from:http://www.angelfire.com/bc/sanfranartillery/mines1.html

GOLDEN GATE UNDERWATER MINEFIELDS
The U.S. Army planted several rows of underwater mines across the harbor entrance to block hostile ships, especially submarines, from coming into the Bay.



THE EXPLODING BUOYANT MINE
Army mine-planting crew hauls up a seaweed-covered buoyant mine. Each mine carried 800-pounds of TNT and was connected by electric cable to a shore-based detonating station. When a vessel struck a mine, an impact-sensitive device in each mine sounded the alarm in the control bunker. The order could then be given to detonate the mine and blow up the vessel which hit it.

LOCATION OF GOLDEN GATE MINEFIELDS
The underwater mines were planted in a semi-circle across the harbor entrance. Double rows of mines went across the shallow bottom of the shoreline and across the main channel. Coast Guard picket boats were also stationed at the main channel to control shipping. A last line of mines was stretched across the Golden Gate itself. Beyond the bridge, the U.S. Navy installed a submarine net



THE MINEPLANTER
Those who served at the San Francisco harbor defenses fondly remember the mineplanter Niles, one of the most graceful ships to serve in the Army mineplanter service. This vessel was equipped with davits and other specialized gear to plant mines and maintain them. The crews which served aboard mineplanters were all Army personnel. This ship mounted several .50-caliber machine guns for protection on the high seas. The Niles, along with two other mineplanters, were permanently assigned to the San Francisco defenses during World War Two



MORE GOLDEN GATE MINEFIELDS
The mining operations were the most complex activity of the harbor defenders; there were vessels to maintain, mines to safe-guard in special storage facilities on shore, 24-hour duty at mine casemates and surveillance outposts. An entire Mine Battalion was entrusted with this important job.

THE MINE FLOTILLA
Many smaller boats aided the mineplanter ships in mining operations off the harbor entrance. Some mineplanter soldiers were recruited from the crab fishermen of San Francisco's famed Fisherman's Wharf. Occasionally, in course of their mineplanting duties, these men also planted crab pots. The resulting crab bounty provided the dinner for the big gun defense batteries which chipped in for crab bait.



THE MINE CASEMATE
All mines were connected to the control panels in the concrete bunker of the mine casemate. This one is located in the sand dunes of Baker Beach in San Francisco.

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