RED ROCK HYDROELECTRIC PROJECT | IOWA
Schnabel’s Red Rock Hydroelectric Facility project wins Deep Foundations Institute Outstanding Project Award 2021
The project successfully converted an existing flood control dam on the Des Moines River in Iowa into a hydroelectric facility that now provides clean and reliable power to the surrounding communities. Schnabel was the tieback anchor contractor for the project and installed 153 rock anchors up to 173 ft long to support a secant pile wall for the temporary excavation support.
Project Description
The Red Rock Hydroelectric Facility Project successfully converted an existing flood control dam owned by the U.S. Army Corps of Engineers on the Des Moines River in Iowa into a 15,200 SF/63 ft high hydroelectric facility that now provides up to 55 MW of electricity to the communities in its vicinity and an approximate energy output of 178,000 MWh per year. The project started in September of 2011 and was commissioned complete in 2021.
The approximate valuation of the project is $284M and it consisted of key earth retention work such as tie-back anchor installation, diaphragm walls, deep excavations and the treatment of solutioned gypsum deposits.
In 2021, the project won the DFI Outstanding Project Award and the PTI Award of Merit.
OWNER
GENERAL CONTRACTOR
GROUTING CONTRACTOR
ENGINEER
FOUNDATION CONTRACTOR
ANCHOR CONTRACTOR
SCHNABEL’S ROLE
Schnabel was the Tieback Anchor Contractor for this project and installed 153 post-tensioned tieback rock anchors up to 173 ft long. The tieback anchors used up to 15 0.6-inch Grade 270 strands and were tested to loads of up to 700 kips. The tieback anchors helped support a large 60 ft tall temporary secant pile wall that was positioned above a 40 ft tall rock cut to allow for the construction of a new powerhouse on the existing flood control dam. The tieback anchor post-tensioning phase of the project concluded in 2015 but Schnabel and the Red Rock team monitored the anchored secant pile wall for three years using strand load sensors to ensure there was no loss in load in the anchors.
CHALLENGES
This complex project provided many unique design and construction challenges to the Red Rock team. One challenge was drilling tieback anchors through overburden and into rock which had an artesian water condition. This challenge was met by the use of drill slurry during installation and sealing the tieback penetrations post-installation in the secant pile wall. Other challenges encountered by the Red Rock team can be attributed to the project’s waterfront setting, confined work area, reservoir water surface elevation and spillway release fluctuations. Working with the rest of the Red Rock team, Schnabel was able to overcome these challenges and deliver a successful project to the owner.
