Abstract:
A water quality apparatus and system utilized in permanent extended dry detention basins having an outlet control structure vertically mounted within a basin and a semi-round pipe (typically including gravel) attached to the forward edge. Typically, in this type of structure, debris flows over the top of the pipe and clogs the semi-round pipe and its outlet into the outlet control structure. The water quality apparatus is typically a pipe fixture having an outlet end that fits into the control structure and an inlet end comprising several perforated pipes (forming a series of holes) that protrude into the semi-round pipe. The holes allow the water to flow into the piping system and discourage any debris from flowing into the piping system and clogging it. As water flows through the gravel and into the perforated pipe, water can drain into the water quality apparatus and through the outlet control structure.

Description:
BACKGROUND 
     I. Field of the Invention 
     The present invention relates generally to the field of water quality enhancement and more particularly to an apparatus and system for permanent extended-detention basins to treat storm water runoff through gravitational settling. 
     II. Description of the Related Art 
     Permanent extended-detention basins and other types of detention/retention basins are used in order to impound and temporarily store storm water runoff for a specified period and discharge it through a hydraulic outlet structure to a down stream conveyance system. An extended-detention basin is usually dry during non-rainfall periods. These basins are necessary and designed to provide for one, or all of the following: a) water quality enhancement, b) channel erosion control and, c) downstream flood control. These basins are installed when impervious surfaces are created from new development activities, which include subdivisions, commercial sites and other new developments. Hydraulically speaking, these basins ensure that post-development will not be different from pre-development conditions. 
     A standard extended-detention basin includes inlet head-walls, which release storm water runoff to the basin from the storm water drainage pipes/system created by the installation of impervious surfaces for new development. Once the storm water runoff travels to the basin, it is detained and released through an outlet control structure at different design rates. The outlet control structure has an inlet side and an outlet side. The inlet side allows the impounded water to enter the outlet structure at different designed rates. These rates provide for water quality enhancement, channel erosion control, and downstream flood control. The outlet side consists of an outlet pipe, which allows the water to drain through the embankment dike. The typical extended-detention basin allows water to pass through the outlet structure up to the 100-year storm frequency (typically, 7.92 inches of rainfall in a 24 hour period). Once a 100-year storm frequency occurs an emergency spillway (indentation channel on and over the top of the embankment dike) is provided to allow the 100-year storm frequency to pass through the basin. 
     Extended-detention basins are typically designed to treat the first 1.2 inches of rainfall (also known as first flush) of storm water runoff by releasing it over a 24 to 48 hour period. In so doing, the quality of incoming storm water is improved through gravitational settling of the pollutants. To allow for this 24 to 48 hour draw down time water quality inlet (or orifice) must be sized to allow for the water to be detained for this period. The water quality volume is thus needed to calculate the correct size water quality orifice. The water quality volume is determined using a hydrological equation determined by local governmental regulations/standards. This equation factors in all newly impervious surfaces and takes the first 1.2 inches of rain from these surfaces to determine the water quality volume. Once the water quality volume is determined the correct size orifice can be calculated using a hydrological equation determined by local governmental regulations/standards. The water quality orifice is then protected from clogging by a measure determined by the designer/engineer. There have been attempts to filter the debris, including using filter stone surrounding filter fabric that surrounds an elongated perforated pipe which sits on the basin floor and is attached to the outlet structure. This type of filtration system risks becoming clogged and water is unable to penetrate the elongated perforated pipe and thus cannot enter the outlet structure for release. An additional failed method was to drill the correct size water quality orifice directly into the outlet structure and place a ½ round perforated pipe surrounded by gravel in front of it. Often, water would overflow the ½ round pipe thus bypassing the filtration gravel. Therefore, larger debris such as large sediment, branches, leaves, garbage, can clog the water quality orifice of the outlet control structure, requiring maintenance after every rain event. It is therefore necessary to prevent the water quality orifice from becoming clogged so the extended-detention basin function as it was designed and the first 1.2 inches of rain drains in 24–48 hours. 
     After the first 1.2 inches of rainfall channel erosion control becomes the next factor in storm water management. To protect against channel erosion the 1-year storm frequency (or typically 3.36 inches of rainfall in 24 hours) is detained for a 24-hour period. To achieve the 24-hour draw down time a channel protection inlet (or orifice) is sized to release 3.36 inches of additional rainfall. This channel protection orifice is calculated from the channel protection volume. The channel protection volume is calculated using a hydrological equation determined by local governmental regulations/standards. This equation factors in all the newly impervious surfaces and takes 3.36 inches of storm water runoff from these surfaces to determine the channel protection volume. Once the channel protection volume is determined the correct size orifice can be calculated using a hydrological equation determined by local governmental regulations/standards. The channel protection orifice is protected from clogging by a measure determined by the designer/engineer. With this invention system the channel protection orifice is protected by an elbow piece of pipe that angles down inside the perforated pipe. On the inside of the structure on this pipe is a screwed in end cap where the corrected sized channel protection orifice is drilled at the invert of the cap. A trash rack may also be used to protect this orifice from clogging if the orifice is drilled exactly sized into the outlet structure. 
     The next concern that extended-detention basins address is flood control. To control flooding the peak flows of the 2-year through 25-year storm frequencies must be controlled so the flows from the developed site do not exceed those from pre-developed conditions at the project boundary. To accomplish this task v-notched weir, different sized orifices, square weirs, or some other method may be incorporated into the outlet structure to accomplish flood control. 
     SUMMARY 
     In general, the invention features a water quality apparatus sits inside a 48-inch ½ round pipe if the outlet structure is box shaped or a 48-inch ¾ round pipe if the outlet structure is round shaped. This 48-inch % or ¾ pipe is perforated with ½ inch min. holes from top to bottom. The height of the pipe is determined by the water quality elevation height. Surrounding all sides of this pipe is a # 4 size stone; this stone comes to the top of the pipe and extends out with a width of 2 feet. The stone provides added filtration before the storm water runoff enters the perforated pipe and water quality apparatus. The water quality apparatus sits on a gravel or concrete base at the bottom of the basin. The water quality apparatus is grouted into place. The sizes of the pipes and stone described above are variable. 
     The above extended-detention basin system includes a water quality aspect, a channel protection aspect and a flood control aspect; each of which treats different storm frequencies but are all based on a 24-hour rainfall event. The water quality aspect engages first, followed by (if necessary) channel protection concluding with flood control all the way up to the 100-year storm frequency. 
     The invention features a water quality device/apparatus that is utilized in permanent extended-detention basins to treat the first 1.2 inches of storm water for a given area. This detention pond water quality apparatus and system aims to minimize maintenance while enhancing water quality and ease of inspection. By using the  ½ or  ¾ round perforated pipe and the #4 stone in combination with the water quality device, the likelihood of clogging is greatly reduced with minimal maintenance. 
     The water quality device/apparatus includes a pipe fixture with an outlet end which fits into the outlet control structure and an inlet comprising several perforated pipes (forming a series of holes) that protrude into the or ¾ round perforated pipe. The purpose of the holes is to allow water to flow into the piping system, but discouraging any debris from flowing into the piping system and clogging it. As the water flows through the gravel, through the ½ or ¾ perforated pipe, into the water quality device/apparatus, through the correct sized water quality orifice, into the outlet control structure, out through the outlet pipe, through the embankment dike and released from the basin. 
     In general, in one aspect, the invention features an apparatus, including a hollow main body having a longitudinal axis, a forward end and a rear end, a plurality of hollow inlet pipes connected to the main body at the forward end and a hollow outlet pipe connected to the rear end. 
     In one implementation, the main body further includes pipe bases connected to each of the plurality of pipes. 
     In another implementation, the apparatus further includes end caps connected to each of the pipes. 
     In another implementation, the apparatus further includes a pipe cap connected to the outlet pipe. 
     In another implementation, the apparatus is a single integral piece with perforations and a water quality orifice in the lower portion. 
     In another implementation, the pipe cap is in threaded engagement with the outlet pipe. 
     In another implementation, the pipe cap includes a water quality orifice. 
     In another implementation, the apparatus includes an upper and lower portion. 
     In still another implementation, the upper portion includes a series of holes. 
     In yet another implementation, the holes are located on the main body and the inlet pipes. 
     In another aspect, the invention features a water quality system located in a water detention basin, the system including a hollow outlet control structure, an outlet pipe connected to the outlet control structure, a water quality inlet orifice, a semi-round pipe basin (such as half-round pipe) connected to the outlet control structure and surrounded the inlet orifice, a water quality apparatus connected to the water quality inlet orifice, the apparatus including a main body having a series of holes on an upper portion of the body, a longitudinal axis, a forward end and a rear end, a plurality of inlet pipes having a series of holes on an upper portion of the pipes, the pipes being connected to pipe bases located on the main body at the forward end, an outlet pipe connected to the rear end and a pipe cap having a water quality orifice, the pipe cap being in threaded engagement with the outlet pipe. 
     In one implementation, the outlet pipe of the water quality apparatus is located within the outlet control structure. 
     In another implementation, the water quality apparatus can vary in hollow diameter. 
     In another implementation, the plurality of inlet pipes on the water quality apparatus are located outside the apparatus and inside the semi-round pipe basin. 
     In another implementation, the system further includes gravel located around and in contact with the semi-round pipe basin. 
     In another implementation, the semi-round pipe basis includes a series of perforations. 
     In another implementation, the system can be used to detain storm water and during non-rain events allow the base flow of a creek to flow through the system. 
     In another implementation, the system can be used to detain storm water and not built on a creek or stream. 
     In another implementation, the outlet control structure further includes a certain distance between the water quality apparatus and the start of the overflow weir. 
     In another implementation, the system further includes a channel protection pipe connected to the outlet control structure and located between the overflow weir and the water quality apparatus. 
     In another aspect, the invention features a water quality kit, including a water quality apparatus having an inlet portion and an outlet portion, the outlet portion being adapted to the connected to the water quality inlet orifice of a detention pond control structure, the apparatus including a hollow main body having a series of holes located on an upper portion of the main body, a longitudinal axis, a forward end and a rear end, a plurality of hollow inlet pipes connected to the main body at the forward end and having a series of holes on an upper portion of the pipes and a hollow outlet pipe connected to the rear end, the outlet pipe having a threaded end. 
     In one implementation, the kit further includes a threaded pipe cap being adapted to be placed in threaded engagement with the threaded end of the outlet pipe. 
     In another implementation, the pipe cap includes a water quality orifice that is designed to control the outflow of water from the basin. 
     In another implementation, the kit further includes grout to connect the apparatus to the control structure and seal any leakage around the water quality apparatus. 
     One advantage of the invention is that it allows water to drain from the pond in virtually the same amount of time as by specification of the pond because debris typically does not clog the inlet of the control structure. 
     Another advantage of the invention is that a plurality of inlet pipes of the invention increase the available amount of surface area for filtered drainage. 
     Another advantage of the invention is that debris that gathers on the invention can easily be removed by hand, and further does not clog the control structure. 
     Another advantage of the invention is that it includes a pipe cap that can be removed to provide orifices of varying size that provide different flow rates through the invention. 
     Another advantage of the invention is that all aspects can be observed and maintenance can easily be identified. 
     Other objects, advantages and capabilities of the invention will become apparent from the following description taken in conjunction with the accompanying drawings showing the preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of an embodiment of a detention basin water quality apparatus; 
         FIG. 2  illustrates a top view of an embodiment of a detention basin water quality apparatus; 
         FIG. 3  illustrates a front view of an embodiment of a detention basin water quality apparatus; 
         FIG. 4  illustrates a bottom view of an embodiment of a detention basin water quality apparatus; 
         FIG. 5  illustrates a rear view of an embodiment of a detention basin water quality apparatus; 
         FIG. 6  illustrates a partial cut away top view of an embodiment of a water control outlet system; 
         FIG. 7  illustrates a partial cut away side view of an embodiment of a water control outlet system; 
         FIG. 8  illustrates a top view of an embodiment of a detention basin water quality apparatus connected to an outlet control structure; 
         FIG. 9  illustrates a top view of an embodiment of a detention pond water quality apparatus connected to an outlet control structure and having debris; 
         FIG. 10  illustrates a perspective view of a detention pond built on a creek or stream in a moderately empty state through which the base flow travels; and 
         FIG. 11  illustrates a perspective view of a detention pond in a moderately overflowed state after a rain event where the storm water runoff is detained for a designed period of time and the base flow still passes through. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings wherein like reference numerals designate corresponding parts throughout the several figures, reference is made first to  FIG. 1  that illustrates a perspective view of an embodiment of a detention basin water quality apparatus  100 . The apparatus  100  generally includes a central body  105  oriented about a longitudinal axis  110 . The central body  105  generally includes a forward end  106  and a rear end  107 . 
     The apparatus  100  can further be defined and cut by a plane  115  separating the main body  105  into an inlet portion  120  and an outlet portion  125 . The outlet portion  125  generally includes the rear end  107  of the main body  105  as well as an outlet pipe  126 . The outlet pipe  126  typically includes a ring  127  connected to the end of the outlet pipe  126 . In a typical implementation, the ring includes inner threads that are in threaded engagement with a removable pipe cap  128 . 
     The inlet portion  120  generally includes the forward end  106  of the main body  105  as well as pipes  130 ,  135 ,  140 . Another way of defining the inlet portion  120  is by defining a plurality of pipes that include the pipes  130 ,  135 ,  140 . In general, the inlet portion  120  can include any number of suitable pipes. In the embodiment shown in the figure, the inlet portion  120  is defined by the three pipes  130 ,  135 ,  140 . In a typical implementation, the pipes  130 ,  135 ,  140  are oriented with respect to each adjacent pipe  130 ,  135 ,  140  by an angle Θ. 
     The main body  105  is a junction between the inlet portion  120  and the outlet portion  125 . From the rear end  107 , the main body  105  fans out into several pipe bases  145 . Each of the pipe bases  145 , in turn, tapers into the rear end  107  that is predominantly defined as a ring  108 . Each respective pipe base  145  generally has a cylindrical cross section at the end that connects to the pipes  130 ,  135 ,  140 . However, each of the pipe bases  145  merge into each other and taper into the rear end  107 . In the embodiment shown, there are three pipe bases  145  although, as described above with respect to the pipes  130 ,  135 ,  140 , there can be fewer or more pipe bases  145 . The pipe bases  145  terminate into a ring brace  150 , each pipe base  145  having a respective ring  155 . The ring brace  150  is connected to the three pipes  130 ,  135 ,  140  to provide support for the inlet portion  120  with respect to the pipes  130 ,  135 ,  140 . A flange  160  is defined and connected between adjacent rings  155  to provide further support between the pipes  130 ,  135 ,  140 . The pipes  130 ,  135 ,  140  each respectively protrudes from their respective pipes base  145  and ring  155 . Each pipe  130 ,  135 ,  140  terminates in an end cap  165 . 
     In general, the entire apparatus  100  is hollow. The pipes  130 ,  135 ,  140  and the outlet pipe  126  each generally have a cylindrical shape and hollow interior. As mentioned above, the pipe bases  145  of the main body  105  each generally have a cylindrical cross section at the ring  155  end and taper and merge into a single piece adjacent the rear end  107  and ring  108 . Therefore, the hollow interior of the main body  105  is generally a merger of the interiors of the pipe bases  145 . All of the hollow interiors of the pipes  130 ,  135 ,  140 , the outlet pipe  126  and the main body  105  are continuous and contiguous so that there can be a continuous flow of water from the inlet portion  120  to the outlet portion  125 . As is appreciated further throughout the detailed description, the generally hollow interiors allow for free flow of water through the apparatus  100 . 
     The apparatus  100  generally further includes a series of holes  170  at various points of he apparatus  100 . The holes  170  allow water to flow into the apparatus  100  as needed. In a typical embodiment, the holes  170  are located on a portion of the main body  105  and a portion of the pipes  130 ,  135 ,  140  including a portion of the end caps  165 . The locations of the holes  170  are discussed further in the description below. 
       FIG. 2  illustrates a top view of an embodiment of a detention basin water quality apparatus  100  having the central body  105  having the forward and rear ends  106 ,  107  and oriented about the longitudinal axis  110 . The plane  115  generally separates the main body  105  into an inlet portion  120  having the forward end  106  of the main body  105  as well as the pipes  130 ,  135 ,  140 , and an outlet portion  125  having the rear end  107 , the ring  108 , the outlet pipe  126  ring  127  and pipe cap  128 . The pipes  130 ,  135 ,  140  are typically oriented with respect to each adjacent pipe  130 ,  135 ,  140  by an angle Θ. The main body  105  typically includes the pipe bases  145 , one end terminating in the ring  108 , the other ends terminating in the ring brace  150 , each pipe base  145  having a respective ring  155  and flanges  160 . The ring brace  150  is connected to the three pipes  130 ,  135 ,  140  that respectively protrudes from their respective pipes base  145  and ring  155 . Each pipe  130 ,  135 ,  140  terminates in an end cap  165 . The apparatus  100  is generally hollow and includes a series of holes  170  as described above. 
       FIG. 3  illustrates a front view of an embodiment of a detention basin water quality apparatus  100 . This figure generally illustrates the forward end  106  and inlet portion  120  of the apparatus  100 . The figure illustrates the main body  105  and the front angular orientation of the pipes  130 ,  135 ,  140  and respective end caps  165  and pipe bases  145 . The ring base  150  having rings  155  and flanges  160  is also shown. The figure further illustrates that the apparatus  100  can be further divided by a plane  175  that defines the apparatus into an upper portion  180  and a lower portion  185 . The division of the upper and lower portions  180 ,  185  illustrates that the upper portion  180  includes the holes  170  on the main body  105 , pipes  130 ,  135 ,  140  and end caps  165 . The lower portion  185  does not include the holes  170  on a portion of the apparatus  100 . As is further appreciated in the discussion below, the apparatus  100  begins to receive water once the level of the water rises above the plane  175 . Once the water rises above the plane  175 , water can begin to seep into the holes  170 . Once water flows into the apparatus  100 , the water generally flows from the inlet portion  120  to the outlet portion  125 . The small surface are of the apparatus  100  that does not include holes  170  on the lower portion  185  is desirable so that sediment and other debris does not unnecessarily enter the apparatus  100  from beneath the apparatus. In addition, with the lack of holes  170  on the bottom of the apparatus  100 , plants and other growth is prevented from growing into the apparatus  100 . It is understood that in other implementations, the holes can be located on any area of the apparatus  100  including all areas of the upper and lower portions  180 ,  185 . 
       FIG. 4  illustrates a bottom view of an embodiment of a detention basin water quality apparatus  100  having the central body  105  shaving the forward and rear ends  106 ,  107  and oriented about the longitudinal axis  110 . The plane  115  generally separates the main body  105  into an inlet portion  120  having the forward end  106  of the main body  105  as well as the pipes  130 ,  135 ,  140 , and an outlet portion  125  having the rear end  107 , the ring  108 , the outlet pipe  126  ring  127  and pipe cap  128 . The pipes  130 ,  135 ,  140  are typically oriented with respect to each adjacent pipe  130 ,  135 ,  140  by an angle Θ. The main body  105  typically includes the pipe bases  145 , one end terminating in the ring  108 , the other ends terminating in the ring brace  150 , each pipe base  145  having a respective ring  155  and flanges  160 . The ring brace  150  is connected to the three pipes  130 ,  135 ,  140  that respectively protrudes from their respective pipes base  145  and ring  155 . Each pipe  130 ,  135 ,  140  terminates in an end cap  165 . The apparatus  100  is generally hollow as described above. This view of the embodiment of the apparatus  100  illustrates that the lower portion  185  includes a surface area that does not typically include any holes  170 . 
       FIG. 5  illustrates a rear view of an embodiment of a detention basin water quality apparatus  100 . This figure generally illustrates the rear end  107  and outlet portion  125  of the apparatus  100 . The figure illustrates the main body  105  and the rear angular orientation of the pipes  130 ,  135 ,  140  and respective end caps  165  and pipe bases  145 . A portion of the ring base  150  having rings  155  is also shown. The figure further illustrates the plane  175  that defines the apparatus into an upper portion  180  and a lower portion  185 . Although it is generally desirable to include the holes  170  on the upper portion  180 , the figure shows the apparatus  100  inverted with the holes  170  on the lower portion  185  to illustrate that the apparatus  100  could be oriented so that the holes  170  can be located below the plane  175 . In general, as described above, once water flows into the apparatus  100 , the water generally flows from the inlet portion  120  to the outlet portion  125 . The figure further illustrates that the pipe cap  128  includes an orifice  129  that leads into the hollow interior of the apparatus  100 . As discussed in further detail in the description below, the orifice  129  is designed to allow a certain flow of water from the apparatus  100  during a storm event. Therefore, different pipe caps  128  with different sized orifices  129  can be connected to the outlet pipe  126  to provide different flow rates to the apparatus  100 . The orifice is typically located in the lower portion  185  so that water located within the apparatus  100  can completely drain from the apparatus  100 . 
     In a typical embodiment, the apparatus is constructed of a suitable material that is durable and long lasting such as polyvinylchloride (PVC). It is contemplated that in other embodiments, other suitable materials can be used. 
       FIG. 6  illustrates a partial cut away top view of an embodiment of a water control outlet system  200 . As described above, the apparatus  100  is typically used in permanent extended dry detention ponds and other types of water detention basins that are used in order to collect water in a concentrated area during storm events. Therefore, the system  200  includes a pond shown as pond area  205 . The system  200  further includes an outlet control structure  210  from which a large outlet pipe  215  allows the water to drain. The control structure  210  typically includes a large hollow housing  211  and a lid or top  212 . A base  213  typically is included in front of the control structure  210 . In a typical embodiment, the outlet control structure  210  is concrete but can be other materials such as corrugated metal pipe or CMP. The lid  212  typically further includes a man access point  217 . 
     An inlet portion of the control structure  210  is surrounded by a large semi-round (typically half round or three-quarter) pipe basin  220  with perforations (see  FIG. 7  below). The large semi-round pipe  220  typically rests on the base  213  and surrounds an inlet hole on  225  the outlet control structure  210 . The semi-round pipe  220  can vary in the amount of full circle that is encompassed in the pipe  220 . Typically, for a square control structure  210 , the pipe  220  is half round. For a circular control structure (not shown) the pipe  220  is three quarter round. It is understood that various different types of pipe are used in other embodiments. Gravel  230  (typically #4 stone although other types of stone are contemplated) typically surrounds the exterior of the semi-round pipe  220  and in contact with the storm water from the pond area  205 . The gravel  230  provides filtration before the water enters the semi-round pipe basin  220  and the control structure  210 . 
     The system  200  further includes the embodiment of a detention pond water quality apparatus  100  as described above. Since water overflows over the semi-round pipe basin  220  thereby bypassing the filtration gravel  230 , the apparatus  100  is placed in the inlet hole  225  to provide filtration of the water that overflows the semi-round pipe basin  220  thereby preventing larger debris such as large sediment, branches, leaves, garbage and the like from clogging the inlet hole  225  of the control structure  210 . The apparatus  100  typically rests on the base  213 . In another embodiment, the base  213  can be gravel instead of concrete to provide further filtration underneath the apparatus  100 . 
     Typically, the outlet portion  125  of the apparatus  100  (which includes the entire or a portion of the rear end  107 ) is connected to the inlet hole  225  (water quality orifice) of the control structure  210 . It is understood that different areas of the apparatus  100  can be connected into the inlet hole  225 . However, it is desirable that the surface area of the apparatus  100  including the greatest number of holes  170  is far enough away from the control structure  210  so that the flow of water into the apparatus  100  is not impeded. In a typical implementation, the apparatus  100  can be connected by concrete or grout, or any other suitable material. Grout is typically used to connect the typical concrete outlet structure  210  to the typical PVC apparatus  100 . The grout or concrete is used to secure the apparatus  100  to the control structure  210  and to prevent leakage around the apparatus into the interior of the control structure  210 . 
       FIG. 7  illustrates a partial cut away side view of an embodiment of a water control outlet system  200 . As described above, the system  200  includes the pond area  205 , the control structure  210  having housing  211 , top  212  and base  213 , and large outlet pipe  215 . The outlet structure  210  further includes inlet hole  225  surrounded by the large semi-round pipe basin  220  with perforations  221 . Gravel  230  surrounds the exterior of the semi-round pipe basin  220  and in contact with the storm water  250  from the pond area  205 . The apparatus  100  is further included in the system  200  and rests on the base  213 . The figure further illustrates that the control structure  210  typically also includes an overflow weir  214  between the housing  211  and the top  212 . The overflow weir  214  is open to the hollow interior of the housing  211 . In certain events, the storm water can rise to the level of the space  214  and water flows into the outlet control structure  210  in order to prevent flooding. Grating can be placed around this overflow weir  214  to prevent large debris from flowing into the hollow interior of the control structure  210 . In large storm events, water typically flows into overflow weir  214  and possibly an accompanying “v” notch of square weir to allow for the peak flow rates of the 2–25 year storm frequencies. These features help to prevent off-site flooding. If a storm frequency greater than 25 years enters the basin, it is typically detained and released and the peak 25 year rate is controlled. The 25 year up to the 100 year rate typically flows through the overflow weir  214  until it reaches the 100-year frequency where it then passes over a dam or specified area called the emergency spill-way. These features are based on basic required design standards for extended detention basins. The control structure  210  can further include a channel protection pipe  270  based on a one year storm frequency. 
     It is now appreciated that during a storm event, storm water  250  gathers in the pond (or basin) area  205  and slowly seeps through the gravel  230  into the semi-round pipe basin  220  through the perforations  221 . With the apparatus  100  in place, as water gathers in the semi-round pipe basin  220 , the water flows through the holes  170  on the pipes  130 ,  135 ,  140  and main body  105  on the apparatus  100 . As described above, the water flows through the apparatus  100  from the inlet portion  120  to the outlet portion  125 , through the orifice  129  on the pipe cap-invert  128  and into the outlet control structure  210 . Once in the outlet control structure  210 , the water finally flows through the outlet pipe  215 . The apparatus  100  is typically desirable to filter the first flush volume of water during a storm event for purposes of enhancing the water quality before leaving the site for nearby streams, rivers and other bodies of water of site. 
     It is further appreciated that if the storm water  250  does overflow the gravel  230  and the semi-round pipe basin  220 , directly into the semi-round pipe  220 , that debris may also flow into the semi-round pipe  220 . In such a case, the apparatus  100  prevents this debris from clogging the inlet hole  225  and control structure  210 . Typically, the holes  170  on the pipes  130 ,  135 ,  140  and the main body  105  are small enough to prevent the large clogging debris from entering the inlet hole  225  and control structure  210 . However, the individual pipes  130 ,  135 ,  140  are fanned and spread out independently of one another thereby increasing the available filtering surface area through which the storm water can flow. Therefore, if one of the pipes  130 ,  135 ,  140  becomes lodged with a large piece of debris, the other pipes  130 ,  135 ,  140  are available for allowing the water to flow through the apparatus  100 . 
     Furthermore, in a typical embodiment where the holes  170  are located on the apparatus  100  above the plane  175  as described with respect to  FIGS. 3 and 5 , water in the semi-round pipe  220  typically does not flow into the apparatus once that level is below the plane. In such an implementation, finer sediments and debris are not able to flow into the apparatus from underneath the apparatus  100  and therefore the inlet hole  225  and control structure  210 . This feature further prevents finer sediments from gathering and clogging the control structure  210  and the apparatus  100  itself. Furthermore, any plant growth underneath the apparatus  100  is prevented from growing into the apparatus. 
     In still another feature of the apparatus, once the storm water has drained, the apparatus  100  is readily visible from the top of the semi-round pipe basin  220  for inspection and maintenance. After the water has drained, a technician can remove any debris from the pipes  130 ,  135 ,  140  and main body  105  that may still be resting on top of or around the apparatus  100 . Furthermore, the pipe cap  128  can be removed from the inside of the control structure  210  to inspect the hollow interior of the apparatus  100  to ensure that no debris has entered the apparatus. In the case when debris has entered the apparatus  100 , it can easily be removed when the pipe cap  128  is removed. It is now appreciated that since the lower portion  185  of the apparatus does not include any holes  170 , if any sediment or debris has entered the apparatus  100 , there is a smooth surface inside the apparatus  100  that is free of holes in which sediment and debris can easily be cleaned. Furthermore, if a different pipe cap  128  with a different size orifice  129  needed to be placed, it can be placed inside the control structure  210 . 
       FIG. 8  illustrates a top view of an embodiment of a detention pond water quality apparatus  100  connected to an outlet control structure  210 . This figure illustrates a clean and dry semi-round pipe basin  220  having perforations  221  and a clean and dry apparatus  100  before a storm event or after cleaning and drying after a storm event. The apparatus  100  including the pipes  130 ,  135 ,  140 , main body  105  and pipe bases  145  are clear of debris. The semi-round pipe  220  is also free of debris and water. The outlet control structure  210  can have a constant flow of water through gravel  230  through semi-round pipe  220  and into the apparatus  100  if the extended detention basin is built online (that is, on a creek or stream). 
       FIG. 9  illustrates a top view of an embodiment of a detention pond water quality apparatus  100  connected to an outlet control device  210 . This figure illustrates that the semi-round pipe basin  220  having perforations  221  has debris  275  and residual water  280  and that pipes  130 ,  135 ,  140  of the apparatus  100  are covered with the debris  275  and partially surrounded by the water  280 . This figure can be a typical illustration of a post-storm event situation where the storm water  280  and debris  275  has overflown the semi-round pipe basin  220  and where the storm water  280  has subsequently drained from the pond and into the control structure  210 . The apparatus  100  including the pipes  130 ,  135 ,  140 , main body  105  and pipe bases  145  includes a fair amount of the debris  275  that can subsequently be removed. Without the apparatus  100  in place, the same debris  275  has been prevented from clogging the inlet hole  225  and the control structure  210  and thereby prevented the unnecessarily slow drainage of the storm water from the detention pond. As discussed above, the large filter surface area provided by the pipes  130 ,  135 ,  140  still allows controlled drainage through the holes  170  despite the presence of the debris  275  on the pipes  130 ,  135 ,  140 . It is understood that in other embodiments, the apparatus  100  can include additional pipes in order to further increase the available independent surface area from draining. 
       FIG. 10  illustrates a perspective view of a detention pond area  205  in a moderately empty state with a constant base flow (creek or stream). As mentioned above, the outlet control structure  210  including the apparatus can be located on a basin that is not connected to a creek or stream. This figure illustrates the pond area  205  where the majority of the base flow of the creek or stream  280  has drained though the control structure  210 . The control structure  210  shown is round and includes the housing  211 , top  212  and overflow weir  214 . Gravel  230  surrounds the three quarter round pipe  220  shown. The apparatus  100  is at the bottom of the three quarter round pipe. 
       FIG. 11  illustrates a perspective view of a detention pond area  205  in a moderately overflowed state being filled with storm water  280 . The figure illustrates that the pond area  205  is filled to such an extent that only the top  212  of the control structure  210  is showing. This situation is a typical event where the semi-round pipe  220  has been overflowed and submerged therefore typically resulting in debris from gathering in the semi-round pipe basin  220 . Therefore, the apparatus is used in order to prevent the debris from flowing into and clogging the control device  210 . 
     The foregoing is considered as illustrative only of the principles of the invention. Further, various modifications may be made of the invention without departing from the scope thereof and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and which are set forth in the appended claims.