548 FORD, FOREMAN, GRUBBS, KROLL, AND WATTS 



raphy, La Jolla, Calif. Filtered seawater supplied from depths of 3 to 

 5 m at the end of the Scripps pier was used. 



Field-Temperature Records 



Water temperatures at two locations (stations 2 and 3) influenced 

 by the thermal plume from the largest generating units of the station 

 were monitored continuously. Station 2 was located 84 m (275 ft) 

 and station 3, 335 m (1100 ft) from the discharge structure. Spring- 

 driven Powers model 101 two-pen circular-chart temperature 

 recorders (Powers Regulator Co.) were installed at each location to 

 provide a 7-day temperature record accurate to ±0.5°C. 



One of the temperature sensors at each station was placed on the 

 rock substrate at a depth of 0.6 m (2 ft) below mean lower low water 

 (MLLW), aiid the second was placed at a depth of 3.7 m (12 ft) 

 below MLLW. Temperature records from the 0.6-m depth were used 

 as treatment conditions for the simulation experiments because the 

 primary influence of the thermal plume on the shoreline was near the 

 surface. 



Laboratory System for Simulation Experiments 



Circular, fiber glass holding tanks 150 cm in diameter, 76 cm 

 deep, and with a capacity of 1100 liters were used for all size groups 

 of test species. Each tank was fitted with surface and bottom drains 

 to assure effective removal of detritus and uniform, rapid water 

 circulation by vortex action. The experimental tanks were arranged 

 in interconnected groups of 20 replicates, with common recirculation 

 through two heated sumps, each serving 10 tanks. Supplementary 

 electrical heating of the sump water was necessary to maintain 

 experimental temperature conditions because temperatures produced 

 by the generating units were sometimes quite vsiriable and did not 

 correspond to those required in the experiments. 



Water temperatures in different groups of 20 replicate treatment 

 tanks were controlled to duplicate the varying temperatures mea- 

 sured continuously at stations 2 and 3 in the thermal plume. Weekly 

 chart records of field temperatures were used as patterns to cut 

 aluminum cams, and the cams, in turn, were used to drive separate 

 time-cycle controllers associated with each group of tanks. A Powers 

 model VP657 three-way mixing valve operated pneumatically by a 

 Powers model 101 time-cycle controller was used to blend effluent 

 water from the heated sumps with ambient source water in changing 

 proportions to duplicate the temperature regime measured at a field 

 station 2 weeks previously. The 2-week lag was required to allow 

 time for the field record to be made, retrieved, and converted to a 



