9. SHORELINE PROTECTION

Transcription

1 9. Shoreline protection is defined as those response activities that take place at or near the shoreline, rather than on open water, to protect the shore zone from becoming oiled or to protect vulnerable shore-zone resources that are at risk. Although the open water techniques described in Section 6, Offshore Response (mechanical recovery, dispersant application and in-situ burning) also protect the shoreline by keeping oil from coming ashore, they are not addressed in this section. This section describes the protection techniques that could be implemented in the nearshore and at the shoreline after source control and control on water. Near- and on-shore responses will focus on areas where oil is threatening the shoreline. Much of the material in this section is derived from Owens, Planning for shoreline protection should begin even if the oil is still on the water and away from the shoreline to prevent a last-minute operation to protect resources at risk. All shoreline response operations should: avoid causing more damage in responding to the spill than the oil would cause alone, use available resources in a safe, efficient, and effective manner, limit the generation and handling of waste materials Sensitivity of Shorelines Protection response objectives, strategies and methods will change from one area to another depending on the variability of the resources at risk (sensitivity), the risk of oiling (vulnerability), and on feasibility considerations. The protection decision process requires input on: where the oil will go (fate and trajectory analysis, Sections 4 and 5), what is in the spill path (Appendix A, ESI maps; ASOSRPs), plus an estimate of the effects of the oil and the response activities on resources at risk at the time of the spill (vulnerability) is required (Table 9-1 and Section 4.2). Environmental Sensitivity Index (ESI) maps of the shoreline between the southern Cameroon border and the entrance to the Douala estuary for spill response planning have been prepared and are included in Appendix A, Environmental Sensitivities. These ESI maps present shoreline types and characteristics, environmentally sensitive habitats, breeding areas, various land use areas (industrial, recreation, residential, parks, reserves, etc.), and shoreline access points. This information, combined with the cleanup scenarios (Appendix B), the ASOSRPs, and surveys at the time of the spill, will be taken into account to design effective response strategies and staffing and equipment requirements for the response. When developing a response strategy it is necessary to consider: proximity of oil to identified sensitive areas (time to impact), weather forecast shoreline contour (strait, promontory, tidal channel, estuary, etc.) water movement (erosion or deposition, current/rip speed and direction, tides, waves) conformation of bottom (water depth, smooth, rocky, reef, gradient, stability) accessibility and unanticipated logistical difficulties Section 09 Page 9-1 of 26 September 1999

2 In dealing with these factors, the Operations Manger will allocate resources with the goal of reducing overall environmental impact. Section 09 Page 9-2 of 26 September 1999

3 Table 9-1. Summary of Shoreline Sensitivities (modified from Owens, et al., 1992) Shoreline Type/ Sensitive Feature Exposed Bedrock Sheltered Bedrock Sand Beach Mixed Sediment Beach Sand Tidal Flat Delta/Estuary/ Wetland Anadromous Fish Stream/Spawning Ground Bird Rookeries or Colony Light, Volatile Oils Relative Sensitivity by Oil Class* Low Medium Viscosity Viscosity Oils Oils Very Viscous or Semi-solid SHORE TYPE ECOLOGICAL FEATURE Marshes/ Mangroves Rare/Endangered Species Archaeological Site Historical Site CULTURAL FEATURE Subsistence Use Area HUMAN USE FEATURE Commercial Fishing Area Boat Harbor/ Marina Recreation Area Comments Probability of persistence is low; low biological value. Probability of persistence high; high biological value. Low permeability except for light oils: low biological value. Low permeability except for light oils: low to moderate biological value. Typically fine-grained sand tidal flats with migrating sand waves: exposed to winds, waves, and currents; probability of persistence generally low but varies depending upon oil class; moderate biological value. Probability of persistence high; high biological value. Typically sensitive during fry outmigration and spawning periods. If birds are migratory, the areas could be sensitive primarily during periods of occupation. If not, then the area would be sensitive year-round. Probability of persistence high; sensitive year-round and especially during periods of migratory bird use. Corals, Goliath Frog, and other species: habitats are typically sensitive all year. Primarily sensitive to disruption or destruction by cleanup activities. Primarily sensitive to disruption or destruction by cleanup activities. Mainly sensitive only during periods of use, although food source may be affected for a longer time period. Typically sensitive only during times of use; losses due to closure can be significant. Sensitive all year. Greatest sensitivity during periods of high use. Section 09 Page 9-3 of 26 September 1999

4 Residential Area Key: 1 = High, 2 = Moderate, 3 = Low Protection Decision Process Sensitive all year, especially for the lighter, aromatic oils. Decisions related to the selection and management of protection activities involve a process that allows for operational strategies and actions to be developed within a set of specified goals or objectives. This decision process should be applied to each sensitive area or shoreline segment. The steps in the protection decision process are outlined below. 1. Gather information and assess the situation. Surveillance and tracking (Section 5). Trajectory, volume, and weathering analyses (Sections 4, 5). Estimate spill path time to impact (Section 5). Assess sensitivity (to oil and response activities) and/or vulnerability (potential to be impacted) of resources at risk in the spill path (Section 9.1, and Appendix A, ESI maps). 2. Define response objective(s): prevent contact between oil and the shore zone or a resource at risk in the shore zone, or limit the degree of contact between oil and the shore zone or a resource at risk in the shore zone. [Be specific: define whether the goal is to prevent contact or limit the degree of contact ] At each site there also may be operational objectives, such as: prevent the movement of oil alongshore into adjacent shore-zone areas or adjacent resources at risk, contain oil that has already stranded at the shoreline to prevent remobilization, prevent the movement of oil into an inlet or channel. 3. Develop strategies to meet the defined objectives (Table 9-2). 4. Select appropriate technique(s) or method(s) to implement the strategy (Table 9-3 and Section 9.2). 5. Evaluate the feasibility of the strategies and methods in view of the environmental conditions and the nature of the spill. Do shoals or reefs affect access by water? Is there direct back-shore access to the shore? Is the coast exposed to storm wave action? Are strong along-shore (>0.5 m/s) currents usually present in the area? What are the safety factors? Are the proposed operations and procedures able to achieve the objectives effectively and efficiently? What are the effects these activities will have on the area to be protected? What is the Net Environmental Benefit of the proposed action? Section Prepare an action or response Page 9-4 of plan, 26 and Implement the September field 1999 response operation.

5 Table 9-2. Protection Objectives and Response Strategies (Owens, 1998) Table 9-3. Protection Strategies and Response Methods (Owens, 1998) Section 09 Page 9-5 of 26 September 1999

6 9.2. Protection Strategies Protection objectives can be achieved by the development of a number of specific operational strategies (Table 9-2), which include: containing and recovering oil on the water prior to shoreline impact, altering the direction of movement of the oil on the water, preventing the movement of oil landward in a channel during a flooding tide, trapping or containing and collecting oil at the shoreline, preventing oil being washed over a beach into a lagoon or backshore area, preventing stranded oil from remobilizing to affect adjacent shoreline areas, removing shoreline debris before the oil is washed ashore. The practical shoreline protection options are to contain, redirect or exclude the oil by the deployment/construction of booms or barriers, or prevent contact between the oil and resource by installing physical barriers. The range of protection methods or response actions used to implement the protection strategies includes: On Water: booms to contain oil for recovery by skimmers or other techniques (Section 9.2.1), booms to redirect the oil away from the shore (Section 9.2.2), booms to redirect the oil towards the shoreline for recovery by skimmers or other techniques (Section 9.2.2), and booms to exclude oil (Section 9.2.3), On Shore: intertidal or shoreline booms to contain, trap, or redirect oil for recovery by skimmers or other collection methods (such as sorbents) (Section 9.2.4), barriers, berms, or sumps to contain and recover oil that washes ashore (Section 9.2.5), on-shore chemical, hydraulic, or physical barriers to prevent oil contact with the shoreline (Section 9.2.6), and shoreline booms, barriers, or dams to exclude oil from channels (Section 9.2.7). The relationship between shoreline protection strategies and these options or methods is shown in Table 9-3. Practical guidelines, or rules of thumb, concerning protection strategies are outlined in Table 9-4. In practice, two or more protection methods commonly are employed to achieve the operational objectives. The protection techniques are summarized in Table 9-5. The applicability of these methods in certain shoreline conditions is shown in Tables 9-6 (on water) and 9-7 (on shore). The following subsections then describe and illustrate specific techniques in more detail. Strategies that are practical for specific shorelines within the project area are discussed in Section 9.3 and in the ASOSRPs. Information on boom types, selection, applicability, and deployment is provided in Section 6, Offshore Response, that generally applies to nearshore environments. Section 09 Page 9-6 of 26 September 1999

7 Table 9-4. Shoreline Protection Rules of Thumb # 1 Protection Strategies Protection is a defensive strategy for resources at risk in the anticipated spill path. Think ahead, it may be already too late to protect a resource at risk. Be specific and define whether the protection goal is to prevent contact between the oil and the resource at risk or reduce the degree of contact this will make a big difference to the level of effort and the degree of commitment by Planning and Operations. Protection by exclusion booming can be effective in sheltered areas; on open coasts redirection (deflection diversion) may be the only feasible protection strategy. Do not promise to keep oil away from an area or a location if it not feasible or practical to do so; this will avoid disappointment and loss of credibility. # 2 Protection Priorities Pay attention to local sensitivities and priorities Local priorities may, in some cases, need to take precedence over environmental sensitivities that are rated as most sensitive on ESI maps and lists. For example in the 1993 Tampa Bay spill, the local population considered the tourist sand beaches a much higher priority than the back-bay mangroves (which they considered to be weeds that had grown on dredge-spoil piles and messed up the boating ). In many cases, response consultants are outsiders and rarely immediately recognize the local concerns or priorities. The response will have the greatest effect on the resources and activities of the local inhabitants. Area or Regional response plans, atlases, and other environmental documents do not necessarily reflect local concerns or priorities. Continuously review and field check sensitive shoreline areas. Shoreline conditions may change over time or be seasonal (e.g., bird migration, fish spawning) and require that changes be made to protection priorities. Sensitivity and Vulnerability are two different concepts: a resource may be sensitive to oil but not vulnerable, and vice versa. Sensitivity refers to the degree which a resource is perceived to be important and at risk from oil and response operations, whereas vulnerability is the potential that a resource or activity that is sensitive may be impacted by the oil or response operations. Section 09 Page 9-7 of 26 September 1999

8 Table 9-5 Summary of Protection Techniques (modified from Owens, 1992) Technique Description Limitations Potential Environmental Effects Containment Exclusion Redirection/ Towards Shoreline Redirection/ Away from Shoreline Boom Filter or Sorbent Barrier Intertidal/ Shoreline Boom On Water Boom is deployed in nearshore waters in a J or U shape in front of the oncoming slick. The ends of the boom are anchored by work boats or drogues and the oil is contained within the U, or the ends can be brought together to encircle the oil for recovery. Boom is deployed across or around sensitive areas and anchored in place. Approaching oil is deflected or contained by boom. Single or multiple booms are deployed from the shoreline at an angle towards the approaching slick and anchored or held in place with a work boat. Oil is diverted towards the shoreline for recovery. Single or multiple booms are deployed from the shoreline at an angle away from the approaching slick and anchored or held in place with a work boat. Oil is deflected away from the shoreline where it may be contained for recovery. A barrier is constructed by installing two parallel lines of stakes across a channel or inlet, fastening wire mesh to the stakes and filling the space between with loose sorbents. On Shore Boom can be deployed across or along the shore, on the beach or in the water, to contain oil. Designed for use where the water level will change. Water-filled chambers provide a seal as the boom grounds and a skirt when afloat. Can prevent remobilization of stranded oil. High winds Swells >2 m (6.5 feet) Currents >0.5 m/s (1 knot) Breaking waves >50 cm (2 feet) Currents >0.5 m/s (1 knot) Breaking waves >50 cm (2 feet) Water depth >20 m (65 feet) Currents >1.0 m/s (2 knots) Breaking waves >50 cm (2 feet) Currents >1.0 m/s (2 knots) Breaking waves >50 cm (2 feet) Currents >0.5 m/s (1 knot) Waves >0.3 m (1 foot) Currents > 0.5 m/s (1 knot) Breaking waves > 50 cm (2 feet) No significant effects. Minor disturbance to substrate at shoreline anchor points. Minor disturbance to substrate at shoreline anchor points and can cause heavy shoreline oiling at down-stream end of boom (collection point). Minor disturbance to substrate at shoreline anchor points, could affect unprotected downstream areas. Minor disturbance of inlet or channel substrate. Minor disturbance to substrate at anchor points. Can cause heavy oiling if oil concentrated by the booming strategy. Section 09 Page 9-8 of 26 September 1999

9 Technique Description Limitations Beach Barriers, Berms Sumps and Trenches Chemical Barriers Solid Physical Barriers (Geotextiles) Water (Hydraulic) Barriers Solid Exclusion Barriers A berm is constructed along the mean high water level. The berm should be covered with plastic or geotextile sheeting to minimize wave erosion and oil penetration or burial. Dug by machinery to contain and collect oil for recovery as it is washed ashore. Prevents or minimizes remobilization of stranded oil. Likely would have to be lined to prevent penetration or mixing of oil and sediment by wave action. Surfactants or shoreline cleaners are applied as a pre-treatment agent before the oil comes ashore to prevent the oil from adhering to shoreline surfaces. A roll of geotextile, plastic sheeting, or other impermeable material is spread along the bottom of the supra-tidal zone and fastened to the underlying logs or stakes placed in the ground. Flooding or low-pressure hoses are used to form a water barrier so oil cannot penetrate or contact the sediments. Hoses can be used to simultaneously move oil away from the shoreline and herd it to a containment/recovery area. A dam is constructed across a channel, water intake, inlet, or culvert where there is a limited flow, using local soil or beach sediments, sandbags, or wood sheeting to seal the opening or culvert and exclude oil from entering the area. Breaking waves >0.3 m (1 foot) Strong alongshore currents Breaking waves >0.3 m (1 foot) Coarse sediments (cobble and boulders) Heavy oils Agents are washed away by tides/waves High winds or waves Time and resources to install the material Tearing of the materials Heavy surf Accessibility Implementation time Length of shoreline area to be protected Water outflow Waves >0.3 m (1 foot) (for soil or sediment barriers) Potential Environmental Effects Disturbs upper cm (20 24 inches) of foreshore zone. Disturbance of the substrate and, if not lined, greater oil penetration. No significant effects. Washing sediments into lower intertidal areas may harm attached plant and animal communities. Disturbs channel substrate and adds suspended sediments to water. Can be harmful to landward biota. Section 09 Page 9-9 of 26 September 1999

10 Table 9-6. Nearshore/On Water Protection Technique Applicability Matrix (modified from Owens, 1992) Wave Heights > 2m (6.5 ft.) Wave Heights < 2m (6.5 ft.) Breaking Wave Heights > 1m (3 ft.) Breaking Wave Heights < 1m (3 ft.) Current/Vessel Speed > 0.5 m/s (1 knot) Current/Vessel Speed < 0.5 m/ s (1 knot) Containmen t Booming Exclusion Booming Redirection Away Redirection Towards Boom Filter/ Sorbent Barriers Table 9-7. Onshore Protection Technique Applicability Matrix (modified from Owens, 1992) Breaking Wave Heights > 1m (3 ft.) Breaking Wave Heights < 1m (3 ft.) Fine-Grained Substrates Coarse-grained Substrates Breaking Wave Heights > 1m (3 ft.) Breaking Wave Heights < 1m (3 ft.) Fine-Grained Substrates Coarse-grained Substrates Beach Barriers/ Berms Sumps and Trenches Solid Exclusion Barriers Steep or Inclined Shoreline Geotextile Barriers Water Barriers Low Angle or Flat Shoreline Key: 1 = Good Effective in most situations. 2 = Fair May be Applicable (usually effective, but not always). 3 = Poor Rarely, if ever, effective and should not be considered, except in unusual circumstances. Section 09 Page 9-10 of 26 September 1999

11 Nearshore (On-Water) Containment and Recovery Near-shore skimming and collection operations will be initiated where appropriate to intercept and recover oil that threatens to impact the shoreline, as shown in Figure 9-1. This technique is essentially the same as mechanical containment and recovery described in Section 6 for offshore response except that the activities take place at or near the shoreline. In almost all cases, it is easier, more efficient, less damaging to the environment, and cheaper to remove the oil from the water surface than to clean or treat a shoreline. The potential for oil recovery is high under favorable operating conditions (wave heights <2m (6.5 feet), breaking waves <1m (3 feet), and current speeds <0.5 m/s (1 knot). This protection activity can be used in any situation where it is safe and practical to recover the oil. The activity is most appropriate where the protection objective is to prevent oil from making contact with the shore or a vulnerable resource at risk. The equipment used in such cases would be shallow-draft vessels with: boom types suitable for the prevailing wave and current conditions (Section 6.3), and skimmers or other recovery techniques appropriate for the type(s) of oil that is to be recovered (Section 6.4). When skimming in shallow water, crews can position skimmers with boats and tag lines. The skimmers should be placed where concentrations of floating oil are greatest and conditions are appropriate. Recovered liquids can be discharged into lined pits, portable tanks, or leased barges. Separation of the recovered oil and water will be necessary to increase effective oil storage capacity. Constraints/Limitations The primary limitation for deployment is the time window of opportunity. Limitations for operations are weather, wave and surface current conditions, and water depth. Figure 9-1. Nearshore Containment and Recovery of Oil on Water Section 09 Page 9-11 of 26 September 1999

12 Nearshore (On-Water) Redirection Booming Redirection booming can involve deflection or diversion so that the oil is transported in a direction other than where it would go naturally. When boom is deployed at an angle in nearshore waters, the objective is to change the direction of oil movement rather than to place a barrier in the slick path to contain or control. Redirection can be used to divert oil away from a vulnerable resource at risk or towards a nearshore (on-water) location for subsequent collection and recovery. This activity may be employed to prevent oil from reaching vulnerable down-drift environments or resources, or to divert oil towards a location where shoreline cleanup may be easier and/or more effective. This alteration of the direction of oil movement can be effected either in nearshore areas or at the shoreline. This technique often is used where current speeds or breaking waves preclude exclusion booming (Section 9.2.3) or where there is insufficient boom available for an exclusion booming strategy. The activity is appropriate where the protection objective is to prevent oil form making contact with the shore or a vulnerable resource at risk. Booms can be deployed in a number of configurations to redirect oil including: (a) single, (b) cascading, (c) chevron, or (d) open chevron (Figure 9-2). The choice of the most appropriate configuration will depend on: the size or area of the approaching slick, the amount of redirection necessary, and flow conditions (currents) in the deployment area. Multiple or cascading booms will be required if the slick width is greater than approximately one-quarter to one-half of the boom length to incrementally alter the location of the oil (the cascading configuration in Figure 9-2). Usually, it is easier to deploy and maintain several short sections of boom than a single long section. Typically, in higher flow conditions (>0.5 m/s; 1 knot) a redirection strategy can be more effective than exclusion booming as boom(s) may be set at a higher angle. The higher deployment angle also can be used to redirect the oil seaward where it can be released without recovery (Figure 9-3a) or contained and recovered (Figure 9-3b), or to a selected shoreline location where it can be collected and recovered (Figure 9-4). This strategy may be used in combination with intertidal or shoreline boom to minimize the amount of contact between the oil and the intertidal zone as shown in Figure 9-4. Constraints/Limitations The effectiveness of nearshore booms is limited by current speed, breaking waves, and by the accumulation or presence of floating debris. The angle of deployment of booms is governed by the current speed. As the current speed increases, it becomes necessary to decrease the boom angle with respect to the shoreline (i.e., the boom angle becomes progressively parallel to the current direction) to prevent splash over, drainage, and entrainment (see Figures 6-6 and 6-7 and Table 6-6 in Section 6.2.1). Even with a higher boom angle, entrainment likely would occur when redirecting oil towards the shoreline if removal or recovery of the oil cannot keep pace with the accumulation against the apex of the boom and the shore. In most cases, a second boom, or even more layers of boom, will be required to ensure that no oil reaches a sensitive area or resource at risk. Section 09 Page 9-12 of 26 September 1999

13 Redirection away from a section of shore without recovery may prevent contact with the oil at one location, but the oil remains mobile and this may mean shoreline contact will occur at another location, presumably with a lesser impact (i.e., at a less sensitive location). Figure 9-2. Boom Configurations for Redirecting Oil on Water (Owens, 1998) a. Single Direction of Oil Movement boom b. Cascading anchor points Direction of Oil Movement c. Chevron Direction of Oil Movement d. Open Chevron Direction of Oil Movement Section 09 Page 9-13 of 26 September 1999

14 Figure 9-3. Nearshore Redirection Away From the Shoreline (Owens, 1998) Redirection Away from Shore Without Recovery (a) Direction of Oil sensitive area Single or Multiple Redirection Boom(s) to an On-water Recovery Point Direction of Oil (b) on-water recovery point sensitive area Figure 9-4. Nearshore Redirection Towards the Shore (Owens, 1998) Single or Cascading Redirection Boom(s) and Shoreline Boom recovery point skimmer deployed on water or from shore Direction of Oil sensitive area shoreline boom Section 09 Page 9-14 of 26 September 1999

15 Nearshore Exclusion Boom This activity can include a number of nearshore, conventional booming strategies to provide a barrier around a resource at risk or across an embayment (Figure 9-5). In the case of a resource that is entirely in the nearshore zone, the exclusion boom may be deployed partially around the site to redirect oil away or to completely encircle the site to prevent contact (bottom, Figure 9-5). The objective of the activity is to prevent contact by making the oil move in a direction different from that which it would follow naturally. A single boom may be effective in very calm wave and no current flow conditions. In most cases, a multiple set of booms is required to ensure exclusion, particularly with variable tidal currents. Recovery may or may not be part of the strategy. Figure 9-5. Shoreline and Nearshore Exclusion Booms (Owens, 1998) Single or Multiple Exclusion Boom Direction of Oil anchor lines sensitive area Direction of Oil sensitive site Constraints/Limitations On open coasts, the wave height and surface current velocity control the effectiveness and feasibility of a proposed boom deployment. The feasibility of exclusion booming also is limited by water depths and by the accumulation or presence of floating debris. The size of the area to be protected by the booms also is a limiting factor. Exclusion booms or barriers may prevent oil from contacting the shoreline or a resource at one location, but, without recovery, the oil remains mobile and this may result in shoreline contact at another location, presumably with a lesser impact. Section 09 Page 9-15 of 26 September 1999

16 Intertidal or Shoreline Boom for Containment and Recovery Intertidal booms have been designed to maintain a barrier against oil movement as the water level rises or falls. Intertidal boom is used where tidal water levels are expected to change, but also is useful in areas where the water level is relatively constant. These booms have water-filled lower chambers that provide ballast and that assume the contour of the shore when aground (Figures 9-6 and 9-7). This skirt presents a subsurface oil barrier when afloat (Figure 9-7). A similar type of boom can be fabricated on site by draping a sorbent roll over a conventional boom or a log boom. This has a similar design concept and may be effective in calm water conditions. Intertidal booms can be set perpendicular, or across the shore, to act as a barrier to the along-shore movement of oil (Figures 9-6 and 9-8), or deployed parallel to the water line to minimize contact between the oil and the shore or to prevent remobilization of stranded oil (Figure 9-7 and 9-8). Figure 9-6. Intertidal Boom Deployed Across the Shoreline (Owens, 1998) Figure 9-7. Intertidal Boom (a) Afloat, and (b) Aground (Owens, 1998) Section 09 Page 9-16 of 26 September 1999

17 Constraints/Limitations This type of boom is relatively stable in shallow water, due to the two water-filled chambers that sit below the waterline. It is, nevertheless, susceptible to being rolled over, rendering it ineffective, in the presence of breaking waves. The boom chambers should also be resistant to puncture by sharp objects. Grounded intertidal boom cannot be repositioned when the ballast chambers are filled (with water), so that moorings must be designed to allow for the boom to move vertically, but also to stay in place or have little lateral movement as the tidal level rises. The effectiveness of intertidal booms also is limited by current speed, the slope of the shoreline, and by the accumulation or presence of floating debris. Boom effectiveness decreases as the slope of the shore zone increases. Figure 9-8. Intertidal Boom Deployed Parallel to the Waterline and Also to Redirect and Contain Oil at the Shoreline (Owens, 1998) Section 09 Page 9-17 of 26 September 1999

18 Shoreline Barrier, Berm, or Sump for Recovery Berms or barriers can prevent oil from stranding on the upper beach or from being carried over a beach onto backshore areas. Barriers or dams can be built across overwash channels to prevent waves carrying oil over a beach into a backshore lagoon or marsh. The berm or barrier should be constructed at or near the predicted upper high-tide level to catch oil as it is carried up a beach by breaking waves. Berms and barriers are particularly appropriate where low over-wash channels present an unobstructed pathway for waves to carry oil into sheltered, backshore lagoons or marshes. Berms can be constructed on a beach parallel to the waterline to contain oil, with or without a ditch or trench to collect oil as it is washed ashore (Figure 9-9). If oil has stranded at a time of higher water levels (i.e., during spring tides), a berm can be constructed near the lower limit of the oil to prevent remobilization by wave action before cleanup can take place. Ditches, trenches, or sumps can collect oil as it is washed ashore, for recovery by skimmers or other physical removal techniques. If oil has stranded at a time of higher water levels (i.e., during spring tides), a ditch can be constructed near the lower limit of the oil to prevent remobilization by wave action before cleanup can take place. Oil that is collected in ditches, trenches, or sumps is easier to recover than oiled beach sediments. If recovered, this oil is not remobilized to oil or re-oil adjacent or down-drift shorelines. Figure 9-9. Berm and Trench System Along a Shoreline (Owens, 1998) Earth-moving equipment can construct berms or ditches along long sections of beach in a short time. If constructed above the highest tide levels, these may remain unmaintained for some time. Berms or dams are more easily constructed on sand beaches that have an appropriate bearing capacity for the intended equipment. Constraints/Limitations The size of the area to be protected and the time available to deploy equipment or to construct berms can limit effectiveness. Section 09 Page 9-18 of 26 September 1999

19 The berm should be at or above the anticipated highest tide level. If the barrier or berm is constructed too far down on a beach the effectiveness is limited by breaking waves and the berm may be overtopped. If it is located in an overwash channel that would be overtopped by high tide levels, it may be necessary to construct the berm or dam using sand bags or other more durable materials. Steep beach slopes and pebble-cobble size sediments limit the ability of equipment to operate on these beach types. Depending on the character of the stranded oil and the sediment size, it usually would be necessary to line the trench or sump to prevent penetration. Only weathered, viscous oils on fine-grained (sand) beaches will not penetrate. Lining also may be necessary to prevent swash action from mixing oil and sediment Contact Barrier This activity can include a number of methods to prevent contact between the oil and the vulnerable resource or shoreline by using a chemical or hydraulic (water) barrier, or by placing a physical barrier or cover over the shoreline. One advantage of this protection technique is that the impacts usually are low, provided that the operational activities themselves do not affect the organisms or resources that are being protected. Flooding (deluge) or low-pressure hoses can be used to form a water barrier and simultaneously move oil away from the shoreline (see Flooding and Low-pressure Washing in Section 10). This hydraulic approach keeps the shore wet, when it would otherwise be dry, and raises the water table in a beach so that oil cannot penetrate the sediments. As oil is washed ashore, the water barrier prevents contact with the shore-zone materials and the down-slope water movement carries the oil towards the water line where it can be contained and recovered. A physical barrier, such as plastic sheeting, a geotextile, or sorbent material, can be installed to prevent contact and protect underlying materials (Figures 9-10 and 9-11). Generally, the barrier material is staked or held down by sandbags, cobbles, or other weights (Figure 9-10). A primary application is for riprap, harbors, docks, wharves, crib work, or other man-made structures, where oil likely would penetrate or be difficult to access or remove. This type of barrier also successfully prevents oil from coating the shore where logs, debris, or vegetation may be present. Section 09 Page 9-19 of 26 September 1999

20 Figure Geotextile Barrier Along a Riprap Shoreline (Owens, 1998) Figure Geotextile Barrier Installed to Protect Dock and Pilings (Owens, 1998; photo courtesy of W. Robson) Chemical barriers also may protect a shoreline as they can provide a surface to which oil will not stick. Also known as surfactants, these chemical shoreline cleaners described in Section 10 can be used as a protection or pre-treatment agent when applied before the oil comes ashore. An advantage of this technique is that the agents dissolve in water and therefore do not require removal. This may be a disadvantage as multiple applications may be necessary if the threat from the oil extends over several tidal cycles. Field tests may be required to determine if the desired results Section 09 Page 9-20 of 26 September 1999

21 can be achieved. Constraints/Limitations Flooding or water barriers involve the use of pumps and hoses that could require regular or continuous maintenance. This operation may have to be maintained for several days while oil is moving onto a shoreline. The primary constraints for physical barriers are the time and resources required to cover long sections of coast. High winds and strong wave action could make deployment and maintenance difficult. Plastic sheeting can tear easily, whereas geotextiles are more resistant. Geotextile barriers are more sturdy and have been deployed on open coasts with wave heights up to 0.5m and can maintain a continuous protective barrier in areas with tidal ranges up to 5m. Physical barriers are most suited to harbors and other manmade shorelines. It might not be practical to cover wide intertidal areas, except in very sheltered waters. Section 09 Page 9-21 of 26 September 1999

22 Shoreline Exclusion Boom, Barrier, or Dam Booms, filter barriers, or dams can prevent oil from entering backshore or backwater areas through narrow or small inlets, stream channels, canals, or ditches. This activity can include a number of methods. Booms or filter barriers can be deployed to contain oil on the water surface. These allow the normal passage of water through the channel while preventing the movement of oil on the surface. Conventional or intertidal booms can be anchored across the channel, or at an angle if necessitated by the speed of the current flow (see Figure 9-12). Barriers can be fabricated from available materials, such as fencing or nets, combined with sorbent materials (Figure 9-13c and 9-13d). In tidal channels, barriers should be designed to allow for the rise and fall of the water level and for current reversal. Dams can be built using available materials, such as fill, planks, or sandbags (Figures 9-13 and 9-14). Water flow usually should be maintained, particularly in streams and tidal environments, to avoid disruption of the local ecology. Where necessary, water flow can be maintained using underwater pipes or underflow techniques (Figure 9-15). The design of single or multiple culverts, pipes, and siphons should factor in the lowest anticipated water level, flow volumes, and the potential for oil to build up against the dam and become entrained with the water that passes through the pipe system. Dams can be constructed quickly using earthmoving equipment, such as front-end loaders or bulldozers. Figure Exclusion Boom Deployed Across a Channel Constraints/Limitations Usually, the width and depth of the channel and the water velocity control the selection and design of practical and effective methods. In areas where river or tidal flow is not an issue, blocking a channel, canal, or ditch without culverts or pipes can result in ponding from the backup of rainfall and allowance should be made for possible flooding. Section 09 Page 9-22 of 26 September 1999

23 Barrier or boom deployment and effectiveness are limited by current speed, although well-designed filter barriers can be more effective in higher velocity currents than conventional booms. Boom or berm effectiveness also is limited by breaking waves in the nearshore zone and by the accumulation or presence of floating debris. A single barrier may not be sufficient to exclude all oil and, frequently, two or more barriers may be required. The time available to deploy equipment or to construct dams or barriers can limit the effectiveness of this approach. Exclusion booms or barriers may prevent oil from contacting the shoreline at one location, but, without recovery of the oil, this may result in contact at another location, presumably with a lesser impact. Figure Channel Barriers (after CONCAWE, 1983) Section 09 Page 9-23 of 26 September 1999

24 Figure Earthen Shoreline Protection Dam (adapted from ABSORB, 1981) Figure Earth Dam with Multiple Siphon Pipes (Owens, 1998) Section 09 Page 9-24 of 26 September 1999

25 9.3. Guidelines for Protection of Each Shore Area Protection strategies for specific shoreline areas are shown on the ESI maps included in Appendix A. Detailed shoreline protection strategies will be included in the ASOSRP for the coastal area. These strategies will be developed in conjunction with the ESI and local priorities. The following table shows, in general, the strategies that are practical for specific shoreline configurations. Table 9-8. Decision Guide for Specific Shoreline Configurations (Exxon, 1992) Configuration of Area to be Protected Straight Coastline with Sensitive Areas Are Breaking waves >0.5 m (1.5 ft.) present in area where boom will be deployed? Yes No Beach berm or containment booming of slick outside of surf zone Redirection booming away from shore upstream of sensitive area Entrance to Bays, Harbors, Lagoons, etc. Are Breaking waves >0.5 m (1.5 ft.) present in area where boom will be deployed? Yes Can booming location be moved to calmer area? No Containment booming of slick outside of entrance No Yes Water Current Speed Less than 0.5 m/s (1 knot) Greater than 0.5 m/s (1 knot) Exclusion booming across entrance Redirection booming at an angle in Narrow Tidal Channel Water Current Speed Less than 0.5 m/s (1 knot) Greater than 0.5 m/s (1 knot) Sorbent barrier across entrance or Exclusion booming across channel Diversion booming at an angle across channel Section 09 Page 9-25 of 26 September 1999

26 Tier 1 Shoreline Protection Equipment for Tier 1 response is available from stockpiled equipment maintained at the FSO, and other in-region resources (see Section 11) Tier 2 and Tier 3 Shoreline Protection Additional equipment to be used for Tier 2 and Tier 3 protection and near-shore responses can be obtained from response organizations (e.g., candidate response organizations such as CNA) and from international oil-spill response equipment stockpiles. These stockpiles have a variety of oil spill response equipment, including booms, oil skimmers, oil storage tanks, and sorbents (see Section 11). Section 09 Page 9-26 of 26 September 1999