Millbrae, San Bruno, and San Andreas Lake

San Andreas Lake is a

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

adjacent to the

San Francisco Peninsula The San Francisco Peninsula is a peninsula in the San Francisco Bay Area that separates San Francisco Bay from the Pacific Ocean. On its northern tip is the City and County of San Francisco. Its southern base is Mountain View, south of Palo A ...

cities of

Millbrae Millbrae is a city located in northern San Mateo County, California, United States. To its northeast is San Francisco International Airport, San Bruno is on its northwest, and Burlingame on its southeast. It is bordered by San Andreas Lake to ...

and

San Bruno San Bruno (Spanish for " St. Bruno") is a city in San Mateo County, California, United States, incorporated in 1914. The population was 43,908 at the 2020 United States Census. The city is between South San Francisco and Millbrae, adjacent to ...

San Mateo County, California San Mateo County ( ), officially the County of San Mateo, is a county (United States), county located in the U.S. state of California. As of the 2020 United States Census, 2020 census, the population was 764,442. Redwood City, California, Redwoo ...

. It is situated directly on the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonics, tectonic boundary between the Pacific Plate and the North American Plate, and its motion is Fault (geology)#Strike-slip fau ...

, which is named after the valley it is in.

History

After discovering San Francisco Bay from

Sweeney Ridge Sweeney Ridge, is a hilly hiking area of ridges and ravines between San Bruno, California, San Bruno and Pacifica, California, about a 25-minute drive south from San Francisco. The ridge's 1,200-foot-high summit, covered with coastal scrub and gra ...

on November 4, 1769, the

Portolá expedition thumbnail, 250px, Point of San Francisco Bay Discovery The Portolá expedition ( es, Expedición de Portolá) was a Spanish voyage of exploration in 1769–1770 that was the first recorded European land entry and exploration of the interior of t ...

descended what Portolà called the ''Cañada de San Francisco'', now

San Andreas Creek San Andrés Creek (''Spanish for'': St. Andrew's Creek), now called San Andreas Creek, is a perennial stream that flows southeasterly along the San Andreas Fault from Sweeney Ridge in San Mateo County, California, providing the inflow to and outf ...

, to camp in the vicinity of today's San Andreas Lake. The next day they reached a "Laguna Grande" which today is covered by the Upper Crystal Springs Reservoir. The campsite is marked by California Historical Marker No. 94 "Portola Expedition Camp", located at Crystal Springs Dam, on Skyline Boulevard, 0.1 mi south of Crystal Springs Road. They camped here a second time on November 12, on their return trip. Padre Palóu, on an expedition from Monterey to explore the western side of San Francisco Bay led by Captain

Fernando Rivera y Moncada Fernando Javier Rivera y Moncada (c. 1725 – July 18, 1781) was a Mexican-born soldier of the Spanish Empire who served in The Californias (''Las Californias''), the far north-western frontier of New Spain. He participated in several early ove ...

, renamed Portola's ''Cañada de San Francisco'' to ''Cañada de San Andrés'' on November 30, 1774, it being the feast day of

St. Andrew Andrew the Apostle ( grc-koi, Ἀνδρέᾱς, Andréās ; la, Andrēās ; , syc, ܐܰܢܕ݁ܪܶܐܘܳܣ, ʾAnd’reʾwās), also called Saint Andrew, was an apostle of Jesus according to the New Testament. He is the brother of Simon Peter ...

. Captain Juan Bautista de Anza, after forging the first overland route from

Monterey, California Monterey (; es, Monterrey; Ohlone: ) is a city located in Monterey County on the southern edge of Monterey Bay on the U.S. state of California's Central Coast. Founded on June 3, 1770, it functioned as the capital of Alta California under bo ...

to San Francisco Bay, explored the peninsula and selected the sites for

Mission San Francisco de Asís Mission San Francisco de Asís ( es, Misión San Francisco de Asís), commonly known as Mission Dolores (as it was founded near the Dolores creek), is a Spanish Californian mission and the oldest surviving structure in San Francisco. Located i ...

(''Mission Dolores'') and the

Presidio of San Francisco The Presidio of San Francisco (originally, El Presidio Real de San Francisco or The Royal Fortress of Saint Francis) is a park and former U.S. Army post on the northern tip of the San Francisco Peninsula in San Francisco, California, and is part o ...

. De Anza returned to Monterey via the Cañada de San Andrés and camped on the banks of San Mateo Creek on March 29, 1776. In de Anza's diary on March 29, 1776, he wrote: "Night having fallen, at a quarter past six I went down to the arroyo of San Andreas and to another, that of San Matheo, where it descends to empty into the estuary..."

Description

Originally a small natural sag pond, the lake was expanded by the construction of a 100 foot high earth dam in 1868. The dam survived the 1906 earthquake despite the fact that the fault runs directly under the dam. In 1895, Professor

Andrew Lawson Andrew Cowper Lawson (July 25, 1861 – June 16, 1952) was a Scots-Canadian geologist who became professor of geology at the University of California, Berkeley. He was the editor and co-author of the 1908 report on the 1906 San Francisco earthq ...

of the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

, conferred the name of the lake on the

earthquake fault In geology, a fault is a Fracture (geology), planar fracture or discontinuity in a volume of Rock (geology), rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust (geolo ...

he discovered in its vicinity.

Ecology

Construction of the 1868 dam would have trapped salmonids such as

coho salmon The coho salmon (''Oncorhynchus kisutch;'' Karuk: achvuun) is a species of anadromous fish in the salmon family (biology), family and one of the five Pacific salmon species. Coho salmon are also known as silver salmon or "silvers". The scientif ...

(''Oncorhynchus kisutch'') and

coastal rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coastal ...

(''Oncorhynchus mykiss irideus'') as both stream resident and steelhead life forms, both known to have been historically present in the San Mateo Creek watershed. San Mateo Creek once hosted coho salmon as evidenced by specimens collected by Professor Alexander Agassiz of

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher le ...

in the 1850s and 1860s. The historical presence of coho salmon is also suggested in an 1877 description by Charles Hallock: " Pilarcitos, one of the Spring Valley Water Company's reservoirs, is now well filled with fair-sized trout, and San Andreas, chiefly with

silver salmon The coho salmon (''Oncorhynchus kisutch;'' Karuk: achvuun) is a species of anadromous fish in the salmon family and one of the five Pacific salmon species. Coho salmon are also known as silver salmon or "silvers". The scientific species name i ...

of generally moderate size".

Public access

Since the lake is a public water source, it is closed to the public. However, hikers and bicyclists may travel along the eastern shores of the lake on a paved trail that runs just west of

Skyline Boulevard A skyline is the outline or shape viewed near the horizon. It can be created by a city’s overall structure, or by human intervention in a rural setting, or in nature that is formed where the sky meets buildings or the land. City skyline ...

from San Bruno Avenue to Millbrae Avenue. A connecting trail, called the

Sawyer Camp Trail Sawyer Camp Trail is a popular trail located in the San Andreas Fault rift valley in San Mateo County, California near Hillsborough and the San Mateo Highlands. Officially, it is a segment of the longer Crystal Springs Regional Trail. Approxima ...

, crosses the

rift valley A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear dep ...

on the San Andreas Dam. This 6 mile (10 km) trail eventually reaches the eastern shores of the Lower Crystal Springs reservoir and the

Crystal Springs Dam Crystal Springs Dam is a gravity dam constructed across the San Mateo Creek which is in San Mateo County, California. It impounds water to form the Lower Crystal Springs Reservoir which sits atop the San Andreas Fault in a rift valley created ...

References

External links