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16 Does Your Dam Measure Up? – Developing an Effective Instrumentation Program for Small Earth Dams Introduction An effective dam surveillance and monitoring program is an important component to any dam safety program. The goal of a dam surveillance and monitoring program is to detect if the dam is not performing per the design or if the dam is developing a condition that could lead to adverse performance of the dam. These conditions, if left undetected, could culminate in a dam safety incident or failure and may present a risk to the public, property, or environment. There are two necessary elements of an effective program: surveillance (visual observations) and monitoring (instrumentation measurements). This article focuses on developing an effective instrumentation program for small earth dams based on a identifying a clear set of objectives and selecting the right instrument for the job. Surveillance The article Dam Safety Inspections…A Closer Look (Volume 3 Issue 2 Western Dam Engineering Technical Note) presented the aspects of visual inspections. Surveillance is the most important component in a dam safety program and consists of the routine visual inspection of the dam. However, not every potential deficiency can be detected or understood by visual surveillance alone. The need for both instrumented and visual monitoring exists for nearly every dam. For example, while visual inspections for slides, slumps, cracking, and bulging are important visual indications of a potentially unstable slope, additional water pressure data from piezometers and sediment traps will help the owner and engineer understand the extent and possible cause of any observed abnormality. Instrumentation provides the necessary quantitative data to support a safety evaluation on a dam’s performance. These data are used to detect changes in dam behavior and potential slowly developing problems. Monitoring The main objectives of a monitoring program are to verify the performance of the project structures with respect to the design parameters, quickly identify any change in conditions that has a potential for safety concerns, and develop data for analytical assessment and prediction of future performance. Detecting a developing problem early through active monitoring can allow for successful intervention, thereby reducing the risks of economic loss and downstream consequences. A good monitoring program should include monitoring for potential failure modes (PFMs) of the dam as well as monitoring for general health of the structure. General health monitoring refers to implementing best-practices to gather data vigilant dam owners should know about their structure, regardless of specific failure modes, such as reservoir level and periodic measurement of crest elevation. Monitoring for identified PFMs requires that specific defects or conditions that could lead to failure be identified by a thorough review of the design, construction, operation, and performance history of the dam. This review helps establish the objectives of any measurement device and identify the best instrument and location to obtain the targeted measurement. This will be described throughout this article. Typical Instruments for Small Earth Dams The information below focuses on common instrumentation that may be appropriate for small earth dams. Information on all the possible types of instrumentation can, and has, filled books (see References [2] and [3]). This section provides a basic overview of the most commonly used instruments. Typical instrumentation appropriate for small earth dams includes means for measuring water levels; weirs to measure seepage flow and turbidity; observation wells/piezometers to measure pore water pressure, and survey monuments to measure settlement and crest elevation. The reader is encouraged to review the references at the end of this article for more details regarding the proper selection, design, installation, and readings for each instrument they plan to implement into their monitoring program.