### U N ITED STATES E NVIRONMENTAL PROTEC T ION AGENCY REG ION IX 75 Hawt h or ne Street San F ranc isco , CA 94 10 5 Memorandum
Ma y 9, 2 0 16
From: Di a n e E

. F l eck, P

. E

. , Es q . W a t e r Qu a l ity Assess me nt Sect i on W a ter Divi sion, US EPA R eg i o n 9
T o: Admi n i st r a t i ve R e co r d for Pro po sed S e l e niu m Cr it e ri a f o r t h e Sa n Fra n c i sco Ba y an d De lt a
Re: Ca l c u l at ion s to Det erm i n e C orbu f a Val u e i n th e Te ch ni ca l S u p po rt Do c um e nt f o r t h e Pro po se d Aqu at i c Life a n d Aq u at i c- De p e nd e nt W i l d l ife Se l e n i u m Cri te ri a f or t h e Sa n Fr a nci sco Ba y and De lta {2 0 1 6)

Ca l c ul a ti o n s t o d eter min e th e m a ximum Co rb ufa se l e n iu m co n ce nt r ati on fro m t h e Pr e di ct ed In ve rt e brate Se l e niu m C on ce nt r a t i ons in Ta b l e 4
- 9, to prot ect ea ch ca te gory of d a rn -e at i n g s p ecies : 1. For Clam-eat in g f ish : The Pre d i c t e d Inv e rt eb ra t e (pr ey ) Di et ary Co n ce ntrat i on = 7

. 7 1J. g/ g dw (from Ta bl e 4
- 9 ) ; 7

.7 1J. g/ g dw =s u m of : (% prey di et ) x ( prey TI F ) x (p art i cu l ate con ce nt r a t i on )

. U sin g a d i et of 40% Co rb uf a ( TI F = 17 ) , 6 0% A n ne li ds / Cru st ace an s ( TIF = 1 .3 ) and a p red i c te d pa rt i c ul ate co n ce nt ra ti on of 1

. 0 17 IJ.g/ g dw ( f rom Tab l e 4
- 9 ) : T h e p re di cte d d i eta ry contr i b ution fro m Cor b uf a = 0 .40 x 17 x 1. 0 17 = 6

. 9 2 IJ.g/ g dw; a n d th e pred i cte d d i et ary contribu t ion fro m A nn e l i d/ Cru st acea ns = 0

. 6 x 1 .3 x 1. 0 1 7 = 0

. 7 9 1J. g/ g d w . (To Ve r if y : 6

. 92 

### + 0

.79 IJ.g/ g dw = 7

.71 o r 7 . 7

**~J. g**  dw)
Si n ce t h e Cl a m -ea t i n g Fi sh Di et i s co m p ri sed of 4 0% Corb ula, t h e Target C on ce ntra t i on in C orbula t o p rot e ct d a rn - e a ti n g fi sh i s : (P r e di cte d d i eta ry contrib ut i on from C orbu/ a ) 

## I ( %

of di et ) = 6

. 9 2 1J. g/ g dw 

## I 0 .40 = 17

.3 0 IJ. g/ g dw 

# -+ Target Co n ce ntrat i on i n Cor buf a

**~** 1 7 1J. g/ g dw (or rn g/k g d w)

.

12 . F o r C lam - ea ti ng b ir d s : Rails : T h e P re di c t e d Inv erte b r ate ( p r e y) D i e t a ry Co n ce ntr at i on = 15.6**g** d w ( from T ab l e 4 - 9 ) ; 1 5 .6**~g g**  d w = s u m of : ( % d i et ) x ( TI F) x (p art i c u l ate co n ce n trat i o n ) . U s in g a di e t of 2 0 % Co r b u! a ( TIF =17 ) , 4 0 % Ot h e r M o llu s k ( TIF = 2.8 ), 3 0 % I n sec t (TTF = 2 . 8 ), 1 0 % Pl a n t ( n eg li g i b l e con t r i b u t i on ) a nd a pr e d icted part i c u l ate c o nc e n tr a t i o n of 2 . 894 u g l g d w ( f rom T a b l e 4 - 9 ) : T h e p re d i c te d di eta r y c on t ribu t io n from Corbu l a = 0 . 2 0 x 17 x 2 .894 = 9 .84**g** dw ; t he p r e d i cte d d i e tar y co n tri b u t i o n fr o m ot h e r mo ll u s k s = 0 .4 0 x 2 . 8 x 2.89 4 = 3 . 2 4**~gig** dw; t h e pr e d i cte d di eta ry co n t ribu t ion fro m i n s ects= 0 . 3 0 x 2 . 8 x 2 .894 = 2.43**g** dw; a nd th e pr e di c t e d di e t a ry c ontribu t ion fr o m p l a n t= > neg li g i b l e (0) .

( To V e rify : 9 . 84 + 3 . 24 + 2 . 43 = 15 . 5 1 o r 15.6**g** dw ) S i n c e th e C l a m - e a t in g Ra i l Di e t i s c om p ri sed of 2 0 % C orbu l a , t h e T a r ge t Co n ce n t r at i on i n Co r b ul a t o pro t ect cl a m - ea t in g rai ls i s : ( Pr e di c t ed d i e tary co ntrib u t i o n fr om Co rbu l a ) I( % of d i e t ) = 9 . 84**~g g**  d w I 0 .2 0 = 49 .2 0**g** dw -+ T a r g e t Co nc e n t r at i o n in C o rb u l a**~** 49**g** dw ( or mglk g d w ) . 3. Fo r Cla m -eating b i rd s: M i gr a tory D u c ks (50 % of time s p e n t in E st ua ry) : T h e P r e di ct e d I n v ert e b r ate (pr e y ) C o nc e n tration= 6 .9**g** dw (from T a b le 4 - 9 ) ; 6.9**~g/g** d w = s u m of: (% d i e t ) x ( TI F) x ( p art i c ul a t e c o n cent r at i on ) ;

U s in g a di et of 45% C o r b u/ a ( TIF=1 7 ) , 5% O t h e r An i m a l (TI F = 2. 8 ), 5 0 % Out s i de of E st u a ry (n e g li g i b l e co n t r i b u t ion) a nd a pr ed ict e d p a rt i cu l a te co n ce ntr a tion o f 0 . 89 0**~g g**  dw ( fro m T a b l e 4 - 9 ) :

T h e pr e d i c t e d d i e tar y c ontribut i on f r om C o rb u / a = 0.45 x 17 x 0 .89 0 = = 6. 8 1**/k g**  dw ; t h e pr e d i c t e d di etar y c o n t r i b u t i o n fro m Ot h e r An i m a l = 0 . 05 x 2 . 8 x 0 .89 0 = 0 . 1 2**g** dw ; a nd t h e p r ed i c ted d i e t ar y c o n tr i but i o n f ro m out side of estu a ry => ne g li g ible (0) . (T o Ver if y : 6 . 8 1 + 0 .1 2 = 6 . 93 o r 6 . 9**g** dw) S in ce t he C l a m - e at in g D u c k D i e t i s com prised o f 45% Co r bu / a , t h e T a r g et C onc e n t ra t i on i n C o r bu / a to p r ot e ct cl a m - e a t in g du c k s i s : (P r e di ct e d d i e t a r y c o ntri b u t io n from C o rb u l a) / ( %o f di e t ) = 6 . 8 1**g** dw I 0 .4 5 = 1 5 . 13**g** d w -+ Targe t C on c e n tra tion i n Co rb u l a :S 15**g** dw (or m g / k g d w ) . In or d er t o p r o te ct all t hree categori es of s p e cies using th e pr o p o se d dietary contribu t ion s , the c o ncen t r a t i on i n Corbu / a s hould be::::; 1 5**~g g**  dw ( or mg / kg dw ) . 2