Types of boom
Fence
These booms are made of rigid or semi-rigid material, in order to contain the floating oil. They are more able to resist abrasion, easy to handle, clean and store, besides being highly reliable.
They are used in calm quiet waters.
The disadvantages are they have low stability in strong winds and currents, slight flexibility for towing, low efficiency in waves and need reinforcement to prevent wear or breaking and are therefore used in calm areas.
Curtain
Air filled curtain booms have the advantage of being relatively compact when empty, they are easily stored, handled and are efficient. The float elements are chambers filled with air,. They are very good for towing and installing and are good in rolling seas. On the other hand, they have the disadvantage of low resistance to abrasion and are easily punctured if mishandled. They have a flexible skirt maintained by a ballast of either chain or wire rope which is also their tension member.
Solid flotation curtain booms are made of chambers filled with polyurethane, polystyrene, bubble rap or cork. They display high reliability and efficiency when towed, besides being easily handled; the disadvantage is they have large volume from a logistics point of view. They also have little horizontal flexibility in rolling seas. The booms are normally manufactured from oil resistant fabric, being coated with neoprene, polyurethane or PVC.
Fence/Curtain
This manufacturer has a copyright on a boom that can be a fence boom and can be used in calm waters.
It can also be inflated to become a curtain boom for rougher waters on the right. The permanent floatation along both sides of the boom should provide more resistance in areas where abrasion is a problem.
Shore sealing
Photo left is a version of the shore sealing boom which has an air inflated floatation tube on top and two lower tubes that are filled with water to make up the skirt of the boom and act as its ballast.
They are used in the inter tidal section of the shoreline, from the high tide mark to the low tide mark where a Curtain type boom is connected for the area below the low water mark.
The photo left also shows how not to do it, the black oil line on the boom shows that at high tide the oil passed the end of the boom.
The boom should always be deployed above the high tide line. At low tide, the lower tubes settle on the substrate, maintaining a seal and preventing the passage of oil as shown in the diagram below.
The line on a shore where all the plastic bottles, dead fish and flip flops are found is the high tide mark. In many cases the low tide line is difficult to find without local knowledge.
The photo right shows the boom positioned correctly passing the high water mark shown by the line of seaweed.
Be aware when pumping water into this type of boom that small pebbles and or sand may be pumped into the tube as well. This will cause serious problems later by both increasing the weight of the boom as well as the difficulty of getting it back out without damaging the boom.
In some places kelp or other types of sea weed may block the intake, I have seen this problem solved by using the drum of a washing machine which allowed the water to enter through the holes but kept the weed at bay. They are also made of stainless steel so it became part of the kit for that group of responders.
The water tubes (bottom) have a pair of white relief valves to reduce the risk of damage during tidal changes especially on steep inclines. Without them the weight of all the water pushes against the end connection which in some cases it parts company with the boom material.
Some manufactures of this type of boom include pressure relief valves in the water tubes, others say they are optional extras but use the photo above left. Remember just because the photo in the brochure shows them. does not mean you will get them without asking.
Without these valves the water pump should be pumping water before it is connected to the boom or the pump will add air and not allow the section to be fully filled with water thus reducing the weight dramatically.
It also means the water has to be pumped from the end in the water as the other end is 20 or 25 meters away from the water. When this is done the onshore end valve can be opened to let the air out. In my opinion these valves are not optional extras they are necessary and reduce damage and new operator errors.
The water chamber valve caps should be painted blue to allow for quick recognitition during deployment.
The two photos below show the bay at São Luiz in northern Brasil, the tidal range is approx. 10 meters but the shore line is flat and so there are huge sand and mud banks from the high to low tide lines. In this case there is approx. 1 kilomete of mud. This is the area where the shore sealing boom needs to cover.
In areas like this tanks should be filled with water at the high tide mark and water pumped into the boom link tubes photo right maybe used to fill the boom during low tide. This allows for one point inflation for various lengths of boom. They may be removed at high tide to keep the integrity of the boom deployment
It must be mentioned that they are susceptable to damage and if you get a leak in one boom all of them will deflate.
When the tide comes in with the oil, only when the boom is floating totally will the oil stop escaping under the skirt.
Diagram taken from oil spill training.