375974

FIL E PLAN

INTERIM STATUS REPORT

CONSOLIDATED FINDING S

OF SOIL-LEAD INVESTIGATIONS AT T HE CALIFORNIA GULCH NPL SITE

VOLUME H — APPENDICES

June 1996

U.S. Environmental Protection Agency Region VIH One Denver Place

999 18th Street, Suite 500 Denver, Colorado 80202-2405
INTERIM STATUS REPORT CONSOLIDATED FINDINGS OF SOIL-LEAD INVESTIGATIONS AT T HE CALIFORNIA GULCH NPL SITE

June 1996

Prepared for

U.S. Environmental Protection Agency Region Vm One Denver Place

999 18th Street, Suite 500 Denver, Colorado 80202-2405

EPA Work Assignment No. 04601-037 Document Control No. 4800-37-0205

Prepared by

R OY F. WESTON, INC.

215 Union Blvd., Suite 550 Lakewood, Colorado 80228-1842
APPENDIX A

SOIL LEAD REMEDIAL INVESTIGATION
APPENDIX A

SOIL LEAD REMEDIAL INVESTIGATION

TABLE OF CONTENTS

Section Title Page

A.1 MAPPING ...................................... A-l

A .2 AIR PATHWAY INVESTIGATION (WCC, 1992a) ............ A-2 A.2.1 Objectives ................................. A-2 A.2.2 Methods ................................... A-3 A.2.2.1 Meteorological Measurements .............. A-3 A.2.2.2 Air Quality Measurements ................ A-3 A.2.3 Results ................................... A-4 A.2.3.1 Meteorological Conditions ................ A-4 A.2.3.2 Air Quality Monitoring .................. A-7

A .3 POPULATED STUDY AREA SURFACE SOIL INVESTIGATIONS . A-8 A.3.1 State of Colorado Department of Law (E-S, 1986) ......... A-8 A.3.1.1 Soil Sampling ...................... A-10 A.3.1.2 Soil Sampling Method ................. A-l l A.3.1.3 Chemical Analysis .................... A-l l A.3.1.4 Soil Survey Results ................... A-l l A.3.2 Remedial Investigation Report (CH2

M Hill , 1987) ........ A-15 A.3.2.1 Geology .......................... A-15 A.3.2.2 Soils ............................ A-17 A3.2.3 Surface Water ...................... A-17 A.3.2.4 Climate .......................... A-17 A.3.2.5 Air Quality ........................ A-18 A.3.2.6 Nature and Extent of Contamination ......... A-18 A.3.3 Soils Investigation in the Leadville Study Area (Walsh, 1988) . A-25 A.3.3.1 Methods .......................... A-25 A.3.3.2 Results ........................... A-26 A.3.4 Residential Surface Soils and Household Dust Sampling (Walsh, 1990) ..................... A-27 A.3.4.1 Sampling Procedures .................. A-27 A.3.4.2 Sampling Locations ................... A-28 A.3.4.3 Analysis of Surface Soil and Dust Samples ..... A-28 A.3.4.4 Results ........................... A-28 A.3.5 Soils Investigation Data Report (CDM, 1993) ........... A-29 A.3.5.1 Soils Investigation Sample Locations ......... A-29 A.3.5.2 Soil Sampling ...................... A-30 A.3.5.3 Sampling Method .................... A-30

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

Document Control No. 4800-37-0205 Interim Status Report Page A-ii

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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APPENDIX A

TABLE OF CONTENTS (continued)

Section Title Page

A.3.5.4 Analysis of Soil Samples ................ A-31 A.3.5.5 Results ........................... A-32 A.3.6 Soils Investigation, California Gulch Study Area

(Walsh, 1992a) ............................. A-33 A.3.6.1 Geology .......................... A-34 A.3.6.2 Soils ............................ A-34 A.3.6.3 Soil Sampling ...................... A-35 A.3.6.4 Soil Sampling Method ................. A-36 A.3.6.5 Surficial Geologic Mapping .............. A-36 A.3.6.6 Laboratory Analysis ................... A-37 A.3.6.7 Results ........................... A-37 A.3.7 Smelter Remedial Investigation Report (Walsh, 1993) ...... A-47 A.3.7.1 Air Dispersion Modeling ................ A-48 A.3.7.2 Smelter Soil Sampling ................. A-48 A.3.7.3 Areas Impacted by Smelter Emissions ........ A-49 A.3.7.4 Results ........................... A-50 A.3.8 Surface Water Remedial Investigation Report (WCC, 1993c) . . A-58 A.3.8.1 Surface Water Flow Monitoring and Sample Collection System Locations .............. A-59 A.3.8.2 Surface Water and Bed Material Sampling ..... A-59 A.3.8.3 Analysis of Surface Water and Bed Material .... A-60 A.3.8.4 Nature and Extent of Contamination ......... A-60 A.3.9 Metal Speciation and Source Characterization

(Drexler, 1995) ............................. A-64 A.3.10 WESTON XRF Residential Surface Soils Investigation

(WESTON, 1991b) ........................... A-65 A.3.10.1 Sampling ......................... A-66 A.3.10.2 Results ........................... A-67 A.3.11 Data Report for Lead Occurrence in and Immediately Adjacent to Residential Areas, California Gulch Site, Leadville, Colorado (University of Cincinnati, 1991) ....... A-68 A.3.11.1 Data Collection Process ................ A-69 A.3.11.2 Sample Collection .................... A-69 A.3.11.3 Interior Dust Sampling ................. A-69 A.3.12 Pre-mining Soils Geochemistry Report (Walsh, 1993) ...... A-70 A.3.12.1 Geologic Mapping .................... A-71 A.3.12.2 Methods for Estimating Pre-mining Soil Metal Concentrations ............... A-71 A.3.12.3 Development of Soil-Geologic Units ......... A-75

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-iii THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN

WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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Section

APPENDIX A

TABLE OF CONTENTS (Continued)

Title Page

A.3.12.4 Distinguishing Between Disturbed and Undisturbed Soils .................... A-75 A.3.12.5 Results ........................... A-77 A.3.12.5.1 Background Metal Concentrations

in Landscape Positions ........ A-77 A.3.12.5.2 Background Metal Concentrations in Soil-Geologic Units .......... A-78 A.3.12.5.3 Metal Concentrations in Disturbed and Undisturbed Soils ........... A-78

A4 REFERENCES .................................. A-83

LIST OF FIGURES

Figure Title Page

A-l Colorado Mountain College Wind Rose, October 1990—1991 ........ A-5

A-2 Yak Tunnel Wind Rose, October 1990—1991 ................. A-6

A-3 Radial Groups of Soil Sample Locations as a Function

of Distance from Emissions Sources ...................... A-14

A-4 Surface Water Parameter Variance Along California Gulch ........ A-24

A-5 Cumulative Probability Plot for Pb for Soils of Alluvial Landscape Positions ................................ A-74

LIST OF TABLES

Table No. Title Page

A-l PM-10 Lead Mean Concentration ......................... A-9

A-2 Soil Lead Concentrations in Study Areas of Leadville, Stringtown,

and Control Area .................................. A-12

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-iv THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. FT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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APPENDIX A

TABLE OF CONTENTS (Continued)

LIST OF TABLES (Continued)

Table No. Title Page

A-3 Most Prominent Minerals of the Ore Deposits of

the Leadville Mining District.......................... . A-16

A-4 Soil/Sedimen t Samples .............................. A-20

A-5 Surface Water Flow Rates and pH, California Gulch-Arkansas River At High and Low Flow Periods ......................... A-22

A-6 Metal Concentrations, California Gulch - Arkansas River

at High and Low Flow Periods ......................... A-23

A-7 Acreages of Map Units .............................. A-30

A-8 Classification of Map Units for the Residential Study Area Soil Inventory ............................ A-41

A-9 Land Types for the Residential Study Area Soil Inventory ......... A-42

A-10 Physical and Chemical Analyses of Soil Pedons in the Residential Soils Study Area ........................... A-44

A-11 Average Metal Concentrations at Former Smelter Sites ........... A-51

A-12 Mean Metals Concentrations by Depth Interval for < 2mm Soil s Data

for Disturbed and Undisturbed Sample Sites ................. A-54

A-13 Average Concentrations of Pb, Zn, As, and Cd for Areas Impacted Predominantly by Smelter Emissions ................ A-57

A-14 Surface Water Samples - Parameters Analyzed, Analytical Methods

and Detection Limits ............................... A-61

A-15 Bed Material Samples - Parameters Analyzed, Analytical Methods

and Detection Limits ............................... A-63

A-16 Procedure for Partitioning a Single Population Into Two Normally Distributed Populations ..................... A-73

A-17 Soil-Geologic Units and Corresponding Dominant Soil Map Units .... A-76

A-18 Estimated Background Metal Concentrations for Upland and Alluvial Landscape Positions ................................ A-79

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-v THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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APPENDIX A

TABLE OF CONTENTS (Continued)

LIST OF TABLES (Continued)

Table No. Title Page

A-19 Common Metal Ranges in Soil s of the U.S. ................. A-80

A-20 Estimated Background Metal Concentrations and Depth Weighted Averages for Soil-Geologic Units .................. A-81

A-21 Comparison of Soil Horizon Average Metal Concentrations to Background Concentrations ............................ A-82

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-vi THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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APPENDIX A

TABLE OF CONTENTS (Continued)

LIST OF ACRONYMS

A SA American Society of Agronomy CDH Colorado Department of Health CDL Colorado Department of Law CDM Camp Dresser & McKee CEC Cation Exchange Capacity CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

cfs cubic feet per second

CLP Contract Lab Program

cm centimeter

CMC Colorado Mountain College CRDLs contract required detection limits

EDXRX Energy Dispersive X-Ray Fluorescence

EG Extended Grid EMPA electron microprobe

EP exposure point

E-S Engineering-Science

EW existing private wells F degrees fahrenheit GFAA Graphite Furnace Atomic Absorption GFAAS Graphite Furnace Atomic Absorption Spectroscopy

(/min liters per minute

m meters

meq/g milliequivalents per gram

mg/kg milligrams per kilogram

mg/t milligrams per liter

mm millimeters

mph miles per hour MSL mean sea level NAAQS National Ambient Air Quality Standard N PL National Priorities List NW monitoring wells PG Primary Grid PIXE Proton-Induced X-ray Emission RI Remedial Investigation RI/FS Remedial Investigation/Feasibility Study S AS special analytical services S CS Soil Conservation Service SEM scanning electron microscopy SG Secondary Grid

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-vii THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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LIST OF ACRONYMS

S RK Steffan , Robertson and Kirsten S TP Sanitary Wastewater Treatment Plant T CL Target Compound List T SP total suspended paniculate micrograms/liter

micrograms per cubic meter

micrometers WESTON Roy F. Weston, Inc. USDA U.S. Department of Agriculture XRF X-Ray Fluorescence

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-viii

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
APPENDIX A

SOIL LEAD REMEDIAL INVESTIGATION

This section describes the historical site characterization data in terms of lead contamination hi

the environmental media: soils, ambient air, and surface water; and in mining derived wastes.

A .1 MAPPING

At the request of the U.S. Environmental Protection Agency (EPA), a standard site base map

for the California Gulch National Priorities List (NPL) Site was developed. This site base map

was developed primarily from electronic map files compiled by IntraSearch, Inc. The

IntraSearch map files were generated from aerial photographs of the site.

Additional data sources were combined with the IntraSearch files to provide the locations and

other map features not included with the Intrasearch map file set. The site base map identifies

man-made transportation and structural features that include: roads, railroads, parking lots,

airport, buildings and historic features. Natural hydrography features such as stream networks

and other water bodies are shown. Topographic features include 5-foot elevation contours and

spot elevations.

Other features represented on these map products include Remedial Investigation/Feasibility

Study (RI/FS) and Residential Area site boundaries as defined by EPA. Certain contamination

sources such as the historical locations of smelters and mills and the locations of mine wastes

such as slag piles, waste rock, and tailing impoundments are identified. Data on tailin g

impoundments, waste rock piles, and slag piles were compiled by Roy F. Weston, Inc.

(WESTON®), from Steffan , Robertson and Kirsten (SRK) (1989) and Walsh and Associates

(1993). Locations of fluvial tailing areas were compiled by Woodward-Clyde Consultants (1993)

and smelter locations by ASARCO (1991).

These map features were compiled by IntraSearch using photogrammetric methods and were

ortho-rectified. The ground control survey for the photography was performed by Foresight

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-l

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. FT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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West Surveying, Inc. using extended National Geodetic Survey horizontal and vertical control. All WESTON map products used in this report were developed using these standard base map

elements, and were compiled using the "Colorado State Plane Coordinate System, Central Zone"

and National Mapping Accuracy Standards for 1:2,400 scale maps.

Although these map features came from the diverse sources described and were developed using

various methods (electronic digitizing, photo map spotting, conventional surveying, etc.), the

geographic positioning of these features is based on the common coordinate system of the

Colorado Plane system.

A .2 AIR PATHWAY INVESTIGATION (WCC. 1992a)

This section describes the ambient air monitoring program and data developed for the purpose

of evaluating the significance of the air route for migration of lead contaminants in the Popukted

Study Area.

A.2.1 Objectives

The purpose of the ambient air monitoring program (WCC, 1992a) was to evaluate the

significance of the air pathway for the migration of contaminants of concern, such as lead, to

residential areas of the California Gulch Site. Seasonal meteorological conditions can cause the

resuspension of soils and mine wastes that may result in the generation of airborne particulate

contaminated with lead. Particulate matter with a aerodynamic diameter of ^ 10 microns

represents a health concern because these particles can be inhaled and deposited in the lungs. These particles are referred to as the PM-10 fraction. An ambient air monitoring program,

conducted during the period of 1 October 1990 through 31 October 1991, was designed to meet

t he following objectives:

• Establish baseline pollutant levels.

• Determine the impact of soil particulate emissions and emissions from mine

wastes on the environment.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-2

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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• Provide inhalable paniculate (PM-10) air quality data for the risk assessment.

• Integrate applicable data from other monitoring programs.

A.2.2 Methods

A.2.2.1 Meteorological Measurements

The meteorological data were collected at the 10 meter meteorological towers located at the

CMC meteorological station located on the CMC campus, and near the Yak Tunnel. The data

collected covered a 13-month period from 1 October 1990 through 31 October 1991. The

meteorological parameters recorded were wind speed, wind direction, sigma theta (the standard

deviation of the horizontal wind direction fluctuations), temperature, and relative humidity.

Solar radiation and precipitation were collected at the Yak Tunnel station. Hourly Pasquill- Gifford atmospheric stability classes were computed using values of sigma-theta and wind speed

in conjunction with the time of day. Snow cover measurement data collected at the Leadville

Airport were obtained from the Colorado Climate Center, Colorado State University, Ft.

Collins, Colorado.

A.2.2.2 Air Quality Measurements

The ambient air quality monitoring data were collected at four sites within the Residential Soil s

Study Area. Dichotomous samplers fitted with a PM-10 air intake were used to collect airborne

paniculate. At one of the sites two samplers were co-located for assessment of instrument

precision. To obtain background data, one dichotomous sampler was located at the Fish

Hatchery, a site outside of the study area. The dichotomous sampler filters were analyzed for

the following air quality parameters for which federal and state of Colorado ambient air quality

standards exist:

Respirable Paniculate Mass (PM-10) Lead

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-3 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jim
The PM-10 filter were also analyzed for the following additional metals:

Aluminum Antimony Arsenic Beryllium Cadmium Chromium Cobalt Copper Manganese Mercury Nickel Selenium Thallium Vanadium Zinc

A.2.3 Results

A.2.3.1 Meteorological Conditions

Wind speed and wind direction measured at the CMC and Yak stations reflect the strong

influence the complex terrain has on these parameters in the Leadville Region. The Sawatch and

Mosquito mountain ranges have a major influence on the prevailing winds in the study area.

The CMC wind rose data for October 1990 to 1991 presented in Figure A-1 show the prevailing

winds are from the northwest through the north with a second maximum occurring from the eastnortheast. The Yak station wind rose data for the same measurement period presented in Figure

A-2 show the strongest wind direction to be westerly with a secondary maximum from the eastnortheast. The Yak station's wind direction measurements are strongly influenced by Carbonate

Hill topography.

The meteorological data collected at the CMC site during the 13 months of the study indicate

that the average monthly wind speed is 5.1 mph. The minimum monthly average wind speed

of 2.0 mph occurs during the month of October, and the maximum average monthly wind speed

of 7.1 mph occurs during the month of May. Calm conditions based on hourly averages were

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-4

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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<nC

CMM

s

C MC - SITE ANNUAL (OCT 1990 - OCT 1991)

N N N W N N E

NE

W N W E NE

W

W SW E SE

SW SE

S SW S S E

LEGEN D

0.0 - 4.0

4.0 - 7.0

7.0 - 12.0

12.0 - 18.0

18.0 - 24.0

> 24.0

MILES / HOUR

NNWXR S DESOCB/CONStlTAWS

215 Union Boulevard Suite 550 Lokewood. CO 80228

(303) 980-6800

U.S. ENVIRONMENTAL PROTECTION AGENCY CALIFORNIA GULCH, LEADVILLE, COLORADO

COLORADO MOUNTAIN COLLEGE (CMC) WIND ROSE, OCTOBER 1990-1991

FIGURE

A-1

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-5 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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Y AK - SITE ANNUAL (OCT 1990 - OCT 1991)

N

N N W N N E

NE

W N W E NE

W

W SW E SE

SE

ssw S SE

LEGEND

0.0 - 4.0

4.0 - 7.0

7.0 - 12.0

12.0 - 18.0

18.0 - 24.0

> 24.0

MILES / HOUR

WMUEXS

215 Union Boulevord Suite 550 I® Lokewood, CO 80228

(303) 980-6800

U.S. ENVIRONMENTAL PROTECTION AGENCY CALIFORNIA GULCH, LEADVILLE, COLORADO

Y AK TUNNEL WIND ROS E OCTOBER 1990-1991

FIGURE

A-2

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

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reported during the months of October and November. The maximum hourly average wind

speed of 20.4 mph was reported in December. The maximum monthly hourly average wind

speed at the CMC station is 15.4 mph.

There is a significant seasonal variation in wind direction at the CMC station. Wind direction

data for the CMC station show a large variable in wind direction during the period of March

through October. The wind direction during the spring and summer months is determined to

a large extent by convective cloud formation and associated weather activity. During the winter

months of November through February, wind direction is primarily influenced by large-scale

weather systems and by the passage of frontal systems.

The meteorological data from the Yak station would suggest there is no significant seasonal

variation in wind direction. These data are primarily influenced by the topography and in

particular the location of the meteorological tower in close proximity to Carbonate Hill . The

wind speed and wind direction as measured by this station are not representative of the site's

prevailing winds.

A.2.3.2 Air Quality Monitoring

PM-10 Samplers, 1A and IB are co-located at Harrison Street and Monroe Street in Leadville.

Sampler 2 is located at 5th Street and Hazel Street. Sampler 3 is located at the Leadville High

School. Sampler 4 is located at the Fish Hatchery and represents background conditions in the

Leadville Region.

All dichotomous filter samples were analyzed by the University of California at Davis. The

analyses were performed using Proton-Induced X-ray Emission (PDO3). All 24-hour

dichotomous sampler filters were analyzed gravimetrically for PM-10 paniculate. The maximum

24-hour concentration of PM-10 reported during the 1-year study was 73 micrograms per cubic

meter (/ig/m3) for the 19 March 1991 sampling period. This value is below the 24 hour PM-10

federal standard of 150 /*g/m3 (52 FR 105, 1987).

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-7

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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The PM-10 filter samples were also analyzed for contaminants of concern that included lead. The mean 24-hour concentrations of lead found in the PM-10 fraction are shown in Table A-1. The quarterly National Ambient Air Quality Standard (NAAQS) for lead, 1.5 jig/m3

, was not

exceeded during the study period at any of the PM-10 sampling locations.

A .3 POPULATED STUD Y AREA SURFACE SOIL INVESTIGATIONS

Numerous site characterization studies have been performed at the California Gulch Site to

develop adequate data to evaluate remedial alternatives and complete a feasibility study. A

summary of the objectives of these site investigations includes the characterization of soils; the

identification of areas that have been impacted by historical smelter emissions; the speciation of

lead and other metals of concern in soils and mine waste; and the distribution of lead in surficial

soils located in the Populated Study Area. The specific studies that were conducted to

characterize the Populated Study Area within the California Gulch Site are summarized below.

A.3.1 State of Colorado Department of Law (E-S. 1986)

In October 1986 the Colorado Department of Law (CDL) conducted a soils investigation of the

residential and commercial lands within the city of Leadville and the community of Stringtown. The soil sampling study design was based on earlier air quality studies conducted by

Engineering-Science (E-S) (E-S, 1986) and air modeling of the Leadville region by Biggs (E-S,

1986). The objectives of the study were:

• To collect and analyze surface, surface to 2 inches, and near-surface (2 to 6

inches) soil samples from residential areas.

• To determine the nature and geographic extent of metal contaminants within the

study area.

• To define potential sources, pathways, and metal receptors in residential and

commercial soils.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-8

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Table A-l

PM-10 Lead Mean Concentrations

Element

Lead

Mean PM-10 Concentrations (/ig/m3) at Dichotomous Sampler Stations

1A

0.036

IB

0.0346

2

0.0566

3

0.0377

4

0.0124

Source: WCC, 1992a

jig/m* = micrograms per cubic meter

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A Document Control No. 4800-37-0205 Interim Status Report

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June 1996 PageA-9 IT SHALL NOT BE RELEASED OR DISCLOSED IN
The native soils in the Leadville and Stringtown study area consist primarily of deep, welldrained materials that are formed in stony and cobbly, medium-textured glacial outwash. The

primary soils in the study area occur in the Troutville-Leadville association. The study area to

be sampled was divided into three quadrants, identified as Areas 1,2, and 3. Areas 1 and 3

were separated from Area 2 by Harrison Street. Areas 1 and 3 were separated by East 8th

Street. Area 2 is located by south of West 8th Street. Control samples were taken from an area

northwest of Leadville. The soils sampled were from the Leadville sandy loam and Pierian

gravelly sandy loam. The majority of the soils sampled were slightly to moderately moist,

indicating moderate permeability and water capacity. Soil pH ranged from moderately acid, 5.6,

to neutral, and to slightly basic, 7.3, in the surface layers.

A.3.1.1 Soi l Sampling

During the soil survey, 168 surface soil samples were collected. These samples included 140

samples that were collected from 82 blocks within the city limits of Leadville. Leadville was

divided into four quadrants, and samples were taken from the northeastern, southeastern, and

southwestern portions of Leadville. The northwestern quadrant was not sampled because it was

not within the California Gulch drainage. In addition, 17 surface soil samples were collected

from 10 locations in Stringtown. Subsurface soil samples were collected from 47 locations

where surface samples were also taken. In order to compare metals concentration in soils

sampled from heavy-use areas in Leadville and Stringtown with light-use areas, nine vacant lots

located adjacent to sampled residential properties were identified for sampling. Heavy-use areas

are defined as residential properties, and vacant lots are defined as light-use areas.

A random number generator was used to locate the exact sampling site where soil samples were

to be collected. Soil samples were not taken from garden areas, coal ash deposit areas, or areas

near streets and alleys.

Control areas were identified outside of the study area that were considered to be undisturbed

by historical mining activities. These samples were used for baseline characterization of the

study area. In selecting these control areas, consideration was given to wind patterns, soil types,

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

Document Control No. 4800-37-0205 Interim Status Report Page A-10

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epa\soils-ri\append-a.jun
topography, land use, and drainage patterns. The control areas were selected within the

Leadville series soils, and the locations were believed to be upwind of current and past emission

sources. Soil samples were taken from these control areas, and the sampling locations were

selected based on randomly generated numbers.

A.3.1.2 Soil Sampling Method

Soil samples were collected using a 3.75-inch stainless-steel bucket auger. Each soil sample was

a composite of three subsamples collected within a 5-foot radius of the sample point, and at

equal radial and angular distances. All sampling equipment was decontaminated between soil

depth sampling and between subsample locations at each sampling point.

A.3.1.3 Chemical Analysis

Surface and subsurface soil samples were analyzed for concentrations of lead, cadmium, arsenic,

and nickel by inductively-coupled plasma-atomic emission spectroscopy.

A.3.1.4 Soi l Survey Results

Soil s throughout Leadville and Stringtown exhibit varying concentrations of lead. On average,

soil samples from Leadville have lead concentrations two to five times higher than those in the

control area. The margin of difference for lead concentrations in Stringtown soils compared to

control area soils was even higher than that of Leadville. The concentration ranges and

geometric mean concentrations of lead found within the study area and control area samples are

summarized in Table A-2. The highest mean concentrations of lead in soil were from samples

collected in the southeast and southwest quadrants of Leadville. These areas of Leadville are

nearest to the tailings ponds and waste piles. These results are supported by the data obtained

in the air quality modeling studies of the Leadville region performed by Biggs in 1986.

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epa\soils-ri\append-a.jun
Table A-2

Soil Lead Concentrations in Study Areas of Leadville, Stringtown,

and Control Area

Sampling Area

Area 1

Surface Subsurface

Area 2

Surface Subsurface

AreaS

Surface Subsurface

Control Area

Surface Subsurface

Lead Concentration (mg/kg)

Range

280 - 7,000

250 - 12,000

110 - 9,000

150 - 8,000

300 - 2,600

910 - 3,500

240 - 2,600

36-500

Geometric Mean

2,538

2,240

1,144

1,201

1,283

1,515

822

89

mg/kg = milligrams per kilogram

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-12

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epa\soils-ri\append-a.jun
Surface soil lead concentrations in eight of the nine vacant lot samples exceed the lead

concentrations found in surface soil samples taken from adjacent residential properties. However, this difference was found to be statistically insignificant.

The highest surface soil lead concentration in Leadville of 9,000 mg/kg was 11 times higher

than the geometric mean concentration for surface soils in the control area. The highest

subsurface lead concentration of 12,000 mg/kg was more than 17 times higher than the

maximum average lead concentration in soils of mineralized areas of the western United States

(E-S, 1986). Average lead concentrations in Stringtown soils were 2 and 17 times higher than

the lead concentrations in control site surface and subsurface soils, respectively. The highest

concentrations of lead were found in the eastern section of Stringtown where slag piles and

tailings impoundments were present.

To determine the effect s of distance from emission sources on lead concentrations, the Leadville

portion of the study was subdivided radially, and soil sample points were separated into groups

representing distances within 1,000 feet, within 2,600 feet, and beyond 2,600 feet of the tailings

and waste piles in California and Stray Horse Gulches. Figure A-3 portrays the three soil

sample groups as a function of radial distance from the emission sources represented by the

tailings and waste piles in California and Stray Horse Gulches. The data indicate a steady

decline in surface soil lead concentrations to the west and northwest in Leadville. The surface

geometric mean concentration for lead in soils within 1,000 feet of the waste sources is

2,954 mg/kg. This concentration is nearly twice the concentration of lead in the group of soil

samples obtained between 1,000 feet and 2,600 feet of the mine wastes. The CDL soil survey

indicates that an anomaly in lead concentration exists in a group of soil samples taken from near

the corner of East 7th Street and Hemlock in Leadville. This location is incorrect. This

anomaly is attributed to the Coronado Shaf t and the railroad spur junctions. A lead

concentration anomaly of 12,000 mg/kg exists at soil sample location 1-21B and is located near

the Coronado waste pile in east Leadville and north of 7th Street.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-13

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epa\soils-ri\append-a.jun
4601026.CW-022294

T )

I

I

11

800 meters

FIGURE A-3 RADIAL GROUPS OF SOI L SAMPL E LOCATION S AS A FUNCTION OF DISTANCE FROM EMISSION S SOURCES

I CONTRO L ARE A
A.3.2 Remedial Investigation Report (CHJM Hill. 1987)

The objective of the Phase I Remedial Investigation (RI) Report for the California Gulch Site

was to characterize the site and summarize the data collected during the Phase I investigations.

The site characterization includes identifying contaminants in surface water within the site

drainage area; the nature and extent of groundwater contamination along the California Gulch;

and sources of metal contamination within the site drainage basin and their relative contributions

to water quality degradation in the Arkansas River at the confluence with California Gulch.

The RI Report identified over 2,000 waste dumps that range in size from a few tons to over

100,000 tons. These are located near mine shafts or portals in the upper California Gulch,

Carbonate Hill, Stringtown, and Stray Horse Gulch. Some of the piles in the Stray Horse Gulch

are near residential areas within the Populated Study Area. Slag pile locations were identified

in Leadville on Harrison Street and in Stringtown.

A.3.2.1 Geology

Within this report, the bedrock geology of the Leadville Mining District is described as

consisting of Precambrian crystalline rocks overlain by quartzites, shales, limestones, dolomites,

and sandstones of Paleozoic age. Several types of surficial deposits were identified and include

talus debris, landslide deposits, and rock glaciers. Glacial, glaciofluvial, and alluvial deposits

were identified at lower elevations in the area. These deposits were disturbed by placer gold

mining activities during the 1800s. Numerous faults exist within the mining district. Two of

these faults , the Valentine Fault and the Pendery Fault, are located within the Populated Study Area.

The most prominent ore minerals that are present in the Leadville Mining District are presented

in Table A-3.

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epa\soils-ri\append-a.jun
Table A-3

Most Prominent Minerals of the Ore Deposits of the Leadville Mining District

Mineral

Arsenopyrite

Barite

Calcite

Cerussite

Chalcanthite

Chlorite (Clinochlore)

Dolomite

Galena

Gold

Hematite

Jarosite

Limonite

Manganosiderite

Melanterite

Pyrite

Pyrolusite

Pyromorphite

Quartz

Sericite

Siderite

Silver

Smithsonite

Specularite

Sphalerite

Chemical Formula

FeAsS or FeS2 • FeAs j

BaSO4

CaCO3 PbCO3

CuSO4 • 5H2O

H4M g3S i

2O9

 • H<Mg2A l

2SiO9 CaMg (C03)2 PbS

Au

F eA

KFejCSO^OH^ Fe(OH)3

(Fe, Mn, Mg) CO3 FeSO4 -7H2O

FeS2 MnO2 Pb

5(P04)3Cl

SiO2 K H2A l

3(SiO4)3 FeCO3 Ag

ZnCO3 F eA

ZnS

Source: Emmons et al., 1927 as cited in Jacobs Engineering Group, Inc., 1991.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-16

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epa\soils-ri\append-a.jun
A.3.2.2 Soils

The predominant soils associated with the California Gulch Site and the Populated Study Area

are classified as Bross, Leadville, Pierian, and Troutville series. No background information

is available concerning the geochemistry of site soils prior to mining activities. Placer and

hydraulic gold mining and early milling operations resulted in significant alteration of surface

materials and structure in the Populated Study Area and the California Gulch Site. Placer and

hydraulic mining created mixed and rework alluviums and altered natural stream-beds and flood

plains. Uncontrolled mine waste from historic ore milling operations in the Upper California

Gulch have added sediments to the lower Gulch.

A.3.2.3 Surface Water

The California Gulch drains approximately 7,400 acres of watershed into the Arkansas River.

The mainstem of the Gulch receives water from several ephemeral drainages that include the

Starr Gulch, the upper California Gulch, the Oregon Gulch, the Pawnee Gulch, the Airport

Gulch, and the Malta Gulch. The average flow at the confluence of the California Gulch with

the Arkansas River ranges from 2.2 to 6.4 cubic feet per second (cfs).

During rapid snowmelt in the spring, flooding in the area may occur. The flood potential in the

upper Gulch is quite high because of the relatively sparse vegetation. The Corp of Engineers

estimate of the 100-year flood event indicates that the area where the California Gulch crosses

U.S. Route 24 would be impacted by the event.

A.3.2.4 Climate

Weather conditions are recorded at the National Weather Service' s Leadville airport

meteorological station located 2 miles southwest of Leadville. The normal temperature extremes

range from a high of 86 F to a minimum of -30 F. The average minimum temperature being

21.9 F.

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epa\soils-ri\append-a.jun
The average annual precipitation is 17.53 inches with maximum precipitation occurring during

the months of July and August. Months in which the lowest amounts of precipitation occurred

are December and January. Summertime precipitation is associated with the occurrence of rain

showers.

The annual snowfall depths for the mountains in the region outside of the study area range from

79 to 203 inches. This snowfall occurs within the watershed that impacts the Populated Study Area. During the winter months the average snow depth on the ground in Leadville is 6 inches.

The runoff from the snowmelt reaches a peak in the month of June.

A.3.2.5 Air Quality

Limited air quality data were available for the Leadville area from the Colorado Department of Health (CDH). CDH has operated high-volume air samplers in Leadville for measurement of

total suspended paniculate (TSP) and lead.

A.3.2.6 Nature and Extent of Contamination

The remnants of mining related activities such as mine waste dumps, slag piles, soils, and

sediments are potential sources of metal contamination to surface water and soils. The mined

ores were processed in the milling operation to produce silver, lead, and zinc concentrates. The

ore milling produced tailings that contained pyrite. The oxidation of pyrite present in mine

wastes results in the mobilization of metals and the production of sulfuric acid that acidifies

surface waters. This process also results in producing compounds (oxidation states of some

metals) that may be more soluble in surface waters or the process merely releases them from an

immobile matrix and produces a mobile material that could be transported by water erosion or

wind erosion.

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epa\soils-ri\append-a.jun
The tailings from the milling operation are chemically heterogeneous since the ores mined varied

in their composition over time. This made the tailing difficul t to sample in order to obtain

representative samples for analyses to determine the chemical constituents making up the

tailings. The tailings characterization goal was to assess if any of the tailings impoundments

contained a potential source of metals that were found in nearby surface water and groundwater.

Samples were collected from the tailings impoundments with the use of an auger. The auger

was used to sample to a depth of approximately 7 feet.

The major factor affectin g the potential failure of the impoundments appears to be embankment

erosion from surface water runoff. These impoundments can act as sources of heavy metals to

surface water.

Stream Sediments

There is a seasonal variation in surface water flow within the California Gulch. The stream flow

is generally controlled by the discharge from the Yak Tunnel and the Sanitary Wastewater

Treatment Plant. During snowmelt and heavy rainstorms, the ephemeral drainages such as the

Oregon Gulch, Starr Ditch, and the upper California Gulch contribute significantly to the

amounts of additional flow. The additional flow during peak runoff periods increases stream

velocity and potential for erosion. This can result in the resuspension and transport of

significant quantities of sediments. The delta near the confluence of the Gulch and the Arkansas

River is an example of the sedimentation process. During the construction of the flume at

location SW-12, two soil/sediment samples were taken for characterization. The samples were

collected at the surface and at a depth of 4 feet. The soil/sediment samples were analyzed, and

the metals concentrations are presented in Table A-4. The soil/sediment metal concentrations

were compared to the concentrations of these metals in tailings. This comparison showed that

the soil/sediment had: similar iron concentrations; higher lead concentrations; and lower

cadmium, zinc, and manganese concentrations. The surface soil/sediment sample had higher

concentrations of cadmium, copper, iron, lead, manganese, zinc, arsenic, mercury, and silver

than the subsurface sample. The soil/sediment samples were subject to the EP-Toxicity test, and

the surface sample exceeded the criteria for lead.

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epa\soils-ri\append-a.jun
Table A-4

Soil/Sediment Samples

Parameter

Aluminum, Al

Chromium, total Cr

Barium, Ba

Beryllium, Be

Cadmium, Cd

Cobalt, Co

Copper, Cu

Iron, total Fe Lead, Pb

Nickel, Ni

Manganese, Mn

Zinc, Zn Boron, B

Vanadium, V

Calcium, Ca

Magnesium, Mg Sodium, Na

Potassium, K

Arsenic, As

Antimony, Sb

Selenium, Se

Thallium, Tl

Mercury, Hg Tin, Sn

Silver, Ag Cyanide, total CN Sulfur, total S

PH

Moisture

Sulfate (SO4), Soluble

Chloride, Cl

SW-12 Soil

(Surface' )

AsRec' d (nig/kef)

1,680

3.55

154

<0.2

9.89

2.17

52.6

13,600

1,790

2.37

1,030

1,550

39

3.9

456

266

26.4

185

18.4

<10

<1.10

<2

4.21

<20

5.73

<0.02

2,260

3.9

125,000

6,580

696

SW-12 Soil/Clay

Dry

(ma/kg)

1,920

4.05

176

<0.2

11.3

2.48

60.2

15,500

2,040

2.71

1,180

1,770

44

4.4

521

304

30.2

211

21.0

<11

<1.10

<2

4.81

<23

6.55

<0.02

—

—

—

—

—

(at

AsRec' d (mg/kg)

9,590

20.9

78.3

1.26

0.088

4.92

8.08

6,550

15.9

8.21

454

351

12.6

26.5

2,310

2,640

15.1

258

4.17

6.3

0.105

<1

0.660

<13

0.13

<0.02

1,200

5.0

318,000

2,620

2,680

Depth)

Dry

(ma/ka)

140,000

30.6

115

1.85

0.129

7.21

11.8

9,600

23.3

12.0

665

514

18.5

38.8

3,390

3,870

22.1

378

6.11

9.2

0.15

<2

0.967

<19

0.19

<0.02

—

—

—

—

—

mg/kg milligrams per kilogram

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-20 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA, FT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Slags

Field investigations of the slag piles were not performed at the California Gulch site during this

investigation.

Surface Water

Surface water acts as the primary transport mechanism for both soluble metals and metal-laden

sediments. The principal contributors to surface flow in the mainstem of the Gulch are the

discharges from the Yak Tunnel and the Sanitary Wastewater Treatment Plant (STP). Flow

from the Yak Tunnel varies seasonally between 1 and 2 cfs, and the flow from the STP is at a

nearly constant rate of 1 cfs.

Surface water samples were collected during five quarterly sampling periods at flume locations

starting with the Yak Tunnel and ending at the Arkansas River. Surface water samples were

also collected during times of high flow rates and low flow rates. These water samples were

analyzed for pH and dissolved and total metals. The pHs at low flows were consistently higher

than those observed at high flows for the same flume sampling locations. The concentrations

of dissolved metals, measured in samples taken during a high flow period, were higher than the

concentrations of the same metals found in samples that were taken during low stream flow.

The pH and metals data for low and high flow periods are summarized in Tables A-5 and A-6,

respectively. Dissolved cadmium, zinc, and sulfate concentrations during low and high Gulch

flow s are presented in profile in Figure A-4. This figure identifies key surface water flow

locations and potential contributors of contaminants. Beginning with sampling location SW-1

in the upper California Gulch the metals concentrations are relatively low. As a result of the

Yak Tunnel discharge there is observed a rapid increase in metals concentrations. The metals

concentration continue to increase at sampling location SW-4. This contribution of metals is

coming from the tailings impoundments. There appears to be an anomaly in the cadmium

concentration reported for SW-4 during high flow. The expected concentration would be much

higher than that reported for high flow conditions. The concentration of metals continued to

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epa\soils-ri\append-a.jun
Table A-5

Surface Water Flow Rates and pH California Gulch-Arkansas River At High and Low Flow Periods

Location DescriptionStation Name

High Flow June 1985

Flow

(eft)

pH(s.u.)

Low Flow November 1984

Flow

(eft) PH (s.u.)

California Gulch Mainstem

Upper Cat Gulch

Millyard Flume

Tailings Area

Below Apache Middle Flume

Stringtown

SW-1

SW-2

SW-3

SW-3A

SW-4

SW-4A

2.67

Dry

2.70

3.52

6.15

NA

3.4

NA

3.2

3.2

3.2

NA

0.31

0.15

1.10

1.57

0.89

NA

8.1

7.6

6.0

6.0

3.7

NA

Tributaries

Parkville Leak

Y ak Tunnel

Stair Ditch

Oregon Gulch

Berthod Sprin g

Storm Drain

Georgia Gulch

Super 8 Spring

Pawnee Gulch

Airport Gulch

Slag Pile Spring

S TP

Malta Gulch

SW-5

SWI-1

SW-6

SW-7

SWI-2

SWI-3

SW-8

SWI-4

SW-9

SWI-5

SW-10

SW-11

SWI-6

0.35

0.04

0.08

3.88

Dry

0.03

1.02

Dry

5.76

Dry

0.03

0.93

Dry

3.3

2.8

4.1

3.2

NA

6.6

7.1

NA

3.3

NA

6.6

7.4

NA

0.58

Dry

Dry

2.53

Dry

0.03

0.01

Dry

2.38

Dry

0.11

1.13

Dry

7.6

NA

NA

6.3

NA

6.8

7.5

NA

5.5

NA

6.3

8.3

NA

Confluence

Lower Flume

Upper Arkansas River

Lower Arkansas River

SW-12

SW-13

SW-14

3.85

300

NA

4.0

7.4

7.1

1.52

30

NA

7.0

8.8

8.5

cfs = cubic feet per second NA = Not available/not analyzed S.U. = standard pH units

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

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epa\soils-ri\append-a.jun
Table A-6

Metal Concentrations California Gulch - Arkansas River

at High and Low Flow Periods

Parameter

Aluminum (Al)

Cadmium (Cd)

Calcium (Ca)

Copper (Cu)

Iron (Fe)

Magnesium (Mg)

Manganese (Mn)

Zinc (Zn)

HIGH FLOW (June 1985)

Lower end of Cal Gulch

(SW-12)

Dissolved

fog/* )

3,920

277

101,000

2,500

4,110

50,200

18,400

55,600

Total

fog/O

5,140

282

109,000

2,560

16,900

50,000

19,500

57,700

Ark River above Conf l (SW-13)

Dissolved

(Atg/0

26

U

9,950

4.9

83

3,960

40

109

Total

0<g/0

144

U

10,500

4.0

324

3,980

58

132

Ark River below Conf l (SW-14)

Dissolved

w>

49

7.3

11,500

21

88

4,730

218

594

Total

G*g/0

355

4.0

12,200

29

664

4,730

253

709

Parameter

Aluminum (Al)

Cadmium (Cd)

Calcium (Ca)

Copper (Cu)

Iron (Fe)

Magnesium (Mg)

Manganese (Mn)

Zinc (Zn)

LOW FLOW (November 1984)

Lower end of Cal Gulch

(SW-12)

Dissolved

(IVft)

U

47

66,510

13

56

33,530

9,074

14,710

Total

fog/O

368

62

67,270

26

1,092

32,020

9,222

20,170

Ark River above Conf l (SW-13)

Dissolved

fog/0

81

U

23,030

U

101

8,450

103

240

Total

fog/0

265

U

17,600

12

619

7,039

145

331

Ark River below Confl (SW-14)

Dissolved

(Ml*)

U

U

28,160

U

38

11,860

649

1,317

Total

fog/0

419

U

28,380

U

459

11,120

657

1,625

U = Undetected at detection limits.

pgll = micrograms per liter

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

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epa\soils-ri\append-a.jun
4601023.CW-022294

I s :

f g 1 s

is

2

ii»

w *! R

>

si

400-|

300-

200-

100-

0-

90-i

80-

70-

60-

-=- 50-

40-

30-

20-

10-

0-

DISSOLVED Cd (6/85)

1600

^1200

-800

-400

I

SW-12 SW-11 SW-9 SW-7 SW-4 SW-3A SW-1

HIGH FLOW

LOW FLOW

KSOOS/CONSUltAWS

2 15 Union Goulevord Suite 550 Lakewood. CO 80228

(303) 980-6800

EPA CALIFORNIA GULCH LEADVILLE, COLORADO

SURFAC E WATER PARAMETER VARIANC E ALON G CALIFORNIA GULCH

FIGUR E

A-4
remain high through sampling station SW-8. From SW-9 to SW-12 the marked decrease in

metals concentrations is due to the effect of dilution by the discharge from the STP. The pH

of the surface water was also observed to increase under both low and high flow conditions after

sampling location SW-9 as shown by Table A-5. This is due to the high alkalinity of the STP

discharge. During the high flow conditions the observed increase in metals concentrations is

probably associated with the entrainment of sediments. Potential sources of heavy metals

contaminants include the Yak Tunnel (SW-3) , the Starr Ditch (SW-5) , and the Stringtown area

(above SW-9). Starr Ditch contributes metals that are probably originating from mine wastes

located on the north side of Carbonate Hill and Stray Horse Gulch and include Hamms Mill

Tailings and Penrose Waste Pile. The consistently high levels of metals and sulfates at SW-9

may be originating from nearby slag piles.

A.3.3 Soil Investigations in the Leadville Study Area (Walsb. 1988)

The objective of the soil investigation study was: to develop information on soil-metal levels in

the Leadville, Colorado area; to evaluate background soil-metal levels; to identify sources of

contamination; and to delineate the extent of soils contamination in the study area. This study

focused on soils contaminated with lead. The study area was centered over the towns of

Leadville and Stringtown, and extended outside of the Populated Study Area down the California

Gulch and the Arkansas River.

A.3.3.1 Methods

An intensive soil sampling program in Leadville, Stringtown, and the vicinity was conducted

from August through October of 1987. Most city blocks in Leadville and Stringtown that were

not sampled in the 1986 CDL (E-S, 1987) survey conducted by E-S, were sampled as part of

this soils investigation program. In each city block, a relatively undisturbed area was selected,

and a random point was chosen within the area for sampling. Surface soil samples (0 to 2

inches) were collected with a trowel. Subsurface soil samples from 2 to 6 inches were collected

with a 3 1/4-inch auger and from 6 to 12 inches with a 2 3/4-inch auger. A few samples were

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not randomly selected at a site because of sampling constraints imposed by the landowner or

limited sampling area.

Additional soil samples were taken from test pits; the test pits were dug by backhoe to a depth

of 5 feet and hand dug pits to a depth of 40 inches. Soil samples were collected in each strata

or soil horizon at about 6-inch intervals to the bottom of the pit.

A.3.3.2 Results

Most of the soils of Leadville tend to have loamy A-horizons about 6 to 10 inches thick that

overlie sandy, gravelly, and cobbly subsoils. The A-horizons are all higher in lead

concentrations than the underlying subsoils. The A-horizons absorb metals more readily

compared to the sandy subsoils, because of their higher exchange capacities.

Seven backhoe pits were excavated in the town of Leadville, and samples were collected at 2-

to 6-inch intervals to a depth of 5 feet. Three backhoe pits located east of Harrison Avenue in

Leadville went through up to 2.5 feet of mine wastes before encountering buried A-horizons in

native soil. The top 2 inches of the buried A-horizons below the mine waste were analyzed and

found to have lead concentrations of 950, 3,750, and 750 mg/kg. The mine wastes overlying

the A-horizons had lead concentrations greater than 2,500 mg/kg. West of Harrison the mine

wastes were not as thick in the remaining four backhoe pits. One pit had 8 inches of waste

overlying the native soil. In 54 hand dug locations samples were collected from 0 to 2 inches,

2 to 6 inches, and 6 to 12 inches. Eight samples were collected from cellars and crawl spaces

of Leadville houses, and one was collected from under the log foundation of an old cabin in

Jacktown. Three houses, constructed in 1898, 1882, and 1880, had 2,120, 330, and 190 mg/kg

of lead, respectively, in the A-horizons under the foundations. Lead concentrations in samples

taken from A-horizons from under the foundations of the remaining five houses ranged from 50

to 1,260 mg/kg. These five houses were constructed after 1900. The concentration of lead

found in the buried A-horizon under the cabin at Jacktown was 2,820 mg/kg.

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The major sources of lead contamination in Leadville were described as mechanically transported

mine waste rock and tailings, smelter fumes, and slag. These mine wastes cover significant

parts of Leadville and were apparently mechanically transported by man and spread throughout

the town.

The mine wastes are thickest on the east side of Leadville. The data suggest that mine waste

rock has up to 25,000 mg/kg of lead and that values of 1,000 to 10,000 mg/kg are common.

Slag represents a smaller volume of waste material than either tailings or waste rock and is

found throughout the Leadville area. One of three grab samples of slag was found to contain

14,920 mg/kg of lead. As early as 1881, slag was used as a road gravel throughout the town

of Leadville. Slag and waste rock were also used as a railroad ballast by the Denver and Rio

Grande Railroad as early as 1887.

In the California Gulch and Stringtown area the lead concentrations exceed 1,000 mg/kg, and

large portions of the area have concentrations of lead above 2,500 mg/kg. A few areas are

above 5,000 mg/kg of lead. About half of Stringtown has lead concentrations above

2,500 mg/kg.

A.3.4 Residential Surface Soils and Household Dust Sampling (Walsh. 1990)

The objective of this sampling program was to obtain soils and household dust samples that were

analyzed for EPA Target Compound List (TCL ) metals and metal speciation analysis for lead.

A.3.4.1 Sampling Procedures

Soil samples from a depth of 0 to 2 inches were taken with a stainless steel scoop. The soils

were placed in a stainless steel bowl for the purpose of generating a composite sample.

Household dust samples were collected using a personal air sampling pump and a polystyrene

sampling cassette containing a 0.8 micrometers (/*m) mixed cellulose ester filter. A stainless

steel nozzle with a 1-centimeter (cm) X 5-cm opening was connected to the filter cassette with

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Tygon® tubing. The air pump was adjusted to a sampling flow rate of 2 liters per minute

(f/min) .

Each floor area was sampled with the aid of a plexiglass template with a 22-cm X 22-cm

opening. Three passes, each uni-directional, was made over the area exposed by the template. The second pass was made perpendicular to the first and the third pass was made at a 45 ° angle

to the second pass. When deep pile carpets were sampled, a fourth pass was made at a 90

angle to the third pass.

A.3.4.2 Sampling Locations

Residential soils were sampled in the Leadville and Stringtown communities to provide data on

potential exposure pathways for mining waste to inhabitants in these communities. Fifty soil

samples were taken from Leadville and 10 from Stringtown. These samples were taken from

front and/or backyard residential areas where the children spent most of their outdoor tune. A

total of five locations were sampled and composited for each residential location. Household

dust samples were taken from areas frequented by children. These locations include the

childrens bedroom; the kitchen; and the living room. Using the template and personal air

sampling pump, composite dust samples were taken at each residence.

A.3.4.3 Analysis of Surface Soil and Dust Samples

Soil and dust samples were analyzed for lead by Graphite Furnace Atomic Absorption (GFAA).

A.3.4.4 Results

Lead was reported in all soil and dust samples collected during this study. Lead concentrations

in soil ranged from approximately 500 mg/kg to 4,980 mg/kg. Lead concentrations in dust

samples ranged from 270 mg/kg to 5,440 mg/kg. The highest dust-lead value of 5,440 mg/kg

was reported in Stringtown.

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A.3.5 Soils Investigation Data Report (CDM. 1994)

The objectives of the CDM Soils Investigation Data Report were:

• To determine the concentration of elements identified by the EPA as being of

potential concern and their distribution in site soils. These elements include lead

(Pb), arsenic (As), zinc (Zn), and cadmium (Cd).

• To provide data necessary to characterize the sources of these elements so that the

sources may be identified and controlled in a manner that would mitigate

additional source impact to the site and its residents.

This study focused on characterizing the nature, extent, and distribution of potential elements

of concern at the California Gulch Site. A significant number of soil samples were taken from

the Populated Study Area, with an emphasis on the characterization and distribution of lead.

A.3.5.1 Soils Investigation Sample Locations

Soil sample locations were established by a grid pattern prior to the field investigation and

detailed in the CDM's Sampling and Analysis Plan (1991). Three categories of sampling

locations were identified in this study. A primary grid (PG) pattern, oriented N 45 W, was

established in the Populated Study Area with sampling points spaced at 500-foot intervals.

Outside of the Populated Study Area, an extended grid (EG) pattern was established with

sampling points located at 500-foot or 1,000-foot intervals. The EG sampling locations were

determined by extending the PG grid outside of the Populated Study Area. The grid sampling

locations for the CDM soils investigation are shown in Plate I. The decision to sample soils in

the EG was based on analytical results obtained from PG samples. Based on analytical results

from soil sample analysis from the PG and EG grids and requirements to augment geostatistical

interpretation, an SG was used to identify soil sampling locations at intermediate distances

between certain PG and EG locations. A fourth category of sampling locations, exposure point

(EP), was identified independently of the grid pattern and was based on increased probability

of exposure to the public. The sampling grid locations are shown in Plate 1.

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Soil sample grid points were located in the field using expanded scale (1 inch = 100 feet or

1 inch = 200 feet) base maps by measuring from physical features such as buildings, roads,

power lines, or other landmarks shown on the maps. In undeveloped areas, the sample location

was transferred to high resolution aerial photographs (1 inch = 200 feet), and grid points were

located relative to physical features shown on the photograph. Locations were transferred by

overlaying the photograph on the site base map showing the sample location, using physical

features shown on both the map and photograph, and marking the location on the photograph.

Each plotted sampling point was located on the map or aerial photograph at the field facility and

cross-checked on the applicable parcel map.

A.3.5.2 Soil Sampling

Each sampling point was located on the map or aerial photograph and cross-checked on an

applicable parcel map at the field facility. At each sampling location, a triangular plastic

template, 1 meter long on each side, was pkced over the sampling point with the center point

of the template positioned over the sample point and with one point of the triangular form

aligned along the northeast-southwest trending grid line. Three excavations were made, one at

each point of the triangular template. Each excavation was dug to a depth of 21 inches,

exposing an approximate 18-inch-wide soil sampling face. Soils were taken from the following

sample depth intervals; 0 to 1, 1 to 2, 2 to 6, 6 to 12, and 12 to 18 inches.

A.3.5.3 Sampling Method

A flat , four-sided scraper was used to scrape clean the soil surface in the excavated pit from

which soil samples were taken. This procedure was repeated in each of the three excavations. A separate scraper was used for each of the three sampling faces, and each soil depth interval

was scraped clean with an unused side of the scraper beginning with the upper most sampling

interval and working down the face. The procedure called for scraping one face at a time,

beginning with the 0- to 1-inch sampling interval and working down the face of the excavation.

Soil samples from each sampling interval were collected into a separate pre-labeled cup

beginning with the 12- to 18-inch sampling interval and working up the face of the excavated

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pit toward the surface. Soil from the root zone, when present, was included in the 0- to 1- and

1- to 2-inch sampling interval. The three excavated pits generated a total of 15 samples per

sample location. The three samples from the same sample depth interval were composited and

placed in a plastic bag, labeled, and then placed in a second plastic bag. Samples collected from

the field were sent to the field facility where the samples were logged in and the sample ID

number on the plastic bag was cross-checked against the field log sheets. All samples were

handled in accordance with established chain-of-custody procedures.

A.3.5.4 Analysis of Soil Samples

Soil samples were prepared for XRF and CLP analysis at the field facility supporting the soils

investigation. Sample preparation included drying the sample to a consistently low moisture

level to facilitate the following subsequent steps; and sieving, weighing, splitting, and grinding. The samples were sieved to produce a fraction containing particles > 2 mm and a second

fraction containing sample particles <2 mm. The sample fraction represented by <2 mm

particle size was separated into two fractions, the first representing particles < 250 jwm and the

second fraction representing particles < 2 mm to > 250 /*m. The soil sample fractions were

then ground to produce a sample of uniform particle size for subsequent analysis by XRF.

Twenty-five percent of the samples representing the < 250 /tm particle size were also analyzed

for metals including lead. The other portion of the split sample was archived for future use and

possible CLP analysis.

Soil samples were analyzed by XRF for 11 elements including As, Cd, Zn, and Pb. Twentyfive percent of the samples were also analyzed using CLP-special analytical services (SAS)

protocol. Samples were analyzed using the inductively coupled plasma technique. If lead

concentrations were reported below the contract required detection limits (CRDLs), the samples

were then analyzed by GFAA. The samples destined for CLP analysis were selected based on

XRF analytical results.

To produce high quality analytical data using the XRF analytical technique, calibration standards

were selected to include specific analytes, contaminants of concern, and matrix materials known

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to be present in site soil samples. This was necessary in order to minimize matrix effect s and

replicate spectral response. A set of 60 soil samples previously collected from the California

Gulch Site were obtained for the purpose of XRF instrument calibration. Theses calibration soil

standards were collected during the Residential Soils and Dust Survey (CDM, 1993). Of the 60

calibration soil standards, only 30 were selected for initial field calibration. This selection was

based on the concentration distribution of the contaminants of concern in these tentative

calibration soil standards. For final calibration of the XRF instrument, only 15 of the 30

calibration soil standards were retained for recalibration purposes, and 15 samples collected

during the field investigation were added to serve as calibration soil standards. These calibration

soil samples were processed in accordance with sample preparation procedures described in this

section and then submitted for analysis by two CLP laboratories. The bulk version of these

calibration soil samples was also analyzed by yet a third CLP laboratory. This was necessary

because the analytical results, for the calibration soil samples that were to be used as calibration

standards, were not available during the field investigation. Therefore, during the field

investigation the XRF instrument was calibrated using analytical data obtained by the CLP

analysis of the bulk version of the calibration soil standards. Following the field sampling

investigation, the XRF instrument was recalibrated using analytical data obtained from the

analysis of soil calibration standards, and all of the original analytical data were reprocessed

using the new calibration factors.

A.3.5.5 Results

From the CDM sampling program, the statistical results were able to assign data quality levels

for XRF analyses. These levels are as follows:

EPA Level ffl . XRF-analyzed elements qualifying as Level in are Ca, Cu, Fe, Pb, Mn, and Zn. These data can be utilized for support of engineering studies

such as the FS and may be used to assess risk in the endangerment assessment.

EPA Level n. XRF-analyzed elements qualifying as Level n are Ba, Cd, and Ar. This level data may be used to support engineering studies. This data should

be used with caution for endangerment assessment purposes.

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Geostatistical analysis and concentration contour maps were used to characterize the spacial

distribution of As, Ba, Ca, Cu, Fe, Mn, Hg, Pb, and Zn. These contour maps were produced

for each of the depth intervals and for all soils and native/undisturbed soils. The contour maps

for all soils characterize concentration distributions that may be used for FS and EA purposes.

The native/undisturbed contour maps may be used in conjunction with results from the metal

speciation program to characterize relative source impacts.

A.3.6 Soils Investigation. California Gulch Study Area (Walsh. 1992a)

The objectives of the soil investigation were to develop a soil and a surficial geology map of the

study area to evaluate a possible correlation between soil map units, surficial geology, and soil

metal concentrations.The objectives of surficial geologic mapping were to compile existing

surficial geologic information of the study area on to one map and field check the mapping to

support the domain analysis. This included field checking existing Soil Conservation Service

(SCS) soil map units and delineations and description of soil and surficial materials in the CDM

soil sampling program (CDM, 1991a). A secondary objective of geologic mapping was to

provide information relative to the origin of naturally occurring surficial materials. To

accomplish these objectives, specific tasks for the soil investigation included the following:

• Identify and delineate soil map units.

• Describe the soils and surficial materials to a depth of 18 inches.

• Define the physical and chemical characteristics of the soils.

• Estimate the percentage of human artifacts, mine waste rock, tailings materials,

smelter waste, clean fill, and slag present in the soils.

In the populated regions of the Residential Study Area, an Order I soil survey was conducted.

The Order I soil survey includes map units that are mainly constitutions and some complexes,

in which phases of soil series were identified. The minimum map unit size delineation in the

populated area was approximately 0.25 acres. Initial soil map units were based on the Soil

Survey ofChaffee-Lake Area, Colorado, and parts of Chaffee and Lake Counties (Walsh, 1992a).

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The inventory of soil proceeded in two stages. Guidelines and procedures outlined in Soil

Taxonomy and Keys to Soil Taxonomy (Walsh, 1992a) were used in the first stage for the

purpose of identification, description, and characterization of soils within the study area. The

second stage involved mapping the distribution of soils and mine waste materials. Soil samples

from approximately 406 shallow pits and 9 backhoe pits were taken from the residential study

area.

A.3.6.1 Geology

The geology of the eastern portion of the California Gulch Site is dominated by the foothills of

the Mosquito Range. This area is composed of porphyry, rhyolite, granite, and other intrusive

igneous rocks. The western portion of the California Gulch Site, including the town of Leadville

and the areas to the west and south of Leadville within the Populated Study Area, consists of

thick deposits of unconsolidated glacial outwash materials form the Pleistocene Period. These

unconsolidated materials are derived from various types of lithologies existing in the Mosquito

Range east of Leadville, and includes: several varieties of porphyry, rhyolite, granite, and other

intrusive igneous rocks; and quartzite, dolomite, limestone, and sandstone. These materials were

transported and redeposited by glacial and fluvial processes. These deposits are poorly sorted,

loose, and porous. The Lake Fork Trailer Park area, located in the extreme western portion of

the California Gulch Site, is composed of young Holocene stream terrace deposits and young Holocene stream channel and floodplain deposits.

Numerous fault s exist within the area of the California Gulch Site. The Valentine Fault is

located within the Residential Study Area and the Pendery Fault is located directly to the south

of the southern boundary of the study area.

A.3.6.2 Soils

Soils of the study area have formed from three major distinct parent materials: (1) soils in the

eastern portion of the study area formed from a variety of igneous, sedimentary, and

metamorphic rocks, which form the steep foothills of the Mosquito Range; (2) soils that occur

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throughout Leadville and that extend to the Arkansas River Valley were derived primarily from

weathering of poorly consolidated glacial drift and outwash fan deposits of the Pleistocene glacial

epoch; (3) soils along the Arkansas River Valley were derived from recent (Holocene) floodplain

deposits.

Soils occurring on the steep foothills belong predominately to the Alfisol s soil order. Soils on

the glacial terraces and moraines and the outwash fans belong to the Alfisols , Mollisols, and

Histosols soil orders. Soil s occurring on low river terraces, swales, and floodplain s along the

Arkansas River belong to the Mollisols, Histosols, Inceptisols, and Entisols soil orders.

Alfisol s are light-colored soils that have genetic horizons enriched in silicate clay in the subsoil

relative to the overlying horizons. These soil occur on upland landscape positions. Mollisols

are soils that have a thick, dark-colored, base-enriched surface horizon due to the accumulation

and decomposition of organic matter in these layers. They generally occur along stream

channels and terraces such as California Gulch. Histosols are organic-rich soils that contain at

least 12 percent organic carbon by weight and are generally more than 40 centimeters thick.

They occur in a marshy area near Adelaide Park. Inceptisols are soils that contain some degree

of pedogenic development. They generally exhibit subsurface structural development and have

some color development below the A horizon. Entisols are soils without natural pedogenic

horizons or with only the beginnings of such horizons. They typically have thin A horizons over

parent material.

A.3.6.3 Soil Sampling

Pedon sampling sites were excavated with a backhoe. A trench 3- to 5-meters (m) long was

excavated to a maximum depth of 5 feet. The trench was opened to a width of approximately

1.5 m. A stepped entry way was excavated at a right angle to the main trench that served as

an exit/entry route during sampling. Soil pedons were sampled by recognized soil horizons and

by depth increments. The soil horizons were identified according to criteria in Soil Taxonomy

Soil Survey Staff, 1975, 1990 (Walsh, 1992a). Soil profiles were evaluated from: backhoe pits

dug to a depth of 60 inches; soil sampling pits dug by CDM to a depth of 22 inches; and soil

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observation pits dug by Walsh to a depth of 20 to 30 inches. Soil samples were taken from the

0- to 1-, 1- to 2-, 2- to 6-, 6- to 12-, and 12- to 18-inch depth intervals. These soil increments

are identical to those used by CDM in the soils investigation (CDM, 1991a).

Soils were sampled and examined for the presence of mine waste materials and materials that

were historically used in mining activities, such as slag, mine waste rock, tailings, smelter

waste, refractory bricks, coal, charcoal, cinders, glass fragments, metallic fragments, asphalt,

manganese oxides, dark colored dolomite, and iron stained fragments. The percentages of

manmade materials present in soil were estimated for all soil horizons using the following

percentage increments; 0.0 to 0.1, 0.1 to 1.0, 1 to 5, 5 to 25, 25 to 50, 50 to 75, and 75 to 100.

These data were used to describe the soil characteristics of each map unit for the survey area

and to help identify the nature and kind of contaminants in the soil map unit.

A.3.6.4 Soil Sampling Method

The sides of the soil pedons were prepared for sampling by scrapping the entire face to remove

loosened debris and rocks. Next, starting with the lowermost soil horizon or depth increment,

the face of the pedon was scrapped with a plastic scrapper to provide a fresh, non-crosscontaminated surface for sampling. Using a stainless steel trowel, the soil was sampled and

allowed to fall into a plastic 16-ounce cup. Horizon and depth increment samples were taken

from two separate areas to ensure that representative samples were taken. Two to three cups

of soil material were composited in a stainless steel mixing bowl and then homogenized. A

portion of the homogenized sample was pkced in a 16-ounce glass jar for subsequent analysis

by the laboratory.

A.3.6.5 Surficial Geologic Mapping

Delineation of surficial Quaternary geologic units was based on a review of existing information

and field observations of topographic position and relief, surface morphology, sedimentology,

and stratigraphy. Field reconnaissance mapping of surficial geologic units was compared to

observations from aerial photographs. Stereo aerial photographs provided an enhanced threeResidential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-36 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

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dimensional view of large portions of the study area. This enabled observation of large-scale

features not recognizable from a ground perspective and allowed comparison of similar geologic

and topographic features over the study area. Photographic identification of their geomorphic

surfaces associated with field mapping units was based on textural, tonal, and color

characteristics unique to each surface. The three-dimensional aspect of the stereo photographs

allowed the observation of topographic relationships between units as well as their surface

topography.

A.3.6.6 Laboratory Analysis

Soil pedon samples were analyzed, using analytical methods employed for agronomic parameters

identified by the American Society of Agronomy (ASA) or the U.S. Department of Agriculture

(USDA), for the following physical and chemical parameters:

p H, Saturated Paste Conductivity, Saturated Paste Cation Exchange Capacity Carbon, Organic Lime Acid/Base Potential Sulfur, Total Neutralization Potential Particle Size Analysis Bulk Density

The samples were also analyzed for lead, arsenic, cadmium, and zinc by XRF.

A.3.6.7 Results

Soils

This section presents the results of the soil mapping (Walsh, 1992) within the study area. For

clarity and simplicity, map units having similar physical and chemical characteristics were

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combined to form generalized map units. A map of the study area showing generalized map

units is shown in Figure 2-3 (Volume I). The acreage of each map unit is shown in Table A-7.

Within the non-populated study area, 426 shallow observations (to 18 inches) and 13 backhoe

pits were used to characterize and map the soils. These areas primarily are composed of native

undisturbed soils. Areas not composed of undisturbed soils in non-populated areas include the

numerous mine waste piles occurring in the eastern portion of the study area; areas consisting

of eroded soils, such as the northwest facing hillside south of the former AV smelter site; the

former AV smelter site which is composed of slag piles and slag/mine waste mixed with

construction fill; slag and tailin g piles occurring in various locations; and many of the major

drainages. These drainages, including California Gulch, portions of Evans Gulch, Oregon

Gulch, Malta Gulch, Stray Horse Gulch, Little Stray Horse Gulch, and along the Arkansas River

consist of alluvial soils mixed with various types of mine waste. The mine waste piles are either

sulfide- or carbonate-rich. The sulfide-rich piles contain little or no vegetation, are commonly

acid generating, and are basically waste land. The carbonate waste piles, on the other hand, do

contain some grasses and sagebrush.

Within the Residential Study Area, 406 shallow observations (to 18 inches) and 18 backhoe pits

were used to characterize and map the soils. The soil map units and land types occurring within

the Residential Study Area are shown in Tables A-8 and A-9. Soils in the City of Leadville are

predominately Leadville sandy loam with overlying construction fill . The construction fil l varies

in composition and in thickness, from a couple inches to more than 50 cm thick. The fill is

usually thicker west of Harrison Street. In general, the fill is very heterogenous and commonly

contains brick fragments, glass, charcoal, slag, mine waste rock, and other debris. The eastern

portion of the City of Leadville contains numerous mine waste piles and the Harrison slag pile

is located in southeast Leadville.

Soils in the Stringtown area are predominantly Pierian gravelly sandy loam with overlying fill

material which may contain some mine waste. Both the southwest and northeast ends of

Stringtown are composed of alluvium mixed with mill tailings.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-38

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
N

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Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A Document Control No. 4800-37-0205 Interim Status Report THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun

June 1996 Page A-39

IT SHALL NOT BE RELEASED OR DISCLOSED IN
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Tailings impoundments Alluvium with tailings Construction fill mixed with alluviu

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Buildings, parking lots, and streets Asphal t and concrete structures

> 150 cm fill material over native s Landfill s and dumps Gravel pits Water

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Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-40 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
I 1 f 1 I I I

Table A-8

Classification of Map Units for the Residential Study Area Soil Inventory

M ap Unit N o.

3

4

5

7

8

9

11

13

16

20

21

22

25

26

30

34

40

42

45

46

50

55

57

59

M ap Unit Name

Leadville sandy loam, 3-8 % slopes Leadville sandy loam, 3-8 % slopes, eroded

Leadville sandy loam, 3-8 % slopes, disturbed Leadville sandy loam, 3-8 % slopes, with surface slag Leadville sandy loam, 3-8% slopes, disturbed with construction fill, surface slag and cinders

Leadville sandy loam, 3-8% slopes, with overlying mine waste <50 cm thick Leadville sandy loam, 3-8% slopes, with overlying tailings <50 cm thick Leadville sandy loam, 3-8% slopes, with overlying construction fill <50 cm thick

Leadville sandy loam, 3-8 % slopes, with overlying construction fill > 50 cm thick

Leadville sandy loam, 3-35 % slopes Leadville sandy loam, 3-35 % slopes, eroded

Leadville sandy loam, 3-35 % slopes, disturbed Leadville sandy loam, 3-35% slopes, with overlying mine waste <50 cm thick Leadville sandy loam, 3-35 % slopes, with overlying construction fill < 50 cm thick

Newfork gravelly sandy loam, 1-3 % slopes Newfork gravelly sandy loam, 1-3% slopes, with overlying construction fill <30 cm thick

Pierian gravelly sandy loam, 3-9 % slopes Pierian gravelly sandy loam, 3-9% slopes, with overlying mine waste and construction fill >30 cm

thick Pierian gravelly sandy loam, 3-9% slopes, with overlying fill >30 cm thick Pierian gravelly sandy loam, 3-9 % slopes, disturbed

Troutville gravelly sandy loam, 3-8 % slopes Troutville gravelly sandy loam, 3-8% slopes Troutville gravelly sandy loam, 3-35 % slopes, disturbed Troutville gravelly sandy loam, 3-35% slopes, with overlying fill

Classification

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy or loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

sandy-skeletal, mixed Typic Cryaquolls

sandy-skeletal, mixed Typic Cryaquolls

sandy-skeletal, mixed Typic Cryoborolls

loamy or loamy-skeletal, mixed Typic Cryorthents

loamy or loamy-skeletal, mixed Typic Cryorthents

sandy-skeletal, mixed Typic Cryoborolls

loamy-skeletal, mixed Psammentic Cryoboralfs

loamy-skeletal, mixed Psammentic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

loamy-skeletal, mixed Typic Cryoboralfs

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Table A-9

Land Types for the Residential Study Area Soil Inventory

Map Unit No. Map Unit Name

70

71

72

74

80

81

82

91

92

102

Waste rock piles. Mine waste — waste rock and tailings. Mixed mine waste with construction fil l >50-cm thick.

Construction fill <50-cm thick over mine waste.

Slag piles. Slag — mine waste — construction fil l >50-cm thick. Mixed slag (>5% slag throughout) with construction fill > 50-cm thick.

Alluvium with tailings. Construction fill mixed with alluvium and tailings.

> 150-cm fill material over native soil.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-42

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
_ The Lake Fork Trailer Park area contains Newfork gravelly sandy loam and Newfork gravelly

sandy loam with overlying fil l material. The fil l material is generally less than 30 cm thick.

-w

Turquoise Lake Estates and the residential areas in the northwest portion of the study area

^ (Silver Hills, Gem Valley, Four Seasons, and Matchless Estates) are composed predominantly

of native soils, Leadville sandy loam and Troutville gravelly sandy loam. The A horizon within

— some of these areas has been partially or completely eroded.

s^ Physical and Chemical Characterization of Soil Pedons in the Study Area

•* The results of physical and chemical analyses of the soil backhoe pits (pedons) located within

the Residential Soils Study Area are contained in Table A-10. Pedons 01 and 03 are located

^ outside of the study area; however, they are included in this discussion because of their

immediate proximity to the Residential Soil Study Area.

The pH of the saturated soil paste from pedons within the study area ranged from 4.9 to 8 with

v

 an average of 6.3. The pH of an undisturbed Leadville sandy loam (SIP-004) ranged from 5.1

to 5.8. Mine waste materials within the study area often exhibit lower pH conditions than found

s_rf"i __

in native soils. For example, Pedon 11, which is located in California Gulch just below the

former Oro City site, exhibits a pH of 4 from 0 to 60 inches depth - which corresponds to the

^v*

occurrence of mine waste. Highly acidic conditions can arise from exposure of mine wastes to

air. In addition to chemical processes, biological processes play a very important role in

determining the acidity of soils. The metabolic processes of thiobasillus and metallogenium

organisms result in the oxidation of pyrite converting the sulfide into sulfuric acid.

The acid/base potential is a measure of the maximum potential acidity against total neutralizing

v material present in soils. The potential acidity is indicated by the total sulfur present in the soil. A measure of the neutralization potential (capacity) includes the presence of basic cations present

'•^Nt f

as carbonates and exchangeable cations derived from clays. The total sulfur and neutralization

potential are then used to calculate acid/base potential of the soil. Natural soils within the X Residential Soil s Study Area generally exhibit a positive acid/base potential. Mine waste

_ Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

Document Control No. 4800-37-0205 Interim Status Report Page A-43 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
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Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-44

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
^ commonly exhibits a negative acid/base potential, for example Pedons 03 and 11, which occur

outside the Residential Soils Study Area, contain mine waste and corresponding acid/base

« potentials of from -5 to -151 CaCO3/kton. An example of this neutralization potential is found

in pedon SIP-012 located in map unit 09, a Leadville sandy loam with overlying mine waste.

The pH within the mine waste is neutral to slightly basic, and the average acid/base potential

is 88, which suggests that the origin of the predominant mine waste is carbonate based material.

•-^- Total sulfur in the same horizon ranges from .01 to .5 percent indicating that the mine waste

also contains sulfide bearing waste. As this sulfide mineral continues to be oxidized the acid

v potential will remain high until the sulfide is depleted.

"•" High cation exchange capacity (CEC) is associated with high content of organic matter and to

a lesser extent with high clay content. Within the study area the highest CEC value, 23.1

^ milliequivalents per 100 grams (meq/100 g) of soil, was reported in the 0-to 5-inch increment

of pedon 006. Pedon 006 is located in an undisturbed Leadville sandy loam soil found in map

"~ unit 03.

v Soil Lead Results

The soil pedons in the study area were sampled by both soil horizon and specific depth

increments to assess the extent of lead contamination. It was found that lead concentrations are

generally the highest in the upper most one inch of soil and decrease with increased soil depth. The highest lead concentrations are associated with mine waste materials, fil l material of

unknown origin, and human artifacts. Some of the soil pedons with no visible mine waste and

fill materials contain elevated levels of lead in the upper inch or two of soil. Lead levels tend

to drop off significantly in the native soil below the waste or fill material. An example of this

in Leadville is found in Pedon 01 (incremental sample), the lead level dropped from 953 mg/kg

in the 0 to 1 inch interval, which corresponds to the occurrence of slag, to 19.5 mg/kg below

2 inches depth in the undisturbed native soil. Pedon 014, located in soil map unit 16 (Leadville

sandy loam with overlying construction fill > 50 cm thick), consists of fil l material from 0 to

35 inches. The highest lead concentration (6,410 mg/kg) in this pedon occurs in fill material

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-45

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epa\soils-ri\append-a.jun
from 22 to 25 inches depth, and then concentrations decrease to less than 100 mg/kg in the

native soil.

Lead concentrations average 1,861 milligrams per kilogram (mg/kg) in the 0 to 1 inch interval,

1,499 mg/kg in the 1 to 2 inch interval, decrease to 486 mg/kg in the 2 to 6 inch interval, and

average less than 300 mg/kg from 6 inches to 18 inches depth. In surface horizons of the soil

pedons containing mine waste or fill material, Pb concentrations are commonly greater than

2,000 mg/kg and range from 443 mg/kg to 10,900 mg/kg. In pedons without visible mine waste

and fill material in the A horizon, Pb concentrations are generally less than 600 mg/kg and range

from 143 mg/kg to 1,880 mg/kg. Lead values generally decrease to less than 100 mg/kg at

depths below 3 to 12 inches in pedons with no visible mine waste or fill material. Arsenic

concentrations average 80 mg/kg in the 0 to 1 inch interval, 62 mg/kg in the 1 to 2 inch interval,

59 mg/kg in the 6 to 12 inch interval, and drop below 20 mg/kg from 6 to 18 inches. Soil

pedons without visible mine waste and fill material contain less than 50 mg/kg As in the surface

horizon and decrease to less than 10 mg/kg below 3 to 12 inches. Cadmium concentrations

average 13 mg/kg in the 0 to 1 inch interval, 8 mg/kg in the 1 to 2 inch interval, and decrease

to 4 mg/kg or less below 2 inches depth. Zinc concentrations average 1,093 mg/kg in the 0 to

1 inch interval, 741 mg/kg in the 1 to 2 inch interval, and decrease to 378 mg/kg in the 2 to 6

inch interval. Zinc concentrations are generally less than 100 mg/kg in the substratum.

Linear regression was applied to lead with selected agronomic properties which demonstrated

that a correlation at the 95 percent level of significance exists between organic carbon and lead.

Of the four elements (lead, zinc, cadmium, and arsenic) lead is the least mobile in soil (Kabata- Pendias, 1984) because of the insolubility of lead compounds. The low solubility of lead

compounds and its affinity to chelate with organic compounds, in part, explain the presence of

elevated lead concentrations in the upper 2 inches of undisturbed soils.

Background Lead Concentrations

A pre-mining metals study (Walsh, 1994) estimated the background range for lead in upland

soils to be between 8 and 150 mg/kg. The majority of the residential study area is included in

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

Document Control No. 4800-37-0205 Interim Status Report Page A-46

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epa\soils-ri\append-a.jun
upland landscape positions. This background range is supported by the fact that lead levels in

native undisturbed soil pedons within the Residential Soils Study Area average less than 18

mg/kg below 6 inches depth. Furthermore, in pedons containing mine waste or fill material,

the lead concentrations in the underlying native soil generally fall s below 100 mg/kg.

Schacklette and Boerngen (1984) and Bowen (1979) estimated the range of lead in soils of the

western U.S. to be < 10 to 700 mg/kg and 2 to 300 mg/kg, respectively.

A.3.7 Smelter Remedial Investigation Report fWalsh. 1993)

The purpose of the Smelter Remedial Investigation was to collect soil data and historical smelter

information to identify and evaluate the impacts of historical smelting operations on human

health and the environment. To accomplish this goal, physical and chemical soil data collected

during this investigation and from previous soil sampling events were compiled and interpreted. This information was used to evaluate the impacts of smelter operations on soils and to

characterize the geographic distribution of soil metals originating from historic smelter facilities. An air dispersion model was used to evaluate depositional patterns of smelter emissions and to

identify potential areas of maximum metals concentrations resulting from smelter emissions.

Soils within these areas predicted to have maximum metals concentrations were then targeted

to be sampled. In addition, the literature and historic records pertaining to historic smelter

design and operations was reviewed. This information was used to conduct a field

reconnaissance and to identify the locations of historic smelter facilities. The field

reconnaissance confirmed the locations of the historic smelter sites, identified building debris

or evidence of former structures, identified areas where bag house and flue dust waste may have

been managed, and located disposal areas for smelter slag.

The soils data used in the Smelter Investigation were taken from the CDM Soils Investigation

Data Report (1993) and from 77 samples collected in areas identified by the air dispersion

model. The CDM soils investigation was conducted in 1991 and 1992 at which time 719 soil

samples were collected. All samples were analyzed by energy dispersive X-ray fluorescence

(EDXRF) for metal contaminants of concern including lead. The sampling locations, the

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-47

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
^ sampling methodology, the analytical method, and the analytical data pertaining to the CDM

Soils Investigation are described in Section A.3.5.

«^i

A.3.7.1 Air Dispersion Modeling

»— T he DSTCST model of the EPA's UNAMAP series was used to predict deposition of smelter

— emissions on soils at the California Gulch Site. The parameters input to the model are (1)

location and elevation of each smelter, (2) dates of operation (emissions start and end dates,

^ length of operation), (3) types and number of stacks, (4) stack heights and inner diameters, (5)

exhaust gas temperatures and velocities, (6) metal concentration in exhaust (related to production

-» rate), and (7) particle size distributions for smelter emissions. Attempts were made to obtain

actual data specific to each smelter for each parameter of interest. The meteorological

*•*• information collected from the Colorado Mountain College monitoring station was used for the

deposition modeling with the INCST model.

Metal concentrations were computed assuming that the smelter emission over the life tune of the

v

 smelter occurred in one year and that all metals deposited at a particular location are mixed into

the soil to a depth of 20 centimeters because of risk assessment considerations.

- \,w

A.3.7.2 Smelter Soil Sampling

— v

Seven former smelter sites were selected for soil sampling for assessment of metal

concentrations, including lead, and for identification of mining related materials in soil sample

pits to a depth of at least 18 inches. The soils were sampled at the same depth intervals and

-v>

using the same procedures as those described in the CDM Soils Investigation Data Report

(1993). The seven smelter sites include: the Arkansas Valley/American Smelter site; the La

Plata Smelter/Bi-Metallic Smelter site; the Western Zinc Smelter; the Grant/Union smelter site;

the Harrison Reduction Works site; the Elgin Smelter/Boston Gold-Copper Smelter site; and the

group of former smelters in the upper Evans Gulch. The samples were collected on the CDM

grid. Discrete smelter samples were collected from areas where historic smelter baghouses, dust

^ chambers, or roasting furnaces were located.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-48

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
In addition to the CDM soil sampling data (CDM, 1993), 77 additional soil samples were taken

in support of the Smelter Remedial Investigation. These procedures are described in Sections

A.3.5.1, A.3.5.2, and A.3.5.3 of this report. Seventy-one of the 77 soil sample locations,

based on dispersion modelling, were determined by the ISCST air dispersion model. All except

for three locations, based on dispersion modeling, were sampled. Access was denied to three

locations. The sampled locations were laid out on a 700-foot grid in accordance with

ASARCO's letter to K. Wangerud, dated 28 October 1991 (ASARCO, 1991). The soil sampling

locations were positioned on the 1,000-foot grid oriented N 45 W. The categories of soil

sampling and the sampling locations are described in Section A.3.5.1. The soil samples were

collected from the Arkansas Valley, the Western Zinc, and the Elgin smelter sites in the vicinity

of historic bag houses, dust chambers, or waste piles identified from the literature and smelter

reconnaissance.

A.3.7.3 Areas Impacted by Smelter Emissions

A combination of graphical and statistical procedures were employed to identify soil sample sites

that were likely impacted by historical smelter emissions. All soil sample locations at the site

were classified as either disturbed (containing visible mine waste, slag fill material, and/or

human artifacts) or undisturbed (lacking visible mine waste, fill material, and/or human

artifacts). The presence or absence of these materials was used to assist in the identification of

sample locations as areas impacted primarily by smelter emissions. If any of these materials

were observed as being present in one or more sampling intervals, the location was classified

as disturbed.

To assist in delineating the areal extent of smelter emission impacts, the Site was divided into

eight geographic areas. These areas were defined on the basis of soil type (disturbed versus

undisturbed), populated, and unpopulated. The area, immediately south of the former AV

smelter, was used as the control area. The control area consists of predominantly native

undisturbed soils, so any impacts would most likely be the result of smelter emissions. The

areas that fall within the Residential Soils Study Area include the North Leadville, the East

Leadville, and the West Leadville. Turquoise Lake Estates fall s within the Northwest Study

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-49

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Area, and the Lake Fork Trailer Park is located within the Lower California Gulch-Malta Gulch

Area.

*?

Metal pair ratios having significant (99 percent level of confidence) correlated concentrations

•^ were identified in the control area and were used to establish a metal signature for soils impacted

primarily with smelter emissions. Only undisturbed samples in the control area were used as

^- control samples (samples representing soil impacted exclusively by historic smelter emissions).

There are nine metal combinations (ratios) that have significant correlations in the control area

"? and include the following: Pb:Zn, Pb:Fe, PbrCu, ZnrFe , Zn:Ca, Fe:Cu, FerCa, and Fe:Ba. These metal ratios were then compared to the same metal ratios found in the 0- to 1-inch and

^ 1- to 2-inch depth intervals of disturbed and undisturbed soils throughout the study area. Those

soils in the study area exhibiting metals ratios similar to the ratios found in soils from the control

area were considered to have been impacted by smelter emissions. A 750-foot buffer zone was

drawn around all sample sites exhibiting a smelter signature for at least seven out of the nine

~" metal combinations. This zone established a boundary around areas identified to be impacted

by smelter emissions.

y

A.3.7.4 Results

••.«*•

Metal concentrations of soil samples collected from the former smelter sites are shown in Table

s* A-ll . The metal concentrations, including lead, do not decrease with increasing depth as they

do in most soils sampled within the California Gulch Site. In general, soils at the former

^>

smelter sites exhibit significant metal concentrations that occurred over the lifetime of the

smelters operations.

***

The environmental impacts, via the air pathway due to past smelter activities, occurred as a

V

result of the deposition of airborne particulates and gaseous smelter emissions followed by their

subsequent redistribution to other soils, to vegetation, and to surface water. The processes that

contributed to this redistribution include the following:

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

Document Control No. 4800-37-0205 Interim Status Report Page A-50 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-ll

Average Metal Concentrations at Former Smelter Sites

0- 1

1 -2

2 -6

6-12

12-18

illlilliiillll l Itiiiii^iiiiii

6,769

8,131

4,001

3,099

928

;ii:^l®pt^iPii

5,747

4,334

1,732

1,290

712

§*?S:i:?M|j^iiliiiiii

:

:

:

;

:

:

:

:

:

:

:

;

:

;

:-:

:

:::-:

:

::::X:::<*a::::v:

:

:::::

:

:::

:

:

:

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:

: PipS^siiiiii

665

615

535

354

51

lllllliiBli i

liiiiiiiiiiilii

221

176

49

52

12

lilliillill i

lliyilasp^iili

20

20

20

20

15

l;^;::;^

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0- 1

1 -2

2 -6

6- 12

12- 18

WMJmiis mmift^§mm

6,380

6,615

6,693

8,749

6,569

lllllllillllll l

iili-fiii^lllii

3,268

2,813

3,879

3,645

3,600

Illlllillltllfl i

lillliS^pSiillllll l

465

461

521

913

1,075

• . • S: ::

 : : ;- • -:

 :

 :M^^:iml::XiSim^^^^^^li^^i^^^^&^

^^^3$$;

:::;^'

:

'j:'V'i@ni):n---^ - :::1

0- 1

1 -2

2 -6

6- 12

12- 18

liiiiiiiiiii mw^i^^iifim

999

899

565

385

376

ITOJ:;;S;li^.i;e;S;:;:; :J

16,700

13,161

6,826

2,764

697

liiiiiiiiiiilii

iilliiliPiiillll l

262

139

53

38

4

lll^ll^lHIfsll l

til:ip:|#ll;|:|:;:::::;l

110

22

16

15

16

IlllliiliillP i m^^j^mmi:

4

4

4

4

4

IlllPlilii^liii l

32

43

39

30

4

Illllililill l K|i|l;iSiniiyfeig;iii;

7

7

7

7

5

;

 : ..".:. /•-. :

 ;..:; . -..:•: -: xi: : l^illiliS^

:^:: :.::{:••::. Depth,;-: •;: Hi

^;;H;!

:

»^:i

;

:l

0- 1

1 -2

2 -6

6-12

12- 18

!:&;;;i:l::-;;^li|lifi P

:

i i

;

ilK^iil^

2,225

2,122

2,301

2,397

2,252

:^!:x^fe-:-:::::s;;l;:-:::>:: :>:x>-

:

^: ' ^ s^fmvtti&itmmtSffti

563

564

654

906

828

lii::;i:;:i;?;:;^;lPili;: :;:¥::::::•:::•:,::;:::•;:«*»:¥::::: :'::::.:::v:::::. S K

| i::;P:^lSi^iStllIII

14

21

40

25

24

lillllliillll l

iillliiiiiilllPl

0

3

2

7

6

ll||;:||l||l|l|

||;|ijSSii((ii^ijii

2

2

2

2

2

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-51

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-ll (continued)

Average Metal Concentrations at Former Smelter Sites

111!!!!!^

lllliiiiiliilii

ifiiiitiii^iPii

0- 1

1-2

2 -6

6-12

llllillllll^ll l IPII;

li§iiiilill l

3,724

4,599

5,019

4,335

2,926

||l|l||||l|l|||

ili;i:llsii!®P^;S?*;;:l;SM

5,346

6,003

5,563

3,320

1,873

:^::::::i^:;^:::^:

:

::^!^:::^:::^:::^:^:::^i::

llllliiiiililil l

186

169

185

282

155

!iiliip|i!!p!!:j

32

42

27

16

9

Illlllllllli l Ilii^^m^pisilsf ;

 :; ;

3

3

3

3

3

liiisiiiiiM

litlliiliililtll l

0- 1

1 -2

2 -6

6-12

12- 18

llfitlfipilllfl l

8,520

5,536

3,831

5,436

139

lilllliiilll^lll

i?PP^»lfci?ii

5,073

3,294

2,511

3,039

475

illlllllllli l Iliil^diji;|;:s:::::g::;::

307

252

160

259

0

:S?:5:jSS;?SiS:^SKi:JTM::;:;i;:;:; :S m&mrniyfaxmxm IllPliSiiii^illl:;:;:

31

15

12

17

1

^l:iiliiill^illl S^Sm^^S'-A

3

3

3

3

2

i

;

iCii£: ;:JilJ||^

liM^pi m^<mmmM

0 -1

1 -2

2 -6

6- 12

12- 18

l:|;;l|lltltflllll IW:ti-:

iS*iBWSf l

3,159

2,469

3,859

7,487

1,780

itiiiiiliiiiiiti

liillllllpiiPil i

1,712

1,811

1,600

1,026

498

iiiiislliliiii

iiftiipi^iiiiil

0

0

72

41

4

mfmm^ifmiim

7

7

6

8

0

iillfii^iiiiii m^fMiJaiiiaiJ^mm

3

3

3

3

3

in. =

mm =

ppm =

inch

millimeter

parts per million

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-52 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
• The effect of wind erosion and the subsequent airborne transport of resuspended

paniculate contaminated with lead and other metals.

• The chemical transformation of smelter emission contained in impacted soils by

the action of thiobacillus and metallogenium organisms and by the action of acidic

surface waters resulting in an increased mobility of new chemical species.

• The accumulation of lead and other metals in the organic fraction of soils and

subsequent uptake by vegetation.

• The removal of surface soils impacted by smelter emissions and the mixing of

impacted surface soils with construction fill due to land development, land

contouring, and related activities.

The air dispersion modeling predicted the contribution of metals of concern, including lead, from

historic smelter emissions to the soils of the study area. The study areas that were predicted to

be impacted by smelter emissions include the Stringtown area and the entire southern half of

Leadville. The modeling task combined the metals of concern in its projection and reported a

maximum of 2,750 to 3,000 mg/kg at a depth of 0 to 20 cm in the Stringtown area. It predicted

total metals concentrations, in the southern half of Leadville, to range from 1,200 to 2,250

mg/kg at a depth of 0 to 20 cm. To validate the predicted impacts from historic smelter

emissions, measured values of the same metals from sample locations within the study area were

composited and compared to the predicted values. The two data sets were analyzed both

statistically and graphically. Statistical analysis entailed regression analysis to detect any linear

correlation between predicted and actual values. A Kruskall-Wallis Rank Sum test was also used

to compare the two data sets. There appears to be little agreement between the predicted and

actual values over most of the study area.

Metal concentrations, including lead, in disturbed and undisturbed soils were observed to

decrease with soil depth (except at former smelter sites). The concentrations of lead in disturbed

soils at all soil depth intervals are higher than those found in the same depth intervals of

undisturbed soils. The mean metal concentrations in disturbed and undisturbed less than 2 mm

soils are summarized in Table A-12.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-53

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-12

Mean Metals Concentrations by Depth Interval

for < 2 mm Soils Data for Disturbed and Undisturbed Sample Sites

Depth

(inches)

0-1

1-2

2-6

6-12

12-18

Disturbed?

Y es

No

Y es

No

Y es

No

Yes

No

Y es

No

Mean Concentration

As (ppm) (n)

128 (443)

115 (347)

123 (442)

70 (347)

79 (443)

26 (347)

58 (444)

17 (346)

37 (415)

13 (299)

Cd

(ppm) (n)

26 (443)

13 (347)

23 (442)

8 (347)

13 (443)

4 (347)

11 (444)

2 (346)

8 (415)

1 (299)

Pb

(ppm) (n)

2,734 (442)

2,075 (347)

2,545 (442)

925 (347)

2,063 (443)

293 (347)

1,696 (444)

110 (346)

1,456 (415)

99 (299)

Zn

(ppm) (n)

3,291 (443)

704 (347)

2,866 (442)

492 (347)

2,088 (443)

277 (347)

1,529 (444)

131 (346)

1,239 (415)

120 (299)

n = number of cases constituting that particular average

ppm = parts per million

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-54

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epa\soils-ri\append-a.jun
Areas found to exhibit the smelter emission signature include: the area south of California Gulch

and downwind of the former Arkansas Valley, California, La Plata, and American smelters

(essentially the control area); the west and northwest sections of the study area; and portions of

Evans Gulch that correspond to the former smelter sites along the gulch, and a small area near

the former Little Chief Smelter.

The control area is considered to be a prime example of an undisturbed area that has been

impacted primarily by smelter emissions. There are no signs of historical mining activity here

and the area has not been used as a dumping site for slag, tailings, or other mine waste.

Areas determined to be impacted predominantly with sources other than smelter emissions

include: Leadville proper consisting mostly of various types of fill material; the east study area

(includes the areas east and south of Leadville) consisting mostly of alluvial tailings and mine

waste rock; California and Malta Gulches which contain mostly alluvial tailings and mine waste

rock; the Hecla tailings area; Lake Fork Trailer Park which consists mostly of fil l material; and

channels and low terraces of the Arkansas River which are impacted by fluvial tailings.

The geographic areas of West Leadville and North Leadville contain an average of 1,534 ppm

Pb and 898 ppm Pb in the 0 to 1 inch interval, respectively. Most of the 0 to 1 inch soil

samples in these areas are impacted by sources other than smelter emissions yet 11 percent of

the sites exhibit a smelter signature. This indicates that both smelter emissions and other sources

have impacted soil metal concentrations in these areas.

The remainder of the Residential Soils Study area contained no sites with significant metal

signatures resembling the control sites. This does not exclude smelter emissions as a source of

impact in these areas. The fact that smelter impacted soils surround Leadville proper on the

west, north, and south suggests that Leadville proper has had some impact from smelter

emissions. However, this study demonstrates that other sources are the predominate source of

impact to Leadville proper.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-55

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epa\soils-ri\append-a.jun
The areas impacted predominantly with smelter emissions contain 276 undisturbed soil sample

sites. Average metal concentrations of these 276 samples by sample interval are shown in Table

A-13. Lead concentrations in the undisturbed areas impacted predominantly with smelter

emissions drop off dramatically from the 0 to 1 inch sample interval (average 1,895 ppm Pb)

to the 1 to 2 inch interval (average 792 ppm Pb) and to the 2 to 6 inch interval (average 174

ppm Pb). The other three metals of concern display a similar decrease with depth. This

demonstrates that undisturbed areas impacted predominantly with smelter emissions, in general,

contain elevated metal concentrations in the upper two inches, and below two inches metal

concentrations decrease dramatically.

Within the California Gulch Site the areas with the highest lead concentrations were found to

correspond to either gently sloping topographic highs or gently sloping tree-covered topographic

highs. These high lead concentrations were found in the 0- to 1-inch soil sample increment. A prime example of such a gently sloping topography with a lead concentration in excess of

5,000 mg/kg is located between western Leadville and the Turquoise Lake Estates. These

elevated areas are prone to erosion and can impact the Residential Study Area. This example

area to the west of Leadville and other similar areas are all located outside of the Residential

Study Area. Areas of low lead concentrations, in the 0- to 1-inch soil sample increment, are

found on more strongly sloping topographic areas that are devoid of vegetative cover. The

surface soils of strongly sloped areas are more prone to erosion during periods of strong surface

water runoff. This process not only removes soils contaminated with smelter emission but can

result in the transport of lead contaminated soils and paniculate onto the Residential Study Area

and into surface water features.

Wind erosion results in the resuspension of soils, smelter emissions paniculate, and lead

containing mining wastes at the California Gulch Site and the Residential Study Area. Wind

erosion represents an airborne transport and redistribution process. This process is multidirectional and is driven by the prevailing meteorological conditions. This process is most

effective during late fall and spring when soils are dry. Wind erosion is also affected by soil

texture and the quantity and type of vegetative cover that is present in the area.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-56

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WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-13

Average Concentrations of Pb, Zn, As and Cd for Areas Impacted Predominantly by Smelter Emissions

IIIBIII I ilitl$l^lll

lilflilllll l

flilfllllll l

lilllillli l

S:;:i|Si;:iijp;|;g5:;:s;;iS ;:;:::S:::S:;:;:ili*5|*:5s:;:;:;-;:s:::

1,869

751

173

75

67

KiSiijSj^HjiSifHg: ;

lllilill l

466

300

168

116

112

isliiilll mxm^mm

123

74

25

18

13

13

8

4

2

1

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-57

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epa\soils-ri\append-a.jun
The strongest winds on an annual basis that can result in the erosion of soils came from the

southwest through west-southwest with velocities of 18 to 24 mph. The most persistent wind

directions on an annual basis, for the period of October 1990 to October 1991, were from the

northwest through the northeast and the northeast through the east (Woodward-Clyde Consultants

[WCC], 1992a). This suggests that historically, soils impacted by smelter emissions from the

American, Arkansas Valley, California, Western Zinc, and Leadville smelters were subject to

wind erosion. A persistent wind direction from the west-southwest suggests that wind erosion

played a role in redeposition of these smelter emissions in the communities of Stringtown and

Leadville. Soils containing lead in excess of 3,500 mg/kg (Walsh, 1993) located in the

Stringtown community represent a significant potential for airborne transport of these materials

to Leadville when the prevailing winds are from the west-southwest.

A.3.8 Surface Water Remedial Investigation Report (WCC. 1993c)

The Surface Water Remedial Investigation Report is an element of the Phase n RI of the

California Gulch CERCLA site. This report describes the investigation of several surface water

drainages located within and near the Residential Study Area. The field investigations were

performed during the 1991 Ice-of f event, the 1991 Spring Runoff, the 1991 Summer, the 1991

Summer Storms, the 1991 Fall, and during the Winter of 1992. The work was performed in

accordance with The Surface Water, Bed Material and Aquatic Ecosystem Data Collection

Program Work Plan (WCC, 1991d).

The first objective of the surface water data collection system was to evaluate the physical and

chemical characteristics of the surface water associated with the California Gulch site. This

included an evaluation of the subdrainages within the California Gulch in order to identify

significant contributors to contamination loading in the Gulch; and to evaluate the seasonal

variations in water flow and contaminant loading. This characterization includes stream flow

measurements and stream surface water and bed material sampling and analysis. The data from

this monitoring and sampling program will also be used to evaluate the field program in terms

of identifying new locations of sampling and flow measuring stations and the relocation or

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-58

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epa\soils-ri\append-a.jun
elimination of existing stations. The second objective involves the evaluation of the aquatic

ecosystem to determine the nature and extent of contamination of this ecosystem. This

evaluation includes toxicity assessments of surface waters using standard bioassays of the water

flea and the fathead minnow, analyses of benthic macroinvertebrates, and qualitative analyses

of periphyton.

A.3.8.1 Surface Water Flow Monitoring and Sample Collection System Locations

The surface water monitoring and sample collection system used fixed sampling and gaging

stations within the watersheds. The stations were located where a permanent flow measuring

device (flume) or permanently installed staf f gages existed or were subsequently installed. The

field investigation area was divided into the following watersheds: Starr Ditch and Stray Horse

Gulch, East Fork of the Arkansas River, the Evans Gulch and tributaries, the Halfmoon Creek

the Tennessee Creek, and Lake Fork Creek. Thirteen sampling stations were located within

California Gulch and tributaries. Two sampling locations were located on the Starr Ditch and

Stray Horse Gulch. Two sampling stations were located along the East Fork of the Arkansas

River. Three stations were located along the Evans Gulch and the Little Evans Gulch. One

station was located along the Tennessee Creek and one along the Iowa Gulch. One station was

located along Halfmoon Creek and one along the Lake Fork Creek. Four sampling stations were

located along the Empire Gulch. Six stations were located along the Arkansas River.

A.3.8.2 Surface Water and Bed Material Sampling

Surface water samples were collected with a beaker and placed into a churn splitter during all

of the sampling events except for the 1991 Summer Storms event. Samples were distributed

from the chum splitter to sampling bottles. During the 1991 Summer Storms sampling program,

automatic sampling equipment was installed at stations AR3A, ARSE, AR02, and CG06. Three

storm events (occurring on 24 August, 30 August, and 11 September 1991) were sampled using

the automatic sampling equipment. Surface water samples to be analyzed for alkalinity,

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-59

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epa\soils-ri\append-a.jun
chloride, fluoride, and dissolved metals were filtered using a 0.45 /xm membrane filter and

peristaltic pump. Samples that were analyzed for total metals were not filtered.

Bed material was sampled using a stainless steel scoop. A composite bed material sample was

obtained by collecting bed material from across the entire width of the stream bed and mixing

the sampled materials in stainless steel bowl. Bed material samples were taken from the same

locations after the surface water samples

A.3.8.3 Analysis of Surface Water and Bed Material

Surface water samples and bed material samples were analyzed for the analytes listed in

Tables A-14 and A-15, respectively. These tables also identify the analytical methods used for

each analyte and the method detection limits.

A.3.8.4 Nature and Extent of Contamination

Based on the analytical data for surface water and bed material, and station flow data for all of

the sampling stations and sampling events, the following characterizations were made:

During all sampling events, the California Gulch drainage exhibits elevated

concentrations and loads of aluminum, arsenic, barium, cadmium, copper, iron,

lead, manganese, mercury, nickel, silver, and zinc in surface water compared to

those in other tributaries of the Arkansas River.

Concentrations of aluminum, arsenic, cadmium, copper, iron, lead, manganese,

and zinc in the Arkansas River surface water downstream of the confluence with California Gulch are greater than concentrations in the Arkansas River upstream

of the California Gulch confluence during certain times of the year.

Metals at the California Gulch site may originate from several potential sources, and include the

following:

• Surface water runoff from waste rock piles, slag piles, smelter sites, tailings

impoundments, and other mineralized-fill areas.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-60 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-14

Surface Water Samples - Parameters Analyzed, Analytical Methods and Detection Limits

Parameter

Field Analysis

pH

Specific conductivity (SC)

Dissolved Oxygen (DO)

Alkalinity*

Chlorine*

Laboratory Analysis

PHb

Specific conductivity (SC)b

Total suspended solids (TSS)b

Total dissolved solids (TDS)b

Dissolved Organic Carbon

(DOC)b

Alkalinityd

Calcium (Ca)d>

e

Magnesium (Mg) d e

Sodium (Na)d>

e

Potassium (K)d>

e

Chloride (Cl)b>

d

Sulfate (SO 4 )

b d

Silica (SiO2) b d

Total phosphorusb ) d

Fluoride (F) b d

Nitrate + Nitrite b ) d

Cyanide

Metals (Total and Dissolved)

Aluminum (Al)e

Antimony (Sb) e

Arsenic (As)e

EPA Method

N /A

N /A

N /A

N /A

N /A

150.1

120.1

160.2

160.1

ASTM D

4129-82

310.1

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

325.3

375.4

200.7

365.1

340.2

353.2

335.3 CLP-M

200.7 CLP-M

200.7 CLP-M

206.2 CLP-M

CRDL

N /A

N /A

N /A

N /A

5

5

5

5

N /A

N /A

N /A

N /A

N /A

N /A

10

200

60

10

I DL

2

C

2

C

1

l

c

1

1

1

1

l

c

4

C

l

c

0.01

C

O.lc

0.02

C

10

50

40

1

Reporting Units

/tmhos/cm

mg/l

mg/t

mg/ f

^mhos/cm

mg/£

mg/£

mg/t

mg/f

mg/t

mg/t

mg/f

mg/t mg/t

mg/t

mg/t

mg/t

mg/t

mg/t

mg/t

Mg/ f

Mg/ f

Mg/ f

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A Document Control No. 4800-37-0205 Interim Status Report

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epa\soils-ri\append-a.jun

June 1996 Page A-61 IT SHALL NOT BE RELEASED OR DISCLOSED IN
Table A-14 (Continued)

Surface Water Samples - Parameters Analyzed, Analytical Methods and Detection Limits

Parameter

Barium (Ba)e

Cadmium (Cd)e

Chromium (Cr)e

Copper (Cu)e

Iron (Fe)e

Lead (Pb)e

Manganese (Mn)e

Mercury (Hg)e

Nickel (Ni)e

Selenium (Se)e

Silver (Ag)e

Zinc (Zn)e

EPA Method

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

239.2 CLP-M

200.7 CLP-M

245.2 CLP-M

200.7 CLP-M

270.2 CLP-M

200.7 CLP-M

200.7 CLP-M

CRDL

200

5 (0.1)f

10

25 (l) f

100

3

15

0.2

40

5

10(0.1)f

20

IDL

10

0.1

10

1

20

1.1

10

0.2

20

1.1

0.55/0.5

10

Reporting Units

Mg«

PS/I

ftg/l

US"

us/*

us"

w't

wit

mi* pg/e

ngit

n<

a

 Parameter measured only for water collected at one station downstream of the sewage treatment plant. b

 USEPA Method for Chemical Analysis of Water and Wastes, EPA 600/4-79-020, March 1979, revised March 1993, or documented

comparable procedure. c

 Contract Laboratory Reporting Limits. Sample was not filtered. e

 USEPA Contract Laboratory Program Statement of Work for Inorganics Analysis, Multi-media, Multi-concentration SOW 788 (July 1988), Document Number ILMO1.0, March 1990. Parameter analyzed to a lower detection limit only in aquatic sampling events in which biota are also sampled.

ASTM = American Society for Testing and Materials. CLP-M = Contract Laboratory Protocol-M. CRDL = Contract Required Detection Limit. IDL = Instrument Detection Limit. mg/t = milligrams per liter

pglt = micrograms per liter

/unhos/cm = micromhos per liter

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-62

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epa\soils-ri\append-a.jun
Table A-15

Bed Material Samples - Parameters Analyzed, Analytical Methods and Detection Limits

Parameter

Sulfate

Chloride

Cyanide Metals (Total Only)

Aluminum

Antimony

Arsenic

Barium

Cadmium

Calcium

Chromium

Copper

Iron

Lead

Magnesium Manganese Mercury

Nickel

Potassium

Selenium

Silver

Sodium

Zinc

EPA Method

375.3

325.3

335.2 CLP-M

200.7 CLP-M

204.2 CLP-M

206.2 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

239.9 CLP-M

200.7 CLP-M

200.7 CLP-M

245.5 CLP-M

200.7 CLP-M

200.7 CLP-M

270.2 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

200.7 CLP-M

CRDL

N /A

N /A

2

40

12

2

40

1

1,000

2

5

20

0.6

1,000

3

0.1

8

1,000

1

2

1,000

4

Reporting Units

mg/kg

ing/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

NOTES: Method 200.7 CLP-M is ICP analysis. Methods 206.2 CLP-M, 239.9 CLP-M, and 270.2 CLP-M are Graphite Furnace AA analysis. Method 245.5 CLP-M is Cold Vapor AA analysis. Method 335.2 CLP-M is Spectrophotometric. A ll analysis followin g CLP methodologies may be from either USEPA Contract Laboratory Program Statement

of Work for Inorganics Analysis, Multi-media, Multi-concentration SOW 788 (July 1988) or Document N o. ILMO1.0 (March 1990). Sample specific CRDLs for solid samples are adjusted for percent moisture, and any dilutions, and will be

higher than those listed above,

mg/kg = milligrams per kilogram

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-63

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. FT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
• Seeps created by infiltration through tailing impoundments.

• Surface water runoff from naturally mineralized areas within the watershed.

• Stream bed sediments that may become suspended during high flows.

• Dissolution of metals in stream bed sediments as a result of changes in pH or

stream chemistry.

• Springs or seeps discharging groundwater that has been in contact with highly mineralized area or hydraulically connected to a contaminated aquifer.

• Fluvial tailings or piles that come in direct contact with surface water flows.

• Discharge from mine drainages and portals.

• Runoff adjacent to major roads where slag or other highly mineralized materials

have been used to "sand" roadways.

• Airborne transport of resuspended soil or mine waste contaminated with metals.

The mean concentrations of total lead for all stations were as follows: 5,068 pg/t during the

Ice-Off event; 146 pg/t during the Spring Runoff event; 1998 pg/t during the Summer event;

41 ng/t during the Fall event; and 102 g/t during the Winter event. Lead concentrations in the

California Gulch ranged from a low of 15 \*%lt during the Winter event to a high of 38,800 \i%ll

during the Summer event. Total lead concentrations were elevated in the tributaries to

California Gulch, particularly in Oregon Gulch and Stray Horse Gulch, compared to other

sampling sites in the study area. Dissolved lead concentration are generally not detected in the

Arkansas River for all sampling events and are not detected in the California Gulch during the

Summer and Winter events.

A.3.9 Metal Speciation and Source Characterization (Drexler. 1995)

This study identifies the lead species in both primary source materials (tailings, smelter ash,

slag, mine waste) and secondary sources (soils and dust) in order to provide information useful

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report . Page A-64

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epa\soils-ri\append-a.jun
for the assessment of lead bioavailability in soils, mine waste, and dust from Leadville. The

objectives of the lead speciation study are to:

Identify the principal sources of lead in the soils and dusts of the area and to

characterize how the lead species differ in these materials.

Determine whether a soil contaminated with tailings, mine waste, smelter ash, or

slag exhibits similar lead speciation distributions as the pure source material (e.g.,

tailings).

Determine the ultimate weathering products and how they differ in solubility

when compared to the source material.

Explain differences in speciation patterns between the suspected primary source

materials and the impacted residential soil.

Results of this investigation are found in the Findings of Metal Speciation Investigations at the

California Gulch NPL Site (WESTON, 1995)

A.3.10 WESTON XRF Residential Surface Soils Investigation fWESTON . 1991b)

T he objective of the WESTON Energy Dispersive XRF (EDXRF) Residential Surface Soils

Investigation was to determine if a field portable XRF analytical technique could be used for the

characterization and mapping of metals-contaminated soils in the Populated Residential Soil

Study Area of Leadville. This investigation was divided into two phases. The first phase

focused on the calibration of the field portable XRF instrument with respect to the soil/mine

waste types found in the study area and was designed to determine if the field generated XRF

data were comparable in quality to the conventional fixed-base laboratory XRF analytical

technique. With the successful completion of the first phase, the second phase of the

investigation involved the collection of soil samples using a defined sampling grid to characterize

metals distribution in the residential soils using the portable XRF analytical technique.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-6S

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
A.3.10.1 Sampling

The sampling of residential soils in Leadville during the 1991 summer resulted in the collection

and analysis of approximately 3,700 samples. Soil sampling occurred at 25-foot intervals, along

a series of surveyed transects. The transect lines for sampling were located along easements of

streets and unpaved alleyways in residential areas of Leadville. These easements were

contiguous to residential properties for sampling soils. The sampling locations and the

concentrations of lead at each location are presented in Plate 1.

During Phase I, 850 soil samples were collected at 25-foot intervals along the transects. At each

sample location, a soil area 6 inches in diameter was desegregated with a pick and shovel to a

depth of 6 inches. This soil was mixed repeatedly in place to make it homogeneous after which

approximately 500 grams (g) of soil was place in a plastic bag, labeled, and shipped to the

laboratory under chain-of-custody procedures. In the laboratory, the field moist samples in the

plastic bag were analyzed three times by the field portable XRF instrument. This mode of

analysis was analogous to in situ analysis. After this initial analysis the samples were dried

overnight in an oven at 100 C, sieved to remove grass and twigs, and then thoroughly mixed.

The samples were reanalyzed by the portable XRF and the laboratory KEVEX XRF instruments. Again, the samples were analyzed three times by the field portable XRF instrument because of

the short counting times involved and only once by the KEVEX laboratory instrument.

During Phase n, 2,850 soils were sampled following the same procedures as in Phase I. Soil

to a depth of 6 inches was mixed thoroughly in place to ensure the soil was homogeneous. Approximately 500 g of soil was then sampled from three points that were located 120 degrees

apart on a 4-inch radius. The soil was placed in a plastic bag, labeled, and sent to the

laboratory for analysis by the portable XRF instrument. Each soil was analyzed three times, and

the analytical values were averaged to provide the metal concentrations in the soil for that

location. At every 20th sample location a split of the soil sample was sent to the laboratory for

analysis by the fixed-base XRF instrument. Originally, the work plan called for the sample

analysis to be performed in the field. With three sampling crews in the field collecting samples,

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-66

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHAL L NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
it was more efficient to bring the samples to a central field laboratory where the samples were

analyzed.

Approximately 200 split soil samples out of a total of 3,700 were analyzed for lead and zinc in

the laboratory using CLP protocol.

A.3.10.2 Results

Forty-five residential soils from a 1990 sampling effort conducted by Walsh were made available

for the Phase I portion of the study. During the Walsh soil investigation, these soils were

analyzed by the CLP protocol and the analytical results were made available for the Phase I

portion of this study. Ten of these soils were used to co-calibrate the laboratory-based KEVEX

XKF and three different field portable X-Met XRF instruments. The remaining 35 characterized

soils were then analyzed by both instruments to confirm the accuracy of the calibrations of the

two types of XRF instruments.

Approximately 50 percent of the Phase n soil samples came from alleyways in close proximity

to residences. This study prompted the question of whether the concentrations of lead in

alleyway easement soils or nearby residential soils were representative of lead concentrations in

soils of backyard residences adjoining these easements. To answer this question, 38 locations

were identified where samples were taken from both alley easements and nearby residential soils.

Statistical comparison between the alley easement and nearby residential soils showed no

significant differences between the two.

The preliminary Baseline Human Risk Assessment (WESTON, 1991c) established 250 microns

as the largest ingestible particle size of concern. From the 1991 Phase I FPXRF study, 68

samples were randomly selected from the archived Leadville soil samples. Out of the 68

samples, 40 were collected from the edge of alley right-of-ways and the remaining 28 from

residential yards. These samples were sieved and the less than 250 micron fraction was sent to

the University of Colorado, Boulder for analysis by EDXRF. The two subsets of data were

analyzed statistically.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-67

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
From the 1991 Phase H FPXRF study, 86 samples were selected from 16 residential yards

sampling locations where replicate samples had been taken. These samples were also sieved and

the less than 250 micron fraction was sent to the University of Colorado, Boulder for analysis

by EDXRF. The analytical results for both Phases I and n 250 micron sieved samples were sent

to the Environmental Monitoring Systems Laboratory, Las Vegas, Nevada for comparison to the

results obtained by the FPXRF on whole soil samples (EPA, 1993b).

The conclusion of these two analyses is that at a 95 percent confidence level, the mean

concentrations of lead in the whole soil samples and in the 250 micron fractions are significantly

different for alleyways (alley edges) and not significantly different for residential yard soils. The

mean concentrations of lead in whole soil samples appear to be higher than the mean lead

concentrations in the less than 250 micron fractions in the alleyway samples. Therefore, the

mean concentrations in whole soils can be viewed as a conservative estimate for the mean lead

concentrations in fine soil fractions.

T he WESTON XRF Residential Surface Soils Investigation confirmed that the field portable

XRF instrumentation is capable of generating data comparable to laboratory based XRF

instrumentation and data generated by use of CLP protocol.

The highest lead concentrations in soils were found in the eastern and southeastern areas of

Leadville. Maximum lead concentrations ranged from 10,000 to 28,270 mg/kg.

A.3.11 Data Report for Lead Occurrence in and Immediately Adjacent to Residential Areas. California Gulch Site. Leadville. Colorado (University of Cincinnati.

1991)

Based on a door-to-door census conducted by the University of Cincinnati and the Lake County Health Department, 245 residences were selected to participate in an environmental sampling

program. The locations of residences participating in this study were not disclosed. Dust, paint,

water, and soil samples were collected at each of these residential environments and analyzed

for lead, arsenic, and cadmium.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-68 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
A.3.11.1 Data Collection Process

Eght study areas, A through H, were identified from which samples were collected in the

Leadville area. A ninth area outside of Leadville, Area M, was selected as a control area.

These areas were selected to provide a wide range of potential lead exposures from dust, soil,

paint, and water. Houses that were sampled varied in their proximity to: known historic

smelter operations; waste rock piles; tailing piles; and slag piles. The houses sampled also

varied in terms of the existence of lead-based paint; lead water pipes; and lead-based solder.

A.3.11.2 Sample Collection

Sampling at each house was conducted by two sampling teams trained by the University of

Cincinnati. The interior sampling team collected interior dust and water samples, and performed

the interior and exterior lead-in-paint sampling. The exterior sampling team collected exterior

dust and soil samples.

A.3.11.3 Interior Dust Sampling

Interior sampling locations were selected based on high traffic areas such as an area adjacent to

the front door; an area in the most frequently used room (living room or kitchen); and a floor

area near the doorway of the subject child's bedroom. A template exposing a 25-cm by 25-cm

area was placed over the area to be sampled. The sampling apparatus consisted of a monitoring

pump, an air monitoring cassette fitted with a 0.8 p cellulose acetate filter, and a collection

nozzle.

There is no discussion of lead data here since the sampling locations remain confidential and

unknown to EPA; however, this data can be used for risk assessment purposes.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-69

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
A.3.12 Pre-mining Soils Geochemistry Report (Walsh. 1993)

The purpose of the Pre-mining Soils Geochemistry Report was to determine pre-mining soil

metal concentrations at the California Gulch Study Area by evaluating existing soil metals data

and by gathering additional soils data from the mineralized areas of Leadville. The metals

evaluated for background concentrations were arsenic (As), cadmium (Cd), copper (Cu), lead

(Pb), and zinc (Zn).

The objectives of this study were to:

• sample soil pedons within the mineralized zone that are relatively undisturbed;

• produce a more accurate and detailed surficial geology map of the study area;

• develop and define soil-geologic units in the study area;

• differentiate between background and disturbed soil bodies in the study area; and,

• estimate ranges of pre-mining concentrations of metals in soils.

Data sets utilized in this study are primarily from Phase n Remedial Investigations at the

California Gulch NPL Site. The metals data are from five increments (0 to 1, 1 to 2, 2 to 6,

6 to 12, and 12 to 18 inches) and from surface to approximately 60 inches depth in soil backhoe

pits. Some locations were sampled by both increments and soil horizons. All soil samples were

analyzed for total metals using energy dispersive X-ray fluorescence (EDXRF) or by Contract

Laboratory Program methods.

During this study, four backhoe pits were sampled in locations east of town expected to be

mineralized and that appeared relatively undisturbed by mining activities. Samples collected

from these backhoe pits were analyzed to help assess metal background concentrations in

undisturbed soils occurring over mineralized parent material.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996

Document Control No. 4800-37-0205 Interim Status Report Page A-70 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. FT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
A.3.12.1 Geologic Mapping

A detailed surficial geologic map was produced to define soil-geologic units. The original

surficial geologic map of the study area prepared by Woodward-Clyde Consultants (WCC) was

revised by additional field mapping on 1:7,200 scale color stereo aerial photographs. The map

was then co-rectified with the detailed soils map on the orthophotograph. The new geologic map

followed the established geologic age subdivisions.

A.3.12.2 Methods for Estimating Pre-mining Soil Metal Concentrations

Pre-mining soil metal concentrations were estimated for two principle elements of the study area:

soil-geologic units and different landscape positions.

Pre-mining (background) soil metal concentrations were estimated for soil-geologic units using

metals data from the five depth increments (0 to 1, 1 to 2, 2 to 6, 6 to 12, and 12 to 18 inches)

at 629 locations. The analyses incorporated field documented soil conditions including

disturbance from mining activities, depth, geomorphology, and parent material. A limitation of

this approach, however, is that the samples are from intervals within the top 18 inches of the

soil profile. In many places, mine waste, fill material, and other surface disturbances are thicker

than 18 inches. Because the estimated metal background ranges may include a mixture of native

soil and impacted material, they may not accurately represent the pre-mining metals background

of that unit.

Using another approach, metal background ranges were computed for two generalized landscape

positions (alluvial and upland), using geochemical data from 33 five foot deep soil backhoe pits. Alluvial landscapes include nine backhoe pits while upland landscapes include 24 backhoe pits. Because soil backhoe pits are deep and penetrate into the undisturbed glacial parent materials,

they probably better represent pre-mining metal ranges over the entire site, whereas the

background ranges computed for the soil-geologic units display the variations that would be

expected in different parent materials and in materials undergoing different soil forming

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-71

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
processes. The background ranges computed from the backhoe pits were compared to the ranges

computed for the soil-geologic units.

Background metal ranges were estimated for both the landscape positions and the soil-geologic

units by applying the cumulative probability graphical technique to the corresponding metals

data. This method is commonly used in mineral-exploration to distinguish ore grade metal

abundance from host rock metal concentrations. A step-by-step outline for constructing

cumulative probability plots is shown in Table A-16.

The cumulative probability graphical procedure involves plotting the cumulative frequency of

metal concentrations on log probability paper and partitioning into anomalous and background

populations. The cumulative percent scale on probability paper is graduated so that a normal

distribution plots as a straight line. A mixture of two normal populations results in plots with

nearly linear segments separated by curved segments containing an inflection point. The

inflection point gives an estimate of the proportions of the two populations. Once the inflection

point, which partitions the frequency distribution into background and anomalous populations,

is established, a threshold value is selected. A threshold value of 99 percent for background

samples was selected for all background analyses. For instance, a threshold of 99 percent

means that 99 percent of the background samples were correctly identified as background and

1 percent was missed. In other words, the background value computed from the cumulative

probability plots is the upper limit of background for that metal. The lowest concentration, other

than zero, of each metal for each soil landscape position was selected to be the lower limit of

background. Reported values of zero were not used as the lower limit of background, since all

soils contain some amount of As, Cd, Pb, Cu, and Zn.

Figure A-5 is an example of a cumulative probability plot of Pb for soils of alluvial landscape

positions. Figure A-5 graphically shows the inflection point at 25 percent on the X axis, or log

concentration 3.2 on the Y axis. The solid circles represent the cumulative percentages of metal

concentrations from the original data; the "Xs" are points which define the background and

anomalous populations; and the triangles are calculated check points. The closer the check

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-72

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epa\soils-ri\append-a.jun
Table A-16

Procedure for Constructing Cumulative Probability Plots

1) Metal data were converted to logarithms.

2) Logarithmic metal concentrations were classified into 10 to 20 groups, with at least five samples in most

of the groups.

3) Cumulative percentages were computed, starting at the high concentrations, ending with 100 percent at

low concentrations.

4) The cumulative percentages were plotted against the lower class limits on probability paper, and a curve

was drawn through the points.

5) The inflection point of the curve was selected. This point defines the approximate proportions of the

two populations.

6) PA = Pt/fA was computed from each cumulative data point in population A, where Pj is the observed

cumulative percentage, and/] , is the proportion of samples fallin g in Population A.

7) New points were plotted at PA. Step 6 was continued until the inflection point was reached or until

newly calculated points markedly diverged from a straight line.

8) A line was drawn to fit the points plotted in Step 7. This line defines the anomalous population.

9) Analogous points were computed starting at low concentrations, using fB (proportion of samples in Population B, as determined by inflection point), and cumulative percentages were computed as 100-P. A line was drawn for background population.

10) The calculated populations were checked by combining them in the proper proportions, using Pm=fA

+ fJ*A + fsPs' where Pm is the cumulative percentage in the mixture. The values of Pm were plotted

and compare with original points. If Pm points diverged significantly from the original data points, a

slightly differen t inflection point was selected.

From Sinclair (1974, 1976).

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-73

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
B8X10B1

4.2

I"

S,., aQ

6

 3 6

sI "

3.0

2.8

2.6

2.4

2.2

2.0

1.8

0.

""••*

\

\

• Cumulative percentage of metal concentrations from (he original data.

X Points that defin e the two populations

A Check points

Background = 870 mg/kg

63 Samples

--*

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nil

--^

eshol

^^

1

•

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ulation

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01 0.05 0.1 0.2 0.5 1 2 5 10 20 30 40 50 60 70 80 Cumulative Frequency (%)

MWttGERS\_yKSICNERS/CONSUlTANTS (3Q3) 980-6800

U.S . ENVIRONMENTA L PROTECTION AGENC Y CALIFORNI A GULC H LEADVILLE , COLORADO

oint

\

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^s

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90 95 98 99 99.8 99.9 99.99

CUMULATIV E PROBABILIT Y PLOT FOR FIGUR E Pb FOR SOILS OF ALLUVIA L LANDSCAP E POSITION S A-5

5

I

§

p

1

(a

g

gD

Ml

I
points are to the original data points (cumulative percentages of metal concentrations) the more

accurate the computed background level is for that metal (Sinclair, 1974).

A threshold of 99 percent (or 1 percent on the bottom left of the plot) was selected and

corresponds to a log concentration of 2.94 or 870 mg/kg Pb. The computed background level

of 870 mg/kg Pb represents the upper limit of background. The lowest Pb value of the alluvial

landscape position was 80 which represents the lower limit of background.

Estimated background metals concentrations for each soil-geologic unit were compared to mean

metal values of each depth interval (for disturbed and undisturbed soils) by soil-geologic unit.

Background ranges for As and Cd for the soil-geologic units were obtained by assigning the

computed As and Cd background values from the soil landscape positions to the corresponding

soil-geologic units. This was done because 80 percent of the data for these two metals was

below the established practical quantitation limit.

A.3.12.3 Development of Soil-Geologic Units

Soil-geologic units were developed so pre-mining metal ranges could be evaluated based on soil

type and geologic parent material. The soil-geologic units are hybrid mapping units developed

by integrating general surficial geologic units (derived from the detailed surficial geologic map)

with the corresponding dominant soil types which were taken from the soil map of the study area

(Walsh, 1992a). Grouping the soils and geology in this manner allowed evaluation of the data

based on units having similar geology, depositional age, landscape positions, soil type, and

degree of disturbance. Table A-17 contains the relative age of the soil-geologic units, a

description of each unit, the acreage of each soil-geologic unit, and the percent of the total area.

A.3.12.4 Distinguishing Between Disturbed and Undisturbed Soils

To assess pre-mining metal background concentrations in soils, each sampled soil horizon within

the backhoe pits and soil sample increments were classified as either undisturbed or disturbed.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-7J THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-17

Soil-Geologic Units and Corresponding Dominant Soil Map Units

P

I

8

8

ll^l^^IO^K:v:::v

iiSlilif :I£

iliill^lIP;:;

M/D S

(Recent)

A/AS

(Recent - 8,000

ybp)

c/us

(Recent -

140,000 ybp)

PD/DS

(14,000 -30,000

ybp) BL/ULT

(140,000 ybp)

PBL/ULT (> 250,000 ybp)

B/UT

(> 1,600,000

ybp) TOTAL

;||;:;$j^^

0'p:;i:

:

:

:

i::|l:i^in(fe;^::;;;:::

:

;-!:^;;v\::V:

Man-Impacted/Disturbed Soils

Recent Alluvial Deposits/ Alluvial Soils

Colluvial Deposits/Upland Soils

Pinedale Deposits/Disturbed Soils

Bull Lake Deposits/Upland Soils: Leadville, Troutville

Pre-Bull Lake Deposits/Upland Soils: Leadville, Troutville

Bedrock/Upland Soils: Troutville

•^;f3^;^

j^r;?^::; .- ..:. . . •'•: :••'••• •:•••: y - •^

 -.•:•

 : xXxX :

 • :••••':'•• :•:••'•• ' 'X'X ; • :'••:•

 : : ': 'x: :':'xx.V::

.

:

.Xx'.V. : :

:

 Xx: xXxX.XxXXXx. .xxX:X

 : :: :-:-:-:: x:

.

: :: :':: :; :; :: :: :;i: : xXXXr-xXx1 :

 : : x ::

 •;.•; • : Man-Impacted Deposits: includes tailings, mine spoils, slag piles,

construction debris, and man-made fill . This unit dates from present to

historic mining activities in the 1800s. Geologic map units in this

grouping are: m, m/al , m/a3, m/a4, m/al, a/f, m/gl , m/g3, s, and t. Recent Alluvial Deposits: includes present to Pleistocene non-glaciated

alluvial deposits. Geologic map units in this grouping are: al, ay, af,

and ac.

Colluvial Deposits: includes all colluvial deposits which range from

present to Bull Lake. Geologic map units in this grouping are: cc, cf,

cf/a, and cf/b. Pinedale Deposits: includes alluvial and glacial deposits of the Pinedale

glacial advance. Geologic map units in this grouping are: a4, a4/a2,

a5, g4, and g5.

Bull Lake Deposits: includes alluvial and glacial deposits of the Bull Lake glacial advance. Geologic map units in this grouping are: a2, a3,

g2, and g3.

Pre-Bull Lake Deposits: includes alluvial and glacial deposits of the Pre-Bull Lake glacial advance. Geologic map units in mis grouping are:

al, gl, and glib.

Bedrock: includes all pre-Cenozoic deposits. These deposits range

from Tertiary through Precambrian. This geologic map unit corresponds

to the original "b" surficial geologic map unit.

Dominant Soil

:|;||iiiiif;

: :iiiiiii^||:

: {;^lfei^Cieoiogies;x:.

20, 70, 72, 73,

80, 81, 82, 90,

92, 103, 102

40, 44, 60, 61,

63

1, 55, 70

1, 13, 16, 34,

44, 45, 50, 55,

60, 70, 75, 100

3, 4, 8, 13, 50,

55

1, 3, 4, 55, 56

55

ilfil^xufs l

liiiiif

1,139

768

441

934

1,897

4,328

231

9,738

;:£i^V:":::S:::

:

:

: :

:

:

:

:

::>:

:

: ^mi^m

111:111111

11.5

7.7

4.5

9.4

19

43.5

2.3

97.9*

1

 ybp = years before present

* The total does not equal 100%, because the surficial geology was not mapped in two small portions (approximately 200 acres) of the study area due to lack of aerial

photographic coverage.
Undisturbed soil horizons show no apparent evidence of disruption of the natural soil profile and

lack visible mine waste, fill material, and human artifacts, whereas disturbed soil horizons

contain visible mine waste, fill material, and/or human artifacts. These materials and soils were

identified in the field and recorded on soil observation description forms by WALSH soil

scientists during the soil inventory.

A.3.12.5 Results

A.3.12.5.1 Background Metal Concentrations in Landscape Positions

T he background concentrations computed from cumulative probability plots for As, Cd, Cu, Pb,

and Zn for upland and alluvial soil landscape positions are presented in Table A-18. These

computed background metal ranges were then compared to common metal ranges in soils of the

U.S. (Table A-19).

Alluvial landscape positions are the unglaciated bottomland drainages and modern floodplains

and include the Arkansas River Valley and California, Malta, and Evans Gulches. Upland

landscape positions include the elevated landscapes of the study area, which comprise the

majority of the study area and include Leadville and all other residential areas.

Upland soils of the study area have background concentrations within common metal ranges

found in soils of the western U.S. For example, the computed background range of Pb in

upland positions is 8 to 150 mg/kg, and the common Pb range in western U.S. soils is from less

than 10 to 700 mg/kg. Alluvial landscape soils on the other hand exhibit As and Pb background

concentrations that exceed common As and Pb ranges found in soils of the western U.S. For

example, the computed background range of Pb in alluvial landscape positions is 870 mg/kg. Background metals concentrations within the alluvial landscape positions are naturally higher

than in upland landscapes, because soils from higher positions in the watershed are transported

downgradient and deposited in or along stream channel margins concentrating metals in the

alluvial channels, furthermore alluvial channels dissect mineralized zones.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-77

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR DM PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
A.3.12.5.2 Background Metal Concentrations in Soil-Geologic Units

T he ranges of background concentrations computed from cumulative probability plots for Cu,

Pb, and Zn for soil-geologic units are presented in Table A-20. Depth-weighted metal averages

of the incremental soil samples for each soil-geologic unit to be used as a comparison to the

computed background metal ranges are also in Table A-20.

The youngest soil-geologic unit (M/DS) exhibits the highest upper limit of background Pb, which

is most likely due to the shallow sample depths and the large amounts of mine waste materials

in this unit. The upper limit of background concentrations for Cu, Pb, and Zn generally

decreases with an increase in age of the seven soil-geologic units. Most of the estimated

background concentrations of the soil-geologic units are within common metal ranges in soils

of the western U.S. (refer to Tables A-19 and A-20). The As background range of soil-geologic

unit A/AS (120 mg/kg) exceeds the common As ranges found in western U.S soils (< 0.1 to

97 mg/kg). Cadmium background ranges of all soil-geologic units exceed the common Cd

ranges found in U.S. soils. (There is no Cd range presented in Schacklette and Boerngen (1984)

for western U.S. soils; however, western soils tend to have higher background metals levels

when compared to soils of the entire U.S.) .

A.3.12.5.3 Metal Concentrations in Disturbed and Undisturbed Soils

As a means of verifying the calculated background concentrations, the calculated values were

compared to measured metal concentrations in undisturbed soil horizons of the backhoe pits.

The data was separately categorized by soil horizons A, E, B, and C, which increase in depth

from shallow to parent rock material. Average metal concentrations of soil A,E, B, and C

horizons for upland and alluvial soil landscape positions are in Table A-21. For upland

landscape soils, the soil A horizon (surface horizon) exhibits metal concentrations greater than

the calculated background ranges. The soil A horizon is generally 2 to 3 inches thick in upland

soils (Walsh, 1992a). Below the A horizon, metal concentrations fall to within the background

ranges. These data suggest that, in general, downward transport (exuviation) of metals is not

an active process in upland landscape positions.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-78

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-18

Estimated Background Metal Concentrations for Upland and Alluvial Landscape Positions

Upland Landscapes

N o. of samples No. of backhoe pits

Alluvial Landscapes

N o. of samples N o. of backhoe pits

Illitlflillill i

;

:

:

:

:

.

:

:

:

:

:

:

:

:o:

:

:

:

:

:

:

:

:

:

:.f!lka;:

:

:

:

:

;

:

:

:v:

:

:::

:

:v:

:

:

:

liiiiiiiili

0.3-30

144

24

0.7-120

64

9

lilllillllil: l;ll|jij£gilll:l l

0.01-4

144

24

0.5-8

64

9

iiiiiiiiiii

lllliliil i

0.4-40

144

24

8-190

64

9

IIIII1II1III11 ! psIIJSi^fe^iliiiSJ i

8-150

126

1

24

80-870

63

2

9

lillliBII!! MfMl&W^M

16-100

144

24

37-660

64

9

1

 18 samples were omitted due to rejected data 2

 1 sample was omitted due to rejected data

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-79

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-19

Common Metal Ranges in Soils of the U.S.

Schacklette & Boerngen,

1984

Lindsay, 1979

iiiiliiiiiii

iiiiliiiii

< 0.1 -97

1 -50

1111^

lillllllili l

____*

0.01 - 0.7

2-300

2- 100

< 10-700

2-200

:'r-:

: :-:: :-:: :: :: :: :: :':: :^^.: :':: : :: :-:: :: :; :: :: :-:: :':-: - •:-:-:-:-:-:-:-:-:-:-.-.-:-y— •:•.-:•:•:••.•:•:-:•:::;:•:.: ^:.^^-£4L:<-:

:

:^^:

10 - 2,100

10-300

no reported values

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-80

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-20

Estimated Background Metal Concentrations and Depth Weighted Averages for Soil-Geologic Units

•:-:-••••:':•:'•':•:•.•:•:•• x-: x

:

x

:

x :

: :

x

: :

x

:

 -:•:•:'•'.-•'• ' -.•:'• :•'•: x

:

x-:':':

: :

x

: :

: x

:

:

;

:

:

x'x

:

:

:

: x 'X;x -;X x ••:•:•. :

:

x- .-'•'.'•: '.•:•'• x-x :

:x : :•.;. -:•.•: -:•:•'•:•:•••:•:-• -::

 •;• -: :

:x ::

x

:

:

;

x

:

:

M/DS Background Range Weighted Average2

N o. of samples3

A/A S Background Range Weighted Average N o. of samples

c/us Background Range Weighted Average N o. of samples

PD/DS Background Range Weighted Average N o. of samples

BL/ULT Background Range Weighted Average

N o. of samples

PBL/ULT Background Range Weighted Average N o. of samples

B/UT Background Range Weighted Average

N o. of samples

liiiHllllI tiillllllli i

0.3-30

86

144

0.7-120

27

64

0.3-30

12

144

0.3-30

36

144

0.3-30

23

144

0.3-30

46

144

0.3-30

3

144

0.01-4

16

144

0.5-8

9

64

0.01-4

8

144

0.01-4

9

144

0.01-4

4

144

0.01-4

4

144

0.01-4

2

144

2-210

139

459

6-150

120

243

2.5-170

39

110

1.6-200

140

393

0.7-80

48

980

1.5-150

45

1,117

0.5-65

11

35

23-630

2,417

465

21-260

1,554

275

18-460

1,193

114

33-270

1,332

413

6-160

611

984

2-350

477

1,313

19-210

165

35

45-220

1,752

465

35-630

1,146

275

22-220

1,343

114

59-270

1,564

413

17-210

752

984

15-260

578

1,313

46-300

278

35

Background ranges obtained from soil landscape positions Weighted averages calculated using incremental samples within each soil-geologic unit Number of samples used to calculate the background range

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-81

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Table A-21

Comparison of Soil Horizon Average Metal Concentrations to Background Concentrations1

Illlil i

t&:<+-i-j&-tt5:j5;s.y:- mm&&mm lllill i

liiipii :-:•:•:-:•:•:-:-:•:-*:-•!*:-:•:-:.:•:-:::.;•: llilll l IfSJil l

UPLAN D

A

E

B

C

background

11

13

23

19

144

41

8

7

10

30

7.6

2

0.7

0.6

4

46

9

11

11

40

MS

110

78

68

150

435

72

91

77

100

ALLUVIAL SOILS

A

B

C

background

6

2

8

64

27

10

18

120

20

4

9

8

270

179

198

190

436

182

223

870

2,204

639

801

660

1

 All data are from undisturbed soils only. Numbers in bold italicize typeface are at or below

the estimated background concentration for that element and landscape position.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-82

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Cadmium, Cu, and Zn concentrations in C horizons of alluvial soils exceed the calculated

background ranges for alluvial soils. The average Zn concentration in the A horizon of alluvial

landscape positions (2,204 mg/kg) exceed the common ranges of Zn found in soils of the

western U.S. Additionally, most of the average Cd and Cu concentrations in soil horizons of

alluvial landscapes exceed common ranges in soils of the U.S. This data implies that exuviation

of Cd, Cu, and Zn is an active process in the alluvial landscape soils.

Metals data from undisturbed soil C horizons best reflect the chemical composition of the parent

material, or pre-mining metals conditions in soils. Walsh (1992a) demonstrated that elevated

metal levels in surface horizons from mine waste, slag, smelter emissions, and fil l material

seldom influence metal levels in native C horizons that are well below the surface. The average

metal concentrations from undisturbed upland soil C horizons all fall within the background

ranges calculated from the cumulative probability plots (Table A-21).

Mean metals concentrations in undisturbed soils decrease to the calculated pre-mining values for

each soil-geologic unit at 2 to 6 inches depth for the five metals, with the exception of Pb and

Zn in the alluvial (A/As) and the Pinedale (PD/DS) soil-geologic units. These exceptions are

the result of the physical and chemical properties of the soils within these soil-geologic units;

both of which are located in areas that were impacted by placer mining, acid mine drainage,

smelting, and urban development. A/AS commonly contains fluvial tailings, such as the

Arkansas River floodplain, and Malta and California Gulches. PD/DS is generally composed

of various types of fill material and mine waste, and includes much of Leadville proper,

Stringtown, and Lake Fork Trailer Park.

A.4 REFERENCES

ASARCO, Inc. 1991. Letter to Mr. Kenneth Wangerud dated 28 October 1991.

ASARCO, Inc. The Denver & Rio Grande Western Railroad Company, and Resurrection Mining Company. 1993. Screening Feasibility Study for Remediation Alternatives, Draft Final, California Gulch Site, Leadville, Colorado.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-83 THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
CDM (Camp Dresser & McKee, Inc.) 1991a. Prepared for Resurrection Mining Company. Soil s Investigation Work Plan, California Gulch CERCLA Site, Leadville, Colorado.

CDM (Camp Dresser & McKee, Inc.). 1991b. Prepared for Resurrection Mining Company. Sampling and Analysis Plan, Final., California Gulch CERCLA Site, Leadville, Colorado.

CDM (Camp Dresser & McKee, Inc.). 1992. Prepared for Resurrection Mining Company. Metal Speciation and Source Characterization Work Plan, California Gulch CERCLA Site, Leadville, Colorado.

CDM (Camp Dresser & McKee, Inc.). 1994. Soils Investigation Data Report, California Gulch Site, Leadville, Colorado.

C H2M Hill, Inc. 1987. Phase I Remedial Investigation Report, California Gulch Site, Leadville, Colorado.

Chryssoulis, S.L. 1992. Prepared for Resurrection Mining, Inc. Metal Speciation and Source Characterization, California Gulch CERCLA Site, Leadville, Colorado.

Colorado Climate Center, Colorado State University, Ft. Collins, Colorado.

Colorado Department of Health, University of Colorado, and U.S. Department of Health and Human Services. 1989. Leadville Heavy Metals Exposure Study , Leadville, Colorado.

Drexler, J.W . 1994. Speciation, Extent and Source of Contamination at California Gulch CERCLA Site, Leadville, Colorado.

Drexler, J.W . 1994. Personal Communication from John Drexler, University of Colorado, Boulder to Frank J. Kabot, Roy F. Weston, Inc., Denver, Colorado, January 1994.

EPA (U.S. Environmental Protection Agency). 1988. Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA, Interim Final. EPA/540/G89/004, OSWER Directive 9355.3-01. Office of Emergency and Remedial Response.

E PA (U.S. Environmental Protection Agency). 1993a. Final Screening Feasibility Study For Remediation Alternatives, California Gulch NPL Site, Leadville, Colorado.

EPA (U.S. Environmental Protection Agency). 1993b. Statistical Comparison of Lead Concentrations in Whole and Fine Soil Fractions from California Gulch (Leadville) Superfund Site, Leadville, Colorado. Environmental Monitoring Systems Laboratory, Las Vegas, Nevada.

E-S (Engineering-Science, Inc.) 1986. Prepared for Colorado Department of Law. Leadville/Stringtown Soil s Investigation, Leadville, Colorado.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-84

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC. , EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
Geraghty & Miller, Inc. 1988. Prepared for Colorado Department Of Highways. Metals Concentrations and Special Handling Consideration for Soils Adjacent to State Highway

24, Leadville, Colorado.

Jacobs Engineering Group, Inc. 1991. Historical Mineral Processing Operations of the Leadville Mining District, California Gulch Superfund Site, Leadville, Colorado.

Kabata-Pendias, A. and H. Pendias. 1984. Trace Elements in Soil s and Plants, CRC Press, Boca Ratan.

Kurtz, J. and R. Bryan. 1993. Nature, Extent and Source of Contamination at the California Gulch NPL Site.

Lindsay, W.L. 1979. Chemical Equilibria in Soils , John Wiley & Sons, New York. M-K (Morrison Knudsen, Inc.). 1992. Lead Slag Pile Remedial Investigation, California Gulch Site, Leadville, Colorado.

University of Cincinnati, Department of Health. 1991. Prepared for ASARCO/Resurrection. Dust Work Plan, Leadville, Colorado.

Walsh (Walsh & Associates, Inc.). 1988. Soil Investigations in the Leadville Study Area, Lake County, Colorado. Prepared for John Jacus, J.D. , Bradly, Campbell, and Carney. March, 1988.

Walsh (Walsh & Associates, Inc.). 1990. Residential Surface Soils and Household Dust Sampling, California Gulch Site, Leadville, Colorado.

Walsh (Walsh & Associates, Inc.). 1992a. Soil s Investigation and Mapping, California Gulch Site, Leadville, Colorado.

Walsh (Walsh & Associates, Inc.). 1993. Prepared for ASARCO, Inc. Smelter Remedial Investigation Report, Volumes I, U, and HI, California Gulch Site, Leadville, Colorado.

W CC (Woodward-Clyde Consultants, Inc.). 1991a. Prepared for ASARCO, Inc. Remedial Investigation Scoping Document, California Gulch Site, Leadville, Colorado.

W CC (Woodward-Clyde Consultants, Inc.). 1991b. Prepared for ASARCO, Inc. Smelter Site Investigation Work Plan, California Gulch Site, Leadville, Colorado.

W CC (Woodward-Clyde Consultants, Inc.). 1991c. Prepared for ASARCO, Inc. Soil Investigation Work Plan, Draft Final, California Gulch Study Area, Leadville, Colorado.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-85

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
WCC (Woodward-Clyde Consultants, Inc.). 1991d. The Surface Water, Bed Material and Aquatic Ecosystem Data Collection Program Work Plan, California Gulch, Leadville, Colorado.

W CC (Woodward-Clyde Consultants, Inc.). 1992a. Prepared for Res-ASARCO, Inc. Air Quality Monitoring Report. Volumes I and n. California Gulch Site, Leadville, Colorado.

W CC (Woodward-Clyde Consultants, Inc.). 1992b. Prepared for ASARCO, Inc. Smelter Site Reconnaissance, California Gulch Site, Leadville, Colorado.

WCC (Woodward-Clyde Consultants, Inc.). 1993c. Surface Water Remedial Investigation Report, California Gulch Site, Leadville, Colorado.

W CC (Woodward-Clyde Consultants, Inc.). 1993d. Prepared for ASARCO, Inc. Data Report

for Lead Occurrence In and Immediately Adjacent to Residential Area, California Gulch Site, Leadville, Colorado.

WESTON (Roy F. Weston, Inc.). 1990. Prepared for the U.S. Environmental Protection Agency, Region Vm. Residential Soils Sampling and Air Monitoring Work Plan, California Gulch, Leadville, Colorado.

WESTON (Roy F. Weston, Inc.). 1991a. Prepared for the U.S. Environmental Protection Agency, Region Vm, Site Management Plan, Volume m, California Gulch NPL Site, Leadville, Colorado.

WESTON (Roy F. Weston, Inc.). 1991b. Prepared for the U.S. Environmental Protection Agency, Region VEIL Soil Sampling and X-ray Fluorescence Analysis Work Plan, Leadville, Colorado.

WESTON (Roy F. Weston, Inc.). 1991c. Preliminary Human Health, Baseline Risk Assessment, California Gulch Site, Leadville, Colorado.

WESTON (Roy F. Weston, Inc.). 1993. Prepared for the U.S. Environmental Protection Agency, Region Vm. Residential Areas Enforcement Support Work Plan, Revision 3, California Gulch Site, Leadville, Colorado.

WESTON (Roy F. Weston, Inc.). 1995. Prepared for the U.S. Environmental Protection Agency, Region VIE. Draft Final Findings of Metal Speciation Investigations at the California Gulch NPL Site.

Residential-Populated Soils Study Area Consolidated Findings Report APPENDIX A June 1996 Document Control No. 4800-37-0205 Interim Status Report Page A-86

THIS DOCUMENT WAS PREPARED BY ROY F. WESTON, INC., EXPRESSLY FOR EPA. IT SHALL NOT BE RELEASED OR DISCLOSED IN WHOLE OR IN PART WITHOUT THE EXPRESS, WRITTEN PERMISSION OF EPA.

epa\soils-ri\append-a.jun
APPENDIX B

EPA/EMSL FIELD PORTABLE XRF REPORTS
EPA/600/R-93/073 March 1993

AN X-RAY FLUORESCENCE SURVEY OF LEAD

CONTAMINATED RESIDENTIAL SOILS

IN LEADVILLE, COLORADO:

A CASE STUDY

by

C A. Kuharic and W.H. Cote Lockheed Environmental Systems and Technologies Company Las Vegas, Nevada

and

A.K. Singh and D. Gonzales University of Nevada, Las Vegas Harry Reid Center for Environmental Research Las Vegas, Nevada

Project Officer

Kenneth W. Brown Technology Support Center for Monitoring and Site Characterization Environmental Monitoring Systems Laboratory Las Vegas, Nevada

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY L AS VEGAS, NEVADA 89193-3478

Printed on Recycled Paper
TABLE OF CONTENTS

NOTICE ......................................................... ii

TABLE OF CONTENTS ............................................. ill

LIST OF FIGURES .................................................

 v

LIST OF TABLES .................................................. vi

ACKNOWLEDGEMENTS ...........................................

 vii

FOREWORD ..................................................... 1

INTRODUCTION .................................................

Background .................................................. 2 History ..................................................... 2 Site Description ................................................ 3 Migration of Waste Materials ..................................... 3 The Role of EMSL-Las Vegas .................................... 4

PRINCIPLES OF X-RAY FLUORESCENCE ............................ 4 THE X-MET 880 ............................................. 5 THE KEVEX 770 ............................................ 5

INSTRUMENT CO-CALIBRATION ................................... 5

SAMPLE HANDLING ...........................................

FIELD SAMPLING ........................................... 

SAMPLE PREPARATION ..................................... 

The First 850 samples ..................................... 8 The Rest of the Samples ................................... 9

DATABASE MANAGEMENT ...................................

QUALITY CONTROL .............................................. 9 INTERNAL CONSISTENCY ................................... 

QUALITY CONTROL CHARTS ................................ 10 CLP VERSUS X-METs ....................................... 11 PRECISION, ACCURACY AND DETECTION LIMITS .............. 13 TOTAL VERSUS ESTIMATION ERROR ......................... 16

FALSE POSITIVES/FALSE NEGATIVES ............................

i ll
LIST OF FIGURES

Figure 1. Calibration results for the Kevex and X-Mets 1, 2, and 3. ............. 7 Figure 2. Correlation plots between Kevex and moist/dry X-Met. .............. 10 Figure 3. Quality control charts for Kevex and X-Met #1. ................... 12 Figure 4. Correlation plot between CLP and combined X-Mets, and Kevex. ...... 13 Figure 5. Frequency distribution of %RSD for moist field duplicates. ........... 15 Figure 6. False negatives and false positives .............................. 18
ACKNOWLEDGEMENTS

The authors are indebted to Mr. Ken Wangerud, the Remedial Project Manager,

personnel from the Roy F. Weston, Inc., Denver office, and to Dr. Rex Bryan and Dr. John Drexler for their valuable technical suggestions and advice.

vii
FOREWORD

Continuing concern over the adverse impacts to human health due to exposure to

lead has prompted characterization effort s at numerous sites across the United States . One

of the primary potential exposure routes is through ingestion and inhalation of lead

contaminated soils. This problem can be serious at old mining and smelting sites, especially

in the western United States.

T he California Gulch Superfun d Site in Leadville, Colorado was added to the National Priority List (NPL) in 1983. It is an historic mining and smelting site that is

currently the focus of extensive studies on soil lead contamination and bioavailability. Studies of ground and surface water impacts are also in progress. Personnel from the

Environmental Protection Agencies (EPA) Environmental Monitoring Systems Laboratory

at Las Vegas (EMSL-LV) , the Denver offic e of Roy F. Weston, Inc., and Geostat Systems, Inc. (GSI) used field-portable X-ray fluorescence (FPXRF) to determine the spatial

distribution of lead concentrations in residential soils.

This report details the FPXRF program sample collection, preparation, and analysis

procedures, database management, and program quality assurance effort s at Leadville. The

program clearly demonstrates that small, field portable XRF instrumentation can produce

large quantities of acceptable quality data in a timely and cost-efficient manner when used

properly.

When combined with the results of blood lead level and bioavailability studies, this

data can help to develop a true assessment of the risks posed by lead in the residential soils

of Leadville.
Eventually, the mining and processing turned from the oxidized, carbonate ores to the

less desirable sulfide ores of the more mundane metals, lead and zinc. Activity since has

been cyclic, following trends in the base metals markets. Total metal production to 1966 was

about 24,000,000 tons. There is currently only one active major operation in the area, ASARCO's Black Cloud Mine. The last smelter ceased operations in 1960.

T he extensive underground mining activity lef t a legacy of drainage tunnels, perhaps

most notably the Yak tunnel, and numerous mine waste rock and tailings piles dotting the

landscape, almost entirely to the east and upslope of the town. The processing activities,

which were scattered around the town, lef t behind large amounts of slag. Owing to the

relative inefficiency of the recovery methods of the time, much of the waste material

contains high amounts of lead and zinc, along with some other metals.

A preliminary EPA site evaluation took place in 1982 and 1983, and the site was

placed on the NPL in 1983. The initial concern was on the effluen t from the Yak tunnel. A surge pond and treatment system have since been constructed to deal with this aspect of

the mining legacy. However, as is sometimes the case around old mining districts, material

has been taken from abandoned dumps for use as fill, slag has been used as railroad ballast,

and it has been crushed for use on streets in the winter. This use, taken in conjunction with

the spread of smelter dust and wind transport of fine grained particles from various dumps,

prompted concern about the effect s of lead on people living in the town, especially the

children.

Site Description

The town of Leadville lies about 100 miles southwest of Denver. It is situated on the

western slope of the Mosquito Range, just east and upslope of the Arkansas River, at an

elevation of approximately 10,200 feet. The mining activity was predominantly on the

eastern side of town, along the drainages of California, Evans, Stray Horse, Oregon, Malta

and Georgia Gulches. The area lies within the Colorado Mineral Belt and is highly mineralized0

.

The soils in the affected area are sandy loams to gravelly sandy loams, with varying

amounts of admixed slags and tailings. The Leadville sandy loam predominates, with lesser

amounts of Pierian and Troutville gravelly sandy loams present

0

*. Large piles of slag and

tailings are also scattered around the site.

Migration of Waste Materials

Contaminant transport occurred from natural processes, such as wind and water

dispersion, but in Leadville as previously stated, the problem was exacerbated by human

impacts, ranging from smelter stack emissions to slags that were crushed and spread on icy

roads and used for railroad ballast. Tailings and mine waste rock were thoroughly mixed

into local soils by over a century of mining and commercial activities where these materials
the photon bombardment fluoresce simultaneously to produce a spectrum of characteristic

radiation. It is this spectrum that the XRF detector senses and counts.

There are two types of XRF spectrometers, energy dispersive and wavelength

dispersive. The principal differences are in the method of detection of the fluorescent

energies of the specimen and the method of quantifying the analytes of interest. For more

detailed information on X-ray fluorescence, the reader is referred to Jenkins et al.(4).

THE X-MET 880

The X-Met 880 used on the Leadville site is a field-portable, energy dispersive XRF

spectrometer marketed by Outokumpu Electronics, Inc., Langhorne, PA. The unit is selfcontained, battery powered, microprocessor based, and weighs 8.5 kg. The surface analysis

probe is specifically designed for field use. The X-Met 880 is hermetically sealed and can

be decontaminated with soap and water. The probe includes two radioisotope sources, Americium-241 and Curium-244, a proportional tube counter, and the associated electronics. The source is protected by a Nuclear Regulatory Commission approved safety shutter. The

electronic unit has thirty-two calibration memories called "model". Each model can be

independently calibrated for as many as six elements. Using a multivariate regression

procedure with the proper isotope sources, the instrument can be calibrated to measure

elements from silicon to uranium. Unknown sample intensities are then compared to the

calibration curves to yield quantitative concentrations.

THEKEVEX77 0

The Kevex 770 is a laboratory-grade, energy dispersive XRF instrument marketed by Fisons Instruments, San Carlos, CA. The instrument contains a 198 watt, Rh anode, liquidcooled X-ray tube, and a cryogenically cooled, lithium drifted silicon solid state detector. Optimal excitation conditions for analytes ranging from Na to U can be achieved using tube

direct excitation with filters or using secondary targets for essentially monochromatic

excitation. The higher resolution of the Kevex (over five times that of the X-Met) allows

for excellent qualitative scans for analytes that interfere with the analytes of interest.

Calibration curves were chosen over Fundamental Parameters (FP)1 for quantitating

the analytes of interest. It was decided in committee that calibration curves based on a suite

of site specific calibration standards would be a more robust approach than using FP.

INSTRUMENT CO-CALIBRATION

Forty-five residential soil samples from a 1990 sampling effort by Walsh and Associates, Denver, Colorado, were available with corresponding EPA CLP analytical results.

'Fundamental Parameters is a mathematical approach which resolves analyte interferences and

produces quantitative results for all analytes in the sample.
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diameter polyethylene X-ray cell and sealed with 0.2 mil polypropylen e film. The cupped

sample was then analyzed on the Kevex and again on one of the three X-Mets. The

remaining dried soil was put into archive, still under chain-of-custody. All Pyrex loaf dishes

were decontaminated with an Alconox/distilled water solution, rinsed with distilled water, and

air dried.

All X-Met measurements were done in triplicate and the values averaged partly due

to the relatively short acquisition time (30 seconds livetime), but mostly to obtain a more

representative composite value of each sample. A sample is measured only once on the Kevex due to the long acquisition time (200 seconds livetime2).

T he Rest of the Samples

Once good correlation was established between X-Met and Kevex analysis (see Figure

2), only one in ten samples was dried, cupped, and analyzed on the Kevex. The X-Met

procedure continued in the same manner throughout the rest of the program; that is,

samples were brought in by the field crews, analyzed in triplicate in the plastic bag, and then

archived.

DATABASE MANAGEMENT

A database management system was developed using the Statistical Analysis Software

supported by the SAS Institute Inc., Gary, NC. Screens were designed to look exactly like

the data recording forms. Along with all the analytical data (all triplicate measurements and

associated QC samples), other data including easting, northing, analytical date and time,

sample type, instrument ID, and a unique serial number for each sample were tracked by

the management system.

Data were entered in batches (30 samples per batch) and as each batch was

completed, it was printed out and 'hand checked against the data recording forms for entry

errors. All changes made to the database were tracked by a comparison procedure, and a

printout of each set of changes made to the data set was put into the hard copy dataset for

documentation purposes.

QUALITY CONTROL

As the database grew, comparison plots were periodically generated between the Kevex and th$ X-Mets to assess the degree of correlation, as was done with the cocalibration, thus demonstrating internal consistency within the data collection effort . Once

the CLP corroboratory data were available, the same type of correlation was generated,

confirming the accuracy of the data.

2At an average deadtime of 40 percent, this equates to 280 seconds acquisition time per sample.

9
The low-range sample was used to calculate detection limits (discussed in section entitled

"PRECISION, ACCURACY AND DETECTION LIMITS" below), and the mid-range was

plotted in a control chart to monitor instrument stability. These control charts are shown

in Figure 3.

There are notable differences in the charts that need explanation. There were

considerably more samples run on X-Met Number One than on the Kevex, thus the

difference in a horizontal sense. There was only one set of QCCS run on the Kevex;

however, there were at least three sets run on X-Met Number One due to breakage of the

polypropylen e film and loss of sample. What was not foreseen, mainly because the authors

had not engaged in an XRF survey of this magnitude, was that time would wreak havoc with

the QCCS. The 0.2 mil polypropylene film, through which the samples are X-rayed,

developed small holes with time and the soil leaked out. Consequently, the film had to be

replaced periodically and, being highly electrostatic, it extracted portions of the very fin e

fraction from the soil, thus biasing the standard. Occasionally, the film would simply break

and another QCCS would have to be used. The bias between the differen t QCCS samples

could be seen as several distinct concentration groupings, the first break being at run

number 117 (for X-Met Number One). All of these potential sources of error manifested

themselves, particularly in the control chart for X-Met Number One, because the majority

of the samples were analyzed on this instrument. Also, the QCCS were analyzed in triplicate

on the X-Mets and were shaken and tapped between each measurement. The least

variability is evident from the Kevex chart because considerably fewer samples were run on

this instrument and samples were run only once, thus much less abuse of the polypropylen e

film occurred.

In retrospect, the QCCS should have been pulverized and pressed to pellets ,

alleviating the biases with time. The accuracy of the X-Met is clearly displayed in the

correlation between CLP and X-Met data (see Figure 4). Ninety-six of the 140 samples sent

to the CLP were run on X-Met Number One (R2 = 0.86).

C LP VERSUS X-METs

Figure 4 shows the correlation plots between combined X-Met and CLP and between

the Kevex and CLP. These plots show very good agreement between XRF measurements

and those of the CLP, thus supporting the high degree of accuracy achieved in this field

survey. The higher R2 value for the less sophisticated X-Mets is probably a result of the

triplicate measurement average accounting for the heterogeneity of the sample better than

the single, longer measurement used on the Kevex.

11
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PRECISION, ACCURACY AND DETECTION LIMITS

The system precision can be estimated from the moist field duplicates. These

samples were split in the field after the in situ preparation of the soil. The sampling trowel

would scoop alternately to two bags and each sample went through the system in an identical

manner. The analysis of a routine sample and its field duplicate often occurred in differen t

batches, so there is a large time component in the overall variability of these duplicates. The

frequency distribution and univariate statistics shown in Figure 5 are on the percent relative

standard deviation (%RSD, or percent coefficient of variation) between the routine sample

and its field duplicate for samples over 0.05 wt% (500 ppm) Pb. At the 95th percentile, %RSD is 27, so a very conservative estimate of precision is ±27%. This is not just analytical

error but includes field sampling error and sample preparation errors as well.

Accuracy can be estimated from the correlation with the CLP. With an 88%

correlation (Figure 4, left plot), the accuracy can be estimated at approximately ±6% (half

of the 12% non-correlation).

13
FREQUENCY

220

200

180

160

140

120

100

80

60

40

20

****

****

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***«

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««** ***» *««* **••

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2.5 7.5 12.5 17.5

Moments

H 531 Mean 8.8 Variance 80.8

Std Dev 9.0 Skewness 2.1 Kurtosis 5.5 Coef Var U2.0

QuantUes(Def>5)

lOOXMax 58.3 99X 43.8

75X03 11.9 95X 26.8

50X Ned 5.9 90X 19.5

25X01 2.6 10X 1.0 OX Min 0 5X 0.5

1X 0.1

»***

 

•»**  **»»

  •** * »»** ***» ****

22.5 27.5 32.5 37.5 42.5 47.5 52.5 57.5 RSO_PB MIDPOINT

Figure 5. Frequency distribution of %RSD for moist field duplicates.

15
Action Level (ppm)

500

1000

1500

2000

2500

3000

Fals e Positive

2 (8.7%)

9 (22.0% )

13 (22.4%)

21 (26.6% )

13 (14.6%)

8 (8.4%)

Fals e Negative

3 (2.5% )

2 (2.0% )

3 (3.6% )

6 (9.5% )

4 (7.5% )

8 (17.0%)

Tabl e 1. Fals e positives and fals e negatives generated at six

action levels.

POPULATION TESTIN G

As explained above, residential access was extremely limited

at the beginning of the field season, so the firs t 50% or more of

the samples came from shoulders of alleys in direct proximity with

residences. The obvious question was whether the contaminant

concentrations along the alleyways were significantl y differen t

from contaminant concentrations in nearby residential soils (i.e.,

are alley samples representative of yard material?). To answer

this question, 38 'cells were located where samples were taken

both within alle y rights-of-way and in the nearby residential

yards. The paired-sample t-test and the nonparametric Kolmogorov- Smirnov procedures of the SAS software were used to show that,

with very few exceptions, there is no significant differenc e

between contaminant concentrations in the alleys and in the nearby

yards.

The results of the tests on the individual cells are shown in Table 2. The test results are shown for test size 0.05.

Two testing methods were employed, one a parametric

statistical approach (2-sample t Test) , the other a nonparametric

statistical test (Kolmogorov-Smirnov Test) . The two approaches

were tried because the distribution of data values was tending

toward the lognormal, but not strongly so. Thus in order to cover

all the bases, both methods were tried. Of the 38 pairwise

comparisons of yard and nearby alleyway samples, five were

significantl y differen t using the parametric test, while only two

were significantl y differen t using the nonparametric test. Thi s

confirms the more nearly lognormal distribution of values. Both methods point to the same conclusion, that the two population s are

essentially the same.

17
Cell Number

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

2&

t Test

N SD

N SD

N SD

SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

SD

N SD

N SD

N SD

N SD

N SD

KS Test

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

Cell Number

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

t Test

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

SD

N SD

N SD

N SD

N SD

N SD

SD

SD

KS Test

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

N SD

SD

N SD

N SD

N SD

N SD

N SD

SD

N SD

Table 2. List of results of t-test and Kolmogorov-Smirnov (KS) test. "NSD" means no

significant difference, "SD" means significant difference.

19
REFERENCES

1. Tweto, Ogden. 1968. Leadville District, Colorado, in Ore Deposits in the United States. 1933/1967. J.D. Ridge, ed. American Institute of Mining, Metallurgical, and Petroleum Engineers. New York, New York. pp. 681-705.

2. United States Department of Agriculture, Soil Conservation Service, in cooperation.

with the Colorado Agricultural Experiment Station. 1975. Soil Survey of Chaffee- Lake area, Colorado and Parts of Chaffe e and Lake Counties. United States Government Printing Office, Washington, D.C.

3. Workplan Soil Samplin g and X-ray Fluorescence Analysis, Volume 1, Leadville Colorado. September 1991. Roy F. Weston, Inc. Denver, Colorado.

4. Jenkins, Ron, R.W. Gould, and D. Gedcke. Quantitative X-ray Spectrometry. 1981. Marcel Dekker, Inc. New York and Basel. 586 pages.

5. American Chemical Society. 1983. Principles of Environmental Analysis. Analytical Chemistry, Vol. 55. pp 2210-2218.

6. Flatman, G.T., E. Englund, A. Yfantis . 1988. Geostatistical Approaches to the Design of Samplin g Regimes, in L.H. Keith, ed. Principles of Environmental Sampling. American Chemical Society, pp. 73-84.

7. United States Environmental Protection Agency. March 1987. Data Quality Objectives for Remedial Response Activities - Development Process. EPA 540/G87/003. Washington, D.C.

ftUJ . GOVUNMCNT HUNTING OFFICE IM1 - 79MK/MMZ

21
Jul y 28, 1993

STATISTICAL COMPARISON OF LEAD CONCENTRATIONS IN WHOLE AND FINE SOIL FRACTIONS FROM CALIFORNIA GULCH (LEADVELLE) SUPERFUND SIT E

U.S. EPA Region YIH Denver, Colorado

Task Lead W JL Cole and C.A. Kuharic Lockheed Enviromneotal Systems and Technologies Co. Las Vegas, Nevada

A.K. Singh ADLInc . Socorro, New Mexico

Technology Support Center for Monitoring and Site Characterization Environmental Monitoring Systems Laboratory U.S. Environmental Protection Agency Las Vegas, Nevada 89193-3478

(702) 798-2270
TABLE OF CONTENTS

NOTICE ....................................................... i

TABLE OF CONTENTS ............................................. ii

LIST OF FIGURES ............................................... iii

LIST OF TABLES ................................................. iv

ABSTRACT ..................................................... v

INTRODUCTION ................................................. 1

SUMMARY STATISTICS AND RESULTS OF STATISTICAL COMPARISONS ......... 2 F OR LEAD CONCENTRATIONS IN WHOLE AND FINE SOIL FRACTIONS

REFERENCES .................................................. 12

APPENDIX A ................................................... 13

u
LIST OF TABLES

Table 1: Summary statistics, correlation coefficients, . . least squares regression lines, and results

of paired t-tests for lead concentrations in

fine and whole soils of Leadville site obtained

from Phase 1 investigation.

Table 2: Summary statistics, correlation coefficients, . .

least squares regression lines, and results

of paired t-tests for lead concentrations in

fine and whole soils of Leadville site obtained

from Phase 2 investigation.

IV
I. INTRODUCTION

The town of Leadville, Colorado lies about 100 miles southwest of Denver, Colorado. Gold,

silver, lead and zinc mining activities in the vicinity of Leadville, which date back to the 1859 discovery

of placer gold in California Gulch, have left behind large amounts of slag, mine waste, tailings and

smelter emissions containing lead, zinc, cadmium, arsenic and other metals.

T he United States Environmental Protection Agency (USEPA) conducted a preliminary site

investigation hi 1982-83, which resulted in the Leadville site being placed on the National Priority List

(NPL) in 1983. In 1991, at the request of Region 8, Environmental Monitoring Systems Laboratory at Las Vegas (EMSL-LV) assisted hi conducting an intensive soil sampling and measurement effort . Utilizing Field Portable X-Ray Fluorescence (FPXRF) instruments lead levels were determined in over

3700 soil samples. The data obtained from these samples were then used to determine and identify the

spatial distribution of lead hi the Leadville area. Another goal of this investigation was to demonstrate

the ability of the FPXRF instrumentation to generate quantitative data of known quality. The approach

and methods used hi this site investigation are addressed and identified hi a EMSL-LV TSC technical

report (USEPA 1993).

This report deals with another aspect of the soil lead analysis. Concern has been expressed that

only the fine soil fraction is ingestible, therefore whole soil analysis yields invalid data for assessment

of bioavailable soil fractions at the site (ASARCO 4/23/92). This prompted the Region 8 Remedial Project Manager (RPM) to initiate a two-phase study of lead concentrations as a function of soil size

fraction.

The Phase 1 study utilized 68 samples randomly selected from the Leadville soil samples which

were archived following the 1991 field FPXRF survey. These samples were sieved and the 'less than

250/t* soil fractions were sent to the University of Colorado, Boulder (UCB) for XRF analysis on a Kevex 770.

The Phase 2 study utilized 86 samples selected from 16 yards where replicate samples had been

obtained during the 1991 field activities. The samples were sieved and the 'less than 250/t* soil fractions

were sent to UCB for XRF analysis.

T he analytical results from the two phases 'on the 'less than 250^ soil fraction were sent to EMSL-LV to compare to the results previously obtained by FPXRF on the whole soil. These two data

sets are shown in Tables A-l and A-2 of Appendix A.

Out of the 68 sample locations selected for the Phase 1 investigation, 40 locations were collected from

the edge of alley right-of-ways (alleyways) and the remaining 28 hi residential yards, not necessarily hi

close proximity to one another. The soil sample(s) population of most interest were those collected in the

residential yards. The two subsets of data (alleyways and yards) were statistically analyzed separately.
Table 1: Summary statistics, correlation coefficients, least-squares regression lines, and results of paired

t-tests for lead concentrations in fine and whole soils of Leadville site obtained from Phase 1

investigation.

Statistical Method Used

Correlation and

straight

line

fittin g

by method of

least

squares (LS)

(simple

linear

regression)

Summary Statistics

and 95%

Confidence Interval*

for difference in

means

ALLEYWAY S

Number of paired samples n

40

(see Figure 1)

Correlation Coefficien t

r = 0.47

LS estimate of

straight line:

slope = 0.53 Intercept = 1474.53

% variability

explained by LS

= 22.1%

Estimated mean difference (whole-fine)

= 352.1

standard deviation of

differences in lead

measurements

(d = whole - fine)

sd(diff) = 786.43

95% Confidence Interval for

difference in means (wholefine)

= (100.79,603.41)

YARDS

Number of paired samples n

28

(see Figure 2)

Correlation Coefficient

r = 0.91

LS estimate of

straight line:

slope = 0.94 Intercept = 840.45

% variability

explained by LS

lineaOOr2) = 82.1%

Estimated mean difference

(whole-fine)

= 352.5

standard deviation of

differences in lead

measurements

(d = whole - fine)

sd(diff) = 1229.74

95% Confidence Interval for

difference in means (wholefine)

= (-124.38,829.38)

* If 0 lies inside the 95% Confidence Interval for difference in means, then at test size a = 0.05 the null

hypothesis of no difference in means is NOT REJECTED; if 0 lies outside the 95% Confidence Interval

for difference in means, then at test size a = 0.05 the null hypothesis of no difference in means is REJECTED.
5000

4500

4000

3500

3000

2500

2000

1500

1000

i>a

i__ s_oj o_ i __•__

! I I ! *«. »«M.«^M.«M» ...........

t

.—— .......•«..««••.•

O O

Q I

Fne lead

Figure 1: Least: squares

regression line for ALLEYWAYS

of Phase 1:

# Pairs Correl. Coeff . Slope Intercept

40

0.47

0.53

1474.53

1

4000

Fkw tad

Figure 2: Least squares

regression line for RESIDENTIAL YARDS of Phase 1:

# Pairs = 28

Correl. Coeff . = 0.91

Slope = 0.94

Intercept = 840.45
Whole lead Fne lead

Figure 5: Histogram for

whole_lead for Phase 1 (ALLEYWAYS) :

Figure 6: Histogram for

fine_lead for Phase 1 (ALLEYWAYS) :

Mean

sdMinimum

25th % Median

75th % Maximum

2739.4

805.2

1390

2133

2763.5

3217

4867

Mean

sdMinimum

25th % Median

75th % Maximum

- 2387.3

= 708.2

= 1135

= 1746

= 2417

= 2824

= 3825
It can be seen from Table 1 that at the 95% confidence level (test size a = 0.05), the null

hypothesis of no difference in means of lead concentrations hi whole and fine soils is REJECTED FOR ALLEY EDGES (ALLEYWAYS), and NOT REJECTED FOR YARDS of Leadville. In other words,

we can conclude that we are 95% certain that the means of lead concentrations in whole soil fractions

a nd fine soil fractions are SIGNIFICANTLY DIFFERENT FOR ALLEY EDGES (ALLEYWAYS) and N OT SIGNIFICANTLY DIFFERENT FOR YARDS. However, the mean lead concentration in whole

soil fractions appears to be higher than the mean lead concentration in fine soil fractions, and hence the

mean lead concentration hi whole soil fractions can be viewed as a conservative estimate for the mean

lead concentration in fine soil fractions.

The results hi Table 2 show that at 95% confidence level (test size a = 0.05), the null hypothesis

of no difference hi means of lead concentrations hi whole and fine soils is NOT REJECTED for Phase

2 data. In other words, we can conclude with 95% certainty that there is no difference hi means of lead

concentrations hi whole soil-fractions and fine soil fractions for Phase 2 data.

Tables 1 and 2 also show that:

(1) the distributions of the difference, d, Qead in whole soil fraction minus lead hi fine soil fraction) for

residential yards of Phase 1 and Phase 2 investigations are quite different. This difference hi distributions

may be due to the much higher lead concentrations and larger standard deviation (sd) of d for the Phase

1 residential yards.

(2) the sizes of the 95% confidence intervals for the difference hi means of lead concentrations hi whole

and fine soil fractions are:

• 502.6 mg/kg for ALLEY EDGES (ALLEYWAYS) of PHASE 1

• 953.8 mg/kg for YARDS of PHASE 1

• 273.1 mg/kg for PHASE 2 (ALL YARDS),

showing mat the data from Phase 2 are more reliable than Phase 1 data.

(3) hi both phases of the investigation, there is good correlation between lead concentrations hi whole soil

fractions and fine soil fractions from residential yards of Leadville. Ideally, for good agreement hi lead

measurements hi whole and fine soil fractions, the slope of the line should be close to 1 and the intercept

of the line close to 0. For the two investigations of residential yards, the slopes range from 0.80 to 0.94,

but the intercepts are not close to zero. The intercepts probably reflect the tendency of the whole soil

fraction to overestimate the lead results of the fine soil fraction.

On the basis of strong correlations, slopes near 1.0 and no significant difference for paired data

from residential yards, the lead concentrations in whole soil fractions can be used to predict lead

concentrations hi fine soil fractions hi Leadville.

11
APPENDIX A

Lead concentrations in fine and whole soil fractions from Phase 1 and Phase 2 investigations

13
Lead concentrations in fin e and whole soil fractions: Phase 1 Data

(Continued from previous page ) Sample ID Fine_Pb Locat. Easting

34440.00

35030.00

35064.00

35069.00

35075.00

35092.00

35098.00

35106.00

35130.00

35145.00

35190.00

35200.00

35205.00

35229.00

35241.00

35243.00

35244.00

35307.00

35344.00

35444.00

35608.00

8633.00

10453.00

10596.00

7415.00

7881.00

7309.00

5405.00

9586.00

6380.00

5470.00

5716.00

8038.00

7799.00

6280.00

7963.00

9586.00

6770.00

6884.00

7150.00

9075.00

6057.00

YYYYYYYYYYYYYYYYYYYYY

1776787.00

1774362.00

1777865.00

1777937.00

1777277.00

1778363.00

1777319.00

1776691.00

1778710.00

1776208.00

1775163.00

1774152.00

1773443.00

1775822.00

1775465.00

1775462.00

1775459.00

1778143.00

1778577.00

1775117.00

1769448.00

Northin g Whole_pb

517138.00

514845.00

515694.00

515599.00

518431.00

515251.00

515898.00

515551.00

516853.00

514663.00

514204.00

514380.00

514252.00

518138.00

515082.00

515126.00

515112.00

516746.00

517317.00

517336.00

512284.00

8723.00

8203.00

100.00

6383.00

7197.00

7990.00

6600.00

8807.00

6967.00

6480.00

7270.00

7243.00

8013.00

7003.00

8037.00

8173.00

7220.00

8313.00

8550.00

7850.00

6637.00

15
Lead concentrations in fin e and whole Data (continued from previous page ) Location Whole_Pb Fine_Pb SAM_ID

427

427

429

42,9

429

429

429

429

429

523

523

523

523

525

525

525

525

525

525

617

617

617

617

617

617

617

617

618

618

618

618

618

800

800

800

800

800

800

800

3167

1837

3773

1273

4290

1423

1367

1190

2427

1390

2760

3353

1507

3763

4237

4233

4867

1083

4257

2147

1693

4700

2353

3947

2873

2480

2470

2073

3163

1400

2063

4983

3773

1690

93

1290

2490

1357

1053

2700

1700

3400

1200

4100

3800

1600

876

2600

1500

3200

3600

1300

4000

3800

3700

5100

567

4400

3300

1700

3800

3000

4700

3300

1100

2500

2400

3500

1100

1700

5700

2600

1900

162

882

2400

841

1600

33886

33887

34213

34214

34215

34216

34217

34218

34219

34056

34057

34058

34059

35326

35327

35328

35329

35330

35331

34103

34104

34105

34106

34107

34108

34109

34110

34153

34154

34155

34156

34157

33917

33918

33919

33920

33921

33922

33923

soil fractions: Phase 2

Easting Northin g

1777544.00

1777553.00

1774569.00

1774551.00

1774557.00

1774533.00

1774512.00

1774502.00

1774516.00

1778368.00

1778358.00

1778385.00

1778372.00

1777997.00

1778019.00

1778005.00

1778056.00

1778056.00

1778089.00

1773736.00

1773725.00

1773700.00

1773706.00

1773723.00

1773737.00

1773706.00

1773741.00

1778411.00

1778378.00

1778450.00

1778421.00

1778381.00

1773170.00

1773141.00

1773130.00

1773135.00

1773101.00

1773105.00

1773106.00

517731.00

517710.00

514076.00

514081.00

514099.00

514112.00

514093.00

514068.00

514038.00

516132.00

516107.00

516084.00

516050.00

517302.00

517287.00

517258.00

517242.00

517273.00

517274.00

514173.00

514144.00

514151.00

514141.00

514125.00

514107.00

514096.00

514081.00

517501.00

517521.00

517543.00

517607.00

517575.00

513790.00

513793.00

513815.00

513853.00

513844.00

513800.00

513870.00

17