[Federal Register Volume 62, Number 146 (Wednesday, July 30, 1997)]
[Proposed Rules]
[Pages 40784-40786]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-19940]
[[Page 40784]]
-----------------------------------------------------------------------
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 300
[FRL-5864-3]
National Oil and Hazardous Substances Pollution Contingency Plan;
National Priorities List
AGENCY: Environmental Protection Agency.
ACTION: Notice of intent to delete Silver Mountain Mine from the
National Priorities List.
-----------------------------------------------------------------------
SUMMARY: The Environmental Protection Agency (EPA) Region 10 announces
the intent to delete the Silver Mountain Mine site (``the site'') from
the National Priorities List (NPL) and requests public comment on this
proposed action. The NPL constitutes Appendix B of 40 CFR part 300
which is the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP), which EPA promulgated pursuant to section 105
of the Comprehensive Environmental Response, Compensation and Liability
Act (CERCLA) of 1980, as amended. EPA and the State of Washington
Department of Ecology (Ecology) have determined that the remedial
action for the site has been successfully executed.
DATES: Comments on this site may be submitted to EPA on or before
August 29, 1997.
ADDRESSES: Comments may be mailed to: Anne D. Dailey, U.S.
Environmental Protection Agency, 1200 Sixth Avenue, Mailstop ECL-111,
Seattle, WA 98101.
Comprehensive information on this site is available through the
Region 10 public docket which is available for viewing by appointment
only. Appointments for copies of the background information from the
Regional public docket should be directed to the EPA Region 10 docket
office at the following address: SUPERFUND Records Center, U.S.
Environmental Protection Agency, Region 10, 1200 Sixth Avenue, Seattle,
WA 98101.
The deletion docket is also available for viewing at the following
location:
County Clerks Office, Okanogan County Courthouse, 149 N. 3rd,
Okanogan, Washington 98840.
FOR FURTHER INFORMATION CONTACT: Anne D. Dailey, U.S. Environmental
Protection Agency, 1200 Sixth Avenue, Mailstop ECL-111, Seattle, WA
98101, (206) 553-2110 or 1-800-424-4372.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Introduction
II. NPL Deletion Criteria
III. Deletion Procedures
IV. Basis of Intended Site Deletion
I. Introduction
The U.S. Environmental Protection Agency (EPA) Region 10 announces
its intent to delete the Silver Mountain Mine site in Okanogan County,
Washington, from the National Priorities List (NPL) and requests public
comment on this proposed action. The NPL constitutes Appendix B of 40
CFR part 300 which is the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP), which EPA promulgated pursuant to
section 105 of the Comprehensive Environmental Response, Compensation
and Liability Act (CERCLA) of 1980, as amended. EPA identifies sites
that appear to present a significant risk to public health, welfare, or
the environment and maintains the NPL as the list of these sites. EPA
and the State of Washington Department of Ecology (Ecology) have
determined that the remedial action for the site has been successfully
executed.
EPA will accept comments on the proposal to delete this site for
thirty (30) days after publication of this document in Federal
Register.
Section II of this document explains the criteria for deleting
sites from the NPL. Section III discusses the procedures EPA is using
for this action. Section IV discusses the Silver Mountain Mine site and
explains how the site meets the deletion criteria.
II. NPL Deletion Criteria
Section 300.425(e)(1) of the NCP provides that releases may be
deleted from, or recategorized on the NPL where no further response is
appropriate. In making a determination to delete a release from the
NPL, EPA shall consider, in consultation with the state, whether any of
the following criteria have been met:
i. Responsible parties or other parties have implemented all
appropriate actions required;
ii. All appropriate response under CERCLA has been implemented, and
no further action by responsible parties is appropriate; or
iii. The remedial investigation has shown that the release poses no
significant threat to public health or the environment and, therefore,
taking remedial measures is not appropriate.
Even if a site is deleted from the NPL, where hazardous substances,
pollutants, or contaminants remain at the site above levels that allow
for unlimited use and restricted exposure, EPA's policy is that a
subsequent review of the site will be conducted at least every five
years after the initiation of the remedial action at the site to ensure
that the site remains protective of public health and the environment.
If new information becomes available which indicates a need for further
action, EPA may initiate additional remedial actions. Whenever there is
a significant release from a deleted site from the NPL, the site may be
restored to the NPL without application of the Hazard Ranking System.
In the case of this site, the selected remedy is protective of
human health and the environment. Consistent with the State Superfund
Contract, Ecology has agreed to take over operation and maintenance of
the site and conduct an annual inspection. EPA has conducted the first
five-year review of the final remedy, and will also perform future
five-year reviews.
III. Deletion Procedures
The following procedures were used for the intended deletion of
this site: (1) All appropriate response under CERCLA has been
implemented and no further action by EPA is appropriate; (2) Ecology
has concurred with the proposed deletion decision; (3) a notice has
been published in the local newspapers and has been distributed to
appropriate federal, state, and local officials and other interested
parties announcing the commencement of a 30-day public comment period
on EPA's Notice of Intent to Delete; and (4) all relevant documents
have been made available in the local site information repositories.
Deletion of the site from the NPL does not itself create, alter, or
revoke any individual's rights or obligations. The NPL is designed
primarily for informational purposes and to assist Agency management.
As mentioned in section II of this notice, Sec. 300.425(e)(3) of the
NCP states that the deletion of a site from the NPL does not preclude
eligibility for future response actions.
For deletion of this site, EPA's Regional Office will accept and
evaluate public comments on EPA's Notice of Intent to Delete before
making a final decision to delete. If necessary, the Agency will
prepare a Responsiveness Summary to address any significant public
comments received.
A deletion occurs when the Regional Administrator places a final
notice in the Federal Register. Generally, the NPL will reflect
deletions in the final update following the Notice. Public notices and
copies of the Responsiveness Summary will be made available to local
residents by the Regional Office.
[[Page 40785]]
IV. Basis of Intended Site Deletion
The following site summary provides the Agency's rationale for the
proposal to delete this site from the NPL.
Site Background and History
Silver Mountain Mine is an abandoned heap-leach mining operation
located approximately six air miles northwest of Tonasket, in Okanogan
County, Washington. The site consists of five acres of range land on a
358-acre tract of privately owned land. The site was placed on the NPL
in 1984 due to concerns about a cyanide-contaminated leachate pond,
saturated mine tailings, and the potential for arsenic and cyanide
contamination of the regional ground water aquifer.
The risk assessment identified arsenic and cyanide as the primary
contaminants of concern. The Remedial Investigation (RI) identified and
evaluated three potential sources of contaminants at the site: the heap
leach pile, the unprocessed rock, and the mine drainage water.
Potential exposure pathways for contaminants were identified as: On-
site soils, on-site surface water, on-site ground water in a shallow
aquifer, and off-site ground water in the region. During the RI, the
highest arsenic levels found were in the mined material (1080 mg/kg)
and in the water from a stock water tank (95 ug/l). Both arsenic and
cyanide were also found in the perched shallow aquifer just at the edge
of the heap leach pile.
The Feasibility Study screened twenty-three various methods of
cleaning up the site. From this list, eight alternatives were developed
and evaluated against criteria listed in the NCP. Alternatives ranged
from capping on-site to treatment and off-site disposal.
Response Actions
The Record of Decision (ROD) for Silver Mountain Mine was signed on
March 27, 1990, and included a number of construction elements to
implement the Remedial Action. In October 1994, EPA completed an
Explanation of Significant Differences (ESD) to document changes in the
Remedial Action due to unforeseen conditions encountered at the site
during implementation of the selected remedy. The remedial action at
the site ultimately included:
--Consolidating and contouring contaminated mine waste overburden and
tailings,
--Covering and capping the site with a soil and clay cap,
--Fencing the site to protect the cap and allow seeded grass cover to
develop,
--Closure of the mine entrance and diversion of the mine drainage so
that it flows away from the site, and
--Deed restrictions on property to protect the cap.
Construction was completed during 1992 and the deed restrictions were
finally obtained in December 1996.
The five-year review inspection occurred on May 27, 1997, and
determined that the remedial objectives have been achieved. The
constructed remedy is performing as designed and is controlling the
risks to human health and the environment as specified in the ROD and
ESD. The cap was in excellent shape with no evidence of subsidence,
erosion, or animal burrows. The grass cover is well established and
provides thorough coverage of the cap; minimal weeds and woody
vegetation were growing on the cap. The mine entrance and mine vent
were both closed and covered with rocks.
Cleanup Standards
The remedial action cleanup activities at the Silver Mountain Mine
site are consistent with the objectives of the NCP and will provide
protection to human health and the environment. The cleanup standards
for the heap leach pile and mine dump materials and the surrounding
soils are 200 mg/kg for arsenic and 95 mg/kg for total cyanide.
According to the data obtained during the construction work, the
cyanide in the soils is below detection (0.5 mg/kg), and the
concentrations of arsenic that remain in the areas that were cleaned up
are less than 100 mg/kg. Risks at the site have been reduced below the
Hazard Index of 1.0 or health based levels; and for arsenic, a human
carcinogen, the cancer risk factor has been reduced below one in ten
thousand.
The major source of contaminants identified in the ROD, the rock
material from the mining operations (heap and mine dump), has been
addressed. The mine drainage was reevaluated in the Explanation of
Significant Differences and it was determined that the mine drainage
did not pose an ecological threat. According to the risk assessment and
amended risk assessment, the inhalation and ingestion of the
contaminated soils were the major routes of exposure. The arsenic-laden
waste rock from the mine was contained and capped. The cleanup also
reduced the impacts to the ground water by diverting the run-on water
away from the capped mine waste and by limiting potential leachate
generation.
Operations and Maintenance
The site is designed to require very little maintenance. The area
is remote and the semi-arid climatic conditions suggest that only
minimal maintenance is expected. The mined rock material under the
cover is not expected to settle which is often the major cause of cap
disturbance. The rainfall is low with an annual average precipitation
of 11 inches/year which is primarily as snow and spring rain. It is
expected that the Ecology personnel, per the State Superfund Contract,
will be able to provide the annual maintenance with a minimal amount of
work.
Five-Year Review
The Comprehensive Environmental Response, Compensation and
Liability Act (CERCLA or Superfund) requires a five-year review of all
sites with hazardous substances remaining above the health-based levels
for unrestricted use of the site. Since the cleanup of the Silver
Mountain Mine site utilized containment of the hazardous materials as
the method to reduce the risk, the five-year review process will be
used to insure that the cap is still intact and blocking exposure
pathways for human health and the environment. As indicated above, EPA
has conducted the first five-year review and has determined that the
remedy selected for Silver Mountain Mine remains protective of human
health and the environment. For future five-year reviews, EPA will
review Ecology's annual reports on the operation and maintenance at the
site and as needed perform a five-year review inspection.
Community Involvement
EPA published its Community Relations Plan in December 1987, after
interviews with local residents and officials. An information
repository was established at the Okanogan County Courthouse and all of
the documents used to make the decision were placed there before the
final Record of Decision was signed. All other reports and fact sheets
were sent to the repository as they were completed. Those individuals
on the mailing list were informed by fact sheet prior to construction
activities on-site. No public meetings have been requested thus far.
Applicable Deletion Criteria
One of the three criteria for site deletion specifies that EPA may
delete a site from the NPL if ``all appropriate Fund-financed response
under CERCLA has been implemented, and no further response action by
responsible parties is appropriate.'' 40 CFR 300.425(e)(1)(ii). EPA,
with the concurrence of Ecology, believes that this criterion for
deletion has been met. Subsequently, EPA is proposing deletion of this
site from the
[[Page 40786]]
NPL. Documents supporting this action are available from the docket.
State Concurrence
The Washington Department of Ecology concurs with the proposed
deletion of the Silver Mountain Mine Superfund site from the NPL.
Dated: July 17, 1997.
Charles Findley,
Acting Regional Administrator, U.S. EPA Region 10.
[FR Doc. 97-19940 Filed 7-29-97; 8:45 am]
BILLING CODE 6560-50-P
