Tech Briefs

Surge shaft liner installed without dewatering

An innovative technique was used to line a 10-foot-diameter surge shaft at the 122-MW Middle Fork powerhouse without dewatering the shaft.

This powerhouse is part of the 224-MW Middle Fork American River project. This surge shaft, which is 10 miles long and runs 600 feet deep, had longitudinal cracks in its original unreinforced concrete liner. In 1997, leakage through these cracks, coupled with intense rainfall, contributed to the mobilization of a debris flow that ran down the adjacent hillside into the river and filled the Middle Fork interbay with sediment, says Jon Mattson, hydro engineer with owner Placer County Water Agency.

Dewatering this shaft to repair the liner was not an option because the permeable volcanic mudflow formation through which most of the leakage flow had traveled was near the crown of the project tunnel, Mattson says. This proximity had resulted in previous collapses in the tunnel, beginning in 1975. Dewatering the tunnel to line the surge shaft likely would result in another tunnel collapse.

Placer County Water Agency, working with power purchaser Pacific Gas & Electric Co., hired Black & Veatch to design the remediation work and Kiewit Pacific Co. to perform the work. The agency decided to install an 8-foot-diameter steel liner without dewatering the project tunnel.

The annular space between the old and new liner would be filled with tremie concrete. The annular seal at the bottom of the steel liner was made using dual inflatable rubber packers that also supported the early tremie concrete backfill placements until they reached the required strength. A slightly expansive concrete mix was used to provide a permanent annulus bottom seal and support for the liner in the more competent rock formation at the bottom of the liner, Mattson says. Instrumentation was used to monitor liner movement during the backfill operation, evaluate load transfer to its bottom support system, and monitor water quality in the shaft and surrounding ground.

Installation of the liner was completed within a three-month outage in late 2007. Groundwater levels around the shaft have reduced to natural pre-project elevations. This reduced the potential for landslides and increased the amount of water available for energy production.

Reclamation offers draft report on hydro development

The U.S. Department of the Interior’s Bureau of Reclamation offers its Hydropower Resource Assessment at Existing Reclamation Facilities Draft Report.

The draft report is an assessment of the economic and technical potential for hydropower development at Reclamation-owned non-powered dams and structures. The report provides an inventory of hydropower potential at existing sites using broad energy and economic criteria. It does not make any recommendation for development of the sites in the report.

Reclamation signed a memorandum of understanding (MOU) with the Department of Energy and U.S. Army Corps of Engineers to increase renewable energy generation by focusing on development of sustainable, low impact and small hydropower projects. To help meet the goal of the MOU, Reclamation produced an updated list of facilities and sites best suited for projects to increase sustainable hydropower generation.

The draft report is available for download at

California DWR installsnon-physical salmon barrier

The California Department of Water Resources (DWR) is using a non-physical barrier at the divergence of the Old River from the San Joaquin River to keep fish on course as they migrate to the Pacific Ocean.

In this area, both the State Water Project and Central Valley Project divert waster from the Sacramento-San Joaquin River Delta. Fish are entrained by these diversions, which could have a significant negative effect on threatened fish populations, says Mark D. Bowen, fishery biologist with the Fisheries Applications Research Group of the U.S. Department of the Interior’s Bureau of Reclamation. Reclamation has been testing non-physical barriers and recommended a bio-acoustic fish fence to California DWR.

The bio-acoustic fish fence combines sound and a strobe-lit curtain of bubbles to create an underwater wall of light and different sound frequencies. A bubble pipe located under a sound projector constrains sound within the curtain. This allows the sound level to drop back to ambient within 3 meters of the barrier. Strobe lights are reflected off the bubbles, making the barrier look more solid.

The barrier was installed as part of the Vernalis Adaptive Management Program, a long-term experimental/management program designed to protect juvenile chinook salmon migrating from the San Joaquin River through the Sacramento-San Joaquin Delta.

Testing of the barrier shows it is working. California DWR has used acoustic tags supplied by Hydroacoustic Technology Inc. to track fish movement near the barrier. Results indicate that the barrier has increased the number of fish staying in the San Joaquin River to migrate to the ocean. In 2009, deterrence efficiency was 81.4 percent.

Estimated cost of the barrier to protect a 100 cubic feet per second (cfs) diversion is $195,750, Bowen says.

Colfax expands factory, builds pump systems test lab

Colfax Corp. has added 17,000 square feet to its factory in Monroe, N.C. The $3 million space includes a 6,000-square-foot laboratory for high-tech pump testing.

Colfax designs‚ engineers‚ manufactures‚ and supports pumps and systems for applications worldwide, including hydro industry applications. Colfax will design and manufacture a variety of fluid-handling systems in the expanded facility.

The facility provides 30 feet of clearance under the two 30-ton cranes used for positioning equipment during manufacturing, which is twice as much space as the existing facility offered, Colfax says.

Colfax technicians will use the laboratory portion of the expansion to conduct testing of pumps, motors, and auxiliary systems. Its equipment will be fully instrumented and interfaced for high-speed data collection and analysis.

Fishway installation complete at Thompson Falls Dam

The new upstream fish ladder at the 94-MW Thompson Falls project in Montana is ready to pass fish, reported GEI Consultants Inc., the firm selected by PPL Montana to provide ecological and engineering services for the project.

The new steel and concrete ladder system has 48 step pools that will permit fish to gradually ascend about 75 feet to the top of, and over, the dam. The $7.5 million fish ladder is the first full-height fish passage ladder in the U.S. built specifically for bull trout, a threatened species, reports indicate.

The project is designed to provide rare species of trout and other fish species unhindered access to hundreds of miles of the upstream Clark Fork River and its tributaries. The fishway is part of PPL Montana’s federal operating license in compliance with the Endangered Species Act.

The project was developed as a collaborative effort through an inter-agency team composed of PPL Montana; the U.S. Fish and Wildlife Service; Montana Fish, Wildlife and Parks; Montana Department of Environmental Quality; Federal Energy Regulatory Commission; Confederated Salish and Kootenai Tribes; GEI Consultants; and others.

Garlock receives environmental excellence award in New York

Garlock Sealing Technologies received the New York State Department of Environmental Conservation (NYSDEC) Environmental Excellence Award. This award was given because Garlock replaced a volatile organic compound/hazardous air pollutant with a more environmentally friendly solvent in the production of its industrial gasketing.

Garlock’s three-year, $3 million solvent replacement project began in 2006. It involved eliminating an Environmental Protection Agency (EPA) regulated volatile organic compound/hazardous air pollutant from the manufacture of Garlock’s sheet gasket products. These products are used to seal pipe flanges in a wide range of process industries, including power generation. In addition, Garlock installed a high-efficiency recovery system that captures 95 percent of the new solvent for reuse.

NYSDEC says the awards program honors work to improve and protect New York’s environment.

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