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U.S. Army Corps of
Amendment 1
Environmental Protection Agency Region 7
Superfund Program
DATE: 20 November 2015
WLLFOIA4312- 001 – 0055680
Table of Contents
Isolation Barrier Alignment Alternatives Assessment
West Lake Landfill, Bridgeton, Missouri
Section Page
Introduction …………………………………….••………………………… 2
Background ………………………………….••••••………………………… 3
RIM Isolation Alternatives ……………..•••••••…………………………… 3
Concrete Isolation Barrier Wall ……… ,. •••…. v •••••••••••••••••••••••••••••••••• 4
Excavation to Create an Air Gap .. “‘ ……………. ,~ • .; ••…………………….. 5
Heat Extraction Barrier ………•.••••………………. ~,~”””•~•.• ……………….. 6
IB Alternatives Assessment ……………………………. · .. ,'””” …………… 7
Assessment Factors ……………….. , ……………………… · ………………. 7
IB Alternatives -Advantages and Duadvantages ………….. ·····~· …….. 7
Relative Comparison of Alternatives by Assessment Factor …………… 10
Structural IB Alignment 1 Advantages Dis~ussion …………………….. 10
Structural IB Alignmentl Disadvantages Diseus~ion ………………….. 11
Structural IBAlignment 2 Advantages Discussion …………………….. 12
StructurafiB Alignment 2 rii:sa.dvantsrges Discussion …………………. 12
Structn:tal IB Alignment 3 Advantages Discussion ……………………… 14
Structural IB Alignment 3 Disadvantages Discussion ………………….. 14
Heat.Extraction IB Advantages Discussion …………………………….. 19
Heal Extraction IB Disadvantages Discussion …………………………. 19
Design Considerations …………………………………………………… 20

Design Schedule Consider.ations …………………………………………. 22
Airport Negative EasementAgreement …………………………………. 24
Table 1 Relative Comparison of Alignment Alternatives …………………… ll
Table 2 Options to Address Remaining RIM ………………………………… 21
References ………………………………………………………………………… 25
WLLFOIA4312- 001 – 0055681
1. Introduction
Isolation Barrier Alignment Alternatives Assessment
West Lake Landfill, Bridgeton, Missouri
In 2014, the U.S. Environmental Protection Agency (EPA) requested the United States Army
Corps ofEngineers (USACE) evaluate information conveyed by the Responsible Parties (RPs)
during discussions between US ACE, the RPs, EPA Superfund nersonnel (EPA), and EPA’s
Office ofResearch and Development (ORD) regarding proposedJocations and alignments of an
Isolation Barrier (IB) at West Lake Landfill in Bridgeton, Missouri. The purpose for
constructing an IB is to prevent a subsurface smoldering event (SSE) in the adjacent Bridgeton
Sanitary Landfill from coming into contact with radiologically rmpacted materials (RIM) located
in Operable Unit 1 (OU1) Area 1 of the West Lake Landfill. In August, 2014, USACE
submitted an Isolation Barrier Alignment Alterriatives Assessment Report. The 2014
assessment focused on the proposed alignments,the feasibility of constructing the IB, the
comparative advantages and disadvantages of the proposed alignments, anCI the associated risks.
One of the key findings from the repprl was that the extent of radiological material in the West
Lake Landfill was not fully characterized which was necessru:y to be able to quantify risks
associated with RIM remaining south of any battier. and inform EPA’s decision on alignment.
During spring and summer of2015, the RPs perforllfed additionalinvestigations to determine the
extent of RIM. In ad~iti()11, ~ver the last year,the RP~shave been performing a thermal barrier
pilot study in which 1iqqid is circulated through.converted Gas Interceptor Wells ( GIW) south of
the neck area (narrow section betWeen south and north quarry landfills) to determine if this could
remove sufficient heat from the waste to halt advancement of the SSE.
This 2015 a:Ssessment amends the 2.014 assessment to take into consideration results of the
additional RIM investig~tiadvantages and disadvantages by
assessment factor.
WLLFOIA4312- 001 – 0055690
Odor Potential
Bird Hazard
South of

Potential for
Future SSE
North of
On-Site Safety
Table 1: Relative Comparison of Alignment Alternatives
Alignment 1
Least volume than
Least odor
potential due to the
lowest volume of
waste handling
Least bird hazard
potential due to the
lowest volume of
waste handling
Mostrunount of
RIM to remain
south ofiB
… ~o~pared to the
other :aligmneilts
Anticipated to have
the lowest potential
for future SSEon
, the north side ofm
Largest volume to be
excavated due to
excavation for working
platformand 180-foot
depth in North Quarry,
and increased thickness
of wall to resist
increased loads
Highest odor potential
than both Alignment 1
and 3 due to highest
volume of waste
handling. Wouldbe
similar to active landfill
operations. ….. .
Highest bird hazard·
potenti;1l than both ……. .
Alignment} and 3 due ···
to lii~est v:oiume of
expos.ed waste. Would
be similar to active
landfill operations.
.. ·····
None -assum.es that no
RIM material wa:s
placed in the North
Qiuu:ry .landfill
Anticipated to be the
higbestpotential for a
future SSE on the north
side of the IB due to
highest volume of
newer, less degraded
waste remaining north
due to waste being
oldet and likely
more fully
degracted: .> of the lB.
Potentially greater
on-site safety risk
than Alternative 3
due to known RIM
being excavated.
Greatest on-site safety
risk compared to
Alignment 1 and 3 due
to the significantly
higher volume of waste
excavated and handled.
Lowest on-site safety
risk due to RIM.
Approximately twice as
much as Aligmnent 1
~95,000 CY ±.,.
significantly less than
Higher odor potential than
Alignment 1 due to higher
volume ofwaste handling
Htgner bird hazard
pQ’tential than Aligmnent ··
1 due to higher volume of
waste handling
Least amount of RIM
would remain south ofiB
compared to Aligmnent 1
and potentially no RIM
would remain .
Anticipated to be higher
potential than Aligmnent
1for a future SSE on north
side of the IB due to
newer, less degraded
waste remaining north of
the IB but less than
Alignment 2 due to less
volume of newer waste
remaining north of the IB
Lower on-site safety risk
than Aligmnent 1 if little
or no RIM excavated but
higher general safety risk
than Aligmnent 1. Higher
on-site safety risk than
Aligmnent 2 if RIM is
Least amount of
excavated volume of all
alternatives. System
requires wells and near
surface coolant loop
Least odor potential of all
options. Least amount of
waste to be removed
during well and cooling
loop installation.
Minimal bird hazard
potential due to limited
waste handling.
No RIM anticipated to be
located south of the
thermal lB.
Anticipated to have the
highest potential for a
future SSE north of the
lB. Can be offset by
flexibility and ease of
system expansion.
Lowest on-site safety risk
due to no open excavation
and no limited RIM
WLLFOIA4312- 001 – 0055691
Criteria Alignment 1 Alignment2 Alignment3 ThermaliB
Off-Site Safety Potentially higher Highest off-site safety Lower off-site safety risk Lowest off-site safety risk
off-site safety risk risk due to the than Aligmnent 1 if no due to limited dust from
than Alignment 3 significantly higher RIM (dust generation). well installation and
during installation volume of waste being Higher off-site safety risk surface line excavation.
due to RIM excavated requiring off- than Alignment 1 due to Lowest risk for RIM
excavation (dust site transportation, off-site transportation exposure.
generation) and which increases truck (traffic accidents)
off-site traffic and risk for
transportation of traffic accidents.
RIM (traffic
Off-Site Waste RIM waste Largest volume of off- Off-tsitedisposal No offsite waste transport
Transportation excavated as part site disposal of non- potentially not required if anticipated.
and Disposal of wall installation RIM waste will be ~1 RIM is located north
will require off-site required due to limited .· ofaligmnent
disposal. on-site waste dispo:sal
Duration of Shortest design Longest design i.l. ··u•· ration Longer design dl.lration Shortest design duration
Design duration due to due to more than 180- than Alignment 1 due to due to well design
shortest wall and foot depth requiring longer duration of pre._ completed. Requires
shorter pre-design pre-design investig~tion des~gn investigations and surface equipment and
investigations an.d. highly complex more complex wall design coolant design
de&J:gn (:lue to increased depth preparation.
Duration of Shortest Loirgest construction ~onger construction Shortest duration of
Construction construction duration than both driration than Alignment construction. No
duration due to Alignment 1 and 3due 1 due to 30 to 40-foot excavation, just well
shortest wall to 180-foot depth, increased~epth of wall installation and cooling
significantly }Vider w:all loop installation.
to handle increase
loading ·.
Impact to No impaetto Greatest impacts to the Moderate impacts to the No impact to existing
Existing existing North Quarry North Quarry infrastructure on North
Infrastrucwre infi:astn,1cture on Inffastrt,u::.ture used to Infrastructure used to Quarry and no impact to
North Quarry brit balance lanilfill·gas balance landfill gas operation of the transfer
may impact extraction and extraction and station.
operation of the control/monitor the control/monitor the SSE
transfer station, SSR
which could result
” in delayed or
reduced trash
servi’ce to impacted
customers •··
Technical Technically At the limits of Technically Feasible Technically feasible –
Feasibility Feasible- however technical feasibility – although more difficult Application of heat
there are no known potentially not feasible than Aligmnent 1 – extraction wells for this
past application of Feasible- however there purpose has had limited
the use of concrete are past application of the testing (the RP’s pilot
as a heat barrier in use of concrete as a heat study)
a landfill. Studies barrier in a landfill.
have shown Studies have shown
degradation of degradation of concrete
concrete strength strength properties from
properties from prolonged exposure to
prolonged exposure high heat
to high heat
WLLFOIA4312- 001 – 0055692
4.4 Structural IB Alignment 1 Advantages Discussion
Of the three structural IB alignments, Alignment 1 is considered the most technically feasible
and will require the least volume of waste to be excavated. The RPs have estimated the total
volume of waste for Alignment 1 to be approximately 50,000 cubic yards. Because this
alignment requires excavation of the least amount of waste, it is expected that it will have the
shortest construction duration. A shorter construction duration will reduce the duration in
which the community is exposed to odors from the excavation. Landfill odor has been an
ongoing concern for the surrounding community and reduced duration for odor emissions
would be a favorable advantage.
Bird hazards to air traffic are a significant safety conc~m t0 the St. Louis Airport Authority
as West Lake Landfill is located within 10,000 feet o£ the nearest Lambert St. Louis Airport
runway (see Section 7). Alignment 1 will resultinthe least amount of excavated waste and
will therefore present less risk of bird hazards and other nuisance species (insects, rodents)
that can, in tum, attract more birds, when compared to the other alignments. While this
alignment offers the least bird hazard risk, mitigation efforts will still be.required to
minimize waste exposure during excavation ahd handling o{ waste materiaL
Based on a 2013 bird survey performed during well i:l:lstallation and toe drain excavation
activities in the North and South Quan”ies ofthe Bridgetol;l Sanitary Landfill, 256 gulls,
geese, doves, and raptors were observed within:~ 20-day period. According to the Federal
Aviation Administration (Dol beer et al, 2014 ), these bird species were among the species
most frequently struck.byair:planes betwee~ 1990 and 2~ 13. It is expected that geese and
doves would not he attractecf:~to the excavation and waste handling operations to be
undertaken as they typically do not consume decomposed waste. However, gulls and raptors
are expected to be attr~ted to thesite operations as they will seek out easy food sources
including decemposed waste. With/gulls, miti:g~tion efforts such as sudden loud noises from
bird scaring devices (canons, warning horns) are .effective only for a period of a few days as
gulls can rapidly adaptto these sounds (AirpdrtOperators Association and General Aviation
Awareness Council, 2066). Add1tionally, since gulls tend to feed at operating landfills as the
trucks hauli:l:lg in trash are”tipped”, it is expected that gulls will likewise feed as excavation
is being conducted and trucks are being loaded to move the excavated waste to the staging
areas and to load trucks for off-site waste transport. Therefore, minimizing the amount of
excavation exposed and reducing the duration of construction will be one of the best bird
hazard mitigation strategies for the site.
Storm water management will also require mitigation efforts as birds are attracted to standing
water sources. For work previously performed at the Bridgeton Sanitary Landfill, the RPs
have ensured that detention basins drain within 24 hours, thereby not providing a continued
standing water source to attract birds. It is expected that a similar mitigation method for
storm water management would be implemented for each of the IB alignments.
Alignment 1 would be located where there will be no newer waste located on the north side
of the IB and will be placed in an area with a maximum waste depth of approximately 40
feet. The extent of waste decomposition and the pressure and insulating conditions in a
WLLFOIA4312- 001 – 0055693
landfill (often determined by the depth or thickness of the waste) are two of several factors
that can contribute to the generation of a future SSE. Older waste and shallower waste
located north of the Alignment 1 IB are considered an advantage as these conditions are less
likely to support the generation of a future SSE than the newer and deeper waste of
Alignments 2 and 3.
Another advantage of Alignment 1 is that the design time would likely be shorter than the
design time for Alignment 3 primarily because some of the data required for design of the IB
has already been collected. Some geotechnical data would still be required to be collected
before design could begin, but these pre-design investigations would likely be shorter in
duration than those that would be required for the other alignments, therefore allowing design
efforts to be completed in a shorter duration than the other alignments.
Alignment 1 also has an advantage of not having to remove existing North Quarry
infrastructure (monitoring wells, landfill gas collection wells, andassociated piping) for the
installation of Alignment 1. The North Quarry infrastructure was installed as part of the
May 2013 First Agreed Order of Preliminary Injunction for the RPs to install infrastructure to
monitor for the SSE and control landfill gas. Therefore, the least impact to the existing
infrastructure will minimize the design and construction duration as the RPs will not have to
remove, redesign, and reinstall the North Quarry infrastrUcture.
4.5 Structural IB Alignment 1 Disadvantages Discussion
While Alignment l has comparatively more advantages than Alignments 2 and 3, the
disadvantages of Alignment 1 carry some amount of risk that must be considered. While it
may be possible to manage the risk associated with these disadvantages, these risks must be
considered. when selecting an align;ment.
The first disadvantage .of Alignment 1 is that although the vast majority of RIM will be
isolated north of the IB, some RIM will remain on the south side of the IB. Since the
purpose ofinstalling the IBis to prel(ent the SSE in the Bridgeton Sanitary Landfill, from
coming into contact with RIM in the West Lake Landfill, leaving some RIM on the south
side of the IB would not completely fulfill that purpose. To mitigate this significant
disadvantage, the Alignment 1 design would need to include a means for mitigating the RIM
remaining on the southside of the IB. Field and laboratory results from the recent sampling
performed by the RPs must be evaluated to determine what information is required to
evaluate technologies fotaddressing the remaining RIM, if the risk is shown to be such that
remediation is required. Section 5 includes a list of potential options that the RPs could
consider to address remaining RIM.
The second disadvantage of Alignment 1 is that the IB would be installed through RIM.
Handling RIM during excavating, staging, screening, transporting, and disposal of the RIM
are activities that must be appropriately planned during design and carefully managed during
construction due to the potential impact to the safety of on -site workers and the potential for
RIM release during off-site transportation to disposal facilities.
WLLFOIA4312- 001 – 0055694
The on-site worker safety risks can be mitigated through the preparation and thorough
execution of Health and Safety Plans; however, preparing and following these procedures
does add time to the construction process. Similarly, off-site disposal of RIM will require
some over the road transportation. This will result in increased truck traffic in the vicinity of
the site and could lead to increased risk for traffic accidents, which could result in spilling
RIM along the transportation route.
Excavation through RIM can also lead to off-site exposure risks associated with airborne
dust, which could contain RIM. Qualitative assessment of the relative off-site risk due to
airborne RIM exposure would be dependent upon the depth of the RIM and the RPs’ material
handling processes. Mitigation is planned through use Gf afi air monitoring network to
monitor for RIM and through proper dust control dur:ing ex~a~ation activities. Proper
planning and response plans to include these mitigation actions will be required to reduce the
risk but the preparation and implementation of t}tese mitigation efforts will increase the
design and construction durations.
Off-site waste transportation itself is a risk fornotonly s~fety reasons, but.due to how it can
impact the duration of construction. The time it takes to stage, screen, segreg~te, sample,
load, and transport the RIM can ~dd ~~nificant time !O the construction duration. The exact
impacts to the design and construction efforts cannot be quantified at this time and will need
to be addressed by the RPs as they determine how the RIM will be managed. The amount of
RIM, the saturation of the waste, how the waste will be transported, and the location,
permitting, and samplingtequirements of the disposal facility will contribute to the schedule
risk associated with handling RIM.
There are no know~ past applications using a concrete wall as a heat barrier in a landfill.
There have h~en. studies showing. thed~gradation of strength properties of concrete when
exposed to high heat. It maybe possibleto,overcome these issues during design, but more
study would be necessary to determine if speci~l mix designs could overcome this issue.
4.6 Structural IB Alignment 2 Advantages Discussion
The primary advantage of Alignment 2 is that this alignment should separate all identified
RIM from the existing SSKin:the Bridgeton Sanitary Landfill. This is a significant
advantage as that is the primary reason for the installation of the IB.
Another advantage is that from an off-site safety standpoint, because no RIM is anticipated to
be encountered, the risk for on-site and off-site exposure to RIM is low.
4.7 Structural Alignment 2 Disadvantages Discussion
The primary disadvantage of Alignment 2 is the significant volume of waste that would need
to be excavated. Because the depth of the IB would be approximately 180 feet and the
WLLFOIA4312- 001 – 0055695
potential for differential settling of the waste on the opposite sides of the IB, the IB design
would have to be significantly wider than the IB for Alignment 1 to be capable of
withstanding these differential stresses. This effort will significantly increase the design
duration as additional time will be required to ensure the design is stmcturally sound and that
the proper cooling system is incorporated. Additional geotechnical data will also need to be
collected and getting that data from a deeper depth will take longer. One potential way to
mitigate the width of the Alignment 2 IB would be to implement an on-going operation and
maintenance plan that restores the surface of the settled waste to prevent the overturning
stresses caused by differential settlement of the wastes adjacent to the barrier. The RPs will
need to make a determination on which means is most effective for addressing this issue,
should this alignment alternative be selected.
Due to the large depth and width of the excavation, thelength of time the excavation would
remain open would be significantly increased and the odor potential and duration of the odor
would, in tum, be significantly increased. The negative impact of the odor and the duration
of the odor to the quality of life for the nearby community may not be acceptable.
The significant volume of waste and the length of time to excavate will al~osignificantly
increase the bird hazard potentiaL As discussed itt Section 4.4, gulls and raptors are expected
to be attracted to the site operations as they will seeK: out easy food sources. Due to their
ability to rapidly adapt to loud and active surroundings, mitigation techniques would have to
be aggressive and vary frequently due to the significant dutation required to constmct this
alternative. Additionally, since gullswould be expected tofeed as excavation is being
conducted and tmcks are ~eing loadedlo move the exc~vated waste to the staging areas and
to load tmcks for off-site waste transport, bird nlifigation for this alignment alternative is
expected to be challenging over the extendedcmistmction duration expected for this
alignment alternative.
Alignment 2 would be located. within the Bridgeton Sanitary Landfill, therefore, a large
amount of the newer waste in this landfill will be located on the north side of the IB. The
maximum depth on the north side of the IB would be approximately 180′. The greatest depth
of this ‘hewer waste wouHfb’e located between the IB and the Quarry wall, which could
potentially i11crease the pressure and insulating factors, which, if other conditions are right,
could contribute to a future SSE on the north side of the IB.
Alignment 2 would be locate(! in the North Quarry of the Bridgeton Sanitary Landfill and
should not encounterRJM.because there has been no evidence that RIM was placed in this
area and because a review of historical records indicated that in 1973, while the RIM was
being placed in the West Lake Landfill, the North Quarry was still be excavated. This site
conceptual model does not support the presence of RIM from the Latty A venue site in the
North Quarry. Because of this, the risk to the safety of on-site workers due to RIM is
determined to be the lowest compared to the other alternatives. However, because of the
significant volume and depth to be excavated, the constmction techniques, and the length of
constmction required to install the IB, the general constmction safety risk to workers is
considered significantly higher than Alignments 1 and 3.
WLLFOIA4312- 001 – 0055696
With regards to off-site safety, due to the large volume of waste and limited space on site for
staging, off-site disposal will be required. The increased tmck traffic in the vicinity of the
site will increase the risk for traffic accidents. Additionally, the increased tmck traffic
waiting to enter and exit the site will impact the existing Transfer Station operations. This
could dismpt some of the Transfer Station’s operations including customer’s trash collection
Another disadvantage of Alignment 2 is that monitoring wells, gas collection lines, and gas
extraction wells located in the North Quarry would have to be removed prior to installation
of the IB and then reinstalled after constmction is completed. Due to the long constmction
duration, that North Quarry infrastmcture would not be in place for a long duration. The
North Quarry infrastmcture was installed as part of an Qrder for Preliminary Injunction for
the RPs to monitor temperature fluctuations, carbon monoxide emissions, and control landfill
gas. This infrastmcture is important for detecting potential movement of the SSE and
controlling landfill gas.
The volume of waste to be excavated with Alignment 2 would result in daily conditions that
are considered similar to those of an operating landfill. Th~. number and the significance of
the disadvantages of Alignment 2 far outweigh the Aligmnent 2 advantages. Therefore, all
parties were in agreement of not suppoJ;ting selection ofAlignment 2.
4.8 Structural IB Alignment 3 Advantage~ Discuss ion
The primary advantages of A~gnment 3 are that 1t is tecllnically feasible and requires
significantly less volume of waste to be excavated compared to Alignment 2 while
minimizing and potentially eliminating RIMremaining south of the IB and potentially
exposed ~o the SSE when comparet:l to Alignment 1.
Anotlfler advantage ofAlignmeat 3 is that the on-site safety risk to workers due to RIM
exposure will be lowerthan Alignment 1 and the on-site safety risk to workers due to general
constmction efforts would be less than Alignment 2 because of the shorter constmction
duration and less challenging installation.
4.9 Structure/} Alignment 3 Disadvantages Discussion
Although Alignment 3 has significantly less volume of waste to be excavated than Alignment
2, the volume of waste to be excavated for Alignment 3 is considered a disadvantage when
compared with the volume of waste to be excavated for Alignment 1. Alignment 3 could
have as much as double the volume of waste as Alignment 1. As previously stated, the
volume of waste drives the disadvantages with each alignment, so more than doubling the
volume of waste will increase the risk associated with those disadvantages.
Alignment 3 will have less potential for odor than Alignment 2, but will have a greater
potential for odor than Alignment 1 due to the increased volume of waste to be excavated. In
WLLFOIA4312- 001 – 0055697
addition to the longer excavation duration, multiple staging areas will also be required for
Alignment 3 in order to stage the larger amount of excavated waste so it can be screened
prior to disposal. Having multiple staging areas will also contribute to the longer overall
construction duration and odor potential. As odor is a quality of life issue for the community,
this could be considered a significant disadvantage to the community.
Alignment 3 will also have a significantly less potential for bird hazard compared to
Alignment 2 due to the lower volume of excavated waste; however, when compared to
Alignment 1, the bird hazard potential increases and therefore, is considered a disadvantage.
As discussed in Section 4.4, gulls and raptors are expected to be attracted to the waste and
some mitigation efforts are not expected to be effective for more than a few days.
Additionally, since gulls tend to feed as the excavated material is loaded onto trucks for
transport, netting or other means of mitigation will likely be required to minimize bird
A disadvantage of Alignment 3 is that it would need to move 50-feet closer to the high
quarry wall than the alignment evaluated as Gption 3 Alignment in the R.Ps October 2014
report entitled “Isolation Barrier Alternatives Analysis, West Lake Superfund Site.” This
will require additional design effort and potentially a thick;er wall in the w’esteJ;U third of the
wall to account for potentially higher differential settlement forces from North Quarry waste
settlement. Despite this, the overall level of effort as compared to the Option 3 Alignment in
the 2014 report is unlikely to be substantially. higher.
With Alignment 3, S(JMepfthe newer Waste in the North Quarry will be located on the north
side of the Alignment 3 IB. Tfiis overlay area; when combined with the West Lake Landfill
Area 1 waste below it, has a maximum depth ()f waste of approximately 90-feet. The
additional depth ofwasJe from the North Quarry overlay and the newer waste located on the
north side of the Alignment 3 IB are two factors that can contribute to the generation of a
future SSE on the north side of the IB. Because these conditions would exist if this
alignment were installed, they are considered·~ disadvantage. The on-site safety risk for
Alignment 3 would be lower wlien compared to Alignment 1 if little or no RIM is excavated
to ins tail this IB. The relative risk for Alignment 3 RIM exposure would be equal or slightly
higher compared to Alignmtnt 2 as noRIM is expected to be encountered during excavation
of Alignment 2. From a general construction standpoint (not considering RIM), the on-site
safety risk for Alignment 3 is higher than Alignment 1 due to the length of the construction
duration and higher revel of Qifficultly associated with a deeper wall. The general on-site
safety risk for Alignnfent3is considered significantly less than Alignment 2 due to the depth
of excavation and the amount of material handling required for Alignment 2.
Alignment 3 ‘s off-site risk for exposure to airborne dust containing RIM is considered lower
than Alignment 1 ‘s risk because Alignment 3 will be placed in an area that is expected to
encounter limited RIM, if any, based upon recent sampling results. As indicated in the
Alignment 1 discussion, mitigation measures, including air monitoring and dust control, can
be employed to control risks during excavation and waste handling.
WLLFOIA4312- 001 – 0055698
The duration of design for Alignment 3 will be longer than Alignment 1 due to the need to
for a more robust design to address differential settlement. The depth of the waste will
increase the amount of time required to collect the data necessary for design. Additionally,
because the IB will be deeper in the western portion of the alignment, additional design time
will be required due to more complex loadings and structural requirements of the wall. The
construction duration for Alignment 3 will also be longer than Alignment 1 due to the
increased depth of the western portion of the IB.
Another disadvantage of this IB alignment is the impact to existing infrastructure. The
monitoring wells, gas collection lines, and gas extraction wells located in the North Quarry
would have to be removed prior to installation of the IB and then reinstalled after
construction is completed.
There are no known past applications using a concrete wall asaheat barrier in a landfill.
There have been studies showing the degradation of strength properties of concrete when
exposed to high heat. It may be possible to oxercome these issues during design, but more
study would be necessary to determine if special mix designs could overcome this issue.
4.10 Heat Extraction Barrier Advantages
The most significant advantage oftheheat e~traction IBis that the volume of waste to be
removed will be negligible compared to any other option. The waste to be removed results
from drilling coolant wells. This amount of waste <;an easily be handled on site. As a result of the mfuimized waste, the odots. and bird hazards for this alternative is significantly less than the other alternatives. On-site safety risk is also the least of all alternatives due to limited, if any, :exwsure to R1;M or other chemicals. Additionally, offsite exposure to RIM :Fisk would l:>e the least ofall the other alternatives as well due to the limited
amount of waste handlfug. A€lditionally, thilalternative would have limited truck traffic
when compared to the other alternatives, significantly reducing the off-site traffic accident
One of the oth’er more significant advantages of the heat extraction barrier alternative is that
the design time is shorter than the other alternatives and it can be installed within a shorter
duration than the strUcturaliB+alternatives. Given that there are varying views of the
movement of the SSE, shorter design and installation durations are a strong advantage.
Because of the shorter design and installation time, the system can be expanded quickly in
the event actual monitoring data shows that additional cooling is necessary to contain the
heat front.
Data from the RP’s pilot study provides a proof of concept for the heat extraction barrier
alternative. The proposed heat extraction system combined with the heat sink properties of
the surrounding limestone makes the neck area between the North and South Quarries the
optimal location to install a cooling system.
WLLFOIA4312- 001 – 0055699
4.11 Heat Extraction Barrier Disadvantages
The primary disadvantage of the heat extraction barrier is the wells will be subject to high
heat, a corrosive environment, and waste settlement. This can be mitigated by planning for
well replacement if heat and corrosion or waste settlement impacts the cooling wells. In
addition, application of heat extraction wells for this purpose has had limited testing (the
RP’s pilot study).
Another disadvantage is that the proposed placement of the heat extraction barrier in the neck
is that if a future SSE were to occur in the North Quarry, the heat extraction barrier would
not be positioned to prevent the SSE from moving into the West Lake Landfill and coming in
contact with the RIM. However, the flexibility of the lieat: extraction barrier alternative is
such that additional wells and coolant capacity could he quickly installed at a location
between a new SSE and the RIM.
5. Design Considerations
Options to address some of the technical challenges anticipated during design and construction
were identified. Following are some of those design considerations.
For Alignment 1 and potentially for Afignment 3, the possibility of encountering RIM during
excavation exists. During discussions, the RPs i:ttdicated they Were considering utilizing a panel
wall construction method to install the IB, Utilizing a panel wall construction method would
reduce the amount of e~cavated materials arid drilling fluids/slurry tfrat would come into contact
with RIM when compared to a cont~uous trench excavation; kowever, there could still be a
significant volume ofwa~te and flui~s resulting from the in panel wall construction that would
require handling and disposal as RIM. Because ilie safe handling and disposing of additional
material as RIM. will increase the Qyerall duration and cost of the project, alternative construction
methods.thatcouldfurther minimize the potential amount of radiologically impacted slurry or
drilling fluids should be investigated.
One potential construction method that could be considered to minimize the use of fluids or
slurry is the use of a secant pile.wall for that portion of the IB that extends through RIM. A
secant pile wall w~:Uld not require ;use of a slurry, so it would minimize the potential spread of
RIM and eliminate handling of :RIM contaminated slurry. It is also suitable for installation in
difficult subsurface c6n~iti~ns, It also can be used in combination with panel wall installation
(panel wall installation on ilie east portion of the IB and a secant pile wall installation on the west
portion of the IB). The primary disadvantage of a secant pile wall installation is that there is less
certainty in the continuity of the wall; however, there are installation and down-hole verification
techniques to minimize this uncertainty. The RPs would also need to determine how to
incorporate an internal cooling system with both the secant pile wall and the panel wall
construction methods.
Depending upon the alternative selected, there may be some RIM remaining on the south side of
the IB wall that needs to be addressed as part of the IB design. Table 2 summarizes some
potential mitigation measures to consider.
WLLFOIA4312- 001 – 0055700
Table 2 – Options to Address Remaining RIM
Option Description Advantages Disadvantages
RIM handling, screening, transport,
Open excavation and increase in odor
Open excavation and increase in bird
hazard to air traffic
Ensuring IB stability while RIM
Excavate identified excavation is conducted adjacent to the
Excavate RIM remaining on Minimizes risk of RIM contact lB. This is a significant disadvantage
RIM south side ofiB with SSE and will increase the size of the IB, the
\l’olume of waste to be excavated, and
6tlfer associated risks. It is possible that
.excavation after IB installation may not
be technically feasible depending upon
the t?cation of the remaining RIM with
respectto the IB structure.
Off-site hauling for disposal may
increases risk of traffic accidents and
RIM release.
Reduces the amount of waste Effects of SSE in C:ontact with stabilized
Utilize deep soil to be handled, transported, and R.lM are unknown. Will likely require
mixing techniques di&posed .. • bench scale testing to verify
to auger down to
··················• May be difficult to implement in the
RIM, inject cement landfill due to potential loss of grout (in
In-Situ grout, and mix Reduces tlfe amoimt of situ deep soil mixing has been
Stabilization grout with the exposed waste and therefore successful in nonnal soil conditions).
waste to reduces the amount of od.or Some components of waste may hinder
immobil.izethe hydration of waste so bench scale
RIM and adjacent testing would be required to determine
waste intoa the appropriate stabilization agents.
hardened block less Reducesthe amount of Requires thorough identification of RIM
sl)St:;eptible to tlte exposed waste and therefore to know area requiring stabilization
SSE reduces the bird llit?:ard
Eftective for smaller areas of Requires ability to identify location of
Inject liquid N2 or RIM SSE. Difficult to detect SSE movement
1 ;n~~=~~c~h:s the
Wastefiandling/disposal Reliable supply ofliquid N2 and C02 is
would be limited to waste not currently available.
LiquidN2 or SSEapproaches to generated for injection well
C02 Injection cool tlfe. subsurface installation
and extinguish the Limited odors- no open
SSE excavation Increased worker safety issues when
Limited bird hazard-no open handling liquid N2
Heat Install closed- Flexible and can be Wells may settle as waste settles and
Extraction system cooling implemented quickly. Can be could impact effectiveness of system,
Barrier loop and wells to expanded easily if additional causing need for new wells. Well
cool the heat front cooling is required. material could be impacted by high heat
between the RIM and corrosion.
and the SSE to
prevent the SSE
from coming into
contact with the
WLLFOIA4312- 001 – 0055701
Option Description Advantages Disadvantages
Allows for capture of landfill
Install synthetic gas. Landfill gas collected may require
Synthetic cover over top of Eliminates excavation, reduces treatment prior to discharge.
Landfill landfill south ofiB need to handle, transport, or
Cover& Gas where remaining dispose of waste
Collection RIM is located. Eliminates excavation, Any cover could potentially be
System Install gas minimizes bird hazard. susceptible to damage from SSE or
collection system RPs already planning to install natural events.
synthetic cover at North
If any of these options were to be incorporated, the RPs wou:ld’:need to evaluate each one and, if
necessary, conduct the appropriate studies required for design and construction. As part of the
design to address any RIM remaining south of the I]3, the RPs should evaluate the possible risks
to receptors should the SSE come into contact with the remaining RIM.
6. Design Schedule Considerations
It is not known that the SSE will reach the RIM; however, due to the unpredictable nature and
movement of the SSE, the length ofti:nte for the SSE to reach the RIM in QUI, Area 1 is
currently unknown. Therefore, length df time required to design and install the IB was a
consideration during this assessment.
The standard industry practice is to complete the d~s1gn in stages with reviews conducted at each
stage. Typical design stages are the 3 0%, 60%, 90% and 1 00% i:fesign stages. The 3 0% design
stage is conceptual and many of the specific details of the design are not complete and are still
being evaluated, T~e 60% and 90% d~sign stages ate more complete with almost all of the
details defined, The Final Design represents the completed design product. It is USACE ‘s
understanding that a similar design process will be followed for the IB effort and that the
documents produced at each stage of the design will be subject to government review and
This staged approa¢h to the designallows for good quality control and helps ensure that all
design objectives are met. However, at each stage in the process, a set of documents is produced
that requires sufficient time to prepare, review, and then respond to any technical review
comments so that those revisiotis may be carried forward into the next stage. There may be ways
to shorten the time required t6complete each design stage. Typical methods to speed up the
design process are: increase the number of designers; conduct “over the shoulder” or “in
progress” reviews while the design team continues working instead of requiring the designers to
stop and respond to review comments in between each stage; and reduce the time allowed for the
reviewers to perform their review. Each of these methods introduces some chance of error.
Rushing the design and quality control reviews in order to start construction earlier may result in
problems or delays during construction because those problems w