Tech Briefs

Book covers dam and levee remediation techniques

Specialty Construction Techniques for Dam and Levee Remediation, edited by Donald A. Bruce with Geosystems L.P., addresses various specialized geotechnical processes used for dam and levee remediation.

This type of remediation has become more prevalent since the start of the 21st century, and keeping up with maintenance needs is very difficult given the vastness and complexity of the infrastructures involved, the book says. The challenge has been to develop methods that ensure safe, effective, reliable and robust solutions for current and future remediation issues.

The 447-page book deals with the construction of hydraulic cutoffs in fill, soil and rock, which are mainly applicable to embankment dams and levees. The book explains how to use pre-stressed rock anchors to stabilize concrete dams and appurtenant structures and includes an outline of the means, methods, materials and properties involved in the process.

Case histories are included that cover quality assurance, control and verification, background issues, instrumentation, and specification and contracts. The book also summarizes lessons learned and recommendations for future applications.

Chapters cover:
– Drilled and grouted cutoffs;
– Mix in place cutoffs;
– Backfilled cutoffs;
– “Composite” walls;
– Rock anchors for concrete structures;
– Instrumentation monitoring and performance;
– Specifications and contracts; and
– Lessons learned.

– The book can be purchased for $165 at www.crcpress.com/product/isbn/ 9780415781947.

Two reports available on detecting quagga, zebra mussels

The U.S. Department of Interior’s Bureau of Reclamation has released two reports identifying a new sampling method to improve the accuracy of quagga and zebra mussel detection while still at the microscopic larval stage.

The reports are:

– Improving Accuracy in the Detection of Dreissenid Mussel Larvae, a 32-page guide that covers testing methods, veliger (larvae) degradation, decontamination procedures, controlling contamination, and a quagga mussel model study using polymerase chain reaction (PCR); and

– Polymerase Chain Reaction: Preparation and Analysis of Veliger Water Samples, a 25-page guide that provides guidance on the method developed.

The reports, developed by the Bureau’s Detection Laboratory, also outline the process and procedures used to identify invasive mussels through DNA testing.

For early detection, Reclamation personnel search water samples for the microscopic larval form of quagga and zebra mussels. Multiple testing methods are used, including cross-polarized light microscopy, scanning electron microscopy and PCR testing of the DNA of larvae in the water sample.

– Both reports are available for free at www.usbr.gov/mussels.

Columbia River dams provide resilience to climate change

Dams have provided engineering resilience to the alterations in streamflow expected as a result of climate change, according to the results of a study published in a special edition of the journal Atmosphere-Ocean that focused on the Columbia River basin.

According to the study authors, climate-warming effects on streamflow have been limited to headwaters, and flow regulation has obscured the expression of climate change on streamflow below dams in the Columbia River basin.

The authors tested the ecological resilience (capacity of headwater ecosystems to sustain streamflow under climate change) and engineering resilience (capacity of headwater ecosystems to overprint a climate change signal) in seven sub-basins of the river from 1950 to 2011. The sub-basins had a headwater gauge above dams with a long-term streamflow record and a nearby climate station with a long-term record of air temperature and precipitation, as well as matching long-term streamflow records at gauges downstream of dams.

Consistent with predicted response to climate warming, annual snow melt runoff peaks in five of the seven headwater basins shifted to a few days earlier over the period from 1950 to 2010, but the changes were small, displaying ecological resilience. Below dams, streamflow change was attributable to reservoir operation for flood control and irrigation, as well as flow management for hydropower, navigation and recreation.

– The article, “Climate and Streamflow Trends in the Columbia River Basin: Evidence for Ecological and Engineering Resilience to Climate Change,” is available at www.tandfonline.com/doi/full/10.1080/07055900.2013.808167.

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