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Sunday
Nov012015

Waterway Boom Deployment & Oil Extraction

There are a large number of factors to consider for a waterway boom deployment incident and all these factors must be pre-arranged BEFORE the incident occurs. Additionally, these must be in-place and manpower staffed BEFORE the operation begins. The need for this is that most waterway spills are long term incidents. Therefore, these items and techniques will need to have replacement personnel, scheduled breaks for issues that arise during the incident length as well as equipment replacement, switch-outs, or breakages that occur throughout the incident. A breakdown in this chain will cause a quick back-up of the ongoing processes and may result in contaminant re-spillage. This of course, is what you want to avoid at all costs, as this is a clear indication of failure to; plan, implement, continue, organize, and operate at your level of expertise. This month, we will take a closer look at seven (7) of the main concepts that make up the backbone of a waterway response.

1] Waterway Booms – Types & Uses; The type of Boom chosen depends on waterway to be protected, general weather conditions for the geographic area involved, waterway speed, waterway depth, and waterway current. All these must be calculated for the worst possible conditions on the waterway that you are attempting to confine the spill in. Two basic types exist; absorbent and shielding. One has the ability to entrap contaminant within it’s’ fibers and then be removed from the waterway when totally saturated. A shielding style is constructed of an inert material that is arranged to form extraction points for removal from the waterway by vacuum or additional absorption materials. See my 1st book, “Practical Haz Mat” for an in-depth discussion of these principles. Commonly, these types can be used in conjunction or separately depending on the manpower resources and the geographic location involved. Waterway speed and depth of current are related factors when choosing a Boom for deployment. The depth must be great enough to prevent the Booms Skirt front dragging on the stream bottom. (This could cause the tipping of the Boom floatation configuration allowing product escape downstream) while the speed of the surface flow must be slow enough to prevent “splash-over” over the freeboard of the Boom you have chosen resulting in lost product downstream.. If you have the option of responding to a known location in or around your municipality, careful planning like this must be done before your final choice is made to maximize your response operations.

2] Waterway Weather Conditions – Remember; the current controls the sub-surface spillage while the wind controls the surface spillage. Weather conditions affect two (2) main control issues; surface contaminants and below-surface contaminants that have collected over spill time elapsed, and volume flow. Your Boom choice must have the highest Boom freeboard possible for your waterway response. This feature affords your incident the lowest possible volume of splash-over from high winds or sudden gusts due to unbalanced storm activity. Secondly, the “skirt” must be long enough to protect against “under-flow” from current increases due to excessive water flow filling the upstream side of your incident. Remember without Dam issues involved, this factor will only increase with rainfall. Now, a simple solution would be to choose the biggest Boom possible for all waterways. This may or may not be correct depending on the speed and depth of your waterway. If you respond to a waterway that is shallow and fast, having a deep skirt with a tall freeboard Boom may touch the stream bottom causes the current or wind age to tilt the Boom after deployment causing increased splash-over. Waterway weather conditions are the primary reason for multiple Boom deployments across the same area of spillage. This technique allows for accidents due to weather causes while creating a back-up Boom that retains the over or under flow of product. While one Boom style may accomplish your goals, at a bare minimum there should be a secondary boom deployed for these unexpected events. Many deployments use a minimum of three (3) Boom deployments to circumvent any issues that might occur to the secondary deployment. This is most environmentally safe method and should be looked at by any response group drawing up a plan for their waterway response activities.

3] PPE – Gloves, Respiratory Protection, Eyewear, Etc.; Not enough can be said for the proper site personnel PPE. This also needs replacement or possible up-grading throughout the incident, so there will always be “tweaking” of your personnel’s ensemble’. The proper choice is to always exceed expected safety protocols. You can always downgrade later for more comfortable personnel operations if the conditions and contaminant dictate. You cannot however, upgrade AFTER personnel have been exposed or contaminated. This action not only endangers the lives of response personnel, but will be forced to remove them from service during the incident when they become ill from contamination or exposure. This in turn will increase your personnel requirements possibly past your resources. Consider the initial PPE choice “carefully” BEFORE you begin operations.

4] Extraction/Collection Points/Boom Forces – Extraction points are often decided upon by geographic location points for the “tools” of extraction rather than for Boom deployment angles. The forces exerted on Booms in the waterway are tremendous! A simple way to calculate boom length is based on these forces via the “Angle” of the Boom relative to the shoreline. The rule of thumb is; the more gradual the slope, the more spread-out the forces exerted on Boom as a whole. The smaller these stresses are the less likely a Boom breach will occur causing lost contaminant downstream.

Besides wind and currents, winds and waves can generate escape velocities above the limits of your Boom causing “splash-over” of the product you are attempting to confine. Product escape can also occur from turbulence along a Boom due to projections, so your Boom configuration should maximize a uniform profile while in the water. The size and length of Boom sections are also important considerations. Freeboard and Skirt sizes should be proportional to each other to minimize product escape. Boom connections and lengths should not coincide with the heaviest portion of product concentration as connections interfere with profile and can result in product escape.

Forces exerted on Booms are tremendous and you must have a way of calculating this value to decide on a Boom choice. To estimate the F (force in kg) exerted on a Boom section with an underwater area S (skirt in m2) with an acting velocity or current Vc (in knots) the following relationship is true; (if the Boom were at right angles to Force)

F=26 (constant) X S (0.6 (skirt) X 100’ (boom length)) X Vc2 (speed in knots X (2) (constant))

So, for a 100’ boom section and a current of 0.5 knots having a skirt depth of 0.6m2 the calculation for overall force of that section would be; F=26 X (0.6X100) X (0.5X2) = 1560kg (of Force)

While this expression is true for right angles, responders know that right angles are destructive to collection, collection points, and extraction processes. Softening this angle of inclination to the river flow by half can reduce these forces to as much as 1/3 this value. So, at 45 degrees inclination to the water flow, this force reduces to around the 500kg range. At 65 degrees to the water flow this value decreases to the 150 to 200 kg range, and so on.

When towing your boom to a location or through a pattern, your towing boat speed should be entered in this calculation as current speed in knots (Vc X 2). Doing this and seeing the results demonstrates that doubling the towing speed entails a four-fold increase in load on your Boom system. Be careful not to over speed the towing vessel.

The Force (Fw) exerted by wind (Vw) on the freeboard (Af) of your boom also is considerable. The following formula is used; F=26 X Af(area od freeboard in m2) X Vw(wind in knots) X 2/40.

So if,   F= 26 X Af X (Vw)/40 X 2

A force on a 100m boom with 0.5m of freeboard in a 15 knot wind or tow would be;

F= 26 X 0.5 X 15/40 X 2 = 26 X 0.5 X 0.75 = 9.75kg. While this force is much smaller, remember it is usually added to underwater forces upon the same boom section. Ultimately, the values of Force used to determine your operational limits can help you decide which Boom will work in your particular response situation.

 

5] Extraction Methods – Currently there are two (2) main techniques for extraction on waterways. One is by the use of absorbents, while the second is through the use of a vacuum system. Both accomplish the same end through different means. While absorbents allow sometimes more proper placement of extraction points, they do involve high numbers of manpower for both operational extraction and removal to transportation. Vacuum systems minimize these issues but restrict the proper placement of extraction points due to vehicle equipment placement. Improper placement of extraction points can easily result in splash-over or under-flow, resulting in lost spillage downstream. If your particular situation does not allow the absorbent method due to manpower issues, realize that multiple boom deployments may become a “MUST” to minimize downstream product loss resulting from these improperly chosen collection/extraction points.

6] Transportation – Transportation from the collection/extraction point whether it be in the form of used absorbents or “Vactor” Truck tanks, must be continuous. Due to the depth and freeboard of your Boom chosen, the spillage will continue to build up towards its splash-over or under-flow point whether or not you have to wait for transportation tanks or absorbent replacements. This means, you must always have an extra empty storage tank waiting to be filled. Likewise, you must have un-used absorbent materials on hand ready for deployment. This involves great planning and logistical management before and during the incident mitigation. Having a separate branch officer just allocated to the transportation end of your incident is a wise choice to handle any problems throughout the incident extraction process. Boom freeboards and skirt depths have definite limits. If you overload those due to transportation (wait time) problems, all your hard work travels downstream.

7] Recycle, Reuse, & or Rerun – The reclaiming of the spillage product is not normally a concern of the emergency response, but if your group does emergency management it should be! The ultimate end-point collection of your spillage product should be re-claimed in a responsible way. In many cases, environmental contractors “specializing” in Reuse/Rerun activities can easily handle the loads delivered from your site, thus relaxing the transportation issues just discussed. Make sure that your Emergency Manager does his planning well. This one feature can resolve much stress during a waterway incident. With the media and governmental departments wanting information on your emergency activities, delivering an environmental acceptable end result can place them quickly on your side. Oil spillage in particular can be easily re-run and used as the original fuel it was intended for as it is under a processing infrastructure specifically set-up for large quantities delivered.

Next Month; we will begin an in-depth look at the Foam series updates!

                              Haz Mat Mike

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