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Horse Mesa Dam Repair

Maintaining access to Apache Lake without a ripple in the local boat and business community

  • $8M

    Project Value

  • Maricopa County, Arizona

    Maricopa County, Arizona

Living and working in pressurized conditions to repair equipment 160-feet underground

In June 2012, a 50-ton piece of concrete broke free and fell into the intake at Horse Mesa Dam on Apache Lake. The resulting damage forced a complete shutdown of hydroelectric Unit #4, resulting in a loss of 97,000 kW in the middle of the peak power generation season. Normally, repairing the now missing vane would simply mean forming and placing concrete, but lowering the lake level to make the repairs would eliminate boat access and significantly impact the local economy.

Instead, dam owner Salt River Project decided to undertake complicated underwater repairs.  Four divers worked in two-person teams, living and working in pressurized conditions due to the 160-foot depth. In addition to the difficult working conditions, there were no as-built drawings of the intake vane. We used a remote operated vehicle to gather sonar data, which was translated into a three-dimensional image of the intake. But even with this new data, exact measurements could not be made, leaving a great deal of uncertainty regarding the final size of the replacement vane.

With an aggressive schedule to restore generating capacity, we developed a design that was flexible enough to accommodate project uncertainties while remaining manageable for the underwater team. The replacement vane was built in 15 prefabricated steel components, totaling more than 100,000 pounds. Each piece was individually lowered and fit into place, making construction more manageable. The pieces were fastened together with more than 4,000 pounds of bolts, nuts, washers, and concrete fasteners. Rather than circular bolt holes, slotted holes allowed the final size of the vane to be adjusted to fit the uncertain dimensions.

At a Glance

Offices
Meet Our Team

Fangbiao Lin, Vice President, Global Practice Leader for Environmental Hydraulics

CFD modeling is my passion, solving flow problems is my satisfaction!
Fangbiao Lin Vice President, Global Practice Leader for Environmental Hydraulics Read More

George Sabol, Principal, Water Resources

I enjoy handing off what I’ve accomplished to the next generation and seeing the excitement that it brings to them.
George Sabol Principal, Water Resources Read More
  • Fangbiao Lin

    Vice President, Global Practice Leader for Environmental Hydraulics

  • George Sabol

    Principal, Water Resources

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