A barge is a flat-bed, shallow-draft vessel with no superstructure that is used for the transport of cargo and ships' stores or for general utility purposes. Transport barges or scows can be defined as cargo-carrying craft that are towed or pushed by a powered vessel on both inland and ocean waters. Barges are flat-bottomed vessels, usually nonself-propelled, used chiefly on inland waterways. Barges are a common type of hull that are important assets as lighters, pulling or lifting platforms, support units, etc. Various configurations are used by commercial and military interests. Large barges may have installed cargo handling or ballasting equipment, including pumps and piping for loading, shifting, or ballasting equipment. Ballast systems may be used for correcting trim, list, and stability problems imposed by cargo loading or casualty damage.
Some ships [Lighter Aboard Ship - LASH] are constructed to carry special barges (lighters). These barges can go to smaller docks, go into inland waterways, load cargo at those places, and then carry it back to the ship which lifts the barges aboard, with their cargo, and transports them overseas. Discharge of cargo is accomplished in the same manner.
Barge hulls can be of either single- or double-walled construction. The bow and/or stern of a barge hull is either vertical (box-shaped) or raked (angled). Raked hulls provide less tow resistance, thereby resulting in fuel savings, while box-shaped hulls are typically limited to barges on the interior of an integrated tow of multiple barges. Barges operated in moderately high wave areas can be constructed with a notched stern in which the towboat bow fits. This connection provides greater resistance to longitudinal movement along the vessel interface and enhances control under adverse conditions.
The transportation of goods by barge can have advantages. Barges use less fuel to move goods compared to other methods of transportation and, therefore, cause less air pollution. The noise generated by barges and the visual intrusion of the barges is less than other modes of transportation. Barge transport is the most common means of transport for mechanically dredged material.
It is generally safer to transport goods by barge than by trucks or rail. Trucks travel in mixed traffic with automobiles and other trucks. When truck-involved accidents occur, they usually result in injuries, loss of cargo and substantial traffic delays. Rail transport generally involves a large number of rail cars in a straight line moving at high speeds. If an accident occurs, usually multiple rail cars are involved resulting in a loss of cargo and the temporary shutdown of the rail line. Barges traveling in coastal waters are generally traveling well away from other vessels and, therefore, the chances of an accident or loss of goods are relatively limited. The inland navigation system is, by far, the safest mode of transportation. For example, the death rate for barge tows in 1993 was 0.01 death per billion ton-miles, compared with 0.84 for trucks and 1.15 for railroads (Haulk). And barges are more than 200 times safer than railroads in terms of injuries.
A US Army Corps of Engineers' (COE) study stated that commercial marine navigation has the least damaging impact on air quality compared to truck and rail. The Canadian National Railway also produced a study that supported this conclusion. Their report stated that the amount of emissions produced moving one-million tons of cargo by diesel trucks is 26,500,000 cubic feet, by rail is 7,440,000 cubic feet, and by water is 5,600,000 cubic feet. The movement of goods by barge would emit 33 percent less pollutants then diesel trains and 373 percent less than diesel trucks. Barge transportation not only emits fewer hydrocarbons, carbon monoxide, and nitrous oxide per ton-mile than rail or trucking, but pollutants tend to be emitted in more remote locations, which further reduces the impact of pollution on population centers.
One of the main advantages of waterway transportation is its very low rate structure, averaging 0.73 cent per ton-mile in 1995, versus 2.49 cents for railroads, the next cheapest transportation mode. This low rate structure fosters competition and exerts downward pressure on the rates of alternative modes of transportation, most notably rail. The waterways' cost effectiveness enables export price advantages for some U.S. exports. For example, corn produced in Iowa cost $2.33 per bushel to grow and harvest in 1996, compared with $1.33 per bushel in Argentina. However, after domestic transportation, the cost of Argentine corn delivered to the mouth of the Plata River increases to $3.21 per bushel, compared with $3.01 per bushel for U.S. corn delivered to the Gulf of Mexico
Coastal barge traffic has little noise impact along the shoreline. Barges are transported by tugboat, distant from the shoreline. The engines of a tugboat are below the water line, which muffles the engine noise. Levees and seawalls in urban areas function as a noise barrier to lessen the noise of the operation.
There are many different types of barges, for the same reason that there are many types of merchant ships:
- Hopper barges for the transport of bulk cargo, which may be fitted with weathertight or watertight hatch covers. Bottom dump hopper barges are fitted with bottom opening doors for dumping rip-rap, dredge spoil, garbage, and the like, or for dumping coal and stone cargoes alongside piers where it is picked up by shore operated grabs or conveyers. Hopper barges are designed specifically to deliver bulk material to open-water disposal sites, and are the most commonly used barges for transporting dredged material. Early hopper barge designs used mechanically driven chain, cable, sheave, and releases to open the cargo compartment door(s). Recent designs use high-pressure hydraulic systems. Split-hull and continuous compartment bottom and side-dump hopper barges are simultaneously dumped, whereas bottom and side-dump hopper barge sections can be dumped individually. All hopper barges leak to some degree. They concluded that all hull seams should be carefully shut and stabilized with sandbags, hay bales, and/or plastic liners to help minimize hull leakage.
- Deck barges, which are essentially flat-topped pontoons designed for the transportation of vehicles or other heavy equipment, general cargoes, or for use as floating work platforms. Some are fitted with coamings for the transport of nonperishable cargo like scrap metal. Some deck barges are fitted with a light, shed-like structure to protect cargo or enclose work spaces. Deck barges are simply a flat work surface and may be used as a work barge (i.e., anchor, derrick, jack-up, mooring, office, pontoon, quarterboat, service, shop, store, or survey barges) or the platform for a dredge. During sediment remediation projects, a single deck barge may be used as the platform for a bucket dredge and several dumpsters that are used to contain the dredged sediments. After the dumpsters were filled, the barge is brought to the shore, where the dumpsters are offloaded to flatbed trucks and hauled to a nearby disposal site.
- Tank barges for carrying petroleum or other liquids. Tank barges may be quite specialized with regard to tank design and cargo handling systems. A significant amount of hazardous cargo, including liquefied and pressurized gases, is moved by barge on inland and coastal waterways. Some barges, especially those designed for the carriage of petroleum products, may have double bottom ballast tanks. Tank barges are most frequently used to haul coal, petroleum and petroleum products, agricultural products, iron, steel, and chemicals. Sectionalized compartments provide structural stability to the barge hull, distribute cargo loads more evenly, help prevent cargo from shifting while in tow, and allow each section to carry different types of cargo.
- Dry cargo barges with holds and hatch covers like general cargo ships.
- Multi-deck RO/RO barges for the transport of vehicles and containers.
- Float-on/float-off barges for carrying smaller vessels, LASH lighters, or inland waterways craft on coastal or ocean voyages.
- Barges that combine some of the above features.
Despite specialization, all barges share certain features. Cargo distribution within the hull is not constrained by the requirements of propelling machinery or accommodations. Because tow speeds are quite low, barges have very full lines. Ocean barges may be 300 feet or more in length. Spoon, ship-shape, or flat rake bows may be fitted, while the stern is normally a flat transom with some cut up in the afterbody. Parallel midbody extends for as much as 80 percent of the length. Because of the low towing speeds, slamming and other ship motion induced forces are less than in a self propelled ship of the same size. Scantlings are therefore somewhat lighter than for a similarly sized ship.
In general, barges for inland and harbor use are not as rugged as those designed for the open sea. The tug and barge systems developed on the rivers of the Mississippi basin and in wide use on the Gulf Intracoastal and Atlantic Intracoastal waterways, use standard square barges lashed tightly together and connected to the tug at the bow. Considerable attempts have been made to standardize barge size on the river systems to facilitate making up tows. A common size for lower river barges is 175 feet by 35 feet by 11 feet. Barges intended for use together in a regular service are sometimes constructed as units of an integrated tow, that is, there are lead barges with forward rake, a number of square ended barges for the main part of the tow, and shorter after end barges.
Many barges that contain chemicals, flammable/combustible liquids, or dry bulk cargoes may require cleaning. There is a special need to clean the barges between transporting different cargoes. Barge cleaning can involve many hazards. The most important hazards are to due flammable materials, and inhalation or skin contact from chemical exposures.
Barge cleaning is the process of removing residual cargo and cleaning the tanks on the barge in order to load a new or different cargo, inspect, or repair. Cleaning may be conducted on a barge while at a pier, in a drydock, while beached, or at anchor. Pre-Planning and preparing to clean includes securing the barge, reviewing the structural plan of the vessel, preventing static discharge, connecting hoses, ballasting, and identifying hazardous materials. Setup for cleaning includes setting up cleaning equipment, opening covers and manholes, and visually inspecting tanks from the outside. Cleaning includes the cleaning processes, such as tank washing, pumping of residues, ventilating for entry, entry procedures, hand-cleaning in tanks, and cleaning of piping and pumps. Completion includes obtaining gas free/product certifications if necessary, final inspection, equipment removal and closing up the barge (closing of butterworth and manhole lids).
Commercial barge traffic on inland rivers consists of strings of barges pushed by towboats. This configuration is commonly known as a "tow." Typically, commercial tows on the Tennessee River average about 15 barges. A fully loaded tow can carry the same weight as about 900 semi-trailer trucks, with all the obvious problems of maneuverability. For this reason, commercial tows have the right-of-way in the main channel of the river. It is important to give them lots of room since they cannot get out of the channel to steer around you and may need up to one and a half miles to stop. A person falling from a personal watercraft about 1,000 feet in front of a tow has less than a minute to get out of the way.
Tank and hopper barges are typically loaded by first pulling the barge adjacent to the dredge floating plant. Dredged sediment is frequently splashed or dropped onto the deck of a barge during loading operations. Spillage can be reduced by minimizing the height from which the bucket releases its load. Dredge operators should place the bucket into the cargo compartment before releasing the load and not drop it with any freefall. In addition, tank barges should be loaded uniformly to prevent excessive tilting or overturning.
During maintenance dredging of uncontaminated sediments, supernatant is allowed to overflow during filling to increase the barge's payload (i.e., reduce the amount of water hauled). Because of the potential for contaminant release and the inefficiency of barge overflow for fine-grained sediment, supernatant overflow should not be permitted on contaminated sediment dredging projects. Methods to remove free-standing water from barges, including the use of polymer flocculants, have been investigated by some Corps districts to produce more economical loads with contaminated dredged material.
Most barges can be unloaded using a variety of mechanical equipment, including cable, hydraulic, or electrohydraulic rehandling buckets. Backhoes and belt conveyors or bucket line dredges can also be used to unload barges. All unloading facilities should be equipped with drip pans or aprons to collect material spilled while unloading the barge and loading the material onto a railcar, truck trailer, or conveyor or directly into a disposal or rehandling facility.
Mechanically dredged sediments have been unloaded from barges to CDFs using a modified hydraulic dredge or submerged dredge pump. Water from the rehandling site or disposal facility (where available) is added to the barge and mixed in with the sediment to provide a uniform slurry for the rehandling dredge pump.
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