Red Rock powers up11 May 2015
Missouri River Energy Services in the US is developing a new hydropower facility at the existing Red Rock Dam in Iowa. Joni Livingston gives an insight into this huge undertaking.
The Red Rock Dam is located on the Des Moines River approximately 4.8km southwest of Pella and 72km southeast of Des Moines, Iowa in the US. Original construction of Red Rock dam was completed in 1969 at a cost of about US$88.8M when it was built as a flood control project to protect communities and agricultural lands downstream. Red Rock reservoir, formed by the construction of the Red Rock Dam, is Iowa's largest lake with over 60.7km2 of water and 141.6km2 of land. There are numerous recreational opportunities on the water and surrounding public lands, including swimming, fishing, hiking, camping, birding, and more.
The dam consists of a rolled earth-filled embankment and a gravity concrete control section. It is 1730m long and 33.5m high above the flood plain, with a crest elevation of 243m above sea level. The dam is operated in run-of-release mode by the US Army Corps of Engineers (USACE).
Nelson Energy, the developer of the project, received a preliminary permit from the Federal Energy Regulatory Commission (FERC) in 2006 and a licence to construct and operate a hydropower project at the dam in 2011. Missouri River Energy Services (MRES) purchased the rights to construct and operate the project and proceeded with the regulatory design review and final permitting, which were completed in 2014.
Permitting and licensing processes are always time-consuming and the general nature of licence terms and conditions leaves room for interpretation, so the process is not easy. More than 30 permits, applications and plans had to be filed and approved before construction could begin. The major permits included the FERC licence, the 408 permit for modification of an existing structure from the USACE, and the 401 Water Quality Certification from the Iowa Department of Natural Resources.
Since MRES began work on the project, actions have been taken at both the federal and state level to accelerate and encourage hydroelectric projects. In 2013, President Obama signed a law to expedite the licensing process for hydro plants and Congress passed a bill granting production tax credits to hydro projects. President Obama specifically designated the RRHP in his Infrastructure Permitting Dashboard, which is intended to prioritise major infrastructure projects. Unfortunately, MRES was not able to take advantage of expedited permitting. However, in 2013 the Iowa Legislature also passed a much-appreciated bill to allow hydro projects to receive the same tax exemptions that are given to wind energy projects. The RRHP will be the first beneficiary of that new law.
The Red Rock Hydroelectric Project is rated to produce 36.4MW of power, with the capacity to generate up to 55MW during peak seasons, generally between April and July. The energy produced each year will be enough to power about 18,000 homes or 178.6GWh. Steady electrical demand growth by its members meant that MRES needed to find new power resources and chose this hydroelectric project as it would enable diversification of both its resource portfolio and the location of its resources
RRHP is a huge undertaking but MRES has tremendous confidence in the abilities of the engineering firm and general contractor to complete this project in a safe and efficient manner. Both MWH Americas and Ames Construction have solid experience and proven abilities in designing and building similar projects. Like any construction project, the RRHP presents at least two unique challenges. The first is the fluctuation of the reservoir and releases through the existing dam, both of which are controlled by the USACE. The second is the limited room within the project site. MRES and MWH Americas have taken additional steps during the design and planning phase to try to mitigate these challenges.
Construction of the upstream project features will include:
- Installation of a 73m by 40m deep diaphragm T-wall on the upstream side of the dam, which will include 26 elements of varying sizes. The larger elements will contain about 63,502kg of steel reinforcement and 658m of concrete. Some of the elements are set 42 feet into bedrock.
- Installation of a 30m by 26m deep concrete diaphragm cut-off wall under Highway T-15 to ensure dam stability during project construction.
- Construction of a secant pile cofferdam to facilitate construction of the intake structure.
- Construction of an intake structure to draw water into the penstocks.
- Construction of two penstocks, which will convey water from the intake to the powerhouse.
The downstream facilities will include
- Installation of a cellular cofferdam and earthen dike to facilitate construction of the powerhouse on dry ground.
- Installation of a secant pile retaining wall to hold back the earth embankment of the dam during construction of the powerhouse.
- Construction of the 56m long, 39m wide, 40m tall concrete powerhouse.
- Installation of owner-furnished equipment, including turbines, generators, controls, and transformers.
- Construction of a 69-kV substation and transmission line.
- Construction of a 13.9-kV backup distribution line and utilities.
Construction at RRHP began in August 2014. Work thus far has included construction of the downstream secant pile wall, installation of the downstream cofferdam, construction of the upstream diaphragm cut-off wall, and construction of the upstream diaphragm T-wall. The next steps are to excavate and begin construction of the powerhouse on the downstream side of the dam. While on the upstream side installation of a secant pile cofferdam will facilitate construction of the intake structure.
Project completion and the start of operation are anticipated in the first quarter of 2018. Construction has been carefully planned so as to not interfere with the operation of the existing dam. We don't anticipate any changes to the run-of-release operation of the dam, as directed by the USACE, throughout construction or after the plant is in operation.
Report by Joni Livingston, Director of Member Services and Communications, Missouri River Energy Services. Email [email protected]
Various companies have an important role to play in this project. These include:
- Western Minnesota Municipal Power Agency (WMMPA) is the owner of the project and obtains the financing for and is the owner of facilities used to serve municipal utilities who are members of Missouri River Energy Services (MRES). WMMPA is composed of MRES members in the State of Minnesota and MRES and WMMPA work together under the terms of power supply and administrative service agreements. MRES is building the plant and will be the plant's operator when the project is complete.
- MWH Americas, Chicago office, is the design engineering firm for the RRHP. MWH is the engineer for the generation package, which includes the intake structure, the penstocks, and the powerhouse.
- DeWild Grant Reckert and Associates (DGR) of Rock Rapids, Iowa, is the engineering firm for the transmission/utility package, which includes the electrical substation, the transmission line, and the utilities associated with the project.
- Ames Construction is the general contractor for the RRHP. Ames Construction is headquartered in Burnsville, Minn., and has offices in several locations throughout the Midwest, Western US and Canada.
- Voith Hydro is the supplier of major powerhouse equipment, such as the turbines and generators.