In 2015, the Village of Sayward (Village) retained Northwest Hydraulic Consultants (NHC) to complete a dam safety review (DSR) of the Newcastle Dam, located on the perimeter of the community. The dam, a 17.4 m-tall concrete arch, featured a small freshwater reservoir that supplied the Village’s water system.

The DSR scope included a detailed hydrologic analysis of the area, determination of the Inflow Design Flood, review of the dam structure and spillway capacity, and assessment of the downstream inundation from a hypothetical dam breach and corresponding potential loss of life to meet the BC Dam Safety Regulation. Following the DSR, NHC recommended increasing the consequence classification of Newcastle Dam from High to Very High, completing several upgrades, and monitoring if the Village chose to continue operating the dam. Given the high cost and complexity of the recommended upgrades, NHC also provided alternative solutions to either lower the dam to reduce its hazard rating or decommission it and construct new diversion works for the community’s raw water supply. The Village decided on dam decommissioning and constructing a new water supply intake.

Starting in 2018, NHC provided detailed hydrotechnical design and construction engineering services to decommission the dam and replace the diversion works with a new intake and supply pipeline, which included using a bedrock-abutted concrete weir with a coanda screen spillway intake that feeds a gravity-fed pipeline bolted to the ex-reservoir’s rock face. Concurrently, the Village installed a new treatment plant and water storage tank, rendering the reservoir upstream of the dam redundant for demand buffering and storage for fire suppression. Between July 2019 and September 2022, NHC worked with the Village and its contractor to complete decommissioning activities and construction works in phases, and final inspection was completed on September 7, 2022.

NHC’s initial scope was to complete a DSR of Newcastle Dam. The team consulted with the Village to understand the dam’s history, structural stability, and ability to withstand return-period events, such as an Inflow Design Flood or Maximum Design Earthquake. NHC also considered community requirements: the facility provided the Village with a freshwater source, and limited resources were available to meet increasing maintenance demands and improve dam safety. During the DSR process, NHC collaborated with the Village and water treatment plant experts to develop viable solutions, from modifying the existing dam to full decommissioning. Given the complexities and cost of dam maintenance, the Village decided to remove it and replace it with a low head weir and intake structure. NHC developed a decommissioning plan and detailed design of a new system to supply raw water to the community. The decommissioning plan involved removing the dam in conjunction with constructing a new water intake with a bedrock-abutted concrete weir and a coanda screen spillway intake that feeds a pipeline attached to the rockface of the ex-reservoir. NHC worked with the contractor to develop a comprehensive staged construction plan for the dam decommissioning and construction of the water supply intake. The new water intake system was completed in summer 2022, and the project is now operational. NHC continues to work with the Village to support the long-term success of this critical infrastructure.

As a result of NHC’s work and collaborative efforts, the Village of Sayward no longer owns, operates, or maintains a Very High Consequence dam. A new water intake and supply line now provides the Village with reliable, low-maintenance infrastructure, that diverts water from the creek to the treatment plant.