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6.0 Impact Considerations Version :27.10.4 Spills in Subtidal Environment Mixed and Hard Bottom • Description . This habitat consists of subtidal substrates composed of rock, boulders, or cobbles, though there can be patches of sand veneer covering a hard bottom. . There may be rich, diverse communities of attached and associated algae and animals; often there is little open space. • Some of these habitats form a relief (reef or bank) several meters high that attracts a diversity of fish. • Predicted Oil Behavior • Mixed and hard-bottom habitats are usually considered to have low sensitivity to oil spills. . Oil in the water column seldom reaches toxic levels and benthic organisms have little exposure. . There is little risk of deposition of oil or oiled sediments in these habitats. . There could be a short-term exposure as oiled sediments are transported through the habitat into deeper areas. • Concerns about seafood contamination from dispersed oil or oiled sediments can become a significant issue. Real, potential, or fear of contamination can close seafood harvesting activities. • Response Considerations . Natural cleansing is expected to occur quickly, especially in the higher-energy environments. . Avoid anchoring booms in known sensitive areas, such as unique live-bottom areas. • Dispersants can be used directly over these habitats to protect sensitive intertidal areas. The deeper the water, the greater the dilution, and hence the lesser effect it will have on the mixed and hard-bottom habitats. • In situ burning can be used directly over these habitats to protect sensitive intertidal environments. When burned, some oils can produce a sinkable residue; the potential effects of these residues will depend on the composition and amount of oil to be burned. Shell Supply and Distribution 6-51 Stockton Terminal FRP ©2019 Witt O' Brien's Revision Date:October, 2019