It's now a mainstay. Dropped in front of a blaze or around structures, it's helpful at both slowing a fire and reducing it's heat, said Sarah Gallup, fuels forester for the Arapaho-Roosevelt national forests. With crews stretched thin, the summer of 2000 was just such a time. Bombers dropped 135,000 gallons of slurry on Montana's 15,000-acre Bucksnort Fire in a single day. When the U.S. Forest Service reinstated the use of slurry in April of 2000, it also commissioned several studies to examine everything from the retardant's toxicity to its runoff capability and lifespan.
Ammonia remains an ingredient in several retardants.
Past studies weren't as comprehensive as the one completed last spring, Solarz said. They never really looked into it. In the meantime, a new agency guideline prohibits slurry drops within 300 feet of water. They aren't pinpoint precise with delivery of that retardant. Digging fireline by hand also is gentler on the land, Foley said - but often too slow to be effective.