The repair contract was awarded to: Truesdell Corporation of California, Inc. 1310 West 23rd Street Tempe, AZ 85282 on August 17, 2009. The spillway images were taken July 9, 2010. This gives a period of close to 11 months for the construction repair work to be completed before the image shots.
Truesdell Corp has a history of high tech experience and repair of concrete structures including dams & dam structures. I would imagine they completed the project before the images, although I've been unable to find a specific completion date. (see Clips below on Truesdell Corp website).
Truesdell Corp In The Spotlight - Projects, Experience...
= = = Truesdell Corporation: Reference info & experience:
The Truesdell Corporation has built a solid reputation nationwide by providing quality repair, restoration, strengthening, protection, and maintenance of concrete structures. Services range from initial diagnosis to final completion. Headquartered in Phoenix, AZ, Truesdell has successfully completed a wide variety of national and international repair projects ranging from high-rise buildings, nuclear power generating plants, airports, residential projects, water treatment facilities, and a sizeable amount of public agency and DOT work.
Among its more notable projects, Truesdell has completed the Arizona Dam Spillway Rehabilitation project—recipient of the prestigious Award of Excellence presented by the International Concrete Repair Institute (ICRI). This $2.5 million project consisted of repair and restoration of two spillway structures situated near the top of a damthat houses a hydroelectric power generating station. It was a significant project due to the remote location, difficult access, and the multitude of methods and materials specified and used. Products included lithium nitrate to treat alkali-silica reaction (ASR), super-low-viscosity (SLV) epoxy for micro crack healer-sealer, expandable chemical urethane to stop multiple leaks, and a variety of conventional products including bagged dry-mix shotcrete with added fibers. The spillways were situated on a shear 300-ft-tall cliff, where the only access available was from the top of the dam.
Construction began in the summer with temperatures on the spillway slab reaching 130 °F and continuing into the winter where mild freezing conditions were encountered. Dry process shotcrete was determined to be the most efficient and cost-effective method to perform the repairs for logistical and quality reasons. Ultimately 11,000 bags of material were placed successfully without a single loss-time injury or accident, even though much of the work was performed from ropes, swing stages, and custom system scaffolding.
I think that the primary problem with this spillway, and something that would probably cost more than 775,000 to repair, involved the underlying earth and fill, particularly under the section that failed. By all rights, the section below that (although battered by the 100,000 CFS flows crashing into it) as well as the area above were built on solid bedrock. Despite the cracking, the upper part has held up fairly well.