The environmental impact report was published recently (read it here.). Comments on the Environmental Impact Report can be made at a public meeting from 4 p.m. to 6 p.m. Jan. 15 at the Hammon Senior Center, 1033 W. Las Palmas Ave., in Patterson. Written comments will be accepted until Jan. 27 at Del Puerto Water District, 17840 Ward Ave., Patterson 95363. If you appreciate the intrinsic value of our precious local canyon, I hope you will comment and make your voice heard.
I've written often about Del Puerto Canyon over the years (see many of the articles here), and to give you a feel for the unique nature of the canyon, I'm adapting an article from last May.
|The strange and alien landscape in upper Del Puerto Canyon.|
|"Del Puerto" refers to "The Gate", the constriction of hard sandstone at the mouth of the canyon. This will be the site of the proposed dam. It will be more than 200 feet high.|
|This is an active landslide that will be partially inundated by the proposed reservoir. I am concerned about the effect of adding water to the slip plane. California's first discovery of dinosaur bones was at the top of this slope.|
In Del Puerto Canyon, the ocean floor is covered by...a bit of sediment. About 25,000 feet of it! The sediments poured off the mountainous edge of the continent during the later part of the dinosaur era, the Cretaceous Period. There was a huge subduction zone that formed as oceanic crust plunged into the mantle beneath the edge of the North American continent. This so-called Cascadia Subduction Zone caused volcanoes to form where the Sierra Nevada is today, but the area offshore of the volcanic arc, the forearc basin, collected sediments. As the sediments accumulated, they pressed the crust downward and even more sediment piled on top. Eventually the layers reached a thickness of five miles.
The basin collected fossils as well. There were the usual shells of clams, snails and ammonites, a variety of shark teeth, and three groups of seagoing reptiles, the plesiosaurs (think Loch Ness), ichthyosaurs (think reptilian version of a dolphin), and 35-foot-long mosasaurs (think "swim for your life!"). Even dinosaur fossils have been found. The first dinosaur ever found in California, a Saurolophus, was discovered in the lower reaches of Del Puerto Canyon in 1935.
Eventually, one will reach the base of the oldest sediments, and encounter the ocean crust itself. Faulting obscures some of the relationships, and so in the picture below we see some of the oldest sediment on the right (somewhat brownish shale) and basaltic/andesitic volcanic rock on the left (greenish gray), separated by a fault. The volcanic rocks are harder, and the canyon takes on a more rugged aspect as we climb higher into the mountains.
There is a spot in one of the most rugged parts of the canyon to investigate the gabbro where it was pierced by a vein of quartz (below). People have looked for gold here, but I doubt they found any.
Just a few more miles up the canyon we penetrate the uppermost part of the mantle. The rock originally consisted of ultramafic minerals like olivine and pyroxene, but here the rock has been metamorphosed into serpentine, California's state rock. The rock was sheared and faulted on its way to the surface, leaving shiny green and black polished surfaces (below).
Del Puerto Canyon is traversed (slowly) by Highway 130, originating in Patterson on the floor of the Great Valley. It can also be reached by way of Mines Road out of Livermore, a winding road out of the San Jose area over Mt. Hamilton and the Lick Observatory complex. It is not a fast way to go!
I know that there is a need for water in the Central Valley. But no matter how many dams get built, there will never be enough to meet the expressed needs and desire of agribusiness. But I feel that we need to keep some of the wild places, and Del Puerto is one of those especially unique places to learn about our planet. I hope you will make your voice heard about this project.