A p a c h e T a i l i n g I m p o u n d m e n t sOperable Unit 7Proposed Plan

Public Mee t ingJ a n u a r y 25, 2000

P R E S E N T A T I O N P A C K E TPrepared by:

Asarco I n c o r p o r a t e d130 Wes t 9 th Stre e t 495 East 51 s t Ave.L e a d v i l l e , CO 80461 Denver, CO 80216

M A S A f i C Oc o n s u l t i n gs c i e n t i s t s a n de n g i n e e r s

Color MapThe f o l l o w i n g map containscolor that does not appear on

scanned image.

• DenverGeorgetown

D E N V E R A N D R I O G R A N O EW E S T E R N

C A N T E R B U R Y T U N N E L

J

L E A D V I L L E D R A I N A G E T U N N E LEvens G u l c h

S t r a y H o r s e G u l c hS t o r r Dit chO U 7 - A P A C J ^ E T A I L I N G SY / K T U N N E L

C A L I F O R N I A G U L C H

C A L I F O R N I A G U L C H .S U P E R F U N D S I T E B O U N D A R YN

A S A R C OO U 7 - A P A C H E T A I L I N G SF I G U R E 1 - 1G E N E R A L S I T EL O C A T I O N M A P

P R O J E C T : 5344.4 D A T E : S E P T E M B E R 1 9 9 9B Y : S C G I C H E C K E D : D L L

M F C , I n c .consulting scientists and engineers

R I / F S P R O C E S S F O R O P E R A B L E U N I T 7S u p e r f u n d L i s t i n g

1983

S i t e - W i d e R e m e d i a lI n v e s t i g a t i o n s ( R l )1991-1993

Consent Decree1994i

D r a f t F e a s i b i l i t y S t u d y1996

S u p p l e m e n t a l I n v e s t i g a t i o n & E v a l u a t i o n ,I n t e r i m R l & F S S u b m i t t a l s1997-1999

Removal A c t i o n s1997 & 1999

F i n a l F o c u s e d F e a s i b i l i t y S t u d y2000

Propo s ed P l a n / P u b l i c Comment2000

Record of Decision (ROD)2000

Remedia l A c t i o n2000-2001 A S A f i C O

S i t e Descr ip t ionT a i l i n g I m p o u n d m e n t s

• Four distinct tai l ing impoundments• Main Impoundment:

11.3 acres- 630,000 cy

maximum thickness of 50 ft• N o r t h Impoundment:

1.8 acres- 14,500 cy

maximum thickness of 12.5 ft• T a i l i n g Ponds 2 and 3:

2.0 acres total- 41,200cy- 6 to 14 ft thick ASARCO

S i t e Descript ion (cont.)S u r f a c e Water• C a l i f o r n i a Gulch channel below Main

Impoundment ta i l ing via two 24-inch clay-t i l e culverts

• W o o d e n box culvert drains upgradientsurface water

• Starr Ditch conveys runo f f from StrayHorse Gulch and east L e a d v i l l e

Groundwater• Pore water within ta i l ing• Alluv ia l aquifer - in unconsol idated

sedimentary d e p o s i t s beneathimpoundments

• Bedrock aquifer - in conso l idated bedrock• Numerous springs in area

A S A f i C O

Color MapThe f o l l o w i n g map containscolor that does not appear on

scanned image.

Eo.fOo

oooOJoCNI

•<*•nin0*

Oo

o<U (D

N O R T HI M P O U N D M E N TJS , — T - —-JIOHOJO'

T A I L I N G S ) P O N D, N O . 3( R E M O V E D ) L I N G S P O N Dwn

1 T M W T I SA P 1 T M W 1

PAVEO ROADGRAVEL ROAD

W A T E RB U U H N G / S T R U C T U R EPOUER POLE

E X P L A N A T I O NS U R F A C E W A T E R S A U P t l L O C A T I O NCKOUNOWATER UOMTOR1NC 1KU.

SOn.BO«NGU I N I - R E Z O U E T E RP I E Z O U E T E R L O C A T I O N

A S A R C OO U 7 - A P A C H E T A I L I N G SS I T E M A POPERABLE U N I T 7A P A C H E T A I L I N G S I M P O U N D M E N T

P R O J E C T : 5344.4REV:

D A T E : J A N U A R Y 2000B Y : J M K | C H E C K E D :M F C , I n c .consulting scientists and engineers

Summary of RemedialInve s t i ga t i on s

Objec t ive - evaluate the nature andextent of contaminationCharacterization of sources,groundwater, and surface water1 Act iv i t i e s :

groundwater s a m p l i n g / a n a l y s i sgroundwater level monitoringgeotechnical t e s t ingsurface water s a m p l i n g / a n a l y s i sgeochemical t e s t ing/ana ly s i spond water s a m p l i n g / a n a l y s i sr a i n f a l l - r u n o f f s a m p l i n g / a n a l y s i s1 S u r f a c e water and groundwater mass

load ing analyses to i d e n t i f y sourcesASARCO

RI SummaryMain Impoundment (MI):

acid-generating at and near surfaceacid-neutralizing at base

North Impoundment ( N I ) :high ly acid-generating t a i l i n ghigh i n f i l t r a t i o n

T a i l i n g Ponds N o s . 2 and 3 (TP2/3)high ly acid-generating t a i l i n gremoved in 1997

Groundwater loading mechanisms:r u n o f f f r om MI embankmentspercolat ion through T P 2 / 3perco la t ion through NI ta i l ing

ASARCO

RI SummaryS u r f a c e Water• F l o w / l o a d s vary seasonal ly and

yearly• Loads predominantly f rom

upstream i n f l o w s• Load ing f rom springs

downgradient o f TP2/3decreased sub s tant ia l ly a f t e rta i l ing removal in 1997

A S f l f i C O

Removal Act ions1997-1999

1997• Removed T a i l i n g Pond N o s . 2 and 3• B a c k f i l l e d / r e g r a d e d excavation areas• Regraded unstable area and p laced

rock protec t ion along toe of SWs l o p e of Main Impoundment

1999• Regrading/p lac ement of pre-load f i l lon southern portion of Main

Impoundment• I n s t a l l e d wick drains in pre-load fill

area• Placed fil l over N o r t h Impoundment

ASARCO

Remedial Act ionOb j ectives

Control airborne transport oft a i l i n g par t i c l e sControl erosion of t a i l i n gmaterials and d epo s i t i on intolocal water coursesControl leaching and migrationof metals from ta i l ing intosurface waterControl leaching and migrationof metals f rom ta i l ing intogroundwater ASARCO

Cul tura l ResourcesCons idera t i on s

Two resources ( s i t e s) evaluated:Apache M i l l / T a i l i n g P i l eP o s s i b l e stamp mill

M i l l / t a i l i n g in e l i g i b l e and non-contributingS t a m p mill i s p o t e n t i a l l y e l i g i b l e fornomination to the NHRP, but is notcontributing as a landscape featureData recovery plan submitted toS H P OImplement Data Recovery Plan andp e r f o r m mit igat ion, i f necessary,prior to disturbance ASARCO

Remedial ActionAlt erna t iv e s

• #1: No Action• #2A: S i m p l e S o i l Cover• #2B: #2A + Groundwater Contro l s• #2C: #2A with A l t . Channel Alignment> #3A: S o i l Cover with Geosynthet ic Barrier• #3B: #3 A + Groundwater Contro l s• #3C: #3 A with A l t . Channel Alignment• #4A: Removal/On-Site Con so l i da t i on• #4B: Removal/Placement in Reposi tory

> Preferred Alternative A S f f i G O

Alternat ive #1N o Action

No further cleanup orremediationNo action provides a baselinefor comparison of otheralternatives

ASARCO

Alterna t iv e #2AS i m p l e Soi l Cover

> Regrade impoundment surface andembankment

> Excavate channel for C a l i f o r n i aGulch to carry 500-year f l o o d event

> Create a s ingle combined t a i l i n g area• Place 18" cover soil over 6" coarse

sand and 12" compacted ta i l ing s> Revegetate capped surface> Construct run-on diversion ditches> Evaluate e f f e c t i v e n e s s via

monitoring program> Common to all in-place closure alternatives

A S A f i C O

G E O S Y N T H E T I C C L A Y L I N E R ,K = 3 . 0 X I D ' 9 C M / S E C G E O N E T O R S I M I L A R

D R A I N A G E M A T E R I A L ,K = 1 C M / S E C

- T A I L I N G M A T E R I A L r ' - - * . ~ - ' ~ \ ' - ' ,' 4" ^

A L T E R N A T I V E 3 : M U L T I - L A Y E R C O V E R S E C T I O N

3%. 5:L OR 3:1 SLOPE ^6 " S A N D L A Y E R . K = 1 0 ~ 2

C M / S E C

' , - , . , .' , M ; ' " : ( , x x v x J A I L I N G M A T E R I A L " ^ . 0 ' ^ ' ' , / / ' - 1 - ' " > ^ /

l v^ - > j \ ' • ~ - i • - i . o-̂ . % \ i

-x-~ . ' - - - . V . ' - V " ^ x / ' - V - J - .;•>.•,-"- .^V--^* ' " - { - . . " ' " " ' ' - X V - " v X J ~ i - ' - ' ^ '- r.^ ,.r, ̂ .:- - ; r ^ , N / ^ . 7 ?^:v;v ^ A ' ^ f l v - 1

A L T E R N A T I V E 2 : S I M P L E S O I L C O V E R S E C T I O NN O T E :

1 . T H I S D R A W I N G I S N O T T O S C A L E . A P A C H E T A I L I N G S I M P O U N D M E N T

A L T E R N A T I V E COVERS E C T I O N SP R O J E C T : 5344.4REV:

D A T E : S E P T E M B E R 1999B Y : C A A | C H E C K E D : F L C

M F C , I n c .consulting scientists and engineers

Color MapThe f o l l o w i n g map containscolor that does not appear on

scanned image.

E5 i \

POND NO. 2

APCROXIWATE LOCAOf RE-CONSTRUCTED500-YEAR C A L I F O R N I A

ooB555ii iuE"ot^~Oo_oX Q _

E X P U N A H O NS U R F A C E W A T E R S A M P L E L O C A T I O NG R O U N O W A T E R M O N I T O R I N G W E L LS O I L B O R I N GM I N I - P I E Z O M E T E RP I E Z O M E T E R L O C A T I O N

A-i-PAVED ROADGRAVEL ROADW A T E RB U I L D I N G / S T R U C T U R EPOWER POLE

A S A R C OA P A C H E T A I U N G S I M P O U N D M E N TALTERNATIVES 2A, 2B, 3A, & 3B:R E G R A D I N G P L A N

P R O J E C T : 5344.4REV:

D A T E : J A N U A R Y 2000B Y : J M K | C H E C K E D :M F G , Inc.consulting scientists and engineers

T E M P O R A R YH A U L ROAD

T E M P O R A R YH A U L R O A D S . : . : ; :

G U U C HT A I L I N G I M P O U N D M E N T

A S A R C OO U 7 - A P A C H E T A I L I N G SCOVER S O I LBORROW AREA

P R O J E C T : 5344.4 D A T E : J A N U A R Y 2000B Y : J M K j C H E C K E D :M F G , I n c .

consulting scientists and engineers

A l t e r n a t i v e s #2B & 2C•2B: S i m p l e S o i l Cover with

Groundwater Contro l s• Same as Alternative #2A, with

addi t i on of groundwater controls• I n s t a l l trench drain immediate ly

downgradient of Main Impoundment•2C: S i m p l e Soil Cover with

Channel Alignment• Same as Alternat ive #2A, with

alternate channel alignment• Construct channel to convey

C a l i f o r n i a Gulch farther to the north

A S A f i C O

P l o t t i m e : 12:30 p mP l o t d o t e : 01-21-2000 J M K D:\5344\5344-283.dwg 01-20-2000 01:44 p m

l i• i

S 5I §

D f

|Sir _I P

•yn m

O

OJO

IIo

A L T E R N A T I V E 2 A / 3 A A L T E R N A T I V E 2 C / 3 C

oo E X P L A N A T I O NPAVED ROADGRAVEL ROAO

W A T C RI I

Q_Q.

A S A R C OO U 7 - A P A C H E T A I L I N G SC H A N N E L A L I G N M E N T

2A/3A VS. 2C/3CP R O J E C T : 5344.4R E V :

D A T E : J A N U A R Y 2000B Y : J M K I C H E C K E D :M F C , Inc.

consulting scientists and engineers

Alternat ive #3ASoil Cover with Geosynthet i c

BarrierSame as Alternat ive #2A,except multi-layer cover insteadof s impl e soil coverConstruct multi-layer coversystem, with 18" cover soil overgeo t ex t i l e drainage net andgeosynthetic barrier

A S W C O

Alterna t iv e s #3B & 3C•3B: S o i l Cover with Geosynthe t i c

Barrier with GroundwaterContro l s

• Same as Alternat ive #3A, withaddi t ion of groundwater controls

• I n s t a l l trench drain immediate lydowngradient of Main Impoundment

•3C: Soi l Cover with Geosynthe t i cBarrier with Channel Alignment• Same as Alternative #3 A, with

alternate channel alignment• Construct channel to convey

C a l i f o r n i a Gulch farther to the northASARCO

Alterna t iv e #4ARemoval and On-Site C o n s o l i d a t i o n

• C o m p l e t e l y remove t a i l i n g materialf rom Main and North Impoundment s

• Transpor t material to on-siteconso l idat ion area at the H e c l a( M a l t a Gulch) T a i l i n gImpoundment s (prepare areas f i r s t )

• Cap consol idat ion area with s impl esoil cover

• Regrade excavation area and/orp lac e import material, as needed

• Revegetate consol idat ion site andremoval area

ASAROO

Alternat iv e #4BRemoval and Disposal in On-Site

RepositoryC o m p l e t e l y remove ta i l ing materialf rom Main and N o r t h Impoundment sDevelop new reposi tory in upperOregon Gulch, along with haul roadsand runon/runo f f controlsTranspor t material to new repos i toryCap repository with multi-layercoverRevegetate reposi tory and removalareas

A S f l f i C O

msmu p~\\

oocOC C Na-1L E G E N D :

CM

0) a)E o' ^ " D

~O~C>Q.CL

A L T E R N A T I V E 4 A : P O T E N T I A L R O U T E S T O M A L T A G U L C HA L T E R N A T I V E 4 B : P O T E N T I A L R O U T E S T O O R E G O N G U L C HA P P R O X I M A T E L O C A T I O N O F M I N E R A L B E L T B I K E T R A I L

A S A R C OO U 7 - A P A C H E T A I L I N G SP O T E N T I A L T R A N S P O R T R O U T E S T OC O N S O L I D A T I O N A N D R E P O S I T O R YS I T E SP R O J E C T : 5344.4 D A T E : J A N U A R Y 2000REV: B Y : J M K | C H E C K E D :

M F C , I n c .consulting scientists and engineers

Evaluation CriteriaOverall protec t ion of human healthand the environmentCompliance with ARARsLong-term e f f e c t i v e n e s s andpermanenceReduction of tox ic i ty, mobility., orvolume through treatmentShort-term e f f e c t i v e n e s sI m p l e m e n t a b i l i t yCostS t a t e acceptanceCommunity acceptance

ASARCO

T A B L E 7-1S u m m a r y o f C o m p a r a t i v e A n a l y s i s o f R e m e d i a l A l t e r n a t i v e s

OU7- A p a c h e T a i l i n g s

e v a l u a t i o n C r i t e r i o nDveral l p r o t e c t i o n

of human h e a l t h andthe environment"ompl iance

w i l t iA R A R s

. X M i g - l e r me f f e c t i v e n e s s andpermanenced e d u c t i o n o f

t o x i c i t y , m o b i l i t y ,or volumeS l i o r t - l u r me f f e c t i v e n e s s

nip l cmcn l a b i l i t y

Cost

S t a t eacceptance *

C o m m u n i t yacceptance *

N o Act ionA l t e r n a t i v e #1

Nol p r o t e c t i v e o f humanhealth and theenvironmentDoes not comply withA R A R s

No long-term decreasein loading to groundwater

M i n i m a l reduction (16%)o f m o b i l i t y . N o reduct ionof toxici ty or volumeN o short-term reductionin risk

Readi ly i m p l e m e n t a b l e

$0

S i m p l e S o i l Cover

A l o n eA l t e r n a t i v e #2A

P r o t e c t i v e , would meetRAOs f o r i m p o u n d e d t a i l i n gW o u l d c omply wi th A R A R s

Very good long-termef f e c t iv ene s s andpermanenceM o b i l i t y reduced by 88%.No reduction o f t o x i c i t yor volumeModerate short-term

e f f e c t i v e n e s s due torisk during regrading

Good to moderatemptemen l a b i l i t y ,

excavation and accessconsiderat ions$3,641.883

W i t h Groundwater Contro l sA l t e r n a t i v e #2B

Protec t ive, would meetRAOs for impounded t a i l i n g

W o u l d comply with A R A R s

Very good long-terme f f e c t ivene s s andpermanenceM o b i l i t y reduced by 88%.No reduct ion o f t ox i c i tyor volumeModerate short-terme f f e c t i v e n e s s due torisk during regrading

Moderate technicali m p l e m e n t a b i l i t y ;d i f f i c u l t trenchingdue to large d e p t h

13,973,383

A l t e r n a t e Channel A l i g n m e n tA l t e r n a t i v e #2C

Prot e c t iv e , would meetRAOs f or impounded t a i l i n g

W o u l d c omply wi th ARARs

Good long-termef f e c t ivene s s andperm an en coM o b i l i t y reduced by 88%.No reduction o f t o x i c i t yor volumeLow short-terme f f e c t i v e n e s s due torisk during regradingand working with wett a i l i n gModerate to low

i m p l e m e n t a b i l i t y , due tod i f f i c u l t i e s excavatingand working with largevolume of wet tailings.$4,127,057

M u l t i Layer Cover

A l o n eA l t e r n a t i v e #3 A

Protec t ive, would meetRAOs f o r i m p o u n d e d t a i l i n g

W o u l d c omply wi th A R A R s

Very good long-terme f f e c t i v ene s s andpermanenceM o b i l i t y reduced by 96%.N o reduction o f t o x i c i t yor volumeModerate short-terme f f e c t i v e n e s s due torisk during regrading

Good to moderatei m p l e m e n t a b i l i t y ,excavation and accessconsiderations

$4.077.736

W i t h G r o u n d w a t e r C o n t r o l sA l t e r n a t i v e #3 B

Prote c t iv e , would meetRAOs f o r i m p o u n d e d t a i l i n g

W o u l d c o m p l y with A R A R s

Very good long-terme f f e c t iv ene s s andpermanenceM o b i l i t y reduced by 96%.No reduction o f t o x i c i t yor volumeModerate short-terme f f e c t i v en e s s due torisk during regrading

Moderate technicalm p l e m e n t a b i l i t y ;

d i f f i c u l t trenchingdue to large d e p t h

$4,409.236

A l t e r n a t e Channel A l i g n m e n tA l t e r n a t i v e #3C

Protec t ive , would meetRAOs f o r i m p o u n d e d t a i l i n g

W o u l d c o m p l y wi th A R A R s

Good l o n g - t e r me f f e c t iv ene s s andpermanenceM o b i l i t y reduced by 96%.No reduct ion o f t o x i c i t yor volumeLow short-terme f f e c t i v e n e s s due torisk during regradingand working with wett a i l i n gM o d e r a t e to lowm p l e m e n t a b i l i t y , due to

d i f f i c u l t i e s excavatingand working with largevolume of wet tailings.$4,562,910

Removal

W i t h On-site C o n s o l i d a t i o nA l t e r n a t i v e #4A

P r o t e c t i v e , would meetRAOs f o r impounded t a i l i n g

W o u l d c o m p l y wi th A R A R s

Very good long-terme f f e c t iv ene s s andpermanenceM o b i l i t y reduced by 96%.N o reduc t ion o f t o x i c i t yor volumeLow short-terme f f e c t i v e n e s s due to riskdur ing removal andt r a n s p o r t , higher p o t e n t i a lTor releases and increased

durat ionD i f f i c u l t i e s associated w i t harge vo lume, excavation/

water h a n d l i n g , andd e v e l o p m e n t o fconsolidation site$12,060.100

Depos i t in On-site R e p o s i t o r yA l t e r n a t i v e M4B

Prote c t ive , would meetRAOs f o r i m p o u n d e d t a i l i n g

W o u l d c o m p l y wi th A R A R s

Very good l ong- t erme f f e c t iv ene s s andpermanenceM o b i l i t y reduced by 96%.N o r educ t i on o f t o x i c i t yor volumeLow short-terme f f e c t i v e n e s s due to riskduring removal andtranspor t , higher p o t e n t i a lfor releases and increased

durat ionD i f f i c u l t i e s associated wi tharge volume, excavation/

water h a n d l i n g , andd e v e l o p m e n t o frepository site$13,177.200

N O T E S :A l t e r n a t i v e #1: No A c t i o n (beyond removal of T a i l i n g Ponds Nos . 2 and 3)A l t e r n a t i v e W2A: Cover soil + 6" drainage layer + 12" c o m p a c t e d t a i l i n g s over t a i l i n g sA l t e r n a t i v e #2B: A l t e r n a t i v e #2A p l u s graundwaler c on tro l sA l t e r n a t i v e #2C: Alternat ive #2A with alternate channel alignment for Cal i f orn ia GulchA l t e r n a t i v e / /3A: Cover soi l + dra inage net + geo synthe l i c c lay l i n e r over t a i l i n g sA l t e r n a t i v e #3B: A l t e r n a t i v e #3A p l u s groundwater controlsA l t e r n a t i v e #3C: A l t e r n a t i v e # 3 A with a l t e r n a t e channel a l ignment f o r C a l i f o r n i a G u l c hA l t e r n a t i v e W 4 A : Removal and on-site c on so l ida t i onA l t e r n a t i v e #4B: Removal and d i s po sa l in an on-site r epo s i t o ry* T h o s e criteria w i l l be eva lua t ed a f t e r the p u b l i c comment period.

J : \ 5 3 4 4 \ 5 3 4 4 - 4 \ F S \ T A B 7 - 1 .WB2 Page 1 of 1 M F G . I n c .

Propos ed PlanAlternat ive #3A

Soil Cover withGeosynthe t i c Barrier

f l S f l f i C O

Alternat iv e #3A -Propos ed Plan

Provides overall protec t ion of humanhealth and the environmentAchieves RAOsC o m p l i e s with ARARsProvides permanence and long-terme f f e c t i v e n e s sCan be implemented with standardt echnologie sReduces exis t ing metal l oad ing tosurface water and groundwaterEliminates risk to terrestrialecosystem ASARCO

Cost SummaryAlternat ive #3A• Estimated C a p i t a l Cos t s

$2,504,000• Annual O&M Cos t s

$85,000• F i v e - Y e a r Review Cos t s

$41,500• T o t a l Present Worth

$4,078,000ASARCO

OU7 S c h e d u l e of WorkI n i t i a t e construction in 2000

Anti c ipa t ed comple t ion in2001

ASARCO