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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
       [0001]    A rotatable drain grate in an opening into a sewer system which when closed retains trash and debris upstream from the opening while permitting slow flow of water, and which pivotally opens when confronted with high rates of water flow to allow overflow water into the sewer while restraining the heavier debris. 
       BACKGROUND OF THE INVENTION 
       [0002]    Storm drains such as are found in gutters and drainage channels, receive trash, cuttings, trimmings and other debris constantly throughout the year and are subject to clogging. Despite regular sweeping upstream from the opening, considerable amounts of trash will enter the drain system, while still permitting the slow flow of water. Ground water run-off frequently carries petroleum products with it. Such pollutants include oil, gasoline, greases, etc. that originate in streets, parking lots, service garages, etc. Pollution and contamination of waterways is damaging to human health and the environment. It is important to try to eliminate these pollutants from the water run-off before it reaches the water table. One physical property of these pollutants that can be exploited in trying to separate them from the water run-off is that most of them float (i.e., they are less dense than water). Prior efforts to remove such petroleum pollutants from water run-off have been less than completely successful. To maintain freshwater systems, most cities and counties have regulations that require the removal of some of the pollutants from the storm-water runoff before entering their storm sewer systems. In order to meet these regulations, facilities typically install on-site pollution traps to filter the storm-water runoff. These pollution traps are sometimes referred to as “oil/grit separators.” 
         [0003]    Serious trouble arises when later storms or other circumstances present water to these systems at high rates of flow while they are congested with the accumulated trash. Clogging of this system can result in upstream flooding, or the washing downstream of the accumulated material. To avoid this situation, throughout the year maintenance crews are sent to clear out trash and debris that has entered the system through the openings. This is a considerable expense, and in the event that a storm strikes before the system is cleared, serious damage can occur despite those earlier efforts. 
         [0004]    Most conventional pollution traps provide only “first flush” filtration during the typical local storm event, but permit bypassing the filtration stage for larger storms. In fact, many jurisdictions require bypassing, some even at typical storm water flows. Bypassing filtration is a problem because most pollutants are more easily picked up and transported by storm water during higher flow periods. Unfortunately, just when the traps are needed most, a lot of pollutants bypass them and are delivered into the storm sewer systems. And most pollution traps that do not provide for bypassing accommodate the larger flows because they are oversized, which adds significantly to the cost to build, install, and maintain them. 
         [0005]    In addition, most filter systems included in the catch basin of storm sewer systems which, under low flow conditions, often act as biological incubators that add to the microbial contamination of storm water runoff. Such bacterial pollutants, unlike chemical ones, are dynamic, continue to grow exponentially, and may quickly reach dangerous level. Some filter systems use chemicals, which can be damaging to the environment. 
         [0006]    Therefore, what is needed is a means to be installed in the drain opening of a catch basin of a typical storm drain system to trap, block or reduce the entry of unwanted leaves, litter and similar debris without interfering with the flow of rainwater through filtration system and into the storm sewer system. Also needed is a filtration system that will powerful, cost effective and durable system for water filtration with antimicrobial action. 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, it is an object of this invention to provide a sewer water gate to be located at the opening to a subsurface catch basin of a storm drain system that will exclude trash and debris from the system while still permitting a flow of water, but which will partially open to allow full access for water (and entrained material) when the rate of flow is sufficiently high while still obstructing the flow of heavier materials. When fully closed, the gate will permit the trash upstream from it to be removed by routine collection sweeping, so as to remove trash that otherwise would later be driven into the system by storm runoff. Another object of this invention is to provide a sewer water gate system that includes a filter system that reduces the buildup of microbial contamination from storm water runoff. 
     
    
     
       DRAWINGS 
         [0008]      FIG. 1  is a front perspective view disclosing the water gate of the invention. 
           [0009]      FIG. 2  is a top view of the water gate of the invention. 
           [0010]      FIG. 3  is rear perspective view of the water gate of the invention. 
           [0011]      FIG. 4  is rear perspective view of the water gate of the invention disclosing a filtration system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring to  FIGS. 1 and 2 , the gate system  100  of the invention comprises two side brackets  120  and  140 , which when attached to a lower fixed screen  160  and upper screen section  180  comprise a frame to which upper gate  200  and rotatable means  230  are affixed. Side brackets  120  and  140  are 1¼″ angle iron braces of sufficient length to span the vertical distance between the street gutter and the top of the standard sewer drain opening. In this preferred embodiment side brackets  120  and  140  are constructed of 0.125″ 304 stainless steel. 
         [0013]    Side brackets  120  and  140  are opposingly affixed to lower gate screen  160  by means of standard cap screws  165 . Lower gate screen  160  is sized to span the horizontal distance between the left and right sides of a sewer drain opening, such that when gate system  100  is installed, lower gate  160  effectively blocks debris and other solid matter entering the sewer drain opening at the gutter level. In this preferred embodiment, lower gate  160  is constructed of 10-gauge, 0.75 inch expanded metal stainless steel. Also shown in  FIGS. 1 and 2  are anchor plates  145 , affixed to both side brackets  120  and  140 , and which are used to anchor gate system  100  the opening to the subsurface catch basin. Positioned above lower gate screen  160  and spanning between side brackets  120  and  140  is upper bracket  180 , comprised of a 1×1×0.125 inch stainless steel angle iron. Upper bracket  180  is affixed to side brackets  120  and  140  by standard stainless steel nuts and bolts, as would be obvious to one of ordinary skill in the art. The combination of side brackets  120  and  140  with upper bracket  180  form an upper frame for receiving upper gate  200  and rotatable means  230 . 
         [0014]    Upper gate  200  and rotatable means  230  form the rotatable gate portions of the water gate of the invention. In this preferred embodiment, rotatable means  230  is comprised on a standard hinge commonly known as a piano hinge, which is sized to substantially span the distance between side bracket  120  and side bracket  140  while permitting the hinge action to freely move without contacting either side bracket  120  or side bracket  140 . Rotatable means  230  is also constructed of 1×1 inch stainless steel. Although rotatable means  230  is comprised of a piano hinge in this embodiment, such hinge is not a limitation of the invention, other types of rotatable means may be used, including other types of hinges, springs, or other devices. The only requirement is that the rotatable means be adaptable to being affixed to upper bracket  180  and to rotatably support upper gate  200 . However, a hinge has certain advantages over a spring, that being that the hinge need not be manually reset. Upper gate  200  is comprised of 0.375 inch lexan-polycarbonite screen, having openings for the passage of water. As shown in  FIG. 1 , upper gate  200  has been formed with various sized openings, consisting of slots and pour holes. Although a lexan-polycarbonate material was used in this preferred embodiment, any material for upper gate  200  may be employed as long as the resulting gate is not so heavy that the gate does not rotate when a specified amount of water pressure and debris applies pressure upper gate  200 . Such other material could be a 16-gauge, 0.25 thick stainless steel, or equivalent material. 
         [0015]    Gate system  100  additionally includes bias means  240  for biasing rotatable upper gate  200  in a closed position. In this preferred embodiment, bias means  240  comprises a pair of magnets selected with sufficient magnetic strength to cause upper gate  200  to rotate to a closed position when the pressure of the water and debris drops below a selected level. Referring to  FIGS. 2 and 3 , limit brackets  210  and  215  are opposingly affixed to side brackets  120  and  140 , respectively, and spaced intermediate to fixed lower gate  160  and upper bracket  180 . Limit brackets  210  and  215  form a stop to restrain upper gate  200  from swinging street ward so that there would not be a potential for upper gate  200  to be blocked in an open position. In this preferred embodiment, permanent magnets  240  are mounted on opposing ends of upper gate  200 , adjacent the left and right sides of upper gate  200 . Permanent magnets  240  are vertically positioned such that they will oppose limit brackets  210  and  215 , and such that limit brackets  210  and  215  also function as magnet stops. Limit brackets  210  and  215  are made from a galvanized, ferromagnetic material. In this preferred embodiment permanent magnets  240  are 1 inch diameter, 0.25 inches thick, with a coating of molybdenum epoxy, with a center hole of ⅜ inches, and affixed to upper gate  200  by means of magnet cap screw  245 . Alternatively, magnets  240  could be mounted on limit brackets  210  and  215 , and opposing paramagnetic metals affixed to upper gate  200  that would be attracted to magnets  240 . Once water/debris pressure is removed from upper gate  200 , gravity will bias upper gate  200  toward the closed position, and magnetic attraction will induce upper gate to seat against limit brackets  210  and  215 . Bias means  240  is not limited to ferromagnetic devices such as magnets. Other means of biasing upper gate  200  in a closed position would be well know to ones of ordinary skill in the art, such as coil springs, leaf springs, etc. Alternatively, the piano hinge of the preferred embodiment could be spring loaded to bias upper gate  200  against limit brackets  210  and  215 . 
         [0016]    Referring now to  FIGS. 3  and.  4 , filter bracket  270  is attached to the upper edge of fixed lower gate  160  by standard stainless steel nuts and bolts, as would be obvious to one of ordinary skill in the art. Suspended from filter bracket  270  is filter means  280 . In this embodiment, filter means  280  is comprised of a plurality of filter strips  285  fabricated from membranes. Filter strips  285  are fabricated form X-Tex anti-microbial filter media that kills or inhibits the growth of microbes such as bacteria, fungi, or viruses so that such microbes will not enter the sewer system. Membrane filters are constructed in very thin layers from polymers and other advanced synthetic materials. Membrane filter thickness varies from 100 to 300 micro-meters, and are usually designed and manufactured with approximately 70 to 90 percent porosity. Membrane filters are commonly manufactured from MCE (nitrocellulose), Cellulose Acetate, Coated PTFE (Teflon), Hydrophobic PTFE, Nylon, polycarbonate, or glass. The invention is not restricted to any particular anti-microbial material, and any other anti-microbial material may be employed. 
         [0017]    Although preferred embodiments of the invention have been described herein in detail, it will be understood that those skilled in the art can make modifications thereto without departing from the spirit of the invention or the scope of the appended claims. For example, filter means  280  could also be comprised of a material that absorbs hydrobarbons.

Summary:
The present invention comprises a sewer water gate to be located at the opening to a subsurface catch basin of a storm drain system that will exclude trash and debris from the system while still permitting a flow of water, but which will partially open to allow full access for water and entrained material when the rate of flow is sufficiently high while still obstructing the flow of heavier materials.