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New Technologies For Subsurface Barrier Wall Construction
Robert D. Mutch, Ir., P.Hg., P.E., Robert E. Ash, TV, P.E., Nashville, Tennessee, and
Jeffrey R. Caputi, P.E., CHMM, ECKENFELDER INC., MaLwah, New Jersey
INTRODUCTION
During much of the 1980s, barrier walls of any type were regarded In some quarters as
crude and antiquated. It was predicted correspondingly that remediation would be dominated bv
. . . . . ~ 1 · 1 1 · ~ ~ ~ ~ _ ~ ~ ~A~ ~ ~;~ ~
emerging treatment technologies SUCh as nloremeclatlon, air sparing, alla surIaclaIll 1lusmrlg.
Notwithstanding the considerable successes of these emerging technologies, particularly
bioremediation, the fact remains that a significant percentage of Superfitnd' RCRA-corrective
action and other waste disposal sites present hydrogeologic, chemical, and waste matrix
complexities that far exceed the capabilities of current treatment-based remedial technologies.
Consequently, containment-based technologies such as subsurface barrier walls and caps are
being recognized once again as irreplaceable components of practical remediation programs at
many complex sites.
Until quite recently, most barrier walls were constructed using traditional technologies
such as soil-bentonite slurry trench, conventional sheet piles, vibrating beam technology, and in
the case of shallow cut-off walls, compacted clay. Today, the remediation engineer considering a
subsurface barrier wall-based cleanup is confronted with a baffling array of new technologies
and permutations of these technologies. Table 1 presents a partial listing of available barrier wall
technologies.
TABLE 1 Subsurface Barrier Wall Technologies
Compacted Clay
Soil-Bentonite Slurry Trench
Self-Harden~ng Slurries
Plastic Concrete Slurry Trench
Deep Soil Mixing
let Grouting
Vibrating Beam
Ground Freezing
Waterloo Barrier(~) Sheet Pilings
Permeation Grouting
Geomembrane Technologies
Each of the technologies listed in Table 1 also many permutations. For instance, there
are many varieties of self-hardening slurries that can be tailored to specific site conditions and
design objectives. There are also a wide variety of permeation grouts and several different
geomembrane technologies, as well as a variety of different materials, that can be used in
vibrating beam barrier walls.
Subsurface barrier walls have been constructed of compacted clay, soil-bentonite slurry
trench and vibrating beam techniques for many years. These technologies are well-understood
and well documented and are thus considered conventional cutoff wall technologies. Each
technique has inherent advantages and disadvantages, and the cost of each is typically tied to
D-23
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D-24
BARRIER TECHNOLOGIES FOR ENVIRONMENTAL MANAGEMENT
site-specific factors. (For further information on these conventional technologies, see, e.g.,
Mutch and Ash (1994) and Cavalli et al. (19921.)
ADVANCEMENTS IN BARRIER WALL TECHNOLOGIES
In the remainder of this paper, we overview the different emerging barrier wall
technologies, addressing their advantages, disadvantages, limitations, documented track records,
and costs.
Deep Soil Mixing Barrier Walls
Development of deep soil mixing (DSM) barrier walls can be traced back to the early
1960s when the Intrusion Prep akt Co. patented a process for "mixed-in-place piles" (Jaspers,
1989~. In the early 1970s, Japanese geotechnical companies developed several different types of
soil-mixing methodologies and, to date, have conducted thousands of deep soil-mixing projects.
Deep soil mixing involves a crane-supported set of leads that guide a series of two to four
hydraulically driven mixing paddles and augers 30 to 36 inches in diameter. As the auger guides
make their way through the earth, they break the soil loose and lift it to the mixing paddles,
which blend the soil with a slurry that is injected through the augers. The slurry can consist of
lime, bentonite, cement, or proprietary mixtures designed to solidify or stabilize the soil. A
continuous barrier wall is created by sequential penetration of the augers overlapping with
previous auger-treated zones. DSM can be used to create cutoff walls more than 100 feet deep.
DSM offers several advantages over conventional cutoff wall methods. First, the soil
does not have to be fully excavated, minimizing soil disposal costs if soils are contaminated.
Since the wall is constructed In small sections, there is considerably less danger of collapse in
soft soils. The technique is also capable of construction within confined areas and requires less
staging and above-ground mixing areas than slurry trench techniques. A disadvantage of the
technique lies ~ the fact that in-situ soils are used in the slurry soil admixture. If the soils are
unsuitable or if waste materials are encountered, then additional costs and construction
difficulties can result. The cost of deep soil mixing usually falls in the range of $6 to $12 per
vertical square foot.
Jet Grouting Cutoff Walls
Jet Grouting evolved in Japan during the early 1970s from a water cutting technology
originally used in American coal mines (Guaterri, 19881. Jet grouting is a general term
describing construction techniques where ultra-high-pressure fluids are injected into the soil at
about 800 to 1,000 feet per second. The high-speed fluid is used to cut, replace, and mix the
native soil with a cementing material, typically a cement-based grout. There are three general
forms of jet grouting that involve injection of a single fluid (grout), two fluids (grout/air), or
three fluids (grout/air/water). Jet grouting proceeds first by drilling a vertical guide hole down to
the required depth. Actual jet grouting then follows, proceeding typically from the bottom to the
top of the borehole. Panels or columns can be formed by controlling the rotation of the drill rods
while lifting the jet grouting device. Columns are formed when the drill rods are rotated during
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APPENDIX~PAPERS PRESENTED
D-25
lifting. Panels can be created by lifting the drill rods without rotation. Subsurface cutoff walls
can be created by jet grouting adjoining columns of soil sequentially. Although jet grouting has
been used extensively in Japan, Italy, Germany, and South America, it has received only limited
attention here in the United States, but it is expected that the technique will be used more
frequently here as acceptance of the procedure grows.
An advantage of jet grouting over other cutoff wall techniques is the fact that it can be
used to stabilize a wide range of soils, ranging from grave! to heavy clays. Another advantage is
that large-diameter columns or panels can be created, starting from relatively small-diameter
boreholes. Therefore, cutoff walls can be constructed beneath buildings with limited disruption
of the structure itself. let grouting also has been conducted to depths in excess of 200 feet. All
three forms of jet grouting have some portions of their process covered by U.S. patents. The cost
of a nominal three-foot-wide barrier wall constructed by jet grouting generally lies in the range
of $15 to $30 per vertical square foot.
Waterloo Sealable Sheet Piles
The University of Waterloo has developed a sealable sheet pile wall that reportedly is
capable of achieving bulk hydraulic conductivities of less than 10-8 centimeters per second. This
product, which has patents or patents pending in several countries, is termed the Waterloo
garner_. The technology involves specially fabncated sheet piles with a sealable cavity
incorporated into the pile interlock. Figure 1 depicts the dimensions at the medium wall
Waterloo Barrier_ constructed of 0.295-inch-thick steel. A heavier gauge, 0.375-inch-thick
steel, Waterloo Barrier_ is scheduled to go into production during November of this year. The
sealable cavity of the Waterloo Ba~TierTM can be sealed with clay-based, cementitious, polymer,
or mechanical sealants. A footplate at the toe of the sealable cavity prevents most of the soil
from entering the cavity during driving. After driving, the sealable cavities are waterjetted to
remove loose soil In preparation for injection of sealant. Waterloo Barriers can be installed to
depths of 70 feet and deeper if necessary by splicing piles together. Costs of the Waterloo
BaIliers are on the order of $15 to $30 per vertical square foot (R. Jowett, personal
communication, 19951.
r SETTLE
/ CAVITY
FIGURE 1 Medium wall Waterloo Barrier_.
22.25 in.
(565 mm)
SEALABLE:
CAVITY
me,
8.17 in.
(208 mm)
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D-26
BARRIER TECHNOLOGIES FOR E~IRONMENTAL MANAGEMENT
Self-Hardening Slurries
Slurry trench cutoff walls can be constructed using self-hardening slurries, designed to
set up in place, producing low-strength barrier walls. This type of cutoff wall is constructed in
panels. A continuous wall is formed by re-excavating the end of the adjacent pane! after it has set
up. Alternatively, an end-stop pipe can be placed between panels. The pipe is removed prior to
full setting of the slurry, allowing the self-hardening slurry in the active panel to flow up against
and form a good seal with the hardening slurry in the previously completed panel.
The most commonly used self-hardening slurry consists of Portland cement and
bentonitic clay (cement-bentonite). Bentonite is blended with water to produce a hydrated slurry,
typically consisting of 6 percent bentonite by weight. Cement is added just prior to pumping the
slurry to the trench. The cement content is typically in the range of 10 to 20 percent by weight.
Upon setting, the mix resembles a stiff clay with ultimate strength in the range of 5 to 50 psi.
While cement-bentonite cutoff-wall technology has been around for many years, its use in site
remediation has been limited by the inability to achieve sufficiently low permeability. The
permeability is typically in the range of 10-5 to 10-6 centimeters per second, whereas 10
centimeters per second commonly is specified in site-remediation applications. The relatively
high permeability of cement-bentonite slurries is due, in part, to the adverse effect of the
Portland cement on the swelling properties of the bentonitic clay.
Alternative self-hardening slurry mixes are now available that consistently can achieve
permeabilities below 1 x 10 centimeters per second. Ground, granulated blast furnace slag can
be blended with Portland cement to produce slag cement. When slag cement with a slag to
Portland cement ratio of 3:1 to 4:1 is combined with bentonite slurry, the permeability of the
-7 ~
mixture is generally in the range of 10 to 10 centimeters per second (lefferis, 1985; Chipp,
19901. The use of slag cement also enhances chemical resistance and ultimate strength. A
proprietary mix marketed by Liquid Earth Support, Tnc., called Impermix~, consists of slag
cement (containing no Portland cement) and attapulgite. Attapulgite is a clay mineral with a
different crystalline structure than bentonite. The combination of slag cement and attapulgite
produces a mix with extremely low permeability, as well as greater resistance to chemical attack
and higher ultimate strength. Permeabilities of less than 10 have been attained (Tallard, 19921.
An advantage of self-hardening slurries in comparison to conventional soil-bentonite
slurry trench cutoff walls is that there is no separate backfilling operation. The slurry can be
prepared in a remote area and pumped to the trench. This allows for construction in limited
access areas and also minimizes the time workers must spend in the exclusion zone in the case of
highly contaminated sites. In addition, there is little or no slurry displaced from the trench that
could require special treatment or handling. Additionally, the panel methods of construction is
advantageous when working in unstable soils or near structures, since the length of open trench
can be minimized. Panel lengths typically range from 10 to 30 feet. This method also allows the
barrier wall to be constructed In discontinuous sections, where necessary for coordination with
other site activities. The cost of self-hardening slurry walls is typically in the range of $10 to $20
per vertical square foot for a nominal two-foot wide barrier and depths less than 100 feet.
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APPEND~PAPERS PRESENTED
D-27
Permeation Grouting
Permeation grouting has been used extensively In the United States and abroad in the
mining and geotechnical engineering fields. The most common type of grout is a mixture of
Portland cement and water. Other types of grout, which have been used under certain conditions,
include cement-sand-water, cement-rock flour, cement-hydrated lime, cement-calcium chloride,
cement-diatomaceous earth, lumnite cement, cement-clay, or cement-bentonite (Krynine and
Judd, 1957~. Asphaltic emulsions and other bituminous compounds have also been used for
grouting (Krynine and Judd, 19571. More recent advancements ~nc~ucte the use of microfine
cement, mineral wax, sodium silicates, and colloidal silica gel.
The amenability of various soils to grouting is in large measure a function of the soil's
permeability, as indicated in Table 2 (Karol, 19901. Soils with permeabilities less than 1 x 10
centimeters per second essentially are ungroutable, while soils with permeabilities greater than
-1
10 centimeters per second require suspension grouts or chemical grouts containing filler
materials. Grouting is also more difficult in heterogeneous soil, as the grout tends preferentially
to follow pathways of least resistance through the soil.
TABLE 2
1 990)
Permeability
(cm/see)
lo-6
10-5 to 10-6
10-3 to 10-5
-l to 10-3
lo-l
Approximate Relationship Between Soil Permeability and Groutability (Karol,
Groutability
(Ability of Soil to Receive Grout)
Ungroutable
Groutable with difficulty by grouts with viscosity <5 cP and
ungroutable with grouts having a viscosity >5 cP
Groutable with low-viscosity grouts but difficult with grouts with a
viscosity greater than 10 cP
, ~
Groutable with all commonly used chemical grouts
Requires suspension grouts or chemical grouts containing a filler
material
The Department of Energy, through its Sandia National Laboratories, has been
conducting a study of two grouting materials, a montan wax emulsion and a glyoxal-modified
sodium silicate material. Montan wax is a fossilized plant wax with properties similar to that of
natural plant waxes, such as those found In canauba palms. It is a hard, high-melting point
material comprised of waxes, resins. asDhaltene-like materials with C-24 to C-32 carbon chain
esters ot iong-cna~nect acids and alcohols (doss et al., 19951. Laboratory testing of soils
permeated with a montan wax emulsion showed a significant reduction In soil permeability. The
initial permeability of the soil tested varied from 6.5 x 10-4 to 3.6 x 10-2 centimeters per second.
After permeation grouting by the montan wax emulsion, the soil permeability was reduced to
between 3.7 x 10-8 and 1.6 x 10-4 centimeters per second.
The glyoxal-modified sodium silicate material originally was developed by a French
company, Societe Franchise Hoechst. The glyoxal-modified sodium silicate material consists of
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D-28
BOWER TECHNOLOGIES FOR ENVIRONMENTAL MANAGEMENT
four proprietary components, the composition of which can be adjusted to modify set times.
Laboratory testing of glyoxal-modified sodium silicate-grouted soil revealed final permeabilities
of 6.2 x 10-6 to 5.1 x 10-5 centimeters per second. The initial soil permeability was the same as
that cited above for the montan wax permeation study. It also should be noted that they were
unable to grout soil with a permeability less than 5 x 10-4 centimeters per second with either the
montan wax emulsion or the modified glyoxal sodium silicate material.
DuPont has also developed a permeation grouting material based on a colloidal silica
gel. This technology was adapted from a technology developed by Conoco for oil field
applications and is termed Ludox~. The gel times of the Ludwig material cart be controlled to
vary from a few hours to a few thousand hours. Its density and viscosity are similar to that of
water. In laboratory experiments, it is reported that three orders-of-magnitude decrease in
permeability was achieved following injection grouting by the Ludox(~) technique. Soils with
initial permeability of 7.7 x 10 to S.6 x 10 centimeters per second were reduced
8
an
In
permeability to between 3.5 x lo and 5.4 x lo centimeters per second. However, in a larger
sandbox-sized study, the permeability of the Ludox~-grouted soil was found to be 4 x 10
centimeters per second. Nonetheless, this represented a four orders-of-magnitude improvement
over the permeability of the ~.ngrouted sand (Noll et al., 1993~.
Ground Freezing
Artificial ground freezing has been used in geotechnical construction for more than 100
years. The first application of ground freezing for construction purposes reportedly took place in
Genmany in 1883 (Braun and Nash, 19851. The maximum frozen depth achieved has been 3,000
feet (Braun and Nash, 1985~. Ground freezing is accomplished by circulating a coolant through a
network of closely spaced vertical or inclined pipes. The coolant can be calcium chloride brine,
liquid nitrogen, or ethylene glycol. Due to relatively high maintenance costs, ground freezing
generally is considered as a temporary containment measure.
The Department of Energy has undertaken a pilot scale study of ground freezing at its
Oak Ridge, Tennessee facility (Peters, 1994~. The test site is approximately 60 feet by 60 feet
and 28 feet deep. It consists of a double ring of inclined and vertical freeze pipes to form a V-
shaped bathtub ring within which is a 750-gallon steel tank. An inner, single ring of heat pipes is
used to control inward growth of the freeze zone. A variety of tests are planned to evaluate the
integrity of the frozen ground battier (Peters, 19941. It is reported that the cost of maintaining a
frozen ground battier for approximately 70 days is comparable to the cost of constructing a
conventional soil-bentonite slurry trench (Iskander, 19871.
Geomembrane Cutoff Walls
Geomembranes may be used alone or In combination with other technologies to create
low-permeability cut-off walls. A method developed by Nick Cavalli of Hayward-Baker in the
early 1980s consisted of placing a geomembrane into a previously excavated slurry trench.
Vertical panels of high density polyethylene are welded to HDPE pipe. Each connection consists
of panels each with a large-diameter pipe on one edge and a smaller-diameter pipe on the other.
The larger-diameter pipe is slotted vertically, and the smaller-diameter pipe and membrane of the
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APPENDIX DIAPERS PRESENrTED
D-29
adjacent panel are inserted into the slotted, larger-diameter pipe. The interstitial space is then
grouted. A leak detection zone may be created with this technology by placing a geonet within
an envelope constructed of two geomembranes (Cavalli, 19921.
Gundle Lining Systems, Inc. (now GSE) also has developed a process for placement of
high-density polyethylene (HDPE) as a cut-off wall. This process consists of driving vertical
panels of HDPE into the soil with a steel-driving apparatus. Alternatively, the panels can be
lowered into a previously excavated slurry trench. Gundle uses a jointing system that consists of
an interlocking joint similar to steel sheet piling. Each half of the jointing system is welded to the
vertical panels prior to installation. Each successive pane! is then driven into the soil and through
the interlock of the previously placed panel. A hydrophilic gasket, which expands to several
times its own volume in water, is placed within the joint to create a water-tight seal. A typical
cross section of the G'ndle jointing system is shown In Figure 2 (Steve Blume, personal
communication, 1996; Blume, 19951.
Gunfire and Groundwater Control, Inc. have teamed to develop an alternative method for
installing six foot wide, SO-mi! HDPE panels with the jointing system described above.
Groundwater Control utilizes a one-pass trencher to install perforated pipe and gravel drains. The
trencher has been modified to include a boot or narrow trench box that allows installation of the
HDPE panels within the boot as shown in Figure 3. The trailing edge of the boot is fitted with
flexible seals that move along and pass the installed pane! through the end of the boot (including
the joints). This allows space for installation of a subsequent panel. The bottom key typically is
~ HYDROPH ILLIC SEAL
1~
// / HDPE JOINTING SYSTEM FUSION
HDPE INTERLOCKING ~' ~ WELDED TO HDPE MEMBRANE
JOINING SYSTEM PANELS
FIGURE 2 Geolock panel jointing system detail.
1 4. perforated pipe
Gravel surrounding pipe
FIGURE 3 Groundwater control/gundle trencher panel installation.
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D-30
BARRIER TECHNOLOGIES FOR E~IRONMENTAL MANAGEMENT
constructed of approximately one foot of bentonite pellets. A drain pipe and gravel also can be
constructed within the same trench outside of the boot. This installation method can
accommodate trench depths up to approximately 24 feet.
SET Environmental, Tnc. (now GSE) has also developed a process for using HDPE as a
cutoff wall. This process also includes an interlocking joint system. The SLT panel jointing
system is shown in Figure 4. The joint interlock is fusion welded to vertical panels of varying
width prior to a placement. The panels are then lowered into a slurry trench or specialized steel
trench boxes (for shallower trenches). During this process, the interlocking joint enters the
interlock of the previously placed adjoining panel. Depending on the installation, the interlock is
sealed by the slurry present in the trench, by grouting, or by using several hydrophilic sealant
gaskets. Slurry Systems of Gary, Indiana, recently installed two cutoff walls consisting of a
OPTIONAL HYDROPHILLIC
r SEA~(TYP~
HDPE INTERLOCKING
JOINTING SYSTEM
1..'.'.'.-.'.'.
A..
1:
HDPE JOINTING SYSTEM
r FUSION WELDED TO HDPE
\ MEMBRANE PANELS
FIGURE 4 SLT panel joinUng system detail.
combination of two technologies, including a vibrating beam wall and HDPE panels. These
installations consisted of constructing a vibrating beam slurry wall using an attapulgite/cement
slurry. SLT HDPE cutoff-wall panels with the SET joint interlock were then vibrated into the
approximately five-inch-wide cutoff wall using a steel-driving apparatus to create a composite
cutoff wall.
Rodio S.p.a. of Italy has developed a composite cutoff wall involving placement of a
HDPE within a self-hardening cement-bentonite slurry. The process begins with excavation of a
vertical trench to the desired depth under a self-hardening slurry. HI)PE sheets varying in width
from 2 to ~ meters and mounted on a steel framework then are lowered into the self-hardening
slurry. The steel framework is withdrawn after installation of the HDPE. Sealing of adjacent
HDPE membranes is achieved by either overlapping, a variety of socket joints, expansion strip
joints, or in-situ welding. This type of composite cutoff wall was constructed around an ash
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APPENDIX~PAPERS PRESENTED
D-31
landfill near Florence, Italy, In 1992. The wall attained depths of up to 30 meters below ground
surface (De Paoli, 19931.
Although dynamic and subject to a variety of site-specif~c factors, the costs of
geomembrane barrier walls generally fall in the $10 to $30 per square foot range.
Deep Barrier Walls
The hydraulic effectiveness of barrier wall systems is heavily dependent upon the
integrity and permeability of the aquitard into which the barrier wall is keyed (Mutch et al.,
19811. Barrier walls that fail to penetrate deeply enough to key into an aquitard at all are usually
only marginally effective in reducing groundwater flow (Mutch et al., 19811. The growing
importance of barrier walls, together with the fact that in many geologic environments, suitable
aquitards may be at depths of 150 feet or more, has spawned considerable interest and
advancement in the technologies to construct deep barrier walls (defined herein as walls greater
than ~ 50 feet in depth).
Conventional, soil-bentonite slurry trenches generally are not used for trenches in excess
of depths of 150 feet due to stability considerations. Conventional slurry trenches are constructed
in a continuous manner with backfill and excavation done in the same trench as shown In
Figure 5. The backfill is placed in the trench from the bohom upward until the backfill reaches
grade. When backfill reaches grade, it will have an angle of repose under the slurry that normally
is between seven horizontal to one vertical, to ten horizontal to one vertical. This presents two
major problems. In the case of a 150-foot-deep trench, the toe of the backfill is as much as 1,500
feet from the top of the backfill. Along with this, there is often an additional 100 feet of
completed trench and approximately 200 feet of trench being excavated. Therefore, as much as
1,800 linear feet of slurry trench is open at any time. At depths of 150 feet or more, the stability
of the trench often becomes marginal. Second, when the excavation ends, the slurry being
displaced must be recovered and disposed. A trench of this size can necessitate disposal of six to
seven million gallons of contaminated slurry.
~ GROUND SURFACE
SOIL-BENTONITE
BACKRLL
at
it_
Film-';-.:-'
). ' ~
SLURRY
i~. 1'~'.1. 2~'
BACKFILL SLOPE
FIGURE 5 Construction of a deep soil-bentonite slurry trench.
-, ~ ,
COMPOTE WORKING
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D-32
BARRIER TECHNOLOGIESFORENVIRONMENTALMANAGEMENT
Deep soil mixing, vibrating beam, and jet grouting pose a different problem. Each of
these methods Involves a series of Interconnected, short sections. Verticality, therefore, becomes
critical. At depths of over 150 feet, it is difficult to ensure that gaps will not occur between
adjacent panels.
Plastic concrete walls constructed in short panel sections of one to three clamshell bites
have become the preferred type of barriers for deep walls. Alternately, a hydromill can be used.
In this technique, a clam-shell or hydromill is used to excavate a short length of trench to the
desired depth tinder a bentonite slurry. Plastic concrete is then tremied into the trench? displacing
the slurry that is reused In subsequent excavations. Panels are interconnected either forming a
joint by placing an endpipe and extracting it after backfill has been placed, or by re-excavat~ng
several feet of the adjacent completed panels. Re-excavating portions of completed panels
creates the problem of verticality, and therefore, continuity. The joint system, when constructed
In a three-bite secondary pane! between primary panels, is more forgiving with respect to
verticality.
In the joint system, a series of primary panels is constructed at pre-set spacings with
endpipes at both ends (Figure 61. Once the plastic concrete has set (normally 3 days), secondary
~ . ~ · . ~ . ~ , .1 _ _ 1 ~ 1 _ 1 1 _ __ 1 _ _ _ ~ _ __ _ _ 1 1 ~ ~ _ _ 1 ~ 4 _ ~
panels are excavated In a three-step process. First, the ciamsnei~ or nyarom~ excavates a slot al
the midpoint of the space between completed panels. Then on one side of this slot, the remaining
soil between the slot and the adjacent completed panel is excavated, and the endpipe is removed.
The same procedure is then repeated at the opposite side. The removal of the endpipe ensures
that a good interconnection of panels is achieved. If a primary panel is out of vertical and the
first bite is out of vertical, the excavating tool is guided by the space created when the endpipe is
extracted and by the excavation of the first bite. Although the Lamer may not be perfectly
vertical, it should be continuous at all points.
~ STOP ENDS ~
r SLURRY 7
~7 ~ ~ is, ~ :
~ ~ it- - I'-'' ~
_~ MUSTARD ~_~ _~= ~ ID
6(C)
. 6(a)
SLURRY
_ _ _ . . . ~
\
. ~
1~1
,
%.
tiAND'
....
_:
-
_
~ 6(d)
. ~
_ . _
=1
6(b)
~ SLURRY
6 (e)
FIGURE6 An alternating panel method of plastic concrete bamer wall construciton.
(a)Pr~mary panels tremie concentrated with stop ends in place. (b)Stop ends lifted. (c)Excavation
of midsection of secondary panel. (c)Excavation of each end of secondary panel. (e)Tremie
concreting secondary panel.
OCR for page 51
APPENDIX~PAPERS PRESENTED
D-33
Projects such as the Wolf Creek Dam (281 feet deep), and the Manicougan Dam (430
feet deep) have been constructed using this methodology although, due to extreme depths,
special equipment was employed. It is believed that subsurface barriers can be built by this
technique to depths of at least 500 feet.
Vanel ( 1992) describes a related technique wherein a caisson beam of high-strength steel
is used as an end stop. However, rather than being withdrawn prior to excavation of the adjacent
panel, it is left in place to serve as a guide to a specifically designed excavating tool that slides
down the beam. The beam is pulled laterally away from the concreted primary panel once the
secondary panel is fully excavated. The beam can also be fitted with an additional grooved
caisson into which one or more plastic or rubber water stops can be inserted. The free half of the
water stops becomes concreted into the primary panel. Lateral extraction of the beam uncovers
the other half, which is then sealed in the concrete of the secondary panel.
CONCLUSIONS
The limitations of treatment technologies to remediate many waste disposal sites fully
have led to increasing usage of and reliance upon subsurface baITier walls to control contaminant
migration from such sites. This more common usage has been paralleled by considerable
advancements In construction technologies. Battier walls can now be constructed by many
different techniques, each offering particular advantages, disadvantages, and limitations. Many
of these techniques also can attain much greater depths than earlier conventional technologies.
REFERENCES
Blume, Steve. 1995. Unique GundWall Installation Developed Through Team Effort. Trench
Topics 1~21.
Braun, Bernd, and William R. Nash. 1985. Ground Freezing for Construction. Civil Engineering
lanuary:54-56.
Cavalli, Nicholas. 1992. Slurry Walls: Design, Construction, and Quality Control. ed. D.B. Paul,
R.R. Davidson and N.J. Cavalli. Philadelphia, Penn.: ASTM.
Chipp, P.N. 1990. Geotechnical Containment Measures for Pollution Control. Wetherby, West
Yorkshire, England: Keller Concrete.
De Paoli, B., R. Granata, G. Hautmann, and P. Tacconi. 1993. Confinement of Hazardous Waste
by Composite Vertical Cutoff Walls. Paris: Environment et Geotechnique de la
decontamination a la protection du soul-sol.
Guatter~, Giorgio. 1988. Advances in the Construction and Design of let Grouting Methods in
South America. Paper No. 5.32. Second International Conference on Case Histories in
Geotechnical Engineering. St. Louis.
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APPENDIX~PAPERS PRESENTED
D-35
Robert D. Mutch, Jr., P.Hg., P.E., is an Executive Vice President and Corporate Director for
Hydrogeology and Waste Management at ECKENFELDERINC. Mr. Mutch was formerly a
Senior Vice President with Wehran Engineering in Middletown, New York. He is also an
Adjunct Professor at Manhattan College in Riverdale, New York, where he teaches a graduate
course in Applied Geohydrology. He has about 24 years experience in the fields of landfill
design, hydrogeology and remedial engineering. His work has included the investigation and
remedial design of hundreds of municipal and hazardous waste disposal sites, including dozens
of Superfund sites. He has designed and, in most cases, supervised construction of 14 miles and
1,500,000 square feet of subsurface cutoff wall, 2 i/2 square miles of low permeability landfill
caps, 15 miles of retrofitted leachate collection systems, and numerous groundwater extraction
systems ranging in size from 50,000 gallons per day to 2,000,000 gallons per day. He has also
provided consultation to the United Nations Environmental Programme (UNEP) In regard to
international landfill problems. He holds B.S. and M.S. degrees in Civil Engineering from New
Jersey Institute of Technology. He is certified by the American Institute of Hydrology as a
professional hydrogeologist (P.Hg.) and is a licensed professional engineer in several states.
Robert E. Ash, IV, P.E., is Assistant Division Director of the Waste Management Division for
ECKENFELDER INC. in its Nashville, TN office. He has over 14 years of experience in the
environmental consulting field, including site remediation and solid and hazardous waste
management. Mr. Ash is a registered professional engineer with a B.S. degree in Civil
Engineering from Rutgers College of Engineering. He is a member of the National Society of
Professional Engineers and the American Society of Civil Engineers.
Jeffiey R. Caputi, P.E., CHMM is a Senior Manager In the New Jersey Waste Management
Division at ECKENFELDER INC. where, for the past six years, he has worked extensively on
hazardous site remediation projects. His work has primarily Included feasibility studies and
remedial designs for Superfund and RCRA sites, as well as sites regulated under various state
programs such as the New Jersey Industrial Site Recovery Act and the Massachusetts
Contingency Plan. Prior to joining ECKENFELDER INC. Mr. Caputi spent four years at
Malcolm Pirnie, Inc. conducting remedial investigations, feasibility and treatability studies,
remedial actions, and environmental audits. He has a Bachelor of Science degree in
Environmental Engineering Technology and a Master of Science degree in Environmental
Engineering from the New Jersey Institute of Technology. Mr. Caputi is a licensed professional
engineer and a certified hazardous materials manager.
Representative terms from entire chapter:
slurry trench
