Dam Safety

Dam Safety


Non-routine Unpermitted Dam Inspections

Ecology continues inspections of unpermitted dams posing hazards to downstream homeowners and is beginning a second round of dam inspections with letters being delivered statewide to owners of dams and reservoirs built without Ecology permits.

Ecology will be sending letters to the owners of 141 structures built without inspections that appear to be “significant hazard” dams. These dams, identified in aerial photos, appear large enough to hold at least 10 acre-feet of water (3.25 million gallons) and have been built upstream from one or two homes. The letters ask for more information on the dams before Ecology engineers inspect the structures on the ground.

In December 2008, the Department of Ecology completed the process of inspecting 95 private dams and reservoirs built without permits – an effort to prevent dam failures that could flood homes downstream.  The inspections began after Ecology identified hundreds of dams from publicly available aerial photos – dams that weren’t listed in Ecology’s dam inventory.

Of the 95 dams identified as large enough to come under Ecology’s jurisdiction, Ecology’s Dam Safety Office found 30 dams to be “high hazard” (three or more homes downstream), 11 to be “significant hazard” dams (one or two homes downstream) and 27 to be “low hazard” dams, with no homes downstream.  Ecology found 11 high or significant hazard dams needing immediate repairs and have sent Notices of Correction to the owners of those dams.

In recent years, 5 dams in Washington state built without permits and inspections from Ecology have failed, causing flooding and property damage downstream.  These include:

  • An orchard owner from the Royal Slope area who lost approximately $100,000 replacing four acres of producing trees uprooted by a dam breach.
  • In the Walla Walla area, the failure of an unpermitted dam cost one landowner some $200,000 in one season’s fruit production, and flooded a school on his property.

Under state law, a permit is required to construct and maintain a reservoir that holds at least 10 acre-feet (3.26 million gallons) of water or watery materials.  A pond holding 10 acre-feet of water is equivalent to a football field filled with 8 feet of water.

Ecology’s Dam Safety Office oversees dams and dam construction with the sole purpose of protecting public safety.

Letters sent out to request site visits

Ecology has sent letters to the property owners of parcels where unpermitted reservoirs of two acres or more have been identified through aerial photographs.  Names and addresses were accessed through County Assessor’s Offices.

If you have received a letter, we are asking for your cooperation in allowing Dam Safety Office staff to tour the impoundment (a body of water confined by a dam), and conduct an initial assessment of the dam’s reliability.  Our staff will be doing inspections over the next couple months.

You are asked to respond to this letter within 3 days of its receipt to schedule a date and time for our inspection.  If you have received a letter in error, please call us so we can redirect the letter to the appropriate party.

The primary purpose of this site visit is to determine if your dam is a “high hazard” dam, and if it has any major problems (whether it is “high hazard” or not).

What to expect at the initial inspection/site visit

The site visits are expected to last under 2 hours, and you (or your delegate) will likely only need to be present for an hour or less, to answer questions on the history and operation of the dam.

This initial stage of inspection is an opportunity for our staff to visit the site and collect basic information on your impoundment.  The inspection will include:

  • Clarifying the actual population at risk should the dam fail.
  • Identifying any obvious safety problems with the dam and its pipes.
  • Reviewing any as-built plans and construction records and photos.
  • Filling in any gaps in the owner’s Operation & Maintenance and Inspection Plans
  • Confirming an appropriate Emergency Action Plan exists and if not, helping you create one.

In those cases where the dam has serious safety problems that pose an immediate threat of failure, Ecology may order emergency repairs be made right away, or require the reservoir level be lowered.

What happens after the site visit?

Within several weeks of the initial inspection, you will receive our written findings. Upon receipt of this letter, you will be required to:

If your dam is not high hazard:

  1. Repair any major problems immediately.
  2. Submit as-built plans and an Operation & Maintenance Plan, once the dam is repaired.

If your dam is high hazard:

  1. Repair any major problems immediately.
  2. Complete an Emergency Action Plan within 30 days.
  3. Hire an engineering consultant to assess the overall safety of the dam structure, within 30-45 days.
  4. Submit engineering plans to Ecology if structural repairs are needed. (Note: a Construction Permit will be needed.)
  5. Make the necessary repairs, once the plans are reviewed and approved by Ecology.
  6. Pay the $814 yearly inspection fee. This payment is due immediately. You will owe an annual inspection fee from here on, due in July. (Note that the fee amount is adjusted annually for inflation.)

Once the dam has passed an Ecology inspection, all defects are corrected and you have obtained all other needed permits, your dam will be accepted into the Dam Safety inventory and considered a legal facility. Owners failing to correct defects could face fines of up to $5,000 per day.


A Dam Construction Permit is required before constructing, modifying, or repairing any dam or controlling works for storage of 10 or more acre-feet of water, liquid waste, or mine tailings (see Permit Process).

Normally, reservoirs of sufficient size to require a Dam Construction Permit will also need a Reservoir Storage Permit.  You may also need a water right, depending on the source of the water. 

Contact one of Ecology’s Regional Offices for assistance in determining whether a permit or water right is needed.

If you don’t want to manage a dam that falls under Ecology’s authority

If the reservoir impounded behind your dam can store 10 acre-feet (3.26 million gallons) or more above ground level, then it falls under Ecology’s authority, according to state law. There is no minimum impoundment height.

If you want to maintain a dam that will not fall under Ecology’s authority, there are several options:

  • Construct or reduce the height of your dam so that it holds less than 10 acre-feet
  • Excavate the reservoir all or partially below ground level.
  • Remove the dam.

Even if your impoundment is too small to fall under Ecology’s authority, you may be liable for property damage if your dam fails. Therefore it is always a good idea to have a licensed engineer design, oversee the construction, and periodically inspect any impoundment.


For questions and concerns about the current inspections of the 96 unpermitted dams:

Ben Bonkowski, Dam Safety Section Manager
Phone: 360-407-6603
Email: bbon461@ecy.wa.gov