Drain Cover with Mesh Retaining Channel

Abstract

A drain cover assembly that retains mesh on its upper surface via a channel-fastening system that is integrated into the drain cover's perimeter zone. The mesh is retained on the upper surface of the drain cover in a robust and permanent fashion. The drain cover can be configured to provide structural rigidity for supporting a load applied to its upper surface. The drain cover can be adapted to allow for its use in existing or newly constructed drainage system installations. The meshed upper surface of the drain cover can be configured to be flat or raised in profile. The meshed upper surface of the drain cover prevents mosquito habitation and breeding within the associated drainage system and prevents fine debris particles from clogging the drainage system's flow conduit.

Claims

1. A drain cover assembly for use in a drainage system comprising an underground catch basin or an underground flow conduit, comprising: a drain cover having an upper surface and lower surface, the drain cover comprising a zone around its perimeter and a grating grid within the zone, wherein the perimeter zone comprises a channel, and wherein the grating grid comprises a plurality of grating members defining openings in between, wherein the openings are configured to permit a liquid to flow into the underground catch basin or the underground flow conduit, wherein the drain cover is configured to be connected to the underground catch basin or to the underground flow conduit proximate to its lower surface; a channel cover ring having an upper surface and a lower surface, wherein the lower surface of the channel cover ring comprises a shape to mate with a shape of the channel to allow the channel cover ring to be connected to the drain cover; means for connecting the channel cover ring to the drain cover; and a mesh cover, wherein the mesh cover is configured to cover the grating grid at the upper surface of the drain cover, and wherein a periphery of the mesh cover is configured to be fixed within the channel when the channel cover ring is connected to the drain cover.

2. The drain cover assembly of claim 1, wherein the channel is on the upper surface of the drain cover.

3. The drain cover assembly of claim 2, wherein the channel is recessed in the upper surface of the drain cover.

4. The drain cover assembly of claim 1, wherein the upper surface of the channel cover ring is flush with the upper surface of the drain cover when the channel cover ring is connected to the drain cover.

5. The drain cover assembly of claim 1, wherein the periphery of the mesh cover is configured to be fixed within the channel between the channel cover ring and the drain cover.

6. The drain cover assembly of claim 1, wherein the drain cover is configured to connect to the underground catch basin or to the underground flow conduit via contact between the lower surface and a shoulder of the underground catch basin or the underground flow conduit.

7. The drain cover assembly of claim 1, wherein the drain cover comprises an extension at its lower surface, wherein the drain cover is configured to connect to the underground catch basin or to the underground flow conduit by positioning the extension within or around the underground catch basin or the underground flow conduit.

8. The drain cover assembly of claim 7, wherein the extension connects within or around the underground catch basin or the underground flow conduit using a friction fit.

9. The drain cover assembly of claim 1, wherein the means for connecting the channel cover ring to the drain cover comprises screws.

10. The drain cover assembly of claim 1, wherein the means for connecting the channel cover ring to the drain cover comprises a mechanical snap connection between the channel cover ring and the drain cover.

11. The drain cover assembly of claim 1, wherein the means for connecting the channel cover ring to the drain cover comprises a friction fitting connection between the channel cover ring and the drain cover.

12. The drain cover assembly of claim 1, wherein the means for connecting the channel cover ring to the drain cover comprises a latch, a clamp, a band, or an adhesive.

13. The drain cover assembly of claim 1, wherein the means for connecting the channel cover ring to the drain cover comprises a melted connection between the channel cover ring and the drain cover.

14. The drain cover assembly of claim 1, further comprising a gasket, wherein the gasket is positioned within the channel to assist in fixing the periphery of the mesh cover within the channel.

15. The drain cover assembly of claim 14, wherein the lower surface of the channel cover ring comprises a groove to hold the gasket in place.

16. The drain cover assembly of claim 1, wherein the drain cover assembly is configured for use in outdoor or indoor drainage system applications.

17. The drain cover assembly of claim 1, wherein the drain cover assembly is configured for use in collecting and filtering drainage water or wastewater.

18. The drain cover assembly of claim 1, wherein the channel is comprised of a plurality of sub-channels.

19. The drain cover assembly of claim 1, wherein the channel cover ring comprises a single ring-shaped piece.

20. The drain cover assembly of claim 1, wherein the channel cover ring comprises a plurality of pieces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIGS. 1 and 2 depict an example of a prior art outdoor flat drain cover and flow conduit.

[0056] FIGS. 3 and 4 depict an example of a prior art outdoor raised drain cover and flow conduit.

[0057] FIGS. 5 and 6 depict an example of a prior art outdoor flat drain cover, catch basin, and flow conduit.

[0058] FIG. 7 is cross-sectional view of the components shown in FIGS. 5 and 6 with the addition of a filter basket.

[0059] FIG. 8 is cross-sectional view of one example of a prior art outdoor meshed drain cover assembly.

[0060] FIG. 9 is cross-sectional view of another example of a prior art outdoor meshed drain cover assembly.

[0061] FIGS. 10 and 11 depict an embodiment of an outdoor flat drain cover constructed according to the present invention.

[0062] FIGS. 12 and 13 depict another embodiment of an outdoor raised drain cover constructed according to the present invention.

[0063] FIGS. 14-16 depict another embodiment of an outdoor raised drain cover constructed according to the present invention.

[0064] FIGS. 17-19 depict another embodiment of an outdoor raised drain cover constructed according to the present invention.

[0065] FIGS. 20-23 depict different additional embodiments of an outdoor flat drain cover constructed according to the present invention.

DETAILED DESCRIPTION

[0066] The new drain cover invention disclosed herein may be embodied in various forms, some of which are described in this section. There exist other variations which are not described in this section but would be apparent to those familiar with the art. It shall be understood that these variations may be made without departing from the novel features of the disclosed invention.

[0067] One illustrative embodiment of the invention is shown in FIGS. 10 and 11. In this embodiment, an outdoor square drain cover 94 with a flat profile is shown retaining a mesh 86 material on its outside upper surface via a mesh retaining channel 104, channel cover ring 96, spline gasket 100, and channel cover screws 108. The mesh retaining channel 104 is integrated into the drain cover's perimeter zone 95.

[0068] The mesh 86 material utilized in this embodiment is composed of metallic aluminum wire. Aluminum wire mesh 86 is inexpensive and offers basic resistance to tearing and weathering. Aluminum wire mesh 86 is widely available in standard forms with mesh opening sizes small enough to inhibit the passage of mosquito insects and debris (both fine and bulky types), while also being large enough to allow water to freely permeate it. A metallic type of mesh 86 material is generally preferable for use in the present invention, as the mesh 86 can retain a shape after being cut and die formed, thus enabling the assembly process of the drain cover 94 and mesh 86 to be optimized. Some example mesh 86 opening sizes that may be utilized in the present invention include 18×16, 18×14, 16×16 with 0.011″ gauge or similar wire diameter. These mesh 86 sizes all share a common opening size dimension approximately less than 1/16″, which is known to be generally effective in preventing the passage of the adult Aedes aegypti mosquito. Larger sizes of mesh 86 may be utilized for applications where exclusion of small mosquitos is not of concern. Metallic forms of mesh 86 may be utilized in an uncoated “mill finish” state (if a metallic look is desired) or alternatively may be colorized with an epoxy or powder coating for aesthetics.

[0069] The channel 104 is preferably located on top of the drain cover's perimeter zone 95, as shown in the illustration. In other possible embodiments the location of the channel 104 may instead be placed on the outer sides or bottom of the perimeter zone 95. The channel 104 may vary in manner of shape and size but is preferably shaped with a flat bottom and outwardly angled sides 105 for receiving the channel cover ring 96, which also has outwardly angled sides 98. A hollow and flexible spline type gasket 100 is retained and partially embedded by friction fitting in a cavity on the underside of the channel cover ring 96. The spline gasket 100 is preferably composed of a rigid rubber or other similar polymer with a high friction coefficient. The spine gasket 100 is preferably circular in its cross sectional-shape, as shown, with a diameter typically in the range of ⅛″ to ¼″. The spine gasket 100 preferably has axial ribbing on its outside surface to enhance its mesh 86 gripping ability.

[0070] The partial embedment of the spline gasket 100 in the underside of the channel cover ring 96 is advantageous, as it allows the assembly process of the drain cover 94 to be optimized with the spline gasket 100 and channel cover ring 96 being attached to the drain cover 94 in a pre-assembled state. The partial embedment of the spline gasket 100 in the channel cover ring 96 is also advantageous, as it enables the spline gasket 100 to be deformed inward while under compression, which in turn allows the surfaces of the channel cover ring 96 to be in closer contact with the surfaces of the channel 104.

[0071] The spline gasket 100 and channel cover ring 96 are inserted into the channel 104 and held in place by a plurality of channel cover screws 108. The channel cover screws 108 penetrate the base material of the channel cover ring 96 and perimeter zone 95 via screw guide holes 106. The channel cover screws 108 can penetrate the spline gasket 100 and mesh 86 without loss of performance. The force imposed by the tightening of the channel cover screws 108 encourages permanent fixity and tautness of the mesh 86 on the upper surface of the new drain cover 94 through several features acting in tandem. The tightening of the channel cover screws 108 creates a compressive force that sandwiches the spline gasket 100 and mesh 86 between the channel cover ring 96 and channel 104. The spline gasket 100 deforms while under this compressive load, and thus is the first line of compressive contact for fastening the mesh 86. The sides 105 of the channel 104 and the sides 98 the channel cover ring 96 are configured in their respective shapes to ensure that, at some point during the tightening of the channel cover screws 108, the deformation of the spline gasket 100 will be halted when the channel cover ring 96 reaches the point where its own sides 98 wedge with the sides 105 of the channel 104 and with the mesh 86 sandwiched in between. Thus, additional compressive contact for locking the mesh is added above to that which is already established by the compression of the spline gasket 100.

[0072] It shall be understood to those familiar with the art that a mechanical snap connection, a friction fitting connection—or one or more latches, clamps, bands, or adhesives, or a process that melts the components together—may be used as an alternative to channel cover screws 108 for securing the channel cover ring 98 and mesh 86 to the drain cover's perimeter zone 95. Additionally, use of a spline gasket 100, while preferred, is not necessary in all useful embodiments.

[0073] The individual features that positively enhance the fixity and tautness of the mesh 86 may be considered individual resistance mechanisms that prevent the sandwiched mesh 86 from loosening from the channel cover ring 96, spline gasket 100, and channel 104. To become loose the mesh 86 must itself deform in shape to inwardly slip around the shape of the channel cover ring 96. The mesh 86 of this example, being made from aluminum wire, is relatively deformable when compared to the mechanical properties of 304 grade stainless steel wire, and thus may be thought of as a loosening-prone type of mesh 86. It shall be understood that there is a relationship between this embodiment's use of the loosening-prone aluminum wire mesh 86 and the corresponding necessity to incorporate loosening-resistant features into the channel cover ring 96, spline gasket 100, and channel 104 (to prevent mesh 86 loosening).

[0074] In addition to the features described above, the wedge shape of the channel cover ring 96 also enables the manufacturing process of the drain cover to be optimized, as during the tightening of the channel cover screws 108 the mesh 86 is naturally drawn deeper into the channel 104 and thus becomes taut during assembly, as opposed to the need to artificially maintain tautness during the tightening of the channel cover screws 108. The inward-facing corners 103 of the channel 104 and channel cover ring 96 are preferably rounded in order not to puncture the mesh 86 during the channel cover screw 108 tightening process, particularly for embodiments that are flat in profile.

[0075] The metallic mesh 86, once cut to shape, may have residual sharp wires present on its frayed edges 101, which may be a hazard if handled without gloves. Addressing this problem, the channel 104 feature of the device is additionally advantageous, as it provides a means to isolate these frayed edges 101. Isolation of frayed edges 101 is less of a safety issue with other forms of non-metallic mesh material, like polyester, but is nonetheless still desirable for non-metallic mesh if only for the masking of frayed edges for aesthetic reasons. A metallic mesh 86 is preferable for use in the invention due to its mechanical robustness and ease of cleaning, as debris is more easily shed from a metallic wire mesh 86 versus one composed of polyester or other fibrous material. The channel cover ring 96 is preferably rigid to avoid localized deformation while under the compressive load of the tightened channel cover screws 108 or other means of connecting to the channel 104 in the drain cover.

[0076] For greatest economy, the new drain cover 94 is preferably composed of a polymer or composite material like HDPE (optionally, with UV resisting additives suitable for outdoor use). The new drain cover 94 can also be composed of weathering-resistant metallic material, like 304 or 316 grade stainless steels, which may be more suitable than HDPE for some applications. The channel cover ring 96 can be made of polymer, composite, or weathering-resistant metallic materials, like 304 or 316 grade stainless steels. The channel cover screws 108 are preferably composed of a weathering-resistant metallic material, like 304 or 316 grade stainless steel. The channel cover screws 108 may be utilized in an uncoated “mill finish” state or may feature a colored coating for aesthetics.

[0077] The drain cover 94 features a plurality of grating surface openings 93 located beneath the mesh 86. The width of the grating surface openings 93 of this example are 5/16″ in width to qualify as both “heel safe” per industry practice and “ADA compliant” per the Americans with Disabilities Act. Also beneath the mesh 86 is a plurality of associated grating members 91 that can safely support a load applied to the upper surface of the drain cover 94. The grating member 91 grid is attached to (and supported by) the drain cover's perimeter zone 95. The drain cover's 94 open area can be made comparable to that of a conventional drain cover of similar dimensions by increasing the opening size of the grating surface openings 93 beneath the mesh to offset the approximately 30% reduction in open area caused by the presence of the thin mesh 86 wire that covers the drain cover's 94 surface. The location of the grating members 91 below the mesh 86 also reduces the likelihood of the mesh's 86 being deformed or torn by blunt impacts or heavy debris loads.

[0078] The drain cover 94 optionally also features collapsible lifting eyes 30 that permit the drain cover 94 to be ergonomically lifted without causing damage to the mesh 86. The lifting eyes 30 are preferably composed of a weathering-resistant metallic material like 304 or 316 grade stainless steel. The lifting eyes 30 may be utilized in an uncoated “mill finish” state or feature a colored coating for aesthetics. The lifting eyes 30 are composed of an attachment pad 36, a lifting ring 38, and a lifting ring socket 32. The lifting eye 30 of this example is secured to the surface of the drain cover 94 by the same screw 108 used to secure the channel cover ring 96. The lifting rings 38 can rotate within the lifting ring sockets 32 so that they may be used as a lifting point for the drain cover 94 and be collapsible (as shown) when not in use. In a collapsed state the lifting eyes 30 may slightly project beyond the surface of the drain cover 94, perhaps by ⅛″, thus maintaining substantial flushness with the ground. In applications requiring complete flushness, it is possible to recess the lifting eye 30 within the drain cover's perimeter zone 95. As will be apparent to those familiar in the art, the drain cover 94 may also be configured to utilize other forms of lifting devices, both flush and non-flush, that may also be integrated into the perimeter zone 95 or channel cover ring 96, the upper surface of the drain cover 94, or the sides of the drain cover 94.

[0079] The channel cover ring 96 of this embodiment is shown as a single piece, but in other possible embodiments it could alternatively be composed of multiple pieces to overcome manufacturing or assembly limitations.

[0080] Another illustrative embodiment of the invention is shown in FIGS. 12 and 13. In this embodiment, an outdoor circular drain cover 112 with a hemispherical raised grating member 116 grid profile is shown with a mesh 86 cover on its upper surface. The mesh 86 is secured in a retaining channel 121 that is integrated into the drain cover's 112 perimeter zone 115. The mesh 86 shown in this embodiment is composed of 304 grade stainless steel. While 304 grade stainless steel mesh 86 material is more expensive than aluminum, it is also preferable for use in the present invention due to its increased strength, stiffness, and weathering-resistance. The increased strength and stiffness of 304 grade stainless steel mesh 86 offers enhanced resistance to its being deformed or punctured due to surface impacts (like falling hail) or surface loads (like foot traffic).

[0081] A further advantage of the increased strength and stiffness offered by 304 grade stainless steel mesh 86 is its inherently greater resistance to loosening when utilized in the present invention. As with the previous embodiment, to become loose the mesh 86 must itself deform in shape to slip around the shape of the channel cover ring 119. The mesh 86 of this example, being composed of 304 grade stainless steel wire, is more resistant to deformation than is a similar mesh 86 composed of aluminum wire. It shall be understood that the loosening-resistant mesh 86 of this embodiment requires fewer loosening-resistant features (incorporated into the channel cover ring 119 and channel 121) to provide sufficient mesh 86 fixity and tautness.

[0082] The channel cover ring 119 of this embodiment is similar in concept to that of the previous embodiment but is circular in shape to match the shape of the drain cover's 112 perimeter zone 115. The channel cover ring 119 also does not utilize a spline gasket 100 in this example, although it could. While the channel cover ring 119 of this embodiment is shown as a single piece, it could alternatively be composed of multiple pieces, as mentioned previously. Similar to the previous embodiment, the mesh 86 is fastened to the drain cover's 112 outside surface via the combined locking mechanisms of channel cover ring 119, channel cover screws 108, and wedge-shaped sides 97 & 107 of the channel cover ring 119 and channel 121. The downward facing edges 99 of the channel cover ring are sharp edged to increase the resistance to loosening, as it more difficult for the mesh 86 to slip around a sharp edge 99 than a rounded edge. This embodiment's use of loosening-resistant mesh 86 eliminates the need for a spline gasket 100 to be used in conjunction with the channel cover screws 108, channel cover ring 119, and retaining channel 121.

[0083] Beneath the mesh 86, the drain cover 112 features a plurality of grating surface openings 118 that are three dimensional in shape. The open area of the raised drain cover 112 of this example is greater than that of a circular flat drain cover of similar cross-sectional area (e.g., FIGS. 10 and 11). The preferable shape for the upper portion of a raised drain cover is either hemispherical or hemielliptsoidal, as these shapes are most favorable for generally maximizing the drain cover's available open area while minimizing the possibility of the mesh's 86 clumping (or folding over itself) as it is stretched over the raised upper surface during manufacturing. In other possible embodiments the shape of the raised portion of the new drain cover may be varied to include truncated types of cones, cylinders, half sections of other polyhedrons, and other similar shapes.

[0084] As has been previously indicated, it is preferable that the drain cover 112 be adaptable for retrofitting existing municipal, commercial, and residential drainage systems. To meet this goal, the underside of the perimeter zone 115 of this example features a known method for engaging the drain cover 112 on either a round catch basin or round-flow conduit pipe. An outermost shoulder 113 is intended for supporting the drain cover 112 on the ledge of a round catch basin. The small tabs 114 on the shoulder provide some amount of friction fit for engaging with the round catch basin. Alternatively, an innermost shoulder 122 is intended for optionally supporting the drain cover 112 on a round-flow conduit, with a smaller inside diameter than that of the catch basin. The lower neck extension 117 is intended to fit into the inside diameter of a flow conduit and be of sufficient length and relative size to ensure the drain cover fits snugly.

[0085] Another illustrative embodiment of the invention is shown in FIGS. 14-16. In this embodiment, an outdoor square drain cover 124 with a raised elliptical profile is shown with a mesh 86 cover on its outside surface. The mesh 86 is secured in a retaining channel that is integrated into the perimeter zone 126. As has been previously indicated, it is preferable to avoid mesh folding or clumping when fastening the mesh over a raised drain cover surface. A hemispherical profile is suitable profile for this purpose, but it is not able to occupy all the available surface area of a square drain cover, like the type shown in the present embodiment. As an alternative, the elliptically based profile shown in this embodiment may be used, in which the curved top profile is lofted to fully cover the square base shape. FIG. 15 shows a side view of the drain cover's 124 raised mesh-surface profile 128, which is hemielliptic its in shape. The preferred ratio of hemielliptic width to height is between 20% to 40%. FIG. 16 shows a diagonal side view of the drain cover 124. The elliptical profile 130, along the diagonal view, is the same height as that of the previous figure but is elongated in width to maximize the available open area of the square drain cover.

[0086] Another illustrative embodiment of the invention is shown in FIGS. 17-19. In this embodiment, an outdoor square drain cover 132 with a modified hemispherical profile is shown with a mesh 86 cover on its outside surface. The mesh 86 is secured in a retaining channel that is integrated into the perimeter zone 134. As has been previously indicated, it is preferable to avoid mesh folding or clumping when fastening the mesh over a raised drain cover surface. A hemispherical profile is suitable for this purpose, but that profile is not able to occupy all the available surface area of a square drain cover, like the type shown in the present embodiment. As an alternative, the modified hemispherical based profile shown in this embodiment may be used, as its curved upper surface is lofted to fully cover the square base shape. FIG. 18 shows a side view of the drain cover's 132 raised mesh surface profile 136 as being hemispherical in its shape. FIG. 19 shows a diagonal side view of the drain cover 132. The modified hemispherical profile 138 along the diagonal view is the same height as that of the previous figure but is elongated in its width with tangent lines to maximize the available open area of the square drain cover.

[0087] Another illustrative embodiment of the invention is shown in FIG. 20. In this embodiment, an outdoor flat drain cover 140 is shown in cross section with a mesh 86 cover on its outside surface. The mesh 86 is secured in a retaining channel 144 integrated into the perimeter zone 142. The mesh 86 is retained in the channel 144 by the friction fitting of a hollow spline gasket 100. The channel's 144 width and depth are sufficiently narrow to require the spline gasket 100 to be compressed and deformed upon insertion. This embodiment is less preferable to those previously shown in FIG. 11 and FIG. 13, as it lacks the more favorable mesh-retaining characteristics imparted by a channel cover ring and tightening screws shown in previous embodiments. This embodiment is also less preferable to those previously shown, as it lacks a means of isolating and masking the frayed edges 101 of the mesh 86.

[0088] Another illustrative embodiment of the invention is shown in FIG. 21. In this embodiment, an outdoor flat drain cover 160 is shown with a mesh 86 cover on its outside surface. The mesh 86 is secured in a retaining channel 164 that is integrated into the perimeter zone 162. The mesh 86 is retained in the channel 164 by the friction fitting of a hollow spline gasket 100. The channel's 164 width and depth are sufficiently narrow to require the spline gasket 100, upon insertion, to be compressed and deformed. Additionally, the channel 164 features a channel geometry modification 166 to encourage additional mesh 86 fixity by trapping the spline gasket 100. However, this embodiment's channel 164 configuration is again less preferable to those previously shown in FIG. 11 and FIG. 13, as it lacks the more favorable mesh-retaining features shown in those embodiments. This embodiment is also less preferable for its lack of a means of isolate the frayed edges 101 of the mesh 86.

[0089] Another illustrative embodiment of the invention is shown in FIG. 22. In this embodiment, an outdoor flat drain cover 180 is shown with a mesh 86 cover on its outside surface. The mesh 86 is secured in a retaining channel 184 that is integrated into the perimeter zone 182. The mesh 86 is retained in the channel 184 by the compressive force imparted by a channel cover ring 186 and tightening channel cover screws 108. This embodiment is less preferable to those previously shown in FIG. 11 and FIG. 13, as it lacks the more favorable mesh-retaining features shown in those embodiments, particularly in conjunction with loosening-prone types of mesh 86. The relatively shallow channel 184 of this embodiment and lack of downward-facing sharp corners on the channel cover ring 186 results in a meshed drain cover assembly with a lesser resistance to mesh 86 loosening.

[0090] Another illustrative embodiment of the invention is shown in FIG. 23. This embodiment features an indoor flat drain cover 190 with a mesh 86 cover on its outside surface, although this embodiment could be used outside as well. The mesh 86 is secured in a retaining channel 194 that is integrated into the perimeter zone 192. The channel 194 is itself composed of two sub-channels 195. The mesh 86 is retained in the channel 194 by the compressive force imparted by a channel cover ring 198 and tightened channel cover screws 108. The multiple sharp-edged interlocking tongue extensions 197 on the underside of the channel cover ring 198 mate with the sub-channels 195 of the channel 194. This embodiment's use of sub-channels 195 and sharp-edged interlocking tongue extensions 197 results in a meshed drain cover assembly with an increased resistance to mesh 86 loosening. This embodiment's use of multiple sub-channels 195 also permits the drain cover 190 to become more compact in its thickness, which is a preferable feature for indoor drainage systems that favor a more flush surface profile. As is known to those familiar in the art, indoor drainage system components are often composed of highly corrosion-resistant materials, like 316 grade stainless steel or bronze, to avoid discoloration or corrosion when exposed to indoor cleaning agents. The mesh 86 material utilized in this embodiment is composed of 316 stainless steel, which has mechanical properties proximate to those of 304 stainless steel. Likewise, the channel cover ring 198 and the drain cover 190 are also composed of 316 stainless steel material. This use of a metallic drain cover material further enables the embodiment to take on a form of compact thickness, as the material strength of the grating member 199 grid is greater than a similar one composed of HDPE, and thus this embodiment requires less thickness for supporting a surface load.