Abstract:
A flow limiting inlet structure is designed to collect water or other fluids in a pool above grade, and to provide improved capture of sediments and surface pollutants such as oils and greases in the pool, while regulating the flow of water or other fluids during discharge into an outlet pipe. In a conventional storm water detention basin a vertical cylindrical discharge structure can be used to regulate the basin water depth and discharge flow rate of storm water out of the detention basin, in conjunction with the use of a specially designed baffle system that prevents the release of any greases or oils floating on the water surface while capturing any floating trash or debris.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of pending U.S. application Ser. No. 10/692,507, filed on Oct. 24, 2003, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention is drainage management systems, more particularly, flow limiting inlet structures designed to collect water or other fluids in a pool above grade and to regulate water discharge, enabling the system to capture sediments and surface pollutants such as oil and grease in the pool before allowing, the collected water to discharge into an outlet pipe. 
     BACKGROUND OF THE INVENTION 
     Contaminated sediments, greases, and oils, and other pollutants collect on the ground during dry periods when little or no rainfall occurs. When a storm occurs after such a dry period, the accumulated pollutants are mobilized by storm water and get flushed into surface water drainage systems. The flushing of pollutants into such drainage systems is generally undesirable, particularly if the water or other fluids flowing through such drainage systems remain untreated before being discharged into a river, lake, or ocean. The occurrence of a storm after a dry period and the corresponding flushing of pollutants into drainage systems is often referred to as a “first flush” event. First flush events are particularly troublesome in industrial areas due to the types and amounts of pollutants that accumulate. 
     Because the effects of first flush events are undesirable, efforts have been made to limit such effects. A common way to do so is to allow storm waters to initially flow into a detention basin and to use a flow limiting stricture to control flow out of the detention basin. Such flow limiting structures include, among others, risers, trash racks, filters, and weirs. Such structures typically try to allow sediments to settle out, prevent the outflow of surface contaminants, or prevent the outflow of larger sized pollutants. 
     A concern in designing such flow limiting structures is that they should not allow flooding to occur, even if preventing flooding allows pollutants to escape. As a result, flow-limiting structures are typically designed to provide for “overflow” situations during which quantities of water in excess of the design first-flush storm are allowed to flow through the structure untreated if the incoming water volume exceeds the capacity of the system. In an attempt to help prevent overflow from occurring, some structures such as perforated risers are designed to permit a higher flow rate through an outlet as water levels rise. 
     Unfortunately, previously known flow-limiting structures do not always provide a solution that adequately balances the design goals of preventing flooding, allowing sediments to settle, preventing flushing of surface pollutants, and limiting peak discharge flow rates. As such, there is a need for new flow limiting structures such as are disclosed herein. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a flow limiting inlet structure designed to collect water or other fluids in a pool above grade, and to provide improved capture of sediments and surface pollutants such as oils and greases in the pool, while regulating the flow of water or other fluids during discharge into an outlet pipe. More particularly, the present invention is directed to the use of a conventional storm water detention basin, and the use of a vertical cylindrical discharge structure to regulate the basin water depth and discharge flow rate of storm water out of the detention basin, in conjunction with a specially designed baffle system that prevents the release of any greases or oils floating on the water surface while capturing ally floating trash or debris. 
     If a perforated discharge structure is used, the location and diameter of holes in the discharge structure can be varied to produce a wide variety of discharge flow rates so as to control the approach velocity of incoming storm water and promote complete settlement of suspended sediments. This system attenuates the peak storm water inflow rate and reduces the peak discharge flow rate as needed. Flow in excess of “first flush” volumes pass through the system untreated by entering the top of the discharge structure while concurrently flowing over a basin perimeter weir set at the same elevation. These larger storm volumes are not completely attenuated nor treated by the detention basin. 
     After a storm has passed, site staff can shovel out the collected sediment from the detention basin, washout all of the accumulated grease and oil, and in so doing make the system ready for the next storm event. 
     It is contemplated that the methods and systems disclosed herein are particularly well adapted for use in managing the quality of storm waters draining from industrial sites. However, it is also contemplated that the methods and systems disclosed herein will prove advantageous in other drainage and/or fluid control applications. 
     In one embodiment, the present invention comprises a storm water detention basin comprising a basin sized and positioned to accumulate storm water, an outlet, and a flow limiting structure impeding flow of water out of the basin through the outlet, the flow limiting inlet structure comprising: a set of one or more baffles adapted to hinder the flow of surface contaminants into the outlet; and a discharge riser adapted to control the discharge flow rate out of the basin to effectively capture sediment in the basin. In some such embodiments the set of one or more baffles are a tiered set of nested baffles wherein each baffle that is nested within another baffle is positioned at a lower height than the baffle it is nested within, and the baffles of the set of baffles overlap each other. This nested set of baffles is design to prevent the release of a water surface containing floating oils and greases, and has adequate nested baffle overlap to prevent the release of such oil and grease when the water surface is depressed passing through the baffle system. 
     In another embodiment the present invention comprises a flow limiting inlet structure comprising a set of one or more baffles adapted to inhibit the flow of surface materials through the baffle set, wherein the inlet area of the baffle set increases as fluid depth increases. 
     In another embodiment, the present invention comprises a flow limiting inlet structure comprising a discharge riser surrounded by a tiered set of nested baffles. In some such embodiments, each baffle that is nested within another baffle may be positioned at a lower height than the baffle it is nested within, and the baffles of the set of baffles may overlap each other. Such a flow limiting inlet structure comprising a discharge riser surrounded by a tiered set of nested baffles may also have a lower inlet area of a baffle of the set of baffles that is less than the non-overflow inlet area of the discharge riser. In some instances the difference may be great enough that the lower inlet area of a baffle of the set of baffles is less than half or even less than one third of the non-overflow inlet area of the discharge riser. 
     Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an illustration of a flow limiting input structure in a detention basin. 
         FIG. 1B  is a side view of the flow limiting input structure of  FIG. 1A . 
         FIG. 1C  is a cutaway side view of the flow limiting input structure of  FIG. 1A . 
         FIG. 1D  is a bottom view of the baffles and riser of the flow limiting input structure of  FIG. 1   a.    
         FIG. 2A  is a partial cutaway side view of the flow limiting input structure of  FIG. 1A  illustrating operation of the structure at a first fluid depth. 
         FIG. 2B  is a partial cutaway side view of the flow limiting input structure of  FIG. 1A  illustrating operation of the structure at a second fluid depth. 
         FIG. 2C  is a partial cutaway side view of the flow limiting input structure of  FIG. 1A  illustrating operation of the structure at a third fluid depth. 
         FIG. 2D  is a partial cutaway side view of the flow limiting input structure of  FIG. 1A  illustrating operation of the structure at a fourth fluid depth. 
         FIG. 3A  is a cutaway side view of a second flow limiting input structure. 
         FIG. 3B  is a bottom view of the flow limiting structure of  FIG. 4A . 
         FIG. 4  is a bottom view of the baffles and riser of an alternative embodiment of the flow limiting input structure of  FIG. 1   a.    
         FIG. 5  is a partial cutaway view of an alternative baffle set. 
         FIG. 6A  is a cutaway view of an alternative baffle. 
         FIG. 6B  is a cutaway view of an alternative baffle. 
         FIG. 7  is a cutaway side view of the input structure of  FIG. 1  providing reference numbers for various measurements. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1A , a flow limiting structure  100  is positioned in a detention basin  20  where basin  20  is partially bounded by basin bottom  21  and by basin perimeter weir  22 , and basin  20  includes an outlet  160 . Basin  20  contains sediment and surface pollutant containing water  10 , and structure  100  controls the flow of water  10  (or any other fluid in basin  20 ) out of basin  20  through outlet  160 . In preferred embodiments, weir  22  is adapted to spill water out of basin  20  when water  10  reaches a height sufficient to overflow stricture  100 . 
     As can be seen in  FIGS. 1A-1D , flow limiting structure  100  comprises a perforated riser  110  having holes  111  and opening  112  covered by hinged grate  113 , and a set of two nested and tiered baffles  120  and  130 , each baffle ( 120 ,  130 ) comprising lower edges ( 121 ,  131 ) forging lower openings ( 122 ,  132 ), upper edges ( 123 ,  133 ) forming upper openings ( 124 ,  134 ), and a set of support legs ( 125 ,  135 ), separating lower edges ( 121 ,  131 ), from a foundation  150 . Baffles  120  and  130  are tiered in the sense that the distance of separation between lower edges  121  and  131  differs between each of the baffles as do the heights of upper edges  123  and  133 . Baffle  120  is nested within baffles  130  in that baffle  130  at least partially surrounds baffle  120  and baffle  120  is positioned between baffle  130  aid riser  110 . Baffle  120 , in turn, surrounds riser  110 . Baffles  120  and  130  overlap in that upper edge  123  of baffle  120  is higher than lower edge  131  of baffle  130 , while lower edge  121  of baffle  120  is lower than lower edge  131  of baffle  130 . Structure  100  controls fluid flow into outlet  160  and outlet pipe  170 . 
       FIGS. 2A-2D  illustrate the flow input structure  100  of  FIGS. 1A-1D  as the structure operates to control flow of fluid  10  out of the basin through outlet  160 . In  FIG. 2A , fluid  10  has a depth D 1  at which the surface of fluid  10  is below lower edge  121  of baffle  120  and the lowest set of openings  111  in riser  110 . As such, at depth D 1  fluid  10  is prevented from flowing through outlet  160  by riser  110 . In  FIG. 2B , fluid  10  has risen to a level D 2  above edge  121  and the lowermost set of openings  111 . As such, fluid  10  is able to flow through flow paths Fl under baffle  120 , into riser  110 , and out outlet  160 . In  FIG. 2C , fluid  10  has risen to a level D 3  above lower edge  131  and above upper edge  123 . As such, fluid  10  is able to flow under baffles  120  and  130  and into riser  110  through the four lowermost sets of holes  111  in riser  110  via flow paths Fl-F 4 . In  FIG. 2D , fluid  10  has risen to a level D 4  above upper edge  131 , but just below the upper edge of riser  110  that defines opening  112 . As such, fluid  10  is able to flow both over and under baffles  120  and  130  into riser  110  through all the sets of holes  111  in riser  110  via flow paths F 1 -F 5 . 
     It should be noted that flow paths F 1 -F 5  are provided for illustrative purposes only. The actual flow paths through the baffles and riser will likely vary based on a number of factors such as the size, relative spacing, and positions of the holes, risers, and baffles as well as the number and shape of the baffles. 
     Many of the features of structure  110  are equally applicable to side-discharge structures as illustrated in  FIGS. 3A and 3B  as they are to bottom discharge structures as shown in  FIGS. 1A-1D . In  FIGS. 3A-3B , a flow limiting input structure  300  is used to control flow of fluids through side outlet  310  where the structure comprises tiered and nested baffles  320 ,  330 ,  340 ,  350 ,  360 , and  370 . As shown in  FIGS. 3A and 3B , flow limiting input structures as disclosed herein (whether for side or bottom discharge outlets) need not comprise any riser or other flow control device other than the set of nested and tiered baffles. However, although the sizes, positions, and relative spacing of the baffles in a baffle set could be used to control flow rate of fluid into an outlet, it is preferred that a riser or other flow control apparatus be used in conjunction with the baffle set to provide simpler flow rate control, and to provide more options in regard to baffle design. In preferred embodiments, the baffles of a baffle set will be spaced sufficiently far from each other, from the discharge riser, and from the foundation that flow rate through the outlet  160  is substantially, if not totally, determined by any discharge riser or other flow rate control apparatus used in conjunction with the baffle set. 
     If one compares structure  300  of  FIGS. 3A-3B  with structure  100  of  FIGS. 1A-1D , it is apparent that the number of baffles in the baffle set of structure  300  is greater than the number of baffles in the baffle set of structure  100 . The number of baffles will vary between different embodiments, but preferred embodiments will comprise at least two baffles, while more preferred embodiments will comprise three or more baffles. It is contemplated that increasing the number of baffles allows for reduced spacing between baffles and between the innermost baffle and any riser, with a corresponding decrease in surface contaminants that may make it into structures  100  and  300  as being on a surface of fluid  10  inside the perimeter of a baffle as the fluid level rises from below to above the lower edge of the baffle. As such, a design comprising a single baffle sized large enough to allow for maximum flow thorough the outlet may allow larger amounts of initial leakage of surface contaminants at low fluid levels and is the less preferred than designs that utilize a larger number of baffles. 
     Such a comparison between structure  300  and structure  100  also makes it apparent that the shape of baffles differs between structure  100  and structure  300 . When viewed from the top or bottom, the shape of the baffles of a particular embodiment may be square (see  FIG. 1D ), circular (see  FIG. 4 ), semi-circular (see  FIG. 3B ), elliptical, or any other shape. Although the embodiments shown have baffle sets wherein every baffle of the set has substantially the same shape as every other baffle, less preferred embodiments may have any combination of similarly or differently shaped baffles within a baffle set.  FIGS. 3A and 5  illustrate that baffle shapes may vary in other ways as well. In  FIG. 3A , one baffle of the set forms a hood over the other baffles, while in  FIG. 5  each baffle forms a partial hood that can help direct flow from higher baffles or from overflow into the structure. Moreover, baffles need not be elongated such that their height exceeds their width as shown in the pictured embodiments. As such, baffles may comprise any shape so long as they function to minimize the amount of surface contaminants that flow through the flow limiting input structure they are a part of. 
     Although the baffles shown in  FIGS. 1A-1D  comprise support legs ( 125 ,  135 ), other embodiments may utilize different mechanisms for providing baffle support. Any mechanism that supports the baffles while still allowing them to function to prevent flow of a majority of surface contaminants through the inlet structure may be used. As an example, baffles may hang from a bracket or other structure that couples them to a discharge riser, or may all be coupled to one or more baffles that provide support to any other baffles. Another example can be seen in  FIG. 3A  where the baffles  320 - 370  may be coupled directly to the side wall that outlet  310  pass through. Yet another option similar to the use of support legs is to use outer baffles that are self supporting but have slots, perforations, or some other feature that permits water to flow through the lower portions of the baffles such as the baffles of  FIGS. 6A and 6B . 
     It is also contemplated that instead of using “short” baffles (i.e. baffles that don&#39;t extend to the top of the structure), one or more of the baffles, particularly the innermost baffle ( 120 ,  320 ) may be extended upwards but have the extended portion comprise perforations or slots, or otherwise be adapted to allow fluid to flow through such extended portions. It is contemplated that the use of a partially perforated inner baffles would minimize or eliminate the need for any central discharge riser as the functionality of such a riser would be provided by the upper portions of the interior baffles. 
     Gaps between baffles and any gap between the innermost baffle and a riser, may include strainers, filter, vanes, or other fluid control mechanisms. It is contemplated that the use of filters in the gaps between baffles may prove advantageous as at least some materials captured in such filters may fall free once fluid levels drop below the height of the filter. It also is contemplated that the use of vanes or other fluid control mechanisms may be advantageously used to improve flow through the flow limiting input structure. Some input structures may be designed to include such screens or filters and also to facilitate the flushing of such screens of filter, possibly without requiring fluid levels to drop below filter heights. 
     As illustrated by  FIGS. 2A-2D , the number of flow paths through the set of baffles ( 120 ,  130 ) increases as the depth of fluid  10  increases. The term “flow path” is used herein to denote any path through which fluid can flow for the current level of fluid. As such, there are no “flow paths” through structure  100  in  FIG. 2A  as the riser prevents flow of fluid  10  through the structure at a depth/head D 1  (measured between the surface and the top of base  150  which defines the top of outlet  160 ). At a depth D 2 , structure  100  comprises flow paths F 1  under baffle  120  and into the lowermost set of holes  111 . At depth D 3 , structure  100  comprises additional flow paths F 2 -F 4 , and at depth D 4  also includes flow path F 5 . The flow paths through the baffle set ( 120 ,  130 ) do not necessarily increase at the same rate as the flow paths through riser  110 , or structure  100 , as the flow paths through the baffle set depend on the number, size, and relative positions of the baffles in the set. In contrast, the number of flow paths through structure  100  depends on both the number of flow paths through the baffle set and the number of flow paths through riser  110 . 
     In conjunction with the increase in the number of flow paths, the total inlet area of the baffle set ( 120 ,  130 ) and structure  100  increases as the depth of fluid  10  increases. The term “total inlet area” is used herein to denote the sum of the areas of the various openings between the exterior and interior of structure  100  through which fluid can flow for the current level of fluid. In the embodiment shown, this equates to the sum of the areas of the various openings between the interior and exterior of the baffle set ( 120 ,  130 ) for non-overflow levels. At level D 1 , the total inlet area is zero. At level D 2 , the total inlet area is equal to the area of opening  122 , which is approximately equal to the area defined by lower edge  121  minus the cross sectional area of riser  110 . At level D 3 , the total inlet area is equal to the area of opening  122  plus the area of opening  113 . At level D 4 , the total inlet area is equal to the area of openings  122 , plus the area of opening  113 , plus the area of opening  134 . 
     The actual sizes and positions of the baffles will vary between embodiments. However, referring to  FIG. 7 , in preferred embodiments baffles should overlap (i.e. B 22 &lt;BH 1 ) and should be nested (BR 1 &lt;BR 2 ) such that the higher baffles ( 130 ,  430 - 470 ) are outermost in order to prevent flow of surface contaminants out of the detention basin. Although many embodiments may have baffles of similar dimensions (such as having B 11  be approximately equal to B 21 ), it is contemplated that the relative heights of the upper and lower edges of adjacent baffles is much more relevant to proper operation that the sizes of the baffles used. In addition to being higher than the lower edges of outer baffles (BH 1 &gt;B 22 ), the top edges of inner baffles ( 120 ,  420 - 460 ) in preferred embodiments will be lower (BH 1 &lt;BH 2 ) than the top edges of outer baffles ( 130 ,  440 - 470 ) to provide additional access to the upper portions of any riser. In preferred embodiments, the lower edges of outer baffles will be higher than the lower edges of inner baffles (B 22 &gt;B 12 ) in order to spread flow paths across the length/height of the inlet structure rather than concentrating them at the bottom. Spreading the flow paths decreases that amount of fluid flowing into the structure near its base and minimizes the amount of sediment pulled into the structure by such bottom flows. Spreading flow paths along the structure also help to prevent the spacing between the bottoms of the baffles and the foundation from becoming a limiting factor on the flow rate of the structure. As sizes and positions may vary, different embodiments may have different values for B 11 , B 12 , B 21 , B 22 , BH 1 , BH 2 , BB, BR 1 , BR 2 , and R 1 -R 6 . 
     Riser  110  is preferred to be an elongated, perforated cylinder with a vertical central axis, and may be tall enough to extend higher than the highest baffle surrounding it. However, if it has an overflow inlet that is positioned below the top edge of the outermost baffles, the baffles can still act to prevent flow of surface contaminants into riser  110  and orifice  160  even when fluid levels are sufficiently great as to cause overflow of riser  110 . 
     In less preferred embodiments, riser  110  may not be perforated, may be substantially shorter than the baffles surrounding it, or may be eliminated altogether. In less preferred embodiments, the orifices of riser  110  may be positioned above the highest surrounding baffle if surface filtering of contaminants is less desired at higher fluid levels. Similarly, riser  110  may permit fluid that flows under all the baffles of the baffle set to flow into outlet  160  if surface filtering of contaminants is less desired at lower fluid levels. Although a cylindrical shape is preferred, any riser used may be elliptical, polygonal, irregular or have some other shape. Although holes providing passage from the exterior to the interior of riser  110  are preferred, other embodiments may use slits, rectangular orifices, filtered openings, or some other mechanism to control the flow of fluid from the exterior of riser  110  to its interior. Riser  110  may, in some embodiments, be replaced with some other type of flow control apparatus. 
     In preferred embodiments the size and positions of the holes (or other inlets) into riser  110  will be sufficient to allow as much fluid to flow into riser  110  as can flow through outlet  160  such that overflow flows through the top of the riser don&#39;t increase the throughput of the riser unless fluid is prevented from flowing into one or more of the holes in the riser. Similarly, the baffles of the baffle set at least partially surrounding the riser and/or outlet will be sized and positioned such that the maximum amount of fluid that can be handled by the riser and/or outlet flows through the baffle set without having to overflow the baffle set. 
     In preferred embodiments the baffles and riser will comprise an open top to handle overflow conditions that may arise from large quantities of fluid accumulating in the detention basin whether from a large storm, clogged inlets in the input structure, or some other reason. 
     However, less preferred embodiments may have riser and/or one or more baffles that are closed on top. 
     In the embodiment shown, riser  110  comprises a hinged grate  113  that helps prevent objects from flowing into riser  110  during overflow conditions. However, other embodiments may not have any similar type of mechanism, or may use a mechanism other than a hinged grate. In some embodiments, a grate or similar mechanism may be used to filter baffle overflows as well with such grates being used in conjunction with or in place of grate  113 . 
     It is contemplated that the various components of flow limiting inlet structures as disclosed herein may comprise different materials or combinations of materials. The actual choice of materials will likely be determined based on the conditions a structure is expected to have to endure, and the desired life of the structure. In preferred embodiments, flow limiting inlet structures will be constructed of durable and W resistant materials. 
     Thus, specific embodiments and applications of storm water control basins and flow limiting inlet structures have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. As an example, although particularly well adapted for storm water control, the apparatus disclosed herein can be applied equally well to other fluid control applications where settling of sediment and/or filter of surface materials is desired. As an example, fluid accumulating in a detention basin may be the result of a container being drained or a surface being washed rather than a storm. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.