The North Channel Block Dam (NCBD) is situated in a narrow, bedrock‑controlled secondary channel of the Winnipeg River, approximately 45 km northwest of Kenora, Ontario. Prior to remediation, it was only accessible by boat or plane. The dam contains the headpond of the Whitedog Falls Generating Station (GS), located 6 km downstream. The initial 1958 structure was constructed in‑the‑wet to close the north channel, which had previously served as a diversion during the GS construction. It consisted of a zoned rockfill and granular fill embankment with an inclined silty‑sand upstream core. Following a dam safety review, two serious deficiencies were identified: insufficient freeboard and a risk of internal erosion. These concerns were underscored during severe regional floods in 2014 and 2022, which required emergency interventions to prevent failure. OPG began working on a replacement dam once access could be established through an agreement with a local landowner. Seven conceptual rockfill dam alternatives were developed with various types of impervious core materials, including a combination of compacted clay, geomembrane, cement‑bentonite slurry, sheet piles, and reinforced concrete. Options were evaluated using the analytical hierarchy process under weighted criteria which consisted of overtopping resilience, lifecycle maintenance, surveillance, operability, constructability, environmental impact, regulatory considerations, schedule, and cost. A vertical reinforced concrete core wall was ultimately selected as the preferred solution. The final design included a tremie poured concrete‑filled trench to achieve the cut‑off through overburden, bolstered by a grout curtain to improve bedrock and abutment watertightness. The replacement NCBD was successfully commissioned in Fall 2025.