Abstract:
In embodiments of the invention, a dredging head assembly uses vacuum only, or a combination of vacuum and flexible PVC tines, rather than the harsh digging and/or scraping features of conventional dredging equipment. Embodiments of the invention also provide a dredging head assembly that may be used in very shallow water. An embodiment of the invention includes a hose and wand to enable vacuuming around obstacles. One variant of the dredging head assembly is adapted for skimming floating debris from the surface of a body of water.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to a dredging apparatus, and more specifically, but without limitation, to a dredging apparatus having a submersible head assembly that is configured to remove sludge and/or other matter from a waterway. 
         [0003]    2. Description of the Related Art 
         [0004]    Dredging is the process of removing bottom sediments or other matter from a body of water. Dredging may be performed in seas or in fresh water, for instance to improve navigation, for mining purposes, and/or for the remediation of contaminated waters. 
         [0005]    Conventional dredging equipment is not effective in all conditions and applications, however. For example, most conventional dredges are configured to harshly scrape the bed of the waterway. This may be undesirable where fragile aquatic ecosystems could be damaged. 
         [0006]    In addition, conventional dredging equipment that is adapted to remove sand or other sediments often suffer from clogged suction pumps and/or discharge lines in canals or other environments that contain a large amount of sludge. This is because sludge is more viscous than slurries of sand. Similar problems can arise when invasive plant life, trash, or other debris is being removed from a waterway. 
         [0007]    Moreover, it is sometimes necessary to perform dredging operations in very shallow waters. For instance, it may be desirable to dredge at the edge of a lake, or in a shallow stream or pond. Target areas may also include obstacles such as docks, piers, or large boulders. Conventional dredging equipment generally cannot operate in such environments because the dredging boats cannot navigate in very shallow waters or through narrow passages. 
         [0008]    For these and other reasons, improved dredging equipment is needed. 
       SUMMARY OF THE INVENTION 
       [0009]    Embodiments of the invention seek to address one or more of the shortcomings described above with respect to conventional dredging equipment. In embodiments of the invention, a dredging head assembly uses vacuum only, or a combination of vacuum and flexible PVC tines, rather than the harsh digging and/or scraping features of conventional dredging equipment. Embodiments of the invention also provide a dredging head assembly that may be used in very shallow water. An embodiment of the invention includes a hose and wand to enable vacuuming around obstacles. One variant of the dredging head assembly is adapted for skimming floating debris from the surface of a body of water. 
         [0010]    More specifically, one embodiment of the invention provides a dredging apparatus. The dredging apparatus includes: a hull; a boom coupled to the hull adjacent to an aft end of the boom; a winch coupled to the hull; a mast movably coupled to the boom and movably coupled to the hull, the mast having a pulley; a cable coupled to the winch, movably coupled to the pulley, and further coupled adjacent to a fore end of the boom; and a ram coupled to the hull and the boom, the dredging apparatus thus configured to raise and lower the boom using at least one of the winch and the ram. 
         [0011]    Another embodiment of the invention provides a dredging head assembly. The dredging head assembly includes: a frame; a suction pump coupled to the frame; a hydraulic motor coupled to drive the suction pump; and a wheel assembly coupled to the frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention will be more fully understood from the detailed description below and the accompanying drawings, wherein: 
           [0013]      FIG. 1  is an elevation view of a dredging apparatus, according to an embodiment of the invention; 
           [0014]      FIG. 2  is an elevation view of the dredging boat illustrated in  FIG. 1 ; 
           [0015]      FIG. 3  is an elevation view of the dredging boat illustrated in  FIG. 1 ; 
           [0016]      FIG. 4  is an elevation view of the dredging boat illustrated in  FIG. 1 ; 
           [0017]      FIG. 5  is an elevation view of the dredging boat illustrated in  FIG. 1 ; 
           [0018]      FIG. 6  is a plan view of a hydraulic fluid pumping system, according to an embodiment of the invention; 
           [0019]      FIG. 7  is an elevation view of a dredging head assembly, according to an embodiment of the invention; 
           [0020]      FIG. 8  is an elevation view of a dredging head assembly, according to an embodiment of the invention; 
           [0021]      FIG. 9  is a front elevation view of the dredging head assembly in  FIG. 8 ; 
           [0022]      FIG. 10  is a plan view of a dredging head assembly, according to an embodiment of the invention; 
           [0023]      FIG. 11  is a plan view of a dredging head assembly, according to an embodiment of the invention; 
           [0024]      FIG. 12  is a plan view of a dredging head assembly, according to an embodiment of the invention; 
           [0025]      FIG. 13  is a plan view of a dredging head assembly, according to an embodiment of the invention; 
           [0026]      FIG. 14  is an elevation view of a dredging head assembly, according to an embodiment of the invention; 
           [0027]      FIG. 15  is a fluid flow diagram of a dredging head assembly, according to embodiments of the invention; 
           [0028]      FIG. 16  is a fluid flow diagram for the dredging head assembly in  FIG. 14 ; 
           [0029]      FIG. 17  is a fluid flow diagram for the dredging head assembly in  FIG. 14 ; 
           [0030]      FIG. 18A  is a side elevation view of a skimmer dredging head assembly, according to an embodiment of the invention; 
           [0031]      FIG. 18B  is a rear elevation view of the skimmer dredging head assembly in  FIG. 18A ; 
           [0032]      FIG. 18C  is a front elevation view of the skimmer dredging head assembly in  FIG. 18A ; 
           [0033]      FIG. 18D  is a plan view of the skimmer dredging head assembly in  FIG. 18A ; 
           [0034]      FIG. 18E  is a perspective view of the skimmer dredging head assembly in  FIG. 18A ; 
           [0035]      FIG. 19  is a perspective view of a skimmer dredging head assembly, according to an embodiment of the invention; and 
           [0036]      FIG. 20  is a perspective view of a skimmer dredging head assembly, according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    An embodiment of the invention will now be described more fully with reference to  FIGS. 1 through 20 . This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, reference designators may be duplicated for the same or similar features. The figures are not necessarily drawn to scale; some features may be exaggerated for clarity. 
         [0038]      FIG. 1  is an elevation view of a dredging apparatus, according to an embodiment of the invention. As shown therein, a dredging boat  102  is coupled to a dredging head assembly  104 . The dredging boat  102  and the dredging head assembly  104  are shown with respect to a water surface  106  and a floor  108 . The floor  108  may be, for example, a lake, river, or stream bed. 
         [0039]    In the illustrated embodiment, the dredging boat  102  includes a hull  11   0  that is topped by a lower deck  112 . An outboard motor  116  is coupled to the hull  110 . A hydraulic oil tank  118 , hydraulic pump  120 , gear box  122 , gas engine  124 , and cable winch  128  are mounted to the lower deck  112 . The dredging boat  102  further includes an upper deck  114  disposed above the lower deck  112 . A chair  126  is disposed on the upper deck  114 . 
         [0040]    The dredging boat  102  also includes a fore boom section  140  coupled to an aft boom section  144 . The aft boom section  144  is further coupled at an aft portion of the hull  110 . In addition, the aft boom section  144  is coupled to the hull  110  and/or the lower deck  112  via at least one hydraulic ram  130 . As used herein, a ram is a mechanical device that produces pressure. The hydraulic ram  130  preferably produces pressure in two directions. A mast  132  is coupled to the aft boom section  144 . The mast  132  is further coupled to the hull  110  via a skid plate  134 . The mast  132  includes a pulley  136 . A cable  138  is disposed from the cable winch  128  through the pulley  136  and to a forward section of the fore boom section  140 . The fore boom section  140  additionally includes a wheel assembly  142  at a very leading edge. The wheel assembly  142  may include, for instance, 12 inch diameter tires. 
         [0041]    Hydraulic lines  150  extend from the hydraulic pump  120  to the dredging head assembly  104 . The hydraulic lines  150  may pass, for example, within or on the fore boom section  140  and the aft boom section  144 . An outlet (discharge) pipe  146  extending from the dredging head assembly  104  may be disposed on the water surface  106  using one or more flotation devices  148 . 
         [0042]    The hull  110 , lower deck  112 , upper deck  114 , and/or other components of the dredging boat  102  may be fabricated from aluminum to achieve a light weight and a shallow draft with respect to the water surface  106 . 
         [0043]    Variations to the configuration illustrated in  FIG. 1  are possible. For instance, the placement of the hydraulic oil tank  118 , hydraulic pump  120 , gas engine  124 , chair  126 , and other components can be varied according to design choice. Multiple outboard motors  116  could be used. In addition, there are many variations with respect to the configuration of the dredging head assembly  104  that are described below with reference to  FIGS. 7-20 . 
         [0044]    In operation, the dredging boat  102  moves the dredging head assembly  104  within a target dredging area using the outboard motor  116 . In an alternative embodiment described with reference to  FIGS. 12 and 13  below, the head assembly  104  may be self-propelled. In this instance, the outboard motor  116  may not be required during dredging operations, except perhaps to transport the dredging boat  102  and the dredging head assembly  104  to the target dredging area. 
         [0045]    As illustrated in  FIG. 1 , the dredging head assembly  104  may be fully or partially submerged below the water surface  106  during operation. The fore boom section  140  permits the dredging head assembly  104  to roll on the floor  108 , even in very shallow water. 
         [0046]      FIGS. 2-5  show exemplary relative positions of the mast  132 , fore boom section  140  and aft boom section  144  on the dredging boat  102 . 
         [0047]      FIG. 2  is an elevation view of the dredging boat illustrated in  FIG. 1 . In the configuration illustrated in  FIG. 2 , the fore boom section  140  is shown in a raised position.  FIG. 2  also illustrates that the fore boom section  140  may be coupled to the aft boom section  144  at a fore boom pivot joint  205 . Locking bars  210  may be used to limit the rotational position of the fore boom section  140  with respect to the aft boom section  144  (as illustrated in  FIGS. 4 and 5 ). In operation, the fore boom section  140  may be moved to the illustrated raised position by retracting a relatively large amount of the cable  138  using the cable winch  128 . 
         [0048]      FIG. 3  is an elevation view of the dredging boat illustrated in  FIG. 1 . As shown in  FIG. 3 , in a second position, the aft boom section  144  may be rotated about the aft boom pivot joint  305 . In operation, the rotational position of the aft boom section  144  is controlled using the hydraulic ram  130 . For instance, to transition from the position shown in  FIG. 2  to the position shown in  FIG. 3 , the hydraulic ram  130  is compressed. 
         [0049]      FIG. 4  is an elevation view of the dredging boat illustrated in  FIG. 1 . As illustrated in  FIG. 4 , the fore boom section  140  may be placed in a lowered position. In the illustrated configuration, the fore boom section  140  is coupled to the aft boom section  144  via fore boom pivot joint  205 . The locking bars  210  prevent the fore boom section  140  from overextending with respect to the aft boom section  144 . To extend the fore boom section  140 , for instance from the position shown in  FIG. 2  to the position shown in  FIG. 4 , the cable winch  128  releases an additional length of cable  138 . 
         [0050]      FIG. 5  is an elevation view of the dredging boat illustrated in  FIG. 1 . As illustrated in  FIG. 5 , the fore boom section  140  may be disposed in a lowered position and the aft boom section  144  may be disposed in a horizontal position. To transition from the position shown in  FIG. 4  to the position shown in  FIG. 5 , the hydraulic ram  130  is compressed and a relatively small amount of cable  138  is retracted by the cable winch  128 . 
         [0051]      FIG. 6  is a plan view of a hydraulic fluid pumping system, according to an embodiment of the invention. As shown therein, the gas engine  124  is coupled to the hydraulic pump  120  via a gear box  122 . The gas engine  124  may be or include, for instance, a conventional 4-cylinder or 6-cylinder engine. The gear box  122  includes a centrifugal clutch assembly  610 . The gear box  122  may provide mechanical support for a rear portion of the engine  124 . The gear box  122  may be oil-cooled. A drive shaft  605  couples the gas engine  124  to the centrifugal clutch assembly  610 . 
         [0052]    The centrifugal clutch assembly  610  is also coupled to a driven shaft  615 . A first gear (sprocket)  625  is affixed to the driven shaft  615 . The driven shaft  615  terminates at a carrier bearing assembly  620 . The carrier bearing assembly  620  may be or include, for example, a pillow block bearing. The hydraulic pump  120  includes a hydraulic pump shaft  640  that has a second gear (sprocket)  635  affixed. A chain  630  is coupled between the first gear  625  and the second gear  635 . The chain  630  may be, for example, an American National Standards Institute (ANSI) no. 60 roller chain. The first gear  625  and the second gear  635  need not have the same dimensions. For instance, the first gear  625  may be a 12-tooth gear, and the second gear  635  may be a 24-tooth gear. Other gearing could be used to achieve a desired gear ratio. 
         [0053]    In operation, the gas engine  124  rotates the drive shaft  605 . When the drive shaft  605  reaches a predetermined rotational speed (e.g., 1500 rpm), the centrifugal clutch assembly  610  engages the driven shaft  615 . In turn, the driven shaft  615  rotates the hydraulic pump shaft  640  via the chain  630 . The application of the centrifugal clutch assembly  610  may be advantageous because the load of the hydraulic pump  120  is not present when the gas engine  124  is started. The hydraulic pump  120  operates so long as the drive shaft  605  exceeds the predetermined rotational speed. 
         [0054]    Variations to the configuration illustrated in  FIG. 6  and described above are possible. For instance, the gas engine  124  could be replaced by a diesel-powered engine, a steam-powered engine, or another type of prime mover, according to design choice. In an alternative embodiment, the chain  630 , first gear  625 , and second gear  635  could be replaced by a drive shaft, belt and pulley system, or other means of power transmission. 
         [0055]      FIG. 7  is an elevation view of a dredging head assembly, according to an embodiment of the invention. The dredging head assembly illustrated in  FIG. 7  may be, for instance, the dredging head assembly  104  that is shown in  FIG. 1 . The illustrated dredging head assembly  104  includes a head frame  705 . A head coupling  710  is attached to the head frame  705 . The head coupling  710  is configured to couple the dredging head assembly  104  to the dredging boat  102 . 
         [0056]    The illustrated dredging head assembly  104  further includes a hydraulic motor  715  that drives a suction pump  720 . The suction pump  720  may have the capacity, for instance, to pump 900 gallons per minute (GPM). In addition, the dredging head assembly  104  that is illustrated in  FIG. 7  includes a vacuum port  730  and a pressure relief valve  735  coupled to an intake wall  725 . A forward portion of the dredging head assembly  104  includes a wheel assembly  740 . The wheel assembly  740  includes a wheel  750  disposed on an axle  755 . The wheel  750  is fitted with a tire  745 . The tire  745  may be, for example, 22 inches in diameter. 
         [0057]    Variations to the configuration illustrated in  FIG. 7  and described above are possible. For instance, the vacuum port  730  and pressure relief valve  735  are each optional features. In alternative embodiments, there may be multiple suction pumps  720 , each having an associated hydraulic motor  715 . 2-pump and 3-pump variants are expressly described below. There may be more than one wheel assemblies  740  for each dredging head assembly  104 . 
         [0058]      FIG. 8  is an elevation view of a dredging head assembly, according to another embodiment of the invention. As illustrated in  FIG. 8 , the dredging head assembly  104  may further include a beater bar motor  805 . The beater bar motor  805  may be variable speed, and may be capable of both forward and reverse operation. A first sprocket  820  is affixed to a shaft of the beater bar motor  805 . A second sprocket  825  is affixed to a beater bar (not shown in  FIG. 8 ). A roller chain  810  is coupled between the first sprocket  820  and the second sprocket  825 . Tines  815  are coupled to the beater bar. The tines  815  may be fabricated, for instance, from hollow, flexible, ⅝ inch diameter, polyvinyl chloride (PVC). In operation, the beater bar motor  805  rotates the tines  815  to soften the floor  108 . 
         [0059]      FIG. 9  is a front elevation view of the dredging head assembly in  FIG. 8 . As illustrated in  FIG. 9 , the dredging head assembly  104  may include two suction pumps  720 , each driven by a corresponding hydraulic motor  715 .  FIG. 9  further illustrates that the tines  815  are attached to a beater bar  905 . The beater bar  905  may be, for example, a ¼ inch diameter steel rod. To support the beater bar  905 , the dredging head assembly  104  may further include a carrier bearing assembly  910  at or near each end of the beater bar  905 . The carrier bearing assemblies  910  may be or include, for example, a pillow block bearing. In the embodiment illustrated in  FIG. 9 , each of two wheel assemblies  740  are coupled to the head frame  705  via a corresponding axle  755 . 
         [0060]    Variations to the embodiment illustrated in  FIGS. 8 and 9  are possible. For instance, the dredging head assembly  104  may include a single suction pump  720  and associated hydraulic motor  715 . In other embodiments, the dredging head assembly  104  may include more than two suction pumps  720  and associated hydraulic motors  715 . In addition, there may be a fewer or greater number of tines  815  affixed to the beater bar  905 , according to design choice. In an alternative embodiment, the roller chain  810 , first sprocket  820 , and second sprocket  825  could be replaced by a drive shaft, belt and pulley system, or other means of power transmission. The two axles  755  could be replaced by a single continuous axle that supports the two wheel assemblies  740 . 
         [0061]      FIG. 10  is a plan view of a dredging head assembly, according to an embodiment of the invention. As shown therein, the dredging head assembly  104  is coupled to a fore boom section  140  via a boom coupling  1010 . The boom coupling  1010  may be configured, for example, to pivot where the boom coupling  1010  communicates with frame members  1020 . Only a portion of the fore boom section  140  is shown in  FIG. 10 . The fore boom section  140  includes a plank  1025 . The fore boom section  140  also has two wheel assemblies  142  that are disposed on a boom axle  1005 . The dredging head assembly  104  shown in  FIG. 10  includes two suction pumps  720 , each being driven by an associated hydraulic motor  715 . Each of the suction pumps  720  has an outlet port  1015 . The outlet ports  1015  may be, for instance, 4 inches in diameter. 
         [0062]    Embodiments with 900 GPM suction pumps  720  and 4 inch diameter outlet ports  1015  will resist clogging in many dredging environments. 
         [0063]      FIG. 11  is a plan view of a dredging head assembly, according to an embodiment of the invention. As shown therein, an alternative embodiment of the dredging head assembly  104  includes three suction pumps  720 , each of the suction pumps  720  being driven by a corresponding hydraulic motor  715 . 
         [0064]    The embodiments illustrated in  FIGS. 12 and 13  and discussed below present two exemplary alternatives for a self-propelled dredging head assembly. The self-propelled dredging head assembly may eliminate the need for operation of the outboard motor  116  during dredging operations. This may be advantageous because the outboard motor  116  can create undesirable turbulence. 
         [0065]      FIG. 12  is a plan view of a dredging head assembly, according to an embodiment of the invention. As shown therein, the dredging head assembly  104  includes two drive motors  1210 , each coupled to a corresponding drive shaft  1215  via a roller chain  1210  and sprockets (not shown). Each of the drive shafts  1215  may also be coupled to one or more carrier bearing assemblies  1220 . The carrier bearing assemblies  1220  may be or include, for example, a pillow block bearing. The drive motors  1210  may be variable speed, and may have forward and reverse capability. In operation, the drive motors  1205  can be used to propel the dredging head assembly  104 . In addition, differential steering can be accomplished by changing the rate of one drive motor  1210  with respect to the other. 
         [0066]      FIG. 13  is a plan view of a dredging head assembly, according to an embodiment of the invention. The dredging head assembly  104  may also include drive motors  1205  coupled to drive shafts  1215  via roller chains  1210  and sprockets (not shown). In the embodiment illustrated in  FIG. 13 , however, the drive motors  1205  are disposed near a center portion of the head frame  705 . 
         [0067]      FIG. 14  is an elevation view of a dredging head assembly, according to an embodiment of the invention. In the illustrated embodiment, a flexible vacuum hose  1410  is coupled to an intake wall  725 . The flexible vacuum hose  1410  may be, for example, 2 inches in diameter and 30 foot in length. A rigid wand  1405  may be coupled to an opposite end of the flexible vacuum hose  1410 . In operation, the suction pump  720  creates a vacuum within the dredging head assembly  104  and further allows suction at the rigid wand  1405 . An advantage of an embodiment that includes the flexible vacuum hose  1410  and rigid wand  1405  is that a human operator can easily vacuum around docks, large rocks, or other obstacles. Certain features of this embodiment are further described with respect to  FIGS. 16 and 17  below. 
         [0068]      FIG. 15  is a fluid flow diagram of a dredging head assembly, according to embodiments of the invention. As shown therein, the hydraulic pump  120  is configured to transfer oil from the hydraulic oil tank  118  to the hydraulic motor  715  via the hydraulic lines  150 . The hydraulic lines  150  are also coupled to return oil from the hydraulic motor  715  to the hydraulic oil tank  118  on a return path. The hydraulic motor  715  drives the suction pump  720 . An input port of the suction pump  720  is surrounded by an intake wall  725 . The intake wall  725  forms an intake chamber  1505 . During operation of the suction pump  720 , water and particulates enter the intake chamber  1505 , flow through the suction pump  720 , and are expelled from the outlet port  1015 . In alternative embodiments, the hydraulic pump  120  may drive multiple hydraulic motors  715 . 
         [0069]      FIG. 16  is a fluid flow diagram for the dredging head assembly in  FIG. 14 . As shown therein, the hydraulic pump  120  is configured to transfer oil from the hydraulic oil tank  118  to the hydraulic motor  715  via the hydraulic lines  150 . The hydraulic lines  150  are also coupled to return oil from the hydraulic motor  715  to the hydraulic oil tank  118  on a return path. The hydraulic motor  715  drives the suction pump  720 . 
         [0070]    As also illustrated in  FIG. 16 , the intake chamber  1505  may be fully enclosed with the addition of the pan  1605 . The vacuum hose  1410  is coupled to the vacuum port  730  in a portion of the intake wall  725 . Fluid received into the vacuum hose  1410  flows through the intake chamber  1505  and the suction pump  720 , and is expelled through the outlet port  1015 . 
         [0071]      FIG. 17  is a fluid flow diagram for the dredging head assembly in  FIG. 14 . As shown therein, the hydraulic pump  120  is configured to transfer oil from the hydraulic oil tank  118  to the hydraulic motor  715  via the hydraulic lines  150 . The hydraulic lines  150  are also coupled to return oil from the hydraulic motor  715  to the hydraulic oil tank  118  on a return path. The hydraulic motor  715  drives the suction pump  720 . 
         [0072]    As also illustrated in  FIG. 17 , a pressure relief valve  735  is disposed in the intake wall  725 . In the illustrated condition, the vacuum hose  1410  is at least partially clogged with an obstruction  1705  that restricts fluid flow through the vacuum port  730 . When the intake chamber  1505  reaches a predetermined negative pressure, the pressure relief valve  735  opens. This allows fluid to flow through the pressure relief valve  735 , through the suction pump  720 , and out the outlet port  1015 . 
         [0073]      FIG. 18A  is a side elevation view of a skimmer dredging head assembly, according to an embodiment of the invention. As shown therein, a channel  1805  is coupled to a suction pump  720 . The channel  1805  may be fabricated, for example, from a ⅜ inch thick sheet of aluminum. A hydraulic motor  715  drives the suction pump  720 . The dredging head assembly illustrated in  FIG. 18A  can be coupled to, for example, the fore boom section  140  via the head coupling  710 . The fore boom section  140  may suspend the skimmer dredging assembly at or near the water surface  106 . 
         [0074]      FIG. 18B  is a rear elevation view of the skimmer dredging head assembly in  FIG. 18A .  FIG. 18B  reveals that the skimmer dredging head assembly may include two suction pumps  720 , each driven by a corresponding hydraulic motor  715 .  FIG. 18C  is a front elevation view of the skimmer dredging head assembly in  FIG. 18A . The frontal view shows two suction pump inlet ports  1810 . In use, a plane that includes the mouth of the suction pump inlet ports  1810  is disposed at approximately 90 degrees with respect to a plane of the water surface  106 .  FIG. 18D  is a plan view of the skimmer dredging head assembly in  FIG. 18A . As shown in  FIG. 18D , a footprint of the channel  1805  may be an isosceles trapezoid.  FIG. 18E  is a perspective view of the skimmer dredging head assembly in  FIG. 18A . As illustrated in  FIG. 18E , a channel floor  1815  may extend to the end of the channel walls  1820 . A plane that includes the mouth of the suction pump inlet ports  1810  is disposed at approximately 90 degrees with respect to the channel floor  1815 . In use, a plane that includes the channel floor  1810  is disposed approximately parallel to a plane that includes that water surface  106 . 
         [0075]      FIG. 19  is a perspective view of a skimmer dredging head assembly, according to an embodiment of the invention. The skimmer assembly in  FIG. 19  includes a channel  1805  with channel walls  1820  that extend beyond the channel floor  1815 . 
         [0076]      FIG. 20  is a perspective view of a skimmer dredging head assembly, according to an embodiment of the invention. As illustrated therein, a flotation feature  2005  coupled to the channel  1805  may be used to dispose the skimmer dredge head assembly at a predetermined elevation and attitude with respect to the water surface  106 . 
         [0077]    It will be apparent to those skilled in the art that modifications and variations can be made without deviating from the spirit or scope of the invention. For example, alternative features described herein could be combined in ways not explicitly illustrated or disclosed. Thus, it is intended that the present invention cover any such modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.