In 2013 these steel tidal columns were driven into the bay mud beneath the wharf, punctured by six holes below the lowest tide. Each opening is 4 inches in diameter, covered with a screen to keep subterranean guck from filling the hollow pile. As the tides rise and fall, so do the water levels within each pipe - causing the (yellow and black) banded aluminum tubes to bob up and down, counting the height of the tide in feet.
King tides are a great time to check out these tidal columns at Brannan Street Wharf Park. During king tides, the bay will reach its highest and lowest tides of the year, raising and lowering these columns throughout the day.
Engraved around the floor of each tidal column reads part of Otis Redding's 'Dock of the Bay'
Please replace this cache exactly as found, you might just get tide up in the moment!