Dams and reservoirs

Metro Vancouver has fourteen regulated dams. [5] Two of them, Cleveland and Seymour Falls, hold back reservoirs in the region’s drinking water supply, and both are classified “Extreme” failure consequence, the top of the province’s five-tier scale. [5]

That scale measures consequence, not hazard. It describes what is below a dam, and it is assigned before anyone assesses how the dam itself would perform. The Regulation sorts dams by potential loss of life, and Extreme is its top band, for “more than 100”, where the population at risk is permanent: people “ordinarily or regularly located in the dam-breach inundation zone, whether to live, work or recreate”. [6]

What an earthquake is expected to do to the region’s dams, and every dam the province classes Extreme or Very High failure consequence in the Lower Mainland, are on dams. This page is the drinking water side of the same two structures.

Both dams sit at risk level “3 – Stable” in the provincial register, which is how the regulator records that it has not flagged a deficiency at either one. That is also the ceiling: no Extreme dam in British Columbia is rated better than 3, and 20 of the province’s 56 are rated worse. [5]

A dam in that class must be reviewed every seven years by an engineering professional qualified in dam safety analysis, to determine whether it is safe, with the report submitted to a provincial dam safety officer for acceptance. [6] Metro Vancouver publishes the status of each of its dams once a year, in a report to its Water Committee. [3]

Cleveland Dam’s review ran from 2023 to 2024 and “identified no unsafe or unacceptable conditions related to design, construction, or operation”; the consultant’s report went to the province that December. [3] Seymour Falls Dam’s ran from 2021 to 2024, with the report submitted in June 2024:

A review ends in one of three verdicts, signed by an engineer and peer-reviewed by a second: reasonably safe, reasonably safe with deficiencies, or not safe with deficiencies requiring urgent action. “Reasonably safe” is the first of those, and the province treats it as equivalent to the Regulation’s own word, “safe”. [7]

Metro Vancouver has published one of these updates every year since 2021, each naming every dam and its review status. [8] [3] None of them says anything about how either dam would behave in an earthquake. The reports themselves are not published, and the consultants who wrote them are not named. [3]

The capital program is published. It leaves the seismic question open.

MCE stands for Maximum Credible Earthquake, one half of the criterion the province’s design guideline sets for a dam in this class; what that criterion is, and the three things that have to travel with it, are on dams. [9] Metro Vancouver is still paying for the evaluations and has not begun the upgrade.

Between reviews, Metro Vancouver reports site surveillance at least weekly at both dams and formal inspections twice a year, and geotechnical and lake level instrumentation “is reviewed by staff daily (Monday – Friday) through an automated data acquisition system”. [3] Each of those intervals is what the Regulation’s schedule requires of a dam in this class. [6] Cleveland’s two low-level outlet valves, original equipment from the 1950s found badly deteriorated in a 2016 condition assessment, were replaced in 2021. [10]

A provincial dam safety officer audits a dam in this class about every five years. The last audits of Cleveland and Seymour Falls were completed in 2020, and as of June 2026 follow-up audits “are being planned”. [3] In September 2021, on an audit covering 2019 and 2020, the Auditor General of British Columbia found that the ministry “has not effectively overseen the safety of dams in B.C.” [11] All nine recommendations were accepted; two were complete as at 31 March 2025, when the province’s dam safety program reported 10 staff against an assessed need of 25 and said it was “only able to target the very highest risk dams”. [12]

The owner of a dam in this class must prepare an emergency plan and submit it to the province for acceptance, and the province’s template requires an evacuation area map to be inserted in it. [6] [13] Both dams’ plans were updated in March 2026. [3] So the area a failure would flood has been mapped. It had to be: the consequence classification is worked out from who is in it.

The province gets the plan in full. A downstream local emergency authority gets a defined part of it, which the province’s controlled-copy register lists as sections 1, 2 and 4.1 and part of appendix A. [13] The public gets none of it. Nobody has explained why, because the regime never raises the question: it carries no duty to publish an emergency plan or an inundation study, and no confidentiality rule covering one either. [6] [14] BC Hydro publishes dam failure evacuation brochures for Campbell River and the Strathcona Regional District, both on Vancouver Island, and nothing comparable for any of its Lower Mainland dams. [15]

Earthquakes are in those plans even though they are absent from the review summaries. The template lists three of them among the events that escalate a dam emergency: an earthquake felt or reported within 50 kilometres of the dam, one causing visible damage to the dam, and one causing an uncontrolled release of water. [13]