Tech Briefs

Corps begins work to reduce avian predation of salmon

The U.S. Army Corps of Engineers is initiating work to reduce predation by Caspian terns of juvenile salmonids in the lower Columbia River. The work is focused on decreasing the number of Caspian terns nesting and breeding on East Sand Island, near the mouth of the Columbia River.

About 70 percent (9,100 pairs) of the entire western population of Caspian terns in North America nests on this island. The terns consume an average of 4.7 million young salmonids each year as the fish migrate through the Columbia River estuary to the Pacific Ocean.

As part of this work, the Corps will develop six alternative Caspian tern nesting sites in Oregon and California. All of the alternative sites to be developed are on public land, and most already have small populations of terns nesting in the general area or have historically supported nesting terns. By spreading out the habitat, the Corps hopes to both reduce salmonid predation in the area (potentially saving 2.5 million to 3.1 million juvenile salmonids each year) and reduce risk to the birds posed by disease, human disturbance, pollution, predation, and storms.


Hydropower Generation Report Click here to enlarge image

To encourage the birds to move to alternative sites, the Corps plans to develop habitat in the alternative locations, then reduce habitat on East Sand Island. In addition, the Corps will use decoys and a sound system, called “social facilitation,” to draw birds to the alternative nesting sites. Social facilitation has been used in the Pacific Northwest to attract Caspian terns to other nesting locations.

The Corps says the redistribution effort is expected to be completed by 2015.

Using organic ester-based insulating fluid in transformers

The U.S. Department of the Interior’s Bureau of Reclamation installed a transformer filled with ester-based insulating fluid at its 13.5-MW Nimbus hydro plant in California. This insulating fluid, an organic oil made from rapeseed or soy, is an alternative to traditional mineral oil.

The fluid is denoted by the “K” in the cooling system description for the KNAN/KNAF transformer (as opposed to an ONAN/ONAF transformer – oil natural air natural/oil natural air forced).

Before installing this type of transformer at Nimbus, staff at Reclamation’s Technical Service Center extensively researched ester-based insulating fluid. Reclamation discovered several advantages and disadvantages.

Advantages include:


    –Ester-based insulating fluid has a higher flash point and fire point than mineral oil (above 300 degrees Celsius). Thus, this type of insulating fluid is particularly valuable when the transformer sits near other equipment or is near a public access point (which is the situation at Nimbus). Manufacturers and some insurance companies state that using an approved ester-based insulating fluid may mitigate the need for water spray protection and barrier protection walls if a minimum spacing is provided (as little as 5 feet).
    –The Environmental Protection Agency considers ester-based fluids to be non-toxic and biodegradable, meaning spilled fluid can be disposed of through normal means and not treated as toxic waste. In addition, ester-based fluids reduce the effect on the environment should a catastrophic failure occur.
    –Some manufacturers of online dissolved-gas-in-oil monitoring equipment have assured users that their equipment is capable of sampling ester-based fluids. However, Reclamation is collecting and analyzing this data using the same techniques employed for transformers insulated using mineral oil.

Disadvantages include:


    –Compared with mineral oil, ester-based insulating fluids have increased viscosity and are not as efficient at transferring heat. Although the ester-based fluid can be used in almost any oil-filled transformer, the load capacity of an existing transformer may have to be derated or modifications may be required to increase cooling.
    –Retro-filling an existing transformer can be expensive because of the need to flush the transformer several times. This is necessary to dilute the residual mineral oil content to less than a few percent, to maintain the benefits of a high fire flash point and to be considered environmentally friendly.
    –The insulating fluid used in the Nimbus transformer was about 3.6 times more expensive than mineral oil.
    –With regard to diagnostics, ester-based insulating fluids have ant pattern of oil-dissolved gases than mineral oil. In addition, th differee knowledge base for failure mode and fault diagnosis is not as mature. The Institute of Electrical and Electronics Engineers Inc. (IEEE) is developing a guide on dissolved gas analysis for this type of fluid.

Installation of the transformer at Nimbus was completed in December 2007. Reclamation plans to monitor the transformer, to determine if this application is viable for its other hydro facilities.

ASCE releases book onrisk and reliability analysis

The American Society of Civil Engineers (ASCE) announces availability of Risk and Reliability Analysis: A Handbook for Civil and Environmental Engineers. Authors of the book are Vijay P. Singh, PhD, P.E., with Texas A&M University; Sharad K. Jain, PhD, with the National Institute of Hydrology in India; and Aditya Tyagi, PhD, P.E., with CH2M Hill.

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The 785- page book is divided into four parts:


    –An overview of the art of decision-making under uncertainty, as well as a background on probability and random variables;
    –Probability distributions and parameter estimation;
    –Uncertainty analysis; and
    –Risk and reliability analysis.
    – To order the book for $120 (ASCE member) or $160 (non-member), visit the Internet: http://pubs.asce.org/books.

Niagara tunnel to featureimpermeable membrane liner

Construction of the Niagara Tunnel Project involves excavating a 10.4-kilometer-long, 12.7-meter-internal-diameter tunnel through rock. To ensure the fresh water flowing through the tunnel does not escape and cause swelling of the surrounding rock, Ontario Power Generation is installing an impermeable membrane liner.

This project involves building a tunnel under the city of Niagara Falls to divert an additional 500 cubic meters per second of water from above Niagara Falls to the three existing Sir Adam Beck generating stations: 498-MW Sir Adam Beck 1, 1,499-MW Sir Adam Beck 2, and 174-MW Sir Adam Beck Pump-Generating Station.

For the Niagara Tunnel Project, there will be a double-layer polyolefin membrane, installed between the shotcrete that is being sprayed onto the existing rock surface and the final concrete lining. The waterproof membrane prevents fresh water flowing through the tunnel from leaking into the surrounding rock and displacing the salt water trapped in the rock. If this were to occur, the rock around the tunnel would swell and over-stress the concrete lining. The polyolefin membrane is being supplied by Sica AG of Switzerland and will be installed beginning in late 2008 by Strabag Inc., the design/build contractor.

An additional benefit of using this type of liner is that the concrete used to build the tunnel can be thinner and does not require reinforcing steel. The concrete will be 60 centimeters thick, based on structural requirements and placement constraints.

Use of this type of waterproof liner is rare in North America, but it is used in many railway and highway tunnels in Europe, says Aaron Laufer, corporate public affairs officer with Ontario Power Generation.

Waterpower XVI announces call for technical paper abstracts

HCI Publications, organizer of the Waterpower XVI hydropower conference and exhibition, is accepting abstracts for the Technical Papers program. The conference will be held July 27-30, 2009, in Spokane, Wash.

Abstracts are requested on all topics of interest to technical professionals in the hydropower field. Preference will be given to abstracts that focus on innovative, practical, and proven technologies and methods.

Abstracts that describe the focus and content of proposed papers (maximum of 400 words) are due September 5, 2008. Submit abstracts through the Internet at: www.hcipub.com and click on “Waterpower.”

All abstracts will be reviewed by the conference Technical Committee. If accepted, authors will be invited to submit a paper by February 16, 2009, for inclusion in the official conference publication (in CD-Rom format) that will be distributed to all delegates.

– For more information, contact (1) 816-931-1311 or E-mail: techpapers@ hcipub.com.

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