The Greater Vancouver Water District (GVWD)’s Seymour Falls Dam is a key component in the water supply for the Greater Vancouver region. It is a composite structure consisting of a slab and buttress concrete section, an earthfill embankment and an extensive impervious upstream blanket. The dam was constructed in 1961 to a height of 30 m with provision for future raising of 17.4 m. The original seismic design was carried out using a lateral force coefficient of 0.1 g. The safety assessment studies reconstructed an operating basis earthquake imparting a peak ground acceleration of 0.2 g to the dam base, and a maximum credible earthquake (MCE) with up to 0.5 g peak ground acceleration.
The dam was in excellent condition after 40 years of service, but it did not meet current criteria for earthquake safety. Between 2004 and 2007, Klohn Crippen Berger completed designs and tender documents for the rehabilitation of the earthfill portion of the dam and provided resident engineering services during construction. The loose, liquefiable, Cougar Creek fan deposits in the dam foundations were densified in-situ in the area downstream of the existing dam. A new dam was then constructed on the new earthquake resistant foundation and connected to the concrete dam by means of an extension to the concrete gravity transition block. In-situ densification was achieved with a combination of explosive compaction and dynamic compaction. The reservoir remained in service throughout the construction period.
- Safety assessments under extreme loads
- Screening level studies
- Preliminary design studies
- Analysis of earthquake stability and deformation
- Environmental assessments and mitigation designs
- Geotechnical and geophysical investigations
- Project management
- Final design
- Preparation of tender documents
- Engineer’s cost estimate
- Modelling of seepage underflow
- Field trials of compaction methods