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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

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Final Project MOHAVE Report Fact Sheet

EPA is announcing the availability of the final Project MOHAVE report, which assesses the extent to which the Mohave Generating Station, located in Laughlin, Nevada, contributes to visibility impairment at the Grand Canyon National Park.

Q: What is Project MOHAVE?

A: In 1991, the U.S. Congress directed the Environmental Protection Agency (EPA) to conduct a study to determine the extent to which the Mohave Generating Station, in Laughlin, Nevada, contributes to visibility impairment at the Grand Canyon National Park. Together with the National Park Service and the majority owners of the Mohave Generating Station, Southern California Edison, EPA conducted a monitoring, modeling, and data assessment project designed to estimate the power plant's contributions to haze at the Grand Canyon. This cooperative effort was named Project Measurement of Haze and Visibility Effects, more commonly referred to as Project MOHAVE.

Q: What is the Mohave Generating Station?

A: The Mohave Generating Station is a 1580 MW coal-fired power plant located in Laughlin, Nevada, approximately 75 miles southwest of the Grand Canyon. It was built between 1967 and 1971. It emits up to 40,000 tons of sulfur dioxide (SO2) per year and is one of the largest sources of SO2 in the West. In fact, once controls are installed at the Centralia Power Plant in Washington State as scheduled in the next few years, the Mohave Generating Station will be the largest source of SO2 in the West. The Mohave Generating Station is operated by Southern California Edison, the majority owner of the plant. The Los Angeles Department of Water and Power, Nevada Power Company, and Salt River Project also own interests in the plant.

Q: Do the results of the Project MOHAVE study show that the Mohave Generating Station affects visibility in the Grand Canyon?

A: EPA believes that the results of the Project MOHAVE study indicate that the Mohave Generating Station contributes to visibility impairment at the Grand Canyon. As with many such studies, there is some uncertainty in the results and some disagreement among the various models used. Even after considering these uncertainties, the study showed that SO2 emissions from the Mohave Generating Station are transported to the Grand Canyon. The EPA will review the Project MOHAVE findings and other information to determine the magnitude and frequency of visibility impairment that is attributable to SO2 emissions from the Mohave Generating Station. The study results do show that the Mohave Generating Station is not the major cause of visibility impairment in the Canyon. Air pollution from other areas, including Southern California, is also transported to the Grand Canyon and has an impact on visibility in the Park. However, because of the quantity of SO2 emitted from the Mohave Generating Station and its proximity to the Grand Canyon, no other single emissions source is likely to have as great an impact on visibility in the Park. EPA and states have a responsibility under the Clean Air Act to consider pollution controls for specific facilities that emit pollutants which are reasonably anticipated to contribute to visibility impairment at the Grand Canyon National Park, even if a facility is responsible for only a small fraction of the impairment.

Q: What does EPA plan to do with the information from Project MOHAVE?

A: Through formal rulemaking, EPA will consider the results of Project MOHAVE and other available information to officially determine whether visibility impairment in the Grand Canyon is "reasonably attributable" to emissions from the Mohave Generating Station. EPA's visibility regulations require that if EPA finds visibility impairment in a Class I area, such as the Grand Canyon National Park, to be "reasonably attributable" to a specific facility, EPA must determine the appropriate pollution control requirements, known as "Best Available Retrofit Technology (BART)", for the facility. Any EPA rulemaking concerning a determination of "reasonable attribution" and "BART" for the Mohave Generating Station would include an opportunity for public comment.

In the near future, EPA will publish an Advanced Notice of Proposed Rulemaking (ANPR) in the Federal Register which will explain EPA's visibility regulations and reference the findings of Project MOHAVE. In this ANPR, EPA will solicit public input regarding additional information that the Agency should consider in determining whether haze in the Grand Canyon can be reasonably attributed to the Mohave Generating Station. This ANPR will not propose a "reasonable attribution" finding or propose pollution control requirements for the Mohave Generating Station. The purpose of the ANPR is to provide background information and request additional information from the public. After the ANPR process is complete, EPA will decide appropriate next steps.

For More Information

Please contact Bruce Polkowsky of the National Park Service at (303) 987-6944.

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