Sierra and San Francisco Power Company

Insulators Damaged in Vandalism Attack


Publication: The San Francisco Chronicle

San Francisco, CA, United States
vol. CVIII, no. 150, p. 1, col. 4





Steel Structures Supporting

High Tension Wires in San

Mateo County Wrecked

by High Explosive



San Francisco Police Aiding

in Search for Man Said to

Have Engineered Plot to

Cripple Trolley Service

Three big steel power-line towers near the top of San Bruno mountain in San Mateo county were toppled over by explosions of dynamite early Sunday morning. The towers support wires carrying 40,000 volts and belong to the Sierra and San Francisco Power Company, which supplies the United Railroads with electrical energy for its street system in this city.

Convinced that the towers were wrecked for the sole purpose of injuring the United Railroads, detectives of the San Francisco Police Department, assisted by United Railroads detectives, are hot on the trail of the dynamiters.



The police have a good description of the man they say engineered the explosions. This man was seen to leave a meeting of agitators held in this city last Saturday night. When he hurried out of the hall, it is stated, he was seen to carry a large, heavy valise. The police say they are convinced that the dynamite bombs which wrecked the towers were in this valise.

The police further say that the wreck of the towers was accomplished by expert dynamiters and that time bombs, with clock and fuse attachment, were used. The dynamite was placed in such a position that when it exploded the towers fell, bringing down with them a twisted mass of high-tension wires. The wreck disconnected the Visitacion valley power station of the Sierra and San Francisco Power Company from its generating plant in the Sierra Nevada. Instantly, however, the company set its auxiliary steam plant to work, and for this reason no effect was noticed on the car services of the United Railroads in this city.



Constable J. C. Wallace of South San Francisco said yesterday that three explosions were heard in the hills to the north early Sunday morning one at 3:45 A. M., one at 4 A. M., and the third at 4:10 A. M. A crew of men were busy all day yesterday repairing the damage.

H. F. Jackson, vice-president and general manager of the power company, said the work would be completed by today. He said that he was at loss to assign a cause for the vandalism, as his company had had no trouble whatever with any of its men or with any other person or associations. The wreck, he said, will entail a cost to repair of about $1,000.

The force of the explosions was so great as to smash a half-dozen of the clustered high-tension insulators on the Pacific Gas and Electric Company's power line which parallels the Sierra and San Francisco Power Company's wires on the San Bruno mountain.

Keywords:Power Transmission : Vandalism : Pacific Gas & Electric Company : M-2795 : Duncan : Suspension : Locke Insulator Manufacturing Company
Researcher notes:Paul Greaves provided the following: "the Sierra and San Francisco Company used the "Duncan" suspension insulators ... highly desirable now! They were really the first successful suspension insulator used for high voltage long distance power, and are very historically significant. The PG&E line mentioned could have used any of a number of insulator types by 1916. Probably some sort of 4-part multiparts, but even "gutters" (M-2795) is possible. The location is on the San Francisco penninsula, so PG&E had many lines in that area." Elton Gish indicates that the "Duncan" suspension insulators were manufactured by Fred Locke.
Supplemental information: Patent: 880,203
Researcher:Glenn Drummond
Date completed:July 28, 2009 by: Glenn Drummond;