National Dam Safety Authority lays down Guidelines and Checklist for inspection of dams

On 6-5-2024, the Inspection, Instrumentation, Seismic Data, Risk Assessment and Evaluation of Specified Dam Regulations, 2024 were published which were earlier notified by the National Dam Safety Authority on 24-4-2024 to ensure safety monitoring. The provisions came into force on 6-5-2024.

Key Points:

1. Guidelines and checklist for inspection of specified dams:

• Pre- monsoon and post-monsoon inspection to be done by the dam safety unit of each specified dam. The inspection should be conducted:

  ✓ Pre- monsoon inspection- during March and should be completed before 30th April and the report should be sent to the concerned State Dam Safety Organization (‘SDSO’) before 15th May of each year.

  ✓ Post- monsoon inspection- during October and completed before 30th November and report should be sent to SDSO before 15th December.

• Inspection to be done after every flood/ earthquake/ other natural or man-made calamities/ distress or after any unusual behavior noticed in the dam.

• The dam safety unit will have to carry out the following activities:

  ✓ review the past inspection

  ✓ reports/ monitoring data/ photographs/ videos/ maintenance records;

  ✓ carry out on-site examination;

  ✓ review the relevant data base;

  ✓ In case the primary investigation reveals deteriorating dam conditions then carry out more detailed site investigations;

  ✓ Compilation of database in a systematic format- background information, design information, construction records, operation records and monitoring records.

• Inspection teams will have to take safety measures for any potentially hazardous locations at dam sites.

• A permanent database to be created and maintained by the owner which should include inspection records and the measures taken to correct the conditions, if taken.

• During any inspection, it is necessary to take high- resolution photographs.

• An inspector will keep a field notebook to document all the observations and findings and a checklist.

2. The first risk assessment study of specified dams should be done within 5 years from the date of commencement of the Dam Safety Act, 2021 i.e. 30-12-2021. Further, any study can be carried out every 10 years.

3. Mandatory site-specific seismic parameter studies of specified dams in certain areas:

   • The Seismic assessment, including its hydro-mechanical parts should be assessed either under Design Basis Earthquake condition or under 1 in 475 years return period earthquake based on the guidelines of National Committe on Seismic Design Parameters.

   • Each dam should be evaluated separately in case of reservoirs.

   • In case, dams of same type but spanning across separate abutments for a common reservoir, each dam shall be assessed independently of each other for seismic safety.

   • Seismic stability should be assessed as per the guidelines of the National Committee on Seismic Design Parameters, for Maximum Credible Earthquake condition or 1 in 2475 years’ return period earthquake.

4. Owner of every specified dam should comply with these regulations for safety monitoring and ensure:

   • strong motion instrumentation of dam and foundation;

   • visual observations and inspection after an earthquake;

   • data analysis and interpretation;

   • post-earthquake safety assessment.

Note:

1. The dams falling under the category of “Specified Dams” are mentioned in the Form in Schedule-I of these Regulations.

2. A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquakes, floods etc.