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World Environmental and Water Resources Congress 2017 403

ered requisite quantities of limestone for calcining cement at a location about 17 miles above
Mojave, along the rail line crossing Tehachapi Pass. Originally called Aqueduct, the name was
changed to Monolith in 1910. It became the largest cement plant in the United States, and continues
in operation to present. The plant was also utilized for aggregate production, transporting all of the
needed materials on the Southern Pacific Railroad to Mojave.
Along the western slope of Indian Wells Valley, a series of sag pipes (referred to at the time
as inverted siphons) allowed the line to cross significant valleys (a total of 23 sag pipes totaling 11.4
miles in length). Eight of the sag pipes, comprising 2.7 miles, were 10 ft in diameter, while the rest
were between 7.5 and 11.5 ft diameter. The sag pipes allowed the aqueduct traverse steeply-incised
ravines emanating from the southern Sierras and Garlock fault zone. The largest of these was across
Jawbone Canyon, about 20 miles north of Mojave (Fig. 5). Here the 7,000 ft conduit drops 850
feet. The siphons required huge sections of riveted steel pipe had to be fabricated in Pennsylvania
steel mills and shipped via rail to Mojave, from where they were transported on wagon dollies
pulled by 52-mule teams.

Figure 5. Left view shows Haiwee Dam under construction in 1911. All of Mulholland’s
embankment dams utilized hydraulic filling and puddling techniques, shown here. Right
image shows the Sag Pipe crossing Jawbone Canyon, dropping and rising 850 feet (LADWP
Archives).

When water was introduced into the sag pipes in early 1913, the line across Sand Canyon
(10 miles south of Little Lake) began leaking and lifted up out of the canyon slope and become
entangled in a landslide spurred by the seepage. This experience (understanding uplift forces) was a
harbinger of things to come at St. Francis Dam 15 years later. Correcting these problems with the

siphons added six months to the completion schedule.

Seismic hazards and the Elizabeth Lake Tunnel. Southwest of Mojave the aqueduct skirted the
foot of broad alluvial fans emanating from the southern Tehachapi Range. The aqueduct crossed

World Environmental and Water Resources Congress 2017