Note: Descriptions are shown in the official language in which they were submitted.
DESCRIPTION OF THE PRIOR ART
This invention relates to a method and structure for
containment of waste or contaminated material.
There is a global problem regarding disposal of waste
material. Increased production of industrial and household
waste materials has not been met with corresponding advances
in the technology associated with storage and disposal of
wa~te material.
Frequently waste material is transported from the
community where it is generated to a landfill site. Waste
materials are deposited onto the site until such time as the
site is full. The site may be then covered with clean fill,
top soil laid, and the land used for recreational purposes.
No roads or buildings may be constructed over top of a
landfill site due to its instability.
Additionally, contaminants from the waste material
will pervade the surrounding soil and the ground water,
resulting in widespread contamination and toxicity. A~
landfill sites, test wells are installed around the
perimeters of the site and samples of the ground water are
taken on a regular basis. Detection of contaminants in
samples indicates that the landfill site is leaking
contaminants into the ground water below the site. Further,
erosion of the surface landfill allows surface water from
rain to mix with the contaminated waste body below the
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surface landfill, thereby creating more severe problems in
terms of leaka~e of contaminants from the land~ill site.
Several proposals have been made to deal with the
waste or contaminatPd waste.
U.S. Patent 4,6~7,954 discloses a basemented waste
landfill site designed to carry heavy loads far long periods
of time. The floor structure cvnsists of individual
supporting elements o~ upwardly convex or concave forms,
separated by seams from one another. The support: elements
are arranged in a regular pat~ern in which zones are formed.
The upper surfaces of the support elements slop towards the
feet which rest on piers. Such zones enable the gathering
and drainage of seepage.
U.S. Patent 4,375,930 discloses a permanent disposal
vault for containers containing chemical hazardous waste
materials. The containers are distributed on the base
surface of the vault separated from one another. The space
between the deposited containers is filled with cementitious
substance and the containers are then covered with a slab of
cementitious substance. Each individual container is thereby
isolated within a structural skeleton of the cementitious
substance. Multiple tiers o~ containers may be accumulated
in this fashion and then completely encapsula~ed within a
permanent disposal vault. The vaul~ is further provided with
an outlet conduit connected to a sump for monitoring any
liquid accumulations from the encapsulated vault.
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; U.S. Patant 4,844,840 discloses a structure for
hazardous waste containment wherein primary waste containers
are placed in pre-fabricated canisters and sealed with a
curable fluid sealant. The canisters are then stacked in an
interlocking manner to form a stable integrated structure.
The containers are not permanently attached to one another so
that individual containers are able to shift relative to one
another in response to earth movement such as earthquakes.
The structure is placed over an impermeable bed used to
collect leacha~e emanating from the waste canisters. The
structure is covered with a la~er of clay, a layer of gravel
and uncompacted fill which is then landscaped.
The prior art waste landfill sites or waste of
disposal vaults only addresg the current problem of disposal
of the contaminated waste or landfill. They do not address
the long term problem of what to do with the site after it
has been filled to capacity.
OBJECTS OF_INVENTION
The disadvantages associated with the prior art may
be overcome by providing a self supporting structure which
completely encapsulates the waste and which enables the
construction of roads, buildings or recreational structures
over the top of the site without interference with the
encapsulated waste body.
It is a further objec~ of this invention to provide a
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concrete parabolic arch overlying the waste to prevent
surface water ~rom mixing with the encapsulated wast body
and to prevent external interference ~y animals and humans.
It is a further object of this invention to provide a
structure having a basemented floor for supporting the waste
body and for permitting access beneath the waste body to
effect repairs.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is
provided a waste containment structure which completely
encapsulates the waste material, enabling the land above the
structure to be developed and built upon. The structure
consists generally of a graded foundation divided into
sloping fields bordered by side walls and end walls. Arched
support elements are erected upon the foundation, creating a
network of tunnels for supporting a waste body. A graded
surface is prepared overtop of the arched support elements
and divided into zones corresponding to the sloping fields
of the foundation. A first impermeable membrane overlies the
graded surface and underlies the waste body. A second
impermeable membrane overlies the waste body and is sealed
with the first impermeable membrane to completely encapsulate
the waste body. A parabolic arch extends from one side wall
to the othex side wall over the encapsulated waste body,
enclosing the was~e body. Venting is provided through the
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membrane and the arch to the ext~rior through the top of the
structure to remove noxious gases produced by the waste body
for analysis and treatment as requirecl.
In operation, any fluid leak~ng from the waste body
will be collected in the upper zones and drained through to
the corresponding field in the foundat:ion. The fluid will be
collected at a collection basin centrally located in each
field, and will then be analyzed and diverted via valved
pipes to be treated.
The arch is self-supporting, thereby enabling
structures to be constructed over top of the containment
structure.
DESCRIPTION OF THE DRA~INGS
In drawings which illustrate embodiments of the
invention,
Fig. 1 is a front elevational view of the preferred
embodiment of the waste containment structure
illustrated in section,
Fig. 2 is a perspective view, partly in section, of the
waste containment structure of Figure 1,
Fig. 3 is a plan view, partly in section, of the waste
containment structure of Figure 1,
Fig. 4 is a front eleYational view o~ the side wall of the
embodiment of Figure 1,
Fig. 5 is a perspective view o~ a modular form unit of the
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embodiment of Figure 1,
Fig. 6 is a plan view of a plurality of modular form units
arranged in an array of the emhodiment of Figure 1,
Fig. 7 is an obl~que exploded view o~ thP basemented
structure and the field arrangement of the embodiment
Figure 1,
Fig. 8 is a cross-sectional view of the embodimen~ of Figure
l through the expansion join~ between each field,
Fig. 9 is a cross-sectional view of the embodiment of Figure
1 through the high points between each field where no
expansion joints are required.
DETAILED DESCRIPTION OF TH~ PREFERRED EMBODIMEN~
With reference to Figures 1 and 2, the general
arrangement of the waste containment s~ructure 1 is
illustrated. ~enerally, waste containment structure
comprises foundation 10 extending from side wall to side wall
12 and from end wall to end wall 14. Overlying foundation 10
are modular form units 16 which are placed in an array
forming a series o~ tunnels. Over top of the modular form
unit 16 is poured a concrete waste floor 18. The waste floor
is covered with a lower impermeable membrane 20 extending
over the entire surface of the waste floor 18. A concrete
covering 22 is placed over top of the lower permeable
membrane, presenting a surface which the was~e body 24 may be
deposited thereover~ Overlying the waste body 24 and in
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sealing engagement with the lower impermeable membrane 20 is
upper impermeable memb~ane 26. The top of the waste body 24
is covered with a concrete parabolic arch 28. A sealant 30
covers the parabolic arch 28. Landfill 32 may be deposited
over top of the structure ~or landscaping or the construction
of buildings 34. Vents 36 which extend through the landfill
and into the waste body may also be installed.
Governments have passed regulations regarding the
safe disposal of waste. These regulations must be consulted
before a waste site is selected and construction commenced.
However, for the purposes of this invention, any open space
which can be excavated is suitable. Abandoned gravel pits or
other sites of open pit mining would be particularly suited
for this invention. Abandoned gravel pits are particularly
well suited for this invention as large scale excavation has
already been completed.
Once the site is selected, foundation 10 is prepared.
The foundation 10 is graded level and then compa~ted using
known methods. The area to be graded and compacted
corresponds to the selected dimensions overall of the
structuxe 1. In the preferred embodiment, of the waste
structure 1 is rectangular in plan view. However, any number
of shapes may be utilised for the waste structuxe. Further,
a~ illustrated in figure 3, several like structures may be
constructed side by side or end to end using common walls 12
and 14 to increase the capaci~y of the waste site.
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With reference to Figure 7, the foundation 10 is
divided up into a number of zones 38, 40, 42 and 44. The
number of zones depends on the dimensions of the waste
containment structure 1. Each zone is identical and
constructed in a similar manner.
The foundation 10 is providec~ with a gravel layer 46
which is further compacted and leva~led. Installed in gravel
layer 46 is a series of pipes 48 which run substantially
parallel to the side walls 12. At the centre of each zone
38, 40, 42 and 44 is a catch basin 50. Catch basin 50
extends below the surface of the lower level of the gravel
layer 46.
Flexible pipes 48 extend from catch basin 50 of one
zone to the catch basin o~ the next adjacent longitudinally
extending zone. For example catch basin of zone 38 is joined
to the catch basin of zone 42 and similarly the catch basin
of zone 40 is joined by pipe 48 to the catch basin of zone
44. Pipe 48 drains to a water treatment plant for treating
the liquids which accumulate in catch basin and drained
through pipes 48 for the safe disposal thereof. The drainage
system also provides a means for draining water from the site
during the construation process.
; A poured concrete floor 49 is constructed in zones
38, 40, 42 an~ 44, each zone sloping downwardly from the
outer perimeter thereof to the centre where catch basin 50 is
located. Each zone 38, 40, 42 and 44 is constructed using
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reinforced concrete. Between each adjacent zone, a
compressible and expandable material 80 is inserted between
the concrete floors 49 of adjacent zones to keep the ioint
sealed.
5Any time after the preparation of the compacted
gravel layer 46 has been completed, side walls 12 and end
walls 14 may be constructed. The ~imensions of the side
walls 12 and end walls 14 depend on th~ dimensions of the
waste containment structure 1 and the anticipated loading o~
10any structures 34 to be built over ~op of the waste
containment s~ructure 1. The dimensions of the side walls 12
and end walls 14 are dictated by local building codes such as
the National Building Code in Canada. A structural engineer
could easily calculate the requisite dimension~ for specific
15loading requirements.
As illustrated in figure 4, the preferred cross-
sectional shape of side wall 12 and end walls 14 has a
rectangular base portion ex~ending substantially
perpendicular to the level surface of foundation 10 and a
20triangular top portion for joining with the roof as described
hereinafter.
A modular form unit 16 is placed on floor 49, as
illustrated in Figure 5. In plan view, modular form unit 16
is substantially square. Each corner of the modular unit has
25a corner r moved defining surface 52 such that when like
modular units 16 are adjacent to one another in an array as
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illustrated in Figure 6 a pillar s~ructure 54 is defined.
The upper surface 56 of modular fo~n unit 16 has a curved
surface which merges with leg surface 52. Each side wall of
the modular unit 16 is provided with an archway 58 such that
when like units are placed side by side in array there is
defined a series of tunnels forming a grid ~elow upper
surface 56.
As illustrated in figure 6, the first modular form
unit 16 is placed directly over top of catch basin 50 with
like units placed side by side to form an array. Between the
units 16 at each corner thereof, a form for pillar structure
54 is established.
A drain pipe 60 extends through the upper surface 56
of the modular unit at the vertex thereof. Drain pipe 60
drains into the catch basin 50.
Modular unit 16 can be fabricated from a precast
reinforced concrete. They may either be precast and
manufactured away from the site and then delivered upon
completion and when necessary, or cast on site.
Once the modular ~mits have been placed side-by-side
and completely filled a zone the waste floor 18 may then be
prepared. The surface of the waste floor 18 is sloped in a
similar fashion and degree as founda~ion 10. ~t the lower
most point of ~loor 18 is drainpipe 60.
Waste floor 18 is constructed by reinforced cast in
place concrete which is p~ured over top o~ the modular forms
16 and filling the pillars 54, presenting an upper field 62
which corresponds in size to zone 38.
Adjacent fields have corresponding fields 64, 66 and
68, which correspond in size and location. Adjacent fields
are joined in a similar fashion as ~etween zones, namely, a
compressible and expandable material 84 is inserted between
waste floor 18 of adjacent fields to keep the joint sealedO
The joint is then covered with a formed steel p].ate 86 to
cover the joint~ Between the plate 86 and waste floor 1~, a
sealing material 88 available under the trade-mark Bentonite
is injected to seal the joint.
Floor 49 and waste floor 1~ of each field and zone
respectively have been described as being a single poured
concrete unit and ha~ing corresponding ~oints therebetween.
However, floor 49 and waste floor 18 may be constructed using
several sections and therefore would have corresponding
joints. Figure 9 illustrates such a joint. Extending
between adjacent sections of floor 49 and waste floor 18 are
the reinforcing steel rods 90 with cross reinforcements
extending substantially perpendicular to rods 90. Lower tie
strip 92 is poured after floor 49 of adjacent zones is
poured. This will permi~ sufficient time to permit floor 18
to shrink to its finished size. Similarly upper tie strip 94
is poured after waste ~loor 18 is poured to reduce the
effects of shrinkage of the concrete.
The total number of zones and fields depends on their
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respective area. However, the entire area being bounded by
side walls 12 and end walls 1~ must be completely covered.
Each field is covered with a lower impermeable
membrane ~0. The impermeable membrane is preferably made
from a polyvinylchloride (PVC) ma~terial of a thickness
suitable to prevent liquids from passing therethrvugh. Each
adjoining field is covered with an impermeable membrane and
is sealed at its respec~ive edges to the membrane of the
adjoining field. Heat sealing the membrane is suitable
however, other methods may be used of sealing the
impermeable membrane.
Where the field abuts with side wall 12 or end wall
14, and impermeable membrane layer covers the wall 70 of
side wall 12 or end wall 14 upwardly ~rom the lower membrane
20. The side wall covering is joined with the lower membrane
20 using conventional sealing methods.
A thin layer of concrete is poured over top of the
lower membrane 20 to form a waste floor 22, which extends
over the entire area defined by the side walls 12 and end
walls 1~, leaving openings for drainpipes 60 to communicate
with the waste body 24. The waste floor 22 reduces the risk
of the lower membrane 20 ~rom being damaged during the period
of depositing the waste on the site.
The landfill site is now ready for receiving the
contaminated waste or land~ill to form waste body 24. Trucks
loaded with landfill, waste or contaminated waste may drive
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over the waste floor 22 for deposit of the waste where
desired.
The waste or landfill is deposited o~er top of the
waste floor 22 such that the greatest height of the landfill
will be at the mid-point between the end walls 14. The waste
is deposited commencing at one end of the waste floor 18.
The upper surface of the waste body 24 is graded to a
parabolic shape as viewed in cross-section.
The mid-point height of the upper surface of the
waste body increases parabolically in longitudinal cross-
section until a maximum height is obtained. The mid-point
height increases gradually until it reaches a maximum desired
height. As the landfill site continues further
longitudinally from the end wall 14 the mid-point height is
maintained at the maximum until a point where the mid-point
height may ~e gradually decreased as the same rate as
increased of the first part of the landfill site~ The upper
surface of the completed waste body 24 is substantially
Z0 uniorm in cross-section both in the longitudinal and cross-
sectional directions.
As the top of the landfill site is prepared and
graded to the requisite parabolic arch, the landfill may be
covered with an upper impermea~l~ membrane 26. The upper
permeable membrane is sealed with the lower impermeable
membrane 20 where i~ extends upwardly along the wall 70 and
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76.
At approximately 150 ft. intervals, a vent 36 is
installed at the apex of the parabolic arch. The vent
extands from the waste body through the upper impermeable
membrane and through the parabolic arch 28 and continues to
extend upwardly to the desired level.
Once the waste body is completely covered the upper
membran~ is sealed with the lower membrane. The construction
of the parabolic arch commences at one end and prugresses
along the length of the site until it joins and seals at the
end wall o~ the structure. once the waste body is completely
encapsulated, uncontaminated landfill may then be deposited
over top of the parabolic arch and landscaped as desired.
The upper surface of the waste body 24 acts as a
lower form for a parabolic arch 28 to be constructed thereon.
A reinforced concrete parabolic arch 28 is poured over top of
the upper impermeable membrane 26 which extends from the
vertex 78 of side wall 12 to the vertex on the opposite side
wall 12. As the concrete cures, it becomes a self-
supporting structure o~erlying the waste body 24. The
parabolic arch 28 is then coated with an impermeable sealant
30. The thickness of the parabolic arch 28 depends on the
distancP between side walls 12 and endwalls 14 and the
anticipated loading overtop of the arch 28.
The parabolic arch is completely self supp~arting.
Further, ~he parabolic arch is capable of supporting not only
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th0 loading of the uncontaminated landfill but also small
structures in buildings which may ~e used for recreational,
housing or other commercial purpose~;. For instance, golf
courses can be constructed with a club house built on the
site. Other numerous possibilities for the upper surface is
unlimited.
In operation, the waste body is completely
encapsulated within the membrane 20 and 26. Theoretically,
the membrane maintains the waste including any gases
generated by the waste or any liquid within the waste to be
contained within the membrane 20 and 26. However, known
technology does not provide a material which is compl~tely
impermeable to all substances. Therefore it is possible that
leachates may escape from the membrane and pass into the
adjoining s~ruc~ure. Electronic sensors installed throughout
the structure may be used to de~ect the presence of toxic or
contaminated waste which escape from the waste body 24.
If some leachate does pass through the impermeable
membrane, the leachate ought to follow the path of least
resistance. The designed water flow is that the leachate
will flow downwardly along concrete surface 72 and down the
inclination of such surface towards the drainpipe 60. The
leachate will flow down the drainpipe 60 and into catch basin
50. Pipes 48 are provided with valves to regulate the flow
from catch basins 50.
If the leachate does not follow this path and finds
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another path down through the modular unit level, the
leachate will ~hen fall on to the surface of each zone 38,
40, 42 and 44. The water will then flow downwardly towards
the catch basin 50.
Catch basin 50 is regular~y monitored by taking
samples of the leachate uncovered in each catch basin 50. If
the liquid in the catch basin is analyzed to be contaminated
or toxic, the liquid transpor~ed by pipes 4~ to the location
where the leachate may be decontaminated and disposed safely.
10 If the leachate is analyzed to be not toxic or contaminated,
it is then drained in the normal course.
Similarly, vents 36 are used to allow gasses which
are generated by the wa~te body to be exhausted. The exhaust
is sampled to determine whether the exhaust is contaminated
15 or toxic. If it is determined to be safe then the gas is
exhausted to the atmosphere. If not, the exhaust is pumped
to a holding tank where it may be transported for
decontamination.
The invention has been described in some detail by
20 way of illustration and example for ~le purpose of clarity.
However, certain changes and modifications could be made
without departing from the spirit and scope of the invention.
