Appendix A

Key Differences Between the Offshore Environment and the Inland Environment

OIL BEHAVIOR IN INLAND ENVIRONMENTS

Oil fate and behavior in open water have been studied for decades (Reed et al., 1999; Spaulding, 2017). A complex interplay between the oil properties, release conditions, and physical environment affects slick behavior and response options for oil recovery. While additional research and refinement are always beneficial, there are modeling algorithms and software packages available to predict key processes and inform response decision making in open-water conditions. Modeling of oil spill behavior and weathering in inland environments, though, presents complexity due to the large number of variables at play (e.g., physical environment, water flow regimes, basin shapes and sizes, local wind patterns, presence of ice and debris, inhomogeneity of the shorelines, and suspended sediment) (Overstreet and Galt, 1995). It is often found that location-specific factors have more influence on the oil slick fate and behavior than advancements in theoretical modeling approaches can account for. Some of the unique and important factors that affect oil fate and behavior in inland waters, specifically the portion of a spilled volume that is present at the water surface and available for recovery, are discussed below.

The presence of shorelines is the obvious important difference between inland and open-water environments, impacting oil fate and behavior in several ways:

• Shorelines define the size and geometry of the waterway, affecting its flow characteristics as well as corresponding slick behavior and its recovery options.
• Current is a dominating force determining oil transport in the streams, but wind force is likely to drive the slick to the shore much quicker than may happen in the open ocean environment. In many riverine environments, there may be a limited window of opportunity to recover oil on the water surface before it comes to shore.
• Wind is a dominating force affecting slick transport in lakes and ponds. It may eventually herd a slick to one side of a shoreline, potentially allowing for passive collection.
• Shear-dominated flows drive an exchange of water and pollutants between the slower, near-bank regions and the faster, center regions of the river. This results in hard-to-predict movements of oil patches across and along the water basin. It means that while it might be possible to predict the trajectory of the leading edge of the slick moving with the speed of the center flow, thickness distribution and extent of the whole slick can be highly variable.
• The type of the shoreline and its vegetation cover (if any) significantly affects the volume of oil that can adhere to it, its persistence, and its remobilization potential, as well as suitable recovery options.
• Weathering processes such as evaporation can reduce the volume of oil available for recovery in both marine and freshwater environments. Evaporation rates are strongly affected by the area of the air–slick interface. In confined and/or quiescent inland environments, oil slick spreading may be restricted, maintaining higher film thickness, which ultimately results in slower evaporation rates than would be expected in open waters.
• Tidal currents can move the oil slick inland or result in accumulation in estuaries or inland waters.
• Resuspended sediments from swash action or other coastal turbulence can absorb and bury some of the oil.

• Unlike open-water marine environments, inland environments often allow oil to pool in topographical features and shallow waters, making passive collection (e.g. vacuuming) a suitable strategy. However, some oil could be stranded on shorelines or in intertidal areas during low tide, making it impractical or impossible for surface recovery.
• Some oils that would typically float in seawater can be denser than freshwater and, as a result, may submerge or sink making them unavailable for surface recovery. Because of the density difference, even droplets of floating oil dispersed by the vertical turbulence may have longer residence time in freshwater than they would be at sea. Mixing of seawater and freshwaters in coastal areas can create saltwater wedges extending into freshwater systems, creating difficult-to-predict density gradients and complex oil behavior when transitioning through these zones.
• Inland waters are shallower than a typical offshore environment. The shear in currents along the river bottom and banks creates considerable turbulence/mixing energy in the streams and rivers, resulting in a higher percentage of oil being permanently or temporarily dispersed in the water column than would be expected in the wind- and wave-dominated marine environments, making it unavailable for surface recovery.
• Inland streams and rivers as well as estuaries often have higher sediment loads than open, offshore waters. Depending on the oil properties, type, and concentration of the sediment, as well as mixing regime, some portions of the slick could either be dispersed with finer particles acting as natural dispersants or adhere to the larger and/or heavier particles and sink.
• Inland waters are affected by the seasonal presence of ice that significantly changes fate, behavior, and availability of oil during winter months. Typically, the presence of ice restricts oil spreading and slows weathering processes, but it also dictates the need for specialized tools for oil detection and recovery.
• There may be a seasonal variation in the water flow, especially in smaller water bodies. Some creeks can be either dry or flowing in different months of the year.
• Oil in streams and rivers typically moves downstream with the current, except for the tidally affected water bodies with complex mixing and water exchange patterns. In these tidal systems the flow can change direction up to four times a day, affecting oil fate and behavior.
• Natural and engineered hydrodynamic features of streams and rivers (bridges, dams, locks, rapids, waterfalls, etc.) further affect oil transport, weathering processes, and availability for recovery.
• Runoff and flooding events resulting from heavy rainfall and ice or snow melt can add additional complexities to the slick fate and transport.
• An individual spill may pass through various types of water bodies and flow regimes before ’it is stranded or recovered, making it difficult to predict its final fate and properties.
• The types of the hydrocarbon products that are being manufactured, transported, and used in inland environments are more diverse than the types of products that can be released in marine environments. These products would be expected to have a greater variability of behavior and response strategies tailored to their changing purposes.

SPILL RESPONSE IN INLAND ENVIRONMENTS

In a typical offshore oil spill scenario, oil spreads unconstrained on the water surface, subject to various weathering processes (e.g., evaporation, dispersion, emulsification, and photooxidation). Mechanical oil spill response strategies in this case are focused on utilizing booms and skimmers to limit slick spreading and collect, recover, store, transfer, and ultimately dispose of collected oil. In cases where mechanical recovery alone is insufficient, in-situ burning and dispersant use may be considered. Inland response involves a greater diversity of spilled products, release scenarios, physical environments, environmental conditions, resources at risk, logistics, proximity to populated areas, and other considerations, as discussed earlier.

Compared to offshore spills, effective preparedness for inland spills must include a greater variety of response tools and strategies and be flexible and adaptable to effectively respond to an array of fast-changing scenarios. Numerous tools and response strategies have been developed over the years to address these challenges (NOAA and API, 1994; USCG, 2002; Alaska Clean Seas, 2012; ExxonMobil, 2014; Nuka, 2014). Below is a non-exhaustive list of tools and equipment that may be required for robust inland response operations.

• Remote sensing tools for oil detection and monitoring on land, on the water surface, in the water column, and at the bottom of water bodies.
• Air monitoring and safety equipment (e.g., personal protective equipment [PPE]) to ensure safety of response operations.
• Logistics equipment to support successful and sustainable response especially in remote areas (e.g., trucks, power packs, lights, shelters, heaters).
• Response equipment:
  • Variety of “yellow iron” machinery (e.g. front-end loaders, bulldozers, or excavators) for diverse on-land operations. For example, building barriers, ditches, dams, berms, trenches, or sumps that can reduce oil spreading and collect the oil for recovery using skimmers or other physical removal techniques. Some of the heavy machinery can also conduct mechanical collection of oil from land.
  • Miscellaneous tools and materials such as retention walls, fill, planks, sandbags, or pipes that can be used for construction of barriers (e.g., underflow dams to collect oil from small streams).
  • Sorbents, snares, and solidifiers in various shapes and sizes (e.g., loose, pads, booms) as well as insulation materials (e.g., geotextiles).
  • Equipment for manual oil recovery (e.g., rakes, shovels, bags, PPE).
  • Equipment for accessing, containing, and recovering oil under ice.
  • Various configurations of response boats tailored to operating environment.
  • Anchoring and boom deployment equipment such as BoomVane™.
  • Various types of booms tailored to a specific response tactic:
    • Conventional oil collection on open water in a “J” or “U” configuration;
    • Current busters for oil collection in fast currents;
    • Exclusion booming deployed across or around sensitive areas and anchored in place;
    • Deflection of oil away from a sensitive area anchored or held in place with a work boat. Booms can be deployed as a single boom, in cascade, or in open or closed chevron;
    • Deflection toward the shore for shoreside recovery with single or multiple booms that are deployed from the shoreline at an angle toward the approaching slick and anchored or held in place with a work boat;
    • Intertidal or shore-seal booms. These booms have a water-filled chamber that follows the contour of the shore and prevents collected oil from escaping.
  • Various oil recovery devices
    • Advancing skimmers,
    • Stationary skimmers, and
    • Vacuum systems.
  • Equipment for transfer of collected product.
  • Temporary storage containers of various sizes for collected product and generated waste.
  • Equipment for submerged oil detection and recovery.
  • Additional mechanical equipment for the shoreline cleanup:
    • Sediment reworking or tilling,
    • Vegetation removal,

• Flooding or water flashing,
• Physical herding (e.g., water/hydraulic barriers, fire hydrants),
• Steam cleaning,
• Sand blasting, and
• Debris removal.
• Tools for chemical response (e.g. herders, chemical cleaners).
• Tools for biological response (e.g., fertilizers, monitoring equipment for natural attenuation).
• Tools for in situ burning (e.g., igniters, air-monitoring equipment).
• Provisions and equipment for waste management.
• Wildlife management tools.
• Sampling equipment.

The USCG Inland ERSP Calculator’s narrow focus on open-water booming and skimming may have an unintended consequence of diverting the attention of response planners toward this strategy and corresponding equipment rather than evaluating their location-specific strategies, tactics, and equipment needs and enabling a robust response program suitable for diverse response scenarios.

REFERENCES

Alaska Clean Seas. 2012. Alaska Clean Seas Technical Manual, Vol. 1: Tactics Descriptions http://environmentalunit.com/Documentation/05%20Response%20Techniques/ACS%20Technical%20Manual%20Tactics.pdf.

ExxonMobil. 2014. Oil Spill Response Field Manual https://corporate.exxonmobil.com/-/media/Global/Files/riskmanagement-and-safety/Oil-Spill-Response-Field-Manual_2014.pdf.

NOAA and API (National Oceanic and Atmospheric Administration and American Petroleum Institute). 1994. Inland Oil Spills: Options for Minimizing Environmental Impacts of Freshwater Spill Response. https://response.restoration.noaa.gov/sites/default/files/shoreline_countermeasures_freshwater.pdf?msclkid=68783c9fbcfb11ecb425b42d417f66d0.

Nuka (Nuka Research & Planning Group, LLC). 2014. Spill Tactics for Alaska Responders. https://dec.alaska.gov/media/11550/star-manual.pdf.

Overstreet, R., and J. A. Galt. 1995. Physical Processes Affecting the Movement and Spreading of Oils in Inland Waters. HAZMAT Report 95-7, September. Seattle, WA: NOAA/Hazardous Materials Response and Assessment Division https://response.restoration.noaa.gov/sites/default/files/inland.pdf.

Reed, M., Ø. Johansen, P. J. Brandvik, P. Daling, A. Lewis, R. Fiocco, D. Mackay, and R. Prentki. 1999. Oil spill modeling towards the close of the 20th century: Overview of the state of the art. Spill Science Technology Bulletin 5:3-16.

Spaulding, M. L. 2017. State of the art review and future directions in oil spill modeling. Marine Pollution Bulletin 115(1-2):7-19. doi: 10.1016/j.marpolbul.2017.01.001.

USCG. 2002. Section 9302: Oil Response in Fast Water Currents: A Decision Tool. https://www.rrt10nwac.com/Files/NWACP/2016/Section%209302%20v17.pdf?msclkid=aeb875d3bcfb11ecbf9bdb8ab7662d48.