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 CON0008027 00 HRS Documentation Record HRS D OCUMENTATION 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: 38.2491 o North

Longitude: 104.608 o West

Ref: Th e 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 CON0008027 00 HRS Documentation Record

WORKSHEET FOR COMPUTING HRS SITE SCORE

S S 2

1. Ground water Migration Pathway Score (S gw ) 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 (S sw ) NS NS_ Enter the larger of lines 2a and 2b as the pathway score.

3. Soil Exposure Pathway Score (S s ) 100 10000 (fr om Table 5-1, line 22)

4. Air Migration Pathway Score (S a ) (from Table 6-1, line 12) NS NS

_

5. Total of S gw 2 + S sw 2 + S s 2 + S a 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 CON0008027 00 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) 1 55 6b. Level II Concentrations (b) 4 22 6c. Re sident 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) 6 27 Resident Population Threat Score: 11. Resident Population Threat (lines 1 x 4 x 1 0) (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 Quan tity (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 Score d (S s ), (lines [11 + 21]/82,500, subject to a maximum of 100) 100 100 .00

### Page 4 of 50

Colorado Smelter CON0008027 00 HRS Documentation Record a Maximum value applies to waste characteristics category.
b Maximum value not applicable.

c No specific maximum value applies to factor. However, pathway score based solely on terrestrial sensitive environments is limited to maximum of 60.
d Do not round to nearest integer. NS = Not Scored

### Page 5 of 50

Colorado Smelter CON0008027 00 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

Tabl e 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 CompositesA r k

a

n

s

a

s R i v

e

rI-25Santa 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 2,000 4,000 1,000 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, 2012Figure 2: Colorado Smelter Sanborn Fire Insurance Map 1904/05 Sheet 157Front Yard (Zone 1) 5- point multi

increment Back Yard (Zone 4) 5- point multi

increment Side Yard (Zone 2) 5- point multi

increment

Side Yard (Zone 3) 5- point multi

increment



### FIGURE 3 – COLORADO SMELTER RESIDENTIAL SOIL SAMPLING S CHEMATIC NOT TO SCALE Source: Ref.20, Figure 3

## " /

" /

" / " /

" /

" / " / " /

" / " / " /

" / " / " /

" / " / " / " / " / " / " / " /

" /

" /

" / " / " /

" / " /

" / " / " /

" / " /

" / " / " / " / " /

" / " /

" / " /

" /

" / " / " /

" / " /

" / " / " /

" / " / " / " / " / " / " / " /

" / " /

" / " / " /

" /

" /

" /

" / " / " / " / " / " / " /

! .

! .

! . ! .

! . ! . ! . ! .

! . ! . ! .

! .

! . ! . ! .

! . ! . ! . ! . ! . ! .

' 'TAYLOR AVENUESANTA FE AVENUEEILERS AVENUEBERWIND AVENUE MESA AVENUE

NORTHERN AVENUE 

### Ar k



### a



### n

s

a

s 

## R 

## i v



## e



## r I-25 RR TracksSanta 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 

# ± 0 500 1,000 250 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



## " / " / " / " /

! . SO-14- 1.4

### Page 10 of 50

Colorado Smelter CON0008027 00 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 CON0008027 00 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 In ves tigation for the Santa Fe Avenue Bridge Culvert, Pueblo, Colorado. COD #982572513. 49 pages.

14 CD H. June 10, 1995. Analytical Results Report, Expanded Site Investigation for the Santa Fe Av enue 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, Col orado. 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 CON0008027 00 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 CDP HE. March 26, 2012. Figure 5. Surficial Geology Map fo r Background and Release Sample Locations, Colorado Smelter. Figure created by downloading shapefiles f ro m 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 t he 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 CON0008027 00 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 fr om: 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, 20 12. 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. Mc Graw-Hill Book Company, New York. Excerpt, 8 pages.

### Page 14 of 50

Colorado Smelter CON0008027 00 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
t he 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 CON0008027 00 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 recor d 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 i n 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 document ed 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 CON0008027 00 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 ca n 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 in 1908 , 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 addi tion 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 s ample 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 CON0008027 00 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

se nt to a laboratory for confirmatory analysis. There was excellent correlation for lead concentrations between XRF and laboratory results with an r 2 (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 Inspect io n 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 residentia l 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 CON0008027 00 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 com posites, 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 (r 2 ) 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 r 2 value of 0.85 to 1.0 is considered a definitive data qual ity 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 r 2 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 CON0008027 00 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 su rface 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 Fi g. 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 - Februa ry 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 CON0008027 00 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 CON0008027 00 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 Smelte r also contain ed 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 CON0008027 00 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. Th erefore, 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 CON0008027 00 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

r esidential 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).

A ll 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 CON0008027 00 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 com parison 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 anal ysis is presented in the ARR (Ref. 22, Figure 7, p 37). The coefficient of correlation (r 2 ) 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 r 2 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, 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 (r 2 ) 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 CON0008027 00 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 tra ce 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 concentration s (Ref. 11, p. 305, Figure 3) in Pueblo indicates soil sample s collected at sites 31 A/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 CON0008027 00 HRS Documentation RecordPage 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

- BG

01 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. D

1, Appendix G, p. G

- 1, Appendix H, p. H

1

CO

- SO

- BG

02 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. D

1, Appendix G, p. G

- 1, Appendix H, p. H

7

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 CON0008027 00 HRS Documentation Record

### Page 28 of 50

Colorado Smelter CON0008027 00 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 H RS 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

Co lorado Smelter CON0008027 00 HRS Documentation RecordPage 30 of 50 Colorado Smelt er 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 CON0008027 00 HRS Documentation Record Table 3: Residential Soil CLP AliquotsPage 31 of 50 Colorado Smelte r 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

Colora do Smelter CON0008027 00 HRS Documentation RecordPage 32 of 50 Colorado Smelt er 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 Quanti t ation 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 CON0008027 00 HRS Documentation RecordPage 33 of 50

Colorado Smelt er HRS Documentation Record

Colorado Smelter CON0008027 00 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

- 234Page 34 of 50

Colorado Smelter CON0008027 00 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

- 319Page 35 of 50

Colorado Smelter CON0008027 00 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

- 379Page 36 of 50

Colorado Smelter CON0008027 00 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 CON0008027 00 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 CON0008027 00 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) showdrawings 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 - Februa ry 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) contain ed 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 contain ed

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). Th e 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 CON0008027 00 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 incr ease 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 CON0008027 00 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 CON0008027 00 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 20 th 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 ft 2 (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 CON0008027 00 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) Refere nces

CO

- WP

- 01 1.2

MH2WD5 6/21/2010 528 8570 As = 28.5/1.0 Pb = 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. B

87, B

- 113, B

- 118

CO

- WP

- 01 1.3

MH2WD7 6/21/2010 1740 26500 As = 28.5/100 Pb = 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, B

115, B

- 120

CO

- WP

- 02 1.1

MH2WD0 6/21/2010 3240 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. B

87, B

- 108

CO

- WP

- 02 1.2

MH2WB3 6/21/2010 33.1 478 As = 28.5/1.0 Pb = 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. B

87, 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. B

87, 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, B

116, 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. B

87, B

- 112Page 43 of 50

Colorado Smelter CON0008027 00 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, B

111, 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 Quanti t ation 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 kilogramPage 44 of 50

Colorado Smelt er HRS Documentation Record

Colorado Smelter CON0008027 00 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. C

13, 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. C

14, 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. C

14, 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. C

14 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 CON0008027 00 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 CON0008027 00 HRS Documentation Record - V olume: 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

- A rea:
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 CON0008027 00 HRS Documentation Record 5.1 R ESIDENT 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 reco rd 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 CON0008027 00 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: 1 0,000
(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) = 1 00 ,000,000
Waste Characteristics Factor Category Value: 100 (Ref. 1, Table 2-7)

### Page 49 of 50

Colorado Smelter CON0008027 00 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, 4 2, 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 CON0008027 00 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