Inspections

“Inspections of dams are necessary to ensure that they are functioning properly and safely. Inspections shall accomplish the following:^[1]

"Assess performance of the dam;
"Determine compliance with the O&M Plan;
"Assess the adequacy of previous O&M activities;
"Identify O&M needs;
"Identify conditions that may threaten life and property;
"Identify any changed conditions that may affect the hazard classification; and
"Develop a schedule to address O&M needs”.^[1]

“Dams are built on the ground of materials extracted, in one form or another, from the ground; nature does not create a perfect dam site; there are always imperfections or areas of potential trouble. Identifying every such imperfection is not always possible no matter how extensive and thorough an investigation is made. However, limiting the potential for dam failures is possible: in design … in construction … and, perhaps most important of all, during operation, by inspections assessing both how actual performance compares with the designer’s prediction of performance and whether there are any trends indicating that adverse changes are occurring with time. The last of these activities – the periodic inspection program during operation – is the main subject of this guide”.^[2]

“As the term ‘periodic inspection’ implies, evaluation of the safety of a dam and its appurtenant works is a never-ending process. While detailed onetime investigations that involve drilling, testing, and analysis are important and can provide much information that is necessary to help assess dam adequacy, they cannot be wholly conclusive by themselves, nor are the conclusions drawn necessarily valid for all time. As noted above, ensuring that one knows everything about an existing structure and its foundation is never possible; therefore, observation and evaluation of continuing performance are essential to help close the gaps in this knowledge”.^[2]

“Furthermore, the condition of a dam or its foundation can change with time, due either to a natural ‘aging’ process or to the effects of such outside influences as earthquakes, long-term impoundment, or extreme weather variations. Again, observation and evaluation of continuing performance can provide the clues that something is taking place that requires further investigation and may require correction. Thus, field examinations, record reviews, the provision of additional data when required, and periodic reevaluation assume a paramount role in maintaining dam safety”.^[2]

Types of Inspection

"Four types of inspections may be required over the life of a practice:^[1]

"Monitoring of all practices should be routinely conducted to observe operation and assess performance. On-site monitoring may be accomplished by anyone, including landowners, operators, O&M personnel, and NRCS personnel. ^[1]
"Special inspections shall be made during or immediately following the occurrence of major events such as floods, earthquakes, vandalism, and the initial filling of a reservoir. ^[1]
"Annual inspections shall be performed on all structural practices to determine if they are functioning as designed. For ‘significant’ and ‘high’ hazard dams, a qualified engineer shall assist with the annual inspection and sign/certify the inspection report for at least each of the first 3 years after the structure is installed and accepted by NRCS. The downstream floodplain that could be inundated by the failure of all ‘low’ and ‘significant’ hazard dams shall be evaluated at least once every 5 years to determine the current hazard classification. ^[1]
"Formal inspections shall be conducted under the leadership of a qualified engineer at least once every 5 years for ‘significant’ and ‘high’ hazard dams and class I and II dikes. The State Conservationist shall determine if inspections are required for other potentially hazardous practices”.^[1]