Under the Regional Haze Rule, each state must set "reasonable progress goals" toward improving visibility in Class I areas and develop a plan to meet these goals. Idaho must decide which of two strategies it will implement to address emissions from large, industrial sources, Best Available Retrofit Technology (BART) or emissions trading.

BART requires facilities meeting certain requirements to install control technologies that reduce haze-causing emissions. These technologies are different for each industry and process, but are collectively referred to as best available retrofit technology or BART. The other alternative, emissions trading, is a market-based approach which allows facilities to work together to achieve reductions in haze-forming pollution.

Under an emissions trading program, each facility is assigned a maximum level of emissions for each pollutant. A facility that has lower than expected emissions could sell any excess emissions "credits" to other participating companies. A facility that exceeds its allocated emission level would have to purchase credits from another facility. This way, facilities have an incentive to reduce emissions in order to sell their credits. Under the Regional Haze Rule, emissions trading programs must achieve the same level of emission reductions as would be achieved using BART.

Advantages of emissions trading programs include:

• Flexible: Under a trading program, facilities can choose their own way to reach the emission levels, rather than be required to put on a specific control.
• Cost-effective: In some cases, this approach is less expensive for a facility.
• Addresses growth: If a new facility is built in the state, it would not be allocated an emissions level and would be required to purchase credits in order to operate. This prevents a new facility from severely degrading air quality at the expense of existing facilities.

A successful trading program depends on how many states and facilities participate. There must be enough participating facilities to develop an emissions market. Otherwise, facilities will be limited to their first emissions allocations and new businesses must be emissions-free.

Under a trading scenario, Idaho may choose to develop its own instate trading system, partner with other states to develop a regional trading program, or participate in a backstop trading program. Backstop trading is an established emissions trading program for western states developed under the Regional Haze Rule.

If Idaho chooses to develop its own trading system or partner with other states to develop a new system, Idaho lawmakers will have to develop the program and program elements.

Idaho may also choose to join the western states "backstop" trading program already developed as part of the Regional Haze Rule from recommendations of the Grand Canyon Visibility Transport Commission (GCVTC). This option provides a framework for an emissions trading program for sulfur dioxide, the pollutant found to most impact regional haze on the Colorado Plateau. Under this option, an annual emissions level would be set for the multi-state region. Facilities would operate as usual unless the emission level is exceeded. Once the level is exceeded, the emissions trading program would be triggered. To date, five states—Arizona, New Mexico, Oregon, Utah, and Wyoming—have agreed to participate in the backstop trading program.