Custom Freestanding Jib Crane Improves Maintenance and Operations at Pacoima Dam

Overview

The Pacoima Dam, located in Southern California, is approximately 60 miles east of Fresno and was part of the Los Angeles County Public Works Maintenance Initiative. The initiative filed in August of 2007 specified the need for bidding and special provisions for the construction of a jib crane on the crest of the dam. The bid invitation specified that all sealed bids would be received by the County of Los Angeles Department of Public Works, Construction Divisions, for the construction of a support platform and jib crane on the crest in the vicinity of the Sylmar area of Los Angeles. The countywide strategic plan directed that the committee arrange community services, such as the construction of the jib crane, to provide a means to operate and maintain the dam more effectively. In doing so, the county would also facilitate flood control and water conservation services to communities downstream from the dam.

Although the project had been initially scheduled for 2004, it was put on hold due to lack of proficient bidders and cost, according to the board of supervisors in LA County. But, as the Department of Public Works’ program for the construction of flood control facilities continued to expand, it was determined that routine and emergency maintenance activities at the dam required the proposed jib crane and justified the cost of the project. In December of 2007, the state awarded the bid to a local Spanco dealer.

Solution

Working closely with Spanco engineers, the dealer and the Department of Public Works were able to establish their material handling needs, which were very specific to their application and the environmental concerns associated with the dam. Many of these concerns include weather emergencies like damaging earthquakes and harsh wind storms. Spanco manufactured a custom crane to support a 4,000-pound load with as little deflection as possible in a potentially dangerous and corrosive environment.

Spanco was able to custom design a support platform and large jib crane to meet all of their critical needs. The 100 Series Freestanding Baseplate-Mounted Jib Crane provided maintenance workers with full 360-degree boom rotation and a massive coverage area. With a load capacity of 4,000 pounds, the actual length of the boom spans 48 feet, with a height of 17 feet under the boom. The mast is 42 inches in diameter to support the weight of the hoist under load at the end of the boom. The 18-inch I-beam is fully trussed to limit deflection, bringing the overall height of the boom to a full 96 inches. The truss itself is so big that it had to be bolted together on-sight.

The crane is motorized using a Spanco Jib Drive with bottom entry collectors and a weatherized assembly. In fact, the entire crane had to be weatherized to meet the needs of the dam’s harsh environment. The jib drive included a rain cover, and all steel parts were weatherized for longevity. The crane was constructed with 100 percent continuous welds to meet the requirements of Seismic Zone 4 conditions. Due to the nature of the dam, the crane needed to withstand winds up to 80 miles per hour, which required it to be locked down during major wind events. A coat of primer followed by two coats of epoxy finish were applied to prevent corrosion and other environmental factors. The system needed to be freestanding to be installed outdoors over the dam. However, it also needed to be portable—to some degree. It’s a massive system, making it difficult to move. But, Spanco provided a baseplate mount to ensure that the system can be easily mounted to another foundation if necessary. The foundation size for this crane is 15 feet by 15 feet by 7 feet deep. The structural jib mounting base was constructed to provide as close to zero deflection as possible.

Impact

Overall, Spanco was able to manufacture a custom-made freestanding jib crane that would fully support the weight of a 4,000-pound load with as little deflection as possible in a potentially dangerous and corrosive environment. The jib crane was manufactured and installed within 100 working days, with the help of California Steel Industries, who was in charge of installing and assembling the system on the crest. Since then, according to the County of Los Angeles Department of Public Works, the finished project has had a major impact on the county’s initiative by greatly improving operations and maintenance at the crest of the dam.