U.S. EPA Contaminated Site Cleanup Information (CLU-IN)


U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division
Elizabeth Mine
South Strafford, VT
Superfund Removal & NPL
 
 
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TP-4 Before Excavation
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TP-4 After Restoration
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TP-1A Soil Cap
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Soil Manufacturing
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Reclaimed Material
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TP-1A Slope Armor
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Sediment Control
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Slope Repair
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Biodiesel Emissions
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Routine Waste Recycling
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Natural Contours
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Native Tree Plantings
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Solar-Powered Monitoring Station
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Historic Preservation
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Ballasted Solar Racks
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Solar Farm Configuration


Cleanup Objectives: Restore surface water of Copperas Brook, the West Branch of the Ompompanoosuc River, Lord Brook and water resources further downstream that have been negatively impacted by acid rock drainage. The acid rock drainage resulted from runoff passing through waste rock and tailing piles created by historic mining of iron sulfate and copper at this 250-acre site in east central Vermont.

Green Remediation Strategy: Reduce the environmental footprint of activities during excavation, waste consolidation and construction of a 45-acre capping system, with a focus on reducing greenhouse gas (GHG) emissions, using materials that are less toxic, and restoring the landscape and ecosystems in ways mirroring the surrounding area. The strategy was developed in 2011 through a Superfund response action partnership among the U.S. Environmental Protection Agency (EPA) Region 1 office, U.S. Army Corps of Engineers (USACE), Vermont Department of Environmental Conservation (DEC), Nobis Engineering, Inc. and other partners and involved best management practices (BMPs) addressing the five core elements of a greener cleanup. Implementation of the strategy merited the project's receipt of a 2014 Green Dream Team Award under the USACE Sustainability Award Program. Additionally, aspects of plans to reuse the site for renewable energy development and educational purposes were incorporated into design, construction and long-term maintenance of the site remedy. BMPs used during heavy construction in 2011-2012 and ongoing site management include:

  • Using clean diesel technologies to reduce emission of particulate matter, GHGs and other air pollutants when excavating waste rock, segregating and transferring soil for onsite consolidation and use, constructing surface water diversions, and installing the 45-acre soil cap.
  • Using fuel-efficient machinery and vehicles, institutionalizing a project-level fuel conservation plan, and expanding the use of onsite renewable energy systems to directly power monitoring equipment.
  • Exploring innovative methods to better prevent soil erosion and control stormwater runoff while improving ecosystem service protection during construction and long-term maintenance of the cap system.
  • Choosing manufactured products that are verified by EPA or the U.S. Department of Agriculture or follow International Organization for Standardization standards as environmentally friendly or preferable.
  • Using onsite resources to generate "borrow" materials needed for constructing the cap system and manufacturing topsoil as needed, rather than importing raw materials from offsite sources.
  • Adopting a project-wide program for recovering and recycling or re-using construction materials as well as routine consumer products.
  • Restoring excavated/backfilled areas to more natural conditions by seeding with native plants that need little/no irrigation or other maintenance, attract pollinators, and restore habitat for local and migratory wildlife.
  • Conducting a value engineering study during the final design phase of long-term remedial actions to identify potential improvements to the efficiency of cleanup operations.
  • Consulting with local landowners and regional organizations on potential methods to mitigate potentially adverse effects of cleanup activities on historic resources at the site, which is eligible for the National Register of Historic Places. The U.S. EPA, Vermont Division for Historic Preservation and Vermont DEC established an associated memorandum of agreement.
  • Designing the waste caps to be compatible with repurposing the site for large-scale renewable energy development. With technical input from the U.S. EPA and Vermont DEC, a commercial partnership among Wolfe Energy, Brightfields and Greenwood Energy constructed and began operating a 4.99 megawatt solar energy farm on 27 acres of the capped areas in 2017.

Results:

Air Quality Preservation

  • Reduced onsite emission of air pollutants through use of biodiesel fuel (B-20). During six months of heavy construction work in 2012, for example, use of 5,800 gallons of B-20 instead of conventional diesel fuel was estimated to reduce emission of particulate matter by 12%, hydrocarbons by 20%, carbon monoxide by 12%, sulfur dioxide by 20% and carbon dioxide by 16%.
  • Used new excavators equipped with engines meeting Tier 4 standards during the same six-month period in 2012. Tier 4 engines are estimated to improve fuel efficiency by 5%, reduce particulate matter emissions by 90%, and reduce emission of nitrogen oxides by 50% when compared to older engines.
  • Enabling an estimated 7,100 tons of carbon dioxide emissions to be offset each year through operation of the commercial solar farm on the remediated acreage. These emissions are equivalent to the carbon generated by about 1,370 fossil fuel-powered passenger vehicles in one year.

Energy/Fuel Efficiency & Conservation & Renewable Energy

  • Deployed heavy machinery equipped with a diesel-electric power train (rather than a traditional torque converter and mechanical transmission of a power shift drive) during 2012 construction. Use of this technology on a bulldozer, for example, resulted in a 30% decrease in fuel consumption compared to previous models while delivering a 10% increase in production.
  • Reducing onsite and offsite fuel consumption during remedy construction through a "zero idle" policy for field vehicles and machinery, job-related carpooling among site personnel, and use of hybrid/economy vehicles wherever possible.
  • Using small-scale solar energy systems to supply electricity needed for powering water quality monitoring stations at this remote site. Five of the stations were installed by the U.S. Geological Survey in 2001; each includes a data logger and cellular transmitter along with a 50-watt photovoltaic (PV) panel and 12-volt solar battery. During 2012 construction, data loggers operating at other locations (formerly via 6-volt disposable batteries) were also equipped with PV panels.
  • Enabling an average of 8.7 million kilowatt-hours of electricity to be generated each year due to operation of the solar farm on remediated acreage. The facility generates enough electricity to power about 1,300 typical Vermont homes. Its tax revenue provides income for the neighboring towns of Strafford and Thetford and helps defray Vermont DEC costs to maintain the waste caps for at least 25 years.

Water Quality Preservation & Water Resource Conservation

  • Used biodegradable rather than polyethylene sandbags in approximately 1,000 applications during construction to prevent erosion and control stormwater runoff in highly vulnerable areas adjacent to Copperas Brook.
  • Used tubular devices (Filtrexx® SiltSoxx™) made of organic materials such as recycled compost on ground surfaces along the perimeter of the tailing piles during waste consolidation and cap construction, to control sediment and contain and filter stormwater runoff prior to its gradual subsurface infiltration. When compared to a typical silt fence, which requires placement within constructed trenches, performance monitoring over two years suggested that the tubular system contained 50% more surface water runoff and sediment, returned more nutrients to the subsurface, and involved less maintenance.
  • Avoided penetration of the waste cap during solar farm construction, by installing the solar racks and fence posts on ballasts (concrete weights) laid on gravel beds rather than on concrete piers or driven posts.
  • Capturing water impacted by acid rock drainage through use of the various surface water and groundwater diversion structures that were integrated into the capping system or constructed during slope stabilization or surface restoration. From 2008 through 2017, about 48 million gallons of captured water was treated in an onsite plant where a rotating-cylinder treatment system mixes the water with lime amendment to oxidize and precipitate metals.

Material Use & Waste Reduction

  • Used three onsite areas covering a total of 12 acres to develop the natural resource (borrow) materials needed for site preparation, cap construction and site restoration. Over two years, the areas produced nearly 174,400 cubic yards of earthen fill, including 165,000 cubic yards of till/soil and 9,400 cubic yards of boulders. This approach prevented more than 12,400 trucks trips (each with a capacity of 15 cubic yards) that would have been needed to import the materials and averted approximately 1,899,000 pounds of associated carbon dioxide emissions.
  • Manufactured the project's needed topsoil onsite, to minimize hauling and offsite disturbance associated with importing topsoil stripped from a local site. The tailored topsoil consisted of 2 parts manure that was obtained from a local farm and combined with 2 parts woodchips and 3 parts soil that were available as byproducts from other onsite activities. The resulting blend is more resistant to erosion and contains more organic matter than the typical topsoil in this mountainous area. During 2012, approximately 29,903 cubic yards of manufactured topsoil were produced and placed onsite.
  • Contracted with local farms to obtain the hay bales used as mulch in disturbed areas.
  • Salvaged onsite wood debris for use in stabilizing steep slopes on relatively isolated portions of the site.
  • Used weed-free pelletized mulch (EZ Mulch®) made from recycled newsprint and corn fiber to supplement seed establishment, where needed.
  • Reused riprap no longer needed at one tailings area (TP-4) to temporarily stabilize an adjacent tailings area (TP-1A) prior to cap construction, and reused approximately 1,000 cubic yards of TP-4 temporary backfill soil as capping material for TP-1A.
  • Recycled construction materials and incorporated a product recycling evaluation into procurement sourcing during the construction phase; for example, approximately 30 cubic yards of recyclable HDPE geomembrane liner and 96 HDPE liner cores (each 20 feet in length by 6 inches in width) were recycled in 2011.
  • Initiated a project-wide consumable waste recycling program in 2011, which resulted in recycling of approximately 40 cubic feet of cans, 44 cubic feet of paper, 1,800 cubic feet of plastics and 28 cubic feet of glass during the first year. In 2012, the program resulted in recycling of approximately 59 cubic feet of cans, 85 cubic feet of paper, 206 cubic feet of plastics, 35 cubic feet of glass and 167 cubic yards of scrap metal generated during remedy construction.
  • Completed the 45-acre engineered cap, which covers 3 million cubic yards of tailings, by the end of 2012.

Land Conservation & Ecosystem Service Protection

  • Restored nearly 100% of the needed ground cover on the initial, 4-acre waste rock excavation area with tailing piles (TP-4) within three years. The selected seed mixes, which were applied on borrow soil by way of hand-broadcasting or drilling techniques, contained plant species that could thrive in the area's wet meadow and forest, provide erosion control, create habitat and food sources for insects, birds, and other wildlife, and offer grass and wildflower diversity.
  • Installed biodegradable, wood fiber-based material (Flexterra®) to create a blanket on all slopes adjacent to the completed TP-1A soil cap, to control erosion while fostering revegetation initiated by hydraulic seeding and avoiding the hazards to wildlife sometimes posed by synthetic mesh blankets. The material was blown onto target surfaces via a hand-held spray device that could be deployed with minimal foot or truck traffic.
  • Restored land disturbed by excavation in the site's 2.9-acre "mine road sedimentation basin" during 2012, which involved placement of a 6- to 12-inch-thick layer of native till/soil that was topped by a 12-inch layer of topsoil and a native seed mixture that targets State of Vermont conservation and wildlife goals. Also, eight native trees (red oak and sugar maples) were planted along the basin perimeter. Approximately 3,139 cubic yards of the 7-inch riprap used to temporarily stabilize the area before soil placement was salvaged for immediate onsite use or stockpiled for future reuse.
  • Preserved ecological habitat for the region's endangered bats by installing bat grates at the mine openings before beginning construction work.
  • Created more than 10 acres of wetland as of late 2013. A diverse selection of native trees, shrubs, emergent plugs, tubelings and live stakes (totaling approximately 1,500 plants) was planted throughout the various wetland restoration areas to create habitat for wetland species. Additional wetland creation is scheduled for 2019.
  • Salvaged two stable buildings and the foundations of other buildings during demolition of the site's former milling/smelting complex. Prior to demolition, archeological excavations were conducted to extract historic artifacts such as masonry vessels and factory tools and to document former workings of the complex. Past industrial significance of the Elizabeth Copper Mine as a major producer of copperas (iron sulfate) and the site's recent cleanup are documented in a 2014 report, From Copperas to Cleanup: The History of Vermont's Elizabeth Copper Mine, and onsite educational displays facilitate pre-approved tours by interested parties such as school groups.

Property End Use: Environmental or historic education, regional greenspace and renewable energy development

Point of Contact: Ed Hathaway, U.S. EPA Region 1

Update: October 2017

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