CA2732492A1 - Stormwater chamber having multi-layer mat - Google Patents

Abstract

An apparatus is disclosed for receiving and dispersing stormwater underground, wherein the apparatus accumulates debris carried by the stormwater received.
The apparatus includes an arch-shaped cross-section chamber buried in stone aggregate, the chamber having base flanges supported on a stone aggregate floor, the chamber having an interior space bounded by the floor; and a mat connected to the chamber and positioned over the floor. The mat includes one or more filtering layers disposed in proximity to the stone aggregate floor for filtering and retention of a portion of debris carried by the stormwater; and a protective layer disposed above the one or more filtering layers, for both filtering debris and for protecting the one or more filtering layers during a cleaning process. The first layer having an average pore size which is larger than the average pore size of the second; the first layer allowing a portion of debris carried in the water to flow with the water to the second layer. A method for receiving and dispersing stormwater beneath the surface of earth is also disclosed.

Description

STORMWATER CHAMBER HAVING MULTI-LAYER MAT
Related Application [001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 61/307,282 filed on February 23, 2010, the entire disclosure of which is expressly incorporated herein by reference.

Technical Field [002] The present disclosure relates to a multi-layer mat for stormwater chambers that are buried beneath the surface of the earth for receiving and dispersing stormwater.

Background [003] Thermoplastic chambers with arch-shaped cross-sections have been buried beneath the surface of the earth for receiving and dispersing collected stormwater. Examples include Stormtech Model SC310 or Model SC740 stormwater chambers, sold by Stormtech LLC, of Wethersfield, Connecticut. These arch-shaped chambers are positioned in an arrangement below ground and configured to receive a flow of stormwater. For example, stormwater chambers may be positioned in-line with each other, in an array, or both in-line and in an array. Stormwater chambers may be provided with an inlet configured to connect to the outlet of a stormwater collection system, such as a plurality of drain basins associated with a street, parking lot, roof, etc.
Stormwater chambers may be configured to desirably distribute collected stormwater back into the environment through the ground.

[004] Stormwater often carries with it debris that passes through basins and other traps normally associated with stormwater collection systems. For example, the water may bear suspended solids, such as dirt, sand, small pieces of leaf, paper, and plastic. Stormwater chambers are often designed to allow debris to settle (e.g., sink to the bottom of a chamber) before stormwater is released into the ground. State and federal regulations may in some cases control the amounts or proportions of debris that can be reintroduced into the environment after stormwater collection.

[005] In some cases, stormwater systems include a subsystem by which stormwater is first flowed to a primary row of chambers dedicated to capturing a large amount of the debris. Examples of such primary chamber rows include the Isolator row subsystem marketed by Stormtech, LLC. Isolator row chambers are typically encased in a layer of comparatively fine mesh geotextile, often referred to as "filter fabric." Typically, the fabric surrounds the exterior of the chamber and runs along the surface of the porous medium, typically crushed stone, which forms the floor underlying the arch curve of the chamber. To the extent the entrained debris includes leaves or pieces of other sheet materials, those materials may be caught by the filter fabric and locally mask openings in the fabric, reducing the capacity of the fabric to disperse filtered stormwater downwardly.

[006] As a result, maintenance workers periodically remove the debris that collects in primary rows, such as the Isolator row, and systems not having a primary row. Typically, debris is removed using a special apparatus that involves water jetting and vacuuming. For example, a jet, siphon, or both at the end of a hose may be pushed or pulled along the length of each chamber or string of chambers.
Undesirably, the cleaning devices may push, snag, tear, gather, or otherwise disrupt the geotextile which lies on the crushed stone floor that defines the bottom of the chamber interior, thus upsetting its subsequent functionality.

[007] The present disclosure is directed to addressing the above-referenced challenges.

Summary [008] In accordance with an exemplary embodiment, a method is disclosed for receiving and dispersing stormwater, underground. The method includes directing stormwater bearing debris from a source into an interior of one or more chambers buried within water-permeable aggregate, wherein the one or more chambers are supported on a floor of the water-permeable aggregate by opposing side base flanges of the one or more chambers, and the floor defines a lower boundary of an interior space of the one or more chambers. The method further includes filtering a portion of water-borne debris from stormwater flowing toward the floor, by using one or more filtering layers; and protecting the one or more filtering layers from damage during a cleaning process, by using a water permeable protective layer. The one or more filtering layers have a finer porosity than a porosity of the protective layer.

[009] In another exemplary embodiment, an apparatus is disclosed for receiving and dispersing stormwater beneath the surface of the ground, wherein the apparatus accumulates debris carried by the stormwater received. The apparatus includes an arch-shaped cross-section chamber buried in stone aggregate, the chamber having base flanges supported on a stone aggregate floor and an interior space bounded by the floor; and a mat connected to the chamber and positioned over the floor. The mat includes one or more filtering layers disposed in proximity to the stone aggregate floor for filtering and retention of a portion of debris carried by the stormwater; and a protective layer disposed above the one or more filtering layers, for both filtering debris and for protecting the one or more filtering layers during a cleaning process. The first layer has an average pore size that is larger than the average pore size of the second; and the first layer allows a portion of debris carried in the water to flow with the water to the second layer.

[010] Before explaining certain embodiments of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The disclosure is capable of embodiments in addition to those described and of being practiced and carried out in various ways.
Also, it is to be understood that the phraseology and terminology employed herein, as well as in the abstract, are for the purpose of description and should not be regarded as limiting.

[011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain embodiments of the disclosure, and together with the description, serve to explain the principles of the disclosure.

[012] As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present disclosure. It is important, therefore, to recognize that the claims should be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present disclosure.

Brief Description of the Drawings [013] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate several embodiments and aspects of the present disclosure, and together with the description, serve to explain certain principles of the invention. In the drawings:

[014] FIG. 1 is an end view of stormwater chamber showing an exemplary multi-layered mat at the bottom of the stormwater chamber;

[015] FIG. 2 is an elevation view of an exemplary three-layer mat for use within a stormwater chamber;

[016] FIG. 3 is an isometric view of a portion of an exemplary three-layer mat for use within a stormwater chamber;

[017] FIG. 4 is an end view of adjacent stormwater chambers, including an exemplary multi-layer mat disposed under one of the stormwater chambers; and [018] FIG. 5 is a perspective view including a detailed view of exemplary mechanisms for fastening the exemplary multi-layer mat of FIG. 4 to a stormwater chamber.

Detailed Description [019] Reference will now be made in detail to exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[020] In general, the present disclosure is directed to receiving and dispersing stormwater using a chamber apparatus that receives and retains suspended solids in a way that facilitates periodic removal of debris without disrupting geotextile lying inside the chamber. As described above, stormwater may be directed from a collection source into an interior of one or more chambers buried within stone aggregate underground.
Each stormwater chamber may include a plurality of base flanges that rest on a floor comprised of stone aggregate, through which water flows downwardly during use.
A
multi-layer mat may be positioned on or just above the floor surface, defining a bottom of a chamber interior. The mat may include an upper layer having coarse openings for filtering and protecting one or more underlying layers. In particular, the upper layer may be configured to keep leaves and other sheet debris out of intimate contact with the lower layer(s). The one or more lower layers may have finer porosity than the upper layer and therefore filter a portion of the finer debris that passes through the upper layer.

[021] As described in more detail below, any or all of the layers may be fastened to each other. The layers may be positioned under the flanges of a chamber, or deformed upwards and fastened to the inside of the chamber. In one embodiment, one or more of the layers may run around the exterior of the chamber. In one exemplary embodiment, the upper protective layer may be a nonwoven high density polyethylene (HDPE) netting material, and the one or more bottom layers may be a woven slit film polypropylene (PP) geotextile material. In one embodiment, the multi-layer mat may include two layers of the woven slit film polypropylene geotextile material.

[022] Turning now to the figures, FIG. 1 depicts a cross-section of an exemplary stormwater chamber 20 having side base flanges 28 positioned on a floor 34, with a multi-layer mat 18 positioned on the floor 34 under the stormwater chamber 20. Multi-layer mat 18 may include a plurality of layers of water permeable material underlying the arch span of stormwater chamber 20 and defining a lower bound of an interior 30 of the chamber. In one embodiment, floor 34 is composed of water-permeable aggregate, such as stone aggregate. Stone aggregate most commonly comprises crushed stone or gravel; however, the term as used herein shall comprehend any water permeable particulate medium. The spaces between adjacent stormwater chambers and regions above the stormwater chambers may also comprise stone aggregate.

[023] As described above, in one embodiment, stormwater chamber systems may comprise a multiplicity of parallel rows of chambers connected end-to-end.
Thus, FIG. 1 depicts stormwater chamber 20 being flanked by another stormwater chamber 20A, suggestive of the other rows that may be present. In one embodiment, stormwater chambers 20 and 20A may be Stormtech stormwater chambers, Model SC310 or Model SC740, both of which are made of injection molded thermoplastic and sold by Stormtech LLC, Wethersfield, Connecticut.

[024] In one exemplary stormwater system, a primary row subsystem (e.g., Isolator row) first receives stormwater and captures a large proportion of the suspended solids, to keep the suspended solids from being distributed to the rest of the system (e.g., adjacent rows of chambers). In one embodiment, the primary row may have a circumscribing layer of filter fabric surrounding a top of the chambers arranged in the primary row. The primary row may be configured to filter and direct stormwater into stone aggregate below the chamber and, if desired, into multiple other chambers 20A.
For the construction and function of a system having an Isolator -type primary row of chambers, see U.S. Pat. No. 6,991,734 of Smith, the disclosure of which is incorporated herein by reference. While the present disclosure describes the use of a multi-layer mat in relation to a primary row of chambers, multi-layer mats consistent with the present disclosure may be used with any chambers of other kinds of stormwater systems;
and also with chambers having cross sections other than those shown in the present disclosure.

[025] During use, stormwater first flows into the interior 30 of stormwater chamber 20. Then, under the influence of gravity, the water flows downwardly and sideways. In one embodiment, stormwater chamber 20 may include perforations (not shown) in sidewalls of the arch, for allowing stormwater to exit the interior 30 laterally.
Stormwater may also exit the interior 30 through multi-layer mat 18.
Stormwater in stormwater chamber 20 may therefore flow into interstices of the stone aggregate surrounding stormwater chamber 20. Eventually, stormwater may flow into the soil in which the stormwater system is contained, or by means of a conduit or outlet to a discharge point, such as a pond or stream.

[026] Multi-layer mat 18 may include a plurality of layers and, in one exemplary embodiment, may include three layers. As shown in FIG. 2, in one embodiment, multi-layer mat 18 may include two adjacent lower filtering layers 24, which lie on or in close proximity to the stone aggregate floor 34 of the chamber interior space; and an upper protective layer 26 which lies on top of the lower filtering layers 24. Any or all of the layers may be formed from plastic or other water resisting material, and include a multiplicity of openings, or pores, which make the multi-layer mat water permeable. In one embodiment, lower filtering layers 24 may be made from a woven slit film polypropylene (PP) geotextile material, while upper protective layer 26 may be made from a nonwoven high density polyethylene (HDPE) netting material.

[027] The function of filtering layers 24 may be to catch fine suspended solids, and to diminish the propensity for the suspended solids to fill the interstices in the stone aggregate below stormwater chamber 20 over time. The function of protective layer 26 may be to protect filtering layers 24 from mechanical disruption, as can occur during water jet cleaning or other modes of cleaning. Protective layer 26 may be a sturdy material having coarse openings compared to the openings of filtering layers 24. The material of protective layer 26 may have openings that are large enough to allow smaller suspended solids, such as sand and dirt, to pass through protective layer 26.
However, the mesh size of protective layer 26 may be fine enough to protect filtering layers 24 from snagging or damaging engagement with mechanical cleaning devices sliding along the floor of the chamber space, and to resist the forces of water jets as they blast loose settled debris. Thus, the average size of the pore openings, or the porosity, of the top protective layer 26 is larger than the average size of the pore openings, or the porosity, of the lower filtering layers 24.

[028] In one embodiment, the upper protective layer 26 provides a filtering function in combination with the lower filtering layers 24. While, in an exemplary case, the average opening sizes of the protective layer 26 are several times larger than the average opening sizes of the filtering layers 24, the protective layer 26 may still block, or filter, larger objects that might mask and reduce the flow capacity of the filtering layers 24. For instance, the protective layer 26 may stop flat sheet matter, such as paper and leaves from coming in intimate contact with the filtering layers 24. Thus, a portion of the water-borne debris will be captured on the top protective layer 26; and a portion of the debris which passes through the top layer will be captured on the lower filtering layers 24. In one embodiment, the two filtering layers 24 may nominally have the same porosity as each other. Even when the filtering layers 24 have the same pore size, experimental data shows a significant increase in the capture of the finer suspended solids is achieved with two filtering layers, when compared to one filtering layer.

[029] In one embodiment, protective layer 26 and the filtering layers 24 may be fastened to each other by adhesives, mechanical fasteners, stitching, and/or welding (when compatibility of the materials allows). Fastening the layers to each other can make installation of the multi-layer mat 18 more convenient and can provide an overall stronger composite mat structure which resists the forces associated with installation, use, and cleaning.

[030] While filtering layers 24 are pictured as lying on the aggregate floor 34, in general, the filtering layers 24 may be spaced apart from the floor surface.
Likewise, spacers may be placed between aggregate floor 34, filtering layers 24, and/or protective layer 26. In one embodiment, the layers may be discrete pieces of material having lateral dimensions that allow the discrete pieces of material to fit within the interior edges of the base flanges 28. Alternatively, one or more layers may be sufficiently wide to extend under base flanges 28, so the weight of each stormwater chamber 20 helps to hold the layers in place.

[031] In yet another embodiment, the layers may be curled up at opposing ends 18A and 18B, as shown in FIG. 3, for connection to chamber 20. FIG. 4 depicts another perspective view of a stormwater chamber 20 between adjacent stormwater chambers 20A. As shown in FIG. 4, multi-layer mat 18 may be curved up at opposing ends and fastened to an inside surface of stormwater chamber 20. FIG. 5 shows how multi-layer mat 18 may be fastened to an inside surface of stormwater chamber using one or more fasteners 36 (shown in detail cut-out). Fasteners 36 may be any suitable device known to those of skill in the art, including but not limited to nails, screws, tacks, staples, push-pins, anchors, and/or hooks.

[032] In one exemplary embodiment of multi-layer mat 18, the one or more filtering layers 24 may include a non-woven material, such as a geotextile;
and the upper protective layer 26 may be a woven net-like material of orthogonal welded ligaments. In one embodiment, the lower filtering layers 24 may be formed from a non-woven material conforming with standard AASHTO M288 Class 2 of American Association of Highway Transport Officials; and the protective layer 26 may be formed from a woven material conforming with standard AASHTO M288 Class 1.

[033] One exemplary material for the lower filtering layers 24 is Geotex 315ST
woven polypropylene geotextile (Propex Inc., Chattanooga, Tennesee).
Functionally, the geotextile may have an average opening size of about 0.425 mm, more nominally about 0.5 mm. An exemplary material for upper protective layer 26 may include Skaps Transnet geonet 220 comprised of 220 mil thick high density woven polyethylene resin (SKAPS Industries, Commerce, Georgia), which has an average opening size of about 0.03 square inches (equivalent to a diameter of about 0.195 inch (3.8 mm)).
Thus, the nominal opening size of the protective layer 26 may be about 9 times larger than the nominal opening of filtering layers 24. Table 1 discloses other exemplary materials that may be used in substitution of the foregoing examples.

Table 1: Exemplary materials useful for layers 24 and 26.

AASHTO M288 Class 2 AASHTO M288 Class I
Source Non-Woven, for Layers 24 Woven, for Layer 26 Belton Industries Beltech 977 Carthage Mills FX-60HS, FX-80HS FX-66 GSE Lining NW6, NW8 Technology MacTex MX245, MacTex Maccaferri MX275 Pavco-Amanco NT3000M, NT4000M TR4000 Geotex 651, Geotex 861, Geotex 315ST, Geotex Propex Geotex 2x2HF, Geotex 250ST

601, Geotex 701, Geotex 801 SKAPS Industrites GT 160NW, GT 180NW W315 Mirafi 600X, Filterweave 403, Filterweave Tencate Mirafi Mirafi 160N, Mirafi 180N 404,Geolon HP570, Geolon HP665, Geolon HP770 TNS Advanced R060 , R070, R080, R100 Tech.
US Fabrics US 205NW, US 160NW US 315 TABLE 2: EXEMPLARY PP GEOTEXTILE PROPERTIES FOR FILTERING LAYERS
24.

Property Test Method English Metric Physical / Mechanical Thickness ASTM D 5199 20 mils 0.5 mm Grab Tensile Strength ASTM D 4632 315 lbs 1,400 N
Grab Tensile Elongation ASTM D 4632 15% 15%
Wide Width Tensile ASTM D 4595 175 lbs/in 30.6 kN/m Trapezoidal Tear ASTM D 4533 120 lbs 530 N
Mullen Burst ASTM D 3786 600 psi 4134 kPa Puncture Strength ASTM D 4833 125 lbs 555 N
UV Resistance (at 500 hrs) ASTM D 4355 70% 70%
Hydraulic 70 US Std Apparent Opening Size ASTM D 4751 Sieve 0.212 mm Permittivity ASTM D 4491 0.05 sec-1 0.05 sec-1 Water Flow Rate ASTM D 4491 4 gpm/ft2 I/min/m2 Table 3: Exemplary HDPE Geonet Properties for Protective Layer 26.
Property Test Method English Metric Physical / Mechanical Thickness ASTM D 5199 0.125 in 3 mm 12,400 Tensile Strength at Yield ASTM D 638 1800 psi kPa Tensile Elongation ASTM D 638 600% 600%
UV Resistance (at 500 hrs) ASTM D 4355 90% 90%
Hydraulic Apparent Opening Size ASTM D 4751 0.03 in2 19 mm2 [034] As a result of the use of protective layer 26 disposed above one or more filtering layers 24 having, for example, the properties listed above, filtering layers 24 may be protected when debris is removed from a stormwater chamber provided with multi-layer mat 18. For example, when a jet and/or siphon at the end of a hose is pushed or pulled along the length of each chamber or string of chambers, protective layer 26 may prevent filtering layers 24 from being pushed, snagged, torn, gathered, or otherwise disrupted from laying on the aggregate that defines the bottom of the chamber interior.

[035] It will be appreciated that the above described materials, mechanical properties, hydraulic properties, and performance estimates are merely exemplary in nature, and are not to be construed as limiting.

[036] The many features and advantages of the present disclosure are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the disclosure which fall within the true spirit and scope of the disclosure. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.

Claims (16)

1. A method for receiving and dispersing stormwater underground, the method comprising:

directing stormwater bearing debris from a source into an interior of one or more chambers buried within water-permeable aggregate, wherein the one or more chambers are supported on a floor of the water-permeable aggregate by opposing side base flanges of the one or more chambers, and the floor defines a lower boundary of an interior space of the one or more chambers;

filtering a portion of water-borne debris from stormwater flowing toward the floor, by using one or more filtering layers; and protecting the one or more filtering layers from damage during a cleaning process, by using a water permeable protective layer;

wherein the one or more filtering layers have a finer porosity than a porosity of the protective layer.

2. The method of claim 1, further comprising retaining one or more of the filtering and protective layers between the base flanges of the chamber and the water-permeable aggregate floor.

3. The method of claim 1, further comprising attaching the one or more filtering layers to the protective layer.

4. The method of claim 1, further comprising filtering the stormwater using two similar filtering layers.

5. The method of claim 1, further comprising fastening one or more of the protective layer and one or more filtering layers to an inside of the chamber.

6. The method of claim 1, further comprising fastening the protective layer and one or more filtering layers to an inside of the chamber.

7. The method of claim 1, wherein the water-permeable aggregate is a stone aggregate.

8. The method of claim 1, further comprising arranging a plurality of the one or more chambers in an array of parallel columns of chambers connected end-to-end.

9. An apparatus for receiving and dispersing stormwater underground, wherein the apparatus accumulates debris carried by the stormwater received, the apparatus comprising:

an arch-shaped cross-section chamber buried in stone aggregate, the chamber having base flanges supported on a stone aggregate floor, the chamber having an interior space bounded by the floor; and a mat connected to the chamber and positioned over the floor, the mat having:
one or more filtering layers disposed in proximity to the stone aggregate floor for filtering and retention of a portion of debris carried by the stormwater; and a protective layer disposed above the one or more filtering layers, for both filtering debris and for protecting the one or more filtering layers during a cleaning process;

wherein the first layer has an average pore size larger than the average pore size of the second layer; the first layer allowing a portion of debris carried in the water to flow with the water to the second layer.

10. The apparatus of claim 9, wherein the one or more filtering layers includes two filtering layers.

11. The apparatus of claim 9, wherein the one or more filtering layers have openings of average size that is less than an average size of openings in the protective layer.

12. The apparatus of claim 9, wherein the protective layer and one or more filtering layers are connected to each other.

13. The apparatus of claim 9, wherein an average pore size of the protective layer is about nine times larger than an average pore size of the one or more filtering layers.

14. The apparatus of claim 9, wherein an average diameter of pores in the protective layer is about 0.5 mm.

15. The apparatus of claim 9, wherein the one or more filtering layers are made from a slit film polypropylene filter geotextile; and the protective layer is made from a high density polyethylene geonet.

16. The apparatus of claim 9 wherein the one or more layers of the mat underlies the opposing side base flanges of the chamber.