The largest dam in the world; that was what Fort Peck was destined to be when it was on the drawing table in 1933. At nearly four miles long, 250 feet high and more than 3/4 mile wide at the base, it was the biggest, by far. When only a fifth complete, it was already the largest dam in the world.
By the numbers
125 million cubic yards of fill material
34 million pounds of steel in the cut off wall
53 million pounds of steel in the spillway
4 million cubic yards of gravel
4,900 feet – the width of the base
50 feet – the width of the top of the dam
250 feet – the distance separating the base from the top of the dam
1,600 miles of shoreline along the reservoir
134 miles – the length of the reservoir
18.7 million acre-feet of water in the reservoir
$12.1 billion – amount of flood damage reduction to date
$2.4 million – annual economic benefit from tourism to the project
The concept of the Fort Peck Dam was conceived as a whisper of an idea in 1866. For the next 67 years, the region surrounding the northeast Montana settlement called Durfee and Peck suffered numerous crippling flood events and slashing "ice gorge" attacks, which tore stockades and dwellings asunder.
By 1932, politicians, local business owners and home owners were serious about getting a massive dam in place on the upper Missouri River to protect them from the ravages of flooding and to boost the economy. Four years of The Great Depression had bled Montanans – as it had all Americans. Then came the life-saving clarion call from the White House.
The Fort Peck Dam Project was authorized in late 1933 by President Franklin Delano Roosevelt, who hoped it would serve the dual purpose of providing jobs for a Depression-plagued workforce and providing flood protection on the Missouri River, which had been a major problem since the 1860s.
When the idea to build an earth fill dam across the great valley was shared with Glasgow Mayor Leo B. Coleman, he surveyed the site and said "My God, man…that would cost a million dollars." In the dollars of the day, it actually cost $158 million for the dam, spillway, hydropower facilities and real estate transactions.
Major milestones in
Fort Peck construction
Oct. 14: Project approved by President Roosevelt under public works program
Oct. 23: First day of work on project
First day of work on project
Dec. 18: First earth moved on project
First earth moved on project
April 5: Town buildings and services started
Town buildings and services started
May: Work begins on diversion tunnels
Work begins on diversion tunnels
June 19: Work to strip base of dam begins
Work to strip base of dam begins
Oct. 13: First dredge starts work and first material placed in the dam
First dredge starts work and first material placed in the dam
Nov. 15: Spillway excavation started
Spillway excavation started
Nov. 19: Stripping of base of dam completed 1935
Stripping of base of dam completed 1935
May 13: Construction begins on spillway gate structure
Construction begins on spillway gate structure
Nov. 25: Cutoff wall completed at spillway top
Cutoff wall completed at spillway top
June: Construction begins on lower spillway cutoff wall
Construction begins on lower spillway cutoff wall
May 10: First gate placed in spillway
First gate placed in spillway
June 23: Tunnels completed
June 24: Closure of dam made and river diverted through tunnels
Closure of dam made and river diverted through tunnels
Aug. 10: Concrete-lined channel of spillway completed
Concrete-lined channel of spillway completed
Aug. 24: Last spillway gate set in place
Last spillway gate set in place
Nov. 9: Spillway gate structure completed
Spillway gate structure completed
Sept. 22: The Slide occurs; 8 men killed
The Slide occurs; 8 men killed
August: Construction of first power plant begins
Construction of first power plant begins
November: Topping out of dam with fill earth completed
Project approved by President Roosevelt under public works program First day of work on project First earth moved on project Town buildings and services started Work begins on diversion tunnels Work to strip base of dam begins First dredge starts work and first material placed in the dam Spillway excavation started Stripping of base of dam completed 1935 Construction begins on spillway gate structure Cutoff wall completed at spillway top Construction begins on lower spillway cutoff wall First gate placed in spillway Tunnels completed Closure of dam made and river diverted through tunnels Concrete-lined channel of spillway completed Last spillway gate set in place Spillway gate structure completed The Slide occurs; 8 men killed Construction of first power plant begins
Later to become part of the famed Pick-Sloan Plan, which includes the six U.S. Army Corps of Engineers managed dams on the upper Missouri River basin, Fort Peck was not thought of by its creators in the same way it is thought of today. In those days it was considered a project of salvation which breathed new life into a populace desperate for work. They could not see, nor did they care, that one day it would be seen as a memorial to human skill, stamina and the ability to overcome hopelessness.
Engineers were tasked with building the world’s largest dam in a remote location with no roads, no power, and no housing, where temperature extremes of 110 degrees F to -60 degrees F were not uncommon. It became the single largest project of the New Deal, employing 10,560 at the peak of construction, nearly doubling the work force at Hoover Dam and topping Grand Coulee Dam by more than 2,500 workers.
One of the most formidable obstacles faced by the workforce is described by Major Clark Kittrell, who arrived at Fort Peck in 1933 and served as District Engineer from 1937 to 1940. He wrote "no engineering job of this magnitude had ever been attempted with so short a time for planning."
Indeed, the work on the dam began a mere ten days after its authorization. By the time closure of the dam was made in June 1937 so many hardships had been conquered that some who worked on the dam consider it first and foremost a monument to perseverance.
Building the world’s largest dam in such a remote location created many challenges and led to many seemingly unusual decisions. One of the first was to build the dam by hydraulic fill; using hydraulic fill to build a dam this size had never before been attempted. Hydraulic fill meant dredges. The dredges would be built onsite, resulting in the creation of a shipyard and the Fort Peck Navy.
Delivery time for large diesel motors the size needed for the massive dredges was two years, and the availability of fuel was inconsistent. This led to another major decision – the dredges would be powered by electricity. A 154,000 kVA power line, 288 miles long, was constructed from Rainbow Falls to Fort Peck to power the dredges and the rest of the construction.
An entire town would be built to house the workers. Roads and a railroad would be constructed to haul materials and people. At the same time, clearing operations were going on at the dam site, where more than 4 million cubic yards of material would be removed.
On June 24, 1937, the culmination of the past three and half years’ worth of decisions, planning and millions of hours of hard work came to fruition with the closing of the dam. Thousands of details, big and small, had to be carefully coordinated to be ready for this event.
At 4:20 a.m., the dike separating the river from the tunnel intake portals was blown up and water began flowing into the tunnels. Train car after train car dumped gravel and boulders into the river below the Missouri River Bridge, placing some 20,000 cubic yards in the river in one day. The Missouri River was cut off.
A congratulatory letter was sent from the Chief of Engineers, Major General Markham, describing the closure as "a unique, delicate and highly successful engineering achievement."
Although closure took place in mid-1937, the dam was not finished until 1940. The four-mile-long dam was considered the engineering feat of its time.
At the time of construction it was the largest dam in the world.
Seventy-five years later it remains the world’s largest hydraulically filled dam and is now the eighth largest dam in the world.