Nestled among the rolling hills of Northern California’s Diablo Range, along the western edge of the San Joaquin Valley, lies the narrow entrance to a unique canyon long known for its geological, biological, archaeological and paleontological significance.
Of late, however, Del Puerto Canyon is becoming better known for some very fast- tracked and heretofore little-known plans to build a 260 foot high dam and reservoir in an area with unstable seismic fault lines—but more on that later.
Del Puerto Canyon was named by Spanish explorers conducting their first inland traverse of the Central Valley en route to the San Francisco Bay Area in the late 1700s. They described the narrow rock opening in the mountain to the canyon beyond as, “Del Puerto,” meaning the doorway/entryway in Spanish.
After entering through that historic gateway where Del Puerto Creek emerges, the first of Del Puerto Canyon’s intimate valleys opens up and an idea of the canyon’s scale can be sensed.
Flanked by steep rolling hills and colorful wildflowers in the spring, the first few miles of Del Puerto Canyon are among state’s most intriguing landscapes. There are bobcat and mountain lion sightings, one of the west’s largest golden eagle populations, remnant evidence of the endangered San Joaquin Kit Fox and Burrowing Owls, and badgers, among others.
The Gateway and surrounding land once belonged to the Hoyumne and Miumne Yokuts Indians, who lived in this area and migrated between Del Puerto Canyon and the San Joaquin River. Evidence of their presence has been found up and down the canyon, as well as along the San Joaquin River, in the form of grinding rocks, cooking ovens, burial grounds, dwelling structures, and— maybe the most unique Native American evidence in West Stanislaus County—a prehistoric pathway carved into the Gateway rocks.
Handholds and steps, weathered away over the years, still exist on the Gateway rock feature once used to help the natives, Spanish explorers, Mexican horse wranglers, and American miners through this canyon.
While Del Puerto Creek is currently perennial and gentle in nature, it at one time flowed as a strong river, giving more need for the pathway to be used to avoid its dangerous waters as it funneled through the Gateway narrows.
The rocks that make up the Gateway consist of exposed Coast Range Ophiolite, sediment that once was the seafloor off California’s coast before being tilted up and exposed during tectonic movement in the late Cenozoic era to present time.
Over time, the Coast Range Ophiolite was eroded away by the waters of the prehistoric Del Puerto Creek, carving the narrow opening to the valley that exists today. The days of large flows along the creek are now mostly gone, but there is still water to be found year round with many natural springs up and down the Del Puerto Creek watershed.
The most notable is Adobe Springs, about 18 miles up, known for its high flow of magnesium-rich water. Today, thousands of gallons of Adobe Springs water is shipped and sold daily to 7Up bottling in Modesto, but at one time it was a very important natural watering hole that natives and travelers alike relied upon.
The flowing artesian well was an important stop along “La Vereda de Montana” or “the Mountain Trail,” that was used by cross country Native American and Mexican travelers between Northern and Southern California who wanted to make their way through the Diablo Range undetected. The hidden trail through the lower Gateway and along Del Puerto Creek was a natural pathway that connected travelers with Adobe Springs, the San Antone Valley, and La Vereda Montana.
Indians looking to escape the coastal missions were also able to ditch Spanish search parties in the mazes of the mountains here, giving credence to their description of the mountains being “of the devil,” hence the name, “Diablo Range.” Tributaries of the canyon with names such as “Hideout Canyon,” “Murderer’s Gulch,” and others allude to their mysterious pasts.
Following the Spanish and Native American era in the canyon, Mexican horse drovers from Sonora Mexico—including the infamous Joaquin Murrieta—traveled through the Gateway from the 1820s when the land was Mexico, up until United States occupation in the early 1850s.These skilled horsemen utilized Del Puerto’s many “box” canyons to stash wild mustangs until gathering them for the annual drove of up to 300 head south through the mountain trail to the next watering hole, and eventually to their hometown in Sonora, Mexico where the healthy mustangs would be sold.
Geologic Importance and Magnesite Mining
In 1936, while exploring just within the entrance to the canyon, a curious young man from the nearby valley stumbled upon remains of animals that had been buried in the ground for millions of years. His name was Allan Bennison, and in 1936 he discovered what local legends claim are the first dinosaur bones to be found in California, those of the hind limbs of a Hadrosaur, buried since the late Cretaceous period.
A year later he found the skull of a Mosasaur. To call Del Puerto Canyon important geologically would be an understatement.
Remember the Coast Range Ophiolite that the Gateway is composed of? Those rocks were lifted and tilted by tectonic plate movement that affected the entire mountain range in a similar fashion.
So in essence, starting from the newest rocks nearest the earth’s surface beginning at the Gateway, and traveling west into Del Puerto Canyon, is a literal trip back in time past the era of the dinosaurs, through metamorphic layers, and up to where rocks and minerals from the earth’s mantle are exposed and resemble other worlds.
Geologists from all over have come to study Del Puerto Canyon for this very reason.
The first to really take advantage of the unique geology deep within the canyon were the magnesite miners of 1916. World War I had begun and there were only a few places in the U.S. where magnesite, needed for the war effort, could be mined, and it was found deep within Del Puerto Canyon.
Once located, engineers quickly began grading a path up the canyon for the narrow gauge Patterson and Western Railroad to traverse up to Jones Station, where the ore could be hauled out for processing.
They avoided the challenge of traversing Del Puerto Canyon’s narrow entrance by accessing the canyon from adjacent Black Gulch Canyon to the south.
From there, the natural path through the mountains created by Del Puerto Creek’s erosion was used to create the gradually ascending railroad grade to the magnesite mines. Utilizing Black Gulch Canyon (currently the I-5/Sperry Road interchange) also had its advantages because of its proximity to the recently incorporated City of Patterson, where the Sperry Road processing facility accessed the Southern Pacific Railway via a rail spur connecting to the narrow gauge railway.
By 1920, a few years after the end of the war, magnesite mining was no longer profitable, and by 1921 the two locomotives of the narrow gauge Patterson and Western Railroad were sold off to logging operations. When the rails of the railway were removed, a perfectly graded road bed was left where current day Del Puerto Canyon Road exists.
There are a few places where the road deviates from the historic Patterson and Western Railroad bed. Most of these locations are still visible within the first few miles of the canyon and would be inundated by the proposed Del Puerto Reservoir.
The creation of the right of way through the canyon following the demise of the magnesite mining literally paved the way for modern day recreation in Del Puerto Canyon. The canyons of the Diablo Range had already been a popular destination for trappers and hunters, but with the development of the automobile, Del Puerto Canyon became the perfect destination for day trippers from Patterson going into the canyon for picnics.
To this day the 100 year old road grade is still used for recreational and educational access through the canyon. Frank Raines Park, Deer Creek OHV access, and the Minnear Day Use Area are popular recreational destinations established deeper in the canyon, but the first few miles of canyon have been historically associated with folks enjoying hikes and picnics by the creek.
For decades canyon ranchers allowed day use access on portions of creek front rangeland that remained unfenced. That access has diminished over the years, given increased illegal activity, including dumping, graffiti, off-roading, and shooting of livestock.
With the increase of illegal activity, more and more fences have gone up, even though the majority of people who continue to recreate in Del Puerto Canyon do so responsibly. Volunteers periodically conduct cleanups to help rid the area of excess refuse.
Given this continual use for recreation, the first few miles of Del Puerto Canyon have featured in the City of Patterson’s history since its founding. Destruction of this area with the creation of a dam and consequent inundation of the biological, geological, and archaeological resources would be a serious loss to the residents of Patterson, Stanislaus County and the state of California if the Del Puerto Water District goes through with its plans.
Not everything in Del Puerto Canyon would be lost if the dam and reservoir were built, only everything within the first five miles.
The Gateway—the natural feature for which it is named— would be utilized to help ease the construction of the proposed dam. Lead agency in this proposal, the Del Puerto Water District, would use the dam to shut the Gateway and store water within the first five miles of the Del Puerto Creek drainage, offering no recreational access to the area.
The historic roadway would have to be re-routed away from the proposed reservoir and connected to Diablo Grande Parkway.
The trees, the sacred Cottonwood trees which are the last living link to the Hoyumne and Miumne Yokuts, would be be cut down by order of the Stanislaus County Board of Supervisors.
If built, water from the Del Puerto Reservoir would envelop an area of the Del Puerto Creek drainage known to be some of the fastest eroding land in the state of California, with active landslides currently documented. Local geologist Garry Hayes and environmental compliance expert Dr. Tom Williams have both warned that studies for the possibilities of landslides are inadequate. Williams added recently,
“The geological formations and current topography are conducive to mass movements, slumps, and landslides at present and when their lower supporting slumps are wetted and lost strength to carry the loads of the ‘dry’ materials. Many landslides are waiting to happen when they get wet. Numerous slide/slumps may interfere with the efficient and reasonable storage and operations of the reservoir.”
The Del Puerto Water District’s plans also show its earthen dam situated almost directly along the San Joaquin Fault Line, which last broke in the 1860s with an estimated 6.0 magnitude earthquake.
The City of Patterson—which so far has chosen to remain relatively quiet about the dam—currently has plans showing growth and infrastructure in an area that would be in the dam’s inundation zone. The city’s general plan shows infrastructure supporting a population up to 55,000 people, including plans for a new I-5 interchange, right below the dam.
Interstate 5, the California Aqueduct and Delta Mendota Canals would be in danger of being washed away were there a catastrophic failure of the dam, not to mention losses of life by residents of Patterson.
Members of the Del Puerto Water District board have already said they are trying to fast track this project in order to take advantage of federal WIIN Act funding. In December, the water district released its draft Environmental Impact Report, shortly after announcing the beginning of the project in mid-2019.
Many years would be needed to accurately study the unique nature of Del Puerto Canyon—at the very least one full year of habitat and environmental study is in order. But for the Del Puerto Water District to claim they have an accurate study of the canyon after five months since inception of the project is absurd.
Though the City of Patterson has stayed relatively quiet about the dam, the City Parks and Recreation Department worked to produce documents in the Parks and Recreation Master Plan that called for preservation of the Gateway when development from the City of Patterson ensued.
What is being Done
The City Parks and Recreation Department, as well as previous city leaders have all recognized the Gateway as an area of great cultural and ecological significance and have called for preservation of the area with recreational access for horseback riding, hiking, mountain biking, as well as plans for an outdoor amphitheater.
Opposition to the proposed Del Puerto Reservoir is growing among those in Patterson who are becoming more aware of the hazards posed by the dam, as well as the potential for loss in property value and rise in insurance rates.
Those aware of Del Puerto Canyon’s unique beauty and special habitat have been chiming in from all over the country, appalled at the thought of losing this natural treasure.
Online and physical petition signatures have amassed over 2,000 within a short time frame and continue to gain support as those opposed to the dam continue to be heard among Water District, County, and City of Patterson meetings of elected officials.
Dam opponents anticipate a Feb. 25th presentation to the City of Patterson from the Del Puerto Water District regarding the proposed dam where they hope the City will take a stand against the dam.