Preliminary Design Fort Shepherd Bar Re-contouring

Author: Golder Associates Ltd

Golder Associates Ltd. (Golder) was retained by Waneta Expansion Power Corporation (WEPC) to provide consulting services for the preliminary design of a shallow water habitat compensation plan for the Waneta Expansion Project. The project involves the re-contouring of the Fort Shepherd Bar (the Site) on the Columbia River, located upstream of the river’s confluence with the Pend D’Oreille River (refer to Figure 1). This report describes the geomorphic and hydrotechnical analyses undertaken for the preliminary design of the Fort Shepherd Bar habitat compensation works. Other components of the project will be addressed in separate documents. The scope of work described in this report is limited to the hydrotechnical engineering and geomorphic aspects only, and does not include any specific provisions for geotechnical engineering, the investigation, testing or assessment of the potential presence or impact of soil or groundwater contamination at the site, or bioscience services. This report shall be read in conjunction with “Important Information and Limitations of This Report” which is appended following the text of this report. The reader’s attention is specifically drawn to this information as it is essential that it is followed for the proper use and interpretation of this report.

The preliminary plan and cross-sections for the proposed bar re-contouring are provided in Figures 4 and 5, respectively. The excavated area shall be covered with the specified geotextile, a 0.1 m thick layer of 12 mm to 19 mm clear crushed gravel, and a 0.6 m thick layer of rock riprap at the surface. To allow for drainage during lower flows, the re-contouring was designed to slope down at approximately 1% towards the river and 0.4% in the direction of river flow. The re-contouring extends east until approximately 15 m to 25 m from the toe of the existing embankment of Highway 22A, where it slopes up to the existing ground at 4H:1V.

The preliminary plan and cross-sections for the proposed bar re-contouring are provided in Figures 4 and 5, respectively. The excavated area shall be covered with the specified geotextile, a 0.1 m thick layer of 12 mm to 19 mm clear crushed gravel, and a 0.6 m thick layer of rock riprap at the surface. To allow for drainage during lower flows, the re-contouring was designed to slope down at approximately 1% towards the river and 0.4% in the direction of river flow. The re-contouring extends east until approximately 15 m to 25 m from the toe of the existing embankment of Highway 22A, where it slopes up to the existing ground at 4H:1V.