News letter Dam edition

Ingeokring Newsletter
Fig. 2 Glen Canyon Dam and Bridge (note the white band on the
Navajo Sandstone, result of the low level of the reservoir behind the
dam) (source: author’s photo).
Upon completion of Glen Canyon Dam the Colorado River
and its tributaries began to back up, no longer being diverted
through the tunnels. The newly flooded Glen Canyon
formed Lake Powell, stretching for over 300 km upstream.
As the lake filled over the years, seismic activity in the area
increased as the ground shifted beneath the increasing
weight of the water. It took 17 years for the lake to rise to
the high water mark, which was reached on June 22, 1980.
Since then the reservoir level has fluctuated wildly and is
currently less than 60% of its total capacity. The reservoir is
currently suffering from prolonged drought. The reservoir
has been evaporating as much as ever, and the longsubmerged
side canyons are being revealed. This lower level
can be clearly seen as the so-called ‘bathtub ring’ (white
band) in Figure 2.
Construction of the dam started in 1956 with the creation of
water diversion tunnels. By 1959, nearby Glen Canyon
Bridge was completed (see Figure 2), allowing trucks to deliver
equipment and materials for the dam and the new
town of Page. Concrete placement started around the clock
on June 17, 1960. The last bucket of concrete was poured on
September 13, 1963 (see Figure 3 for typical bucket size).
Over 3.7 million m 3 of concrete was used. Construction of
the dam, bridge and all other adjacent facilities cost $314
million (adjusted for inflation) and 18 people’s lives.
Next, turbines and generators were installed from 1963 to
1966. The plant consists of eight 155 500 horsepower Francis
turbines that generate more than 1 300 MW of electricity
with each of the 40 ton steel shafts turning at 150 rpm. With
all eight generators operating at full output, over 55 million
litres of water will pass through the power plant's penstocks
each minute.
Fig. 4 Aerial photo of Hoover Dam with the U-shaped power plant in
front and Lake Mead in the back (source: photo.net/photo/pcd2882/
hoover-dam-aerial-91.4.jpg) .
Hoover Dam
Almost 2 200 km and 5 days later we had arrived at the last
stop before leaving from Las Vegas again: the giant Hoover
Dam. Hoover Dam is situated in another NPS administered
National Recreation Area: Lake Mead, which stretches out
over an area of 750 km 2 . Hoover Dam is situated in the Black
Canyon of the Colorado River valley, on the border between
Nevada and Arizona (the actual border runs over the crest of
the dam), some 50 km southeast of Las Vegas.
Fig. 3 Bucket which was used to pour concrete (source: author’s photo).
In total, 21 000 people worked on the project which was
completed in 1936. Construction costs of the dam were
$676 million (adjusted for inflation) and 114 people’s lives
were lost over the total project period from 1922 to 1942.
Hoover Dam is a similar type dam as Glen Canyon Dam, a
concrete thick gravity arch dam, with a height of 220 m and
a crest length of 380 m. Width of the dam is 14 m at the crest
and 200 m at the base.
Dam edition | Double Issue 2007/2008 | 54