Patent application title: TEMPORARY WATER BARRIER STRUCTURE
Galen L. Peterson (Coon Rapids, MN, US)
Edward L. Schwarz (Minneapolis, MN, US)
IPC8 Class: AE02B312FI
Class name: Hydraulic and earth engineering bank, shore, or bed protection revetment
Publication date: 2011-12-29
Patent application number: 20110318104
A structure for forming a barrier for an adjacent level of water
comprises a plurality of "A" panels and a plurality of "X" panels. The A
panels have at least two slots each extending from one of first and
second long edges of the A panel to a slot terminus between the two
edges. The X panels each have at least two slots each extending from an
intersection with one of first and second edges of the X panel to a slot
terminus between the two edges. Placing the X panels in a crossed and
interlocked relationship with the A panels forms four sides of at least
one cell. A container filled with water is within each of the cells. The
container is formed of flexible material impervious to water and defining
a closed volume having an unstressed shape approximating that of the
cell's four sides.
1. A structure for holding a plurality of volumes of water to form a
barrier for an adjacent level of water, comprising: a) at least first and
second semi-rigid "A" panels having a predetermined A panel thickness,
each A panel having first and second opposite edges having a
predetermined spacing, and each A panel having at least two slots each
extending from one of the first and second edges of the A panel to a slot
terminus between the two edges, each A panel slot having a width of at
least a predetermined X panel thickness and a predetermined depth; b) at
least first and second semi-rigid "X" panels each having the
predetermined X panel thickness, each X panel having first and second
opposite edges having a predetermined spacing, and each X panel having at
least two slots each extending from an intersection with one of the first
and second edges of the X panel to a slot terminus between the two edges,
each X panel slot having a width of at least a predetermined A panel
thickness and a predetermined slot depth; wherein the X panels are in a
crossed and interlocked relationship with the A panels to form four sides
of at least one cell, said cell comprising portions of two A panels
forming two opposing sides thereof and portions of two X panels forming
two opposing sides thereof, with each A panel within a X panel slot and
each X panel within slots of at least two A panels, and with each X panel
slot in alignment with an A panel slot, and with the termini of each pair
of aligned A and X panel slots in proximity with each other, and further
comprising c) within each of the at least one cell, a container formed of
flexible material impervious to water and defining a closed volume having
an unstressed shape approximating that of the cell's four sides.
2. The structure of claim 1, wherein each of the slots in each of the A panels intersects the panel's first edge and each of the slots in each of the X panels intersects the panel's first edge.
3. The structure of claim 2, wherein the first and second edges of the A panel are parallel, and the first and second edges of the X panel are parallel, wherein each slot in each of the X and A panels are of depth substantially equal to the space the container includes a top and a first side wall, a sealable filler opening in the top, and a sealable drain opening in the first side wall.
3. The structure of claim 2, wherein each A panel has adjacent to the second edge and between each pair of slots, an aperture in alignment with the drain opening.
4. The structure of claim 2, wherein the filler opening is adjacent to the first side wall.
5. The structure of claim 1 wherein the A and X panels each contain at least three equally spaced slots.
6. The structure of claim 1, wherein the A panels have at least four equally spaced slots.
7. The structure of claim 6 wherein the A and X panels comprise plywood.
8. The structure of claim 6 wherein the A and X panels comprise a plastic composite material.
9. The structure of claim 1, wherein the A and X panels are each rectangular, wherein the predetermined first and second distances are substantially equal, and wherein the A panels projecting past an end X panel each have in a lower corner thereof, a hole in a predetermined position adjacent to one X panel and in alignment with each other, and further comprising a brace rod passing through each hole.
10. The structure of claim 9, wherein the brace rod comprises one of steel and wood
11. The structure of claim 1 wherein the A and X panels comprise plywood.
12. The structure of claim 1, wherein the X panel slot widths are at least twice the A panel predetermined thickness, and wherein end slots of two A panels share a slot of at least one X panel in the structure with the remaining portions of said A panels extending in opposite directions, to thereby create a structure of predetermined length longer than a single A panel.
13. The structure of claim 1, wherein a plurality of the containers each include a sealable filler port in a top surface of the container.
14. The structure of claim 13, wherein a plurality of the containers each include a sealable drain port in a side surface of the container and near the bottom thereof., and wherein an adjacent A panel includes a drainage access opening in alignment with the drain port.
15. The structure of claim 1, wherein the structure includes a buffer sheet below the container in a plurality of cells.
16. The structure of claim 1 comprising an upper level barrier portion and a lower level barrier portion, where each of the upper and lower barrier portions comprise a plurality of X panels and a plurality of A panels cooperating to form a plurality of cells, and within each cell, a container for holding water, said upper level barrier and the containers within the cells of the upper level barrier supported at least in part by the A panels of the lower level barrier portion.
17. The structure of claim 16, including a support panel interposed between the upper and lower level barriers.
18. The structure of claim 1, including a water container having a relatively thick and stiff bottom forming an integral part thereof.
 Flooding caused by melting snow and ice has become an unfortunate fact of life for populations along northern rivers. When the threat arises, the usual procedure is to emplace temporary dikes or levees to restrain the rising rivers from flooding valuable buildings.
 At least five current solutions exist. One is to simply give up, and abandon sites subject to flooding. This is expensive and unpopular with the residents of these at-risk areas.
 Houses are sometimes built on stilts or pilings so that the valuable portions of the structure are at all times above the highest level of flooding. This solution leads to structures with very little esthetic appeal. The necessity of climbing stairs every time one enters the occupied space is also inconvenient.
 Another solution is to install permanent levees, which is extremely expensive. Permanent levees also affect the ability to use the shoreland and destroy views of the river involved. When the river is within its banks, the view of the river is of course, an important amenity for selecting the site for residential structures.
 A fourth solution is to install temporary dikes or barriers comprising piles of sandbags. This solution requires filling these sandbags with sand and one by one, heaping them onto each other to form the levee.
 The process of filing the bags and then emplacing them to form the required dikes is extremely time-consuming, expensive, and labor intensive. People from hundreds of miles away are recruited to help with the sandbagging activities. The bags are heavy and huge numbers of them are required. For example, Fargo, N. Dak. used 350,000 sandbags to, as it turned out, successfully repel the 2009 flood on the Red River of the North.
 After the river recedes, all of the bags must be removed and emptied. The sandbags themselves are usually destroyed because drying them is more expensive than replacing them.
 A particularly harmful aspect of this process is the procession of heavy trucks carrying the sand from its source to the levee sites. These trucks travel over roads that are vulnerable to heavy loads and are normally subject to spring load restrictions. Often, the roads are damaged so badly as to require complete reconstruction. In addition, the process for handling the sand and sandbags requires much other heavy equipment.
 A more recent solution is to provide a water-filled flood barrier. The instant application claims benefit of the filing date of an application disclosing an interlocking system of individual water containers. While effective for its purpose, cost and storage issues for this solution may be objectionable.
 It is fair to say that the first four of these solutions are primitive, and all of them are and unsatisfactory in one respect or another.
BRIEF DESCRIPTION OF THE INVENTION
 A structure for holding a plurality of volumes of water to form a levee or barrier for containing an adjacent body of water comprises a number of sheets or panels formed of "semi-rigid" material.
 The term "semi-rigid" in this context means that a sheet or panel formed of such material and having appropriate thickness can support itself when suspended as a horizontal beam between two spaced supports. A sheet formed of such material will also typically sag an appreciable amount between the two supports under its own weight.
 Plywood of various thicknesses comprise one type of such semi-rigid material. Likely, fiberglass and other plastic and composite sheet-like panels will also serve this purpose. In general, suitable materials for panels are able to maintain their semi-rigid characteristics for several weeks while immersed in water.
 The structure includes at least first and second semi-rigid "A" panels, and typically many more than two A panels. Each A panel has first and second opposite edges having a predetermined spacing. Each A panel has at least two slots each extending from one of the first and second edges of the A panel to a slot terminus between the two edges. Each A panel slot has a width of at least a predetermined X panel thickness and a predetermined depth.
 The structure also includes at least first and second semi-rigid "X" or cross panels each having the predetermined X panel thickness. Each X panel has first and second opposite edges spaced a predetermined second distance apart. Each X panel has at least two slots each extending from one of the first and second edges of the X panel to a slot terminus between the two edges. Each of the X panel slots has a width of at least a predetermined A panel thickness and a predetermined slot depth.
 The structure comprises the A panels in a crossed and interlocked relationship with the X panels to form at least one cell. This cell comprises portions of two A panels forming two opposing sides thereof and portions of two X panels forming two opposing sides thereof. Each A panel is within a X panel slot and each X panel is within slots of at least two A panels. In this configuration, each X panel slot is in alignment with an A panel slot, and with the termini of each pair of aligned A and X panel slots in proximity with each other
 A container formed of flexible material within each of the at least one cell defines a closed volume having an unstressed shape and dimensions approximating that defined by the cell's four sides.
 "Flexible material impervious to water" in this context, means a flexible material of sufficient strength and thickness to retain water without leakage and when filled with water, successfully resist tearing or leaking at voids that may be present where panels intersect, at an irregular surface on which the four panels rest, and at the top. Such material also should have flexibility adequate to allow the container to collapse into a substantially flat or compact form for shipping and storage.
 "Unstressed shape and dimensions that approximate that of the cell's four sides" means that when the container is filled with water it substantially conforms to the four sides of the cell without tearing or leaking, by stretching or folding if necessary. Note that when empty or when inflated with air, the container shape may be substantially different from a cell.
 A preferred embodiment includes X panels with slot widths that are at least twice the A panel predetermined thickness. End slots of two A panels fit within each slot of at least one X panel in the structure, with the remaining portion of the A panels extending in opposite directions and forming parts of two different sections of the barrier. This allows creation of a structure of any desired length, and many times longer than a single A panel.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIGS. 1 and 2 show plan views of A and X panels respectively for use in forming a flood barrier.
 FIG. 3 is an exploded perspective view illustrating how the A and X panels fit together to form a flood barrier.
 FIG. 4 is a perspective view showing a plurality of each of the A and X panels assembled in a crossed and interlocking relationship to hold a plurality of water containers, to thereby form a flood barrier.
 FIG. 5 is a perspective view showing the barrier of FIG. 4 and a further barrier in exploded view illustrating how a plurality of barrier portions may be stacked to provide a flood barrier of greater height.
 FIG. 6 is a perspective view showing a particular version of a water container.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A typical temporary barrier B (FIG. 4) or B' (FIG. 5) for retaining flood waters comprises a number of semi-rigid rectangular A panels 11 as shown in plan view in FIG. 1, and a number of semi-rigid rectangular X panels 10 shown in plan view in FIG. 2. A panels 11 and X panels 10 have cooperating features that allow them to interlock in a manner allowing construction of a barrier B or B' of any desired length and width.
 A panels 11 extend along the length of the barrier B or B'. X panels 10 are in an assembled barrier B or B', in a crossed and interlocking relationship with A panels 11 as shown in FIGS. 4 and 5. The A panels 11 and the X panels 10 cooperate to form a number of cells 12. At least one container 40 occupies each cell 12. Each container 40 in an operating barrier B is completely filled with water.
 The plan view of an A panel 11 in FIG. 1 shows a version having four equally-spaced slots 21 extending perpendicularly from a long edge 15 of an A panel 11. A panel 11 as shown in FIG. 1 may be 2 ft.×8 ft., thus comprising one half of a standard 4 ft.×8 ft. plywood sheet. Other dimensions and configurations for A panels 11 and the slots 21 in them may also be desirable.
 The number of slots 21 in an A panel 11 will typically vary from three to five. The two outer slots 21 may each be 4-6 in. from the adjacent parallel (short) edge of an A panel 11. Each outer slot 21 defines a cantilevered tab or arm 39 between itself and the adjacent parallel edge. In addition, A panels 11 preferably have drainage access openings 22 near a lower edge 16 opposite from edge 15, as shown in FIG. 1. At least some of the A panels 11 may also have a brace bar hole 25 near the end of the lower edge 16, and in substantial alignment with the adjacent slot 21.
 The plan view of an X panel in FIG. 2 shows a version having three equally spaced slots 27 extending perpendicularly from a long edge 18 of X panel 18. X panel 10 as shown in FIG. 1 may be 2 ft. H×6 ft. W. The height h of each X panel 10 is preferably equal to the height of the A panels 11. Outer slots 27 may each be 4-6 in. from the adjacent parallel edge, to define a cantilevered tab or arm 36 between an outer slot 27 and the adjacent parallel edge of X panel 10.
 Some applications may require that arms 36 have strengthening beams 30 attached to one or both sides of panel 10 along the length of each arm 36. Beams 30 may comprise lengths of standard 2×4 lumber attached to beams 30 by deck screws for example.
 X and A panels 10 and 11 may comprise standard A-C plywood, marine grade plywood, fiberglass sheets, or a combination of these materials. The thickness of both the A panels 11 and the X panels 10 made from such materials may range from 0.5 in. to 1.0 in. depending on the material used and the dimensions of panels 10 and 11. The thickness preferably is not so great that the weight of the panels 10 and 11 makes their handling difficult.
 For cost reasons as much as anything, each A panel 11 and each X panel 10 preferably has substantially uniform thickness although A panels 11 may be of a different thickness from X panels 10. Even individual A panels 11 may differ in thickness depending on their position in a barrier B or B'.
 The slots 21 in the A panels 11 should be equal to or slightly wider than the thickness of the X panels 10, that is from 0.5 to 1.0 in. Slots 27 in the X panels may be equal to or slightly wider than twice the thickness of the A panels 11, that is from perhaps 1.1 to 2.1 in. wide. The reason for this difference in width will be explained in connection with FIG. 4.
 Assuming that A panels 11 and X panels 10 have equal heights h (preferred), then the sum of the depth dA of a slot 21 in an A panel 11 and the depth dX of a slot 24 in an X panel 10 should be slightly greater than h to allow complete interleaving of the X panels 10 and the A panels 11 in a barrier B or B'. It is unlikely that slots 21 and 27 for which dA+dX<h is true will be desirable. In general, dA=dX will also be approximately true, but certainly not necessary. Note that dA and dX values much greater than h/2 is likely not desirable since this will weaken X panels 10 and A panels 11 unnecessarily.
 FIG. 3 shows an exploded perspective view of a single X panel 10 and two A panels 11 that indicates how the panels 10 and 11 fit together. As FIG. 3 suggests, one section of a barrier constructed from the A panels 11 and X panels 10 of FIGS. 1 and 2 comprises four X panels 10 and three A panels 11.
 As shown in FIG. 3, the slots of the A panels 11 are open upwards and the slots of the X panels 10 are open downwards, and this is likely a preferable orientation. Each A panel 11 fits within a slot 27 of each of four X panels 10 so that each A panel 11 is in a crossed and interlocked relationship with four X panels 10.
 The partially exploded perspective view of FIG. 4 shows the construction of two barrier sections B1 and B2 using A panels 11 and X panels 10 to form a single flood barrier B. Four X panels 10 hold three A panels 11 in a grid arrangement to form six cells 12 for each of the sections B1 and B2. Each cell 12 has four sides comprising parts of two A panels 11 and parts of two X panels 10. Note that the two barrier sections B1 and B2 share an X panel 10'.
 Similarly each X panel 10 and 10' is within slots 21 of three A panels 11 so that each A panel 11 is in a crossed and interlocked relationship with four X panels 10. Taking barrier section B1 as an example, the four X panels 10 and 10A and the three A panels 11 cooperate to form six cells 12 in barrier section B1. The length relationship of dA and dX specified above allows edges 15 and 17 to be approximately coplanar when A panels 11 interlock with X panels 10.
 Each section B1 is designed to also interlock with the neighboring section B2 by sharing a single X panel 10'. An end slot of an A panel 11 from section B1 shares the slot The wider slots 27 in X panel 10' allow two A panels 11 from two adjacent barrier sections and extending in opposite directions, to simultaneously interlock with a single slot 24 of X panel 10'. End slots 21 of each of two A panels 11 interlock with a single X panel 10, with the two A panels 11 extending in opposite directions. In this way, the three A panels 11 in each barrier section B1 and B2 form the crossed and interlocked relationship with shared X panel 10', and interlock to connect barrier sections B1 and B2 to each other.
 As many barrier sections B1, B2, etc. as is necessary can be connected to form an uninterrupted barrier B for holding back flood water. Each barrier section B1, B2, etc. interlocks with a neighboring barrier section B1, etc. at a common X panel 10'.
 Although the structure shown in FIGS. 3 and 4 seems to be the best available for forming barrier B, other arrangements may also be suitable. These other arrangements are considered to be within the definition of the invention and the crossed and interlocked arrangement.
 Each cell 12 of a barrier section B1 has within it a water container 40 formed of flexible material impervious to water. Each container 40 forms a closed volume having an unstressed shape and dimensions approximating that of the parallelpiped defined by the four sides of each cell 12. Note the definitions of "flexible material impervious to water" and "unstressed shape and dimensions that approximate that of the cell's four sides" above.
 Because maintaining the water-holding capacity of containers 40 is critical, the material comprising them must robustly resist bursting and puncturing. A number of sheet materials and nonwoven fabrics of 6-20 mil thickness provide suitable strength for the physical integrity needed during use, and the flexibility for compact storage.
 A and X panels 11, 10 having dimensions as above in a barrier B with arms 36 and 39 having a width equaling 5 in. form cells 12 whose dimensions are approximately 28 in. L×30 in. W×24 in. H. "L," "W," and "H" respectively designate the dimension along the length, width, and height of barrier B.
 Water completely filling a container 40 fitting snugly in such a cell 12 weighs about 725 lb. A barrier B1 comprising six cells 12 thus weighs about 4350 lb. This weight is fully sufficient to resist a level of water rising to the top of barrier section B1 without shifting or tipping. Placing a few sandbags on the water side of a barrier section B1 for example prevents all or nearly all leakage between the ground and barrier section B1.
 While FIG. 4 shows a single container 40, the term "container 40" in this description should also be understood to include a structure comprising two or more individual containers whose collective shapes when placed adjacent to each other approximate that of the four sides of a cell 12. Thus a single cell 12 may contain two or more individual containers that together form container 40.
 Each container 40 includes a filling port 44 and a draining port 47. The port 47 position aligns it with a drainage access opening 22 in an A panel 11. Each port 44 and 47 comprises a hole and a watertight plug. Preferably each hole and plug combination incorporates a means of securing the plug by for example a screw thread in the hole to prevent water leakage, but yet allows easy plug removal to drain container 40 when disassembling barrier B. Because of the substantial pressure that 2 ft. or more of standing water creates, container 40 may need a reinforcement 56 to prevent tearing of container 40 at drainage access openings 24.
 On occasion barrier B may be assembled on terrain having sharp or pointed rocks, stumps, etc. A buffer sheet or panel 50 placed at the bottom of cell 12 can serve to protect the structural integrity of the container 40 within that cell 12.
 FIG. 6 shows an alternative structure, where the functionality of sheet 50 is provided by a relatively thick and stiff bottom 58 forming an integral part of container 40'. Such a bottom does not interfere with the ability of a container 40 to collapse into a relatively compact structure.
 The standing head of water within containers 40 creates substantial outward force at the bottom edges of X panels 10 that do not form parts of two cells 12. Thus, the portions of X panels 10 between slots 27 receive cantilevered loads that may possibly bend, bulge out, or break individual X panel 10 portions between two adjacent slots 27.
 To solve this potential problem, the assembler prior to filling the container 40, inserts a brace bar 53 into brace bar holes 25 of each A panel 11 projecting past an end X panel 10. When the A panels 11 are first placed in crossed and interlocking position with an end X panel 10, brace bar holes 25 are preferably substantially tangent with the outer surface of the adjacent outer X panel 10.
 As hydrostatic pressure forces the bottoms of an end X panel 10 outwards, these bottom edges press against the brace bar 53. The force of the hydrostatic pressure against brace bar 53 places the unslotted lengths of the A panels 11 in tension to resist this hydrostatic pressure. This force also locks brace bar 53 in place.
 Brace bar 53 may comprise a length of reinforcing rod or even a wooden bar such as a 2×4. Obviously, holes 25 must match the cross section of the particular structure selected for brace bar 53.
 A number of other expedients may exist for adding support to the portions of X panels 10 between slots 27. One of these expedients may for example, include blocks or chocks attached to the projecting A panel 11 ends. Another may comprise individual pins inserted into each of the holes 25. These and other expedients providing similar functionality are all meant to be included as a type of brace bar 53.
 During assembly, three individual A panels 11 are placed vertically on the ground, slots 21 upwards, with spacing between adjacent A panels 11 equal to that between individual slots 27 in X panels 10. Then slipping individual X panels 10, slots 27 down, into slots 21 and with A panels 11 in slots 27, forms the crossed and interlocked relationship that creates individual cells 12.
 Then individual containers 40 are placed in each cell 12 with drainage ports 47 within the openings 22 and filler ports 44 facing upwards. Brace bars 53 are inserted in holes 25 as necessary.
 Water is then pumped into each container 40 through filler ports 44. Because of the potential for the hydrostatic force of the water to excessively deflect bottom portions of X panels 10, it may be necessary to only partially fill each container 40 initially, and then complete filling of an individual container 40 after each of its neighbors have been partially filled. Note also that the flexibility of containers 40 may require that the filler hose or nozzle is attached to ports 44 during filling.
 Disassembly is easy. Each drainage port 47 is successively opened and water drains out under the force of gravity. As the water drains, individual containers 40 collapse under atmospheric pressure into a size relatively easy to transport and store.
 FIG. 5 shows a partially exploded view of a two level barrier BB comprising a lower barrier portion B identical to that shown in FIG. 4, and an upper barrier portion B'. Barrier portion B' comprises four A panels 11 and seven X' panels 10' to define seven cells 12. The width (horizontal) dimension of X' panel 10' may be approximately 3.5 ft. wide.
 Each cell 12 in both upper barrier portion B' and lower barrier B is to be occupied by a container 40, omitted for simplicity of illustration in FIG. 5. Barrier B' thus adds substantial weight to the entire barrier BB. For the dimensions suggested above, this added weight is approximately 4350 lb. for the six cells 12 of barrier B'.
 Upper barrier portion B' sits on lower barrier portion B to form barrier BB. In the version of FIG. 5, barrier portion B' sits equally on both sides of center A panels 11 of barrier portion B. X' panels 10' align with X panels 10 of barrier portion B.
 To provide support for the filled containers 40, an optional support panel 59 distributes the substantial load of these containers 40 in barrier portion B' among the X and A panels 10 and 11 in lower barrier portion B. Such a panel 59 may be unnecessary if barrier portion B' uses the containers 40' of FIG. 6 having integral reinforcement.
 However, experience may indicate that more appropriately lengthwise positioning of a barrier portion B' on barrier portion B locates X' panels 10' to fall approximately midway between the X panels 10 below. Similarly, barrier portion B' may also be advantageously positioned so that the A panels 11 in barrier portion B' are in approximately vertical alignment with the A panels 11 of barrier portion B. In such an arrangement, much of each container 40 weight is borne by the container 40 immediately beneath. This will reduce compressive loads on X and A panels 10, 11 in barrier portion B, but increase the hydrostatic forces on outer A panels 11 and end X panels 10 in barrier portion B.
 The X and A panels 10, 11 forming barrier portion B comprise beams in column loading. Filled containers 40 and the crossed and interlocked relationship among X and A panels 10, 11 provide substantial support against lateral buckling by panels 10, 11 in barrier B.
 Given adequate compressive and hydrostatic load bearing ability for the X and A panels 10, 11 in barrier portion B, it is possible to construct a barrier having three to four levels. This provides such a barrier with substantial height, and with sufficient weight to retain a wall of water reaching nearly to the barrier's top.
 As an example of the calculations governing stacking several layers of barrier portions B, consider the following. Engineering tables specifying compressive strength of various softwoods suggest that a reasonably derated wet strength load-bearing ability parallel to the grain is around 500 psi. It is also reasonable to assume that panels 10, 11 when made of fir (softwood) plywood can be designed to orient 75% of the plies in them with their grain vertical as panels 10, 11 are deployed in FIG. 5.
 Assume panels 10, 11 in bottom barrier B of FIG. 5 comprise 1 in. thick fir plywood with vertically oriented grain in 75% of the thickness. Calculations based on these assumptions show that a central A panel 11 in barrier portion B can support more than 3000 lb. per linear foot of A panels 11. Thus, a barrier portion B as shown in FIG. 5 can support more than 11,000 lb. per cell 12, where cell 12 is 30 in. in length.
 This means that three vertically stacked barrier portions B' on such a barrier B are safe. Three barrier portions B' stacked on top of each other will weigh around 2200 lb. per cell 12 in bottom barrier portion B. And these calculations assume that the containers 40 in the bottom barrier portion B bear none of the load, likely an incorrect assumption.
 One can also pyramid a number of levels of barriers. For example, a bottom barrier might be three cells 12 wide, a middle level barrier might be two cells 12 wide, and a top barrier one cell 12 wide might sit on the center of the middle level barrier. It may be necessary for X panels 10 to share slots in A panels 11, in which case the A panel slots 21 must be wide enough to accept two X panels 10.
 The structural integrity of the containers 40 is important. Even slow leaks in even one or two containers 40 over the period of a few weeks that a flood may persist, could result in failure of the barrier. Therefore, ports 44 and 47 must not leak at all, and the material comprising the containers 40 walls, top, and bottom must be robust enough to resist any conceivable penetration. This is particularly true for containers 40 on the flood side of the barrier because inspection of them is not easy.
 Also, prolonged exposure to pressurized flood water at the bottom of a barrier may weaken panels 10, 11, particularly those comprising plywood. Marine grade plywood is designed for service in wet conditions may be appropriate for at least all the A panels 11 on the flood side of a barrier BB, and for all the X panels 10 interlocking with those A panels.
Patent applications by Edward L. Schwarz, Minneapolis, MN US
Patent applications by Galen L. Peterson, Coon Rapids, MN US
Patent applications in class Revetment
Patent applications in all subclasses Revetment