URS Corporation and Sundt Construction have designed and constructed six flood and sediment control facilities for the Los Alamos National Laboratory (LANL), following the largest fire in New Mexico history.

The Cerro Grande fire, which began as a controlled burn to clear 391.7ha of brush at Bandelier National Monument, was whipped out of control by high winds and rolled through the town of Loas Alamos, prompting the evacuation of an estimated 20,000 people and destroying 112 structures and 3035.3ha on LANL land in May 2000. The lab facility, which was the birthplace of the atomic bomb, currently stores nuclear materials and experimental nuclear reactors. Because the fire destroyed surface cover, the potential for soil erosion and flash flooding was enhanced, increasing the risk of facility damage and contamination. LANL contracted with the US Army Corps of Engineers, who enlisted URS and Stundt to build the facilities.

The projects included hardening of an existing dam and road embankment, gabion sediment control structures, and an RCC flood retention structure in Pajarito Canyon. The US$7.8M, 36m high, 61m long structure was designed and built in approximately three months. It will protect lab property and communities downstream from possible flooding in the aftermath of the Cerro Grande fire.

The requirements for construction of the flood retention structure included a short project completion time (due to the rainy season), security issues, and the ability to contain the 100-year load and handle the probable maximum flood, estimated to be 566m3/sec.