A container ship waiting at Anchorage 9. (Samantha Shanahan/KQED)
Even though the Bay Area is surrounded by water, a lot of people don't know much about the nautical vessels that roam our waters, and many of you have asked Bay Curious about them.
So we turned to the experts — the Coast Guard's Vessel Traffic Services (VTS) — to help us find the answers to your many questions.
What's the difference between the various vessels on the bay?
Most of the large boats on the bay are either barges or cargo ships.
A barge is a floating platform. It doesn't have a motor, like the trailer part of a tractor-trailer.
There are many kinds of barges. Spud barges, for example, use a big steel shaft or spud that goes down to the bay floor to stay anchored in place.
Other barges are used for dredging and construction, which is constantly happening to keep certain channels in the bay deep enough for big vessels to get in and out of the ports.
Many of these dredging barges are anchored at the Treasure Island East Moorings, east of Treasure Island and north of the Bay Bridge. Empty barges are tied there to floating mooring balls, which are anchored to the bay floor.
When silt and rocks are dredged from the bay floor, they're piled onto a barge. Once that barge is full, it's towed away to be dumped, and then one of the empty barges parked at the mooring group is brought in.
"It’s like a big parking lot is what it is," said Michael Roja, who leads VTS for the Coast Guard. "This is the biggest mooring group in the bay."
Cargo ships have an engine and are designed to go long distances. They're often designed to carry specific cargo — cars, fuel — but in theory they can carry anything. Container ships are a type of cargo ship designed to carry shipping containers.
In the Bay Area, there are a lot of container ships that come in from Asia and head to various ports (often the Port of Oakland), filled with all the stuff we buy from overseas. But before these ships can enter the bay, they have to go through a lengthy approval process:
Ship operators have to submit a notice of arrival with the Coast Guard and request pilotage.
Ships are assigned a pilot and a spot in the bay — either a berth at a port or a spot at an anchorage. (An anchorage is a set place in the bay for ships to drop anchor and wait. There are anchorages all over. Anchorage 9, off Hunters Point, is the largest in the bay and the only place fueling is allowed. Anchorage 23, up by Benicia, is for ships to wait out the fog.)
The pilot boards the ship out at the pilot station — about 11 miles into the ocean from the Golden Gate Bridge — and then brings the ship into the bay.
The ship goes straight to the port it's been assigned to unload or load (each port is designed for specific types of cargo) OR the ship goes to an anchorage to wait for a spot at port.
VTS oversees all boat traffic within 38 nautical miles from the top of Mount Tamalpais, so after a big ship enters that circle, they have to notify Roja's people — and they stay in constant communication about conditions and any obstacles.
It looks like some boats stay anchored in the bay for days at a time. Why?
Most of the time big ships are unloaded and reloaded all in a few days, sometimes even just in one day. But it can be a little complicated to line up everything — the staff to unload, and then the next shipment for a company to load up and take to the next port.