Abstract:
A stackable riser having a single side wall having a first open end defined by an edge and a second open channel end. A plurality of risers can be stacked on top of one another. The channel end of a riser mates with the first open end of a second riser. The riser includes a plurality of bosses and ribs connected to an interior surface of the sidewall to the edge of the first open end. A channel, on the channel end of one riser is adapted to receive the bosses and ribs of an adjacent riser.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 09/946,293, filed Sep. 4, 2001, now U.S. Pat. No. 6,655,093, which is a continuation-in-part of application Ser. No. 09/766,795, filed Jan. 22, 2001, now U.S. Pat. No. 6,484,451. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention pertains to stackable riser sections and riser covers for access risers. More particularly, the present invention pertains to connecting a series of riser sections in a way that provides improved vertical support that minimizes the effect of frost heaving and other forces due to vertical ground movement, and resists rotational forces resulting from lateral ground movement and to a removable riser cover for stackable riser sections. It further relates to the configuration of a riser cover that provides a fluid and gas tight seal to a riser section, and to structure to facilitate its removal from a riser section as well as facilitating locating the cover under ground and to the stacking of a plurality of riser covers for compact and stable shipment or storage. It also relates to a system and method of maintaining the position and shape of a riser section while the riser section is being anchored in concrete by using the riser cover for positioning and support during the anchoring process. 
   2. Discussion 
   Meters, splices, junction boxes, and other components of buried utility systems are often located inside hand-holes or manholes to enable easy access by utility workers from above ground. Often, utility systems provide such access facilities at key points, such as a major bend in an underground cable/conduit run or location of water or gas meters and other equipment requiring servicing or inspection. Such access facilities have been constructed using pre-formed or poured concrete side retaining walls. Concrete can be expensive, particularly where the application requires a non-standard size or length, in which case setting forms and pouring concrete adds time and expense. Also, over time, the concrete can crack due to forces caused, for example, by freezing and thawing or by heavy vehicles being driven over the top of the manhole. Tiled sidewalls and concrete block are examples of other labor intensive alternatives. 
   Injection molded, plastic, stackable riser sections made of high density polyethylene and other rigid, light weight polymeric material are known in the art and provide a less expensive, standardized alternative that lends itself to rapid on-site customization. Riser sections can be manufactured in various heights and diameters, and a series of identically sized riser sections can be stacked to achieve a desired depth. 
   Depending on the soil characteristics and overhead traffic, the vertical, horizontal, and rotational forces placed upon these riser sections can be considerable. A major shortcoming of plastic riser sections lies in their tendency to deform or break when subjected to such forces. The use of vertical and horizontal strengthening ribs to alleviate this tendency is common. When placed along the exterior of the sidewall, however, these reinforcing ribs themselves often are subjected to the same vertical and horizontal forces they are intended to protect against. 
   U.S. Pat. No. 5,852,901 for a “Stackable Riser for On-Site Waste and Drainage Systems,” issued to Meyers, illustrates one prior art design of a plastic riser section for forming a depth-adjustable, grade-level access for underground components. The Meyers riser sections form a rigid structure intended to support heavy loads applied to the grade level access lid. Identical riser sections reinforced along portions of both the inner and outer walls are stacked one on top of the other utilizing a single tongue and groove connection. A horizontal rib extending outward along the circumference of the external surface of the side wall of each cylindrical riser section and a plurality of vertical ribs, also on the external surface of the riser, individually anchor each riser section in the ground. A plurality of riser sections can be stacked to form a vertical, air-tight, liquid-tight, and gas-tight riser stack and cover system. 
   The shifting of the ground surrounding the riser stack disclosed in the Meyers patent can twist and move the stacked riser sections, knocking them out of alignment. Eventually, the shifting can lead to rupture of the stacked riser sections&#39; sidewall. The presence of external horizontal and vertical reinforcing ribs extending along the wall of each riser, while strengthening the riser section sidewalls, also exacerbates this problem because shifting soil applies force against each exposed rib. The configuration of the tongue and groove arrangement of the riser sections disclosed in the Meyers patent also precludes the placement of supporting ribs along the full vertical length of the interior riser section wall, which lessens the sidewall&#39;s resistance to forces exerted by the shifting of the soil abutting the sidewalls and external ribs. 
   It is also common for one section of a riser stack to be anchored in concrete. The anchored section, generally the section defining the opening into the chamber defined by the concrete walls of an underground component, is then used as a base for the riser. Other sections are stacked on top of the anchored section to the desired height of the riser. This process involves positioning and securing a hollow riser section inside a concrete mold or form of a shape for forming the top wall of a chamber or underground component. The concrete is then poured into the mold around the riser section. The riser section can be subjected to stress during this process and may deform or break under these conditions. In addition, because it can be made of light weight plastic, it can be difficult to keep the riser section in place while pouring the concrete because the riser section may tend to float in the concrete. 
   One method of preventing deformities in the riser section during anchoring involves the addition of cross braces to the inside of the riser. The braces can conform to the shape of the riser section or can simply be metal or wood rods sufficiently long to provide lateral support for opposed riser section sidewalls. This solution is imperfect, however, because the sidewall support thus provided is not uniform and may still permit deformities to occur. Additionally, this solution adds to the cost and time needed to anchor a riser section in concrete. 
   A variety of methods have been employed to keep a riser section in place during the anchoring process, with almost all involving construction on an ad-hoc basis in the field. One method is to place one or more elastic straps or rubber cords across the top of the concrete form, ensuring contact with the riser section in order to hold it down. This does not address side-to-side movement. One way to attempt to control this is by placing a weight or heavy object, such as a concrete block, on top of the riser section and under the elastic strap. The weight, however, may create an additional problem because it adds to the stresses being applied to the riser section sidewalls during placement of the concrete. 
   Another difficulty with the use of plastic riser sections is locating the riser stack after installation. Many riser access facilities are located in areas where it is easy to locate the opening, such as in streets, sidewalks, and other paved areas, or where the opening is above grade. However, access facilities frequently are located below grade level and are covered by soil and grass or other vegetation. In these situations, it may be difficult to locate the opening of the access facility when required. While a metal cover may be located using a metal detector, plastic stackable riser sections may not. One method of making plastic riser stacks locatable is to mold one or more metal rods into the concrete wall into which a plastic riser section has been anchored. Because the concrete wall is typically lower in the ground than the riser cover, a significant amount of metal is required in order to ensure it can be detected at the surface using a conventional metal detector. This method may also create an added step in casting the wall of the box into which the bottom riser section is anchored. 
   SUMMARY OF THE INVENTION 
   The riser sections and cover of the present invention overcome the foregoing shortcomings. In the preferred embodiment, the stackable riser sections of the present invention have a hollow, cylindrical configuration, although configurations other than cylindrical may be used. The sidewall of the riser section includes a channel end and a tapered end. In the preferred embodiment, the riser section has a nearly smooth exterior surface from which projects outwardly a detachable anchor tab that may run along substantially the full circumference of the riser. The channel end of the riser section sidewall includes two adjoining channels which are defined by interior, middle, and exterior walls that extend down from a horizontal ledge on the interior surface of the side wall at the channel end. The walls project concentrically with, or (in the case of riser sections having, for example, a square or rectangular cross-section) parallel to, the sidewall. The opposite, or tapered, end of the riser section sidewall terminates in a portion tapered to a narrower thickness at the end. A plurality of vertical reinforcing ribs are spaced around the interior surface of the cylindrical sidewall of the riser. Because in the preferred embodiment the ribs extend from the horizontal ledge at or near the channel end to the distal end of the tapered end of the riser section sidewall, they strengthen the sidewall in the area of the joint between each pair of stacked riser sections. 
   In the preferred embodiment, the interior surface of the sidewall also includes at least one, and preferably more than one, boss extending vertically from the horizontal ledge near the channel end to the distal end of the tapered end of the riser. Each boss is adapted to receive a screw, or other fastener, that extends through he horizontal ledge of a riser section stacked above the tapered end for securing that riser section stacked on top of the first riser section. The bosses also may receive a screw to attach a cover at the top of a riser stack. 
   The tapered end of the riser section sidewall is configured to mate with the two concentric channels of either another riser section or a cover. The radially outer channel is shallower than the inner channel in the preferred embodiment and accepts the tapered end of the sidewall of another riser section on which it is placed. An O-ring placed in the outer channel can be used to effect a water-tight and gas-tight seal between two stacked riser sections (or between a riser section and a cover). 
   The radially inner channel is wider than the outer channel, and accepts the interior vertical support ribs and bosses of a riser section on which it rests. The middle wall of the channel end includes slots that permit positioning of the bosses and ribs within the inner channel of a riser section positioned above the ribs and bosses. Projections on the bottom of the horizontal ledge and aligned with the slots support the upper riser section on the bosses as ribs of the lower riser section. 
   In the preferred embodiment, a detachable anchor tab on the exterior surface of the riser section sidewall serves to anchor the lower-most riser section in concrete, for example, in the wall of a concrete distribution box. The concrete is poured around the riser section and its anchor tab, thereby anchoring the bottom riser section after the concrete hardens. Another identical riser section may be placed on top of the bottom riser section, with the tapered end of the bottom riser section mating with the channel end of the riser section placed on top of the bottom riser section. The anchor tab on each of the riser sections stacked above the bottom riser section (i.e., above the riser section anchored in the concrete box) in a given stack can be detached by tearing it away from the exterior of the sidewall. In the preferred embodiment, the anchor tab includes a handle for this purpose. Tearing away the anchor tabs on the riser sections that are not anchored in concrete gives the riser stack a nearly smooth exterior surface, thereby minimizing the forces exerted on the riser stack by movement of the soil in contact with the riser stack. 
   There also is provided, in the preferred embodiment, a cover adapted to be secured to the top of a riser section. Like the stackable riser, the preferred shape is cylindrical, but other configurations, such as square, rectangular or elliptical may be used. 
   The cover has a top surface and a bottom surface, with the top surface being nearly smooth and slightly convex in the preferred embodiment. A sidewall of the cover depends from the top surface. It includes a channel end similar to the channel end of the riser sections. The channel end includes two adjacent concentric channels defined by inner middle and outer walls. The outer wall defines the sidewall outer surface of the cover. 
   Handles to aid in removal of the cover are provided on the top surface of the cover. In the preferred embodiment, each handle pivots about a support shaft which is attached to the cover by a screw or other fastener. The support shaft is set inside a recess adjacent the top surface, and the handle pivots between a position generally perpendicular to the top surface and a position inside the recess, substantially parallel to and flush with the top surface. The recess is large enough to accept the entire handle. 
   The cover preferably has at least two wells open to the top surface. They may be substantially 180° apart in the preferred embodiment, although another embodiment may have only one well or more than two wells. The wells are defined by hollow posts depending from the bottom surface of the cover. 
   In a preferred embodiment, the hollow posts on the bottom surface extend below the bottom edge of the channel end of the cover. The posts define the wells open at the top surface, as described above. Preferably, the posts are located approximately midway between the center of the bottom surface and the cover channel, about 180° apart from each other. In different embodiments, there may be only one post or more than two posts, in which case the posts may be located as desired on the bottom surface. 
   The posts extending from the bottom surface of the riser cover preferably are tapered such that each is of a larger diameter where it joins the bottom surface of the cover than at its free end. There may also be a stepped change in diameter at some point between the bottom surface and the end of the post, creating a shoulder. The diameter of the free end of each post is smaller than the diameter of the hollow well formed by the post. The tapered design of each post and well allows stacking of multiple riser covers by placing the posts of one riser cover into corresponding wells in the top of another riser cover. Stacking of riser covers is beneficial for storage and for shipping multiple riser covers. 
   The wells open to the top of the riser cover may receive a metal bar prior to completion of the underground component such as a concrete distribution box installation in the field. As described above, it is common for riser covers to be buried by soil and vegetation growth. The placement of the metal bar into the well allows the cover and plastic riser sections to be located using a metal detector. 
   The riser cover can be used in a method to secure a riser section while the riser section is being molded in concrete (i.e., while the wet, viscous concrete is poured and is setting). In the preferred method of securing a riser section in concrete, a mounting bracket is provided which is adapted to receive the posts depending from the bottom surface of a cover. The mounting bracket adapted to be secured to the wall of a concrete form preferably has two (or other number corresponding to the number of posts in the cover) holes configured to accept and releasably retain the posts of the riser cover. The holes are sized and tapered such that when the posts are pushed into the holes, the sides of the holes grip the posts in a fraction fit and thereby firmly secure the cover to the bracket. 
   During the concrete casting operation, the mounting bracket is secured to a horizontal wall of a concrete form at a desired location where the access riser is to be provided. The riser section is positioned on the form surrounding the bracket. A riser cover, positioned with the channel end of the cover engaged with the tapered end of the riser section is attached to the bracket. The posts of the cover are aligned with, and pushed into, the holes on the mounting bracket such that the posts are gripped securely by the bracket. The riser section is thus positioned and secured properly relative to the bracket and, particularly, the concrete form. The riser section is also supported against deformation during a pour. Concrete sufficient to secure the riser section is then poured into the form and allowed to cure. The riser cover, which has not been in contact with the concrete, is then removed from the riser section by pulling the posts out of the holes in the mounting bracket. The mounting bracket may then be removed and the form disassembled from the poured concrete wall. 
   It is an object of the present invention to provide an improved connection configuration that resists rotational forces exerted on one or more riser sections in an interconnected system. 
   It is another object of the present invention to provide improved reinforcement of the sidewalls of riser sections stacked one on top of the other. 
   It is still another object of the present invention to provide a detachable anchor on the exterior surface of a riser section, the anchor being used when the riser section is to be molded in concrete, and removed when the riser section is to be in contact with soil. 
   It is a further object of the present invention to provide a riser section adapted for being anchored in concrete, while at the same time minimizing the susceptibility of a riser stack to forces caused by the ground next to the stack shifting. 
   It is a further object of the present invention to provide a riser cover having recessed handles such that the riser cover will have an essentially smooth top exterior surface when the handles are not in use. 
   It is still a further object of the present invention to provide a method for positioning and supporting a riser section being molded in concrete to minimize the susceptibility of movement of the riser section during the molding process and resist deformation of the riser section due to the forces exerted by the concrete while being poured. 
   It is still a further object of the present invention to provide a riser cover adapted for being stacked one on top of another with the posts of the top cover projecting into the wells of the bottom cover such that multiple covers may be stacked compactly and stably for shipping or storage. 
   It is another object of the present invention to provide a plastic riser cover adapted to easily receive a metal bar in order to permit the cover to be located after it has been buried in soil or other material. 
   Other features, objects and advantages of the invention will become apparent from the following description and drawings in which the details of the invention are fully and completely disclosed as part of this specification. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention are explained in more detail with reference to the illustrative embodiments shown in the following drawings. 
       FIG. 1  is a top view of a cylindrical riser section embodying the principles of the present invention; 
       FIG. 1A  is a fragmentary sectional view on an enlarged scale, taken along the line A—A of  FIG. 1 ; 
       FIG. 2  is a cross-sectional view of the riser section embodying the principles of the present invention taken along line  2 — 2  in  FIG. 1 ; 
       FIG. 2A  is a fragmentary cross-sectional view of a riser cover for overlying a riser section embodying the principles of the present invention; 
       FIG. 2B  is a fragmentary cross-sectional view of a pair of riser sections assembled together. 
       FIG. 3  is a side view of a cylindrical riser section embodying the principles of the present invention; 
       FIG. 3A  is a fragmentary sectional view on an enlarged scale of a portion of the riser section of  FIG. 3 ; 
       FIG. 4  is perspective view of a cylindrical riser section embodying the principles of the present invention; 
       FIG. 5  is a perspective view of the top surface of a riser cover embodying the principles of the present invention; 
       FIG. 6  is a perspective view of the bottom surface of a riser cover embodying the principles of the present invention; 
       FIG. 7  is a cross-sectional view of the riser cover embodying the principles of the present invention taken along line  7 — 7  of  FIG. 5 ; 
       FIG. 8  is a detailed view of a handle adapted to fit the riser cover embodying the principles of the present invention; 
       FIG. 9  is a top view of a mounting bracket for use in the method of the present invention employing a riser cover to embed a riser section in concrete; 
       FIG. 10  is a perspective view of the mounting bracket of  FIG. 9 ; 
       FIG. 11  is a is a cross-sectional view of the riser cover embodying the principles of the present invention mounted onto the mounting bracket employed in the method of the present invention taken along a line  7 — 7  of  FIG. 5  for the cover and a line  11 — 11  of  FIG. 10  for the mounting bracket; 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Terms such as upper and lower, top and bottom, above and below, as used to describe the illustrated embodiments have their ordinary and usual meanings and are applied to riser sections and covers as they would normally be oriented in association with an underground component such as a concrete distribution box. The riser sections and covers illustrated are generally concentric about an imaginary vertical centerline. Terms such as inner, internal or interior, mean toward the centerline, and outer, external or exterior mean away from the centerline. 
   Referring to  FIGS. 1–4 , in the preferred embodiment of the present invention a riser section  10  includes generally cylindrical sidewall  12  having a plurality of vertical bosses  24  and a plurality of vertical reinforcing ribs  26  on the interior surface of sidewall  12 . The exterior surface of sidewall  12  is devoid of vertical reinforcement elements. 
   Attached to the substantially smooth exterior surface of sidewall  12  is detachable anchor tab  14  (discussed below). Sidewall  12  has a top, tapered end  37 , and a bottom, channel end  27 . (In an alternative embodiment, end  37  could be straight rather than tapered.) Alternatively, the tapered ends  37  could be on the bottom and the channel ends could be on the top in a stack of riser sections  10  of the present invention. 
   In the preferred embodiment, tapered end  37  includes on the external surface of sidewall  12  a horizontal edge surface  38  (i.e., edge surface  38  is substantially perpendicular to the axis of the vertical riser section and the external face of sidewall  12 ). With reference to  FIG. 4 , edge surface  38  extends around the circumference of sidewall  12 . End  37  includes a tapered portion  30  extending from horizontal edge surface  38  to the distal end of tapered end  37  of sidewall  12  of riser section  10 . Tapered end  37  thereby forms a unique male connector. The opposite end of riser section  10  forms a corresponding female connector, referred to herein as channel end  27 , as described below. 
   Referring to  FIGS. 2 ,  3  and  4 , the channel end  27  of riser section  10  comprises a unique dual channel arrangement in which outer wall  18 , middle wall  20 , and inner wall  22  extend relative to an internal horizontal ledge  28 , and generally parallel to the exterior surface of sidewall  12  to define outer channel  19  and inner channel  23 . 
   Horizontal ledge  28  on the interior surface of sidewall  12  (see  FIGS. 1 ,  2 ,  3 A and  4 ) is generally perpendicular to sidewall  12 . As shown in  FIGS. 2 and 4 , bosses  24  and ribs  26  extend vertically from ledge  28  to the distal end  40  of tapered end  37 . Bosses  24  are attached to or formed on the interior surface of sidewall  12  by an offsetting portion  24   a  (see  FIG. 4 ) that extends from the inside surface of sidewall  12  to the boss  24 , connecting member or offsetting portions  24   a , which preferably runs along the full vertical height of each boss  26 . End  37  of riser section  10  includes the ends  40   b  and  40   r  of vertical bosses  24  and ribs  26 , respectively, the ends  40   b ,  40   r  being flush with the horizontal edge  40  on the end of tapered portion  30  of sidewall  12 . The top surfaces  40   b  of offsetting portions  24   a  and bosses  24  and top surfaces  40   r  of ribs  26  are flush with the top surface  40  of tapered end  37 . 
   Referring to  FIG. 2B , when the tapered end  37  of one riser section  10  and channel end  27  of another riser section  10  are mated, top edge  40  of tapered portion  30  is positioned within outer channel  19 , which is the channel or space between inner surface  32  of outer wall  18  and outer surface  46  of middle wall  20 . Bottom edge  36  of outer wall  18  thus rests upon edge  38  on the exterior surface of sidewall  12 . 
   As seen in  FIG. 2B , when one riser section is placed on top of another, top edge  40  of the riser section on the bottom projects into outer channel  19  of the upper riser section. In the preferred embodiment, an O-ring  45  or similar resilient gasket is positioned at the bottom  19   a  of outer channel  19  such that when the first riser section is placed on top of a second riser section top edge  40  of tapered end  37  abuts against the O-ring  45  to provide a substantially water-tight and gas-tight seal. 
   Sealant can be applied to the area where the tapered end  37  of a first riser section  10  contacts the outer channel  23  of another riser section  12  (or a cover  50 ) stacked on top of the first riser section  10  to further ensure a water-tight, gas-tight seal between adjacent riser sections  10  (or between a riser section  10  and a cover  50 ) beyond that provided by the dual channel design of the present invention. 
   As shown in  FIGS. 2–4 , and in particular  FIG. 3A , channel end  27  of the present invention includes middle wall  20  having slots  16  at regular intervals. The slots  16  are spaced in middle wall  20  of a first riser section  10  such that they align with offsetting portions  24   a  of bosses  24  and with ribs  26  of an end  37  of a second riser section  10  when the first riser section is placed on top of the second riser section. Bosses  24  and ribs  26  of the second riser section  10  thereby extend into inner channel  23  of the first riser section  10 . 
   With reference to  FIGS. 2 ,  3  and  3 A, each slot  16  extends from end  20   a  of wall  20  to top  16   a . The top  16   a  of each slot  16  is flush with the end  42   a  of a vertical projection  42  in inner channel  23 . Each projection  42  (shown partially by the phantom lines in  FIG. 3  and shown in  FIG. 3A ) projects into outer channel  23  a height indicated by line  48  (see  FIG. 2 ). Offsetting portions  24   a  of bosses  24  and supporting ribs  26  of a first riser section are adapted to slide into slots  16  in a second riser section when the second riser section is placed on top of the first rise section. In a preferred embodiment, slots  16  and corresponding projections  42  are spaced midway between bosses  24  and ribs  26  which increase the structural integrity of the riser section  10 . 
   The vertical bosses  24  each contain on their end  40   b  a hollow bore adapted to accept a screw, or other suitable fastener. Projections  42   b  are provided in riser section  10  that align with a boss  24  of another riser section  10  when stacked. Projections  42   b  are somewhat wider than projections  42  not aligned with a boss  24 . Such bosses contain a hollow bore best shown in  FIGS. 1 and 3A  so that a screw or other suitable fastener (not shown) can be inserted through projection  42   b  in the first riser section  10  into the top end of a boss  24  below it in a second riser section  10  to fasten the two riser sections together. In that case, ledge  28  contains an opening  52  over the projections  42   b  having the hollow bores so that a screw or other fastener may be inserted through projection  42   b  and into the top end  40   b  of boss  24  below it when two riser sections  10  are stacked. 
   As shown in  FIGS. 2B ,  3 A and  4 , when two riser sections  10  are placed one on top of the other, slot  16  can accept either, referring now to  FIG. 2 , top edge  40   r  of a rib  26  or top edge  40   b  of offsetting portion  24   a  of a boss  24 . In one embodiment, a riser section is rotated 15° with respect to a riser section above or below it in a stack. As best seen in  FIGS. 1 and 4 , bosses  24  are spaced at 60° intervals about the interior surface of sidewall  12 . Two ribs  26  are equally spaced between each pair of successive bosses. Thus, there is a boss  24  or a rib  26  located every 20° about the interior surface of the sidewall  16 . Slots  16  and corresponding projections  42  are spaced midway between adjacent bosses  24  and ribs  26 . Such slots and projections are, therefore, disposed every 20° about the horizontal ledge  28  but displaced 10° from the bosses  24  and ribs  26 . 
   Referring to  FIGS. 1 ,  2 ,  2 B and  4 , channel end  27  of an upper riser section  10  receives the tapered end  37  of another riser section  10  disposed below it with bosses  24  and ribs  26  disposed in slots  16 . Bosses  24  of lower riser section  10  are aligned with, and support, projections  42   b  of the upper riser section  10 . Ribs  26  are aligned with, and support, the upper riser projections  42 . The two sections are secured together with screws that extend through openings  52  and hollow bores in projections  42   b  into hollow bores in bosses  24 . Additional riser sections  10  can be stacked above or below the first and second riser sections, as desired. In each case, the upper riser section is rotated 30° relative to the lower riser section to permit positioning of the offsetting portions  24   a  of the bosses  24  and ribs  26  of the lower riser section within slots  16  of the upper riser section. 
   The relatively narrow width of slots  16  in middle wall  20 , as shown in  FIGS. 3 ,  3 A and  4 , substantially limits any rotation of riser section  10  with respect to another riser section  10  stacked above or below the first riser section because the offsetting portions  24   a  of bosses  24  and the ribs  26  pass through and are restricted against angular lateral movement by the sides of slots  16 . 
   As best seen in  FIG. 2B , the height of projections  42  and  42   b  is such that the edges  42   a  of projections  42  or  42   b  abut against edges  40   b  and  40   r  of bosses  24  and ribs  26 , respectively, of the second riser. Accordingly, sidewalls  12  are reinforced along the full height of sidewall  12  by the combined height of projections  42  and  42   b  and either bosses  24  or ribs  26 . Outer wall  18  and middle wall  22  prevent horizontal movement of two stacked riser sections  10  with respect to each other. 
   Referring to  FIGS. 1 ,  1 A,  2  and  3 , detachable anchor tab  14  runs along the outside surface of the sidewall  12 . The bottom-most riser section  10  within a vertical stack may be anchored in concrete (e.g., a concrete distribution box not shown), in which case anchor tab  14  serves to anchor the bottom-most riser section  10  within the concrete. In the preferred embodiment, pull handle  15  is attached near ends  13   a ,  13   b  of anchor tab  14 . Anchor tab  14  is severed or has a weakened cross-section at ends  13   a ,  13   b  such that pulling on handle  15  in a radial direction separates ends  13   a  and  13   b . Preferably, anchor tab  14  is attached to the outside of sidewall  12  by a weakened region  14   a , such that continuing to pull handle  15  away from the sidewall  12  causes anchor tab  14  to tear away form the outside surface of riser section  10  in region  14   a.    
   Anchor tab  14  is preferably completely removed from riser section  10  when riser section  10  is not intended to be anchored in concrete. Detaching anchor tab  14  from each of the riser sections placed above the bottom-most riser section (i.e., all of the riser sections except the bottom one that is anchored in concrete) enhances the stability of the entire stack by providing a substantially smooth external surface that is less susceptible to forces caused by ground heaving and shifting than if the external surface contained the anchor tabs  14  (or any other projecting elements, such as support ribs). In this way, the alignment and integrity of the overall riser stack is maintained in areas subject to soil movement caused by freezing and thawing or heavy traffic over the top of the riser. 
   A riser cover  50  (see  FIG. 2A ) can cover the uppermost riser section  10  in a stack of riser sections  10 . Preferably, the cover is made from the same material as the associated riser sections, namely, molded high density plastic, such as polyethylene. 
   The cover  50  may include a similar configuration as the channel end of riser sections  10  and may include projections  42   c  having hollow bores for accepting screws or other fasteners as described above for fastening two riser sections  10  together. In an alternate configuration, the cover  50  will have an end with the same configuration as tapered end  37  of riser sections  10  and the top of the associated riser section will define a channel end such as end  27 . 
   Referring now to  FIGS. 5–7 , there is shown a riser cover  50  of the present invention for removably closing the access to an underground component through a riser formed by stacked riser sections  10 . Riser cover  50  is shown as circular in the preferred embodiment but can be of another shape that corresponds to the shape of the riser section to be covered. 
   Riser cover  50  includes a wall  53  defining a top convex surface  54 , a bottom concave surface  90 . A channel end  27   c  similar to channel end  27  of riser section  10  depends from wall  53 . It includes an outer wall  18   c  that defines the smooth outer peripheral surface of the cover. Channel end  27   c  includes a middle wall  20   c  spaced inward of outer wall  18   c  that includes spaced slots  16   c  shaped and spaced as the slots  16  in middle wall  20  of a riser section  10 . It defines with outer wall  18   c , outer channel  19   c . Channel end  27   c  includes inner wall  22   c  similar to middle wall  22  of channel end  27  of a riser section  10 . It defines with middle wall  20   c , inner channel  23   c.    
   Projections  42   c , best seen in  FIG. 6 , are located within inner channel  23   c  on riser cover  50  and contain a hollow bore defining openings  52   c  at top surface  54 . These bores receive a screw (not shown) to secure the riser cover on a riser section  10  by connection to the hollow bores in ends  42   b  of bosses  42  of a riser section  10 . 
   Top surface  54  of the riser cover  50  includes two hollow wells  56 . Wells  56  are tapered, starting from a largest diameter  58  at top surface  54  to a somewhat smaller diameter, where there is a ledge  60 , then tapered again, starting from a third diameter  62  to a fourth diameter second depth. 
   In the preferred embodiment, wells  56  are located approximately 180° apart at a radius approximately half the radius of the entire riser cover  50 , but can be located anywhere on the riser cover and there can be more or fewer than two. Each well  56  is constructed such that a metal rod  57  can be placed inside the well prior to the riser cover  50  being buried in place while in use. The metal rod  57  shown in  FIG. 5  can be, for example, a length of number four rebar. It serves to provide a mass of metal that can be detected by a metal detector so that the cover and riser stack can be located after it is buried under soil and vegetation. 
   Two recessed openings  64 , for receiving a pivotably mounted, stowable handle  70 , shown in  FIG. 8 , are arranged such that when handles  70  are pivoted down into recess openings  64 , each handle  70  is flush with or recessed from top surface  54  of riser cover  50 . Located inside each recess opening  64  is a space  66  adapted to receive a pivot rod, about which handle  70  pivots. A screw receptacle  68  is located inside space  66 , which is used to secure the pivot rod  72  to the riser cover  50 . 
   Also on bottom surface  90  are two protrusions  105  corresponding to recessed openings  64 , and two cylindrical protrusions  106  corresponding to screw receptacles  68 . 
   Handle  70  includes a grip portion  76  adapted to be easily grasped by a hand, and a pivot portion  78  consisting of two hollow cylindrical portions  80 . Pivot rod  72  is inserted into hollow openings  82  of each cylindrical portion  80 , spanning cylindrical portion  80 , and a screw  74  is placed in screw opening  84  on pivot rod  72  and secured to screw receptacle  68  located inside space  66  of cover  50 . 
     FIG. 6  shows bottom surface  90  of riser cover  50 . One difference in cover channel end  27   c  from channel end  27  of riser section  10  is the protrusions  93  contained at various positions on the middle wall  20   c  of the riser cover  50  disposed between adjacent slots  16   c . Protrusions  93  are used to “child proof” the cover. A screw or other suitable fastener is inserted through webs  34  in outer wall  18  of the top riser section  10  in a riser stack. The fastener pierces aligned protrusion  93  to provide a further connection between cover  50  and the associated top riser section  10 . The fastener must be removed to remove the cover from the top riser section. 
   Referring to  FIG. 6 , a cylindrical wall  94  is located on bottom surface  90 , concentric with channel end  27   c  of riser cover  50 . A plurality of vertically disposed support ribs  96 , each extending radially out from the cylindrical wall  94  to the inner wall  22   c  of the cover channel end  27   c , are provided on bottom surface  90 . Bottom edges  94   a  and  96   a  of cylindrical wall  94  and support ribs  96  define surfaces for contact with top surface  54  of another cover, when such covers are stacked upon each other. In other embodiments, where the riser cover is of a different shape, the central wall may be cylindrical or may have the same general shape as the walls of the channel end and be set in from the interior wall, with reinforcing ribs extending from the central wall to the interior wall of cover channel end, which is concentric with or (in the case of a square- or rectangular-shaped cross-section) parallel to the outer sidewall outer surface. 
   Also on bottom surface  90  of riser cover  50  are two hollow posts  98 . These posts define the wells  56  located on top surface  54  of cover  50 . Posts  98  are vertically elongate and extend below channel end  27   c.    
   Each post  98  has a first diameter  100  at its base, then tapers to a second diameter  101  at a midpoint where there is a shoulder  102 . There, the post transitions to a third diameter  103 , and then tapers to a fourth diameter  104  at the end thereof, similar to the shape of wells  56 . Each post  98  and well  56  is sized such that the post  98  of a first riser cover  50  will fit inside the well  56  of a second riser cover  50 . Thus, the portion of the post  98  between the third and fourth diameters fits within the portion of a well  56  on an associated cover between third diameter  62  and the fourth diameter at the bottom of the well. The portion of the post  98  from its base  100  to second diameter  101  fits within the tapered portion of well  56  between its largest diameter  58  and the smaller diameter at ledge  60 . This arrangement allows for easy stacking of a plurality of riser covers both for storage and for shipping. 
   An actual cover  50  has been constructed which embodies the principles of the present invention. It is approximately twenty-two and one-half inches in diameter at the outer peripheral surface of outer wall  18   c . Each post  98  is about three inches in length from base  100  at bottom surface  90  of cover  50  to end  104 , which is about ¾ inch in diameter. The wells  56  of posts  98  are about ⅞ inch in diameter at top surface  54  of cover  50 . 
   Vertical centerlines passing through each well are 9½ inches apart. The horizontal centerlines of pivot rods  72  are 15½ inches apart. The recesses  64  are aligned with the wells  56  of posts  98 . Six openings  53  are positioned 60° apart on top surface  54 . The slots  16   c , and consequently the projections  42   c , are 20° apart. 
   A mounting bracket  110  (shown in  FIGS. 9–11 ) is provided to secure a riser section in position on a wall of concrete form while the riser section is being molded in concrete. The mounting bracket  110  is generally inverse U-shaped, having a flat top portion  113  and sidewall  116  that diverge from the top portion  113 . Flanges  114  project from sidewalls  116 . Flanges  114  have holes  118  for securing mounting bracket  110  to the floor of a concrete form. Top portion  113  has at least two apertures  120 , which have tapered sides  122  that form gripping webs. 
   It may also include a hole  123  centrally located in top  113  that may be used for sighting to position the bracket over a mark, for example, placed on the wall of the form. As each post or post  98  is inserted into an aligned aperture  120 , tapered sides  122  engage the post at a point between third diameter  103  and fourth diameter  104  of post  98 , creating a tight, friction fit between post  98  and tapered sides  122  of aperture  120 , as shown in  FIG. 11 . 
   As illustrated in  FIG. 11 , mounting bracket  110  is secured on form wall or floor  132  of form  130  by screws or other fasteners inserted in bore holes  118 . A riser section  10  with anchor tab  14  attached is then placed into form  130 , around mounting bracket  110 , with channel end  27  of riser section  10  substantially in contact with floor  132  of form  130 . Riser cover  50  is then placed on riser section  10  and positioned with channel end  27   c  in place on tapered end  37  of the riser section  10 . The cover  50  may be secured to the riser section by screws in openings  52   c . The cover is secured in position as posts  98  are inserted into corresponding apertures  120  of mounting bracket  110  and frictionally grasped by tapered sides  122 . 
   Alternatively, riser cover  50  can be placed and secured on riser section  10  before riser section  10  is placed into form  130 . Then, the riser section  10  and riser cover  50  assembly are placed into form  130 . Posts  98  are inserted into apertures  120  on mounting bracket  110 . 
   After the riser section  10  is positioned and secured on form wall  132 , concrete is poured into the form  130 , preferably to a level above the detachable anchor tab  14  and below riser cover  50 . Once the concrete is cured, riser cover  50  is removed from riser section  10  and mounting bracket  110  by pulling the posts from their frictional engagement with apertures  120 . 
   Riser section  10 , thus anchored in concrete, may then be used as the bottom-most riser section in a stack of riser sections  10  to define an access to an underground component such as a concrete distribution box. Cover  50  is secured to the top riser section to close and seal the access. The cover  50  is removed when access to the underground component is required. 
   Whereas the present invention is described herein with respect to specific embodiments thereof, it will be understood that various changes and modifications may be made by one skilled in the art without departing from the scope of the invention, and it is intended that the invention encompass such changes and modifications as fall within the scope of the appended claims.