What defines arrival ballast according to the USCG?

Arrival ballast, as defined by the USCG, refers to ballast that is taken on board a vessel without leaving visible traces of oil. This designation is crucial in ensuring that environmental standards are upheld and that the risk of pollution is minimized during the vessel's operations. By specifying that the ballast must not leave visible traces, regulations aim to prevent contamination of marine environments, thus protecting ecosystems from potential harm caused by oil spills or discharges.

In the context of other options, ballast discharged in turbulent waters could lead to an increased risk of pollutants being mixed with the surrounding water, compromising maritime safety and environmental health. Ballast mixed with chemicals isn't aligned with the definition since the focus here is on the nature of the ballast relative to oil pollution. Additionally, ballast from moving vessels does not inherently reflect the criteria regarding oil visibility or contamination, which is central to the concept of arrival ballast. Therefore, the definition highlighting the importance of not leaving visible traces of oil is essential for maintaining compliance with environmental regulations.