The rise and fall of Lake Mead at Hemenway Wash
LAS VEGAS (KLAS) — Even with a seven-foot rise in Lake Mead’s water level this year, it is expected to drop significantly this year, possibly up to 20 feet. If this drop happens it will expose much more shoreline around the lake.
The newly exposed land will be prominent in front of Boulder Beach because of its relative shallowness already. Boulder Beach is located just north of Hemenway Harbor – the same location as the largest marinas at the lake.
Hemenway Harbor took its name from what the area used to be known as, Hemenway Wash. This wash can be clearly seen without water in aerial photographs (below) taken in the early 1930s before major construction on the Hoover (Boulder) Dam began.
In the images below the wash can be seen wrapping around the south end of what is now called Rock Island, next to the Big and Little Boulder Islands, ending up at the original Colorado River path. These three named islands are now all once again connected because of the low water level. This begs the question of just how shallow the area between Boulder Beach and Big Boulder Island is now and what it will be later this year.
This is where Six Companies (the single company that built the dam) constructed the Aggregate Classification Plant where rock used in cement would be sorted. This required water which was pumped into a large clarifying tank built on what is now Big Boulder Island.
This structure is 15 feet deep and 110 feet across, and was used as a settling basin for the sediment-rich Colorado River water during the construction of Hoover Dam in the 1930s. Silty water was pumped into this basin from the river, and once the silt settled out, the clean water was then piped to the gravel screening area 130 feet below, to wash the gravel used to make concrete.
In several images from 1933, the clarifying tank can be seen under construction. In the distance, the railroad tracks used to move aggregate can be seen curving across Hemenway Wash.
That same railroad bed seen in the 1933 photos is now becoming exposed on Boulder Beach. Directly across from the exposed clarification tank the curve of the railroad can easily be seen in recent satellite images and in person at the beach.
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The railroad bed used for the water clarifying plant now seen on Boulder Island is emerging from Lake Mead. Dec. 14, 2022 -
The old railbed from the early 1930s is now showing at Boulder Beach at Lake Mead. (Photo: Duncan Phenix – KLAS) -
Water clarifying tank – also known as the batch plant – on what would become Boulder Island. 1933 (Photo: UNLV Digital Collections)
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Water clarifying tank – also known as the batch plant – on Boulder Island. Feb. 6, 2023 (Photo: Duncan Phenix – KLAS) -
Water clarifying tank – also known as the batch plant – on Boulder Island. Feb. 6, 2023 (Photo: Duncan Phenix – KLAS) -
Water clarifying tank – also known as the batch plant – on Boulder Island. Feb. 6, 2023 (Photo: Duncan Phenix – KLAS) -
Water clarifying tank – also known as the batch plant – on Boulder Island. Feb. 6, 2023 (Photo: Duncan Phenix – KLAS)
While it’s not clear exactly how deep the water is in the area between the island and the beach – 8 News Now asked both the U.S. Bureau of Reclamation and the National Park Service and neither could say – looking at the old photographs it is safe to assume if the lake keeps dropping over the next two years there is a chance of a land bridge forming between Boulder Beach and Big Boulder Island. Or, one might say, Hemenway Wash has returned.
As for the Las Vegas Boat Harbor and Lake Mead Marina, both next to Hemenway Harbor, crews continue to move these large marina structures to the south and eventually to the east, according to a worker who spoke to 8 News Now last fall.