FINAL
SAN MANUEL
SULFUR DIOXIDE NONATTAINMENT AREA
STATE IMPLEMENTATION
AND
MAINTENANCE PLAN

AIR QUALITY DIVISION
ARIZONA DEPARTMENT OF ENVIRONMENTAL QUALITY
JUNE 2002

TABLE OF CONTENTS

1.0

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1
Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2
Regulatory Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3
Physical, Demographic, and Economic Description of the San M anuel Area . . . . 7
1.3.1 Climate and Physiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.2 Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.3 Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4 General SIP Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4.1 CAA Section 172(c), Nonattainment Plan Provisions . . . . . . . . . . . . . . . 11
1.4.2 CAA Section 175(A) - M aintenance Plans . . . . . . . . . . . . . . . . . . . . . . . 14
1.4.3 CAA Section 191 and 192 - Plan Submission and Attainment Dates . . . 15
1.4.4 Conformity Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.0

COM PLIANCE WITH OTHER FEDERAL REGULATIONS . . . . . . . . . . . . . . . . . . 16

3.0

SO2 M ONITORING NETWORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1
Current Sampler Type and Siting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2
Ambient Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.0

SO2 EM ISSIONS INVENTORY FOR POINT, AREA AND M OBILE SOURCES . . 26
4.1
SO2 Point Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.1.1 Oracle Compressor Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.1.2 BHP Copper San M anuel Smelter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1.3 BHP Copper M ining and M illing Operations . . . . . . . . . . . . . . . . . . . . . 28
4.2
M ajor Point Sources within the 50 km Buffer Area . . . . . . . . . . . . . . . . . . . . . . 28
4.2.1 Arizona Public Service (APS) - Red Rock . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.2 Tucson Electric Power Co. Irvington . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.3 Tucson Electric Power Co. North Loop . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.4 ASARCO Hayden Smelter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3
Area, M obile, and Total Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.4
Emissions Projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.4.1 Point Source Projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.4.2 Area, M obile, and Total Source Projections . . . . . . . . . . . . . . . . . . . . . . 32

5.0

M ODELING DEM ONSTRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
ii

5.1

5.2

Derivation of New Emissions Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.1.1 Stack Emissions Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.1.2 Fugitive Emissions Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.1.3 Emissions Reductions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Smelter Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

6.0

CONTROL M EASURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.2
Emissions Limitations for BHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
6.2.1 AC Rule R18-2-715(F)(1), R18-2-715(G) and R18-2-715.01 - Standards
of Performance for Existing Primary Copper Smelters: Site specific
requirements; Compliance and M onitoring . . . . . . . . . . . . . . . . . . . . . . . 45
6.2.2 AAC Rule R18-2-715.02 Standards of Performance for Existing Primary
Copper Smelters; Fugitive Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
6.2.3 BHP Permit Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

7.0

M AINTENANCE PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
7.1
M aintenance Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
7.2
Ambient M onitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
7.3
Verification of Continued Attainment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
7.4
Contingency Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
7.4.1 Notification Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
7.4.2 First Action Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
7.4.3 Second Action Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
7.4.4 Special M easure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

8.0

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

iii

LIS T OF TABLES

CHAPTER ONE:
Table 1.1 - Study Area Definition
Table 1.2 - Census Information
Table 1.3 - Population Projections
Table 1.4 - Pinal County Economic Activity
Table 1.5 - Labor Force Data for San M anuel CDP
CHAPTER THREE:
Table 3.1 - Ambient M onitoring Network Data
Table 3.2 - Current M onitoring Network
Table 3.3 - SO2 Ambient Air Quality M onitoring Data
CHAPTER FOUR:
Table 4.1 - SO2 Emissions for San M anuel Nonattainment Area - Point Sources
Table 4.2 - SO2 Emissions for San M anuel Nonattainment Area - 50 Km. Buffer
Table 4.3 - SO2 Emissions for San M anuel Nonattainment Area - All Sources
Table 4.4 - SO2 Emission Projections for San M anuel Nonattainment Area - Point Sources
Table 4.5 - SO2 Emission Projections for San M anuel Nonattainment Area - 50 Km. Buffer
Table 4.6 - SO2 Emission Projections for San M anuel Nonattainment Area - All Sources
CHAPTER FIVE:
Table 5.1 - San M anuel Smelter Configuration (1974 to Present)
Table 5.2 - San M anuel Smelter SO2 Emissions (1974 to Present)
Table 5.3 - Emissions Source Distance from Facility Boundary
CHAPTER S IX:
Table 6.1 - Implementation of SO2 Control Technology
Table 6.2 - Permit Conditions

iv

v

LIS T OF FIGURES

CHAPTER ONE:
Figure 1.1 - San M anuel SO2 Nonattainment Area
Figure 1.2 - San M anuel SO2 Nonattainment Area Latitude and Longitude
CHAPTER THREE:
Figure 3.1 - Locations of Fugitive/Stack Ambient M onitor Sites
Figure 3.2 - Close-Up of Ambient M onitor Sites
CHAPTER FOUR:
Figure 4.1 - SO2 Point Sources
CHAPTER FIVE:
Figure 5.1 - Comparison of 1979 and 2001 M PR Limits
Figure 5.2 - 99th Percentile Total Emissions and Ambient Concentrations
CHAPTER S IX:
Figure 6.1 - Comparison of SO2 Emissions and Percent Control
Figure 6.2 - Comparison of SO2 Emissions and Copper Production
CHAPTER S EVEN:
Figure 7.1 - San M anuel Nonattainment Area SO2 Emissions Projections

vi

1.0

INTRODUCTION

1.1

Executive S ummary

This document includes an attainment demonstration and formal request to the United
States Environmental Agency (EPA) to redesignate the San M anuel, Arizona area, a
nonattainment area for sulfur dioxide (SO2 ), to attainment for the health-based 24-hour average
and annual average SO2 National Ambient Air Quality Standards (NAAQS). It summarizes the
progress of the area in attaining the SO2 standard, demonstrates that all Clean Air Act (CAA)
requirements for attainment have been adopted, and includes a maintenance plan to assure
continued attainment after redesignation.
The air quality record included in Chapter 3 of this document shows that ambient air
quality monitors located in the San M anuel nonattainment area have recorded no violations of the
primary SO2 NAAQS since 1979 or secondary SO2 NAAQS since 1985. This meets the EPA
requirement for demonstrating a minimum of eight consecutive quarters of ambient air quality
measurements that are below the SO2 NAAQS.
This document also demonstrates that the emission reduction control measures
responsible for the air quality improvement are both permanent and enforceable. Based on state
point source and EPA National Emissions Trends (NET) mobile and area source emissions
inventories, the primary source of SO2 in the nonattainment area is the copper smelter located
near San M anuel, Arizona. The 1998 base-year San M anuel nonattainment area emissions
inventory, presented in Chapter 4, lists the sources in the nonattainment area and their SO2
emissions. Details of the of the updated modeling demonstration are contained in Chapter 5.
Chapter 6 describes the primary control measures implemented to achieve attainment. These
measures include implementation of reasonably available control measures (RACM ) to reduce
emissions from the smelter near San M anuel.
Chapter 7 describes in detail measures designed to ensure continued maintenance of the
SO2 NAAQS for at least ten years after redesignation of the area to attainment.
The clean air quality record, enforceable control measures, and projections of future
emissions presented in this document, all demonstrate that the area has attained and will continue
to maintain the SO2 air quality standards. With this submittal, ADEQ requests that EPA
approve this attainment demonstration and maintenance plan for the San M anuel SO2
nonattainment area and redesignate the area to attainment for the 24-hour and annual NAAQS.
1.2

Regulatory Background

The federal air quality standards for SO2 were established to identify maximum ambient
concentrations above which adverse effects on human health and welfare may occur.
Accordingly, the SO2 standards are divided into two types: primary and secondary. The primary
standards are based on the protection of public health and the secondary standard is based on
1

protection of the environment, including protection against damage to animals, vegetation,
buildings, and decreased visibility. The original national primary and secondary NAAQS for SO2
were codified in Volume 42 of the Code of Federal Regulations, Part 410 (42 CFR 410) on April
30, 1971, (36 FR 81875) and recodified to 40 CFR 50.4 and 50.5 on November 25, 1971 (36 FR
22384). On M ay 22, 1996, the EPA promulgated the current primary and secondary NAAQS
for SO2 (61 FR 25566) as follows:1
Standard 2

Annual
0.030 ppm (80 Fg/m3 )

Primary

24-hour

3-hour

0.14 ppm (365 Fg/m3 )
0.5 ppm (1300 Fg/m3 )

Secondary

Areas that do not meet the NAAQS may be designated nonattainment for the respective
standard. The San M anuel SO2 nonattainment area initially comprised all of Pima and Pinal
Counties (43 FR 8968, M arch 3, 1978) but at the request of the state of Arizona, the boundaries
were subsequently reduced to eleven townships in and around San M anuel (44 FR 21261, April
10, 1979). In addition, four adjacent townships were designated as unclassified (See Figure 1.1
for location map).

1

Several technical changes were made at this time including stating the standards in parts per million (ppm) to make the SO2

NAAQS consistent with those for other pollutants. The former standards, stated in micrograms per cubic meter (ug/m3) are in parentheses.
2

Violations of the primary and secondary standards are determined as follows: The annual arithmetic mean of measured

hourly ambient SO2 concentrations must not exceed the level of the annual standard in a calendar year. The 24-hour and 3-hour averages of
measured concentrations must not exceed the level of the respective standard more than once per calendar year (two exceedances of the
standard per year is a violation of that standard).

2

3

All but one of the townships that define the nonattainment area are located in southeastern Pinal
County, with the remaining southernmost township located in neighboring Pima County. The
current boundaries of the nonattainment and unclassified areas are codified at 40 CFR 81.303 and
are defined by the following complete townships:
Table 1.1 - Study Area Definition
San Manuel Area
Description

Does Not Meet
Primary
Standards

T8S, R16E

X

T8S, R17E

X

T8S, R18E

X

T9S, R15E

X

T9S, R16E

X

T9S, R17E

X

T9S, R18E

X

T10S, R15E

X

T10S, R16E

X

T10S, R17E

X

T11S, R16E

X

Cannot Be
Classified

T10S, R18E

X

T11S, R17E

X

T12S, R16E

X

T12S, R17E

X

The relationship between major SO2 point sources and ambient air quality is relatively welldefined. Emissions inventories demonstrate that the BHP Copper (formerly M agma Copper
Company) San M anuel smelter comprises 99 percent of total SO2 emission in the nonattainment area
(See Chapter 4). The primary copper smelter is located near the town of San M anuel, Pinal
County, Arizona; at latitude 32E36'58" N and longitude 110E37'19" W, at an elevation of 3,208 feet
A s required by t he Clean Air A ct
above mean sea level (See Figure 1.2, on the next page).
(CAA), Arizona submitted a State Implementation Plan (SIP) for all major sources in the state in
1972. The portion of the SIP pertaining to attainment and maintenance of the NAAQS for SO2 did
4

not sufficiently define emissions limitations or require permanent control of emissions for existing
copper smelters and was, therefore, disapproved on July 27, 1972 (37 FR 15081). On the same
date, EPA proposed revised regulations for control of sulfur oxides emitted by all existing smelters
in Ariz ona (37 FR 15096). These regulations were never finalized due to issues regarding the
adequacy

5

6

of the air quality data used to develop the limits. EPA subsequently established an SO2 monitoring
network around each smelter (June 1973 - October 1974) to gather air quality data upon which to
base emissions limitations.
EPA and State efforts to develop comprehensive emissions limits continued through the
1970s. In 1977, the State developed rules for the use of Supplementary Control Systems (SCS),
whereby, based on ambient monitoring data, the smelters could intermittently curtail emissions to
meet the SO2 NAAQS. EPA disapproved this approach and required installation and operation of
SO2 emissions controls at all times to adequately to meet the NAAQS. Consequently, on January
4, 1978, EPA published final emissions limits for the Arizona smelters based on the 1973-1974 air
quality data and the use of a proportional rollback model (43 FR 755). These regulations specified
an emission rate and appropriate compliance test methods for each smelter. The 1977 Clean Air Act
Amendments, however, modified smelter control requirements to allow the temporary use of SCS
while the ultimate SO2 emission limits were developed and also allowed certain smelters additional
time for emissions control technology to be installed. In response to this action, Arizona began
development of new regulations and on September 20, 1979, submitted M ulti-point Rollback (M PR)
rules as a proposed revision to the Arizona SIP.3
The use of M PR to establish emissions limits in the rules addressed the p roblem of
inherently variable SO2 emissions from smelting operations by correlatingthe frequency of emissions
at various levels with the probability of violating the ambient standards. This technique, “rolled
back” a yearly emission profile to a level protective of the standards. The new regulations also set
requirements for analyzing the impact of smelter SO2 fugitive emissions on ambient air quality and
the implementation of any necessary fugitive controls. The San M anuel area was subsequently
classified by operation of law as nonattainment for the primary SO2 standards by EPA following
the enactment of the 1990 Clean Air Act Amendments. The nonattainment designation became
effective on November 15, 1990.
The M PR rules, which established stack emission limits for the smelters, were approved by
EPA on January 14, 1983 (48 FR 1717). Following EPA’s approval of the rule, a consent decree
between EPA, ADEQ and M agma Copper Company, now owned by BHP, (#CIV 87-106-TUCWBD, dated September 28, 1987) was agreed to and required implementation of improved control
technology, including replacement of reverberatory furnaces with a flash furnace, installation of
converter secondary hoods for capture and venting of gases to the stack, and a double absorption acid
plant retrofit. These controls significantly reduced emissions and allowed the smelter to come into
compliance with the emissions limits in the M PR rules. The San M anuel smelter came into full
compliance with the M PR regulations in November 1988. Additional consent decree requirements
to install and operate fugitive capture systems on the new flash furnace, as well as the existing
copper converters, also reduced smelter fugitive emissions.
On April 3, 1986, BHP submitted to the State [Arizona Department of Health Services

3

Arizona Code of Rules and Regulations (ACRR): Rule (R)9-3-515 (recodified as Arizona Administrative Code (AAC) R18-2-

715, Standards of Performance for Existing Primary Copper Smelters; Site-specific Requirements)

7

(ADHS)] a plan describing SO2 fugitive emission units, its evaluation, and a demonstration study,
to partially fulfill outstanding SIP commitments for analysis of fugitive emissions. The results of
a fugitive SO2 emissions study of the launders (where slag and matte tapping operations occur) was
submitted on November 18, 1989. A Differential SO2 Ambient Impact Assessment Report was
completed and submitted on January 28, 1993. Subsequently, on M arch 24, 1998, BHP was issued
a Significant Permit Revision (Permit Number 1000681) that allowed the company to perform
multiple equipment upgrades for certain smelter equipment. These upgrades were completed during
a 45-day shutdown beginning in M ay 1999. Although the upgraded smelter was functionally ready
to operate at the end of June 1999, BHP made a decision to temporarily cease operations due to low
copper prices. In 2001, BHP anticipated restarting smelting operations. However, since the smelter
was shut down for more than two years, BHP was required to perform an air quality impact analysis
pursuant to Arizona Administrative Code (AAC) Title 18, Chapter 2, Article 4 (R18-2-411) prior
to resumption of operations and demonstrate that the startup would not cause or contribute to a
violation of the national ambient air quality standards for SO2 .4 BHP conducted the ambient impact
analysis at much lower emissions limits than those stated in the M PR SIP rules. The demonstration
analyzed maximum actual stack and fugit ive emissions, in relation to resulting ambient
concentrations. Based on this analysis, BHP applied for and received a permit revision in 2001 to
incorporate these more stringent emission limits in the permit. A 2001 rulemaking revised R18-2715 to new incorporate the new emissions limits. The revisions further reduced the smelter’s stack
emissions limits and added new limits for converter roof fugitive emissions (See Appendix A). The
new limits provide a considerable margin of safety to ensure protection of the SO2 NAAQS
throughout t he maintenance period to year 2015, thus allowing the state to request the area be
redesignated to attainment for SO2 .
1.3

Physical, Demographic, and Economic Description of the S an Manuel Area

1.3.1

Climate and Physiography

Both desert terrain and mountain ranges are found within Pinal County’s landscape.
Elevations range from near 2,000 to more than 6,000 feet above sea level in the nonattainment area
with the town of San M anuel situated at an elevation near 3,400 feet. This unique environment
experiences both warm desert and cool alpine climates. In San M anuel, the hottest month of the
year is July, when the average daily maximum temperature is 97o Fahrenheit (F). January is the
coolest month with an average daily minimum temperature of 35o F.
Precipitation generally occurs in two seasons. The wettest month in San M anuel is July
when monsoonal thunderstorms produce an average monthly total of 2.67" (inches) of rain. Pacific
winter storms moving across the area in December produce an average of 1.51" monthly precipitation
in the form of rain or snow. The driest month is June, with an average of 0.25" of rain. The average
4

See Appendix A for all pertinent sections of Arizona Administrative Code in this document.

8

yearly precipitation is 14.59".
1.3.2

Population

San M anuel is located in the broad San Pedro River Valley of southeastern Pinal County.
M ammoth and Oracle are located within a ten-mile radius. Florence, located in the central Pinal
County, is the county seat.
Although the growth rate of the San M anuel census designated place (CDP) exceeded 25
percent during the 1970s, by 1990 it lost 30 percent more inhabitants than it gained during the
1970s.5 The 2000 Census showed that San M anuel grew at a rate of 9 percent during the 1990s. In
comparison, M ammoth continued to lose population during each of the three decades. The Oracle
CDP gained more than 22 percent and 17 percent during the 1980s and 1990s, respectively.
During the 1970s when rural counties outpaced the growth of urban counties in the U.S.,
Pinal County grew by more than 32 percent. The county’s growth was 28 percent during the 1980s,
but it sharply increased to 54 percent during the 1990s. The state grew at 40 percent during the
1990s. Decennial census data for San M anuel CDP, M ammoth, Oracle CDP, and Pinal County are
shown in Table 1.2.
Table 1.2 - Decennial Census Population of San Manuel CDP, Mammoth, Oracle CDP,
and Pinal County: 1970-2000
Year

April 1,
1970

April 1, 1980

April 1,
1990

April 1, 2000

San Manuel CDP

4,332

5,443

4,009

4,3756

25.6%

-26.3%

9.1%

1,906

1,845

1,762

Mammoth’s decennial change

-2.4%

-3.2%

-4.5%

Oracle CDP 7

2,484

3,043

3,563

22.5%

17.1%

116,397

179,727

San Manuel’s decennial
change
Mammoth

1,953

Oracle’s decennial change
Pinal County

5

68,579

90,918

Census Designated Places (CDPs) are delineated for decennial censuses. CDPs are places that are not legally incorporated

and represent the statistical counterparts of incorporated places.
6

The 2000 Census shows a population of 4,375 with 1,832 housing units of which 1,458 are occupied (20.4 percent vacant). The

number of occupied housing units equals the number of households residing in San Manuel with 3.0 persons per household. San Manuel has
no group quarters population.
7

No data available for 1970.

9

Table 1.2 - Decennial Census Population of San Manuel CDP, Mammoth, Oracle CDP,
and Pinal County: 1970-2000
Year

April 1,
1970

Pinal’s decennial change

April 1, 1980

April 1,
1990

April 1, 2000

32.6%

28.0%

54.4%

Source: U.S. Bureau of the Census, decennial census counts.

Arizona Department of Economic Security (DES) population estimates are the official
statis t ics for the State and differ slightly from the 2000 Census population counts. Table 1.3
portrays the DES projected growth of San M anuel CDP, M ammoth, Oracle CDP, and Pinal County
in five-year increments from 2000 to 2015. Projected populations by the DES for Pinal County for
2000 is ten percent lower than the 2000 Census population. The Oracle CDP and M ammoth,
however, have DES projected populations for 2000 that are higher than the 2000 Census populations
by about 37 percent and 15 percent, respectively. According to the Arizona Department of
Economic Security, Oracle CDP and M ammoth are p rojected to grow about 44 percent and 6
percent, respectively, between 2000 and 2015. San M anuel CDP is projected to grow 7 percent
during this same time period.
Table 1.3 - Population Projections for San Manuel CDP, Mammoth, Oracle CDP, and,
Pinal County: 2000-2015
Year

July 1,
2000

July 1,
2005

July 1,
2010

July 1,
2015

San Manuel CDPP

4,392

4,503

4,604

4,698

Mammoth

2,020

2,066

2,108

2,146

Oracle CDP

4,909

5,687

6,402

7,048

Pinal County

161,630

181,487

199,715

216,215

Source: Arizona Department of Economic Security, August 1, 1997.

1.3.3 Economy
Pinal County was created in 1875 from portions of M aricopa and Pima Counties by the
eighth territorial legislature. The county covers 5,371 square miles. The State of Arizona is the
county’s largest landholder with 35.3 percent. Individual and corporate ownership accounts for 25.7
percent of the land area. Indian reservations cover 20.3 percent; the US Forest Service and Bureau
of Land M anagement hold 17.5 percent; and other public lands comprise the remaining 1.2 percent.
Pinal County is a great source of mineral wealth. Silver originally attracted settlers to the area, but
as the silver resources were depleted, copper was mined. In 1944, M agma Copper Company
10

purchased existing mining claims in the eastern portion of the county and launched a development
and exploration program. In 1996, M agma was purchased by BHP Copper, which in 2001 became
known as BHP Billiton.
Accordingto the most recent publication of County Business Patterns, economic sectors with
more than 3,000 employees in Pinal County include: mining (3,214), manufacturing (4,151), retail
trade (4,532), health care and social as s is t ance (3,022), and accommodation and food services
(3,653).8 Data exclude agricultural production employees and most government employees, as well
as self-employed, employees of private households, and railroad employees.
Table 1.4 contains employment, expressed as percentages of total nonfarm employees, for
Pinal County for 1994, 1997, and 2000. This table also includes labor force data. Table 1.4 is
included to demonstrate the decline in mining and quarrying activities and the relatively consistent
proportions of the other economic activities in the county.
The major local emp loyer in San M anuel has been BHP Copper Smelting and Refining
Company that operated underground and open pit copper mines and associated activities. However,
the operations were temporarily stopped in June of 1999.
According to Arizona Department of Commerce, smaller mines and quarries, as well as cattle
ranches, in this area provide employment opportunities. Table 1.5 shows a selected time series of
civilian labor force data for San M anuel.

8

U.S. Department of Commerce, U.S. Census Bureau, Table 6, “Counties_Employees, Payroll, and Establishments by Industry:

1999,” issued April 2001. Data represent the number of employees for the week including March 12.

11

Table 1.4 - EconomicActivity in Pinal County by Number of Employees:
1994, 1997, and 2000
Economic activity9

1994

1997

2000

Civilian labor force

48,950

54,450

59,425

Unemployment

2,800

2,725

2,475

Unemployment rate

5.7%

5.0%

4.2%

Total employment

46,150

51,725

56,950

Non-farm employment

36,100

39,775

36,525

Mining and quarrying

10.8%

13.1%

3.7%

Construction

3.3%

4.5%

3.8%

Manufacturing

11.9%

7.6%

8.6%

TCPU

1.9%

2.0%

2.3%

Trade

19.9%

19.0%

21.0%

FIRE

1.7%

2.1%

2.3%

Services and misc.

16.1%

18.1%

20.3%

Government

33.2%

33.2%

38.0%

Source: Derived from Arizona Department of Economic Security data. Totals may not add to 100 percent.

Table 1.5 - Civilian Labor Force Data for San Manuel CDP: Selected Years
Year

1990

1995

1998

1999

2000

Civilian Labor Force

1,704

1,943

2,113

2,252

2,225

Number Unemployed

77

47

44

63

47

Unemployment Rate

4.5%

5.9%

5.1%

6.8%

5.2%

Source: Arizona Department of Economic Security. Data represent annual averages. Numbers for 1999 and 2000 are preliminary.

1.4 General S IP Approach
In November 1990, the United States Congress enacted a series of amendments to the Clean
Air Act (CAA) intended to improve air quality across the nation. One of the primary goals of this
9

TCPU = Transportation, Communication, and Public Utilities; FIRE = Finance, Insurance, and Real Estate.

12

comprehensive revision to the CAA was to expand and clarify the planning provisions for those
areas not currently meeting the NAAQS. The CAA as amended identifies sp ecific emission
reduction goals, requires both a demonstration of reasonable further progress and attainment, and
incorporates more stringent sanctions for failure to attain or to meet interim milestones.
CAA, Title I, Part A, and Title I Part D, Subparts 1 and 5 are applicable to this SIP and
maintenance plan. Sections 172, 175(A ), 191, and 192, in the following section, set forth the
following requirements for SO2 nonattainment areas.
1.4.1

CAA Section 172(c), Nonattainment Plan Provisions

172(c)(1) - In General: “...implementation of all reasonably availabl e con trol
measures (RACM) as expeditiously as practicable (including such reductions in emissions
for existing sources in the area as may be obtained through the adoption, at a minimum, of
reasonably available control technology (RACT)) and provide for attainment of the national
primary ambient air quality standards.”
BHP Copper, the primary source of SO2 emissions in the San M anuel nonattainment area,
succeeded in implementing RACM /RACT at the smelter sufficient to attain the NAAQS for SO2 and
went beyond the required technology to increase the facility’s efficiency in capturing and treating
SO2 . RACT for SO2 emission controls for a flash smelting furnace include:
1.
2.
3.
4.
5.

Dust Collection Equipment (removes dust for better gas treatment),
Wet Scrubber,
M inimization of Leaks,
Hooding and venting of gases to the stack, and
Contact Sulfuric Acid Plant.

Chapter 6 contains further explanation of applicable RACM /RACT for the BHP smelting
facility and other SO2 point sources in the nonattainment area.
172(c)(2) - Reasonable Further Progress (RFP): “...plan provisions shall demonstrate
reasonable further progress such that annual incremental reductions in emissions ensure
attainment of the national ambient air quality standards by the applicable date.”
This submittal demonstrates that the San M anuel nonattainment area has obtained and will
maintain the SO2 NAAQS with current control measures (See Chapter 6).
172(c)(3) - Inventory: “...the plan shall include a comprehensive inventory of actual
emissions from all sources of relevant pollutant(s).”

13

ADEQ maintains a historical and current database of actual emissions from State-permitted
point and area sources. The Pinal County Air Quality Control District maintains a similar database
of actual emissions from County-permitted sources. All non-permitted source emissions data (ie:
mobile sources) is obtained from EPA's national emissions inventory.10 Base-year (1998) emissions
and projected 2015 emissions are contained in Chapter 3 4.
172(c)(5) - Permits for New and Modified Major S tationary S ources: “...the plan shall
require permits for the construction and operation of new and modified major stationary
sources throughout the nonattainment area.”
All new sources and modifications to existing sources in Arizona are subject to state
requirements for preconstruction review and permitting pursuant to AAC, Title 18, Chapter 2,
Articles 3 and 4. All new major sources and major modifications to existing major sources in Arizona
are subject to the New Source Review (NSR) provisions of these rules or Prevention of Significant
Deterioration (PSD) for maintenance areas. The State NSR program was conditionally approved by
EPA in 1992, and is pending final approval. It should be noted that ADEQ currently has full
approval of its Title V permit program.
172(c)(6) - Other Measures: “...the Plan shall incl u de e n forceable emissions
limitations and such other control measures, means or techniques, as well as schedule and
timetables for compliance, as may be necessary or appropriate to provide for attainment of
such standard in such area by the applicable attainment date.”
AAC R18-2-715, Standards of Performance Primary Copper Smelters, Site Specific
Requirements, contains the required annual average emission limitations and number of three-hour
average emission limits for the BHP smelter.11 AAC R18-715.01 (Standards of Performance for
Existing Primary Copper Smelters; Compliance and M onitoring), set forth the compliance date of
January 14, 1986, for monitoring, calibration, measurement system performance requirements, record
keeping, bypass operation, and iss uance of notices of violation. Details regarding emissions
limitations and control measures for all SO2 sources in the nonattainment area may be found in
Chapter 4.
172(c)(7) - Compliance with S ection 110(a)(2): “...the Plan shall be in compliance with
S ection 110 (a)(2) (Implementation Plans) of CAA.”
Section 110(a)(2)(A) of CAA requires that states provide for enforceable emission limitations
10

AIRData provides access to air pollution data for the entire United States and can be found at

http://www.epa.gov/air/data/index.html
11

Standards of Performance for Existing Primary Copper Smelters; Site-specific Requirements, AAC R18-2-515, renumbered

AAC R18-2-715 (1993).

14

and other control measures, means, or techniques, as well as schedules for compliance. Chapter 4
includes the list of control measures utilized to bringthis area into attainment and future maintenance
of the SO2 NAAQS.
Section 110(a)(2)(B) of CAA requires that states provide for establishment and operation
of appropriate devices, met hods, systems, and procedures necessary to monitor, compile, and
analyze data on ambient air quality. Under A D EQ ’s air quality assessment program, ambient
monitoring networks for air quality are established to sample pollution in a variety of representative
settings, to assess the health and welfare impacts and to assist in determining air pollution sources.
The monitoring sites are combined into networks, operated by a number of government agencies and
regulated companies. Each network is comprised of one or more monitoring sites, whose data are
compared to the NAAQS, as well as statistically analyzed in a variety of ways. The agency or
company operating a monitoring network also tracks data recovery, quality control, and quality
assurance parameters for the instruments operated at their various sites.
The collected data are summarized into the appropriate quarterly or annual averages. The
samplers are certified by Federal Reference or Equivalent M ethods. Regular checks of the stability,
reproducibility, precision, and accuracy of the samplers and laboratory procedures are conducted by
either the agency or company network operators. The protocol for SO2 monitoring used by the
State, local agencies, and companies was established by EPA in the following sections of the Code
of Federal Regulations (CFR):
1.

40 CFR Part 50, Appendix A, Reference M ethod for the Determination of Sulfur
Dioxide in the Atmosphere;
2.
40 CFR Part 53, Subpart B, Procedures for Testing Performance Characteristics of
Automated M ethods for SO2 , CO, O3 , and NO2 ; and
40 CFR Part 58, Subpart A, B, and C, Ambient Air Quality Surveillance.
3.
(Chapter 2 includes monitoring network information and data for the San M anuel area.)
Section 110 (a)(2)(C), Section 110 (a)(2)(E), Section 110 (a)(2)(F), and Section 110 (a)(2)(L)
of CAA require states to have permitting, compliance, and source reporting authority. Arizona
Revised Statutes (ARS) § 49-402 establishes ADEQ’s permitting and enforcement authority. As
authorized under ARS 49-402, ADEQ retains adequate funding and employs adequate personnel to
administer the air quality program. Appendix A includes the organization chart for ADEQ’s Air
Quality Division.
Under ADEQ’s air permits program, stationary sources that emit regulated pollutants are
required to obtain a permit before constructing, changing, replacing, or operating any equipment or
process which may cause air pollution. This includes equipment designed to reduce air pollution.
Permits are also required if an existing busines s t hat causes air pollution transfers ownership,
relocates, or otherwise changes operations. Additionally, ADEQ is responsible for assessing annual
fees to recoup the costs of administering a permit pursuant to AAC R18-2-326.
AAC R18-2-327 requires that any source subject to a permit must complete and submit to
15

the Director their responses to an annual emissions inventory questionnaire. A current air pollutant
emissions inventory of both permitted and non-permitted sources within the state is necessary to
properly evaluate the air quality program effectiveness, as well as determine appropriate emission
fees for major sources. This inventory encompasses those sources under state jurisdiction emitting
1 ton per year or more of any individual regulated air pollutant, or 2.5 tons per year (tpy) or more
of any combination of regulated air pollutants.12 ADEQ is responsible for the preparation and
submittal of an emissions inventory report to EPA for major sources and emission points prescribed
in 40 CFR 51.322, and for sources that require a permit under ARS §49-426 for criteria pollutants.
Under ADEQ’s air quality compliance program, scheduled and unscheduled inspections are
conducted at the major sources annually. ADEQ’s Air Compliance Section also implements
compliance assistance initiatives to address non-compliance issues (i.e., seminars and workshops for
the regulated community explaining the general permit requirements, individual inspections of all
portable sources within a geographical area, mailings, etc.). In addition, compliance initiatives are
developed to address upcoming or future requirements (i.e., new general permits) and include such
actions as training for inspectors; development of checklists and other inspection tools for
inspectors; public education works hop s ; targeted inspections; mailings, etc. ADEQ’s Air
Compliance Section also has an internal performance measure to respond to all complaints as soon
as possible, but within five working days.
Section 110(a)(2)(G) of CAA requires that states provide for authority to establish
emergency powers and authority and contingency measures to prevent imminent endangerment.
AAC R18-2-220 prescribes t he procedures the Director of ADEQ shall implement in order to
prevent the occurrence of ambient air pollution concentrations which would cause significant harm
to the public health. As authorized by ARS §49-426.07, ADEQ may seek injunctive relief upon
receipt of evidence that a source or combination of sources is presenting an imminent and substantial
endangerment to public health or the environment.
172(c)(8) - Equivalent Techniques: “...the Plan may use equivalent techniques such
as e qu i valent modeling, emission inventory, and planning procedures allowed by the
administrator, upon application by any state.”
M ulti-Point Rollback modeling was used with EPA’s concurrence to establish emissions
limits for the BHP Copper smelter and updated as part of the current SIP process. M odeling for
the fugitive emissions study at this facility was conducted with models from EPA’s “Guideline on
Air Quality M odels.”
172(c)(9) - Contingency Measures: “...the Plan shall provide for the implementation
12

“Regulated air pollutant” is defined in AAC R18-2-101 as any of the following: (a) Any conventional air pollutant as defined

in ARS §49-401.01; (b) Nitrogen oxides and volatile organic compounds; (c) Any air contaminant that is subject to a standard contained in
Article 9 of Chapter 2; (d) Any hazardous air pollutant as defined in ARS §49-401.01; (e) Any Class I or II substance listed in Section 602 of
the Act.

16

of specific measures to take effect without further action by the state or the Administrator
in the event the area fails to make reasonable further progress (RFP) or to attai n the
primary national ambient air quality standards (NAAQS ).”
As noted in 172(c)(2) above, this s ubmittal includes monitoring data and source permit
information that demonstrate that t he ap p licable area has obtained, and will maintain, the SO2
NAAQS with control measures currently fully implemented. As such, the RFP requirement is met.
1.4.2

CAA Section 175(A) - M aintenance Plans

175(A)(a) - Plan Revisions: “...each state which submits a request for redesignation
of a nonattainment area shall also submit a revision of the applicable S IP to provide for the
maintenance of the NAAQS for at least ten years after the redesignation.”
As documented in Chapter 7, this submittal shows attainment through 2015.
175(A)(b) - S ubsequent Plan Revisions: “...eight years after redesignation as an
attainment area, the S tate shall submit an additional revision of the applicable S IP for
maintaining the NAAQS for 10 years after the expiration of the 10-year period referred to
in subsection (a).”
ADEQ commits to submit an additional SIP revision eight years after redesignation.
175(A)(c) - Nonattainment Requirements Applicable Pending Plan Approval: “...until
such plan revision i s approved and an area is redesignated as attainment for any area
designated nonattainment, the requirements of this part shall continue in force and effect.”
ADEQ commits to keeping all applicable measures in place.
175(A)(d) - Contingency Provisions: “...each plan revis i on submitted under this
section shall contain such contingency provisions to assure that the S tate will promptly
correct any violation of the standard which occurs after the redesignation of the area as an
attainment area. S uch provisions shall include a requirement that the S tate will implement
all measures with respect to the control of the air pollutant concerned before redesignation.”
ADEQ commits to implementing all identified measures as necessary (See Chapter 7).

1.4.3

CAA Section 191 and 192 - Plan Submission and Attainment Dates

17

This document fulfills all outstanding implementation plan requirements for the San M anuel
SO2 nonattainment area. With the submittal of this SIP and M aintenance Plan, ADEQ requests
redesignation of the San M anuel nonattainment area to attainment.
1.4.4

Conformity Provisions

Section 176(c)(1)(A) of CAA requires SIPs to contain information regarding the State’s
comp liance with conformity requirements. As stated in 40 CFR 93.153(a), "Conformity
determinations for Federal actions related to transportation plans, programs and projects developed,
funded, or approved under title 23 U.S.C. or the Federal Transit Act (40 U.S.C. 1601 et seq.) must
meet the procedures and criteria of 40 CFR part 51, subpart T, in lieu of the procedures set for in
this subpart." 40 CFR 93.103(b) waives transportation conformity for SO2 nonattainment areas,
but general conformity for the San M anuel, Pinal County area must still be addressed to assure SO2
emissions from any Federal actions or plans do not exceed the rates outlined in 40 CFR 93.153(b)(1)
for nonat t ainment areas or 40 CFR 93.153(b)(2) for maintenance areas. Criteria for making
determinations and provisions for general conformity as outlined in 40 CFR 93.153 can be located
in R18-2-1438 of the Arizona Administrative Code. There are no federal plans or actions affecting
air quality currently in the San M anuel, Pinal County area, nor are any foreseen through the year
2015.

18

2.0

COMPLIANCE WITH OTHER FEDERAL REGULATIONS

The provisions of 40 CFR 60 Subpart P (§§60.160 - 60.166) Standards of Performance for
Primary Copper Smelters are applicable to dryer, roaster, smelting furnace, and copper converter
equipment in primary copper smelters.13 Any facility that commences construction or modification
after October 16, 1974, is subject to the requirements of this subpart. The San M anuel smelter was
modified in 1988 when the Outokumpu flash furnace, converter secondary hoods, retrofit of the acid
plant, and a flux processing unit were installed, per the 1987 Consent Decree, and again in 1992 when
the #3 converter was rep laced. ADEQ compliance, permit, monitoring, technical, and
correspondence files indicate that the facility has complied with all the requirements of this subpart.

13

Source: 41 FR 2338, Jan. 15, 1976, unless otherwise noted.

19

3.0

S O 2 MONITORING NETWORK

M onitoring began in the San M anuel area as early as 1969 by the State of Arizona.14 BHP
began continuous ambient SO2 air quality monitoring in the San M anuel area in 1973. An extensive
monitoring network was established wit h s ufficient spatial and temporal coverage to
comprehensively evaluate the ambient impact of smelter emissions. M ore than eighteen stationary
and mobile monitoring sites were established throughout the area with as many as ten monitors
operating concurrently (See Table 3.1 and Figure 3.1).15 This ambient SO2 network, comprised of
EPA, state, and BHP monitors, was developed as the result of extensive efforts to identify maximum
ambient impact areas usingdiffusion modeling, monitored atmospheric dispersion parameters, citizen
observations, and ambient SO2 monitoring.
Stanford Research Institute (SRI), a facility contractor, was engaged to study the effects of
SO2 emissions from the San M anuel smelter on the surrounding environment. Criteria for
determining ambient SO2 and meteorological monitoring locations under SRI’s recommendation,
“Environmental Studies at San M anuel, 1972,” included consideration of public health, areas of
frequent high SO2 concentrations and relatively high long-term average concentrations. A gaussian
diffusion model and meteorological records from the Tucson National Weather Service were
employed in the study to predict SO2 dispersion patterns in the San M anuel area. In addition, fortyseven sulfation plate monitoring sites were utilized to characterize ambient SO2 over 500 square
miles surrounding the area.
The studies contributed to the subsequent expansion of the monitoring network including
installation of seven of t he initial stationary sites (M ammoth Courthouse, M inesite, Oracle
Courthouse, Golf Course, Peppersauce, and Redington) and implementation of a mobile analyzer.
Installation of additional meteorological instrumentation at the network sites, measuring wind speed
and direction, temperature, and humidity parameters helped to further define airflow and pollutant
transport in the region. Utilization of mobile monitors allowed evaluation and verification of ambient
SO2 concentrations over a greater area. Numerous sites were monitored and subsequently relocated
under the direction of stat e met eorologists when no significant impacts were observed. All
monitoring for SO2 was performed with guidance and dispersion modeling analysis from the Arizona
Department of Health Services, Bureau of Air Quality Control.
The monitoring network was also developed in accordance with Supplementary Control
Systems (SCS). Prior to implementation of continuous control technology, SCS utilized analysis of
atmospheric conditions and monitored ambient concentrations to vary the rate of smelter emissions
to avoid any exceedance of the NAAQS. In 1977, the state adopted rules that codified requirements
for concurrent operation of at least eight ambient monitors, including a mobile monitor placed at
points representative of observed maximum concentrations. Relocation of a stationary monitor was
14

Sulfur Dioxide Monitoring Network Study, Arizona State Department of Health, Environmental Health Services, Division of Air

Pollution Control, 1969.
15

Protocols for SO2 monitoring established by EPA are found in 40 CFR Part 50, Appendix A, Reference Method for the

Determination of Sulfur Dioxide in the Atmosphere, Part 58, Subpart B, §58.14, Special Purpose Monitors, Subpart C, §58.20, State and Local
Air Monitoring Stations, Air Quality Surveillance: Plan Content, and Subpart D, §58.30, National Air Monitoring Stations (NAMS).

20

allowed only when:
1.
2.

There were no ambient SO2 violations recorded;
No SCS curtailment actions were implemented due to data recorded at that monitor;
Table 3.1 - Ambient Monitoring Network
Monitor Site

Period of Operation

Townsite

1969-1974 and 1979-present

Hospital

1987-present

LDS Church 16

1975-1999

Dorm Site

1978-present

Elks

1987-1994

Industrial Hygiene
Upper Shopping Center

1975-1978

Golf Course

1974-1997

Trailer Park

1974-1975

Minesite

1974-1994

Mercer Ranch

1979-1980

East Peppersauce Wash

1974-1978

Oracle Courthouse

1975-1994

Oracle Holy Cross
Canyon

1978-1979

3-C Ranch

16

1981

1981-1982 and 1987-1994

Mammoth Courthouse

1974-1987

Mammoth Aravaipa
Canyon

1980-1981

Redington

1976-1985

Mobile I

1977-1978

EPA17

1973-1974

The LDS Church monitor was removed in June 1999, due to the temporary closure of the BHP smelter. ADEQ commits to

reestablishing this monitoring station by February 2002.
17

Three EPA established monitoring sites were operated during this period.

21

SOURCE: Locati o n s c o mp i l e d from BHP San Manuel operations and ADEQ archives.
Manual notes eleven experimental mobile monitoring locations to date.

22

The 1977/1978 Operations and Mantenance

23

3.

The foregoing conditions were due to implementation of improved emissions control
techniques or other permanent modifications; and
A new site was shown to be more representative of the ambient air quality of the
area.

4.

Historic ambient SO2 monitoring site locations and periods of operation are provided in
Table 3.1, and Figure 3.1 and 3.2.
Further refinement of the monitoring network was required by the adoption of the M PR
rule that established stack emissions limits for the smelter in 1979 based on permanent controls.
Placement of additional monitors were established with EPA to further evaluate ambient
impacts.
Following BHP’s compliance with emissions limits as defined in AAC R18-2-715(F), and
based on continuous emissions control technology, the number of permanent monitors was
gradually reduced to the current network of four. These are all high impact ambient monitor sites
found to be representative of air quality for the area. These monitoring site decisions were made
by ADEQ and BHP concurrence and in accordance with EPA guidance.

Current S ampler Type and S iting
The three monitoring units operated by BHP are Thermo Electron pulsed fluorescent
(TECO) M odel 40 SO2 analyzers. All of these SO2 analyzers are interfaced to BHP’s data
acquisition system by telemetry. The TECO analyzers measure in the 0-2 ppm range.
Redundant recording systems are operated for all of the BHP analyzers. The samplers are
connected to strip chart recorders for backup and analyzed by planimeter as necessary for
validation of recorded concentrations. The ADEQ SO2 analyzer is also a TECO analyzer,
measuring in the 0-2 ppm range (Figure 3.1 illustrates the current monitor locations and
proximity to the BHP smelter). The BHP and ADEQ monitors are operated and maintained in
accordance with federal regulations as described in 40 CFR parts 58.13 and 58.22 as well as
Appendices A and E of part 58.
3.1

Table 3.2 - Current Monitoring Network
Unit18

Location

Elevation (feet)

Operator

LDS Church

1.75 miles southwest of BHP

3570

ADEQ

Townsite19

1.24 miles southwest of BHP

3480

BHP

18

The Dorm Site and Hospital monitors are primarily fugitive emissions impact sites. Townsite and the LDS site are primarily

stack impact sites.
19

The location of the Townsite monitor remains the same as in 1974. This monitor was the “limiting site” for the original MPR

analysis (“Ultimate Sulfur Dioxide Limits for Arizona Copper Smelters,” Moyers and Peterson, September 14, 1979).

24

Dorm Site20

0.7 miles northwest of BHP

3400

BHP

Hospital20

0.5 miles southwest of BHP

3440

BHP

20

EPA required monitoring site per 1987 consent decree.

25

26

3.2

Ambient Data Analysis
A review of the SO2 monitoring data in the San M anuel nonattainment area verifies that:
There have been no recorded exceedances of the annual NAAQS for SO2 since
1974 and annual averages are generally 17.5 percent of the NAAQS;
There have been no recorded exceedances of the 24-hour NAAQS for SO2 since
1994 and maximum 24-hour average SO2 levels are generally 57 percent of the
NAAQS; and,
There have been no recorded exceedances of the 3-hour NAAQS for SO2 since
1996 and maximum 3-hour averages are generally below 50 percent of the
NAAQS.

1.
2.

3.

The nonattainment area has recorded more than eight current, consecutive quarters of quality
assured, violation-free data from M ay 1997 through April, 1999.21 Data for the current monitoring
network is presented in Table 3.3, on the following pages.
Table 3.3 - SO2 Ambient Air Q uality Monitoring Data (Fg/m3)
Year

Annual
Ave.

24Hour
Max

3-Hour
Max

Number of Exceedances
Annual

24-hr.

3-hr.

No. of
1-hr.
Samples

LDS Church
1999

9

65

220

0

0

0

6121

1998

8

102

707

0

0

0

8494

1997

8

60

291

0

0

0

8626

1996

11

338

1758*

0

0

1

8183

1995

8

55

362

0

0

0

8491

1994

10

466*

720

0

1

0

7857

1993

16

94

721

0

0

0

8696

1992

10

121

519

0

0

0

7794

1991

3

367

1242

0

1

0

8091

1990

13

139

1053

0

0

0

8668

1989

21

267

631

0

0

0

8434

1988

13

125

793

0

0

0

7944

21

The two year period of record prior to the temporary cessation of smelter operations.

27

Table 3.3 - SO2 Ambient Air Q uality Monitoring Data (Fg/m3)
Year

Annual
Ave.

24Hour
Max

3-Hour
Max

1987

42

191

1986

44

282

Number of Exceedances
3-hr.

No. of
1-hr.
Samples

Annual

24-hr.

866

0

0

0

8737

1499

0

0

1

8449

LDS Church con’t
1985

56

388

1601

0

1

3

8667

1984

41

236

1185

0

0

0

8704

1983

34

224

1243

0

0

0

8412

1982

47

303

1064

0

0

0

8058

1981

66

284

1602

0

0

1

8130

1980

32

295

1953

0

0

2

8227

1979

58

524

2024

0

1

5

7403

1978

53

509

2476

0

1

2

6733

1977

58

435

1820

0

1

2

7308

1976

42

471

3117

0

1

2

8002

1975

43

563

3517

0

1

1

3880

Townsite
1999

4

69

290

0

0

0

N/A

1998

8

105

570

0

0

0

8656

1997

33

95

374

0

0

0

8725

1996

18

167

1068

0

0

0

8765

1995

11

71

372

0

0

0

8753

1994

15

121

410

0

0

0

8740

1993

28

166

919

0

0

0

8751

1992

26

197

923

0

0

0

8773

1991

18

180

1064

0

0

0

8752

1990

20

222

1257

0

0

0

8746

1989

42

272

1294

0

0

0

8744

1988

25

167

1062

0

0

0

8771

1987

51

276

999

0

0

0

8723

28

Table 3.3 - SO2 Ambient Air Q uality Monitoring Data (Fg/m3)
Year

Annual
Ave.

24Hour
Max

3-Hour
Max

1986

57

291

1985

61

311

Number of Exceedances
3-hr.

No. of
1-hr.
Samples

Annual

24-hr.

1772

0

0

1

8719

1514

0

0

2

8709

Townsite Con’t
1984

50

337

1224

0

0

0

8712

1983

49

264

1484

0

0

1

8703

1982

59

364

1265

0

0

0

8680

1981

42

312

1641

0

0

1

8663

1980

32

273

1283

0

0

0

8677

1979

73

611

3014

0

2

4

8554

Dorm Site
1999

4

54

311

0

0

0

N/A

1998

8

135

262

0

0

0

8714

1997

11

75

220

0

0

0

8751

1996

15

101

415

0

0

0

8777

1995

16

96

317

0

0

0

8746

1994

13

113

766

0

0

0

6857

1993

29

172

930

0

0

0

8751

1992

32

189

783

0

0

0

8774

1991

22

246

855

0

0

0

8750

1990

16

96

763

0

0

0

8753

1989

39

359

2704*

0

0

1

8749

1988

32

193

766

0

0

0

8772

1987

56

268

1179

0

0

0

8734

1986

59

256

971

0

0

0

8715

1985

67

265

1280

0

0

0

8699

1984

58

332

1353

0

0

1

8745

1983

51

295

1288

0

0

0

8711

1982

73

387

1701

0

1

4

8646

29

Table 3.3 - SO2 Ambient Air Q uality Monitoring Data (Fg/m3)
Year

Annual
Ave.

24Hour
Max

3-Hour
Max

1981

74

275

1980

58

340

Number of Exceedances
3-hr.

No. of
1-hr.
Samples

Annual

24-hr.

1656

0

0

1

8679

2415

0

0

4

8534

Dorm Site con’t
1979

74

412

1869

0

1

4

8521

1978

N/A

254

1085

N/A

0

0

2181

1999

8

214

433

0

0

0

N/A

1998

11

154

712

0

0

0

8642

1997

32

208

705

0

0

0

8742

Hospital
1995

18

141

593

0

0

0

8752

1994

23

223

1632*

0

0

1

8746

1993

33

170

1248

0

0

0

8752

1992

38

242

1179

0

0

0

8768

1991

31

284

2175*

0

0

1

8751

1990

33

60

916

0

0

0

8751

1989

42

279

1881*

0

0

1

8747

1988

41

261

928

0

0

0

8770

0

1017

1987
54
224
695
0
0
* - The exceedance was determined to be due to a process/equipment malfunction.

30

S O 2 EMIS S IONS INVENTORY FOR POINT, AREA AND MOBILE S OURCES

4.0

Emissions inventories from all sources in the San M anuel nonattainment area indicate that
although there are other sources of SO2 emissions, the BHP Copper smelter is the primary source
for SO2 emissions and comprise more than 99 percent of total emissions in the area. Data shows that
no other point, area or mobile sources have contributed, or contribute to the same levels of SO2 in
the San M anuel nonattainment area. Emissions units and rates, and derivation of mobile and area
source emissions for the nonattainment area are described in Section 4.1 through Section 4.3 below.

S O 2 Point S ources

4.1

Three point sources are located within the San M anuel nonattainment area. Point source
locations are illustrated in Figure 4.1, on the following page. The most current inventories for these
sources are presented in Table 4.1.
Table 4.1 - SO2 Emissions for San Manuel Nonattainment Area - Point Sources
Source Name

1997

1998

1999

24 Hr. (tpd)

0

0

0

Annual (tpy)

0

0

0

24 Hr. (tpd)

32

29

30

Annual (tpy)

11,482

10,409

3,62223

24 Hr. (tpd)

<1

<1

<1

Annual (tpy)

<1

<1

<1

24 Hour Total (tpd):

32

29

30

Annual Total (tpy):

11,482

10,409

3,622

Oracle Compressor
Station
BHP Copper smelting
operations22
BHP Copper mining
and milling operations

4.1.1

Oracle Compressor Station

This source is a natural gas transport facility that utilizes a natural gas powered turbine to
compress the natural gas for transmission through a pipeline. The facility did not operate from 1997
through 1999. When operating, the Oracle Compressor Station is a very low contributor to ambient

22

24-hour inventories are a ton per day (tpd) average calculated by dividing the annual facility emissions by the number of

operating days for each year.
23

Smelting operations were temporarily suspended beginning May 1999.

31

SO2 levels with total permitted emissions from existing equipment limited to 0.6 tpy.

32

33

4.1.2

BHP Copper San M anuel Smelter

Smelting and refining of copper ore at BHP’s primary copper smelter operations produces
copper cathode and copper rod as well as byproducts of the smelting process (molybdenum
concentrate, sulphuric acid, and gold and silver) for sale to customers. M ore than 99 percent of all
SO2 emissions in the nonattainment area are generated by this facility when it is operating. Based
on 1998 emissions data, the majority of this facility’s emissions are from the following stack and
fugitive units: flash furnace fugitive stack, acid plant II tail stack, acid plant III tail stack, converter
secondary and flash emergency vent stack, concentrate dryer stack, and fugitive emissions from the
converter building roof vents. The maximum allowable annual average SO2 emission rate for stacks
was reduced from 18,275 lbs/hr to 1,742 lbs/hr with recent revisions to AAC R18-2-715(F)(1) and
(G). The revisions also limited fugitive emissions from the converter building roof vents to 715
lbs/hr. The combined limit for the stack and fugitive emissions units is currently 2,457 lbs/hr (10,762
tpy). Permit #1000681 issued M arch 24, 1998, further limits SO2 emissions from the concentrate
dryer to a maximum 2,073 tpy, based on a 12-month rolling monthly average.
Additional de minimis units include emissions from the anode and utility vessel roof vent.
Emissions from these units at 1998 operating levels were estimated to be 59 tpy. In addition, the
permit limits sulfur content and usage rates for fuel used in all fuel burning equipment. Actual
emissions from fuel burning equipment, are minimal, at less than 2.5 tpy. Emissions units and rates
for the BHP smelter are detailed in Appendix B.
4.1.3

BHP Copper M ining and M illing Operations

This source is a mining and copper ore processing facility where copper sulphide ore is
prepared for smelting and refining at the BHP smelter. The primary source of emissions from these
minimal SO2 sources are natural gas and diesel burning equipment that include concentrate dryers,
generators, and boilers. Permits for the mine and mill require the use of low sulfur natural gas and
propane in the generators and limits the potential to emit (PTE) from all existing equipment to 0.38
tpy of SO2 . Actual emissions, are minimal, at 0.03 tpy.

4.2

Major Point S ources within the 50 km Buffer Area

In addition to the sources located within the nonattainment area, there are several point
sources within 50 kilometers of the San M anuel nonattainment area. There is no information to
suggest that emissions from these sources have contributed t o the same levels of SO2 in the
nonattainment area as are demonstrated by the BHP smelter or that emissions from these sources
could cause violations in the San M anuel nonattainment area. Attainment year inventories are
provided in Table 4.2.

34

Table 4.2 - SO2 Emissions within 50km of the San Manuel Nonattainment Area Point Sources
Source Name:

1997

1998

1999

24 Hr. (tpd)

<1

<1

<1

Annual (tpy)

1

8

8

24 Hr. (tpd)

8

7

9

Annual (tpy)

2,597

1,731

2,862

24 Hr. (tpd)

N/A

0

<1

Annual (tpy)

N/A

0

<1

24 Hr. (tpd)

79

66

58

Annual (tpy)

27,533

22,077

21,081

24 Hour Total (tpd):

87

73

67

Annual Total (tpy):

30,131

23,816

23,951

APS (Red Rock)24

TEP (Irvington)24

TEP (North Loop)24

ASARCO Hayden
Smelter25

4.2.1

Arizona Public Service (APS) - Red Rock

The APS Red Rock electric generating station operates two steam turbine units, two gas
turbine units, and associated auxiliary equipment. The source’s permit limits SO2 emissions from
combustion of fuel in the existing equipment to 15,051 tpy. This station was formerly a “peaking”
plant providing increased electricity generation during periods of high demand. Commencement of
full time operations began in 2000.
4.2.2

Tucson Electric Power Co. Irvington

Production of electricity at this generating station is accomplished by combustion of fuels
in four steam turbine and three gas turbine units. The facility’s operating permit limits allowable SO2
emissions from the existing equipment to 20,150 tpy . Actual emissions, however, are less than 3,000
tpy.
4.2.3

Tucson Electric Power Co. North Loop

24

Daily inventories for the electric facilities were calculated by dividing the annual emissions by the number of operating hours

for each year and multiplied by a factor of 24 to obtain the 24-hour value. These inventories are based on the conservative assumption of 24
hours of operation for each calculated operating day.
25

24-hour inventories are a ton per day (tpd) average calculated by dividing the annual facility emissions by the number of

operating days for each year.

35

The Tucson Electric Power Company North Loop station currently operates four simple
cycle combustion turbine generators for the production of electricity. The turbines are primarily
used as "peaking" units and are only fired when electrical demand requires their use. The permit lists
potential to emit at 4,718 tons of SO2 per year. Actual emissions for this facility are minimal at less
than 1 tpy in 1999.
4.2.4

ASARCO Hayden Smelter

The Hayden primary copper smelter operates a flash furnace, converters, and other auxiliary
equipment for smelting and refining of copper sulfide ore. The permit limits smelter process SO2
emissions to 41,702 tpy. Actual emissions, however, are less than 23,000 tpy. In addition, the
permit limits sulfur content and usage rates for fuel used in all fuel burning equipment. The Hayden
smelter is located in the Hayden SO2 nonattainment area. A separate state implementation plan
(SIP) is being developed for this area and ADEQ anticipates submittal of the SIP to EPA in 2002.

4.3

Area, Mobile, and Total S ources

Emissions for the nonattainment area were derived from EPA NET area and mobile source
inventories for Pinal County based on the assumption that area and mobile source emissions are
proportionate to population levels. The San M anuel SO2 nonattainment area population is estimated
to be seven percent of the Pinal County population based on the aggregate population centers of San
M anuel CDP, M ammoth, and Oracle CDP. The remainder of the nonattainment area has a very low
population density with low traffic levels and minimal commercial or industrial development. Data
shows that there are no urban areas that might be significant area or mobile sources located within
the San M anuel nonattainment area as illustrated in Table 4.3. Area and mobile sources combined
were less than one percent of the total emissions during the period of BHP smelter operations in
1997, 1998, and 1999.
Table 4.3 - SO2 Emissions for the San Manuel Nonattainment Area - All Sources
Source Type:26
Area and
Mobile27

Point

26

1997

1998

1999

24 Hr. (tpd)

<1

<1

<1

Annual (tpy)

83

84

86

24 Hr. (tpd)

32

29

30

Area and mobile source estimates are based on EPA's AIRData for Pinal County. Point source estimates are based on

ADEQ annual emissions inventory data.
27

24-hour inventories are averages based on a 365 day distribution of emissions from these sources.

36

Table 4.3 - SO2 Emissions for the San Manuel Nonattainment Area - All Sources
Annual (tpy)

11,482

10,409

3,622

24 Hour Total (tpd):

32

29

30

Annual Total (tpy):

11,565

10,493

3,708

4.4

Emissions Projections

4.4.1

Point Source Projections

Arizona does not anticipate any substantial increase in existing point source emissions
between 1999 and 2015 for the nonattainment area. Should any growth occur due to construction
of additional SO2 point sources, ADEQ’s permit program limits all emissions as part of the
construction of new point sources or the upgrading of existing sources.
Projections for copper smelters are based on growth rates contained in the Western Regional
Air Partnership (WRAP), Annex to the Report of the Grand Canyon Visibility Transport Commission,
October 16, 2000. This report notes that downward pressure on copper prices resulting from
international competition have produced a consolidation of the copper industry in the Southwestern
United States. Consequently, no expansion of the industry is expected though 2015. Emissions
projection estimates for electric utilities are based on an anticipated industry growth rate of 2.6
percent per year contained in the WRAP report. These estimates are predicated, in part, on existing
capacity and future demand for generation.
The remaining minor sources (Oracle Compressor Station, BHP M ine and M illing
Operations) have existing permits limiting their potential to emit to less than one tpy. Table 4.4 and
Table 4.5 present projected emissions for point sources within the nonattainment area and major
point sources within 50 km of the nonattainment boundary.
Table 4.4 - SO2 Emissions Projections for the San Manuel Nonattainment Area - Point
Sources
Source Name:
Oracle
Compresso
r Station

1997

1998

1999

2005

2010

2015

24 Hr. (tpd)

0

0

0

<1

<1

<1

Annual
(tpy)

0

0

0

1

1

1

37

Table 4.4 - SO2 Emissions Projections for the San Manuel Nonattainment Area - Point
Sources
Source Name:

1997

1998

1999

2005

2010

2015

24 Hr. (tpd)

32

29

30

30

30

30

Annual
(tpy)

11,482

10,409

3,622

10,900

10,900

10,900

24 Hr. (tpd)

<1

<1

<1

<1

<1

<1

Annual
(tpy)

<1

<1

<1

<1

<1

<1

24 Hour Total (tpd):

32

29

30

30

30

30

Annual Total (tpy):

11,482

10,409

3,622

10,901

10,901

10,901

BHP
smelter28,29
BHP mine
and
milling
operations

Table 4.5 - SO2 Projected Emissions within 50km of the San Manuel Nonattainment
Area - Major Point Sources
Source Name:

1997

1998

1999

2005

2010

2015

24 Hr. (tpd)

8

7

9

10

12

14

0

Annual (tpy)

2,598

1,739

2,870

3,892

4,424

5,031

ASARCO
Hayden
Smelter31

24 Hr. (tpd)

79

66

58

66

66

66

Annual (tpy)

27,533

22,077

21,081

23,000

23,000

23,000

87

73

67

76

78

80

Electric
Utilities3

24 Hour Total (tpd):

28
29

Projections for the BHP smelter assumes resumption of smelting operations.
The annual number of operating days used to calculate the projected 24-hour inventories for 2005 through 2015 (annual

emissions divided by the number of operating days) were based on average operating conditions. The average number of operating days for
the period 1997 through 1999 were assumed to represent typical operating rates.
30

Projections for electric utilities are based on the assumption of continued full time operation of the APS (Red Rock) generating
station and were calculated using emissions from the most recent year of full time operations at this facility (497 tons of SO2 emissions were
recorded in 2001, the first year of full time operations).
31

The annual number of operating days used to calculate the projected 24-hour inventories for 2005 through 2015 (annual

emissions divided by the number of operating days) were based on average operating conditions. The average number of operating days for
the period 1997 through 1999 were assumed to represent typical operating rates.

38

Annual Total (tpy):

4.4.2

30,131

23,816

23,951

26,892

27,424

28,031

Area, M obile, and Total Source Projections

ADEQ projects emissions of SO2 from area and mobile sources to grow proportionately
with the population of the nonattainment area. Appendix B describes the source category emissions
projections in greater detail. Table 4.6 presents projected area and mobile, and total source emissions
for the San M anuel nonattainment area.
Table 4.6 - SO2 Emissions Projections for the San Manuel Nonattainment Area - All
Sources
Source Type:

1997

1998

1999

2005

2010

2015

24 Hr. (tpd)

<1

<1

<1

<1

<1

<1

Annual (tpy)

83

84

86

94

101

107

24 Hr. (tpd)

32

29

30

30

30

30

Annual (tpy)

11,482

10,409

3,622

10,901

10,901

10,901

24 Hour Total (tpd):

32

29

30

30

30

30

Annual Total (tpy):

11,565

10,493

3,708

10,995

11,002

11,008

Area and
Mobile

Point

39

5.0

MODELING DEMONS TRATION

Attainment is demonstrated through the clean ambient air quality record of more than ten
years and use of M ulti-point rollback (M PR) modeling. The improvement in air quality is due to
continuous SO2 emissions control technologies implemented by the San M anuel smelter to comply
with the SO2 emission limits regulations adopted for Arizona smelters in September 1979. M PR,
which was approved by EPA in January 1983 as a modeling technique for Arizona smelters, was
selected as the most precise and reliable method for then determining contemporary and future stack
SO2 emission limits.
M PR is a proportional rollback technique founded on the assumption that smelter emissions
and ambient concent rations are proportional for a given set of dispersion conditions. Thus, a
reduction in emissions results in a comparable reduction in ambient concentrations. Based on this
assumption, the appropriate level of emission reductions to protect the NAAQS can be achieved if
emissions are reduced by the ratio of the corresponding ambient concentrations to the air quality
standard.
The use of M PR addresses the high variabilit y of both smelter emissions patterns and
meteorological conditions, in part, by rolling back an entire emissions curve rather than a single
emissions measurement. A rollback fact or is det ermined by fitting a concentration frequency
distribution (from observed data) to an appropriate functional curve and calculating an expected once
per year maximum (limiting) value. The rollback or reduction factor is defined as the ratio of the
ambient standard to the limiting value. Rollback factors are calculated for all applicable NAAQS
averaging periods. The largest calculated rollback factor is used to reduce each emiss ion which
occurred over the period of data accumulation (the emissions profile). The maximum rollback value
is chosen to ensure that all primary and secondary standards are protected. In the case of the San
M anuel smelter, the 3-hour standard was selected as the most conservative limiting standard which
is also protective of the 24-hour and annual standards.32
Because hourly emissions were not available, the original M PR analysis used an estimate of
hourly SO2 emiss ions over the course of a year, based on knowledge of smelter operations and
emissions variability, to construct an emissions curve. The entire curve was then “rolled-back” and
the resultant distribution used directly to construct the original M PR cumulative occurrence and 3hour average emissions limits tables for stacks. Hourly ambient SO2 concentration data from the
Townsite monitor (a stack impact site) for the period October 1973, through September 1974, were
used and average emissions were calculated by sulfur balance.

5.1

Derivation of New Emissions Limits
Based on EPA’s approval as a model, ADEQ utilized M PR as a component of the current
32

A detailed discussion of Multi-point Rollback methodology is contained in Ultimate Sulfur Dioxide Emission Limits for Arizona

Copper Smelters, September, 1979.

40

attainment demonstration, BHP performed a further M PR analysis of stack and fugitive emissions
and resultant ambient impacts based on current operating levels. This analysis utilized data from the
two most recent years of operation (M ay 1997 through April 1999), and included cont inuous
measurement dat a for stack and converter fugitive SO2 emissions and measured ambient
concentrations. These data were used to establish new stack and converter fugitive emission limits
in rule that will maintain emissions below attainment period levels (See Appendix A).
The new SO2 limits for stack and fugitive emissions at the San M anuel smelter maintain the
basic M PR principles. Namely, that smelter emissions and meteorological conditions, which
influence the impact of those emissions on air quality, are two highly variable but independent
p roces s es, and that emissions limits can be set that assure a high probability of attaining t he
applicable ambient air quality standards. The new limits are in the same format as the original M PR
tables. However, the derivation of the new values differs from the original in two important aspects.
First, the new limits are based on actual hourly SO2 measurements. Second, these emissions required
no reduction for compliance with the SO2 air quality standards because those standards were met by
a large margin during the two year period from which the emissions data were obtained (See S ection
3.1 and 3.2). Accordingly, the new M PR limits did not require the complexity of calculation and
assumptions as the original effort.
5.1.1

Stack Emissions Limits

Two years of data, based on actual emissions measurements from M ay 1997 through April
1999, were used in the current analysis to determine new 3-hour average emissions limits for stacks.
The data for this period (17,520 hourly values) were ranked in descending numerical order. Each
successive pair of ranked values were averaged to obtain a single representative profile consisting of
8,760 hourly values for the attainment period. Three-hour running averages were calculated creating
a new database of 8,760 three-hour averages. As with the original M PR, the highest 26 percent or
2,240 hours of the resulting averages was then sorted into 24 categories of cumulative frequency of
occurrence values identical to the occurrence limits in the original M PR tables (0 to 2,240). The
emission limits were selected using the same conceptual method used in the original M PR where in
each category of allowed emission occurrences, the lowest actual emissions value in that range was
used to establish the new limits. For example, the n cumulative frequency of occurrence where n =
7 in the new M PR table for stack emission corresponds to the emissions value E where E = 5660.
The measured emissions values that occur in the frequency, where n = 7, are 5860, 5747, and 5660
(See Appendix C). The selection of the lowest measured emissions value in each frequency of
occurrence mimics the selection of the lowest calculated values of the original M PR analysis, which
were all below the emissions profile or curve.
The annual average emissions limit for stacks was determined from the calculated numerical
average of the combined hourly stack emission values (17,520 hourly values).
5.1.2

Fugitive Emissions Limits

41

The previous M PR limit was based on ambient impacts from stack sources. A similar M PR
analysis was also performed for uncaptured converter fugitive emissions based on the proportional
impacts of these emissions on ambient concentrations at fugitive impact sites (See S ection 3.1 and
3.2). Two years of measured converter roof emissions from M ay 1997 though April 1999, were
used to establish 3-hour average and annual emissions limits for this source. Details of the analysis
are presented in Appendix C.

42

5.1.3

Emissions Reductions

The current rollback reduced allowable annual average stack emissions from 18,275 to 1,742
pounds per hour (lbs/hr). Fugitive SO2 emissions as measured from the converter roof were reduced
from the previous permit limit of 1,115 lbs/hr to 715 lbs/hr. Overall, allowable emissions from stack
and fugitive sources were reduced from 84,928 tpy to 10,762 tpy providing a reduction of 74,166
tpy (approximately 87 percent). This reduction is illustrated in Figure 5.1.

Figure 5.1 - Comparison of 1979 and 2001 MPR Limits33
Allowable 3-hour Average Emissions
80000

Emissions (lbs/hr)

60000

40000

20000

0

0

2

7

20

48
94
180
330
Cumulative Occurance

1979 MRP Stack Limit

560

890

1340

1910

2001 MPR Stack Limit

2001 MPR Converter Roof Fugitive Limit

To ensure that the variety of possible meteorological conditions were represented over the
analysis period and that favorable atmospheric dispersion did not influence the impact of emissions
on ambient concentrations, the variation of emissions and ambient concentrations were compared
from 1995 through 1999.
The upper distribution of short-term (1-hour) total smelter emissions and three-hour ambient
SO2 concentrations from all ambient monitors were determined for each of the five years. Review
of the data demonstrates that emissions levels are relatively consistent throughout the M PR study
period. The 99th percentile emissions values for the five year period differ by only 534 lbs/hr. The
resulting annual values are presented in Figure 5.2. Emissions for the period preceding the 2001
M PR analysis were marginally higher than emissions recorded during the M PR study period. When
adjusted for the difference in emissions between the two time periods (increased by the ratio of the
33

Limits contained in AAC R18-2-715(F)(1) and (G).

43

earlier to later emissions); however, ambient concentrations from the current M PR period do not
vary significantly, and are less than five percent higher than the actual measured concentrations. The
adjusted ambient values continue to demonstrate protection of the NAAQS. A five year period is
cons idered to be long enough to experience potentially restrictive meteorological conditions .
Nonetheless, Figure 5.2 shows that high concentrations varied little from year to year.

Figure 5.2 - San Manuel Smelter

99th Percentile Total Emissions and Ambient Concentrations
5500

600

500

4500

Emissions - 1-hour (lbs/hr)

4000
400

3500
3000

300
2500
2000

200

1500
1000

100

Ambient Concentration - 3-hour (ug/m3)

5000

500
0

0
1995

1996
Emissions

5.2

1997
Year
Townsite

1998
Hospital

Dormsite

1999
LDS

S melter Configuration

Smelter configuration and in particular the location and height, of SO2 releases was a critical
consideration in finding the San M anuel smelter in compliance with the original M PR limits and for
the current demonstration of attainment of the SO2 NAAQS. The original M PR limits for the San
M anuel smelter were based on 1973-1974 records of SO2 emissions and ambient concentrations. The
smelter achieved compliance with M PR emission limits in 1987 and remained in compliance through
shutdown in 1999. Although the smelter underwent major modifications and emission reductions
over the years, the locat ion and heights of SO2 releases have changed only slightly. Basically,
emissions can be grouped into two categories based on the height of release. Low level emissions at
heights less than 200 feet include fugitive and dryer st ack emissions. High level emissions are
predominantly from the reverberatory and converter stacks which are over 500 feet and include
minor emissions form the 250 foot acid tail gas stacks. Table 5.1 and Table 5.2 show the release
heights and SO2 emissions for 1974 compared to the most recent years of operation 1997-1999.
44

Table 5.3 shows the distances of the individual emission points to the facility property boundary.
Thus the ambient SO2 network established in the 1970's and refined in the 1980's, including
extensive sampling and testing for fugitive SO2 impact sites, occurred at a time with quite consistent

Table 5.1 - San Manuel Smelter Configuration 1974 to Present
Emissions
Source

1974
Height
(ft)

Present
Height
(ft)

1974 Process
Emission
Source
High Level
Reverberatory
Furnace process
gases

Reverb
Stack

509

509

Converter
Stack

530

530

Tail I

NA

NA

NA

Tail II

NA

250

NA

Tail III

NA

250

NA

Converter
process gases

Present Process
Emission
Source
Flash furnace captured and
vented fugitive gases
Converter secondary hood
and flash emergency vent
gases
Constructed in 1975;
decommissioned May,
1996
Constructed in 1975
(converted to double
contact in 1987, upgraded
in 1994)
Constructed and upgraded
in 1994

Low Level
Dryer Stack

NA

144

Converter
Fugitives

106

106

NA
Direct Converter
fugitive gases

45

Concentrate dryer
gases(constructed in 1987)
Converter gases not
captured by primary or
secondary hood systems

Table 5.2 - San Manuel Smelter SO2 Emissions 1974 to 1999 (tpy)

Emissions Source

1974

34

1997

1998

1999

Attainment
Period
Average35

High Level
Reverberatory Stack

28,300

1,690

1,612

519

1,620

Converter Stack

39,600

2,436

2,249

969

2,531

Tail II Stack

NA

186

220

69

204

Tail III Stack

NA

538

400

101

414

Tall Stack Total

67,900

4,850

4,481

1,658

4,768

Low Level
Dryer Stack36

NA

3,494

3,018

593

2,764

Fugitive

26,400

3,003

2,846

1,370

3,319

26,400

6,497

5,864

1,963

6,083

3,620

10,851

Low Level Stack
and Fugitive Total

High and Low Level
Total

34

94,300

11,347

10,345

The original MPR analysis projected an hourly emissions rate of 94,242 pounds of sulfur dioxide per hour as the basis for the

“rollback” for the San Manuel Smelter. This projection was based on sulfur balance data submitted by the facility and supports empirical
evidence that approximately thirty percent of the sulfur content in sulfide copper concentrate will be oxidized by an initial melting step such
as occurs in reverberatory furnaces. Of the remaining 70%, it is estimated that the 1980 vintage primary hood system at the San Manuel
smelter was, at best, sixty percent efficient in capturing converter gasses. Consequently, 42% of these emissions actually reported to the
converter stack. The remaining 28% was emitted as low-level fugitive emissions.
35
Values represent average emissions from 1997 through 1999. Because smelter operations were suspended in May 1999,
emissions for this year were estimated based on January through April operating levels to reflect a full year of emissions.
36

A recent permit revision limits dryer SO2 emissions to 2,073 tpy based on a twelve month rolling average.

46

Table 5.3 - Emissions Source Distance from Facility Boundary (feet)
Distance to Property Line1974

Distance to Property LinePresent

Reverb Stack

1,399

1,399

Converter Stack

1,955

1,955

Dryer Stack

NA

144

Tail I

NA

NA

Tail II

NA

2,160

Tail III

NA

1,744

1,735

1,735

Emissions Source

Converter fugitives

release geometry. This consistency of SO2 release locations continued through the 1990's
thereby providing assurance that the ambient SO2 monitoring network continues to represent the
maximum impact of SO2 emissions from the San M anuel smelter. As demonstrated above, SO2
concentrations in the San M anuel nonattainment area have been shown to attain the NAAQS

47

6.0 CONTROL MEAS URES
Because the BHP smelter is responsible for the majority of SO2 emissions in the area, the
following attainment demonstration control measures relate specifically to BHP smelting operations.
Applicable controls for other point sources in the San M anuel nonattainment area are discussed in
Chapter 4.0.

6.1 Background 37
Smelting operations at San M anuel began in 1956. By the late 1950s the facility operated three
reverberatory furnaces to process copper sulfide ore from nearby mines. Today the San M anuel
primary copper smelter utilizes a flash smelting process and has a processing capacity of more than
25 percent of total U.S. smelting capacity.
The processing of copper sulphide ore begins at the mine where ore is crushed and transported
to the San M anuel concentrator. At the concentrator facilities, the ore is ground at milling operations
and processed by froth flotation to separate copper mineral from ore. Further processing at a
molybdenite plant recovers a molybdenum disulphide concentrate from the bulk concentrate, a major
byproduct of the San M anuel operations. Concentrates from this plant are filtered and dried in a
concentrate dryer. These are the copper concentrates used in the s melt ing operations. Dryer
process gas is treated in a baghouse for dust removal and vented to the atmosphere via stack.
The copper concentrate, containing approximately equal parts of copper, iron, and sulfur, is
transferred to the Outokumpu design flash furnace for smelting. Dry concentrate and fluxes are
injected through a concentrate burner into the flash furnace and are rapidly oxidized in an oxygen rich
atmosphere. Oxygen for the flash reaction is produced by fractional distillation at the oxygen plant.
Hot gas from the flash furnace, containing nearly 26 percent SO 2 , is drawn into a waste heat boiler
where the heat is removed for the production of steam by the San M anuel power plant. The cooled
process gas is ducted to two electrostatic precipitators for dust removal prior to additional treatment
in the acid plant and then exhausted to the atmosphere via one of two acid train stacks. Secondary
process gas from the furnace matte skimming and slag tapping launder covers are also treated by
electrostatic precipitator and exhausted to the atmosphere via stack. The remaining products of flash
smelting are matte and slag.
M olten copper matte, containing about 60 percent copper, is tapped through covered launders
into ladles and transferred by overhead cranes to one of three operating hot converters. In the
converters, further oxidation of sulphur and slagging of iron and other metals takes place until the
copper reaches a purity of 99 percent. The molten copper from the converters, called blister copper,
is further fire refined for the removal of oxygen and cast into anodes in the casting department for
37

Calculations used in this section were based on the following:
a. US EPA, AP-42, Compilation of Air Pollution Emission Factors, Fifth Edition, August 31, 1998.
b. BHP Smelter Federal Operating Permit Application, submitted November 1, 1994.
c. BHP Smelter 1998 Emissions Inventory Survey.

48

transport to an electrollytic refinery. Converter primary process gases are treated by Lurgi scrubber
then ducted for treatment in the acid plant. Converter secondary hood gases are directed to
electrostatic precipitators and discharged to the atmosphere via stack.
M olten s lag from the flash furnace and converters, containing small amounts of copper, is
cooled, crushed, and then returned to the mill for grinding and a copper content recovery flotation
operation before joining other concentrate for processing in the flash furnace. Detailed process flow
diagrams are included in this submittal in Appendix C.
Prior to 1974, all smelting operations process gasses were emitted into the atmosphere after
particulate removal by electrostatic precipitators. From sulfur balance data the average emissions
were reported to be 94,242 lbs/hr. The installation of an acid plant in late 1974 added SO2 control
for primary converter gas. A s eries of improvements in 1988 included replacement of the
reverberatory furnaces with an Outokumpu Flash Furnace. During the flash furnace conversion,
BHP also installed a 690 ton per day oxygen plant to enrich t he furnace combustion air and
retrofitted the existing single contact acid plant to a double-contact acid plant with a production
capacity of 4,286 tons of sulfuric acid per day for treatment of all flas h furnace and converter
primary process gases.
The double-absorption sulphuric acid plant is t he predominant control device for primary
process SO2 emissions at this smelter. Process gases produced by the flash furnace and converters
are cleaned of particulates in a gas scrubbing system to prepare the gas stream for treatment in the
acid plant. The flash furnace provides a steady gas feed to the acid plant, enabling optimal plant
performance. In the acid plant, the SO2 is cleaned, dried, and converted by catalyst to sulphur
trioxide (SO3 ). The SO3 is readily adsorbed in circulating dilute sulphuric acid to become salable
grade acid. The acid plant provides cont rol of process gas SO2 at or below the outlet SO2
concentration limit of 0.065 percent by volume set forth in the federal New Source Performance
Standard 40 CFR 60, Part P. The SO2 control performance for the BHP acid plant is an outlet
emission concentration of 0.0200 percent by volume. The maximum annual process rate for this
smelter is estimated at 180-240 tons per hour (tph) of new sulfide concentrates. The production
throughput of this facility, however, is dependent upon the operational capacity of the sulfuric acid
plant to treat SO2 emissions from the flash furnace and converters.
The 1988 conversion included the addition of equipment to improve the collection and control
of fugitive SO2 emissions and minimize the release of fugitive emissions directly to the atmosphere.
The installation of a Lurgi scrubber (a variable flow Venturi radial scrubber to cool and clean process
gas prior to treatment in the acid plant) replaced a previously extensive duct system used for cooling
converter primary process gas. The old, difficult to maintain, ductwork was subject to recurring
leaks and was a major source of fugitive emissions.
The flash furnace, oxygen plant, acid plant, and other improvements made during the transition
from the reverberatory furnaces to the flash furnace, subsequently reduced the SO 2 emissions rate
by 50 percent. This improvement is demonstrated in Figure 6.1, which illustrates the pre-control
and post-control ambient SO2 levels. Figure 6.2 illustrates the reduction in emissions though BHP
was increasing copper production.
Although the converter secondary process emissions are hooded to minimiz e t he release of
49

fugitive emissions directly to the atmos p here, fugitive emission control is also dependent upon
maintenance and operating procedures. The level of control of the converter secondary hood gas is
achieved through the scheduling of the copper converting process. Control of the converter process
is a major contributor to this smelter’s reduction in SO2 emissions. After the secondary hoods were
installed, BHP found that the majority of secondary hood gas is generated during the roll-in and rollout of the converters. By minimizing the amount of blast air during these periods, while at the same
time balancing the primary and secondary hood draft, more of the process gas is captured by the
primary hoods and reports to the acid plant for treatment. This operating technique reduced the
amount of fugitive emissions due to converter activity by 3,040 tpy. BHP continues to identify
fugitive emissions problem areas and correct the deficiencies as necessary.
In 1999, BHP rebuilt the flash furnace, the concentrate dryer burner, and replaced an electrostatic
precipitator with a baghouse for treatment of concentrate dryer off-gas. The new design, completed
during the temporary closure period which began in M ay 1999, improved the capture of fugitive
emissions and minimized the oxidation of sulfur in the dryer circuit. At this time, BHP accepted a
2,073 tpy permit limit for SO2 emissions from the concentrate dryer providing a 50 percent decrease
of allowable emissions from this unit. A net decrease in future SO2 emissions is estimated at 97.17
tpy, which is approximately an 0.8 percent reduction in the total estimated smelter emissions. The
emissions control improvements implemented at the BHP smelter are summarized in Table 6.1 .
Table 6.1 - Implementation of SO2 Control Technology
Year

Control Equipment

1974

Installation of a two train sulfuric acid plant No.1 and No. 2 (primary converter gas only).

1988

Replacement of reverberatory furnaces with an Outokumpu Flash Furnace.
Retrofit to a double absorption acid plant for treatment of all primary process gas (flash furnace and
converters), and installation of a new flux processing unit.
Replacement of primary converter hoods and jackets and installation of a lurgi scrubber.
Installation of matte skimming and slag tapping launder covers, and installation of converter secondary
hoods for capture and venting of fugitive gases to the stack.

1992

Installation of two trim coolers on one acid plant tail stack to control acid temperature and maximize
SO2 conversion to SO3 at the acid plant.

1993

Development and implementation of the optimal operating scenario for majority capture of converter
process gas in primary collection system for treatment in acid plant.

1994

Installation of a new larger capacity third train to supplement the existing two train sulfuric acid
plant and upgrade of Acid Plant Train II. The additional capacity allowed more of the converter offgas to be drawn into the acid plant, thereby lowering emissions from both the converter secondary
hood gas as well as roof fugitives.

1995

Installation and upgrade of Acid plant train III, upgrade acid plant train II, and retrofit of No. 3 converter.

50

Table 6.1 - Implementation of SO2 Control Technology
1996

Installation of stainless steel ducting from the converters to the acid plant eliminating rubber expansion
joints which eventually deteriorate from the sulfuric acid stream.
Redesign of the secondary hooding system to reduce the gap between the hoods and converters during
the scheduled converter rebuild program (rebuild of converters occurs every 2 years to ensure optimum
control of fugitive emissions).

1997

Installation of two additional roof vent fan sulfur dioxide analyzers to quantify converter area uncaptured
fugitive SO2 emissions and further identify processes associated with increased emissions.

1998

Expansion of the emissions capture capacity of the flash smelter furnace launder system by increasing
volume of airflow by over 50 percent.

1999

Rebuild of the Outokumpu type flash smelter, redesign of concentrate dryer burner to minimize the
oxidation of sulfur in the dryer circuit, and replacement of the electrostatic precipitator for treatment of
dryer off gas with a high temperature baghouse to further minimize the oxidation of sulfur.

51

Figure 6.1 - Comparison of SO2 Emissions and Percent Control

52

Figure 6.2 Comparison of SO2 Emissions and Copper Production

53

6.2 Emissions Limitations for BHP
6.2.1 AAC Rule R18-2-715(F)(1), R18-2-715(G) and R18-2-715.01 - Standards of Performance
for Existing Primary Copper Smelters: Site specific requirements; Compliance and M onitoring
Measure Description:
In 1979, ADEQ promulgated site specific emissions limits at Arizona Administrative Rules and
Regulations (AARR) R9-3-515, currently codified at AAC R18-2-715 (See Appendix A). The rule
required all existing primary copper smelters to implement control technology sufficient to comply
with the 1979 M PR stack limits as well as any fugitive emissions control technology necessary to
assure attainment and maintenance of the NAAQS. The following emissions limits were specified
for the BHP copper smelter at San M anuel:
1.

Annual average stack emissions, as calculated purs uant to AAC R18-2-715.01(C)
through (J) s hall not exceed 18,275 lbs/hr. The number of three-hour emissions, as
calculated pursuant to AAC R18-2-715.01(C) through (J) shall not exceed the limits as
listed in AAC R18-2-715(F)(1).

ADEQ’s 2001 rule revision incorporated the following voluntary stack limits and added
converter roof fugitive limits for the BHP smelter (See Appendix A for rule revision):
1.

2.

Annual average stack emissions, as calculated pursuant to AAC R18-2-715.01(C), shall
not exceed 1,742 lbs/hr. The number of three-hour emissions, as calculated pursuant to
AAC R18-2-715.01(C), shall not exceed the revised limits listed in AAC R18-2715(F)(1).
Annual average converter roof fugitive emissions, as calculated pursuant to AAC R18-2715.01(R), shall not exceed 715 lbs/hr. The number of three-hour emissions, as calculated
pursuant to AAC R18-2-715.01(R), shall not exceed the limits as listed in AAC R18-2715(G)(1).

Estimated S O 2 Emission Reduction:
Emissions were reduced 480,273 tpy following compliance with the 1979 rule. Subsequent
implementation of additional emissions collection and control measures enabled the 2001 revision
that provides a further reduction in allowable emissions of 74,166 tpy.
Responsible Agency and Authority for Implementation:
ADEQ is the responsible agency with authority designated by ARS §49-104(A)(11) and ARS §49422.
54

Implementation S chedule:
The 1979 rule provided a compliance date of January 14, 1986, unless otherwise provided in a
consent decree or a delayed compliance order. The compliance date for implementation of the 2001
rule revisions is January 15, 2002.
Level of Personnel and Funding Allocated for Implementation:
No additional personnel are required; implementation funding for ADEQ personnel is
underwritten through emission and inspection fees. The approximate cost to the smelter is
$100,000 per annum for operation and maintenance of the ambient air analyzers. Expenditures for
emissions collection and control improvements at the smelter are noted below.
Enforcement Program:
ADEQ is responsible for tracking the progress made through the implementation of this measure
and for enforcing all applicable regulations through the schedule of inspections and the development
of compliance and enforcement actions. (See S ection 7.3 for a description of inspection and
compliance and enforcement procedures.)
Measure Monitoring Program:
BHP submitted a proposed compliance schedule in response to a 1987 Consent Decree (CIV 87106-Tuc-WDB, dated September 28, 1987), for achievement of the 1979 M PR stack emission limits
as expeditiously as practicable. The smelter subsequently submitted a permit application in 1987
for installation of $157 million worth of emissions collection and control equipment. All on-site
construction and installation of emission control equipment and process modification was completed
in 1988, meeting the incremental compliance schedule requirements of the Consent Decree. The
collection and control technology implemented by BHP has allowed the facility to reduce emissions
sufficient to demonstrate attainment and to request additional emissions reductions in 2001 (See
S ection 6.2 for a description of the implemented equipment).
For purposes of determining compliance with the emissions limits as codified in 1979, BHP was
required to install, calibrate, maintain, and operate a measurement system for continuously
monitoring SO2 concentrations and stack gas volumetric flow rates in each stack that could emit 5
percent or more of the allowable annual average SO2 emissions from the smelter. Demonstrations
of stack gas volumet ric flow rate and SO2 concentration measurement systems required by
subsections AAC R18-2-715.01 (K)(5)(a) and (b) were initiated in 1976. The location of all stack
sampling points were approved by ADEQ in conjunction with the cons ent decree prior to
installation and operation of the continuous emission monitoring systems (CEM S). BHP installed
and operates CEM S at the outlets of the acid plant train I and II (currently II and III), the
55

concentrate dryer, the flash furnace fugitive gas circuit, and the converter secondary hood gas circuit.
In addition to primary process gas, captured fugitive emissions are continuously monitored for SO2
concentrations and stack gas volumetric flow rates, and are included when determining compliance
with the cumulative occurrence and emissions limits contained in R18-2-715(F)(1). M onitoring and
emissions data submit t ed by BHP indicated that the smelter was in compliance with the 1979
emission limits by 1989.
To quantify converter area uncaptured fugitive emissions , BHP also installed and operates
CEM S at the outlets of the converter building forced draft roof vent ilators. Requirements to
maintain and operate CEM S for continuously monitoring SO2 concentrations at the converter roof
vents was included in the 2001 revision for determining compliance with the cumulative occurrence
and emissions limits contained in R18-2-715(G)(1).
Provisions for minimum performance and operating specifications for CEM S at this facility are
contained in AAC R18-2-715.01(K)(5) and R18-2-715.01(S). Additional requirements for emission
monitoring of the sulfuric acid plant are contained in AAC R18-2-313, Existing Source Emissions
M onitoring. The BHP smelter stack and fugitive monitoring system is subject to the manufacturer’s
recommended zero adjustment and calibration procedures at least once per 24-hour operating period
and meets all applicable performance specification and quality assurance procedures contained in 40
CFR 60, Appendix B and F. Daily calibration and quarterly audits conducted by BHP are reported
to ADEQ. To ensure continued compliance, BHP maintains on hand and has ready for immediate
installation sufficient spare parts or duplicate systems for the continuous monitoring equipment to
allow for the replacement within six hours of any monitoring equipment part which fails or
malfunctions during operation.
As required by AAC R18-2-715.01 (L), BHP measures at least 95 percent of the hours during
which emissions occurred in any month and has not failed to measure any 12 consecutive hours of
emissions. BHP maintains records of all average hourly emissions measurements for at least five
years following the date of measurement as required by 40 CFR 60 Subpart P - Standards of
Performance for Primary Copper Smelters. All of the following measurement results are expressed
as pounds per hour of SO2 , summarized monthly, and submitted to ADEQ within 20 days after the
end of each month:
1.
2.
3.

4.

The annual average of the month;
The total number of hourly periods during the month in which measurements are not
taken and the reason for loss of measurement for each period;
The number of three-hour emissions averages which exceeded each of the applicable
emissions levels listed in R18-2-715.01(F)(1) (and R18-2-715.01(G)(1) subsequent to
2001 revision) for the compliance periods ending on each day of the month being
reported;
The date on which a cumulative occurrence limit listed in R18-715.01(F)(1) (and R18-2715.01(G)(1) subsequent to 2001 revision) was exceeded if such exceedance occurred
during the month being reported.

56

These submitted reports have shown continued compliance with all applicable regulations and
averaging standards. ADEQ has not issued any notices of compliance actions for a monitoring
violation to this facility.
As a means of determining total overall emissions, BHP performs a monthly material balance for
sulfur and includes the results in the monthly compliance reports to ADEQ. Based on these reports,
the smelter continues to document a sulfur recovery rate over 98 percent. The average monthly
sulfur recovery rate for M ay 1997, through April 1999, was calculated to be 98.48 percent and
ranged from 98.01 percent to 98.82 percent through the period.
In addition to monthly compliance reports, ADEQ also receives from BHP quarterly audit,
upset, and excess emissions reports, as well as annual emissions inventory reports based in part on
the SO2 CEM S data.
The rule also specifies requirements regarding bypass operations. At each point in the smelter
facility where a means exists to bypass the sulfur removal equipment, the bypass is instrumented
and monitored to detect and record all periods that the bypass is in operation. The bypass has been
used for maintenance failures, especially at the acid plant, with the average bypass time lasting
approximately 10 minutes. All production activities at the smelter cease during a bypass. BHP
reports the required information to ADEQ, not later than the 15th day of each month, and includes
an explanation for the necessity of the use of the bypass.
6.2.2 AAC Rule R18-2-715.02 Standards of Performance for Existing Primary Copper Smelters;
Fugitive Emissions
Measure Description:
This measure provides for an evaluation of the ambient impact of fugitive emissions from the San
M anuel smelter. The regulation requires a measurement or accurate estimate of fugitive SO2
emissions to determine whether these emissions have the potential to contribute to violations of the
ambient SO2 standards in the vicinity of the smelter. The rule also requires the adoption of rules
specifying emission limits or other appropriate measures necessary to maintain the standards.
Estimated S O 2 Emission Reduction:
A reduction of 40,023 tpy is estimated due to implementation of fugitive emissions collection and
control measures.
Responsible Agency and Authority for Implementation:
ADEQ is the responsible agency with authority designated by ARS §49-104(A)(11) and ARS §49422.
Implementation S chedule:
57

The rule provides a compliance date of January 14, 1986.
Level of Personnel and Funding Allocated for Implementation:
No additional personnel is required; implementation funding for the fugitive emission evaluation
study was provided by BHP. The approximate cost of the SO2 fugitive emission evaluation study
was one million dollars.
Enforcement Program:
ADEQ is responsible for tracking the progress made through the implementation of this measure and
for enforcing this measure through the schedule of inspections and the development of compliance
and enforcement actions (See S ection 7.3 for a description of insp ect ion and compliance
enforcement procedures).
Measure Monitoring Program:
Fugitive SO2 emissions at the BHP smelter are primarily generated from the flash furnace,
converter, and anode process areas. Emissions escape the ventilation systems and exit the buildings
through roof vents. These structures mounted on the roofs of the building provide an escape route
for uncaptured emissions. A portion of the SO2 emissions may escape through other exit points,
such as open walls and doors in the building. These alternate exit points were identified by BHP
through flow visualization tests and survey sampling. The following studies and other data gathered
demonstrated that the majority of the SO2 fugit ive emissions escape from the furnace and the
converter processes and identify the converter area as the primary source of uncaptured emissions
at the smelter.
On April 3, 1986, BHP submitted to the Arizona Department of Health Services (ADHS) a
fugitive SO2 emissions description, evaluation, and demonstration study, to partially fulfill the
outstanding SIP commitments for analysis of fugitive emissions. The study analyzed data from
January 1983 through January 1984 and identified converter operations as the major source of
fugitive emissions.
A fugitive SO2 emissions study of the launders was submitted on December, 1989. This study
quantified uncaptured fugitive emissions from flash furnace slag and matte tapping operations and
analyzed the ambient impacts of uncaptured flash furnace and converter fugitive emissions as well
as impacts from the acid plant tail stacks. An assessment of the launders estimated a 90-95 percent
emissions capture from these systems.
A Differential SO2 Ambient Impact Assessment Report was completed and submitted to the
Arizona Department of Environmental Quality (ADEQ) on January, 1993. The study compared
specific ambient monitored concentrations with modeled values based on actual hourly stack and
converter area uncaptured fugitive emissions rates. A second analysis incorporated a cartesian
receptor grid to estimate ambient impacts from each of t he smelter sources and compared the
58

maximum impacts of stack and converter vent fugitives. Although fugitive emissions demonstrated
a higher proportion of ambient impact relative to stack emissions in certain locations close to the
smelter, the studies concluded that fugitive emissions will neither cause nor significantly contribute
to a violation of the NAAQS. Summaries of the fugitive emissions studies are contained in Appendix
C.
M easures to improve collection and cont rol of fugitive emissions together with control of
primary process gasses have reduced total emissions to a level protective of the NAAQS in the San
M anuel area (See S ection 6.2 for a description of implemented equipment). Captured fugitive
emissions currently comprise approximately 36 percent of total facility emissions and are included
when determining compliance with the stack limits described in Section 6.3.1. The section also
details control of an additional 27 percent of total emissions achieved through the adoption of limits
for uncaptured converter area fugitive emissions.

6.2.3

BHP Permit Conditions

Reasonably Available Control Technology (RACT) for sources located in SO2 nonattainment
areas is defined as “that control technology necessary to achieve the NAAQS and is determined by
the technological and economic feasibilit y of the control.”38 Submittal of biennial compliance
certifications under AAC R18-2-309(2)(a) are required to demonstrate the compliance status of the
source with all applicable permit conditions. Controls implemented by BHP to reduce smelter
emissions and comply with emissions limit regulations are included in the following permits outlined
in Table 6.2, found on the following page. Additionally, BHP submitted a standard Title V permit
application form to ADEQ on November 2, 1994. The application for the BHP smelter including
the Outokumpu flash furnace, Pierce-Smith converters, anode furnaces, concentrate dryers, double
absorption acid plants, oxygen plant, gas cleaning plant including electrostatic precipitators, filter
plant, revert crushing plant and associated equipment has been processed and the final permit was
issued on November 19, 2001.
Table 6.2 - Permit Conditions
Permit
Number

Date
October 7,
1987

38

0355-88

Controls39
Retrofit to install Outokumpu Flash Furnace, converter secondary
hoods, double absorption acid plant to treat all process gases and
new flux processing unit.

US EPA Office of Air and Radiation, Office of Air Quality Planning and Standards, “SO2 Guideline Document,” February

1994.
39

All listed controls have been captured in the facility’s Title V permit

59

.

August 28,
1992

1241

Installation of a new larger capacity third train to supplement the
existing two train sulfuric acid plant and replacement of an existing
copper converter. Shortly after the new third Train was completed,
BHP upgraded Acid Plant Train II. The upgrades allowed BHP to
increase the capacity of the new train, Acid Plant Train III, and take
Acid Plant Train I out of service. This permit contained emissions
limits for fugitive SO2 emissions as measured from the converter
roof. The limit for this source was 1,115 lbs/hr (4,884 tpy).

March 24,
1998

1000681

Rebuild of Outokumpu flash smelting furnace and concentrate dryer
burner to minimize sulfur oxidation. Additional emission limitations,
fuel usage limitations, and air pollution emission control devices
were included in this significant retrofit. Permit Section II(A)
further limited SO2 emissions from the concentrate dryer, to less
than 2,073
tpy based on a 12-month, rolling monthly average.

July 23,
2001

1001582

Revised the limits for stack and converter roof fugitive SO2
emissions
to 7,629 and 3,132 tpy respectively.
Requires maintenance and operation of all collection, process, and
control equipment in a manner consistent with good air pollution
control practice.
Continued operation of CEMS is required to monitor and record SO2
discharge emissions rates from the smelting facility.
Continued operation, maintenance, and calibration of all current
BHP ambient monitors are also required.

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7.0 MAINTENANCE PLAN
Section 107 (d) (3) of the amended CAA requires that nonattainment areas must have a fullyapproved maintenance plan meeting the requirements of Section 175 (A) before they can be
redesignated to attainment. Section 175 (A) requires submittal of a SIP revision that provides for
the maintenance of the NAAQS for at least 10 years after the redesignation to attainment. The
required components of the maintenance plan include:
1. A demonstration that future emissions of SO2 will not cause a violation of the SO2 NAAQS,
2. A commitment to continue to operate an appropriate air quality monitoring network to verify
the attainment status of the area,
3. Assurance that the state has the legal authority necessary to implement and enforce all
necessary measures used to attain and maintain the NAAQS,
4. An indication of how the state will track the progress of the maintenance plan, and
5. A contingency plan that contains measures to promptly correct any violation of the NAAQS
that occurs after redesignation.
This submittal demonstrates that all of the above required elements have been met. ADEQ also
commits to a SIP revision subsequent to this submittal providing for maintenance of the NAAQS
for an additional ten years. This subsequent revis ion is due eight years into the first ten year
maintenance period.

7.1 Maintenance Demonstration
Copper smelting operations at the BHP facility are the single greatest source of SO2 emissions
in the San M anuel nonattainment area comprising more than 99 percent of total emissions in the area.
The conservative emissions limits that have been established for the smelter are based on actual
emissions for the most recent eight quarters of smelter operations showing attainment of the SO2
NAAQS (See Chapter 4). Once the area is redesignated, any new sources or modifications to
existing point sources of SO2 are subject to the new source permitting procedures contained in AAC
Title 18, Chapter 2, Article 4, specifically, ADEQ’s Prevention of Significant Deterioration (PSD)
Permitting Program contained in AAC R18-2-406. The regulations were established to preserve the
air quality in areas where ambient concentrations are below the NAAQS and require stationary
sources to undergo precons t ruction review, utilizing BACT, before the facility is constructed,
modified, or reconstructed.
Projections of 1998 base year attainment inventories for the BHP smelter and all other point
sources in the nonattainment area are included in Table 4.3 of this submittal. These projections
indicate that emissions in the area are estimated to demonstrate only slight growth through 2015.
The estimate of mobile and area s ource emissions through the maintenance period is based on
moderate population growth. Projections of 1998 base year attainment inventories for mobile and
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area source emissions in the nonattainment area are included in Table 4.4 of this submittal. Area,
mobile, and point source projections are illustrated in Figure 7.1.40 Chapter 4 contains detailed
projection information for all sources. Although projections indicate an estimated five percent
increase of point, mobile, and area source emissions through 2015, total nonattainment area emissions
are four percent lower than 1997. Because the attainment emissions inventories demonstrate a
stringent level of protect ion of ambient air quality and only slight growth from 1998 base year
inventories is estimated for total source emis s ions, once redesignated, the area is projected to
continue to exhibit a substantial margin of safety protective of the SO2 NAAQS.
Fig. 7.1-San Manuel Nonattainment Area
SO2 Emissions Projections
12000

Emissions (Tons/Year)

10000

8000

6000

4000

2000

0

1997

1998

1999

2005

2010

2015

Year

area/mobile

point

total

7.2 Ambient Monitoring
Continued operation of an appropriate air quality monitoring network is required to verify the
attainment status of the area. To comply with the requirements of this maintenance plan, ADEQ
and BHP, commit to continue monitoring ambient SO2 concentrations for at least 10 years following
the approval of this SIP and maintenance plan. The requirement for BHP to continue to calibrate,
maintain, and operate SO2 ambient monitoring equipment that meets EPA protocol at the Townsite,
40

Projections assume resumption of BHP smelting operations.

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Dorm, and Hospital sites were made enforceable in BHP permit number 1000047. Permit number
1001582 allows the shutdown of the BHP operated ambient SO2 monitoringequipment if the facility
has not operated for more than 24 consecutive months. Ambient SO2 measurement is required to
resume at all facility operated sites three months prior to restarting of smelting operations. To
ensure adequate representation of ambient air quality, ADEQ will continue to calibrate, maintain, and
operate the SO2 monitoring equipment at the LDS site through the maintenance period.
Any changes in monitor location that may be indicated due to future changes in conditions will
be discussed with EPA Region IX prior to final decisions. All ambient monitoring data will continue
to be quality assured to meet the requirements of 40 CFR 58, Ambient Air Quality Surveillance.
Data will also continue to be entered into EPA’s Aerometric Information Reporting System (AIRS)
database in accordance with federal guidelines.
In addition, BHP will continue to monitor ambient temperatures, and wind speed and direction
for at least 10 years following the approval of this SIP and maintenance plan. The requirement for
BHP to continue to calibrate, maintain, and operate ambient meteorological equipment at the
Townsite, Dorm, and Hospital sites will be made enforceable as a permit condition for p ermit
number 1000047. The provisions of this permit also allow the shutdown of the meteorological
equipment if the smelting facility has not operated for more than 24 consecutive months.
M eteorological measurement is required to resume at these sites three months prior to restarting of
smelting operations.

7.3 Verification of Continued Attainment
ADEQ anticipates no relaxation of any of the already implemented control measures used to
attain and maintain the ambient air quality standards. ADEQ commits to submit to EPA Region IX
any changes to its rules or emission limits applicable to SO 2 sources as a SIP revision. ADEQ also
commits to maintain the necessary resources to actively enforce any violations of the rules or permit
provisions contained in this submittal.
Permitted sources are subject to the monit oring and reporting, and certification procedures
contained in AAC R18-2-306 and AAC R18-2-309 respectively. BHP submits all certifications and
reports as required by the above provisions (See S ection 4.3.1). ADEQ has authority pursuant to
ARS §49-101 et seq. to monitor and ensure source compliance with all applicable rules and permit
conditions.
When ADEQ identifies a violation of any applicable permit requirement either through an
inspection or records submitted to ADEQ, a decision will be made whether to issue a notice of
opportunity to correct, a notice of violation (NOV), an administrative order, or to seek injunctive
relief, and/or seek civil penalties. This decision will be made based upon the following
considerations:
1.

Risk to human health, safety, welfare or the environment;
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The violator’s indifference to the law;
The violator’s previous compliance history.

2.
3.

Every notice of violation from ADEQ includes the following elements:
1.
2.
3.
4.

The factual nature of the violation.
The legal authority regarding compliance.
A description of what constitutes compliance and how it is to be documented.
A time frame in which ADEQ expects compliance to be achieved. Time frames shall
require compliance at the earliest possible date.
5.
An offer to meet.
6.
A statement of consequences.
If violations are not corrected within 120 days from receipt of the notice of violation, the facility is
required to enter into a consent order or an executed agreement for a consent decree and a compliance
schedule. M easures for addressing violations of the NAAQS are provided in the contingency plan
(See S ection 7.4).

7.4 Contingency Plan
This contingency plan provides a procedure to ensure future compliance and promptly correct
any violation of the SO2 NAAQS that may occur after redesignation of the area to attainment.
Contingency measures do not have t o be fully implemented at the time of redesignation. The
assurance that the contingency procedures outlined in this plan will be followed and commitments
will be implemented and enforced is contained in state law at ARS §49-402 and §49-404. Because
the BHP Copper San M anuel smelting facility is the major source of SO2 emissions in the
nonattainment area, the contingency measures presented in this section focus primarily on ambient
impacts of emissions attributable to this facility. Contingency measures for all other point sources
are provided by the Prevention of Significant Deterioration (PSD) requirements contained in AAC
R18-2-403 and AAC R18-2-406.41
A first occurrence in a calender year of a verified 3-hour average SO2 level in excess of 0.425 ppm
but less than 0.5 ppm (85 percent of the secondary NAAQS but less than 100 percent) shall require
notification as described in the procedures below. A second occurrence in a calender year of a
verified 3-hour average SO2 level in excess of 0.425 ppm but less than 0.5 ppm (85 percent of the
secondary NAAQS but less than 100 percent) or any occurrence of a verified 3-hour average SO2
level in excess of 0.5 ppm (100 percent of the secondary NAAQS), recorded at any ambient
monitoring station, has been selected as the protective trigger level (P TL). When the PTL is
exceeded, there will be ample time to complete all necessary facilit y inspections and technical
41

State regulations comply with the federal requirements found in: 40 CFR 51.307 (NSR); 40 CFR 51.166 (PSD).

64

evaluations, develop recommendations, and implement necessary mitigation measures to prevent any
violation of the SO2 NAAQS. M ultiple exceedances (either sp at ially or temporally) shall be
considered a single event during an episode.42 Special M easures described below for a second
occurrence in a calender year of a verified 3-hour average ambient SO2 level over 0.5 ppm (a violation
of the secondary N A A Q S), provide added protection to prevent a violation of the air quality
standards.
7.4.1

Notification Procedure

BHP will record the hourly concentrations for all facility operated ambient monitoring sites.
ADEQ will record the hourly concentrations for the state operated ambient monitoring site. For the
BHP operated SO2 monitors, the facility respons ible official must notify ADEQ as soon as
practicable, but no later than the close of the next business day after initially verified monitoring data
indicate that an ambient SO2 level in excess of 0.425 ppm has been recorded. F or the ADEQ
operated SO2 monitor, ADEQ must notify the BHP responsible official as soon as practicable, but
no later than the close of the next business day after initially verified monitoring data indicate that
an ambient SO2 level above 0.425 ppm. The facility will also have access to ADEQ’s data.

7.4.2

First Action Level

These actions must be completed as soon as practicable, but no later than 24 hours following an
event and should include at a minimum:
A full calibration check of the ambient SO2 analyzers and recording systems, and review
of all applicable records of environmental conditions and electrical supply at the monitor
at the time of the exceedance. Final validation will be based on current EPA and ADEQ
quality assurance guidelines,
Inspection of all ductwork and hooding associated with the flash furnace process and
fugitive gases and the converter process and secondary hood gases,
Assessment of the acid plant to ensure that this facility is operating within parameters
recommended by the manufacturer for optimal performance within the New Source
Performance Standards limits, and
Inspection of all other processing equipment.

1.

2.
3.

4.

If it is determined that the exceedance of the PTL or NAAQS was due to invalid ambient monitoring
data no further action is necessary.
42

For this SIP, an episode commences at the time that the first exceedance begins and an episode shall conclude at the end of

the 3-hour period following the last exceedance that can be attributed to the same cause.

65

In the event of a valid exceedance, BHP will, as soon as feasible, perform any needed repairs or
corrective maintenance actions as evidenced by the assessment, including if necessary, cessation of
facility operations. The following preventive measures shall also be implemented:
Walk through inspections and maintenance of emissions collection, control, and
process equipment , shall be increased from bi-weekly to weekly for the 12
month period following an exceedance of the PTL.43 These inspections shall be
targeted to the cause of the exceedance. Should another exceedance of the PTL
or NAAQS occur at any time within the ensuing 12 month period, the frequency
of walk through inspections shall be increased to daily for the 12 month period
following that exceedance. Daily inspections targeted to the cause shall continue
for the 12 month period following any subsequent exceedances.
By the close of the second business day following an exceedance of the PTL, BHP will submit
a report to ADEQ citing the nature of the event, any corrective actions or repairs undertaken to
resolve the event, and recommendations for future corrective actions including specific milestones
to avoid recurrence of such event. Any future repairs or corrective action taken must be reported
to ADEQ within three working days after the repair or action is done. If the cause of the event has
been resolved to ADEQ’s satisfaction, no further action by BHP is necessary.

7.4.3

Second Action Level

Should a triggering of the PTL occur and not be found correctable by actions previously
described, an analysis shall be performed to identify additional mitigation measures needed to ensure
maintenance of the ambient air quality standards. Additional contingency measures considered for
implementation may include:
1.
2.
3.
4.
5.

Additional operating procedures consistent with good air pollution control practices,
Additional emissions collection and control technology,
Application of operating rate/process parameter limitations,
Further decreasing stack and/or fugitive emissions limits, and
Any other measures necessary to protect and maintain the NAAQS.

BHP’s assessment and recommendation of the above measures shall be reported to ADEQ within
30 business days following a triggering of the PTL. No later than 90 business days following receipt
of BHP’s assessment and recommendations, and using all available data, ADEQ will make a
determination regarding the cause and appropriate resolution of t he event and shall require the
43

Current maintenance procedures are described in BHP’s Title V permit.

66

adoption and implementation of additional cont rol measures, if needed, to ensure that the SO2
NAAQS will not be violated. ADEQ commits to initiating any required revisions to rule or permit
as soon as possible. The addition of permanent control measures will be made by SIP revision
following the required public participation. Failure of BHP or the State of Arizona and its agencies
to implement control measures necessary to maintain the SO2 NAAQS may be considered a failure
to fulfill the obligations of this plan.

7.4.4

Special M easure

The following operational change shall be implemented within 24 hours of a monitored violation
of the secondary NAAQS:
Processing of new concentrate shall not exceed the rate as calculated by the following formula:
S /AC * APR = Operating Rate
Where:
S = 3-hour standard (1300 ug/m3);
AC = actual maximum 3-hour average concentration recorded during the exceedance period
(ug/m3); and
APR = average processing rate of new concentrate during the three hour exceedance period
(tons/hour).
BHP shall also comply with the First Action Level requirements and, if necessary, the Second
Action Level requirements. Within the same calender year, should a second and higher concentration
exceedance of the secondary NAAQS be recorded following implementation of the Special M easure,
the operating rate shall be recalculated accordingly. The Special M easure shall remain in effect until
the facility has identified any source of emissions contributing to ambient SO2 concentrations above
the secondary NAAQS and has remedied the cause. If the violation can be attributable to an upset
or malfunction the source may continue regular production while it submits a report within 24 hours
detailing any repair or resolution. As detailed above, and in Chapter 5, the continuation of the SO22
NAAQS will be maintained during the next ten years.

67

8.0

REFERENCES

Supplemental D to Compilation of Air Pollutant Emission Factors, Volume I: Stationary Point
and Area Sources (AP- 42 5th Edition), US Environmental Protection Agency, EPA-454F9903,
Department of Commerce, National Technical Information Service, Springfield, Virginia, August
31, 1998.
Breathing Easier: A Report on Air Quality in California, Arizona, Nevada, & Hawaii, US
Environmental Protection Agency, EPA-909-R-95-001, Region 9, Air and Toxics Division, San
Francisco, California, M ay 1995.
Sulfur Dioxide Guideline Document, US Environmental Protection Agency, EPA-452/R-94-008,
Research Triangle Park, North Carolina, February 1994.
Demonstration for a Fugitive Sulfur Dioxide Study at the BHP, Trinity Consultants Inc., Dallas,
Texas, April 3, 1986.
Differential SO2 Ambient Impact Assessment (San M anuel Smelter), Trinity Consultants Inc.,
Project 9260-094, Dallas, Texas, January 28, 1993.
Arizona Copper Smelter Handbook, Arizona M ining Association, Phoenix, Arizona, April 20,
1982.
Arizona Testing M anual for Air Pollutant Emissions (Revision E), Arizona Department of Air
Quality, M ay 15, 1989.
National Annual Industrial Sulfur Dioxide Emission Trends 1995- 2015, US Environmental
Protection Agency, EPA 454-R-95-001, Air and Radiation, Research Triangle Park, N.C., June
1995.
Western Regional Air Partnership (WRAP), Annex to the Report of the Grand Canyon Visibility
Transport Commission, October 16, 2000.

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