Types of Hydro Development Studies
Many hydro sites in the Yukon have been the subject of engineering studies with various level of detail, ranging from desktop-only studies to complete pre-feasibility studies supported by a field investigation program. An overview of the level of detail of each stage of engineering studies related to the development of a hydroelectric project is presented below. An overview of the associated environmental studies and permitting process for each step is also included.
1) Desktop Study: Simple office calculations and layout determination completed based on existing topographical maps (1:50,000), available flow data (from Water Survey of Canada gauging stations, from the same river if possible, or nearby rivers otherwise), and available geological maps. No site visit is conducted. A site layout drawing may or may not be produced.
2) Reconnaissance/Conceptual Engineering Study: Study that involved first a reconnaissance site visit to observe the site main components, including river layout and abutments, geological features, and may include simple measurements (head drop). Complemented with simple office calculations to determine power benefits. A project layout is proposed based on existing topographical maps and observations from the site visit. A site layout drawing will be produced. An order-of-magnitude cost estimate (+-50-100%) is produced. A scoping level of assessment and regulatory approvals is usually completed to identify the main development issues, and provide recommendations.
3) Pre-feasibility Engineering Study: Detailed conceptual engineering study determines the viable layout and long-term power benefit based on a realistic operation scheme. Preliminary engineering is based on site mapping and site hydrology. The study is initiated by a detailed site visit with a team of experts including a geologist and hydro technical engineer. For larger project, a preliminary field investigation program will be completed, including preliminary topographical survey and geophysical investigations on site. The investigation program will only include a few boreholes at key locations (i.e. control structure site) and seismic lines for example. Planning of detailed geotechnical investigations for the feasibility study is usually conducted. A set of design criteria is established for the project, including a hydrological study. Preliminary design of main works is conducted to define key dimensions. A set of drawings is produced to cover all main works of the project. A cost estimate based on a bill of quantities is prepared at a +-30 to 50% is produced. The site visit will usually also involve an environmental specialist. The environmental and socio economic components for the effects assessment are defined. Baseline study may be conducted at the same time. Consultation and preliminary agreements with First Nation and other governments are usually put in place. Approvals and permits for geotechnical site investigations for feasibility study are obtained.
4) Feasibility Engineering Study: The study is initiated by a complete intrusive geotechnical investigations program and detailed topographic survey. It is conducted for the main works for the project, but also potential construction material sources, access roads and transmission lines. The engineering level of detail is upgraded based on the results of the investigation program. The design criteria are updated and expanded if necessary. Alternative layouts are considered and project optimization is conducted, which can include cost comparison analysis. Works are designed in more details and all components are now assessed. Continuous flow monitoring should continue and will allow updating power estimates. The operation scheme will be optimized. Detailed hydraulic studies (computer or scale modelling) will be conducted to optimize the main works and minimize construction costs. At the end of the study, the proposed layout, design basis and criteria will all be freeze to continue with detailed engineering phase. Detailed project planning is conducted to determine viable construction methods and the associated optimal schedule. A detailed set of drawings is produced; including work and associated components, and construction layout. A cost estimate at a +-15-20% level is prepared.
The environmental effects assessment is conducted at the same time as the pre-feasibility study (may have started before). The environmental effects assessment review process is launched in parallel with the study with a project application to YESAB. Final agreements with First Nation and Governments are established. A formal decision to proceed with the project to construction is usually taken at the end of the feasibility study. Funding for the process must be secured.
5) Detailed Design: Complete detail design drawings and technical specifications are prepared with the short goal to proceed to construction. Project optimization is completed especially regarding hydraulic studies are finalized. A complete set of drawings for construction (to be formally released during procurement) is produced. A final cost estimate at +-10-15% is prepared. Procurement of long-lead items and prequalification of contractors is conducted. Procurement is subsequent to this phase and can be done simultaneously. Engineering support is provided during procurement to review questions, addendum and for proposal review. Regulatory approvals are obtained during this process and funding is made available. Acquisition of land has to be finalized and construction preparation starts. Environmental and regulatory commitments and mitigations have to start to be implemented, if applicable.