The shaking
Dams
There are dams up the valleys all around this region, from the east end of the Fraser Valley to Howe Sound and north to Whistler. Two of them hold Metro Vancouver’s drinking water, and several more generate electricity.
Last reviewed
The province classes each dam by what is below it
The province keeps a public register of every regulated dam and classes each one by what a failure would reach downstream. 17 dams in this region are in the top two classes, 11 Extreme and 6 Very High. The class counts the people and property below a dam. It rates neither the structure nor the shaking, and the register carries no seismic rating, no assessment date and no upgrade programme.
The 17 dams the province classes Extreme or Very High failure consequence in the Lower Mainland, spread from Wahleach at the east end of the Fraser Valley to Howe Sound in the west, and north to Whistler. Only 6 of them, all owned by BC Hydro, are drawn solid: those are the only ones whose owner has said what an earthquake is expected to do.
- Size: what a failure would reach
- Extreme, 11 damsVery High, 6 damsThe province’s classification of what is downstream. It is not a seismic rating and not a statement that a dam is expected to fail.
- Fill: whether the owner has said what an earthquake would do
- Published, 6 damsNothing found, 11 damsThe table below names every dam and gives each statement in the owner’s own words.
These dams are designed for a one-in-ten-thousand-year earthquake
Very High and Extreme carry the same design earthquake: the ground motion expected once in ten thousand years, or the largest earthquake thought credible at the site. One figure therefore covers every dam in the table below.
BC Hydro says the same of its own dams, in filings to the utilities commission.
“Given that these are all Extreme consequence dams, current expectations — as outlined in the Canadian Dam Association’s Dam Safety Guidelines — are that they should be able to withstand an earthquake of intensity expected to occur once every 10,000 years.”
It binds new work. The criterion applies when a dam is built, altered, improved or replaced, and not to a dam that is simply standing there. It is a guideline minimum rather than law, deviations “may be considered but must be clearly stated and justified”, and the Dam Safety Regulation itself gives no seismic number and never uses the word earthquake.
An old dam is covered a different way. Every seven years an engineer qualified in dam safety analysis goes over a dam in the top classes, and the professional guideline for those reviews puts the Maximum Design Earthquake among the design criteria a review updates, directing that potential liquefaction “should also be considered”. So a dam finished in 1954 is measured again, on a cycle, against a current earthquake.
Four dams have parts expected to fail far below that
The gap is widest at Alouette. The power tunnel headworks and the surge tower are expected to fail in shaking of the size expected once every 100 to 200 years, which could block the discharge from Alouette Reservoir into Stave Lake. Those are the works that let water out of the reservoir, not the embankment holding it in. Until the tunnel is upgraded the reservoir is run so that there would be time to respond after a major earthquake.
At Cheakamus, near Whistler, it is the dam. Its resistance to seismic loads is insufficient, and an earthquake of the size expected about once every thousand years or more could bring down the dam, the spillway, the spillway gates or the penstock pedestals.
Coquitlam Dam holds back Coquitlam Lake, and it is built partly of loose material that is expected to liquefy in a moderate to large earthquake: saturated soil that loses its strength and behaves like a liquid while the ground shakes. The same mechanism under roads and buildings is on ground conditions. At Wahleach, at the east end of the Fraser Valley, the intake gates at Jones Lake are expected to fail at about once in 4,800 years, which would leave the water passage open and could flood the utility and transport corridors below.
Each deficiency is priced, and BC Hydro says which it is fixing and which it is living with. At Coquitlam the inlet portal upgrade is in the plan; the outlet portal and the low level outlet are monitored and kept as they are, because what would follow is expected to be minor. Stave Falls carries no seismic problem at all among the significant risks recorded at the dam. Its trouble is turbine design and obsolete controls.
Two of the seventeen are not power dams. Cleveland on the Capilano and Seymour Falls on the Seymour hold Metro Vancouver’s drinking water, and each was reviewed by an engineer in 2024 whose conclusion does not mention an earthquake. What those reviews say, what the capital plan has funded and where the water would go are on dams and reservoirs.
The table names all 17, with what each owner has said an earthquake would do to its own dam. For most of them the column is empty, which is not the same as a finding that the dam is sound.
| Dam | Owner | Structure | Failure consequence | Regulator’s risk level |
|---|---|---|---|---|
| Alouette | BC Hydro | Earthfill, 22.5 m | Extreme | 2b - Caution |
| The power tunnel headworks and surge tower are expected to fail in shaking of the size expected once every 100 to 200 years, which could block the reservoir’s discharge to Stave Lake. Not yet upgraded. The reservoir is operated to leave time for emergency response in the meantime. | ||||
| Cheakamus | BC Hydro | Concrete gravity, 29 m | Extreme | 3 - Stable |
| “Insufficient resistance to seismic loads that may lead to failure of the dam, spillway, spillway gates and/or penstock pedestals in a major earthquake occurring, on average, about once every 1,000 years or more.” | ||||
| Cleveland | Metro Vancouver | Concrete gravity, 92.1 m | Extreme | 3 - Stable |
| Reviewed in 2024. The published conclusion does not mention an earthquake. A $3 million seismic upgrade in 1992 and a $25 million East Abutment upgrade in 2001 and 2002. Both are records of work done, not an assessment of how the dam would perform now. | ||||
| Coquitlam | BC Hydro | Earthfill, 30 m | Extreme | 3 - Stable |
| The dam contains loose materials expected to liquefy in a moderate to large earthquake. The inlet portal upgrade is in the plan. The outlet portal and low level outlet are monitored and retained. | ||||
| Eagle Lake East | District of West Vancouver | Earthfill, 9.7 m | Extreme | 2b - Caution |
| Nothing found | ||||
| Eagle Lake West | District of West Vancouver | Rockfill, 12.7 m | Extreme | 2b - Caution |
| Nothing found | ||||
| Henriette Lake | Woodfibre LNG | Concrete slab and buttress, 17.4 m | Extreme | 2b - Caution |
| Nothing found | ||||
| Ruskin | BC Hydro | Concrete gravity, 59.4 m | Extreme | 3 - Stable |
| Key components were assessed in 2011 as significantly below the earthquake the guidelines required them to survive. Rebuilt. The advisory board concluded the work met its objective of withstanding the Maximum Design Earthquake. That states the design objective; it does not verify performance. | ||||
| Seymour Falls | Metro Vancouver | Concrete slab and buttress, 30 m | Extreme | 3 - Stable |
| Reviewed in 2024. The published conclusion does not mention an earthquake. A $44 million seismic upgrade between 2004 and 2007, which is a record of work done, not an assessment of how the dam would perform now. | ||||
| Stave Falls | BC Hydro | Concrete gravity, 26 m | Extreme | 3 - Stable |
| No seismic issue among the significant risks the filing records at the dam. | ||||
| Wahleach | BC Hydro | Earthfill, 22 m | ExtremeBC Hydro files it Very High. | 3 - Stable |
| The Jones Lake intake gates are expected to fail in shaking of the size expected once every 4,800 years, which “would prevent the closure of the water passage” and could flood adjacent utility and transportation corridors. | ||||
| Blind Slough | BC Hydro | Concrete gravity, 22 m | Very High | 3 - Stable |
| Nothing found | ||||
| Dickson Lake | City of Abbotsford | Combination, 8.7 m | Very High | 1 - Alert |
| Nothing found | ||||
| Lake #7 | Howe Sound Pulp and Paper | Rockfill, 33 m | Very High | 2b - Caution |
| Nothing found | ||||
| Rice Lake North | Metro Vancouver | Embankment, 7.6 m | Very High | 2b - Caution |
| Nothing found | ||||
| Rice Lake South | Metro Vancouver | Embankment, 8.5 m | Very High | 2b - Caution |
| Nothing found | ||||
| Whistler Lower Snowmaking Reservoir | Whistler Mountain Resort | Embankment, 3.5 m | Very High | 3 - Stable |
| Nothing found | ||||
Register fields as at 2026-09-12. Risk level is the regulator’s supervisory grading of its own file on a dam, which measures neither the dam nor the shaking. “Nothing found” means no document was found in which the owner states what an earthquake is expected to do to that dam. It is not a finding that the dam is safe, and it is not a finding that nobody has looked: BC Hydro files seismic detail on some of its dams to its regulator and not others, and the reviews behind Metro Vancouver’s yearly safety summary are not public.
Ruskin Dam was found short, and rebuilt
In 2011 a consultant reported to BC Hydro that key parts of Ruskin Dam and its powerhouse would withstand far less shaking than the guidelines asked of them, with up to 300 people downstream in summer. The dam was rebuilt. After a twenty year dam safety initiative and eleven years of construction the upper part was finished, and the project’s advisory board concluded it had met its objective of withstanding the Maximum Design Earthquake.
Ruskin is in Mission, in the Fraser Valley Regional District, outside Metro Vancouver.
What you can do
- Ask your local government what it holds for the dam nearest you. A municipality downstream of a dam receives a defined part of its emergency plan. A resident can ask for it, and can ask Metro Vancouver directly under freedom of information.
- Look up how the dam is classified. The provincial dam register is public and carries each dam’s owner and its failure consequence classification, which is the measure the design guidelines are written against.
Where the water would go if a dam failed is not something a resident can look up. The register names the class and stops there.
The full preparedness planSources on this page
Numbered in the order they are cited. Each entry links back to where it is used.
- [1]DatasetBC DamsMinistry of Water, Land and Resource StewardshipBC Data Catalogue dataset; BCGW object WHSE_WATER_MANAGEMENT.WRIS_DAMS_PUBLIC_SVW. Public attributes include FAILURE_CONSEQUENCE and DAM_RISK_LEVEL, which makes it the authoritative public record of a dam's consequence classification. The catalogue page assembles itself in the browser; the data is served separatelyOpen the document ↗
- [2]ReportGuidelines for Dam Design and ConstructionBC Ministry of Water, Land and Resource Stewardship, Dam Safety Section · 2026Appendix A, under the named heading "Design criteria", p. 46, Table 3 "Flood and earthquake minimum design criteria": the route by which the 1-in-10,000-year figure enters, the Regulation itself containing no such number. Very High and Extreme carry the same EDGM, "1/10,000 or Maximum Credible Earthquake (MCE)"; High is 1/2,475, Significant "1/200 to 1/1,000", Low 1/100. A deviable guideline minimum, and it governs new work rather than existing damsOpen the document ↗
- [3]ReportBC Hydro F2020–F2021 Revenue Requirements ApplicationBC Hydro / BCUC · 2019Per-dam Facility Asset Plans with quantified seismic withstand (Alouette, Cheakamus, Coquitlam), Dam Safety capital tables, and the Ruskin estimate at completion in Table 6-4. The Downtown Vancouver Electricity Supply Plan appendix carries the Murrin and Dal Grauer statement on seismically unstable soil and prolonged outage, and the downtown study area's approximately 95,000 customers and fiscal-2017 peak of 411 MVA; the asset-management appendix carries 572 power transformers at 60 kV or greater and 10 spares. No link recovered: filed with the BC Utilities Commission and not posted at an address of its own; the proceeding record is at www.bcuc.com/OurWork/ProceedingsNo link to follow
- [4]ReportDam Safety Regulation, B.C. Reg. 40/2016, under the Water Sustainability ActKing's Printer, British Columbia · 2016Ss. 3, 9, 18–21 and 28, and Schedules 1 and 2: the review is mandatory and its interval is fixed by classification. The Regulation nowhere uses the words "seismic", "earthquake", "ground motion" or "Canadian Dam Association", and nowhere states a 1-in-10,000 standard. Last amended 10 Feb 2023 by B.C. Reg. 32/2023; consolidation current to 8 Sep 2026Open the document ↗
- [5]ReportProfessional Practice Guidelines – Legislated Dam Safety Reviews in BCEngineers and Geoscientists BC (as APEGBC) · 2016V3.0: seismic loadings, potential updates to the original design criteria (the MDE), and follow-up to DSR reports; it closes the chain from s.20 of the Regulation to the 1-in-10,000 criterion. A revised edition was published in Sep 2024 and is not the version readOpen the document ↗
- [6]ReportBC Hydro F2007/08 Revenue Requirements ApplicationBC Hydro, filed with the BCUC · 2006Appendix N: "the dam contains loose materials that are expected to liquefy during a moderate to large earthquake", the owner's own words in a regulatory filing. It does not carry the C$65M cost or the backup-dam dimensions. No link recovered: filed with the BC Utilities Commission and not posted at an address of its own. Appendix N sits in exhibit B-5-3 of the F2007/08 revenue requirements proceeding, Volume 3, Appendices J to Y, in the proceeding record at www.bcuc.com/OurWork/ProceedingsNo link to follow
- [7]ReportGVWD Dam Safety Program Annual Update for 2025Metro Vancouver / GVWD, Water Services (Director, Dam Safety) · 2026Report dated 18 Jun 2026, in the Water Committee agenda of 15 Jul 2026. It states the classification of both dams, the seven-year review duty, the dam safety review chronology and conclusions for each, the emergency-plan and operating-manual dates, and the provincial audit statusOpen the document ↗
- [8]ReportCleveland Dam fact sheetMetro VancouverThe $3M 1992 upgrade and the $25M East Abutment upgrade of 2001–02. It also carries two statements by the dam's own owner, evidence that the statements were made and nothing more: that the Regulation "requires owners of major dams to ensure their dams withstand an extreme earthquake or flood", which the Regulation does not say, and that "Metro Vancouver meets or exceeds these safety standards". Review conclusions come instead from the Greater Vancouver Water District's annual dam safety updatesOpen the document ↗
- [9]ReportRuskin Dam and Powerhouse Upgrade Project — Socio-Economic and Environmental Impact Assessment and Management (SEIAM) Draft ReportHemmera, for BC Hydro · 2011P. 12 carries the seismic deficiency, the Maximum Design Earthquake at 1-in-10,000, PGA ~0.7 g and "up to 300 people downstream… during summer months"; p. 4 the environmental-assessment opt-in refusal. A draft report, and its seismic passage rests on an earlier BC Hydro report of 2008 that is not publicOpen the document ↗
- [10]ReportBC Hydro Ruskin Dam and Powerhouse Upgrade quarterly reports, F2019BC HydroQ1 records completion of the upper dam in F2018 after "a 20 year Dam Safety initiative, and 11 years of this project"; Q4 records the Advisory Board finding that the project "Has met the overall project objectives of withstanding the Maximum Design Earthquake (1:10,000 Annual Exceedance Frequency)". A statement of what the upgrade was designed to withstand, not a measurement of the dam as built. No link recovered: the reports are no longer posted: BC Hydro's Ruskin project page is gone, and captures of the earlier page survive for 2013 to 2019No link to follow
- [11]ReportSeymour Falls Dam fact sheetMetro VancouverThe $44M seismic upgrade of 2004–07. It carries the same two statements by the dam's own owner as the Cleveland Dam fact sheet, on the Regulation's content and on compliance, and is evidence that they were made and nothing more. Review conclusions come instead from the Greater Vancouver Water District's annual dam safety updatesOpen the document ↗
- [12]ReportInstructions, Guide & Templates for Preparing a Dam Emergency Plan (DEP) in British ColumbiaB.C. Dam Safety Program · 2024The required content of an emergency plan, including the scenario "Earthquake resulting in uncontrolled release of water from the dam"Open the document ↗