Abstract:
Systems and methods for collecting, storing, and redistributing water, which systems and methods make use of building foundations and surface concrete slab structures. A variety of rainwater collectors are anticipated, including rooftop collection systems (e.g., gutters) and ground surface covering structures (driveways, sidewalks, parking lots, and patios). These collection systems are joined together in a collection conduit system that carries the rainwater to one or more rainwater containment vessels. The stored water may then be redistributed, again through a variety of distribution means, to address part or all of the landscape watering requirements of the property. The system takes advantage of standard foundation and slab construction techniques to establish a major portion of the structure required for the containment vessel.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This original nonprovisional application claims the benefit of U.S. provisional application No. 60/873,150, filed Dec. 5, 2006 and entitled “Systems and Methods for the Collection, Retention, and Redistribution of Rain Water and Methods of Construction of the Same,” which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to systems and methods for storing water. The present invention relates more specifically to systems and methods for the collection, retention, and redistribution of rainwater for landscape watering and other appropriate uses as well as methods for constructing such systems. 
     2. Description of the Related Art 
     Efforts have been made in the past to create rainwater collection systems that provide storage containment in association with habitable dwellings and the like. In most cases, these previous efforts take the form of either tanks having walls that comprise part of the upright foundation, or underground storage tanks that are wholly separated from the building foundation of the habitable structure. Examples of the first type of collection and storage systems may be seen in prior patents that include the Klein and Courier patents (referenced and discussed below), and to a lesser extent the Pratt patent (also referenced and discussed below). Courier describes a system that involves the creation of a storage tank in an area beneath the foundation (such as below a garage) in a manner that does not intrude upon the usual pipes, conduits, and cabling associated with the balance of the structure&#39;s foundation. Courier, however, does not anticipate the use of a separate tank, instead constructing its containment vessel utilizing the support walls of the foundation itself. The systems described by these patents do not provide means for preventing condensation from detrimentally affecting the habitable structure overtop of the storage tank, which essentially remains open to the flooring components of the structure. Any use of the foundation walls themselves to establish the water containment vessel will suffer from a variety of condensation problems for the structure immediately above the foundation. 
     The second approach mentioned above, that of establishing the storage tank apart from the building structure, is described generally in the DeStefano patent and the Zimmerman et al. patent application (both of which are referenced and discussed below). In each of these two systems, the novelty is directed more to the manner in which dual containment tanks and a variety of collection systems are utilized to optimize the efficiencies with which the system collects water and disperses it for use in landscape watering. Some systems, such as that described in Bucherre include tanks that are not associated with building structures and utilize open area collection systems instead. 
     The concept of utilizing an inflatable or non-rigid structure to establish a removable form for pouring a concrete foundation or the like has also been explored in the prior art. Examples such as Heifetz and Hale (referenced and discussed below) disclose this basic concept as well as various specific features and steps designed to optimize the process and eliminate some of the previously identified problems. Efforts have been made, for example, to address and control the deformation of the inflated form, either through increased pressurization or through the provision of an external, rigid, or semi-rigid web or netting around the form. The Williamson patent (referenced and discussed below), utilizes an inflatable form for constructing the rigid walls of a storage tank type device. Most of the previous efforts in this field, however, that utilize the inflatable form approach are generally more concerned with simply establishing the concrete structure in the most economical fashion. Efforts in the past in the above described fields include the following U.S. Patents, the disclosures of which are incorporated herein, in their entirety, by reference: 
     U.S. Pat. No. 5,396,745 issued to Klein on Mar. 14, 1995 entitled Habitable Structure with Water Storage and Distribution describes a habitable structure incorporating a ground supported, water impervious floor and upright foundation walls that define an open top water storage tank. Flooring for the habitable structure provides the cover or top for the rainwater storage tanks. A roof top rainwater collection system is described with conduits directed into the under structure storage tank, while use of the water is carried out by a variety of systems for distributing water from the enclosure, including a sprinkler system for indoor and outdoor usage. Further systems for collecting rainwater from drainage channels outside the structure are also described. 
     U.S. Pat. No. 6,796,325 issued to Courier on Sep. 28, 2004 entitled Apparatus for Storm Water Retention and Release and Method of Use Thereof describes a system and method for the centralized collection of rainwater run off from a number of single family dwellings in a neighborhood. The system describes storage containers and associated “control chambers” typically located underneath or near buildings on the property served by the system. Conduits connect to drainage systems external to the buildings to receive storm water into the container by way of the control chamber. Other conduit systems draw storm water from the container (again through the control chamber) for use as necessary. Various mechanisms for preventing the buildup of debris in the system are described. 
     U.S. Pat. No. 7,080,662 issued to Pratt on Jul. 25, 2006 entitled Rain Recycling System describes a conduit and flow control water recycling system and method of use that relies upon the collection of water from a basement in a building that accumulates in a sump area and is pumped into a holding tank. The water is then distributed for use both inside and outside of the building. 
     U.S. patent application Ser. No. 10/651,570 filed by Zimmerman Jr. et al. on Aug. 29, 2003 entitled Rain Water Recovery System describes a complex system and method that is intended to restore the natural water cycle by collecting storm water run off and reintroducing it into the ground surrounding the area of collection. Various cisterns, pumps, and manufactured dry wells are described. The system includes components to divert polluted run off and capture clean run off for irrigation purposes and non-potable uses. Other water run off is diverted to recharge groundwater supplies. 
     U.S. Pat. No. 4,934,404 issued to DeStefano on Jun. 19, 1990 entitled Water Management System describes a rainwater collection system that relies on water run off from a roof that is diverted into an underground storage reservoir. A second reservoir is described that operates in tandem with the rainwater collection reservoir that collects gray water from within the dwelling which is combined with the rainwater to serve exterior landscape water requirements. 
     U.S. Pat. No. 4,527,927 issued to Bucherre on Jul. 9, 1985 entitled Water Harvesting and Storage System describes a large area arrangement for collecting what is intended to be potable water that includes a sheet or membrane for catchments and one or more flexible closed storage tanks. A system of filtration and piping between the catchments and storage tanks, as well as a number of pump systems and additional piping allow use of the water. 
     U.S. Pat. No. 4,102,956 issued to Heifetz on Jul. 25, 1978 entitled Building Method and Equipment for Use Therewith describes a construction method wherein an inflatable form made of flexible, but inextensible material is anchored to a base and then is inflated to a predetermined pressure. While this pressure is maintained, a cementitious material is applied to the outer surface of the form to a required thickness. After the material has set, the form is deflated, released from the base, and removed for re-use. 
     U.S. Pat. No. 4,746,471 issued to Hale on May 24, 1988 entitled Method of Constructing a Reinforced Concrete Structure describes the use of inflatable forms that are placed on a pre-cast foundation and strapped down (with chain link fence material). The inflatable forms are then highly pressurized to pre-stress the chain link fence and a uniform layer of fiber reinforced cement is applied over the form. 
     U.S. Pat. No. 2,324,554 issued to Billner on Jul. 20, 1943 entitled Building Construction describes yet another inflatable form system comprising an inflation chamber surrounded by a web of flexible cords or constraints. The web of cords or cables establishes the inflated shape of the form for the purpose of pouring concrete. After the concrete has set, the form is deflated and removed through appropriately designed apertures in the inflatable structure. 
     U.S. Pat. No. 3,223,759 issued to Williamson on Dec. 14, 1965 entitled Method of Fabricating Structures describes a process for constructing a plastic walled tank by forming an exterior configuration from an earthen form or the like and an interior configuration from an inflatable form positioned within the exterior enclosure. The space between the two forms is then filled with a hardening material such as concrete, and the interior form is filled with a fluid or the like in order to maintain equal hydrostatic pressures across the walls being formed. 
     In general, therefore, none of the systems previously designed in the area of collection tanks associated with buildings, teach the concept of integrating a separate storage tank immediately underneath or in association with the concrete foundation components of the building to which it is associated. Various collection and distribution systems (roof gutter collection, drainage channel collection, and landscape watering distribution systems) are all described and explored to some extent in the various efforts made in the past. 
     In addition, none of the systems and methods previously described in the field of inflatable or non-rigid concrete forms integrates the form itself into a reservoir or liquid containment vessel. All such efforts in the past have focused on removing the form after use and either do not contemplate a liquid storage capability or rely upon the resultant concrete structure to provide the containment vessel. 
     It would be desirable therefore to provide systems and methods for collecting, storing, and redistributing rainwater for landscape watering, which systems and methods make use of building foundations and surface concrete structures in a manner that provides the benefits of such rainwater redistribution systems without the significant costs associated with their separate construction. It would be desirable to have such systems that could be constructed in conjunction with the new construction of habitable dwellings and/or surface concrete structures (driveways, patios, parking lots, and the like) or that could be constructed as retrofit systems in conjunction with existing buildings and surface structures. 
     SUMMARY OF THE INVENTION 
     In fulfillment of the above and further objectives, the present invention provides systems and methods for collecting, storing, and redistributing rainwater for landscape watering, which systems and methods make use of building foundations and surface concrete structures. A variety of rainwater collectors are anticipated, including rooftop collection systems and ground surface covering structures (driveways, sidewalks, and patios primarily). These collection systems are joined together in a collection conduit system that carries the rainwater to one or more rainwater containment vessels. The stored rainwater may then be redistributed, again through a variety of distribution means, to address part or all of the landscape watering requirements of the property. The system takes advantage of standard foundation and slab construction techniques to establish a major portion of the structure required for the containment vessel. In place of the typical under-slab or under-foundation materials, the present invention places structures and materials that are capable of receiving and retaining run-off rainwater. These structures and materials include waterproof tanks, bladders, liners, and containment trays that may be used with or without being filled with a volume of interstitial material (i.e., multiple particles of material arranged to form interstices therebetween) having sufficient load-bearing characteristics to support the concrete when poured. Such load-bearing interstitial material includes materials such as wash gravel, wash stone, septic rock, crushed gravel, crushed marble, and the like. Specific steps in the construction of the concrete foundation or surface slab are modified to accommodate the requirements of the collection and containment structures. 
     A variety of rainwater redistribution systems are described by the present invention and include gravity-forced release, pump-forced distribution, and/or existing pressurized water system assisted distribution. Collectively, these various systems and sub-systems provide an economical means for storing and re-using rainwater at times when dry weather conditions would otherwise require the use of public (or other pumped) water supplies. 
     The present invention discusses a system and method for the collection, retention, and eventual redistribution of rainwater. The system utilizes at least one containment vessel having an impermeable barrier defining its shape that is constructed beneath a foundation. In particular, the containment vessel may be positioned beneath a portion of the foundation associated with the garage for the house or some other “open” areas beneath the building&#39;s foundation. It is these areas of the foundation that involve few, if any, intrusions such as beams, supports, pipes, conduits, etc. The method of constructing the under-foundation containment vessel would comprise excavating the area for the foundation (when so required by the topography), placing and positioning the containment vessel (or the components thereof), and pouring the foundation over the containment vessel wherein the vessel takes up the space normally occupied by a required crushed rock or earthen fill (i.e., structural fill). 
     The manner of constructing the containment vessel could vary from pre-constructing the vessel and simply placing it in position to constructing a fillable vessel that retains its shape sufficiently for the concrete foundation to set over the top of it. Conduits into and out of the containment vessel can then be positioned and later connected. Structurally, the vessel may be made from any material or combination of materials that provides a barrier to concrete and cementitious material as well as water. For example, EPDM rubber, pond liners, barriers formed from composite rubber polymer, fiberglass and metal sheets (e.g., corrugated galvanized steel) may all be used, although preferably the impermeable barrier defining the containment vessel is flexible and relatively lightweight for ease of handling. Required thickness of the barriers is contingent on the materials from which they are comprised and the weight of the foundation to be supported. 
     The rainwater collection system could include any of a number of different rainwater collection devices, such as roof gutter systems, or drain channel collection systems. Inlets into the containment vessel allow the collected rainwater to be gathered and stored for later use. The re-use of the rainwater in the containment vessel might occur in periods of drought or low water conditions, and would be accomplished by gravity feed of the water through outlet conduits, such as hoses, pipes, and the like, or might include a water pump. The outlet conduits can be associated with sprinkler systems or other water distribution systems. It is anticipated that the rainwater collection system in its simplest form would provide water for landscape watering and the like rather than potable water for household use. It is anticipated, however, that the water could be used for other non-drinking and non-bathing uses. 
     As used herein, a collection device refers to the component of the system that receives the water from a runoff or other surface. In some cases, however, a collection device could also form a part of a conduit system that channels the received water into the containment vessel. For example, a gutter member may serve as both a collection device as well as part of the collection conduit system to initially receive the rainwater and then direct the rainwater to an attached downspout for eventual delivery to a containment vessel. 
     The method of construction is designed to be beneficial, not simply for the later use of the rainwater by the homeowner, but also to benefit the cost of construction by replacement of a labor intensive process of establishing foundation formwork and structural fill, as is presently carried out for most poured concrete foundations. The containment vessel, in whatever form it might be utilized, would be put in the place of the structural fill (e.g., crushed rock and earthen material) that typically require many man hours to construct and establish prior to pouring the foundation. One or more containment vessels that are sized, shaped, and configured to replace these construction forms could be established for any of a number of different dwelling and foundation configurations. For example, while generally described herein with reference to concrete slab foundations, the system and methods are also applicable to pier-and-beam foundations. 
     Those skilled in the art will recognize that the coarseness of the load-bearing interstitial material will determine the volume of space or void remaining in a given volume of a containment vessel. A balance is struck between providing a supportive containment vessel that does not localize forces on any single point in the walled vessel (above or below) such as would puncture the containment to either allow leakage from below or to allow intrusion of poured concrete from above. To some extent the coarseness of the load-bearing interstitial material will be dependent upon the structure under which it is to be placed and the anticipated forces directed onto the structure by the poured foundation and the functional use of the structure. The objective is to maintain as much void space as possible without diminishing the integrity of the enclosure as described. 
     In any of the various embodiments described above, the invention is intended to benefit the homebuilder/homeowner in two ways. First, it provides a mechanism for the collection, retention, and later use of rainwater on the landscape surrounding the home, and second, it provides a cost saving mechanism for the initial construction process of building the foundation for the dwelling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention, as well as further objects and features thereof, are more clearly and fully set forth in the following description of the preferred and alternative embodiments, which should be read with reference to the accompanying drawings, wherein: 
         FIG. 1  is a block diagram showing the various systems and sub-systems of the present invention and the manner in which they connect and function together; 
         FIG. 2  is a partial sectional view of a containment vessel of the preferred embodiment and connected components; 
         FIG. 3  is a partial sectional view of a containment vessel of an alternative embodiment of the present invention and connected components; 
         FIG. 4  is a partial cross-section of a typical existing building structure showing the manner in which rainwater is directed off of the roof and into a containment vessel; 
         FIG. 5  is a top plan view of a typical foundation for a habitable dwelling showing the manner in which interconnections between separated containment vessels beneath the foundation may be established; 
         FIG. 6  is a schematic cross-sectional view of a driveway slab constructed over a containment vessel of one of the preferred embodiments of the present invention; and 
         FIG. 7  is a flowchart of the basic method steps of the present invention carried out in order to economically construct the system of the invention while simultaneously constructing the building foundation or surface slab. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows in schematic form the various components of the system of the present invention in a manner intended to describe their functionality as opposed to their specific structure and geometry. In this figure, the basic components of the system of the present invention are shown with a number of optional components included as may be preferred in certain landscape and/or structural environments. Every system implementing the concept of the present invention will initially include some type of rainwater collection device  20  that gathers rainwater and directs it into a collection conduit system  22 . The collection conduit system  22  then directs the collected rainwater into one or more rainwater containment vessels  24  that provide structural support for the overlaid concrete slab. The collected rainwater is maintained in the rainwater containment vessel  24  until such time as it is to be utilized for landscape watering or the like. 
     Utilization of the collected rainwater may be carried out according to a number of different protocols. Depending upon the landscape with which the system has been established, gravity feed may be all that is necessary to allow sufficient drainage and distribution of the collected rainwater from the containment vessels  24 . Alternately, it may be necessary to establish a pumping system  26  that draws water from the containment vessels  24  and places it into a distribution conduit system  28 . From the distribution conduit system  28  the water is directed into a number of different types of water distribution devices  30  such as sprinklers, soaker hoses, and the like. Water distribution devices  30  are typically those devices that ultimately deliver the collected rainwater to the landscape. 
     As a further alternative embodiment, the distribution conduit system  28  may comprise a manner of incorporating of water flow from an existing water supply  32  such as is typical with established residential or business construction. The manner in which an existing water supply  32 , typically pressurized, may be utilized in conjunction with a system of the present invention is described in more detail below. In general though, the use of an existing water supply  32  to combine with rainwater previously stored provides a significant reduction in the amount of fresh water required for landscape watering and the like. 
     Various nozzle structures  34  are known in the art that allow for the discharge of a fluid under pressure and the associated suction of a second fluid (not under pressure) into the same discharge stream. Such structures may be utilized in conjunction with the system of the present invention to permit stored rainwater to supplement the existing water supply  32 , and thereby reduce the quantity of fresh water being utilized for landscape watering and the like. A hose terminating in one such nozzle fitting may be positioned on the outlet of the containment vessel  24  and, as needed, may be hooked up to a standard garden hose or the like sourced from the existing pressurized fresh water supply system  32  for the property. In this manner a significant reduction in the quantity of fresh water utilized can be achieved while at the same time providing for a means for directing the discharge of the stored rainwater without the need for a separate pump. 
       FIG. 2  illustrates the containment vessel  24  of the preferred embodiment of the present invention. A compacted sand base layer  36  fills an excavated area  38  of ground  40  where the resulting foundation is to be constructed, which base layer  36  provides structural surety for the foundation and resulting structure to minimize shifting over time. A waterproof lower barrier  42 , which is preferably a plastic liner, is oriented in a generally “U” shape with a bottom portion contacting the base layer  36  therebeneath. First and second sides  48 ,  50  of the lower barrier  42  are oriented generally vertically against the concrete slab to prevent water contained within the vessel  24  from seeping through into the base layer  36  and further into the surrounding ground  40 . 
     Thereafter, a quantity of load-bearing interstitial material  52 , which is preferably a quantity of wash gravel approximately equal to the desired volume of the containment vessel  24 , is introduced onto the lower barrier  42 . It is anticipated that other load-bearing interstitial materials, such as crushed granite and/or crushed marble, may be utilized. A waterproof upper barrier  54 , which is preferably a 15-mil vapor barrier available from Stego Inudstries, LLC, is placed over the wash gravel  52  in the storage container  24 . The upper barrier  54  prevents the unset concrete from filling the space between the wash gravel  52  after the foundation is poured. The presence of the load-bearing interstitial material  52  eliminates the need for pressurizing or otherwise stabilizing the containment vessel  24  while the concrete foundation is being established, and provides support for the concrete slab  56  during curing. After curing, while the concrete substantially supports itself, support is still provided by the load-bearing interstitial material  52  through the upper barrier  54 . Framing members  55  may thereafter be connected to the concrete slab  56  as construction progresses. 
     In use, the containment vessel  24  receives water from a collection conduit system  22  through an inlet  58  through the concrete slab  56  and the lower barrier  42 . When water within the vessel  24  reaches a predetermined level, a float-switch activated sump pump  62  placed within the containment vessel  62  displaces water through an outlet  64  in the lower barrier  42  and concrete slab  52  into an attached distribution conduit system  28 . Alternatively, a pump (not shown) placed outside the containment vessel and connected to the distribution conduit system  28  could draw water from the containment vessel through the distribution conduit system  28 . In the preferred embodiment, the distribution conduit system  28  includes a pipe  59  or hose (not shown) directing water received from the outlet  64  of the containment vessel  24  into a barrel  63 . The accumulated volume of water contained by the barrel  63  may thereafter be directed to one or more water distribution devices  30  (e.g., a sprinkler system or faucet) as needed through additional piping  65 . Alternative embodiments may omit the collection barrel  63  and cause water to flow directly to the water distribution devices  30 . In addition, alternative embodiments contemplate the use of an additional sand layer placed between the upper barrier  54  and the concrete slab  52  to provide additional cushioning of the upper barrier  54  during the cement pouring process. 
     Although the preferred embodiment contemplates the use of a single containment vessel  24 , alternative embodiments may include multiple interconnected containment vessels, thus providing increased water storage capability while also providing increased support for the concrete slab or slabs composing the foundation. 
       FIG. 3  illustrates an alternative embodiment of a containment vessel of the present invention wherein the lower barrier  42  is secured in place with a series of stacked filler bags  49  containing gravel or some other heavy material. Construction and operation of the containment vessel  24  in this alternative embodiment is generally as disclosed with reference to  FIG. 2  except that the first and second sides  48 ,  50  of the lower barrier  42  are oriented around filler bags  49  and are folded between the filler bags  49  and sidewalls  60  of the concrete slab  56  to prevent water from ingressing to the space between the sidewalls  60  and the base layer  36 . The bags  49  are filled with a generally “weighty” material, such as sand or gravel, to provide the sidewalls of the concrete slab  56  with support as well as to ensure the first and second sides  48 ,  50  of the lower barrier  42  do not dislodge when the containment vessel  24  fills with rainwater. Use of the bags  49  as a securing mechanism provides an additional advantage of minimizing edges and protrusions on which the lower barrier  42  can snag and tear, thus jeopardizing the integrity of the lower barrier  42 , as such a tear would be difficult to detect and repair after pouring the concrete. However, use of the filler bags  49  as shown reduces the available storage volume within the containment vessel  24  as by the volume of the bags  49  themselves. 
       FIG. 4  is a side sectional view of the preferred embodiment of the present invention. A building, such as a house, includes framing members  72  supporting an inclined roof structure  74 . A gutter member  76  is attached along the eaves  77  of the roof structure  74  to collect rainwater  78  from the roof structure  74  as precipitation  80  falls. As is typical in such buildings, the framing members  72  are secured to a foundation  81  that includes a surface layer  84  of concrete. This surface layer  84  has been set over the concrete slab  56  that rests on a compacted base sand layer  36  to minimize shifting of the building. The concrete slab  56  is shaped to define an interior space in which has been positioned interconnected first and second rainwater containment vessels  24 ,  25  as described with reference to  FIG. 2 . 
     During a period of rain, precipitation  80  falls and contacts the roof structure  74 , the incline of which causes the rainwater  78  to flow to and into the gutter member  76 . A collection conduit system  82 , which is preferably a downspout, provides a path for flow of the collected rainwater  78  from the gutter member  76 . One end of the downspout  84  protrudes through a sidewall  60  of the concrete slab  56  and is connected to the inlet  58  of the water containment vessel  24 . Thereafter, operation is as described with reference to  FIG. 2 . 
       FIG. 4  further partially depicts a second, interconnected containment vessel  25  as previously described wherein a channel  27  connects an outlet  29  of the first containment vessel  24  with an inlet  35  of the second containment vessel  25 . A quantity of load-bearing interstitial material  31  is positioned in the channel  27  between the first and second containment vessels  24 ,  25  to help support an interior beam  33  of the concrete slab  56 . 
       FIG. 5  details the interconnection of a plurality of containment vessels  86 ,  88  beneath a concrete slab  90  according of the present invention. Multiple downspount connections  92  are positioned around the concrete slab  90  and in communication with primary containment vessels  86 . Outlets  94  of the primary containment vessels  86  are in communication with secondary containment vessels  88 , which are those vessels not directly in communication with the downspout connections  92 . The number of primary and secondary containment vessels  86 ,  88  may be varied according to the water storage needs of the site and/or the size of the concrete slab  90 . Additional outlets  95  from the containment vessel provide a communication path from the containment vessels  86 ,  88  through the concrete slab  90  to the water distribution devices via the distribution conduit system (not shown). 
     In addition to constructing any of the various above described embodiments for a rainwater collection and containment system beneath a building structure, such as to benefit from the collection of rainwater from the roof of the structure, it is anticipated that a similar structure might be constructed beneath a poured driveway or other surface slab construction in a similar manner. 
       FIG. 6  discloses in cross-sectional detail an anticipated construction of an embodiment of the present invention. In this embodiment, rainwater collection channels  100  are constructed on either side of the driveway slab  102  in a manner that allows runoff  104  from the driveway slab  102  to be collected through grates  106  into the channels  100 , which eventually drain into the containment vessel  108  through an inlet  107  between upper and lower barriers  109 ,  111  of a containment vessel  110  composed of EPDM rubber that has been formed beneath the driveway slab  102 . The containment vessel  110  is filled with a quantity of load-bearing interstitial material  110 , which is preferably wash gravel, to provide structural support during pouring and curing of the concrete that composes the driveway slab  102 . This containment vessel  108  could operate independently of other containment vessels positioned under the habitable portion of the building structure as discussed with reference to  FIG. 4  or may be joined with those containment vessels into a common reservoir from which rainwater may be dispensed. An outlet  112  of the containment vessel is connected to a distribution conduit  114  that provides a communication path to water distribution devices (not shown) located on the property. The upper and lower barriers  109 ,  111  are affixed to each other to define the shape of the containment vessel  108  and provide for the inlet and outlet  112 . While  FIG. 6  contemplates the use of the system beneath a driveway slab  102 , it is anticipated that the system is equally applicable to use in conjunction with other slab variants, such as parking lots and patios. 
       FIG. 7  provides a flow chart of the basic method steps of one embodiment of the present invention carried out in order to economically construct the system of the invention while simultaneously constructing the building foundation or surface slab. The sequence of steps shown is representative of a variety of construction methods that may be implemented to carry out the objectives of the invention. Additional steps are, of course, required to complete each of the broad level definition of the methodology described by the present invention. In general, however, the process involves the following: 
     (a) Excavating  200  the soil to the desired depth in the area of the proposed foundation or surface slab. The depth depends on the nature of the structure but need not be significantly deeper than might be required without the system of the present invention. The storage volume of the system is achieved by distributing the retention container over a larger area rather than a significant depth in to the soil. 
     (b) Optionally depositing  202  an under-layer of sand to create a soft bed onto which a lower barrier may be placed. The need for this may be dependent on the existing soil conditions in the location of the property. 
     (c) Installing  204  a lower barrier on the bottom and sides of the excavated ground area. Again because the containment is relatively shallow, it is anticipated that the barrier may be a sheet-like material rather or a formed plastic vessel wall. 
     (d) Installing  206  an outlet conduit system, typically at a low point in the excavated ground area through the barrier or containment vessel. Sealed apertures are known in the art for this purpose. 
     (e) Depositing  208  a quantity of load-bearing interstitial material, such as a wash gravel or stone, within the excavated ground area. As described above, the coarseness of this material may depend upon the specific structure that is to be poured over the containment vessel. Effort is made to maintain interstitial space between the particles of the material while retaining sufficient support for the poured concrete. 
     (f) Installing  210  an inlet conduit system, typically within the upper levels of the established containment vessel that permits directing the flow of collected rainwater into the system. 
     (g) Installing  212  a concrete- and water-impermeable barrier (such as a unitary or sealed cover) over the quantity of load-bearing interstitial material to prevent the intrusion of concrete from the poured foundation or slab into the material. It is less important that this over-layer be puncture resistant (compared with the under-barrier), although such is still preferred. 
     (h) Optionally depositing  214  an over-layer of sand over the cover, again to provide a cushion to help prevent punctures into the liner material. 
     (i) Installing  216  the concrete forms required for the foundation or the surface slab; and 
     (j) Pouring  218  the concrete. 
     Once set, the slab, which typically integrates reinforcing steel bars (re-bar) may be self supporting and may not rely further on the support provided by the material included within the established containment vessel. Regardless, the volume established under the foundation or slab provides a very significant storage enclosure to receive and retain rainwater for later use. 
     Use of the system as described above is most beneficial in areas where periods of significant rainfall are followed by periods of significant dry weather. The system of the present invention provides a means for “evening out” the benefits of rainfall and redistributing the rainwater to best benefit the landscape. 
     The present invention is described above in terms of a preferred illustrative embodiment of a specifically described system and method, as well as alternative embodiments thereof. Those skilled in the art will recognize that alternative constructions of such a system can be used in carrying out the present invention. Other aspects, features, and advantages of the present invention may be obtained from a study of this disclosure and the drawings, along with the appended claims.