Abstract:
A concrete structure for replenishing an aquifer and a method for constructing the same is provided. The structure is comprised of a pavement layer with surface drains that extend through the pavement layer and into an aggregate leach field. The leach field includes leach lines spanning the leach field. An aggregate drain extends from the leach field into a sand lens. Precipitation which falls upon the structure thus flows through the surface drain, absorbed into the aggregate leach field, and transported to the aggregate drains by way of aggregate leach lines. The water is then absorbed into the sand lens, ultimately replenishing the aquifer. Existing conventional pavement structures are retrofitted by the removal of a section of the pavement, and filling the same with porous concrete.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 12/075,340 entitled AQUIFER REPLENISHMENT SYSTEM filed Mar. 11, 2008 now abandoned. 
    
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND 
     1. Technical Field 
     The present invention generally relates to concrete structures and the methods for forming the same. More particularly, the present invention relates to concrete structures and forming methods that enhance the replenishment of underground water in aquifers. 
     2. Description of Related Art 
     As is generally understood, a common source of fresh water for irrigation, human consumption, and other uses is groundwater. Usable groundwater is contained in aquifers, which are subterranean layers of permeable material such as sand and gravel that channel the flow of the groundwater. Other forms of groundwater include soil moisture, frozen soil, immobile water in low permeability bedrock, and deep geothermal water. Among the methods utilized to extract groundwater include drilling wells down to the water table, as well as removing it from springs where an aquifer intersects with the curvature of the surface of the earth. 
     While groundwater extraction methods are well known, much consideration has not been given to the replenishment thereof. It is not surprising that many aquifers are being overexploited, significantly depleting the supply. The most typical method of aquifer replenishment is through natural means, where precipitation on the land surface is absorbed into the soil and filtered through the earth before reaching the aquifer. However, in arid and semi-arid regions, the supply cannot be renewed as rapidly as it is being withdrawn because the natural process takes years, even centuries, to complete. It is well understood that in its equilibrium state, groundwater in aquifers support some of the weight of the overlying sediments. When aquifers are depressurized or depleted, the overall capacity is decreased, and subsidence may occur. In fact, such subsidence that occurs because of depleted aquifers is partially the reason why some cities, such as New Orleans in the state of Louisiana in the United States, are below sea level. It is well recognized that such low-lying and subsided areas have many attendant public safety and welfare problems, particularly when flooding or other like natural disasters occur. 
     The problem of rapid depletion is particularly compounded in developed areas such as cities and towns, where roads, buildings, and other man-made structures block the natural absorption of precipitation through permeable soil. Generally, building and paving materials such as concrete and asphalt are not porous, in that water cannot move through the material and be absorbed into the soil. In fact, porous material would be unsuitable for construction of buildings, where internal moisture is desirably kept to a minimum. Thus, these developed areas are typically engineered with storm drainage systems whereby precipitation is channeled to a central location, marginally cleaned of debris, bacteria, and other elements harmful to the environment which were picked up along the drainage path, and carried out to the sea. Instead of allowing precipitation to absorb into the ground, modern developed areas transport almost all surface water elsewhere. 
     One of the methods for replenishing aquifers is described in U.S. Pat. No. 6,811,353 to Madison, which teaches a valve assembly for attachment to aquifer replenishment pipes. However, the use of such replenishment systems required frequent human intervention. Furthermore, in order for the water in the aquifer to remain clean, existing clean water had to be pumped in. Additionally, the volume of water that was able to be carried to these re-charging locations was limited, thus limiting the replenishment capacity. 
     Changes to paving materials have also been considered. As is well known in the art, concrete is a composite material made from aggregate and a cement binder, the most common form of concrete being Portland cement concrete. The mixture is fluid in form before curing, and after pouring, the cement begins to hydrate and gluing the other components together, resulting in a relatively impermeable stone-like material. By eliminating the aggregate of gravel and sand, the concrete formed miniature holes upon curing, resulting in porous concrete. This form of concrete, while allowing limited amounts of water to pass through, was unsuitable for paving purposes because of its reduced strength. Additionally, the aforementioned drainage systems were still required because the porous concrete was unable to handle all of the water in a typical rainfall. Structures designed to increase the strength while maintaining porosity have been attempted, whereby reinforcement in the form of rods, rebar, and/or fibers were incorporated into the structure. Nevertheless, the strength of the structure was insufficient because of the reduced internal bonding force of the concrete due to the lack of an aggregate. 
     Therefore, there is a need in the art for an aquifer replenishment system for collecting precipitation and absorbing the same into the pavement and the soil in the immediate vicinity. There is also a need for aquifer replenishment system that are capable of withstanding environmental stresses such as changes in temperature, as well as structural stresses such as those associated with vehicle travel. Furthermore, there is a need for an aquifer replenishment system that can be retrofitted into existing pavement structures. 
     BRIEF SUMMARY 
     In light of the foregoing problems and limitations, the present invention was conceived. In accordance with one embodiment of the present invention, an aquifer replenishing pavement is provided, which lies above soil having a sand lens above an aquifer, and a clay layer above the sand lens. The structure is comprised of: an aggregate leach field abutting the subgrade (typically comprised of clay); and a layer of suitable surface paving material such as reinforced concrete or asphalt, abutting the aggregate leach field. Additionally, one or more surface drains extend through the concrete layer, and one or more aggregate drains extend from the aggregate leach field to the sand lens. The surface drains have a higher porosity than the paving layer, and is filled with rocks. According to another aspect of the invention, leach lines having a higher porosity than the surrounding leach field are provided. The surface drains are in direct fluid communication with the leach lines, and the leach lines are in direct fluid communication with the aggregate drains. 
     An aquifer replenishing concrete paving method is also provided, comprising the steps of: (a) clearing and removing a top soil layer until reaching a clay layer; (b) forming one or more aggregate drains through the clay layer to a sand lens; (c) forming an aggregate leach field above the clay layer; (d) forming a pavement layer above the aggregate leach field; and (e) forming surface drains extending the entire height of the pavement layer. Additionally, forming of the aggregate leach field also includes the step of forming one or more leach lines therein. 
     In accordance with another embodiment of the present invention, an aquifer replenishing concrete gutter for use on a road surface with an elevated curb section is provided. The gutter is comprised of a porous concrete section having an exposed top surface in a co-planar relationship with the road surface, supported by the elevated curb section and the side surface of the road. According to another aspect of the present invention, a cut-off wall is provided to further support the porous concrete section. A bore extending from the porous concrete down to the aquifer is also provided, and is filled with rocks. 
     An aquifer replenishing concrete gutter formation method is provided, comprising the steps of: (a) forming a gutter section between an elevated curb section and a road surface; (b) boring a hole in the gutter section into the aquifer; (c) filling the hole with rocks; (d) filling the gutter section with porous concrete; and (e) curing the porous concrete. In accordance with another aspect of the present invention, step (a) includes removing a section of the road surface adjacent to the elevated curb section. Finally, step (a) also includes forming a cut off wall extending downwards from the road surface and offset from the elevated curb section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  is a cross-sectional view of the surface of the earth; 
         FIG. 2  is a perspective cross-sectional view of a road surface aquifer replenishment system in accordance with an aspect of the present invention; 
         FIG. 3  is a cross-sectional view of a gutter aquifer replenishment system in accordance with an aspect of the present invention; 
         FIG. 4  is a cross-sectional view of a conventional road; 
         FIG. 5  is a cross-sectional view of a conventional road excavated for retrofitting an aquifer replenishment system in accordance with an aspect of the present invention; 
         FIG. 6  is a cross-sectional view of conventional road after excavation and formation of a cut-off wall in accordance with an aspect of the present invention; and 
         FIG. 7  is a cross sectional view of a road after excavating a bore reaching an aquifer and filling the same with rocks, and depicts the pouring of concrete into the gutter section in accordance with an aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of the presently preferred embodiment of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. It is to be understood, however, that the same or equivalent functions may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. 
     With reference now to  FIG. 1 , a cross sectional view of the earth&#39;s surface is shown. Atmosphere  30  is shown with clouds  32  releasing precipitation  34 , falling towards the ground  50 . As is well understood, ground  50  is comprised of top soil layer  52 . Underneath top soil layer  52  is clay layer  54 , and underneath that is sand lens  56 . Aquifer  60  is a layer of water, and can exist in permeable rock, permeable mixtures of gravel, and/or sand, or fractured rock  58 . Precipitation  34  falls on top soil layer  52 , and is gradually filtered of impurities by the varying layers of sand, soil, rocks, gravel, and clay as it moves through the same by gravitational force, eventually reaching aquifer  60 . In the context of the above natural features, the present invention will be described. 
     Referring now to  FIG. 2 , a first embodiment of the present inventive concrete paving system  100  is shown. Situated above clay layer  54  is an aggregate leach field  82  comprised of sand and gravel particles. Above aggregate leach field  82  is a pavement layer  80 , which by way of example only and not of limitation, is concrete composed of Portland cement and an aggregate. Pavement layer  80  may be reinforced with any reinforcement structures known in the art such as rebar, rods and so forth for increased strength. Preferably, the reinforcement structure has the same coefficient of thermal expansion as the pavement material, for example, steel, where concrete is utilized, to prevent internal stresses in increased temperature environments. By way of example only and not of limitation, pavement layer  80  has reinforcement bars  90 . It will be appreciated by one of ordinary skill in the art that the pavement layer  80  need not be limited to architectural concrete, and asphalt and other pavement materials may be readily substituted without departing from the scope of the present invention. 
     Extending from the top surface to the bottom surface of pavement layer  80  are one or more surface drains  84 . Due to the fact that non-porous concrete, that is, concrete having aggregate mixed into the cement, permits little water to seep through, surface drains  84  expedite the water flow into aggregate leach field  82 . Typically, by way of example only and not of limitation, surface drains  84  are filled with rocks to prevent large debris such as leaves and trash from clogging the same. 
     Within aggregate leach field  82  are one or more leach lines  86 , which assist the transfer of fluids arriving through surface drains  84 . By way of example only, leach lines  86  are in direct fluid communication with surface drains  84 . Leach lines  86  have a higher porosity than the surrounding leach field  82  to enable faster transmission of fluids. Leach field  82  is also capable of absorbing water, and in fact, certain amounts are absorbed from leach lines  86 . Additional water flowing from surface drains  84  is also absorbed into leach field  82 . In this fashion, water is distributed across the entire surface area of leach field  82 , resulting in greater replenishment of the aquifer. A person of ordinary skill in the art will recognize that the leach field  82  acts as a filter by gradually removing particulates from precipitation, and resulting in cleaner water in the aquifer. 
     As is well understood in the art, clay has a lower porosity as compared to an aggregate of, for example, sand, gravel, or soil. In order to expedite the transmission of water into the aquifer, aggregate drains  88  extend from aggregate leach field  82 , through clay layer  54 , and into sand lens  56 . Therefore, a minimal amount of water is absorbed into the clay layer  54 , and the replenishment process is expedited. 
     After the water flows from leach field  82  into sand lens  56  via aggregate drains  88 , it is dispersed throughout sand lens  56 , trickling through to the aquifers in the vicinity. The water in the aquifer is thus replenished through largely natural means, namely the filtration process involved in absorbing precipitation through aggregate leach field  82  and sand lens  56 , despite the existence of a non-porous material such as concrete overlying the ground surface in the form of pavement layer  80 . 
     The aquifer replenishment system as described above is generally formed over previously undeveloped land, or any land that has been excavated to a clay layer  54 . Thus, surfaces that have been previously paved by other means must first be removed so that the natural water absorption mechanisms of the earth are exposed. After this has been completed, aggregate drains  88  are drilled from the exposed clay surface  54  into sand lens  56 . After filling the aggregate drains  88  with aggregate, a generally planar aggregate leach field  82  is formed. Contemporaneously, leach lines  86  are formed, and is encapsulated by the aggregate which constitutes leach field  82 . After leach field  82  is constructed, concrete reinforcements  90  are placed, and uncured concrete is poured to create pavement layer  80 . 
     With respect to the formation of surface drains  84 , any conventionally known methods of creating generally cylindrical openings in concrete may be employed. For example, before pouring the uncured concrete, hollow cylinders may be placed and inserted slightly into leach field  82  to prevent the concrete from flowing into the opening. Yet another example is pouring the concrete and forming a continuous layer, and drilling the concrete after curing to form surface drain  84 . It is to be understood that any method of forming surface drain  84  is contemplated as within the scope of the present invention. 
     With reference to  FIG. 3 , a second embodiment of the aquifer replenishing system  200  is shown, including an elevated curb section  192 , a gutter section  196 , and a road pavement section  190 . Road pavement section  190  is comprised of a pavement layer or pavement surface  195 , which by way of example only and not of limitation, is architectural concrete, asphalt concrete, or any other paving material known in the art, and is supported by base course  194 . Base course  194  is generally comprised of larger grade aggregate, which is spread and compacted to provide a stable base. The aggregate used is typically ¾ inches in size, but can vary between ¾ inches and dust-size. 
     In accordance with the present invention, gutter section  196  has a porous concrete gutter  184  in which the top surface thereof is in a substantially co-planar relationship with the top surface of pavement surface  195 . Optionally, porous concrete gutter  184  is supported by base  185  which is composed of similar aggregate material as base course  194 . Furthermore, extending from optional base  185  into aquifer  60  is a rock filled bore  188 . As a person of ordinary skill in the art will recognize, a bore filled with rocks will improve the channeling of water due to its increased porosity as compared with ordinary soil. Optional base  185  and porous concrete gutter  184  is laterally reinforced by cut off walls  183  and elevated curb section  192 . The cut off walls  183  are disposed on opposing sides of the porous concrete gutter  184  and the base  185  between the elevated curve section  192  and the pavement surface  195 . It is expressly contemplated that the cut off walls  183  may be pre-cast or cast in place. 
     When precipitation falls upon road pavement section  190 , the water is channeled toward gutter section  196 . Porous concrete gutter  184  permits the precipitation to trickle down to aquifer  60 . When optional base  185  and rock filled bore  188  is in place, there is an additional filter effect supplementing that of the porous concrete gutter  184 . A similar result can be materialized where the water drains from the upper surface of elevated curb section  192 , or precipitation directly falls upon porous concrete gutter  184 . Please note a large surface drain may be used in lieu of the porous concrete gutter. 
     This embodiment is particularly beneficial where retrofitting the gutter is a more desirable solution rather than re-paving the entire road surface. In a conventional road pavement as shown in  FIG. 4 , pavement surface  195  and base course  194  extend to abut elevated curb section  192 . In preparation for retrofitting gutter section  196 , a section of pavement surface  195  and base course  194  is excavated as shown in  FIG. 5 , leaving a hole  197  defined by the exposed surfaces of elevated curb section  192 , base course  194 , and pavement surface  195 . This is followed by the optional step of pouring and curing a cut-off wall  183  as illustrated in  FIG. 6 , which, as discussed above, serves to reinforce the gutter section  196 . One or more bores  188  are drilled down to aquifer  60 , and filled with rocks, as shown in  FIG. 7 . An optional base of aggregate  185  is formed above rock filled bore  188 , and compacted by any one of well recognized techniques in the art. Finally, a volume of porous concrete mixture, that is, a concrete without sand or other aggregate material, is poured and cured, forming porous concrete gutter  184 . While recognizing the disadvantages of using porous concrete, namely, the reduced strength of the resultant structure, a person of ordinary skill in the art will also recognize that gutter section  196  sustains less stress thereupon in normal use as compared to road pavement section  190 . 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.