CLIENT: Regional District of Okanagan-Similkameen
PROJECT DESCRIPTION:
The Regional District of Okanagan-Similkameen (RDOS) engaged PRI to complete a Consequence Classification Assessment (CCA) of Chain Lake Dam, located 36 kilometres northeast of Princeton, BC, along the Princeton-Summerland Road. Building on the findings of the CCA, PRI was subsequently retained to advance the preliminary and detailed design of a new spillway and Low-Level Outlet (LLO), through to Issued for Construction drawings and full tender documentation. Construction engineering services are forthcoming, with the project developed in consultation with the public and First Nations.
CHALLENGE:
Establishing an accurate and defensible consequence classification for Chain Lake Dam required thorough analysis of potential failure modes and their downstream impacts. Two breach scenarios — a sunny day piping failure and an overtopping failure — needed to be modelled and mapped to understand the extent and severity of potential inundation. The findings of the CCA then directly shaped the design requirements for new dam safety infrastructure, with the spillway and LLO needing to meet updated regulatory standards while reflecting the sensitivities of a project requiring meaningful public and First Nations consultation.
APPROACH:
PRI conducted a background review and site reconnaissance before completing a dam breach analysis considering both piping and overtopping failure modes. Inundation mapping was completed using FLO-2D software, and an updated consequence classification was provided to the RDOS. Based on the CCA recommendations, PRI proceeded with preliminary and detailed design of the new spillway and LLO. Design development was carried out in consultation with the public and First Nations throughout the process. PRI prepared Issued for Construction drawings, a schedule of quantities, a Class A cost estimate, and full tender documentation to support the RDOS tendering process. Environmental services were also provided, and PRI will deliver construction-phase engineering services including field reviews and post-construction reporting.
OUTCOME:
PRI’s end-to-end involvement — from consequence classification through design, tendering support, and forthcoming construction oversight — has provided the RDOS with consistent, single-source engineering expertise across all phases of this dam safety project. The dam breach analysis and inundation mapping established a technically defensible basis for updated consequence classification, while the subsequent spillway and LLO design addressed the identified deficiencies in accordance with current regulatory requirements. Meaningful engagement with the public and First Nations throughout the design process supported an inclusive and well-informed project outcome.