Bosque del Apache National Wildlife Refuge,
Middle Rio Grande Project, New Mexico
Environmental Assessment and Finding of
No Significant Impact
During the 2008 spring runoff, a sediment pug, approximately 2.2 miles in length, developed in the Rio Grande near Bosque del Apache National Wildlife Refuge (BDANWR) in Socorro County, New Mexico. Sediment plugs typically form when flows and conditions are such that the channel reaches a bankful state causing overbank flooding. When overbank flooding occurs for a period of time, the water velocity in the river channel is lessened along with its ability to convey sediment. The sediment then falls out of the water column allowing sediment plugs to form.
The sediment plug has caused water to back up as well as overbank into the nearby riparian vegetation causing potential water delivery loss downstream. After reviewing literature and consulting with technical experts, the area is considered conducive to sediment plug formation. Additional sediment plugs may form in the future within this general river reach and are not limited to the current plug location. Presently there appears to be no simple solution to this issue and a thorough analysis of the conditions is appropriate. Therefore, a multi-phase approach will be taken with this project starting with a short-term solution which can be implemented quickly to establish a pilot channel for more efficient water delivery while allowing river flows to assist in the plug removal. Work will also begin to address the long-term solution for preventing sediment plugs within this river reach.
|Environmental Assessment and FONSI||