1927+1994 45mw Old & New Waddell Dams and Lake Pleasant north of Phoenix, AZ

1927: (HAER)

1994: (Satellite)

usbr
"New Waddell Dam, constructed between 1985 and 1994, stores Colorado River water for the Central Arizona Project,and also stores Agua Fria River runoff and provides flood protection by controlling river flows. The dam is on the Agua Fria River about 35 miles above the Gila River confluence and is located one-half mile downstream of the now submerged historic Waddell Dam, which was built by the Maricopa Water District (MWD)."

SaltRiverStories
"When completed in 1928, the Carl Pleasant Dam was the largest multiple arch concrete dam in the world. The massive structure stood 76 feet tall and 250 feet long with a crest length of 2,160 feet. The total storage capacity was 157,000 acre-feet of water. Date: 1929"

SaltRiverStories
"Old Waddell Dam in Relationship to current Lake Pleasant This photo illustrates relationship of the "old" dam with the current Lake Pleasant Dam. When completed in 1927, the Old Waddell Dam was the largest concrete arch and buttress dam in the world. It spanned 1,260 feet and was 176 feet above the deepest part of the stream bed. In 1936 a roadway was added to the top of the dam. In the mid-1980's the Central Arizona Project (CAP) folks decided to build a larger dam 1/2 mile downstream. This new Waddell Dam was completed in 1992 - it is an earthen dam. The new dam added tremendous capacity to Lake Pleasant, whose function is to be a storage facility for the CAP. The CAP canal system transports water from the Colorado river to Southeastern Arizona. The new dam allows water levels to tower 100 feet over the top of the old dam by the end of March each year. Source: http://www.porter-az.com/Waddell.htm Date: 2000"

usbr_office
"In the winter, Colorado River water is pumped uphill from the CAP aqueduct into Lake Pleasant when power rates are low. In the summer, when demand for water and electricity increases, water is released through the Pump-Generating plant, producing hydroelectric power that is sold to help repay the CAP's construction costs. In addition, New Waddell Dam adds 7,000 surface acres to the lake, greatly increasing the recreational value of Lake Pleasant Regional Park....The cost of constructing New Waddell Dam was more than $625 million. The Central Arizona Water Conservation District, which operates and maintains the CAP, is repaying $175 million of this cost."
The pumping plant has 8 units that can lift the water 192' (58.m) high and generate 45mw.

This is some serious spillway capacity. Especially since most of the water comes from pumps instead of the river's watershed.

usbr

These HAER photos are two of several construction photos available in HAER_gallery.

HAER ARIZ,7-PHEN.V,5--17
17. Upstream side of arches and buttress supports. Photographer unknown, January 1927. Source: MWD. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

HAER ARIZ,7-PHEN.V,5--19
19. Upstream face of arches and buttresses at west end. Photographer unknown, January 29, 1927. Source: MWD.

"Significance: Waddell Dam, formerly named Pleasant Dam, is the only water storage dam constructed by private interests in central Arizona. It became the largest multiple arch dam in the world upon completion." [HAER_data]

Central Arizona Project posted 15 photos with the comment:

If you’ve visited Lake Pleasant, you’ve likely seen New Waddell Dam, an earth and rock embankment dam that is nearly 4,800 feet long and a structural height of approximately 340 feet. It was constructed by the Bureau of Reclamation and cost $625 million. The dam is on the south end of Lake Pleasant, a popular recreational spot and storage reservoir for Central Arizona Project.

What you may not know is that before there was New Waddell Dam, there was the Carl Pleasant Dam, later renamed Waddell Dam. When its construction was completed in 1928, it was the largest multiple arch concrete dam in the world. 

Waddell Dam was partially dismantled, but left in place, as New Waddell Dam was constructed about ½ mile downstream. As Lake Pleasant filled, water breached the old dam, resulting in a reservoir that was able to hold nearly 886,400 acre-feet of water, which is triple the previous storage capacity. Learn more: https://bit.ly/4iBZOTE

Timothy Wareham: The link says, “The dam stores Colorado River water and runoff from the Agua Fria River.” I am not sure what “runoff” means here, but doesn’t all Agua Fria River water now flow into the lake?

Marie Crockett: Timothy Wareham it has no Colorado river water in it, that I am aware of. Yes the Aqua Fria runs into the lake.

Tom Leufkens: Marie Crockett it absolutely positively does have Colorado River water in it. It is pumped seasonally to maximize during the summer to provide additional water for large portions of Arizona. It is pumped and canaled from the Colorado River. As for the agua fria in the 50 plus years I've lived here that really hasn't run much in the last 15-20 years. But it used to provide some additional water especially during large monsoon floods or snow melts high in the mountains. But the majority of the water probably 98% comes from the Colorado.

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