Using sonic methods to drill in an embankment dam
During installation of a double-line grout curtain at Wolf Creek Dam, the U.S. Army Corps of Engineers used sonic drilling to install the holes through the embankment. This method of drilling provides several benefits over drilling using fluids, says Michael F. Zoccola, chief of the civil design branch of the Corps.
Sonic drilling involves the use of high-frequency resonant vibration to advance a core barrel into a structure, Zoccola explains. The drill loosens soil and allows the core barrel to advance. Personnel can then install an outer casing and remove the core barrel.
Zoccola says the Corps chose sonic drilling for several reasons. First, it poses the least risk to embankments because it does not use water or air, which have the potential to hydrofracture the embankment. Second, it allows collection of continuous soil samples while drilling, which can be used to identify subsurface conditions. Third, sonic drilling can be accomplished relatively quickly, reducing time in the field.
Wolf Creek Dam, on the Cumberland River in Kentucky, impounds water for a 270-MW powerhouse. The dam, a combination of rolled earthfill and concrete gravity construction, was completed in 1952. The dam is 5,736 feet long, and the distance from the crest to the foundation is as much as 250 feet.
Over the years, the dam has experienced problems, such as sinkholes in the downstream face of the dam, due to erosion and piping of material through the karst limestone foundation. To remedy the situation, the Corps is building a permanent cutoff wall that extends through the embankment and up to 100 feet into the limestone foundation, Zoccola says. To support this effort, the Corps installed a double-line grout curtain in the bedrock foundation across the entire length of the dam. This grouting program filled any voids that would pose problems during installation of the wall and provided a method to investigate conditions in the dam, which is aiding in design of the wall.
Work performed to install the grout curtain consisted of:
- – Sonic drilling through the embankment dam and natural alluvial material, to allow for installation of casings into bedrock;
– Collection of continuous core samples during drilling;
– Drilling through the casings into the underlying bedrock, using water hammer-type rigs; and
– Remedial grouting of the bedrock foundation.
Boart Longyear Environment & Infrastructure of South Jordan, Utah, performed the sonic drilling work at Wolf Creek Dam as subcontractor to Advanced Construction Techniques Ltd. of Kettleby, Ontario. Advanced Construction Techniques is building the grout curtain under a $50.9 million contract.
Treviicos Soletanche JV of Boston is installing the cutoff wall under a $341.4 million contract. Work on the wall began in the fall of 2008.
Waterpower XVI offers technical plant tours
Attendees of the Waterpower XVI conference in Spokane, Wash., July 27-30, 2009, can take part in three technical tours of hydroelectric facilities.
The 6,809-MW Grand Coulee project is the focus of a pre-conference tour on Monday, July 27. Grand Coulee, owned and operated by the U.S. Department of the Interior’s Bureau of Reclamation, is on the Columbia River in Washington. This project is the largest hydroelectric facility in North America and features three powerhouses. Reclamation plans to overhaul six turbines in the Third Powerplant, which have been in service since the mid-1970s. The overhaul will involve work on the generators, turbines, shafts, and auxiliary equipment.
On Tuesday morning, July 28, the conference offers a tour of the 71-MW Long Lake facility, owned and operated by Avista Corporation. Long Lake, on the Spokane River in Washington, began operating in 1915. When completed, the 213-foot-high dam at the facility was billed as the “world’s highest spillway dam” and the turbines were the largest – both in size and capacity – of any in existence at that time.
The Long Lake plant, on the National Register of Historic Places, features a combination of old and new equipment. All the generators, turbine casings, and penstocks are original equipment. The utility rewound the generators in the 1950s and the replaced the turbines in the 1990s.
Delegates on this tour will return to the Spokane Convention Center for lunch and a presentation on the history of the Avista Corporation.
The post-conference technical tour begins the morning of Friday, July 31, and ends at 10 a.m. Sunday, August 2. The tour includes visits to four hydro projects in Washington, Montana, and Idaho: Boundary, Box Canyon, Cabinet Gorge, and Noxon Rapids.
Participants first will visit the 1,050-MW Boundary project on Friday morning. This project, owned by Seattle City Light, is on the Pend Oreille River in Washington. Seattle City Light is going through the Federal Energy Regulatory Commission (FERC) relicensing process for the facility. The application for the new license is to be filed with FERC by September 2009.
The next stop on the tour is 72-MW Box Canyon on the Pend Oreille River in Washington. Owner Pend Oreille Public Utility District is in the midst of an extensive overhaul and upgrade that involves replacing the original turbine runners with “fish friendly” models, rewinding generators, replacing governors, upgrading excitation equipment, and adding turbine and equipment automation capabilities. The upgrade will increase plant capacity by 18 MW.
Saturday, delegates will tour the 265-MW Cabinet Gorge and 466-MW Noxon Rapids facilities on the Clark Fork River, which make up Avista Corporation’s Clark Fork Project. Construction of Cabinet Gorge in Idaho was completed in 1952, and the utility concluded a $35 million rehabilitation of the facility in 2007. At Noxon Rapids in Montana, Avista is in the midst of a $35 million rehabilitation that includes replacing the turbine runners in four units, refurbishing bearings, replacing wicket gate operating system bearings with greaseless bearings, and replacing stationary wearing rings. This work is expected to be complete in 2012.
– To register for a tour, go to: www. hcipub.com. To request a conference brochure, telephone: (1) 816-931-1311, extension 129, or E-mail: hydrovision@ hcipub.com. Tour participation is limited; pre-registration by June 5, 2009, is required.
IEEE releases updated Standards Dictionary
The Institute of Electrical and Electronics Engineers Inc. (IEEE) announces availability of its updated IEEE Standards Dictionary: Glossary of Terms & Definitions. This dictionary, available on CD-Rom, features nearly 35,000 terms and definitions, with complete source citations.
IEEE develops standards for a range of industries, including electric power. Over the past decade, hundreds of terms have been added to IEEE’s technology lexicon. These terms describe tools, techniques, and best practices for electrical and electronics engineering.
The Standards Dictionary, prepared by IEEE’s Standards Information Network, allows users to search for definitions of terms by technology area or standard. The terms are listed alphabetically, by technology area, and by standard number. The CD-Rom also allows users to copy and paste definitions.
– To order the CD-Rom for $148 for members or $175 for non-members, contact (1) 800-678-4333, or visit the website at http://standards.ieee.org.
USSD committee preparing two guidance documents
The U.S. Society on Dams’ (USSD) Committee on Construction and Rehabilitation is preparing two guidance documents to address contracting methods and construction costs for dams, says chairman Daniel L. Johnson with GEI Consultants.
The two documents are:
– Alternative Contracting Procedures, to provide education and guidance for selecting a contracting method for a project. The methods being considered for inclusion are design-build, design-bid-build, construction management at risk, and others.
– Guidelines for Responsible Cost Estimating, to provide guidance for designers and owners to better assess the costs of construction. This document addresses the fact that materials prices and construction costs have escalated faster than can be accounted for using traditional methods for preparing the engineer’s cost estimate.
The documents are expected to be available in 2010.
The Committee on Construction and Rehabilitation has 23 members representing consulting engineering firms, construction companies, and federal government agencies.