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EPRI releases report on fish protection technologies

EPRI announces availability of a technical reference manual, Fish Protection at Cooling Water Intake Structures. This manual reviews fish protection technologies, including those used at water intakes for hydroelectric facilities.

This document is an update to a technical report EPRI released in 2004, including newly available case studies. EPRI’s main objectives in updating the 2004 report were to:

 

To complete this update, EPRI conducted a literature search and surveyed industry and resource agency professionals. EPRI then summarized appropriate publications and personal communications describing the evaluations and the effectiveness of the technologies. For those technologies that have not been fully developed, EPRI identified additional information to better define their potential effectiveness.

The report presents site descriptions, study equipment and methods, and effectiveness results for nearly 30 fish protection technologies. Each technology is presented in terms of full-scale applications at cooling water intake structures, other full-scale applications (such as hydro projects), and pilot and laboratory studies.

The research showed that the effectiveness of a specific technology is strongly influenced by the species and life stages to be protected, plant design and operating characteristics, and geographic location and water body type. The report includes a section that allows the selection of fish protection technologies based on species.

EPRI also offers an online version of the report containing information applicable to hydro projects. This report focuses on upstream and downstream fish passage.

– Both versions of the report are free to EPRI members. To purchase the reports, contact (1) 800-313-3774; E-mail: askepri@epri.com.

Testing spillway weirs for fish passage at McNary

The two temporary spillway weirs (TSW) installed at the 980-MW McNary project are being situated side-by-side to determine the effects on fish passage. The TSWs were located in spillway bays 20 and 22 in 2007. For the 2008 fish passage season, the two weirs are in spillway bays 19 and 20.

The McNary project, on the Columbia River in Washington, is owned by the U.S. Army Corps of Engineers. The TSWs were installed in 2007 and feature three individual steel assemblies inserted vertically into spillway gate slots. The assemblies form a shaped weir that allows water to flow over the top and pass to the tailrace below the dam. The 25-foot-tall, 0-foot-wide structures weigh about 250,000 pounds and can be fitted into any one of McNary Dam’s 22 spillway bays.


This temporary spillway weir (TSW), installed at the 980-MW McNary project, is being tested to determine the effects on fish passage during the 2008 season. This and another TSW at the project will be located in adjacent spillway bays.
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For this new configuration, TSW1 was moved from spillway bay 22 to spillway bay 19. TSW2 remains in spillway bay 20. Testing of this configuration is intended to determine if side-by-side operation of the TSWs influences forebay attraction and if moving the weirs further from the powerhouse affects tailrace egress.

The U.S. Geological Service is monitoring biological performance of the TSWs, using acoustic telemetry tagging of yearling and sub-yearling chinook and steelhead.

This research began in March 2008, and preliminary results are to be available in the fall of 2008. The 2008 testing is part of a two-year program for acquiring information before installation of a more permanent system.

Investigation determines effects of defects on geomembrane leakage

Defects in geomembrane liners installed on the upstream face of earth dams can allow leakage, but this leakage may not be enough to cause stability issues in the downstream slope of the dam. This is one finding of a research program undertaken at the University of Texas at Austin to characterize the effects of leakage through defects in geomembranes.

During their installation and throughout their service life, geomembrane liners are vulnerable to damage. Common causes of this damage include: punctures caused by underlying stones, imperfect welds, and equipment impact. The resulting defects affect the ability of the geomembrane to act as a barrier against infiltration, especially under high hydraulic heads. This results in leakage through the liner and into the body of the dam, says Christine Weber, a doctoral candidate in geotechnical engineering at the University of Texas at Austin.

To determine the effects of leakage through these defects, the researchers performed numerical simulations using the finite element method. The goal was to determine how leakage through a geomembrane liner would affect the design of blanket toe drains in an earth dam.

Simulations were conducted to determine the location of the line of seepage (or phreatic surface) in a homogenous dam due to the presence of defects in the liner. Numerical simulations also were conducted to determine the length of the toe drain needed to prevent discharge from occurring on the downstream face of the dam. Finally, researchers analyzed the effect of the elevation of the phreatic surface within the dam on the stability of the downstream face of the dam.

Results from the numerical analyses indicated that installing a geomembrane liner on the upstream face of a dam lowers the phreatic surface within the dam. In addition, a drain at the toe of the dam affects the position and shape of the phreatic surface within the dam and increases the factor of safety for the downstream slope. For this study, although placing a geomembrane liner on the upstream face of the dam increased the factor of safety on the downstream face, the downstream slope was sufficiently stable even if the dam was unlined and did not have a toe drain.

Finally, researchers determined that geomembrane liners significantly reduce the amount of water infiltrating the dam and affect the elevation of the phreatic surface, even if multiple defects are present. Because seepage through the downstream toe of the dam will still occur even if the dam is sufficiently stable, measures should be taken to protect the lower portion of the downstream slope. Leakage through defects could still cause piping and internal erosion.

– For more information, contact Christine Weber, University of Texas at Austin; (1) 512-471-5631; E-mail: ctweber@mail.utexas.edu.

CEATI publishes reports on turbine surface deterioration

CEA Technologies Inc. (CEATI) announces availability of two reports on the effects of surface deterioration on hydraulic turbines. The reports are titled Component Surface Deterioration and Effect on Performance and Surface Roughness Testing on the McNary Turbine Model.

The first report details the results of a literature search, as well as technical discussions with utility experts. In addition, it provides a table listing the characteristics of the most common turbine coatings. This report also provides computational fluid dynamics results of different turbine coatings on one Kaplan and one Francis unit. A highlight of the report is the Excel-based Mathematical Loss Prediction Method, developed by GE Energy, which allows computation of an estimate of efficiency losses attributable to surface roughness.

The second report details the results of model testing on a hydraulic turbine to quantify how changes in surface roughness affect efficiency. A 1:25 scale Kaplan runner model of the existing turbines at the U.S. Army Corps’ of Engineers’ 980-MW McNary project was tested with stepwise increasing roughness, with all other surfaces hydraulically smooth. In six steps, the surface roughness of the runner was increased by sandblasting from smooth to very rough. A strong correlation between surface roughness and efficiency was noted. The results of the measurements and the approach to developing a performance loss estimate provide information about the potential performance gains achievable by decreasing runner surface roughness.

These two reports were developed by CEATI’s Hydraulic Plant Life Interest Group (HPLIG). This group is comprised of more than 40 utilities joined together through CEATI to share their experiences and to address issues pertinent to their day-to-day operations.

– For more information or to purchase these reports, contact Jennifer Forbes at (1) 514-904-5086; E-mail: jennifer.forbes@ceati.com.


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http://www.hydroworld.com/content/hydro/en/articles/hr/print/volume-27/issue-3/departments/rampd-forum.html