Histor y Lesson

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The Colorado River Aqueduct

T
he mighty Hoover Dam tends to be the Nearly 63 mi of con- duits, 28.7 mi of reinforced-concrete cylindri-
focus of the story of how engineers tamed crete-lined canals help cal inverted siphons, six reservoirs, five pumping
the wild Colorado River and brought wa- convey water from plants, and four dams as it makes its way to the

G R A P H S D I V I S I O N , A B O V E ; C O U R T E S Y O F T H E M E T R O P O L I TA N
ter and prosperity to the arid Southwest. the Colorado River to growing cities of Southern California. (Adding

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But the Colorado River Aqueduct, which the coastal plain of the distribution systems, which deliver water to

W AT E R D I S T R I C T O F S O U T H E R N C A L I F O R N I A , B E L O W
linked the river to the Los Angeles region, is per- Southern California. municipalities around Los Angeles, increases the
haps a greater achievement, for it took longer to system length to 392 mi.)
build, cost more money, and involved more workers. Built The project was also a significant boon to workers during
over eight years during the 1930s, the aqueduct was one of the Depression, employing a total of 35,000 people in South-
the great engineering triumphs of the American West and ern California, as many as 10,000 at a time. And the trans-
contributed to the explosive growth of Southern California portation of materials for the project provided jobs for 25,000
after World War II. more Americans across the nation.
The 241.6 mi long aqueduct passes through the remorse- In 1995 asce formally recognized the Colorado River
less Mojave Desert and features 92.1 mi of tunnels, 62.8 mi Aqueduct in its Historic Civil Engineering Landmark Pro-
of concrete-lined open canals, 54.4 mi of cut-and-cover con- gram. It is indeed remarkable that, more than 75 years after its

The Colorado River Aqueduct extends nearly 242 mi across California, gaining more than 1,600 ft in elevation as it runs westward.

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Civ. Eng., 2017, 87(4): 46-49

 The Whitsett pumping plant, on Lake Havasu, behind Park-
er Dam, lifts water 291 ft into the Colorado River Aqueduct.

completion, the structure is little changed and remains an im-

portant means of importing water into Southern California.
As early as 1892, as Los Angeles’s population hit 50,000,
water from the Los Angeles River was disappearing and the
underground water table in southern California was being
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depleted, according to J. Philip Gruen, Ph.D., in a 1998 His-

toric American Engineering Record report. (Gruen is now an
associate professor at Washington State University and the
director of its School of Design and Construction.)
By 1902 voters had approved a bond issue to form the
city’s first public water agency, which was charged with find-
ing a way to provide reliable water to the growing, thirsty
city. The Los Angeles Aqueduct, constructed between 1908
and 1913 to bring water from the distant valley of the
Owens River, in central California, was “built to serve the
water needs of a city with a population of two million people
and to last forty to fifty years,” Gruen wrote.
Completed in 1913, the aqueduct was designed for a ca-
pacity of 400 cfs, but drought during the early 1920s proved
the aqueduct’s inability to supply a growing region by itself.
U . S . N AT I O N A L A R C H I V E S A N D R E C O R D S A D M I N I S T R AT I O N

(Today it provides water exclusively to the city of Los Angeles.)

Water planners knew they needed a superior solution. By
the early 1920s officials in the region were seeking another
source. The legendary Los Angeles water engineer William
Mulholland traveled to the Colorado River in October 1923,
establishing plans to tap the river. Water there was plentiful.
The Los Angeles Aqueduct was powered by gravity, but an-
other solution would be needed here. The river basin was lower
than the coastal plain around the city and would require tra-
versing mountains to reach Los Angeles. Hoover Dam, then
known as Boulder Dam, would provide the electricity needed
to run the pumps that would lift the water from the river.
In 1928 the Metropolitan Water District of Southern

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 California (mwd) was created to help considered an 850 mi long gravity-flow The aqueduct’s cut-and-cover con-
oversee and coordinate water resources aqueduct from the San Juan River in duits were used to “cross areas prone
for the entire region, which by 1931 Utah all the way to a desilting basin in to flooding or blowing sand,” accord-
consisted of the following communi- Mexico. From there a 770 mi tunnel ing to Bissell. To guide the aqueduct
ties, in addition to Los Angeles: Ana- would convey the water north to San across such natural depressions as ra-
heim, Beverly Hills, Burbank, Comp- Diego and Santa Monica. vines and drainage courses, engineers
ton, Fullerton, Glendale, Long Beach, In the end, a route starting from tiny designed 144 inverted siphons. These
Pasadena, San Marino, Santa Ana, Santa Parker, Arizona, was chosen because it ran for 28.7 mi, or 12 percent of the aq-
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Monica, and Torrance. had the best combination of cost, dis- ueduct’s total length.
“The Colorado River aqueduct was tance, and constructability. This route One other challenge loomed silent
therefore planned not as a Los Ange- was formally adopted by the mwd on in the background: engineers were
les project, but as a Southern California January 16,1931, and construction be- bringing the aqueduct across two fault
enterprise,” wrote Charles A. Bissell in gan two years later, on January 25, 1933. lines, the Mission Creek and the San
the mwd’s first annual report, in 1938. The aqueduct would utilize a variety Andreas. They planned for the aque-
The project was conceived, he went on, of conveyances. As Gruen explained, to duct to intersect the fault lines at right
“not on the basis of meeting immediate form the nearly 63 mi of canals, tractors angles. Along the fault zones, Bissell
needs alone, but on the far broader ba- and bulldozers cleared away the surface wrote, the cast-in-place construction
sis of insuring for generations to come soil, and draglines “cut into the earth to was interrupted every 20 ft by lead-
an adequate water supply for the region excavate the soil as closely as possible to caulked steel bell-and-spigot joints;
as a whole.” the canal’s eventual prism shape.” Drill- these joints were capable of transmit-
The Boulder Canyon Project Act ing and explosives also were used to exca- ting shear but not tension.
was passed in 1929, giving a green vate tough stretches of soil. To form the “Movements on these faults in his-
light to Boulder Dam and paving the canal shape into its final dimensions— torical time,” he wrote, “although some-
way for the aqueduct. Two years later a approximately 56 ft across the top, 20 ft times several feet in magnitude, have all
$220-million bond issue ($3.5 billion at the base, and nearly 12 ft in depth— been horizontal, but in order to com-
today) was authorized to fund the aq- one of the contractors, Wood and Bev- pensate for any possible adverse vertical
ueduct’s construction. anda Company, introduced a specialized movement, an allowance of 2.5 ft, in ex-
Throughout the 1920s, however, and machine. This “canal trimmer” moved cess of that required for maintenance of
well before construction began, water along rails on either side of the trench and flow, is made at both...crossings.”
planners, initially led by Mulholland, performed so well that, Gruen wrote, by The joints were designed not only
were initiating an epic survey of the lit- “the fall of 1935, all contracting compa- to provide flexibility in the event of an
tle-known desert between the river and nies working on canals built similar ma- earthquake but also to confine the dam-
the city. Over seven years, surveyors, en- chines to facilitate construction.” age to a short length if a temblor did
gineers, and geologists “traversed over After workers laid out rebar along the rupture the line. Over the years the aq-
25,000 square miles of rugged and bar- slopes and base of the canal and placed the ueduct has not sustained any damage
ren desert to draw detailed topographic concrete, another machine, a canal paver, from seismic activity.
maps of the region,” Gruen wrote. came through to level the concrete. “The The most challenging portion of
“Most of the area mapped was re- concrete was then hand-troweled to pro- the job was the 13 mi tunnel that cut
mote from highways or roads,” Bis- vide a smooth appearance, treated with through the nearly 11,000 ft San Jacin-
sell wrote. “Some of it was exceeding- sealing compound to prevent excessive to Peak, California’s third tallest, which
ly rough and could only be crossed on drying and cracking, and whitewashed towers over Palm Springs. According to
foot or horseback.” Roughly 115 mi to avoid solar overheating and cracking,” Gruen, engineers at the time conclud-
of scratch roads were built between the Gruen noted. Workers could place more ed that the job was one of the most dif-
fall of 1925 and the spring of 1927. than 530 ft of concrete lining per eight- ficult tunnel construction efforts ever
F.E. Weymouth took over as chief hour shift, “a remarkable improvement undertaken. The tunnel would extend
engineer of the mwd in July 1929. A over the non-mechanical hand-operated 8 mi, the greatest distance between ac-
Bureau of Reclamation chief engineer method,” he wrote. cess points of any of the tunnels in the
for 22 years, the 58-year-old had previ- Working with the concrete was project. Workers labored to construct
ously built Arrowrock Dam, in Idaho. difficult. “In general, no concrete was a series of long shafts to bring men and
When Weymouth came on board, no placed in the surface work in the desert material into the tunnel site, but they
fewer than 100 routes for the aqueduct during the months of June, July, Au- faced constant difficulties from flooding.
were under consideration. By the end of gust, and September,” Bissell explained In one particularly harrowing mo-
the year, the number was down to 54. in the mwd report. “At other times of ment, more than 7,500 gal of water
Some of the proposals called for aq- the year when the maximum daily tem- rushed into the tunnel, forcing work-
ueducts that would require less energy perature in the shade exceeded 90º, the ers to flee up ladders a distance of
and take advantage of gravity, but the placing of concrete was restricted to the 796 ft in one of the vertical shafts. The
logistics proved insurmountable. Ac- time beginning two hours before sunset shaft would be flooded on two other oc-
cording to Gruen, planners at one point and ending three after sunrise.” casions as well.

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Civ. Eng., 2017, 87(4): 46-49

 pacity to nine units per plant,
or 45 in all. But it wasn’t until
a decade into Southern Califor-
nia’s postwar population boom
The mwd wound up firing the that the mwd was ready to ex-
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original contractors and hiring its pand the system.

own workers to finish the job, ac- In the mid-1980s the water
cording to Gruen, and this crew district investigated the condi-
installed electric pumps to prevent tion of the pumping units and
flooding. The tunnel was “holed found wear on the impellers,
through” in November 1938. the pump bowls that contain
While the length of the aque- them, and several components
duct is impressive, so too are its and coatings. It rehabilitated all
capacity—1,500 cfs—and pow- 45 pumping units at a cost of
er. The aqueduct uses five sepa- more than $33 million. Glen
rate pumping stations, collective- K. Boyd, the conveyance and
ly rated at 375,000 hp, to lift the distribution section manag-
water more than 1,600 ft along er for the mwd, notes that the
the 242 mi course. “The pumps at original impellers were made of
each of the plants are single-suc- bronze and each pump could
tion, single-stage vertical centrif- move water at 200 cfs. The
ugal pumps set below the level agency replaced the bronze im-
of the water to reduce the risk of pellers with stainless steel ver-
cavitation and to insure self-prim- sions modified to improve ef-
ing,” Gruen wrote. The synchro- ficiency and increase output to
nous motors, which operate at 225 cfs.
400 rpm, were located above the From 2002 to 2005 the
highest inlet water level to avoid mwd replaced 207,600 sq ft
flooding. “Each of the motors is a ver- The aqueduct consists of 54.4 mi of cut- of canal line at a total cost of $6.6 mil-
tical, three-phase, 60-cycle, 6,900-volt and-cover conduits, constructed in areas lion, which required the agency to shut
synchronous motor, enclosed and water prone to flooding or blowing sand. down the aqueduct for a few weeks
cooled,” Gruen wrote. each year; reservoirs and water from the
To control the water, the aqueduct telephone lines, and 199 mi of water massive California State Water Project
employs four dams and six reservoirs. supply lines. picked up the slack. The mwd is now
Parker Dam, along the Colorado River The aqueduct ends in Riverside planning a new round of pump reha-
itself, is, despite appearances, the most County at Lake Matthews, a storage res- bilitation similar to its effort in the late
impressive. Although less than 75 ft ervoir about 20 mi west of the tunnel 1980s, this time including such ancil-
tall, it extends 247 ft below the river- through San Jacinto Peak. From there lary aspects as electrical and cooling wa-
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bed to reach bedrock. a feeder pipe conveys water to the F.W. ter systems and the cranes used to dis-
The reservoir created by Parker Dam, Weymouth Treatment Plant, in La mantle the pumps.
known today as Lake Havasu, helps Verne. (Weymouth died about the time “It’s a very robust system,” says
desilt the Colorado River and, along the project was completed.) The Colo- Boyd. “It was designed to be very, very
with the other five reservoirs, regulates rado River Aqueduct delivered its first reliable, and it has been reliable.”
and equalizes the flow of water along the drops of water to Pasadena in June 1941. On average, Boyd notes, the aq-
system. As Bissell put it in his report, Despite this massive achievement, it ueduct provides about two-thirds of
“The natural flow of the Colorado River wasn’t long before Pearl Har- the imported water that
is variable and the use of water is much bor made it seem like old the mwd delivers to its 26
lower in the winter than in the summer. news. Moreover, the aqueduct member agencies. “With-
If the aqueduct is to be used to full effi- initially had 3 pumping units out that system,” he says,
ciency, capacity must be available at both at each of its five pumping “Southern California would
intake and outlet for storage.” plants, the 15 units consti- not have become what it is
Building the aqueduct required its tuting a third of the system’s today.” —T.R. W itcher
own elaborate infrastructure: 150 mi planned capacity. Between
of new roads, 454 mi of high-voltage 1956 and 1959, the mwd in- T.R. Witcher is a contributing
power lines, more than 1,200 mi of creased the pumping unit ca- Witcher editor to Civil Engineering.

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Civ. Eng., 2017, 87(4): 46-49