The Status of Thermal Discharges on the Pacific Coast

Abstract

Thermal power stations that discharge waste heat from cooling water into tidal areas of California represent 85% or 16,982 megawatts (MW) of the total state thermal power capacity in 1969. The generation on tidal areas in Oregon is 169.5 MW, and in Washington is 77.9 MW. The surface area influenced in 35 measurements at 9 power station discharges was used to calculate a regression equation in which generation in MW was equated to surface area raised above normal temperature in acres. The linear regression for areas raised 2 F above normal was Y = 104.422 + .0902011 X, while the equation for areas raised 10 F above normal was Y = 2.77812 + .0126561 X. The figure of +2 Fis considered a detectable effect, but not siguificant biologically except in the warmest summers, while +10 F is considered significant biologically throughout the year. If all thermal stations in California were operated at maximum capacity, a total of 5.86 square miles of surface water would be raised 2 F above normal, and 0.41 square miles would be raised 10 F above normal, according to the regression equations. California has 400 square miles of bays and estuaries into which power stations discharge, and a shoreline of 1205 miles. These approximations are conservative in that the average load factor (ratio of actual operating load to total capacity) at California tidal stations was 56% in 1966, and the stratification of the warmed discharge water tends to minimize the effects on benthic communities. Thermal power generation at California tidal stations is expected to double by 1980. The trend to larger stations should make the total area influenced less than twice the present areas, because larger stations influence a lesser area per MW than smaller stations.

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