The Spring Valley Water Company (SVWC) had envisioned a large reservoir in the East Bay as early as 1875. They started acquiring land and water rights in Alameda County at this time. The first land they bought was in the Calaveras Valley and at the Vallejo Mills properties near Niles. This was the beginning of the Alameda Division of SVWC.

The company systematically enlarged its holding in Alameda County. The map below shows they bought lands and/or rights again in 1878, and again each year between 1887 and 1892. And they weren’t done yet. There was another in the 1880’s, two more in the 1890’s, and most years from 1900 thru 1907.

It was 1886 that SVWC initiated exploratory assessment for building of the dam. And in 1887 SVWC began construction of a pipeline to divert waters from Alameda Creek at the Vallejo Mille (Niles) Dam. This water was bound for San Francisco via the Sunol Aqueduct.

Definitive plans for the great dam had been developed by 1906. But, while the crisis that year swelled the imperative for pulling more water into San Francisco, the outcomes of the earthquake required recovery and this delayed construction of the dam. Finally, Calaveras Dam construction began in 1913, and was completed in 1925.

In the 1907 map, you can see the plotted Calaveras Reservoir. The dam, of course, had yet to be built. But the plan was solid. I hope you’ll enjoy this beautiful hand-drawn and hand colored map.

Details above pulled from Chapter XIV of History of San Mateo County California by Roy W. Cloud published in 1928. This chapter – “Spring Valley Water Company” – in turn was written by George A. Elliott, Vice President and Chief Engineer of SVWC, at the time of its original publication in 1925.

The entire chapter can be accessed via the following link.
http://www.waterworkshistory.us/CA/San_Mateo/1928SpringValley.pdf