correlation can be drawn between free available chlorine concentration 

 at the discharge weir and total residual levels at the quarry cut (Chlorine 

 Transport Study in 1977 Annual Environmental Operating Report) the 

 dosages are somewhat empirically based on experience. However, values 

 for chlorination time and total residual chlorine concentration at the 

 discharge have remained well below limits established by the Environmental 

 Technical Specifications and the NPDES Permit (TRC <0.1 mg/1; see, for 

 example, the ETS requirement section of the 1981 Annual Report). Prior 

 to 1978, station procedures called for monthly thermal back-flushes of 

 the circulating water systems of both Units, each pump bay to receive 

 110 F water for up to 1 hour. The service water systems cannot be 

 thermally back-flushed. 



Conclusion based on early chlorination experience emphasized the 

 need for optimizing chlorination regimes, within permit limitations, as 

 well as the ineffectiveness of chlorine alone for controlling mussel 

 growth. In January of 1977, a Biofouling Study was proposed, and a 

 Seawater Systems Reliability Task Force was organized in August of 1978, 

 primarily to deal with the problem of Unit I condenser tube leakage. A 

 meeting on 8 September 1978 to discuss mussel fouling (Appendix I) 

 presented an historical background, as well as an outline of the objectives 

 and results of the EPB Biofouling Study to that point. Recommendations 

 presented at the meeting included proposals to conduct laboratory 

 experiments to determine optimum heat and chlorine treatments for mussel 

 control, as well as operational procedures to test various chlorine 

 dosages and thermal back-flush schedules. 



Numerous inspection dives were conducted within the intake screen- 

 houses. The inspections were initially made by contract divers, but 



