Air quality

Construction of the natural gas generating facility at SRP's Santan site - built with state-of-the-art technology - has actually improved air quality in the metropolitan Phoenix airshed. It may sound like a contradiction to say that adding a new generating facility will reduce emissions, but it's a fact, and here's why:

The U.S. Environmental Protection Agency (EPA) and Maricopa County Environmental Services Department mandate that no new major emission sources can be added to the metropolitan Phoenix airshed unless existing emissions are reduced -- no exceptions.

In addition to meeting stringent emissions standards set forth by the EPA and Maricopa County, SRP obtained offsets from other sources that exceeded total new plant emissions by 10% to 50% (the actual amount varies by combustion byproduct and the distance of the offsets from the facility), and made on-site improvements that ensured changes in emissions were insignificant.

The Maricopa County Environmental Services Department issued an air quality permit for the Santan Expansion Project on Feb. 10, 2003. A copy of the permit can be obtained at Maricopa County Environmental Services Department, Air Quality Division, (602) 506-6700.

Link targets are below

Note: Natural gas powers a combustion turbine, a process similar to that which powers a jet engine. The exhaust heat produced in this process is captured to create steam (a process similar to boiling water in a pressure cooker), which powers a second turbine. The exhaust is then filtered through catalytic cleaning systems before it is released through a stack.

Pollution sources

In metropolitan Phoenix, the major sources of pollution continue to be automotive exhaust (on-road mobile sources) and dust caused by construction (included in non-road sources).

Industrial facilities like power plants are minimal contributors - 2% or less - of particulates (PM10) and carbon monoxide (CO). (Source: Maricopa County Environmental Services Department, Emissions Inventory)

Air quality monitoring

SRP has installed continuous emissions monitoring systems (CEMS) on all Santan units for monitoring emissions from the units. Each CEMS system consists of an extractive system with analyzers for the monitoring of nitrogen oxides (NOx) and CO and certified fuel flow meters to calculate emissions of PM10, volatile organic compounds (VOCs) and oxides of sulfur (SO2).

A sample of the flue gas is continuously extracted, conditioned and analyzed by a NOx analyzer, an O2 analyzer and a CO analyzer. This system results in the monitoring and recording of NOx and CO in pounds per hour (lb/hr).

The fuel usage is recorded in hundreds of standard cubic feet per hour and converted to lb/hr data for PM10, VOC and SO2.

Data from the Santan CEMS are provided on a 12-month rolling totals basis for NOx, CO and PM10. Because there are separate permit emissions limits for the existing Units 1-4 and the new Units 5-6, separate graphs are shown to distinguish the old from the new units. These graphs are updated quarterly in the Santan 12-month Rolling Report (PDF).

SRP also constructed an ambient air quality station in Gilbert near the intersection of Gilbert and Warner Roads to monitor air quality. SRP collects data from the station and makes the data available to the public on a quarterly basis. You can view the data collected at the Gilbert air quality station.

Protecting Public Health

The Santan Expansion Project continues to meet all government air quality standards to protect public health and:

  • does not have any visible emissions or odors from the stacks
  • has sound reduction technology to manage the noise.

The expanded generating facility incorporates state-of-the-art technology and clean-burning natural gas to meet air quality standards that protect public health and the environment. The plant will remain subject to federal, state and local air quality regulations, which primarily relate to combustion byproducts.

More information

Back to top