TECHNICAL MEMORANDUM UNDERGROUND WORKINGS BEDROCK HYDROGEOLOGY CHARACTERIZATION

ELY COPPER MINE SUPERFUND SITE – OU2 VERSHIRE, VERMONT

1.0 INTRODUCTION

This Technical Memorandum was prepared by Nobis Engineering, Inc. (Nobis) for the United

States Environmental Protection Agency (EPA) under Contract Number EP-S1-06-03, Task

Order Number 0070-RI-CO-017L (Task Order). The work was performed in accordance with

the January 4, 2012 EPA Statement of Work (SOW). The Task Order SOW includes the

completion of a Remedial Investigation/Feasibility Study (RI/FS) at the Ely Copper Mine

Superfund Site Operable Unit 2, (OU2) (“Site”) located in Vershire, Vermont (Figure 1-1).

OU2 has been created, in part, to assess and address potential groundwater impacts related to

the Site underground workings and associated water pool contained within those workings

(“mine pool”). The goal of the OU2 RI/FS is to develop the minimum amount of data necessary

to support the selection of a remedy that eliminates, reduces, or controls risks to human health

and the environment and that can be used to prepare a well-supported Record of Decision

(ROD).

The purpose of this Technical Memorandum (“Tech Memo”) is to present the results of Nobis’

initial OU2 bedrock hydrogeology investigation. As described in Nobis’ Technical

Memorandum, “Underground Workings Field Investigation” and dated 12 September 2012, this

initial investigation includes an air photolineament study, a field bedrock outcrop fracture

investigation, and a recharge analysis. The results of this investigation will contribute to an

updated conceptual site model (CSM), to be included with a deep bedrock Field Investigation

Plan (FIP) for OU2. As described in the September 2012 Technical Memorandum, the FIP will

also include final surveyed drilling targets and locations and access road layouts.

2.0 OBJECTIVE

The primary objective of the field investigations proposed in the September 2012 Tech Memo is

to assess the potential groundwater impact of the underground workings at Ely Mine. In order

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to accomplish this objective we plan to obtain water samples from the mine pool. Safety and

logistical concerns preclude direct entry to the underground workings and direct collection of

water samples from the mine pool. Therefore, the plan is to drill into the underground workings

from above, encounter the mine pool, and pump water samples from the well(s).

The mine pool was at elevation approximately 1,275 feet above mean sea level (ft amsl) when

measured in 1943. The underground workings originate at the Main Shaft located on property

of Ely Mine Forest, Inc. (EMFI) and plunge in the N40E direction at an angle of approximately

25 degrees, extending onto property of Green Crow Corporation (Green Crow). In this Tech

Memo, the “up-plunge” direction is southwest, and northeast is referred to as the “down-plunge”

direction (Figure 1-1).

Sub-objectives of the field investigations described in the September 2012 Tech Memo include:

1. Select optimal drilling locations: select drilling locations that optimize the chances of successfully encountering the underground workings mine pool;

2. Characterize mine pool water quality: characterize water quality along the length, southwest (up-plunge) to northeast (down-plunge), of the underground workings;

3. Assess the relation of underground workings to Site groundwater flow: characterize the relation of underground workings to overall bedrock groundwater flow at

the Site;

4. Assess the relation of bedrock structure to Site groundwater flow: characterize the relation of bedrock structure in the vicinity of the underground workings to overall

bedrock groundwater flow at the Site;

5. Understand the potential impact of the mine pool on deep groundwater and potential future drinking water sources: evaluate whether future drinking water sources would be impacted in the event that new homes that rely on drilled bedrock

wells for water supply are ever built in the area;

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6. Delineate Institutional Control Zone: delineate an institutional control exclusion zone (in which new drinking water wells should not be drilled) around the underground

workings; and

7. Address data gaps: address key data gaps in the present Site characterization related to the above sub-objectives.

The objectives of the bedrock hydrogeology investigations described in this Tech Memo include

taking initial steps to characterize the bedrock fracture network in the vicinity of the underground

workings and estimating the groundwater recharge that may be available to the underground

workings. These characterizations will enhance the CSM for OU2 and will guide future

investigations such as well siting, delineating the institutional control zone, and others. Results

of future investigations, which may include elements such as drilling, borehole geophysics,

pumping, and sampling, will be integrated with the investigations described in this Tech Memo

for ongoing refinement of the CSM.

3.0 DATA GAPS

Key data gaps related to the primary objective and sub-objectives for the overall OU2

underground workings investigation include:

1. the quality of the water in the underground mine pool, and possible variability along the

length of the underground workings;

2. the land surface projection of the underground mine pool;

3. the current elevation (and variability) of the water surface of the underground mine pool;

4. bedrock fracture orientations and potential bedrock groundwater flow paths in the vicinity

of the mine pool; and

5. the land area (if any) beneath which bedrock groundwater quality might be adversely

impacted by the underground workings.

The investigations described in this Tech Memo address the fourth data gap listed above.

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4.0 BEDROCK HYDROGEOLOGY CHARACTERIZATION METHODS AND RESULTS

Nobis performed an air photolineament analysis, a bedrock outcrop fracture investigation, and a

recharge analysis for the present phase of the bedrock hydrogeology characterization and CSM

update. The methods and results of these investigations are described below.

4.1 Air Photolineament Survey

Nobis selected four sets of air photos that cover the study area and surroundings using the

USGS’ interactive, on-line Earth Explorer tool. Nobis then obtained the photos (either as free

downloads or as purchases from USGS) and printed them in 9-inch by 9-inch format. The air

photos cover a range of scales and dates of acquisition and are listed in Table 4-1.

Nobis examined all of the air photo sets in stereo except one (Table 4-1). Nobis analyzed the

air photos and traced observed photolineaments on mylar overlays on the air photos. Nobis

interpreted each observed photolineament on a subjective scale of “strong,” “intermediate,” or

“weak,” based on the prominence of the feature and the observer’s confidence that the feature

is natural and not man-made. The working definition of photolineament for this study is: “a more

or less linear feature observed on an air photo or other image that is believed to represent a

natural geologic structure.” Photolineaments may represent bedrock faults, fracture zones,

metamorphic foliations, bedrock formation contacts, or other geologic structures. Glacial

features can also appear as linear features on air photos. Photolineaments may appear on air

photos as linear valleys or other topographic features, parallel valleys and ridges, tonal or color

changes, etc. Care must be taken not to interpret roads, property lines, utility corridors, and

other cultural features as photolineaments.

After tracing photolineaments on mylar overlays placed on at least one air photo from each set,

Nobis digitized the lineaments as GIS data layers and compiled them onto a single, air photo-

based figure (Figure 4-1). Photolineaments interpreted on two or more sets of air photos

provide more confidence that they represent real geologic features such as bedrock fracture

zones than lineaments interpreted on only one photograph. For example, a lineament

extending southward from the area of the Ely Mine main shaft (Figure 4-1) appeared as a strong

lineament on the NAPP infrared photos, an intermediate lineament on the GS-AF black and

white photos, and a weak lineament on the NHAP high altitude infrared photos. This lineament

can be attributed to a bedrock structure with much more confidence than if it had only been

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4.2

interpreted on one set of air photos. Of the lineaments shown on Figure 4-1, north-northeast

(NNE) – south-southwest (SSW) appears to be the most common lineament orientation, with

east – west (E-W) lineaments also common, along with lineaments of other orientations.

Within the study area, observed lineaments include the NNE-SSW lineament south of the main

shaft (see above), lineaments that trend approximately E-W and coincide with an unnamed

brook located on Green Crow property, a series of short weak lineaments observed only on the

NHAP infrared photos and located north of the main shaft, and a longer, but weak northeast-

trending lineament located west of the underground workings. Of these features, any whose

trends coincide with key fracture directions noted in bedrock outcrops can be interpreted as

bedrock fracture zones with increased confidence. (See below.)

Bedrock Outcrop Fracture Study

On June 18 and June 28, 2012, two Nobis geologists measured bedrock fractures in a series of

bedrock outcrops at the Ely Mine site (Figure 4-2). Outcrop 1 is located east of the Main Adit.

Outcrops 2, 3, and 5 are located on the hillside northwest of the underground workings but still

south of the ridge crest of Dwight Hill (Figure 1-1) that coincides roughly with the property line of

Green Crow, located to the north. Outcrops 4, 6, and 7 are located along the ridge crest;

outcrop 6 is located in a topographic saddle near where the surface projection of the

underground workings crosses the ridge crest. Outcrops 9 and 10 are located northeast of the

ridge crest and northwest of the underground workings. Outcrop 8 is located north of an

unnamed brook that crosses the projection of the underground workings and flows eastward

within the Green Crow property.

Although detailed lithologic description and geologic mapping were not objectives of the

investigation, the outcrops observed consisted primarily of gray schist with varying amounts of

quartz, in the form of veins or boudins. The primary objective of the field mapping was to

measure the orientation of bedrock fractures that appear to be open or to represent

discontinuities in the rock along which water could possibly flow. In general, the outcrops

observed were relatively massive, with relatively low fracture density (wide fracture spacing),

although most outcrops were not large enough to set up traverses to quantify average fracture

spacing. On the southwest side of Dwight Hill and along the ridge crest, outcrops are frequent

and often appear as hogbacks or small ridges that dip into the hillside and strike relatively

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parallel to the hillside. Northeast of the ridge crest, outcrops are less frequent. At one location

(Outcrop 9; Figure 4-2), the outcrop surface is formed by a fracture along metamorphic foliation,

and this outcrop surface conforms to the topographic slope in the area.

For each outcrop, Nobis obtained location information with a hand-held GPS unit; we noted that

the accuracy of the location information varied, perhaps due to heavy tree cover in some

locations. Other landmarks were also located with GPS, for possible future use in tracing the

surface projection of the underground workings (Figure 4-2). At each outcrop, Nobis measured

the strike and dip of fractures that appeared to be open or potentially open. The strike and dip

measurements were made with a pocket transit, set for a magnetic declination of 15.5 degrees

west, so that the data are relative to true north. For most outcrops, one or more fractures that

coincide with metamorphic foliation were observed and measured, but the majority of fractures

cut across metamorphic foliation.

A compilation of the fracture orientation data for all the outcrops (Figure 4-3) shows a broad

northwest-southeast (NW-SE) statistical peak from N30W to N70W. Northeast-southwest (NE

SW) striking fractures (N20E to N50E) are also common, with lesser statistical peaks trending

east-southeast (ESE; N90E to N100E) and north-northeast (NNE; 0 to N10E). A lower

hemisphere stereographic projection of the poles to all the fractures measured (Figure 4-3)

illustrates a wide scattering of fracture orientations. On the stereo plot, fracture poles on or near

the outer edge of the plot show that a large number of the fractures are steeply dipping or

vertical, with lower-dipping fractures (poles near the center of the plot) present but less

common.

Within the area investigated, predominant fracture strikes vary with location (Figure 4-4). North

of the ridge crest, NNE and NE-trending fractures (0 to N40E in Outcrop 8 and N30E to N40E in

Outcrops 9 and 10) predominate. However, south of the ridge crest, much more variability is

present, with a range of NW-striking fractures predominant in most of the outcrops. Figure 4-4

also shows the potential drilling locations that Nobis identified in the September 2012 Tech

Memo.

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4.3 Underground Workings Recharge Estimate

An estimate of the average annual recharge to groundwater that may reach the underground

workings can provide an order-of-magnitude assessment of the flux of groundwater that may be

expected to reach the underground workings as a result of infiltration of precipitation into the

ground under average conditions. A recharge estimate may also predict the range of yields for

wells that may be drilled in the area. Nobis used an estimation method that assumes that the

portion of the average annual precipitation that infiltrates into the ground and recharges

groundwater can be approximated based on the general soil and surficial geologic deposit type.

For example, areas underlain by glacial outwash sand and gravel receive considerably greater

groundwater recharge than areas underlain by glacial till, bedrock that is close to the surface, or

clay.

Nobis conducted this recharge analysis for the area that is topographically above the trace of

the underground workings, and thus constitutes the catchment or surface drainage basin for the

mapped trace of the underground workings. Nobis subdivided this area into three Recharge

Areas, A, B, and C (Figure 4-5). Recharge Area A is topographically above the up-plunge

portion of the underground workings, on the southwest flank of Dwight Hill. The last known

elevation of the mine pool (Figure 4-4) occurs within this area so that some water infiltrating

from above may reach the workings above (southwest of) the mine pool in the underground

workings. Recharge Area B is the area topographically above the trace of the underground

workings on the northeast (down-plunge) side of Dwight Hill. Recharge Area C is

topographically above the far northeastern portion of the workings, where the trace of the

workings is north of a local sub-drainage basin divide (Figure 4-5).

These recharge areas may not be the actual areas from which the underground workings

receive water because bedrock fractures that might connect to the underground workings may

reach the surface outside of the mapped recharge areas. This is equivalent to saying that

permeable bedrock fractures may cross local sub-drainage basin divides. This uncertainty may

increase, proceeding northeastward, down the plunge of the underground workings, because

the area of the land surface that may be intersected by a dipping fracture that is connected to

the underground workings can be expected to widen as the workings deepen. On the other

hand, the likelihood that permeable, connected bedrock fractures reach from the surface all the

way down to the workings decreases with the depth of the workings. Also, not all water that

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infiltrates the ground in these mapped areas can be expected to reach the underground

workings (or a well that may be drilled in the area). These considerations indicate that the

recharge estimates should be interpreted with caution and should be considered order-of

magnitude estimates only.

The average annual precipitation in Vershire, Vermont is 40.2 inches (Weather.com). For the

present recharge calculations, Nobis assumed that about 25% of the annual average

precipitation infiltrates into the ground and recharges groundwater in the areas identified. This

assumption is based on a recharge estimate of 10 inches per year that replenishes groundwater

in areas where the surface geologic deposits are glacial till or where bedrock is near the surface

(known as till/bedrock uplands) in the Contoocook River Basin of New Hampshire (Harte and

Johnson, 1995) and a recharge estimate of 10 inches per year for “somewhat poorly drained

soils” in Vermont (Vermont Agency of Agriculture website).

Nobis estimated the average recharge to each of the three Recharge Areas and the total for the

three areas by computing the areas in square feet, multiplying this value by 10 inches and

obtaining the average volume of recharge in a year in cubic feet. This value was also converted

to gallons per minute on an average basis. The results are shown on Table 4-2 and show that a

total of more than 2,860,000 cubic feet of water per year may recharge the underground

workings. This is equivalent to about 5.4 gallons per minute, on average. If a recharge rate of

greater or less than 10 inches per year were used, the results would change proportionally but

would be of the same order of magnitude. If permeable fractures connected to the surface

reach the surface considerably outside the mapped Recharge Areas, they may draw water over

a significantly larger area; this would mean that annual recharge may be greater than the

estimate. On the other hand, if deeper portions of the underground workings do not have

permeable fractures that intersect them and also connect to the surface, actual recharge to the

workings may be lower than estimated.

5.0 DISCUSSION AND CONCLUSIONS

• Nobis obtained and analyzed four sets of air photos (black and white and color infrared)

that cover a range of dates and scales. Photolineaments interpreted from these photos

have a variety of orientations, with NNE-SSW and E-W especially prominent in the Ely

Copper Mine vicinity. Particular lineaments in the Ely Copper Mine study area include

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http:Weather.com

NNE lineaments south of the Main Shaft and lineaments that trend just south of E-W that

coincide with an unnamed brook that crosses the projection of the underground

workings. Other, weaker lineaments were also detected.

• Nobis measured the orientation of bedrock fractures in 10 outcrops in the vicinity of the

underground workings. The outcrops consist of gray schist with quartz and are relatively

massive. Some fractures coincide with metamorphic foliation, but most fractures cross

cut foliation. The most common fracture strike direction is N30W to N70W, with

northeast strikes (N20E to N50E) also common, especially north of Dwight Hill. Lesser

statistical peaks occur for NNE and ESE fractures. The majority of the fractures

observed are steeply dipping to vertical, but moderate and low-dipping fractures are also

present.

• Nobis identified three Recharge Areas in which the surface topography is up hill of the

trace of the underground workings. Acknowledging assumptions and inaccuracies,

Nobis estimates that more than 2,860,000 cubic feet per year of water may recharge the

underground workings; this is equivalent to about 5.4 gallons per minute and should be

considered an order-of-magnitude estimate only.

Synthesizing the results of the air photolineament and bedrock outcrop fracture investigations

indicates that the two most prominent lineaments in the study area coincide with secondary

statistical peaks in the outcrop fracture data. These lineaments include NNE-SSW lineaments

south of the Main Shaft and an ESE-WNW lineament coinciding with the unnamed brook.

Because these lineament orientations coincide with observed fracture strikes, this provides

confidence that the lineaments may represent bedrock fracture zones. Less prominent

lineaments in the study area that trend NW or NE may also represent bedrock fracture zones,

since these were common fracture strike orientations. However, north-northwest striking

lineaments do not coincide with measured bedrock fracture strikes, so these lineaments are less

likely to represent bedrock fracture zones. It should be noted that air photolineaments

preferentially represent steeply dipping or vertical fractures, whereas the outcrops examined

had both vertical and horizontal faces, allowing the observation of both low-dipping and steeply

dipping fractures that may intersect those faces.

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Some of the mapped photolineaments in the study area intersect the delineated Recharge

Areas and/or the trace of the underground workings. If these lineaments represent permeable

bedrock fracture zones and if these fracture zones intersect the underground workings, these

may be preferred pathways for actual recharge to the wells and also potential pathways for

transport of any contaminants that may be present in the mine pool.

6.0 REFERENCES

Harte, P. T. and Johnson, W., 1995, Geohydrology and Water Quality of Stratified Drift Aquifers

in the Contoocook River Basin, South Central New Hampshire, USGS Water Resources

Investigation Report 92-4154.

Nobis, 2012, Underground Investigations Field Investigations. Technical Memorandum,

September.

Vermont Agency of Agriculture, Groundwater Dilution Example (posted on Agency website, as

of 2/6/13).

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T A B L E S

Table 4-1 Air Photos Examined

Ely Copper Mine Superfund Site - OU2 Vershire, Vermont

Program Acquisition Date Type Roll & Frame Nos Approximate Scale of 9"x9" print Comments

GS-AF 9/1/1942 black & white 2--189, 201, 202 1:51,000 small scale; quality good but not excellent GS-VCLL 5/29/1970 black & white 1 -- 17 1:38,000 much better resolution; not viewed in stereo HAP 85F 4/17/1985 color infrared 51 -- 80, 81 1:80,000 high altitude; excellent resolution NAPP 5/12/1992 color infrared 4198 -- 134,135 1:40,000 larger scale than HAP; excellent resolution

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Table 4-2 Recharge Analysis

Ely Copper Mine Superfund Site - OU2 Vershire, Vermont

Recharge Area Name and Description Area (sq ft)

General Surficial Geology

Recharge Rate (in/yr)

Estimated Annual Recharge to Groundwater

(cu ft/yr)

Estimated Annual Recharge to Groundwater

(gpm)

Comments

A: southwest of ridge crest 514996 till & bedrock 10 429163 0.82 Catchment area for up-plunge portion of underground workings

B: northeast of ridge crest 2821736 till & bedrock 10 2351447 4.47 Catchment area for down-plunge portion of underground workings

C: far end of underground workings 99044 till & bedrock 10 82537 0.16 Catchment area for far down-plunge end of underground workings (see text) TOTAL 3435776 till & bedrock 10 2863147 5.44

Note: See text for explanation of calculations and limiting assumptions.

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Outc rops , F rac tu re Str i kes , and Po tent i al Dr i l l ing Targe ts

February 2013 Revision No. 00 Underg round Work ings Bedrock Hydrogeol ogy Inves t iga t ion

0 100 200 400 APPROXIMATE SCALE

Ely C opper Mine 1 inch = 400 feet Ve rshi re, Ve rmon t

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Recharge Area A514,996 sqft

Recharge Area B2,821,736 sqft

Recharge Area C99,044 sqft

Ely Copper Mine Study Area

UndergroundWorkings

SchoolhouseBrook

Ely Copper Mine Superfund Site

Main Shaft

APPROXIMATE SCALE

Revis ion No. 00

Drawn By: JH Checked By: AB FIGURE 4-5 February 2013 ³ Recharge Areas Underground Workings Bedrock Quadrangle Location USGS TOPOGRAPHIC MAP VERSHIRE, VERMONT Hydrogeology Investigation 0 100 200 400 600 800 1981; (Photo-inspected 1983) Ely Copper Mine Feet 1 inch = 800 feet Vershire, Vermont

TECHNICAL MEMORANDUM - UNDERGROUND WORKINGS BEDROCK HYDROGEOLOGY CHARACTERIZATION1.0 INTRODUCTION2.0 OBJECTIVE3.0 DATA GAPS4.0 BEDROCK HYDROGEOLOGY CHARACTERIZATION METHODS AND RESULTS4.1 Air Photolineament Survey4.2 Bedrock Outcrop Fracture Study4.3 Underground Workings Recharge Estimate

5.0 DISCUSSION AND CONCLUSIONS6.0 REFERENCESTABLES4-1 - Air Photos Examined4-2 - Recharge Analysis

FIGURES1-1 - Site Locus4-1 - Photolineaments4-2 - June 2012 Outcrops and Other Features4-3 - Bedrock Fracture Orientations4-4 - Outcrops, Fracture Strikes, and Potential Drilling Targets4-5 - Recharge Areas

barcode: *577662*barcodetext: SDMS Doc ID 577662