Land fill for waste materials and method of making the same

A land fill and method of containing solid wastes and/or waste fluids comprises placing the waste and/or waste fluids, either enclosed in a container, free flowing, solidified or treated, in a preformed cavity or pit that is excavated in a naturally occurring deposit of bentonite clay located adjacent or beneath the surface of the earth. The waste and/or waste fluid is of a type that will not pass through a bentonite layer that is left in its natural place after excavation thereby forming a natural liner or bottom wall of the excavated cavity. After the cavity or pit has been substantially filled with waste material, an overlayer of water-swellable bentonite may be provided on top of the mass of waste material and joining the liner wall around the outer peripheral edge to permanently enclose and seal-off the waste material, or the upper surface of the waste filled pit may be left uncovered.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to land fills and a method of forming a below 
ground receptacle or land fill for the storage and containment of solid 
and/or liquid waste materials. Many solid waste materials are capable of 
leaching out fluids during storage and containment, which fluids present 
hazards to the environment, especially when the leached out material comes 
in contact with ground water supplies. 
More particularly, the present invention relates to a new and less costly 
method of containing waste liquids and leachable waste solids, including 
provision for the permanent storage of waste materials in a preformed pit 
that is formed as a result of the excavation or mining of a naturally 
occurring deposit of water-swellable, colloidal clay, such as 
bentonite-clay. 
The storage of waste materials in a land fill cavity or pit that remains 
after mining and removal of water-swellable colloidal clay from the earth 
in accordance with the present invention makes use of a naturally 
compacted layer of clay which is left undisturbed in place and which layer 
provides an unexpectedly highly efficient, water-impermeable, natural pit 
liner that is highly economical, and durable for long periods of time. The 
naturally compacted bentonite layer eliminates the need for installing 
artificial or man-made bentonite liners and/or eliminating the need for 
installing plastic sheeting materials in a land fill pit prior to the 
storage and containment of waste material. 
The laws and regulations issued by the EPA, RECRA and other State and 
Federal regulatory agencies are becoming increasingly more stringent and 
complex with respect to the lawful use of land fills for storing and 
containment of waste materials, particularly toxic waste materials, such 
as polychlorinated biphenyls, dioxins and the like. Burial of waste 
materials in the earth in the past has resulted in the leaching out of 
harmful materials, which materials sometimes pass through the soil bed 
beneath the originally introduced materials and eventually find their way 
into ground water supplies used for potable water, agriculture, and 
industry. When this does occur, both the soil and water supplies become 
contaminated with a resultant, almost immeasurable, human damage and 
economic cost. Regulations directed at land fills for highly toxic waste 
materials are now very stringent in order to make sure that the soil bed 
and water supplies beneath a land fill are permanently protected. These 
regulations generally do not permit the drainage or leaching out of any of 
the buried, potentially harmful, waste material in a land fill pit to pass 
through the soil bed below the land fill because of the possibility that 
these materials may eventually contaminate neighboring ground water 
supplies. 
2. Description of the Prior Art 
The present difficulties in the lawful burial, handling and containment of 
waste materials, particularly toxic materials, are well recognized and 
have resulted in alternative, and prohibitively expensive methods of waste 
material disposition, including recycling, waste-stream treatment, and 
incineration. 
Land fill disposal of aqueous, or potentially aqueous, toxic substances 
typically requires systematically lining the surface area of a land fill 
cavity or pit with an artificially formed barrier of water-impermeable 
material, such as a layer of bentonite, or other water-swellable, 
colloidal clay, or a layer of bentonite laminated to one or more layers of 
an impermeable liner, such as polyethylene film so that toxic materials 
leaching out from the mass of waste material in the pit cannot penetrate 
through the artificially installed liner and eventually move into a ground 
water supply. 
Bentonite clays have played an integral part in some land fill lining 
methods, as disclosed in U.S. Pat. Nos. 4,693,923 (McGroarty), 4,255,067 
(Wright), 4,656,062 (Harriett), 4,501,788 (Clem), 4,344,722 (Blias), 
3,986,365 (Hughes) and British Patent No. 1,029,513. 
The McGroarty, Harriet, Wright, and British patents disclose a soil bed 
liner including a water-impermeable, polymeric material as an integral 
element thereof useful for waste material containment. The Harriet and 
McGroarty patents also disclose an additional or second, water-impermeable 
layer of bentonite clay particles adhered onto an impermeable polymeric 
liner. British patent No. 1,029,513 discloses the concept of providing a 
second layer of foamed plastic or resinous material filled with bentonite. 
The Wright patent discloses a bentonite layer sandwiched between two sheets 
of 10-20 mil thickness, flexible, water-impermeable polymeric sheet 
material. 
Blias U.S. Pat. No. 4,344,722 discloses a waterproofing article formed by a 
layer of bentonite particles sandwiched between two water-permeable 
membranes. 
Clem U.S. Pat. No. 4,501,788 discloses the concept of adhering bentonite 
particles onto a vapor-permeable, non-biodegradable support. 
Published European Patent Application No. 0059625 to Clem discloses a first 
layer of moisture-permeable, sheet material containing bentonite particles 
and having a plurality of layers disposed on both sides of the sheet. 
The above-described patents generally disclose the concept of incorporating 
bentonite as an important element of the inventions thereof and, these 
patents generally teach or suggest that bentonite particles be adhered to 
both water-permeable or water-impermeable type flexible films or 
membranes. These membranes are also used to cover exposed, absorbent earth 
surfaces in a below-grade pit or containment area. The procedure of lining 
a large pit or excavation with a bentonite-containing waterproof liner is 
a relatively costly process and is not always completely effective because 
"breaks" often exist or form in an installed lining over time. Such breaks 
sometimes occur prior to, during or after the initial placement of the 
liner or during the deposition of waste materials into a previously lined 
pit. 
Other approaches to the problem of providing water-impervious, flexible 
liners for land fill sites include the mixing of bentonite with native 
soil, the compacting of native soil and/or the mixing of clay with soil 
and a water-retaining polymer. For example, Hughes U.S. Pat. No. 3,986,365 
discloses the concept of mixing equal parts of soil and bentonite and 
adding to this mixture a water-retaining polymer in order to retain water 
in a land fill. 
OBJECTS OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a new and 
improved land fill for the storage and containment of waste materials, 
including toxic waste materials. 
Another object of the invention is to provide a new and improved method of 
making a land fill for the storage and containment of waste materials. 
Another object of the present invention is to provide a land fill formed by 
the careful excavation of a naturally occurring deposit of 
water-swellable, colloidal clay so as to leave undisturbed a 
water-impermeable layer of naturally compacted, water-swellable clay, 
thereby to form a natural liner for a pit designed to receive and hold 
waste material on a permanent basis. 
Another object of the present invention is to provide a new and improved 
method of disposing of waste materials such as hazardous and toxic wastes, 
including the careful excavation of a naturally occurring deposit of 
water-swellable, colloidal clay in order to leave intact, a naturally 
compacted, water-impermeable bottom surface layer of bentonite clay of a 
desired thickness to hold the waste material and prevent liquids from 
leaching out or seeping into the earth below. 
Another object of the present invention is to provide a land fill of the 
character described having a lower surface layer of naturally compacted, 
water-swellable, colloidal clay having a thickness or depth of at least 25 
cm. or sufficient to provide a coefficient of permeability of less than 
about 1.times.10-7 cm/sec. 
Another object of the present invention is to provide a new and improved 
land fill and method of making the same that is relatively low in cost, 
safe, efficient and reliable in operation and which requires little, if 
any, maintenance over a long useful life. 
Yet another object of the present invention is to provide a new and 
improved land fill and method of making the same that provides efficient, 
permanent long term protection against damage to ground water supplies 
from liquid wastes and/or deleterious fluids that sometimes leach out of 
solid wastes and the like. 
Still another object of the present invention is to provide a new and 
improved land fill and method of making the same which meets or exceeds 
the requirements of the EPA, and other Federal and State agencies for the 
permanent containment and storage of wastes and toxic materials. 
SUMMARY OF THE INVENTION 
In brief, the present invention is directed toward land fills for waste 
materials and to a method of forming such land fills for the permanent 
storage and containment of waste materials, particularly toxic waste 
materials, either in liquid or solid form. Water-swellable colloidal clay, 
such as bentonite clay, is found in naturally occurring deposits in the 
earth and after these deposits are mined and removed, a pit or excavated 
cavity is left in the earth's surface. 
In accordance with the present invention, the mining or excavating 
operation is carefully conducted so as to leave an exposed surface layer 
of water-swellable, colloidal clay in the pit to remain after most all of 
the material in the pit has been mined and removed. This remaining layer 
of clay is left in a naturally compacted, undisturbed condition and has a 
depth or thickness obtaining over substantially the entire surface area of 
the pit of about 1" to 25 centimeters or greater depending on the waste 
material being handled. 
After careful excavation has been completed, the open cavity or pit is 
especially suitable for the storage and containment of waste materials, 
including toxic waste materials and most importantly, the open pit 
requires little if any additional treatment in readiness for receiving 
waste material. The naturally formed and naturally compacted layer of 
water-swellable, bentonite that is left in place after the mining 
operation is completed, provides a liquid-impermeable, natural barrier for 
the pit ready to receive waste material. If during the excavation process, 
accidental cuts beyond and through the water-swellable layer of colloidal 
clay occur, these relatively small areas where the naturally deposited, 
desired thickness of the water-swellable, colloidal clay does not remain 
intact are treated, by adding compacted layers of bentonite clay, or a 
clay-polymeric sheet material which is laminated or otherwise secured into 
place. 
The entire surface area of the open excavation or pit from a lowest point 
therein to an upper peripheral edge substantially adjacent the level of 
the surrounding earth is thus provided with a naturally compacted layer of 
water-swellable, colloidal clay, and waste material can then be introduced 
into the pit. The thickness of the layer of water-impermeable clay is 
selected so as to provide a coefficient of permeability of about 
1.times.10.sup.-7 cm/sec. and the selected thickness may vary somewhat 
dependent on the type of waste material to be stored and the applicable 
EPA and other regulations that obtain. The minimum thickness of the 
liquid-impermeable, naturally compacted layer of colloidal clay is usually 
at least 1 inch, up to about 25 cm. and may be as high as 1 foot or 
greater when the type of material and safety factors required dictate. 
After the pit is substantially filled with waste material, the perimeter 
may be fenced off and secured, or an overlayer of water-swellable, 
colloidal clay may be deposited over the upper surface of the waste 
material and joined around a periphery thereof with the upper periphery of 
the underlying layer of naturally compacted bentonite clay in order to 
completely seal off the large mass of waste material in a substantially 
liquid-impervious barrier or envelope. Preferably, when an overlayer is in 
place, an upper surface thereof is crowned so as to direct moisture and 
water toward the outside of the periphery. After the overlayer is in 
place, a covering layer of ordinary earth may be provided, also with a 
crowned upper surface to shed moisture and water toward the undisturbed 
earth surrounding the periphery of the land fill.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
Water-swellable colloidal clays, such as bentonite clay, exist in naturally 
occurring deposits A, B, C, D, E, etc., located at or beneath the surface 
of the earth 18 in varying thicknesses and at various depths. The 
commercial recovery of bentonite from such deposits has long been 
practiced by excavating or strip mining the bentonite clay with large 
size, powerful excavating equipment such as a paddle wheel or front end 
loader, e.g. bulldozer. Many times these naturally occurring bentonite 
deposits are large in order to justify a mining operation and, 
accordingly, a pit depression or cavity 20 of considerable size is 
produced as a result of the excavating procedure, when substantially all 
of the bentonite has been removed. 
For example, pits reaching 20 to 100 feet in depth, and a quarter mile to 
two miles long or in diameter are common. Depending on the size and 
location of a pit 20, it is sometimes necessary in order to comply with 
Federal and State mining and environmental regulations to reclaim the 
cavity, and leave the land in a better condition than before the mining of 
the bentonite occurred. The cost of refilling strip mines and cavities is 
sometimes extremely high and time-consuming because suitable fill material 
must be located, purchased and sometimes hauled by a truck or other 
conveyances over considerable distances to meet the stringent EPA 
requirements. At the same time, there exists a pressing need for suitable 
sites for the storage and containment of waste materials. 
Toxic liquid wastes stored in drums 21 and various solid wastes 23 that are 
susceptible of leaching out hazardous substances that can eventually 
penetrate and contaminate ground water supplies lying beneath or closely 
adjacent to an excavation pit 20 must be properly contained and protected. 
If such materials are allowed to seep out or leak from a land fill site, a 
neighboring underground water supply 22 is in danger of contamination and 
poisoning. 
In accordance with the principles of the present invention, it has been 
found that an open pit or cavity 20 created by the strip mining or 
excavating of a naturally occurring deposit of bentonite is well suited 
for the permanent storage and containment of waste materials. These pits 
are particularly well suited for hazardous and toxic materials of the type 
that tend to leach hazardous fluids when out rain water and melting snow 
are encountered. After the major amount of bentonite clay is mined and 
removed from a site, the remaining volume of bentonite clay is carefully 
mined and the excavation process is carried on in a precisely controlled 
manner so that only a relatively thin layer 24 of naturally compacted, 
water-swellable colloidal bentonite clay of a suitable thickness is left 
in place in an undisturbed condition. This layer 24 provides a natural 
barrier or pit liner that is impervious to the passage of liquids into the 
soil bed or earth below the pit 20. 
As illustrated, the layer 24 of water-swellable, colloidal clay, in the 
large bentonite deposit "C" that remains after careful excavation in 
accordance with the present invention, begins to hydrate in the presence 
of water or other liquids and the bentonite material swells to form a 
continuous, water-impervious barrier extending from a lowest level in the 
pit 20 to an upper level 26 around a peripheral edge of the pit lying 
adjacent or below the level of the adjacent surface of the surrounding 
undisturbed earth 18. 
In accordance with an important aspect of the present invention, a suitable 
colloidal clay for such land fill duty contains mainly bentonite clay. A 
preferred type of bentonite is sodium bentonite which is basically a 
hydratable montmorillonite clay of the type generally found in the Black 
Hills region of South Dakota and Wyoming having sodium as a predominant 
exchange ion. Other types of bentonite deposits that may be excavated to 
provide a land fill in accordance with the present invention may contain 
other cations such as magnesium and iron, and a suitable colloidal clay 
that may be utilized in the present invention may also comprise peptized 
bentonites. Other suitable water-swellable colloidal clays may comprise 
members of the dioctahedral or trioctahedral smectite group or mixtures 
thereof, and some examples are Beidellite, Nontronite, Hectorite and 
Saponite. 
In situations where only relatively bland or non-toxic wastes are to be 
stored and contained in a land fill pit 20, the layer 24 of naturally 
compacted bentonite can have a thickness as low as 1 inch to provide a 
suitable safety factor and in cases where wastes of a more active nature 
are to be stored, the thickness of the layer 24 may range to 25 cm. up to 
1 foot and even larger. 
In determining the required thickness of the layer 24 that is needed, tests 
are run to establish the permeability coefficient of the existing layer of 
water-swellable material. In general, a thickness of material sufficient 
to provide a coefficient of permeability less than about 1.times.10.sup.-7 
cm/sec. is desirable for almost any types of wastes. In some situations 
where extremely hazardous wastes are involved, stored either in solid 
masses 23 or liquid containers, tanks, 21 and the like, a layer 24 of 
water-swellable, colloidial clay or bentonite having a thickness of about 
1 foot is desirable to provide a higher factor of safety that is needed 
with these more hazardous fluids. 
In all cases, after the general mining operations and final careful 
excavation have been completed, the surface area of the remaining intact 
and undisturbed layer 24 is closely inspected for trouble areas. In these 
trouble areas, the layers 24 may be of insufficient thickness or there may 
be patches of ordinary earth exposed that has no water-swellable bentonite 
present. Such trouble areas are indicated by the numeral 30 and are 
treated locally to attain the needed coefficient of permeability before 
the deposition of waste material begins. Treatment of these trouble areas 
(which are usually relatively small in size) is preferably accomplished in 
accordance with the system and process disclosed in the Clem U.S. Pat. No. 
4,501,788. 
Once the pit lining layer 24 is inspected and treated as necessary, waste 
materials such as liquid drums 21, masses and crates of solid wastes 23, 
or the like, are deposited into the open pit 20, by means of trucks, 
cranes, bulldozers, 10 and other types of equipment, depending on the 
depth and size of the pit. During the land fill operation, casual water 
from surface drainage, rain, snow and melting ice will be retained by the 
water-impervious, underlying, pit lining layer 24. As the pit 20 is 
filled, care is taken to insure that the pit lining layer 24 is not 
disturbed, broken and/or penetrated. 
When the pit 20 is substantially filled with waste material and the upper 
level of the waste mass approaches the upper peripheral edge 26 of the 
water-impervious bentonite layer 24, further deposition of waste material 
is discontinued. The upper level of the waste deposition is spaced far 
enough below the level of the peripheral edge 26 so that drainage water, 
rain, snow and melting ice is retained. If the pit is to be left open, the 
water or moisture may evaporate without ever spilling or flowing-out over 
the edges of the pit 20. Usually open pits containing wastes must be 
fenced off and security is usually provided to prevent accidental or 
unauthorized entry into the area. 
If desired and/or required, an overlayer 24A of water-impervious, 
liquid-swellable, bentonite clay, a plastic liner or a plastic/clay 
laminate of the desired thickness is laid down over the mass of waste 
material in the pit 20. This is done when the mass of waste is 
sufficiently dry and the overlayer 24A is joined around the periphery to 
the peripheral upper edge 26 of the pit lining layer 24 so as to 
completely seal off the mass of waste material against the further entry 
or egress of liquids. The upper surface of the overlayer 24A is crowned so 
as to shed water toward the periphery of the pit to eventually flow onto 
the adjacent surface of the surrounding earth 18. 
In some instances where complete land restoration is required,. a layer of 
ordinary earth 28 is deposited over the mass of waste material in the pit 
20 or on top of the overlayer 24A as the case may be, and this layer of 
earth also has a crowned upper surface to direct and shed water toward the 
periphery. A layer of grass or turf and other plantings may be provided to 
complete the land restoration and provide a surface area over the land 
fill pit 20 that is compatible with the surrounding earth 18. 
Obviously, many modifications and variations of the invention as 
hereinbefore set forth can be made without departing from the spirit and 
scope thereof and therefore only such limitations should be imposed as are 
indicated by the appended claims.