United State- Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R06-93/078
September 1993
SEPA Superfund
Record of Decision
-------
50272.101
REPORT DOCUMENTA 110N 11. REPORT NO. 2. 3. Reclplenr. Acc88a1on No.
PAGE EPA/ROD/R06-93/078
4. Title end Subtitle 5. Report Date
SUPERFUND RECORD OF DECISION 09/22/93
Cleveland Mill, NM 6.
First Remedial Action - Final
7. Author(s) 8. Performing Organization Rept. No.
9. Performing Organization Name and Address 10 Project TaskIWork Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
12. Sponsoring Organization Name and Addrasa 13. Type of Report & Period eovellld
U.S. Environmental Protection Agency 800/800
401 M Street, S.W.
Washington, D.C. 20460 14.
15. Supplementary Notes
PB94-964209
16. Abstract (Limit: 200 words)
The 18-acre Cleveland Mill site is an inactive mill and mining site located near Silver
City, Grant County, New Mexico. The site includes material discarded during mining and
ore processing operations, a water storage reservoir, access roads, building
foundations (including the mill foundation), the mine portal, and portions of streambed
of the mill valley tributary and the Little Walnut Creek itself; and borders Gila
National Forest and private 'lands. Land use in the area is predominantly recreational,
with some agricultural and residential uses. The Continental Divide runs east and west
between the mine to the north and the mill to the south, and is situated at the
headwaters of the mill valley tributary. The estimated 1,200 people who reside within a
three-mile radius of the site rely on private wells for potable water and agricultural
uses. Beginning in the 1900s, the Cleveland Mill site was used for the mining of gold,
silver, zinc, and lead. In 1913, the Empire Zinc Company built the Cleveland Mill to
process ore. The mill originally consisted of a gravity separator, which in 1916, was
replaced by a flotation process. Between 1913 and 1919, records indicated that 121,507
tons of lead,' zinc, and copper ore were taken from the mine and processed at the mill.
Contamination at the site has resulted from 34 years of intermittent stockpiling of
mill tailings and mine waste. Materials in the mill area include two main tailings
(See Attached.Page)
17. Document Analysis L Descrlptora
Record of Decision - Cleveland Mill, NM
First Remedial Action - Final
Contaminated Media: soil, sediment, debris, gw, sw
Key Contaminants: metals (arsenic, lead)
b. IdentifieralOpen-End8d Terms
c. COSATI FIeld/Group
18. Availability Statement 19. Security CIasa (ThIs Report) 21. No. of Pages
None 146
20. Security CIa8s (This Page) 22. Price
None
(See ANSI.Z39.18)
See InstructiDns on RevlIlS8
OPTIONAL FORM 272 (4-77)
(Formerty NTl5-3S)
-------
EPA/ROD/R06-93/078
Cleveland Mill, NM
First Remedial Action - Final
Abstract (Continued)
piles, a cobbed ore pile, western hillside waste piles, dust piles, and roadbed soil;
Other contaminated areas include the mine spoils located in a small drainage adjacent to
the Cleveland Mine portal, and tailings sediment located within the streambed of the mill
valley tributary and the Little Walnut Creek. In 1919, the company ceased mining
operations for unknown reasons. In 1941, Douglas White leased the Cleveland Group of
Mines and operated a small dual-cell flotation lead-zinc recovery mill to reprocess onsite
tailings until 1950. The Mining Remedial Recovery Company (MRRC) is the current property
owner after numerous changes in ownership between 1950 and 1989. Citizen complaints led
to State investigations in 1985 and 1986, and an EPA investigation in 1988, which
indicated that the site posed a significant risk to human health and the environment.
This final source control ROD addresses the surficial contaminated areas, the ground
water, and surface water at the Cleveland Mill site, as OU1. The primary contaminants of
concern affecting the soil, sediment, debris, ground water, and surface water are metals,
including arsenic and lead.
The selected remedial .action for this site includes excavating and transporting
approximately 70,900 yd3 of contaminated tailings and sediment offsite, including those
contaminated tailings and sediment found in the roadbed, the mill area, the mine spoils
area, the streambed of the mill valley tributary to Little Walnut Creek, and the streambed
of Little Walnut Creek; treating the contaminated tailings and sediment offsite at a
reprocessing facility using froth flotation, acid heap leaching, or other effective
reprocessing technology; disposing of and treating the residuals offsite at the
reprocessing facility; monitoring the air to ensure that airborne particulates or other
air emissions from the removal of site materials or transportation of these materials do
not pose a risk to the workers or inhabitants of the area; monitoring ground water and
surface water; installing and monitoring additional wells, and sampling the springs in the
mill area; revegetating disturbed areas; implementing ground wate~ contingency measures.
after 5 years, if ~he selected remedy cannot meet the specified remedial action goals at
any or all of the monitoring points; and implementing institutional and engineering
controls, including deed, land, and ground water use restrictions. The estimated present
worth cost for this remedial action is $6,214,036, which includes an estimated annua~ O&M
cost of $51,250.
PERFORMANCE STANDARDS OR GOALS:
Soil and sediment cleanup goals .are based on a health-risk level of 10-6 or background
risk, and include arsenic 30 mg/kg; beryllium 4 mg/kg; cadmium 140 mg/kg; lead 500 mg/kg;
-------
RECORD OF DECISION
CLEVELAND MILL SUPERFUND SITE
SILVER CITY, NEW MEXICO
FINAL SOURCE ACTION
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
-------
RECORD OF DECXSION
CONCURRENCE DOCUHENTATION
FOR 'rBE
CLEVELAND HJ:LL SUPEUUND SXTB
PINAL SOURCB ACTION
SEPTEHBER 1993
sling
Manager, 6H-SA
Itat.hleen A.
sit.e Remedial proje
.~
James B. Costello
site Attorney
- ~ilrein' Chief
superfund ALHK section, 6H-SA
~
Carl E. Edlund, ~ef
.supe 1- d programs Branch, 6H-S
.~~~
~~ Reg10nal Counsel, 6C
....... .
~~~..\~ ~~J~-
Allyn H. Davis, Director
-------
DECLARATZON
CLEVELAND MZLL SUPERFUND SZTE
RECORD OF DECZSZON
statutory Preference for Treatment as a
principal Element is Met
and Five-Year Review is Required
SITE NAME AND LOCATION
Cleveland Mill Superfund site
Grant County, New Mexico
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for the Cleveland Mill Superfund site (hereinafter, the
"Site"), in Grant County, New Mexico, developed in accordance
with the comprehensive Environmental Response, Compensation,
and Liability Act, as amended by the superfund Amendments and
Reauthorization Act (SARA), ("CERCLA"), 42 U.S.C. S960J. et
seq., and to the extent practicable, the National contingency
Plan 40 CFR Part 300. This decision is based on the
Administrative Record for the site.
The State of New Mexico concurs on the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from
this si te, if not addressed by implementing the response
action selected in this Record of Decision ("ROD"), may
present an imminent and substantial endanqermen~ to public
health, welfare, or the environment.
DESCRIPTION OF THE REMEDY
The site is being handled as one operable unit, in which all
the surficial contaminated areas (soils, main tailings piles,
the western hillside waste piles, the cobbed ore pile, dust
piles, roadbed soils, mine spoils, and creek sediment), and
the contaminated ground water and surface water are being
addressed.
The major components of the selected remedy include:
Institutional Controls: land use restrictions, access
restrictions, posting of signs, and deed restrictions on
-------
On-site ground water monitoring of existing and new wells
(including installation of additional monitoring wells in
the mill area) to determine whether over time, conditions
improve, remain constant, or worsen;
Excavation of soils, including, but not limited to,
tailings and sediment that are contaminated above
Remedial Action Goals.
Off-site treatment of the contaminated soils, including,
but not limited to, tailings and sediment through
reprocessing and reclamation of beneficial metals.
Disposal of the treatment residuals at the off-si te
reprocessor.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment, complies with federal and state requirements that
are legally applicable or relevant and appropriate to the
remedial action, and is cost-effective. contaminated soils,
including, but not limited to, tailings and sediment are
considered to be principal threats at the site. This remedy
satisfies the statutory preference for treatment that reduces
toxicity, mobility or volume, as a principal element of the
remedy. The selected remedy utilizes permanent solutions and
alternative treatment technologies to. the maximum extent
practicable for the site.
Because the ground water and surface water portions of the
remedy may result in hazardous substances remaining in
contaminated media on-site, above health-based levels, a
review of the selected remedy will be conducted within five
years after commencement of the remedial action to ensure that
the remedy continues to provide adequate protection of human
health and the environment.
Jo
Acting
Administrator
~-h2-q?,
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II.
III.
IV.
VI.
I.
V.
TABLE OF CONTENTS
SITE NAME, LOCATION AND DESCRIPTION. . .
SITE HISTORY AND ENFORCEMENT ACTIVITIES.
. . . .
. . .
. . . .
HIGHLIGHTS OF COMMUNITY PARTICIPATION. .
. . . .
SCOPE AND ROLES OF RESPONSE ACTION
. . . .
SUMMARY OF SITE CHARACTERISTICS
. . . . .
. . . .
A.
B.
C.
D.
E.
Regional Geology. . . . . . . . . .
Ground Water Hydrology. . . . . . .
Surface Water Hydrology. . . . . . .
B i eta. . . . . . . . . . . . . . . .
.......
. . . .
. . .
. . . .
. . . .
contamination Characterization
. . . .
1.
2.
3.
4.
Tailings and Sediment. . . . . . .
Surface Water. . . . . . . . . . . . . .
Ground Water. . . . . . . . . . . . . .
Air. . . . . . . . . . . . . . . .
. . .
. . .
F.
Contaminant Fate and Transport Characterization. .
SUMMARY OF SITE RISKS. . . . .
. . . . .
. . . .
A.
B.
C.
D.
Risk Assessment Description. . . . .
Human Health Risks. . . . . . . .
Identification of Chemicals of Concern
Exposure Assessment. . . . . .
. . . .
. . . .
. . . . .
1.
Exposure Pathways. . . .
. . . .
. . .'.
a)
b)
c)
Exposure to Tailings and
Exposure to Contaminants
Exposure to Contaminants
Ground Water
Exposure to Contaminants in .
Surface Water
. . . .
Sediment. .
in Air. . . . . .
in . . . . .
d)
2.
Scenarios.
. . . .
.0 . . . .
. . . .
. . . . .
a)
b)
c)
Current Nearby Residents. . . . . . . . .
Current and Future Site Visitors. . . . .
Future Residents. . . . . . . . . .
E.
F.
Toxici ty Assessment. . . . . . . . . . . . . . . .
Human Health Risk Characterization. . . . .
1.
Current Risk Characterization.
. . . . .
2.
Future Risk Characterization
3.
Evaluation of Lead
. . . . .
. . . .
. . . . .
G.
Uncertainties Associated with Human Heath.
Risk Calculations
. . . .
1
4
6
7
9
9
11
12
13
13
14
16
16
19
23
25
25
27
28
28
28
28
31
31
31
32
32
32
32
35
36
36
39
39
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VII.
VIII.
IX.
TABLE OF CONTENTS (Cont.)
H.
Central Tendency Exposure.
.........
I.
Ecological Risks
. . .
. . . . . .
. . . .
. . . .
REMEDIAL ACTION GOALS.
. . . . .
. . . . .
. . . . . .
DESCRIPTION OF ALTERNATIVES
. . . . . .
. . . . .
Tailings and Sediment. . . . . . . . . . . . . . . . .
Common Elements'. . . . . . . . . . . . . . . . . . . .
1.
Alternative 1a - No Action. . . . . . . . . .
Alternative 1b - Limited Action . . . . .
2.
Alternative 2 - Excavation, On-site. . . . . . 55
Disposal. and MUlti-Layer Capping
3.
Alternative 3 - Excavation, On-site. . .
Stabilization/solidification,
On-Site Disposal and Capping
Alternative 4 - On-site Stabilization/ . . . .
Solidification, Off-site
Disposal and Capping
4.
5.
Alternative 5 - Excavation, Off-Site. . . . .
Reprocessing, Reclamation and
Disposal of Residuals
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVE
. . . .
A. Threshold Criteria
B. Balancing Criteria
C. Modifying Criteria
. . . .
. . . . .
. . . .
. . . . .
. . . .
. . . .
. . .
.......
. . . . .
. . . .
D.
Comparative Analysis of Alternatives
.......
1.
Overall Protection of Human Health
and the Environment
. . . . . .
2. Compliance with Applicable or Relevant . . . . 67
and Appropriate Requirements (ARARS)
3. Long-Term Effectiveness and Permanence . . . . 69
4. Reduction of Toxicity, Mobility or 70
Volume Through Treatment
5. Short-Term Effectiveness . . . . . . . . . . . 73
6. Implementability . . . . . . . . . . . . . . . 74
41
41
43
49
50
51
54
55
56
58
59
62
62
62
64
65
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XI.
X.
TABLE OF CONTENTS (Cont.) -
7.
C,Ost
. . . .
. . . .
........
. . . . .
8.
state Acceptance
. . . . .
.......
9.
cammunity Acceptance
........
. . . . .
THE SELECTED REMEDY
. . . . . .
.......
A.
Remedial Action Gaals far the
cantaminated Tailings and Sediment
. . . .
Remedial Objectives
.......
Remedial Actian Gaals
. . . . .
.......
Graund Water contingency Measures
. . . . . .
B.
Sensitivity Analysis far Selected Remedy.
. . . .
THE STATUTORY DETERMINATIONS
.......
A.
Pratectian .of Human Health and
the Enviranment
. . . . . .
B.
Campliance with ARARs . . .
.......
. . . .
1.
Chemical-Specific ARARs far
Tailings and Sediment
2.
Actian-Specific ARARs for. . .
Tailings and Sediment
.......
a)
76
76
77
78
80
80
81
82
84
84
85
85
85
86
RCRA 40 CFR 262, Manifesting. . . . .. 86
Requirements far Transport of Hazardous Waste
b)
New Mexico Mining Act .of 1993
..--...
3.
Lacation-Specific ARARs for.
Tailings and Sediment
........
a)
Endangered Species Act,
50 CFR 17, 402
. . . .
. . . . .
b)
Fish and Wildlife Caardinatian
Act, 40 CFR 6.302 (g)
. . . . .
c)
d)
New Mexico Wildlife Canservatian Act
Natianal Histaric Preservation Act
40 CFR 6301 (b)
86
86
86
86
86
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XII.
TABLE OF CONTENTS (cont.)
e)
Archaeological and Historical. . . . . .
Preservation Act, U.S.C. 469, et. seq.
f)
New Mexico Cultural Properties Act
4.
ARARs for Ground Water and
Surface Water
.........
a)
Chemical-Specific ARARs for
Ground Water
.......
b)
Action-Specific ARARs for
Ground Water
........
C.
Cost-Effectiveness. . .
.......
. . . . . .
D.
utilization of Permanent Solutions.
and Treatment or Resource Recovery
Technologies to the Maximum Extent Practicable
. . . .
E.
Preference for Treatment as a Principal
Element
. . . . .
DOCUMENTATION OF SIGNIFICANT CHANGES
.........
87
87
87
87
87
87
88
89
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LIST OF FIGURES
Figure 1
Figure 2
site Location Map
Figure 3
Mill Area Map
Geologic Map
Figure 3
Surface Water Sample Locations
Figure 4
Figure 5
Hydrologic Characterization Sample Locations
-------
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Table 8
LXST OF TABLES
Concentrations of Chemicals of potential concern
Monitoring Wells, Dissolved Metals Concentrations
Springs/Leachate, Dissolved Metals Concentrations
Domestic Wells, Dissolved Metals Concentration
Summary of Exposure Scenarios at the Cleveland Mill site
Cancer Risk and Hazard Index Estimates, RME Adult
Cancer Risk and Hazard Index Estimates, RME Child
-------
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
LIST OF APPENDICES
Risk Assessment Tables
Refined Cost Estimates for Alternatives
Transportation Calculations and Considerations
Applicable, Relevant or Appropriate Requirements
Responsiveness Summary
-------
THE DECJ:SJ:OB SUKHARY
I.
SITE NAME, LOCATJ:OB AIm DESCRJ:PTJ:OB
The Cleveland Mill Superfund Site (the "Site") is located in
southwestern New Mexico, approximately 5.5 miles north of Silver
City in Grant County, New Mexico as shown on Figure 1. The site
is situated within the Northeast quarter of Section 2, Township
17 South, Range 14 West at the headwaters of a small tributary of
Little Walnut Creek-. The Continental Divide runs east and west
between the mine to the north and the mill to the south. The
site includes material discarded during mining and ore processing
operations, a water storage reservoir, access roads and other
roads which traverse the Site, building foundations (including
the mill foundation), the mine portal, and the surrounding areas
consisting of about 4 acres. The site also encompasses about 14
acres in and along the streambed of both a small tributary to
Little Wainut Creek, the "mill valley tributary", and Little
Walnut Creek itself.
Natural slopes surrounding the mill area are steep; however, the
slopes become more gentle to the west and proceeding down the
Little Walnut Creek drainage toward Picnic Creek. The elevation,
at the top of the Site, is approximately 7,200 feet above mean
sea level (msl). The elevation at the confluence of Little
Walnut Creek and Silva Creek (Figure 1), is approximately 5,500
feet above msl.
The Cleveland Mill 'and Mine are situated in a sparsely populated
area adjacent to the Gila National Forest and private lands.
Land use in the areas adjacent to the Site is primarily
recreational with some small scale agriculture and livestock
grazing. The reservoir located on the Site, adjacent to the mill
area, has been used for swimming and fishing by local residents.
Downstream residences are concentrated along Little Walnut Creek.
The population within a three mile radius of the Site is
estimated at 1,200 people, almost all of which rely on private
wells for potable water and agricultural uses. The nearest
residence, located approximately 3,200 feet south-southwest of
the tailings piles, does not have a well and imports water for
domestic use. The nearest domestic well is located approximately
4,600 feet south-southwest of the tailings piles.
The Site is contaminated with hazardous substances. The
contamination at the Site is a result of at least 34 years of
intermittent stockpiling of mill tailings and mine wastes from
operations at the n~w abandoned Cleveland Mill and nearby
Cleveland Mine. Contaminated wastes in the mill area on the site
(Figure 2) include two main tailings piles (east and west), a
cobbed ore pile (unprocessed, low grade ore), western hillside
waste piles, dust piles, and roadbed soils. Other contaminated
-------
o
CLEVELAND MILL
SITE
-..... OM DE
- ~...-......
~~ ........
!tJ
~f
~"
--~
/
'./
~
f/
II
\1\ ..
l~ ~.
"I. -.
o -.
\ JJ
( .-1
"'r;.
'.~~
~~
~"
SIL VER CITY
1/2
2 MILES
FIGURE 1
LOCATION MAP
NEW UE'XICO
UUQUERQUE
.
Silver
. City
LECEND
. Site location
ClEVELAND Mill SUPERFUND SITE
Grant County, New Mexico
Tm.E:
SITE lOCATION MAP
Project No. EN3017
ecology & environment. inc. I FlC.
AlBUQUERQUE. NEW MEXICQ 1-1
-------
MILL
FOUNDATIONS
MINE
SPOILS
~
~ c::;::)
COBSED
ORE PILE
EAST AND WEST
TAIUNGS PIlES
MILL VALLEY
TRIBUTARY
SPRING
0-
o
600
1200
Scale in Feet
FIGURE 2
Source: Modified from Site Screening Report (EPA 1990)
ClEVELAND MILL SUPERFUND SITE
Grant Coun~. New Mexico
TITLE:
MILL AREA MAP
Project No. EN3017
ecology & environment, inc. lAG.
ALBUQUERQUE. NEW MEXICO 1-2
-------
areas include the mine spoils located in a small drainage
adjacent to the Cleveland Mine portal, and tailings sediment
located within the streambed of the mill valley tributary to
Little Walnut Creek and within the streambed of Little Walnut
Creek itself.
II.
SITB HISTORY AND ENFORCEMENT ACTIVITIBS
The Cleveland Mill Superfund Site encompasses an area which has
been used for the disposal of mining and ore processing materials
since the early 1900s. The Cleveland Mine, located approximately
1/2 mile north of the Cleveland Mill main tailings piles, is one
of the Cleveland Group of Mines located in the West Pinos Altos
Mining District. The West Pinos Altos Mining District was one of
New Mexico's major producers of gold, silver, zinc, and lead
during the early 1900s.
George H. utter of Silver city staked the Cleveland Mine claims
in the early 1900s and developed the mine until 1913 when he 'sold
his claims to the Empire Zinc Company, a subsidiary of New Jersey
Zinc Company. Empire Zinc Company operated the mine until 1919.
To process the ore, Empire Zinc Company built a milling
operation, the Cleveland Mill, consisting of a specific gravity
separator. This gravity separator was replaced with a flotation
process in 1916 and operated from 1916 to 1919. Records indicate
that 121,507 tons of lead, zinc, and copper ore were taken from
the Cleveland Mine (and possibly other properties) and processed
at the Mill during the period from 1913 until 1919. As of 1929,
the following waste materials in the noted quantities, resulting
from Empire Zinc Company's mining activities, could be found at
the Site: dust -' 12,081 tons, middling - 14,777 tons, tailings -
33,126 tons.
The Empire Zinc Company discontinued mining and milling
operations in 1919 for unknown reasons and moved the original
mill equipment to Hanover, New Mexico. In 1941 Douglas White
leased the Cleveland Group of Mines and operated a small dual-
cell flotation lead-zinc recovery mill at the Site until
approximately 1950. The White Mill reprocessed tailings that
covered the hillslope west of the mill buildings' foundations and
above the currently existing western tailings pile. This
reprocessing was completed sometime between late 1949 and early
1950.
In the late 1960s, New Jersey Zinc Company, which then owned the
Cleveland Mill property, merged into Gulf & Western Industries,
Inc. which thereby acquired the Cleveland Mill property. Gulf &
Western Industries, Inc. changed its name to Gulf + Western Inc.
in 1986, and to Paramount Communications Inc. in 1989. Sharon
Steel purchased the Cleveland Mill property in 1979 and filed for
bankruptcy in 1987. Mining Remedial Recovery Company (MRRC),
-------
then named Bayard Copper Corporation, purchased the Cleveland
Mill property in 1989. MRRC is the present owner of the
property.
citizen complaints to the New Mexico Environment Department
(NMED), formerly the New Mexico Environmental Improvement
Division, led to NMED's 1985 identification of the Site as an
area of potential concern. As a result of the complaints, NMED
conducted investigations in October of 1985 and November of 1986
under provisions of the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA). A more detailed site
assessment was conducted by the EPA Technical Assistance Team
(TAT) in August 1988. The site information and the sampling data
were used to determine if the site posed a significant
environmental and human health risk. The site was proposed for
inclusion on the National Priorities List (NPL) of Federal
Superfund sites in June 1988 (53 Fed. Reg. 23988 (June 24,
1988». In March 1989, (54 Fed. Reg. 13296 (March 31, 1989»,
the EPA added the Cleveland Mill Site to the NPL pursuant to
Sections 105 of the Comprehensive Environmental Response,
Compensation and Liability Act as amended (CERCLA), 42 U.S.C.
section 9605, qualifying the site for investigation and
remediation under CERCLA.
After the site was placed on the NPL, the Agency for Toxic
Substances and Disease Registry (ATSDR) prepared a preliminary
Health Risk Assessment for the Site in May of 1990. Based on the
HRS data and a site visit, ATSDR concluded that the site was of
potential health concern because of the potential risk to human
health resulting from possible exposure to hazardous substances.
In July 1990, Lockheed Engineering and Sciences Company conducted
additional site characterization studies in conjunction with the
EPA Environmental Monitoring Systems Laboratory (EMSL).
On December 27, 1989, EPA sent special notice lett~rs to certain
parties, known as potentially responsible parties (PRPs), who may
be liable, under CERCLA, for the remediation of the site. The
special notice letters gave the PRPs notification of their
potential liability and offered the PRPs the opportunity to
undertake the Remedial Investigation and Feasibility study
(RIjFS) for the Site. The RI is an investigation undertaken to
determine the nature and extent of the problem presented by the
release of hazardous substances at a Superfund site. The FS is a
study undertaken to develop and evaluate options for remedial
actions. Because the PRPs either did not respond to the Special
Notice or declined to conduct or finance the RI/FS, EPA performed
the RIjFS using CERCLA funds. NMED acted as the lead agency for
these studies through a cooperative agreement with EPA.
-------
III.
HIGHLIGHTS OF OOHKUNITY PARTICIPATION
This decision document presents the selected remedial action for
the Cleveland Mill Superfund Site, Silver City, New Mexico,
chosen in accordance with CERCLA, as amended by the Superfund
Amendments and Reauthorization Act (SARA) and, to the extent
practicable, the National Contingency Plan (NCP). The decision
for this site is based on the Administrative Record. An index
for the Administrative Record is included as Appendix F to this
Record of Decision (ROD).
The public participation requirements of CERCLA, Subsection
113(k) (2) (B) (i-v) and Section 117, 42 U.S.C. Subsection
9613(k) (2) (B) (i-v) and Section 9617, were met during the remedy
selection process, as illustrated in the following discussion.
A series of community interviews were conducted in August 1991
during which NMED met with citizens, local officials and state
and federal agencies regarding site concerns. A Community
Relations Plan was completed in January of 1992 and made
available to the public at public information repositories
maintained at the Silver City Public Library in Silver City,
New Mexico; the New Mexico Environment Department Library in
Santa Fe, New Mexico; the EPA Region 6 office in Dallas, Texas;
the NMED District III Field Office in silver City, New Mexico;
and the Geotechnical Information Center in Socorro, New Mexico.
Three fact sheets summarizing the progress of the RI/FS were
mailed out to all individuals on the Site mailing list. The Site
mailing list has been continuously updated as Site activities
progress. A notice of availability for a Technical Assistance
Grant was published in the Silver citv Dailv Press on October 31,
1991, and mailed to all individuals on the mailing list. EPA may
provide Technical Assistance Grants, under Section 117 of CERCLA,
42 U.S.C. Section 9617, to any group of individuals which may be
affected by a release of hazardous substances in order-for such a
group to obtain technical assistance in interpreting information
with regard to the nature of the hazard and the CERCLA
remediation process.
The NMED and EPA held an open house in Silver City on August 27,
1991, to explain the Superfund process and to notify the public
that RI activities were going to begin. The RI fieldwork was
discussed and information about the Site was solicited.
The Remedial Investigation report and the Feasibility Study
report, released in March 1993, and EPA's Proposed Plan for the
remediation of the Site, released on April 8, 1993, were all made
available to the public in both the administrative record and
information repositories maintained at the Silver City Public
Library in Silver City, New Mexico; the New Mexico Environment
Department Library in Santa Fe, New Mexico; and the EPA Region 6
Office in Dallas, Texas. The RI and FS reports were also made
-------
available at information repositories maintained at the NMED
District III field office in silver City, New Mexico and at the
New Mexico Bureau of Mines and Mineral Resources, Geotechnical
Information Center in Socorro, New Mexico. The notice of
availability for these, documents was published in the newspaper
of record, the Silver citv Dailv Press, on April 9, 1993.
On April 8, 1993 the NMED and EPA held an open house in Silver
City to inform the public of the findings of the Remedial
Investigation and Feasibility Study reports including the results
of the Baseline Risk Assessment. The Baseline Risk Assessment is
a study which characterizes the current and potential threats to
human health and the environment that may be posed by the release
of hazardous substances at a site. A public meeting was held in
Silver City on April 27, 1993. At this meeting, representatives
from NMED and EPA solicited comments and answered questions about
the Site, the remedial alternatives under consideration, and the
Proposed Plan. NMED and EPA held a 30-day public comment period
regarding the Proposed Plan, the RI and FS Reports, and the
Administrative Record from April 9, 1993 to May 9, 1993. T~e
public comment period was extended to June 9, 1993, due to a
request for an extension. A notice of extension to the public
comment period was announced at the April 27, 1993, public
meeting and published in the Silver citv Dailv Press on May 15,
1993. A response to verbal and written comments received during
this period is included in the Responsiveness Summary, which is
part of this ROD (Appendix E).
:IV.
SCOPE AND ROLE OP RESPONSE ACTION
The contamination at the Site is principally in the soil medium
which is referred to, for convenience sake, throughout this ROD
as "tailings and sediment." The phrase "tailings and sediment"
should be read with the broadest meaning possible to include, but
not be limited to, the main (east and west) tailinqs piles, the
cobbed ore pile, mine spoils, western hillside piles, roadbed
soils, dust piles, mining and milling wastes, streambed
accumulations, con~~minated soils and any other contaminated
material of any kind' at the Site.
This ROD addresses the risks posed by conditions at the site.
Some or all of the contaminants identified at the site are
"hazardous substances" as that term is defined in section 101(14)
of CERCLA, 42 U.S.C. ~9601(14), and 40 CFR ~300.5 and ~302.4.
Response actions authorized by this ROD will address the source
of contamination including all the contaminated tailings and
sediment at the Site and the contaminated sediment in Little
Walnut Creek and the mill valley tributary. The entire action
will be treated as a single phase, or operable unit.
-------
The studies undertaken at the site have identified the
contaminated tailings and sediment as a principal threat and the
shallow perched ground water as a low level, but significant,
long term threat. Principal threat wastes are those source
materials considered to be highly toxic or highly mobile that
generally cannot be reliably controlled and that present a
significant risk to human health and the environment should
exposure occur. The contaminated tailings and sediment,
including sediments in areas of the Little Walnut Creek
streambed, were found to contain levels of hazardous substances
that pose an unacceptable health risk. These wastes are a threat
because of the potential for exposure of the public to the
contaminants via ingestion, dermal contact and inhalation.
There is an additional threat in that, without remediation,
contaminated tailings and sediment would continue to provide a
source of contaminated leachate generation. Without remediation,
this leachate will continue to contaminate shallow ground water
at the base of the main tailings piles, migrate into Little
Walnut Creek, and potentially contaminate additional aquifers
which are currently used as a source of drinking water.
The shallow perched aquifer, located at the toe of the tailings
pile, is contaminated with hazardous substances, within the
meaning of CERCLA Section 101(14), 42 U.S.C. S9601(14) and
40 CFR ~~300.5 and ~302.4, at concentrations that exceed EPA Safe
Drinking Water Act Maximum Contaminant Levels, 40 CFR 141.2
(MCLs), and New Mexico Water Quality Control Commission '(NM WQCC)
standards. This contaminated ground water at the Site is a low
level, but significant, long term threat because of the
possibility that contaminants in the perched aquifer may migrate
via surface water tb other downstream aquifers which are used as
drinking water sources. .
The wells on residential land along Little Walnut Creek,
downstream of the tailings and sediment, are completed ~n
aquifers that are not directly hydraulically connected to the
shallow perched aquifer at the toe of the tailings pile. These
residential wells are used for irrigation and drinking water
purposes. No CERCLA hazardous substances have been detected
above MCLs and NM WQCC standards in the residential wells. Thus,
human health is not threatened by ingestion of the ground water
in the residential wells in their current condition. EPA and
NMED believe that the residential wells are currently safe for
human use.
The Remedial Objectives for the Site are the fOllowing:
1.
Prevent dermal contact, ingestion of, and inhalation of
contaminated tailings and sediment.
Prevent direct contact with and ingestion of
contaminated ground water and surface water.
2.
-------
3.
Prevent the downstream aquifers from becoming
contaminated with hazardous substances from the
tailings.and sediments, at concentrations which
MCLs and NM WQCC standards.
Return the shallow perched aquifer at the toe of the
tailings to a condition where the concentration of
contaminants is below MCLs and NM WQCC standards.
exceed
4.
v.
SUHHARY OF SITE CHARACTERISTICS
A.
Regional Geology
The geology of the area is diverse and consists of sedimentary,
metamorphic, and igneous rocks (Figure 3). The Paleozoic and
Mesozoic rocks have been folded, offset by faults and intruded by
numerous dikes, sills and stocks. Cretaceous and Tertiary
volcanics form an unconformable cover over much of area.
Sedimentary rocks in the mill area and the Little Walnut Creek
drainage include the Pennsylvanian-age Oswaldo Formation, a
crinoidal limestone':and mudstone, and the Cretaceous Colorado
Formation, a shallow marine sequence consisting of arkose,
sandstone, shale, and limestone. Intrusive igneous rocks in the
local area include a Cretaceous hornblende andesite porphyry and
Tertiary mafic porphyry dikes. Metamorphic rocks include the
Cretaceous Beartooth Quartzite, a thick metamorphic sandstone
with minor interspersed conglomerate beds.
The stratigraphy in the mill valley tributary of Little Walnut
Creek consists of a sequence of Oswaldo Formation limestone
overlain by Beartooth Quartzite which is in turn overlain by
cretaceous hornblende andesite porphyry. A northeast-trending
normal fault (down to the west), parallel to and wi~hin the mill
valley drainage, juxtaposes Cretaceous Beartooth Quartzite west
of the fault and Pennsylvanian Oswaldo limestone east of the
fault (Figure 3). The fault is approximately vertical and trends
directly down the valley floor beneath the two main tailings
piles resulting in the west tailings pile overlying the Beartooth
Quartzite and the east tailings pile overlying the Oswaldo
limestone. Tertiary mafic porphyry dikes intrude the Oswaldo
limestone and Beartooth Quartzite, predominantly on the east side
of the mill valley. outcrops of limestone in the vicinity of the
these intrusions appear to have been contact-metamorphosed
leaving the limestone dense and massive with no well developed
joints or fractures. .
Approximately 2,200 feet southwest and downstream of the mill
area are the contacts between the Oswaldo Formation, Tertiary
andesites and the Colorado Formation which predominate the
remainder of Little Walnut Creek streambed. The interbedded
-------
"
r'.
o 1/2 1 MILE
LEGEND
1 TOol 1 Alluvium
IT;p I Intermediate .tocks
ITmpl Mafic porphyry dike.
t Tpc I Pyroxene porphyry
I Tl
-------
sandstones, siltstones, limestones and shales of the Colorado
Formation are overlain by a thin layer of Quaternary alluvium
along Little Walnut Creek.
B.
Ground Water aydroloqy
The Cleveland Mill site can be divided into two separate
hydrogeologic areas containing aquifers which are not directly
hydraulically connected (although contaminants may travel from
one aquifer to the other via surface water transport). The first
area, within 1/2 mile radius of the mill, consists of the Oswaldo
Limestone, the Beartooth Quartzite, and intrusive and extrusive
volcanic rocks. Approximately 1/2 mile south and downstream of
the mill area, the Colorado Formation and overlying Quaternary
alluvium constitute a second hydrologic area along the streambed
of Little Walnut Creek. Regional ground water flow generally
follows topography and coincides with the surface water flow
direction. Ground water in the vicinity of the mill and Little
Walnut Creek generally flows to the south and southwest, while
ground water in the vicinity of the mine generally flows to the
northwest.
The Oswaldo limestone and the volcanic rocks are locally water-
bearing with unpredictable yields to domestic wells, while the
Beartooth Quartzite is not known to be a water-bearing formation.
Several active and inactive springs were identified in surface
water drainages in the vicinity of the mine and mill. within the
mill valley, the Oswaldo limestone has been intruded with
numerous mafic dikes and sills and subsequently marbleized,
resulting in decreased porosity and permeability. These
intrusive dikes and marbleized limestone may act as impermeable
barriers, blocking both vertical and lateral movement of
groundwater.
During the RI, shallow groundwater was identified within the
colluvium and weathered bedrock on the steeply sloping hillsides
of the mill valley. A monitoring well constructed at the toe of
the west tailings pile encountered ground water within a
saturated zone from 7 to 14 feet below ground surface. The
ground water appears to be perched on the unweathered surface of
the marbleized Oswaldo limestone and intrusive dikes. The
perched colluvium and weathered bedrock aquifer is dissected by
the mill valley tributary and Little Walnut Creek, and is
laterally discontinuous and limited in extent. In an effort to
locate a deeper bedrock aquifer, four exploratory borings were
drilled along the toe of the main tailings piles to depths
ranging from 20 to 110 feet below ground surface. A deeper
bedrock aquifer was not encountered in these borings. Drilling
indicated that the shallow perched aquifer, located at the base
of the main tailings pile, is not hydraulically connected with a
deeper bedrock aquifer in the vicinity of the tailings piles.
-------
Deep ground water was encountered on the continental Divide above
the mill area at a depth of 145 feet in the Oswaldo limestone
within fractures associated with historical faulting. Ground
water within the Oswaldo limestone is locally confined.
In the second hydrologic area, downstream of the mill area, the
Colorado Formation and overlying alluvium constitute the primary
aquifer along the Little Walnut Creek valley. This aquifer is
not directly hydraulically connected with the shallow perched
ground water in the mill area, although contaminants may migrate
via the surface water from the shallow perched aquifer, to the
downstream aquifers. A majority of the domestic wells along
Little Walnut Creek are constructed in the alluvial deposits
and/or the Colorado Formation. The Colorado Formation and
overlying alluvium are hydraulically connected, with the degree
of connectivity controlled by the permeability of the bedrock.
Groundwater was encountered in residential and monitoring wells
completed in the Colorado Formation, at depths ranging from 8 to
155 feet below the ground surface.
The shallow perched aquifer in the mill area is classified by EPA
as a Class III A aquifer because it is not a potential sole
source of drinking water, due to insufficient yield. The ground
water within the Colorado Formation and overlying alluvium, in
which residential wells along Little Walnut Creek are completed,
is classified as a Class II A aquifer because it is a current
source of drinking water. However, all ground water identified
at the site is protected under the New Mexico Water Quality
Control Act and Regulations. The NM WQCC regulations, protect
all ground water of the state of New Mexico, which has a
concentration of 10,000 mg/l or less total dissolved solids, for
present and potential future use as domestic and agricultural
water supply (NM WQCC Regulations 82-1, sections 3-101 and 103).
c.
Surface Water Hydrology
Surface water in the'Cleveland Mill Superfund Site area includes
the mill valley tributary to Little Walnut Creek, the
intermittent Little Walnut Creek, intermittent Picnic Creek
tributary to Little Walnut Creek with its confluence
approximately 2 miles downstream of the mill area, and the water
storage reservoir at the head of Little Walnut Creek. As the
surface water flows to the south and south west from the mill
area down Little Walnut Creek it crosses several discrete
geologic units with increasing distance downstream. Several
springs occur within surface water drainages in the mill area.
The water storage reservoir at the mill site was built initially
with a capacity of 3.2 million gallons. It was filled with water
drained from the Cleveland Mill, rainfall, and flow from a
natural spring located above and approximately 500 feet east of
the reservoir.
-------
D.
Biot.a
According to the u.s. Department of the Interior, Fish and
Wildlife Service, there are two species that are endangered or
threatened in the region of the Site, although they have not been
observed at the site. They are the Mimbres figwort (ScroDhularia
macrantha) and the Southwestern willow flycatcher (EmDidonax
traillii extimus). The Mexican spotted owl (strix occidental is
lucida), which is being proposed as an endangered or threatened
species, may also be in the region.
E.
Contamination Characterization
The media and associated contaminants of concern at the Site were
identified during the Remedial Investigation (RI). Detailed
results from the RI sampling can be found in the Remedial
Investigation report which is a part of the administrative record
for the Site. Background soils samples were collected from
natural geologic formations to assist in distinguishing between
contamination associated with tailings and sediments and
naturally-occurring chemical concentrations. The concentrations
that represent these naturally-occurring chemical concentrations
are called "background concentrations" or "background values".
Background values were determined in the RI on a media-specific
basis, so the background values for each chemical detected during
sampling differ depending upon the media in which the chemical
was found.
Table 1 of this ROD/shows the concentrations of the chemicals of
potential concern (COPCs) at the site and the background soil
concentrations of these contaminants. A COPC is a contaminant
that is detected at a concentration that is higher than the
background concentration of that contaminant at a particular
site. Chemicals of potential concern are furthered evaluated in
a site risk assessment to determine if they pose an unacceptable
risk to either human health or the environment. Those chemicals
of potential concern which pose an unacceptable risk at a
particular site are referred to as contaminants of concern. At
the Cleveland Mill site different media contain different
contaminants of concern. The contaminants of concern are
discussed in detail in Section VI of this ROD.
Based on the results of the RI the following contaminated media
were identified:
o
o
o
Tailings and Sediment
Surface Water
Ground Water
-------
1. Tailings and Sediment
The contaminated tailings and sediment remaining at the mill and
mine areas are found in several places including two main
tailings piles, a cobbed ore pile, several lesser mill waste
piles, the roadbed sediment, and mine spoils piles, as shown in
Figure 2. The mill tailings have been partially eroded and
redeposited in the streambed of Little Walnut Creek. The volume
of contaminated tailings and sediment including sediment in the
streambed is as follows:
Waste Area Volume (cubic yards)
Main Tailings Piles 30,000
Cobbed Ore Pile 15,000
Mine Spoils 15,000
Creek Sediment 6,000
Western Hillside Waste Piles 2,500
Roadbed Soils 1,500
Dust Piles 900
Total Volume 70,900
Seventy-four surface samples were collected for metals analysis,
from the mine and mill areas, from the roadbed soils and from
background soils. Subsurface samples were collected from six
boreholes that were drilled through the main tailings piles into
bedrock beneath the piles. Results of these metals analyses
identified several contaminants, in tailings, sediments, and
soils, at concentrations above background concentrations as shown
in Table 1. Contaminants identified in tailings, sediments and
soils, at concentrations above background, inciuded the CERCLA
hazardous substances arsenic, beryllium, cadmium, lead, copper,
mercury, and zinc.
six chemicals of potential concern, arsenic, cadmium, lead,
copper, silver, and zinc, were identified in creek sediments
within the mill valley tributary and Little Walnut Creek. An
estimated 6,000 cubic yards of tailings material have accumulated
in the upper 7,200 feet of the Little Walnut Creek drainage.
Accumulations of tailings and sediment in the streambed are a
source of contamination for surface water and ground water.
-------
"''''''-~1iI.J .&.
~'V''''''''''.LJH .&.&'-C1J.J.vnto..J V.l" .1Y.1.QJ..t'1JJ.:> Vl" l.,Vl'fl;~KN {Mg/Kg)
West Tailings Pile 2 East Tailings Pile 2 Western Hillside
Waste Plies Dust Plies
Metal range average range average range average range average
Arsenic 25 - 3,020 366 9.8 -132 69.9 101 - 2,730 738 5.1 - 62.9 32.8
Beryllium 1.6 -11.4 2.2 3.5 -12.8 9.5 5.2 - 10 6.6 0.49U - 6.7 3.4
Cadmium 1.4 -190 33.4 2.7 - 298 59.6 4.3 - 376 101.7 15.7 -130 227.9
Chromium 2.1 - 37.6 8.1 4.2 -71.6 13.6 6.8-9.5 I 8.3 4 - 10.5 6.9
Copper 35.8 - 6,000 2029.5 271 - 6,780 2118.2 692 - 4,730 2563 852 - 4,890 2493
Lead 5.8 -11,500 1118.5 18.9 - 4,040 1034 348 - 13,500 5779 41.2 - 444 224
Manganese 11.8 -13,000 550.5 190 - 9,020 2191 258 - 6,460 2099 944 - 3,940 2901
Mercury 0.08 -1.7 0.3 0.09 - 0.9 0.2 0.73 - 3.4 1.8 0.1U - 0.38 0.24
Silver .82 -156 49.7 23.4 -159 79 26.6 - 77.8 43.8 1.3 - 23.6 12.3
Zinc 57.3 - 54,800 9969 3,320 - 53,400 19556 2,830 - 122,000 36924 9,850 - 9,630 4618
Cobbed Ore Pile Mine Spoils Creek Sediment 3 Background Soils
Metal range average range average range average range average
Arsenic 54.5 - 205 145 24.4 - 89.1 59.5 71.6 - 273 139.8 4.1U - 26.6 11.0
Beryllium 3.1 - 7.5 5.6 2.7- 5.5 4.1 0.25 - 0.98 0.5 1.6 - 3.7 2.4
Cadmium 5.5 -130 45.6 16.3 -157 75.6 0.15 - 26.9 6.1 1 U - 3.4 1.8
Chromium 5.4 - 12.6 7.7 9.2 - 36.3 27.3 5.6 - 19.6" 9.7 14.4 - 69.8 42.3
Copper 251 - 6,280 1445 699 - 4,320 2256 257 - 3,310 1073.3 34.1 - 209 95.2
Lead 98.8 - 512 309 172 - 833 414 135 -1,390 706.7 35.7 - 61~6 45.5
Manganese 1,100 - 3,290 2053 2,080 - 4,170 2994 264 - 818 439.9 621 - 2100 1042
Mercury 0.09U - 1.2 0.3 0.09U - 0.84 0.5 0.08U - 0.2 0.12 0.08U - 0.09U 0.09U
Silver "0.86U -17.6 4.4 O.85U - 3.8 2.3 3.2 - 59 28.6 R R
Zinc 1,300 - 27,700 1145 2,710 - 42,100 21802 803 - 6,070 2736 124 - 402 243
1 All analyses are for total metals "
2 Includes concentrations In both surface and subsurface samples.
3 Includes all sediment samples from toe of the main tailings piles to 7350 feet downstream
U = Indicates the element was analyzed for, but was undetected
-------
2. Surface Water
Samples of surface water and stream sediment were collected, for
metals analysis, at 1,000 foot intervals extending seven miles
downstream of the mill area in the mill valley tributary and
Little Walnut Creek (Figure 4). Acid drainage from the tailings
piles has increased the levels of metals and lowered the pH in
these waters as have several large accumulations of tailings and
sediment in the upper 7200 feet of the-Little Walnut Creek
drainage. Results from the analysis of the surface water
samples collected during the RI indicate that concentrations of
metals in the mill valley tributary and portions of Little Walnut
Creek are significantly higher than natural background "
concentrations of metals in Picnic and Silva Creeks which are
unaffected by the site. Background pH in Picnic and Silva Creeks
ranged from 7.9 to 8.7 as compared to a pH ranging from 2.1 to
4.4 in the affected creeks.
Several chemicals of potential concern (COPCs) were detected in
the surface water samples. Contaminants of concern identified in
surface water are arsenic, beryllium, cadmium, chromium, copper,
lead and zinc. Surface water is a source of contamination for
hydraulically discrete aquifers through infiltration of
contaminated surface water as the stream flows across these
units. Concentrations of metals in surface water decrease with
distance away from the mill area, with the highest concentrations
immediately downstream of the main large tailings piles, and"
immediately downstream of each of the tailings accumulations in
the streambed. Further downstream of these accumulations, the
concentrations of metals steadily decrease in sediment and water
with the most significant decrease occurring immediately
downstream of the confluence of Picnic Creek-and Little Walnut
Creek.
3. Ground Water
Four ground water monitoring wells were drilled and installed
during the RI. Information from these wells, together with data
from 11 domestic wells (Figure 5) and 4 active springs, were used
to evaluate the hydrogeology and the potential" for ground water
contamination. Results of the ground water sampling indicate
that ground water contamination is limited to a shallow perched
aquifer located at the base of the main tailings piles. This
shallow perched ground water found in the colluvium and weathered
bedrock at a depth of 7 feet is contained within a thin saturated
zone which is limited in lateral extent. No underlying bedrock
aquifer was identified above a depth of 110 feet and exploratory
borings indicate no hydraulic connection between the perched
water and the underlying bedrock. Ground water collected from
-------
r"'"\
"
o
1/2
2 UII.ES
--
FIGURE 4
CLEVELANO MILL SUPERFUND SITE
Grant County. New M.1Cico
LEGEND
r 1000 It. Ilr..rn Hellmant 18111)1..
~
TITlE:
HYDROLOGIC CHARACTERIZATION
SAMPLE LOCATIONS
5 sediment 88"1)"1 and 1 lurflC. wetll
lample will be coU.cled frern each .'grne"'.
Project No. ENJO 11
ecology & environment. inc. I FIC.
ALBUQUERQUE. NEW MEXICO 3-2
Dot.. 07/91 ~ RSI.I .....,
f"""'\
-------
"
/""'.
o
. ,'~"
o
1/2
FIGURE 5
2 LlILES
1 :24,000
LEGEND
~ OOMESTIC WELL (OWNER)
,EB MONITORING WElL
CLEVELAND MILL SUPERFUND SITE
Grant County, New Me.ico
TITlE:
DOMESTIC AND MONITORING
WELL LOCATIONS
Project No. ENJ017
. ecology & environment, inc. I FIG.
AlBUQUERQUE. NEW MEXICO 2-1
Do,., 3/93 0.... RSM Sc...,
Source: Silver City Ouadrangle, New Me.ico. USGS, 195D
-------
the monitoring well at the toe of the tailings pile and from a
spring adjacent to the western tailings pile has been affected by
infiltration of leachate as evidenced by concentrations of
dissolved metals, sulfate and total dissolved solids elevated
above MCLs and NM WQCC standards and background concentrations
(Tables 2, 3 and 4). This contaminated ground water discharges
from the shallow perched aquifer to the intermittent mill valley
tributary at the headwaters of Little Walnut Creek. Ground water
from the perched aquifer is not currently used as a source of
domestic water supply.
Two of the four monitoring wells, nine downgradient residential
wells along the Little Walnut Creek valley, and one background
well are completed in the Colorado Formation aquifer. Ground
water within the Colorado Formation and overlying Quaternary
alluvium is not in direct hydraulic connection with the
contaminated perched aquifer at the base of the main tailings
piles. However, the contamination in the surface water may
migrate to other hydraulically isolated aquifers downstream as a
result of contaminated surface water infiltrating into discrete
hydrogeologic units as the stream flows across these units" None
of the ground water samples from the downgradient residential
wells or monitoring wells contained concentrations of metals
above regulatory standards. However, concentrations of some
indicator parameters such as sulfate, calcium and zinc in two
residential wells are above background concentrations and suggest
that leachate within Little Walnut Creek may have affected ground
water in the Colorado Formation aquifer. (See section VII of
. this ROD for a more detailed description of the meaning of the
detection of indicator parameters).
4. Air
Air samples and surface soil samples were collected during the RI
to determine the potential for dispersal of conta~inants from the
contaminated tailings an~ sediment by wind. High volume
particulate air samplers for both total suspended particulates
and respirable particulates were operated for eight consecutive
days. six samplers were placed around the perimeter of the main
tailings piles, and two were placed at the nearest accessible
downwind residences. The total suspended particulate sampling
determined that a release of particulates at greater than three
times background occurred during the sampling period in the mill
area. The respirable particulate samplers identified measurable
concentrations of contaminants of concern, although the highest
identified lead concentration was below the National Ambient Air
Quality Standard. No other metals have standards for the
respirable fraction.
~
soil samples were also collected upwind and downwind of the Site
and at nearby residences to evaluate the potential historical
dispersion and deposition of contaminants from the site via
-------
Sample .
Location
A1uminu8
Antimony
Arsenic
Barium
Beryllium
CadJlli u.
Ca1ciu.
ChromiulD
Cobalt
Copper
Iron
Lead
Ha9neaium
MaDCJane.e
Mercury
Nickal
potas.ium
Seleniu8
silver
Sodium
Thallium
vanadium
zinc
CMKW-I0l
11W-2S
HU9he.
45 U
20 U
1.1 UJ
67.1 J
181000
5.6 J
27 U
62600
0.20 U
670J
43800
5.8 J
18.7 J
CHKW-I02
KW-2D
HU9hu
4S U
20 U
1.S UJ
49.8 J
1 U
1 U
TABLE 2
Jll)1InOlWIG WELLS (aaaf)
DISSOLVBD JlB'rALS. P9/L
JUDe 1'92
CMKW-103
HW-2D
(duplicate)
45 U
20 U
1.5 UJ
49.8 J
1 U
3 U
227000
5 U
5 U
4 U
220
1 UJ
65000
343
0.20 U
8 U
1020 J
1 U3
6 U
50200
1 UJ
5 U
9.9 3
CHKW-lO 4
HW-3
Back9round
126 3
20 U
1 UJ
50.5 J
1 U
3 U
113000
9 U
5 U
4.9 oJ
255 J
1 U
13300
164
0.20 U
8 U
19S0 U
1.8 3
6 U
50300
1 U
5 U
85.9
-
0VtW-105
l1W-l
TailinCJ.
5650
366
100 U3
30.5 oJ
24.8
5080
382000
5 U
2670
17200
2520000 J
1 UJ
833000
364000
0.20 U
1030
3520 U
10 UJ
6 U
88100
23.8 3
1190000
C!1HW-I06
P'i81d
Blank
45 U
20 U
127 U
157 J
74.4 J
21.3
0.20 U
746 U
23 U
5 U
78.3
HCL.
SO-200S
10/SPr
1 U
50
3 U
3 U
1 U
1000
1Pr
223000
S U
5 0
S U
1 U
3 U
SPr.
4 U
4 U
5 U
50
68.1 3
1 UJ
1 UJ
S U
4 U
1000S(1300)D
3005
64000
3 U
369
1 U
50 (15)D
0.20 U
8 U
8 U
50S
8 U
2
100Pr
1050 J
1 UJ
1 UJ
1 UJ
50
1005
6 U
6 U
6 U
1 U
2/1Pr
48400
1 03
1 UJ
5 U
SOOOS
HCL - HaximUIII COD~aminant Level. all HCLs are primary unless otherwise noted
S - Secondary (based on on aesthetic considerations)
Pr - Propo.ed MCL
D - DrinkinCJ Water Action Level (FR:S6: June 7. 1991)
R - Analysi. was attempted: however, the data have been rejected.
U - Indicates the element wa. analyzed for but was undetected. The associated numerical value
i. the sample quanti tat ion limit.
J - The element was analyzed for and was positively identified. but the associated numerical
value i5 an e.timated quantity.
UJ - The element wa. analyzed for, but was not detected.
limit i. an e.timated value.
5 U
10.S J
-------
TABLE 3
SPIlIJIGS/LDCIIAD (CIIS.) aDd
KID -'I'D (COI)
DISSOLVED JDn:ALS. 119/1.
Sample' CKSP-OOl CKSP-002 CKSP-003 CKSP-004 CHSP-OOS CMK-001
Spring' SP-01 SP-02 SP-03 SP-04
Location 6000 teet East of Toe of Welt Tailings Welt of Hine
Dovnqradient Reservoir Tailing' Leachate Kine Spoils Water KCL
Aluminum 20 U 48.4 U 20 U 238000 20 U 31 U SO-200S
Antimony 20 UJ 20 U 20 UJ 200 UJ 20 U 47 U 10/SPr
Arsenic 1 UJ 1.3 J 5 U 22 J 1 U 5.2 SO
Bariu. 62.2 J 16.6 J 4.8 J 38.1 J 18.1 J 2.6 U 1000
Beryllium 3.4 J 1.1 J 5.3 91.6 2.9 J 1 U IPr
Cadaiua 1 U 1.1U 7.6 9640 21.2 8 SPr
Calcium 345000 102000 541000 454000 288000 183000
Chro.iu. 3 U 3 U 3 U 30 U 3 U 9.5 U 50
Cobalt 1 U 1 U 1 U 6080 1 U 8 U
Copper 3 U 3 U 5.5 J 176000 6.1 U 8.2 U 1000S(1300)D
Iron 20 U 20 U 20 U 3490000 20 U 17.2 U 300S
Lead 1 U 1 U 1 UJ 1 UJ 1 U 1.2 UJ 50(15)D
Ka9ne,iu. 100000 39600 290000 1260000 54500 19600
Kanganese 404 334 J 22.7 536000 49.4 J 41.7 50S
Kercury 0.2 U 0.2 UJ 0.2 U 0.2 U 0.2 U 0.2 UJ 2
Nickel 20 U 20 U 101 1830 20 U - 11.3 lOOP l'
Potassium 400 U 400 U 400 U 4000 U 400 U 1070
Selenium 2.1 U 2 UJ 16.2 J 20 J 2 UJ 20 UJ SO
Silver 3 U 3 u 3 u 30 U 3 U 7.5 U 100$
Sodium 43900 32300 J 177000 73400 29600 J 14700
Thallium 1 U 1 UJ 1 U 1 J 1 U R 2/1Pr
Vanadium 6.3 J 13.2 J 21.8 J 260 J 3.3 U 5 U
Zinc 18.3 U 3 UJ 19600 2110000 3380 J 4730 5000$
KCL - Maximum Contaminant Level
S - Secondary Ibased on on aesthetic considerations)
P - primary Ihealth based)
PI' - Proposed KCL
D - Drinking Water Action Level IrR:56: June 7, 1991
R - Analysis wa, attempted: however, the data have been rejected.
U - Indicates the ele.ent va' analyzed for but was undetectad. The associated nuaerical value i. the
sample quanti tat ion li.it.
J - The ele.ent wa, analyzed for and was positively identified, but the associated nuaerical value is aL
estimated quantity.
UJ - The ele.ent wa, analyzed for, but was not detected.
estimated value.
-------
.1.fiDLC 'f
DOJlESTIC WELLS (CIUJIf)
DISSOLVJ:D ~ALS. pfJ/L
.;rUDe 11192
Sample' CHDW-101 CKDW-l02 CKDW-104 CHDW-l07 CHOW-108 CHOW-l09 CKDW-ll0 CKDW-111 CHOW-112 CKDW-11] CIU)W-114
'Well I DW-Ol DW-02 DW-04 OW-05 OW-06 DW-07 OW-OS OW-09 ow-09 OW-I 0 DW-11
(Background) (Duplicate) (Background) HCLI
A1uIIlnuII 45 U 45 U 45 U 45U 45 U 45U 45 U 45U 45u 45 U 45 U 50-2005
Antilllony 20 U 20 11 20 11 20 11 20 U 20 U 20 U 20 U 20 U 20 U 20 U 10/51'r
Arsenic 1 UJ 1. 2 UJ 1.1 UJ 1. 6 I1J 1.1 UJ 1.2 UJ 1 UJ 1 UJ 1.2 UJ 1.2 UJ 1.1 UJ 50
Bariull 57 J 21.8 J 28.1 J 77 J 20.2 J 25.7 J 58.4 J 23.8 J 23.8 J 52.5 J 10.1 UJ 1000
Berylliull 1 U 1 II 1 U 1 U 1 U 1 U 1 U 1 U 1 U 1 U 1 II 1Pt
CadJIiulII 3 U 3 U 3 U 3 U 3 U 3 U 3 U 6 U 3 U 3 II 3 II 5Pr
CalciulII 93400 171000 59800 102000 144000 12700!J 114000 308000 310000 137000 172000
ChrolliulII 5 U 5 II 5 U 5 II 5 U 5 II 5 II 5 U 5 II 5 II 5 U 50
Cobalt S U 5 U 5 U 5 U 5 U 5 U 5 U 5 U 5 II 5 U 5 U
Copper 14.6 J 6.1 J 4 U 4 II ]5.9 4 U 4 II 4 U 4 11 4 U 7.9 J 10005 (1300)0
Iron 27 U ]8.2 J 21 U 1090 J nu 261 21 11 69.1 J 93.3 J U9J 27 U 300$
Lead 6.5 J 2.6 U 1 UJ 1.1 UJ 4.1 J 1 UJ 1 UJ 1 UJ 1 UJ 1 U 1 UJ 50 (15)0
Magneslull 37800 51500 ]5200 19100 19000 39200 24600 89500 87900 40800 48800
H.ng.nese ) U 6.5 J ] U 139 3 U 61.] 1U 69.8 69.8 50.4 3 U 50$
Mercury .20 U .20 U .20 U 0.20 U .20 U .20 U .20 U .20 II .20 U .20 U .20 II 2
Nlckel 53. 7 U 8 U 8 U 8 U 8 U 8 U 8 U 8 U 8 U 8 U 8 U 100Pr
Potassiull 437 U 911 U 1120 J 1400 U 1130 J 2910 U 946 J 610 J 893 J 1220 U 959 J
Seleniull 1 IIJ 1 UJ 1 UJ 1 UJ 1 UJ 1 U" 1 IIJ 10 UJ 10 UJ 1 UJ 1 UJ 50
Silver 6 U 6 u .6 U 6 U 6 U 6 U 6 U 6 U 6 U 6 U 6 U 1005
Sodiull 23000 26900 25900 62100 61800 58500 31400 41900 41400 30200 58700
.
Thalliull 1 UJ 1 U 1.1 UJ 1 U 1 UJ 1 U 1 U 1.1U 1.1U 1 U 1.1U 2/1PR
Vanadiull 5 U 5 U 5 u 5 U 5 U 5 U 5 U 5 U 5 U 5 U 5 U
-------
TIillLE4
(Cont.)
MCL - Maximum conta.inant Level. all KCLs a~e p~i.a~y unle.. othe~wi.e noted
S - Secondary (based on on aesthetic considerations)
pr - Proposed HCL
D - Drinking Water Action Level (FR:56; June 7, 1991)
U Indicates the element was analyzed for but was undetected. The associated nu.erical value is the sample quantitation limit.
J - The element was analyzed for and was positively identified, but the associated nu.erical value is an esti.ated quantity.
UJ - The element was analyzed for. but was not detected. The a'iociated la.ple quantitation li.it il an esti.ated value.
-------
airborne migration. Analysis of surface soil samples indicate
that the majority of airborne deposition has occurred within 400
to 500 feet of the mill site. Soil samples collected at the
nearest accessible downvalley residences did not contain elevated
metals concentrations that could be attributed to airborne
dispersal of contaminants from the Site.
P.
contaminant Pate and Transport Characterization
The transport and fate of contaminants from a source are
dependent upon the physical and chemical properties of the
contaminant and the characteristics of the environmental media
through which the contaminants travel when released. Three
mechanisms exist by which contaminants may be released from
primary and secondary sources at the site and become available
for transport through the environmental media: wind entrainment;
leaching with subsequent infiltration to groundwater and/or
discharge of leachate or overland flow to surface water; and
physical transport of tailings and sediment in surface water
run-off.
Metals are persistent in the environment, but their mobility
varies with environmental conditions. Metals may be present in
soils in elemental form, sorbed or chelated by organic matter
oxides, sorbed on exchange sites of soil colloids, or dissolved
in acid leachate. Most metals are immobile in neutral or basic
soils and become significantly leachable only if acidic solutions
infiltrate through the soils. In the range of pHs commonly found
in soils (pH = 6 to 8.4), metals usually do not leach
appreciably; however, acids formed naturally by reactions of
infiltrating rainwater, oxygen, and sulfide ores increase the
mObility of metals. In the case of the Cleveland Mill site, acid
drainage at the toe of main tailings pile has a pH of 2 to 4,
greatly increasing the mobility of Site contaminants.
Through the mining process which took place at the Cleveland Mill
Superfund site, sUlfide-bearing ores were brought to the surface,
exposing the ores to an oxygen-rich atmosphere. The milling
process ground the ore into finer particles and increased the
exposed surface area of the sulfides. These actions further
enhanced the oxidation process and released many of the elements
from their sulfide complexes. Atmospheric oxygen at the surface
and vadose zone of the tailings reacted with the sulfide minerals
(i.e., FeS, ZnS, PbS, FeAsS) causing an oxidation reaction
releasing hydrogen, sulfate, and the accompanying metals to the
environment. The sulfate generated by the reaction combined with
available water, creating a concentrated sulfuric acid containing
high concentrations of deleterious elemental metals. This water
then migrated downward through the tailings into the subsurface
and discharged as leachate seeps at the base of the tailings or
flowed overland into the mill valley tributary and to Little
Walnut Creek streambed. The fine-grained nature of the tailings
-------
also enhanced the potential for off-site migration of
particulates, via the air pathway.
The potential for contaminant migration via the air route at the
Cleveland Mill Superfund site was evaluated through collection of
site-specific meteorological data, air samples, and surface soil
samples. Results of this data collection indicate that
contaminant migration via air dispersal occurred at the site
during the air sampling portion of the RI field investigation.
This air transport mechanism provides the potential for receptor
exposure from contaminated tailings and sediment.
The potential for contaminant migration, due to the infiltration
of water into contaminant sources and the subsequent leaching of
contaminants into surface water, was evaluated through collection
and analysis of tailings and sediment samples, tailings leachate
samples, and surface and ground water samples. Results of these
analyses indicate that leachate from contaminated tailings and
soils is a mechanism for contaminant migration into surface
water. Additionally, perched ground water in the immediate site
vicinity appears to have been contaminated by the leachate.
Long-term concerns include the potential for infiltration of
surface water contaminants into downstream aquifers.
The potential for contaminant migration via physical transport by
surface water run-off was evaluated through collection of
streambed sediment and water samples, and by collection of
reservoir sediment and water samples. The results of sample
analysis indicated that contaminant migration via surface run-off
has occurred at the site.
vx.
SUMMARY OF SITE RISKS
A.
Risk Assessment Description
An evaluation of the potential risks to human health and the
environment from site contaminants was conducted as part of the
baseline risk assessment. The baseline risk assessment was
conducted as part of the RI. The baseline risk assessment is an
analysis of the current and potential threats to human health and
the environment that may be posed by contaminants migrating to
ground water or surface water, releasing to air, leaching through
soil, and bioaccumulating in the food chain. The results of the
baseline risk assessment helped establish acceptable exposure
levels for use in developing remedial alternatives in the FS.
By definition, a baseline risk assessment evaluates risks that
may exist under the'no-action alternative (that is, in the
absence of any remedial actions to control or mitigate releases).
The baseline risk assessment indicates the exposure pathways that
need to be addressed by the remedial action.
-------
The baseline risk assessment presents a compilation and
evaluation of data collected during the site investigation in
order to estimate the upper limit, or highest level, of potential
health and environmental risk which may be present due to the
release of contaminants from and at the site. In the evaluation
of potential human exposure scenarios, on-site sampling and
analysis results were used in conjunction with current federal
and state guidance documents, including the "Risk Assessment
Guidance for Superfund: Volume I, Human Health Evaluation Manual
- Part A" (HHEM) (EPA/540/1-89/002), "Risk Assessment Guidance
for superfund: Volume I, Human Health Evaluation Manual - Part B"
(OSWER Directive 9285.7-01B), "Risk Assessment Guidance for
Superfund: Volume II, Environmental Evaluation Manual"
(EPA/540/1-89/001) and the companion manual "Ecological
Assessment of Hazardous Waste Sites: A Field and Laboratory
Reference" (EPA/600/3-89/013), and professional judgement to
estimate the potential human health risk attributable to
contamination resulting from past Site-related operations.
The "risk" values generated within the human health risk
assessment are designed to describe a plausible upper limit to
the risk of cancer posed by releases of hazardous substances at
and from the Site under the exposure scenarios evaluated. That
is, the risk values arrived at in the site Risk Assessment do not
necessarily provide an actual description of the risk of cancer,
but are instead constructed so as to give an estimate of the
highest risk level that could plausibly be posed by the release
of contamination at and from the site.
Remedial Action Goals for the site were established in a manner
which provides acceptable exposure levels that are protective of
human health and the environment, and by considering applicable
or relevant and appropriate requirements (ARARs) set under
federal environmental or state environmental laws, if available.
Furthermore, certain risk factors were considered in tne
establishment of Remedial Action Goals.
One factor that wa~ considered was that, for known or suspected
carcinogens, acceptable exposure levels under.the NCP, are
generally concentrations that represent an excess upper bound
lifetime cancer risk to an individual of between 10. and 10-6,
using information on the relationship between dose and response.
The NCP also provides that, a risk level of 10-6 shall be used as
the point of departure for determining Remedial Action Goals when
ARARs are not available or are not sUfficiently protective
because of the presence of multiple contaminants at a site or
multiple pathways of exposure, such as at the Cleveland Mill
Superfund site.
Another factor that was considered was that for non-carcinogenic
systemic toxicants under the NCP, acceptable exposure levels
represent concentrations to which the human population, including
-------
sensitive subgroups, may be exposed without adverse effect during
a lifetime, or part of a lifetime, incorporating an adequate
margin of safety. EPA has established criteria for interpreting
non-carcinogenic risk for Superfund sites. These criteria are
called the Hazard Index (HI). Non-carcinogenic riskS are
quantified by the HI which is the ratio of chronic daily intake
(CDI) to the reference dose (RfD) that causes a non-carcinogenic
impact. EPA's Remedial Action Goal for non-carcinogens is to
reduce the HI at a site to less than 1.0, providing that the site
background HI is less than 1. For non-carcinogenic systemic
toxicants, an HI that exceeds 1 indicates that contaminants at
the site may pose adverse health effects.
This section of the ROD, the Summary of site Risks section,
summarizes the results of the baseline risk assessment.
Calculations and a more detailed analysis may be found in the
site Risk Assessment contained in the administrative record. All
tables referenced in this section can be found in Appendix A of
this ROD, Risk Assessment Tables.
B.
Human Health Risks
The baseline risk assessment was divided into two parts: the
human health evaluation and the ecological evaluation. The
baseline risk assessment for the human health risks was based on
Reasonable Maximum Exposure (RME). RME is an estimate of risk
using exposure factors which are a reasonable maximum based on
scenarios assumed for the Site. The human health evaluation
considered all contaminated media, such as tailings, sediments,
and surface water. The Risk Assessment evaluated the potential
risk to the following populations which are most likely to be
exposed to materials at the Cleveland Mill site:
o Current nearby residents (adults and children)
ground water as a drinking water source
o CUrrent on-site visitors (adolescents) .
o Future recreational users (adolescents)
o Future on-site residents (adults and
children)
using
The major components of the baseline risk assessment are:
identification of chemicals of potential concern, exposure
assessment, toxicity assessment, and risk characterization.
Highlights of the findings for the major components of the human
health portion of the site Risk Assessment are summarized below.
Iden~ificatioD of Chemicals of Potential Concern and
contaminants of Concern
Analytical data from the tailings, sediment, air, surface water,
and ground water were evaluated to identify contaminants of
potential concern at the Site. Nine (9) chemicals were selected
C.
-------
as chemicals of potential concern for the. entire site: arsenic,
beryllium, cadmium, copper, lead, manganese (which is not a
hazardous substance), mercury, silver, and zinc. Of these,
arsenic, beryllium,. cadmium, lead, and zinc, in tailings and
sediment, were found to significantly contribute to the risk, and
were therefore selected as contaminants of concern.
D.
Exposure Assessment
The human populations which could potentially be exposed to
hazardous substances from the site are discussed below. The
pathways which contaminants might travel to reach human
populations are also discussed below. The discussions of
populations and pathways include discussions of exposure under
both current and projected future conditions. The Site Risk
Assessment refers to the various combinations of populations and
contaminant pathways, under current and projected future
conditions, as "scenarios". Table 5 summarizes the various
current and future scenarios which were considered in the Site
Risk Assessment for the site. That is, Table 5 summarizes and
lists the various combinations of populations which could be
exposed and the pathways that contaminants might travel to reach
those populations under current and projected future conditions.
1. Exposure Pathways
An exposure pathway is the course that a chemical or physical
agent takes from a.source to an exposed organism. An exposure
pathway describes a unique mechanism by which an individual or
population is exposed to chemicals or physical agents at or
originating from a site. Each exposure pathway includes a source
or release from a source, and exposure point, and an exposure
route. An exposure point is a location of potential contact
between an organism and a chemical or physical agent. An
exposure route is the way that a chemical or physical agent comes
in contact with and organism (i.e. by ingestion, inhalation,
dermal contact).
a) Exposure to Tailings and Sediment (The tailings and
sediments exposure pathway may also be referred to as the
soil exposure pathway in this ROD.) - All humans ingest
small amounts of soil and other soil-like material each day
through hand to mouth activity both indoors (e.g. intake of
house dust) and outdoors (e.g while playing or gardening).
Therefore, ingestion of contaminated surface tailings and
sediment was selected for quantitative assessment as a
probable exposure route for both adults and children.
Likewise, dermal contact and inhalation of airborne
particles from tailings and surface sediment are probable
exposure routes for both adults and children. Exposure to
subsurface tailings and sediment was not evaluated as a
contaminant pathway for any population because exposure to
-------
TABLE 5
SUIUIARr 01' DPOSu:az SCEIWt%OS Ar DB c:r.EVBLNID IaLL 8J:D
Exposu~e Sc.na~io. by
Potentially Exposed
Population
Expo.u~e Pathway
Reason fo~ Selection
or Excluaion
CD-Site a.poauEe
Future
Site Residentl
Incidental ingestion of
conta.inated 8urface loils
and dUlt.
Direct der.a1 contact with
conta.inated surface loi11.
Inhalation of conta.i-
nated airborne particles.
Incidental ingea~ion,
der..l contact, and inhal-
ation of airborne particu-
lates of reservoir sedi.ent.
C:urrent Site
Visitors (Tres-
passers and
Recreational
Users)
Incidental ingestion of
contaminated aurfaca aoils
and dust.
Direct dermal contact with
contaminated surface soila.
Inhalation of contami-
nated airborne particles.
. Incidental ingestion
contaminated aurface
and sediment of the
reaervoir.
of
vater
Direct dermal contact with
contaminated surface water
and sediment of the
~e.ervoir.
Pathway
Selected for
£Valuation7
Yea
Yea
Yea
Yes
Yes
re.
Yes
Ro
No
Future residenta .ay co.e
into contact with conta.i-
nated aoila.
Although COPC:s are .etala
and dermal abso~ption of
metals is negligible,
default value. were uaed
to evaluate pathway.
Conta.inanta in aite aoils
.ay beco.e airborne.
Although the .edi.ent sa--
pIes are from the deepeat
(8 ft.) part of the lates
reservoir and currently
inacce.sible, it is pos-
. sible the reservoir viII
dry out in the future.
Local re.idents are
reported to use the lite
for a variety of recrea-
tional activities and .ay
contact contaminated soill.
Although cOPC:s are .etall
and der.al ablorption of
.etals i8 negligible,
default value. vere uaed to
evaluate pathvay.
conta.inantl in aite loill
.ay beco.e airborne. Hotor
bikers would be a reason-
able worst-case receptor.
Trespaaaers are reported to
swim in the re.ervoir, but
'concentration. of COPC. are
quite lov in lurface vater.
sa.ples of aedi.ent are troD
the deepest (8 ft.) and
currently inacce.aible.
COPC. are .etals and der.al
absorption of metal. is
negligible. S..ples of
s~di.ent are quite deep
and currently inaccessible.
-------
TABLE 5
CCOII~. )
potentially
Exposed
population
Exposure Pathway
Pathway
selected for
Evaluation?
off-site Saposur.
Reason for Selection
or Exclusion
Current Near~y
Resident.s
Fut.ure
Recreational
Users
Incident.al ing.stion,
ingestion. direct. der.al
contact and inhalation
of conta.inated airborne
particles of surfac.
80il and dry .ecU.ent.
Ingestion of groundwat.er
as drinking vater-, and
der.al cont.act. with
groundwat.er u.ed as a
do.estic vater supply.
Incident.al inge.tion and
direct dermsl contact
vit.h surface wat.er of the
strealll.
incidental ingestion,
der.sl cont.act., and
inhalation of airborne
particles of .oil and
sediaent. n.ar the Hughes
bOllle.
Incidental ingest.ion snd
direct. dermal contact. vith
the surface vater of tbe
stream.
Yes
Yes
Ye.
Ye.
re.
Site contaminsnt.s have
migrated in .edi.ent and
accuaulated behind the da.
at t.he Hughes property. .
Although there i. no
evidence of cOlIIIDunication
between t.he on-sit.e aquifer
vith t.he deep veIl used at
the Hughe. property, such
groundwat.er migration could
not be completely ruled
out.
Surface water sa.ples from
the stream near the Hughe.
ho.e contain site-derived
contaminants.
If the area is developed,
nearby edolescents .ay
us. the are. and come in
cont.act with site-derived
contaminants.
Surface water s.mples from
the strealll on the Hughes
prop.rty contain .ite-
derived contaminants.
Source:
Ecology and Environment.. Inc. 1992.
-------
subsurface tailings and sediment is less likely than
exposure to surface materials. Evaluation of risk due to
exposure to tailings and sediment was carried out for both
the mill area and for nearby residential areas where
tailings have been deposited in Little Walnut Creek.
b) Exposure to Contaminants in Air - Air monitoring
conducted during the Remedial Investigation for the
Cleveland Mill site indicated that a release of total
suspended particulates at greater than three times
background occurred during the sampling period in the mill
area. However, respirable particulate sampling indicated
that there were no chemicals of potential concern present at
concentrations exceeding regulatory standards. The primary
inhalation route for exposure to contaminants is through
inhalation of particulates from tailings and contaminated
sediment. Therefore, inhalation was not evaluated in the
air pathway, but in the inhalation route of the soil
exposure pathway.
c) Exposure to contaminants in Ground water - Under
reasonably anticipated future conditions, there are no known
human populations who would employ the shallow perched
aquifer in the mill area as a sole source of drinking water.
Therefore, the ground water exposure pathway was not
evaluated for the smaller perched aquifer in the mill area.
Nearby residences obtain drinking water from aquifers which
are not directly hydraulically connected with the shallow
perched aquifer in the mill area, but which may be affected
by contaminated stream water and sediment in Little Walnut
Creek. Therefore, the ground water exposure pathway was
evaluated in the risk assessment for the nearby areas
located along Little Walnut Creek.
d) Exposure to contaminants in surface Water ~ Surface
water bodies of concern at the site include the mill valley
tributary, Little Walnut Creek and the on-site reservoir.
The mill valley tributary and Little Walnut Creek contain
contaminated sediments which have been eroded from the main
tailings piles and redeposited in these surface water
bodies. Surface water within the mill valley tributary,
Little Walnut Creek and the reservoir is a pathway through
which contaminants might travel to reach site visitors who
use these waters for recreational use. Dermal contact with
and incidental ingestion of surface water are probable
exposure routes for both adults and children. Evaluation of
risk due to exposure to surface water was carried out for
visitors to the mill area reservoirs and for nearby
residential areas along Little Walnut Creek. Evaluation of
risk due to contaminated sediments was included in the soil
exposure pathway.
-------
The risk that humans would be exposed to Site contaminants was
quantified using standard default values. Tables 7-5 to 7-16 in
Appendix A summarize the assumptions used in the site Risk
Assessment for the Cleveland Mill Superfund site.
2.
scenarios
a) CUrrent Nearby Residents
Land nearby the mill area and along Little Walnut Creek currently
includes residences. The nearest residence is located within one
mile of the mill area. The closest major population center is
Silver City, located about 5.5 miles south of the site. Ground
water is the primary source of drinking water for downstream
residences which are concentrated along Little Walnut Creek.
The regional and site hydrogeology is discussed in detail in
Section V of this ROD. .
CUrrent nearby residents may be exposed to contaminants from
ingestion of ground water, incidental ingestion and dermal
contact with tailings and sediment, and incidental ingestion and
dermal contact with surface water. Risk was estimated for
current nearby residents using the soil exposure pathway, ground
water pathway, and surface water pathway.
b) CUrrent and Future site visitors
The site Risk Assessment also considered individuals who actually
go on-site and the 'risk that they would be exposed to site.
contaminants. CUrrently there are no people who live or work in
the mill area. Therefore, a scenario based upon recreational
users traversing the site was selected as representative of the
situation most likely to expose humans to the site under current
conditions. Under this scenario, the visitor was ass~ed to be
an area resident who was first exposed to the contaminants while
visiting the site at age seven and who continued to visit the
site until age sixteen (a total of ten years). Adolescents are
the most sensitive population at risk which would be likely to
visit the Site. It was assumed that the visitor moved about the
Site at random, coming into contact with all accessible
contaminated media. Adolescent site visitors may be exposed to
contaminants from incidental ingestion and dermal contact with
tailings and sediment, and incidental ingestion and dermal
contact with surface water. Future adolescent Site visitors may
have additional exposure to sediments in a potentially dry
reservoir. Risk was estimated for adolescent site visitors using
the soil exposure p~thway and surface water pathway.
c) Future Residents
In the future it is possible that the site might be developed as
a recreational area or as a residential area. Under the site
-------
Risk Assessment, development for residential use was considered
the most likely future land use, since residences are being built
in the surrounding area. Therefore, the persons who might use
the site as a residential area in the immediate future were
selected as the population group most likely to be exposed to
Site contaminants in the future. Future residents may be exposed
to contaminants from incidental ingestion and dermal contact with
tailings and sediment. Risk was estimated for future residents
using the soil exposure pathway. Surface water of mill valley
and the reservoir were not included as pathways of exposure for
future residents because the mill valley tributary is
intermittent and is not expected to pose a significant exposure
compared to other sources and routes. Water in the reservoir did
not exceed primary MCLs for chemicals of potential concern
(COPCs).
E.
Toxicity Assessment
The toxic effects of a chemical generally depend on the level of
exposure (dose), the route of exposure (oral, inhalation,
dermal), and the duration of exposure (acute, subchronic, chronic
or lifetime). Thus, a full description of the toxic effects of a
chemical includes a listing of what adverse health effects the
chemical may cause (carcinogenic and non-carcinogenic), and how
the occurrence of these effects depends upon dose, route, and
duration of exposure.
For the human population groups evaluated for this risk
assessment (current and future adolescent recreational users,
current nearby child and adult residents, and future on-site
child and adult residents), Human Intake Factors (HIFs), also
called Chronic Daily Intake Factors (CDIs), were calculated.
These CDIs were calculated using the exposure point concentration
factors for each medium. An exposure point concentration is the
90th percentile concentration for a particular che~ical in the
area being evaluated.
Slope factors (SFs) have been developed by EPA's Carpinogenic
Assessment Group for estimating excess lifetime cancer risks
associated with exposure to potentially carcinogenic contaminants
of concern. SFs, which are expressed in units of milligrams of
contaminant intake per kilogram of body weight per day
(mg/kq-day) -', are multiplied by the estimated intake of a
potential carcinogen, in mq/kg-day, to provide an upper-bound
estimate of the excess lifetime cancer risk associated with
exposure at that intake level. By "excess lifetime cancer risk"
EPA means the additional risk, over and above the average
national risk of cancer (estimated to be slightly less than one
in three), which is posed by contaminants from a site. By
"upper-bound" EPA means that it has based its risk estimates
using the 90th percentile of concentration of contaminants
measured at a site for the area being evaluated. By using upper
-------
bounds, EPA ensures a conservative estimate of the risks
calculated from the SF. Use of this approach makes
underestimation of the actual cancer risk highly unlikely. Slope
factors are derived from the results of human epidemiological
studies or chronic animal bioassays to which animal-to-human
extrapolation and uncertainty factors have been applied (i.e., to
account for the use of animal data to predict effects on humans).
EPA assigns a cancer weight-of-evidence category to each chemical
in order to reflect the overall confidence EPA has that the
chemical is likely to cause cancer in humans. These categories
and their meanings are summarized in the following table.
Cateqorv
Meanina
A
Known human
carcinogen
B1
Probable human
carcinogen
Basis
Sufficient evidence of increased cancer
incidence in exposed humans.
Sufficient evidence of increased cancer
incidence in animals, with suggestive
evidence from studies of exposed
humans.
Probable human Sufficient evidence of increased cancer
carcinogen incidence in animals, but lack of data
or insufficient data from humans.
B2
c
possible human Suggestive evidence of carcinogenicity
carcinogen in animals.
D
Cannot be
evaluated
E
Noncarcinogen
Toxicity information for
slope factor, the weight
toxicity information, is
Appendix A.
No evidence or inadequate evidence of
cancer in animals or humans.
Evidence of noncarcinogenicity for
humans.
each chemical of concern, including the
of the evidence, and the source of the
summarized in Tables 7-18 and 7-20 in
Reference doses (RfDs) have been developed by EPA for indicating
the potential for adverse health effects from exposure to
contaminants of concern exhibiting non-carcinogenic adverse
health effects. RfDs, which are expressed in units of mg/kg-day,
are estimates of daily (maximum) exposure levels for the human
population, including sensitive subpopulations, that are likely
to be without an appreciable risk of deleterious effects during a
lifetime. Estimated intakes of contaminants of concern from
environmental media, (e.g., the amount of a contaminants of
concern ingested from contaminated drinking water) can be
compared to the RfD. RfDs are derived from human epidemiological
-------
"
studies or animal studies to which uncertainty factors have been
applied (e.g., to account for the use of animal data to predict
effects on humans).
F.
Buman Health Risk Characterization
The risk of cancer from exposure to a chemical is described in
terms of the probability that an exposed individual will develop
cancer by age 70. For carcinogens, risks are estimated as the
incremental probability, over and above the national average risk
of cancer, of an individual developing cancer over a life-time as
a result of exposure to the chemical. Excess lifetime cancer
risk is calculated from the following equation:
Risk = CDI x SF
where:
Risk = a unitless probability (e.g., 2 X 10-5) of an individual
developing cancer;
CDI = chronic daily intake averaged over 70 years (mg/kg-day);
and .
SF = slope-factor, expresse~ as (mg/kg-day)-'
These risks are probabilities that are generally expressed in
scientific notation (e.g., 1 x 10-6 or 1E-6). An excess lifetime
cancer risk of 1 x 10-6 indicates that, as a reasonable maximum
estimate, an individual has a 1 in 1,000,000 chance of developing
cancer as a result of Site-related exposure to a carcinogen over
a 70-year lifetime under the specific exposure conditions at a
site.
Tables 7-18 and 7-20 in Appendix A provide a brief-summary of the
characteristic cancer effects of chemicals of potential concern
at the Cleveland Mill site and lists available inhalation SFs and
cancer weight of evidence categories. using the average lifetime
daily intake values and the slope factors previously shown in
Table 7-12, cancer risks were calculated for populations who may
be chronically or sub-chronically exposed at the Cleveland Mill
Superfund Site. Risk was calculated for several scenarios
involving exposure to tailings and sediment, surface water, and
ground water.
The potential for noncarcinogenic effects is evaluated by
comparing an exposure level over a specified time period (e.g.,
life-time) with a reference dose derived for a similar exposure
period. The ratio of exposure to toxicity is called the Hazard
Quotient (HQ). By adding the hazard quotients for all chemicals
of potential concern which affect the same target organ (e.g.,
liver) within a medium or across all media to which a given
-------
population may reasonably be exposed, the Hazard Index (HI) can
be generated. For an explanation of the HI, See section IV.A. of
this ROD.
The Hazard Quotient (HQ) is calculated as follows:
Non-cancer HQ = DI/RfD
where:
DI = Daily Intake (either chronic or sub-chronic)
RfD = reference dose
DI and RfD are expressed in the same units and represent the same
exposure period (e.g., chronic, subchronic, or short-term).
1.
current Risk Characterization
Under the current Site visitor scenario, the estimated overall
risk of carcinogenic effects is high as 3.1X10-' for a current
adolescent site visitor who visits the site 60 times per year and
is exposed to contaminated tailings and sediment through
ingestion and dermal contact, and inhalation of airborne
particulates (See Appendix A, Table 7-21). This risk is greater
than the EPA's acceptable risk levels of 10-4 to 10-6. The main
contaminants contributing to this risk are arsenic and beryllium.
For the current site visitor scenario, noncancer risk (hazard
index or HI) is as high as 5.1 from contact with contaminated
sediment and tailings (See Appendix A, Table 7-22). This exceeds
the EPA target HI of 1. Arsenic, cadmium, and zinc are the
contaminants contributing most to this HI for site visitors.
Under the current nearby resident scenario, the excess cancer
risk from inhalation, ingestion, and dermal contact with
contaminated tailings and sediment, ingestion and dermal contact
with surface water, and ingestion of ground water may be as high
as 3. 9x10-4 for adults and 2. 7x10-4 for children (See Appendix A,
Table 7-21 and Tables 6 and 7). These risks ~xceed the
acceptable risk levels for carcinogenic compounds of 10-' to 10-6.
The main contaminants contributing to this risk are arsenic and
beryllium (See Appendix A, Table 7-27). The non-cancer risk
(Hazard Index) from contact with contaminated tailings and
sediment, contact with surface water, and ingestion of ground
water may be as high as 2.0 for adults and 7.1 for children (See
Appendix A, Table 7-22). These HIs exceed the target HI of 1 for
non-carcinogenic compounds. Arsenic, cadmium, and copper are the
contaminants contributing most to this HI (See Appendix A, Table
7-27). For drinking water alone, under the current nearby
resident scenario, risk was calculated to be 4.6x10-s for adults
and 2.1xlO-s for children, with HIs of 0.008 for adults and 0.45
for children (See Appendix A, Table 7-21 and 7-22). Section VII
-------
TABLE 6
CANCER RISK AND NONCARCER HAZARD INDEX ESTIMAT£S
Future On-site Re.idential Soil Exposure
Location: On site
Rec:eptor: Adult
Case: Re..onable Maximum Exposure
Chemic:al
Carc:inoienic: £ffec:ts
Exposure
Point
Conc:entration
(mg/lti)
Intake
(lIIg/kg/day)
Canc:er
Risk
Non-Carc:inogenic: £ffec:ts
Intake
(mg/ki/dayl
Hazard
Index.
Exposure Route: Ingestion of Chemic:als in Soil
:Arsenic
Beryllium
Cadmium
Copper
Manianese
Mercury (inorianici
Silver
zinc
Ingestion Route Subtotal:
5.74£+02
7.04£+00
7.24£+01
1.96£+03
1.62£+03
7.89£-01
5.89£+01
2.30£+04
4.80£-04
5.88£-06
Exposure Route: Dermal Contac:t with Contaminated Soil
Arsenic
Beryllium
Cadmium
Copper
Manganese
Merc:ury (inorianicl
Silver
Zinc:
Dermal Route Subtotal:
5.74£+02
7.04£+00
7.24£+01
1.96E+03
1.62£+03
7.89£-01
5.89£+01
2.30£+04
6.60£-04
8.09E-06
Exposure Route: Inhalation of Airborne Soil Particles
Arsenic
Beryllium
Cadmium
Copper
Manganese
Mercury (inorianic:1
Silver
Zinc:
Inhalation Route Subtotal:
Receptor Total:
5.74£+02
7.04£+00
7.24£+01
1.96E+03
1.62£+03
7.89£-01
5.89£+01
2.30£+04
4.781:-07
5.8n-09
6.03£-08
8.40£-04
2.53£-05
8.65E-04
1. 16E-03
3.48E-05
1.19£-03
7.17£-06
4.92£-08
3.68£-07
7.59£-06
2.07£-03
1;12£-03
1.37£-05
1.41£-04
3.82E-03
3.16£-03
1.54£-06
1.15£-04
4.49£-02
1.54£-03
1.89E-05
6.47£-04
5.26£-03
4.34£-03
2.12£-06
1.58£-04
6.17£-02
1.12£-06
1.37£-08
1. 41£-07
3.15£-06
1.53£-09
1.14£-07
4.47£-05
3.73£+00
2.74£-03
2.82£-01
1.03£-01
3.16£-02
5.13£-03
2.30£-02
2.25£-01
4.40£+00
5.13E+00
3.78£-03
1.29£+00
1.42£-01
4.34£-02
7.07£-03
3.16£-02
3.09£-01
6.95£+00
3.73£-03
2.74£-06
2.82£-04
3.15£-02
1.70£-05
2.28£-05
2.24£-04
3.57£-02
1.14£+01
Sourc:e: £colOiY and Environment, Inc:. 1992.
-------
TABLE 7
CAHc:n R:tSIt J\RD RONc:ANCER HAZARD INDEX ESTIMATES
Future On-site Residential Soil Exposure
Location: On Site
Receptor: Child
Case: Reasonable Maximum Exposure
Carcinogenic Effects
Non-Carcinogenic Effects
Chemical
Exposure
Point
Concentration
(mg/kg)
Intake
(lig/kg/day)
Cancer
Risk
Intake
(mg/kg/day)
Hazard
::Endex
Exposure Route: Ingestion of Chemicals in Soil
'Arsenie 5.74E+02 6.29E-04 1.10E-03 7.34E-03 2.45E+01
Bery1l:ium 7.04E+00 7.72E-06 3.32E-05 9.00E-05 1.80E-02
::ac!mium 7.24E+01 9.26E-04 1.85E+00
Copper 1.96E+03 2.51£-02 6.77E-01
Hanganese 1. 62E+03 2.07£-02 2.07E-01
Mercury (inorganic) 7. 89E-01 1.01£-05 3.37E-02
SUver 5.89E+01 7.53£-04 1.51£-01
Zinc 2.30E+04 2.94£-01 1. 47£+00
Ingestion Route Subtotal: 1.13£-03 2.79E+01
Exposure Route: Dermal Contact with Contaminated Soil
.orsenie 5.74E+02 1.87E-04 3.27£-04 2.18£-03 7.27£+00
. Beryllium 7.04£+00 2.29£-06 9.85£-06 2.67£-05 5.34£-03
:ac!miUID 7.24£+01 9.16E-04 1.83E+00
Coppet 1.96£+03 7.44£-03 2.01£-01
Manganese 1.62E+03 j; .15£-03 6.15£-02
Mercury (inorganic) 7.89£-01 3.00E-06 1.00£-02
SUver 5.89E+01 2.24£-04 4.48£-02
Zinc 2.30E+04 8.73£-02 4. 37E-Ol
Dermal Route Subtotal: 3.37£-04 9.86£+00
Exposure Route: Inhalation of Airborne Soil Particles
Arsenic
Beryllium
Cadmium
Copper
Hanglnese
Mercury (inorganic)
Silver
Zinc
5.74£+02
7.04£+00
7.24£+01
1. 96£+03
1.62£+03
7.89£-01
5.89£+01
2.30£+04
3.76E-07
4.61E-09
4.74E-08
5.64£-06
3.87£-08
2.89E-07
4.39E-06
5.38£-08 -
5.53E-07
1.46£-02
1.08£-05
1.11£-03
-
1. 24£-05
6.03£-09
4.50£-07
1.76E-04
1.24£-01
6.70£-05
9.00E-05
8.80£-04
Inhalation Route Subtotal:
5.97£-06
1.41E-01
aeceptor Total:
1. 48£-03
3.78£+01
EN3015:D4028/2357/12
-------
of this ROD more fully describes ground water remediation.
2.
Fu~ure Risk Cbarac~eriza~ioD
Under the future Site resident scenario, the estimated excess
cancer risks to a hypothetical future resident from inhalation,
ingestion, and dermal contact with contaminated tailings and
sediment in the mill area of the site is as high as 2.lx10-3 for
adults and 1.5x10-3 for children (See Appendix A, Table 7-21),
which are greater than EPA's acceptable risk range of concern of
1x10-4 to 1x10-6. The contaminants contributing most to risk
under the future site resident scenario are arsenic and beryllium
(See Appendix A, Table 7-26). The estimated HIs due to the non-
carcinogenic effects from contact with contaminated tailings and
sediment may be as high as 11 for adults and 38 for children (See
Appendix A, Table 7-22), well above EPA's target HI of 1 for both
children and adults. Arsenic, cadmium, and zinc are the
contaminants contributing most to this HI (See Appendix A, Table
7-26. )
Under the future residential soil exposure scenario, carcinogenic
and non-carcinogenic risk estimates were also calculated for the
cobbed ore pile and the mine spoils area of the site using
surface soil data from these areas (See Appendix A, Table 7-25).
Risks for these two areas were evaluated separately, from the
risks calculated for the tailings, due to the possibility that a
single residence could be located on either of the tailings
piles, on the cobbed ore pile, or on the mine spoils pile-but not
on two of these piles at one .time. For the cobbed ore pile, risk
was calcu1ated to be 7. 4X10-4 for adults and 5. 3X1.0-4 for
children, with HIs of 7.4 for adults and 23 for children. For
the mine spoils area, risk was calculated to be 3.6x10-4 for
adults and 2.6x10-4 for children, with HIs of 6.6 for adults and
19 for children. All of these calculated risk estimates exceed
both the EPA target risk range of 10-4 to 10.6 for carcinogenic
risk and the target HI of 1. for non-carcinogens.
Under the future recreational user scenario, the estimated excess
cancer risk to future adolescent recreational users due to
contact with contaminated tailings, sediments, and surface water
may be as high as 3.8x1.0.4 (See Appendix A, Table 7-21.),
primarily from arsenic and beryllium (See Appendix A, Table 7-
28). The HI may be as high as 6.8 (See Appendix A, Table 7-22),
primarily from arsenic, cadmium, and zinc (See Appendix A, Table
7-28). These risks exceed both the EPA target risk range of 10-4
to 10-6 for carcinogenic risk and the target HI of 1 for non-
carcinogens.
3.
Evaluation of Lead
Since there are no EPA-approved RfD values for lead, it is not
possible to evaluate the noncancer risks of lead by calculation
-------
of a Hazard Index. An alternative approach is to estimate the
likely effect of lead exposure on the concentration of lead in
the blood using the, EPA uptake/Biokinetic (UBK) model. Input
parameters are lead concentrations for all exposure pathways.
The model produces a probability function that predicts the
probability of blood-lead in child residents. Remedial Action
Goals are established to provide no greater than a 5% probability
that a child in the exposed population will have a blood-lead
level greater than 10 ug/dl. That is, in an exposed population
of 100 children, no more than 5 would have a blood-lead level
greater than 10 ug/dl.
Model input parameters for the Cleveland Mill superfund site were
site-specific concentrations of lead in the soil, water and air.
Default values based on models were used when site-specific
concentrations were unknown. Table 7-30 in Appendix A lists lead
modelling results for various areas at the Cleveland Mill
Superfund site. In order to be protective, EPA has established
there can exist no greater than a 5% probability that a child in
the exposed population will have a blood-lead level above
10 ug/dl as calculated using the UBK model. At the Cleveland
Mill superfund site, EPA determined, based on the UBK model, that
the lead concentrations in the tailings and sediment would result
in blood lead levels greater than 10 ug/dl with more than a 5%
probability in the future child residents, which would exceed EPA
recommendations and, therefore, pose an unacceptable health ri~k.
Based on the UBK model, a soil lead concentration of 500 ppm is
approximately the maximum allowable concentration that will
result in a 95% probability that the children will have blood
lead levels below 10 ug/dl. The concentration of 500 ppm is
deemed adequately protective for direct human contact in
residential settings (OSWER Directive *9355.4-02). Soil lead
concentrations in the tailings and sediment and as a site-wide
average are greater than 500 ppm. Therefore, a Remedial Action
Goal for lead of 500 ppm was established.
G.
UDcer~aiD~ies Associa~ed wi~h Human Heal~h Risk Calcula~ioDs
Within the Superfund process, baseline quantitative risk
assessments are performed in order to provide risk managers with
a numerical representation of the severity of contamination
present at the Site, as well as to provide an indication of the
potential for adverse public health effects. There are many
inherent and imposed uncertainties in the risk assessment
methodologies. Uncertainties in the Human Health Risk Assessment
include sampling data that may not fully characterize the
contaminants at the site, exposure factors that are extrapolated
from animal or laboratory studies, and inhalation concentrations
derived from a soil exposure model. Uncertainties in the
Ecological Risk Assessment include sampling data that may not
fully characterize the contaminants, estimations of the range and
exposure factors for the affected species, the use of literature
-------
information and not site-specific ecological studies, the
exclusion of bioaccumulation or bioavailability as factors, and
extrapolation of toxicity values from literature or laboratory
studies.
Note that the Reasonable Maximum Exposures calculated in the
assessment are intended to represent. the upper end o.f the
distribution curve. Therefore, most people are likely to be
exposed to lower doses than this calculated value.
risk
B.
Central Tendency Exposure
Based on a February 26, 1992, memorandum from Deputy
Administrator F. Henry Habicht, EPA is required to evaluate both
the "reasonable maximum exposure" (RME) to which humans may be
subjected due to contamination at a Superfund site, and "central
tendency" in the risk assessment at Superfund sites. Exposure
assumptions discussed to this point in the ROD have been
associated with the RME which was used to estimate the baseline
risks and ultimately the Remedial Action Goals at sites. The
"central tendency" scenario represents the risk expected for
humans due to an estimated "average" exposure, instead of a
"reasonable maximum" exposure. The Risk Assessment portion of
the Remedial Investigation includes a central tendency risk
assumption labeled as "Typical Exposure". (See Appendix A,
Tables 7-5 to 7-15, and 7-23 and 7-24.)
:t.
Ecological Risks
The baseline ecological risk assessment provides a qualitative
evaluation of the environmental risks at the Cleveland Mill Site.
The site ecology was evaluated to determine if contamination from
the Site could be causing any significant adverse ecological
impact. The two exposure media potentially presenting the
greatest threat to biota were addressed: contamina~ed tailings
and sediment, and surface water. Terrestrial biota may be
exposed to contaminants in the soil through dermal contact,
ingestion, inhalation, and absorption. Aquatic and terrestrial
biota may be exposed to Site contaminants in the surface water
and contaminated sediments of Little Walnut Creek.
The region surrounding the Cleveland Mill site supports one
proposed threatened species, the Mexican spotted owl, and two
Category I species, the Mimbres figwort and the Southwestern
willow flycatcher. Category I species are candidates for which
there is substantial information to support listing as endangered
or threatened. In addition, deer, small mammals, birds,
amphibians, and reptiles are wildlife species that may be exposed
at the Site, as well as aquatic invertebrates and fish in Little
Walnut Creek. Animals may also be exposed through consumption of
organisms that have accumulated site-related chemicals.
Potential risk exists for vegetation growing in contaminated
-------
tailings and sediment of Little Walnut Creek.
Resident wildlife, which spend less than a lifetime on-site, are
likely to receive low to moderate exposures to site contaminants.
Small mammals whose home range is contained entirely on-site are
likely to receive a proportionately greater exposure than larger
mammals and birds that may spend a fraction of their time on-site
throughout the year or on a seasonal basis. It is assumed that
organisms occurring near sample locations are likely to be
exposed to measured contaminant concentrations.
Twelve metals present in soil, sediment and surface water
associated with the Site were selected as contaminants of concern
for the purposes of the ecological risk assessment. These are
listed in Table 7-31 of Appendix A for the various media. Heavy
metals can have toxic affects on wildlife. They may also act
synergistically, antagonistically, or competitively in living
systems and environments. The risk generated by contaminants can
be qualitatively determined through comparison with benchmarks
for aquatic environments, and through studies of their toxic
affect on plants and animals in the terrestrial environment.
Ecological risk for the Cleveland Mill Site was evaluated
qualitatively so contaminant intake by animals was not measured.
However, concentrations of metals in tailings and sediments and
in the surface water' are significantly elevated above background
concentrations. Therefore, the Site poses a potential risk to
flora and fauna.
A number of uncertainties are associated with the analysis of
potential adverse ecological effects at this site. The use of
regional species studies and toxicological studies presents
uncertainties for Site-specific ecological risk assessment.
These uncertainties include (1) extrapolating toxicity criteria
and exposure parameters for home range and dietary estimates from
literature studies to Site-specific assessment, (2) assumptions
regarding dietary habits of the receptors assessed and (3)
representativeness of species selected.
Bioavailability is a major uncertainty in interpreting the
potential for adverse biological effects from exposure estimates
based on measurements of bulk chemical concentrations in
environmental media. Chemical and physical changes in
environmental media that increase or decrease the solubility of
metals also increase or decrease their bioavailability.
Synergisms among chemicals present at exposure points may
increase the risk of adverse effects occurring in exposed
organisms.
-------
Imminent and substantial Endangerment
Actual or threatened releases of hazardous substances from the
Cleveland Mill Site, if not addressed by implementing the
response action selected in this ROD, may be an imminent and
substantial endangerment to public health or welfare or the
environment. This determination that the release at. and from the
site may present an imminent and substantial endangerment was
made using EPA Risk Assessment guidance including, but not
limited to, "Risk Assessment Guidance for SUDerfund: Volume I.
Human Health Evaluation Manual - Part A" (HHEM) (EPA/540/l-
89/002). "Risk Assessment Guidance for Superfund: Volume I. Human
Health Evaluation Manual - Part B" (OSWER Directive 9285.7-01B).
"Risk Assessment Guidance for SUDer fund: Volume II. Environmental
Evaluation Manual" (EPA/540/l-89/00l) and the companion manual
"Ecoloaical Assessment of Hazardous Waste. sites: A Field and
Laboratorv Reference (EPA/600/3-89/0l3).
VII. REMEDIAL ACTION GOALS
The reader should note that there are two terms used in this ROD
which may sound similar, but which have distinct meanings. A
Remedial Objective is a broad intent to address a type of risk to
human health and the environment. A Remedial Action Goal is the
allowable concentration of contaminants which may remain in a
specific medium (such as soil, surface water or ground water) at
the Site, after implementation of this ROD. .
~he contaminated tailings and sediment are considered to be
principal threats at the site. They are considered principal
threats because of the risk they pose through direct contact,
ingestion, and inhalation. The contaminated tailings and
sediment are also considered principal threats because of the
potential for migration of the contaminants in the tailings and
sediment to the ground water and surface water. At the Site,
ARARs are not available for certain contamina~ed media, or are
not sufficiently protective because of the presence of mUltiple
contaminants at the Site, or multiple pathways of exposure;
therefore, for known or suspected carcinogens, the 10.6 risk
level (or one in one million risk of getting cancer during a
lifetime, or a part of a lifetime, of exposure to site
contaminants) was used as a point of departure in establishing
Remedial Action Goals. For non-carcinogenic systemic toxicants,
Remedial Action Goals were set based on a Hazard Index of 1 (See
the Summary of site Risks section of this ROD, section VI).
Remediation of the tailings and sediment is necessary because the
carcinogenic risk from these media is greater than 1 x 10-6 (one
in one million) and the Hazard Index (HI) for three contaminants
at the site is greater than one. The risk posed by each
individual contaminant
in the contaminated tailings and sediment is at least one order
-------
of magnitude greater than the background risk for that individual
contaminant.
Ground water is also a concern at the Site because the ground
water in the shallow perched aquifer at the toe of the tailings
pile is contaminated above federal and state standards called
Maximum contaminant Levels (MCLs) and New Mexico Water Quality
Control Commission (NM WQCC) standards. Surface water is also
contaminated above. these federal and state standards. Safe
Drinking Water Act (SWDA) Maximum contaminant Levels (MCLs)
represent the maximum permissible concentration of a contaminant
in water that may be delivered to the free-flowing outlet of the
ultimate user of a public water system under federal law (40 CPR
S141.2). New Mexico Water Quality Control Commission (NM WCQQ)
standards specify the maximum permissible concentration of a
contaminant which may remain in ground water as a result of
discharge onto or below the surface o£ the ground.
The Remedial Action Goals for the contaminated tailings and
sediment are given in terms of a numerical value. Tailings and
sediment shall be remediated until the contaminant concentrations
in the remaining tailings and sediment, including, but not
limited to, all Site soils does not exceed any of the values
given in Table 8.
The methodology for determination of the Remedial Action Goals
for lead, carcinogenic contaminants and non-carcinogenic
contaminants follows:
Lead: The Remedial Action Goal for lead was calculated using
EPA's uptake/Biokinetic (UBK) model. The UBK model was used to
predict a lead concentration in soils such that 95% of the
exposed- residential population of children would have resulting
blood lead levels less than 10 ug/dl. The soil lead
concentration corresponding to this percentage and this blood
lead level is 500 ppm, .which was chosen as the Remedial Action
Goal.
carcinogenic contaminants: The major contributors to the
carcinogenic risk at the site are arsenic and beryllium. The
calculated risk-based remediation concentrations which would
bring the risk within EPA's acceptable risk range, for both
arsenic and beryllium, are less than the background
concentrations, so the background concentrations of 30 ppm for
arsenic and 4 ppm for beryllium were chosen as the Remedial
Action Goals.
Non-carcinogenic contaminants: The major contributors to the
non-carcinogenic risk at the site are arsenic, cadmium and zinc.
Non-carcinogenic risk is measured by the Hazard Index (HI)'which
is considered unacceptable for an individual contaminant if it is
above 1. In other words, a contaminant is normally remediated if
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TABLE ~ - FINAL REMEDIAL ACTION GOALS FOR THE CLEVELAND MILL SUPERFUND SITE
Final Remedial Action Goals Corresponding Risk Levels
Chemical Specific RME Risk (a)
Remediation Point of Basis of
Medium Chemical Level (ODm) Comoliance Goal Cancer Risk Non-Cancer Hazard Index
Tailings Arsenic 30 \ Background 1.1E-04 0.41
and Beryllium 4 All Site Background 3.6E-05 3.4E-03
Sediment Cadmium 140 Grounds Risk 7.1 E-07 1
Lead 500 ~ UBK Model N/A N/A
Zinc 82000 Risk N/A 1
Footnote (a): Cancer risks are measured as individual
Incremental lifetime; non-cancer as Hazard
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it has a Hazard Index greater than 1. If the background HI is
higher than 1 for a certain contaminant, that contaminant is
normally remediated to the background HI. The HI is also
additive across a site which means that the HI of all
contaminants can be added together to determine a cumulative HI
for a site. At the Cleveland Mill Superfund site, arsenic,
cadmium and zinc all have an HI greater than 1. Therefore, the
site cumulative HI is greater than 3. The background cumulative
HI at the site is 2.3.
The Remedial Action Goals for the three major contaminants
contributing to the non-carcinogenic risk at the site are given
individually and as a cumulative site HI. Individually, arsenic
has a background HI of 1.13 which is greater then 1. Therefore,
the background value of 30 ppm was chosen as the individual non-
carcinogenic Remedial Action Goal for arsenic. For the remaining
major contaminants that contribute to the non-carcinogenic risk,
the concentrations corresponding to an individual HI of 1, 140
ppm for cadmium and 82,000 ppm for zinc, were chosen as the
individual non-carcinogenic Remedial Action Goals.
The Remedial Action Goal for the cumulative site HI must also be
met in addition to the individual Remedial Action Goals for the
three major non-carcinogenic contaminants. After excavation, the
cumulative site HI must be less than or equal to the site
background HI of 2.3. Again, the site HI is additive and it is
calculated by adding the HIs of all contaminants at the Site, not
only the HIs of each of the three major contaminants that
contribute to the non-carcinogenic risk. Therefore, if each
major non-carcinogenic contaminant were brought to an HI of 1 and
added with several minor contaminants with fractional HIs, the
cumulative site HI would be slightly more than 3, which would
still be above the background HI. Because the contaminants may
not be distributed homogeneously in a vertical direction, it is
possible that during excavation, one or all of the contaminants
may be reduced to an HI of much less than 1, causing the
cumulative HI to be less than 2.3. Because of the numerous
combinations of HIs and their corresponding concentrations that
could result in a cumulative HI of less than background, the
individual HIs are given in this ROD. This ROD requires that all
individual non-carcinogenic Remedial Action Goals (HIs) be met.
As far as the cumulative HI for the site is concerned, EPA has no
preference as to how this cumulative HI of 2.3 (Site background)
is met. That is, clean-up of the site could meet the Remedial
Action Goals for the cumulative HI in any number of ways.
Note that the HI for zinc shown in the March 1993 Remedial
Investigation Report has been changed. (The recalculation using
a reference dose of .3 mg/kg-day, instead of .2 mg/kg-day,
appears in Appendix'A of this ROD and is further explained in
Question #68 of the Responsiveness Summary, Appendix E of this
ROD). The recalculation of the HI for zinc did not change the HI
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. .
dramatically. For a child, the HI changed from 1.91 to 1.27 for
the future residential scenario. The recalculated HI remained
greater than 1 and must be remediated. .
The approximate volume of the material which must be remediated
is 70,900 cubic yards. The contaminated tailings and sediment
are found in several areas of the site. For a detailed breakdown
of the areas of contamination and their corresponding volume, see
section V.E. .
One of the Remedial Objectives for the site is to return the
shallow perched aquifer at the toe of the tailings to a condition
where the concentration of contaminants is below MCLs and NM WQCC
standards. Because ground water at the site has been identified
as a potential source of drinking water, MCLs and NM WQCC
standards are applicable. The ground water at the Site and in
the. surrounding area was sampled and evaluated against these
federal and state standards.
Sample results from a monitor well completed in the shallow
perched aquifer showed that several dissolved metals and
indicator parameters were found in the ground water in
concentrations exceeding background levels, MCLs and NM WQCC
standards. An indicator parameter is a substance which is not a
contaminant, but which is frequently associated with
contaminants. The indicator parameters detected in the ground
water are substances which are found in the tailings and sediment
at the site. The substances do not normally occur in area waters
in such high concentrations. These dissolved metals and
indicator parameters were identified at a depth of 7 feet in near
surface colluvium and weathered bedrock that comprise a shallow
perched aquifer at the toe of the main tailings piles. A spring
located immediately south of the western tailings pile also
showed elevated levels of some contaminants and indicator
parameters. No underlying bedrock aquifer was identified, though
exploratory drilling was done to a depth of 110 feet. Ground
water discharges from the shallow perched aquifer at the toe of
the tailings in the form of seeps and springs which flow into the
headwaters of Little Walnut Creek. In short, except for
discharges to the surface through the springs and seeps, the
ground water contamination appears to be limited in vertical and
lateral extent within the shallow perched aquifer at the toe of
the main tailings piles. Ground water from this aquifer is not
currently used for human consumption.
The shallow, perched aquifer in the mill area is not directly
hydraulically connected with the aquifers from which downstream
residents obtain their drinking water. Therefore, contaminated
ground water discharges from the perched aquifer and contributes
to surface water contamination in the mill valley tributary and
Little Walnut Creek. Therefore, the potential exists for
contaminants to migrate downstream and into residential wells via
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infiltration of contaminated surface water from Little Walnut
Creek which flows across the Colorado Formation and Quaternary
alluvial aquifers that are used for drinking water. Ground water
samples from residential wells and monitoring wells located 1.3
to 3.8 miles downstream in the Quaternary alluvium and Colorado
Formation aquifers did not exceed regulatory standards.
Therefore, EPA and NMED have determined that active treatment of
the ground water is not warranted at this time. This
determination is based upon EPA's and NMED's evaluation of site-
specific data indicating that ground water contamination is
currently limited to the shallow perched aquifer at the base of
the main tailings piles which is not directly hydraulically
connected with the aquifers from which downgradient residences
obtain their drinking water. Under the selected alternative,
removal of the contaminated tailings and sediment, the source of
the ground water contamination, along with natural attenuation,
should eliminate any potential threat to human health or the
environment posed by contamination of ground water.
It is difficult to determine how long it will take for natural
attenuation of contamination, in the shallow perched aquifer, to
occur once the tailings and sediments are removed. Based on the
nature of the aquifer and its contaminants, EPA and NMED estimate
that natural attenuation will take 5 years. Contingency measures
may be implemented in the event that contamination exceeding
Remedial Action Goals persists after 5 years of monitoring.
Ground water contingency plans may be required by EPA, in
consultation with NMED, in the following situations:
1)
If, after five years of monitoring (5 years begins on
the date that the contaminated tailings and sediments
are removed), the shallow perched aquifer is still
contaminated above remedial action goals; or
2)
If any other aquifer at or near the site shows
contamination above Remedial Action Goals.
If EPA requires contingency measures to be implemented, the
ground water shall be remediated to MCLs or NM WQCC standards,
whichever is more stringent, for each contaminant. For the
contaminants of concern, these Remedial Action Goals (MCLs except
as noted) under the ground water contingency measures are
arsenic, .05 milligrams per liter (mg/l); beryllium, .004 mg/l;
cadmium, .05 mg/l; lead (NM WQCC standards), .05 mg/l; copper,
1.0 mg/l; mercury, 0.002 mg/l; silver, 0.05 mg/l (NM WQCC
standards); and zinc, 5 mg/l. For newly discovered contaminants
of concern, without promulgated MCLs and NM WQCC standards,
maximum concentrations left untreated will be those which produce
a human health risk of 10-6 or less, unless the background
concentration is higher than the concentration producing the 10-6
risk, in which case" the maximum concentration left untreated
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will be the background concentration. For newly discovered non-
carcinogenic compounds without promulgated MCLs and NM WQCC
standards, the maximum concentrations left untreated will be
those that correspond to a Hazard Index less than or equal to 1
of the background HI for that contaminant, whichever is higher.
The risk will be calculated using the assumptions in the Site
Risk Assessment for, the future resident scenario.
vz :n: .
DESCRZPTZOH OP ALTERNATIVES
A feasibility study was conducted to ensure that appropriate
remedial alternatives were developed and evaluated for the site
such that relevant information concerning the remedial
alternatives could be reviewed and an appropriate remedy selected
for the contamination at the site. Remedial alternatives were
assembled to address potential problems identified in source
material (contaminated tailings and sediment) which has,
contaminated surface water and the shallow perched aquifer at the
toe of the tailings and which may contaminate other media such as
downstream ground water and surface water. Through remediation
of the contaminated tailings and sediment, adverse effects on
surface water are expected to be mitigated, and the potential for
adverse effects on the ground water that supplies the residential
wells downstream is expected to be significantly reduced. Each
alternative includes ground water monitoring to assure that
during and after the remediation, the ground water in the
downstream aquifers remains safe for human consumption. In
addition, the monitoring of surface water and ground water at the
toe of the tailings will show if the remediation of the source of
'the contaminants and natural attenuation are causing a decrease
in the levels of contaminants. In the event that control of the
contaminated tailings and sediment does not provide for
decreasing levels of contaminants in the ground water in the
shallow perched aquifer at the toe of the tailings, contingency
measures, as described later in this section, shall be
implemented if BPA so requires.
The remedial action alternatives for this response action are
presented below with a description of the common elements
contained in each alternative. The costs of several of the
alternatives differ from those costs described in the Proposed
Plan because the estimates have been refined based on several
factors. These factors include a revised estimate of
transportation cost, both for those alternatives that involve
taking the waste material off-site and for those alternatives
that leave the waste material on-site. These factors also
include refinements to the alternatives themselves based on
public comments. The refined cost estimates are presented in
Appendix B.
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A.
Tailings and Sediment
This section discusses remedial alternatives designed to address
the contaminated tailings and sediment site-wide. Tailings and
sediment is the principal contaminated media at the site. The
total amount of tailings and sediment that shall be addressed in
the remediation of the site is approximately 70,900 cubic yards.
In addition to the health and environmental risks posed directly,
the tailings and sediment are also the source of surface water
contamination, and the source of the shalloW perched ground water
contamination in the mill area.
certain contaminants at the site are responsible for most of the
risk to human health or the environment at the site. In other
words, these certain contaminants "drive the risk". The
contaminants of concern driving the risk to human health, due to
potential exposure to contaminated tailings and sediment, are
arsenic, beryllium, cadmium, lead and zinc. The contaminants of
concern are all inorganic chemicals.
Of the 89 surface and subsurface samples taken of tailings and
sediment in the mine and mill area and from the roadbed sediment,
79 were analyzed using the Toxicity Characteristics Leaching
Procedure (TCLP). TCLP is a type of leaching test described
under the Resource and Recovery Act ("RCRA"), 42 U.S.C. 6901
et seq., that can be performed to determine whether or not metals
will leach from a waste. Of the 79 samples, 8 samples exceeded
the RCRA TCLP regulatory level set for cadmium in 40 CFR
~261.24 Table 1 of 1.0 milligrams per liter, and 1 sample
exceeded the regulatory level set for lead of 5.0 milligrams per
liter. Fifty-two samples taken of tailings and sediment in the
streambed of Little Walnut Creek and its tributary were analyzed
using TCLP. Of the 52 samples, 1 exceeded the RCRA TCLP
regulatory level set for lead of 5.0 milligrams per liter.
Although some of the samples exceeded the RCRA regula~ory limit
for lead and cadmium, the contaminated tailings and sediment are
not considered a "hazardous waste" as that term is defined in
RCRA. (See section IX. D.2. of this ROD.)
A brief description of the five detailed alternatives evaluated
to address the contaminated tailings and sediment follows. For
convenience, in this ROD, Alternatives la and lb are referred to
generally as one alternative, and sometimes called collectively
"Alternative 1" or the "No Action Alternative", because neither
requires remediation of the contamination. The alternatives are:
o
Alternative 1a; No Action
Alternative 1b; Institutional controls
Alternative 2; Excavation, on-site Disposal and
Multi-layer Capping
Alternative 3; Excavation, on-site stabilization/
Solidification, on-Site Disposal and Capping
o
o
o
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o
Alternative 4;
Solidification,
Alternative 5;
Reclamation and
remedy selected
Excavation, On-site Stabilization/
Off-site Disposal and capping
Excavation, Off-site Reprocessing,
Disposal of Residuals (This is the
by EPA and NMED)
o
Common Elements:
The volume and locations of the various materials to be addressed
under all of the remedial alternatives reviewed in the FS, except
Alternative 1, are listed below. These volumes assume excavation
of all tailings and sediment with concentrations of contaminants
which exceed Remedial Action Goals. The actual volume of
tailings and sediment to be excavated will be further refined
during the remedial design phase of the remedy, based on
additional sampling to determine the depth of contaminated
tailings and sediment with contaminant concentrations above
Remedial Action Goals.
waste Area Volume (cubic yards)
Main Tailings piles 30,000
Cobbed Ore pile 15,000
Mine Spoils 15,000
Creek Sediment . I. 6,000
Western Hillside Waste Piles 2,500
Roadbed Soils 1,500
Dust piles 900
-
Total Volume 70,900
-.
Each of the alternatives listed above, other than Alternative 1,
are intended to address the tailings and sediment, . and have the
following common elements: site preparation, restoration of the
site surface upon completion of the remedial action, improvement
of and repair of roads that are affected by the remedial action,
and issuance of deed notices to advise future owners about the
risks of disturbing the cover and/or the underlying material.
All of the alternatives, except the No Action Alternative, have a
ground water monitoring element, which includes monitoring of the
shallow perched aquifer in the mill area, monitoring of the
springs in the mill and mine area, and monitoring of selected
downgradient residential wells. Ground water monitoring shall be
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conducted to ensure that, under each of the alternatives, removal
of the source of the contamination and natural attenuation of
contaminants results in decreasing levels of contaminants in the
shallow perched aquifer at the toe of the tailings and in the
mill area springs, and to ensure that the residential wells do
not become contaminated above MCLs or NM WQCC standards. The
number and placement of the monitoring wells will be determined
by EPA, in consultation with NMED, during the Remedial Design
Phase. The wells and the springs which are part of the ground
water monitoring program shall be analyzed for, at the minimum,
the contaminants of concern, total dissolved solids, pH and major
cations and anions.
One of the Remedial Objectives for the site is to return the
shallow perched aquifer at the toe of the tailings to a condition
where the concentration of contaminants is below MCLs and NM WQCC
standards. The length of time and the frequency of monitoring
vary from one alternative to the other. Under Alternatives 2 and
3, which leave the waste material on-site, the ground water
monitoring program would include institutional controls,
installation of monitoring wells downgradient of the disposal and
excavation area, quarterly sampling of new and existing
monitoring wells for the first five years, and annual sampling
for up to 30 years. Under Alternatives 4 and 5, which involve
waste excavation and transport off-site, the ground water
~onitoring program would include institutional controls,
installation of monitoring wells downgradient of the excavated
mill tailings, and quarterly sampling of new and existing
monitoring wells for the first five years. Under Alternatives 4
and 5, ground water monitoring would continue for up to 30 years
if elimination of the source material (tailings and sediment) and
natural attenuation did not bring the levels of contaminants in
the monitoring wells below the regulatory levels discussed in the
Remedial Action Goals section of this ROD.
An additional part of the monitoring program in each alternative,
except in the No Action Alternative, would be monitoring of the
surface water in the mill valley tributary and in Little Walnut
Creek. The surface water monitoring would be conducted annually
for at least 5 years'as determined by EPA, iri consultation with
NMED.
All remedial alternatives were assessed as required under CERCLA
to determine whether they attain applicable or relevant and
appropriate requirements under federal and state environmental
laws. These requirements are called ARARs. RCRA is not an ARAR
for the remediation of the site under any of the remedial
alternatives. RCRA is not applicable to the contaminated
tailings and sediment since the tailings and sediment are exempt
from categorization as a hazardous waste, under 40 CFR ~261.4.
The Subtitle C requirements of RCRA were determined to be
relevant in that certain samples did leach toxic materials at
-------
levels that failed RCRA standards when the Toxicity
Characteristic Leaching Procedures (TCLP) was applied. However,
EPA has completed an extensive national study of the type of
contaminated material found at the site-- solid waste from the
extraction, benefication, and processing of ores and minerals,
and determined that it should not be regulated under RCRA
Subtitle C (see e.g. 54 Fed. Reg. 36614 (Sept. 1, 1989»;
therefore, RCRA is not an appropriate requirement for any
remedial alternative for the site. .
All of the remedial alternatives listed above will meet ARARs,
which are the same for each of the alternatives. RCRA does not
provide any chemical-specific ARARs which pertain to the
remediation of the site. There are location-specific ARARs,
which do pertain to the remediation due to the fact that the site
is adjacent to a National Forest which contains endangered
species, and due to the fact that the Site remediation may
involve areas that have cultural and historical significance as
defined in the National Historic Preservation Act. Any
implementation of the off-site removal portion of the selected
remedy, under this ROD, shall be carried out in compliance with
EPA's Off-site POlicy, (CERCLA section 121(d) (3) 42 U.S.C. .
section 9621(d) (3» along with all other applicable federal,
state and local requirements. For a detailed list of ARARs see
Sections IX and section X of this ROD.
All of the alternatives, with the exception of Alternative 1,
involve treating and/or containing tailings and sediment that
have contaminant concentrations which exceed Remedial Action
Goals. Alternative 1 will not meet the Remedial Action Goals for
the site. Alternatives 2, 3, 4 and 5 will meet the Remedial
Action Goals because, under each alternative, the risk from
exposure to contaminated tailings and sediment will be reduced or
eliminated through excavation or treatment of the tailings and
sediment.
All of the alternatives, with the exception of Alternative 1,
include air monitoring during any excavation, during anyon-site
materials handlinq, and durinq any transport of contaminated
materials. The air monitorinq shall be on-site, at the site
boundary during excavation, and in the community during
transportation.
All costs and implementation times are estimates. The costs have
a degree of accuracy of +50% to -30% pursuant to the "Guidance
for Conducting Remedial Investigations and Feasibility studies
Under CERCLA - Interim Final" OSWER Directive 9355.3-01, October
1988. As noted previously, the costs for the alternatives have
been revised since the Proposed Plan. (See Appendix B).
For each of the alternatives, the site shall be re-evaluated five
years after implementation of the remedy to determine if the
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remedy is providing the intended protection to human health and
the environment.
1.
Alternative 1a:
50 Action
capital Cost: $0
Annual operation and Maintenance:
Present Worth: $15,000
Implementation Time: o.months
Major components of the Remedial Action: EPA is required by the
National contingency Plan (40 CFR 300) to consider a No Action
alternative as a basis of comparison when evaluating other
alternatives. The No Action alternative would not involve any
remedial actions. The site would remain as it exists at the
present time.
$5,000
Treatment and containment components: No treatment or
containment of the contaminated tailings and sediment would
occur.
General components: There are no costs associated with this
alternative. operation and maintenance (O&M) costs are estimated
to be $5,000 every five years for the performance of a five-year
review, required under CERCLA when contaminated material is left
on-site. The present worth cost is estimated to be $15,000.
EPA and NMED do not favor this alternative because it would not
decrease the toxicity, mObility, or volume of contaminants or
address risks to public health or risks to the environment.
Alternative 1b:
Limited Action
capital Cost: $0
Annual operation and Maintenance:
Present worth: $246,878
Implementation Time: 2 months
Major componeDts of the Remedial ActioD: Under Alternative lb,
a limited action would be taken with respect .to the tailings and
sediment at the site.
$56,750
under the limited action alternative provisions would be made for
monitoring and institutional controls to limit use of the mill
site and the ground water, but the limited action would not
remediate the contamination. warning signs would be posted to
restrict access to the site by unauthorized people. The
institutional control used would be deed notices that would
advise future owners of the potential health risks from exposures
the tailings, soils, and surface water. These deed notices would
only provide an alert, and it may be that they could not be used
to restrict activities on the site through legal action. The
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contaminated tailings and sediment would continue to be a source
of leachate generation and this leachate would continue to
contaminate shallow ground water at the base of the tailings,
migrate into Little Walnut Creek, and potentially contaminate
downstream aquifers.
As described in the Common Elements section of this ROD, a
long-term ground water monitoring program would be established to
monitor existing ground water contamination at the mill site and
potential migration of contaminants to downstream aquifers. The
ground water monitoring program in this alternative differs from
the other alternatives in that this alternative, the Limited
Action Alternative, would not include the installation of
additional monitoring wells. The well network currently in place
would be used. .
Treatment components: There is no treatment element in
Alternative 1, because it will involve institutional controls
only.
containment components: There is no containment element in this
alternative because the contaminated material is left in place
without placement of a cover.
General components: The estimated time to implement this remedy
is 2 months for set up of the institutional controls and 30 years
for monitoring of wells. The estimated costs are: capital
Costs: $0: O&M Costs: $56,750 (annual); Present Worth: $246,878.
EPA and NMED do not favor this alternative because it would not
decrease the toxicity, mobility, or volume of contaminants or
address risks to public health or risks to the environment.
2. Alternative 2:
Excavation, on-site Disposal
and HUlti-Layer capping
capital Cost: $2,676,303
Annual operation and Maintenance:
Present Worth: $3,324,701
Implementation Time: 6 months
$138,150
"."
Major components of tbe Remedial Alternative: Under Alternative
2, approximately 70,900 cubic yards of contaminated tailings and
sediment would be excavated, moved, and consolidated in an
on-site disposal area. The consolidation would be followed by
construction of a polyethylene and geo-textile cover that would
be subsequently covered with soil and revegetated. Under
Alternative 2, tailings and sediment would be moved out of the
headwaters of Little Walnut Creek thereby reducing the potential
for acid-leaching of the tailings and sediment by infiltration of
surface and subsurface waters, and transport of the tailings and
sediment into the creek. Under this alternative, surface water
-------
would be diverted away from the capped area and long-term
operation and maintenance (O&M) would be conducted to monitor the
ground water around the disposal area, to ensure the that the
integrity of the cap is consistently maintained.
Treatment components: There is no treatment element in
Alternative 2, since it will only involve consolidation of the
contaminated material.
containment Components: Under Alternative 2, the tailings and
sediment would be excavated and disposed of in an on-site
disposal area located away from natural drainages areas and
covered. The action would serve to consolidate the acid-
producing material and keep water from contacting the surface of
the disposal area. The disposal cell would be unlined, with the
bottom at least 50 feet above the seasonal high ground water
table.
Under Alternative 2, the polyethylene and geo-textile cover would
be designed and constructed to promote drainage around the
disposal cell, minimize erosion, and provide long-term
minimization of migration of liquids through the underlying
tailings, sediment and soil. The "revegetated soil cover would
offer added protection by further preventing rain water from
migrating to the tailings and sediment and would require minimal
maintenance.
,.
General components: The estimated time to implement this
alternative is 6 months. Institutional controls, ground water
monitoring, and, if necessary, repair and improvement of Little
Walnut Road would be implemented, as part of the remedy under
Alternative 2. The estimated costs of Alternative 2 are:
Capital Costs $2,676,303: O&M Costs $138,150 (annual): Present
Worth $3,324,701.
3.
Alternative 3: Excavation, on-site stabiliz~tionl
Solidification, on-site Disposal and capping
capital Cost: $5,980,216
Annual operation and Maintenance:
Present Worth: $6,619,187
Implementation Time: 12 months
$136;150
Major components of the Remedial Alternative: Under Alternative
3, approximately 70,900 cubic yards of contaminated tailings and
sediment would be treated on-site by stabilization and
solidification, moved to an on-site disposal area, and covered
with a soil cap. The soil cap would" be subsequently revegetated
with native plants. Like under Alternative 2, under Alternative
3, tailings and sediment would be moved out of the headwaters of
Little Walnut creek thereby reducing the potential for acid-
leaching of the tailings and sediment by infiltration of surface
-------
and subsurface waters and transport of the tailings and sediment
into the creek. Surface water would be diverted away from the
capped area and long-term operation and maintenance (O&M) would
be conducted to monitor the ground water around the disposal
area, to ensure the that the integrity of the cap is consistently
maintained.
Unlike Alternative 2, Alternative 3 contains a treatment element
which reduces the mObility of the contaminants in the tailings
and sediment. The purpose of the treatment is to immobilize th~
inorganic contaminants. Long-term operation and maintenance
(O&M) would be conducted to monitor the ground water around the
disposal area and to ensure the integrity of the soil cap.
Treatment components: Alternative 3 does have a treatment
element, since it would involve on-site stabilization and
solidification. Stabilization and solidification are a
combination of treatment technologies whereby a waste is mixed
with various reagents such as cement or fly ash, which harden and
transform the waste into a solid mass. The contaminants within
the solid mass are held in place by strong chemical bonds which
minimize the leaching of the contaminants. Stabilization limits
the sOlubility or mObility of the contaminants by maintaining
them in their least mobile or toxic form. The effectiveness of
stabilization is generally measured through a series of tests
that determine whether or not the contaminants will leach out of
the stabilized mass and if they do, the concentration of the
contaminants in the leachate. Solidification produces a solid
block of material with high structural integrity, the
effectiveness of which is measured through testing the material's
compressive and tensile strength in order to prove that a
physical bond exists.
Under Alternative 3, the inorganic contaminants would be
chemically bonded, thus minimizing their leaching~otential into
the ground water. Stabilization is an established and effective
means of treating most types of inorganic contamination in soils.
Based on historical treatability studies conducted on similar
tailings and sediment; however, the ability to stabilize high
concentrations of arsenic is uncertain. In addition, the limited
stabilization and solidification treatability study conducted on
Cleveland Mill contaminated tailings and sediment was
inconclusive regarding the effectiveness of stabilization of
contaminants of concern besides the arsenic.
Although arsenic cannot be stabilized, the presence of arsenic as
a contaminant in the tailings and sediment will not adversely
affect the solidification process. Based on preliminary site
treatability studies, the tailings and sediment can be
successfully solidified with a minimum of a 30% volume increase.
Additional treatability studies would be necessary, under
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Alternative 3, to further define the most effective means of
stabilization and solidification.
containment Components: Under Alternative 3, the tailings and
sediment would be excavated, solidified and stabilized, disposed
of in an on-site disposal area located away from natural surface
drainage areas, covered and revegetated. The action would serve
to consolidate the acid-producing material, reduce the mobility
of the contaminants, and keep water from contacting the surface
and subsurface of the disposal area. The disposal cell would be
unlined, with the bottom at least 50 feet above the seasonal high
ground water table.
Like under Alternative 2, under Alternative 3, the soil cap would
be designed and constructed to promote drainage around the
disposal cell, minimize erosion, and provide long-term
minimization of migration of liquids through the underlying
stabilized and solidified mass. The revegetated soil cover would
offer added protection by preventing rain water from directly
contacting the stabilized and solidified mass, but the soil cover
would require maintenance.
General components: The estimated time to implement Alternative
3 is 12 months. Institutional controls, ground water monitoring,
and, if necessary, repair and improvement of site access roads,
including Little Walnut Road, would be implemented, as part of
the remedy under Alternative 3. The estimated costs are:
Capital Costs $5,980,216, O&M Costs $136,150 (annual): Present
Worth $6,619,187.
. .
4.
Alternative 4:
on-site stabilization/Solidification,
Off-site Disposal and capping
capital Cost: $11,101,596
Annual Operation and Maintenance:
Present Worth: $11,479,046
Implementation Time: 12 months
$51,250
Kajor Components of the Remedial Alternative:. Implementation of
Alternative 4 would involve the same activities as Alternative 3
with respect to excavation, solidification and stabilization of
the contaminated tailings and sediment. However, the stabilized
and solidified tailings and sediment would be disposed of in an
off-site landfill permitted to accept these materials. The
contaminated tailings and sediment is not defined as a hazardous
waste under RCRA: however, the stabilization and solidification
would be performed in order to provide added protection to human
health and the environment. Once the material was stabilized, it
would be less hazardous to transport because the chance of a
release of contaminated material would be greatly reduced.
However, a large volume increase would occur as a result of the
stabilization and solidification prior to transportation off-
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site. The large number of trucks that would be required
transport this increased volume of tailings and sediment
pose some short-term transportation risks. (See the
Transportation Appendix, Appendix C of this ROD.)
Treatment components: The treatment element in Alternative 4 is
the on-site stabilization and solidification of tailings and
sediment prior to transportation to an off-site disposal
facility. After stabilization and solidification, the inorganic
material would be chemically bonded, thus reducing its leaching
potential. Stabilization is an established and effective means
of treating most inorganic contamination in soils. Based on
historical treatability studies conducted on similar wastes, the
ability to stabilize high concentrations of arsenic is
uncertain, but the presence of arsenic in the tailings and
sediment will not adversely affect the solidification process.
to
could
Under Alternative 4, the solidified and stabilized tailings and
sediment would be sent off-site for disposal; consequently, it
would no longer pose a risk at the site. Under Alternative 4,
additional treatability studies would be necessary to further
define the most effective means of stabilization and
Solidification. .
containment components: Under Alternative 4, the stabilized
tailings and sediment would be disposed of in a manner consistent
with the state and federal requirements for the off-site
landfill. No contaminated material would be stored or contained
at the Cleveland Mill superfund site.
General components: The estimated time to implement this remedy
is 12 months. Institutional controls, ground water monitoring,
and, if necessary, repair and improvement of site access roads,
including Little Walnut Road, would be implemented, as part of
the remedy under Alternative 4. The estimated co~ts are capital
Costs $11,101,596; O&M Costs $51,250; Present Worth $11,479,046.
s.
Alternative 5: Excavation, Off-site Reprocessing,
Reclamation and Disposal of Residuals
EPAand NMED's preferred Alternative
capital Cost: $5,836,586
Annual operation and Maintenance:
Present Worth: $6,214,036
Implementation Time: 12 months
$51,250
Major components of the Remedial Alternative: Implementation of
Alternative 5 would involve the same activities as Alternative 4
with respect to excavation, and off-site transport of the
contaminated tailings and sediment. Under Alternative 5, the
contaminated tailings and sediment would be transported to an
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off-site facility where they would be reprocessed using the
reprocessing method chosen by the off-site facility. The purpose
of the reprocessing would be to reclaim valuable metals and to
render the residual material less toxic and the contaminants in
the residual material less mobile. The residual material would
be disposed of at the reprocessing facility.
Treatment components: Under Alternative 5, the contaminated
tailings and sediment would be reprocessed at an ore-processing
facility. Reprocessing shall remove both contaminants and metals
that can be beneficially reused. The determination of the metals
that would be removed from the tailings and sediment would depend
upon the process employed by the reprocessing facility.
containment components: The residual would be disposed of in a
disposal area at the reprocessing facility with other tailings
and residuals from ore-processing. The disposal activities would
be required to be conducted in accordance with applicable state
and federal laws, as determined by EPA and the state in which the
disposal facility is located. The reprocessing activity would
have to meet and all federal and state laws.
General components: The estimated time to implement the selected
remedy is 2 months for site preparation, 8 months for excavation
of and transport of the contaminated tailings and sedimeht, and 2
months for site restoration. The contaminated tailings and
sediment must be reprocessed within one year of delivery to the
reprocessing facility. Institutional controls, ground water
monitoring, and, if necessary, repair and improvement of site
access roads, including Little Walnut Road, would be implemented,
as part of Alternative 5. The estimated costs are capital Costs
$5,836,586; O&M Costs $51,250; Present Worth $6,214,036.
The cost of Alternative 5, is based, in part, upon EPA and NMED's
projection that some valuable metals would be recovered and kept
by the reprocessing facility. The recovery of valuable metals
would help lower the cost of the remedy. Costs may go up, if the
reprocessing facility cannot keep the valuable metal.
Ground Water contingency Heasures:
If the selected remedy, Alternative 5, cannot meet the specified
Remedial Action Goals at any or all of the monitoring points,
including those in the perched aquifer, after 5 years, the
contingency measures and objectives described in this section of
the ROD may be implemented. These measures are considered to
protect human health and the environment, and are technically
practical under the corresponding circumstances. Under the
selected remedy, Alternative 5, EPA, in consultation with NMED,
may require one or more of the following contingency measures to
be put into effect if EPA, in consultation with NMED, later
determines that there is contamination in ground water above
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Remedial Action Goals. EPA may make
or NM WQCC standards are exceeded in
well, including, but not limited to,
perched aquifer.
Ground water contingency plans may be required by EPA, in
consultation with NMED, in the following situations:
such a determination if MCLs
any ground water monitoring
those wells completed in the
1)
If, after five years of monitoring (5 years begins on
the date that the contaminated tailings and sediments
are removed), the shallow perched aquifer is still
contaminated above remedial action goals; or
2)
If any other aquifer at or near the site shows
contamination above Remedial Action Goals.
EPA may also make such a determination if EPA has any other
reason to believe that ground water contamination above Remedial
Action Goals exists 5 years from completion of removal of the
contaminated tailings and sediment. The ground water contingency
measures will be one or more of the following as determined by
EPA in consultation with NMED:
Installation of additional monitoring wells to confirm
and better define the changing conditions in ground
water contaminant concentrations.
Development of a Remedial Action Plan which provides
for the extraction, treatment, and reinjection or
discharge or disposal of contaminated ground water in
order to achieve ARARs.
Implementation of a Remedial Action Plan subject to
EPA disapproval of the plan, after NMED has had an
opportunity to review and comment upon_the plan.
waiving the ground water ARAR for the aquifer based on
the technical impracticability of achieving
contaminant reduction.
Establishment of an Alternative Concentration Limit
"(ACL") for the detected contaminants provided
complian~e with CERCLA 121 (d) (2) (B) (ii) can be
demonstrated.
The ground water monitoring which is required under the selected
remedy, provides for quarterly monitoring of ground water wells
at the site. Wells established as part of the ground water
monitoring program during remedy design shall be used to
determine 1) whether natural attenuation of the ground water
contamination is taking place, and 2) whether the extent of
ground water contamination has spread or diminished.
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If contingency measures are implemented, EPA, in consultation
with NMED, may require modification of the existing network of
wells, changes in the type of analyses performed, or changes in
frequency of sampling, in order to identify changes in ground
water quality. The selected remedy is expected to prevent
continued ground water contamination. However, as explained in
section VII, Remedial Action Goals, if monitoring wells detect
contaminant concentrations which exceed MCLs or NM WQCC
standards, site background or a concentration producing a risk
greater than 10-6 or, if EPA determines, for any other reason,
that ground water has become contaminated and requires
remediation, EPA may require that the contingency measures listed
be implemented.
:IX.
SUHKARY OF COHPAlmT:IVE ANALYS:IS OF ALTERNAT:IVES
The EPA uses nine criteria to evaluate alternatives for
addressing a Superfund site. These nine criteria are categorized
into three groups: threshold, balancing, and mOdifying. The,
thr~shold criteria must be met in order for an alternative to be
eligible for selection. The threshold criteria are overall
protection of human health and the environment and compliance
with ARARs. The balancing criteria are used to weigh major
tradeoffs among alternatives. The five primary balancing
criteria are long-term effectiveness and permanence; reduction of
toxicity, mobility or volume through treatment; short-term
effectiveness; implementability; and cost. The modifying
criteria are state acceptance; and community acceptance.
A. Threshold criteria
OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
This criterion addresses whether or not the alternative in
question can adequately protect human health and the environment,
in both the short- and long-term, from unacceptable risks posed
by hazardous substances, pollutants, or contaminants present at a
site by eliminating, reducing, or controlling exposures to levels
established during development of remediation goals. Overall
protection of human health and the environment draws on the
assessments of other evaluation criteria, especially long-term
effectiveness, and compliance with the Applicable or Relevant and
Appropriate Requirements "(ARARs) under federal and state
environmental laws.
COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS (ARARs)
This criterion addresses whether or not the alternative attains
applicable or relevant and appropriate requirements under federal
environmental laws and state environmental or facility siting
laws or provides grounds for invoking one of the waivers of these
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requirements. There are three types of ARARs. Chemical-specific
ARARs are usually health- or risk-based numerical values of
methodologies used to determine acceptable concentrations of
chemicals that may be found in or discharged to the environment,
e.g. MCLs that establish safe levels in drinking water.
Location-specific ARARs restrict actions or contaminant
concentrations in certain environmentally sensitive areas.
Examples of areas regulated under various federal laws include
flood plains, wetlands, and location where endangered species or
historically significant cultural resources are present. Action-
specific ARARs are usually technoloqy- or activity-based
requirements or limitations on actions or conditions involving
specific substances.
B.
Balancing cri~eria
LONG-TERM EFFECTIVENESS AND PERMANENCE
This criterion assesses the alternative for the long-term
effectiveness and permanence that it affords, along with the
degree of certainty that the alternative will prove successful.
Factors that are considered, include the following: (1)
Magnitude of residual risk remaining from untreated waste or
treatment residuals remaining at the conclusion of the remedial
activities. The characteristics of the residuals are considered
to the degree that they remain hazardous, taking into account
their volume, toxicity, mObility, and propensity to
bioaccumulate. (2);' Adequacy and reliability of controls such as
containment systems and institutional controls that are necessary
to manage treatment residuals and untreated waste. This factor
addresses in particular the uncertainties associated with land
disposal for providing long-term protection from residuals; the
assessment of the potential need to replace technical components
of the alternative, such as a cap, a slurry wall, or a treatment
system; and the potential exposure pathways and ri~ks posed
should the remedial action need replacement.
REDUCTION OF TOXICITY, MOBILITY, OR VOLUME THROUGH TREATMENT
This criterion addresses the degree to which alternatives employ
recycling or treatment that reduces- toxicity, mobility, or volume
shall be assessed, including how treatment is used to address the
principal threats posed by a site. Factors that are considered
include the following: (1) The treatment or recycling processes
the alternatives employ and materials they will treat; (2) The
amount of hazardous substances, pollutants, or contaminants that
will be destroyed, treated, or recycled; (3) The degree of
expected reduction in toxicity, mObility, or volume of the waste
due to treatment or recycling and the specification of which
reduction(s) are occurring; (4) The degree to which the
treatment is irreversible; (5) The type and quantity of
residuals that will remain following treatment, considering the
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persistence, toxicity, mobility, and propensity to bioaccumulate
of such hazardous substances and their constituents: and (6)
The degree to which treatment reduces the inherent hazards posed
by principal threats at a site.
SHORT TERM EFFECTIVENESS
This criterion assesses the short-term impacts of alternatives
considering the following: (1) Short-term risks that might be
posed to the community during implementation of an alternative:
(2) potential impacts on workers during remedial action and the
effectiveness and reliability of protective measures:
(3) potential environmental impacts of the remedial action and
the effectiveness and reliability of mitigative measures during
implementation; and (4) Time until protection is achieved.
IMPLEMENTABILITY
This criterion addresses the ease or difficulty of implementing
the alternatives by considering the following types of factors as
appropriate: (1) Technical feasibility, including technical
difficulties and unknowns associated with the construction and
operation of a technology, the reliability of the technology,
ease of undertaking additional remedial actions, and the ability
to monitor the effectiveness of the remedy (2) Administrative
feasibility, including activities needed to coordinate with other
offices and agencies and the ability and time required to obtain
any necessary approvals and permits from other agencies (for
off-site actions); (3) Availability of services and materials,
including the availability of adequate off-site treatment,
storage capacity, and disposal capacity and services; the
availability of necessary equipment and specialists, and
provisions to ensure any necessary additional resources: the
availability of services and materials; and availability of
prospective technologies.
COST
This criterion addresses the types of costs that shall be
assessed including the following: (1) Capital costs, including
both direct and indirect costs: (2) Annual operation and
maintenance (O&M) costs: and (3) Net present values of capital
and O&M costs.
c.
Hodifying criteria
STATE ACCEPTANCE
Assessment of state concerns may not be completed until comments
on the RIfFS are received but may be discussed, to the extent
possible, in the proposed plan issued for public comment. The
state concerns that are assessed under this criterion include the
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following: (1) The state's position and key concerns related to
the preferred alternative and other alternatives: and (2) state
comments on ARARs or the proposed use of waivers.
COMMUNITY ACCEPTANCE
Assessment of community acceptance includes determining which
components of the alternatives interested persons in the
community support, have reservations about, or oppose. community
Acceptance allows for a public comment period for interested
persons or organizations to comment on the proposed remedy. EPA
considers these comments in making its final remedy selection.
The comments are addressed in the Responsiveness summary which is
included as Appendix E of this ROD.
D.
comparative Analysis of Alternatives
Overall protection of Human Health and the Environment
1.
The discussion regarding whether the alternatives can adequately
protect human health and the environment in both the short- and
long-term from unacceptable risks, posed by the hazardous
substances at the Site, follows immediately below, and also
appears under the short-term effectiveness and long term
effectiveness sections. Likewise, the discussion regarding
whether the various alternatives meet ARARs, in the sections
which follow, incorporates some discussion as to whether the
alternatives examined can protect human health and the
environment. EPA and NMED's overall view as to whether the
alternatives are protective appears immediately below.
. 0'
All of the remedial alternatives considered for the site, except
No Action, will provide some degree of overall protection of
human health and the environment. The degree to which each
alternative provides this protection is discussed ~elow.
Alternatives 1a and 1b, the No Action and Limited Action
alternatives, provide no increase or an insignificant increase in
the overall protection to human health and the environment.
Under these alternatives, all of the potential risks to human
health and the environment associated with the Cleveland Mill
site would remain. Institutional controls would only minimally
address the risk because the controls are only temporary and do
nothing to address the contamination. The long-term risk
associated with potential exposure would not be reduced, nor
would these alternatives address the potential short-term risk to
future on-site workers or residents. ARARs would not be met
under these alternatives. Alternatives 1a and Ib do not provide
overall protection of human health and the environment and were,
therefore, eliminated from further consideration.
Alternative 2, On-Site Disposal without Treatment, would reduce,
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to a moderate degree, the risk from direct contact with the
tailings and sediment on-site by consolidating the site tailings
and sediment and covering the consolidated material with a multi-
layered geo-textile and soil cap. The cap would also minimize
the potential for air emissions from the site as long as it is
undisturbed. Under Alternative 2, exposure to levels of site
contaminants above the Remedial Action Goals would be controlled.
Human health and the environment would be protected to the extent
that the cap was maintained, and did not allow humans or animals
to access the disposal area, and to the extent that the cap kept
water from coming in contact with the contaminated tailings and
sediment.
Alternative 2 would pose some short-term risks such as risk to
workers and residents from the heavy equipment and risk from
inhalation of dust from the excavation. These short term risks
are controllable by employing engineering controls such as
transportation controls, limiting site access and using dust
suppression techniques. Alternative 2 would also meet ARARs.
Because Alternative 2 would not reduce the mobility, or toxicity
of the contaminated material through treatment and would not "be
permanent, the possibility of contaminant leaching would still
remain and, therefore, this alternative would be only moderately
protective of human health and the environment. It would not be
protective of human health and the environment in the long term
because it is not permanent.
Alternative 3, stabilization/Solidification and On-site Disposal,
would be significantly more protective than Alternative 2 because
it would do more to prevept humans and animals from having direct
contact with contaminated tailings and sediment, and it would do
more to prevent humans from ingesting contaminated sediment and
tailings by encapsulating and immobilizing many of the
contaminants, solidifying the tailings and sediment, and covering
the solidified mass. Under Alternative 3, the inorganic
contaminants would remain, but it is expected that aIr the
contaminants except possibly arsenic would be stabilized, and all
the contaminants would be consolidated and capped. Because the
inorganic contaminants except possibly arsenic would be
chemically bonded, their leaching potential into the ground water
would be reduced. In addition, water would be kept from
contacting the surface and subsurface of the disposal area,
further reducing the potential for contaminant" migration to the
ground water, surface water, or soil. Because humans and ground
water and surface water would be kept from directly contacting
the contaminants, the potential for exposure to the site
contaminants would be greatly reduced and controlled.
Alternative 3 can adequately protect human health and the
environment in the short term, but because of uncertainties in
stabilizing arsenic, it is not known whether it could adequately
protect human health and the environment in the long term from
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the unacceptable risk posed by hazardous substances at the site.
Alternative 3 would pose the same short term risks as Alternative
2 and these risks are controllable using the same engineering
controls as Alternative 2. Alternative 3 would also meet ARARs.
Alternative 3 would have a high long term effectiveness for all
site contaminants except arsenic. As previously mentioned, the
ability to permanently stabilize arsenic is uncertain, so some
risk of adverse human health and environmental effects from
direct contact with the arsenic, and some risk of adverse effects
to the environment from contaminant migration to site soils,
sediment, and surface water and infiltration into the ground
water would remain. .
Alternative 4, On-site Solidification and Off-site Disposal and
Alternative 5, Off-site Reprocessing and Off-site Disposal,
provide the maximum site-specific protection of human health and
the environment by the removal of the contaminated material from
the site. Alternative 4 and 5 can adequately protect human
health and the environment, in both the short and long term, from
unacceptable risk posed by hazardous substances at the site.
Both alternatives eliminate exposure to site contaminants
consistent with Remedial Action Goals and both meet ARARs. Both
have a high degree of long term effectiveness and permanence with
respect to the site. Due to the fact that the contaminated
material would be removed, the potential for future contaminant
migration to the site soils, surface water and ground water, and
the potential for air emissions at the site would be eliminated.
Short term risks, such as transportation risks, would pose a
temporary risk that would be mitigated through engineering
controls. See the Transportation Appendix, Appendix C of this
ROD, for examples of transportation risks and their appropriate
engineering controls. Alternatives 4 and 5 both use an off-site
facility for disposal of the contaminated tailings and sediment;
however, under Alternative 5, reprocessing would be employed to
reduce the toxicity of the tailings and sediment. -
2.
Compliance with Applicable or Relevant and Appropriate
Requirements (ARARS)
ARARs are federal and state environmental requirements that the
selected remedy must meet. All of the alternatives would comply
with ARARs. Because the contaminated material is a type of mining
waste which is exempt from categorization as a hazardous waste
under the Resource Conservation and Recovery Act (RCRA)
subtitle C, RCRA regulations are not applicable. The Subtitle C
requirements of RCRA were determined to be relevant in that
certain samples did leach toxic materials at levels that failed
RCRA standards when the Toxicity Characteristic LeaChing
Procedures (TCLP) test was applied. However, EPA has completed
an extensive national study of the type of contaminated material
found at the site--solid waste from the extraction,
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benefication, and processing of ores and minerals, and determined
that it should not be regulated under RCRA Subtitle C (See e.g.
54 Fed. Reg. 36592, ~6621 (September 1, 1989); therefore, RCRA is
not an appropriate requirement for any remedial alternative.
Under the selected remedy, Alternative 5, residuals from the
reprocessing of the contaminated material are expected to contain
elevated concentrations of contaminants, but none are anticipated
to be at levels that fail TCLP. However, even if residuals fail
TCLP, the residuals remain solid waste from the extraction,
benefication, and processing of ores and minerals and,
consequently, as previously explained, RCRA Subtitle C, is not an
appropriate requirement for the residuals. The residuals are
also exempt fromNMED Solid Waste Management Regulations (See NM
SWMR-3 at Part I section 105 (FFF», so those regulations are not
applicable. Moreover, since the purpose of the mining waste
exemption from the NMED Solid Waste Management Regulations is to
exempt the type of waste that exists at the site, those
regulations are not an appropriate requirement for the
contaminated tailings and sediment. In order to be as protective
as possible during the transport of the contaminated tailings and
sediment, however, uniform hazardous waste manifests will be
utilized for all contaminated materials that are transported
off-site.
A list of ARARs for the site is provided in Appendix D.
Because the tailings and sediment are not a hazardous waste,
chemical-specific ARARs that are listed in RCRA, do not apply to
the alternatives at the Cleveland Mill site. However, the
alternatives are designed to eliminate the source of
contamination of the shallow perched aquifer and the surface
water in Little Walnut Creek and its tributary, so that both the
ground water and surface water meet federal and state
environmental standards. The alternatives are also designed to
ensure that air emissions above state and federal established
levels do not occur. Therefore, chemical-specific ARARs for
ground water, surface water and air do exist. These chemical-
specific ARARs include provisions of the Clean Water Act, 33
U.S.C. S1251 et sea.; the Safe Drinking Water. Act, 33 U.S.C.
S300 f et sea.; the New Mexico Water Quality Act, NM stat. Ann.
S74-6-1 et sea.; NM WQCC Regulations 82-1, sections 3-101 and
3-103; NM WQCC Regulations 91-1, sections 1-102, 2-205, and
3-101; the Clean Air Act, 42 U.S.C. S7401 et sea.; New Mexico
Ambient Air Quality Control Act," NM stat. Ann. S72-2-1 et sea.;
and OSHA requirements for worker safety, 29 CFR S1910.120.
For those alternatives that involve off-site disposal of the
contaminated site material, action-specific ARARs include the
CERCLA Off-Site Response Policy.
Location-specific ARARs such as those laws and regulations
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protecting endangered species that have been found in the region
surrounding the site including the Endangered Species Act,
16 U.S.C. ~1531 et sea., will be met by all alternatives.
Additionally other location-specific ARARs are applicable and
must be met due to the historic significance of the site. These
ARARs include the National Historic Preservation Act 16 U.S.C.
i470 et sea. and its implementing regulations, 36 CFR Part 800:
the Archaeological and Historic Preservation Act 16 U.S.C. .
~469a-1: and the New Mexico CUltural Properties Act. New Mexico
Solid Waste Management regulations protecting fault areas,
archaeologically sensitive areas and public water supply areas,
would have to be considered under any of .the alternatives which
require the contaminated tailings and sediment to be placed in an
on-site disposal area.
All ARARs can be met for all alternatives and a detailed
discussion of ARARs for the selected remedy is presented in the
Selected Remedy section of this ROD.
3.
Long-term Effectiveness and per.manence
Alternative 2 would provide long-term effectiveness only to the
extent that the geo-textile cover is not compromised and is
maintained. Since all such covers have a finite design life, the
cover would have to be replaced on a regular basis. This
alternative, therefore, is not considered permanent and the
magnitude of residual risk would remain unchanged.
.Alternative 3 involves treatment of the contaminated materials by
stabilization and solidification which is a proven technology for
. all of the contaminants of concern at the site except arsenic,
based on historical studies at other sites. Because of the
previously mentioned difficuities in stabilizing arsenic and the
inconclusiveness of the stabilization and solidification
treatability study at the Cleveland Mill Superfund site, both the
adequacy and reliability of these controls is believed to be
moderate. Assuming that the stabilization and solidification
would be effective for all contaminants, including arsenic, the
magnitude of residual risk would be reduced so that a.moderate
risk remained under Alternative 3. Although exposure to the
inorganic contaminants at the Cleveland Mill property would be
expected to be significantly reduced by the stabilization and
capping of the contaminated material under Alternative 3,
management of the stabilized and solidified mass on-site does not
fully eliminate the potential for exposure to arsenic, beryllium,
cadmium, lead, and zinc.
For both Alternatives 2 and 3, the containment system of
stabilization and solidification with a cap would be adequate to
provide long-term protection, though it would not be reliable and
over time would fail. The cap would have to be maintained and
would eventually need replacement at the end of its design life.
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Releases to the air could occur if the cap failed as could
releases to the ground water if cap failure allowed rainwater to
come in contact with the waste material. The risks posed by
this failure could range from a minimal level to the same level
of risk posed at the site were the material to remain in place at
the site.
Alternatives 4 and 5 both involve moving the waste off-site which
provides for a permanent solution for the Cleveland Mill site.
The residual risk at the site would be completely eliminated.
Some risk would be relocated to the off-site landfill in
Alternative 4. Some risk would also be relocated to the
receiving facility's disposal area in Alternative 5. The
adequacy of controls in both these alternatives would be high
because the contaminated tailings and sediment in Alternative 4
and the residual material in Alternative 5 would be disposed of
in disposal areas which are subject to state regulation.
Alternative 4 and 5 would be the most effective long-term and
permanent alternatives for the site.
The adequacy and reliability of the controls in Alternatives 4
and 5 would be the same as those of Alternatives 2 and 3, for the
waste material that is taken off-site; however, the risks would
be lower since, in Alternative 4, the waste would be handled in a
lined landfill and in Alternative 5, the waste would be treated
to remove some of the contaminants and precious metals. In
addition, the sites to which the waste material would be taken in
Alternatives 4 and 5 would be in commercial areas where contact
by residents, children, would be much less probable.
4.
Reduction of Toxicity, Mobility or Volume Through
Treatment
Because Alternative 2, does not contain a treatment element, it
does not provide a reduction in the waste's mobility, _toxicity or
volume (See 55 Fed. Reg 8666, 8721 (March 8, 1990».
Alternatives 3 and 4 are expected to reduce the mobility of the
contaminants in the contaminated tailings and sediment through
stabilization and solidification. Alternative 5 reduces the
toxicity and slightly reduces the volume of the contaminated
tailings and sediment through reprocessing. Alternative 5 will
may also reduce the mobility depending upon the reprocessing
technology selected during the Remedial Design.
Alternative 3 uses stabilization and solidification to treat all
the contaminated tailings and sediment. Although EPA believes
that mObility of each of the contaminants would be significantly
reduced, based on historical treatability studies, it is
uncertain whether arsenic can be permanently stabilized, low
concentrations may still leach. As mentioned previously, the
site treatability study on stabilization and solidification was
inconclusive in the determination of whether or not the
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stabilization was effective in reducing the mObility of the
contaminants in the tailings and sediment. The solidification
portion of the treatment is essentially irreversible because the
monolith produced through solidification should retain its
structural integrity based on both historical and site-specific
studies. However, in practice, it is not known how long
stabilization and solidification of contaminants will remain
effective. The volume of the contaminated tailings and soil
would increase by at least 30% and up to 100% with this treatment
due to the addition of stabilizing and solidifying agents. The
residue that would remain after treatment would be a monolithic
structure on-site~ however, the inherent hazards posed by the
waste would be reduced since it would be stabilized, solidified
and covered. Under Alternative 3, the direct exposure pathway
would be almost totally eliminated because as long as the cap
remained intact, humans could not contact the contaminants. The
potential for the contaminants to leach into the surface and
subsurface water and 'be ingested by humans would also be reduced,
providing the stabilization was effective. The possibility of
human exposure through the air pathway would be eliminated.
Like Alternative 3, Alternative 4 utilizes the chemical bonding
and structural integrity of the stabilization and solidification
process to reduce the mobility of the waste and the inherent
dangers associated with the waste. Under Alternative 4, disposal
is carried out off-site. This is an important distinction
insofar as the significance of low level leaching is considered
less of a risk in a regulated commercial area than it is in a
residential area.
Alternative 5 also uses reprocessing to alter the principal
threat wastes at the site to reduce the toxicity and volume of
the waste. The percentage change in concentration of the
contamin~nts that was demonstrated in the site treatability study
ranged from a low of 1% to 9% for arsenic to a maximum of 38% to
61% for copper. These percentages were calculated-by comparing
assays of the original tailings and sediments to assays of the
residual from the reprocessing. The reason that these
percentages are given as a range is because the reductions in
contaminant concentration also varied depending upon the type of
site material (tailings or dust piles, for example) that was
evaluated. The reprocessing will reduce the toxicity of the
waste because these metals will be permanently removed and sold
for beneficial reuse. The residuals that will remain, after
reprocessing, will still contain a percentage of the original
contaminants~ however, the degree to which the treatment will
reduce the inherent hazards posed by the waste may be increased
because the acid-producing potential which was high in the
initial tailings and sediment may be lowered depending upon the
reprocessing method that is utilized. Sulfide minerals such as
pyrite may be concentrated and removed from the tailings and
sediment at the reprocessing facility which would result in a
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reduction in acid-producing potential in the residual material,
reducing the chance that the contaminants present in the
residuals will leach from these residuals.
Depending upon the reprocessing technology selected,
Alternative 5 may reduce the mobility of the contaminants in the
tailings and sediment by reducing the potential to generate
acidic leachate. In EPA's view: however, it is more important to
employ a reprocessing technology on the basis of the percentage
of contaminants removed. Therefore, a reprocessing technology
which does not reduce the mobility, but which will remove a
higher percentage of contaminants, may be selected, thereby
making mobility less of a concern.
Unlike the other alternatives, Alternative 5 is expected to
slightly reduce the volume of contaminated materials by
reprocessing and reclaiming the usable metals. The
reprocessing, under Alternative 5, will be wholly irreversible.
EPA has established, as a guideline, that treatment as part of
CERCLA remedies should generally achieve reductions of 90 to 99
percent in concentrations or mobility of the contaminants of
concern, although there will be situations where reductions
outside the 90 to 99 percent range that achieve health-based or
other site-specific remediation goals are appropriate. (See 55
Fed. Reg 8666, 8721 (March 8, 1990». The Cleveland Mill
Superfund site is a situation in which reductions outside the 90
to 99 percent range are appropriate because the contaminants of
concern at the site are inorganic constituents which cannot be
destroyed, so a 90 percent reduction in concentration of
contaminants through destruction cannot be achieved. According
to the site Froth Flotation Treatability study and historical
data on ore reprocessing using other treatment technologies, a
90 percent removal rate for the contaminants present at the site
cannot be achieved. In addition, due to the uncertainty
associated with the stabilization of arsenic, a 90 percent or
greater reduction in mObility through stabilization cannot be
achieved for the Cleveland Mill Superfund site wastes. Rather
than specifying a percentage reduction that the reprocessing must
achieve, EPA and NMED have instead chosen to rely upon excavation
of the tailings and sediment to the Remedial Action Goals.
Excavation to the Remedial Action Goals for the carcinogenic
contaminants assures that carcinogenic risk at the Cleveland Mill
Superfund site is brought to, at the maximum, the risk that is
currently posed by background values of these contaminants.
Excavation to the health-based levels for the non-carcinogenic
contaminants assures that, in the excavated areas, non-
carcinogenic risk at the Cleveland Mill Superfund site falls
below a Hazard Index of 1 individually for beryllium and cadmium
and below a Hazard Index of the background value of 1.13 for
arsenic.
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All the metals identified in the Cleveland Mill tailings and
sediment have a tendency to bioaccumulate. None of the
alternatives destroy or chemically reduce the toxicity of the
main contaminants of concern. Alternative 5, however, will
remove a percentage of these contaminants and treat the
contaminated material so that it is rendered less likely to
leach, and is rendered less toxic, and, consequently, is rendered
less hazardous. .
5.
Short-Term Bffectivenesss
There would be potential short-term risks to site workers during
implementation of all the alternatives, since all alternatives
will require some excavation of the contaminated material. Some
increase in air emissions that could adversely affect human
health and the environment might occur during excavation
activities, which are required under all of the alternatives, and
might also occur during the stabilization/solidification process
in Alternatives 3 and 4. However, engineering controls,
including dust control and air monitoring, during excavation or
treatment will reduce the potential for any adverse impacts due
to air emissions during implementation of any of the remedial
alternatives. A contingency plan would be developed, under any
of the alternatives which require excavation, to address any
potential air emissions during remedial activities.
There is also a potential risk for accidental release of
contaminants from transportation of excavated material to an
off-site facility under Alternatives 4 and 5. Each of the
alternatives evaluated would involve an increase in trucking and
its associated risks, either in taking the contaminated material
away from the site or in bringing material and equipment to the
site to implement on-site disposal. Therefore, each of the
alternatives evaluated, except the No Action alternative, would
cause additional transportation risks including those risks
associated with trucking, in general, such as traffic accidents,
additional noise, and risk to automobiles or pedestrians
traveling the same roads as trucks. These risks do not
necessarily involve the release of. contaminants.
Under Alternative 2, trucks bringing liner material and
earthmoving equipment would travel to the site. This would
increase the truck'traffic to approximately 8 trucks per day over
the period of time that the excavation and capping would be
implemented, approximately 6 months. Under Alternative 3, on
average, a total of approximately 24 trucks per day (12 going to
the Site loaded with materials necessary for stabilization and
solidification and 12 leaving the site empty) would travel to and
from the site over an 8-month period. Under Alternative 5, on
average, approximately 48 trucks per day (24 going to the Site
empty and 24 leaving the site full of contaminated tailings and
sediment enroute to the off-site reprocessing facility) would
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travel to and from the site over an 8 month period. Because
Alternative 4 would involve the same stabilization and
solidification steps as Alternative 3 and the same off-site
transport as Alternative 5, Alternative 4 would require the most
truck trips, 74 per day (37 going to the site, some carrying
stabilization raw materials and 37 leaving the site full of
stabilized contaminated tailings and sediment). The number of
truck trips, when compared to the number of trucks already using
the roads for mining activities in the area is low, so the
corresponding increase in overall risk from implementation of any
of the alternatives is low. There is also a potential for
accidental release of contaminants during transportation of
waste material to an off-site facility under Alternatives 4
and 5. The short term risk due to truck traffic can be greatly
reduced through the use of strict transportation controls. (See
Appendix C for trucking calculations.)
Alternative 2 would take approximately 6 months to implement.
The other alternatives each would take approximately 12 months to
imp~ement. This is not a significantly different amount of time.
6.
Implementability
Alternative 2, On-Site Excavation and Disposal, could be
implemented using readily available equipment and materials.
Implementation of Alternative 2, however, would be hindered by
the steep slopes on the site, the lack of ready access to the
areas of the streambed that would be excavated, and the limited
amount of space available on-site for disposal of the excavated
material. Nonetheless, generally speaking, the technical
feasibility of Alternative 2 is high.
Implementation of Alternative 3 would face the same problems as
those of Alternative 2. Although technically feasible, the
on-site disposal of' .the material in Alternative 3 would
necessitate strict engineering controls to ensure that the
stabilized and solidified material did not come into contact with
site water, and to ensure that the slope of the disposal area
would provide permanent structural soundness. Historical
treatability studies conducted on materials similar to those
found at the Cleveland Mill Superfund site indicate that
stabilization and solidification could effectively immobilize and
eliminate the hazardous characteristics of the contaminants of
concern found at the site for all the contaminants except
arsenic. However, the solidification and stabilization
treatability study conducted on the actual Cleveland Mill
contaminated tailings and sediment was inconclusive in its
determination of the effectiveness of the stabilization of the
contaminants and additional treatability studies would have to be
conducted to verify the effectiveness and implementability of
this process.
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As previously noted, the ability to permanently stabilize high
concentrations of arsenic is uncertain, but the presence of
arsenic in a waste does not adversely affect the solidification
process. The Cleveland Mill stabilization and solidification
treatability study showed that effective solidification of the
contaminated tailings and sediment was possible and
implementable. The technical feasibility of Alternative 3 is
slightly lower than that of Alternative 2, but generally
speaking, it is still considered high.
It is expected that Alternatives 4 and 5, Off-site Disposal and
Off-site Treatment and Reclamation could be more easily
implemented technically than Alternatives 2 and 3. Alternative 4
and 5 are more easily implemented partly because an on-site
disposal area would not have to be constructed under Alternative
4 or 5. Like the previous alternatives, the excavation of
contaminated material for these two alternatives would be
hindered by the steep slopes at the site, and by the difficult
access to the streambed.
All of the alternatives are implementable with respect to the
availability of services and materials, specialists and
equipment, and with respect to the availability of technology.
Services to construct disposal areas and to stabilize and
solidify materials are easily obtained locally, and there are
several disposal and reprocessing facilities, within a 150-mile
radius of the site, with the capacity to handle the contaminated
tailings and sediment from the site.
EPA was concerned that there might not be an off-site facility
which could reprocess and dispose of the contaminated tailings
and sediment, as required under Alternative 5. EPA expressed its
concern in the Proposed Plan for the site. since the release of
the Proposed Plan, the business community has expressed
interest, to both EPA and HMED, in implementing the remedy
proposed under Alternative 5, which is now the selected remedy.
The two agencies believe that several facilities with the ability
and capacity to reprocess this waste will bid on the selected
remedy. without the formal solicitation of contractual bids,
however, business interest in Alternative 5's off-site
reprocessing and disposal cannot be fully substantiated. The
uncertainty in determining the availability of off-site
reprocessing facilities is one factor that slightly lessens the
implementability of Alternative 5.
All of the alternatives have a high administrative feasibility
because coordination with other agencies will be. easily achieved,
and the time required to obtain necessary approvals and permits
will be short. One reason that administrative feasibility is
high for all alternatives is that EPA and NMED have worked
together closely on the site and each agency has coordinated with
associated agencies throughout the RIjFS process.
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The effectiveness and reliability of all the alternatives can be
easily evaluated by monitoring the ground water.
7. COS~
The approach that the NCP takes requires that alternatives must
be determined to be adequately protective and ARAR-compliant
before cost effectiveness is considered in remedy selection (See
55 Fed. Reg 8666, 8727 (March 8, 1990». The selected remedy,
Alternative 5, provides greater long term effectiveness and
permanence than any other alternative other than Alternative 4
which is comparable in its long term effectiveness and
permanence, but which is more expensive. Alternative 5 removes
the contaminated tailings and sediment from the site and
eliminates the residual risk at the Site. In addition, depending
upon the reprocessing technology selected, Alternative 5 may
reduce the mobility of the contaminants in the contaminated
tailings and sediment. Alternative 5 performs better than any of
the other alternatives when it comes to reduction of toxicity
since it removes contaminants. Alternative 5 also reduces volume
more than any other alternative by removing recoverable metals.
The short-term effectiveness of Alternative 5 is approximately
the same as the other alternatives. Alternative 5, the selected
remedy for Cleveland Mill Superfund site contaminated tailings
and sediment, is adequately protective and cost-effective. The
cost of the preferred alternative, Alternatives 5, is" $6,214,036
(present worth). No Action and On-site Disposal without
Treatment (Alternatives 1 and 2) have lower present worth costs
than Alternative 5, $246,878 and $3,324,701, respectively, but
they not protective of human health and the environment and they
are not as effective. Alternative 3 also has a lower present
worth cost than Alternative 5, $6,619,187, but it is not as
protective of human health and the environment as Alternative 5.
Alternative 4, Off-site disposal is less protective of human
health and the environment than Alternative 5, because, unlike
Alternative 5, it does not decrease the toxicity of the
contaminants in the tailings and sediment or reduce the volume of
the tailings and sediment. Moreover, Alternative 4 does not
recover valuable metals that can be beneficially reused. At
$11,479,046, Alternative 4 would also be more" costly to implement
than Alternative 5.
8.
state Acceptance
Under the Superfund law, EPA is required to ensure that states
have a meaningful and continuing role in remedy selection and
execution. EPA and NMED worked closely in the development of the
alternatives for remediation of the Cleveland Mill site and in
the identification development of ARARs. NMED was the lead
agency for the RIfFS process through preparation of the final
RI/FS report. EPA selected the remedy presented in this ROD,
Alternative 5, Excavation, Off-site Reprocessing, Reclamation,
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and Disposal of Residuals, to address the contaminated tailings
and sediment at the site and to prevent future ground water and
surface water contamination. The state's concurrence with the
selected remedy is set forth in a letter from Judith Espinosa,
Secretary of NMED dated June 29, 1993, included in the
Administrative Record for this site.
9.
community Acceptance
EPA recognizes that the community in which a Superfund site is
located is the principal beneficiary of all remedial actions
undertaken. EPA also recognizes that it is its responsibility to
inform interested citizens of the nature of Superfund
environmental problems and solutions, and to learn from the
community what its desires are regarding these sites.
EPA and NMED solicited input from the public on the remedial
alternatives proposed to address the contamination at the site.
The comments from the residents are mixed and indicate that some
residents would like to see the tailings and sediment permanently
removed from the site and some would like to see the tailings and
sediment remain at the site. Of the residents who indicated that
they would like the contaminated tailings and sediment to remain
at the site, some did not feel that any action at all was
necessary and some supported variations on Alternatives 2 and 3.
The primary reason that many residents are opposed to the off-
site alternatives is that they feel that these alternatives would
greatly increase truck traffic on local unpaved road which could
pose an uncontrollable risk from the trucks themselves and not
necessarily from the contaminated tailings and sediment. They
feel that the traffic could destroy roads that are already in
poor condition and have an adverse effect on the amount of
tourism and business in the area.
Several members of the residential and industrial community and
representatives of several federal and state agencIes indicated
support for the reprocessing of the mining wastes and the
beneficial reuse of the recovered metals. However, the limited
rate of metal recovery and the perception that the contamination
might threaten an off-site area, once it was removed were
considered, by some commenters, to be negative aspects of the
reprocessing option.
EPA believes and NMED agrees that community concerns can be
addressed through strict transportation controls and through
repair and improvement of access roads where needed. In
addition, the receiving facility will be regulated through state
authority. The tr~~sportation controls and other responses to
specific residential and business community concerns are
discussed in the Responsiveness summary in Appendix E.
Calculations showing the increase in the amount of truck traffic
under each alternative are included in Appendix C.
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x. THE SELECTED REMEDY
Based upon consider~tion of the requirements of CERCLA, the
detailed analysis of the alternatives using the nine criteria,
and public comments, EPA has determined that Alternative 5,
Excavation, Off-Site Reprocessing, Reclamation and Beneficial
Reuse and Disposal of Residual, is the most appropriate remedy
for the Cleveland Mill Superfund site in Grant County, New
Mexico. NMED concurs with the selection of this remedy.
The Remedial objectives for the site are the following:
1.
Prevent dermal contact, ingestion of, and inhalation of
contaminated tailings and sediment.
Prevent direct contact with and ingestion of
contaminated ground water and surface water.
2.
3.
Prevent the downstream aquifers from becoming
contaminated with hazardous substances from the
tailings and sediments, at concentrations which
MCLs and-NM WQCC standards.
exceed
4.
Return the shallow perched aquifer at the toe of the
tailings to a condition where the concentration of
contaminants is below MCLs and NM WQCC standards.
These Remedial Objectives shall be met under this ROD.
The ROD requires removal of the contaminated tailings and
sediment that contain concentrations of hazardous substances at
levels which exceed Remedial Action Goals. Removal of the
contaminated tailings and sediment under the selected remedy is
intended to remove the source of the on-site soil and ground
water contamination, and the source of the surface water
contamination. An additional benefit of the selected remedy is
that the toxicity of the contaminated tailings and sediment will
be reduced through reprocessing and beneficial reuse of the
valuable metals that are recovered as a result of the
reprocessing. The ROD requires that the contaminated tailings
and sediment, which are removed from the Site, shall be taken to
a reprocessing facility. The reprocessing facility shall remove
all or some of the recoverable metals and dispose of the
reprocessed material at the facility's disposal area. The length
of time the reprocessing facility shall be given to reprocess the
contaminated tailings and sediment will be determined during the
Remedial Design phase of the project. The facility's disposal
area shall be in physical compliance with all applicable state,
and federal environmental requirements. It is the intent of this
ROD that recoverable metals shall become the property of the
reprocess or , thereby lowering the cost of the reprocessing. If,
for any reason, the reprocessor cannot or will not take
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possession of the recovered metals, the cost of this selected
remedy may increase.
Approximately 70,900 cubic yards of contaminated tailings and
sediment shall be removed from the site, including but not
limited to, the roadbed, the mill area, the mine spoils area, the
streambed of the mill valley tributary to Little Walnut Creek,
and the streambed of Little Walnut Creek itself, and taken to an
off-site reprocessing facility. A percentage of some of the
contaminants of concern, along with several other valuable metals
such as copper, shall be recovered from the contaminated tailings
and sediment. One of several available processes such as froth
flotation, acid heap leaching, or other effective reprocessing
technologies shall be used to treat the contaminated tailings and
sediment. The process used to reprocess the tailings and
sediment, the facility selected to reprocess the tailings and
sediment, and the disposal method used for the residual material,
which is material that remains after reprocessing, shall all be
subject to disapproval by EPA, in consultation with NMED. One
consideration in the selection of the reprocessing facility
shall be the outcome of additional treatability studies which
shall be undertaken during the design phase of the project to
determine recovery rates for the contaminants of concern and the
other valuable metals.
The residuals which remain after the contaminated tailings and
sediment are processed shall be disposed of at the off-site
reprocessing facility which is subject to state regulation.
During the design and implementation phases of the remedial
action, air monitoring shall be conducted at the site to ensure
that airborne particulates or other air emissions from the
removal of site materials or transportation of these materials do
not pose a risk to the workers or inhabitants of the area.
~
A transportation plan shall be designed and implemented to assure
that risks incurred from the increase in truck traffic are
mitigated as mu~h as possible. Transportation controls shall be
implemented as a part of this plan and they shall include, but
shall not be limited to, engineering controls such as dust
suppression and control of transportation routes. Road repairs
or improvements shall be performed, if necessary as determined by
EPA in consultation with NMED, after state and local governmental
agencies have had an opportunity to provide information to EPA
regarding road repairs. The road repairs shall be performed at
the completion of the remedial action in order to return the road
to the condition it was in at the time this ROD was signed,
unless the road, in EPA's opinion, is badly damaged during the
remedial action, in which case repairs shall be made upon EPA's
determination, in consultation with NMED, that the road is badly
damaged. EPA, in consultation with NMED, will provide to the
Town of Silver City and the Grant County Commission an
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opportunity to comment on the development of the transportation
plan for the remedial action.
Ground water at the site shall be monitored on a quarterly basis,
beginning immediately and for a minimum of the first five years
after removal of the contaminated tailings and sediment. If
monitoring results indicate, in EPA'S opinion, that additional
monitoring for a longer period of time is required, EPA may
require such monitoring, after NMED has had an opportunity to
review and comment. The ground water monitoring program shall
include, but shall not be limited to, monitoring of the existing
wells, the installation of and monitoring of additional wells,
and sampling of the springs in the mill area. EPA may require
implementation of the contingency measures for the remediation of
ground water as described in the Description of Alternatives
section, section VIII of this ROD, if ground water contamination
concentrations at the site remain above Remedial Action Goals
five years after the tailings and sediment with concentrations of
contaminants above Remedial Action Goals have been removed from
the site.
Surface water at the site shall-be monitored on a quarterly
basis, beginning immediately and continuing for a minimum of the
first five years after removal of the contaminated tailings and
sediment. If monitoring results indicate, in EPA's opinion, that
additional monitoring for a longer period of time is required,
EPA may require such monitoring. The surface water monitoring
program shall include, but shall not be limited to, sampling
locations in the mill valley tributary, Little Walnut Creek and
picnic Creek.
The site shall be replanted with native vegetation in disturbed
areas. The estimated costs for the entire remedy including
stabilization and solidification of residuals at the off-site
facility are: capital costs: $5,836,586, Annual operation and
Maintenance: $51,250, and Present Worth: $6,214,036. -
A.
Remedial Action Goals for the contaminated Tailings and
Sediment
The Remedial Objectives for the site are the following:
Prevent dermal contact, ingestion of, and inhalation of
contaminated tailings and sediment.
Prevent direct contact with and ingestion of
contaminated ground water and surface water.
Prevent the downstream aquifers from becoming
contaminated with hazardous substances from the
tailings and sediments, at concentrations which
MCLs and NM WQCC standards.
exceed
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Return the shallow perched aquifer at the toe of the
tailings to a condition where the concentration of
contaminants is below MCLs and NM WQCC standards.
The Remedial Action Goals at the site are designed so that the
Remedial objectives will be met.
The results of the baseline risk assessment indicate that risk to
human health under a projected future scenario in which there are
residences on site indicate that contamination at the site could
pose an excess lifetime cancer risk as high as 2.1xlO-3 for
adults and 1.5xlO-3 for children from direct contact with the
contaminated tailings and sediment. This cancer risk is mainly
due to the arsenic concentrations in the tailings and the
sediment, and to the predisposition of the tailings and sediment
to leach arsenic and other hazardous metals because of the acid-
producing conditions at the site. The acid-producing conditions
are caused by numerous water sources including springs and
rainfall that react with the high sulfide tailings to produce
sulfuric acid. Non-carcinogenic risk to human health due to
contamination from the Site is mainly due to arsenic, cadmium,
lead and zinc.
The Remedial Action Goals for arsenic,' beryllium, cadmium, lead
and zinc are stated in this section of the ROD. Remedial Action
Goals are the maximum concentration of contaminants that may be
left on the Site. Under this ROD, all tailings and sediment with
concentrations of any contaminants which exceed Remedial Action
'Goals shall be excavated, manifested and transported away from
the site, and taken to a facility for reprocessing. Manifests
shall meet RCRA Subtitle C requirements. Remedial Action Goals
are consistent with either a risk to human health that is within
EPA's acceptable risk range or background, whichever is higher.
For additional explanation of Remedial Action Goals and the Risk
Assessment, See sections VI and VII.
Tailings and sediment that contain concentrations of contaminants
above any of the following Remedial Action Goals shall be
excavated and removed from the site:
carcinoaenic
Arsenic-------------------------------30
parts per million
Beryllium------------------------------4 part per million
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Non-carcinoaenic
Individual
Arsenic-------------------------------30 parts per million
Cadmium------------------------------140 parts per million
Zinc------------~-----------------82,000 parts per million
CUmulative (Site Wide)
Hazard Index less then 2.3 once individual goals have been met
Lead
Lead----------------------------------500
parts per million
Ground Wa~er con~ingency Keasures
If the selected remedy, Alternative 5, cannot meet the specified
Remedial Action Goals at any or all of the monitoring points,
including those in the perched aquifer, after 5 years, EPA may
require the contingency measures and objectives described in this
section of the ROD to be implemented. In the event that EPA
requires active ground water contingency measures to be
implemented, the ground water shall be remediated to MCLs or NM
WQCC standards, whichever is more stringent, for each
contaminant. For the contaminants of concern, these Remedial
Action Goals (MCLs except as noted) under the ground water
contingency measures are arsenic, .05 milligrams per liter
(mg/l); beryllium, .004 mg/l; cadmium, .05 mg/l; lead (NM WQCC
standards), .05 mg/l; copper, 1.0 mg/l; mercury, 0.002 mg/l;
silver, 0.05 mg/l (NM WQCC standards); and zinc, 5 mg/l. For
newly discovered contaminants, without promulgated MCLs and NM
WQCC standards, maximum concentrations left untreated will be
those which produce a human health risk of 10-6 or less, unless
background is higher than the concentration producing the 10-6
risk, in' which case, the maximum concentration left untreated
will be the background concentration. The risk will be
calculated using the assumptions in the site Risk Assessment for
a future resident child. For newly discovered non-carcinogenic
compounds without promulgated MCLs and NMWQCC standards, the
maximum concentrations left untreated will be those that
correspond to a Hazard Index less than or equal to 1.
'C
The contingency measures are considered protective of human
health and the environment, and are technically practical under
the corresponding circumstances. Under the selected remedy,
Alternative 5, EPA, in consultation with NMED, may require one or
more of the following contingency measures to be put into effect
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if EPA, in consultation with NMED, later determines that there is
contamination in ground water above Remedial Action Goals. EPA
may make such a determination if MCLs or NM WQCC standards are
exceeded in any ground water monitoring well, including, but not
limited to, those wells completed in the perched aquifer. EPA
may also make such a determination if EPA has any other reason to
believe that ground water contamination above Remedial Action
Goals exists 5 years from completion of removal of the
contaminated tailings and sediment. The ground water contingency
measures will be one or more of the following as determined by
EPA in consultation with NMED:
Installation of additional monitoring wells to confirm
and better define the changing conditions in ground
water contaminant concentrations.
Development of a Remedial Action Plan which provides
for the extraction, treatment, and reinjection or
discharge or disposal of contaminated ground water in
order to achieve ARARs.
Implementation of a Remedial Action Plan subject to
EPA disapproval of the plan, after NMED has had an
opportunity to review and comment upon the plan.
Waiving the ground water ARAR for the aquifer based on
the technical impracticability of achieving
contaminant reduction.
Establishment of an Alternative Concentration Limit
II (ACL") for the detected contaminants, provided
compliance with CERCLA 121 (d) (2) (B) (ii) can be
demonstrated.
The ground water monitoring which is required under the selected
remedy, provides for quarterly monitoring of ground water wells
at the site. Wells established as part of the ground water
monitoring program during remedy design shall be used to
determine 1) whether' natural attenuation of the ground water
contamination is taking place, and 2) whether the extent of
ground water contamination has spread or diminished.
If contingency measures are implemented, EPA, in consultation
with NMED, may require modification of the existing network of
wells, changes in the type of analyses performed, or changes in
frequency of sampling, in order to identify changes in ground
water quality. The selected remedy is expected to prevent
continued ground water contamination. However, as explained in
section VII, Remedial Action Goals, if monitoring wells detect
contaminant concentrations which exceed MCLs or NM WQCC
standards, site background or a concentration producing a risk
greater than 10.6 or, if EPA determines, for any other reason,
-------
that ground water has become contaminated and requires
remediation, EPA may require that the contingency measures listed
be implemented.
Upon completion of the tailings and sediment remedy
implementation, overall site risk is expected to be less than or
equal to the risk posed by site background.
B.
SENSITIVITY ANALYSIS FOR SELECTED REHEDY
In an effort to more accurately assess the viability of this
remedial action in. light of potential waste volume increases
during actual remediation, a sensitivity analysis was conducted.
The intent of this analysis was to determine if unexpected volume
increases would adversely impact the selection of this particular
alternative because waste volume was determined to be the most
critical factor affecting cost.
The evaluation revealed that if the volume of contaminated
tailings and sediment to be excavated and transported off-site
were to double, the cost for the selected remedy would
approximately double. Likewise, the cost estimates for each of
the other alternatives, except the No Action alternative, would
approximately double if the volume of tailings and sediment
doubled. An unanticipated increase in volume of tailings and
sediments that had to be remediated, therefore, would not change
the remedy selection decision.
Because the majority of the remedial action involves excavation
of material that was deposited surficially and not subsequently
buried, the extent of the area needing treatment is fairly well-
defined and large volume increases are not expected to impact
this aspect of the remediation.
XI.
THE STATUTORY DETERMINATIONS
EPA's primary responsibility at Superfund sites is to select
remedial actions that are protective of human health and the
environment. section 121 of CERCLA also requires that the
selected remedial action for a site comply with applicable or
relevant and appropriate environmental standards established
under Federal and state environmental laws, unless a waiver is
granted. The selected remedy must be cost-effective and utilize
treatment or resource recovery technologies to the maximum extent
practicable. The statute also contains a preference for remedies
that include treatment as a principal element. The following
sections discuss how the selected remedies for tailings and soils
at the Cleveland Mifl site meet the statutory requirements.
-------
A.
protection of Human Health and the Environment
In order to protect human health and the environment, the
tailings and soils that exceed Remedial Action Goals will be
removed from the site. They will be transported to a
reprocessing facility where they will undergo a treatment through
reprocessing and off-site disposal of residual. The metals
reclaimed from the reprocessing of the tailings and soils will be
beneficially reused. The residuals will be contained at the
disposal site. These Remedial Action Goals will assure that site
risks due to carcinogens are less than or equal to those risks
posed by site background. The Remedial Action Goals will also
assure that the non-carcinogenic hazard index will be reduced to
less than one (1) for each of the contaminants of concern.
The selected remedy protects human health and the environment by
reducing concentrations of contaminants through treatment,
reclamation and containment of residuals. Of all the
alternatives evaluated for the tailings and soils, the selected
alternative provides the best overall protection to human health
and the environment. No unacceptable short-term risks will be
caused by implementing this remedy. ROD section IX, Summary of
comparative Analysis of Alternatives, and ROD section X, The
Selected Remedy, provide an analysis of the ways in which the
selected remedy provides the best overall protection of human
health and the environment, and explains that the selected remedy
causes no unacceptable short-term risk.
B.
compliance with ARARs
The selected remedy which addresses the tailings and sediment by
off-site reprocessing and disposal of residuals will attain all
applicable or relevant and appropriate requirements (ARARs).
Appendix D lists ARARs developed for the Cleveland Mill Superfund
site. The ARARs are as follows:
1. Chemical-specific ARARs for Tailings and Sediment
a. National Emission standards for Hazardous Air
pollutants (40 CFR Part 61) (NESDAPS).
Relevant and appropriate during removal of tailings and soils
and transportation.
b. New Mexico Ambient Air standards, Air Quality
control Regulations, section 201A. (NK stat. Ann. S
72-2-1 et sea.)
Relevant and appropriate during removal of tailings and soils
and transportation.
-------
2. Action-specific ARABs for Tailings and Sediment
RCRA 40 CFR 262, Manifesting Requirements for
Transport of Hazardous Waste
Relevant and appropriate because manifesting method to be used
to keep track of Superfund wastes which will be transported.
The material involved is not a RCRA hazardous waste, but the
manifesting method is helpful and protective.
a.
b.
New Mexico Kininq Act of 1993
Remediation on-site falls under the definition of "mining" in
the "New Mexico Mining Act (effective July 1, 1993)", and so
is subject to the Act. However, since regulations have not,
yet, been promulgated under the Act, remediation need only
comply with the Act to the extent that it clearly defines
procedures to be used. Once regulations are promulgated,
application of the Act and its regulations to the remediation
of the site may be re-evaluated by EPA. Under CERCLA, ARARs
do not apply to off-site activity.
3. Location-specific ARARs for Tailinqs and Sediment
a.
Endangered species Act, 50 CIR 17, 402
Although no endangered species have been observed at the site,
there are two endangered species in the Gila wilderness which
is located about 10 miles northwest of the site. Federal
activities must not jeopardize the continued existence of
endangered or threatened species or adversely modify their
critical habitat.
b.
Fisb'and wildlife Coordination Act,
40CFR 6.302 (q)
Consultation between federal agencies is required when a water
body is modified and it could affect wildlife which may be the
case during excavation of tailings from the stream.
c.
New Mexico Wildlife conservation Act
Consultation with state agencies is required to avoid or
mitigate adverse impacts to endangered species listed by the
New Mexico Departments of Natural Resources and Game and Fish.
d.
National Historic Preservation Act,
40 CFR 6301 (b)
coordination with state agencies is required in order to
ensure that properties, the impact on them, and the effects on
them are identified, and that the alternatives to avoid or
-------
mitigate an adverse effect on property eligible for the
National Register of Historic Places are adequately considered
in the planning process.
Archaeological and Historical preservation Act,
16 O.S.C. 469, et. seq.
Any federally-funded or licensed construction project is
covered by this act that provides a mechanism for funding the
protection of historical and archaeological data.
e.
f.
Hew Kexico CUltural properties Act.-
Relevant and Appropriate because state agencies shall conduct all
plans necessary to preserve, protect and enhance significant
historical cultural properties under this act.
4.
ARARs for Ground Water and surface Water
EPA and NMED will evaluate, at the least, the following
regulations before contingency measure selection, should the
implementation of contingency measures become necessary:
a.
Chemical-specific ARARs for Ground Water
The regulations that will be evaluated will include National
Primary Drinking Water Regulations (40 CFR Part 141); New
Mexico Water Quality Act, NM stat. Ann. S 74-6-1 et sea.; NM
WQCC Regulations 82-1, sections 3-101, and 103; and NM WQCC
Regulations 91-1, section 1-102, 2-105, and 3-101.
b.
Action-specific ARARs for Ground Water
The regulations that will be evaluated will include Standards
for Owners and Operators of Hazardous Waste Treatment, storage
and Disposal Facilities should it become necessary to
construct a pumping and treating operation on-site for any
treatment of any contaminated ground water resulting in
residuals (for instance filter cake) that contained a
hazardous waste.
c.
cost-Effectiveness
EPA and NMED believ~ that the selected remedy is cost-effective
in mitigating the threat of direct contact with site wastes and
in reducing the potential for ground water contamination from the
Site wastes. section 300.430 (f) (ii) (D) of the NCP requires
EPA to determine cost-effectiveness by evaluating the following
three of the five balancing criteria to determine overall
effectiveness: long-term effectiveness and permanence, reduction
of toxicity, mobility or volume through treatment, and short-term
effectiveness. Overall effectiveness is then compared to cost to
-------
ensure that the remedy is cost effective.
the selected remedy meets these criteria.
The estimated cost of the selected remedy (present worth) for the
tailings and soils is $6,214,036. Note that this cost includes a
fee paid to the reprocessing facility to account for the fact
that the reprocessing of the old, oxidized tailings and soils
from this 'facility will be an expensive process that will not be
fully offset by the sale of the usable metals.
EPA and NMED believe
The selected remedy, Alternative 5, costs less than Alternative
3, On-site stabilization/Solidification, and Alternative 5 is
much more effective. Alternative 5 also uses resource recovery.
Alternative 5 is significantly more protective than Alternative 3
because the waste is removed from the mountain drainage
minimizing the potential for acid leachate generation at the
site. In addition, Alternative 5, in keeping with SARA
preferences, reduces the volume and reduces the toxicity of the
waste because it separates some of the metals from the tailings
and soil so that they can be beneficially reused. Remedies wh~ch
recover resources are preferred by SARA. In that Alternative 5
provides greater effectiveness for a slightly lower cost than
Alternative 3, with a greater overall effectiveness than
Alternative 3. The cost is proportional to the overall
,effectiveness. The reprocessing will be wholly irreversible.
The selected remedy is the most protective of human health and
the environment because it eliminates risk at the site.
Alternative 2, which is less expensive than Alternative 5 was not
included in the final cost comparison because it does not provide
overall protection of human health and the environment (see
section IX).
All of the alternatives meet ARARs and all of the alternatives
had similar, controllable short term effects, so these criteria
were not a part of the overall effectiveness and cost-
effectiveness evaluation.
D.
utilization of Permanent Solutions and Treatment or Resource
Recovery Technologies to the Maximum Extent practicable
EPA and NMED believe the selected remedies represent the maximum
extent to which permanent solutions and treatment/resource
recovery technologies can be utilized in a cost-effective manner
for the Cleveland Mill Superfund site. Alternative 5 is the only
alternative that involves a resource recovery technique to
permanently separate metals from the tailings and soils so that
they may be sold and beneficially reused. Remedies which involve
resource recovery are preferred under SARA.
Of those alternatives that are protective of human health and the
environment and comply with ARARs, EPA and NMED have determined
-------
that the selected remedy provides the best balance of trade-offs
in terms of long-term effectiveness and permanence, reduction in
toxicity, mobility, or volume achieved through treatment, short-
term effectiveness, implementability, and cost. The selected
remedy takes into consideration state and community concerns.
The selected remedy is the most effective in the long-term. In
comparison to the other alternatives, Alternative 5 clearly
produces the greatest reduction in toxicity, mobility and volume;
therefore, Alternative 5 meets the statutory preferences set
forth in SARA better than any other alternative. The selected
remedy has nearly identical high short-term effectiveness and
implementability compared with the other alternatives and is a
reasonable value for the money.
The selected remedy complies with the statutory requirement to
utilize permanent solutions (separation of metals) and treatment
technologies (reprocessing) to the maximum extent practicable.
E.
preference for Treatment as a principal Element:
The statutory preference for remedies that employ treatment as a
principal element will be satisfied through implementation of the
reprocessing of the contaminated tailings and sediment and the
reclamation of usable metals as explained in the Description of
Alternatives Section, Section VIII of this ROD, and in the
Selected Remedy Section, section X of this ROD. Through
reprocessing, a percentage of the valuable metals will be
recovered and the contaminated tailings and sediment will be
rendered less toxic. The selected remedy meets the statutory
preference for treatment as a principal element.
xxx. DOCUMENTATXOH OF SIGNXFICANT CHANGES:
The Proposed Plan for the Cleveland Mill site was released for
public comment on April 8, 1993. The Proposed PI~n identified
Alternative 5, Off-site Reprocessing, Reclamation and Disposal of
Residuals, as the preferred alternative to address the tailings
and soils and the potential threat to surface water and ground
water. EPA and NMED reviewed all written and verbal comments
submitted during the public comment period. Upon review of these
comments, it was determined that no significant changes to the
remedy, as originally identified in the Proposed Plan, were
necessary. Since the publication of the Proposed Plan, the name
of the remedy has been changed to Reprocessing and Reclamation to
more accurately reflect the processing the waste will undergo.
One minor difference between the ROD and the proposed Plan are
the revision of costs for Alternatives 2 through 5, based on
public comment on the transportation costs associated with the
remedies. (See Appendix B of this ROD). These costs did not
significantly affect the relative comparison between
alternatives, since the cost of the alternatives increased by
-------
about the same amount. The costs of
forth in this ROD are within +50% to
for the preferred alternative in the
differences did not affect selection
the Selected Remedy as set
-30% of the costs estimated
proposed Plan. These cost
of the final alternative.
The risk from beryllium and the associated Remedial Action Goal
were inadvertently left out of the proposed Plan. Beryllium
contributes to the carcinogenic risk and therefore, is a
contaminant that must be remediated. The Remedial Action Goal
for beryllium in the contaminated tailings and soils is 4 ppm
which is the background level. In ground water, the Remedial
Action Goal for beryllium is .004 mg/l. The Hazard Index for
zinc was recalculated using a new reference dose. The Hazard
Index changed from 1.91 to 1.27 for a future resident child.
This change did not change the decision to remediate zinc. The
recalculation is shown at the end of Appendix A.
Stabilization and solidification of residuals had been included
in the proposed Plan as part of Alternative 5, the proposed
remedy, if necessary to reach commercial treatment standards. In
that the reprocessing residuals is subject to state regulation,
stabilization and solidification was deleted from Alternative 5,
the selected remedy. The deletion of the stabilization and
solidification of the residuals under Alternative 5 caused a
decrease in cost of approximately 2 million dollars. This
decrease in costs is detailed in the cost calculations in
Appendix B. The Selected Remedy costs are within +50% to -30% .of
the cost estimated for the preferred alternative described in the
Proposed Plan. These cost differences did not affect selection
of the final alternative.
The implementation time was changed for several of the remedies.
based upon new calculations regarding the length of time that it
will take to excavate the tailings, and the number of trucks that
could travel to and from the site during a 6 day work_week. The
implementation time for Alternative 2 was recalculated and
changed from 4 months to 6 months to account for the time it
would take to bring material to the site to construct the
disposal cell, excavate and dispose of the contaminated tailings
and sediment, and construct a cap. The implementation time for
Alternative 3 was recalculated and changed from 4 months to 12
months to account for the time it would take to bring material to
the site for construction of the disposal cell and waste
treatment, excavate the contaminated tailings and sediment,
stabilize and solidify this material and construct a cap. The
implementation times for Alternative 4 and 5 were recalculated
and changed from 4 months to 12 months to account for the time it
will take to excavate the contaminated tailings and sediment and
transport them off-site. For Alternatives 3 through 5, the
implementation time includes 2 months for site preparation, 8
months for excavation of and transport of the contaminated
tailings and sediment, and 2 months for site restoration.
-------
Appendix A
-------
~able 7-5
USIDEft'DL KDOSU88 sc:BIIA8%o:
1".u'IIWAr 1.1. - %IIGEnI08 or c:maa:c:aLS D son. a
ADULn/CIIILDUII 0 '10 , nus OLD
Equation:
c:s a IRx cr x zr It ED
where:
Intake (a9lkg-dayl .
PaM'
CS . Che.ical concentration in 50il (ag!kg)
IR . Ingestion Rate (a, 80!1/day)
CF . conver8ion Factor (10 kg/mg)
EF . Expoaure Frequency (eventa/year)
ED . Exposur. Duration (year8)
BW . Body Weight (k,)
AT . Averaging Ti.e (period ov.r which exposure is averaged, in days)
Variable
Receptor
value (Rationale/Source)
Case
CS
Adult/
ChUd
Av.ra,e concentration8 in surface soils and/or
sediaenta "
IR
Adult
ChUd
EF
Adult/
Child
ED
Adult
ChUd
BW
Adult
child
AT
Adult/
ChUd
Typical
IlK!
Typical/
IUU
'l'ypical/
IUU
'l'ypical/
RKJ: "
'l'ypical
IUU
Typical/
IUU
'l'ypical/
uu:
Typical/
uu:
Typical/
uu:
VCL or .aximum concentration. in surfac, soi1.
and/or .ediment.
200 .g/day (6 yeara) and 100 .g/day (24 y.ara)
(EPA 1992&'
200 .g/day (EPA 1992a)
350 days/year (EPA 1992a)
9 years 150th percentile ti.e at one reaideDce
(EPA 1989b))
30 year8 [90th percentile ti.e at ODe residence
(EPA 1991c and 1992a»)
6 yearl (entire duration of a,e group)
lS"kg (6 years) and 70 kg (24 year81 (EPA 1992a)
15 kg laverage for 0- to 6-year-01d a,e group (E'A
1989b and 1992a)J
Pathway-specific period of exposure for non-
carcinogenic effects (i.e., ED x 365 days/y.ar),
and 70-year lifetime for carcinogenic effects
(i.e.. 70 y.ars x 365 days/year)
Itey:
02[EH)EN3015:D4028/2292/16
RME . Reasonable Haximum Exposure.
UCL = Upper 95' confidence limit on the arith.etic average.
Source:
Ecology and Environment, IDC. 1992.
-------
!lab1e 7-6
US:rDZIft'%AL UPOSUBB sCZ1IAIt%o:
PA~ 1B - DDIIAL COftAC'r WIft ClDDttCALS :r. SO:rL BY
ADULYS/au:LDUJI D ~ , nABS OLD
Equation:
CS x ASS x cr x SA X A7 x EF x ED
Absorbed Dose (mg!ks-day) -
vhere:
BW x A't
CS - Chemical Concentration in soil (mg!kg)
ASS - Absorption Factor (un!&le.a)
CF - Conversion Factor (10 kglag)
SA - Skin Surface Area Available for cont~ct (cmZ/event)
A7 - Soil to Skin Adherence ractor (mg/cm )
EF - Exposure Frequency (event.lYear)
ED - Exposure Duration (years)
BW - Body Weight (kg)
A't - Averaging 'time (period over which exposure is averaged, in days)
Variable
Receptor
Value (Rationale/Source)
Case
CS
Adultl
Child
Average concentrations in surface soils and/or
sediments
ASS Adultl
Child
SA Adult
Child
A7 Adultl
Child
EF MultI
Child
ED Adult
Child
sw
Adult
Child
A't
Adultl
Child
'typical
RKE
Typical/RKE
Typica1/RKE
Typical/ME
Typical/ME
Typical/RKE
Typical
RKE
'l'ypical/ME
Typical/RKE
Typicd/RKE
Typicd/RKE
VCL or maximum concentrations in aurface soils
and/or sediments.
0.01 default value for .etals
and cadmium (EPA 1992b)
5,000 c.Z (EPA 1992a)
1,800 c.2 (EPA 1992a)
1.0 mg/cm2 (EPA 1992a)
(EPA 1992a)
350 days/year (EPA 1992a)
9 years (50th percentile t~e at one residence
(EPA 1989b)
30 years (90th percentile time at one residence
(EPA 1991c and 1992a)J
6 years (entire duration of 8,e group)
15 kg (6 years) and 70 kg (24 years) (EPA 1992al
15 kg (average for 0- to 6-year-old age group
(EPA 1989b and EPA 1992a»
Pathway-specific period of exposure for non-
carcinogenic effects (i.e., ED x 365 days/yearl,
and 70-year lifetime for carcinogenic effects
(i.e., 70 years x 365 days/year)
Key:
02(EK)EN301S:D4028/.2293/l8
RME = Reasonable maximum exposure.
UCL E-upper 95' confidence limit on the arith.etic average.
Source:
Ecology and Environment, Inc. 1992.
-------
'.rabl. 1-1
USDlBftXAL DI'OSUU: SCIIIAIt%O:
1'AftWA% lC - %JlllALl.rI08 or AIItBOJ1118 SOIL PAKnCLBS
ADVL'!'S/CBILDUII 0 ~ , nus OLD
Equation:
CA x IR x ET x Er x ED
where:
In~ake (.,/kg-day) .
BW x A'r
CA . Conta.inant concenjration in Air (8g/83)
IR . Inhalation Rate (m /hour)
E'r . Exposur. 'ri.. (bourl/day)
EF . Exposure Frequen~ (days/year)
ED . Exposure Duration (years)
BW . Body Weigbt (k,)
AT . Avereging Ti.e (period over wbich exposure is avera,ed, in days)
variable
Receptor
Value (Rationale/Source)
Ca.e
CA
Adult/
Child
IR
Adult
Child
ET
Adult/
Chil d
tr
Adult/
Child
tD
Adult
Child
BW
Adult
ChileS
AT
Adult/
Child
Typical
RKE
Typical/
J\KE
Typical/
J\KE
Typical/
J\KE
Typical/
J\KE
Typical
J\KE
Typical/
RKE
Typical/
RKE
Typical/
ME
Typical/
ME
Modeled value based on average concentration in
site-wide surface soils
Kod.ltd value based on VCL lurface soil concentra-
tions (Eplt. 1989a)
0.83 .3/hour (£1'1. 1989a)
0.83 .3/hour (EPA 1989a)
24 hours/day (EPA 1992a)
350 days/year (EPA 1992a)
9 y.ars [50tb percentile time at one-resid.nce
(EPA 1989bll
30 years [90th percentile ti.e at one residence
(EPA 1991c and 1992a)]
6 years (entire duration 'of a,e
group)
15 kg (6 yearl) and 70 kg (24 yearl) (EPA 199Za)
15 kg (average for 0- to 6-year-old a,e ,roup (EPA
1989b and 1992a)]
pathway-specific period of exposure for non-
carcinogenic effects (i.e.. ED x 365 days/year),
and 70-year lifetime for carcinogenic effects
(i.e., 70 years x 365 days/year)
Key:
OZ\EKJEN3015:D4028/Z294/16
RME = Reasonable maximum exposure.
UCL . Upper 95' confidence limit on the arithmetic avera,e.
Source:
Ecolo9Y and Environ.ent, Inc. 1992.
-------
rab1e "7-8
UCII.BA%IOlVoL D1'OS1JU SCBJIA2%O:
PArBDr 2A - XIICXDDftAL XIIGBftXOIi or c:maac:ALS XII SOXL AIID/OIl SZDUIEft
(ADOr.acar USXDBftS "7-16 'I1WtS OLD)
Equation:
CS It III It cr It Er x ED
Intake (.,!kg-day) .
&WxA!'
when:
CS . Che.ical Concentration in Sediment (.'!kg)
IR . In,esti~n aate (mg so!~)
CF . Converslon Factor (10 kg/ag)
EF . Exposure Frequency (dayslYear)
ED . Exposure Duration (years)
BW. Body Wdght (kg)
AT . Averaging Ti.e (period over which exposure is averaged, in days)
Variable
Ileceptor
Case
Value (Rationale/Source)
CS
Adolescent
Typical
Avera,e concentration in sediments and/or
surface soil
ME
VCL or maxiaua observed concentrations in
sedi.ents and/or surface soil
IR Adolescent
EF Adolescent
ED Adolescent
BW Adolescent
AT Adolescent
Typical/RME
Typical/lU'SE
100 8,/day (EPA 1992a)
60 dayslYear (EPA 1992a)
Typicd/RME
Typical/lU'SE
10 years (entire duration of age group)
43 kg (EPA 1992a)
Typicd/RME
Pathway-specific period of exposure for non-
carcinogenic effects (i.e., ED x 365 dayslYear),
and 70-year lifetiae for carcinogenic effects
(i.e., 70 years It 365 daYS/Y8ar)
02(EH1EN301S:D4028/2296/16
Key:
RME . Reasonable Maximum Exposure.
Source:
Ecology and Environment, Inc. 1992.
-------
bble 7-'
UOD1'%OIlAL aPOSVU Sc:ICIID%O:
1'~ 28 - DIuer DDIGL ~ 1I%'ftI CllZUcr.LS D 8O:lL MD/OR S&DIImIft
(.IDOLUC8Ift' US:lDDml '7-15 TUItS OLD)
Equation:
Absorbed Dole (aglkg-daYI .
where:
C:S It ASS It a It SA It M It EF x ED
BW It AT
CS - Che.ical cOllcentratlon In Sedi.ent (ag/kgl
ASS - Fraction Ablorbed (un!11els)
CF - Converaion Factor (10 kg/8g)
SA - Skin Surface Area Available for c:ont,ct (c.2/event)
M - Soil-to-Skin "dherence ractor (ag/c. 1
EF - Exposure Frequency (dayelYear)
ED - Exposure DuratioD (y.ar.)
BW - Body Weight (k91
"T . Averaging Ti.. (period over which expolure is averaged, in days)
Variable
tteceptor
Ca.e
value (Rationale/Source)
cs
.Adolucent
'l'yp1eal
"clole.cent
JIKE
AIlS
"dolescent
'l'ypic al,l1Ut£
'l'ypical,l1Ut£
SA
"clolescent
AT
Mol.lcent
'l'ypical/IIHE
'1'ypical,l1Ut£
EP'
Molescent
ED
"clolescent
'l'yp i c al/IIHE
'1'ypical/1lKE
BW
"clolescent
A'r
"clolelcent
'l'yp ical,l1Ut£
Average eoncentration in sedi.entl and/or
surface soU
UCL or maximum observed concentrations in
.edimellts ancl/or surface soil
Che.ical-speeific values
5,000 c.Z (EPA 19'Za)
1.0 mg/cm2 (EPA 1992a)
60 daysIVeaf (EPA l'92a)
10 years (entire duration of age g:oup)
43 kg (EPA 19'2al
Pathway-specific period of exposure for non-
carcinogenic effects li.e., ED It 365 days/year),
and 70-year lifetime for carcinogenic effects
(i.e., 70 years It 365 daY.lYear)
Key:
RKE . Reasonable Maximum Exposure.
Source:
Ecology and Environment, Inc. l'9Z.
02[EHIEN30l5:D4028/2Z'5/16
-------
~all1. '7-10
U~OKAL Ul'OSUIIB SCEIIAIt%O:
PArll1CA% ZC - :I~08 01' AXItBOUJ: DIl~ SZDDIBIW AJID/Olt SOU PAltflCLES
(AJJOL!SCZft USIDBftS '7 'fO 16 nus OLD)
Equation:
CA x :IR x ET x EP x ED
whe re :
:Intake (.,/k,-day) -
BW x AT
CA . contaminant concen~ration in Air (.'/83)
IR . Inhalation Rate (m /hour)
ET . Exposure Time (hours/day)
Er . Exposure rrequency (4ays/year)
ED . Exposure Duration (years)
BW . B04y Wei,ht (kg)
AT . Avera,in, Tim. (period over which exposure is averaged, in days 1
Variable
value (Rationale/Source)
Receptor
Ca.e
CA
Modeled value ba.ed on average concentration in.
lurface soils and/or sedi.ents
IR
£'1'
Er
ED
BW
AT
Adole.cent Typical
ME
Adolescent Typical
ME
Adolescent Typical/
ME
Adolescent Typical/
ME
Adolescent Typical/
ME
Adolescent Typical/
ME
Adolescent Typical
lUtE
Modeled value based on .aximu. or VCL dry sedi.ent
and/or surface soil concentrations (EPA 1989a)
0.83 m3/hour (EPA 1989a)
0.83 m3/hour most activities: 2.5 .3/hour
motor-bikers (moderate activity, EPA 1989b)
2 hours/day (professional judgment 1
60 days/ye.r (EPA 1992al
10 years 'entire duration of a,e group (EPA
19921) I
43 kg (EPA 1992a)
Pathway-specific period of exposure for non-
carciftogenic effects (i.e., ED x 365 days/year I,
and 10-year lifetime for carcinogenic effects
(i.e., 70 yeara x 365 daya/year)
Key:
02!EHIEN3015:D4028/2297/16
RME = aeasonab1. .aximum exposure.
UCL = Upper 95' confidence limit on the arith..tic average.
Source:
Ecology and Environment, Inc. 1992.
-------
~abl. 7-11
C'DIIBZIft' USJ:DIDftUoL Dl'OSftB:
I'AmDr 3A - %ItOZnIOR OP CBBII%CALS D DUIIKDG 1IlmDt
CADUL'r .MD CBU.D RZS%DEIft'S)
Equation:
Intake (.~/k~-4ay) .
where:
CW - Che.ical Concentration in Water
III - Ingestion Rate (L/day)
EF . Exposure Frequency (days;year)
ED . Expo8ure Duration lyear8)
BW . Body Weight (kg)
AT . Averaging Ti.e (daY8)
cw x IR x EP It ED
nxAT
I-'lL)
Variable
Value (aationale/Source)
III
aeceptor c.ae
Adult/Child Typical
Adul t/Child lIKE
Adult '!'ypical/RKE
Child Typical/RKE
Adult/Child Typical/ME
Adult Typical
Adult lIKE
Child Typical/RKE
Adult Typical/ME
Child Typical/ME
Adult/Child Typical/ME
c:w
Average concentration-in groundwater
EF
ED
BW
AT
Maximum observed concentration in 9roundvater
2.0 L/day (EPA 1992., percentile: EPA 1989b)
1.0 L/d.y (EPA 1992a)
350 daYI/y,ar (EPA 1992a)
9 years (national medi.n time (50th percentile)
at one residence (EPA 1989b)
30 yearl (EPA 1992a)
6 years (entire duration of a,e ~roup)
70 kg (EPA 1992a)
15 k, (EPA 1992a)
Pathway-specific period of exposure for non-
carcinogenic effects (i..., ED x 355 days;y..r).
and 70-year lif.ti.. for carcinogenic .ffect8
(i.e., 70 years It 365 days/year)
K.y:
RME . a.asonabl. Maximum Exposur..
Source:
Ecology and Environ..nt, Inc. 1992.
02[EHIEN3015:D4028/2298/16
-------
~abl. 7-12
CUUD'1' USXDanAL Ul'OS1JltE:
l'ADBr 3B - OaIIAL COftA~ wxm c:maac:ALS DU1t%- SBCJIIDDIG
C~ NIl) CBJLD USIOEftS)
Equa~ion:
CN x PC x SA X ET X EF X ED X CF
Absorbed Ooa. (ag/kg-day) .
BWxAT
where:
Chemical Concen~ration in Water (ag/liter)
Chemical-Specific Der.al Permeability const~nt (cm/hr)
Skin Surface area Available for Contact (em)
Exposure Ti.e (hours/day)
Exposure Fraquency (dayatYear)
Exposure Duration (yeara)
volumetric conversion Factor ror Water (1 liter/l,OOO ca)
Body Weight (kg)
Averaging ~ime (period over which expolure is averaged, in
cw.
PC .
SA .
ET .
EF .
ED .
CF .
BW .
AT .
deys)
Value (Rationale/Source)
Receptor Ca.e
Adult/Child Typical
Adult/Child 1UIE
Adult/Child Typical/ME
Adult Typical;'BKE
Child Typical;'BKE
Adult/Child Typical/ME
Adul t/Chil d Typical/ME
Adul~ Typical
Adult ME
Child Typical/RHE
Mul t 'ripical/RKE
Child 'rypicd/1U'tE
Adult/Child 'rypical/1U'tE
variable
Average concentrations in groundwa~er
cw
Maximum de~ected concentrations in groundwater
0.001 cm/br derault value for inorganics
(EPA 1992b)
20,000 cm2 (total body SA for adul~s: EPA 1992a:
EPA, 19 89b I
7,200 cm2 (average total body SA, 3- to 6-year
old child: EPA 1992e: EPA 1989b)
PC
SA
0.2 hour/day (EPA 1992a: EPA 1989b)
ET
350 daye;year (1991b)
EF
9 years (national median ti.e (50th percentile)
at. one residence, EPA 1989b)
ED
30 y.ar. (EPA 1992a)
6 years Centira duration of age group)
70 kg (EPA 1991b)
15 kg (EPA 1992a)
BW
Pathway-specific period of exposure tor non-
carcinogenic effects Ci.e., ED x 365 days/y.arl,
and 'O-year lifetime for carcinogenic effects
(i..., 70 years x 365 days/year I
AT
02IEH)EN3015:D4028/2299/16
Key:
RHE = Reasonable Maximum Exposure.
Ecology and Environ.ent, Inc. 1992.
Source:
-------
7ab18 7-13
CU1tBKIft USIDanAL DI'OSUII8:
pAfttlAr U. - DClDaftAL Il1GunO. or c::&aaCALS D S1JBPACB 1IUD
(AD0L7 MD CRUD JlBSlDaftS)
Equation:
cw x la x zr x ED
Intake (89lkg-day) -
vhere:
cw-
lR -
Er -
ED -
BW -
AT -
Che.ical concentration in Water
Ingastion .ate (L/day)
Exposure rrequency (days/year)
Exposure Duration (year.)
Body Weight Ikg)
Averagin9 'ti.e (daya)
8W x A't
(8g/L)
vadable Receptor Case
CW Adult/Cbild 'I'yp i cal
Adult/Child ME
IR Adult/Child 'typical/IIHE
Er Adult 'typical/IIHE
Cbild 'fypical/IIHE
ED Adult 'typical
Adult ME
Child 'typical/IIHE
BW Adult 'typica1/ME
Child 'typica1/ME
AT Adult/Child 'fypica1/RHE
Value (Rationale/Source)
Averag8 conc8ntration in .urface water
Kaximua observed concentration in surface vater
0.01 ~day (profe.sional judgment)
12 days/year (professional judgment)
60 days/year (EPA 1992a)
9 years (national .edian ti.e [50th percentile)
at one residence, EPA 1989b)
30 year. (90th percentile time at one residence:
EPA 1992a, EPA 1989b)
6 years (antire duration of age group)
70 kg IEPA 1989b)
15 kg (E1'A 1992a)
Pathway-specific period. of exposure for non-
carcinogenic effects (1.e., ED x 365 claY8lYear),
anel 70-year lifeti.. for carcinogenic effect.
Ii..., 70 year8 x 365 days/ye.r)
Key:
IME . Raasonable Kaximum Exposure.
Sourca:
Ecology and Environ.ent, Inc. 1992.
02[EH)EN301S:D4028/2300/16
-------
~abl. 7-14
CUJUtD'I' US%DZIft%AL Dl'OSUBZ:
P~ U - DDJIAL COft~ wrrB c:uaaCALS D SUU'ACZ 1IA'rD
(~ AIID CllXLD US%DElftS)
Equation:
Absorbed Dos. (mg/k9-day) -
where:
cw x PC x SA x ET x Er x ED x cr
BV x AT
CW - Che.ical Concentration in Water (m9/1iter)
PC - Chemical-Specific Dermal Per.eability const!nt (cm/hr)
SA - Skin Surface ar.a Available for Contact (em)
ET - Exposure Tim. (hours/day)
EF - Exposure Frequency (days/year)
ED - Exposure Duration (years I 3
CF - volumetric Converaion Factor for Water (1 liter/l,OOO ca )
BW - Body Weight (k9)
AT - Averaging Ti.e (period over which exposure is averaged, in
deys)
variable
Value (aationale/source)
PC
Receptor Case
Adult/Child Typical
Adult/Child ME
Adult/Child Typical/ME
Adult Typical/RHE
Child Typical/RME
Adult Typical/RME
Child Typical/RME
Adult Typical/ME
Child Typical/ME
Adult Typical
Adult 1tKE
cw
Average concentrations in surface water
SA
ET
Ef"
ED
Child Typical/llME
BW Adult Typical/ME
Child Typical/ME
AT Adul t/Child Typical/ME
Maximum detected conce~trations in surface water
0.001 cm/hr default value for inor9anica
(£pA 1992bl
'5,000 cm2 [area of hands, ar.s, and 1/2 le9s
(£pA 1989bl]
3,000 cm2 (area of hands, arms, 1895, and feet
(EPA 19Ub)]
1 hour/day (protessional judgment)
2.6 hours/day (EPA 1992al
12 days/year (professional jud9ment)
60 days/year (EpA 1992al
9 years (national mecSian time (50th percentile]
at one residence, EPA 1989f)
30 years (90th percentile time at one residence:
£PA 1992a, EPA 1989bl
6 years (entire duration of age group)
70 k9 (EPA 1989b)
15 k9 (EPA 1992al
Pathway-specific period of exposure for non-
carcinogenic effects (i.e., ED x 365 days/yearl,
and 'O-year litetime for carcin0genic effects
(i.e., 70 years x 365 days/year)
Key:
RKE = aeasonable Maximum Exposure.
Source:
Ecoloqy and Environment, Inc. 1992.
02 (EHJEN3015:D4028/2301/16
-------
'rabl. '7-15
ItBc:lt&An:ODL DPOS1JIt& 8CJDIA8I0:
I'AftWU SA - UGU'.rIOB 0.. CBalICALS Dr StJUPACB 1IU'D
(ADOLBSc::KftS '7-16 tUJtS 01.1»
Equation:
vhere:
CW It IR It E" It ED
Intake (.g/kg-day) -
CW - Chemical Concentration in Water
IR - Ingeltion Rate (L/day)
EF - Expolure Frequ.ncy (daYI/year)
ED - Expo lure Duration (yearl)
BW - Body Weight (kg)
AT - Averagin9 Ti.e (daya)
BW It A'r
(119/10)
Variable Receptor
CW Adolelcent
Adolelcent
IJ\ Adolelcent
Er Adolelcent
ED Adolescent
BW Adolelcent
AT Adolescent
C:al.
Value (Rationale/Source)
Typical
1IHE
Typical/RKE
Typical/RKE
'l'ypic al/RKE
'l'ypical/RKE
'1'ypical/RKE
Average concentration in surtace vater
MaltillUII observed concentratioD in surtace vater
0.01 L/da,
60 daYI/y.ar (EPA 19928)
10 yearl (entire duration ot a98 group)
43 kg IEPA 1992a)
Pathway-sp8citic period ot expolure tor non-
carcinogenic effecta (i.e., ED x 365 daYI/year),
and '70-year lifeti.e for carcinogenic errectl
(i.e., 70 yeara It 365 daYI/year)
Key:
02IEHJEN3015:~4028/2J02/16
RKE a Realonable MaxillUII Eltpolure.
Source:
Ecology and Envi~oDllent, Inc. 1992.
-------
~abl. 7-16
UCItD%IOIUoL DPOS1lltE SCE1lA1t%O:
PADDY 58 - DDJIAL COIft'A~ 1Ir1'B CllEllICALS Dr smtrACZ WA'rD
(.ADOI.I:SCZlft'S 7-16 n:us OLD)
Equation:
where:
ON X PC. X SA X ET X EF X ED X CF
Absorbed Do.e (ag/kg-day) -
BWxAT
ON-
PC .
SA -
ET .
EF -
ED -
CF .
BW-
AT .
Cbemical Concentration in Water (ag/liter)
Cbemical-Specific Dermal per.eability const,nt (cm/hr)
Skin Surface area Available for Contact (cm )
Exposure Time (hours/day)
Exposure Frequency (dayslYear)
Exposure Duration (yeara)
Volumetric Converaion Factor for Water (1 liter/l,OOO cm3)
Body Weight (kg)
Averaging Time (period over whicb exposure is averaged, in
days)
Variable
Value (Rationale/Source)
Receptor
Case
cw
Average concentratioDs in surface water
PC
SA
ET
EF
ED
BW
AT
Adolescent
Typical
~ximu. detected concentrations in surface vater
Che.ical-specific values used (EPA 1992b)
5,000 c.2 (EPA 1992a)
2 hours/day (EPA 1992a)
60 daysIYear (EPA 1992a)
10 years (entire duration of age group)
43 kg (EPA 1989b)
Pathway-specific period of exposure for non-
carcinogenic effects (i.e., ED x 365 dayslYear),
and 70-year lifetime for carcinogenic effects
(i.e., 70 years x 365 dayslYear)
Xey:
Adolescent
1lHE
Adolescent
'l'yp ic al/lU'tE
'l'yp ic a l/lU'tE
Adolescent
Adolescant
Typical/lU'tE
'l'yp ic al/lU'tE
Adolescent
Adolescent
'l'yp ic al/lU'tE
'l'yp ical/lU'tE
Adolescent
Adolascent
'l'ypical/lUlE
RME . Reasonable Maximum Exposure.
Ecology and Environment, Inc. 1992.
Source:
02[EHIEH3015:D4028/2303/l6
-------
Table 7-18
'rQ][IClft VALUBS roa I'OI'EIIrIAL CARClIIOGDlC KFFKC'!'S
Weight-ot-
Slope Factor ifF) Evidence 'l'ype ot SF Bash/
Chellical Route (1I'J/kCJ/dayl classitication Cancer SF Source
IDorCJuica
Arsenic oral 1.75. A Skin DdnkinCJ vater/
IRIS
Inhalation 15 A Lun'J Inhalation
occupational/IRIS
Berylliull Oral 4.3 82 Total tUllora Ddnkin'J vater/
IRIS
'Inhalation 8.4 82 LunCJ Inhalation
occupational/IRIS
"
I Cadmium Oral NA ND NA RA/IRIS
~
00 Inhalation 6.3 81 Lung occupational/IRIS
Copper Oral NA D If A RA/IRIS
Inhalation If A D NA RA/IRIS
Lead Oral If A 82 NA If A/IRIS
Inhalation If A 82 If A NA/IRIS
Manganese . Oral I'll. D I'll. NA/IKIS
Inhalation If A D NA NA/IRIS
Hercu~y Oral NA D NA 1fA/IRIS
Inhalation NA 0 NA IfA/IRIS
Silver Oral 1'11. 0 If A NA/lalS
Inhalation NA D NA RA/IRIS
Zinc Oral NA 0 If A RA/IaIS
Inhalation NA 0 NA RAllalS
02(EHJE~3015:D4028/2270/16
Key:
HEAST .. £PA's Health Effects Assess.ent summa~y Tables.
IRIS .. EPA's Integrated Risk Infor.ation Syste..
N1. .. Not applicable.
NO .. Not deter.ined.
-------
orable 7-20
'I'OXICIft VALUES FOa ~IAL 8OIICAltCIIIOGD'IC aFnC'rS
Reference Dose IRfD)
Uncertainty IUr)
and
Value Confidence Critical RrD Bads/ Modifying eMr)
Chellical Route Type Img/kg/day) Level Effects Source ractors
IDorgaaics
Arsenic onl Chronic 3 x 10-4 !tediul8 Hyperpigmentation, Human oral/IRIS vr..3
keratosis, and Mr-l
possible vascular
cOllplications
subchronic 3 x 10-4 NS Keratosis and Human oral/HEAST Ur.l
..... hyperpigmentat10n
I 3 x 10-4
Vt Inhalation Chronic NA Extrapolated fro. oral
0
Subchronic 3 x 10-4 NA Extrapolated fro. oral
Beryllium onl chronic 5 It 10-3 Low None observed Drinking water/IRIS
subchronic 5 x 10-3 NS None observed Drinking water/HEAS'1'
Inhalation Chronic 5 x 10-3 NA Extrapolated fro. oral
subchronic 5 x 10-3 NA Extrapolated frol8 oral
cadmium Onl Chronic 5 x 10-4 H1gh Significant Drinking water/IRIS Ur.lO
proteinuria Mr.l
subchronic 5 x 10-4 NS NA Extrapolated from chronic
Inhalation Chronic 5 x 10-4 NA Extrapolated fro. oral
Subchronic 5 x 10-4 NA Extrapolated fro. oral
02(£HIEN3015:D4028/2271/6
-------
~eble 1-20 (Coat.)
Reference Dose (RfD)
Uncertainty (Ur)
end
Value Confidence Critical RrD Buh/ "odifyinq (Kr)
Che.ical Route 'l'ype (.q/kq/day) Level Effect. Source ractor.
Copper Oral Chronic (3.1 It 10-2)0 IfS Loca]. GI Oral/H£AST If A
irritatioD
Subchronic (3.1 It 10-2)0 IfS Local GI Oral/HEAST If A
irritaUoD
Inhalation Chronic RO If A NAlIRIS . BlAST
subchronic ND If A IfA/HEAST
"-J Lead Oral chronic liD IfS CRS eUect. RA/IRIS . BEAST
I
VI
.- SubchroDic RD IfS CNS e U acts NA/HEAST
Inhalation chronic RD CNS effects RAlIRIS r. KEAST
Subchronic ND RA 1fA/H£AST
"anganese oral Chronic 1 It 10-1 Kediu. CRS effects Diet/IRIS Ur.l
Kr..1
subchronic 1 It 10-1 IfS CNS eUect. Diet/HEAST Ur.l
Inhalation ChroDic 1 It 10-4 Kediu.. Increa.ed preva- occupational Inhalation/ Ur.300
lence of re.plra- IRIS Kr-3
tory syapto.s and
psychoaotor di.-
turbanca.
Subchronic 1 & 10-4 us Resp! ratory Occupational Inhalationl Ur..900
.ffects, psycho- KEAST
8otor disturbance.
02(ERIEN301S:D4028/2212/6
-------
Table 7-20 (CODt.)
Reference Dose IRtDI
Uncertainty (Ur)
and
Value Confidence Critical RrD Bashl Modifying (Mr)
Che.ical Route Type I ag/kg/day I Level Effects Source ractors
Mercury Oral Chronic 3 II 10-4 RS Kidney effects Oral rat/HEAS'r U,..lOOO
Subchronic 3 x 10-4 liS Itidney effects oral rat/HEAST Ural000
Inhalation Chronic 9 II 10-5 ItS neurotoxicity Hu.an Occupational/REAST Ur.30
Subchronic 9 II 10-5 RS neurotoxicity Hu.an occupational/HEAST ur.30
SHver Oral Chronic 5 x 10-3 Low Argyria oral/IRIS ura)
Mr..l
...... Subchronic 5 II 10-3 RS Argyria oral/HEAS'r Ur-3
I 5 II 10-)
\J1 Inhalation Chronic If A Extrapolated fro. Oral
N
Sub chronic 5 x 10-] If A Extrapolated fro. Oral
Zinc Oral Chronic Z II 10-1 5S Ane.ia Therapeutic Do.age/ Ur-l0
HEAST
Subchronic 2 II 10-1 liS Ane.ia Therapeutic D088l)el Ur.l0
HEAST
Inhalation Chronic 2 II 10-1 If A Extrapolated fro. oral
Subchronic 2 x 10-1 nA Extrapolated fro. Oral
02(EH)EH3015:D4028/2212/6
-------
~
I
~
~
Table 1-10 (Coat.)
Key:
D m Implied value calculated fro. current drinking-vater
KEAST a EPA'S Health Effects Assess.ent su..ary Tables.
IRIS a EPA's Integrated Risk Information syste..
RA . Not available.
ND . Not determined.
NS . Not specified.
UF a uncertainty factor.
KF a Modifying factor.
Source:
Ecology and Environment, Inc. 199Z.
OZ(~H)SH]OlS:D40Z8/ZZ1l/'
-------
orable 7-:U
CLEVBLAIID IlILL SIn
SUJlltAJtY or .sorIJIA~.D aczss CAIICBR USO -
11m CASK
Exposure
Scenario and
Pathway
Sack9round
Neareat Accessible
Downstre.. aesidence
Kill Area
Residential
Adult
Child
Adult
Child
Adult
Child
soil Exposure
Drinking Water
Surface Water
1.Z It 10-4 8.9 x 10-5 3.4 It 10-4. 2.5 x 10-4 2.1 It 10-3 1.5 It 10-3
7.1 It 10-5 3.3 It 10-5 4.6 It 10-5 2.1 It 10-5
7.6 x 10-8 8.0 It 10-7
1.9 It 10-4
1.2 It 10-4
3.9 It 10-4
2.7 It 10-4
2.1 It 10-3
1.5 It 10-3
......
I
0-
\0
Total
Recreational
soil Exposure
Motorbikers
- other Activ-
ities (hikinCJ.
tarqet shoot-
in9. etc. I
Surface Water
Adolescent
Adolescent
Adolescent
9.6 It 10-6
9.0 It 10-6
1.6 It 10-4 .
1.5 It 10-4
(Future at Dry Reservoir)
6.5 It 10-5
-5
2.5 x 10
-7
4.1 x 10
Total
(Current)
(ruture)
1.9 It 10-5
2.5 It 10-5
-4
3.1 x 10_4
3.8 It 10
-------
orable 7-22
c:x..BnLAIID IIJ:LL SI'%B
SUIUtNlY 0.. IS~I.IIUBD aass IIOBCJUlCD IIAURD IBDICBS -
JUm CASK
Background
Nearest Accessible
Downstre.. Residence
"ill Area
Exposure
scenario and
Pathway Adult Child
Residential
Soil Exposure 0.56 2.3
Ddnkinq Water 0.37 0.87
Su~face Water
-J
I
...,
0 Total 1.03 3.17
Rec~eational Adolescent
Soil Exposure 0.30
- Moto~bikers
- othe~ Activ- 0.14
lUes (hikinq.
t.~get shoot-
1°9. etc.)
Su~face Water
Total
Adult
Child
Adult
CbUd
1.8 6.1 11 38
0.23 0.53
0.008 0.45
2.04 7.08 11 38
Adolescent Adolescent
2.6
0.39 2.5
(Future at D~y Reservoir)
1.7
0.14
0.44
0.53
5.1
6.8
(Current)
(Future)
-------
Table 7-23
CLZVELNID lULL SID
SUJOIARY or J:STIIQftD J:J:CBSS CAllCBa RISKS -
ftPICAL UPOSUU CASE
Backqround
Exposure
Scenario and
Pathway Adult Child
Residential
Soil Exposure 1.8 It 10-5 -5
4.2 x 10
Drinking Water 0.00 0.00
surface Water
.....,
I
-..J It 10-5 4.2 x 10-5
too" Total 1.8
Recreational Adolescent
Soil Exposure It 10-6
- Motorbikers 4.4
- other Activ- 4.3 It 10-6
ities (hiking.
target shoot-
ing, etc.)
Surface Water
Total 8.7 It 10-6
Hearest Accessible
Downstream Residence
Kill Ana
Adult
Child
Adult
child
7.1 x 10-5
4.6 x 10-6
7.1 x 10-4
7.2 It 10-6
4.4 II: 10-4
1.0 It 10-3
0.00
0.00
-5
7.6 x 10
1.8 It 10-4
4.4 II: 10-4
1.0 It 10-]
Adolescent
Adolescent
-5
1. 7 It 10
1.1 II: 10-4
1.1 II: 10-4
(Future at Dry !g.ervoirl
3.4 II: 10
0.00
-5
1. 7 II: 10
-4
2.2 II: 10_4
2.5 It 10
(Current)
(Futu"e)
-------
Table 1-24
CLEVSLMD IIXLL SID
SUIIIIAB'f 0.. BsrIIIA%BD UCBSS 1I01'ICAlllCER IIAZABD 18D:tCBS -
nPICAL Dl'OSUU CASS
aackCJround N.ar..t Accessible Mill Aua
Downstr.am aesidance
Exposu..e
scenario and
Pathway Adult Child Adult Child Adult Child
Residential
50i1 Exposure 0.29 1.0 1.2 4.1 8.0 27
Drinking Water 0.08 0.18 0.09 0.22
surface Wate.. 0.006 0.32
....,
I 0.31 :n
'" Total 1.2 1.3 4.6 8.0
N
aee..eational Adol.scent Adolescent Adolescent
Soil ExposUl:e 0.09 1.8
- Hotol:biken
- othel: Activ- 0.06 0.26 0.61
Hies (hiking, (FutUI:. at Dry R..ervoir)
taE'CJet shoot- 0.89
in9. etc. I
SUE'face Water 0.10
Total 0.15 0.36 2.4 (Current)
6.8 (Futun)
-------
~abl. 7-25
suppLERZIft'AJ. USE ZftJ:IIM'BS
USJ:DZlftIAL SOJ:L Dl'OSUBB
.. CASZ.
Cancer Risks
Roncancer aalard Indice.
Location
Adu.t
Child
Adult Child
0.66 2.3
7.4 23
6.6 19
Cobbed Ore
1.2 x 10-4 8.9 x 10-5
7.4 x 10-4 5.3 x 10-4
3.6 x 10-4 2.6 x 10-4
Background
Kine spoils
02(EH)EN3015:D4028/2316/25
.Ba.ed on maximum concentration. found in the.e area..
-------
Yabl. 1-26
SUJUIARY or 8SYDIAY&D DCBSS CAlleD RISKS
AIID 1I08CA111CD DZdD XIIDICBS
ASSOCJ:M8D WID ft8 CLKVZLUID IIXLL ADD
(Futur. a.sidential 8apGsur. in Rill Ar..)
(a..soDabl. Kaai8U8 lapoaura)
Total Risk P.r Receptor
Exposure
Scenario
Adult
Child
o to 6 years
Risk contributions
by Eapos1:re
Rout.
Risk
Contributions
by ch..iea1a
cancel' 811111s
.....
,
.....
0\
Future
usidentia1
scenario
2.1 It 10~3
1.5 It 10.3
Ingestion - 42\. ,,\
Der.a1 - 51\. 23\
Inhalation - <1\, <1\
Arsenic - 91\. 91\
seryl1iua - 3\, 3\
"ODeancer aisks
Future
res idential
scenario
11
38
Ingestion - 39\, 74\
Der.a1 - 61\, 2'\
Inhalation - <1\, <1\
Arsenic - 78\, 84'
cad8ius - 14\. 10\
Zinc - 5', "
Copper - 2\, Z\
"anganes. - 1\, 1\
021&81&83015:D4028/2286/19
aThe percentages given are for the adult and the child, r.spectively.
Source:
-------
Table 1-Z1
SU!DIAa'f or ISTIJIAUD aass CAIIaR RISKS
. AIm IIOJlCAIICBR IIAZARD IIIDIC:ZS
ASSOCIATED WITH THB IlEARBST ACC:ZSSIBLB DOIIJISTRBM USIDna
(CU~~eat offaite a.aideatial Eapoaure SceDario)
(a.aaoDabl. naaiaua Kapoaur.)
Expoaure
Scenario
Total Risk Per Receptor
Adult
child
o to 6 years
Riak cont~ibution8
by Exposvre
Route
Risk
Contributions
by Cbe.icala
CaDcer Risks
Current offsite
residential
scenario
lIoncaneer Rists
-..J
I
-..J
~
Current offsite
~esidential
scenario
3.9 x 10-4
2.7 x 10-4
Ingestion - 49', 71'
Derm.l - 51', 21'
Inhalation - <1\, <1\
Ingestion - 46', 17'
Der.al - 52', 23'
Inhalation - <2\, <1'
Araenie - 90', 91'
Beryllium - 10', 8'
Cad8iu8 - <1'. l'
Arlenic - 16'. 71'
csdaiu. - 11', 10'
Zinc - 1\. <1\
Copper - n. 5'
Kanganese - 2', 3'
Beryllium - 1\. <1\
Kercury - <1'. <1'
sUYe~ - 2'. 2'
2.04
7.08
Soucce:
aThe pe~centages 9iven are for the adult and the child, respectively.
Ecology and EnYi~onaent, Inc. 1992.
-------
orable 1-18
SUl'IIIARY or SS'rXftATBD Dass CNlCD USKS
AIID 80IICNlCSIt IIAZA8D IIIDICCS
ASSOCIA'rID 1fn'B U8 CLEVELAIID RILL ADA
and Future Site Visitor .e.ldeDtial saposgre iD Rill
(aeasonable Kaai8W8 .aposu~e'
Ana'
( cunent
Total Risk ror Receptor
Exposure
Scenado
Adolescent
Risk contributions
by Expos~re
Route
Risk
contributions
by Cbe.i.cala
Cucer Risks
Current sit.
visitor
scenari.o
-4
3.1 x 10 -c(currentl
3.8 x 10 (future I
Ingestion - 36\, 36\
Der.al - 60\, 60\
Inhalation - C\. 4\
Arsenic - "\, ",
Berylliu8 - Z', Z'
Cad8lu8 - <1', <1'
lIoncancer alsks
....,
I
())
.....
Current site
visitor
scenario
5.1 (current)
6.8 (futun)
Ingestion - 34'. 33'
Der..1 - 64'. 65'
Inbalation - 2\. 2\
Arsenic - 16', '0'
Cad8iu8 - le" 18'
Zinc - 5\, 6'
copper - Z\, :n
"an9anese - 3', 3'
02(EHIER301S:DC028/2286/1'
aThe percentages given a~e for the current .nd futu~e ca.es, respectively.
Source:
-------
~able 1-29
SmuwtT or IftlftAftD UCESS CA8'CZR RISKS
AlII) 80IICAIICD BAUJU) IBOICES
ASSOCIUBD WI'I'B 'l'B1 CLlVJ:LUD lULL un
CaecreatioDal Saposure iD Off-site Ac.a.
Caeasoaabl. Raai8U8 saposure.
Total Risk For Receptor
Exposure
scenario
Adolescent
Risk contributions
by Exposure
Route
Risk
contributions
by Che.ical
CaDcer Risks
Future
ncreational
scenario
2.S x 10-5
Ingestion - 38\
Derllal - 61\
Inhalation -
-------
'fable 1-30
rBlDlC'fBD BLOOD LEAD LSnLS nOK aPQSVRB N UAD III SOIL AIID AI.
uanoal CBILD, 0 N C YKAIIS OLD
Area
Rullber
of soil
and/or
Sediaent
Samples
RaneJe of
soil Lead
Concentration
(mCJ/kCJ)
Geoaetric "ean
SoU Lead
Concentration
(meJ/keJ)
Esti.ated
Lead Uptake
Fro.
Soil and Dust
( jig/day I
£stimated
Lead Uptake
rro. All
Sources
(PCJ/dayl
predicted
Geo.etric Kean
Blood Lead
concentration
(PCJ/dL)
Percant of
Blood Lead
Levals
Predicted
to aacead
10 PCJ/dL
('I
currant off-site .esidential s:&posare
Natural 5 35.1 - 61.6 44.6 1.34 5.12 1.91 0.00
BackeJround
-.J Nearest 9 17.1 - 1,390 146 4.38 8.63 2.74 0.01
I Accessible
00 Residence
0\
ruture OD-Site aesidential Sapo.are
site-wide 45 46.8 - 13,500 819 24.6 28.8 8.48 30.8
East pUe 15 218 - 1,860 191 23.1 21.9 8.24 21.4
West pile 15 438 - 11,500 1,340 40.2 44.4 12.9 73.2
and Center
West Hill ., 348 - 13,500 1,280 38.4 n.1i 12.4 10.6
Dust pile ] 46.8 - 444 195 5.85 10.0 3.16 0.05
cobbad Ora 5 98.8 - 512 262 1.86 12.1 3.13 0.23
02(£HI£1'I3015:D4028/2289/10
Note: The EPA reco..ended cutoff probability for aacessiva aaposura 1s 95\ of tha .ost sansitiva population havin9 blood
levels below 10 PeJ/dL.
-------
'!'able 7-31
SBLBaBD COIl'l'AJlDlAJft'S OF hnlUlXtAL BCOLOGXCAL COJICII:JIII
Surfaee
Element/Compound Water Sedi.enta SoU.
Aluainum X
Antimony
Araenic X X X
aariua
aerylliua
Cad.aiua X X X
Calcium
Chromium
Cobalt X
copper X X X
%ron
Lead X X X
Ha9ne.iUII X
Hangane.e X
Hercury X
Nickel X
potaaaium
Selenium
silver X X
Sodiu8
Thallium
Vanadium
Zinc X X X
cyanide
02[EHIEN301S:D4028/2318/34
Source: Ecology and Environment. Inc. 1993
-------
CALCULATIONS OF HAZARD INDICES (HI) FOR ZINC USING ALTERNATIVE
REFERENCE DOSE (RfD), CLEVELAND KILL SITE
ALL CALCULATIONS ARE FOR RME RESIDENTIAL SCENARIO, SOIL EXPOSURE
PATHWAY (Ingestion, Dermal and Inhalation Routes).
Basic equation:
HI = CDI/RfD
CDI is chronic daily intake.
CDIs are taken from: Tables 6-B-2 and 6-B-2 in the Risk Assessment
(Section 7 of the Remedial Investigation for the Cleveland Mill
site, March 1993), and are the same for either RfD.
-------------------------------------------------------------------
for RfD = 0.2, HI = CDI/0.2
Route Adult CDI Adult HI Child CDI Child HI
Ingest 4.49E-02 2.25E-01 2.94E-01 1.47
Dermal 6.l7E-02 3.09E-01 8.73E-02 4.37E-01
Inhal 4.47E-05 2.24E-01 1.76E-04 8.80E-01
TOTAL 5.34E-01 1.91
NOTE: The HIs for zinc calculated using RfD = 0.2 are those ~hat
appear in the Risk Assessment.
-------------------------------------------------------------------
for RfD = 0.3, HI = CDI/0.3
Route Adult CDI Adult HI Child CDI Child HI
Ingest 4.49E-02 l.50E-01 2.94E-Ol 9.80E-01
Dermal 6.17E-02 2.06E-01 8.73E-02 2.91E-01
Inhal 4~47E-05 1. 49E-04 1.76E-04 5.87E-04
-------
Appendix B
...1
-------
Estimated Cost Recalculations
Road Improvement/Repair Estimate
Road improvements or repairs shall be performed, if necessary, as
determined by EPA, after state and local go.vernmental agencies have
had an opportunity to provide information to EPA regarding road
repairs. Al though EPA does not know if road repairs or road
improvements will be necessary, costs for each of these items have
been included in the site cost estimates. Actual costs for the
selected remedy will be determined during the Remedial Design Phase
of the site clean-up.
Repair:
$5,000 per mile, 4 times in 8 months
a)
4 mile stretch of Little Walnut Road from Highway 180 to site
turn-off
$5,000/mile x 4 times x 4 miles = $80,000
b)
2 mile stretch to site
$s,ooo/mile x 4 times x 2 miles =
$40,000
Improvement:
Pavement Base for 2 mile stretch to site
(12" deep, bank run gravel, spread and compacted)
(2 miles) (5,280 ft/mile) (1 ft deep) (15 ft wide) ($15/yd3)
(1 yd3/27 ft3) = $88,000
Turnouts
(50 ft long) (15 ft wide) (8 ft deep/turnout) (2 turnouts) ($15/yd3)
(1 yd3/27 ft3) = $6,666
Grand Total Transportation
-------
Individual Alternative cost Recalculations
Alternative 5, The Selected Remedy
$7,999,370
$3,000,000
$1,000,000
$ 214,666
original Proposed Plan estimate
stabilization/solidification removed
reprocessing fee paid (15% profit)
transportation costs
+
+
--------------------
$6,214,036
TOTAL
$5,621,920 + $214,666 = $5,836,586 TOTAL (capital cost)
Alternative 2
+
$3,110,035
$ 214,666
---------------------
$3,324,701
TOTAL (present worth)
$2,461,637 + 214,666 = $2,676,303
TOTAL (capital cost)
Alternative 3
+
$6,404,521
$ 214,666
---------------------
$6,619,187
TOTAL
(present worth)
$5,765,550 + 214,666 = $5,980,216
TOTAL
(capital cost)
Alternative 4
+
$11,264,380
$ 214,666
----------------------
$11,479,046
TOTAL (present worth)
$10,886,930 + $214,666 = $11,101,596
-------
Appendix C
-------
Transportation Calculations and Considerations
community concerns exist with regard to potentially heavy truck
traffic through the community during implementation of the remedy
at the Cleveland Mill Superfund site. Implementation of either
Alternative 3, On-site Solidification and Stabilization and
Disposal; Alternative 4, On-site Solidification and stabilization
with Off-site Disposal; or Alternative 5, Off-site Reprocessing
will cause an increase in truck traffic in the short-term. EPA and
NMED believe that short-term risks from the increase in traffic
could be mitigated by using engineering controls and consulting
closely wi th the ci ty and the County to develop transportation
routes.
Based on EPA's calculations included in this appendix,
approximately 4700 truck loads or 24 trucks a day each way (or 4
trucks per hour) would travel on Little Walnut Road to move the
70,900 cubic yards of contaminated materials to a reprocessing
facility as specified in Alternative 5. All calculations assume an
eight-month transportation period which has been expanded since the
publication of the Proposed Plan to more accurately reflect the
time the work will require. The calculations also assume a 6-day
work week, 12 hour days and 24 ton trucks. The assumptions made in
these calculations were checked with mining companies in the area
and wi th the contacts at both the County and state Highway
departments to be sure that they accurately reflect realistic and
local conditions.
Alternative 3 would require a lower number of truck trips, 1300
truckloads, about 7 trucks per day each way (or about 1-2 trucks
per hour) in order to bring stabilizing and solidifying material
and water to the site. This calculation assumes the minimum amount
of cement and water necessary to adequately stabilize and solidify
the waste material and assure protection from leaching. The amount
of cement and water may increase as a result of design phase
treatability studies, resulting in an increase in truck traffic for
this alternative.
The volume of the waste material would be greatly increased under
Alternative 4, due to on-site stabilization and solidification of
the contaminated tailings and sediment prior to transportation.
Therefore, a greater number of trucks than under any other
alternative would be employed if Alternative 4 were implemented.
Alternative 4 would take 7400 truckloads, 39 trucks per day each
way (or about 7 trucks per hour).
To further facilitate truck traffic the City and County will be
invited to help design trucking routes and suggest possible safety
considerations for use in any transportation plan. For instance,
the trucks traveling to the site could follow a reduced speed
limit, be rerouted around school zones, and have flashing lights.
The assumptions used in the traffic calculations are not firm and
-------
during the design phase. EPA and NMED would like to point out that
the increase in truck traffic through silver city is not a very
high percentage increase when compared to the number of trucks
already traveling between other local mines, mills and smelters.
Both the EPA and the NMED believe that this level of truck traffic
over a short time period is very manageable.
The concerns with the truck traffic fall into the short-term
effectiveness and community acceptance criteria which are explained
in detail in the Record of Decision for this site. All of the
alternatives have some short-term impacts. Alternatives 3, 4 and
5 would all involve an increase in truck traffic and some short-
term risks. EPA believes that these risks can be addressed through
engineering controls such as road improvements, dust suppression
and air monitoring and also through consulting with the City and
County on transportation routing.
-------
TRUCK LOAD CALCULAT:ION
ALTERNATIVE 5, OPP-S:ITB RBPROCESS:ING
CLEVELAND H:ILL SUPERFUND S:ITB, GRANT COUNTY, NEW HEX:ICO
:1.)
volume/weight calculation
(:1.6.875 ft3/ton) (yd3/27 ft3)
= :1..6 tons/yd3 sand, gravel, rock
2)
truckload calculations (one way)
For a 24 ton truck:
(24 ton/truck) / (1.6 tons/yd3) = 15 yd3/truck
(70,900 yd3) / (15 yd3/truck)
= 4727 trucks
For 8 months of work, 6 days/week, 12 hours/day (32 weeks, :1.92
days):
4727 trucks/192 days
~
24 trucks/day (each way)
«24 trucks/day one direction)/(12 hours/day» (28) ~ 4 trucks/hour
(one way trip)
*
2 directions, going to the site and coming from the site
~
.,.
-------
TRUCKLOAD CALCULAT:ION
ALTERNATIVE 3, ON-SITE SOL:ID:IJ'ICATION/ STAB:IL:IZAT:ION
AND ON-S:ITE D:ISPOSAL
CLEVELAND H:ILL SUPERFUND S:ITB, GRANT COUNTY, NEW HEX:ICO
1)
weight of cement that must be added (assumes 10% by volume
cement)
(1 ton/2000 lbs) (2700 lbs/yd3) «.10)(70,900 yd3»
= 9571.5 tons
2)
Number of trucks of cement
(9571.5 tons)/(15 ton/truck)
= 638 trucks
3) Number of truckloads to bring portable cement mixing plant,
equipment and other supplies (electrical hook-up): 60 truckloads
TOTAL for Cement and supplies:
638 trucks + 60 trucks = 700 trucks
4) Water Calculation: Assume that about 1 million gallons is the
maximum that can be taken from the site reservoir in an average
year without destroying its use. This entire quantity of water
would be necessary for decontamination and revegetation.
The following calculation is for the actual water needed to make
the cement.
a)
conversion
1 gal = «231 in3)/(123 in3» (ft3)/(27 ft3/yd3)
= .00495 yd3
Number of Gallons of water needed for cement (assumes 20%
by volume water):
(.20)(70,900 yd3)/(.00495 yd3/gal) = 2.86 million gallons
= 3 million gallons
b)
c)
Using a 5000 gallon tanker (about 20 tons of water):
3,000,000 gal water/(5000 gal/tanker)
= 600 tankers
Total:
700 + 600 =
1300 tanker truck loads
5)
6)
Truckload calculation (one-way):
1300 truckloads/192 days
= 7 trucks/day = 1-2 trucks/hour
(each way) (one way)
-------
CLEVELAND H:ILL
TRUCKLOAD CALCULAT:ION
ON-S:ITE SOL:ID:IF:ICAT:ION/STAB:IL:IZAT:ION AND
OFF-S:ITE D:ISPOSAL .
SUPERFUND S:ITE, GRANT COUNTY, NEW KEX:ICO
ALTERNAT:IVE 4,
Alternative 4 would require the same number of trucks as
Alternative 3 to stabilize and solidify the waste plus 1.3 times
the number of trucks as Alternative 5 (because the volume will
increase by at least 30% due to water and cement that is added
during stabilization and solidification) to take the increased
volume of waste off-site:
1.3(4727) + 1300 = 7445 trucks/day ~ 7 trucks/hour
(each way) (one way)
-------
Appendix D
-------
APPENDIX D - CLEVELAND KI:LL ARARS
1. Chemical-Specific ARARs for Tailings and sediment
1. National Emission standards for Hazardous Air pollutants (40
CFR Part 61) (NESBAPS).
Relevant and appropriate during removal of tailings and soils
and transportation.
2. New Mexico Ambient Air standards, Air Quality control
Regulations, Section 201A. (NK stat. Ann. S 72-2-1 et sea.)
Relevant and appropriate during removal of tailings and soils
and transportation.
2. Action-specific ARARs for Tailings and Sediment
RCRA 40 CFR 262, Manifesting Requirements for
Transport of Hazardous Waste
Relevant and appropriate because manifesting method to be. used
to keep track of superfund wastes which will be transported.
The material involved is not a RCRA hazardous waste, but the
manifesting method is helpful and protective.
a.
b.
New Hexico Hining Act of 1993
Remediation on-site falls under the definition of "mining" in
the "New Mexico Mining Act (effective July 1, 1993)", and so
is subject to the Act. However, since regulations have not,
yet, been promulgated under the Act, remediation need only
comply with the Act to the extent that it clearly defines
procedures to be used. Once regulations are promulgated,
application of the Act and its regulations to the remediation
of the site may be re-evaluated by EPA. Under CERCLA, ARARs
do not apply to off-site activity.
3. Location-specific ARARs for Tailinqs and sediment
a.
Endangered species Act, 50 CPR 17, 402
Although no endangered species have been observed at the site,
there are two endangered species in the Gila wilderness which
is located about 10 miles northwest of the site. Federal
activities must not jeopardize the continued existence of
endangered or threatened species or adversely modify their
-------
b.
Fish and wildlife Coordination Act,
40 CFR.6.302 (q)
Consultation between federal agencies is required when a water
body is modified and it could affect wildlife which may be the
case during excavation of tailings from the stream.
c.
New Mexico wildlife conservation Act
Consultation with state agencies is required to avoid or
mitigate adverse impacts to endangered species listed by the
New Mexico Departments of Natural Resources and Game and Fish.
d.
National Historic preservation Act,
40 cn 6301 (b)
coordination with state agencies is required in order to
ensure that properties, the impact on them, and the effects on
them are identified, and that the alternatives to avoid or
mi tigate an adverse effect on property eligible for the
National Register of Historic Places are adequately considered
in the planning process.
e.
Archaeological and Historical preservation Act,
16 D.S.C. 469, et. seq.
Any federally-funded or licensed construction project is
covered by this act that provides a mechanism for funding the
protection of historical and archaeological data.
f.
New Mexico cultural properties Act.
Relevant and Appropriate because state agencies shall conduct all
plans necessary to preserve, protect and enhance significant
historical cultural properties under this act.
4.
ARARs for Ground water and surface water
EPA and NMED will evaluate, at the least, the following regulations
before contingency measure selection, should the implementation of
contingency measures become necessary:
a.
Chemical-specific ARARs for Ground water
The regulations that will be evaluated will include National
Primary Drinking Water Regulations (40 eFR Part 141); New
Mexico Water Quality Act, NM stat. Ann. S 74-6-1 et sea.; NM
WQCC Regulations 82-1, sections 3-101, and 103; and NM WQCC
Regulations 91-1, section 1-102, 2-105, and 3-101.
-------
b.
Action-specific ARARs for Ground Water
The regulations that will be evaluated will include Standards
for Owners and Operators of Hazardous Waste Treatment, Storage
and Disposal Facilities should it become necessary to
construct a pumping and treating operation on-site for any
treatment of any contaminated ground water resulting in
residuals (for instance filter cake) that contained a
hazardous waste.
-------
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