Report

348516

ADMINISTRATIV E RECORD Zinc Slag Pile Remedial Investigation

AR P8SKEYW

V

at the California Gulch Site, Leadville t

, Colorado

 FILfc

 L

(Administrative Order on Consent CERCLA-VIII-92-06)

prepared for Denver & Rio Grande Western Railroad Company

prepared by Morrison Knudsen Corporation

Environmental Services Division

December 11,1992
FINAL REPORT ZINC SLAG PIL E REMEDIAL INVESTIGATION AT THE CALIFORNIA GULCH SITE LEADVILLE, COLORADO

TABLE OF CONTENTS

Executive Summary

Section Title Page

1.0 INTRODUCTION 1-1

1.1 Purpose of the Remedial Investigation 1-1

1.2 Report Organization 1-2

2.0 SITE AND DESCRIPTION 2-1

2.1 Site Description 2-1

2.2 Zinc Slag Description 2-4

2.3 Previous Investigations 2-4

3 .0 ZINC SLAG PILE INVESTIGATION 3-1

3.1 Historical Research 3-1

3.2 Field Activities 3-1

3.2.1 Reconnaissance 3-2

3.2.2 Surveying 3-2

3.2.3 Sampling 3-3

3.3 Laboratory Activities 3-4

3.3.1 Compositional Analyses 3-5

3.3.2 Leachability Testing 3-7

3.3.3 Physical Testing 3-8

3.4 Air Quality Investigation 3-9

3.4.1 Meteorological Data 3-10

3.4.2 Emission Rate Estimates 3-10

3.5 Relationship With Other Investigation Programs 3-15

3.5.1 ASARCO Meteorologic Monitoring Program 3-15

4.0 CHARACTERISTICS OF THE ZINC SLAG PILE 4-1

4.1 Smelter History and Slag Pile Development Summary 4-1

4.1.1 Brief History of Leadville Smelting 4-1

4.1.2 Western Zinc Smelter and Slag Pile History 4-1

4.2 Field Reconnaissance of the Zinc Slag Pile and Smelter Area 4-2

4.2.1 The Western Zinc Smelter 4-2

4.3 Physical Characteristics 4-2

4.3.1 Particle Size 4-3

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TABLE OF CONTENTS, Continued

Section Title Page

4.3.2 Historic and Current Zinc Slag Pile Surface Areas and Volumes 4-4

4.4 Slag Pile Stability 4-5

4.4.1 Analysis of Structural Stability 4-5

4.4.2 Deflation/Emissions Potential 4-6

4.4.3 Effect s of Freeze/Thaw Cycling 4-6

4.5 Chemical Characteristics of Zinc Slag Material 4-7

4.5.1 Compositional Analyses 4-8

4.5.2 Leaching Analyses 4-10

4.6 Analytical Data Validation 4-12

4.6.1 CLP Data Validation 4-14

4.6.2 Non-CLP Data Validation 4-15

5.0 INTERPRETATION OF RESULTS 5-1

5.1 Statistics 5-1

5.1.1 Methodology 5-1

5.1.2 Statistical Results 5-2

5.1.3 Cumulative Probability Plots 5-4

5.1.4 Statistical Summary 5-5

5.2 Potential for Water Quality Impacts 5-5

5.2.1 Metal s Loading Based on SPLP Results 5-6

5.2.2 Metals Loading Based on Column Leach Results 5-7

5.2.3 Metals Loading Based on Combination of SPLP and Column Leach Results 5-8

5.3 Potential for Soil Impacts 5-9

5.4 Slag Pile Stability 5-9

5.5 Potential for Air Quality Impacts 5-9

5.6 Anthropogenic Distribution 5-10

6 .0 SUMMAR Y AND CONCLUSIONS 6-1

6.1 Summary of Zinc Slag Characteristics 6-1

6.2 Conclusions Regarding the Site Conceptual Model 6-3

7.0 REFERENCES 7-1

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LIST OF TABLES

Table Title

3-1 Zinc Slag Sample Analysis Summary

3-2 Matrix, Analysis, Analytical Methods and Modifications and Sample Size Requirements

3-3 Summary of Selected Colorado High Country Station Annual Precipitation Weighted Average pH Values (NADP, 1990)

4-1 Particle Size Testing Results

4-2 Weight Percents of Zinc Slag Samples That Are Potentially Inspirable and Respirable

4-3 Frequency of Occurrence - TAL Metals

4-4 Zinc Slag Sample Acid Forming Potential

4-5 Column Leach Test Results

5-1 Concentration Ranges of Populations for Analyses of Slag Determined from Cumulative Probability Plots

5-2 Major Constituents (mg/kg) in Slag and Subsoils with Values Assigned to Concentration Range Populations

5-3 Trace Metal s (mg/kg) in Slag and Subsoils with Values Assigned to Concentration Range Populations

5-4 Miscellaneous Measurements (mg/kg) and Sulfur Species (%) in Slag and Subsoils with Values Assigned to Populations

LIST OF FIGURES

Figure Title

1 -1 Site Map with Zinc Slag Pile Location

3-1 Zinc Slag Pile Sample Locations and Reconnaissance Information

4-1 Zinc Slag Pile Current Surface Area, Volume, and Angles of Repose

4-2 Zinc Slag Pile Historic Volume

4-3 Column Leach Results - Zinc Slag Cations

4-4 Column Leach Results - Zinc Slag Anions

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APPENDIX

Appendix Title

A Field Work Documentation Al Sample Logs

B Subcontractor Reports Bl Resource Technologies Group, Inc., Column Leach Test Results B2 Interpro, Inc. Preparation and Size Analysis Report

C Statistics

D Calculation Documentation Dl Pile Volume Calculations D2 Pile Metals Loading Calculations

E Analytical Documentation

El SDG Data Validation Reports E2 Analytical Data Base

E3 Analytical Data Packages - Form I Summary Sheets

F Air Quality - Emission Rate Estimate Documentation Fl Relevant pages from Simiu & Scanlan, 1978 F2 Table 11.2.1-1 from AP-42

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FINAL REPORT

ZINC SLAG PIL E REMEDIAL INVESTIGATION

AT THE CALIFORNIA GULCH SITE

EXECUTIVE SUMMARY

In late 1991 and 1992, Denver & Rio Grande Western Railroad Company (D&RGW)

undertook a remedial investigation (RI) of the slag pile associated with the former Western

Zinc Smelter within the California Gulch site at Leadville, Colorado. Lake County is the

current owner of this pile. Although D&RGW has never owned the zinc slag pile or used

it for any purpose, they agreed to undertake the investigation concurrent with a remedial

investigation for the lead slag piles at the site. D&RGW was named a Potentially Responsible Party at the California Gulch site in 1986 due to their ownership of three lead

slag piles, which had been purchased for use as railroad ballast. Both remedial

investigations were performed under Administrative Order on Consent CERCLA-Vni92006.

The purpose of the RI was to characterize the zinc slag pile in sufficien t detail such that its

chemical and physical properties could be evaluated for potential impacts on human health

and the environment. No previous investigations of this pile had been undertaken at the

site and, therefore, no data existed for the pile. During the scoping process, data gaps were

identified as the pile size and volume, particle sizes, geochemical characteristics, leachability,

deflation potential, and geotechnical stability. RI data was collected to fill these gaps, as

well as to assess the viability of five potential release mechanisms identified in the site

conceptual model. These five release mechanisms included wind, leaching, mixing by human

activities, runoff by particulates, and direct contact. Direct contact was discounted in the

baseline human health assessment conducted by EPA, leaving four remaining mechanisms

to be evaluated during this RI.

The investigation consisted of several major tasks, including literature and document review,

field investigation and sampling, laboratory testing and analysis, and data evaluation and

summary.

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Available literature was reviewed to summarize the history of zinc smelting and slag pile

development. Aerial photographs were also reviewed to determine gross changes in volume

over time, indicating use of the slag.

During site reconnaissance, the former smelter site was investigated for evidence of slag,

other smelter debris or byproducts, general physical properties, and visual indications of

impact to the surrounding environment. Structural features of the piles were mapped for

input to geotechnical stability determinations and the pile was surveyed for accurate

calculation of the current pile volume. Indications of environmental impacts from zinc slag,

particulate movement from precipitation runoff , and stability concerns were not observed.

Samplin g locations were selected by identifyin g grid locations using a random number

generator. Four discrete samples were then collected from the surface to a depth of 3 feet

using shovels and a backhoe. Appropriate quality assurance procedures were adhered to

during the sampling phase, as well as the analytical phase, of the work.

Each of the samples was submitted for laboratory compositional, leachability, and particle

size testing. A portion of each sample was also sent to Resurrection' s field laboratory for

incorporation in the Resurrection/ASARCO metals speciation program. Compositional

analyses included total metals, water-soluble anions, and acid-base accounting. Leachability

testing included Synthetic Precipitation Leaching Procedure (EPA Method 1312) and

column leach tests, which were intended to simulate, as closely as possible, in situ

conditions.

Compositional results showed that the slag is an iron silicate with substantial amounts of

aluminum, manganese, calcium, and zinc. Geometric mean concentrations for the four

primary metals of concern at the site are as follows:

- Arsenic 211 mg/kg

- Cadmium 14.1 mg/kg

- Lead 568 mg/kg

-Zinc 66,000 mg/kg

The dominant form of sulfur is sulfate. Acid generation potential, when detected, was more

than compensated for by the neutralization potential due to the presence of carbonate.

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Leaching analysis, which included both SPLP and column leach studies, showed minimal

leaching of metals of concern. SPLP results for all elements tested in slag were below the

toxicity characteristic criteria, listed in 40 CFR 261.24. Mean values for the contaminants

of concern were generally two orders of magnitude lower than these regulatory thresholds.

Column leach tests showed similar low levels of leaching, although studies were not

continued long enough to determine the steady state concentrations of lead in leachate for

two of the piles. It should be noted that several test design factors make the leaching results

more conservative than what is expected under normal site conditions. These factors

include the following:

The lixiviant used contained none of the carbonates typically found in natural

rainwater. The lixiviant was a sulfuric/nitric acid mixture which is a more

aggressive solution.

The leaching test used equal periods of wet and dry simulating an eight year

period of precipitation. Insitu conditions would indicate that the piles are

generally dry the majority of the time.

• Leaching of metals did not begin until approximately half way through the

testing period indicating that leaching does not begin until surface conditions

are altered to be conducive to leaching.

SPLP leach testing, assumed to be at equilibrium, showed leached metals

values less than the maximal values in cycles at the end of the column leach

test. In situ leaching conditions would more closely approximate equilibrium.

• Analysis of subslag materials from beneath three major lead slag piles showed

low values of metals of concern, indicating that any leaching produced by the

piles has not severely impacted the materials under the piles.

The buffering capacity of the slag was still in effect at the conclusion of both

the SPLP and column leach tests, evidenced by the raising of pH values from

the initial 5.0 to greater than 7.0 in the lixiviant.

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Particle size data and site-specific meteorological data were used to determine whether zinc

slag fines have the ability to become airborne. Threshold friction velocities (the wind speed

above which the surface material becomes airborne) were calculated using the mode of the

aggregate size distribution. Wind data and the height of the piles were used to calculate the

friction velocity. Results for the pile are:

Threshold Friction Velocity 1.0 m/sec

Friction Velocity 0.55 m/sec

A friction velocity lower than the threshold demonstrates that sustained wind gusts in

Leadville are not fast enough to cause wind erosion of the zinc slag. As with the leaching

tests, several factors built in to the calculations make the results more conservative than

what would be expected at the site. These factors include the following:

If values more representative of air flow over rough terrain were used in the

calculations, the friction velocity would have been lower than estimated.

Air density, and therefore the liftin g force of the wind at the same speed, is

lower in Leadville.

• Periods of high moisture, snow cover and frozen ground would also limit the

potential for dust emissions.

The results of the remedial investigation were compared to the site conceptual model

developed during the scoping process. Of the five potential release mechanisms for waste

piles (wind, leaching, mixing by human activities, runoff of particulates, and direct contact),

only leaching of metals through contact with precipitation or other site waters was retained

as viable for zinc slag piles within the California Gulch site.

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FINAL REPORT

ZINC SLAG PILE REMEDIAL INVESTIGATION

AT THE CALIFORNIA GULCH SITE LEADVILLE, COLORADO

1.0 INTRODUCTION

This document presents the results of the Zinc Slag Pile Remedial Investigation (RI) at the

California Gulch Superfund site at Leadville, located in Lake County, Colorado. The report

was prepared by Morrison Knudsen Corporation (MK) for the Denver and Rio Grande

Western Railroad Company (D&RGW) in compliance with Administrative Order on

Consent (AOC) CERCLA-VIII-92-06. D&RGW was named as a Potentially Responsible

Party in 1986 (Civil Action No. 86-C-1675, United States District Court, State of Colorado)

due to their ownership of three lead slag piles in the California Gulch that had been

purchased for use as railroad ballast. Although D&RGW does not own the zinc slag pile

in Leadville, nor use it for any purpose, they have investigated it as part of an overall RI

f or slag piles within the California Gulch site.

The Zinc Slag Pile RI was performed concurrent with the Lead Slag Pile RI in accordance

with the Work Plan for Slag Pile Remedial Investigation at California Gulch Site (MK,

1991a) and the Samplin g and Analysis Plan for Slag Pile Remedial Investigation at

California Gulch Site Plan (MK, 1991b).

1.1 Purpose of the Remedial Investigation

The purpose of the RI was to characterize the single zinc slag pile located within the

California Gulch site in sufficien t detail such that its chemical, physical, and mineralogical

properties could be evaluated for potential impacts on human health and the environment. The RI fills data gaps relating to pile size and volume, slag particle sizes, geochemical

characteristics, teachability, deflation potential, and geotechnical stability.

The scope of this remedial investigation includes only the zinc slag pile associated with the

Western Zinc Smelter. It is often referred to as the High School pile, based on its location

(Figure 1-1), or the County pile, based on its ownership by Lake County. D&RGW has also

investigated the major lead smelter-derived slag piles within the California Gulch site. As

the lead slag (MK, 1992) is distinctly differen t from zinc slag, the RI reports have been

submitted separately.

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HISTORI C SMELTER LOCATION

RI/F S SIT E BOUNDAR Y

ZINC SLAG VENEER OR SCATTERED ZINC SLAG PIECES

SAMPLE LOCATION

CALIFORNIA GULCH CERCLA SIT E ZIN C SLA G PIL E INVESTIGATIO N LJADVIUE , COLORAD O

SIT E MA P WITH ZIN C SLA G PIL E LOCATION

DENVER & RIO CRANDE WESTERN RAILROAD DENVER. COLORADO

NOTE: TOPOGRAPHIC CONTOURS AND SURFACE FEATURES DIGITIZED BY INTRASEARCH FROM 1990 AERIAL PHOTOGRAPHY AND PROVIDED BY ROY F. WESTON. INC. MORRISON-KNUDSEN CORPORATION

FIII NAU C (CM) ) 1B93N054/XR893039 IDATtJ/M/9 2
1.2 Report Organization

This report is organized to present RI field and laboratory activity summaries, data

validation, analytical results and interpretations, and conclusions. Section 2.0 presents an

overview of site conditions. No previous investigations have been conducted for the zinc

slag at the site and, therefore, no historical information is included in this section. The

scope of the Zinc Slag Pile Remedial Investigation, including all field, laboratory, and data

analysis activities, is presented in Section 3.0. Section 4.0 presents the physical and chemical

characteristics of the zinc slag pile determined during the RI, and Section 5.0 presents an

interpretation of these results. Section 6.0 presents the summary and conclusions. Section

7.0 contains references. The appendices provide field documentation, the analytical

database, data validation reports, summary sheets of laboratory data packages, calculation

documentation, and statistical analysis backup.

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2 .0 SITE AND DESCRIPTION

T he following description of the California Gulch site includes a brief history of the

Leadville mining district, a general description of the physiographic and hydrologic

properties of the site, and a description of zinc slag. Site information presented in this

section is summarized primarily from studies performed prior to the 1991-1992 remedial

investigation work.

2.1 Site Description

The California Gulch site has experienced over 130 years of mining and smelting activity. The site encompasses the town of Leadville, Colorado, which is approximately 100 miles

southwest of Denver at an elevation of 10,000 feet above mean sea level. Silver, gold,

copper, lead, and zinc were mined by underground and placer methods from the major

sulfide/carbonate ore deposit in the Leadville Mining District. Approximately 17 smelters

are reported to have operated here. Only a few small- to moderate-sized mining operations

now exist and no smelters currently operate in Leadville.

The main mining-related features in the Leadville area today include the following:

Tailings impoundments

Slag piles

More than two thousand waste rock dumps

Abandoned mine, milling, and smelting facilities

A few active mining and reprocessing operations

• Mine water drainage tunnels

The Yak Tunnel, which drains into California Gulch, was the main point-source discharge

of acidic metal-laden water to California Gulch before treatment plant operations began in

1992. Thi s tunnel drains underground mining areas east of Leadville. In 1983, the

California Gulch site was placed on the EPA's National Priorities List because of heavy

metals loading to the Arkansas River.

Climatology The climate of the Leadville area is typical of mountainous areas in central Colorado. The

area has extreme temperature changes from summer to winter and in any season can

experience rapid changes of weather caused by storms travelling primarily from west to east.

Local topographic features strongly influence climatic variations in the study area. Average

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annual precipitation is 12.67 inches (Res-Asarco, 1991). July and August have the most

precipitation, and December and January have the least. Summertime precipitation is

usually associated with convective showers. Precipitation occurs sporadically, causing

occasional flash floods . Annual snowfall depths for mountains in the area range between

200 and 300 inches. During winter months, the depth of snow on the ground in Leadville

is commonly 6 inches. The precipitation and temperature cycles give rise to an annual peak

runoff , usually occurring during June. The temperature extremes range from 86 ° F to -30 ° F,

with an average minimum daily temperature of 21.9 °. The average frost-free season is 79

days. Wind is predominately from the northwest (CDL, 1986).

Geology The geology of the Leadville Mining District is complex. Bedrock consists of the

Precambrian crystalline rocks overlain by quartzites, shales, limestones, dolomites, and

sandstones of the Paleozoic era. Numerous fault s exist at the eastern edge of the site,

ranging in width from several feet to hundreds of feet. Several episodes of faulting, both

pre-mineralization and post-mineralization, have been documented (EPA, 1989c).

T he primary minerals deposited by hydrothermal solutions were predominantly sulfides of

iron, zinc, and lead, but also included copper, silver, and gold. Late-Tertiary tectonic

activity faulted the mineralized zones into blocks and exposed them to oxygenated ground

waters. Sulfide minerals were oxidized, formed sulfuric acid, and released metals into

solution. These solutions were transported to carbonate zones, where precipitation reactions

occurred between the mineralized sulfuric acid solutions and the carbonate rock. This

deposition zone of secondary, or remobilized, minerals is termed the oxidized zone. The

resulting carbonate ores formed the dominant ore zones in many of the area's early mines

(EPA, 1989c).

The change in geology is significant west of the Pendry Fault , which is often used to

demarcate upper from lower California Gulch and is located at the eastern edge of

Leadville. Above the fault , Precambrian crystalline rocks are an upthrust relative to

stratigraphic units of sediments or alluvium. Below the fault , three identifiable geologic

units are noted: bedrock, lake bed sediments, and high-terrace gravels. The thickness of the

upper and middle stratigraphic units (gravels and lake bed sediments) increases from east

to west. The upper unit varies in thickness from approximately 50 feet near the Pendry Fault to several hundred feet near the Arkansas River. Placer operations and mine waste

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disposal probably altered the surface and near-surface features of the high-terrace gravels

stratigraphic unit (EPA, 1989c).

Ground Water

The complex geology in the upper California Gulch area has a significant impact on groundwater movement. Ground water occurs in both bedrock and alluvial systems, and recharge

is principally from infiltration of snowmelt and rainfall. Ground water migrating through

the bedrock system east and southeast of Leadville discharges directly to California Gulch

surface waters, into mine workings and the Yak Tunnel, or into downgradient bedrock or

alluvial ground-water systems (EPA, 1989c).

In lower California Gulch, there is an active interchange between the shallow ground-water

system and the surface water. Therefore, a pathway exists for metal contaminants

originating from the Yak Tunnel, or other sources that contribute to surface water

contamination, to affect ground-water quality. Ground-water quality is strongly influenced

by depth, with the poorest quality found at the shallowest depths. Generally, the highest

metal concentrations are within 25 to 50 feet of the surface (EPA, 1989c).

Surface Water

The California Gulch site encompasses about 15 square miles of surface water drainage

upstream from the confluence of California Gulch with the Arkansas River. The main stem

of California Gulch flows east to west, just south of Leadville, and drains water from several

small tributaries to the north and south. The Stray Horse Gulch/Starr Ditch watershed is

the largest subbasin and drains lands extensively affected by mining operations. All

tributaries to California Gulch, as well as the upper California Gulch itself , are ephemeral

drainages. California Gulch receives flows from two continuous point-source discharges: the

Yak Tunnel treatment plant at 1 to 2 cubic feet per second (cfs), and the Leadville

wastewater treatment plant at approximately 1 cfs (EPA, 1989c).

Annual flows in both the Arkansas River and California Gulch are normally highest in the

spring during snowmelt and lowest in the fal l and winter. Local summer thunderstorms are,

however, capable of producing high-intensity, short-duration flows in the Gulch. Floodin g

potential in the Gulch is high because of lack of vegetative cover. Maximum flood

conditions in the area are expected in the May-June snowmelt period (EPA, 1989c).

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According to previous data, water quality in the upper Arkansas River is degraded below

the discharge from the Leadville Drainage Tunnel, markedly degraded below California

Gulch, and improved by the clean water inflow from creeks further downstream. The

highest metal concentrations occur in the spring during snowmelt. During the 1984, 1985,

and 1987 investigations by EPA, primary drinking water standards for cadmium and lead

were commonly exceeded, as were the Aquatic Water Quality Criteria (AWQC) for

cadmium, copper, lead, and zinc (EPA, 1989c).

22 Zinc Slag Description

Slag in the vicinity of the Western Zinc Smelter area is a mineralized by-product resulting

from the volatilization of zinc from zinc oxide and carbonate ores in a Wetherill furnace. In this furnace, briquettes of ore and anthracite were fed onto fuel burning on a cast-iron

grate. A zinc vapor evolved and was subsequently oxidized. The fumes, generally zinc

oxide, were collected in the baghouse as the smelting product. The zinc smelter by-products

are scoriaceous slag, coal clinker, and ash. The slag is a highly vesicular material, often with

a yellow or reddish oxide rind. The specific gravity of the zinc slag resulting from the

Wetherill process is notably less than that of lead slag, likely due to the vesicles formed by

the expansion of gases. The slag typically contains approximately 16 percent iron and 14

percent silicon, substantial amounts of aluminum, manganese, calcium and zinc, as well as

traces of other residual base metals.

Figure 1-1 is a map of the site that shows the historic zinc smelter location and the slag pile

sampled under this RI. The general characteristics and history of this slag pile are discussed

in following sections.

2.3 Previous Investigations

Several previous investigations at the California Gulch site have addressed lead slag;

however, no existing data is available for the Western Zinc slag pile.

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3 .0 ZINC SLAG PILE INVESTIGATION

The Zinc Slag Pile RI consisted of literature research, field investigation, and laboratory

analyses. Historical research was performed relating to the development of the Western

Zinc smelter and its associated slag pile. Field activities included inspecting, surveying, and

sampling the pile. Laboratory activities included compositional, teachability, and physical

testing of the slag and subslag samples. The samples were also submitted to the metals

speciation program undertaken by ASARCO and Resurrection Mining Corporation, other

PRPs at the California Gulch site.

3.1 Historical Research

Available literature was reviewed to summarize the history of Leadville area smelters and

the development of associated slag piles. The key resource for this summary was Historical

Mineral Processing Operations of the Leadville Mining District, (EPA, 1991), a report of

historical smelter and milling operations prepared for the site by Jacobs Engineering Group. Other references reviewed include:

Leadville: Colorado's Magic City, by Edward Blair. Pruett Publishing

Company, Boulder, Colorado, 1980. Draft Remedial Investigation Scoping Document California Gulch Site, Leadville, Colorado, Prepared by Woodward-Clyde Consultants for Res- ASARCO Joint Venture, April 1991. Ores to Metals, by James E. Fell, Jr., University of Nebraska Press, Lincoln, Nebraska, 1979.

32 Field Activities

The Zinc Slag Pile RI activities included field reconnaissance to describe the Western Zinc

slag pile and materials in the vicinity of the pile. Additionally, the pile was surveyed to

document its size and location. Samples were obtained from locations randomly selected

from a grid system established for the pile.

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3.2.1 Reconnaissance

Several decades of aerial photography were used to assist in identifying the gross

characteristics of the smelter and slag area. A summary of the photography reviewed is as

follows:

Date Agency Project Scale Roll Frame Numbers

9-23-56 Forest Service DZZ 1:20,000 6 122-124

9-21-58 Forest Service DZZ 1:20,000 21 30-32

9-23-64 USGS GS-VAXS 1:31,500 1 156,157,161,162

8-31-75 Forest Service 08065 1:15,840 974 068,069,095,096

9-4-76 Forest Service 08065 1:15,840 1,275 187,188

8-27-90 Intrasearch Denver 90145 1:14,400 90,145 9-11, 22-24

The historic smelter location was visited by an MK geologist and field engineer on May 11,

1992. The slag pile was described for physical properties such as size, color, general particle

size, texture, and signs of weathering. The pile was photographed and plotted on the base

topographic map of the site. Proximity of the pile to residences or other structures, streams,

ephemeral runoff channels, and other smelter- or mining-related wastes or structural debris

was noted. Additionally, any evidence of slag impacting the surrounding environment, such

as fines transported from the pile by wind or water, stressed vegetation, and iron staining

was noted.

The zinc slag pile structural features were observed for bedding and layering, including

thickness and orientation. The presence of fractures or cracks was investigated, along with

any conditions that might have indicated block movement either by rotation or normal

faulting. Any talus at the base of slag pile was noted and angles of repose were determined

to assess slope stability.

Surveying The Western Zinc slag pile was surveyed by a professional survey team on May 11, 1992,

after the December 1991 sampling effort , because snow cover prohibited accurate surveying

at the time of sampling. The survey was performed to allow the addition of slag pile

contours to the existing base map and calculation of the pile volume to within approximately

10 percent error. Elevational data for the slag pile perimeter, top and toe, and grade breaks

were determined so that the pile height, side slopes and volume could be calculated. A data

file of the coordinates for each point surveyed was used in conjunction with AutoCAD to

develop contour maps of the pile and integrate them into the existing base map. Volumes

were also calculated using the AutoCAD software, AutoCOGO.

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3.2.3 Samplin g Zinc slag pile sampling was performed on December 4, 1991. The details of the sampling

procedures are presented in the Samplin g and Analysis Plan (SAP) (MK, 1991b). No

variances from these procedures were required at the Western Zinc Pile.

3.2.3.1 Sample Locations

The sample locations were randomly selected on a rectangular grid system overlain on maps

of the slag pile. This procedure for selecting random sample locations is provided in

Methods for Evaluating the Attainment of Cleanup Standards (EPA, 1989b) and the base map

with the superimposed grid system is provided in the SAP (Section 3.0, MK 1991b).

Four discrete sample locations were selected using a random number generator to identify

cell numbers within the grid system (MK, 1991b). The cells were then located in the field

by tape and/or pace compass traverses from recognized points on the base maps. Samples

were collected from the center of a grid cell. Generally, cells that occurred entirely on a

portion of the slag pile that had a slag thickness greater than three feet and were accessible,

were sampled. One cell at the Western Zinc pile did not meet the thickness criteria, and

an alternate cell was randomly selected.

The sample locations are depicted on Figure 3-1. Photographs of each location were taken

and the slag pile features were noted in the log book.

3.2.3.2 Surface Slag Sampling Procedures

The four slag samples were obtained with a backhoe, over a 0- to 3-foot depth range. The

initial sample size collected was 400 pounds. This sample size was based on

recommendations from Standard Practice for Sampling Aggregates, ASTM Method D-75,

(ASTM, 1992b).

Each sample was placed on a high density polyethylene (HDPE) sheet and a sample

homogenizing procedure was performed by successively liftin g each corner of the HDPE and

rolling the sample over itself . This was performed repeatedly until the sample was

thoroughly mixed.

The sample was then piled into the shape of a cone, flattened, and divided into quarters

using plastic shovels. One quarter was randomly selected and, along with its opposite

quarter, collected for laboratory testing and analysis.

MORRISON KNUOSEN CORPORATION

88\1893\2INCRPT\Final-RI 3-3 [Rev 001/13/93)
N 515,00

0 -

N 514,500 j ACCESS KOW,____

_ j __ ____/

LEGEN D

SURFACE CONTOUR INTERVA L 2

BUILDING

A HSS10 1 SAMPLE LOCATION S A N D IDENTIFICATIO N

SMELTER RUBBLE AREA

NOTE : TOPOGRAPHI C CONTOUR

S AN D SURFACE FEATURES DIGITIZED B Y INTRASEARCH FROM 1990 AERIA L PHOTOGRAPHY AND PROVIDED B Y ROY F . WESTON, INC. 50

SCALE FEET

100 150

1"=100

200

LAK E COUNT Y HIG H SCHOO L

CALIFORNIA GULCH CERCLA SITE ZIN C SLA G PIL E INVESTIGATIO N LEADVILLE , COLORADO FIGURE 3-1 ZIN C SLA G PIL E SAMPL E LOCATION S A N D RECONNAISSANC E INFORMATIO

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DENVER & RIO GRANDE WESTERN RAILROA D ______DENVER. COLORADO______

( 6& MORRISON-KNUDSEN CORPORATION

FILE NAME (CAD) 1893N014

PROJECT SUFFIX TASK

1893 630 06-900

lD»TE:9/06/91

DRAWIN G NUMBER FIGUR E 3-

1

REV. A
Each sample for testing and analysis was placed in two five-gallon buckets and one onegallon bucket. The buckets were sealed and labeled with identification numbers. At the

end of each day, all samples were transported to a locked shed for shipment to the sample

preparation and splitting laboratory.

3.2.3.3 Decontamination Procedures

Decontamination was performed to prevent cross-contamination of samples. Sampling tools

such as shovels, trowels, and plastic buckets were initially cleaned by mechanically removing

any loose materials. Next, the equipment was scrubbed with a non-phosphate detergent

(Alconox) and water solution until no visible material remained, and then rinsed with tap

water and deionized water. HDPE sheets and parts of heavy equipment in contact with slag

were decontaminated with a high pressure, hot water sprayer, and then rinsed with deionized

water. Decontamination was performed as close as practical to the associated sample

location and spent water was discarded on the ground. One equipment rinsate sample was

collected to verify that the decontamination procedures were adequate. Sampling

equipment was stored in clean plastic bags after air drying. Clean tools and HDPE sheets

were used for each sample location.

Laboratory Activities

Samples were transmitted to the laboratories under chain-of-custody protocol. Laboratory

activities were performed as specified in the SAP (MK, 1991b). Chemical analyses included

both compositional and leachability testing. Physical analyses were performed to determine

the particle size distribution of the zinc slag material. Table 3-1 presents the analyses

performed on the zinc slag samples. Table 3-2 summarizes the analytical methods and

sample size requirements.

Sample preparation and particle size determination were performed by Interpro of Golden,

Colorado. Silver Valley Laboratories, Inc. (SVL ) of Kellogg, Idaho performed

compositional and Synthetic Precipitation Leaching Procedure (SPLP) testing. The column

leach test was performed by Resource Technologies Group (RTG), Wheat Ridge, Colorado.

Eluate from the column leach test was analyzed by SVL. Prepared zinc slag samples were

also submitted to Resurrection Mining Corporation at their Leadville, Colorado field office

for analyses under Final Work Plan - Metals Speciation and Source Characterization at

California Gulch CERCLA Site Work Plan (Resurrection, 1992).

MORMSON KNUD8EN CORPORATION

BB\1893\ZINCRPT\Flnal-W 3~4 [Rev 001/13/83 ]
TABLE 3-1 ZIN C SLA G SAMPL E ANALYSI S SUMMAR Y

SAMPL E NO. COMPOSITIONA L ANALYSE S

LEAC H TEST S PHYSICA L ANALYSES

.

m om N *~ Z v . tn

CO 3 CO

— •> t- o
Table 3-2

Matrix Analysis Type Analytical Method Reference Sample Size Modifications

Zinc Slag Total Metals Digestion CLP SOW 03/90 Bureau of Mbes D3683-78

CLP SOW ASTM

100 grams Add Silicon, delete Mercury More Rigorous Disgestion

Zinc Slag Rainfall Shake Method 1312 SW-846 1000 grams No Particle Size Reduction Increase Sample Size

Zinc Slag Sulfur forms Neutralization Potential Cation Exchange Capacity

3Z4/3.2.6

3.2.3

ERA 9080

EPA 600/2-78-054

EPA600/5-78-054 SW-846

500 grams Analysis Performed on Water-Soluble Fraction of Material

Zinc Slag AnionK CT, SO** NO» NO' , Method 300.0/310.1

following water soil

extraction

EPA 600/4-78 500 grams None

Zinc Slag Particle Size Analysis Seive Analysis Hydrometer Microtrac

ASTMD422 ASTMD422

Varies Microtrac to augment

hydrometer
Sample Preparation and Laboratory Submittal

The bulk samples of zinc slag, with the exception of the SPLP and the column leach sample,

were delivered to Interpro of Golden, Colorado for sample preparation. The SPLP samples

were forwarded immediately to SVL for analysis without particle size reduction or other

preparation. At Interpro, sample preparation was preceded by particle size analysis of the

samples.

After the particle-size determinations were performed, the seived materials were

recombined in the original sample container. The entire sample was crushed to minus 3

mesh (6.7mm) with a jaw crusher and a roll crusher. The minus 3 mesh material was

blended and a 10- to 11- pound sample was split from the mixture. This sample split was

further reduced in a plate pulverizer to minus 60 mesh (250 microns). The pulverized

sample was then blended and split into 1-pound samples, each placed in a glass bottle,

labeled, and sealed. The 1-pound, minus 250 micron prepared samples were submitted to

S VL and interested parties for analysis. Interpro has archived pulverized samples (1-pound

jars) and unprepared 5-gallon buckets of each sample.

3.3.1 Compositional Analyses

Compositional analyses were performed to determine the bulk chemistry of the zinc slag. The compositional analyses included the following:

Total Metals

Anions

Acid Forming Potential including all Sulfur Forms

Neutralization Potential

• Cation Exchange Capacity

3.3.1.1 Total Metals

Total metals were determined for the zinc slag samples by inductively coupled plasma (ICP)

and graphite furnace atomic absorption (GFAA). Analyses were performed according to

methods described in the Contract Laboratory Program Statement of Work for Inorganics Analysis (SOW 4/90) (EPA, 1990a). As the method for total digestion in SOW 4/90 is not

rigorous enough to completely digest the slag matrix, the U.S. Bureau of Mines digestion

method was used for sample preparation as reported in A Simple Low-Cost Method for the

Dissolution of Metal and Mineral Samples in Plastic Pressure Vessels (Bureau of Mines, 1980).

MORRISON KNUDSEN CORPORATION

BB\1893\2INCRPT\Flnal-RI 3-5 [Rev 001/13/93]
The U.S. Bureau of Mines digestion method uses more reactive reagents. This digestion

method is included in Appendix H of the Slag Pile SAP (MK, 1991b).

Each sample was prepared for Target Analyte List (TAL) metals analysis according to

procedures required by SOW 4/90. The sample is initially crushed and mixed thoroughly. A representative one-gram subsample is then digested using the U.S. Bureau of Mines

digestion method with hydrofluoric acid, nitric acid and hydrochloric acid. After the

digestate is boiled and cooled, boric acid is added. The solutions are then rebelled, cooled

and analyzed. Arsenic, lead, and selenium were measured by GFAA. The concentrations

of the remaining analytes (aluminum, antimony, barium, beryllium, cadmium, calcium,

chromium, cobalt, copper, iron, magnesium, manganese, nickel, potassium, silicon, silver,

sodium, thallium, vanadium and zinc) were measured by ICP. Mercury concentrations were

not determined, as specified in the SAP (MK, 1991b).

3.3.1.2 Anions

Method 300.1/310.1 (EPA, 1982) following water/soil extraction was used to determine the

following anions in the zinc slag material:

Chloride

Sulfate

Nitrate/Nitrite

Anions were analyzed to determine concentrations for input to geochemical modeling and

as corroboration with metals speciation results.

3.3.1.3 Sulfur Forms

Potential acidity of zinc slag was determined for each sample by measuring sulfur

concentrations according to EPA Method 3.2.4 from Field and Laboratory Methods

Applicable to Overburdens and Minesoils EPA-600/2-78-054 (EPA, 1978). A less than 60

mesh slag sample is heated as oxygen is passed through the sample. A starch solution,

which collects the sulfur dioxide as it is released, is then titrated and the percent total sulfur

calculated based on the starting mass and the titration measurement.

If all of the sulfur occurs in pyritic forms, the calculation of maximum potential acidity from

sulfur corresponds with actual potential acidity from sulfur. If part of the sulfur occurs in

other insoluble forms, i.e., sulfate, the maximum as calculated will overestimate acid-forming

MORRISON KNUDSEN CORPORATION

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potential. In order to determine the true acid forming potential, a second method for

determining the sulfur content of the samples was utilized. This was EPA Method 3.2.6

(EPA, 1978). This method determines the hydrochloric acid extractable, nitric acid

extractable, and non-extractable forms of sulfur, which are not considered to be acid

formers.

3.3.1.4 Neutralization Potential

Neutralization potential was determined by Method 3.2.3 (EPA, 1978). The amount of

neutralizing base, including carbonates, present in overburden materials is determined by

treating a sample with a known excess of standardized hydrochloric acid. The sample and

the acid are heated to ensure that the reaction between the acid and the neutralizes goes

to completion. A calcium carbonate equivalent of the sample is obtained by determining

the amount of unconsumed acid by titration with standardized sodium hydroxide.

3.3.1.5 Cation Exchange Properties

Cation Exchange Capacity (CEC) is a measure of how readily a material will sorb cations

onto its surface or into its matrix. The CEC was measured using EPA method 9080 (EPA,

1986), in which results are expressed in milliequivalents (meq) per 100 grams of material.

3.3.2 Leachability Testin g

Each of the collected zinc slag samples was subjected to leaching tests following EPA

Method 1312, the Synthetic Precipitation Leaching Procedure (SPLP). One sample was also

subjected to column leach testing. Both tests are described below.

Method 1312 - Synthetic Precipitation Leaching Procedure (SPLF) SPLP analyses were performed according to standard methodology, with two minor

modifications. The method states that the sample passing a 9.5mm sieve (particles smaller

than about 3/8 inch) will be utilized. For the zinc slag samples, neither size reduction nor

screening was employed. Secondly, the method states that the minimum sample size is 100

grams. The sample size used for the slag was 1000 grams. A corresponding increase in the

extraction fluid maintained the specified extraction fluid to sample ratio of 20:1. These

method modifications were initiated to ensure that field conditions were represented as

closely as possible.

As specified by the method (for soils west of the Mississippi River), the extraction fluid was

pH 5.0 ±0.2 units using a 60:40 ratio of sulfuric and nitric acid. This pH corresponds to that

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BB\1883\2INCRPT\Fln«l-W 3'7 (R«vO 01/13/93]
estimated for the area. As no data specific to Leadville exists, MK compiled data for

rainfall from numerous weather stations in mountainous regions of Colorado. Based on this

state-wide data, the average pH of the rainfall in the Leadville area is assumed to be

approximately 5.0 (Table 3-3).

The extraction fluid and samples are mechanically shaken for a 24-hour period. The eluate

is then filtered through a 0.6 -O.Sum glass fiber filter and analyzed for metals and anions of

interest.

Column Leaching Test s

The column leach test was run using a downflow unsaturated configuration. A column

diameter of eight inches was selected to be several times the nominal diameter of the zinc

slag particles to be tested. The testing laboratory prepared, packed, and consolidated the

material into the three-foot-long column. The unsaturated downflow column required

periodic presentation of the lixiviant followed by an equal period of draining and aeration.

Each introduction of fluid was designed to simulate a one-inch rainfall event for the eightinch diameter column, and each event was equal to approximately 0.8 liters of lixiviant. One

hundred cycles or "rainfall events" were conducted with collection of the eluate at the

conclusion of each event.

Initially , the eluate from events 5, 25, 50, 75 and 100 were analyzed for anions and TAL

metals (plus silicon minus mercury). After evaluation of the results from these events,

additional event eluates were analyzed to fill data gaps (Section 4.5).

Physical Testing Sieve, hydrometer, and Microtrac analyses were performed to determine the particle-size

distribution of zinc slag.

Sieve Analysis

Sieve analysis was conducted following ASTM D 422-63 (ASTM, 1992a). This method

provides for quantitative determination of particle size distribution in soil matrices. The

distribution of particle sizes greater than 75 microns (retained on a number 200 sieve) is

determined by mechanically shaking the material through a series of successively smaller

sieves. The material retained on each sieve is weighed to determine the percent of each

particle size. For this analysis, Standard Tyler sieve sizes were used.

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Table 3-3

pH (Standard Units)

StatfoB Name County

Elevation

(meters) 1984 1985 1986 1987 1988 1989 1990

Sugarloaf Boulder 2524 4.97 5.00 5.18 4.87

Niwot Saddle Boulder 3520

Four Mile Park Garfield 2502 5.05 5.50 5.29

Sunlight Peak Garfield 3206

Rocky Mtn Nat'1 Park

- Beaver Meadows Larimer 2490 5.14 4.99 5.07 5.19 526 524

-Loch Vale Larimer 3159

Dry Lake Routt 2527 4.78

Buffalo Pass Routt 3234

Engineer Mtn Guard Station San Juan 2758 4.92 5.08

MolasPass S an Juan 3286

Manitou Teller 2362 4.90 4.86 4.82 4.85 5.09 4.94

The geometric average of these values is 5.04. Blanks indicate no data was collected.

- indicates the data did not meet the NADP completeness criteria. The stations in the same county are paired mountain/valley meteorological stations.
Hydrometer Analysis

Hydrometer analyses were conducted on materials passing the number 10 Tyler sieve, i.e.,

material sizes less than 1.7mm, following ASTM Method D422-63 (ASTM, 1992a). This

technique involves placing the material in solution containing a dispersing agent and

measuring the density of the solution as the material settles. Size fractions are determined

from the time required for the material to settle out of solution. The specific gravity of the

minus 10 mesh slag was determined for use in particle size calculations.

Microtrac Analysis

The Microtrac method was used to evaluate only the smaller particle size fractions in the

sample portion that passed the 48 mesh sieve. The Microtrac method uses the general

theories of low angle, forward light scattering, combined with microprocessor technology. A "cloud" of particles is passed through a helium-neon laser beam causing light to be

scattered at angles related to particle size. Specially-designed optical equipment

unscrambles the light information into distinct channel sizes over the range of 0.12 to 700

microns. Thi s technique provides a continuum of particle size measurements over the range

of interest. The data is reported as a percentage of material, by volume, within a certain

size range.

3.4 Air Quality Investigation

Air pathway analysis was used to determine potential ambient air concentrations of metals

and particulates resulting from the wind erosion of the zinc slag pile. The first step in this

approach is to characterize the emission potential of material from the zinc slag pile. In the

absence of site-specific emission measurements, the emissions are estimated. It is also

necessary to characterize the conditions under which emissions from the zinc slag pile occur.

Once the emission information is obtained, the dispersion of this material downwind and

resulting concentrations are determined as a function of atmospheric characteristics, i.e.,

wind speed, wind direction, and atmospheric stability. The dispersion model is the tool that

performs the calculations necessary to determine the downwind concentrations from the

emission rates and meteorological conditions.

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3.4.1 Meteorological Data

MK coordinated with ASARCO to obtain meteorological data collected under their

Administrative Order on Consent for the Yak Tunnel. ASARCO's technical consultant had

established two meteorological stations within the California Gulch site: one near the Yak

Tunnel and one near the Colorado Mountain College. A year's worth of data had been

collected at each of these stations. The Leadville airport also has a meteorological station

within the site that has been established for several years.

Data from the Colorado Mountain College (CMC) station (Res-ASARCO, 1991) was

selected as the most representative data set available for assessing air quality impacts from

the zinc slag pile. The Yak Tunnel station data is likely affected by local topography that

results in wind flow patterns not representative of the zinc slag pile location. The airport

observations are limited to periods when personnel are working, typically not through the

night, and are therefore not appropriate to reliably serve as input to air emissions

calculations or an quality dispersion model.

The data from the CMC station consists of hourly averages of temperature, wind speed,

wind direction, and sigma theta (the standard deviation of the horizontal wind direction used

as an indication of atmospheric stability) measured at 10 meters above ground level. Missing data values were noted by MK but not filled. Sixty-five days were reported for

which some or all hours had missing data. Most of these days occurred in May, September, October, and November resulting in an 82 percent data collection efficiency. Instead of

fillin g in inappropriate data, MK deleted each day with missing data from the data set. The

final meteorological data file covered the period from October 1990 to September 1991.

3.42 Emission Rate Estimates

Potential fugitive dust emissions from the zinc slag pile were estimated using the procedure

outlined in AP-42, section 11.2.7 (EPA, 1988a), as recommended by the EPA (EPA, 1992).

The first step in this procedure is to determine the threshold friction velocity (i.e., the wind

speed above which surface material becomes airborne) from the mode of the particle size

distribution. The procedure to determine particle size by sieve analysis is described in AP42. Variations from this procedure included using a sample of material collected from the

surface to a depth of three feet instead of collecting just the surface layer of loose particles,

and sieving with several more sizes of sieves than the five mentioned in the method. Using

the zero-to-three-foot sample data is considered representative of the surface material

MORRISON KNUDSEN CORPORATION

BB\1883\ZINCRPT\Final-RI 3" 10 [Rev 001/13/93 ]
because the pile is relatively homogeneous with respect to depth. The data from the sieve

analysis was re-grouped so that the sieve categories would match those specified in the

method.

The results of the size distribution are presented in Table 4-1. Of the four samples

collected, only one sample, HSS102, had a bimodal distribution, with a high percentage of

large material and fines. Most of the material for the other three samples did not pass

through the Tyler number 5 sieve and the data was not bimodal.

The wind speed that is necessary to erode the Western Zinc slag pile material and suspend

it in the atmosphere is determined by relating the mode of the size distribution to the

threshold friction velocity (that wind velocity at which particles begin to become entrained

into the ambient air). The information in Table 11.2.7.1 in AP-42 relates modes of particle

size distributions to threshold friction velocities. The data in the table, reproduced in

Appendix F, was determined empirically through research effort s by the EPA. The table

indicates that the threshold friction velocity for particles the size of the zinc slag is greater

than 100 centimeters per second (cm/sec).

The next step is to determine if the wind speeds in the area are great enough to entrain

surface material into the ambient air. This is done by comparing the threshold friction

velocity with the wind speed. However, using hourly-averaged wind speed data for the

comparison is not appropriate because most erosion events typically last between one and

four minutes (EPA, 1988a). It is the sustained wind gusts embedded in the hourly-averaged

wind speeds that are more relevant.

The "fastest mile" parameter is the most routinely measured meteorological variable that

best reflect s the magnitude of sustained wind gusts. The fastest mile is defined as the value

that represents the wind speed corresponding to the whole mile of wind movement that has

passed by the one mile contact anemometer in the least amount of time. Typically , fastest

mile data is available from Local Climatological Data (LCD) summaries. Since it is not

collected at the Leadville airport, a literature search was conducted to find a suitable

empirical relationship for deriving fastest mile data from hourly averaged on-site wind speed

data. A suitable equation is contained in E. Simiu and R. H. Scanlan's book Wind Effects

on Structures: An Introduction to Wind Engineering, (Simiu and Scanlan, 1978):

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Final-RI 3-11 [Rev 001/13/93 ]
U

t(z) = U3600(z)[l + (0.98 c(t))/ln(z/z0) ]

where z = height at which wind speed is to be determined

z

0

 = roughness height

c(t) = constant = 1.02 for an averaging period of 100 seconds

Uaeoo = hourly averaged wind speed

U

t(z) = averaged wind speed at time "t"

(The section presenting this conversion has been duplicated and provided in Appendix F.)

Since a typical erosion event lasts one to four minutes (EPA, 1988a) and is capable of

completely depletin g the erosion potential for a given source area, a wind speed averaging

time of 100 seconds was selected as a value that would yield a wind speed similar to the

fastest mile speeds in LCD summaries. Application of this equation results in a

"100-second" wind speed about 1.13 times higher than the "3600 second" wind speed. Thus,

it is appropriate to multiply the maximum observed hourly wind speed by 1.13 to obtain the

fastest mile. For example, the maximum observed hourly average wind speed was 9.12

m/sec, or 20.4 miles per hour (mph). Multiplyin g this value by 1.13 equals a 10.3 m/sec

(23.05 mph) fastest mile.

The 100-second period was selected to represent the duration of the typical erosion event

for two reasons. First , it was within the range of erosion events, which the EPA specifies

in AP-42, Section 11.2.7, Industrial Wind Erosion (EPA, 1988a), as lasting between one and

four minutes (60 to 240 seconds). Second, in order to determine the wind speed that

corresponds to the fastest mile, Equation 2.3.30 of Simiu and Scanlan (1978) needs to be

solved. In order to solve this equation, the value of the coefficien t c(t) needs to be

quantified. Table 2.3.2 in the referenced text book lists several coefficient s for select time

periods (a copy of this table has been included in the Simiu and Scanlan attachment to this

Appendix F). Only two coefficient s are given for time periods that are within the 60- to

240-second range: 100 and 200 seconds. Of these two values, the 100-second coefficien t

was chosen. The 100-second value is conservative because it results in a greater fastest mile

value than the 200-second coefficient; therefore, increasing the calculated emission rate.

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Final-Rl 3-12 [Rev 001/13/93 )
Two articles have been reviewed with the intent of providing supporting evidence to verify

applicability of the relationship between the hourly averaged wind speed and the wind speed

which corresponds to the fastest mile. The two articles reviewed are as follows:

Glidden, D.E. "Winter Wind Studies in Rocky Mountain National Park." Rocky Mountain Nature Association, Estes Park, Colorado, 1982.

Judson, A. "The Weather and Climate of a High Mountain Pass in the Colorado

Rockies." Rocky Mountain Forest and Range Experiment Station. Fort Collins,

Colorado, 1965.

Although the articles did not contain information on the wind speed corresponding to the

fastest mile, the articles did contain wind data summarized over several time periods

differen t from those recorded in Leadville, such as the fastest gust, 5-minute summaries,

hourly summaries, and daily summaries. These summaries included maximums, minimums,

and averages for the time period.

To compare the data presented in the articles to the method which is used to calculate wind

blown emissions for the zinc slag pile, the equation was modified slightly to compare the

ratio of the fastest 1-second wind speed (gust) to the hourly wind speed. This corresponds

to using c(t)= 3.00 in the Simiu and Scanlan equation (1978).

The following table summarizes the results of the ratio of the fastest gust to the 1-hour wind

speed (1-hour gust ratio) for four locations mentioned in the above referenced articles. The

Mines Peak station was located near Berthoud Pass at an elevation of 3808 meters. The

other three stations were located within the boundaries of Rocky Mountain National Park. TR3 and TRIO were located along Trail Ridge Road at an elevation of 11,601 feet and

11,817 feet , respectively. The Longs Peak station was located at the summit of Longs Peak

and an elevation of 14,255 feet.

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Observed and Calculated 1-Hour Wind Speeds:

Maximum Gust Ratios for Four Mountain Locations

SIT E Mines Peak

TR3

Longs Peak

TRI O

A VG MIN

N /A

1.27

1.30

1.21

AVERAGE

2.0

1.61

2.0

1.58

A VG MAX

N /A

2.53

3.20

2.20

CALCULATED

1.36

1.42

1.42

1.37

The values presented represent the ratio of the maximum gust observed each hour to the

1-hour averaged wind speed. For example, for location TR3, the maximum gust was 1.61

times greater than the average 1-hour wind speed. The column labelled AVG MIN

represents the minimum of all ratios of the fastest gust represents the maximum of all ratios.

The above values were calculated using parameters corresponding best to each individual

site. The anemometer height for each station was obtained from the references. A surface

roughness height of 0.35 cm was assumed for each site, which corresponds to that of snow.

The methodology used to calculate the 1-hour gust ratio appears to be within the range

observed at several mountain locations. It was not possible to compare the calculated and

observed values for other time averaging periods due to the lack of data presented in the

articles.

The fastest mile of 10.3 m/sec needs to be adjusted from the height of measurement (10

meters) down to the height of the pile surface; the adjusted wind speed at the surface is

referred to as the friction velocity (u'). This is done using the logarithmic wind profile

relationship as specified in AP-42, section 11.2.7, Equation 4:

u* = 0.053 U10

T he friction velocity is then compared to the threshold friction velocity calculated for the

zinc slag to determine if the friction velocity is greater, indicating potential for wind erosion. Results from this step (presented in Section 4.4.2) eliminated the need to proceed with

dispersion modeling.

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Final-RI 3-14 [Rev 001/13/93 ]
3.5 Relationship With Other Investigation Programs

This Zinc Slag Pile RI required coordination with other California Gulch Remedial

Investigation programs implemented by others. The information shared to date between the

various programs as it relates to the Slag Pile RI is discussed below.

Mineralogy and metal speciation studies are being performed by Resurrection and ASARCO

under the Final Work Plan - Metals Speciation and Source Characterization at California Gulch CERCLA Site (Resurrection, 1992). Analytical data will be developed that

characterize the distribution, geochemistry, and morphology of differen t metal compounds

at the site. These factors may be critical variables in the determination of the bioavailability

of lead and assessing the potential human health risk.

The zinc slag samples were prepared (pulverized to minus 250 microns) and delivered to

the Camp Dresser & McKee field laboratory in Leadville. It is understood that these

samples will undergo various tests, including XRF, XRD, microprobe, optical microscopy,

and lead isotope analysis.

It is anticipated that these results will be used to determine metals ratios of the Western

Zinc slag, origin of the ore that was smelted to form the slag, and relative bioavailability of

slag particles based on the species of metals in the slag.

3.5.1 ASARCO Meteorologic Monitoring Program

As stated previously, meteorologic data (Res-ASARCO, 1991) developed by Res-ASARCO

under the California Gulch Air Monitoring Work Plan (EPA, 1990b) has been provided to

MK and was used for input to the Western Zinc slag pile air dispersion modeling.

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Flnal-FH 3-15 tRev 001/13/93 ]
4 .0 CHARACTERISTICS OF THE ZINC SLAG PILE The results of historical research relating to the development of the zinc smelter and slag

pile, field reconnaissance of the smelter and slag pile, and the physical and stability

characteristics of the slag pile are reported in this section. A summary is also provided of

the results of compositional and teachability analyses along with quality assurance sample

data and data validation procedures.

4.1 Smelter History and Slag Pile Development Summary The intent of this summary is to give an overview of Leadville area smelter history, as it

relates to the Western Zinc slag pile development.

4.1.1 Brief Histoiy of Leadville Smeltin g Although placer gold was found in California Gulch in 1859, lead-silver mining did not begin

until the summer of 1874. By 1875, the Malta Smelter was built to process the silver ore.

The following 27 years were Leadville's most productive and active period for mining and

smelting. By 1879, all of the major lead smelter areas in the Leadville Mining District were

operating; however, by August 1880, half of them were closed largely due to the coke famine

of the previous winter (Blair, 1980).

The smelters often changed ownership, capacity and processes. Several burned to the

ground. By 1892, the smelters were resmelting older slag deposits for recovery of residual

metals. In 1893, there was a silver panic during which all of the smelters closed with only

a few of them reopening. Zinc smelting began in the early 1900s in Leadville and continued

for only about 12 years. Lead smelting continued in Leadville until 1961.

4.1.2 Western Zinc Smelter and Slag Pile History The Western Zinc Mining and Reducing Company built a zinc smelter west of Leadville in

1914. The company changed its name to the Western Zinc Oxide Company in 1915 and to

Western Zinc Concentrating Company in 1918. Thi s smelter used a Witherell furnace,

which oxidized ores to produce zinc oxide. It has been reported that some of the slag

produced at this zinc smelter was sent to other smelters, including the Arkansas Valley Smelter, in order that lead, silver, gold and copper could be recovered. The zinc smelter

closed in 1926 after generating an estimated 51,000 to 70,000 tons of slag (EPA, 1991). The

Western Zinc slag pile is currently owned by Lake County.

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\FinaI-R! 4-1 [Rev 001/13/83 ]
42 Field Reconnaissance of the Zinc Slag Pile and Smelter Area

The field investigation phase of the Zinc Slag Pile RI included a reconnaissance of the

historic zinc smelter location and slag pile. Reconnaissance activities included describing

the old zinc smelter location, the slag pile and property in the vicinity of the slag pile for

any other smelting debris or by-products, and other major physiographic or cultural features. Figure 3-1 presents observations from the field reconnaissance. The cross-hatched lines on

the figure represent areas of smelter foundations and rubble.

42.1 The Western Zinc Smelter

The Western Zinc Smelter slag area covers several acres near the Lake County Fair

Grounds west of Lake County High School. The smelter foundation is located just east of

the slag. This zinc slag is substantially differen t from the dense lead slag of the Leadville

area, as it was formed by a differen t process, recovering a differen t metal. The colors ofte n

range from red to brown and the material is more vesicular than lead slag. Particle sizes

range from soil-sized material up to pieces several inches in diameter. Much of the slag pile

appears to have been worked, although there is one large area consisting of mostly welded

material. Some of the soils in the area of the pile appear to be disturbed (excavated). The

thinner zinc slag areas and soils support trees, bushes and grasses. Railroad tracks run

nearby, as do several roads. No streams or ponded water were observed in the area. Also,

no evidence of fines were observed to have washed from the pile by precipitation runoff .

A number of bag-shaped mounds of grey cementicious material were located near the

foundation ruins. Based on the smelting method used at this site and the coarsely woven

fabric still adhering to several of the mounds, this material appears to be solidified zinc

oxide baghouse dust.

There are two locations in Leadville where zinc slag was observed on dirt roadways: on the

road off of McWethy Drive that leads towards the La Plata slag pile and on a section of the

road that passes to the north of the Hecla tailings ponds. Other potential uses of this

material that could account for volume loss have not been documented.

4.3 Physical Characteristics

Particle size and pile volumes are the major physical characteristics of the Western Zinc slag

pile that were determined during the RI.

MORRISON KNUDSEN CORPORATION

BB\1883\ZINCRPT\Final-« 4-2 [Rev 0 01/13/93)
TABU* 4-1

PARTICLE SIZE TESTING RESULTS

ZINC SLAG PILE (HSS101)

SEIV E ANALYSI S

SEIVE NO.

6

4"

3"

2

1"

1/2"

3M

4

6

8

10

14

20

28

35

48

65

SEIVE OPENING, mm

152.4

101.6

76.2

50.8

26.5

13.2

6.70

4.75

3.35 .

2.36

1.70

1.18

0.850

0.600

0.425

0.300

0.212

% PASSING

100.0

100.0

100.0

94.8

83.4

69.4

53.4

49.1

41.9

35.5

30.4

25.4

21.6

17.8

14.6

12.3

10.3

HYDROMETER ANALYSIS

SEIVE NO.

10

35

48

65

100

150

200

HYDROMETER RESULTS

SEIVE OPENING, pm

1700

425

300

212

150

106

75

EQUIVALENT DIAMETER (fun)

29

19

11

8

6

3

1

% PASSING

30.4

16.4

13.9

12.2

10.6

9.2

7.8

% FINER

4.2

3.4

2.5

2.3

1.9

1.5

1.3

SPECIFIC GRAVIT Y 3.3

MICROTRAC ANALYSI S

EQUIVALENT

DIAMETER (pm)

704.0

592.0

497.8

418.6

352.0

296.0

248.9

209.3

176.0

148.0

124.5

104.7

88.0

74.0

62.2

52.3

44.0

37.0

31.1

26.2

22.0

18.5

15.6

13.1

11.0

9.25

7.78

6.54

5.50

4.62

3.89

3.27

2.75

2.31

1.94

1.64

1.38

1.16

0.97

0.82

0.69

% FINER

12.30

12.09

11.82

11.47

11.04

10.51

9.89

9.20

8.47

7.75

7.06

6.40

5.77

5.15

4.55

3.99

3.49

3.04

2.65

2.31

2.03

1.79

1.58

1.39

1.23

1.09

0.97

0.87

0.77

0.68

0.60

0.52

0.44

0.37

0.31

0.24

0.18

0.12

0.07

0.03

0.00

BB\123\zinctblsUbt4-1 6/29/92
TABLE 4-1, coot'd

PARTICLE SIZE TESTING RESULTS

ZINC SLAG PILE (HSS102)

SEIV E ANALYSI S

SEIVE NO.

6"

4"

3"

2

1"

172

3M

4

6

8

10

14

20

28

35

48

65

SEIVE OPENING, mm

152.4

101.6

76.2

50.8

26.5

13.2

6.70

4.75

3.35 .

2.36

1.70

1.18

0.850

0.600

0.425

0.300

0.212

% PASSING

100.0

100.0

100.0

97.3

89.2

77.3

63.8

61.2

56.3

52.3

49.4

46.6

44.7

42.9

41.4

40.4

39.5

HYDROMETER ANALYSIS

SEIVE NO.

10

35

48

65

100

150

200

HYDROMETER

RESULTS

SEIVE OPENING, pm

1700

425

300

212

150

106

75

EQUIVALENT

DIAMETER (jan)

30

19

11

8

6

3

1

% PASSING

49.4

19.9

15.6

12.5

10.2

8.2

6.6

% FINER

6.2

5.1

3.4

2.7

2.4

1.7

1.7

[SPECIFI C GRAVIT Y 3.3

MICROTRAC ANALYSI S

EQUIVALENT

DIAMETER (pm)

704.0

592.0

497.8

418.6

352.0

296.0

248.9

209.3

176.0

148.0

124.5

104.7

88.0

74.0

62.2

52.3

44.0

37.0

31.1

26.2

22.0

18.5

15.6

13.1

11.0

9.25

7.78

6.54

5.50

4.62

3.89

3.27

2.75

2.31

1.94

1.64

% FINER

40.40

39.85

39.14

38.19

36.93

35.35

33.39

31.10

28.60

25.99

23.35

20.72

18.09

15.50

13.04

10.80

8.83

7.17

5.80

4.71

3.85

3.17

2.63

2.20

1.84

1.54

1.28

1.06

0.86

0.68

0.51

0.36

0.22

0.13

0.04

0.00

BBV123tfnctblsttbl4-1a 6/29/92
TABLE 4-1, coot'd

PARTICLE SIZE TESTING RESULTS ZINC SLAG PILE (HSS1Q3)

SEIV E ANALYSI S

SEIVE NO.

6

4

3

2"

r

1/2"

3M

4

6

8

10

14

20

28

35

48

65

SEIVE OPENING, mm

152.4

101.6

76.2

50.8

26.5

13.2

6.70

4.75

3.35

2.36

1.70

1.18

0.850

0.600

0.425

0.300

0.212

% PASSING

100.0

100.0

100.0

93.8

75.5

61.2

44.0

41.3

34.3

27.9

23.0

18.2

15.2

12.3

9.9

8.1

6.7

HYDROMETER ANALYSIS

SEIVE NO.

10

35

48

65

100

150

200

HYDROMETER

RESULTS

SEIVE OPENING, pm

1700

425

300

212

150

106

75

EQUIVALENT DIAMETER dim)

26

17

10

7

5

3

1

% PASSING

23.0

13.0

11.5

10.3

9.3

8.4

7.5

% FINER

5.2

4.4

3.3

2.7

2.3

1.6

1.4

[SPECIFI C GRAVIT Y

MICROTRAC ANALYSIS

EQUIVALENT DIAMETER 0*m)

704.0

592.0

497.8

418.6

352.0

296.0

248.9

209.3

176.0

148.0

124.5

104.7

88.0

74.0

62.2

52.3

44.0

37.0

31.1

26.2

22.0

18.5

15.6

13.1

11.0

9.25

7.78

6.54

5.50

4.62

3.89

3.27

2.75

2.31

1.94

1.64

1.38

1.16

0.97

0.82

% FINER

8.10

8.03

7.92

7.73

7.45

7.11

6.72

6.30

5.85

5.39

4.95

4.53

4.12

3.73

3.35

2.98

2.64

2.30

1.98

1.68

1.41

1.19

1.01

0.86

0.74

0.63

0.54

0.46

0.40

0.34

0.29

0.24

0.20

0.16

0.13

0.09

0.06

0.03

0.01

0.00

BB\123WnctbNW4-1b 6/29/92
TABLE 4-1, cooTd

PARTICLE SIZE TESTINO RESULTS ZINC SLAG PILE (HSS104)

SEIVE ANALYSIS

SEIVE NO.

6"

4"

3"

2"

1"

1/2

3M

4

6

8

10

14

20

28

35

48

65

SEIVE OPENING, mm

152.4

101.6

76.2

50.8

26.5

13.2

6.70

4.75

3.35 .

2.36

1.70

1.18

0.850

0.600

0.425

0.300

0.212

% PASSING

100.0

100.0

97.0

92.2

81.1

72.5

60.6

59.4

32.5

9.9

8.1

6.3

5.1

4.0

3.1

2.4

1.9

HYDROMETER ANALYSIS

SEIVE NO.

10

35

48

65

100

150

200

HYDROMETER

RESULTS

SEIVE OPENING, pm

1700

425

300

212

150

106

75

EQUIVALENT DIAMETER Cim)

32

21

12

9

6

3

1

% PASSING

8.1

4.3

3.5

2.9

2.4

2.0

1.6

% FINER

0.5

0.4

0.4

0.3

0.2

0.2

0.1

[SPECIFIC GRAvrnr 3.0

MICROTRAC ANALYSIS

EQUIVALENT

DIAMETER (pm)

704.0

592.0

497.8

418.6

352.0

296.0

248.9

209.3

176.0

148.0

124.5

104.7

88.0

74.0

62.2

52.3

44.0

37.0

31.1

26.2

22.0

18.5

15.6

13.1

11.0

9.25

7.78

6.54

5.50

4.62

3.89

3.27

2.75

% FINER

2.40

2.37

2.33

2.26

2.17

2.04

1.88

1.71

1.53

1.35

1.18

1.02

0.87

0.73

0.61

0.50

0.41

0.33

0.26

0.21

0.17

0.14

0.11

0.09

0.08

0.06

0.05

0.04

0.03

0.02

0.01

0.01

0.00

BB\123tfnctblsttbl4-1c 6/29/92
4.3.1 Particle Size

Particle size distributions of the zinc slag samples were determined by sieve, hydrometer,

and Microtrac analyses. The specific gravity of the less than No. 10 mesh, or 1.7 mm,

portion of the sample was also evaluated.

The results of the particle-size analyses for the zinc slag samples are presented in Table 4-1.

The results indicate 90 percent or more of three samples which consisted of material

between screen sizes 0.212 mm and 3 inches. Only 60 percent of the other zinc slag sample

(HSS102) was material between 0.212 mm and 3 inches. This finer sample was obtained

from the north side of the higher, welded area (Figure 3-1). The results of all three particle

size determination techniques - Microtrac, sieve and hydrometer ~ compare well.

The particle size data was analyzed in order to determine the potentially inspirable

(inhalable) and respirable (capable of being deposited in the alveoli) weight fraction of the

zinc slag sample. According to Threshold Limit Values given by the American Conference

of Governmental Industrial Hygienists (ACGIH, 1990), inspirable particulate mass is

calculated based on aerodynamic diameters up to 100 jum and respirable particulate mass

is based on aerodynamic diameters of 3.5 jum. The EPA document, Risk Assessment

Guidance for Superfund Volume I, Human Health Evaluation Manual (Part A), Interim Final

(p. 6-43) (EPA, 1989a) considers respirable particles to be those with diameters of 10 /xm

or less. The industrial hygiene reference, The Industrial Environment - Its Evaluation and

Control, (NIOSH, 1973) predicts the inhalable particle size based on the known behavior

of particles in air suspension and the anatomical arrangement of the connecting tubes in the

lung. The reference predicts that particles larger than 10 /nm would be removed from the

airstream when passing through the nose and upper airways and that particles between 5 jum

and 10 jim in diameter would be deposited mainly in the upper airways on the mucociliary

escalator. Only particles in the range of 1 /zm to 2 jum would penetrate to the deeper

portions of the lung where deposition in the alveoli may occur. Based on these references,

it will be conservatively assumed that particles less than 100 Mm in diameter are potentially

inspirable, and those less than 10 /um are potentially respirable. Total suspendable

particulates (TSP) are those particles less than 30

The particle size data was analyzed so that the weight percent of material equal to or finer

than 100/im, 30/im, and lO/itm in diameter could be calculated. For the hydrometer data,

the weight percent of material finer than 30jum and finer than lO^m was linearly

interpolated. For the sieve data, the percent of material finer than lOO/xm was linearly

MORRISON KNUOSEN CORPORATION

BB\1893\ZINCRPT\Final-RI 4-3 [Rev 001/13/93 )
TABLE 4-2

% < 100 jan % < 30 inn % < 10 ion

mean mean max mean max

Western Zinc D422

Microtrac

6.7 8.9 0.48 4.1 033 Zl

0.99 025 5.6 0.070 OJS9 L7

BB\1V9\ZINCRR\W-TMH£4-12 REV 0
interpolated. The Microtrac data provided percent of sample finer than 100 /im, 30 urn, and

10 nm. The minimum, average, and maximum values for the zinc slag samples are

presented in Table 4-2. The data show that approximately 7 percent of the material is less

than 100 /Ltm, 3 percent is less than 30 pm, and only 1 percent is less than

The specific gravity was determined for the less than No. 10 mesh, or 1.7 mm, portion of

each of the samples, as required for calculations in the hydrometer test. The specific gravity

of this fraction of the zinc slag samples averages 3.25.

4.3.2 Historic and Current Zinc Slag Pile Surface Areas and Volumes

The historic volume of the zinc slag pile was estimated based on its size in late 1956. Thi s

volume was calculated in order to estimate the amount of slag generated by the smelter. The historic volume was then compared to the current slag pile volume calculated from the

survey performed for this RI. (The current topographic surface of the zinc slag pile is

shown in Figure 4-1. The historic topographic surface of the pile is shown in Figure 4-2.)

The volume decrease between 1956 and 1992 is attributed to the material being removed

from the site.

The 1956 aerial photographs from which the historical slag pile topography was digitized,

are described in Section 3.2.1. Surface topography was digitized in two-foot contour

intervals by IntraSearch, Inc. of Englewood, Colorado. AutoCAD software generated the

surface of the slag pile. The topography around the perimeter of the slag pile was used to

estimate the ground surface before slag deposition. Elevation differences between the two

surfaces were used to develop an isopach map, from which the slag pile volume was

calculated. The result of this calculation shows that the Western Zinc slag pile volume in

1956 was 35,100 cubic yards.

In the spring of 1992, a professional survey team examined the zinc slag pile, according to

procedures reported in Section 3.2.2. From this survey information, a topographic map of

the pile surface, with five-foot contours, was developed. The current volume of the zinc slag

pile was determined using procedures as described for estimating the historic volume in the

preceding paragraph. The current volume of the Western Zinc slag pile is 22,600 cubic

yards. The pile surface area from a map view perspective, is 201,000 square feet.

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Flnal-« 4-4 [Rev 001/13/93 ]
s

US5

nl

LJ

£Ld

N 515,500

LEGEND - 2 SURFACE CONTOUR INTERVAL A DD 9000 TO CONTOUR INTERVA

MONITOR WELL

• BOUNDARY OF VOLUME CALCULATION

ANGLE OF REPOSE CALCULATION SECTION

SMELTER RUBBLE AREA

N 515,250 N 515,000 N 514,750 N 514,500

VOLUMES BY FLATIRON S SURVEYING , INC . GRI D METHO D AVERAG E EN D AREA METHOD T I N SUBTRACTIO N METHO D

21,900Cu. Yds .

23,130 Cu. Yds .

22,960 Cu. Yds .

SURFACE AREA 201,29

0 Sq. Ft.

DATUM : 10795.0,

DATUM =

10785.0,

6 co l l

DATUM

10800.0

50 1

AVERAGE ANGLE OF REPok = 34.1*

OUTLIN E OF HISTORI C (1956) PILE SUPERIMPOSED ON CURRENT SURFAC

E F OR READER COMPARISION

SCALE FEET

<CPD: 9/23/92>

CALIFORNIA GULCH CERCLA SITE ZIN C SLA G PIL E INVESTIGATIO N LEADVILLE . COLORADO

FIGURE 4-1 ZIN C SLA G PIL E CURREN T SURFAC E AREA , VOLUME AND ANGLES OF REPOSE DENVER & RI O GRAND E WESTERN RAILROA D DENVER , COLORADO IMORRISON-KNUDSEN CORPORATION

FILE NAME (CM)) 1893N048 PROJEC T SUFTI X

1893 630

TASK

06

|DATE:6/02/92 DRAWIN G NUMBE R

FIGURE 4-1

REV. A
N 515,50

0

I

N 519,250 N 515,000 N 514,750 N 314,300

U .4

III

UJ

LEGEN D , .- 2 SURFACE CONTOUR INTERVAL — BOUNDARY OF VOLUME CALCULATION

VOLUME CALCULATION

Method of Calculation:... . QuickSurf Grid Size:.........................10 X 10

35,100 Cubic Yards

SCALE FEET

0 50 100 150 2QO

TOPOGRAPHY DIGITIZED FROM 1956 AERIAL PHOTOGRAPHY BY INTRASEARCH. INC.

<CPO:06/23/92>

CALIFORNIA GULCH CERCLA SIT E ZIN C SLA G PIL E INVESTIGATIO N LEADVILLE. COLORADO_____

_ FIGURE 4-2 ZIN C SLA G PIL E HISTORI C VOLUM E DENVER & RIO GRANOE WESTERN RAILROAD DENVER , COLORADO

IMORRISON-KNUDSEN CORPORATION

rill N«Mt JC«D) 1893NQ20 PROJEC T SUFTI X

1893 630

IDMI3/17/9?

DRAWING NUMBER FIGURE 4-

2

RCV. A
Slag pile volumes were calculated using three differen t methods: average end area, grid

subtraction, and triangular irregular network (TIN) subtraction. The average end area

method generates sections through the pile along predetermined grid lines. The volume

between two sections is calculated by determining the average area of each sectional face

and multiplying it by the width of the grid. The volumes between each pair of sections is

summed to give the total volume of the pile.

Using the Grid Subtraction Method, upper and lower surfaces around the pile are generated

by interpolating elevations at prescribed rectangular grid nodes from existing data. The total

volume between the upper surface and a datum for a rectangular grid cell is then calculated

and designated as fill. Then the volume is calculated between the lower surface and a

datum for the same cell and designated as cut. The difference between fill and cut for each

grid cell is summed to give the total volume of the pile.

T he TIN Subtraction Method is performed similarly to the grid method, except triangular

grid cells are generated, exactly honoring all of the actual data points surveyed. The

difference between the volume of fill and cut within each of the triangular grid cells is

summed to give the total volume of the pile.

4.4 Slag Pile Stability The stability of the zinc slag pile, as it currently exists, was evaluated with respect to

structural stability, deflation potential, and effect s of freeze/thaw cycling. The geotechnical

stability evaluation was based on the results of the field reconnaissance and the slag pile

contour map. The deflatio n potential of the slag was estimated from particle size

information and air emissions calculations. The effect s of freeze/thaw cycling on the

stability of the slag pile was based on a literature review and observed conditions.

4.4.1 Analysis of Structural Stability The structural (geotechnical) stability of the zinc slag pile was evaluated based on the results

of the field reconnaissance task. Angles of repose were calculated from the topographic

survey.

The zinc slag pile has been partially excavated and currently consists of a core of welded

material approximately 15 feet high with vertical faces surrounded by loose material. No

obvious talus was noted at the zinc slag pile because of the highly disturbed nature of the

pile and the existence of large quantities of loose material. At areas where welded slag

MORRISON KNUDSEN CORPORATION

BB\1883\ZINCRPT\Flnal-RI 4-5 [Rev 001/13/93 ]
outcrops were observed, only a trace of loose material was noted at the pile base. Based

on three measurements, the average angle of repose is 34 degrees (Figure 4-1). There were

no fissures or fault blocks noted at this pile and the pile presents no stability concern.

4.43 Deflation/Emissions Potential

Emission calculations using the 1991 meteorological data from the Colorado Mountain

College (Res-ASARCO, 1991) and the mode of the aggregate size distribution have

demonstrated that wind erosion does not occur from the zinc slag pile. This conclusion is

based upon standard procedures and guidance from the EPA regional offic e in Denver,

Colorado (EPA, 1992). The procedures, described in Section 3.4.2, were used to determine

the friction velocity (or wind speed at the pile surface) and the threshold friction velocity

(minimum wind speed at which particles will become airborne) of the zinc slag pile. The

results are as follows:

Friction Velocity .55 m/sec

Threshold Friction Velocity 1.0 m/sec

T he friction velocity was then compared to the threshold friction velocity. A friction velocity

lower than the threshold shows that Leadville wind speeds are not fast enough to cause wind

erosion from the Western Zinc pile.

It should be reiterated that a number of factors, not accounted for by the method, make the

emission rate estimates conservative. It is useful to note that if a lower "beta" value more

representative of air flow over rough terrain was used, the conversion factor would be even

lower than 1.13. ("Beta" value is discussed in the Simiu and Scanlan attachment to these

responses.) The Leadville slag has a greater density than the sand and gravel piles at the

Midwest site used to develop empirical data for the EPA method. Furthermore, the air

density, and therefore the liftin g force of wind at the same speed, is much lower in

Leadville. Additionally, periods of high moisture, snow cover, and frozen ground also would

limit the potential for fugitive dust emissions. The emissions calculations do not take into

account any conditions other than those ideal for wind erosion of material.

4.4.3 Effect s of Freeze/Thaw Cycling Literature was researched to determine how freezing water may disaggregate material

similar to slag, such as rock. Also, literature was reviewed to determine if freeze/thaw

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Flnal-RI 4-6 [Rev 001/13/93 ]
testing has been done on zinc slag or slag-like material. Material considered in the

literature search included slag, igneous rocks, natural glasses and vitrified waste.

The disintegration of rock due to pressure exerted by water freezing in cracks and pores is

called congelifraction. When water freezes under atmospheric conditions, its molecules

organize into a rigid hexagonal crystalline network, and it increases nine percent in specific

volume. As ice expands, the pressure of the remaining water increases, and the temperature

must be lowered further in order to continue this increase in pressure. Ice is not strong

enough to seal water into a fracture and produce the maximum possible pressure, as the

plastic deformation of ice is so rapid that water is quickly extruded (Bloom, 1978).

Water in very thin cracks will not freeze, even at very low temperatures, because of the

strong capillary adhesion of the water to rock. Most of the rock fractures attributed to

freezing are probably due to capillary or monomolecular films of unfrozen water that spread

along pre-existing cracks in rocks. Thin films of water form a semicrystalline "ordered"

molecular structure on mineral surfaces that can pry apart microfractures and propagate

cracks. Shallow freezing may aid in forcing capillary films of water deeper along tight joints

and pre-existing microfractures, thereby hydrofracturing rocks well below the depth of actual

freezing (Bloom, 1978).

Based on the literature review, freeze/thaw cycling may have some effect on zinc slag. Small surface vugs of the zinc slag may fill with water that subsequently freezes. Recurrent

freeze-and-thaw action in the slag surface layer could loosen zinc slag fragments, causing

eventual breakdown of the material to finer particles.

4.5 Chemical Characteristics of Zinc Slag Material

The chemical characteristics of the zinc slag material, as determined by the analytical

program outlined in the SAP and discussed in earlier sections, are presented in this section.

Chemical analyses included total compositional analysis, Synthetic Precipitation Leaching

Procedure (SPLP) analysis, and column leaching tests with analysis of the effluent . Compositional analyses included the analyses of the TAL metals (minus mercury plus

silicon), water soluble anions, neutralization potential, sulfur forms and cation exchange

capacity. SPLP and column leach eluate were analyzed for anions and TAL metals (minus

mercury plus silicon).

MORRISON KNUDSEN CORPORATION

BB\1883\ZINCRPT\Rnal-RI 4-7 [Rev 001/13/83 ]
TABLE 4-3

FREQUENCY OF OCCURRENCE OF TAL METALS — ZINC SLAG

Chemical Name

Aluminum, total Antimony, total Arsenic, total Barium, total Beryllium, total Cadmium, total Calcium, total Chromium, total Cobalt, total Copper, total Iron III, total Lead, total Magnesium, total Manganese, total Nickel, total Potassium, total Selenium, total Silicon, Total Sodium, total Vanadium, total Zinc, total

TOTALS

Number of Detections

4

3

4

4

4

4

4

4

4

4

4

4

4

4

4

4

0

4

4

4

4

79

Number of Analyses

4

4

4

4

4

4

4

4

• 4

4

4

4

4

4

4

4

4

4

4

4

4

84

RANGE OF DETECTED CONCENTRATIONS Minimum Value (mg/kg)

21100.00 HSS102MOO

5.30 HSS102MOO

112.00 HSS104MOO

782.00 HSS104MOO

1.40 HSS104MOO

2.50 HSS103MOO

12500.00 HSS101MO O

35.90 HSS101MOO

9.90 HSS104MOO

125.00 HSS103MOO

108000.00 HSS104MOO

192.00 HSS103MOO

6570.00 HSS101MOO

51600.00 HSS101MOO

41.90 HSS104MOO

5510.00 HSS102MOO N /A

134000.00 HSS102MOO

604.00 HSS104MOO

44.50 MSS104MOO

63200.00 HSS101MOO

Maximum Value (mg/kg)

22900 HSS101MOO

52.2 HSS101MOO

414 HSS101MOO

1420 HSS101MOO

2 HSS101MOO

29.5 HSS101MOO

42200 HSS103MOO

700 HSS102MOO

19.8 HSS102MOO

3310 HSS102MOO

198000 HSS102MOO

925 HSS102MOO

18800 HSS103MOO

76500 HSS104MOO

392 HSS102MOO

7690 HSS103MOO N /A

154000 MSS103MOO

1010 HSS103MOO

58 HSS101MOO

70000 HSS103MOO

* . _ *i. i.. t »i-. i
4.5.1 Compositional Analyses

A ll four slag samples from the Western Zinc Smelter area were submitted to the

compositional analysis program.

4.5.1.1 TAL Metals

Target Analyte List (TAL) metals were analyzed following digestion by a U.S. Bureau of Mines method as the preparatory technique (Bureau of Mines, 1980). After digestion, most

metals analyses were conducted by Inductively Coupled Plasma (ICP) techniques, although

some of the metals were analyzed by graphite furnace atomic absorption (GFAA) methods. The elements analyzed by GFAA include arsenic, cadmium, lead and selenium. The use

of GFAA was necessitated by matrix interference problems caused by the particular

digestion fluid used.

Table 4-3 presents the frequency of occurrence of the elements, along with the minimum

and maximum values of each of the elements. Iron and silicon comprise the majority of the

slag matrix. Iron ranges from 10.8 to 19.8 percent of the zinc slag material, while silicon

ranges from 13.4 to 15.4 percent. Manganese values ranged from 5.2 to 7.7 percent. The

concentration range and geometric mean of each of four primary elements of concern in

zinc slag at the California Gulch site are as follows:

- Arsenic-112 to 414 mg/kg, mean 211 mg/kg

- Cadmium-2.5 to 29.5 mg/kg, mean 14.1 mg/kg

- Lead-192 to 925 mg/kg, mean 568 mg/kg

- Zinc-63,200 to 70,000 mg/kg, mean 66,000 mg/kg

4.5.1.2 Anions

Water-soluble anions chloride, sulfate, and nitrate/nitrite were analyzed in the zinc slag

samples. Although carbonate was not directly measured in the water-soluble extracts, its

concentration was calculated from the neutralization potential results, which are reported

as total calcium carbonate. The anions are reported in solid units, mg/kg, by backcalculation from the analyses conducted in the water-soluble extract.

The most prevalent anion in the zinc slag is the carbonate anion with a mean of 79,200

mg/kg as CaCO3 or about 8 percent of the total mass of the material. The range of

concentrations of carbonate is from 58,800 to 100,200 mg/kg. The second most prevalent

water-soluble anion is sulfate. Ranges and means for the anions are listed below:

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BB\1893\ZINCRFT\Final-RI 4-8 [Rev 001/13/93 )
TABLE 4-4

Sample ID Neutralization Potential

Acid Generation Potential due to Pyritic SulfurN et Acid Forming Potential

HSS101MOO Zinc Slag HSS102MOO Zinc Slag HSS103MOO Zinc Slag HSS104MOO Zinc Slag

125

149

98

167

0.30

1.30

0.30

0.60

-124.70

-147.70

-97.70

-166.40

zinctb!s\tbW-4 6/29/92
- Sulfate - 1,463 to 13,040 mg/kg, mean 4,099 mg/kg

- Chloride - 2.3 to 20.8 mg/kg, detected 2 times out of 4

- Nitrate - 5.8 to 45.4 mg/kg, mean 20.5 mg/kg

- Nitrite - < 1.0 to 2.1 mg/kg, detected 1 time out of 4

4.5.1.3 Sulfur Forms Sulfur forms were determined by EPA Method 3.2.4 and 3.2.6 (EPA, 1978) for input to

calculations of acid-base accounting. Total sulfur is comprised of pyritic sulfur, sulfate, and

other non-extractable sulfur forms. The mean concentration for total sulfur is 0.41 percent,

with sulfate sulfur the largest fraction by weight of total sulfur. The following provides a

breakdown of the sulfur form concentration ranges:

- Total sulfur--0.34 to 0.55%, mean 0.41%

- Sulfate sulfur-0.01 to 0.54%, mean 0.13%

- Pyritic sulfur-0.01 to 0.04%, mean 0.012%

- Non-extractable sulfur~0.03 to 0.22%, mean 0.10%

Evaluation of the results for pyritic sulfur versus total sulfur indicate that pyritic sulfur

averages 9.9 percent of total sulfur for all of the slag samples collected. The geometric

mean for pyritic sulfur was calculated using non-detect values as one half of the quantitation

limit.

For use in acid-base accounting, the percent of pyritic sulfur is converted to units of tons of

CaCO3 equivalents per 1000 tons of material (t/kt) by multiplying by 31.25, yielding

potential acidity. The potential acidity due to pyritic sulfur is presented in Table 4-4. The

geometric mean potential acidity due to pyritic sulfur for the zinc slag samples is 0.5 t/kt . These values indicate that the zinc slag has a low potential for acid generation due to the

low levels of pyritic sulfur.

4.5.1.4 Neutralization Potential and Acid-Base Accounting Neutralization Potential (NP) was measured by EPA Method 3.2.3 (EPA, 1978) and

reported in units of tons of CaCO3 per 1000 tons of material (t/kt) . These values are

presented in Table 4-4. The NP for the zinc slag material showed that it has a mean

neutralization potential of 132 t/kt, ranging from 98 to 167 t/kt .

Acid-base accounting is a technique developed for identifyin g potentially toxic acidity levels

of pyritic materials in surface mining overburden. The weathering of pyritic overburden

materials can produce acid over time, thereby lowering the pH and creating an environment

conducive to leaching metals. The net acid-base account of a mine overburden is defined

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BB\1883\ZINCRPT\Rnal-Rt 4-9 [Rev 0 01/13/93]
as its maximum potential acidity minus its neutralization potential, with both expressed in

units of tons calcium carbonate (CaCO3) equivalents per 1000 tons of material. Potential

acidity is equivalent to the amount of acidity that can be generated from sulfur compounds

(generally sulfide) and is calculated using the measured pyritic sulfur values. Neutralization

potential is the bufferin g capacity of the material. The difference between potential acidity

and neutralization potential is net acid generation potential. Each of these values for the

slag samples are presented in Table 4-4.

According to Mine Spoil Potential for Soil and Water Quality (EPA, 1974), page 128, "From

the acid-base account, potentially toxic material is defined as a rock or earth material having

a net potential deficiency of 5.0 tons of calcium carbonate equivalent or more per 1,000 tons

of material."

A net acid-forming potential less than 5.0 t/kt indicates excess neutralization potential in

relation to the potential acid generation. All zinc samples showed a net acid-forming

potential less than 5.0; the geometric mean was -132 t/kt . Thus, the slag sampled is not

potentially acid toxic due to acid generation potential.

4.5.1.5 Cation Exchange Properties

Cation Exchange Capacity (CEC) is a measure of how readily a material will sorb cations

onto its surface or into its matrix. The CEC was measured using EPA method 9080 (EPA,

1986), in which results are expressed in milliequivalents (meq) per 100 grams of material. The material tested has a low CEC, with values of 2.0, 4.9, 5.9 and 15.2 meq/lOOg. The

CEC results for the four zinc slag samples show a geometric mean of 5.4 mg/lOOg.

4.5.2 Leaching Analyses

Two types of leaching tests were performed on zinc slag. One method, the Synthetic

Precipitation Leach Procedure (SPLP) is a liquid shake extraction test developed to simulate

leaching of mine waste impacted by acidic precipitation. The other test is a laboratory

column leach test designed to simulate percolation of precipitation through the material.

4.5.2.1 Synthetic Precipitation Leaching Procedure

The SPLP (EPA Method 1312) was conducted on each of the zinc slag samples collected. The sample size was increased to 1 kilogram rather than the 100 gram sample specified by

the method to avoid particle size reduction. Particle size reduction to less than 9.5mm, as

called for in the method, was not conducted on these samples so as to mimic in-situ

conditions of the piles as closely as possible.

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BB\1883\ZINCRPT\Rnal-RI 4-10 [Rev 001/13/93 ]
T he SPLP method calls for comparisons of eluate concentrations to applicable regulatory

thresholds, but does not state what these thresholds are. Because the test most closely

resembles the TCLP or EP toxicity tests, regulatory thresholds associated with these tests

were utilized. The results for all elements for all zinc slag samples were below the toxicity

characteristic criteria listed in 40 CFR 261.24. The maximum value for each of the eight

metals for which toxicity characteristic criteria exist was generally more than two orders of

magnitude lower than the criterion. The exception to this is manganese, which was more

than one order of magnitude lower. The following summary compares the mean and

maximum values of the leachate to the toxicity criteria or 100 times the secondary drinking

water standards:

Element Arsenic Barium Cadmium Zinc Manganese Iron

Toxicity Criteria

5.0 mg/1

100 mg/1

1.0 mg/1

500 mg/1*

5.0 mg/1*

30 mg/1*

Mean Value

0.030 mg/1

0.084 mg/1

0.002 mg/1

0.063 mg/1

0.016 mg/1

0.010 mg/1

Maxinum Value

0.051 mg/1

0.141 mg/1

0.006 mg/1

1.04 mg/1

0.141 mg/1

0.022 mg/1

100 times secondary drinking-water standards.

Chromium, copper, lead, selenium and silver values were below detection limits for all four

samples. The geometric means for arsenic, cadmium and iron were calculated using nondetect values (2 of 4 for iron and 1 of 4 for arsenic and cadmium) as one half the

quantitation limit.

4.5.2.2 Column Leach Studies

Column leach testing was conducted on one zinc slag sample. The material in the column

was subjected to one-hour leaching cycles, each representing a one-inch rainfall event. The

column criteria were as follows:

Test

Material

Zinc Slag

Mode

Downflow

Column

Diameter (in.)

8

Volume of

one-inch of rainfall)

823

The lixiviant used for the column leach testing was the simulated precipitation for areas west

of the Mississippi, as specified in Method 1312 of SW-846. The precipitation fluid is made

by adding a 60/40 weight percent mixture of sulfuric and nitric acids to deionized water

until the pH is 5.00 ±0.05 units. The fluid was prepared in a 55-gallon polyethylene drum

by adding approximately 2 ml of the acid mixture to 50 gallons of deionized water and

mixing. Due to the lack of bufferin g capacity in the water, the pH dropped to about 4.5 and

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Final-RI 4-11 [Rev 001/13/93]
was readjusted to pH 5.00 ±0.05 by the dropwise addition of 10 percent sodium hydroxide

(NaOH) .

The simulated precipitation was introduced to the column over a one-hour interval, followed

by a one-hour desaturation/aeration period during which the lixiviant was allowed to drain

from the test material. The tests took place over a period of two hundred hours,

corresponding to one hundred rainfall events. Considering that Leadville receives about

twelve and one half inches of rainfall per year the column leach test cycles corresponded

to eight years of rainfall. The following table presents loading data for the zinc-slag column:

Test Weight Packed Total Pore

Material Materialfg) Lengthfiiri Volfmn VcKmf t

Zinc Slag 8,813 19 15,642 3,800

Effluen t was collected from each of the precipitation events. Upon collection, pH, Eh, and

conductance measurements were made using calibrated probes connected to pH/m v and

conductance meters. After these measurements were completed, the sample was filtered

through Whatman #40 (S^m) filter paper. The samples was split into two separate

containers; one for anions analysis and the other for metals analysis. The samples for

metals analysis were preserved with nitric acid to a pH less than 2.0.

At the completion of one hundred cycles, the pore volume of the column was determined. This measurement was made by pumping water to the top of the test material and then

measuring the volume of water collected as the water level was lowered to the bottom of

the test material.

Table 4-5 summarizes the analytical results for selected metals and anions from the column

leach test. Figures 4-3 and 4-4 depict in graphical form the concentrations of selected

metals and anions as a function of effluen t number (precipitation event). The complete

results of the column leach testing are presented in Appendix Bl.

4.6 Analytical Data Validation

Data validation was performed on 100 percent of the analytical data reported by the

laboratory. CLP methods were evaluated using accepted criteria and control limits defined

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Final-RI 4-12 [Rev 0 01/13/93]
TABLE 4-5

Leaching Event #

Lead

ug/l Cadmiumug/l Arsenicug/l Zincug/l

Bicarbonate mg/l SuKate mg/l

5

25

50

75

100

31 u

31 u

41.9

31 u

44

141

126

76.5

42.2

20.1

49u

49u

49u

49u

53.6

31500

26200

13900

7200

3680

29.2

13.1

14.1

14.7

1742

1479

1079

428.7

u - non-detect

— - not analyzed

zinctbls\tbl4-6 6/29/92
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by the draft Laboratory Data Validation, Functional Guidelines for Evaluating Inorganics Analyses (EPA, 1988b) (Functional Guidelines) and the USEPA Contract Laboratory

Program, Statement of Work for Inorganic Analysis (EPA, 1990a) (SOW). Non-CLP methods

were validated using criteria consistent with guidelines applicable to those methods. Control

limits specified in the Functional Guidelines were used as guidance in the evaluation of nonCLP quality control data from duplicates, spikes, and laboratory control samples. The

sample group from each data package is referred to as the sample delivery group (SDG). A SDG Analytical Data Validation Summary report was prepared for each SDG and includes

three sections:

1. A summary of the sample numbers, sample type and matrix, methods of

analysis, and overall data useability

2. The CLP data validation results

3. The non-CLP data validation results—laboratory performance on each of the

CLP Quality Assurance/Quality Control (QA/QC) criteria are summarized

and any data reporting or functional problems in the data package are

discussed in detail

Precision, accuracy, representativeness, completeness, and comparability (PARCC)

parameters for analytical data were developed as part of the overall data quality objectives

(MK, 1991b). The data validation process plays an integral part in determining if analytical

data met the PARCC criteria.

Validation of the analytical data showed that all data collected is usable for the intended

purpose. Usable data in some cases is qualified by the laboratory and/or the data reviewer

and the qualifiers placed on the data should be considered when assessing the relative error

in any particular data point.

Overall, the data quality objectives set forth for this project were obtained with greater than

98% of the data being available for quantitative usage.

Appendix El presents the SDG summary reports, which include sampling, receipt, and

analytical dates for each sample, and a summary of all analytical data considered to be

quantitative estimates based on validation parameters.

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BB\1883\ZINCRPT\Final-RI 4-13 [Rev 001/13/93]
4.6.1 CLP Data Validation

The following data quality issues were addressed in the data validation and review process

for CLP analyses.

Field and Transportation OA/OC Documentation was reviewed to verify that uninterrupted chain-of-custody protocol was

followed and reported in a manner consistent with the SOW criteria.

Holdin g Times

As stated previously, a listing of sampling date, laboratory receipt date, and analysis date

was prepared and summarized for each sample in the SDG and reported in Appendix El. The time elapsed between the sampling and analysis dates was compared with holding time

criteria required by the SOW. A general summary of holding time compliance is provided

in the text of the report.

Initial and Continuing Calibration Verification

Start-up calibration records generated by the laboratory were reviewed and validated to

demonstrate that the instruments were capable of producing acceptable quantitative data.

Continuing Calibration and Preparation Blanks

Blank data was assessed to determine the existence and magnitude of any contamination

that may have been introduced during the calibration or sample preparation process.

Interference Check Sample

Interference check sample results were reviewed to verify that instrument inter-element and

background correction factors were correct.

Spiked Sample Recoveries

Spiked sample results were reviewed to evaluate the accuracy of sample results and to

evaluate the effect each sample matrix had on the digestion and measurement methodology. Data qualifiers applied by the laboratory were reviewed to ensure they were correctly

applied and reported.

Graphite Furnace-Atomic Absorption Spectroscopy (GFAA) Duplicates

Duplicate injections consisting of sample and spiked-sample are required for GFAA analysis. Duplicate analysis is performed by the laboratory to establish the precision and accuracy of

MORRISON KNUDSEN CORPORATION

B8\1883\2INCRPT\Final-R 4-14 [Rev 001/13/93 )
individual analytical determinations. Duplicate recoveries presented by the laboratory were

recalculated by the reviewer and duplicate values were verified from GFAA raw data to

ensure that qualifiers were correctly applied.

Duplicate Recoveries

Analyses of lab-choice duplicate samples were evaluated to determine the laboratory

precision based on the sample matrix. Duplicate recoveries were recalculated and data

qualifiers verified.

Laboratory Control Sample (LCS) The LCS sample results were verified and evaluated to ensure that overall analytical and

preparation performance in the laboratory were adequate.

Method of Standard Additions (MSA^ Results

MSA is required for quantification of analytes determined by GFAA that do not meet spike

recovery criteria. Spike recovery data were reviewed to determine if MSA was correctly

applied, as needed. Statistical variance of the MSA results was evaluated to determine if

the data were useable without qualification.

Inductively Coupled Plasma (IPC) Spectrophotometry Serial Dilution

Serial dilution is required to determine whether significant physical or chemical

interferences existed due to sample matrix. Results for high concentration analytes were

reviewed to ensure serial dilution results were correctly calculated and qualified, as required.

4.6.2 Non-CLP Data Validation

The following data quality issues were addressed in the data validation and review process

for non-CLP analyses.

Holdin g Times

A listing of sampling date, laboratory receipt date, and analysis date was prepared for each

sample in the SDG (Appendix El). The time elapsed between the sampling and analysis

dates was compared with holding time criteria required by 40 CFR 136, if applicable. A

general summary of holding time compliance by the laboratory for each analytical method

is presented in the SDG report.

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BB\1893\ZINCRPT\Final-« 4-15 [Rev 001/13/93 ]
Standard OA/OC for Individual Analytes or Methods

The applicability of QA/QC analysis provided by the laboratory was compared to method

specific or industry accepted standards as required. Control limits specified for CLP analysis

of standards, duplicates and spikes were generally applied to non-CLP methods.

MORRISON KNUDSEN CORPORATION

B8\1893\ZINCRPT\Rn«l-RI 4-16 [Rev 0 01/13/93)
5.0 INTERPRETATION OF RESULTS

The following section of this RI report presents the interpretation of results developed from

zinc slag sample collection and analyses activities. The release mechanisms of primary

concern investigated during the Zinc Slag Pile RI were leaching, wind erosion, runoff of slag

particles, and transport by human activities. (Direct contact has been discounted as a

release mechanism for slag piles in EPA's Preliminary Baseline Human Health Risk

Assessment [EPA. 1991a]). The environmental media potentially impacted by these release

mechanisms are water, soil, and air.

As data are obtained from the speciation and other site-related programs additional data

analyses of potential release mechanisms and impacts as they relate to zinc slag may be

performed. If this additional data affect s interpretations, an addendum to the RI report will

be prepared.

5.1 Statistics

Statistical analyses were used to determine relationships between elemental metal

concentrations in zinc slag samples and those concentrations in the population of all slag

samples. The statistical procedures were performed on total compositional results of the

four primary elements of concern (lead, arsenic, cadmium and zinc), as well as key elements

of the slag matrix (e.g., aluminum, calcium, copper, iron, manganese and silicon). The zinc

slag data set consisted of the four samples collected from the Western Zinc slag pile. The

types of statistical methods are described in Section 5.1.1, and the results are presented in

Section 5.1.2.

5.1.1 Methodology T he types of statistical procedures included the following:

- Summary Statistics

- Cumulative Distribution Functions

- Histograms

- Analysis of Variance

- Cumulative Probability Plots

- Correlation Analysis

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BB\1883\ZINCRPT\Final-RI 5-1 [Rev 0 01/13/93)
Statistical analyses were performed on the discrete zinc slag data set as well as on the lead

slag data sets, for comparative purposes. Summary statistics compiled for each of the data

sets include the range, average, geometric mean, minimum and maximum.

The following table lists the data sets utilized and the number of samples in each of the data

sets:

Arkansas Valley (AV) Water-Quenched Fines 4

AV Sorted Fines 4

AV Air-Cooled 6*

AV Ballast-Sized 4

AV Old Slag 2

Harrison Surface 4

Harrison Old Slag 2

La Plata Surface 5**

La Plata Old Slag 3**

Evans Gulch/Georgia Gulch 4

Western Zinc Slag 4

Subslag Material 1 9

'include s two duplicate samples

**includes an additional sample collected for column leaching tests

5.12 Statistical Results

T he results of the statistical analyses confirm that the constituents within the slag samples

are log-normally distributed; therefore, geometric means have been used to report results.

Lognormality was determined from the data set containing all slag samples (42 samples),

not from individual data subsets. The individual subsets were assumed to be lognormal

based on the observation that the entire data set is lognormal. The followin g discussion is

based on summary statistics, analyses of variance, and cumulative distribution functions.

Arsenic

Arsenic was detected in each of the slag samples analyzed. The range of concentrations

varies from 9.9 to 2,160 mg/kg. The geometric mean of all slag samples analyzed is 217

mg/kg. The zinc data set has a geometric mean of 211 mg/kg, which is not significantly

differen t than the data set as a whole.

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BB\1893\ZINCRPT\Final-RI 5-2 [Rev 0 01/13/93)
Cadmium

Cadmium was detected in 33 of the 42 slag samples analyzed, which is about 79 percent of

the samples. The range of detected values varies from a low of 2.5 mg/kg to a high of 37

mg/kg. The mean of all concentrations is 4.93 mg/kg. Because of the narrow range of

values for cadmium, no discernable difference in populations can be seen from the data,

although the zinc samples are among the highest concentrations with a mean of 14.1 mg/kg.

Lead

Total lead was detected in each of the 42 slag samples analyzed. The concentrations of total

lead ranged from a low of 192 mg/kg to a high of 30,200 mg/kg, or 3 percent lead. The

geometric mean of the samples was 6,660 mg/kg. The Western Zinc pile showed the lowest

mean concentrations for total lead at 568 mg/kg, ranging from 192 to 925 mg/kg.

Zinc

Zinc was detected in all 42 of the slag samples analyzed, ranging from 9,800 to 77,300

mg/kg. The mean of the values is 38,600 mg/kg. The zinc slag pile data set showed the

highest mean concentration of 66,000 mg/kg.

Calcium

Calcium was detected in all of the 42 slag samples analyzed, with a range of concentration

from 12,500 to 145,000 mg/kg. The mean of all slag samples is 83,000 mg/kg. The mean

concentration of the zinc pile is distinctly lower than other piles, at 19,100 mg/kg.

Copper

Copper was detected in each of the 42 slag samples submitted for analysis, with a range of

125 to 3,310 mg/kg. The geometric mean of the copper values is 1,390 mg/kg. The mean

value of the zinc slag is 570 mg/kg.

Iron

Total iron, detected in each of the samples, ranges from 10.8 to 33.2 percent of the slag

matrix. The mean value is 23.8 percent, indicating that iron is a major constituent of the

slag. The Western Zinc slag with a mean of 15.7 percent, is lower in iron than other data

sets.

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Flnal-RI 5~3 (Rev 001/13/93 ]
Manganese

Manganese, also detected in each of the 42 slag samples analyzed, ranges from a low of

4,850 to a maximum of 76,500 mg/kg. The mean of all values is 19,000 mg/kg. The mean

concentration of the Western Zinc samples, 58,400 mg/kg, is elevated with respect to the

other slag samples.

Iicon

Silicon was detected in each of the 42 slag samples collected, with total concentration values

ranging from 101,000 to 154,000 mg/kg or 10 to 15 percent. The geometric mean of all

samples is 130,000 mg/kg. The data is relatively uniform with means for all of the data sets

between 108,000 and 141,750 mg/kg. The geometric mean for the Western Zinc samples

is 14.2%.

5.1.3 Cumulative Probability Plots

Cumulative probability plottin g is a method used to display the data in a way that will

identify the various populations within a data set. A normal cumulative probability plot

consists of an arithmetic horizontal axis and a cumulative probability vertical axis scaled so

that the distribution function will plot as a straight line. A change in slope between linear

segments of a distribution of values represents differen t populations.

Plots of the concentrations of each element analyzed in the slag and subslag samples are

provided in Appendix C, as are rank correlation analysis backup data. From these plots, the

ranges of concentrations representing various populations were identified. The ranges of

concentrations assigned to these populations are summarized in Table 5-1; the population

to which each concentration value belongs is indicated in Tables 5-2, 5-3 and 5-4.

As the data plotted were not transformed prior to generating cumulative probability plots,

breaks in the slope of the lines but do not have significance other than they appear to

represent differen t populations. Relationships between differen t elements were not evident

from the collected data. That is, if a certain set of samples were grouped in a given

population for one element, a second element for that set of samples would also be

expected to fall into a like population grouping. Upon examination of the data, these

correlations were not evident and this analysis was not carried further. Therefore, the

populations are designed only to provide groupings of data in four distinct sets for each

element. Certain elements, based upon the cumulative probability plots , did not appear to

MORRISON KNUDSEN CORPORATION

BB\1883\ZINCRPT\Flnal-RI 5-4 (Rev 0 01/13/93]
TABLES-1. Concentration Ranges of Populations

for Analyses of Slag Determined from Cumulative Probability Plots in Appendix E.

Element

Aluminum, mg/kg

Calcium, mg/kg

Chloride, mg/kg

Iron, mg/kg Magnesium, mg/kg

Manganese, mg/kg

Nitrate, mg/kg

Nitrite, mg/kg

Potassium, mg/kg

Silicon, mg/kg

Sodium, mg/kg

Sulfete, mg/kg

Antimony, mg/kg. Arsenic, mg/kg

Barium, mg/kg

Beryllium, mg/kg

Cadmium, mg/kg

Chromium, mg/kg

Cobalt, mg/kg

Copper, mg/kg

Population 1

min

13,100

1,970

<1

14,000

1,900

650

<1

<1

3,000

100,000

170

29

<5

<4

346

0.3

<0.4

6

<0.8

21

max

20,700

18,900

4

33,000

4,900

1,900

9

4

3,700

113,000

1010

82

31

55

782

0.97

<0.4

44.3

4.9

137

Population 2

min

21,100

42,200

8

108,000

5,700

2,500

20

-

4,400

121,000

1,050

132

46

112

917

1.0

2

45

7.2

261

max

25,300

83,800

20.8

220,000

7,900

10,000

20

-

9,100

139,000

2,100

480

99

414

1,880

1.3

13

81

41.1

602

Population 3

min

30,900

92,800

39

226,000

8,500

11,000

22.7

-

18,000

142,000

5,100

508

108

427

2,070

1.4

14

132

62.6

768

max

63,400

117,000

39

251,000

19,000

26,000

45.4

-

22,000

154,000

8,900

880

197

549

2,870

2.0

18

684

75.4

1,730

Population 4

min

-

121,000

-

260,000

24,000

30,000

-

-

24,000

169,000

13,800

1,000

243

842

3,480

3.4

18.9

943

-

1,940

max

-

145,000

-

332,000

32,000

76,500

-

-

28,000

211,000

13,800

13,040

842

2,160

4,950

3.4

37

1,210

-

3,310
Table 5-1, Page 2 of 2

Element

Lead, mg/kg

Nickel, mg/kg

Selenium, mg/kg

Vanadium, mg/kg

Zinc, mg/kg

Acid Gen.1

Cat. Ex.2

Neutral.

S/Pyrite, %

S/Sulfate, %

S/Non-Ext., %

S/Total, %

Population 1

min

85

<3

<2

8

188

<0.3

0.4

<1

<0.01

<0.01

<0.01

<0.01

max

925

3.3

11.2

40

1,290

<0.3

1.4

84

0.01

0.02

0.30

0.04

Population 2

min

1,590

3.7

44

44.5

9,800

0.6

1.8

98

0.02

0.19

0.50

0.34

max

2,650

8.5

94

103

33,900

3

5.9

300

0.09

0.8

0.75

2.0

Population 3

min

7,580

10.2

-

117

37,200

4.7

6.1

330

0.15

0.8

0.78

2.1

max

12,000

55.6

-

290

55,400

10

15.2

350

0.32

1.4

1.2

2.7

Population 4

min

12,700

190

-

461

63,200

13

24.1

400

0.42

1.6

1.6

3.9

max

30,200

587

-

461

77,300

19

24.1

450

0.60

1.7

2.0

3.9

1

 Acid Generation Potential in units of tons CaCO, equivalents per 1000 tons of material

2

 Cation Exchange Capacity in units of milliequivalents per 100 grams

1

 Neutralization Potential in units of tons CaCO3 equivalents per 1000 tons of material
TABLE 5-2. Major Constituents (ing/kg), in Slag and Subsoils with Values Assigned to Concentration Range Populations- as indicated by Boxes and Shading

{ Population 2

SAMPLE Al Ca O FcII I Mg MB (as NO3) (as NOZ) SI Na

AVO101MOO

AV0102MOO

AVS101MOO

AVS102MOO

AVS103MOO

AVS109MOO

AVS104MOO

AVS105MOO

AVS106MOO

AVS10BMOO

AVS110MOO

AVS112MOO

AVS113MOO

AVS116MOO

AVS107MOO

AVS111MOO

AVS111MOOD

AVS1HMOO

AVS115MOO

AVS11SMOOD

18,000 5.20

3.00

120

230

120

100

100

1.90

1.90

1.80

110

1.80

100

1.90

110

1.90

1.80

170

3.10

180
Table 5-2, Page 2 of 3

(as N03) (as NO2)

1.80

140

120

160

100

SAMPLE

HRO1Q5MOO

HR0106MOO

HRSIOIMOO

HRSIOIMOO

HRS103MOO

HRS104MOO

LPCOLUMNl

LFCOLUMN2

LPOIOSMOO

LPO106MOO

LPS101MOO

LPS102MOO

LPS103MOO

LPS104MOO

OOS101MOO

LES101MOO

MBS101MOO

UES101MOO

Al

i 21,900 ! 78,100 i

K SI Na

! 4,790 ! 123,000 \ 538 } S 5,090 S 121,000 S 884 { i 4,740 ! 131,000 ! 877 i

SO4

<1.00 384.00

<1.00 } 5,090 S 121,000 S 884 { 293.00 IM i 4,740 ! 131,000 \ 877 J -»"

1________________5 ,,_____ .._._.« - —-----_IM[* .

<1.00 i 4mn ! iranm

4,460

"I————————*

! 108,000

.+————-I

<1.00 i 4,460 ! 123,000 |

<1.00 ! 5^30 ) 109,000

<1.00

<1.00 :::!::::;::A::::::::::;:;:;:::::::;::::x:

:5:::::: W::::

:S:ttv:v::::::::::::::::::*:::::::::

577 l;;||||w|i^|ll

3,610 \ 137,000 S 232 LmmmmmmmmmmJ

3,040 i 132,000 j i"

<1.00 ! 5,620 {

<1.00

1^ 22^00 ! 68,900 j
Table 5-2, Pag

e 3 of 3

(as NO3) (as NO2)

AVB101T14

AVB102T17

AVB103T145

AVB104T19

HRB101T10

HRB102T10

HRB103T23

LPB101T34

LFB1021305

LPB1Q31377

HSSIOIMOO

HSS102MOO

HSS103MOO

HSS104MOO
TABLE 5-3. Trace Metals (mg/kg), in Slag and Subsoils with Values Assigned to Concentration Range Populations, as Indicated by Boxes and Shading

Population 1 { Population 2

AVO101MOO

AVO102MOO

AVS101MOO

AVS102MOO

AVS103MOO

AV5109MOO

AVS104MOO

AVS105MOO

AVS106MOO

AVS10SMOO

AVS110MOO

AVS112MOO

AVS113MOO

AVS116MOO

AVS107MOO

AVS111MOO

AVS111MOOD

AVS114MOO

AVS11SMOO

AVS115MOOD

J 440 ! • r

 r TM TMTM TMTM~~

, 1Z.CW , -1—————— H I A AA I

I 1,530 I
Table 5-3, Page 2 of 3

SAMPLE Sb Aa Co Co Pb Nl Se Zn

t

4.20 45.10 '

"————" T

6.70 S 35.60

»mo i «*«w | o.rv |

L

7.40 i 61.90 ! 1.30

j^ ,.l r_t_mj

«*TM1MOO 272.0 | 272.0 0 0 1

SSiiSiiiiSiliiii-------- LES101MOO j ^10

 j 2350,, ! 235.00 I 1,410

MBSIOIMOO a*) |

 moo

uEsioiMoo r"sir"teH

HR0105MOO .

 5770

HR0106MOO | »w~r~MJOO~T~i«"~

HRS101MOO 7i90 ! 220.00 969*"

HRS102MOO

HRS103MOO

HRS104MOO

LPOOLUMN1 I 52^0""]

LPGOLUMN2 | """""""

LPO105MOO i

LP0106MOO j ww j

LFS101MOO

LPS102MOO

LFS103MOO

H\UM\LBADI»T\IU.TAILB54 RBVO
Table 5-3, Page 3 of 3

AVB101T14

AVB102T17

AVBKOTMS

AVB1MT19

HRB101T10

HRB102T10

HRB103TI73

LPB101T34

LPB10CT377

HSS101MOO !

HSS102MOO

HSS103MOO

HSS104MOO

ra\UM\UADIVr\IU-TABLB54 RHV 0
TABLE 5-4. Miscellaneous Measurements in Slag and Subsoils with Values Assigned to Populations, as indicated by Boxes and Shading MMHWMWWV — — —v.......................................,.................^

Population 1 { PopuHUonZ

SAMPLE AGP1 CaEX* N P1 NEx/S4

 Py/S* S<V S* Total ST

AVO101MOO

AVO102MOO

AVS101MOO

AVS1Q2MOO

AVS109MOO

AVS109MOO

AVS104MOO

AVS1QSMOO

AVS106MOO

AVS108MOO

AVS110MOO

AVS112MOO

AVS113MOO

AVS116MOO

AVS107MOO

AVStllMOO

AVS111MOOD

AVS114MOO

AVS11SMOO

AVS115MOOO

220

1.90

150

fr — •

1

1

-j

iI

1

!

l.UI

2.00

IM

050

0.40

0.90

1.00

0.40

——— —

____

——— —

——— —

...

0.90

0.80

130 r

QSO

ISO !

1.40

1.67
Table 5-4, Page 2 of 3

SAMPLE AGP* CaEX* N P* NEx/S4 Py/S5 SO«/S* Total S7

HRO1QSMOO

HRO106MOO

HRS101MOO

HRS102MOO

HRS103MOO

HRS104MOO

LPCOLUMN1

LPCOLUMN2

LP010SMOO

LPO106MOO

LFS101MOO

LPS102MOO

LPS103MOO

LPS104MOO

OOS101MOO

LES101MOO

MES101MOO

UES101MOO

<OJO

<OJO

1.02

.__

I 0.65 ]

|j mMmMMMma^MJ

<0.01 I 0.60

(._____—_..

iiiiiriiriiii'iiiriiia'ffiif c '^jiiiiiiii't'i iii'i'i iri'i^iM.'iikiai'iii» 0.65 I 1.00

1.19

M\im\UMIHVIMU-TABLB54. RBV «
Table 5-4, Page 3 of 3

AVB101T14

AVB102T17

AVBKOTUS

AVBUMT19

HRB101T10

HRD102T10

HRB107T23

LPB101T34

LPB1Q2TM5

LPBUBTI377

HSS101MOO

HSS102MOO

HSS103MOO

HSS104MOO

1

1 Acid Generation Potential (tons of CaCO, equivalents per 1000 tons material)

3 Cation Exchange Capacity (milliequtvalents per 100 grams)

4 Neutralization Potential (tons of CaCO, equivalents per 1000 tons material)

 Non-Extractablc Sulfur (%)

•yiiai nri» • «r»^>nin

4 Neutralization roienuai ^101

5 Non-Extractablc Sulfur (%)

 Pyritic Sulfur (%)

*

7 Sulfatc(%)

 Total Sulfur

•B\im\LEADIVniU-TABLa5-4. REV 0
contain four populations. In these cases, populations were assigned based upon the number

of discernable groups of data.

Comparison of the major elements shows differences between the zinc slag and the other

slag sample data sets (Table 5-2). The differences between slag from the differen t piles is

illustrated by the aluminum, calcium, iron, sulfate, and manganese concentrations. The zinc

data set is generally higher in manganese and sulfate and lower in iron, aluminum and

calcium when compared to the data sets as a whole. The concentrations of trace metals are

generally variable throughout the slag piles (Table 5-3). The Western Zinc data set is low

in lead and high in zinc and cadmium when contrasted with the other slag samples.

In summary, the Western Zinc samples are higher in manganese, sulfate, zinc and cadmium,

and lower in lead, aluminum, iron and calcium when compared to all slag data.

5.1.4 Statistical Summary Information from which the above discussions and conclusions were derived are presented

in Appendix C of this report. The log normality of the data is verified through the

examination of histograms. The statistical results show that the Western Zinc slag pile

differs in certain elements from the slag data set as a whole.

5.2 Potential for Water Quality Impacts

Test results showed that the tendency for zinc slag to leach metals to aqueous solutions is

minimal, as all eluate concentrations were well below toxic characteristic criteria for the

primary metals of concern. However, as with all metals-containing environmental media,

some leaching does occur. Calculations were performed to determine the potential metals

load from the zinc slag pile, based on the results of the SPLP and column leach tests. Data

from the other PRP RI effort s may be used to refine assumptions used in these loading

calculations and to evaluate whether the potential loadings represent a significant

environmental impact.

Calculations were performed for three of the primary elements of concern -- lead, cadmium

and zinc. Loading calculations for arsenic, the fourth primary element of concern, were not

performed because of the significant number of non-detect results in the analytical data. In the subsection 5.2.3, the SPLP and column leach loading estimates have been combined

to develop a best estimate based on the results of both tests and site-specific information. The assumptions and calculation methods used, a tabulation of results, and a discussion

MORRISON KNUOSEN CORPORATION

BB\1883\ZINCRPT\Rnal-RI 5~5 [Rev 001/13/93 ]
concerning the potential for water quality impacts are presented below. Appendix D2

contains the calculation sheets and supporting documentation. Summaries of the leaching

test methodologies, as well as the results of the actual tests, were presented earlier in this

report.

52.1 Metals Loading Based on SPLP Results

The SPLP test (Method 1312) was designed to determine the mobility of metals by

simulating the effec t of high country precipitation percolating through a mine waste pile. Results of the procedure simulate the buffered, oxygen-depleted conditions in the ulterior

of the piles. Annual metals loading from the zinc slag pile (mass per year) was estimated

by multiplying the SPLP eluate concentration (in ug/1) by the number of liters of

precipitation contacting the zinc slag pile in one year. The following assumptions have been

used to estimate annual loading:

• The annual precipitation for Leadville is 12.67 inches per year (Res-ASARCO, 1991)

• All precipitation infiltrates the pile; runon and runoff were considered to balance

out and evaporation/sublimation was not considered

No ground water flows into the piles to interact with percolating water

Precipitation percolates through the pile, achieving a metals concentration

represented by the eluate chemical concentrations, and exits the pile to the California

Gulch hydrologic system

• The metals concentrations are geometric means of the SPLP data

Pile surface area is assumed to be the 'footprint* of the pile, calculated from the plan

view (Figure 4-1) as 201,000 square feet , and is used for precipitation volume

calculations

T he results of the zinc slag pile loading calculations from SPLP concentrations for lead,

cadmium, and zinc are estimated at 0.1, 0.01, and 0.4 kilograms per year, respectively.

The SPLP tests are considered to overestimate the actual mass leached under oxygendeficient conditions for the reasons given below:

MORfflSON KNUDSEN CORPORATION

BB\1883\ZINCRPT\Rnal-RI 5"6 [Rev 001/13/93 ]
The lixiviant contains none of the carbonate buffer in natural rainfall. The absence

of carbonate buffering capacity may intensify leaching, especially in cases where the

dominant mineral species are carbonate or sulfide based.

The samples are tumbled during the test, allowing the sample material to constantly

impact and grind together, potentially generating fresh surfaces for the lixiviant to

contact. This does not occur under the relatively static conditions of a slag pile.

522 Metals Loading Based on Column Leach Results

A column leach test was performed on a zinc slag sample in order to simulate high country

precipitation percolating through the slag pile under unsaturated conditions. Results of this

test represent the situation at the surface of the pile. Annual metals loading from the zinc

slag pile (mass per year) was estimated by scaling the total mass of leached metal of concern

from column leach testing (in ug) to the total mass of the slag pile and the number of years

of precipitation represented by the test. The following assumptions, in addition to those

stated in the SPLP section above, have been used to estimate annual metals loading:

Mass of metal leached from column leach tests

• mass leached equaled integration by trapezoidal rule of the eluate

concentrations from event 0 to event 100 (i.e., the area under the curve)

• event 0 leached 0.0 ug/1

• for values reported as below detection limit, one-half of the detection limit

was used

Mass of slag pile

• mass was calculated based on measured pile volumes, specific gravity and

estimated porosity

• volume of the slag pile was taken from Figure 4-1 as 35,000 cubic yards

• specific gravity of the slag (3.25) was equal to that of the < 10 mesh fraction

• slag pile porosity was conservatively estimated at 25%

MORRISON KNUOSEN CORPORATION

BB\1883\ZlNCRFT\Flnal-Rl 5-7 [Rev 001/13/93 )
The results of the zinc slag pile loading calculations based on column leach test eluate

concentrations for lead, cadmium and zinc are estimated at 0.6, 2, and 380 kilograms per

year, respectively.

The column leach tests are more aggressive than actual site conditions for several reasons:

The IMviant contains none of the carbonate buffer in natural rainfall. The

absence of carbonate buffering capacity will likely intensify leaching, especially

where the dominant mineral species is carbonate or sulfide based. The

sulfuric acid/nitric acid based lixiviant is more aggressive than a carbonic

acid-based lixiviant that would be more similar to natural rainfall.

The effec t of wet and dry cycling during testing simulates the reaeration

period that likely occurs near the surface of the slag pile between

precipitation events when snow cover is not present. If these results were

extrapolated to the slag pile at depth, loading calculations would be overly

aggressive because reaeration of the material in the interior of the pile would

not likely occur under site conditions. Additionally, in the natural setting, a

much longer drying or aeration period is expected rather than equivalent

periods of wet and dry. These longer dry cycles are expected to facilitate

reformation of oxidation rinds on the particles.

The column leach testing performed can also be considered aggressive since

results indicated that the slag piles have not reached steady-state leaching

conditions in Leadville, as would be assumed from the number of years

exposure to atmospheric conditions. The depletion of bicarbonate and sulfate

and increasing trends in leached metals concentrations during testing indicated

that steady-state conditions, as they likely exist in Leadville, were not

completely simulated. If column conditions were similar to expected in situ

conditions, the anions would not show a depletion effec t or the metals an

increasing trend.

5.2.3 Metals Loading Based on Combination of SPLP and Column Leach Results

Based on the above discussion, the use of a combination of SPLP and column leach results

would provide the best estimate of the annual metals load leached from the zinc slag pile. The column leach results were used to estimate the leaching that occurs in the area of the

MORRISON KNUDSEN CORPORATION

BB\1883\ZINCRPT\Final-RI 5"8 [Rev 001/13/93 ]
slag pile where reoxygenation of the slag is likely to occur either by exposure to atmospheric

oxygen or oxygenated water. Four feet, a distance that is slightly greater than two times the

length of the columns used, has been assumed to represent this zone. The use of this

distance is further justified by the observation that the column leach eluate pH approached

the SPLP final pH after percolation through the columns. The SPLP results have been used

to estimate the quantity of metals that could be leached from any part of a slag pile at

depths greater than four feet where the environment is oxygen-deficient. The amount of a

given pile greater than or less than four feet thick was estimated from the average thickness,

determined by dividing the pile volume by the plan view surface area. Using the

combination of SPLP and column leach results, the resulting estimated metals load from the

zinc slag pile for lead, cadmium and zinc is 0.5,1.6 and 330 kilograms per year, respectively. These loading estimated may be refined as additional information becomes available.

5.3 Potential for Soil Impact s

The results of the reconnaissance of the zinc slag pile showed no significant impact to

surface soils in the vicinity of the pile. No evidence of particulate movement off the piles

was noted in the field. In addition, air pathway analysis did not indicate the potential for

windblown fines to impact soils. Subslag material was not sampled at the zinc slag pile.

5.4 Slag Pile Stability The structural (geotechnical) stability of the zinc slag pile was evaluated during the field

reconnaissance task. The pile is generally low, with only a small area of significant height

(approximately 15 feet) , and exhibits no signs of significant fracturing. Therefore, the pile

presents no stability concern.

Because of the vesicular nature of the zinc slag, freeze/thaw cycling may have some impact

on zinc slag. Some disintegration of the slag may be occurring due to pressure exerted by

freezing water in the slag vugs. However, as there does not appear to be significant runoff

from the pile or wind erosion, any disintegration does not appear to have an impact on the

environment.

5.5 Potential for Air Quality Impact s

Analysis of emissions calculations using the 1991 meteorological data from the Colorado

Mountain College (Res-ASARCO, 199 la) and the mode of the aggregate size distribution

have demonstrated that wind erosion does not occur from the Western Zinc slag pile. This

conclusion was reached by following industry-standard procedures and guidance from the

MORRISON KNUDSEN CORPORATION

BB\1893\ZINCRPT\Final-R1 5-9 [Rev 001/13/83]
EPA regional office in Denver, Colorado (EPA, 1992). The procedures, described in

Section 3.4.2, were used to determine the friction velocity (wind speed at the pile surface)

and the threshold friction velocity (minimum wind speed at which particles will become

airborne). The friction velocity of 0.55 m/sec was then compared to the threshold friction

velocity for the zinc slag (1.0 m/sec). A friction velocity lower than the threshold, shows

that Leadville wind speeds are not fast enough to cause wind erosion from the pile.

The results can be further explained by examining the factors involved in emissions

potential. The small silt and clay size fractions, defined as the amount of material that

passes through a 200-mesh sieve, have the greatest potential for erosion. In the Western

Zinc pile, this fraction is less than 6 percent. This, along with the moderate maximum

hourly average wind speed in Leadville, limits the fines ability to become airborne.

An additional factor that was not included in the calculations, but would further limit

credibility is the extended periods of snow cover in Leadville. Periods of high moisture and

winter snow cover would suppress any potential for fugitive dust emissions. Climatological

observations from the Leadville airport indicate that there is a persistent snow cover from

November through April. In addition, July and August are typically months of high

precipitation (Res-ASARCO, 199 la). The emissions calculations do not take into account

any conditions other than those ideal for wind erosion of material.

5.6 Anthropogenic Distribution

Distribution of the zinc slag has not been documented; however, a significant volume

decrease has occurred over the last several decades. Site reconnaissance showed what

appears to be material from the Western Zinc pile on roadways and road shoulders within

the site. Zinc slag has not been used by railroads in the Leadville area.

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6 .0 SUMMARY AND CONCLUSIONS

This section summarizes the findings of the Zinc Slag Pile Remedial Investigation based on

the data collected and evaluated to date. Each of these results have been described in

greater detail earlier in the RI.

6.1 Summary of Zinc Slag Characteristics

The results of the field reconnaissance, physical testing, and analytical testing, as well as

impacts to water, soil, and air are summarized below.

Physical Characteristics

Zinc slag is a highly vesicular material consisting of mostly coarse particle sizes. The

fraction of zinc slag passing the 200-mesh sieve is less than 6 percent. For the fine fraction,

approximately 7 percent of the material is < 100 /xm and one percent is < 10/xm.

The zinc slag pile is generally low, with only a small area of significant height

(approximately 15 feet). The zinc slag pile does not present a stability concern.

Because of the vesicular nature of the zinc slag, freeze/thaw cycling may have some impact

on zinc slag. However, as there does not appear to be significant runoff from the pile or

wind erosion, any disintegration does not appear to have an impact on the environment.

Chemical Characteristics

Iron and silicon compose the majority of the zinc slag material ranging up to 20% and 15%

respectively. The geometric mean concentrations of the primary metals of concern are as

follows:

• Lead-568 mg/kg

•Cadmium— 14.1 mgkg

•Arsenic-211 mg/kg

•Zinc-66,000 mg/kg

The mineral species with which these metals are bound (e.g., oxide, sulfide, sulfate) will be

determined by other investigators and reported in forthcoming metals speciation reports.

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The dominant form of sulfur is sulfate sulfur. Acid generation potential due to pyritic

sulfur, when detected, is more than compensated by neutralization potential due to

carbonate species. This results in a negative acid forming potential.

T he Synthetic Precipitation Leaching Procedure (SPLP) results for all elements for all

samples were below the toxicity characteristic criteria listed in 40 CFR 261.24 of 100 times

primary drinking water standards. Mean values were generally more than two orders of

magnitude lower than toxicity criteria. Additionally, results for those analytes that were

compared to criteria of 100 times the secondary drinking water quality standards were lower

than those criteria.

Statistical Analyses

The results of the statistical analyses indicate that the constituents within the zinc slag

samples are log-normally distributed.

Comparisons of the zinc slag data with lead slag data sets show that the zinc slag pile is

lower in lead and iron and higher in zinc and manganese than the lead slag.

Water Quality Impacts

Based on the metals concentrations in the eluants of the two types of leaching tests

performed on zinc slag samples (SPLP and column leach), potential annual metals loading

from the zinc slag pile has been estimated. Calculations were performed for three of the

primary elements of concern — lead, cadmium and zinc. Arsenic metal loading was not

calculated because of non-detectable arsenic concentrations for the majority of the leachate

samples.

Using the combination of SPLP and the zinc column leach results, the metals load for the

zinc slag pile for lead, cadmium and zinc is conservatively estimated at 0.5, 1.6 and 330

kilograms per year, respectively. These loading estimates may be refined as additional

information becomes available.

Soil Quality Impacts

Results of the reconnaissance of the zinc slag pile showed no obvious impacts to surface

soils in the vicinity of the pile. No evidence of particulate movement off the pile was noted.

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A ir Quality Impacts

Emissions calculations demonstrate that wind erosion does not occur from the zinc slag pile

and it can be concluded that there are no significant impacts from the zinc slag pile during

undisturbed conditions.

62 Conclusions Regarding the Site Conceptual Model

The site conceptual model for the Slag Pile RI (Figure 1-2) was developed by EPA and the

Risk Assessment Technical Assistance Committee and presented in the work plan for the

Slag Pile RI (MK, 1991a). The conceptual model presents five potential release

mechanisms for the slag piles. These are:

- wind

- leaching

- mixing by human activities

- runoff (of particulate slag)

- direct contact

If certain release mechanisms can be shown not to occur, then secondary sources, exposure

routes and potential receptors do not form a complete pathway. The following discussion

applies the conclusions of the RI activities to each of the primary release mechanisms in

order to show whether the conceptual model is valid for that particular mechanism. Each

release mechanism is addressed in the order presented above.

Release Mechanism 1 - Wind

Wind erosion, or deflation of the zinc slag pile by wind, is addressed in Sections 4.4.2 and

5.5 of this report. Hourly average wind speed data multiplied by the appropriate factor to

determine the maximum sustained wind gust does not meet or exceed the frictional velocity

necessary to lift particles off the stationary pile. Therefore, the air pathway analysis results

show that wind erosion is not a viable release mechanism for the zinc slag pile.

Release Mechanism 2 - Leaching

Leaching of elements of concern were tested by two differen t leaching procedures (SPLP

and column leach), yielding the quantities of metals leached from a given mass or volume

of the zinc slag pile. Quantity of metals leached were calculated by portioning the pile by

whether it could most likely be represented by column leach or SPLP testing results. The

zinc slag pile has the potential to contribute a small metals load of three of the elements

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of concern. However, the concentration of zinc, lead, and cadmium are all below leaching

criteria established by EPA of 100 times drinking water standards.

Additional data collection activities are currently being undertaken under other PRP work

plans to better define the hydrologic system in the vicinity of the major slag piles and along

California Gulch. Key additional data to be evaluated include the portions of the Gulch

that are gaining and losing streams, water quality data from piezometers, monitor wells and

surface water sampling, and flow rates during the course of the year. Another consideration

is the calculation of the residual sediment load and the contribution from other sources (i.e.

tailings and soils) to the stream channel. At this time, the evaluations of impacts from

leaching have been conservatively calculated. Additional considerations such as soil

sorption, evaporation, dilution by ground and surface water, and sheet runoff of precipitation

will need to be further evaluated before estimates of contribution to the hydrologic system

can be completed. At this time, leaching as a release mechanism is retained.

Release Mechanism 3 - Mixing by Human Activities

Distribution of zinc slag by human activity has not been documented; however, volume

decreases and evidence of the material on Leadville roadways indicate use.

Release Mechanism 4-Runoff of Slag No evidence of transport of slag fines by surface runoff was observed at the zinc pile. Slag

does not appear to run off piles onto adjacent soils in rivulets or channels. This primary

release mechanism for slag should be eliminated as a concern at the site.

Release Mechanism 5-Direct Contact

Direct contact with the slag piles was considered insignificant in EPA's Preliminary Baseline

Human Health Risk Assessment (EPA, 1991a). Therefore, it can be eliminated as a release

mechanism.

Summary of Verification of the Conceptual Model

Of the five primary release mechanisms identified in the site conceptual model, only one

can be considered viable based on findings provided in this Zinc Slag Pile Remedial

Investigation. The one retained release mechanism is leaching. Before determining the

actual contribution of leached constituents from the zinc slag pile, and their potential

environmental significance, collation and summarization of data collected as part of other

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work programs will need to be evaluated. All other primary mechanisms have been

eliminated as a result of this remedial investigation.

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7.0 REFERENCES

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(Reapproved 1990), Annual Book of ASTM Standards, 1992.

ASTM, 1992b. Standard Practice for Sampling Aggregates, Designation: D-75-87, Annual

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Blair, 1980. Leadville: Colorado's Magic City by Edward Blair, Pruett Publishing Company, Boulder, Colorado, 1980.

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Environmental Protection Agency, December, 1991.

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EPA, 1990a. Contract Laboratory Program Statement of Work for Inorganics Analysis, SOW4/90.

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and Solid Media, February 1989.

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California Gulch Site, Leadville, Colorado, U.S. EPA, Prepared by CH2M Hill, May

1989.

EPA, 1988a. Compilation of Air Pollutant Emission Factors, Volume 1: Stationary Point

and Area Sources, Fourth Edition. AP-42. U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711. Update of Fugitive Dust Emission

Factors in AP-42 Section 11.2 - Wind Erosion. MRI No. 8985-K, Midwest Research

Institute, Kansas City, MO., 1988.

EPA, 1988b. Laboratory Data Validation Functional Guidelines for Evaluating Inorganics Analyses (draft) , U.S. EPA Hazardous Site Evaluation Division, July 1, 1988.

EPA, 1986. Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, SW-846

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and Wastes, U.S. EPA, Environmental Monitoring and Support Laboratory,

Cincinnati, Ohio, December 1982.

EPA, 1978. Field and Laboratory Methods Applicable to Overburdens and Minesoils, EPA600/2-78-054, U.S. Environmental Protection Agency, March 1978.

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MK, 1992. Interim Draft Report Lead Slag Pile Remedial Investigation at the California Gulch Site, Leadville, Colorado, prepared by Morrison Knudsen Corporation for Denver & Rio Grande Western Railroad Company, July 6, 1992.

MK, 199 la. Work Plan for Slag Pile Remedial Investigation at California Gulch Site •

Leadville, Colorado, Prepared by Morrison-Knudsen Corporation for Denver & Rio

Grande Western Railroad Company, October 1991.

MK, 199 Ib. Sampling and Analysis Plan for Slag Pile Remedial Investigation at California Gulch Site, Leadville, Colorado, Prepared by Morrison Knudsen Corporation

Environmental Services Division for Denver & Rio Grande Western Railroad

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NADP, 1990. National Atmospheric Deposition Program (lR-7)/National Trends Network, NADP/NTN Coordination Office , National Resource Ecology Laboratory Colorado

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