HRS DOCUMENTATION RECORD COVER SHEET

Name of Site: Colorado Smelter 

EPA ID No. CON000802700 

Contact Persons

Site Investigation: Martin O’Grady (303) 692-3366

 Colorado Department of Public Health and Environment 

 4300 Cherry Creek Drive South 

 Denver, Colorado 80246 

 

Documentation Record: Sabrina Forrest (303) 312-6484

 NPL Coordinator 

 U.S. Environmental Protection Agency, Region 8 

 1595 Wynkoop Street, Mail Code: 8EPR-B 

 Denver, Colorado 80202 

Pathways, Components, or Threats Not Scored

Ground Water Migration Pathway 

The ground water pathway was not scored because the soil exposure pathway achieves a score sufficient 

to qualify the site for NPL listing. 

Air Migration Pathway 

The air migration pathway was not scored because the soil exposure pathway achieves a score sufficient 

to qualify the site for NPL listing. 

Surface Water Pathway 

The surface water pathway was not scored because the soil exposure pathway achieves a score sufficient 

to qualify the site for NPL listing. 
Page 1 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

HRS DOCUMENTATION RECORD

Name of Site: Colorado Smelter 

Date Prepared: May 2014 

EPA Region: Region 8 

Street Address of Site*: Interstate 25 and Santa Fe Avenue 

City, County, State, Zip Code: Pueblo, Pueblo County, Colorado 81006 

General Location in the State: The site is located in the south-central part of the state in the City 

 of Pueblo. Within Pueblo, the site is located south of the 

 Arkansas River, west of South Santa Fe Avenue, and east of 

 Interstate 25. 

Topographic Map: Southeast Pueblo, Colorado 1974; Northeast Pueblo, Colorado 

 1974 

Latitude: 38.2491o North 

Longitude: 104.608o West 

Ref: The point of reference from which the coordinates were taken is 

_ from Figure 4, Sample WP-01.1. 

*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. 

Scores

Air Pathway NS

Ground Water Pathway NS 

Soil Exposure Pathway 100.00 

Surface Water Pathway NS 

HRS SITE SCORE 50.00

 NS = Not Scored 
Page 2 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

WORKSHEET FOR COMPUTING HRS SITE SCORE 

 S S2 

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

(from Table 3-1, line 13) 

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

(from Table 4-1, line 30) 

2b. Ground water to Surface Water Migration Component NS NS 

(from Table 4-25, line 28) 

2c. Surface Water Migration Pathway Score (Ssw) NS NS_

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

3. Soil Exposure Pathway Score (Ss) 100 10000 

(from Table 5-1, line 22) 

4. Air Migration Pathway Score (Sa) 

(from Table 6-1, line 12) NS NS_

5. Total of Sgw

2

+ Ssw

2

+ Ss

2

+ Sa

2 10000 

6. HRS Site Score Divide the value on line 5 

by 4 and take the square root 50.00
Page 3 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

 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) 155

 6b. Level II Concentrations (b) 422

 6c. Resident Population (lines 6a + 6b) (b) 577

7. Workers 15 NS

8. Resources 5 0

9. Terrestrial Sensitive Environments (c) 0

10. Targets (lines 5 + 6c + 7 + 8 + 9) (b) 627

Resident Population Threat Score:

11. Resident Population Threat (lines 1 x 4 x 10) (b) 34,485,000

Nearby Population Threat

Likelihood of Exposure:

12. Attractiveness/Accessibility 100 NS

13. Area of Contamination 100 NS

14. Likelihood of Exposure 500 NS

Waste Characteristics:

15. Toxicity (a) NS

16. Hazardous Waste Quantity (a) NS

17. Waste Characteristics 100 NS

Targets:

18. Nearby Individual 1 NS

19. Population Within 1 Mile (b) NS

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

Nearby Population Threat Score:

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

Soil Exposure Pathway Score

22. Soil Exposure Pathway Scored(Ss), (lines [11 +21]/82,500, 

subject to a maximum of 100) 100 100.00
Page 4 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

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. 

NS = Not Scored 
Page 5 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

LIST OF FIGURES 

Figure 1: Pueblo Former Smelter Locations 

 Figure 2: Sanborn Fire Insurance Map 1904/05 Sheet 157 

 Figure 3: Residential Soil Sampling Schematic 

 Figure 4: Map Depicting 

 (8.5x11”) Area A: Residential Soils and 

 Area B: Slag Pile 

 

 

LIST OF TABLES 

 Table 1: Background CLP Aliquot 

 Table 2: Background XRF Composites 

 Table 3: Residential Soil CLP Aliquots 

 Table 4: Residential Soil XRF Composites 

 Table 5: Slag Pile CLP Aliquots 

 Table 6: Slag Pile XRF Composites 
Arkansas River I-25

Santa Fe Avenue

Colorado Smelter

(former location)

Philadelphia Smelter

(former location)

Massachusetts Smelter

(former location)

Pueblo Smelter

(former location)

Blende Smelter

(former location)

Rocky Mountain Steel Mills

(formerly Colorado Fuel and Iron)

Base Map from Pueblo County

± 0 1,000 2,000 4,000

Feet

Source of the Aerial Photograph basemap: Ref. 37 NAIP 2009 (National Agricultural Imagery Project)

Source of the former smelter locations: Ref. 7 1897 Map of Pueblo compiled from official records and

Ref. 8 Sanborn Maps 1883 -2004/05

Colorado Smelter Pueblo

Figure 1: 

Pueblo former Smelter

Locations

March 27, 2012
Figure 2: Colorado Smelter Sanborn Fire Insurance Map 1904/05 Sheet 157 
Front Yard 

(Zone 1)

 5-point multiincrement

Back Yard

(Zone 4)

5-point multiincrement

Side Yard

(Zone 2)

5-point multiincrement

Side Yard 

(Zone 3)

5-point multiincrement

FIGURE 3 – COLORADO SMELTER RESIDENTIAL SOIL SAMPLING SCHEMATIC

NOT TO SCALE

Source: Ref.20, Figure 3
"/

"/

"/

"/"/

"/

"/"/

"/

"/

"/

"/"/

"/

"/

"/ "/ "/ "/

"/

"/ "/

"/

"/

"/ "/

"/"/

"/

"/ "/

"/

"/"/

"/

"/

"/ "/

"/

"/ "/

"/

"/"/

"/

"/ "/

"/

"/

"/ "/

"/

"/ "/

"/ "/

"/ "/"/

"/

"/

"/

"/

"/

"/

"/

"/"/

"/ "/

"/ "/

"/"/

"/

!.

!.

!.

!.

!. !. !.

!.

!. !.

!.

!.

!. !.

!.

!.

!.

!.

!.

!.

!.

'

'

TAYLOR AVENUE

SANTA FE AVENUE

EILERS AVENUE

BERWIND AVENUE

MESA AVENUE

NORTHERN AVENUE

Arkansas River

I-25

RR Tracks

Santa Fe Avenue

S0-01-3

SO-38-1

SO-08-1

SO-41-1

SO-42-1

SO-18-4

SO-32-4

SO-40-4

SO-40-1

S0-07-4

SO-43-4

SO-43-1 SO-24-1

SO-31-4

SO-28-4

S0-22-3

SO-12-1

WP-02-1

WP-04-1

WP-03-1

WP-01-1

Ba se M ap from Pue blo Co unt y

± 0 250 500 1,000

Feet

Colorado Smelter Pueblo

Figure 4: Depicting

Area A: Residential Soil and

Area B: Slag Pile

April 4, 2012

Source of the Aerial Photograph basemap: http://www.gis.co.pueblo.co.us/imagery.htm (Ref. 35)

Source of the parcel data (lot outlines):http://www.gis.co.pueblo.co.us/landbase.htm (Ref. 36)

Source of the former Colorado Smelter location: Ref. 7 1897 Map of Pueblo compiled from official records

and Ref. 8d, Sheet 157. Source of CDPHE 2010 Sampling Data: Ref. 22

Source of the Slag Pile Outline: Ref. 27

Source of the Stack and Chimney Locations: Ref. 8c, Sheet 23, Ref. 8d, Sheet 157

Legend

' Main Stack and Chimney Locations

!. CDPHE 2010 Slag Pile Samples (CLP Aliquots)

Area B Slag Pile

CDPHE 2010 Residential Soil Samples (CLP Aliquots)

pb_lab_adj

!. < 69 mg/kg (below 3x CLP Aliquot BG)

!. > 69 mg/kg (above 3x CLP Aliquot BG)

CDPHE 2010 Residential Soil Samples (XRF Composites)

Lead

"/ < 141 mg/kg (below 3x XRF bg)

"/ > 141 mg/kg (above 3x XRF bg)

Area A Residential Soil

Residential Lots within Area A

Former_Colorado_Smelter_Location

Lead

"/

"/
Page 10 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

REFERENCES 

Ref. 

No. Description of the Reference

1 U. S. Environmental Protection Agency (EPA). Hazard Ranking System; Final Rule. Federal 

Register, Vol. 55, 55 FR 51532. December 14, 1990. 145 pages. An electronic copy is available 

at http://www.epa.gov/superfund/sites/npl/hrsres/index.htm

2 EPA. Superfund Chemical Data Matrix (SCDM), Excerpt; Table of Contents and Hazardous 

Substance Reference Tables BI and BII. 52 pages. January 2004 (includes updates through 

January, 2014). A complete copy of SCDM is available at: 

http://www.epa.gov/superfund/sites/npl/hrsres/tools/scdm.htm. 

3 U. S. Geological Survey (USGS). 7.5 Minute Topographic Quadrangle Maps: 4 Maps: 

Southeast Pueblo, Colorado 1960, photorevised 1970 and 1974; Northeast Pueblo, Colorado 

1961, photorevised 1970 and 1974; Northwest Pueblo, Colorado 1961, photorevised 194; 

Southwest Pueblo, Colorado 1961, photorevised 1994. 

Maps downloaded from the following website: 

http://store.usgs.gov/b2c_usgs/usgs/maplocator/(xcm=r3standardpitrex_prd&layout=6_1_61_48

&uiarea=2&ctype=areaDetails&carea=%24ROOT)/.do

4 Fry, Eleanor. 2000. Smelters of Pueblo. International Standard Book Number (ISBN) 0-915617-

19-6. Printed by the Spearville News, Spearville, Kansas. 171 pages.

5 Pueblo Chieftain. May 6, 1888, p. 10, Columns 1-4. Article: A Model Smelter. Article obtained 

from Pueblo Public Library (main Rawlings branch at 100 E Abriendo Avenue) on January 5, 

2012. 3 pages. 

6 Pueblo Chieftain. January 31, 1971. Article: History of Smelters in Colorado. In the Pueblo Star 

Journal of the Sunday edition of the Pueblo Chieftain. Obtained from the Colorado Historical 

Society (201 B Street, Pueblo) on January 5, 2012. 2 pages. 

7 E.W. Hathaway, 1897. Map of Pueblo compiled from official records. Published by Pueblo 

Litho and Print Company. Excerpt: 5 pages including title block and portions of the map 

covering the area of the Colorado Smelter, Pueblo Smelter, Philadelphia Smelter and 

Massachusetts Smelter. Map obtained from Pueblo Public Library (main Rawlings branch at 100 

E Abriendo Avenue) on January 5, 2012. 

8 Sanborn Fire Insurance Maps (13 pages) including: 

8a: 1883, Index and Sheet 8 showing Colorado Smelter; 

8b: 1886, Index and Sheet 12 showing Colorado Smelter, Sheet 13 showing Pueblo Smelter; 

8c: 1889, Index and Sheet 23 showing Colorado Smelter, Sheet 24 showing Pueblo Smelter, 

 Sheet 26 showing Philadelphia Smelter. 

8d: 1904/1905, Indexes (2) and Sheet 71 showing Pueblo Smelter, Sheet 157 showing 

 Colorado Smelter, Sheet 189 showing Philadelphia Smelter. 

All maps downloaded from the Denver Public Library website: 

http://history.denverlibrary.org/collections/maps_description.html
Page 11 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

9 Historical Photograph of the Colorado Smelter. Undated. Obtained from Pueblo Public Library 

(main Rawlings branch at 100 E Abriendo Avenue) on January 5, 2012. 1 page. 

10 Fry, Eleanor. September 1990. Pueblo 1927. Pueblo Lore Magazine. Volume 15, Number 9. 

Pueblo County Historical Society. 1page. 

11 Diawara, Moussa M., et al. 2006. Arsenic, Cadmium, Lead, and Mercury in Surface Soils, 

Pueblo, Colorado: Implications for Population Health Risk. Environmental Geochemistry and 

Health, 28:297-315. 19 pages. 

12 Colorado Department of Health (CDH). July 31, 1991. Preliminary Assessment for the Santa Fe 

Bridge Culvert, Pueblo, Colorado. COD #982572513. 30 pages. 

13 CDH. February 22, 1994. Sample Report (Analytical Results Report), Screening Site 

Investigation for the Santa Fe Avenue Bridge Culvert, Pueblo, Colorado. COD #982572513. 49 

pages. 

14 CDH. June 10, 1995. Analytical Results Report, Expanded Site Investigation for the Santa Fe 

Avenue Bridge Culvert, Pueblo, Colorado COD #982572513. 43 pages. 

14a: Appendix D - Large Scale Soil Results Map. 1 page. 

14b: Sampling Field Notebook. 20 pages. 

14c: CLP Data Validation Package for Sample Data Group MHAS49. 35 pages. 

15 Ecology and Environment, Inc. July 20, 1995. Analytical Results Report for the Boston Smelter 

Site (aka Colorado Smelter), Pueblo, Colorado. 28 pages. 

16 Ecology and Environment, Inc. October 4, 1995. Site Screening Report for the Boston Smelter 

Site (aka Colorado Smelter), Pueblo, Colorado. 11 pages. 

17 CDPHE. July 16, 2007. Site Discovery Report for Pueblo, Colorado. 87 pages including Figures 

and Appendix A. 

18 US EPA, November 28, 2011. Pollution/Situation Report. Subject: Final Removal Pollution 

Report (POLREP) for the Blende Smelter Site: 

http://www.epaosc.org/site/sitrep_profile.aspx?site_id=7222&counter=16694 accessed on March 

15, 2012. 7 pages. 

19 CDPHE. April 28, 2008. Preliminary Assessment for the Colorado Smelter, Pueblo, Colorado. 

CON000802700. 72 pages. 

20 CDPHE. May 2010. Site Inspection Sampling and Analysis Plan for the Colorado Smelter, 

Pueblo, Colorado. CON000802700. 36 pages. 

21 CDPHE. 2010. Field Log Book for June 21-23, 2010 Sampling of the Colorado Smelter, Pueblo, 

Colorado. CON000802700. 12 pages. 

22 CDPHE. 2011. Site Inspection Analytical Results Report Colorado Smelter, Pueblo, Colorado. 

CON000802700. June 22, 2011. 75 pages. 

22a: Colorado Smelter ARR Letter Amendment, March 19, 2013, 4 pages. 
Page 12 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

22b: Colorado Smelter ARR Letter Amendment, September 9, 2013, 1 page. 

23 USGS. 2002. Generalized Surficial Geologic Map of the Pueblo 1° x 2° Quadrangle, Colorado. 

Miscellaneous Field Studies Map MF-2388, Version 1.0. Map by Moore, David W. , Straub, 

Arthur W. , Berry, Margaret E. , Baker, Michael L. , and Brandt, Theodore R. 1 page. 

http://pubs.usgs.gov/mf/2002/mf-2388/mf-2388_print.pdf

24 USGS. 2002. Generalized Surficial Geologic Map of the Pueblo 1° x 2° Quadrangle, Colorado. 

Miscellaneous Field Studies Map MF-2388. Version 1.0. Pamphlet accompanying the Map by 

Moore, David W. , Straub, Arthur W. , Berry, Margaret E. , Baker, Michael L. , and Brandt, 

Theodore R. Pamphlet, 25 pages. http://pubs.usgs.gov/mf/2002/mf-2388/mf-2388pamphlet.pdf

25 CDPHE. March 26, 2012. Figure 5. Surficial Geology Map for Background and Release Sample 

Locations, Colorado Smelter. Figure created by downloading shapefiles from the USGS website 

and importing them to ArcMap. 1 page. 

26 Western Regional Climate Center. Wind Rose Plots for Pueblo Memorial Airport, Station ID 

93058. Available at: http://www.wrcc.dri.edu/ 11 pages. 

26a: For time period January 1, 1948 through December 31, 1969 accessed on March 4, 2012 

26b: For time period January 1, 1970 through December 31, 1989 accessed on March 4, 2012. 

26c: For time period January 1, 1990 through February 28, 2012 accessed on February 29, 

 2012. 

27 CDPHE. June 27, 2012. Memorandum to file. Subject: Determination of the surface area under 

the Slag Pile at the Colorado Smelter Site. 3 pages. 

28 URS Operating Services. 2012. Data Quality Assessment Colorado Smelter, Final March 21, 

2012. 34 pages, 2 Figures, 5 Tables, 40 pages. Appendices A-H. Appendix A (1,290 pages); 

Appendix B (132 pages); Appendix C (18 pages); Appendix D (37 pages); Appendix E (21 

pages); Appendix F (15 pages); Appendix G (4 pages); and Appendix H (541 pages). 

29 U.S. Environmental Protection Agency (EPA). 2007. Method 6200: Field Portable X-ray 

Fluorescence Spectrometry for the Determination of Elemental Concentrations in Soil and 

Sediment. Revision 0, February 2007. Excerpt, 33 pages. Obtained from 

http://www.epa.gov/wastes/hazard/testmethods/sw846/online/6_series.htm

30 U.S. Environmental Protection Agency (EPA), 1998. Office of Research and Development. 

Environmental Technology Verification Report: Field Portable X-Ray Fluorescence Analyzer, 

Niton XL Spectrum Analyzer. EPA/600/R-97/150. March 1998. 93 pages.

http://www.epa.gov/nrmrl/lrpcd/site/reports/600r97150/600r97150.pdf. Site accessed March 23, 

2012. 

31 U.S. Environmental Protection Agency. May 25, 2004. X-ray Fluorescence (XRF) Instruments 

Frequently Asked Questions (FAQ). Technology Innovation Office. 5 pages.

http://www.epa.gov/superfund/lead/products/xrffaqs.pdf. Site accessed March 23, 2012. 

32 CDPHE. 2012. 

32a: CDPHE. February 27, 2012. Figure 6, Colorado Smelter 2010 XRF Lead Results for 

 Multi-increment Composite Samples. 1page. 
Page 13 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

32b: CDPHE. February 27, 2012. Figure 7, Colorado Smelter 2010 XRF Lead Results for 

 Aliquot Samples. 1 page. 

33 Smith, David B. 2012. February 27, 2012 Signed email from David B. Smith, USGS. Subject: 

Lead and Arsenic levels in Pueblo Soils. 1 page. 

34 US Census Bureau. State & County Quick Facts. Data for Pueblo County, Colorado. Obtained 

from: http://quickfacts.census.gov/qfd/states/08/08101.html accessed on March 15, 2012. 3 

pages. 

35 Pueblo County Aerial Imagery, 2004-2008. This Pueblo County Data is a combination of two 

data sets, both from Pueblo County: 1-foot pixel full color aerial photography (acquired spring 

2004); and 4-inch pixel full color aerial photography (acquired in 2008). 3 pages. 

http://www.gis.co.pueblo.co.us/imagery.htm 

36 Pueblo County Parcel Data, 2008. 3 pages. http://www.gis.co.pueblo.co.us/landbase.htm 

37 Aerial Photography. 2009. National Agricultural Imagery Project (NAIP). 2 pages. This site is 

the source of the imagery in ArcGIS used to generate Figure 1. 

http://www.fsa.usda.gov/FSA/apfoapp?area=home&subject=prog&topic=nai

38 CDPHE. April 4, 2012. Figure 4 (11”x17” enlargement): Depicting Area A, Residential Soil and 

Area B, Slag Pile. 1 page. 

39 CDPHE. June 8, 2012. Memorandum to file from Martin O’Grady. Subject: Residential Soil 

Sampling Methodology for the Site Inspection Conducted June 21-23, 2010 for the former 

Colorado Smelter Site. 1 page. 

40 CDPHE. June 13, 2012. Memorandum to file from Martin O’Grady. Subject: Number of 

Persons Living in Residences with Level 1 Arsenic Contaminated Soil based on CLP data from 

the Site Inspection Conducted June 21-23, 2010 for the former Colorado Smelter Site. 1 page. 

41 CDPHE. July 10, 2012. Memorandum to file from Martin O’Grady. Subject: Determination of 

the Unpaved Portion of AOC A. 2 pages. 

42 Lowsley, I. H., Jr. The Missouri Lead Study. National Science Foundation, Research Applied to 

National Needs (RANN) Volume 1. 1977. Excerpt, Chapter IV, Air Quality, cover and pages 52 

– 94. 46 pages. 

43 Bennett, Roy L, and Kenneth T. Knapp. Characterization of Particulate Emissions from NonFerrous Smelters. Journal of Air Pollution Control Association. Volume 39, No. 2: 169-174. 

February 1989. Reproduced by United States Department of Commerce, National Technical 

Information Service, EPA/600/J-89/043, PB89-197461. 10 pages. 

44 Stoughton, B., and Butts, A. 1926. Engineering Metallurgy. A Textbook For Users of Metals. 

McGraw-Hill Book Company, New York. Excerpt, 8 pages. 
Page 14 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

45 ARCO Environmental Remediation, L.L.C. and Cascade County and the City of Great Falls, 

Montana. 2000. Montana Voluntary Cleanup and Redevelopment Act (VCRA) Application, 

Former Great Falls Refinery Site, Great Falls Montana. June 26, 2000. 350 pages plus 1 map, 

Appendix I. 

46 Rocky Mountain Steel Mills. 2003-2009. Wind Rose Plots for Meteorological Station located in 

the northern end of the Steel Mill. 3 pages. 

47 CDPHE. August 6, 2012. Figure 8. Map depicting samples from Diawara, Moussa M., et al. 

(CSU) 2006 study (Ref. 11 of this HRS documentation record) proximal to the Colorado Smelter. 

1 page. 

48 U. S. Environmental Protection Agency (EPA). November 1996. Quick Reference Fact Sheet: 

Using Qualified Data to Document an Observed Release and Observed Contamination, EPA 540-

F-94-028. 18 pages. 

49 URS Operating Services, Inc. November 2, 2012. Memorandum regarding J Qualified Data for 

Colorado Smelter Contract Laboratory Program Sample Delivery Group MH2W82. 1 page. 

50 Tetra Tech EM Inc. June 2004. Final Analytical Results Report for the Expanded Site 

Inspection, Anaconda Minerals Company Great Falls Refinery, CERCLIS ID #MT093291599. 

208 pages. 
Page 15 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

SITE HISTORY and DESCRIPTION 

The Colorado Smelter, also known as the Boston Smelter or the Eilers Smelter, after its builder, Anton 

Eilers (Ref. 4, p. 33), operated from 1883 until 1908 (Ref. 4. pp. 4, 33; Ref. 5). The former smelter is

located in Pueblo, south of the Arkansas River at the south end of Santa Fe Avenue and was constructed 

in a large ravine between Santa Fe Avenue and the Denver & Rio Grande railroad tracks (Ref. 4, pp. 4, 

33). The owners of the Madonna Mine, located in the mountains far to the west in Monarch, Colorado 

built the Colorado Smelter in order to smelt the extracted silver-lead ore in a cost effective manner (Ref. 4 

p. 4; Ref. 5). 

Between the 1880’s and the 1920’s, five smelters operated in the City of Pueblo and its nearby 

subdivisions. These included the Colorado Smelter, the Pueblo Smelter, the Philadelphia Smelter, the 

Massachusetts Smelter, and the Blende Smelter (Ref. 4, pp. 1-5; Figure 1 of this HRS documentation 

record). The proliferation of smelters in Pueblo was due to the nearby availability of coal (Ref. 6) and 

limestone (Ref. 4. p. 3), and the service of the area by two railroads, the Denver & Rio Grande (D&RG), 

and the Atchison, Topeka and Santa Fe (Ref. 4, p. 3). The source of ore was mines located in the 

mountains, including the Madonna Mine in Chaffee County (Ref. 4, p. 34; Ref. 5). In the late 1880’s 

Pueblo was the most imposing smelting city in the world processing about 400 railroad car loads of ore 

daily (Ref. 6). 

This HRS documentation record for the Colorado Smelter identifies three sources of contamination 

including: (1) an area of observed contamination (AOC) that includes residential soils referred to as AOC 

A; (2) residual slag material that remains onsite referred to as AOC B; and (3) historic smelter stacks that 

emitted particulates that were dispersed to areas surrounding the site resulting in contamination of the soil 

in the neighborhoods located nearby. 

The pathway scored in this HRS documentation record is the soil exposure pathway based on documented 

impacts to residential properties surrounding the site from historic smelter stack emissions. It has been 

documented that smelter stack emissions contain particulates of heavy metals (Ref. 42, pp. 53, 55; Ref. 

43, pp. 170, 172). Samples of the slag generated by the Colorado Smelter contain lead and arsenic (Ref. 

22, p. 58) and it is reasonable to conclude that particulate emissions from the Colorado Smelter stacks 

also contained lead and arsenic. In addition, the ore from the Madonna mine processed at the Colorado 

Smelter contained 30 percent lead (Ref. 4, p.34, Ref. 5, p. 1). 

In the smelting process, it is not possible to separate all the desired metal from other products including 

slag and flue dust (Ref. 44, p. 92). Flue dust samples collected from the Anaconda Minerals Company 

(AMC) smelter in Montana contain arsenic and lead at concentrations up to 14,300 ppm and 55,000 ppm, 

respectively (Ref. 45, pp. 38, 98, 106). Slag from the AMC smelter contains arsenic and lead (Ref. 50, 

Table 2, p. 46) as does slag from the Colorado Smelter (Ref. 22, pp. 58, 59), an indication that stack 

emissions from the Colorado Smelter would similarly contain arsenic and lead (see Section 2.2.2 of this 

HRS documentation record). 

The Colorado Smelter included a blast furnace building that measured 127 feet long, 45 feet wide and 39 

feet high that housed four water-jacketed blast furnaces with a melting capacity of 168 tons of ore per day 

(Ref. 4, p. 38, Ref. 5). From August 28, 1883 to January 1, 1888 37,659 tons of bullion containing 

4,436,099 ounces of silver and 11,887 ounces of gold were produced (Ref.4, p. 43). Historical maps, 

including official city maps (Ref. 7) and Sanborn Fire Insurance maps (Ref. 8) show the location of the 

Colorado Smelter and other smelters in Pueblo. The Sanborn Maps note the height of the main smelter 

stack as 135 feet in 1889 (Ref. 8c, sheet 23). Comparison of Sanborn Maps of 1889 and 1904/05 reveals 

the smelter underwent considerable expansion to the south to Mesa Avenue with the addition of several 
Page 16 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

roaster houses and a 200-foot-tall brick chimney and two 125-foot-tall chimneys in the southern part of 

the facility (Figure 2) (Ref. 8d, sheet 157). The further addition of two more blast furnaces by 1904/05 

increased the capacity of the smelter by fifty percent (Ref. 4, p. 44). Historical photographs of the 

Colorado Smelter (Ref. 4, p. 32, Ref. 9) show the smelter building and smoke stacks with smoke plumes 

drifting southeast. Historical photographs of the facility can generally be oriented using the building 

details contained in the Sanborn Fire Insurance Maps (Ref. 8). 

In the later part of the nineteenth century several smelters in Colorado, including the Colorado Smelter, 

organized into the American Smelting and Refining Company (ASARCO) (Ref. 4, p. 5) and in1908, the 

Colorado Smelter closed (Ref. 4, p. 4). Some of the slag generated by the smelter was removed and used 

as track ballast for the D&RG track constructed between Florence and Canon City (Ref. 4. p. 46, Ref. 10), 

though significant amounts of slag remain at the property (Ref. 19, Photolog, Photos 1-7). In 1923, the 

smelter stack was demolished and some of the bricks were used to construct the St. Mary School (Ref. 4, 

p. 46) located immediately south of the former smelter. At present, there are remnants of destroyed 

buildings and large slag piles at the property (Ref. 19, Photolog, Photos 1-7). 

In addition to the smelters, the Colorado Fuel and Iron Co. (CF&I) located south of the Colorado Smelter 

(Figure 1) began operations in Pueblo in the late 1800s processing pig iron to make steel and iron 

products (Ref. 11, p. 298). This facility continues in operation today under the name Rocky Mountain 

Steel Mills. The facility is an active Resource Conservation and Recovery Act (RCRA) facility with 

dozens of solid waste management units (SWMUs) in various stages of assessment and cleanup. The mill 

continues to operate under a state Resource Conservation and Recovery Act permit (CO-05-09-29-01) 

and a Clean Air Act Title V Operating Permit (95OPPB086) (Ref. 19, p. 3). 

Several previous investigations have been performed at the Colorado Smelter and at nearby locations by 

the Colorado Department of Public Health and Environment (CDPHE) and the United States 

Environmental Protection Agency (EPA) contractors Ecology and Environment Inc. (E&E), and by other 

entities. In 1989, a citizen contacted the Pueblo City-County Health Department regarding a colored 

discharge flowing from a pipe into the Arkansas River, directly under the Santa Fe Street Bridge, adjacent 

to and north of the Colorado Smelter facility (Ref. 12, p. 1). In January 1990, the facility was entered into 

the Comprehensive Environmental Response, Compensation and Liability Information System 

(CERCLIS) database under the name Santa Fe Avenue Bridge Culvert and given the EPA ID 

COD982572513. In 1991 CDPHE conducted a preliminary assessment (PA) of the Santa Fe Bridge 

Culvert (Ref. 12). 

CDPHE performed the first sampling event for the Santa Fe Avenue Bridge Culvert/Colorado Smelter on 

April 14, 1992 (Ref. 13, p. 6). A sample of the slag pile, SF-SS-3, was found to contain lead at a 

concentration of 1,950 milligrams per kilogram (mg/kg) (equivalent to parts per million (ppm)) (Ref. 13, 

Table 9). Two residential soil samples collected near the smelter, samples SF-SO-02 and SF-SO-03, 

contained lead at concentrations of 239 and 336 mg/kg, respectively (Ref. 13, Table 15). 

In September 1994 CDPHE performed a more geographically extensive sampling event designed, in part, 

to evaluate the impact from stack emissions to surficial soils from the smelters that operated in Pueblo 

beginning in the 1880’s (Ref. 14, p. 1). Two samples of the Colorado Smelter slag pile were collected 

and sample SS-7 contained lead at a concentration of 7640 mg/kg and arsenic at a concentration of 79.4 

mg/kg (Ref. 14, Table 4). Seventeen of the 34 residential soil samples for the investigation were collected 

within a 1-mile radius of the Colorado Smelter (Ref. 14, Appendix D) and among these the highest lead 

concentration was 692 mg/kg in sample SO-13 and the highest arsenic concentration was 44 mg/kg in 

sample SO-15 (Ref. 14, Table 7). 
Page 17 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

On May 10, 1995 E&E performed an in-situ X-ray Fluorescence (XRF) screening investigation of the 

Colorado Smelter facility (Ref. 15, p. 1). Twelve locations within the slag pile were measured with the 

XRF with the highest lead reading of 9700 mg/kg at location BS-XRF-11 and the highest arsenic reading 

of 140 mg/kg for arsenic at location BSXRF-10 (Ref. 15, Table 1, Fig. 2). In addition, in-situ XRF 

readings were obtained at 26 locations within 1-mile of the Colorado Smelter in the surrounding 

residential area and the highest lead level of 860 mg/kg was recorded at location BS-XRF-25 and the 

highest arsenic level of 130 mg/kg was recorded at location BS-XRF-15 (Ref. 15, Table 1, Fig. 2). Four 

samples were collected for laboratory confirmation including a sample from location BS-XRF-15 where 

the laboratory value for arsenic was 144 mg/kg (Ref. 15, p. 2, Table 2). 

On August 17 &18, 1995 E&E performed a detailed investigation of the Colorado Smelter slag pile by 

gridding the property and collecting 88 samples for XRF analysis (Ref. 16). Seventeen samples were also 

sent to a laboratory for confirmatory analysis. There was excellent correlation for lead concentrations 

between XRF and laboratory results with an r2 (coefficient of correlation) of 0.93 (Ref. 16, Table 2). The 

highest lead value was 14,700 mg/kg from a laboratory analysis of sample BS-SO-U1 (Ref. 16, Table 2, 

p. 3) and the highest arsenic value was 3,400 mg/kg from an XRF analysis of sample BS-SO-D4 (Ref. 16, 

Table 3). 

A study of the metal content of surface soils in Pueblo conducted by affiliates of Colorado State 

University was published in 2006 (Ref. 11). Sixty-eight soil samples were collected at 33 locations in a 

coarsely spaced grid. The average lead concentration was 88 ppm, over five times the average for the 

conterminous US of 16 ppm (Ref. 11, p. 304) and twice the average of 35 ppm reported for soils in the 

Front Range Urban Corridor of Colorado (Ref. 11, p. 304). The average arsenic concentration was 12.6 

ppm, 2.4 times higher than the average of 5.2 ppm reported for the conterminous US (Ref. 11, p. 309) and 

3.6 times higher than the average of 3.5 ppm reported for soils in the Front Range Urban Corridor (Ref. 

11, p. 309). 

In 2007 CDPHE performed a Site Discovery Project in Pueblo to identify sites for further evaluation 

under the Site Assessment Program (Ref. 17). This document identified the Blende Smelter and the 

Colorado Smelter (Ref. 17, p. 41) as locations warranting further investigation based on a review of 

existing data. The Blende Smelter is located approximately two miles east of the Colorado Smelter 

(Figure 1). 

CDPHE performed a PA on the Blende Smelter and a site inspection (SI) in 2009. In April 2010, EPA 

Region 8’s Emergency Response Program conducted a Removal Site Inspection that focused on the 10 

residential properties within the historic footprint of Blende Smelter. The investigation found that these 

properties were significantly contaminated by the historic smelting operation (Ref. 18). EPA targeted 11 

properties for removal, 2 properties for drainage improvements and applied cover material to 1 additional 

property (Ref. 18). 

A Colorado Smelter PA report was prepared by CDPHE in 2008 (Ref. 19). Following the PA, CDPHE 

prepared a Site Inspection Sampling and Analysis Plan (SAP) (Ref. 20) and sampling activities were 

conducted from June 21 – 23, 2010 (Ref. 21). As reported in the 2011 Site Inspection Analytical Results 

Report (ARR) (Ref. 22) the soil exposure (SE) and surface water (SW) pathways were evaluated with 

primary emphasis on the SE pathway. Samples were collected from 57 locations including 47 residential 

properties, 3 vacant lots, 1 road right-of-way, 4 slag pile samples, and 2 background samples (Ref. 22, p. 

4). Background soil samples were collected approximately 2 miles northwest of the smelter and outside 

the area likely to be impacted by emissions from the former smelter (Ref. 22, p. 4).

All of the samples were collected using a multi-incremental sampling technique. Residential yards with 

homes were divided into 1 to 4 zones, or decision units, including the front yard, back yard, and side 
Page 18 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

yards as shown on Figure 3 (Ref. 22, p.47). The number of zones sampled per residence depended on site 

specific conditions such as the size of the side yards and the extent of paved areas. In each zone, 5 

individual aliquots were collected. Based on the small lot sizes (Figure 4 of this HRS documentation 

record, Ref. 36), all of the individual aliquots for all 47 residential properties’ samples were collected 

within 200 feet of the houses. Five individual aliquots were also collected from 4 vacant lots or road 

right-of-way, 2 background and 4 slag pile samples (Ref. 22, pp. 4, 12, 21). 

All samples were collected from the top 2-inches of the ground surface (Ref. 22, p. 12). A total of 434 

individual samples were collected into 1-quart plastic bags. All 434 of the sample aliquots were delivered 

to URS Operating Services (UOS), EPA’s Superfund Technical Assessment and Response Team 

(START) laboratory in Denver, Colorado (Ref. 28, Appendix G) where they were analyzed using an 

Innov-X model Omega X-Ray Fluorescence analyzer (XRF) (Ref. 22, p. 12; Ref. 28 p. 2). The samples 

were analyzed directly in the bags using the XRF (Ref. 22, p. 12). Subsequently, the samples were 

composited, dried, sieved, placed in method specific polyethylene sample cups per EPA Method SW-846 

6200 guidelines (Ref. 29), and analyzed with the XRF (Ref. 28, p.1). The 434 aliquots were thus 

combined into 87 multi-increment samples (also known as composite samples) including 77 residential 

soil (from 47 different properties), 3 vacant lots, 1 road right-of-way, 2 background and 4 source samples 

(Refs. 22, p. 4; 22b; 28, p. 2). In summary, a total of 521 samples, including 434 individual aliquots and 

87 composites, were analyzed for metals in soil with XRF using applicable sections of EPA Method 6200 

(Refs. 28, p. 2; 29). 

Fifty-seven samples, representing the full range of lead concentrations of the sample set, were submitted 

for confirmatory analysis through the EPA’s Contract Laboratory Program (CLP) as a quality control 

(QC) protocol for XRF analysis (Ref. 28, p. 3). Prepared composite samples (in XRF cups) were sent 

intact, and aliquot samples were divided evenly after homogenization and XRF analysis. Eleven 

composite samples and 46 aliquot samples (including 2 duplicates) for analysis under the CLP were 

delivered to: Sentinel, Inc., 4733 Commercial Drive, Huntsville, Alabama 35801via Federal Express (Ref. 

28, p.3, Appendix A, pp A-7 to A-9). The samples were analyzed for Target Analyte List (TAL) Metals 

without mercury by Atomic Emission Spectroscopy-Inductively Coupled Plasma (AES-ICP), by EPA 

Method CLP ISM01.2 (Ref. 28, p. A-1). 

A comparison between XRF and laboratory lead results was performed using a routine statistical 

regression analysis. A correlation graph for lead results in the two data sets, XRF and CLP analyses, is 

presented in the ARR (Ref. 22, Figure 7, p 37) and in the Data Quality Assessment (DQA) (Ref. 28, p. 

12) prepared by EPA’s START 3 contractor, URS Operating Services, Inc. The coefficient of correlation 

(r2) value for lead was 0.869, demonstrating there is excellent correlation between the XRF and CLP lab 

data (Ref. 22, p. 36). Any data sets demonstrating an r2 value of 0.85 to 1.0 is considered a definitive data 

quality level (Ref. 30, p. 15), meaning the sets show statistically similar results (Ref. 28, p. 8). 

Both CLP and XRF data are validated (Ref. 28, p. 9). In this HRS documentation record the site score is 

based on CLP data, specifically CLP analytical results of individual aliquot samples. XRF analyses are 

also presented to provide additional evidence supporting the background and release sample 

concentrations and to provide confirmation that the area between the observed contamination sample 

locations, as defined by CLP aliquot samples, is contaminated. 

XRF technology is well established and its applicability in measuring metals concentrations in soil 

samples has been verified (Ref. 30, Ref. 31). The EPA Environmental Technology Verification (ETV) 

program evaluated 7 field portable XRF analyzers and found that measurements of soil lead 

concentrations made with FP-XRF analyzers compared well with those made by fixed-based reference 

laboratories using CLP methods with r2

values between the field based XRF measurements and reference 

laboratories ranging from 0.85 to 0.97 (Ref. 31, p. 2). Other studies have also shown good correlation 
Page 19 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

between lead levels measured by CLP and by XRF (Ref. 31, p. 2). 

Data from the SI (Ref. 22) were used to establish an area of observed contamination (AOC A) for lead for 

residential soils as depicted on Figure 4 of this HRS documentation record. This AOC is based on CLP 

aliquot samples and is verified by XRF composite results. Targets within this AOC include 177 

residences that are subject to level II contamination with lead and an additional 5 residences that are 

subject to level I contamination for arsenic as defined by the HRS (Ref. 1, p. 51647). Data from this SI 

(Ref. 22) were also used to establish an AOC for the slag pile (AOC B) based CLP aliquot samples as 

depicted on Figure 4 of this HRS documentation record. 

Six surface water samples, including one duplicate, were collected from on-site, Probable Points of Entry 

(PPE) and Arkansas River. Four co-located sediment samples were also collected (Ref. 22, p. 26 and Fig. 

4). All surface water and sediment samples were sent to an analytical laboratory for analysis of metals 

through EPA’s CLP. The samples were submitted to ChemTech Consulting Group for analysis of total 

and dissolved metals by ICP-MS (ILM05.4) (Ref. 22, p. 27).

Prevailing winds at the Colorado Smelter during the time of operation were out of the north and northwest 

as noted on Sanborn Fire Insurance Maps for the years 1883-1904 (Refs. 8a, p.1; 8b, p. 1; 8c, p. 1; 8d, p. 

1). Wind rose diagrams from a meteorological station located just south of the Colorado Smelter on the 

Rocky Mountain Steel Mill for the time period January 1, 2003 - December 31, 2005 and March 1, 2008 - 

February 28, 2009 show prevailing winds out of the west-northwest (Ref. 46, pp. 1-3).

Meteorological data for the Pueblo Municipal Airport located 4-miles northeast of the Colorado Smelter 

for the time period 1948-1990 indicate that winds are variable (Ref. 26). Wind rose diagrams for the 

airport location for the time period of January 1, 1948 through December 31, 1969 (Ref. 26a) indicate 

prevailing winds were out of the west to northwest. For the time period of January 1, 1970 through 

December 31, 1989 (Ref. 26b) winds were primarily from the west, east, southeast and north. For the 

time period of January 1, 1990 through February 28, 2012 (Ref. 26c) winds were primarily out of the east, 

west and north. 
Page 20 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

2.2.1 SOURCE IDENTIFICATION 

Name of Source: Residential Soil 

Number of Source: 1

Source Type: Contaminated Soil 

Description and Location of the Source:

Source 2, Residential Soil, is characterized in Section 5.0.1 of this HRS documentation record as area of 

observed contamination (AOC) A. 

2.2.1 SOURCE IDENTIFICATION 

Name of Source: Slag Pile 

Number of Source: 2 

Source Type: Pile 

Description and Location of the Source:

Source 2, the Slag Pile, is characterized in Section 5.0.1 of this HRS documentation record as area of 

observed contamination (AOC) B. 

2.2.1 SOURCE IDENTIFICATION 

Name of Source: Smelter Stack air emissions 

Number of Source: 3 

Source Type: Other 

Description and Location of the Source:

The Colorado Smelter included a blast furnace building that measured 127 feet long, 45 feet wide and 39 

feet high that housed four water-jacketed blast furnaces with a melting capacity of 168 tons of ore per day 

(Ref. 4, p. 38, Ref. 5). From August 28, 1883 to January 1, 1888, 37,659 tons of bullion containing 

4,436,099 ounces of silver and 11,887 ounces of gold were produced (Ref.4, p. 43). Historical maps, 

including official city maps (Ref. 7) and Sanborn Fire Insurance maps (Ref. 8) show the location of the 

Colorado Smelter and other smelters in Pueblo. The Sanborn Maps note the height of the main smelter 

stack as 135 feet in 1889 (Ref. 8c, sheet 23). Comparison of Sanborn Maps of 1889 and 1904/05 reveals 

the smelter underwent considerable expansion to the south to Mesa Avenue with the addition of several 

roaster houses and a 200-foot-tall brick chimney and two 125-foot-tall chimneys in the southern part of 

the facility (Figure 2 of this HRS documentation record) (Ref. 8d, sheet 157). The size increase of two 
Page 21 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

more blast furnaces by 1904/05 increased the capacity of the smelter by fifty percent to 252 tons of ore 

per day (Ref. 4, p. 44). Historical photographs of the Colorado Smelter (Ref. 4, p. 32, Ref. 9) show the 

smelter building and smoke stacks with smoke plumes drifting southeast. Historical photographs of the 

facility can generally be oriented using the building details contained in the Sanborn Fire Insurance Maps 

(Ref. 8). 

The Colorado Smelter operated from 1883 until 1908 (Ref. 4, p 4). Gaseous and particulate emissions 

from several smoke stacks were dispersed into the neighborhoods adjacent to the smelter site (Ref. 4, p. 

32, Ref. 9). Several investigations conducted between 1992 and 2010 indicate soils in areas surrounding 

the Colorado Smelter exhibit elevated concentrations of lead and sometimes arsenic (see Site History and 

Description Section and Section 5 of this HRS documentation record). 

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE 

It has been documented that smelter stack emissions contain particulates of heavy metals (Ref. 42, pp. 53, 

55; Ref. 43, p. 170). Samples of the slag generated by the Colorado Smelter contain lead and arsenic 

(Ref. 22, pp. 58, 59) and it is reasonable to conclude that particulate emissions from the Colorado Smelter 

stacks also contained lead and arsenic. In addition, the ore from the Madonna mine processed at the 

Colorado Smelter contained 30 percent lead (Ref. 4, p.34, Ref. 5). In the smelting process, it is not 

possible to separate all the desired metal from other products including slag and flue dust (Ref. 44, p. 92). 

Flue dust samples collected from the Anaconda Minerals Company (AMC) smelter in Montana contain 

arsenic and lead at concentrations up to 14,300 ppm and 55,000 ppm, respectively (Ref. 45, pp. 38, 98, 

106). Slag from the AMC smelter contains arsenic and lead at concentrations of 217 ppm and 3,120 ppm, 

respectively (Sample AM-SO-06) (Ref. 50, Table 2, p. 46). In comparison, the average concentration of 

arsenic and lead in slag for the Colorado Smelter based on nine CLP aliquot samples is 503 ppm and 

10,333 ppm, respectively (Ref. 28, Table 1, p. 14) further indicating that stack emissions from the 

Colorado Smelter also contained arsenic and lead. 

Location

The outline of the area occupied by the Colorado Smelter is shown on Figure 4 of this HRS 

documentation record along with the approximate location of the 135-foot tall main blast furnace stack 

(Ref. 8c, Sheet 23) and the main roaster house 200-foot-tall chimney (Figure 2 of this HRS 

documentation record). 

Containment

Gas release to air: The air migration pathway was not scored; therefore, gas containment was not 

evaluated. 

Particulate release to air: The air migration pathway was not scored; therefore, particulate containment 

was not evaluated.

Release to ground water: The ground water pathway was not scored; therefore, ground water 

containment was not evaluated. 

Release via overland migration and/or flood: The surface water pathway was not scored, therefore 

surface water containment was not evaluated. 
Page 22 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

2.4.2 HAZARDOUS WASTE QUANTITY 

2.4.2.1.1. Hazardous Constituent Quantity (Tier A) – Not Calculated.

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

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

and cannot be estimated with reasonable confidence [Ref. 1, pp. 51590-51591 (Section 2.4.2.1.1)]. There 

are insufficient historical and current data (manifests, PRP records, State records, permits, waste 

concentration data, etc.) available to adequately calculate the total mass of all CERCLA hazardous 

substances in Source 3 and the associated releases from Source 3. As a result, the evaluation of hazardous 

waste quantity proceeds to the evaluation of Tier B, hazardous waste stream quantity (Ref. 1, pp. 51590, 

51591). 

2.4.2.1.2. Hazardous Wastestream Quantity (Tier B).

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

HRS requirements; that is the total mass of all CERCLA hazardous wastestreams in the source is not 

known and cannot be estimated with reasonable confidence [Ref. 1, pp. 51591 (Section 2.4.2.1.1)]. There 

are insufficient historical and current data (manifests, PRP records, State records, permits, waste 

concentration data, etc.) available to adequately calculate the total mass of all CERCLA hazardous 

wastestreams in Source 3 and the associated releases from Source 3. However, based on the historical 

information presented in sections 2.2.1 and 2.2.2 above, it is known that a hazardous wastestream existed.

As such, a hazardous wastestream value of greater than 0 is assigned to this source. 

Sum (pounds): > 0 

Sum of Wastestream Quantity/5000 (Ref. 1, p. 51591, Table 2-5): > 0 

Hazardous Wastestream Quantity Assigned Value: > 0 

2.4.2.1.3. Volume (Tier C) – Not Calculated.

Insufficient historical information exists concerning the volume of the source. Therefore, it is not 

possible to adequately determine the volume (Tier C) for Source 3 (Ref. 1, p. 51591). 

2.4.2.1.4. Area (Tier D) - Not Calculated.

Area, Tier D, is not evaluated for Source Type “other” (Ref. 1, p. 51591) 

2.4.2.1.5. Source Hazardous Waste Quantity Value

Source 3 is assigned a source Hazardous Waste Quantity value of greater than zero, but unknown. 

Source Hazardous Waste Quantity Value: > 0 
Page 23 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

5.0 SOIL EXPOSURE PATHWAY

5.0.1 General Considerations 

Letter by which this Area is to be identified: A 

Name of area: Residential Soils 

Location and Description of the area (with reference to a map of the site): 

Observed contamination has been scored at 176 residential properties in a neighborhood adjacent to the 

former Colorado Smelter facility (see the following sections for documentation) including 171 residences 

for lead contamination at Level II and 5 residences for arsenic contamination at Level 1. The reader is 

referred to Figure 4 of this HRS documentation record for the location of residential soil samples used to 

define Area A and, for additional detail, to Figures 5 and 6 of the ARR (Ref. 22). 

CDPHE performed a Site Inspection on the Colorado Smelter in 2010 (Ref. 22). Sampling activities were 

conducted from June 21 – 23, 2010 (Ref. 21). Samples were collected from 57 locations including 47 

residential properties, 3 vacant lots, 1 road right-of-way, 4 slag pile samples, and 2 background samples 

(Ref. 22, pp. 12, 21). Background soil samples were collected from an open field approximately 2 miles 

northwest of the Colorado Smelter and outside the area likely to be impacted by emissions from the 

former smelter (Ref. 22, p. 21). 

All of these samples were collected using a multi-incremental sampling technique. Residential yards with 

homes were divided into 4 zones or decision units such as front yard, back yard, and side yards as shown 

on Figure 3 (Ref. 22, p. 4, 47). The number of zones sampled per residence depended on site specific 

conditions such as the size of the side yards and the extent of paved areas. One or two zones were 

sampled at each residence and in many instances samples were collected from the front and back yards 

(Zones 1 and 4) but the side yards were not sampled as they were too narrow (Ref. 21, p. 2-11). In each 

zone, 5 individual aliquots were collected (Ref. 22, p. 12). All of the individual aliquots for all 47 

residential properties’ samples were collected within 200 feet of the houses. The distance from the 

sample locations to the residences was less than 200 feet because the residential properties on which the 

soil samples were collected are less than 200 feet in width and length (Figure 4 of this HRS 

documentation record, Ref. 36; Ref. 39). Five individual aliquots were also collected for each of the 

vacant lots, road right-of-way, background and slag pile samples. All samples were collected from the 

top 2-inches of the ground surface (Ref. 22, p. 12).

A total of 434 individual samples were collected into 1-quart plastic bags. All 434 of the sample aliquots 

were delivered to URS Operating Services (UOS), EPA’s Superfund Technical Assessment and Response 

Team (START) laboratory in Denver, Colorado (Ref. 22, p. 4;Ref. 22b; Ref. 28, Appendix G) where they 

were analyzed using an Innov-X model Omega X-Ray Fluorescence analyzer (XRF) (Ref. 28 p. 2). The 

samples were analyzed directly in the bags using the XRF (Refs. 22, p. 12; 28, p. 1). Subsequently, the 

samples were composited, dried, sieved, placed in method specific polyethylene sample cups per EPA 

Method SW-846 6200 guidelines (Ref. 29, pp. 19,20), and analyzed with the XRF (Ref. 28, p.1). The 434 

aliquots were thus combined into 87 multi-increment samples (also known as composite samples) 

including 77 residential soil (from 47 different properties), 3 vacant lots, 1 road right-of-way, 2 

background and 4 slag pile samples (Ref. 22, pp. 12, 21; Ref. 22b; Ref. 28, p. 2). In summary, a total of 

521 samples, including 434 individual aliquots and 87 composites, were analyzed for metals in soil with 

XRF using applicable sections of EPA Method 6200 (Refs. 28, p. 2; 29). 

Fifty-seven samples representing the full range of lead concentrations of the sample set were submitted 
Page 24 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

for confirmatory analysis through the EPA Contract Laboratory Program (CLP) as a QC protocol for XRF 

analysis (Ref. 28, p. 3). These samples were selected by START and CDPHE to demonstrate XRF and 

laboratory correlation over the entire sample set. In order to achieve the highest degree of correlation 

between XRF and laboratory analysis, prepped composite samples were sent intact, and aliquot samples 

were divided evenly after homogenization and XRF analysis. The fifty-seven samples submitted for 

laboratory analysis included 11 composite samples and 46 aliquot samples (including 2 duplicates) for 

analysis under the CLP and were delivered to: Sentinel, Inc., 4733 Commercial Drive, Huntsville, 

Alabama 35801via Federal Express (Ref. 28, p. 3, Appendix A). The samples were analyzed for Target 

Analyte List (TAL) Metals without mercury by Atomic Emission Spectroscopy-Inductively Coupled 

Plasma (AES-ICP), by EPA Method CLP ISM01.2 (Ref. 28, p. A-1). 

A comparison between XRF and laboratory lead results was performed using a routine statistical 

regression analysis. A correlation graph for lead results in the two data sets – XRF and laboratory 

analysis is presented in the ARR (Ref. 22, Figure 7, p 37). The coefficient of correlation (r2

) value for 

lead was 0.869, demonstrating there is excellent correlation between the XRF and CLP lab data (Ref. 22, 

p. 36). Any data sets demonstrating an r2value of 0.85 to 1.0 is considered a definitive data quality level 

(Ref. 30, p. 15), meaning the sets show statistically similar results (Ref. 28, p. 8). 

Both CLP and XRF data are validated (Ref. 28, pp. 2, 3). In this HRS documentation record the site score 

is based on CLP data, specifically CLP analytical results of individual aliquot samples. Within Areas of 

Observed Contamination (AOCs) based on CLP aliquot samples (Table 3 and Table 5 of this HRS 

documentation record) XRF multi-increment sample results are also presented (Table 4 and Table 6 of 

this HRS documentation record). The HRS allows for inferring contamination within an AOC for 

contaminated soil (Ref. 1, p. 51646). XRF analyses are presented to provide additional evidence 

supporting the background and release sample concentrations and to provide additional evidence that the 

area between the observed contamination sampling locations is contaminated. Inferring contamination 

within AOC A is also supported by the mode of deposition (aerial deposition from stack emissions). At 

least a portion of residential neighborhoods within AOC A were established during the time of stack 

emissions (Ref. 7, p. 3; Ref. 38).

It should be noted that the XRF aliquot data comprises a larger, and therefore more robust, data set than 

either the laboratory data or the XRF composite data and that the XRF aliquot data set corroborates the 

HRS score derived and presented in this documentation record. All data obtained during the June 21-23, 

2010 sampling event are presented in the ARR (Ref. 22) and DQA (Ref. 28). XRF composites and 

aliquot sample lead concentrations are illustrated on Figures 6 and 7 contained as References 32a and 32b 

to this HRS documentation record. 

XRF technology is well established and its applicability in measuring metals concentrations in soil 

samples has been verified (Ref. 30, Ref. 31). The EPA Environmental Technology Verification (ETV) 

program evaluated 7 field portable XRF analyzers and found that measurements of soil lead 

concentrations made with FP-XRF analyzers compared well with those made by fixed-based reference 

laboratories using CLP methods with correlations (r2) between the field based XRF measurements and 

reference laboratories ranged from 0.85 to 0.97 (Ref. 31, p. 2). Other studies have also shown good 

correlation between lead levels measured by CLP and by XRF (Ref. 31, p. 2). 

Background Sample Locations and Concentrations for Area A, Residential Soils

Two background soil samples were collected from an open field three miles northwest of the Colorado 

Smelter (Ref. 25). Each sample consisted of 5-point multi-increments or aliquot grab samples that were 

collected into 1-quart zip-lock bags (Ref 22, pp. 12, 21). Each aliquot was analyzed with the XRF and 

then composited for XRF analysis. One background aliquot was submitted for CLP analysis (Ref. 28, 
Page 25 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

Appendix G). The CLP and XRF analysis are presented in the tables below. 

The background locations were selected to obtain soil samples that were sufficiently far enough away that 

they were unlikely to be impacted by aerial deposition from the stacks. A map of the surficial geology of 

the Pueblo area by the United States Geologic Survey (USGS) (Ref. 23 and Ref. 24) was used to compare 

background and release samples. The map shapefiles were downloaded from the USGS webpage and 

imported into ArcMap. A map (Ref. 25) was created and shows that the background samples were 

collected in a Holocene-age unit designated as “xci” and described as a sandy clay disintegration 

residuum (Ref. 24, p. 13). In comparison, the release samples collected from areas surrounding the 

former smelter were collected in a Holocene-age unit designated as “es” and described as an eolian sand 

(Ref. 24, p. 8). 

The suitability of the background samples for comparison to release samples for metals concentrations for 

the purpose of determining if a release sample is greater than three-times the background concentration is 

supported by correspondence on February 27, 2012 from the USGS (Ref. 33). Regarding naturally 

occurring arsenic and lead levels in the surficial units from which samples were collected, the USGS 

states that the “xci” unit is formed from in-situ weathering of the Pierre Shale, known to be enriched in 

trace elements including arsenic and, less so, lead. In comparison, the “es” unit would be expected to 

have lower concentrations of naturally occurring arsenic and lead (Ref. 33). Therefore, the surficial 

geologic unit “xci” from which the background samples were collected would, if anything, be expected to 

be biased high relative to the release samples collected from within the “es” unit. 

Three background soil samples collected on September 29, 1994 (Refs. 14b, pp. 10-14; 14c, p.2) for the 

Santa Fe Avenue Bridge Culvert Expanded Site Investigation (Ref. 14) corroborate arsenic and lead 

background soil concentrations presented in Tables 1 and 2 of this HRS documentation record. 

Background soil samples SO1, SO2, and SO3for the Santa Fe Avenue Bridge Culvert Expanded Site 

Investigation were collected from three locations located several miles from the Colorado Smelter (Ref. 

14b, pp. 13, 14). Arsenic concentrations for these samples ranged from 5.0 ppm to 6.1 ppm and lead 

concentrations ranged from 13.9 ppm to 32.5 ppm (Ref. 14, p. 18, p. 40; Ref 14c, pp. 18-20). 

A study of arsenic, cadmium, lead and mercury in surface soils in Pueblo (Ref. 11) also corroborate 

background arsenic and lead concentrations presented in Tables 1 and 2 of this HRS documentation 

record. A local map of lead concentrations (Ref. 11, p. 305, Figure 3) in Pueblo indicates soil samples 

collected at sites 31A/31B in the northern portion of the study area (Ref. 11, Figure 1) should best 

represent background conditions. At sites 31A and 31B arsenic concentrations are 13.2 ppm and 14.7 

ppm, and lead concentrations are 18 ppm and 30 ppm, respectively (Ref. 11, Table 1, p. 303). 
Page 26 of 50

Colorado Smelter HRS Documentation Record 

Table 1: Background CLP Aliquot 

Colorado Smelter Background Soil Sample (0-2") CLP Aliquot

Sample ID/ 

CLP No.

Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) SQL (mg/kg) References

CO-BG-02 1.5 

MH2W93 6/23/2010 9.5 15.8 J (22.75)

As = 1.0 

Pb = 1.0

Ref. 21, p. 9; Ref. 28, Table 1, p. 14, 

Appendix A, p. A-7, Appendix B, pp. B-1, 

B-11, B-26

Bold Concentration meets or exceeds the Cancer Risk Screening Concentration (CRSC) for arsenic of 0.71 mg/kg (Ref. 2, p. BII-14). 

J The associated numerical value is an estimated quantity and is the approximate concentration of the analyte in the sample (Ref. 

28, Appendix B, p. B-13). 

J qualified result has an unknown bias (Ref. 49). 

( ) Adjusted value as per EPA Fact Sheet “Using Qualified Data to Document an Observed Release and 

Observed Contamination” (Ref. 48, 18 pages). 

SQL Sample Quantitation Limit. The SQL represents the Contract Required Quantitation Limit (CRQL) that has been adjusted 

for sample-specific factors (Ref. 28, p. 6). It is equivalent to the HRS-defined SQL (Ref. 1, Section 1.1, Table 2-3). 

 mg/kg milligrams per kilogram 

Colorado Smelter CON000802700

HRS Documentation Record 
Page 27 of 50

Colorado Smelter HRS Documentation Record 

Table 2: Background XRF Composites

Colorado Smelter Background Soil Samples (0-2") XRF Composites 

Sample ID Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) DL/RL(mg/kg) References

CO-SO-BG01 6/23/2010 16 J 47 As = 6.3/21

Pb = 4.64/15.5

Ref. 21, p. 9; Ref. 28, Table 1, p. 14, 

Appendix C, p. C-14, Appendix D, p. D1, Appendix G, p. G-1, Appendix H, p. H1

CO-SO-BG02 6/23/2010 13.5 J 22 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 9; Ref. 28, Table 1, p. 14 

Appendix C, p. C-14, Appendix D, p. D1, Appendix G, p. G-1, Appendix H, p. H7

Bold Concentration meets or exceeds the Cancer Risk Screening Concentration (CRSC) for arsenic of 0.71 mg/kg (Ref. 2, p. BII-14).

DL Detection Limit. HRS Table 2-3 allows for the use of the Detection Limit in place of the Sample Quantitation Limit (SQL) (Ref. 1,

Table 2-3, p. 51589).

RL Reporting Limit

J Analyte detected above the DL but not above the RL (Ref. 28, Appendix H, p. H-1).

mg/kg milligrams per kilogram

Colorado Smelter CON000802700

HRS Documentation Record 
Page 28 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

Observed Contamination Locations and Concentrations for Area A, Residential Soils

As shown on Figure 4 of this HRS documentation record, the AOC A is located proximal and to the south 

and east of the former Colorado Smelter. The following table identifies the CLP Aliquot samples that 

meet the HRS Table 2-3 criteria for establishing observed contamination. 
Page 29 of 50

Colorado Smelter HRS Documentation Record 

Table 3: Residential Soil CLP Aliquots 

Colorado Smelter Residential Soil Samples (0-2") CLP Aliquots within and bounding AOC Area Letter A. 

Sample concentrations meet the HRS Table 2-3 criteria compared to CLP Aliquot background concentrations 

(Ref. 1, Table 2-3, p. 51589).

Sample ID/ 

CLP No.

Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) 3xBG/SQL (mg/kg) References

CO-SO-01 3.4 

MH2WC9 6/21/2010 12.7 828 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 2; Ref. 28, Table 1, p. 15, 

Appendix A, p. A-9, Appendix B, pp. B-87, 

B-107

CO-SO-07 4.1 

MH2W96 6/22/2010 4.3 J+(2.47)

270 J 

(187.5)

As = 28.5/1.0 

Pb = 68.25/1.0

Ref. 21, p. 4; Ref. 28, Table 1, p. 17, 

Appendix A, p. A-7, Appendix B, pp. B-1, 

B-3, B-4, B-11, B-13, B-29 

CO-SO-08 1.5 

MH2W97 6/22/2010 5.5 J+(3.16)

158 J 

(109.7)

As = 28.5/1.0 

Pb = 68.25/1.0

Ref. 21, p. 4; Ref. 28, Table 1, p. 17, 

Appendix A, p. A-7, Appendix B, pp. B-1, 

B-3, B-4, B-11, B-13, B-30

CO-SO-18 4.5 

MH2WC8 6/22/2010 6.6 223 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 5; Ref. 28, Table 1, p. 19, 

Appendix A, p. A-9, Appendix B, pp. B-87, 

B-106

CO-SO-22 3.1 

MH2W99 6/22/2010 13.3 201 J (139.6)

As = 28.5/1.0 

Pb = 68.25/1.0

Ref. 21, p. 6; Ref. 28, Table 1, p. 20, 

Appendix A, p. A-7, Appendix B, pp. B-1, 

B-4, B-11, B-32 

CO-SO-24 1.1 

MH2WA0 6/22/2010 31.3 253 J (175.7)

As = 28.5/1.0 

Pb = 68.25/1.0

Ref. 21, p. 6; Ref. 28, Table 1, p. 20, 

Appendix A, p. A-7, Appendix B, pp. B-1, 

B-4, B-11, B-33 

CO-SO-24 1.2 

MH2WA3 6/22/2010 39.3 275 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 6; Ref. 28, Table 1, p. 20, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-58 

CO-SO-28 4.3 

MH2WC7 6/22/2010 9.6 945 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 7; Ref. 28, Table 1, p. 21, 

Appendix A, p. A-9, Appendix B, pp. B-87, 

B-105 

Colorado Smelter CON000802700

HRS Documentation Record 
Page 30 of 50

Colorado Smelter HRS Documentation Record 

Colorado Smelter Residential Soil Samples (0-2") CLP Aliquots within and bounding AOC Area Letter A. 

Sample concentrations meet the HRS Table 2-3 criteria compared to CLP Aliquot background concentrations 

(Ref. 1, Table 2-3, p. 51589).

Sample ID/ 

CLP No.

Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) 3xBG/SQL (mg/kg) References

CO-SO-31 4.5 

MH2WB6 6/22/2010 11 364 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 7; Ref. 28, Table 1, p. 22, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-71 

CO-SO-32 4.4 

MH2WB5 6/22/2010 5.5 423 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 7; Ref. 28, Table 1, p. 22, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-70 

CO-SO-38 1.4 

MH2WB0 6/23/2010 19.5 387 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 9; Ref. 28, Table 1, p. 23, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-65 

CO-SO-40 1.1 

MH2WA1 6/23/2010 211 312 J (216.6)

As = 28.5/1.0 

Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-1, 

B-4, B-11, B-34 

CO-SO-40 1.2 

MH2WA2 6/23/2010 133 319 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-57 

CO-SO-40 1.4 

MH2WA9 6/23/2010 94.1 411 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-64 

CO-SO-40 4.1 

MH2WA7 6/23/2010 53 329 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-62 

CO-SO-40 4.2 

MH2WC6 6/23/2010 343 962 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-9, Appendix B, pp. B-87, 

B-104 

Colorado Smelter CON000802700

HRS Documentation Record 

Table 3: Residential Soil CLP Aliquots 
Page 31 of 50

Colorado Smelter HRS Documentation Record 

Table 3: Residential Soil CLP Aliquots 

Colorado Smelter Residential Soil Samples (0-2") CLP Aliquots within and bounding AOC Area Letter A. 

Sample concentrations meet the HRS Table 2-3 criteria compared to CLP Aliquot background concentrations 

(Ref. 1, Table 2-3, p. 51589).

Sample ID/ 

CLP No.

Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) 3xBG/SQL (mg/kg) References

CO-SO-40 4.3 

MH2WB9 6/23/2010 112 540 As = 28.5/1.0 

Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-74 

CO-SO-41 1.1 

MH2WB2 6/23/2010 72.6 364 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-67 

CO-SO-41 1.2 

MH2WB1 6/23/2010 47.1 373 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-66 

CO-SO-41 1.4 

MH2WC0 6/23/2010 58.7 353 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-9, Appendix B, pp. B-45, 

B-75 

CO-SO-41 1.5 

MH2WA8 6/23/2010 37 401 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-63 

CO-SO-42 1.1 

MH2WC4 6/23/2010 191 565 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-9, Appendix B, pp. B-87, 

B-102 

CO-SO-42 1.3 

MH2WB7 6/23/2010 78.6 499 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-72 

CO-SO-42 1.5 

MH2WA6 6/23/2010 32.8 351 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-61 

CO-SO-43 1.1 

MH2WB8 6/23/2010 26.9 463 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-73 

Colorado Smelter CON000802700

HRS Documentation Record 
Page 32 of 50

Colorado Smelter HRS Documentation Record 

Table 3: Residential Soil CLP Aliquots

Colorado Smelter Residential Soil Samples (0-2") CLP Aliquots within and bounding AOC Area Letter A. 

Sample concentrations meet the HRS Table 2-3 criteria compared to CLP Aliquot background concentrations 

(Ref. 1, Table 2-3, p. 51589).

Sample ID/ 

CLP No.

Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) 3xBG/SQL (mg/kg) References

CO-SO-43 1.2 

MH2WA4 6/23/2010 17.6 268 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-59 

CO-SO-43 1.4 

MH2WA6 6/23/2010 190 836 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, 

Appendix A, p. A-9, Appendix B, pp. B-45, 

B-61 

CO-SO-43 1.5 

MH2WB4 6/23/2010 119 406 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, 

Appendix A, p. A-8, Appendix B, pp. B-45, 

B-69 

CO-SO-43 4.1 

MH2WC3 6/23/2010 217 755 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, 

Appendix A, p. A-9, Appendix B, pp. B-87, 

B-101 

CO-SO-43 4.3 

MH2WC2 6/23/2010 144 683 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, 

Appendix A, p. A-9, Appendix B, pp. B-87, 

B-100 

CO-SO-43 4.4 

MH2WC1 6/23/2010 85.5 554 As = 28.5/1.0 Pb = 68.25/1.0

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, 

Appendix A, p. A-9, Appendix B, pp. B-45, 

B-76 

Bold Concentration meets or exceeds the Cancer Risk Screening Concentration (CRSC) for arsenic of 0.71 mg/kg (Ref. 2, p. BII-14).

J

The associated numerical value is an estimated quantity and is the approximate concentration of the analyte in the sample (Ref. 

28, Appendix B, p. B-55).

J qualified results have an unknown bias (Ref. 49).

J+ The associated numerical value is an estimated quantity, but the result may be biased high (Ref. 28, Appendix B, p. B-13).

( ) Adjusted value as per EPA Fact Sheet “Using Qualified Data to Document an Observed Release and

Observed Contamination” (Ref. 48, 18 pages).

SQL Sample Quantitation Limit. The SQL represents the Contract Required Quantitation Limit (CRQL) that has been adjusted

for sample-specific factors (Ref. 28, p. 6). It is equivalent to the HRS-defined SQL (Ref. 1, Section 1.1, Table 2-3).

mg/kg milligrams per kilogram

Colorado Smelter CON000802700

HRS Documentation Record 
Page 33 of 50

Colorado Smelter HRS Documentation Record 

Colorado Smelter CON000802700

HRS Documentation Record 

Table 4: Residential Soil XRF Composites 

Colorado Smelter Residential Soil Samples (0-2") XRF Composites within and bounding AOC Area Letter A. Sample 

concentrations meet the HRS Table 2-3 criteria compared to both CLP Aliquot and XRF Composite background 

concentrations (Ref. 1, Table 2-3, p. 51589).

Sample ID Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) DL/RL (mg/kg) References

CO-SO-01-2 6/21/2010 662 As = 6.3/21

Pb = 4.64/15.5

Ref. 21, p. 2; Ref. 28, Table 1, p. 15, Appendix C, p. 

C-14, Appendix D, p. D-1, Appendix G, p. G-1, 

Appendix H, p. H-13 

CO-SO-01-3 6/21/2010 785 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 2; Ref. 28, Table 1, p. 15, Appendix C, p. 

C-14, Appendix D, p. D-1, Appendix G, p. G-1, 

Appendix H, p. H-19 

CO-SO-07-4 6/22/2010 194 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 4; Ref. 28, Table 1, p. 17, Appendix C, p. 

C-14, Appendix D, p. D-3, Appendix G, p. G-1, 

Appendix H, p. H-94 

CO-SO-08-1 6/22/2010 263 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 4; Ref. 28, Table 1, p. 17, Appendix C, p. 

C-15, Appendix D, p. D-3, Appendix G, p. G-1, 

Appendix H, p. H-100 

CO-SO-10-1 6/22/2010 371 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 4; Ref. 28, Table 1, p. 17, Appendix C, p. 

C-15, Appendix D, p. D-3, Appendix G, p. G-1, 

Appendix H, p. H-120 

CO-SO-18-4 6/22/2010 339 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 5; Ref. 28, Table 1, p. 19, Appendix C, p. 

C-15, Appendix D, p. D-5, Appendix G, p. G-1, 

Appendix H, p. H-195 

CO-SO-22-1 6/22/2010 180 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 6; Ref. 28, Table 1, p. 20, Appendix C, p. 

C-15, Appendix D, p. D-5, Appendix G, p. G-2, 

Appendix H, p. H-227 

CO-SO-22-3 6/22/2010 235 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 6; Ref. 28, Table 1, p. 20, Appendix C, p. 

C-15, Appendix D, p. D-6, Appendix G, p. G-2, 

Appendix H, p. H-234 
Page 34 of 50

Colorado Smelter CON000802700

HRS Documentation Record 

Table 4: Residential Soil XRF Composites 

Colorado Smelter Residential Soil Samples (0-2") XRF Composites within and bounding AOC Area Letter A. Sample 

concentrations meet the HRS Table 2-3 criteria compared to both CLP Aliquot and XRF Composite background 

concentrations (Ref. 1, Table 2-3, p. 51589).

Sample ID Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) DL/RL (mg/kg) References

CO-SO-24-1 6/22/2010 373 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 6; Ref. 28, Table 1, p. 20, Appendix C, p. 

C-15, Appendix D, p. D-6, Appendix G, p. G-2, 

Appendix H, p. H-246 

CO-SO-28-1 6/22/2010 412 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 21, Appendix C, p. 

C-15, Appendix D, p. D-6, Appendix G, p. G-2, 

Appendix H, p. H-270 

CO-SO-28-4 6/22/2010 448 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 21, Appendix C, p. 

C-15, Appendix D, p. D-6, Appendix G, p. G-2, 

Appendix H, p. H-276 

CO-SO-29-4 6/22/2010 236 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 21, Appendix C, p. 

C-15 Appendix D, p. D-7, Appendix G, p. G-2, 

Appendix H, p. H-288 

CO-SO-30-2 6/22/2010 510 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 21, Appendix C, p. 

C-15 Appendix D, p. D-7, Appendix G, p. G-2, 

Appendix H, p. H-288 

CO-SO-30-4 6/22/2010 406 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 2; Ref. 28, Table 1, p. 21, Appendix C, p. 

C-15 Appendix D, p. D-7, Appendix G, p. G-2, 

Appendix H, p. H-301 

CO-SO-31-1 6/22/2010 351 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 22, Appendix C, p. 

C-15 Appendix D, p. D-7, Appendix G, p. G-2, 

Appendix H, p. H-307 

CO-SO-31-4 6/22/2010 473 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 22, Appendix C, p. 

C-15 Appendix D, p. D-7, Appendix G, p. G-2, 

Appendix H, p. H-313 

CO-SO-32-3 6/22/2010 280 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 22, Appendix C, p. 

C-16, Appendix D, p. D-7, Appendix G, p. G-2, 

Appendix H, p. H-319 
Page 35 of 50

Colorado Smelter CON000802700

HRS Documentation Record 

Table 4: Residential Soil XRF Composites 

Colorado Smelter Residential Soil Samples (0-2") XRF Composites within and bounding AOC Area Letter A. Sample 

concentrations meet the HRS Table 2-3 criteria compared to both CLP Aliquot and XRF Composite background 

concentrations (Ref. 1, Table 2-3, p. 51589).

Sample ID Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) DL/RL (mg/kg) References

CO-SO-32-4 6/22/2010 379 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 22, Appendix C, p. 

C-16, Appendix D, p. D-8, Appendix G, p. G-2, 

Appendix H, p. H-325 

CO-SO-33-1 6/22/2010 328 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 7; Ref. 28, Table 1, p. 22, Appendix C, p. 

C-16, Appendix D, p. D-8, Appendix G, p. G-2, 

Appendix H, p. H-331 

CO-SO-34-2 6/22/2010 147 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 8; Ref. 28, Table 1, p. 22, Appendix C, p. 

C-16, Appendix D, p. D-8, Appendix G, p. G-2, 

Appendix H, p. H-337 

CO-SO-35-1 6/22/2010 394 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 8; Ref. 28, Table 1, p. 23, Appendix C, p. 

C-16, Appendix D, p. D-8, Appendix G, p. G-2, 

Appendix H, p. H-348 

CO-SO-36-3 6/22/2010 519 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 8; Ref. 28, Table 1, p. 23, Appendix C, p. 

C-16, Appendix D, p. D-8, Appendix G, p. G-2, 

Appendix H, p. H-355 

CO-SO-37-1 6/23/2010 369 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 9; Ref. 28, Table 1, p. 23, Appendix C, p. 

C-16, Appendix D, p. D-8, Appendix G, p. G-2, 

Appendix H, p. H-361 

CO-SO-38-1 6/23/2010 407 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 9; Ref. 28, Table 1, p. 23, Appendix C, p. 

C-16, Appendix D, p. D-8, Appendix G, p. G-2, 

Appendix H, p. H-367 

CO-SO-38-4 6/23/2010 616 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 9; Ref. 28, Table 1, p. 23, Appendix C, p. 

C-16, Appendix D, p. D-9, Appendix G, p. G-2, 

Appendix H, p. H-373 

CO-SO-39-1 6/23/2010 363 As = 6.3/21 

Pb = 4.64/15.5

 Ref. 21, p. 9; Ref. 28, Table 1, p. 23, Appendix C, p. 

C-16, Appendix D, p. D-9, Appendix G, p. G-2, 

Appendix H, p. H-379 
Page 36 of 50

Colorado Smelter CON000802700

HRS Documentation Record 

Table 4: Residential Soil XRF Composites

Colorado Smelter Residential Soil Samples (0-2") XRF Composites within and bounding AOC Area Letter A. Sample 

concentrations meet the HRS Table 2-3 criteria compared to both CLP Aliquot and XRF Composite background 

concentrations (Ref. 1, Table 2-3, p. 51589).

Sample ID Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) DL/RL (mg/kg) References

CO-SO-39-4 6/23/2010 428 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 9; Ref. 28, Table 1, p. 23, Appendix C, p. 

C-16, Appendix D, p. D-9, Appendix G, p. G-2, 

Appendix H, p. H-385 

CO-SO-40-1 6/23/2010 188 515 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, Appendix C, 

p. C-16, Appendix D, p. D-9, Appendix G, p. G-2, 

Appendix H, p. H-392 

CO-SO-40-4 6/23/2010 149 581 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, Appendix C, 

p. C-16, Appendix D, p. D-9, Appendix G, p. G-2, 

Appendix H, p. H-398 

CO-SO-41-1 6/23/2010 105 542 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, Appendix C, 

p. C-16, Appendix D, p. D-9, Appendix G, p. G-2, 

Appendix H, p. H-404 

CO-SO-42-1 6/23/2010 135 538 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, Appendix C, 

p. C-16, Appendix D, p. D-10, Appendix G, p. G-2, 

Appendix H, p. H-417 

CO-SO-42-4 6/23/2010 359 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 10; Ref. 28, Table 1, p. 24, Appendix C, 

p. C-16, Appendix D, p. D-10, Appendix G, p. G-2, 

Appendix H, p. H-423 

CO-SO-43-1 6/23/2010 129 616 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, Appendix C, 

p. C-16, Appendix D, p. D-10, Appendix G, p. G-2, 

Appendix H, p. H-429 

CO-SO-43-4 6/23/2010 195 742 As = 6.3/21 

Pb = 4.64/15.5

Ref. 21, p. 10; Ref. 28, Table 1, p. 25, Appendix C, 

p. C-16, Appendix D, p. D-10, Appendix G, p. G-2, 

Appendix H, p. H-435 

Bold Concentration meets or exceeds the Cancer Risk Screening Concentration (CRSC) for arsenic of 0.71 mg/kg (Ref. 2, p. BII-14).

DL Detection Limit. HRS Table 2-3 allows for the use of the Detection Limit in place of the Sample Quantitation Limit (SQL) (Ref. 1,

Table 2-3, p. 51589).
Page 37 of 50

Colorado Smelter CON000802700

HRS Documentation Record 

RL

Reporting 

Limit

Arsenic Blank Cell Arsenic not detected above DL, or concentration is less than 10% of Pb concentration

mg/kg milligrams per kilogram
Page 38 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

Attribution

Between the 1880’s and the 1920’s, five smelters operated in the City of Pueblo and its nearby 

subdivisions. These included the Colorado Smelter, the Pueblo Smelter, the Philadelphia Smelter, the 

Massachusetts Smelter, and the Blende Smelter (Ref. 4, pp. 1-5; Figure 1 of this HRS documentation 

record). In addition to the smelters, the Colorado Fuel and Iron Co. (CF&I) located south of the Colorado 

Smelter (Figure 1) began operations in Pueblo in the late 1800s processing pig iron to make steel and iron 

products (Ref. 11, p. 298). This facility continues in operation under the name Rocky Mountain Steel 

Mills. The facility is an active Resource Conservation and Recovery Act (RCRA) facility with dozens of 

solid waste management units (SWMUs) in various stages of assessment and cleanup. The mill continues 

to operate under a state Resource Conservation and Recovery Act permit (CO-05-09-29-01) and a Clean 

Air Act Title V Operating Permit (95OPPB086) (Ref. 19, p. 3). 

Historical photographs (Ref. 4, p. 32, Ref. 9) of the Colorado Smelter show plumes of smoke carried by 

wind being dispersed away from the stacks to the southeast. Sanborn Fire Insurance maps (Ref. 8) show 

drawings of the Colorado Smelter and note the height of the main smoke stack as 135 feet and a 200-foottall brick chimney for the roaster house as well as several other stacks (Ref. 8c, Sheet 23, Ref. 8d, Sheet 

157). 

Prevailing winds at the Colorado Smelter during the time of operation were out of the north and northwest 

as noted on Sanborn Fire Insurance Maps for the years 1883-1904 (Refs. 8a, p.1; 8b, p. 1; 8c, p. 1; 8d, p. 

1). Wind rose diagrams from a meteorological station located just south of the Colorado Smelter on the 

Rocky Mountain Steel Mill for the time period January 1, 2003 - December 31, 2005 and March 1, 2008 - 

February 28, 2009 show prevailing winds out of the west-northwest (Ref. 46, pp. 1-3). 

It has been documented that smelter stack emissions contain particulates of heavy metals (Ref. 42, pp. 53, 

55; Ref. 43, pp. 170, 172). Samples of the slag generated by the Colorado Smelter contain lead and 

arsenic (Ref. 22, p. 58) and it is reasonable to conclude that particulate emissions from the Colorado 

Smelter stacks also contained lead and arsenic. In addition, the ore from the Madonna mine processed at 

the Colorado Smelter contained 30 percent lead (Ref. 4, p.34, Ref. 5). In the smelting process, it is not 

possible to separate all the desired metal from other products including slag and flue dust (Ref. 44, p. 92). 

Flue dust samples collected from a smelter in Montana (the AMC smelter) contained arsenic and lead at 

concentrations up to 14,300 ppm and 55,000 ppm, respectively (Ref. 45, pp.8, 98, 106). Slag from the 

AMC smelter contained arsenic and lead at concentrations of 217 ppm and 3,120 ppm, respectively 

(Sample AM-SO-06) (Ref. 50, Table 2, p. 46). In comparison, the average concentration of arsenic and 

lead in slag for the Colorado Smelter based on nine CLP aliquot samples is 503 ppm and 10,333 ppm, 

respectively (Ref. 28, Table 1, p. 14) further indicating that stack emissions from the Colorado Smelter 

also contained arsenic and lead. 

The area of area of observed contamination as shown on Figure 4 of this HRS documentation record is 

located within 1800 feet of the northern (and most distal) smoke stack depicted and within 1663 feet of 

the southern (and more proximal) smoke stack depicted. The proximity of the stacks to the area of 

observed contamination along with the historic prevailing wind direction is evidence that at least a portion 

of the significant increase in lead and arsenic in AOC A is attributable to the Colorado Smelter stacks. 

The map (Ref. 14a) from the 1995 ARR for the Santa Fe Avenue Bridge Culvert (Ref. 14) shows the 

spatial distribution of arsenic and lead contamination in soils surrounding the five smelters that were 

operating in Pueblo from 1878 (Ref. 4, p. 13) until 1921 (Ref. 4, pp. 114-115). The map shows a pattern 

that indicates a significant increase in lead and arsenic levels adjacent to the Colorado Smelter. 
Page 39 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

The study of the metal content of surface soils in Pueblo conducted by affiliates of Colorado State 

University published in 2006 (Ref. 11) also show an increase in lead concentration near the Colorado 

Smelter. Sites 19A/19B and 20A/20B located southeast of the Colorado Smelter indicate lead 

concentrations ranging from 149 ppm to 287 ppm (Ref. 11, Figure 1 and Table 1; Ref. 47). 

The increase in lead soil concentrations in residential areas proximal to the Colorado Smelter based on 

data from the Colorado Smelter Site Inspection ARR (Ref. 22) is illustrated by Figures 6 and 7 (Refs. 32a 

and 32b). These maps present the lead soil concentration using graduated symbols that graphically depict 

lead concentrations which are hence easily observed to be higher in the residential areas immediately 

south and east of the Colorado Smelter. 

For the area of observed contamination comprising 176 residential properties a portion of the significant 

increase is attributable to the Colorado Smelter. The presence of lead and arsenic soil contaminated to 

levels meeting HRS Table 2-3 criteria indicate lead and arsenic were emitted from the smelter’s smoke 

stacks and deposited on nearby soil. 

Area of Contamination Hazardous Waste Quantity

- Hazardous Constituent Quantity: 

Description

The hazardous constituent quantity for AOC A could not be adequately determined according to 

the HRS requirements; that is, the total mass of all CERCLA hazardous substances in the area is 

not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 51590-51591 (Section 

2.4.2.1.1)]. There are insufficient historical and current data (manifests, PRP records, State 

records, permits, waste concentration data, etc.) available to adequately calculate the total mass of 

all CERCLA hazardous substances in AOC A and the associated releases from AOC A. 

Therefore, hazardous constituent quantity is not scored (NS). 

Are the data complete for Hazardous constituent quantity for this area? NO 

Hazardous Constituent Quantity Assigned Value: NS 

- Hazardous Wastestream Quantity: 

Description

The hazardous wastestream quantity for AOC A could not be adequately determined according to 

the HRS requirements; that is the total mass of all CERCLA hazardous wastestreams in the area 

is not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 51591 (Section 

2.4.2.1.1)]. There are insufficient historical and current data (manifests, PRP records, State 

records, permits, waste concentration data, etc.) available to adequately calculate the total mass of 

all CERCLA hazardous wastestreams in AOC A and the associated releases from AOC A. 

Therefore, hazardous wastestream quantity is not scored (NS). 

Are the data complete for Hazardous Wastestream quantity for this area? NO 

 Sum (pounds): NA 

 Wastestream Quantity/5,000 (Ref. 1, Table 5-2): NA 

Hazardous Wastestream Quantity Assigned Value: NS 
Page 40 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

- Volume: 

Description

In accordance with HRS Table 5-2, Volume, Tier C, is not evaluated for source type 

contaminated soil. 

Are the data complete for Hazardous volume for this area? NO 

 Sum (yd3/gal): NA 

 Equation for Assigning Value (Ref. 1, Table 5-2): NA 

Volume Assigned Value: NS

- Area: 

Description 

AOC A as depicted on Figure 4 of this HRS documentation record encompasses a total of 

2,110,110 square feet (Ref. 41). The unpaved portion of AOC A is 645,216 square feet (Ref. 41). 

Calculation 

By following the stated procedure outlined in Sections 2.4.2 and 5.1.2.2 and Table 5-2 of the 

HRS (Ref. 1, p. 51647, Table 5-2), the area value is assigned as follows: 645,216 /34,000 = 18.97 

Area Assigned Value: 18.97 
Page 41 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

Letter by which this Area is to be identified: B 

Name of area: Slag Pile 

Location and Description of the area (with reference to a map of the site): 

As a by-product of the smelting process, the Colorado Smelter generated molten material that cooled and 

formed slag as it was deposited in a topographic low or ravine north and west of the smelter location (Ref. 

4, pp. 34, 35, 36). Although some of the slag material was removed from the facility in the early 20th

century for use as railroad ballast (Ref. 10), a significant slag pile remains. Photographs of the slag pile 

are contained in the PA (Ref. 19, pp. 46, 47). The land surface area under the slag pile was derived using 

ArcMap and a high resolution aerial photograph obtained from Pueblo County (Ref. 35) resulting in an 

area of 728,171 ft2 (Ref. 27). 

Background Sample Locations and Concentrations for Area B, the Slag Pile

Background samples, concentrations and considerations are the same as for Area A, Residential Soil, 

described and presented in Tables 1 and 2, above. 

Observed Contamination Sample Locations and Concentrations for Area B, the Slag Pile

Samples from 4 locations within the slag pile were collected and analyzed during the CDPHE Site 

Inspection as described in Section 5.0.1 above for Area A, Residential Soils. The area of observed 

contamination for Area B, the Slag Pile, and the sample locations used to define it are shown on Figure 4 

of this HRS documentation record and presented in the Tables 5 and 6, below. 
Page 42 of 50

Colorado Smelter CON000802700

HRS Documentation Record 

Colorado Smelter HRS Documentation Record 

Table 5: Slag Pile CLP Aliquots 

Colorado Smelter Slag Pile Samples (0-2") CLP Aliquots within AOC Area Letter B. Sample concentrations meet the 

HRS Table 2-3 Criteria compared to CLP Aliquot background concentration (Ref. 1, Table 2-3, p. 51589).

Sample ID/ 

CLP No.

Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) 3xBG/SQL (mg/kg) References

CO-WP-01 1.2 

MH2WD5 6/21/2010 528 8570 As = 28.5/1.0Pb = 68.25/25

Ref. 21, p. 2; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-900, A-1289, Appendix B, pp. B87, B-113, B-118

CO-WP-01 1.3 

MH2WD7 6/21/2010 1740 26500 As = 28.5/100Pb = 68.25/100

Ref. 21, p. 2; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-1289, Appendix B, pp. B-87, B115, B-120 

CO-WP-02 1.1 

MH2WD0 6/21/2010 3240 As = 28.5/1.0Pb = 68.25/50

Ref. 21, p. 2; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-899, A-901, Appendix B, pp. B87, B-108

CO-WP-02 1.2 

MH2WB3 6/21/2010 33.1 478 As = 28.5/1.0Pb = 68.25/1.0

Ref. 21, p. 2; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-8, A-477, Appendix B, pp. B-45, B-68

CO-WP-02 1.3 

MH2WD1 6/21/2010 53.5 8500 As = 28.5/1.0 Pb = 68.25/50

 Ref. 21, p. 2; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-899, A-901, Appendix B, pp. B87, B-109

CO-WP-03 1.1 

MH2WD6 6/22/2010 452 12400 As = 28.5/1.0 Pb = 68.25/50

 Ref. 21, p. 4; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-900, A-1289, Appendix B, pp. B87, B-114, B-119

CO-WP-03 1.3 

MH2WD8 6/22/2010 1200 18100 As = 28.5/50 Pb = 68.25/50

 Ref. 21, p. 4; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-1289, Appendix B, pp. B-87, B116, B-121 

CO-WP-03 1.5 

MH2WD4 6/22/2010 359 7950 As = 28.5/1.0 Pb = 68.25/25

 Ref. 21, p. 4; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-900, A-902, Appendix B, pp. B87, B-112
Page 43 of 50

Colorado Smelter CON000802700

HRS Documentation Record 

Table 5: Slag Pile CLP Aliquots

Colorado Smelter Slag Pile Samples (0-2") CLP Aliquots within AOC Area Letter B. Sample concentrations meet the 

HRS Table 2-3 Criteria compared to CLP Aliquot background concentration (Ref. 1, Table 2-3, p. 51589).

Sample ID/ 

CLP No.

Sample 

Date

Arsenic 

(As) 

(mg/kg)

Lead 

(Pb) 

(mg/kg) 3xBG/SQL (mg/kg) References

CO-WP-04 1.3 

MH2WD3 6/23/2010 133 7260 As = 28.5/20 Pb = 68.25/20

Ref. 21, p. 9; Ref. 28, Table 1, p. 14, Appendix 

A, pp. A-9, A-1288, Appendix B, pp. B-87, B111, B-117

Bold Concentration meets or exceeds the Cancer Risk Screening Concentration (CRSC) for arsenic of 0.71 mg/kg (Ref. 2, p. BII-14).

SQL Sample Quantitation Limit. The SQL represents the Contract Required Quantitation Limit (CRQL) that has been adjusted

for sample-specific factors (Ref. 28, p. 6). It is equivalent to the HRS-defined SQL (Ref. 1, Section 1.1, Table 2-3).

mg/kg milligrams per kilogram
Page 44 of 50

Colorado Smelter HRS Documentation Record 

Colorado Smelter CON000802700

HRS Documentation Record 

Table 6: Slag Pile XRF Composites

Colorado Smelter Slag Pile Samples (0-2") XRF Composites within AOC Area Letter B. Sample concentrations 

meet the HRS Table 2-3 criteria compared to both CLP Aliquot and XRF Composite background concentrations 

(Ref. 1, Table 2-3, p. 51589).

Sample ID Sample 

Date

Lead 

(Pb) 

(mg/kg) DL/RL (mg/kg) References

CO-WP-01 6/21/2010 5417 Pb = 4.64/15.5

Ref. 21, p. 2; Ref. 28, Table 1, p. 14, Appendix C, p. C13, Appendix D, p. D-12, Appendix G, p. G-1, 

Appendix H, p. H-515 

CO-WP-02 6/21/2010 1468 Pb = 4.64/15.5

Ref. 21, p. 2; Ref. 28, Table 1, p. 14, Appendix C, p. C14, Appendix D, p. D-12, Appendix G, p. G-1, 

Appendix H, p. H-522 

CO-WP-03 6/22/2010 8066 Pb = 4.64/15.5

Ref. 21, p. 4; Ref. 28, Table 1, p. 14, Appendix C, p. C14, Appendix D, p. D-12, Appendix G, p. G-1, 

Appendix H, p. H-528

CO-WP-04 6/23/2010 1278 Pb = 4.64/15.5

Ref. 21, p. 9; Ref. 28, Table 1, p. 14, Appendix C, p. C14 Appendix D, p. D-12, Appendix G, p. G-1, 

Appendix H, p. H-534 

DL Detection Limit. HRS Table 2-3 allows for the use of the Detection Limit in place of the Sample Quantitation Limit (SQL) 

(Ref. 1, Table 2-3, p. 51589).

RL Reporting Limit

mg/kg milligrams per kilogram
Page 45 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

Attribution

The contamination in Area B, the Slag Pile, is attributable to the site by virtue of the fact that the slag 

material was generated by the Colorado Smelter during its years of operation from 1883-1908 (Ref. 4. pp. 

4, 33, 35, 36; Ref. 5). A slag pile was evident at the Colorado Smelter dating back to 1888 (Ref. 4. p. 34, 

Ref. 5). 

Area of Contamination Hazardous Waste Quantity

- Hazardous Constituent Quantity: 

Description

The 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 area is 

not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 51590-51591 (Section 

2.4.2.1.1)]. There are insufficient historical and current data (manifests, PRP records, State 

records, permits, waste concentration data, etc.) available to adequately calculate the total mass of 

all CERCLA hazardous substances in Area B and the associated releases from Area B. Therefore, 

hazardous constituent quantity is not scored (NS). 

Are the data complete for Hazardous constituent quantity for this area? NO 

Hazardous Constituent Quantity Assigned Value: NS 

- Hazardous Wastestream Quantity: 

Description

The hazardous wastestream quantity for Area B could not be adequately determined according to 

the HRS requirements; that is the total mass of all CERCLA hazardous wastestreams in the area 

is not known and cannot be estimated with reasonable confidence [Ref. 1, pp. 51591 (Section 

2.4.2.1.1)]. There are insufficient historical and current data (manifests, PRP records, State 

records, permits, waste concentration data, etc.) available to adequately calculate the total mass of 

all CERCLA hazardous wastestreams in Area B and the associated releases from Area B. 

Therefore, hazardous wastestream quantity is not scored (NS). 

Are the data complete for Hazardous Wastestream quantity for this area? NO 

 

 Sum (pounds): NA 

 Wastestream Quantity/5,000 (Ref. 1, Table 5-2): NA 

Hazardous Wastestream Quantity Assigned Value: NS 
Page 46 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

- Volume: 

Description

In accordance with HRS Table 5-2, source type pile is not eligible to be evaluated for Volume, 

Tier C, in the soil exposure pathway. 

Are the data complete for Hazardous volume for this area? NO 

 

 Sum (yd3/gal): NA 

 Equation for Assigning Value (Ref. 1, Table 5-2): NA 

Volume Assigned Value: NS

- Area: 

Description 

AOC B as depicted on Figure 4 of this HRS documentation record measures 728,171 square feet 

(Ref. 27).

Calculation 

By following the stated procedure outlined in Sections 2.4.2 and 5.1.2.2 and Table 5-2 of the 

HRS (Ref. 1, p. 51647, Table 5.2), the area value is assigned as follows: 728,171 /34= 21,416.79 

Area Assigned Value: 21,416.79
Page 47 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

5.1 RESIDENT POPULATION THREAT 

All samples listed in Section 5.0.1 of this HRS documentation record for Area A, Residential Soil, were 

collected within 200 feet of the residences because the properties from which the soil samples were 

collected are less than 200 feet in width and length (Figure 4 of this HRS documentation record and Ref. 

36). Analysis of sample CO-SO-40 4.2 (CLP number MH2WC6) collected on June 23, 2010 with an 

arsenic concentration of 343 mg/kg and a lead concentration of 962 mg/kg, in surface soils from a 

collection depth < 2 feet bgs (Ref. 39) documents the resident population threat (Ref. 21, p. 10; Ref. 28, 

Table 1, p. 24, Appendix A, p. A-9, Appendix B, pp. B-87, B-104). 

5.1.1 Likelihood of Exposure 

As documented above, the soil samples collected from Area A, Residential Soils, meet the criteria for 

observed contamination (Ref. 1, Section 5.0.1, p. 51646). The contamination is within the property 

boundary of each residence and within 200 feet of each residence; therefore, the likelihood of exposure 

factor for the resident population threat is assigned a value of 550 (Ref. 1, Section 5.1, p. 51646). 

Resident Population Threat Likelihood of Exposure Category Value: 550
Page 48 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

5.1.2 Waste Characteristics 

5.1.2.1 Toxicity 

The toxicity value of both arsenic and lead is 10,000 (Ref. 2, p. B-1, B-8). The toxicity factor value of 

10,000 is assigned in accordance with Reference 1, p. 51646, Section 5.1.2.1. 

Highest Toxicity Factor Value: 10,000 

5.1.2.2 Hazardous Waste Quantity 

The sum of the Hazardous Waste Quantity for AOC A and AOC B is (18.97 + 21,416.79 = 21,435.76).

Hazardous Waste Quantity for AOC A and AOC B = 21,435.76 

Hazardous Waste Quantity Factor Value: 10,000 

(Ref. 1, Table 2-6) 

5.1.2.3 Calculation of Waste Characteristics Factor Category Value 

The waste characteristics factor value for the soil exposure pathway is calculated below, as specified in 

the HRS (Ref. 1, Section 5.1.2.3, p. 51647) 

Toxicity: 10,000 

HWQ Factor Value: 10,000 

Toxicity (10,000) x HWQ Factor Value (10,000) = 100,000,000 

Waste Characteristics Factor Category Value: 100 

(Ref. 1, Table 2-7) 
Page 49 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

5.1.3 TARGETS 

5.1.3.1 Resident Individual 

Level of Contamination (Level I/Level II): Level I 

There are residential soil samples that exhibit Level I arsenic contamination in Area A as listed in Table 3 

of this HRS documentation record and including sample CO-SO-40 1.1(Ref. 28, Table 1, p. 24). These 

samples were all collected on the resident individual’s property and within 200 linear feet of the 

residence; therefore a resident individual factor value of 50 is assigned (Ref.1, Section 5.1.3.1, p. 51647, 

Figure 4 of this HRS documentation record). 

Resident Individual Factor Value: 50

5.1.3.2 Resident Population 

5.1.3.2.1 Level I Concentrations 

Area Letter Sample ID Number of 

Residences 

No. of 

Residents 

A CO-SO-24, 40, 41, 42, 43 5 15.47

Analysis from residential surface soil samples indicates the presence of arsenic at levels meeting the HRS 

observed contamination criteria (see Table 3 of this HRS documentation record and Reference 1, Table 2-

3 and Section 5.0.1), and exceeding the applicable health based benchmark of 0.71 ppm (Cancer Risk 

Screening Concentration (CRCS)) (Ref. 2, p. BII-14) at 5 residences. The EPA determined that the actual 

number of persons living in four of the residences totaled 13 people (Ref. 40). The actual number of 

persons living in the fifth household was not determined, so the county average of 2.47 persons per 

household in Pueblo County, Colorado was used (Ref. 34) for that household for a total of 15.47 

individuals subject to Level I arsenic concentrations. For individuals subject to Level I contamination, 

the appropriate factor value is determined by multiplying by 10 (Ref. 1, Section 5.1.3.2.1, p. 51647) 

yielding a total factor value of 155. 

Level I Concentrations Factor Value: 155

5.1.3.2.2 Level II Concentrations 

Besides the five residences that have Level I contamination within 200 feet of the residence, 171 

residences are exposed to Level II contamination. The number of residential properties subject to Level II 

concentrations was obtained by counting the number of residential properties within the area of observed 

contamination shown on Figure 4 of this HRS documentation record, and Ref. 38. Please see Tables 3 and 

4 of this HRS documentation record for specific samples that delineate the area shown on Figure 4 (Ref. 
Page 50 of 50 

Colorado Smelter CON000802700

HRS Documentation Record 

28, Table 1). 171 residences with a county average of 2.47 individuals per residence results in 422 people 

being exposed to Level II concentrations. 

Sum of individuals subject to Level II contaminations: 422 

Level II Concentrations Factor Value: 422

5.1.3.3 Workers 

Total workers were not scored (NS) 

Workers Factor Value: NS 

5.1.3.4 Resources 

Resource Description: There is no commercial agriculture, silviculture, or commercial livestock 

production or grazing within the area of observed contamination. 

Resources Factor Value: 0 

5.1.3.5 Terrestrial Sensitive Environments 

Sensitive Environment Description: There are no terrestrial sensitive environments identified within the 

area of observed contamination. 

Terrestrial Sensitive Environments Factor Value: 0 

5.2 NEARBY POPULATION THREAT 

Nearby population threat was not scored. 

Nearby Population Threat Factor Value: NS