V
3
United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R06-90/060
September 1990
Superfund
Record of Decision:
Cimarron Mining, NM
NVlRONfc/iiiNTM
AGKNOY
SAkLAS, TSCAt
Printed on Recycled Paper
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H72-101
REPORT DOCUMENTATION i. REPORT Ma t.
PAGE EPA/ROD/R06-90/060
4. THeendSJMNo
SUPERFUND RECORD OF DECISION
Cimarron Mining, NM
First Remedial Action
7. Al*hor(*)
t. P*rfoimineOrgdnln*onMMmindMdm«
12. Sponeoring OrgjrizKkm M»m» «nd *d*m
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
* NAcipioflC Accoooton No.
i. Report D«M
09/21/90
t.
1. Perfuming OrgenizeHon Rept Me.
M. ProjeeVTeefc/Work UnH Me.
11. Comrad(C) or Qram(a) No.
(C)
(Q)
IX Type of Report* Period Covered
800/000
u.
15. SupptemenUvy Not**
16. Atamel(UinH: 200 word*)
The 10.6-acre Cimarron Mining site, Lincoln County, New Mexico, is an inactive milling
facility used to recover iron from ores transported to the site. The land surrounding
the site supports agricultural, commercial, and residential uses. A shallow aquifer,
which is not a potential drinking water source, and a deeper primary drinking water
aquifer lie beneath the site. The iron recovery process was conducted onsite between
the late 1960s and 1979. Although cyanide was not used in the original iron-recovery
milling process, operations changed in 1979, and cyanide was used until 1982 to recover
precious metals. The operation of the mill resulted in the discharge of contaminated
liquids onsite. The sources of environmental cyanide contamination at the site are the
processed waste materials, including tailings piles and cinder block trench sediment
piles, the cyanide solution and tailings spillage areas, and the cyanide solution
recycling and disposal areas, including cinder block trenches and an unlined discharge
pit. The major sources of ground water contamination by cyanide are the cinder block
trenches and the discharge pit. These areas of prolonged contact between cyanide
solution and underlying soil led to cyanide contamination in the shallow aquifer.
(See .Attached Page)
17. Document Anelyele a Descriptor*
Record of Decision - Cimarron Mining,
First Remedial Action
Contaminated Medium: gw
Key Contaminants: inorganics (cyanide)
b. MenlMere/OpeivEnded Terme
NM
c. COSATJ FMoVGroup
18. AveMebilty Statement
1*. 3wwHy Ct*H (Thto n»port)
None
20. SMtvMy CtaM flhto P*g»)
None
21. No. ofPagM
71
22. Price
M ANSI-ZM.18)
SM MMrucltaM on AtmwM
OPTIONAL FORM 272 (4-77)
(Formoity HT1S-3S)
DttpwiniMtt of Cofiwnorct
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EPA/ROD/R06-90/060
Cimarron Mining, NM
First Remedial Action
Abstract (Continued)
Field investigations revealed another abandoned mill, known as Sierra Blanca, operated
by the same owner nearby, which will be addressed in a second Record of Decision (ROD).
This ROD addresses contaminated shallow ground water at the Cimarron Mining mill area as
Operable Unit 1 (OU1). The primary contaminants of concern affecting the ground water
are inorganics including cyanide.
The selected remedial action for this site includes pumping and discharging contaminated
shallow ground water to an offsite publicly owned treatment works (POTW); ground water
monitoring; removal and offsite disposal of process chemical drums, decontaminated
tanks, and associated piping; filling in the discharge pit and cinder block trenches
with onsite soil and waste pile material and covering these areas with clean soil;
plugging the onsite abandoned water supply well; and inspecting and maintaining the
existing fence. The estimated present worth cost for this remedial action is $105,000,
which includes a total estimated O&M cost of $50,825.
PERFORMANCE STANDARDS OR GOALS: The discharge to the POTW will comply with the
pretreatment standard of cyanide 5 mg/1 (CWA). Ultimate cleanup goals for the shallow
aquifer are based on Federal MCLs and State action levels including cyanide 200 ug/1
(State and MCL). The Hazard Index (HI) of cyanide will be remediated to less than or
equal to 1.
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Decision Summary
Cimarron Mining Corporation Site
Operable Unit 1
Record of Decision
September 1990
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DECLARATION FOR THE RECORD OF DECISION
CIMARRON MINING CORPORATION SITE
OPERABLE UNIT 1, CARRIZOZO, NEW MEXICO
Statutory Preference for Treatment as a
Principal Element is Met
and Five-Year Review is Not Required
SITE NAME AND LOCATION
Cimarron Mining Corporation
Carrizozo, Lincoln County, New Mexico
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the
Cimarron Mining Corporation site in Carrizozo, Lincoln County, New Mexico,
which was chosen in accordance with the Comprehensive Environmental Response,
Compensation and Liability Act of 1980 (CERCLA), as amended by the Superfund
Amendments and Reauthorization Act of 1986 (SARA) and, to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency
Plan (NCP).
This decision is based upon the contents of the administrative record
file for the Cimarror, Mining Corporation site.
The United States Environmental Protection Agency and the New Mexico
Environmental Improvement Division agree on the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if
not addressed by implementing the response action selected in this Record
of Decision (ROD), may present an imminent and substantial endangerment
to public health, welfare, or the environment.
DESCRIPTION OF THE SELECTED REMEDY
This final remedy addresses remediation of shallow ground water contamination
at the Cimarron Mining Corporation (Operable Unit 1) mill location. The
principal threats posed by the site will be eliminated or reduced through
treatment and enaineerinq controls.
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The major components of the selected remedy include:
o Pump and discharge around water to the Carrizozo Publicly Owned
Treatment Works (POTW)
- The discharge will comply with the pretreatment standard of 5 milligrams
per liter (mg/1) of cyanide as cited in 40 CFR 413.24 Subpart B and
deemed relevant for this action. Sampling will be conducted onsite
prior to the discharge entering the POTW collection system. Current
data indicates pretreatment will not be necessary.
- Biological activity within the existing treatment lagoons, in addition
to effluent chlorination and photodecomposition will provide treatment to
reduce the cyanide concentration to acceptable concentrations.
- Monitoring of the treatment plant effluent and sludge will be
conducted to ensure no adverse impacts on the POTW processes.
CRITERIA: A treatment goal of 200 micrograms per liter (uq/1) of cyanide
will be utilized, if possible, for remediation of the shallow
ground water. New Mexico Water Quality Control Commission
Regulations requires protection of all ground water of less
than 10,000 milligrams per liter (mg/1) total dissolved
solids for potential future beneficial use as a source of
drinking water. In addition, this treatment goal will
provide protection of the lower, currently used drinking
water zone, from potential future migration of contamination.
o Ground Water Monitoring
The ground water monitoring program may be amended and/or eliminated if
data indicates effective remediation has occurred.
In addition to the ground water remedy, the following measures will be
implemented:
o Removal of the process chemical drums, and decontamination of tanks
and associated piping;
o Filling in the discharge pit and cinder block trenches with onsite
soils and waste pile material and covering with clean fill;
o Plugging of the onsite abandoned water supply well; and
o Inspection and maintenance of the existing fence.
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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. This remedy utilizes permanent solutions and alternative
treatment technologies (or resource recovery) to the maximum extent
practicable and satisfies the statutory preference for remedies that
employ treatment that reduces toxicity, mobility, or volume as a
principal element.
Because this remedy will not result in hazardous substances remaining
onsite above health-based levels, a five-year review of the remedial
action is not required.
_ _ ,
Ro'bert E. Layton Jr/, P.&T Date
Regional Administrator
U.S. EPA - Reaion 6
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Toble of Contents
Page
I. Location and General Description 1
II. Site History and Enforcement Activities 1
III. Community Participation 5
IV. Scope and Role of the Operable Unit 6
V. Site Characteristics 7
Classification of Ground Water 20
Extensive Sampling Program 23
Contaminant Sources 34
VI. Summary of Site Risks 35
Hazard Identification 36
Exposure Assessment 36
Toxicity Assessment 39
Summary of Baseline Risk Estimates 40
VII. Description of Alternatives 43
Remedial Objectives 43
Remediation Goal and Corresponding Risk 44
VIII. Summary of Comparative Analysis of Alternatives 62
IX. Selected Remedy 64
X. Statutory Determination .'.... 67
XT. Documentation of No Significant Changes 68
XII. Responsiveness Summary 68
Community Preferences 68
Integration of Comment 68
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List of Fiaures and Tables
figure/Table Page
Site Location Map, Figure 1 2
Site Map, Figure 2 4
Site Area Land Use Figure 3 8
Surface Geology, Figure 4 10
Stratigraphic Column, Figure 5 11
Cross-Section Locations, Figure 6 13
Geologic Cross-Section A-A, Figure 7 14
Geologic Cross-Section B-B, Figure 8 15
Site Topography, Figure 9 16
Regional Ground Water Elevations, Figure 10 18
Site Wells Water Quality Parameters, Table 1 ?5
Surface Soil Sampling Locations, Figure 11 ?1
Typical Metals Concentrations in Soils, Table 2 26
Waste Pile Sampling Locations, Figure 12 28
Site Monitor Well Samples, Table 3 31
Cyanide Contaminated Ground Water, Figure 13 33
Ground Water Remediation Alternatives, Table 4 47
Proposed Extraction Well Locations, Figure 14 52
Alternative 3, Pumo and Evaporate Ground Water, Figure 15 54
Alternative 4, Pump and lischarge Ground Water to POTW, ... 56
Figure 16
Alkaline Chiorination Process Schematic, Figure I7 58
Alternative 5, Pump Treat and Discharge to POTW, 59
Figure 18
Alternative 6, Pump Treat and Recharge Ground Water, 61
Fiaure 19
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Decision Summary
Cimarron Mining Corporation Site
Operable Unit 1
Record of Decision
I . Location and General Description
Cimarron Mining Corporation site is located approximately 1/4
mile east of Carrizozo, Lincoln County, New Mexico and approximately
100 miles south-southeast of Albuquerque. The site is about 10.6 acres
in size, and is located in the NE 1/4 Section 2, Township 8S, Range
10E, on the north side of U.S. Highway 380 (Figure 1). The facility
consisted of a conventional agitation mill, which resulted in
unpermitted discharge of contaminated liquids, the stockpiling of
contaminated liquids, and the stockpiling of tailings and other waste
sediment. Access to the site is restricted by a 8- foot fence.
Approximately 1500 people live within a two mile radius of the site.
While conducting the RI field work at the Cimarron site, the
existence of another abandoned mill became known. The other
location, known as Sierra Blanca, exists approximately one mile to
the south of Cimarron (Figure 1). The two mills were owned by the
same parent company (Sierra Blanca Mining and Milling Company^, and,
for a short period, operated concurrently. File information discusses
a possible spill at Cimarron, which prompted all milling operations
to be relocated to Sierra Blanca. Investigation of the Sierra Blanca
mill is being performed as a second operable unit of the Cimarron NPL
site, and the results will be presented as a separate RI/FS report.
II. Site History ar,d Enforcement Activities
The Cimarron Mining Corporation site is an inactive milling facility
originally owned by Zia Steel Inc., and used to recover iron from
ores transported to the site. The iron recovery process took place
between the late 1960's and 1979 and involved crushing of the ore
material, formation of a pumpable slurry by mixing with fresh and
recycled water, and collection of the ferric (iron) portion using a
magnetic separator. Cyanide was not used in this original process,
and tailings were transported from the site and used as fill material.
In 1979, the site was sold to Southwest Minerals Corporation, which
apparently began using cyanide soon thereafter to extract precious
metals from ore. Details on the operation between 1979 and 1981 are
not available other than a 1980 New Mexico Environmental Improvement
Division (NMEID) sample analysis report, which noted the presence of
cyanide contamination.
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CONTOUR INTERVAL: 100 FEET
SOURCE: USGS, Cimorron East-West. NM 7.5' Quodrongles. 1982.
N
0 1000 2000
&1
FEET
FIGURE 1
SITE LOCATION MAP
CIMARRON MINING CORPORATION
NEW
MEXICO
QUADRANGLE LOCATION
'CAMP DRESSER V McKEE INC.-
2
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Southwest Minerals, a subsidiary of the Sierra Blanca Mining and
Milling Company, operated without the required permits necessary for
conducting cyanide processing at the site. In mid-1981, the operation
was expanded by adding several large mixing tanks, cyanide solution
tanks, thickeners, and associated pumping and conveying equipment.
NMEID sent a certified notice of violations to Cimarron Mining
Corporation on June 22, 1982, for discharging into a non-permitted
discharge pit and, in July 1982, the site ceased operation. No legal
action was taken by the state; the company -filed for bankruptcy in
July 1983, and a court assigned bankruptcy trustee was appointed for
the site.
NMEID field inspections of the site in February 1980, June 1982, and
in May and June 1984 revealed the presence of cyanide and elevated
metals in shallow ground water, soil and mill tailings.
An Expanded Site Inspection (ESI) was conducted from January to
October 1987, by an EPA Field Investigation Team (FIT). The objective
of the ESI was to collect additional data for the Hazard Ranking
System (HRS) and facilitate RI/FS planning. A topographic base map
indicating locations and elevations of on-sHe features is presented
in Figure 2.
On-site activities performed during the ESI included surface and
subsurface soil sampling, visual inspection of process tanks,
sampling of remnant materials in the tanks, quantifying waste
volumes, sampling and geologically describing subsurface soil borings
during installation of monitor wells, sampling ground water in the
monitor wells and in nearby water supply wells, testing in-situ
permeability at the monitor wells, and identifying adjacent land
uses.
Based on the findings of the site investigations and the preparation
of the HRS package, the Cimarron Mining Corporation site was proposed
for addition to the National Priority List (NPL) on June 24, 1988.
On October 4, 1989, the listing was promulgated.
In March 1989, EPA tasked the firm of Camo Dresser and McKee, an
Alternative Remedial Contracts (ARCs) contractor to conduct a
Remedial Investigation and Feasibility Study (RI/FS; for the site.
A preliminary sampling program was conducted on June 19-23, 1989,
to sample existing monitoring wells and known contaminant source
areas. Results of the preliminary sampling program were utilized to
refine the sampling plan for the extensive RI ^ield investigation.
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z o
58
§
01
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The extensive RI field work and feasibility study began in August 1989
and was completed in June 1990. The data generated was used to
estimate the extent and magnitude of contamination at the Cimarron
Mining site and to develop and evaluate remedial alternatives. The
alternatives evaluated included various pump and treat alternatives
for the shallow ground water, institutional controls and no action.
Ill. Community Participation
Community interest in the Cimarron Mining site has been relatively
high due to the close proximity of the site to the town of Carrizozo.
Major community interest has focused on alleviating the stigma of a
hazardous waste or Superfund site as it relates to the community and
the desire to have an expeditious solution to allow future industrial
development of the site.
A public "open house" workshop was conducted in May 1989 to inform
the community of the RI/FS activities and process and to answer any
questions. Approximately 35 people attended including out of town
individuals, representatives of the local newspapers and the New
Mexico Bureau of Mines.
Questions and comments ranged from concerns regarding the level of
site contamination, potential impacts on the community and possible
solutions to a disregard for the previous analytical data from the
site and an unwillingness to accept the potential of long term impacts
from the site contamination.
Numerous informal status briefings have beer, conducted with various
interested citizens and local officials including presentations, by
invitation, at the local chapter of the Rotary Club.
In March 1990, a second public workshop was conducted to notify the
community of the preliminary RI results and to answer questions.
Approximately 25 people attended this workshop. Most questions
evolved around potential remedial solutions and the schedule of
future activities. A major portion of the meeting involved
discussions of the "Sierra Blanca" operable unit and the responsible
party status of the town of Carrizozo, which leased the property
to the operators of the mill.
The RI/FS documents for the Cimarron Mining site and a Proposed Plan of
Remedial Action were released for public comment in July 1990.
Public notices were published in the Lincoln County News, fact sheets
were mailed to interested individuals and the documents were
available for review in local repositories. An "open house" public
workshop to discuss the Proposed Plan was conducted on July 16, 1990.
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Approximately 10 people attended this workshop. Most comments on the
proposed plan of pumping the shallow ground water and discharging to
the POTW for treatment focused on a need for additional information
in laymans terms in order to form an opinion. No comments were presented
which aaamantly opposed the proposed pump and discharge to the POTW
alternative.
On July 30, 1990, a formal public meeting was held to discuss and
accept public comments on the proposed plan of pumping shallow
ground water and discharging to the POTW for treatment. The meeting
was conducted at the Carrizozo City Hall and approximately 20 people
attended. Presentations summarized the purpose of the meeting,
the Remedial Investigation, the Feasibility Study and the remedy
selection process. The proposed remedy of pump and discharge to the
POTW for treatment was endorsed by the New Mexico Bureau of Mines and
officials of the town of Carrizozo. In general, this proposed plan
was acceptable to the public with relatively few comments relating to
the remedy cost, time of implementation and technical capabilities of
the POTW to remove contaminants.
IV. Scope and Role of the Operable Unit
The principal threat at the Cimarron Mining site is ground water
contamination (approximately 4000 parts per billion cyanide) and
it is primarily contained in the shallow ground water which is
encountered at approximately 55 feet. Soils and mill tailings contam-
ination, as discussed in the Risk Assessment portion of the RI/FS
documents, is not significant and does not present a public health threat.
The deeper primary drinking water aquifer, encountered at approximately
120 feet was found to be uncontaminated oirectly beneath the area of
highest contamination although minimal contamination (24 ppb cyanide) was
detected in an upgradient on-site production water well. This contamination
is believed to be due to poor well construction rather than percolation
from the upper, more highly contaminated water bearing zone. The Feasibility
Study has evaluated remedial alternatives which address the major
shallow ground water contamination based on the potential for migration
of contamination to the lower primary drinking water aquifer.
Consideration has also been given to achieving a clean-up goal of 200 ug/1
cyanide based on the potential future beneficial use of the shallow
ground water as a source of drinking water as required by the New Mexico
Water Quality Control Commission Regulations.
Modeling indicates that remediation of the major area of ground water
contamination (approximately 500,000 gallons) will prevent any significant
off site or lower drinking water zone impacts. Because the major
contamination will be removed and treated and threats to public health
and the environment will be alleviated, the five year review of the
remedy will not be required.
As previously'discussed, the Sierra Blanca milling location which is
located approximately 1 mile south of the Cimarron location, will be
addressed as a second operable unit.
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V. Site Characteristics
The climate In the Carrizozo area is semi-arid characterized by relatively
long, hot summers and mild winters. The total annual precipitation reported
by the Office of State Climatologist averages 13.2 inches, while total
lake evaporation averages 62.4 inches. The average measured temperatures
in the Carrizozo area range between 70.9° and 40.4°F. The lowest
recorded temperature was -18°F during January 1971 and the highest
was 105°F during June of 1981.
Native vegetation in the vicinity of Carrizozo and the site is
characteristic of the Desert grassland association, typically found in
this part of New Mexico at elevations of 4,200 to 6,000 feet. Trees are
generally absent and small shrubs and grasses dominate. The tailings
piles and many of the waste piles are largely devoid of plant life.
Volunteer species have invaded the site locally, especially in low
traffic areas and where site processes resulted in high moisture.
Several species of lizards and snakes survive in this habitat. In
addition, several small mammals including the mice, rabbits and coyotes
are common. The pronghorn (antelope) are larger mammals also common to
the area.
The land surrounding the site supports agricultural, commercial,
recreational and residential uses (Figure 3). The predominant land use
north of the site is fenced range land. A stock pen is located
immediately north of the site and was utilized in the past to hold
stock prior to loading onto rail transports. A construction company
yard and buildings are located on £he adjacent property to the east
of the site. U.S. Hiahway 380 and right-of-way borders the site to
the south with recreation facilities beyond. The recreation facilities
consist of a golf course, a little league field, a'playground, and a
picnic area. Railroad tracks and right-of-way for Highway 54 are
west of the site.
Based on a 1982 U.S. Geological Survey Topographic map of the area, 1,200
people reside within a one-mile radius of the site and about 1,500 reside
within a two-mile radius of the site. The closest inhabited
residence in Carrizozo is approximately 1/4 mile south of the site.
The main population center of Carrizozo is approximately 3/4 mile
from the site. Census data for the region indicate that the population
of Carrizozo is relatively stable, with less than five percent increase
in population between 1970 and 1988.
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Brooks
Construction
Company
RANGELAND
CONTOUR INTERVAL' 100 FEET
SOURCE: USGS. Cimorron East-West. NM 7.5' Quadrangles. 1982.
N
FIGURE 3
SITE /KEA LAND USE MAP
WOO 2000
Eri-
nrr
NEW
MEXICO
QUADRANGLE LOCATK3N
-CAMP DRESSER t McKEE INC^
8
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Geology
The Cimarron Mining Corporation site is situated near the axis of the
northern portion of the Tularosa Basin. This basin forms an elongated
valley that extends more than 200 miles from the vicinity of
Carrizozo, New Mexico, southward into Chihuahua, Mexico.
Regional Stratigraphy
The northern portion of the basin, in the vicinity of Carrizozo, consists
of Quaternary aged alluvial and material underlain by Tertiary to Permian
aged rocks. Figure 4 illustrates the surface exposure of these deposits.
A stratigraphic column is shown as Figure 5.
Most of the rocks in the area are of sedimentary origin. The rocks range
from Permian limestones, sandstones, and shales to Cretaceous sandstones,
coals, and shales. Intrusive and extrusive igneous rocks originated
during the Tertiary times, and basaltic lava beds were deposited during
the late Quaternary time. The lava flowed from a vent a few miles north
of Carrizozo and formed an extensive lava bed, referred to as the
Malpais, in the northwest portion of the area. Alluvial material is at
the surface throughout most of the area with only scattered outcrops of
Tertiary and older rocks. Outcrops of Permian rocks are restricted to
the western portion of the area.
Site Geology
The site geology is based upon the results of the RI field investigation
in which eight monitor wells were installed and three additional
boreholes were drilled. The boreholes and monitor wells were
continuously sampled, where possible, during drilling.
Site Stratigraphy
The stratigraphy at the site was found to consist of two principal units.
The uppermost unit is a fine grained alluvium consisting of brown to tan
calcareous and sulfate rich silty clays and clayey sands. This unit,
which is present to depths of 16 to 27 feet, was found to be unsaturated
in the vicinity of the site. The lower unit, extending to a depth of at
least 200 feet, is a fine grained Cretaceous unit consisting of
interbedded shales and fine grained sandstones and sUtstones. The
Cretaceous units were observed to have fractures and joints to a depth of
at least 7Q feet below the surface. Most of the fractures and joints
appeared to be sealed by iron precipitates.
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Source: New Mexico Bureau of Mines and Mineral Resources, Bulletin 67, Plate 2 (Griswold, G.B., 1959).
109° IO7° 105° 103°
'
OLOS Cfucts j
109° 107° 105" 103°
INDEX MAP SHOWING LINCOLN COUNTY
Contact
Fault
Road
Stream or orroyo
FIGURE 4
SURFACE GEOLOGY MAP
CAMP DRESSER & McKEE INC.'
10
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Two geological cross-sections, as located in Figure 6 have been developed
from information gathered during the RI. Figure 7 is a southeast to
northwest cross-section which shows the Quaternary alluvium overlying the
dipping Cretaceous beds. As shown in this figure, the individual units
within the Cretaceous sediments are generally discontinuous in the
direction of the dip over most of the site. Figure 8 is a south to north
cross-section which shows that some of the units may be laterally
continuous across the site in a direction perpendicular to the dip of the
Cretaceous units.
Topography
The ground surface is unpaved and slopes down to the northwest across the
site. Figure 9 illustrates the topography and the noted drainage
patterns across the site. The abandoned railroad spur on the north end
of the site provides a drainage pathway along the northern boundary of
the site, sloping down to the northwest. The northwest portion of the
site is sloped from the main milling area to the railroad spur drainage
near the northwest corner of the security fence. A drainage pathway is
also present on the south side of the site, sloping to the west, bending
north along the western boundary of the site, and converging with the
drainage from the mail milling area near the northwest corner of the
site. Surface drainage also flows from the tailings area on the east
side of the site into the railroad spur drainage on the northeast end of
the site which eventually converges with the rest of the site drainage
pathways at the northwest corner of the site.
Water was observed to flow across the surface along the indicated
pathways during two separate storm events which occurred during the RI
field investigation. The overall slope is approximately 1.1° to the
northwest but may vary from 0° around the noted ponding areas to as much
as 85° around the "H" pile. There is a man-made depression of a foot or
less forming the ponding area west of the "D" pile. The water which
collected in the ponding areas noted on Figure 9 was observed to
disappear within a day of the storm event by a combination of evaporation
and soil saturation. Water was also observed to collect in the two
cinder block trenches north of the processing plant. This collected water
also disappeared within a few days. Additionally, some storm water
drainage enters the discharge pit.
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16
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Hydrogeology
Regionally, ground water exists in both the alluvial deposits and the
sedimentary rocks. Although all material below the water table is
potentially water saturated, the very low permeability of some deposits,
such as shales, siltstones, and lignites, effectively prevents water
penetration in significant quantities. Fine-grained porous material,
although water saturated, will not yield significant water to wells
because of low permeability. Significant aquifers are within the
relatively coarse alluvial material or in underlying porous or fractured
sedimentary rocks. Both the alluvial and Cretaceous aquifers have
highly variable yields from a few gallons per minute (gpm) to several
hundred gpm. No other units in the area produce significant amounts
of ground water.
Shallow ground water occurs primarily in unconfined water table conditions
at depths ranging from about 20 to 200 feet. East of the malpais or
lava flow, the water table slopes to the west and northwest as does
the ground surface. Elevation contours on the water table and ground water
flow directions are depicted in Figure 10. The gradient steepens in
areas of lower permeability or where other significant barriers to
flow exist. Ground water may pond behind zones of low permeability
such as dipping shales or intrusive igneous rocks. At some locales,
springs occur where the ponded region of the water table intersects
the land surface.
Regional Ground water Quality
Many of the rocks in the area are of sedimentary origin, with relatively
high concentrations of chloride and sulfates in some locals. In a
significant number of private wells in the area, these dissolved
constituents exceeded drinking water standards. Concentrations
of these and other constituents are not high enough to prevent use of
ground water throughout most of the area, and due to their origin, are not
considered in violation of regulations by the State of New Mexico.
Occurrence and Availability of Ground water
Ground water in the area is recharged chiefly by runoff from the mountains
in the southern and eastern parts of the area. Some limited direct
recharge from local precipitation in the arid basin may also occur in some
areas where the shallow water table is near the ground surface, however,
at the Cimarron site, this mode of recharge is expected to be negligible
or nonexistent. The Hydrologic Evaluation of Landfill Performance (HELP)
-------
III
« Ul i « Ml
Tit
Modified from Cooper. 1965
SEDIMENTARY ROCKS
QUATERNARY Qal - Alluvium
- Clay. Silts Gravel
Qld - Landslide Debris
TERTIARY & TKcm - Cub Mountain Formation
CRETACEOUS - Sandstone. Quartzite. Conglomerate
CRETACEOUS Kmv - Mesa Verde Group
- Coal Bearing Sandstone & Shale
Km - Mancos Shale
- Dark Fissile Shale
Kd - Dakota Sandstone
- Buff Sandstone
TRIASlC TRd - Dockum Group-
- Red Beds, Siltstone. Sandstone.
Conglomerate
PERMIAN Psg - Glonetta Sandstone and San Andreas
Limestone:
- Limestone, Gypsum and Sandstone
Py - Yeso Formation:
- Gypsum, Siltstone. Limestone,
Sandstone
FIGURE 10
IGNEOUS ROCKS
Qb - Basalt Flow
TV - Extrusive
Ti - Intrusive
Tei - Extrusive and Intrusive
Td - Dike
55M Water-table contours, elevation m ft
above MSl
Direction of Groundwater Flow
Well in alluvium
Well m Cretaceous rocks
We!! in alluvium and Cretaceous
rocks
Spring
STRATIGRAPHY, SURF1CIAL GEOLOGY, AND
GROUNDWA!°ER ELEVATIONS IN THE NORTHERN TULAROSA BASIN
CAMP DRESSER a McKEE INC..
18
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Model (U.S. EPA, June 1984) was used to approximate ground water recharge
at the site based on climatologlc data and site lithology. The results
of the model application Indicate that Infiltration of precipitation to
the shallow ground water unit at the site is very minimal. Precipitation
is absorbed by the surface and near surface soils at the site and
subsequently lost through evapotransplratlon. This indicates that
current migration of contaminants in surface source areas to the
ground water is negligible, although some site earthwork to fill-in storm
water collection areas which Increase the chances of Infiltration should
be performed.
Ground water at the site is found only 1n the sedimentary rocks. The
alluvium was not observed to be saturated. The ground water 1s present
under water table conditions at depths ranging from 27 to 42 feet. The
water yielding units are thin, apparently discontinuous sandstone and
siltstone units which are Interbedded with thick shales. Slug tests were
performed on five of the eight monitor wells installed in the RI. The
slug tests indicated variable but low permeability across the site.
The hydraulic conductivity varied from 2.8 ft/day (1 x 10"3 cm/sec) 1n
well MW-10 to 5.7 x 10'2 ft/day (2.0 x 10'5 cm/sec) in well MW-16.
The yield of all wells installed at the site 1s poor (approximately two
gallons per minute or less).
The water levels 1n adjacent wells MW-10 and MW-11 which are screened 1n
separate stratigraphlc units show a strong downward gradient exists at
the site. The static level elevations measured in MW-10 and MW-11 on
1/10/90 were 5,432.82 and 5,389.80 feet respectively. There 1s
approximately 111 feet of sediment between the two screened sandstone
units. The downward gradient 1n the area of MW-10 an MW-11 1s 0.38 ft/ft.
This indicated that ground water within the Individual sandstones and
siltstones at the site flows 1n the downdip direction of the units. When
the individual units pinch out against adjacent and underlying shales,
the water will either seek to move laterally until 1t finds another
permeable strata, or 1t may move downward through open fractures and
joints until another permeable unit is encountered. In general, most of
the fractures and joints observed during the RI field investigation
appeared to be sealed by Iron precipitates; however, there may still
be enough open fractures to allow some downward migration of ground water
through the shale units. It should be noted that no cyanide
contamination has yet to be observed in the deep monitor well MW-11,
which is located below the area of the site where the shallow ground water
is most contaminated with cyanide.
19
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Site Ground water Use
There is one water well on the site which was installed by Cimarron
Mining Corporation to supply water for the gold extraction process.
This well is no longer in use. No reliable well completion records are
available. The well is at least 126 feet deep and the screen location
is not known. This water well is located in the southeast corner of
the site, upgradient of the most contaminated area of the site, but is
in an area where some low level cyanide contamination is present in the
shallow zone. Some cross contamination of water units has apparently
occurred through this hydraulic connection between ground water zones.
Cyanide was found at a concentration of 24 ppb in the deep well.
Although the cyanide concentration of 24 ppb in the deep well is below
the 200 ppb standard, it is evidence of the potential for the downward
migration of contamination.
Site Ground water Quality
The quality of the shallow ground water at the site is poor in terms
of TDS, chloride and sul fate content. Table 1 contains the results
of chemical analyses performed on the 17 monitor wells and one water
well on the site.
Classification of Ground water
It is the policy of EPA's Superfund program to use as a guide the
framework provided by EPA's Ground water Protection Strategy
(U.S. EPA, 1984) in determining the appropriate remediation for
contaminated ground water. Three classes of ground water have been
established on the basis of ground water value and vulnerability to
contamination.
The various ground water classes are below:
Special ground water (Class I) is highly vulnerable to contamination
because of the hydrological characteristics of the areas in which it
occurs, and characterized by either of the following factors:
o The ground water is irreplaceable; no reasonable alternative source
of drinking water is available to substantial populations.
The ground water
flow for a pa
would destroy
d water is ecologically vital; the aquifer provides the base
a particularly sensitive ecological system that, if polluted,
troy a unique habitat.
20
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Current and potential sources of drinking water and water having other
beneficial uses includes all other around water that is currently usea
(IIA) or is potentially available (HB) for drinking water, agriculture,
or other beneficial use.
The shallow ground water not considered a potential source of drinking
water and of limited beneficial use (Class IIIA and Class IIIB) is
saline, i.e., it has a total dissolved solids level of 10,000 milligrams
per liter (mg/L), or is otherwise contaminated by naturally occurring
constituents or human activity that is not associated with a particular
waste disposal activity or another site beyond levels that allow
remediation using methods reasonably employed in public water treatment
systems. Class III also includes ground water that is not available
in sufficient quantity at any depth to meet the needs of an average
household.
Class IIIA includes ground water that is interconnected to surface water
or adjacent ground water that potentially could be used for drinking
water. Class IIIB includes ground water that has no interconnection to
surface water or adjacent aquifers. For Class IIIA ground water,
establishing cleanup levels should take into consideration the degree
of interconnection to Class I or Class II ground water or the rate of
discharge to surface water so that levels of contaminants in higher
class ground water do not increase as a result of the interconnection.
Aquifer testing results of the contaminated shallow ground water unit
at Cimarron indicate that a pumping yield of only two gallons per minute
(GPM) or less can be achieved. This is not enough yield to meet the
needs of an average household. The shallow ground water body is separated
from potential Class I or II aquifers by a thick shale unit, although
some limited interconnection is possible through fractures, joints, and
an abandoned well which intersects both zones.
Based on the above classification criteria and site data, the shallow
ground water zone at the Cimarron site could be considered a Class IIIA
aquifer. However, due to the limited availability of ground water in
some areas of New Mexico, the New Mexico Water Quality Control
Commission Regulations (NMQCCR) require protection of all ground waters
of less than 10,000 mg/1 total dissolved solids. Because of this
criteria, this Record of Decision considers the NMQCCR 200 ug/1 standard
as a clean up goal based on the potential future beneficial use of
the shallow around water as a source of drir.kina water.
-------
Preliminary RI Sampling
The results of the preliminary sampling verified that organic
contamination is not present in the ground water at the site above
detection limits. Cyanide was detected in all of the wells with highest
concentrations in shallow monitoring wells 4 (2.84 mg/1) and 6 (0.498 mg/1)
Preliminary sampling also indicated chromium, iron and lead were present
in some of the shallow monitoring wells at concentrations greater than
Federal and State drinking standards.
Drums (approximately 150) containing magnetic mineral concentrate were
sampled however no organics or cyanide were detected. These drums were
sold by the bankruptcy trustee and removed from the site prior to the
extensive RI field investigation.
Surface and near surface soils in the spillage areas were also collected
during the preliminary sampling program and analyzed for total cyanide
and metals. Total cyanide was detected at the following depths and
concentrations: 0" to 2" (6.4 mg/kg); 2" to 6" (7.3 mg/kg); 6" to 12"
(1.5 mg/kg); and 12" to 18" (1.3 mg/kg). This indicated that most of
the cyanide in the spillage areas is confined in the upper few inches of
the soil. A similar pattern of decreasing concentration with depth was
found for the metals chromium, copper, cobalt, iron, magnesium, manganese,
nickel , uranium and zinc.
Based on the preliminary sampling program and full chemical analysis
of the ground water and soils, it was determined that the contaminants
of concern at the Cimarron site are cyanide and metals. The preliminary
sampling program verified that no organics contamination is present
at the site.
Extensive Sampling Program
As discussed above, the contaminants of concern were verified by the
Preliminary Sampling Program to be cyanide and metals. To determine
the degree and extent of contamination, all samples were analyzed for
Target Analyte List (TAL) metals and total cyanide. To gather
information useful in predicting mobility of contaminants and forms
of cyanide, select samples were analyzed for pH, forms of sulfur,
acid potential, neutralization potential, noncomplexed cyanide and
cyanide amenable to chlorination. In addition, air samples were
collected and analyzed for total cyanide (vapor and dust), total
dust, total respirable dust, and TAL metals (as dust). To gather
system chemistry information, in addition to that provided by the
above analyses, ground water samples were also analyzed for various
anions and cations, total suspended solids, total dissolved solids,
and nitrate/nitrite. To provide information useful in evaluation of
remedial technologies, in addition to that provided by above analyses,
select samples were analyzed for gold, dry density and particle size
distribution.
23
-------
Soils at the Cimarron site were sampled to verify the nature and extent
of contaminants in source areas and to determine the area! extent of
surface contamination resulting from wind and water erosion processes
and random waste disposal practices. This information is necessary
for developing remedial action alternatives for the site.
Surface soil samples were, in most cases, collected from two separate
levels of the surface/near surface soils. Since degradation and
volatilization of cyanide may be greater at the soil/air interface than
below the surface, and in order to assess potential transport of
contaminants from the surface by wind, one of the two samples was
collected from the top of the soil (0-2"). In order to assess the
degree of cyanide contamination in the near-surface soils, and to
gather information on the dynamics and vertical mobility of contaminants
in the near-surface soils at the site, the second surface soil sampling
location was collected from the 2-6" interval.
Samples were collected on a 200 foot grid in the apparently contaminated
process area and along a transect leading away from the I tailings pile
to the northeast, which is the prominent wind direction in the Carrizozo
area. Surface soil sampling locations, including those locations sampled
during the preliminary sampling program are shown in Figure 11.
Typical background metals concentrations were compiled in order to
provide for comparison with metals concentrations of samples collected in
areas of the site affected by facility operations. Background cyanide
concentrations were analytically undectable.
Review of the data indicates that there are several metals which have
distinctly higher concentrations in particular areas of the site.
Those areas include processed and unprocessed waste piles, cyanide
solution and tailings spill areas, and the cinder block trenches and the
discharge pit. The metals with elevated concentrations in these areas
are arsenic, barium, calcium chromium, cobalt, copper, iron, lead,
magnesium, nickel, selenium, sodium, vanadium, and zinc.
With the exception of copper, cobalt and iron, these concentrations still
fall into the range of typical concentrations listed for soils in the
United States as shown in Table 2.
Cyanide was detected at only one Ml surface soil location. Total cyanide
(2.1 mg/kg) was detected in sample Ml-016, which was located in a drainage
ditch at the northeast corner of the I pile. Total cyanide was also
detected in the discharge pit (7.0 to 46.5 mq/kg), and sample locations
M2-001, -002, -003, -005, -006, -010, -Oil, and"-012 (1.2 to 40.5 mg/kg).
Also included in the analysis was the concentrations of cyanide which
would be amendable to destruction by chlorination. The percentage of
cyanide amendable to chlorination is generally less than 50 percent
of the total cyanide concentration, this indicates that a large
24
-------
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TABLE 2
TYPICAL METALS CONCENTRATIONS IN SOILS
OF THE UNITED STATES
mgAg
Element
Range
Typical Medium
Source
Aluminum
Antimony
Arsenic
Barium
Beryllium
Bromine
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Flouride
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Selenium
Silver
Sodium
Vanadium
Zinc
Al
Sb
AS
Ba
Be
Br
B
Cd
Ca
Cr
Co
Cu
F
Fe
Pb
Mg
Mn
Hg
Ni
Se
Ag
Na
va
zn
10,000 - 300,000
1 - 150
0.1 - 194
100 - 3,000
0.1 - 40
1-10
2 -130
0.01 - 0.70
< 150 - 320,000
1 - 1,000
1-40
2 - 100
10 - 4,000
7000 - 550,000
2 -200
600 - 6,000
50 - 18,300
0.01 - 0.03
5 - 500
0.1 - 2
0.01 - 8
750 - 7,500
20 - 50
10 - 300
71,000
6
11
430
6
5
10
0.06
24,000
100
8
30
200
38,000
10
5,000
850
0.03
40
0.
0.
6,300
100
50
,3
.4
5
3, 4
2
5
5
5
1
5
3
5
1, 5
5
5
5
5
5
1, 2
5
2
5
2, 5
5
5
5
1. Parr, James F., Marsh, Paul B., Kla, Joanne M., Land Treatment of Hazar-
dous Wastes, Agricultural Environmental Quality Institute, Agricultural
Research Service, USDA, Beltsville, MD, Noyes Data Corp., Park Ridge,
NJ, 1983.
2. Ure, A.M., and Berrow, M.L., "Elemental Constituents of Soils" Environ-
mental Chemistry, Vol. 2, pp 94 - 204 ed H.J.M. Bower, Royal Society of
Chemistry, Burlinhouse, London, U.K., 1983.
3. Ragaini, R.C., et al., "Environmental Trace Contamination in Kellog
Idaho near Lead Smelting Complex." Environmental Science and Technology
11 773-780, 1977.
4. Lisk, D.J., "Trace Metals in Soils, Plants and Animals." Gov Ageon 24
267-311, 1972.
5. Lindsay, W.C. Chemical Equilibria in Soils. Wiley Interscience, 1979.
26
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portion of the total cyanide is in the form of strong metal complexes.
The wastepiles were sampled using a hand auger for chemical parameters,
and a tube sampler for geotechnical samples. Samples for chemical
analysis were collected at 6-inch intervals, until contact was made
with the natural ground surface. The processed waste piles contain
material which has been milled and subjected to cyanidation. These
are identified as Waste Piles "C, I, J, K and I" as shown on Figure 12.
The materials in these piles is distinguished by extremely fine
grain size and brown to black color, the ore piles contain boulder
sized ore which has not been processed. Waste piles "A, B, D, E, F,
J-ore and N" are ore piles.
The remaining waste piles "G, H, M and 0" are identified as
miscellaneous. A review of the waste pile data indicates that the
waste piles have concentrations of arsenic, barium, beryllium, calcium,
chromium, cobalt, copper, iron, lead, magnesium, manganese, nickel,
selenium, sodium, vanadium and zinc, which are greater than the
concentrations found in background surface soil samples. Copper,
cobalt, and iron are most elevated and are the only metals present at
levels greater than the range of concentration listed as typical of
soils in the United States.
Total cyanide was detected in the processed waste piles. The processed
waste piles derived from the cinder block trenches have higher concentra-
tions (24.3 to 33.9 mg/kg) of total cyanide than tailings piles C, I
and K (4.7 to 12.6 mg/kg).
Subsurface samples were collected during the installation of the
ground water monitor wells and from soil borings located in specific
source areas. Subsurface soil samples were collected from eight monitor
well locations and three borehole locations across the site. The samples
were collected to determine the vertical extent of contamination at the
site. Cyanide was detected at concentrations of 2.0 mg/ka at 2.5 to
3.0 feet and 1.8 mg/kg at 4.5 to 5.0 feet in the shallow subsurface at
pile I (SL-002), and in samples collected in the discharge pit to
4.5 feet. Cyanide was not detected in any other subsurface soil
samples. Concentrations of TAL metals in the Alluvial samples were
compiled separately from the Cretaceous samples to allow for differences
based on lithologies of the two units.
In general, barium, calcium, magnesium, manganese, potassium, sodium and
vanadium concentrations are greater in Alluvial units than Cretaceous
units. Beryllium, copper, lead, nickel, and zinc concentrations were
27
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generally greater in Cretaceous units than Alluvial units. Data indicate
that elevated levels of TAL metals are present in the subsurface soils at
the site at depths less than five feet in areas which had elevated levels
of TAL metals at the surface. Sediments below five feet were not found
to contain elevated concentrations of TAL metals.
Air samples for toxic metals, total cyanide, total dust and total
respirable dust were collected at the site using air sampling pumps
and associated filters which were provided by the CLP laboratory. Air
samples were collected in the vicinity of tailings pile "I", the cinder
block trenches (referred to as the Spill Area), an "upwind" site location,
and a "downwind" site location.
The samples were collected over a two day period. Total dust and TAL
metals samples were collected on the same filter. Total respirable
dust was collected at the same time and place but with a separate
pump and filter. Total cyanide samples were collected on the second
day of sampling. The total cyanide included both the gas vapor concen-
tration collected through an impinger system and the dust concentration
collected on the filter system. Only two samples contained detectable
levels of TAL metals. The afternoon sample from the 5-foot height
station at the "spill" area by MW-4 had detectable beryllium, the
morning sample from the same station had detectable silver. Cyanide
(total) was detected in several of the samples at low levels (0.5547
to 30.84 ug/m3).
Eight monitor wells, in addition to the nine already existing at the
site, were installed during the RI. There are now seventeen monitor
wells and one abandoned water well on or adjacent to the Cimarron site.
In addition, there are numerous private and public water supply wells
in the vicinity of the Town of Cam'zozo. In June 1989, the nine
existing monitoring wells were sampled for organics and inorganics
analyses to verify the contaminants of concern and to provide information
used to select the number and location of additional wells. All of
those wells, plus the new wells, were sampled once during the extensive
sampling conducted during the RI.
In addition to the on-site monitor well, ten area residential wells and
one spring were sampled in order to evaluate the area ground water quality
and chemistry and to compare them with the site ground water quality and
chemistry. There was no detectable impact from the site on the
ground water quality of the residential wells or spring. Cyanide was not
detected in any of the residential wells. Comparison of metals
concentrations between the residential wells and the site monitor wells
also indicates that the residential wells have not been impacted.
29
-------
The site monitor wells and the abandoned water well were sampled to
determine the degree and extent of ground water contamination across
the site. Some metals are present at elevated levels in the on-site
ground water; and as shown in Table 3 chromium, lead, iron, manganese
and selenium are at concentrations exceeding State and Federal drinking
water criteria. Selenium, and the nonmetals chloride, sulfate, and
total dissolved solids which are at concentrations exceeding the
drinking water standards are also high in the off-site residential
wells which indicates that these constituents are naturally high in
the Carrizozo area ground water. The pattern of fluoride concentrations
across the site, and fluoride's non-association with the milling
process, indicate that fluoride is naturally high in the shallow
ground water unit at the site. Total cyanide and nitrate concentrations
exceed drinking water standards in several on-site wells. Nitrate,
which can be a byproduct of cyanide biodegradation, appears to be
associated with the cyanide contamination.
Concentrations of cyanide which exceed the State and proposed Federal
criteria of 0.2 mg/L have been detected in wells MW-4, MW-5, MW-6, MW-8,
and MW-10. Figure 13 indicates the extent of cyanide contamination in
the shallow ground water.
The deep well (MW-11) installed near the cinder block trenches and
screened between 147 and 157 feet, is not contaminated with cyanide,
and indicates that the contamination has not reached the deeper ground
water zones in the most contaminated area of the site. Low level
cyanide contamination (0.024 mg/L), was found in the abandoned deep
water production well in the southeast corner of the site. This is
probably due to a cross-connection between the upper and lower zones
created by this well. The shallow ground water zone in this area of
the site is slightly contaminated with cyanide (0.040 mg/L in MW-02).
During the field investigation a storm event occurred which resulted
in surface water runoff across the site which was collected. The
storm water runoff had total cyanide and TAL metals concentrations
which could indicate the possibility that cyanide and metals are
being mobilized by heavy precipitation events. Of note, the runoff
sample had 0.031 mg/L of total cyanide, 0.048 mg/L of arsenic,
0.0008 mg/L of mercury, 0.0004 mg/L of cadmium, and 0.026 mg/L of
lead. Iron and manganese were detected at 75 mg/L and 1.19 mg/L,
respectively. The concentrations of cyanide and metals detected in
this runoff sample may be somewhat elevated above actual concentrations
in the runoff water. As noted in the sample collection discussions
in Section 4.2.11 of the Remedial Investigation Report, the samples
were very turbid, with a high amount of suspended solids resulting
30
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SUMMARY or SITE MONITOR WELL SAMPLES EXCEEDING
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from the sample collection method which resulted in an inordinant
amount of suspended materials from the sampling location. The detected
metals and cyanide concentrations may reflect the suspended solids
concentrations which were dissolved after sample preservation, rather
than concentrations actually present in the storm water runoff.
In addition, the sample collection location was in a known surficially
contaminated area. The concentrations measured in this sample would be
greatly decreased as this water mixes with other storm water runoff from
uncontaminated areas as it leaves the site.
Surface soil sampling was situated within the major pathway of surface
water runoff leaving the site. No cyanide was detected in the soil
samples, indicating that significant concentrations of cyanide do not
appear to leave the site by the drainage pathway.
Contaminant Sources
Based on the evaluation of the milling process, findings of previous
investigations and the RI field investigation, the sources of
environmental contamination at the Cimarron site are cyanide and
elevated metals within the processed waste material (tailings piles I,
C and K and cinder block trench sediment piles J and L), cyanide solution
and tailings spillage areas (around process facilities), and cyanide
solution recycling and disposal areas (cinder block trenches and the
discharge pit). Contaminated material is also present in the on-site
process tanks and in process chemical drums, however that material is
contained and does not presently serve as a source of contaminant transport
to the environment. Negotiations with the site bankrupty trustee has
resulted in an agreement that the process chemical drums will be removed
regardless of the final remedy selected.
The unprocessed waste piles at the site do not contain cyanide, but do
contain elevated levels of various metals.
Evaluation of the ground water contamination at the site indicates that
although some cyanide contamination has occurred below tailings piles,
I, C, and K, the major sources of cyanide contamination of the ground water
are the cinder block trenches, and to a lesser degree, the discharge
pit. During operation of the plant, concentrated cyanide solution was
stored in the cinder block trenches for recycling, and disposed in the
discharge pit. The discharge pit is an unlined impoundment and the
cinder block trenches have cracked, leaky concrete bottoms. Based on
these findings, and the findings of the application of the computer
34
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modeling, it is surmised that most of the ground water contamination
from cyanide occurred during the period of plant operation. These
areas of continual contact of cyanide solution with underlying soils
would have established saturated conditions to the ground water surface,
allowing direct communication between contaminated liquids and the
ground water. Since direct contact of cyanide solution to the soils
has not occurred since the mill closed in 1982, it is expected that
current transport of cyanide contamination to the ground water is
negligible. Without continued contact with overlying cyanide solution,
the saturated conditions would disappear.
Re-formation of saturated conditions between the surface source areas
at the site and the ground water surface is unlikely due to the dry
climate of the Carrizozo area and the vertical length of the current
saturation break (dry soils) between the ground surface and the ground
water surface (30 ft). This is supported by the results of the computer
modeling application.
The computer modeling application did not, however, consider collection
of runoff water. The cinder block trenches and the discharge pit act
to collect storm runoff water from their surrounding areas. This
increases the chances of infiltration to the ground water during storm
events, but this potential migration route could be closed by filling
in and grading those locations.
The findings of the computer modeling application can also be applied to
assessment of contaminant migration from the tailings piles. As is the
case for the cinder block trenches and the discharge pit, tailings piles
I, C and K would have created saturated conditions to the ground water
during the period of plant operation. The tailings were applied
to their disposal locations in a slurry form.
VI. Summary of Site Risks
An assessment of the potential human health risks associated with the
existing conditions at the Cimarron Mining Site was prepared using the
standard four step risk assessment process. In the first step, Hazard
Identification, the nature of the risks potentially posed by the site
is qualitatively identified. This includes determination of the contami-
nants present at the site, their toxic effects, and identification of
potentially exposed populations and possible exposure pathways. In the
next two steps, Exposure Evaluation and Toxicity Assessment the two
necessary components of risk (exposure and toxicity) are further examined
and are quantified to the extent possible. Finally, in the fourth step,
Risk Characterization, exposure and toxicity data are combined to develop
estimates of health impacts.
35
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Hazard Identification
The initial step in performing a human health risk assessment
consists of a qualitative evaluation of the potential risks posed
by the site. This includes assessment of the presence of
potentially toxic compounds at the site and of the potential for
human exposures to these compounds.
The Cimarron site ceased operation as a milling facility in 1982.
No occupational activities have taken place on the site since that
time. Therefore, occupational exposures are not included in this
health risk assessment. The pathways representing the greatest
current potential for exposure to contaminants at the site are
incidental soil contact and ingestions during visits to the site,
and inhalation of fugitive dusts migrating from the site.
Contaminant exposures via these pathways to current residents of
Carrizozo nearest to the site are one focus of this assessment.
In addition, to assist in the determination of appropriate
remediation strategies for this site, several potential future
exposure scenarios are also evaluated. These include evaluation
of soil ingestion and inhalation of dust for potential future
onsite residents.
Exposure Assessment
Following hazard identification, a more detailed examination of
potential exposure routes is undertaken. Potential exposures to
contaminants and the corresponding health risks under current
conditions in the site area and for a hypothetical future residential
population on the site are evaluated. Specifically, potential risks
from incidental ingestion and dermal contact with soils and
sediments at the site, inhalation of contaminated dusts, and
consumption of contaminated ground water are assessed. Once potential
exposure populations and pathways have been identified, the
magnitude of exposures via each pathway are estimated in a two
step process. First, contaminant concentrations in the
environmental media of concern (e.g.; water, air, or soil) are
determined using either monitoring data or environmental models.
Then, human exposures or contaminant intake rates are quantified
based on data and assumptions regarding environmental intake
rates, physiological parameters, and activity patterns. The
1 ik^'i i (vj'jd of occurrence of each exposure pathway and the
potential existence of subpopulations with special susceptibilities
to particular contaminants or exposures are also considered.
36
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The environmental media of primary concern at the Cimarron site
are ground water, soil, and air (contaminated with fugitive dust).
Surface water and sediments do not appear to play a major role in
exposures in the vicinity of the site.
The nature of the inorganic contaminants present at the site
suggests that dermal absorption will not contribute significantly
to exposures, as these substances are typically poorly absorbed
through the skin. Ingestion of contaminants, via drinking water
or incidental ingestion of soil, and inhalation of fugitive dust
present the most significant routes of exposure. Ingestion of
agricultural croos affected by site contaminants, e.g., crops
irrigated with contaminated ground water or cattle ingesting
contaminants via water and grazing, may also contribute to total
exposures, however, the magnitude of exposure from this pathway is
expected to be insignificant relative to the primary pathways identi-
fied above.
- Surface Soils and Waste Piles
Direct contact with contaminated soils typically is a primary
pathway of contaminant exposure, particularly where such soils
occur close to residential areas. As discussed above, however,
the Cimarron site is not in immediate proximity to any residential
areas, nor does it offer any identified recreational opportunities.
Therefor^, it is unlikely that, under current conditions, any
individual would visit the site with high frequency or that
regular, ongoing exposures vial soil contact would occur.
Occasional visitation, however, is possible, and could result in
direct contact with soils at the site.
Potentially, future exposures which differ in character from
current exposures could take place if development were to occur on
or near the site. As with occasional visitation, exposures via
contaminated soils could occur following direct contact with soils
if such a development were to occur, and exposure routes would
include absorption following dermal contact with soils and
incidental ingestion. Under a residential scenario, such
exposures can be assumed to occur daily over the entire duration
of residence on the site. In light of census data for the region
indicating that the population of Carrizozo is relatively stable,
with a less than 5% increase in population between 1970 and 1988,
the probability of any residential development on the site is
negligible. To be thorough in the evaluation and to assist in
assessment of remedial options for the site, however, exposure from
onsite residence is included in the exposure assessment and risk
character!zation.
37
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- Subsurface Soils
Exposures to soils more thar, six inches below the surface have
been excluded from this assessment because significant contact with
these soils is unlikely under the scenarios evaluated. Elimination
of these soils from the evaluation will not alter exposure or risk
estimates, as the concentrations of contaminants at the site were
found to diminish significantly with soil depth.
- Tank Sediments
Contaminated sediments stored in tanks on the site present no
avenue for exposure under current conditions because the sediments
are contained and virtually inaccessible at this time. In the
event that one of these tanks should rupture, or the contained
sediments should otherwise be dispersed or, the ground, exposures
could occur following direct contact with the sediments. In such
an instance, exposures would be similar to those for exposure to
soils and waste piles, as described above.
- Air
The exposed, unvegetated soils present at the site may be subject
to wind erosion. Following erosion, soils may be carried by the
wir.a, and individuals downwind of the site could be exposed to
site contaminants via inhalation of windblown dust. Additionally,
such exposures could be experienced by individuals onsite
following potential future development of the area. The magnitude
of exposure depends on how well the surface material is entrained;
particle size; concentration of contaminants in the dust; wind
speed and direction; duration of exposure; and numerous other
factors that influence suspension and transport of dry soils.
- Ground water
Data obtained during the remedial investigation indicate that
ground water in the shallow aquifer under the site is contaminated
with cyanide, and also contains elevated concentrations of some
metals. No current exposures to contaminated ground water are
believed to be occurring, as samples from residential wells, and
site data, indicate that the residential wells have not been
impacted by site contamination. Additionally, the residential
wells are completed in different deeper ground water units than
the contaminated shallow water body under the site.
38
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Potentially, future exposures could occur if ground water from the
shallow aquifer under the site were to be used as a source of potable
water. Development of water from the shallow aquifer located under
the site, however, is unlikely due to several factors. Due to high
mineral content, the palatability of the water in the shallow aquifer
is poor, and therefore does not present an attractive source of domestic
water. Hydrogeologic and hydraulic information also indicates that
withdrawl of water from this aquifer is difficult and may not provide
enough water for household use. Based on these factors, the site
ground water unit can be characterized as a Class IIIA aquifer.
Additionally, if the site was to ever be developed as residential
area, the city of Carrizozo water distribution system would likely be
used as the water supply. However, to provide an indication of possible
health risks that might arise should this water be tapped for domestic
uses, consumption of this water is evaluated.
- Surface Water
No bodies of surface water or perennial streams exist on the site
or in nearby areas. Some drainage occurs across the site following
storms. Because of soil absorption and evapotranspiration in the
arid environment, however, all surface water disappears within a
few days. Due to the ephemeral nature of surface water at and, in
the area of the site, it is not considered to present a significant
pathway for human exposures to contaminants, and is not included
further in this evaluation.
Toxicity Assessment
The toxicity assessment portion of the risk assessment compiles
available information on the potential adverse health impacts of
the contaminants of concern. This includes a qualitative
discussion of the types of effects associated with each
contaminant, the nature of the evidence indicating each type of
effect, available dose-response data and toxicity factors, and an
evaluation of the certainty of the qualitative and quantitative
toxicity information. Identified quantitative toxicity factors,
e.g., reference dose (RfDs) for noncancer health effects and
cancer potency factors (CPFs) for carcinogens, are used to
calculate risk estimates.
39
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Cancer potency factor (CPF's) have been developed by EPA's
Carcinogenic Assessment Group for estimating excess lifetime cancer
risks associated with exposure to potentially carcinogenic chemicals.
CPFs, which are expressed in units of (mg/kg-day)~l, are multiplied
by the estimated intake of a potential carcinogen, in mg/kg-day, to
provide an upper-bound estimate of the excess lifetime cancer risk
associated with exposure at that intake level. The term "upper bound"
reflects the conservative estimate of the risks calculated from the
CPF. Use of this approach makes underestimation of the actual cancer
risk highly unlikely. Cancer potency factors are derived from the
results of human epidemiologies! studies or chronic animal bioassays
to which animal-to-human extrapolation and uncertainty factors have
been applled.
Reference doses (RfDs) have been developed by EPA for indicating
the potential for adverse health effects from exposure to chemicals
exhibiting noncarcinogenic effects. RfDs, which are expressed
in units of mg/kg-day, are estimates of lifetime daily exposure
levels for humans, including sensitive individuals. Estimated intake
of chemicals from environmental media (e.g., the amount of a chemical
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).
These uncertainty factors help ensure that the RfDs will not
underestimate the potential for adverse noncarcinogenic effects to
occur.
Risk Characterization
In the risk characterization, quantitative estimates of exposure
and toxicity are combined to develop estimates of human health
risk. Both carcinogenic and noncarcinogenic health impacts are
examined. Where appropriate, risks encountered via different
exposure pathways are combined to develop estimates of overall
risks to total exposures associated with the site. Corresponding
with exposure estimates, conservative screening level estimates of
individual risks are calculated in most of the scenarios examined.
Summary of Baseline Risk Estimates
Potential exposures to the site contaminants and the corresponding
health risks under current conditions in the area and for a
hypothetical future resident population on the site are evaluated
40
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in the endangerment assessment. Specifically, potential risks from
incidental ingestion and dermal contact with soils and sediments
at the site, inhalation of contaminated dusts, and consumption of
contaminated ground water are assessed.
Incidental ingestion of soil was evaluated for exposures by adults
and children from Carrizozo and for hypothetical future on-site
residents. Soil ingestion did not result in contaminant exposures
in excess of the acceptable health based limits in any of the scenarios
examined.
Excess lifetime cancer risks are determined by multiplying the intake
level with the cancer potency factor. 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 plausible upper-bound, an individual has a one in one million
chance of developing cancer as a result of site-related exposure to a
carcinogen over a 70-year lifetime under the specific exposure condi-
tions at a site.
The cancer risk value associated with onsite residence (2.9 x 10"5)
is higher than for the other soil ingestion scenarios evaluated.
This finding is expected since this scenario assumes 30 years of
daily exposure, whereas the risk values for adults and children in
Carrizozo are based on a single visit. Excess lifetime cancer
risks associated with soil ingestion are 2.3 x 10"9 and 4.7 x 10"9
for Carrizozo adults and children, respectively. Under the
scenarios described above, to reach an incremental risk of 10"6,
an adult would have to visit the site more than 430 times (or once a
month for more than 35 years). A young child would have to visit
the site more than 210 times, or once per week for 4 years, to
.achieve this risk level.
Due to the low absorption of contaminants across skin, risks
associated with dermal absorption from soil are significantly
lower than those associated with incidental ingestion. Using the
assumptions for Carrizozo child dermal exposures to soil, a young
child would have to visit the site 4000 times, or daily for 11 years, '
to attain an incremental lifetime cancer risk of 10"6.
41
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Inhalation exposures to site contaminants by residents of the
town of Carrizozo result in an excess lifetime cancer risk of
4.7 x 10*8. Actual risk is likely to be significantly lower
since the primary contributor to this value is hexavalent
chromium. In the absence of information on chromium speciatior,,
these calculations conservatively assumed that all of the
chromium reported in site samples was in this form, an assumption
which is likely to overestimate the amount of hexavalent chromium
actually present at the site. Inhalation exposures by
hypothetical future onsite residents are ten-fold higher, with a
total excess lifetime cancer risk of 4.7 x 10"7. Again, this
value is due mostly to an assumed exposure to hexavalent chromium.
Potential concern for noncarcinogenic effects of a single contaminant
in a single medium is expressed as the hazard quotient (HQ) (or the
ratio of the estimated intake derived from the contaminant
concentration in a given medium to the contaminant's reference dose).
By adding the HQs for all contaminants within a medium or across all
media to which a given population may reasonably be exposed, the
Hazard Index (HI) can be generated. The HI provides a useful
reference point for gauging the potential significance of multiple
contaminant exposure within a single medium or across media.
Ground water contained in the shallow aquifer under the site
contains eleven compounds at concentrations that are elevated
above established MCL values. Of these, oral RfD values exist for
five compounds; chromium, cyanide, manganese, nitrate, and
selenium. Evaluation of risks associated with consumption of
these compounds at the maximum concentration detected in the
ground water indicates possible RfD exceedance for cyanide and
nitrate by adults and for chromium, cyanide, and nitrate by a
child. None of the compounds present at values above the MCL are
believed to be carcinogens following oral exposure. The
noncarcinogenic Hazard Index derived from the potential RfD
exceedance is 4.1 for adults and 9.5 for children.
As part of the baseline risk assessment for the Cimarron Mining
Site, an environmental risk assessment was performed to evaluate
potential ecological hazards posed by site contamination. The
purpose of this risk assessment is to quantify, to the extent
possible, harmful ecological effects to terrestrial fauna and
flora inhabiting the site or potentially coming into contact with
site-related materials.
The specific literature was searched for information on
environmental impacts of cyanide and cyanide compounds. Special
emphasis was placed on those studies involving species and
ecosystems similar to those found at the site. As reported below,
limited data were located for certain of the animal species found
at the site, including coyotes, wild birds, and rabbits.
42
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The primary medium of concern for ecological exposures is
contaminated soil which may be incidentally ingested during
feeding or may be in contact with plant roots. Soil
concentrations used in the exposure scenarios were developed based
on review of the available data on cyanide concentrations in the
various types of soil samples collected at the site.
Available data in the literature on cyanide toxicity to plants
were insufficient to perform a quantitative evaluation and an
assessment of plant ecological risk was not possible. No data are
available to allow assessment of toxic concentrations in soil.
However, it should be noted that cyanide has not been detected in
any of the wells reportedly used for irrigation purposes.
Analyses performed based on available data indicate virtually no
concern for ecological hazards due to cyanide at the Cimarror,
site. For both coyotes and rabbits, estimated intake rates were
well below reported oral lethal doses. For coyotes, the most
probable case hazard quotient was in the no concern range. For
rabbits, the most probable case hazard quotient was in the
possible concern range, however, this value was obtained using
very conservative assumptions. Since local wild bird species
reportedly do not tend to feed on the ground surface, exposure and
consequent potential hazard are likely to be negligible. No
quantitative estimates could be made for effects or, plant species
due to lack of appropriate toxicity data.
VII. Description of Alternatives
Remedial Objectives
Remedial action objectives are proposed in order to protect human
health and the environment. The objective specifies the
contaminant(s) of concern, exposure routes's) and receptors^s) ,
and an acceptable contaminated range for each exposure route.
Preliminary remediation goals are based, where possible, on the
baseline risk assessment and Federal and State ARARs.
As determined by the Endangerment Assessment concentrations of
cyanide and metals in soils, waste piles and sediment at the
Cimarron site do not constitute the need for remedial action.
Site ground water, however, has been impacted by cyanide and
associated nitrate contamination to a degree that remedial action
is considered appropriate. Although federal drinking water standards
are not considered due to the characterization of the site ground water
as Class IIIA, remediation is appropriate in the source area ground water
so as to control potential impacts of migration from the contaminated
upper ground water zone to potential underlying drinking water aquifers.
43
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Also, consideration has been given to utilizing the New Mexico Water
Quality Control Commission Regulations (NMWQCCR) standard of 200 ug/1
cyanide as a remediation goal due to the potential future beneficial
use of the shallow ground water as a source of drinking water. NMWQCCR
require protection of all ground water of less than 10,000 mg/1 total
dissolved solids. The table below outlines the final remediation
goal and corresponding risk.
Remediation Goal and Corresponding Risk
Final Remediation Goal Corresponding Risk Level
Remediation Point of Reasonable Maximum Exposure
Medium Chemical Goal Compliance Pathway Risk (HAZARD INDEX*)
Child Adult
Ground Cyanide 200 ug/1 On Site .1 .3
Water Shallow
Ground Water
*Values represent the greatest estimated risks to an individual or group subject
to reasonable maximum exposures assuming a hypothetical onsite residence
utilizing the shallow ground water as a source of drinking water. A hazard
index less than or equal to 1 anticipates no adverse health effects over a
lifetime exposure.
The degree of metals contamination in the site ground water does not
constitute a need for specific remedial action towards those metals.
The degree and extent of cyanide contamination in site ground water
was defined during Remedial Investigations. The major sources of
that contamination were the cinder block trenches and, to a lesser
degree, the discharge pit during the period of plant operation.
Continued migration of contamination from these source areas to
the ground water is expected to be minimal since application of the
computer modeling indicates that infiltration of precipitation to
the ground water at the site occurs in only small amounts due to site
lithology and area cl imatography. Migration of the contamination
apparently occurred during the period of plant operation when saturated
conditions would have existed between the surface sources and the
around water surfaces.
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As shown In Figure 13, the area of highest cyanide contamination
of ground water (exceeding approximately 200 ug/L total cyanide)
is in the area of the cinder block trenches, treatment of
ground water in this area of the site would effectively address
cyanide contamination in the shallow zone and the potential impact of
migration to lower drinking water aquifers.
Accordingly, remedial action alternatives for the site focus on
removal of the heavily contaminated area of shallow ground water below
the cinder block trenches, with some continued monitoring to ensure
long-term effectiveness.
The computer modeling application did not, however, consider collection
of storm runoff water at the source areas of the site. The cinder
block trenches and the discharge pit act to collect storm runoff
water from their surrounding areas. This increases the chances of
infiltration to the ground water during storm events, but this
potential migration route could be alleviated by filling in and
grading those locations.
Potential remedial action alternative technologies were evaluated
to address the shallow ground water contamination at the Cimarron
site. This evaluation was performed by progressing through the series
of analyses which are outlined in the National Contingency Plan,
(NCP), in particular, 40 CFR Section 300, along with various guidance
documents issued by the EPA, Office of Solid Waste and Emergency Response
(OSWER).
This process addresses the Superfund Amendments and Reauthorization Act
(SARA) Section 121 requirements of selecting a remedial action
that is protective of human health and the environment, that is
cost-effective, that at least meets Federal and State
requirements that are applicable or relevant and appropriate, and
that utilizes permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable. Additionally, SARA Section 121 and the
guidance documents referenced above require EPA to give preference
to remedies which employ treatment which permanently and
significantly reduces the mobility, toxicity, or volume of
hazardous substance as their principal element.
45
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Alternate technologies were identified using best engineering
judgement following the guidelines presented in Guidance for
Conducting Remedial Investigations and Feasibility Studies Under
CERCLA (EPA, 1988), Guidance on Remedial Actions for Contaminated
Ground water at Superfund Sites (EPA, 1988), and the Handbook for
Remedial Action at Waste Disposal Sites (EPA, 1988).
The initial step in determining the appropriate remedial action
for the Cimarron Mining site was to identify suitable remediation
technologies. A review and analysis of the available remediation
methods was conducted and feasible alternatives were developed and
are presented in Table 4.
A total of six alternatives for the Cimarron site remediation were
analyzed in detail. The alternatives consist of the following:
Alternative 1 - No Action
Alternative 2 - Institutional Controls
Alternative 3 - Pump and Evaporate Ground Water
Alternative 4 - Pump and Discharge Ground Water to POTW
Alternative 5 - Pump, Treat and Discharge Ground Water to POTW
Alternative 6 - Pump, Treat and Recharge Ground Water
The detailed evaluation process is a structured format, designed to
provide relevant information needed to adequately compare and evaluate
feasible alternatives to allow selection of an appropriate remedy for the
site by EPA through the Record of Decision (ROD) process. The remedy
must meet the following statutory requirements:
o Be protective of human health and the environment;
o Attain ARARs (or provide ground for invoking a waiver):
o Utilize permanent solutions and alternative treatment technologies or
resource recovery technologies to the maximum extent practicable; and
o Satisfy the preference for treatment that reduces toxicity, mobility,
or volume as a principal element, or provide an explanation in the
ROD as to why it does not.
Nine evaluation criteria have been developed to address the statutory
requirements listed above and to address additional technical and policy
considerations that have proven to be important for selecting remedial
alternatives. These criteria are listed and briefly described below:
46
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TABLE 4
GROUNDWATER REMEDIATION ALTERNATIVES
General Respons
Technology Type
Monitoring
Deed Restrictions
on Well
Development
Groundwater
Collection via
Extraction Wells
Oxidation
Treatment
On-Site Disposal
Off-Site Disposal
>e Action
Area or
Volume
All wells
twice per
year
Entire site
Area of
heaviest
cyanide
contamination
Area of
heaviest
cyanide
contamination
Evaporation
Recharge
POTW
1
No
Action
2
Institu-
tional
Controls
3
Pump&
Evaporate
4
Pump&
Discharge
to POTW
5
Pump.
Treat &
Discharge
to POTW
6
Pump,
Treat 4
Recharge
47
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o Overall Protection of Human Health and the Environment - How well
the alternative reduces risks to human health and the environment,
through treatment, engineering or institutional controls.
o Compliance with ARARs - How well the alternative complies with all
applicable or relevant and appropriate requirements or, if a waiver
is required, how it is justified.
o Long-Term Effectiveness and Permanence - How well the alternative
maintains long-term effectiveness in protection of human health and
the environment. Alternatives which afford the highest degree of long-
term effectiveness and permanence are those that leave little or no
waste at the site.
o Reduction of Toxicity, Mobility or Volume through Treatment -
Anticipate performance of the specific treatment technologies that
an alternative may employ and their ability to destroy or
irreversibly treat contaminants.
o Short-Term Effectiveness - How well the alternative protects human
health and the environment during construction and implementation
of a remedy.
o Imp!ementabil ity - Whether the alternative is technically and
administratively feasible and whether the required goods and
services are available.
o Cost - Analysis of capital and O&M costs of each alternative to
determine cost-effective remedies. Cost estimates are developed
with relative accuracy (-30% to +50%) and are presented as
present worth costs so that alternatives can be reasonably
compared.
o State Acceptance - To be completed for the most part after the
public comment period; this criterion describes the preference of
the State or support agency.
o Community Acceptance - To be completed for the most part after the
public comment period; this criterion reflects the preferences of
the community.
Each of the six alternatives for Cimarron ground water contamination are
individually evaluated then comparatively analyzed or. the basis of the
first seven of the nine criteria above. The last two criteria (State and
community acceptance) were fully addressed after the public comment
period.
48
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The No Action alternative (Alternative 1) provides a baseline for
comparing other remedial alternatives for the Cimarron site. Because no
remedial activities would be implemented to mitigate contamination
present at the site under this alternative, long-term human health and
environmental risks for the site are as presented in the baseline risk
assessment. Alternative 1 would consist of continued monitoring on a
periodic basis.
Criteria Assessment
Alternative 1 is implementable, however, it provides no treatment,
engineering, or institutional measures to control the exposure of
receptors to contaminated ground water, with the exception of the agreement
with the bankruptcy trustee regarding removal of the process chemical
drums on site. No reduction in risks to human health and the environment
would occur.
No controls (in addition to the already existing fence) for exposure
and no long-term or short-term site management measures are included
under Alternative 1. This alternative provides no reduction in the
toxicity, mobility, or volume of the contaminated ground water underlying
the site. All existing and potential future risks associated with
the site would remain. With respect to soils, risks are minimal as
presented in the baseline risk assessment. With respect to ground water
the baseline risk assessment indicates noncarcinogenic Hazard Index
of 4.1 for aaults and 9.5 for children. A Hazard Index of less than
or equal to 1 is considered acceptable, with no adverse health effects.
As previously discussed, the shallow aquifer at the Cimarron site can
be classified as a Class IIIA ground water due to its general poor
quality. As a result Federal drinking water standards are not applicable
or relevant and appropriate at the site. Consideration must be given,
however, to the possibility of contamination migrating from the shallow
zone to a usable lower zone. Also, New Mexico Water Ojuality Control
Commission Regulations require protection of all ground water of less
than 10,000 ma/1 total dissolved solids for potential future beneficial
use.as a source of drinking water.
Capital costs are zero since 17 ground water monitoring wells exist at the
site. Annual operation and maintenance costs include semi-annual
ground water sampling and analysis for TAL metals and cyanide for a period
of 30 years. Present worth analysis of O&M costs is based on a discount
rate of nine percent over a 30-year period, and total $32,025.
49
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Alternative 2 - Institutional Actions
Alternative 2 consists solely of institutional control measures designed
to isolate receptors from site-based risks. Under this alternative, no
actual remedial measures to directly address contaminated ground water
are implemented; rather, legal controls, such as site access and land and
ground water use restrictions, are employed to minimize the likelihood of
receptor contact with contaminated media. Monitoring of ground water as
described for Alternative 1 is included under Alternative 2 to ensure
that the risks to human health are being addressed by the institutional
controls.
One institutional control at the Cimarron site consisting of site
restriction by fencing has been previously implemented. Access
restrictions by fencing would be maintained under Alternative 2, as well
as under other site alternatives. Other institutional control measures
that could be implemented consist of land use restrictions or deed
notices, and restrictions and zoning ordinances which would limit
activities on the site. They could possibly include ground water use
restrictions which would prevent the unlikely construction of ground water
extraction wells in contaminated areas. These additional measures
could also be selectively included as elements of other remedial
alternatives.
Criteria Assessment
The use of institutional control measures provides a greater degree of
protection of human health than the No Action alternative alone, since
institutional actions can reduce the potential exposure of receptors.
Access restrictions and ground water use limitations can prevent the direct
ingestion of contaminated ground water. Land use restrictions further
limit activities on the property, and could be implemented in a manner
such that the only activities permitted on-site would minimize potential
exposure.
This alternative does not address the potential for contamination
migration from the site to accessible off-site drinking water aquifers.
Although reduction in the potential for human exposure would be recognized
under this alternative, only limited long-term effectiveness would be
likely due to difficulties in enforcement. Additionally, this alternative
provides no reduction in the toxicity, mobility, or volume of contaminants
at the site through treatment. No short term effectiveness concerns
are identified for this alternative.
50
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Although Alternative 2 is readily implementable, associated costs are
difficult to assess given the potential complexity of rezoning and
establishing deed restrictions or deed notices and ground water use
limitations. Capital expenditures under this alternative include costs
for warning signs and additional fencing, as well as initial
administrative costs for deed, access, zoning and well permitting
restrictings.
Annual costs associated with this remedial action are attributed to
ground water monitoring costs. Total present worth of this alternative is
$145,000. This includes capital costs in combination with the present
worth of annual O&M costs over 30 years at an annual discount rate of
nine percent.
Alternative 3 - Pump and Evaporate Ground water
Description
Alternative 3 consists of collection of contaminated ground water followed
by on-site evaporation, which includes some natural degration. Ground
water collection using extraction wells to bring the shallow ground water
to the surface for treatment is common to Alternatives 3, 4, 5 and 6.
The suggested locations of the recovery wells and monitor wells are also
show, in Figure 14. The number of recovery wells and their locations
was established in the feasibility study merely for comparing various
ground water remediation alternatives. The actual number of recovery
wells and their locations will be further refined in the Remedial
Design in consultation with the New Mexico Environmental Improvement
Division. The suggested locations were chosen for the following
reasons :
o Recovery wells would be located directly adjacent to the primary
source(s) of ground water contamination (the cinder block trenches).
The locations are chosen so as to allow removal of the primary
source of potential continued migration of cyanide contaminated
ground water.
o The wells would be installed deep enough to capture the entire
vertical extent of the area of heaviest ground water contamination,
and provide adequate available drawdown for efficient well pumping.
o The positioning of the wells with respect to nearby monitor wells
(MW-04, MW-05 and MW-10) enable monitoring of drawdown and
ground water quality within the area influenced by the extraction
wel 1 s.
51
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APPROXIMATE
UMFT OF
MEASURABLE
DRAWDOWN
\
\
PROCESSING
PLANT
s
d
TOO
FEET
SCALE: 1" = 50'
1.0' -
LEGEND
PROPOSED EXTRACTION WELL
EXISTING MONfTOR WELL
CINDER BLOCK TRENCHES
DRAWDOWN CONTOUR
FIGURE 14
PROPOSED EXTRACTION WELL LOCATIONS
CAMP DRESSES 8 McKEE INC.i
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Under Alternative 3, water brought to the surface by the recovery wells
will be placed in an on-site evaporation area. Figure 15 shows an on-site
evaporation area of approximately 103,000 ft . This area would be bermedd
around the perimeter from three to nine feet to assure adequate storage
during wet weather periods. A synthetic membrane or other liner system
would be needed to prevent direct infiltration. This liner would be
anchored within the berms, and would be resistant to ultraviolet degradation,
A total suspended solids (TSS) plus total dissolved solids (TDS) concentra-
tion of approximately 4,900 parts per million (ppm) was measured in monitor
well MW-10 ground water during the RI.
Based on an estimated 2,600 Ibs. dry solids per cubic yard (typical),
approximately 51 cubic yards of residual would remain at completion of
the estimated remediation period. The level of contamination of the
residual solids in the evaporation basin would require quantification
prior to disposal of those solids.
Demobilization activities following clean-up would consist of
dismantling the extraction well system, regrading the evaporation area,
and disposal of the liner material.
Alternative 3 would serve to protect human health and the environment
since the contaminated ground water within the source zone would be
collected and evaporated. Residual solids from evaporation would require
analysis prior to disposal. The alternative would be in compliance with
ARARs.
The long-term effectiveness in protecting human health and the
environment is higher for Alternative 3 than for Alternatives 1 and 2, in
that a reduction in toxicity and volume of cyanide in the shallow aquifer
would result. Short-term concerns could be addressed -by ensuring that
the evaporation pond is inaccessible to the public. Alternative 3 is
readily implementable.
The total projected capital cost is $160,900.
Operational costs associated with the system are estimated based on labor
at $60/hour for 24 hours/month over 13 months for a total of $18,800.
Total present worth cost of annual ground Water sampling is $32,025.
Total present worth cost for Alternative 3 is $212,000.
53
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STORMWATER
DIVERSION
DITCH
ADDiTiONALy*
FENCING^
[ARTHEN
TRIMETER
3ERM
'ERFORATED
1PE OVER
:OCK BERM
PUMP
/ /DISCHARG
STORMWATER
DIVERSION
DITCH
FIGURE 15
FEET
SCALE: 1" = 100'
OTE: ELEVATIONS SHOWN ARE FEET
ABOVE 5400 FT. M.S.L
PUMP
ALTERNATIVE 3
EVAPORATE GROUND WATER
-CAMP DRESSER & McKEE INC
-------
Alternative 4 - Pump and Discharge Ground water To POTW
Description
The extraction well design previously described for Alternative 3 is
identical for Alternative 4. A proposed site plan for Alternative 4 is
present in Figure 16. A two-inch diameter PVC well discharge header
would be installed below grade using a trenching machine, the pipe would
be brought above grade and secured inside the existing 24-inch diameter
storm water culvert underneath U.S. Highway 380. On the south side of the
highway, the pipe would be buried for approximately 200 feet to the
existing PVC sewer tap, located above grade. The extraction well pumps
would transport the estimated maximum 6 gpm flow of ground water to this
sewer tap.
The sewer would convey Cimarron ground water several miles to the
Carrizozo POTW. The estimated flow to the POTW is 180,000 gallons per day,
according to Carrizozo plant personnel. The total cyanide concentration
reaching the POTW is estimated to be 208 ug/L, assuming all of the pumped
ground water is contaminated with 4,330 ug/L of total cyanide, which is a
conservative estimate, considering that the average concentration detected
was approximately 1500 ug/1 of total cyanide. For comparative purposes,
Federal and State drinking water standards for total cyanide are both
200 ug/L. All discharges to the POTW will comply with the pretreatment
standard of 5 mg/1 of cyanide as cited in 40 CFR 413.24 Subpart B and
deemed relevant for this action.
Biological activity with the existing treatment lagoons, coupled 'with
effluent chlorination and photodecomposition, would constitute treatment to
further reduce the cyanide concentration.
Criteria Assessment
Alternative 4 would provide overall protection of human health and the
environment by reducing the mobility and volume of cyanide in the
shallow aquifer. The toxicity of cyanide would be reduced through
treatment at the POTW.
The long-term risks associated with the Cimarron ground water
contamination would be minimized. Short-term risks could be addressed by
ensuring that the sewer hookup is inaccessible to the public.
Alternative 4 could be readily implemented, since no special technologies
would be required and the pretreatment regulations which exist regarding
discharge to waters from CERCLA sites to POTWs would be met.
55
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EXISTING 24'0
CULVERT
TIE IN TO
EXISTING
PVC
SEWER TRAP
FEET
SCALE: 1" = 100'
t: ELEVATIONS SHOWN ARE FEET
ABOVE 54-00 FT. M.S.L
FIGURE 16
PUMP
ALTERNATIVE 4
DISCHARGE GROUND WATER TO POTW
CAMP DRESSER it McKEE INC.*
56
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Capital costs for Alternative 4 are estimated at $43,?00. System
operating costs are estimated at $18,800, based or, 13 months of
operation, as described for Alternative 3.
As presented for Alternative 3, present worth O&M costs associated with
continued ground water monitoring would total $32,025. Total present worth
cost of Alternative 4 is $95,000]
Alternative 5 - Pump, Treat and Discharge to POTW
Description
Alternative 5 consists of an extraction well system identical to
Alternatives 3 and 4. Once above grade, all ground water would be treated
prior to discharge to the POTW. The treatment system is illustrated in
schematic form in Figure 17, and the site plan is presented as
Figure 18. Treatment using the alkaline chlorination technology would
occur in an existing 20-feet square by 10-feet deep solution tank. The
tank would be fitted with a beam-mounted mechanical mixer designed to
disperse chemical additions. Two relatively simple chemical feed systems
would be required; one for liquid hypochlorite and one for a liquid
caustic, such as sodium hydroxide. Chemical storage in drums would be
sufficient.
Automatic system control would be accomplished using a programmable logic
controller. This would minimize the labor cost for treatment operations.
Additionally, an alarm tank level sensor would automatically shut off the
extraction well pumps if the water level approached overflow conditions.
A large portion of the cyanide is expected to be amenable to
chlorination; however, further analysis would be required as part of a
design investigation or preliminary design investigation prior to
implementation of an alkaline chlorination treatment system. Influence of
the treatment system on suspended solids contamination would also be
evaluated.
Discharge of treated ground water to the POTW in the same manner described
for Alternative 4 is illustrated in Figure 19.
Alternative 5 is evaluated so as to provide a POTW discharge option which
includes prior treatment. This alternative provides overall protection
of human health and the environment by reducing the toxicity and volume
of cyanide in the shallow aquifer.
S7
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MIXER
SAMPLE
PORT
CONTROL/
ISOLATION
VALVE
FLOW
METER
CHECK
VALVE
TYPICAL OF 3 WELLS
COMMON
WELL
DISCHARGE
HEADER
LIQUID CHLORINE
METERING PUMP
AND
CHEMICAL DRUM
CAUSTIC METERING
PUMP AND
CHEMICAL DRUM
TO POTW
EXISTING TANK DISCHARGE PUMP
FIGURE 17
PROCESS SCHEMATIC
ALKALINE CHLORINATION PROCESS
CAMP DRESSER 8 McKEE INC.
58
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EXISTING 24"0
CULVERT
FEET
SCALE: 1" = 1001
TIE IN TO
EXISTING
PVC
SEWER TRAP
NOTE: ELEVATIONS SHOWN ARE FEET
ABOVE 5400 FT. M.S.L
SANITARY SEWER
FIGURE 18
ALTERNATIVE 5
PUMP, TREAT & DISCHARGE TO POTW
-CAMP DRESSER & McKEE INC.-
59
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The long-term risks associated with the Cimarron ground water contamination
would be minimized, as significant cyanide destruction using alkaline
chlorination would be accomplished, and further natural degradation processes
could occur in the POTW. Short-term risks could be addressed by ensuring
that the sewer tap discharge point is inaccessible to the public.
Alternative 5 would be technically implementable, however, more specialized
skills would be required for design and operation when compared with
Alternatives 1 through 4.
Capital costs for Alternative 5 are estimated at $85,700. System
operating costs are $18,800 based on 13 months of operation, as described
for Alternative 3.
As presented for Alternative 3, present worth O&M costs associated with
continued ground water monitoring would total $32,025. Total present
worth cost of Alternative 5 is $136,000.
Alternative 6 - Pump, Treat and Recharge Ground water
Description
Alternative 6 consists of an extraction well and treatment system
identical to Alternative 5, but a different treated water disposal
system. In Alternative 5, treated ground water would be recharged
on-site (Figure 19). A combination of evaporation and infiltration
would result. The recharge area could be bermed as described in
Alternative 3 to isolate the recharge area from storm water additions
and possible subsequent overfill.
Long-term risks associated with the Cimarron ground water contamination
would be minimized as significant cyanide destruction using alkaline
chlorination would be accomplished. Short-term risks could be addressed
by ensuring that the on-site recharge area is inaccessible to the public.
Alternative 5 would be technically implementable, however, as for
Alternative 5, more specialized skills would be required for design and
operation when compared to Alternatives 1 through 4. Alternative 6 would
also be more expensive that Alternative 5 due to recharge area
construction costs, and might require more stringent monitoring to ensure
effective treatment is occurring, so as to prevent recharge of
contaminated water.
Capital costs for Alternative 6, are estimated at 132,700. System costs
are estimated at $18,800 based on 13 months of operation, as described
for Alternative 3.
60
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STORMWATER
DIVERSION
DITCH
ADDITIONAL
FENCIN
EARTHEN
PERIMETER
BERM
PERFORATED
PIPE OVER
ROCK BERM
STORMWATER
DIVERSION
DfTCH
FEET
SCALE: 1" = 1001
NOTE: ELEVATIONS SHOWN ARE FEET
ABOVE 5400 FT. M.S.L
FIGURE 19
ALTERNATIVE 6
PUMP, TREAT & RECHARGE GROUND WATER
CAMP DRESSER & McKEE INC.-
61
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As presented for Alternative 3, present worth O&M costs associated with
continued ground water monitoring would total $32,025. Total present
worth cost of Alternative 6 is $184,000.
VIII. Summary of Comparative Analysis of Alternatives
Comparison of Alternatives
o Overall Protection of Human Health and the Environment
With respect to overall protection of human health and the
environment, Alternative 1 provides none other than the already
existing fence at the site. Alternative 2 provides some
protection by limiting future site uses. Alternatives 3 through
6 provide the most protection by reducing the concentration of
cyanide in the site shallow ground water which could potentially
migrate to lower drinking water zones.
o Compliance With ARARs
Compliance with drinking water and water quality criteria is met
by all of the treatment alternatives. The No-Action and
Institutional Controls alternative would not meet the New Mexico
Water Quality Control Commission Regulation which requires
protection of all ground water of less than 10,000 mg/1 of total
dissolved solids for potential future beneficial use as a
source of drinking water.
o Long-Term Effectiveness and Performance
Longer-term effectiveness and performance would be nonexistent
for Alternative 1 and difficult to ensure for Alternative 2
because of enforcement requirements. Long term effectiveness
and performance of Alternatives 3 through 6 'however, would be
considerably higher because of associated reduction of
contamination in the shallow aquifer.
o Reduction of Toxicity, Mobility or Volume Through Treatment
Reduction of toxicity, mobility or volume through treatment
would be achieved in Alternatives 3 through 6. Alternatives 3,
5 and 6 would provide treatment by site processes. Alternative 4
would rely on treatment through chlorination and natural degradation
processes within the POTW.
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o Short Term Effectiveness - (How well the alternative protects
human health and the environment during construction and
implementation of a remedy) Short term effectiveness is zero for
Alternative 1 since no actions would be taken. Alternative 2
short term effectiveness is relative to the speed at which
institutional controls are implemented. Alternatives' 3 and 6
short term effectiveness could be addressed by ensuring that the
evaporation pond or recharge area are inaccessible to the
public. Alternatives' 4 and 5 short term effectiveness could be
addressed by ensuring that the sewer tap discharge point is
inaccessible to the public.
o State Acceptance
The New Mexico Environmental Improvement Division (NMEID) has
concurred on the selected remedy. (Letter from Dr. Kirkland Jones
dated 6/22/90 and official statement at public meeting 7/30/90).
o Community Acceptance
The City of Carrizozo, the New Mexico Bureau of Mines and the
citizens of Carrizozo support the selected remedy.
o Implementability
All of the alternatives are technically and administratively
implementable. Alternative 1 is most easily implemented.
Alternative 2 requires long term management of the institutional
controls. Alternative 3 is easily implementable due to the
technical simplicity of installing and maintaining an extraction
well system and an evaporation basin. Alternative 4 is easily
implemented from a construction standpoint, however,
coordination and agreement with the City of Carrizozo regarding
use of the POTW would require some legal and administrative
effort. Alternative 5's implementability is the same as
Alternative 4 except that an on-site treatment system would be
constructed. This would increase construction and maintenance
effort, but could reduce the administrative, legal and
analytical effort required under Alternative 4. Alternative 6
implementability is similar to that of Alternative 4, except
that a chemical treatment system would have to he constructed
and maintained. Additionally, more stringent monitoring of
effluent contaminant levels would be required under Alternative
6 than for Alternative 3.
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o Cost
Present worth costs of the six alternatives are as follows:
Alternative 1: $32,000
Alternative 2: 145,000
Alternative 3: 212,000
Alternative 4: 95,000
Alternative 5: 136,000
Alternative 6: 184,000
None of these costs consider the additional preventative remedial option
of filling in the cinder block trenches and the discharge pit to ensure
that on-site precipitation runoff will not collect and infiltrate to
ground water. Estimated additional cost is $10,000. Additionally,
Alternative 4 and 5 might require on-site sedimentation prior to
discharge to the POTVI. This would increase costs of these alternatives
by approximately $10,000.
Alternative 4:
IX. Selected Remedy - Pump and Discharge Shallow Ground Vlater to POTW
As stated in the risk assessment, soil contamination at the Cimarron
site is below action levels, and the ground water contaminant of
concern is cyanide.
A proposed site plan for the selected remedy is presented in Figure 17.
Extraction well pumps would transport an estimated maximum 6 gpm
flow of ground water to a sewer tap located approximately 200 feet
south of the site.
The sewer would convey Cimarron ground water several miles to the
Carrizozo POTW. The estimated flow to the POTW is 180,000 gallons
per day, according to Carrizozo plant personnel. Total cyanide
concentration reaching the POTU is estimated to be 208 ug/1,
assuming all of the pumped ground water is contaminated with
4,330 ug/1 of total cyanide, which was the highest detected cyanide
concentration. This is a conservative estimate, considering the
average concentration of cyanide detected was approximately 1500 ug/1.
For comparative purposes, Federal and State drinking water standards
for total cyanide are both 200 ug/1. The discharge to the POTW will
comply with the pretreatment standard of 5 mg/1 of cyanide as cited
in 40 CFR 413.24 Subpart B and deemed relevant for this action.
Biological activity with the existing treatment lagoons at the POTW,
coupled with effluent chlorination and photodecomposition, will constitute
treatment to further reduce the cyanide concentration.
This remedy also includes filling in the cinder block trenches and
discharge pit, plugging the abandoned water supply well and inspection
and maintenance of the existing fence.
64
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Based or, calculations, an estimated 133,242 Ibs of suspended solids
could be introduced to the POTW. Potential impacts of contaminated
solids have not been quantified. If, however, the solids are found
to be a problem during the Design Investigation, they will be
removed at the Cimarron site, by sedimentation, prior to discharge
of the ground water to the POTW.
The goal of this remedial action is to restore the ground water to
its potential future beneficial use as a drinking water aquifer,
as required by the New Mexico Water Quality Control Commission
Regulations. A remediation goal of 200 ug/1 of cyanide will be
utilized, if possible, for the shallow ground water. Based on
information obtained during the remedial investigation, and the
analysis of all remedial alternatives, EPA and the New Mexico
Environmental Improvement Division believe that the selected remedy
will achieve this goal. Ground water contamination may be
especially persistent in the immediate vicinity of the contaminants'
source, where concentrations are relatively high. The ability to
achieve cleanup goals at all points throughout the area of
attainment, or plume, cannot be determined until the extraction
system has been implemented, modified as necessary based on engineering
design changes and plume response monitored over time. If the selected
remedy cannot meet the health-based remediation goals, at any or all
of the monitoring points during implementation, contingency
measures and goals as discussed below may replace the selected remedy
and goals. Such contingency measures may also include ground water
extraction and onsite treatment. These measures are still considered
to be protective of human health and the environment, and are technically
practicable under the corresponding circumstances.
The selected remedy will include ground water extraction for the
estimated period of 13 months, during which time the system's
performance will be carefully monitored on a regular basis and
adjusted as warranted by the performance data collected during
operation. The operating system may include:
a) discontinuing operation of extraction wells in the area where
cleanup goals have been attained;
b) alternating pumping at wells to eliminate stagnation points; and
c) pulse pumping to allow aquifer equilibration and encourage
adsorbed contaminants to partition into ground water.
65
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If, in EPA's judgement, implementation of the selected remedy clearly
demonstrates, in corroboration with strong hydrogeological and chemical
evidence, that it will be technically impracticable to achieve and
maintain remediation goals throughout the area of attainment, the
contingency plan will be implemented. At a minimum, and as a necessary
condition for invoking the contingency plan, it must be demonstrated that
contaminant levels have ceased to decline over time and are remaining
constant at some statistically significant level above remediation goals,
in a discrete portion of the area of attainment, as verified by multiple
monitoring we!1s.
Where such a contingency situation arises, ground water extraction and
treatment would typically continue as necessary to achieve mass reduction
and remediation goals throughout the rest of the area of attainment.
If it is determined, on the basis of the preceding criteria and the
system performance data, that certain portions of the aquifer cannot be
restored to their beneficial use, all of the following measures involving long-
term management may occur, for an indefinite period of time, as a
modification of the existing system:
a) low level pumping will be implemented as a long-term gradient
control, or containment, measure;
b) chemical-specific ARARs will be waived for the cleanup of those
portions of the aquifer based on the technical impracticability of
achieving further contaminant reduction; and/or
c) institutional controls will be implemented to restrict access to
those portions of the aquifer which remain above health-based goals,
should this aquifer be proposed for use as a drinking water source.
The decision to invoke any or all of these measures may be made during
periodic reviews of the remedial action.
An Explanation of Significant Differences will be issued to inform the
public of the details of these actions when they occur.
Capital costs for the selected remedy are estimated at $43,700. System
operating costs are estimated at $18,800, based on 13 months of operation.
Present worth O&M costs associated with continued ground water
monitoring would total $32,025. Total present worth cost is
$95,000.
66
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If on-site sedimentation were to be included, based on the Remedial
Design Investigation, capital costs would increase by an estimated
$10,000 for on-site tank retrofitting and pumping equipment. As
previously stated, an agreement with the bankruptcy trustee has been
reached regarding the removal of the process chemical drums on site.
X. Statutory Determination
Actual or threatened releases of hazardous substances from this site, if
not addressed by implementing the response action selected in this Record
of Decision (ROD), may present an imminent and substantial endangerment
to public health, welfare, or the environment.
Pumping and discharge to the POTW would provide protection of human
Health and the environment by reducing the mobility and volume of
cyanide in the shallow aquifer. The toxicity of cyanide would be
reduced through treatment at the POTW. Hazard Indices for
noncarcinogens at the site will be less than 1 upon completion of
remedial activities. Additionally, implementation of the selected
remedy will not pose unacceptable short-term risks or cross-media
impacts. The selected remedy also meets the statutory requirement
to utilize permanent solutions and treatment technologies to the
maximum extent practicable.
The long-term risks associated with the Cimarron ground water
contamination would be minimized. Short-term risks could be
addressed by ensuring that the sewer hookup is inaccessable to the
public. The selected remedy could be readily implemented, since no
special technologies would be required; and, pretreatment
regulations which exist regarding discharge to waters from CERCLA
sites to POTWs will be met.
All Federal and State requirements for this remedy that are Applicable
or Relevant and Appropriate (ARARs) can be met through adequate
design and planning.
Long-term effectiveness is achieved through removal and ultimate
destruction of the contaminants of concern. In addition, treatment
is utilized to the maximum extent practicable in this alternative.
This remedy is cost effective in comparison to other
alternatives. The total cost of the selected remedy is estimated to
be $95,000 net present worth collars (+50% or -30%). Five-year
facility reviews will not be necessary for the soils since
67
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contaminants are not above health based levels. Ground water
monitoring will continue for 30 years if sample analysis deems it
necessary.
The selected remedy provides the best balance of tradeoffs among
the selection criteria used to evaluate the six proposed alternatives
for the site, as discussed in Section VIII of this Record of Decision.
Community and state acceptance is favorable to this remedy in
comparison to other alternatives presented during public comment.
XI. Documentation of No Significant Changes
The Proposed Plan for the Cimarron Mining Corporation site was
released for public comment in July 1990. The Proposed Plan
identified Alternative 4, pump and discharge shallow ground water to
the POTU, as the preferred alternative. EPA 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 it was originally identified in the
Proposed Plan, were necessary.
XII. Responsiveness Summary
Community Preferences
The citizens of Carrizozo, town officials and the New Mexico
Bureau of Mines expressed preference for the selected remedy of pump
and discharge ground water to the PQTW for treatment at the public
meeting conductea on July 30, 1990. Local preference was also
indicated in the August 16, 1990, article in the Lincoln County
News, page 1, entitled "EPA, Town concurs with cleanup option".
The New Mexico Environmental Improvement Division has also provided
formal concurrence with the proposed remedy.
Integration of Comments
1. Comment: The Hispanic Community is not aware of the problem at
the Cimarron site. There are some people that live
near the Cimarron mill who speak only Spanish.
Response: In April 1989, prior to the initiation of the
Remedial Investigation at the site, a fact sheet
containing a request form for addition to the EPA
mailing list was produced in Spanish and distributed
in Carrizozo. None of the Spanish-language request
forms were returned. In addition, no indication of a
need for Spanish translation has been expressed at
any of the "open house" or formal public meetings.
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2. Comment:
Response
3. Comment:
Response
Due to the lack of response to the initial Spanish-
language fact sheet and the apparent lack of interest
in Spanish-translation at the public meetings, the
Spanish-language fact sheets were discontinued.
Spanish-language translation will however, be
reconsidered for future fact sheets and meeting
announcements.
The remedial work at the Cimarron site should be
conducted by local residents as much as possible.
Following the Remedial Design EPA will formally
advertise for bids and Federal procurement
regulations will be followed. The contract will be
awarded to the lowest responsive, responsible bidder.
The potential for utilizing local labor would be
through either the contractor that is awarded the
contract or any possible subcontractors.
EPA should take .advantage of local expertise in
reviewing technical documents, inspection reports,
feasibility studies, etc.
EPA agrees and has taken steps to involve the local
community. Beginning in January 1989, EPA has continued
to announce the availability of a Technical Assistance
Grant for use by local residents to obtain technical
expertise to assist in conducting reviews of documents
and gain assistance in interpreting reports. No
requests to obtain a Technical Assistance Grant have
been submitted to date.
EPA has attempted to utilized local expertise by way
of interviews and discussions with previous employees
of the Cimarron mill and those familiar with local
mining and mill practices. This has proven to be
very valuable in identifying the mill processes
utilized at the Cimarron site and the location of
potential contaminant sources. In addition, all Remedial
Investigation and Feasibility Study reports have been
made available for review and comment through the
public comment process.
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4. Comment:
Response:
5. Comment:
Response
6. Comment:
Response
7. Comment:
Response
8. Comment:
How many gallons of the contaminated around water from
the Cimarron site would you have to drink to be a
fatal dose? How toxic is the 4330 ug/1 of cyanide
which was the highest level detected in the
ground water? What are the effects to the body?
The State and Federal Drinking Water Standards for
cyanide have been established at 200 ug/1. Based on
the highest concentration of 4330 ug/1 of cyanide
detected at this site, a fatal adult dose would be
approximately 3.2 gallons. A fatal dose for a child
would be approximately 1/2 gallon. Cyanide primarily
attacks the nervous system with death resulting from
respiratory paralysis. An adult could begin to experience
nervous system disorders after consuming 1/10 of a
gallon and a child after consuming 1/100 of a gallon.
How much money has been spent on the project so far?
(As of July 30, 1990).
The most recent financial report (expenditures
through June 1990) indicates approximately $551,000
has been spent on the Cimarron Remedial Investigation
and Feasibility Study.
Can the contaminated monitoring wells be used to
treat the ground water in-place by putting bleach in
the well to break down the cyanide by chlorination?
The extremely low permeabilities of the underlying
soils would not allow for adequate diffusion and
mixing to treat the area of contamination through
chlorination. Removal of the contaminated ground water
for treatment is the most viable approach.
How many gallons of contaminated ground water will
need to be treated?
Based on the area of contamination and the
permeability of the soils, approximately
3,000,000 gallons.
It seems like an awful lot of money has been spent on
the site.
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9.
Response: The studies required by Super-fund regulation and statute
are very costly due to the extensive sampling, analysis,
and expert consultations required. For this reason
potential Superfund sites are screened before these
studies are begun. For example, of 3,000 possible
hazardous waste sites EPA Region 6 has examined, only 73
were found to present enough risk to be eligible for
study. The average cost of these studies is $750,000
compared to $551,000 at Cimarron. Although by no
means "cheap", the cost of studies at Cimarron was, in
EPA's judgment, the minimum expenditure needed to
characterize what is an environmental problem as well
as what is not a problem (e.g. toxic metals in surface
soils).
Comment: How can we be assured that the POTW can adequately
treat the contaminated ground water?
Response: Water entering the collection system and POTW
effluent and sludges will be sampled to ensure no
adverse impacts to the POTW. The POTW has adequate
capacity and the capability through the chlorination,
aeration and photodecomposition within the treatment
plant to effectively treat the contaminated ground water
from the Cimarron site.
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