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Upstream work at hydroelectric plant temporarily suspended

Upstream work at hydroelectric plant temporarily suspended

Dec 21

Work on the upstream side of the Red Rock Dam at the hydroelectric project will be temporarily suspended as water levels are expected to rise to an elevation of 764 feet by Christmas Day.

The U.S. Army Corps of Engineers (USACE) recently announced that it expects the rise in water levels following heavy rains that dumped three inches in much of the Red Rock Dam drainage basin over a two-day period Dec. 12 and 13. The dam is located on the Des Moines River near Pella, Iowa.

Work has been under way at the 750-foot elevation on the upstream side of the dam as crews prepare the site to build an intake structure for the hydroelectric plant that will be operated by Missouri River Energy Services (MRES) of Sioux Falls, S.D. 

Crews have demobilized, moving equipment and materials to higher ground, in preparation for the anticipated high water levels. All upstream work will be temporarily suspended until water levels return to normal. Work is continuing as usual on the downstream side of the dam. 

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Safety is first priority during blasting at hydro project

Nov 27

Blasting of bedrock to prepare for the construction of a powerhouse is proceeding as designed at the Red Rock Hydroelectric Project (RRHP) near Pella, IA.  Approximately 21,000 cubic yards of bedrock has been removed from the powerhouse excavation, with approximately 11,300 cubic yards yet to be removed.  Blasting began Oct. 28 to loosen the bedrock so that it can be removed from the site. 

Watch the two videos here:
Nov. 2, 2015 Video
Nov. 3, 2015 Video

The safety of the public and workers continues to be of the utmost importance; therefore, additional safety precautions are taken before, during, and after each blast.  In preparation for each blast, explosives are placed into holes that are strategically drilled into the bedrock.  Large rubber pads are placed on top of the explosives to minimize flying rock and debris. 

Before the explosives are ignited, a warning siren sounds throughout the area to indicate the blast will take place in 10 minutes and all workers move to designated safe areas.  A second warning siren sounds 5 minutes before the explosives are ignited. Traffic is stopped and Highway T-15 is closed during the entire blasting sequence. Variable message boards and additional signage provide advance warnings of the road closures.

Spotters watch each blast for any irregularities or other problems. Following the blast, the spotters check in and give their reports. Next, a worker goes down to the blast site to verify that a device called the “tattletale” has received the blast signal. The charges are wired together in a series with an electrical charge setting off the explosives one at a time.  The tattletale is the last device in the series.  If the tattletale received the signal, the crew can be assured that all of the explosives have discharged. Once that assurance is verified, the “all clear” signal is given and Highway T-15 is immediately reopened.  Road closures have typically been only 10 to 15 minutes in duration.  However, longer closures may be needed in the future if one or more of the charges fails to ignite. 

Excavation using the blasting method is expected to continue through mid-December. 

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Excavation at hydro project site now includes blasting

Excavation at hydro project site now includes blasting

Oct 28

Excavation for the powerhouse and tailrace at the Red Rock Hydroelectric Project (RRHP) site at the Lake Red Rock Dam has now reached bedrock, which means that explosives will be needed to remove the final layers of bedrock before the powerhouse foundation can be set. 

Excavation using explosives starts with holes being drilled into the bedrock.  Explosives are then placed in the holes and ignited causing the rock to crack and splinter.  Crews can then break up and haul the rock away from the site. The first blast occurred at 12:35 p.m., Wednesday and went very well, according to Ray Wahle, Power Supply and Operations director at Missouri River Energy Services (MRES). “We plan to excavate in this manner over a two-month period,” Wahle said. “The powerhouse, where electricity from the project will be generated, will be located at that spot.”

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Intermittent road closures planned for T-15 over dam

Oct 23

Highway T-15, at the Lake Red Rock Dam, will be closed for short durations beginning Oct. 27 as work continues on the Red Rock Hydroelectric Project (RRHP) at the dam site.

The road closures, which will occur between the hours of 8 a.m., and 8 p.m., Monday through Friday, will be less than an hour in length and are necessary for the safety of the public and crews working on RRHP.

Variable Message Boards will be posted along T-15 on both the Pella and Knoxville sides of the dam to inform drivers of the closures. The intermittent, short-duration road closures are expected to continue until late December, and a separate press release will be issued once the need for the closures has passed.

Missouri River Energy Services (MRES), which supplies wholesale electricity and energy services to 60 communities, including Pella, in the states of Iowa, Minnesota, North Dakota, and South Dakota, is building RRHP. When the project is completed in 2018, it will be the second largest hydropower facility in Iowa and will be capable of supplying enough electricity to meet the needs of 18,000 homes.

“We regret that these road closures will cause inconveniences to people in the area, particularly those who use T-15,” said MRES Director of Member Services and Communications Joni Livingston. “But the safety of the public and of the workers at the project site remains our primary concern.”

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Diaphragm wall completed at Red Rock Hydroelectric Project

Diaphragm wall completed at Red Rock Hydroelectric Project

Aug 19

Work has been completed on a 240-foot diaphragm wall at the Red Rock Hydroelectric Project near Pella, Iowa.

The diaphragm wall is designed to hold back the existing Red Rock earthen dam on the upstream side of the dam and provide a channel for water to enter an intake structure that will send water to the hydroelectric turbine/generator.

Ames Construction, the general contractor for the project, also has completed installation of the secant pile support structure on the downstream side of the project. The secant pile wall consists of nine rows of walers (horizontal steel I-beams) and 153 tie-back anchors that were drilled into bedrock. This structure is designed to hold back the existing downstream earthen dam and to ensure stability of the dam during excavation for the powerhouse. The bottom of the excavation is currently at 25 feet below river level.  In the upcoming weeks, the excavation procedure will include underground blasting to break up rock for removal. Missouri River Energy Services (MRES) will issue a news release prior to the commencement of blasting.

In all, it is estimated that about 28 percent of construction work for the project has been done. When the project is completed in the spring of 2018, it will provide 36.4 megawatts of clean, renewable hydroelectricity, enough to power about 18,000 homes.

At its Aug. 13 meeting, the Western Minnesota Municipal Power Agency, which is providing financing for, and is the owner of the Red Rock project, approved a transmission construction contract with Aevenia of Moorhead, Minn.

The contract calls for Aevenia to build about five miles of 69-kilovolt single-pole transmission line between the Red Rock Hydro substation and the Pella West substation. It is anticipated that this transmission project will be completed in October 2016.

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