The following material is taken from Crown Hydro’s website. This brief description is the only information that has been made available to the public about the latest version of Crown’s proposed hydro project. The Figures referred to in the text are included in the .pdf file attached below.
Crown Hydro Project Description 2013-11-08 (D0175026)
Proposed Amendment to Crown Hydro Company’s License for The Crown Mill Upper Saint Anthony Falls Hydroelectric Project
November 9, 2013
Crown Hydro, LLC holds a Federal Energy Regulatory Commission (FERC) license to construct and operate the Crown Mill Upper Saint Anthony Falls Hydroelectric Project, FERC Project No. 11175. The Project is to be located in Minneapolis, Minnesota on the west bank of the Mississippi River at Upper St. Anthony Falls. Crown Hydro is preparing an application with FERC to amend its existing license. The as-licensed project is proposed to be revised in the following ways:
· Move the powerhouse approximately 150 feet closer to the river at the downstream end of the Upper Lock and Dam intake channel.
· Construct new tailrace tunnel under Upper Lock and Dam parking area.
A description of the project as proposed to be amended follows.
Description of Crown Mill Upper Saint Anthony Falls Hydroelectric Project
The Crown Hydro Project (Project) will encompass a 3.2 megawatt (MW) hydropower facility on the U.S. Army Corps of Engineers (USACE) Upper St. Anthony Falls Lock property along the Mississippi River in Minneapolis, Minnesota. The Project will generate an estimated 18,000 megawatt-hours (MWh) of carbon-free electric energy per year, which could power approximately 2,000 homes. It is the intent of Crown Hydro, through a power purchase agreement with Xcel Energy, to sell the renewable electricity produced by the Project to Xcel Energy for markets in the Midwest. Figure 1 shows the overall location of the project and Figure 2 provides more detail.
The Proposed Project, a green, carbon-free source of electricity, would use up to a maximum of 1,000 cubic feet per second (cfs) of the Mississippi River flow to generate power by a natural elevation drop with limited or no storage of water upstream. If river flows are inadequate, the Project will be shut off and no power would be generated. The elevation drop will be augmented by the existing Upper St. Anthony Falls Lock. In effect, it will add hydro energy production to an existing lock and dam that currently does not produce any energy. The Project will use the reservoir and Upper St. Anthony Falls, a horseshoe shaped dam with a concrete spillway about 50 feet high (also known as St. Anthony Falls). Xcel Energy (formerly Northern States Power) St. Anthony Falls Project (FERC No. 2046) is located on the east side of the dam.
The Project will have two 1.6 megawatt turbines, for a total of 3.2 megawatts of capacity. The Project is expected to function at 64 percent capacity, so production is estimated to be just over 2 megawatts, which would produce approximately 18,000 megawatt hours of electricity per year. Operation of the proposed project will use automated equipment with the capability to be manually overridden from the powerhouse and the Upper St. Anthony Lock control room.
Principal Features of the Project
The principal features for the Project, shown in Figure 2, consist of a headrace canal, an intake structure, two turbine shafts, and a tailrace tunnel. An existing lock and dam intake canal will be used for the headrace canal, while the remaining features would be new construction. A profile of the Project is provided in Figure 3.
The generating equipment (i.e., turbines) will be placed 42 feet below ground, inside the powerhouse. The powerhouse structure will be approximately 62 feet by 42 feet. The intake screen facility will extend about 25 feet upstream. The roof of the powerhouse structure will approximately match the parking lot level to the south (Elevation 807), extending about 17 feet above the USACE parking lot to the east. The two turbines will each have a direct shaft to a generator. The turbines will be 8 feet in diameter and 10 feet tall. The Project is designed to run at times of average and above-average water flow, which, based on average flow of the Mississippi River in this area, equates to about 64 percent of the time. Approximately 415 million gallons per day (MGD) of river water will be appropriated for use with the Project. The Project would have two vertical Kaplan hydroelectric generating units with a hydraulic capacity of 1,000 cfs from a 45-foot hydraulic head, which will also be housed in the powerhouse.
The intake structure will be adjacent to the Mississippi River in the lock and dam intake canal with two 8-foot, 6-inch diameter penstocks (pipes). A trash rack will be installed in the intake structure to prevent fish entrainment and impingement. The powerhouse for the Project will be located on the upstream side of the Project and lock and dam area. There will be two discharge draft tubes which will deliver water to a new tailrace tunnel, approximately 930 feet in length. An underground transmission line connection to the Xcel grid will also be installed.
Construction of the Project
Construction of the project will occur on USACE owned property, using approximately two acres for staging and excavation as shown in Figure 4. The majority of the Project will be underground. The above ground footprint of the Project totals approximately 3,000 square feet (sq ft). Crown Hydro is in the process of securing approval from the USACE for construction of the Project. Construction of the Project would begin after environmental clearance and permitting has occurred. This is anticipated in the fall/winter season of 2014/2015. Construction is estimated to take approximately four months for the major components. Heavy equipment, such as bobcats, dump trucks, and excavators would be used. Major construction would occur during the fall and winter in order to minimize the potential impacts to recreational use, barge traffic, and seasonal weather conditions, such as heavy rain.
Prior to starting excavation, cofferdams will be used on the downstream end of the existing headrace canal and also downstream at the discharge point of the tailrace tunnel to keep water out of the construction area and reduce the potential for sedimentation. This will affect less than one third of an acre of water and will prevent water flow into the construction area.
Project construction will remove accumulated debris and excavate the headrace canal, if necessary. A tailrace tunnel will be constructed using both boring and open-cut methods. The upstream 400 feet of tunnel will be bored starting from the powerhouse extending under the existing USACE parking lot to a point on the upstream side of the Stone Arch Bridge (Bridge), as shown on Figure 3. Boring will use jetting or another method to remove sandstone, but will not require blasting. The remaining 530 feet of tunnel will be constructed using an open-cut trench that will be backfilled and restored.
A portion of the roadway that crosses under the Bridge, providing access to a dead end area of the Mill Ruins Park, will be temporarily removed and replaced with new roadway after installation of the tailrace tunnel is complete. No disturbance to the Stone Arch Bridge structure or foundations will occur from construction of the Project. Temporary access during construction for USACE employees will be provided from Portland Avenue to the USACE facilities until completion.
The powerhouse, which includes the penstock, turbine, and generator, will be constructed on the upstream side of the Lock and USACE parking lot along the right bank. The housing for the generator will be visible, but the majority of the powerhouse components will be located underground, including the electrical cable to transport the power generated by the Project. A rendering of the powerhouse has been superimposed on an existing Google Earth oblique view in Figure 5. Figure 6 provides a similar presentation of the other portion of the Project that would be visible, the outlet of the tailrace tunnel.
This link is to a .pdf file containing the maps and drawings of the project that are referred to in the text above: Project-Maps-and-Figures