California Gulch Five-Year Report

Page i of v 

 

Five-Year Review Report

Table of Contents

 

Executive Summary.................................................................................................................. ES-1 

1.0 Introduction......................................................................................................................... 1 

2.0 Site Chronology .................................................................................................................. 2 

3.0 Background......................................................................................................................... 4 

4.0 Administrative Components and Community Involvement ............................................... 9 

5.0 Operable Units .................................................................................................................. 11 

6.0 Operable Unit 1-Yak Tunnel/Water Treatment Plant....................................................... 12 

6.1 Description............................................................................................................ 12 

6.2 Response Actions.................................................................................................. 13 

6.3 Progress Since the Last Five Year-Review........................................................... 13 

6.4 Five-Year Review Process.................................................................................... 14 

6.5 Technical Assessment........................................................................................... 15 

6.6 Issues..................................................................................................................... 16 

6.7 Recommendations and Follow-Up Actions.......................................................... 17 

6.8 Protectiveness Statement ...................................................................................... 17 

7.0 Operable Unit 2 - Malta Tailing Impoundment, Malta Gulch Tailing Impoundment and 

Lower Malta Gulch Fluvial Tailing .................................................................................. 18 

7.1 Description............................................................................................................ 18 

7.2 Response Actions.................................................................................................. 20 

7.3 Progress Since the Last Five Year Review........................................................... 21 

7.4 Five-Year Review Process.................................................................................... 21 

7.5 Technical Assessment........................................................................................... 22 

7.6 Issues.................................................................................................................... 23 

7.7 Recommendations and Follow-Up Actions.......................................................... 24 

7.8 Protectiveness Statement ...................................................................................... 24 

8.0 Operable Unit 3 - Denver & Rio Grande Railroad (D&RG) Slag Piles/Railroad 

Easement/Railroad Yard ................................................................................................... 25 

8.1 Description............................................................................................................ 25 

8.2 Response Actions.................................................................................................. 27 

8.3 Progress Since the Last Five Year Review........................................................... 28 

8.4 Five-Year Review Process.................................................................................... 29 

8.5 Technical Assessment........................................................................................... 29 

8.6 Issues.................................................................................................................... 30 

8.7 Recommendations and Follow-Up Actions.......................................................... 30 

8.8 Protectiveness Statement ...................................................................................... 31 

9.0 Operable Unit 4 - Upper California Gulch ...................................................................... 32 

9.1 Description............................................................................................................ 32 

9.2 Response Actions.................................................................................................. 33 

9.3 Progress Since the Last Five Year Review........................................................... 36 

9.4 Five-Year Review Process.................................................................................... 36 

9.5 Technical Assessment........................................................................................... 36 

9.6 Issues..................................................................................................................... 37 
California Gulch Five-Year Report

Page ii of v 

9.7 Recommendations and Follow-Up Actions.......................................................... 38 

9.8 Protectiveness Statement ...................................................................................... 38 

10.0 Operable Unit 5 - Asarco Smelters/ Colorado Zinc-Lead Mill Site ................................. 39 

10.1 Description............................................................................................................ 39 

10.2 Response Actions.................................................................................................. 41 

11.0 Operable Unit 6 - Starr Ditch/Penrose Dump/Stray Horse Gulch/Evans Gulch ............. 43 

11.1 Description............................................................................................................ 43 

11.2 Response Actions.................................................................................................. 45 

11.3 Progress Since the Last Five Year Review........................................................... 48 

11.4 Five-Year Review Process.................................................................................... 48 

11.5 Technical Assessment........................................................................................... 49 

11.6 Issues..................................................................................................................... 50 

11.7 Recommendations and Follow-Up Actions.......................................................... 50 

11.8 Protectiveness Statement ...................................................................................... 51 

12.0 Operable Unit 7 - Apache Tailing Impoundments............................................................ 52 

12.1 Description............................................................................................................ 52 

12.2 Response Actions.................................................................................................. 54 

12.3 Progress Since the Last Five Year-Review........................................................... 56 

12.4 Five-Year Review Process.................................................................................... 56 

12.5 Technical Assessment........................................................................................... 56 

12.6 Issues..................................................................................................................... 57 

12.7 Recommendations and Follow-Up Actions.......................................................... 58 

12.8 Protectiveness Statement ...................................................................................... 58 

13.0 Operable Unit 8 - Lower California Gulch...................................................................... 59 

13.1 Description............................................................................................................ 59 

13.2 Response Actions.................................................................................................. 61 

13.3 Progress Since the Last Five Year Review........................................................... 64 

13.4 Five-Year Review Process.................................................................................... 64 

13.5 Technical Assessment........................................................................................... 65 

13.6 Issues..................................................................................................................... 66 

13.7 Recommendations and Follow-Up Actions.......................................................... 66 

13.8 Protectiveness Statement ...................................................................................... 67 

14.0 Operable Unit 9 - Populated Residential Areas ................................................................ 68 

14.1 Description............................................................................................................ 68 

14.2 Response Actions.................................................................................................. 70 

14.3 Progress Since the Last Five Year-Review........................................................... 72 

14.4 Five-Year Review Process.................................................................................... 72 

14.5 Technical Assessment........................................................................................... 73 

14.6 Issues..................................................................................................................... 74 

14.7 Recommendations and Follow-Up Actions.......................................................... 75 

14.8 Protectiveness Statement ...................................................................................... 75 

15.0 Operable Unit 10 - Oregon Gulch..................................................................................... 76 

15.1 Description............................................................................................................ 76 

15.2 Response Actions.................................................................................................. 77 

15.3 Progress Since the Last Five Year Review........................................................... 80 

15.4 Five-Year Review Process.................................................................................... 80 

15.5 Technical Assessment........................................................................................... 81 

15.6 Issues..................................................................................................................... 82 
California Gulch Five-Year Report

Page iii of v 

15.7 Recommendations and Follow-Up Actions.......................................................... 82 

15.8 Protectiveness Statement ...................................................................................... 83 

16.0 Operable Unit 11- Arkansas River Valley Floodplain...................................................... 84 

16.1 Description............................................................................................................ 84 

16.2 Removal Actions................................................................................................... 85 

16.3 Progress Since the Last Five Year-Review........................................................... 87 

17.0 Operable Unit 12............................................................................................................... 88 

18.0 Next Review...................................................................................................................... 89 

 Tables

Table 2-1: Chronology of Activities at California Gulch Site....................................................... 2 

Table 3-1: Land Use-Based Remediation Goals............................................................................ 7 

Table 6-1: Chronology of Site Events for OU1 Yak Tunnel and Water Treatment Plant.......... 12 

Table 6-2: OU1 Issues Identified................................................................................................. 16 

Table 6-3: OU1 Recommendations for Follow-Up Actions........................................................ 17 

Table 7-1: Types of Contamination in Each Media for OU2 ...................................................... 19 

Table 7-2: Chronology of Site Events for OU2........................................................................... 19 

Table 7-3: Removal Actions for OU2.......................................................................................... 20

Table 7-4: OU2 Issues Identified................................................................................................. 23 

Table 7-5: OU2 Recommendations for Follow-Up Actions........................................................ 24 

Table 8-1: Types of Contamination in Each Media for OU3 ...................................................... 26 

Table 8-2: Chronology of Site Events for OU3........................................................................... 26 

Table 8-3: OU 3 Issues Identified................................................................................................ 30 

Table 8-4: OU3 Recommendations for Follow-Up Actions........................................................ 30 

Table 9-1: Chronology of Site Events for OU4........................................................................... 33 

Table 9-2: Remedial and Removal Activities at OU4 ................................................................. 34 

Table 9-3: OU4 Issues Identified................................................................................................. 37 

Table 9-4: OU4 Recommendations for Follow-Up Actions........................................................ 38 

Table 10-1: Types of Contamination in Each Media................................................................... 39 

Table 10-2: Chronology of Site Events for OU5......................................................................... 40 

Table 10-3: Remedial Actions for OU5....................................................................................... 41 

Table 11-1: Types of Contamination in Each Media................................................................... 44 

Table 11-2: Chronology of Site Events for OU6......................................................................... 44 

Table 11-3: Removal Actions for OU6........................................................................................ 45 

Table 11-4: OU6 Issues Identified............................................................................................... 50 

Table 11-5: OU6 Recommendations for Follow-Up Actions...................................................... 50 

Table 12-1: Types of Contamination in Each Media................................................................... 52 

Table 12-2: Chronology of Site Events for OU7......................................................................... 53 

Table 12-3: Removal and Remedial Actions for Apache Tailing Impoundments....................... 54 

Table 12-4: OU7 Issues Identified............................................................................................... 57 

Table 12-5: OU7 Recommendations for Follow-Up Actions...................................................... 58 

Table 13-1: Types of Contamination in Sites Within OU8 ......................................................... 60 

Table 13-2: Chronology of Site Events for OU8......................................................................... 61 

Table 13-3: Removal/Remedial Actions for OU8 ....................................................................... 62 

Table 13-4: OU8 Issues Identified............................................................................................... 66 

Table 13-5: OU8 Recommendations for Follow-Up Actions...................................................... 66 
California Gulch Five-Year Report

Page iv of v 

Table 14-1: Chronology of Site Events for OU9......................................................................... 68 

Table 14-2: Removal Actions for OU9........................................................................................ 70 

Table 14-3: Trigger Levels for Lead............................................................................................ 71 

Table 14-4: OU9 Issues Identified............................................................................................... 74 

Table 14-5: OU9 Recommendations for Follow-Up Actions...................................................... 75 

Table 15-1: Types of Contamination in Each Media................................................................... 76 

Table 15-2: Chronology of Site Events for OU10....................................................................... 77 

Table 15-3: Removal and Remedial Actions for OU10............................................................... 78 

Table 15-4: OU10 Issues Identified............................................................................................. 82 

Table 15-5: OU10 Recommendations for Follow-Up Actions.................................................... 82 

Table 16-1: Chronology of Site Events for OU11....................................................................... 85 

Table 16-2: Removal Actions for OU11...................................................................................... 85 

Figures

Figure 3-1 Operable Unit Boundaries 

Figure 7-1 OU2 Site Map 

Figure 8-1 OU3 Site Map 

Figure 9-1 OU4 Site Map 

Figure 10-1 OU5 AV/CZL Site Map 

Figure 10-2 OU5 EGWA Smelter Site Map 

Figure 11-1 OU6 Previous Removal Actions 

Figure 12-1 Post Remedial Condition OU7 and OU10 

Figure 13-1 OU8 Site Map 

Appendix

Appendix A Figures 

Appendix B Summary of Public Comments 

Appendix C Site Photographs 
California Gulch Five-Year Report

Page v of v 

List of Acronyms

AOC Administrative Order on Consent 

ARD Acid Rock Drainage 

ARARs Applicable or Relevant and Appropriate Requirements 

AV Arkansas Valley 

BERA Baseline Environmental Risk Assessment 

CD Consent Decree 

CDPHE Colorado Department of Public Health and Environment 

CERCLA Comprehensive Environmental Response, Compensation and Liability Act 

CZL Colorado Zinc-Lead 

D&RG Denver and Rio Grande Railroad 

D&RG W Denver and Rio Grande Western Railroad 

DMR Discharge Monitoring Report 

EE/CA Engineering Evaluation/ Cost Analysis 

EPA Environmental Protection Agency 

ESD Explanation of Significant Differences 

FS Feasibility Study 

FTS Fluvial Tailing Site 

HASP Health and Safety Plan 

HDPE High Density PolyEthylene 

LCCHP Lake County Community Health Program 

MOU Memorandum of Understanding 

NCP National Oil and Hazardous Substances Pollution Contingency Plan 

NPL National Priorities List 

O&M Operation and Maintenance 

OCC Ore and Chemical Company 

OU Operable Unit 

PRG Preliminary Remediation Goals 

POC Point of Compliance 

PPM Parts Per Million 

RA Remedial Action 

RD/RA Remedial Design/Remedial Action 

RI/FS Remedial Investigation/Feasibility Study 

ROD Record of Decision 

SFS Screening Feasibility Study 

SPLP Synthetic Precipitation Leaching Procedure 

TDS Total Dissolved Solids 

TRV Toxicity Reference Values 

TSS Total Suspended Solids 

TVS Table Value Standards 

UAO Unilateral Administrative Order 

U.S. EPA United States Environmental Protection Agency 

USGS United State Geological Survey 

WQC Water Quality Criteria 

WQS Water Quality Standards 
California Gulch Five-Year Report

ES-1

Executive Summary 

The U. S. Environmental Protection Agency (EPA) Region VIII has conducted a five-year 

review of the remedial actions implemented at the California Gulch Site in Lake County, 

Colorado. The purpose of this five-year review is to determine whether the remedy at the site is 

protective of human health and the environment. In addition, this five-year review report 

identifies deficiencies found during the review, if any, and identifies recommendations to address 

them. 

The California Gulch Site is located in Lake County, Colorado in the upper Arkansas River 

watershed, approximately 100 miles southwest of Denver. The site encompasses approximately 

18 square miles and includes the towns of Leadville and Stringtown; various parts of the 

Leadville Historic Mining District; and a section of the Arkansas River from the confluence of 

California Gulch downstream to the confluence of Two-Bit Gulch. The California Gulch Site 

consists of the following 12 Operable Units (OUs): 

OU1 - Yak Tunnel/Water Treatment Plant 

OU2 - Malta Gulch Fluvial Tailing/Leadville Corp. Mill/Malta Gulch Tailing Impoundments 

OU3 - Denver & Rio Grande Railroad (D&RG) Slag Piles/Railroad Easement/Railroad Yard 

OU4 - Upper California Gulch 

OU5 - Asarco Smelters/Slag/Mill Sites 

OU6 - Starr Ditch/Penrose Dump/Stray Horse Gulch/Evans Gulch 

OU7 - Apache Tailing Impoundments 

OU8 - Lower California Gulch 

OU9 - Residential Populated Areas 

OU10 - Oregon Gulch 

OU11 - Arkansas River Valley Floodplain 

OU12 - Site Water Quality 

This is the third five-year review of the California Gulch Site. The trigger action for this review 

is the completion of the second five-year review on September 29, 2001. Due to the fact that 

hazardous substances, pollutants, or contaminants remain at the site above levels that allow for 

unrestricted use and unlimited exposure, another five-year review is required. 

Remedies have not been completed in OUs 5, 6, and 11. In addition, a record of decision (ROD) 

has not been released for OU12. Therefore, these OUs were not formally assessed under the 

Five-Year Review although a summary of progress to date and potential issues of concern is 

provided in the body of the Report. Remaining OUs were subjected to a comprehensive 

performance review. 

Remedies are being monitored and maintained as required and generally are performing as 

intended. The primary issue of concern identified in this Five-Year Review is the lack of 

adequate land use controls (institutional controls (ICs)) to ensure future remedy protectiveness. 

In some instances ICs are required under RODs but have not been implemented, as is the case 

with OUs 7 and 8. In other instances, ICs are necessary to ensure long-term protection but were 

not required under the ROD, as is the case in OUs 3, 4 and 10. 
California Gulch Five-Year Report

ES-2

Operable Unit 2 may also require the development and implementation of additional ICs. Several 

waste features were operated under an active mining permit until November of 2005 when the 

permit expired. The Colorado Division of Reclamation Mining and Safety (DRMS) initiated a 

bond forfeiture with the permitee, Leadville Corporation, for the reclamation of OU2 facilities 

operated under the permit. In accordance with the ROD, risks remaining after reclamation will be 

assessed by EPA and the need for additional response actions (including ICs) will be evaluated. 

An Institutional Control Overlay (ICO) District was established to meet most of the RODrequired land use restriction requirements. However, the ICO District was repealed by Lake 

County in 2006. As a result, concerns remain regarding protectiveness of the remedies. 

Other issues identified in this Five-Year Review specific to individual OUs include: 

OU1 

The Yak Tunnel improvements, including the bulkhead and monitoring network reportedly are 

operating as intended. However, the presence of rising water levels in the upper reaches of the 

tunnel indicates the presence of a blockage within the tunnel. Mitigation measures have been 

implemented in accordance with Monitoring and Contingency Plans as intended by the decision 

documents. Water levels in the Yak Tunnel should be carefully monitored to determine 

effectiveness of mitigation measures and to minimize the potential for a sudden release of 

impounded water. 

OU2 

The 2004 monitoring report identified numerous areas with sparse to no vegetation on the Malta 

Tailing Impoundment. Minimal vegetation success and the presence of invasive plant species 

were identified at the Malta Gulch Tailing (HECLA facility). EPA attributed this condition to 

recent drought conditions. Mitigation will be performed should the condition persist during the 

summer of 2007. In addition, settlement funds for operation and maintenance of the remedy are 

exhausted and use Superfund resources is not feasible. Therefore, the funding for operation and 

maintenance requires clarification. 

OU6 

Control of water levels in the Leadville Mine Drainage Tunnel (LMDT) as required under the 

ROD was intended to mitigate environmental and other risks associated with acid rock drainage 

(ARD) currently impounded behind one or more suspected blockages in the LMDT. Until the 

selected remedy is fully implemented, risks associated with this suspected “mine pool” remain. 

These risks include migration of ARD away from the mine pool into mine workings, natural 

fractures/faults with potential discharge to alluvial groundwater and/or springs and seeps. There 

also remains some concern about a sudden release of ARD at the LMDTs portal should suspect 

blockage(s) in the LMDT fail. 

OU8 

The 2005 Inspection Report identified areas of limited vegetation at FTS-1 and Non-Residential 

Soils Areas and recommended additional seed and fertilizer. No documentation exists indicating 

whether maintenance had been performed. In addition, the condition of FTS-2 suggests that the 

tailings are vulnerable to erosion and remain a source for metal loading to California Gulch. 

Therefore, the affected portion of these remedies requires repair or replacement in order to meet 

the intent of the decision documents. 
California Gulch Five-Year Report

ES-3

OU9 

An ICO District was established to satisfy ROD required ICs. However, the ICO District was 

repealed by Lake County in 2006. As a result, concerns remain regarding protectiveness of the 

remedy. In addition, no Operation and Maintenance Plan is in place for remediated properties in 

OU9. EPA continues to negotiate with Lake County towards adoption of the LCCHP as a formal 

IC. Implementation of an operation and maintenance plan will also be resolved through 

discussions between EPA and Lake County. 

OU10 

RAO’s articulated in the ROD requiring, among other things, control of leaching and migration 

of metals from contaminated materials into the surface water, may be not have been achieved to 

the degree originally intended. This is indicated by metal loading and concentration trends at a 

surface water monitoring station in Oregon Gulch for the period 1995 through 2005. The 

frequent appearance of contaminated seepage from the toe of the constructed embankment may 

be indicative of lower than expected performance of the cover system installed on the tailings. 

This situation will require continued monitoring before a final determination of protectiveness 

would be made. 

This Site required on-going five-year reviews in accordance with CERCLA §121(c). The next 

five-year review for the California Gulch Site will be performed five years from the date of 

completion of this review. 
California Gulch Five-Year Report

ES-4

Five-Year Review Summary Form

SITE IDENTIFICATION

Site name: California Gulch 

EPA ID: COD980717938 

Region: VIII State: CO City/County: Lake County 

SITE STATUS

NPL status: Final Partial Deletion Other (specify) 

Remediation status (choose all that apply): Under Construction Operating 

Complete 

Multiple OUs? YES Construction completion date: Not 

Identified 

Has site been put into reuse? Partial 

REVIEW STATUS

Reviewing agency: EPA 

Name: Rebecca Thomas 

Title: Remedial Project Manager Affiliation: EPA 

Review period: 8/06 through 9/07 

Date(s) of site inspection: 08/24/2006 

Type of review: Statutory 

Review number: 3 

Triggering action: Previous Five-Year Review Report 

Triggering action date: 9/28/01 

Due date (five years after triggering action date): 9/28/06 

[“OU” refers to operable unit.] 
California Gulch Five-Year Report

ES-5

Five-Year Review Summary Form, cont’d 

Issues:

Operable 

Unit 

Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

2, 3, 4, 7, 

8 and 10 

Additional institutional controls (ICs) are or may be needed 

to ensure protection of human health in the event of changes 

in zoning or to preclude disturbance of engineered remedies 

as a result of development consistent with current zoning. 

No Yes 

1 Rising water levels in upper portion of Yak Tunnel. No Yes 

1 

Financial assurance for continued operation of the Yak 

Treatment Plant has not been established. No Potentially 

2 Settlement funds have been exhausted and use of Superfund 

resources is not permitted. No No 

2 Vegetation in need of maintenance. No Yes 

6 Delay in establishing control of the Mine Pool Potentially Potentially 

8 

A portion of Non-Residential Soils Areas, Fluvial Tailing 

Site (FTS) No. 1 and FTS-2 remedies in need of repair or 

replacement. 

Yes Yes 

9 

An ICO District was established to satisfy ROD required 

ICs. However, the ICO District was repealed by Lake 

County in 2006. As a result, concerns remain regarding 

protectiveness of the remedy. 

Yes Yes 

9 

Isolated areas of soils in outlying potions of OU9 were 

identified as containing arsenic at levels that exceed the 

upper range of plausible action levels for residential land 

use. The arsenic exceedences occurred where the 

corresponding lead concentration was below the residential 

action level. Therefore, it is possible that unacceptable 

exposure of sensitive populations might occur should these 

areas be developed. 

No Potentially 

9 No O&M Plan exists for remediated properties Yes Yes 

10 Additional seeps have been identified in the toe and 

downgradient from the impoundment. Yes Yes 
California Gulch Five-Year Report

ES-6

Five-Year Review Summary Form, cont’d 

Recommendation and Follow-up Action: 

OU Issue Recommendation for Follow-Up Party 

Responsible Due Date 

2 

Additional ICs may be needed to 

ensure protection of human health 

in the event of changes in zoning 

or to preclude disturbance of 

engineered remedies as a result of 

development consistent with 

current zoning. 

Investigate the impacts of mine 

permit expiration on remedy 

protectiveness and develop/ 

implement ICs, as necessary. CDPHE 12/08 

3, 4, and 

10 

Institutional controls are needed 

to ensure protection of human 

health in the event of changes in 

zoning or to preclude disturbance 

of engineered remedies as a result 

of development consistent with 

current zoning. 

Prepare an ESD identifying 

appropriate ICs and implement the 

controls. Resurrection 

UPRR 

EPA 

12/08 

7 and 8 

Institutional controls are needed 

to ensure protection of human 

health in the event of changes in 

zoning or to preclude disturbance 

of engineered remedies as a result 

of development consistent with 

current zoning. 

Develop and implement ICs. ASARCO/Res

urrection 12/08 

1 Rising water levels in upper 

portion of Yak Tunnel. 

Monitor effectiveness of 

dewatering of the Black Cloud 

Mine. 

ASARCO 

Res-ASARCO On-going 

1 

Financial assurance for continued 

operation of the Yak Treatment 

Plant has not been established. Establish financial assurance ASARCO 

Res-ASARCO 12/07 

2 

Settlement funds have been 

exhausted and use of Superfund 

resources is not permitted. 

Funding of operation and 

maintenance requires clarification. EPA/CDPHE 12/08 

2 Vegetation in need of 

maintenance. 

Perform maintenance as required 

following the next scheduled 

annual inspection. 

Responsibility 

for O&M 

requires 

clarification 

12/07 

6 Delay in establishing control of 

the Mine Pool Perform remedial action EPA 

Re-evaluate 

at next fiveyear review

8 

A portion of Non-Residential 

Soils Areas, Fluvial Tailing Site 

(FTS) No. 1 and FTS-2 remedies 

in need of repair or replacement. 

Modify/repair the existing 

remedies, as necessary, so that 

vegetation is established and/or 

mine waste does not come into 

contact with California Gulch 

flows or allow precipitation to 

pond on the tailing surface. 

Resurrection 12/07 
California Gulch Five-Year Report

ES-7

Five-Year Review Summary Form, cont’d 

Recommendation and Follow-up Action: 

OU Issue Recommendation for Follow-Up Party Responsible Due Date 

9 

An ICO District was established 

to satisfy ROD required ICs. 

However, the ICO District was 

repealed by Lake County in 

2006. As a result, concerns 

remain regarding protectiveness 

of the remedy. 

Formalize ICs EPA/Lake 

County 12/08 

9 

Isolated areas of soils in outlying 

potions of OU9 were identified 

as containing arsenic at levels 

that exceed the upper range of 

plausible action levels for 

residential land use. The arsenic 

exceedences occurred where the 

corresponding lead 

concentration was below the 

residential action level. 

Therefore, it is possible that 

unacceptable exposure of 

sensitive populations might 

occur should these areas be 

developed. 

Consider creation of an IC to 

address areas of elevated arsenic in 

soils where development may 

result in unacceptable exposure of 

sensitive populations 

EPA/Lake 

County 12/08 

9 

No O&M Plan exists for 

remediated properties 

Prepare and implement an O&M 

Plan 

EPA/Lake 

County 12/08 

10 

Additional seeps have been 

identified in the toe and 

downgradient from the 

impoundment. 

Continue to monitor potential for 

seeps from the toe of and 

downgradient from the 

impoundment. 

Resurrection On-going 
California Gulch Five-Year Report

ES-8

Five-Year Review Summary Form, cont’d. 

Protectiveness Statement(s) for each OU is provided below: 

OU1 – Yak Tunnel

The remedy is currently protective of human health and the environment. However, mitigation of rising water levels 

caused by a suspected blockage in the Yak Tunnel through dewatering via the Black Cloud Mine should be carefully 

monitored to determine effectiveness. 

OU 2 - Malta Tailing Impoundment, Malta Gulch Tailing Impoundment and Lower Malta Gulch Fluvial Tailing and 

OU 3 - Denver & Rio Grande Railroad (D&RG) Slag Piles/Railroad Easement/Railroad Yard

The remedy is currently protective of human health and the environment. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted past or current 

protectiveness as the remedies were undisturbed at the time of this Five-Year Review. However, the potential exists 

for future impacts on remedy protectiveness if such an institutional control is not developed and implemented. EPA 

and CDPHE are informally notified by the County of any changes in zoning. Although this is not a formalized IC, it 

allows the remedy to be protective until an IC is formalized. 

Operable Unit 4 - Upper California Gulch

The remedy is currently protective of human health and the environment. However, future remedial work may be 

required in order to attain final Site-wide water quality standards as determined pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted past or current 

protectiveness as the remedies were undisturbed at the time of this Five-Year Review. However, the potential exists 

for future impacts on remedy protectiveness if such an intuitional control is not developed and implemented. EPA 

and CDPHE are informally notified by the County of any changes in zoning. Although this is not a formalized IC, it 

allows the remedy to be protective until an IC is formalized 

Operable Unit 5 - Asarco Smelters/ Colorado Zinc-Lead Mill Site

Remedial work at the Arkansas Valley Smelter and Colorado Zinc-Lead Mill is incomplete. Therefore, the remedy 

is not yet protective although overall protectiveness is expected to be achieved once remedial construction is 

completed. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted past or current 

protectiveness as the remedy remains incomplete. However, the potential exists for future impacts on remedy 

protectiveness if such an intuitional control is not developed and implemented. EPA and CDPHE are informally 

notified by the County of any changes in zoning. Although this is not a formalized IC, it allows the remedy to be 

protective until an IC is formalized 
California Gulch Five-Year Report

ES-9

Five-Year Review Summary Form, cont’d. 

Protectiveness Statement(s) for each OU is provided below: 

Operable Unit 6 - Starr Ditch/Penrose Dump/Stray Horse Gulch/Evans Gulch

The remedy is currently protective of human health and the environment. However, future remedial work may be 

required in order to attain final Site-wide water quality standards as determined pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning and to identify properties where 

special precautions may be necessary has not impacted past or current protectiveness as the remedies were 

undisturbed at the time of this Five-Year Review. However, the potential exists for future impacts on remedy 

protectiveness if such an IC is not developed and implemented. The selected remedy will address the mine pool. 

Operable Unit 7 - Apache Tailing Impoundments

The remedy is currently protective of human health and the environment. However, future remedial work may be 

required in order to attain final Site-wide water quality standards as determined pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted past or current 

protectiveness as the remedies were undisturbed at the time of this Five-Year Review. However, the potential exists 

for future impacts on remedy protectiveness if such an IC is not developed and implemented. 

Operable Unit 8 - Lower California Gulch

Although the remedy is currently considered to be protective of human health and the environment, the poor 

condition of FTS-2 remedy requires repair or replacement in order to meet the intent of the decision documents. In 

addition, future remedial work may be required in order to attain final Site-wide water quality standards as 

determined pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted past or current 

protectiveness as the remedies were undisturbed at the time of this Five-Year Review. However, the potential exists 

for future impacts on remedy protectiveness if such an IC is not developed and implemented. EPA and CDPHE are 

informally notified by the County of any changes in zoning. Although this is not a formalized IC, it allows the 

remedy to be protective until an IC is formalized. 

Operable Unit 9 - Populated Residential Areas

The remedy is protective of human health and the environment. 

Performance standards for OU9 were met in March 2006 as a result of the LCCHP. Given that hazardous substances 

remain within OU9, operation and maintenance of the LCCHP is necessary to ensure the protectiveness of the 

remedy. 

Operable Unit 10 - Oregon Gulch

The remedy is protective of human health and the environment. However, future remedial work may be required in 

order to attain final Site-wide water quality standards as determined pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted past or current 

protectiveness as the remedies were undisturbed at the time of this Five-Year Review. However, the potential exists 

for future impacts on remedy protectiveness if such an IC is not developed and implemented. EPA and CDPHE are 

informally notified by the County of any changes in zoning. Although this is not a formalized IC, it allows the 

remedy to be protective until an IC is formalized. 
California Gulch Five-Year Report

ES-10

Five-Year Review Summary Form, cont’d. 

Protectiveness Statement(s) for each OU is provided below: 

Operable Unit 11- Arkansas River Valley Floodplain

The remedy for Operable Unit 11 (OU11) selected in the 2005 ROD has not been implemented. 

Operable Unit 12 

Operable Unit 12 covers the entire California Gulch site and was designated to address Site-wide surface and 

groundwater. Under the provisions of the 1994 CD, OU12 will be addressed after completion of source remediation 

in OUs 2 through 10. This will include a determination of protectiveness of surface and groundwater and the 

establishment of points of compliance and performance standards. 

The OU12 Remedial Investigation and Feasibility Study were underway at the time of this Five-Year Review with a 

ROD anticipated to be released in 2008. 

Other Comments:

None 

 
California Gulch Five-Year Report

Page 1 of 89 

Five-Year Review Report 

1.0 Introduction 

Purpose of the Review 

The purpose of five-year reviews is to determine whether remedies implemented at the 

California Gulch National Priority List (NPL) Site (the Site) in Lake County, Colorado are 

protective of human health and the environment. The methods, findings and conclusions of 

reviews are documented in Five-Year Review reports. In addition, Five-Year Review reports 

identify issues found during the review, if any, and recommendations to address them. 

This is the third five-year review for the Site. The triggering action for this review is the previous 

Five-Year Review report, signed on Septmber 29, 2001. Because hazardous substances, 

pollutants or contaminants remain at the Site above levels that allow for unlimited use and 

unrestricted exposure, a Statutory Five-Year Review is required. 

Authority for Conducting the Five-Year Review 

The U.S. Environmental Protection Agency (EPA) is preparing this five-year review pursuant to 

CERCLA §121 and the National Contingency Plan (NCP). CERCLA §121 states: 

If the President selects a remedial action that results in any hazardous substances, 

pollutants, or contaminants remaining at the site, the President shall review such 

remedial action no less often than each five years after the initiation of such remedial 

action to assure that human health and the environment are being protected by the 

remedial action being implemented. In addition, if upon such review it is the judgment 

of the President that action is appropriate at such site in accordance with section 

[104] or [106], the President shall take or require such action. The President shall 

report to the Congress a list of facilities for which such review is required, the results 

of all such reviews, and any actions taken as a result of such reviews. 

The EPA interpreted this requirement further in the National Contingency Plan (NCP); 40 CFR 

§300.430(f) (4) (ii) states: 

If a remedial action is selected that results in hazardous substances, pollutants, or 

contaminants remaining at the site above levels that allow for unlimited use and 

unrestricted exposure, the lead agency shall review such action no less often than 

every five years after the initiation of the selected remedial action. 

Who Conducted the Five-Year Review 

EPA Region 8 conducted the Five-Year Review of remedial actions implemented for Operable 

Units 1 through 11 at the Site in and around Leadville, Colorado. This review was conducted 

from September 2006 through September 2007. This report documents the results of the review.

HDR Engineering, Inc. (HDR) of Denver, Colorado was retained under a subcontract to Project 

Resources Inc. (PRI) to prepare this Five-Year Review Report for EPA. PRI was retained by the 

US Army Corps of Engineers, Omaha District under a Rapid Response Program contract. 
California Gulch Five-Year Report

Page 2 of 89 

2.0 Site Chronology 

Table 2-1 presents a chronology of activities at the Site. 

Table 2-1 

Chronology of Activities at California Gulch Site 

Date Event

1859 Placer gold discovered in California Gulch and mining began in the District. 

1877-1893 The Harrison Reduction Works in Operable Unit (OU) 3, the only smelter reported to have 

processed gold ores, opened on the northeast corner of Harrison Avenue and Elm Street in 

1877, but closed in 1893. 

1878-1882 The Grant Smelter operated from 1878 to 1882. 

1878-1887 Berdell and Witherell Smelter operated near the La Plata slag pile in OU3. 

1879-1882 Area comprising OU2 developed with placer claims. 

1879-1886 The Cummings and Finn Smelter Works began operations at Big Evans Gulch in OU3 1879. 

The plant, which also operated under the name of the Fryer Hill Smelting Company was 

dismantled in 1886. Other smelters that operated in the Big Evans Gulch Area included the 

Ohio and Missouri Smelter, the Gage-Hagaman Smelter, and the Raymond, Sherman, and 

McKay Smelter. 

1879-1903 The Elgin Smelter operated intermittently from 1879 until 1903. 

1879-1961 The Elgin, Grant, and Arkansas Valley Smelters in OU5 were constructed. The Arkansas 

Valley Smelter processed lead ore and reprocessed slag to produce lead, silver, and other 

metals and operated until 1961. 

1882-1960 Arkansas Valley Smelter operated in OU5. 

1892-1900 The Union Smelter operated from 1892 to 1900. 

1892-1900 Bimetallic Smelting Company leased the La Plata area in OU3 for pyritic smelting of lowgrade ores. 

1893-1902 The Elgin Smelter works in OU5 were leased and operated by several different companies. 

1895 Yak Tunnel driven to dewater mines and to facilitate mineral exploration and development in 

OU1. 

1900 American Smelting and Refining Company purchased the La Plata works in OU3 in 1900. 

1914-1926 The Western Zinc Mining and Reducing Company constructed a smelter to the west of the 

City of Leadville in OU5 that extracted zinc from ores. 

1917 Harrison Recovery Works was established to rework the Harrison Street slag pile in OU3. 

1923 Last extension to Yak tunnel occurred - total length of tunnel measures 3-1/2 to 4 miles into 

Iron Hill and Breece Hill in OU1. 

1925-1940 The Colorado Zinc and Lead (CZL) site operated a flotation mill that processed zinc-lead ores 

sporadically between 1925 and 1940. The tailing impoundment at the CZL site is the only 

fluvial tailing impoundment in OU8. 

1926-1938 In 1926, the Colorado Zinc-Lead Mill in OU5 began processing ores with a custom flotation 

process to produce zinc, lead, gold, silver, and some copper concentrations. The mill closed 

in 1930, but was remodeled in 1935. Between 1935 and 1938, when it closed for good, the 

mill processed ores from several local mines and waste dumps. The history of the Arkansas 

Valley South Hillside Slag Pile is unknown. It is possible that either the Arkansas Valley or 

the Grant/Union Smelters disposed of slag at this site. 

1939-1956 The mill that generated the tailing placed in the Main Impoundment, and possibly the North 

Impoundment in OU7, was located on the hillside northeast of the North Impoundment. This 

mill was known as the Venir Mill, the California Gulch Mill, and the ASARCO Leadville 

Milling unit. 

1945-1957 The Oregon Gulch Tailing Impoundment in OU10 received tailing from the ResurrectionASARCO mill in California Gulch. 

1943-1946 Ore & Chemical Company (OCC) used OU2 as a disposal site. 
California Gulch Five-Year Report

Page 3 of 89 

Table 2-1, cont’d 

Chronology of Activities at California Gulch Site 

Date Event

1947-1987 Hecla Mining Company, which later purchased Day Mines (Hecla/Day), leased OU2 

property. 

1961 D&RGW purchased the Arkansas Valley (AV) slag pile in OU3 from ASARCO for use as 

ballast. 

1968 Leadville Corporation purchased OU2 property. 

1970 D&RGW purchased the La Plata slag pile in OU3 from the Leadville Sanitation District in 

1970. 

1970s-1980s The Apache Mill began operations in the late 1970s and continued operations into the 1980s. 

1970s-1986 A mill facility utilized a cyanide leach process to extract silver from ore obtained from the 

Sherman and Diamond Resurrection mines. The mill was purchased by the Leadville 

Corporation in the early 1980's and continued operations until the mill closed in 1986. 

1983 D&RGW purchased the Harrison Street Slag Pile in OU3 from NL Industries for use as a 

ballast production. 

1983-1988 Leadville Silver & Gold operated a pyrite recovery process on OU2. 

09/08/83 California Gulch site placed on NPL. 

1992 Yak Water Treatment Plant begins treated Yak Tunnel discharge 

1994 Sitewide Consent Decree 

02/02/96 First Five-Year Review 

04/01 OU10 deleted from NPL 

06/01 OU2 deleted from NPL 

09/28/01 Second Five-Year Review 

1988 - 2005 Records of Decision were signed for OU1, OU2, OU3, OU4, OU5, OU6, OU7, OU8, OU9, 

OU10 and OU11. 

1994-2006 Various response actions performed by parties to the Consent Decree 
California Gulch Five-Year Report

Page 4 of 89 

3.0 Background 

Location and Setting 

The Site is comprised of approximately 18 square miles (see Figure 3-1, Appendix A) in Lake 

County, approximately 100 miles southwest of Denver. It includes the towns of Leadville and 

Stringtown, various parts of the Leadville Historic Mining District, and a section of the Arkansas 

River from the confluence of California Gulch downstream to the confluence of Two-Bit Gulch 

Creek. 

The elevation of the Site ranges from 9,300 feet at the confluence of Two-Bit Gulch and the 

Arkansas River at the southwestern boundary of the site to over 12,000 feet near Ball Mountain 

east of Leadville, Colorado. 

The Site includes, but is not limited to, the City of Leadville. The area is a predominantly rural 

county with a population of 7,812 (United States Bureau of the Census, 2000). The zoning uses 

for the area are industrial/mining, commercial, recreational, and residential. 

Site History and Nature of Contamination 

The Site has been the location of mining, mineral processing, and smelting activities that have 

produced gold, silver, lead, and zinc for more than 140 years. Mining activities in Leadville 

began in 1859 when gold bearing placer deposits were found along California Gulch. Since that 

time, mining activity has almost been continuous, although there have been production 

cessations or slowdowns because of economic conditions or labor issues. An estimated 26 

million tons of ore were produced in the Leadville Mining District from 1859 through 1986. 

Nearly all of the mines within the Site presently are inactive, and all of the mills and smelters 

have been either decommissioned or demolished. 

Numerous mining methodologies were used at the Site including placer mining, exposed fissure 

veins, and underground mining. Waste rock was excavated and left near the mine entrances 

while metal ores were processed by crushing, milling, and smelting resulting in the generation of 

several different types of waste. The types of waste generated as a result of mining activities are 

described below: 

• Waste Rock Piles- Waste rock removed from underground workings was placed near 

mine entrances. This waste rock often contains elevated levels of heavy metals and 

sulfide minerals. In the presence of water, sulfide minerals can generate acid that lowers 

the pH of the water. This low pH water promotes the leaching of heavy metals from the 

rock and into surface and groundwater. 

• Slag and other Smelter Wastes- In the smelters, high-grade ores were refined and 

concentrated into higher-grade products. Waste products from the smelters include slag 

flue dust and stack emissions all containing heavy metals. Contaminants in smelter stack 

emissions often commingled with soils as particulates settled out of the atmosphere. 

There were forty-four known smelters in the district. 
California Gulch Five-Year Report

Page 5 of 89 

• Acid Rock Drainage - Groundwater, which began flooding into the mines, produces acid 

rock drainage. This process brought oxygen in contact with the pyritic ores. These 

materials, when oxidized, break down and alter the sulfide minerals to form acid rock 

drainage (ARD) water that has low pH levels. This low pH water leaches heavy metal 

constituents from rocks and into surface water runoff. 

• Mill Tailing - At mills on the Site, ores were crushed and separated into metallic 

concentrates and waste products by physical processes. Metallic concentrates were then 

shipped elsewhere or further processed at a smelter in the area. Waste products (mill 

tailing) were generally placed in nearby tailing ponds. Release of contaminants from 

tailing material can be attributed to seepage from existing tailing deposits and from 

fluvially deposited tailing. Release of soluble inorganic metals contained in runoff from 

tailing deposits and contained in seeps emanating from the toe of some tailing deposits 

have contributed to metal contamination of sediments and surface water. 

More than 2,000 mine waste piles have been identified in the Site that are associated with the 

estimated 26 million tons of ore produced over the history of operations. A few of these waste 

piles are located within the residential areas of Leadville and Stringtown. Contamination of soil 

and surface water drainage in populated areas occurs throughout the Site with large amounts of 

water being treated by on- and off-Site water treatment facilities. 

Groundwater and surface water studies were conducted by private parties, as well as by the 

United States Geological Survey (USGS) and EPA. The initial Phase I of the Remedial 

Investigation (Phase I RI) was released by U.S. EPA in May 1987, with subsequent Remedial 

Investigation/Feasibility Studies (RI/FS) performed by Woodward-Clyde in 1990 and 1991. The 

1987 Phase I RI indicated that surface water in California Gulch exceeded primary drinking 

water standards for lead and cadmium and that the site surface water contained cadmium, copper, 

lead, and zinc at levels that exceeded water quality criteria. Additionally, soils at the site were 

found to contain elevated levels of arsenic, zinc, lead, copper, and cadmium. 

Summary of Baseline Risk Assessment 

Baseline human health risk assessments (BRAs) characterized baseline risks at the Site. Riskbased numerical clean-up goals were also established for the entire populated area as a function 

of land use. A summary of Site risks and numerical clean-up goals as well as an assessment of 

their validity at the present time is discussed below. 

Under the 1994 CD, assessment of Site-wide surface and groundwater quality relative to 

appropriate performance standards was deferred to OU12. A ROD for OU12 setting final surface 

and groundwater performance standards has not been developed (scheduled to be released in 

2007). Therefore, Site risks and associated numerical clean-up goals applicable to the OUs 

subject to this Five-Year Review are limited to soils and mine wastes (solid media). 
California Gulch Five-Year Report

Page 6 of 89 

A number of BRAs have been completed for the NPL Site, and are listed below: 

• Preliminary Human Health Baseline Risk Assessment for the California Gulch NPL 

Site (Weston, 1991). The presence of elevated levels of heavy metals in soils in and 

around the residential and commercial areas of Leadville was discovered during early 

site investigations. This information was used in the preliminary risk assessment, 

which indicated that contaminant levels were high enough to be of potential human 

health concern. Lead and arsenic were identified as the primary chemicals of potential 

human health concern. 

• Baseline Human Health Risk Assessment for the California Gulch Superfund Site. 

Part C: Screening Level Soil Concentrations for Workers and Recreational Site 

Visitors Exposed to Lead and Arsenic (Weston, 1995). 

3⁄4 Baseline Human Health Risk Assessment for the California Gulch Superfund Site. 

Part C: Evaluation of Worker Scenario. This part of the BRA was conducted to 

evaluate risks to current or future workers in the commercial and business district 

of the community. This study focused on the risks associated with exposure to 

lead and arsenic in soil and dust through ingestion. The study concluded that risks 

to current workers from lead and arsenic are likely to be below a level of concern. 

The study further concluded that some uncertainty exists regarding the magnitude 

of potential future risks as well as the potential for unacceptable current risks in 

specific sublocations within the Site. 

3⁄4 Baseline Human Health Risk Assessment for the California Gulch Superfund Site. 

Part C: Evaluation of Recreational Scenarios. This part of the BRA was 

conducted to evaluate risks which environmental contamination poses to people 

who engage in recreational activities (hunting, hiking, bike riding, picnicking, 

etc.) in areas in and around the community. This study focused on the risks 

associated with lead and arsenic at the site. The study concluded that average lead 

levels are generally below that recreational action level for areas where 

recreational scenarios are considered likely. 

• Final Baseline Aquatic Ecological Risk Assessment for the California Gulch NPL Site

(Weston, 1995). The Aquatic Ecological Risk Assessment evaluated the impact of 

mine waste contamination on the aquatic ecosystem in the NPL Site. The mine wastes 

in the area are associated with increased heavy metal loading to the surface water and 

sediments within the site drainages and the Arkansas River. The study concluded that 

discharges of metals from California Gulch continued to result in conditions (in the 

Arkansas River) that were of concern, especially near the confluence. 
California Gulch Five-Year Report

Page 7 of 89 

• Baseline Human Health Risk Assessment for the California Gulch Superfund Site. 

Part A – Risks to Residents from Lead (Weston, 1996). This document focuses on the 

risks of lead exposure to young children (age 0-6 years). Young children were 

selected as the focus because they typically have higher intake rates of environmental 

media per unit body weight than adults, they tend to absorb a higher fraction of 

ingested lead than adults, and they tend to be more susceptible to some of the adverse 

effects of lead than adults. The EPA used Site-specific inputs to an integrated 

exposure, uptake, and biokinetic model along with structural equation modeling of 

empirical blood lead and environmental lead data, to assess risk to residents from 

lead. The study concluded that residential lead exposure may result in adverse health 

effects above a level of concern. 

• Baseline Human Health Risk Assessment for the California Gulch Superfund Site. 

Part B – Risks to Residents from Contaminants other than Lead (Weston, 1996). This 

document focuses on risks to current and future residents of Leadville from 

environmental media contaminated with mine related wastes other than lead. The 

assessment adopted a Preliminary Remediation Goal (PRG) approach to the risk 

analysis where a concentration for each contaminant of potential concern (COPC) 

was identified using a specific level of health risk for each medium. This PRG was 

then compared to site-wide data to determine if, where, and by how much site 

concentrations exceed the calculated value. This study concluded that non-lead metals 

in surface soils do not pose a significant health risk to residents. 

Human Health Risks 

As discussed above, Part B of the Human Health Risk Assessment concluded that there are no 

locations on the Site where antimony, barium, cadmium, beryllium, chromium, copper, mercury, 

nickel, silver, thallium, or zinc are of significant concern in soils. The risk assessment also 

concluded that risk exceedences are small for arsenic and manganese and occur only in the most 

conservative risk calculations. This, combined with the recognition that assumed uptake 

(bioavailability) of metals used in risk calculations may be higher than actual, lead to the 

conclusion that non-lead metals in surface soils do not pose a significant health risk to residents. 

Thus, the only contaminant of concern is lead. 

To evaluate risk, calculations were performed to identify concentrations (action levels) of lead in 

soil that were of potential concern. The land use-based remediation goals are summarized in 

Table 3-1. 

Table 3-1 

Land Use-Based Remediation Goals 

Land Use Lead Remedial Goal 

(mg/Kg) 

Reference 

Recreational 16,000 BRA Part C 

Worker 6,100-7,700 Plausible Action Levels; BRA Part 

C 

Residential 3,500 BRA Part A and OU9 ROD 
California Gulch Five-Year Report

Page 8 of 89 

In order to identify areas where land use-based remediation goals might be exceeded, the goals 

were compared to findings of soil concentration values in previous Remedial Investigations 

(RIs). Average lead levels over an exposure area are compared to the soil remediation goal. 

Occasional measurements of concentrations above the remediation goal do not necessarily 

constitute evidence that an area is unsafe. 

Inspection of the prior RIs shows that average lead levels are generally well below the action 

level of 16,000 milligrams per Kilogram (mg/Kg) for areas where recreational scenarios are 

considered likely. For the worker scenario, the average lead levels are mostly below the centraltendency range of plausible action levels (6100-7700 mg/Kg) for most areas zoned for 

commercial land use, with the possible exception of some areas in the historic mining area east 

of town and in the vicinity of the former AV Smelter located southwest of town. 

Soil samples collected subsequent to the Human Health Risk Assessment in support of deletion 

activities, identified several isolated areas where arsenic concentrations exceeded the upper range 

of plausible action levels for residential land use (120-340 mg/Kg; BRA Part B). The arsenic 

exceedences occurred where the corresponding lead concentration was below the residential 

action level of 3,500 mg/Kg. These isolated areas are located in outlying, undeveloped portions 

of OU9 (Populated Areas). 

Current Validity of COC List and Remediation Goals 

Exposure assumptions, toxicity values and other inputs to the risk assessment have not been 

revised so as to result in any new COCs. In addition, the Lake County Community Health 

Program (LCCHP) 2005 Annual Report concludes that remedial action objectives established by 

EPA for OU9 (Populated Areas) have been met in 2005. This conclusion was based on an 

evaluation of the Program in accordance with the established performance standards expressed as 

goals for blood lead levels in children. Given that these objectives have been met, it is reasonable 

to conclude that remediation goals for lead described above remain protective of human health. 

This is also discussed in Section 14.0 (OU9). 

The exposure assumptions and toxicity data used to develop range of plausible action levels for 

arsenic, published in the Human Heath Risk Assessment (Part B), remain valid. 
California Gulch Five-Year Report

Page 9 of 89 

4.0 Administrative Components and Community Involvement 

Administrative Components 

This is the third five-year review for the Site. The five-year review was led by Rebecca Thomas, 

EPA Remedial Project Manager for the Site. The following Team Members participated in the 

review: 

3⁄4 Rebecca Thomas, EPA Remedial Project Manager 

3⁄4 Stan Christensen, EPA Remedial Project Manager 

3⁄4 Jennifer Lane, Community Involvement Coordinator 

3⁄4 Richard Sisk, EPA Attorney 

3⁄4 Doug Jamison, CDPHE Project Manager 

EPA Contractors: 

3⁄4 Kenneth Napp, HDR Engineering, Inc. 

This five-year review consisted of the following activities: a review of relevant documents; 

interviews with technical personnel in public and private practice as well as elected officials and 

the public; data review; and a site visit. The schedule for the review extended through December 

2006. 

Community Involvement 

A notice that the five-year review was in progress was placed in the Leadville Herald Democrat 

and Leadville Chronicle on August 24, 2006. The notice invited members of the public to submit 

their questions or comments regarding the review to EPA. 

A notice of the completion of the five-year review report will be placed in the local newspaper. 

The completed report is available in the Lake County Public Library, located in Leadville 

Colorado and in the EPA Superfund Records Center in Denver, Colorado.

 

U.S. EPA Region 8 Records Center 

999 18th Street (3rd Floor South Tower) 

Denver, CO 80202 

(303) 312-6473 

Interviews 

Interviews were conducted with 17 community members representing city and county 

government, the county’s advisory group, the county health department, the Colorado Mountain 

College, potentially responsible parties, and citizens. Most of the interviews occurred one-onone with the exception of one meeting with six representatives of the County’s Institutional 

Control Advisory Group and three telephone interviews. The Lake County Commissioners 

requested that they provide information in writing, so their concerns are reflected in the summary 

that follows and their written account is included with the appendixes of the Five-year Review. 
California Gulch Five-Year Report

Page 10 of 89 

EPA received numerous comments that do not directly pertain to the protectiveness of remedy 

operations at the Site. These comments are important and EPA will use them to develop an 

update of the Community Involvement Plan at a future date. A written summary of responses 

from interviews and from the Lake County Commissioners written comments for each of 

interview questions is provided in Appendix B. 
California Gulch Five-Year Report

Page 11 of 89 

5.0 Operable Units 

The Site is divided into twelve media and/or geographically-based OUs. Records of Decision 

have been completed for 11 of the 12 OUs. The Site OUs are listed below and identified on 

Figure 3-1 (Appendix A). 

OU1 - Yak Tunnel/Water Treatment Plant 

OU2 - Malta Gulch Fluvial Tailing/Leadville Corp. Mill/Malta Gulch Tailing Impoundments 

OU3 - Denver & Rio Grande Railroad (D&RG) Slag Piles/Railroad Easement/Railroad Yard 

OU4 - Upper California Gulch 

OU5 - Asarco Smelters/Slag/Mill Sites 

OU6 - Starr Ditch/Penrose Dump/Stray Horse Gulch/Evans Gulch 

OU7 - Apache Tailing Impoundments 

OU8 - Lower California Gulch 

OU9 - Residential Populated Areas 

OU10 - Oregon Gulch 

OU11 - Arkansas River Valley Floodplain 

OU12 - Site Water Quality 

A Consent Decree (CD) was executed in 1994 between EPA, State of Colorado and the 

following Responsible Parties: 

• ASARCO Corporation (ASARCO) 

• Joint Venture between ASARCO and Resurrection Mining Company (Res-ASARCO) 

• Resurrection Mining Company and its parent, Newmont Mining Company (Resurrection) 

The CD specified that RODs selecting response actions to effect source remediation would be 

implemented before a ROD is issued for OU12. The ROD for OU12 will address site-wide 

surface water and groundwater. The ROD for OU12 is scheduled for release in 2008. 
California Gulch Five-Year Report

Page 12 of 89 

6.0 Operable Unit 1-Yak Tunnel/Water Treatment Plant 

6.1 Description 

Operable Unit 1 consists of the Yak Tunnel and Water Treatment Plant. The Yak Tunnel was 

constructed to dewater mines and to facilitate mineral exploration and development. The tunnel 

was driven in 1895, as an extension of the Silver Cord Tunnel, to drain the Iron Hill mines. The 

Yak Tunnel was extended several times, with the last extension occurring in 1923. The Yak 

Tunnel extends underground approximately 3-1/2 to 4 miles into Iron Hill and Breece Hill. The 

tunnel has several major laterals and drifts that extend from the tunnel into various mine 

workings, such as the Horseshoe, the Rubi, the North Mike, the South Mike, the Ibex No. 4, the 

Little Winnie, the Resurrection No. 1, the Fortune, the Resurrection No. 2, and the Dolly B. U.S. 

EPA estimated that 60,000 feet of tunnels and major laterals and 55 to 74 million cubic feet of 

void space are associated with the tunnel mining activities. The location of OU1 is shown on 

Figure 3-1 (Appendix A). 

At the time of the ROD in March 1988, studies indicated that a combined total of 210 tons per 

year of cadmium, lead, copper, manganese, iron, and zinc were discharged from the Yak Tunnel 

into California Gulch, which drains into the Arkansas River. Surface water contamination is the 

major impact of the Yak Tunnel discharge. Shallow alluvial groundwater and stream sediment 

may have been impacted by historic releases from the Yak Tunnel. 

Table 6-1 lists the chronology of site events for Operable Unit 1- Yak Tunnel and Water 

Treatment Plant of the California Gulch site. 

Table 6-1 

Chronology of Site Events for OU1 

Yak Tunnel and Water Treatment Plant 

Date Event

09/08/83 California Gulch site placed on NPL 

05/87 Phase I Remedial Investigation (RI) report released 

06/87 Feasibility Study (FS) report released 

08/87 Proposed remedial action plan released for OU1 

03/29/88 Record of Decision (ROD) 

09/88 Began Surge Pond and Interim Treatment Plant Remedy 

03/23/89 Modification of ROD based on negotiations with Respondents 

03/29/89 Unilateral Administrative Order (UAO 89-20) 

2/90 Began Construction of Yak Tunnel Water Treatment Facility 

06/91 Completed Surge Pond and Interim Treatment Plant Remedy 

10/22/91 Explanation of Significant Differences (ESD) 

2/92 Completion of the Yak Tunnel Water Treatment Facility 

04/30/93 First amendment to UAO 89-20 

06/16/93 Second amendment to UAO 89-20 

03/94 Began Yak Tunnel Bulkhead Remedy 

11/94 Completed Yak Tunnel Bulkhead Remedy 

5/02 Rising water levels detected in Yak Tunnel 

3/06 Begin dewatering Black Cloud Mine 
California Gulch Five-Year Report

Page 13 of 89 

6.2 Response Actions 

Response Action Selection/Implementation 

In June 1987, EPA released a FS report and in August 1987 released a proposed remedial action 

plan for the Yak Tunnel. EPA issued a Unilateral Administrative Order (UAO) to ASARCO 

Incorporated, Newmont Mining Corporation, Res-ASARCO Joint Venture, and Resurrection 

Mining Company on March 29, 1989 for the Remedial Design/Remedial Action of the Yak 

Tunnel. Two amendments were made to the UAO on April 30, 1993 and June 16, 1993. 

The remedies for the Yak Tunnel were initially selected in the 1988 ROD, changed in the 1989 

ROD modification, and further altered in the 1991 ESD. The final remedy consists of the 

following elements: 

• Construction of a surge pond to capture drainage from the tunnel and to minimize the 

impact of surges on California Gulch and the Arkansas River.

• Installation of a permanent water treatment system to treat contaminated groundwater 

from the Yak Tunnel before discharge in California Gulch 

• Construction of a flow control bulkhead within the tunnel to prevent surges. 

• Establishment of a surface and groundwater monitoring system to detect leakage, seeps, 

or migration of contaminated groundwater. 

• Development and implementation, as necessary, of a contingency plan to address any 

adverse effects on surface or groundwater from tunnel modifications or collapse. 

• Inspection, operation and maintenance of the remedy. 

 

The Yak Tunnel Water Treatment Plant has been in operation since it’s completion in 1992. 

System Operation/O&M 

According to the 1988 ROD, routine operation and maintenance would be required including 

repairing grouted areas of structures due to corrosion, settlement or other factors; occasional 

repair or replacement of monitor well pumps and surface water monitoring equipment; repair of 

access roads; routine repair or replacement of pumps, motors, mixers, piping, and tankage; and 

inspections. 

6.3 Progress Since the Last Five Year-Review 

The last site-wide Five-Year review, which was finalized on September 29, 2001, indicated that 

the Water Treatment Plant met the ROD, ROD Modification, and ESD requirements; remains 

effective, is operating and functioning as designed, and is protective of human health and the 

environment. 
California Gulch Five-Year Report

Page 14 of 89 

Since the last review, flows from a new contaminated seep associated with the Oregon Gulch 

Tailing impoundment are now being collected and piped to the Yak Treatment Plant. This 

additional action was not triggered by decision documents associated with OU1. Rather, it was 

done to comply with decision documents for Oregon Gulch (OU10). 

Additional new influent waters to the Yak Treatment Plant include waters are being pumped 

from the Black Cloud Mine. This additional action was triggered by the provisions of the OU1 

Monitoring and Contingency Plans as discussed in the Data Review Section, below. 

6.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report 

• Additional Investigation Work Plan, Yak Tunnel Operable Unit, MFG, June 2004 

• Status Report – Yak Tunnel Rising Water Levels, MFG, June 2003 

Interviews were conducted with the following individuals to provide supplemental technical 

information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Tim Runnels – MFG 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 

Data Review 

The remedy includes a ground water monitoring program designed to track ground water levels 

and quality in and around the Yak Tunnel. The remedy also includes an effluent monitoring 

program for the Yak Water Treatment Facility. In preparing this Five-Year Review Report, data 

from the following reports were reviewed and evaluated: 

• Monthly effluent monitoring reports for the period January 2004 through August 2006 

(prepared by ASARCO and MFG). 

• Quarterly Data Transmittal – Yak Tunnel Enhanced Monitoring Program, ASARCO, 

September 2003. 

• Effluent quality monitoring frequency required under the 1988 ROD and subsequent 

modifications was relaxed in August 2002 from weekly to monthly with the addition of 

Whole Effluent Toxicity (WET) as a new analytical method. A review of monthly 

monitoring reports indicated that effluent quality has consistently met quality standards 

and reporting requirements required by the ROD and subsequent modifications. 
California Gulch Five-Year Report

Page 15 of 89 

Various Yak Tunnel monitoring reports (listed above) identified rising water levels in the upper 

reaches of the tunnel as well as the Black Cloud Mine indicating an apparent blockage in the 

upper region of the Yak Tunnel. In accordance with the provisions of the Routine Monitoring 

Plan and Contingency Plan (MFG, 1999), enhanced monitoring was initiated in 2002 and 

pumping of water from the Black Cloud Mine commenced in March 2006. Extracted water is 

piped to the Yak Water Treatment Plant. As a result, the Yak plant reportedly is operating at 

capacity (850 gallons per minute). 

Pumping from the Black Cloud Mine is intended to lower water levels in the Yak Tunnel above 

the suspected blockage. The contingency plan calls for one year of continuous pumping to assess 

how water levels respond. 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project Manager, 

Stan Christensen and Kenneth Napp, the HDR Project Manager. The assessment of Site 

conditions relied heavily on the recent observations of regulatory agency personnel interviewed 

during this Five-Year Review. 

Based on the Site Inspection, conditions documented during the last Five-Year Review and 

discussions with regulatory agency personnel, all physical remediation elements in OU1 have 

been constructed and are in working order. 

6.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• The Yak Tunnel improvements, including the bulkhead and monitoring network 

reportedly are operating as intended. However, the presence of rising water levels in the 

upper reaches of the tunnel indicates the presence of a blockage within the tunnel. 

Mitigation measures have been implemented in accordance with Monitoring and 

Contingency Plans as intended by the decision documents. 

• The primary indicators of treatment plant performance are capacity and effluent quality. 

Capacity remains adequate to treat all waters emanating from the Yak Tunnel. Therefore, 

this portion of the remedy is functioning as intended by the decision documents. 

However, mitigation of rising water levels in the Yak Tunnel requires active pumping of 

the Black Cloud Mine. The pumping rate is limited by the available excess capacity of 

the Yak Treatment Plant (beyond the flows emanating from the Yak Tunnel). Pumping of 

the Black Cloud Mine began in March 2006 and it is premature to quantify the 

effectiveness of this mitigation method. 

• A review of monthly monitoring reports indicated that effluent quality has consistently 

met quality standards and reporting requirements required by the ROD and subsequent 

modifications. 
California Gulch Five-Year Report

Page 16 of 89 

Question B: Are the exposure assumptions, toxicity data, and cleanup levels and RAOs used 

at the time of the remedy selection still valid? 

• The purpose of the OU1 remedy is to control and treat waters emanating from the Yak 

Tunnel. Numerical discharge limits are relevant only for effluent quality. Therefore, a 

review of exposure assumptions, toxicity and other risk assessment-related issues is not 

necessary. 

• No new or changed ARARs have been identified by the State of Colorado or EPA at the 

time of this Five Year Review that would affect treatment plant effluent standards. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• Mitigation of rising water levels caused by a suspected blockage in the Yak Tunnel 

through dewatering via the Black Cloud Mine should be carefully monitored to determine 

effectiveness and minimize the potential for a sudden release of impounded water. 

• Financial assurance for continued operation of the Yak Treatment Plant has not been 

established. 

6.6 Issues 

Based on the information collected during the Five-Year Review, the following issues were 

identified: 

Table 6-2 

OU1 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 Rising water levels in upper portion of Yak Tunnel. No Potentially 

2 

Financial assurance for continued operation of the Yak 

Treatment Plant has not been established. No Potentially 
California Gulch Five-Year Report

Page 17 of 89 

6.7 Recommendations and Follow-Up Actions 

Table 6-3 

OU1 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow-Up 

Party 

Responsible Due Date

1 Rising water levels in upper 

portion of Yak Tunnel. 

Monitor effectiveness of 

dewatering from Black Cloud 

Mine 

ASARCO, 

Resurrection. 

Res-ASARCO 

On-going

2 

Financial assurance for 

continued operation of the Yak 

Treatment Plant has not been 

established. 

Establish financial assurance. Resurrection/EP

A 12/07 

6.8 Protectiveness Statement 

The remedy is currently protective of human health and the environment. However, mitigation of 

rising water levels caused by a suspected blockage in the Yak Tunnel through dewatering via the 

Black Cloud Mine should be carefully monitored to determine effectiveness. 
California Gulch Five-Year Report

Page 18 of 89 

7.0 Operable Unit 2 - Malta Tailing Impoundment, Malta Gulch Tailing Impoundment 

and Lower Malta Gulch Fluvial Tailing 

7.1 Description 

Operable Unit 2 consists of three waste features: Malta Tailing Impoundment, Malta Gulch 

Tailing Impoundment and Lower Malta Gulch Fluvial Tailing (Figure 7-1; Appendix A). Malta 

Tailing Impoundment consists of three small impoundments occupying 4.6 acres and estimated 

contain approximately 10,000 cubic yards or waste. It was constructed by Leadville Silver & 

Gold for a pyrite recovery process mill that operated from 1983 to 1988. 

Malta Gulch Tailing Impoundment is approximately 23 acres in size, located at the upper end of 

Malta Gulch, and contains an estimated total of 1,510,000 tons of waste. The first tailing 

impoundment was created by the Ore & Chemical Company (OCC) as part of a sink-float mill 

that operated from 1943 to 1946. After purchase in 1968 by the Leadville Corporation, the 

property was leased from 1974 to 1987 to the Hecla Mining Company (known as Hecla/Day). 

Hecla/Day used the site for disposal of silver ore tailing from the Sherman Mine, constructing 

four additional impoundments and two clarification ponds in the area of the original OCC tailing 

impoundment. Further, the Leadville Corporation (or its precursors) operated a mill utilizing a 

cyanide leach process for silver extraction from the early 1970's until 1986. This operation 

disposed of approximately 50,000 tons of cyanide bearing tailing at the Malta Gulch site. On 

November 17, 2005 the Colorado Division of Reclamation Mining and Safety (DRMS) initiated 

a bond forfeiture with the permitee, Leadville Corporation, for the reclamation of OU2 facilities 

operated under the permit. 

Lower Malta Gulch is directly downstream of the Malta Gulch Tailing Impoundment. When 

OCC operated, the tailing impoundments were not entirely effective for containment, as 

approximately 600,000 tons of the tailing washed or flowed down Lower Malta Gulch. As a 

result, the Lower Malta Gulch Fluvial Tailing area was created. The Lower Malta Gulch Fluvial 

Tailing area is approximately 26 acres in size, consisting of fluvial tailing deposits with an 

estimated volume of 30,000 cubic yards. 
California Gulch Five-Year Report

Page 19 of 89 

Table 7-1 indicates the types of contamination found in the different media on-site: 

Table 7-1 

Types of Contamination in Each Media for OU2 

Media Contamination

Shallow Tailing Elevated lead and zinc. 

Deeper Tailing Elevated lead and zinc are found in the Hecla and Pre-Hecla tailing. 

Fluvial Tailing Elevated lead. 

Table 7-2 lists the chronology of important events for Operable Unit 2 of the California Gulch 

site. 

Table 7-2 

Chronology of Site Events for OU2 

Date Event

09/08/83 California Gulch placed on NPL 

01/87 Phase I Remedial Investigation Report 

09/91 Administrative Order on Consent for EE/CA at the Malta Gulch Tailing Impoundments 

01/93 Partial Consent Decree with Hecla Mining Company to settle Hecla’s Site wide Liabilities 

01/93 Partial Consent Decree with Leadville Silver and Gold Company to settle their Site wide 

Liabilities 

08/93 EE/CA issued for Malta Gulch Tailing Impoundments 

09/10/93 Action Memorandum issued for Removal Action at Malta Gulch Tailing Impoundments 

08/14/95 Action Memorandum issued for Time Critical Removal Action at the Lower Malta Gulch 

Fluvial Tailing 

09/05/95 Start date for Removal Action at Lower Malta Gulch Fluvial Tailing (8/14/95 Action 

Memorandum) 

10/05/95 Start date for Removal Action at Malta Gulch Tailing Impoundment (9/10/93 Action 

Memorandum) 

08/09/96 Action Memorandum issued for Time Critical Removal Action at Malta Tailing 

Impoundment 

09/04/96 Start Date for Time Critical Removal Action at Malta Gulch Tailing Impoundment (8/9/96 

Action Memorandum) 

11/07/97 Discovery of drums at Leadville Mill 

03/31/97 Completion of Removal Actions identified in Action Memorandum dated 9/10/93, 8/14/95, 

8/9/96 

04/15/98 Action Memorandum issued for Time Critical Removal Action of Leadville Mill drums 

07/02/98 Time critical drum Removal Action completed 

08/18/98 Final Pollution Reports on 9/10/93, 8/14/95, 8/9/96 Action Memorandum 

09/30/99 Record of Decision 

02/12/01 Intent to delete OU2 from the NPL 

6/01 Deleted from NPL 
California Gulch Five-Year Report

Page 20 of 89 

7.2 Response Actions 

Response Action Selection/Implementation 

In September of 1991, EPA and Hecla Mining Corporation signed an Administrative Order on 

Consent for the performance of an engineering evaluation/cost assessment (EE/CA) at the Malta 

Gulch Tailing Impoundments. The purpose of the EE/CA was to determine the nature and extent 

of releases and to determine an appropriate response action. 

EPA entered into agreements in January of 1993 with Hecla/Day, Leadville Corporation, and 

Leadville Silver & Gold to define the extent of liability these companies would have in paying 

for cleanup at the Malta Gulch Tailing Impoundment and Malta Tailing Impoundment. Under a 

subsequent partial consent decree between U.S. EPA and Hecla/Day, $680,000 was set aside to 

perform cleanup at the site. An August 1994 Consent Decree allowed the US, as the successor to 

OCC, to settle their liabilities at the Lower Malta Gulch Fluvial Tailing. 

The remediation of OU2 occurred through four separate Removal Actions. In September 1999, 

the U.S. EPA issued a ROD for OU2 that determined that no further action was needed as a 

result of the four separate Removal Actions. These Removal Actions are summarized in Table 

7-3.

Table 7-3 

Response Actions for OU2 

Area

Action 

Memorandum 

Date

Removal Action Taken Start 

Date

Completion 

Date

Malta Gulch 

Tailing 

Impoundment 

09/10/93 

Grade and revegetate contiguous fluvial 

tailing. 

Remove non-contiguous pockets of 

fluvial tailing and dispose of the material 

in the Malta Gulch Tailing Impoundment. 

Provide for long term maintenance and 

monitoring. 

10/05/95 03/17/97 

Lower Malta 

Gulch Fluvial 

Tailing 

08/14/95 

Grade and revegetate contiguous fluvial 

tailing. 

Remove non-contiguous pockets of 

fluvial tailing and dispose of the material 

in the Malta Gulch Tailing Impoundment. 

Provide for long term maintenance and 

monitoring. 

09/05/95 03/17/97 

Malta Tailing 

Impoundment 08/09/96 

Grade, compact, and revegetate the 

impoundments. 

Dispose of pyritic materials from Apache 

Energy and Materials property. 

Provide for long term maintenance and 

monitoring of the vegetated cap/cover. 

09/04/96 03/31/97 
California Gulch Five-Year Report

Page 21 of 89 

Table 7-3, cont’d 

Response Actions for OU2 

Area

Action 

Memorandum 

Date

Removal Action Taken Start 

Date

Completion 

Date

Leadville 

Drums 

04/15/98 

Stage 42 drums in secure location. 

Dispose or recycle oily liquids in 

accordance with Standards for the 

Management of Used Oil, 40 CFR 279. 

Transport hazardous wastes to RCRAapproved treatment or disposal facility. 

05/26/98 07/02/98 

System Operation/Operation and Maintenance 

In addition to the four removal actions, the 1999 ROD specified the following monitoring 

requirements to maintain the effectiveness of the removal actions: 

• Monitor vegetative cover. 

• Inspect impoundments. 

• Review zoning definition to ensure consistency with the remedy. 

• Review the status of the Colorado Division of Mining and Geology (DMG) permit and 

use of the mill and impoundments. 

• Upon termination of the DMG permit, ensure that the final facility reclamation is 

protective of human health and the environment. 

• Monitor groundwater in June of each year at nine locations for metals and other inorganic 

parameters. 

7.3 Progress Since the Last Five Year Review 

The last site-wide Five Year Review, which was finalized on September 29, 2001, indicated that 

all of the removal actions had occurred. In addition, Operable Unit 2 was nominated by U.S. 

EPA for deleting as an NPL site on February 12, 2001 and deleted in June of 2001. 

Activities since the last Five-Year Review include the preparation of two monitoring summary 

reports (2002 and 2004) limited to an assessment of vegetative cover and erosional features. 

7.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report. 

• OU2 2004 Monitoring Summary, California Gulch Superfund Site Operable Unit 2 - 

Malta Gulch, Colorado Mountain College, March 2005. 

• Site-Wide Groundwater Sampling, Summer 2005, California Gulch Superfund Site, Tetra 

Tech RMC, December 2005. 
California Gulch Five-Year Report

Page 22 of 89 

Interviews were conducted with the following individuals to provide supplemental technical 

information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Mike Holmes – USEPA 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 

Data Review 

Surface water quality data for the period 1995 through 2005. 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project Manager, 

Stan Christensen and Kenneth Napp, the HDR Project Manager. The assessment of Site 

conditions relied heavily on the recent observations of regulatory agency personnel interviewed 

during this Five-Year Review. 

Based on the Site Inspection, conditions documented during the last Five-Year Review, 

discussions with regulatory agency personnel, and monitoring reports, all physical remediation 

elements in OU2 have been constructed and are in working order. Distressed vegetation was 

noted during the summer of 2004 (2004 Monitoring Summary) and was again reported by EPA 

personnel in 2006. 

7.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• The 2004 monitoring report identified numerous areas associated with sparse to no 

vegetation on the Malta Tailing Impoundment. Minimal vegetation success and the 

presence of invasive plant species were identified associated with the Malta Gulch 

Tailing (HECLA facility). EPA attributed this condition to a drought that had occurred 

during the summer of 2004. EPA personnel reported that areas of sparse or no vegetation 

remain in OU2. 

• On November 17, 2005 the Colorado Division of Reclamation Mining and Safety 

(DRMS) initiated a bond forfeiture with the permitee, Leadville Corporation for the 

reclamation of OU2 facilities operated under the permit. Once the DRMS completes final 

reclamation activities, EPA and CDPHE will assess the reclaimed facilities for 

unacceptable residual risks to human health or the environment. This will include the 

potential need for additional ICs to prevent disturbance of remediation/reclamation 

features under current zoning for industrial/mining uses. 

• Procedures are in place for notification of EPA and CDPHE should a change in land use 

be approved by local governments. 
California Gulch Five-Year Report

Page 23 of 89 

• Monitoring of vegetative covers appears to be occurring in accordance with the ROD 

requirements. The Site-Wide Groundwater Sampling Report (Summer 2005) identifies no 

exceedences of human health (primary) groundwater standards for the nine monitoring in 

the vicinity of OU2, however, one well showed a secondary and agricultural exceedence 

for one analyte. 

• Based on document review, the Site Inspection and discussions with regulatory agency 

personnel, the remedy is functioning as intended by the decision documents. 

Question B: Are the exposure assumptions, toxicity data, and cleanup levels and RAOs used at 

the time of the remedy selection still valid?

• See Section 3.0 for a discussion of the Human Health and Risk Assessments. 

• No new or changed ARARs have been identified by the State of Colorado or EPA at the 

time of this Five Year Review that would apply to OU2. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• An Institutional Control Overlay (ICO) District was established to meet post-reclamation 

land use restriction requirements. However, the ICO District was repealed by Lake 

County in 2006. As a result, concerns remain regarding protectiveness of the remedy. 

• Settlement funds for operation and maintenance of the remedy are exhausted and the use 

Superfund resources is not feasible. 

7.6 Issues 

Based on the information collected during the Five-Year Review, the following issues were 

identified: 

Table 7-4 

OU2 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 Vegetative cover requires maintenance. No Yes 

2 

Additional ICs may be needed to ensure protection of human 

health in the event of changes in zoning or to preclude 

disturbance of engineered remedies as a result of development 

consistent with current zoning. 

Potentially Potentially 

3 Settlement funds have been exhausted and use of Superfund 

resources is not permitted. No Potentially 
California Gulch Five-Year Report

Page 24 of 89 

7.7 Recommendations and Follow-Up Actions

Table 7-5 

OU2 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up Party Responsible Due Date 

1 Vegetative cover requires 

maintenance. 

Perform maintenance as required 

following the next scheduled 

annual inspection. 

Responsibility for 

O&M requires 

clarification 

12/07 

2 

Additional ICs may be needed to 

ensure protection of human 

health in the event of changes in 

zoning or to preclude disturbance 

of engineered remedies as a result 

of development consistent with 

current zoning. 

Investigate the impacts of mine 

permit expiration on remedy 

protectiveness and develop/ 

implement ICs, as necessary. CDPHE 12/08 

3 

Settlement funds have been 

exhausted and use of Superfund 

resources is not permitted. 

Funding of operation and 

maintenance requires clarification EPA/CDPHE 12/08 

7.8 Protectiveness Statement 

The remedy is currently protective of human health and the environment. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted 

past or current protectiveness as the remedies were undisturbed at the time of this Five-Year 

Review. However, the potential exists for future impacts on remedy protectiveness if such an 

institutional control is not developed and implemented. EPA and CDPHE are informally notified 

by the County of any changes in zoning. Although this is not a formalized IC, it allows the 

remedy to be protective until an IC is formalized. 
California Gulch Five-Year Report

Page 25 of 89 

8.0 Operable Unit 3 - Denver & Rio Grande Railroad (D&RG) Slag Piles/Railroad 

Easement/Railroad Yard 

Operable Unit 3 (OU3) includes three slag piles (Arkansas Valley, La Plata, and Harrison St.) 

owned by the Denver & Rio Grande Western Railroad Company (D&RGW), an easement that 

runs diagonally through the City of Leadville, and a portion of the rail yard owned by D&RGW. 

Figure 8-1 (Appendix A) illustrates the major features of OU3. 

8.1 Description 

Arkansas Valley

The Arkansas Valley (AV) Slag Pile covers approximately 40 acres just west of Stringtown. The 

pile generally consists of slag produced by the AV Smelter that operated from 1882 to 1960. 

Based upon aerial photography, the pile volume in the late 1950s was approximately 1.2 million 

cubic yards, whereas in 1998 approximately 422,000 cubic yards of slag remained. The volume 

of stockpiled fine slag at the AV Smelter slag pile is approximately 190,000 cubic yards. 

La Plata

The La Plata Slag Pile, located west of the city limits of Leadville on Elm Street, has a volume 

estimated at 105,000 cubic yards. 

Harrison Street

The Harrison Street Slag Pile was located near the northeast corner of Harrison Avenue and Elm 

Street, in a residential area. The original slag pile ranged from 20 to 50 feet in height and 

covered an area of approximately 3 acres. The Harrison Street Slag Pile was removed to original 

grade and relocated to the AV Slag Pile in March 1998. 

Rail yard

The rail yard, located between 12th Street, Highway 24 and 17th Street, has seen over 130 years 

of transportation activities, mostly associated with mining in the area. The portion of the rail yard 

formerly owned by D&RGW is located near the north end of the town of Leadville and 

encompasses an area of roughly 43 acres and is crossed by abandoned rail lines and access roads. 

Slag was used in the rail yard as ballast and as a road base to provide support for heavy vehicle 

traffic. Slag was also deposited around the loading dock due to spillage during transportation 

activities. 

Rail Easement

The rail easement includes the portion of railroad track that runs diagonally through the town of 

Leadville and consists of approximately 25 feet on either side of the track centerline. Slag was 

used as a road base to provide support for heavy vehicle traffic. Slag was also deposited as 

spillage from passing rail cars.
California Gulch Five-Year Report

Page 26 of 89 

Table 8-1 indicates the types of contamination found in the different media on-site:

Table 8-1 

Types of Contamination in Each Media for OU3 

Media Contamination

Slag Elevated levels of zinc, lead, arsenic, and cadmium. Low acid-generating potential and a 

neutral to basic pH. 

Fine Slag (less than 

3/8 of an inch) 

Elevated lead. 

Table (8-2) lists the chronology of important events for OU3 of the California Gulch site. 

Table 8-2 

Chronology of Site Events for OU3 

Date Event

09/08/83 California Gulch placed on NPL 

1986 U.S. EPA’s contractor sampled the three slag piles as part of the California Gulch site 

Remedial Investigation 

01/87 Phase I Remedial Investigation Report 

1988 Soils Investigation conducted that included sampling of slag from the Harrison Street pile, La 

Plata pile, and an area west of Leadville (AV Smelter Slag Pile not included) 

05/89 U.S. EPA conducted second sampling of slag to determine the concentrations of metals in 

three D&RGW slag piles and to evaluate potential of migration 

12/03/91 Administrative Order on Consent with D&RGW for remedial investigation/feasibility study 

(RI/FS) of slag piles 

1992 Remedial Investigation/Feasibility Study (RI/FS) completed for seven major lead slag piles 

and a zinc slag pile 

03/93 Site-Wide Screening Feasibility Study (SFS) completed 

09/15/93 Administrative Order on Consent with D&RGW for completion of investigation and 

remediation activities 

07/95 D&RGW submitted a ballast operations plan to U.S. EPA 

08/95 Ballast operations commenced 

05/96 D&RGW submitted a feasibility study for the stockpiled fine slag at the AV Smelter slag pile 

according to Consent Decree terms 

05/06/98 Record of Decision signature for OU3 (only address the fine slag stockpiled as a subpile of 

the Arkansas Valley Smelter Slag Pile 

02/25/99 Request for Certification of Closure from Union Pacific Railroad Company 

11/03/2000 Request for Partial Deletion of the Mineral Belt Trail from the State of Colorado to the U.S. 

EPA 
California Gulch Five-Year Report

Page 27 of 89 

8.2 Response Actions 

Response Action Selection/Implementation 

Arkansas Valley Slag Pile

Only fine slag, a separate stockpile at the AV Slag Pile consisting of slag with a particle size of 

3/8" or less, is addressed by the ROD. Based on consideration of CERCLA requirements, 

detailed analyses of alternatives, and public comments, U.S. EPA determined that a No Action 

alternative was the appropriate remedy. The No Action alternative leaves the stockpiled fine 

slag in its existing condition with no control or cleanup planned. The selected remedy is 

protective of human health and the environment and is considered effective because no complete 

human or ecological exposure pathways were identified for the stockpiled fine slag and the 

potential for release of metals in leachate from the stockpiled fine slag is minimal. The ROD 

also provides a contingency to use the slag in the future if regional market demand exists for the 

material as a component in construction materials. 

La Plata Slag Pile

Based on the lack of fine slag or leachate generation, the ROD did not require remedial action at 

this location. 

Harrison Street Slag Pile

As part of their ballast operations, D&RGW, approximately 104,000 cubic yards of slag were 

relocated to the AV Slag Pile in March 1998 to bring the Harrison Street Slag Pile to grade. As a 

result, soils were exposed containing elevated concentrations of lead. These soils create the 

potential for unacceptable human health risks should the property be developed for residential 

use. To date, the land remains vacant. 

Easement

In work done under a Consent Decree with the D&RGW submitted a work plan proposing the 

easement to be converted into a segment of the Mineral Belt Bike Trail. The Mineral Belt Trail 

was completed in the late 1990's. Ownership of the easement was subsequently donated to Lake 

County via a quitclaim deed. 

Rail yard

During the summer and fall of 1997 D&RGW removed 1,264 cubic yards fine slag from the Rail 

yard and placed it onto the AV Slag Pile. As a result, soils were exposed containing elevated 

concentrations of lead. These soils create the potential for unacceptable human health risks 

should the property be developed for residential use. To date, the land remains vacant. 

System Operation/ Operation and Maintenance 

No system operation is required for the fine slag piles because the no action alternative was 

chosen. The1998 MOU entered into between Union Pacific, Lake County and US EPA 

indicated that the fine slag on the easement would be incorporated into the Mineral Belt Trail and 

that Lake County is responsible for long term maintenance on the Mineral Belt Trail. Slag has 

potential for resource utilization. 
California Gulch Five-Year Report

Page 28 of 89 

However, any use of the slag would require it to be encapsulated for reuse. Encapsulation can 

include the use of fine slag in concrete or asphalt aggregate, as a road base, or as backfill (so 

long as the slag is chemically bound or physically separated from an exposure by a barrier 

consisting of a different material). 

8.3 Progress Since the Last Five Year Review 

Activities related to OU3 since the last Five-Year Review finalized on September 29, 2001 was 

limited to maintenance of the Mineral Belt Trail.
California Gulch Five-Year Report

Page 29 of 89 

8.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report 

Interviews were conducted with the following individuals to provide supplemental technical 

information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Mike Holmes – USEPA 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 

Data Review 

Surface water quality data for the period 1995 through 2005. 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project Manager, 

Stan Christensen and Kenneth Napp, the HDR Project Manager. The assessment of Site 

conditions relied heavily on the recent observations of regulatory agency personnel interviewed 

during this Five-Year Review. 

Based on the Site Inspection, conditions documented during the last Five-Year Review and 

discussions with regulatory agency personnel, all physical remediation elements in OU3 have 

been constructed and are in working order. 

8.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• The remedial goals of OU3 are being met for fine slag, as fine slag has been either been 

consolidated or capped. 

• Remaining contaminated surface soils at the former Harrison Street slag pile will be 

capped should the land use change to residential. Procedures are in place for notification 

of EPA and CDPHE should a change in land use be approved by local governments. 

• The Mineral Belt Trail is being maintained as required under the 1998 MOU. 

• Based on document review, the Site Inspection and discussions with regulatory agency 

personnel, the remedy is functioning as intended by the decision documents. 
California Gulch Five-Year Report

Page 30 of 89 

Question B: Are the exposure assumptions, toxicity data, and cleanup levels and RAOs used at 

the time of the remedy selection still valid?

• See Section 3.0 for a discussion of the Human Health Risk Assessments. 

• No new or changed ARARs have been identified by the State of Colorado or EPA at the 

time of this Five Year Review that would apply to OU3. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• No ICs exist (or were called for in the ROD) to ensure protection of human health in the 

event of changes in zoning. An Institutional Control Overlay (ICO) District was 

established to meet land use restriction requirements. However, the ICO District was 

repealed by Lake County in 2006. As a result, concerns remain regarding protectiveness 

of the remedy. 

8.6 Issues 

Based on the information collected during the Five-Year Review, the following issues were 

identified: 

Table 8-3 

OU 3 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 No ICs exist to ensure protection of human health in the 

event of changes in zoning. No Potentially 

8.7 Recommendations and Follow-Up Actions 

Table 8-4 

OU3 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up Party Responsible Due Date 

1 

No ICs exist to ensure protection 

of human health in the event of 

changes in zoning. 

Prepare an ESD identifying 

appropriate ICs and implement the 

controls 

EPA 12/08 
California Gulch Five-Year Report

Page 31 of 89 

8.8 Protectiveness Statement 

The remedy is currently protective of human health and the environment. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted 

past or current protectiveness as the remedies were undisturbed at the time of this Five-Year 

Review. However, the potential exists for future impacts on remedy protectiveness if such an 

intuitional control is not developed and implemented. EPA and CDPHE are informally notified 

by the County of any changes in zoning. Although this is not a formalized IC, it allows the 

remedy to be protective until an IC is formalized. 
California Gulch Five-Year Report

Page 32 of 89 

9.0 Operable Unit 4 - Upper California Gulch 

9.1 Description 

The Upper California Gulch site, OU4, is part of the Leadville mining district. Placer gold 

mining started with the discovery of gold in California Gulch in 1860. When the placer deposits 

were exhausted, underground mining was used to extract gold, silver, lead, and zinc ore. Breece 

Hill, above Upper California Gulch, was networked with underground mines, in an area 

approximately 8 square miles in size. As mines were developed, waste rock was excavated and 

left near the mine entrances. Although a total of 131 waste piles were initially identified in OU4, 

the number of waste rock piles of concern in the OU has been reduced to 20 through remedial 

investigation and analytical screening. A map of OU4 is provided as Figure 9-1 (Appendix A). 

The waste piles are identified in the Upper California Gulch site by sub-basin: Garibaldi, Whites 

Gulch, Nugget Gulch, AY Minnie, Iron Hill, and South Area (also includes Fluvial Tailing Site 4 

known as Oro City). The twenty waste rock piles in these sub-basins contain a total estimated 

volume of 431,000 cubic yards, impacting 28.3 acres. Waste rock piles are primarily weathered 

porphyry with limited to no vegetation, and with highly oxidized surfaces. 

Fluvial tailing and fluvial tailing mixed with alluvial sediments are located in the South Area and 

Fluvial Tailing Site 4, and are estimated at 102,000 cubic yards in volume. The tailing are 

approximately 75 percent unvegetated with grasses and lodgepole pine in the remainder. There 

is also a wetland area along the Upper California Gulch channel within the site. Fluvial Tailing 

Site 4 (Oro City) is considered a cultural and historic resource for the Leadville mining district. 

Flow in the Upper California Gulch tributaries is primarily attributable to spring runoff, 

generally occurring from early May to late summer, with a peak in early June. Flow can also 

occur as a result of summer thunderstorms and other rain events. 

The Upper California Gulch site is zoned for Industrial/Mining uses. 
California Gulch Five-Year Report

Page 33 of 89 

Table 9-1 lists the chronology of important events for Upper California Gulch. 

Table 9-1 

Chronology of Site Events for OU4 

Date Event

09/08/83 California Gulch placed on NPL 

1986 Final Yak Tunnel/California Gulch Remedial Investigation 

01/87 Phase II Remedial Investigation Report 

8/94 Resurrection enters into a Consent Decree with the United States, the State of Colorado, and 

other PRPs to perform remediation work in OU4 

07/95 EE/CA issued for Upper California Gulch 

08/04/95 Action Memorandum issued for Removal Action at the Garibaldi Mine site 

09/22/95 Start date for Removal Action at Garibaldi Mine site (08/04/95 Action Memorandum) 

10/31/95 Action Memorandum issued for Time Critical Removal Action at a portion of Upper 

California Gulch 

01/96 Completion of Removal Action at Garibaldi Mine site (08/04/95 Action Memorandum) 

07/19/96 Action Memorandum issued for Removal Action at the Whites Gulch Sub-basin 

08/28/96 Start date for Removal Action at the Whites Gulch Sub-basin, Agwalt Mine site (07/19/96 

Action Memorandum) 

10/03/96 Start date for Time Critical Removal Action at a portion of Upper California Gulch (10/31/95 

Action Memorandum) 

11/18/96 Action Memorandum amendment to July 19, 1996 memorandum. Amendment deletes the 

Removal Action at the Waste Rock Pile UCG-92A. 

07/97 Completion of the Whites Gulch Sub-basin (Agwalt Mine) and a portion of Upper California 

Gulch (10/31/95 and 07/19/96 Action Memorandum) 

01/15/98 U.S. EPA Proposed Plan 

03/31/98 Record of Decision OU4 

07/30/98 Final Pollution Reports on 08/04/95, 10/31/95, and 07/19/96 Action Memorandum 

1998-2001 Remedial Action 

02/03 Construction Completion Report 

03/04 Explanation of Significant Differences deferring remedial action at Oro City to OU12 

9.2 Response Actions 

Response Action Selection/Implementation 

In March, 1998, the U.S. EPA issued a ROD for OU4. Removal activities completed prior to the 

issuance of the ROD include the Garibaldi Sub-basin, the Agwalt Mine in Whites Gulch, and the 

Upper California Gulch Surface Water Diversion. The ROD identified additional response 

activities in Whites Gulch (Printer Girl Waste Pile), Nugget Gulch Waste Rock, AY Minnie 

Waste Rock, Iron Hill Waste Rock, and Fluvial Tailing Site 4. 

Fluvial Tailing Site 4, which is also known as Oro City, was not subject to any remediation 

because of concern regarding the historical significance of the area as an early mining camp. 

U.S. EPA has deferred remediation activities at this particular site until a determination can be 

made if the remaining areas of remedy specified in the OU4 ROD are sufficient to meet any 

subsequent water quality standards established for the site. This assessment will be performed 

under OU12. 
California Gulch Five-Year Report

Page 34 of 89 

The RAOs for OU4 are identified in the ROD as: 

• Control erosion of contaminated materials into local water courses 

• Control leaching and migration of metals from contaminated materials into the surface water 

• Control leaching and migration of metals from contaminated materials into the groundwater 

Specific response actions are summarized in Table 9-2. 

Table 9-2 

Response Actions at OU4 

Area

Removal 

Action 

Memorandum 

Date and 

Action

Action Taken Start Date Completion 

Date

Garibaldi Mine 

Sub-bas 

8/4/95 

Non- Time 

Critical 

Removal Action 

Construct portal flow and run-on 

collection system to capture portal 

flow and divert it around the waste 

rock pile 

Construct riprap outlet structure 

Construct ditch crossing 

Construct two interceptor trenches to 

collect shallow alluvial flow and divert 

it around the waste rock pile 

09/22/95 01/96 

Upper California 

Gulch Surface 

Water Diversion 

8/14/95 

Time critical 

Removal Action

Excavate diversion pond embankment 

to the invert of existing pipe outlets. 

Remove waste rock and tailing to 

Oregon Gulch Tailing Impoundment. 

Rebuild embankment and regrade 

diversion pond slopes. 

Excavate and grade area upstream of 

diversion pond to increase pond water 

retention to 0.25 acre feet. Remove 

waste rock and tailing to Oregon 

Gulch Tailing Impoundment. 

Construct diversion pond spillway to 

prevent overtopping of flows up to 50 

cubic feet per second. 

Construct reinforced concrete 

diversion pond outlet structure on west 

end of diversion pond. 

Install rock filled High Density 

Polyethylene (HDPE) gabion check 

dam structures across the Upper 

California Gulch channel in three 

separate locations upstream of the 

diversion pond. 

11/31/95 06/97 
California Gulch Five-Year Report

Page 35 of 89 

Table 9-2, cont’d 

Response Actions at OU4 

Area

Removal 

Action 

Memorandum 

Date and 

Action

Action Taken Start Date Completion 

Date

Whites Gulch 

(Agwalt Mine 

Site) 

7/19/96 

Non-Time 

Critical 

Removal Action 

Collect and divert portal flow and runon away from the waste rock pile. 

Regrade disturbed area to blend into 

surrounding terrain and revegetate 

using broadcast seeding at a rate of 30 

pounds per acre 

08/28/96 06/97 

Nugget Gulch Remedial 

Action 

Consolidate waste rock piles Rubie 

(UCG-74), UCG-76, UCG-77, and 

North Mike (UCG-85) into Colorado 

Number 2 (UCG-71). 

Regrade, cover, and revegetate 

Colorado Number 2 waste pile. 

Construct run-on diversion ditches. 

1998 2001 

AY Minnie Waste 

Rock Pile 

Remedial 

Action 

Construct diversion ditches to reduce 

surface run-on and to reduce leaching 

and erosional releases. 

Realign Lake County Road 2 to 

provide area for construction of 

sediment pond and further add 

protection from stability failures of 

timber cribbing without destroying 

mining heritage and cultural resources. 

1998 2001 

Iron Hill Remedial 

Action 

Regrade, cover and revegetate waste 

Rock Pile UCG-12. 1998 2001 

Fluvial Tailing 

Site 4 and South 

Area 

Remedial 

Action 

Reconstruct Upper California Gulch 

stream channel and regrade selected 

fluvial tailing areas. 

Revegetate south area channel. 

The Oro City area in Fluvial Tailing 

Site 4 has not been addressed as 

specified in a March 2004 ESD. 

2000. 

Revegetation 

started in 2001. 

Oro City 

activity is 

deferred 

2001 

System Operation/ Operation and Maintenance 

OU4 has the following monitoring requirements: 

• Monitor vegetation cover and diversion channels. 

• Inspection and repair/cleanout sediment ponds and other features. 
California Gulch Five-Year Report

Page 36 of 89 

9.3 Progress Since the Last Five Year Review 

Activities in OU4 since the last Five-Year Review were limited to maintenance and reporting in 

accordance with Final California Gulch Superfund Site Operation and Maintenance Plan, Operable 

Units 4, 8 and 10 as revised in January 2005. Remedy elements identified in the previous Five-Year 

Review are limited to actions at Oro City which were subsequently deferred to OU12 under a March 

2004 ESD. 

9.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report 

• OU4, OU8 and OU10 Fall 2005 Inspection Report, Resurrection Mining Company 

Interviews were conducted with the following individuals to provide supplemental technical 

information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Mike Holmes – USEPA 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 

Data Review 

Surface water quality data for the period 1995 through 2005 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project Manager, Stan 

Christensen and Kenneth Napp, the HDR Project Manager. The assessment of Site conditions relied 

heavily on the recent observations of regulatory agency personnel interviewed during this Five-Year 

Review. 

Based on the Site Inspection, conditions documented during the last Five-Year Review and 

discussions with regulatory agency personnel, all physical remediation elements in OU4 have been 

constructed and are in working order. 

9.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• The 2005 Inspection Report described minor amount of accumulated debris in constructed 

channels as well as minor amounts of erosion. Based on this assessment, the remedy is 

functioning as intended by the design documents. 
California Gulch Five-Year Report

Page 37 of 89 

• Procedures are in place for notification of EPA and CDPHE should a change in land use be 

approved by local governments. 

• Based on document review, the Site Inspection and discussions with regulatory agency 

personnel, the remedy is largely functioning as intended by the decision documents. 

However, as discussed under Question C, below, the control of leaching and migration of 

metals from contaminated materials into the surface water may not have been achieved to the 

degree originally intended. 

Question B: Are the exposure assumptions toxicity data, and cleanup levels and RAOs used at the 

time of the remedy selection still valid?

• See Section 3.0 for a discussion of the Human Health Risk Assessments. 

• No new or changed ARARs have been identified by the State of Colorado or EPA at the time 

of this Five Year Review that would apply to OU4. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• RAO’s articulated in the ROD requiring, among other things, control of leaching and 

migration of metals from contaminated materials into the surface water may not have been 

achieved to the degree originally intended. This issue will be addressed under OU12 as 

specified in the 1994 CD. 

• No ICs exist (or were called for in the ROD) to ensure protection of human health in the 

event of changes in zoning or to prevent disturbance of engineered remedies as a result of 

development consistent with current zoning. An Institutional Control Overlay (ICO) District 

was established to meet post-response action land use restriction requirements. However, the 

ICO District was repealed by Lake County in 2006. As a result, concerns remain regarding 

protectiveness of the remedy. 

9.6 Issues 

Based on the information collected during the Five-Year Review, the following issues were 

identified: 

Table 9-3 

OU4 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 

Institutional controls are needed to ensure protection of 

human health in the event of changes in zoning or to 

preclude disturbance of engineered remedies as a result of 

development consistent with current zoning. 

No Yes 
California Gulch Five-Year Report

Page 38 of 89 

9.7 Recommendations and Follow-Up Actions 

Table 9-4 

OU4 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up Party Responsible Due Date 

1 

Institutional controls are needed 

to ensure protection of human 

health in the event of changes in 

zoning or to preclude disturbance 

of engineered remedies as a result 

of development consistent with 

current zoning. 

Prepare an ESD identifying 

appropriate ICs and implement the 

controls. Resurrection 

EPA 12/08 

9.8 Protectiveness Statement 

The remedy is currently protective of human health and the environment. However, future remedial 

work may be required in order to attain final Site-wide water quality standards as determined 

pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted 

past or current protectiveness as the remedies were undisturbed at the time of this Five-Year Review. 

However, the potential exists for future impacts on remedy protectiveness if such an intuitional 

control is not developed and implemented. EPA and CDPHE are informally notified by the County 

of any changes in zoning. Although this is not a formalized IC, it allows the remedy to be protective 

until an IC is formalized. 
California Gulch Five-Year Report

Page 39 of 89 

10.0 Operable Unit 5 - Asarco Smelters/ Colorado Zinc-Lead Mill Site 

10.1 Description 

Remedial action at OU5 was approximately 50% complete at the time of the Five-Year Review. 

Therefore, the remedy was not subjected to the Five-Year Review process. A summary of the OU 

and the remedy status is provided below. 

Operable Unit 5 (OU5) includes five smelter sites (Elgin Smelter, Grant/Union Smelter, Western 

Zinc Smelter, Arkansas Valley South Hillside Slag Pile collectively known as the EGWA sites), the 

Arkansas Valley Smelter and one mill site known as Colorado Zinc-Lead Mill (CZL). Maps of OU5 

are provided as Figures 10-1 and 10-2 (Appendix A). 

Prior to the remedial action smelter debris covered the site consisting primarily of demolition debris 

such as brick, concrete, metal, tile, wood, and glass as well as residual mine waste and smelter 

materials including slag, coke/charcoal, limestone, ore, matte, tailing, and flue dust. 

Table 10-1 lists the types of contamination found within OU5. 

Table 10-1 

Types of Contamination in Each Media 

Media Contamination

Soils 

Arkansas Valley Smelter – Results of the Soils Investigation indicate elevated arsenic, 

cadmium, lead, and zinc levels. Levels were highest from the samples taken from the 

bag-house area. 

Colorado Zinc-Lead Mill – Elevated lead levels. 

Elgin Smelter – Elevated lead and arsenic levels. 

Grant/Union Smelter – Elevated lead and arsenic levels. 

Western Zinc Smelter – Elevated lead and arsenic levels. 

Arkansas Valley South Hillside Slag Pile – Elevated arsenic and lead levels. 
California Gulch Five-Year Report

Page 40 of 89 

Table 10-2 summarizes the chronology of important events in OU5. 

Table 10-2 

Chronology of Site Events for OU5 

Date Event

09/08/83 California Gulch placed on NPL 

01/87 Phase I Remedial Investigation Report 

09/90 U.S. EPA and ASARCO entered into an Administrative Order on Consent for the 

performance of soils sampling and air monitoring. 

1991 U.S. EPA issued a Unilateral Administrative Order requiring ASARCO to conduct studies 

and complete RIs. 

1991 Smelter Site Reconnaissance 

1991 Surface Water RI of the California Gulch site conducted 

1991 through 

1992 

Hydrogeologic RI of the California Gulch site conducted 

1993 Screening Feasibility Study conducted to initiate the overall CERCLA feasibility study 

process at the California Gulch site. 

04/93 Smelter Remedial Investigation Report 

08/94 ASARCO entered into a Consent Decree with the United States, State of Colorado, and other 

PRPs. ASARCO agreed to perform certain remediation work in OU5, OU7, and OU9. 

1996 Final Surface Water RI Report 

1996 Final Hydrogeologic RI Report 

02/99 Focused Feasibility Study for Operable Unit 5, EGWA Sites submitted by ASARCO. 

02/00 Focused Feasibility Study for Operable Unit 5 Arkansas Valley Smelter and Colorado ZincLead Mill Site submitted by ASARCO. 

07/27/00 Proposed Plan describing U.S. EPA’s preferred alternative issued. 

09/29/00 Record of Decision for AZ/CZL site of Operable Unit 5. 

10/31/00 Record of Decision for EGWA site of Operable Unit 5. 

Fall 2004 to 

Present 

Remedial Action 
California Gulch Five-Year Report

Page 41 of 89 

10.2 Response Actions 

Response Action Selection/Implementation 

The ROD for the EGWA smelter sites was issued in October of 2000 and the AV/CZL ROD was 

issued in September of 2000. The remedy is summarized in Table 10-3: 

Table 10-3 

Response Actions for OU5 

Area Remedy to be Implemented Start 

Date

Completion 

Date

Arkansas Valley 

Smelter/Colorado 

Zinc-Lead Mill 

Demolish smelter structures and excavate/transport flue 

dust to a lined repository. 

Perform site grading to promote positive surface water 

drainage. 

Consolidate tailing and non-residential soils located at 

the AV Smelter site and place an 18-inch thick soil 

cover. Construct run-on diversion ditches. 

Establish ICs such as deed notices or deed restrictions to 

provide notification that a barrier is in place and to 

restrict land. 

Provide services and cleanup consistent with the Lake 

County Community Health Program to one occupied 

residence. 

Develop and implement an operation and maintenance 

program to include inspection and maintenance of the 

cover and surface water controls. 

06/02 In Progress 

Elgin Smelter/ 

Grant/Union 

Smelter/Western 

Zinc Smelter/ 

Arkansas Valley 

South Hillside Slag 

Pile 

Establish ICs to warn of potential hazards and to 

maintain the effectiveness of the remedy by limiting 

access to or use of the property. 

Modify Lake County and/or City of Leadville zoning 

ordinances to create a zoning “overlay district” to 

provide a screening process to identify properties where 

special precautions or requirements may be necessary 

and a mechanism to notify owners and/or developers of 

these requirements. The Grant/Union, Western Zinc and 

Elgin Smelter sites will be included in the “overlay 

district.” 

Develop and implement an operation and maintenance 

program for the “overlay district”. 

10/31/00 In Progress 
California Gulch Five-Year Report

Page 42 of 89 

10.3 Progress Since Last Five Year Review 

Progress since the last Five Year Review, which was finalized on September 29, 2001 includes the 

following: 

• Completion of all Removal Actions 

• Maintenance of the Removal Actions 

• Release of the ROD 

• Remedial design activities. 

10.4 Protectiveness Statement 

Remedial work at the Arkansas Valley Smelter and Colorado Zinc-Lead Mill is incomplete. 

Therefore, the remedy is not yet protective although overall protectiveness is expected to be 

achieved once remedial construction is completed. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted 

past or current protectiveness as the remedy remains incomplete. However, the potential exists for 

future impacts on remedy protectiveness if such an intuitional control is not developed and 

implemented. EPA and CDPHE are informally notified by the County of any changes in zoning. 

Although this is not a formalized IC, it allows the remedy to be protective until an IC is formalized
California Gulch Five-Year Report

Page 43 of 89 

11.0 Operable Unit 6 - Starr Ditch/Penrose Dump/Stray Horse Gulch/Evans Gulch 

11.1 Description 

Remedial action at OU6 was incomplete at the time of the Five-Year Review. Therefore, the remedy 

was not subjected to the Five-Year Review process. However, unlike OU5, the remedy for OU6 

largely consists of modifications to Response Actions implemented under Action Memoranda. 

Therefore, the following discussion of OU6 includes an overall assessment of Response and (partial) 

Remedial Action effectiveness. 

Operable Unit 6 consists of several consolidated mine waste piles (including Hamm’s Tailing 

Impoundment and the Penrose Mine Waste Pile); and approximately 2,200 acres of mining wastes 

in Stray Horse Gulch, the upper portion and headwater of Evans Gulch, and the lower portion of 

Evans Creek. On its western boundary, OU6 also includes some residential areas in the City of 

Leadville, and a drainage corridor along 5th Street and Starr Ditch downstream of the confluence 

with the Stray Horse drainage. Figure 11-1 (Appendix A) illustrates the major features of OU6. 

The headwaters of Stray Horse Gulch are located east of Leadville in the area of Breece Hill and the 

Ibex/Irene Milling/Mining Complex. This water flows through Leadville via the 5th Street drain and 

Starr Ditch and eventually discharges to Lower California Gulch. 

Hamm’s Tailing Impoundment covers an area of approximately 6.5 acres with a volume of 

approximately 245,000 cubic yards. The impoundment is located in Stray Horse Gulch. 

The Penrose Mine Waste Pile was located south of East 4th Street in Leadville and east of Hazel 

Street. Penrose Mine Waste Pile covered an area of about 4 acres and contained about 173,000 

cubic yards of waste rock. 

Historically, during heavy periods of precipitation or snow melt, tailing materials from both Hamm’s 

and Penrose have been eroded and suspended in surface waters moving downslope through 

residential areas of Leadville. This surface water is collected by Starr Ditch and is conveyed by the 

ditch to California Gulch and the Arkansas River. In addition, metals leached from the multiple other 

mine wastes present in OU6 and were transported to California Gulch via Star Ditch. 

Current site uses for OU6 include recreation, commercial activities, mine tourism, and residential. 

The Leadville area has been classified as a National Historic Landmark, and Little Stray Horse 

Gulch contains several famous historic mines, including the Matchless Mine of Baby Doe and 

Horace Tabor. 
California Gulch Five-Year Report

Page 44 of 89 

Table 11-1 lists the types of contamination found at OU6. 

 Table 11-1 

Types of Contamination in Each Media 

Media Contamination

Sediments Based on data from the EE/CA, elevated metals contamination was found in the sampling 

stations along Stray Horse Gulch. 

Tailing/Waste 

Rock Piles 

The Stray Horse Gulch tailing/waste rock piles were analyzed by X-ray fluorescence for lead 

and arsenic concentrations as part of the Mine Waste Piles Remedial Investigation. Surface 

soils demonstrated elevated arsenic, lead, cadmium, and zinc levels. Subsurface and foundation 

soils contained elevated to significantly elevated arsenic, cadmium, lead, and zinc levels. 

Table 11-2 lists the chronology of important events for OU6 of the California Gulch site. 

Table 11-2 

Chronology of Site Events for OU6 

Date Event

09/08/83 California Gulch placed on NPL 

01/87 Phase I Remedial Investigation Report 

11/06/95 Action Memorandum issued for Time Critical Removal Action at the Stray Horse Gulch 

Sediment Dam 

05/01/96 Action Memorandum issued for Emergency Response Removal Action for the removal of 

sediments from the 5th Street Drainage Ditch and Starr Ditch 

07/26/96 Action Memorandum issued for Time Critical Removal Action at the Hamm’s Tailing 

Impoundment and the Penrose Mine Waste Pile 

06/97 EE/CA for Stray Horse Gulch 

06/24/97 Action Memorandum for Non-Time Critical Removal for Source Control Activities at 

Designated Mine Waste Piles 

05/98 Addendum to EE/CA for Stray Horse Gulch 

07/15/98 Action Memorandum for subsequent Non-Time Critical Removal Actions for Source Control 

at Designated Mine Waste Piles 

08/19/98 Final Pollution Reports on 11/06/95, 05/01/96 Action Memorandums 

10/26/98 Action Memorandum for a Non-Time Critical Removal Action for Water Management 

Activities at the Resurrection #1 Tailing Pile at the Upper End of Evans Gulch 

05/99 Final Addendum No. 2 to EE/CA fro Stray Horse Gulch 

06/02/99 Addendum to Action Memorandum for a Non-Time Critical Removal Action for Water 

Management Activities at the Resurrection #1 Tailing Pile at the Upper End of Evans Gulch 

(10/26/98) 

06/02/99 Addendum to Action Memorandum for subsequent Non-Time Critical Removal Actions for 

Source Control at Designated Mine Waste Piles (07/15/98) 

10/04/99 Final Pollution Report on 07/26/96 Action Memorandum for Time Critical Removal Action 

at the Hamm’s Tailing Impoundment and the Penrose Mine Waste Pile. 

06/20/00 Action Memorandum for a Time Critical Removal Action in the Greenback - RAM Runoff 

Collection System 

08/22/00 Amendment to Action Memorandum for a Time Critical Removal Action in the Greenback - 

RAM Runoff Collection System (06/20/00) 

10/16/00 Final Pollution Report on 06/2/00 Action Memorandum 

12/11/00 Final Phase I, II, III Removal Action Completion Report 

6/25/01 Action Memorandum for Ibex/Irene waste pile 

2002 Record of Decision 

2005 Construction of an outlet structure on the Gaw Shaft under a Non-Time Critical Removal 

2002-present Remedial Action (Removal of Ponsardine Waste Rock Pile, replacement of cribbing at 

Robert Emmett mine site, data collection to support design of bulkhead in LMDT) 
California Gulch Five-Year Report

Page 45 of 89 

11.2 Response Actions 

Response Action Selection/Implementation 

To date the following removal actions in OU6 as addressed in Action Memoranda have been 

completed:

Table 11-3 

Response Actions for OU6 

Area

Action 

Memorandum 

Date and Action

Removal Action Taken Start 

Date

Completion 

Date

5th Street, Starr 

Ditch, Harrison 

Slag Pile 

1990 

Removal Action 

Convert open ditches to covered culverts 

along both sides of 5th Street. 

Fence Starr Ditch from just north of 5th

Street to Monroe Street just east of the 

Harrison Street slag pile. 

1990 1990 

Stray Horse 

Gulch 

11/06/95 

Time Critical 

Removal Action 

Remove sediment from ditches and culverts 

around the Hamm’s Tailing Impoundment 

and from the 5th Street Drainage ditches 

and Starr Ditch 

Construct a sediment control dam across the 

road from the east end of Hamm’s Tailing 

Impoundment in east Leadville. 

08/24/95 08/30/95 

5th Street 

Drainage Ditch 

and Starr Ditch 

05/01/96 

Emergency 

Response 

Removal Action 

Remove sediment from the 5th Street 

Drainage Ditch from its headwall to and 

along Starr Ditch to its confluence with 

Lower California Gulch. 

05/06/96 05/10/96 

Hamm’s Tailing 

Impoundment 

and Penrose 

Mine Waste Pile 

07/26/96 

Time Critical 

Removal Action 

Transport the mine waste in the Penrose 

Mine Waste Pile to Hamm’s Tailing 

Impoundment 

Revegetate the Penrose footprint and 

reshape the Hamm’s Tailing Impoundment 

to a more uniform and stable configuration. 

If subsequent soil and/or air monitoring 

determines that adjacent residential 

properties have been impacted by this 

removal, soils which exceed 3,500 ppm of 

lead will be eligible for remediation under 

the Kids First Program. 

07/26/96 09/30/98 

Maid of Erin 

Wolftone Mine 

Adams Mill 

Mahala Mine 

Waste Piles 

06/24/97 

Phase I 

Non-Time Critical 

Removal Action 

Consolidate approximately 211,000 cubic 

yards waste from Maid of Erin Mine, 

Wolftone Mine, and the Mahala Mine 

Waste Piles. Place a liner system and rock 

cap over consolidated waste piles (3). 

06/24/97 1998 
California Gulch Five-Year Report

Page 46 of 89 

Table 11-3, cont’d 

Response Actions for OU6 

Area

Action 

Memorandum 

Date and Action

Removal Action Taken Start 

Date

Completion 

Date

Adelaide-Ward 

Mikados 

Highland Mary 

Pyrenees Waste 

Piles 

07/15/98 

Amendment to the 

06/24/97 Action 

Memorandum 

(Phase II) 

Construct surface water run-on diversion 

channels around six mine waste rock piles. 

Construct surface water run-off collection 

channels around four waste rock piles to 

capture and convey impacted water into 

retention basins. 

Construct surface water retention basins. 

Construct detention basins in lower Stray 

Horse Gulch to convey a 100 year storm 

event and to remain stable for a 500 year 

storm event. 

Rehabilitate Starr Ditch from 3rd Street to 

5th Street to convey the 100-year, 24- hour 

storm event and to remain stable for a 500 

year storm event. 

Revegetate disturbed areas and the Hamm’s 

and Penrose piles. 

1998 1999 

Ponsardine Pile, 

RAM and 

Greenback, and 

Resurrection No. 

1/Fortune Mine 

Waste Piles 

06/02/99 

Amendment to the 

06/24/97 Action 

Memorandum 

(Phase III) 

Construct surface water run-on diversion 

channels around mine waste rock piles. 

Construct surface water run-off collection 

channels around waste rock piles to capture 

and convey impacted water into retention 

basins. 

Construct surface water retention basins. 

. 

1999 1999 

Resurrection #1 

Tailing Pile 

10/26/98 

06/02/99 

Non-Time Critical 

Removal Action 

Install sediment control structure in the 

drainage basin downstream of the 

Resurrection #1 Tailing Pile. 06/08/98 1999 
California Gulch Five-Year Report

Page 47 of 89 

 

Table 11-3, cont’d 

Response Actions for OU6 

Area

Action 

Memorandum 

Date and Action

Removal Action Taken Start 

Date

Completion 

Date

Greenback - 

 RAM Runoff 

06/20/00 

08/22/00 

Time Critical 

Removal Action 

(Phase IV) 

Identify suspected blockage in drainage 

system leading to the Greenback - RAM 

Collection System. Excavate blockages 

from drainage pathways or modify flow 

paths. 

Install berm and drainage improvements 

from the Greenback collection system to 

direct the flow into a depression. 

Advance a borehole and install a stand pipe 

to convey ARD discharged from abovedescribed collection systems to the Marion 

shaft adit for conveyance to the Leadville 

Mine Drainage Tunnel (LMDT) and 

ultimately the USBOR water treatment 

facility. 

Transfer ponded water in the RAM 

collection system to the Greenback 

collection system to relieve the hydraulic 

pressure on the abandoned railroad grade. 

Develop and implement a water quality 

monitoring plan. 

06/30/00 10/13/00 

Ibex/Irene Waste 

Rock Pile 

6/25/01 

Time Critical 

Removal Action 

Phase V 

Divert run-on around mine waste pile. 

Retain runoff in two impoundments to settle 

out sediments that could impact Parkville 

Reservoir. 

6/25/01 Fall 2001 

 

The OU6 ROD was released in 2003. The selected remedy consisted of the following elements: 

• Maintenance of the existing Response Actions implemented prior to the ROD. 

• Installation of a bulkhead in the LMDT. 

• Pumping ARD impounded behind the bulkhead to the surface with conveyance to the 

USBOR treatment plant via a gravity pipeline. 

• Removal of the Ponsardine mine waste pile with on-Site disposal. 

• Repair of unstable cribbing associated with the Robert Emmett mine site. 

• Institutional Controls on future changes in land use. 

Since the release of the ROD the following remedy elements have been implemented: 

• Maintenance of the existing response actions implemented prior to the ROD 

• Removal of the Ponsardine mine waste pile with on-Site disposal 

• Repair of unstable cribbing associated with the Robert Emmett mine site. 
California Gulch Five-Year Report

 

Page 48 of 89 

System Operation/ Operation and Maintenance 

An operation and maintenance plan will be prepared under the final remedy described in the 2003 

ROD. To date, O/M consists of inspection of the surface water control features implemented prior to 

issuance of the ROD. 

11.3 Progress Since the Last Five Year Review 

Activities related to OU6 since the last Five-Year Review finalized on September 29, 2001 included 

the following: 

• Release of the ROD. 

• Multiple tracer and other studies to investigate the existence and quality of a hydraulic 

connection between the Marion adit and the LMDT. These studies were performed to assess 

the effectiveness of the 2000 Removal Action that diverted ARD discharged by surface water 

control structures to the subsurface for conveyance to the USBOR water treatment facility. 

• Maintenance of the existing response actions implemented prior to the ROD. 

• Remedial design activities. 

• Removal of the Ponsardine mine waste pile with on-Site disposal. 

• Repair of unstable cribbing associated with the Robert Emmett mine site. 

• Installation of monitoring wells in the LMDT as part of data collection to support remedial 

design. 

• A Non-Time Critical Removal Action in 2005 to construct an engineered outlet for the Gaw 

Shaft. The Gaw Shaft is believed to be a relief point for the mine pool impounded behind 

suspected blockages in the LMDT. 

• Negotiation with the USBOR for treatment of ARD to be extracted from behind the LMDT 

bulkhead once constructed. Negotiations are ongoing. 

11.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report 

• OU6 ROD 

Interviews were conducted with the following individuals to provide supplemental technical 

information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Mike Holmes – USEPA 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 
California Gulch Five-Year Report

 

Page 49 of 89 

Data Review 

Surface and groundwater quality data for the period 1996 through 2005. 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project Manager, Stan 

Christensen and Kenneth Napp, the HDR Project Manager. The assessment of Site conditions relied 

heavily on the recent observations of regulatory agency personnel interviewed during this Five-Year 

Review. 

Based on the Site Inspection, conditions documented during the last Five-Year Review and 

discussions with regulatory agency personnel, all physical response action elements required under 

Action Memoranda in OU6 have been constructed and are in working order. The Ponsardine mine 

waste pile has been removed and the unstable cribbing associated with the Robert Emmett mine site 

has been replaced. However, the major elements of the remedy described in the ROD have not been 

constructed nor have ICs been implemented. 

Based on interviews with regulatory agency personnel. Several surface water management features 

require removal of accumulated sediment. These include: 

• Culvert across the road from the Robert Emmett shaft. 

• Ditches near Adelaide waste piles. 

• A ditch at the Resurrection Fortune. 

11.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• Surface water monitoring data indicate a large decline in metal loading emanating from Stray 

Horse Gulch since the completion of major Response Actions in 2000. Tracer studies 

confirm a hydraulic connection between the Marion adit and the LMDT indicating that ARD 

collected in OU6 and discharged to the subsurface is being treated at the USBOR water 

treatment facility. Regulatory agency personnel reported minor amount of accumulated 

debris in constructed channels. Constructed caps on mine waste features are in good 

condition. Based on this assessment, the remedy is functioning as intended by the Action 

Memoranda. The adequacy of observed reduction in metal loading to surface water will be 

formally assessed under OU12. 

• Installation of a bulkhead in the LMDT with pumping of impounded water as required under 

the ROD was intended to mitigate environmental and other risks associated with ARD 

currently impounded behind one or more suspected blockages in the LMDT. Until the 

selected remedy is fully implemented, risks associated with this suspected “mine pool” 

remain. These risks include migration of ARD away from the mine pool into mine workings, 

natural fractures/faults with potential discharge to alluvial groundwater and/or springs and 

seeps. There also remains some concern about a sudden release of ARD at the LMDTs portal 

should suspect blockage(s) in the LMDT fail. 
California Gulch Five-Year Report

 

Page 50 of 89 

• Institutional controls to protect engineered remedies and to identify properties where special 

precautions may be needed are included in the Selected remedy. Procedures are in place for 

notification of EPA and CDPHE should a change in land use be approved by local 

governments. 

• Given the remedy remains incomplete, it is not fully functioning as intended by the decision 

documents. 

Question B: Are the exposure assumptions toxicity data, and cleanup levels and RAOs used at the 

time of the remedy selection still valid?

• See Section 3.0 for a discussion of the Human Health Risk Assessments. 

• No new or changed ARARs have been identified by the State of Colorado or EPA at the time 

of this Five Year Review that would apply to OU6. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• None 

 

11.6 Issues 

Remedial action at OU6 was incomplete at the time of the Five-Year Review. Therefore, the remedy 

was not subjected to the Five-Year Review process. However, the remedy for OU6 largely consists 

of modifications to Response Actions implemented under Action Memoranda. Therefore, it was 

considered appropriate to identify the following issues related to selected remedy. 

Table 11-4 

OU6 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 Delay in establishing control of the Mine Pool Potentially Potentially 

11.7 Recommendations and Follow-Up Actions 

Table 11-5 

OU6 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up Party Responsible Due Date 

1 Delay in establishing control of 

the Mine Pool Perform remedial action. EPA 

Reevaluate at 

next fiveyear 

review 
California Gulch Five-Year Report

 

Page 51 of 89 

11.8 Protectiveness Statement 

The remedy is currently protective of human health and the environment. However, future remedial 

work may be required in order to attain final Site-wide water quality standards as determined 

pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning and to identify 

properties where special precautions may be necessary has not impacted past or current 

protectiveness as the remedies were undisturbed at the time of this Five-Year Review. However, the 

potential exists for future impacts on remedy protectiveness if such an IC is not developed and 

implemented. The selected remedy will address the mine pool. 
California Gulch Five-Year Report

 

Page 52 of 89 

12.0 Operable Unit 7 - Apache Tailing Impoundments 

 

12.1 Description 

Operable Unit 7 (OU7), the Apache Tailing Impoundments consisted of four distinct tailing 

impoundments located on the southern edge of Leadville adjacent to U.S. Highway 24. These 

impoundments were located in California Gulch, approximately 1,500 feet downstream from the 

Yak Tunnel Water Treatment Plant Surge Pond. A map illustrating the post-remedial Apache Tailing 

Impoundments is provided as Figure 12-1 (Appendix A). 

Tailing placed in the Main Impoundment, and possibly the North Impoundment, was generated by a 

mill known alternatively as the Venir Mill, the California Gulch Mill, and the ASARCO Leadville 

Milling unit, located on the hillside northeast of the Apache Tailings Impoundments. The available 

historical information indicates that this mill operated between 1939 and 1956, producing 

approximately 630,000 cubic yards of tailing in the 11.3-acre Main Impoundment and an estimated 

14,500 cubic yards of tailing in the 1.8-acre North Impoundment. 

Apache Energy & Minerals Company operated the Apache Mill in the late 1970s and continued 

operations into the 1980s. The Apache Mill reprocessed tailing from the Main Impoundment and 

deposited the remaining materials into Tailing Ponds No. 2 and No. 3, which were 1.5 and 0.5 acres 

in size, respectively, and located west and downstream of the Main Impoundment. Tailing Ponds 

No. 2 and No. 3 were removed in 1997, as discussed below. 

Table 12-1 presents the types of contamination present at the Apache Tailings Impoundments. 

 

Table 12-1 

Types of Contamination in Each Media 

Media Contamination

Tailing 

Weathered sulfidic tailing on the surface of the North and Main Impoundments contains 

elevated lead and arsenic concentrations and has a high acid generating potential. 

Dark gray sulfidic tailing occurs below the weathered sulfidic tailing on the North and Main 

Impoundments and contains elevated lead and arsenic concentrations. 

Brown oxide tailing found only on the Main Impoundment contains elevated lead 

concentrations and arsenic concentrations lower than those found in sulfidic tailing. Brown 

oxide tailing has a significant neutralization potential counteracting acidic sulfidic tailing 

leachate. 

Foundation soils found at both the Main and North Impoundments contain elevated lead 

concentrations and slightly elevated arsenic concentrations. 
California Gulch Five-Year Report

 

Page 53 of 89 

Table 12-2 lists the chronology of important events for OU7. 

 

Table 12-2 

Chronology of Site Events for OU7 

Date Event

09/08/83 California Gulch placed on NPL. 

1986 Investigation study conducted by Colorado Department of Law. 

1987 Investigation study conducted by US EPA. 

01/87 Phase I Remedial Investigation Report. 

1989 Investigation study conducted by US EPA. 

09/90 U.S. EPA and PRPs entered into an Administrative Order on Consent (AOC) for the performance of 

soil sampling and air monitoring. 

08/91 U.S. EPA issued a Unilateral Administrative Order (UAO) that required ASARCO to conduct studies 

and complete RIs. 

Fall 1991 Tailing remedial investigation performed. 

1991-1992 Surface Water RI of the California Gulch site conducted. 

Fall 1991- 

Winter 1992 Hydrogeologic RI of the California Gulch site conducted. 

1993 Screening Feasibility Study conducted to initiate the overall CERCLA feasibility study process at the 

California Gulch site. 

08/94 ASARCO entered into a Consent Decree with the United States, State of Colorado, and other PRPs. 

ASARCO agreed to perform certain remediation work in OU5, OU7, and OU9. 

01/94 Final Tailing Disposal Area Remedial Investigation Report. 

08/95 Cultural Resources Investigations of the Apache Tailing Area Report. 

01/96 Draft Apache Tailing Feasibility Study for OU7. 

08/08/96 Action Memorandum issued for Removal (Response) Action at the Apache Energy & Minerals 

Property. 

1996 Final Surface Water Remedial Investigation Report. 

1996 Final Hydrogeologic Remedial Investigation Report. 

04/07/97 Action Memorandum issued for Time-Critical Removal Action for Removal of Tailing Pond No. 2 

and Tailing Pond No. 3 of the Apache Tailing Impoundment (Operable Unit 7). 

1997 Field Investigation Data Report for the Apache Tailing Supplemental Remedial Investigation. 

06/30/98 Final Pollution Reports for Time Critical Removal Actions at Tailing Ponds 2 & 3 of the Apache 

Tailing Impoundment, 04/97; and Apache Energy & Minerals Property, 08/96. 

01/00 Focused Feasibility Study, Apache Tailing Impoundments – Operable Unit 7 (OU7), California 

Gulch Superfund Site submitted by ASARCO. 

01/25/00 Proposed Plan for U.S. EPA’s preferred alternative issued. 

01/26/00 Action Memorandum issued for Time-Critical Removal Action for the Apache Tailing Impoundment 

(Operable Unit 7). 

06/06/00 Record of Decision. 

12/17/03 Construction Completion Report 
California Gulch Five-Year Report

 

Page 54 of 89 

12.2 Response Actions 

Response Action Selection/Implementation 

Multiple Removal Actions were conducted at OU7 between 1996 and 2000. On June 6, 2000, a 

ROD was signed and the selected remedy consisted of the construction of a soil cover with a 

geosynthetic barrier and revegetation followed by implementation of ICs and a long-term monitoring 

plan. The RAOs specified in the ROD for the Apache Tailing Impoundments are: 

• Control airborne transport of tailing particles. 

• Control erosion of tailing materials and deposition into local water courses. 

• Control leaching and migration of metals from tailing into surface water and groundwater. 

The removal and remediation activities performed at the Apache Tailing Impoundments are 

summarized in Table 12-3. 

Table 12-3 

Response Actions for Apache Tailing Impoundments 

Area Action 

Memorandum 

Date and 

Action

Removal Action Taken/Remedy to be 

Implemented

Start 

Date

Completion 

Date

Apache Energy 

& Minerals 

Property 

08/08/96 

Time Critical 

Removal 

Action 

Transport drums and bags of pyrite to the Malta 

Tailing Impoundment 

Decontaminate and demolish the Apache Mill 

building and equipment 

08/08/96 03/97 

Tailing Pond 

Nos. 2 and 3 

04/07/97 

Time Critical 

Removal 

Action 

Remove Tailing Pond Nos. 2 and 3, berm 

material, and native soil and consolidate the 

material on the Main Impoundment 

Pump surface water ponded on Tailing Pond 

Nos. 2 and 3 to Yak Water Treatment Plant 

prior to initiating excavation of tailing. 

Divert potentially contaminated surface run-off 

from the Main Impoundment to a sediment 

control structure. 

Protect the toe of the Main Impoundment. 

04/21/97 12/04/97 
California Gulch Five-Year Report

 

Page 55 of 89

Table 12-3 

Response Actions for Apache Tailing Impoundments 

Area Action 

Memorandum 

Date and 

Action

Removal Action Taken/Remedy to be 

Implemented

Start 

Date

Completion 

Date

Main and North 

Impoundments 

01/26/00 

Time Critical 

Removal 

Action 

 Regrade the material placed on the Main 

Impoundment during the removal of Tailing 

Pond Nos. 2 and 3. 

Regrade the eastern embankment and the 

southwest embankment in the vicinity of the 

wooden box culvert on the Main Impoundment. 

Excavate the tailing material overlying the claytile culvert at the southern edge of the Main 

Impoundment. 

Place fill over a portion of the North 

Impoundment. 

1/00 In Process 

Main and North 

Impoundments 

Remedial 

Activity 

specified in the 

ROD 

Channelization of California Gulch through the 

southern portion of the main impoundment and 

construction of diversion ditches to control 

water run-on and run-off. 

Regrade impoundments; place a multi-layer 

composite cover (including a geosynthetic 

barrier) over the tailing area, and revegetate. 

Institutional controls will be put in place to warn 

of potential hazards and to limit access to the 

use of property . Modifications to city and/or 

county ordinances will involve the creation of a 

zoning overlay district to screen and identify 

properties where special precautions may be 

needed. 

Long-term monitoring program to assess surface 

water and ground water quality. 

6/01 12/03 

System Operation/ Operation and Maintenance 

The previous Five-Year Review Report indicated that an Operation and Maintenance Program for 

the Main and North Impoundments of OU7 will be developed as the remedy is implemented. A 

formal O/M plan has not been prepared. However, the essential components of such a plan were 

presented in Final Focused Feasibility Study Report for OU7. EPA reports that O/M currently 

consists of the following: 

• Periodic inspection and maintenance of the soil cover and surface water control features. 

• Annual monitoring of selected ground water monitoring wells in OU7. 
California Gulch Five-Year Report

 

Page 56 of 89

12.3 Progress Since the Last Five Year-Review 

Activities related to OU7 since the last Five-Year Review finalized on September 29, 2001 included 

the following: 

• Construction of the selected remedy 

• Operation, maintenance, monitoring and reporting. 

12.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report 

• OU7 ROD 

Interviews were conducted with the following individuals to provide supplemental technical 

information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Mike Holmes – USEPA 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 

Data Review 

• Surface and groundwater quality data for the period 1996 through 2005. 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project Manager, 

Stan Christensen and Kenneth Napp, the HDR Project Manager. The assessment of Site conditions 

relied heavily on the recent observations of regulatory agency personnel interviewed during this 

Five-Year Review. 

Based on the Site Inspection, conditions documented during the last Five-Year Review and 

discussions with regulatory agency personnel, all physical response action elements required under 

the ROD have been constructed and are in working order. 

12.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• Based on document review, the Site Inspection and discussions with regulatory agency 

personnel, the remedy is functioning as intended by the decision documents. 
California Gulch Five-Year Report

 

Page 57 of 89

• Institutional controls are needed to ensure protection of human health in the event of 

changes in zoning or to preclude disturbance of engineered remedies as a result of 

development consistent with current zoning. Procedures are in place for notification of EPA 

and CDPHE should a change in land use be approved by local governments. 

• Surface water quality data indicates that metal loading is decreasing in the vicinity of OU7. 

However, OU7 continues to contribute metal load to California Gulch. This is indicated by 

surface water quality data for the period 1995 through 2005. This issue will be addressed 

under OU12 as specified in the 1994 CD 

Question B: Are the exposure assumptions toxicity data, and cleanup levels and RAOs used at 

the time of the remedy selection still valid? 

• See Section 3.0 for a discussion of the Human Health Risk Assessments. 

• No new or changed ARARs have been identified by the State of Colorado or EPA at the 

time of this Five Year Review that would apply to OU7. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• An ICO District was established to meet post-response action land use restriction 

requirements. However, the ICO District was repealed by Lake County in 2006. As a result, 

concerns remain regarding protectiveness of the remedy. 

12.6 Issues 

Based on the information collected during the Five-Year Review, the following issues were 

identified: 

Table 12-4 

OU7 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 

Institutional controls are needed to ensure protection of 

human health in the event of changes in zoning or to preclude 

disturbance of engineered remedies as a result of development 

consistent with current zoning. 

No Yes 
California Gulch Five-Year Report

 

Page 58 of 89

12.7 Recommendations and Follow-Up Actions 

Table 12-5 

OU7 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up Party Responsible Due Date 

1 

Institutional controls are needed 

to ensure protection of human 

health in the event of changes in 

zoning or to preclude disturbance 

of engineered remedies as a result 

of development consistent with 

current zoning. 

Develop and implement ICs. ASARCO 12/08 

12.8 Protectiveness Statement 

The remedy is currently protective of human health and the environment. However, future remedial 

work may be required in order to attain final Site-wide water quality standards as determined 

pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not impacted 

past or current protectiveness as the remedies were undisturbed at the time of this Five-Year 

Review. However, the potential exists for future impacts on remedy protectiveness if such an IC is 

not developed and implemented. 
California Gulch Five-Year Report

 

Page 59 of 89

13.0 Operable Unit 8 - Lower California Gulch 

13.1 Description 

Operable Unit 8 (OU8), identified as the 500 Year Flood Plain of Lower California Gulch, consists 

of the Colorado Zinc-Lead (CZL) Tailing Impoundment, the Fluvial Tailing Impoundments (1,2, 3, 

6, and 8), Gaw Waste Rock Pile, Non-residential Area Soils and Stream Sediments. A map 

identifying the features of Lower California Gulch is presented as Figure 13-1 (Appendix A). 

The area comprising Operable Unit 8 was originally a placer gold mining district starting with the 

discovery of gold in California Gulch in 1860. When the placer deposits began to become 

exhausted, underground mining was started to extract gold, silver, lead, and zinc ore. Ore was 

subsequently crushed and separated into metallic concentrates at nearby mills with mill tailing 

slurried into tailing impoundments. Fluvial deposits of tailing occurred as tailing was released from 

impoundments. Waste rock from underground mining was frequently dumped near mine shafts, as 

was the case with the Gaw Waste Rock Pile. 

The CZL site was an operating flotation mill that processed zinc-lead ores sporadically between 

1925 and 1940. It is located approximately one mile west of Leadville and immediately north of 

Stringtown. The tailing impoundment at the site of the flotation mill operation covered 

approximately 1.6 acres at an average depth of 7 feet. The tailing impoundment contained an 

estimated 17,000 cubic yards of tailing. Impoundment tailings contained a high concentration of 

pyrite. The foundation material below the impoundment consisted of alluvium materials along with 

slag. The CZL tailing was removed to the Oregon Gulch Impoundment pursuant to a 1995 

Removal action. 

Fluvial Tailing Site 1 (FTS1) is adjacent to the LaPlata Slag Pile and extends downstream in a 

westerly direction to a point approximately 1,000 feet upgradient of the CZL Tailing Impoundment. 

California Gulch flows through the tailing and the gulch has cut a channel through the fluvial 

deposit. The fine to coarse grained tailing and alluvial/tailing materials range from 1-6 feet in 

depth. Alluvial sands, gravel, and cobbles lies beneath the tailing. The portion of FTS1 that lies 

within OU8 comprises approximately 3.4 acres. 

Fluvial Tailing Site 2 (FTS2) lies 200 feet downstream of FTS1 and is estimated to be 3.2 acres and 

contains a volume of 5,200 cubic yards (assuming an average depth of 1 foot). The fluvial tailing 

material in FTS2 is generally light brown to brown clayey silts and sands overlying light brown silt 

that contains cobbles and sand. 

Fluvial Tailing Site 3 (FTS3) is located immediately downstream of Lake County Road 6 on 

California Gulch and covers approximately 4.8 acres. The flow of California Gulch through FTS3 is 

split into a north and south channel, with most of the flow occurring in the north channel. 

Fluvial Tailing Site 6 (FTS6) is located on California Gulch between the Yak Tunnel Treatment 

Plant Surge Pond embankment and the Apache Tailing Impoundments comprising approximately 

4.2 acres. A portion of the Gaw waste rock pile also lies within FTS6. 
California Gulch Five-Year Report

 

Page 60 of 89

Fluvial Tailing Site 8 (FTS8) extends from the Arkansas Valley Slag Pile to a point approximately 

6,500 feet downstream of the confluence of California Gulch with the Arkansas River. FTS8 is a 

series of small discontinuous tailing deposits with a total estimated area of 115 acres. However, the 

ROD only addresses the portion of FTS8 that lies within the 500-year flood plain. An estimated 45 

acres of fluvial tailing are within the floodplain boundaries. 

The Gaw waste rock pile is located within FTS 6. The pile covers approximately one half acre and 

is estimated to have a volume of 7,500 cubic yards. The pile surrounds the Gaw Shaft opening 

which has an outflow of approximately 0.1 cubic feet per second. The Gaw shaft was subjected to a 

Non-Time Critical Response Action under OU6 (See Section 12.0). 

Table 13-1 presents the types of contamination located within OU8. 

Table 13-1 

Types of Contamination in Sites Within OU8 

Media Contamination

CZL Fluvial Tailing 

Impoundment 

Elevated concentrations of lead, cadmium, arsenic, and zinc with the potential to 

generate ARD 

Non Residential Soils Metals concentrations are generally low and decrease with depth to the native 

undisturbed soils. 

Gaw Waste Rock Pile Surface soil contained lead at slightly elevated concentrations. 

Outflow from the Gaw shaft demonstrated neutral pH values, with minimally elevated 

sulfate concentrations. Metals typically were below limits of detection. 

FTS 1,2 and 3 Surface tailing had elevated levels of arsenic, cadmium, lead, and zinc. 

Subsurface tailing had elevated levels of arsenic, cadmium, and lead. 

Foundation soils had elevated levels of silver, cadmium, arsenic, lead, and zinc. 

FTS 6 Surface tailing had elevated levels of arsenic, cadmium, copper, lead, mercury, silver, 

and zinc. 

Subsurface tailing had elevated levels of arsenic, cadmium, copper, lead, manganese, 

mercury, and zinc. 

Foundation soils had elevated levels of silver, cadmium, copper, arsenic, lead, and zinc. 

The waste pile has potential for generating ARD. 

FTS 8 Surface tailing had elevated levels of arsenic, cadmium, copper, lead, and zinc. 

Subsurface tailing had elevated levels of arsenic, cadmium, lead, and zinc. 

Foundation soils had elevated levels of cadmium. 

The Hydrologic Remedial Investigation conducted in 1996 indicted that only the alluvial aquifer is 

contaminated. The upper 30 to 50-feet of the aquifer have elevated levels of arsenic, cadmium, 

copper, lead, zinc, and sulfates. Additional groundwater sampling during the Tailing RI in 1994 

indicated elevated levels of arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, 

selenium, silver, thallium, zinc, and sulfates. The metal concentrations and pH vary between all the 

sites in OU8. 

The land surrounding and within OU8 is zoned for industrial use by the City of Leadville and is 

currently not being used by any entity. The area is mostly private property with no land held by 

Resurrection. 
California Gulch Five-Year Report

 

Page 61 of 89

Table 13-2 summarizes the chronology of important events in OU8. 

Table 13-2 

Chronology of Site Events for OU8 

Date Event

09/08/83 California Gulch placed on NPL 

1986 Final Yak Tunnel/California Gulch Remedial Investigation 

01/87 Phase II Remedial Investigation Report 

09/90 U.S. EPA and PRPs enter into an Administrative Order on Consent for the performance of 

soil sampling and air monitoring in OU8 

08/91 U.S. EPA issues a Unilateral Order on Consent that required ASARCO to conduct studies 

and complete RIs 

8/94 Resurrection enters into a Consent Decree with the United States, the State of Colorado, and 

other PRPs to perform remediation work in OU8 

07/95 EE/CA issued for Lower California Gulch Colorado-Lead Zinc site 

08/04/95 Action Memorandum issued for Removal action at the CZL Tailing Impoundment Site 

09/04/95 Start date for Removal Action at CZL Tailing Impoundment Site (08/04/95 Action 

Memorandum) 

01/96 Completion of Removal Action at CZL Tailing Impoundment Site (08/04/95 Action 

Memorandum) 

06/11/98 Action Memorandum issued for Removal Action at Fluvial Tailing Sites 1, 2, 3, 6, and 8 

06/30/98 Final Pollution Report on 08/04/95 Action Memorandum 

08/28/96 Start date for Removal Action at the Fluvial Tailing Sites 1, 2, 3, 6, and 8 (06/11/98 Action 

Memorandum) 

11/07/98 Completion of Removal Action at Fluvial Tailing Sites 1, 2, 3, 6, and 8 (06/11/98 Action 

Memorandum) 

02/05/99 Final Pollution Report on 06/11/98 Action Memorandum 

2000 U.S. EPA Final Focused Feasibility Study for the Lower California Gulch Operable Unit 8 

09/29/00 Record of Decision for OU8 

09/02/03 Construction Completion Report 

13.2 Response Actions 

Response Action Selection/Implementation 

The remediation of OU8 was divided into seven separate removal and response actions. In 

September, 2000, the U.S. EPA issued a Record of Decision (ROD) for OU8 to address the two 

completed Removal Actions and the five planned remediation activities. The RAOs identified in 

the ROD include: 

• Control airborne transport of tailing particles and contaminated non-residential soils. 

• Control leaching and migration of metals from tailing, soil, waste rock, and contaminated 

fluvial and stream sediments into surface water. 

• Control leaching and migration of metals from tailing, soil, waste rock, and contaminated 

fluvial and stream sediments into groundwater. 

• Control erosion of tailing material and soil materials into local water courses. 

• Control contaminant exposure to animals and aquatic life. 
California Gulch Five-Year Report

Page 62 of 89 

The remedy elements are summarized in Table 13-3. 

Table 13-3 

Response Actions for OU8 

Area Action 

Memorandum 

Date and Action

Removal Action Taken/ Response Action 

to be Taken

Start 

Date

Completion 

Date

CZL Tailing 

Impoundment 

8/4/95 

Non-Time 

Critical 

Removal Action 

Diversion and reclamation of a small 

portion of North California Gulch. 

Remove of tailing, including one half acre 

in Fluvial Tailing Site 2 east of the CZL 

impoundment. 

Relocation of tailing at the Oregon Gulch 

Impoundment. 

Recontour and backfill former 

impoundment to promote drainage and 

revegetation. 

09/0495 01/96 

Fluvial Tailing and 

Stream Sediment 

6/98 

Interim 

Removal Action 

Remove approximately 5,800 cubic yards 

of fluvial tailing from poorly vegetated and 

erosion prone areas within FTS2, FTS3, 

FTS6, and FTS8. Fluvial tailing was 

removed to the Oregon Gulch 

Impoundment in OU10. 

Remove approximately 1,350 cubic yards 

of sediment in conjunction with channel 

excavation. Sediment was removed to the 

Oregon Gulch Impoundment in OU10. 

7/20/98 11/07/01 

Non-Residential 

Soils 

Remedial 

Action 

Regrade to promote positive drainage. 

Re-establish vegetation with soil 

amendments such as lime, nutrient, and 

organic matter as needed. 

Institutional controls to include deed 

notices and restrictions, identify as an 

overlay district for zoning purposes. 

Not 

Available 9/2/03 

Impounded Tailing Remedial 

Action 

No action is taken because the impounded 

tailing at the CZL Tailing Impoundment 

was removed pursuant to the 1995 interim 

removal action. 

N/A (No 

Further 

Action 

Remedy) 

N/A 

Gaw Waste Rock 

Pile 

Tunnel Plug 

Remedial 

Action 

Take no action because the rock pile is not 

a source of metals contamination to surface 

or ground water N/A (No 

Action 

Remedy) 

N/A 
California Gulch Five-Year Report

Page 63 of 89 

Table 13-3, cont’d 

Response Actions for OU8 

Area Action 

Memorandum 

Date and Action

Removal Action Taken/ Response Action 

to be Taken

Start 

Date

Completion 

Date

Fluvial Tailing Sites 

1, 2, 3, 6, 8 

Remedial 

Action 

Regrade and re-establish vegetation with 

soil amendments such as lime, nutrient, 

and organic matter as needed. 

Re-vegetate wetland areas with native 

wetland plant species. 

Protect erosion prone areas along the gulch 

channel with riprap and a suitable filter 

fabric (approximately 2400 ft.). 

Institutional controls to include deed 

notices and restrictions, identify as an 

overlay district for zoning purposes. 

Maintenance and inspection of remediated 

areas. 

Not 

Available 09/02/03 

Stream Sediment Remedial 

Action 

- Excavate Fluvial Tailing at: 

- Removal Sites 2 and 3 in FTS2 

- Removal Sites 4 and 5 in FTS3 

- Removal Site 6 in FTS6 

- Removal Sites 9-1 through 9-7, 10, 8-

1 through 8-5 

Remove sediment from Fluvial Site 11 and 

reconstruction of California Gulch in 

geomorphically unstable, braided channel 

areas of FTS3 to divert flow to south 

channel. 

Construct channel through FTS6 to convey 

500 year flood plain. 

Remove sediment and construct channel 

improvements in erosion prone areas. 

Excavate sediment to clear channel at 

Removal Site 12 in FTS 2. 

Not 

Available 09/02/03 
California Gulch Five-Year Report

Page 64 of 89 

System Operation/ Operation and Maintenance 

The following monitoring requirements are imposed under the Final California Gulch 

Superfund Site Operation and Maintenance Plan, Operable Units 4, 8 and 10 as revised in 

January 2005. 

• Biannual inspection/maintenance of vegetation cover and diversion channels. 

• Institutional controls as discussed in the ROD. 

13.3 Progress Since the Last Five Year Review 

The last site-wide Five Year Review, which was finalized on September 29, 2001, 

indicated that no removal actions had been completed. Since the last review, all remedial 

action has been completed. Biannual inspections are performed in accordance with the 

Final California Gulch Superfund Site Operation and Maintenance Plan, Operable Units 

4, 8 and 10 as revised in January 2005. 

13.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report 

• OU4, OU8 and OU10 Fall 2005 Inspection Report, Resurrection Mining 

Company 

Interviews were conducted with the following individuals to provide supplemental 

technical information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Mike Holmes – USEPA 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 

Data Review 

• Surface and groundwater quality data for the period 1996 through 2005. 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project The 

Site Inspection was performed on August 24, 2006 by the EPA Remedial Project 

Manager, Stan Christensen and Kenneth Napp, the HDR Project Manager. The 

assessment of Site conditions relied heavily on the recent observations of regulatory 

agency personnel interviewed during this Five-Year Review. 
California Gulch Five-Year Report

Page 65 of 89 

Based on the Site Inspection, conditions documented during the last Five-Year Review 

and discussions with regulatory agency personnel, most physical response action 

elements required under the ROD in OU8 have been constructed and are in working 

order. However, vegetative cover in a portion of FTS 2 proximal to OU5 was limited 

(See Photo No. 1 – Appendix C). In addition, water ponded on the tailing deposit 

exhibited coloration indicative of ARD. Ponded water appeared to be discharging to 

California Gulch. In addition, the California Gulch channel flowed through the tailing 

deposit. 

13.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• The 2005 Inspection Report identified areas of limited vegetation at FTS-1 and 

Non-Residential Soils Areas and recommended additional seed and fertilizer. No 

documentation exists indicating whether maintenance had been performed. 

• Based on document review, the Site Inspection and discussions with regulatory 

agency personnel, the remedy is largely functioning as intended by the decision 

documents. However, the condition of FTS-2 suggests that the tailings are 

vulnerable to erosion and remain a source for metal loading to California Gulch. 

Recent surface water monitoring data (2003 through 2005) suggests that an 

unacceptable level of metal loading occurs in the vicinity of FTS-2 in the spring, 

during the period when the Arkansas River is most sensitive to metal loads. 

Therefore, the affected portion of the FTS-2 remedy requires repair or 

replacement in order to meet the intent of the decision documents. EPA 

recognizes that limited spatial data density precludes a definitive estimate of 

metal loading from FTS-2. In addition, some of the distressed areas (with ponded 

ARD) lie within the boundaries of OU5 where the remedy remains under 

construction. 

• Institutional controls are needed to ensure protection of human health in the event 

of changes in zoning or to preclude disturbance of engineered remedies as a result 

of development consistent with current zoning. Procedures are in place for 

notification of EPA and CDPHE should a change in land use be approved by local 

governments. 

Question B: Are the exposure assumptions toxicity data, and cleanup levels and RAOs 

used at the time of the remedy selection still valid?

• See Section 3.0 for a discussion of the Human Health Risk Assessments. 

• No new or changed ARARs have been identified by the State of Colorado or EPA 

at the time of this Five Year Review that would apply to OU8. 
California Gulch Five-Year Report

Page 66 of 89 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• An ICO District was established to meet post-response action land use restriction 

requirements. However, the ICO District was repealed by Lake County in 2006. 

As a result, concerns remain regarding protectiveness of the remedy. 

13.6 Issues 

Based on the information collected during the Five-Year Review, the following issues 

were identified: 

Table 13-4 

OU8 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 

A portion of Non-Residential Soils Areas, Fluvial 

Tailing Site (FTS) No. 1 and FTS-2 remedies in need 

of repair or replacement. 

Yes Yes 

2 

Institutional controls are needed to ensure protection 

of human health in the event of changes in zoning or 

to preclude disturbance of engineered remedies as a 

result of development consistent with current zoning. 

No Yes 

13.7 Recommendations and Follow-Up Actions 

Table 13-5 

OU8 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up Party Responsible 

Due 

Date 

1 

A portion of Non-Residential 

Soils Areas, Fluvial Tailing Site 

(FTS) No. 1 and FTS-2 

remedies in need of repair or 

replacement. 

Modify/repair the existing remedy 

so that mine waste does not come 

into contact with California Gulch 

flows or allow precipitation to 

pond on the tailing surface. 

Resurrection 12/07 

2 

Institutional controls are needed 

to ensure protection of human 

health in the event of changes in 

zoning or to preclude 

disturbance of engineered 

remedies as a result of 

development consistent with 

current zoning. 

Develop and implement IC. Resurrection 12/08 
California Gulch Five-Year Report

Page 67 of 89 

13.8 Protectiveness Statement 

Although the remedy is currently considered to be protective of human health and the 

environment, the poor condition of FTS-2 remedy requires repair or replacement in order 

to meet the intent of the decision documents. In addition, future remedial work may be 

required in order to attain final Site-wide water quality standards as determined pursuant 

to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not 

impacted past or current protectiveness as the remedies were undisturbed at the time of 

this Five-Year Review. However, the potential exists for future impacts on remedy 

protectiveness if such an IC is not developed and implemented. EPA and CDPHE are 

informally notified by the County of any changes in zoning. Although this is not a 

formalized IC, it allows the remedy to be protective until an IC is formalized. 
California Gulch Five-Year Report

Page 68 of 89 

14.0 Operable Unit 9 - Populated Residential Areas 

14.1 Description 

Operable Unit 9 (OU9), Residential Populated Areas, includes those portions of the Site 

where the land use is residential or that are currently zoned as residential/populated areas 

and as low-density residential areas (Figure 3-1) (Appendix A). These include residential 

yards, vacant lots, parks, school yards, playgrounds, and community use areas, including 

unpaved streets and alleys. Operable Unit 9 addresses concentrations of lead in soil, 

mine wastes (38 mine waste piles located within the populated areas of eastern 

Leadville), dust, paint, and water that exceed a specific set of trigger criteria. 

Table 14-1 summarizes the chronology of important events in OU9. 

Table 14-1 

Chronology of Site Events for OU9 

Date Event

09/08/83 California Gulch placed on NPL. 

1986 Investigation study conducted by Colorado Department of Law. 

5/86 Emergency response at a private well 

01/87 Phase I Remedial Investigation Report. 

09/28/90 U.S. EPA and settling defendants entered into an Administrative Order on Consent (AOC) for 

the performance of soils sampling and air monitoring. 

08/29/91 U.S. EPA issued a Unilateral Administrative Order (UAO) that required ASARCO to conduct 

studies and complete RIs related to Demographics Work Plan; Final Sampling Plan for 

Sampling and Analysis of Lead Occurrence Within and Immediately Adjacent to Residences; 

Soil Investigation Work Plan; Mine Waste Pile Remedial Investigations; and other issues. 

09/10/91 U.S. EPA issued a UAO that required Resurrection Mining Company to conduct and 

complete the final Soils Investigation Work Plan. 

09/24/92 U.S. EPA entered into an AOC with ASARCO and Resurrection Mining Company for 

performance of a metals speciation program. 

09/04/93 Partial Consent Decree among the United States, State of Colorado, and settling defendants 

settling the U.S. and State’s claim for past response costs incurred prior to February 1, 1991 

and February 1, 1992. 

07/15/94 Final RI pursuant to the UAO dated 09/10/91 submitted by Resurrection Mining Company. 

8/94 Consent Decree with ASARCO and Resurrection Mining Company to define areas of 

responsibility for the two companies and the U.S. government and to develop the Kids First 

Work Group. 

09/94 Metals Speciation Data Report submitted. 

11/94 Engineering Evaluation/Cost Analysis work plan prepared to evaluate lead concentrations in 

soils within parks and playground areas in OU9. 

5/25/95 Initiation of LCHP/ASARCO Outreach Program for Kids First Program 

10/16/95 Action Memorandum issued for time critical removal action for two residences, Kids First 

Program, in Operable Unit 9. 

12/95 Draft Mine Waste Engineering Evaluation/Cost Analysis, California Gulch Superfund Site, 

Leadville, Colorado. 

1996 4 Action Memoranda issued for time critical removal actions at five separate residences, Kids 

First Program, in Operable Unit 9. 
California Gulch Five-Year Report

Page 69 of 89 

Table 14-1 

Chronology of Site Events for OU9 

Date Event

1/96 Human Health Risk Assessment issued 

07/23/96 Responses to Comments #2, Mine Waste Engineering Evaluation/Cost Analysis from 

ASARCO. 

1997 15 Action Memoranda issued for time critical removal actions at 15 separate residences, Kids 

First Program, in Operable Unit 9. 

05/26/98 Final Pollution Report for 20 time critical removal actions performed under the Kids First 

Program, Operable Unit 9 during the time period starting July 31, 1996 through October 30, 

1997. 

1998 18 Action Memoranda issued for time critical removal actions at 18 separate residences, Kids 

First Program, in Operable Unit 9. 

07/01/98 Action Memorandum Amendment for time critical removal action for PRP financed removal 

actions addressing mine waste rock piles located in the residential populated areas in Operable 

Unit 9 dated August 15, 1996. 

12/15/98 Final Pollution Report for 20 time critical removal actions performed under the Kids First 

Program in Operable Unit 9 during the time period starting October 31, 1997 through 

November 6, 1998. 

1999 9 Action Memoranda issued for time critical removal actions at 9 separate residences, Kids 

First Program, in Operable Unit 9. am, in Operable Unit 9. 

09/02/99 Record of Decision, Residential Populated Areas, Operable Unit 9, California Gulch 

Superfund Site, Leadville, Colorado. 

10/12/99 Final Pollution Report for three time critical removal actions performed under the Kids First 

Program in Operable Unit 9 during the time period starting June 22, 1999 through September 

30, 1999. 

10/28/99 Final Pollution Report for three time critical removal actions performed under the Kids First 

Program in Operable Unit 9 during the time period starting August 23, 1999 through 

September 30, 1999. 

12/01/99 Final Pollution Report for four time critical removal actions performed under the Kids First 

Program in Operable Unit 9 during the time period starting September 13, 1999 through 

November 1, 1999. 

2000 Two Action Memoranda for time critical removal actions at the 2 residences , Kids First 

Program, in Operable Unit 9. 

6/1/00 LCCHP was initiated to take the place of the interim Kids First Program 

11/03/00 Petition for a partial deletion of portions of Operable Unit 9. 

1/01 Remedial Design for Lake County Community Health Program (LCCHP) 

02/28/01 Leadville Kids First Program Report, 1994-1999 Progress and Results issued. 

07/31/01 Waste Rock Pile completion report issued 

05/02 LCCHP Guidelines established. 

2006 OU9 Performance standards were met 
California Gulch Five-Year Report

Page 70 of 89 

14.2 Response Actions 

Response Action Selection/Implementation 

The remediation of OU9 was divided into numerous separate Removal Actions as well as 

remedial actions. Table 14-2 summarizes these actions:

Table 14-2 

Response Actions for OU9 

Area

Action 

Memorandum 

Date and Action

Removal Action Taken/Remedy to be 

Implemented

Start 

Date

Completion 

Date

Private Well N/A Water connection to the Parkville 

Water District was provided 5/86 5/29/86 

Kids First 

Program - 

individual 

residences 

10/16/95 - 

04/21/00 

Time Critical 

Removal 

Actions 

Addressed contaminated media 

associated with residential properties 

10/16/95 

- 

04/21/00 

Various 

Waste Rock 

Piles 

08/15/96 

Time Critical 

Removal 

Actions 

Addressed elevated levels of 

contaminants in mine waste rock 

piles 08/15/96 7/31/01 

Morning Star 

Day Care 

Fall 2005 

Time Critical 

Removal 

Action 

Addressed contaminated media 

associated with residential properties 

Fall 

2005 Fall 2005 

LCCHP 

Multiple 

Residences 

2000 through 

mid-2005 

Remedial 

Action 

Addressed contaminated media 

associated with residential properties 2000 In Progress 

 

Removal actions under the Kids First Program started on October 16, 1995 as described 

in the Consent Decree dated August 25, 1994 between U.S. EPA, ASARCO, and 

Resurrection Mining Company. The Lake County Community Health Program (LCCHP) 

described in the ROD was intended to take the place of the Kids First Program. 
California Gulch Five-Year Report

Page 71 of 89 

The ROD, signed on September 2, 1999, describes RAOs for OU9 and the selected 

remedy; the LCCHP. RAOs for OU9 include: 

• RAO-1. No more than 5% of children age 0-72 months residing within OU9, 

either now or in the future, should have blood lead values exceeding 10 

micrograms per deciliter (ug/dl). 

• RAO-2. No more than 1% of children age 0-72 months residing within OU9, 

either now or in the future, should have blood lead values exceeding 15 ug/dl. 

• RAO-3 Reduce direct exposure of lead incurred by children which result in 

optimal risk reduction through effective use of resources. 

This remedy involves an extensive education and intervention program to manage lead 

exposure at the site. The education program focuses on raising public awareness about 

risks from lead and encourages participation in the LCCHP. Through this program, 

Leadville residents may request an investigation of lead levels in soil dust, paint, and 

water on their property. The LCCHP also includes voluntary blood lead monitoring (with 

financial incentives, as appropriate) for all children between the ages of 6 and 72 months 

and pregnant or nursing women. 

If the concentration of lead in blood of a child or a pregnant or nursing woman exceeds 

the blood lead criterion, or if the concentration of lead exceeds a specified set of trigger 

criteria for one or more of the environmental media at a residence, then appropriate 

actions will be taken to address the exceedence. The trigger levels are summarized in 

Table 14-3. 

 

Table 14-3 

Trigger Levels for Lead 

Media Lead Concentration

Soils 3,500 mg/Kg 

Mine Waste Piles 3,500 mg/Kg 

Interior/Exterior Paint Greater than 1 mg/cm2 triggers educational actions 

Greater than 6 mg/cm2

 triggers active remediation. 

Dust Greater than or equal to 2,000 ppm triggers active remediation. 

Tap Water Greater than or equal to 15 μg/L triggers active remediation. 

Blood Lead No more than 5% of children age 0-72 months residing within OU9, either 

now or in the future, should have blood lead values exceeding 10 

micrograms per deciliter (ug/dl). No more than 1% of children age 0-72 

months residing within OU9, either now or in the future, should have 

blood lead values exceeding 15 ug/dl. 
California Gulch Five-Year Report

Page 72 of 89 

When one or more of the trigger criteria are exceeded, a work group evaluates a range of 

different response actions. The most appropriate response action is determined by 

evaluating the nature and extent of the exceedence, overall protectiveness of the action, 

compliance with applicable or relevant and appropriate requirements, long-term 

effectiveness and permanence, short-term effectiveness, implementability, cost 

effectiveness, and community impacts. The work group also considers the views of the 

property owner and no response action will be implemented without permission of the 

property owner. Extensive education and intervention program to manage lead exposure 

at the site is an integral component of each action considered. 

The selected remedy also includes ICs to ensure the effectiveness of the LCCHP. These 

ICs were to include the creation of an overlay district to provide notification and 

information regarding the LCCHP and a data management and tracking system to 

maintain sampling, response action, and other information related to individual 

properties. 

System Operation and Maintenance 

The LCCHP and associated reporting constitute operation and maintenance of the 

remedy. 

14.3 Progress Since the Last Five-Year Review 

The LCCHP was implemented as required by the ROD and under the Methods and 

Standards for Evaluating the Performance of the Program (LCCHP Annual Report, 

2005). ASARCO continued to implement the LCCHP until July 2005 after which EPA 

implemented the LCCHP. Performance standards were met in March 2006. In the spring 

of 2006, EPA offered an opportunity to participate in the Lake County Community 

Health Program to property owners once it was determined that performance standards 

had been met. EPA continues to negotiate with Stakeholders towards adoption of the 

LCCHP as a formal IC for OU9 (residential soils). 

14.4 Five-Year Review Process 

Document Review 

• Second Five-Year Review Report 

• OU9 ROD 

• Methods and Standards For Evaluating The Performance Of The Lake County 

Community Health Program (LLCHP), LCCHP Performance Standards Working 

Group, May 2002. 

• 2005 LCCHP Annual Report 

• Final Lake County Community Health Program, 2005 Annual Report, MFG, Inc., 

April 2006. 

Data Review 

None 
California Gulch Five-Year Report

Page 73 of 89 

Site Inspection 

Operable Unit 9 was not subjected to a formal Site Inspection given the numerous smallscale and diverse remedial actions as well as the adequacy of operation and monitoring 

documentation. 

14.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents? 

• Performance standards for OU9 were met in March 2006. Therefore, the remedy 

is largely functioning as intended by the decision documents. 

• An ICO District was established to satisfy ROD required ICs. However, the ICO 

District was repealed by Lake County in 2006. As a result, concerns remain 

regarding protectiveness of the remedy. EPA continues to negotiate with 

Stakeholders towards adoption of the LCCHP as a formal IC for OU9 (residential 

soils). 

• Isolated areas of soils in outlying potions of OU9 were identified as containing 

arsenic at levels that exceed the upper range of plausible action levels for 

residential land use. The arsenic exceedences occurred where the corresponding 

lead concentration was below the residential action level. Therefore, it is possible 

that unacceptable exposure of sensitive populations might occur should these 

areas be developed. 

• No Operation and Maintenance Plan is in place for remediated properties in OU9. 

Question B: Are the exposure assumptions toxicity data, and cleanup levels and RAOs 

used at the time of the remedy selection still valid? 

• Performance standards established by EPA for OU9 (Populated Areas) were met 

in March, 2006. This conclusion was based on an evaluation of the Program in 

accordance with the established performance standards expressed as goals for 

blood lead levels in children. Given that these objectives have been met, it is 

reasonable to conclude that remediation goals for lead described above remain 

protective of human health. 

The exposure assumptions and toxicity data used to develop range of plausible 

action levels for arsenic, published in the Human Heath Risk Assessment (Part B), 

remain valid. 

• No new or changed ARARs have been identified by the State of Colorado or EPA 

at the time of this Five-Year Review that apply to OU9. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• No 
California Gulch Five-Year Report

Page 74 of 89 

14.6 Issues 

Based on the information collected during the Five-Year Review, the following issues 

were identified: 

Table 14-4 

OU9 Issues Identified 

Item No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness of 

Remedy 

1 

An ICO District was established to satisfy ROD 

required ICs. However, the ICO District was 

repealed by Lake County in 2006. As a result, 

concerns remain regarding protectiveness of the 

remedy. 

Yes Yes 

2 

Isolated areas of soils in outlying potions of 

OU9 were identified as containing arsenic at 

levels that exceed the upper range of plausible 

action levels for residential land use. The arsenic 

exceedences occurred where the corresponding 

lead concentration was below the residential 

action level. Therefore, it is possible that 

unacceptable exposure of sensitive populations 

might occur should these areas be developed. 

No Potentially 

3 No O&M Plan exists for remediated properties Yes Yes 
California Gulch Five-Year Report

Page 75 of 89 

14.7 Recommendations and Follow-Up Actions 

Table 14-5 

OU9 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up 

Party 

Responsible 

Due 

Date 

1 

An ICO District was established to satisfy 

ROD required ICs. However, the ICO 

District was repealed by Lake County in 

2006. As a result, concerns remain regarding 

protectiveness of the remedy. 

Formalize IC EPA/Lake 

County 12/08 

2 

Isolated areas of soils in outlying potions of 

OU9 were identified as containing arsenic at 

levels that exceed the upper range of 

plausible action levels for residential land 

use. The arsenic exceedences occurred where 

the corresponding lead concentration was 

below the residential action level. Therefore, 

it is possible that unacceptable exposure of 

sensitive populations might occur should 

these areas be developed. 

Consider creation of 

an IC to address 

areas of elevated 

arsenic in soils where 

development may 

result in 

unacceptable 

exposure of sensitive 

populations 

EPA/Lake 

County 12/08 

No O&M Plan exists for remediated 

properties 

Prepare and 

implement an O&M 

Plan 

EPA/Lake 

County 12/08 

14.8 Protectiveness Statement 

The remedy is protective of human health and the environment. 

Performance standards for OU9 were met in March 2006 as a result of the LCCHP. 

Given that hazardous substances remain within OU9, operation and maintenance of the 

LCCHP is necessary to ensure the protectiveness of the remedy. 

 
California Gulch Five-Year Report

Page 76 of 89 

15.0 Operable Unit 10 - Oregon Gulch 

15.1 Description 

The area of OU10 is defined as the 500-year floodplain of Oregon Gulch from its 

headwaters to its confluence with lower California Gulch. The Oregon Gulch tailing 

impoundments, miscellaneous tailing, and contaminated stream sediment located within 

the 500-year floodplain of Oregon Gulch are included in OU10. The tailing 

impoundment is located approximately one- half mile upstream from the confluence of 

Oregon and California Gulches and contains approximately 485,000 cubic yards of 

material. A map of the post-remedial Oregon Gulch area is provided as Figure 12-1 

(Appendix A). 

The Oregon Gulch Tailing Impoundment received tailing from the ResurrectionASARCO mill in California Gulch from approximately 1942 through 1957. During 

removal activities in 1995 and 1996, about 28,000 cubic yards of tailing and underlying 

soil from the Colorado Zinc-Lead (CZL) Tailing Impoundment were relocated to the 

Oregon Gulch Tailing Impoundment. An additional 550 cubic yards of sediment 

excavated from the culvert and embankment in California Gulch within OU8 were also 

deposited on top of the Oregon Gulch Tailing Impoundment in September 1996.

The stream sediment within the lower portion of Oregon Gulch has been contaminated 

with metals from tailing and runoff released from the Oregon Gulch tailing embankment. 

Release of tailing material was due to erosion of tailing solids from the embankment that 

were transported and redeposited in the floodplain and stream channel of Oregon Gulch. 

Release of soluble metals contained in runoff from the embankment and contained in a 

seep at the toe of the impoundment had contributed to the metal contamination of the 

sediments. The tailing impoundment had not been in operation since 1957; however, the 

tailing surfaces were not protected against erosion and continued to contribute tailing 

solids and contaminated water to downstream areas during periods of runoff until the 

removal was completed. Table 15-1 presents the types of contamination found in OU10. 

Table 15-1 

Types of Contamination in Each Media 

Media Contamination

Sediments Sediments generally display elevated metal concentration and high concentrations of 

pyrite. Sediments collected at the mouth of Oregon Gulch contain elevated cadmium, 

iron, manganese, and zinc. 

Tailing/ Soils Elevated lead and zinc concentrations were found throughout the depth of tailing 

profiles; while arsenic and cadmium levels decreased as a function of tailing depth. 

Concentrations of foundation soils underneath the tailing were significantly lower than in 

the tailing. 

Seep Water A seep discharges from the base of the tailing embankment year-round. Water quality of 

the seep discharge is poor, with low pH levels and elevated levels of dissolved metals. 
California Gulch Five-Year Report

Page 77 of 89 

Table 15-2 summarizes the chronology of important events in OU10.

Table 15-2 

Chronology of Site Events for OU10 

Date Event

09/08/83 California Gulch placed on NPL 

01/87 Phase I Remedial Investigation Report 

1994 Resurrection entered into a Consent Decree and agreed to perform certain remediation work 

in OU10 

06/25/95 EE/CA for Stream Sediments within Oregon Gulch 

08/04/95 Action Memorandum for PRP Financed Removal Action at the Oregon Gulch Stream 

Sediments Site 

06/97 Removal Action Completion Report 

08/08/97 Record of Decision 

06/03/98 Operation and Maintenance Plan 

11/99 Remedial Action Completion Report 

12/05/00 Vegetation Monitoring Report 

2/15/01 OU10 nominated for deletion 

04/16/01 Operation and Maintenance obligation letter 

04/16/01 OU10 is deleted from the NPL 

 

15.2 Response Actions 

Response Action Selection/Implementation 

Table 15-3 summarizes various Remedial and Removal Actions addressed in decision 

documents. 

 

 
California Gulch Five-Year Report

Page 78 of 89 

Table 15-3 

Removal and Remedial Actions for OU10 

Area

Action 

Memorandum 

Date and Action

Removal or Remedial Action Taken Start 

Date

Completion 

Date

Oregon Gulch 

Stream 

Sediments 

08/04/95 

Removal Action 

Construct a channel following the general 

course of the existing natural stream bed to 

convey the 10-year 24-hour flood event. 

The channel serves as a low-flow channel 

within the 500-year floodplain of Oregon 

Gulch. The construction included 

excavating sediments to an average depth of 

two feet with disposal to the tailing 

impoundment (specified as Channel 

Alternative 1 in the EE/CA). 

Provide stabilization for the 500-year 

floodplain by excavating contaminated 

stream sediment to a depth of one foot in the 

area outside the constructed channel. The 

contaminated sediment was placed in the 

Oregon Gulch tailing impoundment. 

Borrow soils were placed in the excavated 

areas to replace contaminated sediment and 

the area was stabilized and vegetation 

provided (specified as Stabilization 

Alternative 3 in the EE/CA). 

In the reach of stream potentially identified 

as a cultural resources site, the existing 

channel was reconstructed and stabilized 

(specified as Cultural Resource Alternative 

4 in the EE/CA). 

Rehabilitate division ditches of Oregon 

Gulch tailing impoundment to reduce runon flow to the tailing impoundment and 

reduce contributions of run-off from the 

watershed area to the sediment control 

pond. A temporary sediment control pond 

was constructed to retain tailing. 

09/04/95 

and 

08/26/96 

11/22/95 and 

10/15/96 
California Gulch Five-Year Report

Page 79 of 89 

Table 15-3, cont’d 

Removal and Remedial Actions for OU10 

Area

Action 

Memorandum 

Date and Action

Removal or Remedial Action Taken Start 

Date

Completion 

Date

Oregon Gulch 

Tailing 

Impoundment 

Remedial Action Regrade the impoundment surface to 

provide positive drainage. 

Install structural fill over the impoundment 

surface as needed based upon the regraded 

surface configuration. 

Install geosynthetic over the structural fill to 

control infiltration. 

Place 18" thick soil layer with a revegetated 

surface. 

Construct a diversion ditch on the east side 

of the impoundment to control run-on and 

run-off. 

Construct an upgradient groundwater 

interceptor trench to limit the infiltration of 

groundwater into the tailing impoundment. 

Develop a deep discharge drain system to 

manage seep flow from the impoundment 

toe. 

7/20/98 10/26/98 

The 1997 ROD identified the following RAOs: 

• Control airborne transport of tailing particles 

• Control erosion of tailing materials and deposition in local water courses 

• Control leaching and migration of metals from tailing into surface water 

• Control leaching and migration of metals from tailing into groundwater 

System Operation/ Operation and Maintenance 

The following monitoring requirements are imposed under the Final California Gulch 

Superfund Site Operation and Maintenance Plan, Operable Units 4, 8 and 10 as revised in 

January 2005. 

• Biannual inspection/maintenance of seep collection and conveyance system; top 

and sideslopes of impoundment cap for differential settlement, vegetation and 

erosion; and diversion ditches. 

• Maintenance of fencing and signage. 

The Operation and Maintenance Program has been implemented by Resurrection since 

September 1999. 
California Gulch Five-Year Report

Page 80 of 89 

15.3 Progress Since the Last Five Year Review 

The last site-wide Five Year Review, which was finalized on September 29, 2001, 

indicated that all of the removal and remedial actions had been completed and OU10 was 

deleted from the NPL. 

One new seep emanating from the toe of the embankment was identified during the 

Summer of 2006. This seep reportedly has been intercepted (as of September 2006) and 

the flow conveyed to the Yak Tunnel Water Treatment Plant. 

15.4 Five-Year Review Process 

Document Review 

In preparing this Five-Year Review Report, the following documents were reviewed: 

• Second Five-Year Review Report 

• OU4, OU8 and OU10 Fall 2005 Inspection Report, Resurrection Mining 

Company 

Interviews were conducted with the following individuals to provide supplemental 

technical information: 

3⁄4 Doug Jamison – CDPHE 

3⁄4 Mike Holmes – USEPA 

3⁄4 Stan Christensen – USEPA 

3⁄4 Rebecca Thomas - USEPA 

Data Review 

• Surface and groundwater quality data for the period 1996 through 2005 

Site Inspection 

The Site Inspection was performed on August 24, 2006 by the EPA Remedial Project 

Manager, Stan Christensen and Kenneth Napp, the HDR Project Manager. The 

assessment of Site conditions relied heavily on the recent observations of regulatory 

agency personnel interviewed during this Five-Year Review. 

Based on the Site Inspection, conditions documented during the last Five-Year Review 

and discussions with regulatory agency personnel, all physical response action elements 

required under the ROD in OU10 have been constructed and are in working order. 

However, an uncollected seep was observed emanating from the toe of the impoundment 

just west of the pump house (See Photo No. 2 – Appendix B). 
California Gulch Five-Year Report

Page 81 of 89 

15.5 Technical Assessment 

Question A: Is the remedy functioning as intended by the decision documents?

• The 2005 Inspection Report described minor amount of accumulated debris in 

constructed channels as well as areas of limited vegetation below the 

impoundment. A seep identified during the Site Inspections is being collected and 

conveyed to the Yak Tunnel Treatment Plant. However, the continued appearance 

of contaminated seeps is of potential concern with respect to the long-term 

protectiveness of the remedy. Access controls are in place at OU10 including 

fencing and signs installed at the access points to the OU. 

• Procedures are in place for notification of EPA and CDPHE should a change in 

land use be approved by local governments. 

• Based on document review, the Site Inspection and discussions with regulatory 

agency personnel, the remedy is largely functioning as intended by the decision 

documents. However, as discussed under Question C, below, the control of 

leaching and migration of metals from contaminated materials into the surface 

water may be not have been achieved to the degree originally intended. 

Question B: Are the exposure assumptions toxicity data, and cleanup levels and RAOs 

used at the time of the remedy selection still valid?

• See Section 3.0 for a discussion of the Human Health Risk Assessments. 

• No new or changed ARARs have been identified by the State of Colorado or EPA 

at the time of this Five Year Review that would apply to OU10. 

Question C: Has any other information come to light that could call into question the 

protectiveness of the remedy?

• RAO’s articulated in the ROD requiring, among other things, control of leaching 

and migration of metals from contaminated materials into the surface water, may 

not have been achieved to the degree originally intended. This is indicated by 

metal loading and concentration trends at a surface water monitoring station in 

Oregon Gulch for the period 1995 through 2005. The frequent appearance of 

contaminated seepage from the toe of the constructed embankment may be 

indicative of lower than expected performance of the cover system installed on 

the tailings. Continued monitoring will be required for the potential for seeps 

from the toe of and down gradient from the impoundment. This issue will be 

addressed under either OU10 or OU12 as specified in the 1994 CD. 
California Gulch Five-Year Report

Page 82 of 89 

• The current zoning for industrial/mining is considered to be an IC on land use. 

However, no ICs exist (or were called for in the ROD) to ensure protection of 

human health in the event of changes in zoning or to prevent disturbance of 

engineered remedies as a result of development consistent with current zoning. 

An Institutional Control Overlay (ICO) District was established to meet postresponse action land use restriction requirements. However, the ICO District was 

repealed by Lake County in 2006. As a result, concerns remain regarding 

protectiveness of the remedy. 

15.6 Issues 

Based on the information collected during the Five-Year Review, the following issues 

were identified: 

Table 15-4 

OU10 Issues Identified 

Item 

No. Issue 

Affects Current 

Protectiveness of 

Remedy 

Affects Future 

Protectiveness 

of Remedy 

1 

Additional ICs are needed to ensure protection of 

human health in the event of changes in zoning or to 

preclude disturbance of engineered remedies as a result 

of development consistent with current zoning. 

No Yes 

2 Additional seeps have been identified in the toe and 

downgradient from the impoundment. Yes Yes 

15.7 Recommendations and Follow-Up Actions 

Table 15-5 

OU10 Recommendations for Follow-Up Actions 

Item 

No. Issue Recommendation for Follow Up 

Party 

Responsible Due Date

1 

Additional ICs are needed to ensure 

protection of human health in the 

event of changes in zoning or to 

preclude disturbance of engineered 

remedies as a result of development 

consistent with current zoning. 

Prepare an ESD identifying 

appropriate ICs and implement 

the controls. Resurrection/

EPA 12/08 

2 

Additional seeps have been 

identified in the toe and 

downgradient from the 

impoundment. 

Continue to monitor potential 

for seeps from the toe of and 

downgradient from the 

impoundment and implement 

seep collection as determined 

by EPA. 

Resurrection On-going 
California Gulch Five-Year Report

Page 83 of 89 

15.8 Protectiveness Statement 

The remedy is protective of human health and the environment. However, future remedial 

work may be required in order to attain final Site-wide water quality standards as 

determined pursuant to OU12. 

The absence of ICs to preclude disturbance of the remedy under current zoning has not 

impacted past or current protectiveness as the remedies were undisturbed at the time of 

this Five-Year Review. However, the potential exists for future impacts on remedy 

protectiveness if such an IC is not developed and implemented. EPA and CDPHE are 

informally notified by the County of any changes in zoning. Although this is not a 

formalized IC, it allows the remedy to be protective until an IC is formalized. 
California Gulch Five-Year Report

Page 84 of 89 

16.0 Operable Unit 11- Arkansas River Valley Floodplain 

 

16.1 Description 

The remedy for Operable Unit 11 (OU11) selected in the 2005 ROD has not been 

implemented. Therefore, this OU was not subjected to the Five-Year Review process. A 

summary of prior Response Actions and overall OU status is provided below. 

Operable Unit 11consists of mine tailing from the Leadville historical mining activity that 

was transported downstream via California Gulch to the Arkansas River and deposited in 

many locations adjacent to the river. Some contaminated sediments were also transported 

along irrigation channels and deposited in fields in the Arkansas River Valley both above 

and below the 500-year floodplain. The boundaries of OU11 are from the confluence of 

the Arkansas River and California Gulch to an area approximately nine miles 

downstream from the confluence on the Arkansas River (Figure 3-1 Appendix A). The 

OU is subdivided geographically and also by media into four subunits as follows. 

• Irrigated Meadows Area A – 206 acres of pasture in the northern portion of the 

OU above the 500-year flood plain that exhibits elevated metals concentrations 

and acid soil conditions. 

• Irrigated Meadows Area B - 148 acres of pasture in the northern portion of the 

OU above the 500-year flood plain that exhibits elevated metals concentrations 

and slightly acid soil conditions. 

• Fluvial Mine Waste – 65 acres of mine waste deposits within the 500-year flood 

plain that are generally unvegetated. 

• Riparian Areas – 344 acres of vegetated mine waste deposits. 

High metal concentrations in fluvially deposited mine waste has resulted in varying 

degrees of vegetative distress ranging from diminished plant diversity and density in 

pastures to areas completely devoid of vegetation along riverbanks. 
California Gulch Five-Year Report

Page 85 of 89 

Table 16-1 summarizes the chronology of important events in OU11.

Table 16-1 

Chronology of Site Events for OU11 

Date Event

09/08/83 California Gulch placed on NPL. 

1986 Investigation study conducted by Colorado Department of Law. 

01/87 Phase I Remedial Investigation Report. 

06/93 Emergency Response due to high spring run-off threatening severe erosion of a stretch of 

the Arkansas River bank. 

10/28/93 Emergency removal of river tailing. 

09/94 Two time critical removal actions to stabilize the embankments of two properties which 

abutted the Arkansas River. 

11/01/94 Emergency removal of river tailing. 

09/15/97 Action Memorandum issued for Time Critical Removal Action at the Upper Arkansas - 

Fluvial Tailing. 

08/04/98 Amendment to 09/15/97 Action Memorandum. 

06/17/99 Action Amendment issued for Time Critical Removal Action at the Upper Arkansas - 

Fluvial Tailing 

06/09/00 Action Amendment issued for Time Critical Removal Action at the Upper Arkansas - 

Fluvial Tailing. 

08/11/00 Amendment to Action Memorandum dated 06/09/00. 

12/04 Feasibility Study 

09/05 Record of Decision 

16.2 Response Actions 

Response Action Selection/Implementation

The remediation of OU11 to date has consisted of several Removal Actions summarized 

in Table 16-2. 

Table 16-2 

Removal Actions for OU11 

Area

Action 

Memorandum 

Date

Removal Action Taken/Remedy 

to be Implemented

Start 

Date

Completion 

Date

Arkansas River, 

200 feet 

upstream from 

confluence of 

Lake Fork Creek 

N/A Steel beams driven into the 

riverbank and wall of sandbags 

built to stabilize the river bank. 

06/93 06/93 

Arkansas River 

(not specified) 

10/28/93 Emergency Removal of tailing 

along the Arkansas River. 

10/28/93 N/A 

Arkansas River 

(not specified) 

09/94 Two time critical removal actions to 

stabilize the embankments of two 

properties that abutted the Arkansas 

River 

9/94 10/94 
California Gulch Five-Year Report

Page 86 of 89 

Table 16-2, cont’d 

Removal Actions for OU11 

Area

Action 

Memorandum 

Date

Removal Action Taken/Remedy 

to be Implemented

Start 

Date

Completion 

Date

Arkansas River 

south of 

confluence with 

California Gulch 

09/15/97 

Amended 

08/04/98 

Time critical removal action at four 

locations along stretch of Arkansas 

River south of confluence with 

California Gulch. 

9/15/97 10/1/99 

Arkansas River 

south of 

confluence with 

California Gulch 

06/17/99 Time critical removal action at 

three locations along stretch of 

Arkansas River south of confluence 

with California Gulch. Soil 

amendments were applied and the 

area revegetated with native 

species. 

6/17/99 11/06 

Arkansas River 

south of 

confluence with 

California Gulch 

06/09/00 

Amended 

08/11/00 

Time critical removal action at 18 

small areas along stretch of 

Arkansas River south of confluence 

with California Gulch. 

Approximately 12,000 cubic yards 

of tailing were remediated. 

06/99 11/06 

The ROD describing the selected remedy was released in 2005 and included separate 

actions for each of four geographic or media-based areas as follows: 

• Irrigated Meadows Area A – Apply lime, deep till, reseed and implement ICs to 

prevent changes in land use unless risks are demonstrated to be below a level of 

concern. 

• Irrigated Meadows Area B - Apply lime, organic amendment, deep till, reseed and 

implement ICs to prevent changes in land use unless risks are demonstrated to be 

below a level of concern. 

• Fluvial Mine Waste - Apply lime, organic amendment, deep till, reseed and 

implement ICs to prevent changes in land use unless risks are demonstrated to be 

below a level of concern. 

• Riparian Area - Institutional controls to prevent changes in land use unless risks are 

demonstrated to be below a level of concern. 

System Operation/ Operation and Maintenance 

An Operation, Maintenance and Monitoring Plan will be developed as part of the 

remedial design. 
California Gulch Five-Year Report

Page 87 of 89 

16.3 Progress Since the Last Five Year-Review 

Progress since the last Five Year Review, which was finalized on September 29, 2001 

includes the following: 

• Completion of all Removal Actions 

• Maintenance of the Removal Actions 

• Release of the ROD 

• Remedial design activities. 
California Gulch Five-Year Report

Page 88 of 89 

17.0 Operable Unit 12 

Operable Unit 12 covers the entire California Gulch site and was designated to address 

Site-wide surface and groundwater. Under the provisions of the 1994 CD, OU12 will be 

addressed after completion of source remediation in OUs 2 through 10. This will include 

a determination of protectiveness of surface and groundwater and the establishment of 

points of compliance and performance standards. 

The OU12 Remedial Investigation and Feasibility Study were underway at the time of 

this Five-Year Review with a ROD anticipated to be released in 2008. 
California Gulch Five-Year Report

Page 89 of 89 

18.0 Next Review 

This Site required on-going five-year reviews in accordance with CERCLA §121(c). The 

next five-year review for the California Gulch Site will be performed five years from the 

date of completion of this review. 
APPENDICIES 
APPENDIX A 

FIGURES 









APPENDIX B 

SUMMARY OF PUBLIC COMMENTS 
APPENDIX B 

Community Interviews 

Interviews were conducted with 17 community members representing city and county 

government, the county’s advisory group, the county health department, the Colorado Mountain 

College, potentially responsible parties, and citizens. Most of the interviews occurred one-onone with the exception of one meeting with six representatives of the County’s Institutional 

Control Advisory Group and three telephone interviews. The Lake County Commissioners 

requested that they provide information in writing, so their concerns are reflected in the summary 

that follows and their written account is included with the appendixes of the Five-year Review. 

EPA received numerous comments that do not directly pertain to the protectiveness of remedy 

operations at the California Gulch Site. These comments are important and EPA will use them 

to develop an update of the Community Involvement Plan at a future date. Below is a written 

summary of comments received during interviews as well as written comments from the Lake 

County Commissioners. EPAs responses are provided (in italics) for those comments pertaining 

to remedy protectiveness, the subject of this 5-Year Review. 

Question #1: Are you aware of any community concerns about the California Gulch site or 

its remedy operations? If so, please detail. 

The response to this question varied dramatically. Three citizens and two local government 

representatives indicated that they were unaware of any current community concerns about the 

site or remedy operations, although one of these citizens said she is concerned about her one-year 

old child. She said she signed up for soil sampling during the final notification period and is 

anxious to have her property checked and remediated if needed. 

Another citizen said that the overall community is pretty unfamiliar with the site; he said the 

public has never seemed to fully appreciate what has needed to be done and what still needs to be 

done. He added that he appreciates the good work EPA has done but that the agency has never 

really recovered from the negative impacts of community efforts during the early days. He said 

the effort has taken much longer than it should have due to public fighting. A different citizen 

said there seems to be concerns about the need for a repository and who would operate it. 

Representatives of Lake County and their advisory group voiced numerous concerns about the 

amount of time it has taken to clean up the site and about economic impacts on the community. 

Members cited language from the 2001 5-Year Review about moving the project forward and 

deleting OU’s, and noted that little has changed over the last 5 years. They said that the 

community is worn out. One member of the advisory group stated that she believes the site is a 

failure in terms of the (Superfund) process as well as the engineered remedies. She said she 

believes the “administrative process of endless meetings and excessive lawyering doesn’t work, 

and that she believes their group is being ignored.” Group members described numerous 

concerns about relations with representatives of EPA and the Colorado Department of Public 

Health and the Environment. 
It should be noted that while extensive criticism was received from the county and their advisory 

group, five community members raised concerns about the county’s continued fight over issues 

they felt were solved years ago. Some citizens said they had concerns about the county’s 

advisory group because they didn’t feel the group is a representative cross-section of the 

community. One citizen said he submitted a letter of interest to participate in the county’s 

advisory group but that he was only given two days notice to attend the first meeting and then 

never heard from the group again. 

Question #2: Are you aware of any activities on the site (such as vandalism, trespassing or 

redevelopment) that may have affected any of the site remedies? If so, please detail. 

Most of those interviewed said they were not aware of activities that may have affected the site, 

however several citizens said they had seen people driving four-wheelers, dirt bikes, ATVs and 

snowmobiles in areas where remediation has been conducted. Specifically, one citizen said she 

was aware of a problem at Hamms Tailings because four-wheelers are digging into the cap. She 

also said she believes the county is proposing a park there with grassy fields and is curious as to 

whether native vegetation might be better for the remedy with regard to water usage. 

Response No. 1: 

EPA appreciates the commentors concerns and welcomes reports on the condition of Site 

remedies. However, EPA has not noted any breaches in the cover system at Hamms Tailing. 

Question #3: What is your overall impression of the remedial actions performed to date, 

and their operation and maintenance? 

Responses to this question were either extremely favorable or extremely unfavorable. Most of 

those interviewed said they believed the remedial actions performed to date were positive. One 

citizen said he’s had two lengthy tours of EPA’s work in Stray Horse Gulch and that the work 

appears very stable. A local government representative said he does not have any concerns about 

remedial actions performed to date and added that he is impressed with the Yak Treatment Plant. 

Representatives of potentially responsible parties and contractors overseeing some of the nonresidential work activities said they were satisfied with the remedies; one representative said his 

only concern is about the need for institutional controls. 

Response No. 2 

The lack of comprehensive institutional controls (ICs) has been identified by EPA as an issue of 

concern for most operable units. EPA is committed to the implementation of ICs in operable 

units where they are necessary to provide current and future protectiveness before the end of 

2007. 

Several citizens offered praise for the residential work, and one citizen said his impression is that 

EPA has done a pretty good job considering that the agency has often had its hands tied. The 

citizen said it seems that EPA has been swimming against the current and compromised some of 

its remedies to keep the community happy. 
Lake County Commissioners and members of their advisory group offered numerous criticisms 

to remedial actions performed to date. Below is a summary of comments received during an 

interview with the advisory group as well as some statements taken directly from the county’s 

written comments by operable unit. All written comments received by EPA can be found in the 

appendixes of this report. 

Operable Unit 1 

The county and members of their advisory group agreed that the Yak has been a positive step 

forward and they said they hope the treatment plant is continued and maintained in an optimal 

working manner. They said that they believe if the Yak were to be plugged instead of drained 

through a treatment process, that it would spawn numerous contaminated springs and 

underground contaminant sources throughout the district spreading contamination that has been 

mostly contained. They noted that there are seeps below Operable Unit 7, Apache Tailings, 

which need to be addressed. 

Response No. 3: 

Seeps that are present downstream of Apache Tailing are naturally occurring and are not 

associated with the remediation feature.. 

 

Operable Unit 2 

The county and members of their advisory group said that Malta Gulch “looks like a barren 

desert landscape.” They said it was their opinion that EPA placed insufficient emphasis on the 

finish work, and that the tailings pond needs to be capped and properly revegetated. 

Response No. 4: 

The Colorado Department of Reclamation Mining and Safety (DRMS) is evaluating reclamation 

alternatives for the tailing ponds. Once the DRMS reclamation is completed, EPA will determine 

whether unacceptable residual risk remain and take additional action, if necessary. 

Operable Unit 3 

The county and members of their advisory group said they believe the Harrison Slag pile should 

be deleted from the NPL. 

Response No. 5: 

Deletion may be considered once adequate institutional controls are in place to regulate any 

future development activities. The need for ICs was identified during this Five-year Review and 

EPA intends to develop and implement the ICs before the end of 2007. 

Operable Unit 4 

The county and members of their advisory group said they believe Operable Unit 4 should be 

deleted from the NPL. They said existing zoning (industrial mining) is protective of the remedy. 
Response No. 6: 

Institutional controls are needed to ensure protection of human health in the event of changes in 

zoning or to preclude disturbance of engineered remedies as a result of development consistent 

with current zoning. The need for ICs was identified during this Five-year Review and EPA 

intends to develop and implement the ICs before the end of 2007. In addition, potentially 

unacceptable levels of acid mine drainage continues to emanate from Operable Unit 4 during 

periods of high runoff. Therefore, continued monitoring will be required before a determination 

is made on delisting. 

Operable Unit 5 

The county requested an update on the ASARCO status (what work has been completed and 

whether any work is to be done in the future). 

Operable Unit 6 

Members of the county’s advisory group said they believed that several remedies in OU6 are not 

functioning well. They said remedial work is needed around the waste piles where water has 

been directed. 

The county submitted lengthy comments about OU6: 

• They said they believe the Leadville Mining Drainage Tunnel (LMDT) should remain 

operational indefinitely and that responsibility should not be transferred to the Colorado 

Department of Public Health & the Environment. 

Response No. 7: 

EPA is negotiating with the USBOR for federal funding for long-term operation of the LMDT. 

• They said they consider the surface ponds and collection system for OU6 a failed 

remedy, and said that the ponds are leaking and contaminating the Arkansas River.The 

county raised concerns about work conducted at waste dumps and said that they don’t 

intercept groundwater flow toward the bases of the dumps during runoff. 

Response No. 8: 

Available data indicate that the quantity of zinc and cadmium leaving Stray Horse Gulch has 

been reduced by approximately 90% since response actions were initiated (See OU12 Remedial 

Investigation Report, EPA 2007). Although some risk of overtopping remains for several 

retention basins, the overall performance of the remedy is good. In addition, more aggressive 

reclamation (consolidation and capping) was previously rejected by the community because of 

its adverse effect on historic features. 

• The county recommended that EPA contractors use the Elder pit for tunnel sludges. 

• The county also recommended that the Greenback, Pyrenees, Ram and Mikado be remined if possible with public approval and to consider recycling the mine spoils for 

metal recovery. 
Response No. 9: 

EPA would consider beneficial reuse of mine waste by a third party if it were economically 

feasible. 

• The county said they believe seepage from the Mihala pond is contaminating the fresh 

water ditch across the road to the west and said that most ditches are not properly lined 

and infiltrate the runoff into the ground. 

See Response No. 8: 

• The county said they believe work is needed at Starr ditch and 5th Street because acid 

mine drainage appears to be ponding in that area. 

Response No. 10: 

EPA presumes the commentor is referring to the small sedimentation pond associated with the 

5th Street headwall. This pond is designed to detain surface flows to allow sediment to settle 

before the flows are conveyed in a buried pipeline to Starr Ditch. Therefore, the ponding 

observed is part of normal operation. Sediment removal from the 5th street headwall structure is 

planned for 2007. 

• The county recommended that an outside technical board review the hydrological work 

performed at the site with recommendations to be addressed as ongoing operation and 

maintenance of the remedy (not delaying deletion from the NPL). 

Operable Unit 7 

The county noted in their written comments that there are seeps in Apache Tailings which need 

to be addressed. 

See Response No.3: 

Operable Unit 8 

The county said they believe the Gaw is incomplete and poorly understood and that there appears 

to be some sort of reaction where Gaw water enters the gulch that may indicate some mineral 

content, possibly zinc contamination. They recommended that EPA run a pump down test that 

was suggested by Bob Elder. 

Response No. 11: 

The Gaw Shaft will act a relief point once control of water levels in flooded mine workings is 

established under the OU6 remedy. EPA is negotiating with the USBOR to permit completion of 

the OU6 remedy. A pump test of the Gaw Shaft is planned once negotiations are concluded. 

The quality of waters emanating from the Gaw Shaft has been tested and generally is good. 
Operable Unit 9 

Members of the county’s advisory group had numerous comments about OU9. Most of the 

members stated that they believe the OU9 soil remedy has been completely unnecessary and one 

member said that EPA statistics have shown that there was never a need for the Superfund 

designation of OU9. The members agreed that they would like to see soil remediation stopped 

so the (trust fund) money can be used for other health needs. One of the members said they felt 

Bill Clouber’s work seems to have been dismissed since it came from a grassroots level and their 

community doesn’t have money. Members noted that the agencies didn’t seem to care about the 

impact to the community and that the Superfund process seemed to work only in communities 

that have money. 

Members also indicated that institutional controls are not necessary in OU9, and that the Kid’s 

First program already acts as an institutional control. 

One member explained that Leadville’s average blood lead is 2.8, only six tenths above the 

national average blood lead of 2.2, and said that local blood leads have reduced consistently with 

national levels as a result of reduced levels of lead in gasoline. This member stated that he does 

not believe lead in soil is benign, but that it is a tiny contributor. He believes that playgrounds 

and ball fields should have a higher standard (lower action level) but he thinks that the statistics 

show that dust has not been a contributor in residential areas. 

The county submitted lengthy comments about OU9: 

The county said in their comments that Remedial Action Objectives have been met for OU9 as of 

the calendar year 2005, and that currently not a single person in OU9 has a blood lead level 

elevated above 10 ug/dl, the CDC level of concern. They said they believe the remedy is 

complete. 

The county raised a number of concerns pertaining to EPA’s decision to hold a final notification 

of the original Lake County Community Health Program that resulted in 165 additional 

properties. They expressed concerns about completing the remaining residential remediation and 

delaying delisting of OU9 from the National Priorities List. 

Response No. 12: 

The remedy for OU9 requires remediation of properties with surface soils contaminated above 

established trigger levels. The blood monitoring component of the LCCHP and its predecessor, 

Kids First, was intended to provide an indication of trigger level protectiveness but not remedy 

completeness. Remedy completeness will not be achieved until all properties have been 

demonstrated to pose lead risks below a level of concern (probability of blood lead 

concentration equal or greater than 10 micrograms per deciliter is less than 5%). 

The county said much of the current dispute between them, EPA and CDPHE surrounds the risk 

presented by the remaining lead in soils and they provided a detailed account of why they don’t 

believe further soil remediation or “rigid institutional controls” are necessary. The county said 

they believe OU9 “meets and exceeds all current U.S. health standards for blood lead levels,” 
and that “the cost-benefit ratio of soil remediation is so high as to make it a ludicrous course of 

action, particularly now that so much data is available at this site and nationally indicating a very 

weak link between soil and lead exposure.” 

The county urged EPA to take five actions for OU9. Below is an excerpt from the county’s letter 

of comments: 

1. The EPA should immediately transfer the complete operation of the LCCHP program 

to local operation. EPA can complete the 52+165 homes and vacant lots with money 

from its own budget independently of the county-operated maintenance LCCHP 

program. 

2. Transfer the Trust to the county per the Consent Decree and Trust Agreement in 

order for the county to operate the LCCHP maintenance program. The county fully 

intends to operate the LCCHP program for as long as necessary and has submitted a 

revised work plan to do so. 

3. The Consent Decree requires EPA to provide ASARCO with a Certificate of 

Completion for OU9. EPA should begin the process of deletion of OU9 immediately. 

It must be top priority for EPA to remove the residential areas of Leadville from the 

stigma of being listed on the NPL. EPA should publicly commit to a timeframe by 

which time OU9 will be deleted from the NPL and not use the additional homes 

drummed up for the remediation list to hold up the deletion process.

See Response No. 12. 

4. The LCCHP Maintenance program will serve as the institutional control for OU9. 

The county has offered an initial three-year period of more intense oversight from 

CDPHE while the new program becomes completely operational. After that, 

regulatory oversight should occur during the statutorily mandated 5-year review 

process where the continued need for the program should be evaluated. The county 

will make the data available to CDPHE for its own use at any time after the 3-year 

period.

5. The blood lead level action level for the maintenance program should remain 

10ug/dl. Changes to the action level should be based on the CDC national standard 

and with formal notice and comment amendment to the OU9 ROD.

Response No. 13: 

EPA is in agreement with this recommendation. 

Operable Unit 10 

The county said in their written comment letter that the remedy was failing, has been patched, 

and may still be at risk of failing. They said that EPA needs to closely monitor the situation. 

Response No. 14: 

The occurrence of contaminated seepage at the toe and down gradient of the tailing repository 

has been identified as an issue of concern in this Five-Year Review. EPA will monitor the 
potential for continued seepage from the remedy and may require additional response actions 

either under OU10 or OU12. 

Operable Unit 11 

The county said in their written comment letter that they recommend maximum removal of 

contaminated areas in OU11. They said they would like to see the remediation work result in a 

more complete cleanup of the fishery. They also said the soil amendments result in only transfer 

of the metals to vegetation, which die and return to the soil. They said the vegetation will remain 

dangerous to animals. 

Response No. 15: 

The OU11 Focused Feasibility Study (EPA, 2004) concluded that an increase in dissolved metals 

concentrations could not be detected in the Arkansas River from the up- to the down-stream limit 

of the Operable Unit. Therefore, recent impacts to water quality from OU11 appear to be small. 

Risks associated with remobilization of mine wastes during a future flood will be mitigated 

through stabilization and selective removal of wastes. The risks assessment (EPA, 2004) 

determined that risks to herbivores (livestock) are below a level of concern in the pasture areas 

(upland meadow) of OU11. The soil amendment remedy selected for OU11 will increase plant 

density and diversity without increasing risks to livestock. 

 

Operable Unit 12 

The county said in their written comment letter that they do not have a comment at this time; 

there has not been a proposed plan for OU12. They said, in the interest of moving the entire site 

to prompt completion and deletion from the NPL, that they urge EPA to move to the final stage 

of OU12 as quickly as possible, with the inclusion of the Board of County Commissioners and 

citizen input. They said this comment applies to all operable units at the site that remain on the 

National Priorities List. 

Question #4: Do you feel adequately informed about the Superfund activities? 

The majority of those interviewed (13 out of 18) said they did not feel adequately informed about 

the Superfund activities. Community members raised concerns about having their primary 

source of information come from the local newspapers and they are not sure they hear EPA’s 

perspective on the issues. 

A member of the county’s advisory group said he believes EPA has “stopped communicating 

with the community and has stiffened up and withdrawn.” The county said in their written 

statement that “communication between EPA and the Board of County Commissioners has 

basically ground to a halt.” 

Many of those interviewed offered suggestions for improving communications; examples include 

distributing EPA fact sheets and/or newsletters directly to citizens; distributing a simple map that 

identifies areas where construction is complete and where work remains; offering some review 
time for folks to better understand the history, accomplishments and remaining work; providing a 

facilitator to resolve major issues; and holding more regular and sometimes smaller meetings. 

Question #5: Has the presence of this site had any impact on land use in the area? 

Most of those interviewed felt that land use had been impacted and several community members 

said that the Superfund site has likely prevented development of the Union Pacific railroad area 

(Harrison Street Slag). A couple of interviewees also mentioned Apache Tailings as an area 

negatively impacted by the presence of the site. 

Several community members said that either they did not believe land use had been impacted or 

that the Superfund site had positively affected land use. One community member said the site 

had made a contribution to recreational opportunities in the area. Another citizen said she thinks 

that Kids First had a positive impact on residential land use and that prospective purchasers have 

been more comfortable acquiring residential property because they knew the program was 

available to address their concerns. 

Question #6: Are you aware that residual waste will require long-term management, and 

do you have any concerns about this? 

Everyone interviewed was aware that residual waste will require long-term management, and all 

but three interviewees expressed at least some level of concern. Representatives of two 

potentially responsible parties said they were not concerned. 

Many of the concerns mentioned pertained to who would be responsible for the long-term 

management and the associated costs. Several citizens emphasized the importance of having a 

good solid plan in place that can be followed through changes in officials at the local, state and 

federal level, including agencies such as the Bureau of Reclamation with regard to the Leadville 

Mine Drainage Tunnel. 

The county and members of their advisory group expressed numerous concerns about the Lake 

County Community Health Program Trust Fund and the Operation and Maintenance Program 

that will serve as the institutional control for Operable Unit 9. 

Also See Question No. 3. 

Question #7: Do you have any comments, suggestions or recommendations regarding the 

site’s long-term management? If so, what types of future problems do you think either 1) 

could occur or 2) would concern you at the site? 

Most of those interviewed shared comments, suggestions or recommendations regarding longterm management. A couple of community members raised concerns about the Colorado 

Department of Public Health & the Environment’s ability to stay involved with oversight and to 

be responsive in a timely manner. One community member recommended more frequent 

supervision of the remedies, specifically drainage issues. 
Several interviewees, including members of the county’s advisory group, expressed concern and 

frustration with the draft Operation and Maintenance Program for Operable Unit 9. One member 

of the advisory group said there shouldn’t be any more soil remedies in the residential unit unless 

an elevated blood lead indicates the source to be soil, and that he sees the trust fund as a reservoir 

for continuing lead and other environmental health programs for the next 50 years. 

See Response No. 12. 

A couple of citizens countered these arguments by stating that children should not be used as 

“guinea pigs” when making decisions about investigations and remediations. 

One of the advisory group members also provided comments on some of the non-residential 

operable units and said he believed that “a few touch-ups need to be done at Operable Units 6 

and 4, and that more work may be required at OU10. 

Question #8: Are you aware of any concerns about site impacts on historic preservation? 

Several of those interviewed voiced concerns about impacts to historic preservation. A few 

citizens, including a member of the county’s advisory group, raised concerns about the 

appearance of the “wedding cake.” One citizen said he believes the site has resulted in fewer 

visits by tourists who like history. Another citizen asked if an archeologist is still working with 

the site crew handling residential remediations. He voiced concern about documenting artifacts. 

A few community members expressed gratitude to EPA for working with the community to help 

preserve the history. One citizen said the work done on the Robert Emmet property greatly 

improved the appearance of the retaining wall and made it less of an eyesore; he said it also 

improved access to the Mineral Belt Trail. 

Question #9: Are you aware of any concerns about current construction activities? 

Most of those interviewed offered no comments or positive comments about current residential 

construction activities, and one resident said he believed the work was being completed in a 

professional manner. 

One citizen was aware of a residential property owner who had a leftover problem from the 

previous year’s construction season and had to wait to have it resolved. Some members of the 

county’s advisory group said they felt the current residential construction was a waste of money. 

One member of the group was concerned because he said he’d seen the construction trucks 

speeding on the roads. 

One comment was received pertaining to construction work at the AV Smelter Site in Operable 

Unit 5. A citizen said he had noticed lots of dust at the site. 
Additional Comments: 

A resident wanted to know if there were still allowances as part of the lead-paint remediations. 

He said he was told he would be given a $250 allowance toward a new front door prior to 

Asarco’s bankruptcy. 
APPENDIX C 

SITE PHOTOGRAPHS 
Photo No. 1 – View of FTS 2 (semi-vegetated area beyond bare soil) looking to the 

southwest. 
Photo No. 2 – Seep at toe of Oregon Gulch capped tailing.