 3 presents the original catalytic oxidation cost estimate, a
revised estimate for catalytic oxidation after receiving comments from EPA, and the estimated cost
for vapor treatment by GAC with onsite regeneration. The increase in engineering cost of catalytic
oxidation is due to the additional engineering requirements for treatability and start-up tests
required by the EPA. Overall. the costs for catalytic oxidation increased by approximately 45%
due to this treatability testing and reporting. There are no treatability studies required for the GAC
treatment option. Therefore, the cost of GAC is far less than catalytic oxidation, and the use of
GAC enables TFF to start operation ahead of the scheduled March 1993 date in the Remedial
Action Implementation Plan (Dresen et al., 1993).
All appropriate and relevant regulatory requirements. including air emission limits and
monito,ring requirements, disposal of secondary wastes. and any other substantive requirements
that apply to the treatment will be followed during operation of the treatment facility. The
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UCRL-AR-112804
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Explaruztion of Significant Difference
June 15,1993
BAAQMD discharge limits for TFF are 6 ppmv/v for the vapor treattnent system and 10 ppmv/v for
the ground water treatment system.
In summary, the change from catalytic oxidation to GAC for treatment of vapor at TFF
eliminates the possibility of dioxin production, is more cost-effective with current onsite GAC
regeneration equipment, and enables earlier operation of TFF.
Table 3. Comparison of estimated costs for catalytic oxidation and granular activated carbon
(GAC).
Component
Purchase
Engineering
Treatability.
Activation
Start up testingb
Utility connections
Reporting
Air permitting
Dioxin analysis (treatability
and start-up)
FHC and VOC analyses
Totals
Percent change over original
catalytic oxidation estimate
Original
catalytic
oxidation unit
with scrubber
$150,000
25,000
o
60,000
20,000
80,000
10,000
20,000
5,000
Original catalytic
oxidation unit and
EP A requirements
$250,000
70,000
80,000
60,000
80,000
80,000
20,000
20,000
20,000
GAC w/onsite
regeneration
$140,000
25,000
o
40,000
20,000
o
10,000
10,000
o
2,000
$472,000
4,000
$684,000
45
2,000
$247,000
-48
-Includes treatability work plan, quality assurance plan, and detailed performance testing at
manufacturer's facility (varying operating parameters such as residence time and reac:tor
temperature).
blncludes detailed performance testing of installed unit.
4.
Regulatory Agency Comments and Responses
4.1
Responses' to Department of Toxic Substances Control Comments
Comment 1: Both the thermal oxidation and catalytic oxidation systems can treat both VOCs
and FHCs. The ESD does not indicate that the GAC system can treat FHC. How can the GAC
system be justified if it cannot treat the compounds which will be in the vapor waste stream?
The GAC vapor treatment system is an effective treatment alternative for FHCs and is in fact
considered BACT by the BAAQMD for this purpose. Changes have been made in paragraph 6 in
Section 3 of the Draft Final ESD to make it clear that GAC successfully treats FHCs.
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UCRL-AR-112804
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Comment 2: Page 9. Third Paragraoh. Fifth Sentence: What is the purpose of the vac
sensor? What type of sensor is used? How often is it monitored? How will FHCs be monitored?
The FHC (rather than VOC) sensor ensures that hydrocarbon concentrations in the treated
vapor effluent are below the BAAQMD discharge limits. The BAAQMD discharge limits for TFF
are 6ppmv/v for the vapor treatment system and 10 ppmv/v for the ground warer treatment system.
The sensor is a Sierra Monitor Model No. 4100-31, solid state FHC sensor calibrated with
representative vapor samples for weathered gasoline. It is continuously monitored by the control
system. The BAAQMD will provide feedback on the appropriateness of this sensor. VOCs are
not monitored because VOC concentrations in extracted vapor are extremely low compared to
FHCs, and FHCs would break through the GAC long before VOCs. Paragraph 6 in Section 3 of
the Draft Final ESD has been modified to indicate that an FHC rather than VOC sensor is used.
Comment 3: Pa~e 9. Third Para~raoh. Sixth Sentence: How is it possible for a distribution
control sytem to detect chemical breakthrough in the GAC cansiters?
The control system operates electronically and continuously monitors the voltage signals from
. the above-mentioned FHC sensor an~ various other monitoring devices. The voltage signals are
processed by a preprogrammed logic circuit capable of triggering certain controls, such as
pneumatically operated diverter valves that direct the vapor flow into either of the GAC vessels.
The text in Paragraph 6 in Section 3 has been modified to indicate that "breakthrough is
detected by a sensor linked to a control system."
Comment 4: Page 9. Third Paragraoh. Sixth Sentence: Is the first canister flushed with stream
(sic) as the vapor stream from the subsurface is being passed through it? How is the second
canister treated to desorb and remove the VOCs?
The TFF GAC vapor treatment system consists of two vessels, each containing 750 lb of
GAC, which are alternated between vapor treatment and steam regeneration. While one vessel is
treating the extracted vapor stream, the other is being regenerated with steam. The text in
Paragraph 6 of Section 3 has been modified to make it clear that flow is directed to the second
GAC canister while the first is being regenerated.
Comment 5: Page 9. Third Para'iraoh. Last Sentence: How are the FHCs which may have
been collected in the separation tank removed from the waste stream.
The regeneration waste stream is first condensed into liquid in a plate heat exchanger, and then
routed through a product separator that removes both free-phase FHCs (lighter than water) and
VOCs (heavier than water). The product separator is a relatively stagnant tank that allows
gravitational separation of hydrophobic compounds, which are removed from above and below the
aqueous portion of the fluid. The water effluent from the separator, which contains dissolved
concentrations of FHCs and VOCs, is routed into the ground water treatment system influent
Free-phase VOCs and FHCs are collected in 55-gal drums and disposed by the LLNL
Hazardous Waste Management Division according to regulatory standards.
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UCRL-AR-112804
- Explanation of Significant Difference
June 15, 1993
4.2 Responses to Regional Water Quality Control Board Comments
Comment 1: The change from catalytic oxidation to granular activated carbon (GAC) units to
treat the vapors from Treatment Facility F is acceptable to the agency.
Comment noted.
Comment 2: The description of the GAC vapor treatment system on page 9 does not specify
that the unit will also treat the fuel hydrocarbon vapors from Treatment Facility F. Please address
this issue.
See response to DTSC Comment No.1.
Comment 3: The brief description of the design and operation of the GAC units does not
contain enough detail for the agency to comment on or approve the design as outlined in this
document. Our agency has several comments and questions regarding ihe determination of
breakthrough and the disposal of the discharge products from the flushing of the GAC units.
However, is it appropriate to address specific design issues of the GAC units within the
Explanation of Significant Difference (ESD) document? If design specifications are required in the
ESD, then a more complete description of the operation of the GAC units should be included. If
not, then a brief description of the GAC's ability to sorb contaminants and the proposal to
regenerate the carbon onsite should be sufficient to approve the general technology. The specifics
of the design and operation should be proposed to the regulatory agencies in the Remedial Design
document.
As discussed with Elizabeth Adams of the RWQCB, the following sentence has been added to
the end of Paragraph 6 in Section 3: "Details of the remedial design will be addressed in a later
design document that will be subject to regulatory review."
Comment 4: This document should state that all appropriate and relevant regulatory
requirements, such as air emission limits and monitoring requirements, disposal of secondary
wastes generated by the alternate technology and any other substantive requirements that apply to
the treatment chain will be followed during operation of the treatment facility.
Similar language to that suggested in this comment has been added to the end of Section 3 of
the Draft Final ESD.
4.3
Responses to U.S. Environmental Protection Agency Comments
Comment 1. The ESD needs to be signed by representatives of the U.S. EPA and the U.S.
Department of Energy.
Signature blocks for representatives of these agencies have been added to Section 5 of the Draft
Final ESD.
5.
Statutory Determinations
Considering the new information that has been developed and the change that has been made to
the selected remedy, EPA and DOEILLNL believe that the remedy remains protective of human
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6
UCRL-AR-112804
Exp1lmation of Significant Difference
June 15,1993
,
health and the environment. complies with Federal and State requirements that were identified in
the ROD as applicable or relevant and appropriate to this remedial action, and is cost-effective. In
addition, the revised remedy uses permanent solutions and alternative treatment technologies to the
maximum extent practical for this site. The change contained herein is significant. but does not
fundamentally change the remedy.
8.23.Q3
Dare
K/~/Cj3
Dale .
6.
Public Participation Activities
DOE has presented this change to the remedy in the form of an ESD because the change is of a
significant, but not fundamental, nature. DOE provided the EP A and State regulatory agencies
with a comment period on this ESD. In accordance with Section 117(c) of CERCLA, 42 U.S.C.
Section 9617(c), DOE will publish a notice in the local newspaper, which describes this ESD and
its availability for review at the LLNL repositories. This ESD and all documents that support the
change herein are contained in the Administrative Record for the LLNL site.
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II
UCRL-AR-112804
Explanation of Significant Difference
June 15,1993
(.
7.
References
Aines, R., R. Newmark, W. McConachie, K. Udell, D. Rice, A. Ramirez, W. Siegel, M.
Buettner, W. Daily, P. Krauter, E. Folsom, A. Boegel, and D. Bishop (1992), Dynamic
Underground Stripping Demonstration Project, Interim Progress Report 1991, Lawrence
Livermore National Laboratory, Livermore, Calif (UCRL-ID-I09906).
Dresen, M.D., J.P. Ziagos, A.J. Boegel, and E.M. Nichols (Eds.) (1993), Remedial Action
Implementation Planfor the UNL Livermore Site, Lawrence Livermore National Laboratory,
Livermore, Calif. (UCRL-AR-ll0532).
Dresen, M.D., W.F. Isherwood, and J.P. Ziagos (1991), Proposed Remedial Action Plan for the
LLNL Livermore Site, Lawrence Livermore National Laboratory, Livermore, Calif. (UCRL-
AR-105577).
Isherwood, W.F., C.H. Hall, and M.D. Dresen (Eds.) (1990) CERCLA Feasibility Study for the
LLNL Livermore Site. Lawrence Livermore National Laboratory, Livermore, Calif. (UCRL-
AR-10404O).
Lester, George R. (1989) Allied Signal Catalytic Destruction of Hazardous Halogenated Organic
Compounds, Air and Waste Management Association, 82nd Annual Meeting and Exposition,
June 25-30, 1989, Anaheim, Calif.
Thorpe, R.K., W.F. Isherwood, M.D. Dresen, and C.P. Webster-Scholten (Eds.) (1990),
CERCLA Remedial Investigations Report for the LLNL Livermore Site, Lawrence Livermore
National Laboratory, Livermore, Calif. (UCAR-10299).
U.S. Environmental Protection Agency (EPA) (1991), Guide to Addressing Pre-ROD and Post-
ROD Changes, Office of Solid Waste and Emergency Response, Publication 9355.3-02, April
1991.
U.S. Environmental Protection Agency (EPA) (1989), Interim Final Guidance on Preparing
Superfund Decision Documents, Office of Solid Waste and Emergency Response, Directive
9335.3-02.
U.S. Department of Energy (DOE) (1992), Record of Decision for the Lawrence Livermore
National Laboratory, Livermore Site, Lawrence Livermore National Laboratory, Livennore,
Calif. (UCRL-AR-I09105).
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