2.0 PROJECT DESCRIPTION
This project requires an assessment of the St. Mary Dam Irrigation Outlet including all hydraulics, actuators, operating gates, emergency gates, control systems and the outlet tunnel.
2.1 Background
The St. Mary Dam impounds the St. Mary River – a tributary of the Oldman River in southern Alberta and is situated about 35 km upstream of the confluence with the Oldman River, about 20 km northeast of the town of Cardston. 1). The main function of the dam and impounded reservoir are to provide secured water supply for irrigation users and others. Primary users include the St. Mary River Irrigation District (SMRID).
The irrigation outlet works consists of an inlet gallery with trash rack, inlet structure, a concrete lined semicircular tunnel with a discharge capacity of 91 m3/s and an outlet section. The tunnel is 5.2m in diameter and 763m long. The irrigation tunnel conveys flows into the Waterton St. Mary Headwork System canal. The shaft and stairwell are the only means of accessing the irrigation outlet valves, gates and mechanical systems.
3.0 SCOPE OF WORK
Alberta Agriculture and Irrigation requires the services of an Engineering Consultant to undertake an inspection of the St. Mary Irrigation Outlet. The services to be provided shall include:
1. Review previous studies, information, drawings, and technical reports including construction records, previous geotechnical investigations, structural design and structural assessments of the infrastructure.
2. A site visit and thorough inspection of all gates, gate thimbles, and chambers for the operating gates, emergency gates and the upstream side of the outlet tunnel.
3. Inspection of inlet gallery including trashrack and concrete structure.
4. In addition a review of the KCB inspection of 2022 shall be conducted and any gaps in the report regarding the inspection, assessment and recommendation for hydraulics, actuators, operating gates, emergency gates, control systems, and the outlet tunnel shall be addressed.
5. A coffer dam shall be constructed for the purpose of inspecting the outlet tunnel. This will include any access required for construction and inspection by equipment or person.
6. Removal of the coffer dam upon completion of inspection and repairs.
7. In the event that the reservoir level is above 1081 m on November 1st, the inspection will not be conducted.
