Red Rock Hydroelectric Facility

Location:

Des Moines, IA

Client:

Ames Construction, Inc.

Background

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.

Schnabel’s Solution

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.

Results

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.

Quick Facts

Location

Pella, Iowa

Client

U.S. Army Corps of Engineers

Market

Infrastructure / Energy

Work Performed

153 tiebacks

Completion Date

2021

Duration

9 Years (2011–2020)

Contract Value

$284 Million

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Quick Facts

Location

Client

Market

Work Performed

Completion Date

Duration

Contract Value

Pella, Iowa

U.S. Army Corps of Engineers

Infrastructure / Energy

153 tiebacks

2021

9 Years (2011–2020)

$284 Million

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