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Carpenter Snow Creek Mining District
Site Type: Final NPL
Updated October 2014
In consultation with the Montana Department of Environmental Quality (DEQ), EPA issued a proposed plan in July 2014 that identifies the preferred alternative for secure mine-waste disposal locations for placing removed mining waste within the Carpenter Snow Creek Mining District site. The preferred alternative repository locations are the Mackay Gulch and Silver Dyke Glory Hole repositories. The Site-Wide Secure Waste Disposal Area Remedial Investigation and Feasibility Study reports provide more detailed information about the alternatives considered, including the preferred alternative, and are posted in Site Documents. Public comments received during the public comment period are favorable to the preferred alternative. These comments will be addressed as part of the Record of Decision, which will be issued in late November/early December 2014.
An amendment to the 2013 Action Memorandum was issued in August 2014 to address the Silver Dyke tailings impoundment. The amendment, which includes the 2013 Action Memorandum as an attachment, is posted in Site Documents below. The objective of this removal action, which started in September 2014, is to prevent continued releases from the estimated 35,000 cubic yards of tailings at the Silver Dyke tailings impoundment within the No Name Creek drainage area. The action includes the following elements: (1) removing the tailings from the hillside slopes and staging for disposal; (2) constructing an onsite repository, pending the repository location decision; (3) placing the tailings in an onsite repository; (4) reclaiming/restoring removal area slopes. More information about the removal action is available on the EPA On-Scene Coordinator Site Profile page.
EPA, in consultation with DEQ and the U.S. Forest Service (USFS), plans to issue a site-wide Remedial Investigation (RI) report in 2015. The report will provide information concerning metals concentration in tailings, soil, sediment, surface water and groundwater throughout the mining district, for the purposes of characterizing and identifying the extent of material that may require a response action. This will be followed by a Feasibility Study (FS) of the Silver Dyke Mining Complex portion of the site (including the Silver Dyke Glory Hole, Silver Dyke Mill, Upper and Lower Carpenter Creek tailings and all the associated mine contaminated waste along Carpenter Creek) to evaluate the most appropriate cleanup methods. The Silver Dyke Mining Complex FS is expected to be completed in 2016. As part of the feasibility study, EPA, DEQ and USFS are evaluating the use of hydrated lime and sulfate reducing bioreactors in 2014 and 2015 to passively treat several of the 12 adit discharges that have been identified at the site to determine if it is feasible to raise the pH of the water and reduce the metals concentrations. Data collected from these field investigations will support the development of the upcoming OU2 and OU3 FS reports that will assist with choosing appropriate response actions in the Record of Decision and refining these actions as part of the Remedial Design.
James Neihart, a local prospector, was the namesake for the small mining town of Neihart. Mining began in the area in the 1880s when silver deposits were discovered near the future Neihart town site. Mines yielded primarily silver, lead and zinc ores. During the 1920s, lead and zinc were produced in large quantities. The mining district has been largely inactive since the 1940s, although some mines have reported mine development work and some sporadic production.
The Carpenter Snow Creek Mining District Superfund Site (CSCMD) lies in the Little Belt Mountains of southern Cascade County. The site encompasses approximately 9,000 acres with mine tailings, waste rock and mine-influenced waters present throughout the site, due to the many inactive and abandoned mines. The State of Montana’s Abandoned Mine Bureau identified, inventoried and sampled these inactive mines in the Carpenter Snow Creek area in the early 1990s. Sampling showed the presence of a variety of metals in the area surface water and soils that are found in concentrations known to produce risk to human health and the environment. The CSCMD site was listed on the Superfund National Priorities List in 2001.
Approximately 96 abandoned mines have been identified in the Carpenter Snow Creek Mining District Superfund site, and at least 21 of these have been identified as probable sources of contamination to surface water. There are also more than 12 adits (horizontal mine openings) that discharge mine-influenced water, usually of poor quality with low pH and high concentrations of dissolved metals. In general, the flow from these adits increases during and after snow melt and then slowly decreases into fall and winter. The concentration of metals can also vary greatly, depending on whether the water is derived from surface water or groundwater. In addition to the adit discharges, there are also documented impacts from mining waste to soil, surface water and stream sediments in Carpenter Creek, Snow Creek and Belt Creek in reports and technical memorandums generated since 2009. Several of these are posted in Site Documents below.
|Media Affected||Contaminants||Source of Contamination|
|groundwater, sediment, surface water, soils||heavy metals and arsenic||mining wastes|
Since 2001, EPA has been collecting soil/mine waste, surface water, sediment, and groundwater samples throughout the entire site, with expanded efforts in and around the town of Neihart and the Silver Dyke Mining Complex continuing in 2015.
Concentrations of lead and arsenic in soil that exceed the action levels specified in the 2009 Record of Decision have been identified in residential yards and alleys throughout the town of Neihart. Preliminary surface water sampling of Belt Creek as it flows through Neihart did not identify contaminant levels above drinking water standards, or levels that EPA considers unhealthy for aquatic life. Similarly, contaminant levels in the sediment of Belt Creek as it flows through Neihart did not exceed levels considered safe for recreational use.
Sampling conducted since 2009 in the Carpenter Creek, Snow Creek and Neihart slope drainages north of Neihart revealed elevated levels of lead and zinc in the surface water. Elevated levels of lead and zinc were also found in sediments and fluvial (adjacent stream) soils along Carpenter Creek and Belt Creek adjacent and below the various waste rock and tailings piles present in these watersheds. Sampling in 2012 and 2013 indicates that contaminated soils that were deposited in the floodplain during historic Belt Creek flood events, such as the 1953 and 1981 floods, extend all the way to Monarch. In addition, several adits that are discharging from abandoned mines continue to contribute to the degradation of the water quality throughout the mining district. These adits have been monitored continuously since 2011. Several of these adits have the space and are easily accessible year round to allow for passive treatment of mine influenced waters using a biochemical reactor. In 2015, EPA, DEQ and USFS will pilot test a biochemical reactor at either the Moulton or Broadwater mine located on the Neihart Slope. Data collected from this pilot test will support the development of an upcoming feasibility study that will assist with choosing appropriate response actions in the Record of Decision and refining these actions as part of the Remedial Design.
The site has been delineated into three operable units (OUs). Superfund sites are frequently divided into OUs, or more manageable areas, for the activities undertaken as part of a Superfund site cleanup. EPA has established these preliminary study area boundaries for the purpose of planning and developing the initial scope of the Remedial Investigation/Feasibility Study (RI/FS) for OU2 and OU3. As the site is characterized further, these OU boundaries are subject to change.
OU1 is specific to the Neihart Community Soils Area, which includes the town of Neihart and nearby residences impacted by former mining operations or the relocation of mine waste from former mining operations. Further, OU1 includes mine waste (above action levels) on undeveloped properties adjacent to residential property(s), waste above action levels accessible to the general public and the Belt Creek tailings area that also includes the contamination addressed as part of an EPA time-critical removal action in 2004. Over 120,000 cubic yards of waste is in the Neihart Community Soils Area and the Belt Creek tailings. Any investigation for consideration of remedial action for OU1 is specific to elements that may impact residential settings.
OU2 encompasses the abandoned mines, mills, and associated wastes along Snow Creek and the Neihart Slope. These areas contain the majority of the inaccessible adit discharges and almost 500,000 cubic yards of mine-related waste.
OU3 contains waste located in Carpenter Creek and any wastes in the Belt Creek floodplain below Carpenter Creek extending to Monarch. The Silver Dyke Mining Complex is located in the Upper Carpenter Creek basin and includes the Silver Dyke Glory Hole, associated underground workings, mill facilities, tailings piles, and eroded tailings in the floodplain areas of Carpenter Creek. The ore in this complex was mined between 1921 and 1929 and is characterized by a wide body of low grade ore containing zinc and lead and a high proportion of copper, but which also resulted in a large quantity of tailings and refuse along Carpenter Creek. In 1925, a tailings dam next to the Silver Dyke Mill was damaged by an earthquake and resulted in a flood of tailings into the valley below. In 1926, two impoundments were built in Carpenter Creek (upper and lower) for collection of mine tailings. These tailings, now known as the Carpenter Creek tailings, were placed into the impoundments by slurry from the upstream Silver Dyke Mill and are thought to have originally spanned the entire valley. It is estimated that over 500,000 cubic yards of mine-related waste is present within the Carpenter Creek floodplain.
Neihart Community Soils Ongoing and Planned Activities
In 2013, property owners expressed desire to perform modifications to their properties and began participation in Property Owner’s Soil Management Program (POSM) program. The modifications involve movement of soils containing lead above EPA’s action level, some of which were determined to be outside of the owner’s property boundaries. EPA determined that accurate, current and detailed boundary information was needed to support Remedial Design (RD) and subcontracted Global Positioning System (GPS) surveying of OU1 and the surrounding area to better quantify property boundary information and provide greater topographical information.
Information obtained from surveying activities performed in late 2013 is being incorporated into the RD and the POSM program. High level aerial view and topographical maps have been generated. The ongoing focus is to revise individual property designs through 2014.
Enhanced Surveying – Additional topographical survey information was collected in 2013 and 2014. The new survey data will be incorporated into existing topographical information from Neihart and the Neihart Slope. Watershed information will be developed and utilized to determine overland water flows from the slope and through the Town of Neihart. This will aid in minimizing future deposition of mine waste from the slope and better define the adequacy of water channels through the Town of Neihart.
Storm Water and Maintenance Access Roads Design – Survey information will also be utilized to design storm water and maintenance access roads on the east side of Neihart. The maintenance roads are being designed to allow light vehicle traffic to each of the drainages anticipated for any potential collection or treatment systems that may be installed at existing mines or mine waste in these drainages. These roads are also expected to provide drainage from water runoff from the slope.
Haul Road Design – As revised locations for potential mine waste repositories are finalized, EPA has identified a need to design haul roads to these locations. In addition, current access roads may require modifications to safely support haul traffic. Survey information and anticipated traffic patterns will be utilized to aid in development of safe haul road designs for heavy vehicle traffic.
Additional Soil Sampling – EPA is seeking written permission from property owners in close proximity to Neihart to sample properties have not been sampled previously. EPA is taking the opportunity to characterize properties in Johnston and O’Brien Creeks and areas south of Neihart. Access will be sought from property owners prior to the start of any soil sampling campaign. Only properties where permission is obtained will be sampled. In conjunction with sampling, property data will be obtained to aid in the development of RD for each property.
POSM Activities – A few property owners have expressed their desires to perform modifications and enhancements to their properties. To participate in the POSM program owners must have a HAZWOPER Certified contractor if they are not conducting the work and any required property agreements must be in place prior to beginning work. The EPA POSM program assists property owners in identifying soils found to contain metals concentrations above EPA action levels. By identifying these soils and working with property owners, the movement of soils containing lead and arsenic above EPA actions levels will be minimized. This program is in effect while remedial action plans are being finalized. All property owners wishing to move soils onto or off of their property are strongly encouraged to participate in the POSM program.
POSM Revision – Information obtained through recent surveying efforts, soil movement occurring this construction season, and from this season’s sampling and design activities will be reflected in revised copies of POSM program documentation. The POSM contact center located at the Cascade City-County Health Department will maintain the most current information available. POSM program construction activities are monitored during the construction season and the contact center is updated weekly at a minimum to those activities. The overall POSM program Administrative and Implementation Plans will be revised prior to and after this construction season.
Remedial Design Efforts – All information obtained through efforts associated with the 2014 field season will be reflected in revisions to the RD. As repository site locations are finalized, the RD will be completed by EPA, in consultation with DEQ. The RD consists of contractor bid package material to allow EPA to move forward with RA as quickly as possible upon completion of the RD. Emphasis will be placed on performing remedial action associated with OU1 prior to the other Operable Units.
OU2 and OU3 Ongoing and Planned Activities
Multiple important sampling efforts took place within the watershed in 2014. These included:
- Turbidity monitoring at four locations in Carpenter Creek from April through October.
- Biweekly adit discharge sampling at seven of the 12 adits with the remainder being sampled semi-annually.
- Continuous adit flow monitoring at four adits ongoing since May of 2013.
- A tracer dye test of the regional hydrogeology of the Silver Dyke Mine in 2013 and 2014.
- Pilot scale testing of two passive treatment technologies: sulfate reducing bioreactors and hydrated lime addition at the Silver Dyke adit. Additional passive treatment studies are anticipated in 2015.
- Streamside mine waste evaluation of Upper Belt Creek through the town of Neihart north to the confluence of Carpenter Creek.
- Remedial Investigation preparation.
- Installation of five vegetation test plots on mine waste to determine slope stabilization feasibility in 2013. Efforts were expanded in 2014 to evaluate several slope stabilization technologies. Due to the high cost component associated with improvements needed to access these wastes and place in an on-site repository, alternative methods such as in situ reclamation are being considered.
- Conduct LIDAR survey of the site. LIDAR, which stands for light detection and ranging, is a remote sensing Exit method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. These light pulses—combined with other data recorded by the airborne system—generate precise, three-dimensional information about the shape of the Earth and its surface characteristics.
- Semi-annual watershed wide sampling of groundwater, surface water and sediment contained in the 2013 Sampling Activities Report posted in Site Documents below. 2014 results will be posted once these are available.
An Action Memorandum was issued in June 2013 for the Carpenter Creek and Silver Dyke tailings impoundments within OU3. The USFS completed this removal action in 2013. The removal action included interim response actions at the Silver Dyke tailings and upper and lower Carpenter Creek tailings impoundments to stabilize these tailings until a permanent remedial action is taken. Activities at various locations within the Carpenter Creek and Silver Dyke tailings impoundments included: 1) Construction of lined surface run-on and run-off ditches on the upper and lower Carpenter Creek tailings to reduce storm flows and snowmelt from eroding tailings; 2) Installation of diversion channels to route clean water around all three tailings impoundments; 3) Installation of erosion check dams at all three tailings impoundments in areas where deep rills have formed in past erosion events; 4) Installation and maintenance of a certified weed-free straw bale erosion berm at the base of the Silver Dyke tailings, 5) Application of wood straw mulch over tailings piles as an erosion control measure, 6) Placing of riprap to stabilize the access road to Silver Dyke tailings, and 7) Engineering and informational controls, including fencing and signage on the tailings piles in Carpenter Creek, to eliminate trespass with recreational vehicles and to educate the public on the potential dangers. The pollution report is posted in Site Documents below.
An amendment to this Action Memorandum was issued in August 2014 to address the Silver Dyke tailings impoundment. The Action Memorandum and addendum are posted in Site Documents below. The objective of this removal action is to prevent continued releases from the estimated 35,000 cubic yards of tailings at the Silver Dyke tailings impoundment within No Name Creek drainage area. The action includes the following elements: (1) Removing the tailings from the hillside slopes and staging for disposal; (2) constructing an onsite repository, pending the repository decision; (3) placing the tailings in an onsite repository; (4) reclaiming/restoring removal area slopes. More information about the removal action is available on the EPA On-Scene Coordinator Site Profile page.
The administrative record for the Action Memorandums contains documentation of ongoing releases of hazardous substances from the Carpenter Creek and Silver Dyke tailings impoundments into Carpenter Creek and downstream into Belt Creek and is available in the Site Information Repositories identified below.
EPA and DEQ will continue to collect data in 2015 to identify and design remedial response actions. In general, these activities involve small project teams (usually two people) and little if any heavy equipment (e.g., a drill rig or backhoe). Written access will be obtained in advance from all property owners where field activities are planned. Activities include:
Carpenter Creek Monitoring – The water quality of Carpenter Creek will be monitored at multiple locations to determine the water quality and sediment loading. The turbidity and field parameters of the water will be measured regularly through spring runoff and into the fall. The data will be used to identify the main sediment source areas and prioritize remedial response actions.
Adit Discharge Monitoring – There are more than 12 adits within the site that discharge water. In general, the adit flow rate increases during and after snow melt and then slowly decreases into fall and winter. The concentration of metals can vary greatly depending on whether the water is derived from surface water or groundwater. Water quality and flow rate data will be collected from four adits throughout spring runoff and water quality will be measured at four more adits. The data will be used to assess the seasonal changes in water quality and the sources for the water.
Repository Location Study – It is now known that there are greater than 1.2 million cubic yards of mine waste present at the site. A proposed plan was released in July 2014 and discussed at an August 2014 public meeting with the proposed alternatives for placement of mine waste in a secure on-site waste disposal area. Several comments were received during the public comment period and will be incorporated into the responsiveness summary. A Record of Decision is anticipated to be signed in late November/early December 2014 that will document the selection of the repository sites.
Silver Dyke Mine Tracer Study – The glory hole at the Silver Dyke mine is under consideration as a repository location and was proposed as one of the preferred alternative locations in the July 2014 proposed plan. There is very poor quality water discharging from the Silver Dyke mine adit. Dye tracers were placed uphill of the Silver Dyke glory hole to identify the source areas for the water draining from the adit. The objectives were to develop a better understanding of relative contributions from snowmelt and groundwater and to assess whether use of the site as a repository will improve or degrade the water quality or quantity discharging from the adit.
Silver Dyke Mining Complex Feasibility Study – EPA, in consultation with DEQ and USFS, plans to issue a site-wide RI report in 2015 that will provide information concerning metals concentration in tailings, soil, sediment, surface water and groundwater throughout the mining district for the purposes of characterizing and identifying the extent of material that may require a response action. This will be followed by a Feasibility Study (FS) of the Silver Dyke Mining Complex portion of the site (including the Silver Dyke Glory Hole, Silver Dyke Mill, Upper and lower Carpenter Creek tailings and all the associated mine contaminated waste along Carpenter Creek) to evaluate the most appropriate cleanup methods. This Silver Dyke Mining Complex FS is anticipated to be completed in 2016. This will be followed by a proposed plan, a public comment period, and a Record of Decision (ROD) for cleanup. Agency staff will then focus on preparing a FS for the remaining portions of the site, including the abandoned mines within the Snow Creek and Neihart Slope drainages and the mine contaminated flood deposits along Belt Creek.
Mine Discharge Treatment Bench Scale Study – A number of the mines discharge water that contains metals at concentrations above acceptable levels. Some of this water will require treatment in the future. To assess the viability of different treatment technologies, water will be collected from Silver Dyke mine for use in the treatment testing. The study will help identify, or rule out, possible treatability options for the discharges.
Revegetation Pilot Test – Much of the mine waste does not have vegetation. The lack of vegetation may be due to metals toxicity or to physical features like grain size, unstable surfaces, or lack of nutrients. In 2013, the physical features of five sites were systematically modified in test plots. In September 2014, the test plots were monitored to determine if vegetation can be established on the waste rock, in order to evaluate the effectiveness of treating mine waste in place rather than excavating and disposing of it in a repository. Two test plots will also be installed on mine-contaminated slopes to evaluate methods for reducing erosion.
Montana Fish, Wildlife & Parks – Montana Fish, Wildlife & Parks will evaluate fish numbers and distribution in Belt Creek and determine fish mortality. Additional activities will include: marking westslope cutthroat trout with passive integrated transponder tags, sampling for benthic macro-invertebrates, and taking discharge measurements and checking thermographs. Funding was also secured to select a suitable location and complete the design for a fish barrier in Carpenter Creek, to ensure the genetically pure Westslope cutthroat trout are protected once remediation of Carpenter Creek commences.
Community involvement plays an important role in the Superfund process. EPA uses a number of different tools and resources to promote effective, on-going, meaningful community involvement. The goals of the Superfund community involvement program are to:
- Keep communities affected by sites informed throughout the cleanup process.
- Provide opportunities for communities to comment and offer their input about site cleanup plans.
- Facilitate the resolution of community issues tied to a site.
A Community Involvement Plan was prepared in 2011 for the Neihart Community Soils area (OU1) and is being updated to include the entire site. The plan provides a history of the site, a brief background and description of the community of Neihart, and identifies issues of concern to the local community regarding the site. EPA interviewed home and business owners and local government officials in the preparation of the Community Involvement Plan. The interviews provided community members and officials the opportunity to voice concerns and issues related to the Superfund site. In the Community Involvement Plan, EPA specifies objectives and future plans for community involvement and communication at the Carpenter Snow Creek site. EPA plans fact sheets, news releases and focused meetings for community members as part of the agency’s efforts to keep the community informed of site progress. In addition, EPA will maintain an accurate mailing list for those interested in receiving information about the site. If you would like to be on the mailing list, please contact the EPA Remedial Project Manager listed below. The Community Involvement Plan will be available in the Site Documents section once it has been finalized.
A public meeting was held at the Neihart Community Center on August 7, 2014 to discuss the proposed plan for selection of a site-wide secure waste disposal area. The presentation describing the proposed plan shown at the public meeting is posted in Site Documents.
EPA places a high priority on land reuse as part of its Superfund response program mission. The agency tries to select cleanup options that encourage and support future use of a site. EPA uses two fundamental methods to facilitate reuse of Superfund sites:
- Exploring future uses before the cleanup remedy is implemented, an approach that gives the Agency the best chance of designing cleanup remedies to support the likely future use of a site.
- Working with landowners and communities to remove barriers not considered necessary for the protection of human health or the environment at those sites where remedies are already in place.
One option for reuse is the siting of clean and renewable energy projects on contaminated (or formerly contaminated) lands. As part of this effort, EPA is evaluating the potential for energy projects on these properties and working with landowners and communities to identify ways to remove barriers to such projects.
The reasonably anticipated future land use is determined during the RI/FS process. This information is considered during the development and selection of the remedy for the site. Many properties in Neihart are already in continued use as residential or commercial properties.
Land use controls are the most common type of institutional control (IC). ICs are administrative or legal controls that help reduce the likelihood for human exposure to contamination. ICs can also help protect the integrity of the remedy. Examples of ICs are:
- Zoning ordinances.
- Environmental covenants.
- Deed notices.
- Well-drilling restrictions.
- Building permits.
- Informational advisories.
Options for institutional controls are developed as needed during the RI/FS process and selected in the Record of Decision as a part of the remedy. EPA will determine the specific ICs later in the cleanup process.
EPA or the lead agency conducts five-year reviews following the start of a Superfund cleanup when contamination is left on the site. These reviews are repeated every five years. We use these reviews to determine:
- How the remedy is working.
- If the remedy remains protective of human health and the environment.
Remedial action has not begun, therefore five-year reviews are not yet required at this site.
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Action Memorandum Amendment: Request for a Ceiling Increase and a Change in Scope for a CERCLA Removal Action for Operable Unit 3 (Carpenter Creek and Silver Dyke Tailings Impoundments), September 3, 2014
Presentation from County Commissioners' Briefing, May 12, 2014
2013 Sampling Activities Report, January 2014
2012 Field Update presentation from the November 5, 2012 public meeting
Map of OU3 Tailings and Soils by Category, March 2012
Record of Decision (ROD) text, appendices and figures, March 2009 (PDFs located on the FTP site; see individual files there)
- Public Comments on the Revised Proposed Plan
- Transcript of the Public Hearing for the Revised Proposed Plan, January 13, 2009
- Transcript of the Public Hearing for the original Proposed Plan, November 30, 2008
- Transcript of the Public Hearing for the original Proposed Plan, October 25, 2008
Site Update Fact Sheet, April 2014
Site Update Fact Sheet, June 2013
Site Update Fact Sheet, October 2012
Site Update Fact Sheet, April 2012
Remedial Project Manager (for OU1)
U.S. Environmental Protection Agency, Region 8
10 West 15th Street, Suite 3200
Helena, MT 59626
866-457-2690 (toll free)
Roger Hoogerheide (for OU2 and OU3)
Remedial Project Manager
U.S. Environmental Protection Agency, Region 8
10 West 15th Street, Suite 3200
Helena, MT 59626
866-457-2690 (toll free)
State Project Officer
Montana Department of Environmental Quality
1100 N. Last Chance Gulch
PO Box 200901
Helena, MT 59620-0901
Townsend Ranger District
415 South Front Street
Townsend, MT 59644
Site Information Repositories:
EPA Superfund Records Center
10 West 15th Street, Suite 3200
Helena, MT 59626
866-457-2690 (toll free)
Hours: M-F, 8:00 a.m.-4:30 p.m.
Great Falls Public Library
301 2nd Ave North
Great Falls, MT 59401
Hours: Tues-Thu 10 a.m. to 8 p.m.
Fri-Sat 10 a.m. to 6 p.m.
Belt Creek Ranger Station
c/o Neihart, Montana 59465
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