# PROPOSE

D PLA N FO R OPERABL E UNI T 7 APACH E TAILIN G IMPOUNDMEN T Colorad

o Departmen t ofPubli c Healt h

an d Environmen t U.S

. Environmental Protectio n Agenc y 

### Regio n VII I January 200 0 Operabl e Uni t 7 Californi a Gulc h Superfun d Sit e Leadville

, Colorad o 

# E P A Announce s It s Preferre d Alternativ e T h e U.S

. Environmenta l Protectio n Agenc y (EPA)

, i n cooperatio n wit h th e Colorad o Department o f Publi c Healt h an d Environmen t (CDPHE)

, i s announcin g th e preferre d alternative^ t o addres s th e source s o f metal contaminatio n locate d withi n Operabl e Uni t 7 (OU7 ) o f th e Californi a Gulc h Superfun d Sit e (Californi a Gulch Site ) i n Leadville

, Colorado

. OU 7 o r th e Apach e Tailing Impoundmen t i s define d a s fou r distinc t tailing impoundments

, whic h includ e th e Mai n Impoundment

, Tailin g Pon d No

. 2
, Tailin g Pon d No

. 3
, an d th e Nort h Impoundment

, fo r whic h ASARC O Incorporate d (Asarco ) i s th e Potentially Responsible Party (PRP). Th e preferre d cleanu p alternativ e consist s o f regradin g th e Mai n and Nort h Impoundment s t o creat e a singl e combined tailin g area , placemen t o f a soi l cove r wit h a geosyntheti c barrie r an d vegetatin g th e covere d surface

. Moreover

, th e preferre d alternativ e include s surfac e wate r controls

, whic h includ e re-channelizatio n o f Californi a Gulch

, constructio n o f diversio n ditches

, an d implementin g institutiona l controls

. Thi s Proposed Plan als o summarize s th e othe r cleanu p alternatives tha t wer e considere d for th e OU 7 site

. Asarc o remove d Tailin g Pond s Nos

. 2 an d 3 throug h a Removal 

### Action i n 199 7 an d place d th e wast e o n th e Mai n Impoundment

. Th e area s wer e backfille d wit h wasteroc k fro m OU 9 an d regraded

. I n 1999
, Asarc o installe d wic k drain s i n the Mai n Impoundmen t t o facilitat e dewaterin g o f th e subsurfac e slimes

. They als o backfille d th e Nort h Impoundmen t t o promot e surfac e water drainage

. MAR K YOU R CALENDAR : OPPORTUNITIE S

FO R PUBLI C INVOLVEMEN T Publi c Meeting : January 25,2000
, 7:0 0 p.m

. Nationa l Minin g Hal l o f Fam e an d Museu m (10t h Stree t Entrance)

, Leadville

, Colorad o Publi c Commen t Period : Januar y 2 5 - Februar y 24,200 0 Sen d Writte n Comment s to : Rebecca Thoma s (8EPR-SR ) EP A Remedia l Projec t Manage r 99 9 18t h Street

, Suit e 50 0 Denver

, Colorad o 80202-240 5 Thomas.Rebecca@epamail.epa.go v Informatio n Repositories : The Proposed Plan and other documents in the Administrative Record are available at the following locations:

• Lake County Public Library 111 5 Harriso n Avenue Leadville

, C O 8046 1 Colorado Mountain College Library Learnin g Resourc e Cente r Leadville

, C O 8046 1 EPA Superfund Records Center 99 9 18t h Stree t 5 t h Floor

, Nort h Terrac e Denver

, C O 8020 2 (303)312-6473 CDPHE Superfund Records Center 430 0 Cherr y Cree k Driv e Sout h Buildin g 2,2 n d Floo r Denver

, C O 8024 6 (303)692-333 1 

### K e y Contacts : Rebecc a Thomas E P A Remedia l Projec t Manage r (RPM ) (303)312-6552 Toll-fre e (800 ) 227-891 7 x 655 2 Mar k Rudolp h CDPH E Stat e Projec t Office r (303)692-331 1 Mario n Galan t CDPH E Communit y Relation s Coordinato r Toll-fre e (888 ) 569-183 1

'Word s show n in bol d italic s ar e define d in th e glossary a t th e en d o f th e document

.

## PUBLI

C INVOLVEMEN T PROCES S

T h e EP A an d CDPH E encourag e resident s an d othe r intereste d partie s t o rea d an d commen t o n thi s Propose d Plan

. Detaile d informatio n i s containe d i n th e Remedial Investigation (RI)

, an d the Focused Feasibility Study (FFS ) for OU7

. Thes e document s describ e th e OU 7 contaminatio n an d th e cleanu p alternative s considered

. Thi s informatio n an d othe r document s i n the Administrative Record are availabl e at the informatio n repositorie s liste d o n th e firs t pag e o f thi s document

. Th e Administrativ e Recor d contain s al l o f th e informatio n tha t th e E P A wil l us e t o mak e it s fina l remed y (cleanup ) selection

. Afte r considerin g Stat e an d communit y comments
, th e EP A wil l mak e it s fina l cleanu p decision

. Th e EP A ma y modif y th e preferre d alternativ e o r selec t anothe r alternativ e presente d i n thi s Propose d Plan

. T h e EP A an d CDPH E encourag e citizen s t o revie w an d

commen t o n al l identifie d alternatives

, an d provid e an y ne w informatio n fo r th e EP A t o consider

. Verba l o r writte n comment s ma y b e submitte d durin g th e publi c meeting
, o r writte n comment s ma y b e sen t t o th e EP A Remedia l Projec t Manage r (RPM)

, Rebecc a Thomas

, postmarke d or e-mailed n o late r tha n February 24
, 2000

. Upo n timel y request
, th e EP A ma y exten d th e publi c commenl period

. Suc h request s shoul d b e mad e i n writin g t o Ms

. Thoma s
a t th e addres s shown on Pag e 1
, postmarke d n o late r tha n Februar y 24
, 2000

. Onc e the publi c comment s ar e received

, the EPA

, i n consultatio n wit h th e State

, wil l mak e it s fina l decisio n o n th e cleanu p alternative

. Th e EP A wil l the n publis h a Record o f Decision (ROD), a documen t tha t describe s th e selectio n o f th e fina l cleanu p pla n an d respond s t o th e Stat e an d communit y comments

. Th e EP A expect s t o issu e this RO D followin g th e publi c comment period

. T h e EP A prepare d this Propose d Pla n t o fulfil l th e publi c participatio n responsibilitie s i n Section s 113(k) an d 117(a ) o f th e Comprehensive Environmental Response, Compensation,

an d Liability Ac t o f 1980 (CERCLA), a s amende d b y th e Superfund Amendments and Reauthorization

Act of 1986 (SARA). 

## SITE BACKGROUN D

T h e Californi a Gulc h Sit e is locate d i n Lak e County

, Colorado

, i n th e Uppe r Arkansa s River Basin

, approximatel y 10 0 mile s southwes t o f Denve r (see Figur e 1)

. Th e Sit e encompasse s approximatel y 16. 5 square mile s an d include s th e town s o f Leadvill e an d Stringtown

, a portio n o f th e Leadvill e Histori c Minin g District

, an d th e portio n o f th e Arkansa s Rive r fro m it s confluenc e wit h Californi a Gulc h downstrea m t o th e Lake For k Cree k confluence

. Beginnin g i n abou t 1860
, the Leadvill e are a wa s use d extensivel y f o r mining
, milling

, an d smeltin g operations

. A s mine s wer e developed

, wast e roc k wa s excavate d alon g wit h th e or e an d place d nea r th e min e entrances

. Or e wa s crushe d an d separate d int o metalli c concentrate s a t mill s an d th e tailing s wer e generall y slurrie d int o impoundments

, suc h a s th e Apach e Tailin g Impoundment

. Th e metalli c concentrate s wer e the n transporte d t o smelter s fo r furthe r processing

. Sla g an d othe r wast e product s
wer e produce d fro m th e smelters

. T h e Apach e Tailin g Impoundmen t i s locate d o n th e souther n edg e o f Leadvill e adjacen t t o U.S

. Highwa y 24

. Th e tailin g impoundment s ar e locate d i n Californi a Gulch

, approximatel y 1,50 0 fee t downstrea m o f th e Yak Tunne l Wate r Treatmen t Plan t Surg e Pond

. I n th e vicinit y o f th e Apach e Tailin g Impoundment

, Californi a Gulc h i s approximatel y 60 0 fee t wid e an d slope s t o t h e west

. Th e Apach e Tailin g Impoundmen t i s locate d withi n a n
are a zone d fo r industria l us e b y th e Cit y o f Leadville

. Ther e i s

n o curren t residentia l us e o n OU7

. Th e Main Impoundmen t (11. 3 acres ) i s furthes t t o th e east
, an d extend s acros s th e gulch

. Tailin g Pond s Nos

. 2 an d 3
, whic h

wer e remove d i n 1997
, wer e locate d wes t an d downstrea m o f th e Mai n Impoundment

, an d wer e approximatel y 1. 5 an d 0. 5 acre s i n size
, respectively

. Th e Nort h Impoundmen t (1. 8 acres ) i s separate d fro m th e Mai n Impoundmen t b y a n ol d railroa d grade

. T h e Mai n Impoundmen t an d Nort h Impoundmen t contai n approximatel y 630,00 0 an d 14,50 0 cubi c yard s o f tailings

, respectively

. Th e volume s o f materia l removed fro m Tailin g Pond s Nos

. 2 an d 3 wer e approximatel y 36,20 0 an d 5,20 0 cubi c yards

, respectively

. T h e mil l tha t generate d th e tailing s place d i n th e Mai n Impoundmen t an d possibl y th e Nort h Impoundmen t wa s locate d

o n th e hillsid e northeas t o f th e Nort h Impoundment

. Thi s mil l operate d a s th e Veni r Mill

, th e Californi a Gulc h Mill

, an d th e Asarc o Leadvill e Millin g Uni t fro m about 193 9 t o 1956

. Th e Apach e Mill

, whic h wa s locate d a t th e northwes t corner o f th e Main Impoundmen t (remnant s currentl y exist)

, reprocesse d tailing s fro m th e Mai n Impoundmen t an d deposite d th e material s int o Tailin g Pond s Nos

. 2 an d 3

. Th e Apach e Mil l operate d fro m t h e lat e 1970 s int o th e 1980s

. Th e analysi s o f tailin g an d underlyin g foundatio n soi l sample s collecte d fro m th e impoundment s indicate d elevate d concentration s o f metals

, primaril y arsenic
, cadmium

, copper
, lead

, an d zinc

. I n 1983
, EP A place d th e Californi a Gulc h sit e o n th e National Priorities List, becaus e o f concern s about the impac t o f mine drainag e o n surfac e water s i n th e Californi a Gulc h an d th e impac t

o f heav y metal s loading t o th e Arkansas River

. Subsequen t investigation s reveale d th e presenc e o f heav y metal s i n soil s an d wast e pile s i n and aroun d residentia l and commercia l area s o f Leadville

. Severa l RI s hav e bee n performe d t o collec t dat a necessar y t o identif y th e natur e an d exten t o f contamination

. A Site-wid e Screenin g Feasibilit y Stud y (SFS ) wa s undertake n a s

a join t effor t betwee n th e PRP s an d EPA

. Th e SF S wa s complete d i n Septembe r 1993

. I t develope d remedial action objectives (RAO) and identifie d an appropriat e range o f remedia l alternative s applicabl e t o the variou s source s tha t wer e t o b e

'Word s show n i n bol d italic s ar e define d i n th e glossar y a t th e en d o f th e document

.P:\3280-015\OU7\PP\5344-65.DW G 11/29/9 9

*/

CANTERBUR Y TUNNE L

Stra y Hors e Gulc h ^ YA K Tl/NNE L Star r Ditc h

SUPERFUN D SIT E BOUNDAR Y N



# FIGUR E 1 ~ aiar r uiicn

. ^

j 

### OU7-APACHEJ[AllN

G IMPOUNDMEN

T



# GENERA L SITE 

# LOCATIO N MA Pconsidere d

durin g FFS

. Befor e completin g th e SFS

, EP A provide d notic e an d copie s o f th e draf t SF S t o th e publi c an d accepte d comment s o n th e draf t report

. I n 1994
, Asarc o entered a Consent Decree (CD) wit h th e Unite d States

, th e Stat e o f Colorado

, an d othe r PRP s a t th e Californi a Gulc h Site

. Pursuan t t o th e term s an d condition s o f th e CD

, Asarc o complete d a FF S fo r OU7

. Thi s stud y evaluate d an d

screene d remedia l alternative s retaine d i n th e SF S fo r impounde d tailing

. A draf t feasibilit y stud y wa s previousl y submitte d t o EP A b y Asarco

. However

, pursuan t t o comment s receive d fro m E P A an d CDPHE

, additiona l investigation s wer e performe d an d t h e dat a incorporate d int o th e fina l FFS

. T h e Leadvill e are a ha s been classifie d a s a Nationa l Histori c Landmark

. A s par t o f th e CD

, cultura l resourc e survey s wer e complete d fo r OU7

. Cultura l Resourc e Sit e 5KL89 1 include s structura l remain s an d artifac t scatte r o n th e sout h sid e o f bot h t h e Californi a Gulc h channe l an d th e Apach e Tailin g Impoundmen t an d ha s bee n determine d eligibl e fo r nominatio n t o th e Nationa l Registe r o f Histori c Places

. Thi s sit e i s a contributin g featur e t o th e Leadvill e Histori c Minin g Distric t base d o n it s significan t archeologica l potential

, bu t i s no t considere d contributin g as a landscapin g feature

. 

## SUMMAR Y O F SIT E RISK S
EP A performe d human healt h an d ecologica l ris k assessment s at t h e Californi a Gulc h Site t o evaluat e potentia l hazard s fro m exposur e t o contaminate d sit e media

. Contaminate d media at the Apach e Tailin g Impoundmen t ar e impounde d tailing

. Th e primar y contaminant s o f concern a t OU 7 includ e arsenic
, cadmium

, copper
, lead

, an d zinc

. Human Health Risk Assessments: Th e baseline human health risk assessments fo r th e Californi a Gulc h Sit e considere d th e risk s t o worker s an d recreationa l visitor s fro m ingestio n o f soil

and dus t at OU7

. For soil s and dust

, lea d and arseni c are the primary contaminant s o f concern based o n thei r potentia l t o cause advers e healt h effects

. Actio n level s wer e develope d fo r lea d an d arseni c i n soil s unde r residential

, commercial

, an d recreationa l lan d us e scenarios

. Thes e actio n level s ca n b e compare d t o soi l concentration s t o determin e i f a potentia l ris k exists

. Actio n level s ar e compare d t o averag e contaminan t concentration s ove r a n exposur e area

. The actio n level s i n soi l fo r a worke r exposur e scenari o ar e 6,10 0 t o 7,70 0 milligram s pe r kilogram s (mg/kg ) fo r lea d an d 61 0 t o 69 0 mg/k g fo r arsenic

. Th e actio n level s i n soi l fo r a recreationa l 

### exposur e scenari o are 16,000 mg/k g for lea d an d 1,40 0 t o 3,20 0 mg/k g fo r arsenic

. T h e concentration s i n composit e sample s o f surficia l tailing rang e fro m 25 7 t o 35 3 mg/k g for arseni c and 1,09 0 t o 1,74 0 mg/k g fo r lead

. Thes e concentration s ar e belo w th e EP A risk

based actio n level s fo r bot h th e commercial/industria l

an d th e recreationa l

lan d us e scenario

. OU 7 i s not use d fo r residentia l purposes

. Therefore

, th e expose d tailing i n their curren t conditio n d o no t pos e a significan t ris k t o human health

. Ecological Risk Assessments: Thre e ecologica l ris k assessment s (ERA ) wer e conducte d fo r th e Californi a Gulc h Site an d ar e pertinen t t o OU7

. Th e ERA s considere d th e ris k t o ecologica l receptor s (i.e.

, plants

, animals

, an d fish ) fro m exposur e t o surfac e water and soi l contaminate d b y min e wastes

. T h e ERA s conclude d tha t bot h th e impounde d tailin g withi n O U 7 an d surfac e wate r presen t potentia l risk s t o wildlif e an d aquati c receptors

. Th e followin g exposur e pathway s wer e identifie d a s potentiall y exhibiting risk

.

• Ingestio n o f surfac e tailing s contaminate d wit h lead

, cadmium

, coppe r an d zinc b y wildlife ;

• Plan t an d soi l faun a (invertebrate s an d soi l bacteria necessar y fo r health y soil ) directl y expose d t o surfac e tailing s contaminate d wit h arsenic
, cadmium

, copper
, lead

, silver

, an d zinc ; Wildlife ingestin g sediment s an d surfac e contaminate d b y zinc
, cadmium

, an d lead ; an d wate r

• Aquati c lif e expose d t o surfac e wate r an d sedimen t contaminate d wit h arsenic
, barium

, cadmium

, copper
, iron
, and lead

. T h e ris k characterizatio n indicate d potentia l risk s t o th e blu e grouse , mountai n bluebird

, an d th e leas t chipmunk

, throug h ingestio n o f tailing withi n OU7

. Potentia l risk s t o plant s an d soi l faun a fro m exposur e t o tailin g
wer e als o identified

, althoug h ris k t o soi l faun a was characterize d

as low

. Surfac e wate r ingestio n ma y als o resul t i n a potentia l ris k o f som e effects t o wildlife

.



## SUMMAR Y O F ALTERNATIVE S
E P A considere d a wid e range o f cleanu p option s i n th e SFS

. Som e wer e eliminate d durin g preliminar y screenin g becaus e the y woul d no t effectivel y addres s contamination
, coul d no t b e implemented

, o r woul d hav e had excessiv e cost s compare d t o othe r protectiv e alternatives

. Thes e cleanu p option s wer e furthe r evaluate d an d screene d fo r OU 7 durin g th e FFS

. Followin g screening
, nin e alternative s wer e retaine d i n th e FF S f o r furthe r evaluation

. Thes e alternative s ar e discusse d below

.

'Word s show n in bol d italic s ar e define d in th e glossar y a t th e en d o f th e document

.ALTERNATIV

E 1 : N o Action

. N o remediatio n woul d take plac e unde r thi s alternative

. Thi s alternativ e i s presente d as a baselin e conditio n fo r compariso n o f Alternative s 2 A throug h 4B

. 

### Capital Cost $ 0 Tim e t o Implemen t Immediat e Annua l Operation an d Maintenance Cost $

0 30-Year Present Worth Cost _________________$0 

### ALTERNATIV

E 2A : Simpl e Soil Cover

. Thi s alternativ e 

### include s th e followin g components : (1 ) th e applicatio n o f source surfac e control s t o th e impounde d tailing

, consistin g o f regrading

, placemen t o f a simpl e soi l cover , an d vegetatin g the
covere d surface ; (2 ) surfac e wate r controls

, includin g re

channelizatio n o f Californi a Gulc h throug h th e souther n portio n
o f th e Mai n Impoundmen t an d constructio n o f diversio n ditche s t o provid e surfac e water run-o n an d run-of f controls ; an d (3 ) institutiona l controls

. Institutiona l control s includ e dee d notice s

or dee d restriction s t o provid e notificatio n tha t a barrier i s i n place

, and/o r zonin g restriction s t o maintai n th e industria l zonin g currentl y in plac e fo r OU7

. Capita l Cos t Tim e t o Implemen t Annua l Operatio n an d Maintenanc e Cos t 30-yea r Presen t Wort h Cos t $2,055,00 0

2 year s $85,00 0 $3,642,00 0 ALTERNATIV

E 2B : Simpl e Soil Cove r wit h Groundwate r Controls

. Thi s alternativ e include s th e followin g components : ( 1 ) th e applicatio n o f sourc e surfac e control s t o th e impounde d tailing

, consistin g o f regrading

, placemen t o f a simpl e soi l cover , an d vegetatin g th e covere d surface ; (2 ) surfac e wate r controls

, includin g re-channelizatio n

o f Californi a Gulc h throug h th e souther n portio n o f the Mai n Impoundmen t an d constructio n o f diversio n ditche s t o provid e surfac e wate r run-o n an d run-of f controls ; (3 ) institutiona l control s (a s describe d i n Alternativ e 2A) ; and (4 ) groundwate r control s intende d t o reduce the potentia l fo r contac t betwee n th e alluvia l groundwate r an d th e bas e o f th e tailin g unde r th e southwes t portio n o f th e Main Impoundment

. Capita l Cos t Tim e t o Implemen t Annua l Operatio n an d Maintenanc e Cos t 30-yea r Presen t Wort h Cos t $2,396,00 0

2 year s $85,00 0 

### $3,973,00 0 ALTERNATIV

E 2C: Simpl e Soil Cove r (Alternat e Surfac e Wate r Channe l Alignment)

. Thi s alternativ e include s th e followin g components : (1 ) th e applicatio n o f sourc e surfac e control s t o th e impounde d tailing

, consistin g o f regrading

, placemen t o f a simpl e soi l cover, an d vegetatin g th e covere d surface ; (2 ) surfac e wate r controls

, includin g re-channelizatio n
o f Californi a Gulc h throug h th e souther n portio n o f th e Main Impoundmen t

(bu t constructe d furthe r t o th e nort h tha n i n Alternativ e 2A ) an d constructio n o f diversio n ditche s t o provid e surfac e wate r run-o n an d run-of f controls ; an d (3 ) institutiona l control s (a s describe d i n Alternativ e 2A)

. Capita l Cos t Tim e t o Implemen t Annua l Operatio n an d Maintenanc e Cos t 30-yea r Presen t Wort h Cos t $2,555,00 0

3 year s $85,00 0 $4,127,00 0 ALTERNATIV

E 3A : Soil Cover wit h Geosyntheti c Barrier

. Thi s 'alternativ e include s th e followin g components : (1 ) th e applicatio n o f source surfac e control s t o th e impounde d tailing

, consistin g o f regrading

, placemen t o f a multi-laye r composit e
cover, an d vegetatin g th e covere d surface ; (2 ) surfac e wate r controls

, includin g re-channelizatio n o f Californi a Gulc h throug h th e souther n portio n o f th e Mai n Impoundmen t an d constructio n
o f diversio n ditche s t o provid e surfac e water run-o n an d run-of f controls ; an d (3 ) institutiona l control s (a s describe d i n Alternativ e 2A)

. Capita l Cos t Tim e t o Implemen t Annua l Operatio n an d Maintenanc e Cos t 30-yea r Presen t Wort h Cos t $2,504,00 0

2 year s

. $85,00 0 $4,078,00 0 ALTERNATIV

E 3B : Soi l Cover wit h Geosyntheti c Barrier
an d Groundwate r Controls

. Thi s alternativ e include s th e followin g components : (1 ) th e applicatio n o f source surfac e control s t o th e impounde d tailing

, consistin g o f regrading

, placemen t o f a multi-laye r composit e cover , an d vegetatin g the
covered surface ; (2 ) surfac e wate r controls

, includin g re

channelizatio n o f Californi a Gulc h throug h th e souther n portio n
o f th e Main Impoundmen t an d constructio n o f diversio n ditche s t o provid e surfac e water run-o n an d run-of f controls ; (3 ) institutiona l control s (a s describe d i n Alternativ e 2A) ; an d (4 ) groundwate r control s intende d t o reduc e th e potentia l fo r contac t betwee n th e alluvia l groundwate r an d th e base o f th e tailin g unde r th e southwes t portio n o f th e Main Impoundment

. Capita l Cos t Tim e t o Implemen t Annua l Operatio n an d Maintenanc e Cos t 30-yea r Presen t Wort h Cos t $2,845,00 0

2 year s $85,00 0 $4,409,00 0 ALTERNATIV

E 3C : Soi l Cover wit h Geosyntheti c Barrier (Alternat e Surfac e Wate r Channe l Alignment)

. Thi s alternativ e include s th e followin g components : (1 ) th e applicatio n o f sourc e surfac e control s t o th e impounde d tailing

, consistin g o f regrading

, placemen t o f a multi-laye r composit e
cover, an d vegetatin g th e covered surface ; (2 ) surfac e wate r controls

, includin g re-channelizatio n o f Californi a Gulch throug h t h e souther n portio n o f th e Mai n Impoundmen t (bu t constructe d

'Word s show n i n bol d italic s ar e define d i n th e glossar y a t th e en d o f th e document

.furthe r t o th e nort h tha n in Alternativ e 3A ) an d constructin g diversio n ditche s t o provid e surfac e wate r run-o n an d run-of f —controls ; an d (3 ) institutiona l control s (a s describe d i n Alternativ e 2A)

. Capita l Cos t Tim e t o Implemen t Annua l Operatio n an d Maintenanc e Cos t 30-yea r Presen t Wort h Cos t $3,003,00 0

3 year s $85,00 0 $4,563,00 0 ALTERNATIV

E 4A : Remova l an d On-Sit e Consolidation

. Thi s alternativ e entail s th e complet e remova l o f tailin g materia l fro m th e Mai n an d Nort h Impoundment s an d transportin g thi s materia l t o a n on-sit e consolidatio n area

. Potentia l consolidatio n sit e is th e Malta Gulc h Tailin g Impoundmen t (locate d i n OU2)

, locate d abou t 2 mile s wes t o f Apach e Tailin g Impoundmen t area

. Significan t improvement s o f th e Malt a Gulc h Tailin g Impoundmen t wil l b e require d prio r t o placemen t o f materia l fro m th e Apach e Tailin g Impoundment

. A simpl e vegetate d soil

cove r (as describe d unde r Alternativ e 2A ) woul d be constructe d

ove r th e consolidate d tailing

. Fencing an d signag e t o contro l

acces s t o th e wor k area s wil l b e used

. Capita ! Cos t Tim e t o Implemen t Annua l Operatio n an d Maintenanc e Cos t 30-yea r Presen t Wort h Cos t $11,204,00 0

3 year s $85,00 0 $12,060,00 0 ALTERNATIV

E 4B : Remova l wit h Disposa l i n an On-Sit e Repository

. Thi s alternativ e entail s th e complet e removal o f tailin g materia l fro m th e Mai n an d Nort h Impoundment s an d transportin g thi s materia l t o a ne w repositor y locate d withi n th e Californi a Gulc h Superfun d Sit e boundary

. Th e propose d repositor y i s locate d in uppe r Orego n Gulch

, abov e (southeast ) t h e Orego n Gulc h Tailin g Impoundment

. Thi s locatio n is outsid e
o f OU1 0 (Orego n Gulch ) an d withi n th e overal l boundar y fo r OU 9 (Residentia l Populate d Area)

, however

, th e are a i s withi n Lak e Count y Industria l & Minin g zonin g district

. Followin g relocatio n an d placemen t o f th e tailing i n th e repository
, th e are a woul d b e covered wit h a multi-laye r cove r (a s describe d unde r Alternativ e 3A)

. Fencin g an d signag e t o contro l acces s t o th e
wor k area s wil l b e used

. Capita l Cos t $12,491,00 0 Tim e t o Implemen t 3

year s Annua l Operatio n an d Maintenanc e Cos t $85,00 0 30-yea r Presen t Wort h Cost____________$13,177^00 0 

## CRITERI A T O EVALUAT E CLEANU P

- OPTION

S

T h e abov e alternative s wer e evaluate d in detai l usin g th e nine criteri a identifie d i n the National Contingency Plan (NCP). The criteri a ar e summarize d below

. T h e firs t tw o cleanu p evaluatio n criteria
, overal l protectio n o f huma n healt h an d th e environment
, an d complianc e wit h Applicable or Relevant and Appropriate Requirements (ARAR),

ar e threshol d criteria tha t must b e met b y the selecte d remedia l action

. Th e remainin g criteri a ar e use d t o hel p selec t th e preferre d remedy

. N C P Evaluatio n Criteri a 1

. Overal l protectio n o f human healt h an d th e environmen t addresse s whethe r o r no t a remed y provide s adequat e protectio n
an d describe s ho w risk s pose d throug h eac h pathwa y ar e eliminated

, reduced

, o r controlled

. 2

. Complianc e wit h ARARs addresse s whethe r or not a remed y wil l mee t al l Federa l an d Stat e environmenta l law s and/o r provid e ground s fo r a waiver

. 3

. Long-ter m effectivenes s an d permanenc e refer s t o th e abilit y
o f a remed y t o provid e reliabl e protectio n o f human healt h an d th e environmen t ove r time

. 4

. Reductio n o f toxicity
, mobility

, o r volum e throug h treatmen t refer s t o th e preferenc e fo r a remed y tha t reduces healt h hazards

, th e movemen t o f contaminants
, o r th e quantit y o f contaminant s


### a t th e sit e throug h treatment

. 5

. Short-ter m effectivenes s addresse s th e perio d o f tim e neede d t o complet e th e remed y an d an y advers e effect s t o human healt h

an d th e environmen t tha t ma y b e cause d durin g th e constructio n ari d implementatio n o f th e remedy

. 6

. Implementabilit y refer s t o th e technica l an d administrativ e feasibilit y o f th e remedy

, including th e availabilit y o f material s

and service s neede d t o carr y ou t th e remed y and coordinatio n o f Federal

, State

, an d loca l government s t o wor k togethe r t o clea n
u p th e site

. 7

. Cos t evaluate s the^stimate d capita l an d operatio n an d maintenanc e cost s o f eac h alternativ e i n compariso n t o other

, equall y protectiv e measures

. 8

. State acceptanc e indicate s whethe r th e Stat e agree s with

, opposes
, or ha s n o comment on th e preferre d alternative

. 

### 9

. Communit y acceptanc e include s determinin g whic h component s o f th e alternative s intereste d person s in th e communit y support
, hav e reservations about

, o r oppose

. (Thi s assessmen t wil l no t be complete d unti l publi c comment s o n th e Propose d Pla n ar e received.).__________________

_

'Word s shown in bol d italic s ar e define d in th e glossar y a i th e en d o f th e document

.

## COMPARISO N

O F ALTERNATIVE S

Tabl e 1 provide s a compariso n o f the remedia l action alternatives based o n seve n o f th e nin e NC P criteria

. Th e communit y acceptanc e criteri a evaluatio n wil l no t be complete d until comment s o n thi s Propose d Pla n ar e received

. Evaluatio n o f th e 

### overal l protectio n o f huma n healt h and the environmen t i s based 

### primaril y o n th e predicte d abilit y o f th e alternative s t o achiev e t h e followin g RAO s define d fo r impounde d tailing s i n th e SFS :

• Contro l airborn e transpor t o f tailing particles

. • Contro l erosio n o f contaminate d tailing s an d depositio n int o loca l wate r courses

. • Contro l leachin g an d migratio n o f metal s fro m tailing s int o surfac e water

. • Contro l leachin g an d migratio n o f metal s fro m tailing s int o groundwater

. T o compl y wit h th e requirement s o f t h e NCP

, a N o Actio n Alternativ e wa s establishe d as th e firs t optio n i n orde r t o compar e the benefit s and cost s o f the remainin g eigh t alternatives

. A s show n in Tabl e 1
, Alternative s 2A throug h 4 B woul d compl y wit h RAOs

, whic h essentiall y includ e eliminatin g airborn e transpor t o f tailin g an d th e potentia l fo r direc t contact wit h precipitatio n an d surfac e wate r runoff

. However

, th e potentia l contact
, o r som e interaction
, wit h surfac e wate r flowing i n th e constructe d Californi a Gulc h channe l alignmen t considere d unde r Alternative s 2 C an d 3 C ma y b e slightl y highe r tha n th e alignmen t considere d unde r Alternative s 2 A and 3 A due t o it s positio n relativ e t o th e base o f tailing

. Alternative s 3A

, 3B

, 3C

, an d 4 B (soi l cove r wit h geosyntheti c barrier ) woul d provid e a highe r leve l o f infiltratio n reductio n int o th e tailin g impoundmen t tha n Alternative s 2A

, 2B

, 2C

, an d 4 A (simpl e soi l cover)

. Alternative s 2
, 3 an d 4 woul d compl y wit h al l ARARs

. Alternative s 2,3
, an d 4 wer e assesse d t o b e effectiv e an d reliabl e becaus e o f sourc e contro l o r remova l actions

. Institutiona l control s fo r Alternative s 2 an d 3 woul d ensur e permanenc e o f the remedy

. Alternative s 2 B and 3 B woul d provid e essentiall y
n o enhancemen t o f long-ter m effectivenes s b y incorporatin g groundwate r controls

. Th e channel embankmen t slope s woul d b e slightl y les s stabl e unde r Alternative s 2 C an d 3C

. T h e predicte d reductio n in metal s loadin g t o groundwate r wer e calculate d fo r eac h alternativ e an d ar e summarize d i n Tabl e 1

. T h e reductio n i n metal loadin g was calculate d b y comparin g existin g condition s (i.e.

, prio r t o remova l o f Tailin g Pond s Nos

. 2 and 3 ) t o predicte d condition s fo r eac h alternative

. Alternative s 4 A an d 4 B havin g th e greates t reductio n followe d closel y b y Alternative s 3A

, 3B

, an d 3C

. Non e o f th e alternatives

, however

, woul d reduc e th e toxicit y o r volum e o f tailing

. T h e short-ter m effectiveness

, based o n disturbanc e durin g implementation

, woul d b e moderat e for Alternative s 2A

, 2B

, 3A

, 

### an d 3 B becaus e o f ris k due t o regradin g tailing

. Alternative s 2 C

and 3 C woul d hav e a low t o moderat e short-ter m effectivenes s du e t o risks durin g regradin g tailing an d workin g i n we t tailin g material

. Alternative s 4A and 4 B woul d pos e th e greate r short

ter m ris k durin g remova l an d transportatio n o f tailing

. Alternativ e 1 woul d no t hav e an y disturbance

. Alternative s 2 an d 3 ar e administrativel y implementable

, however

, obtainin g acces s fro m th e curren t propert y owner s ma y b e difficult

. Alternative s 2A and 3 A ar e mos t readil y implementable

. Alternative s 2 B an d 3 B presen t additiona l constructio n challenge s fo r th e groundwate r control system

. Alternative s 2 C an d 3 C hav e additiona l difficultie s associate d wit h channelin g Californi a Gulc h furthe r nort h an d requir e excavatin g int o th e deepes t portio n o f th e Mai n Impoundment

. Alternative s 4 A and 4 B woul d b e the mos t difficul t t o implemen t due t o excavatin g and transportin g a larg e volum e o f materia l i n additio n t o preparin g cooperativ e agreement s wit h owner s o f th e consolidatio n o r repositor y site

. T h e cos t estimate s range fro m zer o fo r N o Actio n (Alternativ e 1 ) t o $13,177,00 0 fo r Alternativ e 4B

. 

## RATIONAL E FO R ALTERNATIV E 3 A 

## A S TH E PREFERRE D ALTERNATIVE
E P A has selecte d Alternativ e 3 A (Soi l Cove r wit h Geosyntheti c Barrier ) a s th e preferre d alternative

. / A s required

, Alternativ e 3 A meet s th e threshol d cleanu p evaluatio n criteria (overal l protectio n o f human healt h an d th e environment
, an d complianc e wit h ARARs)

. /Alternativ e 3 A provide s ver y goo d long-ter m effectivenes s an d permanence

. /Alternativ e 3 A eliminate s airborne transpor t o f tailin g particle s
an d minimize s bot h th e erosio n o f tailing an d depositio n int o loca l wate r sources

. /Alternativ e 3 A control s th e risk s (define d b y th e ris k assessment ) including ingestio n o f surfac e tailin g b y wildlife

, contrac t o f plant s an d soi l faun a wit h surfac e tailing

, an d ingestio n o f surfac e wate r b y wildlife

. /Alternativ e 3 A i s readil y implementable

. Th e remediatio n technologie s selecte d fo r thi s alternativ e hav e bee n successfull y employe d a t othe r Superfun d sites

. Based o n this reasoning
, the EP A propose s Alternativ e 3 A a s the preferre d alternativ e fo r OU7

.

'Word s shown i n bol d italic s ar e define d i n th e glossar y a t th e en d o f th e document

.TABL E 1 1 COMPARISO N O F ALTERNATIVE S

FO R TH E APACH E TAILIN G IMPOUNDMEN

T OU 7 - NC P CRITERI A

Evaluatio n Criterio n Overal l Protectio t

o f Huma n Healt h

an d th e Environmen t Complianc e wit h ARAR s Long-Ter m Effectivenes s an d Permanenc e Reductio n o f Toxicity

, Mobility

, o r Volum e throug h Treatmen t (se e Not e 1 ) Short-Ter m iffectivenes s

Implementabilit y

Cos t N

o Actio n

Alternativ e 1 N o t protectiv e o f huma n healt h and the environmen t Doe s not compl y wit h ARARs N o long-ter m decreas e i n loadin g t o groundwate r Minima l reductio n (16% )

o f mobility

. N o reductio n o f toxicit y o r volum e N o short-ter m reductio n i n ris k

Readil y Implementabl e

$ 0 Simpl

e Soi l Cove r Alon e

Alternativ e 2A Protective

, woul d

mee t RAO s fo r impounde d tailin g Complie s wit h ARARs Ver y goo d long

ter m effectivenes s an d permanenc e Mobilit y reduce d b y abou t 88%

. N o reductio n o f toxicit y o r volum e Moderat e short

ter m effectivenes s du e t o ris k durin g regradin g Goo d t o moderat e implementability

, excavatio n an d

acces s considerations S3.642.00 0 Wit

h Groundwate r Control s Alternativ e 2 B Protective

, woul d

mee t RAO s fo r impounde d tailin g Complie s wit h ARAR s Ver y goo d long

ter m effectivenes s
an d permanenc e Mobilit y reduce d b y abou t 88%

. N o reductio n o f toxicit y o r volum e

Moderat e short

ter m effectivenes s due t o ris k durin g regradin g

Moderat e technica l implementability ; difficul t trenchin g due t o dept h requirement s

$3,973,00 0 Alternativ e

Channe l Alignmen t Alternativ e 2 C Protective

, woul d

mee t RAO s fo r impounde d tailin g Complie s wit h ARARs Goo d long-ter m effectivenes s an d permanenc e Mobilit y reduce d b y abou t 88%

. N o reductio n o f toxicit y o r volume
Low short-ter m effectivenes s du e t o ris k durin g regradin g an d workin g wit h we t tailin g Moderat e t o low implementability

, d u e t o difficultie s excavatin g an d workin g wit h larg e volum e o f

wet tailin g $4,127,00 0 Multi-Laye r Cove r Alon e

Alternativ e 3 A Protective

, woul d

mee t RAO s fo r impounde d tailin g Complie s wit h ARAR s Ver y good long

ter m effectivenes s
an d permanenc e Mobilit y reduce d b y abou t 96%

. N o reductio n o f toxicit y o r volum e

Moderat e short

ter m effectivenes s due t o ris k durin g regradin g

Goo d t o moderat e implementability

, excavatio n an d

acces s consideration s

$4,078,00 0 Wit

h Groundwate r Control s Alternativ e 3 B Protective

, woul d

mee t RAO s fo r impounde d tailin g Complie s wit h ARAR s Ver y good long

ter m effectivenes s
an d permanenc e Mobilit y reduce d b y abou t 96%

. N o reductio n o f toxicit y o r volum e

Moderat e short

ter m effectivenes s due t o ris k durin g regradin g

Moderat e technica l implementabilit y ; difficult trenchin g du e t o dept h requirement s
$4,409,00 0 Alternativ e

Channe l Alignmen t Alternativ e 3 C Protective

, woul d mee t RAO s fo r impounde d tailin g Complie s wit h ARAR s Goo d long-ter m effectivenes s an d permanenc e Mobilit y reduce d b y about 96%

. N o reductio n o f toxicit y o r volum e
Low short-term effectivenes s du e t o ris k durin g regradin g
an d workin g wit h we t tailing

Moderat e t o lo w implementability

, du e t o difficultie s excavatin g an d workin g wit h larg e volum e o f we t tailin g
$4,563.00 0 Remova l Wit h On-sit e Consolidatio n Alternativ e 4 A Protective

, woul d

mee t RAO s fo r impounde d tailin g Complie s wit h ARARs Ver y good long-ter m effectivenes s an d permanenc e Mobilit y reduce d b y abou t 96%

. N o reductio n o f toxicit y
o r volum e
Low short-term effectivenes s du e t o ris k durin g remova l

an d transport
, highe r potentia l fo r release s
an d increased duratio n Difficultie s associate d wit h larg e volume

, excavation / wate r handling

, an d developmen t o f consolidatio n sit e
$12,060,00 0 Deposit

i n On-sit e Repositor y Alternativ e 4 B Protective

, woul d

mee t RAO s fo r impounde d tailin g Complie s wit h ARAR s Ver y good long

ter m effectivenes s
an d permanenc e Mobilit y reduce d b y abou t 96%

. N o reductio n o f toxicit y o r volum e

Low short-ter m effectivenes s du e t o ris k durin g remova l

an d transport
, highe r potentia l fo r release s an d increased duratio n Difficultie s associate d wit h larg e volume

, excavation/wate r handling

, and developmen t o f repositor y sit e $13,177,00 0 Notes : 1

. Existin g conditions : prio r t o remova l o f Tailing Pond s Nos

. 2 and 3

.

## ACRONYM S

ARA R Applicable o r Relevan t an d Appropriat e Requirement s Asarc o ASARC O Incorporate d C D Consen t Decre e CDPH E Colorad o Departmen t o f Publi c Healt h an d Environmen t CERCL A Comprehensiv e Environmenta l

Response

, Compensation

, an d Liabilit y Ac t o f 198 0 E P A U.S

. Environmenta l Protectio n Agenc y E R A Ecologica l Ris k Assessmen t F F S Focuse d Feasibilit y Stud y mg/k g Milligram s pe r kilogram s N C P Nationa l Contingenc y Pla n OU 7 Operabl e Uni t 7 P R P Potentiall y Responsibl e Part y R A O Remedia l Actio n Objectiv e R I Remedia l Investigatio n RO D Recor d o f Decisio n R P M Remedia l Projec t Manage r SAR A Superfun d Amendment s an d Reauthorizatio n Ac t o f 198 6 S F S Site-Wid e Screenin g Feasibilit y Stud y 

## GLOSSAR Y

Administrativ e Record : The bod y o f document s EP A use s t o for m th e basi s o f selectio n o f a response

. Alternative : A n optio n fo r reducin g sit e ris k b y cleanin g u p o r otherwis e limitin g exposur e t o contamination

. Applicabl e o r Relevant an d Appropriat e Requirement s (ARAR) : Federa l an d stat e requirement s fo r cleanup

, control

, an d environmenta l protectio n tha t a selecte d remed y fo r a sit e wil l meet

. Baseline Huma n Healt h Ris k Assessment : A CERCL A stud y conducte d a t th e sam e tim e a s th e R I (and containe d i n th e R I report ) that determine s an d evaluate s ris k tha t sit e contaminatio n pose s t o human healt h i n th e absence o f remedia l action

. Capita l Costs : Expense s relate d t o th e labor

, equipmen t an d materia l cost s o f construction

. Comprehensiv e Environmental

Response

, Compensation

, an d Liabilit y Ac t (CERCLA) : A Federa l la w passe d i n 198 0

an d modifie d i n 198 6 b y th e Superfun d Amendment s an d Reauthorizatio n Act

. I t set s u p a progra m t o identif y site s wher e hazardous substanc e hav e been

, o r migh t be

, release d int o the environmen t and t o ensure the y ar e cleane d up

. Mos t o f thes e site s ar e abandone d o r ar e n o longe r active

. Consen t Decre e (CD) : A lega l agreement betwee n EP A an d

on e o r mor e potentiall y responsibl e partie s tha t specifie s th e obligation s t o perfor m an d pa y fo r respons e actions

. Focuse d

Feasibilit y Stud y (FFS) : Th e FF S identifie s an d evaluate s th e most appropriat e technica l approache s t o addres s contaminatio n problem s a t a Superfun d site

. Loading : Mas s concentratio n o f contaminant s in th e surfac e wate r o r groundwater

, whic h result s fro m surfac e wate r an d groundwate r contac t wit h contaminate d media

. Nationa l Contingency Pla n (NCP) : Th e EPA' s regulation s governin g al l cleanup s unde r th e Superfun d program

. Nationa l Prioritie s List : EPA' s lis t o f th e mos t seriou s uncontrolle d o r abandone d hazardous wast e site s identifie d fo r possibl e long-ter m remedia l response

. Operatio n an d Maintenanc e Cost : Th e cos t an d tim e fram e o f operatin g labor

, maintenance
, materials

, energy, disposal

, an d administrativ e activitie s o f th e remedy

. Potentiall y Responsibl e Party : Thos e identifie d b y EP A as potentiall y liabl e unde r CERCL A fo r cleanu p costs

. 30-Yea r Presen t Wort h Cost : A n analysi s o f th e curren t valu e
o f al l costs

. Als o known a s Ne t Presen t Worth

, th e Present Wort h Cos t i s calculate d base d o n a 30-yea r tim e perio d an d a predetermine d interes t rate

. Propose d Plan : A documen t requestin g publi c inpu t o n a propose d remedia l alternative

. Recor d o f Decisio n (ROD) : A documen t whic h i s a consolidate d sourc e o f informatio n abou t th e site
, th e remed y selectio n process
, an d th e selecte d remed y fo r a cleanu p unde r CERCLA

. Remedia l Actio n Objective s (RAO) : Medium-specifi c (e.g

. groundwater

, tailings ) goal s fo r protectin g human healt h an d th e environment

. Remedia l Investigatio n (RI) : A stud y conducte d t o identif y th e types
, amounts
, an d location s o f contaminatio n a t a facility

. I t als o evaluate s possibl e ris k t o publi c healt h an d th e environmen t fro m exposur e t o contamination

. Remova l Action : Th e cleanu p o r remova l o f release d hazardous substance s fro m th e environment

. Superfun d Amendment s an d Reauthorizatio n

Ac t (SARA) : Modification s t o CERCL A enacte d o n Octobe r 17
, 1986

. Tailing : Deposite d wast e materia l fro m millin g operation s o f mine d ores

.

'Word s shown in bol d ilalic s ar e define d in ih e glossar y a t (h e en d o f th e document

.