Saturday, June 23, 2018

Ottumwa and Red Rock Hydro Dams on the Des Moines River

While looking for the BNSF/CB&Q railyard in Ottumwa, I noticed the "hump" of water downstream of the opened Tainter gates next to the 3.2 MW [HydroWorld] powerhouse. My first thought was that the water was hitting a submerged Tumble Bay Weir.

But then I realized that the flow out of the gates is not falling down into a Tumble Bay.
Street View
Looking at some water level photos of spillway flows convinced my that the "hump" is a hydraulic jump as the fast moving water from the gate meets the slower moving water of the river.

Photo from IowaWhitewater, cropped
Hydro dams are not as maintenance free as some would let us believe: KTVO2011 and OttumwaCourier2015. The OttumwaCourier article talked about the last few years of low water levels. In 2018, the river level is high.
The 2018 article mentioned the Red Rock flood control (storage) dam. "In the past, complaints have flown, accusing the Red Rock lake stewards of doing things not for flood control — their primary function — but to have the right amount of water for recreation....Normal flood operations during the growing season are to release outflows up to a maximum of 18,000 cubic feet per second at Red Rock. Under the temporary modifications, outflows will be a maximum of 22,000 cfs at Red Rock when reservoir levels and inflows permit." [OttumawaCourier2018]

When I noticed that they are adding a hydro plant to this flood control dam, I dug deeper. This satellite image catches the dewatering (secant retaining wall, coffer dams, etc.) construction work for the intake structure on the upstream side and for the powerhouse on the downstream side.
HydroWorld has three photos provided by Missouri River Energy System (MRES) showing the construction of the power plant. The dam was built in 1960, and it is a mile long and 95' high. The design capacity is 36.4 MW, but it can peak at 55 MW when the river is running full. It will use two Kaplan turbines, each fed with a 21' penstock. "Construction of the Red Rock hydro project reflects renewed interest in hydropower nationwide, which could bring changes to scores of American dams. Hydroelectricity provides about 7% of the nation’s power using about 2,500 dams - a fraction of the 80,000 in the U.S. Many entities are keeping close watch on the progress at Red Rock. The success of this project could spark a surge in tapping the potential hydroelectric power from more of those existing resources." [HydroWorld]



The wood forms for the draft tubes. "The two custom wood draft tube forms being used are unique to the vertical Kaplan turbine powerhouse being built. The Ames team must position the centerline of the units vertically and horizontally to align within thousandths of an inch. The wood forms must also be very precise - to within an eighth of an inch."
Voith Hydro ($46m contract [HydroWorld]) is supplying the generators and turbines for this $379m facility. [PowerMag] So if the economics of hydro power is that $10m can be spent for 1 MW of capacity, then maybe fixing the dams for the little 3 MW power plants makes sense. I recognize the name Voith Hydro as the supplier for the Smithland Hydro Project.

Examples of reinforced concrete.

Because of the lifting power of modern cranes, rebar is no longer "stick built." Sections are prefabricated off site and then transported and lifted in place. I put a blue rectangle around the section that is being installed in this photo.
Photo from Gallery plus Paint
The forms are so tall that they are steel reinforced.
Photo from Gallery
Two pump trucks, each with room for two concrete trucks so that both pumps can continuously pour concrete.
Photo from Gallery
Photo from Gallery
Ghris Graham commented on my Facebook posting concerning the cranes: "[Manitowoc] 2-999 1-888 1-2250 and link belt"
The first part of this description implies that not only was the cage made offsite, but the cement was also poured offsite. But the last paragraph implies that it was just the rebar cage that was made offsite.
When Ames Construction needed a specialized transport at the 36.4-MW Red Rock Hydroelectric Project in Iowa, equipment suppliers didn’t have one and fabricators wouldn’t engineer one - so they built it themselves.
The transport was needed to move 21 T-shaped diaphragm walls reinforced with steel rebar cages, with some of them weighing more than 90 tons, nearly 10 miles to the upstream construction area with several tight-radius turns along the route.
Ames’ Utah-based team of mechanics spent three weeks building, testing and perfecting prototypes in the equipment yard, simulating expected route challenges. The resulting custom-made transport consisted of three flatbed trailers and two transport trailers with trucks, one in front and one in the center. With a two-point pivot system, each truck steered independently to make the difficult turns while maintaining stability. The custom transport also disassembled into two pieces for transport from Utah to Iowa.
The night of Nov. 13, 2014, three cranes worked in unison to set the cage, and the new transport carried its first load, measuring 157 feet long by 20 feet wide and weighing 320,000 pounds (transport and load). Averaging between 4 and 4 miles per hour, crews completed the move in less than two hours. The remaining cages were transported over the next several months.
Thunder Adms posted
Dennis DeBruler The Manitowoc tilted a little, but did not turn over. You can tell by the vortexes in the water that the current past the project is strong and turbulent. The current caught and drug downstream the cofferdam sheet that they were lifting.

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