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Gravity, Faults and a Reservoir




It was an overcast morning for our Piedmont Recreation Department's Walking on Wednesdays' walk this week. There was a solid turnout of 39 walkers and three K-9 best friends at the Exedra ready to climb to one of Piedmont's least understood structures.


Karin F and Peggy S recently shared a book titled Deep Oakland by Andrews Alden. It tells how geology has shaped Oakland and the East Bay, and includes a chapter on Piedmont. It also explains why the Piedmont Reservoir is up at the top of Blair Avenue. This was an inspiration to go see and learn about it.


We headed off going up Highland, Sierra, Sheridan and Lakeview Avenues, and then Poplar Way, which is really a back driveway for Mountain Avenue homes' garages but still very picturesque. We emerged on Mountain and started our climb up the lovely, but steep Bellevue, Pacific and Hager Avenues to Blair Avenue. Just down Blair was the reservoir and a bus stop bench. It provided a welcomed resting spot where the reservoir's story was told, and the attached group photo was taken.


Alden wrote in Deep Oakland that there is a separate block of the Earth's crust, west of the Hayward Fault on a set of rocky hills measuring about four by two miles, called the Piedmont block. No other East Bay city has anything like it. It is half the elevation of the high Oakland Hills and neatly encloses the city of Piedmont. The block's eastern border is defined by the Hayward Fault that runs along the Montclair district.


The Piedmont block's landscape is different from the high hills east of the fault. The slopes are gentler and more rounded. The high rocky rims on the eastern edge serve as a watershed. They naturally collect water as the Oakland hills do. Their elevation and upward slope cause the moisture in Bay breezes to rise, cool, and condense as fog and rain. The Piedmont block naturally collects more rainfall than the plains around it, and there is enough water to support five permanent creeks which come together at Lake Merritt.


For the first, small East Bay towns water came from household wells. Later, there was a need for bigger wells and they were found in the lowlands near the Bay. Some are still active today. Private companies soon offered more dependable water at low rates. As the East Bay grew, these water companies competed for customers and those on the high ground had an advantage. Their

tanks and reservoirs could use gravity to supply pressure and regulate the flow independent of the weather.


In 1891 William Dingee had plans for a water district to serve fine Piedmont homes. He applied for a supply of water from the Contra Costa Water Company, which was founded by Anthony Chabot, but it turned him down. Undeterred, Dingee went ahead on his own and within a few months had bored the first of 22 tunnels to tap groundwater from springs in the high, uninhabited Oakland hills directly to the east.


Tunnels in high ground are a poor source of water, but it could be piped downhill to a reservoir without pumps. The limited, but cheap supply was enough to get Dingee started. Within two years he was running the Piedmont Springs and Water Company. The Piedmont Reservoir held the water from Dingee's tunnels. Its high position provided good water pressure to the neighborhoods below. It was an open basin that got a lid of concrete and steel 60 years later. Meghan Bennett provided the also attached historical photo of the reservoir in 1917.


The EBMUD "Reservoir Number 2" occupies more than nine acres straddling the Oakland-Piedmont border with 8.3 acres in Piedmont. A 22.8 million gallon water storage tank provided water for the city from 1905 to 2003. The facility was decommissioned and drained in 2003 as part of EBMUD's "facility modernization program." It was also an earthquake flood risk. Piedmont's water now comes from other large tanks in the Oakland hills.


The walkers asked why the reservoir's site wasn't being put to use now. Former Piedmont Planning Commissioner Jim K explained the issue had been raised. The land has a steep grade and construction would be very expensive. Neighbors would probably have issues too. Additionally, the land is in Oakland and Piedmont, and owned by EBMUD. Getting an agreement between the three was not realistic and the Piedmont Reservoir became just a Piedmont landmark.


We went up to near the top of Blair Avenue, where it ends just beyond the reservoir, and then enjoyed a downhill return to the Exedra via Blair, Scenic, Pacific, and Mountain Avenues.



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