When the North American transcontinental railroad was being laid down during the 1860s, the engineers faced a big obstacle in the state of Utah – a great body of water, 4,400 square km in area, called the Great Salt Lake. Initially, the railroad tracks were laid around the lake over the Promontory Mountains on the north, where on May 10, 1869, a golden spike was driven to mark completion of the first transcontinental railroad. This route, called the Central Pacific Railroad, traversed the difficult mountain from Lucin, around the north end of the lake to Brigham City, and then southward to Ogden. Thirty five years later, in 1904, the Southern Pacific Railroad created a shorter route of lesser grade and curvature directly across the lake. Called the Lucin Cutoff, it reduced the distance of the railway by 42 miles (68 km).
Satellite photo of the Great Salt Lake shows the difference in colors between the Northern and Southern portions of the lake, the result of a railroad causeway.
The railroad causeway consisted of two earth and rock-fill embankments, one extending eastward into the lake from Lakeside and the other extending westward from Promontory Point, with a 12-mile open, wooden trestle in between. Building this thing was a herculean project. Not only a huge mountain of earth and rock have to be blasted, excavated, and hauled, along the twenty-two mile length of the causeway, a huge forest of trees - two square miles in area - had to leveled. Altogether, more than 38,000 trees were cut down to make piles for the trestle. In addition, 2 million board feet of redwood decking were used for the actual railbed. Just the portion of the trestle above the waterline contained enough wood to lay a board-walk four feet wide from Boston to Buffalo.
Maintaining the trestle proved to be just as costly. By the early 1950s, when maintenance costs became too high for the railroad company, the trestle was dismantled and replaced by a solid rock-fill causeway. Previously, the open structure of the trestle allowed for the free mixing of brine water between the north and south arms of the lake. The now solid causeway divided the lake into two bodies of water and the mixing of water stopped. Since then the lake’s natural water flow was permanently altered, and its consequence for the lake environment was pretty much unanticipated.
The Great Salt Lake, is the largest salt water lake in the Western Hemisphere, and one of the most saline inland bodies of water in the world. The lake is fed by three rivers - the Jordan, Weber, and Bear, which together deposit around 1.1 million tons of minerals in the lake each year. The lake has but no outlet and besides evaporation, there is no way to lose water. Consequently, the lake water has salinity much greater than that of oceans, so much that the Great Salt Lake is sometimes called “America’s Dead Sea”, after the Dead Sea of Jordan. The high salt content makes the lake itself uninhabitable, but a few minor forms of life, such as brine shrimp and algae thrive.
When the lake was divided into two parts by the Southern Pacific Railroad causeway, the northern end of the lake became more saline than the southern end because all three major rivers flow into the south arm. Water level on the southern end also rose significantly while that on the northern end dropped because it experienced slightly higher evaporation rates than the south arm, further accentuating the salinity imbalance. The salinity on the northern arm of the lake reached a point where the native brine shrimp could not survive in its waters.
Aerial view of the Lucin Cutoff.
To rectify the damage, a 30 meter breach was created in the causeway in 1988 that allowed the elevations and salinity to equalize to a certain extent. Later, three large pumps were installed to keep salinity in the north arm at saturation levels (about 27 percent salt) while the south arm fluctuates between 5 and 15 percent.
The salinity difference has created two different ecosystems on the lake. The south arm is dominated by blue-green algae, which colors the water green. On the north arm, higher salt content has allowed the growth of the alga Dunaliella Salina. This alga and the beta-carotene and bacteria it releases (Haloarchaea) imbue the north arm water with a distinctive wine red color.
However, the causeway has proved to be very economical for commerce. Two industries in particular are booming, one each on either end of the lake. On the northern end, salt extraction industries are thriving on the increased salt and mineral concentration. Solar evaporation ponds at the edges of the lake produce sodium chloride (common salt), potassium sulfate, used as a commercial fertilizer; and magnesium-chloride used in the production of magnesium metal, chlorine gas, and as a dust suppressant. On the southern end, brine shrimp harvesting plants provide 35 to 45 percent of the worldwide supply of brine shrimp.
The Great Salt Lake today contributes an estimated $1.3 billion annually to Utah's economy, including $1.1 billion from mineral extraction industry, $136 million from recreation, and $57 million from the harvest of brine shrimp.
Salt evaporation ponds on the northern arm of Great Salt Lake. Picture taken from the International Space Station.
An aerial shot of a westbound steam excurison crossing the Great Salt Lake on the Lucin Cutoff causeway.
A train on the Lucin Cutoff trestle bridge over the Great Salt Lake in Utah, April 1923.
The line included a rail station called Mid Lake, which was in the middle of Great Salt Lake.