Our company maintains air emissions per megawatt-hour at or below industry averages. This is achieved through the use of nuclear power in the generation mix, emissions control technology, improved power plant efficiency and a more-diverse fuel mix which includes nuclear, gas/oil, coal and renewables. In addition, we have an aggressive demand-side management program that works to improve energy efficiency and reduce per capita demand.

Pollutant Emissions from the APS Generation System
The air emission charts below show our air emissions of primary pollutants from power plant generation over the last five years. 

Other air emission charts (click to view):  Carbon Monoxide,  Lead,  Mercury,  Particulates,  and Volatile Organic Compounds (VOCs),

APS plants comply with existing Clean Air Act (CAA) regulations. However, as we plan for the future, we recognize the need to significantly reduce emissions over the next several years to comply with new, proposed, and expected laws and regulations.

Sulfur and nitrogen oxides (S0₂ and NOx), particulate matter (PM) and mercury (Hg) are by-products of fossil fuel combustion at power plants. The CAA requires the Environmental Protection Agency (EPA) and the Arizona Department of Environmental Quality (ADEQ) to set emission limits for these pollutants to protect public health and the environment. These limits are imposed through regulations and incorporated in the plants’ operating permits. The expectation is that by meeting these permit limits, the emissions will not impact the environment or public health negatively. These limits, however, are based upon what is currently known, and as the state of the science on these pollutants improves, the regulatory agencies revise the emission limits. Thus, since the inception of the CAA in 1970, EPA and ADEQ have periodically set new, more stringent emission limits for operating sources. The regulators setting these limits anticipate that industry will respond by installing state-of-the-art pollution control technology as the standard method to minimize pollutant emissions into the environment.

Voluntary Emission Controls at Four Corners and Cholla Coal-fired Plants
In the late 1990s, APS initiated a dialog with four environmental-interest groups that are involved in environmental issues in the West (Environmental Defense, the Grand Canyon Trust, Western Resource Advocates, and the New Mexico Citizens for Clean Air and Water – hereafter referred to as the “Environmental Groups”).

The goal of this dialog was to discuss the complexities of environmental laws confronting the electric utility industry and explore common ground for navigating that complexity without the historic confrontation that exists between industry and the Environmental Groups.

The dialogue centered on the issue of visibility in the Western United States. The Clean Air Act designates 156 large national parks and wilderness areas as “Class I areas” and provides for protecting visibility in those areas. EPA’s visibility regulations require specific emissions limitations on sources causing, or contributing to, visibility impairment in Class I areas. Those rules focus primarily on SO₂ emissions, and to a lesser extent on NOx and particulate matter (PM) emissions, from large stationary sources such as coal-fired power plants. All three of the APS-owned coal-fired power plants are located on the Colorado Plateau, which contains numerous Class I areas.

The dialogue resulted in APS proposing a plan to voluntarily reduce pollutant emissions (especially SO₂) from its coal-fired plants in a cost-effective manner that would allow APS to meet or exceed the future emissions limits and programs proposed by EPA and ADEQ. This initial plan was then jointly presented to the Navajo EPA, the U.S.EPA and the ADEQ.

Four Corners Power Plant
In 2003, APS, the Environmental Groups, Navajo EPA, U.S.EPA and the National Park Service agreed on a proposal to reduce SO₂ emissions at the Four Corners plant utilizing an 18-month-long test program. The test program involved certain phased operational changes and scrubber chemical process changes to increase the SO₂ control level from 72 percent to 85 percent, without triggering operational problems or incurring significant new capital expenditures. APS initiated the test program in early 2004.

The test program was completed during summer 2005. APS prepared a report concluding that the plant not only was able to meet the goal set in the proposal, but it also improved SO₂ controls to the 88 percent level. At that elevated control level, the plant was able to cut its annual SO₂ emissions by more than 55 percent, compared to the pre-test level.

The figure below shows historic and projected future Four Corners emissions, and illustrates a dramatic drop in SO₂ in 2005 from the test program. APS is working with the EPA, NEPA, the NPS and the Environmental Groups to incorporate the higher SO₂. control level as an enforceable emission limit for the plant. In September 2006, the EPA proposed a Federal Implementation Plan that would incorporate the 88 percent SO₂ controls as an enforceable emissions limit for the plant.

The dialog with the Environmental Groups also dealt with NOx emissions. As a result of those discussions, an independent consultant was retained to assess the potential for reducing the plant’s NOx emissions using combustion modifications. The consultant’s report concluded that there was little room for improving combustion controls at the three smaller units, although further detailed evaluations were needed to assess potential combustion controls for the two larger units. APS is studying such control options and other post-combustion control options.

Results of APS Emission Reduction Program

Four Corners Total Plant Emissions of SO₂ and NO_x

Cholla Power Plant
The APS dialog with the Environmental Groups also resulted in an agreement in 2005 to implement several pollution control enhancements at the Cholla plant. The ADEQ and the EPA also were involved in the year-long discussions on selecting the pollution control upgrades and setting the schedule for implementation. Following this activity, APS filed and received a Title V Operating Permit renewal from ADEQ for the Cholla plant, which includes the following pollution control projects:

• Install new fabric filter bag-houses, low-NOx burners (LNBs), carbon monoxide (CO) continuous emissions monitoring system (CEMS), and upgrade S0₂ scrubber on Unit 1 from 80% to 90% sulfur removal efficiency by 2007.
• Install new LNBs and CO CEMS on Unit 2 by 2008.
• Replace existing hot-side electrostatic precipitators (ESPs) with a new fabric-filter bag-house, install new LNBs, CO CEMS, and a new 95% SO₂controls on Unit 3 by 2009.
• Upgrade existing S02controls to 92.5 percent, install new LNBs and CO CEMS; replace existing hot-side ESPs with a new fabric-filter bag-house on Unit 4 by 2008.

APS designed the new Cholla pollution control equipment to be flexible enough to meet stringent new rules for 90 percent removal of mercury from flue gas as proposed by ADEQ. APS will also evaluate the need for a new fabric-filter bag-house on Unit 2 by 2010 to meet the proposed mercury removal standards. The total costs for these new pollution control projects are estimated to be about $393 million.

The control levels and the associated schedule were developed to ensure continued operational viability with a secure coal supply, minimize costs and allow equipment to be installed during scheduled outages.

This collaborative approach for voluntarily achieving more emission reductions sooner – and at lower costs –assures Cholla’s economic viability and benefit APS shareholders, customers, regulators, the Environmental Groups, and most importantly, the environment.

Results of APS Emission Reduction Program

Cholla Total Plant Emissions of SO₂ and NO_x

Emissions technology mix
APS has a total of about 1,100 MW of generation capacity (all coal) which is scrubbed with Venturi scrubbers, flooded disc scrubbers or absorbers. APS has about 1,500 MW of generation capacity with SCR (all natural gas). APS has another 1,300 MW of generation capacity with low NOx burners.

Travel Reduction Program
Employee Travel Reduction is an important part of our EHS programs, particularly in the Phoenix area – a U.S. Environmental Protection Agency (EPA) non-attainment area for particulate matter and eight-hour ozone standard. We encourage employee travel reduction activity and offer subsidies to further persuade our employees to use alternative means of transportation. Our subsidies cover a portion of the costs for vanpooling, bus fares and carpool parking. We accommodate compressed work weeks, telecommuting and videoconferencing. We also offer assistance to employees in finding carpool partners, and in setting up carpools. The Travel Reduction Program also has a reward program for employees participating in travel reduction on High Pollution Advisory days.

APS maintains a fleet of 167 vans that operate daily for employees commuting between Palo Verde Nuclear Generating Station (PVNGS) and the Phoenix area. APS began operating this program in 1994 and almost 62 percent of the permanent APS employees at PVNGS participate. This program has significantly contributed to the site achieving a single occupant vehicle (SOV) rate well below the 60-percent target. The fleet approaches five million commuting miles annually. The commuting miles eliminated with this outstanding program is more than 32.7 million annually, resulting in a pollution savings of approximately 442 tons each year.

Travel reduction incentives for employees include:

• $25 monthly subsidy toward vanpool expense for employees who commute in any local Valley Metro vans. The employee monthly costs are payroll deducted
• A 50 percent subsidy of the monthly accrued fares up to $20 to employees who commute by bus
• Employees carpooling do not pay the monthly $46 for parking at company headquarters
• Employees carpooling with three or more people do not pay the cost of parking and are given a reserved parking space in the parking garage at headquarters