History of the Sweetwater Dam by Sonya Heiserman
On our May 22nd tour of the Sweetwater Dam and reservoir, we learned about where its water comes
from and how it’s kept clean and what birds live or fly over the lake, and enjoyed the wonderful view of the
early morning sun breaking through the clouds to shine on the water. However, to me, what is more interesting
is the history of this dam.
The San Diego Land and Town Company, a subsidiary of the Santa Fe Railroad, owned and built the dam.
After it was completed on April 7, 1888, they marketed a subdivision on the lake, promising “the town site
to the south slopes in gentle undulation to the blue rippling waters of the charming lake, while on the north
it slightly inclines toward the far famed Spring Valley”. They named this development La Presa (“dam” in
The Land and Town Company also owned the National City & Otay Railroad, which at this time had
plans to extend one of its lines from National City to La Presa. The railroad did come to La Presa; the tracks
reached the dam in December 1887 and aided in its construction. This became Spring Valley’s first connection
by rail. The end of the tracks were near where Mt. Miguel Covenant Village is located today. By 1888 as
many as four dam trains per day carried construction workers, equipment, materials and sightseers. The train
traveled at only 4 miles per hour and with the return trip it was an all day trip. (there was also a second railway
that had a stop in Spring Valley, the San Diego, Cuyamaca & Eastern Railroad which went on to El
The dam was constructed using rocks quarried a short distance downstream and hauled by horse and
wagon. Some of the rocks weighed up to 4 tons. During construction, it was discovered that raising the dam
to 98 feet would store five times more water in the reservoir. So, as the 60-foot high structure was nearing
completion in January 1887, the workers (some of them Chinese) continued work for another 16 months to
raise the dam height and to encase the rock surface in concrete. When completed, it was the highest dam in
the United States by 20 feet.
In 1895, a rain of six inches in a 24-hour period created a catastrophic flood. The result was that Sweetwater
Dam was overtopped for a period of 40 hours, with the highest reservoir level 22 inches over the elevation
of the parapet. The dam remained stable during this event, but the cascading water caused erosion
downstream of the structure and washed away some of the pipeline and other facilities. Following this flood,
the parapet was raised two feet, but 200 feet in the middle left as an overflow weir or spillway. An additional
spillway was added on one side of the dam.
On January 14, 1916 it rained for 6 days and the dam overflowed again. Another storm drenched the
county on January 24 that same year, and the lake rose 3 ½ feet above the top of the dam, creating a huge
waterfall as it spilled over the entire span of the dam. It caused the north abutment wing of the dam to collapse,
and a torrent of water rushed down the Sweetwater Valley, causing extensive damage. At the time
many blamed the rain on the rainmaking services of the infamous Charles Hatfield who was paid $10,000 by
the San Diego City Council to burn chemicals into the sky in the Morena area to alleviate a water shortage.
The dam was repaired and improved once again, and has since been raised even higher; however, the flood
damage to the tracks of the National City & Otay Railroad was never repaired and the track was abandoned
due to lackluster ticket sales preceding the flood. The staff of the Sweetwater Authority mentioned that
there are still remnants of the tracks near the dam.
In more recent history, this lake has seen some interesting events. During World War II, Spring Valley
was the site for 3 auxiliary airfields attached to San Diego North Island. The fields were located near the lake
which was used to test torpedos (!). The Navy later moved the testing to El Capitan Lake.
Other interesting tidbits: Babe Ruth went duck hunting on this lake. (see picture). Also, near the dam is a
small cottage that was used as a Bait Shop at one point. The Sweetwater Authority has plans to hopefully restore
it to its original state if money can be found. It would be a charming addition to Spring Valley history,
most of which has been lost to time. We are lucky to have this 100+ year old working dam and lake in our
midst. Even though it provides water to National City, not Spring Valley, the Sweetwater Authority staff was
happy to share its history, scenery, and biology with our group.
NOTE: Much of the information for this article is from Our Hills and Valleys: A History of the Helix-Spring
Valley Region by Thomas Joseph Adema. San Diego Historical Society, 1993.
Babe Ruth “duck hunting” with Linn Platner on Sweetwater Lake – January, 1927