San Rafael Rock Quarry (Dutra Group)

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  scritch

  This was originally an underground mine for riprap rock. After the underground mining was no longer economical, the mining shifted to open-pit mining. Eventually the mine was played out. There was at one time a scheme to use the underground mine cavities for a pumped-storage energy conservation facility, or a water filtration plant. There was yet another to use the quarry as a lagoon for a high-value housing development. As of the time this photo was taken, it is clear that neither of these ideas have come to pass. The pumped storage scheme would have hydroelectric generators installed near the surface. When electricity rates were expensive, e.g., during morning and evening hours, water would flow from the Bay into the caverns, generating electricity. During cheaper power rate periods pumps would empty out the caverns. The water filtration scheme would have used reverse osmosis to make tap water from Bay water. Reverse osmosis requires high water pressure, and the "head" developed by the elevation difference between sea level and the deep mine cavities would have supplied the pressure.

  15 years ago | reply | hide comment