The Las Conchas Fire was a large wildfire in the state of New Mexico, in the United States, in 2011. The fire started in Santa Fe National Forest and burned more than 150,000 acres, threatening Los Alamos National Laboratory and the town of Los Alamos. After five days of burning, it became the largest wildfire in New Mexico state history at the time. It was surpassed in 2012 by the much larger Whitewater-Baldy Complex Fire and in 2022 by the Calf Canyon/Hermits Peak Fire and the Black Fire making the Las Conchas Fire the fourth-largest fire in New Mexico's recorded history.
Progression
The fire started on June 26, 2011, at approximately 1:00 pm Mountain Daylight Time at when a gust of wind blew a severely rotted aspen tree on private property into a power line on a Jemez Electric Cooperative easement. The ignition point remained largely unburned, with the fire jumping to the canopy farther downwind. On the first day, driven by strong and unpredictable winds, the fire burned 43,000 acres in the Jemez Mountains, near the Pajarito Plateau—a rate of about an acre per second.
By the evening of the first day of the fire, no part was contained, according to local fire officials, and the county was put under voluntary evacuation. The fire burned over 61,000 acres by the end of the day on June 27, pushed north by winds into the Pajarito Mountain Ski Area. The fire also burned south, threatening the town of Cochiti, New Mexico. On June 28, this estimate was increased to nearly 61,000 acres. On June 29, it was reported that the fire was 3 percent contained, 12 miles southwest of Los Alamos, and had burned nearly . By then the fire had pushed farther north into the land owned and held sacred by Santa Clara Pueblo.
By June 30, the burned area had increased to over , making it the largest fire in New Mexico history (the previous largest was the 2003 Dry Lakes Fire, which burned over 94,000 acres).
Mandatory evacuation orders were issued for Los Alamos on June 27, and Los Alamos National Laboratory was closed to all non-essential personnel. The evacuation order was lifted on July 3, at which time Los Alamos residents were allowed to return to their homes. The Los Alamos National Laboratory re-opened on July 6. As of July 14, 2011, the fire was 57% contained.
On June 27, a one-acre spot fire burned on Los Alamos National Laboratory until firefighters extinguished it. Authorities reported that the fire did not threaten essential buildings. That was the only time the fire burned on lab property, as the fire then moved away.
The fire was 100% contained on August 3 with efforts for recovery of the burned areas beginning shortly after. The Las Conchas Fire burned 156,000 acres in the end, much of it at high severity.
Impact
Archeological sites
The Pajarito Plateau is rich in prehistoric Puebloan archeological sites. A study after the fire confirmed 1,104 of the sites were directly in the burn zone. Damage to sites from high-intensity fire includes spalling of stone structures, coating with soot and wax, and heat-induced cracking of stone and ceramic artifacts.
Flooding
Destructive flooding occurred in the burned region as the result of heavy monsoon rainstorms on August 21. The flooding was exacerbated by devegetated land and charred soil covered with waxy burn products, making the land in the burn scar hydrophobic.
Santa Clara Pueblo
Sixteen thousand acres of Santa Clara Pueblo land burned in the fire, much of it in the pueblo's watershed. Forty-five percent of the watershed was burned, leading to fears of flooding. The pueblo responded by preparing for floods. As much of the burned area is still as of 2022 at risk for dangerous flash floods, the pueblo installed three large steel and concrete debris racks on Santa Clara Creek upstream from the pueblo. Videos exist on Youtube.com showing flash flooding and debris flows in the pueblo in the years after the fire.
Bandelier National Monument
In Frijoles Canyon, National Park Service workers piled sandbags and used jersey barriers in a successful effort to protect the historic visitor center at Bandelier National Monument and other structures and cultural assets from flooding along El Rito de los Frijoles. Although the efforts did indeed save structures and assets from damage, widespread damage occurred in the watershed, including to trails, buildings, and archeological sites.