Patent Publication Number: US-7214003-B1

Title: Segmental floating bulkhead assembly

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a bulkhead assembly for dewatering water passages of dams and, more particularly, to a floating bulkhead assembly and, most particularly, to a segmental floating bulkhead assembly for this purpose. 
   2. Background Information 
   The standard means for dewatering dam intakes and outlets, such as spillways, outlet works, penstocks and draft tubes, has been with bulkhead assemblies or stop logs placed in opposing slots set in the passageway walls. A bulkhead assembly is a one-piece fabrication that is positioned across the water passage opening in slots to allow the water passage to be dewatered without having to lower the reservoir. The bulkhead assembly is usually lowered into place from the top of the dam with a mobile crane, gantry crane or permanent hoist. For large openings, where a one-piece bulkhead assembly is impractical, a series of horizontal bulkhead assemblies, called stop logs, are placed in the slots and stacked one on top of the next, using the same type of lifting devices used for the one-piece bulkhead assemblies. Bulkhead assemblies and stop logs are made from timber, aluminum or stainless steel for small passages, but larger openings mandate steel fabrications. When not in use, the bulkhead assemblies or stop logs are suspended above the water passage or placed in a dry storage location. 
   The use of buoyancy for bulkhead assemblies to reduce or eliminate the need for hoists or cranes is known. Older floating bulkhead assemblies often were one-piece steel fabrications used at site-specific intakes and stored permanently in the reservoir or removed with a large capacity crane after use. These bulkhead assemblies are designed similar to a ship. The floating bulkhead assembly&#39;s bottom is filled with ballast to keep it upright, and the bulkhead assembly is partitioned into chambers that are flooded or purged to adjust the trim of the bulkhead assembly. 
   Many of these floating bulkhead assemblies are still in use. However, they are difficult to maneuver and operate, more costly to fabricate than conventional bulkhead assemblies, and expensive to maintain. If not maintained, floating bulkhead assemblies may be deemed unsafe to operate due to unknown conditions in the sealed chambers, internal steel corrosion or unreliable components. 
   Some examples of inventions concerned with bulkhead assemblies for which patents have been granted are found in the following: Mills, U.S. Pat. No. 5,634,742, and Tucker, U.S. Pat. No. 4,729,692. Additionally, various other designs have been used or considered as shown in the literature, including the Northern States Power Company and Ayres Associates hinged bulkhead assembly described in Trends, a Publication of Ayres Associates, “Dam Renovation—Hinged Floating Bulkhead Assembly Proves Flexible, Reusable”, Autumn, 1987 (“Ayres Design”), and further described by Bakken and Vonasek in Proceedings: Small Hydro 1988, Ministry of Energy, Toronto, Canada, “Floating Bulkhead Assembly Installed for Hydro Intake Repair,” July 1988 among others. However, these disclosed devices embody many of the shortcomings outlined above, resulting in a need for an economical, easily fabricated bulkhead assembly, which is readily handled without large, expensive equipment. 
   The Ayres Design, which utilizes wide flange steel beams, has several drawbacks compared to the use of hollow rectangular section steel tubes made from flat sheet. Fabrication using wide flange beams to create a workable caisson requires a great amount of skillful cutting and welding of the beams, which increases the cost of fabrication. Wide flange beams are not produced in many useable varieties or dimensions, and heavy customization is often required. This lack of variety also lessens the engineering options. With wide flange beams, the bottom chamber is generally required to be the sealable chamber of the caisson, which in turn, dictates or limits the engineering options for the size of the caisson. Bakken and Vonasek reference the drawbacks with the use of rolled rectangular tube sections as being quite heavy and, due to the limited depths available in rolled steel tubes, the anticipated deflections of the units at the bottom of the wall would be excessive and could potentially cause problems with the bottom seal. Also, a drawback of using large dimension tube sections, for instance, tube sections greater than approximately 0.7 meters wide, is the excess weight and cost. The device of the present invention meets these needs, while providing many additional features that are unique to the methods and structures described herein. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to the structure of a floatable caisson member and to a segmental floatable bulkhead assembly formed by assembling a plurality of the floatable caisson members. The present invention also includes a method of fabrication of the floatable caisson member. Dewatering a water passage of a dam is achieved by employing a segmental floatable bulkhead assembly formed by assembling a plurality of the floatable caisson members. 
   In one embodiment of the invention, the floatable caisson member includes at least two hollow, rectangular section, HSS steel tubes made from flat sheet steel, each tube sealed at each end by a tube end plate to form at least two sealed chambers. A side plate is secured to the at least two steel tubes, with the at least two steel tubes and the side plate defining at least one intermediate space. At least one pair of intermediate space end plates is secured between adjacent tubes of the at least two tubes. At least one intermediate chamber plate is secured to the at least two steel tubes opposite the side plate. The intermediate chamber plate seals at least a portion of the at least one intermediate space to create at least another sealed chamber. At least one sealed chamber includes at least one sealable aperture to selectively flood the sealed chamber and to evacuate water from the sealed chamber. The sealed chambers may be selectively flooded and evacuated to effectuate the desired submersion, installation and removal of the floatable caisson member from the water passage of a dam. 
   One method of fabrication of the floatable caisson member includes the steps of providing at least two hollow, rectangular section, HSS steel tubes and connecting the tubes in parallel with a side plate, with the tubes and side plate defining at least one intermediate space. The at least two tubes are sealed with tube end plates to form at least two sealed chambers. At least a portion of the at least one intermediate space is sealed to create at least another sealed chamber. At least one sealed chamber includes at least one sealable aperture to selectively flood the sealed chamber and to evacuate water from the sealed chamber. The chambers may be selectively flooded and evacuated to effectuate desired submersion, installation and removal of the caisson member from the water passage of a dam. 
   Another embodiment of the present invention includes a bulkhead assembly for dry isolation of a water passage of a dam. The bulkhead assembly comprises a plurality of floatable caisson members bound together to form a platform assembly adapted to float in a horizontal attitude on a water body surface. At least one of the caisson members includes at least two HSS steel tubes connected in parallel with a side plate, the HSS tubes and the side plate defining at least one intermediate space. The at least two tubes are sealed with tube end plates to form at least two sealed chambers, and at least a portion of the at least one intermediate space is sealed to create at least another sealed chamber, with at least one of the sealed chambers including at least one sealable aperture to selectively flood the sealed chamber and to evacuate water from the sealed chamber to cause the bulkhead selectively to move between the horizontal attitude and a vertical attitude in the water body, and selectively to reduce and increase buoyancy of the bulkhead assembly. At least one of the floatable caisson members includes a sealable conduit for selectively permitting flow of water from the water body through the bulkhead assembly. 
   The invention also comprises one method for isolating a water passage of a dam from a body of water, including the steps of providing a plurality of floatable caisson members adapted for binding together to form a single, panel bulkhead assembly that floats in a horizontal attitude on a water body surface. At least one of the caisson members includes at least two HSS steel tubes connected in parallel with a side plate, the HSS tubes and the side plate defining at least one intermediate space. The at least two tubes are sealed with tube end plates to form at least two sealed chambers, and at least a portion of the at least one intermediate space is sealed to create at least another sealed chamber, with at least one of the sealed chambers including at least one sealable aperture to selectively flood the sealed chamber and evacuate water from the sealed chamber. The floatable caisson members are connected together to form a rigid, single panel bulkhead assembly adapted to float in horizontal attitude on the surface of the body of water. At least one of the sealed chambers is flooded to cause the bulkhead assembly to move from the horizontal attitude to a vertical attitude in the body of water. The bulkhead assembly is moved in the vertical attitude to a position contacting water passage piers. The bulkhead assembly is held against the piers, and at least a further of the at least one sealed chambers is flooded to reduce buoyancy of the bulkhead assembly to cause the bulkhead assembly to sink to the sill of the water passage. Water from an area behind the bulkhead assembly is then evacuated. 
   The invention also comprises another method for isolating a water passage of a dam from a body of water, including the steps of providing a plurality of floatable caisson members adapted for rotatably binding together to form a segmental bulkhead assembly that floats in a horizontal attitude on a water body surface. At least one of the caisson members includes at least two HSS steel tubes connected in parallel with a side plate, the HSS tubes and the side plate defining at least one intermediate space, the at least two tubes sealed with tube end plates to form at least two sealed chambers, with at least a portion of the at least one intermediate space sealed to create at least another sealed chamber, and with at least one of the sealed chambers including at least one sealable aperture to selectively flood the sealed chamber and evacuate water from the sealed chamber. 
   At least two of the floatable caisson members are rotatably connected together to form a rotatable, segmental bulkhead assembly adapted to float in the horizontal attitude on the surface of the body of water. The bulkhead assembly is moved in the horizontal attitude to a position adjacent water passage piers, with one caisson member floating adjacent the water passage and one caisson member floating opposite the water passage. At least one sealed chamber of the bulkhead assembly caisson member adjacent the water passage is flooded to cause the caisson member to move from the horizontal attitude to a submerged vertical attitude in the body of water. The flooding step is repeated for selected sealed chambers of selected floating caisson members to move that caisson member to a submerged vertical attitude, causing the segmental bulkhead assembly to sink to the sill of the water passage. Water from an area behind the segmental bulkhead assembly is then evacuated. 
   The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and detailed description that follow more particularly exemplify these embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
       FIG. 1  shows a perspective view of one step in the fabrication of one embodiment of the floatable caisson member of the present invention. 
       FIG. 2  shows a perspective view of another step in the fabrication of one embodiment of the floatable caisson member of the present invention. 
       FIG. 3  shows a perspective view of another step in the fabrication of one embodiment of the floatable caisson member of the present invention. 
       FIG. 4  shows a perspective view of an alternative step in the fabrication of one embodiment of the floatable caisson member of the present invention. 
       FIG. 5  shows a perspective view of one step in the fabrication of another embodiment of the floatable caisson member of the present invention. 
       FIG. 6  shows a perspective view of another step in the fabrication of the embodiment of  FIG. 5  of the floatable caisson member of the present invention. 
       FIG. 7  shows a perspective view of a further step in the fabrication of the embodiment of  FIG. 5  of the floatable caisson member of the present invention. 
       FIG. 8  shows a perspective view of an alternative step in the fabrication of the embodiment of  FIG. 5  of the floatable caisson member of the present invention. 
       FIG. 9A  shows a perspective view of another step in the fabrication of the embodiment of  FIG. 1  of the floatable caisson member of the present invention. 
       FIG. 9B  shows a perspective view of another step in the fabrication of the embodiment of  FIG. 5  of the floatable caisson member of the present invention. 
       FIG. 10  shows a cross sectional view along line  10 – 10 ′ of  FIG. 9B . 
       FIG. 11  shows a segmental floatable bulkhead assembly made from a plurality of floatable caisson members of the present invention and configured in a vertical attitude. 
       FIG. 12  shows a segmental floatable bulkhead assembly of the present invention during installation, using the rotatably connected method. 
   

   While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not necessarily to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention, as defined by the appended claims. 
   DESCRIPTION OF THE EMBODIMENTS 
   The present invention is directed to a floatable caisson member for use with a bulkhead assembly for dry isolation of water passages of a dam. In one embodiment of the invention, the floatable caisson member includes at least two hollow, rectangular section, HSS steel tubes made from flat sheet steel, each tube sealed at each end by a tube end plate to form at least two sealed chambers. A side plate is secured to the at least two steel tubes, with the at least two steel tubes and the side plate defining at least one intermediate space. At least one pair of intermediate space end plates is secured between adjacent tubes of the at least two tubes. At least one intermediate chamber plate is secured to the at least two steel tubes opposite the side plate. The intermediate chamber plate seals at least a portion of the at least one intermediate space to create at least another sealed chamber. At least one sealed chamber includes at least one sealable aperture to selectively flood the sealed chamber and evacuate water from the sealed chamber. At least one of the sealed chambers is selectively flooded and evacuated to effectuate the desired submersion, installation and removal of the floatable caisson member from a water passage of a dam. 
   One method of fabrication of the floatable caisson member includes the steps of providing at least two hollow, rectangular section, HSS steel tubes and connecting the tubes in parallel with a side plate, with the tubes and side plate defining at least one intermediate space. The at least two tubes are sealed with tube end plates to form at least two sealed chambers. At least a portion of the at least one intermediate space is sealed to create at least another sealed chamber. At least one sealed chamber includes at least one sealable aperture to selectively flood the sealed chamber and evacuate water from the sealed chamber. At least one of the sealed chambers is selectively flooded and evacuated to effectuate desired submersion, installation and removal of the caisson member from water passage of a dam. 
   There are five general criteria for individual caisson members that assemble to form a segmental bulkhead assembly for water passage control during dam or gate repairs.
         1. Each caisson member floats or sinks dependent upon the amount of water it contains.   2. The caisson member structure must resist the maximum hydraulic pressures encountered in all contemplated applications.   3. The caisson member structure must be water tight with no unintended air or water leakage.   4. The caisson member structure must provide for controlled addition and removal of water ballast to prevent sudden or uncontrolled movement of the caisson member structure during installation and removal.   5. The caisson member structure must be of suitable size and strength for portability between points of use.       

   Referring to  FIGS. 1–12 , several embodiments of the floatable caisson member device of the present invention are shown. The structural features of the floatable caisson member of the present invention are best understood by describing the fabrication of such a floatable caisson member. The method of fabrication of the floatable caisson member is also unique and comprises one facet of the present invention. 
   Referring now to  FIGS. 1–3 , the fabrication of one embodiment of the floatable caisson member  110  includes the steps of providing at least two hollow, rectangular section, steel tubes  115 . These tubes are known as Hollow Structural Section (HSS) tubes that are fabricated by bending flat sheet steel, preferably by utilizing a Form-Square Weld-Square Process, or a Submerged Arc Weld Process, which is also known as the Brake Form Process. This embodiment is illustrated with two HSS steel tubes  115 , but three or more HSS steel tubes  115  can be included with equivalent results. The HSS steel tubes  115  are preferably fabricated with a step of bending flat steel sheet that has a thickness sufficient to provide the structural characteristics required for use in a floatable caisson member  110 . The HSS steel tubes  115  have a length sufficient to span a water opening of a dam, so that a bulkhead assembly made from a plurality of floatable caisson members  110  can isolate the water opening from a body of water. The HSS steel tubes  115  are preferably of equal length and of similar rectangular section. 
   A side plate  120  is fastened or joined, preferably by welding, to the at least two HSS steel tubes  115 , with the at least two HSS steel tubes  115  and the side plate  120  defining at least one intermediate space  125 , which has a rectangular cross section. In this embodiment, the side plate  120  extends between adjacent edges of the parallel HSS steel tubes  115 . The side plate  120  is secured, preferably by welding, to the adjacent edges of each HSS steel tube  115 , as shown in  FIGS. 1 and 2 . The HSS steel tubes  115  are sealed with end plates  130  so that the sealed HSS tubes  115  become chambers to selectively hold and release air. At least one pair of intermediate space end plates  135  is secured between adjacent HSS tubes  115 . The intermediate space end plates  135  may be positioned anywhere within the intermediate space or at the end positions of the intermediate space, however, are preferably installed short of the ends of each HSS tube  115 , as illustrated in  FIGS. 2 and 3 , such that the end plates  135  also function as diaphragms between the HSS tubes  115  and impart improved structural integrity to the floatable caisson member  110 . Installing end plates  135  in such a recessed manner also eases the structural fastening of end plates  135  and fabrication of caisson member  110 . Installing at least one intermediate chamber plate  150  to the tubes  115  opposite the side plate  120  seals the intermediate space to provide at least one additional sealed chamber. The intermediate chamber plate  150  may extend the length of the tubes  115 , but preferably more than one plate  150  is utilized. Tubes  115  become sealed when joined with tube end plates  130  to become sealed chambers, and space  125  (or a portion thereof), is also sealed such that space  125  becomes a sealed chamber. Thus, reference made herein to a sealed chamber is reference made to a sealed tube  115  or a sealed space  125  (or portion thereof), or both. 
   In a further embodiment of the invention, at least one diaphragm  140  is installed within the intermediate space  125  to subdivide the space  125 , as illustrated in  FIG. 2 , where three such diaphragms  140  are installed. Installing at least one intermediate chamber plate  150  to the tubes  115  opposite the side plate  120  seals the intermediate space  125  to provide at least one additional sealed chamber. Preferably, the intermediate chamber plate  150  is secured, preferably by welding, to the adjacent tube edges of the intermediate space  125  opposite the side plate  120 . As illustrated in  FIG. 3 , where the intermediate spaces  125  includes three diaphragms  140 , the resulting four intermediate chambers  125  are sealed with four intermediate chamber plates  150 . Each of the four intermediate spaces  125  may therefore be configured as sealable, intermediate chambers or sealed intermediate sub-chamber portions. One or more diaphragms  140  may include an opening  145  that provides fluid communication between adjacent sealed intermediate chambers. The opening  145  may be a central aperture or selectively designed with slots or openings. The chamber plates  150  are secured, preferably by welding to the end plate  135  and the diaphragm  140 , as well as to the adjacent tube edges, to seal the intermediate space  125 . 
   An alternative embodiment of the invention disclosed in  FIGS. 1–3  is shown in  FIG. 4 . Referring to  FIG. 4 , the caisson member&#39;s intermediate space  125  is divided into four subchambers by three diaphragms  140 , as described above. The two end subchambers are sealed by securing, preferably by welding an intermediate chamber plate  150  to the tube edges, the intermediate space end plate  135 , and one diaphragm  140 . The interior intermediate subchambers are covered only by intermediate chamber cover screens  160 , leaving a void that fills with water upon submersion of the floatable caisson member. In a further embodiment, shown in  FIG. 4 , the interior, intermediate subchamber voids beneath the cover screens  160  are filled with buoyant foam material  165  to exclude water from the voids, thereby adjusting the buoyancy of the floatable caisson member  110 . 
   Further aspects of the previous embodiments are described later with respect to a completed caisson such as that shown in  FIG. 9A . 
   Referring now to  FIGS. 5–7 , the fabrication of another embodiment of the floatable caisson member  110  includes the steps of providing at least two hollow, rectangular section, steel tubes  115 . These tubes are known as Hollow Structural Section (HSS) tubes that are fabricated by the processes described in detail above. Again, this embodiment is illustrated with two HSS steel tubes  115 , but three or more HSS steel tubes  115  can be included with equivalent results. The HSS steel tubes  115  are preferably fabricated with a step of bending flat steel sheet that has a thickness sufficient to provide the structural characteristics required for use in a floatable caisson member  110 . The HSS steel tubes  115  have a length sufficient to span a water opening of a dam, so that a bulkhead assembly made from a plurality of floatable caisson members  110  can isolate the water opening from a body of water. The HSS steel tubes  115  are preferably of equal length and of similar rectangular section. 
   A side plate  120  is secured to the at least two HSS steel tubes  115 , with the at least two HSS steel tubes  115  and the side plate  120  defining at least one intermediate space  125 , which has a rectangular cross section. The side plate  120  extends essentially the full width of the parallel HSS steel tubes  115  positioned thereon. This allows both adjacent and opposite edges of each HSS steel tube positioned on the side plate  120  to be secured, preferably by welding, thereto, as shown in  FIGS. 5 and 6 . In this embodiment, the side plate  120  also functions as tube cover plates, providing additional structural integrity for the caisson member  110 . The HSS steel tubes  115  are sealed with end plates  130  so that the sealed HSS tubes  115  become chambers to selectively hold and release air. At least one pair of intermediate space end plates  135  is secured between adjacent HSS tubes  115 . The intermediate space end plates  135  may be positioned anywhere within the intermediate space or at the end positions of the intermediate space, however, end plates  135  are preferably installed short of the ends of each HSS tube  115 , as illustrated in  FIGS. 6 and 7 , such that the end plates  135  also function as diaphragms between the HSS tubes  115  and impart improved structural integrity to the floatable caisson member  110 . Installing end plates  135  in such a recessed manner also eases the structural fastening of end plates  135  and fabrication of caisson member  110 . 
   In a further embodiment of the invention, at least one diaphragm  140  is installed within the intermediate space  125  to subdivide the space  125 , as illustrated in  FIG. 6 , where three such diaphragms  140  are installed. Installing at least one intermediate chamber plate  150  to the tubes  115  opposite the side plate  120  seals the intermediate space  125  to provide at least one additional sealed chamber. Preferably, the intermediate chamber plate  150  is secured to the adjacent tube edges of the intermediate space  125  opposite the side plate  120 . As illustrated in  FIG. 7 , where the intermediate spaces  125  includes three diaphragms  140 , the resulting four intermediate spaces  125  are sealed with four intermediate chamber plates  150 . Each of the four intermediate spaces  125  may therefore be configured as sealable, intermediate chambers or sealed intermediate subchamber portions. One or more diaphragms  140  may include an opening  145  that provides fluid communication between adjacent, sealed, intermediate chambers. The aperture  145  may be a central aperture or selectively designed with slots or openings. The chamber plates  150  are secured, preferably by welding, to the end plate  135  and the diaphragm  140 , as well as to the adjacent tube edges to seal the intermediate space  125 . In addition, tube cover plates  155  may be secured to the tube  115  sides adjacent the intermediate chamber plates  150  for additional structural integrity, as illustrated in  FIG. 7 . Thus, each tube cover plate  155  is secured to a surface of one HSS steel tube  115 , opposite the side plate  120 . 
   An alternative embodiment of the invention disclosed in  FIGS. 5–7  is shown in  FIG. 8 . Referring to  FIG. 8 , the caisson member&#39;s intermediate space  125  is divided into four subchambers by three diaphragms  140 , as described above. The two end subchambers are sealed by securing, preferably by welding, an intermediate chamber plate  150  to the tube edges, the intermediate space end plate  135 , and one diaphragm  140 . The interior intermediate subchambers are covered only by intermediate chamber cover screens  160 , leaving a void that fills with water upon submersion of the floatable caisson member. In a further embodiment, shown in  FIG. 8 , the interior, intermediate subchamber voids beneath the cover screens  160  are filled with buoyant foam material  165  to exclude water from the voids, thereby adjusting the buoyancy of the floatable caisson member  110 . 
   Further aspects of the previous embodiments are described later with respect to a completed caisson such as that shown in  FIG. 9B . 
   The use of hollow rectangular section (HSS) tubes made from flat sheet material accommodates easier and less expensive caisson fabrication, simplified caisson installation and a variety of engineering options. The HSS tubes  115  can be custom fabricated and sized to fit a particular application, whereas the wide flange beams are available only in set sizes. The wide flange member&#39;s flange edges must be butted together to form sealed chambers requiring expensive edge preparation, a difficult partial penetration butt weld that leaves an interior seam that weakens the joint and leaves a location to initiate corrosion The caisson fabrication method does not require personnel access for fabrication as do structures shown in some references. A further advantage of applicant&#39;s invention is the use of HSS tubes  115 , configured with a cover plate  155  to provide additional structural integrity for the caisson member  110 . 
   Referring now to  FIGS. 9A and 9B , fully assembled floatable caisson members  110  are shown. The structure shown in  FIG. 9A  corresponding to the structure shown in the embodiments described earlier concerning  FIGS. 1–3 . The structure shown in  FIG. 9B  corresponds to the structures shown in the embodiments described earlier concerning  FIGS. 5–7 . The sealed, intermediate space  125  and/or an HSS steel tube  115 , includes a means for controlling air and water entry and exit from at least one sealed chamber of the floatable caisson member  110 . For example, the sealed, intermediate space  125  is provided with at least one sealable aperture  175  for controlling air and water entry and exit therefrom. At least one aperture  175  is provided to selectively flood the sealed chamber (either the intermediate space  125  or portion thereof, or a steel tube  115 ), and to evacuate water from the sealed chamber. The sealable apertures  175  preferably include corresponding plugs  180  that are preferably manually inserted or removed to control air and water entry and exit. 
   In addition to use of plugs  180 , aperture  175  may also include a valve as means for controlling air and water entry. It is also appreciated that a hose or tube from a water pump (not shown) or air compressor (not shown), for instance, may be associated with the aperture  175 , such that the water pump or air compressor operate as means for controlling air and water entry. 
   The floatable caisson member  110  includes a plurality of fastening devices  35  installed on at least one exterior surface of the caisson member  110 . Preferably, a pair of spaced apart fastener devices  35  is installed on each of two opposed exterior surfaces of the caisson member  110 , as illustrated in  FIGS. 9A and 9B . The fastening devices are preferably planar members that extend perpendicularly across the width of the caisson member  110 . The fastening devices  35  have fastener openings  40  at each end thereof, with a slot at one fastener end to accept the planar fastener member  35  from another caisson member  110 . Pins, bolts or turnbuckles (not shown) inserted through the mated fastener openings  40 , secure adjacent caisson members  110  together. At least one rotatable fastening device  310  (see  FIG. 12 ), for instance, may be secured to the exterior surface of the caisson member  110  for assembling a bulkhead assembly made of rotatable caisson members. 
   A cross sectional view of the floatable caisson member  110  is shown in  FIG. 10 , where the caisson member side plate  120  extends to opposite edges of the HSS steel tubes  115  and both an intermediate chamber plate  150  and tube cover plates  155  are present. Additionally, a seal  190  extends substantially the length of one said at least two HSS steel tubes  115 , the seal forming a watertight joint between adjacent, joined, floatable caisson members  110 . An adjustable seal  170  (see  FIGS. 9A ,  9 B and  11 ) also extends across the width of the caisson member  110  at both ends. This seal  170  abuts the face of the dam and/or a pier nose  340  (see  FIG. 12 ) adjacent the water passage with the caisson member  110  in place. Seal  170  may be relocated on floatable caisson members  110  for different water passage opening spans. A bottom seal  192  (see  FIG. 11 ) may be positioned on at least one caisson member  110  for forming a water tight joint between the caisson member  110  and sill  335 , seat or structure face of the dam. Seals  170  and  192  accordingly engage the water passage structures such as the sill  335 , pier nose  340 , and dam face (not shown). 
   Referring now to  FIG. 11 , a unique segmental floating bulkhead assembly  205  is shown. The bulkhead assembly  205  consists of a plurality of individual, floatable caisson members  110 , described in detail above, connected together on the upstream side and, optionally as shown, also on the downstream side. Preferably, each floatable caisson member  110  consists of three or more sealed horizontal chambers with a selected chamber used to vary the buoyancy of the bulkhead assembly  205 . The floatable caisson members  110  are constructed of steel tube sections and plate, as described above, to form the various chambers, thereby simplifying fabrication, mitigating internal corrosion, and reducing manufacturing costs. Sealable apertures  175  are covered with corresponding plugs  180  that are manually inserted and removed to control air and water entry and exit to cause the bulkhead selectively to move between a horizontal attitude (not shown) and a vertical attitude (see  FIG. 11 ). Additionally, water and air conduit means such as water hoses and air hoses may be assembled (not shown) to connect with aperture  175  for obtaining fluid communication with a selected one or more of the caissons  110 . Preferrably, apertures  175  are manually sealable, but it may be appreciated that apertures  175  may be sealed non-manually. A sealable conduit  195  (see  FIG. 11 ) is provided in at least one of the floatable caisson members  110  for selectively permitting flow of water from the water body through the bulkhead assembly  205 . An extended valve handle  200  activates opening and closing of conduit  195 . 
   In a further embodiment of the present invention, a method for isolating a water passage of a dam from a body of water is disclosed. The method includes the steps of providing a plurality of floatable caisson members  110  bound together to form a rigid, panel bulkhead assembly  205 , adapted to float in a horizontal attitude on a water body surface. At least one of the caisson members  110  include at least two HSS steel tubes  115  connected in parallel with a side plate  120 , the HSS tubes  115  and the side plate  120  defining at least one intermediate space  125 , with the at least two tubes  115  sealed with tube end plates  130  to form at least two sealed chambers, and at least a portion of the at least one intermediate space  125  sealed to create at least another sealed chamber, with at least one of the sealed chambers including at least one aperture  175  to selectively flood the sealed chamber and evacuate water from the sealed chamber. The floatable caisson members  110  are connected together to form a bulkhead assembly  205 , adapted to float in a horizontal attitude on the surface  325  of the body of water. At least one of the sealed chambers within at least one of the floatable caisson members  110  is flooded to cause the bulkhead assembly  205  to move from the horizontal attitude to a vertical attitude in the body of water. The bulkhead assembly  205  is moved in the vertical attitude to a position contacting water passage piers. The bulkhead assembly  205  is held against the piers, and selectively flooding of at least a further of said at least one sealed chambers occurs to reduce buoyancy of the bulkhead assembly  205  to cause the bulkhead assembly  205  to sink to the sill of the water passage. Water from an area between the dam gate and the bulkhead assembly  205  is then evacuated. 
   Additional details of the above method include the following. Each floatable caisson member  110  is placed on the reservoir and pinned together on the upstream side, as well as fastened together by turnbuckles (not shown) on the downstream side, to form a rigid, unitary bulkhead assembly  205 . Sealable apertures  175  positioned on the downstream face of selected, floatable caisson members  110  are opened to allow reservoir water to flood the caisson member&#39;s selected chamber. Opening an aperture  175  at each end of the bottom caisson member  110 , for instance, floods the selected chamber to initiate descent of the bulkhead assembly  205  as a unitary structure. As the bulkhead assembly moves from a horizontal to a vertical position, the various open apertures  175  in the other, floatable caisson members  110  fill with water to provide ballast, much like the keel of a ship. No air compressors or water pumps are needed for installation, in contrast to prior floating bulkhead assemblies. Further, the buoyant force is distributed among the various floatable caisson members  110  so that high strength rods are not needed to tie the caisson members  110  together. Additionally, the bulkhead assembly  205  of the present invention does not require hoists or rigging to control the descent of the caisson members  110 , as with certain other segmented bulkhead assemblies (Ayres Design). 
   Once in the vertical position, the bulkhead assembly  205  is moved to the dam water passage to be dewatered. The bulkhead assembly  205  is lowered to the dam sill, seat or structure face by opening apertures  175  in another caisson member&#39;s selected chamber until the bulkhead assembly  205  is positioned properly. The water passage of the dam is drained to seat the submerged bulkhead assembly  205  against the water passage structures, such as the sill  335 , pier nose  340  or dam face. Water drains from the ballasted, selected chambers via apertures  175  on the caisson member&#39;s downstream side, as the water passage is emptied. The downstream chamber apertures  175  are closed after draining, except for those needed for ballasting during removal of the bulkhead assembly  205 . In the vertical, floating position, before it is seated, the bulkhead assembly  205  can be moved from one water passage to another without bringing the bulkhead assembly  205  to a horizontal attitude, provided the reservoir pool is sufficiently deep. 
   Gate  315  (see  FIG. 12 ) may be returned to operation when bulkhead assembly  205  is moved from the water passage. Water is evacuated from at least one of the sealed chambers and at least one aperture  175  is sealed to prevent flooding of the chamber. The area A between the dam gate and the bulkhead assembly  205  is flooded to allow the bulkhead assembly to float off the water passage sill  335 , preferably by opening sealable conduit  195 . The bulkhead assembly  205  may also be moved from the pier nose  340 , dam face or water passage. Additional selected sealed chambers may also be evacuated and sealed to allow the bulkhead assembly  205  to move from the vertical attitude to the horizontal floating attitude. The caisson members  110  may be disconnected from each other and removed from the body of water for dry storage. 
   In a further embodiment of the present invention, another method for isolating a water passage of a dam from a body of water is disclosed. Referring to  FIG. 12 , the segmental floating bulkhead assembly  305  is shown during installation at a water passage. The method includes the steps of providing a plurality of floatable caisson members  110  adapted for rotatably binding together to form a segmental bulkhead assembly that floats in a horizontal attitude on a water body surface. At least one of the caisson members  110  includes at least two HSS steel tubes  115 , connected in parallel with a side plate  120 , with the HSS tubes  115  and the side plate  120  defining at least one intermediate space  125 . The at least two tubes  115  are sealed with tube end plates  130  to form at least two sealed chambers, with at least a portion of the at least one intermediate space  125  sealed to create at least another sealed chamber. At least one of the sealed chambers includes at least one sealable aperture  175  to selectively flood the sealed chamber and evacuate water from the sealed chamber. Allowing for the selection of any one of the sealed chambers to be configured to selectively hold and release air provides for a variety of design and engineering options. For instance, selecting the intermediate chamber allows engineers to alter the dimensions of the caisson member and other caissons. 
   At least two of the floatable caisson members  110  are rotatably connected together to form a rotatable, segmental bulkhead assembly  305  adapted to float in a horizontal attitude on the surface  325  of the body of water. The bulkhead assembly  305  is moved in the horizontal attitude to a position adjacent the water passage piers  340  or water passage structure, with one caisson member  110  floating adjacent the water passage and one caisson member  110  floating opposite the water passage structure. Piers  340  and sill  335  define the water passage. A hoist  320  is connected to each end of the caisson member  110  floating adjacent to the water passage structure. At least one sealed chamber of the bulkhead assembly caisson member  110 , which is adjacent the water passage, is flooded and the caisson member  110  is lowered with the hoist  320  to cause the caisson member  110  to move from the horizontal attitude to a submerged, vertical attitude in the body of water. The flooding step is repeated for selected sealed chambers of selected floating caisson members  110  adjacent the water passage and the caisson member  110  is lowered with hoist  320  to move the selected caisson members  110  to a submerged vertical attitude, causing the segmental bulkhead assembly  305  to sink to the sill of the water passage, seat or structure face. Water from an area A between the dam gate  315  and the segmental bulkhead assembly  305  is then evacuated. 
   When the segmental, floating bulkhead assembly  305  requires removal, the hoist line  320  is removed from the bulkhead assembly  305 . Water is evacuated from at least one of the sealed chambers sufficient to allow the bulkhead assembly  305  to float off the sill  325  of the water passage. At least one of the caisson member chamber valves or apertures  175  are then sealed or closed to prevent flooding of the at least one sealed chamber. The water passage gate  315  is closed and at least one sealable bypass conduit  195  located in at least one caisson member  110  is opened to allow reservoir water to fill the water passage. Bypass conduit  195  may be manually sealed or un-sealed with handle  200  to effective desired flooding of space A. It may be appreciated that a variety of valves may be used for sealing and un-sealing conduit  195 . The segmental floating bulkhead assembly  305  rises slowly along the piers once water pressure is equalized between the reservoir and the previously emptied water passage area A. Water is evacuated from one or more caisson members  110  and one or more caisson members is re-sealed until each of the caisson members are moved from the vertical attitude to the horizontal floating attitude. Since the floatable caisson members  110  can rotate about the hinge pins on the upstream side, as each floatable caisson member  110  approaches the surface, buoyant forces causes the caisson members  110  to pivot about the connecting pins  310 , positioning the downstream side of each caisson member  110  upward. No hoists, cranes or other heavy rigging are required to float the bulkhead assembly  305 . The bulkhead assembly  305 , which is now in a horizontal orientation, can be converted to a unitary structure by reconnecting the fasteners  35  between adjacent caisson members  110 . This task is readily accomplished, since the unfastened bulkhead assembly side is atop the floating bulkhead assembly  305 . The bulkhead assembly  305  is then moved to another water passage intake for installation, as described above. Should the segmental floating bulkhead assembly  305  require transport to a distant location or storage, the floatable caisson members  110  are disconnected, and each caisson member  110  is extracted from the reservoir. 
   This segmental, floatable bulkhead assembly  305  provides easy maneuverability and maximum flexibility, compared to other similar bulkhead assemblies. Only a few hours will be required to install or remove the segmental, floatable bulkhead assembly  305 . Also, the need for divers to assist with installation and removal is minimized, thus providing additional cost savings. 
   Thus, the individual caisson members  110  that are assembled to form a segmental bulkhead assembly  305  meet the five general criteria for caisson members enumerated above. The present invention provides an improvement over existing caisson member structures, an improvement in the method of their fabrication and improvement in the methods of isolating a dam water passage from a body of water. 
   While the present invention has been described with reference to several particular example embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention, which is set forth in the following claims.