Dam Safety

Dam Safety


Inspection Services

Owners are required to evaluate the safety of their dams and all appurtenant works, and to make modifications, as needed, to reasonably secure safety to life and property.

Construction Inspections

Construction inspections are performed to verify that the field conditions encountered are compatible with the conditions assumed in design and that the construction is proceeding in accordance with the approved plans, specifications, and construction inspection plan.  Particular emphasis is placed on observing and documenting the construction of elements which are critical to the safe performance of the facility.  The frequency of DSO site inspections depend on the size and complexity of the project.

Owner Conducted Annual Inspections - Owners are required to conduct annual surficial inspections and submit a copy of the inspection checklist to the department within 30 days following the inspection.  Information to assist owners in performing these inspections can be found in Chapter 5 of Part III, Dam Safety Guidelines.  Copies of inspection records must be provided to the DSO upon request.

Typical inspection items would include:

  • Condition of the dam crest and upstream and downstream dam faces with particular attention to settlement, cracking, slumps or other distress.
  • Condition of the outlet works and spillways noting any erosion damage.
  • Testing of infrequently used valves, control works, and other hydraulic mechanisms.
  • Observation and measurement of seepage, noting location and concurrent reservoir water level.
  • Observation and recording of any conditions which are a change from previous inspections.
  • Dam Owner Annual Inspection Form - use this form as guidance for conducting the required annual inspection of your dam.

Periodic Inspections

Periodic inspections are conducted on existing dams that are located in areas where dam failure and release of the reservoir contents could pose the potential for loss of life.  The inspections are intended to identify deficiencies, and to reasonably assure safe operation and confirm that maintenance is being adequately performed.

Inspections are performed by the department every 5 years for dams with high downstream hazard or significant hazard classifications.  The inspections are performed by professional engineers from the DSO and involve:

  • Review and analysis of available data on the design, construction, operation, and maintenance of the dam and its appurtenances.
  • Visual inspection of the dam and its appurtenances.
  • Evaluation of the safety of the dam and its appurtenances, which may include assessment of the hydrologic and hydraulic capabilities, structural stabilities, seismic stabilities, and any other condition which could constitute a hazard to the integrity of the structure.
  • Evaluation of the downstream hazard classification; evaluation of the operation, maintenance, and inspection procedures employed by the owner and/or operator, and
  • Review of the emergency action plan for the dam including review and/or update of dam breach inundation maps.

The department will prepare a comprehensive report of the findings, which includes findings from the inspection, and any required remedial work to be performed.

Non-routine Inspections by the Department

The department may perform non-routine inspections of dams with any downstream hazard classification, separate from the periodic inspection program.

Ecology has identified hundreds of dams from publicly-available aerial photos that weren’t listed in Ecology’s dam inventory.  These inspections continue as staff and funding allow.

Inspection at Public Request

The department may inspect a dam if a complaint from the public is received.


Lake Aberdeen Dam Click to enlarge.

Grays Harbor County

Spillway/Stop Logs Click to enlarge

Lake Sylvia Dam

Small Concrete Dam Click to enlarge

San Juan County

Inspections on unpermitted dams