Large Scale Peer Audit of Dam Instrumentation and Monitoring Program

As a result of the collapse and subsequent project re-insurance requirements, GZA GeoEnvironmental, Inc. (GZA) was retained by the Dam Owner to perform a large-scale peer audit of the existing geotechnical instrumentation and monitoring systems of the dam, powerhouse, and associated facilities. The audit primarily focused on the instrument selection based on subsurface conditions, installation methods, and range of sensors, with a particular focus on data collection, data reduction, quality control, and reporting/alerts. Multiple instrument types were installed across the project site to gauge and measure different properties of the work. GZA’s audit primarily focused on settlement cells, load cells, pressure cells, vertical magnetic extensometers, multipoint extensometers, vibrating wire piezometers, inclinometers, and open tube piezometers with an overview of manual and automated deformation monitoring using optical survey methods. Over 3,400 instruments had been installed on the project site prior to GZA beginning the audit, with millions of manually and automatically collected data points. A detailed step-by-step audit—from installation, maintenance, data collection, and data reduction—was performed on each instrument.

A detailed Audit Report presenting our findings, recommendations, and suggested improvements was provided to the Dam Owner and re-insurance team. After reviewing the report, the design team instituted changes to the instrumentation and data collection systems, where feasible, to conform with US and European industry standards, allowing the instrumentation to be a vital part of the design team’s ability to evaluate the facility’s performance.

This paper includes: a case study; discussion of South American instrumentation practices which likely also impact other developing countries; and recommendations for instrumentation audits or reviews that might be valuable to both the geotechnical and dam safety industries.