water wells in the Sunset & G.G.P. area.greenspun.com : LUSENET : San Francisco History : One Thread
I have heard that the windmills in the park had and still have fresh water wells, also along 44th Ave. the city has a series of fresh water wells? Can someone tell me where the wells are, how deep they are, and in what type of strata would you find water in this area. thanks.
-- Mike Foley (firstname.lastname@example.org), February 14, 1999
The North Windmill in Golden Gate Park, completed in 1902, pumped 30,000 gallons of FRESH water (within several hundred yards of the Pacific Ocean) per hour, and the Murphy windmill (1905) pumped 40,000 gallons per hour. Although the windmills' function as power sources for the pumps have been replaced by electric pumps, those pumps are still at work, yes.
Up until around the 1930s or so, there were still some great fresh water swimming lakes out around the area of 47th Avenue and Quintara. Around the area where 46th Avenue would have cut acrosss Golden Gate Park was a natural tidal lagoon, later relandscaped by John McLaren into Chain of Lakes area in the park.
As for the general condition of water on the San Francisco peninsula, it's an interesting, complicated, and still-being-figured-out terrain. Several years ago, the U.S.G.S was soliciting information from the general public about memories, diary entries, or whatever, regarding springs, wells, etc, in an effort to piece together the water picture. In earlier days, there were inumerable sources of surface water in the forms of springs, creeks, and wells all over the peninsula. Many people still have to have pumps in their basements to handle the large amounts of water still flowing, though at a lowered table level. Polin Spring (whose waters you can watch cutting channels across the sand to the Ocean at Baker Beach) has been supplying two million gallons of water PER DAY to the Presidio for a long time.
The strata conditions and watershed areas are still being mapped locally and are not fully understood (least of all by me). A few years ago, Golden Gate Park commissioned the U.S.G.S. to map out the underlying water tables in the park area.
-- Chris Dichtel (email@example.com), February 18, 1999.
Schlocker (1974) "Bedrock Map of San Francisco North Quadrangle" (Approximate title) provides some information based on limited data in this area. The map indicates bedrock is -256 feet elevation relative to sea level datum at the north windmill, and my guess is that Schlocker used the original well logs for the windmill; these could easily be published in the 1913 O'Shaughnessy report on the City water supply (which may be available in the SF library history room. Further south, wells at 44th and Ortega and Kirkham extend to - 190 feet without hitting rock (reported on the same map).
The bedrock terrain under the city includes rolling hill topography (think of taking Marin Headlands and covering the rock there with 250 feet of sand, and how many hills would stick out). Within a few miles of the San Andreas fault, warping of the soil results in much deeper depth to "bedrock", particularly under Lake Merced and to the west, where soil cover along the supposed "San Bruno Fault Zone" may be over a thousand feet thick
As for what's above bedrock, I don't know for sure either, but based on geology in the area, its gotta be mostly sand. Recent studies (after the Loma Prieta Earthquake, post 1989) were performed by the City of SF on re-utilizing the aquifers under the Sunset District for pumping for emergency use. If I remember correctly, these aquifers have high yield and are sand (similar to the dune sand at the surface) with relatively little interruption. Along a buried bedrock valley approximately under the Golden Gate Park, there could potentially be zones of alluvial silts and sands which are locally less permeable. I have not heard of any bay or estuarine deposits (from sea level changes flooding buried valleys, as happened under downtown SF) under the western part of the city, with the possible exception of Lake Merced
-- jonathan pease (firstname.lastname@example.org), March 11, 1999.
Old folks told me that the city hall has it's own well. There was a really old guy, Mr. Short, that survived the earthquake of 1906 who told me that at Market and Castro where the BofA USE to be (South West Corner) there was a well or spring that a lot of folks used to get water during the recovery. Seems understandable being at the base of Twin Peaks. Then I found out that all that water comes from underground streams out of the Sierras as it moves towards the ocean.
-- Len (email@example.com), May 24, 1999.