Blue Earth Ecological Consultants, Inc.
1345 Pacheco Street, Santa Fe, New Mexico
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Client: New Mexico Department of Transportation
Project Completed in 2011
Rio Nutrias Mitigation Project
Blue Earth developed a design for modification of a box culvert outlet to provide fish passage at the U.S. Highway 84 crossing of the Rio Nutrias in Rio Arriba County, New Mexico.  Modification of the culvert outlet was associated with replacement of the structure during reconstruction of a segment of U.S. Highway 84 by the New Mexico Department of Transportation.  Blue Earth developed the design for a tailwater control structure, which consisted of a series of three low-head dams with a one-foot drop within a length of approximately 15 feet.  The low-head dams created resting pools at 3.1-foot intervals, which raised the tailwater elevation enough to allow for fish passage.  The new structure also dissipated energy and reduced the erosive power of stream flow at the culvert outlet.  Construction of the new box culverts and tailwater control structure was completed in October 2006.

Fish species found in the Rio Nutrias at the U.S. 285 crossing during sampling conducted by Blue Earth included Rio Grande chub (Gila pandora), fathead minnow (Pimephales promelas), flathead chub (Platygobio gracilis), longnose dace (Rhinichthys cataractae), and white sucker (Catostomus commersoni).  Following completion of construction, Blue Earth conducted revegetation activities including collection and planting of dormant cuttings of coyote willow (Salix exigua), planting container-grown herbaceous wetland plants, and seeding disturbed areas.

Blue Earth monitored the site in 2008, 2009, 2010, and 2011.  The tailwater control structure maintained integrity and functioned as planned during the four years of monitoring.  The step pools filled with stream substrate material, providing a wide variety of depth and flow conditions that allowed upstream movement of fish.  Revegetation work at the site restored wetlands at the culvert outlet and stabilized adjacent upland slopes.