Other impact levels, as listed on environmental impact studies, are "not significant," "significant unavoidable," "cumulatively significant" and "beneficial."
"There will be no measurable impact on air quality in Imperial County," Foster said, adding the plant will be among the 10 percent cleanest plants found in the United States and will not contribute to a worsened nonattainment area for the Valley.
No specific data on the emissions were provided.
Foster said as the power plant comes on line he expects it to displace power being generated from older, dirtier power plants. He said the La Rosita plant will use clean-burning technology instead of specialized equipment to clean emissions at the smokestack.
Additionally, he said the plant will result in economic benefits for the local area through increased energy supplies and improved energy infrastructure.
The natural gas-powered La Rosita plant is being built with a 750 megawatt capacity, 500 of which is under a 25-year contract to Mexico and the remainder is uncommitted. InterGen is considering a 160 megawatt increase in the plant's capacity, but Foster said no decision has been made. Construction began March 15 and the plant is expected to be on line by late 2002 or early 2003.
InterGen is a Shell Oil Co. and Bechtel Group venture.
Meanwhile, all 600 megawatts of Sempra Energy's Termoeléctrica de Mexicali plant will be sold in California.
Alberto Abreu, Sempra director of permitting and licensing, said that plant will meet the same emission levels as its most recently permitted plants in this country for certain pollutants, such as nitrogen oxides.
"Once in operation it will be the cleanest operating plant in Mexico," Abreu said.
Abreu — in response to why an American company would build a power plant in Mexico only to send the power back — said the approval process is shorter.
"Compared to the United States it is an expedited permitting process," he said, adding that in this country it can take as long as 22 months to secure the needed permits, while in Mexico it only took five months.
Abreu said the company has voluntarily chosen to install and pay for the latest in technology at its plant.
"We believe and share your concerns about environmental impacts," he said.
Construction of the Sempra plant is expected to begin in September.
The two power companies were present before the Board of Supervisors to allay concerns that their plants would result in too many pollutants being emitted into air shared by residents of Mexicali and the Imperial Valley.
An environmental engineer retained by the county said two concerns are that the plants have failed to provide sufficient information to properly evaluate the effects of the plants' emission and that the area already exceeds certain allowable emission levels, such as particulate matter and ozone in the Imperial Valley and carbon monoxide in Calexico.
County Air Pollution Control Officer Stephen Birdsall said the county will continue to discuss issues of concern with InterGen and Sempra.
Staff Writer Rudy Yniguez can be reached at 337-3440.