December 2008, Carpenter-Snow Creek Mining District NPL Site, Cascade County, MT
EPA Issues A Revised
Proposed Plan for Clean
Up of Soils in Neihart, MT
Site Timeline
2001. The Carpenter-Snow Creek
Superfund site (includes the
Neihart OU) was added to EPA's
National Priorities List of
Superfund sites.
2002 and 2003. EPA sampled
soils, surface water, sediments,
and tailings in Neihart.
2004. Soil removals in residential
areas conducted to eliminate very
high lead levels.
2005. Remedial Investigation
completed.
2006. Human Health Risk
Assessment completed.
2006. Cleanup Feasibility Study
completed.
October 2006. Original Proposed
Plan describes EPA's Preferred
Alternative for cleanup.
2007/08. EPA reassesses
proposed lead cleanup action
level.
October 2008. EPA conducts
additional yard soil sampling.
December 2008. Revised
Proposed Plan issued.
Winter 2009. Record of Decision
issued that documents cleanup
details.
Spring 2009. Yard cleanup
designs prepared with property
owner involvement.
Summer/Fall 2009. Yard
cleanups initiated.
On December 22, 2008, the U.S. Environmental Protection
Agency (EPA) issued the Revised Proposed Plan for Neihart
Operable Unit (OU) 1. This fact sheet summarizes that plan
and the opportunities for public review and comment.
Why A Revised Proposed Plan Is Needed
In October 2006, EPA issued the original Proposed Plan for the Neihart
community soils area. Two public hearings were sponsored by EPA and
Montana Department of Environmental Quality (MDEQ). At that time,
EPA's Preferred Cleanup Alternative was Alternative 2B with a soil
cleanup action level for lead of 1,200 parts per million (ppm). EPA is
retaining Alternative 2B but has lowered the soil lead cleanup action
level to 400 ppm. This change has increased the number of residential
properties to be cleaned up and the associated cost. Since the cost
increase is greater than 50 percent of the original cost and could not
have been reasonably anticipated by Neihart property owners, town
officials, Cascade County, or any other stakeholder, EPA is required to
issue a revised Proposed Plan.
EPA is seeking additional public comment on the revised Proposed
Plan, which was released December 22, 2008, before a final decision
will be made and before the Record of Decision is issued.
As described in more detail in the Proposed Plan and the Feasibility
Study (available at the document repositoriessee box on page 3),
Alternative 2B involves the excavation of contaminated residential soil
and non-paved road base material from the town of Neihart and the
disposal of that material in an engineered, safe repository outside of any
flood plain. Alternative 2B includes the excavation and disposal of the
Belt Creek Tailings pile, located north of Neihart, and reclamation of the
stream channel at that location. Institutional controls are also a key
component of this alternative and are summarized on page 3.
The original Proposed Plan estimated that 14 properties (includes
residential, commercial, and vacant lots) and 10 sections of earthen
roadway in Neihart would require cleanup at an estimated cost of $3.8
million. Based on the revised soil lead cleanup action level, 66 properties
and 24 earthen roadway sections would be addressed at an estimated
present value cost of $11.8 million. This change does not affect the Belt
Creek Tailings pile, which will be removed regardless of the final
selected cleanup strategy for Neihart.
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Questions and Answers About EPA's Revised
What Type of Sampling was Done?
Samples have been collected from mine waste, surface
water, sediment, groundwater, and soils to characterize the
nature and extent of mining contamination in and near
Neihart. Soil at 153 properties (residential, commercial,
public-owned, and vacant lots) have been sampled in
Neihart since work was initiated in 2002. This represents
85% of the properties in the Neihart community soils area
(original townsite) and 95% of properties north of the
Community Center.
Any property owner desiring information or sampling
should contact Scott Brown at 406-457-5035.
Soil lead levels are generally higher north of the community
center compared to the residential area south of the center.
This observation is consistent with the town's former mills
and the main ore transportation corridor previously located
north of the Community Center. Soil lead concentrations
range from about 22 to 2,700 ppm, with an average of
approximately 447 ppm. Elevated lead levels have also
been found in unpaved roadway material.
Surface water is contaminated in Broadwater, Compromise,
and Rock Creeks, but water quality in Belt Creek and
O'Brien Creek (the local drinking supply) meets water quality
standards. Four residential groundwater wells and three
springs were also sampled. One well had a slightly elevated
concentration of mercury, and two springs had elevated lead
concentrations. None of these levels are of concern as long
as these water sources are not used for drinking.
What Health Risks Were Identified?
EPA's human health risk assessment showed that lead and
arsenic are the mining-related contaminants of concern.
The primary concern driving the cleanup is children's
exposure to elevated concentrations of lead.
In Neihart, residential soils are the primary pathway by
which people may be exposed to mining-related
contaminants. Exposure occurs when soil is inhaled (dust)
or ingested (on unwashed vegetables, hands, toys, etc.).
Other pathways (surface water, groundwater, or stream
sediment) were shown to not be a health concern.
Based on EPA's lead exposure model, exposure is a
concern mainly for full-time resident children at
properties having lead concentrations greater than 400
ppm. In addition, EPA has set a cleanup action level for
arsenic of 100 ppm. Visitors or recreationists do not contact
soils frequently enough to have elevated exposures.
Approximately 66 properties are either known or expected
to exceed the 400 ppm lead
concentration. By removing the elevated
concentrations of lead and arsenic in
residential soils in Neihart, human
health risks associated with mining-
related contamination will be reduced to
acceptable levels.
Lead and Arsenic
EPA's Cleanup Objectives in Neihart
Prevent resident exposure to elevated lead levels in residential soil, dust, and road base.
Control the spread of contaminated material by wind and water erosion.
Prevent contamination of cleaned areas by preventing the use of mine wastes as construction fill.
Remove the Neihart Tailings from the Belt Creek flood plain.
What Cleanup Alternatives Were Evaluated in the Feasibility Study?
1
No Action. Superfund requires this alternative to be considered. Cost estimated at $240,000.
2a
Removal/Replacement/Disposal of all Contaminated Soil, Plus Institutional Controls (ICs). Excavation of contaminated
residential soil and non-paved road base material from Neihart and disposal of the excavated material in an engineered
repository. ICs will protect the remedy. Original cost estimated was $1.8 million. Using the new 400 ppm lead level this cost is
now~$9.1 million.
2b
Removal/Replacement/Disposal of all Contaminated Soil and Removal of Neihart Tailings, plus ICs . Same as
Alternative 2a, but includes excavation and removal of the Neihart Tailings. Original cost estimated was $3.8 million. Using the
new 400 ppm lead level this cost is now ~ $11.8 million.
Selective Removal/Replacement/Disposal of Contaminated Based on Home Occupancy, plus ICs. Same as Alternative
2a, but only at properties that are occupied by children under seven years of age. Requires annual consultation with Cascade
County and town of Neihart to determine changes in demographics and to collect soil samples. Original cost was estimated at
$0.7 million. Using the new 400 ppm lead level this cost is now ~$1.1 million.
The primary difference between the alternatives is the amount of contaminated soil removed
and whether the Belt Creek Tailings are removed.
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Proposed Plan for Cleanup in Neihart, Montana
How Would A Cleanup Be Done Under
Preferred Alternative 2B?
EPA will prepare a detailed cleanup plan for yards having
greater than 400 ppm lead or 100 ppm arsenic in soil.
Homeowners will be consulted in advance to discuss details
of the cleanup, schedule, and any specific homeowner
needs. All details will be agreed upon in writing prior to the
start of construction.
EPA will use proven yard cleanup protocols in Neihart. Soil
will be removed with conventional equipment, supplemented
by hand shovels close to buildings, septic systems, trees,
etc. Excavated areas will be backfilled with clean soil and
graded. Vegetation that is removed will be replaced, along
with any structures, such as fences. EPA's on-site
representative will be happy to assist property owners with
any questions or concerns during the construction.
What Are Institutional Controls?
Institutional controls (ICs) are non-engineering actions,
such as legal controls, that help minimize the potential for
exposure to residual contamination once the construction
has been completed. ICs are meant to supplement the
engineering (construction) controls.
Before the soil cleanups are completed, the Cascade
County Health Department, county commissioners, and
Neihart town council will help determine what ICs are
needed. An especially important 1C will be to prevent
the importation of contaminated material into or out of
Neihart. Much of the contamination being cleaned up in
Neihart resulted from the practice of using mine waste from
the dozens of nearby active and inactive mines (see Figure
1) as fill material.
Other important ICs will help prevent residents from being
exposed to residual contaminated material during home
construction and other projects, medical monitoring of
children's blood lead, and developing educational
programs.
Site Contacts: For answers on questions about the
cleanup, please call or write either of the following:
Scott Brown
US EPA,10 W. 15th St, Suite 3200 Helena, MT 59626
406-457-5035/brown.scott@epa.gov
Catherine LeCours
MDEQ,1100 N. Last Chance Gulch, Helena, MT 59620
406-841-5040/clecours@mt.gov
Sandy Johnson
Cascade City County Health Department
115 4th Street South, Great Falls, MT 59401
405-454-6950
How Many Yards Will be Cleaned Up?
Based on the sampling conducted to date, it is estimated
that 66 residential type properties and 24 earthen
roadway sections will have lead or arsenic concentrations
exceeding the cleanup level and will therefore require soil
replacement.
In addition to yards, Alternative 2B includes the removal
of the Belt Creek Tailing pile and the reclamation of the
stream channel in that location.
The preferred alternative will excavate approximately
61,679 cubic yards of material. This includes 29,742
cubic yards of residential soil, 4,087 cubic yards of
roadway material, and 27,850 cubic yards of Belt
Creek Tailings.
J Major Mine Si!
Other Mine Sites
Figure 1: Historic Mine and Mill Sites
Document Repositories
Documents such as the Remedial Investigation, Risk
Assessment, and Feasibility Study can be viewed at any
of the locations listed below:
EPA, 10 W. 15th St, Suite 3200 Helena, MT
Cascade County Health Department, 115 4th Street
South, Great Falls, MT
Belt Creek Ranger Station, (north of Neihart)
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US Environmental Protection Agency
10 West 15th Street, Suite 3200
Helena, Montana 59626
Do You Want to Learn More or Provide Comments on the
Proposed Plan? A comment period for the revised Proposed Plan will run from December 22 to
January 30, 2009. Interested individuals are encouraged to provide their thoughts, ideas, or comments to EPA
during that time period. EPA will review and consider all comments before making its final cleanup decision in the
Record of Decision. There are several ways to learn more about the Proposed Plan and to provide comments:
Read more about it. This fact sheet summarizes the Proposed Plan. Copies of the plan are available for
viewing at the Belt Creek Ranger station and the Cascade County Health Department.
Attend the public meeting. EPA will hold a public meeting to discuss the plan (see below). Everyone is
welcome!
Provide oral comments. If you attend the public meeting, you can provide comments verbally. A stenographer
will be present to record oral comments for the public record.
Provide written comment. You may provide comments to EPA Project Manager Scott Brown in writing by
letter or email (see page three).
Public Meetings
Neihart Community Center
(on US Hwy 89 in Neihart)
January 6, 2009 at 7:00 pm
(in conjunction with the Neihart town council meeting)
Cascade County Commissioner's Chambers
325 2nd Avenue North, Great Falls, MT
January 13, 2009 at 9:30 am
(in conjunction with the Commission's meeting)
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