Ha rdne ss-Ba se d Me ta ls Crite ria in NPDE S Pe rmits BY BRI - PowerPoint PPT Presentation

Ha rdne ss-Ba se d Me ta ls Crite ria in NPDE S Pe rmits BY BRI AN NI CK E L US E PA RE GI ON 10

Ba c kg ro und: Ho w the E PA De te rmine s the 2 Ne e d fo r L imits (“Re a so na b le Po te ntia l”)  A disc ha rg e ha s “Re a so na b le po te ntia l” if the pro je c te d re c e iving wa te r c o nc e ntra tio n e xc e e ds wa te r q ua lity c rite ria . he 99 th pe rc e ntile o f the e fflue nt da ta is e stima te d using sta tistic s in  T Cha pte r 3 o f the E PA’ s T e c hnic al Suppo rt Do c ume nt fo r Wate r Quality- b ase d T o xic s Co ntro l (T SD).  Dilutio n ma y b e c o nside re d in a re a so na b le po te ntia l a na lysis b a se d o n a n a utho rize d mixing zo ne .  “Critic a l” stre a m flo ws fo r mixing a re g e ne ra lly spe c ifie d in Se c tio n 210.03.b o f the I da ho WQS.

Ba c kg ro und: Ho w the E PA Ca lc ula te s 3 Wa te r Qua lity-b a se d E fflue nt L imits  I f the re is “re a so na b le po te ntia l,” the n limits a re e sta b lishe d.  L imits a re g e ne ra lly c a lc ula te d b a se d o n pro c e dure s in Cha pte r 5 o f the T SD.  Mixing zo ne a utho rize d: L imits me e t c rite ria a t the e dg e o f the mixing zo ne .  No mixing zo ne a utho rize d: L imits me e t c rite ria a t the po int o f disc ha rg e (“e nd-o f-pipe ”).  L imits b a se d o n a q ua tic life c rite ria must me e t b o th a c ute a nd c hro nic wa te r q ua lity c rite ria .  Bo th the a ve ra g e mo nthly limit a nd ma ximum da ily limit b a se d o n the sa me c rite rio n (e ithe r a c ute o r c hro nic ), whic he ve r re sults in mo re string e nt limits.  Average monthly limit ≤ chronic wasteload allocation.  Maximum daily limit ≤ acute wasteload allocation.

Me ta ls with ha rdne ss-de pe nde nt 4 c rite ria in I da ho  Mo st wa te r q ua lity c rite ria a re fixe d va lue s.  E .g ., a q ua tic life c rite ria fo r c hlo rine , c ya nide , se le nium, a nd pe stic ide s, a nd huma n he a lth c rite ria .  Aq ua tic life c rite ria fo r se ve ra l me ta ls a re b a se d o n ha rdne ss:  Ca dmium, c hro mium I I I , c o ppe r, le a d, nic ke l, silve r, a nd zinc .  Crite ria c o nc e ntra tio ns inc re a se (i.e ., b e c o me le ss re stric tive ) with inc re a sing ha rdne ss.  T he ha rdne ss va lue (a nd, in turn, the c rite ria ) must b e e sta b lishe d a s pa rt o f the re a so na b le po te ntia l a na lysis a nd e fflue nt limit c a lc ula tio ns.

I da ho WQS Pro visio ns Re g a rding 5 Ha rdne ss (Se c tio n 210.03.c )  Hig h-e nd “c a p” o f 400 mg / L a s Ca CO 3 e ve n if a c tua l ha rdne ss is g re a te r.  L o w e nd “flo o r” o f 25 mg / L , e xc e pt fo r c a dmium, whic h is 10 mg / L , e ve n if a c tua l ha rdne ss is le ss.  “T he ha rdne ss va lue s use d fo r c a lc ula ting a q ua tic life c rite ria fo r me ta ls a t de sig n disc ha rg e c o nditio ns sha ll b e re pre se nta tive o f the a mb ie nt ha rdne sse s fo r a re c e iving wa te r tha t o c c ur a t the de sig n disc ha rg e c o nditio ns g ive n in Sub se c tio n 210.03.b .”  Sub se c tio n 210.03.b re fe rs to the lo w flo w de sig n disc ha rg e c o nditio ns (e .g ., 1-da y, 10-ye a r lo w flo w fo r a c ute c rite ria a nd 7-da y, 10-ye a r lo w flo w fo r c hro nic c rite ria ).

Co nside ring the I nflue nc e o f the 6 Disc ha rg e  Disc ha rg e s c a n b e ha rde r o r so fte r tha n the a mb ie nt wa te r.  T his c a n b e fa c to re d into the a na lysis in two wa ys:  Use ha rdne ss me a sure d do wnstre a m fro m the disc ha rg e .  Ca lc ula te the do wnstre a m ha rdne ss using a ma ss b a la nc e o f the upstre a m a nd e fflue nt ha rdne ss a nd flo w.  I da ho ’ s Dra ft Mixing Zo ne Guida nc e (Se c tio n 4.3.3).  “F o r e fflue nt with g re a te r o r lo we r ha rdne ss…tha n the re c e iving wa te r b o dy, use a n e stima te o f the fully mixe d c o nditio ns to c a lc ula te the a pplic a b le e dg e o f mixing zo ne c o nc e ntra tio n.”  “I f da ta a re a va ila b le , DE Q stro ng ly sug g e sts disc ha rg e rs e xa mine the re la tio n b e twe e n flo w a nd ha rdne ss.”

E xa mple s 7  Use ha rdne ss me a sure d do wnstre a m fro m the disc ha rg e . a s Ca CO 3 , 5 th pe rc e ntile ).  City o f Ca ld we ll (56 mg / L  City o f Me rid ia n (F ive mile Cre e k, minimum ha rd ne ss whe n flo w wa s le ss tha n the se a so na l me d ia n).  28 mg / L a s Ca CO 3 fro m Ma y – Se pte mb e r.  102 mg / L a s Ca CO 3 fro m Oc to b e r – April.  Gro use Cre e k Mine (fo r silve r a nd L e a d ).  Ca lc ula te the do wnstre a m ha rdne ss using a ma ss b a la nc e o f the upstre a m a nd e fflue nt ha rdne ss a nd flo w.  Gro use Cre e k Mine (e xc e pt silve r a nd le a d ).  City o f Me rid ia n (Bo ise Rive r).  Ha rd ne ss wa s c a lc ula te d a t the e d g e o f the mixing zo ne (no t a t c o mple te mix).  5 th Pe rc e ntile wa s use d fo r b o th e fflue nt a nd upstre a m ha rd ne ss.

Wha t’ s spe c ia l a b o ut silve r a nd 8 le a d? Co nc a ve do wn Co nc a ve up Figure 1: Chronic Copper Figure 2: Silver Acute Criterion 12 25.0 Criterion and Mixture and Mixture 10 20.0 8 15.0 Silver (ug/L) Copper (ug/L) 6 10.0 4 5.0 2 0.0 0 20 40 60 80 100 120 140 160 180 200 0 Hardness (mg/L as CaCO3) 0 20 40 60 80 100 120 140 160 180 200 Hardness (mg/L as CaCO3) Chronic Copper Criterion Acute Silver criterion Mixture of Flows Copper Mixture

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