1998-

< 30 ftPresent tops of

Harding, Shag, and Arch Rocksin West San Francisco Bay

33 ft 38-41 ft 38-42 ft 42-46 ft >46 ftDRAFT OF SHIP

MEAN SEA LEVEL-20 ft-40 ft

EVOLUTION OF CONTAINER SHIPSPre-1960

1971-80 1981-90 1988-95 1990-2000

WESTERNSAN FRANCISCO

BAYSanFranciscoSanFranciscoBay

SanPabloBay

WalnutCreek

Fremont

Sunnyvale

HalfMoonBay

Palo Alto

Oakland

Novato Vallejo

AngelIsland

Pacific Ocean

280

880

880680

680

580

780

580

80

80

80

1 4

24

92

1

1

101

101

Mapping Shipping Hazards in San Francisco Bay

John Chin, USGSPaul Carlson, USGS Florence Wong, USGSDavid Cacchione, USGSDave Rubin, USGSPat Chavez, USGSMiguel Velasco, USGSJim Gardner, USGSPete Dartnell, USGS

San Francisco Bay Mapping Team

Photo of sonar equipmentmounted to survey boat

Location of San Francisco Bay

More information on the web: http://walrus.wr.usgs.gov/posters

1997-1998

The USGS mapped western San Francisco Bay using sonar, in cooperation with the National Oceanic and Atmospheric Administration (NOAA) and C&C Technologies.Some parts of the Bay floor are so shallow that a large tanker or container ship could run aground at low tide and create a massive oil spill.

Harding Rock

Harding Rock Shag Rock

Arch Rock

100 yd

100 yd

Computer images of western San Francisco Bay without water.• Rocks less than 55 feet below sea level are outlined in yellow. • Holes deeper than 95 feet are outlined in orange.

The maps show how the rock pinnacles could be lowered and the material deposited in holes in the Bay floor. Ships could navigate freely in the Bay, even at low tide, without having to avoid these areas.The maps will be used to help determine the environmental, economic, and social impact of lowering the rock pinnacles.

What if Harding Rock were shaved off and deposited into a nearby hole?