Pursuant to the National Environmental Policy Act, the U.S. Army Corps of Engineers Los Angeles District is preparing an Environmental Assessment for an update to the water control manual for Alamo Dam, located in La Paz and Mohave counties, Arizona.
As part of the water control manual update process and in accordance with Engineer Regulations 1165-2-119 (Modifications to Completed Projects) and ER 1110-2-240 (Water Control Management), USACE is preparing documentation to comply with the National Environmental Policy Act of 1969, as amended (42 U.S.C. § 4321, et seq) and the Department of Defense NEPA Implementing Procedures, dated June 30, 2025 (90 Fed. Reg. 27857). To this end, USACE is preparing an Environmental Assessment to evaluate potential environmental impacts of proposed changes to the current water control manual.
USACE is required to prepare water control manuals to govern the operation of its dams and reservoirs. A water control manual defines the rules for direction, operation and management of water storage at an individual reservoir or system of reservoirs in addition to other pertinent information subject to criteria in Section 1-6 of ER 1110-2-240.
Water control manuals are prepared to meet initial requirements when the facility first becomes operational and are revised, as necessary, to conform with new requirements resulting from changes to the surrounding area of the reservoir (including downstream areas), improvements in technology, new legislation and other relevant factors, provided such revisions comply with existing federal regulations and established USACE policy. The purpose of the water control manual update for Alamo Dam, specifically, is to identify an operational plan that best meets the facility’s maintenance needs while concurrently balancing other uses that have shifted over time since the completion of previous analyses in 1999.
If the EA identifies significant impacts that cannot be mitigated to a level that is less than significant, an Environmental Impact Statement would be prepared. If no unmitigable, significant impacts are identified, then a Finding of No Significant Impact would be prepared. Preliminary environmental analysis anticipates there would be no unmitigable, significant impacts on environmental resources.
Comments on this public notice will be accepted through Feb. 16, 2026. Comments can be submitted electronically to: AlamoDamSPL@usace.army.mil.
FIGURE 1: Map of Arizona with the approximate location of the project area (red rectangle), Alamo Dam (black bar) and Bill Williams River (blue line) indicated. Locations of major cities and towns in Mohave and La Paz counties are indicated with red squares, with recent population estimates displayed in the legend.
Figure 2: Map of Alamo Dam (red triangle) with overview showing local watersheds and Colorado River.