Aquatic Risk Assessment of the Ely Copper Mine

Nicholas Dove, Meghan Arpino, Kelsey Mcauliff, Jordan Monahan, Walt Auten, Nikola Pejovic

Executive Summary

The extraction, metal processing, and waste disposal stages in an ore mining

operation can increase the availability of heavy metals leading to acid mine drainage

(AMD) into sediment, soil, groundwater, and downstream surface water. AMD is a

process in which sulfuric acid is created and metals such as copper, aluminum,

cadmium, and zinc are mobilized when metal sulfides are in the presence of oxygen

and water (US EPA). The mobilization of these metals from the mine tailing waste

increases their bioavailability. Heavy metals and acidic discharge readily accessible

for ecosystem uptake can become a threat to streams, ecosystems, and human

health. The Ely Copper Mine, in Vershire, Vermont has contributed both heavy metal

contamination, specifically copper, and AMD to its downstream river system.

Although impacts to humans are fairly benign, there are many impacts to aquatic

organisms such as macroinvertebrates and trout species (Seal et al., 2010). Biotic

and abiotic remediation techniques have the potential to reduce the bioavailability

of these heavy metals lower pH discharge, and mitigate the stress these pollutants

are imposing on the stream system near the Ely Copper Mine (US EPA). We will

investigate techniques such as phytoextraction and chemical remediation, for their

potential to remediate Ely Copper Mine and the surrounding watershed.

Problem Statement

Runoff from the Ely Copper Mine’s tailings contain heavy metals and toxins

that have negative impacts on aquatic ecosystems, specifically macroinvertebrate

and fish populations (Seal et al., 2010). Therefore, we aim to assess the impacts of

the Ely Copper Mine and discuss the associated risks for aquatic

organisms. Additionally, we aim to discuss possible remediation techniques that

will facilitate the future success of the site’s many aquatic systems

Justification

Several metallic elements including copper are essential for plants and other

forms of life (Srivastava and Gupta, 1996). However, in large quantities, copper can

become toxic to organisms and have ecosystem-wide detrimental effects through

food web interactions and bioaccumulation (Dixon and Sprague, 2002). Fish can be

directly and indirectly harmed by both pH and aquatic copper concentrations in the

long and short term (Soldo and Behra, 2000). Copper can cause direct harm by

accumulating in the gills and flesh of the fish; in high enough concentrations there

can be acute toxicity resulting in death (MacRae et al., 1999). In lower

concentrations, the fish become more tolerant of higher copper concentrations

resulting in a magnification of copper concentrations flowing up the trophic

pyramid as predation occurs; combined with the increased mortality of rate of

juveniles could magnify the collapse of fish populations and community structure

(Soldo, 2000; Sloman, 2003). Ambient pH is also an important stressor of both

brook trout and blacknose dace; low environmental pH results in a significantly

higher mortality rate of cold-water riverine fish species (van Sickle et al., 1996).

Both species of fish could be indirectly affected by the persistence of a low

environmental pH and high copper concentrations. High amounts of environmental

stress in the riverine ecosystem could cause collapsing trophic cascade from the

bottom-up; the stressors in question will, over time, change the community

structure by eliminating sensitive species (Soldo, 2000). Even singular pollutants

can have devastating effects on fish populations, but stressors have been shown to

have synergistic effects on fish, meaning stressor levels considered to be safe will

have measurable, negative effects on fish (Power, 1997).

The deleterious effects of copper are especially evident in copper mining

operations, where excess copper can cause Acid Mine Drainage (AMD) (Utgikar et al.,

2000). AMD causes devastating effects in aquatic ecosystems including reducing

diversity and biomass of aquatic organisms (Kelly, 1988). It has been estimated that

17,000km of streams within the US are contaminated by AMD (Herlihy et al., 1987).

Copper ore is mostly made up of a class of compounds called sulfide minerals which

are in a class of minerals that are commonly associated with mining. Some forms of

copper sulfides include: Chalcocite (Cu2S), Bornite (Cu5FeS4) and Covellite (CuS).

These compounds are intentionally broken down in the refining process, resulting

in pure elemental copper. When the sulfur that was bound to the copper is removed,

it creates the by-product sulfur dioxide gas, which is then intentionally reacted with

water and oxygen to create sulfuric acid. Sulfuric acid is also produced when mine

wastes containing sulfide minerals are exposed to oxygen and water. In turn,

sulfuric acid contributes to the acidity of water bodies surrounding a mining site,

like the Ely Mine, through AMD. The following reactions show the breakdown of

Chalcocite, one of the most prevalent forms of copper ore, to elemental copper and

sulfuric acid that occurs in AMD (Gray et al., 1997):

2Cu2S + 3O2 → 2Cu2O + 2SO2 (1)

Cu2S + 2Cu2O → 6Cu + SO2 (2) 2 SO2 + 2 H2O + O2 → 2 H2SO2 (secondary RxN)

(Figure)

The Ely Copper Mine in Vershire, VT was in operation from 1821-1905 (Figure

1). In 2001, The Ely Copper Mine Superfund site was placed on the US

Environmental Protection Agency’s (EPA) National Priorities List due to on site acid

mine drainage and contamination from mine wastes (Seal et al., 2010). To be

placed on the National Priorities List the Ely Copper Mine achieved a high numerical

ranking within the Environmental Protection Agency’s Hazards Ranking System

(HRS). The HRS evaluates a site based on the likelihood that the site has/will

released a hazardous substance, characteristics of the substance, and

surrounding/impacted ecological and human communities.

Heavy metal and AMD contamination have major implications for the aquatic

community downstream of the mine (Figure 2). Such contamination and acidity

could reduce overall aquatic biodiversity and anthropogenically important fish

populations. Therefore, it is essential to assess and quantify the specific risks posed

to the aquatic ecosystem around the Ely Mine.

Purpose

The purpose of this project is to assess the environmental risks associated with the

Ely Copper Mine and propose potential remediation plans.

Objectives

1. Find the current state of chemical contamination of the mine site and adjacent areas (Al, Co, Cu, Fe, pH, ect.).

2. Research species in the surrounding water bodies (Ely Brook, Schoolhouse Brook, Ompompanoosuc River) that may be negatively impacted by the contamination.

3. Assess current remediation efforts and propose potential future techniques for remediation.

Methods

Using a variety of sources from EPA reports to scientific articles, we

researched acid mine drainage, The Ely Copper Mine, and mining remediation. We

used the search engines Google Scholar, Web of Science, and Academic Search

Premier. Much of the information specific to the Ely Copper Mine came from

reports by the US EPA and third party researchers. We contacted Ed Hathaway, the

remedial project manager for the Ely Mine, and Pam Harting Barrat, the community

involvement coordinator for the Ely Copper Mine to answer questions about the

current status of the Ely Copper Mine. However, we did not hear back from either of

them.

To identify chemical or abiotic remediation techniques that would be

appropriate at the Ely Mine we reviewed the literature for popular techniques. Once

a technique was chosen, we assessed the benefits and costs that could be associated

with using that specific technique at the Ely mine site. In addition, research was

done on what biotic remediation technique would be appropriate for the Ely Mine

site. The plants, resources, and challenges associated with phytoextraction were

researched to assess the risks and benefits of using phytoextraction at the Ely

Copper Mine.

Results Current State:

Currently, the Ely Copper Mine has the potential to pose threats to organisms

living in the water bodies that surround the contaminated area. For this reason, the

mine was placed on the United States Environmental Protection Agency’s (US EPA)

National Priorities List in 2001 (Seal et al., 2010). The National Priorities List helps

the US EPA to determine which sites warrant further investigation. Being placed on

the National Priorities List is a preliminary step in the Superfund cleanup process.

Once the site has been cleaned so that it no longer poses a threat to human and

environmental health, the site will be taken off the list. Cleanup of the Ely Copper

Mine is still in the planning phase, and thus, the timeline for it coming off the

National Priorities List is quite long.

Metal and acid contamination will continue to persist in soils and streams

around the Ely Copper Mine if no remediation efforts are undertaken. Both of these

stressors will continue to cause environmental degradation; perhaps the most

severe impact will be the loss of biotic diversity and abundance in aquatic systems

(Chiras, 2006). The data collected for biotic assessments conducted by the USGS

shows that the loss of biotic diversity and abundance in the aquatic systems

surrounding the Ely Copper Mine has occurred. The USGS 2010 Aquatic Assessment

report indicated that invertebrate abundance and invertebrate species richness

have declined downstream of the Ely Copper Mine (Figure 3). Cold-water fish

species such as trout and blacknose dace, which are found in riverine ecosystems

adjacent and downstream from the Ely mine, are of special concern because of their

ecological and human-use importance (Seal et al., 2010). Both the brook trout and

the blacknose dace are sensitive to aquatic copper concentrations and acid mine

drainage. In sampling for the USGS 2010 Aquatic Assessment report, it was

determined that the concentrations of Copper in Brook trout exceeded the EPA’s

Critical Body Residue (CBR) value of 2.4 micrograms per gram wet weight at one out

of three downstream sampling location. The concentrations of copper in Blacknose

Dace exceeded the same CBR value at four out of eight downstream sampling

locations (Figure 4) (Seal et al., 2010). CBR refers to the concentration of a chemical

that has bioaccumulated in an aquatic organism that is associated with some level of

toxicity such as mortality or reproduction (Barron et al., 1997). CBR values have

been considered accurate for chemicals that organisms are exposed to through the

water; however, the values for sediment and soil exposure pathways are still being

determined (Barron et al., 1997).

Runoff from the mine is contributing to heavy metal contamination and

highly acidic waters in local streams and surface waters such as the Ely Brook, Ely

Brook Tributaries, Schoolhouse Brook, and the Ompompanoosuc River. The Aquatic

Assessment of the Ely Copper mine found many elements had concentration were

greater than Ambient Water Quality Criteria (AWQC) standards at different

intervals throughout the contaminated area (Table 1 ) (Seal et al., 2010).

Concentration above the AWGC indicate that aquatic species will be stressed in

many of these waters. Even though Ely Brook only contributes 7% of the flow to the

Schoolhouse Brook, it is obvious that Ely Brook’s contribution is impacting the pH of

the water in Schoolhouse Brook as well as introducing heavy metal contaminants

(Seal et al., 2010).

Metal or

pH

Upstream

Background

On-site Ely

Brook

Downstream of the mine Chronic

AWQC for

Aquatic Life

Schoolhouse

Brook 1

Schoolhouse

Brook 2

Ompompan-

oosuc River

Al 730 34,000 1400 700 930 87

Cd 0.02 17 0.051 0.29 <.02 1.1

Co 0.05 630 11 6.2 0.24 3.06

Cu 2 15,000 300 170 0.7 11.8

Fe 700 71,000 1700 800 360 1000

Mn 59 3,600 110 55 38 80.3

Ni 0.83 140 3.6 2 0.65 52

Pb 0.82 3 1.1 0.65 0.5 3.2

Zn 20 2,300 46 27 10 106

Lowest

pH 6.55 3 6.2 6.87 6.34 6.5-9

*Metal Concentrations = ug/L

Table 1 . Al, Co, Fe, and Mn were found in concentrations above the Ambient Water Quality Criteria (AWQC) both on site and in Schoolhouse Brook. Concentrations in red indicate exceedance of EPA criteria. Remediation Technique 1:

Plants take up metals from the soil and incorporate the metals into their

tissue. The rate of metal uptake can vary from one species to the next. Plants also

have varying sensitivity to metal concentrations; a concentration that may be toxic

to one plant may be tolerated, or even necessary for another plant. Plants that are

tolerant of high concentrations of metal(s) are called metallophytes. Plants that

accumulate high amounts of contaminants (not limited to metals) are called

hyperaccumulators.

Phytoextraction is a restoration technique that uses plants that are both

hyperaccumulators and metallophytes to target a specific contaminant.

Phytoextraction is an effective technique that could be used to mitigate the harmful

effects of copper at, and surrounding, the Ely Copper Mine site. The success of

phytoextraction process depends on biomass production and metal concentration in

plant shoots (Raskin et al., 1994). Researchers have determined corn to be a

valuable crop in the phytoextraction process, specifically Zea mays L, because it has

a relatively large biomass. it is also capable of accumulating and tolerating high

levels of heavy metals in their tissue (Ebbs et al., 1997). One challenge associated

with phytoextraction is determining what to do with the plants once they have

extracted the metal. While an expensive process, the plants can be sent to labs

where the metals can be extracted and then reused or disposed of in a safe

manner. Another issue is the threat of metals entering the food chain due to

consumption of the plants by wildlife. However, when done in a responsible

manner in which the stalks of the plants are removed and kept from being

consumed, phytoextraction has proven to be an effective measure with little

negative effects to the ecosystem in which it is carried out.

During or after the phytoextraction has occurred, the area may be

manipulated reach a desired future condition in terms of species composition and

structure. A potential technique that we propose in order to reach a pre-mine state

is to revegetate affected areas with native plant species. These native species may

not be tolerant of copper, so they be inoculated with mycorrhizal fungi. A study in

China found that the presence of mycorrhizal fungi, attached to roots of plants,

inhibit the uptake of copper and other present metals (Chen et al., 2007). If the

results are consistent, this fungi would protect the roots of copper intolerant species;

the fungi also aided in phosphorus uptake, which is vital to the growth of plants.

These plantings could be established among plantings of metallophytes, as the

mycorrhizal fungi that will inhibit copper uptake by non-metallophytes.

Remediation Technique 2:

One of the more commonly used techniques for copper remediation in mine

wastewaters is chemical precipitation. Hydroxides or carbonates can be used to

precipitate available copper from the water column under appropriate high pH

conditions. The resulting precipitate complex is insoluble and not bioavailable to the

surrounding environment. This process can be inexpensive as alkaline products can

be utilized to achieve the desired pH. However, there are some disadvantages to

using a chemical precipitation technique.

Disadvantages include the large volume of sludge that forms after

precipitation. Though there is a large amount of sludge, it must be removed

physically. Physical removal does not solve the problem of what to do with the

precipitate; it must either be disposed of like conventional mining wastes, or further

processed into elemental metals. Secondly the alkaline materials will only

precipitate labile copper within the water column, however a significant portion of

the copper is insoluble and will not be precipitated. This insoluble copper will

remain in the system despite precipitation efforts. Finally, the copper within the

stream network would be permanently lost during this process and could not be

utilized afterward (Jordanov et al., 2007).

One type of system used for chemical precipitation in streams and rivers is a

doser. Image 1 is of a medium sized doser located along a tributary that runs into

the North Branch Potomac River. Studies have found that using dosers in tributaries

of the North Branch Potomac River. The doser releases set amounts of an alkaline

material, such as hydrated lime, pebble quicklime, and limestone.

Image 1. Doser along the Lostland Run that feeds into the North Branch Potomac

River.

Aquafix systems is a company that designs dosers for acid mine drainage

systems. Aquafix provides estimated costs of running dosers for 10 year intervals on

their website. For ten years, running an Aquafix system can cost anywhere in the

range of $128,000-175,500 total (Jenkins, 2012). Costs can vary depending on the

type of alkaline material that is used.

These systems work well when a specific stream is being targeted for

remediation, such as the Schoolhouse Brook. Some other benefits are that the

systems can be heated and used during the winter, are suitable for more rugged

terrain, and require little monitoring or maintenance (Jenkins, 2012). However, it is

important to determine whether or not the economic costs of installing an Aquafix

system are feasible for the Ely Copper Mine. In addition, using alkaline materials

that are mined from another location may mean that the negative impacts of mining

are being shifted from one location to another instead of being solved. Small-scale

reducing and alkalinity producing systems have been found to be effective at

removing metals and increasing the pH at site suffering from AMD on a smaller scale,

such as the Ely Copper Mine (Trumm & Watts, 2009). Field trials of a small scale

chemical precipitation system could be appropriate for raising the pH of the Ely and

Schoolhouse Brooks, since the effects of AMD are not as apparents further

downstream in the Ompompanoosuc River.

Conclusion

If the Ely Copper Mine were to employ a chemical precipitation scheme for

their copper laden waste discharge flowing into the Ely Brook and other local

tributaries, a significant amount of copper would remain within the immediate

ecosystem as sludge. While the remaining copper would be insoluble, the acid mine

drainage that is also an issue at the Ely Copper Mine, has the potential to mobilize

the insoluble copper over time if the precipitate sludge is not removed. While

chemical precipitation may be a useful form of remediation, it is not a technique that

can singularly achieve a satisfactory remediated state. An ideal solution for the Ely

Brook may include a combination of chemical precipitation with a biotic

remediation technique in order to achieve efficient and successful remediation

efforts.

Phytoextraction may be most suitable directly at the Ely Copper Mine site if plants

that are able to stand high heavy metal concentrations and a pH as low as 3.5 are

used. However, it may be difficult to find vegetation that would survive in the

conditions created by the Ely Copper Mine tailings and is naturally found in the

ecosystem that the Ely Mine is located. Using a combination of phytoextraction and a

doser system may be the most effective acid mine remediation technique for Ely

Copper Mine , the Schoolhouse Brook and the Ely Brook. Constructing an alkaline

doser system on only the Schoolhouse Brook would minimize costs. Actively

pursuing remediation techniques may improve the quality of the aquatic systems

within the Ely Copper Mine area so that the area can be removed from the list of

Superfund Sites.

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Figures

Figure 1: Site location of the Ely Copper Mine in Vershire, Vermont (Seal et al., 2010).

Figure 2: Nobis Inc. map delineating surface water contamination (red line), site waste areas (tan), impaired sediment (pink), and stream location (blue line) (Nobis Engineering Inc., 2011).

Figure 3: Invertebrate abundance (graph A) and richness (graph B) in Ely Brook. Horizontal axis indicates river meters, with 1,080 m being a reference site above the mine. (Seal et al., 2010)

Figure 4: Copper concentration in micrograms per liter in the surface waters of Ely Brook Tributaries. The number above the error bar indicates number of samples taken at each tributary location. The red line indicates the EPA’s Ambient Water Quality Criteria (AWQC) standard for Copper (Seal et al., 2010).

Figure : USGS figure. The dashed line represents the critical body residue value for salmonoids (2.4 ug/g wet weight). Each dot represents a single fish sample for Brook trout, and a composite sample for Blacknose Dace. Horizontal axis represents river meters (Seal et al., 2010).