Abstract:
A system usable for dredging may include a suction bypass system for automatically maintaining a sufficiently high, liquid flow velocity. Preferably, a flow sensor monitors flow velocity and when the monitor flow decreases to an extent that plugging may occur, a liquid bypass valve is opened and an intake line valve is closed until the flow velocity increases whereupon the valves are returned to their original positions. An automatic level cut removes a relatively constant layer of material from a contoured bottom. The illustrated automatic level cut process comprises adjusting the force with which the suction head engages the bottom, moving the suction head in a direction opposite to the direction of the swing of the boom to keep the suction head pointing straight ahead, and maintaining the suction head to stay substantially level with the bottom even though the angle of the boom increases to the surface of the water body. A leveling device comprising a parallelogram linkage may be used to maintain the suction head substantially level with the bottom. A predetermined amount of load force may be applied by the head against the bottom. Herein, a winch and cable and the controller are operated to lift some of the head weight until the desired predetermined head force is applied to the bottom. A walking system moves the pipe intake for taking a sideways cut without the use of a spud pole, anchors and anchor lines. Large blade members or feet travels in an endless path with the feet entering the bottom while vertically disposed and remained disposed vertically while entering and leaving the bottom so as not to dig or stir the bottom that will cause large liquid turbidity. A low turbidity head cleaning system prevents the head from being plugged and debris or sticky material. Preferably, a rotatable cone-shaped head is provided with spaced rings and bars that define sized openings that limit the size of debris entering into the intake. A fixed comb removes material stuck on the rotating head. A shroud has an open bottom side thereby preventing bottom material from escaping and increasing with turbidity. A suction head articulation system keeps the head pointed in the forward direction of dredge advancement to create a smooth finish grade.

Description:
[0001]     This invention relates to a dredge pumping system for dredging material from the bottom using an articulated head and a suction pump to cause a mixture of material and liquid to flow into a suction inlet and a pipe and through the pump for later discharge.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many rivers and harbors have contaminated materials on the bottom of the water body usually in a layer. It is desirable to remove this layer and to remediate the contaminated hazardous waste material in this layer by various technologies. Several problems have been encountered which has prevented the widespread removal of contaminated material on the bottom including the turbidity to the water caused by using a conventional drag line and bucket type of dredging removal and the cost of remediation of the dredged material. Often the drag bucket takes a fixed depth of cut, e.g., a three foot depth and leaves a flat bottom. This drag line and bucket is not suitable for following the diverse topography of a river bed to remove substantially only the contaminated layer on the top of the diverse topography. From a cost standpoint, the first depth of cut, e.g., three feet from the bottom, a bucket removes too much material from the bottom where the contaminated layer may vary from, e.g., seven inches to one foot or even two feet in some places. Manifestly, the dredging and pumping of the non-contaminated material involves additional unwanted cost; and moreover, all of the dredged material has to be treated by a remediation process. This excessive removal of non-contaminated material results in a significantly increased remediation costs because all of the dredged material has to be treated. It would be most desirable to remove the contaminated layer with a significantly smaller amount of non-contaminated material, e.g., reaching a goal of only 10 to 15 percent of non-contaminated material.  
         [0003]     Thus, it will be seen that unlike typical drag line and bucket dredging in a river or harbor for maintenance dredging to keep a channel open to a given depth with a flat bottom the goal in environmental dredging, the goal is often to remove only a specific layer in which the contaminated material is located from this uneven, underwater topography or terrain which is also littered with many obstacles and debris as typically found on the bottom of a harbor, river or the like. The depth of the contaminated layer may vary from place to place in the harbor or river and its depth can be ascertained, e.g., by core sampling techniques. In many instances, the contaminated material is a less dense layer deposited on top of a denser, uncontaminated substrate, e.g., a clay or rock bedrock. Rather than using a line and bucket type of removal for marine environmental remediation, attempts have been made to use hydraulic dredging technology that is less damaging to marine life in the water column than the mechanical technologies using a bucket or the like, but have been unsuccessful. Typically, because most of the conventional existing hydraulic dredging technology is unable to closely follow the diverse terrain levels found at the remediation site or are unable to remove the layer without exceeding turbidity standards. As a result of not being able to closely follow the diverse terrain to remove substantially only the contaminated layer, they often either remove too little, leaving some of the contamination behind or they significantly over-dredge and take too much of the uncontaminated material. All of this excess material which is not contaminated must also be treated as if it were contaminated.  
         [0004]     As stated above, in marine environmental remediation, it is desired to have a smooth, level top finish after removing only a specified depth of material; for example, two or three feet, even through the terrain is uneven at the bottom of the harbor or the like. For such dredging, it is desirable that the suction head move and operate automatically in three dimensions, usually swinging to the left and to the right and moving downward into the harbor bottom and moving forwardly in the direction of dredge travel. Thus there is a need for self-leveling, ground following head such that the pump suction is always in close proximity to the targeted material and taking the contaminated material with a minimum amount of over-dredging of non-contaminated material.  
         [0005]     One of the problems involved in dredging harbor bottoms or other bottoms in a liquid is that the slurry often becomes so concentrated that it begins to cause plugging and a substantial slow down of the velocity of the slurry mixture flowing through the pipe. The slurry mixture becomes so concentrated and the velocity slows down to a point, the flow can actually stop when the pipeline has become plugged. Unplugging is one of the worse problems in an environmental remediation project because the operation is stopped with a pipeline full of contaminated material that often backflows into the liquid column causing a turbidity and pollution problem. The plugging often requires pipeline flushing with clean liquid or water before the problem can be assessed and corrected, which again increases the amount of contaminated material and turbidity. Thus, there is a need for a new and improved system which can reduce intake plugging or pipeline plugging and be done with considerably less contamination and turbidity. In addition to the debris there is often encountered a large amount of debris in the bottom of the harbor or the like and the debris being caught in the suction inlet can cause considerable delays and problems before the debris is removed from the inlet.  
         [0006]     The intake to the dredge head often becomes plugged with debris and sticky materials that are present at most dredge sites. Often a screen is provided about the intake line to prevent large debris or materials from entering the intake and plugging the intake. When the intake is plugged, the entire dredging operation stops usually for a considerable period of time and the head is manually cleaned to make it unplugged. This cleaning operation exposes the workers to the contaminants in a remedial dredging operation, and the water column is also filled with contaminated material removed from the intake causing turbidity. The problem with pipeline plugging is that there is often an unavoidable backflow pollution as the material in the intake pipe flows backward into the water column. Manifestly, any plugging and manual labor to unplug results in considerable downtime costs.  
         [0007]     Another problem with conventional dredges is the way that they are repositioned for taking successive cuts on the bottom. Repositioning usually involves an anchor barge and a crew to move a pair of heavy anchors at the opposite ends of the cuts and the dropping of a rigid spud pole which enters the ground at the back of the dredge and which acts as a pivot point for the head and barge to swing about. Cables extend from the barge to the anchors at the opposite ends of the intake and by pulling on the respective swing tables, the head having the pump intake is lowered into the sediment and the swing cables will pull the dredge to the left and to the right to form an arc-shaped cut path. When the amount of the material has been removed from this particular positioning, the spud pole must be again removed and the anchoring barge and crew move the heavy anchors to the new repositioned places for the next cutting operation at which the spud is against dropped to act as a pivot for the next swing. This operation takes a considerable amount of time which could otherwise be spent for producing flow and dredging of material and requires the maintaining of and the expense of an anchor barge and a crew to shift the anchors.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with one embodiment, there is provided a new and improved dredging system which is particularly adapted for remedial, hydraulic projects, although it can be used for other projects where the problem of low turbidity is not a problem and the release of contaminants is not a particular problem. This is achieved by providing systems that solve a number of problems particularly when doing a remedial project to remove and to clean a relatively thin contaminated layer, e.g., two feet or less from the bottom of a harbor, river or the like. Often the depth of the layer may be quite thin, for example, six inches to one foot and it is possible to remove this layer with a very reduced amount of uncontaminated material thereby reducing the cost of dredging and the cost of the remediation process. Also, a unique traction system may be used to shift a suction head without causing a lot of turbidity. More specifically, the environmental dredging system may include one or more of systems for the dredge which includes a suction bypass system for maintaining a sufficiently high velocity of flow to prevent plugging, an automatic level cut system for removing a relatively thin layer of material from a contoured bottom, a low turbidity and anti-plugging head inlet system for preventing sticky material and debris from plugging the head, and a walking system for moving the head to take a cut without having to use a spud pole and the anchored swing lines of conventional systems.  
         [0009]     The problem of intake plugging and pipeline plugging is addressed by a suction bypass system which automatically shifts into a bypass mode when the pipeline flow velocity reaches a critical lower limit causing a stopping of material intake and the replacing of the material intake by a water only intake which dilutes the mixture and allows the velocity to restore to an acceptable value. Thereafter the suction bypass system shifts back to the main suction mode and allows the contaminated material to be taken in through the inlet. In this illustrated embodiment, the bypass system includes a valve at the bypass suction water inlet which is normally closed until the velocity flow being monitored lowers to within a range which indicates that plugging may be about to occur, upon which actuators simultaneously or shortly thereafter open the bypass water inlet valve while a main suction valve adjacent the inlet for the slurry mixture is closed. In this bypass mode, backflow from the main suction pipe is prevented as would be the case if the inlet were not closed by the valve.  
         [0010]     The water flowing through the bypass inlet valve and intake opening dilutes the mixture and the velocity should restore to a acceptable value whereupon the system again shifts back to the main suction mode by closing the bypass water inlet valve and opening the main suction valve to allow the contaminated material to again be sucked into the pipeline for flow therethrough.  
         [0011]     In one illustrated embodiment, the dredge is provided with an automatic level cut system which is designed to provide a smooth level cut, even through the terrain is uneven or contoured and this is achieved by adjusting the suction head so that it is always pointing in the forward direction of dredge advance regardless of the angle of the boom and so that it is in close proximity to the bottom target material being removed with a minimum of over-dredging.  
         [0012]     This is achieved by sensing a change in the swing angle of the boom in one direction and applying force to the suction head to move it in the opposite direction to counteract the change in the swing angle of the boom relative to the dredge. Preferably, a master fluid cylinder has opposite ends connected to the boom and dredge and senses a change in the swing angle of the boom and forces fluid through a line to a slave cylinder, which is connected at opposite ends to the boom and the suction head, to swing the suction head in the opposite direction by an equal and counteracting amount to keep the suction head pointing straight ahead.  
         [0013]     It is preferred to select a preset load or weight that the dredge head is applying to the ground to achieve the automatic level cut and this is accomplished through a mechanical linkage and fluid transfer system that does not require an operator input, unless the operator desires to do so. To this end, a load cell is attached to the end of the hoisting cable to register the total weight of the head system and indicates how much of the system weight is to be supported by the ground. After having inputted a value for the preset weight that the head is to be applying to the ground, the computer or programmable logic controller will automatically adjust the hoisting winch to maintain this desired ground pressure to give the depth of cut desired. Usually for contaminated material such as for example a PCB layer, is usually deposited on top of a denser, uncontaminated substrate such as clay or bedrock and this specific ground pressure selected for the site and the depth of removal allows the dredge head to penetrate the less dense target material and to ride on top of the undesired lower substrate. Thus, the dredge head can follow the uneven terrain and target the less dense or granular contaminated materials and leave the harder, underlying, uncontaminated layers in place so that a large amount of contamination material is not missed or a significant amount of over-dredging occurs that requires the treating of the excess over-dredged material as though it was contaminated.  
         [0014]     The automatic level cut process which is designed to provide a smooth level cut preferably comprises adjusting the force at which the suction head engages the bottom to make a cut removing a layer of bottom material, shifting the suction head from side-to-side while making the cut, pointing the suction head straight ahead in the direction of travel after making a side-to-side cut, and maintaining the suction head substantially level with the bottom when the suction head is making a cut whether in shallow or deeper water.  
         [0015]     It is preferred to maintain the suction head at a substantially level position with respect to the bottom even though the lower end of the boom carrying the suction head increases its angle with respect to the surface of the body of water as the outer boom end is lowered from making a cut in a shallower water to making a cut in deeper water. This is achieved by a leveling device mounted on the boom and connected to the suction head. In the illustrated embodiment, the leveling device is a parallelogram linkage having a pair of longitudinal link members extending longitudinal of the boom and a rear, more vertical link member, and a forward link member connected to the forward ends of the pair of longitudinal link members for positioning the suction head at a level position as the boom forward end swings to a deeper position. In the illustrated embodiment, a bottom side of a cone-shaped guard about the suction head is positioned by the parallelogram linkage to maintain the bottom side of the cone-shaped guard substantially parallel to the bottom as the boom forward is lowered into deeper water to make cuts at deeper depths.  
         [0016]     In accordance with an embodiment of the invention, there is provided a low turbidity head cleaning system which prevents the head from becoming plugged with debris and sticky material and prevents pipeline plugging and a consequential, unavoidable backflow pollution into the water column when the system is shut down and the expensive downtime to unplug the head which is done manually. This is achieved in this embodiment by a cone-shaped, rotatable head mounted around the outside of the stationary, main suction intake pipe. The rotating head is comprised of spaced support bars and rings which have large, sized openings therebetween. The size of the openings depends on the size of the pump being used and the size of the over-sized material desired to be prevented from entering the intake pipe and plugging the system. The cone-shaped, rotating low turbidity head also distributes the weight of the head system onto the ground. Herein the cone-shaped head is cleaned by fixed cone-type assembly mounted adjacent the head to remove material which maybe stuck between the rings. The low turbidity aspect of the system is a result of having a flexible rubber shroud about the cone that prohibits contaminated material from escaping the area inside the cone except through the suction pipe.  
         [0017]     In accordance with one embodiment of the invention, the dredge is provided with a submersible, walking swing system that moves the suction inlet or intake for the pump through the normal swing cut and replaces the conventional swing cables and anchor system of conventional dredges. This system maintains a constant connection with the ground and walks the pump inlet using large bladed members or feet that enter into the ground in the vertical position. While inserted in the ground, a large, vertical face of the foot pushes directly against the shear strength of the bottom material while not tearing it up and out as like a conventional paddle wheel would do. The traction provided by these vertical blade feet and the walking rotation is that it provides high traction with a minimum amount of turbidity. The preferred and illustrated walking system comprises a rotatable head which is motor driven and is located just behind a submersible pump located adjacent the intake head. This walking system has a set of arms extending outwardly about an axis where each of the arms bearing a pair of double bladed feet which are always kept in a vertical position as the arm carries it through a 360° of rotation. Each arm carries the double-bladed foot to engage and move directly into the ground and as the next blade is being pushed down to enter the ground, the previously deepest penetrating bladed foot is being pulled upwardly by its arm to leave the ground with the head having been walked in the direction of rotation of the blade carrying head. Thus, the expensive barge used to move the anchor points and the expense of the crew to move the anchor points and the lost down time for shifting the anchor points may be eliminated with the walking system of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a plan view showing a swinging head movable through an arcuate swinging motion and embodying the novel features herein described;  
         [0019]      FIG. 2  is an elevational view of the dredge and the head shown in  FIG. 1 ;  
         [0020]      FIG. 3  is a diagrammatic illustration of the bypass system when in the main suction mode for sucking material through the head inlet and through the pump to the dredge;  
         [0021]      FIG. 4  is a diagrammatic illustration of the bypass system when in the bypass mode is intaking liquid to reduce the solids content in the liquid flow and thereby increase the velocity of the flow into and through the pipe;  
         [0022]      FIG. 5  is a side-elevational view of a low turbidity intake and a head cleaning system in accordance with an embodiment of the invention;  
         [0023]      FIG. 6  is a side view of a submersible, walking swing system in accordance with an embodiment for moving the dredge head through an arc to take a cut;  
         [0024]      FIG. 7  is a front view showing the head in two different positions as the bladed feet performs the submersible walking between positions  7   a  and  7   b;    
         [0025]      FIG. 8  is a plan view of the automatic head articulation system that assures that the suction head is always pointing straight ahead in the direction of dredge travel as the boom swings from side to side;  
         [0026]      FIG. 9  is a elevational view illustrating a load cell sensor system which provides the amount of desired pressure to be applied to the ground so that a level cut may be made and a parallelogram arrangement which assures that the front suction head assembly always stays level with the bottom no matter what depth the boom and suction head is operating at;  
         [0027]      FIG. 10  is a diagrammatic illustration of a master and slave cylinder arrangement to keep the suction head pointed straight ahead in the direction of advancement;  
         [0028]      FIG. 11  is a side-elevational view of the traction drive system in accordance with the illustrated embodiment;  
         [0029]      FIG. 11   a  is a side-elevational view of the walking feet blades as they are driven into the ground;  
         [0030]      FIG. 11   b  is a side-elevational view of a connector link between the main drive hub and the rotating eccentric hub;  
         [0031]      FIG. 12  is a diagrammatic plan view of the walking system for swinging the boom while making a cut;  
         [0032]      FIG. 12   a  is a side-view of the walking system of  FIG. 12 ; and  
         [0033]      FIG. 13  is an illustration of one of the walking feet as it travels through a revolution and enters and exits the ground to provide the traction for moving the suction head. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]     As shown in the drawings and in particularly in  FIG. 1 , there is a first embodiment which comprises a dredge  10  having an articulated or swingable boom  12  which pivots about a pivot mounting  14  with the dredge, which is usually a floating barge or the like. A suction head  16  extends into and is submersed at its lower end in the water. The suction head is mounted on a forward or distal end  15  of the boom and has an intake  18  for intaking material from the submerged bottom as shown in  FIG. 2 . The illustrated head  16  is also articulated or pivotally mounted at a pivot mounting  20  to the distal end  15  of the boom. As best seen in  FIG. 1  the suction head takes a arcuate cut shown by arrow A for a first cut which is then followed by a second cut B between opposite swing points or ends of the arcuate edge C and D in  FIG. 1 .  
         [0035]     Referring to  FIG. 2 , the head intake  18  is shown at a lower level E having lowered a harbor bottom  22  at the cut shown in  FIG. 2  from the higher elevation for the bottom shown at the level F in  FIG. 2 . The dredge, as illustrated in  FIG. 2 , is involved in an environmental dredging to remove only a specific layer of contaminated material between levels E and F in underwater terrain or bottom  22 . In the present invention, a pump  24  ( FIG. 3 ) is provided on the boom  15  rather than on the dredge itself although it is possible to mount the pump on the dredge rather than on the boom. The pump has a intake and a forward end which is connected to the suction pipe  26  which is connected to an inlet end  27  of the pump and the pump has a discharge end  28  which is connected to the suction pipe end leading to the dredge. Thus, as is seen in  FIG. 3 , the material from the bottom  22  of the cut being made flows inwardly through the intake  18  which is connected to the forward end of the suction pipe  26  and the material flows through the suction pipe to the intake for the pump and then is discharged from the pump at its discharge end  28  for flow through a portion  26   a  of the suction pipe leading to the dredge.  
         [0036]     In accordance with the embodiment illustrated in  FIG. 3 , the system is provided with a bypass system which operates in a main suction mode to remove the material from the bottom through the intake  18  for flow through the pipe  26  and when the flow begins to be restricted and decreases in velocity, the system shifts to the bypass mode to intake water only through a bypass inlet  30 . This increased flow of water only without the bottom material provides a diluted mixture in the suction pipe thereby causing a consequent increase in the velocity of the mixture flowing through the suction pipe. The velocity of the flow through the intake pipe  26  is measured in this instance by a flow sensor  32  which comprises a flow meter  34  which directly monitors the flow within the pipe  26 . The flow meter  34  is connected by a line  35  to a controller such as a PLC controller  36 . The PLC controller  36  controls a pair of hydraulic control valves  38  and  40  over hydraulic lines  39  and  47 , respectively, for bypass valves  44  and  46 . The control valve  38  is preferably a hydraulic control valve which is connected by the hydraulic line  39  to a valve actuator  42  for shifting a bypass valve  44  between open and closed positions. The preferred bypass valve  44  is a knifegate valve which is shown in its closed position in  FIG. 3  with the actuating rod  42   a  of the control valve  42  extended and the valve  44  closed to prevent liquid flow through the suction inlet  30  and into the suction pipe  26 . When the valve actuator  42  pulls the actuating rod  42   a  to the left as viewed in  FIG. 3 , the knifegate valve  44  is opened and water is allowed to flow through the inlet into the suction pipe  26  to dilute the slurry mixture. Manifestly, electrical or other control systems could be used rather than the illustrated and preferred hydraulic control system to open and close the bypass valves  44  and  46 . Also, other than the preferred knifegate type of valves could be employed.  
         [0037]     A large amount of debris and contaminated material may be flowing through the intake  18  and the intake pipe  26  during a hydraulic remediation project and it is undesirable that they be released and dropped into the water column when the system is shifted into the bypass mode to prevent plugging by increasing flow velocity in the pipe  26 . To this end the backflow is prevented by a closing the knifegate valve  46  which is located adjacent the inlet end of the intake pipe  26 . The controller  36  which caused opening of the bypass valve  44  also operates to close the intake pipe, index  6 . The controller causes the hydraulic control valve  40 , which is connected by the hydraulic control flow line  47  to the actuator  44  for the intake knifegate valve  46  to close the valve  46 . The actuator  44  is preferably a hydraulic actuator which has a rod  48  which is shown in  FIG. 3  position to be extended to keep the valve open with the flow flowing through the intake as shown by the directional arrows in  FIG. 3  into the inlet suction pipe section  26   b  and through the valve  46  into the pump inlet  27  and then for flow through the pump discharge into the discharge suction pipe section  26   a .  FIG. 4  illustrates the bypass suction mode as shown by the directional arrows where the water from the water column is flowing through the bypass valve and through the inlet to the pump and then being discharged from the pump with the flow being monitored and by the flow sensor  32  until the velocity of the flow being discharged from the pump reaches a predetermined minimum flow or desirable flow rate so that the system may be switched back to the main suction mode illustrated in  FIG. 3 . As shown in  FIG. 4  in the bypass suction mode, the knifegate valve  46  is in its closed position preventing material from flowing back through the intake  18  into the water column. Thus, it will be seen from the foregoing that when the pipeline velocity is monitored by the flow sensor  32  reaches a critical lower limit, the system shifts into a bypass mode of  FIG. 4  immediately stopping material intake through the intake  18  and replacing it with water intake through the bypass valve  44 . This incoming water dilutes the solids content of the mixture flowing through the pump and the pipe  26  until the velocity is restored to an acceptable value as monitored by the flow sensor  32  and the controller  36  which then causes the shifting back to the main suction mode of  FIG. 3 . Additionally, to provide a total backflow operation where there is no back flow from the pipe  26  and the pump, the controller may close both of the knifegate valves  44  and  46  so that there is no backflow either through the intake inlet  18  or through the bypass inlet  30 .  
         [0038]     The preferred and illustrated bypass system is formed inexpensively by using a simple T pipe  50  which has flanges  50   a  which are connected to the knifegate intake valve  46  and a flange  50   b  which is connected to the bypass knifegate valve  44 . Thus, the bypass knifegate  44  is mounted on the branch of the T pipe  50  while the main suction knifegate valve  46  is mounted on a straight line portion of the T pipe for straight line fluid flow towards the pump. Thus, there is provided a simple and economic design using off-the-shelf knifegate valves for providing bypass and the backflow prevention.  
         [0039]     For a marine environmental remediation, the invention is provided with an automatic level cut articulation system which is designed to provide a smooth, level cut finish even though the terrain is uneven. To this end, the suction head  16  is adjusted such that it is always pointing in the direction of the dredge advancement regardless of the angle of the boom and its swing relative to the dredge. Also, there is provided a sensing system which is to try to remove only the targeted sediment layer of the bottom which is usually in a softer layer containing the contaminated material and which is usually located over a harder substrate or layer so that mostly the targeted material is removed and with only a minimum of over-dredging of the harder underlying base material. Preferably, the sensing allows removal of the targeted soft layer over a contoured bottom which has various terrains by taking off only the upper, soft layer; for example, two or three feet layer even though the depth of the water overhead changes substantially due to the varying height of the terrain.  
         [0040]     To keep the head  16  adjusted so that it is pointing straight ahead in the direction of the advancement of the dredge  10  which would be to the right as shown in  FIGS. 1 and 2 , the head is connected pivotally to the end of the boom  12  at the pivot mount  14  and an actuator drive  51  is provided to position the suction head  16  to be straight ahead, as the boom swings between two extreme, opposite end positions C and D ( FIG. 1 ). In the middle position, the head  16  is shown pointed straight ahead as is the boom  12 . As the boom swings with respect to the dredge  10  to one of its opposite end positions D or C where the head  16  is positioned at the ends of the arc of the cut, the boom is at an acute angle to the suction head  16  which is pointing straight ahead.  
         [0041]     As best seen in  FIGS. 8 and 9 , the actuator drive  51  to point the suction head  21  straight ahead in the direction of the dredge advancement comprises a sensing means for sensing the swinging movement of the boom about its pivot point  14  with the dredge  10  to sense the angle of the swing and comprises a force supplying means for counteracting the boom swing angle change to keep the suction head  16  pointed straight ahead as the boom  12  swings and sweeps between end positions C and D of the arc of the cut. While the sensing means and the force applying means could be various devices to accomplish these functions, a very simplified force supplying and automatic actuating drive  51  is developed, and, as shown in  FIGS. 8 and 9 , comprises a master cylinder  53  for sensing changes in the swing angle and a slave cylinder  54  connected between the boom and the suction head for keeping the suction head  16  positioned straight ahead as the boom swings. A hydraulic circuit  55  having hydraulic lines or pipes ( FIG. 9 ) interconnects the master cylinder  53  and the slave cylinder  54  such that as the boom swings in one direction, for example, to the left as viewed in  FIG. 8 , a piston rod  53   b  in the master cylinder compresses the fluid and causes it to flow through the hose loop circuit  55  causing slave cylinder rod  54   b  to extend by the exact, same amount. The opposite occurs when the boom swings to the right. More specifically, the master cylinder  53 , as shown in  FIG. 10 , has a first end  53   a  pivotally connected to the dredge  10  and has its piston rod  53  having a pivoted end  53   c  pivotally connected to an end of the boom. The head  16  is pivotally mounted at a distal end of the boom  15  by the pivot mount  20  and the slave cylinder  54  has a pivotal mount end  54   a  connected to the distal end  15  in the boom with the opposite end of the piston rod  54   b  connected pivotally at a pivotal connection  54   c  to the suction head  16 . As clearly is shown in  FIG. 10 , as the boom swings in one direction, for example, to the left as being described, the end of the boom is pushing the master cylinder rod  53   b  inwardly into the cylinder causing the fluid to be forced through the hydraulic circuit  55  into the slave cylinder  54  to push the piston rod  54   b  to extend by an equal amount. The fluid being forced outwardly of the slave cylinder is sent through a closed loop into the master cylinder behind the piston rod as it is traveling to the left as viewed in  FIG. 10 . When the boom swings to the right, just the opposite occurs, in that the suction head  16  pushes the piston rod  54   b  inwardly into the slave cylinder to force fluid to flow through the upper hydraulic line  55   a  into the master cylinder to push the piston rod  53   b  to extend to the right as viewed in  FIG. 10 . Thus, it will be seen that there is an automatic head articulation system that counteracts the swing angle and assures that the suction head  16  is always tracking parallel to the side of the slope as the dredge boom  12  swings left and right thereby creating a smooth finish grade.  
         [0042]     The manner in which the boom  12  and the suction head  16  are raised and lowered is best illustrated in  FIG. 9  wherein the boom  12  is shown as being substantially horizontal (upper portion of  FIG. 9 ) for making a shallow cut on the bottom adjacent the water line. When making a deeper cut such as shown in the lower portion of  FIG. 9 , the boom is swung considerably downwardly in the direction of the directional arrow c in  FIG. 9  with a winch cable loop  65  shown in solid lines as having a short loop  66  when the boom is generally horizontal and being a very long extended vertical loop  66  (in dotted lines) when the boom has been lowered to make a deeper water cut. As is stated previously, the boom  12  is pivotally mounted and the pivot mount  14  to the front edge of the dredge. At the front edge of the dredge is a vertical support post  62  having a cable like stay  62   a  extending from the dredge at the lower end of the stay cable to the upper end of the stay which is secured to the top of the vertical dredge post  62 . A horizontally extending upper stay cable  62   b  extends from the top of the post  62  horizontally to the top of an inclined boom support  63  which has its lower end fixed to the boom at the rearward end of the boom at a location adjacent the dredge. The winch cable  65  is fixed at one end at the outer upper end of the boom support  63  and a first portion  65   a  of the cable extends downwardly to form one side of the loop  66  to a lower cable pulley  67  and remote portion  65   b  of the cable then extends upwardly to another pulley  68  secured to the upper outer end of the boom support  63 . From this upper pulley  68 , a cable portion  65   d  extends to the main hoisting winch  64  which includes a winch drum  64   a  and winch motor  64   b . The winch is able to play out the winch cable  65  to increase the length of the cable to increase the length of the loop  66  as shown in dotted lines for lowering the suction head into deeper water or to make a deeper cut. In a reverse manner, the winch can wind the cable  65  on the winch drum to shorten the loop  66  to raise the boom and the suction head  16 . A fixed length of cable  69  is connected to the pulley  67  at the bottom of the loop  66  and extends to a lower end which is connected to the forward portion of the boom, as illustrated.  
         [0043]     To maintain an automatic level cut motion, a load cell sensor  61  of a load sensing system  60  is attached to the fixed end of the cable  65  at the upper end of the inclined boom support  63 . The load sensor cell  61  essentially weighs the weight of the boom  12  and the suction head  16 . When the suction head touches the ground, the load cell measures a reduction in weight force on the cable  65 , that is the difference in tension force at the cable end between when the suction head is not touching the ground and when the suction head is laying on the ground. This reduction in weight force on the cable  65  represents the load which is being applied to the bottom by the boom and head. The operator inputs the desired pressure at which the suction head is to be applied to the ground through an input device  70  which is connected to a controller  71 . Then the controller  71  uses this information to raise or lower the winch in order to maintain the desired pressure that is a set point of which the cut will be made by the suction head.  
         [0044]     Thus, it will be seen that it is possible to register the total weight of the head system and to indicate how much of the system weight is being supported by the ground. The ground head pressure is adjusted to the desired amount in order to remove a specific layer of the ground. This pressure needed to remove a given layer depends on the density of the target material. It is desirable that the suction head  16  ride on top of the harder underlying substrate when removing a softer layer. In practice, the operator will input a value; for example, 800 pounds by an input device  70  into a controller  71  which controls a winch drive  64  to lift the hoisting cable  65  to remove the weight until only the 800 pound value is being used by the head against the ground providing the desired ground pressure to remove the contaminated layer. A preferred controller is a programable logic controller (PLC) which the operator inputs the value and with the controller than performing the adjustment of the winch until the desired pressure of 800 pounds is measured by the load sensor cell  61 . Because the contaminated material is usually a softer layer which is deposited on top of a denser uncontaminated substrate (such as clay, bedrock, etc.), the dredge head should penetrate the less dense target material and ride on top of the undesired harder substrate. Thus is will be seen that the dredge head can follow on uneven terrain and target the less denser, granular contaminated materials and leave the harder, uncontaminated materials in place.  
         [0045]     In addition to keeping the suction head  16  pointing straight ahead as the boom  12  swings and to adjusting the ground head pressure applied by the suction head to the bottom to remove a specific layer, the remediation system also maintains the suction head substantially level with the bottom to make a level cut even though the angle that the forward end  15  of the boom makes with the surface of the body of water changes substantially from a shallow water cut (solid lines in  FIG. 9 ) deeper water cut (phantom lines in  FIG. 9 ). As illustrated in  FIG. 9 , the suction head maintains substantially the same position even though the downward boom angle has increased substantially from the shallow water to a deeper water cut. Preferably, a leveling device  52  is provided to compensate for this change in boom angle.  
         [0046]     In the illustrated embodiment, a leveling device  52  is provided that is simple in construction and operates automatically without operator input or without power driven devices to shift the head to compensate for changes in the boom angle. Manifestly, power devices and sensing systems, with or without operator input could be used to maintain the suction level for a level cut and to reduce overdredging rather than the illustrated parallelogram linkage kind of leveling device illustrated herein. The parallelogram linkage, leveling device  52  comprises a pair of parallel, longitudinal extending link members  56   a ,  56   b  and a pair of parallel end link members  56   c ,  56   d . The rear link member  56   d  has a pivot or articulation mount  57   a  at its upper end to the upper longitudinal link member  56   a  and a pivot mount  57   b  at its lower end to the lower longitudinal link member  56   b . The forward link member  56   c  has a pivot mount  57   c  to the upper forward end of the longitudinal link member  56   a  and a lower pivot mount  57   d  to the lower longitudinal link member  56   b.    
         [0047]     When making a shallow water cut, the longitudinally extending link members  56   a  and  56   b  are spaced farther apart, as shown in solid lines in  FIG. 9  for the shallow water dredging cut, and are spaced close together, as shown in phantom line in  FIG. 9 , when making a deeper water dredging cut.  
         [0048]     In accordance with another aspect, which will be described hereinafter in conjunction with  FIG. 5 , there is provided a low turbidity head cleaning system  75  which functions to prevent the dredge head intake from being plugged with large pieces of debris and sticky materials. The illustrated system includes a cone-shaped, high torque, rotating head  16  which in this instance is in a cone-shape which has openings in the head which allows the contaminated material at the bottom from entering the intake  18  but prevents the larger size of debris or sticky material from falling through the cone-shaped head and into engagement with the intake  18 . Herein the cone-shaped head is comprised of main outer support bars  80  which are held together in spaced relationship with one another along the outside of the cone by equally spaced rings  82  mounted on the outside of the cone and becoming smaller in diameter as approaching the point of the cone. The spacing of the rings and the spacing of the support bars defines the size of the openings  79  which are sized depending upon the size of the pump being used.  
         [0049]     The low turbidity aspect is enhanced by attaching a hood-shaped, flexible rubber shroud  99  that has a flat open bottom  99   a  with vertical side walls  99   b  and a curved top wall. The shroud is a piece of tough flexible rubber that hangs down and prohibits contaminated material from escaping the area inside the rotating cone except through the suction pipe inlet.  
         [0050]     For the purpose of cleaning the rotating head and preventing it from becoming obstructed with debris and sticky material, a cleaner, preferably in the form of a fixed comb assembly  84  is mounted on the top of the rotating head. The comb assembly is pivotally connected at an inner end  86  by a pivot mount or pin  87  to a frame portion  88  which is mounted by flanges on the intake pipe  26  adjacent the bypass valve T pipe  50 . The fixed comb comprises an elongated member or bar  89  which has a series of downwardly projecting members in the shape of blocks  90  which are spaced along the bar to be positioned inside the open space  79  between adjacent rings  82  and to project downwardly toward the support bars  80  and into the spaces  79  to clean any debris or material on the outer surface of the rotating head as the rotating head continuously rotates through the fixed comb.  
         [0051]     To rotate the rotating head  16 , there is provided a drive motor  91  ( FIG. 5 ) which may be electrical or hydraulically driven to rotate and to drive a interior rotating sprocket or pulley assembly  92  fixed thereto and within an enclosed housing and having a transmission belt or chain  94  within the housing extending to a rotatable bearing support  96  having a sprocket fixed on an outer rotatable sleeve  98  which encircles and rotates about the non-rotating intake pipe  26 . The sleeve  98  has a flange  99  which is mounted to the large end of the rotating head to rotate the same about the non-rotatable intake end of the intake pipe  26 .  
         [0052]     In accordance with another aspect, the embodiment uses a submersible walking and swing system rather than the constant repositioning of swing cables and anchors as the dredge advances forward into the next cut. To this end, powered submersible walking system  100  ( FIGS. 6, 7  and  11 - 13 ) is located behind the pump and is motor driven such as by the submersible motor drive  102  ( FIG. 11 ) to provide a left and right swinging motion for the boom  12 . The motor drive  102  drives members  104  about an endless path and into engagement with the bottom to enter into contact with the ground and then to push against the ground to move the boom in the direction of a reaction to the direction of rotation of the members rotating in the endless path. In this illustrated embodiment, the members  104  are in the shape of large, bladed feet  106  that are directed to always enter and exit the ground while in a vertical position. When inserted into the ground, large vertical faces of the feet push directly against the material with a force that does not exceed the sheer strength of the material to tear it up and out like a conventional paddle wheel would do.  
         [0053]     It is most desirable to limit the amount of suspended solids that are put into the water column by the bladed feet while obtaining the maximum traction to move the boom in the forward direction of taking the cut. Herein, each of the illustrated bladed feet  106  comprise a pair of left and right feet in the shape of identical wedge-shaped members  109  each of which has an outer, vertical face  110  and an inclined inner face  112 . The feet are wedge-shaped or triangular in cross-section between the inclined face  112  and vertical face  110 . These wedge-shaped members have a central portion  113 .  
         [0054]     Each blade foot  106  is maintained in a vertical position with the pointed ends down as it is swung downwardly ( FIG. 13 ) into the ground, from position  1  to position  2  in a rotation of 72 degrees. For the next 72 degrees the blade foot is vertically disposed in the ground as it travels from position  2  to position  3 . Then, the bladed foot is raised from the ground as it travels through the next 72 degrees of rotation between positions  3  and  4 , the latter being at 216° of rotation. During the next 144 degrees of rotation of the blade foot, it will move through its highest position  5  and then return to position  1 . Thus, the blade foot pushes against the ground to provide traction without being at an angle that tends to scoop up the ground and deposit it in the water causing increased turbidity.  
         [0055]     Each blade foot  106  is quite wide, as best seen in  FIG. 11  and it extends between a pair of supporting, vertically extending main drive hubs  120 . There are five arms  120   a  on each of these respective hubs projecting outwardly from a central hub portion  120   b  ( FIG. 11   a ) at which the main drive hubs have a central bore  120   c  in which is disposed a main drive shaft  124  which extends horizontally through each blade foot assembly as best seen in  FIG. 11 . The main drive hubs are fixed to the main drive shaft and are rotated by the main drive shaft. The left end of the main drive shaft  124  is mounted for rotation in a frame  118  and is driven by a horizontal output shaft of a vertically extending transmission gear box  126  which is driven by an output shaft  127  of an overhead motor  102   a , which is preferably a high torque, submersible gear motor. Manifestly, other motors may be used other then this gear motor. The drive motor  102  and transmission are carried in the frame which also comprises a large horizontally extending frame portion  118   a  which extends horizontally from the motor drive frame  118  to the right as seen in  FIG. 11  to a depending, stationary, vertical frame plate  118   b . The lower end of the frame plate  118   b  carries a bearing mount  130  for the right hand of the main drive shaft  124  when viewing the main shaft in  FIG. 11 . The left end of the main drive shaft is supported in a bearing mount  130   a  adjacent the output drive of the transmission gear box  126 .  
         [0056]     The main drive shaft  124  is used to drive the blade feet  106  into the ground and to propel the boom  12  and suction head  16  forwardly in the swing direction as illustrated in  FIG. 12  and  FIG. 12   a . As shown in  FIG. 12   a , the motor drive  102  is located closest to the dredge and is supported on the outer end of the boom adjacent the pump head unit. The outer, vertical frame place  118   b  is disposed close to the pump unit.  
         [0057]     The blade feet  106  are raised and lowered and swung through 360 degrees travel path by an eccentric drive  140  that preferably, comprises a rotating eccentric hub  142  and a connector link  144  ( FIG. 11   b ). The illustrated eccentric hub  142  is a pentagon shaped plate having a central bore  145  in which is received a circular eccentric cam  148  which is fixed to the main drive shaft  124  at an off-center eccentric throw distance. That is, the center of the disk shaped, eccentric cam is displaced by a predetermined distance from the rotational axis of the main drive shaft  124 . The rotating eccentric hub  142  carries five cam follower rollers  150  equally spaced about the eccentric hub. Each cam follower comprises a roller  150   a  being mounted on a horizontal shaft  150   b  with each roller having rolling engagement of the periphery of the eccentric cam  148 .  
         [0058]     Extending between the rotating eccentric hub  142  and the inner one of the main drive hubs  120  are the fine connector links  130  ( FIG. 11   b ).  
         [0059]     The upper end of each connector link  130  has a circular aperture  144   a  which is sized to mount on a horizontal shaft and bearing mount  142   a . A lower, square aperture  144   b  is formed in each of the five connector links  144  to prevent the walking feet from rotating relative to the links. This connector link assembly maintains the respective blade feet oriented in the vertical direction as the main drive hubs  120  rotate and the respective blade feet make the revolution illustrated in  FIG. 13 .  
         [0060]     From the foregoing, it will be seen that the motor drive  102  drives the transmission gear box  126  to turn the main drive shaft  124  to rotate the eccentric cam  148  and to rotate main drive hubs  120  fixed to the main drive shaft. The eccentric cam is followed by the cam follower rollers  150  which move each of the respective blade feet  106  down into the ground between positions  1  and  2 , as seen in  FIG. 13  and then through 72 degrees of traction before leaving between positions  3  and  4  while the next following traction foot  106  is moving into the ground at position  2  to continue the traction. Thus, the motor drive  102  drives each of the bladed feet  106  into the ground and to provide an endless path drive or bladed feet to keep swinging the boom  12  first in one direction and then in the opposite direction to make the cut in a continuous manner without having to have a swing system that includes the anchor points and the swing cables as well as a crew to reposition anchor points. It will be seen that the system provides a good traction with a minimum of turbidity and eliminates the need for maintaining expensive anchor barge and crew to move the heavy anchors and the resulting loss of production time while the dredge anchors are being repositioned. Also, it will be seen from the foregoing that the embodiment illustrated in the  FIGS. 6, 7  and  11 - 13  provides a unique traction system for engaging the bottom and moving the suction inlet to the left and the right by a submerged drive system that does not require any barge or overhead system to aid in the shifting of the boom to swing through the cuts.  
         [0061]     Further, it will be seen from the foregoing that the system provides a submersible drive combination that includes a submersible drive for the suction pump as well as a submersible drive for the low turbidity around the suction inlet which prevents large debris and sticky material from clogging the pump inlet and a submersible drive for the traction or walking system for engaging and moving the intake head along the ground in the sweep of a cut while dredging. Use of the submersible pump rotating head and rotating walking system provides unique advantages particularly for remediation dredging.  
         [0062]     While the illustrated embodiment is disclosed and directed to use with a typical installation of an outdoor reclamation of contaminated material from a harbor bottom located underneath a large body of water, it is understood that contaminated material or the material being dredged could be located in a large tank having a liquid other than water and having the suspended material at the bottom of the tank which is desired to be removed while in the highly concentrated form. That is the present invention is not limited to a particular use of a conventional dredge but can be also used to remove material from tanks or the like or in other environments where the liquid is not water but is some other chemical liquid.