69 



Stett« &'30/95 Paga 7 



SpiB 



The Team believes that the role of spill as a component of tt>e inteflm 

 operations of the hydropower system m^its reexamination, and recommeivis to 

 you tfat you undertake sucM a review . 



in our Fefaojary tetter to you and in ourext«nsiv« eartier<iacussions oi thictopic, 

 we supported the conduct o< a spill program aa. ail non-ooltecw projects and m 

 collector projects undef certain t«mw arxl cooditjons :o cre^e in-ilver conditions 

 far a trartisport vs. in-rrver survive evaluation. 



T7» Team ha& further considered fts earlier view and ts concerned aiaoirt the 

 risks of etevaxod dissolved gas concentra ti oaa associated with spil at al the 



dams. H appears to us that the risk to migrating fish may ocswatgh the beoefitB of 

 spiSway passage. We are stiU ioarning about what leveJ of spiit is appropriaae and 

 how we can evatuate the impacts ot spi9 and htgh ^saofved gas levels on 

 rrtigrdting fish. 



We now beBeve that a nrwre Hn^ed use of sp^B wrti ailow for the cont^xied 

 saentJflc evaiuatioo - which we support - whrte fnirBnizjng the rteks that excess 

 s?^l may pose to listed salmcn. We theretore recxMnmend ttiat the NMFS review 

 the core elements of the spiE prcgrajn txased upon the new intofmatton being 

 coltected- We t>eneve mat such a review would be the best example ot applied 

 adaptive management artd wcuW reflect your continuing commrtment to the use 

 of the bea science avatobte in the coodu^ ot the necovafy effort 



This recommendation is based on the Team's anaiysis of The !ike>y 

 charge in survwais due to the tfMi program. The Team h^s deveSopeO these 

 estimatos using ^jsumptiorw from your staff for mortaitjes through the ttree 

 possible dam passage routes and through the reservoirs. The thrae ways tfiat 

 fish pass a dam are over the spjilwery, througfi the turtiines or via the bypess 

 system. Usaig the survival assumptions that we reoeived from NMFS staff, it 

 appears that for those fish emigrating in the river, less than 40 percent of the fish 

 that r99cf\ Lower (Srajvte <iam wiW survive to bekjw BomeviBe Dam. This is with 

 an assumption of nO iflf W"* ^ mortatity due to mtfogen supefsaturation. With 

 a amaA 2.0% increased moftafrty in each reservoir due to gas but)bte cSsease tt^ 

 survtvai of ^h emigrating in the rWer with spil w^) be less than without spiB, The 

 survTva/ of fish thai emigrate in the river is low because of the cumulative 

 moriaity <rf emigrating through eight msanfoiTS and over or through eight dems, 

 v\^h such low in-rrver survivais, s^lng st ttie colector dams is not a viable 

 recovery method even without a gas bub&te disease probienv 



