Cabresto Dam

Challenges

The original Cabresto Dam was a 45-foot-high earthen dam constructed on top of a natural landslide dam.  The reservoir is used for irrigation supply, flood control, and recreation.  The dam required rehabilitation to address numerous dam safety issues related to overtopping; inadequate spillway capacity; uncontrolled seepage; and concerns regarding the structural, hydraulic, and geotechnical adequacy of the outlet works.

The site is located in a narrow, steep mountain valley with challenging access and geologic conditions that resulted in associated complex technical issues.  The dam is owned and operated jointly by two local irrigation companies and is located on U.S. Forest Service (USFS) property.  The rehabilitation project was managed by the New Mexico Office of the State Engineer (NMOSE).

Solution

RJH evaluated multiple rehabilitation alternatives for technical and economic feasibility and, based on these evaluations, developed a final design concept. The final design involved removal of the existing dam, outlet works, and spillway and construction of a new embankment dam about 160 feet downstream of the existing dam. The new dam includes a roller compacted concrete (RCC) overtopping spillway and RCC stilling basin.

RJH addressed numerous technical, site, and administrative issues, and delivered an innovative design approach that achieved dam safety, met the project site requirements of the USFS, and adhered to NMOSE budget constraints. RJH led the work from initial evaluation and assessment of the existing dam through identification of dam safety issues, alternatives development, federal and state permitting, final design, and construction engineering.