The Source of Oakland’s Water Supply.
A very interesting story is told by The Oakland (Cal.) Times about the source of the new water supply for that city. Here is part of the story : Mr. Boardman had long held to the idea that there was a subterranean flow of water from the Sierra Nevada through the Coast Range. According to his theory the Contra Costa hills had sometime or other been lifted up by a volcanic upheaval, which had also thrown up and disturbed the subterranean channel. By striking this channel Mr. Boardman was confident that an abundant supply of water fresh from the Sierra Nevada snowfields could be tapned.
Noting signs of volcanic action around Moraga Peak, Mr. Boardman hit upon that place. His theory was borne out by the presence of numerous small springs gushing out at intervals as the mountain is approached.
Two tunnels were run into Moraga Peak, about a quarter of a mile apart. One is known as the Boardman tunnel and the other as the Gi’es tunnel. Several other tunnels were run in, where surface springs indicated the presence of water in considerable quantities. When 210 feet in the Boardman tunnel a regular beach formation was struck, with shells, sand, pebbles and other indications of a stream or lake.
When this formation was struck an immense body of water gushed forth, which drove the men out of the tunnel and compelled for a time a cessation of work. For some days the flow averaged 1,000,000 gallons every twenty-four hours, but this was largely due to drainage of the crevices above the level of the tunnel. Finally the flow settled down to normal proportions. since which time it has averaged 250,000 gallons a day. Close observation shows that this is the minimum supply from this source. Mr. Boardman held the opinion that by running farther in, so as to strike the other declivity of the upheaval, a still larger supply could be obtained. The tunnel was pushed in to a distance of 316 feet, but as a still larger supply was struck in the Giles tunnel, work in this direction was suspended as being unnecessary for the present.
In the Giles tunnel, at a distance of 268 feet from the surface, a great bed of volcanic ashes was struck, and simultaneously came a huge stream of water pouring forth. This finally settled down to a steady flow of 300 000 gallons every twentyfour hours, which is the minimum supply from this source. The two tunnels afford a steady supply of from 550,000 to 600,000 gallons each twenty-four hours.