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EA-1408: Final Environmental Assessment

Proposed Future Disposition of Certain Cerro Grande Fire Flood and Sediment Retention Structures at Los Alamos National Laboratory, Los Alamos, New Mexico

This environmental assessment (EA) has been prepared to analyze the environmental consequences resulting from the future disposition of certain flood retention structures built in the wake of the Cerro Grande Fire within the boundaries of Los Alamos National Laboratory (LANL). In May 2000, a prescription burn, started on Federally-administered land to the northwest of LANL, blew out of control and was designated as a wildfire. This wildfire, which became known as the Cerro Grande Fire, burned approximately 7,650 acres (3,061 hectares) within the boundaries of LANL before it was extinguished. During the fire a number of emergency actions were undertaken by the Department of Energy (DOE), National Nuclear Security Administration (NNSA) to suppress and extinguish the fire within LANL; immediately thereafter, NNSA undertook additional emergency actions to address the post-fire conditions. Due to hydrophobic soils (non-permeable soil areas created as a result of very high temperatures often associated with wild fires) and the loss of vegetation from steep canyon sides caused by the fire, surface runoff and soil erosion on hillsides above LANL were greatly increased over prefire levels. The danger to LANL facilities and structures and homes located down-canyon from the burned area was magnified.