Tom Kirk, SSA executive director, explained with colder temperatures at Owens, the resultant salt dust is fluffier, lighter and more likely to be picked up by the wind. He also said Owens, considered by the U.S. Environmental Protection Agency to have the highest PM-10 concentrations in the nation, has more and stronger winds. Dust storms at Owens produce as much as 250,000 tons of PM-10s per year.
Kirk said even if the Salton Sea shoreline exposed by the water transfer results in only 1 percent of the dust found at Owens it would be a significant amount of PM-10s that would not be offset by reduced dust emissions elsewhere. He said the amount of PM-10s from a typical power plant is about 150 tons per year.
Regarding Laguna Salada, Kirk said it has similar temperatures and weather as the Salton Sea, and it is thought the two have had similar conditions because both have been wet and dry over thousands of years.
"We don't have a lot of data on Laguna Salada," he said.
Krantz said exposed areas at the Salton Sea will likely not revegetate, which is the case at Laguna Salada. He said when dry, the surface would have a crust, that when broken would cause dust until the ground is wetted again. He said the threshold for wind to pick up dust is about 15 mph.
Krantz said during calm days Owens Lake has no dust problems, while the Salton Sea area has the dry remains of the ancient Lake Cahuilla dust to deal with, making the Imperial Valley a nonattainment area for dust.
Two draw-down scenarios and their effects on air quality were considered: 300,000 acre-feet and 500,000 acre-feet.
With a reduction of 300,000 acre-feet per year — equal to the proposed transfer of water from the Imperial Irrigation District to the San Diego County Water Authority, and two 50,000 acre-foot transfers to the Coachella Valley Water District and/or the Metropolitan Water District of Southern California — the sea's elevation is expected to drop from the current level of 227 feet below sea level to 252 feet, and expose 44,640 acres of shoreline.
With a reduction of 500,000 acre-feet — equal to the above transfers and other expected reductions — the sea's elevation would be lowered to 263 feet below sea level and expose 81,460 acres.
With an evaporation rate of 5.78 feet per year, the 300,000 acre-foot reduction would expose a total of 53,850 acres, while the 500,000 would expose 88,460 acres.
Krantz said the shoreline at the south end of the sea could recede as much as six miles.
Krantz said the area exposed at Owens is only 22,000 acres.
County Supervisor Gary Wyatt, a member of the SSA board, said the sea cannot be allowed to recede.
"We can't afford any more dust than we have right now," he said.
A paper on the issue of air quality is expected to be released by the Salton Sea Authority in about 60 days.
>>Staff Writer Rudy Yniguez can be reached at 337-3440.