OperationsThe first phase of the AWS joint venture, the Arrowsmith dam, was constructed between 1997 and 1999 by Walter Construction (Canada) Ltd of Vancouver. Site work began in September 1997 with clearing and grubbing of the reservoir and construction of the outlet works. Dam construction commenced in April 1998 and was completed by November 1998. Power supply and remote control communications facilities were completed in 2000.
The dam is located at the headwaters of the Englishman River approximately 25 kilometres upstream of the mouth and serves as a storage reservoir to allow augmentation of low summer flows. The Arrowsmith Dam has been a great benefit to fish enhancement on the Englishman River. The principal structures consist of a concrete gravity dam, a high level outlet consisting of a 900 millimetre diameter gravity fed pipe and low level outlet consisting of a 600 millimetre diameter siphon pipe.
Arrowsmith Lake is located on the eastern slope of Mount Arrowsmith, about 4 kilometres east of the peak. The lake occupies the bottom of a steep-sided glacial cirque and is approximately 36 hectares in size with an elevation of approximately 816 metres. The dam site is located at the northeast end of the lake where the natural outlet and lake level were controlled by bedrock sill.
Access to Arrowsmith Dam is from Highway 19 along the Island Timberlands, Northwest Bay Division main logging road which runs west from the highway along the south side of the Englishman River. The road crosses the Englishman River approximately 17 kilometres from the highway, then continues as an Island Timberlands logging road from the bridge to the site. Access to the dam, reservoir and watershed above the dam is closed to vehicles.
Appropriate signs notify the public they are entering a watershed used for domestic water supply purposes. Reporting of spills of hazardous goods and incidents involving potential contamination of the water is encouraged.
The period of low flow (June to October) in the Englishman River coincides with maximum domestic water demand and fish migration.
The Arrowsmith Dam, with a live storage volume of 9 million cubic meters, is used to regulate the flow in the Englishman River during the summer and fall to meet the domestic water demands in the service area. Approximately 50% of the live storage volume behind the Arrowsmith Dam is provided for release of water during low natural river flows, to improve fisheries flow in the downstream reach of the Englishman River.