Abstract:
The invention provides modular units, associated component parts, and assemblies of the modular units and component parts, including storage and filtration systems, that are useful for making and using underground water management systems.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/714,178 filed on Oct. 15, 2012, the subject matter of which is herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to modular units, component parts, and assemblies of the modular units and component parts that are useful for making and using underground water storage systems. 
       BACKGROUND OF THE INVENTION 
       [0003]    Nearly any new development of land must incorporate a system for managing water runoff from the developed land. Current regulatory schemes typically require developers to install underground water detention and/or retention systems that effectively maintain a flow of water into and off of the developed land that mimics the natural (i.e., pre-development) flow from the land. 
         [0004]    Such systems typically are installed under large concrete or asphalt surfaces and often must be capable of bearing highly variable weight loads (e.g., a parking lot). Ideally, such systems should maximize water storage capacity while occupying as small a “footprint” as possible in order to minimize land usage. Such systems should be adaptable to a variety of different storage needs and landscape features, including shallow or deep burial depths, and they should be relatively easy to construct and handle during site construction. The design also should allow enhanced access for maintenance through the life of the system. 
         [0005]    In addition, many regulatory schemes require controlling not only water runoff, but also water quality, such as levels of pollutants. Typically, developed land accumulates pollutants that can contaminate water runoff, particularly after storms. Ideally, underground water management systems should process (e.g., using filtration systems) water flow from the developed land prior to releasing it. Such processing systems should be incorporated into the underground water retention/detention system in order to minimize land usage and construction costs (such as costs for materials and piping), but they also should be accessible for intermittent cleaning, repair, and/or other maintenance. 
         [0006]    Accordingly, there exists a need for an underground water storage system for storm water detention and/or retention that provides strength, structural integrity, increased water storage capacity, and integrated chambers for fluid processing and ease of construction, installation and use. 
       SUMMARY OF THE INVENTION 
       [0007]    In one embodiment, the present invention provides a monolithic arched module component for use in an underground water management system comprising four substantially rectangular side surfaces; a substantially rectangular top surface; and two or more corner pillars extending from adjacent corners of the component, wherein the two corner pillars at least partially define one or more curved openings along at least one of the four side surfaces. In some embodiments, an interior surface extends downward from a portion of the rectangular top surface, wherein the interior surface defines an interior opening in the arched module component. 
         [0008]    In some embodiments, the arched module component comprises a solid shell, wherein said solid shell comprises a single surface that is impermeable to water, wherein the solid shell covers a hollow core. In some embodiments, the arched module component comprises a cube. 
         [0009]    In one embodiment, the invention provides a monolithic, modular unit for use in underground water management systems comprising a structure having six faces (i.e., corresponding to the six substantially rectangular “sides” or “faces” of a cuboid) with a substantially round opening in one or more face and an interior volume. In some embodiments, a wall or a partial wall extends from a portion of the top face. In some embodiments, the modular unit comprises a solid shell that is impermeable to water. In some embodiments, the modular unit comprises an open bottom. In other embodiments, the bottom of the arched module unit comprises one or more round openings that can be in a range of shapes (e.g., circular, generally round, rectangular). In yet other embodiments, the bottom portion of the arched module unit comprises a substantially rectangular slab. 
         [0010]    In one embodiment, the invention provides an underground water management system comprising an assembly of modular units, wherein each modular unit comprises a one-piece structure having a curved opening on at least one side and a substantially hollow, interior volume, wherein at least one side of each of said modular units abuts at least one side of an adjacent modular unit such that the openings in the sides of the adjacent units substantially align, thereby forming a passage between adjacent units. At least one of the modular units further comprises at least two chambers within the unit. In some embodiments, the assembly is surrounded by an impermeable liner (e.g., PVC, HDPE) to function as a storage or detention system. In other embodiments, the assembly is surrounded by a woven or non-woven geotextile liner to function as a water infiltration or retention system. In one embodiment, the system comprises an inlet pipe and an outlet pipe. In another embodiment, the system comprises a riser and a maintenance cover along a top face of a modular unit. 
         [0011]    In one embodiment, the invention provides an underground water management system comprising a plurality of separate zones having different water flow, retention, and/or detention characteristics, wherein said system comprises an assembly of modular units placed adjacent to each other, vertically and/or laterally, wherein said units comprise a structure having one or more curved openings in each side surface, a substantially hollow interior, and a solid shell impermeable to water, and wherein the water flows through at least one opening of one of said plurality of modular units is restricted. In one embodiment, the system of the present invention further comprises a filtration device located at the interface of two different zones. In one embodiment, the system comprises an inlet pipe and an outlet pipe, wherein the inlet pipe is coupled to one zone, and the outlet pipe is coupled to a different zone. 
         [0012]    In another embodiment, the invention provides an underground water management system comprising an assembly of modular units, wherein at least one modular unit comprises an optionally removable filtration system comprising a filter basket or a media filter cartridge. In other embodiments, the system comprises a plurality of filtration devices located within the assembly. 
         [0013]    In another embodiment, the invention provides a method for underground storage of storm water comprising the steps of: passing fluid through one or more openings of a monolithic, arched module component comprising four sides, a substantially rectangular top face, a hollow core, and at least two corner pillars extending from adjacent corners of the component, wherein two corner pillars at least partially define one or more curved openings along at least one of the four sides; storing fluid within the hollow core; and releasing fluid through one or more openings of the monolithic, arched module component. 
         [0014]    In other embodiments, the invention provides a variety of component pieces useful for assembling the arched module components into modular units and the modular units into assemblies that can be used as underground water management systems. Among the various additional components are stacking couplers, lateral couplers, various solid and grated cover panels adapted for the top, bottom, and side face openings of the modular units, and various filtration devices, including filter baskets and media filters that can be removably installed in the openings of modular units. 
         [0015]    In various embodiments of the present invention, materials useful for construction of the arched module components, modular units, and assemblies constructed therefrom include but are not limited to: concrete, polypropylene, high density polyethylene, low-density polyethylene, or any other materials that can be molded or cast including but not limited to rubber and aluminum. In some embodiments, the arched module components, modular units, and assemblies constructed therefrom comprise hollow core construction. 
         [0016]    In some embodiments, it is contemplated that the dimensions of the modular units can vary within a range dependent on one or more design factors including but not limited to: desired water volume capacity, desired weight of each modular unit, desired load-bearing tolerance for assembly, desired amount of water flow to be managed, size and structure of overall assembly in which the unit is used, and/or the desired access space for inspection and maintenance purposes. 
         [0017]    In various embodiments, it is contemplated that the dimensions and/or structural configuration of underground water management systems constructed using assemblies of modular units can vary dependent on one or more design factors including but not limited to: desired overall size of the assembly, desired load-bearing tolerance for assembly, desired amount of water flow to be managed, number and location of inlet and outlet pipes, number and location of pre-treatment zones and filtration systems, and/or the desired access space for inspection and maintenance purposes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Embodiments of the present invention may be described with reference to the accompanying drawings. 
           [0019]      FIG. 1  illustrates schematically an angled side view of one embodiment of an arched module component of the present invention having a solid shell, hollow core construction with two openings located along each of two opposite exterior sides, an opening located along an interior partition, and one opening located along each of the remaining exterior sides. 
           [0020]      FIG. 2  illustrates schematically an angled side view of one embodiment of the arched module component having a substantially cubic shape, a solid shell, hollow core construction, and one opening located on each of the sides. 
           [0021]      FIGS. 3A and 3B  illustrate schematically in angled side view, internal arched module components of the present invention having openings on all four sidewalls and one or more openings along the bottom floor. 
           [0022]      FIGS. 4A and 4B  illustrate schematically in angled side view, corner arched module components. Each module component includes two adjacent closed sidewalls and one or more openings along the bottom floor. 
           [0023]      FIGS. 5A and 5B  illustrate schematically in angled side view boundary, arched module components. Each module component includes one closed sidewall and one or more openings along the bottom floor. 
           [0024]      FIGS. 6A and 6B  illustrate schematically in angled side view, parallel arched module components, with each module component having two substantially parallel closed sidewalls and one or more openings along the bottom floor. 
           [0025]      FIGS. 7A and 7B  illustrate schematically in angled side view, end cap arched module components, with each module component having an open sidewall and one or more openings along the bottom floor. 
           [0026]      FIG. 8  illustrates schematically a partially exploded, angled side view of an underground water management system with multiple arched module components arranged in rows and columns. 
           [0027]      FIG. 9  illustrates schematically a top plan view of an underground water management system with multiple arched module components arranged in rows and columns. 
           [0028]      FIG. 10  illustrates schematically a side cut-away view of an underground water management system with adjacent module components. 
           [0029]      FIG. 11  illustrates schematically a partially exploded, angled side view of an underground water management system with a single row of arched module components. 
           [0030]      FIG. 12  illustrates schematically a partially exploded, angled side view of another embodiment of an underground water management system with a single row of arched module components. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
         [0032]    Also, use of the “a” or “an” are employed to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise. 
         [0033]    Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. 
         [0034]    In the following description, numerous specific details are provided, such as the identification of various system components, to provide an understanding of embodiments of the invention. One skilled in the art will recognize, however, that embodiments of the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In still other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the invention. 
         [0035]    Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
       I. Overview 
       [0036]    The present invention provides a modular underground system for water management applications. A wide range of underground water management applications may be addressed using the systems described herein. These include but are not limited to all water retention/detention applications typically addressed with underground caverns, chambers, cisterns, etc. and typically made using simple piping, pre-cast concrete type assemblies. Particular applications include underground storm water retention and/or detention, rainwater harvesting, and other water runoff related issues. 
         [0037]    The water management systems of the present invention have a structure comprising an assembly of modular units. The modular unit is a six-sided structure bounded by six substantially rectangular faces with one or more arched openings along one or more side faces, such that passages for water flow extend through the structure. As described herein, each modular unit has one or more side face openings that define passages (i.e., virtual pipes) through the structure. Each modular unit comprises a substantially hollow interior volume that is capable of water storage. 
         [0038]    In one embodiment, each modular unit may also have an interior surface formed, for example, from pillars, a wall, or partial wall extending from a portion of the top or bottom face of the modular unit. The interior surface can be solid, or it can include one or more openings or “weirs,” over which fluid may flow through the unit. The presence of the interior surface creates separate chambers for segregated flows within a modular unit. It also provides increased strength and enhances the load carrying capacity of the modular unit. 
         [0039]    In a preferred embodiment, the modular unit is constructed as a single, monolithic unit that can be used with other modular units in an underground water management system. The module can require no further assembly (e.g., be made from pre-cast concrete). This single-piece modular unit simplifies the construction of multiple modules for larger assemblies of modular units and reduces the changes of breakage during handling. 
         [0040]    In some embodiments, the modular unit comprises a substantially cuboid structure with a hollow interior volume and comprises an exterior solid shell (i.e., exterior layer, slab, or “skin”) that is impermeable to water. In some embodiments, the modular unit comprises a solid shell covering a hollow core structure (i.e., a substantially empty volume under the shell). In some embodiments, the core of the modular unit under the shell can include additional internal structural supports (e.g., supporting panels, framework pieces, or beams), which provide increased load bearing strength to the modular unit. These internal structures may be integral to the modular unit structure, or optionally separate pieces that fasten to (e.g., snap-in) the underside of the solid shell. 
         [0041]    Additionally, in some embodiments, the invention provides optional solid, perforated, or grated cover panels (i.e., “plugs”) for openings on the sides of the modular unit, thereby allowing each modular unit to be separately modified for a particular water retention/detention function. 
         [0042]    The structure of the modular units greatly facilitates fabrication of underground systems. Both simple (e.g., adjoining modular units) and highly complex systems (e.g., with outlet flow control, water filtration systems, and other features) can be built using the same modular units. The hollow structure of the modular units further facilitates assembly by minimizing weight (e.g., particularly with the hollow core structure) while maximizing water flow and storage volume. Additionally, the arched openings of the modular unit provide sufficient loading bearing strength and structural integrity for a wide range of underground water management applications. 
         [0043]    The substantially cuboid structure of the modular unit comprises one or more openings along the side faces, a substantially hollow interior volume, and one or more passages for water flow within the unit. Optionally, one or more openings along a top face of a modular unit provides enhanced access for inspection and maintenance of underground assemblies, e.g., for clean-out of debris following a storm. Further, the modular unit of the present invention can be customized in its water flow characteristics with the use of the standard set of coverings that fit over the openings. 
       II. The Modular Unit 
       [0044]    A. Arched Module Component 
         [0045]    1. General Structure 
         [0046]      FIG. 1  illustrates schematically an angled side view of one embodiment of the arched module component  100  having a rectangular cuboid shape with four side faces and top and bottom faces. In this embodiment, two opposite side faces are each shorter in width than each of the other two opposite side faces. Opposite side faces form lateral faces on the shorter sides and longitudinal faces on the longer sides. The arched module component has a solid shell, hollow core construction with six substantially curved side openings defined by pillars or sidewalls extending from the top (upward facing) surface. The corner pillars define an opening  101  along a lateral face of the component, as well as another opening along the opposite lateral face of the component. Two additional pillars extend downward from a central portion of the top surface to define an additional interior opening  102  in the center of the module component. These corner and center pillars also define curved, substantially oval shaped openings  103 ,  104  along a longitudinal face, as well as another set of corresponding openings along the opposite longitudinal face. Although shown here with sharp corners and/or edges, the arched module component can also include rounded corners and/or rounded edges. Standard design options (e.g., the use of structurally stronger or weaker materials) may be selected that allow for a decrease or increase in the relative dimension of the opening diameter to the length of the sides. In a preferred embodiment, the top surface of the component can include one or more lift eyes  105  to facilitate transport and installation. 
         [0047]    The alignment of openings in the arched module component defines passages. The passage can be left unobstructed allowing water and/or air to flow through (i.e., function as a “weep-holes”). In the embodiment shown in  FIG. 1 , the four openings, two aligned on each of the longitudinal faces, form channels for water flow, while the three lateral openings, two on each lateral face and one in the interior of the module component, form another channel for water flow. The use of a minimal number of openings in the arched module component provides the advantage of minimizing surfaces that debris flowing through the modular component can become snagged or otherwise caught resulting in obstructions. 
         [0048]    The center pillars, located in the interior of the module, provide structural support and enhance the load carrying capacity of the module component. In another embodiment, an interior wall or an interior partial wall (or panel) extends from a center portion of the top or bottom face to form separate chambers within a unit. The interior wall can be a solid slab that creates a hydraulic seal, preventing water flow into a portion of the modular component. Alternatively, the interior wall can include one or more openings that allow fluid flow therethrough. In one embodiment, the wall can be solid and include a circular opening that can be fitted with an underground pipe that allows for fluid flow out of the chamber. Sediments settle from water flowing through the chamber, and the filtered flow enters openings in the pipe and exits the chamber. In another embodiment, the interior wall includes one or more weirs cast into the wall that allows for sedimentation, flow control, and/or energy dissipation. In these and other embodiments, the interior wall can create a separate inlet bay within the module and segregate flows for pre-treatment using available filtration systems known in the art or other processing. 
         [0049]    In another embodiment, one or more of the openings is optionally plugged (with e.g., rubber plugs) to prevent water and/or air flow. Alternatively, the openings can be optionally screened to prevent large particle or sediment passage. The bottom of the module can be open to allow water flow, as shown in  FIG. 1 . Alternatively, the bottom of the module can be closed to obstruct water flow (not shown). 
         [0050]    The dimensions of the arched module component and the sizes of the openings may vary to accommodate different design considerations, such as different widths, lengths, and heights (outside and inside dimensions), desired weights for each modular unit, and water storage volumes. The ordinary artisan will also recognize that the absolute dimension of the opening can be selected to accept industry standard pipe connections/fittings (e.g., rubber boots). In this embodiment shown in  FIG. 1 , the openings are shown as substantially rounded. However, any of a multitude of complementary shapes allowing fluid flow through the module and well known to the ordinary artisan could be used. Such fittings can offer flexible and watertight connections between modular components and piping for controlling water flow into and out of an assembly of modular components. 
         [0051]    As shown in  FIG. 1 , in one embodiment the arched module component structure comprises a shell and a hollow core. In a preferred embodiment, the shell comprises a single, solid layer impermeable to water. Typically, the shell and hollow core construction is made of pre-cast concrete. In some embodiments, the hollow core of the arched module can include internal structures providing additional structural strength. For example, it can include a vertical panel extending from the inside of each corner to the internal side of the opening. Such a vertical panel would be integrated into the hollow core structure and add structural integrity by linking the outer rectagular wall to the inner openings in the top and bottom faces of the arched module. 
         [0052]    Another embodiment of the present invention, a “half cube” arched module component, is shown in  FIG. 2 . The arched module component  200  is substantially cuboidal in shape. It has a solid shell, hollow core construction with four substantially curved openings formed by four corner pillars extending downward from the top (upward facing) surface. The corner pillars define openings, one on each of the four side faces. In a preferred embodiment, the top surface can include one or more lift eyes  201  to facilitate transport and installation. These examples are provided for illustration purposes, and additional openings or fewer openings can be included in sides of a given arched module component. 
         [0053]    The alignment of openings on sides of the arched module component defines passages to allow for fluid flow. In the embodiment shown in  FIG. 2 , a pair of openings, one on each opposing side face, forms a channel for water flow, while the remaining two opposite side openings form another channel for water flow. 
         [0054]    2. Exemplary Configurations 
         [0055]    The side faces of the arched module components described above can be designed with difference combinations of open, partially open, or closed sidewalls that allow for fluid flow into and through the module, so as to accommodate the needs of a particular site or system. Arched module components with one or more sidewall openings can be used together in different configurations to form underground stormwater management systems that either allow or impede the flow of fluid though that portion of the system. 
         [0056]    For example, the arched module component of the present invention can be in the form of “internal modules.” The internal modules can be used in one or more interior portions of a stormwater management system in which arched module components are placed in multiple rows. Referring to  FIG. 3A , one or more openings  301  are formed on a bottom slab  302 . The holes may be provided in the bottom slab for retention and infiltration systems. A top slab  303  defines an upper boundary of the module. Each of the sidewalls is open and has one or more holes defining channels for fluid flow. A short or lateral sidewall  304  includes a side opening above the bottom slab, and the opposite short or lateral sidewall also includes a corresponding side opening above the bottom slab. In one embodiment, the bottom-most edge of a side opening can be in contact with the top surface of the bottom slab. In other embodiments, the bottom-most edge of a side opening can be located above the top of the bottom slab. The portion of the sidewall below the side opening may thus impede fluid flow along that portion of the module. A long or longitudinal sidewall  305  includes two openings, while the opposite long or longitudinal sidewall also includes two corresponding openings. Openings in opposite lateral sidewalls form a lateral channel, while openings in opposite longitudinal sidewalls form longitudinal channels. In the half-cube embodiment shown in  FIG. 3B , the internal module similarly includes two open sidewalls. The bottom slab includes an opening  306 , preferably for retention or infiltration systems. 
         [0057]    An assembly may also include “corner modules” that can be placed along a corner of the perimeter in a multiple row system. A corner module includes two adjacent sidewalls with flow orifices, as well as two adjacent sidewalls without flow orifices. For example, in the arched module component shown in  FIG. 4A , lateral sidewall  401  and the adjacent longitudinal sidewall  402  are closed. The remaining sidewalls (and bottom slab) include openings that permit fluid flow in the module. Similarly, in the half-cube module component shown in  FIG. 4B , adjacent sidewalls  403  and  404  are closed, while the remaining sidewalls (and bottom slab) include openings, one on each side, that permit fluid flow in the module. 
         [0058]    “Boundary modules” include a sidewall without flow orifices and three sidewalls, each with at least one flow orifice. The sidewall without flow orifices can be positioned along a perimeter of an assembly of modular units so that stormwater does not flow out of the assembly at that portion of the perimeter. For example, in the arched module component shown in  FIG. 5A , lateral sidewall  501  is closed. The remaining sidewalls (and bottom slab) include substantially rounded openings that permit flow through the module. In another embodiment, a longitudinal sidewall, e.g.,  502 , may be closed so that stormwater does not flow through that sidewall, while the remaining sidewalls of the boundary module each include openings. In the half-cube module component shown in  FIG. 5B , one sidewall  503  is closed, while the remaining sidewalls (and bottom slab) include openings. 
         [0059]    “Parallel modules” can be placed side-by-side in single row assemblies. A parallel module includes sidewalls with one or more flow orifices on opposite ends, through which fluid can flow from or to adjacent modules. The remaining two sidewalls do not have flow orifices. Referring to the exemplary module in  FIG. 6A , longitudinal sidewall  601  and the opposite longitudinal sidewall are closed, while the lateral sidewalls and interior wall include openings that form a channel for fluid flow. In this example, parallel modules can be used together to each other by positioning an open lateral sidewall of each module next to an open lateral sidewall of another module. It may be appreciated that parallel modules can also be used together by placing open longitudinal sidewalls next to each other. In this design, lateral sidewall  602  and the opposite lateral sidewall would be closed, while the longitudinal sidewalls would be open. In the half-cube module component shown in  FIG. 6B , sidewall  603  and the opposite sidewall are closed, while the remaining sidewalls (and bottom slab) include openings. 
         [0060]    In addition, “end cap modules” may be used at one or more ends of a single row assemblies. In this arched module component, fluid may flow through one or more flow orifices in one sidewall into or out of the component, and fluid does not pass through the remaining sidewalls. Referring to  FIG. 7A , one of the four sidewalls—lateral sidewall  701 —includes an opening. In an alternate embodiment, a longitudinal sidewall  702  (shown as closed in the figure) includes an opening. In the half-cube module component shown in  FIG. 7B , sidewall  703  includes an opening through which fluid may pass, while the remaining sidewalls (e.g.,  704 ) are closed to contain fluid within the assembly at the location of the sidewall. 
         [0061]    B. Assembly of Modular Unit from Arched Module Components 
         [0062]      FIGS. 8 through 10  illustrate schematically an embodiment of a modular unit  800  assembled using the arched module components with “half-cube” arched module components  801  along one perimeter side; internal modules with two longitudinal openings  802  in the interior; and corner modules  803  and boundary modules placed along the three remaining perimeter sides. 
         [0063]    In this example, the arched module components of hollow core construction with two openings on each longitudinal side are arranged in a repeating, side-by-side configuration in the interior of the unit. The longitudinal openings of one module component are aligned with longitudinal openings of an adjacent module component to form a continuous internal void area for water storage. Similarly, the lateral openings of one module component are aligned with corresponding lateral openings of an adjacent module component to form a continuous internal void area for water storage between the inlet pipe  901  and outlet pipe  902 . 
         [0064]    In addition, the arched module components with a single opening along a longitudinal side and a lateral side are placed along a perimeter side of the unit. End unit components with one or more substantially solid side faces (without openings) are placed along the remaining perimeter sides. In this example, the arched module components used in the interior of the unit are identical and placed in a repeating pattern, as are the half-cube  903  and end unit  904  arched module components located along a perimeter. It is contemplated, however, that in some embodiments arched module components can be used which are not identical or placed in different configurations. For example, there can be embodiments where the arched modules differ in the position, size, or shape of the openings. The shape and overall dimensions of the arched modules may also differ within a unit. 
         [0065]    One or more riser and cast iron inspection or maintenance covers  804 ,  805  can be incorporated along the top surface of the unit. The riser and inspection or maintenance cover can optionally be placed along a finished surface to enable access to the unit. An inlet pipe  806  can be placed through a side of the unit to allow fluid flow into the unit. An outlet pipe  807  can be placed through a side of the unit to allow fluid to exit. 
         [0066]    The floor of the unit (and the arched module components that make up the unit) can be constructed of a solid material, impermeable to fluid flow, without flow openings. This “closed floor” configuration can be used for detention (storage) systems. In another embodiment, the unit, including the arched module components, can have an “open floor” for retention (infiltration) systems. 
         [0067]    Typically, when installed underground, the assembly can be surrounded by a liner. In some embodiments, to allow for storm water detention (storage), the liner will be impermeable to water (e.g., PVC plastic), and inflow and outflow from the assembly will be only through inlet and outlet pipes. In a preferred embodiment, the exterior of joints and/or seams is sealed with butyl mastic tape. In other embodiments, to allow for storm water retention (infiltration) the surrounding liner will be semi-permeable, allowing water to seep out of the assembly but keeping out coarse dirt. For example, the system or a portion of the system can be encased in permeable filter fabric. In yet embodiments, to allow for rain water harvesting, the system can be encased in non-permeable liner. In some embodiments, the bottom face openings of the modular units in the “floor” of unit will include grated cover panels that allow water to percolate into the underlying ground. 
         [0068]    It is contemplated that in some embodiments, variations in relative length of the exterior dimensions of the modular unit may be implemented due to various design options available to the ordinary artisan. Generally, the dimensions of the modular units can vary within a range dependent on one or more design factors including but not limited to: desired water volume capacity, desired weight of each modular unit, desired load-bearing tolerance for each unit, desired amount of water flow to be managed, size and structure of overall assembly in which unit is used, and/or the desired access space for inspection and maintenance purposes. 
         [0069]    In addition, in a further embodiment, the arched module components may be stacked in a vertical configuration. In this embodiment, in the arched module components and modular units depicted, the one or more openings are not limited to being in the side faces of structure, but they can also be formed through the structure along an axis parallel to the corner pillars (along top or bottom faces). The openings allow for some water flow through the modular unit and assemblies of vertically stacked modular units constructed therefrom. Additionally, the openings allow for the release of air which can become trapped particularly in hollow core embodiments of the modular unit. 
         [0070]    Referring to  FIG. 11 , arched module components can be placed side-by-side in a single row. In this example, an arched module component with at least one lateral opening  1102  is placed at an inlet, while a half cube module component with at least one lateral opening  1101  is placed at an outlet. Channels are formed through openings  1103  along the lateral sides of each module, and the openings are aligned to permit fluid flow through the channels. The longitudinal sides  1104  are closed. In another example, shown in  FIG. 12 , modules may be placed adjacent to each other along longitudinal sides. Here, internal modules with two longitudinal openings  1201  are positioned on the inside of the assembly, between the inlet  1202  and outlet  1203  pipes. Each of the longitudinal sides  1204  is open, while the lateral sides  1205  are closed. 
         [0071]    C. Materials Used for Modular Unit Construction 
         [0072]    The ordinary artisan can recognize that other materials commonly used in applications involving underground retention/detention of water can be employed in the present invention. In a preferred embodiment, arched modular components are constructed using pre-cast concrete, as a one-piece design that provides structural integrity and integral foundation. The arched modular components can be constructed, for example, to support H and HS-20 leading conditions, as defined by the Manual for Condition Evaluation of Bridges, American Association of State Highway and Transportation Officials (AASHTO). In a preferred embodiment, the arched module is typically of solid-body construction due to the greater ease of pre-casting such a structure. But generally any material that can be molded or cast might be used to fabricate an arched module component, including but not limited to polypropylene, high density polyethylene (HDPE), low-density polyethylene (LDPE), rubber, and aluminum. 
         [0073]      FIGS. 1 through 7  depict embodiments of hollow core construction. Hollow core construction greatly reduces weight thereby facilitating storage, transport and assembly of the arched modules. In another embodiment, the material used for the hollow core arched module component is injection-molded polymer. In one embodiment, the polymer selected is a polypropylene, including but not limited to recycled polypropylene. The ordinary artisan will recognize that any polymer capable of injection molding could be used to construct an arched module of the present invention. Similarly, the ordinary artisan will recognize that a variety of design selections can be made for the polymer material used to construct an arched module of the general structure depicted in  FIGS. 1 through 7 . 
         [0074]    D. Solid Shell Construction 
         [0075]    In one embodiment, the modular component comprises a solid shell surface that is impermeable to water. With this solid shell surface the water flow through the modular component is limited to the flow orifices in each face of the structure. For example, in the embodiment shown in  FIG. 1 , assuming the solid shell surface is impermeable to water, flow into or out of the substantially interior volume of the modular unit is restricted to one of the six openings located along the longitudinal and lateral sides. In addition, by fitting cover panels, grates, or plug embodiments over any of these six openings (or in the interior opening), water flow can be further restricted and/or directed as described. 
         [0076]    Because the solid shell surface limits water flow to those passages created by the openings of the structure, it is possible to customize the water flow characteristics of an individual modular unit or a group of units that are part of a larger assembly. For example, a row of four modular units in a larger assembly can be isolated (e.g., by plugging the top, bottom, and two side-face openings), thereby providing a passage or a “virtual pipe” for directed water flow horizontally down the row. 
         [0077]    Similarly, the solid shell construction facilitates isolating a group of modular units inside a water management system made up of a larger assembly of units. For example, to create a separate zone to pre-treat water before it enters a retention/detention zone of the assembly, a group of modular units can be isolated and fitted with filtration systems that filter the water passing through them. 
         [0078]    The ability of the solid shell construction to allow customization of the water flow characteristics of one or a group of modular units also allows for isolated flow control zones in a larger assembly. For example, the outlet water flow rate from an isolated group of modular units can be controlled by fitting the openings of the units with grated or perforated cover panels. 
         [0079]    Alternatively, an isolated outlet flow control zone can be created by sleeving a perforated outlet pipe through the openings of a row of laterally coupled modular units. The perforated outlet pipe provides a controlled rate of water drainage from the adjacent separate retention zone of the assembly. 
         [0080]    E. Water Permeable Surfaces 
         [0081]    It is also contemplated that in some embodiments the modular unit can be constructed of materials having a surface with multiple small holes or pores. For example, the hollow core structure embodiment of  FIG. 1  with a substantially solid surface (except for the weep-holes) could be modified by drilling numerous small holes through surface exterior into the interior hollows. 
         [0082]    It is also contemplated that in applications where the ability to isolate and internally channel water is not necessary and/or coarse debris obstructions are not of concern, a modular unit structure may be used with multiple openings in each face. Thus, in one embodiment, it is contemplated that modular units in an assembly are constructed of materials having a perforated, web-like or lattice structure, rather than a solid shell. 
         [0083]    In an alternative embodiment, it is contemplated that modular units having solid shell construction impermeable to water are combined in a single assembly with modular units (or other water retention/detention structures) having web-like or lattice type structure that allow water flow in all directions. 
         [0084]    F. Modular Unit Inner Volume and Water Retention/Detention Capacity 
         [0085]    An arched modular component has a relatively compact yet strong structure with a hollow interior volume that allows significant water storage. In one embodiment, the “half cube” arched modular component is a substantially cuboidal structure, and the interior volume of the modular unit is substantially spherical. The radius defining the spherical volume extends from the center of the modular unit to the center of the plane defined by a face of the cube (i.e., at the center of an opening in a face). The interior volume of the modular unit can be defined in relation to the total volume defined by the outer dimensions of the substantially cubic modular unit. The ability to utilize higher relative percentage interior volumes will depend on design option selections, for example the use of a material capable of maintaining sufficient structural integrity despite a lower relative volume. 
         [0086]    In addition to the interior volume, the hollow core embodiment of the modular component provides volume for the storage of water throughout the hollow body spaces in the structure. The total available volume will depend on the hollow core structure design selected. In this respect, sufficient structure integrity can be provided by certain materials and structure design choices, even higher hollow-space volumes may be provided in the modular unit. 
         [0087]    The designs of the modular unit embodiments depicted in  FIGS. 1 and 7  are scalable. The ordinary artisan will recognize that the absolute dimensions can be varied based on the range of design options available, e.g., materials, water management applications, excavation sites, etc. For example, smaller modular unit dimensions may be selected for residential water management applications where less underground water retention/detention volume is needed or available. Alternatively, larger modular unit dimensions may be desired for larger industrial applications, particularly where solid body construction modular units are used (e.g., pre-cast concrete embodiments). Such solid body units require larger exterior dimensions in order to create a sufficient interior volume for water storage. 
         [0088]    In one embodiment (discussed for illustration purposes), the modular unit is a substantially cuboid hollow core structure with two openings along a longitudinal side, as depicted in  FIG. 1 . The unit is constructed of pre-cast concrete with outside dimensions of about 6.00 feet in width, 12.00 feet in length, and 3.33 feet (or 40.00 inches) in height. The inside dimensions are about 5.00 feet in width, 11.00 feet in length, and 2.00 feet (or 24.00 inches) in height. The weight is about 19,750 lbs (or 9.88 tons). In this structural embodiment of the modular unit, the storage volume is about 110 cubic feet (or 821 US gallons). 
         [0089]    In another embodiment, the modular unit is a substantially cubic hollow core, “half cube” structure with one opening along a side (as depicted in  FIG. 2 ). The unit is constructed of pre-cast concrete with outside dimensions of about 6.00 feet in width, 6.00 feet in length, and 3.33 feet (or 40.00 inches) in height. The inside dimensions are about 5.00 feet in width, 5.00 feet in length, and 2.00 feet (or 24.00 inches) in height. The weight is about 9,500 lbs (or 4.75 tons). In this structural embodiment of the modular unit, the storage volume is about 50 cubic feet (or 374 US gallons). The storage volume of a unit may vary depending on the system layout, however, and module configuration. 
         [0090]    It is believed that these dimensions for a hollow core, concrete module component provide a compromise of structural integrity, convenient weight for ease of assembly, large interior volume for water storage, and large openings for ease of maintenance access. It is important to note, however, that he sizes and storage volumes are provided for illustrative purposes only. The sizes and corresponding storage volume of a given arched module units of the present invention can vary depending on the system layout and module configuration. 
         [0091]    G. Cover Panels, Grates, and Risers for Openings 
         [0092]    The ordinary artisan will recognize that the top, bottom, and/or side face openings of each modular unit (alone or as part of a larger assembly) can be fitted with (or easily adapted for fitting with) any cover panel, plug, plate, grate, fitting, or valve system, well-known in the art of water management systems. 
         [0093]    In one embodiment, a top cover panel comprises a removable circular piece thereby providing an access port. For example, the top face of an arched modular component can include a circular center opening with a flange capable of supporting a removable cover, such as a man-hole type port. The cover panel can retain an outer groove and inner circular edge that fit the exterior and interior edges of the top (or bottom) face of a modular unit. Typically, the access opening will allow access to the assembly of modular units for cleaning and maintenance. 
         [0094]    Typically, impermeable solid panels would be selected for top cover panels where it is desired to allow water in-flow via underground pipe connections into side face openings on the exterior of an assembly. Grated top cover panels would be selected where percolation of water through the whole top surface of a modular unit assembly is desired, thereby allowing restricted water flow out of the top face opening of the modular units while preventing passage of large floatables. 
         [0095]    In some embodiments, a riser module that fits the top face of a modular component can be used as an adapter to adjust the height of the cover panel. Such a riser module can comprise a rectangular frame-like structure or a cylindrical structure, adapted to fit a stacking coupler on the top modular unit of a stack. 
       III. Filtration Systems 
       [0096]    As described above, the arched modular units of the present invention facilitates the incorporation of a range of filtration devices into underground water management systems made using assemblies of the components. The ordinary artisan will recognize that the top, bottom, or side face openings of the modular units, which align to provide passages for the flow of water through underground assemblies, can also be adapted to accept standard filtration devices known in the art. The use of solid shell construction permits the isolation of individual and/or groups of modular units thereby permitting water flow to be directed through filtration systems installed in one or more units. Furthermore, the modular unit is well-adapted to facilitate access to and maintenance of incorporated filtration devices due to its relatively large interior volume and the availability of openings in each face of the structure. The ability to maintain and/or replace filtration devices in an underground water management system with relative ease provides a great advantage in the use of such systems. 
         [0097]    Additionally, when installed in a modular unit (e.g., as part of the water inlet module), the incorporated filtration system provides filtration capacity within the modular underground water management system. Thus, the ability to incorporate filtration systems can reduce space demands, reduce construction costs, and simplify maintenance procedures. 
         [0098]    In one embodiment, the arched modular component can be used with one or more “media filter” cartridges containing filtering media designed to capture very fine sediments (typically less than about 100 μm), nutrients, metals, oils and grease, organics and bacteria. The media used in the media filter can be customized to target specific pollutants and/or meet site specific pollutant removal criteria. The ordinary artisan will recognize that a wide range of media are available and can be used in the media filter applications of the present invention. As one example, water flow can enter the filtering media through the radially positioned inlet screen of a “radial media filter cartridge design” that is substantially cylindrical in shape. The treated water exits at the center of the bottom through an outlet port. There can be an optional bypass port at the top of the cartridge to accommodate high flow situations. In an underground system using such media filter cartridges, the arched module component unit can include an “inlet bay” comprising an inlet chamber and an adjacent “treatment chamber” comprising a radial media filter installed in its bottom face opening. The sides facing the interior of the assembly can be closed, thereby isolating the inlet water so that it must pass through the filters. Thus, this inlet bay defines a separate zone with different water flow and filtration characteristics than the interior of the rest of the assembly in which some or other units can be left open. The embodiment can be modified to create an additional inlet “sump” module beneath the inlet chamber to better capture coarse debris and sediment and prevent clogging of the radial media filters. 
         [0099]    In another embodiment, the arched modular component can be used with a “filter basket” (also referred to herein as a “basket filter”) that captures coarse debris and gross pollutants, (e.g., coarse sediment, trash and oils). In one embodiment, the filter basket is a drop-in style filter that is removable, such as the FloGard+PLUS® multipurpose catch basin insert designed to capture sediment, debris, trash and oils/grease from low (first flush) flows (KriStar Enterprises, Inc.; Santa Rosa, Calif.). The removable filter basket can fit in the bottom face opening of a chamber in a modular component. The three other side face openings of this modular component are fitted with grated (or perforated) cover panels, thereby channeling the flow through the basket filter. In one embodiment, the filtration device is positioned at the inlet of the assembly, thereby forming an “inlet bay” for the whole retention/detention system. In alternative embodiments, a filter basket may be fit in subsequent modules of an assembly, for example, just before an outlet pipe. In other embodiments of the water management system, multiple filter baskets may be installed in an assembly of modular units. For example, one may install a series of two or more filter baskets with increasingly fine levels of filtration. Thus, coarse debris and trash would be captured by the first filter basket (e.g., a chain or metal screen type filter) and finer sediment and/or oil would be captured by the second filter basket (e.g., a geotextile liner material filter and/or optional media pouches). Clip-in filter pouches containing hydrocarbon capturing media, e.g., Fossil Rock™ media pouches (KriStar Enterprises, Inc.; Santa Rosa, Calif.) can also be included in the filter basket. 
       IV. Underground Water Management Systems 
       [0100]    A. Excavation and Installation 
         [0101]    Typical underground water management applications begin by creating an excavation to a desired dimension, e.g., based on the water storage requirements for the project and/or the available “footprint” on the site. The modular nature of the present invention provides a variety of design options for systems. Generally, it is contemplated that the dimensions and/or structural configuration of underground water management systems constructed using assemblies of modular units can vary dependent on one or more design factors including but not limited to: desired overall size of the assembly, desired load-bearing tolerance for assembly, desired amount of water flow to be managed, number and location of inlet and outlet pipes, number and location of pre-treatment zones and filtration systems, and/or the desired access space for inspection and maintenance purposes. 
         [0102]    For example, a single layer of connected modular units may be installed where a wider surface area is available but depth of excavation is limited. The modular units may be placed side by side and optionally wrapped with a cloth liner or joint tape to seal joints of the modules. Multiple layers (vertical stacks) or connected modular units may also be used for deeper spaces. Further, due to their higher interior volume, the assemblies of connected modular unit stacks can be designed with surface ports (e.g., manholes) that provide access for maintenance and/or cleaning (e.g., changing filters). 
         [0103]    In some embodiments, the modular units are assembled into customized shapes combining single layers, with stacks, and other multi-modular unit assemblies as necessary to fit the available excavation site. 
         [0104]    Depending on the water management application (e.g., storm water retention or detention), either a filter cloth or plastic (e.g., PVC) liner is placed beneath and around the assembly of modular units, thereby forming a semi-permeable or completely water impermeable envelope around the entire system. Typically, prior to sealing an assembly in a liner, plugs (solid or grated), may be placed in the modular unit openings where desired around the assembly. 
         [0105]    As described above, appropriate inlet and/or outlet pipes may be fit to the top, bottom, or side face openings on the exterior of the modular units. Because openings are available everywhere on the assembly of the modular units, piping into and out is not limited to any specific side of the assembly. In one embodiment, cuts are made in the liner to allow the pipes access. 
         [0106]    After installation of the modular unit assembly and appropriate piping in an excavation, backfill material can be placed around and over the system. To enhance the load carrying capacity of the installed system, geo-grid or other suitable solid stabilization material may be installed on the top or bottom sides of the system. 
         [0107]    B. Water Retention/Detention System with Multiple Inlet Ports 
         [0108]    Underground water management systems based on assemblies of modular units of the present invention provide the ability to accept water flow for filtration, retention/and or detention into a single assembly from a plurality of different sources (and directions). Generally, filtration systems (e.g., filter basket or media filter) may be located in any modular unit around the exterior sides (i.e., the “walls”) of the assembly. This ability to locate the filtration system(s) in close proximity to each of several inlet pipes eliminates the need to construct multiple (or one central) pre-treatment device outside the boundaries of the assembly. This greatly reduces the cost and difficulties of piping and construction. 
         [0109]    C. System with Separate Zone for Media Filtration 
         [0110]    The ability to create separate zones and control the water flow characteristics within an assembly of modular units provides a distinct advantage over underground water management systems wherein water flow inside the system is unrestricted. Such systems typically comprise a lattice or web-like structure (e.g., “stacked milk-crate-like” assemblies) through which water flows freely in all directions and generally can only function as retention/detention reservoirs or chambers. It may be possible to install plastic liners to act as boundaries within such systems, but generally, internal installation of such a plastic liner is cumbersome, can interfere with the structural connections (thereby weakening the structure) and is overall very limited in the types of customized internal zones it can be used to make. 
         [0111]    The arched module components can be constructed with one or more internal walls, dividers, or pillars located in the interior of a component to segregate fluid flows. The use of such structures isolates areas within the arched module component, thereby allowing the creation of different water treatment zones within a single assembly. In one embodiment, the arched module components may be used with media filtration modules and components in a chamber to eliminate the need for separate pretreatment systems. The integration of this chamber within the module also reduces or eliminates the need for additional piping for pretreatment. The use of such a system provides the ability to create separate zones and control the water flow characteristics within an assembly of modular units, and it provides a distinct advantage over underground water management systems wherein water flow inside the system is unrestricted. 
         [0112]    The above disclosure is sufficient to enable one of ordinary skill in the art to practice the invention, and provides the best mode of practicing the invention presently contemplated by the inventor. While there is provided herein a full and complete disclosure of specific embodiments of this invention, it is not desired to limit the invention to the exact construction, dimensional relationships, and operation shown and described. Various modifications, alternative constructions, design options, changes and equivalents will readily occur to those skilled in the art and may be employed, as suitable, without departing from the true spirit and scope of the invention. Such changes might involve alternative materials, components, structural arrangements, sizes, shapes, forms, functions, operational features or the like.