Environmental considerations

SRP will ensure that its facilities are designed, constructed and operated to minimize environmental impacts.

Environmental impacts

The advanced technologies of today's natural gas facilities mean that such facilities are one of the cleanest ways to produce electricity. The turbines powering this plant will be equipped with emissions controls. The technology being used minimizes nitrogen oxide (NOx) formation and controls carbon monoxide (CO) emissions.

Permitting process and requirements

Multiple environmental requirements apply to the construction and operation of a natural gas generating plant.

The Pinal Energy Projects will be developed and operated in compliance with all applicable federal, state and local environmental laws. The new plants will operate with the cleanest and most efficient fossil-fuel technology available, using natural gas to generate electricity and will contain state-of-the-art environmental controls.

Together with permitting and regulatory requirements, the plants will be fully protective of local and regional air quality.

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Air quality issues

The plants will incorporate modern technology and clean-burning natural gas to meet air quality standards that protect public health and the environment. The plants are subject to federal, and local air quality regulations, which primarily relate to combustion byproducts.

The advanced technologies of today's natural gas facilities mean that simple-cycle facilities, like the one proposed for the Abel site, are one of the cleanest ways to produce electricity. The turbines powering this plant will be equipped with emissions controls. The technology being used minimizes NOx formation and controls CO emissions. Sulfur dioxide (SOx) emissions are also a consideration although they are far less than NOx or CO at natural gas plants.

The technology under consideration for the Pinal Central location is called combined-cycle generation. Find out more about intermediate load and combined-cycle units. Combined cycle turbines have much the same air quality considerations as simple-cycle generators.

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Water use and disposal at the plants

As a major steward of Arizona's water for more than 100 years, SRP is sensitive to the need to use and release water responsibly. That said, natural gas power plants do use some water. In some types of plants, the cooling tower evaporation process is the primary consumer of water to improve performance and/or to reduce emissions.

The chemicals used to treat water at these types of plants are comparable to those used in a swimming pool. All water released from the new plant will meet state and federal regulations for the protection of groundwater quality.

The Abel site is located in the Phoenix Active Management Area (AMA). SRP has been storing CAP water in two recharge facilities (Granite Reef Underground Storage Project and New River - Aqua Fria Underground Storage Project) for several years. This renewable water supply can be used at SRP's existing Kyrene and Santan generating station locations, but could also be used as a source of supply for the Abel site. SRP also is exploring the option of direct use of CAP water.

The Pinal Central and Eloy sites are located in the Pinal AMA, where the use of groundwater is closely regulated. SRP is currently delivering Central Arizona Project water to several irrigation districts in the Pinal AMA to reduce the districts' use of groundwater, thereby creating a "water credit" that can be used later by SRP for power generation. SRP is being proactive to ensure that its future use of groundwater has no impact to the aquifer.

Water use at simple-cycle plants

Water use by simple-cycle plants is low compared to base load and intermediate load facilities such as coal-fired power plants and combined cycle natural gas fired plants. This is because simple-cycle plants do not have a steam cycle, which is where most water in power production is used (in the form of cooling water to condense the steam). In addition, simple-cycle plants run substantially fewer hours in a year, which limits their water use.

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Water use at combined-cycle plants

At a combined-cycle plant, the primary use of water is for condensing steam. Cooling water is circulated through a heat exchanger, where the heat of the steam is transferred to cooling water. As the steam cools, the cooling water increases in temperature. This cooling water is circulated through a cooling tower, which reduces the temperature of the water primarily by evaporation. The cooled water is then recirculated to the steam condenser. The evaporation of water in the cooling tower is the primary source of water consumption at a combined-cycle plant.

In some locations, primarily where water is physically not available, alternatives to entirely wet cooled systems are possible. One such system is an air-cooled condenser. In such a system, large fans are used to blow air over finned tubes carrying the steam to condense the steam.

In addition, some facilities have been constructed with various forms of hybrid systems, which are generally combinations of wet-cooled technology and air-cooled technology.

In either case, the air-cooled equipment is physically very large (typically it will be the largest structure on a combined-cycle plant site). Application of this kind of technology has tradeoffs. Generally, in hot arid climates like Arizona, increases in water savings are accompanied by decreases in plant output, decreases in fuel efficiency, and increases in construction costs. So for any particular site, the water constraints of the location must be balanced against these factors in determining the appropriate cooling technology for the plant.

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Consideration of renewables

Renewable projects need a back-up source of power, when the sun isn't shining or the wind isn't blowing. Building simple-cycle gas turbines provides an important source of back-up power that will facilitate the development of renewable energy. SRP already offers and continues to explore numerous renewable energy opportunities, which could include projects within Pinal County.

SRP has an aggressive program for incorporating renewable resources and energy conservation efforts into its Resource Plan. The SRP Sustainable Portfolio currently provides 6% of SRP's retail sales and is scheduled to meet 15% of load by 2025. SRP has a wide variety of renewable resources including solar, wind, geo-thermal, biomass, landfill gas and fuel cell. With the exception of biomass, these resources are essentially carbon-free. Renewable resources typically are location specific, i.e., wind projects must be located where wind is abundant, or solar must be located where abundant, low- cost land is available.

Each option is carefully considered to determine the most economical method of meeting not only our customer's power requirements, but also electrical system requirements and environmental considerations.

SRP will continue to evaluate these options over the next several years as these projects are developed to ensure we provide power in the most economical and environmentally friendly manner possible.

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