United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
oEPA
Superfund
Record of Decision:
EP AIROD/R08-91/055
September 1991
C 07'1 f
:rB q '2.-1 ~ '-/" Of,
Central City-Clear Creek, CO
EPA Report Col/ection
Information Resource Center
US EPA Region 3
Philadelphia, PA 19107
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50272.101
REPORT DOCUMENTATION 11. REPORT NO.
PAGE EPA/ROD/R08-91/055
1 ~
3. RecIpient. Acc888Ion No.
4. 11Ie and 8ubtII8
SUPERFUND RECORD OF DECISION
Central City - Clear Creek, CO
Third Remedial Action
7. Aulhor(.)
5. Report Date
09/30/91
6.
8. P8rf0nnlng Organization Rapt. No.
8. P8rf0nnlllll OrgalnlDllon Nama and AddI888
10. Project/T88klWoric Unit No.
11. ContnIct(C) or Grmt(G) No.
(C)
1~ SponaorIng Org8nlz8tlon Nama and AdIhu
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
(G)
13. Type 0' Report' Pariocf CoWf8d
Agency
800/000
14.
15. Suppl8m8nl8ry No'"
16. Abatr.ct (Umlt: 200 _rda)
The Central City-Clear Creek site is an active mining facility in Central City, Clear
Creek and Gilpin counties, Colorado. Land use in the area is predominantly
commercial and recreational, and an artificial wetlands area is located on site. The
site lies within the 400-square mile drainage basin of Clear Creek, which serves as a
drinking water source for several municipalities. Gold mining operations began
onsite in 1859 and portions of the site became some of the most heavily mined areas
of Colorado. Extraction of surface ores led to an increase in the depth of the
mining and, consequently, drainage tunnels were constructed to control water drainage
problems. Presently, six major mine drainage tunnels are thought to be principal
discharge sources of acid mine water containing high concentrations of metals to
surface waters including Clear Creek and its tributaries. In addition, over 21 mine
tailings piles with an estimated total volume of over 2,000,000 cubic yards at
numerous locations throughout the site are thought to be major sources of
contamination. In response to site contamination, EPA has conducted three removal
actions since 1987. In 1987, EPA conducted a removal action to prevent the collapse
of a mine waste pile. Also in 1987, EPA conducted a second removal action, which
(See Attached Page)
17. DcIcun8It An8IyaIa L D8ecrIpIora
Record of Decision - Central City - Clear Creek, CO
Third Remedial Action
Contaminated Media: gw
Key Contaminants: metals (arsenic, cadmium, chromium, lead)
b. Identlfi8r8lOpan-EndIcf Tarma
."
c. COSA 11 RaIcIIGroup
18. Avlll8bl1ty St8t8m8nt
18. Seculty CI... (Thl. Report)
None
20. SecuIty CI... (Thl. Page)
Nnnp
21. No. of Pall"
104
I
~ PrIce
(Sea ANSl-Z38.18)
SHInaITUCllOM on ",,-
(Formetty NTlS-35)
Departm8nt of Commerce
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EPA/ROD/R08-91/055
Central City - Clear Creek, CO
Third Remedial Action
Abstract (Continued)
involved connecting three residences with private wells to the municipal public water
supply. In 1991, EPA conducted a third removal action, which involved removing
uncontaminated mercury from a small trailer. Because of the complexity of the site, EPA
divided the site into several operable units (OUs) for remediation. A 1987 Record of
Decision (ROD) addressed OU1 and provided for passive treatment of acid mine water
discharge from five discharging tunnels: National, Gregory Incline, Argo Tunnel, Big
Five, and Quartz Hill tunnels. A 1988 ROD addressed OU2 and provided for the remediation
of mine waste piles in the immediate proximity of the five discharging tunnels. This ROD
supersedes the remedy provided for OU1 in the 1987 ROD by including active treatment of
the Argo Tunnel and delaying a decision on treating the discharges from the Big Five,
National and Quartz Hill tunnels, and the Gregory Incline. EPA will consider a
subsequent ROD to address treatment of the remaining onsite tunnels pending further
monitoring and treatability studies. The primary contaminants of concern affecting the
ground water are metals including arsenic, cadmium, chromium, and lead.
The selected remedial action for this site includes constructing physical barriers for
mine waste piles (to reduce metals loading to surface water and human health risks from
ingestion or inhalation of metals); treating discharges from the Burleigh tunnel
passively through the use of man-made wetlands; treating discharges from the Argo tunnel
actively along with ground water pumped from the immediate area; providing an alternate
water supply where needed; invoking an interim action waiver of ARARs for discharges from
the National, Quartz Hill, and Big Five tunnels, and the Gregory Incline, and invoking a
technical impracticality waiver for restoring ground water to MCLs; collecting discharges
from the National and Quartz Hill tunnels, and Gregory Incline with final disposition to
be established pending further monitoring and treatability studies; and implementing
institutional controls. The estimated present worth cost for this remedial action is
$23,510,000, which includes an annual O&M cost of $1,204,000 for 30 years.
PERFORMANCE STANDARDS OR GOALS: The passive treatment system will remove approximately
99.5% of the zinc, 99.84% of the copper, and 9.7% of the manganese from tunnel discharge.
Active treatment will remove 100% of the zinc and manganese, and 99.84% of the copper.
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UNITED STATES ENVIRONMENTAL PROTECfION AGENCY
REGION vm
COLORADO DEPARTMENT OF HEALTH
rr;rgrr1
RECORD OF DECISION
"~?--~~\ .~~~/
CLEAR CREEKlCENTRAL CITY SUPERFUND ~rl'~
OPERABLE UNIT #3
GILPIN AND CLEAR CRRRK COUNTIES, COLORADO
SEPI'EMBER 30, 1991
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CLEAR CREEK/CENTRAL CITY SUPERFUND SITE
OPERABLE UNIT #3 .
DECLARATION FOR THE RECORD OF DECISION
site Name and Location
Clear Creek/Central City Superfund site Operable unit #3,
Clear Creek and Gilpin Counties, Colorado
J
Statement of Basis and Purpose
This decision document presents the selected remedial action for
the Clear Creek/Central City Superfund site Operable Unit #3,
Clear Creek and Gilpin counties, Colorado, chosen in accordance
with the comprehensive Environmental Response, Compensation, and
Liability Act of 1980 (CERCLA), as amended by the Superfund
Amendments. and Reauthorization Act of 1986 (SARA) and, to the.
extent practicable, the National oil and Hazardous Substances
Pollution contingency Plan (NCP), 40 CFR Part 300. This
decision document explains the factual and legal basis for
selecting the remedy for this Site, and is based on the
administrative record for the site.
The State of Colorado concurs with the selected remedy.
Assessment of the site
Actual or threatened releases of hazardous substances from this
site, if not addressed by implementing the r:esponse action
selected in this Record of Decision, may present an imminent and
substantial endangerment to public health, welfare, or the
environment.
Description of the Remedv
The Clear Creek/Central city Superfund site consists of three
operable Units which were designated to address heavy metals
contamination associated with historic mining activity in the
Clear Creek drainage basin. Operable unit #1 was designated to
address the discharge of acid mine water from five tunnels
(National and Gregory Incline near Black Hawk, the Quartz Hill
Tunnel southwest of Central City, and the Argo and Big Five
Tunnels in Idaho Springs)-. The Operable Unit #1 Record of
Decision was signed in September, 1987. Operable Unit #2 was
designated to address remediation of mine waste piles in
immediate proximity to the five discharging tunnels referenced
above. The Operable unit #2 Record of Decision was signed in
March, 1988. operable unit #3 was originally designated to
address control of surge events from the Argo Tunnel. The
Record of Decision for Operable Unit #3 was delayed pending the
outcome of the Phase II investigations.
In 19.88 the Phase II investigation was initiated to take a
comprehensive view of the approximately 400 square mile Clear
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Creek drainage basin. This Record of Decision is for the Phase
II investigations. This Record of Decision supersedes the
. operable unit #1 Record of Decision and includes a decision for
. the original operable Unit #3. The' operabte unit "#2 Record of
Decision remains unchanged by this Record of Decision. For the
purposes of Operable unit designation, operable unit #3 is
hereby redesignated and will be equivalent in meaning to the
Phase II investigations.
The selected remedy for Operable unit #3 addresses a portion of
the principal threats remaining at the site by treating highly
toxic and highly mobile liquid wastes, i.e., acid mine
discharges, which present significant risk to the environment.
Treatment of the principal threats will include the use of an
innovative emerging technology passive treatment via
constructed wetlands. This technology has been undergoing
laboratory and pilot scale testing at the site under the
superfund Innovative Technology Evaluation (SITE) program. The
selected remedy addresses low level threat wastes by reliably
managing source materials, i~e., mine tailings and waste rock
material. The selected remedy addresses contaminated ground
water.
The selected
Creek/Central
components:
remedy for operable Unit #3
city site. is describe~ below
at
by
the
its
Clear
major
- capping or physical barriers, and institutional controls for
select mine waste piles.
- An alternate drinking water .supply where required.
- Treatment of the Burleigh and Argo Tunnel discharges.
- A ground water pump and treat system in the Idaho springs area
to address non-point source metals loading to surface water.
- Reduction in the heavy metals load from Woods Creek.
- No action to control surge events from tunnels.
Additionally, this Record of Decision amends the Operable
Unit #1 Record of Decision by:
- Use of the interim wavier of applicable or relevant and
appropriate requirements- for the discharge from the Big Five
Tunnel.
- Collecting the discharges from the Gregory Incline, National
and Quartz Hill Tunnels.
- Delaying a decision on treatment of the Gregory Incline,
National and Quartz Hill Tunnels pending treatability studies
and further delineation of the contamination sources in North
Clear Creek. These studies will serve as a new operable unit
for the site, Operable Unit #4.
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statutory Determinations
The selected remedy is an interim action and is protective of
. human health and the environment, complies with Federal and'
state requirements that are legally applicable or relevant and
appropriate to the limited scope action, and is cost effective.
Although this interim action is not intended to address fully
the statutory mandate for permanence and treatment to the
maximum extent practicable, this interim action does utilize
treatment and is thus a furtherance of that statutory mandate
for this Site. Because this action does not constitute the
final remedy for the site, the statutory preference for remedies
that employ treatment that reduces the toxicity, mobility, or
volume as a principal element, although addressed to a great
extent by this remedy, will also be addressed by the final
response action. Subsequent actions are planned to address fully
the threats posed by the conditions at the site. Because this
remedy will result in hazardous substances remaining on site, a
review will be conducted within five years after commencement of
remedial action to ensure that the remedy continues to.provide
adequate protection of human health and the environment. Because
this is an interim action Record of Decision, review of this
site and of this remedy will be ongoing as the Environmental
Protection Agency, and the State of Colorado continue to develop
final remedial alternatives for the site. .
~
~t4/
W. McGraw
ing Regional Administrator (Region VIII)
. Environmental Protection Agency
Date
~~
Thomas P. 0
Director, 0 ice of Environment
Department of Health
state of Colorado
~~
Date
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CLEAR CREEK/CENTRAL CITY SUPERFUND SITE OPERABLE UNIT #3
DECISION SUMMARY FOR THE RECORD OF DECISION
TABLE OF CONTENTS
section
1.0 site Name, Location, and Description... . . . .
2.0
3.0
4.0
5.0
6.0
7.0
8.0
site History and Enforcement Activities. .
. . . . . .
2.1
2.2
site History. . . . . . . . . . . . . . . . . .
Enforcement Activities. . . .. .....
Highlights of community Participation
Scope and Role of operable unit
........
...........
Summary of site Characteristics. . . . . . . . . . .
5.1 Surface Water. . . . . . . . . ... . . . . . . .
5.2 Ground Water. . . . . . . . . . . . . . . . . . .
5.3 Mine Waste. . . . . . . . . . . . . . . . . . .
5 . 4 Air. . . . . . . . . . . . . . . . . . . . . . .
summary of site Risks. . . . . . . . . .
6.1 Human Health Risks. . . . . . . . . . . . . . .
6.1.1 Surface Water. . . . . . . . . . . . . . . .
6.1.2 Ground Water. . . . . . . . . . . . . . . . .
6.1.3 Mine Waste. . . . . . . . . . . . . . . . . .
6 . 1 . 4 Air. . . . . . . . . . . . . . . . . . . . . .
6.1.5 Ingestion of Fish. . . . . . . . . . . . . .
6.2 Environmental Risks. . . . . . . . . . . . . . .
6.2.1 Macroinvertebrates . . . . . . . . .. . . . .
6.2.2 Other Aquatic Life. . . . . . . .
6.3
Tunnel Surge Events. . .
. . .
.........
Description of Remedial Action Alternatives
. . . . .
comparative Analysis of Alternatives. . . . . . . .
8.1 Overall Protection of Human Health and the
Environment. . . . . . . . . . . . . . . . . . .
8.2 Compliance with Applicable or Relevant and
Appropriate Requirements. . . . . . . . . .
8.3 Long-Term Effectiveness and Permanence. . . . .
8.4 Reduction of Toxicity, Mobility or Volume
through Treatment. . . . . . . . . . . . . . . .
Short-Term Effectiveness. . . . . . . . . . . .
Implementability . . . . . . . . . . . . . . . .
Cos t . . . . . . . . . . . . . . . . . . . . . .
community Acceptance. . . . . . . . . . . . . . .
State Acceptance. . . . . . . . . . . . . . . .
8.5
8.6
8.7
8.8
8.9
9.0
Selected Cleanup Alternative. .
i
. . .
. . . . .
Page
1
3
3
4
5
6
8
8
9
11
12
13
18
18
20
23
23
28
28
30
30
33
33
44
49
50
51
52
53
53
54
55,
56
56
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statutory Determinations. . . . . . . . . . . . . . .
10.1 protection of.Human Health and th~ Environment.
10.2 Compliance with Applicable or Relevant and
Appropriate Requirements. . . . . . . . . ... .
10.2.1 contaminant specific Requirements
10.2.2 Location-specific Requirements. .. . . . .
10.2.3 Action-specific Requirements. . . . .
10.2.4 liTo Be Considered" Requirements. . . . . . .
10.3 Cost Effectiveness. . . . . . . . . . . . . . .
10.4 utilization of Permanent solutions and
Alternative Treatment Technologies to the
Maximum Extent Practicable and Preference
for Treatment as a Principal Element. . .
6-7 . Dust Inhalation Risks in Central city Area . .
6-8 Fish Ingestion Risks . . . . . . . . . . . . .
8-1 comparison of Alternatives Based on Nine
Evaluation criteria. . . . . . . . . . . . . .
10.0
Figure 1-1
Figure 5-1
Table 6-1
Table
6-2
Table
6-3
Table
6-4
Table
6-5
Table
Table
Table
Table
Appendix A
Appendix B
Appendix C
Appendix D
FIGURES and TABLES
Clear Creek Drainage Basin, Colorado,
Location Map. . . . . . . . . . . . . . . . .
Monitoring and Drinking Water Well Locations.
General Toxicological Data and Assumptions
for the Risk Assessment. . . . . . . . . . . .
Surface Water Ingestion Risks. .
.......
Monitoring Well Water Ingestion Risks. .
Domestic Well Water Ingestion Risks. . .
. . .
Mine Waste Pile Ingestion Risks. . . . .
. . .
6-6
summary of Mine Waste Pile Human Health and
Environmental Risks. . .. .........
Water Quality Simulation Program, Version 4,
Computer Model. Results
Federal and state of Colorado Applicable or
Relevant and Appropriate Requirements
Clear Creek/Central City site Phase II/
Operable unit #3 Responsiveness summary
Administrative Record Index
ii
60
60
62
63
64
64
65
65
65
2
10
15
19
21
22
24
25
27
29
46
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CLEAR CREEK/CENTRAL CITY SUPERFUND SITE
OPERABLE UNIT #3 '.
DECISION SUMMARY FOR THE RECORD OF DECISION
1.0
SITE NAME. LOCATION AND DESCRIPTION
The Clear Creek/Central city Superfund site (Site) is located
approximately 30 miles west of Denver, Colorado. The site
boundary has not been narrowly defined because of the nature of
the contamination at the site. Extensive historical mining
activity' at the site took place on a large number of small
mining claims. In general, this resulted in the disposal of
relatively small volumes of mine waste rock and tailings piles,
which are distributed over a very large area. Additionally,
numerous mine tunnels, which were constructed for ore haulage
and mine water drainage, are found in the area. Consequently,
the investigations at the site involved identification and
prioritization of contamination within the approximately 400
square mile drainage basin for Clear Creek. Figure 1-1
identifies those mine waste piles and mine tunnels which are
currently considered priority locations for potential remedial
action under the Clear Creek/Central City Superfund site.
The Clear Creek drainage basin ranges in elevation from
approximately 5,700 feet to over 13,000 feet. Annual
precipitation in the drainage basin ranges between 16 - 18
inches. However, precipitation values two to three times
greater than these values can be seen in localized areas. The
drainage basin is dominated by a series of mountains and
valleys. The steep hillsides exhibit shallow coarse soils, with
ponderosa pine, juniper, and mountain mahogany grasslands the
typical vegetation on south-facing slopes, and douglas fir
communities typical on north-facing slopes. Aspen groves are
also interspersed within these communities. Along valley bottoms
blue spruce, aspen and narrow-leaf cottonwood are the typical
vegetation, with willow and river birch at the edge of
floodplains.
Clear Creek has three major tributaries - South, West, and North
Clear creek as well as numerous smaller tributaries.
'Designated uses of Clear Creek include agriculture, recreation,
and drinking. Recreational uses in Clear Creek include fishing,
kayaking, rafting, and tub~ng. Clear Creek 'and its tributaries
are classified as Cold Water Class I, and in a few cases Cold
Water Class II due to limiting habitat for aquatic life. Clear
Creek and its tributaries are used in whole or in part as a
drinking water source by several municipalities including
Georgetown, Idaho springs, Black Hawk, Golden, westminster,
Thornton, and Arvada. Table 1.1-1 in Appendix B provides a
summary of the use classifications for Clear Creek. .
1
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CLEAR CREEK BASIN,. COLORADO
Site Map
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Figure 1-1
--_____.0_- ..
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" .The ground water system in the Clear Creek drainage basin has
not been classified by the state of Colorado for a particular
use. In addition, at this time the state of Colorado has not
adopted standards in the basin for the contaminants of concern
at the site. There are approximately 4,367 permitted drinking
water wells in Clear Creek and Gilpin Counties. .
The Clear Creek drainage basin is located in Clear Creek and
Gilpin counties. The 1988 population estimates show 2,649
residents in Gilpin County and 7,379 residents in Clear Creek
County. More densely populated areas include the towns of
silver Plume, Georgetown, Empire, and Idaho Springs in Clear
Creek County; and Central city and Black Hawk in Gilpin County.
In addition, a large number of the residents of both counties
live in smaller communities, or are dispersed throughout the
counties and live on small acreage.
Land uses in Clear Creek and Gilpin counties include tourism,
commerce, recreation, and to a limited extent, ranching and
agriculture. Areas of both counties were extensively mined in
the past because of the abundance of precious and base metals.
Active mines are still present at some locations in the
counties. In October 1991 , limited stakes gaming will be
permitted in the towns of Black Hawk and Central City. This
will undoubtedly change the land use and population density in
these areas.
2.0
SITE HISTORY AND ENFORCEMENT ACTIVITIES
2.1 SITE HISTORY
The Clear creek/Central city Superfund site is located on the
east slope of Colorado's Front Range. The Colorado Mineral Belt
transects the site indicating the rich mineralization of the
area. Precambrian gneisses and schists are the predominate host
rock and are cut by a network of faults. Te~tiary Age veins and
stocks within the host rock are the sources of sulfide ores
which contain deposits of several metals including gold, silver,
iron, copper, lead, nickel, zinc, cadmium, manganese, as well as
others.
.
Due to the rich mineralization of the area, portions of the site
became some of the most heavily mined areas of Colorado. There
are well over 800 inactive"mines and tunnels in Clear Creek and
Gilpin Counties. Historically, it is estimated that over $110
million worth of mineral production, in "1900" dollars, occurred
at the site. Gold and silver accounted for the vast majority of
the mining interest.
Mining activity in the area commenced in 1859 with placer gold
being found at the mouth of Chicago Creek, and the first lode
3
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. discovery occurring in Gregory Gulch later that year. By the
summer of 1a60, almost all surface lodes had been claimed.
Extraction of surface ores led to an increase in the depth of
mining. This increase in aepth brought problems with water
drainage, and miners began to encounter more durable sulfide
ores which could not be milled with the same ease as the
oxidized surface ores. To compensate for these problems,
drainage tunnels were constructed and new milling techniques
were developed.
Today most of these mine drainage tunnels are still functioning
and discharge acid mine water, which contains high
concentrations of heavy metals. Mine tailings from milling
operations and waste rock from the development of the mines are
present at numerous locations throughout the Site.
In September 1983, the site was selected for addition to the
Superfund National Priorities List due to the presence of heavy
metals in the environment. since that time, the Environmental
Protection Agency (EPA) and the Colorado Department of Health
(CDH) have conducted several studies in the area and have
previously made certain decisions on cleanup alternatives for
certain areas. These decisions are discussed in greater detail
in section 4.0.
Three removal actions were conducted at the site by EPA's
Emergency Response Branch. In March 1987, a removal action was
initiated at the Gregory Incline to prevent the collapse of the
mine waste pile. A collapse would have allowed the mine waste
to slide into North Clear Creek, and EPA was concerned that a
large load of metals-laden" mine waste would wash downstream into
Clear Creek and contaminate the municipal water supply of the
City of Golden, Colorado. As part of the removal action EPA
removed an old deteriorated wood crib retaining wall, decreased
the slope of the mine waste pile,. and .constructed a gab ion
basket retaining wall. In Fall 1987, a removal action was
initiated in the Idaho Springs area. This removal action
involved connection of three residents to the City of Idaho
Springs water supply. Prior to the removal action the
residences had been served by private ground water wells which
contained elevated concentrations of cadmium. In August 1991,
a removal action was initiated approximately 1/4 mile north of
Idaho springs. This action involved removal of uncontaminated
mercury from a small trailer. The mercury and a small amount of
soil were placed in a ten gallon steel drum and shipped to a
mercury recovery facility.
2.2 ENFORCEMENT ACTIVITIES
A potentially responsible party search was conducted as part of
the earlier investigations at the Site. The search revealed
4
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. informat:ion on the ownership of the five discharging mine
tunnels and five mine waste piles desc~ibed in section 4.0 under
.operableunits #1 and #2. To date, no enforcement activities
have resulted from this search.
EPA also initiated a potentially responsible party search as
part of the Phase II investigations.' This second search has not
been completed and, therefore, no special notices have been
issued. EPA does not believe that remedial action at the site
should be delayed pending finalization of the search and is
proceeding with this Record of Decision. After finalization of
the search, the status of the potentially responsible parties
will be evaluated. If appropriate, EPA will notify potentially
responsible parties of the selected remedy and will initiate
negotiations for the implementation of the remedy. If the
potentially responsible parties do not commit to performing the
remedy in a timely manner, EPA may proceed with a fund-financed
remedial design and remedial action and may attempt to recover
EPA's response costs from the responsible parties. If it is
determined that a potentially responsible party has little or no
liability for the contamination at the site, this information
will be used to determine if a fund-financed remedial action
will be initiated. A fund financed-remedial action would use
Federal and State monies to perform the cleanup.
3.0 HIGHLIGHTS OF COMMUNITY P~~TICIPATION
community participation activities at the site were conducted
pursuant to sections 113 (k) (13) (i-v) and 117 of the
comprehensive Environmental Response, compensation, and
Liability Act. The Colorado Department of Health (CDH), the
lead agency for the site, has developed and maintained an active
community relations effort during the Phase II work to keep the
public informed and to give the public an opportunity for input.
The community relations effort involved the development of a
Technical Review/Advisory Committee, which was composed of local
citizens, downstream water users, and local, state and Federal
officials. project updates were mailed at project milestones to
approximately 200 residents and interested citizens. In
addition, County commissioners and city councils were updated at
various times during the Phase II investigation.
copies of the site work plan, raw data packages, Remedial
Investigation, Feasibility Study, and Proposed Plan were made
available to the public at the Idaho springs Library, Idaho
springs city Hall, Gilpin County Courthouse, EPA Library, and
CDH offices. A public meeting was held on July 24, 1990, to
hear comment on the Remedial Investigation report. A second
public meeting was held on July 11, 1991, to hear comment on the
Feasibility study report. At these meetings members of the CDH
and EPA provided information about the findings of the reports,
including a detailed explanation of the preferred cleanup
5
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. a.lternative for the site, and answered questions about the site.
Notice of both of these meetings were published in the Clear
Creek Courant and the Weekly Register-Call newspapers. A 30-day
comment period was provided for the Remedial Investigation
report and a GO-day public comment period was provided for the
Feasibility Study. A Responsiveness Summary was written to
address public comments received during the comment period. A
copy of the Responsiveness Summary is included as Appendix C of
this Record of Decision.
This Record of Decision presents the selected remedial action
for the Clear Creek/Central city site Operable Unit #3, Clear
Creek and Gilpin Counties, Colorado, which has been chosen in
accordance with the Comprehensive Environmental Response,
Compensation, and Liability Act, as amended by the Superfund
Amendments and Reauthorization Act, and to the extent
practicable, the National contingency Plan. The decision for
remediation of the site is based on the Administrative Record.
A copy of the Administrative Record Index is included as
Appendix D of this document.
4.0
SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
As with many Superfund sites, the problems at the Clear
Creek/Central City site are complex. In order to effectively
address some of .these problems, EPA organized work at the site
into separate working units known as Operable units. The Clear
Creek/Central City Superfund site was organized into three
Operable Units which were designated to address heavy metals
contamination associated with historic mining activity in the
Clear Creek drainage basin. A brief description of. the three
Operable units is provided below.
Operable unit #1 was designated to specifically address
. treatment of the acid mine drainage from five tunnels (National
and Gregory Incline in Black Hawk, the Quartz Hill Tunnel
southwest of Central City, and the Argo and Big Five Tunnels in
Idaho Springs). The Feasibility Study for Operable unit #1 was
completed in 1987 and a Record of Decision was signed in
September 1987. The Record of Decision selected passive
treatment of the discharging acid mine water as the preferred
remedial alternative, if passive treatment could be shown (via
a two to three year study period) to be an effective treatment
option. If it was determined that passive treatment systems
were not effective, the Record of Decision allowed the
flexibility to install active treatment or a combination of
active and passive treatment systems. Implementation of the
Record of Decision for Operable Unit #1 was delayed pending the
Qutcome of the Phase II work, which is discussed below.
G
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. . Operable unit #2 was designated to specifically address
remediation of mine tailings and waste rock in the immediate
proximity of the five discharging tunnels referenced above. The
Feasibility study for Operable unit #2 was completed in November
1987, and a Record of Decision was signed in March 1988. The
Record of Decision selected runon control and slope
stabilization (where applicable) as the preferred remedial
alternative. Remedial action at two of the five mine waste
piles (Gregory Incline and Argo Tunnel sites) was initiated in
April 1990, and is. complete. The Record of Decision for the
Phase II work will not amend the original Record of Decision for
Operable unit #2.
operable Unit #3 was originally designated to address control of
surge events from the Argo Tunnel. A Feasibility study was
completed in August 1988. The Record of Decision for Operable
Unit #3 was delayed until a more comprehensive evaluation of the
Site could be obtained. This Record of Decision for the Phase
II work includes a final recommendation for Operable unit #3.
In June 1988, the EPA transferred the lead role for the site to
CDH. CDH then initiated the comprehensive evaluation of the
site via the Phase II Remedial Investigation and Feasibility
study. The Phase II work. expanded the original study area to
include the approximately 400 square mile Clear Creek drainage
basin above Golden, Colorado. The reason for the expansion was
to obtain a better understanding of the various contamination
sources in the basin; to enable the state, EPA, and the local
coIt'.munities to make informed decisions as to what could and
could not be done to control these sources; and to assess what
effect these controls would have on Clear Creek. The Phase II
Remedial Investigation was completed in september 1990 i the
Draft Phase II Feasibility study was released for public comment
in June 1991. This Record of Decision is for the Phase II
investigations, it will supersede the Operable unit #1 Record of
Decision, and includes a final decision for the original
operable unit #3. For the purposes of Operable Unit
designation, Operable unit #3 is hereby redesignated and will be
equivalent in meaning to the Phase II investigations.
This Record of Decision for Phase II/Operable unit #3 was
intended to be the final response action for the site. However,
due to the complexity of the site, and difficulties in attaining
legally applicable or relevant and appropriate requirements, it
will not be the final decision document for the site. The
cleanup plan outlined in this Record of Decision will be
evaluated as it is being implemented to determine how
effectively it eliminates or reduces the risks posed' at the
site. This evaluation will take place no later than five years
from the date of this Record of Decision. The information
obtained during the evaluation will be used in conjunction with
other pertinent site data to determine what additional response
7
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. actions may be required. This point is discussed in further
detail in Section 10.0 of this document. .
5.0
SUMMARY OF SITE CHARACTERISTICS
5.0
INTRODUCTION
The Phase II Remedial Investigation for the Clear Creek/Central
City Site focused on identifying the nature and extent of heavy
metals contamination to the mainstem of Clear Creek and its
major tributaries. Due to the large geographic size of the
study area, an initial screening study was performed. Potential
sources of. contamination were prioritized based on their
likelihood to threaten human health or the.environment. The
results of the screening and prioritization allowed for a.
focused study of the major sources of contamination at the site.
Investigations at the site have identified the following
potential contaminants of concern: aluminum, arsenic, cadmium,
chromium, copper, fluoride, lead, manganese, nickel, silver,
zinc, and the indicator pH. In addition, mercury was evaluated
in fish tissue, and beryllium was examined in air. The presence
and. concentration of these contaminants vary over time and
location within the Site. In some cases at the time of sampling
some of the contaminants of concern were not found to pose a
threat to human health or the environment. This point is
discussed in greater detail in the summary of Site risks in
section 6.0.
The potential major sources of contamination to the mainstem of
Clear Creek and its major tributaries were identified to be
eight discharging mine drainage tunnels, five of which were
under Operable Unit #1, and 21 mine waste piles, five of which
have an existing Record of Decision under Operable Unit #2 (see
Figure 1-1). These sources of contamination, as well as the
extensive natural mineralization throughout the Site, have
contributed to contamination of both surface water and ground
water.
A complete description of the extent of contamination can be
found in the Phase. II Remedial Investigation report. The
significant findings of the Phase II Remedial Investigation are
summarized by affected media and presented below.
5.1 SURFACE WATER
Surface waters at the site are impacted by both direct
discharges from mine drainage tunnels and from eroding mine
waste piles (see Figure 1-1). A summary of the volumes and
concentrations of contaminants of concern in mine waste piles
can be found in Tables 6-5 and 6-6. A summary of the major
impacts to surface water is presented below.
8
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. .The mainstem of Clear Creek is directly impacted by acid mine
. drainage from the Burleigh, McClelland, Rockford, Big Five and
Argo Tunnels; and from the McClelland bailings, and Big Five
tailings and waste rock piles. The mainstem of Clear Creek is
impacted by non-point source metals loading (ground water) in
the Idaho springs area. The mainstem of Clear Creek is also
impacted by the tributaries described below.
The West Fork of Clear Creek is directly impacted by woods
Creek, which is impacted by discharges from the Urad Mine tunnel
drainage (the Urad tunnel was plugged in 1989) and seepage from
the Urad tailings and waste rock piles. Surface waters in the
Lion Creek drainage (a tributary to West Clear Creek) contain
elevated levels of metals.
The Empire tailings along west Clear Creek were studied during
the Phase II Remedial Investigation, but were not shown to
impact surface water.
Chicago Creek (a tributary to the mainstem of Clear Creek) is
impacted by the Black Eagle mine waste pile.
Soda Creek (a tributary to the mainstem of Clear Creek)
. impacted by the Little Bear tailings pile.
is
The North Fork of Clear Creek is impacted by acid mine drainage
from the Quartz Hill Tunnel (via Gregory Gulch), the Gregory
Incline, and the National Tunnel; and from the Golden Gilpin
tailings, the Gregory Incline tailings and waste rock pile, and
the North Clear Creek tailings. North Clear Creek is also
impacted by the Gregory Gulch #1 and #2 tailings piles in
Gregory Gulch, the' clay County tailings pile in Lake Gulch, the
Chase Gulch #1 and #2 tailings piles in Chase Gulch, the Quartz
Hill tailings pile in Nevada Gulch, and other sources which were
not studied.
The impact on surface water from the North Clear Creek Dredge
placer tailings could not be fully determined from an erosional
standpoint, because they form the bottom and bank of a section
of North Clear Creek.
The impact on surface water from the Boodle tailings could not
be fully determined, due to the lack of stream flow in Eureka
Gulch during sampling.
5.2 GROUND WATER
A total of 33 wells were sampled at the site (14 drinking water
wells and 19 monitoring wells which were located in or near
tailings/waste rock piles) (see Figure 5-1). The 14 drinking
water wells were selected for testing by announcing to the
public, via the local newspapers, that CDH was interested in
9
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. . Figure 5-1
10
~':i/~""~""'i~'; g~""< ~ /':, ~ rTv
: ,-l.....,' ~ I:... ':..,...~ .;~.l'-,~..:' I
~~ r'~ ~ ,.-.:. ; ~~ !: A L
l/ !: 1 "':: ! i \;i"'.
-------
,sampling domestic wells in the area and that volunteers would
receive a free analysis of their well water. Based on the level
of response, CDH was able to accommodate each individual who
requested a well sample.
The 19 monitoring wells were constructed in close proximity to
mine waste piles and were drilled into bedrock and/or alluvium.
The monitoring wells were constructed to evaluate the
interaction between alluvial and bedrock ground water, and to
determine the effect that mine waste piles are having on the
local ground water quality.
In general, the results of the well sampling indicate that
ground water at many locations in the study area contains
elevated concentrations of metals. Several of the monitoring
wells, and one of the drinking water wells, contained
concentrations of some metals which exceeded drinking water
and/ or health based standards. A detailed summary of the
contamination in well water is provided in Section 6.1.2.
The full extent of ground water contamination was not determined
for the following reason: the ,ground water quality was
determined to be highly variable at the locations which were
sampled, and there is no discernable pattern of contamination;
the site encompasses approximately 400 square miles of
mountainous terrain which contains numerous shallow unconfined
aquifers, and numerous fractured bedrock aquifers.
5.3 MINE TAILINGS AND WASTE ROCK
During the Phase II Remedial Investigation, a total of 60
tailings and waste rock piles were inventoried at the site
utilizing area maps, aerial photographs, literature review of
mining and milling history, and direct field observations. The
inventoried piles were then ranked based on total volume,
, proximity to surface water, proximity to flood plain, and the
size of the drainage basin above the piles. The ranking system
yielded 12 sites that were investigated further (the results of
the investigations are summarized in Tables 6-5 and 6-6).
Samples were taken to determine slope stability at ten sites,
while two sites were evaluated utilizing existing data. samples
to determine surface and subsurface chemistry were also taken at
nine sites. In addition, sediment loading estimates for seven
of the sites were performe~ based on a one-hour rainfall event.
Three sites were not evaluated for sediment loading due to
relatively long distance to a flowing receiving stream, low
slope angles (Empire and Boodle tailings), and site location
within the stream channel (North Clear Creek Dredge).
Three additional mine waste piles were included in the Phase II
Feasibility Study as a result of observations made during the
11
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'Phase II Remedial Investigation sampling efforts. The Chase
Gulch #1 and #2 mine waste piles, in lower Chase Gulch, were
added because of the poor water quality observed in Chase Gulch,
particularly during high flow. These two piles were
specifically selected because they are in direct contact with
the stream. The North Clear Creek Tailings pile was added
because of its close proximity to North Clear Creek and a large
amount of sediment that was observed entering the Creek during
a storm event. Since these three piles were added after the
Phase II Remedial Investigation, no chemical or stability data
are available.
It should also be noted that the Urad, Lion Creek, and North
Empire Creek mine waste piles were to be evaluated (in the Phase
II Remedial Investigation) with existing data. The existing
data did not provide a high level of detail. Consequently, the
specific risks for these piles were qualitatively evaluated.
Overall, the primary contaminants of concern in mine waste piles
are arsenic, lead and zinc. Arsenic and lead are a concern with
regard to human health risks, while zinc. is of concern with
regard to environmental risks.
5.4 AIR MEDIA
Mine waste piles at the site contribute metals laden dust to the
air. This contamination problem. was studied in Central city.
Central city was chosen because of the large volume of mine
waste and the relatively dense population in this area of the
site.
An ambient air quality sampling program was performed in Central
City, colorado, from August 11, through November 13, 1989. The
purpose of the study was to obtain direct measurements of metals
concentrations in the air. sampling was conducted every third
day during the sampling period, resulting in a total of 29
sample days. For each sample day, one sample of all airborne
dust particles, and one sample of respirable' dust particles
(particulate matter less than 10 microns in size), were
collected. The dust particles. were analyzed for arsenic,
cadmium, . beryllium, chromium, lead, nickel, and zinc. The
concentrations of metals per volume of air was calculated, and
the daily results were averaged to obtain a 4-month average for
each metal. This 4-month average was extrapolated to a one year
exposure using an arithmetic model. These one year values were
then used to perform a human health risk assessment. The
resul ts of this sampling program are discussed in detail in
section 6.0.
12
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6.0
SUMMARY OF SITE RISKS
A baseline risk assessment was conducted to evaluate potential
human health and environmental risks associated with the
existing contamination at the site. Actual or threatened
releases of hazardous substances from this site, if not
addressed by implementing the response action selected in this
Record of Decision, may pose an imminent and substantial
endangerment to public health, welfare, or the environment. The
following risk summary explains why this endangerment exists.
The information presented in this section is a summary of the
baseline risk assessment which was produced in conjunction with
the Phase II Remedial Investigation reports.
potential risks to human health are expressed in two ways.
There are carcinogenic (cancer causing) risks associated with
exposure to contaminants. carcinogenic risks are expressed as
the potential excess cancer incidence per a specific population
size. There are also noncarcinogenic risks associated with
exposure to contaminants, such as risks of birth defects, damage
to the liver or kidneys, etc.
In order for a human being or any living organism to be at risk
(carcinogenic or noncarcinogenic) from a contaminant, two things
must be considered. First, the contaminant must be present at
high enough concentrations to pose a risk. Second, the person
or organism must be exposed via an exposure pathway. Once this
information is obtained, a quantitative evaluation of risk can
be performed.
The first step in the risk assessment process involves
identifying the contaminants of concern and their
concentrations. At the Clear Creek/Central city site the
contaminants of concern were identified by compiling a list of
contaminants that where found in concentrations which exceeded
typical background levels. As previously mentioned, the
contaminants of concern at the site are: aluminum, arsenic,
cadmium, chromium, copper, fluoride, lead, . manganese, nickel,
silver, and zinc. In addition, mercury was evaluated in fish,
and beryllium was evaluated in air.
The second step in the risk assessment process is to determine
the pathway(s) by which a human or other living organism might
become exposed to contamination. For human health, the exposure
pathways which were identified and evaluated at the site
include: ingestion of surface water, incidental contact with
surface water, ingestion of ground water, incidental ingestion
of mine tailings and waste rock, inhalation of metals in air,
and consumption of fish. The risk assessment for the site
included evaluating human exposure based on current and future
residential uses. Additionally, exposure was evaluated based on
reasonable maximum exposure scenarios in order to ensure that a
13
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. potential health risk was not overlooked" The exposure
assumptions for human health are summarized by environmental
medium in Section 6.1.
For environmental risk tne exposure pathways which were
evaluated include: exposure to contaminants in the water column,
and contact with surface water stream sediments (for aquatic
organisms).
Once an exposure pathway is established, risk is determined by
combining the exposure (intake) of the contaminant with toxicity
data for the contaminant. For carcinogens, this toxicity data
is known as a Slope Factor, which is defined as the statistical
95% upper confidence limit on the slope of the dose-response
relationship at low doses for a carcinogen. Dose-response
relationships are determined from experimental data obtained
from laboratory animals; this data is then extrapolated to human
beings. EPA's acceptable excess cancer risk range is between 1
cancer incidence per 10,000 people and 1 cancer incidence per
1,000,000 people.
For noncarcinogens, risk is presented as a ratio of exposure
(intake) to the Reference Dose for each contaminant for a given
exposure pathway. The Reference Dose is the EPA's preferred
toxicity value for evaluating noncarcinogenic effects. The sum
of the ratios of all contaminants under consideration is called
. the Hazard Index. When the Hazard Index is greater than one it
indicates that the contaminant is likely to present a risk to
human health.
The site risks are summarized below for each exposure pathway.
Human health risks are discussed first, followed by a discussion
of environmental risks. The general toxicological data and
assumptions for each contaminant of concern are presented in
Tables 6-1 (a), (b) and (c). For each exposure pathway, a brief
summary of the other major assumptions which were used in
calculating risk will be provided. In addition, the reader
should note that some of the data tables presented later in this
section provide a "risk-based target concentration" value. For
carcinogens, this value corresponds to an excess cancer rate of
1 cancer incidence per 1,000,000 people. For noncarcinogens,
this value corresponds to a Hazard Index of one. .
When evaluating additive risks for carcinogens, the excess
cancer risk is determined by summing the individual risks posed
by a contaminant, regardless of the type of cancer caused by the
contaminant. For noncarcinogenic additive risks, only chemicals
that affect the same target organ are summed.
When reviewing the information in Tables 6-1 the reader will
notice that lead is not .listed in the" summary of toxic
endpoints for chemicals of potential concern."
14
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TABLE 6-1(a)
SUMMARY OF TOXIC HUMAN ENDPOI~TS FOR CHEMICALS OF POTENTIAL CONCERN
Endpoint (a)
--------------------------------------------------
Cherni caL (e)
Carcinogenic (b)
Noncarcinogenic (c)
Arsenic
Skin cancer;
Lung cancer
Skin keratosis
and hyperpigmentation
BerylL iun
Cancer; Lung cancer
NOAEL (d)
(organ enLargement,
cyanosis, skin lesions)
Cadmiun
Respiratory tract
cancer
Renal toxicity
Chromiun (VI)
Lung cancer
NOAEL (d)
(liver and kidney
toxicity)
Copper NA
Fluoride NA
Managanese NA
Gastrointestinal irritation
Dental fLuorosis
CNS effects; reproductive
effects (for subchronic
exposure)
Mercury itA
Nickel Lung and nasal
cancer
Silver NA.
Zinc NA
Kidney effects
Decreased body weight
Skin and mucous membrane
argyria
Anemia and reduced blood
copper
(a) Endpoint upon which the toxicity criterion is based.
(b) Yhen calculating additive. risks for potential carcinogens, the
Individual cancer risk for each chemical, regardless of the type of
cancer associated with each chemical, are surmed. .
(c) Yhen calculating additive risks for noncarcinogens, the individual
CDI:Rfd ratios are summed only for chemicals wlt~ the same endpoint
(target organ). Therefore, for this assessment, CDI:Rfd ratios for
arsenic, silver, and berylliun are surmed, as are those for cadmiun,
chromlun, and mercury. The individual CDI:RfD ratios for copper,
fluoride, manganese, nickel, and zinc are not surmed with any other
chemical.
(d) Toxicity criterion based on a no-observed-adverse effect level.
Toxic endpoints reported in the Literature are listed in
parentheses.
NA = Not appLicabLe.
Cancer slope factor not developed for this
15
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TABLE 6-1(b)
SUBCHRONIC REFERENCE DOSES FOR CHEMICALS OF POTENTIAL CONCERN
Chemical
Subchronic
Reference"
Dose (RfD) (a)
(mg/kg-day)
Safety
Factor (b)
Source (c)
Aluninun
Arsenic
Beryll iun
Cadmiun
Chromiun (III)
Chromiun (VI)
Copper
Fluoride
Iron
Lead
Manganese
Mercury
inorganic & mercurial
inorganic & alkyl
organic (methyl)
Nickel
Silver
Zinc
1E-03
SE-03
1
100
HEAST
HEAST
IoE-02 (d)
HEAST
SE-01 100 HEAST
3E-0l. 1,000 HEAST
3E-Olo 10 HEAST
3E-04 10 HEAST
2E-01 10 HEAST
(a) Oral subchronic RfD.
(b) "Safety factors u~ed to dev~lop reference doses are the products of uncertainty
and ~ifying factors. Uncertainty factors consist of multiples of 10, with
each factor representing a specific area of uncertainty in the data available.
The standard uncertainty factors include:
- a 10-fold factor to account for the variation in sensitivity among the
members of the human population;
- a 10-fold factor to account for the uncertainty in extrapolating animal
data to the case of humans;
- a 10-fold factor to account for the uncertainty in extrapolating from
less-than-chronic NOAELs to chronic NOAELs; and
- a 10-fold factor to account for the uncertainty in extrapolating from
LOAELs to NOAELs.
Modifying factors are applied at the discretion of the EPA reviewer to cover
other uncertainties in the data.
(c) HEAST . Health Effects Assessment Sunmary Tables (6/1/89).
(d) Based on . drinking water standard of 1.3 mg/l; assuning a 70-kg person ingests
Z liters 01 water per day, 1.3 mg/l = 0.04 mg/kg/day. The Drinking Water
Criteria Document for Copper concluded that toxicity data were inadequate for
calculation of an RfD for copper.
-- = Subchronic RfD has not been developed for this chemical. In the absence of a
subchronic RfD," the chronic RfD will be used to assess subchronic exposures.
16
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TABI.E 6-1(c)
CHRONIC HEALTH EFFECTS CRITERIA FOR CHEMICALS OF POTENTIAL CONCERN
Reference " S l"ope
Dose (RfO) (a) Safety Factor (d) Weight of
Chemical (mg/kg.day) Factor (b) Source (c) (mg/kg.day) -1 Source (c) Evidence (e)
Alunirun 0
Arsenic 0.001 (f) HEAST 1.75 (IJ) A
[50) (h) [IRIS) tAl
BerylliUD 0.005 100 KEAST '.3 IRIS BZ
[8.4) (h) [I R I S) [BZ)
Cadmiun 0.001 (food,i) 10 IRIS [6.11 (h) [1 RI 51 [B1)
0.0005 (water)
Chromiuu (VI) 0.005 500 IRIS ['11 (h) [1 R I 5) tAl
Copper 0.04 (j) KEAST D
Fluoride 0.06 (k) IRIS 0
Iron D
Lead IRIS BZ
Hanganese O.Z 100 HEAST D
[0.00031 (l) (100) [HEAST1
Mercury
Inorganic & mercurial 0.0003 1,000 HEAST D
inorganic & alkyl 0.0003 10 KEAST D
organic (methyl) 0.0003 10 IRIS D
Nickel O.OZ 300 IRIS [1.71 (h,m) [1 R I 5) tAl
SI lver 0.003 Z IRIS 0
Zinc O.Z 10 KEAST D
(a) Oral reference dosl except as notld.
{b) Safety factors used to dev.[op reference doses are the products of un:ertainty and modifying factors. Uncertainty
factors consist of multiples of 10, with each factor representing a specific area of uncertainty in the data
avai~able. The standard uncertainty factors include:
- a 10.fcld factor to .ccount for the variation in sansit;vity amen; th. members of the hUQIn population;
. a 10-fold factor to account for the uncertainty in extrapolatina animal data to the case of humL,.;
. a 10.fold factor to account for the uncertainty in extrapolating from less'chan'chronic NOAEls co chronic
NOAELs; and
. a 10-fold factor to account for the uncertainty in extrapolating from LOAELs to NOAELs.
Modifying factors are applied at the discretion of the EPA reviewer to cover other uncertainties in the dati.
(c) IRIS ~ the chemi~al files of EPA's Integrated Risk Information System (as of 3/1/90); and KEAST. HealCh Effects
"Assessment Sunnary Tables (6/1/89).
(d) Oral slope factor exCept as noted.
(e) EPA weight of evidence classification schem8 for carcinogens:
A . Hunan Carcinogen, sufficient evidence frea hunan epidemiological studies;
B1 . Probable HIA8I\ c.rcinogen, limited evidence from epidemiological studies.and adequate evidence from animal
studies;
BZ . Probable HIo8M c.rcinogen, inadequate evidence frOll epidemiological studies and adequate evidence from animal
studt..: -
C . P088ible HU8Ift c.rclnogen, limited evidence in animals in the absence of hunan data.
D . NoC Cluaiflld.
(f) Under raYf... by che lfa workgroup.
(9) Region Vttl guidance. Personal conversation with Jim lavelle, EPA Region Vllt toxicologist (August Z8, 1990).
(h) Inhalation SI09l factor.
(I) The cacDiUD RfD for food was derived IIsUDing absorption frOll food is one-half that in water. AISUDing that cadmiun
absorption from other non'aqueous material (i.e., soil) would be mare similar to food than to water, the Rfd for food
is used to evaluate potential exposure to cacDiUD in soils.
" .
(j) Current drinking water standard of 1.3 mg/l: assUDing a 7O.kg person ingests Z liters of water per day, 1.3 mg/l ~
0.04 mg/kg/day. The Drinking Water Criteria Document for Copper concluded that toxicity data were inadequate for
calculation of an RfD for copper.
(k) Value is for soluble fluoride.
(l) Inhalation reference dose.
(m) Value is for nickel sulfide.
-. ~ Criterion has not been developed for this chemical.
17
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Lead was evaluated separately from the other contaminarits of
. conc~rn because of the increasing concern over its effects at
low concentrations. Lead is. a carcinogen at high
concentrations, but of greater concern is the effect that lead
has on the central nervous system at lower concentrations. Lead
has been shown to cause learning disabilities and brain damage
in humans. When lead is ingested or inhaled it eventually makes
its way into the blood stream. Most scientists believe that
small amounts of lead in the blood can cause effects in humans,
and to prevent significant negative effects, exposure to lead
should be reduced to the point where lead levels in the blood do
not exceed 10 - 15 micrograms/deciliter.
A pharmacological model has been developed by researchers which
predicts blood lead levels in humans based on various exposure
patterns. This model is known as the Integrated
Uptake/Biokinetic (IU/BK) Model. The IU/BK model was used at
the Site, along with EPA guidance (Office of Solid Waste a~d
Emergency Response Directive 9355.4-02, which recommends that
lead concentrations in soil be cleaned up to 500 1000
milligrams/kilogram), to develop an action level for lead in
mine waste piles. The action level of 500 milligrams/kilogram
of lead was selected because, based on data collected at the
Site, this concentration would ensure that approximately 95
percent of all people exposed under the maximum reasonable
exposure scenario would maintain blood lead levels below 12.5
micrograms/deciliter. The 500 milligram/kilogram action level
for lead is also consistent with the range specified by EPA
guidance.
6.1
HUMAN HEALTH RISKS
6.1.1
Surface Water
Surface water at the site is not expected to present a risk to
human health from ingestion or recreational use based on the
exposure scenarios evaluated in the risk assessment.
Table 6-2 (a) shows the comparison .between risk-based target
concentrations and the concentration of the contaminants at the
municipal water diversion points. Table 6-2 (b) shows a
comparison between risk-based target concentrations, based on
ingestion of surface water while swimming, and the concentration
of contaminants at several location within the Site. Ingestion
of water from mine drainage tunnels and, in some cases, water in
their immediate proximity' could pose a risk to human health.
However, this exposure scenario was not evaluated in detail
because it is not considered to be a reasonable exposure
scenario.
18
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. .
.,
TABLE 6-2 (a)
. .
COMPARISON OF RISK-BASED SURFACE YATER TARGET CONCENTRATIONS 10 MAXIMUM SUR PACE YATER CONCENTRATIONS
AT MUNICIPAL DRINKING YATER DIVERSION POINTS: INGESTION OF DRINKING ~ATER
(Concentrations reported in ug/l)
Risk-Based
Target
Chemical (f) Concentration (a) Idaho Springs(b) Black Kawk(c) Georgetown(d) e~ire(e)
Cadmiun 18 NO 0.5 0.5 NO
Copper 1,1.00 5 12 I. NO
Fluoride 2,100 300 NO 300 NO
Manganese 7,000 11 135 22 7
Zinc 7,000 5 177 a1 21.
(a) Based on noncarcinogenic effects.
(b) Sa~le SY-Oa
(c) Sample SY-t.8
(d) Sa~le SY-25
(e) Sample SY-32 .
(f) only detected chemicals are evaluated for
evaluated because health effects criteria
the contaminants of concern; aluminum and iron are not
are not available.
NO = Not detected.
TABLE 6-2 (b)
COMPARISON OF RISK-BASED SURFACe ~ATER TARGET CONCENTRATIONS TO MAXIMUM
SURFACE YATER CONCENTRATIONS: INGESTION OF SURFACE YATER YHILE SYIMMING
(Concentrations reported in ug/l)
Risk-Based
Target South Fork
Chemical(c) Concentrations(a) CC1 CC2 CC3 CCt. Clear Creek YF1 YF2 NF1 ChC1 FR1
Arsenic 9,100 NO NO NO NO NO NO NO 3 NO NO
31 (b)
CaciniU1l ',600 1 NO 0.9 1.2 0.5 3.1 0.2 19 NO NO
ChromiU1l 1.6,000 NO NO NO NO NO NO NO 59 NO NO
Copper 310,000 30 1.2 3.2 5 , 7 NO 203 5 NO
Fluoride 550,000 600 630 900 '00 300 I.,aoo 500 300 300 NO
Manganese 1,800,000 . 111. 895 1,01.0 t8 22 10,000 111. 1.,5aO 11 30
Nickel 1aO,ooO 1.2 50 NO 30 NO NO NO a7 NO 27
Zinc 1,aOO,ooO 36' 160 215 t.oa a1 998 21 2,220 5 356
(a) Except as noted, all target concentrations derived based on noncarcinogenic effects.
(b) Target concentrations derived based on carcinogenic effects.
(c) Only detected chemicals are evaluated for the contaminants of concern; aluminU1l and iron are not
health effects criteria are available.
evaluated because no
NO 8 Not detected.
Refer to Clear Creek Phase 11 Remedial Investigation for s~le station locations.
Risk based target concentrations for carcinogens are equal to an excess cancer incidence of 1 person per t,OOO,OOO people.
19
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'The assumptions
assessment were:
for
the
surface
water
human
health
risk
Ingestion - Surface water is ingested from the current municipal
diversions; residents are assumed to ingest 2 liters of water
each day for 30 years, and are assumed to weigh 70 kilograms;
for carcinogens (arsenic) an absorption factor of 1 was used.
Recreational use - children between the ages of 9 and 18 swim in
the creeks at the site 3 times/week during the 12-week period
from June through August (swimming during other periods of the
year is unlikely due to low water and air temperature); children
swim for 1 hour and ingest 50 milliliters of surface water per
hour; children are assumed to weigh 45 kilograms.
6.1.2 Ground Water
As previously mentioned, a total of 33 wells were sampled at the
Site (14 drinking water wells and 19 monitoring wells which were
located in or near tailings/waste rock piles). The results of
the sampling are presented in Tables 6-3 and 6-4, and the major
findings are summarized below.
The results of the domestic well sampling program indicate that
only one drinking water well (located in the Virginia Canyon
area) exceeded primary drinking water standards (cadmium
exceeded) and health based criteria (manganese exceeded). This
well is not currently being used for drinking water. In four
drinking water wells (located along the mainstem of Clear
Creek), arsenic was below the primary drinking water standard,
but was present in concentrations that present a potential
excess risk of cancer ranging from 2 cancer incidences per
10,000 people to 7 cancer incidences per 100,000 people. Ten of
the drinking water wells exceeded secondary drinking water
standards for one or more contaminant. Secondary drinking water
standards are not based on potential risks to human health.
Secondary drinking water standards set limits for contaminants
which affect the color, taste or odor of the water. However,
secondary contaminants have been found at the site at levels
exceeding health-based criteria.
The results of the ground water samples taken from the 19
monitorinq wells indicate the following: The three monitoring
wells in the Empire area (West Clear Creek drainage) did not
have high enough metals concentrations to pose a risk to human
health. Along the Clear Creek mainstem, the alluvial ground
water in or near tailings and waste rock piles had
concentrations of cadmium, copper, fluoride, manganese, and zinc
that could pose noncarcinogenic risks to human health if used as
a drinking water supply.
20
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: TABLE 6-3
COMPARISON OF RISK~BASED GROUND~AtER TARGET CONCENTRATIONS TO MAXIMUM
GROUND~ATER CONCENTRATIONS IN MONITORING ~LLS: DRINKING ~ATER INGESTION
(Concentrations reported, in ug/l)
Chemical (c)
Risk-Based
Target
Concentration (a)
Clear Creek
Drainage
loIest Clear
Creek Drainage
North Fork
Clear Creek
Drainage
Alluvium
Cadmium
Chromium
Copper
Fluoride
Manganese
Nickel
Zinc
35 ND ND 3.5
0.047 (b)
18 312 NO 42
175 ND ND 9
1,400 6,700 ND 690
2,100 2,900 500 2,100
7,000 50,000 12 27,800
700 688 ND 278
7,000 60,100 25 34,300
-.-.-...
Arsenic
Bedrock
Cadmio..m
Copper
Fluoride
Manganese
Nickel
Zinc
35 ND NS 3
0.047 (b)
18 2.2 NS 78
1,400 4.1 NS 169
2,100 4,600 NS 600
, 7,000 3,520 NS 26,900
700 48 NS 208
7,000 1,570 NS 23 , 200
Arsenic
(a) Except as noted, target concentrations derived based on noncarcinogenic effects.
(b) Target concentration derived based on potential carcinogenic effects.
(c) Only detected chemicals are evaluated for the contaminants of concern; aluminum
and iron are not evaluated because health effects criteria are not available.
ND . Not detected.
NS . Not ..-pled.
Risk-baaed tlrget concentrations for carcinogens
incidence of 1 person per 1,000,000 people.
are equal to an excess cancer
. .
21
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TABLE 6-4
COMPARISON OF RISK-BASED GROUNO~ATER TARGET CONCENTRATIONS TO
GROUNO~ATER CONCENTRATIONS IN DOMESTIC WELLS: INGESTION
(Concentrations reported in ug/l)
Risk - Based Clear Creek
Target ____e_----....-...----.....-----.---...----------------..-------.............-..
Chemical(c) Concentrations (a) D~-04 D~-05 D~-06 0~-08 O~'09 D~- 10 0~-12
Arsenic 35 NO 2.7 7.5 NO .1.3 NO 1.6
0.047 (b)
Cadmium 18 NO NO NO NO NO NA NO
Copper 1,400 5.6 NO NO NO NO 6.6 1.2
Fluoride 2,100 600 500 1,800 700 1,800 700 1,600
Manganese 7,000 NO 3.5 293 118 27 2 1,510
Nickel 700 NO NO NO NO NO NO 29
5i lver 110 NO NO 0.2 NO NO NO NO
Zinc 7,000 7 4 14 37 37 77 50
North
Clear Virginia Spring
Risk-Based ~est Clear Creek Creek Canyon . Gul.:h FaU River
Target -----------.....----- --------- .-------- --------- .-...-.-.-...--.....--
Chemicalec) Concentrations (a) 0101-01 0~-02 DIJ-03 0~-07 D~-13 0\J-11 0101-14
Arsenic 35 NO NO NO NO NO NO NO
0.047 (b)
Cadmiun 18 5.7 NO NO 28 NO NO NO
Copper 1,400 781 4.6 1.9 2.7 NO 8.5 NO
Fluoride 2,100 1,800 900 300 900 200 200 1,200
Manganese 7,000 6;550 NO NO 18,500 153 3 240
Nickel 700 68 NO NO 160 NO NO NO
Si lver 110 NO NO NO NO ND ND NO
Zinc 1,000 516 15 183 18 18 22 8
(a) Except as noted, target concentrations derived based on noncarcinogenic effects.
(b) Target concentration derived based on carcinogenic effects.
(c) Only detected chemicals are evaluated for the contaminants of concern; aluminum and iron are not evaluated
because health effects criteria are not available.
NO = Not detected.
NA = Not analyzed.
Refer to Clear Creek Phase II Remedial Investigation for sample station locations.
Risk-based target concentrations for carcinogens are equal to an excess cancer incidence of
1 person per 1,000,000 people.
24
-------
. In the Black Hawk and central City area (North Clear Creek
drainage), bedrock and alluvial ground water had concentrations
of cadmium, manganese, and zinc which could pose noncarcinogenic
risks if used as a drinking water supply. Arsenic
concentrations in this area had an associated potential excess
cancer risk of 9 cancer incidences per 100,000 people for
alluvial ground water and 7 cancer incidences per 100,000 people
for bedrock ground water.
The assumptions for the ground water human health risk
assessment were: residents are assumed to ingest 2 liters of
water each day for 30 years, and are assumed to weigh 70
kilograms; for carcinogens (arsenic) an absorption factor of 1
was used.
6.1.3 Mine Tailings and Waste Rock
The potential risk to human health from incidental ingestion of
mine waste was evaluated as part of the Phase II risk
assessment. Table 6-5 provides a summary of the surface
composite data which was collected at the various mine waste
piles. A review of the data shows that. both arsenic and lead
are at concentrations which pose a potential risk to human
health. Table 6-6 provides a complete evaluation of human
health and environmental risks ppsed by each mine waste pile.
Although this section focuses on human health risks, Table 6-6
is presented here for the sake of convenience, and will also be
referenced in the environmental risk assessment section.
The assumptions used for the human health risk assessment for
incidental ingestion of mine waste were:. children between the
ages of 6 and 12 years of age are assumed to play on the mine
waste piles 5 days/week during warmer months(July and August)
and twice per week during the cooler months (May, June,
september, and October) for a total of 72 days/year; children
are assumed to ingest 100 milligrams of soil/day; children are
assumed to weigh 31 kilograms; an absorption factor of 0.80 was
used for arsenic.' .
6.1.4 Air
The results of the air sampling program conducted in Central
city are shown on Table 6-7. comparing the risk-based target
concentrations to the concentrations measured under the average,
and maximum plausible exposures indicates that there is a
potential risk to human health. The combined excess
carcinogenic risk range for inhalation of all contaminants is
4 cancer incidences per 100,000 people and 9 cancer incidences
per 100,000 people for the average and maximum exposure
scenarios, respectively. The greatest proportion of total
inhalation excess cancer risk is attributed to chromium.
23
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TABLE 6-5
COMPARISON OF RISK-BASED TAILINGS TARGET CONCENTRATIONS TO HAXIHUH TAILINGS/WASTE ROCK
CONCENIRAIIONS AT THE CLEAR CREEK SITE: INGESTION Of TAILINGS/WASTE ROCK
(Concentrations reported In mg/kg)
lIaste Rock/
T~lllngs / Waste Rock lIaste Rock Surface Soli
Risk-based Black NCC
larget Enpfre McClelland Eagle Boodle Clay Dredge Golden LI tt Ie Boodle Golden
Chemical (c) Concentrations (a) 1811 fngs I Ln\e I Hitl Hili Gregory County 181 lings Gilpin Beer Mitl Gilpin
Arsenic 1,600 4 12 630 37 106 132 188 106 236 69 33
11 (b)
Caanlun 1,600 NO 0.8 6 14 6.7 4.9 1.7 12 1 28 1,.4
thromlun 7,900 15 11, 24 20 16 1,2 48 20 6 13 83
Copper 61,000 82 58 790 225 623 319 108 386 270 312 172
Manganese 790,000 116 179 1,720 1,380 220 367 662 2,690 139 5,630 1,140
N Nickel 31,000 5 9 12 14 9.3 28 24 11 1,.4 20 38
~ Sliver 4,700 NO 1 15 4 11 7.7 11 15 29 34 6
Zinc 110,000 36 147 1,740 3,120 411 1,240 200 2,040 375 5,830 929
(a) Except as noted, target concentrations based on noncarcinogenic effects.
(b) Target concentration based on potential carcinogenic effects.
(c) Only detected chemlcDls nre evnluated for the c~ntnlRlnnnt!l or concernj oll.llllnl.ln D.ad
because no health effects criteria are available.
Iron DI'e not evaluated
-------
TABlE CHi
SUIoUooWlY Of RISKS. TAIUNGS/WASTE ROCK PIl£S
N
111
Envltonmental Risk Human Hoallh Ri...
T aiIing.JWaS18 RodI AoceIvIng SIluro \Iabn8 Sedlmenl Rank. Total f'l8dIcIed Pill. f'loJdmily to SIluro Eacesa Canc8f Avefag. f'lOllmity to f'IIpuIaIIon
Pila &Im8I8 YIeld Suapand8d SlOfm WhIct1 RI... Ingaa1lon& Sulficlal Lead Conler
~ Rank" Solids Retwn Pe.1od 81. Concenualion
W8fd8) Malnalaml I111118n Metal. MafginaUy mg/kg
T IIbu\ary" ConcenUations Unslable
Ea088d SI.eam
Sland8lds.
Phase I"
Boodl. Mil Gregory GuIcII!NtC 12&,200 HE HE HE Tailings In dose proximity 510 1,000,000 25IiOWR I
-------
TAIIlE 6-6 (CONTINUED)
SUMMARY OF RISKS - TAltINGSfWASTE ROCK PilES
tV
0'\
Envllonmental Risk Human Heallh Risk
T allingaJWas18 Roc:It Rec8Mng SU..m Volume S8dim8nt Rank. T oIaI Pledk:t8d Pilea P,oxlmity 10 SUe.m Exce.. Cance, Ave,eg. Ploxlmlty 10 PopulalJon
Pile ~ YIeld Su8fl8/ld8d SlOfm WIk:II Risk .ation' Sw11d8118ed Cen..,
(cuIIIc RanIc' Solida Retum Pe,1od ... Concenll ation
yanII) Malnelem/ When Metala M81glnaDy mg/kg
T rIbu1ary" Concenllallons Unstable
Exceed SUeam
SIandBlds'
''base 1111
a.egol)' Gulch' I GlegOlV Gulch/NCC 43,900 1 4/3 All X In lloodplain - aleep slopes e e In Cenlla! Cily
Inlo SI.eam
a.egOf)' Gulch '2 GlegOf)' GuIch/NCC 32,400 " 3/2 All X In lloodplain - aleep ilopea 8 in 1,000,000 I260WR In Cenllal City
Inlo sl,eam
aaV aV Tailinga RusseD GuIch/NCC 108.IIOOTl I 1/1 All X In 18ke Gulch - 3.5 mUe. 8 in 1,000,000 1670 App.ox. I mile south Black
115,OODWR '.010 NCC llawk
Gofden Gilpin NoIIh a... Cleek 13,000 4 2/4 All In lloodplain . wooden gill 8 in 1,000,000 I030Tl In Black Uawk
wall upslleam 0' Dlack 613WR
ltawk .ullace wale.
diversion
Black Eagle MiU ChIcago Cleek/a... 340.600 2 5/5 All In lloodplain . "eep iIopes 5 in 100,000 2670 Applox. 0.25 miles 1.001
Cleek inlo ,lIeam houses; working mine
lenced off el enll anee
unle Deal Cleek Soda Cleek/Oeal 143,500 3 6/6 All Soda Cleek On Soda Cleek - 8pplox. 2 In 100,000 1900WR App.ox. 1.5 m~es '.om
Cleek 1.0)lf Oeal Clk 2.3 miles from 0.., Cleek houses; (abandoned mIne)
Empire Ta~ing. We.. Oe., Cleek NO ANI ANI ANI T a~ings do 001 abul '"eam 3 In 10,000,000 11.5 In Empi.e - used 101 bicycle
.iding
Ranked '.om highesl (I) 10 Iowasl (7)
Sto.m evenl.elum pe.lods above this "alue exceeoS existing a"eam "andards 'AII" Indicales thai sueam alandalds .,e exceeded 101 anv alo.m e"elll whlcit occu.s al a 1'8quency 01 eveI)' 1801 mo.e days.
Slaled polential excess cancel risk Is due to the ",esence of .,aenlc In !he wasle male.iaI
Urad ~ing and was.. .ock pllea ..e conlemPOfY englnee.ed alructwe.; designed \0 pan 85~ 01 \he maximum probable precipitalion even\. A atabitity and e.o::loll analysis was 001 pellOlme<1 allhe slie. Based on exisling dala, .isks
10 aur1ace wale. '.om cofIapae Of ..osion appeal \0 be 'aRIOle. Howe"",.evIew 01 !he AMAX Inc. dischBlge "".mil indical.. unde.drains '.om \hese wasle pilea a:e . sou.ce 01 metals loading 10 Woods Cledk.
lluman herdlh ,isk. from GleQOfY Gulch " we believe:! \0 be similBl \0 Gl8!JOf"1 Gulch '2 because the waSle was gene.aled I.om the same mill.
ANI. Assumed no Impact 101' 'easona staled under "PIoximltv \0 Receiving SUeam'
NE . Nol evaluated In Remedial Invealigationa (Phase I Of Phase II)
NO . No Data Ava~able (see T exllo. explanation)
1 L 1
-------
, ~
TABLE 6-7
COMPARISON OF RISK-BASED AIR TARGET CONCENTRATIONS
TO CENTRAL CITY ANNUAL AVERAGE AND MAXIMUM RESPIRABLE
AIR CONCENTRATIONS: DUST INHALATION
(Concentrations reported in ug/m3)
Respirable Concentrations
Risk-based -.---.---................
Target Annual Annua l
Chemical Concentrations (a) Average Haxinun
Arsenic 0.000'1 0.00059 0.0018
Berylliun 0.00065 0.0010 0.0010
Caaniun 0.00089 0.00078 0.0012
Chromiun 0.00013 0.00l00 0 . 0079
Nickel 0.0032 0.010 0.019
(a) All target concentrations derived based on potential
carcinogenic effects,.
Risk-based target concentrations are equal to an excess cancer
incidence of 1 person per 1,000,000 people.
27
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The assumptions used for the human health risk assessment for
inhalation of dust were: residents are assumed to be exposed to
the contaminants in the dust 24 hours/day for 365 days/year for
30 years, and breathe 30 cubic meters of air/day; 30% of the
inhaled arsenic is absorbed in the lung; all chromium is in the
hexavalent form; residents weigh 70 kilograms.
6.1.5 Ingestion of Fish
The risk associated with ingesting fish caught within the Site
was evaluated, and the results are shown in Table 6-8. The
results show that mercury and cadmium levels in the fish tissue
are well below the risk-based target concentrations. Therefore,
ingestion of fish from Clear Creek does not appear to present a
risk to human health. It should be noted that cadmium and
mercury were specifically evaluated because, with the exception
of zinc, these two contaminants accumulate in fish to a greater
degree than the other contaminants of concern. Because of
zinc's low toxicity to humans, it is unlikely to pose a threat
to human health. .
The assumptions used for the human health risk assessment for
ingestion of fish were: residents eat fish from Clear Creek
three times/week during the 20-week main fishing season (May
through September) and once per month for the remainder of the
year, for a total of 67 meals/year; a total of 0.284 kilograms
of fish/meal is eaten; residents eat fish from the Site for 30
years and weigh 70 kilograms. .
6.2
ENVIRONMENTAL RISKS
Determining potential risks to environmental organisms is
greatly influenced by the affected environmental medium. At the
Clear Creek/Central City site, the surface water medium
represents the primary risk to organisms because it presents a
direct exposure pathway and has contamination at relatively high
concentrations. Since aquatic organisms live their life cycle
in water, they ~re at the greatest potential risk at the Site.
The Phase II baseline risk assessment evaluated the potential
risk to aquatic macro invertebrates and to the sensitive fish
populations which currently inhabit, or would normally be
expected to inhabit, Clear Creek and its tributaries. The fish
species which were evaluated include rainbow, cutthroat, brook,
and brown trout. In addition, aquatic toxicity testing of
surface water using surrogate laboratory aquatic species was
conducted as part of the Phase II Remedial Investigation. This
testing provided a direct measurement of potential risk to
aquatic life.
It should be noted that there has been an effort to establish a
greenback trout population in Bard Creek, which is a tributary
to Clear Creek.
28
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TABLE 6-8
COMPARISON OF RISK-BASED FISH TISSUE .TARGET CONCENTRATIONS
TO MAXIMUM FISH CONCENTRATIONS: INGESTION OF FISH
(Concentrations reported in mg/kg)
Risk-Based
Target
Chemical Concentration (a) CC1 CC2 CC3 CCl.
cadmiun 1.3 0.082 0.052 0.064 0.047
Mercury 0.4 0.030 0.025 0.049 0.034
(a) Based on noncarcinogenic effects.
Refer to Clear Creek Phase 11 Remdial Investigation for sample station locations.
29
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.Tpe greenback trout is on the threatened and endangered species
list. Remedial actions at the site are not expected to impair
any of the efforts to establish the greenback trout in Bard
Creek. .
Due to the large amount of data collected at numerous sampling
locations, no attempt will be made to present all of the data in
this document. Only the major findings of the risk assessment
will be provided here. Individuals interested in evaluating all
of the location-specific data can find it in Section 1 of the
Appendix for the Phase II Remedial Investigation.
6.2.1 Macroinvertebrate Risks
Water Column
Acute effects to macro invertebrates are expected in the upper
portions of North Clear Creek, Gregory Gulch, and Lion Creek.
Iron concentrations in the lower section of Clear Creek, upper
section of Fall River, upper section of West Clear Creek, Woods
Creek, ute Creek, Four Mile Gulch, Soda Creek, lower North Clear
Creek, Gregory Gulch, and Chase Gulch may be lethal to some
'species of macro invertebrates . The eight mine tunnel discharges
identified in Figure 1-1 are expected to be lethal to many
species of macroinvertebra~es.
Stream Sediments
1m evaluation of potential risks to macro invertebrates posed by
contaminated stream sediment was conducted at the site. Metal
concentrations in sediments were measured at several Site
locations. In general the results indicate that both tunnel
discharges and tailings and waste rock piles are increasing the
metals load in the sediments immediately downstream of the
sources. The benthic macro invertebrate community was sampled
and shown to decrease in abundance and diversity downstream of
the contamination sources. Results of solid phase sediment
toxicity testinq indicate that, in some locations, the sediment
is ~hronically toxic to the macro invertebrate population.
6.2.2 Risk to other Aquatic Life
Water Column
The remainder of the environmental risk discussion will focus on
potenti~l risks to other aquatic life at the Site. The
contaminants of concern and their concentration in surface water
vary with time and the location in the drainage basin. Acute
toxicity testing of water quality showed that conditions are
toxic to CeriodaDhnia and fathead minnows during both low and
high flow. Although metals concentrations are generally higher
during low flow conditions, high flow conditions were sometimes
30
-------
more acutely toxic to CeriodaDhnia and fathead minnows. This is
. likely due to factors other than metals concentrations such as
pH, hardness, and alkalinity. The eight mine tunnel discharges
were tested and shown to be acutely toxic to Ceriodaohnia and
fathead minnows. .
Additionally, potential risk to aquatic life was evaluated by
comparing instream concentrations of the contaminants of concern
to values necessary to protect aquatic life - state of Colorado
table value standards and literature derived values (state of
Colorado table value standards are equally as or more protective
than Federal water quality criteria for aquatic life). The
results of this comparison indicate that zinc concentrations
consistently exceed aquatic life criteria and state of colorado
table value standards at. many locations in the basin. In
addition, copper, cadmium, and manganese concentrations
frequently exceed state of Colorado table value standards, along
spec if ic stream segments. A more specif ic summary showing
contaminants, and the locations in the drainage basin where the
contaminants exceed state of Colorado table value standards is
presented below. Please note that the segments are based on the
Colorado stream standards designations.
segment 1 - Clear Creek mainstem and tributaries from
headwaters to silverplume: cadmium, copper, zinc,
lead.
Segment 2 - Clear Creek mainstem and tributaries from
silverplume to Argo tunnel: cadmium, copper, zinc,
lead, iron, manganese, nickel. Aluminum, fluoride,
and pH are also exceeded in the Argo, Big Five,
McClelland, and Rockford tunnel discharges.
segment 3a - All of South Clear Creek to confluence
with Clear Creek: Cadmium standard was exceeded by
0.1 part per billion during high flow only. This
exceedance is not considered significant.
segment 4 - West Clear Creek to confluence with Woods
Creek. No contaminants of concern exceeded aquatic
life standards.
segment 5 - West Clear Creek mainstem from Woods Creek
to confluence with Clear Creek: cadmium, manganese,
zinc.
segment 6 - Mad Creek tributary to West Clear Creek.
No contaminants of concern exceeded aquatic life
standards.
Segment 7 - Woods creek mainstem: manganese, zinc.
segment 8 - Lion Creek mainstem: cadmium, copper,
zinc, iron, manganese.
segment 9 - Fall River mainstem: manganese, nickel,
zinc.
segment 10 - chicago Creek mainstem: No contaminants
of concern exceeded. Zinc exceeded in ute Creek a
tributary to chicago Creek.
31
-------
Segment 11 - Clear Creek mainstem from Argo Tunnel to
Golden: copper, zinc, lead.
Segment 12 - Tributaries to the Clear Creek mainstem
from Argo to Golden excluding North Clear Creek. No
significant tributaries identified, therefore not
sampled.
Segment 13 North Clear Creek mainstem and
tributaries: cadmium, copper, zinc, arsenic, iron,
manganese, nickel.
In addition to evaluating direct stream concentrations of
contaminants, Revised Soil Loss Equation computer modeling of
runoff from mine waste piles was conducted to evaluate the
impact that contaminated runoff would have on the receiving
stream. The results of this modeling are presented in section
6.1.3 in Table 6.6. In general, the results indicate that the
majority of the mine waste piles cause an exceedance in state
stream standards for very low intensity rainfall events. For
clarity it should be noted that state table value standards have
been adopted on many of the stream segments at the site. In
these cases the state stream standard is also the Colorado state
table value standard. However, when this is not the case the
state has set site specific numeric standards which, in general,
are great~r than state table value standards. This fact does
not significantly alter the conclusions shown in Table 6.6.
Also, as noted in Table 6.6, several of the mine waste piles are
marginally unstable, and the collapse of these mine waste piles
would likely pose a threat to a~~atic life.
In ~etermining potential risks to aquatic life from ground water
that is tributary to surface water, two areas were identified as
playing an important role. The Argo Tunnel area ground water
has a substantial impact on surface water. The precise location
of the ground water impact in the Argo Tunnel area is not known,
but appears to be largely due to ground water from the Virginia
Canyon area. Further delineation of the ground water impact in
the vicinity of the Argo Tunnel will take place during Remedial
Design for Operable Unit. #3.
The second important potential ground water impact on surface
water is taking place along North Fork Clear Creek between
Gregory Incline and Russell Gulch. The exact location of this
ground water impact was not identified during the Phase II
Remedial Investigation. qonsequently, it is not known whether
the impact is confined to a relatively small area or occurring
over a large diffuse section of the stream, and it is not
completely known how large a role other sources of surficial
mine waste may be playing in this area.
stream Sediments
Arsenic,
cadmium,
copper,
lead,
and zinc concentrations were
32
-------
. ,measured in stream sediments at eight locations at the site and
compared to trout toxicity.data. The results indicate that one
or more of these contaminants pose a potential chronic risk to
trout from exposure to strea~ sediments in the mainstem of Clear
Creek, upper'West Clear Creek, upper North Clear Creek, Gregory
Gulch', and Fall River. These risks are expected to affect trout
reproduction and/or early life stages.
6.3 TUNNEL SURGE EVENTS
In addition to the potential site risks described above, the
Phase I and II Remedial Investigations identified surge events
from mine drainage tunnels as a' potential risk. A surge event
is defined as a sudden, short-term increase in the discharge of
acid mine drainage from a tunnel. Surge events are believed to
result from tunnel roof falls which form small dams that can
retain water within the tunnel. When sufficient water pressure
builds up behind these dams, they can collapse causing a short-
term increase in the tunnel discharge. The frequency, duration,
magnitude, and potential risk resulting from surge events are
not well understood and have not been well documented.
, 7.0
DESCRIPTION OF REMEDIAL ACTION ALTERNATIVES
Remedial action alternatives in the Feasibility Study report
were evaluated in accordance with the comprehensive
Environmental Response, compensation,. and Liability Act, as
amended by the Superfund Amendments and Reauthorization Act, and
the National contingency Plan. Prior to evaluating remedial
action alternatives, several preliminary evaluations occurred.
Remedial action objectives were identified on the basis of the
site characterization results. A broad range of response
actions and technologies were initially considered and screened
based on relative effectiveness, implementability, and cost.
These criteria were utilized to reduce the. number of
technologies being considered to those which show the most
promise, and which cover an appropriate range of approaches to
remediation. After screening the technologies, remedial action
alternatives were then developed out of various combinations of
technologies.
A description of remedial technologies which were eliminated
from undergoing detailed analysis can be found in the Phase II
Feasibility Study. In . general, these technologies were
eliminated because they were either technically infeasible, or
when compared to similar technologies, were less effective, more
costly, and/or more difficult to implement.
Prior to describing the remedial action aiternatives for the
site, it is important to point out that the development of
cleanup alternatives was limited to a selected number of stream
segments (see section 6.2.2 for the list of stream segments at
33
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the site). The process that was used to select stream segments
that require remedial action is discussed below.
As pointed out in section 6.2.2 there are several stream
segments in the Clear Creek. basin where Colorado state table
value standards have been established as the stream standard.
When this is not the case, state numeric standards have been
established as the stream standard. These numeric standards are
generally greater than Colorado state table value standards.
Appendix B provides summary tables which show state stream
standards and Colorado state table value standards.
As previously mentioned, Colorado state table value standards
are equally or more protective than Federal Water Quality
criteria. Therefore, stream segments which did not exceed
Colorado state table value standards were not evaluated because
no risk is present. When a stream segment was shown to exceed
Colorado state table value standards an evaluation was made to
see if the state stream standard was also exceeded. If the
state standard was not exceeded and was considered to be
protective of the designated uses of the stream, based on site
specific considerations such as the geologic and geographic
characteristics of the area, then the stream segment was not
considered for remediation. USing this criterion it was
determined that remedial action was not required for South Clear
Creek and Ute Creek (tributary to Segment 10).
For stream segments where water quality exceeded Colorado state
table value standards and/or State stream standards, an
evaluation of the physical characteristics of the stream and the
types and concentration of the contaminants present was
performed to see if a substantial threat to the environment
exists. An evaluation of the results of the aquatic toxicity
testing was also used when this data was available. Using these
criteria, it was determined that cleanup alternatives would not
"need to "be developed for Fall River (Segment 9), Browns Creek
(tributary to Segment 1), and North spring Gulch (tributary to
Segment 2). This point is discussed in further detail below for
each of these streams.
Fall River exceeded state standards for three contaminants. The
chronic standards for nickel and manganese were only slightly
exceeded, and the acute standard for zinc was exceeded.
However, aquatic toxicity ~esting of samples collected from Fall
River showed little to no toxicity. A non-point source cleanup
of mine waste was recently completed on Fall River by the
Colorado Mined Land Reclamation Division under its abandoned
mined land program. It is expected that this effort will reduce
the concentration of contaminants in Fall River to levels which
will meet stream standards.
Browns Creek is a small tributary to Clear Creek.
During low
34
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. . flow it discharges approximately 0.75 cubic feet per second.
The water quality in Browns Creek only exceeded state standards
for lead. The lower portion of Browns' Creek is very steep as it
passes over rock fragments a~d exposed bedrock. This portion of
Browns Creek does not appear capable of supporting aquatic life
due to the lack of adequate habitat. For these reasons the
water quality in Browns Creek was not judged to be a substantial
risk to the environment.
North Spring Gulch is a very small tributary to Clear Creek.
During low flow it discharges 0.17 cubic feet per second. The
water quality in North spring Gulch only exceeded state stream
standards for zinc. Due to its low discharge and the gradient
of the stream channel, North spring Gulch provides little to no
physical habitat for higher forms of aquatic life. For these
reasons North spring Gulch was not judged to be a substantial
threat to the environment.
Trail creek is a small tributary to Clear Creek. During low
flow it discharges 0.28 cubic feet per second. Trail Creek was
not shown to significantly impact Clear Creek, but state stream
standards for cadmium, copper, lead, and zinc were exceeded in
Trail Creek itself. A remedial action alternative was not
developed for Trail Creek.
Lion Creek is a small tributary to West Clear Creek. During low
flow it discharges 0.28 cubic feet per second. State standards
for metals have not been set for Lion Creek because it provides
very poor physical habitat. Applying State table values
standards to Lion Creek is not considered appropriate because of
its low discharge and steep gradient. Lion Creek was not shown
to significantly impact West Clear Creek, but it does contain
concentrations of cadmium, copper, iron, manganese, and zinc
which exceed State table value standards. For this reason, a
remedial action alternative was developed for Lion Creek.
However, due to insuff icient data, no remedial action was
chosen.
At this time, a definitive decision can not be made regarding
the significance of and, if necessary, the appropriate remedial
action for, Trail and Lion Creeks. EPA and CDH will continue to
evaluate the impact of these streams after implementing this
Record of Decision.
A total of six remedial action alternatives were developed and
evaluated in detail in the Phase II Feasibility Study. During
the development of the Proposed Plan a seventh alternative was
developed using various components of the six feasibility study
alternatives. The seven alternatives encompass various
combinations and levels of cleanup for surface water, ground
water, and tailings and waste rock contamination at the site.
In addition, a method for controlling surge events was developed
35
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'independent of the seven alternatives. This provided decision
makers the ability to add or eliminate the "surge event control"
component of a potential cleanup plan to any of the. seven
alternatives.
Common components of all alternatives, except no action, are:
reduction of the metals load from Woods Creek to . the levels
established in the EPA National Pollutant Discharge Elimination
System permits for the Urad and Henderson Mines; engineering and
institutional controls at active milling sites; treatment of one
or more tunnel discharges; and a method for addressing potential
human health risks from ingesting ground water. In addition,
each alternative involves contamination remaining on-site. The
Comprehensive Environmental. Response, Compensation, and
Liability Act requires that the site be evaluated no less than
every five years when contamination remains on-site. If
indicated by the evaluation, remedial action would be
implemented at that time to remove or take additional action to
control contamination.
Risk to human health from ingestion of ground water at the site
would be addressed under each alternative, except no action, by
providing an alternative water supply (municipal or bottled
water or wellhead treatment) where existing drinking water wells
exceed primary maximum contaminant levels or health-based
criteria for secondary contaminants for the contaminants of
concern at the site. Water well users would be allowed to have
their well water sampled for heavy metals at no expense,
provided tllat the sampling request is made within two years of
the signing date of the Record of Decision for the site. In
addition, in order to be eligible for well sampling, and if
necessary, an alternate drinking water supply, it must be
determined that the ground water became contaminated as a result
of mining activity. This determination will be performed on an
individual basis once the request for sampling has been made.
Future wells drilled at the Site would not be eligible for
testing or an alternative water supply. EPA and CDH will employ
a public education program alerting residents to the potential
risks associated with contaminated ground water and will explore
a notification program through the state Engineer's Office and
Gilpin and Clear Creek Counties. In addition, CDH and EPA will
explore a notification program for new residents to the Counties
who purchase existing homes.
Although the ground water'in the area has not been classified
for use, Federal and Colorado primary drinking water standards
and Colorado ground water regulations have been identified as
relevant and appropriate at the site because of the present and
possible future use of ground water as a drinking water supply.
In addition, health-based standards, for contaminants of concern
that do not have primary standards, will be used to ensure
protection of human health. Treatment of the ground .water
36
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throughout the approximatelY 400 square mile ,study area is
. 'considered technologically impracticable from an engineering
standpoint. The extensive natural mineralization of the area
and the multiple potential .sources of contamination preclude
removal of all potential contamination sources and restoration
of the aquifers. Furthermore, restoration of fractured bedrock
aquifers and multiple alluvial. aquifers is considered
technically impracticable due to, ineffectiveness of treatment
technologies, and the need for multiple treatment units which
would not be effective in removing the sources of contamination,
respectively. For these reasons, the relevant and appropriate
requirements will be waived according to the criteria
established in the National contingency Plan. However,
protectiveness of human health will be provided via an alternate
drinking water supply which will meet relevant and appropriate
requirements and health-based standards.
In the case of arsenic, where the health-based level is lower
than the primary drinking water standard the primary drinking
standard will still be used. A number of,factors are taken into
consideration when setting the primary drinking water standard
for a contaminant. These factors include determining if the
contaminant occurs naturally at elevated concentration,
evaluating limitations of treatment technologies, and economics.
These factors have been considered by EPA' s drinking water
program and form the basis for maintaining the drinking water
standard for arsenic at its current level.
with regard to compliance with legally applicable or relevant
and appropriate requirements most of the alternatives, with the
exception of the no action alternative, will need to meet
similar requirements. A summary of the legally applicable or
relevant and appropriate requirements which are common to each
alternative is provided below. A complete list of the legally
applicable or relevant and appropriate requirements which will
be considered at the site are also included as Appendix B.
The relevant and appropriate requirements for controlling
erosion and contaminant loading to surface waters from mine
waste piles are state table value standards, and state stream
standards are considered legally applicable, because runoff from
these piles could result in an exceedance of these standards.
Federal storm water regulations are also considered relevant and
appropriate for controlling erosion from mine waste piles.
The Clean Water Act requires technology-based requirements to be
applied when setting effluent limitations from treatment units
constructed at the site. since effluent based guidelines have
not been promulgated for releases from comprehensive
Environmental Response" Compensation and Liability Act sites,
technology-based' treatment requirements are determined on a
case-by-case basis using Best Professional Judgement to
37
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determine Best Available Technologies/Best Management Practices.
. The technology-based effluent limitations will be compared to
effluent limitations derived from the in-stream goal of state
table value standards. The water-quality based effluent
limitations will be calculated based on stream segment, low
stream flow, waste load allocations, and background contaminant
concentrations. The results of .this comparison will be
evaluated to determine which of the two limitations are
considered the most appropriate based on the conditions at the
Site. Additionally, section 304(1) of the Clean Water Act
requires the development of an Individual Control Strategy for
significant point sources of contamination. The Individual
Control Strategy will consist of a waste load allocation, total
maximum daily load, a "statement of basis" explaining the
derivation and criteria used to develop effluent limits, and
monitoring and reporting requirements. These requirements of
the Clean Water Act are considered relevant and appropriate for
the treatment systems for inactive mine discharges.
The Comprehensive Environmental Response, Compensation and
Liability Act and National contingency Plan state a statutory
preference for alternative or resource recovery technologies.
However, in the case where an innovative technology, such as
passive treatment using constructed wetlands, is employed the
discharge may not achieve either technology- or water-quality
based effluent limitations for certain contaminants. In this
situation, in order to assure protectiveness, a goal of
achieving no acute toxicity at the "end-of-pipe" will be
considered.
Colorado Solid Waste Regulations will be considered relevant and
appropriate to all nonhazardous waste presently at the Site, or
to any nonhazardous material that is subsequently generated at
the site as a result of treatment. The Colorado and Federal
Hazardous Waste Regulations will be legally applicable if
treatment unit sludge becomes hazardous by definition. It may
be possible to invoke an exclusion from hazardous waste
regulations for some of the treatment sludge". If this is the
case, then the Colorado and Federal Hazardous Waste Regulations
would be considered relevant and appropriate rather than legally
applicable. The Colorado Solid Waste Regulations will be
considered relevant and appropriate for design considerations
for man-made wetlands.
A short description of the remaining components of the seven
alternatives, and the surge event control component, are
presented below.
Control of Surae Events - would involve rehabilitation of 14
high surge potential tunnels, as identified in the Remedial
Investigation report, to a point where a flow control tunnel
plug could be installed. These surge control plugs would be
38
, -'
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designed to allow a controlled flow of acid mine water through
the plug. If large tunnel roof falls were present in the mine
tunnels and created dams which pond mine water behind them, and
if the ponds became large enough to break through the dams, the
surge control plug would allow for a controlled release of the
previously impounded water.
The potential legally applicable or relevant and appropriate
requirements for control of surge events would be state stream
standards and state table value standards because such an event
could result in exceedance of these standards. Control of the
surge event would ensure that an exceedance would not take
place.
capital Cost -
Annual Operation and Maintenance Cost -
Total Cost (30 year total present worth) -
Implementation Time - 1.5 years
$ 10,070,000
$ 16,200
$ 10,300,000
Alternative 1 - No Action
The no action alternative provides a baseline for comparing
other remedial actions at the site. The no action alternative
assumes that no remedy is implemented to control risk posed by
the contaminated media at the site. This alternative would
involve periodic monitoring and evaluation of site risks.
Capital Cost - $ 30,000
Annual operation and Maintenance Cost - Not Applicable
Total Cost (30 year total present worth) - $ 80,000
Implementation Time - No remedial action implemented.
Alternative 2 This alternative combines engineering and
institutional controls and slope stabilization of mine waste
piles with passive treatment at eight discharging mine tunnels.
Sedimentation ponds would be installed in Lion Creek and Gregory
. and Lake Gulches. Risk to human health from ground water would
be addressed by providing an alternate' water supply (where
necessary).
Engineering and institutional controls would be implemented to
limit human exposure to contaminants at the Site. Engineering
and institutional controls at mine waste piles would involve
installing fences completely around the perimeter of the piles
and invoking use restrictions. For active milling sites, use
restrictions would be tied to existing state and/or federal
permit and operational requirements.
Engineering and institutional controls would be implemented at
all mine waste piles that pose an excess cancer risk greater
than 1 cancer incidence per 100,000 people (cancer risk is due
to arsenic in the mine waste) and/or that contain more than 500
mg/kg of lead.
39
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. U.sing these criteria, engineering and institutional controls
would be implemented at Gregory Gulch #1 and #2, Clay County,
Golden Gilpin, Black Eagle, Little Bear, and Boodle Mill. Since
there is no chemistry data for the North Clear Creek tailings,
and the Chase Gulch #1 and #2 mine waste piles, it was
conservatively assumed that metals concentrations would be high
enough to require fencing. However, it should be emphasized
that prior to any remedial design, this assumption would be
verified by sampling.
The North Clear Creek Dredge tailings are located in, and along,
a specific section of North Clear Creek. The extent of
contamination in this section of North Clear Creek was not
clearly defined during the Phase II Remedial Investigation.
This area of Nqrth Clear Creek will need to be evaluated in
further detail in the future.
Slope stabilization of mine waste piles would involve regrading
piles (where possible) to increase slope stability and reduce
ponding on, and erosion from, the piles. Where pile grading is
not possible, barriers such as culverts or retaining walls would
be installed. Storm water runon control would be implemented
under both options.
Passive treatment systems, utilizing man-made wetlands, would be
implemented at the Burleigh, McClelland, Rockford, Big Five,
Argo, National, Quartz Hill Tunnels, and Gregory Incline. The
passive treatment systems would reduce heavy metals loading to
Clear Creek and North Clear Creek.
Passive treatment systems will remove approximately 99.5 % of
the zinc, 99.84 % of the copper, and 9.7 % of the manganese from
each of the discharges. Approximately 785 cubic yards of metals
precipitates will be removed from the discharges per year via
aeration/sedimentation prior to treatment by the eight passive
treatment units, and 95,290 cubic yards of metals laden-wetland
substrate will need to be removed and disposed of approximately
every seven years.
Approximately 6,890 cubic yards of sediment from sedimentation
ponds would be generated each year.
Capital Cost -
Annual Operation and Maintenance Cost -
Total Cost (30 year total present worth) -
Implementation Time - 1.5 years
$ 13,292,000
$ 240,000
$ 23,890,000
Alternative 3 - This alternative contains all components of
Alternative 2, except it eliminates the sediment ponds in
Gregory and Lake Gulches, and adds soil capping where. feasible.
Soil caps would be implemented to more effectively reduce human
health ingestion and inhalation risks and to prevent erosion of
40
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. . the waste piles by surface water. Specifically, soil caps would
be installed at Gregory Gulch #1 and #2, Clay County, Boodle
Mill, McClelland tailings, North Clear Creek tailings, and Chase
Gulch #1, and a non-soil cap would be installed on the north
side of Quartz Hill. Where required, the toe of the mine waste
piles will be moved away from surface water drainages and, if
necessary, rip-rapped. .
Where pile regrading is not feasible due to restrictive
topography or at active mills (Golden Gilpin, Black Eagle,
Chase Gulch #2, and Little Bear), physical barriers such as
retaining walls or culverts would be installed to prevent
erosion from entering streams. Under this alternative,
McClelland tailings and Boodle Mill tailings would also be
relocated away from the stream.
The elimination of the sedimentation pond in Gregory Gulch will
reduce the amount of sediment collected to 5,480 cubic
yards/year.
Colorado Solid Waste Regulations will be considered relevant and
appropriate for the capping of mine waste piles.
capital Cost -
Annual Operation and Maintenance Cost -
Total Cost (30 year total present worth) -
Implementation Time - 1.5 years
Alternative 4 - This alternative contains all components of
Alternative 3 with two modifications. First, the Argo Tunn~l
discharge would be piped to an active treatment plant (rather
than passive treatment). Secondly, the combined flow of
National Tunnel and Gregory Incline would be treated with an
active treatment plant (rather than passive treatment) .
$ 13,632,000
$ 229,000
$ 24,080,000
The addition of active treatment under this alternative results
in slightly higher removal efficiencies for. some metals in the
mine discharges which will be treated actively. Specifically,
active treatment will remove approximately 100 % of the zinc,
99.84 % of the copper and 100 % of the manganese from the mine
discharges that are treated actively. contaminant residuals are
expected to be 15 cubic yards/year of metal precipitates, which
will be. removed from the mine .discharges via
aeration/sedimentation prior to treatment by the five passive
treatment units; 28,880 cubic. yards of metal laden wetland
substrate will need to be removed every seven years; 3,300
tons/year of lime sludge precipitates will need to be disposed.
Colorado Solid Waste Regulations will be considered relevant and
appropriate for the capping of mine waste piles.
41
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Capital Cost - .
Annual Operation and Maintenance Cost -
Total Cost (30 year total present worth) -
Implementation Time - 2.5 years
$ 9,638,000
$ 1,547,000
$ 33,400,000
Alternative 5 - This' alternative contains all components of
Alternative 3 with one addition: treatment of ground water near
the Argo Tunnel in order to reduce its impact on surface water.
A pump and treat system would be installed, and the extracted
ground water would be passively treated along with the Argo
Tunnel discharge.
The addition of passive ground water treatment increases the
amount of metal-laden substrate to 128,290 cubic yards per seven
years. .
Colorado Solid Waste Regulations will be considered relevant and
appropriate for the capping _of mine waste piles.
Capital Cost -
Annual Operation and Maintenance Cost -
Total Cost (30 year total present worth) -
Implementation Time - 2.0 years
$ 15,432,000
$ 249,000
$ 28,630,000
Alternative #6 This alternative involves excavation,
transport, and on-site consolidation of the Gregory Gulch #1 and
#2, Clay' County, Boodle, Little Bear, McClelland, the North
side of Quartz Hill, North Clear Creek tailings, and Chase
Gulch #1 waste piles; engineering and institutional controls and
physical barriers would be constructed at Golden Gilpin, Black
Eagle, and Chase Gulch #2. An active treatment plant would be
installed to treat the Argo Tunnel discharge and the extracted
ground water near the Argo Tunnel. An active treatment plant
would be installed to treat the National and Gregory Incline
discharges, and passive treatment systems would be installed to
treat the other five tunnel discharges.
The addition of active treatment under this alternative results
in slightly higher removal efficiencies for some metals in the
mine discharges which will be treated actively. Specifically,
active treatment will remove approximately 100 % of the zinc,
99.84 % of the copper and 100 % of the manganese from the mine
discharges that are treated actively. contaminant residuals are
expected to be 15 cubic yards/year of metal precipitates which
will be removed from the mine discharges via
aeration/sedimentation prior to treatment by the five passive
treatment units; 28,880 cubic yards of metal-laden wetland
substrate will need to be removed every seven years; and 4,855
tons/year of lime sludge precipitates will need to be disposed.
Colorado Solid Waste Regulations will be considered relevant and
appropriate for the consolidation/capping of mine waste piles.
42
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capital Cost -
Annual Operation and Maintenance Cost -
Total Cost (30 year total present worth) -
Implementation Time - 7.5 years
$ 20,294,000
$ 1,872,000
$ 50,820,000
Selected Alternative The Selected Alternative combines
institutional controls and runoff barriers for mine waste piles
at active mill sites, and soil capping of the other mine waste
piles (see capping description under Alternative 3 for more
detail) with passive treatment of the Burleigh Tunnel, and
active treatment of the Argo Tunnel discharge including ground
water in the area of the Argo Tunnel. A pump and treat system
will be installed, and the extracted ground water will be
treated along with the Argo Tunnel discharge.
Capping of mine waste piles will not be implemented for a
maximum of one year to allow a final opportunity for.owners to
come forward with a remedy which would be considered equally or
more protective, such as remining or reprocessing. It will
still be possible for an owner or their agent to remove and
reprocess or remine mine waste after a waste pile is capped.
However, the action must not exacerbate the contamination and
the final reprocessing or treatment residuals must be disposed
of at a facility which meets applicable or relevant and
appropriate requirements. Additionally, the excess costs
associated with removing the cap in order to gain access to the
mine waste, and subsequent site restoration will be incurred by
the owner or their agent.
No action will be taken at the McClelland and Rockford Tunnels.
The interim action waiver of applicable or relevant and
appropriate requirements will be invoked for the Big Five Tunnel
discharge.
Limited action will be taken on the discharges from the Quartz
Hill and National Tunnels, and the Gregory Incline. This
limited action will involve collecting the discharges and piping
them to a location below the Black Hawk/Central City waste water
treatment plant. Further evaluation of the extent of
contamination in North Clear Creek and an evaluation of
innovative treatment technologies, which would meet the
requirements of the Clean Water Act, would be completed prior to
making a final decision on' these discharges.
Risk to human health from ground water are addressed by
providing an alternative water supply where contaminants of
concern in drinking water wells exceed primary drinking water
standards or health based standards where there are no primary
standards. In the case of lead and copper, if an exceedance of
the lead or copper standard is determined to be the result of
43
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. the water distribution system, rather than the result
contaminated ground water, then 'the property will not
considered eligible for an alternate drinking water supply.
No action will be taken to control surge evertts.
of
be
The Selected Alternative assumes that the metals load from Woods
Creek will be reduced to the levels specified in the EPA
National Pollutant Discharge Elimination System permits for the
Urad and Henderson Mines.
A passive treatment system will remove approximately 99.5 % of
the zinc, 99.84 % of the copper, and 9.7 % of the manganese from
the Burleigh Tunnel discharge. Active treatment will remove
approximately 100 % of the zinc, 99.84 % of the copper and 100
% of the manganese from the Argo Tunnel discharge and the
extracted ground water in the area of the Argo Tunnel.
contaminant residuals are expected to be 14,085 cubic yards of
metal-laden wetland substrate which will need to be removed and
disposed of approximately every seven years, and 3,495 tons/year
of lime sludge precipitates will need to be disposed.
Colorado Solid Waste Regulations will be considered relevant and.
appropriate for the capping of mine waste piles.
Capital Cost -
Annual Operation and Maintenance Cost -
Total Cost (30 year total present worth) -
Implementation Time - 1.5 years
$ 5,560,000
$ 1,204,000
$ 23,510,000
8.0
COMPARATIVE ANALYSIS OF ALTERNATIVES
The Comprehensive Environmental Response, compensation, and
Liability Act and National Contingency Plan require that
Remedial Action Alternatives be profiled against nine evaluation
criteria. A description of the nine criteria is provided below.
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 or reduced, or controlled through
treatment, engineering controls, or institutional controls.
3.
compliance with Applicable or Relevant and Appropriate
Requirements addresses whether or not a remedy will meet
all federal and state environmental laws or regulations
and/or provide grounds for a waiver.
Long-term Effectiveness and permanence refers to the
ability of a remedy to provide reliable protection of human
health and the environment over time.
2.
44
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4.
5.
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.
Short-term Effectiveness addresses the period of time
needed to complete the remedy, and any adverse effects to
human health and the environment that may be caused during
the construction and implementation of the remedy.
6.
Implementability refers to the technical and administrative
feasibility of a remedy. This includes the availability of
materials and services needed to carry out a remedy. It
also includes coordination of Federal, state, and local
governments to work together to clean up the site.
7.
Cost evaluates the estimated capital, operation, and
maintenance costs of each alternative in comparison to
other equally protective alternatives.
State Acceptance indicates whether the state of Colorado
agrees with, opposes, or has no comment on the selected
alternative. .
8.
9.
community Acceptance includes determining which components
of the al ternati ves int.erested persons in the community
support, have reservations about, or oppose.
It is important to understand that the National Contingency Plan
assigns different levels of importance to the preceding nine
evaluation criteria: The first two criteria, overall protection
of human. health. and the environment, and compliance with legally
applicable and relevant and appropriate requirements, are
considered threshold criteria. This means that in order for a
cleanup alternative to be considered for implementation it must,
at a minimum, satisfy these two criteria or provide
justification for invoking a waiver of the requirement(s).
Evaluation criteria three through seven are known as primary
balancing criteria, and are used to identify the alternative(s)
which provide the best combination of individual criteria.
Evaluation criteria eight and nine are known as modifying
criteria and are used in conjunction with the primary balancing
criteria to identify the preferred cleanup alternative. The
modifying criteria are generally determined after public
comment, and may be used to modify the preferred cleanup
alternative.
The seven cleanup alternatives for the site were profiled
against the nine evaluation criteria, and the results are
summarized in Table 8-1.. Some of the key differences between
the alternatives are discussed in greater detail below.
45
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TABl£ 6-1
COMPARISON Of ALTERNATIVES BASED ON NINE EVAlUATION CfUTERIA
CfUTERIA
SeIec88cI
~
C8ppIng Yt\Ih P"""
T raatmenl 81 Burleigh
and kIIv8 81 kgo ~udIng
Gtound Waler Ne., kgo
Maroalive 1
No ktIon
All-live 2
InstIuIIon8I/SIope
Sllblllzalion Yt\Ih
PauIw Trulm8nt
011 Mine Disdlarg..
Allernallva 3
CappIng
WlIh Passive
T raalmenl 01 8 Mine
Di&Ctwga.
Allernalive 4
CappIng
WlIh Passive
Tru\menlol :; and
kIIv8 T raalmenl 01
3 Mine Di&Ctwge.
Allernalive :;
CappIng
WlIh PassIve T rutmanl
01 8 Mine Disdl8lg.. and
Gtound W.... Near kgo
Tunnel
Allernallve 6
On.aI.. ConlOlldaUon
WIh P""" T ra.tmonl 01 :;
and Ac\jva Treatmonl 01 3 Mine
Discharga. and Ground Waler
Near Argo Tunnel
I. OVERALL
PROTECTIVENESS
Human Heallh
Envl,onmanl
low residual ",asia plla
Ingeslion and Inhalation
risk.
High reduclion In Mdimenl
loading; moderate reduc1ion
In metals loading 10 ""'-
wate,s.
2. COMPlIANCE MealS risk based air and
WIT U AAARs eal IOiIs levals al capped
piI...
Meals sllaam standards on
Clear Cr..k. Does 1101 meal
tabla value .tandards
below Well Clear Cr..k.
oJ:>
m
Crile,ia \0 be
Considered.
Colof ado
Division 01
Wildlila
Species
Specilic
Toxicity Dala
ClEAR mEEt(
Brown llout protected
Ihroughoul. erook lloul
protected throughout.
Rainbow \lout protected
\0 Wesl Cle., Craak.
Doe. not prcMde
8ddJ\IonaI proI8CIIon
01 human he8llh and
aquatic liIa.
Doe. 1101 meel risk based
leva.. lor aoII Of air.
Does 1101 meal a\al.
a\laam Of \able ..81...
stand..d..
Brown \10... prolecled Irom
Bu,lelgh \0 Argo T unn".
Brook \loul protec:led
_rywhere a~C8pt kgo
.,aa. Rainbow llOUI not
prOlected below eurleigh.
Modefa.. residual ",asia
pile Ingastion
and Inhalation risk.
low residual ",asta
pilelngeslion
and inhalation ,isle.
low residual "'asia.
plla Ingestion
and Inhalation risk.
High reduc\jon In sedimenl
loading; high reduction In
melals loading 10 sur1ace
water..
Same as Allernative 3.
Same 8$ Allernative 3,
eXOIIpllor additional
manganese removal.
Same as Allernatives 2
and 3.
low residual wasle pile
Ingestion and Inhalation
risk. .
High reduction In sedimenl
loading; higher reduction In
melals loading \0 sur1ace
watera.
Same as Allernatives 3
and 4.
Same as Allernatives 3 and
4, excepl ground waler
\lealmenl al Argo TUMel
area allows stream sland..ds
10 be met; doe. nol
meel tabla value stand..ds
below Wast CIa.. Cr..k.
Manganese ,emoval Is less
Ihan Allernative 4.
Brown llout prolected
Ihroughoul. Brook \loul
prolected Ihroughoul.
RaInbow \loul prolected
10 Wesl Qe.. Creek.
lowesll8sidual waste pile
Ingeslion and Inhalallon risk.
High reduction In sedimenl loading;
highasll8duction In metals loading
10 sur1aOll waters.
Same as Allernatives 3, 4 and 5.
Sama as Allernalive 5. excepl greater
manganese ,,,moval.
Same 8S Alternative 5.
AHARs . legally applicable 01 relevanl and appropriale requiremenls
(a) No allernalives ar. capable o. reduc.ing metals concentrations on Notth caea. ueek 10 levels which meet stream 0' aquatic lite standards. No alternatives bU' designed to tfea'g,ound waler flom drinking wate' wells. All alttunatives. except
no acUon. plcvlde allOlnate wa.u. &upplies whe.e .equired. Welit aeiU ueek meels 5tIeam and aquatic lite slanda,dt it di50Chargea 10 Woods Cleek afe I.uatud '0 the EPA dischalge permit limilations.
"- ,eduction In sedimenl High reduction In sedimenl
loading; moderate ,eduction loading; mode,ate reduction
In metals loading \0 SUI1aca In metals loading 10 aur1-
waters. watera.
Aeducas potential axposur. Meels risk basad air and
\0 tailing.. so~s levels al capped piles.
Meals aIIeam ,Iand..d. on Same as Allernative 2 and
Claar Creak, a.OIIpiIOf prevents runo" "om capped
- :; mila, O8ar Argo T unnal; piles Irom impacIing
does nol meal table value strearns.
atandards below Wast Claar
Creak.
Same as Alternative 2.
Brown \loul protected
axcapIlor Argo area and
marginally protecta.1 below
Argo. Brook I!OUI F'Otectad
."""pI - :; mila, below
Argo. Rainbow \loul prolected
ID West caear Cr...k.
-------
TAlllE 8.1 (CONTINUED)
COMPARISON Of AlTERNATIVES BASED ON NINE EVAlUATION CRITERIA
CRITERIA
SeIectIId
~
CappIng With Pass1v8
T '8&1111801 at Burleigh and
AcIM .1 "'go kIdudIng
Glound W.18I Ne.. "'fIG
AIIMn.1Ive I
No AdIon
AIIem.1Ive 2
InS1l1ullon8l/Siope
Stabiliution With
PUIive T,.a_1
01 8 Mine DI8cII8Igea
AIIemalive 3
CappIng
With Passive
T 'aalmenl 01 8 Mine
Disctwge.
AIIemalive ~
CappIng
With P8S11v8
T ..almenl 01 5 and
AcIM T..8Imen10l
3 Mine Diach..g...
AIIomalive 5
CappIng
Willi P8S11v8 T 'ealmenl
0/8 Mine Disd1..gea
and Glound Wal.. Ne..
"'go Tunnel
~temallve 6
On.slle Consolidation
With Passive T 'oalmenl 01 5
and kIIva T ,aatmant 01 3 Mine
Diac:h..gea and Glound Wal..
Ne.. "'go TUMel
2. Conlinued -
Cllte,'a 10 be
Considered
3. LONG. TERM
EffECTIVE.
NESS AND
PERMAN-
ENCE (II)
.c.
-J
4. REDUCTION IN
TOXICITY,
MOBIUTY AND
VOLUME
5. SHORT.TERM
EffECTIVE-
NESS
Tim.. ..nl~
Remedial Aclioo
Objectives are
Completud
NORTH Q.£AR a£EK
WEST ClEAR CREEK
lie commenl uncle,
aUemalives 2-6
Modellte ..liability 01 fisk
,eduction ptovided by
capping wasle pile..
Mode,ate ..liability 01
paslive Itealmant 'YSlema
a. \hey ..e a ..Ialively
new technology. High
'eliabllity 01 active
Itealmenl .)'Stems.
Modellte ..Iiabilily 01
g'ound wat.. aclive
trealmenl.
lee commenl undet
"Iemalives 2-6
No IIp8dH plaI8d8d lot
- 4 mllea below Woods
Cleek; \hen IIIooIc Itout
ptotacl8d 10 cae.. Cleek
conlluenc:8.
Does no! ,educ:e Of manage
human heellh Of enWOR-
men'" ,Iska.
No Iteatment 01 wastes
und.. \his allemallve.
low to modellte ,isk to the No fisk to \he c:ommunity
community and envi,oomenl Of envi,onment du'ing
"om dusl and ledimen! Implementation 01 thla
loading to .lteama, "'..native.
IIspec:lively, dwing
c:onsluc:lioo.
Hi ye...
No ..medi.. ac:tion objec:\-
Ives Implemenled.
No 1p8de. ptOlec:led unde, any ..Iemalive
Providing that disctwge. to Woods Cleek ..a ".ated to tha EPA diac:harga pe,mlt Umllatlon., ell Itoul apec:iea would be protec:ted.
Risk ,aduc:tion control. 01
lancing and lIIading 01
plies he". low" ..liability
then olhet ahamalives.
Mode,at. ..liability 01
pasalve Itealmenl syslem.
.. \hey ..a a ..Ialively
new tec:hnoIogy.
Modellte ..liability 01 fisk
,eduction plovidod by
capping waste pile..
Modell" ..liability 01
passive treatmenl .)'Stems
as they ..e a ..lallvely
new technologV.
Same .. Altemalive 3,
axcept hlghe' ..liability
01 ac:tive "ealment
.ystem..
S8Ine .. Allernative 3,
with \he addition ellow
10 mode,ate ..liability
01 ground wat.. passive
"aa\lnent.
Highe., ..liability ol,isk ..duc:tion Irom
waste piles because \haV would be
oonsolidated In one place. Aclive
trealment plovldes high.. ..liability
101 environmental fisk ..duc:tion; passive
t..atmenl provides moderate ..Iiabililv.
Modollte ..liability 01 ground water
aclive treatment.
All alternalive., axcept Altemalive2.leduc:ethemobilityolcontamlnantsinllleminewastepiles.Allernative 6 (on-sito oonsolidalion 01 wasle pile) would teduc:e
mobility 01 c:ontemlnants mote then the olhe, "temalives. Passive and active trealment ..a essenliallv equal in the amount 01 contamination lleated, excepllor
manganese llmoval. PaasIve Itealment Is ,eversible it pH changes. Ac:tive "..lment Is '"eve,sIbIe. Altamalives 5 and 6 lIeat the largesl volume 01 waler due
to \he addition 01 ground wate' Iteatment in \he Algo 1 uMel ..ea. .
'-- to mod..ate fisk to tha Same 8S Allemalive 2.
c:onvnunlty and envltonment
I,om dust and aediment
loading to stream,
lIopec:livelV. during
construction.
1.5 ye...
I 5 ye..s
Same a. Alte,nalivea 2
and 3.
2.5 yea,s
(bl All allemallves, eacepl no aclion, ptovide modOlalely ,eliable plotec:tion 01 human health ',om Ingestion 01 contaminated ground waler.
Same .. Allemelive.
2, 3 and 4.
2.0 ye..s
SlightiV hlghe, fisk to community
and environment due to Inc:toased
construclion ac:tivity and long..
lime 101 complolion.
7.5 years
-------
TABU: 6-1 (CONTINUED)
COMPARISON Of AlTERNATIVES BASED ON NINE EVAlUATION CRITERIA
CRITERIA .
SeIec88d
~
CappIng willi Pauive
T '88Im8nt 8\ 8u11e1gh
and ~ at Alga ~udIng
Glound Walal Ne.. Alga
Hlemallve 1
No ktIon
Hle'nallve 2
Inllltutlonal/Siope
StabIlIzation Willi
PaasMo T,eatment
01 8 Mine DiIdl8l"e.
Nlemallve 3
CappIng
WIth PUIM
T ,eatment of 8 Mine
DiIdl8l"..
Nle'nallve 4
CappIng
Willi PI"""
T,eatment 01 5 and
Active T ,eatment 01
3 Mine DIschar"e.
Htemallve 5
CappIng
Willi Paulve T,eatment
01 8 Mine Dischar"e.
and Glound Wal8l Neal
AI"o Tunnel
. Nle,nallve 6
On-1I18 ConaolJdaUon
Willi PauIv8 T ,..tment of 5
and Active T ,eetment 01 3 Mine
DiIChat"e. and Glound Wal8l
Ne.. Alga T UM8I
6.IMPlEMENTABlUTY
..e c:omment under
altemalive.2-6
1. COST (c)
Capital
Annual Operalion
& Maintenance
$5,560,000
$1,204,000
T olal (30 yeSf $23,510,000
net present worIh)
8. STATE ACCEPTANCE
9. COMMUNITY
ACCEPTANCE
04-
00
Euylo~
moclitar'.111 f8III*emenl8.
$30,000.
$480,000.
All alte,nallve. ..e conslde,ed mode,alely easy \0 Implement. Glound wale' ,estrlctions and Instilutlonal control. will 'equlre a mode,ate deg,ee of coordlnaUon
be_n ledefat, 'l8\e and local gowfnment. The equipment, personnel, Iechnology and \and 'equlfed to Implement passiw treatment ..e mace di"icufl \0
oblatn In comp8Ii-.to active treatmenL The addition 01 ,,'ound wale, trealmenl underllle Ptelerred Alternallve and Allernallve. 5 and 6 make these alte,native.
lIighdy mace diWcult \0 Implement.
$t3,272,OOO $13,632,000 $9,638,000 $15,432,000 $22,218,000
240.000 229,000 1,541,000 249,000 1,910,000
$23,890,000 $24,080,000 $33,400,000 $28,630,000 $50,820,000
See exptanetlon In text.
The Stale 01 Colorado concurs wllh Ihe Selected AlternaUve.
'Includes annual monitoring and inspection, and $40,000 10' a Public Health Evaluallon every 5 yeats.
(c) Cost estimales ..0 not Included lor providing an atte,native water supply whe,e necesSatY. See Section 8.1 lor lhese COSI estimale..
The COSI "slll'llale. lor tunnef au,,,e conl'oI plug. ..e nollncluded In Ihe above estimates. See Section 7.0 lor a deSCfiption 0I1he$8 COli estimales.
-------
Please notice in Table 8-1, under criterion nUmber two, there is
. 'a heading entitled "criteria to be ,considered". The information
presented under this heading is based on species-specific
toxicity differences for aquatic organisms. It is generally
agreed that state table valQe standards are protective of the
most sensitive aquatic species, including rainbow trout.
However, concentrations of metals in streams which exceed state
table value standards may still be protective of other trout
species, such as brown anq brook trout. Consequently, when
state table value standards are not met by a cleanup
alternative, there still may be an environmental benefit if the
alternative is protective of brook and/or brown trout. Each
cleanup alternative was evaluated with this fact in mind.
During the Phase II Remedial Investigation a water quality
computer model of the Clear Creek drainage basin was developed
(Water Quality simulation Program, version 4). This model was
developed to project and evaluate the overall effectiveness of
each individual alternative. The results of this modeling
effort helped form the basis for selecting the Preferred
Alternative and are presented in Appendix A.
8 . 1 OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
As shown in Table .8-1, Alternatives 3,4,5,6, and the Selected
Alternative are the most effective in reducing ingestion and
inhalation risks. posed by mine waste. By providing soil caps at
mine waste piles where feasible, the risk to human health is
essentially eliminated. Alternative 6 is considered to be the
most effective in reducing human health risks because most of
the .mine waste . would be consolidated in one disposal site.
However, providing that the individual soil caps on the mine
waste piles are properly 'maintained, and their integrity is not
compromised, this difference in effectiveness would be minimal.
Where waste piles can not be capped, institutional and
. engineering controls will' be used to reduce risk under each
alternative, except no action. .
Each alternative, except no action, is equally effective in
reducing the risk to human health posed by ingestion of ground
water. Risk to human health under all alternatives, except no
action, is reduced by providing an alternative drinking water
supply where required.
with regard to environmental risks, all alternatives, except no
action and Alternative 2, provide a high reduction in sediment
loading to surface water. Runoff from the mine waste piles is
controlled by capping or physical barriers depending on the
specific circumstances at each pile.
All alternatives, except no action, involve various combinations
of active and passive treatment of drainage from mine tunnels to
49
-------
control risks to aquatic life. Active treatment is. more
. e.ffective than passive treatment in removing manganese from the
mine discharges. Consequently, more manganese is removed from
the Argo, National, and Gregory Incline discharges under
Alternatives 4 and 6 than under the other alternatives. More
manganese is removed from the Argo discharge under the Selected
Alternative than under Alternatives 1,2,3 and 5. The additional
manganese removal is important in reducing aquatic life risk
posed by manganese only for the Gregory Incline discharge
because of its large manganese load. The addition of ground
water treatment under Alternatives 5, 6 .and the Selected
Alternative allows for a reduction in risk to aquatic life in
this area of Clear Creek.
Utilizing trout species-specific toxicity data, the Selected
Alternative, and Alternatives 5 and 6 provide protection of both
brook and brown trout throughout the mainstem of Clear Creek;
rainbow trout would be protected in the mainstem of Clear Creek
from the headwaters to approximately the confluence with West
Clear Creek.
Alternatives 2,3 and 4 provide protection of brook and brown
trout on the mainstem of Clear Creek everywhere except for the
Argo Tunnel area; rainbow trout would be protected in the
mainstem of Clear Creek from the headwaters to approximately the
confluence with West Clear Creek.
In West Clear Creek Alternatives 2,3,4,5,6 and the Selected
Alternative provide protection of all trout species, provided
that the Woods Creek discharge is treated to the level specified
in the EPA National Pollutant Discharge Elimination System
Permits CO - 0041467 and CO - 0000230 for Climax-Urad and
Climax-Henderson, respectively.
Alternative 1 does not provide protection of brown trout below
Argo Tunnel, and brook trout are not protected near Argo Tunnel.
Rainbow trout are not protected below Burleigh Tunnel. On West
Clear Creek, no species of trout are protected for approximately
four miles below Woods Creek's confluence with West Clear Creek,
then brook trout are protected to the confluence with Clear
Creek. .
No alternatives are capable of reducing contaminant levels in
North Clear Creek to levels which would be protective of any
species of trout.
8.2
COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS
Alternatives 3,4,5,6 and the Selected Alternative meet risk-
based air and soils levels for the capped piles. Where pile
capping is not feasible, risk from ingestion will be controlled
50
-------
by engineering controls. The risk from inhalation is not
expected to exceed risk-based air levels for the uncapped piles.
In general, the ground water at the Site is not impacted by any
large point sources of contamination. The rich mineralization
of the site contributes to a naturally elevated level of the
contaminants of concern in the ground water. This phenomenon
has been exacerbated by the historic mining and subsequent
acceleration in the weathering of mineralized rock. However, it
is not possible to accurately determine cause-effect
relationships because of complex hydrologic and geochemical
processes, and the large number and different types of ground
water aquifers at the site. consequently, treatment of ground
water to Maximum contaminant Levels, state Ground Water
standards, or health-based standards is considered to be
technically impracticable from an engineering standpoint.
Implementation of the Selected Alternative (as well as
Alternatives 5 & 6) will result in attainment of Colorado stream
standards for the mainstem of Clear Creek. Colorado state table
value standards may not be meet on the mainstem of Clear Creek
below the West Clear Creek confluence. EPA and CDH will monitor
the effectiveness of the Selected Alternative after
implementation to determine if state table value standards will
be met in this section of Clear Creek. .If state table value
standards are not met, EPA and CDH will determine whether it is
possible to meet state table value standards or will seek to
develop. site specific state standard which is protective of
the uses of Clear Creek. .
Implementation of Alternatives 1-4 will not result in attainment
of stream standards in the area of the Argo Tunnel. Zinc
standards for North Clear Creek will not be attained through
implementation of any of the alternatives (i..e., treatment of
the identified point sources). The requirements of .the Clean
Water Act for the Quartz Hill, Gregory Incline, and National
Tunnel will' be waived on an interim basis pending further
evaluation of contaminant loading to North Clear Creek.
8.3
LONG-TERM EFFECTIVENESS AND PERMANENCE
with regard to mine waste piles, Alternative 6 provides slightly
higher reliability of long-term risk reduction because most mine
waste piles would be consolidated in one place. Alternatives
3,4,5 and the Selected Alternative provide moderate reliability
in reducing risk. Alternative 2 provides a lower degree of
reliability of risk reduction because mine waste pile regrading
and fencing are less effective than capping in reducing erosion
and human exposure. Alternative 1 is least effective because it
does not manage or reduce risk.
51
-------
.with regard to treatment of surface water, all alternatives,
except no action, require the ongoing operation and maintenance
of treatment systems. These treatment systems will remain
effective and permanent, as long as they are properly operated
and maintained. The use of "passive treatment systems for mine
drainage is an emerging technology and, therefore, considered
less reliable than active treatment. Because the Selected
Alternative and Alternatives 4 and 6 involve the use of active
treatment at one or more discharges, they would be considered
slightly more reliable for treating the mine discharges than the
other alternatives. .
The treatment of ground water in the Argo Tunnel area is
considered moderately reliable in reducing contaminant loading
to surface water. Since there is no single direct source of
contamination, it is expected that contaminated ground water
will continue to be present at the site fo~ an indefinite period
of time. As with surface water treatment, ground water
treatment will remain effective and permanent, as long as the
treatment system is properly operated and maintained.
Providing an. alternative drinking water supply, where required,
will be effective in reducing long-term risk to human health.
Future ground water users at the site will be responsible for
taking appropriate measures to reduce their risks if required.
This component of the ground water remedy, for each alternative,
is considered to have a moderate to low reliability in reducing
future risks.
8.4
REDUCTION OF TOXICITY, MOBILITY OR VOLUME THROUGH TREATMENT
The no action alternative. does not implement any action to
reduce the toxicity, mobility or volume of contaminants.
with regard to contaminants in mine waste piles, the Selected
Alternative and Alternatives 3-6 reduce the mobility of
contaminants in the mine waste piles. Alternative 6 would
reduce potential mobility of contaminants in mine waste to the
greatest extent because the majority of the waste would be
consolidated in one lined disposal cell. Alternative 2 does not
reduce the mobility of contaminants in the mine waste piles
because the piles are recohtoured but not capped.
With regard to mine tunnel discharges the treatment units
implemented under the Selected Alternative and Alternatives 2-6
are effective in reducing the toxicity of the mine discharges.
The mobility of the contaminants are also reduced since they are
removed from a liquid phase and converted to a solid phase. The
passive and active treatment systems are essentially equal in
the amount of contamination treated, except active treatment
removes approximately 50-90 percent more manganese than passive
treatment. Therefore, the Selected Alternative and Alternatives
52
-------
. . 4 and 6 remove more manganese from the discharges than the other
alternatives. Passive treatment can be reversible if the pH
decreases significantly. Alternatives 2, 3 and 5 rely
exclusively on passive treatment of mine discharges. Active
treatment is not reversible". Alternatives 5 and 6 treat the
largest volumes of water due to the addition of ground water
treatment in the area of the Argo Tunnel. Alternatives 2 - 4
treat equal volumes of water. The Selected Alternative does not
treat as many tunnel discharges as Alternatives 2 - 4, but the
addition of ground water treatment near Argo Tunnel reduces the
difference in the total volume of water treated between the
Selected Alternative and Alternatives 2 - 4.
8.5 SHORT-TERM EFFECTIVENESS
Because no remedy is implemented under no action, this criteria
is not applicable to Alternative 1.
There is low risk to the community and moderate risk to the
environment during implementation of all the alternatives.
Alternative 6 has a slightly higher risk to the community and
environment in comparison to the other alternatives due to the
increased construction activity, and longer time for completion
associated with excavation, transportation, and consolidation of
select mine waste piles.
During all construction activities at the site engineering
controls will be implemented to prevent contamination of surface
water and to minimize airborne dust.
8.6 IMPLEMENTABILIT~
The no action alternative is considered easy to
because it only involves monitoring requirements.
implement
The equipment, personnel, and technology requirements for
installing. passive treatment systems make them more difficult to
implement in comparison to active treatment systems.
Additionally, passive treatment systems require large areas of
flat land. This makes passive treatment more difficult to
implement than active treatment. consequently, alternatives
that rely exclusively on passive treatment (Alternatives 2, 3
and 5) are considered more difficult to implement than the
Selected Alternative and Alternatives 4 and 6. Alternatives 4
and 6 would be more diff1cult to implement than the Selected
Alternative because they. involve construction of five passive
systems rather than one passive system.
The addition of ground water treatment under the Selected
Alternative and Alternatives 5 and 6 make these alternatives
slightly more difficult to implement.
53
-------
. 8. 7 COST
Cost includes capital construction and operation and maintenance
costs.
Cost ranks as follows from lowest to highest:
1
Alternative
No Action
Total Present Worth
$ 480,000
Selected Alternative
. capping of mine waste piles with
passive treatment at Burleigh and active
treatment at Argo including ground water
2
Institutional controls/slope stabilization
of mine waste piles with passive treatment
of 8 mine discharges
$ 23,510,000
$ 23,890,000
$ 24,080,000
$ 28,630,000
$ 33,400,000
$ 50,820,000
. These costs are the estimated thirty year total present worth of
the alternatives including direct and indirect capital costs,
monitoring costs, and annual operation and maintenance costs.
A nine percent annual discount rate was used for calculating
total present worth.
3
capping of mine waste piles with passive.
treatment of 8 mine discharges
As shown in Table 8-1 on page 48, active treatment involves
significantly higher annual operation and maintenance costs.
Therefore, the Selected Alternative and Alternatives 4 and 6
have significantly higher annual operation and maintenance
costs.
5
capping of mine waste piles with passive
treatment of 8 mine discharges and ground
water near Argo Tunnel
The cost for providing an alternate water supply has not been
included in the above costs summary. The full extent of the
ground water contamination has not been determined at this time,
consequently, a precise estimate of cost can not be made. For
planning purposes, a very rough estimate of cost was performed
4
capping of mine waste piles with passive
treatment of 5 and active treatment of 3 .
mine discharges
6
. On-site consolidation of mine waste piles
with passive t~eatment of 5 and active
treatment of 3 mine discharges and ground
water near Argo Tunnel
54
-------
based on the following assumptions: There are 4,367 wells which
will need to be sampled. Seven percent of these wells (312
wells) will be eligible for an alternate water supply. There
are four people using each of the 312 wells. and each person
consumes four liters of water every day. The alternate water
supply will be bottled water at a average cost of $0.66 per
gallon. The costs which result from these assumptions are as
follows: Annual cost $ 158,860; total present worth cost
(30 year) $ 2,057,075, which includes a one time sampling
These cost estimates are considered very conservative and
anticipated that the actual costs will be much lower than
I>rojections.
cost.
it is
these
8.8
COMMUNITY ACCEPTANCE
Many members of the local community continue to question whether
the site should have been designated a Superfund site. They
acknowledge that there is metals contamination at the Site, but
do not feel that the problems are severe enough to warrant a
Superfund designation. Nevertheless, overall the local
communities (Gilpin and Clear Creek counties) support the
Selected Alternative. The communities generally support the
idea of taking effective and reliable action on the tunnel
discharges that significantly impact surface water. They do not
fully support treating discharges that have little to no impact
on surface water. The communities support the idea of providing
an alternate drinking water supply where necessary and were
pleased that a proactive approach is being taken to control this
exposure pathway. The communities support capping of mine waste
piles and like the idea of allowing two years for property
owners to remine/reprocess the mine waste.
Downstream water users support the Selected Alternative, but
generally do not feel it goes far enough. They would like to
see treatment at all mine discharges. They felt that the remedy
focused too narrowly on protection of aquatic life, and should
also aim at reducing the total metals load in addition to
reducing concentrations.
The general acceptance of the Selected Alternative by the local
community was important in the decision to not modify any of the
key components of the remedy. The request by downstream water
users to treat all mine tunnel discharges, regardless of the
effect on instream metals concentrations, and the data which was
submitted discussing met4ls loading to a downstream reservoir
(Standley Lake) will be important factors to consider when
evaluating the remedial action options for North Clear Creek.
A detailed summary of responses to public comment is provided as
Appendix C of this document.
55
-------
. 8.9
STATE ACCEPTANCE
State acceptance typically assesses the comments of the State on
EPA lead projects. As the lead agency the State has
participated fully in the remedy selection process. CDH and EPA
jointly agree that the Selected Alternative is the most
appropriate remedy for the site.
9.0
SELECTED CLEANUP ALTERNATIVE
The objectives of the remedial action are to eliminate or reduce
the potential for exposure of present and future populations to
elevated risk factors based on contaminants which are in excess
of applicable or relevant and appropriate requirements, or which
pose unacceptable risk using the one in ten thousand to one in
a million risk range specified in the National Contingency Plan.
An additional objective is to provide protection of aquatic life
in the surface waters at the Site.
Specifically,
include:
the
objectives
Alternative
preventing incidental ingestion of mine waste posing
an excess risk of 1 cancer incidence per 100,000
people or greater, and. preventing incidental ingestion
of mine waste containing more than 500
milligrams/kilogram of lead;
reducing the excess cancer risk due to inhalation of
dust containing heavy metals;
preventing ingestion of ground water having
contaminant concentrations in excess of Primary
Drinking Water Standards,' or exceed health-based
levels for contaminants which have no primary Drinking
Water Standards for the contaminants of concern at the
Site.
preventing collapse of unstable mine waste piles
through slope stabilization. .
reducing erosion from mine waste piles to the point
where stream standards are not exceeded by storm water
runoff from the mine waste pile.
reducing contaminant loading from the mine drainage
tunnels, for the contaminants of concern at the Site,
to levels which will allow state stream standards, and
state table value standards (where they have been
determined to be.relevant and appropriate) to be met.
section 10.0 of this document, entitled "Statutory
Determination", provides a. discussion of how the Selected
Alternative achieves these objectives. Prior to this
discussion, a brief summary of the process that was used to
choose the selected cleanup alternative is provided.
of
the
Selected
o
o
o
o
o
o
56
-------
. . In selecting the preferred cleanup alternative for the site the
first step was to eliminate those alternatives which were least
effective in protecting human health and the environment, and
did not achieve legally applicable or relevant and appropriate
requirements. using this. criteria, the following cleanup
alternatives were eliminated from further consideration:
Alternative 1 "no action" was eliminated as a site wide remedy
because it does not provide adequate protection of human health
and aquatic life, and it does not achieve legally applicable or
relevant and appropriate requirements.
Alternative 2 "institutional control and slope stabilization,
and passive treatment of the eight mine discharges" was
eliminated from further consideration because it would not
reduce the ingestion and inhalation risks to human health, and
it would not reduce environmental risks posed by erosion of mine
waste piles to the same degree as the other alternatives.
Alternative 3 "capping of mine waste piles and passive treatment
of the eight tunnel discharges"; and Alternative 4 "capping of
mine waste piles', active treatment of the other five tunnel
discharges" were eliminated from further consideration because
they do not allow Colorado stream standards to be met below Argo
Tunnel. . In addition, Alternatives 3 and 4 do not protect
aquatic life (only one species protected below Argo Tunnel) to
the same extent as Alternative 5 and the Selected Alternative.
Alternative 5 "capping of mine waste piles and passive treatment
of the eight tunnel discharges including ground water in the
Argo Tunnel area" provides a high degree of human health and
environmental protection. This alternative meets legally
applicable requirements on Clear Creek and is protective of two
species of trout below Argo Tunnel. This alternative was
eliminated from further consideration because a protective, but
more cost effective, alternative was developed.
Alternative 6 "on-site consolidation of mine waste piles; active
treatment of the Argo Tunnel and Argo area ground water and
National and Gregory Incline, and passive treatment of the other
five mine discharges" was eliminated from further consideration
for the following reasons: On-site consolidation of the mine
waste would take three to five times longer to implement in
comparison to the other alternatives, and the cost of
consolidation the tailings' is at least four times more than the
other alternatives.
This additional cost is not justified because significant
additional protection of human health and the environment is not
provided by this alternative. Also, the short-term risks are
greatest under Alternative 6, due to the longer implementation
time. If it is shown that some consolidation of waste piles can
57
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. be done more cost effectively or more quickly than assumed, then
consolidation would be considered for implementation under the
Selected Alternative.
The Selected Alternative, as described in Section 7.0, was
developed by identifying and retaining the critical components
of Alternatives 5 and 6, and eliminating the components which do
not provide significant additional protection of human health
and the environment. The goal for developing the Selected
Alternative was to select a remedy that would provide the same
level of protection as. Alternatives 5 and 6, but if possible, at
a lower cost. With regard to protection of human health, it was
determined that all components of Alternatives 5 and 6 were
necessary to reduce health risks at the site. In the case of
environmental protection, it was determined that several
environmental components of Alternatives 5 and 6 could be
eliminated without reducing the effectiveness of the cleanup
plan.
Specifically, with the use of computer modeling (see Appendix
A), it was shown that the contaminant loading from the
McClelland, Rockford and Big Five tunnels do not pose
unacceptable risks to aquatic life in the mainstem of Clear
Creek, and that these discharges do not impair achievement of
the water quality standards in Clear Creek. The modeling
results indicate that the contaminant loading from these
discharges is small enough that treatment of the discharges does
not provide additional protection of aquatic life (based on
current metals loading rates in the basin). Therefore, no
action will betaken on these three discharges at this time.
As previously mentioned, the interim waiver of applicable or
relevant and appropriate requirements will be invoked for the
Big Five discharge. The Big Five discharge is currently
designated a priority discharge under section 304 (1) of the
Clean Water Act. This designation was made because the Big Five
was originally identified as a discharge which was impairing the
attainment of the water quality standards for Clear Creek. The
results of the Phase II/Operable unit #3 Remedial Investigation
and Feasibility Study indicate that the section 304(1)
designation needs to be reevaluated by the EPA and state of
Colorado water quality programs. The interim waiver will be
utilized to allow time for this reevaluation, and allow time. for
the development of a wasteload allocation for the Argo Tunnel
Individual Control strategy which may include other nearby point
sources such as the Big Five Tunnel. If it is determined that
the Big Five discharge can be removed from the Section 304(1)
priority list, then no action will be taken on this discharge
under the superfund program.
On North Clear Creek the results of the computer modeling
indicate that, based on existing information, treatment of the
58
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. ' Gregory Incline, National and Quartz Hill Tunnel discharges does
not reduce contaminant loading to a point where aquatic life
would be protected. consequently, at this time the overall
effectiveness of treating these discharges is questionable, and
treatment does not attain a level of benefit which is
proportional to the cost of treatment. Therefore, treatment of
these three discharges will not be implemented under this Record
of Decision. The EPA, in conjunction with CDH, will continue to
evaluate these three discharges under a new Operable unit in
order to develop a cleanup plan which will meet legally
applicable or relevant and appropriate requirements and provide
a balance between the cost of treatment and the benefit derived.
The decision to take limited action on the North Clear Creek
discharges was made for two reasons. First, piping these
discharges away from town would reduce the potential for direct
human exposure to the discharges. Second, collecting these
discharges would minimize the potential for impacting future
land development associated with the legalization of gaming in
the' Black Hawk/central City area. An additional benefit of
collecting these discharges is that it will allow for a better
understanding of the possible sources of non-point metals
loadings in the Black Hawk area.
The Selected Alternative selects active versus passive treatment
at the Argo area for several reasons. First, due to the large
volume of contaminated water in this area the passive treatment
option did not provide as high a level of reliabili ty as
desired. Second, based on existing information, if a passive
treatment system were installed, it would require a very large
area of prime land (approximately 7 acres) and may conflict with
local land use.
It was determined that no action would be taken to control mine
tunnel surge events. Since the frequency, duration, magnitude
, and effect of these events have not been shown to pose
unacceptable risks to human health or the environment, there is
not adequate justification at this time to support
implementation of surge control plugs at the fourteen high surge
potential tunnels. If a surge event were to occur, and if it
resulted in exceedance of drinking water standards in Clear
Creek, potential downstream water users can be notified to take
appropriate action to ensure that the water is not used or, if
necessary, is treated to drinking water standards. It should be
pointed out that the potential for increased flow from mine
tunnels will be considered when designing the treatment units
for the Argo and Burleigh discharges under the Selected
Alternative.
59
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10.0
STATUTORY DETERMINATIONS
Remedial actions selected at Superfund sites must be protective
of human health and the environment. The Comprehensive
Environmental Response, compensation, and Liability Act also
requires that the selected remedy for the Site comply with
legally applicable or relevant and appropriate requirements
established under state and Federal laws, or justify a waiver of
the requirement. The selected remedy must be cost effective and
utilize permanent treatment technologies or resource recovery
technologies to the maximum extent practicable. The Act also
contains a preference for remedies which include treatment as
a principal element. The following sections discuss how the
selected remedy meets these requirements.
The selected remedy meets the statutory requirements of section
121 of the Comprehensive Environmental Response, Compensation,
and Liability Act.
10.1
PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy for the site protects human health and the
environment through the following engineering controls:
o.
Capping of mine waste piles where feasible, and access
restrictions at active mill sites or where capping is not
feasible. This will prevent human exposure to mine waste
piles which present an excess carcinogenic risk of more
than 1 cancer incidence per 100,000 persons (this equates
to an arsenic concentration of 130 milligrams/kilogram or
greater), and will prevent human exposure to mine waste
piles with concentration of lead at 500 milligrams/kilogram
or greater. Where capping is not feasible runoff barriers
will be provided to reduce the amount of erosion entering
surface water from the mine waste pile.
The carcinogenic risk level at the site is due to the
presence of arsenic in the mine waste piles. The
background concentration of arsenic at the site represents
an excess carcinogenic risk of one person in one million.
The potential excess carcinogenic risk level of one cancer
incidence per 100,000 people was selected to ensure that
the concentration of arsenic at this risk level was clearly
distinguishable from background concentrations. In
addition, the one excess cancer incidence per 100,000
people risk level represents the statutory median risk
value that Superfund cleanups should achieve.
The decision to take remedial action on mine waste piles
with concentrations of lead at 500 milligrams/kilogram or
greater was made based on both the use of the Integrated
Uptake/Biokinetic Model which estimates blood lead levels
60
-------
o
in children under various exposure situations, and EPA
guidance (Office of Solid W'aste and Emergency Response
Directive 9355.4-02) which recommends levels of 500 - 1000
milligrams/kilogram (see lead discussion in section 6.0 for
more detail).
Providing an alternate drinking water supply for water
wells when concentrations of the contaminants of concern
exceed primary Maximum contaminant Levels, and when
concentrations exceed health-based standards for
contaminants with no primary standards, will reduce risks
to human health. Water wells drilled more than two years
after the signing of this Record of Decision will not be
eligible for an alternate drinking water supply. Potential
risks to future users of ground water will be controlled
through public education. Future ground water users will
be informed of the potential for encountering contaminated
ground water and the options available to reduce their
risks should contaminated ground water be encountered.
Future ground water users will be financially responsible
for the costs of testing and any remedial action which they
may decide is necessary.
o
The air quality investigation in the Central City area
showed that the potential risk of inhalation of dust
containing heavy metals could not be attributed to any
individual or group of mine waste piles. consequently, the
amount of risk reduction can not be quantitatively
determined. since the selected cleanup alternative
involves capping of mine waste piles where possible, the
inhalation risk at each of the capped piles will be
eliminated and the overall risk reduced. Furthermore, the
reasonable maximum potential excess carcinogenic risk
estimate of 9 cancer incidences per 100,000 people for the
air exposure pathway is currently within the risk range
which should be attained by Superfund. cleanups.
The selected remedy for the site protects human health and the
environment through treatment of the following surface water
discharges:
o
The environmental risks associated with contaminated
surface water at the site will be controlled through
treatment of the mine drainage tunnels, and treatment of
the contaminated groundwater near the Argo Tunnel.
Treatment of the Burleigh and Argo Tunnel discharges, and
contaminated ground water in the Argo tunnel area, will
reduce contaminant loading to surface water to a level
which will allow Colorado state stream standards to be met.
Also, as discussed in the comparative analysis section, the
treatment of these sources of contamination will allow for
additional protection of brown, brook and rainbow trout.
61
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The reduction of contaminant loading from Woods Creek will
be achieved under active National Pollutant Discharge
Elimination System discharge permits. This reduction in
contaminant loading is expected to provide protection of
brook, brown and rainbow trout in West Clear Creek.
The Selected Alternative may not achieve Colorado
state table value standards on Clear Creek below the
West Clear Creek confluence. EPA and CDH will monitor
the effectiveness of the remedy after it is
implemented to determine if state table value
standards are achieved. If they are not achieved, an
evaluation will be made to determine if additional
cleanup is required, or, it may be determined that a
site-specific state stream standard can be established
which is protective of the uses of Clear Creek.
The reduction in point source contaminant loading and
the reduction in erosion from mine waste piles will
reduce the amount of contaminated sediment in the
surface waters at the site. Because the' risks to
aquatic life from this exposure pathway are relatively
small, it is anticipated that the Selected Alternative
will effectively reduce this risk.
Potential environmental risks posed by the Gregory Incline,
National, and Quartz Hill Tunnels will not be completely
addressed under this Record of Decision. The interim remedy
wavier of legally applicable or relevant and appropriate
requirements will be used to defer a final decision on these
discharges. The interim remedy waiver will also be used for the
Big Five Tunnel discharge. These points are discussed in detail
in section 10.2.
During implementation of the selected remedy appropriate
engineering controls will be used to control dust generation,
sediment loading to surface water, and other risks which will be
present during implementation of . the selected remedy.
Therefore, no unacceptable short-term risks will result from
implementation of the selected remedy.
10.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS
The selected remedy will ~ttain legally applicable or relevant
and appropriate requirements (ARARs) for the exposure pathways
which are addressed by the selected remedy.
The limited action of cOllecting the Gregory Incline, National,
and Quartz Hill Tunnels is not considered the final action for
these discharges. This limited action is considered to be an
interim measure and will become part of a total remedial action
62
-------
. - which will attain legally applicable or relevant and appropriate
requirements. The interim waiver of requirements is being used
because, based on existing information, the treatment of these
three discharges does not reduce contaminant loading to a point
where aquatic life would be. protected. Consequently, at this
time the overall effectiveness of treating these discharges is
questionable, and treatment does not attain a level of benefit
which is proportional to the cost. - EPA, in conjunction with
CDH, will continue to evaluate these three discharges under a
new Operable unit in order to develop a cleanup plan which will
met legally applicable or relevant and appropriate requirements
and provide a balance between the cost of treatment and the
benefit derived. A Record of Decision for the new Operable Unit
is expected within three years from the signing of this Record
of Decision.
The interim remedy waiver will be used for the Big Five Tunnel
discharge to allow time for a reevaluation of its designation as
a priority discharge under section 304(1) of the Clean Water
Act. If it is determined that the Big Five discharge can be
removed from the section 304(1) list, then no action will be
taken under the Superfund program.
The following summarizes the primary legally applicable or
relevant and appropriate requirements for the site, and how the
selected remedy will attain the requirements. Appendix B
identifies the legally applicable or relevant and appropriate
requirements for the site in detail.
10.2.1
contaminant-specific Requirements
The Safe Drinking Water Act, 40 CFR Part 141, Colorado Primary
Drinking Water Regulations,S CCR 1003~1, are considered
relevant and appropriate for ground water at the site. The Act
and Regulations establish Maximum contaminant Levels for some of
the contaminants of concern at the site. The selected remedy
does not seek to restore ground water at the site to Maximum
contaminant Levels because it is not technically feasible to
control the sources of heavy metals contamination at the site,
and it is technologically impracticable from an engineering
standpoint to treat fractured bedrock aquifers and the numerous
discrete alluvial aquifers within the 400 square mile study
area. The selected remedy will attain these requirements by
providing an alternative drinking water supply which meets
Maximum contaminant Levels~ where required.
The Federal Solid Waste Disposal Act, Subtitle C, sets
requirements for identification of hazardous wastes and is
considered relevant and appropriate for the mine waste at the
site if the waste is determined to be characteristic for metals.
The Act would be considered legally applicable for any new non-
exempt hazardous waste which may be generated at the site.- The
63
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. selected remedy will attain these requirements if hazardous
waste is generated or encountered. -
contaminant specific ARARs for surface water at the site include
the Federal Clean Water Act,. the Colorado Water Quality Control
Act, Colorado Basic Standards and Methodologies for Surface
Water, Colorado Classifications and Numeric Standards, South
Platte River Basin, et ale The sections of these ARARs that
define effluent limitations are considered legally applicable.
The use of Colorado state table value standards to establish
levels of cleanup/effluent limitations are considered relevant
and appropriate. The selected remedy will attain legally
applicable requirements instream and-will attain relevant and
appropriate requirements at the point of discharge from
treatment units, based on the instream dilution.
10.2.2
Lpcation-Specific Requirements
The Federal Endangered Species Act and Colorado Wildlife
Nongame, Endangered, and Threatened Species Act are considered
legally applicable and, in part, set requirements for the
protection of greenback trout, golden eagles, and migratory
birds. The selected remedy will comply with these ARARs.
The Federal Executive Order for Protection of Wetlands,
Executive Order on Flood Plain Management, Fish and Wildlife
Coordination Act,and section 404 of the Clean Water Act
establish requirements and restrictions when altering waters of
the United States and riparian and wetland areas. These
requirements are legally applicable ARARs at the Site, and the
selected remedy will comply with these requirements.
Federal and State historical and archaeological acts require
protection of historical resources and places and are considered
legally applicable at the Site. The selected remedy will comply
- with these requirements to the extent possible. Documentation
of historical resources will be performed, as ~ecessary, at mine
waste piles which will be altered by' capping and/or slope
stabilization.
10.2.3
Action-Specific Requirements
Federal and State solid waste acts and regulations establish
technical requirements for capping of mine waste piles and
construction of solid waste impoundments. These requirements
are considered relevant and appropriate at the Site and will be
attained by the selected remedy.
Federal storm water regulations establish requirements for
controlling storm runoff. These requirements are considered
relevant and appropriate for controlling runoff from mine waste
piles and will be attained by the selected remedy.
64
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. . Federal and state hazardous waste acts and regulations will be
attained for any hazardous waste which may be generated as the
result of treatment of the mine discharges. This waste would be
disposed of in a subtitle C (hazardous waste) landfill or
treated to render the was'te "non-characteristic" and then
disposed in a subtitle D (solid waste) landfill.
state air quality regulations to control fugitive dust during
remedial action are considered applicable at the site, and the
selected remedy will employ engineering controls to attain this
requirement.
10.2.4
"To Be considered" Requirements
The Colorado Division of Wildlife has established species-
specific toxicity data for rainbow, brown and brook trout. This
data has been used to evaluate the effectiveness of each of the
remedial action alternatives. The selected alternative was, in
part, chosen because it provides the highest level of protection
of trout when compared to the other alternatives developed for
the site.
10.3
COST EFFECTIVENESS
The selected remedy is cost effective in mitigating the risks
posed to human health from contaminated ground wat~r and mine
waste piles at the site. The selected remedy is also cost
effective in mitigating the risk to aquatic life from
discharging mine tunnels. As discussed in detail in section
9.0, the selected remedy was developed by retaining ~he most
effective components of each alternative developed for the site,
and eliminating those components which provided little to no
additional human health or environmental benefit. The cost of
the selected remedy is lower than all other alternatives, except
no action, and provides the same level of ARARs compliance and
protection of human health and the environment.
10.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE
TREATMENT TECHNOLOGIES TO THE MAXIMUM EXTENT PRACTICABLE AND
PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The selected remedy represents the maximum extent to which
permanent solutions and treatment technologies can be utilized
in a .cost effective manner at the site. The selected remedy
utilizes both conventional (active) and innovative (passive)
technologies for treatment of mine discharges, and satisfies the
statutory preference for treatment at Superfund sites. It is
acknowledged that active treatment is more costly than passive
treatment. However, as mentioned earlier in this document, the
long-term effectiveness and reliability of active treatment and
greater ease of implementation, provided the best balance of the
nine evaluation criteria when considering the large volume of
65
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. contamination (flow) which will be treated in the area of the
Argo Tunnel.
Recontouring of mine waste piles alone is not considered to be
effective in reducing human nealth and environmental risks due
to exposure of generally higher metals concentrations at depth
in the mine waste piles. consequently, recontouring and capping
is the selected remedy where capping is technically feasible.
On-site consolidation of the mine-waste piles is considered to
be slightly more effective in mitigating human health and
environmental impacts than recontouring and capping. However,
due to longer implementation time and the fact that it costs at
least four times more than the other alternative, capping in
place is considered to provide the best combination of balancing
factors. Monitoring and institutional controls will be
implemented at the capped mine waste piles to maintain a high
degree of effectiveness, which will serve to minimize the
difference in overall effectiveness between on-site
consolidation and capping in place.
66
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APPENDIX A
Graphics of Modeling Results
Kev to Abbreviations
Cu
Fe
Mn
Zn
ALT
MI
NCC
WFCC
WASP
- Copper
- Iron
- Manganese
- Zinc
- Alternative
- Miles
North Clear Creek
- West Clear Creek
- Water Quality Simulation Program,
version 4, Computer Model
-------
800
700
...1'
---
g' 600
~ 500
i=
< 400
a:
...
ffi 300
o
~ 200
o
100 --
CLEAR CREEK FEASIBiliTY STUDY
WASP4 LOWFLOW SIMULATION - DISSOLVED ZN
Quayle Burleigh
TARGET CONC CHRONIC
. . . CRITERIA
RAINBOW TROUT 47 ug I L
BROWN TROUT 225 ug I L
BROOK TROUT 532 ug I L
WFCC
Big 5 Argo
NCC
Golden
existing Stds. -----------
Chronic TVS = 4S ug I L
300
-----------------------
ALT. II . III & IV
ALT. V & VI
o
35
30 25 20 15 10 5
MAINSTEM DISTANCE FROM GOLDEN, MILES
o
--- ALT. I: NO ACTION -.- ALT. II & III
-e- ALT. V ~ ALT. VI
-+- ALT. IV
--- PREFERRED ALT.
NOTES:
Chronic TVS = Aquatic Ute Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
August 17, 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity Tiering for Rainbow I Cutthroat,
Brown and Brook Trout. Values are Dissolved Metals for Acclimated Fish and
Represent levels to Sustain a Naturally Reproducing Population.
Existing Standards: Colorado Department of Health - Water Quality Control Division, Classification
. and Numeric Standards, South Plait. Riv.r Basin, Feb. 5, 1990, Total Recoverable.
-------
./
500 --------- :~-----~~~~-~~~~~=-~~------------------------
// Chronic TVS = 45 ug I L
.I Target Cone: Rainbows = 47 ug I L ; Browns = 22S ug I L; Brooks = 532 ug I
3000
...J 2500
-.
0)
==
i 2000
o
t=
~ 1500
...
z
~ 1000
z
o
(.)
CLEAR CREEK FEASIBILITY STUDY
WASP4 LOWFLOW SIMULATION - DISSOLVED ZN
National Tunnel
Greg Gulch
Chase Gulch
Russell Gulch,
Clear C
NORTH CLEAR CREEK
ALT. I & PREFERRED ALT.
.
ALTERNATIVES II THROUGH VI
o
10
8 6 4 2
NORTH FORK DISTANCE FROM CONFLUENCE, MI
o
-e- ALT. I: NO ACTION --- ALT. II-VI
~ PREFERRED ALT.
NOTES:
Chronic TVS = Aquatic Life Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
AugU$t 17, 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity Tiering for Rainbow I Cutthroat,
Brown and Brook Trout Values are Dissolved Metals for Acclimated Fish and
Represent levels to SU$tain a Naturally. Reproducing Population.
Existing Standards: Colorado Department of Health. Water Quality Contral Division, Classification
and Numeric Standards, South Platte River Basin, Feb. 5, 1990, Total Recoverable.
-------
z
o
i=
<
a:
I-
z
LIJ
CJ
Z
o
(J
CLEAR CREEK FEASIBiliTY STUDY
WASP4 LOWFLOW SIMULATION - DISSOLVED ZN
1200
Woods. Creek
Mad Ck Won Ck Clear C
..J
--.
a
::s
1000
WEST FORK CLEAR CREEK
All Alternatives Assume Major Load
Reductions From Woods Creek
800
ALT. I: NO ACTION
600
TARGET CONC. CHRONIC
CRITERIA
RAINBOW TROUT 45 ug I L
BROWN TROUT 22S ug I L
BROOK TROUT 532ug I L
400
ExIsting Std. ---------
Chronic lVS = 45 ug I L
200
ALT. II THROUGH VI and Preferred Alternative 100
--- --------------------------------~-----------------
o
10
8 6 4 2
WEST FORK DISTANCE FROM CONFLUENCE, MI
o
-k- ALT. I: NO ACTION -a- ALT. II THROUGH VI -*- PREFERRED ALT.
NOTES:
Chronic" TVS = Aquatic Ute Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
August 17; 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity Tiering for Rainbow I Cutthroat.
Brown and Brook Trout. Values are Dissolved Metals for Acclimated Fish and
Represent levels to Sustain a Naturally Reproducing Population.
Existing Standards: Colorado Department of Health. Water Quality Control Division, Classification
and Numeric Standards, South Platte River Basin, Feb. 5, 1990, Total Recoverable.
-------
50
~ 40
C)
~
z
o 30
~
a:
~ 20
w
(.)
z
o
CJ
CLEAR CREEK FEASIBiliTY STUDY
WASP4 LOW FLOW SIMULATION - DISSOLVED CU
Quayle
Burleigh
WFCC
Big 5 Argo
NCC
Golden
CHRONIC
TARGET CONC. CRITERIA
RAINBOW TROUT 11.4 ug I L
BROWN TROUT 23 ug I L
BROOK TROUT 9.5 ug I L
ExIsting Stds. ----------
Chronic TVS = 8.5 ug I L above Argo
= 6.9 ug I L below Argo
ALT. I
17
ALT. II ,III &
11
--------~ 10 ~~
10 '------------------- ~ ~
. ........"---PREFERRED A~ -.
./ ALT. V & VI "-.--.
o
35
o
30 25 20 15 10 5
MAINSTEM DISTANCE FROM GOLDEN, MILES
--- ALT. I: NO ACTION -.- ALT. II & III
-e- ALT. V ~ ALT. VI
-r- ALT. IV
- PREFERRED ALT.
NOTES:
Chronic TVS = Aquatic Life Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
August 17, 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity iiering for Aainbow I Cutthroat,
Brown and Brook Trout. Values are Dissolved Metals for Acclimated Fish and
Aepresent levels to Sustain a Naturally Aeproducing Population.
Existing Standards: Colorado Department of Health. Water Quality Control Division, Classification
and Numeric Standards, South Platte Aiver Basin, Feb. 5, 1990, Total Aecoverabie.
-------
CLEAR CREEK FEASIBiliTY STUDY
WASP4 LOWFLOW SIMULATION - DISSOLVED CU
300
-' 250
......
a
~
National Tunnel
Greg Gulch
Chase Gulch
Russell Gulch
Clear C
.. 200
z
0
-
~ 150
a:
I-
Z
UJ 100
(,)
Z 64
o
(,) 50
NORTH CLEAR CREEK
ALTERNATIVE I
PREFERRED ALT.
____M!ti.!'i_S.!8!!~~!_-~~:!~~~~T2~~~.:.~_!~~~~~I!~~-
o
10
.....,,/ Chronic TVS = 13.3 ug I L
.../" Target Cone.: Rainbows = 11.4 ug I L; Browns = 23 ug I L ; Brooks = 9.5 ug L
8 6 4 2
NORTH FORK DISTANCE FROM CONFLUENCE, MI
o
I ~ ALT. I
-8- ALT. II-VI
~ PREFERRED ALT. I
NOTES:
Chronic lVS = Aqu8iic Life Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3. 1.0
August 17, 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity 'Tiering for Rainbow I Cutthroat,
Brown and Brook Trout Values are Dissolved Metals for Acclimated Fish and
Represent levels to Sustain a Naturally Reproducing Population.
Existing Standards: Colorado Department of Health - Water Quality Control Division, Classification
and Numeric Standards, South Platte River Basin, Feb. 5, 1990, Total Recoverable.
-------
CLEAR CREEK FEASIBiliTY STUDY
WASP4 .LOWFLOW SIMULATION - DISSOLVED CU
14
Woods Creek
Mad Ck Uon Ck Clear C
WEST FORK CLEAR CREEK
All Alternatives Assume Major Load
Reductions From Woods Creek
12
-I
-
C)
~
Chronic TVS a 10.3
10 ----------------------------------------------------------
z
o
~
a:
I-
Z
W
(.)
Z
o
CJ
8
TARGET CONC.
RAINBOW TROUT
BROWN TROUT
BROOK TROUT
CHRONIC
CRITERIA
11.4 ug/L
23 ug I L
9.5 ug I L
6
existing Standard = 23 ug I L
Chronic TVS = 10.3 ug I L
4
ALL ALTERNATIVES
PREFERRED ALTERNATIVE
2
o
10
8 642
WEST FORK DISTANCE FROM CONFLUENCE, MI
o
....... ALT. I: NO ACTION -e- ALT. II THROUGH VI - PREFERRED ALT.
NOTES:
Chronic TVS = Aquatic Ute Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
August 17, 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity Tiering for Rainbow I Cutthroat.
Brown and Brook TroUt. Values are Dissolved Metals for Acclimated Fish and
Represent levels to Sustain a Naturally Reproducing Population.
Existing Standards: Colorado Department of Health ~ Water Quality Control Division, Classification
. and Numeric Standards, South Platte River Basin, Feb. 5, 1990, Total Recoverable.
-------
1000
900
800
..J
-...
C)
::2. 700
z
o
~
<
c:
....
z
w
(J
z
o
(J
600
500
400
300
200
100
o
35
CLEAR CREEK FEASIBiliTY STUDY
WASP4 LOWFLOW SIMULATION - TOTAL MN
Quayle
WFCC
Golden
Big 5 Argo
NCC
Burleigh
TARGET CONC.
RAINBOW TROUT
BROWN TROUT
BROOK TROUT
CHRONIC
CRITERIA
770 ug / L
existing Stds. = 1000 ug / L
Chronic TVS = 1000 ug / L
~1:lt..
.../:://
ALT. II, III, and V
54----4)1:1'''':
ALT. IV
PREFERRED ALT.
~
ALT. VI
30 25 20 15 10' 5
MAINSTEM DISTANCE FROM GOLDEN, MILES
o
=: ALT. I: NO ACTION -a- ALT. II 8& III
~ ALT. V -f- ALT. VI
~. ALT. IV
--- PREFERRED ALT.
NOTES:
Chronic TVS = Aquatic Ute Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
August 17, 1989. lVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity Tiering for Rainbow / Cutthroat,
Brown and Brook Trout. Values are Dissolved Metals for Acclimated Fish and
Represent levels to Sustain a Naturally Reproducing Population.
Existing Standards: Colorado Department of Health. Water Quality Control Division, Classification
. and Numeric Standards, South Platte River Basin, Feb. 5, 1990, Total Recoverable.
-------
5000
~ 4000
~
z
o
t=
<
a:
...
z
UJ
(J
Z
o
(J
3000
2000
1000
CLEAR CREEK FEASIBiliTY STUDY
WASP4 LOWFLOW SIMULATION - TOTAL MN
National Tunnel
Greg Gulch
Chase Gulch
Russell Gulch
Clear C
NORTH CLEAR CREEK
o
10
ALT. I
/
ALT. II, III, V
ALTERNATIVES IV and VI
./
/
//Chronlc TVS = 1000 ug I L
/ Target Cone.: Rainbows = 770 ug I L ; BrownS/Brooks. none established
8 6 4 2
NORTH FORK DISTANCE FROM CONFLUENCE, MI
o
~ ALT. I: NO ACTION -a- ALT. II, III
~. ALT. V ~ ALT. VI
--t:r ALT. IV
--- PREFERRED ALT.
NOTES:
Chronic TVS = Aquatic Ute Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
August 17, 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity Tiering for Rainbow / Cutthroat,
Brown and Brook Trout. Values are Dissolved Metals for Acclimated Fish and
Represent levels to Sustain a Naturally Reproducing Population.
Existing Standards: Colorado Department of. Health - Water Quality Control Division, Classification
and Numeric Standards, South Platte River Basin, Feb. 5, 1990, Total Recoverable.
-------
CLEAR CREEK FEASIBiliTY STUDY
WASP4 LOWFLOW SIMULATION - TOTAL MN
12
Woods Creek
...J 10
--.
0)
~
Z - 8
en
0 "C
- C
~ res 6
en
a: ~
... 0
Z .c
w '"
- 4
o
:z
0
(J 2
Mad Ck Uon Ck Clear C
WEST FORK CLEAR CREEK
All Alternatives Assume Major Load
Reductions From Woods Creek
TARGET CONC.
RAINBOW TROUT
BROWN TROUT
BROOK TROUT
CHRONIC
CRITERIA
770 ug Il
No Data
No Data
exIstIng Std. -----------
Chronic lVS ... 1000 ug I L
ALT. II THROUGH VI and Preferred Alternative
o
10
8 642
WEST FORK DISTANCE FROM CONFLUENCE, MI .
o
-.... ALT. I: NO ACTION ~ ALT. II THROUGH VI - PREFERRED ALT.
NOTES:
Chronic TVS = Aquatic Ute Protection Criteria Based on Table Value Standards Presented
in the Basic Standards and Methodologies for Surface Water, Section 3.1.0
August 17, 1989. TVSs are for dissolved metals except for Mn and Fe.
Target Concentrations: Based on the lower range of Toxicity Tiering for Rainbow I Cutthroat,
Brown and Brook Trout. Values are Dissolved Metals for Acclimated Fish and
Represent 'evels to Sustain a Naturally Reproducing Population.
Existing Standards: 'Colorado Department of Health - Water Quality Control Division, Classification
and Numeric Standards, South Platte River Basin, Feb. S, 1990, Total Recoverable.
-------
APPENDIX B
Federal and State of Colorado Applicable or Relevant and
Appropriate Requirements
-------
The stream segments numbers referenced in the following tables are
based on state of Colorado designations for the Clear Creek basin.
A narrative description of the specific segment numbers is
presented below. .
segment 1
segment 2
segment 3
segment 3b
segment 4
Segment 5
segment 6
segment 7
Segment 8
Segment.g
segment 10
Mainstem of Clear Creek, including all tributaries,
lakes and reservoirs, from the source to the
Interstate 70 bridge above Silverplume.
Mainstem of Clear Creek, including all of the
tributaries, lakes and reservoirs, from the
Interstate 70 bridge above Silverplume to the Argo
Tunnel discharge, except for the specific listings
in Segments 3 through 9.
Mainstem of South Clear Creek, including all
tributaries, lakes and reservoirs, from the source
to the confluence with Clear Creek, except for the
specific listing in 3b.
Mainstem of Leavenworth Creek from
confluence with South Clear Creek.
to
source
Mainstem of West Clear Creek from the source to the
confluence with Woods Creek.
Mainstem of West Clear Creek from the confluence
with Woods Creek to the confluence with Clear
Creek.
All tributaries to West Clear Creek, including all
lakes and reservoirs, from the source to the
confluence with Clear Creek, except for the
specific listings in Segments 7 and 8.
Mainstem of Woods Creek from the outlet of Upper
Urad Reservoir to the confluence with West Clear
Creek.
Mainstem of Lion Creek from the
confluence wi~h West Clear Creek.
source to
the
Mainstem to the Fall River, including all
tributaries, lakes and reservoirs, from the source
to the confluence with Clear Creek.
Mainstem of Chicago Creek, including all
tributaries, lakes and reservoirs, from the source
to the confluence with Clear Creek.
-------
segment 11
segment 12
segment 13
Mainstem of Clear Creek from the Argo Tunnel
discharge to the Farmers Highline Canal diversion
in Golden, color~do.
All tributaries to Clear Creek, including all lakes
and reservoirs, from the Argo Tunnel discharge to
the Farmers Highline Canal diversion in Golden,
Colorado, except for specific listings in Segment
13.
Mainstem of North Clear Creek, including all
tributaries, lakes and reservoirs, from the source
to the confluence with Clear Creek.
-------
TAULE 1.1-1
STREAM CLASSifiCATIONS fOR CLEAR CREEK UASIN SEGMENTS 1-13
Segment Number
2 3a 3b 4 5 6 7 8 9 10 II 12 13
Recreational Classification
Class I X X X X X X
Class 2 X X X X X X X X
Aquatic Life Classification
Class I Cold X X X X X X X X X
Warm
Class 2 Cold X X X X X
Warm
Use Classification
Domestic Water Supply X X X X X X X X X
Agricultural Supply X X X X X X X X X X X X
Recreational classification:
Class I = Primary contact recreation (e.g. swimming)
Class 2 = Secondary contact recreatiun, those not in Class I
Aquatic Life Classification:
Class I = Colli/warm stream segments capable of sustaining cold/warm water hiota where physical habitat, water flows, and water quality
conditions do not impair biota. Applies to segments with correctable water quality.
Class 2 = Cold/warm stream segments not capable of sustaining cold/warm water biota where physical habitat, water flows, or uncorrectable
water quality conditions impair biota.
Use Classification:
Domestic water supply = suitable for potahle water supplics aftcr standard wilter treatment
Agricultural water supply = suitahle fur irrigation of (flipS or walcring livcstock.
-------
TABLE 2.2-1
CLEAR CREEK SITE
POTENTIAL FEDERAL AND SlATE CHEMICAL-SPECIFIC ARARs
.'!'il~~j~~~..f~~~i.:i~IOD..... .
FEDERAL
. SAFE DRINKING WATER ACf
National Primary Drinking Water Standards
. CLEAN WATER ACf
Water Quality Criteria
Ore Mining and Dressing Point Source
. SOLID WASTE DISPOSAL ACT
(Resource Conservation and Recovery Act)
NJlCU:AR CREEK\T2-2-I.TBL
()J/1J/91 ...
42 USC I 3000
40 CFR Part 141
33 USC 6
1251-1376
40 CFR Part 131
Qual ity Criteria
for Water 1986
40 CFR Part 440
42 USC U 6901-
6987
..
........ ...
...0
...
..
..
..
...--
. .... .
"' -.". ".
.... ," .
DeScription" .:
. .
Establishes health based
standards for public water
systems (MCLs).
Sets criteria for water quality
based on toxicity to aquatic
organisms and human health.
Establishes effluent limitations
on certain mining and milling
operations New source
performance standards.
..
. .. . ~.. .-.
. ... . . .
S:/Appi(~bleJ'::::
:: ~e1evaitt an.d:.
::Appropriate? ..::
...
NoNes
NoNes
NoNes
.. ~olnine~tS/J ustifacation,
":for:~liminauon from:'
. .. .:.:Furilier~DSideration"
Applicable at free flowing
outlet of public water supply
system, relevant and
appropriate for surface water
designated for drinking
water use and for ground
water which is a current or
potential drinking water
supply. Defer to state
regulations because
delegated program.
State standards have been
adopted. This is a delegated
program. Defer to state
Table Value Standards
(IVS).
Relevant and appropriate for
inactive mine sites.
-------
TABLE 2.2-1 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE CHEMICAL-SPECIFIC ARARs
. ... .....
. """ . . ... ..
... "' . -.- ..
.... .. ,,;:.:;:,:;:,;-,:':'::';;',,<"::::,>";:;:;::;:::;';,,:;::::;"'"""""'"""
.. ..." ",".",..;.'.;.;-;.;'...;.'.;.....'.;..'... .'.".".:-:.:.:.;.:'.. .....
.;iiiE~~J~;':.~.irl"!:;!J
. SUBTITLE C
, ,
, ,
Identification and Listing of Hazardous
Waste
Standards for Owners and Operators of
Hazardous Waste Treatment. Storage and
Disposal Facilities
. CLEAN AIR ACT
National Primary arid Secondary Ambient
Air Quality Standards
National Emission Standards for Hazardous
Air Pollutants
2\IO\n.EA1t CllEEK\T2-2-I.TBL
IJ'JI1JIIII Ice
Sec. 3001-3020
40 CFR Part 261
40 CFR Part 264
442 USC iG 740 1-
7642
40 CFR Part 50
40 CFR Part 61
Defines those solid wastes
which are subject to
regulation as hazardous waste.
Defines minimal national
. requirements for treatment,
storage, and disposal of
hazardous waste.
Establishes standards for
ambient air quality to protect
human health and welfare.
Sets emission standards for
designated hazardous
pollutants
. . ... ..
. . . .... . . . . .... . . .
. . .. ..... . .
... .......'. ...
...'Appl-ic..bleiH,
~eleyantarid
'.'App,:opriate7 '
NoNes
NoNes
NoNes
No/No
,,;'.,.".. ". :.", ',':',,"
C~I~lInents/Justification ,
Hfor ~IiJpinati()n from' ,
... Furihex' Consideration'
Relevant and appropriate.
Defer to state standards.
Lead is a contaminant of
concern at the site, Lead
standard is relevant and
appropriate.
Requirements are
promulgated for emissions of
particular air pollutants ' from ,
specific sources. Will be
reconsidered as a potential
action-specific ARAR.
-------
TABLE 2.2-1 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE CHEMICAJ.,SPECIFIC ARARs
\!"i~JI~~"}~it_l~
STATE OF COLORADO
. COLORADO SAFE DRINKING WATER
AUTHORITIES
Primary Drinking Water
. COLORADO WATER QUALITY CONTROL
ACT
Basic Standards for Ground Water
~a.EAR CRIiEK\n-2-I.TBL
OII/DillI i!C
.. ..
.,
..
,.'
..
. ,'''..'.".,"'.".".-.',
..... ....... .
,"".'.'..','."."',','..
. .
.. ..
.. .
qdtatiri~' \:"!;.:::):} .:.
. q
.... .
q
CRS 24-4-104
to -105
CRS 25-1-101,
-101, -109, -114,
114.1
5 CCR 1003-1
CRS 25-8-101
to -103
5CCR 1002-8,
Section 3.11.0
:.'::::,
':":':::"
q":":'., '.:':,.,,::' :,:--.,. ..:,.:.
:"":,.:.::',:,":'::':
:.}"::r::,, ,c:;;,(.,:,., ,::'::
,....,:,:, , .':" :..,.':,:::,
.':::':' ,',
'I!, t!!~~J;~~!t~~~~~:
Establishes standards for
public water systems (MCLs).
NoNes
Establishes a system for
classifying ground water and
adopting water quality
standards to protect existing
and potential beneficial uses.
NoNes
Applicable at free flowing
outlet of public water supply
system, relevant and
appropriate for surface water
designated for drinking
water use and for ground
water which is a current or
potential drinking water
supply. Defer to state
regulations because
delegated program.
Clear Creek site aquifers
have not been classified.
Organic statewide standards
have been adopted but
organics are not chemicals
of concern at the site.
-------
TABLE 2.2-1 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND Sf ATE CHEMICAL-SPECIFIC ARABs
. .. ...... . .- .. ...... . Hu" .... u.. .....
.);~;!!!lli~!._t
Basic Standards and Metbodololia for
Surface Water
Classifications and Numeric.Standards, Soulb
Platte River Basin, et at.
. COLORADO HAZARDOUS W ASTB ACT
Rules and Regulations Pertaining to
Hazardous Waste
. COLORADO AIR QUALITY CONTROL
. ACT
Ambient Air Quality Standards
Regulation No.3
1\IO\Ci.EAR c..'RI:EK\T2-1-I.TBL
OJl2Jl9I ...
5 CCR 1002-8
Section 3.1.0
5 CCR 1002-8.
Section 3.8.0
CRS 25-15-101
to-313
6 CCR 1007-3.
Parts 260. 261.
262.11
CRS 25-7-101
to-512
. 5 CCR 1001-2
to-loo1-14
5 CCR 1001-5
Establishes basic standards.
antidegradation standard.
system for classifying state
waters.
Used in conjunction wilb
Basic Standards and
Melhodologies
(Sec. 3.1.0).
Defines hazardous waste.
requires waste
characterization.
Sets ambient standards for
TSP. S~. oxidants. CO.
N~. Pb.
Restricts exeedance in any
attainment area of any
National Ambient Air Quality
Standards (NAAQS).
. . '" ....' ..
.. .. . "...."...
." .... "P' .....
...... ..... ......... ...
i:~pp'~ca~l~l.
.:Rd~~t~di
AppiOprhit~1:
Yes/No
Yes/No
NoN es
Yes/No
Yes/No
.:;:.'!~o~ritbits/Justifi.ccdion ...
'i:for.. atilltination from .:{
{'(FunbetConsideration .::.
Applicable to any discharge
to state waters. e.g.. mine
adit discharges.
Applicable for classified
surface water stream
segments.
Only an ARAR if current
site conditions or remedial .
activities are a major source
of emissions.
The site is located wilbin an
attainment area.
-------
TABLE 2.2-2 (cont.)
CHEHICAL-SPEClfIC LEGALLY APPLICABLE REQUIREMENTS.FOR CHEHICALS OF CONCERN
C. State of Colorado Water Quality Standards for Clear Creek Stream Segments
----------------------------------------------------------------------------------------------------------------------------------------------------------
SEG- PH-HIH PH-MAX AS CO CRCtrl) CRChex) CU PB FE 0 FE T MN 0 HH T HI AG 1H
HEHT DESCRIPT(){ (SU) (SU) (UG/L) (UG/L) (UG/l.) (OG/L) (UG/L) (UG/L) (UGlL) (UG7L) (UGlL) (UG7L) (UG/L) (UG/L) (UG/L)
----------------------------------------------------------------------------------------------------------------------------------------------------------
1 CC HHSTEH, SOORCE TO 1-70 BRDG ABV SLVPL' 6.5 9.0 50 0.4 50 25 11.0 8.0 300 1000 50 1000 50.0 0.100 80
2 CC HHSTEH..JBDG ABV SLVPLH TO ARGO TUNNL 6.5 9.0 50 2.0 100 25 10.0 5.0 --- 1000 --- 1000 50.0 0.100 280
3 S. CC TO wvLUENCE WITH CC 6.5 9.0 50 0.4 50 25 5.0 4.0 300 1000 50 1000 50.0 0.100 90
~ ~~T~~I=SC~O ~E n~Slw~~W\CC g:~ tg 1~ ~:g 1~ ~~ 2t3 2~:Y . l~ l~ 1~:g g:~ 1~
7 wcms CREEK HAIN 6.5 9.0 50 14.0 100 25 23.0 25.0 1000 9400 100.0 0.100 740
8 LHW CREEK HAIN 3.0 9.0 --- --- --- --- --- --- --- --- --- ---
9 FALL RIVER HHSTEH TO CCWFLUENCE W\CC 6.5 9.0 150 2.0 50 33 I.B 1.1 1000 18.0 0.002 45
10 CHI.CREEK HHSTEH TO CCWfLUENCE W\CC 6.5 9.0 50 0.4 50 25 6.0 4.0 300 1000 50 1000 50.0 0.100 110
11 CC HHSTEH fRD4 ARGO TO GLDH GAUJjfNG STA. 6.5 9.0 150 3.0 50 123 11.0 1.6 1000 1000 59.0 0.030 300
12 TRIBS IN SECTIOf 10 6.5 9.0 50 10.0 50 50 1000.0 50.0 300 _u 50 --- 50.000 5000
13 H.CC FRD4 SOORCE TO CCWFL. W\CC 6.5 9.0 50 0.4 100 25 64.0 45.0 5400 1000 50.0 0.100 . 500
----------------------------------------------------------------------------------------------------------------------------------------------------------
Note: No stream standards are available for aluminum and fluoride.
a) Colorado Department of Health - Water Quality Control Division
Classification and Numeric Standards~~South Platte River Basin, Laramie River Basin, Republican River Basin, Smokey Hill River Basin.
Amended:feb 5,1990 (Effective Harch ~ 1990): All existing water quality standards are total recoverable metals with the exception of
TVSs as noted below.
b) Cd (14.0 uglL), Hn T 'C9400 ug/L) , and 1n (740 ug/L) are temporary modifications en Woods Creek mainstem; underlying standards for Woods Creek are
Cd, 0.2 ug/L, Hn, 1100 ug/L, and ln, 100 ug/L. .
c) Table value standards (TVSs) are promulgated for all metals In Segments 6,9, and for all metals in Segment 11 exce~t Cd (3.0 ug/L) , Cu (11.0 uO/L)
and In (300 uO/L). TVSs are dissolved metals except for Fe and Hn which are total recoverable and ar based on low flow
TVSs are basea on low flow hardness sampled in the Phase II RI sampling, September 1989 (COM 1990).
d) All numeric and TVS standards presented here are legally applicable.
-------
TABLE 2.2-2 (cant.)
CHEMICAL-SPECifIC RELEVANT AND APPROPRIATE REQUIREMENTS fOR CHEHICAlS Of CONCERN
D. State of Colorado Water Quality Criteria During Low flow for Clear Creek Stream Segments
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
SEG- PH-HIN PH-MAX Al AS CO CR&trl) CR~hex~ CU PB fE D fE T HN D HN T HI AG IN
HENT DESCRIPTM (SU) (SU) (UG/L) (UG/L) (UG/L) (U IL) (G/L (UG/L) (UG/L) (UG7L) (UG7L) (UG7L) (UG7L) (UG/L) (UG/L) (UG/L)
----------------------------------------------------------------------------,---------------------------------------------------------------------------------------
AQUATIC lifE CHROOIC TABLE VALUE STANDARDS
-----------------------------------------------
1 CC HHSTEH, SOORCE TO 1-70 BROG ABV SLVPL 6.5 9.0 150 150 0.8 151 11 8.5 2.3 1000 1000 11.3 0.038 45
2 CC HNSTEHa:oo ABV SLVPLH TO ARGO TUNNL 6.5 9.0 150 150 0.8 151 11 8.5 2.3 1000 1000 1.3 0.038 45
3 S. CC TO fLUENCE WITH CC 6.5 9.0 150 150 0.6 112 11 6.2 1.3 1000 1000 53.9 0.021 45
5 HHSTEH W.CC OONF ~wcms TO COOF W\CC 6.5 9.0 150 150 1.0 181 11 10.3 3.1 1000 1000 84.5 0.051 45
6 AlL TRIBS TO W.CC E CEPT ITEMS 1&8 6.5 9.0 150 150 0.2 34 11 1.8 0.2 1000 1000 11.1 0.002 45
1 wcms CREEK HAIN 6.5 9.0 150 150 1.6 296 11 11.2 1.2 1000 1000 133.4 0.160 45
8 lIOO CREEK HAIN 3.0 9.0 150 150 2.6 4B3 11 28.6 16.9 1000 1000 209.8 0.445 81
9 fALL RIVER HNSTEM TO CONfLUENCE W~CC 6.5 9.0 150 150 0.2 35 11 1.9 0.2 1000 1000 18.4 0.002 45
10 CHI.CREEK HNSTEH TO CONflUENCE ~ C 6.5 9.0 150 150 0.4 69 11 3.1 0.6 1000 1000 34.3 0.001 45
11 CC HNSTEH fR()4 ARGO TO GLOM GAUG NG STA. 6.5" 9.0 150 150 0.1 123 11 6.9 1.6 1000 1000 59.0 0.025 45
12 TRIBS IN SECTION 10 6.5 9.0 150 150 0.1 123 11 6.9 1.6 1000 1000 59.0 0.025 45
13 N.CC fR()4 SOORCE TO CONfL.. W\CC 6.5 9.0 150 150 1.3 232 11 13.3 4.1 1000 1000 106.3 0.095 45
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
AQUATIC LifE ACUTE TABLE VALUE STANDARDS
-----------------------------------------------
1 CC HNSTEH, SOORCE TO 1-10 BROG ABV SLVPL 6.5 9.0 950 360 2.5 1266 16 12.2 51.4 --- 681.9 1.050 80
2 CC HNSTEH..",~ ABV SLVPLH TO ARGO TUNNL 6.5 9.0 950 360 2.5 1266 16 12.2 51.4 --- 681.9 1.050 80
3 S. CC TO uunfLUENCE WITH CC 6.5 9.0 950 360 1.1 936 16 8.6 28.3 --- 519.6 0.553 59
~ ~~T~~I~S~O ~J n~SIWH~~taW\CC g:~ ~:g . ~~ ~~ 5J 1~~g l~ I~J 1~:~ ::: n~:l A:~~ ~~
1 WOODS CREEK HAIN 6.5 9.0 950 360 6.4 2486 16 26.5 194.5 --- 1286.1 4.310 155
8 lIOO CREEK HAIN 3.0 9.0 950 360 12.6 4050 16 46.4 509.2 --- 2023.9 1.202 251
9 fALL RIVER HNSTEH TO CONfLUEHCE W\CC 6.5 9.0 950 360 0.3 293 16 2.3 2.9 --- 111.0 0.048 19
10 CHI.CREEK HNSTEH TO CONfLUENCE W\CC 6.5 9.0 950 360 0.9 516 16 5.0 10.9 --- 331.3 0.200 31
11 CC HNSTEH fR()4 ARGO TO GLDN GAUG(NG STA. 6.5 9.0 950 360 1.9 1032 16 9.1 34.4 --- 569.2 0.680 65
12 TRIBS IN SECTION 10 6.5 9.0 950 360 1.9 1032 16 9.1 34.4 --- 569.2 0.680 65
13 N.CC fR()4 SOURCE TO CONFL. W\CC 6.5 . 9.0 950 360 4.6 1941 16 20.0 120.1 --- 1025.6 2.580 122
---------------------------------------------------~---------------------------------------------------------------------------------------------------------------
Note: No Table Value Standards available for fluoride.
a) Taken from existing Table Value Standards (Appendix 41), reported from Basic Standards and Methodologies for Surface Water, Section 3.1.0(August 11,1989)
b) TVSs are not adopted for all stream segments: Criteria are Relevant and Appropriate where not adopted: see Table 2.2-2 for segments where TVSs have been
promulgated and are applicable ARARs.
c) TVSs based on low flow hardness value sampled in Phase II RI, September 1989 (COM 1990).
d) TVSs are dissolved metals except for fe and Hn which are total recoverable.
-------
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
SEG- PH-HIN PH-MAX AL AS CO CR~tri) CR~hexl CU PB FE 0 FE T HN 0 HN T NI AG IN
MENT OESCRIPT~ (SU) (SU) (UG/L) (UG/L) (UG/I.) (U /L) (G/L (UG/L) (UG/L) (UG7L) (UG7L) (UG7L) (UG7L) (UG/L) (UG/L) (UG/L)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
AQUATIC LIFE CHRONIC TABLE VALUE STANOAROS
-----------------------------------------------
1 CC HNSTEM, SClJRCE TO 1-70 BROG ABV SL VPL 6.5 9.0 150 150 0.5 B6 11 4.1 0.8 1000 1000 42.1 0.012 45
2 CC KNSTEM~ROG ABV SLVPLH TO ARGO TUNNL 6.5 9.0 150 150 0.5 86 11 4.7 0.8 1000 1000 42.1 0.012 45
3 S. CC TO FlUENCE WITH CC 6.5 9.0 150 150 0.5 86 11 4.7 0.8 1000 1000 42.0 0.012 45
5 HNSTEH W.CC CONF w~wooos TO CONF W\CC 6.5 9.0 150 150 0.5 86 11 4.7 0.8 1000 1000 42.0 0.012 45
6 ALL TRIBS TO W.CC E CEPT ITEMS 7&8 6.5 9.0 150 150 0.2 42 11 2.2 0.2 1000 1000 21.8 0.003 45
7 WOOOS CREEK HAIN 6.5 9.0 150 150 0.7 132 11 1.4 1.8 1000 1000 63.2 0.029 45
B LION CREEK HAIN 3.0 9.0 150 150 0.9 164 11 9.3 2.6 1000 1000 77.1 0.046 45
9 FALL RIVER HNSTEH TO CONFLUENCE W~CC 6.5 9.0 150 150 0.2 42 11 2.2 0.2 1000 1000 21.8 0.003 45
10 CHI.CREEK KNSTEH TO CONFLUENCE ~ C 6.5 9.0 150 150 0.5 86 11 4.7 0.8 1000 1000 42.0 0.012 45
11 CC KNSTEM FR()4 ARGO TO GlON GAUG NG STA. 6.5 9.0 150 150 0.5 86 11 4.7 0.8 1000 1000 42.0 0.012 45
12 TRIBS IN SECTION 10 6.5 9.0 150 150 0.5 86 11 4.7 0.8 1000 1000 42.0 0.012 45
13 N.CC FR()4 SClJRCE TO m4FL. W\CC 6.5 9.0 150 150 0.5 86 11 4.7 0.8 1000 1000 42.0 '0.012 45
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
AQUATIC LIFE ACUTE TABlE VALUE STANOAROS
-----------------------------------------------
1 CC KNSTEM, SClJRCE TO 1-70 BROG ABV SLVPL 6.5 9.0 950 360 1.2 118 16 6.4 16.8 --- 406.2 0.320 91
2 CC HNSTEM tJ.ROG PSV Sl VPLH TO ARGO TUNNL 6.5 9.0 950 360 1.2 118 16 6.4 16.8 --- 406.2 0.320 91
3 S. CC TO FlUENCE WITH CC 6.5 9.0 950 360 1.2 118 16 6.4 16.8. --- 406.2 0.320 91
5 HNSTEH W.CC CONF W~WOOOS TO CONf W\CC 6.5 9.0 950 360 1.2 118 16 6.4 16.8 --- 406.2 0.320 91
6 ALL TRIBS TO W.CC E CEPT ITEMS 7&8 6.5 9.0 950 360 0.4 353 16 2.8 4.2 --- 210.0 0.011 23
7 \KXXJS CREEK HAIN 6.5 9.0 950 360 2.1 1111 16 10.5 39.8 --- 609.0 0.800 70
8 LION CREEK HAIN 3.0 9.0 950 360 2.9 1377 16 13.5 60.8 --- 744.0 1.240 87
9 FALL RIVER HNSTEH TO CONFLUENCE ~CC 6.5 9.0 950 360 0.4 353 16 2.8 4.2 --- 210.0 0.011 23
10 CHI.CREEK HNSTEH TO CONflUENCE W} C 6.5 9.0 950 360 1.2 118 16 6.4 16.8 --- 406.0 0.320 91
11 CC HNSTEH FR()4 ARGO TO GlOM GAUG MG STA. 6.5 9.0 950 360 1.2 118 16 6.4 16.8 --- 406.0 0.320 91
12 TRIBS IN SECTION 10 6.5 9.0 950 360 1.2 118 16 6.4 16.8 --- 406.0 0.320 91
13 N.CC FR()4 SWRCE TO CONfL. W\CC 6.5 9.0 950 360 1.2 718 16 6.4 16.8 --- 406.0 0.320 91
-----------------------------------------------------------------------------------..-------------------------------------------------------------------------------
TABLE 2.2-2 (~ont.)
CHEMICAL-SPECifiC RELEVANT ANO APPROPRIATE REQUIREMENTS FOR CHEMICALS OF CONCERN
E. State of Colorado Water Quality Criteria During High Flow for Clear Creek Stream Segments
Note: No table value standards available for fluoride.
al Taken f~ existing Table Value Standards (APpendix 41), r~rlnted from Basic Standards and Methodologies for Surface Water, Section 3.1.0 (August 17, 1989)
b TVSs based on high flow hardness satl1>led in the Phase 1 RI In June 1989 (COM 1990).
c TVSs are not adoPted for all segments: Criteria are Relevant and Appropriate where not adopted: See Table 2.2-2C for segments where TVSs are promulgated and
are applicable ARARs.
d) TVSs are dissolved metals except for Fe and Mn which are total r~coverable. .
-------
TABLE 2.2-2
CIlEMICAIrSPECIFIC ARARs AND TBCs FOR CIIEMICALS OF CONCERN (COCs)
W ater(pgn..:)~ .......
.~I
.. .
. ." . .' ~
,'....:.i:~~%~~:~~~...,...
.".RCRA ....
: GtoundW ater ,.,....
";':::::." Maximums- ';:::':
. . . . ... . . . .
/../., ColotadO.; ... .;.... F~~rat. Maxl~um
..'Gro~nd:Wllt~i""". ",'.' Contaminant..'.,.,
'.. Standardsc,.\.... i ~vel.Goalsb,ri
Ag SO
As 50
Be I
Cd 10(5)1
Cr 100
CU -(1,300Y
FI 4,000
Mn
Ni 100
Pb 50(l5~
Zn
50
50
50
50
50
50
10
50
10
50
10
50
o
()P
5
100
1,300P
_J
4,000
4,000
50
50
50
100
()P
-All values are total values, unless otherwise noted
bSafe Drinking Water Act: Drinking Water Regulations, April 1991
cColorado Primary Drinking Water Regulation Part I of Title 25, CRS 1973
d40 CFR Part 264.94, July 1990.
cDissolved values
rMCLGs above zero are relevant and appropriate
J8_8 non established
PPropm~ed
-The Federal Primary Standard for Cadmium is relevant and appropriate and is currently 10 fjglL. In July 1992 the standard for cadmium
will become 5 ,..g/L. The 5 fjglL concentration is a 8to be considered8 (fOC) concentration until July 1992.
2The concentrations of 1300 fjg/L copper and 15 fjg/L lead are TOCs.
29OIClJ!AR CRE£Kln-2-2.TBL
"I lot
-------
TABLE 2.2-2 (cont.)
CHEMICAL-SPECIFIC ARARs FOR CHEMICALS OF CONCERN (COCs)
B. Federal Ambient Water Quality Criteria for Protection of Aquatic LifEf
Chemical uS!1L
Acuteb Chronilf
As ill 36
-------
TABLE 2.2-3
NATIONAL AMBIENT AIR QUALITY STANDARDS.
(NAAQS)
Criteria
Pollutant
Carbon Monoxide
Ozone
Primary
Standards Averaging Time
9 ppm 8-hourb
35 ppm I-hourb
1.5 p.g/m3 Quarterly average
0.053 ppm Annual (arithmetic mean)
50 p.g/m3 Annual (arithmetic mean)C
150 p.g/m3 24-hourA
0.12 ppm I-hour
0.03 ppm Annual (arithmetic mean)
0.14 ppm 24-hourb
3-hourb
Lead
Nitrogen dioxide
Particular Matter
(pM 10>
Sulfur oxides
& Federal requirements bave become State requirements in Colorado by means of the State Implementation Plan
(SIP) approval process established under the CA.A..
b Not to be exceeded more than once per year.
C The standard is attained where the expected annual arithmetic mean concentration, as detennined in accordance
with 52 Federal Register 24667, July 1, 1987, is less than or equal to 50 p.g/m3.
d The standard is attained when the expected number of days per calendar year with a 24-average concentration
above 150 p.g/m3 is equal to or less than 1. .',
C The standard is attained when the expected number of days per calendar year with maximu~ hourly average
concentrations above 0.12 ppm is equal to or less than 1.
~
CCFSfT'l.2-3. dII
-------
TABLE 1.2-4
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE LOCATION-SPECIFIC ARARs
Standard. Requirement
Criteria. or Limitation Citation Description
FEDERAL
FISH AND WILDLIFE 16 USC n 661-666. Requires consultation when a
COORDINATION ACT 40 CFR Part 6.302(g) Federal agency proposes or
authorizes any modification of
any stream to provide
protection of fish and wildlife
resources.
ENDANGERED SPECIES ACT 16 USC U 1531-1543, Requires that Federal agencies
50 CFR Pan-402. 40 insure that any action by the
CFR Pan 6.302(h) agency is not likely to
jeopardize endangered species
or adversely modify their
habitat.
RIVERS AND HARBORS ACT 33 USC 6 540 Prohibits unauthorized
obstruction or alteration of
any navigable water of the
U.S.
EXECUTIVE ORDER ON Executive Order 11988 Requires evaluation of Yes/No
FLOODPLAIN MANAGEMENT 40 CFR 6 6.302(b) and potential effects of action on
Appendix A floodplains.
EXECUTIVE ORDER ON Executive Order Prohibits discharge of dredged
PROTECTION OF WETLANDS 11990, 40 CFR fi or fill material into wetlands
6.302(a) and Appendix or navigable waters of the
A U.S. without permit.
Preserves and enhances
wetlands.
2'>'OIOJ!AR CREEIC\IiII2.2-4
9/12191 ..s
Applicablel
Relevant and
Appropriate?
Comments/J ustification
for Elimination from
Further Consideration
Yes/No
Yes/No
Federally endangered
Greenback trout has been
identified within the site.
Yes/No
. .
-------
TABLE 2.2-4 (~ontinued)
CLF~AR CREEK SITE
POTENTIAL FEDERAL AND STATE LOCATION-SPECIFIC ARARs
Standard, Requirement
Criteria, or limitation
. CLEAN WATER ACT
ARCHAEOLOGICAL AND HISTORIC
PRESERVATION ACT
NATIONAL HISTORIC
PRESERVATION ACT
HISTORIC SITES, BUILDINGS AND
ANTIQUmES ACT .
Citation
Section 404
40 CFR 230
33 CFR 320-330
16 USC fi 469
40 CFR 6.301(c)
16 USC 6 470
40 CFR 66.301(b)
36 CFR Part 800
16 USC 6461-467
Description
Prohibits discharge of dredged
or fill material into wetlands
or navigable waters of the
U.S. without permit.
Preserves and enhances
wetlands.
Establishes procedures to
provide for preservation of
historical and archaeological
data that might be destroyed
through alteration of terrain as
the result of a Federal or
Federally licensed
construction activity.
Requires Federal agencies to
consider effects on historic
places.
Requires Federal agencies to
consider effects on natural
landmarks.
Applicablel
Relevant and
Appropriate?
Yes/No
Yes/No
Yes/No
Yes/No
Comments/Justific~tion
for Elimination from
Further Consideration
There are historic features in
the vicinity of the site.
There are historic places within
the vicinity of the site.
There are natural landmarks in
the vicinity of the site. .
2'JO\CLEAR CIlEEK\IIoI2.2~
9112191 od
(
~ /
-------
TABLE 2.2-4 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE LOCATION-SPECIFIC ARARs
Applicablel Comments/J ustification
Standard, Requirement Relevant and for Elimination from
Criteria, or Limitation Citation Description Appropriate? Further Consideration
STATE OF COWRADO
WILDLIFE, NONGAME, CRS 33-2-101 Provides for regulation of Y es/No
ENDANGERED, AND THREATENED to-108 nongame wildlife and
SPECIES threatened and endangered
species.
HISTORIC PLACES CRS 24-80.1-101 Establ ishes requirements Yes/No There are historic places in the
REGISTER to-108 protecting propenies of vicinity of the site.
historical significance.
HISTORICAL, PREHISTORICAL, CRS 24-80-40 I Regulates historical, Yes/No There are histori~aJ resources
AND ARCHAEOLOGICAL to-410 prehistorical, and in the vicinity of the site.
RESOURCES ACT archaeological resources.
COLORADO STATE HISTORICAL CRS 25-80-20 I Requires preservation of Yes/No There are historic sites in the
SOCIETY to-211 historic character for sites vicinity of the site.
within state or federal historic
preservation areas.
290KU'.AR CREEXIII>I2.2-4
9112191 ...
-------
TABLE 2.2-5
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE ACTION-SPECIFIC ARARs
Alternatives That May Comments/Justification
Standard, Requirement Trigger ARAR for Elimination from
Criteria, or Limitation Citation Description Further Consideration
Tailings Water
FEDERAL
-CLEAN AIR ACT 42 USC f 1401
National Primary and Secondary 40 CFR Part 50 Establishes standards for 2,3,5,6, None No remedial alternatives are
Ambient Air quality Standards ambient air quality to s.a. expected to be a major
protect human health. source of emissions. Some
of the tailing/waste rock
alternatives may require
monitoring to demonstrate
that NAAQS are not
exceeded.
National Emission Standards for 40 CFR Part 61 Sets emission standards None None Source types for which
Hazardous Air Pollutants for designated hazardous standards are pro~ulgated
pollutants. are not expected to part of
any remedial alternative.
Arsenic standard may be a
TBC for some tailings/waste
rock alternatives.
-CLEAN WATER ACT 33 USC f 1251-1316
Dredge and Fill Requirements Section 404 Prohibits discharge of All except All alternatives, except no
40 CFR 230 33 dredged or fill material no action action, may result in
40 CFR 320-330 into wetlands or navigable activities in the vicinity of
waters of the U .5. wetlands.
without permit. Preserves
and enhances wetlands.
2'JOIQ..I!AR CIlEEK\lbI2-2-S
9112191 ..s
..
. .
4
-------
TABLE 2.2-5 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE ACTION-SPECIFIC ARARs
Alternatives That May Comments/Justification
Standard, Requirement Trigger ARAR for Elimination from
Criteria, or Limitation Citation Description Further Consideration
Tailings Water
Ore Mining and Dressing Point 40 CFR Part 440 Establishes effluent 3 None Relevant and appropriate for
Source limitations on certain reprocessing alternatives.
mining and milling
operations.
The National Pollutant 40 CFR Part 122 Requires permits for the 3 2,3,4,5,
Discharge Elimination System discharge of pollutants s.a.
(NPDES) from any point source
into waters of the U.S.
NPDES - Storm water 40 CFR Part 122.26 Establishes permitting 1,2,3,4,5, None Relevant and appropriate for
. Discharges processes and discharge S.a. alternatives where mine
regulations for storm material comes into contact
water. with stonnwater or
snowmelt.
-DOT HAZARDOUS MATERIALS 49 USC fi 1801; Regulates transportation 3,6 2A, s.a.
TRANSPORTATION ACT 49 CFR of hazardous materials.
Parts 101,
111-111
-SOLID WASTE DISPOSAL ACT 42 USC i 6901-6981
(Resource Conservation and Recovery
Act)
SUBTITLE C 40 CFR Regulates placement of a 3 2,3,4,5, If reprocessing or passive
264.258(b) cap over RCRA s.a. treatment results in
(Waste Piles) 40 hazardous waste. production of a RCRA
hazardous waste.
2'JOICU!AR CREEK\lbI2-2-S
911219\ ...
-------
TABLE 2.2-5 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE ACTION-SPECIFIC ARARs
Alternatives That May Comments/Justification
Standard, Requirement Trigger ARAR for Eliminatio!l from
Criteria, or Limitation Citation Description Funber Consideration
Tailings Water
40 CFR 264.310(a) Regulates 3 2,3,4,5 If reprocessing or passive
(Landfills) closure/consolidation of s.a. treatment results in
land units with RCRA production of a RCRA
hazardous waste. hazardous waste.
40 CFR Part 263 Establishes standards 3 2,3,4,5, If reprocessing or passive
which apply to persons s.a. treatment results in
transporting hazardous production and
waste within the U;S. transportation of RCRA
hazardous waste.
SUBTITLE D Section 400 1- Guidelines for the land 3,4,5,6,7, 2B,3,4,5,
401040 CFR disposal of non-hazardous s.a. 5.a.
Part 241 solid waste.
STATE OF COWRADO
-AIR QUALITY CONTROL ACT CRS 2507-101
TO-512
Ambient Air Quality Standards S CCR 1001-14 Sets ambient standards for 2,3,5,6 None If remedial activities are a
TSP, S~, oxidants, CO, major source of emissions.
N~, Pb.
Regulation No. I S CCR 1001-3 Minimize fugitive 2,3,5,6 None Non-specific sources
Reg. I, Sec. III D particulate omission including construction
control plant. activities, storage and
handling operation, haul
roads and tracks.
'2')01CU!AR CREJ!I{\d>I2- 2- S
9/12191 eel
-------
TABLE 2.2-5 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND STATE ACTION-SPECIFIC ARARs
Standard, Requirement
Criteria. or Limitation
Citation
Description
Alternatives That May
Trigger ARAR
Tailings
Water
Commentsl J usti fication
for Elimination from
Further Consideration
Regulation No.3
Regulation No.8
-COLORADO WATER QUALITY
CONTROL ACT
-HAZARDOUS WASTE ACT
Rules and Regulations
Pertaining to Hazardous Waste
5 CCR 1001-5
Reg. 3. Sec. IVD
Restricts exceedance in
any attainment area of any
NAAQS and requires an
Air Pollution Emission
Notice.
Sets forth emission
control requirements for
hazardous air pollutants.
including beryllium.
mercury. and lead
Regulates discharges to
surface waters.
3
None
Only an ARAR if
reprocessing or passive
treatment results in
production of a hazardous
waste.
2'AJlCU!AR CREEIC\tbI2-2-~
9112191 ..t
5 CCR 1001-10
CRS 25-8-101-
TO-703
5CCR 1002-
8.3.1.14
5CCR 1002- ..
3.10.1.3
CRS 25-15-101
TO-313
6 CCR 1007-3.
Parts 260. 261,
262.11
Defines hazardous waste.
requires waste
characterization
None
2.3.4.5.
s.a.
3
2.3.4.5.
s.a.
-------
TABLE 2.2-5 (continued)
CLEAR CREEK SITE
POTENTIAL FEDERAL AND Sf ATE ACTION-SPECIFIC ARARs
Alternatives That May Commentsl Justification
Standard. Requirement Trigger ARAR for Elimination from
Criteria. or Limitation Citation Description Tailings Water Further Consideration
-SOLID WASTES DISPOSAL CRS 30-20-101 Solid waste regulations. 3.4.5.6. 2.3,4,5. Only an ARAR if
SITES AND FACILITIES ACT to-II 8 Establishes broad siting s.a. s.a. reprocessing or. passive
criteria and site evaluation treatment results in
procedures for individual production of a hazardous
storage and disposal units. waste.
Requires consideration of
local land uses.
Solid Waste Regulations. 6CCR 1007-2 Final cover required to 3,4.5,6, 2.3.4,5,
Capping Sees. 2.4.1. 2.4.2, establish vegetative s.a. s.a.
2.4.5. 2.4.6, 4.2.6 erosion protection and
waste isolation for
operation of solid waste
facility. Submit closure
plan and notify the
Colorado Department of
Health.
Solid Waste Regulations. 6 CCR 1007-2 Provide drainage to 3.4.5,6, 2.3,4,5.
Surface. Water Control Section 2.1.4 prevent ponding, erosion. s.a. s.a.
water, and air pollution
Solid Waste Regulations 6 CCR 1007-2 Siting must maximize 3,4,5.6, 2,3.4.5.
Secs. 1.1. 1.2. 1.3.2. wind protection and s.a. s.a.
2.1.1 minimize upstream
drainage. No disposal in
100 year floodplain or
into or below surface
water or ground water.
s.a. - selected Alternative
:NO\C1.£A1l L1lEEX\dI12-1-'
9111/91 ...
p
------- |