A reprint from American Scientist the magazine of Sigma Xi, The Scientific Research Society This reprint is provided for personal and noncommercial use. For any other use, please send a request to Permissions, American Scientist, P.O. Box 13975, Research Triangle Park, NC, 27709, U.S.A., or by electronic mail to
[email protected]. ©Sigma Xi, The Scientific Research Society and other rightsholders ENGINEERING ST. FRANCIS DAM Henry Petroski os Angeles could not have grown into the Mulholland later recalled that he became in- Lmetropolis that it is today without the ex- terested in things technical when serving as pansion of its water supply. In 1900 the city’s a helper on a drill rig digging water wells population was about 100,000 and growing that pierced a buried tree trunk at a depth of rapidly, to reach 175,000 within five years. Since 600 feet. He went to the library to investi- the Los Angeles River watershed was capable of gate the manner by which a tree could be- supporting only about 200,000 people, the city come buried at such great depth, and read had the choice of limiting growth or finding new University of California Professor John sources of water. A drought in 1904 raised the is- LeConte’s Introduction to Physical Geology. sue to crisis proportions. Mulholland liked the subject matter so Los Angeles’s need to import water had been much that he later recalled, “Right there I foreseen a decade earlier by Fred Eaton, who as decided to become an engineer”.… city engineer had identified the Owens Valley, north of the city, as a likely candidate.