Alder Dam

Alder Dam Quick Facts

Location: Pierce, Washington
Coordinates: 46.801036, -122.310163
River: Nisqually River
Primary Purpose: Hydroelectric
Type: Concrete Arch Gravity
Commissioned: 1945
Dam Height: 285 ft (87 m)
Dam Length: 1,487 ft (453 m)
Dam Capacity: 241,195 acre-ft (297,509 Ml)
Condition Assessment: Satisfactory
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Alder Dam Map

Alder Dam Information

Alder Dam is a concrete arch gravity dam located about 18 miles from Yelm, Wa, Pierce, Washington.

The dam, which is on the Nisqually River, was primarily built for Hydroelectric purposes, but also serves for Recreation benefits.

The dam was designed by and commissioned in 1945 and is currently owned by City of Tacoma.

Alder Dam Structure

The Alder Dam is approximately 1,487 feet (453 m) long, 285 feet (87 m) high and has a structural volume of 420,000 cubic yards (321,113 cubic metres).

Alder Dam Storage Capacity & Surface Area

The reservoir has a normal storage capacity of 214,500 acre-ft (264,581 Ml) and maximum capacity of 241,195 acre-ft (297,509 Ml).

The surface area of the reservoir is 3,065 acres (1,240 ha) and the total catchment area is 286 square miles (741 square kilometres).

Alder Dam Spillway

The dam spillway has a maximum discharge capacity of 80000 cubic feet per second (2265 cubic metres per second).

Alder Dam Compared to Five Famous American Dams

Height (ft)
Length (Ft)
Storage Volume (acre-ft)
Drainage Area (sq miles)
 
Alder Dam
Pierce, Washington
Height (ft)
285
Length (Ft)
1,487
Storage Volume (acre-ft)
241,195
Drainage Area (sq miles)
286
Hoover Dam
Clark County, Nevada
Height (ft)
730
Length (Ft)
1,244
Storage Volume (acre-ft)
30,237,000
Drainage Area (sq miles)
167,800
Grand Coulee Dam
Okanogan County, Washington
Height (ft)
550
Length (Ft)
5,673
Storage Volume (acre-ft)
9,562,0000
Drainage Area (sq miles)
74,100
Theodore Roosevelt Dam
Maricopa County, Arizona
Height (ft)
357
Length (Ft)
1,208
Storage Volume (acre-ft)
3,411,500
Drainage Area (sq miles)
5,736
Oroville Dam
Butte County, California
Height (ft)
235
Length (Ft)
6,920
Storage Volume (acre-ft)
3,540,000
Drainage Area (sq miles)
3,611
Glen Canyon Dam
Coconino County, Arizona
Height (ft)
216
Length (Ft)
1,565
Storage Volume (acre-ft)
29,875,000
Drainage Area (sq miles)
108,355

Alder Dam Weather

Current Conditions at Alder Dam

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7-Day Forecast for Alder Dam

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Alder Dam Frequently Asked Questions

In which state is the Alder Dam?

Alder Dam is in Washington.

In which county is the Alder Dam?

Alder Dam is in Pierce County.

How high is the Alder Dam?

Alder Dam is 285 feet high.

How long is the Alder Dam?

Alder Dam is 1,487 feet long.

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Condition Assessment Classification

Satisfactory

No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.

Fair

No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum

Poor

A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.

Unsatisfactory

A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.

Not Rated

The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.

Not Available

Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High

Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.

Significant

Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.

Low

Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner’s property.

Undetermined

Dams for which a downstream hazard potential has not been designated or is not provided.

Not Available

Dams for which the downstream hazard potential is restricted to approved government users.

Source: National Inventory of Dams

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