SITE INFORMATION AND CORRESPONDENCE

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• � ate' -2- discharging agriculture field waste water upstream and downstream of SRWWTP were checked for evidence of toxic discharges. Riota appeared normal in each canal investigated. All dead fish were located in the river between Stockton channel down to Mathews Road. A pesticide source away from SRWWTP is therefore not supported. Low Dissolved Oxygen (D.O. ) Low oxygen tensions in the river near the point of discharge could have been caused from low D.O. in the effluent (because of the large volume discharged compared to river flow) or high biological oxygen demand (B.O.D. ) or chemical oxygen demand (C.O.D. ) in the effluent. Channel catfish have a high tolerance for low D.O. and react to low oxygen tensions in bottom waters by moving to the surface and gulpinq air. This was not observed. D.O. levels measured at the surface by SRWWTP personnel were: 6/18 3. 5 - 4. 5 ppm 6/19 4 . 4 - 4. 5 ppm 6/20 3. 1 - 5.2 ppm Channel catfish are not stressed by D.O. levels as measured in the river, therefore, low ambient D.O. tensions are not supported as a cause of the die-off. Temperature Temperature measurements of the effluent and river reported by SRWWTP personnel were similar and within tolerance range for channel catfish and is ruled out as a possible cause. Disease Fish collected at the scene appeared full bodied in length to weight ratio. No external parasites were apparent. The fish kill was not generalized in the river as would be expected from a disease epidemic. Disease is not supported as a singular cause of the die-off, although not entirely ruled out. High Chlorine in SRWWTP Effluent SRWWTP records indicate high chlorine residuals up to 10. 5 ppm were present in the discharge on the 19th and 20th of June.