Crews at Los Alamos National Laboratory installed barriers to divert water and removed sediment as they work to prevent any trace of nuclear and other contamination from being washed downstream by flooding triggered by a massive wildfire.
Workers also sealed wells and installed sampling stations that will test runoff, lab spokesman Fred deSousa said.
The work is designed to help stabilize canyons and prevent runoff from stirring up trace amounts of Cold War-era contamination.
The Las Conchas fire burned only one acre of lab property but did burn off vegetation in two canyons upstream. Heavy runoff from monsoon storms is expected to cause flash-flooding over the summer.
"There is little doubt that we will see ash in the water reaching the Rio Grande," said Dave McInroy, program director for the lab's flood and erosion control efforts. "This is what you'd expect after any fire in New Mexico. We're working to minimize the transport of any contaminants that have attached to sediments in the canyon bottoms."
Containment of the Las Conchas fire, the largest in New Mexico history, remained at 50 percent Tuesday, but crews were banking on more cloud cover and rain to help them slow the massive blaze.
The fire has charred more than 232 square miles of the Jemez Mountains around Los Alamos and continued to put up columns of smoke that could be seen as far away as Albuquerque on Tuesday afternoon. More than five dozen homes have been destroyed, and firefighters were protecting structures on the southern end of the fire.
Fire information officer Claudia Brookshire said rains helped on the northern end Monday evening and more rain was expected to hit the burned area through the rest of the week.
As of Tuesday morning, Brookshire said fire officials weren't aware of any flooding in the area. There had been no flooding at the lab, deSousa said.
Workers have removed 65 containers of waste soils and debris from environmental investigation sites that are located in the canyon bottoms.
Tanks containing more than 5,000 gallons of water from drilling operations associated with environmental monitoring wells also were removed. All the materials were taken to an area of higher ground on lab property known as Sigma Mesa.
"This is our highest priority right now," said Kevin Smith, manager of the National Nuclear Security Administration's Los Alamos Site Office. "We had employees work through the weekend and the lab has finished this first phase three days sooner than expected."
Los Alamos lab has been the site of nuclear weapons research and production, chemistry and physics studies and work with hazardous and radioactive materials since its beginnings in the 1943 Manhattan Project to develop the world's first atomic bomb.
The lab has been investigating and cleaning up Cold War-era waste sites around its sprawling campus since reaching an agreement with the New Mexico Environment Department in 2005. The consent order set a 2015 cleanup deadline.
Of more than 2,100 sites in existence when the order was signed, about 800 remain. The sites range in size from a small, suspected fuel spill to multi-acre landfills. None of the large sites are in canyon bottoms.
Lab officials said the recent flood preparations come in addition to hundreds of projects since the 2000 Cerro Grande fire, which had also threatened the lab. Previous work included construction of the massive Pajarito flood control structure, earth berms, rock dams and a wetland stabilized by thousands of willow trees.