ASDSO Dam Safety Toolbox

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[[Category:Surveillance and Monitoring]]
[[Category:Surveillance and Monitoring]]
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|image= Oroville_Dam_spillway.jpg
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|caption= Inspection of Oroville Dam's spillway.
(Image Source: [https://commons.wikimedia.org/wiki/File:Oroville_Dam_concrete_reinforcement_of_emergency_spillway.jpg Wikimedia])
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“Inspections of dams are necessary to ensure that they are functioning properly and safely. Inspections shall accomplish the following:<ref name="NOMM">[[National Operation and Maintenance Manual: For Conservation Practices Installed with NRCS Assistance | National Operation and Maintenance Manual: For Conservation Practices Installed with NRCS Assistance, NRCS, 2003]]</ref>
“Inspections of dams are necessary to ensure that they are functioning properly and safely. Inspections shall accomplish the following:<ref name="NOMM">[[National Operation and Maintenance Manual: For Conservation Practices Installed with NRCS Assistance | National Operation and Maintenance Manual: For Conservation Practices Installed with NRCS Assistance, NRCS, 2003]]</ref>
*"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”.<ref name="NOMM" />


“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”.<ref name="EM 7570">[[Guide for Safety Evaluation and Periodic Inspection of Existing Dams (EM 7570) | EM 7570 Guide for Safety Evaluation and Periodic Inspection of Existing Dams, NRCS, 1980]]</ref>
* "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”.<ref name="NOMM" />
 
“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." <ref name="EM 7570">[[Guide for Safety Evaluation and Periodic Inspection of Existing Dams (EM 7570) | EM 7570 Guide for Safety Evaluation and Periodic Inspection of Existing Dams, NRCS, 1980]]</ref>


“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”.<ref name="EM 7570" />
“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”.<ref name="EM 7570" />
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==Types of Inspection==
==Types of Inspection==
"Four types of inspections may be required over the life of a practice:<ref name="NOMM" />
There are many different types of dam inspections including:
#"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. <ref name="NOMM" />
* [[Technical Inspection]]
#"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. <ref name="NOMM" />
* [[Emergency Inspection]]
#"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. <ref name="NOMM" />
* [[Owner Inspection]]
#"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”.<ref name="NOMM" />
* [[Comprehensive Evaluation]]
* [[Conduit Inspection]]
* [[Confined Space Entry]]
* [[Remotely Operated Vehicle Inspection]]
 
The specific requirements associated with each of these types of inspections may differ based upon regulatory jurisdiction of the dam.
 
<noautolinks>==Best Practices Resources==</noautolinks>
{{Document Icon}} [[Pocket Safety Guide for Dams and Impoundments (FEMA P-911) | Pocket Safety Guide for Dams and Impoundments, FEMA]]
{{Document Icon}} [[Technical Manual: Conduits through Embankment Dams (FEMA P-484) | Technical Manual: Conduits through Embankment Dams, FEMA]]


==Best Practices Resources==
{{Document Icon}} [[Pocket Safety Guide for Dams and Impoundments (FEMA P-911)|Pocket Safety Guide for Dams and Impoundments (Federal Emergency Management Agency)]]
{{Document Icon}} [[Technical Manual: Conduits through Embankment Dams (FEMA P-484)|Technical Manual: Conduits through Embankment Dams (Federal Emergency Management Agency)]]
==Trainings==
==Trainings==
{{Video Icon}} [https://youtu.be/lIvGH5bux5Q Dam Owner Academy: Dam Inspections]
{{Video Icon}} [https://youtu.be/lIvGH5bux5Q Dam Owner Academy: Dam Inspections]
{{Video Icon}} [https://youtu.be/kLocKA27hrg YouTube: Introduction to Inspecting Dams for Owners and Operators]
{{Video Icon}} [https://youtu.be/kLocKA27hrg YouTube: Introduction to Inspecting Dams for Owners and Operators]
{{Video Icon}} [[On-Demand Webinar: Low-Level Conduits – What Can Go Wrong, How to Inspect, How to Repair?]]
{{Video Icon}} [[On-Demand Webinar: Low-Level Conduits – What Can Go Wrong, How to Inspect, How to Repair?]]
{{Website Icon}} [[Technical Seminar: Inspection and Assessment of Dams]]


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Latest revision as of 17:47, 19 July 2023

Inspection of Oroville Dam's spillway.

(Image Source: Wikimedia)

“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." [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

There are many different types of dam inspections including:

The specific requirements associated with each of these types of inspections may differ based upon regulatory jurisdiction of the dam.

Best Practices Resources

Pocket Safety Guide for Dams and Impoundments, FEMA

Technical Manual: Conduits through Embankment Dams, FEMA

Trainings

Dam Owner Academy: Dam Inspections

YouTube: Introduction to Inspecting Dams for Owners and Operators

On-Demand Webinar: Low-Level Conduits – What Can Go Wrong, How to Inspect, How to Repair?

Technical Seminar: Inspection and Assessment of Dams


Citations:

  1. ↑ 1.0 1.1 National Operation and Maintenance Manual: For Conservation Practices Installed with NRCS Assistance, NRCS, 2003
  2. ↑ 2.0 2.1 2.2 EM 7570 Guide for Safety Evaluation and Periodic Inspection of Existing Dams, NRCS, 1980


Revision ID: 7326
Revision Date: 07/19/2023

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