PROPOSED PLAN FOR

OPERABLE UNIT 7 APACHE TAILING

IMPOUNDMENT

Colorado Department

ofPublic Health

and Environment

U.S. Environmental Protection Agency Region VII I January 2000

Operable Unit 7 California Gulch Superfun d Site Leadville, Colorado

E PA Announces Its Preferred Alternative

T he U.S. Environmental Protection Agency (EPA), in cooperation

with the Colorado Department of Public Health and Environment

(CDPHE), is announcing the preferred alternative^ to address the

sources of metal contamination located within Operable Unit 7 (OU7) of the California Gulch Superfund Site (California Gulch Site) in Leadville, Colorado. OU7 or the Apache Tailin g Impoundment is defined as four distinct tailing impoundments,

which include the Main Impoundment, Tailin g Pond No. 2, Tailin g Pond No. 3, and the North Impoundment, for which ASARCO

Incorporated (Asarco) is the Potentially Responsible Party (PRP).

The preferred cleanup alternative consists of regrading the Main

and North Impoundments to create a single combined tailing area,

placement of a soil cover with a geosynthetic barrier and

vegetating the covered surface. Moreover, the preferred alternative

includes surface water controls, which include re-channelization of California Gulch, construction of diversion ditches, and

implementing institutional controls. Thi s Proposed Plan also

summarizes the other cleanup alternatives that were considered for

the OU7 site.

Asarco removed Tailin g Ponds Nos . 2 and 3 through a Removal Action in 1997 and placed the waste on the Main Impoundment. The areas were backfilled with wasterock from OU9 and regraded. In 1999, Asarco installed wick drains in the Main Impoundment to

facilitate dewatering of the subsurface slimes. They also backfilled

the North Impoundment to promote surface water drainage.

MARK YOUR CALENDAR : OPPORTUNITIE S FO R PUBLI C INVOLVEMEN T

Public Meeting: January 25,2000, 7:00 p.m. National Mining Hall of Fame and Museum

(10th Street Entrance), Leadville, Colorado

Public Comment Period: January 25 - February 24,2000

Send Written Comments to: Rebecca Thomas (8EPR-SR) EPA Remedial Project Manager

999 18th Street, Suite 500 Denver, Colorado 80202-2405 Thomas.Rebecca@epamail.epa.gov

Informatio n Repositories: The Proposed Plan and other documents

in the Administrative Record are available

at the following locations:

• Lake County Public Library

1115 Harrison Avenue Leadville, CO 80461

Colorado Mountain College Library Learning Resource Center Leadville, CO 80461

EPA Superfund Records Center

999 18th Street

5 th Floor, North Terrace Denver, CO 80202

(303)312-6473

CDPHE Superfund Records Center

4300 Cherry Creek Drive South Building 2,2

nd

 Floor Denver, CO 80246

(303)692-3331

K ey Contacts:

Rebecca Thomas E PA Remedial Project Manager (RPM)

(303)312-6552 Toll-fre e (800) 227-8917 x 6552

Mark Rudolph CDPHE State Project Officer (303)692-3311

Marion Galant CDPHE Community Relations Coordinator Toll-fre e (888) 569-1831

'Words shown in bold italics are defined in the glossary at the end of the document.
PUBLI C INVOLVEMEN T PROCES S

T he EPA and CDPHE encourage residents and other interested

parties to read and comment on this Proposed Plan. Detailed

information is contained in the Remedial Investigation (RI), and

the Focused Feasibility Study (FFS) for OU7. These

documents describe the OU7 contamination and the cleanup

alternatives considered. Thi s information and other documents

in the Administrative Record are available at the informatio n

repositories listed on the firs t page of this document. The Administrative Record contains all of the information that the

E PA wil l use to make its final remedy (cleanup) selection.

After considering State and community comments, the EPA wil l

make its final cleanup decision. The EPA may modif y the

preferred alternative or select another alternative presented in

this Proposed Plan.

T he EPA and CDPHE encourage citizens to review and

comment on all identified alternatives, and provide any new

information for the EPA to consider. Verbal or written

comments may be submitted during the public meeting, or

written comments may be sent to the EPA Remedial Project Manager (RPM), Rebecca Thomas, postmarked or e-mailed no

later than February 24, 2000.

Upo n timely request, the EPA may extend the public commenl

period. Such requests should be made in writing to Ms. Thomas

at the address shown on Page 1, postmarked no later than February 24, 2000.

Once the public comments are received, the EPA, in consultation

with the State, will make its final decision on the cleanup

alternative. The EPA wil l then publish a Record of Decision (ROD), a document that describes the selection of the final

cleanup plan and responds to the State and community

comments. The EPA expects to issue this ROD followin g the

public comment period.

T he EPA prepared this Proposed Plan to fulfill the public

participatio n responsibilities in Section s 113(k ) and 117(a) of

the Comprehensive Environmental Response, Compensation,

and Liability Act of 1980 (CERCLA), as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA).

SIT E BACKGROUN D

T he California Gulch Site is located in Lake County, Colorado,

in the Upper Arkansas River Basin, approximatel y 100 miles

southwest of Denver (see Figure 1). The Site encompasses

approximatel y 16.5 square miles and includes the towns of Leadville and Stringtown , a portion of the Leadville Historic Mining District, and the portion of the Arkansas River from its

confluence with California Gulch downstream to the Lake Fork Creek confluence.

Beginning in about 1860, the Leadville area was used extensively

f or mining, milling, and smeltin g operations. As mines were

developed, waste rock was excavated along with the ore and

placed near the mine entrances. Ore was crushed and separated

into metallic concentrates at mill s and the tailings were generally

slurried into impoundments, such as the Apache Tailin g Impoundment. The metallic concentrates were then transported

to smelters for further processing. Slag and other waste products

were produced from the smelters.

T he Apache Tailin g Impoundmen t is located on the southern

edge of Leadville adjacent to U.S. Highway 24. The tailing

impoundment s are located in California Gulch, approximately

1,500 feet downstream of the Yak Tunnel Water Treatment Plant Surge Pond. In the vicinity of the Apache Tailin g Impoundment , California Gulch is approximatel y 600 feet wide and slopes to

t he west. The Apache Tailin g Impoundmen t is located within an

area zoned for industrial use by the Cit y of Leadville . There is

no current residential use on OU7.

The Main Impoundment (11.3 acres) is furthest to the east, and

extends across the gulch. Tailin g Ponds Nos. 2 and 3, which

were removed in 1997, were located west and downstream of the Main Impoundment , and were approximatel y 1.5 and 0.5 acres

in size, respectively. The North Impoundmen t (1.8 acres) is

separated from the Main Impoundmen t by an old railroad grade. T he Main Impoundmen t and North Impoundmen t contain

approximatel y 630,000 and 14,500 cubic yards of tailings ,

respectively. The volumes of material removed from Tailin g Ponds Nos. 2 and 3 were approximately 36,200 and 5,200 cubic

yards, respectively.

T he mill that generated the tailings placed in the Main Impoundmen t and possibly the North Impoundmen t was located

on the hillside northeast of the North Impoundment . Thi s mill

operated as the Venir Mill, the California Gulch Mill, and the Asarco Leadville Millin g Unit from about 1939 to 1956. The Apache Mill, which was located at the northwest corner of the Main Impoundment (remnants currently exist), reprocessed

tailings from the Main Impoundment and deposited the materials

into Tailin g Ponds Nos. 2 and 3. The Apache Mill operated from

t he late 1970s into the 1980s. The analysis of tailin g and

underlyin g foundatio n soil samples collected from the

impoundment s indicated elevated concentrations of metals,

primaril y arsenic, cadmium, copper, lead, and zinc.

In 1983, EPA placed the California Gulch site on the National Priorities List, because of concerns about the impact of mine

drainage on surface waters in the California Gulch and the impact

of heavy metals loading to the Arkansas River. Subsequent

investigations revealed the presence of heavy metals in soils and

waste piles in and around residential and commercial areas of Leadville. Several RIs have been performed to collect data

necessary to identif y the nature and extent of contamination. A Site-wide Screening Feasibilit y Stud y (SFS) was undertaken as

a join t effor t between the PRPs and EPA. The SFS was

completed in September 1993. It developed remedial action

objectives (RAO) and identified an appropriate range of remedial

alternatives applicable to the various sources that were to be

'Words shown in bold italics are defined in the glossary at the end of the document.
P:\3280-015\OU7\PP\5344-65.DWG 11/29/99

*/

CANTERBUR Y TUNNE L

Stray Horse Gulch ^ YAK Tl/NNEL Starr Ditch

SUPERFUN D SIT E BOUNDAR YN

FIGUR E 1

~ aiarr uiicn .^ j OU7-APACHEJ[AllN G IMPOUNDMEN T

GENERA L SIT E LOCATION MA P
considered during FFS. Before completin g the SFS, EPA

provided notice and copies of the draf t SFS to the public and

accepted comments on the draf t report.

In 1994, Asarco entered a Consent Decree (CD) with the United States , the State of Colorado, and other PRPs at the California Gulch Site . Pursuant to the terms and conditions of the CD, Asarco completed a FFS for OU7. Thi s study evaluated and

screened remedial alternatives retained in the SFS for impounded

tailing. A draf t feasibilit y study was previously submitted to

EPA by Asarco. However, pursuant to comments received from

E PA and CDPHE , additional investigations were performed and

t he data incorporated into the final FFS.

T he Leadville area has been classified as a National Historic Landmark. As part of the CD, cultural resource surveys were

completed for OU7. Cultural Resource Site 5KL891 includes

structural remains and artifact scatter on the south side of both

t he California Gulch channel and the Apache Tailin g Impoundmen t and has been determined eligibl e for nomination

to the National Register of Historic Places. Thi s site is a

contributing feature to the Leadville Historic Minin g District

based on its significan t archeological potential , but is not

considered contributin g as a landscapin g feature.

SUMMAR Y OF SIT E RISK S

EPA performed human health and ecological risk assessments at

t he California Gulch Site to evaluate potential hazards from

exposure to contaminated site media. Contaminated media at the Apache Tailin g Impoundmen t are impounded tailing. The

primary contaminants of concern at OU7 include arsenic,

cadmium, copper, lead, and zinc.

Human Health Risk Assessments: The baseline human health

risk assessments for the California Gulch Site considered the

risks to workers and recreational visitors from ingestion of soil

and dust at OU7. For soil s and dust, lead and arsenic are the

primary contaminants of concern based on their potential to

cause adverse health effects .

Action levels were developed for lead and arsenic in soils under

residential, commercial, and recreational land use scenarios. These action levels can be compared to soil concentrations to

determine if a potential risk exists. Action levels are compared

to average contaminant concentrations over an exposure area. The action levels in soil for a worker exposure scenario are 6,100

to 7,700 milligrams per kilograms (mg/kg) for lead and 610 to

690 mg/kg for arsenic. The action levels in soil for a recreational

exposure scenario are 16,000 mg/kg for lead and 1,400 to 3,200

mg/kg for arsenic.

T he concentrations in composite samples of surficial tailin g

range from 257 to 353 mg/kg for arsenic and 1,090 to 1,740

mg/kg for lead. These concentrations are below the EPA riskbased action levels for both the commercial/industrial and the

recreational land use scenario. OU7 is not used for residential

purposes. Therefore, the exposed tailin g in their current

condition do not pose a significan t risk to human health.

Ecological Risk Assessments: Three ecological risk assessments

(ERA) were conducted for the California Gulch Site and are

pertinent to OU7. The ERAs considered the risk to ecological

receptors (i.e., plants , animals, and fish ) from exposure to surface

water and soil contaminated by mine wastes.

T he ERAs concluded that both the impounded tailin g within O U7 and surface water present potential risks to wildlif e and

aquatic receptors. The followin g exposure pathways were

identified as potentiall y exhibitin g risk.

• Ingestio n of surface tailings contaminated with lead,

cadmium, copper and zinc by wildlife ;

• Plan t and soil fauna (invertebrates and soil bacteria

necessary for healthy soil ) directl y exposed to surface

tailings contaminated with arsenic, cadmium, copper,

lead, silver, and zinc;

Wildlif e ingestin g sediments an d surface

contaminated by zinc, cadmium, and lead; and

water

• Aquatic life exposed to surface water and sediment

contaminated with arsenic, barium, cadmium, copper,

iron, and lead.

T he risk characterization indicated potential risks to the blue

grouse, mountain bluebird, and the least chipmunk, through

ingestion of tailin g within OU7.

Potential risks to plant s and soil fauna from exposure to tailin g

were also identified, although risk to soil fauna was characterized

as low. Surface water ingestion may also result in a potential

risk of some effect s to wildlife .

SUMMAR Y O F ALTERNATIVES

E PA considered a wide range of cleanup option s in the SFS. Some were eliminated during preliminary screening because they

would not effectivel y address contamination, could not be

implemented, or would have had excessive costs compared to

other protective alternatives. These cleanup option s were

further evaluated and screened for OU7 durin g the FFS. Followin g screening, nine alternatives were retained in the FFS

f or further evaluation. These alternatives are discussed below.

'Words shown in bold italics are defined in the glossary at the end of the document.
ALTERNATIVE 1: No Action. No remediation would take

place under this alternative. Thi s alternative is presented as a

baseline condition for comparison of Alternatives 2A through

4B.

Capital Cost $0

Time to Implemen t Immediate

Annual Operation and Maintenance Cost $0

30-Year Present Worth Cost_________________$0

ALTERNATIVE 2A: Simple Soil Cover. Thi s alternative

includes the followin g components: (1) the applicatio n of source

surface controls to the impounded tailing, consisting of

regrading, placement of a simple soil cover, and vegetating the

covered surface; (2) surface water controls, includin g rechannelization of California Gulch through the southern portion

of the Main Impoundment and construction of diversion ditches

to provide surface water run-on and run-of f controls; and (3)

institutional controls. Institutional controls include deed notices

or deed restrictions to provide notification that a barrier is in

place, and/or zoning restrictions to maintain the industrial zoning

currently in place for OU7.

Capital Cost

Time to Implemen t

Annual Operation and Maintenance Cost

30-year Present Worth Cost

$2,055,000

2 years

$85,000

$3,642,000

ALTERNATIVE 2B: Simple Soil Cover with Groundwater

Controls. Thi s alternative includes the followin g components:

( 1) the applicatio n of source surface controls to the impounded

tailing, consisting of regrading, placement of a simple soil cover,

and vegetating the covered surface; (2) surface water controls,

includin g re-channelization of California Gulch through the

southern portion of the Main Impoundment and construction of

diversion ditches to provide surface water run-on and run-off

controls; (3) institutional controls (as described in Alternative

2A); and (4) groundwater controls intended to reduce the

potential for contact between the alluvial groundwater and the

base of the tailin g under the southwest portion of the Main Impoundment.

Capital Cost

Time to Implemen t

Annual Operation and Maintenance Cost

30-year Present Worth Cost

$2,396,000

2 years

$85,000

$3,973,000

ALTERNATIVE 2C: Simple Soil Cover (Alternate Surface Water Channel Alignment). Thi s alternative includes the

followin g components: (1) the applicatio n of source surface

controls to the impounded tailing, consistin g of regrading,

placement of a simple soil cover, and vegetating the covered

surface; (2) surface water controls, including re-channelization

of California Gulch through the southern portion of the Main

Impoundmen t (but constructed further to the north than in Alternative 2A) and construction of diversion ditches to provide

surface water run-on and run-off controls; and (3) institutional

controls (as described in Alternative 2A).

Capital Cost

Time to Implemen t

Annual Operation and Maintenance Cost

30-year Present Worth Cost

$2,555,000

3 years

$85,000

$4,127,000

ALTERNATIVE 3A: Soil Cover with Geosynthetic Barrier. Thi s 'alternative includes the followin g components: (1 ) the

applicatio n of source surface controls to the impounded tailing,

consistin g of regrading, placement of a multi-layer composite

cover, and vegetatin g the covered surface; (2) surface water

controls, includin g re-channelization of California Gulch through

the southern portion of the Main Impoundmen t and construction

of diversion ditches to provide surface water run-on and run-off

controls; and (3) institutional controls (as described in Alternative 2A).

Capital Cost

Time to Implemen t

Annual Operation and Maintenance Cost

30-year Present Worth Cost

$2,504,000

2 years

. $85,000

$4,078,000

ALTERNATIVE 3B: Soil Cover with Geosynthetic Barrier

and Groundwater Controls. Thi s alternative includes the

followin g components: (1) the application of source surface

controls to the impounded tailing, consisting of regrading,

placement of a multi-layer composite cover, and vegetating the

covered surface; (2) surface water controls, includin g rechannelization of California Gulch through the southern portion

of the Main Impoundment and construction of diversion ditches

to provide surface water run-on and run-of f controls; (3)

institutional controls (as described in Alternative 2A) ; and (4)

groundwater controls intended to reduce the potential for contact

between the alluvial groundwater and the base of the tailin g

under the southwest portion of the Main Impoundment .

Capital Cost

Time to Implement

Annual Operation and Maintenance Cost

30-year Present Worth Cost

$2,845,000

2 years

$85,000

$4,409,000

ALTERNATIVE 3C: Soil Cover with Geosynthetic Barrier

(Alternate Surface Water Channel Alignment). Thi s

alternative includes the followin g components: (1) the

applicatio n of source surface controls to the impounded tailing,

consisting of regrading, placement of a multi-layer composite

cover, and vegetating the covered surface; (2) surface water

controls, including re-channelization of California Gulch through

t he southern portion of the Main Impoundmen t (but constructed

'Words shown in bold italic s are defined in the glossary at the end of the document.
further to the north than in Alternative 3A) and constructing

diversion ditches to provide surface water run-on and run-off

—controls; and (3) institutional controls (as described in

Alternative 2A).

Capital Cost

Time to Implemen t

Annual Operation and Maintenance Cost

30-year Present Worth Cost

$3,003,000

3 years

$85,000

$4,563,000

ALTERNATIVE 4A: Removal and On-Site Consolidation. Thi s alternative entails the complete removal of tailing material

from the Main and North Impoundment s and transportin g this

material to an on-site consolidation area. Potential consolidation

site is the Malta Gulch Tailin g Impoundmen t (located in OU2),

located about 2 miles west of Apache Tailin g Impoundment area. Significan t improvements of the Malta Gulch Tailin g Impoundmen t wil l be required prior to placement of material

from the Apache Tailin g Impoundment . A simple vegetated soil

cover (as described under Alternative 2A) would be constructed

over the consolidated tailing. Fencin g and signage to control

access to the work areas will be used.

Capita! Cost

Time to Implemen t

Annual Operation and Maintenance Cost

30-year Present Worth Cost

$11,204,000

3 years

$85,000

$12,060,000

ALTERNATIVE 4B: Removal with Disposal in an On-Site Repository. Thi s alternative entail s the complete removal of

tailin g material from the Main and North Impoundment s and

transporting this material to a new repository located within the California Gulch Superfun d Site boundary. The proposed

repository is located in upper Oregon Gulch, above (southeast)

t he Oregon Gulch Tailin g Impoundment . Thi s location is outside

of OU10 (Oregon Gulch ) and within the overall boundary for OU9 (Residential Populated Area), however, the area is within Lake County Industrial & Minin g zoning district . Followin g

relocation and placement of the tailin g in the repository, the area

would be covered with a multi-layer cover (as described under Alternative 3A). Fencin g and signage to control access to the

work areas wil l be used.

Capital Cost $12,491,000

Time to Implemen t 3 years

Annual Operation and Maintenance Cost $85,000

30-year Present Worth Cost____________$13,177^000

CRITERIA T O EVALUAT E CLEANU P

- OPTIONS

T he above alternatives were evaluated in detail using the nine

criteria identified in the National Contingency Plan (NCP). The

criteria are summarized below.

T he firs t two cleanup evaluation criteria, overall protection of

human health and the environment, and compliance with Applicable or Relevant and Appropriate Requirements (ARAR),

are threshold criteria that must be met by the selected remedial

action. The remaining criteria are used to help select the

preferred remedy.

N CP Evaluation Criteria

1. Overall protection of human health and the environment

addresses whether or not a remedy provides adequate protection

and describes how risks posed through each pathway are

eliminated, reduced, or controlled.

2. Compliance with ARARs addresses whether or not a remedy

wil l meet all Federal and State environmental laws and/or

provide grounds for a waiver.

3. Long-term effectivenes s and permanence refers to the abilit y

of a remedy to provide reliable protection of human health and

the environment over time.

4. Reduction of toxicity , mobility , or volume through treatment

refers to the preference for a remedy that reduces health hazards,

the movement of contaminants, or the quantity of contaminants

at the site through treatment.

5. Short-term effectivenes s addresses the period of time needed

to complete the remedy and any adverse effect s to human health

and the environment that may be caused during the construction

arid implementation of the remedy.

6. Implementabilit y refers to the technical and administrative

feasibilit y of the remedy, includin g the availability of materials

and services needed to carry out the remedy and coordination of Federal , State, and local governments to work together to clean

up the site.

7. Cost evaluates the^stimated capital and operation and

maintenance costs of each alternative in comparison to other,

equally protective measures.

8. State acceptance indicates whether the State agrees with,

opposes, or has no comment on the preferred alternative.

9. Community acceptance includes determining which

components of the alternatives interested persons in the

community support , have reservations about, or oppose. (This

assessment will not be completed until public comments on the Proposed Plan are received.).___________________

'Words shown in bold italics are defined in the glossary ai the end of the document.
COMPARISON OF ALTERNATIVES

Table 1 provides a comparison of the remedial action alternatives

based on seven of the nine NCP criteria. The community

acceptance criteria evaluation will not be completed until

comments on this Proposed Plan are received. Evaluation of the

overall protection of human health and the environment is based

primarily on the predicted ability of the alternatives to achieve

t he followin g RAOs defined for impounded tailings in the SFS:

• Control airborne transport of tailin g particles.

• Control erosion of contaminated tailings and

depositio n into local water courses.

• Control leaching and migration of metals from tailings

into surface water.

• Control leaching and migration of metals from tailings

into groundwater.

To comply with the requirements of

t he NCP, a No Action Alternative was

established as the firs t option in order to

compare the benefits and costs of the

remaining eight alternatives. As shown in Table 1, Alternatives 2A through 4B

would comply with RAOs, which

essentially include eliminating airborne

transport of tailing and the potential for direct contact with

precipitatio n and surface water runoff . However, the potential

contact, or some interaction, with surface water flowin g in the

constructed California Gulch channel alignment considered

under Alternatives 2C and 3C may be slightl y higher than the

alignment considered under Alternatives 2A and 3A due to its

position relative to the base of tailing. Alternatives 3A, 3B, 3C,

and 4B (soil cover with geosynthetic barrier) would provide a

higher level of infiltration reduction into the tailin g impoundment

than Alternatives 2A, 2B, 2C, and 4A (simple soil cover).

Alternative s 2, 3 and 4 would comply with all ARARs. Alternatives 2,3, and 4 were assessed to be effective and reliable

because of source control or removal actions. Institutional

controls for Alternatives 2 and 3 would ensure permanence of

the remedy. Alternatives 2B and 3B would provide essentially

no enhancement of long-term effectivenes s by incorporating

groundwater controls. The channel embankment slopes would

be slightl y less stable under Alternatives 2C and 3C.

T he predicted reduction in metals loadin g to groundwater were

calculated for each alternative and are summarized in Table 1. T he reduction in metal loadin g was calculated by comparing

existin g conditions (i.e., prior to removal of Tailin g Ponds Nos.

2 and 3) to predicted conditions for each alternative. Alternatives 4A and 4B having the greatest reduction followed

closely by Alternatives 3A, 3B, and 3C. Non e of the

alternatives, however, would reduce the toxicity or volume of

tailing.

T he short-term effectiveness , based on disturbance during

implementation, would be moderate for Alternatives 2A, 2B, 3A,

and 3B because of risk due to regrading tailing. Alternatives 2C

and 3C would have a low to moderate short-term effectivenes s

due to risks during regrading tailin g and working in wet tailin g material. Alternatives 4A and 4B would pose the greater shortterm risk during removal and transportation of tailing. Alternative 1 would not have any disturbance.

Alternatives 2 and 3 are administratively implementable,

however, obtaining access from the current property owners may

be difficult . Alternatives 2A and 3A are most readily

implementable. Alternatives 2B and 3B present additional

construction challenges for the groundwater control system. Alternatives 2C and 3C have additional difficultie s associated

with channelin g California Gulch further north and require

excavating into the deepest portion of the Main Impoundment . Alternatives 4A and 4B would be the most difficult to implement

due to excavating and transporting a large volume of material in

addition to preparing cooperative agreements with owners of the

consolidation or repository site.

T he cost estimates range from zero for No Action (Alternative 1)

to $13,177,000 for Alternative 4B.

RATIONAL E FOR ALTERNATIV E 3A AS THE PREFERRED ALTERNATIV E

E PA has selected Alternative 3A (Soil Cover with Geosynthetic Barrier) as the preferred alternative.

/ As required, Alternative 3A meets the threshold cleanup

evaluation criteria (overall protection of human health and the

environment, and compliance with ARARs).

/Alternative 3A provides very good long-term effectivenes s and

permanence.

/Alternative 3A eliminates airborne transport of tailin g particles

and minimizes both the erosion of tailin g and deposition into

local water sources.

/Alternative 3A controls the risks (defined by the risk

assessment) includin g ingestion of surface tailin g by wildlife ,

contract of plant s and soil fauna with surface tailing, and

ingestion of surface water by wildlife .

/Alternative 3A is readily implementable. The remediation

technologies selected for this alternative have been successfully

employed at other Superfun d sites.

Based on this reasoning, the EPA proposes Alternative 3A as the

preferred alternative for OU7.

'Words shown in bold italics are defined in the glossary at the end of the 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

Evaluation Criterion

Overall Protectiot

of Human Health

and the

Environment

Compliance with ARARs

Long-Term

Effectivenes s and Permanence

Reduction of Toxicity , Mobility , or Volume through Treatment

(see Note 1)

Short-Term

iffectivenes s

Implementabilit y

Cost

No Action

Alternative 1

N ot protective of

human health and

the environment

Does not comply

with ARARs

No long-term

decrease in

loadin g to

groundwater Minimal

reduction (16%)

of mobility . No

reduction of

toxicity or

volume No short-term

reduction in risk

Readily Implementable

$0

Simple Soi l Cover

Alone

Alternative 2A

Protective, would

meet RAOs for

impounded

tailin g

Complies with ARARs

Very good longterm

effectivenes s and

permanence

Mobilit y reduced

by about 88%. No reduction of

toxicity or

volume

Moderate shortterm

effectivenes s due

to risk during

regrading

Good to moderate

implementability ,

excavation and

access

considerations

S3.642.000

With Groundwater Controls

Alternative 2B

Protective, would

meet RAOs for

impounded tailing

Complies with ARARs

Very good longterm effectivenes s

and permanence

Mobility reduced

by about 88%. No

reduction of

toxicity or volume

Moderate shortterm effectivenes s

due to risk during

regrading

Moderate technical

implementability;

difficul t trenching

due to depth

requirements

$3,973,000

Alternative Channel Alignment

Alternative 2C

Protective, would

meet RAOs for

impounded tailin g

Complies with ARARs

Good long-term

effectivenes s and

permanence

Mobility reduced

by about 88%. No reduction of

toxicity or volume

Low short-term

effectivenes s due

to risk during

regrading and

working with wet

tailin g

Moderate to low

implementability,

d ue to difficultie s

excavating and

working with

large volume of

wet tailing

$4,127,000

Multi-Layer Cover

Alone

Alternative 3A

Protective, would

meet RAOs for

impounded tailin g

Complies with ARARs

Very good longterm effectivenes s

and permanence

Mobilit y reduced

by about 96%. No

reduction of

toxicity or volume

Moderate shortterm effectivenes s

due to risk during

regrading

Good to moderate

implementability,

excavation and

access

considerations

$4,078,000

With Groundwater Controls

Alternative 3B

Protective, would

meet RAOs for

impounded tailing

Complies with ARARs

Very good longterm effectivenes s

and permanence

Mobilit y reduced

by about 96%. No

reduction of

toxicity or volume

Moderate shortterm effectivenes s

due to risk during

regrading

Moderate

technical

implementability ;

difficul t trenching

due to depth

requirements

$4,409,000

Alternative Channel Alignment

Alternative 3C

Protective, would meet RAOs for impounded

tailin g

Complies with ARARs

Good long-term

effectivenes s and

permanence

Mobilit y reduced by

about 96%. No

reduction of toxicity or

volume

Low short-term

effectivenes s due to

risk during regrading

and working with wet

tailin g

Moderate to low

implementability, due

to difficultie s

excavating and

working with large

volume of wet tailin g

$4,563.000

Removal

With On-site Consolidation

Alternative 4A

Protective, would

meet RAOs for

impounded tailin g

Complies with ARARs

Very good long-term

effectivenes s and

permanence

Mobility reduced by

about 96%. No

reduction of toxicity

or volume

Low short-term

effectivenes s due to

risk during removal

and transport, higher

potential for releases

and increased

duration

Difficultie s

associated with large

volume, excavation/

water handling, and

development of

consolidation site

$12,060,000

Deposit in On-site Repository

Alternative 4B

Protective, would

meet RAOs for

impounded tailing

Complies with ARARs

Very good longterm effectivenes s

and permanence

Mobility reduced

by about 96%. No

reduction of

toxicity or volume

Low short-term

effectivenes s due to

risk during removal

and transport,

higher potential for

releases and

increased duration

Difficultie s

associated with

large volume,

excavation/water

handling, and

development of

repository site

$13,177,000

Notes:

1. Existing conditions: prior to removal of Tailin g Ponds Nos. 2 and 3.
ACRONYM S

ARAR Applicabl e or Relevant and Appropriate Requirements Asarco ASARCO Incorporated CD Consent Decree

CDPHE Colorado Department of Public Health and

Environment

CERCLA Comprehensive Environmental Response,

Compensation , and Liabilit y Act of 1980

E PA U.S. Environmental Protection Agency

E RA Ecological Risk Assessment F F S Focused Feasibilit y Stud y mg/kg Milligram s per kilograms N CP National Contingency Plan OU7 Operable Uni t 7 P RP Potentiall y Responsible Party R AO Remedial Action Objective RI Remedial Investigatio n ROD Record of Decision R PM Remedial Project Manager SARA Superfun d Amendment s and Reauthorization Act of

1986 S F S Site-Wide Screenin g Feasibilit y Stud y

GLOSSAR Y

Administrative Record: The body of documents EPA uses to

form the basis of selection of a response. Alternative: An optio n for reducing site risk by cleaning up or

otherwise limitin g exposure to contamination. Applicable or Relevant and Appropriate Requirements

(ARAR) : Federal and state requirements for cleanup, control,

and environmental protection that a selected remedy for a site

will meet. Baseline Human Health Risk Assessment: A CERCLA study

conducted at the same time as the RI (and contained in the RI

report) that determines and evaluates risk that site contamination

poses to human health in the absence of remedial action. Capital Costs: Expenses related to the labor, equipment and

material costs of construction.

Comprehensive Environmental Response, Compensation,

and Liability Act (CERCLA) : A Federal law passed in 1980

and modified in 1986 by the Superfun d Amendments and Reauthorization Act. It sets up a program to identif y sites where

hazardous substance have been, or might be, released into the

environment and to ensure they are cleaned up. Most of these

sites are abandoned or are no longer active.

Consent Decree (CD): A legal agreement between EPA and

one or more potentiall y responsible parties that specifie s the

obligation s to perform and pay for response actions.

Focused Feasibility Study (FFS) : The FFS identifie s an d

evaluates the most appropriate technical approaches to address

contamination problems at a Superfun d site. Loading: Mass concentration of contaminants in the surface

water or groundwater, which results from surface water and

groundwater contact with contaminated media. National Contingency Plan (NCP) : The EPA' s regulations

governing all cleanups under the Superfun d program. National Priorities List: EPA' s lis t of the most serious

uncontrolled or abandoned hazardous waste sites identified for

possible long-term remedial response. Operation and Maintenance Cost: The cost and time frame of

operating labor, maintenance, materials, energy, disposal , and

administrative activities of the remedy. Potentially Responsible Party: Those identified by EPA as

potentiall y liable under CERCLA for cleanup costs.

30-Year Present Worth Cost: An analysis of the current value

of all costs. Also known as Net Present Worth, the Present Worth Cost is calculated based on a 30-year time period and a

predetermined interest rate. Proposed Plan: A document requesting public input on a

proposed remedial alternative. Record of Decision (ROD): A document which is a

consolidated source of information about the site, the remedy

selection process, and the selected remedy for a cleanup under CERCLA. Remedial Action Objectives (RAO): Medium-specific (e.g.

groundwater, tailings) goals for protectin g human health and the

environment. Remedial Investigation (RI): A study conducted to identif y the

types, amounts, and locations of contamination at a facility . It

also evaluates possible risk to public health and the environment

from exposure to contamination. Removal Action: The cleanup or removal of released hazardous

substances from the environment. Superfun d Amendments and Reauthorization Act (SARA): Modification s to CERCLA enacted on October 17, 1986. Tailing: Deposited waste material from millin g operations of

mined ores.

'Words shown in bold ilalics are defined in ihe glossary at (he end of the document.