The contract was awarded to NAC Construction, a woman-owned small business firm from Marana, Ariz. The project is scheduled to take four months to construct.

"Bonita Creek is home to five species of native fish, including the endangered Gila chub," Johnson said. "This barrier will protect the habitat of these threatened and endangered fish from invasion by non-native species."

Reclamation is constructing the barrier as partial fulfillment of the requirements included in a 2001 Biological Opinion issued by the U.S. Fish and Wildlife Service. In that opinion, the Service concluded that inter-basin water transfers occurring through the Central Arizona Project "seriously and adversely" affect native fish.

The barrier, a reinforced concrete structure, will create a four-foot high drop between the upstream and downstream water surface - a high enough distance to impede the movement of non-native fish species into the native fish habitat. A steeply sloped slab or apron will create a high velocity zone downstream from the barrier, providing additional resistance to non-native fish migration. Scour walls will protect both the upstream and downstream ends of the structure from scour.

Colored concrete will be used for the structure to minimize its visual impact. After construction is complete, the stream in the vicinity of the barrier will be re-contoured. The contractor also will salvage and replace native willow and cottonwood in the clearing area to speed the site's re-vegetation and recovery.

Bonita Creek is a tributary of the Gila River approximately 13 miles east of Safford, Ariz. The work is located on federal lands managed by the Bureau of Land Management.