Question 467Navigation General

The correct answer is D) mean lower low water. On Pacific Coast nautical charts, the reference plane for soundings (water depths) is the mean lower low water (MLLW) level. This is the average of the lower of the two daily low tides, as observed over a 19-year period. MLLW is the standard reference plane used for all charted soundings on the Pacific Coast of the United States. The other options are incorrect because they represent different tidal datums that are not used as the reference plane for Pacific Coast chart soundings. Lowest normal low water, mean low water, and mean low water springs are not the standard reference used on these charts.