Abstract:
A catch basin retrofit that allows stormwater to be diverted from an existing storm sewer to an alternative stormwater management practice (SMP), while maintaining functionality of the catch basin as an overflow device for the alternative SMP.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a division of U.S. patent application Ser. No. 13/691,869, filed Dec. 3, 2012, the entirety of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of stormwater management. More particularly, the present invention is an adaptation to existing conventional stormwater infrastructure to retrofit for an alternative stormwater management practice (SMP). The present invention is particularly applicable where more modern “green infrastructure” technologies are being incorporated into existing urban drainage systems. 
       BACKGROUND OF THE INVENTION 
       [0003]    Urban stormwater management has historically involved collection of rainwater and conveyance via piping either directly to receiving waters or through via wastewater treatment plants (WWTPs). In dozens of cities in the United States such conveyance has occurred through combined sewer systems (CSSs), which convey both stormwater and sewage to WWTPs. Such CSSs are typically equipped with overflow devices that allow discharge directly to receiving waters from the sewer system when the sewer capacity is exceeded. Such combined sewer overflow (CSO) events contain not only stormwater but also untreated human and industrial waste, toxic materials, and debris. They are a major water pollution concern for the approximately 772 cities in the U.S. that have these CSSs. 
         [0004]    Many communities, including New York, N.Y.; Philadelphia, Pa., Kansas City, Mo. and Syracuse, N.Y. are implementing green infrastructure (“GI”) techniques. GI is an approach that communities can choose to maintain healthy waters, provide multiple environmental benefits and support sustainable communities. Unlike single-purpose gray stormwater infrastructure, which uses pipes to dispose of rainwater, green infrastructure uses vegetation and soil to manage rainwater where it falls. By weaving natural processes into the urban constructed environment, green infrastructure provides not only stormwater management, but also flood mitigation, air quality management, and more. It is important to note that GI is a volume-based approach to stormwater management, not typically amenable to managing peak flows associated with storm events. Thus, where GI is being incorporated into urban infrastructure, it is usually required by the locality to incorporate an overflow outlet to provide for drainage during extreme events. 
         [0005]    A component of conventional “gray” stormwater management systems for conveying street runoff to sewer systems are often street side catch basins  1  an example of which is depicted on  FIG. 1 . As will further be seen in  FIG. 1  these systems consist of an underground constructed sump  2  covered by a traffic-rated frame and grate  3  an outlet pipe  4  connected to a sewer system. Stormwater enters the catch basin via gravity either as sheet-flow from the street, or is conveyed along the adjoining curb  5  as can be seen in FIG,  1 . An example of the prior art frame and grate assembly  3  is depicted on  FIG. 2 . In  FIG. 2 , the assembly typically consists of a traffic-rated grate  6  that allows stormwater to enter the catch basin with the slats of the grate serving to screen the waters of “floatables” (i.e. large floating materials) that would otherwise enter the catch basin. The slats of the grate are directed orthogonal to the direction of traffic, which in combination with its construction to meet vehicle traffic standards, allows vehicular traffic to pass over safely and without damage to the device. The grate is set inside a compatible, traffic-rated frame  7 , as shown in  FIG. 2 , that positions and mounts the assembly to the catch basin sump and the surrounding road and curb. Because the device operates by gravity, the catch basin is typically positioned at a locally minimum elevation in the road segment or city block. 
         [0006]    A common GI technique to managing street runoff is through the use of street-side bioretention or tree boxes, as is depicted in  FIGS. 3 and 4 . These techniques usually require the use of constructed curb inlets, as shown in  FIG. 5 , consisting of transitions  8  from granite curbing  9  to form an opening in the curb  9  that allows water from the street  10  to enter the GI measure located on the opposite side of the curb  9 . The GI measure is also typically equipped with overflow devices to allow storm events to be diverted from the GI measure to the storm sewer system. Where these techniques are being adapted to existing urban drainage conditions, curb inlets and overflow devices are necessarily constructed as retrofits to the existing infrastructure. Construction of such overflow devices is typically a costly, invasive endeavor involving setting and plumbing of pre-cast or other manufactured overflow catch basins, plumbed into existing sewer systems located in the public street or right-of-way as discussed below. 
         [0007]    Because, as discussed above, the location of stormwater catch basins are configured at low points in the streetscape in order to effectively capture stormwater runoff via gravity, retrofit curb inlets might be positioned on each side of the existing catch basin. This design allows effective capture of flow along the curbline  11  and  12  to the existing catch basin as is exemplified in  FIG. 6 . As discussed above, a mechanism for managing overflows is a necessary component of these GI measures and this is accomplished under this curb inlet configuration by maintaining the existing streetside catch basin in place so that water may back up and out of the bioretention area  13  into the catch basin during extreme storm events. This configuration does not, however, optimize stormwater collection as water that routes directly to the plane of the catch basin from the street  14  (i.e. not along the curbline) will continue to enter the catch basin and thus the sewer during rain events. 
         [0008]    An alternative design involves the decommissioning and replacement of the existing catch basin with a curb inlet. This configuration effectively captures all runoff (for purposes of this invention, runoff, storm-water runoff and street runoff will be used interchangeably as would be understood by those skilled in the art) to the existing catch basin, up to the retentive capacity of the SMP, but a new overflow structure is required to accommodate runoff exceeding design events. An example of this prior art is shown on  FIG. 7 . Such overflow structures are often precast structures  15  equipped with a slotted opening  16  serving as the overflow entry weir, which must be plumbed into the existing storm sewer  17  system with underground pipes  18 . 
       SUMMARY OF THE INVENTION 
       [0009]    While the aforementioned prior art catch basin designs and associated collection frames and grate fulfills certain objectives and requirements, a need exists for a more efficient, less expensive means for retrofitting such existing catch basins/rack and grate systems for adoption of alternative SMPs, particularly as it relates to GI. In one aspect, the current invention seeks to solve the problems associated with the prior art by utilizing a rack and covered grate assembly that will effectively divert runoff to a GI measure through a common curb inlet structure while allowing the existing catch basin to serve as an overflow device, and that also screens debris from the catch basin as effectively as the replaced system. In one aspect, the benefit of the current invention is the avoided cost of the dedicated additional overflow structure and the greater efficiency of collection of the curb inlet. 
         [0010]    In the various figures, the prior art and SMP/GI technologies are illustrated as well as the exemplary features of the invention are demonstrated so that the detailed description that follows may be better understood, and that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. In no way should the following figures and examples limit the scope of the invention as would be understood and appreciated by those skilled in the art. It will be understood that the aforementioned references are incorporated by reference. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0011]      FIG. 1  shows a cross sectional view of a typical urban street side catch basin with associated horizontal rack and grate assembly. 
           [0012]      FIG. 2  is a plan view of a detailed drawing of a catch basin frame and rack assembly. 
           [0013]      FIG. 3  shows a cross sectional view of a curbside bioretention area that might be used for management of runoff from an urban roadway. 
           [0014]      FIG. 4  is an exemplary representation of a “tree box,” with a similar function for stormwater management. 
           [0015]      FIG. 5  is a cross sectional view of a typical curb inlet used to divert runoff to street/curbside SMP. 
           [0016]      FIG. 6  is a plan view of a possible curb inlet configuration retrofitted around an existing stormwater catch basin. 
           [0017]      FIG. 7  is a profile view of the prior art pre-cast concrete overflow structure. 
           [0018]      FIG. 8  is an exploded, axinometric representation of the catch basin and diversion assembly, including trash screen, cover plate and structural frame as envisioned by the current invention. 
           [0019]      FIG. 9  is a plan view of the exemplary invention as installed. 
           [0020]      FIG. 10  is a profile view of the exemplary invention oriented along its longitudinal axis. 
           [0021]      FIG. 11  is a profile view of the exemplary invention oriented along its lateral axis. 
           [0022]      FIG. 12  is a profile view illustrating a grate and cover of an exemplary stormwater diversion and overflow device as appearing to an observer looking from an SMP toward the street. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIG. 8  shows an exemplary embodiment of a stormwater diversion and overflow device. An exemplary assembly of the diversion and overflow device generally consists of a grate  19  and cover plate  20  set in a frame  21 . The grate  19  and frame  21  portion of the assembly is is typical of a stormwater collection and trash screen device, as represented in  FIG. 2  and as is readily understood by those skilled in the art, but with differences as discussed in the following passages. 
         [0024]      FIG. 9  depicts the frame  21  portion of the stormwater diversion and overflow device in plan view. With reference to  FIG. 8  and  FIG. 9 , it can be seen that on three sides, the frame  21  is similar to the prior art catch basin frame by the presence of angle members forming much of the strength of the assembly. Each angle member comprises a vertical member  22  and a horizontal member  23 . The invention is distinguished, in part, from the conventional frame by the absence of the vertical member  22  from the angle member forming the curbside edge  29  of the frame  21 . This portion of the frame  21  consists of the horizontal member  23  only. The absence of the vertical portion  22  of the curbside angle member will allow the stormwater diversion and overflow device to serve its overflow function by allowing flow to pass from the SMP to the existing catch basin beneath the cover plate of the invention via the curb inlet. 
         [0025]      FIG. 10  depicts the frame  21  portion of the stormwater diversion and overflow device in profile view. The invention members shown are the angle members  24  of the frame  21 , with the frame  21  oriented along the curbline. For purposes of clarity, one of skill in the art will understand that “curbline” and “curbside edge” can be used interchangeably. 
         [0026]      FIG. 11  depicts a second profile view of the frame  21  portion of the stormwater diversion and overflow device with the angle member  24  which has both a vertical member  22  and a horizontal member  23 , located on the street-side of the invention, and the angle member  25 , which has a horizontal member  23  but no vertical member  22 , located on the curbside edge  29  of the invention abutting the curb inlet. 
         [0027]      FIG. 12  shows the grate  19  and cover plate  20  of the stormwater diversion and overflow device in profile as it would appear to an observer looking from the SMP toward the street. With reference to  FIG. 8  and  FIG. 12 , the grate  19  and cover plate  20  are discussed. Similar to the frame  21  portion of the stormwater diversion and overflow device described above, the grate  19  of the stormwater diversion and overflow device is distinguished from a conventional grate by the absence of curbside lateral edge that would otherwise contact the curbside edge of the frame. Again similar to the adaptation for the frame  21  described above, the absence of a vertical edge parallel to the curb will allow the stormwater diversion and overflow device to serve its overflow function by allowing flow to pass from the SMP to the existing catch basin beneath the cover plate  20  of the invention via the curb inlet. Grate slats  27  oriented normal to the plane of the curb and extending over the lateral curbside edge  29  of the frame  21  will function as the trash screen, the functional equivalent of the grate associated with the conventional catch basin grate ( FIG. 2 ). The cover plate  20  of the stormwater diversion and overflow device extends beyond the grate  19  and frame  21  as necessary and over the curb inlet threshold in order to effectively divert runoff to the SMP. The runoff occurs as sheet-flow, which is important to the functionality of vegetated GI such as a bioretention area. 
         [0028]    Of course it will be understood by those skilled in the art that the slots in the grate can be of differing dimensions and spacing depending on the screening objectives, and that the frame, grate and cover can be constructed of different materials including but not limited to steel, galvanized steel, iron, galvanized iron, aluminum, or synthetic materials such as polyvinyl chloride (PVC). It will also be understood by those skilled in the art that cover can be extended varying lengths into the SMP and equipped with a drip edge or other appurtenances to effect proper flow or to dissipate energy as flow occurs from the invention to the SMP. It will further be understood by those skilled in the art that the invention may be of different sizes and configurations to adapt to the many various designs of stormwater catch basins whether they may be located directly under the stormwater frame and grate as described above, or adjoining the assembly, located adjacent to the street or lot. 
         [0029]    Referring back to the exemplary embodiment of  FIG. 8 , a catch basin diversion system  30  is depicted wherein an existing street-side catch basin  17  is retrofitted with the stormwater diversion and overflow device so that stormwater, instead of entering the catch basin  17  and then the public sewer system, is diverted via a cover plate  19  to an alternative SMP  34  (e.g., the bioretention area or tree box of  FIGS. 3 and 4 ). The cover plate  20  is situated above the level of the curb inlet ( FIG. 5 ) elevation by a grate  19  that both provides the opening to the catch basin  32  so that backflow to the catch basin  17  from the SMP  34  ( FIGS. 3 and 4 ) can occur during overflow events, and prevents floatables and other debris from entering the catch basin  17 . 
         [0030]    As conventional catch basin frame and grate assemblies are pre-manufactured in standard sizes, so would the claimed invention be fabricated to a number of common dimensions. The retrofit of existing installations would be performed by simply lifting out the existing assembly then placing the claimed invention while constructing the curb inlet.