Patent Publication Number: US-11041297-B2

Title: Water management system and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     APPENDIX 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention pertains to water management systems adapted to take in, and more slowly drain, an influx of water, such as from a storm. 
     SUMMARY 
     One aspect of the present disclosure is a water management system comprising a plurality of cells having a top flange, a bottom flange, and side openings, the side openings comprised in a peripheral cell area extending from an outer perimeter of the top flange to an outer perimeter of the bottom flange. Each cell is positioned adjacent a side opening of at least one adjacent cell, to permit water to flow laterally through the side opening from either of the adjacent cells to the other adjacent cell. Each cell includes a top module and a bottom module, the top module comprising the top flange and at least one top leg integral to the top flange, a plan area of the top leg being disposed entirely within a plan area of the top flange. The top leg has a vertical longitudinal axis and extends perpendicularly from the top flange to a top leg lower end portion, the top leg lower end portion having an outer peripheral surface and an end surface. The top leg lower end portion may be a narrower projection extending downwardly from a wider portion of the top leg with an annular end face that surrounds the narrower projection. The bottom module comprises the bottom flange and at least one bottom leg integral to the bottom flange, a plan area of the bottom leg being disposed entirely within a plan area of the bottom flange. The bottom leg has a vertical longitudinal axis that extends from the bottom flange to a bottom leg end portion, the bottom leg end portion having a bottom leg sidewall and a recessed end surface forming a bottom leg cavity. The bottom leg cavity has a closed bottom defined by the recessed bottom leg end surface, a closed periphery defined by an inner surface of the bottom leg sidewall, and an open top surrounded by a rim of the bottom leg sidewall. The bottom leg cavity is operative to fit the top leg lower end portion inserted in a centered position therein with a clearance, which may be a lateral clearance in all horizontal directions, between the inner surface of the bottom leg sidewall and the outer peripheral surface of the top leg lower end portion. At least one spacer is disposed within the bottom leg cavity, to adjust for vertical construction tolerance. In an embodiment, the top leg lower end portion is a downward projection from a wider portion of the top leg and has a height approximately equal to a vertical depth of the cavity, the wider portion of the top leg being wider than the cavity, such that a (combined) height of the at least one spacer defines the height of a vertical clearance between the wider portion of the top leg and the rim of the bottom leg sidewall. The top leg lower end portion is at least partially inserted into the bottom leg cavity and positioned on the at least one spacer so that the at least one spacer is clamped between the top leg lower end surface and the bottom leg recessed end surface, at least a part of the outer peripheral surface of the top leg lower end portion being separated from the inner surface of the bottom leg sidewall by a clearance, which may be a lateral clearance in all horizontal directions. A flowable substance in a hardened state occupies at least a portion of the clearance to seat the top leg lower end portion within the clearance, the hardened flowable substance having an exposed top surface. 
     One or both of the top module and the bottom module may be cast from concrete and may be a monolithic casting of concrete. One or both of the top module and the bottom module may be cast in a single casting. 
     In an embodiment, the bottom leg sidewall rim comprises an upwardly facing flat surface of the bottom leg sidewall that defines an opening coinciding with the open top of the bottom leg cavity. The hardened flowable substance, which may be grout, has a flat surface that is flush with the flat surface of the bottom leg sidewall rim. Preferably, the flat surface of the flowable substance that is flush with the flat surface of the bottom leg sidewall does not abut any part of the top leg. 
     Another aspect of the present disclosure is a method of constructing a water management system according to the preceding aspect. The method includes positioning the cell bottom modules in an array so that the bottom flange plan areas are in tessellated alignment; positioning at least one spacer on the bottom leg recessed end surface so that the at least one spacer is disposed entirely below the open top of the cavity; positioning a cell top module on each cell bottom module in the cell bottom module array by inserting each top leg lower end portion into the respective bottom leg cavity in a centered position with a clearance between the inner surface of the bottom leg sidewall and the outer peripheral surface of the top leg lower end portion; horizontally adjusting the top leg lower end portions within the bottom leg cavities so that the top flange plan areas are in tessellated alignment in a manner such that the cells comprise side openings, wherein the side openings are comprised in a peripheral cell area extending vertically from the bottom flange perimeter to the top flange perimeter, and in a manner such that each of the cells is positioned adjacent a side opening of at least one other of cells, to permit water to flow laterally through the side opening from either of the adjacent cells to the other adjacent cell. When each top leg lower end portion is so inserted into and horizontally positioned within the respective bottom leg cavity such that the at least one spacer is disposed between the top leg lower end surface and the bottom leg recessed end surface, a balance of each cavity is at least partially filled with a flowable substance. In an embodiment the flowable substance is filled to a level no higher than the open top of the cavity, and preferably to a level approximately aligned with the open top of the cavity. The flowable substance is caused to harden, such as by leaving the flowable substance in the cavity for a hardening time, to seat the inserted and horizontally positioned top leg lower end portion in the cavity. 
     In an embodiment, the method further includes, before positioning a cell top module on each cell bottom module, mounting an alignment guide on the bottom leg. The alignment guide comprises a peripheral collar, the peripheral collar extending around and engaging an outer peripheral surface of the bottom leg to support the alignment guide when the alignment guide is mounted on the bottom leg, and at least one guide member operatively connected to and tapering upwardly and outwardly from the peripheral collar. For example, the at least one guide member may comprise a plurality of elongate prongs spaced apart about a perimeter of the peripheral collar by small enough distances to restrict the top leg to an area surrounded by the elongate prongs once the top leg is partially inserted into the area surrounded by the elongate prongs. An upper end of the at least one guide member defines an insertion area configured for insertion of an outer peripheral portion of the top leg downwardly therethrough. The alignment guide is adapted and configured such that, when the alignment guide is mounted on the bottom leg, the insertion area is spaced above the open top of the bottom leg cavity. The alignment guide is further adapted and configured such that, when the top leg is positioned above and axially aligned with the bottom leg, the outer peripheral portion of the top leg fits in the insertion area with a clearance, which may be a lateral clearance in all horizontal directions, and which is greater than the clearance between the inner surface of the bottom leg sidewall and the outer peripheral surface of the top leg lower end portion in the centered position. The alignment guide is further adapted and configured such that, when the outer peripheral portion of the top leg meets the insertion area, the top leg end surface is above an elevation of the open top of the bottom leg cavity. The alignment guide is further adapted and configured such that, when the top leg is suspended above the bottom leg with freedom of lateral movement, inserted into the alignment guide in a position in which the top leg lower end portion is laterally out of insertion alignment with the bottom leg cavity, and passively lowered toward the bottom module, the at least one guide member engages the outer peripheral portion of the top leg to cam the top leg towards axial alignment with the bottom leg, so that the top leg end surface is guided to within an area of the open top of the bottom leg cavity when reaching an elevation at or above that of the open top of the bottom leg cavity and held within the area of the open top of the bottom leg cavity when passively lowered for insertion therethrough. The alignment guide peripheral collar may comprises at least two members configured to be at least partially disengageable from each other to open the peripheral collar, and the method may further comprise at least partially disengaging the peripheral collar members to open the peripheral collar, and laterally removing the alignment guide from the bottom leg after the top leg is placed thereon. For example, a peripheral collar member may be articulable relative to another peripheral collar member about a joint, so as to move a portion of one of the members into and out of closure engagement with another of the members. Alternatively, one or more peripheral collar members may be fully removable from one or more other peripheral collar members to open the peripheral collar for removal from the bottom leg. 
     Another aspect of the present disclosure is a water management system comprising a plurality of cells and at least one tension cable extending through at least some of the cells in a series, the tension cable attaching at each end to a different wall panel and being loaded in tension to apply a compressive holding force pressing the series of cells together between the pair of wall panels. Each cell has a top flange and a base, the top flange and base having vertically aligned, like perimeters, and side openings, the side openings comprised in a peripheral cell area vertically extending from the base perimeter to the top flange perimeter. Each cell is positioned adjacent a side opening of at least one other of the cells, to permit water to flow laterally through the side opening from either of the adjacent cells to the other adjacent cell. The system further includes a plurality of wall panels collectively comprising a pair of cable attachment features for each tension cable, each tension cable attachment feature of the pair being adapted and configured for attachment of one of the tension cable ends to a different one of the wall panels. Each cell top flange defines at least a first tension cable channel extending therethrough between two spaced apart open channel ends, each of the two open channel ends being disposed at the top flange perimeter. Each cell includes a support structure extending from the top flange to the base, the support structure being surrounded by the peripheral cell area. The cells are arrayed in a manner such that the cell top flanges form a continuous top deck having a top deck perimeter, in a manner such that the cell base s form a continuous bottom deck having a bottom deck perimeter, and in a manner such that at least one first tension cable path is formed by a series of the first tension cable channels of a corresponding series of the cell top flanges. Each first tension cable path extends through the top deck and has two spaced apart open path ends disposed at the top deck perimeter. The plurality of wall panels are arranged to form a continuous wall around the top deck perimeter and the bottom deck perimeter, so that the system sidewall, the top deck, and the bottom deck cooperate to enclose a system volume that is above the bottom deck, below the top deck, and peripherally surrounded by the system sidewall. Each first tension cable path has a tension cable extending therethrough, each end of the tension cable being attached to a respective wall panel adjacent each open path end of the first tension cable path by engaging an attachment feature of a respective wall panel, the tension cable being tensioned so that the series of cell top flanges corresponding to the first tension cable path are pressed between the respective wall panels. Each cell top flange may be cast from concrete, the respective first tension cable channel comprising a conduit in the cast concrete. The conduit may be, for example, a one-inch diameter PVC pipe or sprinkler pipe. The conduit may alternatively be formed from another material, such as HDPE or another hard plastic, or a metal. A resilient spacer member may be disposed between abutting sides of each adjacent pair of cell top flanges. The resilient spacer member may have an upper flange that overlaps a top side of at least one of the adjacent pair of cell top flanges, to prevent the soft spacer member from falling through a gap between the adjacent pair of cell top flanges during construction of the system. 
     Another aspect of the present disclosure is a method of constructing a water management system according to the preceding aspect. The method comprises positioning the cells in a horizontal array in a manner such that a side opening of each of the cells is positioned adjacent a side opening of at least one other adjacent cell, to permit water to flow laterally through the adjacent side openings from either of the adjacent cells to the other adjacent cell, in a manner such that the cell top flanges form a continuous top deck having a top deck perimeter, in a manner such that the cell bases form a continuous bottom deck having a bottom deck perimeter. Further, the cells in the horizontal array are positioned and such that at least one first tension cable path is formed by a series of the first tension cable channels of a corresponding series of the cell top flanges, each first tension cable path extending through the top deck and having two spaced apart open path ends disposed at the top deck perimeter. The plurality of wall panels are positioned to form a continuous wall around the top deck perimeter and the bottom deck perimeter, so that the system sidewall, the top deck, and the bottom deck cooperate to enclose a system volume that is above the bottom deck, below the top deck, and peripherally surrounded by the system sidewall. A tension cable is positioned so as to extend through each first tension cable path. An attachment feature of a respective wall panel adjacent each open path end of the first tension cable path is engaged to attach a respective end of the first tension cable to the respective wall panel. Tension is imparted to the tension cable to press between the respective wall panels the series of cell top flanges corresponding to the first tension cable path. 
     Further features and advantages, as well as the operation, are described in detail below with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a water management including an array of cells. 
         FIG. 2  is a side elevation view of a portion of a water management system as in  FIG. 1  with a differently arrayed cells. 
         FIG. 3  is an enlarged truncated side elevation view of a leg joint of the water management system of  FIG. 1 . 
         FIG. 4  is a perspective illustration of the assembly of a cell of a water management system of  FIG. 1 . 
         FIG. 5A  is an enlarged truncated side elevation illustration of the assembly of a leg joint of a water management system of  FIG. 1 . 
         FIG. 5B  is a perspective view of an alignment guide used in the assembly of a leg joint illustrated in  FIG. 5A . 
         FIG. 6A  is a side elevation view of cell top modules of the water management system as in  FIG. 2 . 
         FIG. 6B  is a top plan view of a cell top module of the water management system of  FIG. 1 . 
         FIG. 7  is an enlarged cross section of a cell top flange joint of the water management system of  FIG. 1 . 
         FIG. 8  is an elevation view of part of an alternative water management system. 
     
    
    
     Reference numerals in the written specification and in the figures indicate corresponding items. 
     DETAILED DESCRIPTION 
     An embodiment of water management system in accordance with the present invention, which may be a storm water management system, is a water management system  10  shown in  FIGS. 1-4, 5A, 5B, 6A, 6B, and 7 . The water management system  10  comprises a plurality of cells  12  having a top flange  14 , a bottom flange  16 , and side openings  18 , the side openings  18  comprised in a peripheral cell area, which in the illustrated embodiment consists of the lateral sides of a rectangular prism extending from an outer perimeter  22  of the top flange  14  to an outer perimeter  24  of the bottom flange  16 . In the drawings, the peripheral cell area is not separately designated by a separate reference character, but it is a rectangular cylindrical area encompassing the union of all four side openings  18 , lateral faces  25 ,  27 , and end faces  29 ,  31  of top and bottom flanges  14 ,  16 , respectively. System  10  further includes wall panels  13 , which surround an array of the cells  12 . In the array, each cell  12  is positioned adjacent a side opening  18  of at least one adjacent cell  12 , to permit water to flow laterally through the side opening  18  from either of the adjacent cells  12  to the other adjacent cell  12 . Each cell  12  includes a top module  26  and a bottom module  28 . 
     The top module  26  comprises the top flange  14  and at least one top leg  30  integral to the top flange  14 , a plan area of the top leg  30  being disposed entirely within a plan area of the top flange  14 . The top leg  30  has a vertical longitudinal axis and extends perpendicularly from the top flange  14  to a top leg lower end portion  32 , the top leg lower end portion  32  having an outer peripheral surface  34  and a lower end surface  36 . The top leg lower end portion  32  may be, as illustrated in the drawings, a narrower projection that is axially aligned on top leg  30 , having a base  41  disposed on a wider portion of the top leg  30 , such as a shoulder  38  with an annular end face  40  that surrounds the base  41  of the top leg lower end portion  32 , and extending longitudinally from its base  41  to its distal end, corresponding to the lower end surface  36 . A height of the top leg  30 , measured perpendicularly (vertically) from where it meets the top flange  14  to the base  41  of its lower end portion  32 , may be several feet, such as about seven feet. 
     The bottom module  28  comprises the bottom flange  16  and at least one bottom leg  42  integral to the bottom flange  16 , a plan area of the bottom leg  42  being disposed entirely within a plan area of the bottom flange  16 . The bottom leg  42  has a vertical longitudinal axis that extends from the bottom flange  16  to a bottom leg end portion  44 , the bottom leg end portion  44  having a bottom leg sidewall  46  and a recessed end surface  48  forming a bottom leg cavity  50 . The bottom leg cavity  50  has a closed bottom defined by the recessed bottom leg end surface  48 , a closed periphery defined by an inner surface  52  of the bottom leg sidewall  46 , and an open top  54  surrounded by a rim  56  of the bottom leg sidewall  46 . A height of the bottom leg  42 , measured perpendicularly (vertically) from where it meets the bottom flange  16  to the rim  56  of its sidewall  46 , may be several feet, such as about seven feet. At least one spacer  58  is disposed within the bottom leg cavity  50 . Spacer  58  may, for example, be made of hard plastic or other material suitable for spacers or shims in heavy concrete applications. 
     As noted above, in the illustrated embodiment, the top leg lower end portion  32  is a downward projection from the shoulder  38  of top leg  30 . Further, lower end portion  32  has a height H approximately equal to a vertical depth D of the cavity  50 , the top leg shoulder  38  being wider than the cavity  50 , such that the at least one spacer  58  in cavity  50  provides a vertical clearance VC between the top leg shoulder  38  and the bottom leg sidewall rim  56 , while additional spacers  58  may be placed where needed to adjust for vertical construction tolerances. In another embodiment (not shown), a top leg lower end portion height H may be larger than vertical cavity depth D by a desired nominal vertical clearance between the top leg shoulder  38  and the bottom leg sidewall rim  56 , and a spacer  58  may be placed in cavity  50  only when needed or desirable to adjust for vertical tolerance. 
     The top leg lower end portion  32  is at least partially inserted into the bottom leg cavity  50  and positioned on the at least one spacer  58 , so that the at least one spacer  58  is clamped between the top leg lower end surface  36  and the bottom leg recessed end surface  48 , at least a part of the outer peripheral surface  34  of the top leg lower end portion  32  being separated from the bottom leg sidewall inner surface  52  by a clearance C, which may be a lateral clearance in all horizontal directions. A flowable substance, illustrated as a grout G, in a hardened state, occupies at least a portion of the clearance C to seat the top leg lower end portion  32  within the cavity  50 , grout G having a top surface exposed to an air gap within the vertical clearance VC. 
     One or both of the top module  26  and the bottom module  28  may be cast from concrete and may be a monolithic casting of concrete. One or both of the top module  26  and the bottom module  28  may be cast in a single casting. Each of the top leg  30  and the bottom leg  42  may be cast using a common leg base mold (not shown) terminating with a flange that bolts to a support frame, the support frame including one of two interchangeable leg end molds that create the joint detail of the respective top and bottom leg  30 ,  42 . The top and bottom flanges  14 ,  16  may each be rectangular, and may, for example, be several feet wide and several feet long. The length L of each flange  14 ,  16  may be an integer multiple of the width W of each flange  14 ,  16 . This facilitates the use of wall panels  13  of a single size, one wall panel  13  covering each transverse side opening  18  of the outer cells  12  of the array and multiple (two, as illustrated) wall panels  13  covering each open longitudinal side opening  18  of the outer cells  12  of the array. Top and bottom flanges  14 ,  16  may have, for example, a sixteen-foot by eight-foot plan area. A vertical thickness t of each deck may be several inches, such as eight inches. The top leg  30  and bottom leg  42  may each be round (as may be top leg lower end portion  32  and bottom leg cavity  50 ) and include a respective round capital  60 ,  62  where each meets the respective flange  14 ,  16 , each leg and each capital having a frustoconical lateral surface. 
     In the illustrated embodiment, the bottom leg sidewall rim  56  comprises an upwardly facing flat surface of the bottom leg sidewall  46  that defines an opening  64  coinciding with the open top  54  of the bottom leg cavity. The grout G has a flat surface that is flush with the flat surface of the bottom leg sidewall rim  56 . Being exposed to an air gap within vertical clearance VC, the flat surface of grout G does not abut any part of the top leg  30 . 
     In the illustrated embodiment, it is contemplated that the vertical clearance VC is not large enough to permit insertion of grout injection means (not shown) such as a tube or nozzle between top leg  30  and bottom leg  42 , to fill cavity  50  with a grout G. Accordingly, a channel  66  formed in the top leg shoulder  38 , the channel  66  extending inwardly from an outer side  68  of the shoulder  38  toward the base  41  of the top leg lower end portion  32 , the channel  66  being operative to accommodate flow of grout G in a flowable state (in which grout G has a sufficiently fluid consistency to passively form a generally flat, horizontal top surface after settling in the cavity  50 ) from the outer side  68  of the shoulder  38  to the cavity  50  when the top leg lower end portion  32  is positioned on the at least one spacer  58  disposed within the cavity  50 , grout G in its hardened state being formed by curing within the cavity  50  after being introduced therein in its flowable state. Thus the bottom leg  42  and the top leg  30  combine to form a support column  81  configured to transmit a load from the top flange  14  to the bottom flange  16 . 
     Cells  12  are arrayed such that cell top flanges  14  combine to form a continuous top deck  69  having a top deck perimeter  71 , and such that cell bottom flanges  16  combine to form a continuous bottom deck  75  having a bottom deck perimeter  77 . The wall panels  13  are arranged to form a continuous system sidewall  79  around and the top deck perimeter  71  and the bottom deck perimeter  77 , so that the system sidewall  79 , the top deck  69 , and the bottom deck  75  cooperate to enclose a system volume  70  that is above the bottom deck  75 , below the top deck  69 , and peripherally surrounded by the system sidewall  79 . 
     System  10  is configured to be constructed and deployed below ground, embedded in soil, and has an internal volume  70  and one or more features to permit water to enter its internal volume  70  in response to an external influx of water resulting in saturation of the surrounding soil, as well as to permit the water to drain more gradually therefrom. This allows system  10  to act as a passive water management buffer for the surrounding environment. Accordingly, at least one one-way inlet  72  and at least one one-way outlet  74  may be comprised in one or more of wall panels  13 . In addition, each bottom flange  14  comprises a top surface  76 , a bottom surface  78 , and a fluid channel  80  extending from an opening  82  in the top surface  76  to an opening  84  in the bottom surface  78 , the bottom flange top surface  76  forming part of a bottom interior surface  86  of system  10 . Thus, water may seep into internal volume  70  through one-way inlet  72  when the lateral exterior becomes saturated, may rise into internal volume  70  through fluid channels  80  when the underlying exterior becomes saturated, thereby relieving the surrounding environment of excess water above saturation levels, and may begin to gradually drain out of internal volume  70  through one-way outlet  74  and fluid channels  80  once the water pressures at the external sides/ends thereof drop sufficiently to allow a net outflow from internal volume  70 . 
     According to a method of constructing system  10 , cell bottom modules  28  are first positioned in an array so that the plan areas of bottom flanges  16  are in tessellated alignment. The rectangular shape of the plan areas of bottom flanges  16  permit allows for a tessellated array of regular shapes. Other suitable cell shapes that may form tessellated arrays include isosceles or equilateral triangles and regular hexagons. Resilient spacers  88  of a common thickness, such as ½ inch, may be disposed between abutting sides of each adjacent pair of bottom flanges  16 , to inhibit wear resulting from bottom flanges  16  rubbing together. At least one spacer  58  is disposed on each bottom leg recessed end surface  48  entirely below the open top  54  of the cavity  50 . A cell top module  26  is placed on each cell bottom module  28  in the array, after the spacer  58  is placed in its bottom leg cavity  50 , by inserting each top leg lower end portion  32  into the respective bottom leg cavity  50 . The horizontal positions of top leg lower end portions  32  are adjusted within the bottom leg cavities  50  so that the plan areas of top flanges  14  are in tessellated alignment. each of cells  12  being positioned adjacent a side opening  18  of at least one other of cells  12 . Resilient spacers  90 , which may be provided in variable thicknesses ranging from smaller than that of resilient spacers  88  to larger than that of resilient spacers  88 , such as ¼ inch, ½ inch and ¾ inch, to adjust for construction tolerances as needed, are positioned between abutting sides of each adjacent pair of top flanges  14 . Resilient spacers  90  may include an upper flange  92  that overlaps a top side of at least one of the adjacent pair of cell top flanges  14 , to prevent the resilient spacer  90  from falling through a gap between the adjacent pair of cell top flanges  14  before alignment of cell top flanges  14  is completed. When each top leg lower end portion  32  is so inserted into and horizontally positioned within the respective bottom leg cavity  50 , such that the at least one spacer  58  is disposed between the top leg lower end surface  36  and the bottom leg recessed end surface  48 , a balance of each cavity  50  is at least partially filled with a flowable substance, such as grout G. Preferably, grout G is filled to a level no higher than the open top  54  of the cavity  50 , and more preferably to a level approximately aligned with the open top  54  of the cavity  50 , as illustrated in the drawings. Grout G is caused to harden, such as by leaving grout G in the cavity  50  for a hardening time, to seat the inserted and horizontally positioned top leg lower end portion  32  in the cavity  50 . 
     The method may further includes, before positioning a cell top module  26  on each cell bottom module  28 , mounting an alignment guide  94  on the bottom leg  42 . The alignment guide  94  comprises a peripheral collar  96 , the peripheral collar extending around and engaging an outer peripheral surface  98  of the bottom leg  42 , to support the alignment guide  94  when mounted on the bottom leg  42 . At least one guide member, illustrated in the drawings as a plurality of elongate prongs  100 , is operatively connected to peripheral collar  96  so as to taper upwardly and outwardly from the peripheral collar  96 . As illustrated in the drawings, elongate prongs  100  are spaced apart about a perimeter of the peripheral collar  96  by small enough distances to restrict the top leg  30  to an area surrounded by the elongate prongs  100  once the top leg  30  is partially inserted into the area surrounded by the elongate prongs  100 . Upper ends  102  of elongate prongs  100  collectively comprise an upper end of the guide member, defining an insertion area  104  generally surrounded by upper ends  102 , the insertion area  104  configured for insertion of the shoulder  38  of the top leg  30  downwardly therethrough. The alignment guide  94  is adapted and configured such that, when the alignment guide  94  is mounted on the bottom leg  42 , the insertion area  104  is spaced above the open top  54  of the bottom leg cavity. 
     The alignment guide  94  is further adapted and configured such that, when the top leg  30  is positioned above and axially aligned with the bottom leg  42 , the shoulder  38  of the top leg  30  fits in the insertion area  104  with a shoulder clearance SC, which may be a lateral clearance in all horizontal directions, and which is greater than the clearance C between the inner surface  52  of the bottom leg sidewall  46  and the outer peripheral surface  34  of the top leg lower end portion  32  in the centered position. The alignment guide  94  is further adapted and configured such that, when the shoulder  38  of the top leg  30  meets the insertion area  104 , the top leg lower end surface  36  is above an elevation of the open top  54  of the bottom leg cavity  50 . 
     The alignment guide  94  is further adapted and configured such that, when the top leg  30  is suspended above the bottom leg  42  with freedom of lateral movement, inserted into the alignment guide  94  in a position in which the top leg lower end portion  32  is laterally out of insertion alignment with the bottom leg cavity  50 , and passively lowered toward the bottom leg  42 , at least one of the elongate prongs  100  engages the shoulder  38  of the top leg  30  to cam the top leg  30  towards axial alignment with the bottom leg  42 . The top leg end surface  36  is thus guided to within an area of the open top  54  of the bottom leg cavity  50  when reaching an elevation at or above that of the open top  54  of the bottom leg cavity  50 , and held within the area of the open top  54  of the bottom leg cavity  50  when further passively lowered, for insertion therethrough. The alignment guide peripheral collar  96  may comprise at least two members  106 ,  108  configured to be at least partially disengageable from each other to open the peripheral collar  96 , and the method may further comprise at least partially disengaging the peripheral collar members  106 ,  108  to open the peripheral collar  96 , and laterally removing the alignment guide  94  from the bottom leg  42  after the top leg  30  is placed thereon. For example, peripheral collar member  106  may be articulable relative to peripheral collar member  108  about a hinge  110 , so as to move respective distal ends  112 ,  114  of peripheral collar members  106 ,  108  into and out of closure engagement with each other. Alternatively, though not shown, one or more peripheral collar members may be fully removable from one or more other peripheral collar members to open a peripheral collar for removal of the peripheral collar from bottom leg  42  after top leg  30  is in place. When top and bottom flanges  14 ,  16  include a plurality of respective top and bottom legs  30 ,  42 , as in the illustrated embodiment, it is beneficial to mount an alignment guide  94  on at least two of bottom legs  42 , such that, when shoulders  38  of the respective top legs  30  are inserted into the respective alignment guide insertion area  104 , the two alignment guides  94  cooperate to retrain top module  26  from rotating out of alignment with bottom module  28  as it is passively lowered thereon. 
     Turning to another aspect of the present disclosure, a water management system may employ a tension cabling system that provides holding forces tending to resist separation of tightly arrayed (e.g., tessellated) cells thereof in the event of seismic activity. Thus, system  10  includes tension cables  116 , each tension cable  116  extending through an aligned series of the cells  12  along the first horizontal direction, the tension cable  116  attaching at each of its ends  118  to a different wall panel  13  and being loaded in tension to apply a compressive holding force pressing the series of cells  12  together between the pair of wall panels  13  along the first horizontal direction. 
     Wall panels  13  collectively comprise a pair of cable attachment features  120  for each tension cable  116 , each tension cable attachment feature  120  of the pair being adapted and configured for attachment of one of the tension cable ends  118  to a different one of the wall panels  13 . In the illustrated embodiment, tension cable attachment feature  120  comprises a through hole extending through a thickness of the wall panel  13  from an inner side to an outer side of the wall panel  13 . The through hole is sized and shaped to permit a tension cable locking nut assembly  122  that retains a respective end  118  of tension cable  116  to be braced against the outer side of wall panel  13  adjacent the through hole. Additionally, wall panels  13  include a bottom flange  123  to assist with flotation of the structure in saturated soils. 
     Each top flange  14  defines at least one first tension cable channel  124  extending therethrough between two spaced apart open channel ends  126  in a first horizontal direction, each of the two open channel ends  126  being disposed at the top flange perimeter  22 . Cells  12  are arrayed in a manner such that first tension cable paths  128  are formed by a series of the first tension cable channels  124  of corresponding series of the cell top flanges  14 . Each first tension cable path  128  extends through the top deck  69  and has two spaced apart open path ends  130  disposed at the top deck perimeter  71 . Each first tension cable path  128  has a tension cable  116  extending therethrough, each end  118  of the tension cable  116  being attached to a respective wall panel  13  adjacent each open path end  130  of the first tension cable path  128  by engaging an attachment feature  120  of a respective wall panel  13 , the tension cable  116  being tensioned so that the series of cell top flanges  14  corresponding to the first tension cable path  128  are pressed between the respective wall panels  13 . Each cell top flange  14  may be cast from concrete, the respective first tension cable channel  124  comprising a conduit  132  in the cast concrete. The conduit  132  may be, for example, a 1-inch diameter PVC pipe or sprinkler pipe, to fit ½-inch diameter tension cables  116 . The conduit  132  may alternatively be formed from another material, such as HDPE or another hard plastic, or a metal. 
     A portion of one of resilient spacer members  90  is disposed in a respective first tension cable path  128  that extends through each pair of aligned open channel ends  126  of respective first tension cable channels  124  of an adjacent pair of cell top flanges  14  aligned along the first tension cable path  128 . Accordingly, each resilient spacer member  90  has a hole  134  through which the respective tension cable  116  extends. For example, the opening  134  may be pre-formed in the resilient spacer member  90 , or at least part of the portion of the spacer member  90  that is disposed in the first tension cable path  128  may be pre-perforated or otherwise frangible, to permit the tension cable  116  to break through the frangible portion to form the opening  134  as the tension cable  116  is pushed through the tension cable path  128  during construction of the system  10 . 
     Each first tension cable channel  124  comprises a central portion  136  of uniform cross section and two flared end portions  138 , each flared end portion  138  having a cross section that widens from an end of the central portion  136  to a respective one of the two open channel ends  126  of the first tension cable channel  124 . Flared end portions  138  provide for a greater range of relative translation of adjacent top flanges  14  in the vertical plane of their abutting sides, for example, in the event of an earthquake, before the respective tension cable  116  becomes pressed between displaced opposite edges of the corresponding adjacent open channel ends  126 , potentially resulting in damage to the tension cable  116 , the pair of top flanges  14 , or both. 
     Each top flange  14  preferably has at least one first tension cable path  128  extending through a respective first tension cable channel  124  thereof, so as to be held together with neighboring top flanges  14  by the holding force in the first horizontal direction produced by at least one of tension cables  116 . In the illustrated embodiment, two first tension cables  116  extend through each top flange  14  in the first horizontal direction, the respective first tension cable channels  124  extending through and being spaced apart along the long side of top flange  14 . 
     Each cell top flange  14  further defines at least a second tension cable channel  140  extending therethrough in a second horizontal direction intersecting the first horizontal direction. Each second tension cable channel  140  has two spaced apart open channel ends  142 , each of the two open channel ends  142  being disposed at the top flange perimeter  22 . Similarly to first tension cable channel  124 , second tension cable channel  140  has a central portion  141  of uniform cross section and flared ends  143  extending from the central portion  141  to respective open channel ends  142 . The cells  12  are arrayed such that tension cable paths  144  are formed by series of the second tension cable channels  140  of corresponding series of the cell top flanges  14 , each second tension cable path  144  extending through the top deck  69  and having two spaced apart open path ends  146  disposed at the top deck perimeter  71 . Each second tension cable path  144  has a tension cable  116  extending therethrough, each end of the tension cable  116  being attached to a respective wall panel  13  adjacent each open path end  146  of the second tension cable path  144  by engaging an attachment feature  120  of a respective wall panel, the tension cable  116  being tensioned so that the series of cell top flanges  14  corresponding to the second tension cable path  144  are pressed between the respective wall panels  13  along the second horizontal direction. 
     The first tension cable channels  124  and the second tension cable channel  140  of each top flange  14  may be straight, horizontal channels of like diameter, which are vertically offset from each other by a distance larger than their diameter, to avoid intersecting each other, as shown in the drawings. In an alternative embodiment, each of the first tension cable channels of a cell top flange may intersect the second tension cable channel at a respective junction (not shown). The tension cables  116  and/or the junction may be sized, adapted, and configured so that a tension cable  116  already extending through the junction along one of the channels does not undesirably interfere with passing a tension cable  116  through the junction along the other channel. 
     Preferably, and in the illustrated embodiment, the second direction is perpendicular to the first horizontal direction, so that the respective tension cables  116  are likewise perpendicularly oriented, so as to efficiently produce holding forces that combine to resist separation of top flanges  14  in any horizontal direction, while neither the tension cables  116  oriented in the first horizontal direction nor the tension cables  116  oriented in the second horizontal direction produce forces that interfere with the lines of action of the tension cables  116  aligned in the other direction. As with the first tension cable paths  128 , each second tension cable path  144  has portions of resilient spacers  90  extending thereacross at the union of each adjacent pair of second cable channels  140 , each resilient spacer having a hole  134  through which a corresponding tension cable  116  extends. 
     In water management systems of the present disclosure, a greater system height has the advantage of providing greater internal water holding volume for a given construction cost. On the other hand, the environment of a particular water management project may impose a maximum constraint on the height of a system that can be accommodated. Thus, turning to an alternative embodiment, a water management system  10 ′, having a lower vertical profile than system  10 , is shown in  FIG. 8 . System  10 ′ includes the same top modules  26  as in system  10  and wall panels  13 ′ that are similarly configured to wall panels  13  of system  10  but shorter, but differs from system  10  in its alternative bottom modules  28 ′. The bottom module  28 ′ may be, for example, a flat, rectangular concrete pad matching the plan dimensions of top flange  14 , including cavities  50 ′ in its top surface for receiving top leg lower end portions  32 . For environments in which the vertical space available is on the order of the height of a cell module leg that can be cast in a single casting, the configuration of system  10 ′ is believed to have certain advantages over a system in which the top and bottom modules each include shorter legs. For example, a lower module  28  that is out of level alignment at a given tilt angle may result in a significant horizontal offset of cavities  50  from their level positions by legs  42  shifting out of plumb alignment. In contrast, cavities  50 ′, being closer to the bottom of the module and thus to its tilting axis, have their lateral positions less affected by any tilting of bottom module  28 ′. This reduces the likelihood of an upper module, which may, for example, be suspended from a chain during placement as shown in  FIG. 3 , impinging on a neighboring module as lower leg end portions  32  are lowered into place in cavities  50 ′. 
     In view of the foregoing, it should be appreciated that the invention has several advantages over the prior art. 
     It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. 
     As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.