Coolidge Dam

Challenges

Coolidge Dam was constructed in 1930 by the Bureau of Indian Affairs (BIA) as a major component of the San Carlos Irrigation Project.  The dam is 250 feet high and provides over 900,000 acre-feet of storage, which is used to irrigate over 100,000 acres.  The dam consists of three reinforced concrete dome arches with buttress supports.  The dam includes two uncontrolled spillways which each contain three 50-foot-wide bays and inoperable 50-foot-wide by 12-foot-high drum gates.  The outlet works consists of two 250-foot-high intake towers with 8-foot-diameter conduits extending through the dam.

BIA routinely performs Periodic Reviews of its dams to provide a current assessment of each dam and its appurtenant structures.  A main component of each Periodic Review is an on-site inspection performed by a professional engineer.

Solution

RJH was retained by the BIA to perform a Periodic Review of Coolidge Dam.  Prior to performing the inspection, RJH reviewed existing documentation, as-built drawings, and engineering reports to develop a thorough understanding of the dam and appurtenant structures.  RJH also developed a detailed work plan outlining the inspection objectives, procedures, and safety considerations.  The on-site inspection was performed and facilities were examined by RJH staff.  This inspection included discussions with local dam operators, examining visible components of the dam, identifying and documenting potential dam safety concerns, and obtaining over 200 photographs.  Photographs were obtained from about the same location and orientations of those from previous inspections to allow for a comparison of changes.  Following the inspection, RJH evaluated the condition of the dam based on the BIA’s “Guidelines for Performing Comprehensive and Periodic Reviews” and developed a Periodic Review Report.