Patent Number: 048448400
Section: description

DESCRIPTION OF THE SPECIFIC EMBODIMENTS According to the method of the present invention, hazardous and toxic wastes, typically nuclear wastes, are stored temporarily or permanently at a waste disposal site. The waste disposal site may be above ground, or may be excavated to provide for partially buried or underground storage. In any case, the disposal site will initially be graded to a relatively flat profile. The size of the disposal site may vary widely, with areas ranging from about 5 to 150 acres normally being deployed for a single integrated disposal structure. After the disposal site is selected and the earth graded, a relatively shallow collection basin is formed for collecting leachate which is formed as natural rain waters percolate downward through the integrated disposal structure. The basin includes an underlayer or bed which is substantially impermeable to aqueous penetration and a peripheral apron so that the leachate may be collected for disposal and monitoring. Typically, the basin will be divided into zones so that leachate collected in different areas or zones may be sent to different disposal and monitoring locations. Usually, the zones will be isolated from one another and be excavated to include low points where the leachate will collect. Collection manifolds are located at the low points and feed individual collection sumps which have monitoring equipment. By separately monitoring the various collection zones, the location of a leak within a single zone can be quickly determined shortly after it is initially detected. Referring now to FIG. 1, an integrated disposal structure 10 is illustrated in its final, sealed configuration. The integrated structure 10 is formed over a basin 12, which includes a peripheral apron 13 and an impermeable bed 14. The impermeable bed 14 acts to collect the leachate within the basin 12 and prevent penetration of the leachate into the ground water. The bed 14 will usually include multiple layer, typically being formed from a compacted clay layer having a thickness in the range from about one to six feet, more usually being about three feet; a coarse layer of sand 16, typically having a thickness from about two to 12 inches, more typically being about six inches; a layer of soil, typically having a thickness in the range from about one to 12 inches, more typically being about four inches; and a gravel drainage layer 20, typically having a thickness of about six inches to two feet, more typically being about one foot. The layers just described interact to collect the leachate within the gravel drainage layer 20 of the basin 12. The leachate flows laterally through the gravel drainage layer 20, and is collected in a plurality of manifolds 22 (only one of which is illustrated in FIG. 1) which may be directed to separate collection and monitoring stations (not illustrated). The basin 12, of course, is properly excavated and sloped so that one predefined area or zone within the basin drain to particular collection and monitoring stations. After formation of the basin 12, lower level waste canisters 30 (FIG. 3) may be placed over the gravelled drainage layer 20. The gravel conforms to the lower surface of the canisters 30, providing stable support. The canisters 30 are held in place solely by gravity, and adjacent canisters 30 are not interconnected other than by the overlaying layer of upper canister 32, as will now be described. Upper layer canisters 32 are placed over the lower level canisters 30 to form an interlocking stack. As best observed in FIGS. 2, 3, and 4, each lower level canister 30 includes a rectangular receptacle 36 on its upper face. Each upper level canister 32, in turn, includes four lower footings 38 which are disposed at each of the four corners of the lower face of the container 32. It will be appreciated that the canisters 32 may be stacked over the canisters 30 in an interlocking manner by placing the footings 38 in the receptacle 36 so that footings from four adjacent canisters 32 are received in each individual receptacle 36. Such an interlocking stack provides a high degree of stability while allowing for relative movement of the individual canisters 30 and 32 in response to earth movements, such as earthquakes, ground sliding, slipping, subsidence, and the like. Upper level canisters 32 include a receptacle 40 on their upper face which is similar in all respects to the receptacle 36 on the lower level canisters 30. In this way, additional layers of upper level canisters 32 may continue to be stacked on top of one another to provide a desired total number of layers in the final integrated structure 10. As illustrated in Figs. 1 and 4, a total of three canister layers are illustrated. In a typical disposal facility, the canisters may be stacked in from about 2 to 10 layers, more usually in from about 3 to 5 layers. In the usual operation, the second, third, and subsequent layers are started prior to the completion of the underlying layer. Thus, after a sufficient number of lower level canisters 30 have been placed, to form a suitable surface, placement of the next layer of upper level canisters 32 will be commenced. Similarly, after a sufficient number of canisters 32 in the second layer have been positioned, placement of the canisters of the third layer 32 will begin. In this way, the integrated structure 10 will grow laterally, as well as in layers. This approach is much more efficient in that it allows the stacking operations to be concentrated at a particular area until that area is complete. After completion of a given area of the integrated structure 10, side caps 50 and top caps 52 (FIGS. 1 and 4) may be placed to provide for a penetration barrier over the integrated structure. Once the entire integrated structure 10 is completed, it may be sealed under soil to allow for landscaping of the disposal facility. Typically, the structure 10 will be backfilled to provide for a relatively level layer on top. A synthetic liner 60 will then be placed over the backfill, followed by a layer of compacted clay 62, usually being at least several inches thick. A gravel layer 64 is then placed over the compacted clay 62, and an uncompacted fill layer 66 and an earthen layer 68 placed over the gravel layer 64. The waste disposal canisters 30 and 32 are typically reinforced concrete receptacles 69 having a concrete cover 70, as best illustrated in FIGS. 3 and 5. Primary waste containers, such as barrels 71 and waste containment boxes 80, as illustrated in FIG. 5, are placed within the receptacle 69, and the interstitial space within the receptacle filled with a curable fluid sealant, typically grout. The cover 70 is then placed over the receptacle 69 to form the hardened and shielded canister 30 or 32 which is stacked in the structure 10 of the present invention. The handling of the primary waste disposal containers 71 and 80 and filling of the canisters 30 and 32 is handled in a shielded area, with all operations performed remotely, when necessary, in order to protect the personnel. Once the canisters 30 and 32 have been closed and sealed, however, they may be handled without additional shielding since they provide sufficient protection for personnel. Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims. At this point in certain claims which are written out and accompany of a tape what follows is an abstract.