HRS DOCUMENTATION RECORD COVER SHEET

Name of Site: Anaconda Aluminum Co Columbia Falls Reduction Plant 

EPA ID No.: MTD057561763 

Contact Person 

Site Investigation and

Documentation Record: Sabrina Forrest (303) 312-6484 

NPL Coordinator 

U.S. Environmental Protection Agency, Region 8 

1595 Wynkoop Street, Mail Code: 8EPR-B 

Denver, Colorado 80202-1129 

Pathways, Components, or Threats Not Scored 

Soil Exposure Pathway

Although several contaminants are present at elevated concentrations in soils, the distance to nearby 

residents or other targets, the size, and the relative inaccessibility of the former facility precludes easy 

access to all the source areas. Therefore, the pathway score is unlikely to impact the listing decision.

Air Migration Pathway

There are no data to satisfy HRS requirements for establishing an observed release and no evidence to 

suggest a significant release to the air at the Anaconda Aluminum Co Columbia Falls Reduction Plant. 

As such, the air migration pathway will not be scored as part of this HRS package.

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763
HRS DOCUMENTATION RECORD

Name of Site: Anaconda Aluminum Co Columbia Falls Date Prepared: March 2015

Reduction Plant

EPA Region: 8

Street Address of Site: Eastern end of Aluminum Drive

City, County, State: Columbia Falls, Flathead County, Montana 59912

General Location in the State: Approximately 1.5 miles northeast of downtown Columbia Falls. The site 

is just north of the Flathead River (Figure 1). 

Latitude: 48° 23' 16.35" North Longitude: 114° 07' 49.07" West for the easternmost southern 

percolation pond (Figure 2).

* The street address, coordinates, and contaminant locations presented in this HRS documentation record 

identify the general area the site is located. They represent one or more locations the United States 

Environmental Protection Agency (EPA) considers to be part of the site based on the screening 

information EPA used to evaluate the site for NPL listing. EPA lists national priorities among the known 

"releases or threatened releases" of hazardous substances; thus, the focus is on the release, not precisely 

delineated boundaries. A site is defined as where a hazardous substance has been "deposited, stored, 

disposed, or placed, or has otherwise come to be located." Generally, HRS scoring and the subsequent 

listing of a release merely represent the initial determination that a certain area may need to be addressed 

under CERCLA. Accordingly, EPA contemplates that the preliminary description of facility boundaries at 

the time of scoring will be refined as more information is developed as to where the contamination has 

come to be located.

Scores

Air Migration Pathway NS

Ground Water Migration Pathway 93.33

Soil Exposure Migration Pathway NS

Surface Water Migration Pathway 100.00

HRS Site Score 68.39

NS – Not Scored

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 1
WORKSHEET FOR COMPUTING HRS SITE SCORE

 S S2

 

1. Ground Water Migration Pathway Score (Sgw) 93.33 8710.48 

(from Table 3-1, line 13) 

2a. Surface Water Overland/Flood Migration Component NS NS

(from Table 4-1, line 30) 

2b. Ground water to Surface Water Migration Component 100.00 10,000 

(from Table 4-25, line 28)

2c. Surface Water Migration Pathway Score (Ssw) 100.00 10,000 

Enter the larger of lines 2a and 2b as the pathway score.

3. Soil Exposure Pathway Score (Ss) NS NS

(from Table 5-1, line 22) 

4. Air Migration Pathway Score (Sa) NS NS

(from Table 6-1, line 12) 

5. Total of S 2

gw + S 2 sw + S 2s + S 2a 18710.48 

6. HRS Site Score Divide the value on line 5

by 4 and take the square root 68.39 

NS = Not Scored

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 2 
TABLE 3-1 

GROUND WATER MIGRATION PATHWAY SCORESHEET

Factor Categories and Factors Maximum Value Value Assigned

Likelihood of Release to an Aquifer

1. Observed Release 550 550 

2. Potential to Release:

2a. Containment 10 NS

2b. Net Precipitation 10 NS

2c. Depth to Aquifer 5 NS

2d. Travel Time 35 NS

2e. Potential to Release [lines 

2a(2b+2c+2d)] 

500 NS

3. Likelihood of Release (higher of lines 1 and 2e) 550 550 

Waste Characteristics

4. Toxicity/Mobility a 10,000 

5. Hazardous Waste Quantity a 10,000 

6. Waste Characteristics 100 100 

Targets

7. Nearest Well 50 50 

8. Population 

8a. Level I Concentrations b 90 

8b. Level II Concentrations b 0 

8c. Potential Contamination b 0

8d. Population (lines 8a + 8b + 8c) b 90 

9. Resources 5 0 

10. Wellhead Protection Area 20 0 

11. Targets (lines 7 + 8d + 9 + 10) b 140 

Ground Water Migration Score for an 

Aquifer 

12. Aquifer Score [(lines 3 x 6 x 11)/82,500] c

100.00 93.33 

Ground Water Migration Pathway Score 

13. Pathway Score (SWsw), (highest value from 

line 12 for all aquifers evaluated)c

100.00 93.33 

a Maximum value applies to waste characteristics category

b Maximum value not applicable

c Do not round to the nearest integer

NS Not scored

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 3 
(continued)

TABLE 4-25 

GROUND WATER TO SURFACE WATER MIGRATION COMPONENT SCORE SHEET

Factor Categories and Factors Maximum 

Value

Value 

Assigned

Drinking Water Threat

Likelihood of Release: 

1. Observed Release

2. Potential to Release: 

2a. Containment 

2b. Net Precipitation

2c. Depth to Aquifer 

2d. Travel Time

2e. Potential to Release (line 2a[2b+2c+2d]) 

3. Likelihood of Release (higher of lines 1 and 4) 

550 

10 

10 

5 

35 

500 

550 

550 

NS

NS

NS

NS

NS

550 

Waste Characteristics: 

4. Toxicity/Mobility/Persistence

5. Hazardous Waste Quantity

6. Waste Characteristics

(a)

(a)

100 

NS

NS

NS

Targets:

7. Nearest Intake

8. Population 

8a. Level I Concentrations 

8b. Level II Concentrations 

8c. Potential Contamination 

8d. Population (lines 8a+8b+18c) 

9. Resources

10. Targets (lines 7+18d+19) 

50 

(b) 

(b) 

(b) 

(b) 

5 

(b) 

NS

NS

NS

NS

NS

NS

NS

Drinking Water Threat Score:

11. Drinking Water Threat Score ([lines 3×6×10]/82,500, subject to a 

maximum of 100) 100 NS

Human Food Chain Threat

Likelihood of Release: 

12. Likelihood of Release (same value as line 3) 550 550 

Waste Characteristics: 

13. Toxicity/Mobility/Persistence/Bioaccumulation

14. Hazardous Waste Quantity

15. Waste Characteristics

(a)

(a)

1,000 

5 x 106

10,000 

320 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 4 
(continued)

TABLE 4-25 

GROUND WATER TO SURFACE WATER MIGRATION COMPONENT SCORE SHEET

Factor Categories and Factors Maximum 

Value

Value 

Assigned

Targets:

16. Food Chain Individual 

17. Population 

17a. Level I Concentrations 

17b. Level II Concentrations 

17c. Potential Human Food Chain Contamination 

17d. Population (lines 19a+19b+19c) 

18. Targets (lines 16+17d)

50 

(b) 

(b) 

(b) 

(b) 

(b) 

45 

0 

0.03 

0 

0.03 

45.03 

Human Food Chain Threat Score: 

19. Human Food Chain Threat Score ([lines 12×15×18]/82,500, subject 

to a maximum of 100) 100 96 

Environmental Threat 

Likelihood of Release:

20. Likelihood of Release (same value as line 5) 550 550 

Waste Characteristics:

21. Ecosystem Toxicity/Mobility/Persistence/Bioaccumulation

22. Hazardous Waste Quantity

23. Waste Characteristics

(a)

(a)

1,000 

5 x 106

10,000 

320 

Targets:

24. Sensitive Environments 

24a. Level I Concentrations 

24b. Level II Concentrations 

24c. Potential Contamination 

24d. Sensitive Environments (lines 26a+26b+26c) 

25. Targets (value from line 24d)

(b) 

(b) 

(b) 

(b) 

(b) 

0 

150 

0 

150 

150 

Environmental Threat Score: 

26. Environmental Threat Score ( [lines 20×23×25]/82,500, subject to a 

maximum of 60) 60 60 

Surface Water Overland/Flood Migration Component Score for a Watershed 

27. Watershed Scorec (lines 11+19+26, subject to a maximum of 100) 100 100 

Surface Water Overland/Flood Migration Component Score 

27. Component Score (Sof)

c (highest score from line 27 for all 

watersheds evaluated, subject to a maximum of 100)

100 100 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 5 
NS = Not Scored.

(a) = Maximum value applies to waste characteristics category

(b) = Maximum value not applicable

(c) = Do not round to the nearest integer

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 6
REFERENCES

Ref.

No. Description of the Reference

1. U.S. Environmental Protection Agency (EPA), Hazard Ranking System (HRS). December 14, 1990. 

Excerpt. Cover page only. A complete copy is available 

at: http://www.epa.gov/superfund/sites/npl/hrsres/rule/hrsrule.pdf and in the Region 8 Docket. 

2. EPA. Superfund Chemical Data Matrix (SCDM). June 2014. Excerpt. 42 pages. A complete copy of 

SCDM is available at: http://epa.gov/superfund/sites/npl/hrsres/tools/scdm.htm.

3. Weston Solutions, Inc. 2014. Site Reassessment for Columbia Falls Aluminum Company, Aluminum 

Smelter Facility, Columbia Falls, Flathead County, Montana. April 4, 2014. 355 pages.

3a. Weston Solutions, Inc. 2014. Appendix F, Sections 1 through 7. Site Reassessment for Columbia Falls 

Aluminum Company, Aluminum Smelter Facility, Columbia Falls, Flathead County, Montana. April 4, 

2014. Sections 1 through 6, 1517 pages each, Section 7, 1511 pages.

4. U.S. Census Bureau, 2010. Flathead County Quickfacts. July 8, 2014. Available 

from: http://quickfacts.census.gov/qfd/states/30/30029.html. Accessed October 16, 2014. 2 pages.

5. Ecology and Environment, Inc., 1988. Draft Report of Sampling Activities, Columbia Falls Aluminum 

Company, Columbia Falls, Montana. July 15, 1988. 71 pages. 

6. Columbia Falls Aluminum Company (CFAC), 1994. Storm Water Pollution Prevention Plan (SWPPP), 

CFAC, October 1994. 32 pages.

7. MT Department of Environmental Quality (DEQ), 1999. Major Industrial No Bio-monitoring Permit 

No: MT0030066. Authorization to Discharge under the Montana Pollutant Discharge Elimination System. 

January 4, 1999. 26 pages.

8. Ecology and Environment, Inc., 1988. Draft Analytical Results Report, Columbia Falls Aluminum 

Company, Columbia Falls, Montana. November 11, 1988. 294 pages.

9. CFAC, 1998. Letter with attachment. MPDES Permit Renewal and Mixing Zone Application, CFAC. 

July 31, 1998. 41 pages.

10. Reference Number Reserved. 

11. EPA, 1984. Aerial Photographic Analysis of Waste Study Sites, Montana. EPA Region 8. November, 

1984. 59 pages.

12. Reference Number Reserved. 

13. Reference Number Reserved. 

14. Reference Number Reserved. 

15. Olympus Environmental, Inc., 1992. Remedial Activities Report for Transformer Oil Spill at 

Columbia Falls Aluminum Company, Columbia Falls, Montana. April 14, 1992. 6 pages.

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 7
16. Reference Number Reserved. 

17. EPA, 1996. Using Qualified Data to Document and Observed Release and Observed Contamination. 

Office of Solid Waste and Emergency Response (OSWER). November 1996. 18 pages.

18. Hydrometrics, 1985. Hydrogeologic Evaluation, Columbia Falls Aluminum Company, Columbia 

Falls, Montana. September 16, 1985. 177 pages.

19. CFAC, 2013. CFAC EPA Presentation. June 3, 2013. 37 pages.

20. Konizeski, R.L., Brietkrietz, A., and McMurtrey, G.G., 1968. Geology and Ground Water Resources 

of the Kalispell Valley, Northwestern Montana, Bulletin No. 68. Montana Bureau of Mines and Geology. 

July, 1968. 46 pages.

21. Reference Number Reserved.

22. Reference Number Reserved. 

23. Reference Number Reserved. 

24. Parker, Robert, 2013. Site Assessment Manager, EPA Region 8. Email communication with Natalie 

Quiet, September 30, 2013. 1 page.

25. US Geological Survey, 2014. National Water Information System, USGS Surface-Water Annual 

Statistic for the Nation, USGS 12363000 Flathead River at Columbia Falls 

MT. http://waterdata.usgs.gov/nwis/annual/?referred_module=sw&site_no=12363000&por_12363000_5=

66275,00060,5,1922,2014&year_type=W&format=html_table&date_format=YYYY-MMDD&rdb_compression=file&submitted_form=parameter_selection_list. Accessed January 22, 2014. 4 

pages.

26. US Fish and Wildlife Service (USFWS), 2014. Information, Planning, and Conservation System 

(IPaC). Trust Resources List. http://ecos.fws.gov/ipac/. October 17, 2014. 8 pages.

27. Montana State Parks (MSP). Montana Fish, Wildlife & Parks, Montana Fisheries Information System 

(MFish). Waterbody Report. http://fwp.mt.gov/fishing/mFish/. Accessed October 15, 2014. 50 pages.

28. Deleray, Mark, 2014. Email Communication with Natalie Quiet, Weston. Fishery information on 

Cedar Creek. March 19-21, 2014. 1 page.

29. U.S. Fish and Wildlife Service. National Wetlands Inventory. Accessed February 26, 2015. 6 pages. 

30. Wessling, Elizabeth, 2015. Senior Vice President, MECx, Aurora, CO. Email Communication with 

Natalie Quiet, February 18, 2015. 1 page.

31. Quiet, Natalie, 2014. Weston Solutions. Email Communication, Areas of Various Sources for CFAC.

December 3, 2014 - December 18, 2014. 4 pages. 

32. Weston Solutions, Inc., 2013. Sampling and Analysis Plan for the Columbia Falls Aluminum 

Company, Aluminum Smelter Facility, Columbia Falls, Flathead County, Montana. September, 2013. 

140 Pages.

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 8
33. ArcGIS, 2013. Bing Maps Aerial, Layer Package by esri. Last modified on November 25, 2013. 2 

pages.

34. Federal Emergency Management Agency (FEMA). 1988. Flood Insurance Rate Map, Flathead 

County, Montana and Incorporated Areas. Panel 1120G and 1140G of 3525. Map Number 

30029C1120G. Dated September 28, 2007. 2 pages, includes 1 map sheet.

35. Deleray, Mark, 2015. Email Communication, January 23, 2015. 1 page.

36. MT DEQ, 1998. Letter Communications between Steve Wright, Environmental Manager, CFAC, and 

Montana Department of Environmental Quality, February 13 through October 14, 1998. 8 pages.

37. Quiet, Natalie, 2014. Weston Solutions. Email Communication with John Lucotch. December 18, 

2014. 1 page.

38. City of Columbia Falls, 2013. PUBLIC NOTICE, 2013 Annual Drinking Water Quality Report. 4 

pages.

39. EPA, 2015. EnviroMapper. Available from: http://www.epa.gov/myem/efmap/index.html.

Accessed February 11, 2015. 1 page. 

40. MSP, 2014. Montana Fish, Wildlife, and Parks. Bull Trout.

http://fwp.mt.gov/fishAndWildlife/species/threatened/bullTrout/. Accessed February 14, 2015. 1 page.

41. Quiet, Natalie, 2015. Weston Solutions. Memorandum with attachment: Reference 41 – Methodology 

and Source Data Used to Create Figure 1. March 18, 2015. 1374 pages. 

42. Montana Natural Heritage Program, 2014. Animal Species of Concern Report.

http://mtnhp.org/SpeciesOfConcern/?AorP=a. Updated April 21, 2014. 16 pages.

43. Parker, Rob, 2015. U. S. EPA Region 8. Memorandum: Number of residences and residents supplied 

by Pump One Association well. February 25, 2015. 1 page.

44. Sandusky, Eric, Weston Solutions. 2015. Memorandum. February 25, 2015. 1 page.

45. U.S. Fish and Wildlife Service. Critical Habitat for Bull Trout (Salvelinus confluentus) Unit: 31, SubUnit Flathead Lake North Flathead River. 1 page.

46. Department of the Interior. 2010. Fish and Wildlife Service. 50 CFR Part 17. Endangered and 

Threatened Wildlife and Plants; Revised Designation of Critical Habitat for Bull Trout in the 

Conterminous United States; Final Rule. October 18, 2010. 174 pages.

47. Quiet, Natalie, Weston Solutions. 2015. Memorandum: Wetland Calculations in Actual 

Contamination Area. February 27, 2015. 1 page. 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 9
FIGURE 1

SITE LOCATION MAP

COLUMBIA FALLS 

ALUMINUM COMPANY

COLUMBIA FALLS, MONTANA

Date: 3/14/2014

Legend

Property Boundary

0 0.275 0.55 1.1 Miles

Prepared for:

U.S. EPA Region 8

Contract No.:

EP-S8-13-01

TDD:

1305-04

DCN:

W0004.1A.00115

Prepared By:

Weston Solutions, Inc.

START IV

Suite 100

1435 Garrison Street

Lakewood, CO 80215

Montana

Utah

Idaho

Nevada

Wyoming

Colorado

California

Oregon

Arizona New Mexico

Washington

±

!(
RIV-M

RIV-2

RIV-1

W10-TW22

W8-TW2

W1-PW7

W7-TW19

W9-PW5

W3-TW20

W11-TW17

W5-TW15

TW11

TW23

TW12

TW16

TW1

PW6

PW3

PW4

TW9

TW3

TW10

TW14

TW8

W0-CFMW2

FIGURE 2

FEATURES MAP

ANACONDA ALUMINUM

CO COL FLS RED PL

COLUMBIA FALLS, MONTANA

Date: 2/17/2015

Legend

Groundwater Monitoring Wells

MPDES Permit Surface Water Monitoring Locations

MPDES Permit Groundwater Monitoring Wells

Cross Section

Streams and Drainages

Feature Boundary

0 0.15 0.3 0.6 Miles

Prepared for:

U.S. EPA Region 8

Contract No.:

EP-S8-13-01

TDD:

1407-05

DCN: ± W0.1A.00

Prepared By:

Weston Solutions, Inc.

START IV

Suite 100

1435 Garrison Street

Lakewood, CO 80215

Cedar Creek Reservoir 

Overflow Drainage W2-CFMW1

Cedar Creek

Industrial Landfill

Asbestos Landfill

West Landfill Sanitary Landfill

B

Wet Scrubber Sludge Pond

A

North Leachate Pond

Center Landfill

East Landfill

South Leachate Pond

Asbestos Landfill

Industrial 

By-products

North Percolation Pond

North Percolation Pond

West Percolation Pond

A'

South Percolation Ponds

!(

Flathead River

B'

Montana

Utah

Idaho

Nevada

Wyoming

Colorado

California

Oregon

Arizona New Mexico

Washington
FIGURE 3

POTENTIOMETRIC

CONTOUR MAP

COLUMBIA FALLS 

ALUMINUM COMPANY

COLUMBIA FALLS, MONTANA

Date: 3/14/2014

Legend

Groundwater Monitoring Wells

MPDES Permit Surface Water Monitoring Locations

MPDES Permit Groundwater Monitoring Wells

3080 Potentiometric Surface Contour

 (Dashed where Inferred)

Note: Survey data not available; elevations are estimated

0 0.15 0.3 0.6 Miles

Prepared for:

U.S. EPA Region 8

Contract No.:

EP-S8-13-01

TDD:

1305-04

DCN:

W0004.1A.00115

Prepared By:

Weston Solutions, Inc.

START IV

Suite 100

1435 Garrison Street

Lakewood, CO 80215

3040.55

3085.16

3026.97

3025.14

3056.05

3083.19

3058.21

3072.29

3059.28

3013.72

3024

RIV-M

RIV-2

RIV-1

W10-TW22

W8-TW2

W1-PW7

W7-TW19

W9-PW5

W3-TW20

W11-TW17

W6-TW18

W5-TW15

W2-CFMW1

TW11

TW23

TW12

TW16

TW1

PW6

PW3

PW4

TW9

TW3

TW10

TW14

TW8

W0-CFMW2

3014.55

3144.33

3058.31

W4-TW21

3058.03

3073.15

3058.88

3060.01

3055.85

3021.27

NM

NM

NM

NM

NM

NM

±

3013

3012

3010

3080

3070

3060

3050

3040

3030

3020

3140

3130

3120

3110

3090

3100

3140

3130

3120

3110

3100

3090

3080

3070

3060

3050

3040

3030

3020

3010
FIGURE 4

SAMPLE LOCATIONS MAP

ANACONDA ALUMINUM

CO COL FLS RED PL

COLUMBIA FALLS, MONTANA

Date: 2/17/2015

0 0.3 0.6 1.2

Miles

Legend

Feature Boundary

!( Groundwater Sampling Location

!( Surface Water & Waste Source Sampling Location

!( Surface Soil Sample Locations

!( Surface Water & Sediment Sampling Location

Prepared for:

U.S. EPA Region 8

Contract No.:

EP-S8-13-01

TDD:

1407-05

DCN: ± W0157.1A.00381

Prepared By:

Weston Solutions, Inc.

START IV

Suite 100

1435 Garrison Street

Lakewood, CO 80215

!(

!(

!(

!(

!( !(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!( !( !(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!( !(

!(

!( !(

!( !(

!(

!( !(

!(

!(

!(

!( !(

!(

!(

CF-SD-04

CF-SS-07

CF-SS-06

CF-SW-07

CF-SD-07

CF-SD-08

CF-SW-09

CF-SD-09

CF-SD-OP-01

CF-SS-05

CF-GW-MW-14

CF-GW-MW-01

CF-GW-MW-08

CF-GW-MW-09

CF-GW-MW-10

CF-GW-MW-07

CF-GW-MW-02

CF-GW-MW-04

CF-GW-MW-03

CF-GW-MW-11

CF-SW-05

CF-SD-05

CF-SD-06

CF-SS-04

CF-SS-08

CF-SS-03

CF-SS-01 CF-SS-02

CF-SD-02 CF-SD-01

CF-SD-03 CF-SW-19

CF-GW-OP-02 CF-SW-22

CF-SW-21

CF-GW-MW-12

CF-SD-14

CF-SD-13

CF-GW-MW-13 CF-SD-15

CF-SD-16

CF-GW-MW-15

CF-WS-17

CF-WS-18

CF-SW-03 CF-WS-20

CF-WS-19

CF-WS-21

CF-SW-08

CF-SW-13

CF-SW-14

CF-SW-16

CF-SW-15

CF-GW-MW-06

CF-SW-20

CF-GW-MW-05

CF-WS-22

CF-SW-01

CF-SW-06
FIGURE 5

GROUNDWATER SAMPLE LOCATION MAP

ANACONDA ALUMINUM CO COL FLS PLT

COLUMBIA FALLS, MONTANA

Date: 2/16/2015

Legend ! Columbia Falls Municipal Wells !( Groundwater Sampling Location

Feature Boundary

0 0.5 1

Miles

Prepared for:

U.S. EPA Region 8

Contract No.:

EP-S8-13-01

TDD:

1407-05

DCN:

W0157.1A.00381

Prepared By:

Weston Solutions, Inc.

START IV

Suite 100

1435 Garrison Street

Lakewood, CO 80215
FIGURE 6

SURFACE WATER/SEDIMENT AND

SURFACE WATER/WASTE SOURCE

SAMPLE LOCATION MAP

ANACONDA ALUMINUM CO COL FLS RED PLT.

COLUMBIA FALLS, MONTANA

Date: 2/27/2015

Legend

( Surface Water & Sediment

Sampling Location

!( Surface Water & Waste

Source Sampling Location

Wetlands (source: NWI)

0 0.25 0.5 1

Miles

Prepared for:

U.S. EPA Region 8

Contract No.:

EP-S8-13-01

TDD:

1407-05

DCN: ± W0157.1A.00381

Prepared By:

Weston Solutions, Inc.

START IV

Suite 100

1435 Garrison Street

Lakewood, CO 80215

CF-WS-17

CF-WS-18

CF-SW-03

CF-WS-20

CF-WS-19

CF-WS-21

CF-SW-08

CF-SW-13

CF-SW-14

CF-SW-16

CF-SW-15

CF-SW-20

CF-WS-22

CF-SW-01

CF-SW-06

CF-SD-01

CF-SD-02

CF-SD-OP-01

CF-SW-19 CF-SD-03

CF-SW-05

CF-SD-05

CF-SD-06

CF-SW-07

CF-SD-07 CF-SW-21

CF-SD-08

CF-SW-22

CF-SW-09

CF-SD-09

CF-SD-04

CF-SD-13

CF-SD-14

CF-SD-15

CF-SD-16

!

Actual Contamination Actual Contamination

Uppermost PPE Uppermost PPE

PPE PPE

Source 1 Source 1 PPE PPE

Source 4 Source 4

PPE PPE

Source 3 Source 3

PPE PPE

Source 2 Source 2
GROUNDWATER ELEVATION GC = GRAVEL-SAND-CLAY MIXTURE GM = GRAVEL-SAND-SILT MIXTURE GP = GRAVEL-SAND MIXTURE (WELL SORTED) SM = SAND-SILT MIXTURE ROCK = BEDROCK

2800

2900

3000

3100

3200

2800

2900

3000

3100

3200

HORIZONTAL DISTANCE

TW16 W8-TW2 TW1 W11-TW17

TW9

TD=100FT SM

TD=240FT

GC

TD=60FT

GP

TD=90FT GP

GC

TD=195FT

GM

GC

ROCK

A A' 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500

SM

HORIZONTAL

VERTICAL

0 350' 700'

0 70' 140'
2800

2900

3000

3100

3200

2800

2900

3000

3100

3200

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 HORIZONTAL DISTANCE

W10-TW22 TW11 W11-TW17

TW9

TD=300FT

TD=60FT GP

TD=90FT GP

GC

TD=195FT GC

ROCK

B B'

CF-GW-OP-02

TD=169FT

GC GW

GW

GM

GM

GW

SM

SW

SW SW

GP

SC

GC

SW

GW

GW

GROUNDWATER ELEVATION GC = GRAVEL-SAND-CLAY MIXTURE GM = GRAVEL-SAND-SILT MIXTURE GP = GRAVEL-SAND MIXTURE (WELL SORTED)

GW = GRAVEL-SAND MIXTURE (POORLY SORTED) SM = SAND-SILT MIXTURE

SW = WELL – GRADED GRAVELLY SANDS ROCK = BEDROCK

HORIZONTAL

VERTICAL

0 550' 1100'

0 110' 220'
Figure 9 - 15-Mile Target Distance Limit Map for Anaconda Aluminum Co Columbia Falls Reduction 

Plant

This document can be viewed at the USEPA Docket Center, Public Reading Room. Address: USEPA 

West 1301 Constitution Ave, NW Room 3334, Washington, DC 20004. Telephone: 202-566-1744. Fax: 

566-9744. Email: docket-customerservice@epa.gov.
Figure 

References

Figure 1 – Refs. 33; 41 

Figure 2 – Refs. 3, Appendix A, pp. 111-156, Appendix C, pp. 187 and 189; 8, p. 37; 33 

Figure 3 - Refs. 3, Appendix A, pp. 111-156, Appendix C, pp. 187 and 189; 33; p. 55 of this 

HRS Documentation Record 

Figure 4 – Refs. 3, Appendix A, pp. 111-156, Appendix C, pp. 187 and 189; 8, p. 37; 33; p. 55 of 

this HRS Documentation Record 

Figure 5 - Refs. 3, Appendix A, pp. 111-156, Appendix C, pp. 187 and 189; 24; 8, p. 37; 33; 38; p. 55 

of this HRS Documentation Record 

Figure 6 - Refs. 3, Appendix C, p. 187; 29; 33; Figure 2 of this HRS Documentation Record 

Figure 7 - Refs. 3, Appendix A, pp. 111, 112, 115, 127, 128, 130, Appendix C, pp. 187 and 

189, Appendix D, p. 195; 33; p. 55 of this HRS Documentation Record 

Figure 8 - Refs. 3, Appendix A, pp. 115, 130, 119-121, 153-156, Appendix C, pp. 187 and 189, 

Appendix D, p. 195; 33; p. 55 of this HRS Documentation Record 

Figure 9 - Refs. 3, Appendix C, pp. 187; 33; Figures 2 and 6 of this HRS Documentation Record 
SITE DESCRIPTION

The Anaconda Aluminum Co Columbia Falls Reduction Plant site includes the release from an aluminum 

production facility located in Flathead County, Montana. EPA is evaluating the Ground Water and 

Surface Water Migration Pathways for the Anaconda Aluminum Co Columbia Falls Reduction Plant site. 

For HRS scoring purposes, the site consists of five source areas that have been documented through

chemical analysis to contain hazardous substances and releases to ground and surface water. Source No. 1 

comprises the Eastern North Percolation Pond; Source No. 2 is the Western North Percolation Pond: 

Source No. 3 is the Western South Percolation Pond: Source No. 4 is the Eastern South Percolation Pond:

and Source No. 5 is the West Landfill (Ref. 3, pp. 8-12 and Figure 2 of this HRS documentation record). 

Source No. 1 is considered as source type “surface impoundment”; Sources No. 2 through 4 are 

considered as source type “pile”, while Source No. 5 is considered to be source type “landfill” under the 

HRS (Ref. 1, pp. 51587, 51591). Additional possible sources of various hazardous substances at the 

property that have not been characterized to date include six additional landfill areas, three additional 

ponds, storage tanks, a waste pile area, and the cathode pits (Refs. 3, pp. 20-24; 19, pp. 14-17; Figure 2 of 

this HRS documentation record).

The hazardous substances that have been detected in at least one of the sources listed above include, but

are not limited to: Aroclor 1254; and the metals arsenic, cadmium, chromium, cyanide, manganese, and 

zinc (Ref. 3, pp. 46-49; Section 2.2.1 of this HRS documentation record for Sources 1, 2, 3, 4, and 5). 

Samples collected from the Eastern North Percolation Pond (co-located aqueous and solid samples: CFSW-19 and CF-SD-19, and CF-SW-20 and CF-SD-20) were located near the inflow point or depositional 

area of discharge from the Paste Plant Briquette Quench system, Paste Plant Ball Mill Bearing Cooling 

system, Wet Scrubber Blowdown, Air Compressor Cooling, Air Compressor Condensate Blowdown, 

Masonry Shop, and Battery Shop. Samples for the Western North Percolation Pond (CF-SW-17 and CFSD-17, and CF-SW-18 and CF-SD-18) were collected near the inflow point or depositional area of 

discharge from the Eastern North Percolation Pond (Ref. 32, p. 37; Figures 4 and 6 of this HRS 

documentation record).

Samples for the Central South Percolations Pond (co-located aqueous and solid samples: CF-SW-21 and 

CF-SD-21), were located at the inflow point from the western pond, and samples for the Eastern South 

Percolation Pond (CF-SW-22 and CF-SD-22) were located at the center of the pond (Ref. 32, p. 37; 

Figures 4 and 6 of this HRS documentation record).

Some of these hazardous substances have been released into ground water beneath the property, as well as

the Flathead River (located directly adjacent to the property), at concentrations elevated above

background (Section 2.2.2 [Source 5], and Sections 3.1.1 and 4.2.1 of this HRS documentation record). 

According to the MDEQ Pollutant Discharge Elimination System Permit, ground water at the facility, 

which receives process wastewaters, discharge to the surface water of the Flathead River along the 

southwestern portion of the property (Refs. 7, p. 5; 19, pp. 18, 19).

Given the interconnected nature of the wastestreams at the facility and the hazardous substances already 

identified within the percolation ponds and the west landfill (Sources 1, 2, 3, 4, and 5), it is possible that 

the other possible sources listed below would have similar types and concentrations of hazardous 

substances to those identified in the sources evaluated for this documentation record through chemical 

analysis. The west percolation pond, the wet scrubber sludge pond, the north and south leachate ponds, 

the industrial by-products area, and the cathode soaking pits were not directly evaluated during the 2013 

sampling event and therefore chemical analytical data are not available for those potential sources. In 

addition, none of the landfills listed were sampled during the 2013 sampling event. Given the age of the 

plant, fashion in which contaminants present onsite were handled, that some of the landfills were only 

covered (not capped), and the connectivity of ground water with surface water in the area, these other 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 20
possible sources may need to be characterized during the Remedial Investigation/Feasibility Study (Refs. 

3, pp. 21-24).

Targets evaluated for this HRS documentation record were ground water users, fisheries, wetlands and 

sensitive environments. Ground water in the area is used for drinking by both municipal and private 

residents. The nearest private well is located approximately one mile to the west and the city of Columbia

Falls operates two municipal wells between three and four miles to the west (Refs. , 24, 38). The Flathead

River watershed was evaluated for this HRS documentation record. The Flathead River is a fishery that 

supports a variety of finfish that are harvested for human consumption, as well as supporting the federally 

designated threatened bull trout (Refs. 27, pp. 33-34, 48, 4928). Significant areas of wetlands are present 

along the Flathead River, in areas adjacent to and downstream of the facility (Ref. 29). 

The facility is located within the boundaries of Township 30N, Range 20W, Section 3 at 

48.3931351074135 latitude and -114.134158794466 longitude (Figure 1). It is approximately 2.0 miles 

northeast from the population center of Columbia Falls, Flathead County, Montana, at 2000 Aluminum 

Drive (Ref. 3, p. 14). The closest residences are approximately 1 mile north, southeast, and west of the 

facility (Ref. 3, p. 20). According to the 2010 Census, the total population of Flathead County is 90,928 

(Ref. 4). The elevation at the facility is approximately 3,100 feet above mean sea level (amsl). 

Topography at the facility is generally flat with a southern slope at approximately 3° to 4° with the area 

north of the Facility slightly steeper at approximately 5° to 6° (Ref. 5, pp. 2, 3).

The total area of the property owned by Anaconda Aluminum Co Columbia Falls Reduction Plant is 

approximately 3,196 acres (Figure 1). For the purposes of this investigation site is defined as the areas 

where hazardous substances have been deposited, stored, disposed, placed, or have otherwise come to be 

located. (Figure 1, Ref. 3, p. 14). The facility is bordered to the north by Cedar Creek Reservoir, to the 

east by Teakettle Mountain, to the south by the Flathead River, to the west by Cedar Creek, and sits 

within the Flathead River-Columbia Falls watershed. Current Facility use is primarily for minimal plant 

maintenance activities, wildlife corridors, and local specially permitted hunting limited to the west and 

north sides of the Facility in the fall. Access to the Facility is available via Aluminum Drive and through 

private land from the north. The closest residence is adjacent to the western CFAC property boundary and 

is approximately 0.92 mile from the plant (Ref. 3, p. 14).

The Anaconda Copper Mining Company built the Anaconda Aluminum Reduction Facility and began 

production in 1955. The Atlantic Richfield Company (ARCO) purchased the plant in 1978 and operated it 

until 1985 when it was sold to the Montana Aluminum Investor’s Corporation and began operations under 

Anaconda Aluminum Co Columbia Falls Reduction Plant. In 1999, Glencore acquired the company and 

operated until 2009 when production was curtailed due to poor economic conditions for aluminum 

production. The plant is a Vertical Stud Soderberg aluminum reduction facility that uses the Hall Heroult 

process of producing aluminum in carbon–lined “pots” heated to 960 degrees Celsius (°C). Aluminum 

oxide is dissolved in a molten cryolite bath and aluminum oxide is reduced to aluminum metal by 

electrons from direct current through the pot. The molten aluminum is then tapped from the pot and cast 

into ingots. This process uses 350 megawatts, and 600 pots at 100% production. There are currently 451 

pots in place; however the facility has not operated since October 31, 2009 (Refs. 3, p. 20; 19, pp. 6-8).

Aluminum smelting operations are not currently active on-site; however, the plant features identified and 

included in this investigation consist of numerous buildings and industrial operating facilities such as 

offices, warehouses, mechanical shops, laboratory, washhouse, paste plant, coal tar pitch tanks, pump 

houses, and the main pot line facility. Features on the facility property include percolation ponds, leachate 

ponds, sludge ponds, sewage treatment ponds, cathode soaking pits, closed and operational landfills 

(Figure 2). Current Facility conditions are based on observations made during the September 23, 2013 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 21
through October 1, 2013 sampling event. Facility features (Figure 2) observed during the 2013 sampling 

event are described in the table below (Ref. 3, p. 20). 

Feature (Reference) Description

East Landfill

(Refs. 3, p. 21; 19, pp. 15-

16)

The Spent Potliner Landfill, also known as the East Landfill, operated from 

approximately 1980-1990 and is a clay-lined landfill used to dispose of spent potliners 

prior to their declaration as a hazardous waste. The landfill was capped with a 

synthetic cap and revegetated in 1990. MT DEQ was aware of the landfill closure plan 

(October 12, 1989 letter from John Arrigo, MT DEQ Water Quality Bureau, to Don 

Ryan, Anaconda Aluminum Co Columbia Falls Reduction Plant). This area was 

observed to be closed and covered with grass during the field sampling activities.

West Landfill

(Refs. 3, p. 21; 8, p. 9; 19, 

p. 16.)

Anaconda Aluminum Co Columbia Falls Reduction Plant operated an unlined solid 

waste landfill, also known as the West Landfill, from 1955-1981 for which they 

disposed of general garbage including, paper, scrap from the shops, strapping, steel 

scrap and scrap wood, and spent potliner (1955-1970). Spent potliner wasn’t listed by 

the EPA as hazardous waste until 1991. As a result, ground water monitoring around 

the landfill had detected elevated concentrations of cyanide, a byproduct of the carbon 

product pot life. The landfill was capped with a clay cap in approximately 1992 / 

synthetic cap in 1994 (EPA Presentation) as a special permit condition under the 

MPDES Permit No. MT0030066. Solvents and hazardous wastes are known to have 

been buried on-site in the closed landfills (West, Center and Sanitary). This area was 

observed to be closed and covered with grass during the field sampling activities.

Wet Scrubber Sludge 

Pond Landfill

(Refs. 3, p. 21; 9, p. 13; 

19, p. 15. Identified by 

Steve Wright, CFAC, 

during June 2013 facility 

visit.)

Wet Scrubber Sludge Pond Landfill was closed in approximately 1980 and contained 

sludge waste generated from the Wet Scrubber System and for a period from 

approximately 1994-1998 contained spent potliner material. The landfill was 

recontoured, covered with native soil and revegetated with native grasses. This area 

was observed to be closed and covered with grass during the field sampling activities.

Center Landfill

(Refs. 3, p. 21; 8, p. 9; 19, 

p. 16.)

The Center Landfill, also known as the Carbon Pile, is an unlined landfill operated 

from approximately 1970- 1980. Solvents and hazardous wastes are known to have 

been buried on-site in the closed landfills (West, Center and Sanitary). This area was 

observed to be closed and covered with grass during the field sampling activities.

Sanitary Landfill

(Refs. 3, p. 22; 19, p. 15.)

The Sanitary Landfill is a clay-lined historic landfill used for plant garbage. The 

landfill was covered with soil and re-vegetated. Years of operation unknown. Solvents 

and hazardous wastes are known to have been buried on-site in the closed landfill 

(West, Center and Sanitary). This area was observed to be closed and covered with 

grass during the field sampling activities.

Asbestos Landfill

(Location identified by 

Steve Wright, CFAC, 

during June 2013 facility 

visit.)

Based on a review of aerial photography the Asbestos Landfill began operation in 

approximately the early 2000's; date last used is unknown. This area was observed to 

be closed and covered with grass during the field sampling activities.

Industrial Landfill

(Location identified by 

Steve Wright, CFAC 

during June 2013 facility 

visit. 19.)

The Industrial Landfill is an active landfill that receives non-hazardous waste and 

debris. This area was observed to be active and disturbed. The area was covered with 

gravelly soil during the field sampling activities.

North and South 

Leachate Ponds

(Refs. 3, p. 22; 6, p. 11)

Two hypalon-lined leachate ponds were constructed on opposite ends of the East 

Landfill in 1980, one on the north side of the landfill (North Leachate Pond) and one 

on the south side of the landfill (South leachate Pond). The ponds were used to collect 

runoff water from the East Landfill containing the spent potliner material and aerated 

during the summer months to reduce water volume and utilize ultraviolet light to break 

down the cyanide. According to a letter from Donald F. Ryan, Laboratory Manager at 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 22 
Feature (Reference) Description

Anaconda Aluminum Co Columbia Falls Reduction Plant, to MT DEQ dated January 

5, 1990, approximately 150,000 gallons of leachate water containing fluoride and 

approximately 3 mg/L of cyanide was drained from the South Leachate Pond into the 

Wet Scrubber Sludge Pond Landfill. This transfer of leachate was approved by MT 

DEQ (October 12, 1989 letter from John Arrigo, MT DEQ Water Quality Bureau, to 

Don Ryan, Anaconda Aluminum Co Columbia Falls Reduction Plant). The South 

leachate Pond was dried, capped, and subsequently closed in 1993. An underground 

pipe leads from the North Leachate Pond to the Wet Scrubber Sludge Pond. The North 

Leachate Pond held cyanide-free water containing fluoride and was subsequently 

drained into the Wet Scrubber Sludge Pond Landfill. The North Leachate Pond was 

capped and then closed in 1994. These areas were observed to be closed and covered 

with grass during the field sampling activities.

North Percolation Ponds

(Refs. 3, p. 23; 6, pp. 4, 5, 

7-9, 12-15; 7, p. 4; 9, p. 4)

The North Percolation Ponds (smaller eastern pond receives direct discharge, larger 

western pond is overflow) historically received wastewaters from the Paste Plant 

Briquette Quench system, Paste Plant Ball Mill Bearing Cooling system, Wet Scrubber

Blowdown (until approximately 1999), Air Compressor Cooling, Air Compressor 

Condensate Blowdown, Masonry Shop, and Battery Shop. Prior to 1978 the waste 

effluent from the soaking of the carbon cathodes was piped to the North Percolation 

Pond, also known as the Boiler Blowdown Pond (smaller pond). In addition to the 

aforementioned, the ponds currently receive garage waste water, steam cleaning and 

pin crane sumps waters, lab boiler blowdown water, equipment non-contact cooling 

water, and process area storm water. Both ponds contained dark gray/black process 

material and were sparsely vegetated with grasses, shrubs, and trees. No water was 

present in the western pond during the field sampling activities. The smaller eastern 

pond contained water of an unknown depth.

West Percolation Pond

(Refs. 3, p. 23)

The West Percolation Pond receives wastewater from the boiler blowdown 

(Fabrication Shop, Warehouse, and Change House) and storm water from the parking 

lots. The pond was not visited during the field sampling activities.

South Percolation Ponds

(Refs. 3, p. 23; 6, p. 5, 9, 

10; 7. pp. 4, 5; 9, p. 4) 

The South Percolation Ponds receive wastewaters from the Rectifier Oil Separator 

Sump, Facility Production Area storm water, non-contact equipment cooling water, 

Sewage Treatment Plant, Restrooms and Change House sinks, Laboratory Sinks, 

laboratory non-contact cooling water, laboratory non-solvent waste water, plant wide 

lavatories and sinks, Rectifier non-contact cooling water, casting mold cleaning water, 

casting mold steam cleaning, contact cooling water from direct chill casting of 

aluminum ingots, and Fabrication Shop Steam Cleaning Bay. The south percolation 

ponds were predominantly dry with minimal amounts of water in the ponds during the 

field sampling event. Both were vegetated with grasses, shrubs, and trees

Industrial By-products 

Area

(Refs. 3, p. 24; 11, pp. 27-

29.)

The Industrial by-products area and numerous waste piles have been identified in 

various locations throughout the Facility. This area was observed during the field 

activities to be disturbed with some grass cover.

Cathode Soaking Pits

(Refs. 3, p. 24; ) 

Carbon cathode soaking pits contained water and ammonia to expedite the carbon 

removal process. The pits were not observed during the sampling activities.

Cleanup activities that have occurred on the Facility include addressing a transformer fire in the rectifier 

yard that occurred on September 10, 1991. The transformer held approximately 10,000 gallons of 

dielectric fluid that contain approximately 207 parts per million (ppm) polychlorinated biphenyls (PCBs). 

Approximately 4,000 gallons spilled into the containment basin and the explosion resulted in the 

contamination of an approximate 4,000 to 5,000 square-foot area. According to the Remedial Activities 

Report by Olympus Environmental, Inc. the spill area soils and structures were remediated to less than 10 

ug/100 cm3 and no further cleanup was recommended to the MDEQ (Refs. 15, pp. 3, 4, 6; 6, pp. 1, 11).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 23
In 1994 two capacitors in the West Rectifier Yard Capacitor Bank exploded contaminating steel holding 

frames and soil with 3 to 4 gallons of pure PCBs. According to Anaconda Aluminum Co Columbia Falls 

Reduction Plant’s October, 1994 SWPPP the surrounding capacitors, framing, and soils were removed 

and disposed of in a certified Toxic Substances Control Act (TSCA) landfill, and the area cleared for 

operational use. It is unknown what regulatory agency approved this action (Ref. 6, pp. 1, 11).

In February 1998, The State of Montana’s Permitting and Compliance Division of the Air & Water 

Management Bureau requested that Anaconda Aluminum Co Columbia Falls Reduction Plant remove all 

of the spent potliner material (EPA hazardous waste number K088) present in the Wet Scrubber Sludge 

Pond Landfill due to improper disposal of a hazardous waste. Post removal, on July 28, 1998 Anaconda 

Aluminum Co Columbia Falls Reduction Plant sampled the pot diggings material from the Wet Scrubber 

Sludge Pond Landfill to determine if carbon in the Wet Scrubber Sludge Pond Landfill had been 

adequately removed. Results of the sampling indicated that cyanide was detected in all of the pot diggings 

material samples collected (highest concentration 2.1 ppm) and half of the soil samples collected from 

under the waste pile. EPA Region III Residential Risk-Based Criteria was 1600 ppm and thus, in October 

1998, the State declared no further clean-up action required for the pot diggings material or soil under the

pile (Refs. 19, pp. 12, 30; 36, p. 5).

Anaconda Aluminum Co Columbia Falls Reduction Plant conducted sampling on September 25, 2001 

during suspended plant operations in response to inquiries by the Montana Department of Environmental 

Quality Air and Waste Management Bureau as to the determination if waste in accumulation is hazardous 

waste. Materials sampled were anode briquettes, cryolite bath, coal tar pitch, anode dust control bags and

potlines sweepings bags. The analytical results indicated that one of the sampled materials were classified 

as hazardous waste under RCRA regulation but may be eligible substances under CERCLA (Ref. 19, p. 

31-34).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 24
2.2 SOURCE CHARACTERIZATION

Although there are many possible sources contributing to ground water and surface water contamination 

associated with this site, this documentation record is focused on the following five sources, due to the 

relatively recent sampling event that has provided the data regarding the northern percolation ponds, the 

southern percolation ponds, and the west landfill.

2.2.1 SOURCE IDENTIFICATION

Source Number: 1

Name of source: Eastern North Percolation Pond

Source Type: Surface Impoundment

Description and Location of Source (with reference to a map of the facility):

The Eastern North Percolation Pond (also known as the boiler blowdown pond [Figure 2]) received direct 

discharge of the Paste Plant Briquette Quench system, Paste Plant Ball Mill Bearing Cooling system, Wet 

Scrubber Blowdown (until approximately 1999), Air Compressor Cooling, Air Compressor Condensate 

Blowdown, Masonry shop, and Battery shop. Prior to 1978, the waste effluent from the soaking of the 

carbon cathodes was piped to this pond. In addition to the aforementioned, the pond was receiving garage 

waste water, steam cleaning and pin crane sumps waters, lab boiler blowdown water, equipment noncontact cooling water, and process area storm water. Because the primary wastestream generated onsite 

was spent potliner (i.e., RCRA listed waste K088 for cyanide) and this source received effluent containing 

anode material as well as discharge from several shops, metals, cyanide, and miscellaneous organic 

contaminants would be found in this source (Refs. 6, pp. 4, 5, 7, 8, 11-15; 7, pp. 5, 6, 26; 19, pp. 12, 17). 

The pond covered approximately 1.1 acres in the center of the facility as determined using GIS (Ref. 31, 

p. 1; 33). Overflow from this pond flowed via channel into the Western North Percolation Pond (i.e., 

Source 2; see below) (Ref. 7, pp. 4, 5). A total of three (including one duplicate) source surface water 

samples (CF-SW-19, CF-SW-20 and CF-SW-25 [duplicate of CF-SW-19]) were collected from the 

Eastern North Percolation Pond. Concentrations of SVOCs and metals were detected above the reporting 

limit in surface water samples collected from the Eastern North Percolation Pond (Ref. 3, pp. 73, 74; 

Figure 6).

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE

Source Samples:

All source sampling was done in accordance with EPA Environmental Response Team (ERT) SOPs 

2012, 2013, 2016, and 2017 (Ref. 32, p. 47). For example, at each location, the aqueous sample was 

collected before the solid-matrix sample, and a new disposable plastic scoop was used to collect each 

solid-matrix sample to ensure that the aqueous sample didn’t include any solids disturbed by the sampling 

process. All samples were collected during the same September/October 2013 sampling event, over a 

period of nine days (September 23 to October 1) (Ref. 3, pp. 27, 37)

The analytical results of the sludge waste (solid-matrix) source samples (CF-SD-19, CF-SD-20 and CFSD-25 (duplicate for CF-SD-19) [Figure 6])) from the Eastern North Percolation Pond are presented in 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 25
Tables E17-E23, Appendix E of the Site Reassessment Report (SRR) (Ref. 3, pp. 176, 263-275). 

Laboratory data and validation reports are presented in Appendix F of the same document (Ref. 3a, App. 

F, Section 7, pp. 1431-1516). Contaminant concentrations in the solid-matrix waste source samples were 

considered detections when the result was greater than the analytical reporting limit. Although several 

TAL metals contaminants were detected in waste source samples collected from the Eastern North 

Percolation Pond that were consistent with wastes expected to be found, only the following are evaluated

based on their impact in scoring: 

Hazardous 

Substance

Evidence

Sample References

No.

RL 

(mg/kg)

Concentration 

(mg/kg)

Arsenic

CF-SD-19 

(MH0063) 

1 

43.3 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 398, Section 7, pp. 1431, 

1441, 1442

CF-SD-20 

(MH0064) 10.5 

Refs. 3, pp. 47-49, App. B, p. 177; App. D, pp. 

205, 206; App E, Table E22, pp. 273; 3a App. 

F, Section 5, pp. 392, 399, Section 7, pp. 1431, 

1442

CF-SD-25 

(MH0069) 15.3 

Refs. 3, pp. 47-49; App. D, p. 205; App E, 

Table E22, pp. 273; 3a App. F, Section 5, pp. 

393, 402, Section 7, pp. 1431, 1444, 1445

Cadmium

CF-SD-19 

(MH0063) 

0.5 

14 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 398, Section 7, pp. 1431, 

1441, 1442

CF-SD-20 

(MH0064) 4 

Refs. 3, pp. 47-49, App. B, p. 177; App. D, pp. 

205, 206; App E, Table E22, pp. 273; 3a, App. 

F, Section 5, pp. 392, 399, Section 7, pp. 1431, 

1442

CF-SD-25 

(MH0069) 3.8 

Refs. 3, pp. 47-49; App. D, p. 205; App E, 

Table E22, pp. 273; 3a, App. F, Section 5, pp. 

393, 402, Section 7, pp.1431, 1444, 1445

Chromium 

CF-SD-19 

(MH0063) 

1 

36.1 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 398, Section 7, pp. 1431, 

1441, 1442

CF-SD-20 

(MH0064) 21.1 

Refs. 3, pp. 47-49, App. B, p. 177; App. D, pp. 

205, 206; App E, Table E22, pp. 273; 3a, App. 

F, Section 5, pp. 392, 399, Section 7, pp. 1431, 

1442

CF-SD-25 

(MH0069) 21.5 

Refs. 3, pp. 47-49; App. D, p. 205; App E, 

Table E22, pp. 273; 3a, App. F, Section 5, pp. 

393, 402, Section 7, pp. 1431, 1444, 1445

Cyanide 

CF-SD-19 

(MH0063) 0.5 

172 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 398, Section 7, pp. 1431, 

1438

CF-SD-20

(MH0064) 2.9 Refs. 3, pp. 47-49, App. B, p. 177; App. D, pp. 205, 206; App E, Table E22, pp. 273; 3a, App. 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 26 
Hazardous 

Substance

Evidence

Sample References

No.

RL 

(mg/kg)

Concentration 

(mg/kg)

F, Section 5, pp. 392, 399, Section 7, pp. 1431, 

1438

CF-SD-25 

(MH0069) 106

Refs. 3, pp. 47-49; App. D, p. 205; App E, 

Table E22, pp. 273; 3a, App. F, Section 5, pp. 

393, 402, Section 7, pp.1431, 1439

Manganese

CF-SD-19 

(MH0063)

1.5

106

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 398, Section 7, pp. 1431, 

1438, 1440

CF-SD-20

(MH0064) 29.3

Refs. 3, pp. 47-49, App. B, p. 177; App. D, pp. 

205, 206; App E, Table E22, pp. 273; 3a, App. 

F, Section 5, pp. 392, 399, Section 7, pp. 1431, 

1442

CF-SD-25 

(MH0069) 61.4

Refs. 3, pp. 47-49; App. D, p. 205; App E, 

Table E22, pp. 273; 3a, App. F, Section 5, pp. 

393, 402, Section 7, pp.1431, 1444, 1445

Zinc

CF-SD-19 

(MH0063)

6

565

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 398, Section 7, pp. 1431, 

1438, 1440

CF-SD-20

(MH0064) 431

Refs. 3, pp. 47-49, App. B, p. 177; App. D, pp. 

205, 206; App E, Table E22, pp. 273; 3a, App. 

F, Section 5, pp. 392, 399, Section 7, pp. 1431, 

1442

CF-SD-25 

(MH0069) 235

Refs. 3, pp. 47-49; App. D, p. 205; App E, 

Table E22, pp. 273; 3a, App. F, Section 5, pp. 

393, 402, Section 7, pp.1431, 1444, 1445

Notes: mg/kg milligrams per kilogram

J The associated value is an estimated quantity. The value is well above the reporting limit, and as 

such useable for characterization.

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

Source Sample Information

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46; 3a, App. F, p. 1431).

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY (Ref. 1, p. 

51588) 

START did not observe a maintained and engineered cover, a liner, or a functioning, run-on/run-off 

control system during the 2013 field sampling event. Further, since this source is designed to allow water 

to percolate into the aquifer below the plant it can’t have a liner of any low transmissivity (Refs. 3, p. 23; 

6, p. 5; 7, pp. 4, 5, 26; 19, p. 17).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 27
Containment Description Containment

Value References

Gas release to air: NS

Particulate release to air: NS

Release to ground water: No liner present 10 

Refs. 1, Table 3-2; 3, p. 23; 

6, p. 5; 7, pp. 4, 5, 26; 19, p. 

17 

Release to Surface Water via overland migration: NS

Notes: NS = Not Scored

2.4.2 HAZARDOUS WASTE QUANTITY (Ref. 1, p. 51590) 

2.4.2.1.1 Hazardous Constituent Quantity (Tier A) (Ref. 1, pp. 51590, 51591) 

Description 

The hazardous constituent quantity for Source 1 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source is not known 

and cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.1). There are insufficient 

historical and current data (Manifests, PRP records, State records, Permits, Waste concentration data, etc.)

available to adequately calculate the total or partial mass of all CERCLA hazardous substances in the 

source and the associated releases from the source. Therefore, there is insufficient information to evaluate 

the associated releases from the source to calculate the hazardous constituent quantity for Source 1 with 

reasonable confidence. Scoring therefore proceeds to the evaluation of Tier B, hazardous wastestream 

quantity. 

Hazardous Constituent Quantity Assigned Value: Not Scored 

2.4.2.1.2 Hazardous Wastestream Quantity (Tier B) (Ref. 1, p. 51591) 

Description 

The hazardous wastestream quantity for Source 1 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all hazardous wastestreams and CERCLA pollutants and 

contaminants in the source is not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 

51591 (Section 2.4.2.1.2)].There are insufficient historical and current data (Manifests, PRP records, State 

records, permits, etc.) available to adequately calculate the total or partial mass of all CERCLA hazardous 

wastestream and CERCLA pollutants and contaminants in the source and the associated releases from the 

source. Therefore, there is insufficient information to evaluate the associated releases from the source to 

calculate the hazardous wastestream quantity for Source 1 with reasonable confidence. 

Sum (pounds): NA 

Sum of Wastestream Quantity/5,000 (Table 2-5): NA

Hazardous Wastestream Quantity Assigned Value (W): Not Scored 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 28 
2.4.2.1.3 Volume (Tier C) (Ref. 1, p. 51591)

Description

Because the horizontal and vertical extent of the source has not been fully characterized, it is not possible 

to adequately determine the volume of this source. As a volume cannot be determined, a value of zero is 

assigned. (Ref. 1, Table 2-5, p. 51591).

Volume Assigned Value (V): 0

2.4.2.1.4 Area (Tier D) (Ref. 1, p. 51591)

Description

Source 1 is evaluated as a surface impoundment covering roughly 1.1 acres as calculated using GIS to 

determine the area of a provided polygon by the START project manager (Ref. 1, Table 2-5 - p. 51591; 

Figure 2; 31, p.1; 33). There are 43,560 square feet in each acre, so the total number of square feet for 

this source area is 47,916.

Since the equation for assigning value (Ref. 1, Table 2-5) is the area divided by 13, the HWQ value is 

equal to 47,916 ft2 / 13 = 3,685.8

Area Assigned Value (A): 3,685.8

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 29
2.2.1 SOURCE IDENTIFICATION

Source Number: 2

Name of source: Western North Percolation Pond

Source Type: Pile

Description and Location of Source (with reference to a map of the facility):

The Western North Percolation Pond (the larger western pond [Figure 2]) received overflow and high 

flow events from the smaller Eastern North Percolation Pond (i.e., Source 1), which had become partially 

sealed due to settling out of finer particles. In other words, process waters that went to the eastern pond 

flowed to the western pond via a connecting ditch during production operations (Ref. 3, App. B, pp. 175-

177). Because the western pond was still functioning fully as a percolation pond (allowing for the 

transmission of liquids to migrate to the shallow ground water onsite), this source has been evaluated as a 

pile (Ref. 7, pp. 4, 5). Because the primary wastestream generated onsite consisted of spent potliner 

(RCRA listed waste K088 for cyanide) and this source received effluent containing anode material as well 

as discharge from several shops, metals, cyanide, and miscellaneous organic contaminants would be 

found in this source (Refs. 7, pp. 5, 6; 19, pp. 12, 17). 

The Western North Percolation Pond covers approximately 7.6 acres in the center of the facility as 

determined using GIS to determine the area of a provided polygon by the START project manager (Ref. 

31, p. 1; 33). A total of two dried, settled solid waste source samples (CF-SD-17 and CF-SD-18) were 

collected from the Western North Percolation Pond. Concentrations of SVOCs, and metals were detected 

above the reporting limit in waste source samples collected from the Western North Percolation Pond. No 

water was present in the Western North Percolation Pond during the 2013 sampling event. Sample 

locations are shown in Figure 6 (Ref. 3, pp. 73, 74; Figure 6).

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE

Source Samples:

All source sampling was done in accordance with EPA ERT SOPs 2012, 2013, 2016, and 2017 (Ref. 32, 

p. 47). For example, at each location, the aqueous sample was collected before the solid-matrix sample to 

ensure that the aqueous sample didn’t include any solids disturbed by the sampling process. A new 

disposable plastic scoop was used to collect each solid-matrix sample from a depth of approximately 0-6 

inches below the water surface. All samples were collected during the same September/October 2013

sampling event, over a period of nine days (September 23 to October 1) (Ref. 3, pp. 27, 37).

The analytical results of the dried, settled solids waste source samples (CF-SD-17 and CF-SD-18 [Figure 

6]) from the Western North Percolation Pond are presented in Tables E17-E23, Appendix E of the SRR. 

Laboratory data and validation reports are presented in Appendix F of the same document (Ref. 3, Section 

7, pp. 1431-1441). Contaminant concentrations in waste source samples were considered detections when 

the result was greater than the analytical reporting limit. Although several TAL metals contaminants were 

detected in waste source samples collected from the Western North Percolation Pond that were consistent 

with wastes expected to be found, only the following are evaluated based on their impact in scoring:

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 30
Hazardous 

Substance

Evidence

References Sample No. RL 

(mg/kg)

Concentration 

(mg/kg)

Arsenic

CF-SD-17 

(MH0061) 

1 

17.8 

Refs. 3, pp. 47-49, App. B, p. 175; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 396, Section 7, pp. 1431, 

1440

CF-SD-18 

(MH0062) 5.8 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 397, Section 7, pp. 1431, 

1440, 1441

Cadmium

CF-SD-17 

(MH0061) 

0.5 

5.8 

Refs. 3, pp. 47-49, App. B, p. 175; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 396, Section 7, pp. 1431, 

1440

CF-SD-18 

(MH0062) 1.2 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 397, Section 7, pp. 1431, 

1440, 1441

Chromium 

CF-SD-17 

(MH0061) 

1 

43.6 

Refs. 3, pp. 47-49, App. B, p. 175; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 396, Section 7, pp. 1431, 

1440

CF-SD-18 

(MH0062) 34.8 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 397, Section 7, pp. 1431, 

1440, 1441

Cyanide CF-SD-17 

(MH0061) 0.5 5.1 

Refs. 3, pp. 47-49, App. B, p. 175; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 396, Section 7, pp. 1431, 

1438

Manganese

CF-SD-17 

(MH0061) 

1.5 

97.5 

Refs. 3, pp. 47-49, App. B, p. 175; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 396, Section 7, pp. 1431, 

1440

CF-SD-18 

(MH0062) 63.3 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 397, Section 7, pp. 1431, 

1440, 1441

Zinc

CF-SD-17 

(MH0061) 

6 

814 

Refs. 3, pp. 47-49, App. B, p. 175; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 396, Section 7, pp. 1431, 

1440

CF-SD-18 

(MH0062) 128 

Refs. 3, pp. 47-49, App. B, p. 176; App. D, p. 

206; App E, Table E22, pp. 273; 3a, App. F 

Section 5, pp. 392, 397, Section 7, pp. 1431, 

1440, 1441

Notes: mg/kg milligrams per kilogram

J The associated value is an estimated quantity. The value is well above the reporting limit, and as such its presence is not in 

question. 

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 31 
Source Sample Information 

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46).

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY (Ref. 1, p. 

51588) 

START did not observe a maintained and engineered cover, a liner, or a functioning, run-on/run-off 

control system during the 2013 field sampling event. Further, since this source is designed to allow water 

to percolate into the aquifer below the plant it can’t have a liner of any low transmissivity (Refs. 3, p. 23; 

6, p. 5; 7, pp. 4, 5, 26; 19, p. 17).

Containment Description Containment

Value References

Gas release to air: NS

Particulate release to air: NS

Release to ground water: No liner present 10 Refs. 1, Table

5; 7, pp. 4, 5,

 3-2; 3, p. 23; 6, p. 

 26; 19, p. 17 

Release via overland migration NS

Notes: NS = Not Scored

2.4.2 HAZARDOUS WASTE QUANTITY (Ref. 1, p. 51590) 

2.4.2.1.1 Hazardous Constituent Quantity (Tier A) (Ref. 1, pp. 51590, 51591) 

Description 

The hazardous constituent quantity for Source 2 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source is not known 

and cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.1). There are insufficient 

historical and current data (Manifests, PRP records, State records, Permits, Waste concentration data, etc.)

available to adequately calculate the total or partial mass of all CERCLA hazardous substances in the 

source and the associated releases from the source. Therefore, there is insufficient information to evaluate 

the associated releases from the source to calculate the hazardous constituent quantity for Source 2 with 

reasonable confidence. Scoring therefore proceeds to the evaluation of Tier B, hazardous wastestream 

quantity. 

Hazardous Constituent Quantity Assigned Value: Not Scored 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 32 
2.4.2.1.2 Hazardous Wastestream Quantity (Tier B) (Ref. 1, p. 51591) 

Description 

The hazardous wastestream quantity for Source 2 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all hazardous wastestreams and CERCLA pollutants and 

contaminants in the source is not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 

51591 (Section 2.4.2.1.2)]. There are insufficient historical and current data (Manifests, PRP records, 

State records, permits, etc.) available to adequately calculate the total or partial mass of all CERCLA 

hazardous wastestream and CERCLA pollutants and contaminants in the source and the associated 

releases from the source. Therefore, there is insufficient information to evaluate the associated releases 

from the source to calculate the hazardous wastestream quantity for Source 2 with reasonable confidence.

Sum (pounds): NA 

Sum of Wastestream Quantity/5,000 (Table 2-5): NA

Hazardous Wastestream Quantity Assigned Value (W): Not Scored

2.4.2.1.3 Volume (Tier C) (Ref. 1, p. 51591)

Description

Because the horizontal and vertical extent of the source has not been fully characterized, it is not possible 

to adequately determine the volume of this source. As an area has been calculated, volume is assigned a 

value of 0. (Ref. 1, Table 2-5).

Volume Assigned Value (V): 0

2.4.2.1.4 Area (Tier D) (Ref. 1, p. 51591)

Description

Source 2 is evaluated as a pile covering roughly 7.6 acres as calculated using GIS to determine the area of 

a provided polygon by the START project manager (Ref. 1, Table 2-5, p. 51591; Figure 2; 31, p. 1; 33). 

There are 43,560 square feet in each acre, so the total number of square feet for this source area is 

331,056.

Since the equation for assigning value (Ref. 1, Table 2-5) is the area divided by 13, the HWQ value is 

equal to 331,056 ft2 / 13 = 25,465.8

Area Assigned Value (A): 25,465.8

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 33
2.2.1 SOURCE IDENTIFICATION

Source Number: 3

Name of source: Western South Percolation Pond

Source Type: Pile

Description and Location of Source (with reference to a map of the facility):

The Western South Percolation Pond covers approximately 1.7 acres (Figure 2, Refs. 3, App. B, p. 177; 

37 p. 1; 33) and received piped wastewaters from the Rectifier Oil Separator Sump, Facility Production 

Area storm water, non-contact equipment cooling water, Sewage Treatment Plant, Restrooms and Change 

House sinks, Laboratory Sinks, laboratory non-contact cooling water, laboratory non-solvent waste water, 

plant wide lavatories and sinks, Rectifier non-contact cooling water, casting mold cleaning water, casting 

mold steam cleaning, contact cooling water from direct chill casting of aluminum ingots, and Fabrication 

Shop Steam Cleaning Bay (Refs. 7, pp. 4, 5, 26). Process water that overflows from the Western South 

Percolation Pond flows into the west central, central, and eastern ponds, providing additional surface area 

for percolation as needed. The south percolation ponds are all interconnected, with the initial plant 

outfalls (004 and 005) piped into the westernmost pond (Ref. 3, photo 38, p. 177). Because the western 

pond was still functioning fully as a percolation pond (allowing for the transmission of liquids to migrate 

to the shallow ground water onsite), this source has been evaluated as a pile (Ref. 7, pp. 4, 5). Because 

this source received effluent containing anode material as well as discharge from several shops, and storm 

water runoff, Source 3 was found to contain metals and miscellaneous organic contaminants (including 

PCBs from the transformer fire in the early 1990’s) (Refs. 7, pp. 5, 6, 25; 19, pp. 12, 17, 22). 

Co-located source liquid and solid samples (CF-SW/SD-21) were collected from within the area 

delineated as the Western South Percolation Pond (Figure 6) (Ref. 3, pp. 48, 49, photo 38, p. 177). 

Concentrations of SVOCs and metals were detected above the reporting limit in liquid source samples 

collected from the Central South Percolation Pond. SVOCs, pesticides and metals were detected in waste 

source samples at concentrations above the reporting limits in waste source samples collected from the 

Central South Percolation Pond. 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE

Source Samples:

All source sampling was done in accordance with EPA ERT SOPs 2012, 2013, 2016, and 2017 (Ref. 32, 

p. 47). For example, at each location, the aqueous sample was collected before the solid-matrix sample to 

ensure that the aqueous sample didn’t include any solids disturbed by the sampling process. A new 

disposable plastic scoop was used to collect each solid-matrix sample from a depth of approximately 0-6 

inches below the water surface. All samples were collected during the same September/October 2013

sampling event, over a period of nine days (September 23 to October 1) (Ref. 3, pp. 27, 37).

Source Sediment Sample:

The analytical results of the soil waste mix source sample (CF-SD-21 [Figure 6]) from the Western South 

Percolation Pond are presented in Tables E17-E23, Appendix E of the SRR (Ref. 3, Tables E17-E23). 

Laboratory data and validation reports are presented in Appendix F of the same document (Ref. 3a, 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 34
 

 

 

 

 

 

 

 

 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 35 

Section 7, pp. 1431-1443). Contaminant concentrations in the waste source samples were considered 

detections when the result was greater than the analytical reporting limit. Several TAL metals 

contaminants were detected in waste source samples collected from the South Percolation Ponds that were 

consistent with wastes expected to be found: 

Hazardous 

Substance 

Evidence 

Sample References 

No. 

RL 

(mg/kg) 

Concentration 

(mg/kg) 

Arsenic 1 7.5 Refs. 3, pp. 47-49, App. B, p. 177; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F, 

Section 5, pp. 393, 400, Section 7, pp. 1431, 

1443 

Cadmium 0.5 2.4 

Chromium 1 18.5 

Cyanide CF-SD-21 

(MH0065) 0.5 6 

Refs. 3, pp. 47-49, App. B, p. 177; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F, 

Section 5, pp. 393, 400, Section 7, pp. 1431, 

1438 

Manganese 1.5 57.5 Refs. 3, pp. 47-49, App. B, p. 177; App. D, p. 

205; App E, Table E22, pp. 273; 3a, App. F, 

Section 5, pp. 393, 400, Section 7, pp. 1431, 

1443 

Zinc 6 982 

Notes: mg/kg milligrams per kilogram 

J The associated value is an estimated quantity. The value is well above the reporting limit, and as 

such its presence is not in question. 

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30). 

Source Sediment Sample Information 

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46). 

Source Aqueous Samples: 

The analytical results of the aqueous waste source sample (CF-SW-21 [Figure 6]) from the Central South 

Percolation Pond are presented in Tables E9-E15, Appendix E of the SRR (Ref. 3, Tables E9-E15, pp. 

247-261). Laboratory data and validation reports are presented in Appendix F of the same document (Ref. 

3a, App. F, Section 7, pp. 1350, 1360, 1368, 1369). Contaminant concentrations in the source aqueous 

sample were considered detections when the result was greater than the analytical reporting limit. Several 

TAL metals contaminants were detected in waste aqueous sample collected from the Central South 

Percolation Pond that were consistent with wastes expected to be found: 
 

 

 

 

 

 

 

 

 

HRS Documentation Record	 Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 36 

Hazardous 

Substance 

Evidence 

Sample References 

No. 

RL 

(μg/L) 

Concentration 

(μg/L) 

Cyanide 

CF-SW-21 

10 70.8 

Refs. 3, App. D, p. 208; App E, Table E14, p. 

257; 3a, App. F, Section 5, p. 660, 671, 

Section 7, pp. 1350, 1360 

Zinc 

(MH0039) 

2 39 

Refs. 3, App. D, p. 208; App E, Table E14, p. 

257; 3a, App. F, Section 5, p. 660, 671, 

Section 7, pp. 1350, 1368, 1369 

Notes:	 μg/L micrograms per liter 

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30). 

Source Sample Information 

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46). 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY (Ref. 1, p. 

51588) 

START did not observe a maintained and engineered cover, a liner, or a functioning, run-on/run-off 

control system during the 2013 field sampling event. Further, since this source is designed to allow water 

to percolate into the aquifer below the plant it can’t have a liner of any low transmissivity (Refs. 3, p. 23; 

6, p. 5; 7, pp. 4, 5, 26; 19, p. 17). 

Containment Description Containment 

Value References 

Gas release to air: NS 

Particulate release to air: NS 

Release to Ground water; No liner present 10 Refs. 1, Table 3-2; 3, p. 23; 6, p. 

5; 7, pp. 4, 5, 26; 19, p. 17 

Release via overland migration: NS 

Notes:	 NS = Not Scored 

2.4.2 HAZARDOUS WASTE QUANTITY (Ref. 1, p. 51590) 

2.4.2.1.1 Hazardous Constituent Quantity (Tier A) (Ref. 1, pp. 51590, 51591) 

Description 

The hazardous constituent quantity for Source 3 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source is not known 

and cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.1). There are insufficient 

historical and current data (Manifests, PRP records, State records, Permits, Waste concentration data, etc.) 
available to adequately calculate the total or partial mass of all CERCLA hazardous substances in the 

source and the associated releases from the source. Therefore, there is insufficient information to evaluate 

the associated releases from the source to calculate the hazardous constituent quantity for Source 3 with 

reasonable confidence. Scoring therefore proceeds to the evaluation of Tier B, hazardous wastestream 

quantity. 

Hazardous Constituent Quantity Assigned Value: Not Scored

2.4.2.1.2 Hazardous Wastestream Quantity (Tier B) (Ref. 1, p. 51591) 

Description 

The hazardous wastestream quantity for Source 3 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all hazardous wastestreams and CERCLA pollutants and 

contaminants in the source is not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 

51591 (Section 2.4.2.1.2)]. There are insufficient historical and current data (Manifests, PRP records, 

State records, permits, etc.) available to adequately calculate the total or partial mass of all CERCLA 

hazardous wastestream and CERCLA pollutants and contaminants in the source and the associated 

releases from the source. Therefore, there is insufficient information to evaluate the associated releases 

from the source to calculate the hazardous wastestream quantity for Source 3 with reasonable confidence.

Sum (pounds): NA 

Sum of Wastestream Quantity/5,000 (Table 2-5): NA

Hazardous Wastestream Quantity Assigned Value (W): Not Scored 

2.4.2.1.3 Volume (Tier C) (Ref. 1, p. 51591)

Description

Because the horizontal and vertical extent of the source has not been fully characterized, it is not possible 

to adequately determine the volume of this source. As a volume cannot be determined, a value of zero is 

assigned. (Ref. 1, Table 2-5, p. 51591).

Volume Assigned Value (V): 0

2.4.2.1.4 Area (Tier D) (Ref. 1, p. 51591)

Description

Source 3 is evaluated as an pile and covers roughly 1.74 acre as estimated by the sampling team and 

shown in photo 38 (Ref. 3, p. 177) (Ref. 1, Table 2-5, p. 51591; Figure 2; 3, p. 177; 33; 37). There are 

43,560 square feet in one acre, yielding 75794.4 sq. ft. in 1.74 acres.

Since the equation for assigning value (Ref. 1, Table 2-5) is the area divided by 13, the HWQ value is 

equal to 75794.4 ft2 / 13 = 5830.3

Area Assigned Value (A): 5830.3

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 37
2.2.1 SOURCE IDENTIFICATION

Source Number: 4 

Name of source: Eastern South Percolation Pond

Source Type: Pile

Description and Location of Source (with reference to a map of the facility):

The Eastern South Percolation Pond covers approximately 3.98 acres (Figure 2, Ref. 36, p. 1; 33), and 

received wastewaters from the Rectifier Oil Separator Sump, Facility Production Area storm water, noncontact equipment cooling water, Sewage Treatment Plant, Restrooms and Change House sinks, 

Laboratory Sinks, laboratory non-contact cooling water, laboratory non-solvent waste water, plant wide 

lavatories and sinks, Rectifier yard storm water and non-contact cooling water, casting mold cleaning 

water, casting mold steam cleaning, contact cooling water from direct chill casting of aluminum ingots, 

and Fabrication Shop Steam Cleaning Bay (Ref. 7, pp. 4, 5). Process water that overflows from the 

Central South Percolation Pond (i.e., Source 3) flows into the eastern pond, providing additional surface 

area for percolation as needed. The south percolation ponds are all interconnected, with the initial plant 

outfalls (004 and 005) piped into the westernmost pond (photo 38, p. 178). Because the western pond was 

still functioning fully as a percolation pond (allowing for the transmission of liquids to migrate to the 

shallow ground water onsite), this source has been evaluated as a pile (Ref. 7, p. 5). Because this source 

received effluent containing anode material as well as discharge from several shops, and storm water 

runoff, the 2014 SRR found it to contain metals (Refs. 7, pp. 5, 6, 25; 19, pp. 12, 17, 22). 

Co-located source liquid and solid samples (CF-SW/SD-22) were collected from within the area 

delineated as the Eastern South Percolation Pond (Figure 6) (Ref. 3, pp. 48, 49). Concentrations of 

SVOCs and metals were detected above the reporting limit in liquid source samples collected from the 

Eastern South Percolation Pond. SVOCs, pesticides, and metals were detected at concentrations above the 

reporting limits in the solid-matrix waste source sample collected from the eastern South Percolation 

Ponds.

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE

Source Samples:

All source sampling was done in accordance with EPA ERT SOPs 2012, 2013, 2016, and 2017 (Ref. 32, 

p. 47). For example, at each location, the aqueous sample was collected before the solid-matrix sample to 

ensure that the aqueous sample didn’t include any solids disturbed by the sampling process. A new 

disposable plastic scoop was used to collect each solid-matrix sample from a depth of approximately 0-6 

inches below the water surface. All samples were collected during the same September/October 2013

sampling event, over a period of nine days (September 23 to October 1) (Ref. 3, pp. 27, 37). 

Source Sediment Samples:

The analytical results of the soil waste mix source sample (CF-SD-22 [Figure 6]) from the eastern South 

Percolation Pond are presented in Tables E17-E23, Appendix E of the SRR (Ref. 3, Tables E17-E23, pp. 

263-275). Laboratory data and validation reports are presented in Appendix F of the same document (Ref. 

3a, App. F, Section 7, pp. 1431, 1443, 1444). Contaminant concentrations in source sediment were 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 38
 

 

 

 

 

 

 

 

HRS Documentation Record	 Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 39 

considered detections when the result was greater than the analytical reporting limit. Several TAL metals 

contaminants were detected in waste source samples collected from the Eastern South Percolation Pond 

that were consistent with wastes expected to be found: 

Hazardous 

Substance 

Evidence 

References Sample No. RL 

(mg/kg) 

Concentration 

(mg/kg) 

Arsenic 1 2.3 Refs. 3, pp. 47-49, App. B, p. 

178; App. D, pp. 205, 207; App 

E, Table E22, pp. 273; 3a, App. 

F, Section 5, pp. 393, 401, 

Section 7, pp. 1431, 1443, 1444 

Chromium CF-SD-22 1 9.1 

Manganese (MH0066) 1.5 83.4 

Zinc 6 45.4 

Notes:	 mg/kg milligrams per kilogram 

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30). 

Source Sample Information 

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46, 3a, App. F, Section 7, p. 1431). 

Source Aqueous Samples: 

The analytical results of the aqueous waste source sample (CF-SW-22 [Figure 6]) from the eastern South 

Percolation Pond are presented in Tables E9-E15, Appendix E of the SRR (Ref. 3, Tables E9-E15, pp. 

247-261). Laboratory data and validation reports are presented in Appendix F of the same document (Ref. 

3a, App. F, Section 7, pp. 1431-1516). Contaminant concentrations in the source aqueous sample were 

considered detections when the result was greater than the analytical reporting limit. Several TAL metals 

contaminants were detected in waste aqueous sample collected from the Eastern South Percolation Pond 

that were consistent with wastes expected to be found: 

Hazardous 

Substance 

Evidence 

References Sample No. RL 

(μg/L) 

Concentration 

(μg/L) 

Arsenic 1 1.6 Refs. 3, App. D, p. 207; App E, 

Table E14, p. 257; 3a, App. F, 

Section 5, p. 661, 672, Section 7, 

pp. 1350, 1369 

Chromium 2 8.4 

Cyanide CF-SW-22 

(MH0040) 10 24.8 

Refs. 3, App. D, p. 207; App E, 

Table E14, p. 257; 3a, App. F, 

Section 5, p. 661, 672, Section 7, 

pp. 1350, 1360 

Manganese 1 92.1 Refs. 3, App. D, p. 207; App E, 

Table E14, p. 257; 3a, App. F, 

Section 5, p. 661, 672, Section 7, 

pp. 1350, 1369 

Zinc 2 49.3 

Notes	 μg/L micrograms per liter 

RL Reporting Limit. The value shown is the sample specific Contract Required Quantitation Limit 

(Ref. 30). 
 

 

 

 

 

 

 

 

 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 40 

Source Sample Information 

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46). 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY (Ref. 1, p. 

51588) 

START did not observe a maintained and engineered cover, a liner, or a functioning, run-on/run-off 

control system during the 2013 field sampling event. Further, since this source is designed to allow water 

to percolate into the aquifer below the plant it can’t have a liner of any low transmissivity (Refs. 3, p. 23; 

6, p. 5; 7, pp. 4, 5, 26; 19, p. 17). 

Containment Description Containment 

Value References 

Gas release to air: NS 

Particulate release to air: NS 

Release to Ground water: No liner present 10 Refs. 1, Table 3-2; 3, p. 23; 6, 

p. 5; 7, pp. 4, 5, 26; 19, p. 17 

Release via overland migration: NS 

Notes: NS = Not Scored 

2.4.2 HAZARDOUS WASTE QUANTITY (Ref. 1, p. 51590) 

2.4.2.1.1 Hazardous Constituent Quantity (Tier A) (Ref. 1, pp. 51590, 51591) 

Description 

The hazardous constituent quantity for Source 4 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source is not known 

and cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.1). There are insufficient 

historical and current data (Manifests, PRP records, State records, Permits, Waste concentration data, etc.) 

available to adequately calculate the total or partial mass of all CERCLA hazardous substances in the 

source and the associated releases from the source. Therefore, there is insufficient information to evaluate 

the associated releases from the source to calculate the hazardous constituent quantity for Source 4 with 

reasonable confidence. 

Scoring therefore proceeds to the evaluation of Tier B, hazardous wastestream quantity. 

Hazardous Constituent Quantity Assigned Value: Not Scored 
2.4.2.1.2 Hazardous Wastestream Quantity (Tier B) (Ref. 1, p. 51591) 

Description 

The hazardous wastestream quantity for Source 4 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all hazardous wastestreams and CERCLA pollutants and 

contaminants in the source is not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 

51591 (Section 2.4.2.1.2)].There are insufficient historical and current data (Manifests, PRP records, State 

records, permits, etc.) available to adequately calculate the total or partial mass of all CERCLA hazardous 

wastestream and CERCLA pollutants and contaminants in the source and the associated releases from the 

source. Therefore, there is insufficient information to evaluate the associated releases from the source to 

calculate the hazardous wastestream quantity for Source 4 with reasonable confidence.

Sum (pounds): NA 

Sum of Wastestream Quantity/5,000 (Table 2-5): NA

Hazardous Wastestream Quantity Assigned Value (W): Not Scored

2.4.2.1.3 Volume (Tier C) (Ref. 1, p. 51591)

Description

Because the horizontal and vertical extent of the source has not been fully characterized, it is not possible 

to adequately determine the volume of this source. As a volume cannot be determined, a value of zero is 

assigned. (Ref. 1, Table 2-5, p. 51591).

Volume Assigned Value (V): 0

2.4.2.1.4 Area (Tier D) (Ref. 1, p. 51591)

Description

Source 4 is evaluated as a pile and covers roughly 3.98 acres as calculated using GIS to determine the 

area of a provided polygon by the START project manager (Ref. 1, Table 2-5 - p. 51591; 3, pp. 47-48, 

Figure 2; 36, p. 1; 33). There are 43,560 square feet in one acre, yielding 173, 368.8 sq. ft. in 3.98 acres.

Since the equation for assigning value (Ref. 1, Table 2-5) is the area divided by 13, the HWQ value is 

equal to 173, 368.8 ft2 / 13 = 13, 336.06

Area Assigned Value (A): 13,336.06

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 41
2.2.1 SOURCE IDENTIFICATION

Source Number: 5

Name of source: West Landfill

Source Type: Landfill

Description and Location of Source (with reference to a map of the facility):

The West Landfill operated as an unlined solid waste landfill from 1955-1981 (Figure 2). The facility

disposed of general garbage, including paper, scrap from the shops, strapping, steel scrap and scrap wood, 

and spent potliner (from 1955-1970). Spent potliner wasn’t listed by the EPA as hazardous waste until 

1991. State required semi-annual ground water monitoring around the landfill had detected elevated 

concentrations of cyanide, a byproduct of aluminum production found in the carbon anode potliner (a 

RCRA hazardous waste). The landfill was capped with a clay cap in approximately 1992 and a synthetic 

cap in 1994 (Refs. 3, p. 21; 19, pp. 12, 15, 16; 19, p. 13). The landfill covers approximately 7.8 acres as 

determined using GIS (Refs. 3, pp. 48, 49; 31, p. 1; 33). 

A total of four monitoring well locations were sampled for contaminants associated with this source. Two 

background locations CF-GW-MW-01 (and duplicate CF-GW-MW-18) located approximately 0.5 miles 

upgradient of the landfill and monitoring well CF-GW-MW-02 located approximately 300 feet upgradient 

of the landfill ( Figures 3 and 5). Four wells located immediately downgradient of the landfill (CF-MW03, CF-MW-04, CF-MW-05, and CF-MW-06) (Figure 5) were sampled (Figure 3; Ref. 3, pp. 33, 35, 36, 

51-55). Concentrations of metals were detected above the reporting limit in ground water samples 

collected from the downgradient wells and will be used to characterize this source (Refs. 3, pp. 51-55, 

103, 241, 242, 287, Table E 29; 3a, App. F, Section 7, pp. 1458, 1469, 1470, 1471, 1472, 1473, 1482,

1486, 1497 -1499, 1505, 1506, 1507; Figure 5)

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE

Background Samples:

All source sampling was done in accordance with EPA ERT SOPs 2012, 2013, 2016, and 2017 (Ref. 32, 

p. 47). All samples were collected during the same September/October 2013 sampling event, over a 

period of nine days (September 23 to October 1) (Ref. 3, p. 27). The monitoring wells downgradient of 

the West landfill will be compared to the site monitoring well located to the north of the facility area (CFGW-MW-01), as well as to the monitoring well immediately upgradient of the landfill (02), to ensure 

comparability (Figure 3, Section 3.1 Table, p.50).

Because the landfill was capped in the early 1990’s (Refs. 3, p. 21; 19, p. 16), the source was 

characterized by sampling upgradient and downgradient from the monitoring wells installed by the 

facility, rather than collect samples directly from the capped landfill. The analytical results of the 

background sample being evaluated based on their impact in scoring are shown below (Refs. 3, pp. 21, 

241, Table E6). Results flagged with a J and above the reporting limit, were applied a matrix factor as 

described in EPA guidance Using Qualified Data to Document an Observed Release and Observed 

Contamination to determine if the calculated result was above the analytical reporting limit, and therefore 

useable for HRS purposes (Refs. 3, p. 48; 17, pp. 1-5). START took this approach to characterize the 

source in the absence of actual source samples, and erred on the side of caution using the Directive to 

establish the observed release.

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 42
 

Hazardous 

Substance Location Concentration (μg/L)

RL 

(μg/L) References

Total 

Arsenic 

(dissolved)

CF-GWMW-01 

(MH5099)

1.0U 1.0

Refs. 3, Table E30, p. 289, App. D, pp. 

218; 3a, App. F Section 5, pp. 1135, 

Section 7. pp. 1,458, 1,482; 44

CF-GWMW-02 

(MH5002)

1.0U 1.0

Refs. 3, Table E30, p. 243, App. D, pp. 

216; 3a, App. F Section 5, pp. 1135, 

1429, Section 7. pp. 1,458, 1,469, 

1,470; 44

Total 

Chromium 

(dissolved)

CF-GWMW-01 

(MH5099)

2.0U 2.0

Refs. 3, Table E30, p. 289, App. D, pp. 

218; 3a, App. F Section 5, pp. 1135, 

Section 7. pp. 1,458, 1,482; 44

CF-GWMW-02 

(MH5002)

2.0U 2.0

Refs. 3, Table E30, p. 243, App. D, pp. 

216; 3a, App. F Section 5, pp. 1135, 

1429, Section 7. pp. 1,458, 1,469, 

1,470; 44

Cyanide 

(Total)

CF-GWMW-01

(MH0099)

5.7J- [7.752] 10

Refs. 3, Table E29, p. 287, App. D, 

p. 218; 3a, App. F Section 5, pp. 1134, 

1157, Section 7, pp. 463, 1,374, 1385; 

44

Manganese 

(Dissolved)

CF-GWMW-01 

(MH5099)

10.9 1.0

Refs. 3, Table E30, p. 289, App. D, pp. 

218; 3a, App. F Section 5, pp. 1135, 

Section 7. pp. 1,458, 1,482; 44

CF-GWMW-02 

(MH5002)

6.4 1.0

Refs. 3, Table E30, p. 289, App. D, pp. 

216; 3a, App. F Section 5, pp. 1135, 

1429, Section 7. pp. 1,458, 1,469, 

1,470; 44

Notes: μg/L micrograms per liter. 

U The material was analyzed for, but was not detected above the level of the associated value.

UJ The analyte was not deemed above the reported sample quantitation limit. However, the reported 

quantitation limit is approximate and may or may not represent the actual limit of quantitation 

necessary to accurately and precisely measure the analyte in the sample.

J- The associated value is an estimated quantity, biased low.

( ) CLP Laboratory number

[ ] The associated value is adjusted according to the EPA guidance Using Qualified Data to 

Document an Observed Release and Observed Contamination (Ref. 17)

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

Source Sample Information

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 43
Ground Water Samples:

The analytical results of the monitoring well samples (CF-MW-03 to CF-MW-06 [Figure 6]) 

downgradient of the West Landfill are presented in Tables E1-E8, Appendix E of the SRR (Ref. 3, pp. 

231-245). Laboratory data and validation reports are presented in Appendix F of the same document (Ref. 

3a, p. 10532-10617). Contaminant concentrations in the ground water samples used to characterize the 

source were considered detections when the result was greater than the analytical reporting limit. Results 

flagged with a J and above the reporting limit, were applied a matrix factor as described in EPA guidance 

Using Qualified Data to Document an Observed Release and Observed Contamination to determine if the 

calculated result was above the analytical reporting limit, and therefore useable for HRS purposes (Refs. 

3, p. 48; 17, pp. 1-5, 13). The following TAL metals contaminants were detected in ground water that are 

both associated with wastes deposited and exceed background levels collected: 

Hazardous 

Substance Location

Highest 

Background

Concentration

(μg/L)

Concentration 

(μg/L)

RL 

(μg/L) References

Total 

Arsenic 

(dissolved) CF-GWMW-03 

(MH5003)

1.0U 344 1.0

Refs. 3, Table E7, p. 

243, App. D, p. 221; 3a, 

App. F Section 5, pp. 

1,425, 1,430, Section 7, 

pp.1,458, 1,470; 44

Total 

Chromium 

(dissolved)

2.0U 10.3 2.0

Refs. 3, Table E7, p. 

243, App. D, p. 221; 3a, 

App. F Section 5, pp. 

1,425, 1,430, Section 7, 

pp.1,458, 1,470; 44

Total 

cyanide

CF-GWOP-02 

(MH00C7)

5.7J- [7.752]

111 0.5

Refs. 3, Table E29, p. 

287, App. D, p. 208; 3a, 

App. F Section 5, p. 

661, 675, Section 7, pp. 

1,350, 1,360

CF-GWMW-03 

(MH003)

769 10

Refs. 3, Table E6, p. 

241, App. D, p. 221; 3a, 

App. F Section 5, p. 

659, 663, Section 7, p. 

1,350, 1,359; 44

CF-GWMW-04 

(MH004)

1040J- 0.5

Refs. 3, Table E6, p. 

241, App. D, p. 217; 3a, 

App. F Section 7, pp. 

462, 466, 1,332, 1,341; 

17, pp. 1-18; 44

Manganese 

(dissolved)

CF-GWMW-08 

(MH5008)

10.9 109 1

Refs. 3, Table E30, p. 

289, App. D, p. 215; 3a, 

App. F Section 6, pp. 

225, 235, Section 7. pp. 

1,485, 1,499, 1,500

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 44
Highest 

Hazardous 

Substance Location Background Concentration

Concentration 

(μg/L)

RL 

(μg/L) References

(μg/L)

Refs. 3, Table E30, p. 

CF-GW- 289, App. D, p. 215; 3a, 

MW-09 181 1 App. F Section 6, p. 

(MH5009) 225, 236, Section 7. pp. 

1,485, 1,500

Notes: μg/L - micrograms per liter. 

U The material was analyzed for, but was not detected above the level of the associated value. The 

associated value is the reporting limit. 

 J- The associated value is an estimated quantity, biased low.

( ) CLP Sample ID

[ ] The associated value is adjusted according to the EPA guidance Using Qualified Data to Document an 

Observed Release and Observed Contamination (Ref. 17). 

 RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

Source Sample Information 

The source samples listed above were collected during the 2013 sampling effort conducted by START for 

the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work for 

Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46).

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY (Ref. 1, p. 

51588) 

Neither a liner, nor a functioning, run-on/run-off control system were documented during the 2013 field 

sampling event: there is an engineered clay cap in place. The absence of a liner was provided by the 

facility in their Powerpoint presentation (Refs. 3; 9, p. 16).

Containment Description Containment

Value References

Gas release to air: NS

Particulate release to air: NS

Release to Ground water: No liner present 10 Refs. 1, Table 3-2; 

3, pp. 51-57; 6, p. 5 

Release via overland migration: NS. NS

Notes: NS = Not Scored

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 45 
2.4.2 HAZARDOUS WASTE QUANTITY (Ref. 1, p. 51590) 

2.4.2.1.1 Hazardous Constituent Quantity (Tier A) (Ref. 1, pp. 51590, 51591) 

Description 

The hazardous constituent quantity for Source 5 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source is not known 

and cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.1). There are insufficient 

historical and current data (Manifests, PRP records, State records, Permits, Waste concentration data, etc.)

available to adequately calculate the total or partial mass of all CERCLA hazardous substances in the 

source and the associated releases from the source. Therefore, there is insufficient information to evaluate 

the associated releases from the source to calculate the hazardous constituent quantity for Source 5 with 

reasonable confidence. Scoring therefore proceeds to the evaluation of Tier B, hazardous wastestream 

quantity. 

Hazardous Constituent Quantity Assigned Value: Not Scored

2.4.2.1.2 Hazardous Wastestream Quantity (Tier B) (Ref. 1, p. 51591) 

Description 

The hazardous wastestream quantity for Source 5 could not be adequately determined according to the 

HRS requirements; that is, the total mass of all hazardous wastestreams and CERCLA pollutants and 

contaminants in the source is not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 

51591 (Section 2.4.2.1.2)].There are insufficient historical and current data (Manifests, PRP records, State 

records, permits, etc.) available to adequately calculate the total or partial mass of all CERCLA hazardous 

wastestream and CERCLA pollutants and contaminants in the source and the associated releases from the 

source. Therefore, there is insufficient information to evaluate the associated releases from the source to 

calculate the hazardous wastestream quantity for Source 5 with reasonable confidence.

Sum (pounds): NA 

Sum of Wastestream Quantity/5,000 (Table 2-5): NA

Hazardous Wastestream Quantity Assigned Value (W): Not Scored

2.4.2.1.3 Volume (Tier C) (Ref. 1, p. 51591)

Description

Because the horizontal and vertical extent of the source has not been fully characterized, it is not possible 

to adequately determine the volume of this source. As a volume cannot be determined, a value of zero is 

assigned. (Ref. 1, Table 2-5, p. 51591).

Volume Assigned Value (V): 0

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 46
2.4.2.1.4 Area (Tier D) (Ref. 1, p. 51591)

Description

Source 5 is evaluated as a landfill covering roughly 7.8 acres as calculated using GIS to determine the 

area of a provided polygon by the START project manager (Ref. 1, Table 2-5 - p. 51591; Figure 2; 31, p. 

1; 33). There are 43,560 square feet in one acre, yielding 339,768 sq. ft. in 7.8 acres.

The HWQ value per Table 2-5 (Ref. 1) 339,768 ft2 / 3,400 = 99.93

Area Assigned Value (A): 99.93

SUMMARY OF SOURCE DESCRIPTIONS

Source 

No.

Source 

Hazardous

Waste 

Quantity

Value

Source 

Hazardous 

Constituent 

Quantity 

Complete? 

(Y/N)

Available to Pathway (X)

Ground

water

(GW)

Surface Water (SW) Air

Overland/ 

flood

GW to 

SW Gas Particulate

1 3,685.8 N X NS X NS NS

2 25,465.8 N X NS X NS NS

3 5,830.3 N X NS X NS NS

4 13,336.06 N X NS X NS NS

5 99.93 N X X NS NS NS

Total 48,417.89

Description of Other Possible Sources not Evaluated

Given the interconnected nature of the wastestreams at the facility and the hazardous substances already 

identified within the percolation ponds and the west landfill (Sources 1, 2, 3, 4, and 5); it is possible that 

the other possible sources listed below would have similar types and concentrations of hazardous 

substances to those identified in the sources evaluated for this HRS documentation record through 

chemical analysis (Refs. 7, pp. 4, 5; 9, p. 4; 19, p. 17). Given the age of the plant, fashion in which 

contaminants present onsite were handled, the fact that some of the landfills were only covered (not 

capped), and the connectivity of ground water with surface water in the area, these other possible sources

may need to be characterized during the Remedial Investigation/Feasibility Study (Refs. 3, pp. 21-24).

Current facility conditions are based on observations made during the September 23, 2013 through 

October 1, 2013 sampling event. Other possible sources observed during the 2013 sampling event, for 

which there are no chemical analytical data or other direct evidence of hazardous substances, are listed in 

the table below and are shown in Figure 2 (Ref. 3, pp. 20-24). The HRS defines sources as “Any area 

where a hazardous substance has been deposited, stored, disposed, or placed, plus those soils that may 

have become contaminated from hazardous substance migration. In general, however, the volumes of air, 

ground water, surface water, and surface water sediments that may have become contaminated through 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 47
migration are not considered sources.” (Ref. 1, p. 51587). All of the features described below meet this 

definition.

Feature (Reference) Description

East Landfill

(Refs. 3, p. 21; 19, pp. 15-

16)

The Spent Potliner Landfill, also known as the East Landfill, operated from 

approximately 1980-1990 and is a clay-lined landfill used to dispose of spent 

potliners prior to their declaration as a hazardous waste. The landfill was capped 

with a synthetic cap and revegetated in 1990.

Wet Scrubber Sludge 

Pond Landfill

(Refs. 3, p. 21; 6, p. 3; 9, 

p. 13; 19, p. 15. Identified 

by Steve Wright, CFAC, 

during June 2013 facility 

visit.)

Wet Scrubber Sludge Pond Landfill was closed in approximately 1980 and 

contained sludge waste generated from the Wet Scrubber System and for a period 

from approximately 1994-1998 contained spent potliner material. 

Center Landfill

(Refs. 3, p. 21; 8, p. 9; 19, 

p. 16.)

The Center Landfill, also known as the Carbon Pile, is an unlined landfill operated 

from approximately 1970- 1980. Solvents and hazardous wastes are known to have 

been buried on-site in the closed landfills (West, Center and Sanitary). 

Sanitary Landfill

(Refs. 3, p. 22; 19, p. 15.)

The Sanitary Landfill is a clay-lined historic landfill used for plant garbage. The 

landfill was covered with soil and re-vegetated. Years of operation unknown. 

Solvents and hazardous wastes are known to have been buried on-site in the closed 

landfill (West, Center and Sanitary). 

Asbestos Landfill

(Location identified by 

Steve Wright, CFAC, 

during June 2013 facility 

visit.)

Based on a review of aerial photography the Asbestos Landfill began operation in 

approximately the early 2000's; date last used is unknown. 

North and South 

Leachate Ponds

(Refs. 3, p. 22; 6, p. 11) 

Two hypalon-lined leachate ponds were constructed on opposite ends of the East 

Landfill in 1980, one on the north side of the landfill (North Leachate Pond) and one 

on the south side of the landfill (South leachate Pond). The ponds were used to 

collect runoff water from the East Landfill containing the spent potliner material and 

aerated during the summer months to reduce water volume and utilize ultraviolet 

light to break down the cyanide. According to a letter from Donald F. Ryan, 

Laboratory Manager at Anaconda Aluminum Co Columbia Falls Reduction 

Plant, to MT DEQ dated January 5, 1990, approximately 150,000 gallons of 

leachate water containing fluoride and approximately 3 mg/L of cyanide was drained 

from the South Leachate Pond into the Wet Scrubber Sludge Pond Landfill. This 

transfer of leachate was approved by MT DEQ (October 12, 1989 letter from John 

Arrigo, MT DEQ Water Quality Bureau, to Don Ryan, Anaconda Aluminum Co 

Columbia Falls Reduction Plant). The South leachate Pond was dried, capped, 

and subsequently closed in 1993. An underground pipe leads from the North 

Leachate Pond to the Wet Scrubber Sludge Pond. The North Leachate Pond held 

cyanide-free water containing fluoride and was subsequently drained into the Wet 

Scrubber Sludge Pond Landfill. The North Leachate Pond was capped and then 

closed in 1994. These areas were observed to be closed and covered with grass 

during the field sampling activities.

Cathode Soaking Pits

(Refs. 3, p. 24; 13) 

Carbon cathode soaking pits contained water and ammonia to expedite the carbon 

removal process. 

Other areas on the facility may also qualify as sources; however, sampling to date does not document 

association of hazardous substances with these areas.

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 48
3.0 GROUND WATER MIGRATION PATHWAY

3.0.1 GENERAL CONSIDERATIONS

Ground Water Migration Pathway Description

Description: 

The facility is located adjacent to the west side of the Teakettle Mountain, a part of the Whitefish Range. 

The aquifer being evaluated consists of the unconsolidated alluvial deposits that are found in the Flathead 

River valley bottoms, and the smaller, localized glacial outwash lenses that have intermingled and mixed 

along the margins of the mountain/valleys with the river alluvium (Ref. 20, p. 20, Figure 18). In some 

places, the glacial outwash extends to depths of up to 94 below ground surface [bgs], and the alluvium 

ranges from 70 to 300 feet in thickness of glacial, glacio-lustrine, and glacial-alluvial sediments. These 

are underlain by several hundred feet of relatively impermeable till (Refs. 18, p.41; 20, pp. 20, 38, 40). 

This interbedded aquifer is hereinafter referred to as the Alluvial/Glacial aquifer, is the most permeable 

aquifer in the Kalispell Valley consisting of various water bearing gravel strata that were laid down by 

glaciation or the Flathead River and are interconnected above the till layer confining the Pleistocene 

artesian aquifer. These deposits consist of heterogeneous mixtures of gravels, sands, silts and clays (Ref 

18, p. 12; Figure 7 and Figure 8 of this HRS documentation record). The thickness of the sediments at the 

site is known to be at least 300 feet as measured at Well TW-11 (Figure 7 and Figure 8 of this HRS 

documentation record). 

Due to the variability in topography, depth to water across the plant property ranges from less than 20 feet 

bgs to over 100 feet bgs (Ref 3, Table C2, p. 189; the Well Table in Section 3.1.1). While the monitoring 

wells on site are screened at varying depth ranges, the ground water levels measured in 2013 (Ref 3, 

Table C2, p. 189) and historically in 1983 and 1984 (Ref 18, p. 23) indicate hydraulic interconnectivity 

across the site, with ground water flow at the plant property generally south to southwest (Ref 3, Figure 3, 

p.99) towards the Flathead River. Drinking water wells along the Flathead River and downstream of the 

site withdraw water from the interconnected deposits that make up the Alluvial/Glacial aquifer, and there 

is no evidence of aquifer discontinuities between the site and the target wells along the river valley (Refs.

18, pp. 30, 31; 20, pp. 40, 41; 8, p. 38; Figures 5, 7, and 8 of this HRS documentation record).

A detailed study of Site geology was conducted in the early 1980s by Hydrometrics, Inc. (Ref 18). This 

study provided information on local and regional climate, geology, soils and hydrology. Key portions of 

the study are provided below.

Regional Geology:

The upper portion of the Flathead Valley basin, up to the Columbia Falls area, is a major structural feature 

formed by down dropping of a huge block of the earth's crust (Ref. 18, p. 14). A major system of faults is 

assumed to exist along the contact between the valley and mountains that bound the valley on both the 

east and west sides to the south of Columbia Falls. This major block faulting is outside the four mile 

radius of the site. The site is located in the northeast portion of the upper Flathead Valley basin, west of 

Teakettle Mountain (Refs. 18; p. 14; 20, p. 16).

The Flathead Valley basin is underlain at depth by a thick sequence of partially metamorphosed 

Precambrian rocks having a total thickness of several tens of thousands of feet. These rocks are 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 49
predominantly vari-colored argillite, quartzite, and carbonate of the Belt Series. The rocks are tightly 

compacted and have very low porosity and permeability (Refs. 18; p. 15; 20, pp. 13, 14).

Less than 0.2 miles east of the West landfill at the Anaconda Aluminum Co Columbia Falls Reduction 

Plant facility is Teakettle Mountain, part of the Whitefish Mountain Range. The range consists primarily 

of Precambrian undifferentiated sedimentary rocks of the Ravalli Group, overlain by gray, silty, dolomites 

of the Piegan Group. The Whitefish Range is separated from the adjacent Flathead Valley to the west by a 

buried north-south trending normal fault located over eight miles to the west of the site. The downthrown 

western block underlies the upper Flathead River drainage, while the eastern block largely comprises the 

mountains. (Refs. 18, p. 16; 20, pp. 12, 16).

Stratigraphy in the Anaconda Aluminum Co Columbia Falls Reduction Plant area is the result of three 

former coalescing ice streams. Similarly, the topography, surficial geology, and near-surface 

sedimentology are largely due to Pleistocene and Recent glaciation, and by post-glacial fluvial erosion 

and deposition. Konizeski, mapped the area about Columbia Falls and the aluminum plant as being, “ice 

contact, drumlin-forming clay and boulder till; locally overlain by glaciolacustrine deposits". (Refs. 18, p. 

21; 20; p. 16; 8, p. 38).

Superimposed upon the glacial stratigraphy is the depositional result of late Pleistocene and Recent 

glaciofluvial outwash from the Flathead River which flows westerly across the southern border of the site, 

and less so from Cedar Creek, which descends to the west of the Anaconda Aluminum Co Columbia Falls 

Reduction Plant area from the Whitefish Mountain Range to the north. The Flathead River and Cedar 

Creek flow primarily through the recent continuous alluvium consisting dominantly of silts and sands 

comprising the modern flood plains (Ref. 18; p. 17; 20, pp. 41, 43; 8, p. 38).

Ground water is widely used in the Flathead River drainage primarily for domestic and stock use and to a 

lesser extent for irrigation, industry and public water supply. The majority of wells are located in the 

basin's large intermountain river valleys, such as Columbia Falls’ two municipal wells (Refs. 24; 38; 

Figure 5). The occurrence, distribution and quality of ground water is closely related to the geology of the 

basin. The ground water resources are greatly influenced by three geological units. These are Precambrian 

bedrock, Pleistocene glacial deposits and recent alluvial deposits (Ref. 18; pp. 20, 21).

The entire Flathead Valley basin is underlain by a thick sequence of rocks of Precambrian age (over 600 

million years old). Due to their low permeability, very little water is found in these rocks. If fractured and 

broken zones are encountered, the rocks can yield small amounts of fair to good quality water to wells 

(Ref. 18; p. 21). This Precambrian layer is located below the alluvial/glacial aquifer present within the 

Anaconda Aluminum Co Columbia Falls Reduction Plant area as well as the wells used to document an 

observed release (Ref. 20, p. 20, Figure 18).

Glacial outwash channels and layers of lenses of sand and gravel also occur in these mountain areas and 

are the principal water-yielding materials where the alluvial deposits are not present. Thickness of glacial 

deposits varies from thin veneer a few feet thick, to as much as several hundred feet. Wells drilled into 

glacial deposits vary widely in yield. Some wells yield little water, whereas other wells yield over 1,000 

gallons per minute. Ground water is recharged in the glacial deposits by infiltration of water from 

irrigated land; from numerous reservoirs, streams and lakes in the area and from precipitation. Glacial 

deposits are exposed or underlie almost all of the intermountain valley areas in the basin (Ref. 18; p. 22).

Alluvial flood plain deposits of unknown thickness are present along major streams in the basin. These 

sediments are Pleistocene and recent in age, and are derived from the surrounding bedrock and glacial 

debris. In the Flathead Valley, alluvium underlies the flood plain of the Flathead river and constitutes an 

extensive aquifer which is about 30 feet thick and supplies water to a large number of wells in the valley 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 50
bottom. The aquifer is recharged by precipitation and irrigation water; is very permeable and can yield 

large quantities of good quality water to wells. In other areas, recent alluvial deposits supply small to 

moderate quantities of water to wells. Although the quality of water in recent alluvial deposits generally is 

good, there are some localized areas where it is fair to poor (Ref. 18; pp. 22, 24).

Site Specific Geology and Hydrogeology:

The Anaconda Aluminum Co Columbia Falls Reduction Plant is located on the eastern margin of the 

upper Flathead Valley, approximately one-half mile northwest of where the Flathead River leaves the 

mountains through Badrock Canyon. The Flathead Valley is a southern extension of the structural 

depression termed the Rocky Mountain Trench. The major axis of the valley is generally 

northeast/southwest. Surface drainage of the property is to the south (Ref. 18, p. 15). 

A series of nine piezometer placements made by Hydrometrics in July 1980 provided stratigraphic 

evidence to substantiate glacial and glaciofluvial deposition. All nine sites showed a succession of till and 

small patches of glaciolacustrine clays, capped by from one foot to greater than twelve feet of imbricated 

glaciofluvial and alluvial sands, gravels and cobbles. This capping unit appeared to be more extensive and 

thicker north and west of the plant complex than it was to the northeast (Ref. 18; p. 37).

Driller's logs from production and hydrologic test wells in the vicinity of the plant provide more evidence 

of successive depositional modes. Examination of these logs indicate that from 70 to greater than 300 feet 

of interbedded glacial, glaciolacustrine, and glaciofluvial sediments underlie the surface of the site with 

minor occurrences of well-sorted, permeable gravels and cobbles. Hydrologic testing indicates a zone of 

highly transmissive cobbles and gravels at depths greater than approximately 100 feet along the southern 

edge of the plant property. This zone probably represents buried glacial outwash associated with 

advancing or retracting phases of the Flathead Glacier which entered the valley through Badrock Canyon, 

as well as high transmissivity gravels associated with the reworking of glacial debris by the ancestral 

Flathead River (Ref. 18; pp. 37, 38).

- Aquifer Interconnections/Distance from Source

Description

Ground water is present in the glacial (where present) and alluvial deposits beneath the plant property. 

The occurrence, distribution and abundance of ground water is closely related to subsurface geological 

conditions. As described above, this area was influenced by several glacial events and hydrogeology of 

the area is complex (Ref. 18, pp. 38, 39, 42, 43). The glacial and alluvial aquifers are considered to be 

interconnected at the site and within two miles of the sources along the river valley due to the absence of 

any confining layers or aquatards separating the glacial outwash hydrologic unit from the alluvial unit as 

shown in the cross-sections (Figures 7 and 8). Further, the presence of site contaminants in ground water 

on site as well as in a Level I actual contamination well demonstrate an interconnection and absence of 

discontinuities between the sources and the target well (Section 3.3.2 of this HRS documentation record).

In addition, all the layers appear to have hydraulic conductivities within two orders of magnitude (Ref. 1,

Table 3-6). The alluvial/glacial aquifer extends downstream at least to the location of the community 

well CF-GW-OP-02 and constitutes a single hydrogeologic unit, i.e., the Alluvial/Glacial aquifer (Refs. 8, 

p. 38; 18, pp. 37, 38; 20, pp. 20, 38, 40).

Geology of Anaconda Aluminum Co Columbia Falls Reduction Plant area, including the community well 

(CF-GW-OP-02), are shown in Figures 7 and 8 of this HRS documentation record. The cross section 

locations are shown in Figure 2. The cross sections show the absence of any confining layer between the 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 51
prevalent alluvial/gravel water bearing strata and the glacial outwash that overlaps the alluvial along the 

valley sides.

- Aquifer Discontinuities within Target Distance Limit

Description

In the vicinity of the Anaconda Aluminum Co Columbia Falls Reduction Plant site, the alluvial aquifer is 

hydraulically connected with layers/lenses of the glacial aquifer that contain significant supplies of 

ground water and are in direct contact with the alluvial aquifer. The alluvial/glacial aquifer is present in 

valley-fill alluvium that is continuous between the areas of the sources and the Flathead River (Refs. 18, 

pp. 37, 38; 20, pp. 8, 10). There is no evidence that any geologic (e.g., major faults, intrusive formations 

such as dikes or sills), topographic, or other structure or feature (e.g., erosional channels and large bodies 

of water), that entirely transects the alluvial aquifer and that creates a continuous boundary to ground 

water flow, exists anywhere between the sources and the Flathead River (Refs. 18, pp. 37, 38; 20, pp. 8, 

10, 16; Figures 7 and 8 of this HRS documentation record). The interconnected aquifers are found in the 

river valley that extends southward to the Swan Range, south of the Flathead River. The mountain ranges 

of the study area are shown in Reference 20, p. 16, Figure 14; 5, p. 31. The Teakettle Mountain acts as an 

aquifer boundary (discontinuity) for HRS purposes (Ref. 20, p. 16, Figure 18). Furthermore the Flathead 

River does not entirely transect the combined aquifer as described in section 4.2.1.1 of this HRS

documentation record. 

Evidence that there are no discontinuities between the source areas and target wells includes that all 

seepage water from the percolation ponds that had entered the alluvial aquifer eventually reached the river

(Ref. 7, pp. 4, 5). Further, the presence of site contaminants in ground water on site as well as in a Level I 

actual contamination well demonstrate an absence of discontinuities between the sources and target well 

(Section 3.3.2 of this HRS documentation record).

Aquifer 

Name

Is Aquifer 

Interconnected 

within 2 miles? 

(Yes/No)

Is Aquifer Continuous 

within 4-Mile TDL? 

(Yes/No)

Is 

Aquifer 

Karst? 

(Yes/No)

References

Alluvial

Aquifer Yes

Yes, within the Flathead 

River valley/west of 

Teakettle Mountain

No

Refs. 3, pp.16, 17; 5, pp. 9-11; 

18, pp. 20-22, 24, 37-38, 51; 

20, p. 16, 20, 38, 40

Glacial

Aquifer Yes Yes No

Refs. 3, pp.16, 17; 5, pp. 9-11; 

18, pp. 20-22, 24, 37-38, 51; 

20, p. 16, 20, 38, 40

3.1 LIKELIHOOD OF RELEASE (Ref. 1, p. 51595) 

3.1.1 OBSERVED RELEASE (Ref. 1, p. 51595) 

Aquifer Being Evaluated: Alluvial/Glacial Combined Aquifer 

Chemical Analysis 

Prior to ground water sample collection, ground water was field screened with a Horiba U-50 Series 

Multi-Parameter water quality meter to determine water quality parameters and results recorded in the 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 52 
field logbook for temperature, conductivity, pH, dissolved oxygen, and oxygen reduction potential. After 

three well volumes were purged, ground water was collected from each well into a 5-gallon bucket and 

the water quality meter probe placed in the bucket and allowed to sit until the readings stabilized. The 

readings were then recorded in the field logbook (Refs. 3, p. 35; 32, p. 47). 

Decontamination of the meter was conducted by spraying the meter with a non-phosphate detergent 

solution followed by a deionized water rinse in conformance with the SOP presented in the approved SAP 

(Ref. 32, p. 47).

Ground water samples were collected from a total of 16 locations on and offsite. Prior to sample 

collection activities, three well volume casings were purged from each on plant property well. Collection 

of onsite ground water samples was accomplished using the dedicated pumps installed in the wells with 

the exception of CF-GWMW-01, CF-GM-MW-03, CF-GM-MW-06, and CF-GM-MW-07. CF-GW-MW01 did not have a dedicated pump installed in the well and CF-GM-MW-03, CF-GM-MW-06 and CFGM-MW-07’s dedicated pumps were not operational during the sampling event. Wells that had dedicated 

pumps were connected to a Coleman Powermate 6250 generator and the pump turned on. The samples 

were then collected from the sample port or spigot on the well. For the wells that did not have dedicated 

pumps installed, a Grundfos Redi-Flow 2 submersible pump was used. The pump was lowered into the 

well until it reached the bottom of the well. The pump was then extracted approximately 2 feet above the 

total depth to avoid intake of sediments. The pump was connected to a Lincoln Electric Ranger generator, 

the pump turned on and the samples collected directly from the pump tubing (Refs. 3, p. 35; 32, p. 47).

Decontamination of the pump and tubing was conducted by submersing the pump and tubing into a bin of 

tap water and pumping the rinse water through the pump. This was followed by submersion and pumping 

with a non-phosphate detergent solution, followed by a rinse with deionized water in conformance with 

the SOP presented in the approved SAP (Refs. 3, pp. 35, 36; 32, p. 47).

Analysis of the samples collected during 2013 sampling event were performed according to the United 

States Environmental Protection Agency Contract Laboratory Program Statement of Work for Inorganic 

Superfund Methods, ISM01.3 (5/2005) (Ref. 3a, App. F section 7, p. 1355).

Background Ground Water Samples: 

Field measurements were collected from the background wells CF-GM-MW-01 and CF-GM-MW-02. 

CF-GM-MW-01 was measured within the interconnected alluvial aquifer to a total depth of 

approximately 153.15 feet bgs (3,013 feet amsl) and static ground water was measured at 96.85 feet bgs 

(3,073 feet amsl) prior to sampling (Ref. 3, App. D, p. 195). The screened interval was not noted in the 

boring log (Ref. 8, pp. 264, 265). CF-GM-MW-02 was measured within the interconnected alluvial 

aquifer to a total depth of 69.24 feet bgs (3,134 feet amsl) and static ground water was measured at 60.17

feet bgs (3,144 feet amsl) prior to sampling (Ref. 3, App. D, p. 195; the Well Table in Section 3.1.1). The 

well is not screened (Ref. 3, p.115).

A site background sample (CF-GM-MW-01) was collected from a ground water monitoring well located 

north and up gradient of the Site features, but within the Facility boundary (Figure 5) (Refs. 3, pp. 51;

App. D, pp. 218; 3a, App. F Section 5, pp. 1130, 1135, Section 7, pp. 460, 463, 1,402, 1,458, 1,470, 

1,482). An additional monitoring well (CF-GW-MW-02) was selected immediately upgradient of the 

West Landfill to provide another background in a more similar regime to the monitoring wells used to 

document the observed release (Figure 5) (Refs. 3, pp. 241, 243, App. D, p. 216; 3a, App. F Section 5, p. 

1130, Section 7, pp. 463, 1,332, 1,343, 1,458, 1,470); however, the higher sample result from either 

background was used to document an observed release to err on the side of caution.

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 53
The background samples listed below were collected during the 2013 sampling effort conducted by 

START for the EPA. Samples were analyzed using the Contract Laboratory Program Statement of Work 

for Inorganic Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, 

Section 7, pp. 1350, 1355). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory 

Group in Salt Lake City, Utah (Ref. 3, p. 46).

Hazardous 

Substance Location Concentration (μg/L)

RL 

(μg/L) References

Arsenic

Total

(dissolved) 

CF-GWMW-01 

(MH5099)

1.0U 1.0 

Refs. 3, Table E30, p. 289, App. D, pp. 

218; 3a, App. F Section 5, pp. 1135, 

Section 7. pp. 1,458, 1,482; 44

CF-GWMW-02 

(MH5002) 

1.0U 1.0 

Refs. 3, Table E30, p. 243, App. D, pp. 

216; 3a, App. F Section 5, pp. 1135, 

1429, Section 7. pp. 1,458, 1,469, 

1,470; 44

Chromium 

Total

(dissolved) 

CF-GWMW-01 

(MH5099)

2.0U 2.0 

Refs. 3, Table E30, p. 289, App. D, pp. 

218; 3a, App. F Section 5, pp. 1135, 

Section 7. pp. 1,458, 1,482; 44

CF-GWMW-02 

(MH5002) 

2.0U 2.0 

Refs. 3, Table E30, p. 243, App. D, pp. 

216; 3a, App. F Section 5, pp. 1135, 

1429, Section 7. pp. 1,458, 1,469, 

1,470; 44

Cyanide 

(Total)

CF-GWMW-01 

(MH0099) 

5.7J- [7.752] 10 

Refs. 3, Table E29, p. 287, App. D, p. 

218; 3a, App. F Section 5, pp. 1134, 

1157, Section 7, pp. 463, 1,374, 1385; 

44

Manganese 

(Dissolved) 

CF-GWMW-01 

(MH5099)

10.9 1.0 

Refs. 3, Table E30, p. 289, App. D, pp. 

218; 3a, App. F Section 5, pp. 1135, 

Section 7. pp. 1,458, 1,482; 44

CF-GWMW-02 

(MH5002) 

6.4 1.0 

Refs. 3, Table E30, p. 289, App. D, pp. 

216; 3a, App. F Section 5, pp. 1135, 

1429, Section 7. pp. 1,458, 1,469, 

1,470; 44

Notes: μg/L micrograms per liter. 

U The material was analyzed for, but was not detected above the level of the associated value.

UJ The analyte was not deemed above the reported sample quantitation limit. However, the reported 

quantitation limit is approximate and may or may not represent the actual limit of quantitation 

necessary to accurately and precisely measure the analyte in the sample.

 J- The associated value is an estimated quantity, biased low.

( ) CLP Laboratory number

[ ] The associated value is adjusted according to the EPA guidance Using Qualified Data to 

Document an Observed Release and Observed Contamination (Ref. 17). 

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 54 
Contaminated Ground Water Samples:

Field measurements were collected from the contaminated wells. Sample CF-GW-MW-03 was collected 

from monitoring well TW17 which is completed within the Alluvial/Glacial aquifer to a depth of 90 feet 

bgs (3,047 feet amsl) screened between 70 and 85 feet bgs; ground water was static at 63.3 feet bgs after 

completion (Ref. 3, p. 130; the Well Table in Section 3.1.1). Sample CF-GW-MW-04 was collected from 

monitoring well TW21 which had a field measured total depth of 94.74 feet bgs; ground water elevation 

was measured at 3058.88 feet bgs (Ref. 3, App. C, p. 189). Sample CF-GW-MW-09 was collected from 

monitoring well W8-TW2 which had a field measured total depth of 54.29 feet bgs; ground water 

elevation was measured at 3055.85 feet bgs (Ref. 3, p. 112; App. C, p. 189). Sample CF-GW-OP-02 was 

collected from a privately owned well currently supplying five homes west of the site and completed to a 

depth of 169 feet bgs (Ref. 3, pp. 153-155, Appendix D, p. 208; 43, p. 1). A compilation of the well 

information obtained for the wells sampled during the 2013 event is found in the table below.

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 55
Sample ID1 Well ID2

Geographical Coordinates

UTM Zone 11 (NAD83)3 Top of 

Casing 

Elevation

(ft amsl) *4

Ground 

Surface 

Elevation

(ft amsl) *4

Field 

Measured 

Depth to 

Ground

water

(ft btoc)5

Ground

water 

Elevation*

(ft amsl)6

Boring 

Log Static 

Water 

Level from 

TOC

(ft)7

Boring TD / 

Well TD

(ft bgs)7

Screen 

Interval

(ft bgs)7

Field 

Measured 

TD

(ft btoc)5

Latitude Longitude

CF-GW-MW-01 W2-CFMW1 48.4077268600 -114.141032691 3170 3168 96.85 3073 96.79 -- -- 153.15

CF-GW-MW-02 TW9 48.4008761600 -114.132919717 3205 3203 60.17 3144 Dry8 195 / 163 None 69.24

CF-GW-MW-03 W11-TW17 48.3993389588 -114.136443294 3139 3137 79.52 3059 63.3 90 / 90 70-85 82.1

CF-GW-MW-04 W4-TW21 48.3984139600 -114.137148400 3137 3135 78.12 3059 -- -- -- 94.74

CF-GW-MW-05 W5-TW15 48.3979853801 -114.135871277 3136 3134 75.79 3060 70 105 / 96 78-88 92.44

CF-GW-MW-06 W6-TW18 48.3975817909 -114.134063729 3134 3132 76.11 3058 62.79 90 / 90 70-85 90.17

CF-GW-MW-08 W10-TW22 48.3967190870 -114.145543852 3108 3106 35.61 3072 29.45 60 / 60 45-60 51.31

CF-GW-MW-09 W8-TW2 48.3937082010 -114.141720973 3106 3104 50.15 3056 -- Cased from 

2-53

Open 

Bottom 54.29

CF-GW-OP-02 Not Applicable 48.388222000 114.159917000 -- -- -- -- 169 169 / 169 None NM

Notes: 

* Survey data not available; elevations are estimated 

-- Unknown 

ft amsl - feet above mean sea level 

ft bgs - feet below ground surface 

ft btoc – feet below top of casing

NM – Not Measured

TD – Total Depth

References:

1 Ref. 3, p. 103; Figure 5 of this HRS documentation record

2 Ref. 3, p. 97; Figure 2 of this HRS documentation record

3 Ref. 3, pp. 187, 189

4 Ref. 33

5 Ref. 3, p. 195

6 Ground water Elevation = Top of Casing Elevation – Depth to Ground water

7 Ref. 8, pp. 264, 265; 3, pp. 112, 115, 130, 134, 135, 153-156

8 TW9 ran dry following purging and initial sample collection (Ref. 3, pp. 39, 

40) 

 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 56 
Analytical results from the 2013 sampling event were performed according to the United States 

Environmental Protection Agency Contract Laboratory Program Statement of Work for Inorganic 

Superfund Methods, ISM01.3 (5/2005) (Ref. 3a, App. F section 7, p. 1355). The source samples listed 

below were collected during the 2013 sampling effort conducted by START for the EPA. Samples were 

analyzed using the Contract Laboratory Program Statement of Work for Inorganic Superfund Methods, 

ISM01.3—Metals, Mercury and Cyanide (Refs. 3, pp. 34; 3a, App. F, Section 7, pp. 1350, 1355). 

Laboratory samples were analyzed by the CLP laboratory ALS Laboratory Group in Salt Lake City, Utah 

(Ref. 3, p. 46). 

Water quality parameters collected during the 2013 sampling event were similar for all ground water 

monitoring well samples in the site area and CF-GW-MW-01 and CF-GW-OP-02 also had similar 

chemical properties to each other, demonstrating sample similarity for comparison purposes (Ref. 3, 

Table C1, p. 187). The analytical results indicate the presence of several contaminants in ground water 

under and near the facility. Samples collected from both down gradient on facility monitoring wells and a 

down gradient off facility drinking water well show the presence of total arsenic, total chromium, total 

cyanide and dissolved manganese in the alluvial aquifer that meet the observed release criteria as stated in 

HRS Section 2.3 (Refs. 3, pp. 241, 243, 287, Tables E6, E7, E29; 3a, App. F Section 7, pp. 1332, 1,341, 

1,350, 1,360, 1,350, 1359, 1360, 1,362, 1,363, 1374, 1,389, 1,390). 

Hazardous 

Substance Location

Highest 

Background 

Concentration

(μg/L)

Concentration 

(μg/L)

RL 

(μg/L) References

Total 

Arsenic

 (dissolved) 

CF-GWMW-03 

(MH5003) 

1.0U 344 1.0 

Refs. 3, Table E7, p. 

243, App. D, p. 221; 

3a, App. F Section 5, 

pp. 1,425, 1,430, 

Section 7, pp.1,458, 

1,470; 44

Total

Chromium 

(dissolved) 

2.0U 10.3 2.0 

Refs. 3, Table E7, p. 

243, App. D, p. 221; 

3a, App. F Section 5, 

pp. 1,425, 1,430, 

Section 7, pp.1,458, 

1,470; 44

Total 

cyanide 

CF-GWOP-02 

(MH00C7) 

5.7J- [7.752] 

111 0.5 

Refs. 3, Table E29, p. 

287, App. D, p. 208; 

3a, App. F Section 5, 

p. 661, 675, Section 7, 

pp. 1,350, 1,360; 44

CF-GWMW-03 

(MH003) 

769 10 

Refs. 3, Table E6, p. 

241, App. D, p. 221; 

3a, App. F Section 5, 

p. 659, 663, Section 7, 

p. 1,350, 1,359; 44

CF-GWMW-04 

(MH004)

1040J- 0.5 

Refs. 3, Table E6, p. 

241, App. D, p. 217; 

3a, App. F Section 7, 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 57 
Hazardous 

Substance Location

Highest 

Background 

Concentration

(μg/L)

Concentration 

(μg/L)

RL 

(μg/L) References

pp. 462, 466, 1,332, 

1,341; 17, pp. 1-18; 44

Manganese 

(dissolved) 

CF-GWMW-08 

(MH5008) 

10.9 

109 1 

Refs. 3, Table E30, p. 

289, App. D, p. 215; 

3a, App. F Section 6, 

pp. 225, 235, Section 

7. pp. 1,485, 1,499, 

1,500; 44

CF-GWMW-09 

(MH5009) 

181 1 

Refs. 3, Table E30, p. 

289, App. D, p. 215; 

3a, App. F Section 6, 

p. 225, 236, Section 7. 

pp. 1,485, 1,500; 44

Notes: μg/L - micrograms per liter. 

U The material was analyzed for, but was not detected above the level of the associated value. The 

associated value is the reporting limit. 

 J- The associated value is an estimated quantity, biased low.

( ) CLP Sample ID

[ ] The associated value is adjusted according to the EPA guidance Using Qualified Data to 

Document an Observed Release and Observed Contamination (Ref. 17). 

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

Attribution

It has been documented that arsenic, total chromium, total cyanide and manganese have all been found in 

sources onsite. Chromium is used in making aluminum alloys and total cyanide is found in spent potliner 

material that has been disposed of onsite (Refs. 9, p. 7; 19, p. 12). Total cyanide has been previously 

documented in a release to both ground water and surface water (Ref. 3, p. 25). Cadmium, total chromium

and iron are common in aluminum ores. Further, these substances have been documented in onsite 

sources evaluated for this site. There are no other potential sources for these contaminants located either 

up-gradient or in the immediate area (Ref. 39). 

Hazardous Substances Released: Arsenic, total chromium, total cyanide, and Manganese. 

Ground Water Observed Release Factor Value: 550

3.2 WASTE CHARACTERISTICS

3.2.1 TOXICITY/MOBILITY

Hazardous 

Substance

Source 

No.

Toxicity 

Factor 

Value*

Mobility 

Factor 

Value*

Tox/Mobility

(Table 3-9) References

Arsenic 1,2,3,4,5 10,000 1* 10,000 2, p. BI-1

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 58 
Hazardous 

Substance

Source 

No.

Toxicity 

Factor 

Value*

Mobility 

Factor 

Value*

Tox/Mobility

(Table 3-9) References

Cadmium 1,2,3 10,000 1x10 -2 100 2, p. BI-2

Chromium (total) 1,2,3,4,5 10,000 1 10,000 2, p. BI-3

Cyanide 1,2,3,5 10,000 1 10,000 2, p. BI-3

Manganese 1,2,3,4, 10,000 1 10,000 2, p. BI-7

Zinc 1,2,3,4,5 10 1 10 2, p. BI-10

*According to HRS section 3.2.1.2, for any hazardous substance that meets the criteria for an observed release by

chemical analysis to one or more aquifers underlying the sources at the site, regardless of the aquifer being 

evaluated, assign a mobility factor value of 1. Arsenic, total chromium, total cyanide, and zinc have all been 

detected at elevated levels in ground water. The hazardous substances are arsenic, total chromium, and total cyanide.

Toxicity/Mobility Factor Value: 10,000 

(Ref. 1, Section 3.2.1.3) 

3.2.2 HAZARDOUS WASTE QUANTITY

Source Number Source Hazardous Waste Quantity 

Value (Section 2.4.2.1.5)

Is source hazardous constituent 

quantity data complete? (yes/no)

1 3,685.8 No

2 25,465.8 No

3 5,830.3 No

4 13,336.06 No

5 99.93 No

Total 48,417.89

According to Section 2.4.2.2 of the HRS (Ref. 1, pp. 51591, 51592), if any target for the migration 

pathway under consideration is subject to Level I (or Level II) concentrations, assign either the value 

from Table 2-6 (Ref. 1, p. 51591) or a value of 100, whichever is greater, as the hazardous waste quantity 

factor value for that pathway. 

Hazardous Waste Quantity Factor Value: 10,000 

(Ref. 1, Table 2-6, p. 51591) 

3.2.3 WASTE CHARACTERISTICS FACTOR CATEGORY VALUE

Toxicity/Mobility Factor Value: 10,000

Hazardous Waste Quantity Factor Value: 10,000 

Toxicity/Mobility Factor Value X Hazardous Waste Quantity Factor Value: 1 x 108 

(per HRS Section 3.2.3, the Hazardous Waste Quantity Factor Category Value is capped at 1 x 108 ) 

 Waste Characteristics Factor Category Value: 100

(Ref. 1, Table 2-7)

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 59 
3.3 TARGETS (Ref. 1, p. 51602) 

The City of Columbia Falls utilizes two municipal ground water wells as a primary potable water supply 

for 1,040 connections (Refs. 24; 32). The two municipal wells (Louisiana Pacific Well and Clare Park 

Well) are located within the Columbia Falls city limits (Refs. 24; 38; Figure 5). The Clare Park Well is 

located approximately 0.5 mile west of the Flathead River and approximately 3.22 miles down gradient of 

the Site and is 304 feet deep (Refs. 24; 38; Figure 5). The second well (Louisiana Pacific Well) is located 

approximately 1.8 miles west of the Flathead River and approximately 3.4 miles down gradient of the Site 

and is 231 feet deep (Refs. 24; 38; Figure 5). The average number of persons per household in Flathead 

County, Montana, is 2.43 (Ref. 4, p. 1). There are also multiple private wells within the four mile ground

water target distance limit of the site. However, because it is not clearly been demonstrated that the 

alluvial aquifer is continuous from the facility to these wells, they have not been included in the site 

scoring. However, these wells are of concern to EPA.

3.3.1 NEAREST WELL (Ref. 1, pp. 51602, 51603) 

Well CF-GW-OP-02 provides potable water to five residences and concentrations of total cyanide in CFGW-OP-02 meet the observed release criteria found in HRS Table 2-3 (Refs. 1, p. 51603; 3, Table E29, p. 

287). The total cyanide concentration recorded in this well is 111 μg/L (Refs. 3, Table E29, p. 287; 3a, 

App. F, Section 7, pp. 1,351, 1,361). As this is above the applicable health-based benchmark for drinking 

water (the Reference Dose Screening Concentration [RDSC], which is 9.0 μg/L), this well is considered 

to be subject to Level I concentrations (Ref. 1, p.51592) and is considered the nearest well. The well is 

169 feet in depth with an open bottom and cased but not screened, although it is capped. (Ref. 3, pp. 153, 

155). 

In accordance with Table 3-10 and 3-11 within Section 3.3.1 of the HRS, a Nearest Well Factor Value of 

50 has been assigned (Ref. 1, pp. 51602, 51603). 

Well ID: CF-GW-OP-02 

Level of Contamination (I, II, or potential): I 

If potential contamination, distance from source in miles: Not applicable 

Nearest Well Factor Value: 50 

(Refs. 1, pp. 51602, 51603 Table 3-11) 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 60 
3.3.2 POPULATION

3.3.2.1 Level of Contamination

3.3.2.2 Level I Concentrations

Level I Samples

Hazardous 

Substance

Sample ID

(Description)

Hazardous 

Substance Conc. 

(μg/L)

Benchmark

Concentration 

(μg/L)

Benchmark References

Total 

Cyanide 

GW-OP-02: 

private well 

supplying 5 

residences

111 9 RDSC

2, p. BII-4: 3, pp. 36, App. 

D, p. 208; 3a, App. F, 

Section 5, pp. 661, 

Section 7, pp. 1,350, 

1,362; 43, p. 1 

RDSC Reference Dose Screening Concentration

Level I Well Population References

CF-GW-OP-02 9 3, pp. 35, 36, App E, Table E29, pp. 287; 3a, App F, 

Section 7, p. 1361; 4; 43, p.1 

Population served by Level I Wells: 9 

Population served by Level I Wells x 10: 90 

Level I Concentration Factor Value: 90 

3.3.2.3 Level II Concentrations 

Not applicable as no Level II concentrations have been identified. 

Total Population Served by Level II Wells: 0 

Level II Concentrations Factor Value: 0 

3.3.2.4 Potential Contamination

Domestic and municipal wells are present within the 4-mile target distance limit. However, as a sufficient 

site score is achieved using actual contamination, potential contamination is not evaluated in this HRS 

documentation record. However, the threat of contamination migrating to these wells is of concern to 

EPA.

Potential Contamination Factor Value: 0 

3.3.3 RESOURCES

It is not known if any well within the four-mile radius is used for irrigation of commercial food or forage 

crops, or if any well may otherwise be considered a resource for scoring purposes.

Resources Factor Value: 0 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 61 
3.3.4 WELLHEAD PROTECTION AREA

Wellhead Protection Areas (WPAs) were not identified within 4 miles of the sources and as such, were 

assigned a value of 0 (Refs. 1, p. 51604; Figures 1-6).

As per Section 3.3.4 of the HRS, a Wellhead Protection Area Factor Value of 0 has been assigned for the 

principal aquifer (Ref. 1, p. 51604).

Wellhead Protection Area Factor Value: 0 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 62
4.0 SURFACE WATER MIGRATION PATHWAY

4.0.1 Migration Components

The surface water migration pathway score for the Anaconda Aluminum Co Columbia Falls Reduction 

Plant is based on the ground water to surface water migration component, as described in Section 4.2

below (Ref. 1, pp. 51604-51605, Section 4.0.1). The ground water to surface water migration component 

is used to evaluate surface water threats that result from migration of hazardous substances from source(s) 

to surface water via ground water, as has occurred at the Anaconda Aluminum Co Columbia Falls 

Reduction Plant. As per the HRS, three possible threats exist for the surface water migration pathway 

through the ground water to surface water migration component: the drinking water threat, human food 

chain threat, and environmental threat (Ref. 1, pp. 51604-51605, Sec. 4.0.1). For the Anaconda 

Aluminum Co Columbia Falls Reduction Plant site, the human food chain and environmental threats are 

scored for the ground water to surface water migration component of the surface water migration 

pathway. These threats are discussed within Sections 4.2.3 and 4.2.4 of this HRS documentation record.

The overland/flood migration component was not scored because the ground water to surface water 

component scores sufficiently to place the site on the NPL. Given that the south percolation ponds of the 

site (Sources 3 and 4) lie within the 100-year flood plain for the Flathead River, the overland/flood 

migration to surface water component is likely complete at this site (Ref. 34; Figure 2 of this HRS 

documentation record). In addition, for many years the Anaconda Aluminum Co Columbia Falls 

Reduction Plant discharged wastewater to the Flathead River through Outfall D006, a reach extending 

from Latitude 48° North, 23' 18", Longitude 144° East, 7' 19" to Latitude 48° North, 3' 13 ", Longitude 

144° East, 9' 04" (Ref. 7, pp. 5, 24, 25). The outfall is considered a probable point of entry (PPE) for the 

entry of hazardous substances from possibly four identified sources (Sources 1 through 4) into the river, 

as well as from the other possible sources identified within the Summary of Source Descriptions Section 

of this HRS documentation record, for the overland/flood migration component. The Cedar Creek 

watershed is located to the west of the westernmost source (Source No. 2), there is no overland runoff 

pathway from any sources reaching the Creek, and the bottom of the Creek at the westernmost (lowest) 

sample point (CF-SW/SD-06) is approximately 44 feet above the aquifer (Figures 3, 5, 6, 7, and 8 of this 

HRS documentation record). Therefore, the overland flow pathway is not used for scoring the ground 

water to surface water migration component.

4.2 GROUND WATER TO SURFACE WATER MIGRATION COMPONENT

4.2.1 General Considerations

4.2.1.1 Eligible Surface Waters

According to the HRS, surface waters eligible to be scored under the ground water to surface water 

migration component must meet certain conditions. The Flathead River is documented to be an eligible 

surface water for the ground water to surface water migration component, as described below (Ref. 1, p. 

51626, Section 4.2.1.1).

Condition 1:

A portion of the surface water is located within 1 mile of one or more sources at the site having a 

containment value greater than 0: 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 63
Although two watersheds are present in the study area, only the Flathead River is being evaluated for this 

pathway. The Cedar Creek watershed is located to the west of the westernmost source (Source No. 2), 

there is no overland runoff pathway from any sources reaching the Creek, and the bottom of the Creek at 

the westernmost (lowest) sample point (CF-SW/SD-06) is approximately 44 feet above the aquifer

(Figures 3, 5, 6, 7, and 8 of this HRS documentation record). The Flathead River is located approximately 

5,000 feet in straight-line as measured from the east edge of Source No. 1, approximately 3,700 feet in 

straight-line from the east edge of Source No. 2, approximately 600 feet in straight-line from the east edge 

of Source No. 3, and approximately 200 feet in straight-line from the east edge of Source No. 4 (Ref. 33; 

Figure 6 of this HRS documentation record). All four of these sources have a containment value of 10 for 

the ground water migration pathway (Refs. 3, p. 23; 6, p. 5; 7, pp. 4, 5, 26; 19, p. 17; Section 2.2.3 for 

Sources 1, 2, 3 and 4, and Figure 2 of this HRS documentation record).

Condition 2:

The top of the uppermost aquifer is at or above the bottom of the surface water body:

A detailed description of the geology and hydrogeology of the site is found within section 4.2.1.2 

(Definition of Hazardous Substance Migration Path for Ground Water to Surface Water Component) 

below. The pertinent information from section 4.2.1.2 is summarized here.

The uppermost aquifer beneath the Anaconda Aluminum Co Columbia Falls Reduction Plant property is 

the alluvial/glacial aquifer that exists throughout the site vicinity (Refs. 18, pp. 43, 44, 46; 20 p. 20). 

Ground water elevations were measured within existing facility monitoring wells completed in the 

alluvial/glacial aquifer during the 2013 field investigation (as demonstrated by the well logs) (Refs. 3, p. 

189, App. A pp. 111-150; Figures 7 and 8 and Section 3.1.1 of this HRS documentation record). Two 

representative wells, CF-GW-MW-02 and CF-GW-MW-09, have been selected to demonstrate the 

elevation of the top of the uppermost aquifer. These wells have been chosen as they are in line with the 

general ground water flow direction within the aquifer (Table in Section 3.1.1, Figures 8 and 9 of this 

HRS documentation record).

The elevation measured for the bottom of the Flathead River (i.e. its deepest point) was 2,977.67 feet 

amsl, measured at the USGS gauging station in Columbia Falls located at the highway 2 bridge over the 

Flathead River (Ref. 25, pp. 1-3). This elevation is 79 feet lower than the ground water elevation 

measured in CF-GW-MW-09 (3,056 feet amsl), and 127 feet lower than the ground water elevation 

measured in CF-GW-MW-02 (3,104 feet amsl) (Refs. 3, p. 97, 103, 189, 195, 112, 115, 130, 134, 135, 

153-156; 8, pp. 264, 265). Historically, ground water elevations measured in these wells are also higher 

than the elevation of the bottom of the river (Ref. 18, pp. 49, 50). Therefore, the condition that the top of 

the uppermost aquifer is at or above the bottom of the surface water body is met.

Condition 3:

No aquifer discontinuity is established between the source and the portion of the Flathead River within 1 

mile of any of the sources:

In the vicinity of the Anaconda Aluminum Co Columbia Falls Reduction Plant site, the uppermost aquifer 

is present in valley-fill glacial/alluvium that is continuous between the areas of the sources, target wells,

and the Flathead River (Refs. 8, p. 38; 20, p. 20 Figure 18; Figures 7 and 8, and the well log table in 

Section 3.1.1 of this HRS documentation record). There is no evidence that any geologic, topographic, or 

other structure or feature, that entirely transects the aquifer or that creates a continuous boundary to 

ground water flow, exists anywhere between the sources (i.e., ponds and landfill) and the Flathead River

(Figures 7 and 8). Evidence that there are no discontinuities between the source areas and the river 

includes that seepage water from the ponds that entered the uppermost aquifer eventually reached the 

river as documented by the MPDES permit (Ref. 7, pp. 1, 5, 25, 26).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 64
4.2.1.2 Definition of Hazardous Substance Migration Path for Ground Water to Surface Water 

Migration Component

Ground Water Migration Pathway Description:

The hazardous substance migration path includes both the ground water segment and the surface water inwater segment that hazardous substances would take as they migrate away from sources at the site (Ref. 

1, p. 51626).

The ground water segment of the hazardous substance migration path begins at each source and extends 

to the PPE through the uppermost aquifer (i.e., the alluvial/glacial aquifer) to the surface water (Figures 6

and 9 of this HRS documentation record). The PPE is defined as the point at the surface water that results 

from the shortest straight-line distance through the uppermost aquifer beneath the sources with a 

containment factor greater than zero to the surface water (Ref. 1, p. 51626, Section 4.2.1.2). There are 

five sources identified for the site, four within 1 mile and having a PPE into the Flathead River (Figures 2 

and 6 of this HRS documentation record). The ground water segment is restricted to migration via the 

uppermost aquifer between a source and the surface water (Ref. 1, p. 51626). A description of the geology 

and hydrogeology (both regional and site specific) is therefore necessary to evaluate this migration 

pathway.

Site Specific Geology and Hydrogeology: 

The Anaconda Aluminum Co Columbia Falls Reduction Plant is located on the eastern margin of the 

upper Flathead Valley, approximately one-half mile northwest of where the Flathead River leaves the 

mountains through Badrock Canyon. The Flathead Valley is a southern extension of the structural 

depression termed the Rocky Mountain Trench. The major axis of the valley is generally 

northeast/southwest. Surface drainage of the property is to the south (Ref. 18, p. 15). 

A series of nine piezometer placements made by Hydrometrics in July 1980 provided stratigraphic 

evidence to substantiate glacial and glaciofluvial deposition. All nine sites showed a succession of till and 

small patches of glaciolacustrine clays, capped by from one foot to greater than twelve feet of imbricated 

glaciofluvial and alluvial sands, gravels and cobbles. This capping unit appeared to be more extensive and 

thicker north and west of the plant complex than it was to the northeast (Ref. 18; p. 37).

Driller's logs from production and hydrologic test wells in the vicinity of the plant provide more evidence 

of successive depositional modes. Examination of these logs indicate that from 70 to greater than 300 feet 

of interbedded glacial, glaciolacustrine, and glaciofluvial sediments underlie the surface of the site with 

minor occurrences of well-sorted, permeable gravels and cobbles. Hydrologic testing indicates a zone of 

highly transmissive cobbles and gravels at depths greater than approximately 100 feet along the southern 

edge of the plant property. This zone probably represents buried glacial outwash associated with 

advancing or retracting phases of the Flathead Glacier which entered the valley through Badrock Canyon, 

as well as high transmissivity gravels associated with the reworking of glacial debris by the ancestral 

Flathead River (Ref. 18; pp. 37, 38).

- Aquifer Interconnections Between Sources and the Flathead River /Distance from Source

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 65
Description

Ground water is present in the glacial (where present) and underlying alluvial deposits beneath the plant 

property. The occurrence, distribution and abundance of ground water is closely related to subsurface 

geological conditions. As described above, this area was influenced by several glacial events and 

hydrogeology of the area is complex (Ref. 18; pp. 20, 21). The glacial and alluvial aquifers are 

considered to be interconnected at the site and within two miles of the sources along the river valley due 

to the absence of any confining layers or aquatards separating the glacial outwash hydrologic unit from 

the alluvial unit as shown in the cross sections (Figures 7 and 8). In addition, all the layers appear to have 

hydraulic conductivities within two orders of magnitude (Ref. 1, Table 3-6). Further, the presence of site 

contaminants in ground water on site as well as in a Level I actual contamination well demonstrate an 

interconnection and absence of discontinuities (Ref.1, Sections 3.0.1.2.1 and 3.0.1.2.2 and Section 3.3.2 

of this HRS documentation record) between site sources and this target well. The alluvial/glacial aquifer 

extends downstream past Columbia Falls and constitutes a single hydrogeologic unit (due to similar 

hydraulic conductivities and a lack of any confining layers), i.e., the Alluvial/Glacial aquifer (Refs. 8, p. 

38; 18, pp. 37, 38; 20, pp. 20, 38, 40).

Geology of Anaconda Aluminum Co Columbia Falls Reduction Plant area, including the community well 

(CF-GW-OP-02), are shown in Figures 7 and 8 of this HRS documentation record. The cross section 

locations are shown in Figure 2. The cross sections show the absence of any confining layer between the 

prevalent alluvial/gravel water bearing strata and the glacial outwash that overlaps the alluvial along the 

valley sides.

- Aquifer Discontinuities between the Plant Ground water and the Flathead River 

Description

In the vicinity of the Anaconda Aluminum Co Columbia Falls Reduction Plant site, the alluvial/glacial 

aquifer is present in valley-fill alluvium that is continuous between the areas of the sources and the 

Flathead River (Refs. 18, pp. 37, 38; 20, pp. 8, 10, 16). There is no evidence that any geologic (e.g., major 

faults, intrusive formations such as dikes or sills), topographic, or other structure or feature (e.g., 

erosional channels and large bodies of water), that entirely transects the surficial alluvial aquifer and that 

creates a continuous boundary to ground water flow, exists anywhere between the sources and the 

Flathead River (Refs. 18, pp. 37, 38; 20, pp. 8, 10, 16; Figures 7 and 8 of this HRS documentation 

record).

Evidence that there are no discontinuities between the source areas and target wells includes that all 

seepage water from the percolation ponds that had entered the alluvial aquifer eventually reached the river 

(Ref. 7, pp. 4, 5). Further, the presence of site contaminants in ground water on site as well as in a Level I 

actual contamination well demonstrate an absence of discontinuities between the sources and target well 

(Section 3.3.2 of this HRS documentation record).

Elevation of Top of Aquifer (mean sea level):

The elevation measured for the bottom of the Flathead River (i.e. its deepest point) was 2,977.67 feet 

amsl, measured at the USGS gauging station in Columbia falls (Ref. 25, pp. 1-3). Historic ground water

elevations measured in CF-GW-MW-02 (TW9), and CF-GW-MW-09 (TW2) are also higher than the 

elevation of the bottom of the river (Refs. 3, p. 189; the Well Table in Section 3.1.1, and Figures 7 and 8 

of this HRS documentation record). The average gradient of the Flathead River valley above Kalispell is 

six feet per mile (Ref. 20, p. 10).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 66
Elevation of Bottom of Surface Water Body (mean sea level):

The elevation measured for the bottom of the Flathead River (i.e. its deepest point) was 2,977.67 feet 

amsl, measured at the USGS gauging station in Columbia falls (Ref. 25, pp. 1-3). Historic ground water

elevations measured in CF-GW-MW-02 (TW9) and CF-GW-MW-09 (TW2) are also higher than the 

elevation of the bottom of the river (Refs. 3, p. 189; the Well Table in Section 3.1.1, and Figures 7 and 8 

of this HRS documentation record; 18, pp. 47-51).

Surface Water Probable Point of Entry and In-Water Segment Description:

The hazardous substance migration path includes both the ground water segment and the surface water inwater segment that hazardous substances would take as they migrate away from sources at the site (Ref. 

1, p. 51626, Section 4.2.1.2). The hazardous substance migration path for the Anaconda Aluminum Co 

Columbia Falls Reduction Plant site begins at Source No. 4 (eastern south percolation pond), the source 

with the most upstream PPE to the Flathead River (Figure 2 of this HRS documentation record). As the 

south percolation pond is directly adjacent to the Flathead River, the ground water segment of the 

hazardous substance migration path is approximately 200 feet (Figure 2 of this HRS documentation 

record).

The location where this PPE enters the Flathead River marks the beginning of the surface water in-water

segment of the hazardous substance migration path for the ground water to surface water migration 

component (Ref. 1, p. 51626; Figure 5 of this HRS documentation record). From this point, the Flathead 

River flows generally west along the southern edge of the Anaconda Aluminum Co Columbia Falls 

Reduction Plant property, passing the ground water to surface water PPEs from source No. 3, then source 

No. 1, and finally source No. 2 (Figure 2 of this HRS documentation record). The PPE for Source No. 2 is 

the lowest (most downstream) PPE for the site and is located approximately 1.5 miles downstream of the 

PPE for Source No. 3 (Figure 2 of this HRS documentation record). From this lowest PPE, the Flathead 

River (and therefore the migration pathway) then continues generally west, then south to the end of the 

target distance limit (TDL) (Figure 5 of this HRS documentation record). The total distance from the 

highest PPE (most upstream) to the end of the TDL is approximately 16.5 miles (Ref. 1, p. 51626, Section 

4.2.1.4; Figure 2 of this HRS documentation record).

The surface water body being scored for this HRS documentation record is the Flathead River (a large 

river). The in-water segment for HRS purposes begins at the highest upstream ground water to surface 

water PPE on the Flathead River and ends 15 miles downstream of the PPE from Source No. 2, a total 

distance of approximately 16.25 miles (as described above) (Figure 9 of this HRS documentation record).

Dilution Weight Adjustment for In-Water Segment:

A dilution weight adjustment is not calculated because the inclusion of potential contamination in the 

human food chain and environmental threats of the ground water to surface water migration component of 

the surface water migration pathway does not likely contribute significantly to the overall site score.

The mean annual flow rate for the Flathead River, as measured from a USGS gauging station located 

south and adjacent to Columbia Falls, Montana located approximately 1.7 miles downstream from the site 

(USGS station # 12363000), from the years 1952 through 2013 is 9,777 cfs. (Ref. 25). The river is, 

therefore, described as a large stream or river under the HRS (Ref. 1, Table 4-13, p. 51613). However, 

the 2013 annual average of 10,210 will be used to err on the side of caution, due to the nearness of the 

10,000 cfs category change (Refs. 1, Table 4-13, p. 51613; 25, p. 3). It is shown as a perennial river on 

the GIS software package used for this site (Refs. 3; Figures 1-6 of this HRS documentation record; 33).

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 67
Because the gauging station is so close to the site, the overall flow rate was evaluated as greater than 

10,000 cfs and less than 100,000 cfs for the TDL.

Information regarding threatened, endangered, or sensitive species is available for Flathead County but 

not currently available on a site specific basis. A search of the U.S. Fish & Wildlife Service (USFWS) 

Environmental Conservation Online System (ECOS), available online at http://www.fws.gov/endangered/

the Montana Fish, Wildlife & Parks (FWP) Threatened Species list, available online at http://fwp.mt.gov, 

and the and the Montana National Heritage Program (MNHP) Species of Concern report, available online 

at http://mtnhp.org indicates 3 different species (two fish and one insect) to be present in Flathead County 

along the TDL that are considered federal or state listed threatened, endangered, or sensitive species and

are associated with the study area (Refs, 26; 27; 40; 42):

• Bull Trout (Salvelinus confluentus);

• Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi);

• Meltwater Lednian stonefly (Lednia tumana).

A site specific biological assessment has not been performed; however, according to a query of the FWP 

Montana Fisheries Information System database (MFISH), along the Anaconda Aluminum Co Columbia 

Falls Reduction Plant southern property boundary, the Westslope Cutthroat Trout is found in the Flathead 

River (Refs. 27, pp. 17-33; 42). The ECOS and MFISH identified habitat for the Bull Trout (federally 

threatened) and Westslope Cutthroat Trout (federally sensitive) in the Flathead River (Refs. 26; 27, pp. 

17-33; 42). Fish surveys conducted by FWP have confirmed the presence of both species in the Flathead 

River adjacent to the Site and the presence of Westslope Cutthroat Trout in Cedar Creek (Ref. 27, pp. 17-

33; 28; 42). Creel surveys performed by FWP show that fish are caught, and consumption of fish caught

along the Flathead River from well upstream of the facility down to Kalispell occurs (Refs. 27, pp. 17-33, 

47-49; 28; 35).

According to the MNHP Map Viewer-Wetland and Riparian Mapping database, approximately 15.53 

miles (on both sides of the river) of streamside wetlands are present from the site along the Flathead River 

downstream 15 miles (Refs. 29; 33). The dominant vegetation is freshwater palustrine scrub shrub and 

emergent wetlands. These wetland types meet the HRS definition of a wetland, 40 CFR 230.3, and are 

considered eligible for HRS scoring (Refs. 1, Table 4-24, p. 51625; 29).

4.2.1.3 Observed Release

Alluvial/glacial Aquifer:

According to the HRS, in order to establish an observed release of an individual hazardous substance to 

surface water under the ground water to surface water migration component of the surface water pathway, 

an observed release to both ground water and an observed release by chemical analysis to surface water 

must be documented (Ref. 1, p. 51626, Section 4.2.1.3). Please refer to section 3.1.1 of this HRS 

documentation record to see the necessary information to support the observed release conditions present 

in the aquifer beneath Anaconda Aluminum Co Columbia Falls Reduction Plant (alluvial/glacial Aquifer).

Surface Water: Flathead River

All surface water sampling was done in accordance with EPA ERT SOP 2013 (Ref. 32, p. 47). All 

samples were collected during the same 2013 sampling event, over a period of nine days (September 23 

through October 1) (Ref. 3, pp. 27, 198, 219, 220). All samples adjacent to the Site were collected from 

the north bank of the Flathead River, the side closest to the site (Figure 6). Surface water quality 

parameters, such as pH, temperature, and conductivity, were measured at each sampling location and the 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 68
results were similar at each (Ref. 3, p. 187). The specific areas sampled were backwater locations that 

acted as sediment traps for the finer-grained material (sands and silts) that were targeted for sampling

(Figure 6 of this HRS documentation record). All surface water samples were collected from 0 to 1 foot 

depth, and were collected before the sediment samples (Ref. 32, p. 27).

Samples were analyzed using the Contract Laboratory Program Statement of Work for Inorganic 

Superfund Methods, ISM01.3—Metals, Mercury and Cyanide (Ref. 3, pp. 34, 3a, App. F, Section 7, pp. 

1458, 1463). Laboratory samples were analyzed by the CLP laboratory ALS Laboratory Group in Salt 

Lake City, Utah (Ref. 3, p. 46; 3a, App. F. Section 7, p. 1458).

Surface Water Background Concentrations:

The background concentration for each analyte was selected from the highest detected laboratory result of 

the evaluated surface water background samples collected from SW-13, SW-14, SW-15, SW-16 (CF-SW13, CF-SW-14, CF-SW-15, CF-SW-16 [Figure 6]) (Ref. 3, Tables E32-E39, 293-307). Laboratory data 

and validation reports are presented in Appendices of the SRR (Ref. 3, App. D, pp. 219, 220; 3a, App. F, 

Section 5, p. 1136, App. F, Section 7, pp. 1474-1476; Figure 6 of this HRS documentation record). The 

background samples were all collected September 27, 2013: locations are shown on figure 5 of this HRS 

documentation record (Ref. 3a, App. F, Section 5, p. 1136).

Background Surface Water Samples

Sample ID CLP ID Date 

Sampled

Hazardous 

Substance

Concentration

(μg/L) References

CF-SW-13 MH5031 9/27/13

Manganese

(dissolved)

2.2 (1.0)

Ref. 3, p. 219, Table E38, 

p. 305; 3a, App. F, Section 

5, pp. 1136, 1435; Section 

7, p. 1474; 44

CF-SW-14 MH5032 9/27/13 1.2 (1.0)

Ref. 3, p. 219, Table E38, 

p. 305; 3a, App. F, Section 

5, pp. 1136, 1436; Section 

7, pp. 1474, 1475; 44

CF-SW-15 MH5033 9/27/13 1.0 U (1.0)

Ref. 3, p. 220, Table E38, 

p. 305; 3a, App. F, Section 

5, pp. 1136, 1437; Section 

7, pp. 1475, 1476; 44

CF-SW-16 MH5034 9/27/13 1.0 U (1.0)

Ref. 3, p. 220, Table E38, 

p. 305; 3a, App. F, Section 

5, pp. 1136, 1438; Section 

7, pp. 1476; 44

Notes: μg/L micrograms per Liter

 U The material was analyzed for, but was not detected above the sample specific Contract Required 

Quantitation Limit. 

( ) The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

Contaminated Surface Water Concentrations:

The analytical results of the Flathead River surface water samples (CF-SW-05 through CF-SW-12 [Figure 

6]) were compared to three times background concentration for surface water to further ensure that 

contaminants attributed to site activities were not also naturally occurring at similar concentrations and 

meeting observed release criteria. The three times background concentration was calculated for each 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 69
analyte using the highest detected laboratory result of the evaluated Flathead River surface water 

background samples (CF-SW-13, CF-SW-14, CF-SW- 15, CF-SW-16, CF-SW-24 [duplicate] [Tables 

E32-E39, Appendix E]) (Ref. 3, pp. 293-307; 3a, App. F, Section 7, pp. 1458, 1474-1476). If the 

background results are non-detect for a specific analyte, then a detection in a release sample above the 

reporting limit for the Flathead River background sample for the associated analyte is considered an 

exceedance of the background concentration. (Ref. 1, Section 2.3, p. 51589).

Contaminated Surface Water Samples

Sample ID Sample 

Location

Distance from 

Upper PPE Depth Date References

CF-SW-07 Flathead 

River 0.8 miles 0 -12” 9/25/13

Refs. 3, Figure 4; Table E38, p. 

305, App. D, p. 198; 3a, App. F 

Section 6, pp. 226, 247, Section 

7, pp. 1485, 1508, 1509; 32, p. 

27

Sample ID CLP ID Hazardous 

Substance

Concentration

(μg/L)

RL

(μg/L) References

CF-SW-07 MH5025 Manganese

(dissolved) 31.4 1.0

Ref. 3, Table E38, p. 305, 

Appendix D, p. 198; 3a, App. F, 

Section 5, pp. 1131,1132, Section 

6, pp. 225, 226, 247; Section 7, pp. 

1485, 1508, 1509

Notes: mg/kg milligrams per kilogram

RL The value shown is the sample specific Contract Required Quantitation Limit (Ref. 30).

Attribution

Manganese is an analyte associated with the Anaconda Aluminum Co Columbia Falls Reduction Plant

sources listed in Section 2.2.1. No sources were found to be fully contained and the southern ponds are 

located adjacent to the surface water (Ref. 3, p. 23; 6, p. 5; 7, pp. 4, 5, 26; 19, p. 17; Figure 2 of this HRS 

documentation record). There are no other potential sources for these contaminants located either upgradient or in the immediate area (Ref. 39).

Hazardous Substances Released

Analyses of surface water samples collected during the 2013 sampling event indicate that concentrations 

of manganese are significantly above background concentrations in the Flathead River (Ref. 3, Figure 4, 

Ref. 3, p. 48, App E, Table E38, pp. 305, Table E22, pp. 273, Table E45, p.319). According to the HRS, 

if an observed release can be established for the watershed, an observed release factor value of 550 is 

assigned (Ref. 1, Section 4.1.2.1.1, p. 51609).

Surface Water Observed Release Factor Value: 550 

4.2.2 Drinking Water Threat

No drinking water intakes are located on the Flathead River within the downstream Target Distance Limit 

(Figure 5 of this HRS documentation record). As such, the drinking water threat was not scored because it 

is not expected to contribute significantly to the overall site score.

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4.2.3 Human Food Chain Threat

4.2.3.1 Human Food Chain Threat Likelihood of Release

As was shown above in Section 4.2.1.3 of this HRS documentation record, an observed release of site 

attributable contaminants is established for both the alluvial/glacial aquifer as well as the Flathead River. 

Therefore, an observed release factor value of 550 is assigned for the watershed (Ref. 1, pp. 51629, 

51638, Sections 4.2.2.1.1 and 4.2.3.1).

Surface Water Observed Release Factor Value: 550 

4.2.3.2 Human Food Chain Threat Waste Characteristics

4.2.3.2.1 Toxicity/Mobility/Persistence/Bioaccumulation

Hazardous 

Substance

Source 

No.

Toxicity 

Factor 

Value

Mobility 

Factor 

Value

Persistence 

Factor 

Value*

Bioaccumulation 

Value**

Toxicity/Mobility/

Persistence/

Bioaccumulation

Factor Value 

(Table 4-16)

Reference

Arsenic 1,2,3,4 10,000 1 1.0 5 50,000 2, p. BI-1

Cadmium 1,2,3 10,000 1 x 10-2 1.0 50,000 5 x 106 2, p. BI-2

Chromium 1,2,3,4 10,000 1 1 5 50,000 2, p. BI-3

Cyanide 1,2,3, 4 10,000 1 0.4 0.5 2,000 2, p. BI-3

Manganese 1,2,3,4 10,000 1 1.0 500 5 x 106 2, p. BI-7

Zinc 1,2,3,4 10 1 1.0 500 5,000 2, p. BI10

Notes:

* Persistence value for Rivers

** Bioaccumulation factor value for Freshwater

The hazardous substance with the highest Toxicity/Mobility/Persistence/Bioaccumulation Factor Value is 

cadmium with a value of 5 x 106 (Ref. 1, Section 4.2.3.2.1.5, Table 4-16; Ref. 2, pp. BI-2).

Toxicity/Persistence/Bioaccumulation Factor Value: 5 x 106

4.2.3.2.2 Hazardous Waste Quantity

Source No. Source Type Source Hazardous Waste Quantity

1 Surface impoundment 3,685.8

2 Pile 25,465.8

3 Pile 5,830.3

4 Pile 13,336.06

Total 48,317.96

Hazardous Waste Quantity Factor Value: 10,000 

(Ref. 1, Sec 2.4.2.2)

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4.2.3.2.3 Waste Characteristics Factor Category Value

The hazardous substance cadmium associated with four of the waste sources (which all have surface 

water pathway containment factors of greater than 0 for the watershed) corresponds to a toxicity/ 

mobility/persistence factor of 100 and a bioaccumulation potential factor value of 50,000 (Ref. 1, Tables 

3-9, 4-26; 2, p. BI-2).

Toxicity/Mobility/Persistence/ Hazardous Waste Quantity Factor Value: 1 x 106

Bioaccumulation Factor Value: 5 x 104

Waste Characteristics Factor Category Value: 320 

(Ref. 1, Table 2-7) 

4.2.3.3 Human Food Chain Threat Targets

Actual Human Food Chain Contamination

Fish are caught and consumed from within the zone of actual contamination (Refs. 35; Figure 6 of this 

HRS documentation record). The zone of contamination begins at the uppermost PPE (for the eastern 

south percolation pond) and continues a distance of 0.8 miles downstream to the furthest downstream 

observed release sample (CF-SW-07) containing a hazardous substance with a bioaccumulation potential 

factor value of 500 or greater (Refs. 1, Sec. 4.2.3.3; 3a, App. F Section 7, pp. 1485, 1508, 1509; 35; 

Figure 6 of this HRS documentation record). Level II concentrations of manganese were detected in 

surface water samples within the zone of contamination. The Table below represents the zone of actual 

contamination in the Flathead River.

Sample 

ID

Sample 

Medium

Distance 

from 

uppermost 

PPE

Hazardous 

Substance

Bioaccumulation 

Factor Value

References

CF-SW-07 Surface 

water 0.8 miles Manganese(dissolved) 500

Refs. 2, pp. BI-7; 3, Table E38, 

p. 305, Appendix D, p. 198; 

3a, App. F, Section 5, pp. 

1131,1132, Section 6, pp. 225, 

226; Section 7, pp. 1485, 1508, 

1509

- Closed Fisheries:

According to the MFW&P, the Flathead River is a producing fishery with fish harvested for 

consumption, with no portion of the TDL closed. (Refs. 27; 28; 35).

Level I Fisheries

Without finfish tissue samples, Level I actual contamination cannot be documented. As such, no Level I 

fisheries will be evaluated. (Ref. 1, p. 51620).

Most Distant Level II Sample

The most distant Level II observed release surface water sample, CF-SW-07, was collected from the 

Flathead River approximately 1,000 feet down stream of the facility’s NPDES discharge location, a reach 

extending from Latitude 48° North, 23' 18", Longitude 144° East, 7' 19" to Latitude 48° North, 3' 13 ", 

HRS Documentation Record Anaconda Aluminum Co Columbia Falls Reduction Plant 

MTD057561763 72
Longitude 144° East, 9' 04"(Ref. 7, p. 5). The sample qualifies as an observed release because the 

concentration of dissolved manganese in sample CF-SW-07 is greater than three times the highest 

background concentration (Section 4.2.1.3 of this HRS documentation record). This area of Level II 

actual contamination is approximately 0.8 miles downstream of the uppermost Anaconda Aluminum Co 

Columbia Falls Reduction Plant PPE (at the eastern end of the southern percolation ponds) (Figure 6 of 

this HRS documentation record).

Level II Fisheries

Identity of 

Fishery

Extent of Level II 

Fishery

(Relative to PPE)

Refs.

Flathead River 0.8 miles

Figure 6, Figure 9; Refs. 3, Table E38, p. 305, 

Appendix D, p. 198; 3a, App. F, Section 5, pp. 

1131,1132, Section 6, pp. 225, 226; Section 7, 1485,

1508, 1509; 27; 28; 35

4.2.3.3.1 Food Chain Individual

As noted previously, an observed release of the hazardous substance manganese, which has a 

bioaccumulation factor value of 500 or greater, is documented in a perennial surface water body that is a 

fishery (the Flathead River), thus documenting Level II actual contamination for the human food chain 

portion of the surface water pathway (see Section 4.2.3.2.1 of this HRS documentation record). The 

Flathead River is a cold water fishery and is used by anglers (Refs. 27; 35). According to the MFWP the 

portion of the Flathead River adjacent to the Anaconda Aluminum Co Columbia Falls Reduction Plant

property is fished and the fish are kept and consumed (Refs. 27; 35; Figure 6 of this HRS documentation 

record).

As a portion of the Flathead River where fish are taken and consumed is subject to Level II 

contamination, this portion of the river is assigned a food chain individual factor value of 45 (Ref. 1, p. 

51638, and Section 4.2.3.3.1).

Food Chain Individual Factor Value: 45 

4.2.3.3.2 Population

4.2.3.3.2.1 Level I Concentrations

No Level I concentrations have been documented

Level I Concentrations Factor Value: 0 

4.2.3.3.2.2 Level II Concentrations

The extent of the Level II contamination of the Flathead River fishery is 0.8 miles (distance from the 

upper most PPE (Source 4)) to the sample CF-SW-07 (Refs. 3, Figure 4, pp. 59, 60, Table E38, p. 305; 

30). Values for the amount of human food chain organisms produced annually from this fishery has been 

estimated at greater than 0 since actual production is not documented. For an annual production of greater 

than 0 to 100 pounds per year, a Human Food Chain Population Value of 0.03 is assigned for the fishery 

(Ref. 1, Section 4.2.3.3.2.2, Table 4-18).

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MTD057561763 73
Identity of 

Fishery

Annual 

Production 

(pounds)

References

Human Food Chain

Population Value 

(Table 4-18)

Flathead River 

fishery >0

Ref. 1, pp. 51621, 51638; 3, Table E38, p. 

305, Appendix D, p. 198; 3a, App. F, 

Section 5, pp. 1131,1132, Section 6, pp. 

225, 226; Section 7, 1485, 1508, 1509; 

27; 35 

0.03 

Sum of Level II Human Food Chain Population Values: 0.03 

Level II Concentrations Factor Value: 0.03 

4.2.3.3.2.3 Potential Human Food Chain Contamination 

As the actual contamination score is sufficient to score the Human Food Chain threat, potential 

contamination is not scored. However, the EPA is concerned with the threat posed to fisheries 

downstream of the zone of contamination. 

4.2.3.3.2.4 Calculation of Population Factor Value

The population factor value is calculated by summing the value of Level I concentration (0), Level II 

concentration (0.03) and potential human food chain contamination factors for the watershed (0). The 

resulting value is assigned the population factor value for the watershed (Ref. 1, Section 4.2.3.3.2.4). 

Calculations: 

0 + 0.03 + 0= 0.03 

4.2.3.3.3 Calculation of a Human Food Chain Threat - Target Factor Category Value

The Human Food Chain Threat-Target Factor Category Value is calculated by summing the Food Chain 

Individual (45) and Population Factor Value of the watershed (0.03). The resulting value, 45.03, is 

assigned as the Human Food Chain Threat-Target Score (Ref. 1, Sec. 4.2.3.3). 

Food Chain Target Factor Category Value: 45.03 

4.2.3.4. Calculation of a Human Food Chain Threat Score for a Watershed

The Human Food Chain Threat is calculated by multiplying the Human Food Chain Threat Factor 

Category Value for likelihood of release (550), Waste Characteristics (320) and Targets for a Watershed 

(45.03). The product is rounded to the nearest integer and divided by 82,500. The resulting value, of 96, is 

assigned as the Human Food Chain Threat Score for the watershed (Ref. 1, Sec. 4.2.3.4). 

Calculations: (550 x 320 x 45.03) ÷ 82,500 = 96, capped to 100 

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4.2.4 Environmental Threat 

4.2.4.1 Environmental Threat Likelihood of Release 

As was shown above in Section 4.2.1.3 of this HRS documentation record, an observed released of site 

attributable contaminants is established for both the alluvial/glacial aquifer as well as the Flathead River. 

Therefore, an observed release factor value of 550 is assigned for the watershed (Ref. 1, pp. 51629, 

51638, Sections 4.2.2.1.1 and 4.2.4.1). 

Surface Water Observed Release Factor Value: 550 

4.2.4.2 Environmental Threat Waste Characteristics

4.2.4.2.1 Ecosystem Toxicity/Mobility/Persistence/Bioaccumulation

The table below summarizes the ecosystem toxicity, mobility, persistence, and bioaccumulation potential 

factor values for each hazardous substance for which an observed release into the alluvial/glacial aquifer 

has been established (Ref. 1, p. 51638, Section 4.2.4.2.1). As per Section 4.2.4.2.1.5 of the HRS, the 

substance with the highest ecosystem toxicity/ mobility/ persistence/ bioaccumulation potential factor 

value is used to assign the ecosystem toxicity/ mobility/ persistence/ bioaccumulation potential factor 

value for the watershed (Ref. 1, p. 51638, Section 4.2.4.2.1.5). Manganese and total chromium have the 

highest ecosystem toxicity/mobility/ persistence/ bioaccumulation potential factor value of 5 x 106

. 

Toxicity/Persistence/Bioaccumulation Factor Value: 5 x 106

 

Hazardous 

Substance

Source 

No.

EcoToxicity 

Factor 

Value

Mobility 

Factor 

Value

Persistence 

Factor 

Value*

Bioaccumulation 

Value**

Toxicity/Mobility/

Persistence/

Bioaccumulation

Factor Value 

(Table 4-16)

Reference

Arsenic 1,2,3,

4 10 1 1.0 50,000 5 x 105 2, p. BI-1 

Chromium

(total)

1,2,3, 

4 10,000 1 1.0 500 5 x 106 2, p. BI-3 

Cyanide 1,2,3,

4 1,000 1 0.4 0.5 200 2, p. BI-3 

Manganese 1,2,3,

4 100 1 1.0 50,000 5 x 106 2, p. BI-7 

Zinc 1,2,3,

4 10 1 1.0 50,000 5 x 105 2, p. BI10

Notes:

* Persistence value for Rivers

** Environmental Bioaccumulation factor value for Freshwater

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4.2.4.2.2 Hazardous Waste Quantity

Source No. Source Type Source Hazardous Waste Quantity

1 Surface impoundment 3,685.8

2 Pile 25,465.8

3 Pile 5,830.3

4 Pile 13,336.06

Total 48,317.96

The sum of the hazardous waste quantity values for Sources 1, 2, 3 and 4 corresponds to a hazardous 

waste quantity factor value of 10,000 in Table 2-6 of the HRS (Ref. 1, p. 51591). Therefore, a hazardous 

waste quantity factor value of 10,000 is assigned for the ground water to surface water migration 

component of the surface water migration pathway (Ref. 1, Sections 2.4.2.2 and 4.2.4.2.2, pp. 51591, 

51592, 51644).

Hazardous Waste Quantity Factor Value: 10,000 

(Ref. 1, Sec 2.4.2.2)

4.2.4.2.3 Waste Characteristics Factor Category Value

The hazardous substance manganese, associated with percolation pond sources 1, 2, 3 and 4, and

chromium (total) associated with percolation pond sources 1 and 2 (all ponds have a ground water 

pathway containment factor of greater than 0 for the watershed) corresponds to an ecosystem toxicity/ 

mobility/persistence factor of 100 and 10,000 and a bioaccumulation potential factor of 50,000 and 500 

respectively (Ref. 1, Tables 3-9 and 4-29; Ref. 2, pp. BI-3, BI-7; Table 6 of this HRS documentation 

record).

Toxicity/Mobility/Persistence/ Hazardous Waste Quantity Factor Value: 1 x 108

Bioaccumulation Factor Value: 5 x 102

Waste Characteristics Factor Category Value: 320

(Ref. 1, Table 2-7)

4.2.4.3 Environmental Threat Targets

4.2.4.3.1. Sensitive Environments

4.2.4.3.1.1 Level I Sensitive Environments

No level I sensitive environments have been documented for this site.

4.2.4.3.1.2 Level II Sensitive Environments

Actual Environmental Threat Contamination

Targets are documented within the zone of actual contamination. The zone of contamination begins at the 

uppermost PPE (for the eastern south percolation pond) and continues a distance of 0.8 miles downstream 

to the furthest downstream observed release sample (CF-SW-07) containing a hazardous substance with a 

bioaccumulation potential factor value of 500 or greater (Refs. 1, Sec. 4.2.3.3; 3a, App. F, Section 7, pp. 

1485, 1508, 1509; Figure 6 of this HRS documentation record). Level II concentrations of dissolved 

manganese were detected in surface water samples within the zone of contamination. The Table below 

represents the zone of actual contamination in the Flathead River.

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MTD057561763 76
Sample ID Sample 

Medium

Distance from 

uppermost 

PPE

Hazardous 

Substance

Bioaccumulation 

Factor Value

References

CF-SW-07 Surface 

water 0.8 miles Manganese(dissolved) 500

Refs. 2, p. BI-7; Ref. 3, 

Table E38, p. 305, Appendix 

D, p. 198; 3a, App. F, 

Section 5, pp. 1131,1132, 

Section 6, pp. 225, 226; 

Section 7, pp. 1485, 1508, 

1509

Most Distant Level II Sample

The most distant Level II observed release surface water sample, CF-SW-07, was collected from the 

Flathead River below the historical discharge location Outfall D006, approximately 0.8 miles downstream 

of the uppermost Anaconda Aluminum Co Columbia Falls Reduction Plant PPE (Ref. 3, pp. 76, 77, Table 

E48, p. 305; 3a, App. F, Section 5, pp. 1131,1132, Section 6, pp. 225, 226; Section 7, pp. 1485, 1509; 7, 

p. 5; Figures 4, 5, 6, and 9 of this HRS documentation record).

Sensitive 

Environment

Assigned 

Value

Extent of Sensitive 

Environment

(Relative to PPE)

Refs.

Critical Habitat 

for the Bull Trout 100 0.8 miles

Ref. 3, Table E38, p. 305, Appendix D, p. 

198; 3a, App. F, Section 5, pp. 1131,1132, 

Section 6, pp. 225, 226, Section 7, pp. 

1485, 1508, 1509; 26, p. 2; 27, pp. 33-34, 

47-49; 33; 42; 45; 46; Figures 6 and 9 of 

this HRS documentation record 

Wetlands 50 1.45 miles

Ref. 3, Table E38, p. 305, Appendix D, p. 

198; 3a, App. F, Section 5, pp. 1131,1132, 

Section 6, pp. 225, 226, Section 7, pp. 

1485, 1508, 1509; 29; 33; 47; Figures 6 

and 9 of this HRS documentation record 

The ECOS and MFISH identified habitat for the Bull Trout (federally threatened) and Westslope 

Cutthroat Trout (federally sensitive) in the Flathead River (Refs. 26; 27, pp. 17-32; 42; 45; 46). Fish 

surveys conducted by FWP have confirmed the presence of both species in the Flathead River adjacent to 

the Site and the presence of Westslope Cutthroat Trout in Cedar Creek (Ref. 27, pp. 32-35; 28; 42). In 

addition to fish surveys identifying the Bull Trout and the Westslope Cutthroat Trout in the zone of actual 

contamination, the Flathead River in this zone is designated as critical habitat for the Bull Trout by the 

US Fish and Wildlife Service pursuant to 50 CFR 424.02 (Ref. 45, p. 1; 46, pp. 1-174). Further, river 

bottom in the areas of CF-SW-09, CF-SW08, and CF-SW-07 demonstrate the conditions necessary to 

construct the clean cobble and low silt substrates necessary for the species to construct their redds (Ref. 3, 

App. B, pp. 171-172).

According to the US Fish and Wildlife Service National Wetlands Inventory Wetlands mapper, 

approximately 15.53 miles (on both sides of the river) of streamside wetlands were digitally measured 

along the length of the wetland in the riverbed, and are present from the site along the Flathead River 

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downstream 15 miles to the Target Distance Limit. These wetland types meet the HRS definition of a 

wetland, 40 CFR 230.3, and are considered eligible for HRS scoring (Refs. 1, Table 4-24, p. 51625; 29).

Wetlands within the area of actual contamination were digitally measured at 1.45 miles in length by 

drawing a polygon around the portions of the wetlands that are in contact with the river at any time during 

the year (Refs. 29; 33; 47; Figure 6 of this documentation record). The dominant vegetation is freshwater 

palustrine scrub shrub and emergent wetlands, although they are defined as “Freshwater emergent 

wetlands” and “freshwater forest/shrub wetlands” in Wetlands Mapper. 

Actual contamination of sensitive environments in the Flathead River was documented by the Level II 

concentrations in surface water sample CF-SW-07 (Refs. 3, Figure 4, p. 60, Table E38, p. 305; 3a, App. 

F, Section 5, pp. 1131, 1132, Section 6, pp. 225, 226, Section 7, pp. 1485, 1509). Both the federally 

threatened Bull Trout and 1.2 miles of wetlands are subject to Level II concentrations; therefore, a value 

of 125 is assigned to the Environmental Threat Level II Concentration Factor Value (Ref. 1, Sec. 

4.2.4.3.1.2). 

Level II Concentration Factor Value: 150

4.2.4.3.1.3 Potential Contamination

There are targets subject to potential contamination associated with the surface water bodies downstream 

of the zone of contamination and within the TDL, including additional bull trout habitat and wetlands; 

however, as the actual contamination score is sufficient to score the environmental threat, potential 

contamination is not scored (Refs. 1, Section 4.2.4.3.1.3; 26; 27; 29; 40). However, the EPA is concerned 

with the threat to these sensitive environments.

Environmental Potential Contamination Factor Value: 0

4.2.4.3.1.4 Calculation of an Environmental Threat - Target Factor Category Value

The Environmental Threat-Target Factor Category Value is calculated by summing the Level I 

concentrations (0), the Level II concentrations (150), and the potential contamination (NS). The resulting 

value, 125, is assigned as the Environmental Threat-Target Score (Ref. 1, Sec. 4.1.4.3.2.1.4).

Calculations: 0 + 150 + 0 = 150

Environmental Target Factor Category Value: 150

4.2.4.4 Calculation of an Environmental Threat Score for a Watershed

The Environmental Threat is calculated by multiplying the Environmental Threat Factor Category Value 

for likelihood of release (550), Waste Characteristics (320) and Targets for a Watershed (150). The 

product is rounded to the nearest integer and divided by 82,500. The resulting value, subject to a 

maximum of 60, is assigned as the Environmental Threat Score for the watershed (Ref. 1, Sec. 4.2.4.4).

Calculations:

(550 x 320 x 150) ÷ 82,500 = 320, capped at 60

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