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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The instant invention relates to the area of civil engineering and, more particularly, to a multi-use conduit system for the protection and integrated transmission or movement of various utilities, information or services whether solids, liquid, gas, fiber optic, magnetic, or electronic in nature. The same has particular application for location beneath transportation corridors and open space. 
     2. Description of Related Art 
     To the knowledge of the within inventors there has not existed in the prior art a multi-utility conduit system, and certainly has not existed a multi-purpose underground utility conduit system particularly adapted for disposition beneath the transportation corridor and open space. Therefore, to the knowledge of the inventors, the most applicable prior art relates to systems comprising a plurality of integral contiguous channels as, for example, exists in chemical engineering applications where it is desirable to simultaneously discharge or convey to a remote location a plurality of different fluids and gases, each typically hazardous or toxic, within a single integrated containment system. An example of such prior art appears in U.S. Pat. No. 4,751,945 (1988) to Williams, entitled Dual Containment Channel For Fluids. However, with respect to general civil engineering applications, that is, applications in which it is desirable to integrate into a single advantageously located utility conduit, substantially all utility and information services requirements of a community, e.g., electric power cables; drinking water, re-use water and sewer lines, storm water and drainage pipes; natural or synthetic gas lines; telephone, cable television, fiber optic and other communication and data transmission channels; pneumatic tubes; security services; fire services; a low current magnetic conductive track for vehicular propulsion, and storage, maintenance access or transit power equipment for the hybrid multi-use transit corridors, the prior art is entirely silent. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a multi-purpose utility conduit system, definable in terms of an x, y, z Cartesian coordinate system, in which the utility conduit is typically symmetric about a yz or vertical plane, and in which an xz plane defines a truss-like structure having optionally removable lateral extremities. The inventive conduit system is proportioned to interface, at its x-axis extremities, with water drainage facilities and, proximal to said yz plane of the symmetry, with water main locations. Along the xy plane, that is, the ground level surface of the conduit system, is provided a layer of roadway material or equivalent thereof such as natural stone, tarmac or pre-manufactured brick, block or composite roadway material capable of supporting pedestrian, bicycle, and small greenway transit trains or service vehicles. Along the yz plane of symmetry is, in each embodiment of the invention, provided a central or primary, that is, large dimension sub-conduit together with smaller laterally (x-axis) disposed smaller sub-conduits within optional selectably attachable lateral extremities of the truss like structure of the conduit are included sub-conduits of smaller xz plane cross section which, thereby, are particularly suitable for use with all utility information and service requirements of a community such as: electric power cables; drinking water, re-use water and sewer lines, storm water drainage pipes; natural or synthetic gas lines; telephones service; cable television, and fiber optic communications and data transmission, pneumatic tubes; security services; fire services; low current magnetic inductive tracks for vehicular propulsion, and storage, maintenance access or transit power equipment for the ergonomic hybrid transit access corridors. The width (x-axis) and depth (z-axis) of the conduit system may be adapted in response to local ground conditions and design criteria, particularly relative to the parameters of the transportation corridor and open space which will typically overlay the conduit. In the y-axis or length dimension of the conduit are provided manhole-type points of access to the primary sub-conduit. 
     The invention is further definable as a method of housing a plurality of utility services within a single unitary channel, the method comprising the steps of: (a) disposing a plurality of utility services within a substantially integral longitudinal conduit having therein a plurality of sub-conduits each corresponding to a utility service or utility service group to be provided; (b) providing, to earth-embedded surfaces of said integral conduit, means for stabilization of said conduit within the earth; and (c) providing, to upwardly directed, non-embedded surfaces of said conduit, a substantially flat surface adapted in surface effect to aesthetically and functionally integrate into a surface environment associated with said conduit. 
     It is accordingly an object of the present invention to provide a conduit system having particular application underneath ergonomic hybrid transit access corridors as part of inner city and community center re-development efforts to effect the integration of all utilities aforementioned and services requirements of a planning region within a single utility delivery system. 
     It is another object to provide an integrated multi-purpose conduit system to provide, within a common conduit, all utilities, information and services requirement at an underground location which is easily accessible for purposes of service, maintenance and later modification thereof. 
     It is a further object of the invention to provide a conduit system of the above type which is compatible with, and integrable into, an ergonomic multi-use hybrid transit access corridor right-of-way. 
     It is a still further object to provide a conduit system of the above type which can be readily manufactured and simply installed at the construction site. 
     It is a yet further object to provide a conduit system of the above type which is modular and, at the ground level thereof, appears indistinguishable from the surface of a transportation corridor or other surfaces beneath which it is situated. 
     The above and yet other objects and advantages of the present invention will become apparent from the hereinafter set forth Brief Description of the Drawings and Detailed Description of the Invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a xz plane cross-sectional view of a standard width, standard depth embodiment of the instant invention, showing detachable lateral segments thereof. 
     FIG. 2 is a cross-sectional view of a second embodiment thereof adapted to shallow depth applications. 
     FIG. 3 is a further embodiment of the invention showing the same in standard depth, however, without use of the lateral extensions thereof. 
     FIG. 3A is a view showing use of the embodiment of FIG. 3 beneath a transportation corridor. 
     FIG. 4 is a cross-sectional view of a yet further embodiment showing the same without lateral extensions and at said shallow depth of the embodiment of FIG.  2 . 
     FIG. 5 is a top plan schematic view of the invention showing the appearance of an access segment thereof. FIG. 6 is a view, similar to that of FIG. 5, however showing the use of an access segment where x and y-axis adjoining conduit segments are not co-linear relative to each other. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1, the instant inventive multi-purpose utility conduit system  10  may be seen in cross-section to comprise a truss-like structure which is largest along a yz plane of symmetry  12  and which tapers symmetrically outward along an x-axis until lateral end points  14  such that, in a preferred embodiment, the x-axis extent of the truss-defining conduit system is defined by corridor curbs  16  which may be integrated into drainage modules  18  which include drainage pipes  20  capable of accepting drainage from both the street and modular tree planter boxes  22 . Accordingly, in terms of x-axis delineation, the instant conduit  10  will typically have a lateral extent defined by a transit corridor  24 , the edges of which are typically defined by curbs  16  and associated drainage means. This x-axis delineation is typically in a range of 20 to 24 feet in the embodiment of FIG.  1 . 
     The depth of the conduit  10  and, thereby, much of the z-axis stability thereof, is defined by the disposition of a crushed rock base  26  within excavated earth  28  at the time of construction of the transit corridor  24 . 
     Integrally formed at the xy plane top of the conduit  10  is a naturally occurring or pre-manufactured road composite  30  which renders the utility conduit system functionally and aesthetically compatible to a base of an ergonomic hybrid transit access corridor  24 , as it would exist whether or not the present multi-use conduit  10  were employed. In other words, if, as will frequently be the case, a low speed, small transit vehicle is operated upon surface  30 , tracks will be disposed over a section  32  of the conduit, which section typically would have an x-axis width of up to eight feet. From the plane of symmetry  12  of section  32 , surface  30  which would have a typical depth of about eight inches and would slope symmetrically outwardly at a grade of about two percent to the x-axis end  14  of the conduit. 
     As may be noted in FIG. 1, there is provided a plurality of internal sub-conduits varying in size, geometry and position relative to the plane of symmetry  12 . Typically disposed within a large central sub-conduit  34  would be water main locations  36  from which drinking water is supplied to the community. The rest of the large central sub-conduit  34  is typically provided for storm water drainage as may become necessary in the event of a flood or water overflow during a fire fighting event or burst water main. Accordingly, central sub-conduit  34  may be understood to include the function of containment in the event of a break of either of the water mains  36 . 
     Viewed laterally outwardly from central sub-conduit  34 , there is, in the embodiment of FIG. 1, shown outer smaller sub-conduits  38 ,  40 ,  42  and  44 . Typically disposed within the lowestmost sub-conduits  40  and  42  would be those utilities that would require the least service and for which the highest degree of vibrational insulation from transit activity at surface  30  is necessary. Therefore, within conduit  40  might be disposed telephone and optic fibre cables, while within sub-conduit  42  might be disposed natural or synthetic gas lines for the transportation of propane or the like. In distinction, the upper sub-conduits  38  and  44  of central section  32  would contain cables for utilities likely to require more frequent service but which are not as vibrational sensitive as utilities disposed within sub conduits  40  and  42 . Thereby, within sub-conduit  38  might be disposed electric power cables within conduit  44  might be disposed cable television cables. 
     There is further shown in FIG. 1 are optional lateral extensions  46  which include sub-conduits  48  and  50 . Accordingly, where the lateral extensions  46  are employed, further differentiation of utilities may be provided. For example, residential application cables versus business and industrial application cables. Also, greater stability is provided to the central section  32  when lateral extensions  46  are provided. 
     With respect to the materials from which the inventive conduit system  10  may be formed, there exist a number of lightweight high strength materials that may be pre-manufactured using state of the art extrusion means. Such materials include high density polyethylene (HDPE) and so-called polyester concrete which is a concrete aggregate material containing quartz and inert mineral fillers bonded together with a polyester resin. The choice of material will generally be a function of the weight of the load applied to the conduit by the surface transit system operating thereon, whether or not a given site is earthquake prone, annual level of rain, and any toxicity or other hazard associated with the utilities carried within the inventive system. In terms of dimensions, a typical x-axis dimension of the system shown in FIG. 1 would be in said range of 20 to 24 feet while the depth thereof would typically be about six feet. Accordingly, a system of this dimension may be conveniently placed beneath or proximally to a transportation corridor without any requirement for change or enlargement of the right-of-way conventionally associated therewith. 
     In certain civil engineering applications as, more particularly, where the earth or ground is particularly hard, firm, or rock-like, a conduit system of lesser z-axis depth may be employed. Such a system is shown in FIG.  2 . Therein, the number of sub-conduits is reduced from nine to five. However, in many applications, five sub-conduits is an entirely adequate number, particularly where lateral extensions  46   a  are included with central section  32   a  of the system. It is noted that surface  30   a , in any of the embodiments, may be provided with any of a variety of several surface treatments, that is, blocks or special surface treatments to provide improved architectural integration with the surrounding site. 
     In FIG. 3 is shown a further embodiment the invention which consists of only three sub-conduits, that is, sub-conduits  34   b ,  38   b  and  44   b . Therein, no lateral extensions sections are employed and a parabolic crown  52  is provided upon the surface  30   b . This embodiment of the invention is applicable where smaller right-of-way, e.g., ten feet are employed for the public transit corridor  24   b  and where a suitable depth, e.g., six feet of an excavation is available. In this embodiment, the sub-conduits  38   b  and  44   b  will contain multiple different utility service cables and piping. 
     In FIG. 4 is shown a further embodiment of the invention which is generally similar to the embodiment of FIG. 3 where however a shallower x-axis dimension, e.g., about four feet, is employed. This embodiment is applicable where the right-of-way is narrow and where the ground or earth is sufficiently dense to accommodate such a reduced depth of the system. 
     Thereby, from the embodiments of FIGS. 1 to  4 , it may be appreciated that the ratio of x to z axis dimension of the xz plane cross-section of the conduit may be in a range of about 1.5:1 to about 6.0:1 the latter or higher part of this range exists when lateral segments  46 / 46   a  and  48 / 48   a  are employed. 
     In FIGS. 5 and 6 are shown top plan views of the relationship between the central sections  32  of the present conduit system and the rest of the y-axis length thereof. In other words, it is to be understood that a point of entry  54 , substantially in the nature of a manhole, may be provided to a central sub-conduit  34  of central section  32  for purpose of access thereto for service purposes. In other words, since central sub-conduit  34  will typically be empty, and since said sub-conduit  34  will include holes or access points to all adjoining sub-conduits, i.e, sub-conduits  38 ,  40 ,  42  and  44 , the manhole  54  also provides a means of access thereto and for change in relative directionality of adjoining system segments. 
     Appropriate sealing  56  using, for example, a flexible sealed expansion gasket formed of a high density elastomeric polymer, may be employed. Central section  32 , viewed in the xy plane, will typically have a dimension of five feet on each edge. However, central section  32  may have a rectangular dimension  32   d  as is shown in FIG.  6 . This is advantageous when connection of an angled section  58  to a y-axis linear section  60  is necessary. It is noted that such segments  60  of the inventive conduits, in any of their embodiments, will typically exhibit a length in a range of 16 to 40 feet. 
     While there has been shown and described the preferred embodiment of the instant invention it is to be appreciated that the invention may be embodied otherwise than is herein specifically shown and described and that, within said embodiment, certain changes may be made in the form and arrangement of the parts without departing from the underlying ideas or principles of this invention as set forth in the Claims appended herewith.

Summary:
A method of housing various utility services within a single unitary structure includes the steps of disposing such services within an integral longitudinal conduit having sub-conduits, each corresponding to a utility service or utility service group to be provided. Further providing, to earth-embedded surfaces of the integral conduit, elements for stabilization of the conduit within the earth; and providing, to upwardly directed, non-embedded surfaces of the conduit, a substantially flat surface including surface effects to aesthetically and functionally integrate into a surface environment associated with the conduit.