HRS DOCUMENTATION RECORD (HRS)—REVIEW COVER SHEET
 

Name of Site: ARGONAUT MINE 

Contact Person: Sharon Murray, EPA Region 9 (415) 972-4250 

Site Investigation: Leslie Ramirez, EPA Region 9 (415) 972-3978 

Documentation Record: Christina Marquis, Weston Solutions, Inc. (818) 350-7308 

Pathways, Components, or Threats Not Scored 

Ground Water Pathway 

Ground water in most of Amador County is not well defined. The majority of available ground water is 

transient and found in fractured rock (Ref. 7, p. 26). There are no known drinking water wells within the 

target distance limit from Argonaut Mine sources (Ref. 30, p. 1). Therefore, scoring this pathway does 

not contribute significantly to the listing decision for the site. 

Surface Water Pathway – Ground Water to Surface Water 

Ground water within the Tailings Area Tailings Impoundment flows through cracks in the base of the 

dam (Ref. 6, p. 10) to an unnamed intermittent stream that flows to North Fork Jackson Creek (see 

Attachment A-1). However, North Fork Jackson Creek is an intermittent stream, and average annual 

precipitation in the site vicinity exceeds 20 inches (Ref. 3; Ref. 4, p. 45; Ref. 7, pp. 25-26; Ref. 33). 

Therefore, as the threat to surface water via overland flow is sufficient to qualify the site for listing, 

scoring the ground water to surface water component of the surface water pathway would not contribute 

significantly to the listing decision for the site. 

Air Migration Pathway 

The air pathway was not scored because there is no documented observed release to the atmosphere, and 

scoring the potential to release to air would not contribute significantly to the listing decision for the site. 

Soil Exposure Pathway – Nearby Population Threat 

The Argonaut Mining Company historically owned approximately 330 acres of land northwest of 

downtown Jackson. The property was sold after the mine closed, and approximately 90 acres of the 330 

acres of the former property have been developed as residential neighborhoods (Ref. 4, pp. 7, 64; Ref. 

28, p. 8). The threat posed by the mining waste to nearby populations may be considered at a later point. 

However, because the Resident Population Threat score is sufficient to identify the threat to residential 

populations is significant, it was not necessary to evaluate the Nearby Population Threat to support the 

listing decision for the site. 
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HRS DOCUMENTATION RECORD 

Name of Site: ARGONAUT MINE 

EPA ID#: CAD983650011 

EPA Region: 9 

Date Prepared: April 2016 

Street Address of Site: Argonaut Lane 

City, County and State: Jackson, Amador County, California 95642 

Topographic Map: Jackson, California USGS 7.5-Minute Quadrangle (Ref. 3) 

Latitude: 38° 21' 12.0" North, Longitude: 120° 47' 8.7" West (Ref. 3; Ref. 4, pp. 39, 41) 

Latitude/Longitude Reference Point: The latitude and longitude is the location of sample ATS-01, 

collected within Source 1 during the 2014 Site Inspection (SI) (Ref. 3; Ref. 4, pp. 39, 41). 

SCORES 

Air Pathway = Not Scored 

Ground Water Pathway = Not Scored 

Soil Exposure Pathway = 100 

Surface Water Pathway = 60 

HRS SITE SCORE = 58.31 

*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 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. 
 

 

 

 

 

WORKSHEET FOR COMPUTING HRS SITE SCORE 

S S2 

1. Ground Water Migration Pathway Score (Sgw) NS NS 

2a. Surface Water Overland/Flood Migration Component 

(from Table 4-1, line 30) 

60 3,600 

2b. 

2c. 

Ground Water to Surface Water Migration Component 

(from Table 4-25, line 28) 

Surface Water Migration Pathway Score (Ssw) 

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

NS 

60 

NS 

3,600 

3. Soil Exposure Pathway Score (Ss) 

(from Table 5-1, line 22) 

100 10,000 

4. 

5. 

Air Migration Pathway Score (Sa) 

(from Table 6-1, line 12) 

Total of Sgw 

2 + Ssw 2 + Ss 2 + Sa 2 

NS NS 

13,600 

6. HRS Site Score 

Divide the value on line 5 by 4 and take the square root 

58.31 

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HRS TABLE 4-1 -Surface Water Overland/Flood Migration Component Scoresheet 

Factor Categories and Factors Maximum 

Value 

Value 

Assigned 

Drinking Water Threat 

Likelihood of Release: 

1. Observed Release 550 550 

2. Potential to Release by Overland Flow: 

2a. Containment 10 

2b. Runoff 25 

2c. Distance to Surface Water 25 

2d. Potential to Release by Overland Flow 

(lines 2a x [2b + 2c]) 500 

3. Potential to Release by Flood: 

3a. Containment (Flood) 10 

3b. Flood Frequency 50 

3c. Potential to Release by Flood (lines 3a x 3b) 500 

4. Potential to Release (lines 2d + 3c, subject to a maximum of 500) 500 

5. Likelihood of Release (higher of lines 1 and 4) 550 550 

Waste Characteristics: 

6. Toxicity/Persistence (a) NS 

7. Hazardous Waste Quantity (a) NS 

8. Waste Characteristics 100 NS 

Targets: 

9. Nearest Intake 50 

10. Population: 

10a. Level I Concentrations (b) 

10b. Level II Concentrations (b) 

10c. Potential Contamination (b) 

10d. Population (lines 10a + 10b + 10c) (b) 

11. Resources 5 

12. Targets (lines 9 + 10d + 11) (b) NS 

Drinking Water Threat Score: 

13. Drinking Water Threat Score ([lines 5 x 8 x 12]/82,500, subject to a 

maximum of 100) 100 NS 

Human Food Chain Threat 

Likelihood of Release: 

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

Waste Characteristics: 

15. Toxicity/Persistence/Bioaccumulation (a) 

16. Hazardous Waste Quantity (a) 

17. Waste Characteristics 1,000 NS 

Targets: 

18. Food Chain Individual 50 

19. Population: 

19a. Level I Concentrations (b) 

19b. Level II Concentrations (b) 

19c. Potential Human Food Chain Contamination (b) 

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

20. Targets (lines 18 + 19d) (b) NS 

3
 
4

Factor Categories and Factors Maximum

Value

Value

Assigned

Human Food Chain Threat Score:

21.

subject 

Human Food Chain 

to a maximum of 100) 

Threat Score ([lines 14 x 17 x 20]/82,500, 100 NS

Environmental Threat

Likelihood of Release:

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

23. Ecosystem Toxicity/Persistence/Bioaccumulation (a) 500,000,000

24. Hazardous Waste Quantity (a) 10,000

25. Waste Characteristics 1,000 1,000

Targets:

26. Sensitive Environments:

 26a. Level I Concentrations (b)

 26b. Level II Concentrations (b) 25

 26c. Potential Contamination (b)

 26d. Sensitive Environments (lines 26a + 26b + 26c) (b) 25

27. Targets (value from 26d) (b) 25

Environmental Threat Score:

Environmental Threat Score

([lines 22 x 25 x 27]/82,500, subject to a maximum of 60) 60 60

Surface Water 

Watershed

Overland/Flood Migration Component Score For A 

29. Watershed Scorec

(lines 13 + 21 + 28, subject to a maximum of 100) 100 60

Surface Water Overland/Flood Migration Component Score

Component Score (Sof)

c

, (highest score 

evaluated, subject to a maximum of 100)

from line 29 for all watersheds 100 60

28.

30.

aMaximum value applies to waste characteristics category. 

bMaximum value not applicable. 

cDo not round to nearest integer. 
5

HRS Table 5-1 Soil Exposure Pathway Scoresheet

Factor Categories and Factors Maximum

Value

Value

Assigned

Resident Population Threat

Likelihood of Exposure:

1. Likelihood of Exposure 550 550

Waste Characteristics:

2. Toxicity (a) 10,000

3. Hazardous Waste Quantity (a) 10,000

4. Waste Characteristics 100 100

Targets:

5. Resident Individual 50 50

6. Resident Population:

 6a. Level I Concentrations (b) 4,547.2

 6b. Level II Concentrations (b) 4.64

 6c. Resident Population (lines 6a + 6b) (b) 4551.84

7. Workers 15 5

8. Resources 5 0

9. Terrestrial Sensitive Environments (c) 0

10. Targets (lines 5 + 6c + 7 + 8 + 9) (b) 4606.84

Resident Population Threat Score:

11. Resident Population Threat (lines 1 x 4 x 10) (b) 253,376,200

Nearby Population Threat

Likelihood of Exposure:

12. Attractiveness/Accessibility 100

13. Area of Contamination 100

14. Likelihood of Exposure 500 NS

Waste Characteristics:

15. Toxicity (a)

16. Hazardous Waste Quantity (a)

17. Waste Characteristics 100 NS

Targets:

18. Nearby Individual 1

19. Population Within 1 Mile (b)

20. Targets (lines 18 + 19) (b) NS

Nearby Population Threat Score:

21. Nearby Population Threat (lines 14 x 17 x 20) (b) NS

Soil Exposure Pathway Score

22.

subject 

Soil Exposure Pathway 

to a maximum of 100)

d Score (Ss), (lines [11 +21]/82,500, 100 100

aMaximum value applies to waste characteristics category. 

bMaximum value not applicable. 

cNo specific maximum value applies to factor. However, pathway score based solely on terrestrial sensitive 

environments is limited to maximum of 60. 

dDo not round to nearest integer.
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ACRONYM LIST
 

bgs below ground surface 

CRQL EPA Contract Laboratory Program Contract Required Quantitation Limit 

DU Decision Unit 

EMAD Eastwood Multiple Arch Dam 

EPA United States Environmental Protection Agency 

HRS Hazard Ranking System 

mg/kg milligrams per kilogram 

SAP Sampling and Analysis Plan 

SI Site Inspection 

SQL Sample Quantitation Limit 

START Superfund Technical Assessment and Response Team 

XRF X-Ray Fluorescence 

NOTES TO THE READER 

Page numbers have been added to the references in the lower right corner. For reference citations, please 

refer to the page numbers in this location. 

Attachment A contains the following documents: 

• Attachment A Data Citations 

• Attachment A-1: Argonaut Mine Layout 

• Attachment A-2: Argonaut Site Sources 

• Attachment A-3: Source 1 Sampling Locations 

• Attachment A-4: Residential Parcels on the Historical Aerial 

• Attachment A-5: Residential Soil Sampling Locations 

• Attachment A-6: Observed Contamination Areas 

• Attachment A-7: Jackson Junior High School Sampling and Removal Locations 

• Attachment A-8: Source 1 Wetland 
7
 

 

 

 

 

 

 

 

 

REFERENCE LIST 

Reference 

Number Description of the Reference 

1 40 CFR Part 300, Hazard Ranking System; Final Rule, 14 December 1990, Vol. 55, No. 

241, 138 pages. 

Available online: semspub.epa.gov/src/document/HQ/174028 

2 U.S. Environmental Protection Agency (EPA), Superfund Chemical Data Matrix 

(SCDM) Methodology, Accessed February 29, 2016, 13 pages. Available online : 

http://www.epa.gov/superfund/superfund-chemical-data-matrix-scdm 

3 U.S. Geological Survey, 7.5 Minute Topographic Map of Jackson, California, 1962, 

Photoinspected 1973, 1 sheet. 

4 Weston Solutions, Inc., Site Inspection Report, Argonaut Mine, Jackson, Amador 

County, California, July 2015, 1946 pages. 

5 Ecology & Environment, Inc., Removal Assessment Addendum Report; Argonaut Mine 

Tailings Pile, AOCs 1, 2, 4, and 6; Jackson, Amador County, California, February 21, 

2014, 63 pages. 

6 Ecology & Environment, Inc., Argonaut Mine Tailings Pile, Removal Assessment 

Report, Jackson, California, December 2013, 59 pages. 

7 Amador County, Hydrology and Water Quality General Plan Update Working Paper, 

May 2007, 44 pages. 

8 Amador County Environmental Health Department, Letter to Megan Cambridge from 

Margaret Blood and Michael Israel concerning soil cap mitigation, January 21, 1994, 5 

pages. 

9 U.S. Environmental Protection Agency, Solid Waste and Emergency Response, Using 

Qualified Data to Document an Observed Release and Observed Contamination, 

November 1996, 18 pages. 

10 U.S. Environmental Protection Agency, Center of Environmental Computing, Office of 

Technology Operations & Planning, Office of Environmental Information Aerial 

Photographic Analysis of Argonaut Mine Site, June 2014, 70 pages. 

11 Weston Solutions, Inc., Argonaut Mine Residential Removal Assessment Sampling with 

attachments, October 29, 2015, 122 pages. 

12 Anthropological Studies Center, Sonoma State University, A Cultural Resources 

Inventory and Evaluation of the Argonaut Mine Cyanide Plant and Tailings Site, 

Jackson, Amador County, California, April 29, 2014, 166 pages. 

13 Aguilera, Rachel, Amador County Schools, telephone conversation recorded on contact 

report by Christina Marquis, Weston Solutions, Inc., February 5, 2016, signed February 
8
 

 

 

REFERENCE LIST 

Reference 

Number Description of the Reference 

17, 2016. 1 page. 

14 U.S. Environmental Protection Agency, Releasable Chronology of the Argonaut Mine 

Site Ownership & Operation Memorandum, January 28, 2013, 22 pages. 

15 Weston Solutions, Inc., Residential Sample Address Codes, February 5, 2016, 1 page. 

To protect the privacy of individual residents, this reference is not included. The full 

reference may be made available upon request. 

16 EPA Contract Laboratory Program, File 

405780_201158.SS44272.EPW09037.MY9F52, April 15, 2015, 8 pages. 

17 EPA Contract Laboratory Program, File 

405761_201159.SS44272.EPW09037.MY9F22, April 15, 2015, 8 pages. 

18 EPA Contract Laboratory Program, File 

406097_201227.SS44272.EPW09037.MY9EX7, April 15, 2015, 9 pages. 

19 U.S. Environmental Protection Agency, Contract Laboratory Program, Universal 

Spreadsheet Data Field Names, October 7, 2015, 1 page. 

20 EPA Contract Laboratory Program, File 

406087_201229.SS44272.EPW09037.MY9EY0, April 15, 2015, 10 pages. 

21 Bonner Analytical Testing Company, Full Inorganics Complete SDG file, Case No. 

44272, SDG No. MY9F52, August 25, 2014, 267 pages. 

22 Bonner Analytical Testing Company, Full Inorganics Complete SDG file, Case No. 

44272, SDG No. MY9F22, August 25, 2014, 194 pages. 

23 Bonner Analytical Testing Company, Full Inorganics Complete SDG file, Case No. 

44272, SDG No. MY9EX7, August 26, 2014, 206 pages. 

24 Bonner Analytical Testing Company, Full Inorganics Complete SDG file, Case No. 

44272, SDG No. MY9EYO, August 26, 2014, 228 pages. 

25 Bonner Analytical Testing Company, Full Inorganics Complete SDG file, Case No. 

44272, SDG No. MY9F74, August 25, 2014, 186 pages. 

26 Amador County Environmental Health Department, Letter to Gary Urzik from Margaret 

Blood concerning soil cap mitigation, May 25, 1994 and Letter to Dr. McClenahan, 

Amador County Health Dept. from Paul Accinelli, Central Sierra Builders, Inc., May, 

23, 1994, 3 pages. 

27 Amador County Environmental Health Department, Re: Proposed Grading and 

Development, Lots 30 and 31, Argonaut Heights, Jackson (APN 044-071-002, 044-071­
9
 

 

 

 

 

 

 

 

REFERENCE LIST 

Reference 

Number Description of the Reference 

003), January 28, 2003, 4 pages. 

28 URS Corporation, Argonaut Mine Tailings Site, Draft Site Investigation Report, March 

30, 2009, 109 pages. 

29 United States Census Bureau, Quick Facts, Amador County, 

California, http://www.census.gov/data/data-tools.html, data extracted on February 9, 

2015, 3 pages. 

30 Weston Solutions, Inc. (Weston), Drinking Water Sources Map, 

Threatened/Endangered Species and Wetlands Map and Census Block Population and 

Parcels Map, Argonaut Mine Site, 3 pages. 

To protect the security of drinking water intake locations, this reference is not included. 

The full reference may be made available upon request. 

31 URS Corporation, Contract Agreement No. 07-T3375, Draft Final Interim Soil Removal 

Action Work Plan, Argonaut Mine Tailings Site, Jackson, California, June 9, 2011, 233 

pages. 

32 Weston Solutions, Inc., Argonaut Mine Tailings Area Additional Removal Assessment 

Sampling, Jackson, Amador County, California, February 9, 2015, 41 pages. 

33 Western Regional Climate Center, Camp Pardee, California (041428) Climate 

Summary, http://www.wrcc.dri.edu/, data extracted on September 29, 2015, 1 page. 

34 Weston Solutions, Inc., Argonaut Mine Tailings Pile Removal Site, Jackson, Amador 

County, California, Jackson Junior High School Removal Action Report, February 2, 

2016, 618 pages. 

35 Mining and Scientific Press, January 27, 1917, Excerpt, 1 page. 

36 Department of Commerce, United States Bureau of Mines, Information Circular, Milling 

Methods and Costs at the Argonaut Mill, Jackson, CA, July 1931, 16 pages. 

37 EPA Contract Laboratory Program, File 

405808_201157.SS44272.EPW09037.MY9F74, April 15, 2015, 9 pages. 

38 U.S. Fish and Wildlife Service, National Wetlands Inventory, February 5, 2016, 2 pages. 

39 Summary of Confirmation Soil Sampling and Removal Activities, Argonaut Mine 

Tailings Pile, Residential Removal Action, Jackson, California, undated, 148 pages. 

To protect the privacy of individual residents, this reference is not included. The full 

reference may be made available upon request. 

40 U.S. Environmental Protection Agency, Pollution/Situation Report, Argonaut Mine Site 

Residential Yards Removal Action – Removal Polrep, September 5, 2015, 10 pages. 
10
 

 

 

REFERENCE LIST 

Reference 

Number Description of the Reference 

To protect the privacy of individual residents, this reference is not included. The full 

reference may be made available upon request. 

41 Weston Solutions, Inc., Argonaut Mine Tailings Area Geotechnical Sampling, City of 

Jackson, Amador County, California, January 23, 2015, 98 pages. 

42 Weston Solutions, Inc., Final Removal Action Report for Argonaut Mine Tailings Pile 

Removal Site – Area of Concern 5, Jackson, Amador County, California, September 

2015, 49 pages. 

43 Bauer, Richard, U.S. EPA Region 9 Laboratory, email correspondence with Christina 

Marquis, Weston Solutions, Inc., February 11, 2016, 2 pages. 

44 Bronson, C.E., Mining Engineer and Licensed Surveyor, Contour Map of Argonaut Mill 

Tailings, February 1955, 1 page. 

45 Fortner, Tom, Weston Solutions, Inc., telephone conversation recorded on contact report 

by Christina Marquis, Weston Solutions, Inc., February 11, 2016, 1 page. 

46 Fitzgerald, Tara, Weston Solutions, Inc., telephone conversation recorded on contact 

report by Christina Marquis, Weston Solutions, Inc., February 19, 2016, 1 page. 

47 U.S. Environmental Protection Agency, Region 9 Laboratory, Analytical Testing Results 

– Project R15S53, SDG: 15092C, April 20, 2015, 406 pages. 

48 U.S. Environmental Protection Agency, Region 9 Laboratory, Analytical Testing Results 

– Project R15S53, SDG: 15175D, July 15, 2015, 328 pages. 

49 U.S. Environmental Protection Agency, Region 9 Laboratory, Analytical Testing Results 

– Project R15S53, SDG: 15244A, September 17, 2015, 362 pages. 

50 Plan of Property of the Argonaut Mining Co and Hoffman Farms Extension, Jackson – 

Amador Co, California 122, April 1907, 1 page. 
11
 

 

 

 

 

 

 

 

 

SITE SUMMARY
 

The Argonaut Mine site consists of areas of contamination resulting from the release of hazardous 

substances from mining operations conducted on the Argonaut Mine property. Six hazardous substance 

sources are scored as part of the site. Source 1 is a tailings pile containing approximately 1,712,000 tons 

of processed tailings (Ref. 12, pp. 44-45; Ref. 44). Sources 2 through 5 consist of areas of residential 

properties within the former Argonaut Mine property boundary, which were built on imported fill placed 

over waste rock, tailings, and soils contaminated by Argonaut Mine operations (Ref. 4, pp. 16, 40; Ref. 

8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Source 6 is the Jackson Junior High School athletic field, which 

was constructed on a waste rock and tailings pile (Ref. 10, pp. 28, 36; Ref. 34, p. 2). Hazardous 

substances in the sources include arsenic, lead, and mercury. Targets affected by releases from these 

sources include a wetland located on the surface of Source 1, as well as residents, students, and workers 

occupying or working within areas of surface contamination in Sources 2 through 6. 

The Argonaut Mine, located in the City of Jackson, Amador County, California, operated as a gold mine 

from the 1850s until 1942 (Ref. 4, p, 6; Ref. 12, p. 25; Ref. 14, pp. 1, 4-10). The Argonaut Mining 

Company historically owned approximately 330 acres of land northwest of downtown Jackson. The 

property was sold after the mine closed, and approximately 90 acres of the former property have been 

developed as residential neighborhoods (Ref. 4, pp. 7, 64). Argonaut Mine operations comprise two 

principal areas: the Mill Area (mine shafts, buildings, former milling areas, and waste rock piles) and the 

Tailings Area (unprocessed and semi-processed ore storage area, cyanide plant, and tailings 

impoundments) (Ref. 4, pp. 11-12, 64; Ref. 14, p. 1). The Argonaut Mine property layout is shown on 

Attachment A-1. 

Subsurface mining at the Argonaut Mine began in the 1850s (Ref 12, p. 26; Ref. 14, p. 1). The Argonaut 

Mine shaft is located in the northern part of the property, to the west of the current location of State 

Highway 49 (Ref. 12, pp. 9, 11, 12). Raw ore extracted from the shaft was processed at a 40-stamp mill 

on the east side of Highway 49 from 1898 until 1916, when it was replaced by a 60-stamp mill located 

west of Highway 49 (Ref. 4, p. 9; Ref. 12, pp. 12, 28-30, 32; Ref. 36, p. 3). Processed tailings from the 

40-stamp mill were deposited on “adjacent, erodible piles” in the Mill Area (Ref. 12, p. 32). Processed 

tailings from the 60-stamp mill were transported through a flume to the Tailings Area, where they were 

deposited in the Source 1 tailings pile behind the Eastwood Multiple Arch Dam (EMAD) in a gulch 

north and west of Jackson Junior High School (Ref. 4, p. 9; Ref. 12, p. 32; Ref. 14, p. 1; Ref. 36, p. 13). 
12
 

 

 

 

 

 

SITE SOURCES
 

A total of six sources were evaluated for scoring the Argonaut Mine site (see Attachment A-2). Detailed 

information about each source, with reference citations, is available in the following sections. Additional 

sources that were not scored are discussed in the Other Possible Sources Not Scored section. 

Source 1 is the Tailings Area Tailings Impoundment, containing approximately 1,712,000 tons of 

processed tailings. Sources 2 through 5 consist of areas of residential properties within the former 

Argonaut Mine property boundary, which were built on imported fill placed over waste rock, tailings, 

and soils contaminated by Argonaut operations. Source 6 is the Jackson Junior High School athletic 

field, which was constructed on a pile of waste rock and tailings. 

Hazardous substances associated with these sources include arsenic, lead, and/or mercury. 

Argonaut Mine Sources 

Source 

number Source Name Source Type 

1 Tailings Area Tailings Impoundment Pile 

2 Argonaut Estates Tailings Pile Pile 

3 Argonaut Heights – North Tailings Pile Pile 

4 Argonaut Heights – South Contaminated Soil Contaminated Soil 

5 Sierra View Estates Contaminated Soil Contaminated Soil 

6 Jackson Junior High School Tailings Pile Pile 
 

13
 

 

 

 

 

 

 

 

 

Source No: 1 

2.2 SOURCE CHARACTERIZATION: Source 1, Tailings Area Impoundment 

2.2.1 SOURCE IDENTIFICATION 

Name of source: Tailings Area Tailings Impoundment 

Source Type: Tailings Pile 

Description and Location of Source (see Attachment A-2): 

The Tailings Area Tailings Impoundment (EPA AOC-3) consists of a 

Number of source: 1 

tailings pile covering 

approximately 48 acres constructed in a drainage valley (Ref. 4, pp. 8, 13; Ref. 12, p. 9). In 1916, the 

EMAD was constructed in the ravine southeast of the Argonaut Mine shaft and mill to impound tailings 

generated from Argonaut mining and milling operations (Ref. 6, p. 10; Ref. 12, p. 41). The EMAD is 

roughly 390 feet wide and 46 feet tall (Ref. 6, p. 10). The impoundment was expanded in 1931 and 1940 

with two additional dams constructed of tailings (Ref. 12, pp. 41-42; Ref. 41, p. 9). Two wetlands are 

present on the surface of Source 1 (Ref. 4, pp. 8, 65; Ref. 38). 

Sediment and tailings have filled the valley behind the EMAD to within a few feet of its top. Standing 

water flows over the top of the dam during wet periods. Water also flows through cracks in the base of 

the dam, suggesting materials behind the dam are saturated (Ref. 6, p. 10). 

Soils at the surface of Source 1 are predominantly grey tailings. In most areas, vegetation has been 

reestablished and a thin layer of organic material is present, stabilizing the surface. However, large 

portions of Source 1 contain exposed gray tailings that are devoid of vegetation. These soils are easily 

eroded during large magnitude rain events, and large gullies and sinkholes have formed. Some of the 

gullies exceed 20 feet in depth and top-width (Ref. 6, p. 9). 

In February 1955, mining engineer and licensed surveyor C.E. Bronson estimated a total of 1,712,000 

tons of tailings within Source 1 by comparing the existing tailings surface with an estimated contour of 

the original ground surface below (Ref. 12, pp. 43-45; Ref. 44). 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE 

Weston Solutions, Inc. 2014 Site Inspection (SI) Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a 

Sampling and Analysis Plan (SAP) approved by EPA on March 10, 2014. A total of 90 soil samples 

were collected from the surface (0 to 6 inches) and shallow subsurface (up to 2 feet) at 47 sampling 

locations. The subsurface samples were collected using either a track-mounted direct push sampling rig 

and Macro-core soil sampler lined with an acetate sleeve, or by hand auger. A total of 27 sediment 

samples were collected from 25 sampling locations (Ref. 4, p. 22). 
 

14
 

 

 

 

 

 

 

 

 

 

 

Source No: 1 

Soil and sediment samples were submitted to Bonner Analytical, located in Hattiesburg, Mississippi, 

under the EPA Contract Laboratory Program for metal analysis by Inorganic Superfund Methods 

(ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical data were validated by EPA 

(Ref. 4, p. 22). 

Soil samples were collected from five locations within Source 1 (Ref. 4, p. 27). Two sample locations 

(ATA-01 and ATA-02) were gray sands from the upper tailings dam. Sampling location ATA-03 was 

near the Sierra View Estates residential properties off of Detert Lane. Sampling location ATA-04 was at 

the northern end of the lower tailings dam; near Sierra View Estates. Sampling location ATA-05 was 

near residential properties off of Muldoon Place near Sierra View Estates (Ref. 4, pp. 27-28, 65). 

Sediment samples ATS-01 and ATS-02 were collected from the two wetlands on the surface of Source 1 

(Ref. 4, p. 33). Soil and sediment sampling locations are presented in Attachment A-3. 

2014 SI, Source 1 Tailings Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ATA-01-0 

(MY9F89) 0 - 0.5 7/29/14 Arsenic 54.8 1.0 Ref. 4, pp. 28, 39, 65, 1812, 1817, 

1822; Ref. 18, p. 4; Ref. 23, pp. 11, 24 

ATA-02-0 

(MY9F90) 0 - 0.5 7/29/14 

Arsenic 49.4 1.1 Ref. 4, pp. 28, 39, 65, 1812, 1817, 

Mercury 1822; Ref. 18, p. 5; Ref. 23, pp. 11, 25 0.38 0.10 

ATA-03-0 

(MY9F91) 0 - 0.5 7/29/14 

Arsenic 3,490 15.5 

Ref. 4, pp. 28, 39, 65, 1812, 1892; Ref. 

25, pp. 8, 25; Ref. 37, p. 6 Lead 193 1.0 

Mercury 2.5 0.52 

ATA-03-2 

(MY9F92) 1.5 - 2 7/29/14 Arsenic 502 2.1 Ref. 4, pp. 28, 39, 65, 1812, 1892; Ref. 

25, pp. 8, 26; Ref. 37, p. 6 

ATA-04-0 

(MY0F93) 0 - 0.5 7/29/14 Arsenic 362 1.0 Ref. 4, pp. 28, 39, 65, 1812, 1893; Ref. 

25, pp. 8, 27; Ref. 37, p. 6 

ATA-05-1.5 

(MY9F96) 

1 - 1.5 7/29/14 

Arsenic 237 1.1 

Ref. 4, pp. 28, 39, 65, 1812, 1893; Ref. 

25, pp. 8, 30; Ref. 37, pp. 7-9 Lead 27.9 1.1 

Mercury 0.52 0.11 

mg/kg: milligrams analyte per kilogram tailings 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 
 

15
 

 

 

 

 

 

 

 

Source No: 1 

2014 SI, Source 1 Sediment Concentrations 

Sample ID Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ATS-01-0 

(MY9F97) 7/29/14 

Arsenic 1,690 1.3 

Ref. 4, pp. 41, 65, 75, 1812, 1822; Ref. 

18, p. 5; Ref. 23, pp. 11, 26 Lead 95.8 1.3 

Mercury 0.56 0.13 

ATS-02-0 

(MY9F98) 7/29/14 

Arsenic 204 1.3 

Ref. 4, pp. 41, 65, 1812, 1823; Ref. 18, 

pp. 5-6; Ref. 23, pp. 11, 27 Lead 38.8 1.3 

Mercury 1.5 0.13 

mg/kg: milligrams analyte per kilogram sediment 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

List of Hazardous Substances Associated with Source 

Arsenic, Lead, and Mercury 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY 

Containment Description Containment 

Factor Value References 

Release via overland migration: Large portions of Source 1 

contain exposed gray tailings that are devoid of vegetation 

Sediment and tailings have filled the basin behind the EMAD 

to within a few feet of its top. Standing water flows over the 

top of the dam, through cracks in the base of the dam. There is 

no evidence of a liner. 

10 Ref. 6, pp. 9-10 
 

16
 

 

 

 

 

 

Source No: 1 

2.4.2 HAZARDOUS WASTE QUANTITY 

Tier A: Hazardous Constituent Quantity 

The total 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 and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for 

Source 1 with reasonable confidence. Scoring proceeds to the evaluation of Tier B, hazardous 

wastestream quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Source 1 could not be adequately determined according 

to the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Source 1 with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume 

The Tailings Area Tailings Impoundment was estimated to hold approximately 1,712,000 tons of 

processed tailings based on surface contour levels prior to and after creation of the pile and the 

boundaries of each of three piles comprising the entirety of the tailings impoundment pile (Ref. 12, p. 

45; Ref. 44). In accordance with Ref. 1, Table 2-5: 

1,712,000 tons = 1,712,000 cubic yards 

1,712,000 / 2.5 = 684,800 

Volume Assigned Value: 684,800 
 

17
 

 

 

Source No: 1 

Tier D: Area 

Because the volume of Source 1 is determined, Tier D: area is not evaluated. 

Area Assigned Value: 0 

Source Hazardous Waste Quantity Value: 684,800 
 

18
 

 

 

 

 

 

Source No: 2 

2.2.1 SOURCE IDENTIFICATION: Source 2: Argonaut Estates Tailings Pile 

Name of source: Argonaut Estates Tailings Pile Number of source: 2 

Source Type: Tailings Pile 

Description and Location of Source (see Attachments A-4 through A-6): 

From 1989 through 2004, the Argonaut Estates, Jackson View Estates, Sierra View Estates, and 

Argonaut Heights residential developments were reportedly built on areas of known waste rock and 

mine tailings that were covered with imported fill prior to construction of the homes (see Attachment A4) (Ref. 4, pp. 16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). A historical aerial photo review 

conducted by EPA showed that some residential properties in the Argonaut Estates development were 

built on the location of a waste rock pile associated with Argonaut operations (Ref. 4, p. 28; Ref. 10, pp. 

13, 28, 36). Sampling conducted at Argonaut Estates properties ARA-07 and ARA-08 on Spunn Road 

showed the presence of elevated concentrations of arsenic, lead, and mercury in soils from 0 to 2 feet 

below ground surface (bgs) (Attachment A-5) (Ref. 4, pp. 28-29, 66; Ref. 15). 

Attachment A-4 shows the locations of residential properties ARA-07 and ARA-08 overlaid on a 1944 

aerial photo showing the waste rock pile (Ref. 10, pp. 29, 36). The area of Source 2 is estimated to be 

approximately 79,500 square feet based on the footprint of the waste rock pile in the 1944 aerial photo, 

as well as the sampling locations on ARA-07 and ARA-08 showing elevated concentrations of arsenic 

(Attachment A-5). The area includes ARA-33, the property between ARA-07 and ARA-08, because the 

waste rock pile extended across this property as well. The estimated area of Source 2 is shown on 

Attachment A-6. 

In August and September 2015, EPA conducted removal actions at 11 residential properties built within 

the former Argonaut Mine property (Ref. 15; Ref. 40, pp. 1-2, 7). However, this removal did not include 

any actions at the residential properties in Source 2. 
 

19
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Source No: 2 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a SAP 

approved by EPA on March 10, 2014. Samples were submitted to Bonner Analytical, located in 

Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for metals analysis by Inorganic 

Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical data were 

validated by EPA (Ref. 4, p. 22). 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations. Sampling locations ARA-07 and ARA-08 were collected from the Argonaut Estates 

neighborhood developed along the waste rock pile south of the Argonaut Mine Mill Area (Ref. 4, p. 28). 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, soil 

samples are identified by address code only. Address codes are defined in a confidential reference (Ref. 

15). 

2014 Site Inspection, Source 2 Concentrations 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration** ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-07 

ARA07-0 

(MY9F 

56) 

0 - 0.5 7/31/14 

Arsenic 68.5 J+ 1.1 Ref. 4, pp. 40, 66, 1811, 

1873, 1875, 1944; Ref. 16, p. 

2; Ref. 21, pp. 7, 14 

Lead 25.6 J 1.1 

Mercury 0.14 0.11 

ARA07-1 

(MY9F 

57) 

1.5 - 2 7/31/14 

Arsenic 148 1.1 Ref. 4, pp. 40, 66, 1811, 

1865, 1944; Ref. 17, p. 7; 

Ref. 22, pp. 10, 32 

Lead 21.5 1.1 

Mercury 0.16 0.11 

ARA-08 

ARA08-0 

(MY9F 

58) 

0 - 0.5 7/31/14 

Arsenic 68.3 J+ 1.1 Ref. 4, pp. 40, 66, 1811, 

1873, 1876, 1944; Ref. 16, p. 

Lead 13.0 1.1 2; Ref. 21, pp. 7, 15 

mg/kg: milligrams analyte per kilogram soil
 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit
 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J+: The result is estimated and may be biased high (Ref. 4, pp. 1867, 1873). 

J: The result is estimated with an unknown bias (Ref. 4, pp. 1867, 1873).
 

**: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified.
 

^: Page 2 of Reference 16 presents a J- qualifier for qualified arsenic samples, pages 1875 and 1876 of Reference 4 present
 

arsenic concentrations without qualifiers, and Reference 4 page 1873 indicates that the qualified arsenic samples are biased 

high. Regardless of the qualifier assigned, the substance can still be associated with the source. 
 

20
 

Source No: 2 

List of Hazardous Substances Associated with Source 

Arsenic, Lead, and Mercury 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY 

The migration pathways are not scored for Source 2. 
 

21
 

 

 

 

 

Source No: 2 

2.4.2. Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total 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 and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for 

Source 2 with reasonable confidence. Scoring proceeds to the evaluation of Tier B, hazardous 

wastestream quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Source 2 could not be adequately determined according 

to the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Source 2 with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume 

The information available is not sufficient to meaningfully evaluate Tier C: volume, because the depth 

and total extent of the waste rock pile across Source 2 is unknown. Therefore it is not possible to 

adequately determine a volume for Source 2 (Ref. 1, Section 2.4.2.1.3). Scoring proceeds to the 

evaluation of Tier D, area (Ref. 1, Section 2.4.2.1.4). 

Volume Assigned Value: 0 
 

22
 

 

 

Source No: 2 

Tier D: Area 

The area of Source 2 is estimated to be approximately 79,500 square feet based on the footprint of the 

waste rock pile in the 1944 aerial photo, as well as the sampling locations on ARA-07 and ARA-08 

showing elevated concentrations of arsenic (see Attachment A-5). In accordance with Ref. 1, Table 2-5: 

79,500 / 13 = 6,115.4 

Area Assigned Value: 6,115.4 

Source Hazardous Waste Quantity Value: 6,115.4 
 

23
 

 

 

 

Source No: 3 

2.2.1 SOURCE IDENTIFICATION: Source 3 Argonaut Heights North Tailing Pile 

Name of source: Argonaut Heights – North Tailings Pile Number of source: 3 

Source Type: Tailings Pile 

Description and Location of Source (see Attachments A-4 through A-6): 

From 1989 through 2004, the Argonaut Estates, Jackson View Estates, Sierra View Estates, and 

Argonaut Heights residential developments were reportedly built on areas of known waste rock and 

mine tailings that were covered with imported fill prior to construction of the homes (see Attachment A4) (Ref. 4, pp. 16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). A historical aerial photo review 

conducted by EPA showed trenches, pits, and berms for tailings disposal in the northern portion of the 

Argonaut Heights development near Pioneer Street and Argonaut Lane (Ref. 10, pp. 29-30, 36; Ref. 42, 

p. 7). Sampling conducted at these properties showed the presence of elevated concentrations of arsenic, 

lead, and mercury in soils from 0 to 2 feet bgs (Attachment A-5) (Ref. 4, pp. 28-29, 66; Ref. 15). 

Attachment A-4 shows the locations of residential properties overlaid on a 1944 aerial photo of the 

Argonaut Mine property (Ref. 10, p. 36). In March 2015, EPA conducted a removal action of the vacant 

parcel located at the northeast corner of Pioneer Street and Argonaut Lane (EPA AOC-5) (Attachment 

A-1) (Ref. 42, p. 5). During the removal, mine tailings and wastes were observed to extend beyond the 

boundaries of AOC-5 into the neighboring residential properties of Source 3 (Ref. 42, pp. 10, 12, 45). 

In August and September 2015, EPA conducted removal actions at 11 residential properties built within 

the former Argonaut Mine property, including four of the 12 residential properties in Source 3 (Ref. 40, 

pp. 1-2, 4-5, 7; Ref. 15). Based on samples collected pre- and post-removal, as well as samples collected 

during the 2014 SI, the area of Source 5 is estimated to be approximately 97,350 square feet (see 

Attachment A-6). The August 2015 removal action did not change the calculated area of Source 3, 

because soils exceeding 100 mg/kg arsenic were only removed to 12 inches bgs, and confirmation 

sampling showed that soils with elevated concentrations of arsenic were still present beneath the 

excavations (Ref. 39, pp. 7-10; Ref. 40, pp. 2, 4). 

During the August 2015 removal, the following actions were taken at each of the residential properties 

within Source 3 (Ref. 40, pp. 2, 4-5). Properties are identified by address code to preserve the privacy of 

the residents (Ref. 15). 
 

24
 

 

 

 

 

 

 

 

Source No: 3 

Address Code Action 

ARA-09 No action. 

ARA-10 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,223 square 

feet (Ref. 39, p. 8; Ref. 40, pp. 2, 5). 

ARA-11 

Soils exceeding 100 mg/kg arsenic removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,275 square 

feet (Ref. 39, p. 9; Ref. 40, pp. 2, 5). 

ARA-12 No action. 

ARA-13 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 2,846 square 

feet (Ref. 39, p. 7; Ref. 40, pp. 2, 5). 

ARA-23 No action. 

ARA-25 No action. 

ARA-26 No action. 

ARA-27 No action. 

ARA-28 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,025 square 

feet (Ref. 39, p. 10; Ref. 40, pp. 2, 5). 

ARA-31 No action. 

ARA-32 No action. 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a SAP 

approved by EPA on March 10, 2014. Samples were submitted to Bonner Analytical, located in 

Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for metals analysis by Inorganic 

Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical data were 

validated by EPA (Ref. 4, p. 22). 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations. Five sampling locations (ARA-09 through ARA-13) were collected from residential 

properties in Source 3 (Ref. 4, p. 28; see Attachment A-6). Laboratory results are reported below. 

Analytical results from soils that were later removed during the August 2015 Removal Action are not 

reported. 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, sample 

locations are identified by address code only. Address codes are defined in a confidential reference (Ref. 

15). 
 

25
 

 

 

 

 

 

 

 

Source No: 3 

2014 Site Inspection, Source 3 Concentrations 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration** 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-09 

ARA09-0 

(MY9F 

60) 

0 - 0.5 7/31/14 

Arsenic 1,380 J+ 5.2 Ref. 4, pp. 40, 66, 1811, 

1873, 1876, 1945; Ref. 16, p. 

3; Ref. 21, pp. 7, 17 

Lead 226 1.0 

Mercury 1.4 0.21 

ARA09-2 

(MY9F 

62) 

1.5 - 2 7/31/14 

Arsenic 39,900 J+ 123 Ref. 4, pp. 40, 66, 1811, 

1873, 1876, 1945; Ref. 16, p. 

3; Ref. 21, pp. 7, 18 

Lead 3,220 9.9 

Mercury 193 24.6 

ARA-10 

ARA10-2 

(MY9F 

63) 

1.5 - 2 7/31/14 

Arsenic 655 J+ 1.1 Ref. 4, pp. 40, 66, 1811, 

1873, 1877, 1944; Ref. 16, 

pp. 3-4; Ref. 21, pp. 7, 20 

Lead 50.5 1.1 

Mercury 0.30 0.11 

ARA-12 

ARA12-2 

(MY9F 

63) 

1.5 - 2 7/31/14 

Arsenic 58.6 J+ 1.1 Ref. 4, pp. 40, 66, 1811, 

1873, 1878, 1945; Ref. 16, p. 

5; Ref. 21, pp. 7, 24 

Lead 19.2 J 1.1 

Mercury 0.44 0.11 

ARA-13 

ARA13-1 

(MY9F 

69) 

1.5 - 2 7/31/14 

Arsenic 1,200 J+ 4.4 Ref. 4, pp. 40, 66, 1811, 

1873, 1878, 1945; Ref. 16, 

pp. 5-6; Ref. 21, pp. 7, 26 

Lead 225 1.1 

Mercury 1.8 0.33 

mg/kg: milligrams analyte per kilogram soil
 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit
 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J+: The result is estimated and may be biased high (Ref. 4, p. 1873).
 

J: The result is estimated with an unknown bias (Ref. 4, p. 1873). 

**: Qualified data presented in this table reflect a positive identification of the substance, although the data may be 

qualified. 
 

26
 

 

 

 

 

Source No: 3 

March 2015 Superfund Technical Assessment and Response Team (START) Removal Assessment 

In March 2015, START conducted a removal assessment of 20 residential properties in the Argonaut 

Heights and Sierra View Estates neighborhoods (Ref. 4, p. 14; Ref. 11, p. 2). The residential properties 

were divided into two to six decision units (DUs) composed of roughly equal areas at a maximum of 

1,250 square feet each to cover unpaved areas of the property. A 5-point composite sample was 

collected from each DU at sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or 

hand auger and disposable scoops. Discrete samples were collected from some of the residences at the 

locations of play areas and gardens (Ref. 11, p. 2). 

Samples were analyzed for lead and arsenic via X-Ray Fluorescence (XRF), with at least one sample 

from each property submitted to a laboratory for confirmation. Confirmation samples were submitted to 

the EPA Region 9 Laboratory for analysis of arsenic and lead by EPA SW-846 Method 6010C (Ref. 11, 

pp. 3-4). Sampling locations are presented on Attachment A-5. 
 

27
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Source No: 3 

2015 EPA Removal Assessment, Source 3 Concentrations 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA-09 R-12-03­

C-12 12 to 14 3/25/15 

Arsenic 680 10 Ref. 11, pp. 86, 91, 97; Ref. 15; 

Ref. 39, pp. 16, 17; Ref. 47, pp. Lead 4, 29, 32, 42 130 3 

ARA10 (1) 

R-14-01­

C-12 12 to 14 3/25/15 

Arsenic 220 2 Ref. 11, pp. 86, 91, 97; Ref. 15; 

Ref. 39, p. 17; Ref. 47, pp. 4, 

Lead 35 3 30, 33, 42 

ARA11 (1) 

R-13-01­

C-12 12 to 14 3/25/15 

Arsenic 590 10 Ref. 11, pp. 86, 91, 97; Ref. 15; 

Ref. 39, pp. 16, 17; Ref. 47, pp. Lead 4, 29, 32, 42 120 3 

ARA-12 R-04-02­

D-4 4 to 8 3/24/15 

Arsenic 430 2 Ref. 11, pp. 84, 91, 96; Ref. 15; 

Ref. 39, pp. 14, 15; Ref. 47, pp. 

Lead 41 3 3, 28, 32, 41 

ARA13 (1) 

R-10-06­

C-16 16 to 18 3/25/15 

Arsenic 5,100 100 Ref. 11, pp. 85, 91, 97; Ref. 15; 

Ref. 39, pp. 15, 16; Ref. 47, pp. Lead 4, 29, 32, 41 1,900 3 

ARA-23 R-01-02­

C-12 12 to 14 3/23/15 

Arsenic 140 2 Ref. 11, pp. 84, 91, 96; Ref. 15; 

Ref. 39, pp. 12, 13; Ref. 47, pp. 

Lead 7.8 3 3, 28, 32, 41

ARA-25 R-03-02­

C-0 0 to 2 3/23/15 

Arsenic 270 2 Ref. 11, pp. 84, 91, 96; Ref. 15; 

Ref. 39, p. 13; Ref. 47, pp. 3, 

Lead 28 3 28, 32, 41 

ARA-26 R-05-02­

C-0 0 to 2 3/24/15 

Arsenic 40 2 Ref. 11, pp. 86, 91, 96; Ref. 15; 

Ref. 39, p. 14; Ref. 47, pp. 3, 

Lead 83 3 28, 32, 41 

ARA-27 R-06-03­

D-16 16 to 18 3/24/15 

Arsenic 1,000 10 Ref. 11, pp. 86, 91, 96; Ref. 15; 

Ref. 39, p. 14; Ref. 47, pp. 3, 

Lead 110 3 28, 32, 41 

ARA28 (1) 

R-07-01­

C-12 12 to 14 3/24/15 

Arsenic 40 2 Ref. 11, pp. 86, 91, 96; Ref. 15; 

Ref. 39, pp. 14, 15; Ref. 47, pp. 

Lead 12 3 3, 29, 32, 41 

ARA-31 R-18-01­

C-0 0 to 2 3/25/15 

Arsenic 62 2 Ref. 11, pp. 86, 91, 97; Ref. 15; 

Ref. 39, pp. 17, 18; Ref. 47, pp. 

4, 30, 33, 42 Lead 26 3 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits (SQLs) 

(Ref. 43). 

(1): Although a removal was conducted on this property, soils were not excavated to this depth (14-18 inches, as applicable for 

the samples presented above.) (Ref. 15; Ref. 40, p. 2). Therefore, these contaminated soils are still present on the property. 
 

28
 

 

 

 

 

 

 

 

Source No: 3 

EPA August 2015 Removal Action 

In August 2015, EPA conducted removal actions at 11 residential properties built within the former 

Argonaut Mine property, including four of the 12 residential properties in Source 3 (Ref. 15; Ref. 40, pp. 

1-2, 4-5). Soils exceeding the action level of 100 mg/kg for arsenic were removed to 12 inches bgs and 

backfilled with clean topsoil (Ref. 40, p. 2). Confirmation samples were collected from 12 to 14 inches 

bgs within the excavations (Ref. 39, p. 1). Samples were analyzed for lead and arsenic via XRF, with at 

least one sample from each property submitted to a laboratory for confirmation. Confirmation samples 

were submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead by EPA SW-846 

Method 6010C (Ref. 11, pp. 3, 4, 120-121). Laboratory results are presented below. Sampling locations 

are presented on Attachment A-5. 

2015 EPA Removal Action, Source 3 Concentrations 

Address 

Code Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA-10 R-14-01-C12-082715 12 to 14 8/27/15 

Arsenic 1,500 2 Ref. 11, p. 121; Ref. 39, 

pp. 1, 75; Ref. 49, pp. 4, 

Lead 320 3 22-23, 27 

ARA-13 R-10-06-C12-082115 12 to 14 8/21/15 

Arsenic 5,300 4 Ref. 11, pp. 90-92, 120; 

Ref. 39, pp. 1, 77; Ref. 

Lead 1,600 3 49, pp. 3, 22-23, 27 

ARA-28 R-07-01-C12-082615 12 to 14 8/26/15 

Arsenic 25 2 Ref. 11, p. 120; Ref. 39, 

pp. 1, 73; Ref. 49, pp. 3, 

22-23, 27 Lead 15 3 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

List of Hazardous Substances Associated with Source 

Arsenic, Lead, and Mercury 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY 

The migration pathways are not scored for Source 3. 
 

29
 

 

 

 

 

 

Source No: 3 

2.4.2. Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total 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 and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for 

Source 3 with reasonable confidence. Scoring proceeds to the evaluation of Tier B, hazardous 

wastestream quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Source 3 could not be adequately determined according 

to the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Source 3 with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume 

The information available is not sufficient to meaningfully evaluate Tier C: volume, because the depth 

and total extent of the tailings and waste rock pile across Source 3 is unknown. Therefore, it is not 

possible to adequately determine a volume for Source 3 (Ref. 1, Section 2.4.2.1.3). Scoring proceeds to 

the evaluation of Tier D: area (Ref. 1, Section 2.4.2.1.4). 

Volume Assigned Value: 0 
 

30
 

 

 

Source No: 3 

Tier D: Area 

Based on pre- and post-removal samples collected in 2015, as well as samples collected during the 2014 

SI, the area of Source 3 is estimated to be approximately 97,350 square feet (see Attachment A-6). Soil 

areas that were removed during the August 2015 removal action were not included in the area estimate. 

In accordance with Ref. 1, Table 2-5: 

97,350 / 13 = 7,488.5 

Area Assigned Value: 7,488.5 

Source Hazardous Waste Quantity Value: 7,488.5 
 

31
 

 

 

 

 

 

 

 

Source No: 4 

2.2.1 SOURCE IDENTIFICATION: Source 4, Argonaut Heights – South Contaminated Soil 

Name of source: Argonaut Heights – South Contaminated Soil Number of source: 4 

Source Type: Contaminated Soil 

Description and Location of Source (see Attachment A-4 through A-6): 

From 1989 through 2004, the Argonaut Estates, Jackson View Estates, Sierra View Estates, and 

Argonaut Heights residential developments were reportedly built on areas of known waste rock and 

mine tailings that were covered with imported fill prior to construction of the homes (see Attachment A4) (Ref. 4, pp. 16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Elevated concentrations of arsenic, 

lead, and mercury have been detected in surface soils collected from five residential properties on Buena 

Vista Drive and Amador Street adjacent to the former cyanide plant located within EPA AOC-2 (Ref. 4, 

pp. 28, 48, 66; Ref. 15; Ref. 11, p. 86; Ref. 39, p. 1; see Attachment A-6). A historical aerial photo 

review conducted by EPA showed that the cyanide plant was accessed by a dirt road and dirt trail 

through these residential properties. A former flume was also observed extending across all 5 properties 

(see Attachment A-4) (Ref. 10, pp. 31, 36). During sampling conducted in 2014, distinct tailings or 

waste rock were not visually identified in Source 4; therefore, the source type is evaluated as 

Contaminated Soil (Ref. 46). 

In August and September 2015, EPA conducted removal actions at 11 residential properties built within 

the former Argonaut Mine property, including four of the five properties in Source 4 (Ref. 40, pp. 1-2, 

4-5). Based on samples collected pre- and post-removal, as well as samples collected during the 2014 SI, 

the area of Source 4 is estimated to be approximately 72,511 square feet (see Attachment A-6). The 

August 2015 removal action did not change the calculated area of Source 4, because soils exceeding 100 

mg/kg arsenic were only removed to 12 inches bgs, and confirmation sampling showed that soils with 

elevated concentrations of arsenic were still present beneath the excavations (Ref. 39, pp. 3-6; Ref. 40, 

pp. 2, 4). 

During the August 2015 removal, the following actions were taken at each of the residential properties 

within Source 4 (Ref. 40, pp. 2, 4-5). Properties are identified by address code to preserve the privacy of 

the residents (Ref. 15). 
 

32
 

 

Source No: 4 

Address Code Action 

ARA-15 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 2,846 square 

feet (Ref. 39, p. 5; Ref. 40, pp. 2, 4). 

ARA-16 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,798 square 

feet (Ref. 39, p. 6; Ref. 40, pp. 2, 5). 

ARA-17 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,275 square 

feet (Ref. 39, p. 4; Ref. 40, pp. 2, 4). 

ARA-24 No action. 

ARA-30 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 7,297 square 

feet (Ref. 39, p. 3; Ref. 40, pp. 2, 4). 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a SAP 

approved by EPA on March 10, 2014. Samples were submitted to Bonner Analytical, located in 

Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for metals analysis by Inorganic 

Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical data were 

validated by EPA (Ref. 4, p. 22). 
 

33
 

 

 

 

 

 

 

 

 

Source No: 4 

- Background Concentrations: 

Background soil samples were collected from location AB-01 in pasture land located northwest of the 

Source 1 Tailings Impoundment and location AB-02 in pasture land located southwest of the Source 1 

Tailings Impoundment (Ref. 4, p. 24; see Attachment A-3). Background sampling locations are shown 

in Attachment A-3. 

Residential properties built within the former Argonaut Mine property boundary were built on imported 

fill placed over waste rock, tailings, and soils contaminated by Argonaut Mine operations (Ref. 4, pp. 

16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Prior to the construction of the Source 1 Tailings 

Impoundment and the AOC-2 Cyanide Plant, a portion of the property was farmland (Ref. 12, p. 28; 

Ref. 50). Therefore, background samples were collected from nearby pasture lands to be representative 

of local conditions without the Argonaut Mine. Sample depths of the background and release samples 

are all from the upper 2 feet, though depths are not directly comparable as the background locations are 

native soil while soils from the residential properties include tailings and waste rock generated by 

mining activities, as well as imported fill. 

Source 4 Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 25, 39-40, 66, 76, 1808, 

1818-1820, 1944; Ref. 18, p. 1; Ref. 

23, pp. 7, 15 

Lead 14.8 J 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2.0 J­ 1.1 Ref. 4, pp. 25 39-40, 66, 76, 1808, 

1830-1832, 1834, 1944; Ref. 20, p. 1; 

Ref. 24, pp. 6, 10 

Lead 9.0 J 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J­ 1.0 Ref. 4, pp. 25, 39-40, 65, 1808, 1830­

1832, 1834, 1941; Ref. 20, p. 1; Ref. 

24, pp. 6, 11 

Lead 11.2 J 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J­ 1.1 Ref. 4, pp. 25, 39-40, 65, 1808, 1830­

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J 1.1 

Mercury <0.11 0.11 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832, 1867).
 

J-: The result is an estimated quantity, with a low bias (Ref. 4, pp. 1818, 1830-1832, 1867).
 

<: The analyte was not detected.
 

^: Page 1831of Reference 4 presents a J qualifier for arsenic concentrations, and Reference 4 pages 1830 and 1834 indicate 

that the reported results may be biased low. 
 

34
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Source No: 4 

- Source Samples: 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations. Three sampling locations (ARA-15 through ARA-17) were collected from the Argonaut 

Heights neighborhood adjacent to the AOC-2 cyanide plant (Ref. 4, p. 28). Analytical results from soils 

that were later removed during the 2015 Removal Action are not reported. 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, samples 

are identified by address code only. Sample address codes are defined in a confidential reference (Ref. 

15). 

2014 Site Inspection, Source 4 Concentrations 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration** ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-15 

ARA15-1 

(MY9F 

73) 

1.5 - 2 7/31/14 

Arsenic 269 J+ 1.1 Ref. 4, pp. 40, 1873, 1879, 

1944; Ref. 16, p. 7; Ref. 

21, pp. 8, 30 

Lead 286 1.1 

Mercury 3.3 0.53 

ARA-16 

ARA16-1 

(MY9F 

75) 

0.5 - 1 7/31/14 

Arsenic 147 1.1 Ref. 4, pp. 40, 66, 1889, 

1944; Ref. 21, p. 8; Ref. 

25, pp. 7, 12; Ref. 37, p. 1 

Lead 121 1.1 

Mercury 0.85 0.11 

ARA-17 

ARA17-2 

(MY9F 

77) 

1.5 - 2 7/31/14 

Arsenic 123 1.1 Ref. 4, pp. 40, 66, 1812, 

1888-1889, 1944; Ref. 21, 

p. 8; Ref. 25, pp. 7, 14; 

Ref. 37, p. 2 

Lead 30.0 J 1.1 

mg/kg: milligrams analyte per kilogram soil
 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit
 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J+: The result is an estimated quantity, but the result may be biased high (Ref. 4, pp. 1867, 1873).
 

J: The result is an estimated quantity with an unknown bias (Ref. 4, pp. 1867, 1873, 1888).
 

**: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified.
 

^: Page 7 of Reference 16 presents a J- qualifier for qualified samples, pages 1875 and 1876 of Reference 4 present arsenic 

concentrations without qualifiers, and Reference 4 page 1873 indicates that the qualified arsenic samples are biased high. 

Regardless of the qualifier assigned, the substance can still be associated with the source. 

EPA March 2015 Removal Assessment 

In March 2015, EPA conducted a removal assessment of 20 residential properties in the Argonaut 

Heights and Sierra View Estates neighborhoods (Ref. 4, p. 14; Ref. 11, p. 2). The residential properties 

were divided into two to six DUs composed of roughly equal areas at a maximum of 1,250 square feet 
 

35
 

 

 

 

 

 

 

 

 

 

 

 

 

Source No: 4 

each to cover unpaved areas of the property. A 5-point composite sample was collected from each DU at 

sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or hand auger and disposable 

scoops. Discrete samples were collected from some of the residences at the locations of play areas and 

gardens (Ref. 11, p. 2). Samples were analyzed for lead and arsenic via XRF, with at least one sample 

from each property submitted to a laboratory for confirmation. Confirmation samples were submitted to 

the EPA Region 9 Laboratory for analysis of arsenic and lead by EPA SW-846 Method 6010C (Ref. 11, 

pp. 3-4). 

Sampling locations are presented in Attachment A-5. Analytical results from soils that were later 

removed during the August 2015 EPA Removal Action are not reported. Background sampling was not 

conducted during this sampling event; therefore, samples are compared to background concentrations 

from the 2014 SI sampling event. 

2015 EPA Removal Assessment, Source 4 Concentrations 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA15 (1) 

R-08-04­

C-12 12 to 14 3/24/15 

Arsenic 340 2 Ref. 11, pp. 85, 96; Ref. 15; 

Ref. 39, pp. 14, 15; Ref. 47, 

Lead 280 3 pp. 3, 29, 32, 41 

ARA16 (1) 

R-09-03­

C-12 12 to 14 3/24/15 

Arsenic 350 2 Ref. 11, pp. 85, 90-92, 96; 

Ref. 15; Ref. 39, pp. 15, 16; Lead Ref. 47, pp. 3, 29, 32, 41 500 3 

ARA-17 

R-19-02­

C-12 (1) 12 to 14 3/27/15 

Arsenic 130 2 Ref. 11, pp. 87, 105; Ref. 

15; Ref. 39, p. 18; Ref. 47, 

Lead 49 3 pp. 9, 31, 33, 44 

R-19-04­

C-0 (2) 0 to 2 6/23/15 

Arsenic 92 2.1 Ref. 11, pp. 87, 115; Ref. 

15; Ref. 39, p. 4; Ref. 48, 

Lead 25 3.2 pp. 4, 25-26, 30 

ARA-24 R-02-02­

C-0 0 to 2 3/23/15 

Arsenic 69 2 Ref. 11, pp. 84, 96; Ref. 15; 

Ref. 39, p. 13; Ref. 47, pp. Lead 3, 28, 32, 41 56 3 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

(1): Although a removal was conducted on this property, soils were not excavated to this depth (Ref. 15; Ref. 40, p.2). 

Therefore, these soils are still present on the property. 

(2): Although a removal was conducted on this property, soils were not excavated at this location because the arsenic 

concentration was below the removal action level of 100 mg/kg (Ref. 39, p. 4; Ref. 40, p. 2). 
 

36
 

 

 

 

 

 

 

Source No: 4 

EPA August 2015 Removal Action 

In August 2015, EPA conducted removal actions at 11 residential properties built in the area of former 

Argonaut Mine operations, including four of the five properties in Source 4 (Ref. 15; Ref. 40, pp. 1-2, 4­

5). Soils exceeding the action level of 100 mg/kg for arsenic were removed to 12 inches bgs and 

backfilled with clean topsoil (Ref. 40, p. 2). Confirmation samples were collected from 12 to 14 inches 

bgs within the excavations (Ref. 39, p. 1). Samples were analyzed for lead and arsenic via XRF, with at 

least one sample from each property submitted to a laboratory for confirmation. Confirmation samples 

were submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead by EPA SW-846 

Method 6010C (Ref. 11, pp. 120-121). Sampling locations are presented on Attachment A-5. 

Background sampling was not conducted during this sampling event; therefore, samples are compared to 

background concentrations from the 2014 SI sampling event. 

2015 EPA Removal Action, Source 4 Concentrations 

Address 

Code Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA-16 R-09-03-C12-082415 12 to 14 8/24/15 

Arsenic 580 2 Ref. 11, p. 120; Ref. 15; 

Ref. 39, pp. 1, 71; Ref. 

Lead 49, pp. 3, 22-23, 27 570 3 

ARA-30 

R-17-02EC-12­

081815 

12 to 14 8/18/15 

Arsenic 120 2 Ref. 11, p. 120; Ref. 15; 

Ref. 39, pp. 1, 66; Ref. 

Lead 8 49, pp. 3, 22-23, 27 .4 3 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

List of Hazardous Substances Associated with Source 

Arsenic, Lead, and Mercury 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY 

The migration pathways are not scored for Source 4. 
 

37
 

 

 

 

 

 

 

Source No: 4 

2.4.2. Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total 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 and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for 

Source 4 with reasonable confidence. Scoring proceeds to the evaluation of Tier B, hazardous 

wastestream quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Source 4 could not be adequately determined according 

to the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Source 4 with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume 

The information available is not sufficient to meaningfully evaluate Tier C: volume, because the depth 

and total extent of the contaminated soil across Source 4 is unknown. Therefore it is not possible to 

adequately determine a volume for Source 4 (Ref. 1, Section 2.4.2.1.3). Scoring proceeds to the 

evaluation of Tier D: area (Ref. 1, Section 2.4.2.1.4). 

Volume Assigned Value: 0 
 

38
 

 

 

Source No: 4 

Tier D: Area 

Based on samples collected pre- and post-removal, as well as samples collected during the 2014 SI, the 

area of Source 4 is estimated to be approximately 72,511 square feet (see Attachment A-6). In 

accordance with Ref. 1, Table 2-5: 

72,511 / 34,000 = 2.1 

Area Assigned Value: 2.1 

Source Hazardous Waste Quantity Value: 2.1 
 

39
 

 

 

 

 

Source No: 5 

2.2.1 SOURCE IDENTIFICATION: Source 5, Sierra View Estates Contaminated Soil 

Name of source: Sierra View Estates Contaminated Soil Number of source: 5 

Source Type: Contaminated Soil 

Description and Location of Source (see Attachment A-4 through A-6): 

From 1989 through 2004, the Argonaut Estates, Jackson View Estates, Sierra View Estates, and 

Argonaut Heights residential developments were reportedly built on areas of known waste rock and 

mine tailings that were covered with imported fill prior to construction of the homes (see Attachment A4) (Ref. 4, pp. 16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Elevated concentrations of arsenic, 

lead, and mercury have been detected in surface soils collected from three residential properties on 

Detert Lane adjacent to the Source 1 Tailings Impoundment (Ref. 4, pp. 23, 48, 66; Ref. 15; See 

Attachment A-2). A historical aerial photo review conducted by EPA showed a former flume across this 

area (see Attachment A-4) (Ref. 10, pp. 23, 28, 32, 36). During sampling conducted in 2014, distinct 

tailings or waste rock were not visually identified in Source 5; therefore, the source type is evaluated as 

Contaminated Soil (Ref. 46). 

In August and September 2015, EPA conducted removal actions at 11 residential properties built within 

the former Argonaut Mine property, including two properties in Source 5 (Ref. 40, pp. 1-2, 4-5, 7; Ref 

15; see Attachment A-6; see table below). Based on samples collected pre- and post-removal, as well as 

samples collected during the 2014 SI, the area of Source 5 is estimated to be approximately 40,341 

square feet (see Attachment A-6). The removal action did not change the calculated area of Source 5, 

because soils with arsenic exceeding 100 mg/kg were only removed to 12 inches bgs, or were left in 

place and covered with wood chips and rock. Confirmation sampling showed that soils with elevated 

concentrations of arsenic were still present beneath the excavation (Ref. 39, p. 2; Ref. 40, pp. 2, 4). 

During the August 2015 removal, the following actions were taken at each of the residential properties 

within Source 5 (Ref. 40, pp. 2, 4-5). Properties are identified by address code to preserve the privacy of 

the residents (Ref. 15). 

Address Code Action 

ARA-18 No soils were removed. An area of 5,324 square feet was covered with wood 

chips and rock (Ref. 40, pp. 2, 4). 

ARA-19 No action. 

ARA-29 

Soil exceeding 100 mg/kg arsenic was removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,275 square 

feet (Ref. 39, p. 2; Ref. 40, pp. 2, 4). 
 

40
 

 

 

Source No: 5 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine (Ref. 4, pp. 6, 22). Samples were collected in 

accordance with a SAP approved by EPA on March 10, 2014 (Ref. 4, p. 22). Samples were submitted to 

Bonner Analytical, located in Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for 

metals analysis by Inorganic Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012 

(Ref. 4, p. 22). The metals analytical data were validated by EPA (Ref. 4, p. 22). 

- Background Concentrations: 

Background soil samples were collected from location AB-01 in pasture land located northwest of the 

Tailings Area and location AB-02 in pasture land located southwest of the Tailings Area (Ref. 4, p. 24). 

Background sampling locations are shown in Attachment A-3. 

Residential properties built within the former Argonaut Mine property boundary were built on imported 

fill placed over waste rock, tailings, and soils contaminated by Argonaut Mine operations (Ref. 4, pp. 

16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Prior to the construction of the Source 1 Tailings 

Impoundment and the AOC-2 Cyanide Plant, part of the property was farmland (Ref. 12, p. 28; Ref. 50). 

Therefore, background samples were collected from nearby pasture lands to be representative of local 

conditions without the Argonaut Mine. Sample depths of the background and release samples are all 

from the upper 2 feet, although the background locations are native soil while soils from the residential 

properties include tailings and waste rock generated by mining activities, as well as imported fill (See 

Source 5 Background Soil Concentrations below). 
 

41
 

 

 

 

 

 

 

 

 

 

 

 

Source No: 5 

Source 5 Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration** ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 39-40, 66, 76, 1808, 1818­

1820, 1944; Ref. 18, p. 1; Ref. 23, pp. 

7, 15 

Lead 14.8 J 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2.0 J­ 1.1 Ref. 4, pp. 39-40, 66, 76, 1808, 1830­

1832, 1834, 1944; Ref. 20, p. 1; Ref. 

24, pp. 6, 10 

Lead 9.0 J 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J­ 1.0 Ref. 4, pp. 39-40, 65, 1808, 1830­

1832, 1834, 1941; Ref. 20, p. 1; Ref. 

24, pp. 6, 11 

Lead 11.2 J 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J­ 1.1 Ref. 4, pp. 39-40, 65, 1808, 1830­

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J 1.1 

Mercury <0.11 0.11 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832, 1867).
 

J-: The result is an estimated quantity, with a low bias (Ref. 4, pp. 1818, 1830-1832, 1867).
 

<: The analyte was not detected.
 

**: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified.
 

^: Page 1831of Reference 4 presents a J qualifier for arsenic, and Reference 4 pages 1830 and 1834 indicate that the reported
 

results may be biased low. 

- Source Samples: 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations (Ref. 4, p. 28). Two sampling locations (ARA-18 and ARA-19) were collected from the 

Sierra View Estates neighborhood adjacent to the Source 1 Tailings Impoundment (Ref. 4, p. 28). No 

soils were removed from these properties during the August 2015 Removal Action (Ref. 40, pp.4-5). 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, sample 

locations are identified by address code only. Address codes are defined in a confidential reference (Ref. 

15). 
 

42
 

 

 

 

 

 

 

 

Source No: 5 

2014 Site Inspection, Source 5 Concentrations 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-18 

ARA18-0 

(MY9F 

78) 

0 - 0.5 7/31/14 

Arsenic 310 1.0 Ref. 4, pp. 40, 66, 1812, 

1890, 1944; Ref. 25, pp. 7, 

15; Ref. 37, p. 2 

Lead 46.0 1.0 

Mercury 0.63 0.10 

ARA18-1.5 

(MY9F 

79) 

1 - 1.5 7/31/14 

Arsenic 423 1.1 Ref. 4, pp. 40, 66, 1812, 

1890, 1944; Ref. 25, pp. 7, 

16; Ref. 37, pp. 2-3 

Lead 115 1.1 

Mercury 1.4 0.21 

ARA-19 

ARA19-0 

(MY9F 

81) 

0 - 0.5 7/31/14 Arsenic 55.3 1.1 

Ref. 4, pp. 40, 66, 1812, 

1888, 1890, 1944; Ref. 25, 

pp. 7, 17; Ref. 37, p. 3 

ARA19-1 

(MY9F 

82) 

1.5 - 2 7/31/14 Arsenic 122 1.1 

Ref. 4, pp. 40, 66, 1812, 

1888, 1890, 1944; Ref. 25, 

pp. 7, 18; Ref. 37, p. 3 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

EPA March 2015 Removal Assessment 

In March 2015, EPA conducted a removal assessment of 20 residential properties in the Argonaut 

Heights and Sierra View Estates neighborhoods (Ref. 4, p. 14; Ref. 11, pp. 2, 6). The residential 

properties were divided into two to six DUs composed of roughly equal areas at a maximum of 1,250 

square feet each to cover unpaved areas of the property (Ref. 11, p. 2). A 5-point composite sample was 

collected from each DU at sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or 

hand auger and disposable scoops (Ref. 11, p. 2). Discrete samples were collected from some of the 

residences at the locations of play areas and gardens (Ref. 11, p. 2). Samples were analyzed for lead and 

arsenic via XRF, with at least one sample from each property submitted to a laboratory for confirmation. 

Confirmation samples were submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead 

by EPA SW-846 Method 6010C (Ref. 11, pp. 3-4). 

Sampling locations are presented in Attachment A-5. Background sampling was not conducted during 

this sampling event; therefore, samples are compared to background concentrations from the 2014 SI 

sampling event. 
 

43
 

 

 

 

 

 

 

Source No: 5 

2015 EPA Removal Assessment, Source 5 Concentrations 

Address 

Code Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA18 (2) 

R-16-01­

C-0 0 to 2 3/26/15 

Arsenic 210 2 Ref. 11, pp. 86, 91, 97; 

Ref. 39, p. 18; Ref. 47, 

pp. 4, 30, 33, 39 Lead 32 3 

R-16-04­

C-0 0 to 2 6/23/15 

Arsenic 100 2 Ref. 11, pp. 86, 107, 115; 

Ref. 48, pp. 4, 24, 26, 30, 

32 Lead 23 3.1 

ARA29 (1) 

R-15-02­

C-12 12 to 14 3/26/15 

Arsenic 910 10 Ref. 11, pp. 86, 91, 97; 

Ref. 39, p. 18; Ref. 47, 

pp. 4, 30, 33, 39 Lead 66 3 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

(1): Although a removal was conducted on this property, soils were not excavated to this depth (Ref. 15; Ref. 40, p. 2). 

(2): Although a removal was conducted on this property, no soils were excavated. Soils exceeding the action level were 

covered with wood chips and rock (Ref. 40, pp. 2, 4). 

List of Hazardous Substances Associated with Source 

Arsenic, Lead, and Mercury 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY 

The migration pathways are not scored for Source 5. 
 

44
 

 

 

 

 

 

 

 

Source No: 5 

2.4.2. Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total 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 and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for 

Source 5 with reasonable confidence. Scoring proceeds to the evaluation of Tier B, hazardous 

wastestream quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Source 5 could not be adequately determined according 

to the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Source 5 with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume 

The information available is not sufficient to meaningfully evaluate Tier C: volume, because the depth 

and total extent of the contaminated soil across Source 5 is unknown. Therefore it is not possible to 

adequately determine a volume for Source 5 (Ref. 1, Section 2.4.2.1.3). Scoring proceeds to the 

evaluation of Tier D: area (Ref. 1, Section 2.4.2.1.4). 

Volume Assigned Value: 0 

Tier D: Area 

Based on samples collected pre- and post-removal, as well as samples collected during the 2014 SI, the 

area of Source 5 is estimated to be approximately 40,341 square feet (see Attachment A-6). In 

accordance with Ref. 1, Table 2-5: 

40,341 / 34,000 = 1.2 
 

 

Source No: 5
 

Area Assigned Value: 1.2 

Source Hazardous Waste Quantity Value: 1.2 

45 
 

46
 

 

 

 

 

 

 

 

 

 

Source No: 6 

2.2.1 SOURCE IDENTIFICATION: Source 6 Jackson Junior High School Tailings Pile 

Name of source: Jackson Junior High School Tailing Pile Number of source: 6 

Source Type: Tailings Pile 

Description and Location of Source (See Attachment A-7): 

Exposed fill material resembling processed tailings was observed in the east-facing slope of the athletic 

field embankment of Jackson Junior High School (Ref. 4, pp. 28, 77; Ref. 34, pp. 2, 609, 611-612). The 

upper athletic field playing area may have been constructed using mine tailings imported from the 

Argonaut Mine (Ref. 10, p. 36; Ref. 34, pp. 2, 4, 609, 611-612). It appears the tailings were 

subsequently covered with imported soil to establish a grass field (Ref. 10, pp. 28, 36; Ref. 34, p. 2). The 

extent of mine tailings and soil cover at the athletic field is unknown. At several locations, a mound of 

black tailings was observed adjacent to a ground squirrel burrow, suggesting that ground squirrels are 

bringing tailings to the surface of the playing field (Ref. 34, pp. 2, 609, 610). 

Elevated concentrations of arsenic, lead, and mercury were detected in samples collected from the 

athletic field embankment, as well as from the outdoor lunch area above the embankment (Ref. 4, pp. 

28, 31, 40; Ref. 11, pp. 5, 88, Ref. 34, pp. 2-3). 

In July 2015, EPA conducted a removal action at Jackson Junior High School (Ref. 34, pp. 1, 3). The 

eastern portion of the athletic field was divided into 10 DUs (see Attachment A-7) (Ref. 11, pp. 5, 20; 

Ref. 34, p. 13). DUs 1 through 5 were along the exposed eastern embankment of the athletic field. DUs 

6 through 10 were in the outdoor lunch area above the embankment (Ref. 11, p. 5). DU 6 is adjacent to 

the snack bar (Ref. 34, p. 612). DUs 1 through 5 were capped with shotcrete and fenced (Ref. 34, pp. 3­

5, 13). Tailings-impacted soils were excavated from DU-6 and the northern portion of DU-7 to a 

maximum depth of one foot bgs (Ref. 34, pp. 4, 612). The excavations were backfilled with clean fill 

(Ref. 34, p. 5). 

Based on a 1944 aerial photograph, the area of the tailings pile beneath the Jackson Junior High School 

athletic field is estimated to measure approximately 109,215 square feet (see Attachment A-7) (Ref. 10, 

p. 36). The July 2015 removal action did not change the area of Source 6, because soils exceeding 100 

mg/kg arsenic were capped in place, or were only excavated to a depth of one foot bgs (Ref. 34, pp. 3­

5). 
 

47
 

 

 

Source No: 6 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE 

EPA June and July 2015 Removal Assessment 

In June and July 2015, EPA conducted a removal assessment of Jackson Junior High School (Ref. 11, p. 

2). A total of 20 composite soil samples (10 surface and 10 subsurface) from 10 DUs were collected 

from the athletic field for metal analysis (Ref. 11, p. 2). A 5-point composite sample was collected from 

each DU at sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or hand auger and 

disposable scoops (Ref. 11, p. 2). Samples were analyzed for lead and arsenic via XRF (Ref. 11, p. 3). 

Laboratory samples were submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead by 

EPA SW-846 Method 6010C (Ref. 11, pp. 3-4). DUs are shown on Attachment A-7. 
 

48
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Source No: 6 

2015 EPA Removal Assessment, Source 6 Concentrations 

DU Sample 

ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

DU-1 (1) 

JJHS-01­

0 0 to 2 6/23/2015 

Arsenic 100 2 Ref. 11, p. 88, 114; Ref. 39, p. 

Lead 17 3 86; Ref. 48, pp. 3, 23, 26, 30 

JJHS-01­

12 6 to 12 6/23/2015 

Arsenic 85 2.1 Ref. 11, p. 88, 114; Ref. 39, p. 

Lead 17 3.1 86; Ref. 48, pp. 3, 23, 26, 30 

DU-2 (1) 

JJHS-02­

0 0 to 2 6/23/2015 

Arsenic 82 2 Ref. 11, p. 88, 114; Ref. 39, p. 

Lead 19 3 86; Ref. 48, pp. 3, 23, 26, 30 

JJHS-02­

12 6 to 12 6/23/2015 

Arsenic 81 2.1 Ref. 11, p. 88, 114; Ref. 39, p. 

Lead 13 3.1 86; Ref. 48, pp. 3, 23, 26, 30 

DU-3 (1) 

JJHS-03­

0 0 to 2 6/23/2015 

Arsenic 170 2 Ref. 11, p. 88, 114; Ref. 39, p. 

Lead 31 3 86; Ref. 48, pp. 3, 23, 26, 30 

JJHS-03­

12 6 to 12 6/23/2015 

Arsenic 290 2.1 Ref. 11, p. 88, 114-115; Ref. 

39, p. 86; Ref. 48, pp. 3-4, 24, 

26, 30 Lead 26 3.2 

DU-4 (1) 

JJHS-04­

0 0 to 2 6/23/2015 

Arsenic 300 2 Ref. 11, p. 88, 107-110, 115; 

Ref. 39, p. 86; Ref. 48, pp. 4, 

24, 26, 30 Lead 20 3 

JJHS-04­

12 6 to 12 6/23/2015 

Arsenic 230 2.2 Ref. 11, p. 88, 115; Ref. 39, p. 

Lead 11 3.3 87; Ref. 48, pp. 4, 24, 26, 30 

DU-5 (1) 

JJHS-05­

0 0 to 2 6/23/2015 

Arsenic 48 2.1 Ref. 11, p. 88, 115; Ref. 39, p. 

Lead 13 3.1 87; Ref. 48, pp. 4, 24, 26, 30 

JJHS-05­

12 6 to 12 6/23/2015 

Arsenic 57 2.2 Ref. 11, p. 88, 115; Ref. 39, p. 

Lead 14 3.3 87; Ref. 48, pp. 4, 24, 26, 30 

DU-6 (2) 

JJHS-C02-14­

072715 

12 to 14 7/27/15 

Arsenic 290 2 Ref. 11, p. 88, 120; Ref. 34, 

pp. 600- 601; Ref. 39, pp. 20, 

Lead 15 3 22; Ref. 49, pp. 3, 21, 23, 27 

DU-7 (2) 

JJHS-C06-14­

072715 

12 to 14 7/27/15 

Arsenic 100 2 Ref. 11, p. 88, 120; Ref. 34, 

pp. 600-601; Ref. 39, pp. 20, 

22; Ref. 49, pp. 3, 21, 23, 27 Lead 15 3 

DU-9 

JJHS-C10-2­

072715 

0 to 2 7/27/15 

Arsenic 62 2 Ref. 11, p. 88, 120; Ref. 39, 

pp. 21-22; Ref. 34, pp. 600­

601; Ref. 49, pp. 3, 21, 23, 27 Lead 24 3 

mg/kg: milligrams analyte per kilogram soil
 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits (SQLs)
 

(Ref. 43). 

(1): These sampling locations were covered with shotcrete during the July 2015 EPA Removal Action (Ref. 34, pp. 3-4, 13-14). 

(2): Although a removal was conducted in this DU, soils were not excavated to this depth (Ref. 34, p. 4). 
 

49
 

 

 

 

 

 

Source No: 6 

EPA July 2015 Removal Action 

In July 2015, EPA conducted a Removal Action at the Jackson Junior High School athletic field (Ref. 

34, pp. 1, 4). Confirmation soil samples were collected from the excavations, and analyzed for lead and 

arsenic via XRF (Ref. 34, pp. 1, 6-7). Laboratory samples were submitted to the EPA Region 9 

Laboratory for analysis of arsenic and lead by SW-846 Method 6010C (Ref. 34, p. 600). The sampling 

location is shown on Attachment A-7. 

2015 EPA Removal Action, Source 6 Confirmation Sampling Concentrations 

DU Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

DU-7 JJHS-C-17­

12-080315 12 to 14 8/3/15 

Arsenic 79 2 Ref. 34, pp. 19, 600, Ref. 39, 

p. 34; Ref. 49, pp. 3, 22-23, 

Lead 27 18 3 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

List of Hazardous Substances Associated with Source 

Arsenic and Lead 

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY 

The migration pathways are not scored for Source 6. 
 

50
 

 

 

 

 

 

 

Source No: 6 

2.4.2. Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total Hazardous Constituent Quantity for Source 6 could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for 

Source 6 with reasonable confidence. Scoring proceeds to the evaluation of Tier B, hazardous 

wastestream quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Source 6 could not be adequately determined according 

to the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Source 6 with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume 

The information available is not sufficient to meaningfully evaluate Tier C: volume, because the depth 

and total extent of the tailings and waste rock pile across Source 6 are unknown. Therefore it is not 

possible to adequately determine a volume for Source 6 (Ref. 1, Section 2.4.2.1.3). Scoring proceeds to 

the evaluation of Tier D, area (Ref. 1, Section 2.4.2.1.4). 

Volume Assigned Value: 0 
 

51
 

 

 

 

Source No: 6 

Tier D: Area 

Based on a 1944 aerial photograph, the area of the tailings pile beneath the Jackson Junior High School 

athletic field is estimated to measure approximately 109,215 square feet (see Attachment A-7) (Ref. 10, 

p. 36). In accordance with Ref. 1, Table 2-5: 

109,215 / 13 = 8,401.2 

Area Assigned Value: 8,401.2 

Source Hazardous Waste Quantity Value: 8,401.2 
52
 

 

SUMMARY OF SOURCE DESCRIPTIONS
 

Source 

No. 

Source Hazardous 

Waste Quantity 

Value 

Containment 

Surface 

Water 

1 684,800 10 

2 6,115.4 NE 

3 7,488.5 NE 

4 2.1 NE 

5 1.2 NE 

6 8,401.2 NE 

TOTAL 706,808.4 

Notes: 

NE = Not Evaluated. 
53
 

 

 

 

OTHER POSSIBLE SOURCES NOT SCORED 

Tailings Pile in AOC-1 Ore Storage Area (see Attachment A-1) 

The approximately 5-acre AOC-1 Ore Storage Area was used for storage of middlings, a type of tailings 

that are neither clean mineral products nor pure waste (Ref. 4, p. 9; Ref. 12, pp. 9, 46). Approximately 

159,000 tons of tailings are estimated to remain in the AOC-1 tailings pile (Ref. 31, p. 16). Tailings 

samples collected from this area contained elevated concentrations of arsenic, lead, and mercury (Ref. 5, 

pp. 13-14; Ref. 6, pp. 33-34). 

Tailings Pile in AOC-2 Cyanide Plant Area (see Attachment A-1) 

The approximately 6.5-acre AOC-2 Cyanide Plant Area contains a former cyanide plant and the 

foundation of a probable mercury amalgamation building (Ref. 4, p. 8; Ref. 6, p. 9; Ref. 12, pp. 9, 59). A 

tailings pile covers most of the surface of the area (Ref. 6, p. 9). Tailings samples collected from this 

area contained elevated concentrations of arsenic, lead, and mercury (Ref. 5, pp. 13-16; Ref. 6, pp. 33­

36; Ref. 32, p. 12). 

Cyanide Plant in AOC-2 Cyanide Plant Area (see Attachment A-1) 

Various abandoned cyanide processing tanks and vats still remain in the AOC-2 Cyanide Plant Area 

(Ref. 4, p. 8; Ref. 6, p. 48; Ref. 12, pp. 9, 56, 59, 64, 75). Samples collected from some of the tanks and 

vats contained elevated concentrations of arsenic, lead, and mercury (Ref. 5, pp. 15-16, 23, 27, 45-46, 

59; Ref. 6, p. 48). 

Mill Area (see Attachment A-1) 

The Mill Area occupies approximately 80 acres in a residential area of Jackson, north of the Tailings 

Area. Mine shaft adits and buildings associated with former Argonaut Mine operations in the Mill Area 

are located on the east and west sides of Highway 49 (Ref. 4, pp. 7, 11, 64). Tailings were stored in the 

Mill Area until 1917, after which they were transported by flume to the Tailings Area (Ref. 4, p. 9; Ref. 

12, pp. 32, 36; Ref. 14, p. 7; Ref. 35; Ref. 36, p. 13). Waste rock and tailings piles are present 

throughout the Mill Area, but the area is overgrown and their sizes and locations are not well 

characterized (Ref. 4, pp. 7-8, 11, 25-26, 38, 64, 66-67). Samples collected from waste rock and tailings 

in the Mill Area contained elevated concentrations of arsenic, lead, and mercury (Ref. 4, pp. 25-27). 
 

 

4.0 SURFACE WATER MIGRATION PATHWAY 

4.1 OVERLAND MIGRATION COMPONENT 

Based on the 2014 SI sampling, there are four wetlands with a documented observed release attributable 

to Argonaut Mine (Ref. 4, pp. 41, 46-47; Ref. 38). However, these wetlands are not considered to be 

within the same watershed, as they are not connected by perennially-flowing surface water, and average 

annual precipitation in the site vicinity exceeds 20 inches (Ref. 30, p. 2; Ref. 33; Ref. 38). Therefore, 

only the largest of these wetlands is scored, as scoring of the others does not affect the listing decision. 

The largest wetland is located on the surface of Source 1, above the EMAD (Ref. 38). 

Photo 1: Source 1 Wetland, July 29, 2014 

54 SWOF-Likelihood of Release 
55 SWOF-Likelihood of Release 

 

 

 

 

 

 

4.1.1.1 Definition of Hazardous Substance Migration Path for Overland Component 

Surface water from both the Mill Area and the Tailings Area of Argonaut Mine flows to North Fork 

Jackson Creek, then to Jackson Creek, then 7 miles westward to Lake Amador Reservoir. However, 

North Fork Jackson Creek is an intermittent stream, and average annual precipitation in the site vicinity 

exceeds 20 inches (Ref. 3; Ref. 4, p. 45; Ref. 33). Therefore, this watershed is not scored. 

The Source 1 wetland is located on the surface, and entirely within the boundary, of Source 1. The 

wetted perimeter of the wetland, measuring 2,313 feet, or 0.44 mile, is in contact with Source 1. 

Therefore, the Probable Point of Entry is the interface between the wetland and Source 1 (Ref. 4, pp. 8, 

45, 65; Ref. 38). Using Attachment A-8, the wetted perimeter of the Source 1 wetland was measured 

based on the mapped boundary in the U.S. Fish and Wildlife Service Wetlands Inventory. The Wetlands 

Inventory classifies the Source 1 wetland as PEMAh, or Palustrine, Emergent, Water Regime, 

Diked/Impounded (Ref. 38). This is an HRS-eligible wetland, in accordance with 40CFR Section 230.3 

and Ref. 1, Table 4-24. 

4.1.2.1 Likelihood of Release 

4.1.2.1.1 Observed Release 

Direct Observation 

- Basis for Direct Observation: 

The wetland above the EMAD is located on the surface, and entirely within the boundary, of Source 1, 

the Tailings Area Tailings Impoundment. The approximate location of the Source 1 wetland is shown on 

Attachment A-8 (Ref. 38). The wetland is in direct contact with hazardous substances in Source 1, based 

on concentrations of hazardous substances in sediments collected from the Source 1 wetland (Ref. 4, pp. 

33, 41, 1724, 1750; see 2014 SI, Source Sediment Concentrations Table below). 

- Hazardous Substances in Release: 

Weston Solutions, Inc. 2014 SI Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a SAP 

approved by EPA on March 10, 2014. A total of 90 soil samples were collected from the surface (0 to 6 

inches) and shallow subsurface (up to 2 feet) at 47 sampling locations. The subsurface samples were 

collected using either a track-mounted direct push sampling rig and Macro-core soil sampler lined with 

an acetate sleeve, or by hand auger. A total of 27 sediment samples were collected from 25 sampling 

locations (Ref. 4, p. 22). 

Soil and sediment samples were submitted to Bonner Analytical, located in Hattiesburg, Mississippi, 

under EPA Contract Laboratory Program for metal analysis by Inorganic Superfund Methods (ISM01.3) 

and cyanide by EPA Method 9010/9012. The metals analytical data were validated by EPA (Ref. 4, p. 

22). 
56 SWOF-Likelihood of Release 

 

Soil samples were collected from five locations within Source 1 (Ref. 4, p. 27). Two sample locations 

(ATA-01 and ATA-02) were gray sands from the upper tailings dam. Sampling location ATA-03 was 

near the Sierra View Estates residential properties off of Detert Lane. Sampling location ATA-04 was at 

the northern end of the lower tailings dam; near Sierra View Estates. Sampling location ATA-05 was 

near residential properties off of Muldoon Place near Sierra View Estates (Ref. 4, pp. 27-28, 65). 

Sediment sample ATS-02 was collected from the Source 1 wetland (Ref. 4, p. 33). Soil and sediment 

sampling locations are presented in Attachment A-3. 
57 SWOF-Likelihood of Release 

 

 

 

2014 SI, Source 1 Sediment Concentrations 

Sample ID Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ATS-02-0 

(MY9F98) 7/29/14 

Arsenic 204 1.3 Ref. 4, pp. 41, 65, 1812, 1815-1819, 

1823, 1942; Ref. 18, pp. 5-6; Ref. 23, pp. 

11, 27 

Lead 38.8 1.3 

Mercury 1.5 0.13 

mg/kg: milligrams analyte per kilogram sediment 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

Hazardous Substances Released 

Arsenic, Lead, and Mercury 

Surface Water Observed Release Factor Value: 550 
58 

4.1.2.2 Drinking Water Threat Waste Characteristics 

There are no drinking water intakes in the Source 1 wetland. Therefore, the Drinking Water Threat is not 

scored. 

4.1.3.2 Human Food Chain Threat Waste Characteristics 

A fishery is not present in the Source 1 wetland. Therefore, the Human Food Chain Threat is not scored. 

SWOF/HFC-Targets 
 

 

 

 

 

 

 

4.1.4.2 Environmental Threat Waste Characteristics 

4.1.4.2.1 Ecosystem Toxicity/Persistence/Bioaccumulation 

Hazardous 

Substance Source No. 

Ecosystem 

Toxicity 

Factor 

Value 

Persistence 

Factor 

Value* 

Ecosystem 

Bioaccumulation 

Value** 

Ecosystem Toxicity/ 

Persistence/ 

Ecosystem 

Bioaccumulation 

Factor Value 

(Ref. 1, Table 4-21) 

Reference 

Arsenic 1 10 1 50,000 500,000 Ref. 2, p. 1 

Lead 1 1,000 1 50,000 50,000,000 Ref. 2, pp. 

7-8 

Mercury 1 10,000 1 50,000 500,000,000 Ref. 2, pp. 

9-10 

Notes: 

* Persistence value for Lakes
 

** Bioaccumulation factor value for Freshwater
 

Ecosystem Toxicity/Persistence/Environmental Bioaccumulation Factor Value: 500,000,000 

4.1.4.2.2. Hazardous Waste Quantity 

Source No. Source Type Source Hazardous Waste Quantity Source Hazardous Constituent 

Quantity Complete? 

1 Pile 684,800 No 

Sum of Values: 684,800 

Hazardous Waste Quantity Factor Value: 10,000 

(Ref. 1, Table 2-6) 

59 SWOF/ENV-Waste Characteristics 
60 SWOF/ENV-Waste Characteristics 

 

 

 

4.1.4.2.3. Waste Characteristics Factor Category Value 

Ecosystem Toxicity/Persistence Factor Value: 10,000 

Hazardous Waste Quantity Factor Value: 10,000 

Ecosystem Toxicity/Persistence Factor Value x Hazardous Waste Quantity Factor Value: 100,000,000 

(Ecosystem Toxicity/Persistence Factor Value x Hazardous Waste Quantity Factor Value) x 

Environmental Bioaccumulation Factor Value: 5,000,000,000,000 

Waste Characteristics Factor Category Value: 1,000 

(Ref. 1, Table 2-7) 
61 

 

 

 

 

 

4.1.4.3 Environmental Threat Targets 

Most Distant Level I Sample 

Level I Concentrations are not established, as benchmarks are not available for sediment, and surface 

water was not sampled in the Source 1 wetland (Ref. 2, p. 14, 21-22). 

Most Distant Level II Sample 

Sample ID: ATS-02-0 

Distance from the probable point of entry: 0 mile 

Reference: Ref. 4, pp. 41, 65, 1812, 1823; Ref. 18, pp. 6-7; Ref. 23, pp. 11, 27; Ref. 38; see Attachments 

A-3 and A-8 

4.1.4.3.1 Sensitive Environments 

4.1.4.3.1.1. Level I Concentrations 

Level I Concentrations are not established, as benchmarks are not available for sediment, and surface 

water was not sampled in the Source 1 wetland (Ref. 1, Sections 4.1.2.3 and 4.1.4.3.1.1, Ref. 2, p. 14, 

21-22). As an observed release by direct observation is scored, targets associated with this observed 

release by direct observation are evaluated using Level II concentrations for that location. (Ref. 1, 

Sections 4.1.2.3, 4.4.3.1, 4.1.4.3.1.1, 4.1.4.3.1.2.) 

4.1.4.3.1.2. Level II Concentrations 

Level II Wetland Frontages
 

The wetted perimeter of the Source 1 wetland measures approximately 2,313 feet, or 0.44 mile (Ref. 

38). As the Source 1 wetland is in contact with Source 1 and the PPE to surface water is in the wetland,
 

the perimeter of the wetland is evaluated as the length of wetlands subject to Level II concentrations
 

(Section 4.1.2.1.1 of this HRS documentation record; Ref.1, Section 4.1.4.3.1.2). Using Attachment A-8, 

the wetted perimeter of the Source 1 wetland was measured based on the mapped boundary in the U.S. 

Fish and Wildlife Service Wetlands Inventory. The Wetlands Inventory classifies the Source 1 wetland 

as PEMAh, or Palustrine, Emergent, Water Regime, Diked/Impounded (Ref. 38). This is an HRSeligible wetland, in accordance with 40CFR Section 230.3 and Ref. 1, Table 4-24.
 

Wetland Wetland Frontage 

(miles) References 

Source 1 wetland, classified as 

PEMAh, or Palustrine, Emergent, 

Water Regime, Diked/Impounded 

0.44 Ref. 1 Section 4.1.4.3.1.2; Ref. 

4, p. 45; Ref. 38 

Sum of Level II Wetland Frontages: 0.44 mile 

SWOF/ENV-Targets 
62 SWOF/ENV-Targets 

 

 

Wetlands Value (Ref. 1, Table 4-24): 25
 

Sum of Level II Sensitive Environments Value + Wetlands Value:
 

Level II Concentrations Factor Value: 25
 
 

 

 

 

 

 

 

5.0 SOIL EXPOSURE PATHWAY
 

The Argonaut Mining Company historically owned approximately 330 acres of land northwest of 

downtown Jackson. The property was sold after the mine closed, and approximately 90 acres of the 

former property have been developed as residential neighborhoods (Ref. 4, pp. 7, 64). Six areas of 

observed contamination attributable to the Argonaut Mine site were evaluated for scoring (see 

Attachment A-2). Descriptions of the individual areas are provided in the sections below. 

Area A is the Tailings Area Tailings Impoundment, a tailings pile containing approximately 1,712,000 

tons of processed tailings. Areas B through E are areas of residential properties within the former 

Argonaut Mine property boundary that were built on imported fill placed over waste rock, tailings, and 

soils contaminated by Argonaut Mine operations. Area F is the Jackson Junior High School athletic 

field, which was constructed on waste rock and tailings. Observed contamination of arsenic, lead, and/or 

mercury is documented in Areas A through F. 

Approximately 53 residents occupy residential properties within the areas of observed contamination. 

Currently, there are 406 students and 45 staff members at Jackson Junior High School (Ref. 13; see 

sections 5.1.3.2.1 and 5.1.3.2.2 of this HRS documentation record). 

Argonaut Mine Areas of Contamination 

Area Source Name Source Type 

A Tailings Area Tailings Impoundment Pile 

B Argonaut Estates Pile Pile 

C Argonaut Heights – North Pile Pile 

D Argonaut Heights – South Contaminated Soil Contaminated Soil 

E Sierra View Estates Contaminated Soil Contaminated Soil 

F Jackson Junior High School Tailings Pile Pile 

63 SE-General 
 

 

 

 

 

 

 

 

 

 

 

Area Letter: A 

5.0.1 GENERAL CONSIDERATIONS: Area A, Tailings Area Tailings Impoundment 

Letter by which this area is to be identified: A 

Name of area: Tailings Area Tailings Impoundment 

Source Type: Tailings Pile 

Location and description of area (see Attachment A-2): 

Area A correlates with Source 1, as identified in Section 2.2.1. Area A consists of a tailings pile 

covering approximately 48 acres constructed in a drainage valley (Ref. 4, pp. 8, 13; Ref. 12, p. 9). In 

1916, the EMAD was constructed in the ravine southeast of Argonaut Mine to impound tailings 

generated from Argonaut mining and milling operations (Ref. 6, p. 10; Ref. 12, pp. 9, 41). The EMAD is 

roughly 390 feet wide and 46 feet tall (Ref. 6, p. 10). The impoundment was expanded in 1931 and 1940 

with two additional dams constructed of tailings (Ref. 12, pp. 41-42; Ref. 41, pp. 9, 47-48). Two 

wetlands are present on the surface of Source 1 (Ref. 4, pp. 8, 65; Ref. 38). 

Sediment and tailings have filled the valley behind the EMAD to within a few feet of its top. Standing 

water flows over the top of the dam during wet periods. Water also flows through cracks in the base of 

the dam, suggesting materials behind the dam are saturated (Ref. 6, p. 10). 

Soils at the surface of Area A are predominantly grey tailings. In most areas, vegetation has been 

reestablished and a thin layer of organic material is present, stabilizing the surface. However, large 

portions of Area A contain exposed gray tailings that are devoid of vegetation. These soils are easily 

eroded during large magnitude rain events and large gullies and sinkholes have formed. Some of the 

gullies exceed 20 feet in depth and top-width (Ref. 6, p. 9). 

In February 1955, mining engineer and licensed surveyor C.E. Bronson estimated a total of 1,712,000 

tons of tailings within Source 1 by comparing the existing tailings surface with an estimated contour of 

the original ground surface below (Ref. 12, pp. 43-45; Ref. 44). 

Weston Solutions, Inc. 2014 Site Inspection Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples throughout the former Argonaut Mine property. Samples were collected in accordance 

with a SAP approved by EPA on March 10, 2014. Samples were submitted to Bonner Analytical, 

located in Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for metals analysis by 

Inorganic Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical 

data were validated by EPA (Ref. 4, p. 22). 

- Background Concentrations: 

Background soil samples were collected from location AB-01 in pasture land located northwest of Area 

A and location AB-02 in pasture land located southwest of Area A (Ref. 4, p. 24). Background sampling 

locations are shown in Attachment A-3. 

The Area A tailings pile was constructed in a ravine on farmland (Ref. 6, p. 10; Ref. 12, pp. 28, 41; Ref. 

50). Therefore, background samples were collected from nearby pasture lands to be representative of 

64 SE-General 
 

 

 

 

 

 

 

 

 

 

 

 

Area Letter: A 

local conditions without the Argonaut Mine. Sample depths of the background and contaminated 

samples are all from the upper 2 feet, although the background locations are native soil while soils in 

Area A consist of tailings generated by Argonaut Mine operations. 

2014 SI, Area A Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 39-40, 66, 76, 1808, 1818­

1820, 1944; Ref. 18, p. 1; Ref. 23, pp. 

7, 15 

Lead 14.8 J (21.3) 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2.0 J- (3.5) 1.1 Ref. 4, pp. 39-40, 66, 76, 1808, 1830, 

1832, 1834, 1944; Ref. 20, p. 1; Ref. 

24, pp. 6, 10 

Lead 9.0 J (13.0) 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J- (5.4) 1.0 Ref. 4, pp. 39-40, 65, 1808, 1832, 

1834, 1941; Ref. 20, p. 1; Ref. 24, pp. 

6, 11 

Lead 11.2 J (16.1) 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J- (2.1) 1.1 Ref. 4, pp. 39-40, 65, 1808, 1830, 

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J (10.2) 1.1 

Mercury <0.11 0.11 

3X Highest Background (to 

establish concentrations 

significantly above background): 

Arsenic 26.7 

Lead 63.9** Ref. 9 

Mercury 0.45 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832, 1867). Therefore, the background 

value is multiplied by a factor of 1.74 for arsenic and 1.44 for lead. The adjusted value is included in parentheses (Ref. 9, pp. 

8, 18). 

J-: The result is an estimated quantity, with a low bias (Ref. 4, pp. 1818, 1830-1832, 1867).
 

<: The analyte was not detected.
 

**: Calculated with the adjusted value.
 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified.
 

^: Page 1831of Reference 4 presents a J qualifier for arsenic concentrations, and Reference 4 pages 1830 and 1834 indicate that
 

the reported results may be biased low.
 

- Contaminated Samples: 

Soil samples were collected from five locations within Source 1 (Ref. 4, p. 27). Two sample locations 

(ATA-01 and ATA-02) were gray sands from the upper tailings dam. Sampling location ATA-03 was 

near the Sierra View Estates residential properties off of Detert Lane. Sampling location ATA-04 was at 

the northern end of the lower tailings dam; near Sierra View Estates. Sampling location ATA-05 was 

near residential properties off of Muldoon Place near Sierra View Estates (Ref. 4, pp. 27-28, 65). 

Sampling locations are presented in Attachment A-3. 

65	 SE-General 
 

 

 

 

 

 

 

 

 

 

Area Letter: A 

2014 SI, Area A Tailings Concentrations Significantly Above Background 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ATA-01-0 

(MY9F89) 0 - 0.5 7/29/14 Arsenic 54.8 1.0 Ref. 4, pp. 28, 39, 65, 1812, 1817, 1822; Ref. 18, p. 4; Ref. 23, pp. 11, 24 

ATA-02-0 

(MY9F90) 0 - 0.5 7/29/14 Arsenic 49.4 1.1 Ref. 4, pp. 28, 39, 65, 1812, 1817, 1822; Ref. 18, p. 5; Ref. 23, pp. 11, 25 

ATA-03-0 

(MY9F91) 0 - 0.5 7/29/14 

Arsenic 3,490 15.5 

Ref. 4, pp. 28, 39, 65, 1812, 1892; Ref. 

25, pp. 8, 25; Ref. 37, p. 6 Lead 193 1.0 

Mercury 2.5 0.52 

ATA-03-2 

(MY9F92) 1.5 - 2 7/29/14 Arsenic 502 2.1 Ref. 4, pp. 28, 39, 65, 1812, 1892; Ref. 25, pp. 8, 26; Ref. 37, p. 6 

ATA-04-0 

(MY9F93) 0 - 0.5 7/29/14 Arsenic 362 1.0 Ref. 4, pp. 28, 39, 65, 1812, 1893; Ref. 25, pp. 8, 27; Ref. 37, p. 6 

ATA-05-1.5 

(MY9F96) 1 - 1.5 7/29/14 

Arsenic 237 1.1 Ref. 4, pp. 28, 39, 65, 1812, 1893; Ref. 

Mercury 25, pp. 8, 30; Ref. 37, pp. 7-8 0.52 0.11 

mg/kg: milligrams analyte per kilogram tailings 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

66 SE-General 
 

 

 

 

 

 

 

 

Area Letter: A 

Area A Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total Hazardous Constituent Quantity for Area A could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for Area 

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

quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Area A could not be adequately determined according to 

the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Area A with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume 

Tier C, volume is not applicable to source type pile for the soil exposure pathway (Ref. 1, Section 

5.1.2.2). 

Volume Assigned Value: 0 

Tier D: Area 

Area A consists of a tailings pile covering approximately 48 acres (Ref. 12, p. 9). In accordance with 

Ref. 1, Table 5-2: 

48 acres = 2,090,880 square feet 

2,090,880 / 34 = 61,496.5 

Area Assigned Value: 61,496.5 

Area Hazardous Waste Quantity Value: 61,496.5 

67 SE-General 
 

 

 

 

 

 

 

 

Area Letter: B 

5.0.1 GENERAL CONSIDERATIONS: Area B, Argonaut Estates Tailings Pile 

Letter by which this area is to be identified: B 

Name of area: Argonaut Estates 

Source Type: Tailings Pile 

Location and description of area (see Attachment A-4 through A-6): 

Area B correlates with Source 2, the Argonaut Estates Tailings Pile. From 1989 through 2004, the 

Argonaut Estates, Jackson View Estates, Sierra View Estates, and Argonaut Heights residential 

developments were reportedly built on areas of known waste rock and mine tailings that were covered 

with imported fill prior to construction of the homes (see Attachment A-4) (Ref. 4, pp. 16, 40; Ref. 8, p. 

1; Ref. 26, p. 2; Ref. 27, pp. 2-3). A historical aerial photo review conducted by EPA showed that some 

residential properties in the Argonaut Estates development were built on the location of a waste rock pile 

associated with Argonaut operations (Ref. 4, p. 28; Ref. 10, pp. 13, 28, 36). Sampling conducted at 

Argonaut Estates properties ARA-07 and ARA-08 on Spunn Road showed the presence of arsenic at 

concentrations significantly above background in soils from 0 to 2 feet bgs (Attachment A-5) (Ref. 4, 

pp. 28-29, 66; Ref. 15). 

Attachment A-4 shows the locations of properties ARA-07 and ARA-08 overlaid on a 1944 aerial photo 

showing the waste rock pile (Ref. 10, pp. 29, 36). The total area of Area B is estimated to be 

approximately 79,500 square feet based on the footprint of the waste rock pile in the 1944 aerial photo, 

as well as the sampling locations on ARA-07 and ARA-08 showing elevated concentrations of arsenic 

(see Attachment A-6). This includes the property between ARA-07 and ARA-08 (ARA-33) because the 

waste rock pile extended across this property as well. However, some of this area is covered by 

permanent or otherwise maintained, essentially impenetrable material. The average home is estimated to 

cover approximately 2,500 square feet, and an estimated 1,000 square feet of each property is paved (see 

Attachment A-5 and A-6) (Ref. 45). Therefore, the Area of Contamination for Area B is estimated to be 

approximately 69,000 square feet (i.e., 79,500 square feet – (3 properties * 3,500 covered square feet per 

property)). 

In August 2015, EPA conducted removal actions at 11 residential properties built within the former 

Argonaut Mine property (Ref. 40, pp. 1-2, 7). However, this removal did not include any actions at the 

properties in Area B. 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a SAP 

approved by EPA on March 10, 2014. Samples were submitted to Bonner Analytical, located in 

Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for metals analysis by Inorganic 

Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical data were 

validated by EPA (Ref. 4, p. 22). 

68 SE-General 
 

 

 

 

 

 

 

 

 

Area Letter: B 

- Background Concentrations: 

Background soil samples were collected from location AB-01 in pasture land located northwest of the 

Area A Tailings Impoundment and location AB-02 in pasture land located southwest of the Area A 

Tailings Impoundment (Ref. 4, p. 24; See Attachment A-3). Background sampling locations are shown 

in Attachment A-3. 

Residential properties built within the former Argonaut Mine property boundary were built on imported 

fill placed over waste rock, tailings, and soils contaminated by Argonaut Mine operations (Ref. 4, pp. 

16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Prior to the construction of the Area A Tailings 

Impoundment and the AOC-2 Cyanide Plant, a part of the property was farmland (Ref. 12, p. 28; Ref. 

50; see Attachment A-2). Therefore, background samples were collected from nearby pasture lands to be 

representative of local conditions without the Argonaut Mine. Sample depths of the background and 

release samples are all from the upper 2 feet, although the background locations are native soil while 

soils from the residential properties include tailings and waste rock generated by mining activities, as 

well as imported fill. 

2014 SI, Area B Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 25, 39-40, 66, 76, 1808, 

1818-1820, 1944; Ref. 18, p. 1; Ref. 

23, pp. 7, 15 

Lead 14.8 J (21.3) 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2.0 J- (3.5) 1.1 Ref. 4, pp. 25, 39-40, 66, 76, 1808, 

1830, 1832, 1834, 1944; Ref. 20, p. 1; 

Ref. 24, pp. 6, 10 

Lead 9.0 J (13.0) 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J- (5.4) 1.0 Ref. 4, pp. 25, 39-40, 65, 1808, 1832, 

1834, 1941; Ref. 20, p. 1; Ref. 24, pp. 

6, 11 

Lead 11.2 J (16.1) 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J- (2.1) 1.1 Ref. 4, pp. 25, 39-40, 65, 1808, 1830, 

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J (10.2) 1.1 

Mercury <0.11 0.11 

3X Highest Background (to 

establish concentrations 

significantly above background): 

Arsenic 26.7 

Lead 63.9** Ref. 9 

Mercury 0.45 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832, 1834-1839, 1867). Therefore, the 

background value is multiplied by a factor of 1.74 for arsenic and 1.44 for lead. The adjusted value is included in parentheses 

(Ref. 9, pp. 8, 18). 

J-: The result is an estimated quantity, with a low bias (Ref. 4, p. 1830). The adjusted value is included in parentheses (Ref. 9, pp. 

8, 18). 

<: The analyte was not detected. 

**: Calculated with the adjusted value. 

69	 SE-General 
 

 

 

 

 

 

 

 

Area Letter: B 

2014 SI, Area B Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 25, 39-40, 66, 76, 1808, 

1818-1820, 1944; Ref. 18, p. 1; Ref. 

23, pp. 7, 15 

Lead 14.8 J (21.3) 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2.0 J- (3.5) 1.1 Ref. 4, pp. 25, 39-40, 66, 76, 1808, 

1830, 1832, 1834, 1944; Ref. 20, p. 1; 

Ref. 24, pp. 6, 10 

Lead 9.0 J (13.0) 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J- (5.4) 1.0 Ref. 4, pp. 25, 39-40, 65, 1808, 1832, 

1834, 1941; Ref. 20, p. 1; Ref. 24, pp. 

6, 11 

Lead 11.2 J (16.1) 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J- (2.1) 1.1 Ref. 4, pp. 25, 39-40, 65, 1808, 1830, 

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J (10.2) 1.1 

Mercury <0.11 0.11 

3X Highest Background (to 

establish concentrations 

significantly above background): 

Arsenic 26.7 

Lead 63.9** Ref. 9 

Mercury 0.45 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified. 

^: Page 1831of Reference 4 presents a J qualifier for arsenic, and Reference 4 pages 1830 and 1834 indicate that the reported 

results may be biased low. 

- Contaminated Samples: 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations. Sampling locations ARA-07 and ARA-08 were collected from the Argonaut Estates 

neighborhood developed along the waste rock pile south of the Argonaut Mine Mill Area (Ref. 4, p. 28). 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, soil 

samples are identified by address code only. Address codes are defined in a confidential reference (Ref. 

15). 

2014 Site Inspection, Area B Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-07 

ARA07-0 

(MY9F5 

6) 

0 - 0.5 7/31/14 Arsenic 68.5 J+ (39.4) 1.1 

Ref. 4, pp. 29, 40, 66, 1811, 

1873, 1875, 1944; Ref. 16, p. 

2; Ref. 21, pp. 7, 14 

70 SE-General 
 

 

 

 

 

 

 

 

Area Letter: B 

2014 Site Inspection, Area B Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA07-1 

(MY9F 

57) 

1.5 - 2 7/31/14 Arsenic 148 1.1 

Ref. 4, pp. 29, 40, 66, 1811, 

1865, 1944; Ref. 17, p. 7; 

Ref. 22, pp. 10, 32 

ARA-08 

ARA08-0 

(MY9F 

58) 

0 - 0.5 7/31/14 Arsenic 68.3 J+ (39.2) 1.1 

Ref. 4, pp. 29, 40, 66, 1811, 

1873, 1876, 1944; Ref. 16, p. 

2; Ref. 21, pp. 7, 15 

mg/kg: milligrams analyte per kilogram soil
 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit
 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J+: The result is estimated and may be biased high (Ref. 4, pp. 1867, 1873). Therefore, the value is divided by a factor of 1.74.
 

The adjusted value is included in parentheses (Ref. 9, pp. 8, 18). 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified. 

^: Page 2 of Reference 16 presents a J- qualifier for qualified arsenic samples, pages 1875 and 1876 of Reference 4 present 

arsenic concentrations without qualifiers, and Reference 4 page 1873 indicates that the qualified arsenic samples are biased 

high. 

71 SE-General 
 

 

 

 

 

 

 

Area Letter: B 

Area B Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total Hazardous Constituent Quantity for Area B could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for Area 

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

quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Area B could not be adequately determined according to 

the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Area B with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume: 

Tier C, volume is not applicable to source type pile for the soil exposure pathway (Ref. 1, Section 

5.1.2.2). 

Volume Assigned Value: 0 

Tier D: Area: 

The total area of Area B is estimated to be approximately 79,500 square feet based on the footprint of 

the waste rock pile in the 1944 aerial photo, as well as the sampling locations on ARA-07 and ARA-08 

showing elevated concentrations of arsenic (see Attachment A-6). However, some of this area is covered 

by permanent or otherwise maintained, essentially impenetrable material. The average home is estimated 

to cover approximately 2,500 square feet, and an estimated 1,000 square feet of each property is paved 

(see Attachment A-5 and A-6) (Ref. 45). Therefore: 

79,500 square feet – (3 properties * 3,500 covered square feet per property) = 69,000 square feet 

69,000 / 34 = 2,029.4 (Ref. 1, Table 5-2) 

72 SE-General 
 

SE-General 

 

Area Letter: B 

Area Assigned Value: 2,029.4 

Area Hazardous Waste Quantity Value: 2,029.4 

73 
 

 

 

 

 

 

 

 

 

Area Letter: C 

5.0.1 GENERAL CONSIDERATIONS Area C, Argonaut Heights – North Tailings Pile 

Letter by which this area is to be identified: C 

Name of area: Argonaut Heights – North 

Source Type: Tailings Pile 

Location and description of area (see Attachment A-4 through A-6):
 

Area C correlates with Source 3, the Argonaut Heights - North Tailings Pile. From 1989 through 2004, 

the Argonaut Estates, Jackson View Estates, Sierra View Estates, and Argonaut Heights residential
 

developments were reportedly built on areas of known waste rock and mine tailings that were covered
 

with imported fill prior to construction of the homes (see Attachment A-4) (Ref. 4, pp. 16, 40; Ref. 8, p.
 

1; Ref. 26, p. 2; Ref. 27, pp. 2-3). A historical aerial photo review conducted by EPA showed trenches,
 

pits, and berms for tailings disposal in the northern portion of the Argonaut Heights development near
 

Pioneer Street and Argonaut Lane (Ref. 10, pp. 29-30, 36; Ref. 42, p. 7). Sampling conducted at these 

properties showed the presence of elevated concentrations of arsenic, lead, and mercury in soils from 0 

to 2 feet bgs (Attachment A-5) (Ref. 4, pp. 28-29, 66; Ref. 15).
 

Attachment A-4 shows the locations of residential properties overlaid on a 1944 aerial photo of the 

Argonaut Mine property (Ref. 10, p. 36). In March 2015, EPA conducted a removal action of the vacant 

parcel located at the northeast corner of Pioneer Street and Argonaut Lane (EPA AOC-5) (Attachment 

A-1) (Ref. 42, p. 5). During the removal, mine tailings and wastes were observed to extend beyond the 

boundaries of AOC-5 into the neighboring residential properties of Area C (Ref. 42, pp. 10, 12, 45). 

In August and September 2015, EPA conducted removal actions at 11 residential properties built within 

the former Argonaut Mine property, including four of the 12 residential properties in Area C (Ref. 15; 

Ref. 40, pp. 1-2, 4-5, 7). Based on samples collected pre- and post-removal, as well as samples collected 

during the 2014 SI, the total area of Area C is estimated to be approximately 97,350 square feet (see 

Attachment A-6). However, some of this area is covered by permanent or otherwise maintained, 

essentially impenetrable material. The average home is estimated to cover approximately 2,500 square 

feet, and an estimated 1,000 square feet of each property is paved (see Attachment A-5 and A-6) (Ref. 

45). Therefore, the Area of Contamination for Area C is estimated to be approximately 55,350 square 

feet (i.e., 97,350 square feet – (12 properties * 3,500 covered square feet per property)). 

The August 2015 removal action did not change the calculated area of Area C, because soils exceeding 

100 mg/kg arsenic were only removed to 12 inches bgs, and confirmation sampling showed that soils 

with elevated concentrations of arsenic were still present beneath the excavations (Ref. 39, pp. 7-10; 

Ref. 40, pp. 2, 4). 

During the August 2015 removal, the following actions were taken at each of the residential properties 

within Area C (Ref. 40, pp. 2, 4-5). Properties are identified by address code to preserve the privacy of 

the residents (Ref. 15). 

74 SE-General 
 

 

 

 

 

 

 

Area Letter: C 

Address Code Action 

ARA-09 No action. 

ARA-10 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,223 square 

feet (Ref. 39, p. 8; Ref. 40, pp. 2, 5). 

ARA-11 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,275 square 

feet (Ref. 39, p. 9; Ref. 40, pp. 2, 5). 

ARA-12 No action. 

ARA-13 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 2,846 square 

feet (Ref. 39, p. 7; Ref. 40, pp. 2, 5). 

ARA-23 No action. 

ARA-25 No action. 

ARA-26 No action. 

ARA-27 No action. 

ARA-28 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,025 square 

feet (Ref. 39, p. 10; Ref. 40, pp. 2, 5). 

ARA-31 No action. 

ARA-32 No action. 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a SAP 

approved by EPA on March 10, 2014. Samples were submitted to Bonner Analytical, located in 

Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for metals analysis by Inorganic 

Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical data were 

validated by EPA (Ref. 4, p. 22). 

- Background Concentrations: 

Background soil samples were collected from location AB-01 in pasture land located northwest of the 

Area A Tailings Impoundment and location AB-02 in pasture land located southwest of the Area A 

Tailings Impoundment (Ref. 4, p. 24). Background sampling locations are shown in Attachment A-3. 

Residential properties built within the former Argonaut Mine property boundary were built on imported 

fill placed over waste rock, tailings, and soils contaminated by Argonaut Mine operations (Ref. 4, pp. 

16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Prior to the construction of the Area A Tailings 

Impoundment and the AOC-2 Cyanide Plant, the property was farmland (Ref. 12, p. 28; Ref. 50). 

Therefore, background samples were collected from nearby pasture lands to be representative of local 

conditions without the Argonaut Mine. Sample depths of the background and release samples are all 

from the upper 2 feet, though depths are not directly comparable as the background locations are native 

soil while soils from the residential properties include tailings and waste rock generated by mining 

activities, as well as imported fill. 

75 SE-General 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Area Letter: C 

2014 SI, Area C Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 39-40, 66, 76, 1808, 1818­

1820, 1944; Ref. 18, p. 1; Ref. 23, pp. 

7, 15 

Lead 14.8 J (21.3) 1.0 

Mercury 0.15 0.10 

AB-01-1.5 1.0 -

1.5 7/31/14 

Arsenic 2.0 J- (3.5) 1.1 Ref. 4, pp. 39-40, 66, 76, 1808, 1830, 

1832, 1834, 1944; Ref. 20, p. 1; Ref. 

24, pp. 6, 10 

Lead 9 J (13.0) 1.1 

Mercury <0.11 0.11 

AB-02-0 0 - 0.5 7/28/14 

Arsenic 3.1 J- (5.4) 1.0 Ref. 4, pp. 39-40, 65, 1808, 1832, 

1834, 1941; Ref. 20, p. 1; Ref. 24, pp. 

6, 11 

Lead 11.2 J (16.1) 1.0 

Mercury <0.10 0.10 

AB-02-1.5 1.0 -

1.5 7/28/14 

Arsenic 1.2 J- (2.1) 1.1 Ref. 4, pp. 39-40, 65, 1808, 1830, 

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J (10.2) 1.1 

Mercury <0.11 0.11 

3X Highest Background (to 

establish concentrations 

significantly above background): 

Arsenic 26.7 

Lead 63.9** Ref. 9 

Mercury 0.45 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832, 1867). Therefore, the background 

value is multiplied by a factor of 1.74 for arsenic and 1.44 for lead. The adjusted value is included in parentheses (Ref. 9, 

pp. 8, 18) 

J-: The result is an estimated quantity, with a low bias (Ref. 4, p. 1830). The adjusted value is included in parentheses (Ref. 9, 

pp. 8, 18).
 

<: The analyte was not detected.
 

**: Calculated with the adjusted value.
 

^: Page 1831of Reference 4 presents a J qualifier for arsenic concentrations, and Reference 4 pages 1830 and 1834 indicate
 

that the reported results may be biased low.
 

- Contaminated Samples: 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations. Five sampling locations (ARA-09 through ARA-13) were collected from residential 

properties in Area C (Ref. 4, p. 28). Laboratory results are reported below. Analytical results from soils 

that were later removed during the August 2015 Removal Action are not reported. 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, sample 

locations are identified by address code only. Address codes are defined in a confidential reference (Ref. 

15). 

76	 SE-General 
 

 

 

 

 

 

 

 

 

 

 

 

 

Area Letter: C 

2014 Site Inspection, Area C Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-09 

ARA09-0 

(MY9F 

60) 

0 - 0.5 7/31/14 

Arsenic 1,380 J+ (793) 5.2 Ref. 4, pp. 40, 66, 1811, 

1873, 1876, 1945; Ref. 16, p. 

3; Ref. 21, pp. 7, 17 

Lead 226 1.0 

Mercury 1.4 0.21 

ARA09-2 

(MY9F 

61) 

1.5 - 2 7/31/14 

Arsenic 39,900 J+ 

(22,931) 123 Ref. 4, pp. 40, 66, 1811, 

1873, 1876, 1945; Ref. 16, p. 

3; Ref. 21, pp. 7, 18 Lead 3,220 9.9 

Mercury 193 24.6 

ARA-10 

ARA10-2 

(MY9F 

63) 

1.5 - 2 7/31/14 Arsenic 655 J+ (376) 1.1 

Ref. 4, pp. 40, 66, 1811, 

1873, 1877, 1944; Ref. 16, 

pp. 3-4; Ref. 21, pp. 7, 20 

ARA-12 

ARA12-2 

(MY9F 

67) 

1.5 - 2 7/31/14 Arsenic 58.6 J+ (33.7) 1.1 

Ref. 4, pp. 40, 66, 1811, 

1873, 1878, 1945; Ref. 16, p. 

5; Ref. 21, pp. 7, 24 

ARA-13 

ARA13-1 

(MY9F 

69) 

1.5 - 2 7/31/14 

Arsenic 1,200 J+ (690) 4.4 Ref. 4, pp. 40, 66, 1811, 

1873, 1878, 1945; Ref. 16, 

pp. 5-6; Ref. 21, pp. 7, 26 

Lead 225 1.1 

Mercury 1.8 0.33 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J+: The result is estimated and may be biased high (Ref. 4, pp. 1867, 1873). Therefore, the arsenic value is divided by a factor 

of 1.74. The adjusted value is included in parentheses (Ref. 9, pp. 8, 18). 

J: The result is estimated with an unknown bias (Ref. 4, pp. 1867, 1873). Therefore, the arsenic value is divided by a factor of 

1.74. The adjusted value is included in parentheses (Ref. 9, pp. 8, 18). 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified. 

^: Pages 3, 5 and 6 of Reference 16 present a J- qualifier for qualified arsenic samples, pages 1876-1878 of Reference 4 present 

arsenic concentrations without qualifiers, and Reference 4 page 1873 indicates that the qualified arsenic samples are biased 

high. 

March 2015 START Removal Assessment 

In March 2015, START conducted a removal assessment of 20 residential properties in the Argonaut 

Heights and Sierra View Estates neighborhoods (Ref. 4, p. 14; Ref. 11, p. 2). The residential properties 

were divided into two to six DUs composed of roughly equal areas at a maximum of 1,250 square feet 

each to cover unpaved areas of the property. A 5-point composite sample was collected from each DU at 

sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or hand auger and disposable 

scoops. Discrete samples were collected from some of the residences at the locations of play areas and 

gardens (Ref. 11, p. 2). 

Samples were analyzed for lead and arsenic via XRF, with at least one sample from each property 

submitted to a laboratory for confirmation. Confirmation samples were submitted to the EPA Region 9 

77 SE-General 
 

 

 

 

 

 

 

 

 

 

 

 

 

Area Letter: C 

Laboratory for analysis of arsenic and lead by EPA SW-846 Method 6010C (Ref. 11, pp. 3-4). Sampling 

locations are presented on Attachment A-5. Background sampling was not conducted during this 

sampling event; therefore, samples are compared to background concentrations from the 2014 SI 

sampling event. 

2015 EPA Removal Assessment, Area C Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA-09 R-12-03­

C-12 12 to 14 3/25/15 

Arsenic 680 10 Ref. 11, pp. 86, 91, 97; Ref. 

15; Ref. 39, pp. 16, 17; Ref. 

Lead 130 3 47, pp. 4, 29, 32, 42 

ARA10 (1) 

R-14-01­

C-12 12 to 14 3/25/15 Arsenic 220 2 

Ref. 11, pp. 86, 91, 97; Ref. 

15; Ref. 39, p. 17; Ref. 47, 

pp. 4, 30, 33, 42 

ARA11 (1) 

R-13-01­

C-12 12 to 14 3/25/15 

Arsenic 590 10 Ref. 11, pp. 86, 91, 97; Ref. 

15; Ref. 39, pp. 16, 17; Ref. 

Lead 120 3 47, pp. 4, 29, 32, 42 

ARA-12 R-04-02­

D-4 4 to 8 3/24/15 Arsenic 430 2 

Ref. 11, pp. 84, 91, 96; Ref. 

15; Ref. 39, pp. 14, 15; Ref. 

47, pp. 3, 28, 32, 41 

ARA13 (1) 

R-10-06­

C-16 16 to 18 3/25/15 

Arsenic 5,100 100 Ref. 11, pp. 85, 91, 97; Ref. 

15; Ref. 39, pp. 15, 16; Ref. 

Lead 1,900 3 47, pp. 4, 29, 32, 41 

ARA-23 R-01-02­

C-12 12 to 14 3/23/15 Arsenic 140 2 

Ref. 11, pp. 84, 91, 96; Ref. 

15; Ref. 39, pp. 12, 13; Ref. 

47, pp. 3, 28, 32, 41 

ARA-25 R-03-02­

C-0 0 to 2 3/23/15 Arsenic 270 2 

Ref. 11, pp. 84, 91, 96; Ref. 

15; Ref. 39, p. 13; Ref. 47, 

pp. 3, 28, 32, 41 

ARA-26 R-05-02­

C-0 0 to 2 3/24/15 

Arsenic 40 2 Ref. 11, pp. 86, 91, 96; Ref. 

15; Ref. 39, p. 14; Ref. 47, 

pp. 3, 28, 32, 41 Lead 83 3 

ARA-27 R-06-03­

D-16 16 to 18 3/24/15 

Arsenic 1,000 10 Ref. 11, pp. 86, 91, 96; Ref. 

15; Ref. 39, p. 14; Ref. 47, Lead 110 3 pp. 3, 28, 32, 41 

ARA28 (1) 

R-07-01­

C-12 12 to 14 3/24/15 Arsenic 40 2 

Ref. 11, pp. 86, 91, 96; Ref. 

15; Ref. 39, pp. 14, 15; Ref. 

47, pp. 3, 29, 32, 41 

ARA-31 R-18-01­

C-0 0 to 2 3/25/15 Arsenic 62 2 

Ref. 11, pp. 86, 91, 97; Ref. 

15; Ref. 39, p. 18; Ref. 47, 

pp. 4, 30, 33, 42 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

(1): Although a removal was conducted on this property, soils were not excavated to this depth (Ref. 15; Ref. 40, p. 2). 

Therefore, these soils are still present on the property. 

78 SE-General 
 

 

 

 

 

Area Letter: C 

EPA August 2015 Removal Action 

In August 2015, EPA conducted removal actions at several residential properties built within the former 

Argonaut Mine property, including four of the residential properties in Area C (Ref. 15; Ref. 40, pp. 1-2, 

4-5). Soils exceeding the action level of 100 mg/kg for arsenic were removed to 12 inches bgs and 

backfilled with clean topsoil (Ref. 40, p. 2). Confirmation samples were collected from 12 to 14 inches 

bgs within the excavations (Ref. 39, p. 1). Samples were analyzed for lead and arsenic via XRF, with at 

least one sample from each property submitted to a laboratory for confirmation. Confirmation samples 

were submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead by EPA SW-846 

Method 6010C (Ref. 11, pp 3-4, 120-121). 

Sampling locations are presented on Attachment A-5. Background sampling was not conducted during 

this sampling event; therefore, samples are compared to background concentrations from the 2014 SI 

sampling event. 

2015 EPA Removal Action, Area C Concentrations Significantly Above Background 

Address 

Code Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA-10 R-14-01-C12-082715 12 to 14 8/27/15 

Arsenic 1,500 2 Ref. 11, p. 121; Ref. 39, 

pp. 1, 75; Ref. 49, pp. 4, Lead 22-23, 27 320 3 

ARA-13 R-10-06-C12-082115 12 to 14 8/21/15 

Arsenic 5,300 4 Ref. 11, pp. 90-92, 120; 

Ref. 39, pp. 1, 77; Ref. 

Lead 1,600 3 49, pp. 3, 22-23, 27 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

79 SE-General 
 

 

 

 

 

 

 

 

 

Area Letter: C 

Area C Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total Hazardous Constituent Quantity for Area C could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for Area 

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

quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Area C could not be adequately determined according to 

the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Area C with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume: 

Tier C, volume is not applicable to source type pile for the soil exposure pathway (Ref. 1, Section 

5.1.2.2). 

Volume Assigned Value: 0 

Tier D: Area: 

Based on pre- and post-removal samples collected in 2015, as well as samples collected during the 2014 

SI, the total area of Area C is estimated to be approximately 97,350 square feet (see Attachment A-6). 

Any area where removal actions removed all hazardous substances at observed contamination levels in 

the top two feet of soil and/or tailings were not included in this area estimate. However, some of this 

area is covered by permanent or otherwise maintained, essentially impenetrable material. The average 

home is estimated to cover approximately 2,500 square feet, and an estimated 1,000 square feet of each 

property is paved (see Attachment A-5 and A-6) (Ref. 45). Therefore: 

97,350 square feet – (12 properties * 3,500 covered square feet per property) = 55,350 square feet 

55,350 / 34 = 1,627.9 (Ref. 1, Table 5-2) 

80 SE-General 
 

SE-General 

 

Area Letter: C 

Area Assigned Value: 1,627.9 

Area Hazardous Waste Quantity Value: 1,627.9 

81 
 

 

 

 

 

 

 

 

 

 

Area Letter: D 

5.0.1 GENERAL CONSIDERATIONS: Area D, Argonaut Heights – South Contaminated Soil 

Letter by which this area is to be identified: D 

Name of area: Argonaut Heights - South 

Source Type: Contaminated Soil 

Location and description of area (See Attachment A-4 through A-6): 

Area D correlates with Source 4, the Argonaut Heights - South Contaminated Soil. From 1989 through 

2004, the Argonaut Estates, Jackson View Estates, Sierra View Estates, and Argonaut Heights 

residential developments were reportedly built on areas of known waste rock and mine tailings that were 

covered with imported fill prior to construction of the homes (see Attachment A-4) (Ref. 4, pp. 16, 40; 

Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Elevated concentrations of arsenic, lead, and mercury have 

been detected in surface soils collected from 5 residential properties on Buena Vista Drive and Amador 

Street adjacent to the former cyanide plant located within EPA AOC-2 (Ref. 4, pp. 28, 48, 66; Ref. 11, 

p. 86; Ref. 15; Ref. 39, p. 1; see Attachment A-6). A historical aerial photo review conducted by EPA 

showed that the cyanide plant was accessed by a dirt road and dirt trail through these residential 

properties. A former flume was also observed extending across all 5 properties (see Attachment A-4) 

(Ref. 10, pp. 31, 36). During sampling conducted in 2014 and 2015, distinct tailings or waste rock were 

not visually identified in Area D; therefore, the source type is evaluated as Contaminated Soil (Ref. 46). 

In August 2015, EPA conducted removal actions at 11 residential properties built within the former 

Argonaut Mine property, including four of the five properties in Area D (Ref. 40, pp. 1-2, 4-5, 7). Based 

on samples collected pre- and post-removal, as well as samples collected during the 2014 SI, the total 

area of Area D is estimated to be approximately 72,511 square feet (see Attachment A-6). However, 

some of this area is covered by permanent or otherwise maintained, essentially impenetrable material. 

The average home is estimated to cover approximately 2,500 square feet, and an estimated 1,000 square 

feet of each property is paved (see Attachment A-5 and A-6) (Ref. 45). Therefore, the Area of 

Contamination for Area D is estimated to be approximately 55,011 square feet (i.e., 72,411 square feet – 

(5 properties * 3,500 covered square feet per property)). 

The August 2015 removal action did not change the calculated area of Area D, because soils exceeding 

100 mg/kg arsenic were only removed to 12 inches bgs, and confirmation sampling showed that soils 

with elevated concentrations of arsenic were still present beneath the excavations (Ref. 39, pp. 3-6; Ref. 

40, pp. 2, 4). 

During the August 2015 removal, the following actions were taken at each of the residential properties 

within Area D (Ref. 40, pp. 2, 4-5). Properties are identified by address code to preserve the privacy of 

the residents (Ref. 15). 

82 SE-General 
 

 

 

Area Letter: D 

Address Code Action 

ARA-15 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 2,846 square 

feet (Ref. 39, p. 5; Ref. 40, pp. 2, 4). 

ARA-16 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,798 square 

feet (Ref. 39, p. 6; Ref. 40, pp. 2, 5). 

ARA-17 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,275 square 

feet (Ref. 39, p. 4; Ref. 40, pp. 2, 4). 

ARA-24 No action. 

ARA-30 

Soils exceeding 100 mg/kg arsenic were removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 7,297 square 

feet (Ref. 39, p. 3; Ref. 40, pp. 2, 4). 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine. Samples were collected in accordance with a SAP 

approved by EPA on March 10, 2014. Samples were submitted to Bonner Analytical, located in 

Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for metals analysis by Inorganic 

Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012. The metals analytical data were 

validated by EPA (Ref. 4, p. 22). 

- Background Concentrations: 

Background soil samples were collected from location AB-01 in pasture land located northwest of the 

Source 1 Tailings Impoundment and location AB-02 in pasture land located southwest of the Area A 

Tailings Impoundment (Ref. 4, p. 24; see Attachment A-3). Background sampling locations are shown 

in Attachment A-3. 

Residential properties built within the former Argonaut Mine property boundary were built on imported 

fill placed over waste rock, tailings, and soils contaminated by Argonaut Mine operations (Ref. 4, pp. 

16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Prior to the construction of the Area A Tailings 

Impoundment and the AOC-2 Cyanide Plant, a portion of the property was farmland (Ref. 12, p. 28; 

Ref. 50). Therefore, background samples were collected from nearby pasture lands to be representative 

of local conditions without the Argonaut Mine. Sample depths of the background and release samples 

are all from the upper 2 feet, although the background locations are native soil while soils from the 

residential properties include tailings and waste rock generated by mining activities, as well as imported 

fill. 

83 SE-General 
 

 

 

 

 

 

 

 

 

 

 

 

Area Letter: D 

2014 SI, Area D Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 25, 39-40, 66, 76, 1808, 

1818-1820, 1944; Ref. 18, p. 1; Ref. 

23, pp. 7, 15 

Lead 14.8 J (21.3) 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2.0 J- (3.5) 1.1 Ref. 4, pp. 25, 39-40, 66, 76, 1808, 

1830, 1832, 1834, 1944; Ref. 20, p. 1; 

Ref. 24, pp. 6, 10 

Lead 9 J (13.0) 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J- (5.4) 1.0 Ref. 4, pp. 25, 39-40, 65, 1808, 1832, 

1834, 1941; Ref. 20, p. 1; Ref. 24, pp. 

6, 11 

Lead 11.2 J (16.1) 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J- (2.1) 1.1 Ref. 4, pp. 25, 39-40, 65, 1808, 1830, 

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J (10.2) 1.1 

Mercury <0.11 0.11 

3X Highest Background (to 

establish concentrations 

significantly above background): 

Arsenic 26.7 

Lead 63.9** Ref. 9 

Mercury 0.45 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19).). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832, 1867). Therefore, the background 

value is multiplied by a factor of 1.74 for arsenic and 1.44 for lead. The adjusted value is included in parentheses (Ref. 9, pp. 

8, 18). 

J-: The result is an estimated quantity, with a low bias (Ref. 4, pp. 1818, 1830-1832, 1867).
 

<: The analyte was not detected.
 

**: Calculated with the adjusted value.
 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified.
 

^: Page 1831of Reference 4 presents a J qualifier for arsenic, and Reference 4 pages 1830 and 1834 indicate that the reported
 

results may be biased low.
 

- Contaminated Samples: 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations. Three sampling locations (ARA-15 through ARA-17) were collected from the Argonaut 

Heights neighborhood adjacent to the AOC-2 cyanide plant (Ref. 4, p. 28). Analytical results from soils 

that were later removed during the 2015 Removal Action are not reported. 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, samples 

are identified by address code only. Sample address codes are defined in a confidential reference (Ref. 

15). 

84	 SE-General 
 

 

 

 

 

 

 

 

 

 

 

Area Letter: D 

2014 Site Inspection, Area D Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-15 

ARA15-1 

(MY9F 

73) 

1.5 - 2 7/31/14 

Arsenic 269 J+ (154) 1.1 Ref. 4, pp. 40, 1873, 1879, 

1944; Ref. 16, p. 7; Ref. 21, 

pp. 8, 30 

Lead 286 1.1 

Mercury 3.3 0.53 

ARA-16 

ARA16-1 

(MY9F 

75) 

0.5 - 1 7/31/14 

Arsenic 147 1.1 Ref. 4, pp. 40, 66, 1889, 

1944; Ref. 21, p. 8; Ref. 25, 

pp. 7, 12; Ref. 37, p. 1 

Lead 121 1.1 

Mercury 0.85 0.11 

ARA-17 

ARA17-2 

(MY9F 

77) 

1.5 - 2 7/31/14 Arsenic 123 1.1 

Ref. 4, pp. 40, 66, 1812, 

1888-1889, 1944; Ref. 21, p. 

8; Ref. 25, pp. 7, 14; Ref. 37, 

p. 2 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J+: The result is an estimated quantity, but the result may be biased high (Ref. 4, pp. 1867, 1873). Therefore, the value is divided 

by a factor of 1.74. The adjusted value is included in parentheses (Ref. 9, pp. 8, 18). 

J: The result is an estimated quantity with an unknown bias (Ref. 4, pp. 1873) The adjusted value is included in parentheses (Ref. 

9, pp. 8, 18). 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified. 

^: Page 7 of Reference 16 presents a J- qualifier, page 1944 of Reference 4 presents a J qualifier, and Reference 4 page 1879 

indicates that the reported results may be biased high. 

EPA March 2015 Removal Assessment 

In March 2015, EPA conducted a removal assessment of 20 residential properties in the Argonaut 

Heights and Sierra View Estates neighborhoods (Ref. 4, p. 14; Ref. 11, p. 2). The residential properties 

were divided into two to six DUs composed of roughly equal areas at a maximum of 1,250 square feet 

each to cover unpaved areas of the property. A 5-point composite sample was collected from each DU at 

sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or hand auger and disposable 

scoops. Discrete samples were collected from some of the residences at the locations of play areas and 

gardens (Ref. 11, p. 2). Samples were analyzed for lead and arsenic via XRF, with at least one sample 

from each property submitted to a laboratory for confirmation. Confirmation samples were submitted to 

the EPA Region 9 Laboratory for analysis of arsenic and lead by EPA SW-846 Method 6010C (Ref. 11, 

pp. 3-4). 

Sampling locations are presented in Attachment A-5. Analytical results from soils that were later 

removed during the August 2015 EPA Removal Action are not reported. Background sampling was not 

conducted during this sampling event; therefore, samples are compared to background concentrations 

from the 2014 SI sampling event. 

85	 SE-General 
 

 

 

 

 

 

 

 

 

 

Area Letter: D 

2015 EPA Removal Assessment, Area D Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA15 (1) 

R-08-04­

C-12 12 to 14 3/24/15 

Arsenic 340 2 Ref. 11, pp. 85, 96; Ref. 39, 

pp. 14, 15; Ref. 47, pp. 3, 

29, 32, 41 Lead 280 3 

ARA16 (1) 

R-09-03­

C-12 12 to 14 3/24/15 

Arsenic 350 2 Ref. 11, pp. 85, 90-92, 96; 

Ref. 39, pp. 15, 16; Ref. 47, 

pp. 3, 29, 32, 41 Lead 500 3 

ARA-17 

R-19-02­

C-12 (1) 12 to 14 3/27/15 Arsenic 130 2 

Ref. 11, pp. 87, 105; Ref. 

39, p. 18; Ref. 47, pp. 9, 31, 

33, 44 

R-19-04­

C-0 (2) 0 to 2 6/23/15 Arsenic 92 2.1 

Ref. 11, pp. 87, 115; Ref. 

39, p. 4; Ref. 48, pp. 4, 25­

26, 30 

ARA-24 R-02-02­

C-0 0 to 2 3/23/15 Arsenic 69 2 

Ref. 11, pp. 84, 96; Ref. 39, 

p. 13; Ref. 47, pp. 3, 28, 32, 

41 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

(1): Although a removal was conducted on this property, soils were not excavated to this depth (Ref. 15; Ref. 41, p. 2). 

Therefore, these soils are still present on the property. 

(2): Although a removal was conducted on this property, soils were not excavated at this location because the arsenic 

concentration was below the removal action level of 100 mg/kg (Ref. 39, p. 4; Ref. 40, p. 2). 

EPA August 2015 Removal Action 

In August 2015, EPA conducted removal actions at 11 residential properties built in the area of former 

Argonaut Mine operations, including four of the properties in Source 4 (Ref. 15; Ref. 40, pp. 1-2, 4-5). 

Soils exceeding the action level of 100 mg/kg for arsenic were removed to 12 inches bgs and backfilled 

with clean topsoil (Ref. 40, p. 2). Confirmation samples were collected from 12 to 14 inches bgs within 

the excavations (Ref. 39, p. 1). Samples were analyzed for lead and arsenic via XRF, with at least one 

sample from each property submitted to a laboratory for confirmation. Confirmation samples were 

submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead by EPA SW-846 Method 

6010C (Ref. 11, pp. 120-121). 

Sampling locations are presented on Attachment A-5. Background sampling was not conducted during 

this sampling event; therefore, samples are compared to background concentrations from the 2014 SI 

sampling event. 

86 SE-General 
 

 

 

 

Area Letter: D 

2015 EPA Removal Action, Area D Concentrations Significantly Above Background 

Address 

Code Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

ARA-16 R-09-03-C12-082415 12 to 14 8/24/15 

Arsenic 580 2 Ref. 11, p. 120; Ref. 

15; Ref. 39, pp. 1, 71 Lead 570 3 

ARA-30 R-17-02E-C12-081815 12 to 14 8/18/15 Arsenic 120 2 Ref. 11, p. 120; Ref. 

15; Ref. 39, p. 1 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

87 SE-General 
 

 

 

 

 

Area Letter: D 

Area D Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total Hazardous Constituent Quantity for Area D could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for Area 

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

quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Area D could not be adequately determined according to 

the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Area D with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume: 

Tier C, volume is not applicable to Contaminated Soil for the soil exposure pathway (Ref. 1, Section 

5.1.2.2). 

Volume Assigned Value: 0 

88 SE-General 
 

 

 

 

Area Letter: D 

Tier D: Area: 

Based on pre- and post-removal samples collected in 2015, as well as samples collected during the 2014 

SI, the area of Area D is estimated to be approximately 72,511 square feet (see Attachment A-6). Any 

area where removal actions removed all hazardous substances at observed contamination levels in the 

top two feet of soil and/or tailings were not included in this area estimate. However, some of this area is 

covered by permanent or otherwise maintained, essentially impenetrable material. The average home is 

estimated to cover approximately 2,500 square feet, and an estimated 1,000 square feet of each property 

is paved (see Attachment A-5 and A-6) (Ref. 45). Therefore: 

72,511 square feet – (5 properties * 3,500 covered square feet per property) = 55,011 

55,011 / 34,000 = 1.6 (Ref. 1, Table 5-2) 

Area Assigned Value: 1.6 

Area Hazardous Waste Quantity Value: 1.6 

89 SE-General 
 

 

 

 

 

 

 

 

Area Letter: E 

5.0.1 GENERAL CONSIDERATIONS; Area E, Sierra View Estates Contaminated Soil 

Letter by which this area is to be identified: E 

Name of area: Sierra View Estates Contaminated Soil 

Source Type: Contaminated Soil 

Location and description of area (See Attachment A-4 through A-6): 

Area E correlates with Source 5, the Sierra View Estates Contaminated Soil. From 1989 through 2004, 

the Argonaut Estates, Jackson View Estates, Sierra View Estates, and Argonaut Heights residential 

developments were reportedly built on areas of known waste rock and mine tailings that were covered 

with imported fill prior to construction of the homes (see Attachment A-4) (Ref. 4, pp. 16, 40; Ref. 8, p. 

1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Elevated concentrations of arsenic, lead, and mercury have been 

detected in surface soils collected from three residential properties on Detert Lane adjacent to the Source 

1 Tailings Impoundment (Ref. 4, pp. 23, 48, 66; Ref. 15; see Attachment A-6). A historical aerial photo 

review conducted by EPA showed a former flume across this area (see Attachment A-4) (Ref. 10, pp. 

23, 28, 32, 36). During sampling conducted in 2014 and 2015, distinct tailings or waste rock were not 

visually identified in Area E; therefore, the source type is evaluated as Contaminated Soil (Ref. 46). 

In August and September 2015, EPA conducted removal actions at 11 residential properties built within 

the former Argonaut Mine property, including two of the three properties in Area E (Ref. 40, pp. 1-2, 4­

5, 7; Ref. 15; see Attachment A-6). Based on samples collected pre- and post-removal, as well as 

samples collected during the 2014 SI, the area of Area E is estimated to be approximately 40,341 square 

feet (see Attachment A-6). However, some of this area is covered by permanent or otherwise 

maintained, essentially impenetrable material. The average home is estimated to cover approximately 

2,500 square feet, and an estimated 1,000 square feet of each property is paved (see Attachment A-5 and 

A-6) (Ref. 45). Therefore, the Area of Contamination for Area E is estimated to be approximately 

29,841 square feet (i.e., 40,341 square feet – (3 properties * 3,500 covered square feet per property)). 

The removal action did not change the calculated area of Area E, because soils with arsenic exceeding 

100 mg/kg were only removed to 12 inches bgs, or were left in place and covered with wood chips and 

rock. Confirmation sampling showed that soils with elevated concentrations of arsenic were still present 

beneath the excavation (Ref. 39, p. 2; Ref. 40, pp. 2, 4). 

During the August 2015 removal, the following actions were taken at each of the residential properties 

within Area E (Ref. 40, pp. 2, 4-5). Properties are identified by address code to preserve the privacy of 

the residents (Ref. 15). 

90 SE-General 
 

 

Area Letter: E 

Address Code Action 

ARA-18 No soils were removed. An area of 5,324 square feet was covered with wood 

chips and rock (Ref. 40, pp. 2, 4). 

ARA-19 No action. 

ARA-29 

Soil exceeding 100 mg/kg arsenic was removed to a depth of 12 inches and 

backfilled with clean topsoil. Removed soils covered an area of 1,275 square 

feet (Ref. 39, p. 2; Ref. 40, pp. 2, 4). 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine (Ref. 4, pp. 6, 22). Samples were collected in 

accordance with a SAP approved by EPA on March 10, 2014 (Ref. 4, p. 22). Samples were submitted to 

Bonner Analytical, located in Hattiesburg, Mississippi, under the EPA Contract Laboratory Program for 

metals analysis by Inorganic Superfund Methods (ISM01.3) and cyanide by EPA Method 9010/9012 

(Ref. 4, p. 22). The metals analytical data were validated by EPA (Ref. 4, p. 22). 

- Background Concentrations: 

Background soil samples were collected from location AB-01 in pasture land located northwest of the 

Tailings Area and location AB-02 in pasture land located southwest of the Tailings Area (Ref. 4, p. 24). 

Background sampling locations are shown in Attachment A-3. 

Residential properties built within the former Argonaut Mine property boundary were built on imported 

fill placed over waste rock, tailings, and soils contaminated by Argonaut Mine operations (Ref. 4, pp. 

16, 40; Ref. 8, p. 1; Ref. 26, p. 2; Ref. 27, pp. 2-3). Prior to the construction of the Source 1 Tailings 

Impoundment and the AOC-2 Cyanide Plant, a part of the property was farmland (Ref. 12, p. 28; Ref. 

50). Therefore, background samples were collected from nearby pasture lands to be representative of 

local conditions without the Argonaut Mine. Sample depths of the background and release samples are 

all from the upper 2 feet, although the background locations are native soil while soils from the 

residential properties include tailings and waste rock generated by mining activities, as well as imported 

fill (See 2014 SI, Area E Background Soil Concentrations and 2014 Site Inspection, Area E Soil 

Concentrations Significantly Above Background Tables below). 

91 SE-General 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Area Letter: E 

2014 SI, Area E Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 39-40, 66, 76, 1808, 1818­

1820, 1944; Ref. 18, p. 1; Ref. 23, pp. 

7, 15 

Lead 14.8 J (21.3) 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2.0 J- (3.5) 1.1 Ref. 4, pp. 39-40, 66, 76, 1808, 1830, 

1832, 1834, 1944; Ref. 20, p. 1; Ref. 

24, pp. 6, 10 

Lead 9 J (13.0) 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J- (5.4) 1.0 Ref. 4, pp. 39-40, 65, 1808, 1832, 

1834, 1941; Ref. 20, p. 1; Ref. 24, pp. 

6, 11 

Lead 11.2 J (16.1) 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J- (2.1) 1.1 Ref. 4, pp. 39-40, 65, 1808, 1830, 

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J (10.2) 1.1 

Mercury <0.11 0.11 

3X Highest Background (to 

establish concentrations 

significantly above background): 

Arsenic 26.7 

Lead 63.9** Ref. 9 

Mercury 0.45 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832). Therefore, the background value is 

multiplied by a factor of 1.74 for arsenic and 1.44 for lead. The adjusted value is included in parentheses (Ref. 9, pp. 8, 18) 

J-: The result is an estimated quantity, with a low bias (Ref. 4, pp. 1818, 1830-1832, 1867). 

<: The analyte was not detected. 

**: Calculated with the adjusted value. 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified. 

^: Page 1831of Reference 4 presents a J qualifier for arsenic concentrations, and Reference 4 pages 1830 and 1834 indicate that 

the reported results may be biased low. 

- Contaminated Samples: 

Surface soil and shallow subsurface soil samples were collected from 19 residential lots and from 

Jackson Junior High School to assess whether the properties were impacted by historical Argonaut Mine 

operations (Ref. 4, p. 28). Two sampling locations (ARA-18 and ARA-19) were collected from the 

Sierra View Estates neighborhood adjacent to the Source 1 Tailings Impoundment (Ref. 4, p. 28). No 

soils were removed from these properties during the August 2015 Removal Action. 

Sampling locations are presented in Attachment A-5. To preserve the privacy of local residents, sample 

locations are identified by address code only. Address codes are defined in a confidential reference (Ref. 

15). 

92	 SE-General 
 

 

 

 

 

 

 

 

 

Area Letter: E 

2014 Site Inspection, Area E Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

ARA-18 

ARA18-0 

(MY9F 

78) 

0 - 0.5 7/31/14 

Arsenic 310 1.0 Ref. 4, pp. 40, 66, 1812, 

1890, 1944; Ref. 25, pp. 7, 

Mercury 0.63 0.10 15; Ref. 37, p. 2 

ARA18-1.5 

(MY9D 

79) 

1 - 1.5 7/31/14 

Arsenic 423 1.1 Ref. 4, pp. 40, 66, 1812, 

1890, 1944; Ref. 25, pp. 7, 

16; Ref. 37, pp. 2-3 

Lead 115 1.1 

Mercury 1.4 0.21 

ARA-19 

ARA19-0 

(MY9F 

81) 

0 - 0.5 7/31/14 Arsenic 55.3 1.1 

Ref. 4, pp. 40, 66, 1812, 

1888, 1890, 1944; Ref. 25, 

pp. 7, 17; Ref. 37, p. 3 

ARA19-1 

(MY9F 

82) 

1.5 - 2 7/31/14 Arsenic 122 1.1 

Ref. 4, pp. 40, 66, 1812, 

1888, 1890, 1944; Ref. 25, 

pp. 7, 18; Ref. 37, p. 3 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

EPA March 2015 Removal Assessment 

In March 2015, EPA conducted a removal assessment of 20 residential properties in the Argonaut 

Heights and Sierra View Estates neighborhoods (Ref. 4, p. 14; Ref. 11, pp. 2, 6). The residential 

properties were divided into two to six DUs composed of roughly equal areas at a maximum of 1,250 

square feet each to cover unpaved areas of the property (Ref. 11, p. 2). A 5-point composite sample was 

collected from each DU at sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or 

hand auger and disposable scoops (Ref. 11, p. 2). Discrete samples were collected from some of the 

residences at the locations of play areas and gardens (Ref. 11, p. 2). Samples were analyzed for lead and 

arsenic via XRF, with at least one sample from each property submitted to a laboratory for confirmation. 

Confirmation samples were submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead 

by EPA SW-846 Method 6010C (Ref. 11, pp. 3-4). 

Sampling locations are presented in Attachment A-5. Background sampling was not conducted during 

this sampling event; therefore, samples are compared to background concentrations from the 2014 SI 

sampling event. 

93 SE-General 
 

 

 

 

 

 

 

 

 

Area Letter: E 

2015 EPA Removal Assessment, Area E Concentrations Significantly Above Background 

Address 

Code 

Sample 

ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

mg/kg 

QL 

(mg/kg) References 

ARA18 (2) 

R-16-01­

C-0 0 to 2 3/26/15 Arsenic 210 2 

Ref. 11, pp. 86, 91, 97; Ref. 

39, p. 18; Ref. 47, pp. 4, 30, 

33, 39 

R-16-04­

C-0 0 to 2 6/23/15 Arsenic 100 2 

Ref. 11, pp. 86, 107, 115; 

Ref. 48, pp. 4, 24, 26, 30, 

32 

ARA29 (1) 

R-15-02­

C-12 12 to 14 3/26/15 

Arsenic 910 10 Ref. 11, pp. 86, 91, 97; Ref. 

39, p. 17; Ref. 47, pp. 4, 30, 

Lead 66 3 33, 39 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

(1): Although a removal was conducted on this property, soils were not excavated to this depth (Ref. 15; Ref. 41, p. 2). 

(2): Although a removal was conducted on this property, no soils were excavated. Soils exceeding the action level were 

covered with wood chips and rock (Ref. 40, pp. 2, 4). 

94 SE-General 
 

 

 

 

 

Area Letter: E 

Area E Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total Hazardous Constituent Quantity for Area E could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for Area 

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

quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Area E could not be adequately determined according to 

the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Area E with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume: 

Tier C, volume is not applicable to Contaminated Soil for the soil exposure pathway (Ref. 1, Section 

5.1.2.2). 

Volume Assigned Value: 0 

95 SE-General 
 

 

 

 

 

Area Letter: E 

Tier D: Area: 

Based on pre- and post-removal samples collected in 2015, as well as samples collected during the 2014 

SI, the area of Area E is estimated to be approximately 40,341 square feet (see Attachment A-6). Any 

area where removal actions removed all hazardous substances at observed contamination levels in the 

top two feet of soil and/or tailings were not included in this area estimate. However, some of this area is 

covered by permanent or otherwise maintained, essentially impenetrable material. The average home is 

estimated to cover approximately 2,500 square feet, and an estimated 1,000 square feet of each property 

is paved (see Attachment A-5 and A-6) (Ref. 45). Therefore: 

40,341 square feet – (3 properties * 3,500 covered square feet per property) = 29,841 

29,841 / 34,000 = 0.9 (Ref. 1, Table 5-2) 

Area Assigned Value: 0.9 

Area Hazardous Waste Quantity Value: 0.9 

96 SE-General 
 

 

 

 

 

 

 

 

Area Letter: F 

5.0.1 GENERAL CONSIDERATIONS: Area F, Jackson Junior High School Tailings Pile 

Letter by which this area is to be identified: F 

Name of area: Jackson Junior High School Tailings Pile 

Source Type: Tailings Pile 

Location and description of area (See Attachment A-7): 

Area F correlates with Source 6, the Jackson Junior High School Tailings Pile (See Attachment A-2) 

(Ref. 4, p. 26). Exposed fill material resembling processed tailings was observed in the east-facing slope 

of the athletic field embankment (Ref. 4, pp. 28, 77; Ref. 34, p. 2, 609, 611-612). The upper athletic 

field playing area may have been constructed using mine tailings imported from the Argonaut Mine 

(Ref. 10, p. 36; Ref. 34, pp. 2, 4, 609, 611). It appears the tailings were subsequently covered with 

imported soil to establish a grass field. The extent of mine tailings and soil cover at the athletic field is 

unknown. At several locations, a mound of black tailings was observed adjacent to a ground squirrel 

burrow, suggesting that ground squirrels are bringing tailings to the surface of the playing field (Ref. 34, 

pp. 2, 3, 609, 610). 

Elevated concentrations of arsenic, lead, and mercury were detected in samples collected from the 

athletic field embankment, as well as from the outdoor lunch area above the embankment (Ref. 4, pp. 

28, 31; Ref. 11, pp. 5, 88, Ref. 34, pp. 2-3) 

In July 2015, EPA conducted a removal action at Jackson Junior High School (Ref. 34, p. 3). The 

eastern portion of the athletic field was divided into 10 DUs (see Attachment A-7) (Ref. 11, pp. 5, 10; 

Ref. 34, p. 13). DUs 1 through 5 were along the exposed eastern embankment of the athletic field. DUs 

6 through 10 were from the outdoor lunch area above the embankment (Ref. 11, p. 5). DU 6 is located 

adjacent to the snack bar (Ref. 34, p. 612). DUs 1 through 5 were capped with shotcrete and fenced (Ref. 

34, pp. 3-5, 13). Tailings-impacted soils were excavated from DU-6 and the northern portion of DU-7 to 

a maximum depth of one foot bgs (Ref. 34, p. 4). The excavations were backfilled with clean fill (Ref. 

34, p. 5). 

Based on laboratory sampling results from DU-6, DU-7, and DU-9, elevated concentrations of arsenic 

are still present in these DUs within 2 feet of the surface (Ref. 11, p. 88, Ref. 34, pp. 17, 19, 612; see 

Attachment A-7). Laboratory samples were not collected from DUs 8 and 10 (Ref. 34, p. 17). Therefore, 

a minimum area of the Area F tailings pile is estimated based on the areas of DU-6, -7, and -9. The area 

of DU-6 is 1,513 square feet, the area of DU-7 is 2,002 square feet, and the area of DU-9 is 2,918 square 

feet (see Attachment A-7). 

- Background Concentrations: 

Weston Solutions, Inc. 2014 SI Soil Sampling 

From July 28, 2014 through August 1, 2014, Weston Solutions, Inc. collected soil, sediment and surface 

water samples as part of a SI of the Argonaut Mine (Ref. 4, pp. 1, 22). Samples were collected in 

accordance with a SAP approved by EPA on March 10, 2014 (Ref. 4, pp. 1, 22). Samples were 

submitted to Bonner Analytical, located in Hattiesburg, Mississippi, under the EPA Contract Laboratory 

97 SE-General 
 

 

 

 

 

 

 

Area Letter: F 

Program for metals analysis by Inorganic Superfund Methods (ISM01.3) and cyanide by EPA Method 

9010/9012 (Ref. 4, p. 22). The metals analytical data were validated by EPA (Ref. 4, p. 22). 

Background soil samples were collected from location AB-01 in pasture land located northwest of the 

Tailings Area and location AB-02 in pasture land located southwest of the Tailings Area (Ref. 4, p. 24). 

Background sampling locations are shown in Attachment A-3. 

The Jackson Junior High School upper athletic field playing area appears to have been constructed of 

mine tailings covered with imported soil (Ref. 10, p. 36; Ref. 34, pp. 2, 4). Prior to the construction of 

the Source 1 Tailings Impoundment and the AOC-2 Cyanide Plant, the property was farmland (Ref. 12, 

p. 28; Ref. 50). Therefore, background samples were collected from nearby pasture lands to be 

representative of local conditions without the Argonaut Mine. Sample depths of the background and 

release samples are all from the upper 2 feet, although the background locations are native soil while 

soils from the Jackson Junior High School athletic field include tailings generated by mining activities, 

as well as imported fill (See 2014 SI, Area F Background Soil Concentrations and 2015 EPA Removal 

Assessment, Area F Concentrations Significantly Above Background Tables below). 

2014 SI, Area F Background Soil Concentrations 

Sample ID 

Sample 

Depth 

(feet) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration+ ^ 

(mg/kg) 

Sample 

Adjusted 

CRQL* 

(mg/kg) 

References 

AB-01-0 

(MY9EX7) 0 - 0.5 7/31/14 

Arsenic 8.9 1.0 Ref. 4, pp. 39-40, 66, 76, 1808, 1818­

1820, 1944; Ref. 18, p. 1; Ref. 23, pp. 

7, 15 

Lead 14.8 J (21.3) 1.0 

Mercury 0.15 0.10 

AB-01-1.5 

(MY9EY0) 

1.0 -

1.5 7/31/14 

Arsenic 2 J- (3.5) 1.1 Ref. 4, pp. 39-40, 66, 76, 1808, 1830, 

1832, 1834, 1944; Ref. 20, p. 1; Ref. 

24, pp. 6, 10 

Lead 9 J (13.0) 1.1 

Mercury <0.11 0.11 

AB-02-0 

(MY9EY1) 0 - 0.5 7/28/14 

Arsenic 3.1 J- (5.4) 1.0 Ref. 4, pp. 39-40, 65, 1808, 1832, 

1834, 1941; Ref. 20, p. 1; Ref. 24, pp. 

6, 11 

Lead 11.2 J (16.1) 1.0 

Mercury <0.10 0.10 

AB-02-1.5 

(MY9EY2) 

1.0 -

1.5 7/28/14 

Arsenic 1.2 J- (2.1) 1.1 Ref. 4, pp. 39-40, 65, 1808, 1830, 

1832, 1834, 1941; Ref. 20, pp. 1-2; 

Ref. 24, pp. 6, 12 

Lead 7.1 J (10.2) 1.1 

Mercury <0.11 0.11 

3X Highest Background (to 

establish concentrations 

significantly above background): 

Arsenic 26.7 

Lead 63.9** Ref. 9 

Mercury 0.45 

98 SE-General 
 

 

 

 

 

 

 

Area Letter: F 

mg/kg: milligrams analyte per kilogram soil 

CRQL: EPA Contract Laboratory Program Contract Required Quantitation Limit 

*: The Sample Adjusted CRQL is the CRQL adjusted for sample weight, volume, dilution, and percent solid (Ref. 19). 

J: The result is an estimated quantity, with an unknown bias (Ref. 4, pp. 1818, 1830-1832). Therefore, the background value is 

multiplied by a factor of 1.74 for arsenic and 1.44 for lead. The adjusted value is included in parentheses (Ref. 9, pp. 8, 18) 

J-: The result is an estimated quantity, with a low bias (Ref. 4, pp. 1818, 1830-1832, 1867). 

<: The analyte was not detected. 

**: Calculated with the adjusted value. 

+: Qualified data presented in this table reflect a positive identification of the substance, although the data may be qualified. 

^: Page 1831of Reference 4 presents a J qualifier for arsenic concentration, and Reference 4 pages 1830 and 1834 indicate that 

the reported results may be biased low. 

99 SE-General 
 

 

 

 

 

 

 

 

 

 

 

Area Letter: F 

- Contaminated Samples: 

EPA June and July 2015 Removal Assessment 

In June and July 2015, EPA conducted a removal assessment of Jackson Junior High School (Ref. 11, p. 

2). A total of 20 composite soil samples (10 surface and 10 subsurface) from 10 DUs were collected 

from the athletic field for metal analysis (Ref. 11, p. 2). A 5-point composite sample was collected from 

each DU at sampling intervals of 0 to 2 inches and 12 to 18 inches bgs using a trowel or hand auger and 

disposable scoops (Ref. 11, p. 2). Samples were analyzed for lead and arsenic via XRF (Ref. 11, p. 3). 

Laboratory samples were submitted to the EPA Region 9 Laboratory for analysis of arsenic and lead by 

EPA SW-846 Method 6010C (Ref. 11, pp. 3-4). 

Sampling locations are shown on Attachment A-7. Analytical results from soils that were later removed 

or covered with shotcrete during the July 2015 EPA Removal Action are not reported below. 

Background sampling was not conducted during this sampling event; therefore, samples are compared to 

background concentrations from the 2014 SI sampling event. 

2015 EPA Removal Assessment, Area F Concentrations Significantly Above Background 

DU Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

DU6 (1) 

JJHS-C-02­

14-072715 12 to 14 7/27/15 Arsenic 290 2 

Ref. 11, p. 88, 120; Ref. 34, 

pp. 600- 601; Ref. 39, pp. 

20, 22; Ref. 49, pp. 3, 21, 

23, 27 

DU7 (1) 

JJHS-C-06­

14-072715 12 to 14 7/27/15 Arsenic 100 2 

Ref. 11, p. 88, 120; Ref. 34, 

pp. 600- 601; Ref. 39, pp. 

20, 22; Ref. 49, pp. 3, 21, 

23, 27 

DU-9 JJHS-C-10­

2-072715 0 to 2 7/27/15 Arsenic 62 2 

Ref. 11, p. 88, 120; Ref. 34, 

pp. 600- 601; Ref. 39, pp. 

21-22; Ref. 49, pp. 3, 21, 

23, 27 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

(1): Although a removal was conducted in this DU, soils were not excavated to this depth (Ref. 34, p. 4). 

EPA July 2015 Removal Action 

In July 2015, EPA conducted a Removal Action at the Jackson Junior High School athletic field (Ref. 

34, pp. 1, 4). Confirmation soil samples were collected from the excavations, and analyzed for lead and 

arsenic via XRF (Ref. 34, pp. 1, 6-7). Laboratory samples were submitted to the EPA Region 9 

Laboratory for analysis of arsenic and lead by SW-846 Method 6010C (Ref. 34, p. 600). The sampling 

location is shown on Attachment A-7. Background sampling was not conducted during this sampling 

event; therefore, samples are compared to background concentrations from the 2014 SI sampling event. 

100 SE-General 
 

 

 

Area Letter: F 

2015 EPA Removal Action, Area F Sampling Concentrations Significantly Above Background 

DU Sample ID 

Sample 

Depth 

(inches) 

Date Hazardous 

Substance 

Hazardous 

Substance 

Concentration 

(mg/kg) 

QL 

(mg/kg) References 

DU-7 JJHS-C-17­

12-080315 12 to 14 8/3/15 Arsenic 79 2 

Ref. 34, pp. 19, 600, 

Ref. 39, p. 34; Ref. 49, 

pp. 3, 22-23, 27 

mg/kg: milligrams analyte per kilogram soil 

QL: Quantitation Limit. EPA Region 9 Laboratory Quantitation Limits are equivalent to Sample Quantitation Limits 

(SQLs) (Ref. 43). 

101 SE-General 
 

 

 

 

 

 

Area Letter: F 

Area F Hazardous Waste Quantity 

Tier A: Hazardous Constituent Quantity 

The total Hazardous Constituent Quantity for Area F could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the source and 

releases from the source is not known and cannot be estimated with reasonable confidence (Ref. 1, 

Section 2.4.2.1.1). Insufficient historical and current data (permits, waste concentration data, annual 

reports, etc.) are available to adequately calculate the total mass, or a partial estimate, of all CERCLA 

hazardous substances in the source and the associated releases from the source. Therefore, there is 

insufficient information to calculate a total or partial Hazardous Constituent Quantity estimate for Area 

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

quantity (Ref. 1, Section 2.4.2.1.2). 

Hazardous Constituent Quantity Value: NE 

Tier B: Hazardous Wastestream Quantity 

The total Hazardous Wastestream Quantity for Area F could not be adequately determined according to 

the HRS requirements; that is, the total mass, or a partial estimate, of all hazardous wastestreams and 

CERCLA pollutants and contaminants for the source and releases from the source is not known and 

cannot be estimated with reasonable confidence (Ref. 1, Section 2.4.2.1.2). Insufficient historical and 

current data (permits, waste concentration data, annual reports, etc.) are available to adequately calculate 

the total mass, or a partial estimate, of all hazardous wastestreams and CERCLA pollutants and 

contaminants for the source and the associated releases from the source. Therefore, there is insufficient 

information to adequately calculate or extrapolate a total or partial Hazardous Wastestream Quantity for 

Area F with reasonable confidence. Scoring proceeds to the evaluation of Tier C, volume (Ref. 1, 

Section 2.4.2.1.3). 

Hazardous Wastestream Quantity Value: NE 

Tier C: Volume: 

Tier C, volume is not applicable to source type pile for the soil exposure pathway (Ref. 1, Section 

5.1.2.2). 

Volume Assigned Value: 0 

Tier D: Area: 

Based on samples collected pre- and post-removal, the area of Area F is estimated to be approximately 

6,433 square feet (see Attachment A-7). Any area where removal actions removed all hazardous 

substances at observed contamination levels in the top two feet of soil and/or tailings were not included 

in this area estimate. This area was calculated by adding the areas of DU-6, -7, and -9. In accordance 

with Ref. 1, Table 5-2: 

6,433 / 34 = 189.2 

Area Assigned Value: 189.2 

Area Hazardous Waste Quantity Value: 189.2 

102 SE-General 
 

 

 

 

 

 

 

5.1 RESIDENT POPULATION THREAT 

5.1.1 LIKELIHOOD OF EXPOSURE 

During the 2014 SI and the 2015 Removal Assessment, soil samples collected from residences built 

within the former Argonaut Mine property contained arsenic, lead, and/or mercury at concentrations 

significantly above background (see Areas B through E for sampling results). Soil samples collected 

from Jackson Junior High School contained arsenic, lead, and/or mercury at concentrations significantly 

above background (see Area F for sampling results). These sampling locations are within an area of 

observed contamination due to the release from the Argonaut Mine site. Arsenic was detected at 

concentrations exceeding the Cancer Risk Screening Concentration of 0.71 mg/kg ((Ref. 1, [Sections 

2.5.1 and 5.3.1], pp. 51596, 51647; Ref. 2, p. 27). Therefore, Level I Actual Contamination is assigned. 

The residential properties all measure less than 200 feet in length and width; therefore, the observed 

contamination sample from the same property is located within 200 feet of the residence on that property 

(see Attachment A-6). The observed contamination at Jackson Junior High School is located at the edge 

of the athletic field in a regularly-occupied lunch area adjacent to the snack bar (see Attachment A-7) 

(Ref. 34, pp. 2-3, 8, 13, 612-613). 

Resident Population Threat Likelihood of Exposure Factor Category Value: 550 

5.1.2 WASTE CHARACTERISTICS 

5.1.2.1 Toxicity 

Hazardous Substance Toxicity Factor Value References 

Arsenic 10,000 Ref. 2, p. 1 

Lead 10,000 Ref. 1, p. 51590; Ref. 2, pp. 7-8 

Mercury 10,000 Ref. 2, pp. 9-10 

Toxicity Factor Value: 10,000 

5.1.2.2 Hazardous Waste Quantity 

Area Letter Source Type Area Hazardous Waste Quantity 

A Pile 61,496.5 

B Pile 2,029.4 

C Pile 1,627.9 

D Contaminated Soil 1.6 

E Contaminated Soil 0.9 

F Pile 189.2 

Sum of Values: 66,889.6 

103 SE-Resident Population Threat 
 

 

 

 

Hazardous Waste Quantity Factor Value (Ref. 1, Table 2-6): 10,000 

5.1.2.3 Calculation of Waste Characteristics Factor Category Value 

Toxicity Factor Value: 10,000 

Hazardous Waste Quantity Factor Value: 10,000 

Toxicity Factor Value x Hazardous Waste Quantity Factor Value: 100,000,000 

Waste Characteristics Factor Category Value (Ref. 1, Table 2-7): 100 

104 SE-Resident Population Threat 
 

 

5.1.3 TARGETS
 

Level I Concentrations 

Address 

Code Sample ID Hazardous 

Substance 

Hazardous 

Substance 

Concentration* 

mg/kg 

Benchmark 

Concentration 

mg/kg 

Benchmark Reference 

Argonaut Estates (Area B) 

ARA-07 

ARA-07-0 Arsenic 68.5 J+ (39.4) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-07-1 Arsenic 148 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-08 ARA-08-0 Arsenic 68.3 J+ (39.2) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

Argonaut Heights – North (Area C) 

ARA-09 

ARA-09-0 Arsenic 1,380 J+ (793) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-09-2 

Arsenic 39,900 J+ 

(22,931) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

Mercury 193 10 Non-Cancer Risk Screen 

Conc. Ref. 2, p. 11 

R-12-03-C-12 Arsenic 680 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-10 

ARA-10-2 Arsenic 655 J+ (376) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-14-01-C-12 Arsenic 220 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-14-01-C-12­

082715 Arsenic 1,500 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-11 R-13-01-C-12 Arsenic 590 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-12 

ARA-12-2 Arsenic 58.6 J+ (33.7) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-04-02-D-4 Arsenic 430 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-13 

ARA-13-1 Arsenic 1,200 J+ (690) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-10-06-C-16 Arsenic 5,100 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-10-06-C-12­

082115 Arsenic 5,300 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-23 R-01-02-C-12 Arsenic 140 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-25 R-03-02-C-0 Arsenic 270 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-26 R-05-02-C-0 Arsenic 40 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-27 R-06-03-D-16 Arsenic 1,000 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-28 R-07-01-C-12 Arsenic 40 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-31 R-18-01-C-0 Arsenic 62 0.71 Cancer Risk Screen Conc. Ref. 2, p. 27 

Argonaut Heights – South (Area D) 

ARA-15 

ARA-15-1 Arsenic 269 J+ (154) 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-08-04-C-12 Arsenic 340 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-16 

ARA-16-1 Arsenic 147 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-09-03-C-12 Arsenic 350 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-09-03-C-12­

082415 Arsenic 580 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

105 SE-Resident Population Threat 
 

 

 

 

Level I Concentrations 

Address 

Code Sample ID Hazardous 

Substance 

Hazardous 

Substance 

Concentration* 

mg/kg 

Benchmark 

Concentration 

mg/kg 

Benchmark Reference 

ARA-17 

ARA-17-2 Arsenic 123 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-19-02-C-12 Arsenic 130 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-19-04-C-0 Arsenic 92 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-24 R-02-02-C-0 Arsenic 69 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-30 R-17-02E-C12-081815 Arsenic 120 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

Sierra View Estates (Area E) 

ARA-18 

ARA-18-0 Arsenic 310 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-18-1.5 Arsenic 423 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-16-01-C-0 Arsenic 210 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

R-16-04-C-0 Arsenic 100 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-19 

ARA-19-0 Arsenic 55.3 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-19-1 Arsenic 122 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

ARA-29 R-15-02-C-12 Arsenic 910 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

Jackson Junior High School (Area F) 

DU-6 JJHS-C-02­

14-072715 Arsenic 290 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

DU-7 

JJHS-C-06­

14-072715 Arsenic 100 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

JJHS-C-17­

12-080315 Arsenic 79 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

DU-9 JJHS-C-10-2­

072715 Arsenic 62 0.71 Cancer Risk Screen Conc. Ref. 2, p. 2 

J+: The result is estimated and may be biased high (Ref. 4, pp. 1867, 1873).
 

*: The possible impact of the potential bias associated with the qualified contaminant concentrations was evaluated
 

consistent with the EPA factsheet, Using Qualified Data to Document an Observed Release and Observed Contamination
 

(Ref. 9) to ensure that the contaminant levels are above the applicable benchmark.
 

106 SE-Resident Population Threat 
 

 

 

 

 

5.1.3.1 Resident Individual 

Area Letter: B through F 

Level of Contamination: Level I 

According to the HRS, hazardous constituents (as identified in the Superfund Chemical Data Matrix) 

that meet the criteria for an observed release (or observed contamination) and exceed media-specific 

benchmark values meet the criteria for Level I contamination (Ref. 1, Sect. 2.5). Based on results from 

the 2014 Weston SI, the 2015 EPA Removal Assessment, and the 2015 EPA Removal Action, Level I 

concentrations of arsenic and/or mercury have been established on residential properties and on a 

regularly occupied area of Jackson Junior High School (refer to HRS Documentation Record Section 

5.0.1, Summary of Site Contamination, above). A value of 50 is assigned to resident individual because 

there is at least one resident individual subject to Level I concentrations (Ref. 1, Sect. 5.1.3.1). 

Resident Individual Factor Value: 50 

107 SE-Resident Population Threat 
 

 

 

 

 

5.1.3.2 Resident Population 

5.1.3.2.1 Level I Concentrations 

Level I Resident Population Targets
 

Observed contamination has been documented at residences in Areas B through E (see Section 5.0.1).
 

Each residence is multiplied by the U.S. Census persons per household for Amador County to determine
 

the resident population (Ref. 29). 

Current enrollment in Jackson Junior High School (Area F) is 406 students (Ref. 13). The observed 

contamination at Jackson Junior High School is located at the edge of the athletic field in a regularlyoccupied lunch area adjacent to the snack bar (see Attachment A-7) (Ref. 34, pp. 2-3, 612-613). 

Therefore, all students are likely to occupy the area of contamination at Jackson Junior High School. 

Area 

Letter 

Residences 

with Observed 

Contamination 

Number of 

Residences 

County 

Multiplier 

Total No. 

of Residents/ 

Students 

References 

B ARA-07 

ARA-08 2 2.32 4.64 Ref. 29 

C 

ARA-09 

ARA-10 

ARA-11 

ARA-12 

ARA-13 

ARA-23 

ARA-25 

ARA-26 

ARA-27 

ARA-28 

ARA-31 

11 2.32 25.52 Ref. 29 

D 

ARA-15 

ARA-16 

ARA-17 

ARA-24 

ARA-30 

5 2.32 11.6 Ref. 29 

E 

ARA-18 

ARA-19 

ARA-29 

3 2.32 6.96 Ref. 29 

F Jackson Junior 

High School N/A N/A 406 students Ref. 13 

Sum of individuals subject to Level I concentrations: 454.72 

Sum of individuals subject to Level I concentrations x 10: 4,547.2 

Level I Concentrations Factor Value: 4,547.2 

108 SE-Resident Population Threat 
 

 

 

 

5.1.3.2.2 Level II Concentrations 

Residential property ARA-32 is located in Argonaut Heights – North (Area C) between ARA-26 and 

ARA-28 (see Attachment A-6). Though a composite laboratory sample collected on the property did not 

contain hazardous substances at concentrations significantly above background, XRF sampling showed 

the presence of elevated concentrations of arsenic and lead (Ref. 11, p. 86; Ref. 15). Therefore, Level II 

Actual Contamination is assigned to ARA-32. 

Residential property ARA-33 is located in Argonaut Estates (Area B) between ARA-07 and ARA-08. 

Historical aerial photographs show that a waste rock pile beneath the neighborhood extends across all 

three properties (see Attachment A-6) (Ref. 10, pp. 28, 36; Ref. 15). Therefore, Level II Actual 

Contamination is assigned to ARA-33. 

Area 

Letter 

Residences with 

Observed 

Contamination 

Number of 

Residences 

County 

Multiplier 

Total No. 

of Residents References 

B ARA-33 1 2.32 2.32 

Ref. 1, Section 

5.1.3.2.2; Ref. 

29 

C ARA-32 1 2.32 2.32 

Ref. 1, Section 

5.1.3.2.2; Ref. 

29 

Sum of individuals subject to Level II concentrations: 4.64 

Level II Concentrations Factor Value: 4.64 

5.1.3.3 Workers 

Current staff at Jackson Junior High School is 45 people (Ref. 13). The observed contamination at 

Jackson Junior High School is located at the edge of the athletic field in a regularly-occupied lunch area 

adjacent to the snack bar (see Attachment A-7) (Ref. 34, pp. 2-3, 612-613). Therefore, all workers are 

likely to occupy the area of contamination at Jackson Junior High School. 

Area Letter Number of Workers References 

F 45 Ref. 13 

Total workers: 45 

Workers Factor Value (Ref. 1, Table 5-4): 5 

109 SE-Resident Population Threat 
 

5.1.3.4 Resources 

No known commercial agriculture, silviculture, or livestock production or grazing is known to be 

conducted within the area of observed contamination attributable to the Argonaut Mine site. 

5.1.3.5 Terrestrial Sensitive Environments 

There are no known terrestrial sensitive environments within the area of observed contamination 

attributable to the Argonaut Mine site. 

110 SE-Resident Population Threat 
 

 

5.2 NEARBY POPULATION THREAT 

The Nearby Population Threat was not scored, although the threat posed by the mining waste to nearby 

populations may be considered at a later point. However, as the Resident Population Threat is sufficient 

to identify that a threat to the residential population is present and significant, it is not necessary to score 

the Nearby Population Threat. 

111 SE-Resident Population Threat 
ATTACHMENT A DATA CITATIONS 

Attachment A-1: Argonaut Mine Layout 

Argonaut Investigation Area 

- Reference 4 

Argonaut Historical Boundary 

- Weston Solutions, Inc. (Weston) digitized from Reference 50. 

Parcel 

- GIS Division of the Amador County Information Technology Department. Parcel boundaries from 

georeferenced scanned Assessor maps, May 2011 

Wetland 

- CONUS_wet_poly Classification of Wetlands and Deepwater Habitats of the United States. U.S. 

Department of the Interior, Fish and Wildlife Service, Washington, DC. FWS/OBS-79/31, May 

2009 (Reference 38). 

Surface Water 

- U.S. Geological Survey - National Hydrography Dataset, March 2012 

Underground Culvert 

- Weston digitized from U.S. Geological Survey - National Hydrography Dataset, March 2012 

Elevation Contour 

- U.S. Geological Survey - The National Elevation Dataset 

Aerial Image 

- ArcGIS Imagery from Microsoft, Resolution 0.03 meter, June 14, 2011 

Attachment A-2: Argonaut Site Sources 

Argonaut Mine Sources 

- Reference 4 

Argonaut Historical Boundary 

- Weston digitized from Reference 50 

Residential Parcels 

- References 4, 11, 15 

- GIS Division of the Amador County Information Technology Department. Parcel boundaries from 

georeferenced scanned Assessor maps, May 2011 

Surface Water 

- U.S. Geological Survey - National Hydrography Dataset, March 2012 

Aerial Image 

- ArcGIS Imagery from Microsoft, Resolution 0.03 meter, June 14, 2011 
Attachment A-3: Source 1 Sampling Locations 

Argonaut Investigation Area 

- Reference 4 

Argonaut Historical Boundary 

- Weston digitized from Reference 50 

Wetland 

- CONUS_wet_poly Classification of Wetlands and Deepwater Habitats of the United States. U.S. 

Department of the Interior, Fish and Wildlife Service, Washington, DC. FWS/OBS-79/31, May 

2009 (Reference 38). 

Surface Water 

- U.S. Geological Survey - National Hydrography Dataset, March 2012 

Aerial Image 

- ArcGIS Imagery from Microsoft, Resolution 0.03 meter, June 14, 2011 

Attachment A-4: Residential Parcels on the Historical Aerial 

Residential Parcels 

- References 4, 11, 15 

Argonaut Historical Boundary 

- Weston digitized from Reference 50 

Aerial Image 

- Weston Georeferenced - National Aerial Survey Center Corp./Visual Image Presentations Silver 

Spring, Maryland, October 02, 1944. Scale: 1:20,000, Black & White Film, Mission I.D.: DDE 

Frame Numbers 107 and 108. 

Attachment A-5: Residential Soil Sampling Locations 

Residential Parcels 

- References 4, 11, 15 

Argonaut Historical Boundary 

- Weston digitized from Reference 50 

Aerial Image 

- ArcGIS Imagery from Microsoft, Resolution 0.03 meter, June 14, 2011 

Attachment A-6: Observed Contamination Areas 

Residential Parcels 

- References 4, 11, 15 

Argonaut Historical Boundary 

- Weston digitized from Reference 50 

Aerial Image 

- ArcGIS Imagery from Microsoft, Resolution 0.03 meter, June 14, 2011 
Attachment A-7: Jackson Junior High School Sampling and Removal Locations 

Residential Parcel 

- Reference 34 

Aerial Image 

- ArcGIS Imagery from Microsoft, Resolution 0.03 meter, June 14, 2011 

Attachment A-8: Source 1 Wetland 

Argonaut Investigation Area 

- Reference 4 

Wetland 

- CONUS_wet_poly Classification of Wetlands and Deepwater Habitats of the United States. U.S. 

Department of the Interior, Fish and Wildlife Service, Washington, DC. FWS/OBS-79/31, May 

2009 (Reference 38). 

Aerial Image 

- ArcGIS Imagery from Microsoft, Resolution 0.03 meter, June 14, 2011 
MAIN

ARGONAUT

STATE HIGHWAY 49

SPUNN

EL DORADO

PIONEER BUENA VISTA

ROSE

RIDGECREST

AMADOR

1320

1340

1360

1380

1520

1500

1300

1400

1280

1480

1460

1440

1420

1260

1540

1560

1240

1580

1600

1220

1620

1640

1400

1320

1580

1420

1400

1540

1260

1300

1540

1340

1400

1260

1440

1420

1320

1400

1260

1580

Legend

Argonaut Investigation Area

Argonaut Historical Boundary

Parcels

Former Mill

Wetland

Surface Water

Underground Culvert

Elevation Contour

Unnamed Intermittent Stream

Waste

Rock Pile Cyanide Process Area

Argonaut Mine (estimated location)

40-Stamp Mill

(former)

Argonaut Mine

60-Stamp Mill

(former) Argonaut Mill

Buildings

North Fork Jackson Creek

0 Scale in Feet 1,000

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

PREPARED FOR:

EPA Region 9

Pacific Southwest

ATTACHMENT A-1

ARGONAUT MINE LAYOUT

Argonaut Mine

Jackson, Amador County, California

Argonaut

Mine Shaft

Processed

Tailings

(Gray Sands)

Waste Rock Pile

Unnamed Intermittent Stream

Argonaut

High School

Amador County

Superior Court

Cyanide

Plant

Ore

Storage

Area

Upper Tailings

Impoundment

(Gray Sands Area)

Concrete Dam

Jackson

Junior High

School

Middle Tailings

Impoundment Lower Tailings

Impoundment Upper Earthen Tailings Dam Lower Earthen Tailings Dam

AOC-5

AOC-1

AOC-2

AOC-3

AOC-4

Probable

Amalgamation

Building

RS

Argonaut

Mine

Argonaut Mine

Mill Area

Argonaut Mine

Tailings Area

STATE HIGHWAY 88

JACK
ARA-32

ARA-33

MAIN

HOFFMAN SUTTER

ARGONAUT

STATE HIGHWAY 49

VOGAN TOLL

CHURCH

 VISTA

SU

ARA-31

ARA-11

ARA-10

ARA-25

ARA-07

ARA-08

ARA-29

ARA-30

ARA-19

ARA-17

ARA-15

ARA-18

ARA-24

ARA-16

ARA-23

ARA-13

ARA-26

ARA-12

ARA-09

ARA-28

ARA-27

Unnamed Intermittent Stream

North Fork Jackson Creek

Argonaut

High School

Amador County

Superior Court

Cyanide

Plant

Ore

Storage

Area

Upper Tailings

Impoundment

(Gray Sands Area)

Concrete Dam

Jackson

Junior High

School

Middle Tailings

Impoundment

0 Scale in Feet 1,000

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

PREPARED FOR:

EPA Region 9

Pacific Southwest

ATTACHMENT A-2

ARGONAUT SITE SOURCES

Argonaut Mine

Jackson, Amador County, California

Lower Tailings

Impoundment

Upper Earthen Tailings Dam

Lower Earthen Tailings Dam

AOC-5

AOC-1

AOC-2

Source 1

(AOC-3) AOC-4

Probable

Amalgamation

Building

Legend

Argonaut Mine Sources

Argonaut Property Boundary

Residential Parcel

Surface Water

North Fork Jackson Creek

Source 2

Source 3

Source 4

Source 5

Source 6

BUENA

EER

BLUE O

MMIT

ATTLEY

ARGONAU
!.

"/

!.

"/

!.

!.

!.

!.

!.

MAIN

HOFFMAN

SUTTER

STATE HIGHWAY 49

VOGAN TOLL

B

AB-01

AB-02

ATA-05

ATA-03

ATA-01

ATA-02

ATS-01

ATA-04

ATS-02

Unnamed Intermittent Stream

North Fork Jackson Creek

Argonaut

High School

Amador County

Superior Court

Cyanide

Plant

Ore

Storage

Area

Upper Tailings

Impoundment

(Gray Sands Area)

Concrete Dam

Jackson

Junior High

School

Middle Tailings

Impoundment

0 Scale in Feet 500

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

PREPARED FOR:

EPA Region 9

Pacific Southwest

ATTACHMENT A-3

SOURCE 1 SAMPLING LOCATIONS

Argonaut Mine

Jackson, Amador County, California

Lower Tailings

Impoundment

Upper Earthen Tailings Dam

Lower Earthen Tailings Dam

AOC-5

AOC-1

AOC-2

Source 1

(AOC-3)

Probable

Amalgamation

Building

Legend

Argonaut Mine Sources

Argonaut Property Boundary

Wetland

Surface Water

!. Soil Sampling Location "/ Sediment Sampling Location

North Fork Jackson Creek

ONAUT

CHURC

LUE OA

SUMMIT

ATTLEY
ARA-32

ARA-33

MAIN

HOFFMAN SUTTER

STATE HIGHWAY 49

VOGAN TOLL

CHURCH

SU

ARA-31

ARA-11

ARA-10

ARA-25

ARA-07

ARA-08

ARA-29

ARA-30

ARA-19

ARA-17

ARA-15

ARA-18

ARA-24

ARA-16

ARA-23

ARA-13

ARA-26

ARA-12

ARA-09

ARA-28

ARA-27

Unnamed Intermittent Stream

Argonaut

High School

Amador County

Superior Court

Cyanide

Plant

Ore

Storage

Area

Upper Tailings

Impoundment

(Gray Sands Area)

Concrete Dam

Jackson

Junior High

School

Middle Tailings

Impoundment

0 Scale in Feet 500

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

PREPARED FOR:

EPA Region 9

Pacific Southwest

ATTACHMENT A-4

RESIDENTIAL PARCELS ON THE

HISTORICAL AERIAL

Argonaut Mine

Jackson, Amador County, California

Lower Tailings

Impoundment Upper Earthen Tailings Dam Lower Earthen Tailings Dam

AOC-5

AOC-1

AOC-2

Source 1

(AOC-3)

AOC-4

Probable

Amalgamation

Building

Legend

Argonaut Mine Tailings Area

Argonaut Property Boundary

Residential Parcel

Athletic Field

North Fork Jackson Creek

Parcel boundaries from:

Amador County Assessor Parcel Data,

GIS Division of the Amador County

Information Technology Department

May 2011. 

Background Aerial Photograph From 1944

Source 3

Source 2

Source 4

Source 5

Source 6

Athletic Field

EER

BLUE O

MMIT

ATTLEY

ARGONAU
!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

ARA-32

ARA-33

MAIN

STATE HIGHWAY 49

VOGAN TOLL

CHUR

ARA-31

ARA-11

ARA-10

ARA-25

ARA-07

ARA-08

ARA-29

ARA-30

ARA-19

ARA-17

ARA-15

ARA-18

ARA-24

ARA-16

ARA-23

ARA-13

ARA-26

ARA-12

ARA-09

ARA-28

ARA-27

Unnamed Intermittent Stream

North Fork Jackson Creek

Argonaut

High School

Amador County

Superior Court

Cyanide

Plant

Ore

Storage

Area

Upper Tailings

Impoundment

(Gray Sands Area)

Concrete Dam

Jackson

Junior High

School

Middle Tailings

Impoundment

0 Scale in Feet 500

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

PREPARED FOR:

EPA Region 9

Pacific Southwest

ATTACHMENT A-5

RESIDENTIAL SOIL SAMPLING LOCATIONS

Argonaut Mine

Jackson, Amador County, California

Lower Tailings

Impoundment

Upper Earthen Tailings Dam

Lower Earthen Tailings Dam

AOC-5

AOC-1

AOC-2

Source 1

(AOC-3)

AOC-4

Probable

Amalgamation

Building

Legend

Argonaut Property Boundary

Residential Parcel

Decision Unit Composite Sample

!. Discrete Sampling Location

North Fork Jackson Creek

Only sampling locations with arsenic

laboratory results above three times

background concentrations are shown. 

HOFFMAN SUTT

CH
ARA-32

ARA-33

MAIN

STATE HIGHWAY 49

VOGAN TOLL

CHUR

ARA-31

ARA-11

ARA-10

ARA-25

ARA-07

ARA-08

ARA-29

ARA-30

ARA-19

ARA-17

ARA-15

ARA-18

ARA-24

ARA-16

ARA-23

ARA-13

ARA-26

ARA-12

ARA-09

ARA-28

ARA-27

Unnamed Intermittent Stream

North Fork Jackson Creek

Argonaut

High School

Amador County

Superior Court

Cyanide

Plant

Ore

Storage

Area

Upper Tailings

Impoundment

(Gray Sands Area)

Concrete Dam

Jackson

Junior High

School

Middle Tailings

Impoundment

0 Scale in Feet 500

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

PREPARED FOR:

EPA Region 9

Pacific Southwest

ATTACHMENT A-6

OBSERVED CONTAMINATION AREAS

Argonaut Mine

Jackson, Amador County, California

Lower Tailings

Impoundment

Upper Earthen Tailings Dam

Lower Earthen Tailings Dam

AOC-5

AOC-1

AOC-2

Source 1

(AOC-3)

AOC-4

Probable

Amalgamation

Building

Legend

Observed Contamination Area

Argonaut Property Boundary

Residential Parcel

North Fork Jackson Creek

Parcel boundaries from:

Amador County Assessor Parcel Data,

GIS Division of the Amador County

Information Technology Department

May 2011. 

Source 3

Source 2

Source 4

Source 5

Source 6

HOFFMAN SUTT

CH
0 Scale in Feet 40

Legend

? ? Fence

óóóóóó Drainage Swale

Concrete Cover

Observed Contamination Area

Excavated and Backfilled Area

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

PREPARED FOR:

EPA Region 9

Pacific Southwest

ATTACHMENT A-7

JACKSON JUNIOR HIGH SCHOOL SOURCE

Argonaut Mine 

Jackson, Amador County, California

Hoffman Street

Athletic Field

Gate

Lunch

Area

Canopy

JJHS-C-02-14

JJHS-C-06-14

JJHS-C-10-2 DU-9

DU-7

DU-6

JJHS-C-17-12

(One Foot Depth)
"/

Lower Earthen Tailings Dam

Concrete Dam

LEGEND

0 Scale in Feet 100

!. Sediment Sampling Location

Property Boundary

Wetland

PREPARED BY:

Weston Solutions, Inc.

1340 Treat Blvd, Ste 210

Walnut Creek, CA 94597

ATTACHMENT A-8

SOURCE 1 WETLAND

Argonaut Mine

Jackson, Amador County, California

Argonaut Drive

PREPARED FOR:

EPA Region 9

Pacific Southwest

U.S. Fish & Wildlife Service National Wetlands Inventory

identifies the lower tailings impoundment wetland as a 

Palustrine Emergent, Temporary Flooded, Dikes/Impounded.

Sediment Sample ATS-02

Arsenic: 240 mg/kg

1340

1420