Environmental Evaluation of La Oroya Metallurgical Complexicsidfiles.worldbank.org/icsid/ICSIDBLOBS/OnlineAwards/C3004/C-008_Eng.pdf · installed Larox filtering system (operational

September 1996 Knight Piesold LLC CONSULTING ENGINEERS AND ENVIRONMENTAL SCIENTISTS

Final Report

Environmental Evaluation of La Oroya Metallurgical Complex

Prepared for:

~ii;!~ EMPRESA MINERA DEL CENTRO DEL PERU, S.A. '! .~ Special Committee of Privatization (CEPRl) .... ~

Prepared by:

Knight Pit.~sold LLC Denver, Colorado USA

Knight Piesold Consultores S.A. Lima, Peru

CENTROMIN PERU S.A. LA OROYA METALLURGICAL COMPLEX

ENVIRONMENTAL EVALUATION FINAL REPORT

September 18, 1996

Prepared for: CENTROMIN Peru S.A. Empresa Minera del Centro del Peru S.A Av. Javier Prado Este 2155 Lima 41, Peru

Prepared by: Knight Piesold LLC 1050 17th St. Ste. 500 Denver, Co 80201 USA (303)629-8788

Knight Piesold Consultores S.A. Los Tucanes 135-142 San Isidro Lima 27, Peru (511)422-0844

PROJECT 1450A

Knight Piesold -



Table of Contents

CENTROMIN-La Oroya-1450A 50A-OROY A6 .FNL September 18, 1996

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. 1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. 2 Report Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 3 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.4 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.0 SITE DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2. 1 La Oroya Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.1.1 Processing Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2. 1.1.1 Copper Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1.1.2 Lead Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.1.1.3 Zinc Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.1.2 Wastes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.0 ENVIRONMENTAL SETTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.1 Topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.2 Climate/Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.3 Air Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.4 Seism1c1ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.5 Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.6 Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.6.1 Monitoring Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.6.2 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3. 7 Flora and Fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.0 LEGAL ENVIRONMENTAL FRAMEWORK ..................... 25 4.1 Mining/Metallurgical Activities . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4.2 Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.3 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

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Knight Piesold -CENTROMIN-La Oroya-1450A

SOA-OROYA6.FNL September 18, 1996

5.0 OPERATIONAL CONSIDERATIONS ........................... 30 5.1 Air Quality Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 5.2 Operational Modifications - Air Quality ...................... 33 5.3 Soil Quality Conditions ................................ 35 5.4 Water Quality Conditions .............................. 38

5.4.1 Smelting Complex .............................. 38 5.4.2 Refining Complex .............................. 40 5.4.3 Huanchan Slag and Zinc Ferrite Storage Facility ............ 42 5.4.4 Vado Arsenic Trioxide Storage Facility ................. 44 5.4.5 Malpaso Arsenic Trioxide Storage Facility ............... 45

5.5 Operational Modifications -Water Treatment .................. 46 5.5.1 Smelter Complex ............................... 46 5.5.2 Lead/Copper Refinery ............................ 48

6.0 CLOSURE AND RECLAMATION STRATEGIES ................... 50 6.1 Metallurgical Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 6.2 Slag and Ferrite Disposal Area ........................... 51

6.2.1 Lead and Copper Slag ............................ 51 6.2.2 Zinc Ferrites .................................. 52

6.3 Arsenic Trioxide Disposal Sites ........................... 53 6.4 Impacted Soils from Airborne Contaminants ................... 55 6.5 Miscellaneous Impacts ................................ 57

7.0 CONCLUSIONS ........................................ 58

References Tables Figures Photos Appendix A - Ambient Monitoring Network Description

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LIST OF TABLES

1 History of La Oroya Plant

2 Installations at the La Oroya Metallurgical Complex

CENTROMIN-La Oroya-1450A SOA-OROY A6.FNL September 18, 1996

3 Environmental Improvement Works Executed by the Metallurgical Operational Manager

in 1994-1995-1996

4a Classification of Surface Water Monitoring Stations

4b Description of Surface Water Monitoring Stations

5 Smelting Complex, 3/94-2/95 Average Loading Statistics

6 Smelter Complex - Water Quality Results

6a Upgradient - Water Quality Results

7 Refinery Complex, 3/94-2/95 Average Loading Statistics

8 Refinery Complex, Water Quality Results

9 Environmental Guidelines Published by the MEM

10 Comparison of Ambient Air Standards for S02 (ug/m3)

11 Peruvian Maximum Permissible Limits for Effluent from Mining and Metallurgical

Operations

12 Summary of Existing Regional Ambient Air Quality Maximum Observed Concentrations

(January 1994 through March 1996)

13 Summary of Estimated Maximum Existing Deposition Rates

14 Description of Individual Discharges

15 Smelting Complex - Characteristics of Priority Discharges

16 Discharges from Huanchan Slag/Zinc Ferrite Storage Facility, Water Quality and

Loading Statistics

17 Existing Environmental Programs, Programa de Ejecucion del Proyecto Ambiental

(PEPA)

18 Terms of Reference for Proposed Studies

111

Knight Piesold -

LIST OF PHOTOS


1 La Oroya Smelting Complex with the Mantaro River in the foreground

2 Lead and copper slag deposits at Huanchan, La Oroya

3 Zinc Ferrite deposits at Huanchan

4 Malpaso arsenic trioxide deposit (inactive)

5 Vado arsenic trioxide deposit

6 Soils affected by La Oroya air emissions

LIST OF FIGURES

1 Location Map of La Oroya Metallurgical Complex

2 La Oroya Metallurgical Complex

3 La Oroya Smelter Complex and Effluent Monitoring Stations

4 Huaymanta Refinery Complex and Effluent Monitoring Stations

5 Conceptual Design for Metal Removal

lV

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Abbreviation amsl ABA ARD c cm cm/s CENTROMIN

CEPRI CON AM EIA

EVAP

g g/1 ha km 1/s 1/m m m2 m3 m3/min mg/1 mm m/s MEM MPL NIC NR PAMA

PM-10 SNA so2

su TDS

LIST OF ABBREVIATIONS

Term Above mean sea level Acid-base accounting Acid rock drainage Degree Celsius Centimeter Centimeter per second Empresa Minera del Centro del Peru S.A./Mining Industries of Central Peru Special Committee of Privatization

CENTROMIN-La Oroya-1450A 50A-OROY A6.FNL September 18, 1996

National Environmental Council (Spanish acronym) Estudio de impacto ambiental/environmental impact assessment Evaluaci6n ambiental preliminar/preliminary environmental assessment Grams Grams per liter Hectare Kilo meter Liters per second Liters per minute Meter Square meters Cubic meters Cubic meters per minute Milligrams per liter Millimeter Meters per second Peruvian Ministry of Energy and Mines Maximum permissible limit National Institute of Culture Not Reported Program de adecuaci6n y manejo ambiental/environmental adjustment and management program Particulate matter less than 10 microns in diameter Environmental Management National System (Spanish Acronym) Sulphur dioxide Standard units Total dissolved solids

V

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Abbreviation tpd tpy TR UBC ug/m3

USEPA

ABBREVIATIONS continued Term Tonnes per day Tonnes per year Traces Unified Building Code Micrograms per cubic meter United States Environmental Protection Agency

VI

CENTROMIN-La Oroya-1450A SOA-OROY A6 .FNL September 18, 1996

Knight Piesold -



EXECUTIVES~ARY


The La Oroya Metallurgical Complex is a non-ferrous smelting and refining network which

produces a range of major and minor metals and other products from a number of

chemical/industrial plants. The complex is the primary smelting and refining unit being offered

for privatization by CENTROMIN Peru S.A. La Oroya is located approximately 180 kilometers

(km) northeast of Lima in the Junfn Department of the Yauli Province and Andres Avelino

Careceres Region at an elevation of about 3,800 meters above mean sea level (amsl) (Figure 1).

Smelting and refining of copper concentrates began in 1922 with the addition of lead-silver and

zinc recovery of concentrates in 1934 and 1952, respectively. Development of these

metallurgical activities have resulted in the disturbance of approximately 350 hectares of land

surface (Figures 2, 3, and 4).

In order to advise CENTROMIN and its prospective buyers on the environmental conditions and

compliance status of the La Oroya Metallurgical Complex, the Special Committee of

Privatization retained Knight Piesold LLC to highlight key environmental issues at the

metallurgical unit and to identify remediation strategies that may be used to mitigate any

remaining environmental concerns. Based on discussions with CENTROMIN personnel and site

observations made by members of the Knight Piesold project team in May of 1996, and also our

review of certain documents and other information provided by CENTROMIN, it is Knight

Piesold's opinion that operational modifications will be required to promote continued operations

at La Oroya in compliance with Peruvian and generally accepted environmental standards. The

following issues represent what we believe are the key environmental considerations for the La

Oroya Metallurgical Complex:


50A-OROY A6.FNL September 18, 1996

• Airborne emissions of sulphur-dioxide (S02), metals, and PM-10 particulate

matter are high and exceed generally accepted international standards.

CENTROMIN has plans to evaluate control methods that will modify processing

and facility operations in order to comply with future air quality standards.

However, remedial actions to bring the facility into compliance with proposed

Peruvian standards and generally accepted world standards would involve a

significant capital expenditure. (Section 5.1 and 6.1)

• Airborne emissions have impacted the soils surrounding the facility. Metal

concentrations, in some areas, exceed those that are generally accepted for

agricultural and residential areas. Large areas surrounding the project site have

characteristics of soil bum out which may decrease vegetation levels due to the

defoliation action of the S02 emissions and acid rain. (Section 5 .2)

• The La Oroya Metallurgical Complex is situated at the confluence of the Yauli

and Mantaro Rivers. These rivers are influenced by human, mining and other

industrial activities upgradient of the La Oroya Complex (Section 5.4).

Water quality in the Mantaro River upgradient from the La Oroya complex

(except the arsenic trioxide deposits) exceeds Peruvian Class Ill standards for

nitrate only. Downgradient of the La Oroya Complex in the Mantaro River, Pb,

Cu, As, and N03 concentrations exceed Peruvian Class Ill standards. (Section

5.4.1)

The Yauli River water quality upgradient from the La Oroya complex exceeds

Peruvian Class Ill standards for lead and nitrate. Sulfate and iron concentrations

2



are also high. Operational procedures and closure strategies must continue to

prioritize the protection of these receiving waters. (Section 6.0 & 7.0)

The quality of the Yauli River may be improved by the operation of the recently

installed Larox filtering system (operational since June of 1996). This system is

a zero emission system which filters fines from waste electrolyte, captures a

portion of the acidic solutions from process waters, and recycles the remaining

waters to the Lead Refinery. The recovered acidic solutions are recirculated to

the Acid Plant. (Section 2.1.1.2 and 6.2)

• Smelting and refining facilities must continue to be managed to control releases

of waste waters to the Mantaro and Yauli Rivers. The quality of discharge water

must continue to be monitored for compliance with Annex 2 and Annex 1

standards and for changes in chemical character. (Section 4.3)

• Lead/copper slag and zinc ferrite disposal facilities do not meet existing siting

requirements, and ferrite effluent are being discharged to the Mantaro River.

CENTROMIN is considering alternative locations of disposal facilities as well as

alterations in the production and disposal methods of refined metals and wastes

to aid in meeting site requirements. (Section 5.3.3)

• The amount of arsenic trioxide deposited at the Vado and Malpaso storage

facilities is unknown. Discharge from and structure stability of both facilities

require continued monitoring to determine overall impacts to the La Oroya

region. (Sections 5.3.4 and 5.3.5)

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50A-OROY A6 .FNL September 18, 1996

• Operational modifications to air and water control systems may be required to

facilitate continued operations at La Oroya in compliance with Peruvian and

generally-accepted environmental standards. (Section 6.0)

• CENTROMIN has complied with its regulatory obligation to submit an EV AP

and is currently in the process of initiating further studies to characterize physical

and geochemical conditions in order to establish an appropriate environmental

management and closure plant. CENTROMIN, or its successor, is required to

submit these plans as part of the PAMA by August 31, 1996. (Section 4.0)

• It appears that remediation technologies exist for the effective closure and

reclamation of site disturbances. (Sections 7. 0)

It is our opinion that most existing environmental impacts at the La Oroya complex can be

adequately controlled if readily available and commonly used operating, reclamation and

remediation, and closure techniques are employed. CENTROMIN is presently evaluating

alternatives (i.e., process changes) to bring the facility into compliance with existing and

proposed Peruvian and international standards. The responsibility for continued regulatory

compliance and for the implementation of any necessary environmental controls and remediation

technologies lies with the owner and/or operator of the metallurgical unit.

4

Knight Piesold -

1.0 INTRODUCTION


CENTROMIN Peru S.A. (CENTROMIN) is a state-owned company in the process of becoming

privatized. To accommodate this privatization, Knight Piesold LLC (Knight Piesold) has been

appointed by the Special Committee of Privatization (CEPRI) for CENTROMIN to conduct

environmental evaluations on seven of their polymetallic mines including Yauricocha, Casapalca,

Andaychagua, Morococha, San Crist6bal, Cobriza, and Cerro de Pasco. Knight Piesold is also

evaluating the La Oroya smelting and refining complex which processes the majority of

concentrates from the above mentioned mines. This report is specific to the La Oroya

Metallurgical Complex.

1.1 Purpose

Facility operation, maintenance, environmental control, regulatory compliance and the

appropriate closure and reclamation of site disturbances are the responsibility of the

owner/operator of the unit. In order to advise both CENTROMIN and its prospective buyers

of the important environmental issues and to identify plausible closure concepts in the absence

of detailed studies and engineering evaluations that may be effective for long-term site

stabilization, CEPRI retained Knight Piesold to visit each CENTROMIN owned mining and

metallurgical unit, interview CENTROMIN personnel, review certain reports and documents

supplied through May 1996 by CENTROMIN, and prepare a report citing its independent third

party opinion of the important environmental issues to be considered in preparing and negotiating

financial terms for the privatization of each mining and metallurgical unit.

This report presents what Knight Piesold believes are the key environmental issues to be

considered in preparing a suitable offering for the La Oroya Metallurgical Complex. It also

presents what we believe to be credible closure and reclamation strategies that may be suitable

for long term site stabilization based on the conditions observed at the time of the site visit and

our experience with closure and reclamation of other mining and processing facilities. It is our

5


50A-0ROYA6.FNL September 18, 1996

opinion that the information contained in this report should be factored into any credible

financial offering for the La Oroya complex.

1.2 Report Organization

This report is intended to give the reader an overview of the La Oroya metallurgical unit

and to present our impressions and findings regarding environmental compliance, controls and

remediation concepts. The report has been divided into six sections as follows:

SECTION 1.0

SECTION 2.0

SECTION 3.0

SECTION 4.0

Introduction - describes the report objectives, organization, and

study methodologies. It also cautions the limits to which the

reader should rely on the information presented.

Site Description - provides a general overview of the activities

occurring and wastes generated from ongoing operations and

identifies key project components affecting environmental

conditions.

Environmental Setting - gives an overview of the background

environmental conditions in order to aid the reader in

understanding the environmental effects of project activities and

the need for suggested mitigation measures.

Legal Environmental Framework - describes the significant

regulatory programs under which project operations must comply.

It presents our impression of the compliance status of the current

CENTROMIN operations and also presents our opinions regarding

the adequacy of ongoing environmental monitoring programs.

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Knight Piesold -

SECTION 5.0

SECTION 6.0

SECTION 7.0

1.3 Methodology

CENTROMIN-La Oroya-1450A SOA-OROY A6 .FNL September 18, 1996

Operational Considerations - presents the environmental issues,

affects and controls associated with ongoing project operations.

Closure and Reclamation Strategies - presents what we believe to

be plausible closure and reclamation concepts for mitigating

environmental impacts associated with project operations.

Conclusions - summarizes what Knight Piesold believes to be the

important environmental conditions and remediation concepts that

should be factored into establishing a fair purchase price for the La

Oroya Metallurgical Complex.

In order to provide an independent assessment of the environmental conditions and

liabilities at each of the CENTROMIN facilities, Knight Piesold formed a team of well-qualified

individuals, each with many years of practical experience in their respective disciplines, to

evaluate the site conditions. The team comprised individuals participating in field, interpretive,

analytical, and reporting components as well as in technical oversight roles. These individuals

were also assisted by a well-qualified team of engineers, environmental scientists, technicians,

and administrative personnel in developing and finalizing the information presented in this

report.

The primary project and field evaluation team involved with all aspects of this evaluation

included:

• Ms. Barbara A. Filas, P.E., Project Principal and Mining Engineer, 18 years experience;

7


50A-OROYA6.FNL September 18, 1996

• Ms. Pamela J. Stella, M.S., Project Manager and Hydrogeologist, 13 years of experience;

• Mr. Mario D. Villavisencio, M.S., Civil Engineer and Manager of Knight Piesold's Peruvian Operations, 12 years experience;

• Ms. Liliana Unten, M.S., Chemist and Environmental Science Specialist, 10 years experience;

• Mr. Charles L. Jackson, M.S., Biologist and Regulatory Compliance/Reclamation Specialist, 22 years experience; and

• Dr. George McVehil, Ph. D., Principal Meteorologist and Air Quality Expert, 33 years experience.

• Mr. Bret A. Peterson, M.S., Meteorologist and Air Quality Specialist, 11 years experience.

Technical review and oversight, as well as participation in program planning, direction,

and meetings with CENTROMIN involved Mr. Leonard Harris, Metallurgical Engineer and

Peruvian Mining Industry Expert, with 53 years experience, over 17 of which were spent as

Metallurgical Manager and/or Operations Manager at the La Oroya Complex.

Other significant technical contributors to the preparation of this report included:

• Dr. Ronald L. Schmiermund, Ph.D., Geologist and Geochemist, 20 years experience;

• Mr. James J. Gusek, P.E., Mining Engineer and Reclamation Specialist, 22 years experience;

• Mr. Robert W. Reisinger, P. E., M. S., Mining and Environmental Engineer, 19 years experience;

• Mr. Brett F. Flint, P.E., Civil and Structural Engineer, 12 years experience;

8



• Dr. Gary G. Van Riper, Ph.D, Chemical Engineer and Water Treatment Specialist, 24 years experience.

The project team performed the following tasks in preparing this report:

• Reviewing operational and environmental data and materials provided by CENTROMIN;

• Conducting a site visit and interviews with CENTROMIN personnel;

• Assessing the environmental conditions based on the information provided by CENTROMIN and integrating that information with the conclusions and impressions drawn by the team during their site visit; and

• Conceptualizing plausible reclamation and remediation strategies for existing environmental conditions based on the information provided, site observations, and the experience of the project team at other mining sites in the absence of sitespecific re mediation plans and designs for this facility.

1.4 Disclaimer

This report is intended solely to convey the opinions and impressions of the Knight

Piesold project team regarding the La Oroya Metallurgical Complex. No technical or

engineering evaluations, stability analyses, geochemical investigations, or construction material

sourcing were conducted as part of this assignment. The information presented in this document

is intended solely to appraise CENTROMIN and its prospective buyers of our opinions regarding

the existing environmental programs, conditions, and impacts and to identify what Knight

Piesold believes to be plausible reclamation and remediation strategies based on our observations

on site and our team's experience with analogous situations in Peru and elsewhere. The opinions

presented in the report do not circumvent the need for detailed engineering and environmental

evaluations to substantiate the technical adequacy of any of the identified environmental

conditions and remedial measures.

9


SOA-OROY A6.FNL September 18, 1996

Analyses in this report are based on regulations, guidelines, and laws which were in

effect during the site visit, May 1996, and therefore may not be comparatively representative

of current guidelines at the time of issuance of this report.

10

Knight Piesold _..._ ___ _ 2.0 SITE DESCRIPTION


The description of the environmental setting and site conditions at La Oroya is intended to

provide an overall picture of this CENTROMIN complex to assist in the evaluation of potential

environmental issues associated with La Oroya. Information used for this section is derived

from the field evaluation team visit to the site in May of 1996, on-site discussions with and other

information provided by CENTROMIN personnel, the 1995 La Oroya Preliminary

Environmental Assessment (Spanish acronym EVAP), and Knight Piesold's experience with

similar facilities within the region.

2.1 La Oroya Description

The La Oroya Metallurgical Complex is a non-ferrous smelting and refining network

which produces a range of major and minor metals and other products from a number of

chemical/industrial plants. La Oroya is located approximately 180 kilometers (km) northeast of

Lima in the Junin Department of the Yauli Province and Andres Avelino Careceres Region at

an elevation of about 3,800 meters above mean sea level (amsl) (Figure 1). The primary access

route to La Oroya is the Carretera Central (Highway 20). This paved highway runs

approximately 175 km from the port of Callao in Lima to La Oroya, and is in good condition.

La Oroya is also served by the Centro Ferrocarril (Central Railroad) spanning 190 km from

Callao to the La Oroya region. The town of La Oroya neighbors the processing complex and

is situated at the confluence of the Yauli, Mantaro a..'l.d Tishgo Rivers.

The La Oroya Plant was established in 1922 when the Cerro de Pasco Corporation began

smelting of copper concentrates. In 1934, lead-silver smelting operations supplemented copper

production and, since 1952, zinc has also been added to the La Oroya complex activities. The

history of the plant is presented in Table 1. Since the 1950's expansions made to the complex

include the addition of copper, lead-silver, and zinc refineries, as well as the construction of

byproduct recovery plants. La Oroya processes ores and concentrates supplied from the

11



formerly owned Cerro de Pasco Corporation mining units and other purchased or custom

sources. The Cerro de Pasco Corporation was nationalized in 1974 and is now managed by

CENTROMIN Peru S.A. The CENTROMIN units which are currently in operation include:

• Cerro de Pasco Mine;

• Morococha Mine;

• Casapalca Mine;

• San Crist6bal Mine;

• Yauricocha Mine;

• Cobriza Mine; and

• Andaychagua Mine .

2.1.1 Processing Activities

La Oroya is composed of an integrated three circuit system that smelts and refines

lead-silver, copper, and zinc ores and concentrates, some of which contain considerable amounts

of impurities. Chemical byproducts such as sulfuric acid, sodium sulfite, copper sulfate, zinc

sulfate, zinc oxide, and zinc dust (among others) are produced as saleable subproducts. The

annual production capacity of the complex is approximately 66,500 tonnes of copper, 99,000

tonnes of lead, and 70,000 tonnes of zinc. The major complex is split into two main sites of

processing which have a combined affected area of approximately 45 ha. The first site borders

the Mantaro River and contains the primary smelters, the zinc and silver refineries and ancillary

plants for the production of zinc, copper, and lead, as well as secondary products such as

arsenic, antimony, bismuth, cadmium, coke, gold, indium, silver, selenium, and tellurium

(Photo 1). The second main site, known as Huaymanta, is approximately 3 km west of the

smelting complex, and contains the copper and lead refineries in addition to the copper-sulphate

and copper rod plants (Figure 4). These plants occupy the site adjacent to the Yauli River which

is a tributary of the Mantaro River.

12

Knight Piesold -CENTROMIN-La Oroya-l450A


The smelting and refining processes require approximately 75,700 liters per

minute (llm) of water which is drawn from the Tishgo and Mantaro Rivers. CENTROMIN

reports that the subsequent industrial effluent produced by metallurgical processing discharged

into the Yauli and Mantaro Rivers have been reduced from the average rate of 71,500 1/m to

49,000 1/m. The final copper, lead, and zinc products as well as the above mentioned sub

products are either consumed on site or sold on the world market.

The general arrangement of the La Oroya complex is shown in Figure 2 with the

major components listed in Table 2. The individual processing and recovery operations at the

La Oroya Metallurgical Complex are detailed below.

2.1.1.1 Copper Circuit

Copper smelting processes are initiated at the copper preparation plant.

Recirculated material, fluxes, and copper ores and concentrates are proportioned and combined

at this plant in accordance with the established metallurgical guidelines, and deposited in piles

known as beds. This mixture is roasted to eliminate impurities such as arsenic, sulfur,

antimony, and lead, and produce a calcine material (containing the valuable copper minerals)

for smelting. Particulates contained in gases produced from the roasting processes are recovered

in the roasting recirculation ducts for reprocessing. Fines escaping the recovery ducts are

recovered in the Cottrell electrostatic precipitator. Arsenics are subsequently produced from the

captured precipitates, isolating arsenic from the copper metallurgical process. The arsenic

byproducts are precipitated into expansion beds to form arsenic trioxides with a purity of 95%.

The calcine materials produced from the roasting process are then

transported to the copper smelter to separate the matte (FeS and Cu2S) from waste/slag material.

Copper smelting is conducted in reverberatory furnaces fired by oxy-fuel burners. Waste/slag

from the smelting process is granulated and later stored at the Huanchan waste storage area

(Section 2.1.2).

13



The matte is tapped from the furnaces and transported in ladles by crane

to the converters. The conversion of the matte to metallic copper is completed in two stages.

First, the matte is charged together with silicate fluxes to the converters and blown with air to

generate ferrous oxides. These oxides react with silica to separate iron oxide wastes from the

desired copper sulfides. Second, the partially oxidized matte is further oxidized by blowing air

to form blister copper that is casted into anodes. The waste/slag produced from this process is

returned to the reverberatory furnaces for further copper recovery. Particulates emitted during

the converting and casting processes are recovered as precipitates at the Cottrell electrostatic

plant and later reprocessed in the roasting plant. Sulfur dioxide, however, is emitted to the

atmosphere primarily through the main chimney, and as fugitive emissions, to a lesser extent.

Copper refining begins with the anode blister copper produced during the

converting and casting processes. These anodes are treated through an electrolysis process to

produce refined copper cathodes which can be sold or melted and cast at the Asarco and

Alambron Plants to produce wire bar. Slimes resulting from this process are treated at the

Anode Residue Plant where gold, silver, selenium, tellurium, and bismuth metals are recovered.

Part of the electrolytic solution (which contain sulfuric acid) is purged of

accumulated impurities which would otherwise diminish the quality of the final copper products.

The purged solution is first neutralized with copper oxide, copper cement and metal scrap from

the refinery, and later crystallized to produce commercial grade copper sulfate. About 75% of

the solution is returned as electrolyte while the remaining 25% is sent to a cementation plant to

recover the residual coppet.

2.1.1.2 Lead Circuit

The lead smelting process is initiated at the Lead-Preparation Plant where

recirculated materials, fluxes, and lead-silver ores and concentrates are proportioned and

combined in accordance with the established metallurgical guidelines, and deposited in piles

14

Knight Piesold -CENTROMIN-La Oroya-14SOA

SOA-OROYA6.FNL September 18, 1996

known as beds. These beds are treated in the Lead-Sinter Plant to reduce the sulfur content of

the feed and produce an agglomerated material suitable for the smelting operations. Particulates

produced during sintering activities are recovered via bag filter, while fines contained in the

gaseous emissions are recovered through the electrostatic processes at the Cottrell electrostatic

plant. Sulfur dioxide produced from the process is emitted to the atmosphere through the main

chimney.

The sinter is smelted in two blast furnaces employing coke as the

reductant. The smelted products are discharged to settlers, where the lead bullion and waste/slag

products are separated by density. The slag is granulated and transported together with the

copper slags via cable car to the Huanchan waste storage area. As a result of the insufficient

holding capacity of the cable car system, approximately 40% of the copper and lead slags are

discharged directly to the Mantaro River.

The lead bullion is transported to copper-drossing kettles at the

Copper/Dross Treatment Plant. Upon cooling, a dross containing arsenic, antimony, copper,

and some lead separates on top of the lead-bullion, and is subsequently skimmed off for

treatment in the reverberatory furnace. The products at the reverberatory furnace are copper

matte, speiss (Cu-As, Sb) and lead bullion. The copper matte and speiss complexes are

transferred to the copper smelter for further processing while the lead bullion is cast into lead

anodes. The anodes which still contain antimony, bismuth and silver are refined electrolytically

using a modified Betts process. The refined lead is cast into 46 kg ingots to be sold on the

commercial market. Prior to mid-1996, the slimes from the Betts process were centrifuged to

produce a moist cake which was subsequently treated at the Anode Residue Plant. The solution

from the centrifuges passed to settling tanks before being discharged to the Yauli River.

However, since June of 1996, Larox filters have replaced the centrifuges in efforts to produce

a drier filter cake for the Anode Residue Plant. In this process, the fluorosilicic acid solution

is partially recovered and recycled to the Acid Plant. CENTROMIN reports that the remaining

15



solution from this circuit is recycled to the lead refinery, and is no longer discharged to the

Yauli River.

2.1.1.3 Zinc Circuit

The zinc concentrates are prepared for treatment in two roaster circuits;

the first circuit employs fluid-bed roasters that treat materials which have been previously

agglomerated. The second circuit, known as the turbulent-layer roaster, treats materials which

require no previous treatment. The zinc concentrates contain on average about 53% zinc and

9.5% iron. Roasting of the zinc concentrate produces calcine composed of zinc-oxide and an

iron- and zinc-oxide complex referred to as "ferrites". Calcines produced from both roasting

processes are ultimately transported to storage silos at the zinc leaching circuit.

Zinc calcine dust contained in the gaseous emissions of the fluid-bed

roasters are recovered by cyclones and electrostatic precipitators, and partially returned to be

mixed with zinc concentrates in the pelletizing plant. The remainder is processed in the leaching

plant. Sulfur dioxide produced from this roasting process is emitted to the atmosphere through

the main chimney. Sulfur dioxide produced from the turbulent-layer roaster is recovered and

processed to produce sulfuric acid in the Sulfuric Acid Plant (capacity 55,000 tonnes per year).

Calcines produced from zinc roasting are leached with spent electrolyte in

agitated tanks. The principal objective of the leaching stage is to dissolve the zinc oxides and

zinc sulfates from the calcine produced at the roasters. Zinc oxide reacts with the electrolytic

solution to form zinc sulfates. The ferrites contained in the calcine are insoluble, thus, they do

not react during the leaching stage. The resulting leach-pulp contains zinc sulfate, ferrites, and

other insoluble materials.

The zinc sulfate solution is separated from the solids employing a series

of thickeners and rotary filters. The solids recovered from the thickener and filtering processes

16



are re-pulped and floated to capture the maximum amount of unreacted zinc sulfide present in

the pulp. About 35% of the tailing produced during flotation are processed pyrometallugically

in the Waelz rotary kiln to recover zinc, lead, cadmium and indium metals. The remaining 65%

of the tailings are pumped as pulp to storage ponds at Huanchan. The solids are settled out and

the overflow drains to the Mantaro River.

The zinc sulphate solution is purified by precipitating copper, cadmium,

and small amounts of arsenic and antimony from the solution. The precipitates are sent to the

Cadmium Plant for further treatment while the purified zinc solution is sent to electrolysis

employing aluminum cathodes and lead-silver anodes. After 16 hours, zinc is stripped from the

cathodes and melted in an induction furnace, and subsequently cast into 24 kg ingots to be sold

on the world market.

2.1.2 Wastes

The majority of materials processed at La Oroya contain impurities that are

recovered independently of the refined metals. The primary residues include copper and lead

slag, zinc ferrite, and crude arsenic trioxide. These wastes are captured during smelting and

refining activities and stored at waste storage deposits situated along the Mantaro River. The

slag and zinc ferrite residues which are shown in Photos 2 and 3 are placed at the Huanchan

disposal site (approximately 4 km south of the smelter), while the active and abandoned arsenic

trioxide waste storage areas are located at Vado and Malpaso, respectively (Photos 4 and 5).

These wastes are environmental concerns due to their potential to affect the Mantaro River and

to emit particulates to the surrounding atmosphere (Section 5.1 and 5. 3).

In response to some of the environmental issues listed above, La Oroya has been

modernized over time to include technical innovations such as a dust recovery system as well

as the an oxygen plant in February 1994, and a Larox filter system in 1996. The innovations

implemented to date are listed in Table 3.

17

Knight Piesold -

3.0 ENVIRONMENTAL SETTING

CENTROMIN-La Oroya-l450A 50A-OROY A6.FNL September 18, 1996

The environmental setting is presented to establish the background conditions against which the

project impacts (Section 5.0) can be assessed and to provide a basis for understanding the

operational modifications as well as reclamation and remediation strategies (Sections 6.0 and 7.0,

respectively).

3.1 Topography

The La Oroya complex is located east of the continental divide and has an average

elevation of approximately 3,800 meters amsl. Regional topography is influenced by high

mountain peaks and narrow V -shaped valleys. The town of La Oroya and the main smelter

complex area are situated in the valley at the confluence of the Yauli and Mantaro Rivers.

Near-vertical rock faces and steeply sloping canyon walls surround the complex, nesting it

tightly within the narrow river valleys. Each of the rivers flow eastward toward the Mantaro

River Basin.

3.2 Climate/Meteorology

Understanding the typical climatic conditions at La Oroya, and the relation between

precipitation and evaporation in the region is important to developing effective closure,

mitigation, and/or remediation strategies. Thus, the temperature, precipitation, wind, and

evaporation conditions of the La Oroya metallurgical site are discussed below.

According to the classification of Natural Regions of Peru (Pulgar Vidal, 1967), La

Oroya is classified within the Jalca ecological/climatic region. The Jalca is characterized by

mountains and cliffs with narrow valleys, and is humid and cold with a well-defined winter

season. Average monthly temperatures range from 6.6 and 10.5 degrees Celsius during the

summer and winter months, respectively. However, extreme temperature events occurring

within a month are typical to high Andean regions.

18



The average monthly precipitation is about 570 mm, the majority of which falls as rain

or snow during the October to April wet season. No records were available documenting

evaporation rates at the project site. However, it has been our experience at other high altitude

Peruvian mine sites that evaporation rates at the project site are often elevated during the dry

season but often decrease to essentially zero during the wet season.

Wind direction varies within the La Oroya region but would be expected to generally

parallel the valley axis, with airflow being upgradient or downgradient depending on the season

and/or time of day. According to the La Oroya EV AP ( 1995), the maximum recorded wind

velocities average approximately 2.5 kilometers per hour (km/h). Thus, air particulates from

the smelter and refineries are not emitted systematically in one direction, nor are they likely to

be transported significant distances off-site. Defined dispersion characteristics, however, may

be suspect due to the positioning of the monitoring stations.

3.3 Air Emissions

Because of the nature of the smelting and refining processes, and the constituents of

normal metallic ores, the potential for emissions of air pollutants from the La Oroya facility is

high. These pollutants include particulate matter, metals and sulfur dioxide (S02) which could

affect the health of the population and the viability of the local soils. CENTROMIN has

installed controls applied (Cottrell precipitators) to accomplish a significant reduction in

emissions of dust and metals; however, S02 emjssions are reduced by only a small fraction

through production of limited quantities of sulfuric acid.

The main stack at La Oroya currently emits on the order of 815 tons per day of S02•

Dust emissions total approximately 10 tons per day, consisting of roughly 2.5 tons of lead, 1.4

tons of arsenic, 0.8 tons of zinc, and smaller quantities of other metals. Though the main stack

is the largest source of air emissions, significant quantities of the same pollutants are emitted

from numerous smaller stacks, as well as from many fugitive (non-stack) emission sources.

19

Knight Piesold -CENTROMIN-I..a Oroya-1450A


Though some stack testing has been carried out in the smaller stacks, no definitive data exist

from which to quantify actual total facility emissions.

It is possible to estimate total S02 emissions from all sources on the basis of total ore

processed and the sulfur content of the raw ore (taking into account the S02 currently controlled

by sulfuric acid production). By this method, CENTROMIN has calculated (EV AP, 1995) that

total S02 emissions are approximately 350,000 tons per year, or 962 tons per day. Thus, about

85% of total S02 emissions originate from the main stack. There are no comparable data to

estimate total metals or dust emissions from all sources combined. However, because of the

control of main stack dust emissions, the fraction of total dust and metals released from low

altitude sources as compared to the main stack is probably larger for particulate matter than for

S02 •

The above mentioned data are derived from CENTROMIN's air monitoring program at

the La Oroya Metallurgical Complex. This program monitors the ambient air quality at five

sites in the vicinity of La Oroya in accordance with the proposed regulations discussed in Section

4.2. The Huancha.n monitoring site, however, is located atop a large slag pile which likely

affects monitoring results. While this facility can assess the stability of the Huanchan site, the

obstruction to normal air flow created by the slag may detract from the certainty of the sampling

results. Further discussion of the La Oroya monitoring program and its current results are

presented in Appendix A.

3.4 Seismicity

Tectonic activity within Peru is regionally attributed to the interactions of the South

American and Nazca plates which have produced vast geologic and physiographic changes

throughout Peru. Western Peru lies within the subduction zone between the two tectonic plates,

explaining the high seismicity throughout the country. In addition, La Oroya is known to have

fractures and faults that can be locally active.

20



Based on the interrelations and activities of regional and local (faults and fractures)

seismic influences in the project region, the Peruvian seismicity code classifies the La Oroya

area, including the project site, as a Zone 1 seismic region. This is the highest seismicity

ranking of the three zone system. The Peruvian code is generally based on the Unified Building

Code (UBC) system used in the U.S.A. Zone 1 of the Peruvian code roughly corresponds to

the UBC Zone IV, the highest seismicity used in the United States. Seismic issues related to

La Oroya may include potential damage to major structures, particularly chimneys, stacks,

columns, and retaining walls. These seismic conditions should be considered when planning

closure and reclamation strategies.

3.5 Soils

Local soils are susceptible to wind and a1r eros10n due to the lack of vegetation

surrounding the project area. This lack of regional plant cover is partly attributed to the natural

geologic, topographic and altitude conditions existing at La Oroya. However, soil burnout

caused by S02 emission from the smelting activities may also be affecting vegetation populations

(Section 5.2). According to studies performed by CENTROMIN, La Oroya soils generally

contain small amounts of nitrogen and elevated amounts of calcium. Overall, the La Oroya soils

are considered to be slightly acidic except for areas around the smelter. There, calcium

carbonates render the soils slightly alkaline.

3.6 Hydrology

Because the project area lies east of the continental divide, both mine and natural effluent

drain eastwardly and ultimately converge with the Mantaro River within the Mantaro watershed.

The drainage of concern for the purposes of this report are the Yauli, Tishgo, and Mantaro

Rivers which accept drainage from the La Oroya metallurgical complex and the town of La

Oroya. The regional watershed is supplied by high-altitude tributaries that accept drainage from

other industrial operations and drain to the Yauli and/or Mantaro basins upgradient of the La

Oroya complex.

21



To date, La Oroya water monitoring programs have been conducted in three separate

stages. The first sampling stage was conducted in 1992 and analyzed effluent most likely to

affect the environment surrounding La Oroya. The second monitoring stage was conducted

between March of 1994 and February of 1995 for inclusion in the La Oroya EVAP. The third

monitoring program is modeled after the plan established during stage two as well as the recently

established Annex 2 water-quality guidelines set forth in January of 1996

(R.M.Oll-96-EM-VMM) (discussed further in Section 4.0). This stage was initiated at the

beginning of 1996 and is expected to be continued throughout the year. CENTROMIN reports

that water samples are filtered prior to analyses. A summary of the water-quality analysis is

provided below.

3.6.1 Monitoring Sites

No routine water-quality monitoring was performed at the La Oroya site prior to

1992. Between 1992 and early 1994, limited sampling of site effluent was conducted. In March

of 1994, monthly monitoring was instituted at 49 points along various surface-water courses and

process effluent streams, continuing through February 1995 (Table 4a and 4b). Tables 5 through

8 summarize the first year of monthly data and present average values for water quality

parameters. Monthly monitoring is ongoing at twelve sites (R-1, R-3, D-115, -118, -119, -123,

-126, -131, -134, -135, -136,and -137) (Table 4a). No information is available regarding

groundwater quality in the La Oroya area.

3.6.2 Water Quality

In the absence of Peruvian water-quality guidelines and standards specific to

smelting and refining, water quality of the various metallurgical-related discharges is compared

to World Bank guideline liquid effluent values for underground mining operations and the

newly-adopted Peruvian Annex 2 effluent standards for existing mining operations. The river

sampling monitoring points (M-1, M-2, M-3, M-4, M-5, Y-1, Y-2, and Y-3) were compared

to Peruvian Class Ill standards for agricultural use since they are aggregate receptors of effluent

22


SOA-OROY A6 .FNL September 18, 1996

contributions. Comparisons to the Class Ill standards and World Bank guidelines could result

in undetected exceedences of these standards because the metals are reported as dissolved for

comparisons with Annex 2 standards (the primary mine discharge effluent criteria) rather than

total metals as cited in the World Bank Guidelines and Peruvian Class Ill standards.

Average metal loads delivered to the local rivers are shown in Table 5, 6 and 6a.

Based on these metal load calculations, the Yauli and Mantaro watersheds are affected by human

and/or industrial (hydro-electric, mining, agriculture) activities prior to entering the La Oroya

area of influence (Stations M-3 and Y-1). However, La Oroya also contributes a significant

amount of metals to the Yauli and Mantaro Rivers (comparing M-3 to M-5 and Y-1 to Y-3).

The most significant current sources of constituent loading from La Oroya to these surface

receiving waters are as follows:

• R-1 Effluent from the lead refinery

• 118 Effluent from granulation of Cu-Pb slags

• 119 Principal Canal No.2, Cu-Pb smelter

• 126 Electrolytic effluent from the zinc plant

• 135 Principal Canal No.l

• 136 Canal parallel point 135

• 137 Effluent from the zinc ferrite well

These effluent sources contribute more than 90% of the total metal loading from

La Oroya to the local river system.

3. 7 Flora and Fauna

Based on the on-site visit to the region and expected typical conditions of high-Andean

regions, the La Oroya area is likely to contain hill, plains, and rocky outcrop habitats capable

of supporting a variety of flora and wildlife typical to this Andean region. Vegetation is sparsely

23



composed of shrubs and natural grasses conducive to alpine and subalpine life zones with a

combination of reeds and grasses highest in population. Due to the steep slopes and thin soils,

vegetation distribution may be sporadic with the majority of plants found outside the region of

the La Oroya town on gentle slopes and neighboring watercourses. In addition, vegetation

populations typically change between wet and dry seasons with the most plant diversity occurring

during the summer wet season. Resident inhabitants are expected to be typical to the

high-Andean habitats, and may include a variety of birds, snakes, frogs and toads, and small

mammals such as rodents and foxes.

24

Knight Piesold -

4.0 LEGAL ENVIRONMENTAL FRAMEWORK


In order to provide an accurate environmental evaluation of the La Oroya complex, this report

includes a review of applicable environmental obligations with respect to Peruvian mining and

metallurgical activities as a whole and the La Oroya plant in particular. This review is generally

based on the ability of the facility to comply with existing and pending Peruvian laws and

regulations as well as with generally recognized international guidelines. This section provides

an overview establishing the basis for this environmental evaluation.

Guidelines for environmental control systems and water quality discharges established by the

World Bank, as well as the project team experience in many countries around the world were

used to measure conformance with generally-accepted international mining practices.

4.1 Mining/Metallurgical Activities

For most mining and metallurgical activities, the Ministry of Energy and Mines (MEM)

is the ultimate Peruvian authority, and the MEM Directorate of Environmental Affairs is

responsible for control and enforcement of environmental regulations. However, the Peruvian

government recently created the National Environmental Council (Spanish acronym: CONAM)

as the supreme agency in charge of overseeing the environment and advising the government

regarding environmental policies, regulations, and guidelines. CON AM is already preparing the

master plan for the Environmental Management National System (Spanish acronym: SNA) that

will probably include the existing regulations for the mining and metallurgical sector under their

jurisdiction. Thus, it is likely that CONAM will work closely with MEM in the future to

regulate environmental mining and metallurgical activities.

The Peruvian government is currently in the process of promulgating new environmental

laws and regulations for the mining and metallurgical sector. Until the new programs are

established, existing laws and regulations still apply to mining and metallurgical operations. A

25



summary of these laws and regulations is presented as Table 9. These regulations provide

specific guidelines for current and new mining and/or metallurgical operations making them

responsible for implementing and maintaining prevention and control programs. The programs

are to be described in each company's Environmental Impact Assessment (EIA), Preliminary

Environmental Assessment (Spanish acronym: EVAP), and/or Environmental Adjustment and

Management Program {Spanish acronym: PAMA). Peruvian law requires all new mining or

metallurgical operations and existing operations undergoing major expansions to prepare an EIA.

Existing mining and metallurgical operations must prepare an EVAP. All operations must

prepare a PAMA.

To date, La Oroya has completed the EVAP (CENTROMIN, 1995), while the PAMA

investigations are currently ongoing. The Ministry of Energy and Mines approved the La Oroya

EVAP and its monitoring programs in 1995. CENTROMIN has until August 31, 1996 to submit

the PAMA for the La Oroya Metallurgical Complex. After approval by the MEM, the PAMAs

and/or EIAs will be used as the basis for implementing and maintaining prevention and control

programs to meet Peruvian environmental standards for current mining or metallurgical

operations. Based on these documents, the titleholder could sign an environmental stability

agreement with the government to establish: environmental adjustment duration, monitoring

frequency, control points, maximum permissible limits (MPLs), remediation programs, closure

plans, investment amounts, and performance timetables.

It is noted that CENTROMIN has instituted programs to improve control of

environmental impacts based on the results of the 1995 EV AP. Such programs include a

domestic and waste water treatment program designed to dispose of and treat waste waters

before they flow to the Yauli and Mantaro Rivers.

26

Knight Piesold -

4.2 Air

CENTROMIN-La Oroya-1450A 50A-OROYA6.FNL September 18, 1996

Current requirements for air pollution analysis and control in mining and metallurgical

processing are contained in Supreme Decree No 016-93-EM "Environmental Protection in

Mining and Metallurgical Activities" (May, 1993). These requirements tend to be general in

nature, rather than setting forth quantitative limits or standards. In general, the terms of

Supreme Decree 016-93-EM states that air emissions must not exceed any existing maximum

permissible limits or produce damaging or hazardous characteristics.

The PAMA must identify and quantify emissions of particulate matter and gases to the

atmosphere, and describe controls and processes used for reduction of emissions. There is a

general requirement for controls if any air emissions adversely impact the atmosphere.

Meteorological studies and dispersion modeling analyses are required as part of the EIA or

EVAP for air emission sources. General requirements also exist for evaluation and control of

dust emissions as they may arise from processing and refining operations and for mitigation of

soils, vegetation, and land uses affected by air pollutants.

Air quality guidelines and quantitative limits are currently being established in Peru. The

Peruvian government has proposed ambient air-quality standards for sulfur dioxide and other

pollutants, as well as emission standards specifically applicable to metallurgical operations such

as La Oroya. After a process of review and comment, final standards are expected to be issued

in the near future.

A comparison of the proposed ambient S02 standards to standards and guidelines applied

in other countries is provided in Table 10. The comparison indicates that the proposed Peruvian

S02 standards (572 ug/m3 for a 24-hour average and 172 ug/m3 annual average) are generally

higher (less restrictive) than S02 standards in most other nations. Proposed standards for

ambient air are similar for lead and less restrictive for arsenic compared to standards applied

elsewhere.

27



It is noted that the proposed Peruvian standards apply at normal conditions (i.e., one

atmosphere and oo C). This is similar to the U.S. Environmental Protection Agency's (USEPA)

policy which requires compliance at standard conditions (i.e., one atmosphere and 25 o C). This

means that pollutant samples collected under different conditions must be corrected to the normal

or standard condition. Considering the high elevations at which CENTROMIN conducts

operations, the net effect of applying the correction will be a more restrictive air standard. For

example, the 572 ug/m3 24-hour S02 standard applicable to a source at sea level is reduced to

356 ug/m3 for a source at 3,700 m above sea level such as La Oroya.

The proposed ambient standards as written are much more stringent for facilities located

at high elevation, and we have found an adequate technical or toxicological justification for

imposing more restrictive standards at higher elevations. While it would seem more equitable

"micrograms per actual cubic meter," the standards currently being proposed in Peru will

discriminate against facilities at higher altitudes.

It is our opinion that the final promulgated rules will affect La Oroya's ability to operate

in compliance with air quality laws. Considerable flexibility in the implementation and

application of new standards may be necessary if La Oroya is to continue its current operating

procedures.

4.3 Water

The "General Water Law," Supreme Decree 17752 (July 24, 1969) regulates the use of

water within the country and has dual jurisdiction between the Ministry of Agriculture and

Ministry of Health. However, as of January 13, 1996, the MEM further promulgated

Ministerial Resolution No. 0 11-96-EM/VMM which established maximum permissible limits

(MPLs) of contaminant discharges specific to mining and metallurgical operations.

28



These MPLs and a standardized schedule of effluent monitoring have been established

for effluent with different criteria established for current and new operations (Annex 2 and

Annex 1 criteria, respectively). New operations are required to keep concentrations of discharge

contaminants below the Annex 1 MPLs, while current operations have five years to adjust

discharge concentrations to the less stringent Annex 2 MPLs (Table 11). Current operations,

however, are required to further adjust discharge concentrations to comply with Annex 1 MPLs

within the next 10 years.

CENTROMIN has designed a water monitoring program according to the, "Protocolo de

Monitoreo de Calidad de Agua," issued by the General Director of Environmental Affairs in

1994. The results of the ongoing monitoring program indicate that numerous effluent discharges

at La Oroya exceed Peruvian and/or World Bank discharge MPLs. Smelting related discharges

with one or more MPL exceedences include D-1 02 through D-136 except D-11, D-122 and D-

130. Of the three monitored discharges from the refinery complex, R-1 consistently exceeds

Peruvian and/or World Bank discharge guideline concentrations for pH, TSS, Pb, Cu, Zn, Fe,

As and possibly Cd. In addition, the March 1994-February 1995 average concentrations for R-2

exceeded Cu MPLs as do the averages for Pb, Cu and Zn in the R-3 discharge.

CENTROMIN has implemented effluent treatment projects of the Lead Refinery,

Alambron Plant and the Asarco Oven Plant (Table 3). The details of these projects were not

provided by CENTROMIN. However, concentration levels ofPb, Cu and Zn were significantly

reduced at the refinery monitoring stations in early 1996. These treatment projects may be

responsible for the Pb, Cu and Zn remediation.

29

Knight Piesold -

5.0 OPERATIONAL CONSIDERATIONS


General disturbances to the La Oroya region have resulted from development of metallurgical

activities including the processing of zinc, lead-silver, and copper concentrates. The primary

impacts at La Oroya are related to air, soil, and water quality. Sources of these impacts include

the smelter and refinery as well as the lead-copper slag, zinc ferrite, and arsenic trioxide

deposits located along the Mantaro River. The significant impacts related to these installations

require operational modifications to air and water control systems to facilitate continued

operations at La Oroya in compliance with Peruvian and generally accepted environmental

standards. These impacts and recommended operational modifications are discussed below.

5.1 Air Quality Conditions

Comparing the maximum measured ambient concentration at La Oroya to various ambient

atr standards, it is evident that ambient concentrations in the region around La Oroya are

exceedingly high. Nearly all measured pollutant levels are well above the standards set by the

World Bank and the United States Environmental Protection Agency (USEPA), as well as

proposed Peruvian standards.

Due to the large size and complexity of the La Oroya facility, its age, and location, there

are significant air quality concerns for continuing operations at La Oroya. These issues relate

both to S02 discharges and elevated metals concentrations and deposition rates.

The existing air quality in the region has been evaluated for this report using data

collected at the monitoring sites and a previous air dispersion modeling study. The quality of

the collected data and operational procedures used at the monitoring sites are questionable based

on findings presented in Appendix A of this report. Table 12 summarizes recent air quality data

for S02 and metals sampled at the air monitoring stations surrounding the La Oroya complex.

The table shows that maximum 1-hour S02 concentrations at La Oroya exceed 5,000 ug/m3, and

30



the highest annual S02 concentration (at Huanchan) was 492 ug/m3• The World Bank standard

for annual S02 concentrations is 100 ug/m3• The highest reported S02 concentrations apparently

represent the upper limit of monitor response and may not reflect actual S02 levels. Maximum

24-hour PM-10 concentrations exceed 350 ug/m3 while maximum 1-hour PM-10 concentrations

exceed 1000 ug/m3• The World Bank standards for 24-hour PM-10 concentrations is 500 ug/m3•

Maximum 24-hour concentrations of As, Pb and Cd were 35.3, 58.3, and 2.1 ug/m3,

respectively. The Peruvian guideline for maximum 24-hour concentrations of arsenic is 6

ug/m3• There are no guidelines for daily concentrations of lead or cadmium.

A modeling study of only the main stack emissions was performed, and presented in

abbreviated form in the report, "Technical and Economic Valuation of Environmental Issues,"

(IMCL, 1992). A United States Environmental Protection Agency (USEPA) approved model

for complex terrain was used in conjunction with meteorological data from a similar mountain

(Cuzco) site to assess the La Oroya region.

The IMCL air dispersion modeling results for the main stack predict maximum annual

concentrations of S02 and PM-10 to be on the order of 7,000 ug/m3 and 175 ug/m3, respectively,

and the highest impacted areas to be from one to two kilometers south of La Oroya in the

general area between the smelting complex and Huanchan. This predicted annual S02

concentration appears to be very high; however, it is not unreasonable given the topographic

setting in which the complex is located. The existing monitoring stations are located at lower

elevations, and probably do not reflect the highest so2 impacts from the main stack.

Though the largest quantity of emissions are released from the main chimney, significant

amounts of both S02 and metals are emitted at lower levels within the plant and from shorter

stacks. It is important to recognize that these low altitude emissions probably affect ambient

concentrations in the local community and on the plant site more than the main stack. Thus it

is emphasized that emission reduction cannot be restricted to the main stack. In fact, the

31



greatest incremental improvement to ground-level air quality is likely to be achieved initially by

control of some of the larger sources of low altitude emissions.

Ambient air monitoring was not conducted prior to 1994 so historical air quality is

difficult to assess. However, according to the report titled, "Adjustment of the Environmental

Management Plan for the La Oroya Metallurgical Complex- June 5, 1994," CENTROMIN's

installation of a series of air emission controls between 1941 and 1971 have substantially reduced

the area impacted by emissions from the La Oroya complex. For example, 800,000 ha were

estimated to be impacted by La Oroya air emissions between 1922 and 1941. The addition of

the Cottrell precipitators in 1941 reduced this area of impact to approximately 14,190 ha, and

since 1971 (with the installation of additional Cottrell facilities and the sulfuric acid plant) the

impacted area decreased to approximately 4,170 ha.

The current area of attrition (approximately 4,000 ha) seems to be realistic based on a

visual inspection of the area (via 4-wheel drive vehicle). It would appear that though particulate

and metal concentrations greatly decreased after 1941, the current level of S02 concentrations

can be considered typical of conditions from the 1940's through 1996. This conclusion suggests

that a contributing factor for the larger impact area in 1941 may have been the elevated

deposition rate of metals. Visual inspections also verified that the area beyond the current area

of near total attrition (lack of vegetation) is not fully recovered, but appears to have recovered

to about 50% of typical regional vegetation coverage levels.

For La Oroya to achieve compliance with the proposed S02 emission standards (Section

4.2) would require an approximate 75 to 80% reduction in the present so2 emissions, for a total

control efficiency of at least 75 to 80%. While 75 to 80% control is probably a realistic goal

for a new smelter, it may be unrealistic for an older facility such as La Oroya. Based on the

evaluations conducted for this report, it appears that achievement of this level of control at La

32



Oroya cannot be expected except by multiple process changes and/or major modifications to

much of the smelter. Such changes or modifications will be required over a ten-year period.

The achievement of the proposed emission limits may not ensure compliance with all

proposed ambient standards. Because of localized topography and meteorological effects at La

Oroya, even lower emissions (or taller stacks) could be required to meet the proposed ambient

standards. It is also noted that the proposed emission limits may be adjusted provided

compliance with all proposed ambient standards is ensured and approved by the Ministry of

Energy and Mines. Insufficient data are currently available to determine the emission levels

necessary to meet the proposed ambient standards. However, CENTROMIN has a study within

their PAMA that includes the design of a more extensive monitoring network, and the design

of a dispersion model, to predict air quality conditions during adverse meteorological events (i.e.

inversions).

5.2 Operational Modifications - Air Quality

There is no simple remedy to the existing air quality situation as the selection of an

economical and effective pollution control technology for La Oroya will require detailed

engineering evaluation which is beyond the scope of the present evaluation. Compliance with

future standards will require a number of control improvements, process changes, and major

facility additions. Many of the necessary changes will be costly, and implementation of adequate

controls to meet standards may well take in excess of the ten year implementation schedule being

considered by the Peruvian Ministry. Considerable flexibility in the implementation and

application of new standards will be necessary if La Oroya is to continue as an economically

viable operation. Continued long-term operation of the smelter and progress on privatization

can be achieved only if La Oroya is subject to realistic requirements to gradually reduce

emissions.

33


.SOA-OROY A6.FNL September 18, 1996

It is not feasible at this time to provide a list of specific actions and facility improvements

to assure compliance from an operational perspective. Any proposed change at one production

facility will have implications for other parts of the plant. Both cost effectiveness and

operational/production implications must be evaluated for any proposed pollution control. To

efficiently determine the more cost-effective actions to reduce air quality impacts, priority should

be to undertake a comprehensive survey of the complete La Oroya works. The survey should

estimate pollutant emissions from all operations, including fugitive sources, and should then

detail potential methods and costs for controlling each of these emissions.

CENTROMIN is initiating plans to obtain contractor services for a range of evaluations,

including emissions estimates, control strategy development, monitoring studies, and dispersion

modeling. These evaluations are appropriate, and when accomplished in conjunction with the

engineering evaluation of emissions and possible control methods and costs, represent necessary

steps for effective pollution control.

Dispersion modeling will be most useful after emissions have been fully quantified. For

reliable dispersion modeling, meteorological monitoring should be upgraded to acquire

representative meteorological data. Data collected at the present monitoring sites are not fully

representative of meteorological conditions at the facility and at the top of the main stack. When

a complete emissions evaluation is available and at least one year of appropriate meteorological

data has been collected, dispersion modeling analyses will be more reliable and useful for

assessing the air quality benefits to be gained by various improved controls, stack modifications,

or process changes.

However, it should also be recognized that the ultimate reduction of emissions from La

Oroya will have to involve: (1) collection of additional dust from low altitude and fugitive

sources that are not currently processed through the Cottrell precipitators, and (2) removal of

a larger fraction of S02 from the process gases. The second requirement is the most difficult

34

Knight Piesold -CENTROM1N-La Oroya-1450A


and costly. There appears to be only two options for significant S02 removal. One involves

cleaning of the gases by lime or limestone scrubbing; the second requires production of sulfuric

acid. (_ f..lt/3) t.. S Of... ~

Scrubbing of S02 from stack gases is routinely done at many large power plants.

However, it has not been applied, to our knowledge, to smelters with stack gas flows or S02

concentrations of La Oroya's magnitude. Application would probably have to involve a number

of separate units to treat portions of the total flow, and allow for complete treatment even when

individual units break down or are taken out of service for maintenance. In addition, a

substantial volume of scrubber sludge would be generated which would require transportation

and disposal in a suitable landfill.

Sulfuric acid production has been the most generally applied method for S02 removal at

smelters. The major disadvantages for application at La Oroya are the absence of a market for

the sulfuric acid, and the need to change processes so as to produce gases with a suitably high

S02 content. In the absence of a use for produced sulfuric acid, it could be neutralized with

limestone; again a very large quantity of waste material would be created requiring transport and

disposal.

5.3 Soil Quality Conditions

The primary impact to soils surrounding the facility is the soil bum and metal

contamination from the airborne particulates and S02 emissions. Metal concentrations, in some

areas, exceed those that are generally accepted for agricultural and residential areas. Areas

surrounding the project site have been left without vegetation due to the defoliation action of the

S02 emissions and the acid rain derived from the airborne S02 (Photo 6). Because of the lack

of vegetation in these areas, which is also attributed to the natural geologic, topographic, and

altitude conditions of the La Oroya region, the soils are subject to erosion from wind and

meteoric waters. The deep erosion gullies are present on many of the hillsides near the project

35



area. The sediments resulting from the erosion increase the sediment loading of the surface

waters and also contribute to contaminant loading by transporting the metals and other

constituents contained in the soils to the surface waters.

A limited soil sampling study was commissioned by CENTROMIN in the area of current

vegetation attrition. The study is dated March, 1996, and involved 13 sampling locations. The

maximum surface soil concentration of Pb was determined to be 1 kg/ton of soil. This

maximum was observed in two areas, approximately 1 km south and 1 km northeast of the

smelter complex on higher terrain on either side of the Mantaro River. The maximum

subsurface concentration was determined to be 0.28 kg/ton (sample taken at 20 cm depth) about

2.5 km to the southeast in the Mantaro River Valley.

As a comparison to the above data, deposition of metals, including As, Pb and Cd has

been estimated for this report using the maximum observed ambient air concentrations discussed

previously, in conjunction with estimates of particle size distribution and deposition velocities.

The derived deposition rates can be considered to be most representative of the area two or three

kilometers south southeast of La Oroya (Photo 6). Deposition rates will be less in areas

generally upwind and probably higher in the immediate vicinity of the smelter and within one

to two kilometers downwind.

The deposition estimation method is based on the following mathematical expression:

The equation states that the deposition flux (F J is given by the product of the ambient

metals concentration in the air (X.J and the deposition velocity (V J. Measured data are

available for Xm. and V d can be estimated if assumptions are made regarding the particle size

distribution within the effluent gas and the surface roughness of the surrounding countryside.

36



The assumed particle size distribution for this analysis is representative of copper

smelting operations using reverberatory furnaces (AWMA, 1992). The corresponding Vd for

each particle size class is based on the work of Sehmel and Hodges, as reported by the U.S.

Department of Energy (1984), and assumes a surface roughness length appropriate for land void

of significant brush and a friction velocity equal to 10 cm/s. Table 13 lists these parameters and

shows estimated deposition rates.

The annual deposition rate of As is estimated to be 2.38 g/m2• For Pb and Cd the rates

are estimated to be 3. 79 and 0.14 g/m2, respectively.

If it is assumed that deposition rates of this magnitude have occurred over a period of 60

years, and the deposited metals are mixed uniformly through the uppermost 10 cm of exposed

soil, estimated surface soil metal concentrations are:

Arsenic Lead Cadmium

840 mg/kg 1338 mg/kg 50 mg/kg

The maximum measured surface lead concentration in soils near La Oroya as noted above

is about one kg/ton, or 1000 mg/kg, in reasonable agreement with the calculated maximums.

For comparison, "acceptable" levels of metals in soils for residential and agricultural

areas according to U. S. and other international guidelines are on the order of 2 to 50 mg/kg for

arsenic, 50 to 500 mg/kg for lead, and one to 25 mg/kg for cadmium. On the basis of the

limited available data and estimated deposition rates, it appears that maximum arsenic, cadmium,

and lead concentrations in some La Oroya soils probably exceed generally acceptable levels.

37



Soil chemistry data were not available for the plant sites. However, soils in the area of

the smelting and refining facilities appear to have been significantly affected by solid and liquid

effluent from the process.

5.4 Water Quality Conditions

According to CENTROMIN, the primary water receptor bodies at La Oroya (the Yauli

and Mantaro Rivers) are also influenced by human and industrial activities upgradient of the La

Oroya Complex (Stations Y-1 and M-1, M-2, and M-3). However, at La Oroya, these receiving

waters are further influenced by smelting, refining, and waste disposal operations. The primary

water quality issues related to La Oroya operations include effluent emissions from the smelter

and refinery complexes as well as the Huanchan, Vado and Malpaso waste storage locations.

Water samples are currently monitored and collected at these sites by CENTROMIN personnel

and analyzed in the on-site laboratory. The data presented and discussed in this section were

developed under this monitoring program.

5.4.1 Smelting Complex

The La Oroya smelting complex and current water monitoring program are shown

on Figure 3. A total of 36 individual discharges originating from the La Oroya smelting

complex have been recognized and characterized as inputs to the Mantaro River. Thirty-five of

these discharges (D-102 through D-136) enter the Mantaro River between sampling points M-3

(upstream) and M-4 (downstream). One station, D-101, is located upstrearo of M-3.

Numerous exceedences of Peruvian and/or World Bank discharge MPLs are

present in the various discharges from the La Oroya smelting complex as indicated in Table 6.

Discharges with one or more MPL exceedences include D-1 02 through D-136 except D-11 , D-

122 and D-130. The river sampling monitoring points (M-1 through M-5) were compared to

Peruvian Class Ill standards for agricultural water use. Exceedences of this standard included

TSS, Pb, and N03 upgradient (M-1, M-2, and M-3) of the smelting complex. Monitoring

38



stations located downgradient from the smelting complex (M-4 and M-5) reported exceedences

of TSS, Pb, As, Cd, Cu, and N03 •

Individual documented discharges may be ranked in terms of relative loadings.

Table 14 and 15 list the loading statistics and characteristics, respectively, of the five discharges

which account for 90 percent of the volumetric flows reported to be discharged to the Mantaro

River. These five discharges also account for 90 percent or greater of the sum of individual

discharge loads of all measured constituents except for N03 (82 %) and S04 (86 %) .

Based upon material balances in the Mantaro River, there are several conclusions

that can be drawn:

• The impact of the smelter is greater than the refinery in both flow and

kilograms of pollutant.

• The single largest impact stream is discharge from the Slag separation

area (sample point 118). This flow accounts for 57% of the overall area

flow volume.

• The five highest sources of pollutant loading are:

1. Slag Separation discharge (point 118)

2. Canal No. 2 (point 119)

3. Canal parallel to Canal No. 1 (point 134)

4. Canal No. 1 (point 135); and

5. Electrolytic zinc area (point 126)

• As with the refinery there are three categories of impacts on the Mantaro

River that can be identified when considering the overall smelter impacts:

39

Knight Piesold _._ ___ _

1. Minimal impact - N03 ( < 1 %) ;

CENTROMIN-La Oroya-1450A 50A-OROY A6 .FNL September 18, 1996

2. Small but significant impact- TSS (4%0, Cu (9.8%), Fe (9%),

Mn (4%), S04 (4%); and

3. Significant impact- Pb (28%), Zn (46%), As (24%), Cd (69%).

• The high contribution of Cd is important, as Cd is a toxic heavy metal and

has been classified as a carcinogen by the USEPA.

5.4.2 Refining Complex

La. Oroya refining complex is described in Section 2.1. Three individual

discharges (R-1, R-2 and R-3) originating from the La. Oroya refining complex have been

recognized and characterized as inputs to the Yauli River between sampling points Y -1

(upstream) and Y-2 (downstream). Discharge stations R-1, R-2 and R-3 correspond to Lead

Refinery, the Alambron Plant, and Asarco Oven Plant, respectively.

Tables 7 and 8 present the absolute load of each measured constituent in each

discharge from La. Oroya refining complex, and the analytical data for the refinery discharges

and associated sampling stations on the Yauli River, respectively. The absolute loads were

based on the average flows and concentrations during the period March 1994-February 1995.

Table 7 also presents the relative (as percent) load contribution from each discharge to the total

load. Total load was calculated in two ways: as a sum of all individual discharge loads and as

the difference between loads in the Yauli River at Y-1 and Y-2. Data for Table 8 include

averages for the period March 1994 through February 1995 and three individual monthly

sampling rounds (January, February and March 1996) where available.

Of the three monitored discharges from the refinery complex, R-1 consistently

exceeds Peruvian and/or World Bank discharge guideline concentrations for pH, TSS, Pb, Cu,

Zn, Fe, As and possibly Cd. In addition, the March 1994-February 1995 average concentrations

40

Knig_h_t _P_ie_, s_ol_d

CENTROMlN-La Oroya-1450A 50A-OROY A6.FNL September 18, 1996

for R-2 exceeded Cu MPLs as do the averages for Pb, Cu and Zn in the R-3 discharge. For the

latter three cases, concentrations were significantly reduced in early 1996 (Table 8).

CENTROMIN has implemented effluent treatment projects of the Lead Refinery, Alambron

Plant and the Asarco Oven Plant (Table 3). The details of these projects were not provided by

CENTROMIN. However, these projects may be responsible for the reduction of Pb, Cu and

Zn.

The cumulative impacts of monitored and unmonitored refinery point-source

discharges and any non-point sources to the Yauli River are apparently minor. Surface water

monitoring stations Y -1, Y -2, and Y -3 were compared to Peruvian Class Ill standards for

agriculturally used water (1994). A comparison March 1994-February 1995 data for upstream

(Y -1) and downstream (Y -2 and Y -3) monitoring points on the Yauli River reveals that Pb, Cu,

As and N03 concentrations increase appreciably as a result of inputs of effluent from the refinery

complex. Even in the case of these constituents, the standard deviations are sufficiently large

so as to cause considerable overlap in the populations, thus reducing the significance of any

apparent increase.

The combined loading from R-1 through R-3 has been compared to the apparent

loading as defined by concentrations and flows in Yauli River (Y-2- Y-1). This comparison

was conducted as described in the previous section. Percentages of constituents not accounted

for in the sum of discharges are: TSS, 98%; Pb, 94%; Cu, 99%; Zn, 97%; Fe 58%, As, 93%;

Cd, 39%; Mn, 98%; N03, 98%; S04 , 42%. The data suggests that either one or more sources

of loading to the Yauli River have not been documented or that Y -1 and/or Y -2 are not

representative of upstream and downstream water quality in the Yauli River.

Individual documented discharges may be ranked in terms of relative loadings.

Table 14 provides information for R-1, R-2 and R-3 and ranks them based on volumetric

discharge averaged over the period March 1994 through February 1995. All three sources must

41

Knight Piesold -------CENTROMIN-La Oroya-1450A


be considered for determining treatment alternatives because each source contributes significant

portions of the load of one or more constituents. R-1 represents only 4 percent of the volumetric

flow but provides over 90 percent of the Pb, Cu, Fe, As and S04 loads. R-3 represents 47

percent of the volumetric flow and the majority of the Zn, Mn and N03 loads. Similarly, R-2,

which represents 48 percent of the volumetric flow carries nearly half of the Cd and N03 loads.

5.4.3 Huanchan Slag and Zinc Ferrite Storage Facility

Slags from the La Oroya copper and lead smelter operations, along with

associated water from their granulation, are transported across the Mantaro River via a bucket

aerial tram and deposited four kilometers downstream of the smelter complex at Huanchan in

an unlined repository adjacent to the zinc ferrite depository. Approximately 20-30 percent of

the tailings are reported to be disposed directly into the Mantaro River by leaking from the

tramway. CENTROMIN reports a remaining five year storage capacity at the Huanchan facility.

75-80 tpd of the 120-130 tpd of zinc ferrites produced by the roasting-leaching

processes are sent to settling ponds adjacent to the Mantaro River; 6 tpd of the zinc ferrites

wastes are transported with Zn-Ag concentrate obtained by flotation of part of the zinc ferrites,

and; 39-44 tpd of the zinc ferrites are treated in the Waelz rotary kiln (Section 2.1.1.3).

CENTROMIN estimates there to be sufficient storage capacity at the Huanchan waste storage

facility for 2-3 more years. The facility is an unlined pond which is separated from the

Mantaro River only by an earthen dike. If these materials are allowed to enter the river, they

will increase the sediment load and if the zinc is in a soluble form it can have an adverse effect

on aquatic life. The materials are stored on the inside curve of the river and during normal

flows are not subject to the high velocity/energy of the outside curve of the river. However,

these wastes would be subject to erosion in the event of high water in the Mantaro River.

Seepage from the ferrite facility was not directly observed but it is likely that

subsurface leachate is in direct communication with the river. The deposits contain significant

42

Knig._h_t -~-ie_' so....,ld_

CENTROMIN-La Oroya-l450A 50A-0ROY A6.FNL September 18, 1996

(25%) zinc metal and silver values. The possibility of reprocessing to recover these values

(which might partially offset the costs of proper disposal in a lined facility) should be

considered. It has been acknowledged by CENTROMIN that neither the slag nor the ferrite

disposal sites meet existing siting requirements (Codigo del Media Ambiente) and that both have

limited reserve capacity. Accordingly, consideration has been given to additional sites located

at greater distances from La Oroya, to modifications in the slag waste deposition, recycling of

the zinc ferrite waste which contains 25 percent zinc, and to altering the zinc circuit to eliminate

its production. A site at Cachibamba is under consideration for zinc ferrite storage but does not

meet siting requirements.

Discharges from the slag and zinc ferrite disposal facilities occur between M-4

(upstream) and M-5 (downstream) on the Mantaro River. A single discharge sampling point (D-

137) is located near the downstream end of the zinc ferrite settling pond. No point-source

discharges specific to the slag storage facility have been described or sampled but liquids were

seen to leak from the tram buckets into the Mantaro River during their transport.

The March 1994-February 1995 average concentrations from discharge D-137

exceeded the Peruvian and/or World Bank discharge MPLs for pH, TSS, Pb, Cu and Zn.

Concentrations of all these constituents improved during early 1996 but Zn continued to exceed

the MPL.

Table 16 shows the quality of discharge water collected at site D-137 and loading

statistics. A comparison of apparent loading to the Mantaro River (M-4 - M-5) with loading

from D-137 indicates that only a small fraction of the apparent total load is contributed by D-

137. Percentages of constituents not accounted for in the sum of discharges are: Pb, 99%; Cu,

>99%; Fe >99%, As, 67%; Mn, 97%; N03, >99%. TSS, Zn, Cd and S04 are reported in

significantly greater concentrations in the Mantaro River upstream of the slag and zinc ferrite

disposal areas (M-4) than downstream, suggesting that M-4 is not representative of upstream

43

Knight Piesold -~----


quality. This possibility is supported by the fact that the downstream-most point source

discharges associated with the smelter (D-135 and D-136) represent significant loadings of TSS,

Zn, Cd and S04 • Since sample site M-4 is probably located on the same side of the river as the

smelter discharges, it is likely that M-4 is enriched in these constituents relative to the bulk of

the river due to incomplete mixing.

Although the available data is incomplete and potentially misleading, the

possibility exists that one or more point sources or non-point sources originating from the

Huanchan slag and zinc-ferrite disposal area have not been addressed in the sampling plan. The

bulk of the copper and lead slags are reported to be composed of low-solubility silicates and

oxides but leaching data is not available. Zinc ferrite is also expected to have a low solubility

but, as in the case of the slags, there is no leaching data available and concentrations of zinc in

D-137 indicates that some component of the zinc ferrite waste is soluble or that zinc is contained

in fluids deposited with the zinc ferrite.

Zinc ferrite disposal area discharges average 554 m3/day, are moderately acidic

and contain very high concentrations of Zn and S04 , high concentrations of Mn and TSS and

low levels of other constituents (see Table 16).

5 .4.4 V ado Arsenic Trioxide Storage Facility

Arsenic trioxide is recovered from waste gases generated during the roasting of

high-arsenic copper ores. Recovery is accomplished using a series of Cottrell-type electrostatic

precipitators. Solid arsenic trioxide is transported by rail to the Vado site seven kilometers

upstream of La Oroya where it is deposited under water spray for dust suppression. Based on

the presence of secondary copper mineral formations on the deposits at the Vado site, copper

is also a component of material deposited. A small portion of the material disposed at V ado has

been placed in experimental storage structures in order to demonstrate a viable closure and

reclamation concept. The arsenic trioxide is placed in a two-meter lift above a drainage layer

44



covered with a clay cap or a geo-fabric membrane, which is irrigated, soiled and vegetated

(Photo 5). The entire structure is stabilized by an unmortared brick wall. With the exception

of the material in the experimental storage structures, no protection from precipitation infiltration

or drainage interception has been provided.

Arsenic trioxide is readily soluble in water at ordinary temperatures to form

arsenious acid (HAs02). Solubilization of arsenic trioxide with transfer of arsenic to infiltration

water and thus to the Mantaro River is likely. Mass wasting of the arsenic trioxide during

flooding is possible. Surface water monitoring points M-1 and M-2 are approximately 2.5 km

and 3.2 km downstream of the Vado deposit, respectively. Water quality results between March

1994 and February 1995 were compared to Peruvian Class Ill agricultural water use standards

(1994). Only N03 levels exceeded the guideline limits at M-1 and Fe at M-2. Average arsenic

values were 0.11 and 0.07 at M-1 and M-2 respectively. CENTROMIN reported a monitoring

station, M-0 upstream from the Malpaso deposit, but the data was not available to review for

comparison.

5.4.5 Malpaso Arsenic Trioxide Storage Facility

The Malpaso arsenic trioxide (As40 6) disposal site is located about 15 kilometers

upstream of La. Oroya smelting complex on the east side of the Mantaro River. This site was

recently identified as having been used for an unknown length of time. The quality and quantity

of the deposit will be studied as part of the PAMA, as well as its closure and reclamation. The

existence of other arsenic trioxide deposits, other than Vado and Malpaso, are not known.

Observation of the Malpaso site indicated that accumulations of arsenic trioxide now lie within

a flood plain a few tens of meters from the Mantaro River. The arsenic trioxides stored at this

site are covered by a thin veneer of river gravel (Photo 4).

Similar to the Vado site, the quantity of arsenic trioxide in this location 1s

unknown and the potential impacts are similar to those discussed for the Vado site.

45

Knight Piesold -

5.5 Operational Modifications - Water Treatment


The quality of current discharges from both the main smelter complex and the Huaymanta

lead/copper refinery indicate a need for waste water treatment in order to meet current

regulations and guidelines. Because these sites are physically separated and therefore function

independently, water treatment strategies will be addressed separately.

Ul Smelter Complex

The combined flow from all sources at the smelter averages about 50 m3/minute

(13,000 gpm). A number of sources comprising that total flow contain stormwater. In addition,

runoff from site disturbances may contain elevated pollutant concentrations from process spills

and from particulate emissions which settle on local soils. With these in mind, and in order to

reduce environmental impacts to the Mantaro River, it is recommended that stormwater flows

be studied to determine volume and loading data from which source control plans can be

developed and implemented. In addition, other water conservation measures should be

considered, including:

• Identify and isolate sources of uncontaminated waters such as non-contact cooling water;

• Recycle whatever water is possible, for example, implement reuse of slightly contaminated process waters to units that can utilize water of lesser quality;

• Identify unit processes that contribute significant loadings to the system and implement process changes that will reduce these loadings, for example, replacement of wet scrubbers with dry baghouses. As a side benefit, this effort can lead to improved product recoveries that will help offset the capital and operating costs of the modification; and

• Educate operations personnel as to the importance of tight water control for both environmental improvements and for improved product recovery.

46



Water discharge volumes and chemistry information provided by CENTROMIN

for the La Oroya facility suggest that active water treatment will be needed to bring the

contaminant levels in the site effluent into compliance with Peruvian and international standards

and guidelines. Based on this flow volume and chemistry, a tentative system for waste water

treatment and metals removal is presented in the conceptual flow sheet included as Figure 5.

The pH required to remove metals from the smelter waste water is higher (10.8)

than for the refinery waste water in order to assure that cadmium is reduced. The clarifier must

be adequately sized and should consistently remove 99% of the solids as the filter can only serve

as a polishing step. Excessive solids loading to the filter will blind it off quickly and result in

a bypass of only partially treated waters.

Lime and settle technology is only partially effective in removing arsenic. The

mechanism for removal of As in such a process is physical adsorption onto the surface of freshly

precipitated compounds like Fe(OH)3 ; therefore the percentage of As removal is more related

to the quantity of precipitate generated in water treatment than to solution pH.

The chemical character of arsenic is dominated by the readily changing oxidation

state or chemical form through chemical or biological reactions that are common in the

environment. Therefore, rather than solubility equilibria controlling the mobility of arsenic, it

is usually controlled by redox conditions, biological activity, adsorption/desorption reactions and

pH. Arsenic in soluble form is almost exclusively found as arsenite or arsenate. The arsenate

form predominates at high Eh conditions, as compared to arsenite. There are a number of

processes that have been investigated for the removal of arsenic. The four most effective

processes are iron eo-precipitation, alum eo-precipitation, lime precipitation, and activated

alumina. The iron eo-precipitation process, which achieves discharge concentrations ten times

lower than the alum eo-precipitation process, is similar to what will occur in La Oroya's overall

water treatment process, due to the high iron concentrations in the collected waste water feed.

47

Knight Piesold -:-----CENTROMIN-La Oroya-1450A

50A-OROYA6.FNL September IS, !996

It is recommended that, prior to selecting the final process flow and

commissioning a detailed design effort, a pilot plant be constructed, to evaluate and optimize the

process flow options. A pilot program will allow testing of treatment schemes and optimizing

of reagent additions and equipment sizing which, in turn, may -reduce capital and operating cost.

5.5.2 Lead/Copper Refinery

Based upon a material balance in the Yauli River upstream and downstream from

the refinery operations, there are three classes of impacts by the refinery operations:

• The first category represents minimal impacts on the River Yauli loading, and includes TSS, zinc, cadmium, manganese, nitrate and sulfate. These all fall below a 1 percent contribution to the river loading;

• The second classification constitutes small but significant impacts and includes lead, iron, and arsenic. These impacts range from 4 to approximately 6 percent; and

• The third category is that of significant impact and only copper at 21 percent falls within the significant impact category.

A Larox filter system was recently installed at the lead refinery to treat and

recycle the process solutions which in the past were discharged to the Yauli River. The system

captures fluorosilicic acid from the waste waters which is then returned to the Lead Refinery

tank house. Continued monitoring of this system (operational since June of 1996) as well as the

Yauli River is recommended to assess the overall benefits of the La.rox treatment system.

While the filter system may benefit the water quality, it does not mitigate all

impacts to the Yauli River. In reviewing the R-1/R-2/R-3 process flowstreams, R-1 is the major

contributor of those parameters in the medium and high impact categories. Therefore, the

following suggestions in terms of treatment options are made:

48



• Process streams R-2 and R-3 are of suitable quality to be recycled either within the refinery operations or to the smelter operations. They represent a high volume, low pollutant loading and are candidates for recycle.

• Only treatment of process stream 1 is required to reduce the impacts of copper, lead, iron and arsenic.

• The total average flow for 1995 in R-1 is approximately 53 gallons per minute. The suggested treatment scenario is alkaline treatment via lime or sodium hydroxide to a pH of approximately 10.5, followed by settling with the clear overflow being combined with R-2 and R-3 for recycle and the sludge being dewatered and returned to the process stream. Figure 5 is a conceptual process flowsheet and includes lime addition, polymer addition, settling and recycle.

It is noted that the removal of arsenic is extremely difficult chemically, however

it is anticipated that the high TSS loading that will be created in the neutralization step will

enhance the arsenic removal. Prior to the final design of a treatment system, bench tests should

be run on site to determine the neutralization requirements, i.e., reagent requirements, the

polymer characterization and quantities required, and the settling characteristics in order that the

appropriate vessel sizes and feed pump sizes can be designed.

It is also recommended that a pollutant source study be conducted to identify

specific activities or processes that contribute significant loadings to each waste water stream.

For example, stream R-3 quality varies considerably over time, and in general is close to

meeting discharge standards. A detailed process evaluation would identify the reasons for

loading variance and particular sources of loading. This information can then be used to modify

process or operations so as to reduce variability and loading.

49

Knight Piesold -

6.0 CLOSURE AND RECLAMATION STRATEGIES


Closure and reclamation strategies to address the impacts of the La Oroya facility have been

evaluated for each of the major metallurgical components. Reclamation strategies are

recommended for physical stability. Closure strategies are performed for chemical stability.

Alternate strategies for each component were evaluated on the basis of the available information,

the site visits and the experience of the project team. The closure and reclamation strategies that

are presented are intended to limit the future impacts of the project on the environment and to

provide for a closure and reclamation strategy that will meet Peruvian regulations and generally

accepted international standards.

Proposed and existing programs for the La Oroya site are presented on Tables 17 and 18.

Information on the existence of these programs was provided by CENTROMIN but the details

regarding what the programs involve were not available for review. Consequently, we cannot

comment on the adequacy of the current programs.

6.1 Metallurgical Complex

Studies for the closure of the metallurgical complex are presently being proposed by

CENTROMIN. In the absence of these studies, the following closure and reclamation

alternatives are suggested.

Smelting and refining equipment are commonly sold for salvage and the proceeds will

usually offset the cost for removal and demolition. Following demolition of buildings and other

structures in the area, the plant site would typically be reclaimed for use as building sites or as

agricultural land. Soils should be excavated a minimum of 0.5 m in order to provide a suitable

soil chemistry to support the post-process land use. Contaminated, excavated soils should be

disposed of in an engineered waste facility.

50



The main smelter complex and the Huaymanta refinery affect an area of approximately

1 ha. Assuming that 0.5 m of soil is excavated from each facility, some 3,000 m3 of soil will

need to be placed, compacted, covered and revegetated. Based on our site observations, it

appears that the soils can be shaped and compacted to a condition which is sufficient to promote

runoff and minimize infiltration to the extent practical. For reclamation purposes, it is assumed

that the contaminated soil is used as a low-permeability cover material over the arsenic trioxide

deposits. A discussion on the closure concept for the arsenic trioxide deposits is included in

Section 6.3.

Foundations would typically be buried in place and the hard pack surface ripped and

graded to provide drainage of runoff to the natural water courses. A layer of soil should be

placed over the surface, and the area revegetated with a grassland seed mixture.

6.2 Slag and Ferrite Disposal Area

Primary concerns for the Huanchan slag and ferrite disposal areas are to physically

stabilize the materials to prevent migration into the surface waters and chemically stabilize or

isolate the material to prevent leaching of chemical constituents into the surface and ground

water.

6.2.1 Lead and Copper Slag

The lead and copper smelting slag alternatives for reclamation include:

• grade slag pile to a 2.5:1 or flatter slope, push soil from hillside above,

revegetate;

• excavate slag pile, move to alternate location,

• do nothing.

51

Knight Piesold


The geochemical character of the slag material is not known at this time, however,

smelter slag is often silica-based and geochemically stable. Although there is little evidence of

wind blown slag, transport of the material from the site by wind, or run-off actions remains a

possibility. Regrading and the construction of a soil/vegetative cover is the most likely

successful remediation scenario at this site. Slope reduction to a nominal 3H: 1 V should be

conducted prior to the application of cover soil. A calcareous parent material on the slopes

above the deposit may be suitable as a soil cover. The soil cover should be applied, fertilized

and a native grass seed mix applied. Organic carbon may need to be added to achieve

reasonable sustainable planting success. Water diversion structures should be designed to insure

the continued integrity of the soil and vegetative cap over the reclaimed copper and lead slag

deposit.

Alternative methods of transporting and depositing slag materials to the disposal

site are currently being investigated to reduce the loss of material into the river that occurs with

the bucket tram system. In addition, CENTROMIN is in the early stages of evaluating

alternative slag disposal sites.

6.2.2 Zinc Ferrites

The release of soluble metals is the primary concern for the zinc ferrite storage

area. Possible remedial/reclamation actions for this site include:

• reprocess zinc ferrites and dispose of the residuals m an engineered

facility;

• excavate and dispose of in engineered facility; or,

• cap in place, stabilize slope face using HDPE grids, concrete retaining

wall between slope toe and river, key retaining wall to bedrock, install

seepage collection system.

52

Knight Piesold _._ ___ _ CENTROMIN-La Oroya-1450A


One remediation option is to reprocess this waste deposit for the zinc and silver

values and to utilize a modified process to minimize waste generation. CENTROMIN has

Terms of Reference in place to evaluate this option, which will require modifications to the

refining facility.

A second option would be to excavate the material without reprocessing and place

it in an engineered fill outside of the river flood plain. This situation would alleviate the need

for a fully-lined facility. The waste material should be covered with compacted clay, followed

by a crushed limestone drainage layer, and a revegetated soil layer. Diversion ditches should

be constructed to keep runoff from the adjacent slopes off the capped area.

The option that may be more cost-effective is to reclaim the material in place.

A critical element in the remedial design will be to permanently stabilize the waste impoundment

which is proximal to the river. The construction of a concrete retaining wall keyed into bedrock

and of sufficient height to prevent inundation of the deposit during a design hydrologic event

(lOO Year flood). The slopes of the deposit should then be stabilized using a geogrid or similar

methods and the top surface should be graded to allow run-off. The surfaces of the deposit

should be covered with a growth media and seeded for revegetation. Seepage through the

deposit could be further minimized by placing a synthetic liner below the growth media layer.

6.3 Arsenic Trioxide Disposal Sites

The arsenic trioxide deposits present a potential source of soluble arsenic that is in close

proximity to surface waters. Two sites have been identified, Vado and Malpaso, but it is

conceivable that additional areas may be identified, probably along the railroad line. Options

for both sites include:

• excavation and disposal in an engineered waste facility, or

53



• in place stabilization; capping to prevent seepage, hydraulic break (limestone),

soil and revegetate.

CENTROMIN is currently evaluating an option to place an engineered cap over the

deposits at this site. Two test plots were constructed in 1995 to study the capping remediation

alternative. Two above-ground test cells (one with a clay cap, the other with a geomembrane

cap) were constructed as follows:

• underdrains were placed on the ground,

• large rock and smaller graded rock covered the underdrains,

• arsenic trioxide was placed on top of the underdrains,

• a cap of clay or geomembrane was placed on top of the arsenic trioxide,

• 10-15 centimeters of soil was placed over the impermeable layer, and

• a vegetation and fertilizer mixture was added.

The precipitation and amount of water added to the plots to establish and sustain the grass

was measured. After one year, the vegetative cover and diversity is good. There was no

evidence of moisture discharging from the underdrains at the time of the site visit.

CENTROMIN reports no discharge during this one year period, although it may be the case that

the moisture content of the arsenic trioxide is not yet high enough to drain as seepage out the

pipes or the ground surface beneath the cell is too permeable to allow sufficient seepage to

accumulate enough to discharge at the pipe outlets. Thus, it is unclear if either the clay cap in

plot one and the membrane cap in plot two prevented the infiltration of water through to the

arsenic trioxide.

As this disposal site is within the flood plain of the Mantaro River, any in place

reclamation plan will have to consider the potential effects of flooding of the disposal site. The

currently available information does not provide data on flood levels, so the potential for

54



flooding of this site can not be evaluated at this time. If the probability of flood waters reaching

the disposal site is high, another reclamation option may be more suitable.

CENTROMIN presently has a study to determine the extent of the material at Malpaso

and to determine how to proceed with the remediation. The identification of the Malpaso site

raises a question if there are other unidentified disposal areas which have been generated by the

La Oroya Complex. Interviews or review of maps, reports or other documentation could the

first step to resolving this question.

The study and test plots being researched at the Vado area should be reviewed for their

application at this location. This disposal site is also in the flood plain and the discussion of

reclamation options for the Vado site is valid for this site as well. While the extent of the

arsenic trioxide deposit at this site is not known, it is reasonable to assume that the closure

concept would be similar as that for the Vado site.

6.4 Impacted Soils from Airborne Contaminants

Revegetation of barren areas can best be accomplished after air emissions and resulting

ambient concentrations have been reduced. Options to accomplish such a reduction of impacts

are:

• control the operational emissions and allow nature to take its course;

• excavate soil and dispose of it in a containment facility; and

• stabilize soil erosion, evaluate key areas such as townsite and agricultural areas

and do it selectively.

Sudbury, Ontario (Gunn, 1995) is a good example of successful restoration of a region

adversely impacted by decades of metal sulfide processing. This site had extensive impacts from

airborne emissions similar to those at La Oroya, the airborne emissions were reduced, the soils

55



were selectively treated and revegetation was successful in a reasonably short period of time.

The following studies and/or actions should be considered in order to develop a successful

remediation strategy:

• Consideration of methods to minimize soil erosion from barren and damaged areas.

• Identification of suitable plant species for revegetation of damaged areas, and optimum methods for initiating revegetation.

• Studies of the effect of soil metal concentrations and soil acidity on the potential for revegetation, and the potential hazards of metals uptake by vegetation in revegetated areas.

The contamination of existing soils by metals, especially lead and arsenic, from historical

operations represents a concern that may require remediation. Only limited soil sampling has

been done to date, and the available data are insufficient to characterize the magnitude and

geographical extent of the affected areas. It is probably not realistic to consider remediation of

soil in the extended impact areas of high terrain to the south and southeast of the smelter.

However, elevated lead and arsenic levels in soils of La Oroya residential areas could constitute

a concern to local residents. Based on the available soil sampling data and deposition estimates

(Section 5.2), surface lead concentrations at some locations may exceed levels considered

acceptable for residential and agricultural areas in most countries (100 to 500 mg/kg).

More extensive evaluation of soil metal content will be necessary to determine the need

and feasibility of remediation. In conjunction with the studies recommended above, additional

risk assessment-type evaluations should include:

• Detailed soil sampling, concentrating on areas of population exposure and potential revegetation, to determine the magnitude and physical extent of the affected area.

56

Knight Piesold -

• Evaluation of human health related effects.

CENTROMIN-La Oroya-!450A 50A-OROY A6.FNL September 18, !996

• Evaluation of the effect of grazing or other use of affected areas by animal spectes.

• Determination of the feasibility and cost associated with any necessary site remediation.

It is noted that current CENTROMIN studies and analyses of affected areas represent

significant progress toward the recommended evaluations. These efforts should be continued and

expanded to include the additional issues identified here.

6.5 Miscellaneous Impacts

There were a number of minor impacts that would need to be addresses as well as those

already discussed. These are discussed briefly below:

There were several oil-filled transformers observed throughout the property and it was

not possible to verify from reading the identification tags on the transformers whether they

contained any PCBs (polychlorinated biphenyls). A potential buyer will be interested in the

verification that electrical transformers or capacitors which use oil as a coolant do not contain

PCBs as there is a potential cost to manage and dispose of PCBs.

The discharge of untreated waste water to the rivers contributes pollutants in the form

of solids and human-health threatening bacteria. While the solids contribution from this source

compared to others is not major, the potential negative health impacts from lack of treatment

would be measurable in terms of disease statistics for dysentery, cholera and other illnesses

related to untreated sewage. The list from March, 1996, which noted completed Major

CENTROMIN Work Projects, did not list any improvements performed or planned relative to

these residential sewage discharges.

57


7.0 CONCLUSIONS


The La Oroya facility has submitted its EV AP in compliance with the reporting requirements

of the Ministry of Energy and Mines and is in the process of developing its PAMA detailing the

environmental management program for ongoing operations. Environmental monitoring

programs are ongoing, and procedures are in place for data gathering, analyses, reporting and

record keeping. Adherence to established monitoring and reporting procedures is important to

assure data quality.

Based on discussion with and information provided by CENTROMIN personnel, and on site

observations made by members of the Knight Piesold project team in May of 1996, it is Knight

Piesold's opinion that the La Oroya site has a number of significant environmental concerns that

could affect continued operation of the metallurgical complex if current airborne emissions and

impacts are not brought into compliance with proposed Peruvian and international standards.

CENTROMIN is presently evaluating alternatives (i.e., process changes) to bring the facility into

compliance with existing and proposed Peruvian and international standards.

Considerable flexibility in the implementation and application of new standards will be necessary

for La Oroya to continue as an economically viable operation. Continued long-term operations

of the smelter and progress on privatization can be achieved only if La Oroya is subject to

realistic requirements to gradually reduce air and effluent emissions. The proposed emission

limits may be adjusted provided compliance with all proposed ambient standard is ensured and

approved by the Ministry of Energy and Mines.

Protection of air resources and surface receiving waters emerge as the most important

environmental considerations for the La Oroya Metallurgical Complex. CENTROMIN has

progressively implemented programs to reduce the airborne emissions and has a number of

programs underway to continue the improvements. Programs are also planned or underway to

58



reduce the liquid effluent impacts from the complex (i.e. Larox Filter). Waste disposal areas

also present potential impacts to the air and surface waters.

Reclamation and closure obligations are less significant when compared to the modifications

needed to comply with the operational air and water discharge criteria. It appears that the

existing environmental impacts can be feasibly mitigated with reclamation and closure strategies

similar to those discussed in this report.

59

Knight Piesold -

REFERENCES


"Estudio del Area Afectada por los Humos AGI-DIS 071-95," March 1996,

Empresa Minera del Centro del Peru S.A.;

"Absolution de Observaciones al EVAP Unidad de Produccion de La Oroya," Julio 1995,


"Evaluacion Ambiental Preliminar (EVAP) Unidad de Produccion de La Oroya," Marzo 1995,


"Reporte, Enero-Diciembre," 1995, Empresa Minera del Centro del Peru S.A ..

"Adjustment of the Environmental Management Planfor the La Oroya Metallurgical Complex,"

June 5, 1994, Empresa Minera del Centro del Peru S.A.;

"Initial Evaluation of Environmental Liability and Responsibility," October 1993, L. M.

Broughton and J. W. Gadsby;

"Information Memorandum," 1993, CHASE and Coppers & Lybrand;

"Technical and Economic Valuation of Environmental Issues, Appendix No. 11" July 1992,

International Mining Consultants Ltd.; and

"Air Pollution Engineering Manual (AWMA)," 1992, edited by Anthony J. Buonicore and Wayne

T. Davis.

60

I Year I 1902

1904

1906

1922

1923

1928

1929

1934

1937

1939

1940

1941

1942

1944

1947

1948

1950

1951

July 17, 1996

CENTROMIN-La Oroya-1450A 50A-HIST. TBL

July 17, 1996

TABLE 1 History of La Oroya Plant CENTROMIN - La Oroya

Formation of the Cerro de Pasco Copper Corporation.

Cerro de Pasco Railway completed from La Oroya to Cerro de Pasco, a distance of 83 miles.

First copper poured at Tinyahuarco.

First blister copper cake poured at La Oroya

Electrolytic oxygen plant commenced operation

Lead blast furnaces commenced smelting

Research Department formed.

Electrolytic refining of land on a pilot plant scale.

Production plant for the electrolytic refining of lead and the anode residue plant commenced operation.

Sulphuric acid plant started up.

Pilot plant constructed for electrolytic refining of zinc. Spectrographic laboratory completed.

Completion of Cottrell System. Antimony plant commenced production.

Pilot plant constructed for the electrolytic refining of copper.

By-product coke plant in operation.

Calcium arsenate plant commenced operation.

Production plant for electrolytic refining of copper completed.

New silver refinery completed.

Lead refinery moved to Huaymanta and capacity doubled. Liquid air oxygen plant in operation. Production plant for the electrolytic refining of zinc completed. Name of company changed to ''Cerro de Pasco Corporation."

I

I

Knight Piesold LLC 50A-HIST.TBL

1952

1953

1954

1955

1957

1958

1959

1960

1962

1963

1964

1965

1966

1967

1968

1969

July 17, 1996

TABLE 1 cont. CENTROMIN-La Oroya-1450A

SOA-HIST.TBL August 26, 1996

50th anniversary of the corporation. First slab of zinc poured in the new electrolytic plant. Cadmium plant commenced production.

Electrothermic zinc plant commenced operation.

First selenium produced on commercial scale.

First Tellurium produced on commercial scale.

Second liquid air oxygen plant erected. Width of copper reverberatory furnaces increased. Lead dressing plant commenced operation. Capacity of electrolytic zinc plant increased to 90 ST/day.

Lead blast furnace top ventilation system installed.

Sinter plant extension completed.

Sinter plant ventilation system completed. Copper refinery capacity increased by installation of M.G. set.

Zinc plant expansion to 150 ST/day. Suspended basic roof installed on No. 2 copper reverberatory furnace.

Sinter Plant conversion to one-pass sintering.

Improved ventilation of lead blast furnace slag taps, canals and lead wells.

Suspended basic roof installed on No. 2 copper reverberatory furnace. Asarco copper cathode melting furnace installed.

New waste-heat boiler and air preheater installed on No. 2 copper reverberatory furnace. Sinter plant ventilation improved by installation of additional scrubbers. Additional 10 coke ovens completed. Lurgi Turbulent-layer zinc roaster installed.

New 200 tpd sulphuric acid plant commenced operation. CIDECSA rod mill inaugurated. Central Cottrell modernization commenced.

Continuous "Roy" tapping system installed on lead blast furnace No. 1. Construction of zinc leach residue pilot plant completed. Expansion of electrolytic zinc plant tankhouse from 150 to 220 S.T./day completed.

New hot Cottrell in arsenic plant commenced operation. Phase I of dust handling and blending plant put in operation. New ITE silicon rectiformer installed at copper refinery. Central Cottrell modernization program completed.

Knight Piesold LLC SOA-HIST.TBL

CENTROMIN-1450A

Table 2

Installations at the La Oroya Metallurgical Complex CENTROMIN - La Oroya

I ZONE OF ACTIVITY Copper Circuit

Lead Circuit

Zinc Circuit

Secondary Recovery Plant

i INSTALLATION i Smelter Plant \ Refinery

Converter and Molding Plant Wire Production Plant Smelter Plant

i ! Refinery Plant

Roaster Leach-Purification System Recovery Plant (Zinc Powder) Electrolytic Refining Plant Sulfate Recovery System Leached Waste Recovery System Residual Anodic Recovery Plant Selenium-Tellurium Plant

; Silver-Gold Refinery , Cadmium Plant

lndium Recovery Plant 1

Antimony Plant i Arsenic Plant

~--=~----------------~ Sodium Bisulfate Plant Miscellaneous Plants

i Coke Plant Sulfuric Acid Plant

: Fines Recovery Plant

f---=----=-----:-~--,----:---=----:-:-:-c-:-----------,-i --=0==--xy~,--F ue I PI ant Service and Infrastructure Facilities 1 Railroad System- central railway

08/26/96

~ Workshops 1 Construction Shops 1 Maintenance Shops

Power House Laboratory Living Quarters

, Recreation Facilities ' Television Station

Knight Piesold LLC

11 I

0ROYINST.WK4

TABLE 3

CENTROMIN-La Oroya-1450A SOA-WRKS.TBL

July 17, 1996

Environmental Improvement Works Executed by the Metallurgical Operational Manager in 1994-1995-1996 CENTROMIN - La Oroya

I INSTALLATIONS I PROJECT NAME I OBSERVATIONS I Smelter and Refmeries Cooling, sewage and Completed in December

industrial waters - Stage I 1994

Smelter and Refineries Solid Waste Completed characterization and studies

Smelter Main Stack repairing Completed, November 1994

Power house Cooling water recirculation 80% Completed (see - cooling water recycled to PEPA Descriptions) 1 million gallon storage tank used in the granulation of copper and lead slag

Copper smelter Cooling water, converter Completed gases, conditioning tower -installing a decant water line generated from toweres coniditioning water, gas and air at the Cadmium, Indium and Metallurgicl Investigations Plants

Agglomeration plant Main channel water uptake Completed, November 1994

July 17 ,1996 Knight Piesold LLC 50A-WRKS.TBL

TABLE 3 cont.

I INSTALLATIONS I PROJECT NAME

Zinc roaster Water recirculation from gas washer - Pelletization Units - reutilize waters exiting gas purifiers installed in the Pelletization Plant. Automatic controls monitoring water level in the purifier allow the plant to reduce the consumption of fresh water and use the pulp in concentrate mixture

Zinc refmery Zinc ferrites sediment ponds preventive maintenance- Huanchan -maintaining permanent retaining walls around the ferrite sedimentation zones

Copper smelter As20 3 deposit -construction of retaining walls

Coke plant Liquid effluents elimination - recycling water for reuse at the Coke Plant

Coke plant Relocation of tar distillation plant - move plant from rail line region

Alambron plant Effluent treatment

July 17 ,1996 Knight Pi~sold LLC

CENTROMIN-La Oroya-1450A

50A-WRKS.TBL July 17, 1996

I OBSERVATIONS I Completed

Completed

Not completed, will be part of the As20 3

management study (See PEPA Description)

Completed

Completed February, 1995

Completed February, 1995

50A·WRKS.TBL

TABLE 3 cont.

INSTALLATIONS PROJECT NAME

Lead refinery Effluent treatment - Three treatment methods being considered -1) clean anodes via mechanical scraper in place of water immersion 2) reduce consumption of water in final wash 3) introduce a filtration press process to form an anodic slime to be dried at the Anodic Residual Plant

Smelter Cleaning and reforestation of right margin of the Mantaro River - grade and clean righ bank; fill some areas with borrow material; forest area with native species; place mesh matting in the perimeters of the smelting installation

Asarco Oven plant Effluent treatment -establish sedimentation well and construct yute holding frames that will filter suspended solids in the presence of aluminum flocculant

Shops and garage Pilot septic tank construction

Lead refinery Solid waste management at Fluorsilic acid plant

Copper refmery Mother solution treatment

July 17 .1996 Knight Piesold LLC

CENTROMIN-La Oroya-1450A 50A-WRKS.TBL

July 17, 1996

OBSERVATIONS

was included as part of the PECET, filters are being installed

Completed except reforestation is lacking

Sedimentation pond incrementation. Completed.

Completed (See PEP A description)

detailed engineering maps done, US$70 000 AGI approved

laboratory test fmished, pilot test currently being done

.'iOA-WRKS.TBL

TABLE 3 cont.

I INSTALLATIONS I PROJECT NAME

Power house Relocation of cooling and waste waters, discharged into the channel below the copper reverberator pipeline - repairing supply line from Tishgo River to the Power house

Copper smelter - Maintenance of the cooling Converter area water drainage system -

reinstalling vent lines to avoid the spilling of waters toward the dines deposit within the converters

Power house Reinstallation of the water, air and vapor lines that feed Cadmium and lndium and Mateallurgical Investigations Plants which have deteriorated over time

July 17 ,1996 Knight Piesold LLC

I


50A-WRKS.TBL July 17, 1996

OBSERVATIONS I Cuchimachay main pipeline was reinstalled

Spills are being repaired

Lines are being relocating

50A-WRKS.TBL

TABLE 4a

CENTROMIN-La Oroya-1450A 50A-WTRSTN.TBL

July 17, 1996

Classification of Surface Water Monitoring Stations CENTROMIN - La Oroya

Industrial Sample Type Monitoring Station Component

Background/ Upstream, Mantaro River M-2 Upstream of La Upstream, Tishgo River T-1 Oroya

Smelting Complex Upstream, Mantaro River M-3 Downstream, Mantaro River (M-4) Point-Source Discharge D-101, D-102, D-103, D-104,

D-105, D-106, D-107, D-108, D-109, D-110, D-111, D-112, D-113, D-114, D-115<*>, D-116, D-117, D-us<·> D-119<*>

' ' D-120, D-121, D-122, D-123<*>, D-124, D-125, D-126<*>, D-127, D-128, D-129, D-130, D-131 <·>, D-132, D-133 D-134<*> D-135<*> D-

' ' ' 136(*)

Refining Complex Upstream, Yauli River Y-1 Downstream, Y auli River Y-2, Y-3 Point-Source Discharge R-1<•> R-2 R-3<*>

' '

Huanchan Slag and Upstream, Mantaro River (M-4) Zinc Ferrite Downstream, Mantaro River M-5 Storage Facility Point-Source Discharge D-137<•>

NOTES: * indicates those samples selected for continued monitoring in 1996

(M-4) This stations serves as downstream sampling station for the smelter and an upstream sampling station for the Huanchan storage complex.

July 17, 1996 Knight Piesold LLC WTRSTN.TBL

TABLE4a

CENTROMIN-La Oroya-1450A 50A-wrRSTN.TBL

July 17, 1996

Classification of Surface Water Monitoring Stations CENTROMIN - La Oroya

Industrial Sample Type Monitoring Station Component

Background/ Upstream, Mantaro River M-2 Upstream of La Upstream, Tishgo River T-1 Oroya

Smelting Complex Upstream, Mantaro River M-3 Downstream, Mantaro River (M-4) Point-Source Discharge D-101, D-102, D-103, D-104,

D-105, D-106, D-107, D-108, D-109, D-110, D-111, D-112, D-113, D-114, D-115<·>, D-116, D-117, D-118<*>, D-119<*>, D-120, D-121, D-122, D-123<"l, D-124, D-125, D-126<*!, D-127, D-128, D-129, D-130, D-131<•>, D-132, D-133, D-134<">, D-135<·>, D-136(*)

Refining Complex Upstream, Y auli River Y-1 Downstream, Y auli River Y-2, Y-3 Point-Source Discharge R-1 <"l R-2 R-3<*>

' '

Huanchan Slag and Upstream, Mantaro River (M-4) Zinc Ferrite Downstream, Mantaro River M-5 Storage Facility Point-Source Discharge D-137<*>

NOTES: * indicates those samples selected for continued monitoring in 1996

(M-4) This stations serves as downstream sampling station for the smelter and an upstream sampling station for the Huanchan storage complex.

July 17, 1996 Knight Pi~sold LLC WfRSTN.TBL

I

July 17, 1996

TABLE 4b

CENTROMIN-La Oroya-1450A 50A-WTRDES. TBL

July 17, 1996

Description of Surface Water Monitoring Stations CENTROMIN - La Oroya

Monitoring

I Description

I Station#

T-1 Tishgo River - Casaracra

M-1 Mantaro River - Chulec bridge I

M-3 Mantaro River - downstream of confluence with Y auli River

Y-1 Yauli River - upstream of copper and lead refinery

R-1 Lead refinery - Settling pond exit

R-2 Alambron plant

R-3 Asarco Oven plant - Settling pond exit

Y-2 Yauli River - downstream of copper and lead refinery -Huaymanta bridge

Y-3 Yauli River - downstream of Y -2 and upstream of confluence with Mantaro River - Sudete bridge

101 Coke plant - sewage and industrial water

M-3 Mantaro River - upstream of smelting complex -Cascabel bridge

102 Structural shop

103 Structural shop and internal protection - sewage water

104 Internal protection - jefatura sewage water

105 Acetilene plant- industrial water

106 Iron smelter - Maestranza

Knight Piesold LLC WTRDES.TBL

Monitoring Station#

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

July 17, 1996

TABLE 4b cont.

Description

CENTROMIN-La Oroya-1450A SOA-WfRDES.TBL

July 17, 1996

Antimony plant, acid tanks, instrumental shop, offices and light equipment

Components shop, garage

Components shop, patio

Instrumental wood shop

Training center

Heavy equipment, fire house

Industrial engineering

Control testing - Power house

Ionic plant, Power house

Oxygen plant

Oxygen plant, old

Copper and Lead smelter - slag sizing

Copper and Lead smelter - #2 Main channel

Zinc EW plant- sewage water

Anode waste plant- Se, Te discharges and sewage water

Anode waste plant - laundry settling pond exit

Anode waste plant -settling pond

Zinc EW plant -Anode washing effluent

Zinc EW plant- Cleaning Cells sludges

Knight Piesold LLC WfRDES.TBL

Monitoring Station#

126

127

128

129

130

131

132

133

134

135

136

M-4

137

M-5

July 17, 1996

TABLE 4b cont.

Description


50A-WfRDES.TBL July 17. 1996

Zinc EW plant, cooling water and spills from plant purification

Zinc plant sub-station cooling water

Zinc fusion oven, cooling water

Smelting construction - sewage water

Construction offices - sewage water

Cadmium plant

Pilot plant and mechanical shop

Indium plant - spills and sewage waters

Indium plant - cementation pond exit

Main channel #1

Parallel channel

Mantaro River - downstream of smelting complex and upstream of slag and zinc ferrite storage

Zinc ferrite effluent

Mantaro River - downstream of slag and zinc ferrite storage

Knight Piesold LLC WfRDES.TBL

Sample# Date

M-3 3194--2195 Avg Upstream Mantaro

M-4 3/94-2195 Avg DOH!lstream

Msntaro D-102 3/94-2195 Avg Concentration

!Average Loading, kg/day• Site Percentage of Total Load for Parameter

D-103 3/94-2195 Avg Concentration fo.,verage Loading, kg/day• Site Percentage ofTotal Load for Parameter

D-105 3/94-2195 Avg Concentration Average Loading, kg/day• Site Percentage of Total Load for Parameter

D-106 3/94-2195 Avg Concentration Average Loading, kgldey• Site Percentage of Total Load for Parameter

D-107 3/94-2195 Avg Concentration !Average Loading, kg/day" Site Percentage of Total Load for Parameter

D-108 3194-2195 Avg Concentration ~verage Loading, kg/day• Site Percentage of Total Load for Parameter

D-109 3/94-2195 Avg Concentration !Average Loading, kgldey• Site Percentaae of Total Load for Parameter

D-110 3/94-2195 Avg Concentration ~verage Loading, kg/day• Site Percentag_e of Total Load for Parameter

D-111 3/94-2195 Avg Concentration Average Loading, kg/dey• Site Percentage of Total Load for Parameter

D-112 3/94-2195 Avg Concentration !Average Loading, kg/day• Site Percentage of Total Load for Parameter

D-113 3194-2195 Avg Concentration !Average Loading, kg/day• Site Percentage of Total Load for Parameter

D-114 3/94-2195 Avg Concentration !Average Loading, kg/day• Site Percentage ofT otal Load for Parameter

D-115 3/94-2195 Avg Concentration Average Loading, kg/day• Site Percentage ofTotai Load for Parameter

D-116 3/94-2195 Avg Concentration Average Loading, kg/day• Sile Percentage of Total Load !Of Parameter

D-117 3/94-2195 Avg Concentration !Average Loading, kg/day• Site Percentage of Total Load for Parameter

D-118 3/94-2195 Avg Concentration !Average Loading, kgldey• Site Percentaae of Total Load for Parameter

D-119 3194-2195 Avg Concentration ft..verage Loading, kg/day• Sile Percentage of Total Load for Parameter

08126196

Table 5 3/94-2195 AVERAGE LOADING STATISTICS CENTROMIN- La Oroya -Smelting Complex

Flow pH ',~~

Pb Cu Zn m31min su m n_ man man man

~u 50.42 0.12 0.1 1.17

354602.569 843.956928 703.2974-4 8228.58005

4929.94 ------rAG 37.9 0.31 0.15 12.34 269056.405 2200.72522 1064.86704 87603.0618

7.7 20.33 1.17 0.17 2.83

0.021 0.59 0.03 0.00 0.08

0.~ 0.01% 0.00% 0.00% 0.00% 7.98 42.56 0.1 0.05 0.31

0.04 2.45 0.01 0.00 0.02 0.08% 0.03% 0.00% 0.00% 0.00%

8.28 19.2 0.47 0.17 0.32 0.11 3.04 0.07 0.03 0.05

0.23% 0.03% 0.01% 0.01% 0.00% 8.15 18.78 0.56 0.2 1.07

0.11 2.97 0.09 0.03 0.17 0.23% 0.03% 0.01% 0.01% 0.00%

8 22.42 0.35 0.14 1.62

o.58/ 18.73 0.29 0.12 1.35 1.19%. 0.21% 0.04% 0.03% 0.01%

7.44 430.63 0.76 0.29 1.651 0 0.00 0.00 0.00 0.00

0.00% 0.00% 0.00% 0.00% 0.00% 7.25 24.76 0.3 0.16 1.23

0.01 0.36 0.00 0.00 0.02 0.02% 0.00% 0.00% 0.00% 0.00%

7.41 20.67 0.5 0.25 2.36 0.26 7.74 0.19 0.09 0.88

0.53% 0.09% 0.03% 0.03% 0.01% 8.25 9 0.06 0.13 0.3

0 0.00 0.00 0.00 0.00 0.00% 0.00% 0.00% 0.00% 0.00%

7.42 254.22 3.27 1.11 16.96 0.02 7.32 0.09 0.03 0.49

0.04% 0.08% 0.01% 0.01% 0.00% 7.76 60.6 3.57 1.82 10.27

0.07 6.11 0.36 0.18 1.04 o.14% I 0.07% 0.05% 0.05% 0.01%

7.35 26.58 0.68 0.6 3.42 0.77 29.45 0.75 0.67 3.79

1.58% 0.33% 0.11% 0.18% 0.03% 8.88 84.67 1.83 0.29 1.49

0.25 30.48 0.66 0.10 0.54 0.51% 0.34% 0.10% 0.03% 0.00%

9.21 25.44 0.28 0.15 0.2 1.12 41.03 0.45 0.24 0.32

2.29% 0.46% 0.07% 0.07% 0.00% 6.89 22 0.43 0.25 2.03

0.16 5.70 0.11 0.06 0.53 0.37% 0.06% 0.02% 0.02% 0.00%

7.9 120,62 <-::.::.::,9;19 . ,5,5,4 ::::::-.· 11~1. 28.24 4,905.06 373.72 225.29 459.93

57.86% : >tss:za% .,,,, ,,:,::<54.38%' ,,,·<::61:89% _: :>:-:>3.1!l•!!( '>--4.38 . . '·: '' 201:84 . ' ,,,,,,,, 28.4-4 :::::::;:::;: 2(),62 : ·>·.>. :lll}~6

3.45 1,002.74 141.29 102.4-4 493.22 7.07% : '':ft.:JO% ' ,:,::::::· 20.56% ',, ,.,>>211:14% ,,,,_,.,,:,:'3.38%'''

Knight Pitlsold LLC

CENTROMIN·1450A

re As ~;d Mn N03 S04 man man man man man man

3.85 0.13 0.01 0.88 0.9 200.76 27078.9514 914.286672 70.32974-4 6189.01747 6329.67696 1411939.94

3.82 0.21 0.06 2.4 1.21 24-4.04 27118.614 1490.61386 425.946816 17037.8726 8589.92746 1732467.68

5.21 0.06 0.02 0.09 3.92 165.58 0.15 0.00 0.00 0.00 0.11 4.77

0.01% 0.00% 0.00% 0.00% 0.13% 0.01% 0.4-4 0.03 0.01 0.01 3.88 72.96 0.03 0.00 0.00 0.00 0.22 4.20

0.00% 0.00% 0.00% 0.00% 0.26% 0.01% 0.73 0.05 0.01 0.03 3.8 76.08 0.12 0.01 0.00 0.00 0.60 12.05

0.00% 0.00% 0.00% 0.00% 0.71% 0.02% 1.07 0.06 0.02 0.05 3.4 76.12 0.17 0.01 0.00 0.01 0.54 12.06

0.01% 0.00% 0.00% 0.00% 0.84% 0.02% 0.68 0.13 0.03 0.03 ··"""'""-'z;ez_ 78.58 0.57 0.11 0.03 0.03 2.36 65.63

0.02% 0.04% 0.02% 0.00% . ''"'' 2.80% 0.12%

1.091 0.21 0.03 0.14 1.03 78.15 0.00 0.00 0.00 0.00 0.00 0.00

0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.79 0.15 0.02 0.12 2.93 76.57 0.01 0.00 0.00 0.00 0.04 1.10

0.00% 0.00% 0.00% 0.00% 0.05% 0.00% 0.72 2.72 0.06 0.13 3.68 90.96 0.27 1.02 0.02 0.05 1.38 34.06

0.01% 0.34% 0.02% 0.01% 1.84% 0.06% 0.15 0.14 0.01 0.03 3.05 148.55 0.00 0.00 0.00 0.00 0.00 0.00

0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 10.6 1.32 0.3 2.12 2 114.89 0.31 0.04 0.01 0.06 0.06 3.31

0.~~-- 0.01% 0.01% 0.01% 0.07% 0.01% 7.25 0.98 0.12 0.24 3.45 83.7 0.73 0.10 0.01 0.02 0.35 8.4-4

0.03% 0.03% 0.01% 0.00% 0.41% 0.02% 1.25 0.5 0.21 0.11

I 4.72 77.78

1.39 0.55 0.23 0.12 5.23 86.24 0.05% 1 0.18% 0.16% 0.02% ,,.<:,·: 6.21%' 0.16%

3.3 0.31 0.04 0.17 2.33 1292.57 1.19 0.11 0.01 0.06 0.84 465.33

0.04% 0.04% 0.01% 0.01% 1.00% ~ 0.74 0.1 0.01 0.02 '''"-''2.23_ 120.5 1.19 0.16 0.02 0.03 3.60 194.34

0.04% 0.05% 0.01% 0.00% . 4.27% 0.35% 1.52 0.32 0.05 0.39 -4.11 111.69 0.39 0.08 0.01 0.10 1.07 29.00

0.01% 0.03% 0.01% 0.01% 1.27% 0.05% <::::::::::,-::z1.f3, ·.-.. ,,\)4;74 ,,,,:_();49_. ·.·. -:.:,,,2;~l_, ,.,,,, ,,_,,23_::, -.,,:.,: .. :~~~

883.86 192.75 19.93 90.68 50.02 8,169.72 : :3();4~% :>:-:··· 6-(25% /<·'<·· 13)3% ':''''''':::::::'i1:23%' << 59.40% ' >14;74%

'>::v•r~ , __ ,:<''' ,, > 1.1'38 .. _., ,, ""'':,:1_0 .. 2.8, : "~;~~ .·. '''''''"''''i1~6 ::::_,1~,1~ . 753.15 . . 56:54 51.07 12.52 7.95 7,671.29

i25J:I5'i6 -':>>:<::18.85%' :: ,,,,:.,,,,.:35;20% :.:::·:: '''''''''''1:.55% > :··&:44% :: >:::>:::13:84%

OROY ·LD1.\M<4

CENTROMIN • 1450A

Table 5 3/94 • 2195 AVERAGE LOADING STATISTICS CENTROMIN -La Oroya • Smelting Complex

Sample# Date How pH J:;:; PD {.;U Ln 1-e ~

t;a Mn N03 S04 m3/min su man man man man rnt~n man man man man

u-1~u ~V95AvgConcenbation 7.73 33.89 0.48 0.25 4.27 2.34 0.18 0.03 0.74 2.88 99.42 Average Loading, kg/day" 0.16 7.81 0.11 0.06 0.98 0.54 0.04 0.01 0.17 0.66 22.91 Site Percentage of Total Load for Parameter 0.33% 0.09% 0.02% 0.02% 0.01% 0.02% 0.01% 0.00% 0.02% 0.79% 0.04%

0-121 3194-2195 Avg Concentration 6.28 99.58 6.47 0.88 30.07 17.57 4.35 0.03 0.34 2.02 367.78 Average Loading, kg/day• 0.15 21.50 1.40 0.19 6.50 3.80 0.94 0.01 0.07 0.44 79.44 Site Percentage of Total Load for Parameter 0.31% 0.24% 0.20% 0.05% 0.04% 0.13% 0.31% 0.00% 0.01% 0.52% 0.14%

0-123 3194-2195 Avg Concentration 3.08 151.14 . ,' > ·' '16 1.05 41.28 18.79 ·::,:::><16.54. 0.2 0.61 0.77 2244.13 f.verage Loading, kg/day• 0.12 26.12 3.11 0.18 7.13 3.25 8.31 0.03 0.11 0.13 367.79 Site Percentage of Total Load for Parameter 0.25% 0.29% ::::::>:;>: o:45% 0.05% 0.05% 0.11% :::::::: •>:·:::1<1% 0.02% 0.01% 0.16% 0.70%

0-124 3194-2195 Avg Concentration 3.54 61.67 13.09 -o:rr 143.18 2.54 0.24 0.08 7.66 0.31 1108.33 Average Loading, kg/day" 0.12 10.66 2.26 0.13 24.74 0.44 0.04 0.01 1.32 0.05 191.52 Site Percentage of Total Lottd for Parameter 0.25% 0.12% 0.33% 0.03% 0.17% 0.02% 0.01% 0.01% 0.16% 0.06% 0.35%

0-125 3194-2195 Avg Concentration 6.58 108.52 2.58 2.47 156.58 2.38 0.25 0.1 10.62 1.28 455.58 !Average Loading, kg/day< 0.04 6.25 0.15 0.14 9.02 0.14 0.01 0.01 0.61 0.07 26.24 SHe Percentage ofT otal Load for Parametlll' 0.08% 0.07% 0.02% 0.04% 0.06% 0.00% 0.00% 0.00% 0.08% 0.09% 0.05%

0-126 f3194-2195 Avg Concentration 5.16 (;7Jl4 :.:·:·,··: ::•1,18. ::>;: .2.84 :;: .:< :1182 .. 51: :;:-·-:··· : ~.42 ·:::::::::,:,,•:,::::0.37' 1.03 .••. : ::::_:.:::,::75 ,:: <> 1>.1!4 \1.:!~5! !Average Loading, kg/day• 3.05 294.44 5.i8 12.47 5,193.65 19.41 1.63 4.52 329.40 3.69 Site Percentage of Total Lottd for Parametlll' 6.2_~ '-----

. 3.32% -·•·o.75% : -:. ,,_ : 3.43% --35.84% ·-·::.::::·o.e7% 0.54% 3.12% •:40.8.1% -.,,::_-4:38% :/ 21:10% D-127 3194-2195 Avg Concentration 7.74 14 0.12 0.09 1.06 0.58 0.19 0.01 0.04 1.59 230.28

Average Loading, kg/day• 0.14 2.82 0.02 0.02 0.21 0.11 0.04 0.00 0.01 0.32 46.42 Site Percentage of Total Load for Parameter 0.29% 0.03% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.38% 0.08%

0-128 3194-2195 Avg Concentration 7.52 15.79 0.15 0.08 1.38 0.83 0.02 0.01 0.06 2.22 77.76 Average Loading, kg/day" 0.17 3.87 0.04 0.02 0.33 0.15 0.00 0.00 0.01 0.54 19.04 Site Percentage of Total Load for Parameter 0.35% 0.04% 0.01% 0.01% 0.00% 0.01% 0.00% 0.00% 0.00% 0.65% 0.03%

0-129 13J94..2195 Avg Concentration 7.83 15.22 0.34 0.03 1.21 2.09 0.08 0.03 0.06 1.74 75.66 !Average Loading, kg/day• 0.07 1.53 0.03 0.00 0.12 0.21 0.01 0.00 0.01 0.18 7.63 Site Percentage ofTotal Load for Parametlll' 0.14% 0.02% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.21% 0.01%

0-131 3194-2195 Avg Concentration 7.33 1609.78 3.43 9.05 2112.77 10.89 2.26 r::•o:_,,,,,,,,,_4?-~ 27.17 0.93 4134.01 !Average Loading, kg/day• 0.07 162.27 0.35 0.91 212.97 1.10 0.23 5.02 2.74 0.09 416.71 Site Percentage of Total Load for Parameter 0.14% 1.83% 0.05% 0.25% 1.48% 0.04% 0.08% '' > 3:-46~ 0.34% 0.11% 0.75%

0-132 f3194-2195 Avg Concentration 7.71 27.58 0.33 0.18 2.85 0.96 0.07 0.18 0.06 1.9 166.98 !Average Loading, kg/day• 0.18 7.14 0.09 0.05 0.74 0.25 0.02 0.05 0.02 0.49 48.98 Site Percentage of Total Loaa for Parameter 0.37% 0.08% 0.01% 0.01% 0.01% 0.01% 0.01% 0.03% 0.00% 0.58% 0.09%

D-133 3/94-2195 Avg Concentration 3.18 ·. : :3030.::/5:: 2.01 5.94 2266.99 _: ,.,:, :>1073.45. 17.19 !.-- -----:-:- 84:E! 76.21 0.86 16380.08 il>.verage Loading, kg/day" 0.05 - 216.18 0.14 0.43 163.22 77.29 1.24 4.65 5.49 0.06 1,179.37 Site Percentage of Total Load for Parameter 0.10% ···'2A-6% 0.02% 0.12% 1.12% :-:-:- ·::·::::::-2:66% 0.41% s;21% 0.68% 0.07% 2.13%

0-134 3194-2195 Avg Concentration 2.11 1183.56 3.26 5.69 1170.17 430.34 38.89 35.4 150.5 0.18 12519.17 Average Loading, kg/day• 0.02 34.09 0.09 0.17 33.70 12.39 1.12 1.02 4.33 0.01 360.55 Site Percentage of Total Lottd for Parameter 0.04% 0.38% 0.01% 0.05% 0.23% 0.43% 0.37% 0.70% 0.54% 0.01% 0.65%

0-135 3194-2195 Avg Concentration 2.79 .-.:.,._: 115.13 -·--:_,_,:_:, 5:73 1;57 ·:-::463.83 <<··_3();68 . -:-:-:-> ____ :--2,84 --•:-·::-:-:. 3:96 -·:-::··::: :.•'7.86 0.18 '"111M9 !Averaoe Loading, kg/day" 6.88 1,140.62 56.77 15.55 '4,595.26 303.95 28.14 39~23 77.87 1.78 11,008.78 Site Percentage of Total Load for Parameter 14.10% -::,. : ::: •12.85% lt26% -::-:·::::::•·:.(.27% 3tc53%- .·.· >: :10.47o/,; •:.:•:::. •: .. &.38%'' :·-· ''"2Ul4% :::::::>::: :-:,-9.65% 2.12% 19'.66%

0-136 3194-2195 Avg Concentration 4.56 .- -'-<: 257.65 .. : _·29,2~ 1,29 . > 989,62 :-:·:,::_2'!!):87,- .·.·.··· ':::<2,57 : ·. 5.64 •-••·•·•·:::...•-a2.79 0.39 )!87!1,78 Average Loading, kg/day< 2.35 875.6o 99.34 4.38 3,363.12 835.58 8.73 19.17 281.35 1.33 13,185.04 Site Percentage of Total Load for Parameter 4.84% . ·.:o_: :: :::>•9.86% "•-•':-:14c45'1ti _::· >:&~ : . 23c08% ::::.:::•:•>28:79%' :-.-:- -----:c}2.91%•- : ·-:13c21% 34~86% 1.57% ::,:::- ::::,::;23;78%

1-:-::-• ::: : Sumc Total Smelter Discherge

:-:-: :•:::: . ---<:•::>•>. .,:: ·.·.· •---::, ,•-:•<a ~1ti21hr'Oilati0:.136f ::: .·. .;:-::-46-:!11 '"8 876.68 ::. ''687:26 364.00 :-:::•:14 574;32 .-:,:, •'•':2 90t91 ''''•:•::•:::-299-,99 145.09 . ,:: 807:21 84:21 55436.53

• All Joadings are In kg/day of constituent except for ftow which Is giVftn as m31mln

Knight Piesold LLC OROY-LD1.VIIK4

Sample# Date Flow pH m3/min su

1wona tiank t:muent Guidelines• 6-9 Peru Standards- 5.5-10.5

D-102 3194-2195 Avg Concentration 0.02 7.70

D-103 3194-2195 Avg Concentration 0.04 7.98

0-105 3194-2195 Avg Concentration 0.11 8.28






0-111 3194-2/95 Avg Concentration 0.00 8.25

I 0-112 3194-2195 Avg Concentration 0.02 7.42

f---0-113 3194-2195 Avg Concentration 0.07 7.76


0-115 3194-2195 Avg Concentration 0.25 8.88 Jan 96 0.07 I' 9.90 Feb 96 0.12 8.00 Mar96 0.03 7.00

0-116 3194-2195 Avg Concentration 1.12 . >< .. 9.21


World Bank Effluent Guidelines• 6-9 Peru Standards- 5.5-10.5

Table 6 Smelter Complex- Water Quality Results

CENTROMIN-La Oroya

Effluent Sources

~~ Pb (.;U

~ mall mgll

1~ 0.6 0.3 1 1 2 6

20.33 1·'·>''. 1.17 0.17 : : ;2,63

42.56 0.10 0.05 0.31

19.20 0.47 f--·"""0,17 0.32

18.78 0.56 0.20 :'>01.07

I 22.42 0.35 0.14' '':<J.e:l

[> 430.63 ( 0.76 0.29 .·. 1.65

I

24.78 0.30 0.16 >.,>._t.23

I 20.67r----o:-so 0.25 2.36

9.00 0.06 0.13 0.30

~e As mgll mgll

2 1 5 1

,,,,,,:,$.21 0.06

0.44 0.03

0.73 0.05

1.07 0.06

0.68 0.13

1.09 0.21

0.79 0.15

0.72 2.72

0.15 0.14

,,_·:·· 25-4.22 3.27 1.11 -16 96 I 1000 1.32

·~ X~ ''"I ...

-BO .. W 3,57.

~rJ-,w 26.56 0.68

,:,,,:_ 84.67,. 1.63 0.29 1 ... 1.49 3.30 0.31 16.00 0.91 0.05 0.12 2.00 0.25 44.10 0.71 0.10 0.04 0.66 0.15

4.96 0.38 0.10 0.37 0.32 0.13

25.44 0.28 0.15 0.20 o.i4 0.10

22.00 0.43 0.25"' ''{2.~ 1.52 0.32

50 0.6 0.3 1 2 1 100 1 2 6 5 1

Cd mall

0.1

0.02

0.01

0.01

0.02

0.03

0.03

0.02

0.06

0.01

0 .. 30

0.12

(}.21

0.04

0.01

0.05

0.1

''>Represents exceedance of World Bank effluent guidelines or Peru effluent standards (Annex 2, instantaneous)

• World Bank Effluent Guidelines -World Bank Environment, Health and Safety Guidelines, Minino and Milling - Open Pii/Underground, August 11, 1995 -Peru maximum permissible limas for liquid effluents for mining operations in existence prior to May 1993 (RM 011-96, Annex 2)

Knight Pi6sold LLC

CENTROMIN - 1450A

Mn Nu3 S04 mall mgll mall

0.09 3.92 165.58

0.01 3.86 72.96

0.03 3.80 76.08

0.05 3.40 76.12

0.03 2.82 78.58

0.14 1.03 78.15

0.12 2.93 76.57

0.13 3.68 90.96

0.03 3.05 148.55

I 2.12 2.00 114.89

0.24 3.45 83.70

I 0.11 4.72 77.78

0.17 2.33 1,292.57

0.02 2.23 120.50

0.39 4.11 111.89

LAOROYA2.WK4

Sample 11 Date

World Bank Effluent Guidelines• Peru Standards-

0-118 31!)4-2195 Avg Concentration

0-119

Jan96 Feb96 Mar96

3194-2195 Avg Concentration Jan96 Feb96 Mar96

0-120 3194-2195 Avg Concentration


0-123 3194-2195 Avg Concentration Jan 96 Feb 96 Mar96

D-124 3194-2195 Avg Concentration


0-126 3194-2195 Avg Concentration Jan 96 Feb 96 Mar96




Flow m31min

28.24 27.20 28.56 27.88

3.45 2.73 3.25 2.93

0.16

0.15

0.12 0.24 0.18 0.14

0.12

0.04

3.05 0.92 1.44 2.42

0.14

0.17

0.07

pH su

6-9 5.5-10.5

7.90 8.80 7.70 7.40

7.73

Table 6 Smelter Complex- Water Quality Results

CENTROMIN-La Oroya

Emuent Sourcea

:~ Pb (;U

~ mg/1 mgll 50 0.6 0.3 1

100 1 2 6 :-·. . 12:0.62 '<· 9.~9 $.$4 .,,.:,< tt:u·

'''~()(),()(j 0.41 0.04 <>>.,,J;!i(l 16.;~91!.31 0.16 0.02 ,)!i~ 219:37 0.83 0.07

33.89 0.48

t-e r:n mg/1 2 1 5 1

2U3 ,4.7.4 tH9 6.:20 0.27 0.04 0.24 0.21

0.18

6.28 .. "' !19·56· ' ' 6.47 .;·O.Il!l · .. ·.30.07 .' .;:>,1h. ., ,,,.

.... ·:, :3.08 151.14 '''18.00 ·.''''t05 ,.,,,-41.28 ,:-,"' ,,, 18~7.9 ><:36.54

'•<i •••. , ... ~:~- '-':130.00 8.50 '.0 .. 55 26.50 ><N:~ 0.63 32:61 16~50 ci.55 59:oo <.JMO

2.90 403.a1 · tO..so ... 0.3-4 > 48.00 >zt.1o . 46.00

·'< 3.54 61.67 .13.09 (t73 143.16 2.54. 0.24

6.58 1 , 1013.s2 2.581 2A7 .. 156.56 '""''·· 2.38

0.25

., 5.18 '· 97,04 ~.18 2 .. 84 1,182.57 ,. ,,,,,. 4.4:2 0.37 )5;10 21.00 ''··· 1.5o :z:oo 299.00 < 2.!i(l' 0.01

6.70 . 117.85 0.18 0.04 455.00 2.00 0.04 6.90 45.01 0.14 0.07 1t.60 0.18 0.03

7.74 14.00 0.12 0.09 1.C6 0.55 0.19

7.52 15.79 0.15 0.08 I 1.36 0.63 0.02

7.83 15.22 0.3-4- 0.03 1.21 ·. ;2.09 0.08

Cd mall

0.1

... OA9

0.03

0.03

.. ,,,,,, 1>20:

0.08

0.10

1,():3

0.01

0.03

'-'1 '-=-""""'""""-'--'"=""-;..,;=""'-'IRepresents exceedance of W0<1d Bank effluent guidelines or Peru effluent standards (Annex 2, instantaneous)

• VVor1d Bank Effluent Guidelines -World Bank Environment, Health and Safety Guidelines, Min•ng and Milling - Open Pit/Underground, Auguot 11, 1995 -Peru maximum permissible lirn~s for liquid effluents for mining operations in existence prior to May 1993 (RM 011-96, Annex 2)

08126196 Knight Pillsold LLC

CENTROMIN- 1450A

Mn NU3 504 mall mg/1 mall

2.23 1.23 200.90

2.52 1.60 1,544.14

0.74 2.88 99.42

0.3-4 2.02 367.78

0.61 0.77 2,244.13

7.66 0.31 1,108.33

10.62 1.28 455.58

75.00 0.84 2,662.70

0.04 T· O.C6 2.22 77.76

O.C6 1.74 75.66

LAOROYA2.VvK4

Table 6 Smelter Complex -Water Quality Results

CENTROMIN-La Oroya

Elftuent Sources

c.l_,·,~· =~~~~=-~"'·~·''''~''·'= .. qRepresents exceedance of World Bank effluent guidelines or Peru effluent standards (Annex 2, instantaneous)

• World Bank Effluent Guidelines -World Bank Environment, Health and Safety Guidelines, Mining and Milling - Open Piii\Jnderground, August 11, 1995 •• Peru maximum permissible lim~s for liquid effluents for mining operations in existence prior to May 1993 (RM 011·96, Annex 2)

Aggregate Sources

ample# Date Flow pH TSS Pb cu :'g,'l_

Fe As cd m3/min su mg/1 mg/1 mg,'l_ ma/1 men ma/1

World Bank Effluent Guidelines• 6-9 50 0.6 0.3 1 2 1 0.1 Peru Agricuttural Standards - 0.1 0.5 25 0.2 0.05

M-3 3194-2195 Avg Concentration 4,884.01 7.70 1 <50.42 ·'" 0.121

0.10 1.17 3.85 0.13 0.01

M-4 3194-2195 Avg Concentration 4,929.94 7.46 37.00 .,.,,,_., 0.31 0.15 12.34 3.82 i·<: . ,, ,().2t' ""'' .. ·.,.,0.06.

I

M-5 3194-2195 Avg Concentration 4,930.85 7.67 28.91 0.34 . 0~_5,2, 5.31 4.49 . Q21 0.03'

I : · · ·. ''''·'''''··I Represents exceedance of World Bank ef!luent guidelines or Peru agncuHural standards (Class Ill)

• World Bank Effluent Guidelines -Work! Bank Environment, Health and Safety Guidelines, Mining and Milling - Open Piii\Jnderground, August 11, 1995. -Peruvian Class Ill Standards for water used for agricuftural purposes (irrigation and stock watering) 1994.

Knight Pilltold LLC

I

CENTROMIN -1450A

:-TN03 ··so4

mo.1 m !!!ll!! -01!

0.88 0.00 20C.76

2.40 . ,,z;--244~54

2.83 '··'1.36 227.23

I I

LAD ROYAl WK4

Sample#

r-t-1

M-2

Date

1wono Hank t:ffiuent uuidelines* Peru Ag_ricuHural Standards -

3194-2195 Avg Concentration

3194-2195 Avg Concentration

Flow pH m3/min su

6-9

3,333.67 7.98

NR NR

Table &a Upgradlent. Water Quality Results

CENTROMIN-La Oroya

Aggregate Soureea

~~ t'b Cu :0, mall mall :>U 0.1) U.3 1

0.1 0.5 25 12.25 0.09 0.05 0.66

NR 0.10 0.08 1.34

Fa As Cd mall mg/1 m_g/1_

2 1 U.1

0.2 0.05 1.12 0.11 0.00

<:2;72 0.07 O.Q1

I·''·'·<·· ., "''·\::·!Represents exceedance of World Bank effluent guidelines or Peru agricuHural standards (Class Ill)

Mn mall

0.33'

1.11

• World Bank Effluent Guidelines -World Bank Environment, Health and Safety Guidelines, Mining and Milling - Open Pit/Underground, August 11, 1995. - Peruvian Class Ill Standards for water used for agricuKural purposes (irrigation and stOCk watering) 1994. Note: NR signifoes "Not Recorded. •

Knight Pi6told LLC

CENTROMIN- 1450A

N03 S04 mall mall

0.1 . _0,8J 155.86

NR 210.13

LAOROY JU. \IVK4

~ample# Date Flow m31min

T-1 3194-2195 Avg concentratron Average Loading, kglday* 58.42 Site Percentage of Total Load for Parameter

Y-1 3194-2195 Avg Concentration Average Loading, kglday* 646.33 Site Percentage of Total Load for Parameter 33.04%



Load Differences kglday* Y2- Y1 7.42 Y3- Y1 10.04

H-1 3/94-2195 Avg concentratron Average Loading, kglday* 0.2 Site Percentag_e of Total Load for Parameter 4.33%

R-2 3194-2195 Avg Concentration Average Loading, kglday* 2.23 Site Percentage of Total Load for Parameter 48.27%

R-3 3194-2195 Avg Concentration Average Loading, kglday• 2.19 Site Percentage of Total Load for Parameter 47.40%

Total Load (R1+R2+R-3) (kglday)* 4.62

-

Table 7 3/94- 2/95 Average Loadings Statistics

CENTROMIN - La Oroya- Refinery Complex

pH TSS Pb cu Zn su mQII mQII mQII mQII

8 9.88 0.21 0.03 0.65 831.15 17.67 2.52 54.68

i.B3 - 80.86 0.36 0.4 3.45 75,257.63 335.06 372.29 3,210.97

25.15% 11.44% 7.22% 27.49% 7.53 100.45 1.5 2.72 4.6

94,563.63 1,412.10 2,560.61 4,330.44 31.60% 48.22% 49.68% 37.07%

7.64 136.94 1.25 2.35 4.38 129,431.96 1,181.47 2,221.16 4,139.86

43.25% 40.34% 43.10% 35.44%

19306.00 1077.04 2188.321 1119.47 54174.33 846.41 1848.87 928.89

1.35 492.82 180.55 1713.53 39.94 141.93 52.03 493.50 11.50

43.93% 90.49% 92.59% 42.19% 7.86 24.82 0.23 8.17 0.39

79.70 0.74 26.24 1.25 24.67% 1.28% 4.92% 4.59%

8~01 r-----32.18 1.50 4.21 4.60 101.48 4.73 13.281 14.51

31.41% 8.23% 2.49% 53.21%

323.12 57.50 533.01 27.26

* All loadings are in kglday of constituent except for flow which is given as m31min

08/26196 Knight Piesold LLC


Fe As Cd Mn NU3 S04 mgll mgll mgll mgll mgll mgfl

0.3 0.02 0.01 0.01 1.33 122.79 25.24 1.68 0.84 0.84 111.89 10,329.68

21.52 0.11 0.01 4.04 3.2 770.58 20,028.99 102.38 9.31 3,760.09 2,978.29 717,190.52

29.32% 3.58% 33.04% 26.44% 31.24% 33.55% 24.43 1.5 0.01 5.34 3.44 772.37

22,998.40 1,412.10 9.41 5,027.08 3,238.42 727,109.12 33.67% 49.43% 33.42% 35.35% 33.97% 34.01%

26.75 1.42 0.01 5.75 3.51 733.83 25,283.37 1,342.15 9.45 5,434.74 3,317.56 693,596.16

37.01% 46.98% 33.55% 38.21% 34.80% 32.44%

2969.41 1309.72 0.11 1266.99 260.13 9918.60 5254.38 1239.77 0.14 1674.65 339.27 -23594.36

4240.3!! 275.8!! 0.12 11.83 0.07 18281.94 1,221.23 79.74 0.03 3.41 0.02 5,265.20 99.51% 98.35% 51.84% 16.67% 0.37% 91.46%

0.95 0.27 0.01 0.06 0.72 86.85 3.05 0.87 0.03 0.19 2.31 278.89

0.25% 1.07% 48.16% 0.94% 42.64% 4.84% 0.94 0.15 0.00 5.34 0.98 67.51 2.96 0.47 0.00 16.84 3.09 212.90

0.24% 0.58% 0.00% 82.39% 56.99% 3.70%

1,227.24 81.08 0.07 20.44 5.42 5,756.99

50A-OROYREF1.WK4

jSample# Sample Site

World Bank Effluent Guidelines Peru Agricultural Standards ~

Y-1 Marcavalle Bridge

Y-2 Huaymanta Bridge

Y-3 Sudete Bridge

Date Flow m3/min

3/94-2/95 Avg 646.33

3/94-2/95 Avg 653.75

3/94-2/95 Avg 656.37

Table 8 Water Quality Results

CENTROMIN ·La Oroya· Refinery Complex

Aggregrate Sources

pH TSS Pb Cu Zn su mg/1 mgil mg/1 mg/1

6.0- 9.0 50 0.6 0.3 1 0.1 0.5 25

7.83 80.86 0;361···· •.oA .. 3A5 1·'--·

7.53 100:45 ····· .· 1:5 ·········· ······2.72 ... 4.6

7.64 1~6.94 · ...• ·.·•.··.(25 2:35 4.381.··

Fe As mg/1 mgll

2 1 0.2

21:52 0.11

. 24.43 .... 1;5

2tt75 :: 1;42

'--;__;__.c:c..:"-'.....JIRepresents exceedance of World Bank effluent guidelines or Peru agricultural standards (Class Ill)

• World Bank Effluent Guidelines- World Bank Environment, Health and Safety Guidelines, Mining and Milling - Open Pit/Underground, August 11, 1995. ~Peruvian Class Ill Standards for water used for agricultural purposes (irrigation and stock watering) -1994.

JSample # I Sample S1te

1Wor1d Bank Effluent Guidelines Peru Standards ...

R-1 Refinery Lead Effluent

R-2 Effluent from Alambron

R-3 Effluent from Asarco

Date ---r-rrow I m3/min I

3/94-2/95 Avg 0.2 Jan 96 0.28 Feb 96 0.28 Mar96 0.43

3/94-2/95 Avg 2.23

3/94-2/95 Avg 2.19 Jan 96 1.97 Feb96 1.86 Mar96 2.20

pH TSS su m~ I

6.0-9.0 50 5.5- 10.5 100

······•1;35 < 492;82 I 3;70 .: 140.00 · ... 3,20 •-·· .... sit~.

:.••.:.··· 2:60 / -31ita'f

7.86 24.82

8.01 32.18 8.60 33.00 8.00 31.31 7.60 169.61

Effluent Sources

Pb Cu Zn Fe ~ mgll mg/1 mg/1 mg/1 mgll

0.6 0.3 1 2 1 1 2 6 5 1

.18.0 .. 65 < 1_713.53 . . : 39.94 4240.38 • :276;88

.142..50 59.00 0.79 12Mi:l ····>•·········· ~.50 288,00 ··'26;501···· 7.00 sfp(l .t~i:l

11:30 55;00 1.6() 11:t()9 )t;ao

0.23 .·• 8.17 0.39 0.95 0.27

··.··•·1.50 4.21 4.60 0.94 0.15 0.05 . 0:40 0.20 0.26 TR 0.58 0.30 0.08 0.08 0.01 0.27 0.20 0.07 0.30 0.03

CN (tot) mall

1 0.005

CN (tot) mg/1

TR 0

TR

TR 0

TR

V:::: ·• ·.·• .. > . >I Represents exceedance of World Bank effluent guidelines or Peru effluent standards (Annex 2, instantaneous)

• Wor1d Bank Effluent Guidelines -World Bank Environment, Health and Safety Guidelines, Mining and Milling -Open Pit/Underground, August 11, 1995 ... Peru maximum permissible limits for liquid effluents for mining operations in existence prior to May 1993 (RM 011-96, Annex 2)

08/26/96 Knight Piesold LLC


Cd Mn N03 504 mall mQ/1 mgll mg/1

0.1 0.05 0.1 0.01 4.04 }•· . 3:2. 770.58

0.01 5.34 3.44 772.37

0.01 5.75 .. 3:51 733.83

Cd Mn NU3 ::;u4 mg/1 mg/1 mg/1 mgll

0.1

.. > 0:12 11.83 0.07 18281.94

0.01 0.06 0.72 86.85

0.00 5.34 0.98 67.51

50A-OROYREF1.WK4

Title

Guideline for Preparation of Environmental Adjustment and Management Program (PAMA)

Guideline for Preparation of Environmental Impact ~ssesment (EIA)

Environmental Guideline for Water Management in Mining and Metallurgical Operations

Environmental Guideline for Heap Leach Projects

Environmental Guideline for \Disturbed Vegetation Areas by the Mining and Metallurgical Industry

Environmental Guideline for Ore Deposits Exploration Activities in Peru

Environmental Guideline for Tailings Management

Environmental Guideline for Mine Closure and Abandon

I

Environmental Guideline for trilling and Blasting

Mining Operations

08/26/96


TABLE9 Environmental Guidelines Published by the MEM

CENTROMIN-La Oroya

Published Brief Content Description

February 1995 Detailed PAMA's content; requirements,mitigation plans, closure plans, monitoring, specific requirements.

February 1995 Detailed EIA's content; requirements,mitigation plans, closure plans, monitoring, specific requirements.

May 1995 Contamination sources, water management structures, acid mine drainage, water storage, process water, sewage, passive/active treatments, monitoring.

May 1995 Conceptual design, hydrology, water balance, site selection, liners, operation, heap stability, closure.

May 1995 Baseline, soil characteristics, leveling, drainage sampling,fertilizers, seeding, mulching, erosion control, irrigation, monitoring.

May 1995 Operation plan, remediation strategies,operation, I reporting.

July 1995 Tailings characteristics, Peruvian physiography, tailings disposal alternatives, site selection, dam stability, I seepage control, closure. I

11 July 1995 Mine closure, characteristics, closure design, ~

closure alternatives, monitoring, cost estimation.

September 1995 Blasting operations, explosives storage, handling, transportation, surface and underground blasting, drilling.

I

Knight Piesold LLC 50A-CENTRO.WK4

Country

Peru Mexico China Thailand USA Canada Poland Germany Kuwait ~ustralia IYY_orld Bank

08/26/96

CENTROMIN- La Oroya- 1450A

TABLE 10 Comparison of Ambient Air Standards

for 502 (ug/m3) CENTROMIN-La Oroya

Averagin~ Times 0.5-hour 1-hour 3-hour

500 780

1,300 450

600 400 453 450

Knight Piesold LLC

24-hour Annual _J

572 1721 341 150 60 1

300 1001 365 80 150 30 300 32

140 160 8011 160 501 500 100\1

CMPAQSS.WK3

TABLE 11 Peruvian Maximum Permissible Limits for Effluent from Mining and Metallurgical Operations

CENTROMIN-La Oroya

CENTROM IN-La Oroya-1450A

c: Current Operations New Operations

Constituents Instantaneous Annual Instantaneous Annual Value Average Value Average

Value Value >5.5,<10.5 >5.5,<10.5 >6 <9 >6,<9

Suspended Solids (mctlll 100.0 50.0 50.0 25.0 Lead (mqll) 1.0 0.5 0.4 0.2 Copper (mgll) 2.0 1.0 1.0 0.3 Zinc (mgll) 6.0 3.0 3.0 1.0 Iron (mg/1) 5.0 2.0 2.0 1.0 Arsenic (mgll) 1.0 0.5 1.0 0.5 Total Cyanide {mg/1)* 2.0 1.0 1.0 1.0

• Total Cyanide is equivalent to 0.1 mg/1 of free Cyanide and 0.2 mg/1 of WAD (weak acid dissociable) cyanide

08/26/96 Knight Piesold LLC 50A-CENTRO.WK4

1-hr Annual Monitoring Avg. 502 Avg. 502 Location (ug/m3) (ug/m3)

Hotel Inca 3,282 jSindicato 5,240 Cushurupampa 5,240 Huanchan 5,240 Casaracra 3982

08/26/96

TABLE 12 Summary of Existing Regional Ambient Air Quality

Maximum Observed Concentrations (January, 1994 through March, 1996)

CENTROMIN-La Oroya

1-hr Annual 24-hr Avg. PM10 Avg. PM10 Avg.TSP

(ug/m3) (ug/m3) (ug/m3)

115 709 46 214 181 1,288 50 349 291 no data no data 139 492 no data no data 350 117 no data no data 329

Knight Piesold LLC

CENTROMIN- La Oroya- 1450A

24-hr 24-hr 24-hr Avg.As Avg.Pb Avg. Cd (ug/m3) (ug/m3) (ug/m3)

1.057 1.688 0.041 6.211 4.185 0.060 0.843 1.064 0.044

35.260 58.256 2.054 1.440 0.335 0.033

50A-EXSTAQ.WK3

Particle Size Mass Mean Diameter

Categories (urn) (urn)

0 to 0.625 0.3 0.625 to 1.25 0.9 1.25 to 2.5 1.9 2.5 to 5.0 3.9 5.0 to 10.0 7.8 10.0 to 15.0 12.7

>15.0 15.0

Total Deposition

TABLE13 Summary of Estimated Maximum Existing Deposition Rates

CENTROMIN-La Oroya

Mass Deposition As Fraction Velocity Deposition

(%) (m/sec) (g/m2 year)

32 0.0002 0.01423 8 0.0004 0.00712

16 0.0010 0.03558 13 0.0029 0.08384 9 0.0080 0.16012 5 0.0200 0.22239

17 0.0490 1.85252

2.37581

Maximum annual air concentrations estimated from maximum observed 24-hr concentrations and U.S. EPA conversion factors: As= (35.260/0.4)*0.08 =7.052 ug/m3 Pb = (58.256/0.4)*0.08 = 11.251 ug/m3 Cd = (2.054/0.4)*0.08 = 0.411 ug/m3



Pb Cd Deposition Deposition (g/m2 year) (g/m2 year)

0.02271 0.00083 0.01135 0.00041 0.05677 0.00207 0.13377 0.00488 0.25547 0.00933 0.35482 0.01295 2.95563 0.10792

3.79052 0.13840

DEP.WK3

Sampling Site#

R-2

R-3

R-1

July 17, 1996

Sampling Site Description

TABLE 14 Description of Individual Discharges

CENTROMIN - La Oroya (Refinery Complex)

Principal Conditiom or Characteristics of Effluent Comtituents of Concern

(Ranking in Terms of Loading to Yauli River)

Overflow from the cooling water Flow (1), TSS (3), Cd Neutral to slightly basic, moderately warm sedimentation well associated with the (2), N03 (2) water with low concentrations of measured copper bar rolling mill (Alambron constituents. Plant).

Overflow from the cooling water Flow (2), TSS (2), Zn Neutral to slightly basic, hot water with low sedimentation well associated with the (1), Mn (1). NO, (1) concentrations of measured constituents copper bar at the Asarco Furnace.

Overflow from the sedimentation well TSS (1). Pb (1), Cu (1), Acidic water with high to very high associated with production of lead Zn (2), Fe (1), As (1), concentrations of TSS, Pb, Cu, Fe, As and sulfate at the lead refmery. Cd (1), S04 (1) so •.

Knight Piesold LLC

CENTROMIN-La Oroya-1450A 50A-INDDIS. TBL

July 17, 1996

Comments

A project to treat the effluent from the Aiambron Plant are reported to have been completed in February 1995. Significant changes in water quality between January 1994 and January 1995 are not apparent.

Treatment of effluent from the Asarco Furnace sedimentation wells is reported to have been implemented. No change in water quality is evident in early 1996 relative to the period March 1994-February 1995.

Any modifications made to operations affecting this effluent are unclear but significant reductions in Cu, Zn Fe and As concentrations are evident in early 1996 relative to the period March 1994-February 1995.

INDDIS.TBL

Sampling Site #

118

135

July 17, 1996

TABLE 15 Smelting Complex - Characteristics of Priority Discharges

CENTROMIN - La Oroya

Sampling Site Description Principal Conditions or Characteristics of Effiuent Constituents of Concern

(Ranking in Terms of Loading to Mantaro River)

A combination of effluents from Flow (1), TSS (1), Pb (1), Cu This is the highest volumetric discharge Cu-Pb Slag grinding and power (1), Fe (1), As (1), Cd (3), Mn (58 %) from the smelter complex. house (compressor) cooling water. (4), NO, (1), SO, (4) Water quality is neutral to slightly

basic, contains intermediate suspended solids and relatively low concentrations and metals, and low sulfate.

Principal Canal #1. A combination Flow (2), TSS (2), Pb (4), Cu Second largest volumetric discharge (14 of effluents from rhc smelter, coke (3), Zn (2), Fe (4), As (3), Cd %) from the smelting complex. plant, agglomeration plant acid (2), Mn (5), SO, (1) Neutral pH water with intermediate plant, zinc roaster and electrolytic zinc and sulfate concentration.~ and zinc refinery. relatively low concentrations of other

metals and nitrate.

Knight Piesold LLC

CENTROMIN-La Oroya-1450A 50A-SMEDIS.TBL

July 17, 1996

Comments

The identity of contributions to 118 are unclear but may include point sources with significantly different volumetric discharges and water quality. Isolation of these individual sources may change water treatment requirements. Recirculation of power house cooling waters is reported to have been implemented - other modifications are planned. Water quality improved in early 1996 but volumetric discharge remained the same.

Elimination liquid effluents from the coke plant and rehabilitation of the coke plant distillation circuit are reported to

have implemented. Flow remained unchanged in 1996 relative to early 1995 average but concentrations of TSS, Pb, Zn, and Fe decreased.

SMEDIS.TBL

Sampling Site # Sampling Site Description

119 Principal Canal #2. A combination of effi11ents from Warehouse #5, Cadmium Plant #2, lavatory wastes, waters associated with processing of copper slags, cooling water from copper anode molds, cooling water from fans associated with arsenic trioxide processing, cooling water for condensation of gasses from the lead furnace and waters from the silver refmery.

126 A combination of sewage, residual water from the lixiviation and purification unit of the electrolytic zinc plant, and cooling waters associated with electrical rectifiers.

136 Canal Parallel to Principal Canal # 1. A combination of effluents from cooling of the agglomeration machine, condensate water from the petroleum tank, runoff water, cooling water associated with the Kiln furnace, cleaning water from the hydrometallurgical plant and sewage.

July 17, 1996

TABLE 15 cont.

Principal Conditions or Characteristics of Effiuent Constituents of Concern

(Ranking in Tenns of Loading to Mantaro River)

Flow (3), TSS (3), Pb (2), Cu Third largest volumetric discharge (7 (2), Zn (5), Fe (3), As (2), Cd %) from the smelting complex. Acidic (1), N~ (2), so. (5) water containing intermediate

concentrations of most constituents

Flow (4), TSS (5), Pb (5), Cu Fourth largest volumetric discharge (6 (4), Zn (1), Mn (1), N~ (4), %) from the smelting complex. Acidic so. (2) water containing elevated

concentrations of zinc and sulfate and relatively low to intermediate concentrations of other metals, TSS and nitrate.

Flow (5), TSS (4), Pb (3), Cu Fifth largest vol11metric discharge (5 (5), Zn (3), Fe (2), As (4), Cd %) from the smelting complex. Acidic (5), Mn (2), so. (2) water containing elevated

concentrations of zinc, sulfate and TSS and relatively low to intermediate concentrations of other metals and niuate.

Knight Pi6sold LLC


50A-SMEDIS.TBL July 17, 1996

Comments

Any actions taken to reduce this source are unclear. Flow remained unchanged in early 1996 relative to 1995 average but concentrations of Pb, Cu, and Fe were gready decreased and concentrations of Zn and As were also reduced (except for February 1996).

Any actions taken to reduce this source are unclear. Flow appears to been reduced in early 1996 relative to 1995 average and concentrations of TSS, Pb, Cu, Zn, Fe and As were also reduced significandy (except for February 1996 TSS and Zn).

Any actions taken to reduce this source are unclear. Flow remained unchanged in early 1996 relative to 1995 average but concentrations of TSS, Pb, Cu, Zn and Fe were gready decreased (except for January 1996 Zn).

SMEDIS.TBL

Water Quality Sample# Date

World Bank Efflu Peru Standards

D-137 3/94-2/95 Avg Jan 96 Feb96 Mar96

Loadin Statistics

I Sample# I Date

M-4 3/94-2/95 Avg Load (kg/day)

M-5 3/94-2/95 Avg Load (kg/day}_

D-137 3/94-2/95 Avg Load (kg/day)

%of (M-5- M-4) (M-5)-(M-4) Load (kg/day)

Flow mJ/min

nt Guidelines

Flow 3/ . m mm

0.77 0.58 0.35 0.72

4929.94

4930.85

0.77

84.62% 0.91

Table 16 Discharges from Huanchan Slag/Zinc Ferrite Storage Facility

Water Quality and Loading Statistics CENTROMIN - La Oroya

pH su

6.0-9.0 5.5-10.5

'~4'

7.3 7

6.6

pH su

7.46

7.67

5.4

TSS mCIII

50 100

,., /67;5() 47

18.4 12.78

TSS 11 mg 37.9

269,056.41 28.91

205,273.26 87.56 97.09 .

-63783.15

,, ..... , ..

Pb mQ/1

0.6 1

"1.7'1 0.59 0.52 0.49

Pb /I mg 0.31

2,200.73 0.34

2,414.14 1.71 1.90

0.89% 213.42

Cu Zn mQ/1 mg/1

0.3 1 2 6

.. _, •.•.• ,, .• ,.,_. 0.$ >2560;89 0.03 Z41 0.06 ~ :::. :< . -: ·.··''267"' 0.08 ,,_,,,,_,, ... 257

Cu /1 mg 0.15

1,064.87 0.52

3,692.22 0.9

1.00 0.04%

2627.35

Zn /1 mg

12.34 87,603.06

5.31 37,703.25

2560.89 2,839.51 .

-49899.81

Fe mg/1

2 5

1.08 0.27 0.05 0.17

Fe /I mg 3.82

27,118.61 4.49

31,880.90 1.08 1.20

0.03% 4762.29

I As

mg/1 1 1

0.11 0.01 0.04 0.28

As 11 mg 0.21

1,490.81 0.21

1,491.09 0.11 0.12

44.32% 0.28

I < < I Represents exceedance of World Bank effluent guidelines and Peru standards •Apparent loading to Rio Mantaro is negative •-world Bank Effluent Guidelines- World Bank Environment, Health and Safety Guidelines, Mining and Milling -Open PiVUnderground ... Peru maximum permissible limits for liquid effluents for mining operations in existence prior to May 1993 (RM 011-96, Annex 2)


I

Cd mg/1

3.3

Cd /1 mg 0.06

425.95 0.03

213.01 3.3

3.66 . -212.93


~~~11

86.59

Mn /I mg 2.4

17,037.87 2.83

20,094.20 86.59 96.01

3.14% 3056.33

IN03 mg/1

0.33

N03 /1 mg 1.21

8,589.93 1.38

9,798.59 0.33 0.37

0.03% 1208.66

I!~~ I

4010.51

m 244.04

1,732,467.68 227.23

1,613,429.35 4010.51

4,446.85 . -119038.34

50A-OROYSLAG.WK4

TABLE 17

CENTROMIN-La Oroya-1450A 50A-OROYA. PEP

August 26, 1996

Existing Environmental Programs Programa de Ejecucion del Proyecto Arnbiental (PEPA)


PEPA PROJECT NAMES PROJECT STATUS OBJECTIVES

Domestic and Waste Water Initiated: September 1994 To define and develop Treatment System - La Status: 100% completed water treatment alternatives Oroya Completed: November 1995 for domestic waste waters

Manager: A. Comejo before they flow to the Supervisor: L. Sanchez Yauli and Mantaro Rivers.

The treatment system and method of waste disposal will be analyzed to determine the optimal methods of preserving the environment, population health and legal requirements.

Study for a Potable Water Initiated: September 1994 To develop engineering System - La Oroya Status: 100% completed studies that will identify

Completed: November 1995 optimal alternatives to the Manager: A. Cornejo current waste storage Supervisor: A. Quispe system.

The implementation of any anyalternative should guarantee that the quality and the distribution of the potable water will preserve the health of the population and comply with legal requirements.

August 26, 1996 Knight Pieso1d LLC OROY.PEP

Knight Piesold

Photo 3 - Zinc Ferrite deposits at HuancMn

Photo 4 - Malapaso arsenic trioxide deposit (inactive)

Knight Piesold -

Photo 5 - Vado arsenic trioxide deposit Operational deposit (right), Pilot reclamation (left)

Photo 6 - Soils affected by La Oroya air emissions Oroya Smelter emissions in background


1.0 INTRODUCTION

APPENDIX A

Ambient Monitoring Network Description

CENTROMIN-La Oroya-14SOA SOA-OROY A6.FNL September 18, 1996

As of March, 1994, Peruvian Government regulations require that all mining and metallurgical

companies establish an ambient monitoring program. Ambient monitoring protocols (Marlatt,

1994) were published to standardize the monitoring program procedures for all such companies.

These protocols were used to evaluate the existing ambient monitoring network at La Oroya.

Ambient air quality is currently monitored at five sites in the vicinity of the La Oroya smelting

complex. One of the sites, Sindicato, is located in the immediate vicinity of La Oroya in the

Mantaro River Valley. The Huanchan and Hotel Inca sites are located 2 kilo meters south

southeast and west northwest of La Oroya, respectively, in the 'Mantaro River Valley. The

Cushurupampa site is located about 3 kilometers west in the Yauli River Valley. The Casaracra

site is located 10 kilo meters to the northwest, also near the Mantaro River Valley.

Based on regional topography, typical mountain meteorology and limited meteorological data that

have already been collected, it appears that the monitoring sites are located generally upwind of

La Oroya, except for Huanchan. Selection criteria for the establishment of air monitoring

stations included the monitoring protocol established by the MEM as well as: accessibility to the

area; availability to a power source; security from vandalism, representativeness of the area

(urban, semi-urban, rural); environmental conditions in the region; and the location of impacted

areas. The site selection generally conforms with the monitoring protocol guidance which

indicates that monitoring sites should be located at the following locations:

• near the emission source,

• at the nearest downwind population center,

• at a rural upwind location typical of background conditions, and



• at sites of sensitive agricultural or natural ecological interest.

Sindicato is located very near the emission source (within less than 1 km). Hotel Inca, as well

as Sindicato, are both representative of the nearest population centers (La Oroya and La Oroya

Antigua). Note that there are no nearby population centers downwind. Casaracra is

representative of background conditions since it is located 10 km upwind. Huanchan is located

in the area of expected maximum impacts immediately downwind of the smelter complex.

Cushurupampa documents weather and pollutant impacts in the Yauli River Valley which is the

nearest tributary to the Mantaro River Valley. The Yauli River flows into the Mantaro River

about 1 km upstream of the smelter complex. There are no significant agricultural sites near

La Oroya.

Ambient concentrations of sulfur dioxide (S02), total suspended particulate matter (PM) and

heavy metals (As, Pb, and Cd) are sampled at all of the sites. Particulate matter with

aerodynamic diameter less than 10 ,urn (PM-10) is sampled at Hotel Inca and Sindicato.

Meteorological parameters (wind speed and wind direction) are sampled at only two sites,

Huanchan and Cushurupampa.

1. 1 Observations

Site visits to each monitoring station were conducted on May 8, 1996. The visits

identified concerns in the areas of instrumentation siting, instrumentation maintenance, and

sample analysis procedures. These concerns are directly related to data quality and usefulness.

Generally, the data are adequate for estimating relative areas and times of high or low pollutant

impacts, and they provide an indication of overall air quality, but they may not be adequate for

assessing compliance with any specific air standard or determining a precise maximum impact

level. The meteorological data collection sites probably do not provide a complete definition of

regional dispersion meteorology. Some specific observations regarding significant issues are

discussed below.

2

Knight Piesold -------CENTROMIN-La Oroya-1450A


The Huanchan site is located very near a large slag pile. The slag pile likely affects the

wind data collected there. While this facility can assess the stability of the Huanchan site, the

obstruction to normal air flow created by the slag probably explains the absence of a

predominate wind direction along the valley axis in measurements from Huanchan. Such flows

are typical in steep mountain valleys, and they are evident in the wind rose for the other

meteorological monitoring site at Cushurupampa. In order to obtain representative wind data

in the Mantaro River Valley, the Huanchan site would need to be moved to a location free of

nearby obstacles.

Periodic maintenance of the monitoring instrumentation is important to ensure data

quality. Maintenance includes items such as regular instrument calibrations. The Preliminary

Ambient Evaluation (EVAP) (CENTROMIN, 1995) referred to a six month calibration schedule.

However, specific documentation regarding calibration and audit schedules was not identified

during the evaluation. Because of the importance of these activities, the calibration schedule

should be reviewed.

Sample analysis procedures for PM filter weighing allow for the introduction of errors

that could bias the sampling results. For example, the filters from various sampling days and

sites are stored side-by-side so that dust from one sample filter could be transferred to another

filter. The filters are not stored in individual folders or envelopes. Latex gloves are not used

during filter handling. Although filters are dried before pre- and post-weighing, reproducibility

of environmental conditions (i.e. relative humidity) during weighing was not evident. General

quality control during sample analysis needs to be reviewed and upgraded where necessary.

All but one of the S02 analyzers and all PM and PM-10 analyzers are manufactured by

Kimoto, which is a brand recommended in the monitoring protocol document. The technology

utilized by Kimoto in the CENTROMIN S02 analyzers is antiquated and has not been widely

3



used in the U.S. during the last 15 to 20 years. Nevertheless, these instruments are probably

adequate for use so long as appropriate maintenance and sample analysis procedures are utilized.

4

Photo 2 - Lead and copper slag deposits at Huanchin, La Oroya

11

'11

.,,

11

·1r

11

11

11

11

11

11

11

11

Knight Piesold -

Photo 1 - La Oroya Smelting Complex wit

' '===================

mplex with the Mantaro river in the foreground

Smelter Waste Water

Central Water Collection and Storage

Lime Slurry

' ob ,.....----t--~-

Filtrate

Filtration

CO

PH Reduction

To r-----~~~--------~~ pH10.8 Settler/ River

..._ Clarifier ..-

Polymer addition

Recycle Water...--------. .----.---~

Sludge De watering t Polymer

eo

Sludge to recycle or disposal

Sludge Storage Tank

Backwash Backwash water pumped to head of circuit -Collection tank

Cll£NT PROJECT TITLE Empress Miners del Centro LA OROYA CONCEPTUAL DESIGN

tJel Peru.~. S.~. METALLURGICAL FOR METAL REMOVAL FROM tCENTRvMIN, COMPLEX SMELTER WASTE WATER

Knight Piesold LLC~---------------+------~--------~ CONSULTING E-0:11$ AND I:HVI-IoiiHTAL SCIENTISTS PROJECT NO 1450A DATE tJ/Ot!J/961FIGURE 5

·-- ------~------------..__ ___________ -~... ___________ --~, _____ __._ _____ ___,

E 7,200

Lead Refinery

ASARCO Oven

(Y-2 is downstream of point indicated on map)

Laboratory

n orosilicic Acid Plant

TO L I M

Larox Filter

Sedimentation Well

REFERENCE: LEGEND: Digitized from Centromin drawing No.: B-1-590-00454, Titled: "Piano General Huaymanta Refineria y Construccion", Revised: July, 1996.

1=76.2 ocu

R-1 • Effluent Monitoring Station

River Monitoring Station

XREF FILE NAME: N/A AUTOCAD Fll..E NAME: 1 450:

~~Ah=========-=-=-=-=-=-=-=t=-__.

1LE NAME: N/A lLE NAME: 1450F02A

NOTES: !. This map is to be used for planning

purposes only. lt is not to be used for engineer/ng design.

2. This drawing is not to scale. Approximate scale 1:3,000.

3. Map shows only selected facti/ties at the complex.

CLIEflfPRESSA MINERA del PROJECT

CENTRO del PERU, S.A. (CENTROMINI

CENTROMIN, PERU S.A. LA OROYA

Knight Piesold LLC PROJECT No 1450A ~TlHO ~[I:RS- -IITAL ~

TITLE HUA YMANT A REFINERY

COMPLEX AND EFFLUENT MONITORING STA TIOHS

!DATE 07/22/961 FIGURE 4

METAlWRGICAL

I.AiiiORATORY ATMENT PLANT ZINC RESIDUE TRE

ZINC FOUNDARY

ZINC LEACHING :ro FILTRATION PLA

~·~ARSENIC L_________j--.- COTTREL

LEAD CONCENTRATE

ooooc ACID TAN!

CADMIUM PLANT No. 2

D COPPER BOA/:TEB PI ANT

0 ACIDTANI(S

NTNo. 2

.. r·---,

AROIINFO Fie: 146GOCWIA

·-- La Oroya smelur ju:llities

<I> 1 fB -EJI.uDII monitoring sttJtion

SOURCES FROM CENTROMIN: DJ•awing Number: MS1-69Q-00455 1itle: 'FUNDI CION OROYA, MAPA DE LA PLANTA' L.ut Revised: May 1994

1l1is map is to be used for planning purposes only. lt is not to be used for engineering design.

\ MEillRS .------·----------' 0 40 80 120 160

Empresa Minera del Centra del Peru, S.A. (GENTROMIN)

flGURE3 L.cl OROYA SMELTER COMPLEX AND EFFLUENT MONITORING STATIONS

~·------------------------------------~

li!!i&~!.!l~!!!!!!!:l:Tl£ June 5, 1996- Denver, Colorado

11.5? s

12.5° s

13.5° s

.. ..

OCEANO PACIFICO

~ 0 . an ,... ,...

·.·~ 0 ,... ,...

,·

. ·~ ... ~.,···; ·. ~-1 (J~/

~0,/ ,/ .. // I

~HUAT

LagoHuarmica

\

Huarmicachk .\ ') HU~GAV~ICA

0 an ... &ri .....

I I

\

I I

ARCIINFO Fie: 1-GO:!/\

~:.

----·

-' .-+-!--+-+-

I"-

•

8tretl1Piif and canals

Pri:mtuy roads

Secondary roails

Tmils

Railroad

Railroad P,bantltmed)

Re)Mry

KILOMEml\5 .-----·----· ··-·-···-···' 0 15 3() 45 60

Empresa Minera del Centro del Peru, S.A. (CENTROMIN)

FIGURE1 LOCATION MAP OF LA OROYA METALLURGICAL COMPLEX

!!!!G!l.!.!Jl!,~!t!f~£ June 5, 1996- Denver, Colorado

ARCIINFOFh: 141i11QQSA

- Re)Mry

1 [ Anenic Trioxide Deposit

- La Oroya prt~perty bmi.ndariu

• Water Monitt~ring Site

NOTE: Coordinates are in UTM Zone 18

SOURCES FROM CENTROMIN: Drawing Number: PRE-05-94 Ti';le: 'LA OROYA- PUNTOS DE MUESTREO DE AGUAS' Last Revised: 1994

TI-ds map is to be used for planning purposes only. lt fS not to be used for engineering design.

MEIERS r----·----- __ _____. 0 500 1000 1500 2000

Empresa Minera del Centra del Peru, S.A. (GENTROMIN}

F!GURE2 L4 OROYA METALLURGICAL COMPLEX

Knight Pie sold LLC CONSULTING ENGINEERS AND ENVIRONMENTAL SCIENTISTS

June 5, 1996- Denver, Colorado

TABLE 17 cont.

Management of Arsenic Initiated: August 1994 Trioxides - La Oroya Status: 70% completed

Completion Date: June 1996 Manager: A. Comejo Supervisor: G. Oporto

August 26, 1996 Knight Piesold LLC


SOA-OROY A.PEP August 26, 1996

1) Study of the current process of Arsenic Trioxide Production in efforts to improve the quality of the product. The feasibility of installing a refmery capable of producing 99% pure trioxides for commercial sale will be defmed.

These actions will be taken to reduce the storage of these trioxides.

2) To evaluate the current storage methods of arsenic trioxides to determine optimal management alternatives and propose a new storage area.

3) To define plans for abandonment of the Malapaso and Vado deposits. Included would be an investigation of the existing arsenic trioxide impacts upon to the Mantaro River and ground water resources.

OROY.PEP

TABLE 17 cont.

Huanchan Wastes, Initiated: June 1994 Recirculation of Slag Status: 80% completed Granulation Waters Completion Date: March

1996 Manager: A. Comejo Supervisor: A. Quispe

August 26, 1996 Knight Piesold LLC


50A-OROYA.PEP August 26, 1996

To develop engineering. studies oriented at reducing Cu and Pb slag contamination of the Mantaro River by avoiding the emission of effluents and solid wastes. Recirculating the liquid effluents is the preferred method to optimize and complement the current transport and storage of these wastes.

OROY.PEP

CENTROMIN-La Oroya-1450A 50A-OROY A.PEP

August 26, 1996

TABLE 18 Terms of Reference for Proposed Studies


!sTUDY Processing of Iron Zinc Complexes at the La Oroya Smelter

Mitigative Actions Taken by CENTROMIN

Closure Plan for the Smelter Copper and Lead Slags

Integral Evaluation of the Area Impacted by Air Borne Particles From the Smelter

I OBJECTIVE

To process the Iron Zinc complexes in the deposits at Hunachan.

To avoid hazards to the environment in accordance with current and future regulations.

To complete a Closure Plan for the copper and lead slags from the smelter and to develop a Contingency Plan for the extreme situations that could present environmental risks.

To characterize the gases emitted from the metallurgical complex, establish the existing air quality and base line and determine the impact of the gases on the area of influence. To recommend mitigative methods for the existing situation and for the prevention of future environmental deterioration. Recommend methods to progressively reduce air quality impacts. To verify migration routes of solid particulates in the atmosphere, determine the receptor areas and establish the levels of existing contamination. To design a monitoring program to lower atmospheric emissions of gas and particulates. To design and/or adapt a computerized mathematical model of contaminant dispersion that determines effects to the atmosphere resulting from the mitigative recommendations.


TABLE 18 cont. CENTROMIN-La Oroya-1450A 50A-OROYA.PEP

August 26, 1996

Plan for Temporary Closure and/or Processing of Zinc Leachate Residue (RLZ) from the Smelter

Closure Plan for Arsenic Trioxide Deposits from V ado and Abandoned Deposits from Malpaso

Closure Plan for the Metallurgical Complex

To reduce the general contamination due to runoff and precipitation from the RLZ deposits from the smelter. To improve the techniques for processing the RLZ located in Huanchan at the industrial level to result in a final residue less harmful to the environment. To develop a temporary closure plan for the zinc ferrites deposits in order to reduce the contamination from: the effluent produced in pulp sedimentation, the runoff across the leaching deposits and the filtration affecting surface and ground water. To eliminate the dispersion of solid residues from erosion in the vicinity of the deposits.

To complete a Closure Plan for the Arsenic Trioxide Deposits located in Vado and develop a design for a new deposit location for the arsenic trioxide. To develop a plan for abandonment of the arsenic trioxide deposits in Malpaso. To develop a contingency plan on extreme situations that could present environmental risks.

To complete a closure plan for the Metallurgical complex and develop a contingency plan on extreme situations that could present environmental risks.


Documents

Environmental Evaluation of La Oroya Metallurgical Complexicsidfiles.worldbank.org/icsid/ICSIDBLOBS/OnlineAwards/C3004/C-008_Eng.pdf · installed Larox filtering system (operational